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Overview HeatWave Modeling Temperature
“Temperature compensation of the LC oscillator is a primary concern in developing all-silicon clocks. Gradient’s Virtual Thermography service provided the means for modeling on-die thermal gradients and their effects on circuit performance. The analysis showed us areas where thermal gradients mattered and others where their effect was negligible. These results were not obvious and helped us to better focus our design effort and shorten time to market.”

Dr. Michael McCorquodale
General Manager, Silicon Frequency Control, Communications Division, Integrated Device Technology

Modeling Temperature

HeatWave™ computes the temperature inside the chip or 3D-IC by first building a solid-body heat conduction model of the domain. This thermal model is constructed with adaptive resolution, commensurate with the feature sizes of the power sources and heat conduction paths inside the chip.

Using Layout Data

The thermal model uses IC layout data (all the shapes on all the layers, as generated by layout tools such as Cadence Virtuoso), plus a thermal techfile containing the layer thicknesses and material properties, including their temperature dependencies. The model uses full-chip layout, because even non-functional geometries such as metal fill may significantly affect heat transport.

Using Power Data

Power sources are modeled as volumes dissipating specified power values (as generated by your circuit simulator). In the case of steady-state temperature simulation, this is the average power dissipated per circuit instance, which may be a transistor, a transistor segment, a standard cell or a macro instance.

Using Package Thermal Data

HeatWave calculates the temperature within the die (or die stack), containing structures with submicron feature sizes, so the thermal model requires similar resolution. A package macro model is used for the region outside the die (package and board) containing features at millimeter length scales. The package model bridges the two different physical length scales.

HeatWave takes into account the influence of the bond wires/bumps and the package thermal characteristics, including die-attach and ambient temperature. You may specify them as a set of 6 boundary thermal resistances or heat fluxes as seen at the die faces, as shown below.

Computing Temperature

HeatWave then computes the temperature using all of the above data, by numerically solving the heat diffusion equation within the chip or 3D-IC. Finally, it reports the volume-averaged temperature of all power sources, and design objects. Click here to see some results of temperature simulations.