JPS592221A - Thin film magnetic head - Google Patents

Abstract

PURPOSE:To improve an S/N ratio and to decrease the induction of external noise, by forming magnetoresistance effect elements MR and thin film transistor circuit parts of a field effect type on an insulation substrate. CONSTITUTION:Integrated head parts 5 formed with MR head parts and thin film transistor circuit parts of a field effect type are formed on a substrate 4. The electrodes 9 on the conductive layers 3 connecting to both ends of MR elements 2 and the input sides of the thin film transistor circuit parts are electrically connected. Constant current is supplied to each element 2 from the thin film transistors Q1, Q2 of a field effect type. The resistance change of the MR element modulated by an external magnetic field is converted to the voltage change is amplified with an amplifier constituted of thin film transistors Q3- Q13 of a field effect type and is drawn out as an output to the outside. Since the MR element and a preamplifier are formed in extreme proximity to each other in the thin film magnetic field, the sectional area formed of the signal line connecting both is virtually negligible. As a result, the amt. of noise is considerably reduced and the S/N ratio of the reproduction signal is considerably improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thin film magnetic head, and more particularly to a thin film magnetic head in which a magnetoresistive magnetic head (hereinafter referred to as MR head) and a field effect thin film transistor circuit are provided on the same substrate. It's a thing.

As magnetic recording and reproducing technology improves, thin-film magnetic heads using magnetoresistive elements (hereinafter referred to as MR elements) are attracting attention in order to increase recording density and improve two-frequency characteristics.

For example, in order to respond to the trend toward multi-channel technology such as in digital tape recorders, magnetic heads with a large number of heads and a high degree of integration are required.

The MR element is an element whose resistance value changes depending on the strength of an external magnetic field when a constant current is passed through it, and a magnetic signal can be detected based on this change in resistance value.

On the other hand, regarding the playback head, the playback voltage of a conventional magnetic induction type thin-film magnetic head is proportional to the relative speed between the head and the recording medium, so the playback output is also low at low speeds. The number of turns of the coil is several 100 to 1
,000 turns, making it practically difficult to manufacture as a thin film read magnetic head.

In contrast, magnetic flux responsive MR heads that are not affected by the relative speed between the head and the magnetic recording medium are attracting attention.

An example of a conventional MR head is shown in FIG.

In FIG. 1, the reference numeral 1 indicates a substrate, and this substrate 1
An MRR element 2 is formed on the recording medium sliding surface side by a thin film deposition method or the like.

Both ends of the MRR element 2 are connected to a conductive layer 3, which is also formed on the substrate by a thin film deposition method or the like.

Based on the above configuration, if a constant current is supplied to the MRR element 2 through the conductive layer 3, when an external magnetic field such as a magnetic signal recorded on a magnetic tape approaches, the MR element 2 resistor The value changes.

Now, assuming that the changed resistance value of the MR element is ΔR and the current is I, the reproduced output voltage ΔV is expressed by the following equation (1).

ΔV−ΔR−I ・・・・・・・・・・・・・・・
(1) The rate of change in resistance of the MRR element 2 due to an external magnetic field is generally about 1 to 3q6 for elements made of Ni ("e, Ni--Co, etc.).

Therefore, in order to increase the reproducing power, it is necessary to increase the absolute resistance value of the MR element.

That is, the resistance value of the MR element is expressed by the following equation (2), where R2ρMR is the specific resistance value of the MR element, l is the length of the MR element, t is the warp width, and t is the thickness.

R= ρM 几
(2) As is clear from equation (2), the resistance value of the KMR element can be increased by increasing its length and decreasing its width and thickness.

However, the thickness of the MR element cannot be made very thin using the current thin film technology, and the width of the MR element cannot be made very small due to manufacturing constraints such as the cutting edge and etching techniques.

- On the other hand, the length of the MRR element 2 corresponds to the track width of the reproducing head, and in the current state of increasing density and multi-channeling, it is necessary to reduce the track width, that is, the length of the MR element. It's been requested.

As described above, there is a tendency for the reproduction output to become small at present.

Furthermore, when actually using a thin film magnetic head, the conductive layer 3 and an external preamplifier circuit, etc. are connected with a flexible lead wire to process the reproduced output signal, so the specific resistance of the conductive layer 3 and the flexible lead wire is also cannot be ignored.

Further, since the conductive portion and the flexible lead wire are long, when actually detecting the reproduced signal, the signal is induced by surrounding noise, resulting in an output with a poor S/N ratio.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional technology, and an object of the present invention is to provide a thin-film magnetic head configured to improve the S/N ratio and reduce the induction of external noise. .

In order to achieve the above object, the present invention employs a structure in which an MR head section and a field effect thin film transistor circuit section are formed on a substrate by a thin film deposition method.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 2 is a schematic sectional view illustrating an embodiment of the present invention.
In the figure, numeral 4 is a substrate, which can be made of glass, quartz, alumina, etc.
It is made of an insulating material such as ferrite. This board 4
An integrated head section 5 in which an MR head section and a field effect thin film transistor circuit section are formed is formed on the top, as will be described later. The upper surface of the end of the integrated-rad section 5 on the side where the magnetic recording medium slides is covered with a protective plate 6 made of an insulating material such as glass, quartz, alumina, ferrite, or the like.

The reference numeral 7 indicates a flexible lead wire, which is used to electrically connect the above-mentioned field effect thin film transistor circuit to an external circuit. A wire 8 is connected to the lead wire 7 .

FIG. 3 shows a partially enlarged plan view of the collecting head section 5. As shown in FIG. Third
In the drawing, reference numeral 9 indicates an electrode connected to the conductive layer 3, and this electrode 9 is electrically connected to the input side of the thin film transistor circuit section.

Reference numeral 10 indicates the output side electrode of the thin film transistor circuit section, and the portion sandwiched by lines X-X and Y-Y in FIG. 3 is the thin film transistor circuit section. FIG. 4 shows an example of a preamplifier circuit composed of this thin film transistor.

In FIG. 4, the part indicated by the symbol -C 2 is an MR element, and the symbols A and B are parts corresponding to the electrode 9 and the conductive layer 3 shown in FIG.

A constant current is supplied to the MR element designated by numeral 2 in FIG. 4 from field effect thin film transistors QI and Q2.

Then, the resistance change of the MR element modulated by the external magnetic field is converted into a voltage change, and the field effect thin film transistor Q
The signal is amplified by an amplifier constituted by Q3 to Qr3, and taken out as an output to the outside.

Note that the field effect thin film transistor Q. , Q5. teeth,
This is for supplying a bias voltage to the gate electrodes of the field effect thin film transistors Q+ and Q6. Code R
is a resistor for stabilizing the DC operating point of the amplifier, and C is a capacitor.

In FIG. 4, the shape, R and C of each transistor are determined so that the gain of the amplifier is 20 to 30 dB and a desired frequency band is obtained.

Incidentally, a field-effect thin film transistor (TPT) is known as a transistor using a semiconductor layer, an electrode layer, and an insulating layer. In other words, a voltage is applied between a source electrode and a drain electrode that have an ohmic contact adjacent to the semiconductor layer, and the channel current flowing there is modulated by the bias voltage applied to the gate electrode provided through an insulating layer. . FIG. 5 shows an example of a typical basic structure of such a TPT.

That is, what is indicated by reference numeral 11 in FIG. 5 is an insulating substrate, and a source electrode 13 is formed on a semiconductor layer 12 formed thereon. A drain electrode 14 is provided in contact with the drain electrode 14, and an insulating layer 15 is formed to cover these.
A gate electrode 16 is formed thereon.

The semiconductor layer 12 shown in FIG. 5 is composed of a polycrystalline silicon thin film having the characteristics described above, and includes the semiconductor layer 12 and two electrodes, namely, a source electrode 13. A first N+ layer 17 made of amorphous silicon is provided between each of the drain electrodes 14 . A second layer 18 is provided, forming an ohmic contact. The insulating layer 105 is formed by CVD (Che
(Mical Vapor De-position)
, LPGVD (Low Pressure C
chemical vapor deposition)
, or PCVD (Plasma Chemi-ca
1 Vapor Deposition) etc., cylindrical nitride, St, 2. Aff
It is made of materials such as 1, 03, etc. The reactive gas used in the production of the polycrystalline silicon thin film forming the semiconductor layer 12 is mono7ran (a substance that makes up silicon constituent atoms).
SiH2) + disilane (S I 2H6), etc., and these can be combined with H2, fiJ, He
It can also be used diluted with a gas such as

Field-effect TPTs are classified into types with a gate insulating layer on the gate electrode (lower gate type) and types with the gate electrode on the gate insulating layer (upper gate type).

In addition, there is a type (C0pIanar type) in which the source electrode and drain electrode are at the interface between the insulating layer and the semiconductor layer, and a source type.

It is known that the drain electrode is located on the semiconductor surface facing the interface between the insulating layer and the semiconductor layer (Stagger type), and there are four types for each combination.

The structure shown in FIG. 5 shows an example called a "nigate coplanar field-effect TPT," but it goes without saying that the field-effect TPT applied to the present invention may be any of these. .

Next, a method of manufacturing the collecting head section 5 will be explained.

Example 1 In this example, a polycrystalline silicon thin film is formed on a substrate, and TPT
It was created using the apparatus shown in FIG. In FIG. 6, the reference numeral 20 indicates a substrate, and #7059 glass manufactured by Corning Co., Ltd. was used. First, after cleaning this substrate 20, (HF + HNO3 + C
After lightly etching its surface with a mixed solution of H3CO0H) and drying it, it is mounted on the substrate heating holder 22 placed on the anode side in the Pelger vacuum deposition chamber 21.

Next, the Pelger 21 is evacuated using the diffusion pump 23 to a background vacuum level of 2 x IO-"I'orr or less. At this time, if this vacuum level is low, the reactive gas will not be effectively deposited into a film. Not only does it not move, but O and N are mixed into the film, significantly changing the resistance of the film.

Next, increase the substrate temperature Ts to bring the temperature of the substrate 20 to 500°C.
to hold. The substrate temperature is monitored by thermocouple 24.

Next, H2 gas is introduced into the Pelger 21 while being controlled by the mass flow controller 25 to clean the surface of the substrate 20, and then a reactive gas is introduced. At this time,
The substrate temperature Ts was set at 450''Cvc.

In this example, the reaction gas to be introduced is H2 gas, which is easy to handle, and SiH4 diluted to 1 volume.
A gas (SiH, abbreviated as +(1)/H2) was used. The gas flow rate was controlled by a mass flow controller 26 to be introduced at 505 CCM.

The pressure inside the Pel Jar 21 is determined by adjusting the pressure regulating pulp 27 on the exhaust side of the Pel Jar 21 and using the absolute pressure gauge 28 to a value of 0. The pressure was set to 1 so that the pressure was OI Torr. After the pressure inside the Pelger 21 became stable, a high frequency electric field of 13.561 viHz was applied to the cathode electrode 29 by the power source 30 to start glow discharge.

At this time, the voltage was 0.5 KV, the current was 48 mA, and the RF discharge power was IOW. The thickness of the film thus formed was 5,000 mm, and its uniformity was within ±10 inches with respect to the substrate size of 120×120+y+x when a circular ring-shaped outlet was used.

The amount of hydrogen in the formed film is 0.5 atom
It was icchi.

The surface roughness was 200, and the etching rate with the above-mentioned etching solution was 15λ, which was the same as the etching rate of a silicon wafer having a value of ρ-03Ω.

In addition, when the orientation characteristics of the above thin film were investigated using X-ray diffraction data, it was found that 90% (=1 (220)/], to
talx 1oo), and the average crystal grain size was 900.

Next, using the film formed as described above as a material, a TPT was created according to the process outlined in FIG. 7.

That is, first, as shown in step (a), the glass substrate 2
After depositing the polycrystalline silicon film 40 formed as described above, PH3 gas (PH3 (100 ppm)/H2 diluted to 1100 VoIpp with hydrogen gas)
(abbreviated as 5iH4 (abbreviated as 5iH4GO)/H2) diluted with H2 to 1 OVol·H2 at a molar ratio of 5 x 10-'' into the Pelger 21, Pressure inside Pelger 21 to 0
．． Glow discharge was performed at a pressure of 12 Torr to form an N+ layer 41 doped with P to a thickness of 500 mm.

This is the step shown in (b).

Next, as shown in step (C), the star layer 41 was removed by photoetching except for the source electrode 42 and drain electrode 43 regions. Next, in order to form a gate insulating film, the above-mentioned substrate was again mounted on the heating holder 22 on the anode side inside the Pelger 21. Then, as in the case of creating polycrystalline/recon, the inside of Pelger 21 is evacuated,
Assuming the substrate temperature Tswo is 250°C, NH31f Suwo2
0 SCCM, 55CC of 5iH4 (10)/horse gas
After introducing M and generating glow discharge, a 5iNH film 44 was deposited to a thickness of 250 OA.

This is the step shown in (d).

Next, the source electrode 42.
Contact hole 45°46 for drain electrode 43
It was opened as shown in Figure (e), and then SiNl (M) was evaporated on the entire surface of the film 44 to form an electrode film 47.

This is the step shown in (f)K. Next, the M electrode film 47 is processed by a first etching process to form a source electrode extraction electrode 48 as shown in FIG. A drain electrode extraction electrode 49 and a gate electrode 50 were formed.

After that, heat treatment was performed at 250° C. in a He atmosphere.

The preamplifier circuit section shown in FIG. 4, which is made of field-effect thin film transistors formed by such a process, exhibited good and stable characteristics.

Example 2 In this example, the parts other than the electrode parts 9 and 10 of the preamplifier shown in Example 1 were protected with an insulating layer such as phosphoric acid glass, and then 81% Ni -MR element film made of Fe alloy, aluminum, Cu.

A conductive portion 3 made of gold or the like was formed by vapor deposition. Then, the electrode part 9 is etched by the first etching method.
．． Conductive part 3. MR element 2 is formed by selective etching,
A collecting head portion was formed as shown in FIG. Next, the protective cover and flexible lead wires were connected to complete the integrated head section.

Using the integrated magnetic head obtained in this way, we tested the playback output on a magnetic tape and found that the amplifier gain was 30 dB, indicating that it was a good integrated magnetic head with a good S/N ratio and not inducing external noise. Understood.

The thin film magnetic head obtained in this way can shorten the distance between the MR element and the preamplifier circuit composed of TFTs on the same substrate, and improve the S/N ratio of the reproduced signal. There was a significant improvement effect.

That is, when using an MR head, noise generated by the induced magnetic field crossing the signal line connecting the MR element and the preamplifier becomes a problem.

The magnitude of this noise is proportional to the cross-sectional area of the closed loop formed by the signal lines described above. However, in the conventional structure, M
Since the R element and the preamplifier located at a remote location are connected by a lead wire such as a flexible lead wire, the above-mentioned cross-sectional area becomes large and the amount of noise is also large.

In contrast, in the thin-film magnetic head obtained by the present invention, the MR element and preamplifier are formed extremely close to each other, so the cross-sectional area formed by the signal line connecting them can be almost ignored, and as a result, the amount of noise is also reduced. significantly decreased.

In this case, the output end of the preamplifier is connected to the input end of the next stage using a lead wire as before, and noise is generated in that part due to the induced magnetic field, but with the above structure, the signal component is amplified by the preamplifier. Therefore, even if the same noise as in the conventional example occurs in this part, the S/N ratio is improved by the amount that the signal has been amplified in advance.

In addition, the lead portion and the resistance of the lead wire that take out the signal from the MR element become a source of noise.
Regarding the noise in 1, in the conventional example, noise occurs at a stage where the signal voltage before and after the preamplifier is small, so the S/N
However, in the present invention, the resistance of the lead portion is located at the rear stage of the preamplifier, so that the noise caused by this can be almost eliminated.

For these reasons, the S/S of the reproduced signal is lower than that of the conventional structure.
The N ratio can be significantly improved.

Furthermore, in the case of the conventional structure, in a structure having n MR elements, the number of connection terminals is nX2.In contrast, in the structure of the present invention, the preamplifier circuit has two common drive voltage terminals, a common ground A total of n+3 terminals (one terminal and n output terminals) is sufficient. As a result, when the number of MR elements becomes three or more, the number of terminals in the structure of the present invention becomes smaller, and the area of the flexible lead wire becomes smaller.

Furthermore, when creating a thin film transistor circuit, the substrate can be made not only of Si but also of insulating materials such as quartz, alumina, and ferrite. Although durability is an issue, a wear-resistant substrate suitable for the medium can also be arbitrarily selected.

In the above-mentioned embodiment, a multi-track MR head such as a digital tape recorder is described, but the MR head can also be applied to a V'I''R phase position detection sensor, a rotation speed detection sensor, etc. It can also be fully used as a sensor that is less affected by external magnetic fields.

As is clear from the above description, according to the present invention, since a structure in which an MR element section and a field effect thin film transistor circuit section are formed on an insulating substrate is adopted, the induction of external noise can be reduced. A thin film magnetic head with improved s//N ratio can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a partially enlarged plan view illustrating the conventional structure, Fig. 2 and the following are circuit diagrams illustrating the present invention in detail, and Fig. 5 is a partially enlarged longitudinal section illustrating the structure of a field-effect thin film transistor. A side view and FIG. 6 are schematic configuration diagrams of a manufacturing apparatus applied to the present invention, and FIGS. 7(a) to (g) are process diagrams showing manufacturing steps. 1.4...Substrate 2...MR element 3.
...Conductive layer 5...Integration head section 6...
Protective plate 7... Flexible lead wire 8... Wire 9, 10... Electrode 11...
- Insulating substrate 12... Semiconductor layer 13... Source electrode 14... Drain electrode 15... Insulating layer 16... Gate electrode 17... First furnace layer 1st... Second N+ layer Fig. 4 VFI H3 PH3/H2 Fig. 5 A last e Fig. 6

Claims (2)

[Claims] (1) A thin film magnetic head characterized in that a magnetoresistive element and a field effect thin film transistor circuit section are formed on an insulating substrate. (2) The thin film magnetic heald according to claim 1, wherein the semiconductor layer of the field effect thin film transistor circuit section is made of a polycrystalline silicon thin film.