BACKGROUND

Technical Field

The present invention relates to magnetic random access memory devices and apparatuses, and more particularly to increasing the magnetic exchange stiffness of material layers used in magnetic random access memory devices.

Description of the Related Art

Magnetic random access memory (MRAM) devices differ from conventional random access memory (RAM) in that data is stored through the use of magnetic elements as opposed to storing data through electric charges or current flows. In accordance with MRAM, two magnetic elements are separated by a barrier. In addition, one of the magnetic elements can be a permanent magnet set to a fixed polarity while the polarity of the other magnetic element is adaptable to store data. The different digital states (i.e. one or zero) can be differentiated by assessing whether the polarity of the two elements are the same or different. Data can be read by measuring the electrical resistance of the cell. For example, a transistor can switch a current through the cell such that charge carriers tunnel through the barrier in accordance with the tunnel magneto resistance effect. The resistance of the cell is dependent on the magnetic moments of the two elements. Writing data in an MRAM can be conducted using a variety of methods. Spin transfer torque (STT), which employs a spin polarized current, is one such method.

In accordance with STT, the spin-polarized current is altered as it passes through the adaptable magnetic element, thereby applying a torque to the magnetic element and changing its polarity. Further, there are multiple types of STT MRAM devices. For example, reference layers and free layers of in-plane STT MRAMs have magnetic moments that are parallel to the wafer plane. Alternatively, reference layers and free layers of Perpendicular Magnetic Anisotropy (PMA) STT MRAMs have magnetic moments that are perpendicular to the wafer plane.

SUMMARY

In one embodiment, a method is provided for forming a memory device that includes providing a free layer of an alloy of cobalt (Co), iron (Fe) and boron (B) overlying a reference layer. A metal layer comprising a boron (B) sink composition may be deposited atop the free layer. An anneal process diffuses boron (B) from the free layer to the metal layer comprising the boron sink composition. At least a portion of the metal layer including the boron (B) sink composition is removed. A metal oxide is formed atop the free layer, wherein the free layer comprises a crystalline cobalt and iron alloy and an interface between the metal oxide and free layer provides perpendicular magnetic anisotropy character.

In another embodiment, a method is provided for forming a memory device that includes providing a free layer of an alloy of cobalt (Co), iron (Fe) and boron (B) overlying a reference layer. A metal layer comprising a boron (B) sink composition may be deposited atop the free layer. An anneal process diffuses boron (B) from the free layer to the metal layer comprising the boron sink composition. The metal layer including the boron (B) sink composition is removed. An alloy layer of cobalt and iron is formed atop an exposed surface of the free layer. A metal oxide is formed by oxidation anneal atop the free layer. The free layer comprises a crystalline cobalt and iron alloy and an interface between the metal oxide and free layer provides perpendicular magnetic anisotropy character.

In another aspect, a memory device is provided that includes a magnesium oxide tunnel layer atop a reference layer, and a crystalline free layer comprised of cobalt and iron alloy that is substantially free of boron, wherein the crystalline free layer is substantially lattice matched to the magnesium oxide tunnel layer. A metal oxide layer may be present on the opposite surface of the crystalline free layer to provide an oxide interface on opposing surfaces of the crystalline free layer in order to generate perpendicular magnetic anisotropy character.

These and other features and advantages will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.

