oht management

**OHT management** is the **operation and optimization of overhead hoist transport systems that move wafer carriers through fab ceiling-track networks** - effective management is essential to maintain low-latency intra-fab logistics. **What Is OHT management?** - **Definition**: Control of OHT fleet routing, dispatch priorities, traffic balancing, and reliability maintenance. - **System Scope**: Includes vehicle controllers, track segments, stocker interfaces, and exception handling logic. - **Performance Metrics**: Move time, queue time, delivery reliability, fleet utilization, and congestion frequency. - **Operational Constraints**: Must satisfy cleanliness, safety, and deterministic handling requirements. **Why OHT management Matters** - **Flow Efficiency**: Poor OHT control creates transport bottlenecks that starve expensive process tools. - **Cycle-Time Stability**: Predictable transport latency reduces variability in lot progression. - **Capacity Utilization**: Balanced vehicle dispatch improves effective throughput across the fab. - **Downtime Risk**: OHT failures can trigger broad ripple effects across multiple tool groups. - **Scalability Requirement**: Advanced OHT management is needed as fab complexity and WIP volume grow. **How It Is Used in Practice** - **Traffic Analytics**: Monitor route congestion and dynamically rebalance fleet assignments. - **Priority Governance**: Apply dispatch rules based on bottleneck tools, due dates, and hot lots. - **Reliability Program**: Maintain preventive service and rapid recovery procedures for transport assets. OHT management is **a key determinant of fab logistics performance** - strong overhead transport control improves cycle time, tool utilization, and overall manufacturing responsiveness.