CHARACTERIZATION OF POLYCRYSTALLINE SILICON THIN-FILM TRANSISTORS FABRICATED BY ULTRAHIGH-VACUUM CHEMICAL-VAPOR-DEPOSITION AND CHEMICAL-MECHANICAL POLISHING

A high performance top-gate thin film transistor (TFT) has been fabric ated using an as-deposited polycrystalline silicon (poly-Si) film by u ltrahigh-vacuum chemical vapor deposition (UHV/CVD) followed by chemic al mechanical polishing (CMP). In this process, due to the ultraclean environment and very low-pressure deposition of UHV/CVD, high-quality poly-Si films can be obtained and no long-term or post-recrystallizati on in channel films is needed. Maximum field mobilities of 58 cm(2)/V. s adn 98 cm(2)/V.s for p- and n-channel TFTs, respectively, an ON/OFF current ratio of 1.1 x 10(7) for both p- and n-channels, and threshold voltages of -0.54 V for p-channel and 0.36 V for n-channel, devices, respectively, are achieved. Finally, an analytical model of poly-Si TF Ts was used to simulate the gate-voltage-dependent activation energy o n the threshold and above the threshold regions and showed good agreem ent.