Etch A Sketch The Perfect Modern Toy

2. (10 points) A 0.5 um layer of silicon dioxide on a silicon substrate needs to be etched down to the silicon. Assume that the oxide etch recipe has etch rate of 0.3 um per minute. There is a ± 5% variation in the oxide thickness and a ± 5% variation in the oxide etch arte.(a) How much overetch is required (in %) in order to ensure that all oxide is etched?(b) What selectivity of the oxide etch rate to the silicon etch rate is required so that a maximum of 5 nm of silicon is etched?

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