EP1269466A1

EP1269466A1 - Integrated magnetic head for helical magnetic recording on tape and method for making same

Info

Publication number: EP1269466A1
Application number: EP01919534A
Authority: EP
Inventors: Micka[L Fievre; Jean-Baptiste Albertini; Pierre Gaud; Henri Sibuet
Original assignee: Commissariat a lEnergie Atomique CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2000-03-22
Filing date: 2001-03-21
Publication date: 2003-01-02
Also published as: JP2003528415A; FR2806826B1; FR2806826A1; WO2001071714A1; US20030076625A1; US6885520B2

Abstract

The invention concerns an integrated magnetic head comprising a thin-layered structure, the thin-layered structure containing, in the edge of the structure forming the reading and/or writing surface of the magnetic head, two polar components (47, 48) separated by an air gap (46A) and longitudinally aligned. The polar components are contained in the transverse direction relative to the structure between two parallel planes of the thin-layered structure, the magnetic head comprising two layers made of wear-resistant material (52, 53) which enclose the thin-layered structure to reinforce wear resistance of the reading and/or writing surface.

Description

INTEGRATED MAGNETIC HEAD FOR HELICO DAL MAGNETIC RECORDING ON TAPE AND METHOD FOR PRODUCING THE SAME

MANUFACTURING

Technical area

The present invention relates to an integrated magnetic head for helical magnetic tape recording. It also relates to a method of manufacturing such an integrated magnetic head.

The main area of application for this magnetic head is magnetic recording. More specifically, it concerns consumer or professional video (home video recorders, camcorders) as well as computer recorders. The other fields of application are computer mass storage (microcomputing, workstations and mainframe systems) and data storage on tape or disk for other consumer applications (multimedia, photo, audio ...) .

State of the art

- A magnetic recording medium for mass memories (video, audio or computer) includes many tracks on which information is written in the form of magnetic domains. To increase the information density, the number of pieces of information per unit area is increased. For this, the width of the tracks and the interval separating them are reduced simultaneously until they are joined together as for example in the standard helical recording. Track width is precisely defined in each standard (for example 6.7 μm in Long-Play DVC systems).

FIG. 1 shows a particular case where the tracks 10 are adjacent. To avoid the problems of crosstalk between tracks, the bits are written at two opposite angles + i and -i with i different from 0 °.

As can be seen in FIG. 2, for reading and / or writing information, a magnetic head 12a, 12b is assigned to each type of track. Through; example, the magnetic head 12a for. "reading and / or writing on a track on which the bits are written at the angle + i, has a magnetic gap or spacer 14 located opposite the track (not shown) and having an azimuth other than 0 °. The azimuth is the angle between the direction of the air gap 14 and a straight line perpendicular to the direction of travel of the track, symbolized by an arrow referenced D in FIG. 2. It is equal to the angle + i in the case of the head referenced 12a.

In the case of the magnetic head 12b for reading and / or writing the tracks on which the bits are written at an angle -i, the air gap 14 has an azimuth equal to the angle -i.

The two heads can be assembled or not in a single system.

Currently, the magnetic recording heads which relate to this field and which are available on the market are manufactured by micro-machining. They are manufactured in a unitary fashion, without the advantages of collective technologies imported from microelectronics. However, with the current reduction in track widths, ^' the required heads are becoming increasingly larger reduced. These dimensions are now reaching the limits of micro-machined technology.

An alternative manufacturing technique has been proposed in patent application FR-A-2 664 729. It is a technique for producing magnetic heads integrated with an azimuth air gap. Figures 3A to 3C are sectional views illustrating the main steps of producing a magnetic head according to the teaching of this document. FIGS. 3A to 3C relate to an exemplary embodiment in which it is desired to manufacture an integrated head on silicon with an air gap azimuthed at 20 ° relative to the vertical of the sheet. To do this, a silicon substrate 30 oriented <115> and offset by 0.5 ° is used, in which a cavity 32 is formed from one of its main faces 31 (see FIG. 3A). anisotropic etching. The etching defines an etching profile with in particular a pan 33 inclined according to the desired azimuth.

The etching is followed by a thermal oxidation of the substrate which makes it possible to obtain the air gap of the magnetic head. FIG. 3B shows the thermal oxide layer 34 formed on the etched face of the substrate 30. The part 34A of the oxide layer 34, deposited on the face 33, corresponds to the azimuth air gap of the magnetic head. The cavity is then filled with a magnetic material 35 which is possibly laminated to alleviate the problem of eddy currents. A first pole piece is thus formed. To constitute the second pole piece, part of the oxide layer adjacent to the air gap 34A is eliminated. Selective isotropic etching is then carried out so as to etch the substrate 30 without attacking the thermal oxide. A second cavity 36 is formed (see FIG. 3C). Cavity 36 is in turn filled with magnetic material to form the second pole piece 37. One thus obtains two pole pieces 35 and 37 separated by an azimuth air gap 34A. This technique has some drawbacks which can be grouped into two categories. A ^'first category concerns the problems of wear and a second category relates to the form 1 and the alignment of the pole pieces. With regard to wear problems, it is difficult to find a substrate which makes it possible "to produce the magnetic heads as is disclosed in the document FR-A-2 664 729 and which also has good mechanical properties to resist the wear that can occur from contact between the magnetic head and the magnetic strip, especially during the lifetime of a professional system. Conventionally, but this is only an example, a substrate of silicon to produce magnetic heads, but silicon offers insufficient wear resistance for certain applications.

As far as the shape of the pole pieces is concerned, the technique proposed by document FR-A-2 664 729 makes it possible to perfectly align an edge of the pole pieces (that which corresponds to the face of the substrate from which the engravings are made ). However, this is not the case for the other edge which corresponds to the bottom of the two cavities. The tolerances on the thicknesses of the pole pieces (the dimension e indicated in FIG. 3A) are increasingly tight. Given the etching inhomogeneities over the depth, it becomes difficult to maintain these tolerances.

The part of the pole pieces which is located under line L of Figure 3C does not participate when writing bits. On the other hand, it participates in induced currents *. There is then an interest in minimizing it.

Still with regard to the shape of the pole pieces, FIG. 4 shows an exemplary embodiment for which the second etching 36 'has passed under the air gap 34A of the magnetic head (see region 38). Such a head should be automatically removed. This makes it necessary to provide a second depth cavity such that the upper tolerance limit on the depth does not pass under the air gap.

All these problems mean that the technique described in document FR-A-2 664 729, even if it represents an important advance compared to micro-machined heads as regards in particular the alignment of the pole pieces, is not simple and remains difficult to industrialize.

Statement of the invention

The present invention was designed to jointly solve the problem of wear of the heads and that of their self-alignment.

A first object of the invention consists of an integrated magnetic head comprising a thin layer structure, the thin layer structure containing, in the edge of the structure constituting the reading and / or writing face of the magnetic head, two pole pieces separated by an air gap and in longitudinal alignment, the pole pieces being contained in the transverse direction with respect to the structure between parallel planes of the thin layer structure, the magnetic head comprising two layers of wear-resistant material that frame the thin layer structure for reinforce the wear resistance of the reading and / or writing face, characterized in that it also comprises a layer-shaped element containing the complementary circuits of the magnetic head, between the thin layer structure and a layer of wear-resistant material.

Optionally, the air gap is an azimuth air gap.

The wear-resistant material can be chosen from Al ₂ 0 ₃ -TiC, CaTi0 ₃ and Zr0 ₂ .

The thin layer structure may include a layer of monocrystalline silicon containing the pole pieces. It can also include a layer, called the stop layer, forming one of the parallel planes of the thin layer structure. This barrier layer can be made of Si0 ₂ .

The pole pieces can be laminated pole pieces.

A second object of the invention is a magnetic reading and / or writing device consisting of a stack of magnetic heads as defined above.

A third object of the invention consists of a method for producing at least one integrated magnetic head, comprising the steps of:

- supply of a substrate comprising a support covered with a layer, called stop layer, itself covered with a thin layer of monocrystalline material of appropriate orientation, - anisotropic etching of a first box in said thin layer with a view to accommodating therein a first pole piece of magnetic head, the etching revealing the stop layer and providing a sidewall of a box in a direction corresponding to a desired azimuth for the air gap of the magnetic head, - formation on the side of the box of a layer of air-gap material,

filling of the first box with a magnetic material flush with the free face ^' of said thin layer to form the first pole piece,

- isotropic etching of a second box in said thin layer in order to accommodate a second pole piece of magnetic head, the second pole piece to be separated from the first pole piece by the air gap material, the etching revealing the layer stop,

filling of the second box with a magnetic material flush with the free face of said thin layer to constitute the second pole piece,

fixing on the free face of said thin layer a layer-shaped element containing the complementary circuits of the magnetic head (electrical circuits, closing of magnetic circuits for example),

- fixing of a first layer of wear-resistant material on the element in the form of a layer containing the complementary circuits, - elimination of the support to reveal the stop layer,

- fixing of a second layer of wear-resistant material on the barrier layer,

- transverse cutting to reveal on the edge of the thin layer of monocrystalline material pole pieces made of magnetic material and separated by an air gap.

Advantageously, the step of supplying a substrate comprises supplying a substrate of the silicon-on-insulator type, the insulator being a layer silicon oxide. The step of forming a layer of air-gap material on the side of the box can then be a step of thermal oxidation.

The boxes can be filled by electrolytic deposition followed by planarization of the magnetic material deposited. This electrolytic deposition can be carried out alternately with the deposition of insulating layers in order to obtain a laminated magnetic material. The removal of the support can be obtained by selective etching.

Brief description of the drawings

The invention will be better understood and other advantages and particularities will appear on reading the description which follows, given by way of nonlimiting example, accompanied by the appended drawings among which: - Figure 1, already described, schematically represents a partial view of a magnetic recording medium with contiguous tracks,

FIG. 2, already described, schematically represents a system of magnetic heads for reading and / or writing on a recording medium with contiguous tracks,

- Figures 3A to 3C, already described, are sectional views illustrating the main steps of producing a magnetic head according to the prior art, - Figure 4, already described, is a sectional view illustrating a defective magnetic head , made according to known art,

- Figures 5A to 5H illustrate different stages of the production of an integrated magnetic head according to the invention. Detailed description of an embodiment of the invention

FIGS. 5A to 5H illustrate the production of an integrated magnetic head for helical recording on tape according to the present invention. They are cross-sectional views.

FIG. 5A shows a silicon-on-insulator substrate 40 (or SOI substrate) comprising a silicon support 41 successively covered with a layer of silicon oxide 42 and with a thin layer of monocrystalline silicon 43. The silicon layer 43 is chosen with a crystal orientation appropriate to the desired air azimuth. The thickness of the layer 43 is also chosen as a function of the desired thickness for the pole pieces to be formed.

The SOI substrate 40 will be subjected to operations well known to those skilled in the art in microelectronics. The thin layer 43 is subjected locally to an anisotropic etching until reaching the oxide layer 42. The etching time can be a little longer than expected in order to eliminate any trace of silicon on the revealed oxide layer 42 . A first box 44 is obtained, the side 45 of which is oriented in accordance with the desired azimuth.

Then proceed (see Figure 5B) to thermal oxidation of the silicon of the thin layer

43. A layer of silicon oxide 46 is then formed on the surface of the thin layer 43. A portion 46A of this oxide layer 46 covers the side 45 of the box

44. This part 46A will constitute the air gap of the magnetic head. The bottom of the box 44 does not receive additional oxide since this bottom is already made of silicon oxide and can therefore no longer be oxidized. An electrolytic deposit of magnetic material followed by planarization makes it possible to fill the box 44 with magnetic material to constitute the first pole piece 47 (see FIG. 5C). The electrolytic deposition can optionally be carried out in alternation with the deposition of electrically insulating layers in order to obtain a laminated magnetic material to limit the eddy currents.

Then an etching of a second box 48 is carried out (see FIG. 5D) in the thin layer

43 after having opened the oxide layer 46 at the appropriate place. It is an isotropic etching which is carried out to reveal the oxide layer 42 and which stops on the part 46A. As shown in FIG. 5E, the second box 48 is filled with magnetic material, in the same way as for the first box, in order to constitute the second pole piece 49. The upper face 50, or free face of the device, is therefore a flat face.

The next step, illustrated by FIG. 5F, consists in making or fixing on the free face 50 an element 51 in the form of a layer and containing the complementary circuits of the magnetic head (for example the solenoids). At this stage, the functional part of the magnetic head is finished.

A first layer 52 of wear-resistant material is then fixed to the element 51 in the form of a layer (see FIG. 5G). The support 41 can then be eliminated. This can be done by selective etching, the oxide layer 42 also serving as an etching stop layer.

A second layer 53 of wear-resistant material is then fixed on the. oxide layer 42. The electrical contacts can be taken up on layer 52, for example using intra-connections or by etching through layer 52.

The layers of wear-resistant material 52 and 53 can be made of Al ₂ 0 ₃ -TiC, CaTi0 ₃ or Zr0 ₂ .

For example, the thin layer 43 of silicon may have a thickness of 8 μm. The air gap 46A can have a thickness of 0.09 μm. The production method according to the invention has been described from an SOI substrate. _However. - the process remains valid if the thin surface layer is made of another monocrystalline material. The stop layer may also be made of a material other than silicon oxide, provided that this material stops etchings and can be buried under a thin monocrystalline layer. In addition, the types of etching may be different, for example of the type used in document FR-A-2 716 995. In this case, the advantages provided by the present invention remain, but the etchings are different and the air gap n is not azimuth.

The present invention makes it possible to solve the problem of wear of the silicon by making the head-strip contact bear on an assembly made up for the most part of wear-resistant materials. The process makes it possible to obtain pole pieces that are self-aligned on both sides since the etching inhomogeneities are overcome by relying on the buried stop layer. The thickness of the pole pieces can be calibrated through the chosen thickness of the thin layer ^'of the SOI substrate. The SOI substrates currently available offer very good tolerances which make it possible to comply with the specifications of the recording standards. The problem of passing the second engraving under 1.! air gap, illustrated in Figure 4, no longer exists in the case of the invention.

The frequency resistance of the magnetic heads is improved since the thickness of magnetic material and the induced currents are minimized.

The invention allows a collective process for manufacturing magnetic heads from the same substrate. It allows multiple heads to be produced using several structures of the type shown in FIG. 5E to stack several levels of pole pieces.

Claims

1. Integrated magnetic head comprising a thin layer structure, the thin layer structure containing, in the edge of the structure constituting the reading and / or writing face of the magnetic head, two separate pole pieces (47,49) by an air gap (46A) and in longitudinal alignment, the pole pieces being contained in the transverse direction relative to the structure between parallel planes _. of the thin layer structure, the magnetic head comprising two layers of wear resistant material (52, 53) which frame the thin layer structure to enhance the wear resistance of the reading and / or writing, characterized in that it also comprises a layer-shaped element (51) containing the complementary circuits of the magnetic head, between the thin-layer structure and a layer (52) of wear-resistant material.

2. Integrated magnetic head according to claim 1, characterized in that the air gap (46A) is an azimuth air gap.

-3. Integrated magnetic head according to one of claims 1 or 2, characterized in that the wear-resistant material is chosen from Al ₂ 0 ₃ -TiC, CaTi0 ₃ and Zr0 ₂ -

4. Integrated magnetic head- according to any one of claims 1 to 3, characterized in that the thin layer structure comprises a layer of monocrystalline silicon (43) containing the pole pieces (47, 49).

5. Integrated magnetic head according to any one of claims 1 to 4, characterized in that the thin layer structure also comprises a layer, called stop layer (42), forming one of the parallel planes of the structure thin layer.

6. Integrated magnetic head according to claim 5, characterized in that the barrier layer (42) is made of Si0 ₂ .

.

7. Integrated magnetic head according to one of any of claims 1 to 6, characterized in that the pole pieces (47, 49) are laminated pole pieces.

8. Magnetic reading and / or writing device, characterized in that it consists of a stack of magnetic heads according to any one of claims 1 to 7.

9. Method for producing at least one integrated magnetic head, comprising the steps of:

- Supply of a substrate (40) comprising a support (41) covered with a layer, called stop layer (42), itself covered with a thin layer

(43) of monocrystalline material of appropriate orientation,

- anisotropic etching of a first box

(44) in said thin layer (43) in order to accommodate there a first pole piece of magnetic head, the etching revealing the stop layer _. (42) and providing a sidewall

(45) of a box in a direction corresponding to a desired azimuth for the air gap of the magnetic head,

- Formation on the sidewall (45) of a box of a layer (46A) of airgap material, - filling of the first box (44) with a magnetic material flush with the free face of said thin layer to form the first pole piece (47), - isotropic etching of a second box

(48) in said thin layer (43) in order to accommodate therein a second pole piece of magnetic head, the second pole piece to be separated from the first pole piece (47) by the air gap material (46A), the etching revealing the barrier layer (42),

- filling the second box (48). by a magnetic material flush with the free face of said thin layer to form the second pole piece (49), - fixing on the free face of said thin layer of an element (51) in form of layer containing the complementary circuits of the magnetic head,

fixing a first layer (52) of wear-resistant material on the element (51) in the form of a layer containing the complementary circuits,

- elimination of the support (41) to reveal the barrier layer (42),

- fixing a second layer (53) of wear-resistant material on the barrier layer

(42),

- transverse cutting to reveal on the edge of the thin layer of monocrystalline material pole pieces (47, 49) made of magnetic material and separated by an air gap (46A).

10. The method of claim 9, characterized in that the step of providing a substrate comprises providing a .substrate of the type silicon-on-insulator, the insulator being a layer of silicon oxide.

11. Method according to claim 10, characterized in that the step of forming on the side

(45) of a layer of air gap material box is a thermal oxidation step.

12. Method according to any one of claims 9 to 11, characterized in that the filling of the boxes (44, 48) is carried out by electrolytic deposition followed by planarization of the magnetic material deposited.

13. Method according to claim 12, characterized in that the electrolytic deposition is carried out alternately with the deposition of insulating layers in order to obtain a laminated magnetic material.

14. Method according to any one of claims 9 to 13, characterized in that the elimination of the support (41) is obtained by etching.