用AI指导随机游走,高效精准计算芯片电容。
DeepRWCap: Neural-Guided Random-Walk Capacitance Solver for IC Design
- 用双阶段神经网络预测每步游走的转换量,提升采样精度。
- 相比商用工具误差仅1.24%,工业设计平均提速23%。
- 适合芯片设计中的电容提取,尤其复杂结构加速显著。
蒙特卡洛随机游走方法因无需网格且天然并行,广泛用于电容提取。但现代半导体中密集结构与多高对比度介电材料导致游走步中过渡区域难以无偏采样。本文提出DeepRWCap,一种机器学习引导的随机游走求解器,可预测每步所需的转移量,包括泊松核、梯度核以及权重的符号与大小。该模型采用两阶段神经架构,将结构化输出分解为面分布和立方体面上的空间核;利用3D卷积网络捕捉体域介电相互作用,2D深度可分离卷积建模局部核行为。设计融入基于网格的位置编码及由立方体对称性启发的结构选择,减少学习冗余并提升泛化能力。在10万组程序生成的介电配置上训练后,针对10个涵盖12至55纳米节点的工业设计自电容估计,与商用Raphael求解器对比,均方相对误差为1.24±0.53%。相较当前最优随机差分方法Microwalk,平均加速23%;在运行时间超过10秒的复杂设计上,平均加速达49%。
原文摘要 · Abstract (English)
Monte Carlo random walk methods are widely used in capacitance extraction for their mesh free formulation and inherent parallelism. However, modern semiconductor technologies with densely packed structures present significant challenges in unbiasedly sampling transition domains in walk steps with multiple high contrast dielectric materials. We present DeepRWCap, a machine learning guided random walk solver that predicts the transition quantities required to guide each step of the walk. These include Poisson kernels, gradient kernels, and the signs and magnitudes of weights. DeepRWCap employs a two stage neural architecture that decomposes structured outputs into face wise distributions and spatial kernels on cube faces. It uses 3D convolutional networks to capture volumetric dielectric interactions and 2D depthwise separable convolutions to model localized kernel behavior. The design incorporates grid based positional encodings and structural design choices informed by cube symmetries to reduce learning redundancy and improve generalization. Trained on 100000 procedurally generated dielectric configurations, DeepRWCap achieves a mean relative error of 1.24 +/- 0.53% when benchmarked against the commercial Raphael solver on the self capacitance estimation of 10 industrial designs spanning 12 to 55 nm nodes. Compared to the state of the art stochastic difference method Microwalk, DeepRWCap achieves an average speedup of 23%. On complex designs with runtimes over 10 seconds, it reaches an average acceleration of 49%.
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