SURFACE MORPHOLOGY OF SILICON ON INSULATOR FILMS PREPARED BY ZONE-MELTING RECRYSTALLIZATION

RESEARCH IS DIRECTED AT TECHNIQUES TO IMPROVE SURFACE MORPHOLOGY IN SILICON ON INSULATOR (SOI) WAFERS PREPARED BY ZONE MELTING RECRYSTALLIZATION (ZMR). THE THREE AREAS OF PRIMARY IMPORTANCE IN IMPROVING THE SURFACE MORPHOLOGY OF ZMR PROCESSED WAFERS ARE: SLIP, BOW AND WARP, AND SURFACE SMOOTHNESS. SLIP IS CAUSED BY THERMALLY INDUCED STRESS THAT RESULTS FROM THE TEMPERATURE GRADIENT IN THE MELT ZONE. METHODS OF REDUCING THIS PROBLEM WILL BE EXAMINED BY VARYING SEVERAL FACTORS INCLUDING THE SUBSTRATE TEMPERATURE, SCAN SPEED, WIRE WIDTH AND SUBSTRATE ORIENTATION. THE ABOVE PARAMETERS WILL ALSO BE VARIED TO IDENTIFY THE EFFECTS ON BOW AND WARP. IN ADDITION, BOW AND WARP MEASUREMENTS WILL BE COMPLETED BEFORE AND AFTER THE ZMR PROCESS TO IDENTIFY POSSIBLE CORRELATION WITH STARTING MATERIAL. SURFACE ROUGHNESS IN ZMR IS DIRECTLY RELATED TO THE QUALITY OF THE STARTING POLYSILICON LAYER. PARAMETERS AFFECTING THE POLYSILICON CVD DEPOSITION WILL BE VARIED TO OPTIMIZE THE QUALITY OF THIS LAYER AND ALTERNATIVE POLYSILICON GROWTH TECHNIQUES WILL ALSO BE STUDIED. SOI MATERIAL OFFERS MANY INHERENT ADVANTAGES OVER CONVENTIONAL SILICON BULK WAFERS: RADIATION HARDNESS, VOLTAGE ISOLATION, IMPROVED SPEED PERFORMANCE, GREATER PACKING DENSITY, AND CMOS LATCH-UP IMMUNITY. CURRENT METHODS OF FABRICATING SOI MATERIAL RESULT IN EITHER COST AND/OR QUALITY PROBLEMS. THE ZMR PROCESS OFFERS AN ALTERNATIVE TO OTHER SOI PROCESSES.