A LOW DAMAGE SIC GRATING FOR SYNCHROTRON RADIATION BY PHOTOELECTROCHEMICAL ETCHING

DIFFRACTION GRATINGS THAT OPERATE IN THE VACUUM ULTRAVIOLET (VUV) AND X-RAY SPECTRAL REGIONS ARE IMPORTANT COMPONENTS OFSPECTROSCOPIC INSTRUMENTATION USED WITH THE SYNCHROTRON LIGHT SOURCE (SLS). SILICON CARBIDE (SIC) IS THE SUBSTRATE OF CHOICE FOR THESE COMPONENTS, NOT ONLY FOR ITS HIGH REFLECTIVITY IN THE VUV/X-RAY REGIONS, BUT ALSO FOR ITS EXCEPTIONAL HARDNESS, LOW THERMAL EXPANSION, AND HIGH RESISTANCE TO RADIATIVE DAMAGE. UNFORTUNATELY, DIFFRACTION GRATINGS CANNOT BE MADE IN SIC BY CONVENTIONAL METHODS. THIS PROJECT WILL FABRICATE GRATINGS IN THE SURFACE OF CHEMICAL VAPOR DEPOSITED (CVD) SIC BLANKS USING PHOTOELECTROCHEMICAL ETCHING. ULTIMATELY, IT SHOULD BE POSSIBLE TO ETCH PATTERNS PROJECTED ONTO THE SIC SURFACE IN ONE-STEP PROCESS, WITH RESOLUTION EXCEEDING 6,000 LINES/MM. THE PROCESS HAS THE ADVANTAGE OF EXTERNAL MONITORING AND CONTROL OF GROOVE UNIFORMITY, SMOOTHNESS, AND DEPTH. IN PHASE I, THE FEASIBILITY OF PHOTOELECTROCHEMICAL ETCHING IN N-DOPED CVD-SIC WILL BE DETERMINED, INCLUDING THE DEMONSTRATION OF GRATING STRUCTURES USING PHOTORESIST MASKS. IN PHASE II, DIRECT FABRICATION OF HOLOGRAPHIC GRATINGS WILL BE SOUGHT, WITH THE ULTIMATE OBJECTIVE OF PRODUCING GRATINGS UP TO 3 IN. DIAMETER WITH A VARIETY OF GROOVE SPACINGS AND BLAZES.