A $\backslash (1\backslash$mu $\backslash$mathrm$\{$~m$\}\backslash$mathrm$\{$SiO$2\}\backslash )$ layer is deposited on a $(100)$ Si substrate, and it is to be patterned and released over a cavity to form a free$-$standing cantilever beam having length $\backslash (70\backslash$mu $\backslash$mathrm$\{$~m$\}\backslash )$ and width $\backslash (20\backslash$mu $\backslash$mathrm$\{$~m$\}\backslash ).$ If the beam is to have a clearance on all three free sides of $\backslash (10\backslash$mu $\backslash$mathrm$\{$~m$\}\backslash ),$ draw the mask used for this etch process. Is it an isotropic or anisotropic etch? What is the depth of the trench? Ignore any possible problems due to undercutting.

This time, it is aimed to deposit some metal contacts before making the KOH bulk etch. Two candidate metals are Aluminum and Chromium. Based on etch selectivity of KOH $,$ which one should be used as metal contacts.