Silicon carbide and process for its production

Details Silicon carbide and process for its production Silicon carbide and process for its production

2000-07-31

2002-08-20

Nguyen, Ngoc-Yen (Department: 1754)

Chemistry of inorganic compounds

Silicon or compound thereof

Binary compound

C423S346000, C427S589000, C427S585000

Reexamination Certificate

active

06436361

ABSTRACT:

The present invention relates to silicon carbide having a high resistivity and a process for its production.
In recent years, along with the progress in the high densification technique and the microfabrication technique of semiconductor integrated circuits, importance of a plasma treatment apparatus such as a plasma etching apparatus or a plasma CVD apparatus has been increasing which is capable of forming a fine circuit pattern in high precision on a semiconductor wafer. Parts to be used for a plasma treatment apparatus include, for example, an electrostatic chuck, a heater, a protective ring, a sleeve and a chamber, and these parts are required to have desired resistivities and have of high purity, high corrosion resistance and uniformity. Among them, the protective ring is required to have a high resistivity for the purpose of carrying out etching uniformly within a wafer, and the sleeve and the chamber are required to have high resistivities for the purpose of minimizing the wearing rate.
Heretofore, parts made of alumina or silica have been used as parts for a plasma etching apparatus, which are required to have high resistivities. However, parts made of alumina have had a problem that high purity products are hardly obtainable, and semiconductor wafers to be treated are likely to be contaminated. Further, parts made of silica have had a problem that wearing by a plasma gas is substantial, such being disadvantageous from the viewpoint of costs. Therefore, in recent years, parts made of silicon carbide have been proposed as parts to be substituted therefor.
On the other hand, as a method for controlling the resistivity of silicon carbide ceramics, a method is known which employs e.g. beryllium, beryllium carbide, beryllium oxide or boron nitride, as a sintering aid (“Silicon Carbide Ceramics”, Uchida Roukakuho, p.327). However, this method has had a problem that since another component is incorporated as a sintering aid, it is impossible to obtain highly pure silicon carbide ceramics, and when used as parts for the semiconductor production apparatus, such parts tend to contaminate semiconductor wafers.
Further, methods for controlling resistivities of silicon carbide ceramics are proposed, for example, in JP-A-52-110499, JP-A-11-79840 and JP-A-11-121311. However, the silicon carbide ceramics obtained by such methods have had problems such that the resistivities are not sufficiently high, the purities are low or the productivity is not good.
JP-A-9-255428 discloses a method for controlling the resistivity of silicon carbide ceramics, which comprises mixing &agr;-type silicon carbide powder, &bgr;-type silicon carbide powder and super fine powder of silicon carbide, followed by sintering. However, this method has had a problem such that it is impossible to obtain a product having a large size or a complicated shape, the controllable range of the resistivity is relatively low at a level of not higher than 10
2
&OHgr;·cm, and it is difficult to obtain silicon carbide ceramics having high resistivities.
Further, JP-A-11-71177 discloses silicon carbide ceramics comprising silicon carbide and silica as the main components and having the resistivity controlled to be from 500 to 50,000 &OHgr;·cm. However, such silicon carbide ceramics have a problem such that silica portions in the sintered body are likely to be selectively eroded by an acid or by a plasma gas, or the obtained sintered body has high porosity and low corrosion resistance.
Still further, JP-A-6-239609 discloses &bgr;-type silicon carbide having a resistivity of at least 10
4
&OHgr;·cm, which is obtainable by a CVD method. However, this &bgr;-type silicon carbide has had a problem that the resistivity fluctuates substantially, and it is difficult to obtain a product having a uniform resistivity.
It is an object of the present invention to provide silicon carbide which has a high, uniform resistivity, high purity and high corrosion resistance.
Namely, the present invention provides silicon carbide having a resistivity of from 10
3
to 10
6
&OHgr;·cm and a powder X-ray diffraction peak intensity ratio of at least 0.005 as represented by I
d1
/I
d2
where I
d1
is the peak intensity in the vicinity of 2&thgr; being 34° and I
d2
is the peak intensity in the vicinity of 2&thgr; being 36°.
Further, the present invention provides a process for producing such silicon carbide, which comprises forming &bgr;-type silicon carbide on a substrate by a CVD method, then removing the substrate, and heat-treating the obtained &bgr;-type silicon carbide at a temperature of from 1,500 to 2,300° C.
Now, the present invention will be described in detail with reference to the preferred embodiments.
The silicon carbide of the present invention is formed by a CVD method and has a gas-impermeable dense crystal structure, and it hence exhibits high corrosion resistance against a gas such as CF
4
or CHF
3
to be used in an etching step.
Further, the silicon carbide of the present invention is characterized in that the powder X-ray diffraction peak intensity ratio represented by I
d1
/I
d2
where is I
d1
the peak intensity in the vicinity of 2&thgr; being 34° and I
d2
is the peak intensity in the vicinity of 2&thgr; being 36°, is at least 0.005.
Here, the peak in the vicinity of 2&thgr; being 34° means the peak at 2&thgr; being 33.2°≦2&thgr;≦34.8°, and the peak in the vicinity of 2&thgr; being 36° means the peak at 2&thgr; being 35.0≦2&thgr;≦37.0°.
If the ratio of I
d1
/I
d2
is smaller than 0.005, it is not possible to constantly obtain silicon carbide having a resistivity of at least 10
3
&OHgr;·cm. Further, if it exceeds 0.5, the effect for increasing the resistivity tends to be small. Accordingly, the ratio of I
d1
/I
d2
is preferably from 0.005 to 0.5, more preferably from 0.007 to 0.2.
I
d1
is the intensity of a peak detected as the sum of &agr;-type silicon carbides of 2H structure, 4H structure, 6H structure and 15R structure, and I
d2
is the intensity of a peak detected as the sum of &agr;-type silicon carbides and &bgr;-type silicon carbides of 2H structure, 4H structure, 6H structure and 15R structure.
It is considered that the larger the ratio of I
d1
/I
d2
, i.e. the larger the proportion of &agr;-type silicon carbides, the larger the resistivity.
In the present invention, I
d1
and I
d2
are values measured under the following conditions by means of a powder X-ray diffraction apparatus. Using CuK&agr;-ray as the X-ray source, the accelerating voltage of the X-ray tube is set to be 40 kV, and the accelerating current is set to be 20 mA. The divergence slit (DS) is set to be 1°, the receiving slit (RS) is set to be 0.15 mm, and the scattering slit (SS) is set to be 1°. The sample to be measured is one pulverized to have a particle size of at most 20 &mgr;m, so that it is free from orientation.
Further, I
d1
, and I
d2
are peak intensities obtained by smoothing treatment (an adaptive smoothing method to remove background noises, followed by smoothing by a Savitzky-Golay method), followed by removing the background by a Sonneveld method.
As the powder X-ray diffraction apparatus, GEIGERFLEX RAD-IIA, manufactured by Rigaku Denki K.K. may, for example, be employed.
The silicon carbide of the present invention has a resistivity of from 10
3
to 10
6
&OHgr;·cm. Silicon carbide having a ratio of I
d1
/I
d2
of at least 0.005 and containing a certain amount of &agr;-type silicon carbide, constantly has a resistivity within the above range.
Further, the above resistivity can be measured, for example, by a potentiometer method by means of a four-terminal resistor.
The silicon carbide of the present invention can be obtained by forming &bgr;-type silicon carbide on a substrate by a CVD method, then removing the substrate, and heat-treating the obtained &bgr;-type silicon carbide at a temperature of from 1,500 to 2,300° C.
The process for producing the silicon carbide of the present invention is characterized in that the &bgr;-type silicon carbide obtained by a CVD method, is heat-treated at a temperature of from 1,500

Affiliated with

Also associated with

Rating

Silicon carbide and process for its production does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Silicon carbide and process for its production, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Silicon carbide and process for its production will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2971632