JP2011049428A - Support device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a support device preventing a metal contamination etc. from scattering into a working space by reducing an air leak from the inside to the outside with simple configurations. <P>SOLUTION: The support device 1 includes a heater plate 2, a shaft 3, and a fixing member 22 that mechanically fixes them in a joined state. The heater plate 2 has a plane where a wafer 4 is mounted, and a heating resistor 6. The shaft 3 is joined to the heater plate 2 on a plane opposed to the plane where the wafer 4 is mounted. A junction surface for the heater plate 2 and a junction surface for the shaft 3 are surface-treated so that an air leak in a gap between the junction surface for the heater plate 2 and the junction surface for the shaft 3 is equal to or less than 0.05 sccm. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a support device for supporting an object to be processed such as a semiconductor wafer.

  2. Description of the Related Art Conventionally, as a supporting device for supporting an object to be processed such as a semiconductor wafer, a heater plate in which a heater and a high-frequency electrode are embedded and a shaft for supporting the heater plate are provided. There is known a support device integrated by, for example, welding.

  However, since the heater plate and the shaft of the supporting device are integrated, it is necessary to replace both the heater plate and the shaft even when only one of them is damaged. For this reason, there is an inconvenience that the running cost becomes high from a long-term viewpoint.

  Therefore, a support device is known in which the heater plate and the shaft are configured separately and fixed with screws (for example, Patent Document 1).

JP 7-153706 A

  By the way, in the support device, the heater and the high-frequency electrode are connected to the lead wire through the shaft.

  Therefore, the support device fixed with the screw has a problem that the lead wire is corroded when process gas such as fluorine gas used in the manufacturing process enters the shaft through the gap between the heater plate and the shaft. There is a point.

  An object of the present invention is to provide a support device capable of eliminating such inconvenience and reducing leakage with a simple configuration.

  In order to achieve this object, the support device of the present invention includes a heater plate having a surface on which a wafer is placed, a heating resistor, and a surface of the heater plate facing the surface on which the wafer is placed. A support device comprising a shaft that joins a heater plate and a fixing member that mechanically fixes the heater plate and the shaft, and leaks from a gap between the joining surface of the heater plate and the joining surface of the shaft The surface of the joint surface of the heater plate and the joint surface of the shaft is surface-treated so as to be 0.05 sccm or less.

  Generally, in a semiconductor manufacturing process in which the support device is used, a process gas such as fluorine gas is filled in a work space (chamber). On the other hand, the support device of the present invention performs surface treatment (for example, polishing) on the joining surface of the heater plate and the joining surface of the shaft so that the leakage to the outside of the shaft is 0.05 sccm or less.

  As a result, in the support device of the present invention, leakage can be reduced by a simple configuration in which the joining surface of the heater plate and the joining surface of the shaft are surface-treated.

1 sccm is 1.69 × 10 ⁻³ Pam ³ / s.

  In the support device of the present invention, it is preferable that the joining surface of the heater plate and the joining surface of the shaft each have a flatness of 2 μm or less and a surface roughness Ra of 0.2 μm or less.

  In the supporting device having this configuration, the joining surface of the heater plate and the joining surface of the shaft are subjected to surface treatment so that the flatness is 2 μm or less and the surface roughness Ra is 0.2 μm or less.

  When the flatness of any one of the joint surfaces is 2 μm or more, or the surface roughness Ra is 0.2 μm or more, it cannot be ignored from the viewpoint of reducing leakage between the joined heater plate and the shaft. A gap is created. Further, the engagement of the fixing member that fixes the heater plate and the shaft may be deteriorated, and there is a possibility that problems such as breakage of the fixing member may occur.

  Therefore, in the support device having this configuration, the heater plate and the shaft can be easily fixed by the fixing member, and the bonding surface of the heater plate and the bonding surface of the shaft are brought into close contact with each other. Leakage can be reduced.

  In the support device of the present invention, the shaft includes a groove portion formed on the joint surface of the shaft, and a gas supply path that communicates with the groove portion through the inside of the side wall portion of the shaft. It is preferable to provide a purge gas supply means for supplying a purge gas having a pressure equal to or higher than the pressure outside the shaft to the groove through the gas supply path.

  The shaft of the present invention has a gas supply path that communicates with the groove portion through the groove portion formed on the joint surface and the inside of the side wall portion. The groove is formed in an annular shape along the circumference between the inner circumference and the outer circumference of the shaft on the joint surface.

  For example, at least one gas supply path is formed in the side wall portion along the axial direction of the shaft. The gas supply path has a supply outlet communicating with the groove and a supply port for supplying purge gas, and is connected to the purge gas supply means at the supply port.

In the support device of the present invention, a purge gas (for example, N ₂ gas) is supplied to the space formed by the groove and the joining surface of the heater plate from the purge gas supply means via the gas supply path. It can supply with the predetermined pressure more than the above and the pressure inside a shaft.

  In addition, the purge gas supplied to the groove on the shaft end surface flows to the outside of the shaft and is also supplied to the inside of the shaft. Therefore, the purge gas tries to enter the inside from the outside of the shaft through the gap between the joining surface of the heater plate and the joining surface of the shaft. Process gas can be pushed back towards the outside. Since the purge gas passes through a narrow gap, the purge gas flow rate can be kept small and the influence on the process can be minimized.

  As a result, in the support device having this configuration, the groove can be provided on the joint surface of the shaft and the purge gas can be filled to prevent intrusion of process gas from the outside of the shaft to the inside, and the joint surface of the heater plate. Leak to the outside can be reduced by a simple configuration in which the surface treatment is performed on the joint surface of the shaft and the shaft.

  The purge gas supply path can be evacuated. By evacuating, the process gas entering from the outside of the shaft can be exhausted, and the terminals inside the shaft can be protected.

  In the support device of the present invention, it is preferable that a metal foil is sandwiched between the joint surface of the heater plate and the joint surface of the shaft.

  In a support device having this configuration, a metal foil is sandwiched between the joint surface of the heater plate and the joint surface of the shaft. This metal foil is elastically deformed and plastically deformed along slight irregularities on the surface of each joint surface by the fixing force of the fixing member.

Therefore, in the supporting device having this configuration, the gap can be further reduced by sandwiching and deforming the metal foil. As a result, in the support device having this configuration, leakage can be reduced by a simple configuration in which the metal foil is sandwiched.
According to the configuration of the present invention described above, leakage from the heater plate 2 and the shaft 3 can be reduced, and at the same time, the temperature distribution of the heater plate can be reduced by heat transfer due to physical contact between the heater plate 2 and the shaft 3. Can be improved.

Sectional drawing which shows the support apparatus in this embodiment. (A) is a top view which shows the shaft of this embodiment, (b) is sectional drawing which shows the shaft of this embodiment. Sectional drawing which shows the junction part of the heater plate and shaft of this embodiment.

  As shown in FIG. 1, the support device 1 of this embodiment includes a heater plate 2 and a shaft 3, and holds the wafer 4 on the heater plate 2. The support device 1 is placed in a process chamber (not shown), and is placed in a process gas atmosphere corresponding to each process such as fluorine gas while holding the wafer 4. The process gas is supplied at a predetermined pressure into the chamber through a supply path (not shown).

The heater plate 2 is formed in a substantially disk shape from a ceramic made of AlN, SiC, Mg ₂ Al ₂ O ₄ , Al ₂ O ₃ or the like. The heater plate 2 may have a triangular plate shape, a square plate shape, or the like. Among the raw materials, AlN is preferable because it has high thermal conductivity among ceramics, and is excellent in heat uniformity. Further, by adding Y ₂ O ₃ , heat uniformity can be improved.

  A heater 6 is embedded in the heater plate 2 at a position close to a surface (hereinafter simply referred to as a bonding surface) where the heater plate 2 is bonded to the shaft 3. Moreover, the electrode 7 is embedded at a position close to the surface holding the wafer 4 facing the electrode 7.

The heater 6 is a heating resistor, for example, a mesh-like heater 6 is disposed, and generates Joule heat by passing an electric current. At both ends of the heater 6, a substantially bottomed cylindrical heater terminal 8 is connected and fixed, for example, by brazing, at a substantially central portion of the joining surface of the heater plate 2. A rod-shaped Ni rod electrode 9 is connected and fixed to the cylindrical hole of the heater terminal 8 by brazing. The pair of Ni rod electrodes 9 are each connected to a heater power source (not shown), and by operating them, the heater 6 can generate heat. The Ni rod electrode 9 is covered with a cylindrical insulating sleeve (Al ₂ O ₃ sleeve) in order to prevent discharge between terminals.

  The heater 6 is manufactured using a metal having excellent heat resistance and a small thermal expansion coefficient, or a metal (for example, Mo, W, etc.) whose thermal expansion coefficient is close to the thermal expansion coefficient of the ceramic forming the heater plate 2. It is preferable. The terminal 8 is preferably manufactured using Kovar, Mo, or Ni as a raw material.

The electrode 7 is an RF electrode used when plasma processing is performed on the wafer 4. Similarly to the heater terminal 8 for the heater 6, the electrode 7 is connected and fixed to the Ni rod electrode 11 via the RF terminal 10. The Ni rod electrode 11 is also covered with a cylindrical insulating sleeve (Al ₂ O ₃ sleeve) in order to prevent discharge between terminals.

  In addition, the heater plate 2 may incorporate other ESC electrodes.

The shaft 3 is formed in a substantially cylindrical shape by a ceramic made of AlN, SiC, MgAl ₂ O ₄ , Al ₂ O ₃ or the like.

  In particular, AlN is preferable as a ceramic because of its high thermal conductivity and excellent thermal uniformity. That is, as shown in FIG. 1, when a power supply terminal is provided at the center of the disk-shaped heater plate 2, heat tends to be generated at the center, and the temperature distribution may be higher as it goes to the periphery. On the other hand, when the raw material of the shaft 3 is AlN, the shaft 3 can release the heat accumulated in the center portion, so that the temperature distribution can be easily averaged.

  The shaft 3 is provided with a purge gas supply means (not shown), a purge gas supply passage, and a lid 20 through which the Ni rod electrodes 9 and 11 pass on the opposite side of the joint surface. A flange for fixing a process chamber and a shaft (not shown) is attached to the end face of the lid 20. The kind of purge gas may be Ar, He or the like as long as it does not affect the process.

  As shown in FIG. 2, the shaft 3 has a substantially rectangular cross-sectional passage 12 surrounding the terminal 8 and the terminal 10 and a substantially circular cross-sectional through-hole 13, 14, 15 on the joint surface with the heater plate 2. And a substantially annular groove 16 between the inner periphery and the outer periphery of the shaft 3, and a screw hole 17.

As shown in FIG. 3, the through holes 13 and 14 are provided along the axial direction inside the side wall portion of the shaft 3. Further, the through hole (gas supply path) 15 is produced by branching from the through hole 14 or by obliquely passing the through hole from the end surface of the shaft 3 on the joining surface side. Communicate. The through hole 14 can be used as a passage for evacuation and can also be used as a gas supply passage. Specifically, by the purge gas supply means, the pressure of the process gas filled into the chamber with a purge gas such as N ₂ or the pressure of the process gas filled into the chamber, and the inside of the space of the shaft 3 Fill at a pressure higher than.

  As a result, the purge gas is supplied into the space formed by the groove 16 and the joining surface of the heater plate 2 by the purge gas supply means at a pressure higher than the pressure inside or outside the shaft 3.

  As shown in FIG. 3, the shaft 3 includes a flange 18 having a screw hole 17 on the joint surface with the heater plate 2. The heater plate 2 and the shaft 3 are fastened by screws (fixing members) 22 through screw holes 17. In addition to the screws, the fixing member may be a mechanism that can mechanically fix the heater plate 2 and the shaft 3 such as a clamp.

  The screw 22 is made of metal or ceramic. In the case of a metal screw, inconel, Ni, Ti, and Mo are used in consideration of heat resistance and an expansion coefficient. In order to reduce the influence of plasma on the manufacturing process, the screw 22 needs to be fastened inside the shaft 3 by providing the flange 18 inside the shaft 3. The torque for fastening the screw is preferably about 6 Nm when using an M5 screw, and if it is 10 Nm or more, the screw part may be damaged.

  Further, it is preferable to perform surface polishing processing such as lapping on the joining surface of the heater plate 2 and the joining surface of the shaft 3 to be fastened until the surface roughness Ra is 0.2 μm or less and the flatness is 2 μm.

Further, a metal foil 23 is sandwiched between the joint surface of the heater plate 2 and the joint surface of the shaft 3. The metal foil 23 is preferably manufactured using heat-resistant Au, Pt, Al, or the like as a raw material.
Further, the thickness of the metal foil 23 is less than 1 μm, and it is difficult to produce the metal foil 23. If the thickness is 10 μm or more, a large fastening force is required for deformation and there is a possibility of breakage of the screw portion.

  As a method for controlling the leak, an O-ring, a brazing material, an adhesive, or the like may be used. In a process at a high temperature of 300 ° C. or higher, it is preferable to use a seal member such as a metal O-ring or C-ring or a surface treatment such as silver plating or gold plating.

  In the support device 1 having the above configuration, the bonding surface of the heater plate 2 and the bonding surface of the shaft 3 are subjected to surface polishing until the surface roughness Ra is 0.2 μm or less and the flatness is 2 μm. It is increasing. In particular, a metal foil 23 is sandwiched between the joint surface of the heater plate 2 and the joint surface of the shaft 3, and this metal foil 23 is slightly exposed to the surface of each joint surface by the fastening torque of the screw 22. Since the elastic deformation and plastic deformation are performed along the unevenness, the degree of adhesion between the heater plate 2 and the shaft 3 is extremely high.

  As a result, in the support device 1, leakage from the gap between the joining surface of the heater plate 2 and the joining surface of the shaft 3 can be reduced with a simple configuration of surface polishing and sandwiching the metal foil 23.

  In this example, the support device 1 was manufactured as follows.

First, a powder mixture composed of 97% by mass of AlN powder and ₃ % by mass of Y ₂ O ₃ powder was formed, filled in a mold, and a first layer was formed by uniaxial pressure treatment at a pressure of 9.8 MPa. Next, a W heating element was placed on the first layer.

  Subsequently, the previously formed powder mixture was filled on the heating element to form a second layer. A sintered body was obtained using a hot press method at a firing temperature of 1840 ° C. and a firing temperature of 2 hours at a pressure of 10 MPa. The obtained sintered body was processed to produce a heater plate 2 of Φ300 mm × t23 mm. In addition, M5 screw holes for fixing bolts (outer diameter of 5 mm and triangular screw holes of 60 ° angle) were formed in the heater plate 2 on the shaft joint surface.

  Next, IPA, an organic binder, and a plasticizer were added to the raw material AlN powder, mixed, and spray-dried to obtain AlN granules. This granule was CIP-molded, and a sintered body was obtained using normal pressure firing at a firing temperature of 1900 ° C. and a firing time of 6 hours. The obtained sintered body was processed to produce a shaft 3 having an inner diameter of 50 mm, an outer diameter of 60 mm, and a height of 200 mm.

  The heater plate 2 and the shaft 3 were fastened with a fastening torque of 6 Nm using M5 Ti screws 22 and washers.

  The terminals 8 and 10 were made of Kovar, Ni rods 9 and 11 were added to the tips, and these were gold brazed.

  In this example, the joining surface of the heater plate 2 was lapped by a flatness of 1.0 μm and a surface roughness Ra of 0.08 μm. On the other hand, the joining surface of the shaft 3 was lapped to have a flatness of 0.14 μm and a surface roughness Ra of 0.06 μm.

  This flatness was measured by a method according to ISO1101 (JISB0621) with a three-dimensional measuring machine according to ISO10360 (JISB7440). Further, this surface roughness was measured by a stylus type surface roughness measuring instrument according to ISO 1879, 1880, 3274 (JISB 0651) by a method according to ISO 4287 (JIS B0601).

  In this embodiment, no metal foil is sandwiched between the joining surfaces, and no gas purge is performed. The support device 1 was manufactured under the above conditions.

  In this example, the following measurement was performed. First, the set temperature of the heater 6 was set to 500 ° C., and the temperature was measured using thermography. ΔT represents the difference between 500 ° C. and the lowest temperature in the heater plate 2.

  Further, the degree of corrosion and the degree of oxidation of the terminals on the back surface of the heater plate 2 after temperature measurement were determined.

  Next, in the present embodiment, the support device 1 and the vacuum chamber are connected via a flange and a valve, the exhaust pump connected to the vacuum chamber is operated, and the difference ΔP in the ultimate vacuum degree of the vacuum chamber when the valve is opened and closed The leak (Q = CΔP) was calculated from the exhaust speed C of the exhaust pump. The results are shown in Table 1.

  In Example 2, the support device 1 was manufactured in exactly the same manner as in Example 1 except that the gas purge was performed.

  Next, leakage was measured for the support device 1 obtained in Example 2 in exactly the same manner as in Example 1. The results are shown in Table 1.

  In Example 3, the supporting device 1 was manufactured in exactly the same manner as in Example 1 except that an Au metal foil having a thickness of 2.5 μm was sandwiched between the joining surfaces.

  Next, leakage was measured for the support device 1 obtained in Example 3 in exactly the same manner as in Example 1. The results are shown in Table 1.

  In Example 4, the supporting device 1 was manufactured in exactly the same manner as in Example 2 except that an Al metal foil having a thickness of 5.0 μm was sandwiched between the joining surfaces.

  Next, leakage was measured for the support device 1 obtained in Example 4 in exactly the same manner as in Example 1. The results are shown in Table 1.

In Example 5, the shaft 3 was manufactured using Al ₂ O ₃ having a purity of 99.5% or more as a raw material. The Al ₂ O ₃ shaft 3 had a flatness of 0.20 μm and a surface roughness Ra of 0.07 μm. Moreover, only the gas purge was performed. Other conditions are the same as those of the support device 1 of the first embodiment.

  Next, leakage was measured for the support device 1 obtained in Example 5 in exactly the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
In Comparative Example 1, the supporting device 1 was manufactured in exactly the same manner as in Example 1 except that the flatness of the heater plate 2 was set to 3.0 μm.

  Next, leakage was measured for the support device 1 obtained in Comparative Example 1 in exactly the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
In Comparative Example 2, the supporting device 1 was manufactured in exactly the same manner as in Example 2 except that the surface roughness of the heater plate 2 was 0.30 μm.

  Next, leakage was measured for the support device 1 obtained in Comparative Example 2 in exactly the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 3]
In Comparative Example 3, the supporting device 1 was manufactured in exactly the same manner as in Example 1 except that the surface roughness of the shaft 3 was 0.25 μm.

  Next, leakage was measured for the support device 1 obtained in Comparative Example 3 in exactly the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 4]
In Comparative Example 4, the support device 1 was manufactured in exactly the same manner as Comparative Example 1 except that a 2.5 μm thick Au metal foil was sandwiched between the joining surfaces.

  Next, leakage was measured for the support device 1 obtained in Comparative Example 4 in exactly the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 5]
In Comparative Example 5, the supporting device 1 was manufactured in exactly the same manner as Comparative Example 2 except that an Al metal foil having a thickness of 5.0 μm was sandwiched between the joining surfaces.

  Next, leakage was measured for the support device 1 obtained in Comparative Example 5 in exactly the same manner as in Example 1. The results are shown in Table 1.

表１から、実施例１〜５の支持装置１によれば、比較例１〜５の場合より、リークが少ないことは明らかである。したがって、ヒータープレート２及びシャフト３２の平面度を２μｍ以下かつ表面粗さをＲａ０．２μｍ以下とすることにより、リークを０．０５ｓｃｃｍ（８．４５×１０^−５Ｐａ・ｍ^３／ｓ）以下に低減できることが明らかである。

From Table 1, according to the support apparatus 1 of Examples 1-5, it is clear that there are few leaks compared with the case of Comparative Examples 1-5. Therefore, by setting the flatness of the heater plate 2 and the shaft 32 to 2 μm or less and the surface roughness to Ra 0.2 μm or less, the leak is reduced to 0.05 sccm (8.45 × 10 ⁻⁵ Pa · m ³ / s) or less. Clearly, it can be reduced.

  According to the support device of Comparative Example 2, it is clear that the amount of leakage is smaller than that of Comparative Example 1. Therefore, both flatness and surface roughness are important for leakage, but it is clear that leakage increases especially when the surface roughness becomes rough.

  It is clear that the support device 1 of Examples 3 and 4 has less leakage than the cases of Examples 1 and 2, and the support device of Comparative Example 4 has less leakage than the case of Comparative Example 1. Therefore, it is clear that leakage can be further reduced by sandwiching a metal foil having a predetermined thickness between the joining surfaces.

According to the support device of Example 5, it is clear that ΔT is higher than that of Example 2. Therefore, it is clear that the AlN shaft 3 has a soaking effect rather than the Al ₂ O ₃ shaft 3.

  Further, according to Examples 2, 4, and 5 and Comparative Examples 2, 4, and 5, it was confirmed that corrosion and oxidation of terminals inside the shaft could be prevented by using a gas purge.

  DESCRIPTION OF SYMBOLS 1 ... Support apparatus, 2 ... Heater plate, 3 ... Shaft, 4 ... Wafer, 6 ... Heater, 15 ... Through-hole, 16 ... Groove part, 22 ... Screw, 23 ... Metal foil.

Claims (4)

A heater plate having a surface on which the wafer is placed and a heating resistor;
On the surface of the heater plate facing the surface on which the wafer is placed, a shaft joined to the heater plate;
A support device comprising a fixing member that mechanically fixes the heater plate and the shaft,
The heater plate joint surface and the shaft joint surface are surface-treated so that an air leak from a gap between the heater plate joint surface and the shaft joint surface is 0.05 sccm or less. Supporting device.   2. The support device according to claim 1, wherein the joining surface of the heater plate and the joining surface of the shaft each have a flatness of 2 μm or less and a surface roughness Ra of 0.2 μm or less. The shaft has a groove formed on the joint surface of the shaft, and a gas supply path that communicates with the groove through the inside of the side wall of the shaft,
3. The support device according to claim 1, wherein the support device includes a purge gas supply unit that supplies a purge gas having a pressure equal to or higher than the pressure outside the shaft to the groove portion through the gas supply path. . The support apparatus according to any one of claims 1 to 3, wherein a metal foil is sandwiched between a joining surface of the heater plate and a joining surface of the shaft.

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