Patent ID: 8921232

Claim:
A taper-etching method for taper-etching a layer to be etched, the layer to be etched being made of a dielectric material and having a top surface, the taper-etching method comprising the steps of: forming an etching mask on the top surface of the layer to be etched, the etching mask having an opening; and taper-etching a portion of the layer to be etched, the portion being exposed from the opening, by reactive ion etching so that a groove having two wall faces that intersect at a predetermined angle is formed in the layer to be etched, wherein: the step of taper-etching employs an etching gas containing a first gas contributing to the etching of the layer to be etched and a second gas contributing to deposition of a sidewall protective film, and changes, during the step, a ratio of a flow rate of the second gas to a flow rate of the first gas so that the ratio increases; the layer to be etched is made of SiO 2 or SiON; the etching mask contains elemental Al; and the second gas contains N 2 .