Abstract: A process, and structure, used to monitor and control the level of photoresist removed at the periphery of a photoresist coated, semiconductor substrate, has been developed. A monitoring structure comprised of a group of graduated scribe marks, laser formed near the periphery of the semiconductor, monitoring substrate, is included with product semiconductor substrates, during the application of a photoresist layer, and during the photoresist edge bead removal procedure. The width of the photoresist edge bead, removed from product semiconductor substrates is determined via examination of the monitoring semiconductor substrate, in terms of measuring the level of graduated scribe marks, now exposed. This measurement determines the status of the product semiconductor substrates, in regards to continued processing, or rework.

Abstract: An audio frequency muting arrangement includes one circuit for detecting intelligence signals in a received audio frequency signal, and a further circuit for detecting noise signals, so as to compare the levels of the noise and intelligence signals and to control a muting switch in dependence thereon. The invention is applicable to noisy environments, e.g. aircraft, in which a threshold circuit is used to track the ambient noise level. Particular signal detection circuits are described.