Etching a substrate: processes – Forming or treating article containing magnetically...
Reexamination Certificate
2000-12-18
2002-11-19
Alanko, Anita (Department: 1746)
Etching a substrate: processes
Forming or treating article containing magnetically...
C216S037000, C216S067000, C204S192200, C134S021000
Reexamination Certificate
active
06482329
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of manufacturing a magneto-resistance element, and in particular, to a method of manufacturing a magneto-resistance element having a large rate of change of magneto-resistance (MR). The magneto-resistance element made by the method of the present invention is suitably applied to a head for reproducing a magnetic signal written into a hard disk, floppy disk, magnetic tape, or the like.
BACKGROUND ART
Conventionally, as structure of a magneto-resistance, are widely known an artificial lattice type (A) of a structure in which ferromagnetic layers are laminated a plurality of times on a surface of a substrate body putting non-magnetic layers (spacers) between them, and a spin valve type (B) of a structure in which ferromagnetic layers are laminated on a surface of a substrate body putting non-magnetic layers between them and an antiferromagnetic layer is formed on the surface of said ferromagnetic layer provided last.
To manufacture the magneto-resistance element of such a structure, since each layer is an ultra thin film having thickness of several nm, technological development has been demanded for sequentially laminating high purity thin films superior in flatness, under an atmosphere as clean as possible. Japanese Patent Application No. 7-193882 is mentioned as an example of such technique. The specification of that patent application describes that by making oxygen concentration in the above described structure less than or equal to 100 wt ppm, a magneto-resistance element having a high MR ratio is obtained. Further, it reports that such structure having a trace of oxygen concentration is superior in flatness.
However, in the present state that higher recording density is being promoted, it is strongly desired to realize a magneto-resistance element that can reproduce a magnetic signal with higher sensitivity, i.e., a magneto-resistance element having a higher MR ratio (at room temperature) as compared to the conventional one. To accomplish it, it is desired to develop a manufacturing method that is superior in controllability and can easily form a magneto-resistance element that is better in its flatness of its lamination interfaces and has fewer defects in its crystal structure.
An object of the present invention is to provide a method of manufacturing a magneto-resistance element having such a high MR ratio that a magnetic signal can be reproduced with higher sensitivity.
DISCLOSURE OF THE INVENTION
The present invention provides a method of manufacturing a magneto-resistance element of a structure in which ferromagnetic layers are laminated a plurality of times on a surface of a substrate body putting non-magnetic layers therebetween, comprising steps of:
depressurizing an inside of a deposition chamber in which said non-magnetic layers and said ferromagnetic layers are formed, to an ultimate degree of vacuum at a level of 10
−9
Torr or less;
introducing a gas a containing at least oxygen or water into said deposition chamber to change the ultimate degree of vacuum inside the deposition chamber to a certain pressure higher than the level of 10
−9
Torr, then, introducing a gas b consisting of Ar, and carrying out plasma etching processing of the surface of said substrate body using a mixed gas of said gas a and said gas b; and
sputtering prescribed targets in said deposition chamber using the mixed gas of said gas a and said gas b to form said non-magnetic layers and said ferromagnetic layers by a sputtering technique on the substrate body processed by said plasma processing.
In the method of manufacturing a magneto-resistance element according to the present invention, first, owing to the step of depressurizing the inside of the deposition chamber in which said non-magnetic layers and said ferromagnetic layers re formed to an ultimate degree of vacuum at a level of 10
−9
Torr or less, it is possible to remove substances absorbed discontinuously onto the substrate body at atmospheric pressure, from the surface of the substrate body in the stage preceding the film formation.
Next, owing to the step of introducing the gas a containing at least oxygen or water into the deposition chamber to change the ultimate degree of vacuum inside the deposition chamber to the certain pressure higher than the level of 10
−9
Torr, then, introducing the gas b consisting of Ar, and carrying out plasma etching processing of the surface of the substrate body using the mixed gas of said gas a and said gas b, it is possible to make a controlled amount of impurities such as oxygen be uniformly absorbed onto the surface of the substrate body from which impurities have been sufficiently removed in the step of degreasing the ultimate degree of vacuum to the level of 10
−9
Torr or less.
Then, owing to the step of sputtering the prescribed targets in said deposition chamber using the mixed gas of said gas a and said gas b, to form said non-magnetic layers and said ferromagnetic layers by a sputtering technique on the substrate body processed by said plasma processing, it is possible to form a multi-layer film under an atmosphere that is controlled in its cleanliness although that cleanliness is low. By this, there are many impurities on the surface of the substrate body and on the surfaces of the films and it becomes difficult for crystals to grow, and accordingly, diameters of crystal grains become smaller. Accordingly, at the same time, the flatness of the lamination interfaces is improved. Or, the impurities act like a surface active agent to suppress aggregation of atoms constituting the non-magnetic layers and the ferromagnetic layers so that the interfaces are flattened. As a result, a magneto-resistance element having a high MR ratio is obtained.
Further, in the method of manufacturing a magneto-resistance element according to the present invention, by making the ultimate degree of vacuum inside the deposition chamber more than or equal to 3×10
−7
Torr and less than or equal 8×10
−5
Torr, after introducing said gas a, in said step of carrying out the plasma etching processing and said step of film formation by a sputtering technique, there is obtained a magneto-resistance element having a higher MR ratio than a magneto-resistance element obtained by depressurizing the inside of the deposition chamber to an ultimate degree of vacuum at a level of 10
−9
Torr or less, etching the surface of the substrate body using only Ar gas, and then forming the non-magnetic layers and the ferromagnetic layers by a sputtering technique.
Further, when the ultimate degree of vacuum inside the deposition chamber is more than or equal to 3×
−6
Torr and less than or equal to 2×10
−5
Torr, after introducing said gas a, in said step of carrying out the plasma etching processing and said step of film formation by a sputtering technique, there is obtained a magneto-resistance element having an MR ratio twice as high as the magneto-resistance element obtained by depressurizing the inside of the deposition chamber to the ultimate degree of vacuum at the level of 10
−9
Torr or less, etching the surface of the substrate body using only Ar gas, and then forming the non-magnetic layers and the ferromagnetic layers by a sputtering technique.
EMBODIMENTS OF THE INVENTION
As a film-formation apparatus suitable for carrying out the method of manufacturing a magneto-resistance element according to the present invention, is mentioned a facing target DC sputtering system (made by Osaka Vacuum, Ltd.) shown in
FIGS. 5 and 6
, for example.
FIG. 5
is a system diagram showing a vacuum pumping system of the apparatus, and
FIG. 6
is a schematic cross section of the inside of a sputtering chamber of the apparatus shown in
FIG. 5
, seen from above. In
FIG. 5
, reference numeral
501
refers to a load-lock chamber,
502
to the sputtering chamber,
503
to a gate valve,
504
to a means for moving a substrate body,
505
to a turbo-molecular pump,
506
to a scroll vacuum pump,
Miura Satoshi
Takahashi Migaku
Tsunoda Masakiyo
Alanko Anita
Knuth Randall J.
Takahashi Migaku
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