Hi Jed,

I'm wondering if you have heated the KOH. For an etch rate of about 80 µm/h
you'll need to heat the etchant to about 70-80 °C.

Regards

Fabio Tagliareni


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Auftrag von Jed Ley
Gesendet: Mittwoch, 18. Februar 2004 04:00
An: [email protected]
Betreff: [mems-talk] <100> Si Etch rates in KOH?


Hi.

I am trying to etch 100um deep V-pits in on 1-0-0 Si wafers.
I am etching n-type (phosphorous doped) wafers of resistivity
7.5 - 12.5 ohm-cm.  I'm using a 10-weight % aqueous solution of
KOH (i.e. 50g KOH pellets + 450 mL D.I. water) , and a ~1um-thick
thermal oxide as an etch mask.  The etch pits are defined by 120
um square holes in the oxide.  I am getting an etch rate of only
 ~10 um/ hr for <100> Si.   From the literature I have read (Seidel,
et al.  J. Electrochem. Soc. V. 137, No.11, Nov 1990), I expected an etch
rate of ~80 um/hr.  I am getting an etch rate for the oxide
that is close to what I expected (800-900 Angstrom/hr).   Can
anybody suggest to me what I'm doing wrong?   Any suggestion will
be greatly appreciated.

Thanks,

Jed Ley
Colorado School of Mines
Golden, Colorado
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