Three-dimensional etch rate distribution of Si is necessary in analyzing th
e anisotropic etching of Si. As three-dimensional etch rate distribution ca
n be composed by a series of two-dimensional distributions, a novel method
is suggested in this paper for measuring the two-dimensional distributions
with simple tools and high efficiency. For example, vertical sidewalls of a
series of U-shaped trenches in (0mn) silicon wafers are first created by d
eep reactive ion etching (DRIE) technique. By measuring the etch rates in n
ormal directions of the vertical sidewalls, two-dimensional distributions o
f etch rate in (0mn) planes can be found. As the height of vertical sidewal
ls formed by DRIE can be very large, the planes of sidewall can withstand a
relatively long etch time before they are replaced by emerging slow etchin
g planes. No special measuring facilities but a conventional microscope is
needed for the measurement. Presented in this paper are etch rate distribut
ions in (001) and (0 (1) over bar 1) crystal planes in 40% KOH and 25% TMAH
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