JP2002255647A - Yttrium oxide sintered body and wafer holding tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a yttrium oxide sintered body which has high corrosion resistance to corrosive atmospheres such as halogen-containing gas plasma used for a semiconductor production process or the like, and in which contamination caused by metal is hard to occur, and a wafer holding tool in which particles are hard to occur in addition to those characteristics. SOLUTION: The yttrium oxide sintered body contains metallic trace components of, by weight, <=200 ppm Si, <=100 ppm Al, and Na, K, Ti, Cr, Fe and Ni by <=200 ppm in total. The wafer holding tool holding a wafer in a wafer treatment process using corrosive gas or the plasma thereof consists of the yttrium oxide sintered body. The surface roughness at least of the contact face with the wafer is controlled to <=0.5 μm in terms of Ra.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a yttrium oxide sintered body which is a highly corrosion-resistant material suitable for a semiconductor manufacturing process and the like.
And a wafer holder using the same.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, there is a process under a highly corrosive environment typified by wafer etching, and a bell jar, a chamber, a susceptor, a clamp ring, and a focus ring used for such a process. Quartz glass and high-purity alumina sintered bodies are frequently used for such members. Garnet Y ₂ O ₃ -Al ₂ O ₃ compound excellent in corrosion resistance has recently has also been studied adopted to these members.

However, recently, in order to improve the degree of integration and the productivity of semiconductors, etching conditions with higher density plasma have been required, and the corrosion rate by plasma has been remarkably high in the conventionally used quartz glass. There is a problem that the life of the member is short. Further, although the high-purity alumina sintered body has higher corrosion resistance than quartz glass, it causes Al component contamination to the device, and may pose a problem from the viewpoint of reliability. Garnet _Y 2 _{O 3 -Al} 2 _O 3
Although the compound is more excellent in corrosion resistance, it contains Al as a constituent component, so that it also causes Al component contamination. In particular,
Such a tendency is remarkable in a wafer holder such as a clamp ring which directly contacts the wafer. In the case of a wafer holder, there is also a problem of generation of particles since the wafer holder comes into direct contact with the wafer.

[0004] On the other hand, yttrium oxide has been studied as a corrosion resistant material which does not cause contamination by Al. However, at present, satisfactory corrosion resistance is not always obtained with a conventional yttrium oxide sintered body, and a problem of contamination sometimes occurs.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has high corrosion resistance to a corrosive atmosphere such as a halogen-containing gas plasma used in a semiconductor manufacturing process and the like, and is unlikely to cause metal contamination. An object of the present invention is to provide a yttrium oxide sintered body and a wafer holder in which particles are hardly generated in addition to these characteristics.

[0006]

Means for Solving the Problems As a result of repeated studies to solve the above-mentioned problems, the present inventors have limited the specific metal component present as an impurity to a specific range, so that a halogen-containing gas plasma or the like can be obtained. It has been found that a yttrium oxide sintered body having excellent corrosion resistance against a corrosive atmosphere and substantially not causing device contamination can be obtained.
In addition, by forming the wafer holder with such a yttrium oxide and defining the surface roughness of the wafer contact surface in a specific range, the device has excellent corrosion resistance to a corrosive atmosphere, and has a device It has been found that a wafer holder having substantially no contamination and having less particles is obtained.

The present invention has been completed on the basis of such findings. As a first invention, the content of a trace metal component is 200 ppm or less of Si and 1: 1 of Al by weight.
Provided is a yttrium oxide sintered body characterized by being at most 00 ppm and the total amount of Na, K, Ti, Cr, Fe and Ni: at most 200 ppm.

According to a second aspect of the present invention, there is provided a wafer holder for holding a wafer in a wafer processing process using a corrosive gas or its plasma, wherein at least the wafer contact surface has a metal trace component content of, Si:
200 ppm or less, Al: 100 ppm or less, Na,
Provided is a wafer holder, wherein the total amount of K, Ti, Cr, Fe, and Ni is 200 ppm or less and the surface roughness is made of an yttrium oxide sintered body having a surface roughness Ra of 0.5 μm or less. .

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described specifically. In the yttrium oxide according to the present invention, the content of a trace metal component is, on a weight basis, Si: 200 ppm or less,
Al: 100 ppm or less, Na, K, Ti, Cr, F
e, total amount of Ni: not more than 200 ppm.

[0010] Trace metal components contained in the yttrium oxide sintered body as impurities are mainly condensed in the grain boundary layer,
In a corrosive environment such as plasma, the corrosion rate of these trace components is higher than that of yttrium oxide. Some of the yttrium oxide particles fall off. The trace components which cause such a thing include Si, Na, K, Ti, C
r, Fe, and Ni, among these trace components, 200 ppm or less of Si, Na, K, Ti, Cr, Fe, Ni
Is regulated to 200 ppm or less, it is possible to greatly reduce the amount of scattering of the grain boundary components due to the corrosion of the trace components at such grain boundaries, and also to reduce the corrosion damage due to the falling off of the particles in the matrix portion. It becomes possible.

On the other hand, when Al is contained in the yttrium oxide sintered body, even a small amount thereof may adhere to the wafer and adversely affect the device. However, if the amount is 100 ppm, Al hardly adheres to the wafer and substantially no adverse effect on the device occurs.

Therefore, the yttrium oxide sintered body of the present invention is effective for a member which comes into direct contact with a wafer, and is suitable as a wafer holder.

In order to keep the trace metal element within the above range,
Implementing measures such as minimizing impurities mixed from the raw material powder manufacturing process and strictly managing jigs and furnaces so that the trace metal elements do not mix during molding and sintering.

The wafer holder holds the wafer in a wafer processing process using a corrosive gas or its plasma. At least the wafer contact surface is made of the above-described yttrium oxide sintered body. Has a surface roughness of 0.5 μm or less in Ra.

If the surface roughness exceeds 0.5 μm in Ra, the number of particles due to wafer contact damage increases, which is not preferable as a wafer holder. Ra is 0.
When the thickness is 5 μm or less, the generation of particles due to the contact of the wafer can be set to a value having substantially no problem.

Next, an example of the wafer holder will be described with reference to FIGS. FIG. 1 is a plan view showing an example of a wafer holder, and FIG. 2 is a vertical sectional view showing a state where a wafer mounted on a stage is held by the wafer holder. The wafer holder 1 includes a main body 2 and a holding portion 3 provided to protrude inward from the main body 2 and holding the wafer 4 on the stage 5. As shown in FIG. 2, the holding portion 3 has a contact portion 3a that comes into contact with the wafer 4, and at least the contact portion 3a is made of the yttrium oxide sintered body of the present invention and has a surface roughness. Ra is 0.5 μm or less. In this case, a part of the holding portion 3 including the contact portion 3a may be made of a yttrium oxide sintered body,
The entire holding section 3 may be made of a yttrium oxide sintered body, or the entire wafer holder 1 may be made of a yttrium oxide sintered body.

When the wafer 4 is held by the wafer holder 1, the wafer holder 1 is lowered from a standby position above the stage 5 by an appropriate drive mechanism (not shown) such as an air cylinder. Press from above. The configuration of the wafer holder is not limited to the illustrated one.

[0018]

Embodiments of the present invention will be described below. A predetermined raw material powder was charged into a polyethylene pot together with ion-exchanged water, an organic dispersant, an organic binder and a nylon ball containing an iron core, and mixed for 24 hours. The obtained slurry was dried with a spray drier to prepare granules. After the CIP molding, the granules were fired at a predetermined temperature to produce a disc-shaped sintered body. The upper surface of the disc-shaped sintered body was mirror-polished to obtain a sample for evaluation. Further, trace components of the sintered body were analyzed by glow discharge mass spectrometry (GD / MS).

A sample for evaluation was set in a chamber as shown in FIG. 3, and CF ₄ + 20% O ₂ was used as a plasma gas.
Is introduced into the chamber, and the ion impact strong energy 10
Plasma treatment was performed together with the silicon wafer at 0 eV. Impurity analysis was performed on the processed wafer using total reflection X-ray fluorescence. The corrosion resistance of the sample was evaluated by measuring the etching rate by plasma. The etching rate at this time was calculated by performing a plasma treatment by masking a part of the surface of the polished sample similarly prepared, measuring the corrosion depth before and after the plasma treatment, and dividing by the plasma exposure time. . Table 1 shows the results.

[0020]

[Table 1]

As shown in Table 1, the yttrium oxide sintered body No. 1 which is within the scope of the present invention. In Nos. 1 to 3, the Al component was not detected in the wafer, and the etching rate was as excellent as about 1/2 to 1/3 that of sapphire. No. 4
Is a comparative example in which Si exceeds 200 ppm in the trace metal component, and the Al component is not detected in the wafer,
The etching rate was slightly higher, and yttrium oxide particles fell off due to scattering of grain boundary components. In addition, No. Sample No. 5 is a comparative example in which Al of the trace metal component exceeded 100 ppm, and the etching rate was about 1/2 of that of sapphire, but the Al component was slightly detected in the wafer. N
o. 6 is a trace metal component among Na, K, Ti, Cr,
This is a comparative example in which the total amount of Fe and Ni exceeded 200 ppm. Although the Al component was not detected in the wafer, the etching rate was slightly higher, and the yttrium oxide particles dropped off due to the scattering of the grain boundary component. No. 7 and 8 are made of Yttrium Aluminum Garnet (YAG)
In this comparative example, the etching rate was 1 for sapphire.
/ 3, which is excellent in corrosion resistance, but since Al is contained as a matrix component, the detected amount of Al component in the wafer was high. No. 9 is a comparative example in which the constituent material is sapphire, and the matrix component is Al,
The amount of detected Al in the wafer was extremely high. No. 1
0 is a comparative example in which the constituent material was SiO ₂ , and the Al component was not detected in the wafer, but the etching rate was remarkably large and the corrosion resistance was poor.

Next, the above No. The raw material powder used in 2 was charged in a polyethylene pot with ion-exchanged water,
It was charged together with an organic binder and a nylon ball containing an iron core, and mixed for 24 hours. The obtained slurry was dried with a spray drier to prepare granules. After granulating the granules by CIP, the granules were baked at a predetermined temperature and polished to produce four wafer holders having the structure shown in FIG. 1 in which the surface roughness of the contact portion with the wafer was changed.

The wafer is held in the chamber by these wafer holders, and CF ₄ + 20% is used as a plasma gas.
The O ₂ is introduced into the chamber, and a plasma treatment with a silicon wafer by ion impact strength energy 100 eV,
The number of particles scattered on the wafer was measured. Table 2 shows the results. In Table 2, the evaluation of the generated particles was No. 12 is shown as a ratio to the number of generated particles.

[0024]

[Table 2]

As shown in Table 2, when the surface roughness is Ra of 0.
No. 5 μm or less. 11 to 13, the ratio of the number of generated particles was 0.8 to 1.1, whereas the surface roughness Ra
No. exceeding 0.5 μm. In No. 14, the ratio of the number of generated particles increased to 1.5.

[0026]

As described above, according to the present invention,
By regulating the predetermined metal trace component to a predetermined range, it is possible to obtain a yttrium oxide sintered body having high corrosion resistance against a corrosive atmosphere such as a halogen-containing gas plasma used in a semiconductor manufacturing process or the like and hardly causing metal contamination. it can. In addition, by forming a wafer holder with such a yttrium oxide sintered body and setting the surface roughness of the contact portion with the wafer to 0.5 μm or less in Ra, in addition to these characteristics, the wafer that hardly generates particles can be obtained. A holder can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a wafer holder of the present invention.

FIG. 2 is a vertical sectional view showing a state in which a wafer mounted on a stage is held by a wafer holder.

FIG. 3 is a plan view showing a state in which a sample for evaluation in an embodiment is set in a chamber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Wafer holder 2 ... Main body 3 ... Holder 3a ... Contact part 4 ... Wafer 5 ... Stage

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Eiichi Uchino 3-5 Meido, Izumi-ku, Sendai City, Miyagi Prefecture Inside of Japan Ceratech Co., Ltd. No. 5 F-term in the Japan Ceratech headquarters factory (reference) 4K030 CA12 DA04 GA02 KA46 LA15 5F004 AA14 AA15 BA00 BB18 BB29

Claims (2)

[Claims] Claims: 1. The content of a trace metal component is, on a weight basis,
Si: 200 ppm or less, Al: 100 ppm or less, N
a, total amount of K, Ti, Cr, Fe, Ni: 200 ppm
A yttrium oxide sintered body characterized by the following. 2. A wafer holder for holding a wafer in a wafer processing process using a corrosive gas or its plasma, wherein at least the wafer contact surface has a metal trace component content of 200 ppm or less of Si by weight, A
l: 100 ppm or less, Na, K, Ti, Cr, Fe,
A wafer holder characterized by being composed of a yttrium oxide sintered body having a total amount of Ni of 200 ppm or less and a surface roughness Ra of 0.5 μm or less.