Low Power Clock Routing for 3D IC

This chapter focuses on low-power and low-slew clock network design and analysis for through-silicon-via (TSV)-based three-dimensional stacked ICs (3D ICs). First, we study the impact of the TSV count and the TSV RC parasitics on clock power consumption. Several techniques are introduced to reduce the clock power consumption and slew of the 3D clock distribution network. We analyze how these design factors affect the overall wirelength, clock power, slew, and skew in 3D clock network design. Second, we study a two-step 3D clock tree synthesis method: (1) 3D abstract tree generation based on the three-dimensional method of means and medians (3D-MMM) algorithm; (2) buffering and embedding based on the slew-aware deferred-merge buffering and embedding (sDMBE) algorithm. We also extend the 3D-MMM method (3D-MMM-ext) to determine the optimal number of TSVs to be used in the 3D clock tree so that the overall power consumption is minimized. Related SPICE simulation indicates that: (1) a 3D clock network that uses multiple TSVs significantly reduces the clock power compared with the single-TSV case; (2) as the TSV capacitance increases, the power savings of a multiple-TSV clock network decreases; and (3) our 3D-MMM-ext method finds a close-to-optimal design point in the TSV count vs. power consumption tradeoff curve very efficiently.