Dry processing of silicon solar cells in a large area microwave plasma reactor

Abstract We report a dry Si solar cell process that replaces all wet chemistry by various microwave-excited plasma treatments. The key steps are: (i) SF 6 plasma etching to clean the wafer prior to the emitter diffusion, (ii) CHF 3 plasma etching to remove the phosphor silicate glass (PSG) after diffusion, (iii) SF 6 plasma treatment for mesa etching of the emitter, and (iv) the plasma deposition of an antireflection coating. We also avoid wet chemistry during the metallization. The best completely dry-processed float-zone Si cell shows a power conversion efficiency of 14.7%. The wet-processed reference has an efficiency of 15.1%.