What Is Scanning Capacitance Microscopy (SCM)?
Scanning Capacitance Microscopy (SCM) is a specialized scanning microscopy technique that provides detailed information about charge carrier in semiconductors with sub-100nm resolution.
SCM evaluates carrier concentration by measuring the local capacitance, namely dC/dV, under an applied AC voltage between the conductive AFM tip and the sample. This technique simultaneously acquires AFM images, enabling direct correlation between electrical properties and device structure for comprehensive semiconductor analysis.
Correlated Imaging
Analytical Depth
Resolution
Why Use SCM?
- Advanced sample preparation techniques support high data reliability.
- Although STEM-EDX helps detect impurities with a 1e21 cm⁻³ concentration or more, SCM is necessary for concentrations below 1e20 cm⁻³.
- Evaluates charge carrier polarity and concentration with a sub-100nm resolution.
Analytical Depth
Material Compatibility
Depth Profiling
How Scanning Capacitance Microscopy (SCM) Works
SCM utilizes an AFM probe to measure local capacitance changes under AC bias voltage. The technique generates dC/dV signals that directly correlate with carrier polarity and concentration. Cross-sectional specimens enable depth profiling in any region of interest. Simultaneous AFM imaging provides structural correlation with electrical properties. Advanced sample preparation ensures reliable data from 1E16 to 1E20 cm⁻³ carrier concentrations.
Equipment Used for SCM
Bruker Dimension XR (SCM option), NanoScope V
- AFM platform: Large-sample SPM with PeakForce Tapping for routine atomic-defect and sub-nanometer imaging in air and liquid.
- Nanomechanics: AFM-nDMA for quantitative nanoscale storage/loss modulus over 0.1 Hz–20 kHz, linked to bulk DMA.
- Nanoelectrical: DataCube modes for hyperspectral electrical mapping, giving electrical and mechanical spectra at every pixel.
- Nanoelectrochemistry: PeakForce SECM / EC-AFM for <100 nm-resolution electrochemical imaging with simultaneous topography, electrical, and mechanical contrast.
Key Differentiators
SCM provides direct feedback on fabrication processes for impurity injection verification. The technique offers exceptional sensitivity for low-concentration carriers below 1e20 cm⁻³ where other methods fail.
Strengths
- Detects carrier polarity and detects small amounts of charge carriers.
- Provides direct feedback on the fabrication process.
- Highly reliable experimental data due to Covalent’s advanced technique.
Limitations
- Not for metals or insulators.
- Best resolution: 20 nm (decreases at low concentration); max area 80×80 μm².
- Higher carrier sensitivity, but lower spatial resolution than STEM-EDX.
Example Outputs
Sample Requirements
- Semiconductor sample (patterned device or wafer).
- Semiconductors with carrier concentrations of 1e16 cm-3 to 1e20 cm-3.
- The sample area of interest should be larger than 0.5×0.5 μm2.
- Cross-sectional sample preparation is necessary for SCM measurements.
SCM Applications by Industry
Power Electronics
Semiconductor
SCM enables precise metrology of p, p+, n, and n+ regions by measuring their width and thickness with nanoscale accuracy. The technique evaluates charge carrier distribution patterns critical for device performance optimization. SCM proves invaluable in failure analysis and reverse engineering by identifying dopant migration, junction degradation, and process variations.