# US 5,700,380 A · Simplified method of making vias for merged MR head

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- Number: US 5,700,380 A
- Document ID: US5700380A
- Status: Granted
- Kind: A
- Application number: 08/476,241
- Filed: 1995-06-07
- Granted: 1997-12-23
- Earliest claimed: 1994-03-02
- Assignees: International Business Machines Corporation
- Inventors: Mohamad Towfik Krounbi; James Hsi-Tang Lee
- Web page: https://patentgrep.com/patent/US5700380A

## CPC

- G11B 5/3967: {Composite structural arrangements of transducers, e.g. inductive write and magnetoresistive read (G11B5/3906 takes precedence)}
- G11B 5/3116: {Shaping of layers, poles or gaps for improving the form of the electrical signal transduced, e.g. for shielding, contour effect, equalizing, side flux fringing, cross talk reduction between heads or between heads and information tracks (G11B5/3113, G11B5/245 take precedence)}
- G11B 5/312: {for reducing flux leakage between the electrical coil layers and the magnetic cores or poles or between the magnetic cores or poles}
- G11B 5/313: {Disposition of layers}
- G11B 5/3163: {Fabrication methods or processes specially adapted for a particular head structure, e.g. using base layers for electroplating, using functional layers for masking, using energy or particle beams for shaping the structure or modifying the properties of the basic layers}
- G11B 5/488: {Disposition of heads (G11B5/49, G11B5/52 take precedence)}
- G11B 5/00: Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor (G11B11/00 {and G11B13/00} take precedence)
- Y10T 29/49032: Fabricating head structure or component thereof
- Y10T 29/49039: with dual gap materials
- Y10T 29/49064: by coating
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

An improved method of manufacturing is provided for making an improved merged MR head. The method employs a photoresist mask with appropriately-sized openings for simultaneously etching numerous vias to various depths over a set time period. After formation of the vias, a single photoresist mask is employed to pattern in one step gap layers G3, G2, G1 and a first shield layer S1 to the desired lateral configuration for the merged MR head. Subsequent to patterning these thin film layers, double insulation layers I2 and I3 are individually soft baked on top of the coil structure of the head followed by patterning of the layers I2/I3 by a single photoresist mask. These layers are then hard baked to retain the desired smooth configuration of the layers. The improved merged MR head has a smooth configuration to its top pole piece P2 because of the smooth configuration of the I2/I3 layer so that flux leakage and saturation problems are minimized.

## Claims

### Claim 1

A method of making a thin film magnetic head comprising the unordered steps of:
forming a plurality of thin film layers;
simultaneously etching first and second vias in the thin film layers employing a common photoresist mask and a common etchant;
the photoresist mask having first and second openings for forming the first and second vias, the first via having a depth d.sub.1 which is less than a depth d.sub.2 of the second via; and
the first opening having a width which is reduced in size based upon a time required for the etchant to etch a depth d=d.sub.2 -d.sub.1.

### Claim 2

A method of making a thin film magnetic head comprising the steps of:
forming a plurality of etchable thin film layers, which can be etched by an etchant, on top of a plurality of non-etchable thin film layers which cannot be etched by said etchant;
forming a photoresist layer on top of the etchable thin film layers;
forming at least first and second openings in the photoresist layer for forming first and second vias which extend through said etchable thin film layers to first and second of said non-etchable thin film layers, the first via extending through at least one of the etchable thin film layers and the second via extending through at least one more etchable thin film layer than the first via; and
each of the first and second holes having a lateral dimension, the lateral dimension of the first opening having a downsizing factor applied so that lateral etching of said at least one of the etchable thin film layers etches a desired laterally sized first via from a time when said etchant in the first opening first reaches said first one of the non-etchable thin film layers to a time when said etchant in the second opening first reaches said second non-etchable thin film layer.

### Claim 3 (depends on 2)

A method as claimed in claim 2 including the step of:
applying said etchant in the first and second openings in the photoresist layer.

### Claim 4 (depends on 3)

A method as claimed in claim 3 including the step of:
the second non-etchable thin film layer being a conductor lead and the first non-etchable thin film layer being a first magnetic layer.

### Claim 5 (depends on 4)

A method as claimed in claim 4 including the step of:
said at least one etchable thin film layer being a third non-magnetic layer and said at least one more etchable thin film layer being a second non-magnetic layer.

### Claim 6

A method of making a thin film structure comprising the steps of:
forming first and second electrically conductive layers between first and second non-magnetic layers and forming the first and second non-magnetic layers between first and second magnetic layers;
forming a third non-magnetic layer on top of the second magnetic layer;
forming a photoresist layer with at least first, second and third openings on top of the third non-magnetic layer for making first, second and third vias, each of the second and third vias being through the third and second non-magnetic layers to the first and second electrically conductive layers and the first via being through the third non-magnetic layer to the second magnetic layer;
simultaneously introducing an etchant into the first, second and third openings to etch through the third and second non-magnetic layers to the first and second electrically conductive layers and to the second magnetic layer, the etchant in the first opening reaching the second magnetic layer before the etchant in the second and third openings reaches the first and second electrically conductive layers; and
downsizing a lateral dimension of the first opening with respect to lateral dimensions of the second and third openings so that the etchant in the first opening will etch the first via with a desired lateral configuration upon the occurrence of the etchant in the second and third openings first reaching the first and second electrically conductive layers.

### Claim 7 (depends on 6)

A method as claimed in claim 6 including the steps of:
after etching the vias removing the photoresist;
filling the vias with a conductive material; and
forming a third magnetic layer on top of the third non-magnetic layer and the vias.

### Claim 8 (depends on 7)

A method as claimed in claim 7 including the step of:
each lateral dimension being a diameter.

### Claim 9

A method of making at least first and second vias in etchable layers down to non-etchable layers, the first via being deeper than the second via comprising the unordered steps of:
forming a single photoresist layer on top of the etchable layer;
forming first and second openings in the single photoresist layer above first and second locations for said first and second vias;
applying an etchant in the first and second openings which etches through the etchable layers to the non-etchable layers, the etchant in the first opening first reaching a first non-etchable layer before the etchant in the second opening reaches a second non-etchable layer;
the first opening being downsized relative to the second opening to account for the etchant in the first opening reaching the first non-etchable layer before the etchant in the second opening reaches the second non-etchable layer.

### Claim 10

A method employing a wet etchant for forming at least first and second holes in etchable material overlaying non-etchable material, the etchable material being etchable by the wet etchant and the non-etchable material being non-etchable by the wet etchant, the first and second holes having widths W1 and W2 and depths d1 and d2 respectively, the depth d1 being less than the depth d2, and the wet etchant being capable of etching downwardly to form said depths while etching laterally to form said widths, the method comprising the steps of:
forming a photoresist layer on the etchable layer having first and second openings with first and second widths W' 1 and W' 2 respectively;
placing said wet etchant simultaneously in said first and second openings so that the wet etchant etches said etchable material downwardly and laterally to said non-etchable material in time t1 to form a partially completed hole with the depth d1 but a width less than W1 and etches said etchable material downwardly and laterally to said non-etchable material in time t2 to form said second hole with width W2 and depth d, the time t1 being less than time t2; and
in the step of forming the photoresist layer, downsizing the width W' 1 in the first opening in the photoresist layer so that during a time duration t2-t1 the partially completed hole is etched laterally an additional amount to provide said first hole with width W1.

### Claim 11 (depends on 10)

A method as claimed in claim 10 wherein the etchable and non-etchable materials comprise thin film layers.

### Claim 12 (depends on 11)

A method as claimed in claim 11 wherein the etchable material is alumina and the non-etchable material is NiFe.

### Claim 13 (depends on 10)

A method as claimed in claim 10 including:
etchable material at the first hole comprising a first thin film and etchable material at the second hole comprising said first thin film and a second thin film, the first thin film overlaying the second thin film; and
non-etchable material at the first hole comprising a third thin film and non-etchable material at the second hole comprising a fourth thin film.

### Claim 14 (depends on 13)

A method as claimed in claim 13 wherein the method is employed to construct holes in a structure having an electrically conductive layer sandwiched between first and second non-magnetic layers, the first and second non-magnetic layers being sandwiched between first and second magnetic layers and a third non-magnetic layer on the second magnetic layer, the method including:
the first thin film being the third non-magnetic layer, the second thin film being the second non-magnetic layer, the third thin film being the second magnetic layer and the fourth thin film being the electrically conductive layer.

### Claim 15 (depends on 14)

A method as claimed in claim 14 wherein the etchable material is alumina and the non-etchable material is NiFe.

### Claim 16 (depends on 15)

A method as claimed in claim 15 wherein the photoresist layer has substantially an equal thickness.

### Claim 17 (depends on 10)

A method as claimed in claim 10 wherein the first and second holes and the first and second openings are circular, the first and second widths W1 and W2 are first and second diameters D1 and D2 and the first and second widths W' 1 and W' 2 are first and second diameters D' 1 and D' 2.

### Claim 18 (depends on 17)

A method as claimed in claim 17 wherein the etchable and non-etchable materials comprise thin film layers.

### Claim 19 (depends on 18)

A method as claimed in claim 18 wherein the etchable material is alumina and the non-etchable material is NiFe.

### Claim 20 (depends on 17)

A method as claimed in claim 17 including:
etchable material at the first hole comprising a first thin film and etchable material at the second hole comprising said first thin film and a second thin film, the first thin film overlaying the second thin film; and
non-etchable material at the first hole comprising a third thin film and non-etchable material at the second hole comprising a fourth thin film.

### Claim 21 (depends on 20)

A method as claimed in claim 20 wherein the method is employed to construct holes in a structure having an electrically conductive layer sandwiched between first and second non-magnetic layers, the first and second non-magnetic layers being sandwiched between first and second magnetic layers and a third non-magnetic layer on the second magnetic layer, the method including:
the first thin film being the third non-magnetic layer, the second thin film being the second non-magnetic layer, the third thin film being the second magnetic layer and the fourth thin film being the electrically conductive layer.

### Claim 22 (depends on 21)

A method as claimed in claim 21 wherein the etchable material is alumina and the non-etchable material is NiFe.

### Claim 23 (depends on 22)

A method as claimed in claim 22 wherein the photoresist layer has substantially an equal thickness.

### Claim 24

A method employing a wet etchant for forming at least first and second circular holes that extend downwardly in etchable layers to non-etchable layers, wherein a first etchable layer overlays a first non-etchable layer and the first and second etchable layers overlay a second non-etchable layer, the etchable layers being etchable by the wet etchant and the non-etchable layers being non-etchable by the wet etchant, the first and second holes having diameters D1 and D2 and depths d1 and d2 respectively, the depth d1 being less than the depth d2, the method comprising the steps of:
forming a photoresist layer on the first etchable layer with first and second circular openings having first and second diameters D' 1 and D' 2 respectively;
placing said wet etchant in said first and second openings so that the wet etchant etches downwardly and laterally through said first etchable layer to said first non-etchable layer in time t1 to form a partially completed hole with a diameter less than D1 and etches downwardly and laterally through said first and second etchable layers to said second non-etchable layer in time t2 to form said second hole with said diameter D2, the time t1 being less than the time t2; and
in the step of forming the photoresist layer, the diameter D' 1 in the first opening of the photoresist layer having a downsizing factor applied so that during a time duration t2-t1 the partially completed hole is etched laterally to provide said first hole with diameter D2.

### Claim 25 (depends on 24)

A method as claimed in claim 24 wherein the first and second etchable layers comprise first and second etchable thin films respectively and the first and second non-etchable layers comprise first and second non-etchable thin films respectively.

### Claim 26 (depends on 25)

A method as claimed in claim 25 wherein the first and second etchable thin films are alumina and the first and second non-etchable thin films are NiFe.

### Claim 27 (depends on 26)

A method as claimed in claim 26 wherein the photoresist layer has substantially an equal thickness.