| 摘要 |
PROBLEM TO BE SOLVED: To provide a corona discharge gun which includes a bias type needle electrode, a bias type focusing ring electrode and a bias type masking electrode, which are arranged coaxially; and which can suitably measure a thickness of a very thin insulating layer on a semiconductor substrate accurately. SOLUTION: The corona discharge gun includes a bias type needle electrode 13 which can form an ion source having a predetermined polarity at its tip end. The gun also includes a bias type focusing ring electrode 11 and a bias type masking electrode 12 having a disc formed with a hole in its center. The ring electrode 11, disc and needle electrode 13 are coaxially arranged as insulated from each other and supported thereby. The ring electrode 11 is positioned between the needle and masking electrodes 13 and 12. Further, as an example, the ring and masking electrodes 11 and 12 are biased by a voltage having the same polarity as that of ions. |
