Overcoming the quantification barrier in reverse tip sample scanning spreading resistance microscopy for efficient nanoscale carrier profiling

Abstract

Abstract The quick tip exchange capability of reverse tip sample (RTS) scanning probe microscopy (SPM) provides significant efficiency benefits over conventional SPM, especially in highforce modes like scanning spreading resistance microscopy (SSRM). While prior developments in RTS SSRM have addressed conductive diamond probe chip fabrication, sample preparation for electrical SPM measurements, and qualitative measurement capabilities, the challenge of achieving quantitative carrier profiling remained unresolved, primarily due to focused ion beam (FIB) damage that is introduced during RTS sample preparation. In this work, we present two different FIB-based RTS sample preparation protocols for mounting multiple samples on a single tipless cantilever. The core postulation is that co-mounting the target and calibration samples together ensures that they undergo identical ion beam exposure, thereby enabling accurate SSRM quantification. The first protocol employs sequential mounting of individual samples, while the second involves bonding the samples together, polishing their surfaces, and then, mounting them as a single, unified assembly. It is also worth noting that the latter protocol supports a sample layout that enables quantitative analysis to be done on each individual scanline, which can reduce the impact of measurement artefacts resulting from tip degradation or just unstable tip-sample contact during scanning. Quantitative validation of RTS SSRM for both preparation protocols was accomplished by implementing two different staircase calibration samples, comprised of layers having well-defined carrier concentrations. Finally, mounting a calibration sample alongside an actual device sample confirmed that RTS SSRM delivers results equivalent to those obtained with conventional SSRM, affirming its quantification reliability for practical applications. By establishing quantitative SSRM in RTS configuration, this work addresses a critical gap and further positions RTS SPM as a valuable approach for advancing electrical SPM characterization.