Patent ID: 6947804

Claim:
A method for detecting sequential processing effects on integrated circuits to be manufactured in manufacturing process, comprising the steps of: (a) predetermining a first random sequence for a plurality of units in a batch of units; (b) performing a first process step on the plurality of units by a first process tool in accordance with the first random sequence, wherein the performing step comprises: (b1) associating each of the plurality of units with a slot in a cassette; (b2) removing each of the plurality of units according to the first random sequence by the first process tool; (b3) performing the first process step on each of the removed units by the first process tool; and (b4) replacing each of the units into its associated slot by the first process tool; (c) determining a second random sequence for the plurality of units; and (d) performing a second process step on the plurality of units by a second process tool in accordance with the second random sequence.