Metal Reaction-Induced Bulk-Doping Effect in Forming Conductive Source-Drain Regions of Self-Aligned Top-Gate Amorphous InGaZnO Thin-Film Transistors

Huan Yang; Xiaoliang Zhou; Haishi Fu; Baozhu Chang; Yuxin Min; Hao Peng; Lei Lu; Shengdong Zhang

doi:10.1021/acsami.0c21123

Metal Reaction-Induced Bulk-Doping Effect in Forming Conductive Source-Drain Regions of Self-Aligned Top-Gate Amorphous InGaZnO Thin-Film Transistors

ACS Appl Mater Interfaces. 2021 Mar 10;13(9):11442-11448. doi: 10.1021/acsami.0c21123. Epub 2021 Feb 16.

Authors

Huan Yang¹, Xiaoliang Zhou¹, Haishi Fu¹, Baozhu Chang¹, Yuxin Min¹, Hao Peng¹, Lei Lu¹, Shengdong Zhang^{1

2}

Affiliations

¹ School of Electronic and Computer Engineering, Peking University, Shenzhen 518055, China.
² School of Electronics Engineering and Computer Science, Peking University, Beijing 100871, China.

PMID: 33591715
DOI: 10.1021/acsami.0c21123

Abstract

In this paper, the aluminum (Al) treatment-induced doping effect on the formation of conductive source-drain (SD) regions of self-aligned top-gate (SATG) amorphous indium gallium zinc oxide (a-InGaZnO or a-IGZO) thin-film transistors (TFTs) is systematically investigated. Average carrier concentration over 1 × 10²⁰ cm^-3 and sheet resistance of around 500 Ω/sq result from the Al reaction doping. It is shown that the doping effect is of bulk despite the treatment at the surface. The doping process is disclosed to be a chemical oxidation-reduction reaction, that generates defects of oxygen vacancies and metal interstitials at the metal/a-IGZO interface. Both the generated oxygen vacancies and metal interstitials act as shallow donors, and the oxygen vacancies diffuse rapidly, leading to the bulk-doping effect. The fabricated SATG a-IGZO TFTs with the Al reaction-doped SD regions exhibit both high performance and excellent stability, featuring a low width-normalized SD resistance of about 10 Ω cm, a decent saturation mobility of 13 cm²/(V s), an off current below 1 × 10^-13 A, a threshold voltage of 0.5 V, a slight hysteresis of -0.02 V, and a less than 0.1 V threshold voltage shift under 30 V gate bias stresses for 2000 s.

Keywords: amorphous indium−gallium-zinc oxide (a-IGZO); amorphous oxide semiconductors (AOS); bulk-doping effect; metal treatment; oxidation−reduction reaction; oxygen vacancy diffusion; thin-film transistors (TFT).