VERY LOW DEFECT SIMOX FOR ANALOG DEVICES WITH NEUTRON TOLERANCE

METHODS OF FORMING VIRTUALLY DEFECT-FREE SIMOX WAFERS (INCLUDING THICK EPITAXIAL SI LAYERS) FOR APPLICATION TO "TOTALLY RADIATION HARD" ANALOG INTEGRATED CIRCUITS WILL BE DEVELOPED. THE VERY THIN DEVICES REQUIRED FOR NEUTRON RADIATION HARDENED CIRCUITS POSE EVEN MORE STRINGENT SI QUALITY REQUIREMENTS THAN DO STANDARD ANALOG SUBSTRATE MATERIALS. PROGRAM EMPHASIS WILL BE ON PROVIDING SIMOX WAFERS TO A DESIGNATED RADIATION HARD ANALOG DEVICE FABRICATOR WHO WILL BUILD ANALOG CIRCUITS FOR TEST AND EVALUATION IN PERTINENT NEUTRON ENVIRONMENTS. SPIRE HAS DEVELOPED TWO METHODS OF REDUCING DISLOCATION DENSITY. THE FIRST PREVENTS FORMATION OF DISLOCATIONS, USING A MULTIPLE LOW DOSE IMPLANTATION AND HIGH TEMPERATURE ANNEALING PROCESS INSTEAD OF THE STANDARD SINGLE HIGH DOSE IMPLANTATION AND HIGH TEMPERATURE ANNEAL. MULTIPLE LOW DOSE IMPLANTATION REDUCES DISLOCATION DENSITY BY THREE TO FIVE ORDERS OF MAGNITUDE. THE SECOND METHOD REDUCES THE DENSITY OF ALREADY FORMED DISLOCATIONS BY IMPLANTATION OF GE AND SUBSEQUENT SOLID PHASE EPITAXY REGROWTH; THIS DECREASES DISLOCATIONS AT THE SI SURFACE OF STANDARD SIMOX WAFERS BY TWO TO THREE ORDERS OF MAGNITUDE. WORK AT SPIRE HAS ALSO RESULTED IN THE DEVELOPMENT OF A PROCESS TO GROW HIGH QUALITY EPITAXIAL SI ON THE SI TOP LAYER OF SIMOX WAFERS.