JP2001338913A - Plasma etching silicon electrode plate generating less particles - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma etching silicon electrode plate having less particle adhesion. SOLUTION: A plasma etching silicon electrode plate is made by a single crystal silicon or a casted silicon material having unilaterally solidified composition, with a COP(Crystal Originated Particle) defect density of 104 pcs/cm3 or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon electrode plate used in a plasma etching apparatus and having a small particle generation, and more particularly to a silicon electrode plate having a very small particle generation when etching an interlayer insulating film constituting a semiconductor device. Things.

[0002]

2. Description of the Related Art Generally, one of the processes for manufacturing a semiconductor device includes a process for etching a Si wafer, and a plasma etching device is used as a device for etching a Si wafer. More specifically,
An interlayer insulating film made of silicon oxide is formed on the surface of a Si wafer, a photoresist film is locally formed thereon, and etching is performed using a portion of the interlayer insulating film without the photoresist film as an etching surface. Have been. In the plasma etching apparatus used at this time, for example, as shown in FIG. 1, an electrode plate 2 and a gantry 3 are provided at an interval in a vacuum vessel 1, and an interlayer insulating film (FIG. The silicon wafer 4 on which the electrode plate 2 and the pedestal 3 are mounted by the high-frequency power source 6 while flowing the etching gas 7 toward the Si wafer 4 through the through holes 5 provided in the silicon electrode plate 2. A high frequency voltage can be applied in between.

The supplied etching gas 7 is turned into a plasma 10 in the space between the silicon electrode plate 2 and the gantry 3 by application of the high frequency voltage, and the plasma 10 hits the Si wafer and the surface of the Si wafer 4 is etched. . The silicon electrode plate 2 is made of a disc-shaped single-crystal silicon, and a plurality of through-holes 5 are provided in a direction perpendicular to the plane of the single-crystal silicon disc.

However, when a conventional silicon electrode plate made of single-crystal silicon is used to plasma-etch a Si wafer, a large number of coarse particles having a particle size of 0.5 μm or more adhere to the surface of the plasma-etched Si wafer. A Si wafer to which a large number of particles have adhered becomes a defective product, and the yield of the plasma-etched Si wafer has been reduced.

In order to solve this problem, conventionally, as shown in FIG. 2A, a chamfer 8 is formed at the end of the through hole 5 of the silicon electrode plate 2, or as shown in FIG. As shown in ()), when forming the through pores 5 of the silicon electrode plate 2, the length of the microcracks 9 growing from the wall surface toward the inside is suppressed to 10 μm or less, and the particle diameters are as follows:
The generation of coarse particles of 0.5 μm or more is prevented.

[0006]

However, in recent years, as the performance of semiconductor devices has been improved, it has been required to further reduce the number of particles adhering to the surface of the Si wafer. And particle size: 0.
Although the generation of coarse particles of 5 μm or more can be prevented,
Particle size: generation of finer particles of 0.3 μm or more cannot be reduced.

[0007]

Means for Solving the Problems Accordingly, the present inventors have
As a result of research to prevent not only coarse particles but also fine particles from adhering to the surface of the plasma-etched Si wafer, the single crystal silicon ingot obtained by the conventional pulling method generally has COP.
(Crystal Originated Parti
cle) defects, FDR (flow pattern defect) defects, and growth defects (As-grown defects) such as LSTD (infrared scatterer) defects. Among these growth defects, there are few COP defects. When plasma etching is performed using an electrode plate made of single crystal silicon, the number of particles generated during plasma etching is reduced, and the density of COP defects is 10 ⁴ / c.
Research results have shown that when plasma etching is performed using an electrode plate made of single crystal silicon containing more than m ³ , the number of particles of 0.3 μm or more adhering to the surface of the Si wafer rapidly increases.

The present invention has been made based on the results of such research, and (1) the density of COP defects is 10 ⁴
The present invention is characterized by a plasma etching silicon electrode plate made of single crystal silicon having a particle size of not more than ³ pieces / cm ³ and having few particles.

In order to manufacture a single-crystal silicon electrode plate having a COP defect density of 10 ⁴ / cm ³ or less, when pulling a single-crystal silicon ingot from a silicon melt, a conventional temperature range (over the entire length) is used. By holding the single crystal silicon ingot in a temperature range of 1200 to 1400 ° C. higher than 900 to 1100 ° C. for one hour or more, a single crystal silicon ingot having a COP defect density of 10 ⁴ / cm ³ or less is produced. COP defect density obtained by
^{It is obtained} by cutting a single crystal silicon ingot of ⁴ pieces / cm ³ or less to produce a single crystal silicon disk, and forming through-pores in the single crystal silicon disk.

In order to measure the number of COP defects contained in single-crystal silicon, SC1 cleaning liquid (RCA standard 1 liquid = NH
The surface of the single crystal silicon is repeatedly washed with ₄ OH / H ₂ O ₂ / H ₂ O to enlarge the etch pits appearing on the surface of the single crystal silicon. SS6
200). Even if the COP defect is fine, it can be detected because it appears as an enlarged etch pit by repeated cleaning.

Further, the present inventors have found that (a) a cast silicon ingot having a unidirectionally solidified structure has a higher purity and a lower COP defect density than an ordinary cast silicon ingot, Density is 10 ⁴
When plasma etching is performed using a silicon electrode plate manufactured from a cast silicon ingot having a unidirectional solidification structure of not more than ³ pieces / cm ^{3, the} number of particles generated during plasma etching is reduced.
A cast silicon ingot having a unidirectional solidification structure with a P defect density of 10 ⁴ / cm ³ or less has a temperature gradient in the solidification direction of G (mm / hour) and a solidification rate of the unidirectional solidification of R: (K /
mm), the GR (K / hr) is reduced within the range of 1 to 20 and the G / R (mm ² / K · hr) is reduced to 10 to 1
Thus, research results were obtained, such as that it could be obtained by controlling to a range of 000.

Accordingly, the present invention is characterized by (2) a silicon electrode plate for plasma etching, which is made of a silicon casting having a unidirectionally solidified structure having a COP density of 10 ⁴ / cm ³ or less and has little particle generation. Things. Eliminating the COP defects at all costs too much, so a more preferable range of the COP defect density in terms of cost is 10 to 10 ³ / cm ³ .

In order to measure a COP defect contained in a high-purity silicon casting having a unidirectionally solidified structure, etching is performed in the same manner as in the measurement of the COP defect in the single crystal.
It can be detected by removing those due to grain boundaries during counting.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 When a single-crystal silicon ingot is pulled up from a silicon melt, the single-crystal silicon ingot is held at the temperature and time shown in Table 1 over its entire length, so that the straight body portion is removed. Diameter: 300mm, length: 300mm, total length: 6
A single crystal silicon ingot having a size of 00 mm was prepared, and the straight body of the single crystal silicon ingot was cut into a thickness of 7 mm with a diamond hand saw and polished to dimensions of a diameter of 280 mm and a thickness of 4.5 mm. A silicon electrode plate for plasma etching of the present invention (hereinafter, referred to as the electrode plate of the present invention) is prepared by forming a through-hole having a diameter of 0.45 mm by drilling a single crystal silicon plate having 1) to 6 and a conventional silicon electrode plate for plasma etching (hereinafter referred to as a conventional electrode plate) 1.

The surfaces of the electrode plates 1 to 6 of the present invention and the conventional electrode plate 1 are mirror-polished and then heated to 85 ° C.
The SC1 cleaning was performed by immersing in one cleaning solution for 40 minutes. The SC1 cleaning solution used at this time was an H ₂ O ₂ aqueous solution (specific gravity 1.1), NH ₄ OH (specific gravity 0.9), and H ₂ O as H ₂ O: H ₂ O ₂ : NH ₄ OH = 5: It was prepared by mixing at a volume ratio of 1: 1. When the mirror-polished surfaces of the electrode plates 1 to 6 of the present invention and the conventional electrode plate 1 are washed three times with the SC1 cleaning solution, COP defects are revealed as etch pits, and the number of the revealed etch pits is measured by a particle counter. The COP defect densities contained in the electrode plates 1 to 6 of the present invention and the conventional electrode plate 1 were determined, and the results are shown in Table 1.

On the other hand, a Si wafer having a diameter of 200 mm, on which SiO ₂ was laminated by CVD, was prepared, set in a plasma etching apparatus, and a chamber was formed using the electrode plates 1 to 6 of the present invention and the conventional electrode plate 1. Internal pressure: 50 Pa, gas flow ratio: Ar / CHClF3 / CH4 = 300/1
Plasma etching was performed under the following conditions: 5/15 (SCCm), high frequency power: 1.5 KW, etching time: 2 min., And the number of particles having a diameter of 0.3 μm or more adhering to the surface of the Si wafer was measured. The results are shown in Table 1.

[0017]

[Table 1]

From the results shown in Table 1, the electrode plate of the present invention 1
When the plasma etching was performed using the electrode plates 1 to 6 of the present invention, the plasma etching was performed using the electrode plates 1 to 6 of the present invention. 0.3μm to adhere
It can be seen that the number of generated particles below is extremely small.

Example 2 The temperature gradient in the longitudinal direction of the unidirectional solidification mold was G (mm / h),
The unidirectional solidification rate was adjusted so that R (K / mm) became the value shown in Table 1, and the cooling rate GR (K / h) and G / R
A circle having a unidirectionally solidified structure and a diameter of 300 mm and a length of 300 mm by being unidirectionally solidified while controlling the value of (mm ² / Kh) to be the value shown in Table 1. A columnar cast silicon ingot was prepared, and the body was cut to a thickness of 7 mm with a diamond hand saw and polished to give a cast silicon having a unidirectionally solidified structure having a diameter of 280 mm and a thickness of 4.5 mm. A plate was prepared, and through-holes having a diameter of 0.45 mm were formed in the cast silicon plate having the unidirectional solidification structure by drilling to prepare the electrode plates 7 to 11 of the present invention and the conventional electrode plate 2.

The surfaces of the electrode plates 7 to 11 of the present invention and the conventional electrode plate 2 are mirror-polished and then heated to 85 ° C.
SC1 cleaning was performed by immersing in C1 cleaning solution for 40 minutes. The SC1 cleaning solution used at this time was the same as in Example 1.
The same SC1 washing solution as that used in the above was used. When the surfaces of the electrode plates 7 to 11 of the present invention and the conventional electrode plate 2 were cleaned with the SC1 cleaning solution, the count number of the crystal grain boundaries was excluded because the COP defects became obvious as etch pits and the crystal grain boundaries also appeared. Measure the correction value as the number of etch pits with a particle counter,
C contained in the electrode plates 7 to 11 of the present invention and the conventional electrode plate 2
The OP defect density was determined, and the results are shown in Table 2.

The thus obtained electrode plates 7 to 7 of the present invention
11 and the conventional electrode plate 2 were set in the plasma etching apparatus prepared in Example 1, plasma etching was performed under the same conditions as in Example 1, and the number of particles having a diameter of 0.3 μm or more adhering to the surface of the Si wafer was measured. The results are shown in Table 2.

[0022]

[Table 2]

From the results shown in Table 2, the electrode plate 7 of the present invention was
Comparing the case where the plasma etching was performed using Nos. 11 to 11 and the case where the plasma etching was performed using the conventional electrode plate 2, it was found that the number of particles of 0.3 μm or less adhering to the surface of the Si wafer was extremely small. .

[0024]

As described above, when a silicon wafer is plasma-etched using the silicon electrode plate of the present invention, the occurrence of defective products due to the generation of particles can be greatly reduced, and can greatly contribute to the development of the semiconductor device industry. Things.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of a conventional plasma etching apparatus.

FIG. 2 is an explanatory cross-sectional view of a through hole in a conventional silicon electrode plate.

[Description of Signs] 1 vacuum vessel 2 silicon electrode plate 3 mount 4 Si wafer 5 penetrating pore 6 high frequency power supply 7 plasma etching gas 8 chamfering 9 micro crack 10 plasma

Claims (2)

[Claims] 1. A silicon electrode plate for plasma etching with less generation of particles, comprising a single crystal silicon having a COP density of 10 ⁴ / cm ³ or less. 2. A silicon electrode plate for plasma etching with less generation of particles, comprising a silicon casting having a unidirectionally solidified structure having a COP density of 10 ⁴ / cm ³ or less.