WHAT IS A DEFECT

Anything that breaks the pattern

a physical flaw with an electrical consequence

A defect is any physical flaw, a stray particle, a pattern error, a void, that changes a circuit's electrical behavior. Not every flaw matters: one sitting somewhere harmless never shows up in a test. The ones that do are the ones a fab spends enormous effort chasing.

A defect only counts once it changes how the circuit behaves.

WHERE DEFECTS COME FROM

A few repeat offenders

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Particles

Dust, flakes, or residue landing on the wafer mid-process

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Pattern defects

Lithography or etch that prints a shape wrong

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Contamination

Trace chemicals or metal ions where they shouldn't be

Most defect sources trace back to something that shouldn't have been there.

KILLER VS. NON-KILLER

Location decides everything

Killer defect Sits on a feature that matters, and breaks the circuit

Non-killer defect Sits somewhere harmless, and the die still works

Same defect, different fate Identical particles can kill one die and do nothing to another

Size and location matter more than the defect's simple existence.

A KILLER DEFECT IN ACTION

One particle, one short

A stray particle landing between two metal lines that were never meant to touch can bridge them, creating an unwanted electrical short. If that short sits on a net the circuit depends on, the die fails.

The particle didn't care about the design; it just landed where it landed.

DEFECT DENSITY

The number fabs actually track

D₀: defects per unit area

Fabs summarize defect performance as defect density, often written D₀, defects per unit area of wafer. A lower D₀ means fewer chances for a die of any given size to catch a killer defect, and tracking it over time shows whether a process is improving or slipping.

D₀ is the single number that predicts how yield will scale as die size changes.

UNIT 32 STUDY COMPLETE

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Ready for the Fab Challenge?

You've covered what a defect actually is, where it comes from, and which ones matter.