Specific contact resistance of IGZO thin film transistors with metallic and transparent conductive oxides electrodes and XPS study of the contact/semiconductor interfaces

Rivas-Aguilar, M.E.; Hernández‐Como, N.; Gutiérrez-Heredia, Gerardo; Sánchez-Martínez, A.; Ramirez, M. Mireles; Mejía, I.; Quevedo‐Lopez, Manuel

doi:10.1016/j.cap.2018.04.002

Cited by 29 publications

(21 citation statements)

References 25 publications

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“…For In 3d signals at the Al/a-IGZO interface shown in Figure b, in addition to peak centers at 444.3 eV for In 3d 5/2 and 451.8 eV for In 3d 3/2 , extra peak centers at lower binding energies can be observed that are related to metallic In interstitials. The shift toward lower binding energy of In peaks also suggests a reduction of the oxidation state of In, consistent with the increase in oxygen vacancies . However, no obvious change is found in Ga 3d 5/2 and Zn 2p signals (not shown).…”

Section: Resultssupporting

confidence: 61%

“…The shift toward lower binding energy of In peaks also suggests a reduction of the oxidation state of In, consistent with the increase in oxygen vacancies. 34 However, no obvious change is found in Ga 3d 5/2 and Zn 2p signals (not shown). Regarding Al 2p signals at the interface, only the oxidation state can be observed in the treated a-IGZO (Figure 4c).…”

Section: ■ Results and Discussionmentioning

confidence: 88%

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

Yang

Zhou

et al. 2021

ACS Appl. Mater. Interfaces

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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.

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Section: Resultssupporting

confidence: 61%

Section: ■ Results and Discussionmentioning

confidence: 88%

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

Yang

Zhou

et al. 2021

ACS Appl. Mater. Interfaces

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“…3(c), no obvious difference is seen in Zn 2p signals. It is thus inferred that an oxidation-reduction reaction between Al and a-ZTO system takes place in the doping process, much similar to what happens in the Al, titanium (Ti) or manganese (Mn) reaction-doped a-IGZO [26,28,29] [26,28,29], forming oxygen vacancies and simultaneously leaving the displaced Sn interstitials that act as shallow donors. Thus, the oxidationreduction reaction could be described as…”

Section: Resultsmentioning

confidence: 76%

“…As shown, with Al reaction treatment, the area percentage of the red subpeak increases from 30 to 54%. The result suggests that large amounts of oxygen vacancies be generated during the Al reaction process [26][27][28]. Regarding the Sn 3d signals shown in Fig.…”

Section: Resultsmentioning

confidence: 86%

Self-Aligned Top-Gate Amorphous Zinc-Tin Oxide Thin-Film Transistor With Source/Drain Regions Doped by Al Reaction

Yang

Zhou

et al. 2021

IEEE J. Electron Devices Soc.

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A self-aligned fabrication process for top-gate amorphous zinc-tin oxide (a-ZTO) thin-film transistors (TFTs) is developed, in which the source/drain (S/D) doping is realized through depositing a thin aluminum (Al) film on S/D regions and performing a thermal annealing. Results indicate that a chemical oxidation-reduction reaction between Al and a-ZTO films takes place during the thermal annealing process, and shallow donors of oxygen vacancies and metal tin (Sn) interstitials are thus generated. The formed S/D regions have a high carrier concentration over 1 × 10 20 cm −3 , low sheet resistance of 0.57 kΩ/sq, and high thermal stability even in oxygen ambient. The fabricated a-ZTO TFTs exhibit excellent electrical performances, including a low channelwidth-normalized S/D resistance of about 7.05 Ω cm, a high fieldeffect mobility of 15.7 cm 2 /Vs, a high on/off current ratio of over 10 8 , and near-zero turn-on voltage. Moreover, good electrical stability with less than 0.2-V threshold voltage shift under ±30-V gate bias stresses is also achieved. Index Terms-Amorphous zinc-tin oxide, self-aligned top-gate, thin-film transistor, Al reaction doping, oxidation-reduction reaction. I. INTRODUCTIONMORPHOUS metal oxide semiconductors (AOS) thin-film transistors (TFTs) have been demonstrated to have relatively high carrier mobility, good performance uniformity over large-area, and low fabrication cost, and thereby regarded as one of the most promising devices applicable to advanced large area electronics and high-end integrated circuits [1][2][3][4][5][6][7][8][9]. The high mobility of AOS TFTs is usually attributed to the heavy metal cations, such as indium (In), which have an electronic configuration of (n-1)d 10 ns 0 (n ≥ 5) allowing largeradius spherical s orbitals and sufficient orbital overlapping [6][7][8]. As a result, the superiorities of the In-based AOS TFTs, like amorphous indium-gallium-zinc oxide (a-IGZO) [5-8] and amorphous indium-zinc oxide (a-IZO) [8][9][10][11] have earned them popularity in various applications. Unfortunately, In is toxic and short of reserve in earth [5,12,13]. On the other hand, the metal tin (Sn) is safe and abundant [12,13], and has the similar electronic configuration [8] and close coordination number [14] to indium in an amorphous oxide system. Thus, the In-free amorphous zinc-tin oxide (a-ZTO) has been investigated as a promising non-toxic low-cost AOS, and reasonably high This work was conducted in Shenzhen TFT and Advanced Display Lab and supported financially by NSFC under project 61774010, Shenzhen Municipal Scientific Program under Grants JCYJ20180504165449640, JCYJ20200109140610435, and XMHT20190201013.

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“…In theory, lower work function metals such as Al, Ti, Mo, or Cu are preferred as S/D electrodes to the formation of ohmic contact. Nevertheless, except for electrode work function, it has been confirmed that different types of electrodes lead to different contact resistances and interface electrical characteristics, which depend on the electronic structure and carrier density of the channel contact surface [ 37 ]. As a result, it is possible to modulate the carrier transport through chemical reactions with a specially designed alloy electrode.…”

Section: Introductionmentioning

confidence: 99%

Alloy-Electrode-Assisted High-Performance Enhancement-Type Neodymium-Doped Indium-Zinc-Oxide Thin-Film Transistors on Polyimide Flexible Substrate

Yao

et al. 2021

Research

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Flexible thin-film transistors with high current-driven capability are of great significance for the next-generation new display technology. The effect of a Cu-Cr-Zr (CCZ) copper alloy source/drain (S/D) electrode on flexible amorphous neodymium-doped indium-zinc-oxide thin-film transistors (NdIZO-TFTs) was investigated. Compared with pure copper (Cu) and aluminum (Al) S/D electrodes, the CCZ S/D electrode changes the TFT working mode from depletion mode to enhancement mode, which is ascribed to the alloy-assisted interface layer besides work function matching. X-ray photoelectron spectroscopy (XPS) depth profile analysis was conducted to examine the chemical states of the contact interface, and the result suggested that chromium (Cr) oxide and zirconium (Zr) oxide aggregate at the interface between the S/D electrode and the active layer, acting as a potential barrier against residual free electron carriers. The optimal NdIZO-TFT exhibited a desired performance with a saturation mobility (μsat) of 40.3 cm2·V-1·s-1, an Ion/Ioff ratio of 1.24×108, a subthreshold swing (SS) value of 0.12 V·decade-1, and a threshold voltage (Vth) of 0.83 V. This work is anticipated to provide a novel approach to the realization of high-performance flexible NdIZO-TFTs working in enhancement mode.

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Specific contact resistance of IGZO thin film transistors with metallic and transparent conductive oxides electrodes and XPS study of the contact/semiconductor interfaces

Cited by 29 publications

References 25 publications

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

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

Self-Aligned Top-Gate Amorphous Zinc-Tin Oxide Thin-Film Transistor With Source/Drain Regions Doped by Al Reaction

Alloy-Electrode-Assisted High-Performance Enhancement-Type Neodymium-Doped Indium-Zinc-Oxide Thin-Film Transistors on Polyimide Flexible Substrate

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