Burn-in effect on yield

By removing infant mortalities, burn-in of semiconductor devices improves reliability. However, burn-in may affect the yield of semiconductor devices since defects grow during burn-in and some of them end up with yield loss. The amount of yield loss depends upon burn-in environments. Another burn-in effect is the yield gain. Since yield is a function of defect density, if some defects are detected and removed during burn-in, the yield of the post-burn-in process can be expected to increase. The amount of yield gain depends upon the number of defects removed during burn-in. In this paper we present yield loss and gain expressions and relate them with the reliability projection of semiconductor devices in order to determine burn-in time.