JP2011159678A - Substrate holder equipped with electrostatic chuck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate holder whose electrostatic chuck is neither warped nor broken even when a cooling speed is increased. <P>SOLUTION: The substrate holder includes the electrostatic chuck 10 and an electrostatic chuck support 20. In this case, a deformation preventive plate 21 and a cooling mechanism 22, which constitute the electrostatic chuck support 20, are arranged in this order from a side close to the electrostatic chuck 10, the deformation preventive plate 21 is held slidably on both surfaces thereof, and ΔT<SB>1</SB>/ΔT<SB>4</SB><0.1 and ΔT<SB>2</SB>/ΔT<SB>4</SB><0.1 and ΔT<SB>3</SB>/ΔT<SB>4</SB><0.1 are satisfied, wherein ΔT<SB>1</SB>is a temperature difference between top and reverse sides of the electrostatic chuck 10 in processing on a substrate W, ΔT<SB>2</SB>is a temperature difference between top and reverse sides of the deformation preventive plate 21, ΔT<SB>3</SB>is a temperature difference between top and reverse sides of the cooling mechanism 22, and ΔT<SB>4</SB>is a temperature difference between a temperature of a substrate mounting surface 10a of the electrostatic chuck 10 and a temperature of the surface of the cooling mechanism 22 on the opposite side from the surface opposed to the deformation preventive plate 21. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a substrate holder provided with an electrostatic chuck used in a semiconductor manufacturing apparatus or the like.

  In processing steps such as sputtering and etching in semiconductor manufacturing, a substrate holder that holds a substrate such as a silicon wafer to be processed is used. The substrate holder includes an electrostatic chuck that places and fixes a substrate to be processed, and an electrostatic chuck support that supports the electrostatic chuck. The electrostatic chuck support not only has a role of supporting the electrostatic chuck, but also includes a cooling mechanism for preventing the substrate and the electrostatic chuck from being excessively heated during the processing of the substrate. .

  Various structures have been proposed so far for the structure of the substrate holder including the electrostatic chuck and the electrostatic chuck support. For example, in Patent Document 1, a metal plate having a coolant passage is used as an electrostatic chuck support, and an insulating film and an insulating adhesive layer are interposed on the metal plate to form a dielectric as an electrostatic chuck. A structure for bonding substrates is described. Further, it is described that a silicone resin to which an alumina or aluminum nitride filler is added is used for the insulating adhesive.

  In Patent Document 2, in order to increase the cooling efficiency of the substrate holder, a metal bonding film containing aluminum is used in place of the resin having low thermal conductivity, and the electrostatic chuck and the electrostatic are interposed through the bonding film. A structure for joining a chuck support has been proposed.

JP 2007-251124 A JP 2009-141204 A

  In recent years, the demand for improving throughput in semiconductor manufacturing has become extremely strict, and accordingly, the necessity for improving the cooling rate of the electrostatic chuck has been increasing. As described in Patent Document 2, the cooling rate itself is improved by using a metal plate having high thermal conductivity such as aluminum as a bonding film on the electrostatic chuck support and bonding it to the electrostatic chuck. This is possible.

  However, when such a configuration is employed in order to improve the cooling rate, a large temperature difference occurs between the substrate mounting surface of the electrostatic chuck and the opposite surface, resulting in a large warp of the electrostatic chuck. As a result, the problem that the substrate cannot be normally chucked has become apparent. In this case, the substrate placement surface becomes hotter and expands than the opposite surface, so that the substrate placement surface bulges convexly toward the substrate placement surface, that is, deforms upward.

  Further, when the electrostatic chuck and the metal plate are joined by the method shown in the above prior art, an excessive stress is applied to the joining surface due to a temperature difference between the electrostatic chuck and the metal plate and a difference in thermal expansion coefficient of these members. As a result, the electrostatic chuck and the electrostatic chuck support are damaged.

  The above-mentioned problems have become prominent with the recent improvement of the cooling rate, and have not been particularly considered so far. As a result of intensive studies in order to solve these problems, the present inventors have found a structure that can suppress warping of the electrostatic chuck and can be prevented from being damaged even when the cooling rate is improved. Invented.

That is, a substrate holder provided by the present invention supports an electrostatic chuck having a substrate mounting surface on which a substrate to be processed is mounted, and the electrostatic chuck from a surface opposite to the substrate mounting surface. An electrostatic chuck support including at least a deformation prevention plate and a cooling mechanism, and the deformation prevention plate and the cooling mechanism are arranged in this order from the side close to the electrostatic chuck, and the deformation prevention plate The temperature difference between the front and back surfaces of the electrostatic chuck during substrate processing is ΔT ₁ , the temperature difference between the front and back surfaces of the deformation preventing plate is ΔT ₂ , and the cooling is performed. The temperature difference between the front and back surfaces of the mechanism is ΔT ₃ , and the temperature difference between the temperature of the substrate mounting surface of the electrostatic chuck and the temperature of the surface opposite to the surface facing the deformation prevention plate in the cooling mechanism is ΔT ₄ . These are ΔT ₁ / ΔT ₄ <0.1 and ΔT ₂ / ΔT ₄ <0.1 and ΔT ₃ / ΔT ₄ <0.1.

  According to the present invention, even when the cooling rate is improved, the warping of the electrostatic chuck can be suppressed and the substrate holder is not damaged. Therefore, a high quality product can be manufactured with high throughput.

1 is a schematic cross-sectional view of a substrate holder according to an embodiment of the present invention, and a graph showing a temperature gradient generated in the substrate holder during substrate processing. It is a schematic diagram which shows the shape which the board | substrate holding body shown on the right side of FIG. 1 exhibits when it has the temperature gradient shown on the left side of FIG. It is a graph which shows the schematic cross-sectional view of the conventional substrate holder, and the temperature gradient which arises in this conventional substrate holder in the case of a process of a board | substrate. It is a schematic diagram which shows the shape which the conventional board | substrate holding body shown on the right side of FIG. 3 exhibits when it has the temperature gradient shown on the left side of FIG. It is a schematic diagram which shows the shape of a board | substrate holding body when a deformation | transformation prevention board deform | transforms excessively. It is the top view and sectional drawing which show the shape of the groove | channel for thermocouple embedding provided in the electrostatic chuck, deformation | transformation prevention board, and cooling mechanism of an Example.

  Hereinafter, the substrate holder according to the present invention will be described in detail with reference to the accompanying drawings. The right side of FIG. 1 schematically shows a longitudinal sectional view of a substrate holder including an electrostatic chuck 10 and an electrostatic chuck support 20 according to an embodiment of the present invention. The electrostatic chuck 10 has a substantially disk shape, and a substrate placement surface 10a for placing and fixing the substrate W to be processed is provided on the upper surface side thereof. Furthermore, an electrostatic chucking electrode and a resistance heating element (not shown) are provided inside the electrostatic chuck 10, and chucking and heating of the substrate W placed on the substrate placement surface 10a are performed by these.

  An electrostatic chuck support 20 that supports the electrostatic chuck 10 is provided below the electrostatic chuck 10. In other words, the electrostatic chuck support 20 supports the electrostatic chuck 10 from the surface opposite to the substrate mounting surface 10a. As will be described later, the electrostatic chuck support 20 is placed on the deformation prevention plate 21 that plays a role of preventing excessive deformation of the electrostatic chuck 10, and the electrostatic chuck 10 and its substrate placement surface 10a. It has at least a cooling mechanism 22 that plays a role of cooling the substrate W. The deformation preventing plate 21 and the cooling mechanism 22 are arranged from the side close to the electrostatic chuck 10 in the order described. In other words, the electrostatic chuck 10 and the cooling mechanism 22 are arranged above and below the deformation prevention plate 21, respectively.

  A refrigerant passage 22 a is provided inside the cooling mechanism 22. By circulating a coolant such as water or Fluorinert through the coolant passage 22a, the heat transmitted from the electrostatic chuck 10 to the cooling mechanism 22 via the deformation prevention plate 21 can be discharged out of the system. Therefore, the electrostatic chuck 10 and the substrate W placed on the substrate placement surface 10a can be quickly cooled.

  The substrate holder including the electrostatic chuck 10 and the electrostatic chuck support 20 is installed in a chamber of a semiconductor manufacturing apparatus (not shown), for example, and used for semiconductor manufacturing. Specifically, the substrate W to be processed is placed on the substrate placement surface 10a of the electrostatic chuck 10, fixed by electrostatic adsorption, and heated by the resistance heating element. In this state, the substrate W is subjected to processing such as sputtering and etching. The substrate W that has been processed is cooled, then picked up from the substrate placement surface 10a, and transported to the next processing step. Another substrate W is continuously placed on the substrate placement surface 10a of the electrostatic chuck 10, and thereafter the same processing is repeated.

  The electrostatic chuck 10 and the cooling mechanism 22 are coupled to each other by a coupling means 30 such as screwing in a state where the deformation preventing plate 21 is sandwiched from both sides as shown in the vertical sectional view on the right side of FIG. In this coupling method, the electrostatic chuck 10 and the deformation prevention plate 21 and the deformation prevention plate 21 and the cooling mechanism 22 are in contact with each other without any gap, but are fixed using a fixing means such as an adhesive. Because it is not, it is slidable.

  In the case where the substrate W is processed using the substrate holder having such a structure, the substrate W has heat input from above in FIG. 1 due to the processing such as sputtering and etching. Further, as described above, when a resistance heating element is provided inside the electrostatic chuck 10, there is also heat input from there. On the other hand, when cooling is performed subsequent to or in parallel with the process involving heat input, the cooling mechanism 22 cools the electrostatic chuck 10 from below.

As a result, a temperature gradient as shown on the left side of FIG. 1 is generated inside the electrostatic chuck 10 and the electrostatic chuck support 20. That is, the electrostatic chuck 10 has a temperature gradient ΔT ₁ between the front and back surfaces, the deformation prevention plate 21 has a temperature gradient ΔT ₂ between the front and back surfaces, and the cooling mechanism 22 has a temperature difference between the front and back surfaces. A temperature gradient of ΔT ₃ occurs. Furthermore, the temperature difference between the temperature of the surface opposite to the surface facing the deformation inhibitor 21 in the temperature and the cooling mechanism 22 of the substrate mounting surface 10a of the electrostatic chuck 10 becomes [Delta] T _4.

As for the temperature difference of each member, the front surface side (that is, the substrate placement surface 10a side) is higher than the back surface side, and as a result, each member is deformed in a convex shape toward the substrate placement surface 10a side. However, if ΔT ₁ , ΔT ₂ and ΔT ₃ , which are the temperature differences between the front and back surfaces of each member of the substrate holder, are sufficiently smaller than the temperature difference ΔT ₄ between the front and back surfaces of the entire substrate holder, Deformation can be kept small. Specifically, when the temperature difference has a relationship of ΔT ₁ / ΔT ₄ <0.1 and ΔT ₂ / ΔT ₄ <0.1 and ΔT ₃ / ΔT ₄ <0.1, The deformation of the member can be suppressed to a small level, and as a result, the change in flatness on the substrate placement surface 10a of the electrostatic chuck 10 can be suppressed.

By the way, in the substrate holder in one embodiment of the present invention, ΔT ₅ which is a temperature difference at the contact surface between the electrostatic chuck 10 and the deformation prevention plate 21, and the contact surface between the deformation prevention plate 21 and the cooling mechanism 22. ΔT ₆ is larger than ΔT ₁ , ΔT _2, and ΔT ₃ , which are the temperature differences between the front and back surfaces of each member described above, and there is a large temperature difference between these adjacent members. Is recognized.

  However, as described above, since the deformation prevention plate 21 is slidably sandwiched on both surfaces thereof, the electrostatic chuck 10, the deformation prevention plate 21, and the cooling mechanism 22 are each deformed by the influence of heat. As shown in FIG. 2, it can be deformed while sliding on the contact surface between adjacent members. Therefore, even if a relatively large temperature difference occurs between adjacent members as described above, unreasonable stress due to this will not be applied to these members.

  On the other hand, in the conventional substrate holder, the electrostatic chuck 1 and the cooling mechanism 3 including the coolant passage 3a are joined by the joining layer 2, as shown in the vertical cross-sectional view on the right side of FIG. . Since the bonding by the bonding layer 2 is performed by brazing with a molten metal, adhesion with a silicone resin, or the like, the electrostatic chuck 1 and the cooling mechanism 3 are not only in contact with each other but also slidable with each other. Can not.

When the conventional substrate holder having such a configuration is processed on the substrate W under the same processing conditions as described above, a temperature gradient as shown on the left side of FIG. 3 is generated. That is, a temperature gradient of front and back temperature difference ΔT ₁ is generated in the electrostatic chuck 1, a temperature gradient of front and back temperature difference ΔT ₂ is generated in the bonding layer 2, and a temperature difference ΔT of the front and back surfaces is generated in the cooling mechanism 3. A temperature gradient of ₃ results. The temperature difference between the temperature of the substrate mounting surface 1 a of the electrostatic chuck 1 and the temperature of the surface opposite to the surface facing the bonding layer 2 with respect to the cooling mechanism 3 is ΔT ₄ .

Further, in the temperature gradient shown on the left side of FIG. 3, there is no temperature difference between the members corresponding to ΔT ₅ and ΔT ₆ as shown in the temperature gradient on the left side of FIG. Therefore, the conventional substrate holder shown on the right side of FIG. 3 has a slightly improved cooling rate in principle compared to the structure on the right side of FIG.

However, the structure on the right side of FIG. 3 is different from the structure on the right side of FIG. 1 in which each member slides between adjacent members when the members are deformed by heat. It will not be resolved. Furthermore, the temperature differences ΔT ₁ , ΔT ₂ , ΔT ₃ in each member are larger than the corresponding temperature differences on the left side of FIG. As a result, as shown in FIG. 4, a large deformation occurs as compared with FIG. 2, and an excessive stress is applied to each member.

  As described above, the cooling rate of the structure shown on the right side of FIG. 1 is slightly lower than that of the structure shown on the right side of FIG. However, in the structure shown on the right side of FIG. 1, the amount of deformation of each member is small as described above during substrate processing, so that a gap generated between adjacent members can be kept small. Therefore, the decrease in cooling rate is small. In other words, the conventional structure sacrifices suppression of deformation in exchange for eliminating the temperature difference between the members and prioritizing the cooling rate, whereas the structure of the present invention dares to prevent the temperature difference between the members. In order to reduce the temperature difference between the front and back surfaces of each member and to allow sliding between adjacent members, it is possible to prevent the member from being greatly deformed without substantially sacrificing the cooling rate. It is very different from the conventional structure.

The materials of the electrostatic chuck 10, the deformation prevention plate 21, and the cooling mechanism 22 are ΔT ₁ / ΔT ₄ <0.1, ΔT ₂ / ΔT ₄ <0.1, and ΔT ₃ / ΔT ₄ <0.1. It can be selected as appropriate so as to satisfy each. Here, as the material of each member is higher, the temperature difference between the front and back surfaces is less likely to occur as the thermal conductivity is higher. Therefore, the above equations can be easily satisfied, and the degree of freedom in design is improved. However, even if the thermal conductivity is low, if the thickness of the member is reduced, the temperature difference between the front and back surfaces can be reduced. Therefore, the material is not limited to a material having a high thermal conductivity.

  Specifically, as described above, since the material of the electrostatic chuck 10 needs to be a dielectric in terms of its function, resin, ceramics, and the like are conceivable. However, since the material of the electrostatic chuck 10 is often required to have heat resistance up to about 300 ° C. during substrate processing, ceramics such as aluminum nitride and alumina are preferable. Among these, aluminum nitride having a high thermal conductivity of about 160 W / mK is more preferable in consideration of reducing the temperature difference between the front and back surfaces.

  The deformation prevention plate 21 is a member that is interposed between the electrostatic chuck 10 and the cooling mechanism 22 and plays a role of suppressing deformation of the electrostatic chuck 10, and the material thereof does not need to be a dielectric, In view of the gist of the present invention to reduce the temperature difference on the back surface, it is preferable that the thermal conductivity is as high as that of the electrostatic chuck 10. However, if a metal material is selected only under these conditions, many metal materials have a significantly higher coefficient of thermal expansion than aluminum nitride, and the following disadvantages may occur.

  That is, if the thermal expansion coefficient of the deformation preventing plate 21 is too large compared to that of the electrostatic chuck 10, the deformation preventing plate 21 lifts the electrostatic chuck 10 during the processing of the substrate W as shown in FIG. The shape tends to facilitate the deformation of the electrostatic chuck 10 slightly. As a result, even if aluminum nitride having high thermal conductivity is used for the electrostatic chuck 10, the effect cannot be sufficiently exhibited.

Note that FIG. 5 is an extreme one, and if ΔT ₂ / ΔT ₄ <0.1 is satisfied, the deformation preventing plate 21 will not be greatly deformed to the extent shown in FIG. When aluminum nitride is used as the material of the electrostatic chuck 10, considering that the thermal expansion coefficient of aluminum nitride is about 3.5 to 5.5 × 10 ⁻⁶ / K, the deformation preventing plate 21 has a heat It is preferable to use a material having an expansion coefficient of 7.0 × 10 ⁻⁶ / K or less. Thereby, the deformation of the deformation preventing plate 21 can be suppressed to an extremely small extent.

  Since the cooling mechanism 22 itself has a temperature adjustment function, a large temperature difference does not occur inside, and it is not particularly necessary to pay attention to the thermal expansion coefficient. Considering that the cooling mechanism 22 is desired to move and remove heat as efficiently as possible, the material thereof has a relatively high thermal conductivity, such as copper, aluminum, or alloys thereof. It is preferable to use a high thermal conductivity material.

  As a method for absorbing the stress caused by the deformation of the adjacent members, for example, the electrostatic chuck and the cooling mechanism can be flexed after the silicone resin or the like is cured, in addition to making the contact surfaces of the adjacent members slidable. It is also conceivable that the thickness of the silicone resin is increased to such an extent that the stress accompanying the deformation can be absorbed. However, in this method, the thick silicone resin becomes a thermal resistance, and the cooling rate is greatly reduced.

  Further, a structure in which the electrostatic chuck and the cooling mechanism are slidably coupled without using a deformation preventing plate is also conceivable. However, in this structure, since there is only one interface between the members where the temperature difference occurs, the temperature difference between the front and back surfaces of each member is larger than that of the present invention, and it is avoided that each member is greatly deformed. I can't. Furthermore, since there is only one sliding surface, the stress accompanying the deformation cannot be sufficiently absorbed. Conversely, a structure in which two or more deformation prevention plates are sandwiched is also conceivable. However, in this case, since there are three or more interfaces that cause a temperature difference between the members, these become large thermal resistances and the cooling rate is greatly increased. It will decline.

  As described above, in the substrate holder of the present invention, the temperature difference between the adjacent members is increased while the temperature difference between the front and back surfaces of each member is reduced. In this case, when the members are joined together by resin adhesive or metal brazing as in the prior art, a large stress is generated due to the temperature difference between adjacent members, and the electrostatic chuck and There was a risk of damage to the electrostatic chuck support. On the other hand, the substrate holding body of the present invention has a structure in which the deformation preventing plate is slidably held without joining adjacent members, so that such a large temperature difference is adjacent to the member. Even if it occurs in between, it will not be damaged.

  As mentioned above, although the board | substrate holding body of this invention was mentioned and mentioned about embodiment, this invention is not limited to this embodiment, It can implement in the various aspect of the range which does not deviate from the summary of this invention. That is, the technical scope of the present invention extends to the claims and their equivalents.

  As shown on the right side of FIG. 1 or FIG. 2, substrate holders of samples 1 to 8 made of an electrostatic chuck and an electrostatic chuck support are produced, and the time required for warping and cooling of the electrostatic chuck during heating, respectively. Was evaluated. These evaluations were performed without placing a substrate on the substrate placement surface of the electrostatic chuck.

  Specifically, first, an alumina sintered body plate having a diameter of 350 mm and a thickness of 2 mm is prepared, and a tungsten paste is printed thereon by screen printing, so that a chuck electrode is provided on one surface and the opposite side thereof. A resistance heating element was provided on the surface. A plate of an alumina sintered body having a diameter of 350 mm and a thickness of 1 mm was bonded to the surface provided with the chuck electrode by glass bonding. Furthermore, a plate of an alumina sintered body having a diameter of 350 mm and a thickness of 2 mm was similarly bonded to the surface side provided with the resistance heating element by glass bonding. Thereby, a plate-like body having a total thickness of 5 mm is obtained.

  This plate-like body was provided with a through hole having an inner diameter of 7 mm for screwing and a counterbore hole having an inner diameter of 12 mm and a depth of 3 mm. Furthermore, a hole having an inner diameter of 1.7 mm and a depth of 3 mm for installing a temperature measuring element for temperature adjustment was provided in the center on the surface side where the resistance heating element was provided. Thus, the electrostatic chuck was completed.

  Separately from the electrostatic chuck, a copper plate having a diameter of 350 mm and a thickness of 15 mm is prepared, and a through hole having an inner diameter of 7 mm for screwing and a through hole having an inner diameter of 1.7 mm for passing a temperature measuring element are provided in the electrostatic chuck. It provided in the position corresponding to each through-hole. In this way, a deformation preventing plate was completed.

  In addition, a copper plate having a diameter of 350 mm and a thickness of 10 mm is prepared, and a groove for installing a pipe serving as a refrigerant passage is provided in the copper plate. After installing a copper pipe in the groove, a copper plate having a diameter of 350 mm and a thickness of 5 mm is provided. Screwed. Further, a through hole with an inner diameter of 7 mm for screwing and a through hole with an inner diameter of 1.7 mm for passing the temperature measuring element were provided at positions corresponding to the through holes of the electrostatic chuck. In this way, the cooling mechanism was completed. In addition, the thickness of the whole cooling mechanism will be 15 mm.

  In each of the electrostatic chuck, the deformation prevention plate, and the cooling mechanism, in order to measure the temperature of the front surface and the back surface, as shown in FIG. 6, the front and back surfaces of each member P are each 2 mm wide, 20 mm long, A groove Pa having a depth of 0.5 mm was provided, and a thermocouple was embedded in the groove with an adhesive.

  Furthermore, these electrostatic chuck, deformation prevention plate, and cooling mechanism are integrated by fixing by screwing, and a temperature measuring element for temperature adjustment is further installed, and the electrostatic chuck and electrostatic chuck support are A substrate holder for Sample 1 was completed. In addition, this fixing is only clamping by screwing, and fixing by an adhesive or the like is not performed. Therefore, adjacent members can slide with each other.

  The substrate holder of the above sample 1 except that the thickness of the alumina sintered body on which the chuck electrode and the resistance heating element are formed by screen printing is 7 mm instead of 2 mm, and the thickness of the entire electrostatic chuck is 10 mm. In the same manner as described above, a substrate holder for Sample 2 was produced.

  A substrate holder of sample 3 was produced in the same manner as the substrate holder of sample 1 except that the material of the deformation preventing plate was replaced with copper and an aluminum alloy (JIS name 6061, hereinafter referred to as 6061).

  A substrate holder for sample 4 was prepared in the same manner as the substrate holder for sample 1 except that the cooling mechanism was replaced with copper instead of 6061 (but a copper pipe was used for the refrigerant passage). did.

  A substrate holder for sample 5 made of an electrostatic chuck having the structure shown on the right side of FIG. 3 and an electrostatic chuck support was produced. Specifically, an electrostatic chuck and a cooling mechanism were produced in the same manner as Sample 1 except that no through hole or counterbore hole for screwing was provided. The electrostatic chuck and the cooling mechanism were fixed with an adhesive made of silicone resin, a temperature measuring element for temperature adjustment was installed, and a substrate holder for sample 5 was produced.

  The substrate holder of sample 6 is the same as the substrate holder of sample 2 except that the ceramic constituting the electrostatic chuck is replaced by an aluminum nitride sintered body (hereinafter referred to as AlN) instead of the alumina sintered body. Produced.

  Substrate holder for sample 6 except that the deformation prevention plate is a composite material of ceramics (SiC) and metal (Al) (hereinafter referred to as Al-SiC) having a thickness of 10 mm instead of a copper plate having a thickness of 15 mm. In the same manner as described above, a substrate holder of Sample 7 was produced.

  A substrate holder of sample 8 was produced in the same manner as the substrate holder of sample 7 except that the thickness of the deformation prevention plate was changed to 15 mm instead of 10 mm.

  A substrate holder of sample 9 was fabricated in the same manner as the substrate holder of sample 7 except that the deformation preventing plate was replaced with AlN instead of Al—SiC.

  With respect to the substrate holders of these samples 1 to 9, the electrostatic chuck is heated by energizing the resistance heating element in a state where a constant flow rate of refrigerant is passed through the cooling mechanism, and a temperature measuring element for temperature adjustment. The measured value was maintained at a temperature of 100 ° C. In this state, the temperature difference between the front and back surfaces of each member and the temperature difference between the front and back surfaces of the entire substrate holder are measured by the thermocouple embedded in each member, and the substrate mounted on the electrostatic chuck is further measured with an optical displacement meter. The warpage of the surface was measured. Next, the resistance heating element was turned off in a state where a constant flow rate of refrigerant was flowing through the cooling mechanism, and the time until cooling from 100 ° C. to 50 ° C. was measured.

Each value of ΔT ₁ / ΔT ₄ , ΔT ₂ / ΔT ₄ and ΔT ₃ / ΔT ₄ was determined from the temperature difference between the front and back surfaces obtained by the above measurement. These values are shown in Table 1 below together with an outline of the structure of each substrate holder. Table 2 below shows the measurement results of the warpage of each substrate holder on the substrate mounting surface of the electrostatic chuck and the time until cooling from 100 ° C. to 50 ° C.

From these tables, in Sample 1, since the values of ΔT ₁ / ΔT ₄ , ΔT ₂ / ΔT ₄ and ΔT ₃ / ΔT ₄ are all smaller than 0.1, the temperature difference between the front and back surfaces of each member can be kept small. In addition, since the deformation prevention plate is slidably held, the warp on the substrate mounting surface of the electrostatic chuck is small, and the time until cooling from 100 ° C. to 50 ° C. is also short. .

On the other hand, in samples 2 to 4, any of ΔT ₁ / ΔT ₄ , ΔT ₂ / ΔT ₄ and ΔT ₃ / ΔT ₄ was greater than 0.1. In other words, the temperature difference between the front and back surfaces exceeded a predetermined limit in any of the electrostatic chuck, the deformation prevention plate, and the cooling mechanism, and the member was greatly warped. Further, the warpage on the substrate mounting surface of the electrostatic chuck is greatly increased under the influence of the warpage. Further, in a member having a large warp, a gap between the adjacent member and the adjacent member becomes large, cooling efficiency is lowered, and cooling time is increased.

In the sample 5, there is no gap between the members, so that the cooling efficiency is improved and the cooling time is shortened. However, since the electrostatic chuck and the cooling mechanism are bonded, they cannot slide with each other. In addition, ΔT ₁ / ΔT ₄ and ΔT ₃ / ΔT ₄ are greatly increased from 0.1, that is, the temperature difference between the front and back surfaces of each member is greatly increased. The warpage of has become extremely large.

In the sample 6, ΔT ₁ / ΔT ₄ is smaller than that in the sample 1, and accordingly, the warpage on the substrate mounting surface of the electrostatic chuck should be smaller than that in the sample 1. Since the degree of deviation of the thermal expansion coefficient of the deformation preventing plate is larger than that of the sample 1, the electrostatic chuck is lifted up. As a result, the warpage of the electrostatic chuck on the substrate mounting surface is more than that of the sample 1. Almost unchanged.

On the other hand, in Sample 7 and Sample 9, the degree of deviation of the thermal expansion coefficient of the deformation preventing plate from that of the electrostatic chuck is smaller than that of Sample 1 or Sample 6, and the electrostatic chuck is not lifted. The effect of small ΔT ₁ / ΔT ₄ appears, and the warpage of the electrostatic chuck on the substrate mounting surface is extremely small.

On the other hand, in Sample 8, although the degree of deviation of the thermal expansion coefficient of the deformation preventing plate from that of the electrostatic chuck is small as in Sample 7, ΔT ₂ / ΔT ₄ is larger than 0.1. The deformation of itself is large, and the warp on the substrate mounting surface of the electrostatic chuck is large. Thus, the effect seen in the sample 7 is manifested only when both ΔT ₂ / ΔT ₄ is small and the degree of deviation of the thermal expansion coefficient of the deformation preventing plate from the thermal expansion coefficient of the electrostatic chuck is small. I understand that

DESCRIPTION OF SYMBOLS 10, 1 Electrostatic chuck 10a, 1a Substrate mounting surface 20 Electrostatic chuck support body 21 Deformation prevention plate 22, 3 Cooling mechanism 22a, 3a Refrigerant passage 2 Bonding layer W Substrate

Claims (2)

An electrostatic chuck having a substrate placement surface on which a substrate to be processed is placed, an electrostatic chuck that supports the electrostatic chuck from a surface opposite to the substrate placement surface, and includes at least a deformation prevention plate and a cooling mechanism. A substrate holder comprising a chuck support,
The deformation prevention plate and the cooling mechanism are arranged in this order from the side close to the electrostatic chuck, and the deformation prevention plate is sandwiched so as to be slidable on both surfaces thereof, and the substrate is processed during substrate processing. The temperature difference between the front and back surfaces of the electrostatic chuck is ΔT ₁ , the temperature difference between the front and back surfaces of the deformation prevention plate is ΔT ₂ , the temperature difference between the front and back surfaces of the cooling mechanism is ΔT ₃ , and the substrate mounting surface of the electrostatic chuck is When the temperature difference between the temperature and the temperature of the surface opposite to the surface facing the deformation preventing plate in the cooling mechanism is ΔT ₄ , these are ΔT ₁ / ΔT ₄ <0.1 and ΔT ₂ / ΔT ₄ < A substrate holder having a relationship of 0.1 and ΔT ₃ / ΔT ₄ <0.1. The substrate holder according to claim 1, wherein the electrostatic chuck is made of aluminum nitride, and the deformation preventing plate has a thermal expansion coefficient of 7.0 × 10 ⁻⁶ / K or less.

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