Precision comparison of surface temperature measurement techniques for GaAs ICs

Surface temperature measurement technology for GaAs integrated circuits (ICs) is considered. The three predominant techniques are examined and their precision compared quantitatively. Although infrared microscopy is found to be more imprecise than was previously believed, a measurement procedure with high accuracy based on the diode drop technique (an electrical method) and the transition point technique (a liquid crystal method) is established. The latter has been determined to have a precision as great as ±2°C for measuring the actual hot spot of nonsealed GaAs ICs. The former is the only method which is useful for sealed ICs. Although it cannot provide actual hot spot information, an accurate temperature with at most ±1°C error has been obtained at 15 μm from the spot by utilizing small (3.0 μm by 1.5 μm) diodes