Process monitoring vehicle for SRAM critical path using ring oscillator in 7 nm Finfet

Abstract

In the nano-scale fabrication process, one of the major concerns is the impact of the process variation on the functionality of the design. At lower technology nodes, the impact from the second-order elements which were not significant is playing an important role in defining the designs. SRAM being at the forefront of every process node, it is important to assess the impact of the process in the early stages to make the required design changes. Self-time path in SRAM is crucial in defining the functionality, power, and performance. In the early stages of SRAM development, the proposed ring oscillator (RO) design helps in estimating the post-fabrication impact. This paper discusses the design and implementation of the SRAM critical path-based ring oscillator in the 7nm FinFet process and comparing the behavior with a more conventional ring oscillator. The impact from the process parameter variation is captured in the form of frequency variations. It is observed that the process tracking capability of conventional ring oscillator differs by ~17% compared with SRAM critical path behavior.