Novel Free Layer Structure in Magnetic Random Access Memory (MRAM) for Mo or W Perpendicular Magnetic Anisotropy (PMA) Enhancing Layer

A perpendicularly magnetized magnetic tunnel junction (p-MTJ), comprising:

• (a) a reference layer (RL) with a fixed magnetization oriented in a direction perpendicular to a surface thereof;
• (b) a tunnel barrier layer comprised of one or more metal oxides formed between a first surface of a free layer and the reference layer;
• (c) a Hk enhancing layer comprised of W, Mo, or alloys thereof and adjoining a second surface of the free layer that is opposite to the first surface wherein the Hk enhancing layer induces perpendicular magnetic anisotropy (PMA) at an interface with the second surface;
• and
• (d) the free layer (FL) with a trilayer configuration (FL1/FL2/FL3) comprised of at least Co, Fe, and B in a total composition that is FexCoyBz where x is 66-80, y is 5-9, z is 15-28, and x+y+z=100, and with a magnetization oriented perpendicular to the first and second surfaces thereof, wherein the FL magnetization may be switched from a direction parallel to the RL direction to an anti-parallel direction to the RL magnetization, the FL comprises;
• (1) a first layer (FL1) that is FeB and which contacts the tunnel barrier layer;
• (2) a second (middle) layer (FL2) that is FeCoB, and wherein FL2 has a higher Co content than FL1 and FL3;
• and
• (3) a third layer (FL3) that is Fe or FeB and which adjoins the Hk enhancing layer, and wherein FL3 has a higher Fe content than FL2.

A method of forming a perpendicular magnetized magnetic tunnel junction (p-MTJ) comprised of a reference layer (RL) with a fixed magnetization oriented perpendicular to a surface thereof, a free layer with a magnetization that is parallel or anti-parallel to the RL magnetization, and a tunnel barrier layer between the reference layer and free layer, comprising:

• (a) providing a stack of layers having an uppermost layer that is a tunnel barrier layer and wherein the tunnel barrier layer is formed on the RL;
• (b) depositing a free layer on the tunnel barrier layer wherein the free layer comprises at least Fe, Co, and B in a composition that is FexCoyBz where x is 66-80, y is 5-9, z is 15-28, and x+y+z=100, and wherein the free layer is formed by a process comprising;
• (1) depositing a first layer (FL1) that is FeB on the tunnel barrier layer;
• (2) depositing a second layer (FL2) that is FeCoB on FL1 wherein FL2 has a higher Co content than FL1;
• and
• (3) depositing a third layer (FL3) that is Fe or FeB on FL2 wherein FL3 has a higher Fe content than FL2;
• (c) depositing a Hk enhancing layer that is W, Mo, a W alloy, or a Mo alloy on FL3 to give a p-MTJ stack of layers having a RL/tunnel barrier/FL/Hk enhancing layer configuration;
• and
• (d) performing an annealing step at a temperature >380° C.

A method of forming a perpendicular magnetized magnetic tunnel junction (p-MTJ) comprised of a reference layer (RL) with a fixed magnetization oriented perpendicular to a surface thereof, a free layer with a magnetization that is parallel or anti-parallel to the RL magnetization, and a tunnel barrier layer between the reference layer and free layer, comprising:

• (a) providing a Hk enhancing layer that is W, Mo, a W alloy, or Mo alloy;
• (b) depositing a free layer with a FL3/FL2/FL1 trilayer configuration on the Hk enhancing layer wherein the free layer comprises at least Co, Fe, and B in a total composition that is FexCoyBz in which x is 66-80, y is 5-9, z is 15-28, and x+y+z=100, and wherein the free layer is formed by a process comprising;
• (1) depositing layer FL3 that is Fe or FeB on the Hk enhancing layer wherein FL3 has a higher Fe content than in FL2;
• (2) depositing layer FL2 that is FeCoB on FL3 wherein FL2 has a higher Co content than in FL1;
• and
• (3) depositing layer FL1 that is FeB on FL2;
• (c) sequentially forming a tunnel barrier layer and the RL on FL1;
• and
• (d) performing an annealing step at a temperature >380° C.

A method of forming a perpendicular magnetized magnetic tunnel junction (p-MTJ) wherein a stack of layers has a Hk enhancing layer/free layer (FL) or FL/Hk enhancing layer configuration and where a tunnel barrier layer is formed between the FL and a reference layer (RL);

• comprising:
• (a) providing the stack having the Hk enhancing layer/FL or FL/Hk enhancing layer configuration where the Hk enhancing layer is W, Mo, a W alloy, or a Mo alloy, and wherein the FL has a magnetization that is perpendicular to a surface thereof and is switchable to a direction that is parallel or anti-parallel to a fixed reference layer magnetization, and wherein the FL is comprised of at least Fe, Co, and B in a composition that is FexCoyBz in which x is 66-80, y is 5-9, z is 15-28, and x+y+z=100;
• and
• (b) performing an annealing step at a temperature >380° C.