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The sub-threshold swing (SS) of Si n-MOSFETs is experimentally and systematically evaluated in a temperature range of 4–300 K with varying the substrate impurity concentration (N sub) from ~1016 to ~1018 cm−3, to obtain a physical understanding of SS at cryogenic temperatures. It is clarified that the temperature and drain current dependencies of SS in n-MOSFETs are well represented by a model composed of mobile tail states and localized interface states, irrespective of N sub. The densities of these states are found to increase with increasing N sub. A physical origin of band tail states is studied by experimentally examining the impact of substrate bias on these states, which can separate the effects of the N sub and the surface electric field. It has been clarified, as a result, that the band tail states can be explained by the impurity-induced model.

We experimentally characterize sub-threshold swing (SS) of Si n-channel MOSFETs with a substrate boron concentration of 2 × 1016 cm−3 as a function of drain current (I DS) and temperatures from 4 to 300 K in order to verify the validity of the physical model of SS. The minimum SS are obtained experimentally at 4 K of around 4 mV dec−1. The physical model including mobile band tail states and localized interface states with a Gaussian distribution, proposed by Beckers at el., is employed to represent the experimental SS from 4 to 300 K. The impact of each parameter included in the physical model on the SS behavior is examined by changing the value of the parameters in simulation. It is found that the proposed physical model can quantitatively represent experimental SS in a wide range of I DS and temperature under a given set of the parameters regarding the band tail states and the interface states. This finding indicates the validity of the present physical model and the correctness of the physical picture.

In this study, we conducted microwave annealing (MWA) on amorphous In–Ga–Zn–O (a-IGZO) thin films deposited by the sol-gel method, and then investigated the effects of ambient conditions on the electrical properties and reliability of a-IGZO thin-film transistors (TFTs) and on the optical and chemical properties of a-IGZO thin films. On the other hand, pure N2 ambient-treated TFTs exhibited the poorest transfer and output characteristics, but improved with increasing O2 mixing ratio. In terms of stability, pure O2 ambient-treated a-IGZO TFTs were excellent for both positive and negative gate bias stresses, but deteriorated with increasing N2 mixing ratio. Also, static and dynamic tests of resistor-loaded inverters were carried out. As a result, the pure O2 ambient-treated inverter showed excellent characteristics, while the pure N2 ambient-treated inverter had poor characteristics. Meanwhile, pure O2 ambient MWA has excellent carbon removal ability in sol-gel-processed a-IGZO films, lowering oxygen vacancies and impurities. Besides, it has an effect of increasing energy band gap, improving transmittance, increasing Fermi level and electron concentration, and contributing to improvement of mobility. Therefore, it was verified that MWA in pure O2 ambient is very beneficial to improve the optical and chemical properties of the sol-gel-processed a-IGZO thin film and the electrical properties of TFTs.

In this study, we fabricated back-end of line (BEOL) transistors with Cu gate electrodes, Si3N4/SiO2 interlayer dielectric gate insulators, and In–Zn–O (IZO) channel structures. A BEOL thin film transistor capable of operating at a high voltage and a resistor type (R-type) logic device capable of operating the inverter by applying a drain offset have been proposed. We performed low temperature annealing at 350 °C to prevent damage to front-end of line devices. As a result, IZO BEOL TFTs with a drain offset structure exhibited excellent performance, long-term reliability and stability at high voltage. In addition, by using drain channel offset as a resistor, we were able to fabricate R-type inverters and level shifters. Therefore, IZO BEOL TFTs with drain offset channel allow monolithic three-dimensional integration of the transistor into the BEOL of silicon wafers for power management integration circuits and functional circuit device applications.

Amorphous LiNbO3 was produced by the twin-roller quenching method and X-ray diffraction, trace of differential thermal analysis, and temperature- and frequency-dependent dielectric constants were measured. After glass transition and crystallization temperatures were confirmed by differential thermal analysis experiments, activation energies of both processes were calculated using Ozawa's non-isothermal method. From the results of temperature- and frequency-dependent dielectric constant measurements, dielectric relaxation mechanisms below and above glass transition and crystallization temperatures were considered.