Task $2[20$ points$]$: The cross$-$section of a SOI wafer with a photoresist pattern on top is shown. The pattern will be etched by a plasma. You can assume that the etching is $\backslash (100\backslash \%\backslash )$ anisotropic; that the etching selectivity of silicon: $\backslash (\backslash$mathrm$\{$SiO$\}\_\{2\}\backslash )$ :photoresist $\backslash (=2$: $1$: $1\backslash )$; and that the etch rate of silicon is $\backslash (0\mathrm{.}1\backslash$mu $\backslash$mathrm$\{$~m$\}/\backslash$mathrm$\{$min$\}\backslash ).$ Draw cross$-$sections of the wafer after

a$)5$ minutes of etching;

b$)7$ minutes of etching.

Be sure to specify relevant angles and dimensions for each cross$-$section.

$***$ Please do not provide AI or Chatgpt answer. I know how to use AI tools. Please provide the solution in details and sketch. Thank you.