The overhead crane (OHT) in the wafer fab achieves fast, precise, and unmanned handling of wafer boxes between process equipment through aerial rail networks, automated control, and precision mechanical collaboration.
1. System composition and layout
The overhead crane is the core of the Automatic Material Handling System (AMHS), which operates on a precise track network at the top of the wafer fab cleanroom. The track is optimized and designed based on the production process and equipment layout, covering all key process areas and storage areas such as photolithography, etching, and deposition, forming an efficient logistics artery.
2. Workflow
2.1 Task reception and planning: The overhead crane receives handling instructions from the production control system through a communication interface, which includes information such as pick-up and drop addresses, priorities, etc.
2.2 Intelligent Mobile and Navigation: After the crane is started, it relies on encoders or laser positioning sensors to accurately locate and navigate on the track, and communicates in real-time with the central dispatch and other cranes through wireless networks to dynamically avoid collisions, optimize paths, and ensure smooth traffic.
2.3 Precision picking: After arriving at the pickup point (such as equipment port), the overhead crane descends and grabs the wafer box (FOUP) through a mechanical arm or suction cup mechanism. At the same time, integrating RFID or barcode readers to verify wafer identity ensures accurate information.
2.4 Stable transportation: After grabbing, the overhead crane rises to the operating height and runs smoothly along the track at high speed to the target equipment. Continuous communication and status reporting during the period.
2.5 Precise Placement: After reaching the target point, the overhead crane descends again and places the crystal round box precisely into the equipment loading port. After completion of placement, a confirmation signal is sent to the control system.
2.6 Standby and Maintenance: After the task is completed, the overhead crane automatically returns to the idle area or designated standby position, and executes a self-test program to wait for the next instruction.
