Ltps-tft, The Cat-cvd Preparation Of Technical Studies,

The technology of active matrix addressing with thin film transistor- rs (TFT) have become the linchpin upon which high-quality flat panel displays depend , so it will have a big market before long. At present, the mainstream technology of TFT is amorphous silicon (a-Si) TFT. Comparing to a-Si material, polycrystalline silicon (p-Si) material has higher mobility and is prone to be adulterated, and it is fit for making peripheral integrated chip. Owing to those merits, p-Si has become a new material of TFT to be researched. Because glass and soft substrates restrict the process-temperature of TFT within low temperature limits, more and more researchers have devoted to the researching of the method to prepare device-quality p-Si at low temperature and with low cost.In this thesis, the technology of catalytic chemical vapor deposition (Cat-CVD) and p-Si material prepared by Cat-CVD at low temperature are studied mainly. Firstly, I introduce the structure and electrical features of p-Si and expound transfers mechanism of carrier in the p-Si. Then, the dynamic process of Cat-CVD when p-Si films are prepared is discussed in detail. According as these and the results those others have got, we have rebuilt the installation of low press chemical vapor deposition (LPCVD) into the Cat-CVD apparatus.we studied detailedly the effects of hydrogen dilution ratio(H₂/(H₂+SiH₄)) and pressure on the p-Si films prepared by Cat-CVD. The structural properties of these films have been investigated by Raman spectroscopy, X-ray diffraction spectroscop- y, Scan Electric Mirror. The results show the crystalline fraction polycrystalline silicon phase increasedwith increasing the H2/SiH., ratio hydrogen radical improve the crystallinity of the films by dehydrogenizing at the surface of the films, etching weak Si-Si network and capturing the hydrogen covered in the films. The results about pressure show the film-growth rate is proportional to pressure, deposited radicals do not have enough time to dehydrogenize and arrange in higher pressure (³0Pa), when the pressure reduce to 3⁵Pa, the quality of films are improved. When the temperature of the substrates is about 250°C,we get device-quality p-Si films within dilution-rate-range 0.9 0.95 and pressure-range 3⁵Pa.Lastly, the structure and processes of a double-TFT and storage capacitor to be prepared by Cat-CVD, which drives a pixel of OLED, are designed. This design includes five PEP, and gate-dielectric layer and p-Si layer are deposited continuously. The processes is simple and the reliability of TFT will be improved.