Characterization of polymer formation during SiO2 etching with different fluorocarbon gases (CHF3, CF4, C4F8)

Sang Yee Loong; H. P. Lee; Lap Hung Chan; Mei-Sheng Zhou; F. C. Loh; K. L. Tan

doi:10.1117/12.284614

27 August 1997 Characterization of polymer formation during SiO₂ etching with different fluorocarbon gases (CHF₃, CF₄, C₄F₈)

Sang Yee Loong, H. P. Lee, Lap Hung Chan, Mei-Sheng Zhou, F. C. Loh, K. L. Tan

Author Affiliations +

Proceedings Volume 3212, Microelectronic Device Technology; (1997) https://doi.org/10.1117/12.284614
Event: Microelectronic Manufacturing, 1997, Austin, TX, United States

Abstract

In this paper, the polymer composition generated by three different combinations of gas chemistries for oxide etch are studied and the effects of different O₂ plasma strip duration on polymer removal are also presented. The etch chemistries used were CHF₃/CF₄, CO/CF₄/CHF₃ and C₄F₈/CO/CHF₃ chemistry. From the x-ray photoelectron spectroscopy (XPS) C 1s spectra, five distinct peaks are identified which correspond to C-C, C-CF_x, CF, CF₂, and CF₃. The C/F ratio is found to be highest for polymer generated by the C₄F₈/CO/CHF₃ chemistry, about 0.8, whereas the C/F ratios for those by CHF₃/CF₄ and CO/CF₄/CHF₃ chemistries are about 0.6. Atomic force microscopy (AFM) images show that the polymer generated by the C₄F₈/CO/CHF₃ chemistry is much rougher than that by CHF₃/CF₄ and CO/CF₄/CHF₃ chemistries. The XPS spectra of C 1s also show a significant decrease in the intensity of the more fluorinated carbon peaks (CF₃ and CF₂) after O₂ plasma strip. The C/F ratios increased to about 1.4 to 1.8 after O₂ plasma strip. The spectra are similar for different O₂ strip times, indicating the decrease is independent of O₂ strip duration. From the AFM images, all the polymers formed by CHF₃/CF₄ and CO/CF₄/CHF₃ chemistries are rather smooth with no visible change after O₂ strip. However, the polymers generated by C₄F₈/CO/CHF₃ chemistry are flattened with increasing O₂ strip duration. The high energy ion bombardment of oxygen ions probably have flattened the rough polymer surface.

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Sang Yee Loong, H. P. Lee, Lap Hung Chan, Mei-Sheng Zhou, F. C. Loh, and K. L. Tan "Characterization of polymer formation during SiO₂ etching with different fluorocarbon gases (CHF₃, CF₄, C₄F₈)", Proc. SPIE 3212, Microelectronic Device Technology, (27 August 1997); https://doi.org/10.1117/12.284614

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