Transport-Analysis-Based 3-D TCAD Capacitance Extraction for Sub-32-nm SRAM Structures

Capacitance extraction for nanoscale circuits operating at high frequencies plays an important role in accurately modeling postlayout electrical behavior. In this work, for the first time, a layout-independent 3-D technology computer-aided design (TCAD)-based methodology is used to precisely compute front-end-of-the-line (FEOL) and back-end-of-the-line capacitances in SRAM structures using advanced sub-32-nm SOI process assumptions. Results for multicell single-/dual-ported 6T SRAM blocks highlight the need to model FEOL silicon as a semiconductor, incorporating field-carrier interactions (which are completely ignored by field solvers), and the inadequacy of single-cell 3-D TCAD-based capacitance extractions. The 3-D TCAD methodology is applied to an experimental 32-nm SOI process and is in close agreement with measured data, in the presence of FEOL variations.