Chemistry Reference
In-Depth Information
Diffusion plays an important role in the etching of silicon in EDP.
206
A trace amount of
chemical agents such as diazine, pyrazine, and quinone changes the etch rate and the
difference in the etch rates between the crystal planes.
386
The etch rate changes signif-
icantly when exposed to air due to the effect of dissolved oxygen. Also, insoluble
residues and rough raindrop-like patterns tend to form at low temperatures and with
aged solutions.
342,350
Residue formation occurs with certain compositions even at high
temperatures. Etch rate in EPD is independent of illumination.
386
p-n
junctions have
no effect on the etch rate.
398
The effect of potential is shown in Fig. 7.25; the etch stops at the passivation
potential and decreases with cathodic polarization for both
n
-Si and
p
-Si.
112,697
The etch
rate dependence on potential is rather different from that in KOH, where the
p-
etch
rate varies only slightly with cathodic polarization (Fig. 7.15). Also, the etch rates at
Si
