Your problem is not the KOH etch, it is stress in your nitride film. If there
are wrinkles there are compressive stress. The stress can be so high that the
membrane is destroyed when etched free.
Low-stress nitrides usually are silicon rich.

and you 4200 A nitride is actually quite thick. Normal thicknesses are 2000 A.

        -----Oprindelig meddelelse-----
        Fra: kishang [mailto:[email protected]]
        Sendt: ti 15-04-2003 01:18
        Til: [email protected]
        Cc:
        Emne: [mems-talk] KOH Etching



        Has anyone had significant experience etching nitride windows on silicon
using
        a KOH etch? I am trying to create very thin (4200 Angstroms) Silicon
Nitride
        windows, but my yield goes below 50%. My KOH bath is composed of KOH
pellets
        and water at 80 degrees C. Are there any ways to reduce wrinkles in
windows? I
        currently dip my wafers in cool DI water for 10 minutes and then dry
them in a
        120 degree oven with my pits opening upward (i.e. window surface
downward).

        Any help would be great. Thanks.

        -- Kishan Gupta
        UC Berkeley


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