A Low Leakage, High Performance SRAM Cell using 0.18μm Technology

摘要

Aggressive CMOS scaling results in low threshold voltage and thin oxide thickness for transistors manufactured in deep sub-micrometer regime. As a result, reducing the sub-threshold and tunneling gate leakage currents has become one of the most important criteria in the design of VLSI circuits. This paper presents a method based on dual-v_t and dual-t_(ox) assignment to reduce the total leakage power dissipation of static random access memories (SRAMs) while maintaining their performance. The proposed method is based on the observation that read and writes delays of a memory cell in an SRAM block depend on the physical distance of the cell from the sense amplifier and the decoder. Thus, the idea is to deploy different configurations of six-transistor SRAM cells corresponding to different threshold voltage and oxide thickness assignments for the transistors. Unlike other techniques for low-leakage SRAM design, the proposed technique incurs neither area nor delay overhead. In addition, it results in a minor change in the SRAM design flow. The leakage saving achieved by using this technique is a function of the values of the high threshold voltage and the oxide thickness, as well as the number of rows and columns in the cell array.