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Abstract

A method for fabricating a magnetoresistive memory cell with improved roughness uniformity and reduced roughness amplitude of a selected layer of material in the magnetoresistive memory cell by smoothing at an atomic scale an interface surface of the selected layer is disclosed. The smoothing is accomplished by irradiating an interface surface of the selected layer with a collimated beam of gas cluster ions that are accelerated along a beam bath by predetermined acceleration voltage. The gas cluster ions bombard the interface surface and upon impact therewith, the gas cluster ions disintegrate in a direction that is substantially lateral to the beam path. As a result, the gas cluster ions laterally sputter the interface surface and remove one or more monolayers of material from the interface surface. Consequently, an initial surface roughness of the interface surface is reduced and homogenized (i.e. made uniform) to a final surface roughness. By atomic scale smoothing of a data layer or a reference layer that precedes a non-magnetic spacer layer, Nel coupling between the data layer and the reference layer can be reduced and uniformity of tunneling resistance among memory cells in an array can be improved. Smoothing by gas cluster ion bombardment can be used to replace a planarization process or to repair defects caused by the planarization process. Deposition of the layers of the memory cell and gas cluster ion smoothing of a selected one of those layers can be done insitu to reduce or eliminate contamination or surface reactions.

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