JPH07296342A - Magnetoresistance effect thin film magnetic head - Google Patents

Abstract

PURPOSE:To obtain a magnetoresistance effect thin film magnetic head with which an excellent S/N ratio can be realized even if a construction in which a magnetoresistance effect film and a bias conductor are connected in series. CONSTITUTION:The magnetoresistance effect thin film magnetic head is provided with a magnetoresistance effect film 5, a bias conductor 6 for applying a bias magnetic field to the magnetoresistance effect film 5 and wirings with which the magnetoresistance effect film 5 and the bias conductor 6 are connected to external terminals 12c and 12d, and they are connected in series. In this magnetoresiatance effect thin film magnetic head, the total resistance of the magnetoresistance effect film 5, the bias conductor 6 and the wirings is not larger than 20OMEGA.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a magnetoresistive film whose resistivity changes according to a recording magnetic field from a magnetic recording medium, and detects a resistance change of the magnetoresistive film as a reproduction output voltage. The present invention relates to a thin film magnetic head, and particularly to improvement of S / N ratio.

[0002]

2. Description of the Related Art Conventionally, a widely used induction type magnetic head has a problem that the reproduction output depends on the medium speed, and that the reproduction output decreases when the medium speed becomes slow.

On the other hand, a magnetoresistive thin film magnetic head (hereinafter referred to as an MR head) which detects a change in resistance of a magnetoresistive film (hereinafter referred to as an MR film) whose resistivity changes according to a magnetic field as a reproduction output voltage. Has a characteristic that the reproduction output does not depend on the medium speed and a high reproduction output can be obtained even when the medium speed is slow. It is attracting attention as a head. This is because the medium speed of the hard disk device depends on the disk diameter, and the smaller the size, the slower the medium speed.

However, since the MR head can only perform reproduction, as a recording / reproducing head, an induction type thin film magnetic head is laminated on the MR head, reproduction is performed by the MR head, and recording is performed by the induction type thin film magnetic head. A magnetic head of the type to be performed (hereinafter, this type of magnetic head is referred to as a composite type head) has been studied.

The composite head is usually manufactured as follows. First, as shown in FIG. 10, a head material is formed on a flat substrate 101 (for example, an Al—Ti—C-based sintered body) as shown in FIG. 9 by using a thin film process such as sputtering, plating, and photolithography. Head element 1 by stacking
02 (MR head element and induction type thin film magnetic head element)
Are formed in plural. After that, as shown in FIG. 11, each head chip 103 is cut out and processed to determine the external dimensions. Then, as shown in FIG.
The suspension mechanism 105 is attached to the head chip 103 and incorporated in the magnetic head device. In addition,
Lead wires 104 (for example, Cu coated with resin) are soldered to the terminals of the head in order to extract the head output, and are connected to a controller of the hard disk device or the like.

The thin film process for forming the MR head portion of the composite head is performed as follows, for example.

First, as shown in FIG. 13, a thin film magnetic core 202 serving as a lower shield of an MR film is formed on a substrate 201.
And four lead electrodes 203a, 203b, 203c,
203d is formed. After that, as shown in FIG. 14, an insulating film 204a serving as a lower reproducing gap of the MR head is formed on the thin film magnetic core 202, and an MR film 205 is formed on a part of the insulating film 204a. Then, after further forming an insulating film 204b so as to cover the MR film 205,
An opening is formed to expose the rear end portion 205a of the MR film 205.

After that, as shown in FIG. 15, conductive materials such as Ti and Cu are laminated to form a bias conductor 206 and a sense conductor 207. At this time, the bias conductor 2
06 is a lead electrode 2 which crosses over the MR film 205 via the insulating film 204b and has two ends 206a and 206b.
It is formed so as to be connected to 03a and 203d. Note that the lead electrodes 203a, 2a to which the bias conductor 206 is connected
The terminals 03d are referred to as bias terminals 203e and 203h. On the other hand, the sense conductor 207 has one end 207a connected to the exposed rear end portion 205a of the MR film 205.
The other end 207b is formed so as to be connected to the lead electrode 203c. The terminal of the lead electrode 203c to which the sense conductor 207 is connected is called the MR terminal 203g.

After that, an insulating film 204c is formed so as to cover the bias conductor 206 and the sense conductor 207, and then an opening is formed in the insulating film 204c to expose the tip portion 205b of the MR film 205. Then, the metal film 208 to be the upper reproduction gap of the MR head and the tip electrode of the MR film 205 is formed on the exposed tip portion 205 of the MR film 205.
b. (This step is not shown.)

Thereafter, as shown in FIG. 16, a metal film 20 is formed.
8 and the insulating film 204c, a thin film magnetic core 209 having conductivity, which serves as an upper shield of the MR film 205, is formed.
Then, the thin film magnetic core 209 and the lead electrode 203b are connected by the GND electrode 210. The thin film magnetic core 2
09 and the GND electrode 210, the lead electrode 203b connected to the MR film 205 is connected to the GND terminal 20.
3f.

In the case of a composite type head, an induction type thin film magnetic head for magnetic recording is formed on the composite type head. (The step of forming the induction type thin film magnetic head is omitted.)

FIG. 17 shows a cross-sectional view of the composite type head manufactured by the above steps. Thus, the MR head 211 has a structure in which the MR film 205 is sandwiched between the lower shield thin film magnetic core 202 and the upper shield thin film magnetic core 209. Further, the metal film 208, which also serves as the upper reproducing gap of the MR head 211 and the tip electrode of the MR film 205, is formed in the MR film when the charges charged on the surface of the recording medium jump into the tip of the MR head 211. In order to prevent electrostatic breakdown of 205, it also serves as a path for discharging electric charges to the GND terminal 203f through the thin film magnetic core 209. The composite head is
An induction type thin film magnetic head 212 is formed on the MR head 211.
And the protective film 213 are laminated.

When reproduction is performed by the MR head 211, M due to a recording magnetic field from a hard disk or the like is used.
In order to obtain the reproduction output from the resistance change of the R film 205, the MR
A sense current is applied to the film 205 via the sense conductor 207, and a bias current is applied to the bias conductor 206 to apply a bias magnetic field to the MR film 205.

By the way, in the MR head 211, the GND terminal 203f and the MR terminal 203 are used as reproducing terminals.
g, and two bias terminals 203e and 203h in total, 4 terminals are required. And in the case of a composite head,
Further, two terminals are required as recording terminals of the induction type thin film magnetic head 212, and six terminals are required as a whole.

On the other hand, when both recording and reproduction are performed by the induction type magnetic head, the number of terminals may be two for both recording and reproduction. In the case of the SAL type hard film bias type MR head, the number of reproducing terminals is two and the number of recording terminals is two, which is a total of four terminals.

In comparison with these, the MR head is
Since the number of terminals is large, the circuit system and the assembly of the head and the drive are complicated, and it is difficult to reduce the cost. Also, the large number of terminals is a disadvantageous condition in promoting miniaturization.

Therefore, in order to reduce the number of terminals, an MR head in which an MR film and a bias conductor are connected in series and the number of reproducing terminals is two has been studied.

In the above-mentioned MR head in which the MR film and the bias conductor are connected in series, the bias conductor is traversed over the MR film via the insulating film, and the other end is connected to the lead electrode so that the other end is the MR film. It is formed so as to be connected to one end of. The terminal of the lead electrode is a terminal that also serves as an MR terminal and a bias terminal, and is called an MR-bias terminal. Then, the other end of the MR film and the lead electrode are connected via the metal film and the thin film magnetic core. In addition, this lead electrode is
A terminal that doubles as a GND terminal and a bias terminal.
-It is called a bias terminal.

When reproducing, a sense current / bias current flows from the MR-bias terminal to the MR film via the bias conductor. This current serves as a sense current for obtaining a reproduction output from a resistance change of the MR film due to a recording magnetic field from a hard disk or the like, and a bias current for applying a bias magnetic field to the MR film.

[0020]

In the above-mentioned MR head in which the MR film and the bias conductor are connected in series, the number of terminals is reduced, but the S / N ratio of the reproducing system deteriorates. There is.

In particular, when the track width of the MR film is narrowed in order to improve the track density with the increase in recording density, the S / N ratio is significantly deteriorated.

Therefore, the present invention has been proposed in view of such a conventional situation, and is excellent in S / N even when the structure in which the MR film and the bias conductor are connected in series is adopted.
An object is to provide an MR head capable of realizing a ratio.

[0023]

As a result of intensive studies to achieve the above object, the present inventor has found that the cause of the deterioration of the S / N ratio is an increase in the resistance of the MR head. The present invention has been found, and the present invention has been completed based on this finding.

That is, in the MR head in which the MR film and the bias conductor are connected in series, the resistance of the MR head is
It becomes the sum of the resistance of the film, the resistance of the bias conductor, and the resistance of the wiring connecting the MR film and the bias conductor to the external terminal, and tends to be a large value, which causes an increase in resistive noise and deteriorates the S / N ratio. It has become.

The MR head of the present invention is made on the basis of the above findings, and is composed of an MR film, a bias conductor for applying a bias magnetic field to the MR film, and these MR films.
An MR head having wirings for connecting a film and a bias conductor to an external terminal, which are connected in series, in which the total resistance of the MR film, the bias conductor, and the wiring (hereinafter referred to as inter-terminal MR resistance). Is less than or equal to 20 [Ω].

In the above MR head, the method of setting the inter-terminal MR resistance to 20 [Ω] or less is not particularly limited. For example, the length of the MR film may be shortened, the MR film may have a shape with low resistance, the material of the wiring may be changed, and the wiring may be thickened.

The MR head of the present invention may be used alone for reproduction only, or may be integrated with a magnetic head capable of recording such as an inductive thin film magnetic head to form a composite head.

[0028]

The noise in reproducing the magnetic information is classified into the noise Namp depending on the reproducing amplifier, the noise Nhead depending on the magnetic head, and the noise Nmedia depending on the medium. The overall S / N ratio is expressed by the following equation. Is represented as S / N = S / (Namp ² + Nhead ² + Nmedia ² ) ^1/2

Therefore, in order to improve the S / N ratio,
It is necessary to keep Namp, Nhead, and Nmedia all low. However, because Nmedia depends on the media,
Here, Nhead and Namp are focused without considering them. Normal,
Namp is 0.5 to 0.6 [nV / Hz ^1/2 ], which is 15.6 to 2 when converted into input conversion noise of the reproduction amplifier.
It becomes 2.5 [Ω]. Therefore, Nhead is equal to or less than this, that is, the MR resistance between terminals is 15.6 to 22.5.
It is desired to be less than [Ω].

In the MR head of the present invention, the inter-terminal MR resistance is set to 20 [Ω] or less, and the noise dependent on the magnetic head can be suppressed to the same level or lower than the noise dependent on the reproducing amplifier. Therefore, increase in resistive noise is prevented, and the S / N ratio during reproduction is improved.

[0031]

Embodiments of the MR head to which the present invention is applied will be described with reference to the drawings.

In the MR head of this embodiment, as shown in FIG. 1, an MR film 5 having a tip electrode 8 for passing an electric current on its tip and a magnetic field in a desired direction are formed on the MR film 5. The bias conductor 6 is provided.

One end of the tip electrode 8 is laminated on the tip of the MR film 5. The terminal 3d at the end of the wiring pattern drawn out from the tip electrode 8 is connected to the lead wire 1
It is connected to the external terminal 12d via 1d.

The bias conductor 6 is formed as a plane loop wiring pattern, and is laminated on the MR film 5 with a predetermined distance therebetween via an insulating film. Further, one end of the bias conductor 6 overlaps with the rear end of the MR film 5, and the bias conductor 6 curves from the one end and overlaps with the MR film 5 again. In this overlapping part, a direction substantially orthogonal to the MR film 5 is obtained. That is, it is provided so as to cross the MR film 5. Then, one end portion that overlaps the MR film 5 is electrically connected to the rear end portion of the MR film 5 through the opening of the insulating film, and the other end portion that does not overlap the MR film 5 is pulled out and is pulled out. The terminal 3c at the end of the wiring pattern is connected to the external terminal 12c via the lead wire 11c.

When supplying a current to the MR head,
A current is supplied from the external terminal 12d, and the current is supplied to the tip electrode 8
Is supplied as a sense current to the MR film 5 and further continuously supplied to the bias conductor 6 as a bias current, and the current passing through the bias conductor 6 is led out by the external terminal 12c. That is, the two external terminals 12c, 1
By 2d, a sense current to the MR film 5 and a bias current to the bias conductor 6 are simultaneously supplied.

In the MR head, the MR resistance between terminals includes the resistance of the lead wire 11d from the external terminal 12d, the resistance of the wiring pattern to the tip electrode 8, the resistance of the tip electrode 8, and the resistance of the MR film 5. , The resistance of the bias conductor 6, the resistance of the wiring pattern from the bias conductor 6, and the external terminal 12
It is the sum of the resistance of the lead wire 11c to c.

A method of manufacturing the MR head in which the MR film and the bias conductor are connected in series as described above will be described.

In the MR head in which the MR film and the bias conductor are connected in series, a head material is laminated by a thin film process on a flat plate substrate (for example, an Al--Ti--C system sintered body) to form a plurality of head elements. After that, each head chip is cut out and processed to determine the outer dimensions, and is manufactured. Thereafter, a suspension mechanism is attached to this head chip and incorporated in the magnetic head device. A lead wire (for example, Cu coated with resin) is soldered to the terminal of the head in order to take out the head output, and is connected to a controller or the like of the hard disk device.

The thin film process for forming the MR head will be described in detail below. First, as shown in FIG. 2, a thin film magnetic core 2 serving as a lower shield of an MR film is formed on a substrate 1.
Then, two lead electrodes 3a and 3b are formed. afterwards,
As shown in FIG. 3, an insulating film 4a which serves as a lower reproducing gap of the MR head is formed, and the MR film is partially formed on the insulating film 4a.
The film 5 is formed. Then, after forming the insulating film 4b so as to cover the MR film 5, an opening is formed to expose the rear end portion 5a of the MR film 5.

After that, as shown in FIG. 4, the bias conductor 6 is formed. At this time, the bias conductor 6 is the MR film 5
The upper part is traversed through the insulating film 4b so that one end 6a is connected to the lead electrode 3a and the other end 6b is connected to the exposed rear end portion 5a of the MR film 5. The terminal of the lead electrode 3a to which the bias conductor 6 is connected is a terminal that also serves as the MR terminal and the bias terminal, and serves as the MR-bias terminal 3c.

After that, an insulating film is formed so as to cover the bias conductor 6, and then an opening is formed in the insulating film to form the MR film 5.
Expose the tip of the. Then, a metal film serving as an upper reproducing gap of the MR head and an electrode at the tip of the MR film 5 is formed on the exposed tip of the MR film 5. (This step is not shown.)

After that, as shown in FIG. 5, a thin film magnetic core 9 having conductivity, which serves as an upper shield of the MR film 5, is formed on the metal film and the insulating film. Then, the thin film magnetic core 9 and the lead electrode 3b are connected by the GND electrode 10. In addition, through the thin film magnetic core 9 and the GND electrode 10, the MR
The terminal of the lead electrode 3b connected to the film 5 is a terminal that also serves as a GND terminal and a bias terminal, and serves as a GND-bias terminal 3d.

In the MR head manufactured as described above, for example, in order to reduce the inter-terminal MR resistance to 20 [Ω] or less, the following configuration is used.

Example 1 Since the resistance of the MR film is the largest among the MR resistances between terminals, the resistance of the MR film is most effective for reducing the MR resistance between terminals.

Therefore, in the MR head of this embodiment, as shown in FIG.
As shown in FIG. 5, in order to reduce the resistance of the MR film 5, the magnetic sensitive portion 5c of the MR film 5 (the rear end portion 5a of the MR film 5 which is a contact point with the bias conductor and the tip end which is a contact point with the metal film). The length t1 of the portion (excluding the portion 5b) is shortened.

Specifically, the MR film 5 is formed of NiFe / Al ₂
O ₃ / NiFe = 30/6/30 [nm] is formed, and the length t1 and width t2 of the magnetic sensitive portion 5c of the MR film 5 are 5 [μm] and [4 μm], respectively. At this time, the specific resistance of the MR film 5 is 3.0E-5 [Ωcm].
Has a resistance of 6.3 [Ω].

The standard value of the MR resistance between terminals other than the MR film 5 is that the resistance of the bias conductor 6 is 4.5 [Ω] and the resistance of the GND electrode 10 which is the wiring pattern from the tip electrode is 0. 2 [Ω], the lead electrodes 3a, 3 which are the wiring pattern from the tip electrode and the wiring pattern from the bias conductor.
The resistance of b is 0.4 [Ω], the resistance of the thin film magnetic core 9 corresponding to the tip electrode is 0.2 [Ω], and the resistance of the lead wire from the external terminal is 4.0 [Ω].

Therefore, when the MR resistance between terminals other than the MR film 5 has a standard value, the MR resistance between terminals of the MR head is the resistance of the MR film 5 plus the above resistance value, 15.6.
It becomes [Ω].

Comparative Example 1 The MR head of this comparative example has an MR film 5 as shown in FIG.
The length t1 of the magnetic sensing portion 5c is set to 11 [μm], and the other portions are the same as in the first embodiment. At this time, the magnetic sensing portion 5c of the MR film 5
Has a resistance of 13.8 [Ω]. Therefore, the MR resistance between terminals of the MR head of this comparative example is 23.1 [Ω].

Embodiment 2 The resistance of the MR film is the largest among the MR resistances between terminals. Therefore, it is most effective to reduce the resistance of the MR film in order to reduce the MR resistance between terminals.

Therefore, in the MR head of this embodiment, as shown in FIG.
As shown in (1), in order to reduce the resistance of the MR film 5, the length of the magnetic sensitive portion 5c of the MR film 5 is shortened and the shape thereof is made narrower at the front end portion and wider at the rear end portion.

Specifically, the magnetic sensitive portion 5c of the MR film 5 has a shape in which the length t1 from the front end to the rear end is 5 [μm] and the width t3 of the front end is 2 [μm]. The width t4 from the portion retracted 1 [μm] from the front end to the rear end is 4
[Μm]. Except for this, the procedure is the same as in the first embodiment.

At this time, the resistance of the magnetic sensitive portion 5c of the MR film 5 becomes 7.5 [Ω]. Therefore, between the terminals M of this embodiment
The R resistance is 16.8 [Ω].

As described above, by making the shape of the magnetic sensitive portion of the MR film such that the width of the front end portion is narrow and the width of the rear end portion is wide, the front end portion of the MR film is increased in order to increase the track density. Even if the width is narrowed, the MR resistance between terminals can be suppressed low.

Comparative Example 2 In the MR head of this comparative example, the magneto-sensitive portion of the MR film has a rectangular shape with a length of 5 [μm] and a width of 2 [μm].
Except for this, the procedure is the same as in the second embodiment. At this time, the resistance of the magneto-sensitive part of the MR film becomes 27.5 [Ω]. Therefore, the MR resistance between the terminals of the MR head of this comparative example is 36.8 [Ω].
Becomes

In the above embodiments, the resistance of the MR film is lowered to lower the MR resistance between terminals.
The resistance of the portion other than the film may be reduced. Specifically, the thickness of the bias conductor may be increased, the wiring may be increased as much as possible, and the material and diameter of the lead wire may be changed.

[0057]

In the MR head of the present invention, the MR resistance between terminals is set to 20 [Ω] or less, and the noise dependent on the magnetic head can be suppressed to the same level or lower than the noise dependent on the reproducing amplifier. Therefore, increase in resistive noise is prevented, and the S / N ratio during reproduction is improved.

Further, when the sense current / bias current is passed, the smaller the MR resistance between the terminals is, the smaller the power consumption is, which leads to the power saving.

[Brief description of drawings]

FIG. 1 is a schematic plan view showing an example of an MR head to which the present invention is applied.

FIG. 2 is a schematic plan view showing a step of forming a thin film magnetic core and a lead electrode to be a lower shield, sequentially showing thin film steps of an MR head to which the present invention is applied.

FIG. 3 is a schematic plan view showing a process of forming an MR film and an insulating film.

FIG. 4 is a schematic plan view showing a step of forming a bias conductor.

FIG. 5 is a schematic plan view showing a process of forming a thin film magnetic core to be an upper shield and a GND electrode.

6 is a schematic plan view showing the shape of the MR film of the MR head of Example 1. FIG.

7 is a schematic plan view showing the shape of an MR film of the MR head of Comparative Example 1. FIG.

8 is a schematic plan view showing the shape of an MR film of an MR head of Example 2. FIG.

FIG. 9 is a schematic perspective view showing a substrate manufacturing process, sequentially showing the manufacturing process of the conventional MR head.

FIG. 10 is a schematic perspective view showing a head element forming step, which sequentially shows the manufacturing steps of the conventional MR head.

FIG. 11 is a schematic perspective view showing a head chip cutting step, which sequentially shows manufacturing steps of a conventional MR head.

FIG. 12 is a schematic perspective view showing a step of attaching a suspension and a lead wire, which sequentially shows steps of manufacturing a conventional MR head.

FIG. 13 is a schematic plan view showing the steps of forming a thin film magnetic core and a lead electrode to be a lower shield, sequentially showing the steps of forming a thin film of a conventional MR head.

FIG. 14 is a schematic plan view showing a process of forming an MR film and an insulating film.

FIG. 15 is a schematic plan view showing a step of forming a bias conductor and a sense conductor.

FIG. 16 is a schematic plan view showing a process of forming a thin film magnetic core to be an upper shield and a GND electrode.

FIG. 17 is an enlarged transverse cross-sectional view of a main part of a conventional MR head.

[Explanation of reference numerals] 1 substrate 2 thin film magnetic core 3a, 3b lead electrode 4a, 4b insulating film 5 magnetoresistive film 6 bias conductor 8 tip electrode 9 thin film magnetic core 10 GND electrode 11c, 11d lead wire 12c, 12d external terminal

Claims (1)

[Claims] 1. A magnetoresistive effect film, a bias conductor for applying a bias magnetic field to the magnetoresistive effect film, and wiring for connecting the magnetoresistive effect film and the bias conductor to an external terminal. A magnetoresistive thin film magnetic head connected in series, wherein the total resistance of the magnetoresistive film, the bias conductor, and the wiring is 20 [Ω] or less. .