HORIZONTAL GROWTH OF SILICON SHEET CRYSTALS VIA EDGE-SUPPORTED PULLING (ESP) FROM A MELT CONTAINED IN A COLD CRUCIBLE

THE PROGRAM WILL EXPLORE THE FEASIBILITY OF GROWING SILICON SHEET CRYSTALS HORIZONTALLY USING THE EDGE-SUPPORTED PULLING(ESP) PROCESS FROM SILICON MELTS CONTAINED IN AN RF HEATED CRUCIBLE. THEORETICAL EVALUATION OF THE BASIC HORIZONTAL RIBBON GROWTH (HRG) PROCESS HAVE SHOWN QUITE CONCLUSIVELY THE ENORMOUS POTENTIAL OF THIS CRYSTAL GROWTH METHOD; I.E., IT SHOULD BE POSSIBLE TO PRODUCE LARGE, FLAT SHEET CRYSTALS OF SILICON AT EXTREMELY HIGH GROWTH RATES. TO DATE, HOWEVER, THE POTENTIAL OF THE HRG PROCESS HAS NOT BEEN FULLYDEMONSTRATED IN A PRACTICAL SENSE. PROBLEMS INVOLVING CONTROL OF MELT/SHEET TEMPERATURE AND MELT LEVEL HAVE NOT BEEN RESOLVED AND THE OVERRIDING DIFFICULTY, I.E., THE CRUCIBLE WALL, REMAINS A SEEMINGLY IMPENETRABLE BARRIER TO HORIZONTAL CRYSTAL GROWTH. RECENT WORK AT CERES HAS SHOWN THAT IT IS POSSIBLE TO CONFINE LARGE, HIGH PURITY SILICON MELTS IN A COLD CRUCIBLE WHILE MAINTAINING THE LIQUID SURFACE WELL OVER 1 CM. ABOVE THE RIM OF THE CONTAINER WITH A HIGH DEGREE OF STABILITY. MOREOVER, SINCE THE SOLID FEED MATERIAL IS INTRODUCED CONTINUOUSLY IN THE BOTTOM OF THE COLD CRUCIBLE, PRECISE CONTROL OF THE MELT LEVEL CAN BE MAINTAINED DURING CRYSTAL GROWTH. THE VERTICAL EDGE SUPPORTED PULLING (ESP) PROCESS PROVIDES EXCEPTIONALLY STABLE SHEET GROWTH CONDITIONS. HOWEVER, THE SHEET GROWTH RATES ACHIEVED TO DATE ARE SEVERELY RESTRICTED BY THE RATE OF HEAT DISSIPATION FROM THE NARROW SHEET/MELT INTERFACE. MOREOVER, SINCE THE FILAMENTS IN THE ESP PROCESS PASS THROUGH HOLES IN THE BOTTOM OF THE MELT CONTAINER, SHALLOW MELT LEVELS MUST BE USED AND MELT REPLENISHMENT DURING GROWTH HAS YET TO BE ACHIEVED. THIS PROGRAM WILL ENDEAVOR TO INTEGRATE THE UNIQUE OPERATIONAL FEATURES OF THE COLD CRUCIBLE WITH THE EQUALLY UNIQUE ATTRIBUTES OF THE ESP PROCESS IN ORDER TO DEMONSTRATE THE FEASIBILITY OF THE HORIZONTAL EDGE-SUPPORTED PULLING (HESP) METHOD FOR THE PRODUCTION OF SILICON CRYSTALS.