The Research On The Removal Of Phosphine From The Circular Hydrogen Of Polysilicon Reducing Furnace

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 PH₃ are contained in the hydrogen of the chemical vapor deposition?CVD?stove.Thus,it is critical that the content of PH₃ be controlled under a certain level.In contrast to series of metal oxide adsorbents reported in other research,13 X zeolite modified with ZnCl₂?Zn-13X?and CuCl₂?Cu-13X?was prepared to adsorb trace PH₃ 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 CuCl₂ was dispersed on 13 X in monolayer or submonolayer form,and ZnCl₂ would change the structure of 13 X under the experimental condition.New diffraction peaks at 35.6° and 38.8° appeared after loading CuCl₂ in the X-ray diffraction pattern of Cu-13 X,and the peak of Zn-13 X 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-13 X and Zn-13 X were 245.2 and 19.2 m² /g,respectively.The breakthrough time for Cu-13 X was always more than 600 min,whereas it sharply decreased from 350 to 20 min for Zn-13 X 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 PH₃,respectively,for per-gram Cu-13 X and Zn-13 X as the adsorption temperature changed in the chosen range.The working life of Cu-13 X could be prolonged by N2 purging at room temperature according to experimental results because the rate of chemical reaction coupled with the adsorption between PH₃ and the active components was much slower than that of its physical adsorption,but a higher temperature was needed for Zn-13 X.Besides,in order to investigate the effect of different adsorbent supports on removing PH₃,activated carbon?AC?and 13 X zeolite respectively modified with CuCl₂ and Cu?NO₃?₂ were prepared by the similar impregnation methods as the preparation of Cu?Zn?-13 X.Totally,four adsorbents?Cu?NO₃?₂-AC,Cu?NO₃?₂-13 X,CuCl₂-AC,CuCl₂-13X?were used to removing PH₃ in adsorption experiments at different temperature,and the performances of four different adsorbents were compared with each other.We find that the performance of adsorbents which is based on AC was better than 13 X zeolite,and Cu?NO₃?₂ could more significantly improve the performance of AC and 13 X zeolite on removing PH₃.When 13 X zeolite was used as the support,the adsorbent either modified with Cu?NO₃?₂ or CuCl₂ performed better adsorptive ability to PH₃ at high temperature than low.However,when AC was used as the support,Cu?NO₃?₂-AC showed better performance at low temperature,while CuCl₂-AC still kept better at high temperature.According to the different performances among these adsorbents,probable adsorption mechanism was proposed,which indicated that the interaction to active additions?CuCl₂ and Cu?NO₃?₂?of between 13 X and AC was different very much,and the difference could affect the performances of adsorbents greatly.