Dopant Contamination

Dopant Contamination refers to unintended introduction of electrically active impurities during semiconductor processing that alter device characteristics.

## What Is Dopant Contamination?

  • Sources: Cross-contamination from diffusion, ion implant, or handling
  • Common Contaminants: Boron, phosphorus, arsenic from prior wafers
  • Effect: Shifts threshold voltage, increases leakage, device failure
  • Detection: SIMS, spreading resistance, electrical test

## Why Dopant Contamination Matters

At sub-20nm nodes, even 10¹⁰ atoms/cm² of unwanted dopant significantly affects transistor characteristics, causing parametric failures.

Dopant Contamination Pathway:Process Chamber Wall:┌─────────────────────┐│ ████ Prior wafer ││ ████ residue │ ← B, P, As deposits│ ││ New wafer │ ← Contamination transfers│ ●●●●●●●●● │└─────────────────────┘Even ppb-level contamination affects Vt

Prevention Methods:
| Method | Application |
|--------|-------------|
| Dedicated equipment | P-type vs N-type separation |
| Barrier wafers | Dummy runs after contaminating process |
| Chamber cleaning | Periodic in-situ plasma clean |
| Wafer cleaning | Pre-process SC1/SC2/HF sequences |

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