Research On The Fabrication Of Large Grain Size Poly-Si Film By Phase Modulated Excimer Laser Crystallization

In recent decades, Flat Panel Displays (FPDs) technology has significantly evolved, Liquid Crystal Display (LCD) and Organic Light Emitting Device (OLED) presently hold a dominant position in high information-content flat panel displays (FPDs). Since the beginning, in the early80s, visionary researchers and prudent manufacturers have been constantly seeking for ways to increase panel size, improve performance and reduce costs associated with the manufacture of FPDs such as TFT-LCD. In the80s, such a performance improvement was achieved by the transition from passive TN displays to passive supertwisted nematic and subsequently to active-matrix a-Si TFT-LCDs. Forced by market demands, and fueled by technological breakthroughs and a need to effectively utilize older generation a-Si manufacturing lines, a similar transition is seen to occur, whereupon low-temperature polysilicon (p-Si) emerges as a feasible substitute for the mature a-Si technology for active-matrix LCD and active-matrix OLED.In order to enlarge the grain size and decrease the defects between the grain boundaries of the p-Si film, phase modulated Excimer laser crystallization technique is used to fabricate large grain size uniform p-Si film. First, the energy window for super lateral growth is determined by measuring the grain size of p-Si film fabricated with different laser energy intensity. Then, the spatial distribution of the input laser is modulated by a phase mask with a period of1073nm and an artificial controlled lateral temperature gradient is induce on the a-Si film, which leads to the melting of a-Si and the super lateral growth of p-Si grains. Finally, the characteristics of prepared p-Si film are measured and compared with those of a-Si film and p-Si film fabricated by super lateral growth technique. The results show that the grain size of the p-Si film is228.24nm, which is ten times larger than that fabricated by super lateral growth under the same processing parameters; the electrical resistance of the prepared sample is1.89×103Ω·cm, which is lower by an order magnitude than that prepared by super lateral growth. Furthermore, the distribution of the grain is more uniform than that fabricated by other techniques. The reported technique can increase the electrical characteristics of p-Si film greatly and are suitable for the fabrication of high quality p-Si devices.