Fabrication of microcrystalline silicon TFTs using a high-density plasma approach

N-channel microcrystalline silicon (mc-Si) thin film transistors (TFTs) were fabricated using a high density plasma (HDP) approach. An electron cyclotron resonance (ECR) plasma source was employed to deposit all of the thin film materials needed for the transistor; that is, intrinsic mc-Si, n-type mc-Si, and dielectric silicon dioxide were grown with the ECR high density plasmas and the deposition rates for these films were in the range of 120-150 /spl Aring//min. The substrate temperatures during these depositions were maintained below 285/spl deg/C. To complete the fabrication of these TFTs, we used only two masks with one alignment. After 1 h annealing under forming gas atmosphere, the mc-Si TFTs perform with linear field effect mobility of 12 cm
²
/V-s, on/off ratio of 10
⁶
, subthreshold swing of 0.3 V/decade, off-current of 4×10/sup -13/ A/μm and threshold voltage of 5 V.