A case for 3D stacked analog circuits in high-speed sensing systems

In order to build high performance real-time sensing systems every building block in the system should be built with a technology that allows that building block to achieve its best performance. Technologies like BJT and BICMOS are better suited for building basic analog blocks like input buffers and power amplifiers, while CMOS is the best choice for digital data processing. To build mixed-technology systems traditionally system-in-package (SiP) techniques are used. SiP integration uses bonding wires or flip chip instead of on-chip integration. In this paper we study the feasibility of using 3D stacking to integrate heterogeneous blocks built using different technologies within a real-time sensing system. Several of the previous studies on 3D stacking focused on integrating multiple digital blocks and using through-silicon-vias (TSVs) to transfer digital signals between the layers in a stack. In this paper we study the behavior of the analog signals traversing through TSVs and measure how well 3D stacking can enhance or limit the performance of analog and digital stacking. In order to quantify the power and performance characteristics, we modeled bonding wire, flip chip, and through-silicon-via (TSV) interfaces. Using these models we show that 3D stacking of analog and analog/digital components can double the bandwidth, increase sampling frequency by nearly two orders magnitude and and improve the signal integrity by 3 dB compared to bond wires.