RAMAN SPECTROSCOPY AS AN IN-SITU, REAL TIME TOOL FOR CONTROLOF COMPOUND SEMICONDUCTOR GROWTH

RAMAN SPECTROSCOPY IS AN EXCELLENT MEANS FOR NON-CONTACT PROBING OF QUALITY AND TEMPERATURE OF MANY MATERIALS (III-V SEMICONDUCTORS, DIAMONDS, ETC.) WHICH ARE GROWN IN CHEMICAL VAPOR DEPOSITION (CVD) REACTORS. IT CAN MEASURE COMPOSITION, TEMPERATURE, STRAIN, DEGREE OF CRYSTALLINITY, AND PRESENCE OF CONTAMINATION EX-SITU. AS AN OPTICAL PROBE IT CAN READILY PENETRATE THE HIGH PRESSURE GASES WHILE A GROWTH CHAMBER IS IN OPERATION. HOWEVER, THE NORMAL GRATING MONOCHROMETER ASSOCIATED WITH RAMAN SPECTROMETRY IS TOO UNWIELDY AND DOES NOT HAVE THE LIGHT COLLECTION POWER AND THROUGHPUT NEEDED TO BE A TRUE IN-SITU MONITOR. A UNIQUE AND COMPACT RAMAN SPECTROMETER IS DESCRIBED THAT WILL READILY ADAPT THIS REMARKABLY VERSATILE PROBE TO IN-SITU USE. UNLIKE THE CONVENTIONAL RAMAN SPECTROMETERS IT WILL BE SMALL, RUGGED, USER FRIENDLY, OPTICALLY EFFICIENT, AND INEXPENSIVE; HENCE IT IS READILY ATTACHABLE TO A GROWTH CHAMBER. IN ADDITION, THE RAMAN SYSTEM CAN BE DESIGNATED SO THAT IT CAN OBTAIN A SURFACE IMAGE OF THE RAMAN SIGNAL, THUS IRREAULARITIES IN COMPOSITION AND TEMPERATURE ACROSS A WAFER MAY BE MEASURED. IN PHASE I, WE SHALL USE A CONVENTIONAL RAMAN SYSTEM TO SURVEY THE CRITICAL SENSOR NEEDS FOR GROWTH MONITORING OF ALGAAS, GAAS, INGAAS, AND OTHER MATERIALS AS APPROPRIATE. FROM THIS INFORMATION, A GENERAL PURPOSE COMPACT RAMAN SPECTROMETER WILL BE DESIGNED AND BUILT IN PHASE II. USING INFORMATION FROM THE GENERAL PURPOSE COMPACT RAMAN SPECTROMETER, A COMPACT SMART SENSOR WILL BE DESIGNED FOR DEDICATED APPLICATIONS I.E. COMPOSITION AND TEMPERATURE MEASUREMENT OF ALGAAS. THE CONCLUSION OF PHASE II WILL BE THE CONSTRUCTION AND DELIVERY OF SMART SENSORS WHICH CAN BE ATTACHED TO COMMERCIAL CVD REACTORS. THESE WILL PROVIDE FEEDBACK SIGNALS TO CONTROL THE TEMPERATURE, FLOW OF REACTANT MATERIALS, ETC., TO MAINTAIN THE GROWTH WITHIN THE DESIRED PARAMETERS. IMPROVEMENTS IN COMPOSITION, TEMPERATURE AND STRAIN FOR FEEDBACK CONTROL OF CHEMICAL VAPOR DEPOSITION GROWTH OF SEMICONDUCTORS WILL IMPROVE THE QUALITY OF THE MATERIAL BEING GROWN. AT THE COMPLETION OF PHASE II, A MARKETABLE IN-SITU PROBE FOR TEMPERATURE, STRAIN AND COMPOSITION MEASUREMENT OF CVD GROWN MATERIALS WILL BE AVAILABLE FOR PRODUCTION.