JP4934907B2

JP4934907B2 - Electrostatic chuck

Info

Publication number: JP4934907B2
Application number: JP2001138276A
Authority: JP
Inventors: 清川畑; 渉生方; 勇治小笠原; 潔川合
Original assignee: Hitachi Chemical Co Ltd; Showa Denko Materials Co Ltd; Resonac Corp
Current assignee: Resonac Corp
Priority date: 2001-05-09
Filing date: 2001-05-09
Publication date: 2012-05-23
Anticipated expiration: 2021-05-09
Also published as: JP2002334920A

Description

【０００１】
【発明の属する技術分野】
本発明は、半導体デバイス製造装置、液晶デバイス製造装置等の半導体・液晶分野に用いられる静電チャックに関する。
【０００２】
【従来の技術】
半導体デバイスや液晶デバイスを製造する際、特に真空雰囲気においてはシリコンウェーハ、ガラス基板等を保持するために、従来のメカクランプ方式から、面吸着が可能な静電チャックが検討されている。
静電チャックを構成する誘電体材料は、厚さと電極面積で決まる固有の抵抗値を有しており、吸着時に数百Ｖ以上の電圧を印加すると誘電体の固有抵抗に応じた漏れ電流が流れる。
【０００３】
漏れ電流は数1ｍＡ以下であっても微細回路が形成されたウェーハなどの被吸着物内を流れる為、形成された微細素子や回路を破壊させることがある。また表面電流は数μＡであっても、例えば電子線を用いた装置のように微少な電磁界の影響を受ける装置では無視できない。このため漏れ電流の低減が望まれている。
【０００４】
漏れ電流を低減するため、静電チャックの吸着面を凹凸形状に加工し、被吸着物との接触面積を減らし漏れ電流を小さくすることが行われている。このような構造の静電チャックは、被吸着物を吸着する際に誘電体と被吸着物の接触による、被吸着物へのパーティクルの転写も減じる効果も得られる。
【０００５】
しかしながら、上記に示す構造の静電チャックは、接触面積の減少に伴う吸着力の低下に比較して、漏れ電流の減少が少ない。また吸着時の真空度によっては被吸着物と静電チャック表面凹部の間で放電が生じ、漏れ電流が増大する場合があるなどの問題があった。
【０００６】
【発明が解決しようとする課題】
本発明は、静電チャックの誘電体を通して流れる漏れ電流を、安定して低減し、かつ被吸着物と静電チャック表面の凹部での放電に対する耐性を著しく向上させる静電チャックを提供するものである。
【０００７】
【課題を解決するための手段】
本発明は、誘電体を有し、かつ誘電体の被吸着物との接触面側を凹凸形状に加工し、前記接触面側の凹凸形状の凸部で前記被吸着物を吸着させる静電チャックにおいて、前記凸部が前記被吸着物に接触する接触面側の凹部の全面又は一部を、誘電体より高い体積固有抵抗を有する絶縁体で被覆してなる静電チャックに関する。
【０００８】
【発明の実施の形態】
本発明の静電チャックに用いられる誘電体の材料としては、Ａｌ_２Ｏ_３、Ｓｉ_３Ｎ_４、ＡｌＮ、ＳｉＣ、ＢａＴｉＯ_３等のセラミックス材料が用いられる。
誘電体に形成する電圧印加電極としては、例えばＡｇ−Ｐｄ、Ｗ、Ａｇ、Ａｕ等の金属を含むガラスペーストを焼き付けたり、Ａｌ、Ｃｕ、ＳＵＳ等の金属板又は金属箔を密着させて形成することができる。
【０００９】
凹凸形状に加工した被吸着物との接触面側の凹部の全面又は一部を被覆する絶縁体は、誘電体よりも高い体積固有抵抗を有する絶縁体であれば、その材質及び形成法は特に制限はない。例えば被吸着物との接触面側を凹凸形状に加工後、絶縁抵抗の高い高純度Ａｌ_２Ｏ_３（純度９０％以上）、ＳｉＯ_２等を溶射、気相反応等の方法によって全面に形成した後、凸部の表面を研磨して誘電体を再度露出させてもよく、被吸着物との接触面側を凹凸形状に加工後、凹部にエポキシ樹脂、ポリイミド樹脂等を塗布して硬化さてもよい。
【００１０】
誘電体の被吸着物との接触面側に形成した凹部の全面又は一部を被覆する絶縁体は、静電チャックの誘電体より体積固有抵抗が大きいことが必要とされ、誘電体より１０倍以上大きいことが好ましく、５０倍以上であればより好ましく、上限については特に制限はない。
絶縁体の厚さについては特に制限はないが、５〜２０μｍの範囲であることが好ましく、５〜１０μｍの範囲であることがさらに好ましい。
【００１１】
以下、本発明の実施の形態を図面を引用して説明する。
図１は本発明の実施例になる静電チャックの要部を示す断面図、図２はその電気的等価回路を示す図、図３は従来の静電チャックの要部を示す断面図、図４はその電気的等価回路を示す図及び図５は漏れ電流を測定するための測定回路を示す図であり、１は誘電体、２は絶縁体、３は電圧印加電極、４は被吸着物、５は真空容器及び６は静電チャックである。
【００１２】
図1に示す本発明になる静電チャックは、図2に示す従来の静電チャックで生じる誘電体１の凹部の表面抵抗Ｒｓに起因する漏れ表面電流を絶縁体２の大きな抵抗Ｒｚ（Ｒｚ＞Ｒｓ）を介在させることにより低減できる。また絶縁体２の抵抗値Ｒｚを誘電体の表面抵抗Ｒｓよりも甚だ大きくすれば（Ｒｚ》Ｒｓ）誘電体の表面抵抗Ｒｓに起因する表面電流を遮断することもできる。さらに真空度によっては従来の静電チャックでは凹部の空間において気体分子密度と電界により決まる条件で放電が生じるが、本発明になる静電チャックでは絶縁体２の大きな抵抗値により放電も防止することができる。
【００１３】
【実施例】
以下、実施例により本発明を説明するが、本発明はこれに制限されるものではない。
実施例１
図1に示すように、誘電体１として体積固有抵抗が１×１０^９Ωｍで直径が３０ｍｍ及び厚さが２ｍｍのＳｉＣ(日立化成工業（株）製、商標名ヘキサロイ)を準備した。次いでこの誘電体１の片側の面（被吸着物との接触面の反対側の面）に、直径が２８ｍｍの大きさに速乾性導電ペースト(（株）徳力化学研究所製、商標名シルベスト)を塗布し、自然乾燥して厚さが２０μｍの電圧印加電極３を形成した。
なお、図示しないが、誘電体１の電圧印加電極３を形成した側には体積固有抵抗が１×１０^１４Ωｍの絶縁材料 (Ａｌ_２Ｏ_３使用…日立化成工業（株）製、商標名ハロックス)を接着剤で固着した。
【００１４】
次に、誘電体１の被吸着物との接触面側に凹部の深さが３０μｍ及び凸部の直径が１ｍｍの寸法に、４ｍｍのピッチ幅で格子状に凹凸部を形成した。
この後、凹凸部全面に絶縁ワニス(サンハヤト（株）製、商品名ＶＡ−３０)を塗布し、硬化後凸部の表面に付着した絶縁ワニスの硬化物を削り落として、凸部表面に誘電体１を露出させ、凹部の全面に７．５±２．５μｍの厚さに被覆した絶縁体２を有する静電チャックを得た。
【００１５】
比較例１
実施例１で誘電体の被吸着物との接触面側に形成した凹凸部に絶縁ワニスを塗布しない以外は、実施例１と同様の工程を経て静電チャックを得た。
【００１６】
次に、上記の実施例１及び比較例１で得た静電チャックにおいて、各々吸着時に流れる全漏れ電流を測定した。そのときの測定回路を図５に示す。
なお、測定は、被吸着物として直径が１００ｍｍで厚さが０．５ｍｍのシリコンウェーハの裏面を吸着し、各々吸着時に流れる全漏れ電流を測定した。また、真空度は０．１Ｐａと１０Ｐａとに変化させて測定した。測定結果を表1に示す。
【００１７】
【表１】

【００１８】
表１に示されるように本発明になる静電チャックは、比較例の静電チャックに比較して漏れ電流が少なく、また、真空度の影響もなく安定していることが明らかである。
なお、実施例では単極型の静電チャックで説明したが、双極型の静電チャックでも同様の効果が得ることができる。
【００１９】
【発明の効果】
本発明における静電チャックは、静電チャックの誘電体を通して流れる漏れ電流を、安定して低減し、かつ被吸着物と静電チャック表面の凹部での放電に対する耐性を著しく向上させることができ、半導体デバイス製造装置、液晶デバイス製造装置、特に電子線を使用した装置に好適である。
【図面の簡単な説明】
【図１】本発明の実施例になる静電チャックの要部を示す断面図である。
【図２】図１の電気的等価回路を示す図である。
【図３】従来の静電チャックの要部を示す断面図である。
【図４】図３の電気的等価回路を示す図である。
【図５】漏れ電流を測定するための測定回路を示す図である。
【符号の説明】
１誘電体
２絶縁体
３電圧印加電極
４被吸着物
５真空容器
６静電チャック[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrostatic chuck used in a semiconductor / liquid crystal field such as a semiconductor device manufacturing apparatus and a liquid crystal device manufacturing apparatus.
[0002]
[Prior art]
When manufacturing semiconductor devices and liquid crystal devices, electrostatic chucks capable of surface adsorption have been studied from the conventional mechanical clamp system in order to hold a silicon wafer, a glass substrate, etc., particularly in a vacuum atmosphere.
The dielectric material constituting the electrostatic chuck has a specific resistance value determined by the thickness and the electrode area. When a voltage of several hundred volts or more is applied during adsorption, a leakage current corresponding to the specific resistance of the dielectric flows. .
[0003]
Even if the leakage current is several milliamperes or less, it flows in an adsorbed object such as a wafer on which a fine circuit is formed, and thus the formed fine element or circuit may be destroyed. Even if the surface current is several μA, it cannot be ignored in a device affected by a minute electromagnetic field, such as a device using an electron beam. For this reason, reduction of leakage current is desired.
[0004]
In order to reduce the leakage current, the surface of the electrostatic chuck is processed into a concavo-convex shape to reduce the contact area with the object to be attracted and reduce the leakage current. The electrostatic chuck having such a structure can also reduce the transfer of particles to the object to be adsorbed due to the contact between the dielectric and the object to be adsorbed when adsorbing the object to be adsorbed.
[0005]
However, the electrostatic chuck having the above-described structure has a small decrease in leakage current as compared with a decrease in attracting force accompanying a decrease in contact area. Further, depending on the degree of vacuum at the time of suction, there is a problem that discharge occurs between the object to be attracted and the concave portion of the electrostatic chuck surface, which may increase the leakage current.
[0006]
[Problems to be solved by the invention]
The present invention provides an electrostatic chuck that stably reduces the leakage current flowing through the dielectric of the electrostatic chuck and significantly improves resistance to discharge at the object to be attracted and the recesses on the surface of the electrostatic chuck. is there.
[0007]
[Means for Solving the Problems]
The present invention relates to an electrostatic chuck having a dielectric, processing the contact surface side of the dielectric with the object to be adsorbed into a concavo-convex shape, and adsorbing the object to be adsorbed by the concavo-convex convex portion on the contact surface side The electrostatic chuck is formed by covering the entire or part of the concave portion on the contact surface side where the convex portion comes into contact with the object to be attracted with an insulator having a volume resistivity higher than that of the dielectric.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
As a dielectric material used for the electrostatic chuck of the present invention, ceramic materials such as Al ₂ O ₃ , Si ₃ N ₄ , AlN, SiC, BaTiO ₃ are used.
As the voltage application electrode formed on the dielectric, for example, a glass paste containing a metal such as Ag-Pd, W, Ag, or Au is baked, or a metal plate or metal foil such as Al, Cu, or SUS is adhered to the electrode. be able to.
[0009]
If the insulator covering the whole or part of the concave portion on the contact surface side with the object to be adsorbed processed into a concavo-convex shape is an insulator having a volume resistivity higher than that of the dielectric, its material and formation method are particularly There is no limit. For example, after processing the contact surface side with the object to be adsorbed into a concavo-convex shape, high purity Al ₂ O ₃ (purity 90% or more), SiO ₂ or the like having high insulation resistance is formed on the entire surface by a method such as thermal spraying or gas phase reaction Later, the surface of the convex portion may be polished to expose the dielectric again, or the contact surface side with the object to be adsorbed may be processed into an uneven shape, and then the epoxy resin, polyimide resin, etc. may be applied to the concave portion and cured. Good.
[0010]
The insulator covering the whole or part of the recess formed on the contact surface side of the dielectric to be adsorbed is required to have a volume specific resistance larger than that of the dielectric of the electrostatic chuck, and 10 times that of the dielectric. The upper limit is preferably larger, more preferably 50 times or larger, and there is no particular upper limit.
Although there is no restriction | limiting in particular about the thickness of an insulator, It is preferable that it is the range of 5-20 micrometers, and it is more preferable that it is the range of 5-10 micrometers.
[0011]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 is a cross-sectional view showing a main part of an electrostatic chuck according to an embodiment of the present invention, FIG. 2 is a view showing an electrical equivalent circuit thereof, and FIG. 3 is a cross-sectional view showing a main part of a conventional electrostatic chuck. 4 is a diagram showing an electrical equivalent circuit thereof, and FIG. 5 is a diagram showing a measurement circuit for measuring leakage current. 1 is a dielectric, 2 is an insulator, 3 is a voltage application electrode, and 4 is an object to be adsorbed. 5 is a vacuum vessel and 6 is an electrostatic chuck.
[0012]
The electrostatic chuck according to the present invention shown in FIG. 1 has a leakage surface current caused by the surface resistance Rs of the concave portion of the dielectric 1 generated in the conventional electrostatic chuck shown in FIG. Rs) can be reduced. If the resistance value Rz of the insulator 2 is made much larger than the surface resistance Rs of the dielectric (Rz >> Rs), the surface current caused by the surface resistance Rs of the dielectric can be cut off. Furthermore, depending on the degree of vacuum, in the conventional electrostatic chuck, discharge occurs in the space of the concave portion under conditions determined by the gas molecule density and the electric field, but in the electrostatic chuck according to the present invention, discharge is also prevented by the large resistance value of the insulator 2. Can do.
[0013]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not restrict | limited to this.
Example 1
As shown in FIG. 1, SiC (trade name: Hexalloy, manufactured by Hitachi Chemical Co., Ltd.) having a volume resistivity of 1 × 10 ⁹ Ωm, a diameter of 30 mm, and a thickness of 2 mm was prepared as the dielectric 1. Next, a quick-drying conductive paste having a diameter of 28 mm is formed on one surface of the dielectric 1 (the surface opposite to the contact surface with the object to be adsorbed) (trade name: Sylbest). Was applied and dried naturally to form a voltage application electrode 3 having a thickness of 20 μm.
Although not shown, an insulating material having a volume resistivity of 1 × 10 ¹⁴ Ωm is used on the side of the dielectric 1 on which the voltage application electrode 3 is formed (using Al ₂ O _3, manufactured by Hitachi Chemical Co., Ltd., trade name Harox) ) Was fixed with an adhesive.
[0014]
Next, on the contact surface side of the dielectric 1 with the object to be adsorbed, concave and convex portions were formed in a lattice shape with a pitch width of 4 mm and a depth of the concave portion of 30 μm and a diameter of the convex portion of 1 mm.
After this, an insulating varnish (trade name VA-30, manufactured by Sanhayato Co., Ltd.) is applied to the entire surface of the concavo-convex portion, and the cured product of the insulating varnish adhering to the surface of the convex portion after curing is scraped off to form a dielectric on the surface of the convex portion. The body 1 was exposed, and an electrostatic chuck having an insulator 2 covered with a thickness of 7.5 ± 2.5 μm over the entire surface of the recess was obtained.
[0015]
Comparative Example 1
An electrostatic chuck was obtained through the same steps as in Example 1, except that the insulating varnish was not applied to the uneven portion formed on the contact surface side with the dielectric object to be adsorbed in Example 1.
[0016]
Next, in the electrostatic chucks obtained in Example 1 and Comparative Example 1 described above, the total leakage current flowing during the adsorption was measured. The measurement circuit at that time is shown in FIG.
The measurement was performed by adsorbing the back surface of a silicon wafer having a diameter of 100 mm and a thickness of 0.5 mm as an object to be adsorbed, and measuring the total leakage current flowing during the adsorption. Further, the degree of vacuum was measured by changing between 0.1 Pa and 10 Pa. Table 1 shows the measurement results.
[0017]
[Table 1]

[0018]
As shown in Table 1, it is clear that the electrostatic chuck according to the present invention has less leakage current than the electrostatic chuck of the comparative example and is stable without being affected by the degree of vacuum.
In addition, although the embodiment has been described with a single-pole electrostatic chuck, the same effect can be obtained with a bipolar electrostatic chuck.
[0019]
【Effect of the invention】
The electrostatic chuck in the present invention can stably reduce the leakage current flowing through the dielectric of the electrostatic chuck, and can significantly improve the resistance to discharge in the object to be attracted and the concave portion of the electrostatic chuck surface, It is suitable for a semiconductor device manufacturing apparatus, a liquid crystal device manufacturing apparatus, particularly an apparatus using an electron beam.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a main part of an electrostatic chuck according to an embodiment of the present invention.
FIG. 2 is a diagram showing an electrical equivalent circuit of FIG. 1;
FIG. 3 is a cross-sectional view showing a main part of a conventional electrostatic chuck.
4 is a diagram showing an electrical equivalent circuit of FIG. 3;
FIG. 5 is a diagram showing a measurement circuit for measuring leakage current.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Dielectric body 2 Insulator 3 Voltage application electrode 4 Adsorbed object 5 Vacuum container 6 Electrostatic chuck

Claims

Has a dielectric, and a contact surface with the adsorbate dielectric processed into irregularities, the electrostatic chuck for attracting the adsorbate at the convex portion of the concavo-convex shape of the contact surface, the protrusion An electrostatic chuck formed by covering the whole or part of the concave portion on the contact surface side where the portion contacts the object to be adsorbed with an insulator having a volume resistivity higher than that of the dielectric.