JP2004335151A - Ceramic heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic heater capable of shortening the time needed until temperature of heating surface becomes uniform. <P>SOLUTION: Of the ceramic heater made of a ceramic base plate with a resistive heating element set inside or at the bottom, a roughened surface is formed on the surface of the ceramic base plate, and further, a plasma anti-corrosion layer is formed on the roughened surface, with the plasma anti-corrosion layer satisfying conditions of formula (1): 0.015(mm)≤D<SB>1</SB>×D<SB>2</SB>/R<SB>y</SB>≤20,000(mm). In the formula, D<SB>1</SB>(μm) is a thickness of the plasma anti-corrosion layer on the surface of the ceramic base plate, D<SB>2</SB>(mm) is a thickness of the ceramic base plate, and Ry(μm) is a maximum height based on JIS B 0601 showing surface roughness of the ceramic base plate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０１５８】
表１に示したように、本発明では、Ｄ_１×Ｄ_２／Ｒ_ｙの値が０．０１５〜２００００の範囲内であれば、加熱面の温度を迅速に均一化することができる。
特に、表１では、Ｄ_１≧Ｒ_ｙの場合、すなわち、プラズマ耐食層の厚さが粗化面の最大高さよりも大きい方が温度均一化が速いという意外な事実が示されている。この理由は明確ではないが、プラズマ耐食層は熱伝導性に劣り、それが逆に、保温効果を奏し、セラミック基板の粗化面における低い熱伝導性を補うことで、加熱面の温度均一化速度を向上させているのではないかと推定される。
さらに、Ｄ_１×Ｄ_２／Ｒ_ｙの値は、５以上であることが望ましい。５以上であると、温度の均一化速度が特に速くなるからである。
また、実施例１７で作製された、プラズマ耐食層（緻密質炭化ケイ素からなる層）と、セラミック基板（多孔質炭化ケイ素からなる層）とから構成されるセラミックヒータの表面付近のＳＥＭ断面写真を図１１として示した。
【０１５９】
【発明の効果】
以上説明したように、本発明のセラミックヒータは、耐腐食性に優れ、反応性ガスやハロゲンガスに長期間曝され続けた場合であっても、表面が腐食されないので、セラミック基板等からセラミック粒子が脱落してパーティクルが発生し、シリコンウエハ等の被処理物に付着して汚染が発生することがない。
また、本発明のセラミックヒータは、加熱面の温度を迅速に均一化させることができるため、スループット時間を短縮することができる。
【図面の簡単な説明】
【図１】本発明のセラミックヒータの一例を模式的に示す垂直断面図である。
【図２】図１に示したセラミックヒータのＡ−Ａ線断面図である。
【図３】本発明のセラミックヒータを構成する抵抗発熱体の別の一例を模式的に示す水平断面図である。
【図４】本発明のセラミックヒータを構成する抵抗発熱体のさらに別の一例を模式的に示す水平断面図である。
【図５】本発明のセラミックヒータを静電チャックとして機能させる場合の一例を模式的に示す垂直断面図である。
【図６】静電チャックを構成するセラミック基板に埋設されている静電電極の一例を模式的に示す水平断面図である。
【図７】静電チャックを構成するセラミック基板に埋設されている静電電極の別の一例を模式的に示す水平断面図である。
【図８】静電チャックを構成するセラミック基板に埋設されている静電電極のさらに別の一例を模式的に示す水平断面図である。
【図９】（ａ）〜（ｄ）は、本発明のセラミックヒータの製造方法の一例を模式的に示す断面図である。
【図１０】（１１１）配向性を示すＣＶＤ−ＳｉＣ（炭化ケイ素）膜のＸ線回折測定結果を示す図である。
【図１１】プラズマ耐食層（緻密質炭化ケイ素からなる層）と、セラミック基板（多孔質炭化ケイ素からなる層）とから構成される本発明のセラミックヒータの表面付近のＳＥＭ断面写真である。
【符号の説明】
１０、３０、４０ セラミックヒータ
１１、３１、４１ セラミック基板
１１ａ 加熱面
１１ｂ 底面
１２、３２、４２ 抵抗発熱体
１３、５３ スルーホール
１４ 有底孔
１５ 貫通孔
１７ セラミック体
１９ 袋孔
２３ 外部端子
２４ 導電線
２５ ソケット
２６ リード線
５０、６０、７０ 静電チャック
５２ 静電電極
５２ａ 正極静電層
５２ｂ 負極静電層
５４ セラミック誘電体膜
１１０ グリーンシート
１２０ 導電ペースト層
１３０ 導電ペースト充填層
１８０ 側温素子
２００ プラズマ耐食層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a ceramic heater that can be used for heating various objects to be heated. More specifically, the present invention relates to a ceramic heater that can be suitably used mainly for applications such as heating of silicon wafers in the semiconductor industry and for applications such as heating of liquid crystal substrates in the optical field.
[0002]
[Prior art]
2. Description of the Related Art A ceramic heater made of aluminum nitride has been used in a semiconductor manufacturing apparatus using plasma including a plasma etching apparatus and a plasma chemical vapor deposition apparatus. This is because aluminum nitride has excellent corrosion resistance to plasma.
Further, in order to further improve the corrosion resistance of aluminum nitride, a technique of coating a surface of a substrate made of aluminum nitride with a fluorine compound layer has been disclosed (for example, see Patent Document 1).
Further, there is disclosed a technique for improving the corrosion resistance to halogen plasma by coating a surface of a substrate made of aluminum nitride with silicon carbide having a specific orientation (for example, see Patent Document 2).
[0003]
[Patent Document 1]
Japanese Patent No. 3362113
[Patent Document 2]
JP 2000-355779 A
[0004]
[Problems to be solved by the invention]
However, when such a plasma corrosion resistant layer is formed on the surface of the ceramic heater, there is a problem that it takes time until the temperature of the heating surface becomes uniform.
[0005]
[Means for Solving the Problems]
Thus, the present inventors have conducted intensive studies and, as a result, have come to know that such a problem is caused by the low thermal conductivity of the plasma corrosion-resistant layer. Furthermore, the present inventors conducted research with the aim of solving this problem, and as a result, the surface of the ceramic substrate was roughened, and the area of contact with the plasma corrosion-resistant layer was enlarged, so that the temperature of the heated surface was uniform. The inventors have found that the time required for the formation can be shortened, and have completed the present invention.
[0006]
The present invention is a ceramic heater comprising a ceramic substrate provided with a resistance heating element inside or on a bottom surface thereof,
A roughened surface is formed on the surface of the ceramic substrate,
Further, a ceramic heater is characterized in that a plasma corrosion-resistant layer is formed on the roughened surface, and the plasma corrosion-resistant layer satisfies the following expression (1).
0.015 (mm) ≦ D ₁ × D ₂ / R _y ≤20000 (mm) (1)
(In the formula (1), D ₁ (Μm) is the thickness of the plasma corrosion-resistant layer on the surface of the ceramic substrate, ₂ (Mm) is the thickness of the ceramic substrate, and R _y (Μm) is the maximum height based on JIS B 0601 indicating the surface roughness of the ceramic substrate. )
[0007]
According to the ceramic heater of the present invention, since the plasma corrosion-resistant layer is formed on the surface of the ceramic substrate, the plasma corrosion-resistant layer functions as a surface protection film for the ceramic substrate or the like, and improves the plasma corrosion resistance of the ceramic substrate. As a result, even if the ceramic substrate is continuously exposed to plasma such as a reactive gas or a halogen gas for a long period of time, the surface is not corroded, ceramic particles are dropped from the ceramic substrate, particles are generated, and silicon is generated. It is possible to prevent contamination from being attached to an object to be processed such as a wafer.
[0008]
According to the ceramic heater of the present invention, a roughened surface is formed on a ceramic substrate, a plasma corrosion-resistant layer is formed thereon, and the contact area between the plasma corrosion-resistant layer and the ceramic substrate is large. The heat conduction from the substrate to the plasma corrosion resistant layer is improved, and the time until the temperature of the heated surface becomes uniform can be shortened.
[0009]
In the above equation (1), the thickness D of the plasma corrosion-resistant layer on the surface of the ceramic substrate ₁ For example, as an example, 10 cross-sectional SEM photographs of an arbitrary portion of a ceramic heater are taken, and the largest distance from the surface of the plasma corrosion resistant layer to the ceramic substrate in one taken SEM photograph is selected. D ₁ And the selected distance d for 10 SEM pictures ₁ ~ D ₁₀ The average of D ₁ Can be used as
[0010]
Further, a maximum height (hereinafter, also simply referred to as a maximum height) R based on JIS B 0601 indicating the surface roughness of the ceramic substrate R _y Also, for example, 10 cross-sectional SEM photographs of an arbitrary portion of the ceramic heater are taken, and the maximum height r in one taken SEM photograph is taken. ₁ , The maximum height r determined for the ten SEM photographs ₁ ~ R ₁₀ The average of R _y Can be used as
[0011]
The plasma corrosion-resistant layer is not particularly limited, but, for example, a layer made of an yttrium compound, a layer made of a fluorine compound, a layer made of silicon carbide exhibiting orientation, and the like are preferable.
[0012]
The layer made of the above-described yttrium compound and / or fluorine compound can be formed by, for example, a sputtering method. Specifically, for example, a sample is set in a vacuum chamber and 1 × 10 ^-3 After evacuation to Pa, a partial pressure of 0.5 Pa He gas and 0.1 Pa O gas ₂ Gas was introduced into the vacuum chamber and Na ₃ AlF ₆ Using a composite of aluminum and chlorofluoroethylene resin arranged on the cathode as a target, ₃ Can be formed.
[0013]
The layer made of silicon carbide having the above-described orientation can be formed by, for example, a chemical vapor deposition method. In the chemical vapor deposition method described above, for example, methyltrichlorosilane (CH) is used as a reaction gas by a CVD method at a temperature of 1300 ° C. and a degree of vacuum of 250 Torr. ₃ SiCl ₃ , Concentration: 4 to 7%), and hydrogen and argon are supplied as carrier gases and thermally decomposed to form a CVD-SiC (silicon carbide) layer having a β-SiC crystal structure with a thickness of about 4 mm. it can.
[0014]
It is desirable that the layer made of silicon carbide exhibiting the above orientation exhibit (111) orientation. The expression “111” orientation means that the (111) plane of silicon carbide is oriented substantially parallel to the surface of the coating surface, and the (111) plane of silicon carbide is This includes the case where the crystal is oriented with a slight deviation from the perfect parallel to the surface. In addition, the case where most of the layer made of silicon carbide shows (111) orientation is included.
The CVD-SiC (silicon carbide) film shows different orientations depending on the formation conditions. For example, methyltrichlorosilane (CH ₃ SiCl ₃ If the concentration is 4%, a CVD-SiC (silicon carbide) film showing (220) orientation is formed, and if the concentration of methyltrichlorosilane is 7%, CVD-111 showing (111) orientation is formed. An SiC (silicon carbide) film is formed.
[0015]
An X-ray diffraction method is used for analyzing the orientation of the CVD-SiC (silicon carbide) film. As an X-ray diffractometer used for measurement, Rigaku RINT-2000 type or the like can be mentioned. The light source for X-ray tube diffraction is CuKα1. As a measurement method, first, a ceramic substrate having a size of 10 mm × 10 mm × 15 mm covered with a layer made of silicon carbide was fixed to a metal sample holder so that the layer made of silicon carbide was irradiated with X-rays, The sample holder on which the sample is fixed is set on the sample stage of the goniometer. In the goniometer, since the detector rotates at twice the speed of the sample stage, the incident angle and the reflection angle of the X-ray with respect to the crystal are always equal. Next, cooling water is supplied to the X-ray tube to turn on the power of the apparatus, the voltage is gradually increased to 40 kV, and the current adjustment knob is turned to 30 mA. After that, measurement is performed by setting each condition. The measurement conditions include, for example, a divergence slit of 1 °, a scatter slit of 1.26 mm, a light receiving slit of 0.3 mm, a monochromator light receiving slit of 0.8 mm, a counter of a scintillation counter, and a monochromator of a curved monochromator. The scan angle range is 30 to 70 °, the scan speed is 3 ° / min, and the sampling width is 0.02 °. During measurement, primary X-rays from the X-ray tube pass through the divergence slit and irradiate the sample surface on the rotation axis of the goniometer. The diffracted X-rays reach the counter tube through the receiving slit and the diverging slit.
FIG. 10 shows the results of measurement of a CVD-SiC (silicon carbide) film exhibiting (111) orientation by the above-described measurement method.
[0016]
Further, in the ceramic heater according to the present invention, the plasma corrosion-resistant layer, which is the surface protective film, is formed so as to satisfy the relationship of the above equation (1).
The above equation (1) indicates the thickness D of the plasma corrosion resistant layer. ₁ Is the thickness D of the ceramic substrate ₂ The maximum height R _y Means that it needs to be larger. Plasma corrosion resistant layer thickness D ₁ Is the thickness D of the ceramic substrate ₂ When the temperature increases, the thermal conductivity decreases and the time required to make the temperature of the heated surface uniform becomes longer, so the roughened surface is roughened and the surface of the ceramic substrate contacts the plasma corrosion-resistant layer. This increases the area and shortens the time required for uniformizing the temperature of the heating surface.
In addition, the thickness D of the plasma corrosion resistant layer ₁ Is the thickness D of the ceramic substrate ₂ The maximum height R _y By increasing the value, it is possible to prevent the plasma corrosion-resistant layer from peeling off and from generating cracks in the plasma corrosion-resistant layer.
[0017]
Maximum height R _y Is too big and D ₁ × D ₂ / R _y Is smaller than 0.015 (mm), the roughened surface is too rough, and it takes time to raise the temperature of the roughened surface. In addition, the thickness D of the plasma corrosion resistant layer ₁ Is too small, D ₁ × D ₂ / R _y Is smaller than 0.015 (mm), the thickness of the plasma corrosion-resistant layer is too thin, so that the plasma corrosion-resistant layer peels off or cracks occur in the plasma corrosion-resistant layer.
[0018]
On the other hand, the maximum height R _y Is too small, D ₁ × D ₂ / R _y Exceeds 20000 (mm), the roughened surface is too flat, so that the plasma corrosion-resistant layer peels off or cracks occur in the plasma corrosion-resistant layer.
Also, D ₁ Is too big and D ₁ × D ₂ / R _y Exceeds 20000 (mm), the plasma corrosion-resistant layer is too thick, and it takes time to raise the temperature.
[0019]
Further, in the ceramic heater of the present invention, the thickness D of the plasma corrosion-resistant layer ₁ Is the maximum height R _y It is desirable that this is the case. Plasma corrosion resistant layer thickness D ₁ Is the maximum height R _y If the value is less than 1, the surface of the plasma corrosion resistant layer will not be smooth, and irregularities will be formed on the heating surface of the ceramic heater, and the adhesion between the object to be heated such as a semiconductor wafer and the heating surface of the ceramic heater will be reduced. This is because the reaction gas or the reactive gas or the halogen gas tends to stay.
[0020]
In the ceramic heater of the present invention, it is desirable that the high-frequency electrode is embedded in the ceramic substrate. This is because plasma of an atmospheric gas can be generated when a semiconductor wafer or the like placed on a ceramic heater is processed.
[0021]
Further, in the ceramic heater of the present invention, it is desirable that a substantially cylindrical ceramic body is joined to the bottom surface of the ceramic substrate. By storing the wiring from the resistance heating element or the like inside the ceramic body, it is possible to prevent the wiring from being exposed to a corrosive gas such as a reactive gas or a halogen gas and corroded. It is.
[0022]
In the ceramic heater according to the present invention, it is preferable that the ceramic substrate is further provided with an electrostatic electrode.
Since the electrostatic chuck is often used in a corrosive atmosphere, the above-mentioned ceramic substrate and the ceramic body are joined together, and the plasma corrosion-resistant layer as a surface protective film satisfies the above expression (1). This is because the formed structure is preferable.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described based on embodiments. Note that the present invention is not limited to this description.
[0024]
The ceramic heater of the present invention is a ceramic heater comprising a ceramic substrate provided with a resistance heating element inside or on a bottom surface thereof,
A roughened surface is formed on the surface of the ceramic substrate,
Further, a ceramic heater is characterized in that a plasma corrosion-resistant layer is formed on the roughened surface, and the plasma corrosion-resistant layer satisfies the following expression (1).
0.015 (mm) ≦ D ₁ × D ₂ / R _y ≤20000 (mm) (1)
(In the formula (1), D ₁ (Μm) is the thickness of the plasma corrosion-resistant layer on the surface of the ceramic substrate, ₂ (Mm) is the thickness of the ceramic substrate, and Ry (μm) is the maximum height based on JIS B 0601 indicating the surface roughness of the ceramic substrate. )
[0025]
FIG. 1 is a vertical sectional view schematically showing one example of the ceramic heater of the present invention. FIG. 2 is a sectional view taken along line AA of the ceramic heater shown in FIG.
Although the boundaries between the ceramic substrate 11 and the ceramic body 17 and the plasma corrosion-resistant layer 200 are roughened, since FIG. 1 is a schematic diagram, the expression as a rough surface is omitted.
[0026]
As shown in FIG. 1, a ceramic heater 10 of the present invention is configured such that a substantially cylindrical ceramic body 17 is joined near the center of a bottom surface 11 b of a ceramic substrate 11. Has a layer made of an yttrium compound and / or a fluorine compound or a layer made of silicon carbide exhibiting orientation as the plasma corrosion resistant layer 200 so as to satisfy the relationship of the above formula (1). Inside the resistance heating element 12, a through hole 13 formed immediately below the end of the resistance heating element 12, and a blind hole (not shown) for exposing the through hole 13 to the bottom surface 11b of the ceramic substrate 11. ) Is formed. A high-frequency electrode 112 is formed inside the ceramic substrate 11, and a through-hole 113 and a bag for exposing the through-hole 113 to the bottom surface 11 b of the ceramic heater 11 are provided immediately below the end of the high-frequency electrode 112. A hole (not shown) is formed.
The through holes 13 and 113 are connected to a T-shaped external terminal 23 via a solder layer (not shown). In the present specification, a through hole is a hole in which a conductor is filled inside a hole formed for connecting a resistance heating element, a high-frequency electrode described later, an electrostatic electrode, and the like to an external terminal. Say.
A socket 25 having a conductive wire 24 is attached to the external terminal 23 and housed inside the ceramic body 17. The conductive wire 24 is connected to a through hole formed in a bottom plate (not shown) of the support container. It is drawn out and connected to a power supply or the like (not shown). Further, a bottomed hole 14 in which a temperature measuring element 180 to which a lead wire 26 for measuring the temperature of the ceramic substrate 11 is connected is embedded is formed in the bottom surface 11b of the ceramic substrate 11.
The plasma corrosion resistant layer 200 may be formed on the entire ceramic heater 10 including the ceramic body 17 or may be formed only on the surface of the ceramic substrate 11.
[0027]
As shown in FIG. 2, in the ceramic heater 10 of the present invention, the resistance heating element 12 buried inside the ceramic substrate 11 forms a circuit concentrically continuous from the vicinity of the center of the ceramic substrate 11 toward the outer periphery. The end of the resistance heating element 12 is formed near the center of the ceramic substrate 11.
[0028]
When the ceramic heater 10 of the present invention is applied to a semiconductor manufacturing / inspection apparatus, the ceramic substrate 11 is usually provided at an upper end of a supporting container provided with a bottom plate on an end of the ceramic body 17 on the side facing the ceramic substrate 11. Is fixed so as to be in close contact with the bottom plate. As a result, the inside and outside of the ceramic body 17 are completely isolated, the ceramic heater 10 is installed inside the reaction vessel, and the surroundings of the ceramic substrate 11 are set to a corrosive gas atmosphere such as a reactive gas or a halogen gas. Even in this case, the external terminals 23 and the like housed in the ceramic body 17 do not directly come into contact with the corrosive gas and are not corroded. Further, since the ceramic body 17 also has a function of firmly supporting the ceramic substrate 11, even when the ceramic substrate 11 is heated to a high temperature, it can be prevented from warping due to its own weight. In addition to preventing damage to the object to be heated, the object to be heated can be heated to a uniform temperature.
[0029]
The lead wire 26 connected to the temperature measuring element 180 for measuring the temperature of the ceramic substrate 11 is desirably housed inside the ceramic body 17, and when provided outside the ceramic body 17. It is desirable to be protected by insulators and the like. This is to prevent the lead wire 26 from being corroded even when the surroundings of the ceramic heater 10 are in an atmosphere containing a reactive gas, a halogen gas, or the like.
[0030]
In the ceramic heater of the present invention, the plasma corrosion-resistant layer is formed on the surface of the ceramic substrate so as to satisfy the above formula (1). The plasma corrosion-resistant layer is not particularly limited, and examples thereof include an yttrium compound, a fluorine compound, and oriented silicon carbide.
[0031]
The yttrium compound is not particularly limited, and examples thereof include yttrium nitride (YN) and yttrium carbide (YC). ₂ ), Yttrium oxide, yttrium fluoride and the like.
The fluorine compound is not particularly limited, and examples thereof include magnesium fluoride, aluminum fluoride, and calcium fluoride.
[0032]
Thickness D of a layer made of the above-mentioned yttrium compound and / or fluorine compound or a layer made of oriented silicon carbide (plasma corrosion-resistant layer) ₁ Is not particularly limited, but a desirable lower limit is 0.1 μm and a desirable upper limit is 100 μm. When the thickness is less than 0.1 μm, the effect as a plasma corrosion-resistant layer cannot be sufficiently obtained, so that the corrosion resistance of a ceramic substrate or the like may be poor, or the uniformity of temperature on a heated surface may be reduced. On the other hand, if it exceeds 100 μm, the heat transfer from the resistance heating element provided inside the ceramic substrate to the surface of the plasma corrosion-resistant layer may be reduced, or the working efficiency of the process of forming the plasma corrosion-resistant layer may be reduced. .
[0033]
The method for forming the plasma corrosion-resistant layer is not particularly limited, and may be formed directly on the surface of a ceramic substrate or the like by applying a raw material aqueous solution or the like, or may be an yttrium compound contained inside the ceramic substrate or the like. The layer may be formed by exposing the fluorine compound to the surface of the ceramic substrate or the like. For example, a chemical vapor deposition method (chemical vapor deposition method, CVD method), a sputtering method, or the like is preferably used.
The chemical vapor deposition method uses a chemical reaction by flowing a compound gas containing yttrium atoms and / or fluorine atoms or a compound gas containing silicon atoms and carbon atoms in an atmosphere containing a ceramic substrate or the like heated to a high temperature. Then, a layer composed of an yttrium compound and / or a fluorine compound having a desired composition or a layer composed of silicon carbide having an orientation is deposited on the surface of a ceramic substrate or the like. Alternatively, the plasma corrosion-resistant layer may be formed by exposing the ceramic substrate to halogen plasma.
[0034]
Note that the thickness of the layer made of the yttrium compound and / or the fluorine compound or the layer made of the silicon carbide exhibiting the orientation (plasma corrosion resistant layer) is determined by using a compound gas containing an yttrium atom and / or a fluorine atom, or silicon. It can be adjusted by the composition of the compound gas containing atoms and carbon atoms, the flow rate thereof, and the deposition time of the layer.
[0035]
In the ceramic heater of the present invention, the ceramic material forming the ceramic substrate 11 is not particularly limited, and examples thereof include a nitride ceramic, a carbide ceramic, and an oxide ceramic.
Examples of the nitride ceramic include aluminum nitride, silicon nitride, boron nitride, and titanium nitride. Examples of the carbide ceramic include silicon carbide, zirconium carbide, boron carbide, titanium carbide, tantalum carbide, and tungsten carbide. Examples of the oxide ceramic include alumina, silica, cordierite, mullite, zirconia, and beryllia. These ceramic materials may be used alone or in combination of two or more.
[0036]
Of these, nitride ceramics and carbide ceramics are desirable. Since the nitride ceramics and carbide ceramics have a smaller coefficient of thermal expansion than metals and a much higher mechanical strength than metals, they do not warp or warp due to heating even when the thickness of the ceramic substrate is reduced. The ceramic substrate can be thin and light. In addition, since the ceramic substrate has high thermal conductivity by thinning the ceramic substrate, if the temperature of the resistance heating element is changed by changing the voltage and current, the surface temperature of the ceramic substrate will change with the temperature of the resistance heating element. It follows quickly and makes it easier to control the surface temperature of the ceramic heater.
More preferably, it is aluminum nitride or silicon carbide. This is because they have excellent heat resistance and mechanical properties, and also have high thermal conductivity. More preferably, aluminum nitride is used. This is because the coefficient of thermal expansion is as high as 180 W / m · K, and the temperature following property of the ceramic substrate is the most excellent.
[0037]
The ceramic material may contain a sintering aid. Examples of the sintering aid include alkali metal oxides, alkaline earth metal oxides, and rare earth oxides. Among these, CaO, Y ₂ O ₃ , Na ₂ O, Li ₂ O, Rb ₂ O is desirable. When silicon carbide is used as the ceramic material, B ₄ C, C, and AlN are desirable. A desirable lower limit of the content of the sintering aid is 0.1% by weight, and a desirable upper limit is 20% by weight. Note that the ceramic material may contain alumina.
[0038]
The ceramic substrate desirably contains 100 to 5000 ppm of carbon. By containing 100 to 5000 ppm of carbon, the ceramic substrate can have a brightness of N6 or less at a value based on JIS Z 8721, and the ceramic substrate having such brightness has a radiant heat, Excellent concealability. Further, the ceramic heater composed of such a ceramic substrate can accurately measure the surface temperature by the thermoviewer.
Here, N of lightness is 0 for ideal black lightness and 10 for ideal white lightness, and between these black lightness and white lightness, the perception of the lightness of the color is Each color is divided into 10 so as to have a uniform rate, and displayed by symbols N0 to N10.
The actual measurement is performed by comparing the color charts corresponding to N0 to N10. In this case, the first decimal place is 0 or 5.
[0039]
The carbon includes an amorphous carbon and a crystalline carbon. The amorphous carbon can suppress a decrease in the volume resistivity of the ceramic substrate at a high temperature, and the crystalline carbon can suppress a decrease in the thermal conductivity of the ceramic substrate at a high temperature. The type of carbon can be appropriately selected according to the purpose of the ceramic substrate to be formed.
[0040]
The amorphous carbon can be obtained, for example, by calcining a hydrocarbon consisting of C, H, and O, preferably a saccharide, in the air. Examples of the crystalline carbon include graphite powder and the like. Can be used.
Further, carbon can be obtained by thermally decomposing the acrylic resin in an inert atmosphere and then heating and pressurizing. However, by changing the acid value of the acrylic resin used for the thermal decomposition, it is possible to obtain a crystalline (non-crystalline) resin. G) can be adjusted.
[0041]
The porosity of the ceramic substrate 11 is desirably 0 or 5% or less. This is because a decrease in the thermal conductivity at a high temperature and the occurrence of warpage can be suppressed.
The porosity can be measured by the Archimedes method.
[0042]
The shape of the ceramic substrate 11 is desirably a disk shape as shown in FIGS. 2 to 4, and the diameter is desirably 200 mm or more, and more desirably 250 mm or more. This is because a ceramic substrate having such a large diameter can mount a large-diameter semiconductor wafer when the ceramic heater is used as a ceramic heater for a semiconductor manufacturing / inspection apparatus.
[0043]
Thickness D of ceramic substrate 11 ₂ Is preferably 2 mm and a desirable upper limit is 20 mm. If it is less than 2 mm, the strength of the ceramic substrate itself is reduced, so that the ceramic substrate is easily broken. On the other hand, if it exceeds 20 mm, the temperature followability may decrease. A more desirable lower limit is 3 mm, and a more desirable upper limit is 16 mm. If it is less than 3 mm, the heat propagating in the ceramic substrate may not be sufficiently diffused, so that the temperature may vary on the heating surface, and the strength of the ceramic substrate may be reduced and the ceramic substrate may be damaged. On the other hand, if it exceeds 16 mm, heat will not easily propagate in the ceramic substrate, and the heating efficiency tends to decrease.
[0044]
Maximum height R of the surface of the ceramic substrate 11 based on JIS B 0601 _y Is preferably 0.1 μm, and a desirable upper limit is 100 μm. When the thickness is less than 0.1 μm, the plasma corrosion-resistant layer is easily peeled. If it exceeds 100 μm, the surface of the plasma corrosion-resistant layer will not be smooth and the object to be processed cannot be heated on a uniform surface, or the ceramic substrate will be easily damaged.
[0045]
In the ceramic heater of the present invention, when forming the resistance heating element inside the ceramic substrate, it is preferable to use a conductive paste.
That is, when forming a resistance heating element inside a ceramic substrate, a conductive paste layer is formed on a green sheet, and then the green sheet is laminated and fired to produce a resistance heating element inside the ceramic substrate. It is desirable.
[0046]
The conductive paste is not particularly limited, but preferably contains metal particles or conductive ceramic particles to secure conductivity, and further contains a resin, a solvent, a thickener, and the like.
[0047]
The metal particles are desirably particles composed of noble metals such as gold, silver, platinum, and palladium; and lead, tungsten, molybdenum, nickel, and the like. This is because these metals are relatively hard to oxidize and have a resistance value sufficient to generate heat. These metal particles may be used alone or in combination of two or more.
Examples of the conductive ceramic particles include particles made of tungsten, molybdenum carbide, and the like. These conductive ceramic particles may be used alone or in combination of two or more.
[0048]
A desirable lower limit of the particle size of the metal particles or the conductive ceramic particles is 0.1 μm, and a desirable upper limit is 100 μm. If it is less than 0.1 μm, it is easily oxidized. On the other hand, if it exceeds 100 μm, sintering becomes difficult and the resistance value increases.
[0049]
The shape of the metal particles or the conductive ceramic particles is not particularly limited, and examples thereof include a sphere and a scale. It may be a mixture of the sphere and the flake. When the metal particles are flakes or a mixture of spheres and flakes, the metal oxide between the metal particles is easily retained, and the adhesion between the resistance heating element and the ceramic substrate is improved. And the resistance value can be increased, which is advantageous.
[0050]
The resin used for the conductor paste is not particularly limited, and examples thereof include an epoxy resin and a phenol resin. The solvent used for the conductor paste is not particularly limited, and includes, for example, isopropyl alcohol and the like. The thickener used in the conductor paste is not particularly limited, and includes, for example, cellulose.
[0051]
In the ceramic heater according to the present invention, when forming the high-frequency electrode inside the ceramic substrate, it is desirable to use a conductive paste. That is, similarly to the above-described resistance heating element, when forming a high-frequency electrode inside a ceramic substrate, a conductor paste layer is formed on a green sheet, and then the green sheet is laminated and fired to form a ceramic substrate. It is desirable to create a high-frequency electrode inside.
In addition, as the conductive paste used for forming the high-frequency electrode, the same conductive paste as that used for forming the resistance heating element can be used.
[0052]
3 and 4 are horizontal cross-sectional views schematically showing another example of the resistance heating element constituting the ceramic heater of the present invention.
The pattern of the resistance heating element is not particularly limited. For example, in addition to the substantially concentric resistance heating element 12 shown in FIG. 2, a substantially fan-shaped pattern shown in FIG. Resistance heating elements 32 (32a to 32e), a resistance heating element 42 (42a to 42p) combining a concentric shape and a bent line shape shown in FIG. 4, a spiral shape, an eccentric shape, a combination thereof, and the like. Is mentioned.
[0053]
In the ceramic heater 30 shown in FIG. 3, a resistance heating element 32 is embedded inside a ceramic substrate 31. The resistance heating element 32 is divided into substantially fan-shaped resistance heating elements 32 a to 32 e and is divided into a circle of the ceramic substrate 31. They are arranged at equal intervals in the circumferential direction.
Each of the resistance heating elements 32a to 32e has a substantially sector shape due to a repetitive pattern of a plurality of bending lines having different sizes formed from the vicinity of the center of the ceramic substrate 31 toward the outer periphery. The repetitive patterns of the bent lines adjacent in the resistance heating elements 32a to 32e are connected to each other to form one circuit, and the ends of the resistance heating elements 32a to 32e are formed near the center of the ceramic substrate 31. .
[0054]
In the ceramic heater 40 shown in FIG. 4, a resistance heating element 42 composed of a plurality of circuits is embedded in a ceramic substrate 41, and the resistance heating element 42 is circumferentially divided at the outermost periphery of the ceramic substrate 41. Resistance heating elements 42a to 42h formed of repeated bent lines are formed, and resistance heating elements 42i to 421 formed of similar bent line repeated patterns are formed on the inner periphery thereof. , Resistance heating elements 42m to 42p formed in concentric circles.
The ends of the resistance heating elements 42 a to 42 p are formed so as to extend over the entire ceramic substrate 41.
[0055]
When the resistance heating element has a pattern such as the resistance heating element 12 shown in FIG. 2 or the resistance heating element 32 shown in FIG. 3, an end of the resistance heating element is formed near the center of the ceramic substrate. Therefore, a through-hole is formed directly below the end of the resistance heating element, and external terminals are connected to the through-hole. Can be stored in
[0056]
The resistance heating element is preferably divided into a plurality of circuits in order to uniformly heat the heating surface of the ceramic heater of the present invention. Therefore, if the resistance heating element is the resistance heating element 42 shown in FIG. 4, the resistance heating element is divided into a large number of circuits, so that the heating surface of the ceramic heater of the present invention is uniformly heated. It becomes easier.
[0057]
When the resistance heating element has a pattern like the resistance heating element 42 shown in FIG. 4, the end of the resistance heating element is formed so as to extend over the entire ceramic substrate. When a through-hole is formed immediately below, the external terminals connected to the through-hole also extend over the entire ceramic substrate. Therefore, in order to house the external terminal inside the ceramic body joined near the center of the bottom surface of the ceramic substrate, a via hole is formed at the end of the resistance heating element that is not formed above the internal region of the ceramic body. A conductor circuit or the like is connected via the ceramic circuit, and the conductor circuit is extended to above the internal region of the ceramic body. Then, a through-hole is formed directly below the end of the conductor circuit extending to above the internal region of the ceramic body, and external terminals are connected to the through-hole, so that all the external terminals and the like are connected to the ceramic body. Can be stored inside.
[0058]
The cross section of the resistance heating element may be any one of a square, an ellipse, a spindle shape, and a semi-cylindrical shape, but is preferably flat. This is because a flat shape facilitates heat radiation toward the heating surface, so that the amount of heat propagation to the heating surface can be increased, and a temperature distribution on the heating surface is hardly obtained. The resistance heating element may have a spiral shape.
[0059]
A desirable lower limit of the thickness of the resistance heating element is 1 μm, a desirable upper limit is 50 μm, and a desirable lower limit of the width of the resistance heating element is 5 μm and a desirable upper limit is 20 μm. The resistance heating element can change its resistance value by changing its thickness and width, but this range is the most practical. Note that the resistance value of the resistance heating element increases as its thickness decreases and its width decreases.
[0060]
The formation position of the resistance heating element inside the ceramic substrate is not particularly limited, but it is preferable that at least one layer is formed at a position from the bottom surface of the ceramic substrate to 60% of its thickness. This is because heat is diffused while propagating to the heating surface, and the temperature on the heating surface tends to be uniform.
[0061]
In the ceramic heater of the present invention, the material constituting the through-hole is not particularly limited, and examples thereof include noble metals such as gold, silver, platinum, and palladium; metals such as lead, tungsten, molybdenum, and nickel; And conductive ceramics such as molybdenum carbide.
[0062]
Between the through-hole and the end of the resistance heating element, and between the through-hole and the high-frequency electrode, the connection area between the through-hole and the resistance heating element is increased to ensure their conduction. For this purpose, a pad portion may be formed.
The material constituting the pad portion is not particularly limited as long as it is a material having conductivity, and examples thereof include a material similar to a resistance heating element and a material similar to a through hole, and a mixture of these materials. (Alloy) or the like.
[0063]
The external terminal connected to the through-hole may have a T-shape in cross section as shown in FIG. 1. For example, the external terminal may be a rod-shaped member having a thread groove cut at one end thereof. Good. When the external terminal has a thread groove, it is desirable to form a screw hole in the through hole, into which the screw groove of the external terminal can be screwed.
[0064]
The material of the external terminal is not particularly limited, and examples thereof include metals such as nickel and kovar.
The size of the external terminal is not particularly limited because it is appropriately adjusted depending on the size of the ceramic substrate, the resistance heating element, the size of the through hole, and the like, but when the external terminal is T-shaped, the diameter of the shaft portion is Has a preferred lower limit of 0.5 mm and a preferred upper limit of 5 mm, and a preferred lower limit of the length of the shaft portion is 1 mm, and a preferred upper limit is 10 mm.
[0065]
In the ceramic heater of the present invention, the conductive wire connected to the external terminal via the socket is covered with a heat-resistant insulating member to prevent a short circuit between the conductive wire and another conductive wire. Is desirable. Such an insulating member is not particularly limited, and examples thereof include aluminum nitride, oxide ceramics such as alumina, silica, mullite, cordierite, silicon nitride, and silicon carbide.
[0066]
As shown in FIG. 1, a bottomed hole is provided on the bottom surface of the ceramic substrate from the bottom surface of the ceramic substrate to a heating surface on which an object to be heated is placed, and the bottom of the bottomed hole is connected to a resistance heating element. It is desirable to form the temperature measuring element such as a thermocouple in the hole with the bottom relatively relatively close to the heating surface.
This is because the temperature of the resistance heating element can be measured by the temperature measuring element, and the voltage and current amount can be changed based on the data to control the temperature.
[0067]
Further, in the ceramic heater of the present invention, the distance between the bottom of the bottomed hole and the heating surface of the ceramic substrate is preferably 0.1 mm to の of the thickness of the ceramic substrate. If the thickness is less than 0.1 mm, heat is radiated from the bottomed hole, and a temperature distribution may be formed on the heating surface. If the thickness exceeds 1/2 of the thickness of the ceramic substrate, the temperature of the resistance heating element is reduced. This is because accurate control of the temperature cannot be performed because the temperature is easily affected, and a temperature distribution may be formed on the heated surface.
When the distance between the bottom of the bottomed hole and the heating surface of the ceramic substrate is 0.1 mm to の of the thickness of the ceramic substrate, the temperature measurement location is closer to the heating surface than the resistance heating element, It is possible to accurately measure the temperature of an object to be heated such as a semiconductor wafer.
[0068]
A desirable lower limit of the diameter of the bottomed hole is 0.3 mm, and a desirable upper limit is 5 mm. If it is less than 0.3 mm, the workability is reduced and the distance to the heated surface cannot be made uniform. If the thickness exceeds 5 mm, the heat dissipation becomes too large, so that a temperature distribution may be formed on the heating surface.
[0069]
It is desirable that a plurality of such bottomed holes are arranged symmetrically with respect to the center of the ceramic substrate and form a cross. This is because the temperature of the entire heating surface can be measured.
[0070]
Examples of the temperature measuring element include a thermocouple, a platinum temperature measuring resistor, a thermistor, and the like.
Examples of the thermocouple include K-type, R-type, B-type, S-type, E-type, J-type, and T-type thermocouples as described in JIS C 1602 (1980). Then, a K-type thermocouple is preferable.
[0071]
A desirable lower limit of the size of the junction of the thermocouple is the diameter of the strand, and a desirable upper limit is 0.5 mm. If the thickness exceeds 0.5 mm, the heat capacity is increased and the responsiveness is reduced. It is difficult to make the diameter smaller than the diameter of the strand.
[0072]
The temperature measuring element may be adhered to the bottom of the bottomed hole using gold brazing, silver brazing, or the like, and after being inserted into the bottomed hole, sealed with a heat-resistant resin, ceramic (silica gel, or the like), or the like. Or both may be used in combination.
The gold solder is selected from 37-80.5% by weight Au-63-19.5% by weight Cu alloy and 81.5-82.5% by weight Au-18.5-17.5% by weight Ni alloy. At least one is desirable. These are because the melting temperature is 900 ° C. or higher and it is difficult to melt even in a high temperature region.
As the silver solder, for example, an Ag-Cu-based solder can be used.
Examples of the heat-resistant resin include a thermosetting resin, particularly an epoxy resin, a polyimide resin, a bismaleimide-triazine resin, and the like. These resins may be used alone or in combination of two or more.
[0073]
Further, as the temperature measuring means of the ceramic heater of the present invention, it is possible to use an optical temperature measuring means such as a thermoviewer.
When the above-mentioned thermoviewer is used, the temperature of the heating surface of the ceramic substrate can be measured, and the temperature of the surface of the processing object such as a silicon wafer can be directly measured. The accuracy is improved.
[0074]
Further, in the ceramic heater of the present invention, it is preferable that a through hole 15 for inserting a lifter pin (not shown) is provided in a portion near the center of the ceramic substrate as shown in FIG.
[0075]
The lifter pins are adapted to place an object to be heated such as a semiconductor wafer thereon and move it up and down, thereby transferring the semiconductor wafer to a transfer machine (not shown) or transferring the semiconductor wafer. While receiving a semiconductor wafer from the machine, the semiconductor wafer can be placed on a heating surface of a ceramic substrate and heated, or the semiconductor wafer can be supported and heated with a distance of about 10 to 2000 μm from the heating surface. Become like
[0076]
Also, a through-hole is provided in the ceramic substrate, a concave portion is provided in the heating surface, and after inserting a support pin having a spire or a hemispherical tip into the through-hole or the concave portion, the support pin is slightly shifted from the ceramic substrate. By fixing the semiconductor wafer in a protruded state and supporting the semiconductor wafer with the support pins, the semiconductor wafer may be heated in a state of being separated from the heating surface by 10 to 2000 μm.
[0077]
As described above, the ceramic body constituting the ceramic heater of the present invention serves to house the external terminals 23 and the conductive wires 24 and the like therein to protect them from corrosive gas and the like, and to support the ceramic substrate from the bottom surface, It also serves to prevent the ceramic substrate from warping due to its own weight.
[0078]
The ceramic material constituting such a ceramic body is not particularly limited, and examples thereof include nitride ceramics such as aluminum nitride, silicon nitride, boron nitride, and titanium nitride; silicon carbide, zirconium carbide, titanium carbide, tantalum carbide, and tungsten carbide. And the like; and oxide ceramics such as alumina, zirconia, cordierite, and mullite. Of these, aluminum nitride is most preferred. This is because the thermal conductivity is the highest at 180 W / m · K, and is excellent in temperature followability.
The ceramic material forming the ceramic body is desirably the same as the ceramic material forming the above-described ceramic substrate. This is because the ceramic substrate and the ceramic body can be bonded by diffusion bonding.
[0079]
The ceramic body may contain a sintering aid. The sintering aid is not particularly limited, and examples thereof include an alkali metal oxide, an alkaline earth metal oxide, and a rare earth oxide. Among these, CaO, Y ₂ O ₃ , Na ₂ O, Li ₂ O, Rb ₂ O is desirable. A desirable lower limit of the content of the sintering aid is 0.1% by weight, and a desirable upper limit is 20% by weight. Further, the ceramic body may contain alumina.
[0080]
The ceramic body is substantially cylindrical, but the contour of the outer wall in a cross section perpendicular to the wall of the cylinder is not particularly limited, and examples thereof include a circular shape, an elliptical shape, and a polygonal shape. Usually, since the ceramic substrate has a disk shape, it is desirable that the contour of the outer wall in the cross section of the ceramic body be circular.
[0081]
A method for joining the ceramic substrate 11 and the ceramic body 17 will be described later in detail.
[0082]
The ceramic heater according to the present invention is a device in which a resistance heating element is provided inside a ceramic substrate, whereby an object to be processed such as a semiconductor wafer is placed on or separated from the surface of the ceramic substrate, and is held at a predetermined position. It can be heated to a temperature or washed, and can be suitably used as an apparatus for manufacturing a semiconductor or inspecting a semiconductor.
At this time, the ceramic heater of the present invention is placed on a predetermined support container.
[0083]
The support container is not particularly limited, and is, for example, a bottomed cylindrical container having a ring-shaped substrate support portion on the inner upper side, and the ceramic of the present invention is provided on the substrate support portion via an insulating ring or the like. The ceramic heater according to the present invention is a container in which a heater is placed and fixed, and a ceramic body is fixed so as to be in close contact with a bottom plate, or a bottomed cylindrical container in which a support member is provided on the inner bottom plate or on an inner wall. In a state where the ceramic body is not in contact with the wall surface, the bottom surface of the ceramic substrate is supported and fixed by the support member, and the ceramic body is fixed so as to be in close contact with the bottom plate.
[0084]
When an electrostatic electrode is further formed on the ceramic substrate of the ceramic heater of the present invention, the ceramic heater of the present invention functions as an electrostatic chuck provided with a heating unit.
[0085]
FIG. 5 is a vertical sectional view schematically showing the electrostatic chuck according to the present invention.
FIG. 6 is a horizontal sectional view schematically showing the vicinity of an electrostatic electrode formed on a ceramic substrate constituting the electrostatic chuck shown in FIG.
Although the boundaries between the ceramic substrate 11 and the ceramic body 17 and the plasma corrosion-resistant layer 200 are roughened, since FIG. 5 is a schematic diagram, the expression as a rough surface is omitted.
[0086]
In this electrostatic chuck 50, a substantially cylindrical ceramic body 17 is joined near the center of the bottom surface 11 b of the ceramic substrate 11, and an electrostatic electrode composed of chuck positive / negative electrostatic layers 52 a and 52 b is provided inside the ceramic substrate 11. 52 are buried, and a part of each is connected to a through hole 53 exposed on the bottom surface 11 b of the ceramic substrate 11 through a blind hole (not shown), and a ceramic dielectric film 54 is formed on the electrostatic electrode 52. ing. Further, a plasma corrosion resistant layer 200 is formed on the surfaces of the ceramic substrate 11 and the ceramic body 17.
A resistance heating element 12 is buried inside the ceramic substrate 11, and a through hole 13 is formed immediately below an end of the resistance heating element 12. The resistance heating element 12 has an end formed with a through hole 13 and a blind hole. It is exposed on the bottom surface 11b of the ceramic substrate 11 via a not shown (not shown). A high-frequency electrode 112 is embedded in the ceramic substrate 11, and a through-hole 113 is formed immediately below an end of the high-frequency electrode 112. The high-frequency electrode 112 has an end at the through-hole 113 and a blind hole ( Exposed on the bottom surface 11b of the ceramic substrate 11 via a not shown).
The through holes 13, 53 and the through hole 113 are connected to the T-shaped external terminals 23 via respective solder layers (not shown).
[0087]
The external terminal 23 is housed inside the ceramic body 17 with a socket 25 having a conductive wire attached thereto. The conductive wire 24 is connected to the outside through a through-hole formed in a bottom plate (not shown) of the support container. It is drawn out and connected to a power supply or the like (not shown), and supplies power to the resistance heating element 12 or the electrostatic electrode 52 to heat or adsorb an object to be heated such as a semiconductor wafer. Can be done.
Further, a bottomed hole 14 for measuring the temperature of the ceramic substrate 11 is formed on the bottom surface of the ceramic substrate 11, and a temperature measuring element 180 to which a lead wire 26 is connected is formed in the bottomed hole 14. Buried.
[0088]
In the electrostatic chuck 50 shown in FIG. 5, an electrostatic electrode 52 (chuck positive / negative electrostatic layers 52 a and 52 b) and a through hole 53 connected to the electrostatic electrode 52 are formed inside the ceramic substrate 11. Has substantially the same configuration as the above-described ceramic heater 10 of the present invention. Therefore, a detailed description other than the electrostatic electrodes 52 and the through holes 53 will be omitted here.
[0089]
The electrostatic electrode 52 formed inside the ceramic substrate 11 has a semicircular chuck positive electrode electrostatic layer 52a and a chuck negative electrode electrostatic layer 52b arranged opposite to each other as shown in FIG. Each of the chuck positive and negative electrode electrostatic layers 52a and 52b is partially connected to a through hole 53 exposed on the bottom surface 11b of the ceramic substrate 11 through a blind hole (not shown).
[0090]
The material constituting the electrostatic electrode 52 is not particularly limited, and is, for example, a noble metal such as gold, silver, platinum, or palladium; a metal such as lead, tungsten, molybdenum, or nickel; or a conductive material such as carbide of tungsten or molybdenum. Ceramics and the like are preferred. These may be used alone or in combination of two or more.
[0091]
The through hole 53 connected to the electrostatic electrode 52 is the same as the through hole 13 connected to the resistive heating element and the high-frequency electrode described in the ceramic heater of the present invention, except that the connection target is different. Structures and materials can be used.
[0092]
In order to operate such an electrostatic chuck, external terminals connected to the chuck positive electrode electrostatic layer, the chuck negative electrode electrostatic layer, and the resistance heating element are connected to the + and-sides of the DC power supply, respectively. Voltage. As a result, an object to be processed such as a semiconductor wafer placed on the electrostatic chuck is heated to a predetermined temperature and is electrostatically attracted to the ceramic substrate.
[0093]
FIG. 7 is a horizontal sectional view schematically showing the vicinity of an electrostatic electrode formed on a ceramic substrate of another electrostatic chuck.
In the electrostatic chuck 60 shown in FIG. 7, a chuck positive electrode electrostatic layer 62 including a semicircular arc portion 62a and a comb tooth portion 62b inside a ceramic substrate 11 and a semicircular arc portion 63a and a comb tooth portion 63b are also formed. And the chuck negative electrode electrostatic layer 63 are disposed so as to face each other so as to intersect the comb teeth portions 62b and 63b.
[0094]
FIG. 8 is a horizontal sectional view schematically showing the vicinity of an electrostatic electrode formed on a ceramic substrate of still another electrostatic chuck.
In the electrostatic chuck 70 shown in FIG. 8, fan-shaped chuck positive electrostatic layers 72 a and 72 b and chuck negative electrostatic layers 73 a and 73 b formed by dividing a circle into four are formed inside the ceramic substrate 11. Further, the two chuck positive electrostatic layers 72a and 72b and the two chuck negative electrostatic layers 73a and 73b are formed so as to cross each other.
[0095]
In the electrostatic chuck according to the present invention, when the electrostatic electrode has a form in which a circular electrode or the like is divided, the number of divisions is not particularly limited, and may be five or more, and the shape is also a sector shape. It is not limited to.
[0096]
Next, as an example of a method for manufacturing the ceramic heater of the present invention, a method for manufacturing the ceramic heater 10 shown in FIG. 1 will be described with reference to FIG.
FIGS. 9A to 9D are cross-sectional views schematically showing one example of a method for manufacturing the ceramic heater 10 of the present invention.
[0097]
(1) Green sheet manufacturing process
First, a ceramic powder is mixed with a binder, a solvent, and the like to prepare a paste, and the paste is formed into a sheet by a doctor blade method, thereby producing a green sheet 110.
As the ceramic powder, aluminum nitride or the like can be used. If necessary, a sintering aid such as yttria, a compound containing Na or Ca, or the like may be added.
The binder is desirably at least one selected from the group consisting of an acrylic binder, ethyl cellulose, butyl cellosolve, and polyvinyl alcohol.
As the solvent, α-terpineol and / or glycol are desirable.
[0098]
A desirable lower limit of the thickness of the green sheet 110 is 0.1 mm, and a desirable upper limit is 5 mm.
Further, a portion serving as a through hole for connecting to the resistance heating element and the high-frequency electrode is formed in a predetermined green sheet 110.
Further, if necessary, a portion serving as a through hole for inserting a lifter pin for transporting an object to be processed such as a semiconductor wafer into the green sheet 110, and a support pin for supporting an object to be processed such as a semiconductor wafer are inserted. A portion to be a through hole or a concave portion to be formed, a portion to be a bottomed hole for embedding a temperature measuring element such as a thermocouple, and the like are formed. The through holes and the bottomed holes may be formed after a green sheet laminate described later is produced, or after the laminate is produced and fired.
[0099]
(2) Step of printing conductive paste on green sheet
A conductive paste is printed on the green sheet 110 to form a conductive paste layer 120 serving as the resistance heating element 12, and a portion serving as a through hole is filled with the conductive paste to form a conductive paste filling layer. Further, a conductive paste is printed on the green sheet 110 to form a conductive paste layer 122 serving as the high-frequency electrode 112, and a portion serving as a through hole is filled with the conductive paste to form a conductive paste filling layer 133.
At this time, the conductive paste layer 120 serving as the resistance heating element 12 is printed so that the end thereof and the conductive paste filling layer 130 filled in the portion serving as the through hole overlap with each other. Reference numeral 122 denotes printing so that the end portion thereof and the conductive paste filling layer 133 filled in a portion to be a through hole overlap. These conductive pastes contain metal particles or conductive ceramic particles.
[0100]
A desirable lower limit of the average particle size of the tungsten particles, molybdenum particles and the like used as the metal particles is 0.1 μm, and a desirable upper limit is 5 μm. If the thickness is less than 0.1 μm or more than 5 μm, it is difficult to print the conductive paste.
[0101]
As such a conductive paste, for example, 85 to 87 parts by weight of metal particles or conductive ceramic particles; 1.5 to 10 parts by weight of at least one binder selected from the group consisting of acrylic, ethyl cellulose, butyl cellosolve, and polyvinyl alcohol Parts; a composition (paste) obtained by mixing 1.5 to 10 parts by weight of a solvent composed of α-terpineol and / or glycol.
The conductive paste used for the conductive paste filling layers 130 and 133 filled in the portions to be the through holes and the conductive paste used for the conductive paste layers 120 and 122 may have the same composition or different compositions. You may.
[0102]
(3) Green sheet lamination process
On the green sheet 110 on which the conductor paste layer 122 is formed, the green sheet 110 on which the conductor paste layer 120 is not formed is laminated, and under the green sheet 110, only the conductor paste filling layer 133 is formed. Then, under this green sheet 110, a green sheet 110 on which a conductor paste layer 120 is formed is superimposed, and further under the green sheet 110, a green sheet 110 on which conductor paste filling layers 130, 133 are formed, and further processing is performed. Green sheets 110 that have not been stacked are laminated (FIG. 9A).
[0103]
At this time, the number of the green sheets 110 laminated on the upper side of the green sheet 110 on which the conductive paste layer 120 is formed is larger than the number of the green sheets 110 laminated on the lower side, so that the formation position of the resistance heating element to be manufactured is on the bottom surface. Eccentric in the side direction.
Specifically, the number of stacked green sheets 110 on the upper side is preferably 20 to 50, and the number of stacked green sheets 110 on the lower side is preferably 5 to 20.
[0104]
(4) Firing step of green sheet laminate
Next, the green sheet laminate is heated and pressurized to sinter the green sheet 110 and the internal conductor paste layers 120 and 122, and the like, and the ceramic substrate 11, the resistance heating elements 12, 112, the through holes 13, 113, and the like. To manufacture. (FIG. 9B)
A desirable lower limit of the heating temperature is 1000 ° C., and a desirable upper limit is 2100 ° C. Heating is performed in an inert gas atmosphere or in a vacuum. As the inert gas, for example, argon, nitrogen and the like can be used. A desirable lower limit of the pressurizing pressure is 10 MPa, and a desirable upper limit is 20 MPa.
[0105]
In addition, a portion serving as a through hole for inserting a lifter pin for transporting a heated object such as a semiconductor wafer into the green sheet 110 in advance, a through hole for inserting a support pin for supporting the heated object such as a semiconductor wafer, In the case where the recessed portion and the bottomed hole for embedding a temperature measuring element such as a thermocouple were not formed, the through hole and the bottomed hole were subjected to processing such as surface polishing on the ceramic substrate 11. Thereafter, it can be formed by performing blast processing such as drilling or sand blasting.
[0106]
Next, a blind hole 19 is formed on the bottom surface 11b of the ceramic substrate 11 by performing blasting such as drilling or sand blasting, thereby exposing the through holes 13 and 113 to the outside.
[0107]
(5) Manufacturing process of a substantially cylindrical ceramic body
A ceramic powder, such as an aluminum nitride powder, is placed in a substantially cylindrical mold, molded and cut as necessary, and then sintered at a heating temperature of 1000 to 2100 ° C. and normal pressure. The cylindrical ceramic body 17 can be manufactured. At this time, the substantially cylindrical ceramic body to be manufactured is desirably substantially cylindrical.
The sintering is performed in an inert gas atmosphere or in a vacuum. As the inert gas, for example, argon, nitrogen and the like can be used.
Next, the end face of the ceramic body 17 is polished and flattened.
[0108]
(6) Step of joining ceramic substrate and ceramic body
In a state where the vicinity of the center of the bottom surface of the ceramic substrate 11 and the end face of the ceramic body 17 are in contact with each other, the ceramic substrate 11 and the ceramic body 17 are heated and joined. At this time, the ceramic body 17 is joined to the bottom surface of the ceramic substrate 11 so that the through holes 13 and 113 in the ceramic substrate 11 fit inside the inner diameter of the ceramic body 17 (FIG. 9C).
[0109]
The method of joining the ceramic substrate 11 and the ceramic body 17 is not particularly limited. However, since the bonding strength between the ceramic substrate 11 and the ceramic body 17 is excellent, the concentration of the sintering aid inside the ceramic substrate 11 and the ceramic body 17 It is desirable to include a sintering aid so that the concentration of the sintering aid is different from the concentration of the sintering aid in the inside, contact the two at the joining position, and then join them by heating. In this case, the sintering aid moves from a member having a high concentration of the sintering aid to a member having a low concentration, and the particles grow across the interface to form a firm joint surface.
[0110]
As another method for joining the ceramic substrate 11 and the ceramic body 17, for example, a solution containing a sintering aid of a ceramic material constituting the ceramic substrate 11 and the ceramic body 17 is applied to the joint surface between the ceramic substrate 11 and the ceramic body 17. And sintering the same (diffusion bonding); a method of applying a ceramic paste containing the same main component as the ceramic constituting the ceramic substrate 11 and the ceramic body 17 to the joining surface of the ceramic substrate 11 and the ceramic body 17 and sintering the paste; , Silver brazing or the like; bonding using an adhesive such as an oxide glass, or the like.
[0111]
(7) Plasma corrosion resistant layer forming process
Sandblasting is performed on the surface of the joined body of the ceramic substrate 11 and the ceramic body 17 to form a roughened surface, and the maximum height R _y To adjust. Next, the joined body is heated, and a compound gas containing yttrium atoms and / or fluorine atoms is caused to flow on the surface thereof, and a layer made of an yttrium compound and / or a fluorine compound is used as the plasma corrosion resistant layer 200 on the ceramic substrate 11 and the ceramic substrate 11. Is deposited on the surface of the joined body of the ceramic body 17 and the ceramic body 17. As described above, the method for forming the plasma corrosion-resistant layer includes various methods in addition to the method described above. Further, the plasma corrosion resistant layer is not limited to the above compounds.
Examples of the method of the roughening treatment include, in addition to the above-described sand blast treatment, blast treatment using glass beads or ceramic powder.
[0112]
(8) Installation of external terminals
A T-shaped external terminal 23 made of a metal such as nickel or kovar is inserted into a bag hole 19 formed inside the inner diameter of the ceramic body 17 via a solder or brazing material, and heated to reflow, thereby forming an external device. The terminal 23 is connected to the through holes 13 and 113 (FIG. 9D).
The heating temperature is preferably from 90 to 450 ° C. in the case of soldering, and is preferably from 900 to 1100 ° C. in the case of processing with a brazing material.
[0113]
Next, the external terminal 23 is connected to a conductive wire 24 connected to a power supply via a socket 25 (see FIG. 1).
Further, a thermocouple or the like as a temperature measuring element is inserted into a bottomed hole formed on the bottom surface of the ceramic substrate and sealed with a heat-resistant resin or the like, thereby completing the manufacture of the ceramic heater 10 of the present invention.
[0114]
When manufacturing the ceramic heater, an electrostatic chuck can be manufactured by providing an electrostatic electrode inside a ceramic substrate. However, in this case, it is necessary to form a through hole for connecting the electrostatic electrode and the external terminal, and it is not necessary to form a through hole for inserting a support pin.
When an electrostatic electrode is provided inside the ceramic substrate, a conductive paste layer serving as an electrostatic electrode may be formed on the surface of the green sheet as in the case of forming the resistance heating element.
[0115]
Hereinafter, the present invention will be described in more detail.
[0116]
【Example】
(Examples 1 to 5) Production of ceramic heater (see FIGS. 1, 2 and 9)
(1) 100 parts by weight of aluminum nitride powder (manufactured by Tokuyama Corporation, average particle size 1.1 μm), yttrium oxide (Y ₂ O ₃ : Yttria, average particle diameter 0.4 μm) 6 parts by weight, 11.5 parts by weight of an acrylic resin binder, 0.5 parts by weight of a dispersant, and a paste obtained by mixing 53 parts by weight of an alcohol composed of 1-butanol and ethanol were used. Then, molding was performed by a doctor blade method to produce a green sheet having a thickness of 0.47 mm.
[0117]
(2) Next, after drying the green sheet at 80 ° C. for 5 hours, a portion serving as a through hole 15 for inserting a lifter pin for carrying a silicon wafer or the like as shown in FIG. 1, and A portion to be a through hole was formed by punching.
[0118]
(3) 100 parts by weight of tungsten carbide particles having an average particle diameter of 1 μm, 3.0 parts by weight of an acrylic binder, 3.5 parts by weight of an α-terpineol solvent, and 0.3 parts by weight of a dispersant are mixed to form a conductive paste A. Prepared.
[0119]
A conductive paste B was prepared by mixing 100 parts by weight of tungsten particles having an average particle diameter of 3 μm, 1.9 parts by weight of an acrylic binder, 3.7 parts by weight of an α-terpineol solvent, and 0.2 parts by weight of a dispersant.
[0120]
The conductive paste B was filled in portions to be through holes to form conductive paste filled layers 130 and 133.
[0121]
Subsequently, the conductor paste A was printed by screen printing on the green sheet on which the conductor paste filling layer 130 and the conductor paste layer 133 were formed, thereby forming the conductor paste layer 120 for the resistance heating element. The printing pattern was a substantially concentric pattern as shown in FIG. 3, the width of the conductive paste layer 120 was 10 mm, and the thickness thereof was 12 μm. Further, the conductor paste A was printed by a screen printing method on a green sheet on which only the conductor paste filling layer 133 was formed, thereby forming a conductor paste layer 122 for a high-frequency electrode in a punched metal shape.
[0122]
On the green sheet on which the conductor paste layer 120 having been subjected to the above-described processing is printed, 30 green sheets on which only the conductor paste filling layer 133 is formed are superimposed, and the green sheet on which the conductor paste layer 122 is printed is superimposed thereon. Thereafter, six green sheets without any processing were further stacked thereon. Then, after the green sheets on which the conductor paste filling layer 130 and the conductor paste filling layer 133 are formed are stacked under the green sheets thus laminated, 12 green sheets without any processing are further placed under the green sheets. They were stacked and pressed at 130 ° C. under a pressure of 8 MPa.
[0123]
(4) Next, the obtained laminate was degreased in nitrogen gas at 600 ° C. for 5 hours and hot-pressed at 1890 ° C. and a pressure of 15 MPa for 10 hours.
This is cut out into a 230 mm disk shape, and has a thickness D having a resistance heating element 12 having a thickness of 5 μm and a width of 2.4 mm, and a through hole 13 therein. ₂ Was a 15 mm ceramic substrate 11.
[0124]
(5) Next, after the ceramic substrate 11 obtained in (4) is polished with a diamond grindstone, a mask is placed, and a bottomed hole 14 for a thermocouple is provided on the surface by blasting with glass beads. On the bottom surface 11b of the ceramic substrate 11, a portion in which the through holes 13 and 113 were formed was cut out to form a blind hole 19.
[0125]
(6) 100 parts by weight of aluminum nitride powder (manufactured by Tokuyama Corporation, average particle size 1.1 μm), 2 parts by weight of yttrium oxide (average particle size 0.4 μm), 11.5 parts by weight of an acrylic resin binder, and 0.1% by weight of dispersant. Using a composition in which 5 parts by weight and 53 parts by weight of alcohol composed of 1-butanol and ethanol are mixed, granules are produced by a spray drying method, and the granules are placed in a substantially cylindrical mold, and are subjected to normal pressure at 1890 ° C. The ceramic body 17 was manufactured by sintering.
[0126]
(7) The end surface of the ceramic body 17 is brought into contact with the bottom surface of the ceramic substrate 11 at a position where the external terminals 23 fit inside the inner diameter of the ceramic substrate 11 and heated to 1890 ° C. 17 was joined. By the heating, the sintering aid moved from the ceramic substrate 11 to the ceramic body 17, and grain growth was generated so as to cross the bonding interface, whereby a firm bond was formed.
[0127]
(8) Using a silicon carbide particle (particle diameter: 5 to 150 μm), the ceramic substrate 11 is subjected to a sandblasting treatment to obtain a maximum height R _y Was the value shown in Table 1.
Further, the concentration of the yttrium nitrate aqueous solution was adjusted to D ₁ The conditions were adjusted to the formation conditions, which were applied to the surface of the ceramic heater 10 and fired at 1600 ° C. in the air. By this process, the thickness D of the plasma corrosion resistant layer 200 ₁ Formed a layer made of yttria having the values shown in Table 1.
Note that D ₁ , R _y For, the cross section of the ceramic heater was observed with an electron microscope of 1000 times, and 10 photographs of an arbitrary portion in the cross section were taken. In one photograph, the maximum thickness of the yttria layer and the roughened ceramic surface The maximum thickness d of the yttria layer was determined for each of the ten SEM photographs. ₁ ~ D ₁₀ The average of D ₁ And the maximum height r ₁ ~ R ₁₀ The average of R _y Used as
[0128]
(9) Next, a silver solder (Ag: 40 wt%, Cu: 30 wt%, Zn: 28 wt%, Ni: 1.8 wt%, balance: other Element, reflow temperature: 800 ° C.), and the external terminal 23 was attached. Then, the conductive wire 24 was connected to the external terminal 23 via the socket 25.
[0129]
(10) Then, a thermocouple for temperature control is inserted into the bottomed hole 14, filled with silica sol, cured at 190 ° C. for 2 hours and gelled, so that a resistance heating element and a through hole are provided therein. A ceramic heater having a ceramic body bonded to the bottom surface of the ceramic substrate thus manufactured was manufactured.
[0130]
(Comparative Examples 1-2)
Maximum height R of ceramic substrate surface by changing particle diameter of silicon carbide particles used for sandblasting _y And D in Table 1 ₁ As shown in the formation conditions, the thickness D of the plasma corrosion resistant layer was changed by changing the concentration of the yttrium nitrate aqueous solution. ₁ A ceramic heater was manufactured in the same manner as in Example 1 except for changing.
[0131]
(Examples 6 to 10, Comparative Examples 3 and 4)
Thickness D of ceramic substrate 11 ₂ Was changed to the value (5 mm) shown in Table 1, and a ceramic heater was manufactured in the same manner as in Examples 1 to 5 and Comparative Examples 1 and 2, except that aluminum fluoride was used as the plasma corrosion-resistant layer. That is, the sample was set in a vacuum chamber and 1 × 10 ^-3 After evacuating to Pa, a partial pressure of 0.5 Pa He gas and a partial pressure of 0.1 Pa O ₂ Gas was introduced into the vacuum chamber. Na ₃ AlF ₆ A plasma corrosion-resistant layer made of aluminum fluoride having a thickness shown in Table 1 was formed by a high-frequency magnetron sputtering method using, as a target, a composite of the above and a composite of chlorofluoroethylene resin disposed on a cathode. Sputtering time is D ₁ It is shown as a forming condition. D ₁ , R _y In the measurement, the cross section of the ceramic heater was observed with an electron microscope of 1000 times as in Example 1, 10 photographs were taken at arbitrary positions in the cross section, and the maximum thickness of the yttria layer was observed in one photograph. And the maximum height of the roughened ceramic surface, respectively, and the maximum thickness d of the yttria layer determined for ten SEM photographs ₁ ~ D ₁₀ The average of D ₁ And the maximum height r ₁ ~ R ₁₀ The average of R _y Used as
[0132]
(Examples 11 to 15, Comparative Examples 5 to 6)
Thickness D of ceramic substrate 11 ₂ Was changed to the value (20 mm) shown in Table 1, and a ceramic heater was prepared in the same manner as in Examples 1 to 5 and Comparative Examples 1 and 2 except that silicon carbide having a (111) plane orientation was used as the plasma corrosion resistant layer. Manufactured. That is, methyltrichlorosilane (concentration: 7%) is supplied as a reaction gas and hydrogen and argon are supplied as a reaction gas under a condition of a temperature of 1300 ° C. and a degree of vacuum of 250 Torr by a CVD method, and are thermally decomposed. Thickness D shown ₁ A plasma corrosion resistant layer composed of a CVD-SiC layer having a β-SiC crystal structure was formed. Table 1 shows the pyrolysis time. ₁ It is shown as a forming condition.
D ₁ , R _y In the measurement, the cross section of the ceramic heater was observed with an electron microscope of 1000 times as in Example 1, 10 photographs were taken at arbitrary positions in the cross section, and the maximum thickness of the yttria layer was observed in one photograph. And the maximum height of the roughened ceramic surface, respectively, and the maximum thickness d of the yttria layer determined for ten SEM photographs ₁ ~ D ₁₀ The average of D ₁ And the maximum height r ₁ ~ R ₁₀ The average of R _y Used as
[0133]
(Example 16) Production of electrostatic chuck (see FIGS. 5 and 6)
(1) 100 parts by weight of aluminum nitride powder (manufactured by Tokuyama Corporation, average particle size 1.1 μm), 4 parts by weight of yttrium oxide (average particle size 0.4 μm), 12 parts by weight of an acrylic resin binder, 0.5 part by weight of a dispersant A green sheet having a thickness of 0.47 mm was obtained by molding using a composition obtained by mixing 53 parts by weight of alcohol consisting of 1 part butanol and ethanol with a doctor blade method.
[0134]
(2) Next, after drying this green sheet at 80 ° C. for 5 hours, a green sheet A without any processing and a through hole for a through hole for connecting an electrostatic electrode to an external terminal were provided. A green sheet B, a through hole for a through hole for connecting an electrostatic electrode and an external terminal, a green sheet C provided with a through hole for a through hole for connecting an electrostatic electrode and an external terminal, and a resistance heating element Through-hole for connecting the external terminal with the external terminal, through-hole for connecting the electrostatic electrode and the external terminal, and through-hole for connecting the high-frequency electrode and the external terminal. The provided green sheet D was produced.
[0135]
(3) Conductive paste A obtained by mixing 100 parts by weight of tungsten carbide particles having an average particle diameter of 1 μm, 3.0 parts by weight of an acrylic binder, 3.5 parts by weight of α-terpineol solvent, and 0.3 parts by weight of a dispersant. Was prepared.
A conductive paste B was prepared by mixing 100 parts by weight of tungsten particles having an average particle diameter of 3 μm, 1.9 parts by weight of an acrylic binder, 3.7 parts by weight of an α-terpineol solvent, and 0.2 parts by weight of a dispersant. did.
[0136]
(4) The conductive paste B was filled in the through holes for through holes formed in the green sheets BD prepared in (2) to form a conductive paste filled layer.
[0137]
Subsequently, the conductor paste A was printed on the surface of the green sheet D by a screen printing method to form a conductor paste layer serving as a resistance heating element having the circuit pattern shown in FIG. Similarly, a conductor paste layer to be a high-frequency electrode was printed on the surface of the green sheet C. Further, a conductive paste layer composed of an electrostatic electrode pattern having the shape shown in FIG. 6 was formed on the surface of the green sheet B.
[0138]
Next, the green sheets subjected to the above treatment were laminated.
First, 16 green sheets C are laminated on the upper side (heating surface side) of the green sheet D on which the conductor paste layer serving as the resistance heating element is printed, and the green sheet on which the conductor paste layer serving as the high-frequency electrode is printed is disposed above the green sheet C. The sheet C was laminated, and 17 green sheets B were further laminated thereon. Then, after stacking the green sheet D on the lower side (bottom side) of the stacked green sheets, 12 green sheets A were further stacked on the lower side.
On the uppermost part of the green sheets thus laminated, a green sheet B on which a conductor paste composed of an electrostatic electrode pattern is printed is laminated, and two green sheets A are further laminated thereon, and these are laminated at 130 ° C. and 8 MPa. The laminate was formed by pressure bonding under pressure.
[0139]
(5) Next, the obtained laminate was degreased in a nitrogen gas at 600 ° C. for 5 hours, and then hot-pressed at 1890 ° C. and a pressure of 15 MPa for 3 hours.
This was cut into a disk shape having a diameter of 230 mm, and a resistance heating element 12 having a thickness of 5 μm and a width of 2.4 mm, a chuck positive electrostatic layer 52 a having a thickness of 6 μm, a chuck negative electrostatic layer 52 b having a high frequency, 112 and a thickness D having through holes 13, 53, 113 ₂ Was a 15 mm ceramic substrate 11.
[0140]
(6) Next, after polishing the ceramic substrate 11 obtained in (5) with a diamond grindstone, a mask is placed, and a bottomed hole 14 for a thermocouple is provided on the surface by blasting with glass beads. On the bottom surface of the ceramic substrate 11, a through hole 13, 53, 113 was formed to form a blind hole.
[0141]
(7) 100 parts by weight of aluminum nitride powder (manufactured by Tokuyama Corporation, average particle size: 1.1 μm), 4 parts by weight of yttrium oxide (average particle size: 0.4 μm), 11.5 parts by weight of an acrylic resin binder, 0.1% by weight of dispersant. Using a composition in which 5 parts by weight and 53 parts by weight of alcohol composed of 1-butanol and ethanol are mixed, granules are produced by a spray drying method, and the granules are placed in a substantially cylindrical mold, and are subjected to normal pressure at 1890 ° C. The ceramic body 17 was manufactured by sintering.
[0142]
(8) Yttrium nitrate (2.61 × 10 6 ^-1 mol / L) After applying the aqueous solution, the end face of the ceramic body 17 is brought into contact with the bottom surface 11b of the ceramic substrate 11 at a position where the external terminal 23 fits inside the inner diameter of the ceramic substrate 11 and heated to 1890 ° C. Thus, the ceramic substrate 11 and the ceramic body 17 were joined.
[0143]
(9) In the vacuum vessel, the joined body of the ceramic substrate 11 and the ceramic body 17 is ₄ It was kept at 650 ° C. for 30 minutes in down-flow plasma. However, CF ₄ The gas was excited by ICP (flow rate: 50 sccm, 13.56 Hz, 2 kW), and the gas pressure was set to 5 Torr. By this process, the plasma corrosion-resistant layer 200 has a thickness D ₁ Formed a layer of a composite of aluminum fluoride and yttrium fluoride having a thickness of 30 μm.
[0144]
(10) Next, silver brazing (Ag: 40% by weight, Cu: 30% by weight, Zn: 28% by weight, Ni: 1.8% by weight, balance: other elements) , Reflow temperature: 800 ° C.), and the external terminals 23 were attached. Then, the conductive wire 24 was connected to the external terminal 23 via the socket 25.
[0145]
(11) Then, a thermocouple for temperature control is inserted into the bottomed hole 14, filled with silica sol, cured and gelled at 190 ° C. for 2 hours, so that an electrostatic electrode, a resistance heating element and A ceramic body joined to a bottom surface of a ceramic substrate provided with a through-hole and functioning as an electrostatic chuck was manufactured.
[0146]
(Example 17)
(1) 100 parts by weight of silicon carbide powder (SiC powder manufactured by Yakushima Electric Works, average particle size 50 μm, 70%, SiC powder manufactured by Yakushima Electric Works, average particle size 3 μm, 30%) and 5 parts by weight of an acrylic binder were mixed. Using the composition, granules were produced by a spray-drying method, and a molded product was produced by CIP molding using the granules to produce a green molded product having a thickness of 0.50 mm.
[0147]
(2) Next, a laminate was formed by pressing the green compact by the same steps as in (2) and (3) of Examples 1 to 5.
[0148]
(3) Next, the obtained laminate was sintered in an argon atmosphere at atmospheric pressure, 2100 ° C. for 5 hours.
This was cut out into a 230 mm disk shape, and a resistance heating element having a thickness of 5 μm and a width of 2.4 mm inside, and a thickness D having a through hole were formed. ₂ Was a 15 mm ceramic substrate. In addition, since this ceramics substrate is a porous ceramics, it exhibits insulating properties.
[0149]
(4) Next, blind holes were formed by the same steps as in (5) of Examples 1 to 5.
[0150]
(5) 100 parts by weight of silicon carbide powder (SiC powder manufactured by Yakushima Electric Works, average particle size 50 μm, 70%, SiC powder manufactured by Yakushima Electric Works, average particle size 3 μm, 30%) and 5 parts by weight of an acrylic binder were mixed. Using the composition, granules were produced by a spray drying method, and the granules were placed in a substantially cylindrical mold to produce a cylindrical green molded body. The cylindrical green body was sintered in an argon atmosphere at atmospheric pressure, 2100 ° C. for 5 hours to produce a cylindrical ceramic body.
[0151]
(6) The end of the ceramic substrate on which the SiC paste has been applied is brought into contact with the bottom surface of the ceramic substrate where the external terminals are accommodated inside, and heated to 2000 ° C. The cylindrical ceramic body was joined. Grain growth occurred across the bonding interface, and a firm bond was formed.
[0152]
(7) Using a silicon carbide particle (particle diameter: 5 to 150 μm), a ceramic substrate is subjected to sandblasting to obtain a maximum height R _y Was the value shown in Table 1.
Further, methyltrichlorosilane (CH 2) as a reaction gas was formed by CVD at a temperature of 1300 ° C. and a degree of vacuum of 250 Torr. ₃ SiCl ₃ , Concentration: 7%). Hydrogen and argon gas were supplied as carrier gases and thermally decomposed to obtain a thickness D. ₁ Formed a plasma corrosion-resistant layer composed of a CVD-SiC (silicon carbide) layer having a β-SiC crystal structure having the values shown in Table 1. Table 1 shows the pyrolysis time. ₁ The conditions for formation are shown.
Note that D ₁ , R _y As in Example 1, the cross section of the ceramic heater was observed with a 1000 × electron microscope, 10 photographs were taken at arbitrary positions in the cross section, and the (111) plane orientation was measured in one photograph. The maximum thickness of the silicon carbide layer having the (111) plane orientation obtained from ten SEM photographs was obtained by determining the maximum thickness of the silicon carbide layer and the maximum height of the roughened ceramic surface, respectively. ₁ ~ D ₁₀ The average of D ₁ And the maximum height r ₁ ~ R ₁₀ The average of R _y Used as
[0153]
(8) Next, a ceramic heater in which a ceramic body was joined to the bottom surface of the ceramic substrate was manufactured by the same steps as (9) and (10) in Examples 1 to 5.
[0154]
(Evaluation)
The following evaluation tests were performed on the ceramic heaters according to Examples 1 to 17 and Comparative Examples 1 to 6. The results are shown in Table 1 below.
[0155]
(1) Existence of peeling and corrosion of plasma corrosion resistant layer
0.1 Torr ClF excited by ICP ₃ A thermal cycle test was performed in gas. ClF ₃ Was 75 sccm, and the flow rate of argon was 5 sccm. The temperature increase and decrease between 200 ° C. and 100 ° C. are repeated for 5 cycles, and each time the temperature is increased and decreased for one cycle, the temperature is held at 1000 ° C. for a certain period of time, and 5 cycles are held for a total of 78 hours. did.
The presence or absence of corrosion was confirmed by measuring the weight loss of the components of the ceramic heater. The presence or absence of peeling was confirmed by observation with an electron microscope. Table 1 shows the results.
[0156]
(2) Measurement of temperature equalization time
The temperature of the ceramic heater is raised to 450 ° C. in the air, and the time (sec) until the temperature difference of the entire heated surface becomes 90 ° C. or less is measured by setting the time when the 450 ° C. area appears on the heated surface to 0 ° C. did. Table 1 shows the results.
[0157]
[Table 1]

[0158]
As shown in Table 1, in the present invention, D ₁ × D ₂ / R _y Is in the range of 0.015 to 20,000, the temperature of the heated surface can be quickly made uniform.
In particular, in Table 1, D ₁ ≧ R _y In other words, the surprising fact that the temperature uniformization is faster when the thickness of the plasma corrosion resistant layer is larger than the maximum height of the roughened surface is shown. The reason for this is not clear, but the plasma corrosion resistant layer is inferior in thermal conductivity, and on the contrary, it has a heat retaining effect and compensates for the low thermal conductivity on the roughened surface of the ceramic substrate, so that the temperature of the heated surface is made uniform. It is estimated that the speed has been improved.
Furthermore, D ₁ × D ₂ / R _y Is preferably 5 or more. This is because if it is 5 or more, the rate of temperature uniformization becomes particularly high.
Also, an SEM cross-sectional photograph near the surface of the ceramic heater composed of the plasma corrosion resistant layer (layer made of dense silicon carbide) and the ceramic substrate (layer made of porous silicon carbide) manufactured in Example 17 is shown. This is shown in FIG.
[0159]
【The invention's effect】
As described above, the ceramic heater of the present invention has excellent corrosion resistance and does not corrode even if it is continuously exposed to a reactive gas or a halogen gas for a long period of time. Are not generated and particles are generated, and adhere to an object to be processed such as a silicon wafer to prevent contamination.
Further, in the ceramic heater of the present invention, the temperature of the heating surface can be quickly made uniform, so that the throughput time can be reduced.
[Brief description of the drawings]
FIG. 1 is a vertical sectional view schematically showing one example of a ceramic heater of the present invention.
FIG. 2 is a sectional view of the ceramic heater shown in FIG. 1 taken along line AA.
FIG. 3 is a horizontal sectional view schematically showing another example of the resistance heating element constituting the ceramic heater of the present invention.
FIG. 4 is a horizontal sectional view schematically showing still another example of the resistance heating element constituting the ceramic heater of the present invention.
FIG. 5 is a vertical sectional view schematically showing an example in which the ceramic heater of the present invention functions as an electrostatic chuck.
FIG. 6 is a horizontal cross-sectional view schematically illustrating an example of an electrostatic electrode embedded in a ceramic substrate constituting the electrostatic chuck.
FIG. 7 is a horizontal sectional view schematically showing another example of an electrostatic electrode embedded in a ceramic substrate constituting the electrostatic chuck.
FIG. 8 is a horizontal sectional view schematically showing still another example of the electrostatic electrode embedded in the ceramic substrate constituting the electrostatic chuck.
FIGS. 9A to 9D are cross-sectional views schematically showing one example of a method for manufacturing a ceramic heater of the present invention.
FIG. 10 is a view showing an X-ray diffraction measurement result of a CVD-SiC (silicon carbide) film showing (111) orientation.
FIG. 11 is an SEM cross-sectional photograph of the vicinity of the surface of the ceramic heater of the present invention composed of a plasma corrosion resistant layer (a layer made of dense silicon carbide) and a ceramic substrate (a layer made of porous silicon carbide).
[Explanation of symbols]
10, 30, 40 ceramic heater
11, 31, 41 ceramic substrate
11a heating surface
11b bottom
12, 32, 42 Resistance heating element
13, 53 Through hole
14 Bottom hole
15 Through hole
17 ceramic body
19 blind hole
23 External terminal
24 conductive wire
25 socket
26 Lead wire
50, 60, 70 Electrostatic chuck
52 electrostatic electrode
52a positive electrode electrostatic layer
52b negative electrode electrostatic layer
54 Ceramic Dielectric Film
110 Green Sheet
120 conductive paste layer
130 conductive paste filling layer
180 side temperature element
200 Plasma corrosion resistant layer

Claims (6)

A ceramic heater comprising a ceramic substrate provided with a resistance heating element inside or on a bottom surface thereof,
A roughened surface is formed on the surface of the ceramic substrate,
Further, a ceramic corrosion resistant layer is formed on the roughened surface, and the plasma corrosion resistant layer satisfies a condition of the following formula (1).
0.015 (mm) ≦ D ₁ × D ₂ / R _y ≦ 20000 (mm) (1)
(In the formula (1), D ₁ (μm) is the thickness of the plasma corrosion-resistant layer on the surface of the ceramic substrate, D ₂ (mm) is the thickness of the ceramic substrate, and R _y (μm ) Is the maximum height based on JIS B 0601 indicating the surface roughness of the ceramic substrate.) The ceramic heater according to claim 1, wherein an electrostatic electrode is provided on the ceramic substrate. 3. The ceramic heater according to claim 1, wherein a high-frequency electrode is embedded in the ceramic substrate. The ceramic heater according to any one of claims 1 to 3, wherein a substantially cylindrical ceramic body is bonded to a bottom surface of the ceramic substrate. The ceramic heater according to any one of claims 1 to 4, wherein the plasma corrosion-resistant layer is a layer made of a fluorine compound and / or an yttrium compound. The ceramic heater according to any one of claims 1 to 4, wherein the plasma corrosion-resistant layer is a layer made of silicon carbide exhibiting orientation.

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