| 摘要 |
PURPOSE:To perform a simple, accurate feedback to variations in an ion beam current, by fixing sample potential, controlling only a potential difference between a plasma chamber and an ion drawing electrode, and holding the beam current to the specified value. CONSTITUTION:Electric potential 32 of a plasma chamber is determined by output voltage 27 of an iron accelerating high-tension power source 27 and another output voltage 35 of an ion drawing high-tension power source 35, while ion drawing voltage 39 is determined by the output voltage 35 of the ion drawing high-tension power source 23 and output voltage 37 of a controlling high-tension power source 29. Here, when an ion beam current value 34 is varied, the output voltage 37 of the power source 29 is controlled, making the current value constant. At the time of this control, since ground potential in the plasma chamber is always invariable, kinetic energy of an ion beam to be reached to a substrate is constant, and a potential difference between the plasma chamber and mass spectrometric magnetic pressure is also invariable, so that it is unnecessary to change the excitation of an analytic electromagnet. That is to say, the current value of the ion beam is controllable only adjusting output of a controlling high-tension source.
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