Analysis of active semiconductor structures by combined SThM and SThEM

Abstract
In this contribution we present a combined experimental set-up for the simultaneous detection of the thermal and thermoelastic signal of electrically heated semiconductor devices measured by scanning probe techniques. A commercial atomic force microscope has been operated using a wollaston wire thermal tip for temperature oscillations, while simultaneously the oscillations of the cantilever have been measured. This set-up has been applied to semiconductor structures, with the aim of characterizing temperature, heat source and current distribution. In addition, having available a very versatile tool for different thermal scanning application, the simultaneous imaging by scanning thermal microscopy and scanning thermoelastic microscopy can improve contrast and quantitative interpretation. In both cases, the measured signals only give an indirect information on the current and heat source distribution. Therefore, the data has to be interpreted by help of theoretical models based on thermal waves, either by analytical approach or by finite element simulations. Here, the combination of the two techniques, can be helpful to find a more precise set of parameters, that describes both the SThM and SThEM signal. Furthermore, the influence of non-thermal and non-thermoelastic contributions to the SThEM-signal will be analyzed and discussed. When performing simultaneous measurements, especially the influence of the tip expansion, either due to heat diffusion from the sample to the tip or due to the probe current in the tip has to be considered.