Masahiro Hayama

Characteristics of Hydrogenated Amorphous Silicon Films Prepared by Electron Cyclotron Resonance Microwave Plasma Chemical Vapor Deposition Method and Their Application to Photodiodes

The electron cyclotron resonance microwave plasma chemical vapor deposition (ECRPCVD) method has been applied to prepare a-Si:H films. A high deposition rate of 136 nm/min was achieved. Even without substrate heating and with the high deposition rate, a-Si:H films prepared by ECRPCVD have sufficient characteristics, as follows: the dark conductivity is 3-4×10-10S/cm, ηµτ is 4.2×10-5cm2/V and the optical band-gap is 1.81 eV. Furthermore, the electric characteristics are somewhat improved with substrate heating. Hydrogenated amorphous silicon films prepared by ECRPCVD without substrate heating and with a high deposition rate of 136 nm/min have been applied to ITO/a-Si:H/Cr Schottky-barrier photodiodes. These photodiodes have sufficient characteristics to be applied to image sensors for a facsimile reader and other systems.

Large Scale and Large Area Amorphous Silicon Thin Film Transistor Arrays for Active Matrix Liquid Crystal Displays

The preparation and properties of hydrogenated amorphous silicon thin film transistor arrays for active matrix liquid crystal displays are reported. The effect of amorphous silicon film preparation conditions on the field effect mobility of thin film transistors was investigated. The dry etching rate of silicon nitride film was studied.The thin film transistor arrays have 408 ˜ 640 transistors on the first version and 450 ˜ 640 ˜ 3 transistors on the second version. The liquid crystal panel fabricated using the first version arrays showed good characteristics.

Ion bombardment effects on undoped hydrogenated amorphous silicon films deposited by the electron cyclotron resonance plasma chemical vapor deposition method

Ion bombardment effects on undoped hydrogenated amorphous silicon films deposited by the electron cyclotron resonance plasma chemical vapor deposition method without substrate heating using SiH4/Ar gas have been investigated by applying a dc bias voltage to the substrate. Ion bombardment to the growing films plays an important role in decreasing the polysilane phase and dangling bonds in the films, and in the realization of a high deposition rate. As a result, ion bombardment contributes to good photoconductivity at a high deposition rate, such as 170 nm/min, without substrate heating by decreasing the polysilane phase.

Characteristics of a-Si:H films deposited by electron cyclotron resonance plasma CVD

Abstract The relation between the photoconductivity and the deposition rate of a-Si:H films deposited by Electron Cyclotron Resonance Plasma CVD has been investigated. The high deposition rate is a very important factor to obtain large photoconductivity and high-quality of a-Si:H films in ECRPCVD. The ion bombardment on a-Si:H films improves the characteristics. These films are applied to Schottky-barrier photodiodes.

The Application of Hydrogenation to Amorphous Silicon Thin Film Transistors for the Decrease of the off Current

The influence of hydrogenation on OFF current of TFTs with a bottom gate staggered structure has been investigated. The hydrogenation is done by exposing the surface of the a-Si:H channel layer to H2 plasma. The hydrogenation decreases the OFF current by more than one order of magnitude. The decrease in the OFF current is attributed to the increase in the density of states at the interface between the a-Si:H channel layer and the SiN passivating layer.

Fabrication of 10-in.-diagonal 16-gray-level TFT-LCDs by novel processing technologies

— New processing technologies for large-area high-resolution TFT-LCDs have been developed. A taper-etching technology for Cr gate electrodes with a resistivity of 18 μΩ/cm was realized. The technology allows control of the taper angle down to as low as 2°. The breakdown voltage between the gate electrodes and the source-drain electrodes was improved from 140 V to over 400 V. A new end-point-detection method using N2 plasma emission for the photoresist stripping process has been developed. The method decreases the contact resistance and improves the transfer characteristics of TFTs. These processing technologies make possible the realization of 10-in.-diagonal TFT-LCDs with 16 gray levels.

Numerical Analysis of the Optical Response Characteristics of Thin Film Transistor Addressed Liquid Crystal Displays

A simulation method is proposed to analyze the optical response characteristics of TFT-LCDs. Our method using an equivalent circuit takes into account the time and voltage dependence of the dielectric constant of the TN-LC cell. We obtain good agreement between simulations of the optical response characteristics of the TN-LC cell and experimental results. The 30 Hz flicker, which appears in the optical rise state of the TFT-LCD, is analyzed by using our method. Our method enables a large amount of calculation of the optical response characteristics of TFT-LCDs at high speed.

Dark current of hydrogenated amorphous silicon photo-diode

Abstract Dark current of hydrogenated amorphous solicon photo-diode is investigated for the various diode structures. It is found that leakage current from the interface between amorphous silicon and metal is dominant rather than the generation current in the amorphous silicon intrinsic layer.