Removal of Gold Impregnated Post-Etch Residue from Front and Backside Vias in a Single Process

Compound semiconductor processing often uses high density plasma etching to establish through-via metal contacts that typically stops on an inert metal such as gold (Au). The etch process may enter from the front or backside through the substrate and/or an organic dielectric such as polyimide or bisbenzocyclobutene (BCB). An inherent by-product of the etch process is the formation of post-etch residue containing a mixture of species stemming from the plasma ions, resist pattern, etched region, and lastly, material from the etch stop (Au) that impregnates and coats the residue.[1,2] Common strippers are ineffective on Au impregnated post-etch residue, requiring a separate KI-leaching of the metal before the residue is removed. This paper describes a simple and rapid technique to simultaneously remove post etch residue in a single process using common fab manufacturing tools