Suppress temperature instability of InGaZnO thin film transistors by N2O plasma treatment, including thermal-induced hole trapping phenomenon under gate bias stress

Abstract

An abnormal subthreshold leakage current is observed at high temperature, which causes a notable stretch-out phenomenon in amorphous InGaZnO thin film transistors (a-IGZO TFTs). This is due to trap-induced thermal-generated holes accumulating at the source region, which leads to barrier lowering on the source side and causes an apparent subthreshold leakage current. In order to obtain superior thermal stability performance of a-IGZO TFTs, conducting N2O plasma treatment on active layer was expected to avert defects generation during SiO2 deposition process. Reducing defects generation not only suppresses subthreshold current stretch-out phenomenon but also significantly improves the bias stress stability in a-IGZO TFTs at high temperature.

Thermal analysis of amorphous oxide thin-film transistor degraded by combination of joule heating and hot carrier effect

“…Then, the accumulation of holes near the source region reduces the electrical potential wall between the source and the semiconductor and accelerates electron injection from the source. 15 Consequently, it seems that the drain current increase occurred. The drain current increase accelerates Joule heating in the depletion region and the heating accelerates the thermal vibration of atoms for the ITZO channel.…”

Exploring the photoleakage current and photoinduced negative bias instability in amorphous InGaZnO thin-film transistors with various active layer thicknesses

“…Besides the active layer thickness, the intrinsic characteristics of a-IGZO and the front- and back-channel interfaces of the TFT also play a vital role for the high-performance devices. Moreover, to reduce the density of oxygen vacancies in the bulk of the IGZO for the enhancement of electrical properties and stress stability of the TFTs, the following two aspects should be mainly considered: (i) oxidizing the densities of the defect state of oxide semiconductors to suppress charge trapping, for example by oxygen annealing and N 2 O plasma treatment [31]; and (ii) inactivating the defects in the semiconductor by means of introducing new elements to form stable chemical bonds with the defects, for example by fluoride ion implantation and nitrogen annealing [32–33]. …”

High-Performance Homojunction a-IGZO TFTs With Selectively Defined Low-Resistive a-IGZO Source/Drain Electrodes

“…The amount of nitrogen ions is not sufficient enough for detection by means of XPS. Note that nitrogen is known to passivate defects in a-IGZO [10], [11]. Given that the depth profile of the samples is obtained by combining a sequence of ion gun etch cycles interleaved with XPS measurements from the current surface, the large interface between SiO 2 and a-IGZO may be related to chamber contamination during these etch processes.…”

“…The resistivity of the a-IGZO S/D regions is reduced by high-power (200 W) NF 3 plasma treatment. The high-power NF 3 plasma treatment poses three advantages: 1) a substitution reaction between fluorine and oxygen may result in the generation of a free electron, given that the two have similar ionic radii [8], [9]; 2) fluorine atoms can occupy an oxygen vacancy site-reducing the electron trap density in the process; and 3) nitrogen ions may passivate defects and improve the stability of the a-IGZO TFTs [10], [11]. As such, the resistivity of the a-IGZO S/D regions was reduced from 16 to 5.5 × 10 −3 · cm by the NF 3 plasma treatment, and the treated samples exhibited metallic behavior in which conductivity increased with increasing temperature.…”