Full-field pump-probe thermoreflectance imaging for characterization of thin films and 3D integrated circuits

We evaluate optical pump-probe imaging where laser heating and subsequent non-contact full-field thermoreflectance characterization is used to study thin film materials and 3D integrated circuit chips. The diameter of the heated region can range from one micron up to millimeters or centimeters. The shape of the surface or interface thermoreflectance profile is then captured with 50 ns time-resolution using mega-pixel lock-in camera. By combining the measured thermal surface profile with finite-element modeling, we demonstrate the ability to extract the thermal conductivity of thin films on various substrates. With the proper choice of pump and probe wavelengths, the potential of the technique as a general characterization tool is evaluated. There is a lot of interest in structural integrity and failure-analysis of complex chips during manufacturing. Heat sinking in 3D chips is often a key challenge. The sensitivity of the full-field thermal imaging technique to study the quality of buried (below the surface) layers or contacts in 3D chips is quantified.