Document Type


Date of Award

Fall 1-31-2003

Degree Name

Master of Science in Materials Science and Engineering - (M.S.)


Committee for the Interdisciplinary Program in Materials Science and Engineering

First Advisor

Kenneth Rudolph Farmer

Second Advisor

Ken K. Chin

Third Advisor

Roumiana S. Petrova


A laser-based method for measuring feature thickness during the deep reactive ion etching process is investigated. Interference occurs between laser beam reflections from the mask surface, the mask/silicon interface, and the exposed silicon surface of a process wafer. Information from this interference signal allows the etch process to be characterized. Three methods are investigated: laser-on-SiO2, laser-on-photoresist, and laser-on-both SiO2 and silicon at a mask edge.

The measured data from these experiments are found to be in good agreement with theoretical calculations. Differences in reflected beam amplitude and interference fringe frequency represent well the differences SiO2 and photoresist have with each other regarding their etch rates, translucency, thickness and selectivity. In addition, the edge monitoring experiment provides a direct, simultaneous measure of both the silicon and mask etching.

This work has laid a foundation for the development of a real-time, in situ monitoring system in which the interference data is automatically analyzed, allowing the etching process to be computer-controlled.



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