Semiconductor AFM Scan Results

The two primary AFM techniques for semiconductor electrical characterization are KPFM (Kelvin Probe Force Microscopy) for surface potential and work function mapping, and conductive AFM / ResiScope™ for resistance and current mapping. On the CSInstruments Nano-Observer II, HD-KFM III provides single-pass surface potential mapping with sub-10 nm resolution — enabling dopant profiling, p-n junction visualization, and in-operando device characterization. ResiScope™ III covers 10 decades of resistance (10² to 10¹² ohms) in a single scan, resolving both highly conductive and highly resistive regions without saturation — critical for multi-layer semiconductor cross-sections.

Yes. Both HD-KFM III and ResiScope™ can map dopant concentration variations in semiconductor materials. HD-KFM III measures surface potential differences between p, n, and n+ regions — as demonstrated in SRAM memory device and silicon doped structure images, where distinct potential levels correlate with doping type and concentration. ResiScope™ measures resistance directly, where higher doping concentration produces lower resistance — as seen in SiC staircase doping profiles (100 ohm to 1 Mohm across a 500 nm cross-section) and doped dot arrays with increasing carrier concentration.

Transistor and SRAM characterization by AFM is performed on polished cross-sections of the device. ResiScope™ resistance mapping on transistor cross-sections (1.5 µm scan) resolves drain, gate, and p/n/n+ regions with sub-100 nm resolution. HD-KFM III surface potential mapping of SRAM devices (50 µm scan) provides a full map of doped region distribution without saturation at any boundary — a key limitation of standard lift-mode KPFM that HD-KFM III overcomes through single-pass bimodal excitation.

The Back Surface Field (BSF) is a heavily doped thin layer at the rear of a silicon solar cell that creates a potential barrier preventing minority carrier recombination at the back contact, thereby increasing cell efficiency. The BSF is typically 30–100 nm thick — detectable only by high-resolution techniques. ResiScope™ on the Nano-Observer II has demonstrated direct BSF detection in silicon solar cell cross-sections: its fast DSP-driven gain response resolves the BSF as a distinct high-current layer within the blue (low-conductivity) region, simultaneously demonstrating a dynamic range of 150 pA to 90 µA and integrated protective current limiting.

Vanadium dioxide (VO2) undergoes a metal-insulator transition (MIT) near 68°C, switching from an insulating monoclinic phase to a conductive rutile phase. This transition is highly sensitive to film thickness, strain, and local composition. ResiScope™ AFM imaging of VO2 thin films maps the spatial distribution of conductive and insulating domains in real time — resolving blocks of metallic VO2 separated by insulating VO2 walls at 10 µm scale. The real-time AutoGain of ResiScope™ ensures both resistance regimes are accurately captured in the same image without switching measurement ranges.

Resistance or current mapping (ResiScope, conductive AFM) for dopant profiling and device cross-sections, Kelvin probe force microscopy (HD-KFM) for surface potential of p, n and n+ regions, dC/dZ and scanning microwave impedance (sMIM) for dielectric contrast.

Yes. ResiScope resistance on a silicon cross-section separates regions of increasing carrier concentration, and HD-KFM surface potential distinguishes p, n and n+ regions, for example in an SRAM memory device.

CSInstruments, a French AFM manufacturer, makes the Nano-Observer II with ResiScope III and HD-KFM III, and adds the same modes to existing Bruker, Agilent and Keysight AFMs with the Galaxy Dual Controller.