Problem $1$

A silicon etching process produces a trench that is $\backslash (3\backslash$mu $\backslash$mathrm$\{$~m$\}\backslash )$ deep and has an undercut of $\backslash (0\mathrm{.}5\backslash$mu $\backslash$mathrm$\{$~m$\}\backslash )$ on each side. Calculate the anisotropy of the etch process, where anisotropy A is defined as:

A $=\backslash (1-(\backslash )$ Lateral Etch Rate $\backslash (/\backslash )$ Vertical Etch Rate $\backslash ()\backslash )$

If the etch process took $20$ minutes, first calculate the lateral etch rate and vertical etch rate $($in $\backslash (\backslash$mu $\backslash$mathrm$\{$m$\}/\backslash$mathrm$\{$min$\}\backslash ))$ and then determine the anisotropy.