$2$m CMOS N$-$Well Process Flow Example.

The starting substrate material is $(100)$ p$-$type silicon, $10$ ohm$-$cm doping concentration.

The initial masking oxidation for the n$-$well is a $50$ minute $1000$C oxidation in pyrolytic steam.

The N$-$well region is patterned into this oxide using photolithography and etched using either a dry plasma etch or a wet chemical etch in buffered hydrofluoric acid.

A thin N$-$well implant screening oxide is grown for $50$ minutes at $1000$C in dry oxygen.

An N$-$well phosphorus implant dose of $5$x$1012$cm$-2$ is performed at $150$keV.

The N$-$well drive$-$in is performed at $1150$C for $320$ minutes.

All of the oxides are stripped using buffered hydrofluoric acid.

A$)$ Define a predeposition process for phosphorus diffusion that will give the same total dose as the phosphorus implant as defined in step # $5.(20$ points$)$

B$)$ How deep with the N$-$well junction be after the drive$-$in from step $6$ is performed? $(10$ points$)$