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1.5 µm deep Pt etch/ 2 kB

3 µm deep Au etch/ 3 kB IBE schematic/ 8 kB
Noble Metal IBE: Pt, Au...

Noble metals as Au, Pt, Ag etc (as well as Ni or NiCr for example) can only be etched by physical sputter processes. This can be done in parallel plate systems for thin films/ long etch times.

The standard technology for these process is "Ion Beam Etching", also called "Ion Beam Milling". The substrates can be tilted and rotate during the etch process in order to avoid/ reduce redeposition of sputtered material at the etch walls. In the Ionfab 300 Plus the wafer can be cooled by "Helium backside cooling" allowing high rate processes in a Cassette to Cassette system using Photoresist as the etch mask.

 
  • Au, Ag:  50 - 200 nm/ min

  • Selectivity to PR: 1.5 - 5 : 1 (to Al or Ti>20 : 1)

  • Pt, Pd:  20 - 100 nm/ min

  • anisotropic profile, no "redeposition"

  • uniformity over 4" (with 15 cm source) or
    6" (with 38 cm source): ± 5 %

The SEM's show a 3 µm deep Au etch (right SEM) and a 1.5 µm deep Pt etch (left SEM), both with a Photoresist mask.

link    YBCO IBE link   Au, Pt, Ni sputter etching in "RIE"
link    Sputteretch rates link   Angle dependence of sputteretch rates