The impact of self-aligned amorphous Si thin film transistors on imager array applications

Laser processing allows the fabrication of self-aligned amorphous Si thin f ilm transistors (a-Si:H TFTs). These devices have much smaller parasitic ca pacitance between gates and source/drain contacts and can have much shorter channel lengths compared to the conventional a-Si:H TFTs. We have fabricat ed matrix-addressed, optical imager arrays using these new a-Si:H TFTs as p ixel switches. We also have demonstrated that four-phase dynamic shift regi sters using short channel a-Si:K TFTs can be operated at a clock speed of 4 00 kHz (less than 0.625 mu s for each clock phase), indicating the possibil ity of integrating some of the peripheral circuits based oil a-Si:H TFT tec hnology. The advantages of using self-aligned a-Si TFTs as pixel switches i n large-area, flat-panel imagers are discussed. Improved noise performance is expected for large area imager arrays. (C) 2000 Elsevier Science B.V. Al l rights reserved.