Stress relief technique of removing oxide from surface of

Abstract

Creation of structural defects in a trench-isolated island structure is obviated by protecting the bottom of the trench pattern during etching of the hard mask surface oxide. A layer of photoresist is non-selectively deposited on the hard mask oxide layer and in the trench pattern, so that the photoresist buffer layer fills the trench pattern and is formed atop the hard mask oxide layer. The deposited photoresist is controllably flood-irradiated, so as to expose the irradiated photoresist down to a depth in the trench pattern that is at or somewhat deeper than the surface of the hard mask insulating material. The exposed photoresist is then developed, so as to remove the irradiated depth portion of the photoresist lying atop the hard mask oxide layer and partially extending into the trench, thus exposing the hard mask oxide layer, but leaving a sufficient quantity of unexposed photoresist in the trench pattern that provides a surface barrier for the underlying oxide. A wet etch is then non-selectively applied to the hard mask oxide layer, so as to completely remove the hard mask oxide layer from the top surface of the semiconductor islands. Because of the barrier in the bottom of the trench pattern, the oxide etch does not attack the underlying oxide. The undeveloped photoresist is then stripped. Thereafter, when the sidewalls of the trench pattern are oxidized and the trench pattern is filled with material, lattice dislocations are not formed in the islands.