US Patent 9343499 Integrated circuit stack with strengthened wafer bonding

An integrated circuit system includes a first device and second device wafer. A wafer bonding region is disposed at an interface of a front side of a first dielectric layer of the first device wafer and a front side of a second dielectric layer of the second device wafer such that wafer bonding region bonds the first device wafer to the second device wafer. The wafer bonding region includes dielectric material having a higher silicon concentration than a dielectric material of the first and second dielectric layers of the first and second device wafers. A conductive path couples a first conductor of the first device wafer to a second conductor of the second device wafer. The conductive path is formed in a cavity etched through the wafer bonding region between the first conductor and the second conductor.