Efficient vlsi yield prediction with consideration of partial correlations

Abstract

With the emergence of the deep submicron era, process variations have gained importance in issues related to chip design. The impact of process variations is measured using manufacturing/parametric yield. In order to get an accurate estimate of yield, the parameters considered need to be monitored at a large number of locations. Nowadays, intra-die variations are an integral part of the overall process uctuations. This leads to the difficult case where yield prediction has to be done while considering independent and partially correlated variations. The presence of partial correlations adds to the existing trouble caused by the volume of variables. This thesis proposes two techniques for reducing the number of variables and hence the complexity of the yield computation problem namely - Principal Component Analysis (PCA) and Hierarchical Adaptive Quadrisection (HAQ). Systematic process variations are also included in our yield model. The biggest plus in these two methods is reducing the size of the yield prediction problem (thus making it less time complex) without affecting the accuracy in yield. The efficiency of these two approaches is measured by comparing with the results obtained from Monte Carlo simulations. Compared to previous work, the PCA based method can reduce the error in yield estimation from 17.1% - 21.1% to 1.3% - 2.8% with 4.6x speedup. The HAQ technique can reduce the error to 4.1% - 5.6% with 6x - 9.4x speedup.