Tapered Magnetic Memory Device Stray Field Suppression

The patent applies curvature by forming tapered side surfaces on the magnetic layers instead of flat surfaces. The storage layer has a first tapered side surface, and the reference layer has a second tapered side surface. This curved/tapered geometry reduces the volume of the magnetic layers and confines the stray magnetic field generation region, thereby improving write characteristics while maintaining manufacturing feasibility through ion beam etching processes.

The patent segments the magnetic layer structure by introducing intermediate nonmagnetic layers between the storage layer and reference layer. These nonmagnetic layers act as magnetic field shields and divide the magnetic structure into distinct functional segments. The segmentation allows better control over stray magnetic field propagation while maintaining a manageable layered structure that can be manufactured sequentially.

The tapered side surfaces reduce the effective volume of the magnetic layers compared to cylindrical or rectangular structures of the same top area. This curvature reduces the magnetic moment and consequently the stray magnetic field strength while preserving the large top area for sufficient signal strength. The ion beam etching process creates this tapered geometry that simultaneously achieves both objectives.

The patent introduces nonmagnetic intermediate layers between the storage layer and reference layer. These intermediary layers act as magnetic field shields that block and attenuate the stray magnetic field propagation from the reference layer to the storage layer. This allows the magnetic layers to maintain larger areas for signal strength while the intermediaries prevent harmful field interactions.

The patent replaces conventional photolithographic patterning and planar etching methods with ion beam etching to create the tapered structures. While ion beam etching is more complex than standard photolithography, it enables the formation of precise tapered geometries that cannot be achieved with conventional methods. The process substitution is justified by the significant improvement in write characteristics and reduction of write errors.

The patent changes the etching parameters by using ion beam etching with specific angles and energies to create tapered side surfaces. By controlling the ion beam incidence angle and etching conditions, the desired tapered geometry is achieved. This parameter change in the manufacturing process enables the formation of structures that reduce stray magnetic fields while maintaining manufacturing feasibility through process optimization.