FR2495192A1 - METHOD FOR FORMING THIN-LAYERED METALLIC DRAWINGS BY CHEMICAL ATTACK, IN PARTICULAR FOR MAGNETIC RECORDING HEADS - Google Patents

Abstract

A method of making a metallic pattern on a substrate is disclosed. The method comprises depositing an adhesive layer and a base layer 2, 3 on a substrate 1, while a narrow and coherent margin of photoresist defines an anodic region. The photoresist extends to substrate 1 so that after chemical etching the coated region is not etched at all and has sharp edges. Application to the manufacture of magnetic recording heads. (CF DRAWING IN BOPI)

Description

The present invention relates to a method of forming

  thin-layer metal drawings by attack

  chemical, especially for magnetic recording heads.

  In the manufacture of pole pieces of magnetic recording heads in thin layers or other elements that must meet tight tolerances, new electroplating techniques are used.

  and chemical etching of sheet materials whose composition

  position and structure must be precisely

  to ensure that the characteristics obtained are uniform

  these techniques have recently been developed.

  U.S. Patent No. 3,853,715 indicates that conventional capping techniques are not at all effective for the manufacture of such caches.

elements.

  The method conventionally used for the deposition of an alloy such as "Permalloy" which is a mixture of nickel and iron, comprises the coating of the alloy in the form of a sheet, then the attack of the following sheet the desired drawings. However, when depositing the films or layers by electrodeposition, an adhesive layer must be used between the alloy and the substrate intended

  to wear the drawing. Since we can not ensure

  trodeposition on certain adhesive layers, it is

  necessary to deposit a thin layer of a metal

  relatively valuable such as gold, platinum, palladium

  dium, copper, nickel, etc., on the adhesion layer.

  Unfortunately, many deposition base layers and adhesives that are compatible with the magnetic alloy in the substrate become cathodic with respect to the alloy during etching, and thus cause significant scouring. For example,

  a nickel-iron alloy is adhered to glass or silicon

  by interposition of a thin layer of chromium or titanium between the iron and nickel alloy and the associated substrate. The above-mentioned United States Patent No. 3,853,715 indicates that, when several layers of

2 495192

  this type are attacked chemically, we observe a

  important in the subject under attack. This scourge

  This is due to several separate effects that occur during chemical attack and scour is neither reproducible nor adjustable. Scouring is due to the fact

  that chemical attack is an accelerated form of

  erosion. Corrosion is in principle isotropic; she must

  at speeds equal to both perpendicular and

  to the thickness of the etched metal and parallel to this thickness. This phenomenon causes a uniform scour of the metal. However, given the thicknesses

  extremely weak layers and the dimensions of the

  In other words, we can not ignore the dimensions of grains and metallic crystallites. The boundaries of the grains and these are attacked at different speeds

  so that it appears shredded edges.

  During the end of the chemical attack, when the layers of adhesive and / or base metal of the deposit are

  exposed, the different metals form a pile which provokes

  that an extremely rapid chemical attack of the anode metal

  dique. In the case of titanium and chromium, each of these metals is very rapidly passivated and becomes cathodic with regard to nickel, a nickel-iron alloy and metals of the iron group. When metals such as platinum,

  palladium, gold or copper are present in the whole

  laminated with iron group metals, they act cathodically and the chemical attack of nickel, alloy

  nickel-iron, etc., can not be controlled.

  This scour is harmful in the manufacture

  arrangements made in batches, such as

  thin magnetic heads in thin layers.

  The aforementioned U.S. Patent No. 3,853,715 recognizes the aforementioned difficulties and indicates a solution. This patent indicates that a uniform etching of electroplated metals in several layers without scour can be achieved by providing a very thin margin of photographic reserve on the surface.

249519 2

  layer of cathodic metal adhesive before plating

  anodic metal. The narrow margin closes on her

  even so that it constitutes a frame while a second layer of photographic resist is deposited and developed so that it is present only above the anodic material which must be preserved after the chemical attack. photographic covers the

  first so that the anodic layer is fully coated.

  The patent states that the subsequent chemical etching of the surplus of anodic material that is not necessary in the final design, leaves the desired parts of the drawing unaffected, without the scouring that takes place when

  two or more different metals are subject to

common attack.

  It is found according to the invention that the solution

  known to the problem of scouring does not give perfect

  satisfaction. More specifically, it is determined that when electrodeposited anode material such as

  Ni-Fe alloy was removed by chemical etching, the

  the attacking layer then has access to the adhesive and cathodic metal layers and a lateral attack appears

  below the photographic reserve forming the margin.

  When this phenomenon begins to appear, the adhesive that

  keeps the photographic reserve in place, loses

  the reserve itself begins to separate from the substrate and thus increase the acuity of the problem

by the scour.

  The invention virtually eliminates the problem of scouring and relates to the provision of a margin

  or very narrow photographic reserve boundary of

  to delimit the subsequent electrodeposited anodic material

  later, for example "Permalloy". Although, in the known art, more specifically in the aforementioned patent

  United States of America No. 3 853 715, a margin of

  If the photographic image is also used, the invention differs in that the anodic material is completely coated by the photographic reserve which is arranged up to the substrate.

  inert. As in the known art, the invention

  the provision of the narrow margin of reserve

  graphic on the adhesive layer and cathodic metal, in a region forming a very narrow margin, its width and dimensions being such that it delimits the product

  final metallic formed. After the provision of this

  the anodic material is deposited on the adhesive and cathodic metal underlayer and the resist is then removed to expose the adhesive and cathodic metal underlayer only in the regions previously

  covered by the narrow and consistent margin of reserve.

  The adhesive and cathodic metal underlayer is then

  withdrawn from these exposed areas and the reserve is

  again all the way down to the inert support so that it covers and so coats the material

  anodic intended to be present in the final product.

  In practicing the invention, the photographic resist plays the role of a barrier substantially impervious to lateral attack so that it practically eliminates the problem of scouring. The corrosion attack can progress along the adhesive underlayer and cathodic metal but, when the material arrives against the photographic reserve, it encounters

  a barrier that interrupts the process of chemical attack.

  Other features and advantages of the invention

  will emerge more clearly from the following description, made

  with reference to the accompanying drawings, in which: FIGS. 1 and 2 show the processing steps according to a known method as described in the aforementioned U.S. Patent No. 3,853,715, and

  Figures 3 to 7 show the successive steps

  sives of scour elimination treatment during

  a chemical attack according to the invention.

  Figure 1 shows a sheet that has undergone

  electroplating and, during treatment, a sub-

  stratum 1 of silica, glass or other similar coherent insulating material, carries a thin layer of a tackifying metal 2 such as chromium, titanium, tantalum,

  tungsten, niobium, vanadium or zirconium.

  Such an adhesive metal 2 is used essentially to ensure adhesion to the substrate of the main interesting metal such as a Ni-Fe alloy, called "anodic metal".

  Since you can not easily make an electrodepo-

  sotion or a chemical deposit on such a layer of adhesive

  Preferably, it is desirable for the adhesion layer 2 to be metallized successively with the aid of a metal 3 which is easily deposited, such as gold, platinum or palladium.

  copper, nickel, a Ni-Fe alloy or a metal alloy

  lic. Such a layer 2 of adhesion and a conductive layer

  may be applied by spraying, evaporation

or in any other way.

  According to the prior art, at this stage of the sequence of operations, the photoresist 7, 17 is deposited by conventional lithographic techniques and the anodic material 6, for example "Permalloy", is deposited. After the deposition of layer 6 of "Permalloy",

  another layer 8 of reserve is applied by the technicians

  conventional photolithographic

  6. The excess anode material shown in zones 4 and 5 of FIG. 1 is then removed by etching, a material suitable for the Ni-Fe alloy being FeCl 3, the layer 8 reserve and margins.

  7, 17 encapsulating the anode material.

  The aforementioned patent indicates that the resist prevents the chemical attack of the active metal such as the Ni-Fe alloy, in the presence of a cathode metal such as chromium,

  titanium, gold, etc. When the activated metal 6 has been attacked

  FeCl3, the patent teaches that the base metal 3 and the adhesion layer 2 are chemically etched by

  suitable chemicals. As indicated above

  However, it is noted that the materials used for the attack of anodic zones 4 and 5

  and base metal 3 and adhesion layer 2,

  than a side attack of layers 2 and 3 below

  reserve areas 7 and 17, so that it appears that

  ra scour and scourge

  than sharp edges as indicated by the references 9 and 10 in Figure 2. Once the lateral attack begins, the reserve zones 7 and 17 no longer adhere to the layers 2 and -3 support so that the problem

  is further aggravated. Moreover, as the potential

  of the adhesion metal layer 2 such as titanium and anodic metal such as Ni-Fe alloy are different, a stack is formed as soon as the adhesive metal layer is exposed to the etching material so well that the attack speed of the Ni-Fe alloy increases to

  such a point that the setting of the attack becomes very different.

if not impossible.

  Reference is now made to Figures 3 to 7 which show how to remedy these difficulties. FIG. 3 represents the treatment which is practically equivalent to that of the known process, at an equivalent point in the treatment cycle. More specifically, a very thin margin 15, 16 of photographic resist has been applied to a layer 2 of an adhesive metal and a layer 3 of a metal which can be deposited. The anodic layer is then deposited on the layer 3 in the form of a uniform coating as indicated by the regions 4, 5 and 6. This is the region 6 which must form

  the interesting design in the final product, and its

  tion is delimited by the very narrow coherent margin

formed by the reserve 15, 16.

  Unlike the prior art, the reserve margin 15, 16 is not removed by a known method, so that the layer 2 of metaladhesive and the layer 3 of the deposited metal are selectively exposed in the regions which were delimited by the very narrow consistent margin of photographic reserve. As shown in FIG. 4, the adhesive metal layer 2 and the deposited metal layer 3 are selectively removed by a known technique, for example by spray etching or bombardment.

  of ions to form cavities 11 and 12

  geant to the base 1 as indicated by the references 13 and 14. The cavities which preferably have a width of about 2.5 to 5 om, delimit the pattern or finally formed by the anodic material and having to constitute, for example polar parts magnetic heads to

thin layers.

  The cavities 11 and 12 are filled with a reserve 8 which causes a total coating of the anode material 6 on three sides, the fourth side of the coated region.

being closed by the inert base 1.

  As shown in Figure 5, the photogra-

  Figure 8 can extend slightly beyond cavities 11 and 12. The excess of anodic material 4,5, such as electroplated "Permalloy", is then removed by etching, a material which is suitable in the case of the alloy.

  Fe-Ni being FeCl3. The base metal 3 and the adhesive layer 2

  may be attacked by any suitable chemical material. Since the reserve 8 is in physical contact with the base 1, the etching of the zones 4 and 5 as well as the layers 2 and 3 does not affect the integrity of the net edges of the support layers 2 and 3 or the metal at all. anodic, placed within the limits delimited by reserve 8 (Figure 6). The stock material 8 is then removed by any known technique so that finally a sharp-edged drawing is obtained which can not be obtained by

  implementation of the prior art (Figure 7).

  The teachings of the aforementioned United States Patent

  United States of America No. 3 853 715, concerning photographic reserves and chemical attack materials,

  can be used in the context of the invention.

  It is understood that the invention has been described and shown only as a preferred example and that any technical equivalence can be made in its elements.

  constitutive without departing from its scope.

Claims (14)

  1. A method of manufacturing a metallic pattern on a substrate, characterized in that it comprises a) the deposition of a first thin metal layer (2, 3) on an inert substrate (1), b) the deposit of a very narrow coherent margin,   given height, formed of a photoresist   graph on the metal layer (2, 3), this margin   putting the configuration of an interesting pattern of a second metal to be deposited later on the thin metal layer, the second metal being intended to become anodic with respect to the first metal layer during its chemical attack, c) the deposit the second metal (6) on the first, d) the removal of the consistent reserve margin   with exposure of the first metallic layer   than thin (2, 3), e) removing the first thin metal layer (2, 3) in the regions exposed in step d), f) the photoresist deposit (8, 15,   16) so that it practically covers the relevant drawing.   practically filled and filled the occupied   the consistent margin of photographic reserve,   so that the second metal (6) included in the drawing   interesting is fully coated, and g) the chemical etching removal of any   the anodic material (6) which is not coated.   2. A method of manufacturing a metallic pattern on a substrate, characterized in that it comprises a) the deposition, on an inert substrate (1), of an adhesive material, a deposition base material or these two materials (2, 3), intended to become cathodic during a subsequent etching, b) the provision of a very narrow coherent margin of given height of a photographic resist material on the cathode material, the margin delimiting the configuration 2495 1 92   an interesting design of an anode material to be subsequently deposited on the cathodic material, c) the deposition of anodic material (6) on the cathodic material (2, 3), d) the removal of the margin coherent photographic resist with exposure of the cathodic material (2, 3),   e) removing the cathodic material in the areas exposed in step d) f) the photoresist deposit (8, 15,   16) so that it practically covers the relevant drawing.   completely fill the occupied areas previously   by the coherent reserve margin, so that the anodic material found in the drawing of interest is fully coated, and g) the chemical etching removal of any   the anodic material (6) which is not coated.   3. Method according to one of claims 1 and 2,   characterized in that the anode material (6) which is   uncoated is removed by chemical etching.   4. Method according to claim 1, characterized in that the first thin metal layer (2, 3) is removed by sputtering etching in the regions exposed by the removal of the coherent margin photographic reserve.   5. Method according to claim 1, characterized in that the first thin metal layer <2, 3) is removed by ion bombardment in the exposed regions   by removing the coherent reserve margin of photogra- phic.   The method according to claim 2, characterized in that substantially all of the adhesive material and deposition base (2, 3) is removed by etching.   sputtering in areas exposed by   raising the consistent margin of photographic reserve.   Method according to claim 2, characterized in that substantially all of the adhesive material and deposition base (2, 3) is removed by ion bombardment in the exposed areas by removal of the margin   coherent photographic reserve.   8. Method according to one of claims 1 and 2,   characterized in that the anode material (6) is an alloy nickel and iron.   9. pole piece for a thin-layer head, characterized in that it is prepared by implementation   method according to one of claims 1 and 2.   10. Process according to claim 1, characterized   in that the second metal is electrodeposited on the first.   11. The method of claim 2, characterized in that the anode material (6) is electrodeposited on the adhesive material or on the deposition base material (2, 3). 12. The method of claim 1, characterized in that the second metal (6) is deposited on the first metal (2, 3) on a height that does not exceed significantly   the height of the consistent margin of photographic reserve.   Method according to claim 2, characterized   in that the anode material (6) is deposited on the   cathode (2, 3) on a height that does not exceed   significantly that of the consistent margin of reserve graphic.   14. Method according to one of claims 1 and 2,   characterized in that the narrow region has a width of viron 2.5 to 5 Name.