A MTJ stack is deposited on a bottom electrode. A metal hard mask is deposited on the MTJ stack and a dielectric mask is deposited on the metal hard mask. A photoresist pattern is formed on the dielectric mask, having a critical dimension of more than about 65 nm. The dielectric and metal hard masks are etched wherein the photoresist pattern is removed. The dielectric and metal hard masks are trimmed to reduce their critical dimension to 10-60 nm and to reduce sidewall surface roughness. The dielectric and metal hard masks and the MTJ stack are etched wherein the dielectric mask is removed and a MTJ device is formed having a small critical dimension of 10-60 nm, and having further reduced sidewall surface roughness.

A spin-transfer torque magneto-resistive random access memory (STT-MRAM) device is provided. The STT-MRAM device includes a substrate, a dielectric layer and a magnetic tunnel junction (MTJ) stack. The substrate includes a conductor and a landing pad. The MTJ stack includes a reference layer element, a free layer assembly and a barrier layer element. The reference layer element is lined with redeposited metal and is disposed on the landing pad within the dielectric layer. The free layer assembly includes a free layer element, a hard mask layer element disposed on the free layer element, redeposited metal lining sidewalls of the free and hard mask layer elements and dielectric material lining the redeposited metal. The barrier layer element is interposed between and has a same width as the reference layer element and the free layer assembly.

A stack of connecting metal vias is formed on a bottom electrode by repeating steps of depositing a conductive via layer, patterning and trimming the conductive via layer to form a sub 30 nm conductive via, encapsulating the conductive via with a dielectric layer, and exposing a top surface of the conductive via. A MTJ stack is deposited on the encapsulated via stack. A top electrode layer is deposited on the MTJ stack and patterned and trimmed to form a sub 60 nm hard mask. The MTJ stack is etched using the hard mask to form an MTJ device and over etched into the encapsulation layers but not into the bottom electrode wherein metal re-deposition material is formed on sidewalls of the encapsulation layers underlying the MTJ device and not on sidewalls of a barrier layer of the MTJ device.

A method for fabricating semiconductor device includes the steps of first forming a magnetic tunneling junction (MTJ) stack on a substrate, in which the MTJ stack includes a pinned layer on the substrate, a barrier layer on the pinned layer, and a free layer on the barrier layer. Next, part of the MTJ stack is removed, a first cap layer is formed on a sidewall of the MTJ stack, and the first cap layer and the MTJ stack are removed to form a first MTJ and a second MTJ.

A ferromagnetic layer is capped with a metallic oxide (or nitride) layer that provides a perpendicular-to-plane magnetic anisotropy to the layer. The surface of the ferromagnetic layer is treated with a plasma to prevent diffusion of oxygen (or nitrogen) into the layer interior. An exemplary metallic oxide layer is formed as a layer of metallic Mg that is plasma treated to reduce its grain size and enhance the diffusivity of oxygen into its interior. Then the plasma treated Mg layer is naturally oxidized and, optionally, is again plasma treated to reduce its thickness and remove the oxygen rich upper surface.

A method for fabricating a magnetic tunneling junction (MTJ) structure is described. A first dielectric layer is deposited on a bottom electrode and partially etched through to form a first via opening having straight sidewalls, then etched all the way through to the bottom electrode to form a second via opening having tapered sidewalls. A metal layer is deposited in the second via opening and planarized to the level of the first dielectric layer. The remaining first dielectric layer is removed leaving an electrode plug on the bottom electrode. MTJ stacks are deposited on the electrode plug and on the bottom electrode wherein the MTJ stacks are discontinuous. A second dielectric layer is deposited over the MTJ stacks and polished to expose a top surface of the MTJ stack on the electrode plug. A top electrode layer is deposited to complete the MTJ structure.

A method for fabricating semiconductor device includes the steps of: forming a magnetic tunneling junction (MTJ) stack on a substrate; forming a top electrode on the MTJ stack; performing a first patterning process to remove the MTJ stack along a first direction; and performing a second patterning process to remove the MTJ stack along a second direction to form MTJs on the substrate.

A method for forming a magnetic memory device is disclosed. At least one magnetic tunneling junction (MTJ) stack is formed on the substrate. The MTJ stack comprises a reference layer, a tunnel barrier layer and a free layer. A top electrode layer is formed on the MTJ stack. A patterned sacrificial layer is formed on the top electrode layer. The MTJ stack is then subjected to a MTJ patterning process in a high-density plasma chemical vapor deposition (HDPCVD) chamber, thereby sputtering off the MTJ stack not covered by the patterned sacrificial layer. During the MTJ patterning process, sidewalls of layers or sub-layers of the MTJ stack are simultaneously passivated in the HDPCVD chamber by depositing a sidewall protection layer.

A method for etching a magnetic tunneling junction (MTJ) structure is described. A MTJ stack is deposited on a bottom electrode wherein the MTJ stack comprises at least a pinned layer, a barrier layer on the pinned layer, and a free layer on the barrier layer, A top electrode layer is deposited on the MTJ stack. A hard mask is deposited on the top electrode layer. The top electrode layer and hard mask are etched. Thereafter, the MTJ stack not covered by the hard mask is etched, stopping at or within the pinned layer. Thereafter, an encapsulation layer is deposited over the partially etched MTJ stack and etched away on horizontal surfaces leaving a self-aligned hard mask on sidewalls of the partially etched MTJ stack. Finally, the remaining MTJ stack not covered by hard mask and self-aligned hard mask is etched to complete the MTJ structure.

A magnetoresistive sensor includes a magnetic reference layer. The magnetic reference layer includes a permanent closed flux magnetization pattern of a predetermined rotational direction. Furthermore, the magnetoresistive sensor includes a magnetic free layer. The magnetic free layer has a total lateral area that is smaller than a total lateral area of the magnetic reference layer. A centroid of the magnetic free layer is laterally displaced with respect to a centroid of the magnetic reference layer.