Study of nanocrystalline silicon-germanium for the development of thin film transistors

2020 ◽  
Vol 89 (1) ◽  
pp. 10102 ◽  
Author(s):  
Arturo Torres ◽  
Mario Moreno ◽  
Pedro Rosales ◽  
Miguel Dominguez ◽  
Alfonso Torres ◽  
...  
Keyword(s):  
Thin Film ◽  
Silicon Germanium ◽  
Thin Film Transistors ◽  
Chemical Vapor ◽  
Nanocrystalline Silicon ◽  
Subthreshold Slope ◽  
Rf Power ◽  
Crystalline Fraction ◽  
Current Ratio ◽  
Active Layers

In this work, we study the effect of the deposition RF-power on the structural, optical and electrical properties of hydrogenated nanocrystalline silicon-germanium (nc-SiGe:H) thin films obtained by plasma enhanced chemical vapor deposition (PECVD) at substrate temperature of 200 °C. The objective is to produce films with high crystalline fraction in order to be used as active layers in thin film transistors (TFTs). Bottom-gate (BG) thin film transistors were fabricated with nc-SiGe:H active layers, deposited at different RF-power. Values of ON-OFF current ratio, subthreshold slope and threshold voltage of 105, 0.12 V/dec and 0.9 V, respectively, were obtained on TFTs with the nc-SiGe:H active layer deposited at 25 W.

Ambipolar Thin-Film Transistors Fabricated by PECVD Nanocrystalline Silicon

2006 ◽  
Vol 910 ◽  
Author(s):  
Czang-Ho Lee ◽  
Andrei Sazonov ◽  
Mohammad R. E. Rad ◽  
G. Reza Chaji ◽  
Arokia Nathan
Keyword(s):  
Thin Film ◽  
Thin Film Transistors ◽  
Field Effect ◽  
Chemical Vapor ◽  
Hole Mobility ◽  
Complementary Metal Oxide Semiconductor ◽  
Nanocrystalline Silicon ◽  
Oxide Semiconductor ◽  
Hole Injection ◽  
Current Ratio

AbstractWe report on directly deposited plasma-enhanced chemical vapor deposition (PECVD) nanocrystalline silicon (nc-Si:H) ambipolar thin-film transistors (TFTs) fabricated at 260 °C. The ambipolar operation is achieved adopting Cr metal contacts with high-quality nc-Si:H channel layer, which creates highly conductive Cr silicided drain/source contacts, reducing both electron and hole injection barriers. The n-channel nc-Si:H TFTs show a field-effect electron mobility (meFE) of 150 cm2/Vs, threshold voltage (VT) ~ 2 V, subthreshold slope (S) ~0.3 V/dec, and ON/OFF current ratio of more than 107, while the p-channel nc-Si:H TFTs show a field-effect hole mobility (mhFE) of 26 cm2/Vs, VT ~ -3.8 V, S ~0.25 V/dec, and ON/OFF current ratio of more than 106. Complementary metal-oxide-semiconductor (CMOS) logic integrated with two ambipolar nc-Si:H TFTs shows reasonable transfer characteristics. The results presented here demonstrate that low-temperature nc-Si:H TFT technology is feasible for total integration of active-matrix TFT backplanes.

scholarly journals Amorphous Hafnium-Indium-Zinc Oxide Semiconductor Thin Film Transistors

2012 ◽  
Vol 2012 ◽  
pp. 1-4 ◽  
Author(s):  
Sheng-Po Chang ◽  
San-Syong Shih
Keyword(s):  
Thin Film ◽  
Zinc Oxide ◽  
Thin Film Transistors ◽  
Oxide Semiconductor ◽  
Subthreshold Slope ◽  
Field Effect Mobility ◽  
Excellent Performance ◽  
Current Ratio ◽  
Indium Zinc Oxide ◽  
Sputtering Power

We reported on the performance and electrical properties of co-sputtering-processed amorphous hafnium-indium-zinc oxide (α-HfIZO) thin film transistors (TFTs). Co-sputtering-processedα-HfIZO thin films have shown an amorphous phase in nature. We could modulate the In, Hf, and Zn components by changing the co-sputtering power. Additionally, the chemical composition ofα-HfIZO had a significant effect on reliability, hysteresis, field-effect mobility (μFE), carrier concentration, and subthreshold swing (S) of the device. Our results indicated that we could successfully and easily fabricateα-HfIZO TFTs with excellent performance by the co-sputtering process. Co-sputtering-processedα-HfIZO TFTs were fabricated with an on/off current ratio of~106, higher mobility, and a subthreshold slope as steep as 0.55 V/dec.

Hydrogen in Ultralow Temperature SiO2for Nanocrystalline Silicon Thin Film Transistors

2004 ◽  
Vol 814 ◽  
Author(s):  
Alex Kattamis ◽  
I-Chun Cheng ◽  
Steve Allen ◽  
Sigurd Wagner
Keyword(s):  
Thin Film ◽  
Leakage Current ◽  
Current Density ◽  
Thin Film Transistors ◽  
Secondary Ion Mass Spectrometry ◽  
Crystalline Silicon ◽  
Chemical Vapor ◽  
Nanocrystalline Silicon ◽  
Film Deposition ◽  
Silicon Thin Film

AbstractNanocrystalline silicon is a candidate material for fabricating thin film transistors with high carrier mobilities on plastic substrates. A major issue in the processing of nanocrystalline silicon thin film transistors (nc-Si:H TFTs) at ultralow temperatures is the quality of the SiO2gate dielectric. SiO2deposited at less than 250°C by radio frequency plasma enhanced chemical vapor deposition (rf-PECVD), and not annealed at high temperature after deposition, exhibits high leakage current and voltage shifts when incorporated into TFT's. Secondary ion mass spectrometry (SIMS) measurements show that the hydrogen concentration (NH) in PECVD oxide deposited at 150°C on crystalline silicon (x-Si) is ∼ 0.8 at. %. This is much higher than in thermal oxides on x-Si, which display concentrations of less than 0.003 at. %. The leakage current density for thermal oxides on x-Si at a bias of 10 V is ∼9×10−6A/cm2whereas for 200°C PECVD oxides on nc-Si:H the current is ∼1×10−4A/cm2. As the temperature of the SiO2deposition is reduced to 150°C the current density rises by up to two orders of magnitude more. The H which is suspected to cause the leakage current across the PECVD oxide originates from the nc-Si:H substrate and the SiH4source gas. We analyzed the 300-nm gate oxide in capacitor structures of Al / SiO2/n+nc-Si:H / Cr / glass, Al / SiO2/ n+nc-Si:H / x-Si, and Al / SiO2/ x-Si. Vacuum annealing the nc-Si:H prior to PECVD of the oxide drives H out of the nc-Si:H film and reduces the amount of H incorporated into the oxide that is deposited on top. SiO2film deposition from SiH4and N2O at high He dilution has a still greater effect on lowering NH. The leakage current at a 10 V bias dropped from ∼1×10−4A/cm2to about ∼2×10−6A/cm2using He dilution at 250°C, and the vacuum anneal of the nc-Si:H lowered it by an additional factor of two. Thus we observe that both the nc-Si:H anneal and the SiO2deposition at high He dilution lessen the gate leakage current.

scholarly journals Development of Low-Temperature Ambipolar a-SiGe:H Thin-Film Transistors Technology

2012 ◽  
Vol 1426 ◽  
pp. 169-173 ◽  
Author(s):  
Miguel A. Dominguez ◽  
Pedro Rosales ◽  
Alfonso Torres ◽  
Mario Moreno
Keyword(s):  
Thin Film ◽  
Low Temperature ◽  
Silicon Germanium ◽  
Thin Film Transistors ◽  
Transfer Characteristic ◽  
Gate Bias ◽  
Subthreshold Slope ◽  
Semiconductor Interface ◽  
Type Region ◽  
P Type

ABSTRACTWe present the fabrication and characterization of low-temperature ambipolar thin-film transistors (TFTs) based on hydrogenated amorphous silicon-germanium (a-SiGe:H) as active layer. Inverted staggered a-SiGe:H TFTs were fabricated on Corning glass. Spin-on glass silicon dioxide was used as gate dielectric to improve the quality of the dielectric-semiconductor interface. For positive gate bias the transfer characteristic showed n-type TFT behavior, while for negative gate bias p-type behavior was observed. The n-type region exhibits subthreshold slope of 0.45 V/decade while the p-type region shows a subthreshold slope of 0.49 V/decade.

Nanocrystalline Silicon by Microwave CVD for Thin Film Transistors and Solar Cells

2000 ◽  
Vol 638 ◽  
Author(s):  
Young J. Song ◽  
Hak-Gyu Lee ◽  
Lihong Teng ◽  
Wayne A. Anderson
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
Thin Film Transistors ◽  
Chemical Vapor ◽  
Nanocrystalline Silicon ◽  
Dark Conductivity ◽  
Antireflection Coating ◽  
Process Conditions ◽  
Hydrogen Dilution ◽  
Partial Pressures

AbstractMicrowave chemical vapor deposition (MCVD) is utilized to deposit nanocrystalline silicon (nc-si) thin films onto a variety of substrates for application to thin film transistors (TFT's) and solar cells. It is especially important to gain reproducible control of the processing. Thus, an in-situ mass spectrometer (MS) records the plasma conditions with variation of process conditions such as gas selection, pressures, partial pressures, and substrate temperature. These data are correlated with electrical and optical properties of the films. Raman spectra show a FWHM of 11/cm with position at 522/cm as desired for crystalline Si. Typical film thickness is 100nm with grain size of 20-30 nm, using standard deposition, and 50-80 nm when the substrate is intensely optically illuminated during deposition, called photon assist (PA). Hydrogen dilution serves to increase the crystallinity of the films. The ratio of photo-to dark conductivity exceeds 10+5 with dark conductivity as low as 1.5 × 10-10 S/cm. Thin film transistors have been fabricated with Ion/Ioff of 10+7. Hetrojunction solar cells were fabricated using amorphous Si/ nc-Si/ crystlline Si giving a conversion efficiency of above 10.5%, without an antireflection coating. The use of MS in device design will be emphasized.

Properties of Amorphous Silicon Thin Film Transistors with Phosphorous-Doped Hydrogenated Microcrystalline Silicon

1996 ◽  
Vol 452 ◽  
Author(s):  
J. H. Choi ◽  
C. W. Kim ◽  
H. G. Yang ◽  
J. H. Souk
Keyword(s):  
Thin Film ◽  
Vapor Deposition ◽  
Thin Film Transistors ◽  
Field Effect ◽  
Chemical Vapor ◽  
Field Effect Mobility ◽  
Rf Power ◽  
Microcrystalline Silicon ◽  
Silicon Thin Film ◽  
Threshold Voltages

AbstractPhosphorous (P) doped hydrogenated microcrystallme silicon (n+μ c-Si:H) films have been prepared by using the hydrogen-diluted plasma enhanced chemical vapor deposition (PECVD) method. The crystallinity of films deposited over the range of SiH4/H2 flow ratios and RF-power is studied by Raman spectroscopy. For a 900 Å thick film deposited at 250°C, a conductivity of 71Ω−1cm−1 and an average crystallinity of 49% is obtained. n+ μ c-Si:H films as well as n+ a-Si:H films are used for both etch stopper and back channel etch type TFTs and the I4-V8 characteristics are compared. For the etch stopper type TFT, the field effect mobility of 0.85 cm2/V.sec, threshold voltages of 2 – 3 V and Ion/Ioff ratio of ∼107 are obtained.

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