Optimization of the Fabrication Process for ZnO Thin-Film Transistors with HfO<sub>2</sub> Gate Dielectrics

Chen, Henry J. H.; Yeh, Barry B. L.

doi:10.1143/jjap.48.031103

Cited by 11 publications

(8 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…22 Also, in our previous study, 12 the threshold voltage degradation of the ZTO TFT followed the stretched exponential behavior. Figure 5 shows that the time dependence of V th can be well fitted with the stretched-exponential equation.…”

Section: Resultsmentioning

confidence: 83%

“…On the other hand, it is found in our work that there exists an interaction between HfO y and ZTO, therefore, having AlO x on top of HfO y reduces the interaction with ZTO and thus high mobility as well as stable performance can be achieved. Besides, it is found that Zn can diffuse easily into HfO y , 22 have a role of Zn diffusion barrier. This leads to an enhancement of TFT performance.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Low Voltage Driven, Stable Solution-Processed Zinc-Tin-Oxide TFT with HfOy and AlOx Stack Gate Dielectric

Kim¹,

Avis²,

Jang³

2012

ECS Solid State Letters

View full text Add to dashboard Cite

We report on low voltage driven, solution processed zinc-tin oxide (ZTO) transistors with a spin-coated hafnium oxide (HfO y ) and aluminum oxide (AlO x ) stack gate insulator (HfO y /AlO x ). The ZTO TFT with a HfO y /AlO x dielectric processed at the maximum temperature of 400 • C exhibits the field-effect mobility of 3.84 cm 2 /V s, subthreshold swing of 117 mV/dec., and threshold voltage (V th ) of 0.84 V. The positive gate bias stress degradation of V th with time follows a stretched exponential behavior with a time constant of 1.13 × 10 7 s, indicating stable TFT.Recently, there is growing interest in the use of amorphous oxide semiconductors (AOS) such as amorphous indium-gallium-zinc-oxide (a-IGZO) for their applications to thin-film transistors (TFTs) 1,2 and TFT circuits. 3-6 They are generally fabricated by vacuum deposition methods such as reactive sputtering and pulsed laser ablation. In contrast, solution processed TFT leads to low cost manufacturing of TFT arrays for printed electronics. But the stability in oxide TFTs such as a-IGZO is currently the most important and crucial issue to be overcome. Note that the performance of solution processed TFT is inferior as compared to that of vacuum processes. However, the performance of solution processed TFT is being improved recently using the oxide semiconductors based on zinc-oxide (ZnO), 7 indium-zinc-oxide (IZO) 8 and zinc-tin oxide (ZTO), 9,10 and their bias stress stabilities are also improved. 11,12 Silicon dioxide (SiO 2 ) deposited by plasma enhanced chemical vapor deposition (PECVD) is widely used as a gate insulator of oxide TFTs, 12,13 but the TFTs using SiO 2 have high threshold voltage (V th ) because of its low dielectric constant. Nowadays, high-κ dielectrics such as hafnium oxide (HfO y ) and aluminum oxide (AlO x ) are of growing interest in TFT manufacturing for low voltage driven TFTs and arrays. 15-17 Previously, spin coated AlO x was used for ZTO TFT 14 exhibiting high field-effect mobility of 34 cm 2 /V s. HfO y is a high-κ material so that it can be used as a gate insulator of low voltage driven oxide TFTs. In this work we used a stacked dielectric layer of AlO x and HfO y prepared by a solution process to make low voltage driven ZTO TFT arrays. ExperimentalThe ZTO solution was made by mixing zinc chloride (ZnCl 2 ) and tin chloride (SnCl 2 ) into a solvent of acetonitrile and ethyleneglycol, with a zinc tin ratio of 2:1 which leads to high mobility and relatively stable TFT. 12,18 Aluminum oxide and hafnium oxide solutions were prepared respectively by using aluminum chloride (AlCl 3 ) and hafnium chloride (HfCl 4 ) mixed into the same solvent with a concentration of 0.2 M. The solution was stirred vigorously in an N 2 environment. Then, the solution was filtered through a 0.45 μm filter before being spin-coated.In order to fabricate the TFTs, a 40 nm thick Mo layer was deposited on a glass substrate and patterned by photolithography as gate electrode. After the substrate was cleaned, a 65 nm thick HfO y layer was spin-coated and...

show abstract

Section: Resultsmentioning

confidence: 83%

Section: Resultsmentioning

confidence: 99%

Low Voltage Driven, Stable Solution-Processed Zinc-Tin-Oxide TFT with HfOy and AlOx Stack Gate Dielectric

Kim¹,

Avis²,

Jang³

2012

ECS Solid State Letters

View full text Add to dashboard Cite

show abstract

“…High-k gate insulators can offer high capacitance and low leakage current density, so the use of high-k gate insulators is the optimum approach [4]. So far, various high-k gate dielectrics, including Bi 1.5 Zn 1.0 Nb 1.5 O 7 (BZN) [5][6][7][8][9], HfO 2 [10,11], and SiN x [12,13] etc., have been extensively researched because of low leakage current density and high permittivity. Among of those high-k gate insulators, BZN thin films have shown the best performance due to the formation of the partial nanocrystalline BZN phase in the amorphous matrix [14].…”

Section: Introductionmentioning

confidence: 99%

RETRACTED: Effect of thickness of Bi1.5Zn1.0Nb1.5O7 gate insulator on performance of ZnO based thin film transistors

Deng

Wang

et al. 2016

Applied Surface Science

View full text Add to dashboard Cite

“…ZnO-based thin film transistors ͑TFTs͒ [1][2][3][4][5][6][7][8][9][10][11][12][13][14] have been studied extensively in recent years owing to their potential for replacing hydrogenated amorphous or polycrystalline silicon ͑poly-Si͒ TFTs. In addition to the high mobility ͑comparable to that of poly-Si TFTs͒, these ZnO devices do not require prolonged high temperature annealing for dopant activation.…”

mentioning

confidence: 99%

“…This important feature provides faster throughput enhancement and greater energy savings during production. Moreover, ZnO is transparent to visible light and allows low temperature manufacturing; the former advantage especially may assist in the realization of a next generation transparent TFT backplane, [2][3][4][5][6][12][13][14] and if the high quality of the gate dielectric is also available simultaneously in a low temperature process, the latter advantage may assist in the fabrication of flexible electronics. 15 Although many benefits exist for the ZnO TFT, for further applications involving high speed and low power integrated circuits, the TFTs must possess a low threshold voltage and a small subthreshold swing ͑SS͒.…”

mentioning

confidence: 99%

A Low Operating Voltage ZnO Thin Film Transistor Using a High-κ HfLaO Gate Dielectric

Wang

Chin

2010

Electrochem. Solid-State Lett.

View full text Add to dashboard Cite

This study demonstrates the feasibility of producing a ZnO thin film transistor ͑TFT͒ using hafnium-lanthanum-oxide ͑HfLaO͒ as the gate dielectric. By integrating high-HfLaO with an amorphous ZnO channel, the resulting HfLaO/ZnO TFTs display a low threshold voltage ͑V T ͒ of 0.28 V, a small subthreshold swing ͑SS͒ of 0.26 V/dec, an acceptable mobility ͑ sat ͒ of 3.5 cm 2 /V s, and a good I on /I off ratio of 1 ϫ 10 6 . The SS heavily depends on the HfLaO/ZnO interface charges, a property which is related to the degree of crystallization of ZnO. The low V T and the small SS allow device voltage operation below 2 V for low power application.ZnO-based thin film transistors ͑TFTs͒ 1-14 have been studied extensively in recent years owing to their potential for replacing hydrogenated amorphous or polycrystalline silicon ͑poly-Si͒ TFTs. In addition to the high mobility ͑comparable to that of poly-Si TFTs͒, these ZnO devices do not require prolonged high temperature annealing for dopant activation. This important feature provides faster throughput enhancement and greater energy savings during production. Moreover, ZnO is transparent to visible light and allows low temperature manufacturing; the former advantage especially may assist in the realization of a next generation transparent TFT backplane, 2-6,12-14 and if the high quality of the gate dielectric is also available simultaneously in a low temperature process, the latter advantage may assist in the fabrication of flexible electronics. 15 Although many benefits exist for the ZnO TFT, for further applications involving high speed and low power integrated circuits, the TFTs must possess a low threshold voltage and a small subthreshold swing ͑SS͒.In this article, we have investigated the feasibility of producing a ZnO TFT using a HfLaO gate dielectric 16-20 and an amorphous ZnO ͑a-ZnO͒ channel for low voltage and low power applications. The resulting HfLaO/a-ZnO TFT exhibits a small SS of 0.26 V/dec, a low threshold voltage ͑V T ͒ of 0.28 V, an acceptable mobility ͑ sat ͒ of 3.5 cm 2 /V s, and a good on/off current ratio ͑I on /I off ͒ of 1 ϫ 10 6 at an operation voltage below 2 V. The small V T is due to the unique negative flatband voltage of the La 2 O 3 gate dielectric, 21 where the doping of La 2 O 3 into HfO 2 or the capping of HfO 2 has been widely used to lower the V T of high-Si metal-oxidesemiconductor field-effect transistor. [16][17][18] The small SS is highly related to the crystallized or noncrystallized interface of the ZnO channel with the dielectric, where poorer interface charges are found in crystallized ZnO. Therefore, a trade-off between a higher mobility using crystallized ZnO and lower interface charges in an amorphous material should be satisfied in the ZnO TFTs. ExperimentalThe bottom gate TFT was fabricated on the thick insulating SiO 2 grown on a Si substrate. A 50 nm thick TaN gate electrode was first formed by sputtering and patterning through a shadow mask, and subsequently treated by NH 3 + plasma treatment to improve the TaN/high-interfa...

show abstract

Optimization of the Fabrication Process for ZnO Thin-Film Transistors with HfO₂ Gate Dielectrics

Cited by 11 publications

References 14 publications

Low Voltage Driven, Stable Solution-Processed Zinc-Tin-Oxide TFT with HfOy and AlOx Stack Gate Dielectric

Low Voltage Driven, Stable Solution-Processed Zinc-Tin-Oxide TFT with HfOy and AlOx Stack Gate Dielectric

RETRACTED: Effect of thickness of Bi1.5Zn1.0Nb1.5O7 gate insulator on performance of ZnO based thin film transistors

A Low Operating Voltage ZnO Thin Film Transistor Using a High-κ HfLaO Gate Dielectric

Contact Info

Product

Resources

About

Optimization of the Fabrication Process for ZnO Thin-Film Transistors with HfO2 Gate Dielectrics

Cited by 11 publications

References 14 publications

Low Voltage Driven, Stable Solution-Processed Zinc-Tin-Oxide TFT with HfOy and AlOx Stack Gate Dielectric

Low Voltage Driven, Stable Solution-Processed Zinc-Tin-Oxide TFT with HfOy and AlOx Stack Gate Dielectric

RETRACTED: Effect of thickness of Bi1.5Zn1.0Nb1.5O7 gate insulator on performance of ZnO based thin film transistors

A Low Operating Voltage ZnO Thin Film Transistor Using a High-κ HfLaO Gate Dielectric

Contact Info

Product

Resources

About

Optimization of the Fabrication Process for ZnO Thin-Film Transistors with HfO₂ Gate Dielectrics