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hw2hint - Fundamentals of Micromachining BIOEN 6421 EL EN...

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Fundamentals of Micromachining Homework 2 BIOEN 6421, EL EN 5221 & 6221, ME EN 5050 & 6050 2/23/10 Homework #2 Due Monday, March 01, 2010 1. You are using KOH etching to define a 200 μ m thru-hole in a 100 wafer. What should the dimensions on your mask be if you are using a: a) 400 μ m thick wafer b) 600 μ m wafer. What would be the dimensions of the thru-hole be if you used the mask intended for the 400 μ m thick wafer on the 600 μ m thick wafer? Pg 188 text 2. You are using KOH to etch ports in a 400 μ m thick wafer. What minimum thickness of SiO 2 is needed to provide a mask for KOH etching? If Si 3 N 4 etches at 1.5 Å/min using the same conditions, how thick would it need to be to serve as a mask? Assume conditions of 20% KOH at 60 C Etchrate Si=26.7 um/hr Etchrate SiO2= 50 nm/hr 3. If the shape drawn below was used as a mask for KOH etching, draw a top and side view of what the hole would look like if allowed to go until only 111 planes are exposed.

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