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Hafnium oxide-based ferroelectric thin-film transistor with a-InGaZnO channel fabricated at temperatures \u3c= 350°C
Get PDFHfO2-based ferroelectric materials integrated with oxide-based thin-film transistors have been considered as potential candidates for back-end-of-line compatible ferroelectric field-effect transistors, which can be vertically stacked on silicon CMOS circuits to realize high-density neural network applications. However, the formation of ferroelectric orthorhombic phase in HfO2-based materials usually requires an annealing temperature of 400°C or higher. In this work, ferroelectric thin-film transistors (Fe-TFTs) were developed by monolithically integrating HfZrO2 (HZO) ferroelectric capacitors with amorphous indium-gallium-zinc oxide (a-IGZO) TFTs at a maximum processing temperature of 350°C on a glass substrate. A butterfly-shaped C-V curve was clearly observed in the low-temperature annealed metal-HZO-metal capacitor, indicating the formation of ferroelectricity in the HZO layer, as shown in Fig. 1. The positive and negative coercive voltages were 3 V and -2.4 V, respectively. The dielectric constant was 20.65. The field-effect mobility, threshold voltage, subthreshold swing and on/off current ratio of the a-IGZO TFT extracted from the transfer characteristics shown in Fig. 2 were 6.15 cm2V-1s-1, 1.5 V, 0.1 V/dec and 4.3´107, respectively. Fig. 3 shows the transfer hysteresis curves of the low-temperature Fe-TFTs in a metal-ferroelectric-metal-insulator-semiconductor configuration. The Fe-TFTs exhibited large hysteresis memory windows of 2.8 V and 3.8 V when the area ratios between ferroelectric capacitors and gate insulators (AFE / ADE) were 1/8 and 1/12, respectively. The result shows a great potential for back-end-of-line compatible memory applications.
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Room temperature gas sensing with a hybrid poly-Si/ZnO TFT cell
Get PDFIn this work, we study the capability of a novel poly-Si/Zno hybrid TFT cell in sensing NO2 gas. Fabrication and structural features of this cell are identical to that reported in one of our previous works [1] except that the IGZO TFT is replaced by a ZnO one. The equivalent circuit of the hybrid cell is shown in Fig. 1, in which the poly-Si TFT and ZnO TFT are employed as the amplifier and sensor, respectively. In the configuration, the top gate of the poly-Si TFT is electrically connected to the drain of the bottom-gated ZnO TFT, while the top surface of the ZnO channel is exposed to the environment for sensing purposes. For the electrical measurements conducted at room temperature, the current source (IIN) was set at 100 pA with a compliance VG of 2 V. Concentration of the NO2 gas in the ambient was varied from 0 ~100 ppm. Transfer characteristics of the cell are expressed by showing the drain current of the poly-Si TFT as a function of the back-gate bias (VBG) of the ZnO TFT. In the figure, we can see the I-V curves show a parallel and positive shift as the concentration of the NO2 gas is increased. Meanwhile, the transitions in the figure are steep with a slope of around -60 mV/dec whose absolute value is much smaller than the subthreshold slopes of the individual ZnO TFT (\u3e300 mV/dec). The finding provides good evidence showing the potential of this scheme in promoting measurement sensitivity compared with conventional oxide-semiconductor TFTs. The experimental results also show that UV irradiation can recover the characteristics.
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Highly sensitive broadband phototransistors based on gradient tin/lead mixed thin film perovskites
Get PDFHighly sensitive broadband photodetectors are critical to numerous cutting-edge technologies such as biomedical imaging, environment monitoring, and night vision. While near-infrared I-II (NIR I-II, 750–1700 nm) photodetectors is indispensable for medical instruments, commercialized NIR photodetectors are primarily made of inorganic narrow-bandgap materials such as GaAs, PbSe, and InGaAs, which rely on expensive and complicated microfabrication processes. Here, we report ultrasensitive broadband phototransistors based on all-solution processed Sn/Pb mixed-perovskite films, which show spectral response from visible to NIR-II region benefitting from their narrowed bandgap energies compared with other pure Pb or Sn-based perovskites.
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Invited; Progress of p-channel oxide-TFT development and how we improve the performances
Get PDFIt is well known that n-channel oxide-TFTs, i.e. a-IGZO-TFT is a great success in TFT back-plane technology for the state-of-art AMFPDs because of their excellent device performances including high-mobility and low-off current characteristics and good mass-product liability compatible with large sized glass substrates. There are remaining issues such as the development of higher electron mobility and better stability channels and intense device and material developments still take place. Therefore, several high mobility n-channel oxide-TFT have been developed already. (Fig.1) On the other hand, the absence of practical device quality of p-type channel oxide-TFT still remains the largest issue in an oxide semiconductor and is recognized as the technological barrier that should be overcome for next-generation oxide device technology because many circuit applications such as CMOS require a counterpart of n-channel-TFTs.
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Invited: Challenge to next-generation VLSI with VFET using oxide semiconductor and 3D structure
Get PDFon OSLSI by John Wiley & Sons, Inc., in 2017 [1]. OS has attracted such attention that almost 10% of the accepted papers was related to the field at the IEEE International Electron Devices Meeting (IEDM), the world\u27s largest international conference on semiconductor manufacturing, held in December 2022. In the tutorial taught by IBM on the first day of IEEE IEDM 2022, the necessity of vertical field-effect transistors (VFETs) and stacked FETs was anticipated for beyond-1-nm-node semiconductors that are next to the 2- to 3-nm-node semiconductors [2]. A gate-all-around (GAA) structure has been proposed as the new structure in the Si VLSI field. However, we propose a VFET structure that goes a step ahead of the GAA structure and are convinced that a VFET using OS and a 3D structure (stack structure) in which the VFETs are stacked vertically will be the next mainstream.
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Economic and ecological analysis of plastic-degrading enzyme production
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A scalable and flexible solution for robust T cell expansion
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Developing methodologies to optimise production of recombinant antibodies at specific phases of Chinese Hamster Ovary (CHO) cell culture
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Enhancing CHO cell productivity through a novel dual selection system using Aspg and Gs in glutamine free medium
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Screening of chemically defined basal and feed media formulations for IgM production
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