Characterization, modeling and optimization of 3D embedded trench decoupling capacitors in Si-RF interposer

Integrated trench high density MIS (Metal Insulator Semiconductor) capacitors in Si-interposer are of great interest as they provide decoupling in a smart way using the third dimension of the silicon substrate. However, the use of various highly integrated passive components on the same Si-interposer is challenging regarding wide frequency band performances and signal integrity. Both aspects are addressed in this paper based on 300 kHz-20 GHz vector network analyzer measurements on 3D 80 nF/mm² decoupling capacitors produced by IPDIA on a high resistivity substrate. Firstly, a scalable 1 MHz-10 GHz wideband model of a 3D capacitor in the 100 pF-10 nF range is developed. Secondly, 3D electromagnetic simulations of substrate and capacitive coupling between 3D capacitors using guard ring are presented. All simulations show good agreement with measurements. To the best of our knowledge, this is the first time that a wideband mathematical model as well as an RF crosstalk study have been published on embedded trench decoupling capacitors.