The present invention provides a procedure of processing a workpiece such as backside grinding of a device wafer and an apparatus designed for the procedure. The procedure comprises (1) preparing a bonded stack comprising (e.g. consisting of) a carrier layer, a workpiece layer, and an interposer layer therebetween; (2) processing the workpiece layer; and (3) delivering a gas jet at the junction between two adjacent layers in the stack to separate or debond the two adjacent layers. Technical merits of the invention include enhanced efficiency, higher wafer throughput, reduced stress on workpiece surface, and uniformly distributed stress and avoidance of device wafer breakage and internal device damage, among others.