JP6166205B2 - Sample holder - Google Patents

Description

  The present invention relates to a sample holder used for holding each sample such as a semiconductor wafer in a manufacturing process of a semiconductor integrated circuit.

  A sample holder is known as a part for holding each sample such as a semiconductor wafer in a manufacturing process of a semiconductor integrated circuit or a manufacturing process of a liquid crystal display device. Examples of the sample holder include an electrostatic chuck device disclosed in Japanese Patent Application Laid-Open No. 2010-40644 (hereinafter referred to as Patent Document 1). The electrostatic chuck device disclosed in Patent Document 1 includes a base body having a sample holding surface on the outer surface and an electrostatic chucking electrode provided inside the base body.

JP 2010-40644 A

  However, the electrostatic chuck device described in Patent Document 1 is incorporated in an external device such as a plasma etching device, and a high-frequency electric field is provided between the electrostatic chucking electrode of the electrostatic chuck device and the high-frequency applying electrode of the external device. In some cases, a large amount of heat is generated in the substrate due to dielectric loss in the substrate. Thereby, the thermal uniformity of the sample holding surface may be reduced. At that time, when a plasma etching apparatus is used as an external apparatus, there is a problem that uniform etching becomes difficult due to a decrease in the thermal uniformity of the sample holding surface.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a sample holder that can improve the heat uniformity on the sample holding surface by reducing the heat generation at the substrate.

  A sample holder according to one aspect of the present invention includes a base made of ceramics and having a sample holding surface on an outer surface, and an electrostatic adsorption electrode provided inside the base. The base is made of aluminum nitride. Is the main component, cerium is contained in an amount of 8% by mass to 16% by mass, the diffraction intensity of the aluminum nitride in the (100) plane in X-ray diffraction is A, and the diffraction intensity of the aluminum cerium trioxide in the (101) plane When B is B, the diffraction intensity ratio B / A is 0.35 or less.

  According to the sample holder of one embodiment of the present invention, since the base is mainly composed of aluminum nitride and the diffraction intensity ratio B / A is 0.35 or less, high-frequency application between the electrostatic adsorption electrode and the external device is performed. When a high-frequency electric field is applied between the electrodes for use, dielectric loss generated in the substrate can be reduced. Thereby, the heat_generation | fever which arises in a base | substrate can be reduced. As a result, the soaking property of the sample holding surface can be improved.

It is sectional drawing which shows one Embodiment of the sample holder of this invention. It is a graph which shows the relationship between diffraction intensity ratio B / A and a dielectric loss tangent. It is a graph which shows the relationship between diffraction intensity ratio B / A and volume specific resistance. It is a graph which shows the relationship between diffraction intensity ratio B / C and a dielectric loss tangent.

  Hereinafter, a sample holder 10 according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing a sample holder 10 according to an embodiment of the present invention. As shown in FIG. 1, a sample holder 10 according to an embodiment of the present invention includes a base 1 having a sample holding surface 11 on a main surface, and a static provided inside the base 1 so as to face the sample holding surface 11. And an electrode 2 for electroadsorption.

  The substrate 1 is a member made of ceramics and having a sample holding surface 11 on the outer surface. The substrate 1 holds a sample such as a silicon wafer on the sample holding surface 11 of the main surface. The base 1 is a plate-like member having a circular shape when viewed in plan. The dimensions of the substrate 1 can be set, for example, to a diameter of 200 to 500 mm and a thickness of 2 to 15 mm.

  Various methods can be used as a method of holding the sample using the substrate 1, but the sample holder 10 of this embodiment holds the sample by electrostatic force. Therefore, the sample holder 10 is provided with an electrostatic adsorption electrode 2 inside the base 1. The electrode 2 for electrostatic attraction is composed of two electrodes (only one electrode is shown in FIG. 1). One of the two electrodes is connected to the positive electrode of the electrode, and the other is connected to the negative electrode. The two electrodes are each formed in a substantially semicircular shape, and are arranged inside the base 1 so that the semicircular strings face each other with a gap. The outer shape of the electrostatic attraction electrode 22 is circular due to the arc of these two electrodes. The center of the circular outer shape of the entire electrostatic chucking electrode 2 is set to be the same as the center of the outer shape of the circular substrate 1. The electrostatic adsorption electrode 2 is made of a metal material such as tungsten or molybdenum.

  The substrate 1 contains aluminum nitride as a main component and contains cerium in an amount of 8% by mass to 16% by mass. When the cerium content is 8% by mass or more, the volume resistivity of the substrate 1 can be reduced. Thereby, after the sample holder 10 holds the sample with electrostatic force, when the voltage application to the electrode 2 for electrostatic adsorption is stopped to stop holding the sample, the residual adsorption force acting on the substrate 1 is reduced. be able to. Further, when the cerium content is 16% by mass or less, the aluminum nitride sintered body can be satisfactorily sintered. As a method for containing cerium in an amount of 8% by mass to 16% by mass, for example, 10-20% by mass of cerium (II) oxide powder is added to aluminum nitride (AlN) powder that is a raw material of the aluminum nitride sintered body. That's fine. The content of cerium can be confirmed by the following method. Specifically, after the substrate 1 is cut, the cerium in the substrate 1 may be quantitatively analyzed on the cut surface using an ICP emission spectroscopic analyzer (ICPS-8100 manufactured by Shimadzu Corporation).

  Furthermore, the sample holder 10 of the present embodiment is diffracted when the diffraction intensity of the (100) plane of aluminum nitride in X-ray diffraction is A and the diffraction intensity of the (101) plane of cerium trioxide is B. The value of the intensity ratio B / A is 0.35 or less.

  Since the substrate 1 is mainly composed of aluminum nitride and the diffraction intensity ratio B / A is 0.35 or less, a high frequency electric field is applied between the electrostatic adsorption electrode 2 and the high frequency application electrode of the external device. The dielectric loss generated in the substrate 1 can be reduced. Thereby, the heat_generation | fever which arises in the base | substrate 1 can be reduced. As a result, the thermal uniformity of the sample holding surface 11 can be improved.

Hereinafter, description will be given using data obtained by analyzing the actually produced sample holder 10. Table 1 shows a case in which the diffraction intensity ratio B / A and other parameters are changed in the sample holder 10 having the base 1 made of an aluminum nitride sintered body and containing cerium in an amount of 8% by mass to 16% by mass. 2 shows changes in dielectric loss tangent and volume resistivity.

Sample No. in Table 1 1 to Sample No. 2, the horizontal axis represents the diffraction intensity ratio B / A and the vertical axis represents the dielectric loss tangent. As apparent from the results shown in Table 1 and FIG. 2, when the value of the diffraction intensity ratio B / A is 0.35, the dielectric loss tangent is 23 × 10 ⁻⁴ , but the diffraction intensity ratio B / A is It can be seen that as soon as it exceeds 0.35 and becomes 0.37, the dielectric loss tangent increases to 85.4 × 10 ⁻⁴ or more. In other words, by setting the diffraction intensity ratio B / A to 0.35 or less, the dielectric loss tangent can be reduced to about 1/4 compared with the case where the diffraction intensity ratio B / A is greater than 0.35. it can. As a result, the dielectric loss of the substrate 1 can be reduced.

This is considered to be due to the following reasons. Since the crystal structure of aluminum cerium trioxide is a perovskite type, it has a structure in which electric charges are untargeted and polarization occurs. Therefore, the dielectric loss tangent becomes large due to the presence of a large amount of cerium trioxide. Thereby, it is considered that a large dielectric loss occurs in cerium trioxide when a high-frequency electric field is applied. On the other hand, aluminum nitride has a hexagonal crystal structure and has a low dielectric constant because it has a target structure. As a result, the dielectric loss tangent can be reduced by setting the diffraction intensity ratio B / A to 0.35 or less.

  For example, the cavity resonator method can be used for measuring the dielectric loss tangent. As an apparatus used for the cavity resonator method, for example, a C meter 4278A manufactured by HP can be used.

The diffraction intensity ratio B / A is preferably 0.16 or more. Thereby, the volume resistivity of the substrate 1 can be reduced. Therefore, the movement of electric charges on the surface of the substrate 1 is likely to occur, so that the residual adsorption force can be reduced. Specifically, the sample Nos. 1 to Sample No. 5, Sample No. 9, Sample No. 11, Sample No. 13-Sample No. 15 and sample no. 17-Sample No. 3 is a graph in which the horizontal axis represents the diffraction intensity B / A and the vertical axis represents the volume resistivity. As is apparent from Table 1 and FIG. 3, when the diffraction intensity ratio B / A is 0.16, the volume resistivity is 5.1 × 10 ⁹ , but the diffraction intensity ratio B / A is 0.16. It can be seen that the volume resistivity increased to 24 × 10 ⁹ Ω · cm as soon as the value decreased to 0.13. In other words, by setting the diffraction intensity ratio B / A to 0.16 or more, the volume resistivity can be reduced to about 1/5 compared with the case where the diffraction intensity ratio B / A is smaller than 0.16. Can do. As a result, the residual adsorption force can be reduced.

  For the measurement of the volume resistivity, for example, an insulation resistance meter R8340 manufactured by ADVANTEST can be used. Specifically, the surface resistivity is printed on the sample holding surface 11 and the resistance between the electrostatic adsorption electrode 2 and the surface electrode is measured by a three-terminal method using an insulation resistance meter. Can be measured.

Further, when the diffraction intensity of the (101) plane of cerium (III) oxide in X-ray diffraction is C, the diffraction intensity ratio B / C is preferably 2.5 or less. Thereby, when a high frequency electric field is applied between the electrostatic attraction electrode 2 and the high frequency application electrode of the external device, the dielectric loss generated in the substrate 1 can be reduced. Thereby, the heat_generation | fever which arises in the base | substrate 1 can be reduced. As a result, the thermal uniformity of the sample holding surface 11 can be improved.

Specifically, the sample Nos. 1 to Sample No. 4, the horizontal axis represents the diffraction intensity ratio B / C and the vertical axis represents the dielectric loss tangent. As is clear from the results shown in Table 1 and FIG. 4, when the value of the diffraction intensity ratio B / C is 2.5, the dielectric loss tangent is 25.4 × 10 ⁻⁴ , but the diffraction intensity ratio B / C It can be seen that as soon as C exceeds 3.1 and exceeds 3.1, the dielectric loss tangent increases to 85.4 × 10 ⁻⁴ or more. In other words, by setting the diffraction intensity ratio B / A to 0.35 or less, the dielectric loss tangent can be reduced to about 1/3 compared to the case where the diffraction intensity ratio B / A is greater than 0.35. it can. As a result, the dielectric loss of the substrate 1 can be reduced.

Next, the manufacturing method of the sample holder 10 of the present invention will be described. First, a ceramic raw material is prepared by adding cerium (II) oxide powder as a conductivity-imparting agent to aluminum nitride powder having a purity of 99% or more and a low oxygen content. The cerium (II) oxide cerium oxide added as the conductivity-imparting agent has a stable valence of 4 and does not exhibit electrical conductivity as it is. Can be chemically changed to trivalent cerium (III) oxide or aluminum cerium trioxide, and by changing the valence, pores are generated in the cerium oxide crystal, so that it has conductivity. It is thought to do. It is considered that the volume specific resistance of the aluminum nitride sintered body can be lowered by allowing the cerium (III) oxide or aluminum cerium trioxide to continuously exist at the grain boundaries in the sintered body. However, in order to produce cerium (III) oxide or aluminum cerium trioxide, it is necessary to use aluminum nitride powder having a low oxygen content, as described above. Preferably, an aluminum nitride powder having an oxygen content of 1% by mass or less is used. Moreover, in order to make the sample holder 10 capable of exhibiting a large adsorbing force and having a small residual adsorbing force, the cerium (II) oxide powder is in the range of 10% by mass to 20% by mass with respect to the AlN powder. What is necessary is just to add. That is, by making the addition amount of cerium (II) oxide 10% by mass or more, a certain amount of cerium (III) oxide or aluminum cerium trioxide produced in the aluminum nitride sintered body can be secured. Therefore, the volume resistivity of the heating resistor can be reduced. As a result, the residual adsorption force can be reduced. Moreover, when the added amount of cerium (II) oxide is 20% by mass or less, the aluminum nitride sintered body can be satisfactorily sintered.

Here, the particle size d50 of the cerium (II) oxide is preferably 1.3 μm or less. When the particle size d50 of cerium (II) oxide is 1.3 μm or less, the particle size of cerium aluminum trioxide after sintering can be reduced, and the amount of cerium (II) oxide or cerium (III) oxide produced increases. Decrease in cerium trioxide. Therefore, dielectric loss can be reduced. Next, after adding a binder and a solvent to the mixed ceramic raw material to produce a slurry, a plurality of AlN green sheets are formed by a doctor blade method. An electrode pattern to be an electrode for electrostatic adsorption is printed by a screen printing method or the like using a metal paste containing a refractory metal. Next, the remaining AlN green sheets are laminated so as to cover this metal paste, and thermocompression bonded at a temperature of 50 to 150 ° C. and a pressure of 2.9 to 6.9 MPa. At this time, the AlN ceramic molded body may be cut as necessary.

  Firing is performed in a temperature range of 1800 ° C to 1950 ° C. The sample holder 10 can be formed by baking in this temperature range for about 1 to 6 hours. By making the firing temperature higher than 1800 ° C., AlN can be sufficiently sintered, so that a dense substrate 1 can be formed. Further, by making the firing temperature lower than 1950 ° C., the amount of cerium and AlN reacting to produce aluminum cerium trioxide can be reduced.

1: Substrate 11: Sample holding surface 2: Electrode for electrostatic attraction 10: Sample holder

Claims (3)

A substrate made of ceramic and having a sample holding surface on the outer surface, and an electrostatic adsorption electrode provided inside the substrate;
The substrate contains aluminum nitride as a main component and contains cerium in an amount of 8% by mass to 16% by mass. The diffraction intensity of the (100) plane of aluminum nitride in X-ray diffraction is A, and aluminum cerium trioxide ( 101) A sample holder, wherein the diffraction intensity ratio B / A is 0.35 or less when the diffraction intensity by the surface is B.   The sample holder according to claim 1, wherein the diffraction intensity ratio B / A is 0.16 or more. The diffraction intensity ratio B / C is 2.5 or less, where C is the diffraction intensity of the (101) plane of cerium (III) oxide in X-ray diffraction. The sample holder as described.

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