Grain filtering in MILC and its impact on performance of n- and p-channel TFTs

Abstract

Metal induced lateral crystallization (MILC) using nickel di-silicide catalyst is able to grow poly-Si films having a preferential crystal orientation along surface normal direction. The poly-Si film prepared by MILC, however, contains randomly distributed sub-grain boundaries which may degrade the performance of poly-Si TFT fabricated using the MILC film. We have investigated effects of patterning of the a-Si film prior to MILC on the growth characteristics and TFT performance. When the width of a-Si film pattern was narrowed, grain filtering effect occurred and, as a result, poly-Si islands whose active region for TFT is mostly composed of single oriented crystal were successfully grown. We characterized the film thus prepared by fabricating n and p-channel TFTs. TFTs were fabricated using the standard high temperature process. The results indicated that TFT performance is very much improved in terms of carrier mobility, on-current, and sub-threshold swing. We conclude that the pre-growth pattering of a-Si in MILC is useful technique to improve the performance of MILC TFTs.