availability

**Availability** is the **percentage of time equipment is in a ready-to-run state, excluding periods when it is down for failures or planned service** - it reflects mechanical and operational readiness independent of upstream wafer supply. **What Is Availability?** - **Definition**: Uptime divided by uptime plus downtime over a defined measurement window. - **Downtime Scope**: Includes both scheduled and unscheduled outages depending on reporting convention. - **Distinction**: Availability measures readiness, not whether wafers are actually present. - **Use Context**: Fundamental KPI in maintenance management and OEE frameworks. **Why Availability Matters** - **Reliability Signal**: Declining availability indicates worsening equipment health or maintenance control. - **Capacity Planning Input**: Accurate availability assumptions are required for realistic throughput forecasts. - **Benchmarking Value**: Enables objective comparison across tools, fleets, and sites. - **Financial Impact**: Low availability forces overtime, additional tools, or missed output targets. - **Improvement Prioritization**: Guides focus on MTBF and MTTR programs. **How It Is Used in Practice** - **Calculation Standard**: Define consistent uptime and downtime event boundaries across operations. - **Trend Surveillance**: Monitor rolling availability with drill-down by downtime category. - **Action Coupling**: Tie availability losses to corrective maintenance and reliability engineering plans. Availability is **a primary readiness metric for manufacturing assets** - sustained high availability is required for predictable output and efficient capital utilization.