The mechanism of reactive sputtering
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The reactive sputtering of tantalum in mixed argon/oxygen atmospheres at a total pressure of 3.0×10−4 torr has been investigated by means of measurements on deposition and growth rates, density, electrical properties and electron diffraction. The main controlling factor on all of the parameters was found to be the partial pressure of oxygen.
The deposition rate was determined by the partial pressure of oxygen and assumed one of two values — either that associated with a clean tantalum target or that characteristic of an oxidised target. In the former region the oxygen content of the sputtered film was mainly dependent on the partial pressure of oxygen in the sputtering atmosphere and could range from zero to 100%. In the latter region, the films were always oxidised, but were deposited at a rate which was a fifth of that of the oxidised films sputtered under the former conditions.
It is concluded that there is a critical oxygen pressure, below which tantalum metal is sputtered and undergoes reaction at the substrate, and above which tantalum oxide is sputtered from an oxide surface as the result of reaction at the target.
KeywordsPartial Pressure Oxygen Content Electron Diffraction Oxidise Film Deposition Rate
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