AVS 47th International Symposium
    Photonics Tuesday Sessions
       Session PH-TuP

Paper PH-TuP6
Etching of Optical Coating Oxides in Fluorine and Chlorine Plasmas

Tuesday, October 3, 2000, 5:30 pm, Room Exhibit Hall C & D

Session: Poster Session
Presenter: W.B. Song, University of Minnesota
Authors: W.B. Song, University of Minnesota
W. Liu, University of Minnesota
J.J. Talghader, University of Minnesota
Correspondent: Click to Email
With the increasing use of micro-optical components in optoelectronics and MEMS, it is becoming increasingly important to understand the behavior of traditional optical materials in the microfabrication environment. For this purpose, we studied the etching of optical coating oxides in a variety of fluorine and chlorine plasmas. The oxides used in this study are Al@sub 2@O@sub 3@, HfO@sub 2@, Nb@sub 2@O@sub 5@, SiO@sub 2@, Ta@sub 2@O@sub 5@, TiO@sub 2@, Y@sub 2@O@sub 3@, and ZrO@sub 2@. These coatings are transparent from the near IR to UV and have a broad range of refractive indices. Using the well-known etching chemistry of SiO@sub 2@ as a guide, we attempt to correlate the volatility of the etch products of these oxides to the observed etching behavior in CF@sub 4@, SF@sub 6@, Cl@sub 2@, and their derivatives such as CF@sub 4@+O@sub 2@, etc. The results show that the volatility predicts general etch reactions with good accuracy, but is less successful in predicting relative etch rates. For example, our results show that Nb@sub 2@O@sub 5@, Ta@sub 2@O@sub 5@, TiO@sub 2@ and SiO@sub 2@ are etched in fluorine plasmas, while Al@sub 2@O@sub 3@, HfO@sub 2@, Y@sub 2@O@sub 3@, and ZrO@sub 2@ are not. All of the etched oxides have fluorine compounds with melting or sublimating temperatures less than 300°C. Increasing the substrate temperature to 340°C does not affect the behavior of the unattacked oxides. In chlorine plasmas, all of the oxides show some nonzero etch rate, which also matches with published volatility data. Finally, we present the selectivity of the oxides based on the obtained results.