Method for analyzing 7N electronic grade ultrapure ammonia

Abstract

The invention relates to a method for measuring trace impurity concentration of 7N electronic grade ultrapure ammonia. The method comprises the following steps of: separating trace impurities from the ultrapure ammonia by a pipeline system subjected to corrosion-resistant and adsorption-resistant treatment, by large-flow replacement, sweeping and sampling and a three-valve four-column cutting back-flushing gas channel system; and analyzing impurity gases by using a direct current discharging helium ionization detector (DID). The method has the advantages of capacity of providing a balanced (stable state) analysis value within short time, quantitative accuracy, low detection limit and short analysis period.

Description

technical field [0001] The invention relates to an analysis method and system for analyzing gas components, especially trace components in ultra-high-purity ammonia gas, by using a gas circuit system and a DC discharge helium ionization detector (DID). Background technique [0002] The field of LED crystal manufacturing requires the use of ultra-high-purity (UHP) ammonia. This requirement stems from the fact that ultra-high-purity ammonia is used in the epitaxial growth process of metal organic compound chemical vapor deposition (MOCVD), and it is combined with the precursor of metal organic compounds. Trimethylgallium (Ga(CH 3 ) 3 ) undergoes a chemical reaction at high temperature and pressure, Ga(CH 3 ) 3 (g)+NH 3 (g)→GaN(s)+3CH 4 (g). Only when the purity of ammonia gas reaches 6.5N or more, can a high-brightness blue LED and a high-brightness white LED with a light rate of 30lm / W be produced. Therefore, the need to supply 7N electronic grade ultra-pure ammonia ha...

AI Technical Summary

Problems solved by technology

The disadvantages of the above method are: 1. The average detection limit of thermal conductivity detector (TCD) is 50×10 -6 , can not do ppb level trace detection

2. 5A molecular sieve has an irreversible adsorption on ammonia gas. Although most ammonia gas can be resolved at a high temperature of 400°C, some ammonia gas will still be adsorbed on the 5A molecular sieve column, which will affect the quantitative accuracy of impurity components and reduce detection. service life of the device

3. Since ultra-high purity ammonia contains a small amount of CO 2 , but 5A molecular sieves for CO 2 It is also an irreversible adsorption, so this method cannot be used for CO 2 Quantitative analysis, while affecting the column efficiency with the increase of the number of injections

4. Due to NH 3 , CO 2 Enter the 5A molecular sieve column, thereby prolonging the analysis cycle and reducing the analysis efficiency

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