substrate fixing device

Abstract

To ensure sufficient gas flow and prevent premature failure.SOLUTION: A substrate fixing device includes: a base plate having a first through hole penetrating in a thickness direction; a ceramic plate that is caused to adhere to the base plate and has a second through hole, communicates with the first through hole, and attracts an attraction object by electrostatic force generated when a voltage is applied to a built-in electrode; an insulating plug arranged in a connection portion between the first through hole and the second through hole; and a sealing member that is attached to the insulating plug, and seals a periphery of the connection portion.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a substrate fixing device. [Background technology]

[0002] Generally, a substrate clamping device that adsorbs and holds a wafer, for example, when manufacturing semiconductor parts, is also called an electrostatic chuck (ESC) and includes a ceramic plate with a built-in electrode. The substrate clamping device has a structure in which a ceramic plate is fixed to a base plate, and by applying a voltage to the electrode built into the ceramic plate, the wafer is adsorbed to the surface of the ceramic plate using electrostatic force. By adsorbing and holding the wafer on the ceramic plate, processes such as micromachining and etching can be performed efficiently on the wafer.

[0003] In such substrate holding devices, an inert gas such as helium (He) is sometimes introduced between the surface of the ceramic plate and the wafer to be held, thereby controlling the wafer temperature. For example, in processes such as dry etching and film formation (sputtering and CVD) in a plasma environment, the wafer temperature may rise during processing. Therefore, to maintain a constant wafer temperature, an inert gas such as He is introduced between the wafer and the ceramic plate surface that holds the wafer, and the wafer comes into contact with the inert gas, thereby suppressing the rise in wafer temperature.

[0004] The inert gas is introduced through a gas hole provided in the substrate fixing device. Fig. 11 is a cross-sectional view showing the structure around the gas hole of the substrate fixing device. As shown in Fig. 11, the substrate fixing device is configured by bonding a ceramic plate 20 to a base plate 10 with an adhesive 30. A gas hole TH is formed in the base plate 10 and the ceramic plate 20, and the inert gas passes through the gas hole TH from the base plate 10 side and is released onto the surface of the ceramic plate 20.

[0005] The gas hole TH in the base plate 10 has a large diameter near the joint with the ceramic plate 20, and an insulating plug 40 is bonded to the inner wall surface of this large diameter portion with an adhesive 50. The insulating plug 40 is, for example, a porous body, and the inert gas passes through the many pores of the insulating plug 40 and flows into the gas hole TH in the ceramic plate 20. By disposing the insulating plug 40, the inner wall surface of the gas hole TH in the base plate 10 is insulated, making it possible to prevent, for example, abnormal discharge from plasma to the base plate 10. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-195346 [Patent Document 2] Japanese Patent Publication No. 2020-145281 [Patent Document 3] International Publication No. 2016 / 132909 [Patent Document 4] Patent Publication No. 2021-044303 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the substrate fixing device configured as described above has a problem in that the adhesive bonding the base plate and ceramic plate to each other flows into the gas hole, causing clogging or narrowing of the gas hole. For example, in the substrate fixing device shown in FIG. 11, when bonding the base plate 10 and ceramic plate 20, the semi-cured adhesive 30 flows into the gas hole TH, causing the gas hole TH to become completely clogged or narrow. Furthermore, the pores of the porous insulating plug 40 may become clogged. As a result, the flow rate of the inert gas through the gas hole TH decreases, and the temperature of the wafer adsorbed on the surface of the ceramic plate 20 may not be adequately controlled.

[0008] Furthermore, when the substrate fixing device is used in a plasma environment, plasma flows into the gas holes TH, causing damage and deterioration of the adhesive 30 that bonds the base plate 10 and the ceramic plate 20. If the adhesive 30 deteriorates, the base plate 10 and the ceramic plate 20 may peel off, which may cause early damage to the substrate fixing device.

[0009] The disclosed technology has been made in view of the above points, and aims to provide a substrate fixing device that can ensure a sufficient flow rate of gas and prevent early damage. [Means for solving the problem]

[0010] In one aspect, the substrate fixing device disclosed in the present application comprises a base plate having a first through hole penetrating in the thickness direction, a ceramic plate adhered to the base plate and having a second through hole communicating with the first through hole, and which attracts an object to be attracted by electrostatic force generated when a voltage is applied to an electrode built in the base plate, an insulating plug placed at the connection portion between the first through hole and the second through hole, and a sealing member attached to the insulating plug and sealing the periphery of the connection portion. [Effects of the Invention]

[0011] According to one aspect of the substrate fixing device disclosed in the present application, it is possible to ensure a sufficient flow rate of gas and prevent early damage. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing the configuration of a substrate fixing device according to one embodiment. [Figure 2] FIG. 2 is a schematic diagram showing a cross section of a substrate fixing device according to one embodiment. [Figure 3] FIG. 3 is an enlarged cross-sectional view of a substrate fixing device according to one embodiment. [Figure 4] FIG. 4 shows a specific example of an insulating plug and a sealing member. [Figure 5] FIG. 5 is a diagram showing a first modified example of the substrate fixing device. [Figure 6] FIG. 6 is a diagram showing a second modified example of the substrate fixing device. [Figure 7] FIG. 7 is a diagram showing a third modified example of the substrate fixing device. [Figure 8] FIG. 8 is a diagram showing a fourth modified example of the substrate fixing device. [Figure 9] FIG. 9 is a diagram showing a fifth modified example of the substrate fixing device. [Figure 10] FIG. 10 is a diagram showing a sixth modified example of the substrate fixing device. [Figure 11] FIG. 11 is a diagram showing an example of the structure around the gas hole of the substrate fixing device. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of a substrate fixing device disclosed in the present application will be described in detail below with reference to the drawings, although the present invention is not limited to this embodiment.

[0014] 1 is a perspective view showing the configuration of a substrate holding device 100 according to one embodiment. The substrate holding device 100 shown in FIG.

[0015] The base plate 110 is a circular member made of metal such as aluminum. The base plate 110 is a base material for fixing the ceramic plate 120. The base plate 110 is attached to, for example, a semiconductor manufacturing device, and causes the substrate fixing device 100 to function as a semiconductor holding device for holding a wafer.

[0016] The ceramic plate 120 has a built-in conductive electrode and uses the electrostatic force generated when a voltage is applied to the electrode to attract an object to be attracted, such as a wafer. The ceramic plate 120 also has a gas hole opening (not shown) on the surface that attracts the object to be attracted, and controls the temperature of the object to be attracted by an inert gas such as helium (He) released from the opening. The diameter of the ceramic plate 120 is smaller than the diameter of the base plate 110, and the ceramic plate 120 is fixed to the center of the base plate 110. At this time, the ceramic plate 120 is adhered to the base plate 110 with an adhesive such as silicone resin.

[0017] Fig. 2 is a schematic cross-sectional view taken along line II in Fig. 1. As shown in Fig. 2, the substrate fixing device 100 is configured by bonding a base plate 110 and a ceramic plate 120 with an adhesive .

[0018] Base plate 110 is a circular metal member having a thickness of, for example, about 20 to 50 mm. Inside base plate 110, cooling water channels 111 serving as channels for cooling water and through holes 112 serving as channels for inert gas are formed.

[0019] The cooling water channel 111 is a flow path that circulates inside the base plate 110, and cools the ceramic plate 120 with cooling water that flows into the cooling water channel 111 from the outside of the substrate fixing device 100. As a result of the ceramic plate 120 being cooled, an object to be adsorbed, such as a wafer, that is adsorbed to the surface of the ceramic plate 120 is cooled. Note that the base plate 110 may have a cooling gas channel that serves as a channel for cooling gas, instead of the cooling water channel 111. Furthermore, the base plate 110 may have a channel for a heat-retaining medium, instead of the cooling water channel 111. In short, the base plate 110 has a medium passage for adjusting the temperature of the ceramic plate 120 and the object to be adsorbed.

[0020] The through-hole 112 is a through-hole that penetrates the base plate 110 in the thickness direction, and delivers an inert gas such as He that flows into the through-hole 112 from outside the substrate fixing device 100 to the through-hole 122 in the ceramic plate 120. The through-hole 112 has a counterbore portion with an increased diameter near the opening on the ceramic plate 120 side, and an insulating plug is placed in the counterbore portion. The structure of A in the figure near the counterbore portion of the through-hole 112 will be described in detail later.

[0021] The ceramic plate 120 is a circular plate made of ceramic, for example, 4 to 6 mm thick. The ceramic plate 120 is obtained by firing a green sheet made of, for example, aluminum oxide. Inside the ceramic plate 120, a conductive electrode 121 and a through hole 122 that serves as a flow path for the inert gas are formed.

[0022] The electrode 121 is disposed inside the ceramic plate 120, and generates an electrostatic force when a voltage is applied to the electrode 121. This electrostatic force causes the ceramic plate 120 to attract an object to be attracted, such as a wafer, to its surface.

[0023] The through-holes 122 are through-holes that penetrate the ceramic plate 120 in the thickness direction and communicate with the through-holes 112 of the base plate 110. That is, the through-holes 122 discharge the inert gas delivered from the through-holes 112 of the base plate 110 from the openings on the surface of the ceramic plate 120. This allows the object to be adsorbed onto the surface of the ceramic plate 120 to come into contact with the inert gas, thereby cooling the object to be adsorbed.

[0024] The adhesive 130 is made of, for example, silicone resin or epoxy resin, and bonds the base plate 110 and the ceramic plate 120. As will be described later, the connection portion between the through hole 112 and the through hole 122 is sealed by a sealing member arranged around the insulating plug, so that the adhesive 130 does not enter the through hole 112 or the through hole 122.

[0025] Fig. 3 is an enlarged view showing A in Fig. 2. That is, Fig. 3 shows an enlarged view of the connection portion between the through-hole 112 of the base plate 110 and the through-hole 122 of the ceramic plate 120.

[0026] 3, the through hole 112 of the base plate 110 has a larger diameter at the connection portion with the through hole 122 of the ceramic plate 120, and a counterbore is formed. An insulating plug 140 is placed in the counterbore, and a sealing member 150 is pressed against the peripheral edge of the upper surface of the insulating plug 140 from above. Note that, in this description, the direction in which the ceramic plate 120 is positioned relative to the base plate 110 is the upward direction, but the substrate fixing device 100 may be manufactured and used in any position, for example, upside down.

[0027] The insulating plug 140 is a porous body made of, for example, ceramic, and allows the inert gas flowing into the through-hole 112 to pass through the numerous holes and be delivered to the through-hole 122 in the ceramic plate 120. The insulating plug 140 has a cylindrical shape with a lower portion having a diameter approximately equal to the diameter of the counterbore and an upper portion having a diameter smaller than the diameter of the counterbore. In other words, the insulating plug 140 has a shape of two stacked columns of different diameters, with the sealing member 150 pressing against the stepped portion. Because the sealing member 150 presses the insulating plug 140 toward the base plate 110, the insulating plug 140 is not bonded to the inner circumferential surface 112a of the counterbore. In other words, the insulating plug 140 is fixed to the counterbore by the pressure from the sealing member 150 without being bonded to the base plate 110.

[0028] The sealing member 150 is an annular member made of, for example, silicone resin, fluorine-based resin, elastomer resin, epoxy resin, polyimide resin, acrylic resin, phenolic resin, or liquid crystal polymer, and seals the periphery of the connection portion between the through hole 112 and the through hole 122. Specifically, the sealing member 150 is attached to the peripheral portion of the upper surface of the insulating plug 140, with its upper end face abutting the lower surface of the ceramic plate 120 and its lower end face pressing against the peripheral portion of the upper surface of the insulating plug 140. The sealing member 150 presses the insulating plug 140 downward by the adhesive force of the adhesive 130 bonding the base plate 110 and the ceramic plate 120, so that the insulating plug 140 can be fixed to the counterbore portion without adhesive.

[0029] As a material for the sealing member 150, it is desirable to use a material that has excellent sealing properties, heat resistance, and plasma resistance, such as the various resins described above. For example, silicone resin and elastomer resin have excellent sealing properties, so when the sealing member 150 is formed using a silicone resin or an elastomer resin, the sealing properties can be improved. Furthermore, for example, fluorine-based resin has excellent plasma resistance, so when the sealing member 150 is formed using a fluorine-based resin, deterioration of the sealing member 150 due to plasma can be suppressed. Furthermore, for example, polyimide resin has excellent heat resistance, so when the sealing member 150 is formed using a polyimide resin, deformation and damage to the sealing member 150 can be suppressed even if the sealing member 150 is heated, for example, by a heater for keeping the object to be adsorbed warm.

[0030] Fig. 4 is an exploded view showing a specific example of insulating plug 140 and sealing member 150. As shown in Fig. 4, insulating plug 140 has a shape in which large diameter portion 141 having a cylindrical shape with a diameter approximately the same as the diameter of the counterbore portion is stacked on small diameter portion 142 having a cylindrical shape with a diameter smaller than the diameter of the counterbore portion. Due to the difference in diameter between the two-step cylindrical shapes that form insulating plug 140, upper surface 141a of large diameter portion 141 is exposed, forming a step portion.

[0031] On the other hand, sealing member 150 is an annular member having a through hole 151 in the center, and is attached to insulating plug 140 by inserting small diameter portion 142 of insulating plug 140 into through hole 151. That is, the lower end surface of sealing member 150 abuts against upper surface 141a of large diameter portion 141, and when insulating plug 140 is fitted into the counterbore in this state, the upper end surface of sealing member 150 abuts against the lower surface of ceramic plate 120.

[0032] Because the height h1 of the large diameter portion 141 of the insulating plug 140 is smaller than the depth of the counterbore of the through hole 112, the upper surface 141a of the large diameter portion 141 is located lower than the upper surface of the base plate 110. That is, the large diameter portion 141 is completely accommodated in the counterbore of the through hole 112. Furthermore, the height h2 of the small diameter portion 142 of the insulating plug 140 is, for example, about 0.2 to several mm and is larger than the thickness of the adhesive 130. Therefore, the lower end of the small diameter portion 142 reaches a position lower than the upper surface of the base plate 110 and is located at the same height as the upper surface 141a of the large diameter portion 141. Furthermore, the height h3 of the sealing member 150 is equal to or greater than the height h2 of the small diameter portion 142, so that the small diameter portion 142 does not protrude from the through hole 151 when the sealing member 150 is placed on the upper surface 141a of the large diameter portion 141.

[0033] The width d1 of the step portion due to the difference in diameter between the large diameter portion 141 and the small diameter portion 142 of the insulating plug 140 is, for example, about 0.1 to several mm. Furthermore, the width d2 of the ring of the sealing member 150 excluding the through hole 151 is equal to or greater than the width d1 of the step portion, so that when the sealing member 150 is placed on the upper surface 141a of the large diameter portion 141, the upper surface 141a is covered and not exposed. In this case, the side surface of the small diameter portion 142 does not necessarily have to be completely covered by the inner circumferential surface of the through hole 151 of the sealing member 150. That is, the inner circumferential surface of the through hole 151 may have, for example, a convex curved shape and cover only the central portion of the side surface of the small diameter portion 142, or the inner circumferential surface of the through hole 151 may have, for example, a concave curved shape and cover only the upper and lower end portions of the side surface of the small diameter portion 142.

[0034] In this way, the sealing member 150 surrounding the small diameter portion 142 covers the upper surface 141a of the large diameter portion 141, so when the insulating plug 140 is fitted into the counterbore of the through hole 112, the space between the upper surface 141a of the large diameter portion 141 and the lower surface of the ceramic plate 120 is filled with the sealing member 150. That is, the upper end surface of the sealing member 150 abuts against the lower surface of the ceramic plate 120, and the lower end surface presses against the upper surface 141a of the large diameter portion 141. Therefore, the insulating plug 140 can be fixed to the counterbore by the pressure from the sealing member 150, even without bonding the insulating plug 140 to the base plate 110.

[0035] Furthermore, the periphery of the connection portion between the through holes 112 and 122 is sealed, and as a result, the adhesive 130 does not enter the through holes 112 and 122, preventing clogging and narrowing of the through holes 112 and 122, which are flow paths for the inert gas. Similarly, the adhesive 130 does not come into contact with the insulating plug 140, preventing the adhesive 130 from flowing into the holes of the insulating plug 140, which is a porous body. Furthermore, even if plasma flows into the through holes 122 of the ceramic plate 120, the plasma does not come into contact with the adhesive 130, preventing deterioration of the adhesive 130. Therefore, peeling between the base plate 110 and the ceramic plate 120 can be prevented.

[0036] As described above, according to this embodiment, an insulating plug having a large diameter portion and a small diameter portion is disposed at the connection portion of the through hole of the base plate and the ceramic plate, which is the inert gas flow path, and a sealing member is disposed surrounding the small diameter portion, thereby sealing the periphery of the connection portion of the through hole. Therefore, the insulating plug can be pressed by the sealing member and fixed to the base plate without adhesive. Furthermore, the adhesive bonding the base plate and the ceramic plate does not enter the inert gas flow path, preventing clogging and narrowing of the flow path and ensuring a sufficient gas flow rate. Furthermore, plasma flowing from the outside into the inert gas flow path does not come into contact with the adhesive, suppressing deterioration of the adhesive and preventing early damage to the substrate holding device.

[0037] The shapes of the insulating plug 140 and the sealing member 150 described in the above embodiment can be modified in various ways. Modified examples of the substrate fixing device 100 will now be described in detail.

[0038] Fig. 5 is a diagram showing a first modified example of the substrate fixing device 100. In Fig. 5, the same parts as in Fig. 3 are denoted by the same reference numerals.

[0039] 5, the small diameter portion 142 of the insulating plug 140 has a truncated cone shape. Therefore, the lower end surface of the sealing member 150 is sloped according to the side surface of the small diameter portion 142. In this way, the insulating plug 140 can be formed only by tapering, which reduces processing costs and prevents damage to the insulating plug 140 due to the pressure applied to the insulating plug 140 by the sealing member 150.

[0040] Fig. 6 is a diagram showing a second modified example of the substrate fixing device 100. In Fig. 6, the same parts as in Fig. 3 are denoted by the same reference numerals.

[0041] In the modification shown in Fig. 6, the large diameter portion 141 and the small diameter portion 142 of the insulating plug 140 overlap with each other via a truncated cone. Therefore, the lower end surface of the sealing member 150 is inclined in accordance with the side surface of the truncated cone. This allows the insulating plug 140 to be fixed to the sealing member 150 more reliably than in the first modification shown in Fig. 5.

[0042] Fig. 7 is a diagram showing a third modified example of the substrate fixing device 100. In Fig. 7, the same parts as in Fig. 3 are denoted by the same reference numerals.

[0043] 7, small diameter portion 142 of insulating plug 140 has a two-tiered cylindrical shape with different diameters. That is, small diameter portion 142 has a first small diameter cylinder that overlaps large diameter portion 141 and has a smaller diameter than large diameter portion 141, and a second small diameter cylinder that overlaps the first small diameter cylinder and has a smaller diameter than the first small diameter cylinder. Therefore, the lower end surface of sealing member 150 has a step corresponding to the step of small diameter portion 142. This can improve the sealing performance of sealing member 150.

[0044] Fig. 8 is a diagram showing a fourth modified example of the substrate fixing device 100. In Fig. 8, the same parts as in Fig. 3 are denoted by the same reference numerals.

[0045] 8, small diameter portion 142 of insulating plug 140 has a two-tiered cylindrical shape with different diameters. That is, small diameter portion 142 has a first small diameter cylinder that overlaps large diameter portion 141 and has a smaller diameter than large diameter portion 141, and a second small diameter cylinder that overlaps large diameter portion 141 and has a smaller diameter than large diameter portion 141 but a larger diameter than the first small diameter cylinder. Therefore, the upper end surface of sealing member 150 has a step corresponding to the step of small diameter portion 142. This can improve the sealing performance of sealing member 150.

[0046] 9 is a diagram showing a fifth modified example of the substrate fixing device 100. In FIG. 9, the same parts as in FIG. 3 are denoted by the same reference numerals.

[0047] 9, a porous plug 122a is placed in the through hole 122 of the ceramic plate 120. The porous plug 122a is a porous body made of, for example, ceramic, similar to the insulating plug 140. Even when the porous plug 122a is placed in the through hole 122 in this manner, the periphery of the connection between the through hole 112 and the through hole 122 is sealed with the sealing member 150, so that the adhesive 130 does not come into contact with the porous plug 122a and it is possible to prevent the adhesive 130 from flowing into the hole of the porous plug 122a.

[0048] 10 is a diagram showing a sixth modified example of the substrate fixing device 100. In FIG. 10, the same parts as in FIG. 3 are denoted by the same reference numerals.

[0049] In the modification shown in FIG. 10 , the substrate fixing device 100 has a sleeve-type insulating plug 160 instead of the porous insulating plug 140. The insulating plug 160 is an insulating sleeve having a through hole 161 communicating with the through hole 112 of the base plate 110. The inert gas flowing into the through hole 112 of the base plate 110 passes through the through hole 161 of the insulating plug 160 and flows into the through hole 122 of the ceramic plate 120. Even when the insulating sleeve insulating plug 160 is disposed at the connection between the through hole 112 and the through hole 122 instead of the porous insulating plug 140, the sealing member 150 can prevent the adhesive 130 from flowing into the gas flow path. The insulating sleeve can be formed using ceramics such as aluminum oxide, zirconium oxide, yttrium oxide, or aluminum nitride. The insulating sleeve may also be formed using a resin material such as polyimide, fluorine-based resin, PEEK (polyether ether ketone), or polycarbonate.

[0050] The above-described embodiment and each modified example can be implemented in various combinations. For example, the fifth modified example and the sixth modified example may be combined, such that an insulating plug 160 made of an insulating sleeve is placed in the through hole 112 of the base plate 110, and a porous plug 122a is placed in the through hole 122 of the ceramic plate 120. Furthermore, the porous plug 122a of the fifth modified example can be replaced with an insulating sleeve similar to the insulating plug 160. [Explanation of symbols]

[0051] 110 base plate 111 Cooling Channel 112, 122, 151, 161 Through holes 120 Ceramic Plate 121 Electrode 122a Porous plug 130 Adhesive 140, 160 insulated plug 141 Large diameter section 142 Small diameter section 150 Sealing member

Claims

1. a base plate having a first through hole penetrating in a thickness direction; a ceramic plate that is bonded to the base plate, has a second through hole that communicates with the first through hole, and attracts an object to be attracted by electrostatic force that is generated when a voltage is applied to an electrode built therein; an insulating plug disposed in the first through hole at a connection portion between the first through hole and the second through hole; a sealing member attached to the insulating plug and sealing the periphery of the connection portion; and the first through hole has an opening connected to the second through hole at the connection portion, and has a counterbore provided in the opening, one end surface of the sealing member abuts against the bonding surface of the ceramic plate with the base plate, and the other end surface presses against the insulating plug; The insulating plug is not bonded to the base plate but is fixed in the counterbore by pressure from the sealing member. A substrate fixing device characterized by:

2. The insulating plug is a large diameter portion having a diameter substantially equal to that of the first through hole; a small diameter portion overlapping the large diameter portion and having a diameter smaller than that of the large diameter portion, The sealing member is A through hole into which the small diameter portion is inserted 2. The substrate fixing device according to claim 1.

3. The large diameter portion is It has a cylindrical shape with a diameter substantially equal to that of the counterbore portion, and the entirety of it is accommodated in the counterbore portion.

3. The substrate fixing device according to claim 2.

4. The small diameter portion is A cylindrical portion having a diameter smaller than the large diameter portion 4. The substrate fixing device according to claim 3.

5. The small diameter portion A truncated cone portion extends tapered from the large diameter portion.

4. The substrate fixing device according to claim 3.

6. The small diameter portion is a truncated cone portion extending tapered from the large diameter portion; a cylindrical portion overlapping the truncated cone portion; 4. The substrate fixing device according to claim 3.

7. The small diameter portion is a first cylindrical portion overlapping the large diameter portion and having a diameter smaller than that of the large diameter portion; a second cylindrical portion overlapping the first cylindrical portion and having a smaller diameter than the first cylindrical portion; 4. The substrate fixing device according to claim 3.

8. The small diameter portion is a first cylindrical portion overlapping the large diameter portion and having a diameter smaller than that of the large diameter portion; a second cylindrical portion overlapping the first cylindrical portion and having a diameter smaller than the large diameter portion and larger than the first cylindrical portion; 4. The substrate fixing device according to claim 3.

9. a porous plug disposed in the second through-hole and having a plurality of holes through which gas passes; 2. The substrate fixing device according to claim 1, further comprising:

10. The insulating plug is a porous body having a plurality of holes.

2. The substrate fixing device according to claim 1.

11. The insulating plug is an insulating sleeve having a through hole communicating with the first through hole.

2. The substrate fixing device according to claim 1.

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