JP2005252170A - Electrostatic chuck - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic chuck having a small coefficient of thermal expansion at room temperature and capable of exercising high adsorptive power in use. <P>SOLUTION: The electrostatic chuck comprises a ceramic substrate, an electrode layer, and a dielectric layer which is ceramic including at least one type of 97 to 99.99 vol% major material selected from a group of cordierite, spodumene, and eucryptite, and including 0.01 to 3 vol% carbon. The coefficient of the thermal expansion of the dielectric layer is not more than 1×10<SP>-6</SP>/°C at room temperature. The volume resistivity of the ceramic used for the dielectric layer is preferably 1×10<SP>8</SP>to 10<SP>14</SP>Ωcm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrostatic chuck that fixes an object to be attracted by electrostatic attraction force. More specifically, the present invention relates to an electrostatic chuck used for fixing an object to be adsorbed such as a semiconductor wafer in an electron beam exposure drawing apparatus, an etching apparatus, a CVD apparatus, a PVD apparatus, or an inspection apparatus in a manufacturing process of a semiconductor or the like. . Further, the present invention relates to an electrostatic chuck that is small in dimensional change due to temperature change even in a room temperature environment and can firmly fix an object to be attracted.

  With the advancement of integration in LSIs and the like, circuit miniaturization has progressed, and the line width of semiconductors is about to reach a level of 0.1 μm or less. For this reason, also in the semiconductor manufacturing process, for example, the pattern drawn on the wafer through the mask by the exposure apparatus is miniaturized, and accordingly, the exposure apparatus is required to have high definition and is used in the exposure apparatus. A member such as an electric chuck is also required to be a highly accurate member with a small dimensional change due to a temperature change.

Ceramic electrostatic chucks used in the semiconductor manufacturing process have traditionally used Al ₂ O ₃ , AlN, and other materials, but they can be used with high precision in response to higher integration and miniaturization of semiconductors. There is no proposal of an electrostatic chuck using a low thermal expansion material that can be used as a dielectric layer.

Low expansion ceramics include cordierite. For example, an electrode layer is formed on a ceramic substrate made of Al ₂ O ₃ or cordierite, and then a dielectric layer that is in contact with the adsorbent is formed. An electric chuck has been proposed (see Patent Document 1 and Patent Document 2). In this electrostatic chuck, ceramics containing Al ₂ O ₃ as a main component and TiO ₂ added in an amount of 0.2 to 2% by weight are formed as a dielectric layer. Accordingly, cordierite, which is a low thermal expansion material, is used as a material for the lowermost ceramic substrate and is not used for the dielectric layer.

In addition, there has been proposed an electrostatic chuck in which an electrode layer and a dielectric layer are formed on a ceramic substrate, and an exposed portion on the outer periphery of the electrode layer and the dielectric layer is covered with an insulating sprayed film (Patent Document) 3). Cordierite or the like is used for the sprayed coating covering the exposed portion, but the dielectric layer is made of Al ₂ O ₃ , beryllia, SiC, etc., and cordierite is not used.

On the other hand, an electrostatic chuck has been proposed in which positive and negative electrodes are alternately interspersed vertically and horizontally on a ceramic substrate, and the positive and negative electrodes are connected by conductors in the substrate and connected to external terminals. (See Patent Document 4). The positive electrode and the negative electrode are covered with an insulating film, and the ceramic substrate and the insulating film are formed of Al ₂ O ₃ , cordierite, magnesia, titania, forsterite, or the like.
Japanese Patent Publication No. 6-97675 Japanese Patent Publication No. 6-97677 JP-A-6-279974 Japanese Patent Laid-Open No. 1-294938

  However, even if cordierite, which is a low thermal expansion material, is used for the ceramic substrate, if the low expansion material is not used for the dielectric layer that is in direct contact with the object to be adsorbed, the object will be affected by temperature changes. , The dimensional change becomes large. On the other hand, even if cordierite, which is a low thermal expansion material, is used for the dielectric layer, the volume resistance value is increased in an embodiment in which the cordierite is simply used as an insulating material, so that sufficient adsorption force as an electrostatic chuck cannot be expressed.

  An object of the present invention is to provide an electrostatic chuck that has a low coefficient of thermal expansion at room temperature and exhibits a high attraction force during use.

The electrostatic chuck of the present invention has a ceramic substrate, an electrode layer, and a dielectric layer, and the dielectric layer is
97-99.99 vol% containing at least one main material selected from the group consisting of cordierite, spodumene and eucryptite,
A ceramic containing 0.01 to 3 vol% of carbon,
The dielectric layer has a thermal expansion coefficient at room temperature of 1 × 10 ⁻⁶ / ° C. or less. Here, the thermal expansion coefficient at room temperature refers to the thermal expansion coefficient at 10 ° C to 40 ° C. The volume resistivity of the ceramic used for the dielectric layer is preferably 1 × 10 ⁸ to 10 ¹⁴ Ωcm.

The dielectric layer is
62-99.89 vol% of a main material that is at least one selected from the group consisting of cordierite, spodumene and eucryptite,
Containing 0.01 to 3 vol% carbon, and silicon carbide;
Silicon nitride,
Carbides, nitrides, borides and silicides of Group 4a, 5a and 6a elements;
Ceramics containing 0.1 to 35 vol% of at least one selected from the group consisting of

It is preferable that the ceramic used for the dielectric layer is formed on at least the adsorption surface of the dielectric layer, and the thermal expansion coefficient of the ceramic substrate at room temperature is more preferably 1 × 10 ⁻⁶ / ° C. or less. .

  According to the present invention, even when used at room temperature, since the positional deviation due to temperature change is small, it is possible to provide an electrostatic chuck that is highly accurate and exhibits a high attraction force.

  The electrostatic chuck of the present invention has a structure in which an electrode layer and a dielectric layer are formed on a ceramic substrate, and the ceramic used for the dielectric layer is selected from the group consisting of cordierite, spodumene and eucryptite. In addition, at least one kind is contained as a main material. In particular, for electrostatic chucks used in exposure equipment and inspection equipment used at room temperature, in order to perform highly accurate depiction and measurement, dimensions due to temperature changes at room temperature and partial temperature rise due to electron beam irradiation, etc. There is a need to reduce change. By using cordierite, spodumene and eucryptite, which are low thermal expansion materials, as the main material of the dielectric layer, a highly accurate electrostatic chuck can be obtained even when used at room temperature.

  By using these materials for the dielectric layer that is in direct contact with the object to be adsorbed, the influence of temperature change on the object to be adsorbed can be kept low. Therefore, an embodiment in which such ceramics is formed on at least the adsorption surface of the dielectric layer is preferable.

  The ceramic used for the dielectric layer contains carbon. Cordierite, spodumene and eucryptite are low thermal expansion materials that increase the accuracy of electrostatic chucks. However, these ceramic materials alone have large volume resistance, and the electrostatic chuck's adsorption force depends only on Coulomb force. The adsorption power is small. For this reason, it is desirable to reduce the volume resistivity by blending an appropriate amount of carbon in addition to the main material made of ceramics, and to utilize the adsorption effect by the Johnson Rabeck force.

  The main material and carbon have a composition containing 97 to 99.99 vol% of the main material and 0.01 to 3 vol% of carbon. The amount of carbon is required to be 0.01 vol% or more in order to increase the electrical conductivity of the ceramic. On the other hand, if carbon is added too much, the coefficient of thermal expansion increases and the electrical resistance becomes too low, and a leak current is likely to occur due to the applied voltage, which tends to damage the semiconductor or the like to be adsorbed. Therefore, the amount of carbon is preferably 3 vol% or less.

  The carbon in the present invention includes carbon generated by heating. That is, for example, by adding phenol resin or furan resin dissolved in alcohol or water, the addition effect equivalent to that of carbon can be obtained with a smaller amount, and volume resistance without adversely affecting low expansion characteristics. Rate control can be performed.

  In this specification, vol% is obtained by, for example, obtaining the weight% of each component by a method such as secondary ion mass spectrometry (SIMS), atomic absorption spectrometry or ICP emission spectrometry, and then calculating the weight% of the specific gravity of the component. Calculate by dividing by.

The thermal expansion coefficient at room temperature of the ceramic used for the dielectric layer is preferably 1 × 10 ⁻⁶ / ° C. or less, in terms of obtaining a highly accurate electrostatic chuck in a room temperature atmosphere, −0.5 to 0.5 × 10 ^-6 / ° C is more preferable. Further, due to carbon in the form and particle size to be added, although the volume resistivity of the resulting ceramics different, in enhancing the adsorption force of the electrostatic chuck, the volume resistivity of the ceramics is preferably 10 ¹⁴ [Omega] cm or less, 10 ¹² Ωcm or less is more preferable. In addition, the volume resistivity is preferably 10 ⁸ Ωcm or more in order to suppress the leakage current during voltage application.

  The ceramic used for the dielectric layer contains at least one selected from the group consisting of carbide, nitride, boride and silicide of silicon carbide, silicon nitride, 4a group element, 5a group element and 6a group element. Embodiments are preferred. A material selected from the group consisting of carbides, nitrides, borides, and silicides of silicon carbide, silicon nitride, 4a group element, 5a group element, and 6a group element has high hardness and high rigidity. Abrasion resistance and high rigidity can be imparted.

  Examples of the group 4a elements constituting carbides, nitrides, borides, and silicides include titanium (Ti), zirconium (Zr), hafnium (Hf), and the like. Examples of the group 5a elements include vanadium (V ), Niobium (Nb), tantalum (Ta), and the like, and examples of the 6a group element include chromium (Cr), molybdenum (Mo), tungsten (W), and the like.

  Preferable specific examples include tungsten carbide (tungsten carbide), titanium carbide, tantalum carbide, zirconium nitride, tantalum nitride, titanium boride, zirconium boride, tantalum silicide, and molybdenum silicide. Among these, tungsten carbide is more preferable because it has low thermal expansion in addition to high hardness and high rigidity.

  Silicon carbide and silicon nitride are more preferable in that they have lower thermal expansion than the above-described elements. Since the thermal expansion coefficient of the sintered body is related to the thermal expansion coefficient and the mixing ratio of each material to be mixed, when a low thermal expansion material is used, a larger amount than other materials can be used. Therefore, the wear resistance of the sintered body can be further enhanced.

  Silicon carbide and silicon nitride, carbide of 4a group element, 5a group element and 6a group element, nitride, boride and silicide keep the low thermal expansibility, the content is preferably 35 vol% or less, 20 vol % Or less is more preferable. Carbides, nitrides, borides, and silicides of Group 4a element, Group 5a element, and Group 6a element, and silicon carbide and silicon nitride have a compounding amount of 0 in order to improve the rigidity or wear resistance of the sintered body. .1 vol% or more is preferable.

  That is, it contains 62 to 99.89 vol% of at least one main material selected from the group consisting of cordierite, spodumene and eucryptite, 0.01 to 3 vol% of carbon, and silicon carbide. An embodiment containing 0.1 to 35 vol% of silicon nitride and at least one selected from the group consisting of carbides, nitrides, borides, and silicides of group 4a element, group 5a element, and group 6a element is preferable. .

  The addition amount of these wear resistance improving materials is determined in consideration of the material, particle size, conductivity of the selected material, and the like. Further, in the case of a wear resistance improving material having conductivity, it is necessary to consider the influence on the volume resistivity of the entire dielectric layer. The proper blending ratio of the main material and carbon is the same as described above.

Although the ceramics used for the dielectric layer in direct contact with the object to be adsorbed has been described above, an embodiment in which similar ceramics are used for the ceramic substrate is also preferable. By using low thermal expansion ceramics for the ceramic substrate and matching the low thermal expansion of the derivative layer, even if the ambient temperature changes, the electrostatic chuck is prevented from warping and the planar accuracy is maintained. be able to. Therefore, the thermal expansion coefficient at room temperature of the ceramic substrate is preferably 1 × 10 ⁻⁶ / ° C. or less, more preferably −0.5 to 0.5 × 10 ⁻⁶ / ° C., similarly to the dielectric layer.

Example Cordierite powder (CO), eucryptite powder (EU), and spodumene powder (SP) having a purity of 99% or more and an average particle size of 3 μm are used as main materials, and a powdered phenol resin with an average particle size of 0 Each powder of .5 μm silicon nitride (Si ₃ N ₄ ), tungsten carbide (WC), titanium carbide (TiC) or titanium boride (TiB) was prepared so as to have the ratio shown in Table 1 at the raw material stage. . Next, after blending ethanol as a solvent, it was mixed for 24 hours by a ball mill. The obtained mixture was dried and calcined, and then subjected to hot press firing at 1300 ° C. in an argon gas atmosphere at 400 kgf / cm ² to obtain ceramics. Table 1 shows the physical properties of the obtained ceramics.

  Abrasion resistance was measured by the pin-on-disk method. The measured wear resistance was marked with Δ when the wear resistance was almost the same as that of the main material, ◯ when the wear resistance was superior to the main material, and x when the wear resistance was inferior to the main material.

  The adsorptivity was evaluated by preparing an electrostatic chuck with an electrode built therein, and measuring the presence or absence of adsorption with the object to be adsorbed when a voltage was applied to the electrode, and the leakage current to the object to be adsorbed. Those having adsorption were marked with ◯, those without adsorption, or those with adsorption but large leakage current were marked with ×.

As is apparent from the results in Table 1, the ceramics of the present invention had a thermal expansion coefficient of 1 × 10 ⁻⁶ / ° C. or less with respect to temperature rise, and were excellent in adsorptivity. Therefore, the electrostatic chuck using such a low thermal expansion ceramic as a dielectric layer can sufficiently suppress the thermal expansion even when the temperature rises at room temperature during semiconductor manufacturing, and can sufficiently cope with the miniaturization of the circuit. Can be fixed firmly and was useful.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  ADVANTAGE OF THE INVENTION According to this invention, when manufacturing a semiconductor etc., a highly accurate process is possible also in room temperature atmosphere, and the electrostatic chuck which fixes a to-be-adsorbed object firmly can be provided.

Claims (5)

In an electrostatic chuck having a ceramic substrate, an electrode layer, and a dielectric layer, the dielectric layer is
97-99.99 vol% containing at least one main material selected from the group consisting of cordierite, spodumene and eucryptite,
A ceramic containing 0.01 to 3 vol% of carbon,
The electrostatic chuck according to claim 1, wherein the dielectric layer has a thermal expansion coefficient at room temperature of 1 × 10 ⁻⁶ / ° C. or less. The electrostatic chuck according to claim 1, wherein the volume resistivity of the ceramic used for the dielectric layer is 1 × 10 ⁸ to 10 ¹⁴ Ωcm. In an electrostatic chuck having a ceramic substrate, an electrode layer, and a dielectric layer, the dielectric layer is
62-99.89 vol% of a main material that is at least one selected from the group consisting of cordierite, spodumene and eucryptite,
Containing 0.01 to 3 vol% carbon, and silicon carbide;
Silicon nitride,
Carbides, nitrides, borides and silicides of Group 4a, 5a and 6a elements;
An electrostatic chuck comprising 0.1 to 35 vol% of at least one selected from the group consisting of:   The electrostatic chuck according to claim 1, wherein the ceramic used for the dielectric layer is formed on at least an adsorption surface of the dielectric layer. The electrostatic chuck according to claim 1, wherein the ceramic substrate has a thermal expansion coefficient at room temperature of 1 × 10 ⁻⁶ / ° C. or less.