PURPOSE: To eliminate the lack of uniformity on implantation and to prevent the electrification phenomenon on a wafer surface due to positive ion implantation by reducing the degree of vacuum in part of a space in which an ion beam travels than that in the surroundings.
CONSTITUTION: A chamber 7 in which an ion beam 5 travels and a chamber 3 at the end section are invariably keep a high vacuum, and N2 is introduced into a chamber 8 through a port 9. Since the chambers 8 and 7 are communicated, the degree of vacuum in the surroundings is not reduced by the operation of a pump 10, and the degree of vacuum can be reduced only in the chamber 8. When a positive ion beam 5 travelling through the chamber 7 enters the chamber 8, it collides with N2 to generate electrons from N2 molecules, the electrons neutralize the positive ion beam, and the implantation for a wafer 2 is performed in the chamber 3. The degree of vacuum is reduced only in the chamber 8, thus the scattering of the beam is small, and the reduction of the beam current reaching the wafer 2 is small. According to this constitution, there is no expansion due to the repulsion among positive ions, the uniformity of implantation is improved, and the electrification phenomenon can be prevented.
OKABE TAKASHI
WAKE SETSUO
MATSUDA SHINTARO
NAKAYAMA AKIO
MIYATA KAZUAKI
