Surface Coverage

Surface geometry affects the growth of films by shadowing the surfaces from the depositing flux of atoms. Steps, vias, and grooves are of particular importance, and in order to get conformal coverage over such surfaces, the deposition often must be done at an elevated temperature to increase surface mobility or by using backsputtering/redeposition. Off-normal incidence of the depositing flux makes conformal coverage more difficult. The ability of concurrent ion bombardment to improve step-coverage is of great interest in microelectronic fabrication. The improved coverage by concurrent ion bombardment is due to a number of factors, including:

• Forward sputtering (Ref 75)

• Gas scattering—randomizing of direction of adatom flux

• Backscattering of sputtered material

• Ionization and return of sputtered material

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