Process for forming extremely thin integrated circuit dice

Abstract

A wafer processing technique separates an extremely thin wafer into a plurality of completed circuit-containing dice without having to directly handle the wafer. In one embodiment, a substrate is thinned by forming a trench pattern in its top surface, the trench depth being the intended thickness of the die. A polishing resistant material is then formed in the trench and planarized down to a topside passivating layer, which is patterned to expose surface test regions. After wafer-probe testing, the wafer is affixed face-down on a support handle by means of an adhesion material such as wax. The substrate is backside-lapped down to the stop material in the trench, leaving a thin wafer layer. After the trench material is removed. Individual dice are separated from the support handle by melting the wax. In a further embodiment, a thin wafer layer if formed on a buried oxide layer. After trench patterning and face-down wax-mounting, the support substrate is polished down to the buried insulator layer. The buried oxide layer is then etched off. The dice are removed by heating the wax. In another embodiment, an etch resistant material is formed on the passivating layer and on the sidewalls of the trench, with a floor portion of the trench pattern exposing the buried oxide. An etchant is then applied to the buried oxide by way of the exposed floor portion of the trench pattern, so as to etch away the buried oxide, thereby lifting off the dice from the support substrate.