TEMPERATURE MEASUREMENT BY NONCONTACT METHOD FOR CZOCHRALSKITYPE CRYSTAL GROWTH

IN THE GROWTH OF CRYSTALS FROM MELTING MATERIALS USING THE CZOCHRALSKI METHOD, A GOOD TECHNIQUE OF ACCURATELY CONTROLLING THE PROCESS DOES NOT EXIST. THERMOCOUPLES ARE LARGELY USED AT PRESENT, BUT THEY DO NOT PROVIDE ADEQUATE INFORMATION SUCH AS THE THERMAL GRADIENT ACROSS A SINGLE LARGE CRYSTAL. THE USE OF CHARGE-COUPLED DEVICES TO MEASUREAND CONTROL CRYSTAL GROWTH USING THE CZOCHRALSKI METHOD IS THE INNOVATION BEING STUDIED IN THIS PROJECT. ARRAYS OF CHARGE-COUPLED DEVICES AND PHOTOVOLTAIC DETECTORS DETECT TEMPERATURE VARIATIONS OF A SURFACE AREA. THESE DETECTORS CAN BE ADAPTED TO MONITOR THE TEMPERATURE MEASUREMENTS WITHIN THE CRYSTAL GROWTH OVENS AND PROVIDE FEED-BACK CONTROL TO REGULATE THE OVEN. DURING PHASE I, THE WORK CONCENTRATED ON TESTING SENSOR TYPES AND RESEARCHING THE VARIOUS COMPONENTS OF A CONTROL SYSTEM. IT WAS CONCLUDED THAT CHARGE-COUPLED DEVICES WERE SUFFICIENTLY UNIFORM TO BE USED AS A THERMAL SENSOR ABOVE 200 CENTIGRADE.