CD-AFM (Critical Dimension AFM) is a specialized AFM technique designed specifically for measuring critical dimensions of semiconductor features — using boot-shaped (flared) tips to measure the width, height, sidewall angle, and profile of lines, trenches, and contact holes with nanometer accuracy.

CD-AFM Details

• Flared Tips: Boot-shaped tips with a wider end can probe re-entrant sidewalls — overhang beyond the vertical.
• Accuracy: Sub-nanometer reproducibility for CD measurements — the reference standard for CD metrology.
• Profile: Reconstructs the full cross-sectional profile — top CD, bottom CD, middle CD, sidewall angle, height.
• Calibration: Tip shape calibration is critical — the measured profile is a dilation of the tip and sample shapes.

Why It Matters

• Reference Standard: CD-AFM is the NIST-traceable reference for critical dimension metrology.
• OCD Calibration: Scatterometry (OCD) models are calibrated against CD-AFM reference measurements.
• Tip Wear: CD-AFM tips wear during use — tip characterization artifacts (gratings) are essential for accurate measurements.

CD-AFM is the ruler of the nanoscale — providing reference-grade critical dimension measurements with full cross-sectional profiles.