US Patent 7473581 Wafer stacking package method

A method of wafer stacking packaging. The method comprises providing a die array including a plurality of singulated first dies cut from a first wafer; providing a second wafer with inseparate the second dies and an adhesive layer on an active surface thereof; pre-cutting the second wafer to a specified depth from the active surface thereof; stacking the active surface of second wafer onto a backside of the first dies, wherein each of the second dies only stack on one of the first dies; thinning the second wafer from the backside thereof to form a plurality of singulated the second dies stacked on the first dies simultaneously.