JP2001084523A - Tunnel magnetoresistance effect type thin film magnetic head and manufacture of the head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a TMR type thin film magnetic head having a low resistance and a high MR ratio, and its manufacturing method. SOLUTION: In the case of laminating and forming the lower part gap layer of a non-magnetic conductor on a lower part shield layer (S1), laminating and forming a TMR element provided with two ferromagnetic thin film layers laminated holding a tunnel barrier layer there between on the lower part gap layer (S2), laminating and forming the upper part gap layer of the non-magnetic conductor on the TMR element and laminating and forming an upper part shield layer on the upper part gap layer (S5), at least the film-formation of the lower part shield layer and the film-formation of the TMR element are successively performed within the same process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TMR type thin film magnetic head having a tunnel magnetoresistive (TMR) element and usable for a hard disk drive (HDD) device, and a method of manufacturing the thin film magnetic head.

[0002]

2. Description of the Related Art As the density of HDD devices is increased, higher sensitivity and higher output magnetic heads are required. recent years,
To meet this demand, attention has been paid to a TMR element utilizing a ferromagnetic tunnel effect having a multilayer structure of an upper ferromagnetic thin film layer / a tunnel barrier layer / a lower ferromagnetic thin film layer. The terms “upper” and “lower” in the upper ferromagnetic thin film layer and the lower ferromagnetic thin film layer are terms indicating the positional relationship with the substrate, and generally, the lower side is closer to the substrate and the upper side is farther away.

[0003] The ferromagnetic tunnel effect means that when a current flows between a pair of ferromagnetic thin layers sandwiching a tunnel barrier layer, a tunnel current flowing through the tunnel barrier layer depends on the relative angle of magnetization of both ferromagnetic thin layers. Change phenomenon.
The tunnel barrier layer in this case is a thin insulating film,
Electrons can pass while preserving spin due to the tunnel effect.

When the magnetizations of both ferromagnetic thin film layers are parallel to each other (when the relative angles of the magnetizations are small), the tunneling probability of electrons increases, so that the resistance of the current flowing between the two ferromagnetic thin film layers decreases. Conversely, when the magnetizations of the two ferromagnetic thin film layers are antiparallel to each other (when the relative angles of the magnetizations are large), the resistance of the current flowing between the two ferromagnetic thin film layers increases because the probability of electron tunneling decreases. . The detection of the external magnetic field is performed using the resistance change based on the change in the relative angle of the magnetization.

The thinning of the insulator layer as a tunnel barrier layer is very important for a TMR element. This is because reducing the thickness of the insulator layer not only makes it possible to obtain a tunnel effect, but also has a great effect on lowering the resistance of the TMR element. The reason why low resistance is required for the TMR element is roughly divided into the following four. (1) Higher output The output of the TMR head is given by a change in voltage generated when a constant sense current is flowing. Therefore, a higher output can be obtained with a larger resistance change rate. However, when the element resistance value itself is high just because the resistance change rate is large, there is a high possibility that the element will be destroyed due to Joule heat when a current is applied, and it becomes useless. (2) Noise Noise called thermal noise (thermal noise) increases depending on the temperature as the name implies, and further increases when the resistance value of the element is large. Therefore, when the element resistance value is large, no matter how much output can be obtained, the noise also increases at the same time, which is not advantageous in terms of S / N. (3) Frequency response From a practical point of view of the element, it is necessary to consider not only the TMR element part alone but also the entire circuit. A low-pass filter is formed by the resistance of the element and the stray capacitance generated in the circuit wiring. Therefore, if the resistance of the tunnel junction is high, the limit frequency is lowered, and the high-speed performance is impaired. (4) Mass Production (ESD (Electrostatic Discharge) Damage Resistance) Although related to (1), as already experienced in the giant magnetoresistance (GMR) element, the higher the resistance of the element, the higher the ESD.
Easy to take damage. This tendency is applied to the TMR element as it is.

When a TMR element is used with an element size similar to that of a GMR element, the total resistance is at least 300 Ω.
It is reported that it is necessary to: Therefore,
In the TMR element, it is necessary to suppress the resistance value other than the tunnel barrier layer, for example, the resistance value of the lead conductor portion as small as possible.

On the other hand, when considering the structure of a magnetic head having a TMR element, in order to eliminate the non-uniformity of the current density, the low resistance value of the electrode layer is reduced to about 1/30 of the resistance of the TMR element. It has also been reported that it is necessary to:
S. Moodera et. A1, Appl. Phys. Lett. 69 (5) 708, “Ge
ometrically Enhanced Magnetoresistance in Ferromag
net-Insulator-Ferromagnet Tunnel Junctions "). For example, the size of the TMR element is 1 μm ² (the track width is 1
μm, MR height is 1 μm) and the resistance value is 30Ω.
In order to provide a uniform sense current to this element, an electrode layer of 1 Ω or less is required above and below. Now, Cu as an electrode layer
In this case, an upper and lower electrode layer of 30 nm is required.

It is assumed that a gap film made of an insulator such as that used in the case of an AMR element or a GMR element is used in a thickness of 40 nm outside this electrode layer (assuming that a sufficient withstand voltage can be maintained even with such a thin film). , The read gap layer already has a thickness of 0.14 μm,
There is almost no room for the R element to enter.

Therefore, the present applicant has developed and has already proposed a TMR type thin film magnetic head having a “read / shield dual-purpose structure”. In this "lead / shield dual-purpose structure", the gap layers above and below the TMR element are made of a nonmagnetic conductor, and the gap layer and the shield layer are also used as lead conductors.

[0010]

SUMMARY OF THE INVENTION
In a TMR thin-film magnetic head having a "shield-type structure", when the lower gap layer formed of a non-magnetic conductor such as Ta, Ru, and Al and the respective layers of the TMR element are formed in separate processes, The surface oxidizes, adding extra resistance that cannot be ignored.

When a surface treatment such as milling or etching is performed to remove such an oxide film, the surface roughness basically increases. Further, such a surface treatment is not desirable from the viewpoint of controllability of the thickness of the gap layer. That is, the control becomes difficult because two factors, that is, the film thickness and distribution at the time of film formation and the etching amount and distribution must be considered.

Accordingly, an object of the present invention is to provide a low resistance and high MR.
An object of the present invention is to provide a TMR type thin film magnetic head having a ratio and a method of manufacturing the same.

[0013]

SUMMARY OF THE INVENTION The present invention provides a lower shield layer, a lower gap layer of a non-magnetic conductor laminated on the lower shield layer, and a tunnel barrier layer formed on the lower gap layer. A TMR element including two ferromagnetic thin-film layers laminated with a gap therebetween, an upper gap layer of a nonmagnetic conductor laminated on the TMR element, and an upper shield layer laminated on the upper gap layer TM with
An R-type thin film magnetic head is provided. In particular, according to the present invention, the lower gap layer has a smooth upper surface that is not oxidized, and the TMR element is in direct contact with the smooth upper surface that is not oxidized.

According to the present invention, a lower gap layer of a nonmagnetic conductor is formed on the lower shield layer, and two ferromagnetic thin film layers are stacked on the lower gap layer with a tunnel barrier layer interposed therebetween. A TMR element is formed by lamination, and the TM
An object of the present invention is to provide a method of manufacturing a TMR type thin film magnetic head in which an upper gap layer of a non-magnetic conductor is formed on an R element and an upper shield layer is formed on the upper gap layer. In particular, according to the present invention, at least the formation of the lower shield layer and the formation of the TMR element are continuously performed in the same process.

In the manufacture of the AMR element and the GMR element, the "process for forming the lower gap layer" and the "process for forming the TMR element", which are performed as separate processes, are continuously performed in the same process. . Therefore, the upper surface of the lower gap layer is exposed to oxygen, active gas, and the like, and an unnecessary film such as an oxide film is not formed in this portion. As a result, it is possible to suppress an excessive increase in the resistance value in the read portion of the TMR type thin film magnetic head,
A TMR type thin film magnetic head having a low resistance and a high MR ratio can be obtained.

The film formation of the lower shield layer and the film formation of the TMR element are continuously performed in a film formation chamber having a plurality of targets, or a plurality of film formation chambers each having a separate target are provided. It is preferable that the deposition be performed continuously in a plurality of deposition chambers of the same deposition apparatus.

More preferably, the lower gap layer is formed of one non-magnetic conductive material used for the TMR element. By using such a material, it is not necessary to newly add a target.

The lower gap layer is made of Ta, Ru, Al, P
tMn, RuRhMn, Ti, TiW, Rh, Cr, I
n, Ir, Mg, Ru, W, Zn, Cu, Ag and Au
It is also preferred to form them from a selected one of their alloys.

[0019]

FIG. 1 is a sectional view schematically showing a configuration of a main part of a TMR type thin film magnetic head according to an embodiment of the present invention.

In FIG. 1, reference numeral 10 denotes a lower shield layer laminated on a substrate (not shown), 11 a lower gap layer laminated on the lower shield layer 10, and 12 a pattern formed by lamination on the lower gap layer 11. TM
R element 13 is a first upper gap layer made of a non-magnetic conductor laminated on TMR element 12, and 14 is a second upper gap layer made of an insulator laminated on some layers of TMR element 12.
The upper gap layer 15 is an upper shield layer formed on the first and second upper gap layers 13 and 14.
Reference numeral 6 denotes an ABS (floating surface) of the head.

As shown in FIG. 1, the TMR element 12 includes a lower ferromagnetic thin film layer (free layer) 12a, a tunnel barrier layer 12b, an upper ferromagnetic thin film layer (pinned layer) 12c, and an antiferromagnetic thin film layer 12d. It has a multilayer structure including at least a typical layer.

The lower ferromagnetic thin film layer 12a basically has
The magnetization direction of the upper ferromagnetic thin film layer 12c is changed to a predetermined direction by an exchange coupling bias magnetic field between the upper ferromagnetic thin film layer 12d and the antiferromagnetic thin film layer 12d. It is configured to face.

Incidentally, the TMR element 12 is actually
The structure further includes another layer. For example, an underlayer is provided under the lower ferromagnetic thin film layer 12a,
A cap layer is formed on each of the lower ferromagnetic thin-film layers 12a.
A magnetic domain control layer for applying a bias magnetic field for magnetic domain control is formed.

FIG. 2 is a flowchart showing a part of the manufacturing process in the embodiment of FIG. 1. The manufacturing process of the TMR type magnetic head will be described below with reference to FIG.

First, Ti (Ti) is placed on a substrate (wafer) (not shown).
A seed layer such as / NiFe is deposited, and a lower shield layer 10 is formed thereon by plating (step S1). As the lower shield layer 10, NiFe is used in the present embodiment.

Next, after forming a resist pattern of the lower gap layer 11 thereon, the lower gap layer 11 and the TMR element 12 are placed in a sputtering apparatus.
Are continuously formed in one process (step S
2).

As the sputtering apparatus, an apparatus having a single sputter provided with a plurality of targets or an apparatus having a plurality of sputter chambers each provided with a separate target is used. The lower gap layer 11 is formed of Ta, and the underlying layer / lower ferromagnetic thin film layer 12a / tunnel barrier layer 12b / upper ferromagnetic thin film layer 12c / antiferromagnetic thin film layer 12d / cap layer, which are the respective layers of the TMR element 12, Ta
/ NiFe and CoFe two-layer structure / Al oxide film / C
When formed of oFe / RuRhMn / Ta, Ta, NiFe, CoFe, Al and Ru are used as targets.
All of RhMn is attached.

In this state, the wafer on which the resist pattern of the lower gap layer 11 has been formed is put into a sputtering apparatus, and first, Ta is sputtered to form the lower gap layer 11 having a thickness of 35 nm. Subsequently, the respective layers of the TMR element 12 are sequentially formed while keeping the substrate in the sputtering apparatus, and two layers of Ta (5 nm thick) / NiFe (10 nm thick) and CoFe (2 nm thick) are formed. Construction/
Al (0.7 nm thick) oxide film / CoFe (3 n thick film)
m) / RuRhMn (film thickness 10 nm) / Ta (film thickness 5 n)
m) is obtained.

Next, the wafer is taken out of the sputtering apparatus, and after patterning the TMR element 12,
A magnetic domain control layer for applying a bias magnetic field for magnetic domain control is formed at least on both ends in the width direction of the lower ferromagnetic thin film layer 12a (step S3).

Thereafter, a first upper gap layer 13 made of a nonmagnetic conductor such as Ta is formed on the cap layer of the TMR element 12 so as to cover the lower ferromagnetic thin film layer 12a of the TMR element 12. For example, a _second upper gap layer 14 made of an insulator such as Al ₂ O ₃ is formed (step S4).

Next, the upper shield layer 15 is formed by plating (step S5). In this embodiment, NiFe is used as the upper shield layer 15.

As described above, in the present embodiment, the film forming process of the lower gap layer 11 and the film forming process of the TMR element 12 are continuously performed in the same process. For this reason,
The upper surface of the lower gap layer 11 is exposed to oxygen, active gas, and the like, so that an unnecessary film such as an oxide film is not formed at this portion. As a result, it is possible to suppress an increase in the extra resistance value in the read portion of the TMR type thin film magnetic head, and it is possible to obtain a TMR type thin film magnetic head having a low resistance and a high MR ratio.

FIG. 3 is a characteristic diagram comparing the element resistance values of the TMR element of the present embodiment and the TMR element of the prior art. The horizontal axis represents the junction area with the lower gap layer corresponding to the element size, and the vertical axis represents the element size. Represents element resistance values, respectively.

As in the prior art, the lower gap layer and the TMR
It can be seen that in the case where the layers of the element are formed by different processes, the element resistance is larger than in the case where the layers are formed continuously in the same process as in the present embodiment. In the prior art, the element resistance is large for all element sizes (junction areas). It is considered that such a large low resistance is brought about mainly because the upper surface of Ta of the lower gap layer 11 is oxidized. On the other hand, in the case of the present embodiment, it can be seen that an ideal state in which the element resistance increases in inverse proportion to the junction area is obtained.

In this embodiment, the lower gap layer 1
Since Ta, which is one of the materials used for the layer of the TMR element 12, is used as one material, the number of targets of the sputtering apparatus can be reduced.

FIG. 4 shows a TM according to another embodiment of the present invention.
FIG. 6 is a characteristic diagram comparing the element resistance values of the R element and the TMR element of the related art, in which the horizontal axis represents the junction area with the lower gap layer corresponding to the element size, and the vertical axis represents the element resistance value.

In this embodiment, Ru, which is one of the materials used for the layers of the TMR element, is used as the material of the lower gap layer.

Each layer of the TMR element is made of Ta (5 nm thick).
/ NiFe (film thickness 10 nm) and CoFe (film thickness 2n)
m) Two-layer structure / Al (0.7 nm thick) oxide film / C
oFe (thickness 3 nm), Ru (thickness 0.7 nm) and C
It has a two-layer structure of oFe (film thickness: 2 nm) / RuRhMn (film thickness: 10 nm) / Ta (film thickness: 5 nm).

FIG. 4 shows that, when the lower gap layer and each layer of the TMR element are formed by different processes as in the conventional technique, the lower gap layer and each layer of the TMR element are continuously formed in the same process as in this embodiment. As a result, it can be seen that the element resistance value is large. In the prior art, the element resistance is large for all element sizes (junction areas). It is considered that such a large low resistance is brought about mainly because the upper surface of Ru of the lower gap layer is oxidized. On the other hand, in the case of the present embodiment, it can be seen that an ideal state in which the element resistance increases in inverse proportion to the junction area is obtained.

Other structures, materials,
About the film thickness, the manufacturing process, the function and effect, and the change mode,
This is the same as in the above-described embodiment.

FIG. 5 is a characteristic diagram comparing element resistance values of a TMR element according to still another embodiment of the present invention and a TMR element of the prior art, and the abscissa axis indicates a junction with a lower gap layer corresponding to the element size. The area and the vertical axis respectively represent the element resistance values.

In this embodiment, Al, which is one of the materials used for the layers of the TMR element, is used as the material of the lower gap layer.

Each layer of the TMR element is made of Ta (5 nm thick).
/ NiFe (film thickness 10 nm) and CoFe (film thickness 2n)
m) Two-layer structure / Al (0.7 nm thick) oxide film / C
oFe (thickness 3 nm), Ru (thickness 0.7 nm) and C
It has a two-layer structure of oFe (film thickness: 2 nm) / RuRhMn (film thickness: 10 nm) / Ta (film thickness: 5 nm).

As shown in FIG. 4, when the lower gap layer and each layer of the TMR element are formed in different processes as in the prior art, the case where the lower gap layer and each layer of the TMR element are formed continuously in the same process as in the present embodiment is compared. As a result, it can be seen that the element resistance value is large. In the prior art, the element resistance is large for all element sizes (junction areas). It is considered that such a large low resistance is brought about mainly because the upper surface of Al in the lower gap layer is oxidized. On the other hand, in the case of the present embodiment, it can be seen that an ideal state in which the element resistance increases in inverse proportion to the junction area is obtained.

The other configuration, manufacturing process, operation and effect, modified mode, and the like in this embodiment are the same as those in the above-described embodiment.

As the lower gap layer in the present invention,
Obviously, other non-magnetic conductive materials used for the TMR element, such as PtMn and RuRhMn, may be used. Also, non-magnetic conductive materials not used for the TMR element, for example, Ti, TiW, Rh, Cr, In, I
r, Mg, Ru, W, Zn, Cu, Ag or Au, or an alloy thereof may be used. The film thickness is not limited to 35 nm, but is selected, for example, in the range of about 5 to 70 nm. The same applies to the first upper gap layer.

As a material constituting the lower ferromagnetic thin film layer and the upper ferromagnetic thin film layer of the TMR element according to the present invention, other high spin polarization materials, for example, Fe, Co, Ni, Co
A single-layer or multilayer structure such as ZrNb or FeCoNi may be used. The thickness of the lower ferromagnetic thin film layer (free layer) is not limited to 12 nm, but may be, for example, 2 to 5 nm.
0 nm, preferably in the range of about 6 to 20 nm. If the film thickness is too large, the output during head operation decreases, and the output instability increases due to Barkhausen noise and the like. If the film thickness is too small, the output decreases due to deterioration of the TMR effect. The film thickness of the upper ferromagnetic thin film layer (pinned layer) is not limited to the film thickness in the above-described embodiment, and is selected, for example, in the range of about 1 to 10 nm, preferably about 2 to 5 nm. If the film thickness is too large, the exchange coupling bias magnetization with the antiferromagnetic thin film layer is weakened, and if the film thickness is too small, the TMR change rate decreases.

As a material constituting the tunnel barrier layer of the TMR element in the present invention, other materials such as Ni
O, GdO, MgO, Ta ₂ O ₅ , MoO ₅ , TiO ₂
Alternatively, WO ₂ or the like may be used. As described above, the thickness of the tunnel barrier layer is desirably as thin as possible from the viewpoint of lowering the resistance of the device. However, if the thickness is too small and a pinhole is generated, a leak current flows, which is not preferable. Generally, it is selected in the range of about 0.4 to 2 nm.

As a material constituting the antiferromagnetic thin film layer of the TMR element in the present invention, other general antiferromagnetic materials can be used, and the film thickness is not limited to 10 nm. For example, it is selected in a range of about 6 to 30 nm.

As a material constituting the lower shield layer and the upper shield layer in the present invention, other metal magnetic material such as sendust, CoFe or CoFeNi may be used in addition to NiFe.

The embodiments described above all illustrate the present invention by way of example and not by way of limitation, and the present invention can be embodied in various other modified and modified forms. Therefore, the scope of the present invention is defined only by the appended claims and their equivalents.

[0052]

As described above in detail, according to the present invention, the processes for forming the lower gap layer and the process for forming the TMR element, which have been performed as separate processes in the production of the AMR element and the GMR element, have been described. Film process ”is continuously performed in the same process. Therefore, the upper surface of the lower gap layer is exposed to oxygen, active gas, and the like, and an unnecessary film such as an oxide film is not formed in this portion. As a result, it is possible to suppress an increase in the extra resistance value in the read portion of the TMR type thin film magnetic head, and it is possible to obtain a TMR type thin film magnetic head having a low resistance and a high MR ratio.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a configuration of a main part of a TMR type thin-film magnetic head according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a part of a manufacturing process in the embodiment of FIG.

FIG. 3 is a characteristic diagram comparing element resistance values of a TMR element of the present embodiment and a TMR element of a conventional technique.

FIG. 4 is a characteristic diagram comparing element resistance values of a TMR element according to another embodiment of the present invention and a TMR element according to the related art.

FIG. 5 is a characteristic diagram comparing element resistance values of a TMR element according to still another embodiment of the present invention and a TMR element according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Lower shield layer 11 Lower gap layer 12 TMR element 12a Lower ferromagnetic thin film layer (free layer) 12b Tunnel barrier layer 12c Upper ferromagnetic thin film layer (pinned layer) 12d Antiferromagnetic thin film layer 13 First upper gap layer 14 First 2 upper gap layer 15 upper shield layer 16 ABS

Claims (7)

[Claims] 1. A lower shield layer, a lower gap layer of a nonmagnetic conductor laminated on the lower shield layer, and a laminate formed on the lower gap layer, and laminated with a tunnel barrier layer interposed therebetween. A tunnel magnetoresistive element including two ferromagnetic thin film layers; an upper gap layer of a nonmagnetic conductor laminated on the tunnel magnetoresistive element; and an upper shield layer laminated on the upper gap layer Wherein the lower gap layer has a smooth upper surface that is not oxidized, and the tunnel magnetoresistance effect element is in direct contact with the smooth upper surface that is not oxidized. Tunnel magnetoresistive thin film magnetic head. 2. The thin-film magnetic head according to claim 1, wherein the lower gap layer is formed of one non-magnetic conductive material used for the tunnel magneto-resistance effect element. 3. A tunnel magnetoresistance device comprising: a lower gap layer of a non-magnetic conductor laminated on a lower shield layer; and a ferromagnetic thin film layer laminated on the lower gap layer with a tunnel barrier layer interposed therebetween. Effect element, a non-magnetic conductive upper gap layer is formed on the tunnel magnetoresistive element, and an upper shield layer is formed on the upper gap layer. A method of manufacturing a tunnel magnetoresistive thin film magnetic head, wherein at least film formation of the lower shield layer and film formation of the tunnel magnetoresistive element are performed continuously in the same process. . 4. The film formation of the lower shield layer and the film formation of the tunnel magnetoresistance effect element are continuously performed in a film formation chamber provided with a plurality of targets.
The production method described in 1. 5. The method according to claim 1, wherein the lower shield layer and the tunnel magnetoresistive element are formed by a plurality of film forming chambers each having a plurality of film forming chambers provided with separate targets. The method according to claim 3, wherein the method is performed continuously in a room. 6. The film according to claim 3, wherein the lower gap layer is formed of one nonmagnetic conductive material used for the tunnel magnetoresistance effect element.
The production method according to the paragraph. 7. The lower gap layer is made of Ta, Ru, A
1, PtMn, RuRhMn, Ti, TiW, Rh, C
7. The material according to claim 3, wherein the material is formed of a material selected from the group consisting of r, In, Ir, Mg, Ru, W, Zn, Cu, Ag, and Au, and an alloy thereof. The production method described in 1.