Thin-film transistor mfr. leaving no impurities in channel regions - performing source and drain ion bombardment and ohmic contact formation prior to gate isolation and photoetching

摘要

On a well-dried transparent glass substrate (11), source and drain electrodes (12,13) are deposited by vacuum evaporation and photoetching, and covered with about 100 nm of silicide film (14). A bridging layer (15) of semiconductor is added by plasma CVD and ion-implanted to form ohmic layers (16) on both silicides. After further photoetching the SiO2 or Si3N4 gate isolation (17) is superimposed and the gate electrode (18) is formed of 200 to 400 nm of metal (e.g. Al). The method gives a threshold voltage of 4 to 5 V, carrier mobility of 0.3 to 0.4 sq.cm/volt-sec and on/off current ratio of up to 10 million. USE/ADVANTAGE - For an active matrix liq. crystal display, the degradation of transistor properties by impurity particles is reduced together with mfg. costs and rejection rates.