| 摘要 |
PURPOSE:To contrive the prolongation of the lifetime of a cathode by a method wherein the cathode of lanthanum hexaboride which radiates thermal electrons to generate reactive gas ions is stably operated in the atmosphere of an inert gas. CONSTITUTION:For example, Ar gas is introduced inside a cathode cover 8, and the reactive gas is introduced into an ion source chamber 1. Thereafter a positive high bias voltage of several hundred V is impressed on an electron lead- out electrode 10, and a negative one of several hundred V on an accelerating electrode 5. Next, when the thermal electrons are radiated by heating the LaB6 cathode 9, the Ar gas inside the cover 8 is activated and then comes to the state of plasma of isolation into Ar ions and electrons. The reactive gas in the chamber 1 is activated by the electrons in the Ar plasma. The positive ions are led out through a window by the negative high bias voltage impressed on the electrode 5, and perform etching by irradiating the film to be etched formed on the main surface of an Si wafer 6. The cathode 9 is then protected by the inert gas, and besides the heating temperature is low. |
