Stabilization and utilization of coupling MOS capacitance between TSVs

Abstract

Through-silicon via (TSV) is a key enabler for future 3-D integrated circuits. Due to MOS (Metal-Oxide-Semiconductor) effect, the coupling capacitor between TSVs is actually a varactor under different signal/power voltages. This paper offers a discussion on the stabilization and utilization of the TSV varactor for different systems. For digital systems, it is important to ensure that TSV capacitance is stable within the operating voltage. Therefore, different methods are proposed and compared to stabilize the TSV coupling capacitance. For reconfigurable systems, the possibility of the TSV varactor serving as the tunable capacitor is demonstrated by designing a voltage-controlled tunable low-pass filter with a TSV pair. The doping profile of the substrate is modified to maintain a reasonable quality factor of the TSV varactor. The simulated results show that the filter has a cutoff frequency shifting from 1.85GHz at OV to 2.23GHz at 1V, resulting in a tuning range of ±9% centered at 2.04GHz.