Research On Circuit Optimization Methods Based On Yield Analysis

In IC engineering,yield problem comes from process variation.Process variation can influence electrical features of device,which may change performance of circuit and at last,lead to yield problem.With process dimension scaling down,the effect of low power design and other issues,yield problem is becoming more severe.It is limited help that existed methods and tools can offer.To optimize the whole process and system of yield analysis and circuit optimization,following ideas are proposed and implemented.A hybrid performance model is proposed,which increases the efficiency of yield analysis and brings convenience for following circuit optimization.Hybrid performance model can replace an amount of circuit simulation in yield analysis.In special,hybrid performance model considers process variation and design parameters at the same time,which is a preparing work for circuit optimization.Furthermore,hybrid performance model is trained offline,which means no further simulation is necessary once the model is built.Hybrid performance model is built based on elastic net model.To make it more accurate,two optimization algorithms are proposed.The first one is iterative modeling method,which can decrease deviations near standard area of performance.The second one is local compensation method,which can compensate some local areas that have huge model deviation.Besides,Latin Hyper Cube sampling and cross validation methods are also used to optimize the model.Based on hybrid performance model,a new set of methods of yield calculation and circuit optimization is proposed,which is efficient and stable.The method is implemented with importance sampling and Monte Carlo analysis.Research is implemented in two aspects,one is to explore the solution of generating reasonable replacing probability density function in importance sampling,the other is to use numerical calculation algorithm to optimize the programing question.Also,solution on yield driven circuit optimization is also proposed to help designers optimize their work.Through experiments on SRAM circuit unit,it is validated that the whole new process of yield analysis proposed can work efficiently and offer convenience in circuit design.