Microscale and Nanoscale Thermal Characterization Techniques

Abstract

Miniaturization of electronic and optoelectronic devices and circuits and increasedswitching speeds have exasperated localized heating problems. Steady-state and transient characterization of temperature distribution in devices and interconnects is important for performance and reliability analysis. Novel devices based on nanowires, carbon nanotubes and single molecules have feature sizes in 1-100nm range and precise temperature measurement and calibration are particularly challenging. In this paper we review various microscale and nanoscale thermal characterization techniques that could be applied to active and passive devices. Solid-state micro refrigerators on a chip can provide a uniform and localized temperature profile and they are used as a test vehicle in order to compare the resolution limits of various microscale techniques. After a brief introduction to conventional micro thermocouples and thermistor sensors, various contact and contactless techniques will be reviewed. Infrared microscopy is based on thermal emission and it is a convenient technique that could be used with features tens of microns in size. Resolution limits due to low emissivity and transparency of various materials and issues related to background radiation will be discussed. Liquid crystals that change color due to phase transition have been widely used for hot spot identification in integrated circuit chips. The main problems are related to calibration and aging of the material. Micro Raman is an optical method that can be used to measure absolute temperature. Micron spatial resolution with several degrees temperature resolution has been achieved. Thermoreflectance technique is based on the change of the sample reflection coefficient as a function of temperature. This small change in 10 -4 -10 -5 range per degree is typically detected using lock-in technique when the temperature of the device is cycled. Use of visible and near IR wavelength allows both top surface and through the substrate measurement. Both single point measurements using a scanning laser and imaging with CCD or specialized lock-in cameras have been demonstrated. For ultrafast thermal decay measurement, pump-probe technique using nanosecond or femtosecond lasers have been demonstrated. This is typically used to measure thin film thermal diffusivity and thermal interface resistance. The spatial resolution of various optical techniques can be improved with the use of tapered fibers and near field scanning microscopy. While sub diffraction limit structures have been detected, strong attenuation of the signal reducesthe temperature resolution significantly. Scanning thermal microscopy which is based on nanoscale thermocouples at the tip of atomic force microscope has had success in ultra high spatial resolution thermal mapping. Issues related to thermal resistance between the tip and the sample and parasitic heat transfer paths will be discussed.

Temperature and microwave near field imaging by thermo-elastic optical indicator microscopy

“…Therefore, the TS in the non-contact configuration with an air gap of 0.5 mm is around 0.6~1.4 K and 5~14 mK for 1,000 and 10,000 times averaged measurements, respectively. The estimated TS of the TEOIM is comparable to that of modern thermal image technologies (35–200 mK)35624. In addition, we present detailed discussion on the spatial resolution of the TEOIM in the supplement text S9.…”

Extraction of Power Dissipation Profile in an IC Chip from Temperature Map

“…All this makes our method very suitable for practical applications. We would also like to note that by coupling our proposed technique with the in-depth temperature probing methods, such as "Infrared see through" or "Raman 3D temperature probing" [1], this 2-D technique can be extended for power mapping in 3-D.…”

“…As switching speed increases and device feature sizes are further miniaturized, localized heating problems are exasperated [1]. Temperature map measurement of an IC chip is a wellestablished and powerful technique that allows chip designers and process engineers to identify strong temperature nonuniformity (hot-spot) locations where there are fabrication failures [1][2][3][4][5][6][7][8][9].…”

Characterization of Heat Propagation along Single Tin Dioxide Nanobelt Using the Thermoreflectance Method

“…This small change, about 4 5 10~10 − − range per degree, is typically detected using a lock-in technique when the temperature of the device is cycled [2]. The image object (nanobelt) in this study requires ultra high spatial resolution and sensitivity for low illumination intensity, therefore we chose ICCD as the detection device.…”

“…However, measurement of thermal properties on such small objects is non-trivial. As of today, only a few thermal characterization techniques are able to achieve nanoscale spatial resolution and sub-degree temperature resolution at the same time [2]. Here, we utilized thermoreflectance imaging technique.…”