Abstract
A practical trench depth measurement system for VLSI dynamic random access memory vertical capacitor cells has been developed with a Michelson interferometer. The system is composed of an optical head, a Michelson interferometer, and a host computer. A He–Ne laser is used to monitor a prism displacement in the interferometer and to perform the coherent averaging of interferograms. It is found that the accuracy of the measured values with the system is within ±0.1 μm in the 2–5-μm depth range. Both trench depth and reflection coefficient distributions of test wafer trenches are demonstrated by the system.
© 1989 Optical Society of America
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