Using 20-25 wt% TMAH at 70-90°C has resulted in smooth surfaces in all
my experiments. But one very important thing to do before etching is
removing the native oxide. I use 1% HF for 3 minutes.

Adding ammonium persulfate usually makes the surface even smoother, but
this must be replenished after an hour or so.

If you still se hillocks when trying the above, then I think there must
be some impuities in your etch system (either the TMAH, the water or the
equipment).

Good luck

Knut Lian
Process Engineer
Wafer Fab Technology
SensoNor asa
PO Box 196, N-3192 Horten
Norway
http://www.sensonor.com/
Tel: +47 33 03 50 68
Fax: +47 33 03 51 05


-----Opprinnelig melding-----
Fra: 罗元 [mailto:[email protected]]
Sendt: 7. august 2001 20:01
Til: [email protected]
Emne: [mems-talk] TMAH

Dear Sirs:
    We want to etch a V-groove with TMAH.But our experiments showed
that the surface is very rough with many hilllocks. By add IPA or
(NH4)2S2O3, the surface is still rough.And the concentration of the
TMAH we used is 5%(wt)~22%(wt).
    Would someone kindly to tell us how to have a V-groove without
hilllocks by using TMAH?
    Thanks a lot.

    Best Regards!

                       Yours Sincerely:LuoYuan
                           Aug.8,2001


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