High-rate deposition of microcrystalline silicon thin film by multi-step method

Abstract

To improve the uniformity of crystalline volume fraction (Xc) along the deposition direction in microcrystalline silicon films, very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD), combined with parameters smoothly changed two-step method, is adopted to prepare high-rate microcrystalline silicon films on glass subtrates. With a power density of 2.1 W/cm2, silane concentration between 6% and 9.6%, a difference between Xc measured in the film direction and that in the glass direction, is just 2 percent. With a silane concentration of 9.6%, Xc, measured in the film direction and the glass direction respectively reach 50% and 48%, close to 2 percent, relative difference just 4 percent, whereas the deposition rate reaches 3.43 nm/s. What is more, Xc difference can reduce to 1 percent by strictly controlling the transitional parameters. It shows that the new deposition method not only curb the incubation layers and improve the vertical structure, but also give a larger range for film optimizing in the future.