Patent ID: 6908775
Filing Date: 2005-06-21
Classification: G03F,G06T

Abstract:
1. A method for performing an alignment measurement of two patterns in different layers on a semiconductor wafer, with a set of a fixed number of exposure fields selected for the alignment measurement, and with each of the exposure fields having at least one alignment structure, the method which comprises the following method steps: providing the semiconductor wafer to a processing tool for performing the alignment measurement; selecting a first alignment structure in a first exposure field of the set with the fixed number of exposure fields; performing an offset measurement using the first alignment structure, and issuing an error signal if the offset measurement is not feasible due to a poor alignment structure quality or an offset lies beyond a tolerance range; in response to the error signal, selecting a second exposure field as a substitute, wherein the second exposure field is not included in the set of exposure fields on the semiconductor wafer except for the first exposure field; selecting a second alignment structure in the second exposure field; performing an offset measurement using the second alignment structure; and measuring a second relative offset of an alignment structure in a next exposure field of the set with the fixed number of exposure fields.