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Anisotropic wet etching

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  Post Date: Dec 04,2009
  Expiry Date: Dec 04,2010
  Detailed Description: Cas No. :
Anisotropic wet etching
Some wet etchants etch crystalline
materials at very different rates
depending upon which crystal face
is exposed. In single-crystal
materials (e.g. silicon wafers),
this effect can allow very high
anisotropy, as shown in the figure.
Several anisotropic wet etchants
are available for silicon. For
instance, potassium hydroxide
(KOH) can achieve selectivity of
400 between <100> and <111>
planes. Another option is EDP (an
aqueous solution of ethylene
diamine and pyrocatechol), which
also displays high selectivity for
p-type doping. Neither of these
etchants may be used on wafers
that contain CMOS integrated
circuits. Both of them etch
aluminium, commonly used as a
metallization (wiring) material.
KOH introduces mobile potassium
ions into silicon dioxide, and EDP
is highly corrosive and
carcinogenic. Tetramethylammonium
hydroxide (TMAH) presents a safer
alternative, although it has even
worse selectivity between <100>
and <111> planes in silicon than
does EDP.



  Company: Suzhou CSE Semiconductor Equipment Technology Co., Ltd.         
  Contact: Amy Chang
  Tel: +86-18913168552
  Fax: +86-18913168552
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