New projection optics and aberration control system for the 45-nm node
2007
The 65nm and the subsequent 45nm node lithography require very stringent CD control. To realize high-accuracy CD
control on an exposure tool, it is essential to reduce wavefront aberrations induced by projection optics design and
manufacturing errors and then stabilize the aberrations while the exposure tool is in operation. We have developed two
types of new hyper-NA ArF projection optics to integrate into our new platform exposure tool: a dry system and a
catadioptric system for immersion application. In this paper, aberration measurement results of these projection
systems are shown, demonstrating that ultra-low aberration is realized. In addition, a new projection optical system has
been developed which incorporates high degree-of-freedom Aberration Controllers and automatic aberration measuring
sensors. These controllers and sensors are linked together through Aberration Solver, a software program to determine
optimal target values for aberration correction, thereby allowing the projection optics to maintain its best optical
properties. The system offers excellent performance in correcting aberrations that come from lens heating, and makes it
possible to guarantee extremely low aberrations during operation of the exposure tool.
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