SOLID-PHASE GROWTH TECHNIQUE FOR HIGH CUTOFF FREQUENCY POLYSILICON TFT INTEGRATED-CIRCUITS ON A QUARTZ SUBSTRATE

A solid phase growth technique of a polysilicon film on a fused quartz substrate has been developed for fabricating high-frequency polysilicon thin-film transistor (TFT) integrated circuits. The technique features the use of self-implantation at two energy steps, i.e., 150 and 40 keV. The complete amorphization of the initial LPCVD polysilicon is thereby attained throughout the film. Application of the solid phase growth technique has resulted in excellent high-frequency performance of the TFT’s over a large area with high reproducibility. The field effect mobilities obtained for n-channel and p-channel TFT’s are as high as 148 and 68 cm2/V · s, respectively. TFT shift registers which consist of 223 stages of C-MOS D flip-flops can successfully operate at clock frequencies up to 25 MHz under a supply voltage of 15.5 V on a fused-quartz substrate. © 1990 IEEE