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. 2021 Nov 22;11(11):902.
doi: 10.3390/membranes11110902.

Steep Subthreshold Swing and Enhanced Illumination Stability InGaZnO Thin-Film Transistor by Plasma Oxidation on Silicon Nitride Gate Dielectric

Yiming Liu  1 , Chang Liu  1 , Houyun Qin  1 , Chong Peng  1 , Mingxin Lu  1 , Zhanguo Chen  1 , Yi Zhao  1
Affiliations

Steep Subthreshold Swing and Enhanced Illumination Stability InGaZnO Thin-Film Transistor by Plasma Oxidation on Silicon Nitride Gate Dielectric

Yiming Liu et al. Membranes (Basel). .

Abstract

In this paper, an InGaZnO thin-film transistor (TFT) based on plasma oxidation of silicon nitride (SiNx) gate dielectric with small subthreshold swing (SS) and enhanced stability under negative bias illumination stress (NBIS) have been investigated in detail. The mechanism of the high-performance InGaZnO TFT with plasma-oxidized SiNx gate dielectric was also explored. The X-ray photoelectron spectroscopy (XPS) results confirmed that an oxygen-rich layer formed on the surface of the SiNx layer and the amount of oxygen vacancy near the interface between SiNx and InGaZnO layer was suppressed via pre-implanted oxygen on SiNx gate dielectric before deposition of the InGaZnO channel layer. Moreover, the conductance method was employed to directly extract the density of the interface trap (Dit) in InGaZnO TFT to verify the reduction in oxygen vacancy after plasma oxidation. The proposed InGaZnO TFT with plasma oxidation exhibited a field-effect mobility of 16.46 cm2/V·s, threshold voltage (Vth) of -0.10 V, Ion/Ioff over 108, SS of 97 mV/decade, and Vth shift of -0.37 V after NBIS. The plasma oxidation on SiNx gate dielectric provides a novel approach for suppressing the interface trap for high-performance InGaZnO TFT.

Keywords: InGaZnO; NBIS; interface traps; plasma oxidation; thin-film transistor.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Process flow diagram and structure of InGaZnO TFT in this work.
Figure 2
Figure 2
(a) Transfer characteristic curves for Ref. TFT and POG. TFT. The surface morphology for SiNx (b) without plasma oxidation and (c) with plasma oxidation. (d) The atomic ratio for the surface of SiNx thin film without/with plasma oxidation.
Figure 3
Figure 3
Si2p XPS results on the surface SiNx film without and with plasma oxidation.
Figure 4
Figure 4
XPS results for surface of SiNx thin film (a) without (b) with plasma oxidation.
Figure 5
Figure 5
The curves of transfer characteristic before/after NBIS test for (a) Ref. TFT and (b) POG. TFT; (c) spectrum of blue LED used in NBIS test; (d) Gp/ω as the function of frequency for Ref. and POG. MOS capacitor.
See this image and copyright information in PMC

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