JPS62235714A - Formation of magnetic alloy thin film and device therefor - Google Patents

Abstract

PURPOSE:To form a magnetic alloy thin film, having uniform compositional distribution, on a stepped substrate by a method wherein the circulation of a plating solution, the agitation of the plating solution in the vicinity of the substrate surface, and a pulse superposition DC power source are properly combined. CONSTITUTION:When a magnetic alloy thin film is going to be electroplated on a substrate, a horizontal current circuit, having the crosssectional area oorresponding to the shape of the substrate, is formed between an anode plate 24 and a cathode plate 14 droopingly provided facing each other in a plating cell 25 in which a plating solution is circulated. The plating solution is fed into an inflow chamber 18 from an inflow pipe 17 with a circulating pump 28, it is sent to a cathode chamber 12 passing through an inflow hole 19, the plating solution in the cathode chamber 12 is agitated by an agitating spatula 20, and sent to an anode chamber 10 passing through an aperture part 15. A pulse superposition DC plating power source 36, with which a current wherein a rectangular pulse is DC-superposed is supplied through the intermediary of a lead, is connected to the point located between the anode plate 24 and the cathode plate 14.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method and apparatus for forming a magnetic alloy thin film,
In particular, it relates to a method and apparatus for forming a magnetic alloy thin film that can easily plate a magnetic alloy thin film having a uniform alloy composition with good reproducibility on a stepped substrate imparted with electrical conductivity, such as for an inductive thin film magnetic head. .

[Conventional technology]

Conventionally, magnetic alloy thin films, particularly permalloy thin films having an alloy composition of about 8]Ni-19Fe, have been widely used as magnetic materials for high-speed switching elements such as thin-film magnetic heads because they exhibit low coercive force and high magnetic permeability in the high frequency range. ing. For example, in an inductive thin film magnetic head having a cross-sectional structure as shown in FIG. Since the composition distribution of the permalloy thin film greatly affects the strength of the recording magnetic field and the reproducing resolution, it is necessary to form the permalloy thin film so that the composition ratio of Ni and Fe is within a composition tolerance of approximately ±0.5 wt%. Therefore, in order to form a permalloy thin film that satisfies these requirements by electroplating, it is necessary to make the composition distribution uniform within the substrate and to minimize compositional variations between substrates.

In the conventional electroplating method, for example, Japanese Patent Application Laid-Open No. 57-9
894 and Japanese Unexamined Patent Publication No. 57-5890, a method using a cylinder for partial plating;
A method of arranging an electrode and an object to be plated vertically as described in Japanese Patent Publication No. 152200, and a plating apparatus having a stirring mechanism as described in Japanese Patent Publication No. 57-9636 are well known. In the conventional electroplating method for forming the magnetic alloy thin film for the above-mentioned induction type thin film magnetic head, a DC plating method is adopted in which the plating solution is circulated or stirred near the cathode.

However, with the recent increase in the density of thin-film magnetic heads, Ni
It is necessary to reduce the composition tolerance of about ±0.1 in the composition ratio of Fe and Fe, which is difficult to achieve with conventional plating methods.

[Problem that the invention seeks to solve]

The problem with the conventional method of forming a magnetic alloy thin film using electroplating described above is that it is difficult to form a magnetic alloy thin film with a sufficiently uniform composition distribution on a substrate with a step such as for an inductive thin film magnetic head. was there.

An object of the present invention is to improve the problems of the prior art described above, and to produce a magnetic alloy thin film having a more uniform alloy composition on a stepped substrate with electrical conductivity, such as for an inductive thin film magnetic head, with good reproducibility. It is an object of the present invention to provide a method for forming a magnetic alloy thin film that can be easily formed by electroplating, and an apparatus therefor.

[Means for solving problems]

The above purpose is to electroplate a magnetic alloy thin film onto a substrate by circulating a plating solution between an anode plate and a cathode plate, which are vertically opposed to each other in a plating cell. A plating power source is used that supplies a current in which a rectangular pulse current is superimposed on a direct current between the anode plate and the cathode plate by agitating the plating solution near the cathode plate and forming a focused horizontal current path having This is achieved by

[Effect]

In forming a magnetic alloy thin film by the above-mentioned electroplating method, a uniform alloy composition film is formed on the flat surface of the substrate by focusing horizontal current paths and stirring near the cathode, and at the same time, a rectangular pulsed current is applied to the film with a direct current. By using a plating power source superimposed on the substrate, it is possible to form a film with a uniform alloy composition on the stepped portions without concentrating current on the stepped portions of the substrate.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 6.

FIG. 1 is an overall configuration diagram of a plating apparatus showing an embodiment of the method and apparatus for forming a magnetic alloy thin film according to the present invention.

In Figure 1, 8 and 9 are shielding plates, 10 is an anode chamber, 11 is an intermediate chamber, 12 is a cathode chamber,
13 is a substrate holding plate, 14 is a cathode plate, 15 is an opening,
16 is a cylinder for controlling current distribution; 17 is an inflow pipe; 1
8 is the inflow chamber.

19 is an inlet, 20 is a stirring spatula, 21 is an overflow chamber, 22 is an outflow pipe, 24 is an anode plate, and 25 is a plating cell. Further, 26 is a flow meter, 27 is a filter, 28 is a circulation pump, 29 is a storage tank, 30 is a temperature sensor, 31 is a temperature control circuit, 32 is an electric heater, 33 is a stirrer, 34
35 is a PH meter, 35 is a titrator, and 36 is a pulse superimposed DC plating power source.

The plating cell 25 in FIG. 1 has a flowmeter 26. The filter 27 is connected via piping to a storage tank 29 via a circulation pump 28.

The liquid temperature is measured in the storage tank 29 by a temperature sensor 30 made of a platinum resistor, and a temperature control device 31 receives the temperature signal and operates an electric heater 32 to maintain the temperature at a constant temperature. The plating solution is passed through the stirrer 3 in the storage tank 29.
3. Stir constantly. The pH of the plating solution is 3
4, and by inputting the signal, the titrator 35 drips a dilute solution of hydrochloric acid into the storage tank 29, thereby maintaining a constant value. Between the anode plate 24 and the cathode plate 14 is a pulse superimposed DC plating power supply 36 that supplies a current in which rectangular wave pulses are superimposed on DC from a terminal (not shown) via a lead wire.
is connected.

FIG. 2 is a partially cutaway perspective view of the plating cell 25 of FIG. 1. In FIG. 2, the same reference numerals as in FIG. 1 indicate corresponding parts, and 23 is a guide groove. The plating cell 25 made of PVC (polyvinyl chloride) shown in FIG. Intermediate chamber 11. The cathode chamber 14 is partitioned into three chambers. At least one pair of openings 15 (circular in this embodiment) are formed in the shielding plate 8.9 according to the shape of the substrate which is pressed and supported by the substrate holding plate 13 against the substrate contacting portion of the cathode plate 14. , the anode chamber 10 and the cathode chamber 12 are connected by P welded to the shielding plates 8 and 9 so as to connect these openings.
They are communicated through a current distribution control cylinder 16 made of vC. The plating solution enters the inflow chamber 18 from the inflow pipe 17 by the circulation pump 28, and is sent to the cathode chamber 12 through the inlet 19. The plating solution entering the cathode chamber 12 is stirred up and down by the stirring spatula 20, and 15 to the anode chamber 10, the plating solution that overflows the shielding plate 9 enters the intermediate chamber and further passes through the shielding plate 8. The liquid that overflowed the anode chamber 10 wall enters the overflow chamber,
Outflow pipe 22 circulates back to storage tank 29 in FIG.

An anode plate 24 made of soluble nickel or 81Ni-19Fe permalloy is vertically disposed in the anode chamber IO in close proximity to the shield plate 8.

Note that the openings 15 of the shielding plates 8 and 9, whose cross-sectional areas are determined according to the shape of the substrate supported by the substrate holding plate 13, are determined depending on the size of the substrate, various shapes, the distance between the shielding plate 9 and the cathode 14, It is determined by taking into account the length of the current distribution control cylinder 16, the conductivity of the cathode plate 14 and the substrate, etc.

The distance between the stirring spatula 20 and the cathode plate 14 is always kept constant by moving the cathode plate 14 in and out through a guide groove 23 formed in the side wall of the cathode chamber 12. The cathode plate 14 is manufactured so that it is located at the center of the substrate when inserted into a predetermined position. Also, in order to conduct electricity to the board, the cathode plate 1
4 is made of a conductive material such as stainless steel, and has a width of, for example, 5 + nm, excluding the substrate contacting portion, to prevent a plating film from being formed on its surface.

It is covered with an insulating resin film such as PTFE (Teflon) with a thickness of about 0.3 mm. A magnetic field (not shown) can generate a magnetic field of about 50 degrees parallel to the substrate and in the horizontal direction during plating.

FIG. 3 is a sectional view of an example of an inductive thin film magnetic head. Third
In the figure, ■ is a substrate, 2 and 3 are magnetic cores, 4 is an insulating film, 5 is a conductor coil, and 6 is a protective film.

7 is near the stepped portion. In FIG. 3, the composition of the tips of the magnetic cores 2 and 3 made of permalloy thin films formed on the substrate 1 as described above and the composition ratio of Ni and Fe near the step portion forming the slope are determined with a composition tolerance of approximately ±0. , 5vt% or less, especially for high-density thin-film magnetic heads, the composition tolerance is about ±0.1
About wt% is desired.

FIG. 4 is a partial cross-sectional view of the substrate on which the magnetic core 3 with the experimental step shown in FIG. 3 is formed. In FIG. 4, an insulating film 4 having a step with a height of about 10 μm and a taper angle of about 40° is formed on an insulating ceramic substrate 1 such as glass with a diameter of 3 inches.
was formed, and a permalloy base film with a thickness of 0.1 μm was further formed on the insulating film 4 by a sputtering method, and the inner diameter of the current distribution control cylinder 16 was optimized to form a film with a thickness of about 2 μm.
The magnetic core 3 of the permalloy film is plated, and the composition distribution near the stepped portion 7 of the magnetic core 3 is measured. Note that the magnetic core 2 without steps shown in FIG. 3 was not formed for the experiment.

Figures 5(a) and 5(b) show normal DC using the conventional method.
4 is a diagram showing a composition distribution when plating is performed on a substrate with steps shown in FIG. 4 using a power source, and a current mode diagram. FIG. 6th
Figures (a) and (b) are a diagram showing the composition distribution and a current mode diagram when plating is performed on the stepped substrate shown in Figure 4 by superimposing a rectangular wave pulse on a DC power supply using the method of the present invention. be. In this experiment shown in FIG. 1 (FIG. 2), the length of the current distribution control cylinder 16 was 65 ma, the shielding plate 9 and the cathode plate 1 were
The interval of 4 was fixed at 20 m, the flow rate of the liquid was fixed at 5 Q/m, and the stirring speed was fixed at 6 Orpm.

The plating solution was nickel chloride 35 g/ILm nickel sulfate 15 g/i, ferrous sulfate 1.3 g/i, and ferrous acid 25 g/Q.

A low-concentration Watt bath containing 1 g/ml of sodium saccharinate was used, and the plating conditions were PH3 and liquid temperature 20°C.
And so.

Under these conditions, the composition distribution of Ni in the vicinity of the stepped portion 7 is determined when plating is performed in the I)C mode shown in FIG. The measurement results are shown in FIG. 5(a).

Similarly, in the pulse superimposed DC mode shown in Fig. 6(b), a current density of 8 nlA/■ was applied to the DC power supply using a normal DC power supply, and the on-time/m was set at a current density of 25 mA/alY.
.

FIG. 6(b) shows the measurement results of the Ni composition distribution in the vicinity of the stepped portion 7 when a rectangular pulse current with an off time of 3 m5 ec is superimposed.

From these experimental results, the Ni composition unevenness in the vicinity of the stepped portion 7 is ±0, 5wt% when using the DC power source according to the conventional method shown in FIG. / N near the step portion 7 when superimposed on a rectangular pulse teDc power supply with an off time ratio of 1:3, for example.
It has been found that it is possible to reduce the i-composition unevenness to ±0.1 wt%.

〔Effect of the invention〕

As explained above, according to the present invention, by combining the circulation of the plating solution, the stirring of the solution near the substrate surface, and the pulse superimposed DC power supply, it is possible to form a substrate with steps, which is impossible with normal DC plating. Compositional unevenness even near the area ±0.1
It becomes possible to form a magnetic alloy film with a uniform composition distribution reduced to about wt%.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of a plating apparatus showing an embodiment of the method and apparatus for forming a magnetic alloy thin film according to the present invention, Fig. 2 is a partially cutaway perspective view of the plating cell shown in Fig. 1, and Fig. 3 is an induction 4 is a sectional view of a substrate with steps for the experiment shown in FIG. Distribution diagram and current mode diagram. FIGS. 6(a) and 6(b) are a composition distribution diagram and current mode diagram of the experimental results according to the method of the present invention shown in FIG. DESCRIPTION OF SYMBOLS 1... Substrate, 2, 3... Magnetic core, 4... Insulating film, 5... Conductor coil, 6... Protective film, 7... Near step part, 8°9... Shielding plate, 10...Anode chamber, 1
DESCRIPTION OF SYMBOLS 1... Intermediate chamber, 12... Cathode chamber, 13... Substrate holding plate, 14... Cathode plate, 15... Opening, 16...
- Cylinder for current distribution control, 17 - Inflow chamber, 19 - Inflow port, 20 - Stirring spatula, 21 - Overflow chamber, 22 - Outflow pipe, 23 - Guide groove, 24 -
Anode plate, 25... Plating cell, 26... Flowmeter, 27
・Filter, 28...Circulation pump, 29...Storage tank,
30... Temperature sensor, 31... Temperature control device, 32
... Heater, 33 ... Stirrer, 34 ... PH meter, 3
5...Titrator, 36...Pulse superimposed DC plating power supply.

Claims (1)

[Claims] 1. A plating solution is circulated in a plating cell for electroplating a magnetic alloy thin film onto a substrate, and the cathode plate is set between an anode plate and a cathode plate that are vertically disposed opposite each other in the plating cell. A horizontal current path having a cross-sectional area corresponding to the shape of the substrate is focused and formed, the plating solution is stirred near the cathode plate, and a current in which a pulsed current is superimposed on a direct current is supplied between the anode plate and the cathode plate. A method for forming a magnetic alloy thin film on a substrate by electroplating. 2. A plating cell for electroplating a magnetic alloy thin film onto a substrate, a means for circulating a plating solution in the plating cell, and an anode plate and a cathode plate that are vertically disposed opposite each other in the plating cell, and a substrate is placed on the cathode plate. means for converging and forming a horizontal current path having a cross-sectional area according to the shape of the substrate between the anode plate and the cathode plate; means for stirring a plating solution near the cathode plate; A magnetic alloy thin film forming apparatus comprising a plating power source that supplies a current in which a pulsed current is superimposed on a direct current between cathode plates to form a magnetic alloy thin film on a substrate by electroplating.