Neighbor current ratio (NCR): a new metric for I/sub DDQ/ data analysis

Abstract

I/sub DDQ/ test loses its effectiveness for deep sub-micron chips since it cannot distinguish between faulty and fault free currents. The concept of current ratios, in which the ratio of maximum to minimum I/sub DDQ/ is used to screen faulty chips, has been previously proposed. The neighboring chips on a wafer have similar fault free properties and are correlated. In this paper, the use of spatial correlation in combination with current ratios is investigated. By differentiating chips based on their nonconformance to local I/sub DDQ/ variation, outliers are identified. The analysis of SEMATECH data is presented.