Preparation method for hyperpure sulphuric acid

Abstract

The invention discloses a preparation method for hyperpure sulphuric acid, and fuming sulphuric acid is taken as raw materials. The preparation method comprises the following steps of 1 distilling; 2 purifying and filtering; 3 sulfur trioxide liquid separating; 4 evaporating; 5 multi-stage absorbing; 6 gas stripping tower impurity removing; 7 finished product obtaining. In the hyperpure sulphuric acid, the concentration of particles with the particle size larger than or equal to 0.5 micrometer is smaller than 5 p / ml, the concentration of particles with the particle size larger than or equal to 0.2 micrometer is smaller than 100 p / ml, the content of single metal ions is smaller than 0.1 ppb, and the content of sulfur dioxide is smaller than 3 ppm. According to the preparation method for hyperpure sulphuric acid, the technology is simple, the energy consumption is low, purified sulfur trioxide gas is firstly obtained through a reasonable purifying and impurity removing technology, then ppt-grade hyperpure sulphuric acid is obtained through multi-stage absorbing and gas stripping, the content of trace sulfur dioxide impurities in hyperpure sulphuric acid is effectively controlled, and a foundation is laid for production of a new generation of hyperpure sulphuric acid.

Description

technical field [0001] The invention relates to the technical field of preparation of ultra-pure chemicals, in particular to a method for preparing ultra-pure sulfuric acid with ultra-low sulfur dioxide content. Background technique [0002] Ultra-pure sulfuric acid, also known as high-purity sulfuric acid and electronic-grade sulfuric acid, belongs to ultra-clean and high-purity reagents. It is one of the eight ultra-pure chemical materials commonly used in the semiconductor industry and one of the indispensable key basic chemical reagents in the development of microelectronics technology. The consumption of ultra-pure sulfuric acid ranks first in the IC industry. It is widely used in the assembly and processing of semiconductors and ultra-large-scale integrated circuits. It is mainly used in the diffusion, corrosion, and cleaning of silicon wafers, which can effectively remove impurity particles on the wafers. , inorganic residues and carbon deposits. The purity and clean...

AI Technical Summary

Problems solved by technology

Among them, the rectification method consumes a lot of energy and costs, and some impurities are difficult to remove. The waste gas and acid mist produced are harmful to the human body and are not conducive to environmental protection. They are only suitable for small-scale production

The gas absorption method is to purify sulfur trioxide gas, and then absorb it with ultrapure water or wash sulfuric acid to obtain ultra-pure sulfuric acid. This method can effectively avoid the above-mentioned shortcomings of the rectification method, but the existing gas absorption method cannot effectively remove sulfur dioxide. Gas, so that the prepared sulfuric acid contains a certain amount of trace sulfur dioxide impurities, affecting the performance of sulfuric acid