MRAM Shift-Adjustment Layer Segmentation for Etching

The shift-adjustment layer is segmented into multiple thin layers (e.g., CoFeB and Ru layers) rather than using a single thick layer. This segmentation allows the total thickness to be achieved through multiple deposition steps, making the processing manageable even for miniaturized MTJ elements where a large total thickness is required for sufficient shift cancellation.

The patent transitions from a single-layer thickness parameter to a multi-layer stack configuration. By using alternating magnetic and non-magnetic layers, the solution moves from controlling a single dimensional parameter (thickness) to controlling multiple parameters (layer thicknesses, materials, and sequences), thereby resolving the processing difficulty while achieving the required effective thickness.

The thick shift-adjustment layer is divided into multiple thin alternating layers of magnetic material (e.g., CoFeB) and non-magnetic material (e.g., Ru). This segmentation enables each thin layer to be deposited and processed separately, making ion beam etching and other processing steps feasible while maintaining the total thickness required for effective stray field suppression.

The patent uses composite material structures with alternating magnetic (CoFeB) and non-magnetic (Ru) layers. This composite structure provides both the magnetic properties needed for shift cancellation and the structural characteristics that facilitate processing, as the non-magnetic layers act as etch stop layers and the thin magnetic layers can be precisely controlled.