Black silicon is formed under anisotropic etch conditions, and is probably
the result of particles or small spots of impurity deposited on the etched
surface.  These spots mask the etch, which results in spikes or "grass"
which absorb light, giving a black appearance.

I have found black silicon to occur in some etch systems during SF6/O2 etch
only when the temperature of the substrate was controlled, for example by
attaching to the electrode with vacuum grease.  In other systems it seems to
occur without the need to keep the substrate cool.

Henri Janson from the University of Twente has published several papers on
what he call the "Black Silicon Method".  Using this technique one can
develop a highly anisotropic, deep silicon etch, with no grass, in most any
RIE system .

References
H. Janson et al, J. Micromech. Microeng. 5 (1995) p.115-120
M, de Boer et al, Transducers '95 Eurosensors IX  p. 565-568
Legtenberg et. al J. Electrochem. Soc. vol. 142 No. 6, June '95 p. 2020-2027

Roger Shile

-
----- Original Message -----
From: "Isaac Wing Tak Chan" 
To: "General MEMS discussion" 
Sent: Tuesday, May 13, 2003 1:30 PM
Subject: [mems-talk] black silicon


> Dear members,
>
> Does anyone have background information of how black silicon can
> be formed in RIE system? In my case, see black silicon on silicon wafer
> after long (more than 10mins) CF4/H2 plasma exposure. The surface is also
> powdery with this black stuff. If you know anything about it or any good
> reference paper, would you please let me know? Thanks a lot.
>
>
> Yours sincerely,
>
> Isaac Chan
>
> Ph.D. Candidate
> Dept. Electrical & Computer Engineering
> University of Waterloo
> 200 University Ave. W
> Waterloo, Ontario, Canada
> N2L 3G1
> Tel: (519) 729-6409, ext. 6014
> Fax: (519) 746-6321
> [email protected]
> http://www.ece.uwaterloo.ca/~a-sidic
>
>
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