Staring infrared focal plane arrays (FPAs) require pixel-level, three-dimensional (3D) integration with silicon readout
integrated circuits (ROICs) that provide detector bias, integrate detector current, and may further process the signals.
There is an increased interest in ROIC technology as a result of two trends in the evolution of infrared FPAs. The first
trend involves decreasing the FPA pixel size, which leads to the increased information content within the same FPA die
size. The second trend involves the desire to enhance signal processing capability at the FPA level, which opens the door
to the detector behaving like a smart peripheral rather than a passive component—with complex signal processing
functions being executed on, rather than off, the FPA chip. In this paper, we review recent advances in 3D integration
process technologies that support these key trends in the development of infrared FPAs. Specifically, we discuss
approaches in which the infrared sensor is integrated with 3D ROIC stacks composed of multiple layers of silicon
circuitry interconnected using metal-filled through-silicon vias. We describe the continued development of the 3D
integration technology and summarize key demonstrations that show its viability for pixels as small as 5 microns.