Most likely is that your HF in solution is nearly exhausted. The white
powder is SiOx.
Change new solution, use large container for larger volume of solution or
increase the HF concentration.
You can calculate the among of Si been converted to oxide and etched by HF.
When HF
is almost used out. The white powder starts to form on the surface.
Let me know your experimental result using these methods to verify my guess.
At 10:20 AM 1/3/02 -0500, you wrote:
>The parts are <100>, not <110>. The etch solution is 60% nitric, 10%
>acetic, 5% hydrofluoric, rest water. The temperature is 75-80 degrees C.
>The stains are visually detected with an eye loop or naked eye (we don't
>need to go to further magnification for our purposes). The stains are
>whitish, likely silicon oxide. We've run some SEM studies, revealing
>nothing but silicon and oxygen.
>
>George
>
>-----Original Message-----
>From: [email protected] [mailto:[email protected]] On
>Behalf Of [email protected]
>Sent: Wednesday, January 02, 2002 9:05 PM
>To: [email protected]
>Subject: [mems-talk] Re:etch Si(110) and Si(100) in KOH
>
>If you got poor results in etching (110) you either had too much water in
>your etch or your wafer was of axis by several degrees. What is your etch
>solution composed of and at what temperature are you etching at? An off
>axis
>wafer, which are sliced on purpose that way for diffusion control, will show
>what looks like a stair case of many steps. If the cause was too much water
>then you get pits and bumps and even lines. Let us know which problem you
>had and the solution is at hand.
>
>Campman
>_______________________________________________
>[email protected] mailing list: to unsubscribe or change your list
>options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk
>Hosted by the MEMS Exchange, providers of MEMS processing services.
>Visit us at http://www.mems-exchange.org/
>_______________________________________________
>[email protected] mailing list: to unsubscribe or change your list
>options, visit http://mail.mems-exchange.org/mailman/listinfo/mems-talk
>Hosted by the MEMS Exchange, providers of MEMS processing services.
>Visit us at http://www.mems-exchange.org/
Wen H. Ko,
Professor Emeritus. EECS Dept.
Phone: 1-216-368-2071
FAX: 1-216-368-5326
e mail: [email protected]
mailing address:
EECS Department/EDC,
CWR University
Cleveland, Ohio, 44106, USA
