NON-DESTRUCTIVE EVALUATION OF IMPURITIES AND DEFECTS IN ULTRA-THIN SEMICONDUCTOR FILMS

THE SCANNING PHOTOVOLTAGE (SPV) TECHNIQUE IS A NON-DESTRUCTIVE, HIGH RESOLUTION OPTICAL METHOD FOR MAPPING ELECTRICALLY-ACTIVE DEFECTS IN SEMICONDUCTORS. THE POTENTIAL OF THE SPV TECHNIQUE HAS NOT BEEN REALIZED FOR MODERN, ULTRA-THIN FILM MATERIALS, HOWEVER, BECAUSE OF MULTIPLE REFLECTION INTERFERENCE EFFECTS WHICH MASK THE DEFECT-RELATED SIGNALS. MEASUREMENTS ARE FURTHER HAMPERED BY LOW SIGNAL-TO-NOISE RATIOS CAUSED BY THE HIGH IMPEDANCE NATURE OF THE THIN-FILMS. ARACOR PROPOSES TO DEVELOP AN SPV SYSTEM WHICH IS UNIQUELY SUITED TO INSPECT ULTRA-THIN FILM DEVICE MATERIALS IN REAL-TIME AT THE MANUFACTURER. THIS SPECIAL SPV SYSTEM WILL PROVIDE A PROBE LIGHT SOURCE WHOSE WAVELENGTH IS SELECTABLE. THEN, BY MATCHING THE WAVELENGTH OF THE PROBE TO THE ABSORPTION COEFFICIENT OF THE THIN FILM MATERIAL, THE INTERFERENCE EFFECTS CAN BE ELIMINATED. IN ADDITION, THE SYSTEM WILL INCORPORATE A STEADY-STATE BIAS LIGHT TO DECREASE THE FILM RESISTANCE. INPHASE I, THE PROPOSED CONCEPT WILL BE DEMONSTRATED ON THIN SILICON-ON-INSULATOR (SIMOX) MATERIAL. PROBE WAVELENGTH, SPOT SIZE, AND BIAS LIGHT INTENSITY WILL BE VARIED TO DEMONSTRATE HOW THE SIGNAL-TO-NOISE RATIO OF THE PV SIGNAL CAN BE OPTIMIZED. THE DEFECTS DETECTED IN THE SOI SAMPLES USING THE MODIFIED SPV APPROACH WILL BE CORRELATED TO THE DEFECTS IDENTIFIED USING CONVENTIONAL TECHNIQUES. ANTICIPATED BENEFITS/POTENTIAL COMMERCIAL APPLICATIONS - THE RESULT OF THIS PROGRAM WILL BE A DEMONSTRATED, HIGH RESOLUTION, NON-DESTRUCTIVE TEST CAPABILITY TO DETECT AND CHARACTERIZE DEFECTS AND IMPURITIES IN VERY THIN SEMICONDUCTOR FILMS. THIS CAPABILITY WILL AID THE MATERIAL MANUFACTURER IN EVALUATING AND IMPROVING HIS FILMS AS WELL AS THE DEVICE MANUFACTURER IN QUALIFYING AND SORTING