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In this paper, we describe technology methods to improve the read stability (or static noise margin (SNM)) of asymmetrical SRAM cell based on judicious placement of a weakened pull-down device (NL) in the cell. The core concept is to further weaken the strength of NL through device design and technology/process means beyond that achievable by the conventional device sizing or circuit scheme, thus achieving Read SNM comparable to the standby SNM. These methods improve/maximize the SNM of asymmetrical SRAM cell without degrading read/write performance, leakage/dynamic power, and area/density. They are also more scalable for low voltage operations. Write margin and performance can be noticeably improved by further device optimization.
Date of Conference: 23-25 April 2007