Metrology & inspection

Measuring dimensions and finding defects at every critical step.

What you’ll learn

Metrology vs inspection
What gets measured
Why it protects yield

Why it matters

You can't control what you can't measure — metrology keeps a 1000-step process on target.

Explanation

Metrology measures features (film thickness, critical dimensions, overlay alignment); inspection finds defects (particles, pattern errors). Both run throughout the line, often on sampled wafers.

Fast, accurate measurement catches drift and defects early, before they ruin many wafers.

Visual explanation

A wafer scanned by an optical/e-beam tool producing a defect map with flagged spots.

Key terminology

Critical dimension (CD): The size of the smallest patterned features.
Overlay: Alignment error between layers.
Yield: Fraction of good dies per wafer.

Example

An overlay tool checks that a new layer aligns to the previous one within a few nanometres.

Common mistakes

Watch out for:

Confusing metrology (measuring) with inspection (defect finding) — they're complementary.

Real-world application

E-beam and optical inspection are essential for ramping yield on new nodes.

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