Very low temperature polycrystalline silicon films with very large grains deposited for thin film transistor applications

This paper presents the results of low temperature polycrystalline silicon growth on SiO2 and glass substrates. The silicon films were deposited with the hydrogen dilution method by electron cyclotron resonance chemical vapor deposition at or below 250°C without any thermal annealing. Hydrogen passivation of the SiO2 surface was applied to enhance the grain growth of poly-Si deposition. The polycrystallinity of the silicon films was established by transmission electron microscopy (TEM), Raman scattering, and X-ray diffraction. The maximum grain size was about 1 μm. The crystalline fraction of the polycrystalline silicon (poly-Si) films was near 100% as identified by Raman shift spectra. The preferred orientations of the poly-Si film were 〈110〉 and 〈111〉. Poly-Si films with a maximum grain size of 7000 Å were formed at a substrate temperature as low as 100°C.