Bulletin Summer 1975

Electronics Semiconductor-device research There are four general areas of research in the Department of Electronics. Thes e are communications, circuits and instrumentations, systems ami control, and solid-state electronics. Some of these areas overlap to a certain extent, and distinction is not always recognisable between them; neither is it possible to classify strictly some of the research projects under these areas. Low-temperature and superconductivity The low-temperature facilit y in the Department of Electronics provides for research on superconductive devices and study of electronic properties of materials. The facility consists of two cryostats, one of which houses a superconducting magnet with a maximum strength of 6 Tesla and a temperature controlled specimen insert, and the other is a magnetically shielded cryostat where a Squid system capable of measuring fields down to 10 -16 T/ /Hz� and voltage to 10 -13 V is incorporated. Currently, under the supervision of Dr. C.G. Chang, work on the studies of large- junction Josephson Effect is in progress, and radiation loss from superconducting microstrip is also being studied with the cooperation of Mr. J.S. Dahele. With members of the Physics Department, experiments on the enhancement of surface critical curren t and critical temperature of superconductors by high-energy laser pulses are also in progress. Low-temperaturefacility Semiconductor-device researc h is undertaken by Drs. H. Kwok , York Liao and Y .W . Lam. The semi- conductor-device fabrication facilities, which started as a joint venture between the Electrical Engineering Department of the University of Hong Kong and the Department of Electronics of this University, have been functioning for some time. It is now possible to fabricate both bipolar and MOS transistors with reasonable yields. A step-repeat camer a for mask production is being developed and an epitazy system for I C fabrication is being set up. A cooperative programme was established between the Department and a local manufacturer of semiconductor devices, to experiment on the new spin-on diffusion technique. The technique is now successfully developed and is used by both the Department and the manufacturer for the fabrication of semiconductor devices. Research on the properties of spin-on oxide has also been carried out. The oxide is deposited on a silicon wafer from an alcohol solution by first spinning the liquid on the wafer, which is then baked and densified at a higher temperature. The oxide film has been investigated by infrared spectroscopy, gravimetric analysis, etch-rate measurement, conduction measurement and C V - GV studies. Very promising results have been obtained, indicating that the oxide approaches the thermal oxide i n quality and can be used as an active oxide in semiconductor devices. Research is now directed towards the application of spin-on oxide to the fabrication of a charge-coupled device (CCD). A C C D consists of a chain of charge- storage elements along which charge packets are transferred. When fully developed it can result in television cameras as small as a packet of cigarettes, cheap computer memories which can fit inside a pocket calculator and analogue acoustic delay lines the size of a match head. For acceptable, high charge- transfer efficiency, however, spacing between neighbouring electrodes must be kept very small (typically the order of 1 µ m). By the use of spin-on oxide on thermal oxide a technique is being developed in our laboratories which will enable any required spacing to be obtained. A two-phase seven-bit C C D is now being fabricated using this technique. Other Projects Projects in other areas which have jus t been completed or are being undertaken include: Pattern Recognition (supervised by Dr. H.T. Tsui), Solar Radio Astronomy (supervised by Drs. K.F. Lee and R . K . L. Poon), A Chinese Typewriter and Adaptive T V Ghost Suppression (supervised by Mr. T . C . Choy, Mr. J.G.N. Lee and Dr. R . K . L . Poon), Microwave 10