JP2003017223A - Ceramic heater and electrostatic chuck with built-in ceramic heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic heater and an electrostatic chuck with built-in ceramic heater which can restrain generation of hot spots by securing an even distribution of heat through precise adjustment of degree of adhesion between a heating element and a ceramic plate. SOLUTION: The ceramic heater is of multilayer structure composed of two plates made of ceramic sintered body between which a slot-like opening with embedded heating elements are arranged. The heating element of the ceramic heater is of a sheet of waveform structure and the electrostatic chuck has a built-in ceramic heater.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic heater and a ceramic heater built-in electrostatic chuck used in a semiconductor manufacturing process, a liquid crystal manufacturing process, or the like.

[0002]

2. Description of the Related Art In a process for manufacturing a semiconductor or a liquid crystal, it is necessary to heat a substrate such as a silicon wafer (silicon substrate) or a glass substrate, or to fix and heat the substrate in various processing steps. . In order to meet such a demand, for example, a plate-type ceramic heater in which a resistance heating element is integrally sintered in ceramics, an electrostatic chuck with a built-in ceramic heater, and the like have been developed.

A semiconductor manufacturing process will be specifically described. In this process, an LSI is manufactured by forming semiconductor devices such as MOS devices on a wafer surface of single crystal silicon and connecting them by wiring. . This semiconductor manufacturing process consists of (1) oxidation of silicon and chemical vapor deposition (C
VD method) deposition of oxide film and nitride film, (2) ion implantation and heat treatment for forming impurity region of device,
(3) deposition of a metal film to be a connection wiring between devices, and formation of an interlayer film that insulates the wiring, (4) fine processing (lithography, etching, etc.) to form various deposited films into a desired pattern, ( 5) It is composed of each process such as washing that is repeated throughout the process.

In recent years, in the semiconductor manufacturing process, in order to improve the production efficiency and reduce the cost, the diameter of the silicon wafer has been increased. Further, in an apparatus such as CVD, a method of processing a large number of sheets at a time is adopted from a method of processing one or a few sheets in order to improve quality.
The device is being single-wafered. Further, in the processing such as etching, the conventional wet process is being changed to a dry process using plasma or a reactive gas for high fine processing.

In recent semiconductor manufacturing processes, a great change is required also in a method of fixing (chucking) a silicon wafer. In the semiconductor manufacturing process,
Processing steps such as etching and sputtering are performed with the silicon wafer fixed. Also in the electron beam drawing apparatus, it is necessary to fix the silicon wafer so as not to move on the stage that performs the acceleration / deceleration motion in order to prevent drawing position error.

In the conventional method of mechanically fixing a silicon wafer with a gripping tool such as a clamp, the contact point of the gripping tool is easily scratched and the entire surface cannot be processed. A vacuum chuck that sucks a silicon wafer by vacuuming cannot be used because there is no pressure difference under vacuum conditions. Particularly, in the dry process, unlike the wet treatment under normal pressure, accurate uniform heating and cooling under vacuum are required, and therefore conventional clamps and vacuum chucks cannot cope with it.

An electrostatic chuck is attracting attention as a means for fixing a silicon wafer which is compatible with recent semiconductor processes and solves the above problems. The electrostatic chuck is
This is a device that generates an electrostatic force between an object to be attracted (substrate) and a chuck (dielectric) to attract it, and its structure is (1)
One with a pole on the dielectric and the opposite pole bonded to the object to be attracted on the dielectric, (2) A single pole with only the + pole formed in the dielectric to make the plasma potential one pole It is roughly classified into a polar type and (3) a bipolar type in which both positive and negative poles are formed in a dielectric.

The electrostatic chuck is roughly classified into a polymer type and a ceramic type according to the material of the dielectric. In the polymer type, there are silicone rubber, polyimide resin, epoxy resin and the like. Ceramics include alumina, aluminum nitride (AlN), and pyrolytic boron nitride (PBN). For use under high temperature of 350 ° C or higher, or in corrosive plasma or halogen gas, heat resistance, plasma resistance,
Ceramic-based electrostatic chucks with excellent corrosion resistance and durability are selected.

The electrostatic chuck is capable of uniformly adhering and fixing a large substrate by utilizing electrostatic attraction even under a vacuum with no pressure difference, and it is not necessary to clamp the silicon wafer. Has the advantages that it can be microfabricated over the entire surface, that it can be applied to single-wafer processing or dry processing, and that the temperature control of the silicon wafer can be performed quickly and uniformly.

As an electrostatic chuck, a composite type electrostatic chuck incorporating a heater has been developed in order to control the temperature of a substrate such as a silicon wafer or a glass substrate. Particularly in the recent technical field of single-wafer thin film formation, there is a need for a heater for heating a substrate that can be used at a high temperature, which has not been available in the past.

An electrostatic chuck using ceramics as a dielectric substrate can be integrated with a ceramic heater by a highly accurate embedding technique, and the surface temperature of a substrate such as a silicon wafer is ± 1. Some have emerged that can be controlled below%. Further, a plate-type ceramic heater in which a heating element is embedded with ceramics as a base material is also used alone for heating a substrate.

FIG. 6 is a partial cutaway view showing the structure of an example of an electrostatic chuck with a built-in ceramic heater. This electrostatic chuck with a built-in ceramic heater comprises a dielectric layer 61 made of ceramics, an electrode 62, a heating element 63, and an insulating layer 64 made of ceramics.
It has a structure in which electrodes, heating elements, etc. are embedded in an inner layer of a multilayer substrate made of a ceramic sintered body. At the surface 65, a substrate such as a silicon wafer is fixed by electrostatic attraction. The heating element 63 is generally arranged in a spiral or C-shaped pattern over the entire inner layer of the multilayer substrate. The power supply terminals connected to the electrode 62 and the heating element 63 are not shown.

FIGS. 4 and 5 are partial cross-sectional views showing two typical examples of the structure of the ceramic heater portion or the independent ceramic heater of the electrostatic chuck with built-in ceramic heater shown in FIG. FIG. 4 is a cross section of a ceramic heater in which two green sheets made of ceramics such as aluminum nitride are superposed and integrally sintered. The heating element 4 is previously attached to the surface of one green sheet.
A groove-shaped space 43 for accommodating 1 is provided in advance, a heating element is put in the groove-shaped space, and then the other green sheet is superposed and integrally sintered. The plates 41 and 42 formed by sintering the respective green sheets are integrated by sintering to form an insulating layer. Both green sheets may be integrally sintered via a bonding agent layer. Alternatively, two plates formed by sintering two green sheets may be bonded to each other with a bonding agent. The heating element 44 is
It is in the form of a sheet and is generally arranged in various patterns throughout the ceramic heater.

The ceramic heater shown in FIG. 5 has a structure in which, as described above, two green sheets made of ceramics are superposed and integrally sintered. In this ceramic heater, groove-shaped voids are formed in advance on one green sheet in various patterns, and a heating element forming paste such as tungsten (W) paste is filled in the groove-shaped voids by printing or the like. After that, another green sheet is overlaid and integrally sintered. The heating element forming paste is printed in a pattern on one green sheet in advance, and the bonding agent is printed in a pattern on the remaining portion, if necessary, and another green sheet is placed on them. May be superposed and integrally sintered.

2 formed by sintering two green sheets
The plates 51 and 52 are integrated by sintering to form an insulating layer. A sintered heating element 54 is filled in the groove-shaped void 53. The heating element forming paste is prepared, for example, by adding a paste organic solvent (for example, a mixture of butyl carbitol, an acrylic resin, and dibutyl phthalate) to tungsten powder.

However, it has been found that the ceramic heaters having such a structure have defects. The ceramic heater having the structure shown in FIG.
Does not contact the plates 41 and 42 evenly,
A temperature difference easily occurs between the contact portion and the non-contact portion of the heating element 44. Further, the contact portion and the non-contact portion are unevenly distributed. Since the temperature of the contact portion of the heating element 44 becomes higher than the temperature of the non-contact portion, a so-called hot spot appears, so that not only the substrate cannot be heated uniformly, but
The life of the heating element is shortened.

In the ceramic heater shown in FIG. 5, the heating element forming paste formed in a pattern is often contracted during sintering and cracked, resulting in disconnection. Further, since the sintering temperature and the thermal expansion coefficient of the heating element forming paste need to be matched with the ceramics forming the plates 51 and 52, there are restrictions on the material of the heating element. The material of the heating element 54 is limited to those capable of powder sintering such as tungsten powder. Further, the process is complicated, for example, after filling the groove-shaped void 53 with the heating element forming paste, it is necessary to polish and planarize.

[0018]

The problems of the present invention are (1)
The degree of adhesion between the heating element and the ceramic plate can be adjusted precisely, thereby ensuring uniform heating and
The generation of hot spots can be suppressed, (2) the selection range of the material of the heating element is wide, (3) there is no disconnection in the heating element during sintering of ceramics, and (4) the manufacturing process is simple Another object of the present invention is to provide a ceramic heater having excellent durability and an electrostatic chuck incorporating the ceramic heater.

The present inventor has conducted extensive studies in order to achieve the above-mentioned object, and as a result, in a ceramic heater having a multi-layer structure in which a heating element is embedded in a groove-like space between two plates made of a ceramic sintered body. It was conceived that the heating element is a sheet-shaped heating element having a corrugated structure. When the sheet-shaped heating element is dimple processed or corrugated to have a corrugated structure, when the heating element is housed in the groove-shaped void, it can be firmly attached to each plate, and the degree of the attachment can be adjusted. be able to. The present invention has been completed based on these findings.

[0020]

Thus, according to the present invention, in a ceramic heater having a multilayer structure in which a heating element is embedded in a groove-shaped space between two plates made of a ceramics sintered body, the heating Provided is a ceramic heater, wherein the body is a corrugated sheet-shaped heating element.

Further, according to the present invention, a ceramic heater built-in type electrostatic chuck incorporating a ceramic heater having a multi-layer structure in which a heating element is embedded in a groove-shaped space between two plates made of a ceramic sintered body. In the above, there is provided an electrostatic chuck built-in type ceramic heater, wherein the heating element is a sheet-shaped heating element having a corrugated structure.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described with reference to FIG. FIG. 1 is a partial cross-sectional view showing the structure of the ceramic heater of the present invention. A groove-like void 3 is provided inside a multi-layer structure composed of the plates 1 and 2, and a sheet-like heating element 4 having a corrugated structure is embedded in the groove-like void 3. The power supply terminal and other accessory parts are not shown in the drawing.

The plates 1 and 2 are formed by stacking green sheets made of a ceramic material and integrally sintering them. Grooves are formed in advance in one green sheet. The heating elements are generally arranged in various patterns such that they are distributed throughout the ceramic heater. The groove-like voids 3 are formed in a pattern according to the distribution of heating elements. After the heating element 4 is placed in the groove-shaped void 3, another green sheet is superposed on the heating element 4 and integrally sintered. If necessary, a bonding agent layer may be provided between the two green sheets.

Examples of the raw material ceramics include powders of aluminum nitride (AlN), boron nitride, pyrolytic boron nitride (PBN), silicon nitride, silicon carbide, silicon oxide, zirconium oxide, titanium oxide, alumina and the like. . These ceramic powders can be used alone or in combination of two or more. Among these, aluminum nitride powder is preferable.

The green sheet can be prepared by forming a slurry containing ceramic powder as a main component into a sheet by, for example, a doctor blade method. After punching each green sheet into a predetermined shape, a through hole or the like may be formed by drilling or punching if necessary. Alternatively, the slurry containing the ceramic powder may be granulated using a spray dryer, and then the granulated powder may be molded or press-molded into a green sheet having a predetermined shape. Groove-like voids for embedding a heating element are formed in a pattern on the surface of one green sheet. The groove-like voids can be provided on the surface of the green sheet by pressing or embossing.

After arranging the heating element in the groove-like void of one green sheet, another green sheet is positioned and superposed, and in that state, vacuum pressing is performed at a predetermined pressure. Thereby, a laminate in which two green sheets are integrated is obtained. This laminated body is dried by heating it at a temperature of several tens to several hundreds of tens of degrees Celsius for a predetermined time under normal pressure.

After drying, the green sheet laminate is sintered, but before that, a degreasing step and a preliminary sintering step may be arranged. The degreasing step is usually performed by heating to a temperature of 250 to 700 ° C. under vacuum or in a non-oxidizing atmosphere such as nitrogen. The temporary sintering step is usually performed by heating to a temperature of 900 to 1600 ° C. in a non-oxidizing atmosphere such as nitrogen. Next, the green sheet laminate or its pre-sintered body is placed in a sintering furnace, and 1700
Hot press sintering is performed at a temperature of ℃ or more and a predetermined time and a predetermined pressure. After the sintering step, the ceramic heater can be subjected to outer shape processing or chamfering processing using a grinder or the like, if necessary.

It is also possible to sinter the two green sheets and then bond them using a bonding agent. Aluminum nitride (Al
To join the N) sintered plates together, for example, Al
It is preferable to use a binder paste prepared from a mixture of N powder, yttrium compound powder, lithium oxide powder and the like. The joining can be performed by heating and pressing at a temperature of 1500 to 1900 ° C.

The shape and size of the ceramic heater can be appropriately determined according to the shape and size of a substrate such as a silicon wafer using the ceramic heater. The shape of the ceramic heater is often circular. Its diameter is usually
50-500 mmφ, preferably 100-400 mmφ
It is a degree.

The ceramic heater built-in electrostatic chuck having the structure as shown in FIG. 6 uses a large number of green sheets and is laminated in a multi-layered manner in accordance with a conventional method to embed an electrode and a heating element. Can be produced and sintered.

The corrugated sheet-shaped heating element used in the present invention can be produced by subjecting the sheet-shaped heating element to dimple processing or corrugation processing. Specific waveform shapes include, for example, the wavy shape shown in FIG. 2 and the cross-sectional shape such as the uneven shape shown in FIG. In the present invention, the corrugated structure includes not only a typical corrugated sectional structure shown in FIG. 2 but also a corrugated sectional structure formed by dimple processing as shown in FIG. To do.

The thickness and width of the corrugated sheet-shaped heating element, the pitch (a) of the corrugated structure, and the height (b) of the corrugations and irregularities are appropriately selected depending on the size of the ceramic heater and the shape and size of the groove-like voids. Can be set. Generally, pitch (a)
Is usually 2 to 30 mm, preferably 2 to 5 mm. The height (b) of waves or irregularities is usually 0.1 to 3 m
m, preferably about 0.3 to 0.5 mm. The thickness of the sheet-shaped heating element is usually 0.05 to 0.5 mm, preferably about 0.1 to 0.2 mm, and its width is usually 2
It is about 20 mm, preferably about 3 to 10 mm. The height (b) of the wave or unevenness of the sheet-shaped heating element is determined by the groove-like voids 3.
It is preferable to set the height to be the same as or slightly larger than the height (d). It is preferable that b-d is about 0.1 to 2 mm.

By making the sheet-shaped heating element have such a corrugated structure, it is possible to secure uniform contact with the ceramic plate. When the heating element is in close contact with the plate, the temperature of the plate can be made uniform, and hot spots can be prevented from occurring on the heating element. Since the sheet-shaped heating element is used, there is no risk of disconnection due to shrinkage during sintering, which is the case when using the heating element forming paste. Further, since the sheet-shaped heating element is not attached to the plate, it is not necessary to match the coefficient of thermal expansion with that of ceramics, and the range of selection of the material of the heating element is widened.

The temperature distribution can be controlled by adjusting the pitch (a). The sheet-shaped heating elements are arranged in a spiral pattern or a C-shaped pattern over the entire surface of the ceramic heater. For example, the pitch of the corrugated sheet-shaped heating elements arranged in the peripheral portion of the ceramic heater. By making (a) shorter than that in the inner peripheral portion, the in-plane temperature distribution of the ceramic heater can be adjusted to be uniform.

Examples of the material of the heating element include molybdenum, tungsten, tantalum and the like.

[0036]

EXAMPLES The present invention will be described more specifically with reference to the following examples.

[Example 1] Aluminum nitride powder and methanol were mixed to prepare a slurry, and the slurry was formed into a green sheet using a doctor blade. The green sheet was punched to form a circular sheet having a diameter of 300 mm and a thickness of 8 mm. Grooves having a width of 8 mm and a depth of 0.4 mm were formed in a pattern on the green sheet. Meanwhile, from the same slurry, the diameter is 300 mm
A circular green sheet with φ and a thickness of 8 mm was prepared.

As the heating element, a sheet made of molybdenum and having a width of 6 mm and a thickness of 0.1 mm was used. The sheet-shaped heating element was corrugated to form a corrugated structure as shown in FIG. The pitch (a) was 5 mm and the wave height (b) was 0.5 mm. This corrugated heating element sheet was inserted into the groove-like void, another green sheet was overlaid thereon, and vacuum pressed to form an integrated green sheet laminate. This laminate was dried by heating, pre-sintered at 1300 ° C, and then press-sintered at 1900 ° C. The ceramic plate thus obtained has an in-plane temperature distribution of ± 1% at a working temperature of 600 ° C.
It was below, and was excellent in heat uniformity.

[0039]

According to the present invention, the degree of adhesion between the heating element and the ceramic plate can be precisely adjusted, whereby the uniform heating property can be secured and the occurrence of hot spots can be suppressed. And, an electrostatic chuck incorporating the ceramic heater is provided. Further, according to the present invention, a ceramic heater having a wide selection range of the material of the heating element, no breakage of the heating element during sintering of the ceramic and a simple manufacturing process, and an electrostatic chuck incorporating the ceramic heater are provided. Will be provided. Further, the ceramic heater of the present invention can control the in-plane temperature distribution by adjusting the pitch of the corrugated structure.

[Brief description of drawings]

FIG. 1 is a partial sectional view of an example of a ceramic heater of the present invention.

FIG. 2 is a cross-sectional view showing an example of a corrugated structure of a sheet-shaped heating element used in the present invention.

FIG. 3 is a cross-sectional view showing another example of the corrugated structure of the sheet-shaped heating element used in the present invention.

FIG. 4 is a partial cross-sectional view of an example of a conventional ceramic heater.

FIG. 5 is a partial cross-sectional view of another example of a conventional ceramic heater.

FIG. 6 is a partial cutaway view of an example of an electrostatic chuck with a built-in ceramic heater.

[Explanation of symbols]

1: Ceramic plate 2: Ceramic plate 3: Groove-like void 4: Sheet-shaped heating element having a corrugated structure a: Pitch of corrugated structure b: Height of corrugated structure 41: Ceramic plate 42: Ceramic plate 43: Groove 44: Sheet-shaped heating element 51: Ceramic plate 52: Ceramic plate 53: Groove 54: Paste-molded heating element 61: Dielectric layer 62: electrode 63: heating element 64: Insulator layer 65: Surface

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3K034 AA02 AA15 AA27 AA30 BB06                       BB14 BC05 BC17 JA10                 3K092 PP00 QA05 QB02 QB33 QB36                       RF03 RF11 RF27 VV22 VV28                 5F031 CA02 HA03 HA16 HA37 MA29                       PA11 PA18

Claims (2)

[Claims] 1. A ceramic heater having a multilayer structure in which a heating element is embedded in a groove-shaped space between two plates made of a ceramics sintered body, wherein the heating element is a corrugated sheet-shaped heating element. Ceramic heater characterized by. 2. An electrostatic chuck with a built-in ceramic heater having a built-in ceramic heater having a multi-layer structure in which a heating element is embedded in a groove-shaped space between two plates made of a ceramics sintered body. An electrostatic chuck with a built-in ceramic heater, which is a corrugated sheet-shaped heating element.