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

John Moorea, Sergio Luna, Tertius Riversb, Bil Howellb, and Chad Beckerc

aGeneral Chemical, 2340 Bert Drive, Hollister, CA  95023
Phone: (831) 630-6202 Email: jmoore@genchemcorp.com

bTriQuint Semioconductor, 2300 NE Brookwood Parkway, Hillsboro, OR
Phone: (503) 615-9297  Email trivers@tqs.com

cFormerly with Freescale, 2100 E. Elliot Rd., Tempe, AZ  (480) 668-4057
Email: cbecker1@irf.com

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 reside.  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 reside in a single process using common fab manufacturing tools. 

Keywords:  Via, Plasma etching, sputtered Au, ecD Au, BCB

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