Enhanced electrical performance and reliability of Ti-IGZO thin-film transistors with Hf_1-xAl_xO gate dielectrics

Abstract

A thin-film transistor (TFT) with a Ti-IGZO channel layer and Hf1-xAlxO gate dielectric is proposed to improve the performance and reliability of the device. The experimental results show that in three types of TFTs based on HfO2/IGZO, Hf1-xAlxO/IGZO and Hf1-xAlxO/Ti-IGZO gate dielectric/channel structures, the Hf0.88Al0.12O/Ti (2.0%)-IGZO TFT exhibits the best device performance with the subthreshold swing of 86 mV dec−1, field-effect mobility of 28.63 cm2∙V−1∙s−1 and on/off current ratio of 3.26 × 108. In particular, it shows a hysteresis voltage as low as 0.02 V and a threshold voltage shift after 1000 s positive/negative gate bias stress/white light illumination of 0.134 V/−0.089 V/−0.195 V, compared with 0.45 V and 0.612 V/−0.507 V/−0.657 V of the HfO2/IGZO TFT. These improvements are due to the incorporation of Ti into the IGZO channel, which reduces defect density, while adding Al to HfO2 improves surface roughness to inhibit surface scattering and charge capture during stress testing.

Multifunctional Oxygen Scavenger Layer for High-Performance Oxide Thin-Film Transistors with Low-Temperature Processing

“…In other words, the back channel of the OSL/a-IGZO film had a greater number of M–O bonds and a lower V O concentration compared to the back channel of the a-IGZO film, even with a low-temperature annealing at 200 °C. The Hf in the OSL has a stronger Hf–O bond strength (802 kJ/mol) compared to that of Ga–O (374 kJ/mol), In–O (346 kJ/mol), and Zn–O (284 kJ/mol). , It means that Hf can form more M–O bonds with oxygen ions during the sputtering and annealing processes, compared to Ga, In, and Zn. As shown in Figure d, the transfer characteristics of the OSL/a-IGZO TFT showed switching characteristics, even with low-temperature annealing fabrication .…”

“…Regarding the results shown in Figure 6b,d, the area ratio of M−O bonds (O I ) increased from 59.37 to 64.39%, and the area ratio of V O (O II ) decreased from 37.39 to 33.30%. In other words, the back channel of the OSL/a-IGZO film had a 47,48 It means that Hf can form more M−O bonds with oxygen ions during the sputtering and annealing processes, compared to Ga, In, and Zn. As shown in Figure 2d, the transfer characteristics of the OSL/a-IGZO TFT showed switching characteristics, even with low-temperature annealing fabrication.…”

Vertically Graded Oxygen Deficiency for Improving Electrical Characteristics and Stability of Indium Gallium Zinc Oxide Thin-Film Transistors

“…The VGO is realized by oxidation of the CII, which absorbs oxygen from the oxygen-rich a-IGZO channel to form the gradually decreased oxygen concentration from the oxygen-rich back channel to front channel. The CII is a thin layer deposited between the a-IGZO channel and the gate insulator interface and consists of aluminum (Al), which has higher bond dissociation energy with oxygen (791 kJ/mol) than that of indium (In) (346 kJ/mol), gallium (Ga) (374 kJ/mol), and zinc (Zn) (284 kJ/mol). , This means that the Al in the CII can absorb oxygen from the a-IGZO film as it is oxidized during annealing. By controlling the oxygen partial pressure during a-IGZO channel deposition to increase the oxygen concentration of the entire film, the CII can absorb oxygen from the front channel only and the V o concentration can be controlled in the channel.…”

Using thin-film transistor with thick oxygen-doped Si–Zn–Sn–O channel and patterned Pt/NiO capping layer to enhance ultraviolet light sensing performance

“…The difference in ΔV hys may be caused by the number of electrons trapping and detrapping in the channel films and the dielectric/channel interface. [47][48][49] Note that the OFR (16.7%)-SZTO TFT has the smallest ΔV hys ; it can be attributed to the fact that adding the right amount of oxygen to the channel is beneficial for reducing internal defects in the film and improving the film quality [as confirmed by the XPS analysis shown in Fig. 2(c)], so it reduces the probability of Among SZTO TFTs fabricated with various OFR's, the SZTO TFT with an OFR of 16.7% exhibits the best device performance with the lowest I off , the highest I on /I off ratio, and the best electrical reliability.…”