| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for measuring impurity concentration, whereby the impurity concentration can be measured quantitatively and an impurity concentration distribution of a minute region can be measured. SOLUTION: A sample is measured by an STM with a sample voltage of 2.0 V in a constant current mode, where a tunnel current flowing to a probe 11 is 0.2 nA. Then the probe 11 is moved in x and y directions to a measurement position. While a control circuit 15a is turned off, the probe 11 is brought close to the sample 10 by a constant quantity, and current-voltage characteristics are measured. Thereafter, the control circuit 15a is turned on to measure the sample by the STM in the constant current mode. The presence/absence of contact traces is checked. When contact traces are not present, the probe 11 is set farther closer to the sample 10, and current-voltage characteristics are measured. When the contact traces are present, a position where each of the current-voltage characteristics is measured is derived, by setting the position of the probe 11 at the time as the origin, and the impurity concentration is determined with reference to a preliminarily prepared reference table.
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