Analysis of Phosphosilicate Glass Structures Formed by Atmospheric Pressure and High Throughput Low Pressure POCl3 Diffusion

We transfer an industrial-type atmospheric pressure (AP) diffusion process using phosphorus oxychloride (POCl_3) to a low-pressure (LP) system which allows factor two higher throughput. Studying the structure of the phosphosilicate glass (PSG) and silicon dioxide layer system grown during the process reveals different layer compositions for the AP- and LP-POCl
₃
technology. The studies suggest that LP-POCl
₃
diffusion can form an additional top layer with very high phosphorus content. This layer might be relevant for laser doping selective emitters from the PSG. Both AP-POCl
₃
and LP-POCl
₃
processes with in-situ oxidation show evidence for the recently suggested mechanism of “free phosphorus oxidation”.