Etching of Silicon - Electrochemistry of Silicon and Its Oxide - page 333

Surface roughness varies with etching time and thus the mount of material
removed. Roughness increases with etching time for initially micro smooth surfaces
but may decrease for initially rough surfaces. 434,458,557,1002 Figures 7.52 and 7.53 show
that roughness increases with time on the polished front side (initial roughness 2.5 nm)
but decreases with time on the back side (initial roughness 300nm). 1000 Figure 7.54
shows the roughness of the three principal surfaces as a function of etching time. 1002
The roughness of the (110) plane increases with time whereas that of the (111) and
(100) planes remains relatively constant. Similar results are found for the (100)
surface. 557 Etching of the saw-damaged zone of silicon wafers in solutions
results in a reduction of roughness from about to about In KOH solu-
tions as soon as the duration of etching exceeds a critical time, about 15min, charac-
teristic pits or hillocks develop on the etching surface. 672,673