Ultra-thin Capacitors in Silicon for 3D-Integration and Flexible Electronics

Abstract

Current electronic systems and circuits possess approximately 80 % of passive components. Thus, high performance integrated silicon-based passive components with high density are required to reduce the overall cost and bulkiness of the systems. This paper presents the development of high-density ultra-thin 3D capacitors in silicon, one of the important passive components exploited in approximately all the circuits for SiP, 3D-integration and flexible systems. The 3D structure is achieved by using deep reactive ion etching (DRIE) process. The substrate and the polysilicon act as the two electrode plates with silicon dioxide as the dielectric. Two designs with different pitches are investigated with successful back-grinding of the substrate to 50$\mu$ m thin and 22$\mu$ m ultra-thin singulated capacitors. Capacitive densities of 36.25 nF/mm 2 and 28.75 nF/mm 2 over a frequency bandwidth of 100 KHz are presented. The reduced thickness and flexible nature of these ultra-thin capacitors (<50$\mu$ m) makes them a suitable candidate for a wide range of applications.