Metal-Overlayer-Assisted Single-Wavelength Thermoreflectance Imaging for Microscale Thermal Characterization in Semiconductor Devices

As device dimensions scale and operating speeds increase, accurate characterization of localized heat generation has become essential. In this work, thermoreflectance-based measurements were employed to experimentally observe microscale heating in oxide semiconductor structures. Both steady-state temperature rise and transient thermal response under applied bias were successfully captured, demonstrating the capability of thermoreflectance to resolve dynamic heating phenomena. However, the measurement sensitivity was found to be strongly dependent on the incident wavelength, resulting in material-dependent variability. To mitigate this limitation, a thin metal overlayer was introduced, enabling wavelength-independent and reproducible thermal imaging using a single wavelength optimized for the metal layer. Although the metal layer partially functioned as a thermal sink, the intrinsic temporal characteristics of heat generation were preserved. The experimental findings were corroborated through TCAD device simulations. The proposed approach provides a robust and broadly applicable thermal characterization technique suitable for advanced and high-speed semiconductor devices.