A new way to selectively remove Si islands from polycrystalline silicon seed layers made by aluminum-induced crystallization

Polycrystalline silicon (grain size ~ 0.1-100 μm) solar cells on foreign substrates are a promising approach for the next generation silicon solar cells. Aluminum-induced crystallization AIC in combination with epitaxy is a possible way to obtain such absorber layers. It is believed that Si islands present on the surface of AIC seed layers have a negative effect on the epitaxy. The removal of these islands could therefore lead to an increased absorber layer quality and solar cell performance. In this paper, we present a selective island removal procedure based on the Al layer already present after AIC annealing. By selecting an etchant which removes Si at least as fast as Al (in this paper plasma etching using SF6), the Al layer acts as a perfectly aligned etching mask for the fully developed islands.