Layout - S ynthesis Techniques for Yield Enhancement

Several yield enhancement techniques are proposed for the last two stages of VLSI design, i.e., topological/symbolic and physical layout synthesis. Our approach is based on modiications of the symbolic/physical layout to reduce the sensitivity of the design to random point defects without increasing the area, rather than fault tolerance techniques. A layout compaction algorithm is presented and the yield improvement results of some industrial layout examples are shown. This algorithm has been implemented in a commercial CAD framework. Some routing techniques for wire length and via minimization are presented and the results of wire length reduction in benchmark routing examples are shown. We demonstrate through topological optimization for PLA-based designs that yield enhancement can be applied even at a higher level of design abstraction. Experimental results show that it is possible to achieve signiicant yield improvements without increasing the layout area by applying the proposed techniques during layout synthesis.