Purification method and application of electronic-grade trimethylsilane

Abstract

The invention belongs to the technical field of electronic-grade trimethylsilane, and particularly relates to a purification method and application of electronic-grade trimethylsilane. Comprising the following steps that S1, a trimethylsilane raw material and diluent gas are mixed and introduced into an adsorption tower, components with the boiling point similar to that of trimethylsilane are removed, a trimethylsilane crude product is obtained, and filler of the adsorption tower is a mixture of activated carbon and metal oxide; and S2, introducing the trimethylsilane crude product into a light component removal tower to remove light components, and then introducing the trimethylsilane crude product into a heavy component removal tower to remove heavy components so as to obtain the electronic-grade trimethylsilane. Impurity components such as dimethylsilane in the trimethylsilane raw material, which are similar to the boiling point of the trimethylsilane, are reduced in the content of the components such as the dimethylsilane through the adsorption tower. Diluting gas is added before the trimethylsilane raw material is introduced into the adsorption tower, so that the heat release effect during adsorption is reduced, and disproportionation reaction is avoided. Meanwhile, the added metal oxide in the filler has a synergistic effect with the diluted gas, so that the adsorption heat release is reduced.

Description

Technical Field

[0001] The present application belongs to the technical field of electronic-grade trimethylsilane, and specifically relates to a purification method and application of electronic-grade trimethylsilane. Background Art

[0002] Electronic special gases are widely used in key processes of integrated circuits, such as etching, epitaxy, lithography, chemical vapor deposition and atomic layer deposition. They are the core raw materials of the entire electronic industry system. According to the integrated circuit manufacturing process, electronic special gases can be divided into six categories: film-forming gas, lithography gas, etching and cleaning gas, ion implantation gas, precursor and bulk gas. Trimethylsilane (3MS) is an organic silicon compound with a chemical formula of (CH3)3SiH. It is a colorless, volatile gas with special chemical properties and application areas. 3MS is widely used in the semiconductor industry, mainly used in chemical vapor deposition (CVD) processes. 3MS can be used as a precursor gas in the CVD process to deposit silicon thin films or silicon compound thin films on the surface of materials. For example, the Chinese patent with announcement number CN102403220A provides a SiCN diffusion barrier preparation process, which adopts a plasma-assisted chemical vapor deposition method, and the reaction gases are trimethylsilane, ammonia and silane to deposit and form the SiCN diffusion barrier. However, trimethylsilane, as a precursor gas in the CVD process, requires a higher purity, so many scholars have tried to prepare electronic-grade trimethylsilane.

[0003] The common method for manufacturing trimethylsilane is usually to reduce trimethylchlorosilane ((CH3)3SiCl) using an appropriate hydrogenating agent. The Chinese patent with the announcement number CN116082380A discloses a method for preparing electronic-grade trimethylsilane, which uses trimethylchlorosilane as a raw material and is finally purified to obtain electronic grade through catalytic hydrogenation reaction. The Chinese patent with the announcement number CN117567496A discloses a method for preparing high-purity trimethylsilane, which includes introducing hydrogen and trimethylchlorosilane into a reactor equipped with a catalyst at a ratio of 2 to 6:1 to obtain a mixed gas; buffering the mixed gas and then washing it with alkali to obtain crude trimethylsilane; and subjecting the crude trimethylsilane to the processes of de-heavy, de-light and adsorption in sequence to obtain high-purity trimethylsilane. In these two synthesis methods, trimethylchlorosilane, which is a common raw material, is usually mixed with impurities such as methyltrichlorosilane (CH3SiCl3), dimethyldichlorosilane ((CH3)2SiCl2), and silicon tetrachloride (SiCl4). These impurities react with hydrogenating agents to generate corresponding silanes, namely methylsilane (CH3SiH3), dimethylsilane ((CH3)2SiH2) or silane (SiH4), which are mixed into trimethylsilane. In particular, the generated dimethylsilane has a boiling point close to that of trimethylsilane, making subsequent purification difficult.

[0004] In summary, the existing preparation and purification of trimethylsilane has problems such as low purity and complex purification process, and it is urgent to propose a purification method and application of electronic grade trimethylsilane. Summary of the invention

[0005] In view of the problems of low purity and complicated purification process in the preparation and purification of trimethylsilane in the prior art, the present application provides a purification method and application of electronic grade trimethylsilane.

[0006] The technical solution of this application is as follows:

[0007] On the one hand, the present application provides a method for purifying electronic grade trimethylsilane, comprising the following steps: Step S1. Mixing a trimethylsilane raw material and a diluent gas and passing them into an adsorption tower, removing dimethylsilane at a temperature of 25 to 32° C. and a pressure of 220 to 230 KPa to obtain a crude trimethylsilane product, wherein the filler of the adsorption tower is a mixture of activated carbon and metal oxides;

[0008] Step S2: The crude trimethylsilane is passed into a light removal tower to remove light components, and then into a heavy removal tower to remove heavy components to obtain electronic grade trimethylsilane.

[0009] Preferably, in step S1, the metal oxide is doped into the activated carbon, the mass ratio of the activated carbon to the metal oxide is 10:1 to 10:3, the metal oxide is aluminum oxide and iron oxide, and the mass ratio of aluminum oxide to iron oxide is 1:1.

[0010] Preferably, in step S1, the dilution gas is any one of nitrogen or helium, and the volume ratio of trimethylsilane to the dilution gas is 3:1 to 3:2.

[0011] Preferably, the purity of the trimethylsilane raw material in step S1 is ≥99%.

[0012] Preferably, the conditions for removing light components in step S2 are: temperature of 16-22° C., pressure of 200-210 Kpa, and reflux ratio of 6:1-3:1.

[0013] Preferably, the conditions for removing the heavy components in step S2 are: temperature of 16-22° C., pressure of 190-200 Kpa, and reflux ratio of 6:1-3:1.

[0014] On the other hand, the present application provides an application of electronic grade trimethylsilane for use as a precursor gas in a chemical vapor deposition process.

[0015] The beneficial effects of this application are as follows:

[0016] Dimethylsilane and other impurity components in the trimethylsilane raw material with a boiling point close to that of trimethylsilane, where the boiling point of trimethylsilane is 1.7°C and the boiling point of dimethylsilane is -20°C, are removed by the adsorption materials (activated carbon, aluminum oxide and iron oxide) in the adsorption tower, which initially reduces the content of dimethylsilane and other components, not only providing convenience for subsequent light and heavy removal, but also further improving the purity of trimethylsilane. The activated carbon adsorption material has a rich microporous structure and a large specific surface area, and can adsorb a large number of gas molecules. When the trimethylsilane raw material gas passes through the adsorption tower, impurity molecules such as dimethylsilane with a boiling point close to that of trimethylsilane will be adsorbed on the surface of the adsorption material due to physical adsorption.

[0017] In the present application, a diluent gas (nitrogen or helium) is added to the trimethylsilane raw material before it is introduced into the adsorption tower, which can dilute the concentration of the trimethylsilane raw material, reduce the exothermic effect during adsorption, avoid the disproportionation reaction, generate isomers, and reduce the purity of trimethylsilane. At the same time, the ratio of activated carbon and metal oxides (iron oxide and aluminum oxide) is reasonably controlled in the present application to reduce the exothermic heat during adsorption, which can play a synergistic role with the diluent gas, reduce the exothermic heat of adsorption, and avoid the disproportionation reaction of trimethylsilane.

[0018] The trimethylsilane raw material of the present application is subjected to adsorption and then undergoes two-stage distillation reactions of light removal and heavy removal to obtain electronic grade trimethylsilane. DETAILED DESCRIPTION

[0019] In order to further explain the technical means and effects adopted by the present application to achieve the predetermined application purpose, a clear and complete description is given below in conjunction with the preferred embodiments.

[0020] Example 1

[0021] This embodiment provides a method for purifying electronic grade trimethylsilane, which is as follows:

[0022] Step S1. The trimethylsilane raw material with a purity of 99% from the steel cylinder and the diluent gas nitrogen are introduced into the buffer tank in a volume ratio of 3:1.5 for mixing. The diluent gas is used to dilute the trimethylsilane raw material, reduce the exothermic effect during adsorption, avoid the disproportionation reaction, and generate isomers. After being evenly mixed, the adsorption tower is introduced. Under the action of the adsorption tower filler, the temperature in the adsorption tower is controlled to be 30°C and the pressure is 225KPa. Impurity components such as dimethylsilane with a boiling point close to trimethylsilane are removed to obtain a crude trimethylsilane product. The main component of the filler of the adsorption tower is activated carbon. The activated carbon adsorption material has a rich microporous structure and a large specific surface area, and can adsorb a large number of gas molecules. The mixture of iron oxide and aluminum oxide is added to the activated carbon by doping. Impurity molecules such as dimethylsilane with a boiling point close to trimethylsilane will be adsorbed on the surface of the adsorption material due to physical adsorption. The filler in the adsorption tower also contains a small amount of iron oxide and aluminum oxide in order to reduce the heat released during adsorption. The mass ratio of activated carbon to the mixture of iron oxide and aluminum oxide is 10:2, and the mass ratio of aluminum oxide to iron oxide is 1:1.

[0023] Step S2. The crude trimethylsilane is passed into a light-removal tower to remove light components such as hydrogen, oxygen, and nitrogen in the raw material at a temperature of 18°C, a pressure of 205KPa, and a reflux ratio of 5:1. The crude trimethylsilane is then passed into a heavy-removal tower to remove heavy components such as water in the raw material at a temperature of 20°C, a pressure of 200KPa, and a reflux ratio of 5:1 to obtain electronic-grade trimethylsilane. Electronic-grade trimethylsilane is obtained through two-stage distillation reactions of light-removal and heavy-removal. The crude trimethylsilane is finally passed into a fine product tank for collection and charging for use.

[0024] Example 2

[0025] This embodiment provides a method for purifying electronic grade trimethylsilane, which is as follows:

[0026] Step S1. The trimethylsilane raw material with a purity of 99.8% from the steel cylinder and the diluent gas nitrogen are introduced into the buffer tank in a volume ratio of 3:1 for mixing. The diluent gas is used to dilute the trimethylsilane raw material, reduce the exothermic effect during adsorption, avoid the disproportionation reaction, and generate isomers. After being evenly mixed, the adsorption tower is introduced. Under the action of the adsorption tower filler, the temperature in the adsorption tower is controlled to be 32°C and the pressure is 220KPa. Impurity components such as dimethylsilane with a boiling point close to trimethylsilane are removed to obtain a crude trimethylsilane product. The main component of the filler of the adsorption tower is activated carbon. The activated carbon adsorption material has a rich microporous structure and a large specific surface area, and can adsorb a large number of gas molecules. The mixture of iron oxide and aluminum oxide is added to the activated carbon by doping. Impurity molecules such as dimethylsilane with a boiling point close to trimethylsilane will be adsorbed on the surface of the adsorption material due to physical adsorption. The filler in the adsorption tower also contains a small amount of iron oxide and aluminum oxide in order to reduce the heat released during adsorption. The mass ratio of activated carbon to the mixture of iron oxide and aluminum oxide is 10:1, and the mass ratio of aluminum oxide to iron oxide is 1:1.

[0027] Step S2. The crude trimethylsilane is passed into a light-removal tower to remove light components such as hydrogen, oxygen, and nitrogen in the raw material at a temperature of 21°C, a pressure of 200KPa, and a reflux ratio of 6:1. The crude trimethylsilane is then passed into a heavy-removal tower to remove heavy components such as water in the raw material at a temperature of 16°C, a pressure of 195KPa, and a reflux ratio of 6:1 to obtain electronic-grade trimethylsilane. Electronic-grade trimethylsilane is obtained through two-stage distillation reactions of light-removal and heavy-removal. The crude trimethylsilane is finally passed into a fine product tank for collection and charging for use.

[0028] Example 3

[0029] This embodiment provides a method for purifying electronic grade trimethylsilane, which is as follows:

[0030] Step S1. The trimethylsilane raw material with a purity of 99.1% from the steel cylinder and the diluent gas helium are mixed in a volume ratio of 3:2 into a buffer tank, and the diluent gas is used to dilute the trimethylsilane raw material, reduce the exothermic effect during adsorption, avoid the occurrence of disproportionation reaction, and generate isomers. After being evenly mixed, they are passed into an adsorption tower. Under the action of the adsorption tower filler, the temperature in the adsorption tower is controlled to be 25°C and the pressure is 230KPa, and impurity components such as dimethylsilane with a boiling point close to trimethylsilane are removed to obtain a crude trimethylsilane product. The main component of the filler of the adsorption tower is activated carbon, and the activated carbon adsorption material has a rich microporous structure and a large specific surface area, and can adsorb a large number of gas molecules. The mixture of iron oxide and aluminum oxide is added to the activated carbon by doping, and impurity molecules such as dimethylsilane with a boiling point close to trimethylsilane will be adsorbed on the surface of the adsorption material due to physical adsorption. The filler in the adsorption tower also contains a small amount of iron oxide and aluminum oxide in order to reduce the heat released during adsorption. The mass ratio of activated carbon to the mixture of iron oxide and aluminum oxide is 10:3, and the mass ratio of aluminum oxide to iron oxide is 1:1.

[0031] Step S2. The crude trimethylsilane is passed into a light-removal tower to remove light components such as hydrogen, oxygen, and nitrogen in the raw material at a temperature of 22°C, a pressure of 210KPa, and a reflux ratio of 5:1. The crude trimethylsilane is then passed into a heavy-removal tower to remove heavy components such as water in the raw material at a temperature of 18°C, a pressure of 190KPa, and a reflux ratio of 4:1 to obtain electronic-grade trimethylsilane. Electronic-grade trimethylsilane is obtained through two-stage distillation reactions of light-removal and heavy-removal. The crude trimethylsilane is finally passed into a fine product tank for collection and charging for use.

[0032] Example 4

[0033] This embodiment provides a method for purifying electronic grade trimethylsilane, which is as follows:

[0034] Step S1. The trimethylsilane raw material with a purity of 99.5% from the steel cylinder and the diluent gas helium are mixed in a volume ratio of 3:1 into a buffer tank, and the diluent gas is used to dilute the trimethylsilane raw material, reduce the exothermic effect during adsorption, avoid disproportionation reaction, and generate isomers. After being evenly mixed, they are passed into an adsorption tower. Under the action of the adsorption tower filler, the temperature in the adsorption tower is controlled to be 28°C and the pressure is 225KPa, and impurity components such as dimethylsilane with a boiling point close to trimethylsilane are removed to obtain a crude trimethylsilane product. The main component of the filler of the adsorption tower is activated carbon, and the activated carbon adsorption material has a rich microporous structure and a large specific surface area, and can adsorb a large number of gas molecules. The mixture of iron oxide and aluminum oxide is added to the activated carbon by doping, and impurity molecules such as dimethylsilane with a boiling point close to trimethylsilane will be adsorbed on the surface of the adsorption material due to physical adsorption. The filler in the adsorption tower also contains a small amount of iron oxide and aluminum oxide in order to reduce the heat released during adsorption. The mass ratio of activated carbon to the mixture of iron oxide and aluminum oxide is 10:3, and the mass ratio of aluminum oxide to iron oxide is 1:1.

[0035] Step S2. The crude trimethylsilane is passed into a light-removal tower to remove light components such as hydrogen, oxygen, and nitrogen in the raw material at a temperature of 16°C, a pressure of 208KPa, and a reflux ratio of 4:1. The crude trimethylsilane is then passed into a heavy-removal tower to remove heavy components such as water in the raw material at a temperature of 22°C, a pressure of 200KPa, and a reflux ratio of 5:1 to obtain electronic-grade trimethylsilane. Electronic-grade trimethylsilane is obtained through two-stage distillation reactions of light-removal and heavy-removal. The crude trimethylsilane is finally passed into a fine product tank for collection and charging for use.

[0036] Example 5

[0037] Based on the electronic grade trimethylsilane prepared in Example 1, this example provides an application of electronic grade trimethylsilane for use as a precursor gas in a chemical vapor deposition process, as follows:

[0038] The trimethylsilane and dichlorosilane prepared in Example 1 were used in a volume ratio of 4:1. Under the condition of a substrate temperature of 1000°C, hydrogen was used as a carrier gas and introduced into the deposition chamber. The flow rate of trimethylsilane was 200 sccm, the flow rate of dichlorosilane was 50 sccm, and the pressure of the deposition system was 5 mTorr, to form a 3C-SiC epitaxial layer.

[0039] Example 6

[0040] The difference between this embodiment and embodiment 5 is that the trimethylsilane prepared in embodiment 2 is used.

[0041] Example 7

[0042] The difference between this embodiment and embodiment 5 is that the trimethylsilane prepared in embodiment 3 is used.

[0043] Example 8

[0044] The difference between this embodiment and embodiment 5 is that the trimethylsilane prepared in embodiment 5 is used.

[0045] Performance Testing

[0046] The purity of trimethylsilane prepared in Examples 1 to 4 and the thickness of the 3C-SiC epitaxial layer prepared in Examples 5 to 7 were tested. The results are shown in Tables 1 and 2.

[0047] Table 1

[0048] sample Example 1 Example 2 Example 3 Example 4 Purity of trimethylsilane (%) 99.999 99.998 99.991 99.996

[0049] Table 2

[0050] sample Example 5 Example 6 Example 7 Example 8 3C-SiC epitaxial layer thickness (nm) 500 550 520 560

[0051] It can be seen from Table 1 and in combination with Examples 1 to 4 that the purification method of trimethylsilane provided by the present application can prepare electronic grade trimethylsilane with a purity greater than 99.99%. Dimethylsilane and other impurity components with a boiling point close to trimethylsilane in the trimethylsilane raw material are removed by the adsorption material (activated carbon, aluminum oxide and iron oxide) in the adsorption tower, reducing the content of components such as dimethylsilane. The activated carbon adsorption material has a rich microporous structure and a large specific surface area, and can adsorb a large number of gas molecules. When the trimethylsilane raw material gas passes through the adsorption tower, impurity molecules such as dimethylsilane with a boiling point close to trimethylsilane will be adsorbed on the surface of the adsorption material due to physical adsorption. At the same time, the present application adds a diluent gas (nitrogen or helium) before the trimethylsilane raw material is passed into the adsorption tower, which can dilute the concentration of the trimethylsilane raw material, reduce the exothermic effect during adsorption, avoid the occurrence of disproportionation reaction, generate isomers, and reduce the purity of trimethylsilane. In the present application, the ratio of activated carbon and metal oxide (iron oxide and aluminum oxide) is reasonably controlled to reduce the heat release during adsorption, and a synergistic effect can be achieved with the diluent gas to reduce the heat release during adsorption and avoid the occurrence of disproportionation reaction. It can be seen from Examples 5 to 8 that the trimethylsilane purified in Examples 1 to 4 and combined with Table 2 that the thickness of the prepared 3C-SiC epitaxial layer can meet the requirements.

[0052] The above is only a preferred embodiment of the present application and does not constitute any form of limitation to the present application. Although the present application has been disclosed as a preferred embodiment as above, it is not intended to limit the present application. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present application. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application are still within the scope of the technical solution of the present application.

Claims

1. A method for purifying electronic grade trimethylsilane, characterized in that: The steps include: Step S1. Mixing the trimethylsilane raw material and the diluent gas into an adsorption tower, removing dimethylsilane at a temperature of 25 to 32° C. and a pressure of 220 to 230 KPa to obtain a crude trimethylsilane product, wherein the filler of the adsorption tower is a mixture of activated carbon and metal oxides; Step S2: The crude trimethylsilane is passed into a light removal tower to remove light components, and then into a heavy removal tower to remove heavy components to obtain electronic grade trimethylsilane.

2. The method for purifying electronic grade trimethylsilane according to claim 1, characterized in that: In the step S1, the metal oxide is doped into the activated carbon, the mass ratio of the activated carbon to the metal oxide is 10:1-10:3, the metal oxide is aluminum oxide and iron oxide, and the mass ratio of aluminum oxide to iron oxide is 1:

1.

3. The method for purifying electronic grade trimethylsilane according to claim 1, characterized in that: In step S1, the diluent gas is any one of nitrogen or helium, and the volume ratio of trimethylsilane to the diluent gas is 3:1 to 3:

2.

4. The method for purifying electronic grade trimethylsilane according to claim 1, characterized in that: The purity of the trimethylsilane raw material in step S1 is ≥99%.

5. The method for purifying electronic grade trimethylsilane according to claim 1, characterized in that: The conditions for removing light components in step S2 are: temperature of 16-22° C., pressure of 200-210 Kpa, and reflux ratio of 6:1-3:

1.

6. The method for purifying electronic grade trimethylsilane according to claim 1, characterized in that: The conditions for removing the heavy components in step S2 are: temperature of 16-22° C., pressure of 190-200 Kpa, and reflux ratio of 6:1-3:

1.

7. Use of the method for purifying electronic grade trimethylsilane according to any one of claims 1 to 6, characterized in that: Used as a precursor gas in chemical vapor deposition processes.