Selective InAs/GaSb strained layer superlattice etch stop layers for GaSb substrate removal

This paper reports the use of an InAs/GaSb strained layer superlattice (SLS) as an etch stop layer for GaSb substrate removal with a BCl3/SF6 etch chemistry. Optimum chamber conditions were determined by measuring etch rates and selectivities for two types of superlattices. It was found that selectivity of GaSb over a superlattice is maximized if the reactive ion etching (RIE) chamber pressure is maximized and BCl3 is 80 % of the gas mixture. Selectivities of up to about 475 were measured. Greater selectivity was achieved with superlattices composed of thicker InAs layers.