Abstract—This paper discusses, for the first time, how the guard band (GB) designs for the screening-test should be unprecedentedly changed when the shifting amounts of voltage-margin of the post-screening becomes larger than that of pre-screening. Three different types of amplitude-ratios of RTN to RDF (RTN/RDF: 0.25, 1, 4) are assumed in this discussion. The screening yield-loss impacts, made by: 1) larger ratio of RTN/RDF and 2) approximation-error of longer tailed RTN distribution, are discussed. It has been shown that the yield-loss may become crucial issues if RTN could not be reduced because the loss can become 5-orders of magnitude times larger than that for 40nm when RTN/RDF=1. It has been found that the required accuracy-level of statistical model for approximating RTN tail-distributions significantly increases as RTN/RDF gets close to 1. Intolerable yield-loss can be increased by 6-orders of magnitude due to its errors of the GB designs. A fitting method to approximate a longer tailed RTN Gamma-distribution by simple Gaussian mixtures model (GMM) is proposed. It has been verified that the proposed method can reduce the error of the fail-bit predictions by 2-orders of magnitude while reducing the iterations for EM step convergence to 1/16 at the interest point of the fail probability of 10-12 which corresponds to the design target point to realize a 99.9% yield of 1Gbit chips.

Index Terms—Mixtures of Gaussian, random telegraph noise, EM algorithm, heavy-tail distribution, long-tail distribution, fail-bit analysis, static random access memory, guard band design.

W. Somha and H. Yamauchi are with the Information Intelligent System Fukuoka Institute of Technology, 3-30-1, Wajiro-Higashi, Higashi-ku, Fukuoka, Japan (e-mail: bd12002@ bene.fit.ac.jp, yamauchi@fit.ac.jp).