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This paper presents a study on the effectiveness of strained contact-etch-stop-layer (CESL) technologies in aggressively scaled dense structures. The focus is on nested transistors, which is a technologically very important structure that consists of a chain of gates on one active area. It will be shown that the two main channel stress components introduced by CESL, which are the vertical and parallel stresses, have a different sensitivity toward layout variations, which accordingly leads to different scaling guidelines to obtain a layout-insensitive strained CESL technology. Decreasing the CESL thickness is not enough for technology scaling; also, adapting the spacer dimensions is indispensable to scale a strained CESL technology from one technology node to the next.
Date of Publication: June 2007