Filleul, Maria Louise; (1990) An examination of the damage caused by the reactive ion etching of gallium arsenide. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The reactive ion etch (RIE) process, and its applications in gallium arsenic (GaAs) device fabrication, have been examined. The types of damage caused by RIE, and its effect on electronic and appendectomies devices have been assessed. A reactive ion etcher was built to prepare GaAs samples under controlled etch conditions. Three methods were then used to measure and compare the resultant damage. These methods have been examined in detail, both from theoretical and practical viewpoints. Electrical damage has been measured by probing Scotty diodes fabricated on the etched surfaces. Scotty ideality factors and barrier heights have been obtained for these devices and have been used as figures of merit for the comparison of different RIE gases. Optical damage has been assessed using two novel methods. A photo thermal radiometric microscope has been used to compare surface recombination velocities at etched and un etched surfaces. The second experiment involved firing a five picosecond duration laser pulse at an Aston switch fabricated on the etched surface. The laser pulse generates electron-hole pairs in the GaAs surface and their recombination time is measured electrically using the switch. This recombination time is of the order of 100 picoseconds, and so several ultra-fast measurement techniques have been exploited. Experimental results from these three methods are presented, and further data obtained from Auger chemical analysis, scanning electron microscopy and mechanical surface probing is used to reinforce the arguments. These results indicate that optical and electrical damage measurements show different trends after reactive ion etching, and the measurements are used together to build up a picture of the damage caused to GaAs surfaces by RIE.

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