Logi-Thermal Simulation Using High-Resolution Temperature Dependent Delay Models

This paper proposes an accurate temperature dependent delay model for logi-thermal simulations. During the logi-thermal simulation of digital integrated circuits the propagation delays of the standard cells can be calculated from delay-temperature functions. The delay-temperature functions contain exact and precise delay values for each input-output path and temperature value. Temperature characterization corners can be specified in arbitrary fine granularity and range. The model presented in this paper overcome the limitation of the classic SDF (Standard Delay Format) models in that propagation delay values can be given for arbitrary temperatures, not only a few corners. With classic SDF, temperature dependence of timing and thus power can only be taken into account for a few design corners. Between characterization corners, like supply voltage, process variation and temperature, linear interpolation must be used for intermediate data. With our proposed delay model temperature-aware timing simulations would produce more accurate results than the classic SDF model. This paper compares the classic SDF delay model with our temperature dependent detailed model and provides evidence through a simple example for the necessity of temperature-aware timing simulation. The logi-thermal simulations are carried out with the CellTherm[1] application developed in the Dept. of Electron Devices, BME, Hungary. A logi-thermal acceleration technique is also introduced in this paper.