Nickel Contamination

Nickel Contamination in semiconductor processing refers to unwanted Ni atoms that diffuse rapidly in silicon, creating deep-level traps that degrade device performance and reliability.

## What Is Nickel Contamination?

  • Sources: Plating baths, stainless steel equipment, sputtering targets
  • Behavior: Fast interstitial diffuser in Si (D ≈ 10⁻⁴ cm²/s at 1000°C)
  • Effect: Mid-gap trap states, reduced carrier lifetime
  • Detection: TXRF, SIMS, DLTS

## Why Nickel Contamination Matters

Nickel is one of the fastest diffusing metals in silicon. Even low surface contamination distributes throughout the wafer during thermal processing.

Nickel Contamination Sources:Process Equipment:├── Stainless steel chambers├── Ni-containing alloys├── Electroless Ni plating└── Contaminated chemicalsDiffusion During Thermal Processing:Starting: After 1000°C anneal:Surface Ni spots Ni distributed throughout ● ○ ○ ○ ○ ○ ● ○ ○ ○ ○ ○ ○───────────── → ○ ○ ○ ○ ○ ○ ○ ○ ○ Silicon ○ ○ ○ ○ ○ ○ ○ ○ Bulk contamination

Prevention and Detection:
| Method | Application |
|--------|-------------|
| TXRF | Surface detection (<10¹⁰ at/cm²) |
| DLTS | Trap level identification |
| SPV | Lifetime degradation mapping |
| Gettering | Backside or intrinsic gettering |

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