WO1990007177A1

WO1990007177A1 - Process for filling a trough-shaped depression exactly

Info

Publication number: WO1990007177A1
Application number: PCT/EP1989/001277
Authority: WO
Inventors: Dietrich Stephani
Original assignee: Siemens Aktiengesellschaft
Priority date: 1988-12-15
Filing date: 1989-10-26
Publication date: 1990-06-28
Also published as: DE3842246C2; DE3842246A1

Abstract

In the process, a layer of a preliminary product (22) of the layer to be formed is deposited on the substrate (3) provided with the depression (12), forming a cavity (25) corresponding to the depression (12) in the substrate. The cavity (25) of the preliminary product (22) is then almost filled with an auxiliary layer (26), leaving narrow, groove-like trenches (29). This structure is then provided with a levelling layer (30) thick enough to fill the trenches (29). Finally, the levelling layer (30) and the auxiliary layer (26) are completely removed by etching, and the part of the preliminary product (22) projecting above the depression (12) in the substrate is removed by etching to the level of the upper edge of the depression (12) in the substrate.

Description

Process for the exact filling of a trough-like depression

The invention relates to a method for the exact filling of a trough-like depression in a substrate with a thin layer up to a level which is defined by the upper edge of the depression. Such a method is indicated in EP-B-0 185 289.

Magnetic heads for magnetic storage disk devices of high storage density which are to be produced using thin-film technology are generally formed on substrates carrying them. These substrates can be designed as missiles so that they can be guided aerodynamically over disk-shaped recording media of the storage device. In the production of such magnetic heads, there is often the requirement that one or more layers of the magnetic head should be arranged in a trough-like depression (see, for example, the EP-B mentioned at the beginning). Corresponding depressions generally have a depth of between 0.5 and 20 μm and are considerably wider, the maximum extension being up to a few 100 μm. However, if one wants such a depression exactly by using methods known from thin-film technology

Filling the top edge of the recess of the substrate with a correspondingly thin layer, the problem arises with known leveling methods that the surface of the recess in the region of the recess can be undesirably lowered due to the large extent of the recess.

The object of the present invention is therefore to design the method of the type mentioned at the outset in such a way that such reductions are at least largely avoided. According to the invention, this object is achieved by

a layer-shaped preliminary product of the layer to be produced is first deposited on the substrate provided with the recess, with a thickness which is at least equal to the depth of the substrate recess, a depression corresponding to the substrate recess being produced in the layered preliminary product,

- That in the lowering of the preliminary product an auxiliary layer largely filling this lowering is formed with a thickness that is at least approximately equal to the depth of the

Lowering of the preliminary product is, with only narrow channel-like trenches remaining between the preliminary product and the auxiliary layer at the upper edge of the recess,

- That this structure is subsequently provided with a sufficiently thick leveling layer, the groove-like trenches also being filled in, and

- Finally, the leveling layer and the auxiliary layer as well as the part of the preliminary product protruding from the substrate recess are etched off to the level of the upper edge of the substrate recess.

The advantages associated with this embodiment of the method are to be seen in particular in the fact that even with a relatively large expansion of the depression in the substrate, a perfect leveling and filling of this depression with the material of the layer to be produced is made possible. Because of the use of the auxiliary layer, the trenches remaining at the edges of the upper edge of the recess are so narrow that, in the case of a leveling known per se with a leveling layer in the region of these trenches, practically no subsidence of the surface of the leveling layer occurs. With known etching processes, the leveling layer and the auxiliary layer can therefore be removed very uniformly up to the level of the upper edge of the recess. On the so obtained very smooth level, a further structure using thin-film technology, for example parts of a thin-film magnetic head, can then be applied in a known manner.

Advantageous refinements of the method according to the invention emerge from the subclaims.

To further explain the invention, reference is made below to the drawing, in which FIG. 1 schematically illustrates a magnetic head with a layer to be produced according to the invention as an exemplary embodiment. Individual method steps for producing this layer are indicated in FIGS. 2 to 8. Corresponding parts are provided with the same reference numerals in the figures.

In the case of the thin-film magnetic head for writing and reading, which is only partially illustrated as a longitudinal section in FIG. 1, known ring head-like embodiments with layer-by-layer construction for the principle of a longitudinal (horizontal) or in particular a vertical (vertical) magnet are used tization. The head, generally designated 2 in the figure, is formed in thin-film technology on a substrate 3, which can be designed as a missile in a known manner and is not further developed in the figure. The substrate 3 and thus the magnetic head 2 are to be guided aerodynamically along a track at a low flight altitude relative to a recording medium known per se and corresponding to the intended magnetization principle. This direction of movement, relative to the head, of the recording medium rotating, for example, underneath it is indicated by an arrowed line denoted by v.

The magnetic head 2 has a magnetic guide body 5 that guides the magnetic flux and has two magnetic legs! 6 and 7. These magnetic legs each contain at least one magnetic layer 6a or 7a, each of which forms a magnetic pole P1 or P2 on its pole tips 8 and 9 facing the recording medium. Between the two poles P1 and P2, an air gap 10 is formed with an advantageously small longitudinal, that is, in the direction of movement v pointing g of less than 1 μm. Each of the magnetic legs 6 and 7 is reinforced outside of the areas occupied by the pole tips 8 and 9 with an additional, relatively thick magnetic layer 6b or 7b. The two reinforcement layers 6b and 7b are arranged so that they lie on the outer sides of the magnetic guide body 5.

As can also be seen from the figure, the reinforcement layer 6b, which is assigned to the magnetic leg 6 which leads in terms of the direction of movement v, is to be located in a trough-like depression 12. This depression is worked into the substrate 3 and filled according to the invention with the reinforcement layer 6b exactly up to its upper edge K such that the surface 13 of the reinforcement layer 6b facing the magnetic layer 6a together with the non-recessed surface 14 of the substrate 3 in a common level E.

In a central area of the ring head-like magnetic guide body 5, the distance between the two magnetic legs 6 and 7 is widened with respect to the gap width g, in that the rearward (trailing) magnetic leg 7 with respect to the direction of movement v extends in this area to a larger distance W with respect to the front , just formed and the substrate 3 facing magnetic leg 6 leads. Outside of this extended guide body area, the magnetic leg 7 is attached to the magnetic leg 6 in a known manner on the side of the guide body facing away from the recording medium, so that the ring-head-like shape of the guide body 5 then results. By between the two magnetic legs 6 and 7 in the The intermediate space 16 thus existing in the guide body area extends at least one single or multi-layer coil winding 17 with which both the writing and the reading function can be performed. The entire magnetic guide body 5 is covered on its outside with a hard protective layer 18.

Individual steps for producing the magnetic reinforcement layer 6b according to the invention of the magnetic head illustrated in FIG. 1 are explained in more detail below on the basis of the schematic longitudinal sections in FIGS. 2 to 8:

In order to form the trough-like depression 12 in the substrate 3, a layer 20 of a photoresist is deposited on the surface 14 of the substrate lying in the plane E according to known photolithographic methods outside the area of the depression. After exposure and development of the photoresist layer 20, the entire surface of the substrate coated in this way is subjected to ion beam etching. The etching process is carried out until the lacquer layer 20 has been completely removed. The substrate 3 in the non-coated area is also etched down to a depth t of, for example, 2 μm to form the desired depression 12 (FIG. 3).

Thereafter, the surface of the substrate structured in this way is coated at least in the region of the depression 12 and in the adjacent edge regions of the non-recessed surface 14, for example by means of a sputtering process, with a layered intermediate 22 made of the material of the reinforcement layer 6b to be produced (FIG 4). This layered pre-product 22 thus also extends through the area of the trough-like depression 12 and has approximately a structuring corresponding to the structuring of the substrate. The thickness d of the layered intermediate 22 corresponds in the range of the depression 12 at least approximately the depth t of the depression. However, the thickness d can optionally also be greater than the depth t.

Accordingly, a trough-like depression 25 corresponding to the substrate depression 12 is present in the surface 24 of the layered preliminary product 22, which has a relatively large maximum longitudinal and / or transverse extent a of, for example, approximately 200 μm and has a depth t ¹ that is approximately equal the depth t of the depression 12. A leveling of such a structured surface according to known leveling methods is not, however, readily possible. Because of the size of the extent a, these methods would lead to undesired indentations of the surface in the region of the depression 25. According to FIG. 5, it is therefore provided that the depression 25 is filled as far as possible with an auxiliary layer 26 made of a photoresist by means of photolithography. The thickness d ^{1 of} this auxiliary layer is set so that it is equal to the depth t 'of the depression 25. The surface 27 of the auxiliary layer 26 therefore lies together with the non-lowered part of the surface 24 of the layered preliminary product 22 in a common intermediate plane e. When the auxiliary layer 26 is applied, however, it cannot be avoided that narrow channel-like trenches 29 remain in the region of the edges of the depression 25 between the auxiliary layer 26 and the layered preliminary product 22.

Such trenches 29 with a width b of at most a few micrometers can be leveled in a manner known per se. According to FIG. 6, the entire free surface of the layered intermediate 22 and the auxiliary layer 26 is leveled by means of a polymer layer 30, for example with a photoresist, of sufficient thickness. Here, the narrow trenches 29 are filled with the material of the leveling layer 30, without noticeable indentations of the surface the layer 30 occur in the region of these trenches.

The plastic material of the leveling layer 30 is then etched back up to the common intermediate plane e of the surface of the layered preliminary product 22 and the auxiliary layer 26, the trenches 29 remaining filled with the material of the leveling layer (FIG. 7). Reactive ion beam etching with oxygen ions in argon or reactive ion etching with oxygen are particularly suitable as the etching method.

Finally, by means of a further etching process, both the material of the layered preliminary product 22 projecting beyond the depression 12 in the substrate 3 and the material of the auxiliary layer 26 as well as the material located in the trenches 29 are removed up to the surface E of the substrate 3. Here, an approximately equal etching rate is advantageously provided for the material of the preliminary product 22 and for the plastic material (s) of the auxiliary layer 26 and the trenches 29. Reactive ion beam etching with nitrogen ions in argon is particularly suitable for this.

At the end of this etching process, there is then a substrate 3, the recess 12 of which is completely filled up to the common plane E with a material which forms the reinforcing layer 6b (FIG. 8). On level E, the remaining structure of the magnetic head shown in FIG. 1 can then be completed using thin-film technology in a manner known per se.

According to the exemplary embodiment indicated in the figures, the method according to the invention can be used particularly advantageously in the production of a magnetic layer sunk in a substrate of a thin-film magnetic head. However, the method according to the invention is not restricted to such an application. It can generally be used where there is a trough-like depression with a shallow depth and comparatively large expansion in any body with any material to be filled and leveled by thin film technology. It is particularly advantageous to fill and level recesses, the depth of which is between 0.2 μm and 20 μm, in particular between 1 μm and 10 μm, and which are extended in a direction transverse thereto at least 20 μm, in particular over 100 μm.

Claims

1. Method for the exact filling of a trough-like depression in a substrate with a thin layer up to a level defined by the upper edge of the depression, that is, due to the fact that,

- That a layer-shaped preliminary product (22) of the layer (6b) to be produced is first deposited on the substrate (3) provided with the recess (12) with a thickness (d) which is at least equal to the depth (t) of the substrate recess

(12), a depression (25) corresponding to the substrate depression (12) being produced in the preliminary product (22),

- That then in the depression (25) of the preliminary product (22), a depression (25) largely filling this depression (25) is formed with a thickness (d ') which is at least approximately equal to the depth (t ¹ ) of the depression (25) of the preliminary product (22), only narrow channel-like trenches (29) remaining between the preliminary product (22) and the auxiliary layer (26) at the upper edge of the recess (K), - that this structure subsequently has a sufficiently thick leveling layer (30) is provided, the trenches (29) being filled in with, and

- That finally the leveling layer (30) and the auxiliary layer (26) completely and the part of the preliminary product (22) projecting from the substrate recess (12) up to the plane (E) of the upper edge (K) of the substrate recess (12) ¬ be etched.

2. The method according to claim 1, characterized in that the recess (12) is formed in the substrate (3) by means of photolithography and ion beam etching (Figures 2 and 3).

3. The method according to claim 1 or 2, so that the auxiliary layer (26) is formed in the depression (25) from a plastic material.

4. The method of claim 3, d a d u r c h g e k e n n ¬ z e i c h n e t that the auxiliary layer (26) is formed by means of photo lithography.

5. The method according to any one of claims 1 to 4, that the leveling layer (30) is formed from a plastic material.

6. The method according to any one of claims 1 to 5, characterized in that first of all the leveling layer (30) is processed by means of a first ion beam etching process up to an intermediate level (e) in which the surface (24, 27) of the layered intermediate product (22) and the auxiliary layer (26), and that then by means of a second ion beam etching process the part of the preliminary product (22) protruding from the substrate recess (12), the auxiliary layer (26) and the material of the trenches (29) filling the material ¬ leveling layer (30) to the plane (E) of the upper edge (K) of the substrate recess (12) are processed.

7. The method according to claim 6, characterized in that a reactive ion beam etching with oxygen ions in argon or a reactive ion etching with oxygen and / or a reactive ion beam etching with nitrogen ions in argon are provided for the first etching process / becomes.

8. The method according to any one of claims 1 to 7, characterized in that for the production of a thin film magnetic head (2) in the recess (12) of the substrate (3) a sunken magnetic layer (6b) is formed.

9. The method according to any one of claims 1 to 8, dadurc \ characterized in that the recess (12) with a depth (t) between 0.2 microns and 20 microns, preferably between 1 microns and 10 microns, and with a cross for this purpose, the extent (a) to be measured of at least 20 μm, preferably at least 100 μm, is filled with a material of the thin layer (6b).