Patent ID: 7767574

Claim:
A method of forming a micro metal bump comprising the steps of: forming a straight hole in a mask layer covering one side surface of a substrate on which a metal part is formed, wherein a prescribed position of the metal part is exposed in a bottom surface of the straight hole and the straight hole has an inner wall perpendicular to the one side surface of the substrate and a sharp top opening portion; providing cooling means on the other side surface of the substrate; placing the substrate and the cooling means in a vacuum; forming a tapered metal bump with a cross sectional area that is gradually reduced from a bottom part to a top part in contact with the metal part, on the exposed surface of the metal part, which is exposed in the bottom surface of the straight hole, by a gas deposition process, in which metal nanoparticles obtained by evaporating a metal are ejected from a nozzle together with a carrier gas so as to deposit the metal nanoparticles on the prescribed position, with cooling the substrate to a temperature lower than upper temperature limit of resin constituting the mask layer, by the cooling means, so as to retain a configuration of the straight hole, an inner diameter of the nozzle being larger relative to an inner diameter of said straight hole with the inner diameter of the straight hole being narrowed towards an ejection portion, said tapered metal bump having a predetermined height with opening parts of the straight hole being closed by a deposited layer formed on the mask layer without contacting the tapered metal bumps for depositing the metal nanoparticles in the straight hole; and removing the mask layer from the one side surface of the substrate so as to complete the tapered metal bump at the prescribed position of the metal part.