Low-power clock distribution networks for 3-D ICs

Designing a low power clock network in synchronous circuits is an important task. This requirement is stricter for 3-D circuits due to the increased power densities. Resonant clock networks are considered efficient low-power alternatives to conventional clock distribution schemes. These networks utilize additional inductive circuits to reduce the power consumption while delivering a full swing clock signal to the sink nodes. Test is another complex task for 3-D ICs, where pre-bond test is a prerequisite. This paper, consequently, introduces a design methodology for resonant 3-D clock networks that lowers the power of the clock networks while supporting pre-bond test. Several 3-D clock network topologies are explored in a 0.18 μm CMOS technology. Simulation results indicate 43% reduction in the power consumed by the resonant 3-D clock network as compared to a conventional buffered clock network. By properly distributing the inductance within the layers of the 3-D stack, resonance is ensured both in pre-bond test and normal operation. The important aspects of this approach are introduced in this paper.