Chemistry Reference
In-Depth Information
silicon etching and cleaning. In recent years a significant amount of work has been done
to measure the corrosion current in various cleaning solutions due to its importance in
silicon technology.
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Corrosion current generally increases in the presence of oxidizing species such
as dissolved oxygen or dissolved metal ions, particularly those of noble elements which
have low hydrogen reduction overpotentials. Increasing surface carrier concentration,
both electrons and holes (e.g., due to background lighting), or rate of charge transfer
across the interface (e.g., due to surface states) also tends to increase corrosion current.
Since the stability of silicon strongly depends on the stability of its oxide, factors that
inhibit the formation of oxide and promote the dissolution of oxide tend to increase the
corrosion current. Table 2.16 lists some corrosion currents determined in various
silicon/electrolyte systems.
As can be seen in Table 2.16, corrosion current is a very sensitive quantity due
to its exponential dependence on potential. Unlike corrosion potential, corrosion current
is not directly measurable but rather is a quantity derived from other measurable para-
meters such as polarization resistance.
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The value of a current density is thus
not only situation specific, but also has a poor certainty.
