Method for providing distributed material management and flow control in an integrated circuit factory

A method of detecting deadlocks in an integrated-circuit factory comprising:

• a) initialize a variable to a first location in a semiconductor wafer processing system;
• b) determining a successor location to the first location;
• c) determining if the successor location for a wafer cassette is empty or is a stocker, then a deadlock is not detected;
• if the successor location for a cassette is not empty or a stocker and the successor location is a location already identified in a schedule, then identify the existence of a circular wait;
• d) save the location in a schedule;
• e) equate the first location equal the successor location;
• f) repeat steps b), c), d), e) and f) until all successor locations are found.

A method of moving wafer cassettes in an integrated-circuit factory comprising a plurality of possible cassette placement locations comprising:

• generating a bid from at least one cassette placement location in a plurality of cassette placement locations, where each bid contains a request for a wafer cassette;
• transmitting the bids to a central computer;
• comparing bids from a plurality of cassette placement locations;
• assigning wafer cassettes to cassette placement locations in response to said bid comparison;
• and
• moving the wafer cassettes to the cassette placement locations in accordance with the assignments.

A method for providing stocker overflow protection in an integrated-circuit factory comprising:

• sending a transfer request from a first stocker to a second stocker, where said transfer request comprises a window size defining a number of wafer cassettes that the first stocker desires to send to the second stocker;
• comparing the window size to the available space in the second stocker;
• if the window size is greater than the available space in second stocker, rejecting the transfer request;
• and
• if the window size is less than or equal to the available space in the second stocker, accepting the transfer request and transferring said number of wafer cassettes from the first stocker to the second stocker.