JP4124589B2 - Wafer holding device - Google Patents

Description

表１に示されるように、金属製基材とセラミックス層とを複合材を介して接合した場合（図４）には、セラミックス層に発生する最大応力が、複合材を使用しない場合（図３）の約２／３に緩和されることが分かる。また、セラミックス層の表面の反り量は、上側複合材のみを用いた場合（図４）には、複合材を使用しない場合（図３）とほぼ同じである。
【００２２】
それに対して、本願発明により基材の上下面に複合材を用いた場合（図１）には、セラミックス層に発生する最大応力が、複合材を使用しない場合（図３）の約２／３に緩和されていると共に、セラミックス層の表面の反り量は、上側複合材のみを用いた場合（図４）の約１／６まで減少している。このように、基材の上下面に複合材を設けることにより、セラミックス層に発生する最大応力の低減、及びセラミックス層表面の反り量の低減に効果が大である。
【００２３】
【発明の効果】
このように本発明によれば、金属製基板の両面に複合材を設けたことから、金属製基材とセラミックス層との両者間の大きな熱膨張率の差により、温度変化により金属製基板がセラミックス層に対して大きく熱膨張しても、両者間に介装した複合材の熱膨張率を適切化することによりセラミックス層に発生する応力を緩和することができると共に、金属製基板のセラミックス層側とは相反する側の面にも複合材を設けたことから、ウエハー保持装置全体の各部材間の熱膨張率の差に対するバランスを取って、金属製基板とセラミックス層との接合部のはく離や、セラミックス層の変形を低減することができる。
【図面の簡単な説明】
【図１】本発明に基づくウエハー保持装置を概略示す側断面図。
【図２】（ａ）は図３に対応する熱応力解析モデルであり、（ｂ）は図４に対応する熱応力解析モデルであり、（ｃ）は図１に対応する熱応力解析モデルである。
【図３】従来の複合材が無いウエハー保持装置を概略示す側断面図。
【図４】従来の金属製基板に複合材を介してセラミックス層を設けたウエハー保持装置を概略示す側断面図。
【符号の説明】
１ 金属製基材
２ 複合材
３ セラミックス層
４ 複合材
５ 接合部
６ ジャケット
１１ セラミックス層
１２ 金属製基材
１３ 複合材[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bonded body of ceramics and metal and a wafer holding apparatus suitable for a film forming and etching apparatus on a semiconductor substrate such as an electrostatic chuck apparatus using the same.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a wafer holding apparatus used for holding a semiconductor wafer in the manufacture of a semiconductor device, a ceramic layer as a ceramic electrostatic chuck for fixing the wafer by electrostatic adsorption, a cooling jacket or a heater There are those bonded to a metal substrate having
[0003]
[Problems to be solved by the invention]
As a general structure for bonding in a wafer holding device, a ceramic electrostatic chuck (ceramic layer) and a metal substrate (cooling jacket / heater) are fastened with bolts or bonded with an adhesive. Alternatively, a low-melting-point solder such as indium solder (melting point of about 120 ° C.) is used for bonding. An example of the structure of this joined body is shown in FIG.
[0004]
The joined body shown in FIG. 3 is obtained by directly joining the ceramic layer 11 and the metal base 12. Since the thermal expansion coefficient of the metal is larger than that of the ceramic, in the case of FIG. 3, the ceramic layer 11 is deformed in a convex shape (warp) during cooling after being bonded at a high temperature, or the wafer Concave deformation (warping) may occur during high temperature use as a holding device. This is even more prominent when the wafer holding device is required to be enlarged due to the recent trend of increasing the size of the object to be processed. And the problem that the peeling of a junction part and the crack of a ceramic layer arise by the said heat cycle generate | occur | produces.
[0005]
Further, in order to alleviate a large difference in thermal expansion coefficient between ceramics and metal, as shown in FIG. 4, the ceramic layer 11 and the metal base material 12 are joined via the ceramic and metal composite material 13. There is what I did. In this case, the thermal expansion coefficient of the composite material 13 can be set to the same thermal expansion coefficient as that of the ceramic layer 11, stress generated in the ceramic layer 11 is relieved, peeling of the joint portion and cracking of the ceramic layer 11 are performed. Can be prevented.
[0006]
However, even with the structure shown in FIG. 4, as a whole wafer holding device, the thermal expansion coefficient of the upper part (ceramic layer 11) in the figure is small, and the thermal expansion coefficient of the lower part (metal substrate 12) is low. large. Recently, there is a case where the plasma energy is increased in the wafer processing process. In this case, since the wafer becomes high temperature, the wafer holding device tends to be used at a higher temperature. In the joining process for obtaining a joining state capable of withstanding such a high temperature, there is a possibility that a convex deformation (warp) occurs in the ceramic layer 11 during cooling due to a difference in thermal strain between the upper part and the lower part during cooling. In addition, as described above, the wafer becomes high temperature and the ceramic layer 11 is deformed in a concave shape (warp), and the thermal cycle during the wafer processing process causes peeling of the joint and cracking of the ceramic layer 11. Will occur.
[0007]
[Means for Solving the Problems]
Solving these problems, the ceramic layer is prevented from warping and cracking even when the temperature when the ceramic layer and the metal substrate are joined is high, and when used at a high temperature In order to prevent warping and cracking from occurring, in the present invention, a wafer holding device used in semiconductor manufacturing, comprising: a metal base, and a main part of the metal base. Each composite material provided on the back surface where the surface and the main surface are opposite to each other, and a ceramic layer laminated on the composite material provided on the main surface side of the metal base to form a surface for holding the wafer The composite material is a composite material in which at least ceramic particles, fibers, and a porous body are incorporated in a metal matrix, and is joined to the metal base material by brazing. Provided on the main surface of the base material Composite ratio of metal and ceramic of the composite material which alleviates the stress of thermal expansion coefficient between the ceramic layer and the composite material is generated in the ceramic layer during bonding to the major surface of the metal substrate The composite ratio of the metal and ceramic of the composite material adjusted to be a value and provided on the back surface of the metal base material is the total of the metal base material, each composite material, and the ceramic layer. In order to balance the thermal expansion coefficient in the use state, when used in a state where the temperature on the back surface side is lower than the main surface side of the metal substrate, the metal substrate is provided on the back surface of the metal substrate. It was adjusted so that the thermal expansion coefficient of the composite material was increased, and in the opposite case, the thermal expansion coefficient of the composite material provided on the back surface of the metal base material was decreased.
[0008]
According to this, when each member constituting the wafer holding apparatus is cooled after being joined at a high temperature, or when the wafer holding apparatus is used at a high temperature, a large coefficient of thermal expansion between the metal substrate and the ceramic layer is obtained. Due to the difference, even if the metal substrate greatly expands with respect to the ceramic layer, the thermal expansion coefficient of the composite material is optimized by adjusting the composite ratio of ceramic and metal in the composite material interposed between the two Therefore, the stress generated in the ceramic layer can be relieved to prevent warping or cracking in the ceramic layer. Furthermore, since the composite material is also provided on the back surface of the metal substrate, the above-mentioned ceramic layer side is contradictory so as to suppress the influence due to the difference in thermal expansion coefficient on the ceramic layer side of the metal substrate from the opposite side. By optimizing the coefficient of thermal expansion of the composite material on the side, it is possible to balance against deformation due to the difference in coefficient of thermal expansion of the entire wafer holding device.
[0009]
In particular, the metal base is formed using aluminum, aluminum alloy, titanium, titanium alloy, or stainless steel, or the metal of the composite material is aluminum, aluminum alloy, copper, copper alloy, nickel, nickel / iron. -Cobalt alloy may be used, or silicon carbide, silicon nitride, alumina, or aluminum nitride may be used for the composite ceramic.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail based on specific examples shown in the accompanying drawings.
[0011]
FIG. 1 is a side sectional view schematically showing a wafer holding apparatus to which the present invention is applied. As shown in the figure, a composite material 2 is provided in a laminated state on the upper surface in the figure as the main surface of the metal substrate 1, and a wafer (not shown) is placed on the upper surface in the figure of the composite material 2 by, for example, an electrostatic chuck. Ceramic layers 3 forming a holding surface for holding are arranged in a laminated state. Moreover, the composite material 4 is provided also in the lower surface in the figure as a back surface contrary to the said upper surface of the metal base materials 1. FIG.
[0012]
The composite materials 2 and 4 are composite materials in which ceramic particles, fibers, porous bodies and the like are incorporated in a metal matrix, and an aluminum alloy is desirable as the metal matrix, and ceramic particles / fibers. -SiC is desirable as the porous body, for example, Al-SiC. The composite materials 2 and 4 are arranged in a joined state by casting or joining (for example, brazing) on the upper and lower surfaces of the base material 1.
[0013]
Aluminum or an aluminum alloy is used for the metal of the metal substrate 1. Moreover, titanium, a titanium alloy, or stainless steel can be used as another metal. In addition to aluminum, aluminum, copper, copper alloy, nickel, nickel / iron / cobalt alloy can be used as the metal of the composite materials 2 and 4. In addition to silicon carbide, silicon nitride, alumina, or aluminum nitride can be used for the ceramics of the composite materials 2 and 4.
[0014]
In the composite material 2 disposed on the upper surface of the metal substrate 1, the thermal expansion coefficient of the ceramic used for the ceramic layer 3 is reduced in order to relieve the stress generated in the ceramic layer 3 during bonding. The composite ratio of the metal and the ceramic used for the composite material 2 is adjusted so that the thermal expansion coefficient of the composite material 2 is substantially the same. Further, in the composite material 4 arranged on the lower surface of the metal base material 1, in order to balance the thermal expansion coefficient of the entire joined body (base material 1, composite material 2, ceramic layer 3, composite material 4). The composite ratio of the metal and the ceramic used for the composite material 4 is adjusted so as to be a value required for the above.
[0015]
According to the present invention, such composite materials 2 and 4 are arranged on both the upper surface and the lower surface of the wafer holding device, thereby joining the composite materials 2 and 4 to the metal substrate 1. At the time of use or when used as a wafer holding device for executing a wafer processing process, it is possible to reduce deformation in which the metal substrate 1 warps due to a temperature difference between high and low temperatures. Therefore, the stress generated in the ceramic layer 3 is alleviated, and the peeling of the joint portion 5 between the ceramic layer 3 and the composite material 2 and the cracking of the ceramic layer 3 do not occur.
[0016]
Moreover, in the composite material 4 on the lower surface side of the metallic substrate 1, it is possible to suitably cope with a temperature change (gradient) during use by changing the thickness and composite ratio. For example, when the wafer holding device is provided with a jacket 6 through which a coolant passes for cooling as shown in FIG. 1 and the lower surface side is lower in temperature than the upper surface side, If the composite materials 2 and 4 have the same coefficient of thermal expansion, the amount of thermal expansion of the composite material 2 on the upper surface side increases, which causes a problem that the entire wafer holding device is deformed upward. In this case, by changing the composite ratio of ceramics and metal in the composite material 4 on the lower surface side so as to increase the coefficient of thermal expansion of the composite material 4 on the lower surface side than the composite material 2 on the upper surface side, It is possible to reduce deformation in the use state.
[0017]
A heater may be provided in place of the jacket 6, and a refrigerant or a heating medium can be passed through the jacket 6. In the case of heating, the above may be reversed, and in this manner, various usage conditions can be suitably handled.
[0018]
Next, based on the thermal stress analysis model (schematic side sectional view) shown in FIG. 2, in the case of no composite material corresponding to FIG. 3 in Table 1 (a), composite only on the upper surface corresponding to FIG. When the temperature is raised from 25 ° C. to 300 ° C. in the three types (b) when the material 13 is provided (b) and when the composite materials 2 and 4 are provided on the upper and lower surfaces corresponding to FIG. 1 according to the present invention (c) 2 shows an example of the results of thermal stress analysis of the amount of warpage of the ceramic layers 3 and 11 and the stress generated in the ceramic layers 3 and 11.
[0019]
In the thermal stress analysis model of FIG. 2, FIG. 2 (a) corresponds to FIG. 3, FIG. 2 (b) corresponds to FIG. 4, and FIG. 2 (c) corresponds to FIG. In the case of FIG. 2A, both composite materials are not present, and the portion is formed by the base material 12. In the case of FIG.2 (b), only the upper side composite material 13 is provided and the thickness of the base material 12 is made thin by that much. In the case of FIG.2 (c), both the composite materials 2 * 4 are provided, and the thickness of the base material 1 is thin by that much.
[0020]
In FIG. 2, each member is circular, the thickness of the ceramic layers 3 and 11 is 6 mm, and the diameter is 210 mm. The diameters of the base materials 1 and 12 are 250 mm, the outer diameter of the upper composite material 2 (13) is the same as that of the ceramic layer 3 (11), and the outer diameter of the lower composite material 4 is the same as that of the base material 1 (12). The same. The reason why the central portion of the lower composite material 4 is a hole is that it is adapted to the shape to be mounted on the actual processing apparatus.
[0021]
[Table 1]

As shown in Table 1, when the metal base material and the ceramic layer are joined via the composite material (FIG. 4), the maximum stress generated in the ceramic layer is when the composite material is not used (FIG. 3). As can be seen from FIG. Further, the amount of warpage of the surface of the ceramic layer is almost the same when only the upper composite material is used (FIG. 4) as when the composite material is not used (FIG. 3).
[0022]
On the other hand, when the composite material is used on the upper and lower surfaces of the base material according to the present invention (FIG. 1), the maximum stress generated in the ceramic layer is about 2/3 of that when the composite material is not used (FIG. 3). The amount of warping of the surface of the ceramic layer is reduced to about 1/6 of the case where only the upper composite material is used (FIG. 4). Thus, by providing the composite material on the upper and lower surfaces of the base material, the effect of reducing the maximum stress generated in the ceramic layer and the amount of warpage of the ceramic layer surface is great.
[0023]
【The invention's effect】
As described above, according to the present invention, since the composite material is provided on both surfaces of the metal substrate, the metal substrate is changed due to a temperature change due to a large difference in thermal expansion coefficient between the metal substrate and the ceramic layer. Even if the thermal expansion of the ceramic layer is large, the stress generated in the ceramic layer can be relieved by optimizing the thermal expansion coefficient of the composite material interposed therebetween, and the ceramic layer of the metal substrate Since the composite material is also provided on the side opposite to the side, the balance between the thermal expansion coefficients between the members of the entire wafer holding device is balanced, and the joint between the metal substrate and the ceramic layer is peeled off. In addition, deformation of the ceramic layer can be reduced.
[Brief description of the drawings]
FIG. 1 is a side sectional view schematically showing a wafer holding device according to the present invention.
2A is a thermal stress analysis model corresponding to FIG. 3, FIG. 2B is a thermal stress analysis model corresponding to FIG. 4, and FIG. 2C is a thermal stress analysis model corresponding to FIG. is there.
FIG. 3 is a side sectional view schematically showing a conventional wafer holding apparatus without a composite material.
FIG. 4 is a side sectional view schematically showing a wafer holding apparatus in which a ceramic layer is provided on a conventional metal substrate with a composite material interposed therebetween.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Metal base material 2 Composite material 3 Ceramic layer 4 Composite material 5 Joint part 6 Jacket 11 Ceramic layer 12 Metal base material 13 Composite material

Claims (4)

A wafer holding device used in semiconductor manufacturing,
A main surface of the metal base material to form a metal base material, each composite material provided on the back surface opposite to the main surface of the metal base material and the main surface, and a surface for holding the wafer A ceramic layer laminated on a composite material provided on the side,
The composite material is a composite material in which at least ceramic particles, fibers, and a porous body are incorporated in a metal matrix, and is joined to the metal base material by brazing,
The composite ratio of the metal and ceramic of the composite material provided on the main surface of the metal substrate is such that the coefficient of thermal expansion between the composite material and the ceramic layer is bonded to the main surface of the metal substrate. Adjusted to reduce the stress generated in the ceramic layer ,
The composite ratio of the metal and ceramic of the composite material provided on the back surface of the metal base material is a coefficient of thermal expansion in the entire use state of the metal base material, the composite material, and the ceramic layer. In order to balance, when used in a state where the temperature on the back surface side is lower than the main surface side of the metal base material, the thermal expansion coefficient of the composite material provided on the back surface of the metal base material is increased. In the opposite case, the wafer holding device is adjusted so as to reduce the coefficient of thermal expansion of the composite material provided on the back surface of the metal substrate.     The wafer holding apparatus according to claim 1, wherein the metal substrate is formed using aluminum, an aluminum alloy, titanium, a titanium alloy, or stainless steel.     3. The wafer holding apparatus according to claim 1, wherein aluminum, an aluminum alloy, copper, a copper alloy, nickel, a nickel / iron / cobalt alloy, or the like is used as the metal of the composite material.     4. The wafer holding apparatus according to claim 1, wherein silicon carbide, silicon nitride, alumina, or aluminum nitride is used as the composite ceramic.

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