BBr3 Diffusion: Process Optimization for High-Quality Emitters with Industrial Cycle Times
We demonstrate tube furnace BBr3 diffusion processes for the formation of high-quality homogeneous boron emitters with industrial cycle times of around 2 hours. They feature emitter dark saturation current densities as low as 17 fA/cm² for textured surfaces at a sheet resistance of about 150 O/sq. In order to achieve the respective doping profiles with a maximum charge carrier concentration slightly above 1019 cm-3 and profile depths of about 800 nm, we optimize the atmospheric pressure BBr3 diffusion such that we make use of an increased maximum temperature (below 1000°C) that yields accelerated diffusion of boron atoms. In addition, careful parameter adjustment assures that the total boron doping dose in the silicon is maintained, despite the temperature increase. This optimization shows a great potential in reducing cycle times without compromising the quality of the formed boron emitters and their respective doping profiles.