Retention device

Abstract

To provide a retainer capable of improving uniformity in in-plane temperature on an object to be retained.SOLUTION: An electrostatic chuck 1 that has a plate-like member 10 comprising a retention surface 11 having a plurality of projection parts 16, 17 and 30a formed and a reverse surface 12 provided on the opposite side from the retention surface 11, and then retains a semiconductor wafer W on the retention surface 11 of the plate-like member 10 has, on a bottom surface 18a of a recessed part 18 other than the projection parts 16, 17 and 30a, a first region 181 which is at distances, larger than a predetermined distance A, from bottom side faces BS of the projection parts 16, 17 and 30a and a second region 182 which is at distances, equal to or less than the predetermined distance A, from the bottom side faces BS of the projection parts 16, 17 and 30a, the first region 181 having larger surface roughness than the second region 182.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a holding device for holding an object.

Background Art

[0002] There is known a holding device in which a holding surface for holding an object is an uneven surface, the convex portions of the uneven surface serve as the holding surface for holding the object, and the concave portions of the uneven surface serve as supply paths for gas (such as helium). In such a holding device, when particles (fine particles) are generated, the yield of the product decreases, so it is necessary to suppress the generation of particles. Therefore, for example, in the adsorption fixing device (holding device) described in Patent Document 1, the top surface and side surfaces of the convex portions of the uneven surface and the bottom surface of the concave portions of the uneven surface are both mirror-polished to suppress the generation of particles.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, on the holding surface of the above holding device, the convex portions contact the object, while the concave portions do not contact the object and heat transfer occurs between the object and the concave portions through gas. Therefore, a difference in heat transfer occurs between the object and the holding device, resulting in non-uniform in-plane temperature of the object. That is, in the object, heat transfer is likely to occur in the contact area with the convex portions (the portion directly above the convex portions), while heat transfer is less likely to occur in the non-contact area with the convex portions (the portion directly above the concave portions). And in the concave portions, the gas inside the concave portions is likely to be heated (or cooled) due to the influence of heat transfer in the convex portions near the convex portions, while there is almost no influence of heat transfer in the convex portions in the portion far from the convex portions. Therefore, a difference in heat transfer also occurs between the portion near the convex portions and the portion far from the convex portions. Thus, on the holding surface, a difference in heat transfer occurs between the holding device and the object, so the in-plane temperature of the object is likely to become non-uniform, and the uniformity of the in-plane temperature has decreased.

[0005] Therefore, the present disclosure has been made to solve the above-described problems, and an object thereof is to provide a holding device capable of improving the uniformity of the in-plane temperature of an object to be held.

Means for Solving the Problems

[0006] One aspect of the present disclosure made to solve the above problems is having a plate-like member including a first surface formed with a plurality of convex portions and a second surface provided on the side opposite to the first surface, in a holding device for holding an object on the first surface of the plate-like member, on the bottom surface of the concave portions other than the convex portions on the first surface, having a first region which is a region where the distance from the bottom side surface of the convex portion is greater than a predetermined distance, and a second region which is a region where the distance from the bottom side surface of the convex portion is within the predetermined distance, characterized in that the surface roughness of the first region is greater than the surface roughness of the second region.

[0007] When comparing the first region and the second region, since the second region is the peripheral region of the convex portion and is affected by heat transfer through the convex portion, heat transfer through the gas filled in the space formed by the object and the concave portion is promoted more in the second region than in the first region. Here, since the first region is farther from the convex portion than the second region, the influence of heat transfer through the convex portion is small. If the surface roughness of the bottom surfaces of the first region and the second region is the same, the first region is disadvantaged in terms of heat transfer through the gas filled in the space formed by the object and the concave portion compared to the second region.

[0008] Therefore, in this holding device, since the surface roughness of the first region is made larger than that of the second region, the contact area between the plate-like member and the gas filled in the concave portion becomes larger in the first region, and heat transfer between the plate-like member and the gas filled in the concave portion can be promoted. Therefore, heat transfer between the plate-like member and the object through the gas filled in the concave portion is promoted at the non-contact portion with the convex portion of the object. Also, in the second region which is easily affected by heat transfer in the convex portion, since the surface roughness is made smaller than that of the first region, generation of particles can be suppressed. As a result, heat transfer between the plate-like member and the object is improved at the non-contact portion (the first region and the second region of the concave portion) between the object and the convex portion, so the non-uniformity of the temperature distribution between the contact portion and the non-contact portion (the first region and the second region of the concave portion) with the convex portion in the object is alleviated, and the in-plane temperature uniformity of the object can be improved, and generation of particles can be suppressed.

[0009] In the holding device described above, the surface roughness in the first region is 1.0 μm or less in Ra (Sa), and the surface roughness in the second region is preferably less than 0.5 μm in Ra (Sa).

[0010] The greater the surface roughness, the more heat transfer through the gas filled in the recess between the object and the plate-like member can be promoted in the recess. On the other hand, the risk of particle generation increases. Therefore, by setting the surface roughness of each of the first region and the second region in this way, it is possible to achieve both an improvement in the in-plane temperature uniformity of the object and the prevention of particle generation.

[0011] In the holding device described above, It is preferable that the size from the bottom side surface of the convex portion in the second region is smaller than 1 / 3 of the distance between the adjacent convex portions.

[0012] Here, if the size of the second region is 1 / 3 or more of the distance between the adjacent convex portions, most of the bottom surface of the recess becomes the second region and the first region becomes very small. Then, in the recess, it becomes impossible to promote heat transfer through the gas filled in the space formed by the object and the recess, and there is a risk that it becomes difficult to improve the in-plane temperature uniformity of the object.

[0013] Therefore, by setting the size of the second region to be smaller than 1 / 3 of the distance between the adjacent convex portions in this way, heat transfer through the gas filled in the space formed by the object and the recess can be surely promoted. As a result, in the object, heat transfer with the plate-like member through the gas filled in the recess in the portion (recess) that is not in contact with the convex portion is surely promoted. Therefore, since the non-uniformity of the temperature distribution in the object is alleviated, the in-plane temperature uniformity of the object can be surely improved.

[0014] In the holding device described above, It is preferable that the longitudinal cross-sectional shape of the convex portion is a trapezoidal shape in which the upper surface side dimension is smaller than the bottom surface side dimension.

[0015] By forming the convex portion into such a shape, it is possible to gently change the temperature distribution (temperature gradient) around the contact portion with the convex portion in the object. As a result, the in-plane temperature uniformity in the object can be further improved.

Advantages of the Invention

[0016] According to the present disclosure, it is possible to provide a holding device that can improve the in-plane temperature uniformity in an object to be held.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Modes for Carrying Out the Invention

[0018] A holding device according to an embodiment of the present disclosure will be described in detail with reference to the drawings. In this embodiment, as the holding device, for example, an electrostatic chuck used in a semiconductor manufacturing apparatus such as a film forming apparatus (CVD film forming apparatus, sputtering film forming apparatus, etc.) or an etching apparatus (plasma etching apparatus, etc.) will be exemplified and described.

[0019] [First Embodiment] First, the electrostatic chuck 1 of the first embodiment will be described with reference to FIGS. 1 to 4. The electrostatic chuck 1 of this embodiment is a device that adsorbs and holds a semiconductor wafer W (object) by electrostatic attraction, and is used, for example, to fix the semiconductor wafer W in a vacuum chamber of a semiconductor manufacturing apparatus. As shown in FIG. 1, the electrostatic chuck 1 includes a plate-like member 10, a base member 20, and a bonding layer 40 that bonds the plate-like member 10 and the base member 20.

[0020] In the following description, for convenience of explanation, the XYZ axes are defined as shown in FIG. 1. Here, the Z axis is the axis in the axial direction (vertical direction in FIG. 1) of the electrostatic chuck 1, and the X axis and the Y axis are the axes in the radial direction of the electrostatic chuck 1.

[0021] As shown in FIG. 1, the plate-like member 10 is a disk-shaped member and is formed of ceramics. As the ceramics, various ceramics are used, but from the viewpoints of strength, wear resistance, plasma resistance, etc., for example, ceramics mainly composed of aluminum oxide (alumina, Al2O3) or aluminum nitride (AlN) are preferably used. Here, the main component means the component with the highest content ratio (for example, the component with a volume content ratio of 90 vol% or more).

[0022] Further, the diameter of the plate-like member 10 is, for example, about 150 to 300 mm. The thickness of the plate-like member 10 is, for example, about 2 to 6 mm. The thermal conductivity of the plate-like member 10 is desirably in the range of 10 to 50 W / mK (more preferably 18 to 30 W / mK).

[0023] As shown in FIGS. 1 and 2, the plate-like member 10 includes a holding surface 11 for holding the semiconductor wafer W and a lower surface 12 provided on the side opposite to the holding surface 11 in the thickness direction of the plate-like member 10 (the direction coinciding with the Z-axis direction). Note that the holding surface 11 is an example of the "first surface" of the present disclosure, and the lower surface 12 is an example of the "second surface" of the present disclosure.

[0024] Inside the plate-like member 10, as shown in FIG. 2, a chuck electrode 50 and a heater electrode 52 are provided. The chuck electrode 50 has, for example, a substantially circular shape when viewed in the Z-axis direction and is formed of a conductive material (for example, tungsten, molybdenum, etc.). The heater electrode 52 forms a pattern that extends, for example, in a substantially spiral shape when viewed in the Z-axis direction and is formed of a conductive material (for example, tungsten, molybdenum, platinum, etc.).

[0025] Then, when power is supplied from a power source (not shown) to the chuck electrode 50, an electrostatic attraction force (adsorption force) is generated, and the semiconductor wafer W is adsorbed and fixed to the holding surface 11 of the plate-like member 10 by this electrostatic attraction force. Further, when power is supplied from a power source (not shown) to the heater electrode 52 and the heater electrode 52 generates heat, the holding surface 11 and thus the semiconductor wafer W are heated.

[0026] The holding surface 11 of the plate-like member 10 has an uneven shape. Specifically, as shown in FIGS. 2 and 3, an annular convex portion 16 is formed near the outer edge of the holding surface 11, and a plurality of independent columnar convex portions 17 are formed inside the annular convex portion 16. Note that the annular convex portion 16 is also called a seal band. The shape of the cross section (XZ cross section) of the annular convex portion 16 is substantially rectangular as shown in FIG. 2. The height (dimension in the Z-axis direction) of such an annular convex portion 16 is, for example, about 10 μm to 20 μm. Also, the width (dimension in the X-axis direction) of the annular convex portion 16 is, for example, about 0.5 mm to 5.0 mm.

[0027] As shown in FIG. 3, each convex portion 17 is substantially circular in a view in the Z-axis direction (plan view) and is arranged at substantially equal intervals. Also, as shown in FIG. 2, the shape of the cross section (XZ cross section) of each convex portion 17 is substantially rectangular. The height of such convex portions 17 is substantially the same as the height of the annular convex portion 16 and is, for example, about 10 to 20 μm. Also, the width of the convex portion 17 (the maximum diameter of the convex portion 17 in a view in the Z-axis direction) is, for example, about 0.5 to 1.5 mm. And the distance B (see FIG. 4) between adjacent convex portions 17 is about 10 mm. Note that, inside the annular convex portion 16 on the holding surface 11 of the plate-like member 10, a portion where no convex portion 17 is formed is a concave portion 18.

[0028] As shown in FIG. 3, the plate-like member 10 is formed with lift pin insertion holes 30 that penetrate the electrostatic chuck 1 in the Z-axis direction. Around the lift pin insertion holes 30, annular convex portions 30a are formed on the holding surface 11 so as to surround the lift pin insertion holes 30. A lift pin (not shown) for pushing up the semiconductor wafer W from above the holding surface 11 is inserted into the lift pin insertion holes 30 from the lower surface 22 side of the base member 20. By the tip (upper end) of this lift pin protruding outside from the holding surface 11 of the plate-like member 10, the semiconductor wafer W placed on the holding surface 11 is separated from the holding surface 11 (the semiconductor wafer W is lifted by the lift pin).

[0029] In the electrostatic chuck 1 of this embodiment, three lift pin insertion holes 30 are formed, and lift pins are inserted into the respective lift pin insertion holes 30. Note that the three lift pin insertion holes 30 are formed at equal intervals in the circumferential direction of the electrostatic chuck 1 (see FIG. 3).

[0030] Further, as shown in FIG. 3, the plate-like member 10 is formed with a gas hole 31 that penetrates the electrostatic chuck 1 in the Z-axis direction. This gas hole 31 is a gas flow path through which an inert gas (for example, helium gas) flows. By supplying the inert gas (for example, helium gas) into the gas hole 31 from the lower surface 22 side of the base member 20, the inert gas can be filled in the space S between the lower surface of the semiconductor wafer W and the holding surface 11 (recess 18) of the plate-like member 10.

[0031] The semiconductor wafer W is supported by the annular convex portion 16, the plurality of convex portions 17, and the convex portion 30a on the holding surface 11 of the plate-like member 10 and is held by the electrostatic chuck 1. In a state where the semiconductor wafer W is held by the electrostatic chuck 1, a space S exists between the surface (lower surface) of the semiconductor wafer W and the holding surface 11 (specifically, the recess 18 of the holding surface 11) of the plate-like member 10 (see FIG. 2). An inert gas (for example, helium gas) is supplied to this space S through the gas hole 31.

[0032] Here, the top surfaces of the convex portions 16, 17, 30a on the holding surface 11 (and in some cases, the side surfaces (circumferential surfaces) as well) are mirror-finished. This prevents the semiconductor wafer W and the convex portions 16, 17, 30a from sliding and finely shaving the surfaces of the semiconductor wafer W and the convex portions 16, 17, 30a to generate particles (fine particles).

[0033] On one side, on the bottom surface 18a of the recess 18 in the holding surface 11, there are two regions with surface roughness greater than the top and side surfaces of the convex portions 16, 17, 30a and with different surface roughnesses respectively. That is, as shown in FIG. 4, a first region 181 which is a region where the distance from the bottom side surface BS of the convex portions 16, 17 (30a) is greater than a predetermined distance A, and a second region 182 which is a region where the distance from the bottom side surface BS of the convex portions 16, 17 (30a) is within the predetermined distance A are provided. Specifically, the second region 182 is formed in an annular shape so as to surround the convex portions 16, 17 (30a) around the convex portions 16, 17 (30a), and the first region 181 is formed in the portion other than the second region 182. Note that the bottom side surface BS of the convex portions 16, 17 (30a) means the portion where the side surface of the convex portions 16, 17 (30a) is connected to the bottom surface 18a (second region 182) of the recess 18. The first region 181 and the second region 182 can be provided by performing polishing or sandblasting with different conditions for each region.

[0034] And the predetermined distance A which is the size (width dimension) from the bottom side surface BS of the convex portions 16, 17 (30a) in the second region 182 can be appropriately set so that the in-plane temperature in the semiconductor wafer W has a desired temperature distribution, but it is set to be smaller than 1 / 3 of the distance B between adjacent convex portions (in this embodiment, for example, about 10 mm). Note that the distance B is the shortest distance between the bottom side surfaces of adjacent convex portions. In this embodiment, the predetermined distance A corresponding to the size (width dimension) of the second region 182 is, for example, about 1 to 2 mm. And the surface roughness of the first region 181 is greater than the surface roughness of the second region 182. For example, the surface roughness of the first region 181 is Ra (Sa) 1.0 μm or less, and the surface roughness of the second region 182 is less than Ra (Sa) 0.5 μm. In this embodiment, for example, the surface roughness of the first region 181 is Ra (Sa) 0.8 μm, and the surface roughness of the second region 182 is Ra (Sa) 0.5 μm. Also, the difference in surface roughness between the first region 181 and the second region 182 may be 0.1 μm or more, and more preferably 0.3 μm or more.

[0035] Note that as methods for measuring surface roughness, there are "contact measurement" and "non-contact measurement", and detailed measurement methods can be measured and gauged based on the following. Contact type: JIS B 0633:2001 Non-contact type: ISO25178

[0036] As shown in FIGS. 1 and 2, the base member 20 includes an upper surface 21 and a lower surface 22 provided on the side opposite to the upper surface 21 in the thickness direction of the base member 20 (i.e., the Z-axis direction), and is formed in a cylindrical shape. This base member 20 is preferably formed of a metal (for example, aluminum, an aluminum alloy, etc.), but may be other than a metal.

[0037] The diameter of the base member 20 is, for example, about 180 mm to 350 mm. Also, the thickness (dimension in the Z-axis direction) of the base member 20 is, for example, about 20 mm to 50 mm. Note that the thermal conductivity of the base member 20 (assuming aluminum) is greater than that of the plate-like member 10, and is desirably in the range of 180 to 250 W / mK (preferably about 230 W / mK).

[0038] Note that a refrigerant flow path (not shown) for flowing a refrigerant (for example, a fluorine-based inert liquid, water, etc.) is formed in the base member 20, and by flowing the refrigerant in this refrigerant flow path, the base member 20 is cooled, and thereby, the plate-like member 10 is cooled via the bonding layer 40.

[0039] The bonding layer 40 is disposed between the lower surface 12 of the plate-like member 10 and the upper surface 21 of the base member 20, and bonds the plate-like member 10 and the base member 20. Through this bonding layer 40, the lower surface 12 of the plate-like member 10 and the upper surface 21 of the base member 20 are thermally connected. The bonding layer 40 is composed of an adhesive such as a silicone-based resin, an acrylic-based resin, or an epoxy-based resin. Note that the thickness (dimension in the Z-axis direction) of the bonding layer 40 is, for example, about 0.1 to 1.0 mm. Also, the thermal conductivity of the bonding layer 40 is, for example, 1.0 W / mK. Note that the thermal conductivity of the bonding layer 40 (assuming a silicone-based resin) is desirably within the range of 0.1 to 2.0 W / mK (preferably 0.5 to 1.5 W / mK).

[0040] Here, on the holding surface 11 of the electrostatic chuck 1 of the present embodiment, a difference in heat transfer occurs between the convex portions 16, 17, 30a and the concave portion 18 between the semiconductor wafer W and the plate-like member 10. That is, since the convex portions 16, 17, 30a are in direct contact with the semiconductor wafer W, heat transfer easily occurs between the semiconductor wafer W and the plate-like member 10. On the other hand, since the concave portion 18 does not contact the semiconductor wafer W, heat transfer between the semiconductor wafer W and the plate-like member 10 is performed through the gas filled in the concave portion 18 (space S), so heat transfer between the two is difficult to occur. In a conventional electrostatic chuck, as shown in FIG. 5, in the concave portion 18, heat transfer occurs in the vicinity of the convex portions 16, 17, 30a, so heat transfer between the semiconductor wafer W and the plate-like member 10 is promoted compared to the concave portion 18 other than the vicinity of the convex portions 16, 17, 30a. That is, even in the concave portion 18 which is a non-contact portion between the plate-like member 10 and the semiconductor wafer W, a difference in heat transfer occurs.

[0041] Therefore, on the holding surface of the conventional electrostatic chuck, the order of the ease of heat transfer between the semiconductor wafer W and the plate-like member 10 is as follows: the convex portions 16, 17, 30a, the vicinity of the convex portions 16, 17, 30a of the concave portion 18 (near the second region 182), and the portions of the concave portion 18 away from the convex portions 16, 17, 30a (near the first region 181). That is, the portions away from the convex portions 16, 17, 30a (near the first region 181) are the regions most disadvantageous for heat transfer. In the conventional electrostatic chuck in this way, on the holding surface, a difference in heat transfer occurs between the semiconductor wafer W and the plate-like member 10, so a temperature difference is likely to occur in the semiconductor wafer W and the in-plane temperature is likely to become non-uniform.

[0042] Therefore, in the electrostatic chuck 1 of the present embodiment, the surface roughness of the bottom surface 18a of the concave portion 18 is made larger than the top surface and the side surfaces of the convex portions 16, 17, 30a, and in the bottom surface 18a of the concave portion 18, a second region 182 having a smaller surface roughness than the first region 181 is formed in an annular shape so as to surround the convex portions 16, 17, 30a around the convex portions 16, 17, 30a. As a result, in the concave portion 18, the contact area with the gas filled in the concave portion 18 (space S) becomes larger, so the heat transfer between the plate-like member 10 and the gas filled in the concave portion 18 is promoted. As a result, the heat transfer between the plate-like member 10 and the semiconductor wafer W through the gas filled in the concave portion 18 is promoted.

[0043] And since the surface roughness of the first region 181 is made larger than that of the second region 182, as shown in FIG. 6, in the first region 181 where heat transfer is most disadvantageous, the contact area with the gas filled in the recess 18 (space S) becomes larger than that of the second region 182. As a result, in the first region 181, heat transfer between the plate-like member 10 and the semiconductor wafer W through the gas filled in the recess 18 is further promoted. In this way, on the holding surface 11, in the portion where the semiconductor wafer W is not in contact, heat transfer between the plate-like member 10 and the semiconductor wafer W through the gas filled in the recess 18 (space S) is improved. That is, in the semiconductor wafer W, heating in the portion (the portion directly above the recess 18) that is not in contact with the convex portions 16, 17, 30a is performed uniformly and efficiently. Therefore, in the semiconductor wafer W, the difference in heat transfer (heating amount) between the contact portion with the convex portions 16, 17, 30a and the non-contact portion (the first region 181 and the second region 182 of the recess 18) can be reduced. Thereby, the temperature difference in the semiconductor wafer W can be alleviated, and the in-plane temperature uniformity can be improved.

[0044] Here, the larger the surface roughness of the bottom surface 18a of the recess 18, the more heat transfer between the semiconductor wafer W and the plate-like member 10 through the gas filled in the recess 18 can be promoted, while the possibility of particle generation increases. Therefore, in the electrostatic chuck 1 of the present embodiment, the surface roughness in the first region 181 is set to Ra (Sa) 1.0 μm or less, and the surface roughness in the second region 182 is set to less than Ra (Sa) 0.5 μm, respectively. Thereby, since the generation of particles can be prevented, it is possible to achieve both the improvement of the in-plane temperature uniformity in the semiconductor wafer W and the prevention of particle generation. In particular, in the second region 182 which is easily affected by heat transfer in the convex portions 16, 17, 30a, since the surface roughness is made smaller than that of the first region 181, the generation of particles can be effectively suppressed.

[0045] In the electrostatic chuck 1 of the present embodiment, a predetermined distance A (i.e., the size of the second region 182) from the bottom side surface BS of the convex portions 16, 17, 30a of the second region 182 is set to be smaller than 1 / 3 of the distance B between the adjacent convex portions 16, 17, 30a. As a result, most of the bottom surface 18a of the concave portion 18 becomes the second region 182, and the first region 181 does not become very small. Therefore, in the first region 181 where heat transfer is most disadvantageous, heat transfer between the semiconductor wafer W and the gas filled in the concave portion 18 can be surely promoted. As a result, in the concave portion 18, heat transfer between the plate-like member 10 and the semiconductor wafer W through the gas filled in the concave portion 18 is surely promoted. Thereby, since the temperature difference in the semiconductor wafer W is surely relaxed, the in-plane temperature uniformity in the semiconductor wafer W can be surely improved.

[0046] As described above, according to the electrostatic chuck 1 of the present embodiment, the first region 181 and the second region 182 having a surface roughness smaller than that of the first region 181 are provided on the bottom surface 18a of the concave portion 18 at the holding surface 11. Therefore, in the concave portion 18, in the first region 181, the contact area with the gas filled in the concave portion 18 becomes larger than that in the second region 182, so that heat transfer between the semiconductor wafer W and the gas filled in the concave portion 18 is promoted. Therefore, in the concave portion 18 which is a non-contact portion between the semiconductor wafer W and the convex portions 16, 17, 30a, heat transfer between the plate-like member 10 and the semiconductor wafer W is improved. Thereby, since the non-uniformity of the temperature distribution in the contact portion and the non-contact portion between the semiconductor wafer W and the convex portions 16, 17, 30a is relaxed, the in-plane temperature uniformity in the semiconductor wafer W can be improved. Further, in the second region 182 which is easily affected by heat transfer in the convex portions 16, 17, 30a, since the surface roughness is made smaller than that of the first region 181, generation of particles can be effectively suppressed.

[0047] [Second Embodiment] Next, the second embodiment will be described with reference to FIG. 7. The second embodiment has the same basic configuration as the first embodiment, but is different from the first embodiment in that it does not include a heater electrode. Therefore, the same reference numerals are given to the same configurations as those in the first embodiment, and the description thereof will be omitted as appropriate, and the description will focus on the differences from the first embodiment.

[0048] In the electrostatic chuck 1a of this embodiment, as shown in FIG. 7, inside the plate-like member 10, there is no heater electrode, and only the chuck electrode 50 is provided. That is, in the electrostatic chuck 1a, it is not possible to heat the semiconductor wafer W, and it is only possible to cool the semiconductor wafer W (draw heat from the semiconductor wafer W). In such an electrostatic chuck 1a, for example, during the execution of a process, heat is drawn from the semiconductor wafer W heated by the heat input from the plasma to cool the semiconductor wafer W.

[0049] Also in this electrostatic chuck 1a, the surface roughness of the bottom surface 18a of the concave portion 18 is made larger than the top surfaces and side surfaces of the convex portions 16, 17, 30a, and on the bottom surface 18a of the concave portion 18, a second region 182 having a smaller surface roughness than the first region 181 is formed in an annular shape so as to surround the convex portions 16, 17, 30a around the convex portions 16, 17, 30a. And since the surface roughness of the first region 181 is made larger than the surface roughness of the second region 182, as shown in FIG. 7, in the first region 181 where heat transfer is most disadvantageous, the contact area with the gas filled in the concave portion 18 (space S) becomes larger than that of the second region 182. As a result, in the first region 181, heat transfer between the plate-like member 10 and the semiconductor wafer W through the gas filled in the concave portion 18 is further promoted.

[0050] Therefore, on the holding surface 11, in the portion where there is no contact with the semiconductor wafer W, heat transfer between the plate-like member 10 and the semiconductor wafer W through the gas filled in the concave portion 18 (space S) is improved. That is, in the semiconductor wafer W, cooling in the portion that is not in contact with the convex portions 16, 17, 30a (the portion directly above the concave portion 18) is performed uniformly and efficiently. Therefore, in the semiconductor wafer W, the difference in heat transfer (heat extraction amount) between the contact portion and the non-contact portion (the first region 181 and the second region 182 of the concave portion 18) with the convex portions 16, 17, 30a can be reduced. Thereby, the temperature difference in the semiconductor wafer W can be alleviated, and the in-plane temperature uniformity can be improved.

[0051] Here, when there is a heater electrode 52 in the electrostatic chuck 1 as in the first embodiment, when the in-plane temperature in the semiconductor wafer W is non-uniform, it is also possible to adjust the in-plane temperature by adjusting the arrangement and resistance value of the heater electrode 52. However, when there is no heater electrode as in the electrostatic chuck 1a of the present embodiment, such temperature control by the heater electrode cannot be performed. Therefore, when there is no heater electrode, by adopting the configuration of the electrostatic chuck 1a of the present embodiment, it is possible to make the in-plane temperature of the semiconductor wafer W uniform.

[0052] [Third Embodiment] Next, the third embodiment will be described with reference to FIG. 8. The third embodiment has the same basic configuration as the first embodiment, but the shape of the convex portion is different from that of the first embodiment. Therefore, the same components as those in the first embodiment will be denoted by the same reference numerals and the description will be appropriately omitted, and the description will focus on the differences from the first embodiment.

[0053] In the electrostatic chuck 1b of this embodiment, as shown in FIG. 8, the cross-sectional shapes (XZ cross-sections) of the annular convex portion 116 and the convex portion 117 provided on the holding surface 11 of the plate-like member 110 are not rectangular but trapezoidal. That is, the cross-sectional shape (XZ cross-section) of the annular convex portion 116 is trapezoidal with the upper surface side dimension smaller than the bottom surface side dimension. More specifically, only the inner peripheral side surface of the annular convex portion 116 is inclined to form a trapezoid. Also, the cross-sectional shape (XZ cross-section) of each convex portion 117 is trapezoidal with the upper surface side dimension smaller than the bottom surface side dimension. More specifically, the entire peripheral surface (side surface) of the convex portion 117 is an inclined surface. Note that the sizes (areas) of the top surfaces of the convex portions 116 and 117 are the same as those of the convex portions 16 and 17 in the first embodiment. Also, the bottom side surfaces BS of the convex portions 116 and 117 serving as the reference points for the predetermined distance A are the portions where the concave portion 18's bottom surface 18a (second region 182) is connected to the side surfaces of the convex portions 116 and 117.

[0054] In such an electrostatic chuck 1b, in addition to obtaining the same effects as in the first embodiment, in the semiconductor wafer W, the change (temperature gradient) in the temperature distribution around the contact portions with the convex portions 116 and 117 can be moderated. Thereby, in the semiconductor wafer W, the abrupt temperature change occurring at the boundary between the contact portion and the non-contact portion with the convex portions 116 and 117 can be alleviated, so that the in-plane temperature uniformity can be further improved.

[0055] <Modification example> Here, a modification example in the above embodiment will be described with reference to FIG. 9. In the first to third embodiments, the case where the bottom surface 18a of the concave portion 18 is flat, that is, there is no step at the boundary between the first region 181 and the second region 182, is illustrated. However, as shown in FIG. 9, a step may be formed at the boundary between the first region 181 and the second region 182. More specifically, at the boundary between the first region 181 and the second region 182, a step may be formed such that the second region 182 with a larger surface roughness on the bottom surface 18a of the concave portion 18 is on the lower stage, and the first region with a smaller surface roughness is on the upper stage. Although FIG. 9 illustrates a convex portion having a substantially rectangular cross-sectional shape, the cross-sectional shape of the convex portion may be trapezoidal as in the second embodiment. Note that the bottom side surfaces BS of the convex portions 16, 17(30a) serving as the reference for the predetermined distance A are the portions that connect to the upper stage (second region 182) of the bottom surface 18a of the concave portion 18 among the side surfaces of the convex portions 16, 17(30a).

[0056] Note that the above embodiments are merely illustrative and do not limit the present disclosure in any way. It goes without saying that various improvements and modifications are possible without departing from the gist thereof. For example, in the above embodiments, the case where the present disclosure is applied to an electrostatic chuck is illustrated. However, the present disclosure can be applied not only to an electrostatic chuck but also to all holding devices that hold an object on the surface.

[0057] In addition, in the above embodiments, an electrostatic chuck including a base member is illustrated. However, the present disclosure can also be applied to a holding device that does not include a base member (for example, a ceramic heater, etc.). When a heater electrode is provided in such a holding device without a base member, the heater electrode may be built into a plate-like member or may be provided on the lower surface (the surface opposite to the holding surface) without being built into the plate-like member.

Description of Reference Numerals

[0058] 1 Electrostatic chuck 10 Plate-like member 11 Holding surface 12 Lower surface 16 Annular convex portion 17 Convex portion 18 recess 18a bottom surface 30a convex portion 40 bonding layer 181 first region 182 second region A predetermined distance (size of the second region) B distance between adjacent convex portions BS bottom side surface W semiconductor wafer

Claims

1. A plate-like member having a first surface formed with a plurality of convex portions and a second surface provided on the side opposite to the first surface, In a holding device for holding an object on the first surface of the plate-like member, On the bottom surface of the concave portion other than the convex portion on the first surface, A first region which is a region where the distance from the bottom side surface of the convex portion is greater than a predetermined distance, And an annular second region composed of a region where the distance from the bottom side surface of the convex portion is within the predetermined distance, The surface roughness of the first region is greater than the surface roughness of the second region A holding device characterized by this.

2. In the holding device according to Claim 1, The difference between the surface roughness of the first region and the surface roughness of the second region is greater than Ra (Sa) 0.17 μm A holding device characterized by this.

3. In the holding device according to Claim 1 or Claim 2, The surface roughness in the first region is Ra (Sa) 1.0 μm or less, The surface roughness in the second region is less than Ra (Sa) 0.5 μm A holding device characterized by this.

4. In any one of the holding devices according to Claims 1 to 3, The predetermined distance is smaller than 1 / 3 of the distance between adjacent convex portions A holding device characterized by this.

5. In any one of the holding devices according to Claims 1 to 4, The longitudinal sectional shape of the convex portion is a trapezoidal shape in which the dimension on the upper surface side is smaller than the dimension on the bottom surface side A holding device characterized by this.

Images