Chemistry Reference
In-Depth Information
species, which shows a concentration peak at a pH of about 6. According to Fukidome
et al
.,
260
the etch rate in HF is determined by the competing reactions of Si with HF,
and the concentration of which depends on pH. The concentration of surface
Si-F bonds has a peak at a pH of about 6.4. The low etch rate in the low-pH region is
due to the large coverage of SiH bonds resulting from reaction with HF, which has a
high concentration at low pH. On the other hand, the low etch rate in the high-pH region
is attributed to the decrease of In
solutions, the etch rate decreases with
increasing HF at a constant
concentration and it increases with increasing
468
Figure 7.4 shows the etch rate of
at a constant HF concentration.
solution as a function of pH.
904
Etch rate depends on the time of immersion. Figure 7.5 shows that the etch rate
at 1 min
n
-Si(111) in 10M
of
p-
Si in concentrated HF decreases with immersion time from about
at 10 days.
715
The relatively higher rate at the beginning is attrib-
uted to the etching of native oxide and the lower etch rate at longer times is due to the
to about
