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Start with a lightly boron-doped p-type Si wafer. Define an implantation opening for the pMOS region using an oxide/nitride implantation mask, then implant donor ions, commonly phosphorus, at energies and doses giving the required well depth and concentration. An anneal activates donors and repairs damage; thermal drive-in can deepen and smooth the well profile. The donor concentration must exceed the original acceptor concentration in the well. Retain p-type material outside it for the nMOS device. Form a later n+ well contact to tie the n-well to the positive supply; the p+ substrate contact ties the substrate to ground. Diffusion from a donor source is an alternative to ion implantation and drive-in.

The conspicuous approximately vertical streaks are focused ion beam milling curtaining: different sputtering rates beneath the rough, compositionally varying cap and interfaces leave stripes of different foil thickness. The uneven lower foil edge, contrast gradient and locally thinned regions are also consistent with nonuniform milling; redeposition can add material to other regions.

A dark gap or pull-out may have been enlarged or created during milling, so its original dimensions cannot be inferred securely from this one image. ion implantation and an amorphized surface layer are additional possible focused ion beam milling effects, but they are not independently demonstrated by these intensity variations. A lower-energy final polish, improved protective cap and examination of another lamella could test the preparation contribution.

Diffuse a donor such as phosphorus into the textured p-type surface, then control the thermal drive-in to form the shallow n-type emitter. A phosphorus-containing vapour source can supply the donor over the exposed area. Diffusion and activation create an n-on-p p-n junction; remove the phosphorus-rich surface glass and isolate the rear and wafer edges as required to avoid shunts.

An alternative is ion implantation followed by an activation and damage-repair anneal. The diffusion route is particularly convenient for large-area coverage of a textured wafer. The indicated roughly $1\mu \mathrm{m}$ layer is a depth target for process control, not an instruction to grow an undoped film and assume that it becomes n-type.