JP2018174256A - Repair method for substrate holding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a repair method for a substrate holding device capable of restraining a change in cooling characteristics of the substrate holding device as a module, before and after repair.SOLUTION: A repair method for an electrostatic chuck 100 including a substrate 10 composed of ceramic and having a front face 11 for mounting a wafer and a rear face 12, and a cooling board 30 joined to the rear face 12 of the substrate 10 via a junction layer 20, and in which a cooling pipe 32 is formed, includes a step of removing a front face part of the substrate 10, and a step of forming a ceramic spray deposit 40 by spraying ceramic to the front face of the substrate 10 appearing by removing the front face part, while causing a cooling medium to flow through the cooling pipe 32.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a repair method for a substrate holding device that holds a substrate such as a wafer.

  2. Description of the Related Art There is known a substrate holding device that holds a substrate such as a semiconductor wafer to be processed such as film formation or etching on an upper surface of a base made of ceramics. In such a substrate holding device, there is a risk that good holding of the substrate may not be possible if the upper surface of the substrate is worn, damaged, such as cracks, or corroded by plasma. When damage, corrosion, etc. are minor, it is preferable from the viewpoint of cost to repair and use again.

  For example, Patent Document 1 describes that a dielectric material is sprayed on a rough surface formed by polishing a surface portion of a chuck body (base body), and then an initial shape is formed by blasting.

Special table 2014-522572 gazette

  In the technique described in Patent Document 1, it is assumed that the chuck body (base body) is repaired alone. However, the substrate holding device is usually configured as a module in which a base and a cooling board are integrated via a bonding layer.

  Therefore, once it is separated from the cooling plate to repair the base, it is necessary to join the cooling plate after the base is repaired. However, since the bonding layer changes before and after the repair, the cooling characteristics of the substrate holding device as a module may change, and it becomes necessary to reset the flow rate of the cooling medium supplied to the substrate holding device after the repair.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for repairing a substrate holding device capable of suppressing a change in cooling characteristics of the substrate holding device as a module before and after the repair. To do.

  The present invention includes a base body made of ceramics having a front surface and a back surface on which a substrate is placed, and a cooling plate bonded to the back surface of the base body via a bonding layer and having a cooling medium flow path formed therein. A method for repairing a substrate holding device, comprising: removing a surface portion of the base body; spraying ceramics on the surface of the base body that appears by removing the surface portion while flowing a cooling medium through the cooling medium flow path; And a step of forming a ceramic sprayed film.

  According to the present invention, it is not necessary to separate the base body and the cooling plate in all the steps, and the bonding layer for bonding them can be made the same. Thereby, compared with the case where it is necessary to isolate | separate a base | substrate from a cooling board at the time of repair like the technique of the said patent document 1, the change of the cooling characteristic of a board | substrate holding | maintenance apparatus is suppressed.

  Furthermore, since the thermal spraying is performed while supplying the cooling medium to the cooling medium flow path, it is possible to suppress the possibility that the bonding layer is altered or damaged by the heat generated by the thermal spraying.

  In the present invention, it is preferable that an electrode is provided on the substrate, and the ceramic sprayed film has a volume resistivity or a surface resistivity of 0.01 times or more and 100 times or less as compared with a surface portion of the substrate.

  In this case, it is possible to suppress a change in the cooling characteristics of the substrate holding device as a module and a change in electrostatic attraction force that is generated by applying a voltage to the electrodes before and after the repair.

The schematic cross section of the electrostatic chuck concerning the embodiment of the substrate holding device before repair of the embodiment of the present invention. The schematic cross section which shows the state which removed the surface part of the base | substrate of the electrostatic chuck of FIG. The schematic cross section of the electrostatic chuck which concerns on embodiment of the board | substrate holding | maintenance apparatus after the repair of embodiment of this invention. The schematic cross section of the electrostatic chuck which concerns on embodiment of the board | substrate holding | maintenance apparatus before the repair which concerns on the modification of embodiment of this invention.

  An electrostatic chuck 100 according to an embodiment of a substrate holding apparatus before repair according to an embodiment of the present invention will be described with reference to FIG. Note that the drawings are schematic for easy understanding, and are different from the actual aspect ratio.

  The electrostatic chuck 100 before repair includes a base body 10 on which a wafer (substrate) is placed on the front surface 11, and a cooling board (cooling pedestal) 30 that is bonded to the back surface of the base body 10 through a bonding layer 20. ing.

  The substrate 10 has a front surface (upper surface) 11 on which a wafer is placed and held, and a rear surface (lower surface) 12 that is a surface opposite to the front surface 11. The base 10 is made of a ceramic sintered body made of alumina, aluminum nitride, silicon nitride or the like. A large number of convex portions 14 are formed on the surface 11, and the wafer is held by the upper end surface of the convex portions 14. The upper end surface of the convex portion 14 constitutes the surface 11 of the base body 10.

  Furthermore, an electrode 13 is embedded in the base 10 for sucking the wafer toward the surface 11 by Coulomb force. Note that a resistance heating element may be embedded in the base 10, and in this case, the substrate holding device of the present invention functions as a heater. Alternatively, the resistance heating element and the electrode 13 may be embedded in the base body 10. In this case, the substrate holding device of the present invention functions as an electrostatic chuck with a heater function. Furthermore, it may include an annular convex portion 14 and the substrate holding device of the present invention may function as a vacuum chuck.

  The cooling board 30 is preferably made of a material having a high thermal conductivity, and is made of a material having a higher thermal conductivity than at least the base 10. Examples of such a material include metals such as aluminum, copper, tungsten, and molybdenum, composite materials of ceramics and aluminum, composite materials of ceramics and silicon, and the like. When the cooling plate 30 is made of metal, it may be a high-purity metal made of a substantially single material or an alloy. For example, an alloy to which an appropriate element is added in order to improve mechanical characteristics may be used.

  The material of the base 10 and the cooling board 30 may be determined according to the usage environment such as the corrosion resistance against the gas used during the plasma treatment in addition to the thermal conductivity.

  The base body 10 and the cooling board 30 are fixed via the bonding layer 20. The bonding layer 20 is formed by solidifying an adhesive such as an organic adhesive or an inorganic adhesive. The thermal conductivity of the bonding layer 20 is preferably lower than that of the substrate 10.

  The type or the like of the adhesive may be selected according to the required performance such as the wafer operating temperature, the corrosion resistance against the gas used during the plasma processing, and the airtightness between the substrate 10 and the cooling board 30. For example, an epoxy adhesive, an acrylic adhesive, a silicone adhesive, or a polyimide adhesive can be used for an organic adhesive. In the case of an inorganic adhesive, an adhesive containing at least one of silica, alumina, zirconia, calcia, and aluminum nitride can be used.

  In addition, joining of the base | substrate 10 and the cooling board 30 is not limited to the method using an adhesive agent, You may perform it by a known method. For example, the base 10 and the cooling board 30 may be bonded using a low melting point metal such as indium or a low melting point alloy.

  Although not shown, a heat insulating plate may be interposed between the base 10 and the cooling board 30. In this case, for example, the bonding layer 20 may be provided between the base 10 and the heat insulating plate and between the cooling plate 30 and the heat insulating plate. The thermal conductivity of the heat insulating plate is preferably lower than the thermal conductivity of the substrate 10, similarly to the bonding layer 20.

  The cooling board 30 includes a groove 31 formed inside, and a cooling pipe 32 disposed in the groove 31. The cooling pipe 32 is supplied with a cooling medium such as water or a fluorine-based cooling refrigerant from a cooling medium supply unit (not shown), and the cooling medium flows through the cooling pipe 32. The cooling pipe 32 corresponds to the cooling medium flow path of the present invention.

  The cross-sectional shape of the groove 31 is not particularly limited, and is, for example, a square, a rectangle, a circle, or an ellipse. The path of the groove 31 is not particularly limited, but may be the same path as a groove supplied with a conventional cooling medium.

  The material of the cooling pipe 32 is not particularly limited. For example, a metal or resin pipe can be used. However, the cooling pipe 32 is preferably made of a material having low thermal conductivity, and for example, a SUS pipe can be suitably used. The cross-sectional shape of the cooling pipe 32 is not particularly limited, and is, for example, a square, a rectangle, a circle, or an ellipse. The cross-sectional area of the cooling pipe 32 may be the same as the cross-sectional area of a groove to which a conventional cooling medium is supplied.

  The cooling pipe 32 may not be provided, and the cooling medium may flow directly in the groove 31. In this case, the groove 31 corresponds to the cooling medium flow path of the present invention.

  Next, an embodiment of the method for repairing a substrate holding apparatus of the present invention will be described with reference to FIGS. 1 to 3 for the case of repairing the electrostatic chuck 100 described above.

  First, as shown in FIG. 2, a step of removing the surface portion of the substrate 10 is performed. In this step, a surface portion of the substrate 10, for example, a portion from the surface 11 to several hundred μm is removed by rough polishing using a polishing machine or the like. Thereafter, finish polishing is performed by lapping or the like so that the polished surface becomes a smooth surface.

  Next, as shown in FIG. 3, a step of forming a ceramic sprayed film 40 by spraying ceramics on the surface 11 of the substrate 10 which appears by removing the surface portion is performed.

  Specifically, in this step, first, the electrostatic chuck 100 from which the surface portion of the substrate 10 has been removed is fixed to a support base of a thermal spraying apparatus (not shown), and the cooling pipe 32 is connected to a cooling medium supply means (not shown). Then, the ceramic material is sprayed onto the surface of the substrate 10 by a thermal spraying apparatus while supplying the cooling medium from the cooling medium supply means to the cooling pipe 32. Thereby, the ceramic sprayed film 40 is formed on the surface of the substrate 10.

  The thermal spray material constituting the ceramic thermal spray film 40 is made of the same material as the base 10 or a material obtained by adding a small amount of additives to the same material. The ceramic sprayed film 40 preferably has a volume resistivity or surface resistivity of 0.01 times or more and 100 times or less as compared with the substrate 10.

  If the volume resistivity or surface resistivity of the ceramic sprayed film 40 is less than 0.01 times that of the substrate 10, the contact resistance between the wafer (substrate) and the electrostatic chuck becomes too small to attract the wafer. The electrostatic attraction force necessary to do this is not expressed. When the volume resistivity or surface resistivity of the ceramic sprayed film 40 is more than 100 times that of the substrate 10, the voltage required for electrostatically attracting the wafer is higher than that of the electrostatic chuck 100 before repair. If the electrostatic chuck 100 is used under the same condition as that of the electrostatic chuck 100 before being repaired, the required electrostatic attraction force cannot be obtained.

  The thickness of the ceramic sprayed film 40 may be determined so that the sum of the thickness of the base 10 from which the surface portion is removed and the thickness of the ceramic sprayed film 40 exceeds the initial thickness of the base 10.

  Next, a step of removing the surface portion of the ceramic sprayed film 40 is performed. In this step, the surface portion of the ceramic sprayed film 40 is removed so that the sum of the thickness of the substrate 10 from which the surface portion has been removed and the thickness of the ceramic sprayed film 40 is the same as the initial thickness of the substrate 10.

  Finally, although not shown in the figure, a process of forming the projections and the like formed on the surface 11 of the substrate 10 is performed on the surface portion of the ceramic sprayed film 40. In this step, a mask is placed on the surface of the ceramic sprayed film 40 and blasting or the like is performed.

  As described above, according to the embodiment of the present invention, it is not necessary to separate the base 10 and the cooling board 30 in the entire repair process, and the bonding layer 20 for bonding them can be maintained as it is. . Thereby, the change of the cooling characteristic of the electrostatic chuck 100 is suppressed compared with the case where it is necessary to separate the base body from the cooling plate at the time of repair as in the technique described in Patent Document 1. Accordingly, the degree of resetting the flow rate of the cooling medium supplied to the cooling pipe 32 after the repair is reduced.

  Further, since the thermal spraying is performed while supplying the cooling medium to the cooling pipe 32, it is possible to suppress the possibility that the bonding layer 20 is deteriorated or damaged by the heat generated by the thermal spraying. Further, since the substrate 10 is cooled during the thermal spraying and does not excessively increase in temperature, a dense ceramic sprayed film 40 can be formed.

  As shown in FIG. 4, the base 10 of the electrostatic chuck 100 includes a main body portion 10A made of a ceramic sintered body, and an insulating layer 10B made of ceramic formed on the upper surface of the main body portion 10A. It may be a thing. In this case, for example, the insulating layer 10B is formed by spraying ceramics on the surface of the main body 10A.

  In such a case, only the insulating layer 10B may be removed or the insulating layer 10B and the main body 10A may be removed in the step of removing the surface portion of the base body 10 described above.

Example 1
A substrate 10 made of an alumina sintered body and having an insulating layer 10B having a thickness of 1 mm formed on the surface of a disc-shaped main body portion 10A having a diameter of 200 mm and a thickness of 7 mm was prepared. The insulating layer 10B was made of an alumina spray, and had a volume resistivity of 1 × 10 ¹¹ [Ω · cm] and a surface resistivity of 5 × 10 ¹⁰ [Ω / □].

  As the cooling board 30, a disk-shaped disk made of copper and having a diameter of 200 mm and a thickness of 25 mm was prepared.

  The base 10 and the cooling plate 30 are bonded using indium (melting point 157 ° C.), and the thickness of the bonding layer 20 is 200 μm.

  The surface portion of the base 10 of the electrostatic chuck 100 configured as described above was removed by 0.5 mm with a grinding machine.

  Next, the electrostatic chuck 100 was fixed to a support base of a thermal spraying apparatus (not shown), and the cooling pipe 32 was connected to a cooling medium supply means (not shown). The surface of the substrate 10 is then sprayed by a thermal spraying apparatus using alumina granules added with 2.5% by weight of titanium oxide as the thermal spraying raw material while supplying water at a flow rate of 3 [l / m] to the cooling pipe 32 from a cooling medium supply means (not shown). Thermally sprayed on.

  Thermal spraying is carried out by supplying a mixed substrate made of argon at a flow rate of 41 [l / m] and oxygen at a flow rate of 45 [l / m] to the sprayed portion at atmospheric pressure, while the distance between the spray gun and the substrate 10 is 80 [. mm], thermal spray output was 60 [kW], scan speed was 650 [mm / sec], and raw material supply was 30 [g / min]. The thickness of the ceramic sprayed film 40 was 800 [μm].

Next, the surface portion of the ceramic sprayed film 40 was ground by 300 [μm]. The ceramic sprayed film 40 had a volume resistivity of 4 × 10 ¹¹ [Ω · cm] and a surface resistivity of 1 × 10 ¹⁰ [Ω / □].

  In addition, the surface resistivity and volume resistivity were measured using a Mitsubishi Chemical Analytech Co., Ltd. Hirestar. Since the volume resistivity of the ceramic sprayed film 40 is such that no electrode is present on the lower surface side of the ceramic sprayed film 40, the volume resistance of the built-in electrode and the main body 10A of the substrate 10 on the electrode is measured in advance before spraying. The volume resistivity of the ceramic sprayed film 40 was estimated by subtracting from the synthesized volume resistivity of the main body 10A and the ceramic sprayed film 40 after spraying.

(Examples 2 to 5)
In Examples 2 to 5, repair was performed under the same conditions as in Example 1 except that the volume resistivity and surface resistivity of the ceramic spray coating 40 were changed. In addition, in order to change the volume resistivity of Examples 2-5, the addition amount of the titanium oxide in a thermal spray raw material was changed.

(Comparative Example 1)
In Comparative Example 1, the base body 10 and the cooling plate 30 were once separated, then the base body 10 was repaired, and the base body 10 on which the ceramic sprayed film 40 was formed was joined to the cooling board 30. In addition, the material and production conditions which comprise the ceramic sprayed film 40 of the comparative example 1 are the same as Example 1 except that the thermal spraying was not performed while supplying the cooling medium to the cooling pipe 32.

(Evaluation method)
For Examples 1 to 5 and Comparative Example 1, in addition to the surface resistivity and volume resistivity of the ceramic sprayed film 40 described above, an electrostatic adsorption force, a leakage current, and a wafer temperature were evaluated.

  The electrostatic attraction force is evaluated by sealing He gas between the ceramic sprayed film 40 on which the wafer is placed and the wafer through a gas supply hole opened on the upper surface of the ceramic sprayed film 40 (not shown) while the wafer is attracted. Then, the pressure of He gas was measured when the amount of He gas leaking outside from the space between the ceramic sprayed film 40 and the wafer was 2 sccm or more. The gas pressure was measured by using a pressure gauge provided on the gas supply path connected to the gas supply hole.

  The leak current is a microammeter (advantest test), which is a direct current that flows into the wafer when the wafer placed on the electrostatic chuck 100 is electrostatically attracted by applying a potential difference of 500 V to the electrode embedded in the substrate 10. Measurement was performed using R8340A).

  The wafer temperature was measured when the electrostatic chuck 100 was mounted on a plasma process apparatus and plasma etching was performed under the same conditions as before repair.

  According to the repair methods of Examples 1 to 3, when plasma etching was performed under the same conditions as before repair, it was confirmed that the wafer temperature and electrostatic adsorption force can be maintained substantially the same as before repair.

  On the other hand, according to the repair methods of Examples 4 and 5, when plasma etching was performed under the same conditions as before repair, it was confirmed that the wafer temperature could not be maintained substantially the same as before repair. Furthermore, according to the repair method of Comparative Example 1, it was confirmed that when plasma etching was performed under the same conditions as before repair, the wafer temperature greatly changed from that before repair.

  In addition, according to the repair methods of Examples 4 and 5, it was confirmed that when plasma etching was performed under the same conditions as before repair, the electrostatic adsorption force could not be maintained substantially the same as before repair.

  DESCRIPTION OF SYMBOLS 10 ... Base | substrate, 10A ... Main-body part, 10B ... Insulating layer, 11 ... Front surface, 12 ... Back surface, 13 ... Electrode, 14 ... Convex part, 20 ... Joining layer, 30 ... Cooling board, 31 ... Groove, 32 ... Cooling pipe ( Cooling medium flow path), 40 ... ceramic sprayed film, 100 ... electrostatic chuck (substrate holding device).

Claims (2)

A substrate holding apparatus comprising: a base made of ceramics having a front surface and a back surface on which a substrate is placed; and a cooling plate bonded to the back surface of the base via a bonding layer and having a cooling medium flow path formed therein. A repair method,
Removing the surface portion of the substrate;
Forming a ceramic sprayed film by spraying ceramics on the surface of the substrate that appears by removing the surface portion while flowing a cooling medium through the cooling medium flow path. An electrode is provided on the substrate;
2. The method according to claim 1, wherein the ceramic sprayed film has a volume resistivity or a surface resistivity of 0.01 to 100 times that of a surface portion of the substrate.