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THERMAL IMAGING AS A TOOL FOR ASSESSING THE RELIABILITY, HEAT TRANSPORT, AND MATERIAL PROPERTIES OF MICRO TO NANO-SCALE DEVICESE
We utilize thermoreﬂectance (TR) thermal imaging to experimentally study heat transport and reliability of micro to nano-scale devices. TR imaging provides 2D thermal maps with sub-micron spatial resolution. Fast thermal transients down to 50 ns resolution can be captured. In addition, finite element modeling is carried out to better understand the underlying physics of the experiment. We describe four main applications; 1) Development of a full-field thermoreﬂectance imaging setup with a variable optical (laser) heating source as a general characterization tool. We demonstrate the setup’s sensitivity to extract anisotropic
thermal conductivity of thin flms and evaluate its sensitivity for detecting buried (below the surface) defects in 3D integrated circuits. This method provides a low-cost noncontact alternative to destructive defect localization methods. It also doesn’t require any special sample
preparations. 2) Physics of localized electromigration-failures in metallic interconnects is investigated. One can distinguish two separate mechanisms responsible for electromigration depending on the current density and temperature gradient. 3) Thermal transport in silicon near sub-micron electrical heaters is studied. Quasiballistic and hydrodynamic (ﬂuid-like) behavior is observed at room temperature for diﬀerent device sizes and geometries. 4) Temperature-dependent thermoreﬂectance coefcient of phase-change materials is characterized. We focus on tungsten (W) doped VO2 (W0.02V0.98O2) compound, which experiences an insulator-to-metal transition (IMT) at ≈33 °C. Strong TR-signal non-linearity is observed at the IMT temperature. This non-linearity is used to localize the phase-change boundary with resolutions down to ≈0.2 µm. TR full-feld imaging enables a simple and fast characterization complementing near-feld microscopy techniques.