Reliability of laser-activated low-temperature polycrystalline silicon thin-film transistors

Abstract

In this letter, the characteristics and reliability of laser-activated polycrystalline silicon thin-film transistors (poly-Si TFTs) have been investigated by stressing the devices under V-ds=12 V and V-gs=15 V. In comparison with traditional furnace-activated poly-Si TFTs, the leakage current is relatively large for laser-activated poly-Si TFTs. Further, while the degradation rates of threshold voltage and subthreshold swing are comparable to those of traditional furnace-activated TFTs, the post-stress leakage and on/off current ratio for laser-activated poly-Si TFTs degrade much faster than those of furnace-activated counterparts. The laser activation modifies the grain structure between the drain and the channel region, and causes grain discontinuity extending from the drain to the channel region. As a result, an inferior reliability with extra trap state density and larger leakage current was observed in the laser-activated poly-Si TFTs. (C) 2002 American Institute of Physics.