Currently, wafer steppers are capable of routinely meeting a single machine overlay accuracy of 150 nm or less. However, this figure is relatively meaningless in a production environment equipped with multiple machines. The question is how to exploit single machine accuracy in a multiple stepper production environment such that production logistics will be independent of machine allocation. This paper describes the use of a matching management system supported by an overlay simulator and a reference wafer set. Every stepper is measured on a regular basis with respect to a reference wafer to determine possible deviation from the nominal grid. The reference wafers are resistant to multiple use. The simulator can be used to estimate the matching performance between non-measured machine pairs so that the need for particular adjustments can be determined. The theory is completed by an extended overlay budget justified by experimental results and a ten machine overlay experiment.

Date Published: 19 July 1989
PDF: 15 pages
Proc. SPIE 1087, Integrated Circuit Metrology, Inspection, and Process Control III, (19 July 1989); doi: 10.1117/12.953095

Published in SPIE Proceedings Vol. 1087:
Integrated Circuit Metrology, Inspection, and Process Control III
Kevin M. Monahan, Editor(s)