Improving the Consistency of Nanoscale Etching for Atomic Force Microscopy Tomography Applications

Abstract

The atomic force microscope (AFM) empowers research into nanoscale structural and functional material properties. Recently, the scope of application has broadened with the arrival of conductance tomography, a technique for mapping current in three-dimensions in electronic devices by gradually removing sample material with the scanning probe. This technique has been valuable in studying resistance switching memories and solar cells, although its broader use has been hindered by a lack of understanding of its reliability and practicality. Implementation can be preclusive, owing to difficulties in characterizing tip-sample interactions and accounting for probe degradation, both of which are crucial factors in process efficacy. This work follows the existing conductance tomography literature, presenting an insight into the repeatability and reliability of the material removal processes. The consistency of processes on a hard oxide and a softer metal are investigated, to understand the critical differences in etching behavior that might affect tomography measurements on heterostructures. Individual probe behavior stabilizes following a wearing-in stage and etching processes are consistent between probes, in particular on oxide. However, process inconsistency increases with applied force on metal. The effects of scan angle, tip speed and feedback gain are therefore explored and their tuning found to improve the spatial consistency of material removal. With these findings, we aim to present a critical study of the implementation of tomography with the AFM in order to contribute to its methodological development.

Atomic and Close-to-Atomic Scale Manufacturing: A Review on Atomic Layer Removal Methods Using Atomic Force Microscopy

“…Also, c-AFM has been employed in nanopatterning research over highly oriented pyrolytic graphite (HOPG) [25], graphene oxide [26], and other carbon-based materials such as carbon nanotubes (CNT) [27] and graphene flakes [28][29][30]. Also, recent works performed by Buckwell et al [31] and Steffes et al [32] have emphasized the importance of conductance tomographic AFM (T-AFM). A wide range of research has been carried out using AFM in material removal research [33,34].…”

Neuromorphic Dynamics at the Nanoscale in Silicon Suboxide RRAM

“…CAFM measurements were carried out with a Bruker Icon microscope under ambient conditions using platinum-coated (Spark, NuNano and SCM-PIC, Bruker) and full-platinum (RMN-Pt, Rocky Mountain Nanotechnology) probes. The nominal spring constant and deflection sensitivity were used to estimate that the applied force was no more than 100 nN (Buckwell et al, 2019). Anodic oxidation was avoided as electrons were injected from the bottom molybdenum electrode (i.e.…”

Nanoscale Study of the Hole-Selective Passivating Contacts with High Thermal Budget Using C-AFM Tomography

“…34,35 We refer to this experiment as C-AFM tomography. 36 For 3D C-AFM tomography reconstruction presented in this work, six consecutive scalpel C-AFM scans were performed with identical settings on the same region. After the tomography experiment, a standard AFM topography measurement showed that 15 nm of material was removed, indicating a material removal rate of 2.5 nm per scalpel C-AFM scan.…”

“…Such an adaptation of SSRM, first demonstrated on materials for conductive bridging memory (CBRAM) applications, ,, is often called scalpel C-AFM. , All mentioned scalpel C-AFM experiments consist of a single material-removing scan, representing the conductive map 1.5–2 nm below the sample surface. Furthermore, a series of high-force materials removing scalpel C-AFM scans can be performed in the same location to accumulate information on the resistivity throughout the volume of the sample by acquiring the current signal and removing a layer of the material simultaneously with each scan. , We refer to this experiment as C-AFM tomography …”