1、 Introduction to silane gas
Silane (hereinafter referred to as "silane") is a colorless, very active compressed gas under normal temperature and pressure. It can ignite spontaneously in air, is flammable and explosive, and its chemical molecular formula is SiH4. Electronic grade silane gas is mainly obtained from silicon powder, hydrogen, silicon tetrachloride, catalyst, etc. through various reaction distillation and purification. The purity of 3N ~ 4N is called industrial grade silane, and the purity above 6N is called electronic grade silane gas.
As a gas source carrying silicon components, silane gas has become an important special gas that cannot be replaced by many other silicon sources because of its high purity and fine control. Monosilane is one of the methods for large-scale production of granular monocrystalline silicon and polysilicon in the world through pyrolysis reaction. It is widely used in microelectronics and optoelectronics industry. The purity of silane gas will affect the purity of silicon-based crystals, and the purity of silicon-based crystals will greatly affect the performance of downstream industry products. Downstream industries that mainly use electronic grade silane gas include semiconductor industry, display panel industry and photovoltaic industry.
2、 Application fields
Semiconductor industry: electronic grade silane gas is mainly used in the semiconductor industry to produce high-purity polysilicon, silicon dioxide film, silicon nitride film, polysilicon isolation layer, polysilicon ohmic contact layer and heterogenous or homogeneous silicon epitaxial growth raw materials, as well as ion implantation source and laser medium. The silicon surface and its adjacent area are heated to provide the required energy to the reaction system. All substances in the chemical vapor deposition film originate from external gas sources. Atoms or molecules will deposit on the surface of silicon wafer to form a thin film. Electronic grade silane gas is one of the most common gases in chemical vapor deposition.
Display panel industry: electronic grade silane gas is mainly used in the production of TFT (thin film transistor) /lcd (liquid crystal display) in the display panel industry. Each pixel of tft/lcd is controlled by TFT integrated on itself and is an active pixel. Therefore, it has the advantages of small size, light weight, low radiation, low power consumption, full-color, fast speed, high contrast and brightness, large viewing angle of the screen, high resolution, and is currently the mainstream plane display device. Tft/lcd production includes TFT array (including film, lithography, etching), color filter (including black matrix film, red green blue film, transparent conductive layer), panel, module and other processes. In the film process, silane and other gases are deposited on the surface of glass substrate by dissociation reaction under the action of high-frequency alternating electric field in the CVD process (chemical vapor deposition), which can form an insulation layer resistant to water vapor and metal ion corrosion, an electronic channel layer, an ohmic contact layer, and a valve grade insulation layer with high density and good insulation.
Photovoltaic industry: electronic grade silane gas is mainly used in the production process of crystalline silicon solar cells and thin-film solar cells in the photovoltaic industry. Commercially produced crystalline silicon solar cells usually use polysilicon materials. In the production process, antireflective films need to be made on the light receiving surface by chemical vapor deposition, and silane gas needs to be used in this step. The commercially produced thin-film solar cells are divided into amorphous silicon thin film and amorphous / microcrystalline silicon laminated thin film. The latter can absorb and utilize sunlight more fully. In the production process, chemical vapor deposition method is used to make thin films, and silane gas is used in this process. In recent years, high-tech applications of silane are still emerging, including for the manufacture of advanced ceramics, composites, functional materials, biomaterials, high-energy materials, etc., which have become the basis of many new technologies, new materials and new devices.
3、 Preparation process
At present, the mainstream processes for the production of electronic grade silane gas in the world are lithium silicon method, fluorosilicone method, magnesium silicon method and chlorosilicon method (disproportionation method), and the production technology is mainly concentrated in the United States, Japan, Germany and a few western developed countries. These production methods have the characteristics of high cost, many equipment and large investment. Disproportionation method uses industrial silicon powder, silicon tetrachloride and hydrogen as raw materials to produce trichlorosilane. Trichlorosilane undergoes disproportionation reaction under the action of catalyst to produce high-purity silane. The whole production is divided into three parts: silica fume gasification part, distillation part and disproportionation reaction part (silane reaction).
The gasification part of silicon powder is to introduce silicon powder into a fluidized bed reactor for gas-solid reaction with hydrogen and silicon tetrachloride gas. After dedusting, the reaction product will exchange heat, cool and condense with the feed, collect unreacted silicon tetrachloride and trichlorosilane and impurities generated by the reaction, so as to achieve the purpose of separating from hydrogen gas. Unreacted hydrogen will be returned to the gasification part for use. In the distillation part, a distillation system is used to separate trichlorosilane from the condensate obtained by distillation for disproportionation and reverse application. The silicon tetrachloride obtained by separation is returned to the silicon powder gasification part and impurities are removed here. The disproportionation part uses a fixed bed reactor to disproportionate trichlorosilane to obtain the target product silane, and refine it to finally obtain the product silane. The silicon tetrachloride obtained from the reaction returns to the previous silicon powder gasification part.
4、 Industry threshold
The industry threshold for preparing electronic grade silane gas is mainly reflected in the technical threshold and capital threshold. The technical threshold is reflected in the fact that the purity of electronic grade silane gas needs to reach more than 6N. Silane gas is a dangerous flammable and explosive gas, which will burn if leaked at room temperature. It is difficult for safe production and storage, so the process level requirements are high. At present, only a few gas manufacturers in the market have the technology to produce electronic grade silane gas. The capital threshold is reflected in the fact that the preparation of electronic grade silane gas requires the use of large-scale production equipment, and the investment in fixed assets is high in the early stage, which requires a lot of capital.
5、 Industry policy
In 2019, the Ministry of industry and information technology issued the guidance catalogue for the first batch of application demonstration of key new materials (2019 version), which clearly listed the special gases in "129 special gases" of "three advanced chemical materials" of "advanced basic materials" (IV) new electronic chemical materials ", and specifically mentioned silane with purity reaching 6N level.
6、 Market size
According to the statistics and prediction of qyr (Hengzhou Bozhi), the global silane market sales reached $446million in 2021, and it is expected to reach $910million in 2028, with a compound annual growth rate (CAGR) of 10.85% (2022-2028). At the regional level, the market in mainland China has changed rapidly in the past few years. In 2021, the market size was $46.89 million, accounting for about 10.52% of the world. It is expected to reach $138million in 2028, when the global share will reach 15.22%. In terms of consumption, North America is currently the world's largest consumer market, accounting for 24.25% of the market share in 2021, followed by Japan and Taiwan, accounting for 18.90% and 16.11% respectively. It is expected that in the next few years, mainland China will have the fastest growth, with a CAGR of about 16.65% during 2022-2028.
On the production side, North America and China are two important production regions, accounting for 34.52% and 20.82% of the market share respectively in 2021. It is expected that China will maintain the fastest growth rate in the next few years, and the share is expected to reach 32.30% in 2028. In terms of product types, the types with purity above 5N occupy an important position, and it is expected that the share will reach 82.41% in 2028. At the same time, in terms of application, the share of semiconductors in 2021 is about 35.92%, and the CAGR in the next few years is about 13.10%.
7、 Competitive profile
Silane gas belongs to the sub category of electronic special gas. The research of foreign-funded giants in the production of silane gas started early, and its process is also in the leading position in the world. At present, the production technology of electronic grade silane gas in the world is mainly concentrated in the United States, Japan, Germany and a few western developed countries.
Globally, the core manufacturers of silane mainly include rec silicon SK Materials、 Linde Group, liquefied air, Mitsui chemical, etc. China's silane products used to rely heavily on imports. With the improvement of China's scientific and technological level, a small number of gas companies led by silane technology have broken the monopoly of foreign gas companies on electronic grade silane gas. Currently, China's domestic silane can fully meet the quality requirements of photovoltaic solar energy, liquid crystal display, led and other fields. However, for some chip manufacturing users with higher quality requirements, domestic silane still needs efforts in purification, detection and other aspects.