SILCING GALLIUM ARSENIDE (GASS) WITH REDUCED SURFACE DAMAGE FOR MORE COST EFFECTIVE SOLAR CELLS

GASS IS KEY STRATEGIC MATERIAL FOR SPACE ELECTRONICS. IT IS COSTLY BECAUSE OF HIGH RAW MATERIAL COSTS, HIGH CRYSTAL GROWTH COSTS, AND LOW MATERIAL UTILIZATION DUE TO INEFFICIENT SLICING. THE COST CAN BE REDUCED SIGNIFICANTLY BY INCREASING THE MATERIAL UTILIZATION USING A NEW WIRE SLICING TECHNIQUE--FIXED ABRASIVE SLICING TECHNIQUE (FAST). THE FEASIBILITY OF THE MULTI-WIRE FAST APPROACH HAS BEEN DEMONSTRATED FOR PHOTOVOLTAIC SILICON BY REDUCING KERF LOSS, SURFACE DAMAGE AND WAFTER THICKNESS. SUBSTANTIAL ADDITIOAL SAVINGS CAN BE GENERATED, PARTICULAR FOR THE MORE COSTLY GAAS, BY IMPROVING SLICING ACCURACY. BY SLICING ACCURATELY WITH MINIMUM SURFACE DAMAGE, IT WOULD BE POSSIBLE TO ELIMINATE A COSTLY MATERIAL-INTENSIVE GRINDING OPERATION AND GO DIRECTLY TO POLISHING. THE PROPOSED PROGRAM FOR GAAS WILL ADDRESS THREE RELATED AREAS AFFECTING SLICE ACCURACY: WIRE GUIDE ROLLERS, BLADE COMPOSITIO AND CRITICAL CONTACT LENGTH TESTING. IT IS EXPECTED THAT THE GUIDE ROLLER SYSTEM WILL BE OPTIMIZED BY USING ABRASION RESISTANT POLYURETHANE AS A ROLLER MATERIAL. EMPHASIS IN BLADE DEVELOPMENT WILL BE ON PLATING DIAMODS BELOW 30UM IN SIZE ON 100UM DIAMETER WIRE TO ACHIEVE MINIMUM KERF, HIGH SLICING ACCURACY AND LONG LIFE. SLICING EXPERIMENTS WILL BE PERFORMED ON AN EXISTING BREADBOARD SLICER WITH 175-WIRE BLADEPACKS AT 48 WAFERS PER INCH. THE WAFERS WILL BE CHARACTERIZED FOR ACCURACY--I.E., BOW, TAPR, FLATNESS, WAFER-TO-WAFER THICKNESS AND DEPTH OF SURFACE DAMAGE.