Magnetic sensor using giant magnetoresistive elements and methods for manufacturing the same

A method for manufacturing a magnetic sensor that comprises:

• a single substrate;
• a first giant magnetoresistive element disposed on the substrate and formed of a single-layer-pinned spin-valve film comprising a single-layer-pinned fixed magnetization layer including a pinning layer and a single ferromagnetic layer, a free layer whose magnetization direction changes in response to an external magnetic field, and a spacer layer made of a nonmagnetic conductive material, disposed between the ferromagnetic layer and the free layer, wherein the magnetization of the ferromagnetic layer is fixed in a first direction by the pinning layer, so that the ferromagnetic layer serves as a pinned layer;
• and a second giant magnetoresistive element disposed on the substrate so as to overlie or underlie the first giant magnetoresistive element, formed of a plural-layer-pinned spin-valve film comprising a plural-layer-pinned fixed magnetization layer including a first ferromagnetic layer, an exchange coupling layer adjoining the first ferromagnetic layer, a second ferromagnetic layer adjoining the exchange coupling layer, and a pinning layer adjoining the second ferromagnetic layer, a free layer whose magnetization direction changes in response to an external magnetic field, and a spacer layer made of a nonmagnetic conductive material disposed between the first ferromagnetic layer and the free layer, wherein the magnetization direction of the second ferromagnetic layer is fixed by the pinning layer and the magnetization direction of the first ferromagnetic layer is fixed in a second direction antiparallel to the first direction by exchange coupling of the first ferromagnetic layer and the second ferromagnetic layer with the exchange coupling layer therebetween, so that the first ferromagnetic layer serves as a pinned layer, the method comprising:
• a film forming step of forming a film intended to act as the first giant magnetoresistive element and a film intended to act as the second giant magnetoresistive element on the substrate such that one of the films overlies the other film;
• and
• a magnetic field heat treatment step of applying a magnetic field oriented in a single direction to the films at a high-temperature to fix the magnetization direction of each pinned layer.

A method for manufacturing a magnetic sensor, the magnetic sensor comprising:

• a single substrate;
• a first giant magnetoresistive element disposed on the substrate, the first giant magnetoresistive element being formed of a single-layer-pinned spin-valve film comprising a single-layer-pinned fixed magnetization layer which includes a pinning layer and a single ferromagnetic layer, a free layer whose magnetization direction changes in response to an external magnetic field, and a spacer layer made of a nonmagnetic conductive material which is disposed between the ferromagnetic layer and the free layer, wherein the magnetization of the ferromagnetic layer is fixed in a first direction by the pinning layer, so that the ferromagnetic layer serves as a pinned layer;
• a second giant magnetoresistive element disposed close to the first giant magnetoresistive element on the substrate, the second giant magnetoresistive element being formed of a plural-layer-pinned spin-valve film comprising a plural-layer-pinned fixed magnetization layer which includes a first ferromagnetic layer, an exchange coupling layer adjoining the first ferromagnetic layer, a second ferromagnetic layer adjoining the exchange coupling layer, and a pinning layer adjoining the second ferromagnetic layer, a free layer whose magnetization direction changes in response to an external magnetic field, and a spacer layer made of a nonmagnetic conductive material which is disposed between the first ferromagnetic layer and the free layer, wherein the magnetization direction of the second ferromagnetic layer is fixed by the pinning layer and the magnetization direction of the first ferromagnetic layer is fixed in a second direction antiparallel to the first direction by exchange coupling of the first ferromagnetic layer and the second ferromagnetic layer with the exchange coupling layer therebetween, so that the first ferromagnetic layer serves as a pinned layer;
• a first bias magnet film disposed on the substrate so as to be in contact with an end of the first giant magnetoresistive element, the first bias magnet film applying a bias magnetic field oriented in a third direction substantially perpendicular to the first direction to the first giant magnetoresistive element;
• a second bias magnet film disposed on the substrate so as to be in contact with an end of the second giant magnetoresistive element, the second bias magnet film applying a bias magnetic field oriented in the third direction to the second giant magnetoresistive element;
• and
• a third bias magnet film disposed on the substrate so as to be in contact with both the other end of the first giant magnetoresistive element and the other end of the second giant magnetoresistive element, the third bias magnet film applying a bias magnetic field oriented in the third direction to the first giant magnetoresistive element and the second giant magnetoresistive element;
• the method comprising:
• preparing the single substrate;
• forming films intended to act as the first to third bias magnet films on the substrate;
• forming a first film intended to act as one of the first giant magnetoresistive element and the second giant magnetoresistive element on the upper surface of the substrate and the upper surfaces of the first to third bias magnet films;
• forming an insulating layer to cover the upper surfaces of the films intended to act as the bias magnet films and the first film;
• planarizing the upper surfaces of the insulating layer, the films intended to act as the bias magnet films, and the first film by partially removing the insulating layer, the films intended to act as the bias magnet films, and the first film so that the upper surfaces of the films intended to act as the bias magnet film are exposed;
• forming a second film intended to act as the other of the first giant magnetoresistive element and the second giant magnetoresistive element on the planarized surface;
• and
• performing a magnetic field heat treatment by applying a magnetic field oriented in a single direction to the first film and the second film at a high temperature, thereby fixing the magnetization directions of the pinned layers.