IC tool ensures proper heat dissipation

IC-power-analysis-tool ven­­dor Apache Design Solutions has introduced a static-thermal-analysis tool for locating potential heat problems in ICs. Until now, only one other company—Gradient Design Automation—offered on-chip thermal-analysis software. According to Apache's president and chief executive officer, Andrew Yang, the new Sahara-PTE (power-thermal-electrical) tool, ties closely to Apache's RedHawk power-analysis and PsiWinder electrical-analysis tools because thermal analysis directly relates to power and affects timing. Timing, in turn, impacts power, which affects thermal integrity.

Yang says that, starting at the 65-nm node, designers must monitor heat generation by monitoring switching and leakage power, and they must analyze parts of the IC and the package to ensure that heat dissipates properly from paths through the substrate, to the package, the heat sink, and even the metal layers. The priority, however, is to ensure that heat and leakage don't escalate into a thermal runaway. "At 65 nm, thermal-analysis tools are nice to have, but, at 45 nm, they become mandatory," says Yang, who notes that the first thermal-integrity tools are sta-tic, but future thermal tools will need to become dynamic to more accurately analyze thermal integrity in multiple modes and in multiple ambient conditions.

To analyze thermal integrity, Apache outlines two flows for Sahara. In the PT (power-thermal) loop, users analyze temperature and power across the chip for a given period of clock cycles. This analysis runs with Apache's RedHawk and Sahara-PTE. It provides users with a condition in which the design achieves equilibrium over several clock cycles for both power and temperature. During the ana-lysis, if heat and leakage continue to rise for each iteration and clock cycle, the design may be reaching thermal runaway, so users must shift around some functions or find a way to dissipate heat or cool the device.

The PsiWinder flow electrically analyzes the PT loop, creating the PTE loop. In this flow, users analyze the temperature-dependent resistances of the devices. The PTE flow helps to monitor changes in current density and interconnect self-heating, both of which can impact voltage drop, timing, and power and can contribute to or cause electromigration. Both the PT and PTE flows require Apache's library-characterization technology.