Mark J. McLean

This letter reports on pilot tests of microfabricated nanocalorimeters as a metrology platform for rapid (<40 ms response time) and sensitive (in the range of 1020 m−2 s−1–1017 m−3 for radicals’ flux and density, respectively) detection of neutral radicals generated by reactive cold plasmas. The setup consists of a nanocalorimeter resistive sensor coated with a catalyst alongside an inert reference sensor with identical thermal masses. By measuring the temperature increase in the active sensor caused by radical surface recombination reactions and comparing it to the reference sensor, parasitic stimuli such as IR/visible/UV irradiation and ion- and/or electron-induced heat fluxes can effectively be isolated. The system was successfully tested in a hydrogen plasma environment, and critical performance metrics such as sensitivity and response time were evaluated and benchmarked against the existing plasma radical diagnostic techniques.

Frequency Domain Thermoreflectance (FDTR) is a versatile technique used to measure the thermal properties of thin films, multilayer stacks, and interfaces that govern the performance and thermal management in semiconductor microelectronics. Reliable thermal property measurements at these length scales (≈10 nm to ≈10 μm), where the physics of thermal transport and phonon scattering at interfaces both grow in complexity, are increasingly relevant as electronic components continue to shrink. While FDTR is a promising technique, FDTR instruments are generally home-built; they can be difficult to construct, align, and maintain, especially for the novice. Our goal here is to provide a practical resource beyond theory that increases the accessibility, replicability, and widespread adoption of FDTR instrumentation. We provide a detailed account of unpublished insights and institutional knowledge that are critical for obtaining accurate and repeatable measurements of thermal properties using FDTR. We discuss component selection and placement, alignment procedures, data collection parameters, common challenges, and our efforts to increase measurement automation. In FDTR, the unknown thermal properties are fit by minimizing the error between the phase lag at each frequency and the multilayer diffusive thermal model solution. For data fitting and uncertainty analysis, we compare common numerical integration methods, and we compare multiple approaches for fitting and uncertainty analysis, including Monte Carlo simulation, to demonstrate their reliability and relative speed. The instrument is validated with substrates of known thermal properties over a wide range of isotropic thermal conductivities, including Borofloat silica, quartz, sapphire, and silicon.

A batch of 94 silicon chips containing arrays of uniform rectangular cantilevers was microfabricated from a single silicon wafer and their stiffnesses and resonance frequencies calibrated using a laser Doppler vibrometer (LDV). The cantilevers are 50 μm wide, (about the width of a human hair), and vary in length from 600 μm to 300 μm. They have stiffness values nominally ranging from 0.03 N/m to 0.2 N/m and nominal first flexural resonance frequencies in the range of 5 kHz to 21 kHz respectively. The LDV cantilever stiffness calibration measurements proved very reliable and combined expanded uncertainties better than ± 3% in stiffness were obtained for individual devices. These devices can be used as reference artifacts to validate atomic force microscopy (AFM) cantilever stiffness measurement methods as well as directly calibrating AFM test cantilever stiffness using the reference cantilever method. This NIST SP-260 provides details on the source and preparation of the devices as well as the analytical approach of using a laser Doppler vibrometer to accurately measure both stiffness (k), resonance frequency (f0), and Quality factor (Q) of each cantilever. The statistical analysis applied to the data sets is described. An example of the reference cantilever method is also provided for individuals wishing to use these devices to make direct calibrations of AFM test cantilevers.

Laboratory notebooks have been a staple of scientific research for centuries for organizing and documenting ideas and experiments. Modern laboratories are increasingly reliant on electronic data collection and analysis, so it seems inevitable that the digital revolution should come to the ordinary laboratory notebook. The most important aspect of this transition is to make the shift as comfortable and intuitive as possible, so that the creative process that is the hallmark of scientific investigation and engineering achievement is maintained, and ideally enhanced. The smart electronic laboratory notebooks described in this paper represent a paradigm shift from the old pen and paper style notebooks and provide a host of powerful operational and documentation capabilities in an intuitive format that is available anywhere at any time.