Thin Film Semiconductor Devices Research Articles

The use of ion beams in molecular beam epitaxy

Molecular beam epitaxy (MBE) has been developed over the past decade into one of the most versatile techniques for generating thin film semiconductor device structures. This development has been assisted by the use of low energy (0.1–10 keV) ion beams in a number of areas such as substrate surface preparation, film doping, metal-semiconductor contact formation and in situ surface analysis by secondary ion mass spectrometry and Auger depth profiling. Illustrative examples of the applications of ion beams in these areas are given. The use of ion beams in MBE has led to the discovery and exploration of a number of side effects of ion beams on semiconductor surfaces. These include group III metal surface segregation on III–V compound semiconductors, surface n-type channel formation on some III–V and II–VI compound semiconductors and II–VI alloy composition gradation. Some of these effects have been made use of in device structures. Mechanisms responsible for the effects are discussed and future trends in the use of ion beams in MBE are considered.

An improved interconnection technique

This paper deals with an improved interconnection technique for use with thin film hybrid ICs, SAW devices and semiconductor devices based on shallow diffusions eg. MOS-FETS h f transistors etc., In this technique, the thin film strips of specific width and length (or shape) formed photolithographically on specific substrates are floated off and used for bonding the contact pads to the package leads by thermocompression/ultrasonic bonding methods. The technique has been successfully used for bonding SAW devices and discrete MOS-FETS.

Effects of Ionizing Radiation on Thin-Film Semiconductor Devices

Results of an investigation of the transient and permanent effects of ionizing radiation on Al2O3-CdSe thin-film transistors and microcircuits are reported. The total-gamma-dose response of the devices did not differ significantly from that of conventional silicon MOS devices, and the observed shift in threshold voltage is consistent with a positive charge buildup in the gate oxide. In transient response studies, it was found that the thin-film devices will perform without failure up to peak dose rates of ~1010 rads(Si)/s (~30 ns pulsewidth).

Frequency dependence of negative-capacitance effects observed in amorphous semiconductor thin-film devices

A simple thermal model is analysed which explains the observed frequency dependence of the negative capacitance of chalcogenide-glass threshold switches at room temperature.