FABRICATION AND CHARACTERIZATION OF REACTIVE ION-BEAM ETCHED SIC GRATINGS

A holographic SiC grating has been fabricated by means of reactive ion beam etching in Ar + CHF3 mixture and by using photoresist as an etching mask. The etch rates of SiC and photoresist depend on the CHF3 concentration in Ar + CHF3 mixture. A maximum value for a ratio of the etch rate of SiC to that of photoresist was found to be 1.29 for 67%Ar + 33%CHF3 mixture. Diffraction efficiency of an ion-beam etched grating of 1200 l/mm grooves coated with Au was measured by using synchrotron radiation and the Al k-alpha emission line from an x-ray tube. The diffraction efficiency of the first order was 4.5%-9.3% in the soft x-ray region between 8.34 and 120 angstrom with a small amount of the higher order and the scattered light components. In addition, it is demonstrated that SiC can be etched in SF6 gas by synchrotron radiation excitation.