Thin-film transistors(TFT's) were fabricated in low-temperature(600℃) crystallized amorphous LPCVD silicon films.
A channel layer was crystallized using a capping layer in $N_2$ ambient at 600℃ for 24 hours, and an LPCVD oxide film was used as a gate dielectric material.
These devices were found to have a mobility of about 20㎠/V·s, a threshold voltage of about 12.5 V, an inverse subthreshold slope of about 2.73 V/decade, and a maximum ON/OFF current ratio of about 1x$10^5$ after hydrogenation for 3 hours.
A fabricated 1-bit shift register using these devices showed a maximum operation frequency of 3 kHz under a capacitive load of 15 pF.
SPICE simulation was performed to know electrical performances of shift register. As a result, it was found that for normal operation, a drain bias voltage must be as high as 37 V, a input voltage swing as high as 20 V, and clock pulse height as high as 30 V.
