Patent Number: 
Section: claims

1. A focused ion beam apparatus using a liquid metal ion source wherein:a liquid metal being used for said liquid metal ion source is concentrated in the vicinity of an aperture hole and forms a cover which does not expose an edge portion of the hole, said aperture hole is tapered on the side opposite to said liquid metal ion source so that an aperture hole diameter increases as it departs from said liquid metal ion source on the side opposite therein, and said aperture is a current limiting aperture disposed immediately beneath said liquid metal ion source. 2. A focused ion beam apparatus according to claim 1, wherein irregularities of a maximum roughness of 1 to 10 μm are formed at a portion which said liquid metal contacts with said aperture. 3. A focused ion beam apparatus according to claim 1, wherein the liquid metal on said aperture has a volume ranging from 5 mm3 to 17 mm3. 4. A focused ion beam apparatus according to claim 1, wherein said liquid metal is gallium and said aperture is tungsten. 5. A liquid metal ion source attachable to a focused ion beam apparatus, wherein:a liquid metal being used for said liquid metal ion source is concentrated in the vicinity of an aperture hole and forms a cover which does not expose an edge portion of the hole, said aperture hole is tapered on the side opposite to said liquid metal ion source so that an aperture hole diameter increases as it departs from said liquid metal ion source on the side opposite therein, and said aperture is a current limiting aperture disposed immediately beneath said liquid metal ion source. 6. A liquid metal ion source according to claim 5, wherein irregularities of a maximum roughness of 1 to 10 μm are formed at a portion which said liquid metal contacts with said aperture. 7. A liquid metal ion source according to claim 5, attachable to said focused ion beam apparatus, wherein the liquid metal on said aperture has a volume ranging from 5 mm3 to 17 mm3. 8. A liquid metal ion source according to claim 5, attachable to said focused ion beam apparatus, wherein said liquid metal is gallium and said aperture is tungsten.