ON-LINE PURIFIERS FOR CHEMICAL VAPOR DEPOSITION

THE MATERIALS USED IN THIN-FILM PHOTOVOLTAIC CELLS AND MANY OTHER SEMICONDUCTOR DEVICES ARE FREQUENTLY GROWN USING CHEMICAL VAPOR DEPOSITION (CVD) OR OTHER VAPOR-BASED PROCESSES. MANY OF THE PROCESS GASES USED, FOR EXAMPLE, ARSINE, PHOSPHINE, AMMONIA, DIBORANE, AND SILANE, ARE HIGHLY REACTIVE. CONTAMINATION, CHEMICAL OR PARTICULATE, OF THESE REACTIVE GASES SERIOUSLY INTERFERES WITH DEVICE PERFORMANCE. PARTICLE CONTAMINATION CAN BE REDUCED BY FILTRATION, BUT SIMILAR APPROACHES TO ADDRESS CHEMICAL CONTAMINATION ARE NOT COMMONLY AVAILABLE. INERT GASES SUCH AS HYDROGEN AND HELIUM ARE NOW ROUTINELY PURIFIED AT THE POINT OF USE, BUT THE REACTIVE GASES USED IN CVD REQUIRE MORE SOPHISTICATED PURIFICATION TECHNIQUES. BY USING SUPPORTED REAGENTS, ON-LINE PURIFIERS CAN BE DESIGNED THAT WILL REMOVE OXYGEN, WATER, AND CERTAIN OTHER CONTAMINANTS FROM THE BROAD SPECTRUM OF REACTIVE GASES. DURING PHASE I A UNIFYING THEORY FOR REDUCING THE CONTAMINANTS IN THESE GASES TO PARTS PER BILLION LEVELS WILL BE TESTED. A PURIFIER WILL BE BUILT, ANALYTICAL METHODS DEVELOPED, AND ITS PURIFICATION CAPABILITY DEMONSTRATED. PHASE II WILL INCORPORATE THE DESIGN AND TESTING OF PURIFIERS FOR EACH OF THE REACTIVE PROCESS GASES AND ON-LINE EVALUATION DURING ACTUAL DEVICE FABRICATION.