Patent attributes
A method for wafer-to-wafer bonding of a sensor readout circuitry separately fabricated with a silicon substrate to a photodiode device made of non-silicon materials grown from a separate substrate. In preferred embodiments the non-silicon materials are epitaxially grown on a silicon wafer. The bonding technique of preferred embodiments of the present invention utilizes lithographically pre-fabricated metallic interconnects to connect each of a number of pixel circuits on a readout circuit wafer to each of a corresponding number of pixel photodiodes on a photodiode wafer. The metallic interconnects are extremely small (with widths of about 2 to 4 microns) compared to prior art bump bonds with the solder balls of diameter typically larger than 20 microns. The present invention also provides alignment techniques to assure proper alignment of the interconnects during the bonding step.
