Influence of Reduction in Effective Channel Length on Device Operations of In-Ga-Zn-O Thin-Film Transistors With Variations in Channel Compositions

Roles of Oxygen Interstitial Defects in Atomic-Layer Deposited InGaZnO Thin Films with Controlling the Cationic Compositions and Gate-Stack Processes for the Devices with Subμm Channel Lengths

“…In our previous works, in which the devices were prepared with the OI gate stacks composed of 90 nm-thick Al 2 O 3 GI and ITO GE, the shortening effects of effective channel lengths have been demonstrated as results of redox reactions and interdiffusions at interfaces between the IGZO channels and Mo S/D electrodes owing to the formation of MoO x . Furthermore, it was also found that these SCEs were accelerated with increasing the In contents within the IGZO channel layers due to a higher concentration of V O . Alternatively, it was found that the SCEs of fabricated devices using OI gate stacks were effectively suppressed with reducing the Al 2 O 3 GI thickness from 90 to 45 nm, as shown in SI Figure S6.…”

“…Furthermore, it was also found that these SCEs were accelerated with increasing the In contents within the IGZO channel layers due to a higher concentration of V O . 20 Alternatively, it was found that the SCEs of fabricated devices using OI gate stacks were effectively suppressed with reducing the Al 2 O 3 GI thickness from 90 to 45 nm, as shown in SI Figure S6. It was also impressive that the introduction of AZO GE could improve the channel shortening effect of the scaled devices.…”

“…12−18 Alternatively, during the progress of device scaling for the AOS TFTs, short-channel effects (SCEs) of the fabricated devices should be fairly evaluated. 19,20 Particularly, the gate-stack formation conditions and process steps are major concerns to be carefully designed. For conventional topgate structures, the AOS channel layers are exposed prior to the deposition of gate insulator (GI) layers, during which the electronic nature of AOS channel layer may be completely modulated by the unavoidable doping reaction such as hydrogen incorporations.…”

“…From these technical backgrounds, the introduction of AOS channel thin film transistor (TFT) has been pursued to reduce the cell footprint and open the possibility of stacking individual cells. − For developing and characterizing the devices with nanoscale AOS channels, the device feasibility should be urgently explored for potential implementation of highly scaled devices in future logic and memory applications. There have been several approaches to implement short-channel oxide TFTs, such as 3D vertical or self-aligned coplanar structures. − Alternatively, during the progress of device scaling for the AOS TFTs, short-channel effects (SCEs) of the fabricated devices should be fairly evaluated. , Particularly, the gate-stack formation conditions and process steps are major concerns to be carefully designed. For conventional top-gate structures, the AOS channel layers are exposed prior to the deposition of gate insulator (GI) layers, during which the electronic nature of AOS channel layer may be completely modulated by the unavoidable doping reaction such as hydrogen incorporations. − Furthermore, the effects of cationic compositions and defect structures of the AOS thin films on device characteristics should be strategically investigated to secure superior and stable device operations. − In–Ga–Zn-O (IGZO) compositions have been developed and exploited as one of the most functional and stable candidates of AOS channels for implementing various device applications. − Although the device performance could be modulated and improved by controlling the cationic compositions of the IGZO channel layers, there have been still such limitations as controls of turn-on positions and enhancement of both requirements of a more robust bias stability and a higher mobility of the fabricated TFTs. − From these viewpoints, the composition-dependent defect structures of the IGZO and the process conditions for the formation of gate-stack structures should be carefully designed to secure the highly functional device characteristics, because the hydrogen-related species induced during the deposition process of gate stacks can be correlated with various defects such as oxygen vacancies and interstitials located within the IGZO thin films.…”

Analysis on Contact Resistance and Effective Channel Length of Thin Film Transistors Using Composition-Modified In–Ga–Zn-O Active Channels Prepared with Atomic Layer Deposition and Various Electrode Materials

“…Furthermore, the cationic compositions of IGZO channel layers, which intrinsically determine the R CH , are expected to be closely related to the R C and ΔL for the ALD IGZO TFTs. 13 In this work, from these points of view, we carefully analyzed and examined the impact of device process conditions such as cationic composition of ALD IGZO channel layers and types of S/D electrode materials on the device parameters of R C and ΔL extracted from the fabricated ALD IGZO TFTs. The channel compositions were strategically modulated by controlling the subcyclic ratio of ALD supercycles during the deposition of IGZO, and the S/D electrode was varied to indium-tin-oxide (ITO) and molybdenum (Mo) to compare the contact behaviors among the fabricated devices.…”