Thermal wave Images

Thermal reforming Thermal sensitization Thermal stability Thermal transfer Thermal-transfer printing Thermal treatment Thermal wave imaging Thermate Thermate-TH2 Thermate-TH3 Therm-Chek... 

Figure 1 A schematic representation of the physical processes that occur during thermal-wave imaging.

That is, the acoustic waves simply carry or amplify the information describing the thermal-wave event. In thermal-wave imaging, the thermoacoustlc waves are thus used as a monitor to detect the presence of thermal waves scattered or reflected from thermal features. 

Applications. We have performed, with the system described above, high-resolution, thermal-wave imaging on many different materials. We have detected and Imaged subsurface mechanical defects such as microcracks and voids, grain boundaries, grains, and dislocations, and dopant regions and lattice variations in crystals. 

Another example is shown in Figure 5 which shows the electron and thermal-wave images of an Al-Zn alloy. The electron image (a) shows only topographical fetures, while the thermal-wave image (b) clearly shows both the grain structures and the presence of Fe or Sn precipitates. 

Figure 3 Examples of subsurface mechanical defects in a Si device. The electron micrograph (a) shows no defect features. The thermal-wave image (b) shows a subsurface network of microcracks in the lower half of the device and a subsurface delamination or chip-out in the top center.

Correlations with EBIC and XRT. Thermal features that arise either from mechanical defects or from metallic grains and grain boundaries are usually easy to recognize. However, thermal features arising from more subtle crystalline disruptions and variations, such as those described above are more difficult to identify. Before thermal-wave microscopy can be accepted as a routine, standard analytical technique, one needs to establish a direct correlation of some of these less obvious thermal-wave images with those obtained with other more widely accepted techniques. Below, we discuss two such correlations, one with electron beam Induced current (EBIC) and the other with x-ray topography (XRT). 

Thermal-wave microscopy has similarities in resolution and sampling depth. While the contrast mechanisms are very different, we would expect to find many of the same features appearing in both EBIC and thermal-wave images since both electrical conductivity and thermal conductivity are transport properties of the material, and thus will respond to changes in material properties in similar ways. 

Figure 7 Thermal-wave image of Si solar cell material showing grain structure.

Thermal-wave imaging thus appears to be as powerful a technique as x-ray topograhy for imaging dislocations in GaAs materials, but is much faster and simpler. 

Figure 10 Higher magnification (lOOX) thermal-wave image of the LEC-grown GaAs crystal in the regions of the crack, showing both dislocation networks and features (individual dark points) related to individual dislocations.

Thermal wave imaging may be used to inspect ion implantations, to evaluate defects in silicon, and to acquire depth-dependent images of integrated circuit features, or as a general probe for the study of non-radiative processes in semiconductors. Devices may be inspected in active mode (e.g., with current flowing). 

Power JF (1989) Thermal wave imaging in the physicochemical analysis and evaluation of solid-phase samples. Progress in Analytical Spectroscopy 12 453-506. 

Figure 18 Thermal wave images showing a small separation formed in an EBPVD TBCs (diameter 25.4mm) during cooling. It grew and buckled at room temperature [94]...

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