Thin Microcrystalline Silicon by a Microwave Remote Plasma Deposition Scheme for Heterojunction Solar Cells and Thin Film Transistors

Abstract

AbstractA microwave remote plasma system, operating in an electron cyclotron resonance (ECR) condition, has been designed to deposit microcrystalline silicon (μ c-Si). The plasma properties have been studied by Langmuir probe measurements in the deposition region. Microcrystalline silicon films of thickness < 0.3 μm have been grown by the decomposition of 2% SiH4/Ar diluted in H2. The films were analyzed for dark and photoconductivity, crystallinity and total H2 content. Raman spectroscopy indicates >50% crystallinity for films deposited between 300–400 °C at pressures of 10 mTorr with an input power in the range of 200–600 W for a H2/SiH4 ratio of 60. An increase in deposition temperature from 300 to 400 °C resulted in an increase in conductivity along with a decrease in the activation energy. H2 evolution studies indicate that the purely μ c-Si films show a total 2.5% H2 content compared with the 16.5% seen for the totally amorphous films. Better structural and electrical properties have more recently been obtained using 2% SiH4/He mixtures.