Patent ID: 9443737
Filing Date: 2016-09-13
CPC Classification: H01L

Claim Text:
1. A method of forming a high electron mobility transistor comprising: etching a layered structure with a first gas combination to form a number of metal contact openings, the layered structure including a buffer layer that touches and lies over a substrate, a channel layer that touches and lies over the buffer layer, and a barrier layer that touches and lies over the channel layer, each of the metal contact openings having a first bottom surface that lies above and spaced apart from a top surface of the channel layer; and etching the layered structure with a second gas combination to deepen the first bottom surface of each metal contact opening a distance to a second bottom surface that lies below the first bottom surface, the second bottom surface lying above and spaced apart from the top surface of the channel layer, wherein the second gas combination etches more of the barrier layer than does the first gas combination and wherein the first gas combination also etches through a cap layer that touches and lies above the barrier layer, and through a passivation layer that touches and lies above the cap layer, the cap layer including GaN, the passivation layer including silicon nitride.