XLR 600i: recirculating ring ArF light source for double patterning immersion lithography
2008
Double patterning (DP) lithography is expected to be deployed at the 32nm node to enable the extension of high NA
(≥1.3) scanner systems currently used for 45nm technology. Increasing the light source power is one approach to address
the intrinsically lower throughput that DP imposes. Improved energy stability also provides a means to improve
throughput by enabling fewer pulses per exposure slit window, which in turn enables the use of higher scanner stage
speeds. Current excimer laser light sources for deep UV immersion lithography are operating with powers as high as
60W at 6 kHz repetition rates. In this paper, we describe the introduction of the XLR 600i, a 6 kHz excimer laser that
produces 90W power, based on a recirculating ring technology. Improved energy stability is inherent to the ring
technology. Key to the successful acceptance of such a higher power, or higher energy laser is the ability to reduce
operating costs. For this reason, the recirculating ring technology provides some unique advantages that cannot be
realized with conventional excimer lasers today. Longer intrinsic pulse durations that develop in the multi-pass ring
architecture reduce the peak power that the optics are subjected to, thereby improving lifetime. The ring architecture also
improves beam uniformity that results in a significantly reduced peak energy density, another key factor in preserving
optics lifetime within the laser as well as in the scanner. Furthermore, in a drive to reduce operating costs while
providing advanced technical capability, the XLR 600i includes an advanced gas control management system that
extends the time between gas refills by a factor of ten, offering a significant improvement in productive time. Finally, the
XLR 600i provides a novel bandwidth stability control system that reduces variability to provide better CD control,
which results in higher wafer yields.
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