A new high-rate deposition method for thin film crystalline Si solar cells

A new gas-jet electron beam plasma enhanced chemical-vapor deposition (GJEB PECVD) method for high-rate deposition of crystalline silicon films is presented. The method is based on activation of initial gas molecules in an electron beam plasma and convective transfer of the radicals to a substrate by means of a supersonic free jet. The deposition of micro- and polycrystalline Si films is done at a growth rate of 10-20 nm/sec on standard ceramic and stainless steel substrates in the temperature range of 400-650°C. The morphological (TEM, SEM, Raman spectroscopy) and optical (spectroscopic ellipsometry) analysis reveals that the grains have a columnar structure and an average size between 300-1000 nm depending on the growth conditions. Since the conditions in a supersonic gas jet and in the deposition zone are relatively independent on the conditions in a vacuum chamber, the deposition can be made without using an ultrahigh vacuum chamber. This feature in combination with a high deposition rate makes this gas-jet method very attractive for high throughput deposition of micro- and polycrystalline Si thin films on foreign substrates for further solar cell application.