BULK-DENSITY AL(2)O(3) THIN FILMS BY ION BEAM ENHANCED DEPOSITION

ALUMINUM OXIDE IS A WIDELY USED CERAMIC EXHIBITING A NUMBER OF ATTRACTIVE BULK PROPERTIES INCLUDING CHEMICAL NERTNESS, HIGHTEMPERATURE COMPATIBILITY, AND HIGH DIELECTRIC STRENGTH. UNFORTUNATELY, THESE PROPERTIES CANNOT ALWAYS BE ACHIEVED IN THIN FILMS WITH CONVENTIONAL DEPOSITION TECHNIQUES BECAUSE PINHOLES AND COLUMNAR MICROSTRUCTURE RESULT IN REDUCED DENSITY. THESE DEFECTS CAN LOWER THE BREAKDOWN VOLTAGE OF DIELECTRIC FILMS AND REDUCE THE ENVIONMENTAL STABILITY (WATER ABSORPTION) OF OPTICAL COATINGS. SPIRE CORPORATION HAS DEMONSTRATED THAT DEFECT-FREE THIN FILMS CAN BE PRODUCED ON A VARIETY OF SUBSTRATE MATERIALS BY A PROCESS KNOWN AS ION BEAM ENHANCED DEPOSITION (IBED), INVOLVING SIMULTANEOUS PHYSICAL VAPOR DEPOSITION AND CONCURRENT LOW ENERGY ION BOMBARDMENT. IBED FILMS EACH CAN BE GROWN AT RELATIVELY LOW TEMPERATURES COMPARED TO OTHER TECHNIQUES, ARE HIGHLY ADHERENT, FULL DENSE, PINHOLE-FREE, AND DO NOT SHOW THE COLUMNAR MICROSTRUCTURE COMMON TO OTHER LOW TEMPERATURE COATING PROCESSES. THE PROPOSED PHASE I RESEARCH WOULD INVESTIGATE IBED AS A MEANS OF DEPOSITING BULK-DENSITY AL(2)O(3) THIN FILMS ON SILICON (100) SUBSTRATES. THE PROCESS WILL INVOLVE ELECTRON BEAM EVAPORATION OF AL(2)O(3) OR AL UNDER CONCURRENT IRRADIATION WITH A LOW ENERGY (100-1000 EV) OXYGEN ION (O+/O(2+) BEAM FROM A KAUFMAN ION SOURCE. BY VARYING EVAPORATION RATE AND ION BEAM CURRENT DENSITY STOICHIOMETRIC, FULLY DENSE AL(2)O(3) FILMS OF ANY DESIRED THICKNESS CAN BE PRODUCED. THE OXYGEN ION WILL SERVE BOTH TO DENSITY THE COATING AND TO MAKE UP ANY LOSS OF OXYGEN DURING EVAPORATION.