Structure and process for improving high frequency isolation in semiconductor substrates

Abstract

An isolation structure for high frequency integrated circuits is a conductive material disposed over a region of active gallium arsenide substrate. The conductive material over the active region creates a lossy RF path to reduce undesired coupling between adjacent conductors. In one case, two RF signal lines ( ) terminated at the same via pad ( ) have weaker coupling than in prior art via structures due to the lossy RF structure disposed on isolating fractional portions ( ) of the via pad ( ). The isolating fractional portion ( ) are intermediate terminating fractional portions ( ) of the via pad ( ) to which the signal lines ( ) are connected. In another case, two parallel bias lines ( ) are disposed over an active layer region ( ) increasing the RF loss between them and advantageously reducing the RF coupling. The reduced RF coupling improves RF isolation and permits increased miniaturization.