Characteristics of mu c-Si films with a CaF2 seeding layer for TFT applications

Using a remote plasma chemical vapor deposition (RPCVD) system, we deposite d microcrystalline silicon (muc-Si) films on CaF2 film coated glass substra tes. The X-ray diffraction analysis showed that the CaF2 films grew in a (2 20) preferential orientation while the muc-Si films were oriented in the (1 11) and the (220) planes. Employing a CaF2 seed layer. we successfully prod uced a high-quality muc-Si film with the following characteristic parameter s: a grain size as large as 700 Angstrom. a crystalline volume fraction ove r 65 %. a dark- and photo-conductivity ratio less than 124: amid an activat ion energy around 0.49 eV. Our achievements regarding direct muc-Si film gr owth at a low process temperature promise an improved thin film transistor (TFT) operation speed, a high aperture ratio, and a stable light sensitivit y in large-area TFT liquid crystal display (LCD) applications.