Ryan-
There are several papers on this subject.

In general, a KOH etched surface improves in roughness as you increase the
concentration. Of course, this increases the etch rate of your mask as well.
Increasing the concentration also diminishes diffusion effects( When etching
deep cavities in low concentration etchants, the center of the cavity will etch
at a different rate than the edges). Using greater than 30% by wt. KOH with
water should give you a smooth surface.

Intentional or unintentional additives can affect the surface quality. The
additional of various alcohols will change the etch properties. In addition,
contaminates such as iron in the solution can affect the surface of the etch.




"Ryan D. Pooran"  on 03/02/2002 08:28:22 PM

Please respond to [email protected]


To:   [email protected]
cc:    (bcc: Dan W Chilcott/DELCO)

Subject:  [mems-talk] Smooth KOH etching



Good day all,
  Recently I did a KOH etching of Si to make a thin diaphragm to be used
as a pressure sensor. The diaphragm that was etched was very rough on
the backside. Does anyone know how I can etch Si so it gives an almost
perfect smooth surface?

Thank you.
Ryan

Ryan D. Pooran
Graduate Student
Microelectronics- Photonics Graduate Program
University of Arkansas
248 Physics Building
Fayetteville, AR
72701
Ph: 501-575-5596(O)
Ph: 501-575-4150(L)
Email: [email protected]
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