Predicting Shot-Level SRAM Read/Write Margin Based on Measured Transistor Characteristics

Abstract

An SRAM-array test structure provides the capability of directly measuring the characteristics of each transistor and the read/write metrics for each static random access memory (SRAM) cell in the array. However, the total test time of measuring the read/write metrics takes longer than that of measuring each transistor\'s characteristics. This paper presents a model-fitting framework to predict the average read/write metrics of the SRAM cells in a lithography shot using only the measured transistor characteristics. The proposed framework is validated through the measurement result of 4750 samples of a 128-bit SRAM-array test structure implemented in a United Microelectronics Corporation 28-nm process technology. The experimental results show that the learned models can achieve at least 97.77% R-square on fitting the shot-level read static noise margin, write margin, and read current based on 2375-sample testing data.