High-performance tin oxide field-effect transistors deposited by thermal atomic layer deposition

초록

In this study, we investigated the impact of annealing ambient on the performance of SnO2-based field-effect transistors (FETs) while adhering to the thermal budget constraint (process temperature < 450 degree celsius). The SnO2 films were deposited by thermal atomic layer deposition (T-ALD). After annealing the films for 2 h at 400 degree celsius, it was observed that annealing in an O-2 ambient resulted in a SnO2 film with an excessive number of background carriers, which made it difficult to fully deplete the channel. Conversely, annealing in an N-2 ambient led to an unstable channel that could not be effectively modulated, despite having a carrier concentration about an order of magnitude lower than that of the O-2-annealed film. Surprisingly, the devices annealed in an air ambient exhibited the best performance. X-ray photo-emission spectroscopy revealed that annealing in O-2 ambient resulted in a higher level of oxygen vacancy, while N-2 annealing was more effective in creating stoichiometric SnO. The best device performance achieved in this study was observed in a 6-nm thick channel that was annealed in the air. This device exhibited an on/off ratio of 1.2 x 10(11), subthreshold swing of 0.4 V/dec., field-effect mobility of 14.6 cm(2)/V center dot s, and threshold voltage of 1.1 V, operating in an enhancement mode. These results emphasize the potential of ALD SnO2 channels for high-performance transistors that are compatible with back-end-of-line processes in Si technology.

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