Abstract
Although crystalline silicon solar cells are promising candidates for the large-scale solar cell applications, their production cost needs to be reduced to gain widespread acceptance. Recent work has focused on the production of thin silicon films, since the crystalline Si wafers account for about a half of the module cost of solar cells. Thin silicon films should be possible in principle to produce cells with high efficiency at significantly lower cost than current silicon cells, made on cast polycrystalline or monocrystalline silicon substrates. We propose a different approach of a layer transfer process, termed the epitaxial lift-off process, which leads to the production of monocrystalline silicon films.
As a case study of the epitaxial lift-off process, high quality Si / CoSi2 / Si double heteroepitaxial structures were developed using a conventional magnetron sputtering system on a Si (100) substrate with texture patterns and via holes produced by anisotropic etching. A Si layer of a few micrometers thickness was fabricated easily using a chemical vapor deposition (CVD) process on the double heteroepitaxial structure. CoSi2 was etched away by the hydrofluoric acid and the thin film monocrystalline Si could be easily separated from the supporting single crystal silicon substrate, which is found to be reusable.
