High Electron Mobility Transistors Yield Improvement with Ultrasonically Assisted Recess for High-Speed Integrated Circuits

InAlAs/InGaAs high electron mobility transistors (HEMTs) have been a great contribution to the research and development of high-speed integrated circuits, owing to their high electron mobilities, high saturation velocities, and high sheet electron densities. In integrated circuits using a HEMT as active device, the gate recess process has considerable influence on the yield and uniformity. The wet recess of a 0.1 µm gate footprint has difficulty achieving a high yield greater than 98% due to a nonuniform reaction between the etchant and the semiconductor. A uniform initial reaction between the InGaAs cap layer and the wet etchant mainly determines the yield and uniformity. In this paper, we present an ultrasonically assisted recess method of promoting a uniform initial reaction in the recess process. This method enables us to achieve a high yield and a high uniformity in integrated circuits.