CONTOURING THE OXYGEN ION ENERGY TO OBTAIN IMPROVED SIMOX MATERIAL

A PROGRAM IS PROPOSED TO EVALUATE THE FEASIBILITY OF FORMING IMPROVED SIMOX MATERIAL BY CONTOURING THE ENERGY OF THE INCIDENT OXYGEN IONS. DURING THE IMPLANTATION PROCESS OF SIGNIFICANT AMOUNT OF SUBSTRATE MATERIAL IS REMOVED BY SPUTTERING. ALTHOUGH THE RANGE R(P) OF INCIDENT IONS REMAINS CONSTANT, TO FIRST ORDER, DURING THE IMPLANT, THE SPUTTERING AWAY OF THE SURFACE CAUSES INCIDENT IONS TO COME TO REST DEEPER AND DEEPER INTO THE SUBSTRATE. THE MAIN FOCUS OF THIS PROPOSAL IS TO STUDY THE EFFECT OF A STEPWISE REDUCTION IN THE BEAM ENERGY TO COMPENSATE FOR SURFACE EROSION BY SPUTTERING. THIS IS EXPECTED TO RESULT IN THE FORMATION OF A CONTINUOUS BURIED DIELECTRIC LAYER AT A LOWER DOSE I.E. USING A SHORTER IMPLANT TIME AND THUS AT A REDUCED COST. A SUBSIDIARY GOAL WILL BE TO STUDY THE EFFECT OF INCREASING THE BEAM ENERGY DURING THE IMPLANT THEREBY ENHANCING THE EFFECT OF SPUTTERING. THIS TECHNIQUE IS EXPECTED TO RESULT IN THE FORMATION OF A THICKER INSULATING LAYER WITH HIGHER BREAKDOWN STRENGTH. WAFERS WILL BE IMPLANTED, ANNEALED AND THE THICKNESS OF THE SURFACE SILICON LAYER AND THE BURIED OXYGEN LAYER WILL BE MEASURED. THIS STUDY WILL FORMTHE BASIS FOR A PHASE II PROGRAM DURING WHICH THE PROCESSES WILL BE REFINED AND EXTENSIVE ANALYTICAL QUALITY STUDIES OF THE LAYERS WILL BE STUDIED, AND TEST DEVICES FABRICATED. SELECTION OF THE PROPER SIMOX MATERIAL IMPLANT TEMPERATURE, COMBINED WITH OPTIMUM ANNEAL CONDITIONS, ENABLES THE HIGHEST QUALITY SIMOX MATERIAL TO BE PRODUCED. SINCE OPTIMUM ANNEALING CONDITIONS HAVE RECENTLY BEEN ESTABLISHED,THIS PROGRAM EVALUATES THE OPTIMUM IMPLANT TEMPERATURE FOR SIMOX. SIMOX MATERIAL CAN BE PRODUCED MORE ECONOMICALLY AT HIGHER IMPLANT TEMPERATURE; IT IS THEREFORE, CRUCIAL TO ESTABLISH THE HIGHEST IMPLANT TEMPERATURE POSSIBLE. HOWEVER, THE RETENTION OF ABSORBED OXYGEN THERMAL DONORS IN THE SUPERFICIAL SILICON LAYER MAY LIMIT THE MAXIMUM IMPLANT TEMPERATURE USED. ANALYTICAL TECHNIQUES WHICH CAN MEASURE OXYGEN LEVELS BELOW THE SIMS LIMIT ARE ALSO BEING INVESTIGATED IN THIS STUDY. APPLICATIONS INCLUDE MATERIAL FOR GOVERNMENT SPECIFIED RADIATION HARDENED CMOS AND BIPOLARCIRCUITRY.