electrical wafer sort (ews)

**Electrical Wafer Sort (EWS)** is the **first electrical testing step in semiconductor manufacturing** — where every individual die on a wafer is probed with fine needles to verify basic functionality before the wafer is diced and packaged. **What Is EWS?** - **Process**: A probe card with hundreds of tiny needles contacts the bond pads of each die. - **Tests**: Continuity, leakage, basic logic function, IDDQ (quiescent current). - **Speed**: Each die is tested in milliseconds (high-volume production). - **Result**: Each die is marked Pass (ink dot or map) or Fail. Only passing dies proceed to packaging. **Why It Matters** - **Cost Savings**: Packaging a bad die wastes $0.50-$5.00 per unit. EWS prevents this. - **Yield Measurement**: EWS yield = (Good Dies / Total Dies). The key metric for fab performance. - **Binning**: Dies can be sorted into performance bins (speed grades) at this stage. **Electrical Wafer Sort** is **the first exam for every chip** — determining which dies are worthy of becoming finished products.