High retention storage layer using ultra-low RA MgO process in perpendicular magnetic tunnel junctions for MRAM devices
A method for manufacturing a magnetic random access memory element having increased retention and low resistance area product (RA). A MgO layer is deposited to contact a magnetic free layer of the memory element. The MgO layer is deposited in a sputter deposition chamber using a DC power and a Mg target to deposit Mg. The deposition of Mg is periodically stopped and oxygen introduced into the deposition chamber. This process is repeated a desired number of times, resulting in a multi-layer structure. The resulting MgO layer provides excellent interfacial perpendicular magnetic anisotropy to the magnetic free layer while also having a low RA.
1. A method for manufacturing a magnetic randomaccess memory element, the method comprising:
forming a magnetic tunnel junction (MTJ) that includes a magnetic reference layer, a magnetic free layer over the magnetic reference layer in an element height direction, and a thin, non-magnetic, electrically-insulating magnetic barrier layer positioned between the reference layer and the free layer;
forming a capping layer comprising multiple homogeneous layers of MgO, to cover the magnetic tunnel junction, the multiple layers of MgO being formed through alternating DC sputtering and oxidation; and
controlling one or more of the following parameters to maintain a thickness of the capping layer over 1 nanometer and an area resistance of less than 1.5Ωμm 2 : deposition time; oxygen flowrate; Mg thickness; and number of multi-layers.
2. The method as in claim 1 , wherein the oxidation comprises introducing oxygen into a sputter deposition chamber.
3. The method as in claim 1 , wherein the DC sputtering comprises depositing Mg from a Mg target in a deposition chamber using DC power.
4. The method as in claim 1 wherein the MgO is deposited after the magnetic free layer.
5. The method as in claim 1 , further comprising depositing a non-magnetic barrier layer.
6. The method as in claim 5 , wherein the non-magnetic barrier layer comprises MgO.
7. The method as in claim 5 , wherein the non-magnetic barrier layer is deposited before the magnetic free layer and the MgO layer is deposited after the magnetic free layer.