Ultrathin InGaO Thin Film Transistors by Atomic Layer Deposition

In this letter, we report on scaled ultrathin (similar to 3 nm) InGaO (IGO) thin film transistors (TFTs) by atomic layer deposition (ALD) under a low thermal budget of 250 degrees C. The ALD-derived IGO channels are In-rich, with In/Ga atomic ratio of similar to 86:14, providing a high electron mobility of similar to 28.6 cm(2).V-1.s(-1) under a ultrathin thickness of 3 nm. The resulting IGO TFTs exhibit excellent scaling behaviors down to sub-100 nm channel length (L-ch). The IGO TFTs with a L-ch of 80 nm show well-behaved electrical characteristics including a high on/off current ratio (I-on/I-off) of 1.8 x 10(10), a low subthreshold swing (SS) of 92 mV/dec under VDS of 0.8 V. The negative-and positive-gate-bias-stress stability (NBS and PBS) of IGO TFTs are studied in both N-2 and air ambient, where a remarkably high PBS stability can be observed. The negative Vth shifts during PBS and NBS test in N-2 ambient could be explained by the generation of donor-like traps originating from ionized oxygen vacancy, in addition to electron (de)trapping mechanism. This work presents the first demonstration of high-performance IGO TFTs with a miniatured device dimension, showing the potential for back-end-of-line (BEOL)-compatible monolithic 3D integration.

Automated summary

This research presents scaled ultrathin (about 3 nm) InGaO (IGO) thin film transistors (TFTs) with high-performance characteristics. The IGO channels, derived from atomic layer deposition (ALD), have a high In/Ga atomic ratio of approximately 86:14, resulting in a high electron mobility under a thin thickness. The IGO TFTs show excellent scaling behaviors and demonstrate good electrical characteristics, making them potential candidates for back-end-of-line (BEOL)-compatible monolithic 3D integration.