Patent ID: 7301160

Claim:
A method of producing a beam of ions of a desired species for implantation into a substrate, using: an arc chamber having electrodes with exposed surfaces of a material which reacts with oxygen to form an electrically non conducting oxide layer; the desired species being one which is derived from predetermined oxygen containing source gas molecules in a source gas fed into the arc chamber; an arc being generated between the electrodes in the arc chamber to create a plasma in which ions of said desired species are formed from the source gas molecules, said plasma containing oxygen ions; and ions being extracted from the arc chamber and filtered to provide a beam of said ions of said desired species directed at the substrate; wherein said method includes the step of feeding into the arc chamber, simultaneously with said source gas molecules displacement gas molecules containing fluorine and not containing oxygen so that said material of the electrode surfaces reacts with fluorine from the displacement gas molecules, displacing oxygen, to reduce formation of said oxide layer.