reduced yield

**Reduced yield** is the **quality loss associated with lower good-output fraction during startup, transition, or unstable operating conditions** - it is often most visible in early wafers after change events. **What Is Reduced yield?** - **Definition**: Decline in conforming output percentage relative to normal steady-state process performance. - **Common Context**: Startup after PM, chamber clean, tool idle recovery, or major recipe transition. - **Loss Window**: Frequently concentrated in initial wafers before process equilibrium is reached. - **Metric Link**: Tracked through startup yield, first-pass yield, and lot acceptance trends. **Why Reduced yield Matters** - **Direct Quality Penalty**: Good-unit output drops even when the tool is available and running. - **Cost Amplification**: Early-yield losses consume full process steps with little recoverable value. - **Capacity Impact**: Startup scrap reduces effective throughput and increases cycle-time pressure. - **Control Maturity Signal**: Persistent reduced-yield windows indicate weak startup discipline. - **Customer Exposure**: Yield instability increases risk of delayed deliveries and variable product performance. **How It Is Used in Practice** - **Window Characterization**: Quantify yield behavior for first lots after each trigger condition. - **Stabilization Protocols**: Use seasoning wafers, warm-up recipes, and tighter release criteria. - **Trend Monitoring**: Track startup-yield drift and trigger corrective action when deviation widens. Reduced yield is **a high-value quality loss category in OEE management** - controlling startup and transition behavior prevents recurring yield tax on every change event.