Low-temperature full wafer adhesive bonding

We have systematically investigated the influence of different bonding para meters on void formation in a low-temperature adhesive bonding process. As a result of these studies we present guidelines for void free adhesive bond ing of 10 cm diameter wafers. We have focused on polymer coatings with laye r thicknesses between 1 mum and 18 mum. The tested polymer materials were b enzocyclobutene (BCE) from Dow Chemical, a negative photoresist (ULTRA-i 30 0) and a positive photoresist (S1818) from Shipley, a polyimide (HTR3) from Arch Chemical and two different polyimides (PI2555 and PI2610) from DuPont . The polymer material, the banding pressure and the pre-curing time and te mperature for the polymer significantly influence void formation at the bon d interface. High bonding pressure and optimum pre-curing times/temperature s counteract void formation. We present the process parameters to achieve v oid-free bonding with the BCB coating and with the ULTRA-i 300 photoresist coating as adhesive materials. Excellent void-free and strong bonds have be en achieved by using BCB as the bonding material which requires a minimum b onding temperature of 180 degreesC.