Magnetoresistance effect device and a preform therefor
A method of production of a magnetoresistance effect device is able to prevent or minimize a drop in the MR ratio and maintain the high performance of the magnetoresistance effect device even if forming an oxide layer as a surface-most layer constituting a protective layer by the oxidation process inevitably included in the process of production of microprocessing by dry etching performed in a vacuum. Two mask layers used for microprocessing are doubly piled up. This method of production of a magnetoresistivity effect device including a magnetic multilayer film including at least two magnetic layers includes a step of providing under a first mask material that is a nonorganic material a second mask material able to react with other atoms to form a conductive substance, and a device made according to the method.
1. A CPP (current perpendicular to the plane) magnetoresistance effect device comprising:
a substrate;
pinned magnetization layers positioned over the substrate;
a barrier layer formed on the pinned magnetization layers, which barrier layer is an insulation layer;
a free magnetization layer formed on the barrier layer; and
a protective layer formed on the free magnetization layer;
wherein the protective layer comprises a metal layer; and a metal oxide layer positioned on the metal layer and made by oxidation of the metal layer so that the metal oxide layer covers a top surface and a side surface of the metal layer, whose resistivity is 6×10 −6 Ωm or less, and the protective layer is a surface-most layer that is adapted to function as a top electrode for the magnetoresistance effect device.
2. The magnetoresistance effective device as set forth in claim 1 , wherein the metal oxide layer is an oxide of Ru.
3. The magnetoresistance effective device as set forth in claim 1 , wherein a bottom electrode is positioned below the free magnetization layer, and the device is able to pass an electric current between the bottom electrode and the top electrode.
4. The magnetoresistance effective device as set forth in claim 1 , wherein thickness of the protective layer is 20-30 Å.