AVS 60th International Symposium and Exhibition
    Plasma Science and Technology Tuesday Sessions
       Session PS2-TuA

Paper PS2-TuA9
Reduction of Aspect Ratio Dependency in Silicon Trench Etch

Tuesday, October 29, 2013, 4:40 pm, Room 104 C

Session: Deep Etch Processes for Vias, Trenches and MEMS
Presenter: R.L. Bates, University of Texas at Dallas
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The etch rate of deep features in silicon, such as trenches and vias, can vary significantly with the changing aspect ratio of the feature. Developing a better understanding of the complex volumetric and surface chemistry as well as the etching mechanisms controlling the Aspect Ratio Dependent Etch-rate (ARDE) continues to present research opportunities. Recall that ARDE is generally characterized by small AR features etching at faster rates than large AR features. The main causes of ARDE include Knudsen transport of neutrals into and out of the features as well as ion loss to the walls due to angular spread in the velocity distribution function and differential charging of insulating microstructures [1]. This work focuses on using a continuous plasma process utilizing a gas mixture of SF6/C4F8/Ar to produce trenches of varying widths and depths. The experimental results were obtained using a Plasma-Therm Versaline processing system. Experiments were performed to show that the etch rate of low AR features can be reduced through the deposition of a passivation layer and thereby allow larger AR features to catch up. It is also possible to invert the ARDE in certain circumstances. We will present the insights we have gained into the ARDE process and the solution we have tested. [1] R. Gottscho & C. Jurgensen, J. Vac. Sci. Tech. B, 10, 2133, (1992). This research was supported through SRC Award: 2012-VJ-2261. The authors thank the staff of the UTD clean room (G. Pollack, S. Riekena, B. Albert) for their gracious assistance in processing and measuring these samples.