JP7402411B2 - electrostatic chuck - Google Patents

Description

Aspects of the present invention relate to electrostatic chucks.

Ceramic electrostatic chucks are manufactured by sandwiching electrodes between ceramic dielectric substrates such as alumina and firing them.Electrostatic adsorption power is applied to the built-in electrodes, and the substrates, such as silicon wafers, are held together by the electrostatic force. It is adsorbed by. In such an electrostatic chuck, an inert gas such as helium (He) is passed between the surface of the ceramic dielectric substrate and the back surface of the substrate, which is the object to be adsorbed, to reduce the temperature of the substrate, which is the object to be adsorbed. is controlled.

For example, in some apparatuses that process a substrate, such as a CVD (Chemical Vapor Deposition) apparatus, a sputtering apparatus, an ion implanter, and an etching apparatus, the temperature of the substrate increases during the process. In the electrostatic chuck used in such devices, an inert gas such as He is passed between the ceramic dielectric substrate and the substrate to be adsorbed, and the temperature of the substrate is increased by bringing the inert gas into contact with the substrate. is suppressed.

In an electrostatic chuck that controls the substrate temperature using an inert gas such as He, a hole (gas introduction path) for introducing an inert gas such as He is formed in the ceramic dielectric substrate and the base plate that supports the ceramic dielectric substrate. ) is provided. Further, the ceramic dielectric substrate is provided with a through hole that communicates with the gas introduction path of the base plate. Thereby, the inert gas introduced from the gas introduction path of the base plate is guided to the back surface of the substrate through the through hole of the ceramic dielectric substrate.

Here, when processing a substrate within the apparatus, discharge (arc discharge) may occur from plasma within the apparatus toward the metal base plate. The gas introduction path of the base plate and the through hole of the ceramic dielectric substrate may easily become a path for discharge. Therefore, there is a technique to improve the resistance (dielectric strength voltage, etc.) against arc discharge by providing a porous portion in the gas introduction path of the base plate or the through hole of the ceramic dielectric substrate. For example, Patent Document 1 discloses that a ceramic sintered porous body is provided in the gas introduction passage, and the structure of the ceramic sintered porous body and the membrane pores are used as gas flow passages to improve insulation within the gas introduction passage. An electrostatic chuck is disclosed. Further, Patent Document 2 discloses an electrostatic chuck in which a discharge prevention member for a processing gas flow path made of a ceramic porous body is provided in a gas diffusion gap to prevent discharge. Further, Patent Document 3 discloses an electrostatic chuck that is provided with a dielectric insert made of a porous dielectric such as alumina to reduce arc discharge. In an electrostatic chuck having such a porous portion, it is desired to develop an electrostatic chuck that can further suppress the occurrence of arc discharge.

Japanese Patent Application Publication No. 2010-123712 Japanese Patent Application Publication No. 2003-338492 Japanese Patent Application Publication No. 10-50813

The present invention has been made based on the recognition of this problem, and aims to provide an electrostatic chuck that can effectively suppress the occurrence of arc discharge in an electrostatic chuck provided with a porous portion. purpose.

A first invention provides a ceramic dielectric substrate having a first main surface on which an object to be attracted is placed, and a second main surface opposite to the first main surface; a base plate supporting the base plate and having a gas introduction path; a first porous material provided between the base plate and the first main surface of the ceramic dielectric substrate at a position facing the gas introduction path; The first porous portion has a plurality of sparse portions each having a plurality of pores and is spaced apart from each other, and each of the plurality of sparse portions is separated from the base plate. The electrostatic chuck is characterized in that the chuck extends in a direction inclined at a predetermined angle with respect to the first direction toward the ceramic dielectric substrate.

According to this electrostatic chuck, the first porous portion is provided with a plurality of sparse portions each having a plurality of holes and spaced apart from each other, thereby improving resistance to arc discharge and preventing flowing gas from flowing. The flow rate can be ensured. Furthermore, since each of the plurality of sparse portions extends in a direction inclined at a predetermined angle with respect to the first direction from the base plate toward the ceramic dielectric substrate, current flows inside the hole provided in the sparse portion. In this case, electrons are thought to be less likely to be accelerated. Therefore, the occurrence of arc discharge can be effectively suppressed.

A second invention is the electrostatic chuck according to the first invention, characterized in that the plurality of holes allow gas introduced from the gas introduction path to flow therethrough.

According to this electrostatic chuck, gas introduced from the gas introduction path can be guided to the first main surface side of the ceramic dielectric substrate.

A third invention is the electrostatic charger according to the first or second invention, wherein the angle between the first direction and the direction in which the sparse portion extends is 5° or more and 30° or less. It's Chuck.

According to this electrostatic chuck, it becomes easy to suppress the occurrence of arc discharge.

A fourth invention is based on any one of the first to third inventions, wherein the first porous portion is located between the plurality of sparse portions and has a higher density than the sparse portions. The sparse portion further includes a dense portion, and the sparse portion includes the hole and a wall portion provided between the holes, and the sparse portion is arranged in a direction substantially perpendicular to a direction inclined at a predetermined angle with respect to the first direction. , the electrostatic chuck is characterized in that a minimum dimension of the wall portion is smaller than a minimum dimension of the dense portion.

According to this electrostatic chuck, since the first porous part is provided with a sparse part and a dense part, the mechanical strength of the first porous part is maintained while ensuring resistance to arc discharge and gas flow rate. (rigidity) can be improved.

In a fifth invention, in any one of the first to fourth inventions, the ceramic dielectric substrate has a first hole located between the first main surface and the first porous part. at least one of the ceramic dielectric substrate and the first porous portion has a second hole located between the first hole and the first porous portion; An electrostatic chuck characterized in that the dimensions of the second hole are smaller than the dimensions of the first porous portion and larger than the dimensions of the first hole in a second direction substantially perpendicular to the first direction. It is.

According to this electrostatic chuck, the first porous portion provided at a position facing the gas introduction path makes it possible to improve resistance to arc discharge while ensuring a flow rate of gas flowing into the first hole. . Further, since the second hole having a predetermined size is provided, most of the gas introduced into the first porous portion having a large size is transferred to the first hole having a small size through the second hole. can be introduced into In other words, arc discharge can be reduced and gas flow can be made smoother.

A sixth invention is the invention according to any one of the first to fifth inventions, further comprising a second porous part provided between the first porous part and the gas introduction path and having a plurality of holes. , the plurality of pores provided in the second porous part are more three-dimensionally dispersed than the plurality of pores provided in the first porous part, and the proportion of the pores penetrating in the first direction is The electrostatic chuck is characterized in that there are more first porous parts than second porous parts.

According to this electrostatic chuck, a higher dielectric strength voltage can be obtained by providing the second porous portion having a plurality of three-dimensionally distributed holes, so that the occurrence of arc discharge can be more effectively suppressed. . Furthermore, by providing the first porous portion with a large proportion of holes penetrating in the first direction, gas flow can be made smoother.

In a seventh invention, in any one of the first to sixth inventions, the average value of the diameters of the plurality of pores provided in the second porous part is the same as the diameter of the plurality of pores provided in the first porous part. This electrostatic chuck is characterized in that the diameter of the holes is larger than the average value.

According to this electrostatic chuck, since the second porous portion having a large hole diameter is provided, gas flow can be made smoother. Further, since the first porous portion having a small hole diameter is provided on the side of the object to be adsorbed, it is possible to more effectively suppress the occurrence of arc discharge.

In an eighth invention, in any one of the first to sixth inventions, the average value of the diameters of the plurality of pores provided in the second porous part is This electrostatic chuck is characterized in that the diameter of the holes is smaller than the average value.

According to this electrostatic chuck, since the second porous portion with a small hole diameter is provided, it is possible to more effectively suppress the occurrence of arc discharge.

A ninth invention is the invention according to any one of the first to eighth inventions, further comprising a second porous part provided between the first porous part and the gas introduction path and having a plurality of holes. , an average value of diameters of the plurality of pores provided in the second porous portion is larger than an average value of diameters of the plurality of pores provided in the first porous portion. It's an electric chuck.

Since the second porous portion with large pore diameters is provided, smooth gas flow can be achieved. Further, since the first porous portion having a small hole diameter is provided on the side of the object to be adsorbed, it is possible to more effectively suppress the occurrence of arc discharge.

A tenth invention is based on any one of the first to ninth inventions, wherein the first porous portion and the ceramic dielectric substrate contain aluminum oxide as a main component, and the aluminum oxide of the ceramic dielectric substrate The electrostatic chuck is characterized in that the purity of the aluminum oxide in the first porous portion is higher than that of the aluminum oxide in the first porous portion.

According to this electrostatic chuck, performance such as plasma resistance of the electrostatic chuck can be ensured, and mechanical strength of the first porous portion can be ensured. For example, by including a small amount of additive in the first porous part, sintering of the first porous part is promoted, and pore control and mechanical strength can be ensured.

An eleventh invention is the one according to any one of the first to tenth inventions, further comprising a second porous part provided between the first porous part and the gas introduction path, and wherein the ceramic dielectric The substrate has a first hole located between the first main surface and the first porous portion, and the second porous portion includes a ceramic porous body having a plurality of holes, and a ceramic porous body having a plurality of holes. a dense portion that is denser than the porous body, and when projected onto a plane perpendicular to a first direction from the base plate toward the ceramic dielectric substrate, the dense portion and the first hole are The electrostatic chuck is characterized in that the second porous portion and the first hole portion are configured so as not to overlap each other.

Since this electrostatic chuck is configured such that the dense portion and the first hole overlap, the generated current tends to flow bypassing the dense portion. Therefore, the distance through which the current flows (conductive path) can be increased, making it difficult for electrons to be accelerated, which in turn can suppress the occurrence of arc discharge. According to this electrostatic chuck, it is possible to effectively suppress the occurrence of arc discharge while ensuring a gas flow.

A twelfth invention is based on the eleventh invention, wherein the ceramic porous body has a plurality of sparse portions having a plurality of pores and a dense portion having a density higher than the density of the sparse portions, and In the porous body, each of the plurality of sparse portions extends in the first direction, the dense portion is located between the plurality of sparse portions, and the sparse portion is provided between the pores. The electrostatic chuck is characterized in that the electrostatic chuck has a wall portion, and a minimum dimension of the wall portion is smaller than a minimum dimension of the dense portion in the second direction.

According to this electrostatic chuck, since the ceramic porous body is provided with the sparse portion and the dense portion extending in the first direction, the resistance to arc discharge and the gas flow rate are ensured, and the second porous portion is The physical strength (rigidity) can be improved.

A thirteenth aspect of the invention is that in any one of the first to twelfth aspects, when a direction substantially perpendicular to the first direction is a second direction, the first porous portion is arranged in the second direction. The ceramic dielectric substrate has a first region located on the ceramic dielectric substrate side, and the ceramic dielectric substrate has a first substrate region located on the first region side in the second direction, and the first region and the The electrostatic chuck is provided in contact with a first substrate region, and the average particle diameter in the first region is different from the average particle diameter in the first substrate region.

According to this electrostatic chuck, since the average particle size in the first region and the average particle size in the first substrate region are different, the first porous portion The bonding strength between the ceramic dielectric substrate and the ceramic dielectric substrate can be improved.

A fourteenth invention is the electrostatic chuck according to the thirteenth invention, wherein the average particle diameter in the first substrate region is smaller than the average particle diameter in the first region.

According to this electrostatic chuck, the bonding strength between the first porous part and the ceramic dielectric substrate can be improved at the interface between the first porous part and the ceramic dielectric substrate. In addition, the small particle size in the first substrate region increases the strength of the ceramic dielectric substrate and suppresses the risk of cracks and the like due to stress generated during manufacturing and processing.

A fifteenth invention is any one of the twelfth to fourteenth inventions, wherein the ceramic dielectric substrate includes a second substrate region, and the first substrate region is arranged such that the second substrate region and the first porous The electrostatic chuck is characterized in that the average particle diameter in the first substrate region is smaller than the average particle diameter in the second substrate region.

In the first substrate region provided in contact with the first region, it is preferable to increase the interface strength between the first region and the first region through interaction such as diffusion between the first region and the first region during sintering in the manufacturing process, for example. . On the other hand, in the second substrate region, it is preferable that the characteristics inherent to the material of the ceramic dielectric substrate are expressed. According to this electrostatic chuck, the average particle diameter in the first substrate region is made smaller than the average particle diameter in the second substrate region, so that the interface strength in the first substrate region is guaranteed and the ceramic in the second substrate region It is possible to achieve both the characteristics of the dielectric substrate and the characteristics of the dielectric substrate.

A sixteenth invention is the electrostatic chuck according to the fifteenth invention, wherein the average particle diameter in the first region is smaller than the average particle diameter in the second substrate region.

According to this electrostatic chuck, the average particle diameter in the first region is smaller than the average particle diameter in the second substrate region, so that the mechanical strength in the first region can be improved.

A seventeenth invention is characterized in that in any one of the twelfth, thirteenth, fifteenth, and sixteenth inventions, the average particle diameter in the first region is smaller than the average particle diameter in the first substrate region. This is an electrostatic chuck.

According to this electrostatic chuck, the bonding strength between the first porous part and the ceramic dielectric substrate can be improved at the interface between the first porous part and the ceramic dielectric substrate. Further, since the average particle diameter in the first region is small, the strength of the first porous portion is increased, so that drop-off of particles during processing can be suppressed, and particles can be reduced.

According to an aspect of the present invention, there is provided an electrostatic chuck that can effectively suppress the occurrence of arc discharge in an electrostatic chuck provided with a porous portion.

FIG. 1 is a schematic cross-sectional view illustrating an electrostatic chuck according to a first embodiment. FIGS. 2A and 2B are schematic diagrams illustrating the electrostatic chuck according to the embodiment. FIGS. 3A and 3B are schematic diagrams illustrating the first porous portion of the electrostatic chuck according to the embodiment. FIG. 2 is a schematic plan view illustrating a first porous portion of an electrostatic chuck according to an embodiment. FIG. 2 is a schematic plan view illustrating a first porous portion of an electrostatic chuck according to an embodiment. FIGS. 6A and 6B are schematic plan views illustrating the first porous portion of the electrostatic chuck according to the embodiment. FIGS. 7(a) and 7(b) are schematic diagrams illustrating another first porous portion according to the embodiment. FIG. 1 is a schematic cross-sectional view illustrating an electrostatic chuck according to an embodiment. FIGS. 9A and 9B are schematic cross-sectional views illustrating an electrostatic chuck according to an embodiment. FIG. 3 is a schematic cross-sectional view illustrating a second porous portion of the electrostatic chuck according to the embodiment. FIG. 3 is a schematic cross-sectional view illustrating another electrostatic chuck according to an embodiment. FIG. 3 is a schematic cross-sectional view illustrating another electrostatic chuck according to an embodiment. (a) is a schematic cross-sectional view illustrating an electrostatic chuck according to a second embodiment. (b) is a plan view illustrating the second porous part. FIG. 7 is a schematic cross-sectional view illustrating a modification of the electrostatic chuck according to the second embodiment. It is a schematic diagram which illustrates a 2nd porous part. It is an enlarged view showing a part of the 2nd porous part seen along the Z direction. It is an enlarged view showing a part of the 2nd porous part seen along the Z direction. FIG. 3 is an enlarged view showing holes in one sparse section viewed along the Z direction. FIG. 7 is a schematic cross-sectional view illustrating another electrostatic chuck according to the second embodiment. FIG. 7 is a schematic cross-sectional view illustrating another electrostatic chuck according to the second embodiment.

Embodiments of the present invention will be described below with reference to the drawings. Note that in each drawing, similar components are denoted by the same reference numerals, and detailed explanations are omitted as appropriate.

(First embodiment)
FIG. 1 is a schematic cross-sectional view illustrating an electrostatic chuck according to a first embodiment.
As shown in FIG. 1, the electrostatic chuck 110 according to this embodiment includes a ceramic dielectric substrate 11, a base plate 50, and a first porous portion 90.

The ceramic dielectric substrate 11 is a flat base material made of, for example, sintered ceramic. For example, the ceramic dielectric substrate 11 includes aluminum oxide (Al ₂ O ₃ ). For example, the ceramic dielectric substrate 11 is made of high purity aluminum oxide. The concentration of aluminum oxide in the ceramic dielectric substrate 11 is, for example, 99 atomic percent or more and 100 atomic percent or less. By using high-purity aluminum oxide, the plasma resistance of the ceramic dielectric substrate 11 can be improved. The ceramic dielectric substrate 11 has a first main surface 11a on which an object W to be attracted is placed, and a second main surface 11b opposite to the first main surface 11a. The object W to be attracted is, for example, a semiconductor substrate such as a silicon wafer.

An electrode 12 is provided on the ceramic dielectric substrate 11 . The electrode 12 is provided between the first main surface 11a and the second main surface 11b of the ceramic dielectric substrate 11. Electrode 12 is formed to be inserted into ceramic dielectric substrate 11 . The electrostatic chuck 110 generates a charge on the first main surface 11a side of the electrode 12 by applying an attraction and holding voltage 80 to the electrode 12, and attracts and holds the object W by electrostatic force.

Here, in the description of this embodiment, the direction from the base plate 50 toward the ceramic dielectric substrate 11 will be referred to as the Z direction (corresponding to an example of the first direction), and one of the directions substantially orthogonal to the Z direction will be referred to as the Y direction ( (corresponding to an example of the second direction), and a direction substantially orthogonal to the Z direction and the Y direction is referred to as the X direction (corresponding to an example of the second direction).

The shape of the electrode 12 is a thin film along the first main surface 11a and the second main surface 11b of the ceramic dielectric substrate 11. The electrode 12 is an adsorption electrode for adsorbing and holding the object W. Electrode 12 may be monopolar or bipolar. The electrode 12 shown in FIG. 1 is of a bipolar type, and two electrodes 12 are provided on the same surface.

The electrode 12 is provided with a connecting portion 20 extending toward the second main surface 11b side of the ceramic dielectric substrate 11. The connecting portion 20 is, for example, a via (solid type) or a via hole (hollow type) that is electrically connected to the electrode 12. The connection portion 20 may be a metal terminal connected by a suitable method such as brazing.

The base plate 50 is a member that supports the ceramic dielectric substrate 11. The ceramic dielectric substrate 11 is fixed onto the base plate 50 by the adhesive portion 60 shown in FIG. 2(a). The adhesive portion 60 may be made of, for example, a cured silicone adhesive.

The base plate 50 is made of metal, for example. The base plate 50 is divided into an upper part 50a and a lower part 50b made of aluminum, for example, and a communication path 55 is provided between the upper part 50a and the lower part 50b. One end of the communication path 55 is connected to the input path 51 , and the other end of the communication path 55 is connected to the output path 52 .

The base plate 50 also serves to adjust the temperature of the electrostatic chuck 110. For example, when cooling the electrostatic chuck 110, a cooling medium flows in from the input path 51, passes through the communication path 55, and flows out from the output path 52. Thereby, the heat of the base plate 50 can be absorbed by the cooling medium, and the ceramic dielectric substrate 11 attached thereon can be cooled. On the other hand, when keeping the electrostatic chuck 110 warm, it is also possible to put a heat insulating medium into the communication path 55. It is also possible to incorporate a heating element into the ceramic dielectric substrate 11 or the base plate 50. By adjusting the temperature of the base plate 50 and the ceramic dielectric substrate 11, the temperature of the object W held by the electrostatic chuck 110 can be adjusted.

Further, dots 13 are provided on the first principal surface 11a side of the ceramic dielectric substrate 11 as necessary, and grooves 14 are provided between the dots 13. That is, the first main surface 11a is an uneven surface and has concave portions and convex portions. The convex portions of the first main surface 11a correspond to the dots 13, and the concave portions of the first main surface 11a correspond to the grooves 14. The groove 14 extends continuously in the XY plane. A space is formed between the back surface of the object W placed on the electrostatic chuck 110 and the first main surface 11a including the groove 14.

The ceramic dielectric substrate 11 has a through hole 15 connected to the groove 14 . The through hole 15 is provided from the second main surface 11b to the first main surface 11a. That is, the through hole 15 extends in the Z direction from the second main surface 11b to the first main surface 11a, and penetrates the ceramic dielectric substrate 11.

By appropriately selecting the height of the dots 13 (the depth of the grooves 14), the area ratio of the dots 13 and the grooves 14, the shape, etc., the temperature of the object W and particles adhering to the object W can be controlled to a preferable state. be able to.

A gas introduction path 53 is provided in the base plate 50 . The gas introduction path 53 is provided so as to penetrate the base plate 50, for example. The gas introduction path 53 may not penetrate the base plate 50 but may be branched from the middle of another gas introduction path 53 and provided to the ceramic dielectric substrate 11 side. Furthermore, the gas introduction passages 53 may be provided at multiple locations on the base plate 50.

The gas introduction path 53 communicates with the through hole 15 . That is, the gas (such as helium (He)) that has flowed into the gas introduction path 53 flows into the through hole 15 after passing through the gas introduction path 53 .

After passing through the through hole 15, the gas flows into the space provided between the object W and the first main surface 11a including the groove 14. Thereby, the object W can be directly cooled by the gas.

The first porous portion 90 can be provided, for example, between the base plate 50 and the first main surface 11a of the ceramic dielectric substrate 11 in the Z direction, and at a position facing the gas introduction path 53. For example, the first porous portion 90 is provided in the through hole 15 of the ceramic dielectric substrate 11. For example, the first porous portion 90 is inserted into the through hole 15.

FIGS. 2A and 2B are schematic diagrams illustrating the electrostatic chuck according to the embodiment. FIG. 2(a) illustrates the periphery of the first porous portion 90. As shown in FIG. FIG. 2(a) corresponds to an enlarged view of area A shown in FIG. FIG. 2(b) is a cross-sectional view taken along the line CC of the first porous portion 90 in FIG. 2(a).
Note that in order to avoid complication, the dot 13 (for example, see FIG. 1) is omitted in FIG. 2(a).

In this example, the through hole 15 has a hole 15a and a hole 15b (corresponding to an example of a first hole). One end of the hole 15a is located on the second main surface 11b of the ceramic dielectric substrate 11.

Further, the ceramic dielectric substrate 11 can have a hole 15b located between the first main surface 11a and the first porous portion 90 in the Z direction. The hole 15b communicates with the hole 15a and extends to the first main surface 11a of the ceramic dielectric substrate 11. That is, one end of the hole 15b is located on the first main surface 11a (groove 14). The hole portion 15b is a connecting hole that connects the first porous portion 90 and the groove 14. The diameter (length along the X direction) of the hole 15b is smaller than the diameter (length along the X direction) of the hole 15a. By providing the hole 15b with a small diameter, the degree of freedom in designing the space formed between the ceramic dielectric substrate 11 and the object W (for example, the first main surface 11a including the groove 14) can be increased. . For example, as shown in FIG. 2A, the width of the groove 14 (length along the X direction) can be made shorter than the width of the first porous portion 90 (length along the X direction). Thereby, for example, discharge in the space formed between the ceramic dielectric substrate 11 and the object W can be suppressed.

The diameter of the hole 15b is, for example, 0.05 mm or more and 0.5 mm or less. The diameter of the hole 15a is, for example, 1 mm or more and 5 mm or less. Note that the hole 15b may be indirectly connected to the hole 15a. That is, a hole 15c (corresponding to an example of a second hole) connecting the hole 15a and the hole 15b may be provided. As shown in FIG. 2A, the hole 15c can be provided in the ceramic dielectric substrate 11. The hole portion 15c can also be provided in the first porous portion 90. The holes 15c can also be provided in the ceramic dielectric substrate 11 and the first porous part 90. That is, at least one of the ceramic dielectric substrate 11 and the first porous section 90 can have a hole 15c located between the hole 15b and the first porous section 90. In this case, if the hole 15c is provided in the ceramic dielectric substrate 11, the strength around the hole 15c can be increased, and the occurrence of chipping or the like around the hole 15c can be suppressed. Therefore, the occurrence of arc discharge can be suppressed more effectively. If the hole 15c is provided in the first porous portion 90, alignment of the hole 15c and the first porous portion 90 becomes easy. Therefore, it becomes easier to achieve both reduction of arc discharge and smooth flow of gas. Each of the holes 15a, 15b, and 15c has a cylindrical shape extending in the Z direction, for example.

In this case, the size of the hole 15c can be smaller than the size of the first porous part 90 and larger than the size of the hole b in the X direction or the Y direction. According to the electrostatic chuck 110 according to the present embodiment, the first porous portion 90 provided at a position facing the gas introduction path 53 ensures resistance to arc discharge while ensuring the flow rate of gas flowing into the hole portion 15b. can be improved. Further, since the dimension of the hole 15c in the X direction or the Y direction is made larger than the dimension of the hole 15b, most of the gas introduced into the first porous section 90 having a large size is transferred to the hole. It can be introduced into the small-sized hole 15b via the hole 15c. In other words, arc discharge can be reduced and gas flow can be made smoother.

As described above, the ceramic dielectric substrate 11 has at least one groove 14 that is open to the first main surface 11 a and communicates with the first hole 15 . In the Z direction, the size of the hole 15c can be made smaller than the size of the groove 14. In this way, gas can be supplied to the first main surface 11a side through the groove 14. Therefore, it becomes easy to supply gas to a wider range of the first main surface 11a. Further, since the dimension of the hole 15c in the X direction or the Y direction is made smaller than the dimension of the groove 14, the time for gas to pass through the hole 15c can be shortened. That is, the occurrence of arc discharge can be more effectively suppressed while smoothing the gas flow.

As described above, the adhesive portion 60 can be provided between the ceramic dielectric substrate 11 and the base plate 50. In the Z direction, the size of the hole 15c can be made smaller than the size of the adhesive part 60. In this way, the bonding strength between the ceramic dielectric substrate 11 and the base plate 50 can be improved. Further, since the size of the hole 15c in the Z direction is made smaller than the size of the adhesive part 60, it is possible to more effectively suppress the occurrence of arc discharge while smoothing the gas flow.

In this example, the first porous portion 90 is provided in the hole 15a. Therefore, the upper surface 90U of the first porous portion 90 is not exposed to the first main surface 11a. That is, the upper surface 90U of the first porous portion 90 is located between the first main surface 11a and the second main surface 11b. On the other hand, the lower surface 90L of the first porous portion 90 is exposed to the second main surface 11b.

The first porous portion 90 has a porous region 91 having a plurality of pores and a dense region 93 that is denser than the porous region 91. The dense region 93 is a region with fewer pores than the porous region 91, or a region with substantially no pores. The porosity (%) of the dense region 93 is lower than the porosity (%) of the porous region 91. Therefore, the density (grams/cubic centimeter: g/cm ³ ) of the dense region 93 is higher than the density (g/cm ³ ) of the porous region 91 . Since the dense region 93 is denser than the porous region 91, the rigidity (mechanical strength) of the dense region 93 is higher than that of the porous region 91, for example.

The porosity of the dense region 93 is, for example, the ratio of the volume of spaces (pores) included in the dense region 93 to the total volume of the dense region 93. The porosity of the porous region 91 is, for example, the ratio of the volume of spaces (pores) included in the porous region 91 to the total volume of the porous region 91. For example, the porosity of the porous region 91 is 5% or more and 40% or less, preferably 10% or more and 30% or less, and the porosity of the dense region 93 is 0% or more and 5% or less.

The first porous portion 90 is columnar (for example, cylindrical). Moreover, the porous region 91 is columnar (for example, cylindrical). The dense region 93 is in contact with the porous region 91 or is continuous with the porous region 91 . As shown in FIG. 2(b), the dense region 93 surrounds the outer periphery of the porous region 91 when viewed along the Z direction. The dense region 93 has a cylindrical shape (for example, a cylindrical shape) surrounding the side surface 91s of the porous region 91. In other words, the porous region 91 is provided so as to penetrate the dense region 93 in the Z direction. Gas flowing into the through hole 15 from the gas introduction path 53 passes through a plurality of holes provided in the porous region 91 and is supplied to the groove 14 .

By providing the first porous portion 90 having such a porous region 91, the resistance to arc discharge can be improved while ensuring the flow rate of gas flowing into the through hole 15. Furthermore, since the first porous portion 90 has the dense region 93, the rigidity (mechanical strength) of the first porous portion 90 can be improved.

For example, the first porous portion 90 is integrated with the ceramic dielectric substrate 11. The state in which two members are integrated is a state in which the two members are chemically bonded, for example, by sintering or the like. No material (eg, adhesive) is provided between the two members to secure one member to the other member. That is, no other member such as an adhesive is provided between the first porous part 90 and the ceramic dielectric substrate 11, and the first porous part 90 and the ceramic dielectric substrate 11 are integrated. ing.

More specifically, when the first porous portion 90 and the ceramic dielectric substrate 11 are integrated, the side surface of the first porous portion 90 (the side surface 93s of the dense region 93) is in contact with the through hole 15. The first porous portion 90 is in contact with the inner wall 15w, is supported by the inner wall 15w with which the first porous portion 90 is in contact, and is fixed to the ceramic dielectric substrate 11.

For example, a through hole is provided in the base material before sintering that will become the ceramic dielectric substrate 11, and the first porous portion 90 is fitted into the through hole. By sintering the ceramic dielectric substrate 11 (and the fitted first porous portion 90) in this state, the first porous portion 90 and the ceramic dielectric substrate 11 can be integrated.

In this way, the first porous portion 90 is fixed to the ceramic dielectric substrate 11 by being integrated with the ceramic dielectric substrate 11. Thereby, the strength of the electrostatic chuck 110 can be improved compared to the case where the first porous portion 90 is fixed to the ceramic dielectric substrate 11 with an adhesive or the like. For example, deterioration of the electrostatic chuck due to corrosion or erosion of the adhesive does not occur.

When the first porous portion 90 and the ceramic dielectric substrate 11 are integrated, a force is applied from the ceramic dielectric substrate 11 to the outer peripheral side surface of the first porous portion 90 . On the other hand, when a plurality of holes are provided in the first porous section 90 in order to ensure a gas flow rate, the mechanical strength of the first porous section 90 decreases. Therefore, when the first porous portion is integrated with the ceramic dielectric substrate 11, there is a risk that the first porous portion 90 may be damaged by the force applied from the ceramic dielectric substrate 11 to the first porous portion 90. be.

On the other hand, since the first porous part 90 has the dense region 93, the rigidity (mechanical strength) of the first porous part 90 can be improved, and the first porous part 90 can be It can be integrated with the body substrate 11.

Note that in the embodiment, the first porous portion 90 does not necessarily have to be integrated with the ceramic dielectric substrate 11. For example, as shown in FIG. 12, the first porous portion 90 may be attached to a ceramic dielectric substrate using an adhesive.

Further, the dense region 93 is located between the inner wall 15w of the ceramic dielectric substrate 11 forming the through hole 15 and the porous region 91. That is, a porous region 91 is provided inside the first porous portion 90, and a dense region 93 is provided outside. By providing the dense region 93 outside the first porous portion 90, the rigidity against the force applied to the first porous portion 90 from the ceramic dielectric substrate 11 can be improved. Thereby, the first porous portion 90 and the ceramic dielectric substrate 11 can be easily integrated. Further, for example, when an adhesive member 61 (see FIG. 12) is provided between the first porous part 90 and the ceramic dielectric substrate 11, the gas passing through the first porous part 90 comes into contact with the adhesive member 61. This can be suppressed by the dense region 93. Thereby, deterioration of the adhesive member 61 can be suppressed. Further, by providing the porous region 91 inside the first porous portion 90, it is possible to prevent the through holes 15 of the ceramic dielectric substrate 11 from being blocked by the dense region 93, and to ensure the flow rate of gas. .

The thickness of the dense region 93 (the length L0 between the side surface 91s of the porous region 91 and the side surface 93s of the dense region 93) is, for example, 100 μm or more and 1000 μm or less.

The first porous portion 90 is made of ceramic having insulation properties. The first porous portion 90 (the porous region 91 and the dense region 93, respectively) contains at least one of aluminum oxide (Al ₂ O ₃ ), titanium oxide (TiO ₂ ), and yttrium oxide (Y ₂ O ₃ ). Thereby, high dielectric strength voltage and high rigidity of the first porous portion 90 can be obtained.

For example, the first porous portion 90 has one of aluminum oxide, titanium oxide, and yttrium oxide as a main component.
In this case, the purity of the aluminum oxide in the ceramic dielectric substrate 11 can be made higher than the purity of the aluminum oxide in the first porous part 90. In this way, performance such as plasma resistance of the electrostatic chuck 110 can be ensured, and the mechanical strength of the first porous portion 90 can be ensured. For example, by including a small amount of additives in the first porous part 90, sintering of the first porous part 90 is promoted, and it becomes possible to control pores and ensure mechanical strength.

In this specification, the purity of ceramics such as aluminum oxide of the ceramic dielectric substrate 11 is measured by fluorescent X-ray analysis, ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry), etc. be able to.

For example, the material of the porous region 91 and the material of the dense region 93 are the same. However, the material of the porous region 91 may be different from the material of the dense region 93. The composition of the material in the porous region 91 may be different from the composition of the material in the dense region 93.

Further, as shown in FIG. 2(a), the distance D1 in the X direction or Y direction between the porous region 91 (a region provided with a plurality of sparse portions 94 described later) and the electrode 12 is It is longer than the distance D2 between the electrode 11a and the electrode 12 in the Z direction. By increasing the distance D1 in the X direction or Y direction between the porous region 91 provided in the first porous part 90 and the electrode 12, electric discharge in the first porous part 90 can be suppressed. . Moreover, by further shortening the distance D2 in the Z direction between the first main surface 11a and the electrode 12, the force for attracting the object W placed on the first main surface 11a can be increased.

FIGS. 3A and 3B are schematic diagrams illustrating the first porous portion of the electrostatic chuck according to the embodiment.
FIG. 3(a) is a sectional view taken along the line DD of the first porous portion 90 in FIG. 3(b). FIG. 3(b) is a cross-sectional view of the first porous portion 90 in the ZY plane.

As shown in FIGS. 3A and 3B, in this example, the porous region 91 has a plurality of sparse portions 94 and a dense portion 95. Each of the plurality of sparse portions 94 has a plurality of holes. The dense portion 95 is denser than the sparse portion 94. That is, the dense portion 95 is a portion that has fewer pores than the sparse portion 94, or a portion that does not substantially have pores. The porosity of the dense portion 95 is lower than that of the sparse portion 94. Therefore, the density of the dense portion 95 is higher than the density of the sparse portion 94. The porosity of the dense portion 95 may be the same as the porosity of the dense region 93. Since the dense portion 95 is denser than the sparse portion 94, the rigidity of the dense portion 95 is higher than that of the sparse portion 94.

The porosity of one sparse portion 94 is, for example, the ratio of the volume of the spaces (pores) included in the sparse portion 94 to the total volume of the sparse portion 94 . The porosity of the dense portion 95 is, for example, the ratio of the volume of spaces (pores) included in the dense portion 95 to the total volume of the dense portion 95. For example, the porosity of the sparse portion 94 is 20% or more and 60% or less, preferably 30% or more and 50% or less, and the porosity of the dense portion 95 is 0% or more and 5% or less.

That is, the first porous portion 90 has a plurality of sparse portions 94 each having a plurality of pores and spaced apart from each other. The gas introduced from the gas introduction path 53 can flow through the plurality of holes provided in the sparse portion 94 . Each of the plurality of sparse portions 94 extends in a direction inclined at a predetermined angle θ with respect to the Z direction. For example, each of the plurality of sparse portions 94 is columnar (cylindrical or polygonal columnar) and is provided so as to penetrate the porous region 91 at a predetermined angle θ with respect to the Z direction. The dense portion 95 is located between the plurality of sparse portions 94. The dense portion 95 has a wall shape that partitions the sparse portions 94 adjacent to each other. As shown in FIG. 3(a), when viewed along a direction inclined at a predetermined angle θ with respect to the Z direction, the dense portion 95 is provided so as to surround the outer periphery of each of the plurality of sparse portions 94. ing. The dense portion 95 is continuous with the dense region 93 on the outer periphery of the porous region 91 .

The number of sparse portions 94 provided within the porous region 91 is, for example, 50 or more and 1000 or less. As shown in FIG. 3A, when viewed along a direction inclined at a predetermined angle θ with respect to the Z direction, the sparse portions 94 have substantially the same size. For example, when viewed along a direction inclined at a predetermined angle θ with respect to the Z direction, the plurality of sparse portions 94 are isotropically and uniformly distributed within the porous region 91. For example, the distance between adjacent sparse portions 94 (that is, the thickness of dense portions 95) is approximately constant.

For example, when viewed along a direction inclined at a predetermined angle θ with respect to the Z direction, the distance between the side surface 93s of the dense region 93 and the sparse portion 94 closest to the side surface 93s among the plurality of sparse portions 94 is The distance L11 is 100 μm or more and 1000 μm or less.

In this way, by providing a plurality of sparse portions 94 and a dense portion 95 that is denser than the sparse portions 94 in the porous region 91, a plurality of pores are randomly distributed three-dimensionally within the porous region. Compared to this, it is possible to improve the rigidity of the first porous portion 90 while ensuring resistance to arc discharge and a flow rate of gas flowing into the through hole 15.
For example, as the porosity of the porous region increases, the gas flow rate increases, but resistance to arc discharge and stiffness decrease. On the other hand, by providing the dense portion 95, even if the porosity is increased, the resistance to arc discharge and the decrease in rigidity can be suppressed.

Further, arc discharge is often caused by current flowing inside the hole 15b from the ceramic dielectric substrate 11 side toward the base plate 50 side. Therefore, if each of the plurality of sparse portions 94 is inclined at a predetermined angle θ with respect to the Z direction, electrons are considered to be less likely to be accelerated when current flows inside the hole provided in the sparse portion 94. Therefore, the occurrence of arc discharge can be suppressed.
According to the knowledge obtained by the present inventors, the angle θ between the Z direction and the direction in which the sparse portions 94 extend is preferably 5° or more and 30° or less. In this way, it becomes easy to suppress the occurrence of arc discharge. Furthermore, if the angle θ is set to 5° or more and 15° or less, it is possible to suppress the occurrence of arc discharge without reducing the diameter of the hole provided in the sparse portion 94. Further, the required gas flow rate can be secured without increasing the diameter of the hole.

ここで、疎部分９４に設けられた孔の径を小さくすればアーク放電の発生を抑制するのが容易となる。ところが、孔の径を小さくすればガスの流量を十分に確保できなくなるおそれがある。
この場合、表１から分かるように、角度θを大きくすればＤＣ破壊電圧を大きくすることができる。そのため、角度θを大きくすれば、孔の径を小さくすることなく、アーク放電の発生を抑制することができる。
ところが、表１から分かるように、角度θを大きくすれば、孔における管路抵抗が大きくなるのでＨｅの流量が小さくなる。この場合、孔の径を大きくすればＨｅの流量を大きくすることができるが、孔の径を大きくすればＤＣ破壊電圧が小さくなる。
表１から分かるように、角度θが５°以上、１５°以下となるようにすれば、疎部分９４に設けられた孔の径を小さくすることなく、アーク放電の発生を抑制することができる。また、孔の径を大きくすることなく、必要となるガスの流量を確保することができる。 Table 1 shows the relationship between the angle θ, the DC breakdown voltage, and the flow rate of He.
Note that the DC breakdown voltage and He flow rate are 30 Torr.
In addition, in the evaluation, a case where the DC breakdown voltage is 2.5 kV or more and the He flow rate is 4.9 sccm or more is considered to be a pass. In Table 1, a pass is represented by "○", and a failure is represented by "x".

Here, if the diameter of the hole provided in the sparse portion 94 is made small, it becomes easy to suppress the occurrence of arc discharge. However, if the diameter of the hole is made small, there is a possibility that a sufficient flow rate of gas cannot be secured.
In this case, as can be seen from Table 1, the DC breakdown voltage can be increased by increasing the angle θ. Therefore, by increasing the angle θ, it is possible to suppress the occurrence of arc discharge without reducing the diameter of the hole.
However, as can be seen from Table 1, if the angle θ is increased, the pipe resistance in the hole increases, and the flow rate of He decreases. In this case, the flow rate of He can be increased by increasing the diameter of the hole, but the DC breakdown voltage decreases by increasing the diameter of the hole.
As can be seen from Table 1, if the angle θ is set to 5° or more and 15° or less, it is possible to suppress the occurrence of arc discharge without reducing the diameter of the hole provided in the sparse portion 94. . Further, the required gas flow rate can be secured without increasing the diameter of the hole.

Note that, for example, the smallest circle, ellipse, or polygon that includes all of the plurality of sparse portions 94 when viewed along a direction inclined at a predetermined angle θ with respect to the Z direction is assumed. The inside of the circle, ellipse, or polygon can be considered as the porous region 91, and the outside of the circle, ellipse, or polygon can be considered as the dense region 93.

As described above, the first porous portion 90 includes a plurality of sparse portions 94 having a plurality of pores 96 including first pores and second pores, and a dense portion having a density higher than that of the sparse portions 94. 95. Each of the plurality of sparse portions 94 extends in a direction inclined at a predetermined angle θ with respect to the Z direction. The dense portion 95 is located between the plurality of sparse portions 94. The sparse portion 94 has a wall portion 97 provided between a hole 96 (first hole) and a hole 96 (second hole). In a direction substantially orthogonal to a direction inclined at a predetermined angle θ with respect to the Z direction, the minimum value of the dimension of the wall portion 97 can be made smaller than the minimum value of the dimension of the dense portion 95. In this way, since the first porous portion 90 is provided with a sparse portion 94 and a dense portion 95 extending in a direction inclined at a predetermined angle θ with respect to the Z direction, resistance to arc discharge and gas flow rate can be improved. The mechanical strength (rigidity) of the first porous portion 90 can be improved while ensuring the following.
Further, if each of the plurality of sparse portions 94 is inclined at a predetermined angle θ with respect to the Z direction, electrons are considered to be less likely to be accelerated when current flows inside the hole provided in the sparse portion 94. Therefore, the occurrence of arc discharge can be suppressed.

In a direction substantially perpendicular to a direction inclined at a predetermined angle θ with respect to the Z direction, the dimensions of the plurality of holes 96 provided in each of the plurality of sparse portions 94 can be made smaller than the dimensions of the dense portion 95. . In this way, the dimensions of the plurality of holes 96 can be made sufficiently small, so that the resistance to arc discharge can be further improved.

Further, the aspect ratio of the plurality of holes 96 provided in each of the plurality of sparse portions 94 can be 30 or more and 10,000 or less. In this way, resistance to arc discharge can be further improved. More preferably, the lower limit of the aspect ratio of the plurality of holes 96 is 100 or more, and the upper limit is 1,600 or less.

In addition, the dimensions of the plurality of holes 96 provided in each of the plurality of sparse portions 94 in a direction substantially perpendicular to the direction inclined at a predetermined angle θ with respect to the Z direction are 1 micrometer or more and 20 micrometers or less. be able to. In this way, it is possible to arrange holes extending in one direction and having a hole size of 1 to 20 micrometers, so that variations can be suppressed and high resistance to arc discharge can be achieved.

Further, as shown in FIGS. 6(a) and 6(b), which will be described later, the first hole 96a is located at the center of the sparse portion 94 when viewed along a direction inclined at a predetermined angle θ with respect to the Z direction. The number of holes 96b to 96g adjacent to and surrounding the first hole 96a among the plurality of holes 96 can be six. In this way, when viewed along a direction inclined at a predetermined angle θ with respect to the Z direction, it becomes possible to arrange a plurality of holes with high isotropy and high density. Thereby, the rigidity of the first porous portion 90 can be improved while ensuring resistance to arc discharge and a flow rate of flowing gas.

FIG. 4 is a schematic plan view illustrating the first porous portion of the electrostatic chuck according to the embodiment.
FIG. 4 shows a part of the first porous portion 90 viewed along a direction inclined at a predetermined angle θ with respect to the Z direction, and corresponds to an enlarged view of FIG. 3(a).
When viewed along a direction inclined by a predetermined angle θ with respect to the Z direction, each of the plurality of sparse portions 94 has a substantially hexagonal shape (substantially regular hexagonal shape). When viewed along a direction inclined at a predetermined angle θ with respect to the Z direction, the plurality of sparse portions 94 surround a first sparse portion 94a located at the center of the porous region 91 and the first sparse portion 94a. It has six sparse portions 94 (second to seventh sparse portions 94b to 94g).

The second to seventh sparse portions 94b to 94g are adjacent to the first sparse portion 94a. The second to seventh sparse portions 94b to 94g are the sparse portions 94 that are closest to the first sparse portion 94a among the plurality of sparse portions 94.

The second sparse portion 94b and the third sparse portion 94c are arranged in a direction substantially orthogonal to the first sparse portion 94a at a predetermined angle θ with respect to the Z direction. That is, the first sparse portion 94a is located between the second sparse portion 94b and the third sparse portion 94c.

In a direction substantially perpendicular to a direction inclined at a predetermined angle θ with respect to the Z direction, the length L1 (diameter of the first sparse portion 94a) of the first sparse portion 94a is equal to the length L1 of the first sparse portion 94a and the second sparse portion 94b. and longer than the length L3 between the first sparse portion 94a and the third sparse portion 94c.

Note that each of the length L2 and the length L3 corresponds to the thickness of the dense portion 95. That is, in a direction substantially perpendicular to a direction inclined by a predetermined angle θ with respect to the Z direction, the length L2 is the length of the dense portion 95 between the first sparse portion 94a and the second sparse portion 94b. The length L3 is the length of the dense portion 95 between the first sparse portion 94a and the third sparse portion 94c. The length L2 and the length L3 are approximately the same. For example, the length L2 is greater than or equal to 0.5 times and less than or equal to 2.0 times the length L3.

Further, in a direction substantially perpendicular to a direction inclined by a predetermined angle θ with respect to the Z direction, the length L1 is substantially the same as the length L4 (diameter of the second sparse portion 94b) of the second sparse portion 94b, It is approximately the same as the length L5 of the third sparse portion 94c (the diameter of the third sparse portion 95c). For example, each of the length L4 and the length L5 is 0.5 times or more and 2.0 times or less of the length L1.

In this way, the first sparse portion 94a is adjacent to and surrounded by six sparse portions 94 among the plurality of sparse portions 94. That is, when viewed along a direction inclined at a predetermined angle θ with respect to the Z direction, the number of sparse portions 94 adjacent to one sparse portion 94 at the center of the porous region 91 is six. Thereby, it is possible to arrange the plurality of sparse portions 94 with high isotropy and high density when viewed along a direction inclined at a predetermined angle θ with respect to the Z direction. Thereby, the rigidity of the first porous portion 90 can be improved while ensuring resistance to arc discharge and a flow rate of gas flowing into the through hole 15. Further, variations in resistance to arc discharge, variations in the flow rate of gas flowing into the through holes 15, and variations in the rigidity of the first porous portion 90 can be suppressed.

The diameter of the sparse portion 94 (length L1, L4, L5, etc.) is, for example, 50 μm or more and 500 μm or less. The thickness (length L2 or L3, etc.) of the dense portion 95 is, for example, 10 μm or more and 100 μm or less. The diameter of the sparse portion 94 is greater than the thickness of the dense portion 95. Further, the thickness of the dense portion 95 is thinner than the thickness of the dense region 93.

FIG. 5 is a schematic plan view illustrating the first porous portion of the electrostatic chuck according to the embodiment. FIG. 5 shows a part of the first porous portion 90 as viewed along a direction inclined at a predetermined angle θ with respect to the Z direction. FIG. 5 is an enlarged view of the vicinity of one sparse portion 94.
As shown in FIG. 5, in this example, the sparse portion 94 includes a plurality of holes 96 and a wall portion 97 provided between the plurality of holes 96.

Each of the plurality of holes 96 extends in a direction inclined at a predetermined angle θ with respect to the Z direction. Each of the plurality of holes 96 has a capillary shape (one-dimensional capillary structure) extending in one direction, and passes through the sparse portion 94 in a direction inclined at a predetermined angle θ with respect to the Z direction. The wall portion 97 has a wall shape that partitions the holes 96 adjacent to each other. As shown in FIG. 5, the wall portion 97 is provided so as to surround the outer periphery of each of the plurality of holes 96 when viewed along a direction inclined at a predetermined angle θ with respect to the Z direction. The wall portion 97 is continuous with the dense portion 95 on the outer periphery of the sparse portion 94 .

The number of holes 96 provided in one sparse portion 94 is, for example, 50 or more and 1000 or less. As shown in FIG. 5, the plurality of holes 96 have substantially the same size as each other when viewed along a direction inclined at a predetermined angle θ with respect to the Z direction. For example, when viewed along a direction inclined at a predetermined angle θ with respect to the Z direction, the plurality of holes 96 are isotropically and uniformly distributed within the sparse portion 94. For example, the distance between adjacent holes 96 (that is, the thickness of wall portion 97) is approximately constant.

In this way, by arranging the holes 96 extending in one direction within the sparse portion 94, the resistance against arc discharge is higher than when a plurality of holes are randomly distributed three-dimensionally within the sparse portion. This can be achieved with little variation.

Here, the "capillary structure" of the plurality of holes 96 will be further explained.
In recent years, circuit line widths have become thinner and circuit pitches have become finer with the aim of increasing the degree of integration of semiconductors. As higher power is applied to electrostatic chucks, a higher level of temperature control of the target object is required. Against this background, there is a need to secure a sufficient gas flow rate while reliably suppressing arc discharge even in a high-power environment, and to control the flow rate with high precision. In the electrostatic chuck 110 according to the present embodiment, the ceramic plug (first porous portion 90), which is conventionally provided to prevent arc discharge in the helium supply hole (gas introduction path 53), has a hole diameter ( The diameter of the hole 96 is made small, for example, to the level of several to tens of micrometers (the details of the diameter of the hole 96 will be described later). When the diameter becomes small to this level, it may become difficult to control the gas flow rate. Therefore, in the present invention, for example, the shape of the hole 96 is further devised so as to extend along the Z direction. Specifically, in the past, prevention of arc discharge was achieved by ensuring a flow rate with relatively large holes and making the shape three-dimensionally complex. On the other hand, in the present invention, prevention of arc discharge is achieved by making the diameter of the hole 96 minute, for example, at the level of several to tens of micrometers, and conversely, the flow rate is ensured by simplifying its shape. . In other words, the present invention was conceived based on an idea completely different from the conventional one.

Note that the shape of the sparse portion 94 is not limited to a hexagon, but may be a circle (or ellipse) or other polygon. For example, assume the smallest circle, ellipse, or polygon that includes all of the plurality of holes 96 arranged at intervals of 10 μm or less when viewed along a direction inclined at a predetermined angle θ with respect to the Z direction. The inside of the circle, ellipse, or polygon can be considered a sparse portion 94, and the outside of the circle, ellipse, or polygon can be considered a dense portion 95.

FIGS. 6A and 6B are schematic plan views illustrating the first porous portion of the electrostatic chuck according to the embodiment.
6(a) and 6(b) show a part of the first porous part 90 viewed along a direction inclined at a predetermined angle θ with respect to the Z direction, and show the pores in one sparse part 94. 96 is an enlarged view showing 96.

As shown in FIG. 6(a), when viewed along a direction inclined by a predetermined angle θ with respect to the Z direction, the plurality of holes 96 are located at the center of the sparse portion 94 and the first hole 96a. , has six holes 96 (second to seventh holes 96b to 96g) surrounding the first hole 96a. The second to seventh holes 96b to 96g are adjacent to the first hole 96a. The second to seventh holes 96b to 96g are the holes 96 closest to the first hole 96a among the plurality of holes 96.

The second hole 96b and the third hole 96c are aligned with the first hole 96a in a direction perpendicular to a direction inclined by a predetermined angle θ with respect to the Z direction. That is, the first hole 96a is located between the second hole 96b and the third hole 96c.

In the direction perpendicular to the direction inclined at a predetermined angle θ with respect to the Z direction, for example, the length L6 of the first hole 96a (the diameter of the first hole 96a) is the distance between the first hole 96a and the second hole 96b. and longer than the length L8 between the first hole 96a and the third hole 96c.

Note that each of the length L7 and the length L8 corresponds to the thickness of the wall portion 97. That is, the length L7 is the length of the wall portion 97 between the first hole 96a and the second hole 96b in a direction perpendicular to a direction inclined by a predetermined angle θ with respect to the Z direction. The length L8 is the length of the wall portion 97 between the first hole 96a and the third hole 96c. The length L7 and the length L8 are approximately the same. For example, the length L7 is 0.5 to 2.0 times the length L8.

Further, in the direction perpendicular to the direction inclined at a predetermined angle θ with respect to the Z direction, the length L6 is approximately the same as the length L9 (diameter of the second hole 96b) of the second hole 96b, and the length L6 is approximately the same as the length L9 (diameter of the second hole 96b). This is approximately the same as the length L10 of the third hole 96c (the diameter of the third hole 96c). For example, each of the length L9 and the length L10 is 0.5 times or more and 2.0 times or less of the length L6.

For example, smaller hole diameters improve arc discharge resistance and rigidity. On the other hand, if the hole diameter is large, the gas flow rate can be increased. The diameter of the hole 96 (length L6, L9, or L10, etc.) is, for example, 1 micrometer (μm) or more and 20 μm or less. By arranging holes extending in one direction and having a diameter of 1 to 20 μm, high resistance to arc discharge can be achieved with little variation. More preferably, the diameter of the hole 96 is 3 μm or more and 10 μm or less.

Here, a method for measuring the diameter of the hole 96 will be explained. Images are acquired using a scanning electron microscope (eg, Hitachi High Technologies, S-3000) at a magnification of 1000x or more. Using commercially available image analysis software, the equivalent circle diameters of 100 holes 96 are calculated, and the average value thereof is taken as the diameter of the hole 96.
It is further preferable to suppress variations in the diameters of the plurality of holes 96. By reducing the variation in diameter, it becomes possible to more precisely control the flow rate and dielectric strength of the flowing gas. As the variation in the diameters of the plurality of holes 96, the cumulative distribution of the equivalent circle diameters of 100 holes obtained in calculating the diameters of the holes 96 can be used. Specifically, we applied the concept of particle diameter D50 (median diameter) when cumulative distribution is 50 vol% and particle diameter D90 when cumulative distribution is 90 vol%, which are generally used for particle size distribution measurement, and plotted the horizontal axis as pore diameter (μm). ), using a cumulative distribution graph of the pores 96 with the vertical axis as the relative pore volume (%), the pore diameter when the cumulative distribution of the pore size is 50 vol% (corresponding to the D50 diameter) and the pore diameter when the cumulative distribution is 90 vol% (D90 (equivalent to the diameter). It is preferable that variations in the diameters of the plurality of holes 96 are suppressed to such an extent that the relationship D50:D90≦1:2 is satisfied.

The thickness of the wall portion 97 (lengths L7, L8, etc.) is, for example, 1 μm or more and 10 μm or less. The thickness of the wall portion 97 is thinner than the thickness of the dense portion 95.

In this way, the first hole 96a is adjacent to and surrounded by six holes 96 among the plurality of holes 96. That is, when viewed along a direction inclined at a predetermined angle θ with respect to the Z direction, the number of holes 96 adjacent to one hole 96 at the center of the sparse portion 94 is six. Thereby, when viewed along a direction inclined at a predetermined angle θ with respect to the Z direction, it is possible to arrange the plurality of holes 96 with high isotropy and high density. Thereby, the rigidity of the first porous portion 90 can be improved while ensuring resistance to arc discharge and a flow rate of gas flowing into the through hole 15. Further, variations in resistance to arc discharge, variations in the flow rate of gas flowing into the through holes 15, and variations in the rigidity of the first porous portion 90 can be suppressed.

FIG. 6(b) shows another example of the arrangement of the plurality of holes 96 within the sparse portion 94. As shown in FIG. 6(b), in this example, the plurality of holes 96 are arranged concentrically around the first hole 96a. Thereby, when viewed along a direction inclined at a predetermined angle θ with respect to the Z direction, it is possible to arrange a plurality of holes with high isotropy and high density.

Note that the first porous portion 90 having the structure as described above can be manufactured by using extrusion molding, for example. Further, each of the lengths L0 to L10 can be measured by observation using a microscope such as a scanning electron microscope.

Evaluation of porosity in this specification will be explained. Here, evaluation of the porosity in the first porous portion 90 will be described as an example.
An image like the plan view of FIG. 3(a) is acquired, and the ratio R1 of the plurality of sparse portions 94 occupying the porous region 91 is calculated by image analysis. A scanning electron microscope (for example, Hitachi High Technologies, S-3000) is used to acquire images. A BSE image is acquired with an accelerating voltage of 15 kV and a magnification of 30 times. For example, the image size is 1280×960 pixels, and the image gradation is 256 gradations.

Image analysis software (for example, Win-ROOF Ver. 6.5 (Mitani Corporation)) is used to calculate the ratio R1 of the plurality of sparse portions 94 in the porous region 91.
The ratio R1 can be calculated as follows using Win-ROOF Ver. 6.5.
The evaluation range ROI1 (see FIG. 3(a)) is defined as the smallest circle (or ellipse) that includes all the sparse portions 94.
Binarization processing is performed using a single threshold value (for example, 0), and the area S1 of the evaluation range ROI1 is calculated.
Binarization processing is performed using two threshold values (for example, 0 and 136), and the total area S2 of the plurality of sparse portions 94 within the evaluation range ROI1 is calculated. At this time, hole-filling processing in the sparse portion 94 and deletion of small areas considered to be noise (threshold value: 0.002 or less) are performed. Further, the two threshold values are adjusted as appropriate depending on the brightness and contrast of the image.
A ratio R1 is calculated as the ratio of the area S2 to the area S1. That is, the ratio R1 (%)=(area S2)/(area S1)×100.

In the embodiment, the ratio R1 of the plurality of sparse portions 94 in the porous region 91 is, for example, 40% or more and 70% or less, preferably 50% or more and 70% or less. The ratio R1 is, for example, about 60%.

An image like the plan view of FIG. 5 is acquired, and the ratio R2 of the plurality of holes 96 to the sparse portion 94 is calculated by image analysis. The ratio R2 corresponds to the porosity of the sparse portion 94, for example. A scanning electron microscope (for example, Hitachi High Technologies, S-3000) is used to acquire images. A BSE image is acquired with an accelerating voltage of 15 kV and a magnification of 600 times. For example, the image size is 1280×960 pixels, and the image gradation is 256 gradations.

To calculate the ratio R2 of the plurality of holes 96 in the sparse portion 94, image analysis software (for example, Win-ROOF Ver. 6.5 (Mitani Shoji)) is used.
The ratio R1 can be calculated as follows using Win-ROOF Ver. 6.5.
The evaluation range ROI2 (see FIG. 5) is a hexagon that approximates the shape of the sparse portion 94. All the holes 96 provided in one sparse portion 94 are included in the evaluation range ROI2.
Binarization processing is performed using a single threshold value (for example, 0), and the area S3 of the evaluation range ROI2 is calculated.
Binarization processing is performed using two threshold values (for example, 0 and 96), and the total area S4 of the plurality of holes 96 within the evaluation range ROI2 is calculated. At this time, the process of filling in the holes 96 and the deletion of small areas considered to be noise (threshold value: 1 or less) are performed. Further, the two threshold values are adjusted as appropriate depending on the brightness and contrast of the image.
A ratio R2 is calculated as the ratio of the area S4 to the area S3. That is, the ratio R2 (%)=(area S4)/(area S3)×100.

In the embodiment, the ratio R2 of the plurality of pores 96 in the sparse portion 94 (porosity of the sparse portion 94) is, for example, 20% or more and 60% or less, preferably 30% or more and 50% or less. The ratio R2 is, for example, about 40%.

The porosity of the porous region 91 corresponds to, for example, the product of the ratio R1 of the plurality of sparse portions 94 in the porous region 91 and the ratio R2 of the plurality of pores 96 in the sparse region 94. For example, when the ratio R1 is 60% and the ratio R2 is 40%, the porosity of the porous region 91 can be calculated to be about 24%.

By using the first porous portion 90 having the porous region 91 with such a porosity, it is possible to improve the dielectric strength voltage while ensuring the flow rate of the gas flowing into the through hole 15.

Similarly, the porosity of the ceramic dielectric substrate and the second porous portion 70 can be calculated. Note that the magnification of the scanning electron microscope is preferably selected as appropriate in the range of, for example, several tens of times to several thousand times, depending on the object to be observed.

FIGS. 7(a) and 7(b) are schematic diagrams illustrating another first porous portion according to the embodiment.
FIG. 7(a) is a plan view of the first porous portion 90 viewed along a direction inclined at a predetermined angle θ with respect to the Z direction, and FIG. This corresponds to an enlarged view of the section.
As shown in FIGS. 7(a) and 7(b), in this example, the planar shape of the sparse portion 94 is circular. In this way, the planar shape of the sparse portion 94 does not have to be hexagonal.

FIG. 8 is a schematic cross-sectional view illustrating the electrostatic chuck according to the embodiment.
FIG. 8 corresponds to an enlarged view of region B shown in FIG. That is, FIG. 8 shows the vicinity of the interface F1 between the first porous portion 90 (dense region 93) and the ceramic dielectric substrate 11. As shown in FIG. In this example, aluminum oxide is used as the material for the first porous portion 90 and the ceramic dielectric substrate 11.

As shown in FIG. 8, the first porous portion 90 includes a first region 90p located on the ceramic dielectric substrate 11 side in the X direction or the Y direction, and a first region 90p that is continuous with the first region 90p in the X direction or the Y direction. It has two areas 90q. The first region 90p and the second region 90q are part of the dense region 93 of the first porous portion 90.

The first region 90p is located between the second region 90q and the ceramic dielectric substrate 11 in the X direction or the Y direction. The first region 90p is a region approximately 40 to 60 μm from the interface F1 in the X direction or the Y direction. That is, the width W1 of the first region 90p along the X direction or the Y direction (the length of the first region 90p in the direction perpendicular to the interface F1) is, for example, 40 μm or more and 60 μm or less.

Further, the ceramic dielectric substrate 11 has a first substrate region 11p located on the first porous portion 90 (first region 90p) side in the X direction or the Y direction, and a first substrate region 11p located in the X direction or the Y direction. A continuous second substrate region 11q. The first region 90p and the first substrate region 11p are provided in contact with each other. The first substrate region 11p is located between the second substrate region 11q and the first porous portion 90 in the X direction or the Y direction. The first substrate region 11p is a region approximately 40 to 60 μm from the interface F1 in the X direction or the Y direction. That is, the width W2 of the first substrate region 11p along the X direction or the Y direction (the length of the first substrate region 11p in the direction perpendicular to the interface F1) is, for example, 40 μm or more and 60 μm or less.

FIGS. 9A and 9B are schematic cross-sectional views illustrating an electrostatic chuck according to an embodiment.
FIG. 9A is an enlarged view of a part of the first region 90p shown in FIG. 8. FIG. 9(b) is an enlarged view of a part of the first substrate region 11p shown in FIG.

As shown in FIG. 9A, the first region 90p includes a plurality of particles g1 (crystal grains). Further, as shown in FIG. 9(b), the first substrate region 11p includes a plurality of particles g2 (crystal grains).

The average particle diameter (the average value of the diameters of the plurality of particles g1) in the first region 90p is different from the average particle diameter (the average value of the diameters of the plurality of particles g2) in the first substrate region 11p.

Due to the difference between the average particle diameter in the first region 90p and the average particle diameter in the first substrate region 11p, the crystal grains of the first porous portion 90 and the crystal grains of the ceramic dielectric substrate 11 are different from each other at the interface F1. Bonding strength (interfacial strength) can be improved. For example, peeling of the first porous portion 90 from the ceramic dielectric substrate 11 and shedding of crystal grains can be suppressed.

Note that the average value of the equivalent circular diameters of crystal grains in cross-sectional images such as those shown in FIGS. 9(a) and 9(b) can be used as the average particle diameter. The equivalent circle diameter is the diameter of a circle having the same area as the target planar shape.

It is also preferable that the ceramic dielectric substrate 11 and the first porous portion 90 are integrated. The first porous portion 90 is fixed to the ceramic dielectric substrate 11 by being integrated with the ceramic dielectric substrate 11 . Thereby, the strength of the electrostatic chuck can be improved compared to the case where the first porous portion 90 is fixed to the ceramic dielectric substrate 11 with an adhesive or the like. For example, deterioration of the electrostatic chuck due to corrosion or erosion of the adhesive can be suppressed.

In this example, the average particle diameter in the first substrate region 11p is smaller than the average particle diameter in the first region 90p. Since the particle size in the first substrate region 11p is small, the bonding strength between the first porous part and the ceramic dielectric substrate can be improved at the interface between the first porous part and the ceramic dielectric substrate. . In addition, the small particle size in the first substrate region increases the strength of the ceramic dielectric substrate 11 and suppresses the risk of cracks and the like due to stress generated during manufacturing and processing. For example, the average particle diameter in the first region 90p is 3 μm or more and 5 μm or less. For example, the average particle diameter in the first substrate region 11p is 0.5 μm or more and 2 μm or less. The average particle diameter in the first substrate region 11p is 1.1 times or more and 5 times or less than the average particle diameter in the first region 90p.

Further, for example, the average particle diameter in the first substrate region 11p is smaller than the average particle diameter in the second substrate region 11q. In the first substrate region 11p provided in contact with the first region 90p, for example, during sintering in the manufacturing process, the interface strength between the first region 90p and the first region 90p is increased due to interaction such as diffusion between the first region 90p and the first substrate region 11p. It is preferable to do so. On the other hand, in the second substrate region 11q, it is preferable that the original characteristics of the material of the ceramic dielectric substrate 11 are expressed. By making the average particle diameter in the first substrate region 11p smaller than the average particle diameter in the second substrate region 11q, the interface strength in the first substrate region 11p is secured and the ceramic dielectric substrate 11 in the second substrate region 11q is It is possible to achieve both characteristics.

The average particle diameter in the first region 90p may be smaller than the average particle diameter in the first substrate region 11p. Thereby, the bonding strength between the first porous part 90 and the ceramic dielectric substrate 11 can be improved at the interface between the first porous part 90 and the ceramic dielectric substrate 11. Furthermore, since the average particle diameter in the first region 90p is small, the strength of the first porous portion 90 is increased, so that drop-off of particles during processing can be suppressed and particles can be reduced.

For example, in each of the first porous portion 90 and the ceramic dielectric substrate 11, the average particle size can be adjusted by adjusting the material composition and sintering conditions such as temperature. For example, the amount and concentration of sintering aids added during sintering of ceramic materials may be adjusted. For example, magnesium oxide (MgO) used as a sintering aid suppresses abnormal growth of crystal grains.

Further, in the same manner as described above, the average particle diameter in the first region 90p can be made smaller than the average particle diameter in the second substrate region 11q. In this way, the mechanical strength in the first region 90p can be improved.

Referring again to FIG. 2(a), the description of the structure of the electrostatic chuck 110 will be continued. The electrostatic chuck 110 may further include a second porous portion 70. The second porous part 70 can be provided between the first porous part 90 and the gas introduction path 53 in the Z direction. For example, the second porous portion 70 is fitted into the base plate 50 on the ceramic dielectric substrate 11 side. As shown in FIG. 2A, for example, a counterbore portion 53a is provided on the ceramic dielectric substrate 11 side of the base plate 50. The counterbore portion 53a is provided in a cylindrical shape. By appropriately designing the inner diameter of the counterbore portion 53a, the second porous portion 70 is fitted into the counterbore portion 53a.

The upper surface 70U of the second porous portion 70 is exposed on the upper surface 50U of the base plate 50. The upper surface 70U of the second porous section 70 faces the lower surface 90L of the first porous section 90. In this example, a space SP is formed between the upper surface 70U of the second porous section 70 and the lower surface 90L of the first porous section 90. The space SP may be filled with at least one of the second porous section 70 and the first porous section 90. That is, the second porous portion 70 and the first porous portion 90 may be in contact with each other.

The second porous portion 70 includes a ceramic porous body 71 having a plurality of holes and a ceramic insulating film 72. The ceramic porous body 71 is provided in a cylindrical shape (for example, cylindrical) and is fitted into the counterbore portion 53a. The shape of the second porous portion 70 is preferably cylindrical, but is not limited to the cylindrical shape. The ceramic porous body 71 is made of an insulating material. The material of the ceramic porous body 71 is, for example, Al ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , MgO, SiC, AlN, or Si ₃ N ₄ . The material of the ceramic porous body 71 may be glass such as SiO ₂ . The material of the ceramic porous body 71 may be Al ₂ O ₃ --TiO ₂ , Al ₂ O ₃ --MgO, Al ₂ O ₃ --SiO ₂ , Al ₆ O ₁₃ Si ₂ , YAG, ZrSiO ₄ or the like.

The porosity of the ceramic porous body 71 is, for example, 20% or more and 60% or less. The density of the ceramic porous body 71 is, for example, 1.5 g/cm ³ or more and 3.0 g/cm ³ or less. Gas such as He flowing through the gas introduction path 53 passes through a plurality of holes in the ceramic porous body 71 and is sent to the groove 14 from the through hole 15 provided in the ceramic dielectric substrate 11 .

The ceramic insulating film 72 is provided between the ceramic porous body 71 and the gas introduction path 53. The ceramic insulating film 72 is denser than the ceramic porous body 71. The porosity of the ceramic insulating film 72 is, for example, 10% or less. The density of the ceramic insulating film 72 is, for example, 3.0 g/cm ³ or more and 4.0 g/cm ³ or less. The ceramic insulating film 72 is provided on the side surface of the ceramic porous body 71.

Examples of materials used for the ceramic insulating film 72 include Al ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , MgO, and the like. As the material of the ceramic insulating film 72, Al ₂ O ₃ -TiO ₂ , Al ₂ O ₃ -MgO, Al ₂ O ₃ -SiO ₂ , Al ₆ O ₁₃ Si ₂ , YAG, ZrSiO ₄ or the like may be used. .

The ceramic insulating film 72 is formed on the side surface of the ceramic porous body 71 by thermal spraying. Thermal spraying is a method of forming a film by melting or softening the coating material by heating, accelerating it into fine particles, colliding with the side surface of the ceramic porous body 71, and solidifying and depositing the flattened particles. It refers to The ceramic insulating film 72 may be produced by, for example, PVD (Physical Vapor Deposition), CVD, a sol-gel method, an aerosol deposition method, or the like. When the ceramic insulating film 72 is formed by thermal spraying, the film thickness is, for example, 0.05 mm or more and 0.5 mm or less.

The porosity of the ceramic dielectric substrate 11 is, for example, 1% or less. The density of the ceramic dielectric substrate 11 is, for example, 4.2 g/cm ³ .

The porosity of the ceramic dielectric substrate 11 and the second porous portion 70 is measured using a scanning electron microscope, as described above. Density is measured based on JIS C 2141 5.4.3.

When the second porous portion 70 is fitted into the counterbore portion 53a of the gas introduction path 53, the ceramic insulating film 72 and the base plate 50 are in contact with each other. That is, a highly insulating ceramic porous body 71 and a ceramic insulating film 72 are interposed between the through hole 15 that guides gas such as He to the groove 14 and the metal base plate 50. By using such a second porous portion 70, higher insulation can be achieved than when only the ceramic porous body 71 is provided in the gas introduction path 53.

Further, the dimensions of the second porous section 70 can be made larger than the dimensions of the first porous section 90 in the X direction or the Y direction. By providing such a second porous portion 70, a higher dielectric strength voltage can be obtained, so that generation of arc discharge can be suppressed more effectively.

Further, the plurality of holes provided in the second porous portion 70 are more three-dimensionally dispersed than the plurality of holes provided in the first porous portion 90, and the proportion of holes penetrating in the Z direction is The number of first porous portions 90 may be greater than the number of second porous portions 70. By providing the second porous portion 70 having a plurality of three-dimensionally dispersed holes, a higher dielectric strength can be obtained, so that the occurrence of arc discharge can be more effectively suppressed. Further, by providing the first porous portion 90 having a large proportion of holes penetrating in a direction inclined at a predetermined angle θ with respect to the Z direction, gas flow can be made smoother.

Furthermore, the dimensions of the second porous section 70 can be made larger than the dimensions of the first porous section 90 in the Z direction. In this way, a higher dielectric strength voltage can be obtained, so that the occurrence of arc discharge can be suppressed more effectively.

Further, the average value of the diameters of the plurality of pores provided in the second porous portion 70 can be made larger than the average value of the diameters of the plurality of pores provided in the first porous portion 90. In this way, since the second porous portion 70 having a large pore diameter is provided, it is possible to facilitate the flow of gas. Further, since the first porous portion 90 having a small hole diameter is provided on the side of the object to be attracted, it is possible to more effectively suppress the occurrence of arc discharge.
Furthermore, since variations in the diameters of the plurality of holes can be reduced, arc discharge can be suppressed more effectively.

FIG. 10 is a schematic cross-sectional view illustrating the second porous portion 70 of the electrostatic chuck according to the embodiment.
FIG. 10 is an enlarged view of a part of the cross section of the ceramic porous body 71.
The plurality of holes 71p provided in the ceramic porous body 71 are three-dimensionally distributed in the X direction, Y direction, and Z direction inside the ceramic porous body 71. In other words, the ceramic porous body 71 has a three-dimensional network structure that extends in the X direction, Y direction, and Z direction. The plurality of holes 71p are, for example, randomly distributed in the ceramic porous body 71.

Since the plurality of holes 71p are three-dimensionally dispersed, some of the plurality of holes 71p are also exposed on the surface of the ceramic porous body 71. Therefore, fine irregularities are formed on the surface of the ceramic porous body 71. In other words, the surface of the ceramic porous body 71 is rough. Depending on the surface roughness of the ceramic porous body 71, it is possible to easily form the ceramic insulating film 72, which is a sprayed film, on the surface of the ceramic porous body 71. For example, the contact between the sprayed film and the ceramic porous body 71 is improved. Furthermore, peeling of the ceramic insulating film 72 can be suppressed.

The average value of the diameters of the plurality of pores 71p provided in the ceramic porous body 71 is larger than the average value of the diameters of the plurality of pores 96 provided in the porous region 91. The diameter of the hole 71p is, for example, 10 μm or more and 50 μm or less. The flow rate of gas flowing into the through hole 15 can be controlled (restricted) by the porous region 91 having a small hole diameter. Thereby, variations in gas flow rate caused by the ceramic porous body 71 can be suppressed. The diameter of the hole 71p and the diameter of the hole 96 can be determined using a scanning electron microscope, as described above.

Further, the average value of the diameters of the plurality of pores 71p provided in the ceramic porous body 71 can also be made smaller than the average value of the diameters of the plurality of pores 96 provided in the porous region 91. This makes it difficult for current to flow, so it is possible to more effectively suppress the occurrence of arc discharge.
The average value of the diameters of the plurality of holes 71p may be appropriately determined in consideration of the required gas flow rate and suppression of arc discharge.

FIG. 11 is a schematic cross-sectional view illustrating another electrostatic chuck according to the first embodiment.
FIG. 11 illustrates the periphery of the first porous portion 90 similarly to FIG. 2(a).
In this example, the through hole 15 provided in the ceramic dielectric substrate 11 is not provided with a hole portion 15b (a connecting hole connecting the first porous portion 90 and the groove 14). For example, the diameter (length along the X direction) of the through hole 15 does not change in the Z direction and is substantially constant.

As shown in FIG. 11, at least a portion of the upper surface 90U of the first porous portion 90 is exposed to the first main surface 11a side of the ceramic dielectric substrate 11. For example, the position of the upper surface 90U of the first porous portion 90 in the Z direction is the same as the position of the bottom of the groove 14 in the Z direction.

In this way, the first porous portion 90 may be arranged in substantially the entire through hole 15 . Since a connecting hole with a small diameter is not provided in the through hole 15, the flow rate of gas flowing into the through hole 15 can be increased. Furthermore, the first porous portion 90 having high insulation properties can be disposed in most of the through hole 15, and high resistance to arc discharge can be obtained.

FIG. 12 is a schematic cross-sectional view illustrating another electrostatic chuck according to the first embodiment.
FIG. 12 illustrates the periphery of the first porous portion 90 similarly to FIG. 2(a).
In this example, the first porous portion 90 is not integrated with the ceramic dielectric substrate 11.

An adhesive member 61 (adhesive) is provided between the first porous portion 90 and the ceramic dielectric substrate 11. The first porous portion 90 is bonded to the ceramic dielectric substrate 11 with an adhesive member 61 . For example, the adhesive member 61 is provided between the side surface of the first porous portion 90 (the side surface 93s of the dense region 93) and the inner wall 15w of the through hole 15. The first porous portion 90 and the ceramic dielectric substrate 11 do not need to be in contact with each other.

For example, silicone adhesive is used for the adhesive member 61. The adhesive member 61 is, for example, an elastic member having elasticity. The elastic modulus of the adhesive member 61 is, for example, lower than the elastic modulus of the dense region 93 of the first porous portion 90 and lower than the elastic modulus of the ceramic dielectric substrate 11.

In a structure in which the first porous part 90 and the ceramic dielectric substrate 11 are bonded together by the adhesive member 61, the adhesive member 61 is used to absorb heat shrinkage of the first porous part 90 and heat shrinkage of the ceramic dielectric substrate 11. It can be used as a buffer against the difference.

(Second embodiment)
FIG. 13(a) is a schematic cross-sectional view illustrating an electrostatic chuck according to the second embodiment. FIG. 13(b) is a plan view illustrating the second porous portion 70a.
FIG. 14 is a schematic cross-sectional view illustrating a modification of the electrostatic chuck according to the second embodiment.

In the case of the electrostatic chuck according to the first embodiment described above, the second porous portion 70 included a ceramic porous body 71 and a ceramic insulating film 72. On the other hand, in the case of the electrostatic chuck according to the second embodiment, the second porous portion 70a can include a ceramic porous body 73, a dense portion 74, and a dense portion 75. Other components can be the same as those of the electrostatic chuck according to the first embodiment.
The ceramic porous body 73 can be, for example, similar to the ceramic porous body 71 described above.

The dense portion 75 can be similar to the dense region 93 described above, for example.
The dense portion 75 is in contact with the porous ceramic body 73 or is continuous with (formed integrally with) the porous ceramic body 73 . As shown in FIG. 13(b), the dense portion 75 surrounds the outer periphery of the ceramic porous body 73 when viewed along the Z direction. The dense portion 75 has a cylindrical shape (for example, a cylindrical shape) surrounding the side surface 73s of the ceramic porous body 73. In other words, the ceramic porous body 73 is provided so as to penetrate the dense portion 75 in the Z direction. The gas flowing into the second porous part 70a from the gas introduction path 53 passes through a plurality of holes provided in the ceramic porous body 73, and is supplied to the first porous part 90.

By providing the second porous portion 70a having such a ceramic porous body 73, the resistance to arc discharge can be improved while ensuring the flow rate of gas flowing into the through hole 15. Further, since the second porous portion 70a has the dense portion 75, the rigidity (mechanical strength) of the second porous portion 70a can be improved. Further, since the second porous portion 70a has the dense portion 74, the occurrence of arc discharge can be further suppressed.

The dense portion 74 is denser than the ceramic porous body 73. When projected onto a plane (XY plane) perpendicular to the first direction (Z direction) from the base plate 50 toward the ceramic dielectric substrate 11, the dense portion 74 and the first hole portion 15b overlap, and the ceramic porous body 73 and the first hole 15b are configured so as not to overlap. According to such a configuration, the generated current tends to flow bypassing the dense portion 74. Therefore, the distance through which the current flows (conductive path) can be increased, making it difficult for electrons to be accelerated, which in turn can suppress the occurrence of arc discharge. According to this electrostatic chuck, it is possible to effectively suppress the occurrence of arc discharge while ensuring a gas flow.

In this example, the ceramic porous body 73 is provided around the dense portion 74 when projected onto a plane perpendicular to the Z direction. A dense portion 74 is disposed at a position facing the first hole portion 15b to increase resistance to arc discharge, and a ceramic porous body 73 is provided around the dense portion 74, so that a sufficient gas flow can be ensured. In other words, it is possible to both reduce arc discharge and smooth the flow of gas.

As shown in FIG. 13(a), the length of the dense portion 74 along the Z direction may be smaller than the length of the second porous portion 70a along the Z direction. A ceramic porous body 73 may be provided between the dense portion 74 and the base plate 50 in the Z direction. According to these configurations, it is possible to smooth the gas flow while suppressing the occurrence of arc discharge.

Further, as shown in FIG. 14, the length of the dense portion 74 along the Z direction may be approximately the same as the length of the second porous portion 70a along the Z direction. By making the length of the dense portion 74 sufficiently long, the occurrence of arc discharge can be suppressed more effectively.

The dense portion 74 may be made of a dense material having substantially no pores, or may have a plurality of pores as long as it is denser than the ceramic porous material 73. When the dense portion 74 has a plurality of pores, the diameter of the pores is preferably smaller than the diameter of the pores of the ceramic porous body 73.
The porosity (%) of the dense portion 74 can be lower than the porosity (%) of the ceramic porous body 73. Therefore, the density (grams/cubic centimeter: g/cm ³ ) of the dense portion 74 can be made higher than the density (g/cm ³ ) of the ceramic porous body 73 .

Here, arc discharge is often caused by current flowing inside the hole 15b from the ceramic dielectric substrate 11 side toward the base plate 50 side. Therefore, if a dense portion 74 having a low porosity is provided, the current 200 tends to flow bypassing the dense portion 74, as shown in FIGS. 13(a) and 14. Therefore, the distance through which the current 200 flows (conductive path) can be lengthened, making it difficult for electrons to be accelerated, thereby suppressing the occurrence of arc discharge.

The porosity of the dense portion 74 is, for example, the ratio of the volume of spaces (pores) included in the dense portion 74 to the total volume of the dense portion 74 . The porosity of the ceramic porous body 73 is, for example, the ratio of the volume of spaces (pores) included in the ceramic porous body 73 to the total volume of the ceramic porous body 73. For example, the porosity of the ceramic porous body 73 is 5% or more and 40% or less, preferably 10% or more and 30% or less, and the porosity of the dense portion 74 is 0% or more and 5% or less. In this case, the porosity of the dense portion 74 is preferably 50% or less of the porosity of the ceramic porous body 73.
That is, the dense portion 74 is provided in the ceramic porous body 73. The dense portion 74 faces the hole portion 15b. The porosity of the dense portion 74 is 50% or less of the porosity of the ceramic porous body 73.

Further, the diameter of the pores in the dense portion 74 may be 80% or less of the diameter of the pores in the ceramic porous body 73.
Furthermore, the dense portion 74 may have no holes.
Even if the diameter of the pores in the dense part 74 is 80% or less of the diameter of the pores in the ceramic porous body 73, or even if the dense part 74 has no pores, the above-mentioned porosity It is possible to obtain the same effect as when having . That is, even with these configurations, the distance over which the current 200 flows (conductive path) can be lengthened, making it difficult for electrons to be accelerated, thereby suppressing the occurrence of arc discharge.

In the Z direction, the surface of the dense portion 74 on the gas introduction path 53 side may be provided inside the ceramic porous body 73, or may be exposed from the surface of the ceramic porous body 73 on the gas introduction path 53 side. good. The surface of the dense portion 74 on the hole 15b side may be provided inside the ceramic porous body 73, or may be exposed from the surface of the ceramic porous body 73 on the hole 15b side. If the surface of the dense portion 74 on the hole 15b side is exposed from the surface of the porous ceramic body 73 on the hole 15b side, the insulation distance can be increased, thereby preventing the hole 15b from becoming a discharge path. Can be suppressed. If the surface of the dense portion 74 on the gas introduction path 53 side is exposed from the surface of the ceramic porous body 73 on the gas introduction path 53 side, the insulation distance can be increased, so that the hole 15b becomes the discharge path. can be suppressed. For example, as shown in FIG. 14, the dense portion 74 preferably extends in the Z direction from the surface of the ceramic porous body 73 on the gas introduction path 53 side to the surface of the ceramic porous body 73 on the hole 15b side. . In this way, the occurrence of arc discharge can be further suppressed.

Further, it is preferable that the hole portion 15b overlaps the dense portion 74 when viewed along the Z direction. In this way, the current flowing inside the hole 15b from the ceramic dielectric substrate 11 side toward the base plate 50 side can be reliably bypassed by the dense portion 74. Therefore, since the insulation distance can be increased, the hole 15b can be prevented from becoming a discharge path.

FIG. 15 is a schematic diagram illustrating the second porous portion 70a. FIG. 15 is a plan view of the second porous portion 70a viewed along the Z direction.
As shown in FIG. 15, the ceramic porous body 73 has a plurality of sparse portions 76 and dense portions 77. Each of the plurality of sparse portions 76 has a plurality of holes. The dense portion 77 is denser than the sparse portion 76. That is, the dense portion 77 is a portion with fewer pores than the sparse portion 76, or a portion with substantially no pores. Note that the configuration of the second porous portion 70a can be similar to the configuration of the first porous portion 90 described above. In this case, the ceramic porous body 73 may correspond to the porous region 91, the sparse portion 76 may correspond to the sparse portion 94, and the dense portion 77 may correspond to the dense portion 95. Therefore, detailed explanations of these will be omitted.
In this example, when the first porous portion 90a is integrated with the ceramic dielectric substrate 11, and the second porous portion 70a has the same configuration as the first porous portion 90 described above, When the average value of the plurality of pores in the first porous part 90a is made larger than the average value of the plurality of pores in the second porous part 70a, the mechanical strength of the first porous part 90 can be further increased, It is possible to achieve both high arcing resistance and strength.

Further, when viewed along the Z direction, the distance L21 between the side surface 75s of the dense portion 75 and the sparse portion 76 closest to the side surface 75s among the plurality of sparse portions 76 is 100 μm or more and 1000 μm or less. be able to.

FIG. 16 shows a part of the second porous portion 70a viewed along the Z direction, and corresponds to an enlarged view of FIG. 15.
When viewed along the Z direction, each of the plurality of sparse portions 76 has a substantially hexagonal shape (substantially regular hexagonal shape). When viewed along the Z direction, the plurality of sparse portions 76 include a first sparse portion 76a and six sparse portions 76 (second to seventh sparse portions 76b to 76g) surrounding the first sparse portion 76a. . In this case, sparse portions 76a to 76g may correspond to sparse portions 94a to 94g. Furthermore, the lengths L21 to L25 can correspond to the lengths L1 to L5. Therefore, detailed explanations of these will be omitted.

FIG. 17 shows a part of the second porous portion 70a viewed along the Z direction. FIG. 17 is an enlarged view of the periphery of one sparse portion 76.
As shown in FIG. 17, in this example, the sparse portion 76 includes a plurality of holes 78 and a wall portion 79 provided between the plurality of holes 78. In this case, the sparse portion 76 may correspond to the sparse portion 94, the dense portion 77 may correspond to the dense portion 95, the hole 78 may correspond to the hole 96, and the wall portion 79 may correspond to the wall portion 97. . Therefore, detailed explanations of these will be omitted.

FIG. 18 is an enlarged view showing a part of the second porous portion 70a as seen along the Z direction, and showing the holes 78 in one sparse portion 76.
As shown in FIG. 18, the plurality of holes 78 include a first hole 78a located at the center of the sparse portion 76, and six holes 78 (second to seventh holes 78b to 78g) surrounding the first hole 78a. have The second to seventh holes 78b to 78g are adjacent to the first hole 78a. The second to seventh holes 78b to 78g are the holes 78 closest to the first hole 78a among the plurality of holes 78. In this case, the first hole 78a corresponds to the first hole 96a, the second hole 78b corresponds to the second hole 96b, the third hole 78c corresponds to the third hole 96c, and the fourth hole 78d corresponds to the fourth hole. 96d, the fifth hole 78e may correspond to the fifth hole 96e, the sixth hole 78f may correspond to the sixth hole 96f, and the seventh hole 78g may correspond to the seventh hole 96g. Therefore, detailed explanations of these will be omitted.

FIG. 19 is a schematic cross-sectional view illustrating another electrostatic chuck according to the second embodiment.
Similar to FIG. 13(a), FIG. 19 illustrates the periphery of the second porous portion 70a.
In this example, the through hole 15 provided in the ceramic dielectric substrate 11 is not provided with a hole portion 15b (a connecting hole connecting the first porous portion 90 and the groove 14). For example, the diameter (length along the X direction) of the through hole 15 does not change in the Z direction and is substantially constant.

As shown in FIG. 19, at least a portion of the upper surface 90U of the first porous portion 90 is exposed to the first main surface 11a side of the ceramic dielectric substrate 11. For example, the position of the upper surface 90U of the first porous portion 90 in the Z direction is the same as the position of the bottom of the groove 14 in the Z direction.

In this way, the first porous portion 90 may be arranged in substantially the entire through hole 15 . Since a connecting hole with a small diameter is not provided in the through hole 15, the flow rate of gas flowing into the through hole 15 can be increased. Furthermore, the first porous portion 90 having high insulation properties can be disposed in most of the through hole 15, and high resistance to arc discharge can be obtained.

FIG. 20 is a schematic cross-sectional view illustrating another electrostatic chuck according to the second embodiment.
Similar to FIG. 13(a), FIG. 20 illustrates the periphery of the first porous portion 90.
In this example, the first porous portion 90 is not integrated with the ceramic dielectric substrate 11.

An adhesive member 61 (adhesive) is provided between the first porous portion 90 and the ceramic dielectric substrate 11. The first porous portion 90 is bonded to the ceramic dielectric substrate 11 with an adhesive member 61 . For example, the adhesive member 61 is provided between the side surface of the first porous portion 90 (the side surface 93s of the dense region 93) and the inner wall 15w of the through hole 15. The first porous portion 90 and the ceramic dielectric substrate 11 do not need to be in contact with each other.

For example, silicone adhesive is used for the adhesive member 61. The adhesive member 61 is, for example, an elastic member having elasticity. The elastic modulus of the adhesive member 61 is, for example, lower than the elastic modulus of the dense region 93 of the first porous portion 90 and lower than the elastic modulus of the ceramic dielectric substrate 11.

In a structure in which the first porous part 90 and the ceramic dielectric substrate 11 are bonded together by the adhesive member 61, the adhesive member 61 is used to absorb heat shrinkage of the first porous part 90 and heat shrinkage of the ceramic dielectric substrate 11. It can be used as a buffer against the difference.

The embodiments of the present invention have been described above. However, the invention is not limited to these descriptions. For example, although a configuration using Coulomb force is illustrated as the electrostatic chuck 110, a configuration using Johnson-Rahbek force is also applicable. Further, the scope of the present invention includes any design changes made by those skilled in the art in the above-described embodiments as long as they have the characteristics of the present invention. Furthermore, the elements of each of the embodiments described above can be combined to the extent technically possible, and combinations of these are also included within the scope of the present invention as long as they include the features of the present invention.

11 ceramic dielectric substrate, 11a first main surface, 11b second main surface, 11p first substrate region, 12 electrode, 13 dot, 14 groove, 15 through hole, 15a hole, 15b hole (first hole) , 15c hole (second hole), 15w inner wall, 20 connection part, 50 base plate, 50U upper surface, 50a upper part, 50b lower part, 51 input path, 52 output path, 53 gas introduction path, 55 communication path, 60 adhesive part , 70 second porous part, 70a second porous part, 70U upper surface, 71 ceramic porous body, 71p pore, 72 ceramic insulating film, 73 ceramic porous body, 74 dense part, 75 dense part, 76 sparse part, 76a~ 76g 1st to 7th sparse portion, 77 dense portion, 78 hole, 78a to 78g 1st to 7th hole, 79 wall portion, 80 voltage for adsorption and holding, 90 first porous portion, 90L bottom surface, 90U top surface, 90p 1st region, 91 porous region, 91s side surface, 93 dense region, 93s side surface, 94 sparse portion, 94a to 94g first to seventh sparse portion, 95 dense portion, 96 hole, 96a to 96g first to seventh hole, 97 wall, 110 electrostatic chuck, W object, SP space, ROI1 evaluation range, ROI2 evaluation range

Claims (17)

a ceramic dielectric substrate having a first main surface on which an object to be attracted is placed, and a second main surface opposite to the first main surface;
a base plate that supports the ceramic dielectric substrate and has a gas introduction path;
a first porous portion provided between the base plate and the first main surface of the ceramic dielectric substrate at a position facing the gas introduction path;
Equipped with
The first porous portion has a plurality of sparse portions each having a plurality of pores and spaced apart from each other,
The electrostatic chuck is characterized in that each of the plurality of sparse portions extends in a direction inclined at a predetermined angle with respect to a first direction from the base plate toward the ceramic dielectric substrate. 2. The electrostatic chuck according to claim 1, wherein the plurality of holes allow gas introduced from the gas introduction path to flow therethrough. The electrostatic chuck according to claim 1 or 2, wherein an angle between the first direction and the direction in which the sparse portion extends is 5° or more and 30° or less. The first porous portion further includes a dense portion located between the plurality of sparse portions and having a higher density than the sparse portion,
The sparse portion has the hole and a wall portion provided between the hole,
A minimum value of a dimension of the wall portion is smaller than a minimum value of a dimension of the dense portion in a direction substantially perpendicular to a direction inclined at a predetermined angle with respect to the first direction. 3. The electrostatic chuck according to any one of 3. The ceramic dielectric substrate has a first hole located between the first main surface and the first porous part,
At least one of the ceramic dielectric substrate and the first porous portion has a second hole located between the first hole and the first porous portion,
In a second direction substantially orthogonal to the first direction, the size of the second hole is smaller than the size of the first porous part and larger than the size of the first hole. The electrostatic chuck according to any one of items 1 to 4. further comprising a second porous part provided between the first porous part and the gas introduction path and having a plurality of holes,
The plurality of pores provided in the second porous part are more three-dimensionally dispersed than the plurality of pores provided in the first porous part,
The electrostatic capacitor according to any one of claims 1 to 5, wherein the proportion of holes penetrating in the first direction is greater in the first porous part than in the second porous part. Chuck. The average value of the diameters of the plurality of pores provided in the second porous part is larger than the average value of the diameters of the plurality of pores provided in the first porous part. 6. The electrostatic chuck according to any one of 6. 7. An average value of diameters of the plurality of pores provided in the second porous part is smaller than an average value of diameters of the plurality of pores provided in the first porous part. Electrostatic chuck as described in . further comprising a second porous part provided between the first porous part and the gas introduction path and having a plurality of holes,
Claim characterized in that the average value of the diameters of the plurality of pores provided in the second porous part is larger than the average value of the diameters of the plurality of pores provided in the first porous part. 9. The electrostatic chuck according to any one of 1 to 8. The first porous portion and the ceramic dielectric substrate contain aluminum oxide as a main component,
The electrostatic chuck according to claim 1, wherein the purity of the aluminum oxide in the ceramic dielectric substrate is higher than the purity of the aluminum oxide in the first porous portion. further comprising a second porous part provided between the first porous part and the gas introduction path,
The ceramic dielectric substrate has a first hole located between the first main surface and the first porous part,
The second porous part is
a ceramic porous body having a plurality of pores;
having a dense part that is denser than the ceramic porous body,
When projected onto a plane perpendicular to a first direction from the base plate toward the ceramic dielectric substrate, the dense portion and the first hole overlap, and the second porous portion and the first hole overlap. The electrostatic chuck according to any one of claims 1 to 10, characterized in that it is configured so as not to overlap with the electrostatic chuck. The ceramic porous body has a plurality of sparse portions having a plurality of pores, and a dense portion having a density higher than the density of the sparse portion,
In the ceramic porous body,
Each of the plurality of sparse portions extends in the first direction, and the dense portion is located between the plurality of sparse portions,
The sparse portion has a wall portion provided between the holes,
12. The electrostatic chuck according to claim 11, wherein a minimum dimension of the wall portion is smaller than a minimum dimension of the dense portion in the second direction. When a direction substantially orthogonal to the first direction is defined as a second direction,
The first porous portion has a first region located on the ceramic dielectric substrate side in the second direction,
The ceramic dielectric substrate has a first substrate region located on the first region side in the second direction,
the first region and the first substrate region are provided in contact with each other,
The electrostatic chuck according to claim 1, wherein the average particle diameter in the first region is different from the average particle diameter in the first substrate region. 14. The electrostatic chuck according to claim 13, wherein the average particle diameter in the first substrate region is smaller than the average particle diameter in the first region. The ceramic dielectric substrate includes a second substrate region,
the first substrate region is located between the second substrate region and the first porous part,
The electrostatic chuck according to claim 12, wherein the average particle diameter in the first substrate region is smaller than the average particle diameter in the second substrate region. 16. The electrostatic chuck according to claim 15, wherein the average particle diameter in the first region is smaller than the average particle diameter in the second substrate region. 17. The electrostatic chuck according to claim 12, wherein the average particle diameter in the first region is smaller than the average particle diameter in the first substrate region.

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