High resolution photothermal imaging of high frequency phenomena using a visible charge coupled device camera associated with a multichannel lock-in scheme

We have developed a technique using a photothermal microscope from which we can make a thermal image of an electronic component working at a "high fre quency" using a charge coupled device (CCD) camera and a multichannel lock- in scheme. To do this, we have created an electronic "stroboscope": the fre quency F of the thermal signal induced by a high frequency electrical excit ation and the frequency of the light F+f that illuminates the device are ne xt to each other; the signal reflected at the surface of the device whose a mplitude is proportional to the variation of reflectivity and hence to the variation of temperature and whose frequency is the blinking one f is analy zed by a visible CCD camera. Amplitude and phase images of the high frequen cy thermal phenomenon can then be made. Moreover, this technique presents a great advantage: the spatial resolution is better than 1 mu m. The amplitu de and phase images presented show, with a very good spatial resolution, Jo ule and Peltier heating of a polycrystalline silicon 2.5 k Omega resistor a cross which a sinusoidal current is forced. (C) 1999 American Institute of Physics. [S0034-6748(99)03609-6].