Method for sample preparation for exposing a main pole of a recording head

A method for sample preparation. The method includes mechanically polishing portions of an insulating layer over a main pole of a recording head embedded within a sample structure. The insulating layer is polished top down in planar layers perpendicular to an air bearing surface adjoining the main pole. The method also includes selectively wet etching the remaining portions of the insulating layer to expose the main pole, wherein the insulating layer surrounds the main pole. Etching is made without damaging the main pole.

TECHNICAL FIELD

The various embodiments of the present invention relate to perpendicular recording head systems. More specifically, various embodiments of the present invention relate to sample preparation for exposing the main pole of the perpendicular recording head.

BACKGROUND ART

Sample preparation for operation and failure analysis is an important tool in providing a detailed inspection of the physical characteristics of a recording head fabricated on a substrate. With the structure of recording heads decreasing in size and becoming more complex, electron microscopy (e.g., scanning electron microscopy) has emerged as a critical tool for highly site-specific operation and failure analysis. More particularly, an important issue is the measurement of critical parameters on a main pole of the recording head. However, the difficulties associated with exposing the main pole of the recording head using conventional techniques make measurement of these critical dimensions inaccurate.

Physical characteristics of the main pole provide critical factors in determining the overall performance of the recording head. These physical characteristics are directly linked to the properties related to electrical and magnetic conductivity of the recording head. The most critical factors for the main pole properties include the flare point and flare angle.

Preparation of the sample structure for use in electron microscopy is necessary for examining the critical dimensions of the recording head. Conventional sample preparation techniques for the sample structure including the recording head include mechanical sectioning (e.g., mechanical lapping techniques). However, since the main pole target on the recording heads is at least one order of magnitude smaller than the thickness removed through any mechanical sectioning technique employed, it is very difficult to hit the main pole target. For instance, the mechanical lapping of the sample may remove too much of the insulator surrounding the main pole thereby damaging the main pole and rendering the sample useless for examination using electron microscopy. On the other hand, the mechanical lapping of the sample may not remove enough the insulator surrounding the main pole. In this case, the main pole has not been exposed enough for use in electron microscopy. As a result, the success rate for exposing the main pole sufficiently for use in electron microscopy is very low.

Another conventional technique used for sample preparation in electron microscopy is to combine the techniques of mechanical sectioning (e.g., mechanical lapping) with focused ion beam (FIB). For example, many FIB steps are used in conjunction with mechanical lapping to fine tune the exposure of the main pole of the recording head for examination in electron microscopy. However, this combined technique is very labor intensive and expensive, both in terms of human and equipment costs when used for failure analysis. As a result, the expense for sample preparation through a combined mechanical sectioning and FIB is cost prohibitive, especially if more than one sample in a batch of recording heads is to be examined. Additionally, because of the time and cost involved, the combined techniques of mechanical sectioning and FIB is not scalable to examine multiple recording heads in a batch of recording heads.

Thus, a need exists for a preparation technique that provides better main pole exposure for operation and failure analysis.

DISCLOSURE OF THE INVENTION

A method for sample preparation. The method includes mechanically polishing portions of an insulating layer over a main pole of a recording head embedded within a sample structure. The insulating layer is polished top down in planar layers perpendicular to an air bearing surface adjoining the main pole. The method also includes selectively wet etching the remaining portions of the insulating layer to expose the main pole, wherein the insulating layer surrounds the main pole. Etching is made without damaging the main pole.

BEST MODES FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to embodiments of the present invention, a method and system for sample preparation for exposing a main pole of a recording head, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.

Accordingly, embodiments of the present invention provide a method and system for sample preparation for exposing a main pole of a recording head. As a result, other embodiments of the present invention serve the above purpose and provide a preparation technique that provides a high rate of success to expose the main pole or a recording for operation and failure analysis. Furthermore, other embodiments of the present invention serve the above purposes and provide a sample preparation technique that is allows for sample preparation in batches with a high rate of success. Still other embodiments of the present invention serve the above purposes and provide for sample preparation technique that is cost effective to employ during operation and failure analysis.

Embodiments of the present invention are described within the context of recording heads used for magnetic storage. That is, embodiments of the present invention can be used to expose recording heads of any type. However, in particular, embodiments of the present invention are described within the context of perpendicular recording heads used for magnetic storage. Perpendicular recording heads used for perpendicular recording magnetize the storage medium perpendicularly to the film plane, rather than in the file plane, as in horizontal recording. As such, embodiments of the present invention are described within the context of exposing the main pole of a perpendicular recording head sued for magnetic storage.

FIG. 1Ais a diagram illustrating a perspective view of a sample structure100including a main pole of a recording head, in accordance with one embodiment of the present invention. Sample preparation of the structure100is necessary to expose the deposited end of the recording head110for examination in electron microscopy (e.g., scanning electron microscopy [SEM]). The features inFIG. 1Aare not drawn to scale.

While embodiments of the present invention are described within the context of perpendicular recording (e.g., write) heads, other embodiments of the present invention are well suited for exposing any type of recording head, component, or detail of a semiconductor integrated circuit.

As shown inFIG. 1A, the deposited end of the recording head110is embedded within the sample structure100. Also shown is a substrate115upon which the deposited end of the recording head110is deposited. The deposited end of the recording head110is deposited on an upper surface of the substrate115.

An insulating layer surrounds the deposited end of the recording head110. In one embodiment, the insulating layer is comprised of alumina (Al2O3). As shown inFIG. 1A, the insulating layer includes an insulating undercoat145and an insulating overcoat140. The insulating layer also includes a middle coat147of alumina shown inFIG. 1Awithin which the deposited end of the recording head110is formed As such, the deposited end of the recording head110is shown embedded between the insulating overcoat140and the insulating undercoat145within the middle layer147. That is, the deposited end of the recording head110is surrounded by the insulating layer. In one embodiment, the insulating layer provides support for the deposited end of the recording head110in the sample structure100.

In addition, a carbon overcoat layer120is shown inFIG. 1A. The carbon overcoat layer120is formed on a side surface of the sample structure100that includes a side surface of the substrate115and a side surface of the insulating overcoat and undercoat layers140and145. The main pole135of the deposited end of the recording head is exposed to the carbon overcoat layer120through the insulating overcoat140, middle coat147, and undercoat145. In particular, the carbon overcoat layer120provides further protection for the exposed tip of the main pole135of the deposited end of the recording head110. That is, the carbon overcoat layer120protects the pole tip from corrosion.

In addition, an air bearing surface130is shown inFIG. 1A. The air bearing surface130is adjacent to the exposed tip of the main pole135of the deposited end of the recording head110. The air bearing surface130interfaces with a storage medium (not shown). For example, the air bearing surface130lies flat or parallel to the surface of the storage medium as data is being recorded or read from the storage medium.

As shown inFIG. 1A, the distance “x” measured from the deposited end of the recording head110to the top surface of the sample structure100is greater than 5 microns. Arrow105points to the top surface of the alumina overcoat140. In addition, the arrow105points in the direction of a top down view of the sample structure100and the deposited end of the recording head110.

The sample structure as shown inFIG. 1Ais in an unprepared state. The alumina overcoat140in its present state impedes any view of the deposited end of the recording head110using SEM. That is, the dimensions of the insulating layer140are too great to allow SEM to examine the recording head110.

FIG. 2is a flow diagram200illustrating steps in a method for sample preparation for exposing a main pole of a perpendicular recording head, in accordance with one embodiment of the present invention. While embodiments of the present invention are described within the context of perpendicular recording heads, other embodiments of the present invention are well suited to sample preparation for exposure of any type of recording head, or component of an semiconductor integrated circuit. One of the advantages of using the method as described in flow diagram200to expose the main pole is that there is a great increase in the success rate over conventional sample preparation techniques. Since the submicron target is not immediately exposed using mechanical sectioning, there is less of a chance to damage the recording head using the technique outlined in flow diagram200.

At210, the present embodiment optionally removes the carbon overcoat that covers an air bearing surface. The carbon overcoat is adjacent to the main pole of a perpendicular recording head. The recording head is embedded within a sample structure. Removal of the carbon overcoat is not necessary, but does provide improved measurements of the critical parameters as measured using electron microscopy (e.g., SEM). In one embodiment, the process used to remove the carbon overcoat includes an ash process. In particular, a dry strip process using oxygen plasma is used to strip the carbon overcoat layer. For instance, an oxygen ash process is applied for approximately30minutes to remove the carbon overcoat layer, in one embodiment.

At220, the present embodiment mechanically polishes portions of an insulating layer (e.g., alumina) over a main pole of the recording head that is embedded within the sample structure. In particular, the present embodiment removes most of the insulating layer that is present above the main pole of the recording head. In one embodiment, the mechanical polishing is performed through a mechanical lapping process that grinds the surface of the sample structure. The sample structure is polished top down in planar layers perpendicular to an air bearing surface adjoining the main pole

The mechanical polishing is performed to prepare the sample structure for the etching procedure that follows. More specifically, the mechanical polishing is performed to reduce the amount of alumina in the insulating layer that needs to be etched. Not only does this reduce the time for etching, but the mechanical polishing leaves the sample structure in a more uniform state for etching. That is, the surfaces of the insulating layer are more uniformly distant from the recording head, which provides for a more even etching of the insulating layer in relation to the recording head so that the recording head is not prematurely detached from the insulating layer.

In addition, removing most of the insulting layer through mechanical polishing also reduces the amount of debris around the target area of interest, the tip of the main pole of the recording head. Also, to further remove debris, another embodiment includes rinsing the sample structure after the mechanical polishing to further prepare the sample structure for the etching procedure that follows.

FIG. 1Bis a diagram illustrating a perspective view of the sample structure100ofFIG. 1Ashowing the process of mechanical polishing, in accordance with one embodiment of the present invention. As shown inFIG. 1B, the recording head110is surrounded by the insulating layer, to include the overcoat140, the middle layer147, and the undercoat145. Also, the carbon overcoat layer120is shown covering the exposed tip of the main pole135of the deposited end of the recording head110. As described before, inFIG. 1B, the carbon overcoat layer120has not been removed prior to the mechanical polishing. However, other embodiments of the present invention are well suited to performing a removal of the carbon overcoat layer120, in which case, the carbon overcoat layer120would not be shown inFIG. 1B. The features inFIG. 1Bare not drawn to scale.

As shown inFIG. 1B, the sample structure100is polished top down in planar layers perpendicular to the air bearing surface130adjoining the main pole135. As shown inFIG. 1B, the planar layers141and142, for example, are removed from the top down. The top down direction was previously described in relation to arrow105ofFIG. 1A. More particularly, the planar layers of the insulating layer that are removed (e.g., layers142and141) are parallel to a planar surface of the main pole upon which critical parameters can be measured.

As shown inFIG. 1B, planar layers141and142also include portions120A and120B, respectively, of the carbon overcoat layer120. That is, if the carbon overcoat layer120has not been previously removed, the mechanical polishing will also remove portions of the carbon overcoat layer120.

After removal of the planar layers, most of the alumina overcoat140is removed. As shown inFIG. 1B, the distance “x prime” measured from the deposited end of the recording head110to the top surface of the sample structure100is less than 5 microns. Embodiments of the present invention are able to mechanically polish the insulation overcoat to within less than one micron; however, the benefit of embodiments of the present invention is that by first mechanically polishing the insulating overcoat the general area surrounding the deposited end of the recording head is quickly exposed without damaging the main pole135of the deposited end of the recording head110.

Returning now to flow diagram200, at230, the present embodiment selectively wet etches remaining portions of the insulating layer to expose the main pole. The insulating layer surrounds and supports the deposited end of the recording head. For instance, the etch is an isotropic etch that removes the insulating layer from all exposed surfaces.

Embodiments of the present invention use an etchant for the etching process that is an alkaline etching solution. For example solutions of sodium carbonate (Na2CO3) or sodium borate (Na2B4O7), or any other similar solution in varying molar concentrations can be used as an etchant.

The selective wet etch is performed without damaging the main pole. That is, the selective wet etch can be performed without physically altering the characteristics of the main pole, and without dislodging the main pole and the deposited end of the recording head from the insulating layer. More specifically, the molar composition of the etchant used, the temperature (e.g., approximately 50 degrees Celsius) of the etching solution, and the duration of time for etching can be varied to control the rate and an amount of the insulating layer that is etched so that the main pole is not damaged.

In another embodiment, the sample structure is rinsed with a wetting agent after the selective etching process. For instance, the wetting agent is water (H2O), such as de-ionized water. The rinsing is performed to remove the water soluble etch by-products so that the by-products will not crystallize and impede or block views of the main pole of the recording head.

The process outlined in flow diagram200allows for batching various sample structures of recording heads to be prepared simultaneously. As a result, the main pole physical parameters are revealed for SEM imaging without undergoing a laborious focused ion beam process.

After the process outlined in flow diagram200is completed, the main pole of the deposited end of the recording head is sufficiently exposed for viewing using an SEM. As such, the present embodiment further mounts the sample structure for SEM imaging. In another embodiment, the sample structure can be optionally flashed with a conductive coating (e.g., gold palladium [AuPd], carbon, chrome, gold [Au], platinum [Pt], etc.) to increase the electrical stability of the sample structure during the SEM imaging to measure critical parameters, such as flare point and flare angle of finished perpendicular recording heads. Flare point and flare angle provide information as to the performance of the recording head.

FIG. 3is a diagram of top down view of a planar surface of the main pole300of the deposited end of the recording head after exposure through a two step mechanical polish and etch process. As shown inFIG. 3, the main pole parameters can be imaged and measured using SEM. For instance, the distance of the flare point from tip of the main pole at the air bearing surface310to the flare point can be measured.

On the right side, the flare point is the intersection of the vertical portion320and the angled portion325of the main pole300. On the right side, the distance to the flare point from the air bearing surface310is indicated by dR. On the left side, the flare point is the intersection of the vertical portion330and the angled portion335of the main pole300. On the left side, the distance to the flare point from the air bearing surface310is indicated by dL. For example, the distances to the flare point from the air bearing surface310both on the left and right sides can be of dimensions less than 500 nanometers.

In addition, the flare angle can be measured. On the right side, the flare angle is measured as the angle between the vertical portion320that is extended and the angled portion325. That is, the angle θRindicates the flare angle on the right side of the main pole300. On the left side, the flare angle is measured as the angle between the vertical portion330that is extended and the angled portion335. That is, the angle θLindicates the flare angle on the left side of the main pole300.

FIG. 4is an angled view of the main pole300of the deposited end of the recording head after exposure through a two step mechanical polish and etch process. As shown inFIG. 4, the main pole parameters can be imaged and measured using SEM. For instance, the length “L” and width “W” of the pole tip410adjacent to the air bearing surface can be measured. For example, the length “L” and width “W” can be of dimensions less than 200 nanometers. Also, as shown inFIG. 4the distance “dR” between the flare point and air bearing surface, as well as the flare angle “θR” is provided. After the etching process, the main pole of the deposited end of the recording head can be fully exposed. That is, enough of the insulating layer has been etched away to expose the critical parameters of the main pole of the recording head; however, enough of the insulating layer remains to support and attach the main pole and the recording head to the substrate. With proper presentation of the sample structure, measurement of the length “L” and width “W” is possible using SEM imaging.

Accordingly, embodiments of the present invention provide a method and system for sample preparation for exposing a main pole of a recording head. Embodiments of the present invention are able to routinely measure the features of interest in a main pole of a recording head. That is, embodiments of the present invention can be performed in a manufacturing environment on a routine basis to allow physical confirmation of measurements of critical parameters concerning the main pole of the recording head.

A method and system for sample preparation for exposing a main pole of a recording head is thus described. While the invention has been illustrated and described by means of specific embodiments, it is to be understood that numerous changes and modifications may be made therein without departing from the spirit and scope of the invention as defined in the appended claims and equivalents thereof. Furthermore, while the present invention has been described in particular embodiments, it should be appreciated that the present invention should not be construed as limited by such embodiments, but rather construed according to the below claims.