Patent ID: 7375034

Claim:
A method of recessing a trench to a target depth (D T ), the method comprising the steps of: providing a region on a wafer including a trench area including a trench and a field area tat is free of any trench, a material applied over the region so as to fill the trench in the trench area and form a step between the trench area and the field area; first etching the material until a surface of the wafer in the trench area is exposed; second etching the material until the surface of the wafer in the field area is exposed; measuring a height of the step (H S ); determining a target etch duration (t D ) for a third etching far recessing the trench to the target depth; and third etching the trench to the target depth (D T ) for a period approximately equal to the target etch duration (t D ).