Chemistry Reference
In-Depth Information
For a convex square or rectangular structure, etch undercutting occurs at corners
which can be a problem in etching of deep structures.
54,245
The amount of corner under-
cutting is proportional to the depth of the etching feature as shown in Fig. 7.46.
54
Such
clear proportionality is due to the definite etch rate of the particular fast etch planes in
the etchant. Because the fast etchant planes are etchant-specific, surfaces that define the
etched corner may be different depending on the etchant. The planes are found to be
{331} in
They are {411} planes in pure KOH solu-
