JPH1022185A - Dummy wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute a dummy wafer, with low cost, which has a superior thermal resistance, corrosion resistance, and superior workability after manufac turing, working and using, by forming the entire dummy wafer with pyrolytic carbon. SOLUTION: There is provided a dummy wafer 10 which is disposed together with silicon wafers for forming integrated circuits, etc., arrayed in a semiconductor manufacturing device in large numbers. The entire dummy wafer 10 is formed out of pyrolytic carbon, and an outline form thereof is made into the same shape as the silicon wafer to be a product. The dummy wafer 10 has isotropy, and is formed in such a way that the entire surface of a high density and high purity carbon base material 11 is coated with a pyrolytic carbon film 12 whose thickness is not below 10μ. Thereby the dummy wafer, whose thermal resistance and corrosion resistance are superior as a thing to be mounted in the semiconductor manufacturing device, and whose hardness is not so high that workability after manufacturing, working and using is superior, too, is manufactured with relatively low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the monitoring of dust in each step and the processing after processing, when a silicon wafer is subjected to various processes such as sputtering, etching, CVD or ion implantation to produce an integrated circuit. And a dummy wafer used for transport check.

[0002]

2. Description of the Related Art In order to form an integrated circuit, various processes as described above are performed. For example, when an oxide film or the like is formed on the surface of a silicon wafer by a low pressure CVD process,
Many of these silicon wafers must be supported on a jig as shown in FIG. 1, for example, and must be placed in a CVD furnace as a semiconductor manufacturing apparatus as shown in FIG.
Recently, in order to improve the working efficiency, about 150 silicon wafers are simultaneously placed in one CVD furnace, and various processes are performed.

[0003] When a large number of silicon wafers are put into one CVD furnace for processing, it is difficult to uniformly process all the silicon wafers. This is because, as shown in FIG. 2, when a large number of silicon wafers are arranged and placed in an atmosphere such as a source gas, the outermost silicon wafer and the middle silicon wafer are exposed to the source gas and the like. This is because the ratios are necessarily different.

[0004] For this reason, in an actual integrated circuit manufacturing process, about 2 to about 20 silicon wafers arranged on both outer sides of about 150 silicon wafers are regarded as so-called "dummy wafers" which are not commercialized. This dummy wafer is used to maintain a constant gas concentration and flow in the above-mentioned CVD furnace, or as a test sample for film thickness, surface roughness, electric characteristics, etc. Conventionally, a silicon wafer itself, Alternatively, a quartz plate having the same shape as the silicon wafer was used.

Although these dummy wafers have been reused by being washed with nitric acid or the like after use, silicon and quartz have poor corrosion resistance and heat resistance to nitric acid. After three weeks (week to three months), it became useless and was disposed of. In addition, for example, silicon wafers themselves are currently in short supply, and it is naturally uneconomical to use more than 10% of products that should become products as dummy wafers.

[0006] For this reason, it has been proposed to form this kind of dummy wafer with silicon carbide. However, since silicon carbide is excellent in corrosion resistance, there is no problem in its durability or reusability. However, silicon carbide has very high hardness, which makes it difficult to manufacture as a dummy wafer. In addition, since silicon carbide has poor thermal conductivity and electric durability on its surface, it cannot perform the same level of surface treatment as a silicon wafer, and after processing in a CVD furnace, results of processing a silicon wafer made of this silicon carbide It is not suitable as a sample for viewing.

The inventor of the present invention has conducted various studies on how to improve the actual condition of the above-mentioned silicon wafer, and as a result, has completed the present invention described below.

SUMMARY OF THE INVENTION The present invention has been made based on the above circumstances, and an object of the present invention is to provide a dummy wafer which is easy to manufacture and process and has excellent physical properties. It is in.

That is, the object of the present invention is to
It should be relatively inexpensive because it has excellent heat resistance and corrosion resistance in semiconductor manufacturing equipment, as well as not so high hardness, excellent manufacturing, processing, and workability after use. It is to provide a dummy wafer that can be used.

[0009]

Means for Solving the Problems In order to solve the above problems, means according to the first aspect of the invention will be described with reference numerals used in the description of the following embodiments. A dummy wafer 10 which is arranged mixed with a wafer 20 for forming an integrated circuit or the like arranged in a large number in a semiconductor manufacturing apparatus, wherein the dummy wafer 10 is entirely formed of pyrolytic carbon. .

That is, as shown in FIG. 3A, the entirety of the dummy wafer 10 according to the first embodiment is formed of pyrolytic carbon. It has the same smoothness, and is capable of performing the same level of processing as the formation of an oxide film on the surface of the silicon wafer 20 as a product. In addition, since pyrolytic carbon itself is excellent in heat resistance and corrosion resistance, it can sufficiently withstand a high temperature atmosphere (1200 ° C. to 1300 ° C.) in a CVD furnace, and does not change at all. In addition, no change occurs when the oxide film formed on the surface is cleaned with nitric acid.

Of course, in the dummy wafer 10 formed of pyrolytic carbon, since the pyrolytic carbon has a high purity, during the formation of the oxide film on the silicon wafer 20, impurities which adversely affect the oxide film are scattered. However, it is natural that the processing of the silicon wafer 20 can be performed in a stable state. Therefore, the dummy wafer 10 of claim 1 made of pyrolytic carbon is optimal for use in processing the silicon wafer 20 and has excellent durability, so that it can be reused any number of times. Thus, the usefulness is higher than that of conventional quartz and silicon carbide.

[0012] In order to solve the above-mentioned problem, a second aspect is provided.
Means adopted by the invention according to the invention is “a dummy wafer 10 arranged mixedly with a wafer 20 for forming an integrated circuit or the like arranged in a large number in a semiconductor manufacturing apparatus. A dummy wafer 10 "characterized by having a decomposition carbon film 12 formed thereon."

That is, as shown in FIG. 3B, the dummy wafer 10 according to the second aspect is formed by forming the pyrolytic carbon film 12 on the surface of the carbon substrate 11. Due to the presence of the pyrolytic carbon film 12, the same functions and functions as those of the dummy wafer 10 according to the first aspect are exhibited.

Further, in the dummy wafer 10 according to the second aspect, most of the dummy wafer 10 is made of the carbon base material 11 which can be manufactured relatively easily and at low cost, so that the cost of the entire dummy wafer 10 is reduced. As a matter of course, the pyrolytic carbon coating 12 can be made to have a minimum necessary thickness, so that the production itself can be easily performed.

In particular, since the surface of each of the dummy wafers 10 according to the above claims is formed by laminating pyrolytic carbon in a layer, the thermal conductivity and the electrical conductivity in the direction of the surface are extremely low. It is high.

For this reason, first, in the dummy wafer 10 according to the present invention, when the dummy wafer 10 is supported together with the silicon wafer 20 on a support jig as shown in FIG. Even if there is a part that does not directly hit, at least the surrounding part is directly heated by the atmospheric gas, and the heat is quickly conducted inward due to the high thermal conductivity of the pyrolytic carbon. Therefore, the dummy wafer 10 is immediately adapted to the temperature atmosphere of the CVD furnace, and has no adverse effect on the process of forming an oxide film or the like on the silicon wafer 20.

The fact that the surface of the dummy wafer 10 has excellent electric conductivity means that an oxide film can be formed on the surface of the dummy wafer 10 in the same manner as the silicon wafer 20. This means that when the processed dummy wafer 10 is used as a sample for product inspection, an inspection equivalent to directly measuring the surface condition of the silicon wafer 20 can be performed. Become.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following is an explanation of the preferred embodiments of the present invention constructed as described above, with reference to the drawings.

(Regarding Dummy Wafer 10 According to Claim 1) As shown in FIG. 3A, the dummy wafer 10 is entirely formed of pyrolytic carbon, and its outer shape is As shown in FIG. 1, it is the same as the silicon wafer 20 to be a product.

As a method of forming the dummy wafer 10 by using pyrolytic carbon, various chemical vapor deposition methods can be used. Usually, a graphite base material is heated and a hydrocarbon gas such as methane and propane is heated to a high temperature (1200 ° C. to 2200 ° C.).
(C) method of reacting by contacting a graphite substrate to generate pyrolytic carbon on the surface of the graphite substrate (CVD method)
by. In this case, hydrogen gas is suitable for adjusting the concentration of the hydrocarbon gas or for the carrier gas. The reaction is carried out under normal pressure or reduced pressure, but is preferably carried out under reduced pressure in order to obtain uniformity and smoothness of the film.
It is desirable to carry out at orr or less.

As described above, in order to independently take out the pyrolytic carbon laminated on the graphite substrate, it is sufficient to rapidly cool the whole to room temperature. The respective thermal expansion coefficients of these graphite base material and pyrolytic carbon at 25 ° C. to 400 ° C. are 3
Because it is ^{~6 × 10 -6 /℃,1.7×10 -6 / ℃} , the difference between the thermal expansion coefficient, it is the two can be easily peeled off that the. Further, by making the thickness of the formed pyrolytic carbon layer as thick as possible, detachment from the graphite substrate becomes easier. In this case, the thickness of the layer to be formed is 0.5 mm or more, preferably 1 mm or more.

Further, separation from the substrate can be easily performed by reducing the surface roughness of the surface on which the substrate is formed. If the surface of the substrate is rough, the pyrolytic carbon layer enters the uneven portions of the substrate, and it is difficult to separate the layer from the substrate. in this case,
The surface roughness of the substrate to be formed is desirably Rmax = 25 μm or less.

Of course, the pyrolytic carbon formed as described above has high purity, but various impurities such as iron, nickel, and the like are contained in the graphite base material used for laminating the pyrolytic carbon.
Cobalt and vanadium may be mixed in and may remain on the pyrolytic carbon side. A possible route for impurities to be mixed into the pyrolytic carbon is that the impurities in the graphite substrate described above are mixed. These impurities are prevented from being mixed into the pyrolytic carbon by using a high-purity graphite base material and the purity of the supply gas (select the structure and materials of the gas supply parts, supply pipes and reaction vessels, etc.). Is what you can do.

By such a method, the total ash content (impurities such as iron) of the dummy wafer 10 made of the pyrolytic carbon is obtained.
Can be reduced to 10 ppm or less.
Therefore, this dummy wafer 10 is replaced with a C for wafer processing.
Even if it is arranged at the front end or the rear end in the VD furnace, the heating by the processing gas is performed evenly. The same is true for the electric conductivity on the surface of the dummy wafer 10, which is suitable when the state on the dummy wafer 10 as a sample is checked by electricity.

Further, since the dummy wafer 10 is entirely composed of pyrolytic carbon, it has a dense structure different from high-density graphite composed of granular aggregates. Will not occur. Therefore, the silicon wafer 20 is not contaminated by these dummy wafers 10.

Next, a method of manufacturing the above-described dummy wafer 10 will be described. First, a high-purity graphite substrate (coefficient of thermal expansion 3.2 × 10 ⁻⁶ / ° C., substrate surface roughness Rmax = 16 μm)
m) was placed in a furnace. The furnace was heated so that the surface side of the graphite substrate was always at 2200 ° C., and the raw material gas was injected.

A hydrocarbon gas such as methane, propane or benzene from which impurities were sufficiently removed was used as a raw material gas, and a hydrogen gas was used as a carrier gas for adjusting the concentration. As a result, the raw material gas became pyrolytic carbon on the surface of the graphite substrate, which was at a high temperature, due to decomposition, bonding, and the like, and was deposited on the substrate surface.

As described above, after the pyrolytic carbon was deposited on the surface of the graphite substrate at a depth of 5 mm or more, the pyrolytic carbon was separated from the graphite substrate at a normal temperature. By processing this pyrolytic carbon, a dummy wafer 10 was obtained.

(Regarding Dummy Wafer 10 According to Claim 2) FIG. 3 (b) is a partially enlarged sectional view of the dummy wafer 10 according to claim 2, and the dummy wafer 10 is isotropic. (The anisotropic ratio of thermal expansion coefficient is 1.20 or less), high density (1.7 to 2.0 g / cm ³ ), and high purity (total ash content is 10 ppm or less).
1 is coated with a pyrolytic carbon coating 12 having a thickness of 10 μ or more.
Formed by coating with

The carbon substrate 11 itself may be formed in accordance with the shape of the silicon wafer 20 by a general method, and the pyrolytic carbon coating 12 on the surface of the carbon substrate 11 may be, for example, as described in claim 1 above. May be formed by the same method as that described in the embodiment of the dummy wafer 10 according to the first embodiment.

[0031]

As described in detail above, the dummy wafer 10 according to the first aspect is characterized in that the whole is formed of pyrolytic carbon, and the dummy wafer 10 according to the second aspect is characterized in that It is characterized in that it is formed by coating the entire surface of the base material 11 with the pyrolytic carbon film 12, and thus, of course, is excellent in heat resistance and corrosion resistance when put in a semiconductor manufacturing apparatus. Since the hardness is not so high, the manufacturing, processing, and workability after use are excellent, and it can be manufactured as a relatively inexpensive product.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state in which a plurality of dummy wafers according to the present invention are mixed and arranged on silicon wafers arranged on a wafer holding jig.

FIG. 2 is a cross-sectional view of a CVD furnace in which the whole shown in FIG. 1 is put.

FIG. 3 shows a dummy wafer according to the present invention;
(A) is a partially enlarged cross-sectional view of a dummy wafer made of only pyrolytic carbon, and (B) is a partially enlarged cross-sectional view of a dummy wafer in which the entire carbon substrate is covered with a pyrolytic carbon film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Dummy wafer 11 Carbon base material 12 Pyrolytic carbon film 20 Silicon wafer

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[Procedure amendment]

[Submission date] July 15, 1996

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

Claims (2)

[Claims] 1. A dummy wafer which is arranged mixedly with a wafer for forming a large-scale integrated circuit or the like arranged in a large number in a semiconductor manufacturing apparatus, wherein the dummy wafer is entirely formed of pyrolytic carbon. Wafer. 2. A dummy wafer arranged in a wafer for forming large-scale integrated circuits and the like arranged in a large number in a semiconductor manufacturing apparatus, wherein a pyrolytic carbon film is formed on the entire surface of the carbon base material. Dummy wafer characterized by doing.