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Product Briefing Outline: Agilent Technologies has announced the availability of deep-UV optical coating, offering long-lifetime optics that address the growing need for highly accurate and reliable beam delivery in leading-edge semiconductor photolithography systems.

Problem: UV Lithography Systems utilize lasers that can pump 100 million shots per week through an optical system.  Because of the short wavelength and high power of the laser, material interactions in the substrate and coating layers are much more pronounced than in visible and near-IR wavelengths.  In particular, typical UV-grade fused silica substrates suffer significant and permanent changes in their properties when irradiated by millions of high-power laser pulses.  In addition, the high fluence laser pulses can cause the thin-film coating layers to compact through photochemical interactions, resulting in a coating shift that can cause a 95 percent reflector to drop below 90 percent.
 
Solution: Agilent has developed proprietary high-throughput UV coatings that increase component lifetime while minimizing compaction. These long-lifetime optics reduce production costs by extending the time between required maintenance cycles and reducing system downtime.  AR coated calcium fluoride prisms offer an alternative to flat turning mirrors.  Calcium fluoride is more robust than UV-grade fused silica, and has been shown to withstand billions of pulses without serious compaction issues.  Al2O3/AlF3 or LaF3/MgF2 or similar thin-film anti-reflection coatings on the prisms have very low layer counts that allow very little compaction in the coating layer.  By limiting the number of layers and mitigating compaction issues, the effective bandwidth of the thin film coating can be expanded to allow a much wider acceptance angle at the entrance and exit faces, improving the performance of the optical system.

Applications: DUV optics

Platform: Reflectivity and damage-threshold testing have been successfully completed, and in independent tests Agilent has qualified multiple coating chambers, thus ensuring product availability.

Availability: January 2008 onwards.