Keywords:silicon crystal, carbon concentration measurement, infrared absorption
It is shown that the carbon content reduction and sensitivity improvement work together. (1) In Tr & IC (and diode) period, carbon was origin of swirl defects in FZ and CZ Si. Carbon was reduced by (a) suppressing the CO formation and (b) promoting the removal by the gas flow. (2) When LSI period started, the “useful range” of the infrared measurement ASTM standard was 5x1015/cm3 at RT. (3) Around 1980, low pressure CZ furnace was introduced for the larger crystal. Dislocation introduction happened due to SiO2 particle drop. A cover over the melt was introduced to prevent it, which made the gas flow nearer to the melt surface. This problem was solved by some growers realizing below 1x1015/cm3. FTIR became popular and low temperature measurement drew attention. The ASTM standard was revised for such trends. The “detection limit of 5x1014/cm3” was introduced. (4) Around 2005 hybrid car opened the power device period. We realized the comparative sensitivity 1014/cm3. Synthetic reference sample by electron irradiation (down to 1x1013/cm3) made the detection limit limitless. These novel techniques were added to the existing standard for convenience.