\begin{tabular}{|l|l}
\hline Q. 60 & \begin{tabular}{l}
A pure Silicon wafer is doped with Boron by exposing it to $\mathrm{B}_{2} \mathrm{O}_{3}$ vapour at an \\
elevated temperature. It takes 1000 seconds to reach a Boron concentration of \\
$10^{20}$ atoms $m^{-3}$ at a depth of $1 \mu \mathrm{m}$. The time taken to reach the same \\
concentration of Boron at a depth of $2 \mu \mathrm{m}$ is (in seconds): \\
off to nearest integer) \\
Given: Boron concentration on the wafer surface remains constant.
\end{tabular} \\
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\end{tabular}
