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Performance, efficiency, and reliability of modern high power, high speed microelectronics and nanoscale structures are strongly influenced by device self-heating on the micron and nanometer scale. Local temperature "hotspots" on a chip indicate areas of high power density and possible failure locations. This dissertation presents results of case studies using high resolution thermoreflectance imaging microscopy to characterize self-heating in high power silicon transistor arrays, gallium nitride high electron mobility power transistors (HEMTs), and nanoscale percolation network devices. Thermoreflectance imaging microscopy was performed with submicron spatial resolution, 800 ps time resolution, and 50 mK temperature resolution.Thermoreflectance imaging of silicon transistor arrays revealed self-heating nonuniformity greater than a factor of two due to electrical debiasing. At low bias (12 mA/mm), temperature distribution matched state of the art electrothermal simulation. At high bias (47 mA/mm), however, measured self-heating diverged significantly from simulation despite inclusion of temperature dependent material properties in the thermal model. Hotspots with temperature change of 70 K were observed. Results demonstrate nonlinear dependence of current distribution on bias for complex arrayed power devices.Thermoreflectance imaging of GaN HEMTs revealed for the first time temperature gradients as large at 60 K and 80 K between critical gate, channel, and contact features within the first few microseconds of pulsed excitation at 19 W/mm. Fast transient self-heating gradients in the HEMT were confirmed with 5 ns time resolved thermoreflectance images. Thermoreflectance imaging revealed nonuniform self-heating in nanoscale percolation network devices consisting of disordered 90 nm diameter silver nanowires. Microscopic hot-spots at selected nanowire-nanowire junctions in the network exhibited nonlinear thermal properties, with temperature dependence of current excee

Performance, efficiency, and reliability of modern high power, high speed microelectronics and nanoscale structures are strongly influenced by device self-heating on the micron and nanometer scale. Local temperature "hotspots" on a chip indicate areas of high power density and possible failure locations. This dissertation presents results of case studies using high resolution thermoreflectance imaging microscopy to characterize self-heating in high power silicon transistor arrays, gallium nitride high electron mobility power transistors (HEMTs), and nanoscale percolation network devices. Thermoreflectance imaging microscopy was performed with submicron spatial resolution, 800 ps time resolution, and 50 mK temperature resolution.Thermoreflectance imaging of silicon transistor arrays revealed self-heating nonuniformity greater than a factor of two due to electrical debiasing. At low bias (12 mA/mm), temperature distribution matched state of the art electrothermal simulation. At high bias (47 mA/mm), however, measured self-heating diverged significantly from simulation despite inclusion of temperature dependent material properties in the thermal model. Hotspots with temperature change of 70 K were observed. Results demonstrate nonlinear dependence of current distribution on bias for complex arrayed power devices.Thermoreflectance imaging of GaN HEMTs revealed for the first time temperature gradients as large at 60 K and 80 K between critical gate, channel, and contact features within the first few microseconds of pulsed excitation at 19 W/mm. Fast transient self-heating gradients in the HEMT were confirmed with 5 ns time resolved thermoreflectance images. Thermoreflectance imaging revealed nonuniform self-heating in nanoscale percolation network devices consisting of disordered 90 nm diameter silver nanowires. Microscopic hot-spots at selected nanowire-nanowire junctions in the network exhibited nonlinear thermal properties, with temperature dependence of current excee

Static and dynamic hot spots limit the performance and reliability of electronic devices and ICs. We show that transient thermoreflectance imaging using a CCD camera can measure temperature distribution in chips with 0.1 degrees C temperature, 100 nanosecond time, and submicron spatial resolution. It is possible to measure the temperature on metal interconnects in wire-bonded chips and, with through-the-substrate infrared illumination, at the transistor level in flip-chip packages. Recent results in transient thermal imaging of GaN transistors, ESD protection devices, solar cells, and LEDs are presented. We show it is possible to identify non-uniform temperature rise and defects in 200 to 300 nm interconnect vias that have been stressed at high temperatures. Power blurring techniques can be used to obtain transient temperature profiles in packaged IC chips with a calculation time orders of magnitude faster than finite element analysis. The technique is well suited to solve the inverse problem and extract the power dissipation profile from the measured thermal map.

Static and dynamic hot spots limit the performance and reliability of electronic devices and ICs. We show that transient thermoreflectance imaging using a CCD camera can measure temperature distribution in chips with 0.1 degrees C temperature, 100 nanosecond time, and submicron spatial resolution. It is possible to measure the temperature on metal interconnects in wire-bonded chips and, with through-the-substrate infrared illumination, at the transistor level in flip-chip packages. Recent results in transient thermal imaging of GaN transistors, ESD protection devices, solar cells, and LEDs are presented. We show it is possible to identify non-uniform temperature rise and defects in 200 to 300 nm interconnect vias that have been stressed at high temperatures. Power blurring techniques can be used to obtain transient temperature profiles in packaged IC chips with a calculation time orders of magnitude faster than finite element analysis. The technique is well suited to solve the inverse problem and extract the power dissipation profile from the measured thermal map.