Passivation and Annealing for Improved Stability of High Performance IGZO TFTs

Mudgal, Tarun; Walsh, N.; Manley, Robert G.; Hirschman, K.D.

doi:10.1557/opl.2014.906

Cited by 6 publications

(7 citation statements)

References 7 publications

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“…In addition, most sputtering methods have a risk of inducing TFT degradation after deposition due to excess carriers and generation of traps induced by the plasma process. Thus, in other studies, the a-IGZO layer was instead protected by passivation materials fabricated by solution process using B-staged bisbenzocyclobutene [13], paraffin wax [14], and CYTOP [15]. Solution process can coat very uniform films in spite of large device size.…”

Section: Introductionmentioning

confidence: 99%

Fluorine incorporation in solution-processed poly-siloxane passivation for highly reliablea-InGaZnO thin-film transistors

Yoshida

Bermundo

Ishikawa

et al. 2018

J. Phys. D: Appl. Phys.

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We investigated a fluorine-containing polysiloxane (Poly-SX) passivation layer fabricated by solution process for amorphous InGaZnO (a-IGZO) thin-film transistors (TFT). This passivation layer greatly improved the stability of the a-IGZO device even after being subjected to positive bias stress (PBS) and negative bias stress (NBS). The mobility (µ) of TFTs passivated by fluorine-containing Poly-SX increased by 31%–56% (10.50–12.54 cm2 V−1 s−1) compared with TFTs passivated by non-fluorinated Poly-SX (8.04 cm2 V−1 s−1). Increasing the amount of fluorine additives led to a higher µ in passivated TFTs. Aside from enhancing the performance, these passivation layers could increase the reliability of a-IGZO TFTs under PBS and NBS with a minimal threshold voltage shift (ΔVth) of up to +0.2 V and −0.1 V, respectively. Additionally, all TFTs passivated by the fluorinated passivation materials did not exhibit a hump effect after NBS. We also showed that fluorinated photosensitive Poly-SX, which can be fabricated without any dry etching process, had an effective passivation property. In this report, we demonstrated the photolithography of Poly-SX, and electrical properties of Poly-SX passivated TFTs, and analyzed the state of the a-IGZO layer to show the large potential of Poly-SX as an effective solution-processed passivation material.

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Section: Introductionmentioning

confidence: 99%

Fluorine incorporation in solution-processed poly-siloxane passivation for highly reliablea-InGaZnO thin-film transistors

Yoshida

Bermundo

Ishikawa

et al. 2018

J. Phys. D: Appl. Phys.

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“…Deposition of PECVD SiO 2 and sputtered quartz rendered the IGZO too conductive to function as a channel material due to plasma exposure of the back-channel during deposition, which has been discussed in our previous report [5]. The resulting sheet resistance and resistivity values after material deposition, prior to annealing, are provided in table II.…”

Section: Discussionmentioning

confidence: 84%

“…Note that the TCAD structure was slightly modified from actual physical dimensions to provide offsets needed to account for series resistance and parasitic capacitance. After the application of BCB and alumina passivation materials and annealing in air ambient, the long-term consistency of device characteristics was markedly improved [5]. However the hysteresis observed on the slow-sweep dual-trace C-V characteristic taken on a BCB-passivated IDC, shown in figure 3(a), reveals the presence of deep traps possibly created during plasma etch of BCB.…”

Section: Discussionmentioning

confidence: 99%

Study of Back-Channel Defect States on Bottom-Gate IGZO TFTs Using Capacitance-Voltage Analysis

et al. 2015

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This work investigates the quality of back-channel passivation applied to sputterdeposited IGZO bottom-gate TFTs. Passivation materials investigated were alumina, silicon dioxide, and B-staged bisbenzocyclobutene-based (BCB) resins. Sputtered quartz and PECVD (TEOS) SiO 2 rendered the IGZO material highly conductive (ρ < 0.01 Ω·cm), with subsequent annealing in oxidizing ambient unable to restore a high-resistivity state. Appropriate channel resistivity was restored on devices passivated with electron-beam evaporated alumina and spincoated BCB when followed by annealing in air. Alumina passivated devices demonstrated improved stability; however slight distortions in measured I-V and C-V characteristics were observed. TCAD simulation was used to develop an IGZO material/device model, with results indicating the significant presence of oxygen-vacancy (OV) interface traps and negative fixed charge remaining at the back-channel.

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“…Spectroscopic ellipsometry measurements were performed and variation in optical constants appear to be correlated with the electrical behavior of TFT fabrication, leading to a hypothesis of compositional changes in the material associated with the sputter deposition. As with IGZO TFTs, a passivation layer helps to avoid shifting due to interactions with air ambient (11)(12). Future studies will involve investigations into alumina and silicon dioxide passivation to control transfer characteristic shifting.…”

Section: Discussionmentioning

confidence: 99%

Process Development of Amorphous Indium Tin Gallium Oxide (ITGO) Thin Film Transistors

Powell¹,

Kabir²,

Zhu³

et al. 2022

ECS Trans.

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The focus of this study is an investigation on Indium-Tin-Gallium-Oxide (ITGO) TFTs. Unpassivated bottom-gate devices werefabricated with a sputter-deposited 30nm a-ITGO film with 1% and10% oxygen gas ambient, followed by a 1 or 2 hour anneal at 300oCin oxygen. Devices fabricated with PO2 = 1% resulted in a highlyconductive channel, whereas devices with PO2 = 10% displayedsemiconducting behavior and a shallow subthreshold. Followingaging in room ambient for multiple days, devices displayed left-shifted transfer characteristics with steep subthreshold. It ishypothesized that the unpassivated back-channel attains a morehomogeneous trap distribution. The ITGO devices demonstrate aneffective channel mobility approximately 2.5 times higher thanIGZO TFTs. Radial variation in device performance can beattributed to non-uniformities in the as-deposited ITGO film, with acorrelation to the distribution in optical constants across the wafer.

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Passivation and Annealing for Improved Stability of High Performance IGZO TFTs

Cited by 6 publications

References 7 publications

Fluorine incorporation in solution-processed poly-siloxane passivation for highly reliablea-InGaZnO thin-film transistors

Fluorine incorporation in solution-processed poly-siloxane passivation for highly reliablea-InGaZnO thin-film transistors

Study of Back-Channel Defect States on Bottom-Gate IGZO TFTs Using Capacitance-Voltage Analysis

Process Development of Amorphous Indium Tin Gallium Oxide (ITGO) Thin Film Transistors

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