COPLANAR AMORPHOUS-SILICON THIN-FILM-TRANSISTOR FABRICATED BY INDUCTIVELY-COUPLED PLASMA CHEMICAL-VAPOR-DEPOSITION

The electrical and optical properties of the hydrogenated amorphous si licon (a-Si:H) films deposited by inductively coupled plasma (ICP) che mical vapor deposition (CVD) have been investigated. The ICP-CVD a-Si: H films deposited at the pressure of 30 mTorr exhibited the hydrogen c ontent of 17 at. %, a photosensitivity of 10(6) at 100 mW/cm(2) and a conductivity activation energy of 0.9 eV. A novel coplanar self-aligne d a-Si: H thin film transistor was fabricated using Ni-silicide gate a nd source/drain electrodes. The simultaneous Ni-silicide formation of gate and source/drain regions using the stacked layers of thin a-Si:H, silicon nitride (SiNx) and a-Si:H reduces the offset length between g ate and source/drain, which leads to the coplanar a-Si:H thin film tra nsistor (TFT). This self-aligned a-Si:H TFT exhibited a field effect m obility of 0.44 cm(2)/V s, threshold voltage of 5.3 V and subthreshold slope of 0.5 V/ dec. The coplanar geometry reduces the parasitic capa citance and parasitic resistance compared with those of conventional s taggered a-Si:H TFTs. (C) 1998 American Institute of Physics. [S0021-8 979(98)06219-7].