Patent ID: 7897431
Filing Date: 2011-03-01
Classification: H01L

Abstract:
1. A method of stacking wafers, comprising: providing a first wafer including a first device structure layer and a first metal connection layer, including a first metal contact, over the first device structure layer; forming a first passivation layer over the first metal connection layer; forming a first bondpad in the first passivation layer in contact with the first metal contact to form a first bondpad layer; providing a second wafer including a second device structure layer and a second metal connection layer, including a second metal contact, over the second device structure layer; forming a second passivation layer over the second metal connection layer; forming a second bondpad in the second passivation layer in contact with the second metal contact to form a second bondpad layer; forming at least one of a first conductive adhesive layer over the first bondpad layer and a second conductive adhesive layer over the second bondpad layer; stacking the second wafer on the first wafer by bonding respective faces of the second bondpad layer with the first bondpad layer via the at least one of the first conductive adhesive layer and the second conductive adhesive layer; providing a third wafer containing a third device structure layer and a third metal connection layer, including a third metal contact, over the third device structure layer; forming a third passivation layer over the third metal connection layer; forming a third bondpad in the third passivation layer in contact with the third metal contact to form a third bondpad layer; reducing a thickness of a backside of a substrate of the second wafer subsequent to the stacking of the second wafer on the first wafer; forming an intermediate bondpad layer on the backside of the substrate of the second wafer by forming at least one of an intermediate adhesive layer over the intermediate bondpad layer and a third adhesive layer over the third bondpad layer; and stacking the third wafer on the second wafer by bonding respective faces of the third bondpad layer with the intermediate bondpad layer via the at least one of the third adhesive layer and the intermediate adhesive layer.