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6CCVD Research

High precision processing CaF2 application research based on the magnetorheological finishing technology

At a Glance

Section titled ā€œAt a Glanceā€
MetadataDetails
Publication Date2017-10-16
AuthorsXianyun Zhong, Fan Bin, Wu Fan
InstitutionsInstitute of Optics and Electronics, Chinese Academy of Sciences
Citations3

Abstract

Section titled ā€œAbstractā€

Single crystal calcium fluoride (CaF<sub>2</sub>) is the excellent transparent optical substance that has extremely good permeability and refractive index from 120nm wavelength ultraviolet range to 12&mu;m wavelength infrared range and it has widely used in the applications of various advanced optical instrument, such as infrared optical systems (IR), short wavelength optical lithography systems (DUV), as well as high power UV laser systems. Nevertheless, the characteristics of CaF<sub>2</sub> material, including low fracture toughness, low hardness, low thermal conductivity and high thermal expansion coefficient, result in that the conventional pitch polishing techniques usually expose to lots of problems, such as subsurface damage, scratches, digs and so on. Single point diamond turning (SPDT) is a prospective technology for manufacture the brittle material, but the residual surface textures or artifacts of SPDT will cause great scattering losses. Meanwhile, the roughness also falls far short from the requirement in the short wavelength optical systems. So, the advanced processing technologies for obtaining the shape accuracy, roughness, surface flaw at the same time need to put forward. In this paper, the authors investigate the Magnetorheological Finishing (MRF) technology for the high precision processing of CaF<sub>2</sub> material. We finish the surface accuracy RMS Ī»/150 and roughness Rq 0.3nm on the concave aspheric from originate shape error 0.7&lambda; and roughness 17nm by the SPDT. The studying of the MRF techniques makes a great effort to the processing level of CaF<sub>2</sub> material for the state-of-the-art DUV lithography systems applications.

Tech Support

Section titled ā€œTech Supportā€

Original Source

Section titled ā€œOriginal Sourceā€

References

Section titled ā€œReferencesā€
  1. 2009 - Study of haze in 193 nm high dose irradiated CaF2 crystals
  2. 2015 - Surface assessment and mitigation of DUV optics
  3. 2015 - Surface finish in ultra-precision diamond turning of single-crystal silicon
  4. 2007 - Improving surface figure and microroughness of IR materials and diamond turned surfaces with Magnetorheological Finishing
  5. 2008 - Removal of diamond-turning signatures on x-ray mandrels and metal optics by fluid-jet polishing
  6. 1999 - Magnetorheological finishing (MRF) in commercial precision optics manufacturing
  7. 2007 - Surface interactions between nanodiamonds and glass in magnetorheological finishing (MRF)

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