Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Reexamination Certificate
1999-03-22
2001-10-16
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
C428S336000, C428S692100, C428S690000, C428S690000, C428S690000, C428S900000, C360S112000
Reexamination Certificate
active
06303218
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a multi-layered thin-film functional device having stacked thin films and magnetoresistance effect element used in a magnetic sensor. In the field of the functional devices such as magnetoresistance effect elements used for magnetic sensors, electronic elements, and so on, there is a powerful stream toward micro-fabrication and high performance. Along with the improvements in vacuum technologies and film-stacking technologies, stacked thin films have come to be often used as functional devices. Conventional technologies of these multi-layered thin-film functional devices are explained below taking a magnetoresistance effect element using a ferromagnetic thin film.
Magnetic resistance effect is the phenomenon that electric resistance changes when a magnetic field is applied to a magnetic body, and it is used in magnetic sensors, magnetic head, or the like. Ferromagnetic thin films of Ni—Fe alloys, for example, are employed in magnetoresistance effect elements (MR elements) for reading external magnetic field signals, utilizing their anisotropic magnetoresistance effects (AMR), i.e., the phenomenon that the electric resistance changes depending upon the positional relation between the current flowing in a magnetic body and the magnetic orientation.
Also remarked recently are magnetoresistance effect films made by alternately stacking ferromagnetic layers and nonmagnetic layers in cycles of several nm to several decades of nm. In these multi-layered thin films, electric resistance changes depending upon whether the magnetic orientations of ferromagnetic layers opposed to each other via a non-magnetic layer are parallel or not. This phenomenon is called giant magnetoresistance (GMR), and researches are under progress toward the application of this nature, similarly to the anisotropic magnetoresistance effect, in magnetoresistance effect elements (GMR elements) for reading external magnetic signals.
Additionally, large hopes are placed on the giant magnetoresistance effect because it promises a larger change in resistance than the anisotropic magnetoresistance effect also when the film is thin. There are different types of film structures exhibiting giant magnetoresistance effects. Among them, a film structure of one type represented by Fe/Cr artificial lattice films (Phys. Rev. Lett. 61(1988)2472) and Co/Cu artificial lattice films (J. mag. mag. mater. 94(1991)L1), for example, has an anti-ferromagnetic coupling type magnetic interaction between ferromagnetic layers, and changes in resistance are obtained in response to an external magnetic field to change relative directions of magnetic moments between the ferromagnetic. In a film structure of another type represented by Co/Cu/NiFe artificial lattice films (J. Phys. Soc. Jpn. 60(1991)2827), two or more different ferromagnetic layers are used in a multi-layered film made up of a ferromagnetic layer and a non-magnetic layer, and a difference in coercive force of these ferromagnetic layers to change relative directions of magnetic moments between the magnetic layers and thereby obtain changes in resistance in response to an external magnetic field.
Also proposed is a spin valve structure (for example, NiFe/Cu/NiFe/FeMn film (J. Appl. Phys. 69(1991)4774)) having a sandwich film stacking a ferromagnetic layer, non-magnetic layer and ferromagnetic layer and having a weak magnetic interaction among the magnetic layers, in which the resistance can be readily switched by providing an anti-ferromagnetic layer in contact with one of the ferromagnetic layer so that the exchange anisotropy fixes the magnetic moment of the ferromagnetic layer and by changing the magnetic moment of the other ferromagnetic layer in response to an external magnetic field.
As reviewed above, multi-layered thin-film devices made by stacking very thin layers as thin as 100 nm, approximately, have come to be used as magnetoresistance effect elements and other active elements. In these multi-layered thin-film functional devices, characteristics of active elements often vary due to the inter-diffusion of atoms at boundaries between thin-film layers, and thermal stability of their characteristics is an important issue for their practical use.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a multi-layered thin-film functional device having an functional layer made by stacking a plurality of thin films, which is improved in thermal stability and long-term reliability by suppressing inter-diffusion of atoms among the thin-film layers in the functional layer.
Another object of the invention is to provide a magnetoresistance effect element which is improved by thermal stability and long-term reliability by suppressing inter-diffusion of atoms at a ferromagnetic layer and a nonmagnetic layer in the magnetoresistance effect element.
Another object of the invention is to provide a magnetoresistance effect element having excellent magnetoresistance effect characteristics and other various magnetic characteristics and having excellent thermal resistance by well maintaining the function of an electron reflecting layer made to exist in a spin valve film, effectively preventing adverse influences to magnetic characteristics based thereon, and preventing defective fabrication of the layer itself; provide a method for manufacturing such magnetoresistance effect elements with a good reproducibility; and provide a magnetoresistance effect element stably operable as a magnetic head, for example.
According to the one aspect of the invention, a multi-layered thin-film functional device including a base crystal layer, a crystal growth controlling layer formed on said base crystal layer, and a functional layer made up of a plurality of thin-film layers formed on said crystal growth controlling layer, said crystal growth controlling layer containing a compound of at least one element selected from O, N, C, F, B and S, said base crystal layer having a thickness not thicker than 15 nm, and the roughness of the boundary between said crystal growth controlling layer and said functional layer being not larger than 1.5 nm is provided.
According to the another aspect of the invention, a magnetoresistance effect element having a magnetoresistance effect film which includes a crystal growth controlling layer as one of films therein, characterized in that a roughness along a boundary between films overlying said crystal growth controlling layer is smaller than a roughness along a boundary between films underlying said crystal growth controlling layer is also provided.
The inventors found that the thermal instability was caused by the inter-diffusion of the atoms and that the such a diffusion is enhanced by the bulkiness of the grain size of the layers of the functional device.
FIG. 24
schematically shows the bulkiness of the grains. According to the invention, such a bulkiness is prevented by employing the crystal growth controlling layer.
According to the another aspect of the invention, a magnetoresistance effect element comprising a first magnetic layer (free layer) susceptible in magnetization to an external magnetic field, a second magnetic layer (pinned layer) substantially pinned in magnetization, and a non-magnetic intermediate layer interposed between said first magnetic layer and said second magnetic layer, characterized in further comprising a metal barrier layer provided adjacent to said first magnetic layer, and a fourth layer (electron reflecting layer) located adjacent to said metal barrier layer and containing at least one selected from oxides, nitrides, carbides, fluorides, chlorides, sulfides and borides is also provided.
According to the another aspect of the invention, a magnetoresistance effect element comprising a first magnetic layer susceptible in magnetization to an external magnetic field, a second magnetic layer substantially pinned in magnetization, and a non-magnetic intermediate layer interposed between said first magnetic layer and said second magnetic layer, said second magnetic laye
Fukuzawa Hideaki
Hashimoto Susumu
Iwasaki Hitoshi
Kamiguchi Yuzo
Koui Katsuhiko
Foley & Lardner
Kabushiki Kaisha Toshiba
Kiliman Leszek
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