US 5,815,909 AGrant
Method of Making a Thin Film Magnetic Head Including Protected via Connections Through an Electrically Insulative Substrate
Issue Date:1998-10-06
•10 Claims
•17 Drawing Sheets
Abstract
A method is provided for fabricating a thin film magnetic head including a plurality of layered components. One or more vias are formed through an electrically insulative substrate which includes first and second opposed major surfaces. The via includes an interior side surface. The via is filled with electrically conductive material which is situated in contact with the interior side surface of the via. A via connective member is thus formed which extends between the first and second surfaces of the substrate. A protective via cap is formed atop the via connective member to protect the via connective member from subsequent etching operations. A thin film head is formed atop the first surface of the substrate by building up components of the head layer by layer. This forming a thin film head step includes the step of forming a coil for exciting the head by etching, with an etchant, portions of a layer of electrically conductive material within the head. The via protective cap is fabricated from a material which is substantially resistant to etching by the etchant. In this manner the via conductive member is shielded from the potentially deleterious effects of etching. The via connective member typically couples the coil to circuitry external to the thin film head.
Metadata
Assignee
- AIWA Research and Development, Inc.
Inventor
- G. Robert Gray
Application Information
Application Number:US 7027346
Filing Date:1996-08-23
Priority Date:1994-08-26
Art Unit:326
Classifications
IPC:
G11B 5127
Field of Search:
29360216427603.07;603.14;603.16;603.18;603.15;603.25119;120;122;125;126;12722;65131;132
Patent Drawings (17 sheets)
Description
Background of the Invention
1. Field of the Invention
This invention relates in general to magnetic recording/playback heads and, more particularly, to connective structures and techniques for thin film magnetic recording/playback heads.
2. Description of Related Art
In the continuing drive for increased storage density in magnetic media storage devices, thin film magnetic heads have been developed. As opposed to earlier types of magnetic heads, the fabrication of which involves significant piecework and manual handling of individual parts, thin film magnetic heads take advantage of semiconductor fabrication processes to form a large number of heads simultaneously on a common substrate or wafer.
One such head which is formed by a semiconductor thin film process is disclosed in the article, "A New Thin Film Head Generation IC Head" by J.P. Lazzari et al., IEEE Transactions on Magnetics,, Vol. 25, No. 5, September 1989. A cross-sectional view of the Lazzari head is illustrated in FIG. 1 as head 10. Head 10 is fabricated within a recess 15 in a silicon substrate 20. A gap 25 is shown in the uppermost portion of a magnetic layer or yoke 30 situated within recess 15. Head 10 is shown positioned adjacent magnetic recording media 35. A magnetic coil 40 is wound around magnetic yoke 30. A plurality of sliders with respective heads 10 thereon are fabricated from a common silicon wafer or substrate using semiconductor thin film processes. The sliders are then diced up into individual slider assemblies.
To achieve electrical connection to the coils of the head, a through hole connection 45 is made in the silicon substrate. The walls of the hole are coated with an insulator layer 50 and the center of the hole is filled with a conductive layer 55 as shown in FIG. 1.
Efficient connection to the ends of the coil structure of a thin film head is one problem which the thin film head designer faces. Such connections need to be achieved in a manner which is compatible with the fabrication of the remaining structures of the thin film head.
Summary of the Invention
One advantage of the thin film head of the present invention is the establishment of electrical connections to the coil structure of a thin film head using a minimum number of connective structures.
Another advantage of the thin film head of the present invention is that the disclosed thin film head can be fabricated without excavating a recess within the substrate to contain the head.
Still another advantage of the thin film head of the present invention is that the disclosed head can be fabricated in large quantities using thin film semiconductor fabrication equipment.
In accordance with one embodiment of the present invention, a thin film magnetic head is provided which includes an electrically insulative substrate having first and second opposed major surfaces, the substrate including a via between the first and second surfaces, the via including an interior side surface. The head also includes a via connective member of electrically conductive material situated within the via in contact with the interior side surface of the via and extending between the first and second surfaces of the substrate. The head further includes a protective via cap situated atop the via connective member at the first surface of the substrate. The head still further includes a lower pole member of magnetic material situated on the first surface of the substrate and having first and second ends. The head also includes first and second side pole members of magnetic material situated at the first and second ends, respectively, of the lower pole member, the first and second side pole members being built up from a plurality of layers of magnetic material deposited layer upon layer, the first and second side pole members including tops and bottoms. The head further includes an insulative body situated about the first and second side poles and built up from a plurality of layers of electrically insulative material. The head also includes a conductor coil layer of electrically conductive material situated within the insulative body and around one of the first and second side pole members, the coil being formed by etching portions of the coil layer with an etchant.
The head further includes an insulative pedestal situated at the tops of the first and second side pole members, the insulative pedestal extending above the plane of the insulative body below and surrounding the tops of the first and second side pole members. The head still further includes first and second magnetic poles coupled to the tops of the first and second side pole members respectively to form a gap region therebetween. In the disclosed head, the via protective cap is fabricated from a material which is substantially resistant to etching by the etchant. In this manner, the integrity of the via connective member is not degraded by etchants which are used in the fabrication of the head. While one via connective member is mentioned above, it should be understood that multiple via connective members fabricated as described may actually be employed in a particular thin film magnetic head. These via connective members are generally used to establish electrical connection between the coil structure within the head and external electrical circuitry.
Brief Description of the Drawings
The features of the invention believed to be novel are specifically set forth in the appended claims. However, the invention itself, both as to its structure and method of operation, may best be understood by referring to the following description and accompanying drawings.
FIG. 1 is a cross section of a conventional thin film magnetic head.
FIG. 2A is a plan view of a substrate with via holes employed by one embodiment of the magnetic head of the invention.
FIG. 2B is a cross section of the magnetic head of FIG. 2A taken along section line 2B--2B.
FIG. 3 is a plan view of the magnetic head of FIG. 2A with a seed layer added.
FIG. 4A is a plan view of the magnetic head of FIG. 3 with an insulative layer and, open region formed therein.
FIG. 4B is a cross sectional view of the magnetic head of FIG. 4A taken along section line 4B--4B.
FIG. 5 illustrates a plurality of magnetic heads being fabricated on a common substrate.
FIG. 6A is a plan view of the magnetic head of FIG. 4A showing an early stage of side pole build-up
FIG. 6B is a cross sectional view of the magnetic head of FIG. 6A taken along section line 6B--6B.
FIG. 7A is a plan view of the magnetic head of FIG. 6A showing the placement of a lower coil structure.
FIG. 7B is a cross sectional view of the magnetic head of FIG. 7A taken along section line 7B--7B.
FIG. 8A is a plan view of the magnetic head of FIG. 7A showing an insulative layer on the lower coil structure.
FIG. 8B is a cross sectional view of the magnetic head of FIG. 8A taken along section line 8B--8B.
FIG. 9A is a plan view of the magnetic head of FIG. 8A showing placement of an upper coil structure.
FIG. 9B is a cross sectional view of the magnetic head of FIG. 8A taken along section line 9B--9B.
FIG. 10A is a plan view of the magnetic head of FIG. 9A showing an insulative layer on the upper coil structure.
FIG. 10B is a cross sectional view of the magnetic head of FIG. 10A taken along section line 10B--10B.
FIG. 11A is a plan view of the magnetic head of FIG. 10A showing placement of a seed layer and a connective grounding strip.
FIG. 11B is a cross sectional view of the magnetic head of FIG. 11A taken along section line 11B--11B.
FIG. 12 is a cross sectional view of the magnetic head of FIG. 11B showing placement of an insulative pedestal thereon.
FIG. 13A is a cross sectional view of the magnetic head of FIG. 13B showing the further build-up of the magnetic side poles.
FIG. 13B is a close-up plan view of a portion of the head of FIG. 13A showing the side pole and insulative pedestal area.
FIG. 14A is a cross sectional view of the magnetic head of FIG. 14B showing the addition of a first magnetic pole at the top of the magnetic yoke structure of the head.
FIG. 14B is a close-up plan view of a portion of the head of FIG. 14A showing the first magnetic pole.
FIG. 15A is a close-up plan view of a portion of the head of FIG. 14A showing the gap region of the head.
FIG. 15B is a cross sectional view of the magnetic head of FIG. 15A showing the addition of a gap region.
FIG. 16A is a close-up plan view of the side pole and gap region of the magnetic head of FIG. 15A showing the addition of a second magnetic pole at the top of the magnetic yoke structure of the head.
FIG. 16B is a cross sectional view of the magnetic head of FIG. 16A taken along section line 16B--16B and showing the addition of a second magnetic pole.
FIG. 17A is a close-up plan view of the side pole and gap region of the magnetic head of FIG. 16A after addition of an adhesion layer and a diamond-like carbon wear layer to the top of the head.
FIG. 17B is a cross sectional view of the magnetic head of FIG. 17A taken along section line 17B--17B.
FIG. 18 is a cross sectional view of the magnetic head of FIG. 17B showing the magnetic head after a diamond-like carbon wear layer and adhesion layer are patterned and etched in regions other than the insulative pedestal.
FIG. 19A is a close-up view of, the side pole and gap region of the magnetic head when fabrication is complete.
FIG. 19B is a cross section view of the magnetic head of FIG. 19A taken along section line 19B--19B.
FIG. 20 is a plan view of the bottom side of the thin film head of the present invention.
Detailed Description of the Invention
I. VIA CONNECTION FABRICATION--GENERAL DESCRIPTION
FIG. 2A shows a portion of a thin film head 100 which is situated on an insulative substrate 105 such as a ceramic, alumina or other nonconductive substrate. Substrate 105 includes opposed surfaces 105A and 105B. Via holes 110 are formed in substrate 105 and are filled with an electrically conductive material to create conductive paths through substrate 105 at the locations shown. Laser drilling or other high precision via formation technique may be employed to form via holes 110. Via holes 110 are filled with electrically conductive material such as plated copper, thick film processed gold, or sintered tungsten and copper, for example, to form via connective members 112A, 112B and 112C. Connective members 112A and 112C will subsequently be coupled to the ends of a coil structure and connective member 112B will be coupled to ground. In one embodiment of the invention wherein the magnetic head is ungrounded, via hole 112B is omitted. In actual practice, substrate 105 is a wafer on which the FIG. 2A pattern is replicated thousands of times.
A seed layer 115 of an electrically conductive material suitable for plating is sputtered on substrate surface 105A. For example, seed layer 115 may be fabricated from Cr--NiV, namely, a chrome or other adhesion-promoting layer followed by a non-magnetic nickel-vanadium 7% film. Via caps 120 are patterned using photolithographic techniques and plated on seed layer 115 at the tops of vias 110 as shown in FIGS. 2A and 2B. More specifically, to pattern via caps 120, a photoresist layer (not shown) is deposited on seed layer 115 and patterned to include openings above connective members 112A, 112B and 112C at which the formation of respective via caps 120 is desired. Plating is then conducted in these openings using seed layer 115 as the seed. The photoresist is then removed, thus leaving patterned via caps 120. As used in this document, the term "patterning" will mean the formation of a particular layer such that the layer exhibits a specified pattern, such as described with respect to the formation of via caps 120 above, for example.
Via caps 120 are fabricated from NiFe by any suitable deposition or plating process. It is noted that later in the process described herein, portions of seed layer 115 will be removed by sputter etching. While in the particular example described, via caps 120 are fabricated from NiFe, in actual practice via caps 120 can be fabricated from other conductive materials which would not be attacked by the particular etchant used to later remove Cr--Cu seed layers 185, 230 and 275. Via caps 120 are regarded as being a part of via connective members 112A, 112B and 112C.
Seed layer 115 is also used to pattern and NiFe plate photolithographic alignment targets (not shown) for registration of subsequent layers. The exposed portions of seed layer 115 are then sputter etched away leaving via caps 120 and the alignment targets intact. It should be appreciated that seed layer 115 served as a sacrificial layer for the purpose of enabling plating of via caps 120.
II. THIN FILM HEAD BUILD-UP PROCESS
In the next step of the process, a Cr--NiV seed layer 130 is formed on the structure of FIG. 2B after seed layer 115 is etched away. Seed layer 130 is formed in the shape of a ground structure 125 which extends around the periphery of head 100 on substrate 105 and laterally across the middle of head 100 as shown in FIG. 3. Open regions 117A and 117B are thus formed in seed layer 130 which respectively isolate via connective members 112A and 112C from ground structure 125 and via connective member 112B. In the embodiment depicted in FIG. 3, via connective member 112B is coupled to ground structure 125. To actually form seed layer 130, a "lift-off" process is used. In this "lift-off" process, photoresist (not shown) is patterned covering open regions 117A and 117B (see FIG. 3). Seed layer 130 is then sputtered on the entire upper surface of the partially completed head 100. The photo-resist which covers open regions 117A and 117B is now "lifted-off" head 100. To accomplish this lift-off, the partially complete head 100 is placed in an ultrasonic bath including a photoresist solvent such as acetone, for example. The seed layer 130 is sufficiently thin such that it does not cover photoresist layer at open regions 117A and 117B very well. In this manner, there are sufficient avenues of attack by which the solvent can get through seed layer 130 at the edges of open regions 117A and 117B to dissolve the photoresist layer at open regions 117A and 117B. When the photoresist layer at open regions 117A and 117B is thus dissolved, the portions of seed layer 130 immediately above open regions 117A and 117B liftoff and float away. The region of head 100 at open regions 117A and 117B is thus void of seed layer 130 as shown in FIG. 33.
An insulative layer 135 of photoresist is patterned on head 100 as shown in FIG. 4A and FIG. 4B. Insulative layer 135 is cured with an electron beam. Exposing the photoresist to an E-beam for a time within the range of approximately 20 minutes to approximately 40 minutes is found to produce acceptable curing results. Insulative layer 135 includes an open region 140 for receiving the lowermost portion of a magnetic yoke 145 therein. More particularly, a layer 150 of magnetic material such as NiFe is patterned and plated on seed layer 130 within open region 140 to form the lowermost portion of magnetic yoke 145. Magnetic layer 150 exhibits a thickness of approximately 5 microns to approximately 6 microns in this particular embodiment. When reference is made to "magnetic layers" or other magnetic structures in this document, it should be understood that layers of magnetically permeable material are being referenced. Magnetic layer 150 forms the bottom pole of magnetic yoke 145. Seed layer 130, or more specifically the middle section of the ground structure 125 thereof, acts as a base upon which magnetic yoke 145 is built up layer by layer. Magnetic layer 150 is plated up to a level such that it is level with insulative layer 135. For convenience, one half of head 100 is depicted in FIG. 4A and subsequent figures. It should be understood that substantially the same structure as shown in FIG. 4A and the subsequent figures is repeated to form the actual head. More particularly, in the particular embodiment shown, head 100 is symmetric about major axis 155 such that head 100 actually includes two recording or playback portions. In actual practice, a plurality of heads 100 are fabricated simultaneously on a common semiconductor substrate 105 as shown in FIG. 5. For example, 5000 or more heads may be fabricated at the same time on the same substrate. FIG. 5 shows another embodiment of head 100, namely an ungrounded version in which via connective member 112B is omitted.
An insulative layer 160 of photoresist is patterned on head 100 as shown in FIG. 6A and 6B. Insulative layer 160 is electron beam cured to provide a planar surface as illustrated. The thickness of insulative layer 160 in this particular embodiment is approximately 2 microns. Insulative layer 160 includes open regions 165 and 170 in which respective magnetic side poles are built up. More specifically, a magnetic side pole portion 175 is plated in open region 165 up to a height which is level with insulative layer 160, and a magnetic side pole portion 180 is plated in open region 170 up to a height which is level with insulative layer 160.
A seed layer 185 is sputtered on insulative layer 160 of the partially formed head 100 of FIG. 6A to form a plating base for a lower coil layer 190 as shown in FIG. 7A. Seed layer 185 is drawn sufficiently thin such that it does not appear to have significant vertical dimension in FIG. 7A. Seed layer 185 is fabricated from CrCu in one embodiment.
A lower coil layer 190 is formed on seed layer 185 as shown. One way to form lower coil member 190 is to deposit a layer of photoresist (not shown) on seed layer 185. This photoresist layer is then patterned using conventional photolithographic techniques which includes photoresist application, masking, exposure, developing, and so forth. More specifically, the photoresist layer is patterned to cover the entire surface of seed layer 185 except for openings at the locations where the coil elements of lower coil layer 190 are to be formed. Head 100 is then subjected to a plating bath of copper. Copper is thus plated in the openings of the photoresist layer to form lower coil layer 190. The thickness of coil layer 190 is within the range of approximately 3.mu. to approximately 3.5.mu. at this stage.
Lower coil layer 190 includes a connective strip 195 made of electrically conductive material which couples an end 190A of coil layer 190 to the via cap 120 of via connective member 112A. Copper plating may be used to fabricate connective strip 195 as part of the above step of forming lower coil layer 190. The remaining end 190B of lower coil layer 190 is located at the center of the lower coil. Head 100 is then etched to remove seed layer 185 from those portions of head 100 not protected by lower coil layer 190.
An insulative layer 200 of photoresist is patterned on head 100 above lower coil layer 190 leaving an open region 205 for access to coil end 190B as shown in FIGS. 8A and 8B. The thickness of insulative layer 200 is within the range of approximately 5.mu. to approximately 6.mu. Insulative layer 200 is also patterned to leave open regions 210 and 215 above side pole portion 175 and side pole portion 180, respectively. Insulative layer 200 is electron beam cured. Insulative layer 200 electrically isolates lower coil layer 190 from structures subsequently placed above layer 190.
Magnetic side pole portions 220 and 225 are plated on side pole portions 175 and 180, respectively, as shown in FIGS. 8A and 8B. Side pole portions 220 and 225 are plated with a magnetic material such as NiFe up to a level even with that of insulative layer 200.
A seed layer 230 is sputtered on insulative layer 200 of the partially formed head 100 of FIG. 8B to form a plating base for an upper coil layer 235. Seed layer 230 is drawn sufficiently thin such that it does not appear to have significant vertical dimension in FIG. 8B. Seed layer 230 is fabricated from CrCu in one embodiment. Upper coil layer 235 is patterned and copper plated on seed layer 230 as shown in FIG. 9A and 9B. FIG. 9B is a simplified cross-section of head 100 at the described stage of fabrication in which structures in back of upper coil layer 235 are not shown in order to emphasize upper coil layer 235. In this particular embodiment, upper coil layer 235 is substantially similar in geometry to lower coil layer 190 and is fabricated using substantially the same technique. However, other coil arrangements are possible if desired. Head 100 is then etched to remove seed layer 230 from those portions of head 100 not protected by upper coil layer 235.
Upper coil layer 235 includes a connective strip 237 made of electrically conductive material which couples an end 235A of upper coil layer 235 to the via cap 120 of via connective member 112C. Copper may be used to fabricate connective strip 237. The remaining end 235B of upper coil layer 235 is coupled to lower coil end 190B through open region 205, shown later in FIG. 10B, by a plated connection therebetween.
An insulative layer 240 of photoresist material is deposited and patterned on head 100 as shown in FIGS. 10A and 10B. Insulative layer 240 electrically isolates upper coil layer 235 from the other structures of head 100. Insulative layer 240 includes open regions 245 and 250 into which magnetic side pole portions 255 and 260 are respectively plated. More specifically, magnetic side pole portions 255 and 260 are plated up to a level even with insulative layer 240 as shown in FIG. 10B.
Magnetic side pole portions 175, 220 and 255 together form a first side pole 265. Magnetic side pole portions 180, 225 and 260 together form a second side pole 270. First side pole 265, second side pole 270 and bottom pole 150 together form a significant portion of magnetic yoke 145.
A seed layer 275 fabricated of CrCu material is formed on the upper surface of the head structure 100 as shown in FIG. 11B. Seed layer 275 is sputtered, patterned and chemically etched on the upper surface of head 100 to include an open region 280 above the side pole structure also as shown in FIG. 11B. Seed layer 275 is formed by an adhesion layer of chromium (Cr) on the upper surface of head 100 followed by a layer of copper (Cu). The chromium adhesion layer enhances the adherence of the copper portion of seed layer 275 to upper surface of head 100.
The primary requirement in selection of the material for seed layer 275 is that seed layer 275 be chemically etchable without damage to the exposed NiFe. Copper is an example of a material that meets this requirement and is also used for the coil seed layers. Chrome is used as the adhesion layer for copper. It is noted that a titanium-tungsten seed layer (Ti 10%; W 90%) which wet etches easily can also be used for seed layer 275.
Protective caps 285 and 29.0 are patterned over connective strips 195 and 237, respectively. Caps 285 and 290 are fabricated from NiFe by plating in one embodiment. A material such as nickel, nickel-phosphorus 7-10%, or gold may be used to provide environmental protection for the underlying plated copper connective strips.
In an embodiment of head 100 wherein head 100 is grounded, a grounding connective strip 295 is also patterned and plated in the same process step as protective caps 285 and 290. Grounding strip 295 connects ground via connective member 112B and magnetic yoke 145 through seed layer 130. Grounding strip 295 is fabricated from the same material as protective caps 285 and 290 in this particular embodiment.
An electrically insulative layer of photoresist is patterned and electron beam cured to form a protrusion or pedestal 300 on the upper portion of head 100 as shown in FIG. 12. Insulative pedestal 300 exhibits a substantially rectangular geometry with rounded corners in this particular embodiment, although other geometries may be used if desired. Insulative pedestal 300 includes open regions 305 and 310 for side poles 265 and 270 of the magnetic yoke. Open regions 305 and 310 are filled with magnetic material by plating side poles 265 and 270 with NiFe up to the level of the top of insulative layer 300 as shown in FIG. 13A. Magnetic side pole portions 315 and 320 are thus formed in open regions 305 and 310. Magnetic side pole portions 315 and 320 form the uppermost parts of first side pole 265 and second side pole 270, respectively.
A frame 325 of magnetic material, for example NiFe, is patterned around insulative pedestal 300 at the same time that magnetic side pole portions 315 and 320 are plated. Plating or other suitable deposition technique is used to form frame 325. Frame 325 exhibits a thickness of approximately 5.mu. in this particular embodiment. Seed layer 275 acts as the seed for the plating of frame 325. Frame 325 exhibits a substantially rectangular shape in this particular embodiment and surrounds insulative pedestal 300 which forms the inner boundary of frame 325 as seen in FIG. 13B. Shapes other than rectangular can be used for frame 235 as long as frame 325 substantially surrounds, and is located immediately adjacent to, pedestal 300. Frame 325 serves to stiffen insulative pedestal 300 and may provide electrical shielding of the contained structures. FIG. 13B is a close-up view of the coil and side pole regions of head 100 at the present stage in the fabrication of head 100. Alternatively, side pole portions 315 and 320 are fabricated as before, but frame 325 is subsequently patterned and plated with non-magnetic NiP alloy up to a level even with the top of insulative pedestal 300. The innermost boundary of seed layer 275 which abuts its open region 280 is shown in dashed line in FIG. 13B. The exposed CrCu seed layer 275 is removed by wet chemical etching.
Referring now to FIGS. 3, 14A and 14B, a layer of photoresist is patterned covering open regions 117A and 117B (see FIG.3) and further covering side poles 265 and 270 (see FIG.14A and 14B). A Cr--NiV seed layer 330 is sputtered on the exposed upper surfaces of head 100. The photo-resist is stripped as in the earlier-described "lift-off" process, thus "lifting off" the sputtered Cr--NiV film from regions 117A and 117B. During this photoresist stripping step, the photoresist above side poles 265 and 270 is removed to form open regions 335 and 340 as shown in FIG. 14A. Side poles 265 and 270 are thus exposed.
A first magnetic pole 345 is patterned at the top of magnetic yoke 145 as shown in FIG. 14A and 14B. First magnetic pole 345 is fabricated by plating a magnetic material such as NiFe on side pole 265 and on a portion of seed layer 330 adjacent side pole 265. Magnetic control regions 350 and 355, which are adjacent both sides of first magnetic pole 345, may be patterned and plated at the same time as first pole 345. Magnetic control regions 350 and 355 serve to better control local plating current density which influences NiFe composition and enhances the effect of the easy axis magnetic orienting field of between approximately 1000 Gauss to approximately 10,000 Gauss, provided by an external magnet during the first magnetic pole plating step, to give a desired magnetic domain structure in the magnetic pole piece. Head 100 is exposed to the same magnetic field throughout the duration of building up the various magnetic layers thereof.
A substantially rectangular gap region 360 of non-magnetic material is plated adjacent pole end 345A as shown in FIG. 15A and the head cross section of FIG. 15B. One non-magnetic material which may be used to fabricate gap region 360 is NiP. Diamond-like carbon is another material which may be chemically vapor deposited as gap region 360.
A second magnetic pole 365 is patterned and plated at side pole 270 at the top of magnetic yoke 145 as shown in FIGS. 16A and 16B. Second magnetic pole 365 includes a pole end 365A which is situated adjacent pole end 345A and which is separated from pole end 345A by gap region 360. It is noted that pole 345 becomes narrower from side pole 265 to pole end 345A. Similarly, pole 365 becomes narrower from side pole 270 to pole end 365A. This gives poles 345 and 365.a bow tie-like appearance in this particular embodiment. Other pole geometries may be used as well. Pole ends 345A and 365A are alternatively referred to as gap ends. First magnetic pole 345 and second magnetic pole 365 exhibit a thickness of approximately 5.mu..
Magnetic control regions 370 and 375 are patterned and plated adjacent both sides of second pole 365 to enhance magnetic control as shown in FIG. 16A. Control regions 350, 355, 370 and 375 are fabricated from a magnetic material such as the material used to fabricate second magnetic pole 365. For optimal wear performance, the area of NiFe exposed to the recording media should be minimized. Thus, to avoid possible magnetic effects that may degrade recording performance, NiFe plated magnetic control regions 350, 355, 370 and 375 are patterned with photoresist and etched away leaving a pole geometry seen in FIG. 17A.
Magnetic side pole portions 175, 220, 255 and 315 together make up a first side pole which is shown collectively as side pole 265 in FIG. 16B. Magnetic side pole portions 180, 225, 260 and 320 together make up a second magnetic side pole which is shown collectively as side pole 270 in FIG. 16B. Magnetic yoke 145 is collectively made up of bottom magnetic layer 150, side poles 265 and 270, and magnetic poles 345 and 365.
The exposed seed layer 330 is removed by sputter etching. Alternatively, seed layer 330 is not etched, but is permitted to remain. A silicon adhesion layer 380 is sputtered on the exposed upper surface of head 100 as shown in FIG. 17B. A diamond-like carbon (DLC) protective wear layer 385 is then deposited on adhesion layer 380. Adhesion layer 380 enables DLC layer 385 to stick to the upper surface of head 100. This silicon adhesion layer typically exhibits a thickness within the range of approximately 400A.degree. to approximately 1000A.degree.. This silicon adhesion layer exhibits a nominal thickness of approximately 600A.degree. in a preferred embodiment.
DLC layer 385 covers at least the top of magnetic yoke 145 and the immediately surrounding area of the head. As seen in FIG. 17A and more clearly in FIG. 17B, a hard protective wear layer 385 covers magnetic yoke 145 and insulative pedestal 300. Protective layer 385 exhibits a Knoop hardness greater than 700 Knoop and preferably greater than 800 Knoop. The hardness of protective layer should be within the range of greater than approximately 700 Knoop to approximately 2000 Knoop. One material that is satisfactory for formation of protective wear layer 385 is diamond like carbon (DLC).
To form such a DLC wear layer 385, DLC layer 385 is chemically vapor deposited and patterned. More specifically, both DLC layer 385 and adhesion layer 380 are reactive ion etched to leave a DLC wear layer 385' over magnetic yoke 145 and insulative pedestal 300 as shown in FIG. 18. Prior to exposing head 100 to this reactive ion etch, the upper surface of head 100 is covered with a layer of photoresist (not shown). The photoresist layer is patterned to include unprotected open regions for those portions of the head external to frame 325. In this manner, when the head is subjected to the reactive ion etch, the portion of DLC layer 385 external to frame 325 is etched away and the remaining portion of DLC layer 385 is protected and remains as DLC layer 385'.
An alternative to the above described photoresist masking approach to patterning DLC layer 385 into DLC layer 385' is to cover head 100 with a metal layer such as chromium. For example, a relatively thin photomask layer (not shown) of chromium is sputtered over the DLC layer. In this particular example, the photomask layer is approximately 500 A.degree. thick. The metal photomask layer is photo-patterned and etched to expose DLC areas which are to be excavated by reactive ion etching. The DLC layer is then reactive ion etched to the desired DLC structure.
More detail is now provided with respect to the formation of DLC protective wear layer 385. Before DLC protective wear layer 385 is actually laid down on silicon adhesion layer 380, adhesion layer 380 is sputter cleaned. In the course of performing this sputter cleaning, approximately 200A.degree. of the upper surface of silicon adhesion layer 380 is removed. More particularly, the silicon adhesion layer is sputter cleaned in a SAMCO plasma machine, Model No. PD-200D (Plasma Enhanced CVD System For DLC Deposition and Etching), hereafter the "plasma machine". This sputter cleaning is performed with Argon in a plasma within the plasma machine vessel at a pressure of 70 mTorr with 180 watts RF input power at a frequency of 13.56 MHz. The flow rate of Argon is approximately 100 sccm. The partially complete head 100 is situated on a 6 inch diameter cathode (ie. the energized electrode) of the SAMCO plasma machine, Model PD-200D, for approximately 3 to approximately 4 minutes.
Immediately after the Argon plasma cleaning (sputter etching) is complete, the input power is reduced to 110-150 Watts to the same 6 inch cathode electrode. The Argon source is turned off and a source of liquid hydrocarbon DLC source material is turned on. For example, one DLC source material that may be used is Part No. S-12 available from SAMCO, Sunnyvale, Calif. The pressure within the vessel is approximately 20-approximately 25 mTorr at a flow rate of source material of approximately 25 cm.sup.3 /min. Although the temperature is not specifically controlled during this process, the wafer on which the head is fabricated is situated on a water-cooled cathode while in the plasma machine. Under these conditions, a DLC deposition rate of approximately 1000 A/min is obtained which is maintained until the desired DLC thickness is reached, namely approximately 5.mu..
DLC fabricated in this manner results in a DLC layer 385 with a Knoop hardness of approximately 800. It is found that DLC layer Knoop hardnesses of greater than 700 up to approximately 2000 Knoop produce and acceptably hard wear layer 385 for wear protection purposes. DLC wear layer 385 is then reactive ion etched as described to form DLC wear layer 385'.
DLC wear layer 385'is machined as shown in FIG. 19B to expose magnetic gap region 360 as shown in both FIG. 19A and 19B. DLC wear layer 385' protects head 100, specifically gap region 360 and magnetic poles 345, 365, from wear when head 100 is brought into contact with a magnetic media for recording or playback purposes. By using the techniques described herein, very narrow gap regions can be produced. The gap width, W.sub.G, is defined to be the width of gap region 360, namely the distance between pole end 345A and pole end 365A as seen in FIG. 19B. Typical gap widths for head 100 are approximately 0.2 microns to approximately 1 micron.
It is noted that in one embodiment of the invention, the upper magnetic pole elements 345 and 365 are plated directly on magnetic side poles 265 and 270, respectively, Advantageously, no intervening structures are required between upper magnetic pole element 345 and magnetic side pole 265 or between magnetic pole element 365 and magnetic side pole 270. Magnetic pole elements 345 and 365 are thus integral with magnetic side poles 265 and 270, respectively.
III. VIA CONNECTION FABRICATION
From the above discussion it will be appreciated that via connective members 112A, 112B and 112C permit the connection of coil structures (190, 235) on one side of substrate 105 to be electrically coupled to structures on the other side of substrate 105 as seen in FIG. 19B. Unlike other approaches which employ an electrically conductive substrate such as silicon, each via hole in the disclosed head 100 need not be internally coated with insulative material. The disclosed thin film head 100 employs an electrically insulative substrate through which via holes 110 are formed by laser drilling or other highly positionally accurate hole formation technique.
In one embodiment of the invention, via connective members 112A, 112B and 112C are formed as follows: Tungsten (W) is sintered into each via hole. The tungsten is then fired such that it bonds with the tungsten to form a spongy, porous material in the hole. The wafer or substrate with the via holes therein is then exposed to molten copper. When this occurs, the copper wicks up into the porous material in the hole to form a tungsten/copper combination within the hole. Alternatively, the via holes could be plated with copper, or a thick film copper or gold paste is placed in the via holes and fired to form the via connective members.
It is noted that subsequent to the formation of via connective members 112A, 112B and 112C, a number of etching steps occur which could potentially cause damage to these via connective members. For example, assuming that via connective members 112A, 112B and 112C are fabricated by plating copper in the corresponding via holes 110 in one embodiment of the invention, then if coil layers 190 and 235 are likewise fabricated from copper, the via connective members could potentially be damaged by the etchant which is used to pattern coil layers 190 and 235.
In one embodiment of the invention wherein coil layers 190 and 235 are fabricated from copper, an ammonium persulfate--ammonium hydroxide solution is used to pattern or etch these layers. To form this etchant, in one liter of deionized water dissolve 120 gm of ammonium persulfate, and add 64 ml of 30% ammonium hydroxide solution. This is a relatively mild selective etchant which etches copper but does not attack materials such as Ni or NiFe. Via caps 120 are made of a material which is not attacked by the selective etchant used to etch coil layers 190 and 235 and which. is not attacked by the etchant used to etch seed layer 115 away. (It will be recalled that seed layer 115 is the seed layer on which via caps 120 are plated.) In this example, via caps 120 are made of Ni or NiFe. After via caps 120 are plated, the exposed portions of seed layer 115 are sputterd etched away in one embodiment of the invention.
Via caps 120 extend beyond the periphery of via connective members 112A, 112B and 112C by approximately 20 to approximately 30 microns at the tops thereof in one embodiment where vias 110 exhibit a diameter of approximately 150 microns. Via caps 120 thus form a protective coverings for the tops of via connective members 112A, 112B and 112C which prevent the via connective members from being exposed to etchants in the steps of head fabrication subsequent to via connective member formation. The selective etchants employed in the subsequent etching steps selectively attack the subject target material or layer (for example, copper coil layers 190 and 235) but do not substantially erode via caps 120. In this manner, the integrity of via connective members 112A, 112B and 112C is preserved.
The material requirements for via caps 120 are that the cap material be platable and that the material should not be significantly attacked by etchants employed in fabrication steps after via cap formation. Protective material other than Ni and NiFe may be employed as long as such other materials are not affected by the selective etchant. The material requirements for the selective etchant are that it must be able to etch the particular electrically conductive material selected for coil layers 190, 235 and seed layer 275 while not significantly attacking the via cap 120 material.
In this particular embodiment of the invention, while via caps 120 are used to protect via connective members 112A, 112B and 112C on substrate surface 105A from etchants, exposed vias on the reverse side 105B (see FIG. 20) of substrate 105 are protected from etchants with photoresist (not shown) during such etching steps. Such a layer of photoresist is coated and cured on reverse side 105B to provide protection from etchants. The lowermost portions of via connective members 112A, 112B and 112C appear in FIG. 20 as well as the bottoms of the via holes 110 through which such via connective members run.
While a thin film magnetic head apparatus has been described above, it is clear that a method of fabricating such a magnetic head apparatus is also disclosed. Briefly, a method of fabricating a thin film magnetic head including a plurality of layered components is provided. The method includes the step of forming a via through an electrically insulative substrate which includes first and second opposed major surfaces, the via including an interior side surface. The method also includes the step of filling the via with electrically conductive material in contact with the interior side surface of the via to form a via connective member extending between the first and second surfaces of the substrate. The method further includes the step of forming a protective via cap atop the via connective member at the first surface of the substrate. The method still further includes the step of forming a thin film head atop the first surface of the substrate by building up components of the head layer by layer, the forming a thin film head step including the step of forming a coil for exciting the head by etching, with an etchant, portions of a layer of electrically conductive material within the head. In this method, the via protective cap is fabricated of a material which is substantially resistant to etching by the etchant.
The foregoing has described a thin film magnetic head in which the via connective members are protected from potential adverse effects of etching steps used to fabricate the head. Advantageously, the disclosed thin head achieves a very narrow gap width which results in correspondingly high density magnetic recording capabilities. The thin film head can be fabricated without excavating a recess within the substrate to contain the head. Moreover, the disclosed thin film head can be fabricated in large quantities using thin film semiconductor fabrication equipment.
While only certain preferred features of the invention have been shown by way of illustration, many modifications and changes will occur. It is, therefore, to be understood that the present claims are intended to cover all such modifications and changes which fall within the true spirit of the invention.
Claims
What is claimed is:
1. A method of fabricating a thin film magnetic head apparatus including a plurality of layered components, the method comprising the steps of: forming a via through an electrically insulative substrate which includes first and second opposed major surfaces, the via bordering an interior side surface of the substrate; filling the via with an electrically conductive material in contact with the interior side surface of the substrate to form a via connective member extending between the first and second opposed major surfaces of the substrate; forming a protective via cap atop the via connective member and extending from the first major surface of the substrate; and forming a magnetic yoke and coil portion of the thin film magnetic head overlying a portion of the first major surface of the substrate, the magnetic yoke and coil portion being separated from the protective via cap, the magnetic yoke and coil portion being formed by building up components of the magnetic yoke and coil portion in a plurality of layer deposition and etching steps, the step of forming a magnetic yoke and coil portion of the thin film magnetic head including the step of forming a coil for exciting the thin film magnetic head the coil being formed by depositing a layer of the electrically conductive material encircling magnetic poles of the magnetic yoke and etching, with an etchant, portions of the layer of the electrically conductive material; wherein the via protective cap being fabricated of a material which is substantially resistant to etching by the etchant.
2. The method of fabricating a thin film magnetic head apparatus of claim 1 wherein the electrically conductive material is plated in the via.
3. The method of fabricating a thin film magnetic head apparatus of claim 1 wherein the via is formed by laser drilling though the substrate.
4. The method of fabricating a thin film magnetic head apparatus of claim 1 wherein the coil is fabricated from copper and the via protective cap is fabricated from NiFe.
5. The method of fabricating a thin film magnetic head apparatus of claim 4 wherein the etchant is a mixture including ammonium persulfate and ammonium hydroxide.
6. A method of fabricating a thin film magnetic head apparatus including a plurality of layered components, the method comprising the steps of: forming a via through an electrically insulative substrate which includes first and second opposed major surfaces, the via bordering an interior side surface of the substrate; filling the via with an electrically conductive material in contact with the interior side surface of the substrate to form a via connective member extending between the first and second opposed major surfaces of the substrate; forming a protective via cap atop the via connective member and extending from the first major surface of the substrate; and forming a magnetic yoke and coil portion of the thin film magnetic head overlying a portion of the first major surface of the substrate, the magnetic yoke and coil portion being separated from the protective via cap, the magnetic yoke and coil portion being formed by building components of the magnetic yoke and coil portion in a plurality of layer deposition and etching steps, the step of forming a magnetic yoke and coil portion of the thin film magnetic head including the substeps of: depositing a lower magnetic layer of the magnetic yoke on the first major surface of the substrate, the lower magnetic layer having first and second opposed ends; depositing a plurality of layers of magnetic material at the first end of the lower magnetic layer to build-up a first side pole of the magnetic yoke having a first top end; depositing a plurality of layers of magnetic material at the second end of the lower magnetic layer to build-up a second side pole of the magnetic yoke having a second top end; forming a coil element around one of the first and second side poles concurrently with formation of the first and second side poles, the step of forming a coil element including depositing a layer of the electrically conductive material encircling the first and second side poles of the magnetic material and etching, with an etchant, portions of the layer of the electrically conductive material; depositing a first upper magnetic pole element of the magnetic yoke at the first top end, the first upper magnetic pole element including a first gap end extending toward the second top end; forming a gap region of nonmagnetic material at the first gap end of the first upper magnetic pole element; and depositing a second upper magnetic pole element of the magnetic yoke at the second top end, the second upper magnetic pole element including a second gap end situated adjacent the gap region; the via protective cap being fabricated of a material which is substantially resistant to etching by the etchant.
7. The method of fabricating a thin film magnetic head apparatus of claim 6 wherein the electrically conductive material is plated in the via.
8. The method of fabricating a thin film magnetic head apparatus of claim 6 wherein the via is formed by laser drilling though the substrate.
9. The method of fabricating a thin film magnetic head apparatus of claim 6 wherein the coil is fabricated from copper and the via protective cap is formed
10. The method of fabricating a thin film magnetic head apparatus of claim 9 wherein the etchant is a mixture including ammonium persulfate and ammonium hydroxide.
Patent Citations (13)
| Patent | Date | Inventor | Cited By |
|---|---|---|---|
| US4731157 | 1988-03-01 | Lazzari | |
| US4899434 | 1990-02-01 | Roberts | |
| US4949207 | 1990-08-01 | Lazzari | |
| US5013394 | 1991-05-01 | Rolland et al. | |
| US5056353 | 1991-10-01 | Matono | |
| US5123156 | 1992-06-01 | Meunier et al. | |
| US5141623 | 1992-08-01 | Cohen et al. | |
| US5271802 | 1993-12-01 | Chang et al. | |
| US5279026 | 1994-01-01 | Uhde | |
| US5282308 | 1994-02-01 | Chen et al. | |
| US5301418 | 1994-04-01 | Dirne et al. | |
| US5349745 | 1994-09-01 | Kawabe et al. | |
| US5490028 | 1996-02-01 | Ang et al. |