JP2006156691A - Substrate retaining member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate retaining member facilitating the transmission of heat of plasma atmosphere to a wafer immediately after the generation of plasma and suppressing the raise of a wafer temperature while being capable of shortening a time until obtaining a stationary condition wherein the surface temperature of the wafer becomes a given temperature. <P>SOLUTION: The one side main surface of a plate type substrate 2 or the substrate retaining member 1 is a mounting surface 2a for mounting the wafer W, and the other side main surface of the same is connected to one side main surface of a plate type pedestal 7. The pedestal 7 having a thermal conductivity larger than that of the plate type substrate 2 is employed and an annular recess 7a is formed at the central part of the other side main surface of the same. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a substrate holding member for fixing a semiconductor wafer used in a semiconductor manufacturing apparatus, and more particularly to a substrate holding member used in a film forming process such as CVD, PVD, sputtering, or an etching process.

  Conventionally, in a film forming process such as CVD, PVD, sputtering, etc., which is a processing process of a semiconductor wafer for manufacturing a semiconductor device (hereinafter referred to as a wafer) and an etching process, a uniform film with a uniform thickness is formed on the wafer to be processed. It is important to form a film and to etch the formed film at a uniform depth, and a substrate holding member that can easily manage the temperature of the wafer is used.

  As the substrate holding member, for example, one main surface of the plate-shaped substrate is used as a mounting surface on which the wafer is placed, and an electrode for suction is provided on the mounting surface side in the plate-shaped substrate, and the wafer is mounted on the mounting surface. There is an electrostatic chuck that attracts and fixes a wafer to a mounting surface by developing an electrostatic attracting force between the wafer and an electrode.

  There is also a substrate holding member that includes a heating electrode in the vicinity of the other main surface of the plate-like substrate and can heat the wafer. The electrostatic adsorption electrode and the heating electrode are each electrically connected to a power supply terminal, and a voltage is applied between the wafer and the electrode by placing a wafer on the mounting surface and applying a voltage to the power supply terminal. The wafer can be firmly attracted and fixed to the mounting surface by developing an electrostatic attraction force. At the same time, the wafer can be heated to a high temperature by the heating electrode.

  In addition, the substrate holding member with a metal pedestal bonded to the lower surface of the plate-like substrate can efficiently generate plasma above the wafer by applying high-frequency power between the pedestal and the counter electrode. It is.

  In recent years, large-scale LSIs have led to an increase in the diameter of Si wafers, increasing the number of wafers that can be processed within a unit time (throughput), more uniform film formation accuracy, and etching accuracy. There has been a demand for a substrate holding member having the ability. In a semiconductor manufacturing apparatus, when an etching process or the like is performed on a wafer in a plasma atmosphere, the surface of the wafer placed on the mounting surface of the substrate holding member is exposed to plasma such as Ar and becomes high temperature, and the resist film on the surface is baked. Such problems arise. Therefore, in order to suppress this temperature rise, a pedestal having a temperature adjusting function is provided on the lower surface of the plate-like substrate on which the wafer is placed to adjust the temperature of the wafer.

In Patent Document 1, as shown in FIG. 3, an In layer is plated and fused on a surface where a pedestal 26 made of Al and a plate-like base 21 made of Al ₂ O ₃ are joined, and the plate-like base 21 and the pedestal are bonded. There has been proposed a substrate holding member 20 that supplies gas or the like from a through-hole 24 that communicates with 26 and cools the wafer W placed on the placement surface 21a.

  In Patent Document 2, as shown in FIG. 4, a plate-like base 31 and a pedestal 34 made of SiC and Al are joined via a metal joining material 33 such as a brazing material or solder, and a cooling jacket is formed on the bottom of the pedestal 34. A substrate holding member 30 that cools the wafer W placed on the placement surface 31a by bringing them into contact with each other is proposed.

In Patent Document 3, a plate-like substrate is brazed on a pedestal made of a carbon material or a carbon composite material, a cooling medium circulation groove is formed in the bottom surface of the pedestal, and the cooling medium is caused to flow through the groove. A substrate holding member for cooling the wafer W has been proposed.
JP-A-3-3249 Japanese Patent Laid-Open No. 10-32239 JP-A-8-107140

  However, the conventional substrate holding member shown in FIG. 4 has a large pedestal 34 and is not designed with heat capacity taken into consideration, so the heat capacity is generally large, and heat can be efficiently obtained simply by attaching a cooling member to the lower surface of the pedestal. It was insufficient to diffuse out of the substrate holding member well. Therefore, for example, there is a problem that the heat of the plasma atmosphere is transmitted to the wafer immediately after the plasma is generated and the temperature of the wafer continues to rise. That is, there is a problem that the time until the amount of heat applied to the wafer and the amount of heat flowing out of the substrate holding member 30 are balanced is long, and the time until the temperature of the surface of the wafer W reaches a constant state is long. .

  Further, in the conventional substrate holding member shown in FIG. 3, the temperature distribution on the surface of the wafer W placed on the mounting surface 21a is a ring shape in which the temperature at the center and the outer edge is low and the temperature at the middle is high, It has been difficult to form a uniform film with a uniform thickness on the wafer W and to etch the formed film with a uniform depth.

  In order to efficiently release the heat of the wafer W heated by plasma, it is necessary to increase the thermal conductivity of the pedestal. Therefore, the pedestal 26 made of Al and the plate-like substrate 21 are joined together, but when the cooling cycle of −40 to 100 ° C. required in the film forming process and the etching process such as CVD, PVD, and sputtering is repeated, the Al Due to the difference in thermal expansion coefficient between the pedestal 26 and the plate-like substrate 21, the stress generated at the bonding interface is large, and there is a possibility that a gap is formed on the bonding surface between the plate-like substrate 21 and the pedestal 26. For this reason, the heat transfer coefficient of the bonding surface partially changes, and the time until the temperature of the wafer W partially rises immediately after plasma generation or the temperature of the wafer W reaches a steady state is long. There was a problem that the temperature difference was large.

  In addition, the substrate holding member in which a cooling medium circulation groove is drilled in the bottom surface of the pedestal made of a composite material and the cooling medium is directly flowed into the groove, the cracking medium enters the vacuum chamber through the crack when the cradle is cracked. There was a possibility that the vacuum chamber itself could not be used due to leakage.

  In addition, in the semiconductor manufacturing apparatus, it is necessary to periodically remove the substrate holding member from the apparatus in order to wash away dirt and particles accumulated on the mounting surface and the like. However, since the cooling medium is caused to flow in the groove, it is necessary to attach piping or the like for the cooling medium directly to the pedestal by some means, and there is a problem that the substrate holding member cannot be easily attached or detached.

  In view of the above problems, the present invention has proposed a substrate holding member suitable for use in a semiconductor manufacturing apparatus as a result of intensive studies. That is, the present invention is a substrate holding member in which one main surface of a plate-like substrate is a mounting surface on which a wafer is placed, and the other main surface is bonded to one main surface of a plate-like pedestal, A material having a higher thermal conductivity than the plate-like substrate is used, and a ring-shaped recess is formed at the center of the other main surface.

  An electrode for adsorption is provided inside the plate-like substrate.

  The diameter of the recess is smaller than the diameter of the placement surface.

  The depth tc of the recess is 0.3 to 0.7 times the thickness t of the pedestal.

  A cooling member is disposed on the bottom surface of the recess.

  The size of the C surface and / or R surface of the corner portion of the recess is 0.5 to 5.0 mm.

  The convex portion formed by the concave portion is provided with a through-hole penetrating the plate-like substrate and the pedestal, and a groove communicating with the through-hole is formed on the mounting surface.

  The pedestal has a thermal conductivity of 160 W / (m · K) or more.

  The plate-like substrate is made of a ceramic containing any one of nitride and carbide.

  The pedestal is a composite material made of metal and ceramic.

  The pedestal is mainly composed of Al, Si, and SiC.

  The board | substrate holding member of this invention can remove a heat | fever efficiently from a recessed part inner surface by making the heat capacity of the whole pedestal small by providing a ring-shaped recessed part in the center part of the other main surface of a pedestal. That is, since the heat from the plasma atmosphere immediately after the plasma generation can be easily transmitted to the wafer W, the wafer W temperature is increased, and even if the heat is transmitted from the mounting surface to the pedestal, the heat is easily transmitted efficiently by the concave portion, thereby increasing the wafer W temperature. It is possible to shorten the time until the steady state where the surface temperature of the restraining wafer W becomes a constant temperature.

  Further, by providing a ring-shaped recess at the center of the other main surface of the pedestal, it is possible to remove heat from the central portion of the surface of the wafer W and the peripheral portion. Is uniform, and a uniform film with a uniform thickness can be formed on the wafer W, or the formed film can be etched with a uniform depth.

  In addition, since the plate-like substrate and the pedestal are joined and a composite material is used as the pedestal material, it is subjected to a cooling cycle of −40 to 100 ° C. required in the film forming process and the etching process such as CVD, PVD, and sputtering. However, the thermal stress at the bonding interface generated by the difference in thermal expansion between the plate-like base and the pedestal is reduced, and there is no possibility that a gap is generated between the joint surfaces of the plate-like base and the pedestal. For this reason, there is no variation in the heat transfer coefficient on the bonding surface, and the substrate holding member with a small temperature difference in the wafer W surface can be stably supplied with a short rise time of the wafer W temperature immediately after the generation of plasma.

  Further, since the cooling medium does not flow directly to the pedestal, the cooling medium does not leak into the vacuum chamber. Further, since the cooling unit is not built in the pedestal, the substrate holding member can be easily attached and detached.

  Hereinafter, embodiments of the present invention will be described.

  Fig.1 (a) is a perspective view of the electrostatic chuck which is an example of the board | substrate holding member 1 of this invention, FIG.1 (b) shows the XX sectional drawing of (a).

  One main surface of the plate-like substrate 2 is a mounting surface 2a on which the wafer W is placed. A pair of adsorption electrodes 3 are provided inside the plate-like substrate 2, and the lower surface of the plate-like substrate 2 is provided on the lower surface. A power feeding terminal 4 for energizing the electrode 3 is attached. One main surface of the pedestal 7 is bonded to the other main surface of the plate-like substrate 2 via the metal bonding layer 6. Further, a ring-shaped recess 7a is provided at the center of the other main surface of the pedestal 7, and a protrusion 7b is formed at the center of the recess 7a. Further, a groove 2b is formed on the mounting surface 2a of the plate-like substrate 2, and Ar gas or the like is supplied from the through-hole 5 that communicates the plate-like substrate 2 provided on the projection 7b and the pedestal 7 with the wafer W. Gas is filled in the space formed by the groove 2b, heat transfer between the wafer W and the mounting surface 2a is enhanced, and the heat of the wafer W is released.

  2A is a perspective view in which a cooling member 8 having a flow path 8a through which a cooling medium is passed is disposed in the ring-shaped recess 7a of the substrate holding member 1 shown in FIG. 1, and FIG. Shows a sectional view taken along line XX of (a). A pair of cooling pipes 9 are attached to the flow path 8a by welding or the like.

  Then, the wafer W is placed on the mounting surface 2 a, and an adsorption voltage of several hundred volts is applied from the power supply terminal 4 between the pair of adsorption electrodes 3, and electrostatic adsorption between the electrode 3 and the wafer W is performed. Force can be developed, and the wafer W can be adsorbed and fixed to the mounting surface 2a. Further, when a high frequency voltage is applied between the base 7 and the counter electrode (not shown), plasma can be efficiently generated above the wafer W. Further, by flowing a cooling medium through the flow path 8a in the cooling member 8, the heat transferred from the atmosphere such as plasma to the wafer W through the inner surface of the recess 7a can be efficiently dissipated to the outside. It becomes easy to control the temperature of W by the temperature of the cooling medium.

  In the substrate holding member 1 of the present invention, one main surface of the plate-like substrate 2 is a mounting surface 2a on which the wafer W is placed, and the other main surface of the plate-like substrate 2 has a thermal conductivity higher than that of the plate-like substrate 2. One major surface of the large plate-like pedestal 7 is joined, and a ring-shaped recess 7 a is provided at the center of the other principal surface of the pedestal 7. This is because the heat conductivity of the plate-like base 7 is larger than the heat conductivity of the plate-like base 2, so that the heat transferred from the wafer W to the plate-like base 2 passes through the base 7. Thus, it is possible to dissipate efficiently to the outside of the substrate holding member 1 through the interface of the recess 7a. For this reason, even if the wafer W is heated in a plasma atmosphere or the like, it is possible to shorten the time until a steady state where the temperature of the surface of the wafer W is constant.

  Further, by providing the ring-shaped recess 7a, the heat capacity of the entire pedestal 7 is reduced and the rigidity of the pedestal 7 is increased as compared with the case where the pedestal 7 has a planar shape without the recess, and the recess has a large area. The inner surface of 7a can be cooled with the effect of reducing the surface temperature difference of the wafer W. Since the heat on the surface of the wafer W can be efficiently dissipated to the outside of the substrate holding member 1, the time until the temperature of the wafer W reaches a steady state can be shortened.

  Moreover, since the temperature difference in the wafer W surface on the mounting surface 2a is reduced by making the concave portion 7a into a ring shape, the flow of the cooling medium in the cooling member 8 becomes smooth and no stagnation occurs. Heat exchange is performed smoothly, and the substrate holding member 1 with good heat uniformity is obtained.

  The heat capacity of the pedestal 7 is reduced if the thickness of the pedestal 7 is reduced. However, as the thickness of the pedestal 7 is reduced, the processing of the recess 7a becomes more difficult, and when the plate-like substrate 2 and the pedestal 7 are joined. The base 7 may be deformed, which is not preferable. The maximum thickness of the pedestal 7 is preferably 5 to 25 mm.

  Further, the substrate holding member 1 of the present invention preferably includes an electrode 3 for adsorption inside the plate-like substrate 2. The reason is that by providing the electrode 3 for attracting the wafer W inside the plate-like substrate 2, it becomes possible to firmly attract and fix the wafer W to the placement surface 2a. The thermal conductivity between 2a increases, and the heat of the wafer W can be efficiently transmitted to the plate-like substrate 2. Then, the time until the temperature of the wafer W reaches a steady state after the plasma is generated can be further reduced.

The electrode 3 embedded in the plate-like substrate 2 is preferably made of a material having a thermal expansion coefficient approximate to that of the plate-like substrate 2 in order to prevent warpage or cracking of the plate-like substrate 2, for example, 4-6 × 10 ⁻⁶ / Refractory metals such as tungsten (W) and molybdenum (Mo) having a thermal expansion coefficient of ° C. are more preferable, and alloys thereof, tungsten carbide (WC), titanium carbide (TiC), and titanium nitride (TiN) should be used. Can do.

  The adsorption electrode 3 embedded in the plate-like substrate 2 is not limited to a film-like one, and may be a plate-like body such as a metal foil, a mesh body, or a coil. The shape of the electrode 3 includes a semicircular shape, a comb shape, and the like, and can be formed in various pattern shapes according to the function.

  Further, the substrate holding member 1 of the present invention is preferably provided with a through hole 5 penetrating the plate-like base 2 and the base 7 in the convex portion 7b, and a groove 2b communicating with the through hole 5 on the mounting surface 2a. . The reason is that the gas is supplied to the through hole 5 penetrating the plate-like substrate 2 and the pedestal 7 provided in the convex portion 7b, whereby the groove 2b on the mounting surface 2a communicating with the through hole 5 and the wafer are provided. This is because the space formed by W is filled with gas, the heat conduction between the wafer W and the mounting surface 2a is enhanced, and the heat of the wafer W can be more easily released to the plate-like substrate 2. Therefore, compared with the case where the groove 2b is not provided on the mounting surface 2a, the heat transfer from the wafer W to the plate-like substrate 2 is improved, and the temperature of the wafer W is reduced even if heat is transferred from the plasma or the like to the wafer W. It can be held at a constant temperature in a short time without being rapidly increased.

  In the conventional substrate holding member 20 shown in FIG. 3, the gas supplied from the through hole 24 communicating with the plate-like base 21 and the base 26 is uniformly diffused in the circumferential direction from the center of the back surface of the wafer W toward the outer edge. However, since the gas is continuously supplied to the central portion of the wafer W, the wafer W is easily cooled, and the outer edge portion is thermally attracted to the wall surface of the container that stores the substrate holding member. And the temperature of an outer edge part becomes low, and it becomes a ring shape with the high temperature of the intermediate part. On the other hand, the substrate holding member 1 of the present invention is provided with the ring-shaped recess 7a on the bottom surface of the pedestal 7, thereby efficiently depriving the heat of the intermediate portion having a high temperature on the wafer W to cool the entire surface of the mounting surface 2a. And the in-plane temperature difference on the wafer W becomes smaller. Then, it becomes possible to form a uniform film with a uniform thickness on the wafer W corresponding to the latest fine circuit elements, and to etch the formed film with a uniform depth.

  Moreover, as for the board | substrate holding member 1 of this invention, it is preferable that the diameter of the recessed part 7a is smaller than the diameter of the mounting surface 2a. The reason is that if the diameter of the concave portion 7a exceeds the diameter of the mounting surface 2a, the temperature of the outer peripheral portion of the wafer W is further cooled by the cooling member 8 from the periphery of the concave portion 7a in addition to the heat sink to the container wall surface. This is because the temperature becomes low and the temperature difference on the surface of the wafer W may become large and non-uniform.

  The diameter of the mounting surface 2a described above is the maximum diameter of the upper surface of the plate-like substrate 2, and the diameter of the concave portion 2a is an average value obtained by measuring four maximum diameters of the inner surface of the concave portion 2a.

  In the substrate holding member 1 of the present invention, the depth tc of the recess 7 a is preferably 0.3 to 0.7 times the thickness t of the base 7. The reason is that if the depth tc of the recess 7a is less than 0.3 times the thickness t of the pedestal 7, the depth tc of the recess 7a is shallow, so that the area of the inner surface of the recess 7a is small, and the heat capacity of the entire pedestal 7 is small. This is because the heat on the surface of the wafer W may not be efficiently released to the outside of the substrate holding member 1 because it is not reduced. On the other hand, when the depth tc of the concave portion 7a exceeds 0.7 times the thickness t of the pedestal 7, the depth tc of the concave portion 7a is so deep that the thickness of the pedestal 7 at the concave portion 7a becomes thin. 7 may crack. When the depth tc exceeds 0.7 times the thickness t, the surface of the wafer W near the bottom surface of the recess 7a is cooled quickly, but the heat of the projection 7b is difficult to escape, so a time lag occurs and the surface of the wafer W This is because the internal temperature difference may increase.

  By setting the depth tc of the recess 7a provided on the other main surface of the pedestal 7 to 0.3 to 0.7 times the thickness t of the pedestal 7, the overall heat capacity of the pedestal 7 is reduced. Even if this heat is poured onto the wafer W, the heat can be quickly moved from the mounting surface 2a toward the recess 7a, so that the heat can be efficiently dissipated to the outside of the substrate holding member 1. Thus, the time until the temperature of the wafer W reaches a steady state can be further shortened. In addition, the rigidity of the pedestal 7 can be increased while suppressing the heat capacity of the pedestal 7. Furthermore, the depth tc of the recess 7 a of the substrate holding member 1 of the present invention is more preferably 0.45 to 0.7 times the thickness t of the base 7.

  Moreover, it is preferable that the board | substrate holding member 1 of this invention arrange | positions the cooling member 8 on the bottom face of the recessed part 7a. The reason is that by disposing the cooling member 8 on the inner surface of the recess 7a, heat can be transferred from the recess 7a of the base 7 to the cooling member 8, and the cooling efficiency is improved. Further, the cooling medium does not flow directly to the pedestal 7, and there is no possibility that the cooling medium leaks into the vacuum vessel. Further, since the cooling member 8 is not built in the pedestal 7, replacement such as attachment / detachment of the substrate holding member 1 is facilitated. In addition, it is preferable to interpose a grease having a large thermal conductivity at the interface between the recess 7a and the cooling member 8.

  The cooling member 8 is provided with a flow path 8a for flowing a cooling medium, and a pair of cooling pipes 9 intersecting with the flow path 8a are attached by a method such as welding. The cooling pipe 9 sucks and blows out the cooling medium, and efficiently dissipates the heat circulated through the flow path 8a and transmitted from the atmosphere such as plasma to the wafer W to the outside. The cooling member 8 and the cooling pipe 9 are preferably made of stainless steel.

  Moreover, as for the board | substrate holding member 1 of this invention, it is preferable that the magnitude | size of the C surface and / or R surface of the corner part of the recessed part 7a is 0.5-5.0 mm. The reason is that a corner portion is provided on the surface of the cooling member 8 on the side in contact with the recess portion 7a in accordance with the size of the corner portion provided on the bottom surface of the recess portion 7a. There is no gap between the cooling member 8 and the thermal contact area between the recess 7a and the cooling member 8 is increased, but the size of the C surface and / or R surface of the corner of the recess 7a is increased. However, if the thickness is less than 0.5 mm, the pedestal 7 is thermally expanded when a cooling cycle is applied, so that stress concentrates on the corner portion and cracks may occur from the corner portion. On the other hand, when the size of the C surface and / or R surface of the corner portion of the recess 7a exceeds 5.0 mm, the corner portion of the cooling member 8 is accurately processed according to the size of the corner portion of the recess 7a. This is because it becomes difficult to do so, and there is a possibility that the contact area that is in thermal contact with the cooling member 8 on the inner surface of the recess 7a may be reduced.

  Furthermore, it is preferable that the size of the C surface and / or the R surface of the corner portion of the recess 7a is 0.5 to 2.0 mm.

  In the substrate holding member 1 of the present invention, the pedestal 7 preferably has a thermal conductivity of 160 W / (m · K) or more. The reason is that if the thermal conductivity of the base 7 is less than 160 W / (m · K), the heat of the plate-like substrate 2 may not be efficiently transmitted to the base 7. By setting the thermal conductivity of the pedestal 7 to 160 W / (m · K) or more, the flow of heat from the plate-like substrate 2 to the pedestal 7 becomes smooth, and the heat from the plasma atmosphere or the like is obtained from the wafer W. This is because it can be easily removed from the recess 7a of the base 7 to the outside of the system.

In the substrate holding member 1 of the present invention, the plate-like substrate 2 is preferably made of a ceramic containing any one of nitride and carbide. The reason is that ceramics such as nitrides and carbides are excellent in plasma corrosion resistance, so that they are not easily damaged by plasma and impurities are not easily deposited on the wafer W, and the high thermal conductivity is 100 W / ( This is because the temperature difference in the wafer surface becomes smaller because it is large (m · K) to 300 W / (m · K). Examples of the nitride and carbide include AlN, SiC, and Si ₃ N ₄ , and AlN and SiC are particularly preferable.

  Moreover, it is preferable that the base 7 of the board | substrate holding member 1 of this invention is a composite material which consists of a metal and a ceramic. The reason is that by making the base 7 a composite material of a metal having a large thermal expansion coefficient and ceramics having a small thermal expansion coefficient, the thermal expansion coefficient of the base 7 can be brought close to the thermal expansion coefficient of the plate-like substrate 2. Even when a cooling cycle of −40 to 100 ° C. required in a film forming process or an etching process such as CVD, PVD, sputtering, etc. is applied, a gap is hardly generated at the joint surface between the plate-like substrate 2 and the base 7, and the surface of the wafer W This is because a part of the temperature can be made uniform without a partial rise.

  Moreover, it is preferable that the base 7 of this invention has Al, Si, and SiC as a main component. The reason for this is that when SiC is manufactured as a pedestal 7 using SiC with a small coefficient of thermal expansion as the base 7, Al and Si are formed on the joint surface of the pedestal 7 because they form an Al / Si eutectic material. This is because the adhesion to the metal layer is improved. The metal layer is provided on the bonding surfaces of the plate-like substrate 2 and the pedestal 7 by using a method such as plating in order to improve the wettability between the metal-bonding layer 6 and the plate-like substrate 2 or the pedestal 7. Since the adhesion of the Si itself to the metal layer is preferable, the pedestal 7 can be firmly joined to the plate-like substrate 2, so that the heat exchange efficiency between the plate-like substrate 2 and the pedestal 7 is improved. Since the temperature of the substrate holding member 1 can follow the rise or change of the wafer temperature, heat can be efficiently dissipated to the outside of the substrate holding member 1, and the temperature of the wafer W is in a steady state. Can be shortened. Further, the metal layer formed on the bonding surface of the pedestal 7 is greatly improved in wettability with the metal bonding layer 6, and no cavities are generated between the pedestal 7 and the metal bonding layer 6. Therefore, CVD, PVD, sputtering This is because the possibility of a gap occurring at the joint surface between the plate-like substrate 2 and the pedestal 7 is reduced even when a cooling cycle of −40 to 100 ° C. required in the film forming process and the etching process is performed.

  The thermal expansion coefficient of the pedestal 7 is preferably 0.8 to 1.2 times the thermal expansion coefficient of the plate-like substrate 2. The reason is that if the thermal expansion coefficient of the plate-like substrate 2 is less than 0.8 times the thermal expansion coefficient of the pedestal 7, the difference in thermal expansion between the plate-like substrate 2 and the pedestal 7 becomes large. This is because there is a possibility that a gap is generated on the joint surface. On the other hand, if the thermal expansion coefficient of the plate-like substrate 2 exceeds 1.2 times the thermal expansion coefficient of the pedestal 7, the difference in thermal expansion between the plate-like substrate 2 and the pedestal 7 becomes large. This is because there is a possibility that a gap is generated on the joint surface.

  The pedestal 7 is preferably made of a composite material of a metal and a ceramic, and a composite material in which a porous ceramic body having a three-dimensional network structure is used as a skeleton and an aluminum-silicon alloy is filled in the pores without gaps. By adopting such a structure, the thermal expansion coefficient of the plate-like base 2 and the pedestal 7 can be brought close to each other, and a material having a large thermal conductivity of the pedestal 7 is obtained, which is transmitted from the atmosphere such as plasma to the wafer W. It is preferable because heat can be efficiently dissipated to the outside.

  As a manufacturing method of the pedestal 7, a porous preform of a ceramic having a desired shape is formed, and a molten Al-Si alloy is impregnated in the preform in a non-oxidizing gas. To make. Alternatively, the ceramic and molten Al / Si alloy can be dispersed while being stirred, and the mixture of the uniformly dispersed ceramic and metal can be poured into a mold capable of obtaining a desired shape.

  Next, other configurations of the substrate holding member 1 of the present invention will be described.

  The insulating film thickness, which is the distance between the mounting surface 2a of the substrate holding member 1 of the present invention and the electrode 3, is an important part that affects the electrostatic adsorption force, and the thickness is preferably from 50 to 1500 μm. Is set to 100 to 1000 μm. The reason is that if the thickness is less than 50 μm, the film thickness is too thin, so that a sufficient withstand voltage cannot be obtained, and there is a possibility that dielectric breakdown may occur when the wafer W is placed on and placed on the placement surface 2a. On the other hand, if the thickness exceeds 1500 μm, the distance between the wafer W and the electrode 3 increases, so that the attractive force decreases.

  The electrostatic chuck shown in FIG. 1 and FIG. 2 shows an example in which the electrode 3 for electrostatic adsorption is provided as the plate-like substrate 2, but is provided with at least one of a heating electrode and a plasma generating electrode. May be. Moreover, you may provide all these electrodes.

  Further, the pedestal 7 of the present invention is preferably bonded to the plate-like substrate 2 via the metal bonding layer 6. The reason is that bonding failure between the plate-like substrate 2 and the pedestal 7 can be eliminated by bonding via the metal bonding layer 6, and the plate-like substrate 2 can be applied even when subjected to a cooling cycle of −40 to 100 ° C. There is little possibility that a gap will be generated on the joint surface of the base 7.

  Further, the composition of the metal bonding layer 6 preferably contains Al wax as a main component and 0.01 to 10% by mass of at least one selected from Ni, Au and Ag as an additive component with respect to the main component. . The reason is that, in order to improve the wettability between the metal bonding layer 6 and the plate-like substrate 2 or the pedestal 7, a metal layer is provided on the bonding surfaces of the plate-like substrate 2 and the pedestal 7 using a method such as plating. The plate-like substrate 2 and the pedestal 7 are joined by the metal joining layer 6. After joining, the metal layers such as Ni, Au, and Ag always diffuse into the metal joining layer 6. For this purpose, before joining, the metal layer of the plate-like substrate 2, the brazing material for metal joining, and the metal layer of the pedestal 7 become three layers. It was found that the composition contains 0.01 to 10% by mass of at least one selected from Ni, Au and Ag as an additive component with respect to the main component. The metal components of Ni, Au, and Ag not only improve the wettability of the metal bonding layer 6 at the time of bonding, but also diffuse into the metal bonding layer 6 by the end of bonding, and the metal bonding layer 6 and the plate-like substrate 2 Alternatively, it is considered that the joining of the pedestal 7 is strengthened not only by the anchor effect but also by mutual diffusion.

  When at least one selected from Ni, Au, and Ag as an additive component is less than 0.01% by mass with respect to the main component, the amount of diffusion into the metal bonding layer 6 is small, so the metal bonding layer 6 and the plate-like substrate 2 or the pedestal 7 cannot be firmly bonded, and if a -40 to 100 ° C. cooling cycle required in a film forming process such as CVD, PVD, sputtering or the etching process is applied, the plate-like substrate 2 and the pedestal 7 Since a gap is generated in the bonding surface, it becomes difficult to follow the temperature of the substrate holding member 1 against a rise or change in the wafer temperature immediately after the plasma is generated, so that the heat of the substrate holding member 1 can be efficiently and uniformly obtained. This is not preferable because it cannot be diffused to the outside, and the time until the temperature of the wafer W reaches a steady state is long and the heat uniformity deteriorates. On the other hand, if at least one selected from Ni, Au and Ag as an additive component exceeds 10% by mass with respect to the main component, the brazing material itself becomes brittle, so that cracks are likely to occur in the thermal cycle test. It is not preferable.

  For this reason, the composition of the metal bonding layer 6 contains Al wax as a main component and 0.01 to 10% by mass of at least one selected from Ni, Au, and Ag as an additive component with respect to the main component. Therefore, even if a cooling cycle of −40 to 100 ° C. is applied, it is possible to prevent the generation of a gap between the joining surfaces of the plate-like substrate 2 and the base 7.

  Next, the manufacturing method of the substrate holding member 1 of the present invention will be described by taking an electrostatic chuck as an example.

As the plate-like substrate 2 constituting the electrostatic chuck, an aluminum nitride sintered body can be used. In the production of the aluminum nitride sintered body, about 10% by mass of Group 3a oxide in terms of weight is added to the aluminum nitride powder and mixed for 48 hours by ball mill using IPA and urethane balls. The aluminum slurry is passed through 200 mesh to remove urethane balls and ball mill wall debris, and then dried at 120 ° C. for 24 hours in an explosion-proof dryer to obtain a homogeneous aluminum nitride mixed powder.

  The mixed powder is mixed with an acrylic binder and a solvent to produce an aluminum nitride slip, and tape forming is performed by a doctor blade method. A plurality of obtained aluminum nitride tapes are laminated, W is formed thereon as an electrostatic adsorption electrode 3 by screen printing, a desired adhesive liquid is applied to a plain tape, and a plurality of tapes are stacked. Press forming.

  The obtained molded body was degreased at 500 ° C. for about 5 hours in a non-oxidizing gas stream, and further fired at 1900 ° C. for about 5 hours in a non-oxidizing atmosphere to embed the electrode 3 in the aluminum nitride A quality sintered body is obtained.

  The aluminum nitride sintered body thus obtained was machined so as to obtain a desired shape and a desired insulating layer thickness, whereby a plate-like substrate 2 was obtained. Further, a desired groove 2b communicating with the through hole 5 provided in the plate-like substrate 2 was formed on the mounting surface 2a of the wafer W by a method such as sandblasting.

  And a metal layer is formed in the surface on the opposite side to the mounting surface 2a of an electrostatic adsorption part by methods, such as plating, solder plating, sputtering, and metallizing.

  The base 7 impregnates ceramic particles made of SiC with molten Al and Si metal. During the impregnation, only heat is applied to the ceramic particles and molten metal, and no pressure is applied. When the impregnation is completed, the ceramic particles impregnated with the molten metal are mixed for 1 to 10 hours while being heated with a stirring blade having a rotational speed of 10 to 100 rpm.

  Then, a convex portion 7b is provided at the center of the bottom by casting, and a ring-shaped concave portion 7a is provided so as to surround the convex portion 7b, and the diameter of the concave portion 7a is smaller than the diameter of the mounting surface 2a of the plate-like substrate 2. After forming into a desired shape, the through hole 5 was provided in the convex portion 7b, and the inner surface of the concave portion 7a was further finished by adjusting the size of the C surface and / or R surface of the corner portion.

  A metal layer is also formed on the joint surface side of the base 7 made of SiC, Al, and Si by a method such as plating, solder plating, sputtering, metallization, and the base 7 and the aluminum nitride plate. The substrate 2 is bonded with the metal bonding layer 6. At this time, the metal bonding layer 6 is a metal bonding layer 6 containing Al as a main component and containing 0.01 to 10% by mass of one or more selected from Ni, Au, and Ag as an additive component with respect to the main component. It is desirable to be.

  Then, bonding is performed in a non-oxidizing atmosphere while applying a desired load and temperature, or bonding is performed under a desired temperature and a desired pressure while applying pressure by a hot press method. The joined body can be obtained.

  The cooling member 8 and the cooling pipe 9 are made of stainless steel, and are disposed on the bottom surface of the recess 7 a provided in the base 7. The cooling member 8 includes a flow path 8a through which a cooling medium flows, and the flow path 8a and a pair of cooling pipes 9 are attached by a method such as welding. An electrostatic chuck can be obtained by placing the joined body of the plate-like substrate 2 and the base 7 on the cooling member 8.

  10% by mass of Group 3a oxide in terms of weight is added to the aluminum nitride powder, mixed for 48 hours with a ball mill using IPA and urethane balls, and the resulting aluminum nitride slurry is passed through 200 mesh, After removing the ball mill wall debris, it is dried at 120 ° C. for 24 hours in an explosion-proof dryer to obtain a homogeneous aluminum nitride mixed powder. This aluminum nitride mixed powder was mixed with an acrylic binder and a solvent to produce an aluminum nitride slip, and tape-molded by the doctor blade method. Then, a plurality of the produced tapes were laminated, W was formed thereon as an electrode by a screen printing method, a desired adhesion liquid was applied to the plain tape, and a plurality of tapes were laminated to form a plate-like body.

  The above plate-like body is degreased at 500 ° C. for about 5 hours in a non-oxidizing gas stream, and further baked at 1900 ° C. for about 5 hours in a non-oxidizing atmosphere, so that the aluminum nitride-based baking made of a dielectric is performed. A ligature was obtained.

  The aluminum nitride sintered body thus obtained was machined so as to obtain a desired shape and a desired thickness of the mounting surface and the electrode insulating film, thereby obtaining a plate-like substrate. Further, desired grooves communicating with the through holes provided in the plate-like substrate were formed on the wafer mounting surface by sandblasting.

  And the metal layer was formed in the main surface on the opposite side to the mounting surface of a plate-shaped base | substrate by the plating method.

  The pedestal impregnates SiC particles with molten Al and Si alloy. During impregnation, only heat is applied to the molten metal composed of SiC particles and Al and Si alloy, and no pressure is applied. When the impregnation is completed, the SiC particles impregnated with the molten metal are mixed for 1 to 10 hours while being heated with a stirring blade having a rotational speed of 10 to 100 rpm. And by providing a convex part at the bottom center part by casting molding, providing a ring-shaped concave part so as to surround the convex part, the depth of the concave part is 0.5 times the thickness of the pedestal, and Molded into a desired shape so that the diameter of the concave portion is smaller than the diameter of the mounting surface of the plate-like substrate, and then provided with a hole for fixing the chamber and a through hole in the convex portion on the outer peripheral portion. A plurality of pedestals were fabricated by processing the R surface to have a size of 1.0 mm. Further, in the same manner as described above, a circular concave portion was provided at the center of the bottom surface by casting, and the other portions were produced in the same manner as the pedestal provided with a ring-shaped concave portion.

  Also, SUS and Al pedestals were prepared separately.

  And the metal layer was formed in the produced base similarly to a plate-shaped base | substrate, and it joined to the said plate-shaped base | substrate through Al brazing, respectively.

The plate-like substrate and the pedestal were joined in a vacuum furnace of about 1 × 10 ⁻⁶ Pa and joined at a load of 98 KPa at 550 to 600 ° C. to obtain a joined body of the plate-like substrate and the pedestal. .

  Further, the cooling member and the cooling pipe were made of stainless steel and arranged on the bottom surface of the recess provided on the pedestal. The cooling member is provided with a flow path for flowing a cooling medium, and the flow path and a pair of cooling pipes are attached by welding. And the electrostatic chuck | zipper was formed by mounting the joined body of the said plate-shaped base | substrate and a base on a cooling member.

  The electrostatic chuck produced as described above is placed in a vacuum processing chamber, and a DC voltage of 500 V is applied to the electrode for electrostatic adsorption at room temperature of 25 ° C. to adsorb the wafer W onto the mounting surface, and then the plate A space formed by the wafer W and the groove was filled with Ar gas from a through hole communicating with the substrate and the base. Further, a cooling medium of about 20 ° C. is circulated through the flow path in the cooling member at 10 liters / minute, and the wafer temperature before plasma generation is measured using the temperature measuring wafers W at 13 measurement points. The temperature of the cooling medium was finely adjusted so that the value was 20 ° C. Then, while flowing a mixed gas of oxygen and Ar, high-frequency power of 200 W was applied between the pedestal and the counter electrode to start the plasma treatment.

  When the shape of the recess provided on the bottom surface of the pedestal was changed, the time elapsed until the temperature of the wafer W reached a steady state and the in-plane temperature difference were measured. The steady state refers to a state in which the temperature of the central portion of the wafer W is continuously measured using the temperature measuring wafer W immediately after the plasma is generated, and the temperature of the wafer W does not change by 1 ° C. or more per second. It can be said that the sample having a shorter time until the temperature of the wafer W reaches a steady state is superior in cooling capacity. Further, the in-plane temperature difference of the wafer W in the steady state was determined as the difference between the maximum temperature and the minimum temperature using the temperature measurement wafers at 13 measurement points. It can be said that the smaller the in-plane temperature difference is, the better the temperature uniformity of the wafer W is.

  As another embodiment of the present invention, a sample in which no electrode was provided inside the plate-like substrate was prepared, and other samples were prepared and evaluated in the same manner as other samples.

Table 1 shows the results.

  Sample No. 2, the shape of the concave portion provided on the bottom surface of the base made of the Al—Si—SiC composite material is circular, the time until the temperature of the wafer W reaches a steady state is as long as 25 seconds, and the in-plane temperature difference is 15 It was inferior at 4 ° C.

  Sample No. No. 4, since the concave portion provided on the pedestal bottom made of SUS has a circular shape, the time until the temperature of the wafer W reaches a steady state is as long as 35 seconds, and the cooling capacity is inferior. The temperature difference was also inferior at 20.7 ° C.

  In contrast, sample no. 1, no. 3, no. 5, no. 6, no. No. 7 has a ring-shaped recess on the bottom surface of the pedestal, so the time until the temperature of the wafer W reaches a steady state is as short as 19 seconds or less, and the cooling capability is excellent. It was excellent at 9.8 ° C. or lower.

  Sample No. 3, no. 5, no. 6, no. 7 has an electrode inside the plate-like substrate, so that the time until the temperature of the wafer W reaches a steady state is as short as 16 seconds or less, and the cooling capacity is more excellent, and the in-plane temperature difference is 9 .1 ° C and better.

  Furthermore, sample no. 3 and no. 7 is a composite material made of a metal and a ceramic pedestal, so the time until the temperature of the wafer W reaches a steady state is as short as 12 seconds or less, and the cooling capacity is more excellent, and the in-plane temperature difference is 4 .7 ° C. or lower and better.

  Sample No. No. 3, since the pedestal is mainly composed of Al-Si-SiC, the time until the temperature of the wafer W reaches a steady state is as short as 9 seconds or less, and the cooling ability is most excellent. Was the most excellent at 1.5 ° C. or less.

  Similar to Example 1, a plate-like substrate provided with a through hole communicating with a desired groove was produced. Further, the pedestal has a convex portion at the center of the bottom surface by casting, and a ring-shaped concave portion is provided so as to surround the convex portion, and the diameter of the concave portion is smaller than the diameter of the mounting surface of the plate-like substrate, and the thickness of the pedestal Producing a plurality of pedestals molded in a desired shape by changing the ratio of the depth tc of the recess to t (tc / t), and then providing a hole for fixing the chamber and a through hole in the protrusion on the outer periphery, It processed so that the magnitude | size of the R surface of the corner part of the said recessed part might be set to 1.0 mm.

  Then, the plate-like substrate and the pedestal were joined by the same method as in Example 1.

  The substrate holding member produced as described above is placed in a temperature-controlled room, and cold air is circulated through the temperature-controlled room for about 30 minutes until the temperature of the bonded body reaches −40 ° C., and the temperature of the bonded body reaches −40 ° C. Held for 10 minutes. Next, hot air was circulated through the temperature-controlled room for about 1 hour until the temperature of the bonded body reached 100 ° C., and the temperature of the bonded body was maintained at 100 ° C. for 10 minutes. The temperature of the joined body was measured by attaching a thermocouple to the surface of the plate-like substrate. The -40 ° C to 100 ° C cooling cycle was performed 5000 times.

  And the said board | substrate holding member was installed in the vacuum chamber similarly to Example 1, and the plasma processing was started.

  The time until the temperature of the wafer W reached a steady state when the ratio (tc / t) of the depth tc of the recess to the thickness t of the base was changed was measured. The thickness t of the pedestal and the depth tc of the recesses were measured by measuring the maximum thickness and the depth of the deepest portion with a micrometer and a caliper, and taking them as average values.

  The time until the temperature of the wafer W reaches a steady state was measured by the same method as in Example 1.

Table 2 shows the results.

  Sample No. No. 21 is excellent in durability of the pedestal because the ratio of the depth tc of the recess to the thickness t of the pedestal is 0.2. However, since the heat capacity of the pedestal is large, the temperature of the wafer W is in a steady state. The cooling time was slightly inferior, with a long time of 18 seconds.

  Sample No. 27, since the ratio of the depth tc of the recess to the thickness t of the pedestal is 0.8, the time until the temperature of the wafer W reaches a steady state is as short as 7 seconds. Since the depth tc of the pedestal was deep, the thickness of the pedestal in the recessed portion was reduced, and cracking occurred in the pedestal when subjected to a cooling cycle, so the durability of the pedestal was inferior.

  In contrast, sample no. 22-No. 26, since the ratio of the depth tc of the recess to the thickness t of the pedestal is 0.3 to 0.7, the pedestal is free from cracks and has excellent pedestal durability. The time until the temperature reached a steady state was as short as 15 seconds or less, and the cooling capacity was excellent.

  In addition, the ratio of the depth tc of the recess to the thickness t of the pedestal is 0.45 to 0.7. 24-No. No. 26 was excellent in the durability of the pedestal, and the time until the temperature of the wafer W reached a steady state was as short as 9 seconds or less, and the cooling capacity was more excellent.

  Similar to Example 1, a plate-like substrate having through holes communicating with the grooves was produced. Further, the pedestal is provided with a convex portion at the center of the bottom by casting, and a ring-shaped concave portion is provided so as to surround the convex portion, and the depth tc of the concave portion is 0.5 times the thickness of the pedestal 20 mm. In addition, the concave portion is molded into a desired shape so that the diameter of the concave portion is smaller than the diameter of the mounting surface of the plate-like substrate, and then a hole for fixing the chamber and a through hole are provided in the convex portion on the outer peripheral portion. A plurality of pedestals were produced by changing the size of the R surface of the corner portion. The size of the corner portion at the bottom of the recess was measured using an R gauge.

  Then, the plate-like substrate and the pedestal were joined by the same method as in Example 1.

  Then, the cooling cycle was performed 5000 times in the same manner as in Example 2, and the time until the steady state was reached was measured as in Example 2.

Table 3 shows the results.

  Sample No. In No. 31, the R surface size of the corner portion of the recess was 0.2 mm, so the time until the temperature of the wafer W reached a steady state was as short as 6 seconds, and the cooling capacity was excellent. When applied, cracks occurred in the pedestal, and the durability of the pedestal was slightly inferior.

  Sample No. No. 39 was excellent in the durability of the pedestal because the size of the corner of the recess was C / R 6.0, but the clearance between the side surface of the recess and the cooling member was increased, so the temperature of the wafer W The cooling time was inferior for a long time of 18 seconds until it became a steady state.

  In contrast, sample no. 32-No. 38, since the size of the R surface of the corner portion of the concave portion is 0.5 to 5.0 mm, the clearance between the side surface of the concave portion and the cooling member is maintained in a range having a cooling effect. The time required for the temperature to reach a steady state was as short as 15 seconds or less, and the cooling capacity was excellent. The pedestal had no cracks and the pedestal had excellent durability.

  Sample No. 32-No. 35, since the size of the R surface of the corner portion of the recess is 0.5 to 2.0 mm, an appropriate clearance between the side surface of the recess and the cooling member is maintained in a range having a cooling effect. The time until the temperature of W reaches a steady state is as short as 10 seconds, and the cooling capacity is more excellent. Further, cracks are less likely to occur in the pedestal, so the pedestal has excellent durability.

  The present invention relates to a substrate holding device of a semiconductor manufacturing apparatus.

(A) is a perspective view of this invention, (b) shows the XX sectional drawing of (a). (A) is a perspective view of this invention, (b) shows the XX sectional drawing of (a). It is conventional sectional drawing. It is conventional sectional drawing.

Explanation of symbols

1: Substrate holding member 2: Plate-like substrate 2a: Placement surface 2b: Groove 3: Electrode 4: Feeding terminal 5: Through hole 6: Metal bonding material 7: Al-Si-SiC pedestal 7a: Concave portion 7b: Convex portion 8 : Cooling member 8a: Channel 9: Cooling pipe 20: Substrate holding member 21: Plate substrate 21a: Mounting surface 22: Electrode 23: Lead wire 24: Through hole 25: Metal bonding material 26: Al plate 26a: Channel 30: Substrate holding member 31: Plate base 31a: Placement surface 32: Electrode 33: Metal bonding material 34: Al—Si—SiC base

Claims (11)

One main surface of the plate-like substrate is a mounting surface on which the wafer is placed, and the other main surface is a substrate holding member joined to one main surface of the plate-like pedestal, and the pedestal is more than the plate-like substrate. A substrate holding member characterized in that a material having a high thermal conductivity is used, and a ring-shaped recess is formed at the center of the other main surface. The substrate holding member according to claim 1, wherein the wafer adsorption electrode is provided inside the plate-like substrate. The substrate holding member according to claim 1, wherein a diameter of the concave portion is smaller than a diameter of the placement surface. The depth tc of the said recessed part is 0.3 to 0.7 times the thickness t of the said base, The board | substrate holding member in any one of Claims 1-3 characterized by the above-mentioned. The substrate holding member according to claim 1, wherein a cooling member is disposed on a bottom surface of the concave portion. The substrate holding member according to any one of claims 1 to 5, wherein a size of a C surface and / or an R surface of the corner portion of the concave portion is 0.5 to 5.0 mm. 7. A convex portion formed by the concave portion is provided with a through hole penetrating the plate-like substrate and the pedestal, and a groove communicating with the through hole is formed on the mounting surface. The substrate holding member according to any one of the above. The substrate holding member according to claim 1, wherein the pedestal has a thermal conductivity of 160 W / (m · K) or more. 9. The substrate holding member according to claim 1, wherein the plate-like substrate is made of a ceramic containing any one of nitride and carbide. The substrate holding member according to claim 1, wherein the pedestal is a composite material made of metal and ceramic. The substrate holding member according to claim 10, wherein the pedestal comprises Al, Si, and SiC as main components.

Images