Standards Development

Scope

This part of IEC 62607 establishes a standardized method to determine the key control characteristic

– resistance for nanoelectronic devices by

– conductive probe atomic force microscopy (C-AFM).

The resistance is derived using an atomic force microscope where the tip is connected to a low-noise current amplifier. The resistance can be calculated from the measured I -V curve. For traceable absolute values of he resistance (i.e., making resistance values traceable to the SI units) a calibration to a refere nce standard is required.

– The method is applicable to characterize the electrical properties of semiconductor devices such as resistors, memristors, diodes, transistors, and to analyse their performance.

– Determination of the dielectric key control characteristics of materials are important for applications in electronics and communication technology. Typical materials are Si, Ge, III -V, and II-VI, as well as graphene, glasses, polymers, ceramics, and metals.

– Evaluation of nano-enabled electronic devices, such as graphene field effect transistors, and their potential applications in electronics and energy storage. This supports wafer -scale system integration, enabling the utilization of nanomaterials for advanced More -than-Moore applications.

– Typical specifications for using a C-AFM for resistance measurements are:

– Scanning range: 100 μm in the x, y direction, 10 μm in the z -direction

– Spatial resolution: < 50 nm

– Frequency range: DC

– Applied force: < 2 μN

– Bias voltage: - 1 V to + 1 V

– Resistance: 100 to 1 T

– Current: 1 fA to 1 μA

Purpose

Conductive probe atomic force microscopy (C-AFM) is a unique and powerful technique for measuring local electrical quantities (i.e., current, resistance, voltage) at the nanoscale. In C -AFM, a micro-machined conductive probe with a sharp nano-sized tip acts as a top electrode brought into contact with the surface of a sample while applying a potential difference relative to a back electrode. The small currents flowing through the system are measured using a current amplifier, typically ranging from 100 fA to 10 μA for most commercially available microscopes. By sweeping the potential difference while the tip is fixed in contact with the sample, current versus voltage (I-V) curves are acquired. I-V curves are essentially used to extract the values of the resistance which is one of the key control characteristics for electronic components and devices or to characterize their electric behaviors. Alternatively, current variation maps are acquired at a given applied voltage by scanning the AFM tip in contact mode across a defined sample surface area.

Owing to its versatility and high resolution in probing the local conductivity of materials, C -AFM has been extensively used in studying semiconductors, two-dimensional materials, memristive devices, photoelectric systems, dielectric films, molecular electronics, organic and biological systems, and quantum devices.

Various technical methods have been developed in C -AFM to cope with the diversity of its applications, including advanced sensors and low-noise preamplifiers.

Nevertheless, quantifying the measured currents and resistances remains a bottleneck issue in C -AFM, inhibiting an effective comparison of results to comprehend experimental processes. C -AFM measurements are prone to environmental and experimental factors that heavily affect their stability, reproducibility, repeatability, and exactness. The formation of a humidity -induced water meniscus at the tip-sample interface, the presence of surface contamination, and thermal drifts induce significant instabilities in C -AFM measurements. Moreover, local overheating and anodic oxidation phenomena are commonly observed in C - AFM due to highly localized electric fields at the tip apex leading to structural damages considerably affecting the measurements’ reliability. These effects are further amplified during scanning in contact mode due to shear forces and strong mechanical stresses imposed on the tip apex. Therefore, it is common to measure sudden alterations in local currents and resistances in C -AFM unrelated to the sample’s physical properties. The combination of the effects above makes it difficult to quantify and reproduce the measured values in C - AFM experiments, which degrades the method’s efficiency in advancing the understanding of many processes in materials sciences and industrial developments.

To ensure the exactness, reliability and comparability of measured resistance values, the C -AFM measurement setup must be calibrated with the help of a well -known reference standard. Therefore, the reference standard is a key part of the measurement system. The spatial resolution of the setup is determined by the atomic force part, especially the properties of the C -AFM probe (tip and cantilever).

Overall, C-AFMs provide a unique and non-destructive way to probe electrical key control characteristics materials and devices at the nanoscale, and they play a critical role in advancing the understanding of materials science and engineering and can support the optimization of industrial fabrication processes.

This standard focusses on the measurement of the resistance.