Multi-terminal Ultra-thin 3D Nanoporous Silicon Capacitor Technology for High-Speed Circuits Decoupling

As trends in digital ICs are evolving to offer more functionalities with lower power consumption and lower voltages, issues like noise and voltage fluctuation are becoming more and more critical. Indeed, increasing power density comes down to challenging existing voltage regulators and their power distribution network (PDN). To help dealing with such constraints, decoupling capacitors are used to implement efficient decoupling techniques and are integrated in almost every circuit design. For high speed applications such as HPC and Mobile and thanks to their features, Silicon capacitors stand out compared to MLCCs and are already adopted in the latest generations of consumer devices. In our previous research works, we introduced 3D silicon capacitors, using tripod trench structures, enabling higher density and presenting several times smaller area than conventional passives. Silicon capacitor technology is constantly evolving to address the trends and requirements of PDN applications and in this paper we will introduce for the first time our latest silicon process technology based on 3D Nanoporous structures which enable the increase of the effective density to higher than 1.3μF/mm
²
and reduce the thickness of the active capacitor area and consequently the capacitor thickness to less than 50μm. The extremely low ESL (few pH) and low ESR (few mΩ) of these devices grant them the ability to design high performance PDNs with low impedance over a wide frequency bandwidth. A complete overview of these new passive devices will be detailed. Process and design choices to minimize the parasitic will be discussed. Simulations process flow and measurements of these multi-terminal silicon devices will be detailed for the first time. Finally, assembly and packaging aspects will be reviewed and will demonstrate an effective package area reduction. Such Multi-terminal silicon devices reduce the total quantity of capacitors and results in total savings in both bill of materials and mounting costs.