Method of manufacturing a metal pattern

Abstract

Even when materials with different grinding rates, such as a metal layer and an insulating layer, are present on a substrate, a method of manufacturing can grind the surface of the substrate to form a flat surface and can grind the metal layer to a predetermined thickness without fluctuations. The method includes a step of forming an insulating film on a substrate surface to cover a surface of a metal layer that has a predetermined pattern and then forming a stopper film on a surface of the insulating film; a step of forming a resist pattern that exposes only bulging parts of the insulating film that cover the metal layer and then removing the stopper film from the surface of the bulging parts to form a stopper layer on a surface of the insulating film covered by the resist pattern; a grinding step of grinding the surface of the substrate to grind the bulging parts as far as a position regulated by the stopper layer; and a step of removing the stopper layer from the surface of the insulating film and then carrying out finish-up grinding on the surface of the substrate.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The aforementioned and other objects and advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying drawings.

In the drawings:

FIGS. 1A to 1F are diagrams useful in explaining steps up to the formation of a stopper layer on a substrate;

FIGS. 2A to 2C are diagrams useful in explaining steps up to grinding the lower shield layer to a predetermined thickness;

FIGS. 3A to 3D are diagrams useful in explaining steps showing conventional grinding; and

FIG. 4 is an end view showing the construction of a magnetic head when looking from a floating surface side thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of the present invention will now be described in detail with reference to the attached drawings.

FIGS. 1A to 1E and FIGS. 2A to 2C show a process that forms a lower shield layer 10 of a magnetic head as an example application of a method of manufacturing a metal pattern according to the present invention.

FIG. 1A shows a state where a magnetic layer has been formed on the surface of a substrate 5 and the magnetic layer has been patterned into a predetermined pattern to form the lower shield layer 10. The lower shield layer 10 is formed by electroplating a magnetic material such as an NiFe type material. The thickness of the lower shield layer 10 is around 2 to 3 μm.

Next, to flatten the surface of the substrate 5 on which the lower shield layer 10 has been formed, the surface of the substrate 5 is covered with the insulating film 11. FIG. 11B shows a state where the surface of the substrate 5 has been covered with the insulating film 11. On the lower shield layer 10, alumina is used as the insulating film 11. Alumina is sputtered with the same thickness as the lower shield layer 10 or slightly more thickly than the lower shield layer 10 to form the insulating film 11 across the entire surface of the substrate.

When alumina has been sputtered onto the surface of the substrate, as shown in FIG. 1B, at parts where the lower shield layer 10 is formed, the insulating film 11 is formed so as to bulge outward by the thickness of the lower shield layer 10.

After the surface of the substrate has been covered by the insulating film 11, the entire surface of the substrate is covered by a stopper film. The stopper film is formed with a thickness of around 30 nm to achieve a required barrier effect. FIG. 1C shows a state where the surface of the insulating film 11 has been covered by the stopper film 20.

Next, to form the stopper film 20 into a stopper layer 20a used during grinding, the surface of the substrate 5 is covered with a resist, and the resist is then exposed to light and developed to pattern the resist so as to expose bulging parts 11a of the insulating film 11 where the lower shield layer 10 is formed below, thereby forming the resist pattern 22 (see FIG. 1D).

Next, exposed parts of the stopper film 20 are etched and removed with the resist pattern 22 as a mask (see FIG. 1E) and then the resist pattern 22 is removed (see FIG. 1F). In this way, the stopper film 20a is formed on the surface of parts of the insulating film 11 aside from the bulging parts 11a, such parts being formed with approximately the same thickness as the lower shield layer 10.

FIGS. 2A to 2C show steps in a flattening process where grinding is carried out on the substrate 5 on which the stopper layer 20a has been formed.

FIG. 2A shows a state where grinding has been carried out on the surface of the substrate 5 in the state shown in FIG. 1F to flatten the bulging parts 11a of the insulating film 11. When grinding is carried out on the substrate 5, parts that protrude from the surface of the substrate 5 are ground first. In the present embodiment, since parts aside from the bulging parts 11a of the insulating film 11 are covered by the stopper layer 20a, when grinding is carried out on the substrate 5, the parts of the insulating film 11 covered by the stopper layer 20a are protected from being ground. The bulging parts 11a of the insulating film 11 become gradually flatter as the grinding proceeds.

FIG. 2A shows a state where the bulging parts 11a of the insulating film 11 are ground and grinding proceeds until the bulging parts 11a have substantially the same thickness as the surface of the stopper layer 20a. That is, when the stopper layer 20a is provided on the substrate 5 and the surface of the substrate 5 is ground, the bulging parts 11a are flattened using the stopper layer 20a so that the bulging parts 11a are ground until the height of the bulging parts 11a becomes approximately equal to the stopper layer 20a. Note that since the bulging parts 11a of the insulating film 11 are not covered by the stopper layer 20a, if the grinding is allowed to proceed, the lower shield layer 10 will become exposed and will then be ground to become concave.

In this way, even when the stopper layer 20a has been formed, step-like fluctuations in thickness are produced due to the fluctuations in the thickness of the insulating film 11 and the like so that on the surface of the substrate 5, the lower shield layer 10 may be exposed or not exposed. However, when grinding is carried out with the stopper layer 20a having been provided, the fluctuations in thickness across the entire surface of the substrate 5 are greatly reduced compared to the conventional method where bulging parts 11a are formed across the entire substrate. Accordingly, the finish-up grinding carried out afterward can make the difference in thickness between the lower shield layer 10 and the insulating film 11 uniform with high precision across the entire substrate 5.

Since a large number of magnetic heads are fabricated on the substrate 5 and a lower shield layer 10 is formed with a predetermined pattern at each formation position of a magnetic head, during the flattening process carried out on the substrate 5, it is necessary to make the substrate 5 flat with no fluctuations. This means that in the present embodiment, even if the lower shield layer 10 becomes exposed at some positions and not at others and/or steps are produced between the lower shield layer 10 and the insulating film 11 when the surface of the substrate 5 has been ground, by carrying out the finish-up grinding, it is possible to make the thicknesses of the lower shield layer 10 and the insulating film 11 uniform. Excessive grinding of the lower shield layer 10 can be prevented by changing the grinding conditions, so that fluctuations in thickness can be minimized across the entire substrate 5.

Since the stopper layer 20a acts so as to regulate the thickness of the lower shield layer 10 and the insulating film 11, when the bulging parts 11a of the insulating film 11 are ground, it is possible to carry out the grinding process without worrying about whether the lower shield layer 10 or required parts of the insulating film 11 will be ground. Since the bulging parts 11a and also the lowest parts of the insulating film 11 are ground when the bulging parts 11a of the insulating film 11 are ground according to the conventional method, it was necessary to make the insulating film thicker. On the other hand, when the stopper layer 20a is provided as with the present embodiment, the stopper layer 20a serves as a standard position for regulating the grinding position. As a result, the bulging parts 11a of the insulating film 11 are preferentially flattened and it is unnecessary to make the insulating film 11 thicker. By doing so, it is possible to suppress fluctuations in the thickness of the insulating film 11 and to reduce fluctuations in the thickness of the insulating film 11 after the insulating film 11 has been ground.

It should be noted that even if the stopper layer 20a is provided, in reality it is necessary to control the grinding so that the stopper layer 20a is not excessively ground away. As the material of the stopper film 20, it is possible to use tantalum, for example. Tantalum is effective as a stopper film since the grinding rate of tantalum is lower than that of alumina, and is also effective since tantalum is non-magnetic and therefore does not adversely affect the magnetic characteristics of the magnetic head. In this way, it is sufficient to choose a material with a lower grinding rate than the material that constructs the insulating film 11 as the stopper film 20.

FIG. 2B shows a state where the stopper layer 20a remaining on the surface of the substrate 5 has been removed after the grinding process that uses the stopper layer 20a as the standard position. The stopper layer 20a is removed by plasma etching or chemical etching. In FIG. 2B, the lower shield layer 10 is covered by the insulating film 11 and is not exposed, but even if the surface of the lower shield layer 10 becomes exposed at this stage, the grinding process can be carried out in the same way thereafter.

After the stopper layer 20a has been removed, a finish-up grinding process is carried out on the surface of the substrate 5 to make the lower shield layer 10 a predetermined thickness and to make the surfaces of the lower shield layer 10 and the insulating film 11 flat. Since the lower shield layer 10 is already formed with a predetermined thickness during the formation process, the finish-up grinding flattens the difference in thickness (i.e., the stepped parts) between the lower shield layer 10 and the insulating film 11 produced when the stopper layer 20a is removed to make the height of the entire substrate 5 uniform.

The difference in thickness between the lower shield layer 10 and the insulating film 11 when the stopper layer 20a has been removed is around several tens of nanometers, so that the finish-up grinding only needs to grind the surface by a tiny amount. This means it is easy to suppress fluctuations in the amount of grinding across the entire substrate 5 due to the finish-up grinding.

With the grinding method according to the present embodiment, compared to a method where grinding is carried out in a state where the bulging parts 11a have been formed in the insulating film 11 and continues until the lower shield layer 10 is ground to a predetermined thickness, during the grinding process with the larger amount of grinding, such as when grinding the bulging parts 11a of the insulating film 11, the stopper layer 20a acts so as to suppress fluctuations in the amount of grinding across the entire substrate 5. During the finish-up grinding carried out after the stopper layer 20a has been removed, by carrying out only a small amount of grinding starting from a state where the entire surface of the substrate 5 has been ground to become substantially flat until a finished position is reached, it is possible to flatten the substrate 5 with high precision.

When the conventional method and the method of the present invention are compared, the Range/Average of the fluctuation in the thickness after grinding was 10 to 20% with the conventional method, but is improved to 4 to 8% with the present method.

As described above, when carrying out a flattening process that grinds a substrate on which materials with different grinding rates, such as a metal layer (e.g., the lower shield layer) and an insulating layer of alumina or the like are present, by dividing the process into a grinding process that carries out grinding with the grinding position regulated by a stopper film and a machining process that carries out a finish-up grinding after the stopper film has been removed to produce the metal layer with the desired thickness, the substrate can be flattened with high precision. The embodiment described above is an example of a process where the surface of a substrate is flattened during a step that forms the lower shield layer, but it is also possible to apply the same method when flattening the surface of a formed layer beforehand, such as when forming an upper shield layer, a magnetic pole or the like of a write head, and/or when forming a recording coil.

If the surface of a substrate can be flattened with high precision, when forming a magnetic film or the like on the surface of the substrate, it will be possible to form the film precisely without fluctuations, and when patterning a magnetic layer or a conductive layer, it is possible to suppress curvature of the substrate surface and fluctuations in thickness, and therefore patterning can be carried out with high precision. As the recording density of recording media increases, even higher precision becomes necessary for the thickness and machining precision of the magnetic head. The method according to the present invention can be effectively used as the manufacturing process of a magnetic head where high machining precision is required.

Claims

1. A method of manufacturing a metal pattern, comprising: a step of forming an insulating film on a substrate surface to cover a surface of a metal layer that has a predetermined pattern and then forming a stopper film on a surface of the insulating film;a step of forming a resist pattern that exposes only bulging parts of the insulating film that cover the metal layer and then removing the stopper film from the surface of the bulging parts to form a stopper layer on a surface of the insulating film covered by the resist pattern;a grinding step of grinding the surface of the substrate to grind the bulging parts as far as a position regulated by the stopper layer; anda step of removing the stopper layer from the surface of the insulating film and then carrying out finish-up grinding on the surface of the substrate.

2. A method of manufacturing a metal pattern according to claim 1, wherein alumina is sputtered to form the insulating film and tantalum is sputtered to form the stopper film.

3. A method of manufacturing a metal pattern according to claim 1, wherein the metal layer is a lower shield layer of a read head and alumina is sputtered to form the insulating film.