Automated materials handling system having multiple categories of overhead buffers

摘要

An automated materials handling system comprises a plurality of overhead hoist buffers (OHBs) for receiving a plurality of semiconductor wafer carriers. Each OHB is assigned to a respective one of a plurality of categories. Each wafer carrier is associated with one or more of the plurality of categories. Each respective category is associated with at least one of a plurality of event trigger types. An overhead transport (OHT) if provided for transporting each of the plurality of wafer carriers to a respective one of the OHBs in response to a respective trigger event. Each trigger event has one of the plurality of event trigger types. Each wafer carrier is stored in a respective one of the plurality of OHBs assigned to a respective one of the categories associated with the respective event trigger type of the trigger event causing that wafer carrier to be transported and stored.