AVS 53rd International Symposium
    MEMS and NEMS Tuesday Sessions
       Session MN-TuA

Paper MN-TuA5
Borosilicate Glass Deep Etching in NLD Plasma by using Low GWP Gases

Tuesday, November 14, 2006, 3:20 pm, Room 2007

Session: Fabrication and Characterization of MEMS and NEMS
Presenter: Y. Morikawa, ULVAC Inc., Japan
Authors: Y. Morikawa, ULVAC Inc., Japan
T. Hayashi, ULVAC Inc., Japan
A. Kelly, ULVAC Inc., Japan
K. Fuwa, ULVAC Inc., Japan
K. Suu, ULVAC Inc., Japan
Correspondent: Click to Email
One of important etching technologies in MEMS device fabrication is a deep glass etching over 100 um. But the glass contains some elements that the etched products have no vapor pressure at low temperature. So etched surfaces generally show rough morphology, on which the reaction product residue of I to III group elements in periodic table is seen. The deep etching technologies for this glass were reported by X. Li, et al. and T. Ichiki. They used SF6 as an etching gas.@footnote 1,2@ However, it has not been reported that a low GWP gas was used for glass deep etching. So we first tried to etch at the pressure of 1 Pa by using C3F8 as a relatively low GWP gas, by using a NLD etching system. The result showed the rough surfaces. Therefore, we etched the glass at 0.4 Pa in order to eliminate the residue by sputtering and obtained smooth surfaces. Changing the etching gas to C3F7I(GWP < 1) , we also obtained similar smooth surfaces under the same etching condition. Furthermore, the thru hole etching from the top to bottom surfaces of the glass wafer with thickness of 1 mm was examined. This is very difficult because an extremely high selectivity to photo resist is required. Therefore, we examined to use a thin Si wafer with thickness of 50 um as the mask. The thin Si wafer was bonded on the glass by the anodic bonding method, and coated with photo resist (thickness of 50 um), and then patterned by photolithography. Finally, we obtained the etching sample whose structure was Si mask (50 um hole and thickness) / borosilicate glass (Corning 7740 ) with thickness of 1 mm, prepared after the thin Si etching by using a novel deep etching method.@footnote 3@ @FootnoteText@ @footnote 1@X. Li, et al : Sensors and Actuators A 87 (2001) 139. @footnote 2@T. Ichiki, et al : J. Vac. Sci. Technol. B 21 (5) 2188. @footnote 3@Y. Morikawa, et al : 51st AVS, MN-MoP5 (2004) Anaheim.