Method for fabricating magnetic tunneling junction element with a composite capping layer

A method for fabricating a magnetic tunneling junction (MTJ) element, comprising:

• providing a substrate;
• forming a reference layer on the substrate;
• forming a tunnel barrier layer on the reference layer;
• forming a free layer on the tunnel barrier layer;
• and forming a composite capping layer on the free layer, wherein the composite capping layer comprises an amorphous layer, a light-element sink layer, and a diffusion-stop layer;
• wherein the light-element sink layer is provided on the amorphous layer and the diffusion-stop layer is provided on the light-element sink layer,
• wherein the composite capping layer is in direct contact with the free layer and forms a first interface with the free layer, wherein the composite capping layer is in direct contact with a top electrode and forms a second interface with the top electrode, and wherein the top electrode is a ruthenium top electrode having a hexagonal close packed (hcp) crystalline structure, wherein the reference layer, the tunnel barrier layer, the free layer, and the composite capping layer constitute an MTJ stack, wherein the amorphous layer comprises a magnetic metal comprising CoFeB, FeB or CoB, and the light-element sink layer comprises Fe based alloy, and wherein the diffusion-stop layer comprises Mo, W or alloys thereof.