"The most telling aspect of how the HEW4 BSI chip gets integrated into a chip scale camera module involves the use of very high density arrays of polysilicon filled through silicon vias (TSVs), to form the electrical interconnect between the back side wire bonds and the CMOS integrated circuits on the front of the wafer (Figure 5). These are the first true submicron TSVs that Chipworks has seen deployed in volume production."
|Fig. 5. Sub-micron TSVs cross-section|
Chipwork says: "the HEW4 device defines a new category of CIS camera module with its closely packed, poly-filled submicron TSVs that connect the back side aluminum bond pads to the front side copper lines. This technology is non-trivial to implement. Once mastered and with appropriate economies of scale in play, however, this advanced TSV process saves valuable silicon area and can reduce the size of the camera module."