JPH0722127B2 - Method for purifying reaction / treatment device and purification of gas phase substance for reaction / treatment, and reaction / treatment device - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for removing and cleaning contaminants in a reaction / treatment device, as well as a reaction / treatment device equipped with a device for carrying out this method. In particular, it relates to decomposing pollutants, reacting the decomposed products with a reaction gas phase substance to form a solid phase substance, and then removing the solid phase substance.

BACKGROUND OF THE INVENTION When manufacturing a thin film using a chemical reaction or performing heat treatment or reaction treatment, it is desired to reduce the amount of undesired impurities in the thin film as much as possible. However, in the past, the amount of these undesired impurities was considerably large and the quality of the product was deteriorated. For example, FIG. 1 shows the amount of impurities in the film when an amorphous silicon thin film is formed on a glass substrate by the plasma decomposition method of monosilane. As can be seen from FIG. 1, carbon (C),
It can be seen that impurities such as oxygen (O) and nitrogen (N) are mixed deep inside the film. The reason for mixing undesired impurities is (1) device (reaction / processing container,
(2) Desorption of gas molecules adsorbed in the apparatus, (3) Impurities contained in the reaction / processing raw material gas, etc. are considered. Further, when the apparatus has a vacuum exhaust system, the droplets or vapor of vacuum oil that diffuses back from a pump or the like that constitutes the vacuum exhaust system becomes contaminants. When the pump is a high-vacuum pump such as a turbo molecular pump or an ion pump, naturally no contaminant is generated. However, the pressure when manufacturing or processing semiconductor thin films by chemical reaction ranges from atmospheric pressure to vacuum, but is mainly 10 to 10 ³ Pa, and the exhaust system for obtaining the vacuum degree in this range is an oil system. A vacuum pump such as a diffusion pump or an oil rotary pump is generally used. Therefore, the inside of the device is extremely contaminated by the vacuum exhaust system. About 0.1% evaporates. Various gases may be dissolved in this vacuum oil.

It is known that the adsorbed gas molecules in the item (2) can be desorbed by raising the temperature of the apparatus and can be removed to some extent by exhausting the apparatus, but it is not preferable to raise the temperature of the entire apparatus.

As a countermeasure against these problems, JP-A-57-118015 discloses a method using a gas adsorbent, but it is not a practical method. Further, Japanese Patent Application Laid-Open No. 57-78131 describes a method of heating a raw material gas to a high temperature to reach a substrate, but it is not practical because it consumes a large amount of the raw material gas.

[Object of the Invention]

An object of the present invention is to clean the inside of a device for removing contaminants existing or generated in the reaction / treatment device and causing impurities other than desired impurities, and a raw material gas for the reaction / treatment. The object of the present invention is to provide a method for removing impurities for purification and a reaction / treatment device to which these methods are applied.

[Outline of Invention]

The present inventor has found that the main constituent elements of pollutants and impurities existing in the reaction / treatment device and in the reaction / treatment raw material gas are carbon (C), oxygen (O), fluorine (F) and nitrogen ( N)
And that these elements are oxidizable elements such as iron (Fe), silicon (Si), zinc (Zn),
Focusing on bonding with titanium (Ti), molybdenum (Mo), tin (Sn), etc., and also paying attention to the fact that the raw material gas for reaction and processing is composed of or contains these elements. C, O, F and N produced by decomposing the contaminants
Inventing a method for cleaning the inside of the apparatus by combining the above-mentioned raw material gas with an element that is likely to be oxidized and similarly produced by oxidation to form a solid phase substance. That is, the solid phase substance has a lower vapor pressure than the gas phase and liquid phase substances, and cleans the atmosphere in the apparatus. Further, when the apparatus has a vacuum exhaust system, the solid phase substance which is fine powder may be discharged out of the apparatus together with the exhaust flow.

Contaminants contained in the reaction / treatment raw material gas are similarly solidified and purified.

Typical thin films produced using such a reaction apparatus are SiO ₂ , Si ₃ N ₄ , and amorphous silicon, but the reaction raw material gas for producing these is monosilane such as disilane. Higher order silane or chlorosilane. These silanes are decomposed by heating, light irradiation, electric discharge, etc. to generate silicon (Si).

On the other hand, when contaminants inside the equipment, especially vacuum oil, are decomposed by heating, light irradiation, discharge, etc., elements such as C, O, N, F are generated, and these combine with Si to form SiO ₂ , SiC. , Becomes a solid phase substance such as Si ₃ N ₄ . The vapor pressure of these solid-phase substances is extremely small and does not affect the atmosphere inside the device.

Further, when the decomposition product of silane becomes a polycrystal-like silicon cluster, the mist or vapor of vacuum oil is adsorbed to the silicon cluster and is easily discharged to the outside.

As a result, the amount of impurities in the silicon-based thin film such as amorphous silicon and Si ₃ N ₄ produced by using the method or apparatus of the present invention was significantly reduced.

The present invention can also be applied to heat treatment of a sample. For example, when performing hydrogen treatment or heat treatment in an inert gas, if the processing gas and silane are introduced at the same time and then the silane is decomposed, contaminants in the processing equipment are made into fine powder and the atmosphere in the equipment is cleaned. Can be converted.

Needless to say, the vacuum oil and other contaminants adsorbed on the walls of the apparatus are easily desorbed from the walls and decomposed by heating.

As described above, the raw material gas used for forming and processing the thin film should be as pure as possible, but it may be a contaminant existing in the gas inflow system before it reaches the substrate through the gas inflow system pipes and valves. The purity is considerably reduced. The technique of the present invention can also be applied to purifying the raw material gas thus contaminated in the gas inflow system of the apparatus before reaching the substrate. For example, when the reaction raw material gas is a silane such as monosilane or disilane, if this gas is decomposed before reaching the substrate, it will react with the decomposed products of the contaminants in the decomposed raw material gas and solidify. Since the phases are phased, contaminants can be removed from the raw material gas.

Although monosilane has been described as an example above, there are gas phase substances such as higher-order silane-based gases such as disilane, silicon compounds such as silicon tetrafluoride, and germanium compounds such as germane. There are tin compounds such as tin tetrachloride and aluminum compounds such as trimethylaluminum that can be fluidized by oxidization or reaction such as gallium, molybdenum, antimony, tellurium, titanium, tungsten, zinc, tantalum, magnesium and lithium. It is also applicable to the case where a halogenide or an organometallic compound of an element that easily reacts is used as a reaction or treatment gas, and a mixture thereof may be used.

Further, it is more effective when these source gases serve as a catalyst for decomposing contaminants and impurities and for promoting the reaction, and a substance serving as a catalyst may be mixed in the source gas.

As a method for decomposing contaminants, heating, light irradiation, discharge, ion beam irradiation, etc. are effective, but in some cases, it is more effective to use them together. Plasma discharge and corona discharge were particularly effective when discharge was used. As a light source used for light irradiation, a mercury lamp, an ultraviolet lamp, an argon laser, an excimer laser, etc., which directly decomposes, or a carbon dioxide gas laser, which thermally decomposes, can be applied.

In addition, these decomposition mechanism and decomposition device are
Installed in all or part of the reaction / processing source gas inflow system and in the vacuum exhaust system. If installed in the source gas inflow system and vacuum exhaust system, install as close to the reaction / processing container as possible. However, it goes without saying that the effect of implementing the present invention is greater.

Example of Invention

 Examples of the present invention will be described below.

Example 1 will be described with reference to FIG.

FIG. 2 shows a silicon vapor phase growth apparatus using an atmospheric pressure CVD method.
A heater 10 for thermal decomposition is provided in the gas inflow system. The substrate 9 in the reaction vessel 1 is placed on the induction table 13 and is induction-heated by the high frequency power source 12.

A mixed vaporization of silicon tetrachloride and hydrogen was introduced from the reaction gas inlet 8, the high frequency power supply 14 was operated to grow a crystal film on the substrate 9, and the oxygen concentration in the film was measured.
It was 10 ¹⁸ cm ^-3 . Further, the oxygen concentration in the film when the high frequency power source 14 was not operated was 5 × 10 ¹⁹ cm ⁻³ , so that the effect of the present invention was confirmed.

Example 2 FIG. 3 shows a plasma CVD apparatus for producing an amorphous silicon film by using monosilane as a raw material reaction gas. This apparatus is composed of a reaction container 1 having a high frequency electrode 2, a turbo molecular pump 3, a mechanical booster pump 4, and a rotary pump 5, which constitute a vacuum exhaust system. Further, a vacuum switching valve 6 and a pressure adjusting valve 7 are provided so that the gas can flow in through a reaction gas inflow hole 8 such as monosilane. Further, this apparatus is provided with a pre-stage heater 20, a reaction vessel heater 21, and a post-stage heater 22 for decomposing substances and reaction gases that contaminate the inside of the vacuum apparatus.

Next, using this apparatus, amorphous silicon films were formed with and without the use of heaters 20, 21, and 22, and the amounts of impurities in the films were compared.

First, the film forming process will be described. Substrate 9 in reactor 1
And was heated to 250 ° C. Also rotary pump 5
Also, the mechanical booster pump 4 is activated to bring the pressure inside the reaction vessel 1 to 10 ^-1 Pa, and then the turbo molecular pump 3 is switched to reduce the pressure for 30 minutes to bring the pressure to 1 × 10 ^-3.
I chose Pa. Next, the vacuum system switching valve 6 was switched again to form a mechanical booster pump, and 50 S CCM of monosilane was introduced as a reaction gas, and the pressure in the reaction vessel 2 was adjusted to 90 Pa by the pressure adjusting valve 7. In this state, high-frequency power of 10 W was applied to the high-frequency electrode 2 for 40 minutes to form an amorphous silicon film (Sample A) having a film thickness of 1 μm on the substrate 9.

Next, in the above method, the heaters 20, 21 and 22 were heated to 400 ° C. until the film formation was completed after the turbo molecular pump 3 was operated to form an amorphous silicon film (Sample B). .

The amounts of carbon, oxygen, and nitrogen contained as impurities in Sample A and Sample B were measured by the IMA method. The results are shown in Table 1.
As shown in FIG. 5, it was found that the impurity amount of the sample B was 1/10 or less of that of the sample A, and the effect of using the heaters 20, 21 and 22 was confirmed.

Similar results were obtained when silicon tetrafluoride was used as the reaction gas.

Needless to say, the effect of the present invention can be obtained by operating only one or two of the three heaters 20, 21, and 22.

Example 3 will be described with reference to FIG.

The plasma CVD apparatus shown in FIG.
0, a reaction / processing container light irradiation mechanism 31 and a post-stage light irradiation mechanism 32 are provided.

The present apparatus was operated in the same process as that described in Example 1, and an amorphous silicon film (sample B) formed by operating the light irradiation mechanism and an amorphous silicon film (sample A) formed without operating the film were formed. As a result of measuring the amount of impurities therein, the same results as in Table 1 were obtained, and the effect of light irradiation was confirmed.

Example 4 will be described with reference to FIG.

The plasma CVD apparatus shown in FIG.
It is provided with a discharge mechanism 41 in the reaction / treatment vessel and a post-stage discharge mechanism 42.

This apparatus was operated in the same process as in Example 1, and an amorphous silicon film (sample B) formed by operating the discharge mechanism and an amorphous silicon film (sample A) formed without operating When the amount of impurities was measured, the same results as in Table 1 were obtained, and the effect of discharge could be confirmed.

〔The invention's effect〕

According to the present invention, the inside of the reaction / treatment device is cleaned,
By purifying the raw material gas for processing, it is possible to provide a thin film having extremely few impurities. Therefore, it is possible to realize a thin film material having excellent characteristics and a high performance element or device using the thin film material.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of the amount of impurities contained in the amorphous silicon thin film, and FIG. 2 is the atmospheric pressure used in Example 1.
Block diagram of silicon vapor phase growth apparatus by CVD method, No. 3
FIG. 4 is a block diagram of the plasma CVD apparatus used in Example 2, FIG. 4 is a block diagram of the plasma CVD apparatus used in Example 3, and FIG. 5 is a block diagram of the plasma CVD apparatus used in Example 4. Is. 1 ... Reaction / treatment container, 2 ... High frequency electrode, 3 ... Turbo molecular pump, 4 ... Mechanical booster pump, 5
...... Rotary pump, 6 ... Vacuum system switching valve, 7
...... Pressure control valve, 8 …… Raw material gas inlet, 9 …… Substrate, 10 …… Heater in raw material gas inflow system, 11 …… Reaction ・
Induction heating coil in processing container, 12 …… High frequency power source (for induction heating), 13 …… Induction stand, 14 …… High frequency power source (plasma)
(For CVD), 20 …… Preheater heater (for heating in the source gas inflow system), 21 …… Reaction / processing container heat heater, 22 …… Post heating heater (for vacuum exhaust system heating), 30 …… Previous stage Light irradiation mechanism, 31 …… Reaction / treatment vessel light irradiation mechanism, 32 …… Post-stage light irradiation mechanism, 40 …… Pre-stage discharge mechanism, 41 …… Reaction / treatment vessel discharge mechanism, 42 …… Post-stage discharge mechanism.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01L 21/324 Z 8617-4M

Claims (20)

[Claims] 1. A substance polluting the inside of a reaction / treatment device (hereinafter,
(Hereinafter referred to as "pollutant") and / or an element and / or a decomposed product produced by decomposing the contaminated material reacts with an element and / or a decomposed product produced by decomposing a gas phase substance for reaction / treatment and solid phase. A method for cleaning the inside of a reaction / treatment device, which is characterized by 2. An element and / or a decomposition product produced by decomposing the reaction / treatment gas phase substance decomposes undesired impurities contained in the reaction / treatment gas phase substance and / or the impurities. A method for purifying a gas phase substance for reaction / treatment, which comprises reacting with an element and / or a decomposition product generated by the above and solidifying. 3. A reaction / treatment device having at least a reaction / treatment container and a reaction gas-phase substance inflow system, wherein the reaction / treatment device is present in the reaction / treatment container and / or in the reaction gas-phase substance inflow system. Substances that contaminate the inside of the processing equipment (hereinafter,
A reaction / treatment device having a decomposition mechanism for decomposing a pollutant) and / or a reaction gas phase substance. 4. The method for cleaning the inside of the reaction / treatment device according to claim 1, wherein the contaminant and / or the gas phase substance for reaction is decomposed by heating. 5. The method for cleaning the inside of a reaction / treatment apparatus according to claim 1, wherein the contaminant and / or the gas phase substance for reaction is decomposed by light irradiation. 6. The method for cleaning a reaction / treatment apparatus according to claim 1, wherein the contaminants and / or the reaction gas phase substance is decomposed by electric discharge. 7. The method for cleaning a reaction / treatment apparatus according to claim 1, wherein the reaction gas phase substance is a silane-based substance. 8. The method for cleaning a reaction / treatment device according to claim 1, wherein the gas phase substance for reaction is a substance containing a silane-based substance. 9. The method for cleaning a reaction / treatment device according to claim 7, wherein the silane-based substance is monosilane and / or disilane and / or trisilane. 10. The method for purifying a reaction / treatment gas phase substance according to claim 2, wherein the reaction / treatment gas phase substance is decomposed by heating. 11. The method for purifying a reaction / treatment gas phase substance according to claim 2, wherein the decomposition of the reaction / treatment gas phase substance is carried out by irradiation with light. 12. The method for purifying a gas phase substance for reaction / treatment according to claim 2, wherein the gas phase substance for reaction / treatment is decomposed by electric discharge. 13. The method for purifying a reaction / treatment gas phase substance according to claim 2, wherein the reaction / treatment gas phase substance is a silane-based substance. 14. The method for purifying a reaction / treatment gas phase substance according to claim 2, wherein the reaction / treatment gas phase substance is a substance containing a silane-based substance. 15. The method for purifying a reaction / treatment gas phase substance according to claim 2, wherein the reaction / treatment gas phase substance is monosilane and / or disilane and / or trisilane. 16. The reaction / treatment device according to claim 3, wherein the reaction / treatment device has a vacuum exhaust system.
Processing equipment. 17. The reaction / treatment device according to claim 3, further comprising a decomposition mechanism for decomposing the pollutant and / or the gas phase substance for reaction / treatment. 18. The reaction / treatment device according to claim 17, wherein the decomposition mechanism is a heating device. 19. The reaction / treatment device according to claim 17, wherein the decomposition mechanism is a light irradiation device. 20. The reaction / treatment device according to claim 17, wherein the decomposition mechanism is a discharge device.