[Zurück]

D. Dietzel, S. Chotikaprakhan, H. Bangert, C. Eisenmenger-Sittner:
"Cu coatings on carbon - Effects of plasma processing analysed by means of thermoreflectance microscopy";
Poster: 14th International Colloquium on Plasma Processes - CIP 2003, Antibes/Frankreich; 29.06.2003 - 03.07.2003.

In composite systems consisting of Cu coatings on carbon, which are produced with the help of plasma processing, e.g. plasma cleaning and etching of the carbon substrate and PVD of Ti bond layers and Cu coatings, the resulting effective heat transport parameters can vary considerably with the conditions of plasma processing. In thermal wave measurements based on periodically modulated laser beam heating of the sample surface and IR detection of the thermal response [1], the depth profile of the effective thermal properties of such systems can be described by a two-layer model, with an additional thermal contact resistance between the copper coating and the carbon substrate. By conventional heat pulse and thermal wave techniques, however, it is difficult or nearly impossible to measure the effective thermal properties of the thin copper coatings with the coating thickness in the submicron and micron range and to distinguish them from the dominant effect of the thermal contact resistance between copper coating and carbon substrate.
To overcome this experimental problem, an alternative thermal wave technique based on the signal of the modulated optical reflectance [2] has been introduced in this work. This method relies on the excitation of localized thermal waves by means of a focussed modulated pump beam of high intensity. The modulated oscillations of the temperature-dependent reflectance of the sample surface are then probed by a continuous laser beam of low intensity: ? In a first step, using the pump laser beam and the probe laser beam in colinear incidence, lateral inhomogeneities of the coatings and local defects of the contact between coating and substrate in the micron range can be visualized. ? In a second step, a controlled lateral displacement between the pump laser beam and the probe laser beam is introduced. With the beam diameters in the micron range and with the distance bridged by the measured thermal wave increased, the lateral heat transport along the coating becomes accessible to measurement and can be correlated with the conditions of plasma processing