Patent ID: 8303780

Claim:
A method for forming a dry etching mask, comprising: sequentially forming a plurality of aluminum oxide films on a material to be dry etched such that a laminated film comprising the aluminum oxide films is formed to increase an etching rate with respect to reactive ion etching toward a lower layer of the aluminum oxide films; forming, on the laminated film of said plurality of aluminum oxide films, a first mask that has etching resistance with respect to said reactive ion etching; and applying reactive ion etching upon the laminated film with said first mask such that the laminated film is formed into a second mask, wherein the second mask has a bottom width in contact with the material which comes close to a top width in contact with the first mask, and the second mask has side walls which rise substantially perpendicular with respect to a surface of the material from a bottom side of the second mask, the plurality of aluminum oxide films provides different etching rates in respective layers of the aluminum oxide films, and the aluminum oxide films are formed by sputtering in which a bias voltage is set within a range of from 20 to 180 V for each of the aluminum oxide films, and the bias voltage is varied by 80V between adjacent films of the aluminum oxide films.