Patent ID: 7795045

Claim:
A method of manufacturing a semiconductor wafer having at least one device trench, the at least one device trench having a first depth position, the method comprising: (a) providing a semiconductor substrate having first and second main surfaces and a semiconductor material layer disposed on the first main surface of the semiconductor substrate, the semiconductor material layer having first and second main surfaces; (b) pre-determining an etch ratio by (i) forming, in a test wafer, at least one first trench having a first width and at least one second trench having a second width, the first and second widths being different, and (ii) measuring a first depth of the at least one first trench and a second depth of the at least one second trench to thereby calculate the etch ratio based on the first and second widths; (c) simultaneously forming in the semiconductor substrate (i) the at least one device trench from the first main surface of the semiconductor material layer, the at least one device trench having the first width, and (ii) at least one monitor trench from the first main surface of the semiconductor material layer; the at least one monitor trench having the second width, and (d) detecting with an optical profiler whether the at least one monitor trench extends to a second depth position, a ratio of the first depth position to the second depth position being generally equal to the etch ratio.