Effect of 13X Zeolite Modified with CuCl₂ and ZnCl₂ for Removing Phosphine from Circular Hydrogen of a Polysilicon Chemical Vapor Deposition Stove

Abstract

Silicon materials used in semiconductor and photovoltaic products have strict purity requirements. The quality of materials will be affected severely if even trace amounts of PH 3 are contained in the hydrogen of the chemical vapor deposition (CVD) stove. Thus, it is critical that the content of PH 3 be controlled under a certain level. In contrast to series of metal oxide adsorbents reported in other research, 13X zeolite modified with ZnCl 2 (Zn-13X) and CuCl 2 (Cu-13X) was prepared to adsorb trace PH 3 in this study. Breakthrough curves and adsorption capacities at different temperatures from −15 to 50 °C were investigated to determine the performance of the adsorbents. X-ray diffraction and surface analysis were carried out to characterize the adsorbents and the adsorption mechanism. The results showed that CuCl 2 was dispersed on 13X in monolayer or submonolayer form, and ZnCl 2 would change the structure of 13X under the experimental condition. New diffraction peaks at 35.6° and 38.8° appeared after loading CuCl 2 in the X-ray diffraction pattern of Cu-13X, and the peak of Zn-13X at 10° almost disappeared. The half-pore width after modification was mainly centralized at 0.5 nm for each of them, and the specific surface areas of Cu-13X and Zn-13X were 245.2 and 19.2 m 2 /g, respectively. The breakthrough time for Cu-13X was always more than 600 min, whereas it sharply decreased from 350 to 20 min for Zn-13X when the temperature increased to 50 °C from −15 °C. The static adsorption capacity decreased from 106.5 mg to 67.2 mg and from 88.3 mg to 36.1 mg of PH 3, respectively, for per-gram Cu-13X and Zn-13X as the adsorption temperature changed in the chosen range. The working life of Cu-13X could be prolonged by N 2 purging at room temperature according to experimental results because the rate of chemical reaction coupled with the adsorption between PH 3 and the active components was much slower than that of its physical adsorption, but a higher temperature was needed for Zn-13X.