Abstract
This thesis presents the characteristics of low temperature microcrystalline silicon (µc-Si) films deposition on SiO2 and glass substrates and the solar cell fabricated by this films. We deposited the µc-Si films by electron cyclotron resonance chemical vapor deposition (ECR-CVD). The Characterization of µc-Si films were carried out by using Raman scattering, XRD, FTIR, Nanospac, SEM, SRP, α-STEP, and Four point probe. Raman scattering spectra were used to investigate their crystallinity and the crystalline fraction in the µc-Si films. X-ray diffraction pattern (XRD) spectra were used to analyze the preferred orientation of the µc-Si films. Fourier transform infrared (FTIR) absorption spectra were used to study the silicon-hydrogen bonding configurations and the hydrogen content of the µc-Si films. Conductivity measurements were employed to study the electrical properties of µc-Si films. Nanospac and α-STEP were used to measure films thickness. Scanning electron microscopy (SEM) were used to analyze grain geometry and top morphology. Spreading Resistance Profiling (SRP) and Four point probe were used to analyze the doping concentration and resistivity. In our experiments, the growth conditions to prepare the p, i, and n layers of solar cells by using ECRCVD were found. The experimental parameters used in this study are the Top/ Middle/ Bottom magnetic current at 170, 170 and 30A respectively and substrate temperature at 250 oC (for undoped films) ~ 400 oC (for doped films), the range of microwave power at 1200W ~ 1400W, the range of the process pressure at 10mtorr ~ 40mtorr. The hydrogen dilution ratio was varied to analyze the characteristics of thin films. In addition, we also doped the films using phosphine (PH3) and diborance(B2H6) to form the n-type and p-type silicon thin film. The experimented results show that, the maximum crystalline fraction obtained was about 94.5%, and the largest grain size in these µc-Si films have dimension of about 700 Ǻ when the hydrogen dilution ratio was 95%. The preferred orientation of the µc-Si films were found to be <110>, and also it was observed that the hydrogen content decreased with the increase of hydrogen dilution ratio. The doped concentration of N-type is about 1.04e18cm-3, P-type is about 1.56e18cm-3.