Transparent thin-film transistor exploratory development via sequential layer deposition and thermal annealing

Hong, Dezhi; Chiang, Hai Q.; Presley, Rick E.; Dehuff, N. L.; Bender, J.P.; Park, Cheol‐Hee; Wager, John F.; Keszler, Douglas A.

doi:10.1016/j.tsf.2006.03.050

Cited by 18 publications

(12 citation statements)

References 19 publications

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“…The negative slope of I ds was attributed to the influence of the slow trap near the semiconductor-insulator. 15 However, in this study, the negative I ds slope in the saturation region was adversely increased as the oxide channel thickness increased. Therefore, it is suggested that the bulk trap of SnO x thin film itself, rather than the interfacial slow trap at the semiconductor/gate dielectric, would be responsible for the unstable saturation property.…”

Section: Resultscontrasting

confidence: 55%

Improving the Performance of Tin Oxide Thin-Film Transistors by Using Ultralow Pressure Sputtering

Huh

Yang

et al. 2010

J. Electrochem. Soc.

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Thin-film transistors ͑TFTs͒ are fabricated with a tin oxide channel deposited by using ultralow pressure sputtering ͑ULPS͒. The effect of sputtering pressure on the device performance of the tin oxide TFTs was investigated. The TFTs with tin oxide channel deposited by conventional sputtering pressure did not show a promising performance. However, the saturation mobility ͑ sat ͒ and the threshold voltage ͑V th ͒ of the ULPS-deposited SnO x TFTs were improved to ϳ3.9 cm 2 /V s and ϳ0.6 V, respectively. The better device performance of the ULPS-deposited SnO x TFT was attributed to the reduced free electron density ͑ϳ10 17 /cm 3 ͒ resulting from the formation of a nanocrystalline phase.Recently, transparent oxide thin-film transistors ͑TFTs͒ with channel layers comprised of ZnO, In 2 O 3 -ZnO, In 2 O 3 -Ga 2 O 3 -ZnO, or ZnO-SnO 2 have been intensively studied for potential application as the back-plane of active matrix organic light emitting diodes, active matrix liquid crystal displays, and flexible displays due to their relatively high mobility ͑Ͼ5 cm 2 /V s͒ and good transparency in the visible range compared to the counterpart of amorphous Si TFTs. 1-4 Among the various kinds of transparent oxide semiconductor, tin oxide has been extensively studied as a semiconductor material for the channel layer in TFTs due to its wide bandgap of 3-4 eV, high optical transparency ͑Ͼ85%͒ in the visible light range, and good chemical stability. However, all TFTs using tin oxide semiconductors were n-type depletion-mode devices, which indicates a relatively high net electron carrier density ͑N d Ͼ 10 18 /cm 3 ͒, leading to impractically high operation gate voltage and power consumption. 5-7 Therefore, the reduction and/or control of the N d of sputtered tin oxide films has been a major focus of research on TFT applications. The N d of the sputtered tin oxide film has been related to the crystalline structure, oxidation state, and oxygen deficiency. 8-10 Recently, Huh et al. reported the strong dependence of the electrical properties of indium-doped tin oxide ͑ITO͒ films on the sputtering pressure and thus the kinetic energy of the sputtered particles. 11 This study reports the fabrication of TFTs with a SnO x film as the channel layer by using ultralow pressure sputtering ͑ULPS͒, with a sputtering pressure lower than 1.3 ϫ 10 −1 Pa, compared to higher than 6.7 ϫ 10 −1 Pa for a conventional sputtering pressure ͑CSP͒. As the sputtering pressure was decreased from 6.7 ϫ 10 −1 to 6.7 ϫ 10 −2 Pa, the N d of the SnO x thin film was dramatically reduced 100-fold from 10 19 to 10 17 cm −3 , resulting in a transistor performance with a reasonable mobility and on-and off-current ratio ͑I on/off ͒. In addition, the origin of the modulation of appropriate N d is discussed in detail. ExperimentalMo ͑250 nm͒ was deposited as a gate electrode by sputtering on a SiO 2 /p-type Si ͑p-Si͒ substrate. A 400 nm thick SiO x N y film was grown as a gate dielectric by plasma-enhanced chemical vapor deposition at a substrate temperature of 330°C. The S...

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Section: Resultscontrasting

confidence: 55%

Improving the Performance of Tin Oxide Thin-Film Transistors by Using Ultralow Pressure Sputtering

Huh

Yang

et al. 2010

J. Electrochem. Soc.

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“…The work in this field by Körner et al suggests hydrogen incorporation in IGZO and ZTO as a strategy to achieve this objective, by reducing the density of deep level defects and also by contributing as a shallow donor. To date, ZTO TFTs in literature either use thermal SiO 2 , atomic-layer deposited AlO x , or aluminumtitanium oxide (ATO) or chemical-vapor deposited SiON, always imposing (post-) processing temperatures exceeding 250 °C, [9,6,[20][21][22][23][24][25][26][27][28][29][30][31][32][33][34] Thus, an approach to integrate this oxide semiconductor with a low-temperature dielectric enabling good transistor performance and stability is yet to be investigated. Furthermore, in ZnO-based materials temperatures exceeding 220 °C can result in dissociation of substitutional hydrogen (H O ) into oxygen vacancies and interstitial hydrogen (H i ), [18] which is known to be thermally unstable and mobile even at room temperature.…”

Section: Introductionmentioning

confidence: 99%

“…The other is the integration of the optimized sputtered ZTO layers with a dielectric able to provide low operating voltage and good device stability without compromising the thermal budget. To date, ZTO TFTs in literature either use thermal SiO 2 , atomic‐layer deposited AlO x , or aluminum‐titanium oxide (ATO) or chemical‐vapor deposited SiON, always imposing (post‐) processing temperatures exceeding 250 °C, Thus, an approach to integrate this oxide semiconductor with a low‐temperature dielectric enabling good transistor performance and stability is yet to be investigated.…”

Section: Introductionmentioning

confidence: 99%

A Sustainable Approach to Flexible Electronics with Zinc‐Tin Oxide Thin‐Film Transistors

Fernandes

Santa

Santos

et al. 2018

Adv Elect Materials

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display backplanes and creating multifunctional flexible circuitry with thin-film technologies are considered. Within this scenario, amorphous oxide semiconductor (AOS) became one of the most competitive TFT technologies, enabling excellent uniformity in large areas, high transparency in visible spectrum, and field-effect mobility (µ FE ) exceeding 10 cm 2 V −1 s −1 even when fabricated below 200 °C. [1][2][3] The potential of these materials as semiconductors in TFTs started to be recognized in 2004 with the work by Nomura et al. on flexible indium-gallium-zinc oxide (IGZO) transistors. [4] Despite the establishment of IGZO TFTs as a key technology for large-area electronics, indium and gallium are critical raw materials, imposing important constrains regarding the sustainability of this approach. [5] Therefore, the ideal route for the next-generation AOS-based transistor technology should comprise an indium-and gallium-free semiconductor material, providing at least comparable performance and processing temperature to IGZO. Zinc-tin oxide (ZTO) has been recognized as a likely choice. Chiang et al. [6] reported in 2005 the first successful integration of sputtered ZTO as semiconductor layer in TFTs. Their staggered bottom-gate, top contact devices showed µ FE ≈ 20-50 cm 2 V −1 s −1 , turn-on voltage (V on ) between −5 and 5 V, and on/off ratio > 10 7 when annealed at 600 °C. However, µ FE drastically decreased to 5-15 cm 2 V −1 s −1 when lower annealing temperature (300 °C) was used, which is still too high for temperature-sensitive polymeric substrates as polyethylene naphthalene (PEN). Since then more than 150 articles on ZTO TFTs have been published, following both physical and solution-processing routes. Focusing on sputtering, which is the processing technique with easier penetration on an industrial TFT baseline process, aspects as different Zn:Sn ratios, [7][8][9] chamber pressure, oxygen flow ratio, and RF power during sputtering have been studied. [10] Nonetheless, for all these experiments a processing or post-processing temperature exceeding 300 °C was always used to achieve proper device operation (e.g., µ FE > 5 cm 2 V −1 s −1 in devices properly patterned, where overestimation of mobility due to fringing effects can be neglected. [11] A very recent work by Han et al. [12] is the exception to this, where a remarkable saturation mobility (µ sat ) of 67 cm 2 V −1 s −1 is achieved for polycrystalline tin-doped Zinc-tin oxide (ZTO) is widely invoked as a promising indium and galliumfree alternative for amorphous oxide semiconductor based thin-film transistors (TFTs). The main bottleneck of this semiconductor material compared to mainstream indium-gallium-zinc oxide (IGZO) is centered in the larger processing temperatures required to achieve acceptable performance (>300 °C), not compatible with low-cost flexible substrates. This work reports for the first time flexible amorphous-ZTO TFTs processed at a maximum temperature of 180 °C. Different aspects are explored to obtain performance levels comparable ...

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“…Such TFTs may be useful in improving the aspect ratio of conventional displays, in invisible circuitry, and in bendable devices . AOS films are typically grown using vacuum techniques such as sputtering, ion-assisted deposition, pulsed laser deposition, and chemical vapor deposition. − Combinatorial approaches have enabled the discovery of new compositions with high field-effect carrier mobilities (μ) and low carrier doping (n). The latter must be controlled/suppressed to achieve large TFT on-to-off current ratios ( I on / I off ) .…”

mentioning

confidence: 99%

Low-Temperature Solution-Processed Amorphous Indium Tin Oxide Field-Effect Transistors

Kim

et al. 2009

J. Am. Chem. Soc.

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Amorphous indium tin oxide (ITO)-based thin-film transistors (TFTs) were fabricated on various dielectrics [SiO(2) and self-assembled nanodielectrics (SANDs)] by spin-coating an ITO film precursor solution consisting of InCl(3) and SnCl(4) as the sources of In(3+) and Sn(4+), respectively, methoxyethanol (solvent), and ethanolamine (base). These films can be annealed at temperatures T(a) < or = 250 degrees C and afford devices with excellent electrical characteristics. The optimized [In(3+)]/[In(3+) + Sn(4+)] molar ratio (0.7) and annealing temperature (T(a) = 250 degrees C) afford TFTs exhibiting electron mobilities of approximately 2 and approximately 10-20 cm(2) V(-1) s(-1) with SiO(2) and SAND, respectively, as the gate dielectric. Remarkably, ITO TFTs processed at 220 degrees C still exhibit electron mobilities of >0.2 cm(2) V(-1) s(-1), which is encouraging for processing on plastic substrates.

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Transparent thin-film transistor exploratory development via sequential layer deposition and thermal annealing

Cited by 18 publications

References 19 publications

Improving the Performance of Tin Oxide Thin-Film Transistors by Using Ultralow Pressure Sputtering

Improving the Performance of Tin Oxide Thin-Film Transistors by Using Ultralow Pressure Sputtering

A Sustainable Approach to Flexible Electronics with Zinc‐Tin Oxide Thin‐Film Transistors

Low-Temperature Solution-Processed Amorphous Indium Tin Oxide Field-Effect Transistors

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