Abstract: For plasma etching, to obtain high quality, accurate and reproducible results, the temperature of the plasma gas is measured, conveniently as close as possible to the articles to be etched, variations in the temperature from a desired datum being used to control the RF power supply and thus the RF power fed to the reaction chamber. Extremely quick and accurate control of temperature is provided and this provides accurate and reproducible control of etch rate. The rapid temperature response also enables a quick and accurate preheat cycle to be provided prior to the etching cycle. A particularly useful temperature measuring device is a gas thermometer, with a quartz capillary.

Abstract: Gaseous plasma etching of aluminum with conventional plasma etch gases has not hitherto been commercially possible due to a layer of aluminum oxide (Al.sub.2 O.sub.3) which forms on freshly prepared aluminum surfaces. By first plasma etching in the presence of a gaseous trihalide, preferably in a so-called "pancake" or radial-flow type reactor, the oxide layer is removed. Aluminum etching can then continue, either with or without plasma conditions, depending upon the etch gas used.