A method of etching silicon oxide from a narrow trench and a wide trench (or open area) is described which allows the etch in the wide trench to progress further than the etch in the narrow trench. The method includes two dry etch cycles. The first dry etch cycle involves a low intensity or abbreviated sublimation step which leaves solid residue in the narrow trench. The remaining solid residue inhibits etch progress in the narrow trench during the second dry etch cycle allowing the etch in the wide trench to overtake the etch in the narrow trench.