Excimer Laser Annealing Effect on MILC Polycrystalline Silicon Film
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Excimer Laser Annealing Effect on MILC Polycrystalline Silicon Film Kee-Chan Park, In-Hyuk Song, Sang-Hoon Jung and Min-Koo Han School of Electrical Engineering, Seoul National University, Seoul, 151-742, KOREA.
ABSTRACT XeCl excimer laser was irradiated on metal induced laterally crystallized (MILC) polycrystalline silicon (poly-Si) film in order to eliminate the intra-grain defects of MILC poly-Si film which incorporated 2 µm wide metal induced crystallized (MIC) poly-Si line pattern. On the irradiation of the laser beams, different melt and recrystallization phenomena were observed in the MILC and the MIC poly-Si region due to the Ni content difference in each film. The transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS) measurements indicated that the melting temperature of the poly-Si film decreased as the Ni content increased. With the laser irradiation energy density of 370 mJ/cm2, 2 µm long defect-free poly-Si grain was successfully grown in the MILC poly-Si due to the melting temperature variation at the MILC-MIC poly-Si boundary.
INTRODUCTION MILC of amorphous silicon (a-Si) film has attracted considerable attention for possible application to active matrix liquid crystal displays (AMLCD’s) because it has many merits such as low cost, relatively low crystallization temperature, uniform crystallization over large area and very large poly-Si grain size due to continuous grain growth to almost infinite extent [1-3]. However the electrical characteristics such as µFE, IOFF and the stability of the MILC poly-Si thin film transistors (TFT’s) are rather poor compared with those of excimer laser annealed (ELA) poly-Si TFT’s. The superior electrical characteristics of the ELA poly-Si TFT’s are attributed to the lower intra-grain defect density of the ELA poly-Si film due to the melting and resolidification mechanism of ELA [4,5]. However the poly-Si grain size of ELA poly-Si film is usually less than 0.5µm and it is very difficult to control the grain size uniformly over large area [6]. For the application of a poly-Si film as a channel layer in a poly-Si TFT, large poly-Si grain size and low intra-grain defect density are needed to meet the electrical characteristics requirements such as high µFE and low carrier generation rate by field emission which results in the anomalously large off-state current (IOFF) of poly-Si TFT’s. The purpose of our work is to report a new low-temperature recrystallization method of the a-Si film combining the merits of MILC and ELA. We carried out ELA on MILC poly-Si films that incorporated 2 µm wide MIC poly-Si line patterns and which had Ni content through Ni-induced crystallization. TEM and SIMS analysis were used to investigate the role of the Ni content during the excimer laser recrystallization of the MILC poly-Si film.
D3.5.1
EXPERIMENT A 700 Å thick a-Si film was deposited on an oxidized silicon wafer substrate by low-pressure chemical vapor deposition (LPCVD) at 550 oC. A 50 Å thick Ni film was deposited on the a-Si film by evaporation and p
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