Gas circulation system and CVD equipment

Abstract

This invention provides a gas circulation system and CVD apparatus that recover supply gas other than by-product gas from exhaust gas discharged from the reaction chamber of a CVD apparatus, and makes it usable for repeated chemical reactions. [Solution] A gas circulation system according to one embodiment is a gas circulation system that recovers two or more supply gases, including raw material gas, discharged from the reaction chamber of a CVD apparatus and returns them to the reaction chamber, comprising: a gas recovery device that separates by-product gases generated by chemical reactions from exhaust gas discharged from the reaction chamber and recovers two or more supply gases, including raw material gas, as recovered gases; a return pipe for returning the recovered gases to the reaction chamber; a gas analyzer provided in the return pipe or gas recovery device for analyzing the recovered gases; and a gas supply pipe that, based on the analysis results of the recovered gases by the gas analyzer, supplies the supply gases necessary for the chemical reaction into the reaction chamber if there is a shortage of supply gases necessary for the chemical reaction.

Description

Technical Field

[0001] The present disclosure relates to a gas circulation system and a CVD apparatus.

Background Art

[0002] Chemical vapor deposition (CVD) is a method of supplying a gas of a target substance (source gas) to a reaction chamber and forming the target substance on the surface of a substrate by a chemical reaction. Usually, an exhaust device such as an exhaust pump is connected to a reaction chamber in which a chemical reaction is performed in a CVD apparatus, and unnecessary gas is discharged (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Disposal of a huge amount of gas from the exhaust device has problems such as complexity of disposal, high cost, and environmental load. In the exhaust gas discharged from the reaction chamber of the CVD apparatus, in addition to a plurality of supply gases (unreacted source gas, carrier gas, etc.) supplied to the reaction chamber, by-product gas by-produced in the chemical reaction is mixed. Therefore, in order to repeatedly use the supply gas in the chemical reaction, it is necessary to remove the by-product gas from the exhaust gas. Further, since the source gas among the supply gases is consumed in the chemical reaction and the amount is reduced, even if the supply gas after removing the by-product gas from the exhaust gas is directly supplied to the reaction chamber of the CVD apparatus, it may not be usable in the chemical reaction. Therefore, an object of the present disclosure is to provide a gas circulation system and a CVD apparatus that can recover supply gas other than by-product gas from the exhaust gas discharged from the reaction chamber of the CVD apparatus and repeatedly use it in a chemical reaction.

Means for Solving the Problems

[0005] This disclosure relates, for example, to the following [1] to [5]. [1] A gas circulation system that recovers two or more supply gases, including raw material gases, discharged from the reaction chamber of a CVD apparatus and returns them to the reaction chamber, A gas recovery device that separates by-product gases generated by chemical reactions from exhaust gas discharged from the reaction chamber and recovers two or more supply gases, including the raw material gas, as recovered gases, A return pipe for returning the recovered gas to the reaction chamber, A gas analyzer is provided in the return piping or gas recovery device for analyzing the recovered gas, Based on the analysis results of the recovered gas by the gas analyzer, if there is insufficient supply gas necessary for the chemical reaction, a gas supply pipe is provided to supply the necessary supply gas for the chemical reaction into the reaction chamber. A gas circulation system equipped with this system. [2] The gas circulation system according to [1], further comprising a storage tank provided in the return piping for temporarily storing the recovered gas. [3] The gas circulation system according to [1] or [2], wherein the raw material gas is a raw material gas containing carbon. [4] The gas circulation system according to any one of [1] to [3], wherein the chemical reaction is a chemical reaction that produces carbon allotropes. [5] A reaction chamber to which two or more supply gases, including the raw material gas, An exhaust system for discharging gas from the reaction chamber, A gas circulation system as described in any of [1] to [4], A CVD apparatus equipped with the following features. [Effects of the Invention]

[0006] According to this disclosure, the supply gas supplied to the reaction chamber of a CVD apparatus can be repeatedly used in chemical reactions without being discarded. This makes it possible to reduce waste gas, lower costs related to supply gas and gas disposal, and reduce the environmental impact. [Brief explanation of the drawing]

[0007] [Figure 1] A schematic diagram showing a gas circulation system according to one embodiment of the present disclosure. [Figure 2] A schematic diagram showing an example of a CVD apparatus equipped with a gas circulation system according to one embodiment of this disclosure. [Figure 3] A diagram showing an example of gas supply via a gas supply pipe. [Modes for carrying out the invention]

[0008] An embodiment of the gas circulation system and CVD apparatus relating to this disclosure will be described below with reference to the drawings. Note that similar configurations may be denoted by the same reference numerals and their explanations may be omitted.

[0009] In this specification, expressions such as “equipment,” “includes,” or “possess” a component are not exclusive expressions that exclude the existence of other components.

[0010] Figure 1 is a schematic diagram showing a gas circulation system 10 according to one embodiment of the present disclosure. Figure 2 is a schematic diagram showing an example of a CVD apparatus 1 equipped with the gas circulation system 10 of Figure 1. In the CVD apparatus 1, the gas circulation system 10 recovers two or more supply gases, including the raw material gas contained in the exhaust gas discharged from the reaction chamber 2 via the exhaust device 3, and circulates the gas so that it can be repeatedly used in chemical reactions.

[0011] The reaction chamber 2 of the CVD apparatus 1 is where the chemical reaction takes place. In the reaction chamber 2, the raw material gas supplied as raw material for the CVD method is subjected to a chemical reaction using heat, plasma, light, etc., to generate the target substance on the substrate surface. The substrate is, for example, a catalytic substrate equipped with a catalyst layer. In the CVD process, two or more supply gases, including the raw material gas and carrier gases or auxiliary gases that play a role in uniformly diffusing the raw material gas and creating a stable reaction field, are supplied to reaction chamber 2. The supply gases may consist of two types, for example, the raw material gas and the carrier gas, or three types, the raw material gas, the carrier gas, and the auxiliary gas.

[0012] The raw material gas varies depending on the purpose of the chemical reaction. For example, when producing carbon allotropes through a chemical reaction, a raw material gas containing carbon is used as the raw material gas. Examples of the raw material gas include hydrocarbons, sulfur-containing organic gases, phosphorus-containing organic gases, carbon monoxide, and alcohols. Examples of hydrocarbons include alkane compounds such as methane and ethane, alkene compounds such as ethylene and butadiene, alkyne compounds such as acetylene, aryl hydrocarbon compounds such as benzene, toluene, and styrene, aromatic hydrocarbons having condensed rings such as indene, naphthalene, and phenanthrene, cycloalkane compounds such as cyclopropane and cyclohexane, cycloolefin compounds such as cyclopentene, and alicyclic hydrocarbon compounds having condensed rings such as steroids. Examples of alcohols include methanol and ethanol.

[0013] The carrier gas and the auxiliary action gas are, for example, helium, neon, argon, nitrogen, and hydrogen.

[0014] The target substance is, for example, an allotrope. Examples of allotropes include carbon allotropes such as carbon nanotubes (CNT), sulfur allotropes, or phosphorus allotropes. CNT can be either single-walled carbon nanotubes (SWNT) or multi-walled carbon nanotubes (MWNT). Multi-walled carbon nanotubes (MWNT) include double-walled carbon nanotubes (DWNT), and carbon nanotubes with 2 or more layers, for example, 2 to 20 layers, can be mentioned.

[0015] The exhaust device 3 discharges the gas in the reaction chamber 2. The exhaust device 3 is, for example, an exhaust pump. The exhaust gas discharged from the reaction chamber 2 contains the unreacted portion of the raw material gas supplied to the reaction chamber, the supply gas other than the raw material gas, and the by-product gas by-produced through the chemical reaction.

[0016] The gas circulation system 10 includes a gas recovery device 11, a gas discharge pipe P1 connecting the gas recovery device 11 and the exhaust device 3, a return pipe P2 connecting the gas recovery device 11 and the reactor 2, a gas analyzer 12 provided in the return pipe P2 or the gas recovery device 11, and a gas supply pipe 13. In FIGS. 1 and 2, the gas analyzer 12 is provided in the return pipe P2. However, by providing the gas analyzer 12 in the gas recovery device 11, the recovered gas may be analyzed before being supplied to the return pipe P2.

[0017] The gas recovery device 11 separates the by-product gas by-produced by a chemical reaction from the exhaust gas discharged from the reaction chamber 2 and recovers two or more kinds of supply gases including the raw material gas. In the present invention, two or more kinds of supply gases including the raw material gas recovered by separating the by-product gas by-produced by a chemical reaction from the exhaust gas are also referred to as recovered gas. In the gas recovery device 11, a part of the supply gas may be included in the separated by-product gas. The gas recovery device 11 is connected to the exhaust device 3 by the gas discharge pipe P1, and the exhaust gas discharged from the reaction chamber 2 is supplied to the gas recovery device 11 through the gas discharge pipe P1. For the gas recovery device 11, for example, a gas purification filter capable of separating and removing the by-product gas by adsorption can be adopted.

[0018] The return pipe P2 connects the gas recovery device 11 and the reactor 2 and returns the recovered gas recovered by the gas recovery device 11 to the reaction chamber 2. Thereby, two or more kinds of supply gases including the raw material gas among the exhaust gases discharged from the reaction chamber 2 are repeatedly used for the chemical reaction as the recovered gas. The return pipe P2 is, for example, one pipe or two or more pipes for transferring the recovered gas respectively.

[0019] The gas analyzer 12 is installed in the return pipe P2 or the gas recovery device 11 and analyzes the recovered gas. For the analysis of the recovered gas, a gas analyzer capable of qualitative and quantitative analysis (component ratio, amount of each component, etc.) of the components contained in the recovered gas (raw material gas, carrier gas, etc.) can be used. Examples of analytical methods include mass spectrometry. The gas analyzer 12 outputs the analysis results of the recovered gas to the gas supply pipe 13.

[0020] Based on the analysis results of the recovered gas by the gas analyzer 12, the gas supply pipe 13 supplies the necessary supply gas to the reaction chamber 2 if there is a shortage of the supply gas required for the chemical reaction. The gas supply pipe 13 is composed of two or more supply pipes for each type of supply gas, for example, as shown in Figure 2. The gas supply pipe 13 may also include gas flow control equipment such as a mass flow controller (gas mass flow meter). For example, the analysis results of the recovered gas determine whether a chemical reaction can be carried out. If there is a shortage of supply gas necessary for the chemical reaction, the type and amount of the missing supply gas are determined, and the determined supply gas is supplied to the reaction chamber 2 from the gas supply pipe 13. For example, the type and amount of supply gas to be supplied to the reaction chamber 2 from the gas supply pipe 13 is determined based on information (ratio, amount, etc.) of the composition of two or more supply gases, including the raw material gas necessary for the chemical reaction of the target substance. Generally, in the CVD method, the amount of raw material gas and other components of the supply gas supplied to the reaction chamber 2 is reduced as they are consumed in the chemical reaction, making it difficult to use the recovered gas in the chemical reaction with its original composition and quantity. Therefore, the gas supply pipe 13 supplies the supply gas that is insufficient for the chemical reaction, resulting in the predetermined gas composition and amount required for the chemical reaction, thereby enabling the repeated production of the target substance.

[0021] On the other hand, if the analysis results of the recovered gas indicate that the chemical reaction can be carried out, the gas supply pipe 13 does not supply gas into the reaction chamber 2.

[0022] The supply gas supplied to the reaction chamber 2 by the gas supply pipe 13 may be one type of supply gas or two or more types. For example, the supply gas supplied to the reaction chamber 2 by the gas supply pipe 13 may be one type of raw material gas, two types of raw material gas and carrier gas, or three types of raw material gas, carrier gas and auxiliary gas.

[0023] The gas circulation system 10 may include a storage tank (not shown) for temporarily storing the recovered gas recovered by the gas recovery device 11. The storage tank is located in the return piping P2 and stores the recovered gas before or after analysis. By providing a storage tank, it is possible to avoid discarding the supply gas when changing substrates in the reaction chamber 2.

[0024] Next, using Figure 3 as an example, we will explain the gas circulation method using the gas circulation system according to the embodiment and the method for repeatedly producing the target substance. In the example shown in Figure 3, three types of supply gases—raw material gas A, carrier gas B, and auxiliary working gas C—are supplied to reaction chamber 2. After the chemical reaction, exhaust gas is discharged from reaction chamber 2 via exhaust system 3. The exhaust gas contains unreacted raw material gas A, carrier gas B, and auxiliary working gas C, as well as by-product gases generated by the chemical reaction. In Figure 3, raw material gas A is denoted as gas A, carrier gas B as gas B, and auxiliary working gas C as gas C. The exhaust gas is supplied to the gas recovery unit 11 through the gas discharge pipe P1. The gas recovery unit 11 separates and removes by-product gases from the exhaust gas to obtain a recovered gas containing raw material gas A, carrier gas B, and auxiliary working gas C. The recovered gas, i.e., the recovered raw material gas A, carrier gas B, and auxiliary working gas C, is returned to the reaction chamber 2 through the return pipe P2. A gas analyzer 12 is installed in the return pipe P2, and the gas analyzer 12 analyzes the components of the recovered gas. If the gas analysis device 12 analyzes the composition and quantity of each component of the recovered gas and finds that there is insufficient supply gas for the chemical reaction, the gas supply pipe 13 will supply the necessary supply gas for the chemical reaction into the reaction chamber 2. Figure 3 shows an example where the composition and quantity of gas required for the chemical reaction in the reaction chamber 2 are 100 units of raw material gas A, 1000 units of carrier gas B, and 10000 units of auxiliary gas C. In the example in Figure 3, the exhaust gas consists of 60 units of raw material gas A, 900 units of carrier gas B, and 10000 units of auxiliary gas C, and also contains by-product gas. The gas recovery device 11 recovers the by-product gas, and at the same time, some of the supply gas is also recovered. The composition and quantity of the gases constituting the recovered gas are 58 units of raw material gas A, 890 units of carrier gas B, and 9500 units of auxiliary gas C. Since the gas, composition, and quantity required for the chemical reaction in reaction chamber 2 differ from those of the recovered gas, an example is shown in which 42 units of raw material gas A, 110 units of carrier gas B, and 500 units of auxiliary gas C are supplied to reaction chamber 2 from the gas supply pipe 13 to adjust the composition and quantity of the gases. As a result, the supply gas with the predetermined gas composition required for the chemical reaction is supplied into reaction chamber 2, allowing the chemical reaction to proceed in reaction chamber 2 and enabling the repeated production of the target substance.

[0025] As described above, the gas circulation system 10 according to this embodiment circulates supply gases, such as raw material gases, which are conventionally discarded as exhaust gases, making them available for repeated chemical reactions. Therefore, the CVD apparatus 1 equipped with the gas circulation system 10 can significantly reduce waste gas, thereby alleviating the burden, costs, and environmental impact related to gas disposal. It also enables a reduction in the cost of supply gases.

[0026] The embodiments disclosed above are illustrative in all respects and are not restrictive. The above embodiments can be carried out in a variety of other forms and may be omitted, substituted, or modified without departing from the spirit of the invention. [Explanation of Symbols]

[0027] 1 CVD equipment 2. Reaction Chamber 3. Exhaust system 10 Gas circulation system 11. Gas recovery device 12 Gas analyzer 13 Gas supply pipe P1 Gas discharge piping P2 return piping

Claims

1. A gas circulation system that recovers two or more supply gases, including raw material gases discharged from the reaction chamber of a CVD apparatus, and returns them to the reaction chamber, A gas recovery device that separates by-product gases generated by chemical reactions from exhaust gas discharged from the reaction chamber and recovers two or more supply gases, including the raw material gas, as recovered gases, A return pipe for returning the recovered gas to the reaction chamber, A gas analyzer is provided in the return piping or gas recovery device for analyzing the recovered gas, Based on the analysis results of the recovered gas by the gas analyzer, if there is insufficient supply gas necessary for the chemical reaction, a gas supply pipe is provided to supply the necessary supply gas for the chemical reaction into the reaction chamber. A gas circulation system equipped with this system.

2. The gas circulation system according to claim 1, further comprising a storage tank provided in the return piping for temporarily storing the recovered gas.

3. The gas circulation system according to claim 1, wherein the raw material gas is a raw material gas containing carbon.

4. The gas circulation system according to claim 1, wherein the chemical reaction is a chemical reaction that produces carbon allotropes.

5. A reaction chamber to which two or more supply gases, including the raw material gas, An exhaust system for discharging gas from the reaction chamber, The gas circulation system according to claim 1, A CVD apparatus equipped with the following features.

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