Competitive adsorption mechanism of SiHCl3 with BCl3 under a hydrogen atmosphere: boron impurities introduction into polysilicon

The primary method for electronic-grade (EG) polysilicon production is the modified Siemens process. Unfortunately, the EG polysilicon produced through this method contains excessive levels of boron impurities (> 0.2 ppb), thereby diminishing the product quality. This issue impedes the large-scale production of EG polysilicon. This study establishes the structure of the Si (100) surface within a hydrogen-rich environment under the BCl3-SiHCl3-H2 system and investigates the adsorption mechanisms of BCl3 and SiHCl3, as well as the competitive adsorption mechanism of BCl3-SiHCl3, on the Si (100) surface. The results indicate that the adsorption energy barriers for BCl3 and SiHCl3 on the Si (100) surface are 7.8383 kJ·mol-1 and 229.6970 kJ·mol-1, respectively, so that the preferential adsorption of BCl3 onto the Si (100) surface over SiHCl3. The B atom and the Si atom are competing for adsorption on the Si (100) surface and creating an ab-B-Si-ab structure, and the optimal adsorption path is as follows: ab-BCl3→ab-BCl2→ab-BCl2-SiHCl3→ab-BCl-SiHCl3→ab-B-SiHCl3→ab-B-SiHCl2→ab-B-SiHCl→ab-B-SiH-ab→ab-B-Si-ab.