The preparation of microcrystalline silicon (μc-Si) thin films by remote plasma-enhanced chemical vapor deposition

Abstract

We have used remote plasma-enhanced chemical vapor deposition (remote PECVD) to deposit both intrinsic and doped μc-Si thin films at temperatures between 100 and 400 °C. Two different deposition pathways have been studied: (i) plasma excitation of He/H2 mixtures with downstream injection of silane, SiH4, and the dopant gases phosphine, PH3 or diborane, B2H6; and (ii) plasma excitation of He, with downstream injection of SiH4 and H2, as well as the dopant gases. We have observed that the second pathway, (ii) readily promotes nucleation of μc-Si on a number of different substrate materials, including crystalline Si, fused silica, and silicon dioxide, SiO2, deposited by the remote PECVD process. The other pathway, with the H2 coexcited with He, frequency results in the deposition of a thin amorphous silicon transition region between the substrate and the μc-Si film, which then nucleates within the a-Si material, rather than at the substrate itself. The properties of μc-Si films deposited by remote PECVD have been characterized by Raman spectroscopy, transmission electron microscopy (TEM), dark conductivity, and photoconductivity.