Method for fabricating a magnetoresistive element comprising discontinuous interconnect segments
The present disclosure concerns a method for fabricating a magnetoresistive element comprising a magnetic tunnel junction including a tunnel barrier layer, a first ferromagnetic layer and a second ferromagnetic layer; a writing current layer; and an interconnect layer configured for supplying the writing current to the writing current layer. A gap is provided in the interconnect layer such that the latter comprises two discontinuous interconnect segments extending along a layer plane and connecting the writing current layer in series. The method comprises: depositing the interconnect layer, writing current layer, second ferromagnetic layer, tunnel barrier layer and first ferromagnetic layer; forming the gap in the interconnect layer; filling the gap with the gap material; and forming the pillar by performing a single etch step until the interconnect layer, acting as a stop layer, is reached.
1. A method for fabricating a magnetoresistive element comprising a magnetic tunnel junction (MTJ) comprising a tunnel barrier layer sandwiched between a first ferromagnetic layer having a first magnetization and a second ferromagnetic layer having a second magnetization; a writing current layer extending in a layer plane substantially parallel to the layers the MTJ and contacting the second ferromagnetic layer, the writing current layer being configured for passing a writing current adapted for switching the second magnetization by a spin orbit torque interaction; and an interconnect layer configured for supplying the writing current to the writing current layer and in direct contact with the writing current layer; wherein the writing current layer has substantially the same lateral dimension in the layer plane than that of the MTJ such that the MTJ and the writing current layer form a pillar; and wherein a gap is provided in the interconnect layer such that the latter comprises two discontinuous interconnect segments extending along a layer plane and connecting the writing current layer in series;
the method comprising:
depositing the interconnect layer, writing current layer, second ferromagnetic layer, tunnel barrier layer and first ferromagnetic layer;
forming the gap in the interconnect layer;
filling the gap with the gap material;
forming the pillar by performing a single etch step until the interconnect layer, acting as a stop layer, is reached,
wherein filling the gap comprises depositing a gap layer comprising the gap material on top of the interconnect layer.
2. The method according to claim 1 , further comprising planarizing the gap layer such as to free the upper surface of the interconnect layer.
3. The method according to claim 1 , wherein the gap has a gap width between 0.9 and 0.1 the lateral dimension of the writing current layer.
4. The method according to claim 1 , wherein the pillar has a geometrically isotropic shape.
5. The method according to claim 1 , wherein the gap comprises a magnetic material having a bias magnetization configured to provide a magnetic bias field adapted to interact with the second magnetization such as to provide deterministically switching of the second magnetization when the writing current is passed.
6. The method according to claim 1 , wherein the interconnect layer comprises a ferromagnetic material having a bias magnetization providing a magnetic bias field adapted to interact with the second magnetization such as to provide deterministically switching of the second magnetization when the writing current is passed.
7. The method according to claim 1 , wherein the interconnect layer comprises an electrically conductive material such as Cu, W, Au, Ag, Fe, Pt, Al, Co, Ru, Mo, NiSi, carbon nano tubes, graphene or an alloy of these elements.
8. The method according to claim 1 , wherein the gap is formed by using lithographic and etching process.
9. The method according to claim 8 , wherein the single etch step is performed using a multi angle etch.
10. The method according to claim 1 , wherein the pillar has a geometrically anisotropic shape.
11. The method according to claim 10 , wherein a long axis of the pillar is parallel to the gap width, perpendicular to the gap width, or is oriented with an angle relative to the gap width.