MTJ Storage Element Fabrication with Protective Layers

A protective covering layer comprising an inner layer and an outer layer is introduced as an intermediary between the etching environment and the MTJ stack. The inner layer (e.g., silicon nitride or silicon oxide) directly protects the sidewalls of the free layer and upper portions of the barrier layer, while the outer layer provides additional protection against redeposition of etching byproducts. This mediator structure enables conventional etching processes to proceed without damaging the critical MTJ components.

The protective covering layer is formed on the MTJ stack before the etching process begins. This preliminary protective action ensures that when etching byproducts are redeposited during the subsequent etching step, they are deposited onto the protective covering layer rather than directly onto the free layer sidewalls and barrier layer upper portions, thereby preventing damage to these critical structures.

The protective covering layer is designed with specific material parameter choices that balance protection effectiveness with process simplicity. The inner layer uses materials such as silicon nitride or silicon oxide that can be deposited using standard semiconductor fabrication techniques. The thickness parameters are optimized to provide sufficient protection while minimizing the number of additional process steps required.

The protective covering layer is structured as a composite of an inner layer and an outer layer, where each layer serves a specific protective function. The inner layer provides direct protection to the MTJ stack sidewalls, while the outer layer protects against redeposition of etching byproducts. This composite structure achieves superior protection compared to a single-layer approach, while the materials selected are compatible with existing fabrication processes.

An adjusting layer is introduced as an intermediary between the free layer and the hardmask layer. This adjusting layer serves as a protective barrier during oxygen ashing processes, preventing direct exposure of the free layer to oxygen plasma that would cause magnetic stability degradation. The adjusting layer is positioned strategically to provide protection during critical fabrication steps.

The adjusting layer is deposited on the free layer before the hardmask layer is applied, establishing preliminary protection against oxygen ashing damage. This preliminary protective measure ensures that when oxygen-based plasma processing is subsequently performed during fabrication, the free layer's magnetic properties are preserved.