Post-annealing effect of low temperature atomic layer deposited Al2O3on the top gate IGZO TFT

Shuaiying Zheng; Shaocong Lv; Chengyuan Wang; Zhijun Li; Liwei Dong; Qian Xin; Aimin Song; Jiawei Zhang; Yuxiang Li

doi:10.1088/1361-6528/ad1d16

Post-annealing effect of low temperature atomic layer deposited Al₂O₃on the top gate IGZO TFT

Nanotechnology. 2024 Jan 25;35(15). doi: 10.1088/1361-6528/ad1d16.

Authors

Shuaiying Zheng¹, Shaocong Lv¹, Chengyuan Wang¹, Zhijun Li¹, Liwei Dong¹, Qian Xin^{1

2}, Aimin Song^{1

3}, Jiawei Zhang¹, Yuxiang Li¹

Affiliations

¹ Shandong Technology Center of Nanodevices and Integration, and School of Integrated Circuits, Shandong University, Jinan 250101, People's Republic of China.
² State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, People's Republic of China.
³ School of Electrical and Electronic Engineering, University of Manchester, Manchester M13 9PL, United Kingdom.

PMID: 38198735
DOI: 10.1088/1361-6528/ad1d16

Abstract

Electronical properties of top gate amorphous InGaZnO₄thin film transistors (TFTs) could be controlled by post-annealing treatment, which has a great impact on the Al₂O₃insulator. To investigate the effect of post-annealing on Al₂O₃, Al/Al₂O₃/p-Si MOS capacitoras with Al₂O₃films treated under various post-deposition annealing (PDA) temperature were employed to analysis the change of electrical properties, surface morphology, and chemical components by electrical voltage scanning, atomic force microscope (AFM), and x-ray photoelectron spectroscopy (XPS) technologies. After PDA treatment, the top gate TFTs had a mobility about 7 cm²V^-1s^-1and the minimum subthreshold swing (SS) about 0.11 V/dec, and the threshold voltage (V_th) shifted from positive direction to negative direction as the post-annealing temperature increased. Electrical properties of MOS capacitors revealed the existence of positive fixed charges and the variation of trap state density with increasing PDA temperature, and further explained the change of negative bias stress (NBS) stability in TFT. AFM results clarified the increased leakage current, degraded SS, and NBS stability in MOS capacitors and TFTs, respectively. XPS results not only illuminated the origin of fixed charges and the trap density variation with PDA temperatures of Al₂O₃films, but also showed the O and H diffusion from Al₂O₃into IGZO during post-annealing process, which led to the deviation ofV_th, the change of current density, and the negativeV_thshift after positive bias stress in TFTs.

Keywords: Al2O3; IGZO TFT; MOS capacitors; post-annealing; top gate.