VERFAHREN ZUR ELIMINIERUNG VON ÄTZSPERREHINTERSCHNEIDUNGEN

Two methods for wet etch removing an etch stop layer without leaving an undesired undercut are disclosed. In the first method, a reactive ion etch is stopped on an etch stop layer. The exposed etch stop is wet etch removed, leaving an undesirable undercut. The undercut is filled by chemical vapor deposition of a fill material. The filler is then etched to leave a smooth aperture without undercuts. This last etch may be a sputter etch followed by a plasma etch. In the second method, a reactive ion etch is stopped on an etch stop layer as in the first method. Sacrificial sidewalls are then formed within the aperture. The exposed etch stop layer is then removed by wet etching, the positioning of the sidewalls serving to prevent undercutting of the etch stop layer. Finally, the sacrificial sidewalls are etched.