Patent ID: 7141992

Claim:
A method for measuring an iron (Fe) concentration in a silicon wafer by utilizing a surface photovoltage, comprising: a calibration step; and a measurement step, wherein the calibration step comprises the steps of: (A) a measurement section measures the minority carrier diffusion length prior to a calibration activation at a measuring point on a calibration silicon wafer; (B) an activation section conducts a calibration activation on said calibration silicon wafer; (C) said measurement section measures the minority carrier diffusion length at said measuring point of said calibration silicon wafer after said calibration activation and the iron concentration is measured in a manner which does not use the surface photovoltage, when the iron concentration is unknown; (D) a calculation section calculates a dependent relationship between the minority carrier diffusion length in Step (C) relative to at least one factor selected from a group including a period of elapsed time, a dopant concentration and a temperature by inputting the minority carrier diffusion length in Step (A) and the minority carrier diffusion length in Step (C); (E) said measurement section measures a minority carrier diffusion length at a measuring point on a measurement silicon wafer before a measurement activation; (F) said activation section conducts the measurement activation on said measurement silicon wafer; (G) said measurement section measures the minority carrier diffusion length at said measuring point on the measurement silicon wafer after the measurement activation; and (H) said calculation section calculates the metal impurity concentration by inputting the minority carrier diffusion length measured in Step (E), the minority carrier diffusion length measured in Step (G), and said dependent relationship such that the iron concentration is calculated.