POCl_3-based Emitter Diffusion Process with Lower Recombination Current Density and Homogeneous Sheet Resistance for Nanotextured Monocrystalline Silicon with Atmospheric Pressure Dry Etching

摘要

In this work, we investigate the emitter sheet resistance and emitter recombination current density by optimizing the POCl_3emitter diffusion process parameters to achieve improved electrical properties and cell performance. Wafers used in the experiment were boron-doped p-type mono-crystalline silicon samples, nanotextured in an atmospheric pressure dry etching tool (ADE) producing highly textured surfaces and decreased surface reflection. Surface roughness is subsequently reduced by a short isotropic etch, to facilitate the surface passivation. The optimization of the diffusion process is realized by adjusting the phosphorus deposition temperature and its drive-in duration, resulting in decreased emitter saturation current density of ～100 fA/cm~2 and in more homogeneous emitter sheet resistance of ～105 Ω/sq. Compared to the un-optimized diffusion process, it also leads to a decreased Auger recombination.