Because of their unique physical
and electric properties and chemical
stability, the etching kinetics of III–V semiconductors is
of great significance in the fabrication of functional microdevices.
However, the produced oxides result in a surface passivation and hinder
the etching progress. Taking into account the passivation and depassivation
of the insoluble oxides, we investigated the etching kinetics of III–V
semiconductors (i.e., n-GaAs, n-InP, and n-GaP) by scanning electrochemical
microscopy (SECM) as well as the finite element method. By considering
the coupling effect of the mass transport process and surface reactions,
a dynamic deformed geometry module was adopted to determine both the
etching rate and passivation rate individually and further correlate
the kinetic parameters to the topography of the etching pits. The
results show that the etching process will be slowed or will even
cease with increasing kinetic rate of surface passivation. On the
basis of the component analysis of the passivation layer, ligands
are suggested as additives to increase the solubility of the cations
and to avoid the formation of metal oxides. By tuning the relative
rates of the etching and passivation processes, the etching pit will
be deepened with little increase of the diameter. SECM is proved powerful
in the kinetic investigation of a complex etching system coupled with
surface processes. This model allows the prediction of the etching
resolution and removal rate with consideration of the passivation
effect, which is valuable for the electrochemical microfabrication
on III–V semiconductor wafers.
The physicochemical principle of photocorrosion and photoetching is the internal photoelectric effect of semiconductors. However, the kinetic investigation of interfacial charge transfer induced by this phenomenon has been seldom reported due to its microdomain bipolarity. GaAs is a direct band gap semiconductor with high saturated electron velocity and high electron mobility. Once the photogenerated electrons on a n-type GaAs surface are removed by Fe 3+ in the solution, it will dissolve due to the residual positive holes; i.e., the photoetching process will occur. By employing scanning electrochemical microscopy (SECM), the photoetching rates of n-type GaAs are obtained about ∼10 −4 mol•m −2 •s −1 with Fe 3+ cation as electron acceptor. The rate-determining step (rds) is proved as the charge separation process at low illuminating intensity, and the mass transfer of Fe 3+ in the solution at high illuminating intensity. Moreover, the photoetching process is developed as a controllable micromachining method for semiconductor materials.
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