Power transistor near-infrared microthermography using an intensified CCD camera and frame integration

In this work, a high performance near-infrared thermal microscope designed to characterize the thermal behaviour of a power metal-oxide-silicon field-effect transistor (MOSFET) is presented. This non-destructive method is based on the measurement of the thermal radiation emitted by the power transistor in the spectral domain close to 800 nm using an intensified CCD camera. Although the intensifier unit is developed specially for low-level radiant applications, an image processing technique based on lock-in thermography method is proposed to improve the signal-to-noise ratio. The method allows absolute temperature distribution measurements for both the static and periodic modes at the micron scale. In the periodic mode, the transistor is heated (by the Joule effect) at a frequency fitting the camera acquisition speed. The minimum threshold temperature value and the temperature sensitivity to the emissivity factor are examined. Microthermographic images of the power MOSFET are presented and discussed for several values of drain current. For both static and periodic modes, good results of temperature resolution and spatial resolution have been achieved confirming the interest of short wavelengths for microthermography applications.