1. KOH etching. Design a window on the mask for etching through holes on silicon wafer. The wafer is (100) oriented and 500 μm thick. The bottom opening after etching should be 50 μm by 80 μm. Find the dimensions of the window on the mask. 2. Repeat the problem 1, if the etch rate of {111} surfaces is 1/100 that of {100} surfaces, define the window dimensions on the mask. 3. The mask silicon nitride layer on silicon is shown in the following figure. Draw the top and cross-sectional view of the self-limiting etched profile. Assume the etch rate in <111> direction is zero. mask <110> 75° μm 100 μm <110> 30 μm 30 μm mask <100> mask mask Silicon A-A* Cross-section 200 μm 4. Develop a process flow chart for fabrication of pressure sensor shown below. For each step, select appropriate tools and describe the process. Pt electrodes SiO2 Substrate (can be bond at the end)