Last year, Japan suddenly announced that it would suspend the supply of three kinds of semiconductor core raw materials to South Korea. This move is undoubtedly a major blow to South Korea. This has led to the shortage of high-purity hydrofluoric acid that semiconductor, panel and other semiconductor manufacturers such as Samsung, SK, and LG must use to produce semiconductors. Therefore, Korean semiconductor companies have accelerated the testing and use of related raw materials in China. Fluoric acid successfully opened the door to the Korean market.
High-purity hydrofluoric acid is a strongly acidic cleaning and corrosive agent, which is mainly used in the cleaning and corrosion of integrated circuit (IC) and very large-scale integrated circuit (VLSI) chips. It is one of the key basic chemical raw materials in the manufacturing process of the microelectronics industry.
The existing domestic hydrofluoric acid purification technologies mainly include three types: positive pressure distillation, negative pressure distillation, and sub-boiling distillation. Among them, sub-boiling distillation is only suitable for small-scale preparation in the laboratory, and it is not easy for industrial application. Positive pressure distillation and negative pressure distillation are the most widely used hydrofluoric acid purification methods. However, these methods only focus on the removal of cationic impurities such as arsenic. The removal of anionic impurities and fluorosilicic acid components is very small. Because anionic impurities form stable components such as sulfate and phosphate in the water phase, the fluorosilicic acid component is It is stable in the water phase, and it is very difficult to remove anionic impurities and fluorosilicic acid (112SiF6) components.
In order to solve a problem, FFC applied for an invention patent named "a method for preparing high-purity hydrogen fluoride and high-purity hydrofluoric acid" (application number: 201510342500.8), and the applicant was DFC Chemical Co., Ltd.
The preparation method of the high-purity hydrofluoric acid proposed in this patent mainly includes the following steps.
Step 1: First purify the system with nitrogen to remove the air in the system, maintain the room temperature and the temperature of the operating part at about 22.5 ° C, and keep the humidity at 40%. Then, 300 kg of liquid hydrogen fluoride raw material was added to a pretreatment reactor with a heat exchanger, and the temperature was controlled to 10 ° C. After adding calcium fluoride, silicon tetrafluoride, sulfur dioxide, sulfur trioxide, sulfate, phosphate, etc. in the liquid hydrogen fluoride raw material react with calcium fluoride to form insoluble calcium fluorosilicate, calcium sulfate, and calcium phosphate. A mixture was obtained.
Step 2: A certain amount of fluorine-nitrogen mixed gas is introduced into the mixture obtained in Step 1. The introduction amount is 0.075 kg. After 4 hours of reaction, the low-boiling arsenide is converted into a high-boiling arsenide. After the reaction is completed, The gas was filtered through a 5um filter to remove large particles of mechanical impurities, and about 302 kg of crude hydrogen fluoride was obtained.
Step 3: Pass the crude hydrogen fluoride obtained in Step 2 to the bottom of the crude distillation column, control the pressure in the kettle to less than 0.1 MPa, continuously raise the material at 22 ° C, control the reflux ratio, and make the gas and liquid phases in the column repeatedly contact closely. The crude distillation process controls the outlet temperature at the top of the column to -8 ° C, removes low boiling point impurities, such as S02, SiF4, etc., and obtains a mixed gas from the top of the crude distillation column.
Step 4: Pass the mixed gas obtained in Step 3 to the bottom of the rectification tower, control the pressure in the kettle to less than 0.1MPa, continuously raise the material at a temperature of 50 ° C, control the reflux ratio and the temperature at the top of the tower at 17 ° C, and remove the high Boiling point impurities, such as H2S04, H20, and metal ions, etc., give high purity hydrogen fluoride.
Step 5: Pass the high-purity hydrogen fluoride at the outlet of the rectification tower from the bottom of the spray absorption tower and mix and mix with the high-purity water sprayed from the top of the tower in proportion to prepare a 49.3% crude hydrofluoric acid solution. After filtration of um and 0.02um microporous membrane, 579kg of high-purity hydrofluoric acid finished product can be obtained.
Analysis shows that the high-purity hydrofluoric acid provided by the present invention effectively removes anionic impurities such as nitrates, phosphates, sulfates and fluorosilicic acid components on the basis of removing cationic impurities, and the relevant indicators far exceed the requirements of HG / T4509-2013. UP-SS grade, the product meets the requirements of VLSI production.
In the second half of 2019, polyfluoropoly seized the opportunity of the Japan-Korea trade war, enabling domestic high-purity hydrofluoric acid to be stably exported to high-end semiconductor companies in South Korea, opening the door for hydrofluoric acid products to the world.