JPH08269721A - Method for removing dust in exhaust gas of cvd device - Google Patents

Abstract

PURPOSE: To provide a method for removing dust in the exhaust gas of a semiconductor producing device, etc., needing a dense thick-film coating by a CVD device. CONSTITUTION: A raw gas is supplied to a reactor 3 in a CVD device and allowed to react with a sample S, the generated exhaust gas is evacuated by a vacuum pump 7, and the dust is removed by filter elements 5A and 5B. In this case, the filter element 5A provided with a coarse-mesh filter F1 and the filter element 5B furnished with a coarse-mesh filter F2 are arranged in parallel and operated alternately and independently. When the operated element 5A is switched to the suspended element 5B, both elements are transiently operated at the same time, and then only the element 5B is operated. Consequently, a large amt. of exhaust gas is continuously treated for a long time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas dust removing method for a semiconductor manufacturing apparatus or the like which requires a thick film of a dense coating by a chemical vapor deposition apparatus (hereinafter abbreviated as a CVD apparatus) in a high temperature atmosphere.

[0002]

2. Description of the Related Art When a coating film having functions such as conductivity and oxidation resistance is formed on the surface of silicon or carbon material by the CVD (Chemical Vapor Deposition) method, the chemical reaction in the reactor is the essence of CVD. In order to generate fine particles in the gas phase,
A large amount of reaction product particles that have not come into contact with, adhere to, or deposit on the base material, the support tool, the inner wall of the reactor, etc. are scattered in the exhaust gas in a powder form. The powdery particles cause abrasion damage and blockage of a system such as a vacuum pump arranged in a subsequent stage of the CVD apparatus.

Therefore, for example, in Japanese Patent Laid-Open No. 60-13071, a cassette type filter is installed between a CVD device and an oil rotary pump holding a vacuum system, and particulate matter contained in exhaust gas from the CVD device. A technique has been disclosed that can prevent damage to the pump because it collects. Generally, a carbon material is used for a susceptor that constitutes a part of a semiconductor manufacturing apparatus, but a CVD method is used when forming a thick SiC coating film to impart oxidation resistance. For example, when a uniform coating film of several hundred mμ is formed on a substrate having a complicated shape, cumulative operation for several tens of hours or more is usually required.

[0004] Here, the coating by the CVD method will be explained. As shown in FIG. 4, a CVD apparatus is usually equipped with a raw material gas cylinder 1 for storing a raw material gas, a reaction raw material supply device 2, and a sample S for reaction. Reactor 3
A particle removing device 4 having a filter element 5 incorporated therein, an exhaust device 6 having a vacuum pump 7 disposed therein, and an exhaust gas treatment device 8
Composed of and.

As a raw material gas for the raw material gas cylinder 1, a raw material gas containing a volatile metal hydride such as silane (SiH ₄ ) or a metal chloride, and a reaction auxiliary raw material gas such as hydrocarbon or ammonia are used. Further, in the reactor 3, the raw material gas supplied through the reaction raw material supply device 2 is reacted with the sample S at high temperature and under reduced pressure to generate ultrafine particles which are the components of the target coating film and vapor-deposit this. As a result, a coating film is formed on the surface of the sample S.

The particle removing device 4 is provided in order to avoid troubles due to abrasion damage or blockage of the vacuum pump 7 due to ceramic particles having high hardness generated by the CVD reaction by the built-in filtering element 5. 5 is a filter type that directly collects the particulates, or a cold trap type that cools the exhaust gas to an extremely low temperature and liquefies and condenses a part of it, especially the acidic components, and also captures the particulates. What is used.

The exhaust device 6 is for exhausting the reaction gas and adjusting the pressure in the reactor 3, and is described in the above-mentioned JP-A-60.
As in JP-A-13071, one or more vacuum pumps 7 are used. The exhaust gas treatment device 8 is provided to neutralize the strong acid component contained in the reaction gas component. The CVD apparatus configured as described above is a well-known type that has been widely adopted from a small-sized one for a laboratory to a commercial one.

By the way, as described above, it is general that either the filter type or the cold trap type is used for the filtration element 5 of the particle removing device 4, but in the case of the cold trap type, it is a sub reaction depending on the reaction. Since the generated acid gas and the like can be removed, there is an advantage that it is not necessary to provide the exhaust gas treatment device 8 provided after the exhaust system, or that a simple adsorption system such as activated carbon can be used. Further, in the case of the filter type, there is an advantage that the structure of the removing device is simple and an expensive low temperature liquefied gas unlike the cold trap type is unnecessary.

[0009]

However, when the cold trap type is adopted as the filtration element 5 of the above-mentioned conventional particle removing apparatus 4, a very low temperature liquefied gas such as liquid nitrogen is required as a coolant. Therefore, it is not suitable for a device that supplies a large amount of reaction gas for a long time that requires a large amount of cold trap type equipment,
At present, it is widely used in small devices for laboratories.

When the filter type is adopted,
Since the particles produced in the reaction and discharged from the reactor 3 are extremely fine particles, the filters used must also have very fine meshes, so clogging is severe, and operation is constantly stopped for maintenance. Continuous operation is not possible because the filter needs to be replaced.
Therefore, a large number of filters having a large area are required to realize a long-time operation, so that there is a drawback that the equipment cost is also high. This also influences the difficulty of introducing self-cleaning filters such as low-priced bag filters, for example, because the exhaust gas is in a severe environment with strong corrosiveness and the pressure fluctuation of the reaction system is disliked during operation. .

As described above, although the coating technology by the CVD method has been known for a long time, one of the reasons why the processing technology for large-sized members, that is, the development of large-sized equipment has not progressed even nowadays. Another problem is that it is difficult to treat the exhaust gas containing a large amount of fine particles, which is generated when the size is increased, as described above. The present invention
Exhaust from a CVD device that uses a filter that is simple and inexpensive as a single unit, and that can continuously remove particles that have the ability to process a long time or a large amount of exhaust without requiring a large amount of large area. It is intended to provide a dust removal method.

[0012]

According to the present invention, a raw material gas is supplied to a reactor to react with a sample, and the generated exhaust gas is evacuated while a filter element is used to remove dust.
In the exhaust gas dust removal method of the D apparatus, a filter having a coarse opening is used as the filter element, the filter elements are arranged in parallel, and the filter elements are operated independently one by one. There is provided a method for removing dust from exhaust gas of a CVD apparatus, which is characterized in that, when the filter element is switched to, the filter element in operation and the filter element in the switching destination are temporarily overlapped and operated, and then the filter element in the switching destination is independently operated.

The opening of the filter is for the particles to reach.
The roughness is preferably such that 60 to 98% can pass through.

[0014]

As a result of intensive experiments and research to solve the above problems, the present inventors have completed the present invention by obtaining the following knowledge. That is, a fixed filter with the simplest structure is desirable as a means for collecting very fine particles discharged from the reactor 3, and most of the arriving particles are collected without changing the opening of the filter as in the conventional case. Not very fine as can be, 60-98% of the reaching particles, preferably 80-
It is desirable to use a filter with a coarse opening that allows about 95% to pass (hereinafter referred to as a coarse filter). The number of filter elements to be installed may be one or two or more, in order to realize a continuous and long-term operation. When simply switching two or more filter elements to use, the filter element is switched immediately after the filter element in operation and the filter element at the switch destination are temporarily superposed and operated. To replace,
And so on.

Therefore, the particle removing apparatus 4A of the present invention as shown in FIG. 1 is adopted. That is, in the particle removing device 4A, the main exhaust pipe 10 provided between the reactor 3 and the exhaust device 6 is branched into the branch pipes 11 and 12, and the filtering element 5
_One coarse filter F ₁ and _one coarse filter F ₂ are attached to A and 5B, respectively, and stop valves V ₁₁ , V ₁₂ and V are provided before and after them.
₂₁ and V ₂₂ are attached, bypass pipes 13 and 14 are provided between the branch pipes 11 and 12, and stop valves V ₁₃ and V ₂₃ are attached, respectively.

The basic filter replacement or cleaning that accompanies the continuous operation of the particle removing apparatus 4A having the above-described structure is performed by the following switching procedure. i. When the filtration element 5A is in operation, the filtration element 5
When B is in the stopped state; (At this time, the stop valves V ₁₁ and V ₁₂ ;
Open, stop valves V ₁₃ , V ₂₁ , V ₂₂ , V ₂₃ ; closed) a. A check valve V _21, V ₂₃ open Russia. Then close the stop valve V ₁₁ . Open the stop valve V ₂₂ after a predetermined time d. Next, the stop valves V ₁₂ and V ₂₃ are closed (the filter element 5B is in the operating state and the filter element 5A is in the stopped state) e. Replace (or clean) the coarse filter F ₁ in the filtration element 5A ii.
When A is in a stopped state; (At this time, the stop valves V ₂₁ , V ₂₂ ;
Open, stop valves V ₁₁ , V ₁₂ , V ₁₃ , V ₂₃ ; closed) a. Open the stop valves V ₁₁ and V ₁₃ . Then close the stop valve V ₂₁ c. Open the stop valve V ₁₂ after a predetermined time. Next, the stop valves V ₂₂ and V ₁₃ are closed (the filter element 5A is in the operating state and the filter element 5B is in the stopped state) e. Replacing (or cleaning) the coarse filter F ₂ of the filtration element 5B. FIG. 2 shows the filter entry / exit for the usage time (exhaust gas treatment time) of the conventional fine filter (1200 mesh) and the coarse filter of the present invention (100 mesh). It shows the relationship of the differential pressure between them. When the conventional fine filter is used as shown by the curve A shown by the broken line in FIG. 2, the fine particles can be reliably collected, but they reach the limit in a short time and become blocked and unusable.

On the other hand, when the coarse filter of the present invention is adopted, as can be seen from the curve B shown by the solid line in FIG. 2, the particulate collection efficiency is initially low, but after a certain period of time, the conventional fine filter is used. Since the collection efficiency is comparable to that of the conventional filter and it takes a long time to block and become unusable compared to the fine filter, even a single coarse filter is several times to several tens of times larger than the conventional fine filter. Exhaust gas treatment can be performed for a long time twice as long.

Here, considering the difference between the two, in the case of the conventional fine filter, as shown schematically in FIG. 3 (a), when the reaching particle fills the opening, it is blocked or used. It becomes impossible. On the other hand, in the case of the coarse filter of the present invention, as shown in FIG. 3 (b), initially fine particles pass through the openings, but large particles or agglomerates of a plurality of particles are collected. When it fills the openings, the trapped large particle layer becomes a finer particle trapping layer, and unlike a fine filter that can trap particles only on a flat surface, it traps three-dimensional particles. A gathering is made. This principle is the same as that of filter bed filtration known as collection of fine particles in liquid.

If the coarse filter has too coarse an eye to collect 1% of the reaching particles, the above-mentioned layer for collecting finer particles is not sufficiently formed to exert its function. do not do. In addition, with a coarse filter that has a fine mesh that captures 40% or more of the particles that reach it, the time until actual blockage is short, and a significant improvement effect is obtained compared to conventional fine filters. Is difficult.

By configuring the particle removing apparatus 4A of the present invention as described above and using the switching procedure, it becomes possible to realize continuous treatment of a larger amount of exhaust gas for a longer period of time, and to use the coarse filter. It is possible to reliably collect fine particles from the start of the operation of. Further, since the capacity of one of the filtration elements used in the present invention is remarkably improved as compared with the conventional one, a sufficient effect can be obtained by the method of the present invention in which two filtration elements are switched and used. It is easily possible to develop to use three or more filtration elements.

[0021]

EXAMPLES Examples of the present invention will be specifically described below.
explain. [Example 1] In a CVD apparatus for SiC coating
As a raw material, SiCl _Four10 nl / min, C₃H₈5 nl / mi
n, H₂50nl / min is charged and the exhaust gas is the following three types
It processed with the filter.

As a result, it was confirmed that the coarse filter in the filter element of the present invention example greatly extended the continuous usable time by itself and greatly increased the total amount of trapped particles per unit filtration area of the filter. i. Conventional example 1 ・ Fine filter specifications Equivalent to 1200 mesh mesh Particle passage rate 0.5% (Particle collection rate 99.5%) Filtration area 0.31 m ²・ Exhaust gas treatment result Usable time 3 minutes Particle collection amount 95 g (Filtration Collection amount per area 0.31kg / m ² ) Particle passage amount 0.2g (0.2%) ii. Conventional example 2 ・ Fine filter specifications Equivalent to 800 mesh Particle passage rate 1% (Particle collection rate 99%) Filtration area 0.93 m ²・ Exhaust gas treatment result Usable time 15 minutes Particle collection amount 470 g (collection amount per filtration area 0.51 kg / m ² ) Particle passage amount 2 g (0.4%) iii. Examples of the present invention ・ Coarse filter specifications Equivalent to 100 meshes Particle passage rate 75% (Particle collection rate 25%) Filtration area 0.93 m ²・ Exhaust gas treatment result Usable time 125 minutes Particle collection amount 4114 g (Collection amount per filtration area 4.42 kg / m ² ) Particle passage amount 51 g (1.2%) ・ Collection status for each elapsed time; as shown in Table 1.

[0023]

[Table 1]

Example 2 The same CVD apparatus as in Example 1 was operated under the same conditions, and the exhaust gas from the CVD reactor 3 was continuously treated by switching between the two filtration elements 5A and 5B. The results are shown in Table 2. The coarse filters F ₁ and F ₂ used were the same as those used in the example of the present invention of iii of Example 1, and they were replaced with those that were cleaned each time they were switched.

[0025]

[Table 2]

According to this method, a large amount of untrapped particles pass through the coarse filter for 15 minutes at the beginning of use, but thereafter, on average, it is equal to or more than that when the conventional fine filter is used. With the above collection efficiency, it was confirmed that treatment for a continuous long time of, for example, 100 hours or more is possible (it can be said that there is practically no time limit).

[0027]

EFFECTS OF THE INVENTION In the operation of a general CVD method, as compared with a reaction process in which coating is actually performed, preparation such as sample setting or confidential test, purging, and temperature rise, and
The time and labor required for post-treatment such as sample removal or maintenance of equipment parts exposed to a temperature drop / purge / corrosive atmosphere is significantly greater in an apparatus having a particularly large reactor.

Nevertheless, in order to obtain a thick coating film with a large apparatus, the film thickness was increased by repeating the operation many times while interrupting the operation many times. The main reason for this is the large amount of particles removed in the CVD reaction.
As mentioned above, it was not possible to process for a long time because it is difficult to increase the size by the method using the conventional ultra-low temperature refrigerant, and it is not realistic because it is necessary to install a very large filter or a large number of fine filters. .

However, according to the coarse filter of the present invention,
Even though it is a very simple filter system, even a single unit has a much higher collection capacity than conventional ones, and by using a minimum of filter switching, it is possible to process a large amount of exhaust gas for a very long time, and continuous CVD -It has become possible to operate for a long time or a large reactor that generates a large amount of exhaust gas.

As a result, even when a thick film has to be obtained, it is not necessary to interrupt the operation in the middle of the process, so that the sample is contaminated during the process and the coating has a multi-layered structure. As well as solving the problem of not being able to perform as expected,
It has become possible to keep equipment costs and operation costs associated with the removal of a unit amount of particles extremely low.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a main part of a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between filter use time and filter differential pressure.

FIG. 3 is an explanatory view schematically showing the action of a particle capturing mechanism by a filter, in the case of (a) a conventional fine filter and (b) a coarse filter of the present invention.

FIG. 4 is a schematic diagram showing a configuration of a conventional example.

[Explanation of symbols]

1 raw material gas cylinder 2 reaction raw material supply device 3 reactor 4A particle removal device 5A, 5B filtration element 6 exhaust device 7 vacuum pump 8 exhaust gas treatment device 10 main exhaust pipe 11, 12 branch pipe 13, 14 bypass pipe S sample F ₁ , F ₂ Coarse filter V ₁₁ , V ₁₂ , V ₁₃ , V ₂₁ , V ₂₂ , V ₂₃ Stop valve

Claims (2)

[Claims] 1. An exhaust gas dust removal method for a CVD apparatus, wherein a raw material gas is supplied to a reactor to react with a sample, and the generated exhaust gas is vacuumed to remove dust using a filtration element. Using a rough filter,
The filtration elements are arranged in parallel and operated independently one by one, and when the filtration element in operation is switched to another filtration element, the filtration element in operation and the filtration element of the switching destination are temporarily overlapped. After driving
An exhaust gas dust removing method for a CVD apparatus, characterized in that a filter element at a switching destination is independently operated. 2. The aperture of the filter is 60 to 60
The exhaust gas dust removal method for a CVD apparatus according to claim 1, wherein the roughness is such that 98% can pass through.