Chapter 28, Problem 30QTP

To determine

A chlorine-based polysilicon etching process displays a polysilicon-to-resist selectivity of $5:1$ and a polysilicon-to oxide selectivity of $60:1$ . Estimate the amount of resist and exposed oxide will be consumed in etching $3500$ of poly silicon. Determine the poly silicon-to-oxide selectivity have to be in order to reduce the loss to only $40\stackrel{\text{0}}{\text{A}}$ of exposed oxide.