MIXING AND MATCHING DEEP-UV STEP-AND-SCAN WITH I-LINE STEP AND REPEAT

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.