JP2807719B

A method of stabilizing the operation of a liquid metal ion source in a focussed ion beam apparatus, the ion source being composed of a metal needle having a pointed downstream end and a lateral surface, a reservoir for supplying a liquid metal to the surface of the needle, a device for heating the metal, an extraction electrode having a small aperture disposed at a position opposite the metal needle for allowing an ion current to pass through the aperture, and a circuit for applying a voltage between the metal needle and the extraction electrode. According to the method the temperature of the liquid metal in the reservoir is normally maintained at a first value corresponding to a usual operating temperature value, and the temperature of the liquid metal is temporarily raised to a second value higher than the first value, by operation of the heating device, in order to maintain stable long term operation of the ion source. In addition, the extraction voltage may be temporarily raised together with or independently of the temperature raising operation.