ATSim3.5D: A Multiscale Thermal Simulator for 3.5D-IC Systems based on Nonlinear Multigrid Method

TL;DR

This paper introduces ATSim3.5D, a multiscale thermal simulator for 3.5D-ICs that combines a hybrid tree grid structure with a nonlinear multigrid solver, achieving high accuracy and efficiency over traditional tools.

Contribution

It presents a novel multiscale thermal simulation method specifically designed for 3.5D-ICs, addressing heterogeneity and nonlinear thermal effects.

Findings

Achieves <1% mean absolute relative error compared to ANSYS Icepak.

Provides 80x faster simulation speeds.

Effectively captures multiscale thermal features in 3.5D-ICs.

Abstract

To resolve the rising temperatures in 3.5D-ICs, a thermal-aware design flow becomes increasingly crucial, necessitating an accurate and efficient thermal simulation tool. However, previous tools struggle to handle the unique heterogeneous multiscale structures in 3.5D-ICs and the nonlinear thermal effects caused by high temperatures. In this work, we present a multiscale thermal simulator for 3.5D-ICs. We propose a hybrid tree structure to generate multilevel grids and capture the multiscale features and employ the nonlinear multigrid method for quick solving. Compared to ANSYS Icepak, it exhibits high accuracy (mean absolute relative error <1%, max error $<\SI{2}{\degreeCelsius}$), and efficiency ($80\times$ acceleration), delivering a powerful means to evaluate and refine thermal designs.