Novel thinning process for 3 - dimensional integration via wafer bonding

摘要

First and second semiconductor wafers are bonded together, with at least one of the wafers having a first layer of silicon, an intermediate oxide layer and a second layer of silicon. The first silicon layer is initially mechanically reduced by around 80% to 90% of its thickness. The remaining silicon layer is further reduced by a plasma etch which may leave an uneven thickness. With appropriate masking the uneven thickness is made even by a second plasma etch. Remaining silicon is removed by a dry etch with XeF₂ or BrF₃ to expose the intermediate oxide layer. Prior to bonding the semiconductor wafers may be provided with various semiconductor devices to which electrical connections are made through conducting vias formed through the exposed intermediate oxide layer.