Research On The Removal Of Trace Phosphorous From Silicon Tetrachloride Based On Complexing Adsorption

Electronic grade polysilicon is the most basic material for manufacturing semicon-ductor chips and large-scale integrated circuits,which is of great significance to elec-tronics,information and national security fields.Electronic grade polysilicon is de-manding strictly on product purity and impurity control.The purity of silicon tetrachlo-ride mainly determines the quality of polysilicon products.The methods for removing trace phosphorus impurities in silicon tetrachloride in the world still have problems such as low removal efficiency,long reaction time and introducing new impurities.From the perspective of adsorption and reaction,based on the Lewis acid-base neutral-ization mechanism of the complex,we explored a new process path of complex adsorp-tion and attempted to find a more suitable complexing agent to efficiently separate trace phosphorus impurities in silicon tetrachloride.Moreover,a continuous and reliable la-boratory method was established for detecting trace phosphorus impurity.First of all,the detection method of phosphorus content in different valence in aqueous solution and organic solution was determined by ultraviolet-visible spectro-photometry.The detection range of phosphoric acid in aqueous solutions was 0.52?6.4?mol/L,the detection limit was 0.52?mol/L.The detection range of phosphorous acid in aqueous solution was 1.6?6.4?mol/L,and the detection limit was 1.6?mol/L.Secondly,the oxidation effect under static conditions and fixed bed oxidation con-ditions were studied respectively after preparation of polymer-supported chromium ox-idant with D301 anion exchange resin as the carrier.The oxidation efficiency of static reaction at temperature of 95? could reach 25.6%.When the space velocity was25.48h^-1,the temperature of fixed-bed oxidation was 95?,the oxidation efficiency of dynamic reaction could reach 25%.Thirdly,according to the principle of Lewis acid-base neutralization reaction be-tween BCl₃ and PCl₅/POCl₃,the complex insoluble in n-hexane were prepared,which were characterized by ICP-MS,ultraviolet spectrophotometer and nuclear magnetic resonance spectroscopy.The results showed that:BCl₃ could react with phosphorus impurities(PCl₅ and POCl₃)in silicon tetrachloride to form complex.The reaction mo-lar ratio of POCl₃ and BCl₃ was 1:1,and that of PCl₅ and BCl₃ was 2:1,which verified the feasibility of the complex process of boron and phosphorus impurities.Finally,adsorption effect of the adsorbent modified by Al Cl₃ with activated carbon as the carrier were researched based on the change of phosphorus content concentration of the raw material gas per unit time before and after the adsorption in the fixed bed.When the temperature was 120? and the space velocity was 25.48h^-1,the dynamic adsorption capacity was 223.5?g/g after adsorption for 60 minutes and the average ad-sorption efficiency reached 18.63?g/min.This work offered a certain guidance to in-dustrial applications.