idle time

**Idle time** is the **period when a tool is available to run but has no work to process due to flow imbalance or dispatch gaps** - it represents lost capacity caused by system-level starvation rather than equipment failure. **What Is Idle time?** - **Definition**: Nonproductive state where tool readiness exists but no lot is loaded. - **Common Causes**: Upstream bottlenecks, dispatch latency, lot-hold conditions, or poor line balancing. - **Difference from Downtime**: Tool is not broken; the production system is not feeding it. - **Measurement Basis**: Tracked separately from scheduled and unscheduled downtime categories. **Why Idle time Matters** - **Capacity Waste**: High-cost assets depreciate while generating no throughput. - **Flow Instability**: Persistent idle pockets indicate synchronization problems across process steps. - **Delivery Risk**: Starvation in key tools can cascade into cycle-time variability downstream. - **Cost Efficiency**: Reducing idle time improves output without additional maintenance burden. - **Planning Insight**: Idle patterns expose where dispatch and WIP policies need correction. **How It Is Used in Practice** - **Flow Diagnostics**: Correlate idle events with upstream queue and equipment status. - **Dispatch Improvements**: Prioritize lot release and sequencing rules for starvation-prone tools. - **Line Balancing**: Adjust capacity allocation across process areas to smooth wafer movement. Idle time is **a critical indicator of production flow inefficiency** - controlling starvation is essential to realizing the full value of available equipment capacity.