• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.5
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• pp.533-538
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• 2015

Thermal characterization of individual pixels in microbolometer infrared image sensors is needed for optimal design and improved performance. In this work, we used thermoreflectance microscopy on uncooled microbolometer image sensors to investigate the thermal characteristics of individual pixels. Two types of microbolometer image sensors with a shared-anchor structure were fabricated and thermally characterized at various biases and vacuum levels by measuring the temperature distribution on the surface of the microbolometers. The results show that thermoreflectance microscopy can be a useful thermal characterization tool for microbolometer image sensors.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.19-31
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• 2022

With the advent of technologies based on big data, the trend of electronics towards high performance and high integration density continues. However, this development of electronics suffers from overheating issues, which seriously threaten the reliability of the devices. To develop effective strategies for thermal management, it is crucial to accurately evaluate the temperature distribution and design the heat dissipation path within the device in the operating condition. This paper introduces thermoreflectance microscopy that can observe the temperature distribution of a device with high spatial and temporal resolutions in a non-contact way. Specifically, the working principle and various forms of thermoreflectance microscopy are presented along with the latest research trends to improve the temperature, space, and time resolutions. We further review several examples in which thermoreflectance microscopy is applied to investigate the temperature and thermal characteristics of electronic devices.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.2
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• pp.103-108
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• 2019

Non-equilibrium molecular dynamics simulation on the thermal boundary resistance(TBR) of an aluminum(Al)/silicon(Si) interface was performed in the present study. The constant heat flux across the Si/Al interface was simulated by adding the kinetic energy in hot Si region and removing the same amount of the energy from the cold Al region. The TBR estimated from the sharp temperature drop at the interface was independent of heat flux and equal to $5.13{\pm}0.17K{\cdot}m^2/GW$ at 300K. The simulation result was experimentally confirmed by the time-domain thermoreflectance technique. A 90nm thick Al film was deposited on a Si(100) wafer using an e-beam evaporator and the TBR on the film/substrate interface was measured using the time-domain thermoreflectance technique based on a femtosecond laser system. A numerical solution of the transient heat conduction equation was obtained using the finite difference method to estimate the TBR value. Experimental results were compared to the prediction and discussions on the nanoscale thermal transport phenomena were made.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.4
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• pp.528-536
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• 1999

This work studies the effects of transient reflectance on the thermal responses of a metal(gold) thin-film during ultrashort laser heating. The heating process is calculated using the conventional conduction model (parabolic one-step: POS), parabolic two-step model (PTS) with and without variable properties, hyperbolic two-step model (HTS). Results from the HTS model are very similar to those from the PTS model, since the laser heating time in this study is greater than the electron relaxation time. PTS model with variable properties, however, results in totally different temperature profiles compared to those from POS models or calculation with constant properties. Transient reflectances are estimated from electron temperature distributions and based on the linear relationship between the electron temperature and complex dielectric constants. Reflectance of the front surface can be changed with respect to dielectric constants, while those of the rear surface remain unchanged.

• International Journal of Air-Conditioning and Refrigeration
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• v.10 no.1
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• pp.1-9
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• 2002

Effects of temperature coefficients fur dielectric constants on transient reflectances and thermal responses have been investigated for a metal(gold) thin-film during ultrashort pulse laser heating. Heating processes are simulated using the conventional conduction model(parabolic one-step, POS), the parabolic tow-step model(PTS), the hyperbolic two-step model(HTS). Results fro the HTS model are very similar to those from the PTS model, since the laser heating time in this study is considerably greater than the electron relaxation time. PTS and HTS models, however, result in completely different temperature profiles from those obtained by the POS model due to slow electron-lattice interactions compared to laser pulse duration. Transient reflectances are directly estimated from the linear relationship between electron temperature and complex dielectric constants, while conventional approaches assume that the change in reflectances is proportional to that in temperatuer. Reflectances at the front surface vary considerably for various dielectric constants, while those at the rear surface remain unchanged relatively.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.4
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• pp.266-272
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• 2016

This paper presents the investigation of the propagation behavior of bulk longitudinal waves generated by an ultrafast laser system in thin films. A train of femtosecond laser pulses was focused onto the surface of a 150-nm thick metallic (chromium or aluminum) film on a silicon substrate to excite elastic waves, and the change in thermoreflectance at the spot was monitored to detect the arrival of echoes from the film/substrate interface. The experimental results show that the film material characteristics such as the wave velocity and Young's modulus can be evaluated through curve-fitting in numerical solutions. The material properties of nanoscale thin films are difficult to measure using conventional techniques. Therefore, this research provides an effective method for the nondestructive characterization of nanomaterials.