Memory system having thermally stable perpendicular magneto tunnel junction (MTJ) and a method of manufacturing same

A spin-transfer torque magnetic random access memory (STTMRAM) element comprising:

• a free layer including:
• a first and a second free sub-layers having a variable magnetization direction substantially perpendicular to layer planes thereof;
• and
• a first perpendicular enhancement layer (PEL) interposed between the first and second free sub-layers;
• a barrier layer formed adjacent to the free layer;
• and
• a reference layer formed adjacent to the barrier layer opposite the free layer, the reference layer including:
• a first and a second reference sub-layers having a first invariable magnetization direction;
• a second PEL interposed between the first and second reference sub-layers;
• an antiferromagnetic coupling layer formed adjacent to the second reference sub-layer opposite the second PEL;
• and
• a third reference sub-layer formed adjacent to the antiferromagnetic coupling layer opposite the second reference sub-layer and having a second invariable magnetization direction that is substantially perpendicular to a layer plane of the third reference sub-layer and opposite to the first invariable magnetization direction,
• wherein the first reference sub-layer comprises cobalt, iron, and boron, and
• wherein the first and second free sub-layers each comprise cobalt, iron, and boron.

A spin-transfer torque magnetic random access memory (STTMRAM) element comprising:

• a free layer including:
• a first and a second CoFeB free sub-layers having a variable magnetization direction substantially perpendicular to layer planes thereof;
• and
• a first perpendicular enhancement layer (PEL) made of an elemental metal of molybdenum or tungsten interposed between the first and second CoFeB free sub-layers;
• a barrier layer formed adjacent to the free layer;
• and
• a reference layer formed adjacent to the barrier layer opposite the free layer, the reference layer including:
• a first and a second reference sub-layers having a first invariable magnetization direction substantially perpendicular to layer planes thereof;
• a second PEL interposed between the first and second reference sub-layers;
• an antiferromagnetic coupling layer formed adjacent to the second reference sub-layer opposite the second PEL;
• and
• a third reference sub-layer formed adjacent to the antiferromagnetic coupling layer opposite the second reference sub-layer and having a second invariable magnetization direction that is substantially perpendicular to a layer plane of the third reference sub-layer and opposite to the first invariable magnetization direction,
• wherein the first reference sub-layer comprises cobalt, iron, and boron.