Self-heating of laterally grown polycrystalline silicon thin-film transistor

The temperature increase of polycrystalline silicon (poly-Si) thin-film transistors (TFTs) due to self-heating during operation is investigated by determining the thermal resistance from the temperature-dependent negative-drain conductance. TFTs are fabricated using a laterally grown poly-Si film. By aligning the TFT channel direction with the grain growth direction, the effects of the grain boundary on carrier transport become less significant and the direct evaluation of self-heating from drain characteristic becomes possible. Silicon-on-insulator (SOI) metal-oxide-semiconductor field-effect transistors (MOSFETs) are also investigated. The results indicate that the thermal resistance of a TFT is 40 times larger than that of an SOI MOSFET. As a consequence, the temperature increase of TFTs reaches 150K even under normal operation conditions. The heat dissipation path is also investigated by determining the thermal resistances of TFTs with various dimensions. The results indicate that the design of the thermal path through the gate is important for TFTs.