Fabrication of seeded substrates for layer transferrable silicon films

Abstract

The layer transfer process is one of the most promising methods for low-cost and highly-efficient solar cells, in which transferrable mono-crystalline silicon thin wafers or films can be produced directly from gaseous feed-stocks. In this work, we show an approach to preparing seeded substrates for layer-transferrable silicon films. The commercial silicon wafers are used as mother substrates, on which periodically patterned silicon rod arrays are fabricated, and all of the surfaces of the wafers and rods are sheathed by thermal silicon oxide. Thermal evaporated aluminum film is used to fill the gaps between the rods and as the stiff mask, while polymethyl methacrylate (PMMA) and photoresist are used as the soft mask to seal the gap between the filled aluminum and the rods. Under the joint resist of the stiff and soft masks, the oxide on the rod head is selectively removed by wet etching and the seed site is formed on the rod head. The seeded substrate is obtained after the removal of the masks. This joint mask technique will promote the endeavor of the exploration of mechanically stable, unlimitedly reusable substrates for the kerfless technology.

Formation and preferred growth behavior of grooved seed silicon substrate for kerfless technology*

“…Later, efforts had been made to fabricate seeded substrates with shorter rod arrays by a joint resist mask method. [14] Thermal evaporation deposited aluminum film, spin-coated poly methyl methacrylate (PMMA) and photoresist were used to form the joint mask. Protruded seed substrate was achieved by removing the oxide layer selectively from the rod heads under the masking effect of the joint mask.…”