Simplified rear-side patterning for silicon heterojunction IBC solar cells: development of the in situ "nano-envelope" dry clean

Abstract

The heterojunction interdigitated back-contact (HJ IBC) cell technology enables remarkably high cell efficiencies, but requires complex processing for the rear-side patterning of the interdigitated a-Si:H electron and hole hetero-contacts. Therefore, the HJ IBC process flow must be simplified into a sequence that is cost-effective and industrially-compatible. Towards this goal, a litho-free, all-dry process sequence is being developed. As part of this simplified process flow, a novel in situ dry clean process called "nano-envelope" clean is developed to replace the wet cleaning after dry etching of a-Si:H. Surface contamination analysis and passivation studies prove that the developed dry clean is as effective as the standard wet clean. Since the "nano-envelope" clean can be done in the same PECVD tool, the sequence from dry etching to repassivation can be done fully in situ.