Stability improvement of solution-processed IGZO TFTs by fluorine diffusion from a CYTOP passivation layer

Abstract

This study investigated the effects of fluorine (F) diffusion from a CYTOP passivation layer into amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs). The F contained in the CYTOP passivation layer was diffused into a-IGZO through 350 °C annealing. The similar ionic radii of F and oxygen (O) allowed the passivation of oxygen vacancy (Vo) and weakly bonded oxygen by F. As a result, the a-IGZO TFTs with CYTOP passivation were highly stable under various stresses. The threshold voltage (Vth) shifts of a-IGZO TFTs without CYTOP passivation and with CYTOP passivation under a negative bias stress test for 10 000 s were −6.7 V and −2.5 V, respectively. In addition, the Vth shifts of each device under a negative bias illumination stress test for 4000 s were −10.9 V and −5.3 V, respectively. This improvement was caused by a reduction of Vo and a widened band gap of a-IGZO through the F diffusion effect. In addition, the CYTOP passivation layer maintained excellent properties as a barrier against moisture after 350 °C annealing.

Improved Performance and Operational Stability of Solution-Processed InGaSnO (IGTO) Thin Film Transistors by the Formation of Sn–O Complexes

“…Following the electrical properties, the electrical instability of IGTO TFTs with different Ga and Sn molar ratios was further examined by applying a gate bias stress under ambient conditions − without the passivation of the channels to avoid any change in properties of IGTO thin films caused by unintentional diffusion and doping. , The effect of Ga and Sn atoms on oxygen vacancies in IGTO thin films can be estimated by observing the electrical properties of IGTO TFTs under a gate bias stress because oxygen-related defects in AOS thin films determine the Δ V th under the gate bias stress. Thus, IGTO TFTs were stressed to a positive gate bias (PBS, V GS = +10 V) and a negative gate bias (NBS, V GS = −10 V) at room temperature for 1000 s, and Δ V th as a function of bias stress time with various Ga and Sn molar ratios is shown in Figure .…”

A cost‐effective fluorination method for enhancing the performance of metal oxide thin‐film transistors

“…During the thermal curing of PLN, minute fragments such as CF x radicals may be generated and diffuse through the ESL into the AC. Since the electronegativity of fluorine is the largest (3.98) among all elements, 12 it is likely that oxygen vacancies in the AC bulk are passivated by these fluorine species, leading to enhanced electrical performances. The effect of carbon contents on the performance of these devices is still unclear.…”

“…The inset illustrates the selected positions, and there are two samples chosen for measurement at each position F I G U R E 3 (A) Plan-view microscopic image, (B) cross-sectional schematic, and (C) I-V characteristics of the mesh structure into the AC. Since the electronegativity of fluorine is the largest (3.98) among all elements, 12 it is likely that oxygen vacancies in the AC bulk are passivated by these fluorine species, leading to enhanced electrical performances. The effect of carbon contents on the performance of these devices is still unclear.…”

8‐1: Distinguished Paper: A Cost‐Effective Fluorination Method for Enhancing the Performance of Metal Oxide Thin‐Film Transistors Using a Fluorinated Planarization Layer

“…Probably due to the elimination of the additional annealing processes [9], the device owns relatively better S/D contacts with no current crowding effect in its output curves (Fig. 3(c)), leading to a higher on-off ratio of 1.5×10 10 and a boosted saturation mobility (µsat) of 22.3 cm 2 /Vs. The significant thermal budget reduction does not degrade the device uniformity in electrical performance across a large area.…”

“…During the thermal curing step, fragments such as CFx radicals may be generated in the PLN under heat and then diffuse through the ES, which consists of lowdensity PECVD SiO2, and eventually incorporated into the AC bulk. The added fluorine contents may function as efficient agents to passivate oxygen-related deficiencies in MO channels considering that fluorine has the largest electronegativity (3.98) among elements [10]. The incorporated carbon has little positive impact on device performance, as evidenced in Fig.…”