Method to improve ability to perform CMP-assisted liftoff for trackwidth definition

A method is presented for fabricating a read head having a read head sensor and a hard bias/lead layer which includes depositing a strip of sensor material in a sensor material region, and depositing strips of fast-milling dielectric material in first and second fast-milling dielectric material regions adjacent to the sensor material region. A protective layer and a layer of masking material is deposited on the strip of sensor material and the strips of fast-milling dielectric material to provide masked areas and exposed areas. A shaping source, such as an ion milling source, is provided which shapes the exposed areas. Hard bias/lead material is then deposited on the regions of sensor material and fast-milling dielectric material to form first and second leads and a cap on each of these regions. The cap of hard bias/lead material and the masking material is then removed from each of these regions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to magnetic heads for reading data written to storage media, and more particularly to magnetic read heads for disk drives.

2. Description of the Prior Art

In recent years there has been a constant drive to increase the performance of hard disk drives by increasing the areal data storage density of the magnetic hard disk. This is done by reducing the written data track width, such that more tracks per inch can be written on the disk. This naturally requires that the width of the read head be reduced so magnetic field interference from adjacent data tracks is not picked up.

Read sensors, of which one type is referred to as a “spin valve”, developed to read trackwidths smaller than 130 nm depend upon the ability to ion mill the sensor to these very small dimensions, and to reliably lift-off the deposited layer materials. A common problem with the fabrication of such small sensors is illustrated inFIGS. 5-15.

The sensor is typically formed of a stack of layers which are generally formed as a region of magnetic material bounded by strips of dielectric or insulating materials.FIG. 5shows a top plan view of a portion of a wafer41as it is being prepared for shaping into a sensor40. The sensor material region42is shown to be bounded by a first dielectric material region44and a second dielectric material region46. These first and second dielectric material regions44,46are chosen to be of non-conducting material. In the prior art, these are preferably chosen to be alumina so that these make up first and second alumina regions54,56. A band of masking material48such as photoresist is then deposited to protect the material of the sensor material region42, and first and second dielectric material regions44,46from being cut away during shaping processes such as ion milling. The width of the band of masking material48establishes the eventual width of the read head sensor40and thus the trackwidth50. The width of the sensor material region42establishes the stripe height52of the sensor40.

The difficulty arises when the exposed portions of sensor material region42and first and second alumina regions54,56are subjected to ion milling, since the sensor material42and the first and second alumina regions54,56have different milling rates, the sensor material42is removed faster than the alumina54,56. A series of views of cross-sections of the sensor region42, as taken through line6-6inFIG. 5, and the first alumina region, as taken through line7-7ofFIG. 5are shown side-by-side for comparison inFIGS. 6-15. Comparable stages of fabrication of a sensor layer stack58in the sensor region42are shown inFIGS. 6,8,10,12and14, and of an alumina stack60in the alumina region54inFIGS. 7,9,11,13and15respectively. Since the relative heights of the layers at each stage of fabrication is at issue, the bottom of the sensor layer stack58and the bottom of the alumina layer stack60, are aligned in the pairs of drawings.

In the first stage,FIG. 6shows the layer of sensor material62, protective layer64, preferably of material such as Diamond-like carbon (DLC), and then a layer of masking material48, andFIG. 7shows the layer of alumina66, protective layer64and masking material48.

Next Reactive Ion Etching (RIE) is performed to shape the protective layer material64in bothFIGS. 8-9.

FIGS. 10-11show the effect of ion milling, which narrows the sensor material62to the dimensions of the mask material48and establishes the trackwidth50.FIG. 11shows that due to its slower milling rate, the alumina layer remaining68may be 200-300 Å thick, as compared to a typical sensor62thickness of 400 Å.

FIGS. 12 and 13show the effects of depositing the hard bias/leads material70on both the sensor material region42, and the first alumina region54. The hard bias/leads are used to magnetically bias magnetic domains in certain layers of the sensor material42, and also to supply electric current to the sensor40. Therefore, in order to maintain the function of the sensor, it is important that the leads are not shorted together. The hard bias/leads material70is deposited in a blanketing layer over both the sensor material region42and alumina regions54,56, (seeFIG. 5). In the sensor region42, the height of the masking material48is such that the hard bias/leads material70on the masking material48is removed vertically far enough from the material72deposited on the sides of the sensor that a gap74remains, so that three separate elements are formed, namely a first side lead76and second side lead78, and a hard bias/lead material cap80.

However in the alumina region54, shown inFIG. 13, since the residual step68remains, the hard bias/leads material70is raised vertically by this step height82, as shown by the two set of arrows82. Consequently, there is not enough vertical displacement of the side leads76and the cap80, so that there is no gap, and side material72commonly forms bridges84between them. First and second leads76,78are thus no longer electrically isolated, and are thus shorted together.

The next process, shown inFIGS. 14 and 15, is a CMP (Chemical Mechanical Polishing) assisted liftoff. As shown inFIG. 14, this is intended to remove the cap80and the masking material48from the sensor62, leaving the first and second leads76,78electrically isolated from each other, except for the conductive path through the sensor62, as it should be. However, as shown inFIG. 15, in the alumina region54, the masking material48has been unintentionally encapsulated by the hard bias/lead layer70, which is not removed by the CMP assisted process. Thus this leaves an electrical short between the first and second side leads76,78, which must be removed if the sensor62is to function properly.

Thus there is a need for a fabrication method which prevents the formation of bridges in hard bias/lead material layer which produces electrical short circuits in disk drive read sensors.

SUMMARY OF THE INVENTION

A preferred embodiment of the present invention is a method for fabricating a read head for a hard disk drive having a read head sensor and a hard bias/lead layer. The method includes depositing a strip of sensor material in a sensor material region, and depositing strips of fast-milling dielectric material in first and second fast-milling dielectric material regions adjacent to the sensor material region. Next, a protective layer is deposited on the sensor material region and the first and second fast-milling material regions. A layer of masking material is deposited on the strip of sensor material and the strips of fast-milling dielectric material to provide masked areas and exposed areas. A shaping source, such as an ion milling source, is provided which shapes the exposed areas. Hard bias/lead material is then deposited on the regions of sensor material and fast-milling dielectric material to form first and second leads and a cap on each of these regions. The cap of hard bias/lead material and the masking material is then removed from each of these regions.

It is an advantage of the present invention that the production of short circuits between hard bias/leads is minimized, thus increasing production yields.

It is another advantage that photoresist is not encapsulated by hard bias/lead material and is thus more easily removed.

It is a further advantage of the present invention that more uniform topography is produced, thus simplifying subsequent processing steps.

These and other features and advantages of the present invention will no doubt become apparent to those skilled in the art upon reading the following detailed description which makes reference to the several figures of the drawing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiment of the present invention is a method of fabrication of read sensors which utilizes fast-milling dielectric material which more closely matches the milling rate of sensor material. The present invention is also a disk drive read head having milling of the sensor layers above the dielectric layer, and a method for producing this read head.

A hard disk drive2is shown generally inFIG. 1, having one or more magnetic data storage disks4, with data tracks6which are written and read by a data read/write device8. The data read/write device8includes an actuator arm10, and a suspension12which supports one or more magnetic heads14included in one or more sliders16.

FIG. 2shows a slider16in more detail being supported by suspension12. The magnetic head14is shown in dashed lines, and in more detail inFIGS. 3 and 4. The magnetic head14includes a coil18and P1pole, which also acts as S2shield, thus making P1/S220. P1/S2may also be made as two discrete layers. The second pole P222is separated from P1/S2by write gap23.

The read sensor40is sandwiched between the first shield S130and the second shield P1/S220. There is generally included an insulation layer32between the rest of the length of S130and P1/S220. The magnetic head14flies on an air cushion between the surface of the disk4and the air bearing surface (ABS)24of the slider16. The write head portion26and the read head portion28are generally shown, with the read head sensor40and the ABS24.

There are two configurations of read head in common use in the industry today. These are called Current Perpendicular to the Plane (CPP), and Current In the Plane (CIP). In the CPP configuration, Shield S1and P1/S2are made of conducting material which act as electrodes supplying current to the read sensor which lies between them.

The present invention uses a CIP configuration, in which the current flows from side to side through the elements. For CIP read heads, the read sensor40is generally sandwiched between two insulation layers, usually designated G134and G236which are made of non-conductive material, to keep the circuit from shorting out.

Note that this structure is strictly for illustration only, and one skilled in the art will appreciate that sensor structures can vary dramatically from the one shown inFIG. 4, the methodology of the present invention being applicable to formation of all such heads.

The novelty of the present invention is best understood in comparison to processes of the prior art, as discussed above. A common problem with the fabrication of sensors of the prior art is illustrated inFIGS. 5-15. The sensor is typically formed of a stack of layers which are generally formed as a region of magnetic material bounded by strips of dielectric or insulating materials.FIG. 5shows a top plan view of a portion of a wafer41as it is being prepared for shaping into a sensor40. The sensor material region42is shown to be bounded by a first dielectric material region44and a second dielectric material region46. These first and second dielectric material regions44,46are chosen to be of non-conducting material. In the prior art, these are preferably chosen to be alumina so that these make up first and second alumina regions54,56. A band of masking material48such as photoresist is then deposited to protect the material of the sensor material region42, and first and second dielectric material regions44,46from being cut away during shaping processes such as ion milling. The width of the band of masking material48establishes the eventual width of the read head sensor40and thus the trackwidth50. The width of the sensor material region42establishes the stripe height52of the sensor40.

The difficulty arises when the exposed portions of sensor material region42and first and second alumina regions54,56are subjected to ion milling, since the sensor material42and the first and second alumina regions54,56have different milling rates, the senor material42being removed faster than the alumina54,56. A series of views of cross-sections of the sensor region42, as taken through line6-6inFIG. 5, and the first alumina region, as taken through line7-7ofFIG. 5are shown side-by-side for comparison inFIGS. 6-15. Comparable stages of fabrication of a sensor layer stack58in the sensor region42are shown inFIGS. 6,8,10,12and14and of an alumina stack60in the alumina region54inFIGS. 7,9,11,13and15respectively. Since the relative heights of the layers at each stage of fabrication is at issue, the bottom of the sensor layer stack58and the bottom of the alumina layer stack60, are aligned in the pairs of drawings.

In the first stage,FIG. 6shows the layer of sensor material62, protective layer64, preferably of material such as DLC, and then a layer of masking material48, andFIG. 7shows the layer of alumina66, protective layer64and masking material48.

Next Reactive Ion Etching (RIE) is performed to shape the protective layer material64in bothFIGS. 8-9.

FIGS. 10-11show the effect of a shaping operation such as ion milling, which narrows the sensor material62to the dimensions of the mask material48and establishes the trackwidth50.FIG. 11shows that due to its slower milling rate, the alumina layer remaining68may be 200-300 A thick, as compared to a typical sensor62thickness of 400 Å.

FIGS. 12 and 13show the effects of depositing the hard bias/leads material70on both the sensor material region42, and the first alumina region54. The hard bias/leads are used to magnetically bias magnetic domains in certain layers of the sensor material42, but also to supply electric current to the sensor40. Therefore, in order to maintain the function of the sensor, it is important that the leads are not shorted together. The hard bias/leads material70is deposited in a blanketing layer over both the sensor material region42and alumina regions54,56, (seeFIG. 5). In the sensor region42, the height of the masking material48is such that the hard bias/leads material70on the masking material48is removed vertically far enough from the material72deposited on the sides of the sensor that a gap74remains, so that three separate elements are formed, namely a first side lead76and second side lead78, and a hard bias/lead material cap80.

However in the alumina region54, shown inFIG. 13, since the residual step68remains, the hard bias/leads material70is raised vertically by this step height82, as shown by the two set of arrows. Consequently, there is not enough vertical displacement of the side leads76and the cap80, so that there is no gap, and side material72commonly forms bridges84between them. First and second leads76,78are thus no longer electrically isolated, and are thus shorted together.

The next process, shown inFIGS. 14 and 15, is a CMP (Chemical Mechanical Polishing) assisted liftoff. As shown inFIG. 14, this is intended to remove the cap80and the masking material48from the sensor62, leaving the first and second leads76,78electrically isolated from each other, except for the conductive path through the sensor62, as it should be. However, as shown inFIG. 15, in the alumina region54, the masking material48has been unintentionally encapsulated by the hard bias/lead layer70, which is not removed by the CMP assisted process. Thus this leaves an electrical short between the first and second side leads76,78, which must be removed if the sensor62is to function properly.

In contrast,FIGS. 16-25show the method of fabrication of the present invention. In place of alumina, a dielectric material having a milling rate more closely comparable to that of the sensor material is used. This material shall be referred to, purposes of this discussion, and inFIGS. 16-25, which follow, as fast-milling dielectric90. Ideally, the milling rate of this fast milling dielectric would exactly match that of the sensor material. However, an exact match is not necessary, as long as the milling rates are close enough that a step height from residual material is small enough that bridges do not form in the hard bias/lead material which then interfere with the CMP assisted removal of the masking material and excess hard bias/lead material. It is estimated that a step height of 50 A or less in the residual dielectric, which might be achieved through either full or partial mill, including a combination of mill angles, will provide satisfactory results. A partial list of materials which may be used include Ta2O5, SiO2, Si3N4, AlN, variable compositions of Al—Si—O—N, HfO2, ZrO2, and Hf(1-x)SixO2. It will be understood by those skilled in the art that this list is not to be considered limiting and that many other materials would fit the definition of fast-milling dielectrics.

In a similar manner to that shown before,FIG. 5will be used to show the regions of sensor material, and a first region of fast-milling dielectric material94and second region of fast-milling dielectric material96. As before, a series of views of cross-sections of the sensor region42, as taken through line6-6inFIG. 5, and the first fast-milling material region94, as taken through line7-7ofFIG. 5are shown, this time inFIGS. 16-25. Comparable stages of fabrication of a sensor layer stack58in the sensor region42are shown inFIGS. 16,18,20,22and24and of a fast-milling dielectric stack92in the first fast-milling dielectric material region94inFIGS. 17,19,21,23and25respectively. Once again, the bottom of the sensor layer stack58and the fast-milling dielectric stack92, are level in the pairs of drawings.

In the first stage,FIG. 16shows the layer of sensor material62, protective layer64, preferably of material such as DLC, and then a layer of masking material48, andFIG. 17shows the fast-milling dielectric stack92, including the layer of fast-milling dielectric material90, protective layer64and masking material48.

Next Reactive Ion Etching (RIE) is performed to shape the protective layer material64in both the sensor layer stack58and the fast-milling dielectric stack92as seen inFIGS. 18-19.

FIGS. 20-21show the effect of ion milling, using any of a variety of ion beam etch tools, and which narrows the sensor material62to the dimensions of the mask material48and establishes the trackwidth50.FIG. 21shows that the fast-milling dielectric stack92, due to its faster, but not exactly matching milling rate, still retains a reduced residual step98having a residual step height99which is 10-20 Å in height, compared to typical thickness of 400 Å of the sensor material62. As referred to above, it is estimated that a step height of 50 A or less in the residual dielectric will provide satisfactory results. This also compares favorably with a height of 100-200 Å of the residual step68of the prior art (seeFIG. 13).

FIGS. 22 and 23show the effects of depositing the hard bias/leads material70on both regions42,94(seeFIG. 5). In the sensor region42, the height of the masking material48is such that the hard bias/leads material70on the masking material48is removed vertically far enough from the material72deposited on the sides of the sensor62that a gap74remains, so that three separate elements are formed, namely a first side lead76and second side lead78, and a hard bias/lead material cap80. In comparison, in the fast-milling dielectric stack92of the present invention, the reduced residual step98has a residual step height99which is small enough that there is still enough distance that the material72deposited on the sides of the sensor does not join with the material in the first side lead76and second side lead78, and a gap74remains. Now there are three separate elements are formed, namely a first side lead76and second side lead78, and a hard bias/lead material cap80, as in the sensor layer stack58.

When CMP assisted liftoff is completed, as shown inFIGS. 24 and 25, the cap80and the masking material48are removed from both the sensor62, and the fast-milling dielectric stack92leaving both sets of first and second leads76,78electrically isolated from each other, except for the conductive path through the sensor62, as it should be.

While the present invention has been shown and described with regard to certain preferred embodiments, it is to be understood that modifications in form and detail will no doubt be developed by those skilled in the art upon reviewing this disclosure. It is therefore intended that the following claims cover all such alterations and modifications that nevertheless include the true spirit and scope of the inventive features of the present invention.