Reactive ion etching method

Claim 1

A reactive ion etching method which comprises the steps of (a) mounting an object of etching comprising a 3-ply structure having a conductive material formed on a semiconductor body with a thin insulation layer interposed therebetween on a pair of mutually facing electrodes provided in a vacuum vessel on which high frequency power is impressed; (b) impressing said high frequency power between said mutually facing electrodes in an atmosphere of a reactive gas to etch said object body; (c) reducing gradually the cathode drop voltage arising in the proximity of the electrode being impressed with high frequency power, immediately before stopping the impression of high frequency power at the end of ion etching and thereby reducing the voltage impressed on the insulation layer included in said object of etching and caused by the reverse flow of an electric charge stored in the lower electrode to such an extent that a voltage impressed on the insulation layer included in the object of etching drops to a lower level than the breakdown voltage of said insulation layer at the stoppage of the impression of said high frequency power; and (d) thereafter stopping the impression of said high frequency voltage.