High-speed Deposition Of Microcrystalline Silicon Thin Film Research

In this thesis, deposition rate is the center. Deposition conditions were optimized to improve the deposition rate of microcrystalline silicon thin films. RF-PECVD and VHF-PECVD was used to deposit silicon thin films. Spectrophotometer, Raman, XRD, SEM and AFM was used to characterize the thin films. Deposition pressure, excitation power, flow rate and silane concentration was changed to systematically study their effects on deposition rate, crystalline fraction, preferred orientation, crystallite size, surface morphology, microstructure evolvement. It was shown that:A. RF-PECVD:1. Deposition rate is affected significantly by total gas flow and silane concentration, and less significantly by deposition pressure and input power. The deposition rate increase almost linearly with silane concentration.2. Crystalline fraction increased monotonously with input power, and decreased monotonously with deposition pressure and silane concentration, has little relation with flow rate.3. On specific conditions, deposition rate of microcrystalline silicon thin films of about 3 A/s has been achieved.4. Crystallite size is affected not significantly by total flow rate, and the preferred orientation of the crystallite is (111), and the size is about 17 nm.5. The surface of the films is more smooth and less rough under higher pressures. Different substrate, such as glass and polished silicon wafer has little effect on the final surface morphology.6. Conductivity of the intrinsic thin silicon films that deposited in chamber to deposit boron doped films is found to be too high.B. VHF-PECVD7. In contrast with RF-PECVD, under lower deposition pressure (60 Pa), lower input power (40 W), high deposition rate (~lA/s) can be achieved, and high crystalline fraction can be achieved even on high silane concentration of 5%.8. Crystallite size is still about 10 nm, and their preferred orientation is (111) at high hydrogen dilution conditions, and the preferred orientation become less obvious when the silane concentration increases.9. Evolvement of the microcrystalline thin films shows non-crystalline phase, mixed phase, microcrystalline phase was experienced. Crystalline fraction increases with the film growth, and shows saturation in the end.10. Surface roughness increases as a whole with film growth, but an odd peak could be found on the initial stage of growth, and this could be explained by cone growth model.