Chemistry Reference
In-Depth Information
region; (10) the partially oxidized silicon atoms are responsible for the large interface
charge and their further reduction by hydrogen ions is responsible for the nonelectro-
chemical part of silicon dissolution. These characteristics of anodic passive films play
important roles in a diverse range of electrode phenomena observed on silicon elec-
trodes such as electropolishing, porous silicon formation, current oscillation, etch stop,
and so on.
Figure 5.44 shows that in KOH solutions the oxide film thickness as a function
of applied potential has three regions: (1) an oxide ~20 Å thick is formed at the poten-
tial just above
(2) from
to 5 V the growth rate is relatively slow, about 6.8 Å/V;
378
and (3) at higher potentials it is higher, about 42 Å/V.
A similar growth pattern
is observed in NH
4
OH solutions.
139
The thickness of anodic oxide in acidic fluoride
