Production method of ultra-pure electronic grade phosphoric acid

Abstract

The invention discloses a production method of ultra-pure electronic grade phosphoric acid, comprising the following steps of: (1) vaporizing high purity phosphorous oxychloride by heating and allowing phosphorous oxychloride steam to enter a phosphoric acid generator; (2) heating high purity water to prepare water vapor, and allowing water vapor to enter the phosphoric acid generator; (3) adjusting the mass ratio of water vapor to phosphorous oxychloride steam in the phosphoric acid generator, conducting a reaction to generate ultra-pure phosphoric acid and hydrogen chloride steam, adding phosphoric acid into a liquid collection tank, removing bubbles from hydrogen chloride and putting it into a hydrochloric acid liquid trap; (4) heating the obtained phosphoric acid, and separating hydrogen chloride under vacuum to obtain ultra-pure electronic grade phosphoric acid; and (5) allowing the obtained hydrochloric acid to enter an evaporator, vaporizing a hydrogen chloride gas, carrying out cyclic absorption by the use of an absorption liquid to obtain high purity hydrochloric acid; and carrying out condensation and despumation on the tail gas which has undergone absorption, and allowing the tail gas to pass through a tail gas tower and to be discharged into the atmosphere. According to the invention, the gas phase reaction between phosphorous oxychloride and water vapor is conducted, contact surface of reactants is enlarged, reaction speed is effectively controlled, and the contents of water and hydrogen chloride in phosphoric acid are controlled. Therefore, the ultra-pure electronic grade phosphoric acid can be prepared with a by-product of high purity hydrochloric acid.

Description

technical field [0001] The present invention relates to phosphoric acid and, in particular, to a process for the production of ultra-high purity electronic grade phosphoric acid. Background technique [0002] General integrated circuit production and TFT-LCD liquid crystal display production require low phosphoric acid purity, and the content of non-metal ions is not higher than 12×10 -6 (i.e. 12ppm), metal ions do not exceed 1100×10 -9 (ie 1100ppb), the product quality can reach SEMI grade 2 standard. However, for the production of large-scale integrated circuits, the quality index must reach SEMI grade 3, and the phosphoric acid required for high-end chip production and phosphorus source doping requires a higher level, and its metal impurity content does not exceed 10×10 -9 (ie 10ppb). [0003] At present, most of the indicators of the domestic production process for producing SEMI grade 2 ultra-high-purity phosphoric acid are gradually approaching the SEMI grade 3 stan...

AI Technical Summary

Problems solved by technology

But the reaction intensity of the method is inconvenient to control, the amount of water in phosphoric acid is too large, the content of hydrogen chloride is high, a large amount of hydrogen chloride and water need to be removed, and the energy consumption is too high

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