Three-Dimensional Nanothermistors for Thermal Probing

Accessing the thermal properties of materials or even full devices is a highly relevant topic in research and development. Along with the ongoing trend toward smaller feature sizes, the demands on appropriate instrumentation to access surface temperatures with high thermal and lateral resolution also increase. Scanning thermal microscopy is one of the most powerful technologies to fulfill this task down to the sub-100 nm regime, which, however, strongly depends on the nanoprobe design. In this study, we introduce a three-dimensional (3D) nanoprobe concept, which acts as a nanothermistor to access surface temperatures. Fabrication of nanobridges is done via 3D nanoprinting using focused electron beams, which allows direct-write fabrication on prestructured, self-sensing cantilever. As individual branch dimensions are in the sub-100 nm regime, mechanical stability is first studied by a combined approach of finite-element simulation and scanning electron microscopy-assisted in situ atomic force microscopy (AFM) measurements. After deriving the design rules for mechanically stable 3D nanobridges with vertical stiffness up to 50 N m^-1, a material tuning approach is introduced to increase mechanical wear resistance at the tip apex for high-quality AFM imaging at high scan speeds. Finally, we demonstrate the electrical response in dependence of temperature and find a negative temperature coefficient of -(0.75 ± 0.2) 10^-3 K^-1 and sensing rates of 30 ± 1 ms K^-1 at noise levels of ±0.5 K, which underlines the potential of our concept.

AFM-thermoreflectance for simultaneous measurements of the topography and temperature

To understand the thermal failure mechanisms of electronic devices, it is essential to measure the temperature and characterize the thermal properties of individual nanometer-scale transistors in electronic devices. Previously, scanning thermal microscopy (SThM) has been used to measure the local temperature with nanometer-scale spatial resolutions using a probe with a built-in temperature sensor. However, this type of temperature measurement requires additional equipment to process the temperature-sensing signals and expensive temperature-sensor-integrated probes fabricated by complicated MEMS processes. Here, we present a novel technique which enables the simultaneous measurement of the temperature and topography of nanostructures only with a conventional atomic force microscope (AFM) of the type commonly used for topography measurements and without any modifications of the probe and extra accessories for data acquisition. The underlying principle of the proposed technique is that the local temperature of a specimen is estimated quantitatively from the thermoreflectance of a bare silicon AFM probe that is in contact with a specimen. The temperature obtained by our technique is found to be consistent with a result obtained by SThM measurements.

We propose a novel form of AFM-based thermometry capable of sub-100 nm spatial resolution only with a conventional AFM setup by exploiting the thermoreflectance characteristic of the AFM Si probe.

Recent advances in hybrid measurement methods based on atomic force microscopy and surface sensitive measurement techniques

This review summaries the recent progress of the combination of optical and non-optical surface sensitive techniques with the atomic force microscopy.