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SiO 2 Etching Characteristics of Perfluoro-2-butene (l-C 4 F 8 ) and Hexafluoropropene (l-C 3 F 6 )

SiO 2 Etching Characteristics of Perfluoro-2-butene (l-C 4 F 8 ) and Hexafluoropropene (l-C 3 F 6 ). Abstract authors: C.H. Shin and M.Nakamura et al. Environmentally Benign Etching Technology Laboratory Association of Super-advanced Electronics Technologies, Japan Presented by Zhenwei Hou.

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SiO 2 Etching Characteristics of Perfluoro-2-butene (l-C 4 F 8 ) and Hexafluoropropene (l-C 3 F 6 )

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  1. SiO2 Etching Characteristics of Perfluoro-2-butene (l-C4F8) and Hexafluoropropene (l-C3F6) Abstract authors: C.H. Shin and M.Nakamura et al. Environmentally Benign Etching Technology Laboratory Association of Super-advanced Electronics Technologies, Japan Presented by Zhenwei Hou

  2. Reactant Gases in the Dry Etching Processes • Perfluorocarbon compounds (PFCs) are commonly used as a reactant gas in the dry etching processes. • For example: etching of oxide and nitride. • Octafluorocyclobutane (c-C4F8) is widely used as an etching gas instead of conventional CF4. • High C/F ratio of c-C4F8 induces the formation of C:F film on Si or SiN, which acts as an etching barrier, thus improving the selectivity.

  3. Environmental Warning: Greenhouse Gases ! • PFCs are powerful greenhouse gases. • PFCs are not ozone depleting substances, and therefore are not covered under the Montreal Protocol. • PFCs, however, are high global warming potential (GMP) gases. Source: http://www.earthshots.com/ Thumbnails/WholeEarth.htm

  4. Environment-Friendly Semiconductor Manufacturing • The reduction of PFC emissions has become a major issue in the development of semiconductor processes. • The two candidates: l-C4F8 and l-C3F6 are intended to replace c-C4F8, due to their low GWP and short lifetime. Octafluorocyclobutane (c-C4F8) Perfluoro-2-butene (l-C4F8) Hexafluoropropene (l-C3F6)

  5. Selection of Alternatives of PFCs • much lower GWP • short life time • toxicity

  6. Duel-frequency Plasma Reactor • Etchant :l-C4F8/O2/Ar and l-C3F6/O2/Ar • Pressure: 25 mtorr • Frequency • the top electrode: 60 MHz • the bottom electrode: 1.6 MHz • Temperature: 70°C

  7. System Analysis • Electroquadrupole mass spectrometer (EQP): Mass/Energy analyser for analysis of ions and neutrals in plasma processes. • Fourier Transform Infrared Spectroscopy (FTIR) : (organic) functional group analysis technique that can use the unique collection of absorption bands to confirm the identity of a pure compound or to detect the presence of specific impurities. • Quadrupole Mass Spectrometer (QMS): microthermometric techniques that can be use to determine less than 10 um in size composition.

  8. Contact Holes after the Partial Etching with l-C3F6 and l-C4F8-based Chemistries • Open size of contact hole: 0.3 um • Oxide film: 2um-thickness PE-TEOS oxide • Photoresist selectivity of l-C3F6 is about 20% higher than that of l-C4F8 • Oxide etching rate of l-C4F8 is increases 7% in comparison with l-C3F6

  9. Contact Holes after Etching with l-C3F6 and l-C4F8-based Chemistries • 30% over etching of contact holes • The etched profile is almost same for both gas chemistries

  10. Etch Rate and Selectivity for Contact Hole Etching

  11. Conclusion • The oxide etching characteristics of linear chain gases will be more useful than of c-C4F8 as device structures become smaller.

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