US Patent 9553129 Magnetic tunnel junction stack alignment scheme

Device and methods of forming a device are disclosed. The method includes providing a substrate defined with a memory cell region. A first upper dielectric layer is provided over the substrate. The first upper dielectric layer includes a first upper interconnect level with one or more metal lines in the memory cell region. A second upper dielectric layer is provided over the first upper dielectric layer. The second upper dielectric layer includes a via plug coupled to the metal line of the first upper interconnect level. An alignment trench which extends from a top surface of the second upper dielectric layer to a portion of the second upper dielectric layer is formed. Various layers of a MTJ stack are formed over the second upper dielectric layer. Profile of the alignment trench is transferred to surfaces of the various layers of the MTJ stack to form a topography feature which serves as an alignment mark. The various layers of the MTJ stack are patterned to form a MTJ element using the alignment mark visible in top surface of the various layers of the MTJ stack to align the memory element to the underlying via plug.