iTPlace: machine learning-based delay-aware transistor placement for standard cell synthesis

Cell layout synthesis is a critical stage in modern digital IC design. In previous automatic synthesis solutions, algorithms always consider only cell area and routability. This is the first work to propose a method of delay-aware transistor placement for cell library synthesis at the sign-off level. We consider the delay and area of a cell in the transistor placement stage. Our methodology consists of three major steps. First, a search tree finds the candidate placement list that has the smallest area in a large search space. Then, a neural network filters out the unroutable candidates. Finally, a comparative convolutional neural network model, trained by sign-off level data, sorts the delays during the early placement stage. The experimental results show that the proposed CNN-based routable classifier can achieve up to 98% accuracy, and the proposed CNN-based delay ranker also can achieve up to 94.6% accuracy. The work obtains a 1.77% average sequential component delay improvement over the traditional cell synthesis method. Our method also has a 0.97% better delay performance than the human-level design.