JP5243465B2 - Plasma processing equipment - Google Patents

Description

  The present invention relates to a plasma processing apparatus.

  Patent Document 1 discloses an ICP type dry etching apparatus configured to hold a tray containing a substrate in a bottomed concave portion on a substrate susceptor by an electrostatic chuck (ESC). The substrate susceptor is provided with a cooling mechanism. Since the substrate is cooled by indirect heat conduction with the substrate susceptor via the tray, the substrate is cooled relatively uniformly, but the cooling efficiency of the substrate is low. For this reason, the dry etching apparatus described in Patent Document 1 cannot supply high-frequency power in order to achieve a high etching rate.

  Patent Document 2 discloses an ICP type dry etching apparatus capable of batch processing. As shown in FIG. 15, the dry etching apparatus of Patent Document 2 accommodates a substrate 101 in each of a plurality of substrate accommodation holes 100 a formed in the tray 100 in the thickness direction, and the tray 100 together with the ESC 103 of the substrate susceptor 102. The substrate 101 is held. The substrate susceptor 102 is provided with a cooling mechanism including a refrigerant circulation path 104. A heat transfer gas such as helium (He) is filled between the lower surface of each substrate 101 and the ESC 103. The upper end portion of the substrate platform 105 provided in the ESC 103 includes an annular protrusion 106 provided along the outermost peripheral edge, a recess 107 for storing heat transfer gas surrounded by the annular protrusion 106, and a recess. 107 includes a plurality of columnar protrusions 108 provided therein. The upper end surfaces of the annular protrusion 106 and the columnar protrusion 108 function as substrate contact surfaces 106 a and 108 a that contact the lower surface of the substrate 101. The depth De of the recess 107 (the distance from the substrate placement surfaces 106a and 108a to the bottom surface of the recess 107) is constant. The substrate 101 during the plasma processing is cooled by heat conduction with the substrate susceptor 102 through the heat transfer gas filled in the recess 107. Since the substrate 101 can be effectively cooled by direct cooling using a heat transfer gas, it is possible to input high-frequency power required for etching a difficult-to-etch material at a high etching rate. For example, when the etching of a sapphire (SF) substrate, which is a part of the LED manufacturing process, or the etching of a gallium nitride (GaN) epitaxial layer provided on the SF substrate is performed by the dry etching apparatus of Patent Document 2, the diameter of the tray 100 Is 340 mm, the high frequency power supplied to the plasma generating coil is about 1000 to 2800 W, and the high frequency power (bias power) supplied to the substrate susceptor 102 side is about 500 to 2000 W.

  However, when high-frequency power is input using the dry etching apparatus described in Patent Document 2, it is necessary to sufficiently consider the in-plane temperature distribution in each substrate. The upper graph in FIG. 16 shows an example of the distribution of the substrate temperature generated from the center of the substrate toward the periphery (the substrate temperature rises relatively abruptly in a region near the periphery). When there is such a substrate temperature distribution, especially in the case of etching an SF substrate, the substrate temperature dependence of the etching rate (the higher the substrate temperature, the lower the etching rate) is significant. As shown, there is a possibility that the etching rate is also distributed corresponding to the distribution of the substrate temperature (the etching rate is drastically decreased in a region near the periphery). In addition, a distribution corresponding to the distribution of the substrate temperature may occur in the taper angle of the side wall of the structure formed by etching. For example, as shown in the lower graph of FIG. 16, the taper angle of the side wall, which is about 60 degrees at the center of the substrate, increases toward the outside of the substrate, and may be about 75 degrees at the periphery of the substrate. Thus, the in-plane temperature distribution of the substrate can cause in-plane variations in the plasma processing.

  In Patent Document 3, if the gas pressure of the heat transfer gas, which is He or hydrogen, is about 0 to 20 torr (0 to 2600 Pa), the heat transfer coefficient between the substrate and the ESC is mainly determined by the gas pressure, so the controllability of the substrate temperature. Is going to be good. Further, Patent Document 3 states that uniformity of the substrate temperature can be obtained if the depth De in FIG. 15 is set to be less than 40 μm, preferably 20 to 35 μm, within this gas pressure range. Furthermore, according to Patent Document 3, the heat transfer coefficient depends on only the pressure of the heat transfer gas, particularly in the free molecule region where the gas pressure of the heat transfer gas that is He or hydrogen is about 0 to 10 torr (0 to 1300 Pa). Preferably, in the transition region of about 10 to 78 torr (about 1300 Pa to 10140 Pa), the heat transfer coefficient depends on the pressure and depth De of the heat transfer gas, and in the continuum region exceeding about 78 torr (about 10140 Pa), the heat transfer coefficient is deep. It depends on De.

  However, high-frequency power needs to be input to etch difficult-to-etch materials such as SF substrates and GaN epitaxial layers formed on them at a high etching rate, and the cooling efficiency of the substrate is increased corresponding to this high-frequency power. Includes a region in which the gas pressure of the heat transfer gas filled between the substrate and the ESC is higher than about 0 to 10 torr (about 0 to 1300 Pa), specifically 1300 Pa to 3000 Pa. It is necessary to set the degree. Therefore, even if the depth De in FIG. 15 is set to a constant value of less than 40 μm as taught in Patent Document 3, the in-plane distribution of the substrate temperature described with reference to FIG. In-plane variation in rate and shape cannot be resolved.

JP 2000-58514 A JP 2005-297378 A Japanese Patent No. 3176305 (paragraphs 0038 to 0041, 0060)

  The present invention provides a plasma processing apparatus in which a heat transfer gas is filled between a substrate and an ESC, and the gas pressure of the heat transfer gas is a high pressure required for etching, for example, an SF substrate or a GaN epitaxial layer formed thereon. Another problem is to make the in-plane distribution of the substrate temperature uniform and to eliminate in-plane variations in plasma processing.

The present invention comprises a chamber capable of reducing pressure for generating plasma and at least one substrate platform on which a substrate is placed, and statically holds the substrate placed on the substrate platform. A substrate holding unit provided in the chamber, having an electric chuck, a heat transfer gas supply mechanism for supplying a heat transfer gas between the substrate and the substrate mounting unit, and cooling for cooling the substrate holding unit An upper end portion of the substrate mounting portion of the electrostatic chuck is mounted on the lower surface of the substrate together with an annular protrusion provided on the periphery and the upper end surface of the annular protrusion on the same plane. A plurality of protrusions each having an upper end surface constituting a substrate mounting surface, and a recess that is an area surrounded by the annular protrusion, and the annular protrusion is mutually connected by an annular groove provided on the upper end surface. comprising a delimited double or triple annular portion has, before The concave portion, which is a region surrounded by an annular protrusion, includes an inner region including the center of the upper end portion of the substrate platform, and an outer region between the inner region and the annular protrusion, The substrate placed on the substrate placement surface , wherein the second depth from the substrate placement surface to the bottom surface in the outer region is shallower than the first depth from the substrate placement surface to the bottom surface in the region. in the heat transfer gas from the heat transfer gas supply mechanism to the closed the recess is filled, to provide a plasma processing apparatus.

  Specifically, the heat transfer gas supply mechanism has the heat transfer gas supply port in the inner region of the recess. A single heat transfer gas supply port may be provided in the center of the substrate mounting portion included in the inner region of the recess, or a plurality of heat transfer gas supply ports may be provided in the inner region. .

  The outer dimension of the inner region in plan view is set to be not less than 0.5 times and not more than 0.93 times of the outer dimension of the substrate platform in plan view. When the diameter of the substrate is 4 inches (about 100 mm) and the diameter of the substrate platform in the plane is about 90 to 100 mm (for example, 97 mm), the diameter of the inner region is 0.64 of the diameter of the substrate platform. It is set to not less than twice and not more than 0.9 times. When the diameter of the substrate is 6 inches (about 150 mm) and the diameter of the substrate platform is about 140 to 150 mm (for example, 147 mm), the diameter of the inner region is 0 of the diameter of the substrate platform. .73 times or more and 0.93 times or less are set. Further, when the diameter of the substrate is 3 inches (about 76 mm) and the diameter of the substrate mounting portion is about 66 to 76 mm (for example, 73 mm), the diameter of the inner region is 0.6 times the diameter of the substrate mounting portion. It is set to 0.86 times or less. Furthermore, when the diameter of the substrate is 2 inches (about 50 mm) and the diameter of the substrate mounting portion is about 48 to 50 mm (for example, 4.8 mm), the diameter of the inner region is 0 of the diameter of the substrate mounting portion. .5 times or more and 0.8 times or less is set.

  Furthermore, the first depth is 40 μm or more and less than 100 μm, and the second depth is 10 μm or more and less than 40 μm.

  The recess that is closed by the substrate placed on the substrate placement surface and is supplied with heat transfer gas has a deep depth including the center (40 μm or more and less than 100 μm) between the inner region and the annular protrusion. And an outer region having a shallow depth (10 μm or more and less than 40 μm). In the inner region, the depth of the recess is set deep in order to improve the diffusibility of the heat transfer gas. By improving the diffusibility of the heat transfer gas, the gradient of the pressure drop of the heat transfer gas from the center of the substrate (heat transfer gas supply port) toward the periphery becomes small. As a result, in the inner region, the gas pressure of the heat transfer gas is relatively high, and the gas pressure distribution of the heat transfer gas is made uniform.

  A small amount of heat transfer gas leaks from the recess into the chamber through a fine gap between the upper end surface (substrate mounting surface) of the annular protrusion and the lower surface near the periphery of the substrate. If the depth of the outer region of the recess is set to the same depth as the inner region, the pressure of the heat transfer gas filled in the recess near the periphery of the substrate becomes excessively high. Due to this excessively high pressure, the heat transfer gas in the recess leaks from only one or a plurality of specific locations on the periphery of the substrate in plan view, and the heat transfer in the recess from other locations on the periphery of the substrate. There is a risk that gas will not leak. Such uneven leakage of the heat transfer gas from the recesses causes in-plane variations in the temperature of the substrate and causes in-plane variations in the plasma processing. In the plasma processing apparatus of the present invention, the depth of the outer region is set shallower than the inner region, and the gradient of the pressure drop of the heat transfer gas toward the peripheral edge of the substrate is made larger than the inner region. Then, by increasing the gradient of the pressure drop, non-uniform heat transfer gas leakage from the recesses (leakage of heat transfer gas from only a specific portion of the periphery of the substrate) does not occur. The pressure of the heat transfer gas in the recess in the vicinity of the periphery is reduced.

  As described above, in the present invention, in consideration of both gas pressure distribution and non-uniform leakage of heat transfer gas, the depth of the recess is increased in the inner region, while the depth of the recess is decreased in the outer region. It is set.

  In the outer region where the depth of the recess is set shallow, the distance between the lower surface of the substrate and the bottom surface of the recess is shortened, so that the heat transfer coefficient between the substrate and the substrate mounting portion is increased. This increase in the heat transfer coefficient is due to the cooling of the substrate in the outer region caused by setting the depth of the recesses deep (to increase the pressure drop gradient of the heat transfer gas) to prevent uneven leakage of the heat transfer gas. Make up for the loss of efficiency. As a result, the difference in the cooling efficiency of the substrate between the inner region and the outer region due to the different depths of the recesses is minimized.

  For the above reasons, the depth of the recess is set deeper in the inner region, and the depth of the recess is set shallower in the outer region than in the inner region, so that the gas pressure of the heat transfer gas filled in the recess is reduced to the SF substrate or Even in a high pressure (for example, about 1300 to 3000 Pa) required for etching a difficult-to-etch material such as a GaN epitaxial layer formed on the substrate at a high etching rate, the in-plane distribution of the substrate temperature is made uniform and plasma treatment is performed. In-plane variation can be eliminated.

  The annular protrusion includes double or triple annular portions that are separated from each other by an annular groove provided on an upper end surface.

  With this configuration, the path of the heat transfer gas leaking from the recess through the lower surface of the peripheral edge of the substrate becomes a kind of labyrinth. Therefore, leakage of heat transfer gas from the recess is suppressed by a so-called labyrinth effect. By suppressing the leakage, the gas pressure of the heat transfer gas can be maintained at a high pressure in the outer region of the recess, particularly in the vicinity of the annular protrusion, without causing the above-described uneven heat transfer gas leakage, and the substrate near the periphery of the substrate. The value of the heat transfer coefficient between the substrate and the substrate mounting portion can be increased. As a result, the cooling effect of the substrate near the periphery of the substrate is improved, and the uniformity of the substrate temperature distribution is further improved.

  The recess includes a first gas distribution groove provided at a boundary between the inner region and the outer region, a second gas distribution groove provided at a boundary between the outer region and the annular protrusion, and the center side. And a third gas distribution groove that communicates with the first and second gas distribution grooves provided so as to extend toward the annular protrusion.

  With this configuration, the diffusibility of the heat transfer gas in both the inner region and the outer region of the recess is improved. As a result, the uniformity of the pressure distribution of the heat transfer gas in the recess is further improved, and the uniformity of the substrate temperature distribution is further improved.

  A third depth from the substrate placement surface to the bottom surfaces of the first to third gas distribution grooves is 100 μm or less.

  With this configuration, it is possible to prevent local abnormal discharge from occurring between the lower surface of the substrate and the substrate mounting portion of the electrostatic chuck due to the provision of the first to third gas distribution grooves.

Preferably, the apparatus includes a plurality of substrate accommodation holes penetrating in the thickness direction in which the substrate is accommodated, and a substrate support portion protruding from a hole wall of each of the substrate accommodation holes, and the substrate is carried into and out of the chamber. The electrostatic chuck further includes a plurality of the substrate placement portions and a tray support portion from which the substrate placement portions protrude, and is accommodated in the substrate accommodation hole when the substrate is transported. The outer peripheral edge portion of the lower surface of the substrate is supported by the substrate support portion, and when the substrate is processed, the tray is lowered toward the substrate holding portion, thereby corresponding to each of the substrate accommodation holes. substrate platform is inserted from the lower surface of the tray, distance together with the lower surface of the tray is placed on the tray support portion of the electrostatic chuck, from the tray support portion to the upper surface of the substrate support portion There By shorter than the distance from the tray support portion to the substrate mounting surface, a lower surface wherein the substrate is lifted from the upper surface of the substrate support portion is placed on the substrate mounting surface, said tray electrostatic It is electrostatically held by the tray holding part of the electric chuck .

  When the substrate placement portion enters the substrate accommodation hole of the tray, the plurality of substrates are placed on the substrate placement surface of the corresponding substrate placement portion with high positioning accuracy. Therefore, the in-plane distribution of the substrate temperature can be made more uniform for each individual substrate.

In addition , the tray is effectively cooled, and even the slight influence of heat transfer from the hole and the substrate support to the peripheral edge of the substrate due to radiation and convection is eliminated. Further improve. Similar to the substrate, the tray may be electrostatically attracted to the tray holding portion by an electrode built in the electrostatic chuck, or may be self-electrostatically attracted to the tray holding portion.

  A plurality of the substrate support portions project at intervals in the circumferential direction on the hole walls of the individual substrate receiving holes of the tray, and the substrate mounting portions are arranged on the side peripheral walls of the individual substrate mounting portions. A plurality of receiving grooves extending from the upper end of the portion toward the tray supporting portion, and when the substrate is processed, the receiving portion corresponding to each of the substrate supporting portions corresponds to each of the substrate supporting portions as the tray descends toward the tray supporting portion. You may enter the groove.

  With this configuration, since the positioning accuracy of the substrate mounting portion with respect to the substrate mounting surface is further improved, it is possible to substantially match the size and shape of the substrate and the upper end portion of the substrate mounting portion in plan view. . In other words, it is not necessary to set the size of the substrate platform in plan view smaller than that of the substrate in consideration of a case where the position of the substrate relative to the upper end of the substrate platform is shifted. As a result, the substrate mounting surface comes into contact with the vicinity of the outermost periphery of each substrate, so that particularly the vicinity of the periphery of the substrate is effectively cooled, and the uniformity of the substrate temperature distribution is further improved.

  In the plasma processing apparatus according to the present invention, the diffusibility of the heat transfer gas is improved in the inner region of the concave portion of the substrate mounting portion that is closed by the substrate mounted on the substrate mounting surface and supplied with the heat transfer gas. In order to make the gas pressure distribution uniform, the depth is set deep (first depth). On the other hand, the outer region of the recess is set to a shallow depth (second depth) to prevent uneven heat transfer gas leakage from the recess, and to reduce the distance between the bottom surface of the substrate and the bottom surface of the recess. The heat transfer coefficient between the substrate and the substrate mounting portion is increased by shortening. As a result, the gas pressure of the heat transfer gas filled in the recesses is as high as required for etching at a high etching rate of difficult-to-etch materials such as the SF substrate and the GaN epitaxial layer formed thereon (for example, 1300 to 3000 Pa). Even so, the in-plane distribution of the substrate temperature can be made uniform, and the in-plane variation of the plasma processing can be eliminated.

1 is a schematic cross-sectional view of a dry etching apparatus according to a first embodiment of the present invention. The enlarged view of the part I of FIG. The perspective view which shows a board | substrate susceptor, a tray, and a board | substrate. The top view of a tray. The top view of the board | substrate mounting part in 1st Embodiment. The typical partial expanded sectional view of the board | substrate mounting part in 1st Embodiment. The typical perspective view of the board | substrate mounting part in 1st Embodiment. The schematic diagram which shows the relationship between the gas pressure of heat transfer gas, a substrate temperature, and a heat transfer coefficient. The top view of the board | substrate for demonstrating the measurement location of a shape and temperature. The partial expanded sectional view of the board | substrate mounting part which has the protrusion part of a triple structure. The partial expanded sectional view of the board | substrate mounting part which has the cyclic | annular protrusion part which does not have a rabin rinse structure. The partial expanded sectional view of the board | substrate mounting part which has a protrusion part of a quadruple structure. The diagram which shows notionally the difference in pressure distribution by the presence or absence of a labyrinth structure. The perspective view which shows the board | substrate susceptor, tray, and board | substrate in the dry etching apparatus which concerns on 2nd Embodiment of this invention. The elements on larger scale of FIG. 11A. The top view of the board | substrate mounting part in 2nd Embodiment. The typical perspective view of the board | substrate mounting part in 2nd Embodiment. The typical partial expanded sectional view of an example of the conventional dry etching apparatus. FIG. 15 is a diagram showing the relationship between the position from the center of the substrate, the substrate temperature, the etching rate, and the taper angle in the dry etching apparatus of FIG.

  Next, embodiments of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
1 and 2 show an ICP (inductively coupled plasma) type dry etching apparatus 1 according to a first embodiment of the present invention. The dry etching apparatus 1 can execute batch processing for simultaneously performing dry etching processing on six 4-inch (100 mm) substrates 2.

  The dry etching apparatus 1 includes a chamber (vacuum vessel) 3 in which a processing chamber capable of being depressurized for performing plasma processing on a substrate 2 is configured. The chamber 3 is provided with an openable / closable gate 3 a for carrying the substrate 2 in and out of the chamber 3 together with the tray 4. Further, the chamber 3 is provided with an exhaust port 3b to which an evacuation device 11 having a vacuum pump or the like is connected. A substrate susceptor (substrate holding unit) 5 having a function as a lower electrode to which a bias voltage is applied and a function as a holding table for the substrate 2 and the tray 4 is disposed on the bottom side in the chamber 3. . The upper end opening of the chamber 3 facing the substrate susceptor 5 is closed by a top plate 7 made of a dielectric material such as quartz. Above the top plate 7, an ICP coil 8 having a plurality of strip-shaped conductors wound in a cone shape is disposed. A high frequency power supply 13 is electrically connected to the ICP coil 8 via a matching circuit 12. A gas etching supply port 3c provided in the chamber 3 is connected to an etching gas supply source 14 having an MFC (mass flow controller) or the like.

Referring to FIGS. 3 and 4 together, the tray 4 is a thin plate having a constant thickness of about 340 mm and made of a ceramic material such as SiC, alumina (Al ₂ O ₃ ), yttria, and AlN. The tray 4 is provided with six substrate housing holes 9A to 9F penetrating in the thickness direction from the upper surface 4a to the lower surface 4b. A 4-inch substrate 2 is accommodated in each of the substrate accommodation holes 9A to 9F. One substrate accommodation hole 9A is provided in the central region of the tray 4, and the remaining five substrate accommodation holes 9B to 9F are arranged at equiangular intervals around the substrate. In the present embodiment, the tray 4 is provided with an endless annular substrate support portion 10 that protrudes inward from the hole walls of the individual substrate accommodation holes 9A to 9F. One substrate 2 is accommodated in each of the substrate accommodation holes 9A to 9B. The substrate 2 accommodated in the substrate accommodation holes 9 </ b> A to 9 </ b> F is supported by the upper surface of the substrate support portion 10 at the outer peripheral edge portion of the lower surface thereof.

  The substrate susceptor 5 is made of an electrostatic chuck (ESC) 21 made of a dielectric material such as ceramics, aluminum having an alumite coating on the surface, etc., and a metal plate 22 functioning as a pedestal electrode in this embodiment, and a dielectric material such as ceramics A spacer plate 23 is provided. The ESC 21 constituting the uppermost part of the substrate susceptor 5 is fixed to the upper surface of the metal plate 22 by a bonding layer 24 such as indium.

  The ESC 21 that constitutes the uppermost part of the substrate susceptor 5 has a thin disk shape as a whole and has a circular outer shape in plan view. Six substrate mounting portions 27A to 27F corresponding to the number of substrates 2 to be batch-processed project upward from a tray support surface 26 that is the upper end surface of the ESC 21. In the present embodiment, the substrate mounting portions 27A to 27F have a flat short cylindrical shape. One substrate platform 27A is arranged at the center of the tray support surface 26, and the remaining five substrate platforms 27B to 27F are arranged at equal angular intervals in plan view around the substrate platform 27A. Has been. As will be described in detail later, the tray 4 is supported by the tray support surface 26 of the ESC 21, and the six substrates 2 are held on the upper end portions 27a of the substrate platforms 27A to 27F, respectively.

  As shown in FIG. 2, an electrostatic chucking electrode 28 is built in the vicinity of the upper end portion 27 a of each substrate mounting portion 27 </ b> A to 27 </ b> F of the ESC 21. A DC voltage for electrostatic adsorption is applied to the electrostatic adsorption electrodes 28 from the DC voltage application mechanism 15.

  Referring to FIGS. 1 and 3, heat transfer gas (helium in this embodiment) supply holes 29 are provided in the upper end portions 27 a of the individual substrate mounting portions 27 </ b> A to 27 </ b> F. In a closed space between the upper end portion 27a of each of the substrate placement portions 27A to 27F and the lower surface 2a of the substrate 2 placed thereon, the heat transfer gas supply mechanism 16 connected to the supply hole 29 is provided. A heat transfer gas (in this embodiment, helium gas) is supplied by (illustrated in FIG. 1). When supplying the heat transfer gas, the cutoff valve 16a is closed, and the heat transfer gas is sent from the heat transfer gas supply source (helium gas source in the present embodiment) 16b to the supply hole 29 via the supply flow path 16c. The flow control valve 16f is controlled based on the flow rate and pressure of the supply flow path 16c detected by the flow meter 16d and the pressure gauge 16e. On the other hand, when the heat transfer gas is discharged, the cut-off valve 16a is opened, and the heat transfer gas is exhausted from the exhaust port 16h through the supply hole 29, the supply flow path 16c, and the discharge flow path 16g.

  A high frequency applying mechanism 17 that applies a high frequency as a bias voltage is electrically connected to the metal plate 22. Further, a cooling mechanism 18 for cooling the metal plate 22 is provided. The cooling mechanism 18 includes a refrigerant flow path 18a formed in the metal plate 22 and a refrigerant circulation device 18b that circulates the temperature-controlled refrigerant in the refrigerant flow path 18a.

  A controller 30 schematically shown only in FIG. 1 is based on various sensors and operation inputs including a flow meter 16d and a pressure gauge 16e, and a high-frequency power source 13, an etching gas supply source 3c, a vacuum exhaust device 11, and a DC voltage application mechanism. 15, the operation of the entire dry etching apparatus 1 including the heat transfer gas supply mechanism 16, the high-frequency voltage application mechanism 17, and the cooling mechanism 18 is controlled.

  Next, an outline of the operation of the dry etching apparatus of this embodiment will be described.

  The tray 4 in which the substrate 2 is accommodated in each of the substrate accommodation holes 9A to 9F is carried into the chamber 3 from the gate 3a by a transfer arm (not shown) and transferred to the tip of the elevating pin 19 at the raised position (at this time) (The tip of the lifting pin 19 is positioned above the substrate susceptor 5). Next, the lift pins 19 are lowered by the drive mechanism 20, whereby the substrate 2 and the tray 4 are placed on the substrate susceptor 5. Specifically, the lower surface 4b of the tray 4 descends to the tray support surface 26 of the ESC 21. When the tray 4 descends toward the tray support surface 26, the substrate placement portions 27A to 27F of the ESC 21 enter the corresponding substrate accommodation holes 9A to 9F of the tray 4 from the lower surface 4b side of the tray 4. When the lower surface 4b of the tray 4 is placed on the tray support surface 26 of the ESC 21, the distance from the tray support surface 26 to the upper surface of the substrate support portion 10 is the distance from the tray support surface 26 to the upper ends of the substrate placement portions 27A to 27F. Therefore, the substrate 2 in each of the substrate accommodation holes 9A to 9F is lifted from the upper surface of the substrate support surface 10 and placed on the upper end portions 27a of the substrate placement portions 27A to 27F.

  Next, a DC voltage is applied from the DC voltage application mechanism 15 to the electrostatic adsorption electrode 28, and the substrate 2 is electrostatically adsorbed to the upper end portions 27a of the individual substrate mounting portions 27A to 27F. Subsequently, spaces between the individual substrate placement portions 27 </ b> A to 27 </ b> F and the lower surface 2 a of the substrate 2 are filled with the heat transfer gas supplied from the heat transfer gas supply mechanism 16 through the supply holes 29. Thereafter, an etching gas is supplied from the etching gas supply source 14 into the chamber 3, and the inside of the chamber 3 is maintained at a predetermined pressure by the vacuum exhaust device 11. Subsequently, a high frequency voltage is applied from the high frequency power source 13 to the ICP coil 11. An induction electric field is generated in the chamber 3 by the high-frequency magnetic field generated by the ICP coil 8, and electrons are accelerated to generate plasma. The substrate 2 is etched by this plasma. Since six substrates 2 can be placed on the substrate susceptor 6 with one tray 4, batch processing is performed. During etching, the refrigerant circulation device 18b circulates the refrigerant in the refrigerant flow path 18a of the metal plate 22 to cool the ESC 21, and the individual heat conduction with the substrate mounting portions 27A to 27F through the heat transfer gas. The substrate 2 is cooled.

  After the etching is finished, the elevating pins 19 are raised by the drive mechanism 20, so that the tray 4 containing the substrate 2 in the substrate accommodation holes 9 </ b> A to 9 </ b> F is raised from the substrate susceptor 5. Thereafter, the tray 4 holding the substrate 2 is carried out of the chamber 3 through the gate 3a by a transfer arm (not shown).

  Next, the structure of the upper end portion 27a of the substrate placement portions 27A to 27F of the ESC 21 in this embodiment will be described in detail. Since the substrate platforms 27A to 27F have the same structure, the substrate platform 27D will be described below.

  An annular projecting portion 41 projecting upward is provided along the outermost peripheral portion of the upper end portion 27a of the substrate platform 27D in plan view. The annular protrusion 41 in the present embodiment has an annular shape in plan view. The upper end surface of the annular protrusion 41 is a flat surface, and functions as a substrate placement surface 41a that directly contacts the lower surface 2a of the substrate 2 placed on the substrate placement portion 27D.

  As shown in FIGS. 6 and 7, the annular projecting portion 41 is divided into an inner portion 41b and an outer portion 41c by an annular groove 42 provided on the upper end surface (substrate mounting surface 41a). In this embodiment, the width W1 (constant width) of the annular protrusion 41 is 3.2 mm, and the widths W2, W3, and W4 (all constant widths) of the inner portion 41b, the annular groove 42, and the outer portion 41c are each 1. .2mm, 0.8mm and 1.2mm. In the present embodiment, the depth De1 of the annular groove 42 (the distance from the substrate mounting surface 41a to the bottom surface of the annular groove 42) is 25 μm.

  A region surrounded by the annular projecting portion 41 of the upper end portion 27a of the substrate mounting portion 27D is a concave portion 43 for filling the heat transfer gas. A large number of short columnar columnar protrusions 47 and 48 that are spaced apart from each other protrude from the bottom surfaces 45a and 46a of the recess 43 upward. The upper end surfaces of the columnar protrusions 47 and 48 are flat surfaces, and the upper end surface of the annular protrusion 41 described above is in direct contact with the lower surface 2a of the substrate 2 placed on the substrate platform 27D, like the flat surface. It functions as the substrate mounting surfaces 47a and 48a. That is, as shown in FIG. 6, the upper end surface (substrate placement surface 41a) of the annular protrusion 41 and the upper end surfaces (substrate placement surfaces 47a and 48a) of the columnar protrusions 47 and 48 are on the same horizontal plane. The lower surface 2a of the substrate 2 placed on the upper end portion 27a of the placement portion 27D is supported by the upper end portion 27a of the substrate placement portion 27D by directly contacting the substrate placement surfaces 41a, 47a, and 48a. The closed space defined by the inner peripheral surface of the annular protrusion 41, the bottom surfaces 45a and 46a of the recess 43, and the lower surface 2a of the substrate 2 is filled with heat transfer gas. In the present embodiment, the diameter DI of the upper end surfaces (substrate mounting surfaces 47a and 48a) of the columnar protrusions 47 and 48 is about 2.5 to 3.0 mm.

  The recess 43 is divided into an inner region 45 and an outer region 46 in plan view. The inner region 45 is a circular region including the center of the upper end portion 27a of the substrate platform 27D, and the outer region 46 is an annular region between the inner region 45 and the annular protrusion 41. Referring to FIGS. 5 to 7 in addition to FIGS. 1 to 3, only one heat transfer gas supply hole 29 is opened at the center of the upper end portion 27a of the substrate mounting portion 27D in plan view. In the present embodiment, no heat transfer gas supply port is provided except for the supply hole 29. However, a plurality of supply holes 29 may be provided in the inner region 45. In particular, when the size of the substrate is large (for example, when it is 6 inches compared to 4 inches in the present embodiment), the substrate mounting portions 27A to 27D are enlarged accordingly. A plurality of supply holes 29 can be provided in the inner region 45 without any particular restriction.

  In the inner region 45 and the outer region 46, the depths De2 and De3 of the recess 43 are different. Specifically, the depth De2 of the recess 43 in the inner region 45 (the distance from the substrate placement surfaces 41a, 47a, 48a to the bottom surface 45a of the recess 43 in the inner region 45) is greater than the depth De2 of the recess 43 in the outer region 46. De3 (distance from the substrate placement surfaces 41a, 47a, 48a to the bottom surface 46a of the recess 43 in the outer region 46) is set shallow. In the present embodiment, the depth De2 of the recess in the inner region 45 is set to about 50 μm, and the depth De3 of the recess 43 in the outer region 46 is set to about 25 μm. From another viewpoint, the height of the columnar protrusion 48 belonging to the outer region 46 is lower than that of the columnar protrusion 47 belonging to the inner region 45 (the former is 50 μm and the latter is 25 μm). The depth De2 of the inner region 45 is set in a range of 40 μm or more and less than 100 μm, and the depth De3 of the outer region 46 is set in a range of 10 μm or more and less than 40 μm. There is preferably a difference of about 10 to 80 μm, particularly about 10 to 50 μm, between the depth De 2 of the inner region 45 and the depth De 3 of the outer region 46.

  Hereinafter, the setting of the size of the inner region 45, that is, the setting of the boundary between the inner region 45 and the outer region 46 will be described with reference to FIG. In the present embodiment, the substrate 2 is 4 inches (about 100 mm) as described above, and the diameter D1 of the substrate platform 27D is set to 97 mm correspondingly. In addition, when the board | substrate 2 is 4 inches, the diameter D1 in planar view of board | substrate mounting part 27D can be set in the range of about 90-100 mm. When the diameter D1 is set to about 100 mm, that is, about the same as the diameter of the 4-inch substrate 2, the substrate support portion 21 is provided in the receiving groove 55 provided on the side wall of the substrate mounting portion 27 as in the second embodiment described later. The structure which accommodates is employ | adopted. The diameter D2 of the inner region 45 is set in the range of 62 mm or more and 87 mm or less with respect to the diameter D1 (= 97 mm) of the substrate platform 27D. In other words, the diameter D2 of the inner region 45 is set in a range from 0.64 times to 0.9 times the diameter D1 (= 97 mm) of the substrate platform 27D. The width W6 of the outer region 46 (including the width W1 of the annular protrusion 41) is set in a range of 5 mm to 17.5 mm according to the diameter D2 of the inner region 45. Table 1 below shows that the diameter D2 of the inner region 45 when the substrate 2 is 4 inches and the diameter D1 of the substrate platform 27D is 97 mm, and the ratio D2 / of the diameter D2 of the inner region 45 to the diameter D1 of the substrate platform 27D. A relationship between D1 and the width W6 of the outer region 46 is shown.

  Table 2 below shows the diameter D2 of the inner region 45, the ratio D2 / D1, and the width W6 of the outer region 46 when the substrate 2 is 6 inches (about 150 mm) and the diameter D1 of the substrate mounting portion 27D is 147 mm. The relationship is shown. In addition, when the board | substrate 2 is 6 inches, the diameter D1 in planar view of board | substrate mounting part 27D can be set in about 140-150 mm. When the diameter D1 is set to about 150 mm, that is, about the same as the diameter of the 6-inch substrate 2, the substrate support portion 21 is provided in the receiving groove 55 provided on the side wall of the substrate mounting portion 27 as in the second embodiment described later. The structure which accommodates is employ | adopted. As shown in Table 2, when the substrate 2 is 6 inches, the diameter D2 of the inner region 45 is set in the range of 0.73 times to 0.93 times the diameter D1 (= 147 mm) of the substrate platform 27D. The

  Table 3 below shows the diameter D2 of the inner region 45, the ratio D2 / D1, and the width W6 of the outer region 46 when the substrate 2 is 3 inches (about 76 mm) and the diameter D1 of the substrate mounting portion 27D is 73 mm. The relationship is shown. When the substrate 2 is 3 inches, the diameter D1 of the substrate platform 27D in plan view can be set in the range of about 66 to 76 mm. When the diameter D1 is set to about 100 mm, that is, about the same as the diameter of the 3-inch substrate 2, the substrate support portion 21 is provided in the receiving groove 55 provided on the side wall of the substrate mounting portion 27 as in the second embodiment described later. The structure which accommodates is employ | adopted. As shown in Table 3, when the substrate 2 is 3 inches, the diameter D2 of the inner region 45 is set in the range of 0.6 to 0.86 times the diameter D1 (= 73 mm) of the substrate platform 27D. The

Table 4 below shows the diameter D2 of the inner region 45, the ratio D2 / D1, and the width W6 of the outer region 46 when the substrate 2 is 2 inches (about 50 mm) and the diameter D1 of the substrate mounting portion 27D is 48 mm. The relationship is shown. When the substrate 2 is 2 inches, the diameter D1 of the substrate platform 27D in plan view can be set in a range of about 45 to 50 mm. When the diameter D1 is set to about 50 mm, that is, about the same as the diameter of the 2-inch substrate 2, the substrate support portion 21 is provided in the receiving groove 55 provided on the side wall of the substrate mounting portion 27 as in the second embodiment described later. The structure which accommodates is adopted.
As shown in Table 4, when the substrate 2 is 2 inches, the diameter D2 of the inner region 45 is set in the range of 0.5 to 0.8 times the diameter D1 (= 48 mm) of the substrate platform 27D. The

  As apparent from Tables 1 to 4, when the substrate 2 is 2 inches (about 50 mm) to 6 inches (about 150 mm), the diameter D2 of the inner region 45 is equal to the diameter D1 (= 45 to 45) of the substrate mounting portion 27D. 150 mm) is set in a range of 0.5 to 0.93 times.

  Next, the reason why the depth De3 of the recess 43 in the outer region 46 is set deeper than the depth De2 of the recess 43 in the inner region 45 will be described.

  During dry etching, the vicinity of the peripheral edge of the substrate 2 in plan view is mainly cooled by heat conduction due to the lower surface 2a directly contacting the upper end surface (substrate mounting surface 41a) of the annular protrusion 41. On the other hand, during the dry etching, the center side of the substrate 2 with respect to the periphery is closer to the lower surface 2a of the substrate 2 and the substrate mounting portion 27D via the heat transfer gas (He gas in this embodiment) filled in the recess 43. It is cooled by heat transfer with the upper end 27a. When the substrate 2 is an SF substrate and has a high etching rate of about 120 mm / min, the high pressure power is applied to the IPC coil 8 and the substrate susceptor 5 with a low pressure (for example, 0.6 Pa) in the chamber 3 and a high frequency power. . Therefore, in order to cool the substrate 2 to an appropriate temperature (about 110 ° C. in this embodiment), it is necessary to set the gas pressure of the heat transfer gas filled in the recess 43 to a high pressure of 2000 Pa or higher (2600 Pa in this embodiment). There is.

  In the upper graph of FIG. 8, the pressure of the heat transfer gas in the concave portion 43 (the supply hole 29 is defined in the concave portion 43 when the depths De2 and De3 of the inner region 45 and the outer region 46 are assumed to be constant at 25 μm. The relationship between the pressure at a position corresponding to the center of the substrate 2 provided) and the temperature of the substrate 2 is shown (the solid line indicates the vicinity of the periphery of the substrate and the dotted line indicates the center of the substrate). Further, the broken line in the upper graph of FIG. 6 indicates the pressure of the heat transfer gas in the recess 43 from the center to the peripheral edge of the substrate 2 in this case. As shown in the lower graph of FIG. 8, when the gas pressure of the heat transfer gas is 1300 to 10140 Pa, the heat transfer gas is a transition region, and the heat transfer coefficient between the substrate 2 and the substrate platform 27D. Depends on both the pressure of the heat transfer gas and the distance between the lower surface 2a of the substrate 2 and the upper end portion 27a of the substrate mounting portion 27D (depth of the recess 43).

  As shown by the broken line in the upper graph of FIG. 6, when the depth of the recess 43 is constant at a shallow depth (25 μm), heat transfer from the center of the substrate 2 provided with the supply hole 29 toward the periphery. Since the gas diffusivity is not sufficient, the gradient of the pressure drop of the heat transfer gas from the center of the substrate 2 toward the periphery is large. Therefore, as shown in the upper graph of FIG. 8, if the depth of the concave portion 43 is 25 μm and shallow, even when the supply pressure of the heat transfer gas from the supply hole 29 is 2600 Pa and is sufficiently high, There is a temperature difference exceeding 10 ° C. between the temperature (98 ° C.) and the temperature at the center of the substrate 2 (87 ° C.). In the present embodiment, the depth De3 of the recess 43 in the inner region 45 is set deep (50 μm). By increasing the depth De3 and improving the diffusibility of the heat transfer gas, as shown by the solid line in the upper graph of FIG. The gradient of the pressure drop becomes small (the pressure distribution of the heat transfer gas in the inner region 45 is made uniform). This is presumably because the greater the depth of the recess 43, the lower the resistance to diffusion of the heat transfer gas flowing from the supply hole 29 in the recess 43, and the heat transfer gas diffusivity is improved. Since the cooling effect of the substrate 2 becomes uniform when the pressure distribution is made uniform, the substrate temperature distribution is made uniform. Then, as described with reference to FIG. 16, when the substrate temperature distribution is made uniform, the etching rate and the shape obtained by etching are made uniform.

  This is the reason why the depth De2 of the inner region 45 is set deep. Next, the reason why the depth De3 of the outer region 46 is set to be shallow will be described.

  A small amount of heat transfer gas leaks from the recess 43 into the chamber 3 through a fine gap between the upper end surface (substrate mounting surface 41 a) of the annular protrusion 41 and the lower surface 2 a near the periphery of the substrate 2. If the depth De3 of the outer region 46 of the recess 43 is set to the same depth as the inner region, the pressure of the heat transfer gas filled in the recess 43 near the periphery of the substrate 2 becomes excessively high. Due to this excessively high pressure, the heat transfer gas in the recess 43 leaks from only one or a plurality of specific locations on the periphery of the substrate 2 in plan view, and the recess 43 from other locations on the periphery of the substrate 2. There is a risk that the heat transfer gas inside will not leak. Such non-uniform leakage of the heat transfer gas from the recess 43 causes in-plane variations in the temperature of the substrate 2 and causes in-plane variations in the plasma processing. In this embodiment, the depth De3 of the outer region 46 is set shallower (50 μm) than the depth De2 of the inner region 45, and the gradient of the pressure drop of the heat transfer gas toward the periphery of the substrate 2 is larger than the inner region 45. doing. And by increasing the gradient of the pressure drop, non-uniform heat transfer gas leakage from the recess 43 (leakage of heat transfer gas from only a specific portion of the periphery of the substrate 2) does not occur. The pressure of the heat transfer gas in the recess 43 near the periphery of the substrate 2 is reduced.

  As described above, considering both the gas pressure distribution and the prevention of uneven leakage of the heat transfer gas, the depth De2 of the recess 43 is increased in the inner region 45, while the depth De3 of the recess 43 is increased in the outer region 46. Is set shallower.

  In the outer region 46 in which the depth De3 of the concave portion 43 is set shallow, the distance between the lower surface 2a of the substrate 2 and the bottom surface of the concave portion 43 is shortened so that the heat transfer coefficient between the substrate 2 and the substrate mounting portion 27D is large. Become. The increase in the heat transfer coefficient is caused in the outer region 46 by setting the depth De3 of the recess 43 deep (increasing the gradient of the pressure drop of the heat transfer gas) in order to prevent uneven heat transfer gas leakage. The decrease in the cooling efficiency of the substrate 2 is compensated. As a result, the difference in the cooling efficiency of the substrate 2 in the inner region 46 and the outer region 45 due to the different depths De2 and De3 of the recess 43 is suppressed to the minimum.

  As described above, by setting the depth De2 of the concave portion 43 deep in the inner region 45 and setting the depth De3 of the concave portion 43 shallower than the inner region 45 in the outer region 46, the heat transfer filled in the concave portion 43 is performed. The gas pressure of the gas is as high as required for etching at a high etching rate of a difficult-to-etch material such as the substrate 2 made of SF or a GaN epitaxial layer formed on the substrate 2 (for example, about 1300 to 3000 Pa and 2600 Pa in this embodiment). Even so, the in-plane distribution of the substrate temperature can be made uniform, and the in-plane variation of the plasma processing can be eliminated.

  Gas distribution grooves 51, 52, 53 and 54 are provided on the bottom surfaces 45 a and 46 a of the recess 43. As shown in FIG. 5, the gas distribution grooves 51 to 53 are annular grooves arranged concentrically in a plan view, and the gas distribution groove 54 is the center of the recess 43 in the plan view (the upper end of the substrate mounting portion 27A). This is a linear groove extending radially outward from the center of the portion 27a toward the annular protrusion 41. In the present embodiment, six straight gas distribution grooves 54 are arranged at equiangular intervals in plan view. The individual straight gas distribution grooves 54 and the annular gas distribution grooves 51 to 53 communicate with each other at their intersecting positions, and the heat transfer gas flows from the gas distribution grooves 54 to the gas distribution grooves 51 to 53 or It is designed to flow in reverse.

  The gas distribution groove 51 is provided at a position relatively close to the center side in the inner region 45. Further, the gas distribution groove 52 is provided at the boundary between the inner region 45 and the outer region 46, that is, the portion of the bottom surface 45 a of the recess 43 in the inner region 45 that is in contact with the outer region 46. Further, the gas distribution groove 53 is provided at a boundary between the outer region 46 and the annular protrusion 41, that is, a portion of the bottom surface 46 a of the recess 43 in the outer region 46 that is in contact with the inner peripheral surface of the annular protrusion 41. In this embodiment, the width W5 of the gas distribution grooves 51 to 54 is set to about 1.0 mm.

  By providing the gas distribution grooves 51 to 54, the diffusibility of the heat transfer gas (He gas) supplied into the recess 43 from the supply hole 29 is improved. As a result, the uniformity of the pressure distribution of the heat transfer gas in the recess 43 is further improved, so that the uniformity of the substrate temperature distribution is further improved, and the in-plane variation of the etching rate and the etching shape can be further reduced.

  In this embodiment, the depth De4 of the gas distribution grooves 51 to 54 (distances from the substrate placement surfaces 41a, 47a, and 48a to the bottom surfaces of the gas distribution grooves 51 to 54) is set to 100 μm. The reason is as follows. When the pressure of the He gas filled in the recess 43 is 2600 Pa or more as in the present embodiment, discharge (so-called “so-called”) occurs on the lower surface 2a side of the substrate 2 when the distance between the lower surface 2a of the substrate 2 and the surface of the ESC 21 is about 300 μm or more. Bach fire) occurs. Further, when the substrate 2 is formed by forming a GaN epitaxial layer on the SF substrate, a warp of about 150 μm at maximum occurs in the direction in which the substrate 2 moves away from the ESC 21. Therefore, the depth De4 of the gas distribution grooves 51 to 54 is less than 100 μm, which is a difference obtained by subtracting from 300 μm for preventing discharge to 150 μm considering warpage of the substrate 2 and 50 μm considering other factors such as displacement. It is preferable to set. In addition, since the diffusion of heat transfer gas cannot be effectively promoted if it is excessively shallow, it is preferable to set the depth De4 of the gas distribution grooves 51 to 54 to 50 μm or more.

  As described above, in the dry etching apparatus 1 of the present embodiment, the six substrate 2 is formed by the corresponding substrate mounting portions 27A to 27F of the ESC 21 entering the individual substrate receiving holes 9A to 9F of the tray 4. Are placed on the upper end portions 27a of the substrate placement portions 27A to 27F. That is, the placement of the corresponding substrate placement portions 27A to 27F on each substrate 2 is guided by the insertion of the substrate placement portions 27A to 27F into the substrate accommodation holes 9A to 9F. Therefore, the positioning accuracy with respect to the substrate placement surfaces 41a, 47a, 48a of the individual substrates 2 is high. Thus, even in the point that the substrate 2 is placed with high accuracy on the substrate placement surfaces 41a, 47a, and 48a, the in-plane distribution of the substrate temperature for each individual substrate 2 is made uniform, and the etching rate and the etching shape are changed. In-plane variation can be reduced.

(Experimental example)
The substrate 2 was actually dry etched with the dry etching apparatus of this embodiment, and the etching rate, the taper angle of the side wall of the structure formed by etching, and the substrate temperature during etching were measured. Substrate 2 (4 inches) was SF. The heat transfer gas was a mixed gas of BCl ₃ and Ar, and the flow rates of both BCl ₃ gas and Ar gas were 100 sccm. The pressure in the chamber 3 was 0.6 Pa. The high frequency power applied to the ICP coil 8 was 1500 W, and the high frequency power of the bias applied to the substrate susceptor 5 was 1500 W. The DC voltage applied to the electrostatic chucking electrode of the ESC 21 was 2.56 kV. The supply pressure of He gas (heat transfer gas) from the supply hole 29 into the recess 43 was 2600 Pa. The temperature of the substrate susceptor 5 is maintained at 45 ° C. The etching time was 545 seconds. As shown in FIG. 9, a large number of cylinders 2b having a height of 1.0 μm and a diameter of 3.0 μm were formed on the substrate 2 at a pitch of 5.0 μm. The shape of the cylinder 2b is measured at a total of five points including a measurement point P1 that is the center of the substrate 2 and four measurement points P2 to P5 that are arranged at an equal angular interval 1.5 mm from the outer periphery of the substrate 2. did. Specifically, the taper angle θ of the side walls of the plurality of cylinders 2b was measured for each measurement point P1 to P5 using a scanning electron microscope. A value obtained by dividing the difference obtained by subtracting the minimum value from the maximum value by the average value for each measurement point P1 to P5 was obtained, and the value was defined as the taper angle θ at the measurement points P1 to P50. The substrate temperature was measured at one of the center (measurement point P1) of the substrate 2 and the peripheral measurement points P2 to P5 using a thermo label.

  The measurement results are as follows. The etching rate was 110 nm / min. The substrate temperature was 87 ° C. at the center and 98 ° C. on the peripheral side. That is, the temperature difference between the center and the peripheral side was about 5 ° C., and it was confirmed that the in-plane variation of the substrate temperature during etching was very small. Further, the taper angle θ was 60 ° at the center, whereas it was 65 ° on the peripheral side. That is, the difference in taper angle θ between the center and the periphery is about 5 °, and it has been confirmed that uniform plasma processing in which in-plane variation is eliminated can be realized.

  In the present embodiment, for example, as shown in the enlarged view in FIG. 6, the annular projecting portion 41 is divided into two annular portions, that is, an inner portion 41 b and an outer portion 41 c by one annular groove 42. That is, the annular protrusion 41 has a double structure. As shown in FIG. 10A, the annular protrusion 41 may have a triple structure divided into three annular portions 41d, 41e, 41f by concentric annular grooves 42, 42 'in two plan views. Even if the annular protrusion 41 has such a double structure or a triple structure, it is possible to improve the cooling effect of the substrate 2 and improve the uniformity of the substrate temperature portion. The reason will be described below.

  First, when the annular projecting portion 41 has a double or triple structure, the leakage from the recess 43 through the contact portion between the lower surface 2a near the periphery of the substrate 2 and the upper end surface (substrate mounting surface 41a) of the annular projecting portion 41a. The hot gas path is a kind of labyrinth. Therefore, due to the so-called labyrinth effect, leakage of heat transfer gas is prevented from a minute gap between the upper end surface of the annular protrusion 41 and the lower surface 2a of the substrate 2. By suppressing this leakage, the gas pressure of the heat transfer gas can be maintained at a high pressure in the outer region 46 of the recess 43, particularly in the vicinity of the annular protrusion 41. As a result, the value of the heat transfer coefficient between the substrate 2 and the substrate platform 27D in the vicinity of the periphery of the substrate 2 can be increased.

  As shown in FIG. 10B, when the annular protrusion 41 is not provided with an annular groove and has a single structure, the gas pressure of the heat transfer gas is reduced in the vicinity of the annular protrusion 41 (the solid line in FIG. Thus, the case where the path of the heat transfer gas is made labyrinth-like by the annular groove 42 is shown, and the broken line shows the case where the upper end surface (substrate mounting surface 41a) of the annular protrusion 41 is simply a flat surface). The temperature of the substrate 2 was measured under the same conditions as in the experimental example described above, except that the annular groove 42 was not provided (the annular protrusion 41 has a single structure). It was 126 ° C. That is, the temperature difference between the center and the peripheral side exceeds 40 ° C., and the in-plane variation of the substrate temperature during etching is large. This is because the annular protrusion 41 has a single structure, and thus leakage of heat transfer gas cannot be effectively prevented from a minute gap between the upper end surface of the annular protrusion 41 and the lower surface 2a of the substrate 2. This is thought to be because the pressure of the heat transfer gas was reduced on the peripheral side.

  As shown in FIG. 10C, when the annular protrusion 41 has a quadruple structure in which the four annular portions 41d to 41g are separated by three concentric annular grooves 42, 42 ', and 42' ', the annular grooves 42 to 42 ′ and the widths of the annular portions 41d to 41g are the same as in this embodiment (the widths W2, W3, and W4 of the inner portion 41b, the annular groove 42, and the outer portion 41c are 1.2 mm, 0.8 mm, and 1.2 mm, respectively). Then, the width W1 of the annular protrusion 41 reaches about 7.2 mm. When the width of the annular protrusion 41 increases to this extent, the pressure of the heat transfer gas filled in the recess 43 near the periphery of the substrate 2 becomes excessively high. As a result, the heat transfer gas in the recess 43 leaks from only one or a plurality of specific locations on the periphery of the substrate 2 in plan view, and the heat transfer in the recess 43 from other locations on the periphery of the substrate 2. There is a risk that gas will not leak. Such non-uniform leakage of the heat transfer gas from the recess 43 causes in-plane variations in the temperature of the substrate 2 and causes in-plane variations in the plasma processing. Therefore, the annular protrusion 41 is preferably not a quadruple or more structure but a double or triple structure.

(Second Embodiment)
The dry etching apparatus 1 according to the second embodiment of the present invention shown in FIGS. 12A to 14 has a structure for further improving the positioning accuracy of the substrate 2 with respect to the substrate mounting portions 27A to 27F of the ESC 21.

  Referring to FIGS. 12A and 12B, three protruding substrate support portions 10 are provided on the hole walls of the substrate accommodation holes 9 </ b> A to 9 </ b> F of the tray 4 at intervals in the circumferential direction. Specifically, when viewed from the penetration direction of the substrate accommodation holes 9A to 9F, the three substrate support portions 21 are provided at equiangular excess intervals (120 ° intervals) with respect to the centers of the substrate accommodation holes 9A to 9F. . Referring to FIGS. 13 and 14 together, three accommodation grooves 55 extending in the vertical direction from the upper end portion 27a toward the tray support surface 26 are formed on the side peripheral walls of the individual substrate placement portions 27A to 27F of the ESC 21. Has been. In the plan view, three receiving grooves 55 are provided at equiangular intervals with respect to the centers of the individual substrate placement portions 27A to 27F in the plan view. The size and shape of the receiving groove 55 in plan view are set slightly larger than the protruding substrate support portion 19.

  As shown in FIGS. 13 and 14, the portion of the annular protrusion 41 and the gas distribution groove 53 that passes through the accommodation groove 55 partially detours inward so as to surround the accommodation groove 55. That is, although the accommodation grooves 55 are provided in the substrate mounting portions 27A to 27F, the annular protrusion 41 and the gas distribution groove 53 are endless as in the first embodiment.

  As shown in FIG. 12A, when the individual substrate receiving holes 9A to 9F of the tray 4 are arranged in a plan view above the individual substrate placement portions 27A to 27F of the ESC 21, the tray 4 is When descending toward the ESC 21, the three substrate support portions 21 of the individual substrate accommodation holes 9 </ b> A to 9 </ b> F enter the inside from the upper ends of the accommodation grooves 55 of the corresponding substrate mounting portions 27 </ b> A to 27 </ b> F and enter the accommodation grooves downward. Go down 55. Accordingly, in this case, the tray 4 can be lowered until the lower surface 4b of the tray 4 reaches the tray support surface 26 and the lower surface 2a of the substrate 2 is placed on the substrate placement surfaces 41a, 47a, 48a. However, when the positions of the individual substrate receiving holes 9A to 9F in the plan view with respect to the individual substrate placement portions 27A to 27F are shifted, the positions of the substrate support portion 10 and the receiving groove 55 in the plan view are also shifted. The substrate support portion 10 cannot enter the accommodation groove 55, interferes with the substrate placement portions 27A to 27F, and the substrate placement portions 27A to 27F are not inserted into the substrate accommodation holes 9A to 9F. Thus, the positioning accuracy of the individual substrates 2 with respect to the substrate placement surfaces 41a, 47a, and 48a can be further increased by providing the protruding substrate support 10 and the accommodation groove 55.

  By adopting the protruding substrate support portion 10 and the receiving groove 55 to increase the positioning accuracy, the size and shape of the substrate 2 and the upper end portions 27a of the substrate mounting portions 27A to 27F are substantially matched. be able to. In other words, it is necessary to set the dimensions of the substrate platforms 27A to 27F smaller than the substrate 2 in consideration of the case where the positions of the substrate platforms 2A to 27F with respect to the upper end portions 27a are shifted. Absent. As a result, the substrate mounting surface 41a, which is the upper end surface of the annular projection 41, contacts the vicinity of the outermost peripheral edge of each substrate 2, thereby improving the cooling effect in the vicinity of the peripheral edge of the substrate 2 and uniformity of the substrate temperature distribution. Is further improved. For example, if the diameter of the substrate 2 is 100 mm, the diameters of the substrate mounting portions 27A to 27F can be set to the same 100 mm.

  Since other configurations and operations of the second embodiment are the same as those of the first embodiment, the same elements are denoted by the same reference numerals and description thereof is omitted.

  The present invention is not limited to the above-described embodiment, and various modifications such as those listed below are possible.

  The ESC 21 electrostatically attracts the lower surface 4b of the tray 4 to the tray support surface 26 by an electrostatic attracting electrode 28 for electrostatically attracting the substrate 2 or by an electrostatic attracting electrode provided separately from the electrostatic attracting electrode 28. You may hold by. Alternatively, the lower surface 4b of the tray 4 may be electrostatically attracted to the tray support surface 26 of the ESC 21 by self electrostatic adsorption. Even when the pressure in the chamber 3 is low (0.6 Pa) as in the above-described embodiment, the hole walls of the substrate receiving holes 9A to 9F of the tray 4 and the substrate support 10 to the substrate 2 due to radiation or convection are used. There is a slight heat conduction to the periphery. Since the tray 4 is electrostatically attracted to the ESC 21 and cooled in the same manner as the substrate 2, even the slight heat transfer effect due to radiation and convection is eliminated, so that the uniformity of the substrate temperature is further improved.

  Although the present invention has been described by taking a dry etching apparatus as an example, the present invention can also be applied to other plasma processing apparatuses including a chemical vapor deposition (CVD) apparatus.

DESCRIPTION OF SYMBOLS 1 Dry etching apparatus 2 Substrate 2a Lower surface 3 Chamber 3a Gate 3b Exhaust port 3c Etching gas supply port 4 Tray 4a Upper surface 4b Lower surface 5 Substrate susceptor 7 Top plate 8 ICP coil 9A-9F Substrate accommodation hole 10 Substrate support part 11 Vacuum exhaust device 12 Matching circuit 13 High frequency power source 14 Etching gas supply source 15 DC voltage application mechanism 16 Heat transfer gas supply mechanism 16a Cut-off valve 16b Heat transfer gas supply source 16c Supply flow path 16d Flow meter 16e Pressure gauge 16f Flow control valve 16g Discharge flow path 16h Exhaust port 17 High-frequency voltage application mechanism 18 Cooling mechanism 18a Refrigerant flow path 18b Refrigerant circulation device 19 Lifting pin 20 Drive mechanism 21 Electrostatic chuck (ESC)
22 Metal plate 23 Spacer plate 24 Bonding layer 26 Tray support surface 27A to 27F Substrate mounting portion 27a Upper end portion 28 Electrostatic chucking electrode 29 Supply hole 30 Controller 41 Annular protrusion 41a Substrate mounting surface 41b Inner portion 41c Outer portion 42 Annular groove 43 recess 45 inner region 45a bottom surface 46 outer region 46a bottom surface 47, 48 columnar projection 47a, 48a substrate mounting surface 51, 52, 53, 54 gas distribution groove 55 receiving groove 100 tray 100a substrate receiving hole 101 substrate 102 substrate susceptor 103 ESC
104 Circulating path 105 Substrate placement portion 106 Projection portion 106a Substrate placement surface 107 Recessed portion 108 Columnar projection 108a Substrate placement surface

Claims (6)

A depressurizable chamber for generating plasma;
A substrate holder provided in the chamber, comprising an electrostatic chuck for electrostatically holding the substrate placed on the substrate platform, comprising at least one substrate platform on which a substrate is placed And
A heat transfer gas supply mechanism for supplying a heat transfer gas between the substrate and the substrate mounting portion;
A cooling mechanism for cooling the substrate holder,
The upper end portion of the substrate mounting portion of the electrostatic chuck is
An annular protrusion provided on the periphery,
A plurality of protrusions each having an upper end surface constituting a substrate mounting surface for mounting the lower surface of the substrate together with the upper end surface of the annular protrusion on the same plane;
A recess that is a region surrounded by the annular protrusion,
The annular protrusion includes double or triple annular portions separated from each other by an annular groove provided on an upper end surface,
The concave portion, which is a region surrounded by the annular protrusion, includes an inner region including the center of the upper end portion of the substrate platform, and an outer region between the inner region and the annular protrusion, The second depth from the substrate placement surface to the bottom surface in the outer region is shallower than the first depth from the substrate placement surface to the bottom surface in the inner region,
The heat transfer gas from the heat transfer gas supply mechanism is filled with the substrate mounting the recess which is closed by the placed the substrate surface, the plasma processing apparatus. 2. The plasma processing apparatus according to claim 1, wherein an outer dimension of the inner region in plan view is not less than 0.5 times and not more than 0.93 times of an outer dimension of the substrate placement unit in plan view. The plasma processing apparatus according to claim 1 or 2 , wherein the first depth is not less than 40 µm and less than 100 µm, and the second depth is not less than 10 µm and less than 40 µm. The recess is
A first gas distribution groove provided at a boundary between the inner region and the outer region;
A second gas distribution groove provided at a boundary between the outer region and the annular protrusion;
And a third gas distribution groove communicating with said first and second gas distribution groove is provided so as to extend toward the annular projecting portion from the center side, one of claims 1 to 3 2. The plasma processing apparatus according to item 1. 5. The plasma processing apparatus according to claim 4 , wherein a third depth from the substrate mounting surface to a bottom surface of the first to third gas distribution grooves is 100 μm or less. A tray that includes a plurality of substrate accommodation holes penetrating in the thickness direction in which the substrates are accommodated, and a substrate support portion protruding from a hole wall of each of the substrate accommodation holes, and is capable of carrying the substrates in and out of the chamber. Further comprising
The electrostatic chuck includes a plurality of the substrate mounting portions and a tray support portion from which these substrate mounting portions protrude,
When transporting the substrate, the outer peripheral edge portion of the lower surface of the substrate housed in the substrate housing hole is supported by the substrate support portion,
During the processing of the substrate, the tray is lowered toward the substrate holding portion, so that the substrate placement portion corresponding to each of the substrate accommodation holes is inserted from the lower surface of the tray, and the lower surface of the tray is While being placed on the tray support portion of the electrostatic chuck, the distance from the tray support portion to the upper surface of the substrate support portion is shorter than the distance from the tray support portion to the substrate placement surface, The substrate is lifted from the upper surface of the substrate support portion and the lower surface is placed on the substrate placement surface,
The plasma processing apparatus according to claim 1, wherein the tray is electrostatically held by the tray holding portion of the electrostatic chuck.

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