TMCTS for gate dielectric in thin film transistors

The use of the liquid source tetramethylcyclotetrasiloxane (TMCTS) for gate dielectric deposition in low-temperature polysilicon thin film transistor (TFT) processes is investigated. TMCTS was reacted with O-2 in an LPCVD furnace at 580 degrees C to form a gate dielectric. For comparison, a low temperature oxide (LTO) was deposited as a gate dielectric using SiH4-O-2 LPCVD at 450 degrees C. Capacitance and charge pumping measurements indicate fewer interface states for TMCTS gate dielectric. Both NMOS and PMOS TFTs show comparable or superior performance with TMCTS oxide. Post-deposition annealing has less effect on TMCTS gate oxides. Although TMCTS gate dielectrics appear slightly more susceptible to damage in bias-temperature stress tests, TFTs with TMCTS gate oxides still retain better performance after stressing.