This paper reviews all the major aspects of successfully implementing
a ''mix and match'' (Decp-UV/I-line, stepper/scanner) strategy. The re
solution and linewidth-control limits of I-line are quantified for a n
umber of the process levels and compared with the capabilities of Deep
-UV step-and-scan. This analysis predicts the typical mix of steppers
and scanners in a 256 MBit production line for 250 nm lithography. A s
tep-by-step procedure to achieve and monitor successful matching is re
viewed. The procedure begins by defining a ''golden system'', which is
used to produce reference wafers for the setup and monitoring of all
the systems being mixed and matched. The reference wafers are used to
ensure that the pre-aligners of the systems are calibrated and that of
fsets are adapted to allow the transfer of wafers between systems. The
wafers are also used to match both wafer-stage grid and exposure-fiel
d distortions. The matching of both wafer-grid and stepper-field disto
rtions are reviewed, The implementation of stage correction-tables is
demonstrated. It is indicated that grid matching to better than 10 nm
is achievable. It is also indicated that tire dynamic scanning of a st
ep-and-scan system allows the monitoring and correction of such typica
l stepper problems as field magnification and rotation. The critical a
spects of multi-field matching between stepper and scanner are analyze
d. The key factors that allow the successful overlaying of large, sing
le, scanned fields with multiple, small, stepped fields are reviewed.
The total overlay accuracy achieved using step-and-scan, and ''mix-and
-match'' is analyzed and demonstrated.