critical dimension afm

**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.