PHOTOELECTROCHEMICAL FABRICATION OF SPECTROSCOPIC DIFFRACTION GRATING IN SILICON CARBIDE

GRATINGS AND OPTICAL COMPONENTS THAT OPERATE IN THE VACUUM ULTRAVIOLET (VUV) AND THE X-RAY REGION ARE IMPORTANT COMPONENTS OF SPECTROSCOPIC INSTRUMENTATION FOR MANY OF NASA'S SPACE MISSIONS (E.G., LYMAN). SILICON CARBIDE (SIC) POSSESSES THE REQUIREMENTS OF HIGH REFLECTIVITY, LOW SCATTERING, HIGH STIFFNESS AND LOW THERMAL STRESS FOR AN OPTICAL MATERIAL IN THIS REGION. PHOTOELECTROCHEMICAL ETCHING IS A PROCESS FOR PRODUCING DIFFRACTION GRATINGS DIRECTLY IN SEMICONDUCTING MATERIALS, SUCH AS SIC. IN PRINCIPLE, THE PROCESS HAS MOLECULAR LEVEL OF RESOLUTION, AND SHALLOW INTERFERENCE GRATINGS CAN BE PHOTOELECTROCHEMICALLY ETCHED WITH PERIODS EXCEEDING 6000 GROOVES/MM. PHASE I ENTAILS THE DEMONSTRATION OF THE FEASIBILITY OF MAKING DIFFRACTION GRATINGS IN SIC BY PHOTON INDUCED ETCHING. EFFECTS OF ETCHANT COMPOSITION, WAVELENGTH, EXTERNAL ELECTRICAL BIAS, TOTAL EXPOSURE AND SURFACE MORPHOLOGY WILL BE EXAMINED IN RELATION TO THE PHOTOELECTROCHEMICAL ETCHING OF SIC.