A
calibration curve determination method characterized by: a first step (S11) of providing a plurality of
wafer groups, each of which includes a plurality of
silicon wafers having the same
oxygen concentration and different carbon concentrations, the
wafer groups differing from one another in the
oxygen concentration of the
silicon wafers enclosed therein; a second step (S12) of irradiating a plurality of areas of each of the
silicon wafers enclosed in each of the
wafer groups with
electron beams at different
irradiation doses; a third step (S13) of obtaining, by a
photoluminescence method, an
intensity ratio of a first
luminescence intensity derived from silicon to a second
luminescence intensity derived from carbon.for each of the areas irradiated with the
electron beams; a fourth step (S14) of classifying a plurality of data, each containing the
oxygen concentration, the carbon concentration, the
irradiation dose, and the
intensity ratio, in a plurality of data sets, wherein the data contained in each of the data sets have the same
irradiation dose and the same oxygen concentration, and the data sets differ from each other in at least one of the irradiation
dose and the oxygen concentration, and determining a first
calibration curve representing a relationship between the
intensity ratio and the carbon concentration for each of the data sets to obtain a
calibration curve group; a fifth step (S15) of selecting one or more combinations from the calibration curve group, wherein each of the one or more combinations represents a pair of the first calibration curves,which are equal to each other in irradiation dose and differ from each other in oxygen concentration, wherein the one or more combinations differ from each other in irradiation dose, and obtaining a difference between the curves of the paired first calibration curves in a double logarithmic plot for each of the one or more combination(s); and a sixth step (S16) which includes selecting a specific combination from the one or more combination(s), wherein the specific combination has a smaller difference between the curves within a predetermined range than the difference between the curves of one or more other combinations, determining the irradiation dose common to the first calibration curves of the specific combination as the
electron beam irradiation dose for measurement,and determining a second calibration curve using all data included in the pair or pairs of datasets to determine the pair or pairs of first calibration curves connected in at least the specific combination, wherein the second calibration curve represents a relationship between the intensity ratio and the carbon concentration and can be used for measurement in combination with the
electron beam irradiation dose.