JP3965468B2 - Electrostatic chuck - Google Patents

Description

【００７８】
試料Ｎｏ．６は、前記化合物の含有量が０．９重量％であることから熱伝導率が３７Ｗ／（ｍ・Ｋ）と小さく、ウエハＷの面内温度差が１１℃と大きく均熱性が劣った。
【００７９】
試料Ｎｏ．7は、前記化合物の含有量が２１重量％と大きいことから熱伝導率が３４Ｗ／（ｍ・Ｋ）と小さくなり、ウエハＷの均熱性が劣った。また窒化アルミニウム質焼結体の硬度が小さくなるため、パーティクル数が５０００ヶと多かった。
【００８０】
試料Ｎｏ．１０は、前記化合物と結合している酸素量を差し引いた酸素量が０．４重量％と小さいことから、相対密度が９６％と小さくパーティクル数が２００００ヶと多かった。
【００８１】
また試料Ｎｏ．１１は、前記化合物と結合している酸素量を差し引いた酸素量が１．６重量％と多いことから、熱伝導率が３５Ｗ／（ｍ・Ｋ）と小さくなりウエハＷの面内温度差が１２℃と大きかった。
【００８２】
試料Ｎｏ．１３は相対密度が９６％と小さいことからパーティクル数が２００００ヶと多かった。
【００８３】
試料Ｎｏ．１４は、窒化アルミニウム結晶以外の結晶の最大粒径を窒化アルミニウム結晶の最大粒径で除した値Ｒが０．９であることからパーティクル数が６０００ヶと多かった。
【００８４】
試料Ｎｏ．１５は、窒化アルミニウム結晶以外の結晶の最大粒径を窒化アルミニウム結晶の最大粒径で除した値が２．１であることからパーティクル数が６０００ヶと多かった。
【００８５】
この結果、上記板状セラミックス体は、希土類元素及び／又はアルカリ土類金属元素からなる化合物を酸化物換算で１〜２０重量％含有し、前記化合物と結合している酸素量を差し引いた酸素量が０．５〜１．５重量％である窒化アルミニウム質焼結体からなり、相対密度が９７％以上であり、上記板状セラミックス体の載置面におけるビッカース硬度（Ｈｖ）が８００〜１１００であり、更に窒化アルミニウム結晶以外の結晶の最大粒径を窒化アルミニウム結晶の最大粒径で除した値が１．０〜５．０であると、パーティクルの発生を大幅に低減することができることから、静電チャックとして優れた特性を示す事が分った。
【００８６】
また、発熱用の内部電極５を埋設し、前記板状セラミックス体の熱伝導率が４０Ｗ／（ｍ・Ｋ）以上とすることにより、１２インチのウエハＷを加工処理する際に必要な９℃以下の面内均熱性を得ることができ優れていることが分かる。
（実施例２）
次に、試料Ｎｏ.１と同様の製造方法で、焼結助剤の添加量を変えて窒化アルミニウム質焼結体の試料を作製し、室温２５℃において静電吸着用の内部電極４に５００Ｖの直流電圧を印加して１２インチのシリコンウエハＷを吸着させ、このシリコンウエハＷをロードセルにて引き剥がすのに要する荷重を吸着力として測定し、また、シリコンウエハＷと吸着用の内部電極との間の絶縁層の体積固有抵抗値を測定した。その結果を表２に示す。
【００８７】
【表２】

【００８８】
試料Ｎｏ.２４は前記化合物の含有量が０．８重量％と少ないことから、体積固有抵抗値が２ｘ１０¹²Ω・ｃｍと大きく、吸着力は０．９８ｋＰａと小さかった。
【００８９】
また、試料Ｎｏ.２５は前記化合物の含有量が２５重量％と多いことから、体積固有抵抗値が９ｘ１０⁷Ω・ｃｍと小さく、ウエハＷと載置面の間の漏れ電流が大きく、吸着力は０．９８ｋＰａと小さかった。
【００９０】
これに対し、試料Ｎｏ.２1〜２３は前記化合物を１〜２０重量％含有し、静電吸着力が１９．６ｋＰａ〜３４．３ｋＰａと大きく好ましいことが分かった。
【００９１】
【発明の効果】
以上のように、本発明によれば、板状セラミックス体の一方の主面を、ウエハを載せる載置面とするとともに、上記板状セラミックス体中に内部電極を備えた静電チャックにおいて、上記板状セラミックス体は、希土類元素及び／又はアルカリ土類金属元素からなる化合物を酸化物換算で１〜２０重量％含有し、上記化合物と結合している酸素量を差し引いた酸素量が０．５〜１．５重量％である窒化アルミニウム質焼結体からなり、相対密度が９７％以上であり、上記板状セラミックス体の載置面におけるビッカース硬度（Ｈｖ）が８００〜１１００であり、更に窒化アルミニウム結晶以外の結晶の最大粒径を窒化アルミニウム結晶の最大粒径で除した値が１．０〜５．０であるとともに、上記板状セラミックス体の２５℃での体積固有抵抗値が１×１０ ^８ Ω・ｃｍ〜１×１０ ^１２ Ω・ｃｍであることにより、ジョンソン・ラーベック効果を利用した大きな静電吸着力でもってウエハを載置面上に強固に吸着固定することができるとともに、シリコン、ガリウム砒素等からなるウエハの脱着を繰り返したとしても、載置面の硬度がウエハの硬度に近似していることから、載置面及びウエハの磨耗を抑えることができ、パーティクルの発生を大幅に低減することができる。更に１２インチや１８インチのウエハをプロセスする際に必要な面内均熱性を得ることができる。
【図面の簡単な説明】
【図１】（ａ）は本発明に係る静電チャックをベース基体に固定した状態を示す斜視図、（ｂ）は（ａ）のＸ−Ｘ線断面図である。
【図２】図１の静電チャックに備える静電吸着用の内部電極のパターン形状を示す平面図である。
【図３】図1の静電チャックに備える加熱用の内部電極のパターン形状を示す平面図である。
【図４】本発明に係る静電チャックの製造方法を説明するための図である。
【図５】本発明に係る静電チャックの他の実施形態を示す断面図である。
【符号の説明】
１：静電チャック
２：板状セラミックス体
２ａ：絶縁層
２ｂ：あるセラミック部
３：載置面
４：内部電極
４ａ：導体層
５：内部電極
５ａ：帯状導体層
５ｂ：帯状導体層
６：給電端子
７：給電端子
８：ベース基体
９：窒化アルミニウムグリーンシート
１０：密着液
１１：導体ペースト
１２：導体ペースト
Ｗ：ウエハ[0001]
BACKGROUND OF THE INVENTION
The present invention mainly relates to an electrostatic chuck for attracting and holding a wafer such as a semiconductor wafer or a liquid crystal substrate by electrostatic attraction force.
[0002]
[Prior art]
Conventionally, in a semiconductor device manufacturing process, an etching process for performing microfabrication on a semiconductor wafer such as a silicon wafer (hereinafter simply referred to as a wafer), a film forming process for forming a thin film on the wafer, a transfer between various processing processes, etc. In this case, an electrostatic chuck is used because it is necessary to hold the wafer with high accuracy.
[0003]
In this type of electrostatic chuck, one main surface (widest surface) of the plate-shaped ceramic body is used as a mounting surface on which the wafer is placed, and an internal electrode is provided on the mounting surface side in the plate-shaped ceramic body. Therefore, the wafer is forcibly attracted and fixed to the mounting surface by placing the wafer on the mounting surface and developing an electrostatic attraction force between the wafer and the internal electrode.
[0004]
By the way, the electrostatic attraction force includes a Coulomb force due to dielectric polarization and a Johnson-Rahbek force due to a minute leakage current, and it is desired to develop a Johnson-Rahbek force that provides a high attraction force.
[0005]
In order to obtain this Johnson-Rahbek force, the volume specific resistance value of the insulating layer between the wafer mounting surface and the internal electrode is 1 × 10 5 under the operating temperature atmosphere.⁸From Ω · cm to 1 × 10¹²It is necessary to be in the range of about Ω · cm, and in order to express this Johnson-Rahbek force, a low resistance in which the transition metal contains the insulating layer between the mounting surface and the internal electrode almost uniformly. One formed by an alumina sintered body has been proposed (see Patent Document 1).
[0006]
However, the electrostatic chuck disclosed in Patent Document 1 controls the volume resistivity of the insulating layer between the mounting surface and the internal electrode by controlling the amount of transition metal added. It is very difficult to obtain an alumina sintered body that contains transition metal to alumina, which is the main component, and the transition metal is almost evenly contained. There is a problem that a sintered body having a size of 1 mm cannot be obtained.
[0007]
In addition, the electrostatic chuck disclosed in Patent Document 2 disperses the conductor component of the internal electrode in an insulating layer between the mounting surface and the internal electrode, so that in a temperature range of 250 ° C. to 450 ° C., The resistance value of the ceramic part is 1 × 10⁹Ω · cm to 1 × 10¹¹An electrostatic chuck in the range of Ω · cm has been proposed.
[0008]
Further, in Patent Document 3, in the wide temperature range of 150 ° C. to 500 ° C., the insulating layer between the mounting surface and the internal electrode is formed of a carbon-containing aluminum nitride sintered body. There has been proposed an electrostatic chuck in which the surface has a Vickers hardness (Hv) of 800 to 1100.
[0009]
In addition, the electrostatic chuck adheres a metal base to the aluminum nitride sintered body and allows gas to flow inside the base or processes wafers while being heated to a high temperature. In many cases, an aluminum nitride sintered body having higher strength is desired. Patent Document 4 discloses that aluminum nitride sintered having excellent mechanical strength and reliability. The body and its manufacturing method have been proposed.
[0010]
[Patent Document 1]
Japanese Patent Publication No. 6-97675
[Patent Document 2]
JP 2000-77508 A
[Patent Document 3]
JP 2002-110773 A
[Patent Document 4]
JP 2000-327430 A
[0011]
[Problems to be solved by the invention]
By the way, in recent years, miniaturization of circuits formed on a wafer has progressed, and it is desired to fix the wafer with higher accuracy. However, in the electrostatic chuck disclosed in Patent Document 2, the mounting surface is made of ceramic with high hardness. Therefore, when the wafer is detached, the wear of the mounting surface is very small, but the wear of the wafer sliding with the mounting surface is large and generates particles. When the wafer is sucked and fixed, particles are interposed between the wafer and the mounting surface, and there is a problem that the wafer cannot be fixed with high accuracy.
[0012]
That is, when the wafer is attracted to the placement surface by the electrostatic adsorption force, the wafer having a low hardness is slid on the placement surface made of high-hardness ceramic by the high electrostatic adsorption force. Even if the surface was finished flat, the wafer was scratched and worn.
[0013]
Furthermore, in the aluminum nitride sintered body and the manufacturing method thereof disclosed in Patent Document 4, the cumulative value of the grain boundary phase crystal particles at an arbitrary cut surface is 75%, and the cumulative value of the aluminum nitride crystal particles is 50%. An aluminum nitride-based sintered body characterized by a ratio of 0.5 to 1.5 has been proposed. This production method is based on the accumulation of grain boundary phase crystal grains depending on the amount of sintering aid added. In order to control the ratio between the 75% particle size and the 50% cumulative particle size of aluminum nitride crystal particles, it is desirable that the aluminum nitride crystal particles and the grain boundary phase have the same particle size as much as possible. Since the average particle size ratio of the mixed powder of the agent needs to be adjusted to a narrow range of 1.1 to 2, and the temperature distribution during firing needs to be very narrow, products with small shapes such as test pieces Vs. It can be said that it is effective, but the cumulative value of grain boundary phase crystal grains is 75% depending on the amount of sintering aid added from the end to the center of large products such as 8-inch, 12-inch and even 18-inch electrostatic chucks. It can be said that it is extremely ineffective to control the ratio between the diameter and the cumulative value of 50% of the aluminum nitride crystal grains.
[0014]
Furthermore, the trend of the semiconductor industry in recent years is to increase the diameter of wafers to be handled. Until recently, 8-inch wafers were the mainstream, but recently they have expanded to 12 inches. There is a possibility of expanding to 18 inches in the future, and in order to increase the diameter of the wafer, the apparatus for processing the wafer must be enlarged, and a large electrostatic chuck is required. There is a problem that the in-plane temperature difference of the wafer W becomes large in the enlarged electrostatic chuck.
[0015]
An object of the present invention is to firmly hold and fix a wafer on a mounting surface with a high electrostatic attraction force utilizing the Johnson-Rahbek effect, and even if the wafer is repeatedly attached and detached, the mounting surface and the wafer It is an electrostatic chuck that does not cause wear and has very little generation of particles, and further has an in-plane thermal uniformity necessary for a 12-inch or 18-inch wafer processing process. .
[0016]
[Means for Solving the Problems]
  Therefore, in view of the above problems, the present invention provides an electrostatic chuck in which one main surface of a plate-shaped ceramic body is a mounting surface on which a wafer is placed and an internal electrode is provided in the plate-shaped ceramic body. The ceramic body contains 1 to 20% by weight of a compound composed of rare earth elements and / or alkaline earth metal elements in terms of oxides,UpIt is composed of an aluminum nitride sintered body in which the amount of oxygen subtracting the amount of oxygen bonded to the compound is 0.5 to 1.5% by weight, the relative density is 97% or more, The Vickers hardness (Hv) on the mounting surface is 800 to 1100, and the value obtained by dividing the maximum grain size of crystals other than the aluminum nitride crystal by the maximum grain size of the aluminum nitride crystal is 1.0 to 5.0.In addition, the volume resistivity of the plate-like ceramic body at 25 ° C. is 1 × 10 ⁸ Ω · cm to 1 × 10 ¹² Ω · cmIt is characterized by that.
[0017]
  The plate-like ceramic body has an internal electrode for heating, and the plate-like ceramic body has a thermal conductivity of 40 W / (m · K) or more at room temperature.In addition, the plate-like ceramic body was fired at 1800 ° C. or higher.It is characterized by that.
[0018]
Further, the sintering aid for the plate-like ceramic body comprises a compound containing Ce element, and CeO₂It contains 1 to 20% by weight in terms of conversion.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
[0020]
FIG. 1 (a) is a perspective view showing a state in which an electrostatic chuck 1 as an example of the present invention is fixed to a base substrate 8, and FIG. 1 (b) is a sectional view taken along line XX of FIG. 1 (a). In the electrostatic chuck 1, one main surface of the disk-shaped plate-shaped ceramic body 2 is used as a mounting surface 3 on which the wafer W is placed, and in the vicinity of the mounting surface 3 in the plate-shaped ceramic body 2. Includes an internal electrode 4 for electrostatic attraction, and an internal electrode 5 for heating in the vicinity of the other main surface in the plate-like ceramic body 2.
[0021]
As shown in FIG. 2, the internal electrode 4 for electrostatic attraction is composed of two semicircular conductor layers 4a. In addition, the heating internal electrode 5 has a linear strip shape connecting arc-shaped strip-shaped conductor layers 5a arranged substantially concentrically with adjacent arc-shaped strip-shaped conductor layers 5a as shown in FIG. And conductor layer 5b.
[0022]
The two conductor layers 4a forming the internal electrode 4 for electrostatic attraction are electrically connected to the power supply terminals 6 respectively, and the strip-like conductor layer 5b forming the internal electrode 5 for heating is connected to the two conductor layers 4a. Are respectively electrically connected to the power supply terminal 7.
[0023]
Further, a metallic base substrate 8 is attached to the lower surface of the electrostatic chuck 1 and can be used as a heat sink or a plasma electrode.
[0024]
The plate-like ceramic body 2 shown in FIGS. 1A and 1B is made of an insulating aluminum nitride sintered body. The upper insulating layer 2a of the plate-like ceramic body 2 is an important part that affects the electrostatic attraction force, and the normal thickness is 50 to 1500 μm, preferably 100 to 1000 μm. If the thickness is less than 50 μm, the film thickness is too thin, so that a sufficient withstand voltage cannot be obtained, and there is a possibility of causing dielectric breakdown when the silicon wafer W is placed and adsorbed. On the other hand, if the thickness exceeds 1500 μm, the distance between the silicon wafer W and the internal electrode 4 becomes large, and the attractive force becomes small.
[0025]
The electrostatic chuck 1 according to the present invention is the electrostatic chuck in which one main surface of the plate-shaped ceramic body is a mounting surface on which a wafer is placed, and the plate-shaped ceramic body includes an internal electrode. The ceramic body contains a rare earth element and / or a compound comprising an alkaline earth metal element in an amount of 1 to 20% by weight in terms of oxide, and an oxygen amount obtained by subtracting the amount of oxygen bonded to the compound is 0.5 to It consists of an aluminum nitride sintered body of 1.5% by weight, a relative density of 97% or more, a Vickers hardness (Hv) on the mounting surface of the plate-like ceramic body of 800 to 1100, and further aluminum nitride A value obtained by dividing the maximum particle size of crystals other than the crystals by the maximum particle size of aluminum nitride crystals is 1.0 to 5.0.
[0026]
In the present invention, the content of the compound of rare earth element and / or alkaline earth metal element of the plate-like ceramic body 2 in terms of oxide is set in the range of 1 to 20% by weight.
[0027]
The reason is that if the compound composed of rare earth element and / or alkaline earth metal element is less than 1% by weight in terms of oxide, the composite compound phase composed of rare earth element and / or alkaline earth metal element and aluminum is produced. Therefore, the volume resistivity value of the aluminum nitride sintered body is 1 × 10⁸From Ω · cm to 1 × 10¹²Since it becomes difficult to control within the range of about Ω · cm, and sintering does not proceed easily, impurity oxygen remains in the aluminum nitride crystal particles in the sintered body, and a sintered body having high thermal conductivity is obtained. This is because it becomes difficult to obtain.
[0028]
On the other hand, if the compound comprising rare earth elements and / or alkaline earth metal elements exceeds 20% by weight in terms of oxide, the amount of composite compound phase comprising rare earth elements and / or alkaline earth metal elements and aluminum increases, This is because the strength and thermal conductivity of the aluminum nitride sintered body are reduced. Further, since the Vickers hardness of the aluminum nitride sintered body is small, particles are likely to be generated. When these particles adhere to the mounting surface 3, the wafer W can be fixed with high precision when adsorbed and fixed. Because it disappears.
[0029]
The compound comprising a rare earth element or an alkaline earth metal element is preferably added as an oxide, carbonate or nitride of a rare earth element or an alkaline earth metal element together with the aluminum nitride powder. Examples of the oxides, carbonates and nitrides are CeO₂, Y₂O_Three, Er₂O_ThreeAnd CaCO_Three, CeN, and CeON.
[0030]
In addition, a complex compound phase composed of rare earth elements or alkaline earth metal elements and aluminum exists as crystals other than aluminum nitride crystals by reaction of nitrides, oxides, oxynitrides and aluminum nitride of rare earth metals by firing. .
[0031]
In particular, when cerium is used as the rare earth element, CeAlO_ThreeA phase is formed and CeAlO_ThreeSince the phase exhibits electrical conductivity, electrical conductivity can be achieved by allowing this phase to continuously exist between the particles of aluminum nitride, which is an insulating material, that is, as a crystal other than the aluminum nitride crystal. The volume resistivity value of the body can be reduced.
[0032]
In the present invention, the amount of oxygen obtained by subtracting the amount of oxygen bound to the compound comprising the rare earth element and / or alkaline earth metal element in the plate-like ceramic body 2 is 0.5 to 1.5% by weight. Range.
[0033]
The reason is that when the oxygen amount is less than 0.5% by weight, the relative density is less than 97%, and thus particles are likely to be generated. When these particles adhere to the mounting surface 3, the wafer is attracted and fixed with high accuracy. It is because it cannot be fixed to. On the other hand, if the amount of oxygen exceeds 1.5% by weight, oxygen is segregated at the grain boundary and the thermal conductivity at the grain boundary is lowered, resulting in thermal resistance. Therefore, the thermal conductivity of the entire aluminum nitride sintered body is reduced. It is because it becomes small and soaking property also falls.
[0034]
Further, the relative density of the plate-like ceramic body 2 of the present invention is set to 97% or more. The reason is that when the relative density is less than 97%, particles are likely to be generated, and when the particles adhere to the mounting surface 3, the wafer cannot be fixed with high precision when the wafer is sucked and fixed. This is because a dense sintered body cannot be obtained due to the large number of pores, and the corrosion resistance and wear resistance are lowered.
[0035]
In the present invention, the plate-like ceramic body 2 has a Vickers hardness (Hv) in the range of 800 to 1100. The reason is that if the Vickers hardness is less than 800, the aluminum nitride sintered body itself that forms the mounting surface 3 is not sufficiently sintered, and particles are likely to be generated due to degranulation. If it adheres to the wafer 3, it cannot be fixed with high accuracy when the wafer W is sucked and fixed. On the other hand, if the Vickers hardness exceeds 1100, the mounting surface wears very little when the wafer is attached or detached. This is because the wafer that slides on the mounting surface 3 generates much particles, and if the particles adhere to the mounting surface 3, the wafer W cannot be fixed with high accuracy when the wafer W is fixed by suction.
[0036]
In the present invention, the value R obtained by dividing the maximum grain size of the crystal other than the aluminum nitride crystal by the maximum grain size of the aluminum nitride crystal is in the range of 1.0 to 5.0.
[0037]
The reason is that when the value obtained by dividing the maximum grain size of the crystal other than the aluminum nitride crystal by the maximum grain size of the aluminum nitride crystal exceeds 5.0, the aluminum nitride sintered body forming the mounting surface 3 is separated. If particles are likely to be generated and adhere to the placement surface 3, the wafer W cannot be fixed with high accuracy when the wafer W is fixed by suction.
[0038]
Further, when the value obtained by dividing the maximum grain size of the crystal other than the aluminum nitride crystal by the maximum grain size of the aluminum nitride crystal is less than 1.0, the wear of the wafer W is increased, and the wear of the mounting surface is reduced when the wafer W is detached. Although the amount of wear of the wafer W that slides on the mounting surface is large but generates particles, the particles can adhere to the mounting surface 3 and can be fixed with high precision when the wafer is sucked and fixed. Disappear.
[0039]
This is because in the generation of particles, a value obtained by dividing the maximum particle size of crystals other than the aluminum nitride crystal by the maximum particle size of the aluminum nitride crystal is greatly involved in the generation of particles. The crystal of aluminum nitride is originally hard particles, and it is easy to generate particles by wearing the wafer W. Since crystals other than the aluminum nitride crystal have a smaller hardness than the aluminum nitride crystal, they function as a buffer and reduce the wear of the wafer W. However, if the crystal other than the aluminum nitride crystal is too large, the crystal itself other than the aluminum nitride crystal tends to be shed.
[0040]
As a method of measuring the maximum grain size of crystals other than aluminum nitride crystals and the maximum grain size of aluminum nitride crystals, the cross section of the aluminum nitride sintered body is finished to a surface with a surface roughness of Rmax 0.1 μm or less, and the center portion The maximum grain size of crystals other than aluminum nitride crystals within a range of 0.01 square meter per area when the structure was observed at a magnification of 1000 times with BEM (Back-scattering Electron Microscope) at three locations on the outer periphery. The diameter and the maximum particle diameter of the aluminum nitride crystal are measured respectively. Then, the average value of the maximum grain sizes of the crystals other than the aluminum nitride crystal respectively obtained from the central portion and the outer peripheral portion, and the average value of the maximum grain size of the aluminum nitride crystals were calculated. A value obtained by dividing the average value of the maximum grain size of the crystals other than the aluminum nitride crystal by the average value of the maximum grain size of the aluminum nitride crystal was defined as R.
[0041]
The value R obtained by dividing the maximum grain size of the crystal other than the aluminum nitride crystal by the maximum grain size of the aluminum nitride crystal can be controlled by the holding time during firing at 1850 ° C. When the holding time is less than 0.5 hours, the diffusion of crystals other than the aluminum nitride crystal is not sufficient, and the aluminum nitride crystal is not grown, so R is 5 or more. In 0.5 to 3 hours, the value of R changes between 1 and 5, and after 3 hours, R is less than 1.
[0042]
In addition, although the aluminum nitride described in Patent Document 4 does not mention the maximum crystal grain size, the cumulative value of grain boundary phase crystal particles is 75% and the cumulative value of aluminum nitride crystal particles is 50%. The ratio is 0.5 to 1.5, so that the configuration is different from the present invention, and the value obtained by dividing the maximum grain size of the crystal other than the aluminum nitride crystal by the maximum grain size of the aluminum nitride crystal is 1.0. It can be inferred that it is smaller than this.
[0043]
According to the electrostatic chuck 1 of the present invention, even when the wafer W made of silicon, gallium arsenide, or the like is rubbed with the mounting surface 3 when the wafer W is attached or detached, the hardness of the mounting surface 3 is set to the hardness of the wafer W. Since it can be approximated, it is possible to reduce the wear of the wafer W while suppressing the wear of the mounting surface 3. As a result, the generation of particles is greatly reduced, and the adhesion of the particles to the mounting surface 3 is prevented. Can be suppressed.
[0044]
Further, by applying a DC voltage between the two conductor layers 4 a constituting the internal electrode 4 for electrostatic attraction from each power supply terminal 6, electrostatic force due to Johnson-Rahbek force is generated between the wafer W and the internal electrode 4. An adsorption force can be expressed, and the wafer W can be firmly adsorbed and fixed to the mounting surface 3.
[0045]
Thus, if the electrostatic chuck 1 of the present invention is used, the wafer W can be fixed on the mounting surface 3 with high accuracy, so that a film having a uniform thickness is deposited on the wafer W in the film forming process. In the etching process, it is possible to perform fine processing with a predetermined dimensional accuracy.
[0046]
In the present invention, it is preferable that the plate-like ceramic body 2 includes the heating internal electrode 5 and the plate-like ceramic body 2 has a thermal conductivity of 40 W / (m · K) or more at room temperature.
[0047]
By providing the internal electrode 5 for heating in the plate-like ceramic body 2, the wafer W can be heated. If the thermal conductivity of the plate-like ceramic body 2 at room temperature is less than 40 W / (m · K), the average in the wafer W plane of 10 ° C. range at 200 ° C. required for processing a 12 inch or 18 inch wafer. This is because thermal properties cannot be obtained. When the plate-like ceramic body 2 is formed of an aluminum nitride sintered body having a large thermal conductivity among ceramics, the thermal uniformity in the wafer W plane necessary for processing a 12-inch or 18-inch wafer is obtained. It is done.
[0048]
In addition, the throughput in the film forming process and the etching process can be improved, and the temperature distribution on the mounting surface 3 can be made uniform. Therefore, in the film forming process, a uniform film is deposited on the wafer. In the etching process, fine processing can be performed to a predetermined depth.
[0049]
Moreover, since the aluminum nitride sintered body is excellent in corrosion resistance against process gases such as fluorine-based gas and chlorine-based gas used for film forming gas and etching gas, generation of particles due to corrosion wear can be reduced. it can.
[0050]
Next, a specific manufacturing method of the present invention will be described.
[0051]
In order to manufacture the electrostatic chuck 1, oxygen is contained in the AlN powder as the main component, and a sintering aid such as rare earth oxide, alkaline earth metal oxide, and carbonate is added as necessary. In particular, Ce nitride, oxide and oxynitride are added, a binder and a solvent are added and mixed to produce mud, and a plurality of aluminum nitride green sheets 9 are formed by a tape forming method such as a doctor blade method. . As a method for containing oxygen, the oxygen content of the starting material AlN powder is set to 0.5 to 1.5% by weight, or the oxygen content of the AlN powder is less than 0.5 to 1.5% by weight. If the Al content is 0.5-1.5 wt%₂O_ThreeMay be added.
[0052]
Then, a conductive paste forming the internal electrode 4 for electrostatic adsorption is laid on one aluminum nitride green sheet 9 in the pattern shape shown in FIG. 2 and the internal electrode 5 for heating is formed on another aluminum nitride green sheet 9. The conductor paste is laid in the pattern shape shown in FIG.
[0053]
At this time, a conductive paste mainly composed of a metal carbide such as WC or TiC is used as the conductive paste 11 forming at least the internal electrode 4 for electrostatic adsorption. The conductive paste 12 forming the heating internal electrode 5 is made of a conductive paste mainly composed of a metal carbide such as WC or TiC, or a metal such as W or Mo, like the internal electrode 4 for electrostatic adsorption. A conductive paste mainly used may be used.
[0054]
Next, as shown in FIG. 4, each aluminum nitride green sheet 9 is stacked in a predetermined order via an adhesive solution 10 composed of a solvent and a binder, and an aluminum nitride green sheet laminate is manufactured by thermocompression bonding while applying pressure. To do. At this time, you may cut as needed.
[0055]
Thereafter, the aluminum nitride green sheet laminate is degreased and then fired in a nitrogen atmosphere or an inert gas atmosphere. Here, the firing temperature is 1800 ° C. or higher, preferably 1850 ° C. or higher.
[0056]
By firing under the above-described conditions, the plate-like ceramic body 2 in which the electrostatic adsorption internal electrode 4 and the heating internal electrode 5 are respectively embedded can be manufactured.
[0057]
Next, in the obtained plate-like ceramic body 2, the surface on the side where the internal electrode 4 is embedded is ground so that the distance from the internal electrode 4 to the mounting surface 3 is 50 to 1500 μm. The surface 3 is polished to an arithmetic average roughness (Ra) of 0.5 μm or less to form the mounting surface 3 on which the wafer W is placed, and the surface on the side where the internal electrode 5 for heating is embedded is formed on the surface. It can be obtained by drilling holes communicating with the internal electrode 4 for electroadsorption and the internal electrode 5 for heating, and inserting and feeding the power supply terminals 6 and 7 into the holes.
[0058]
As described above, in the embodiment of the present invention, the plate-like ceramic body 2 constituting the electrostatic chuck 1 is integrally formed by sintering, and the internal electrode 4 for electrostatic adsorption is embedded in each plate-like ceramic body 2. However, the plate-like ceramic body 2 may be composed of two members. For example, as shown in FIG. The insulating layer 2a between the internal electrode 4 for adsorption and the other ceramic portion 2b may be divided and bonded together by bonding or brazing. In this case, the insulating layer 2a Simultaneously at a temperature of 1800 ° C. or higher with a conductor paste mainly composed of a metal carbide such as WC or TiC serving as the internal electrode 4 for electrostatic adsorption being printed on the aluminum nitride green sheet 9 serving as the insulating layer 2a. By firing, the insulating layer Internal electrode for electrostatic adsorption onto a may be formed by an aluminum nitride sintered body which is formed integrally.
[0059]
Moreover, it goes without saying that the present invention is not limited to only those shown in the above embodiment, and may be improved or changed without departing from the gist of the present invention.
[0060]
【Example】
Example 1
Examples for specifically explaining the method of the present invention are shown below, but the present invention is not limited to these examples. In addition, the measurement of the various physical-property values in the following examples and comparative examples was performed by the following method.
[0061]
1) Oxygen content of aluminum nitride sintered body
A 3 × 4 × 40 mm test piece was cut out from the plate-like ceramic body 2 made of an aluminum nitride sintered body, pulverized to 200 Mesh under with a silicon nitride mortar, and the amount of oxygen was measured with an oxygen analyzer manufactured by LECO.
[0062]
2) Relative density
A test piece of 3 × 4 × 40 mm was cut out from the plate-like ceramic body 2 made of an aluminum nitride-based sintered body, and the relative density, which is the ratio of the bulk specific gravity obtained by the Archimedes method to the theoretical density, was calculated.
[0063]
3) Thermal conductivity
A test piece of φ10 × 2t was cut out from the plate-like ceramic body 2 made of an aluminum nitride sintered body and measured by a laser flash method.
[0064]
4) Vickers hardness (Hv)
The Vickers hardness of the mounting surface 3 was measured using a Vickers hardness tester manufactured by AKASHI MANUFACTURING Co., Ltd., measuring the length of the indentation after applying 1 kg load for 15 seconds, and calculating the hardness from the Vickers hardness measurement formula defined in JIS.
[0065]
5) Number of particles adhering to the wafer W
After applying a DC voltage of 500 V to the internal electrode 4 for electrostatic adsorption of the electrostatic chuck 1 to adsorb the 12-inch silicon wafer W, the number of particles adhering to the wafer W of 0.3 μm or more is manufactured by TENKOR. And a wafer particle counter (model name: SP1). This particle counter detects an object such as a foreign substance on the surface of the wafer W using an argon ion laser and performs image processing, and is an apparatus widely used in a semiconductor manufacturing process.
[0066]
A specific example of the electrostatic chuck 1 of the present invention shown in FIG. 1 will be shown below.
[0067]
An AlN powder with a purity of 99% and an average particle size of 1.2 μm was added with CeO as a sintering aid.₂Was added at 15% by weight. Further, an organic binder and a solvent were added to prepare mud, and a plurality of aluminum nitride green sheets 9 having a thickness of about 0.5 mm were manufactured by a doctor blade method. Of these, one aluminum nitride green sheet 9 was screen-printed with a conductive paste in the shape of the internal electrode 4 for electrostatic adsorption so as to have a pattern shape as shown in FIG. Further, on the other aluminum nitride green sheet 9, a conductor paste to be the heating internal electrode 5 was laid by a screen printing method so as to have a pattern shape as shown in FIG.
[0068]
As the conductor paste 11 serving as the internal electrode 4 for electrostatic adsorption, a conductor paste whose viscosity was adjusted by mixing WC powder and AlN powder was used. Moreover, the conductor paste 12 used as the internal electrode 5 for heating used the conductor paste which mixed the tungsten powder and the AlN powder and adjusted the viscosity.
[0069]
Then, the aluminum nitride green sheets 9 were stacked in a predetermined order, and thermocompression bonded at 50 ° C. with a pressure of 4.9 kPa to form an aluminum nitride green sheet laminate, which was cut into a disk shape. .
[0070]
Next, the aluminum nitride green sheet laminate is vacuum degreased and then fired at a temperature of 1850 ° C. in a nitrogen atmosphere, whereby the electrostatic adsorption internal electrode 4 and the heating internal electrode 5 are embedded respectively. A plate-like ceramic body 2 made of a sintered material was produced.
[0071]
Thereafter, the obtained plate-shaped ceramic body 2 is ground and ground so that the distance from the mounting surface 3 to the internal electrode 4 is 1200 μm with an outer diameter of 200 mm and a plate thickness of 9 mm. The mounting surface 3 is lapped, and the surface roughness is finished to 0.2 μm in arithmetic average roughness (Ra) to form the mounting surface 3. On the surface opposite to the mounting surface 3, The electrostatic chuck 1 was obtained by drilling holes communicating with the internal electrode 4 for adsorption and the internal electrode 5 for heating, and inserting and brazing the power supply terminals 6 and 7 into the holes.
[0072]
Sample No. 1 was produced by the method described above. Samples Nos. 2 to 7 are sample Nos. Except that the addition amount of the sintering aid was changed. It was produced by the same method as 1.
[0073]
Sample No. 8-11 are AlN powders having an oxygen content of 0.4% by weight to Al₂O_ThreeOf 0.18% by weight, 1.11% by weight, 2.05% by weight and 2.25% by weight of oxygen, respectively, and the amount of oxygen bound to the compound comprising a rare earth element and / or an alkaline earth metal element The oxygen amount after subtracting was adjusted to 0.5 wt%, 1.0 wt%, 1.5 wt%, and 1.6 wt%.
[0074]
Sample No. 14, Sample No. 15 changes the value R obtained by dividing the maximum grain size of crystals other than the aluminum nitride crystal by the maximum grain size of the aluminum nitride crystal, so that the holding time during sintering is 0.5 to 3 hours so far, Samples with different values R as time were produced. For other manufacturing steps, Sample No. 1 was used.
[0075]
Sample No. 17-20 produced the sample which changed the kind of sintering auxiliary agent. For other manufacturing steps, Sample No. 1 was used.
[0076]
The electrostatic chuck manufactured as described above is applied with a DC voltage of 500 V to the internal electrode 4 for electrostatic adsorption at room temperature of 25 ° C. to adsorb the 12-inch silicon wafer W, and then adheres to the wafer W. The number of particles of 3 μm or more was measured with a particle counter. Thereafter, the internal electrode 5 for heat generation was energized, the average temperature of the wafer W was set to 200 ° C., and the in-plane temperature difference of the wafer W was measured using the temperature measuring wafers W at nine temperature measuring points. Table 1 shows the results of measurement for various physical property values.
[0077]
[Table 1]

[0078]
Sample No. In No. 6, since the content of the compound was 0.9% by weight, the thermal conductivity was as small as 37 W / (m · K), the in-plane temperature difference of the wafer W was as large as 11 ° C., and the thermal uniformity was inferior.
[0079]
Sample No. In No. 7, since the content of the compound was as high as 21% by weight, the thermal conductivity was as low as 34 W / (m · K), and the thermal uniformity of the wafer W was inferior. Moreover, since the hardness of the aluminum nitride sintered body was small, the number of particles was as large as 5000.
[0080]
Sample No. No. 10 had a small relative density of 96% and a large number of particles of 20000 because the oxygen amount after subtracting the amount of oxygen bound to the compound was as small as 0.4% by weight.
[0081]
Sample No. No. 11 has a large amount of oxygen obtained by subtracting the amount of oxygen bonded to the compound as 1.6% by weight, so that the thermal conductivity is reduced to 35 W / (m · K), and the in-plane temperature difference of the wafer W is reduced. It was as large as 12 ° C.
[0082]
Sample No. No. 13 had a small relative density of 96%, so the number of particles was as large as 20000.
[0083]
Sample No. No. 14, the value R obtained by dividing the maximum grain size of the crystal other than the aluminum nitride crystal by the maximum grain size of the aluminum nitride crystal was 0.9, so the number of particles was as large as 6000.
[0084]
Sample No. In No. 15, the value obtained by dividing the maximum grain size of the crystal other than the aluminum nitride crystal by the maximum grain size of the aluminum nitride crystal was 2.1, so the number of particles was as large as 6000.
[0085]
As a result, the plate-shaped ceramic body contains 1 to 20% by weight of a compound comprising a rare earth element and / or an alkaline earth metal element in terms of oxide, and an oxygen amount obtained by subtracting the amount of oxygen bonded to the compound. Is 0.5 to 1.5% by weight of an aluminum nitride sintered body, the relative density is 97% or more, and the Vickers hardness (Hv) on the mounting surface of the plate-like ceramic body is 800 to 1100. Further, when the value obtained by dividing the maximum particle size of the crystal other than the aluminum nitride crystal by the maximum particle size of the aluminum nitride crystal is 1.0 to 5.0, the generation of particles can be significantly reduced. It has been found that it exhibits excellent characteristics as an electrostatic chuck.
[0086]
Further, the internal electrode 5 for heat generation is embedded, and the thermal conductivity of the plate-like ceramic body is set to 40 W / (m · K) or more, so that 9 ° C. necessary for processing a 12-inch wafer W is achieved. It can be seen that the following in-plane thermal uniformity can be obtained.
(Example 2)
Next, a sample of an aluminum nitride-based sintered body was produced by changing the amount of the sintering aid added by the same manufacturing method as Sample No. 1, and 500 V was applied to the internal electrode 4 for electrostatic adsorption at room temperature of 25 ° C. A 12-inch silicon wafer W is adsorbed by applying a DC voltage, and a load required to peel off the silicon wafer W with a load cell is measured as an adsorbing force. The volume resistivity value of the insulating layer was measured. The results are shown in Table 2.
[0087]
[Table 2]

[0088]
Sample No. 24 has a volume resistivity of 2 × 10 4 because the content of the compound is as low as 0.8% by weight.¹²It was as large as Ω · cm, and the adsorptive power was as small as 0.98 kPa.
[0089]
Sample No. 25 has a volume resistivity of 9 × 10 5 because the content of the compound is as high as 25% by weight.⁷The leakage current between the wafer W and the mounting surface was large, and the adsorption force was as small as 0.98 kPa.
[0090]
On the other hand, it was found that Sample Nos. 21 to 23 contained 1 to 20% by weight of the above compound, and the electrostatic attractive force was as large as 19.6 kPa to 34.3 kPa.
[0091]
【The invention's effect】
  As described above, according to the present invention, in the electrostatic chuck in which one main surface of the plate-shaped ceramic body is a mounting surface on which a wafer is placed and the internal electrode is provided in the plate-shaped ceramic body, The plate-shaped ceramic body contains 1 to 20% by weight of a compound composed of rare earth elements and / or alkaline earth metal elements in terms of oxides,UpIt is composed of an aluminum nitride sintered body in which the amount of oxygen subtracting the amount of oxygen bound to the compound is 0.5 to 1.5% by weight, the relative density is 97% or more, The Vickers hardness (Hv) on the mounting surface is 800 to 1100, and the value obtained by dividing the maximum particle size of crystals other than the aluminum nitride crystal by the maximum particle size of the aluminum nitride crystal is 1.0 to 5.0.And the volume resistivity value at 25 ° C. of the plate-like ceramic body is 1 × 10 ⁸ Ω · cm to 1 × 10 ¹² Ω · cmAs a result, the wafer can be firmly adsorbed and fixed on the mounting surface with a large electrostatic attraction force using the Johnson-Rahbek effect, and even if the wafer made of silicon, gallium arsenide, etc. is repeatedly desorbed, Since the hardness of the mounting surface approximates the hardness of the wafer, the wear of the mounting surface and the wafer can be suppressed, and the generation of particles can be greatly reduced. Furthermore, it is possible to obtain in-plane thermal uniformity necessary for processing 12-inch and 18-inch wafers.
[Brief description of the drawings]
FIG. 1A is a perspective view showing a state in which an electrostatic chuck according to the present invention is fixed to a base substrate, and FIG. 1B is a sectional view taken along line XX of FIG.
2 is a plan view showing a pattern shape of internal electrodes for electrostatic attraction provided in the electrostatic chuck of FIG. 1. FIG.
FIG. 3 is a plan view showing a pattern shape of a heating internal electrode provided in the electrostatic chuck of FIG. 1;
FIG. 4 is a view for explaining a method of manufacturing an electrostatic chuck according to the present invention.
FIG. 5 is a cross-sectional view showing another embodiment of the electrostatic chuck according to the present invention.
[Explanation of symbols]
1: Electrostatic chuck
2: Plate-like ceramic body
2a: Insulating layer
2b: A ceramic part
3: Placement surface
4: Internal electrode
4a: Conductor layer
5: Internal electrode
5a: Strip conductor layer
5b: Strip conductor layer
6: Feeding terminal
7: Feeding terminal
8: Base substrate
9: Aluminum nitride green sheet
10: Adhering liquid
11: Conductor paste
12: Conductor paste
W: Wafer

Claims (3)

In the electrostatic chuck in which one main surface of the plate-shaped ceramic body is used as a mounting surface on which a wafer is placed and an internal electrode is provided in the plate-shaped ceramic body, the plate-shaped ceramic body includes a rare earth element and / or an alkali. the compound consisting of earth metal element contained 1 to 20% by weight in terms of oxide, oxygen obtained by subtracting the amount of oxygen bonded with the upper title compound is aluminum nitride is 0.5 to 1.5 wt% It consists of a sintered body, the relative density is 97% or more, the Vickers hardness (Hv) on the mounting surface is 800 to 1100, and the maximum grain size of crystals other than the aluminum nitride crystal is the maximum grain size of the aluminum nitride crystal with a value obtained by dividing the 1.0 to 5.0 in diameter, volume resistivity at 25 ° C. of the plate-shaped ceramic body is ^{1 × 10 8 Ω · cm~1 ×} 10 12 Ω · cm An electrostatic chuck characterized and. An internal electrode for heating is provided in the plate-like ceramic body, the plate-like ceramic body has a thermal conductivity of 40 W / (m · K) or more at normal temperature , and the plate-like ceramic body is fired at 1800 ° C. or more. the electrostatic chuck according to claim 1, characterized in that the. The electrostatic chuck according to claim 1 or 2 sintering aids of the plate-shaped ceramic body is a compound containing Ce element, characterized in that it contains 1 to 20% by weight in terms of CeO _2.

Images