A liquid form adhesive system is provided for spin-coating on wafers and
mounting to rigid carrier substrates to support thinning and backside
processing. The liquid adhesive comprises about 30 35% of a rosin,
between 5 10% of a thermoplastic urethane, a nonionic surfactant present
between 1 3%, and a trace of an ultraviolet fluorescing dye. The entire
system is dissolved in 50 65%, by weight, of a dual solvent mixture
composed of dimethylacetamide and propylene glycol monomethyl ether. When
the mixture is made to a specific viscosity, filtered, applied by a
spin-coating method to the wafer frontside surface, and cured, the result
is a uniform and smooth surface of defined thickness. When the coated
wafer is mounted to a rigid substrate, it may be mechanically thinned to
thicknesses down to and beyond 25 um, depending upon the wafer
composition, diameter, and process. Once thinned, the adhesive is safe
for backside processing and is dissolved away at completion to provide a
thinned wafer that is clean and ready for final dicing or chipping
operations.