EP0186531A1 - Method of producing a layer having a strong magnetic anisotropy in a ferrimagnetic garnet - Google Patents

Method of producing a layer having a strong magnetic anisotropy in a ferrimagnetic garnet Download PDF

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EP0186531A1
EP0186531A1 EP85402149A EP85402149A EP0186531A1 EP 0186531 A1 EP0186531 A1 EP 0186531A1 EP 85402149 A EP85402149 A EP 85402149A EP 85402149 A EP85402149 A EP 85402149A EP 0186531 A1 EP0186531 A1 EP 0186531A1
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Prior art keywords
layer
implanted
ferrimagnetic
magnetic
ferrimagnetic garnet
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German (de)
French (fr)
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EP0186531B1 (en
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Thierry Capra
Philippe Gerard
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/14—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates
    • H01F41/18—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates by cathode sputtering
    • H01F41/186—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates by cathode sputtering for applying a magnetic garnet film
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/14—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/14—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates
    • H01F41/22—Heat treatment; Thermal decomposition; Chemical vapour deposition
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/14—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates
    • H01F41/24—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates from liquids
    • H01F41/28—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for applying magnetic films to substrates from liquids by liquid phase epitaxy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S117/00—Single-crystal, oriented-crystal, and epitaxy growth processes; non-coating apparatus therefor
    • Y10S117/917—Magnetic

Definitions

  • the present invention relates to a method of manufacturing a layer having a strong planar magnetic anisotropy in a ferrimagnetic garnet. It applies in particular in the field of the development of magnetic bubble memories and in particular in the development of bubble memories with non-implanted discs, but also in the field of the production of semiconductor or magneto- material. optical.
  • a bubble memory In general, the development of a bubble memory is, firstly, to e p itaxier a ferrimagnetic garnet layer growth anisotropy perpendicular to the layer on an amagnetic substrate, primarily a garnet. It is recalled that the magnetic bubbles are small magnetic domains whose magnetization, directed perpendicular to its surface, is reversed compared to that of the material containing the bubbles. Next, ions are implanted in the epitaxial layer.
  • This ion implantation allows the creation on the surface of the ferrimagnetic garnet layer, of a plane magnetization layer, that is to say, of a layer whose magnetization is parallel to the surface of said layer.
  • the purpose of this plane magnetization layer is in particular to increase the stability of the magnetic bubbles.
  • This ion implantation makes it possible to produce layers with plane magnetization over a thickness of the order of 0.5 ⁇ m.
  • the propagation patterns which are contiguous patterns, having the disc, diamond shape, etc. ; since ion implantation is only performed around these patterns, these patterns are called non-implanted patterns.
  • the ion implantation serves, in addition to the formation of the surface layer with plane magnetization, to remove the "hard” bubbles, that is to say say bubbles with complex wall structures.
  • the propagation of the magnetic bubbles along the propagation patterns is carried out by applying a continuous field rotating in a direction parallel to the surface of the ferrimagnetic layer.
  • the bubbles located below the surface layer with plane magnetization are bonded to the non-implanted propagation patterns via a potential well due to the stress field between the implanted and non-implanted areas.
  • Moving the magnetic bubbles along. propagation patterns comes from the action of the rotating field which creates a moving charged wall causing the bubbles.
  • the magnetostriction properties of the ferrimagnetic garnet layers have been used to obtain this magnetic anisotropy of the surface layer.
  • the ion bombardment creates defects on the surface of the epitaxial garnet layer, thus causing a deformation of the mesh parameter in the direction perpendicular to said ferrimagnetic garnet layer. These defects introduce into the garnet layer strong mechanical stresses, oriented parallel to the surface of said layer; it has been proven that a dilation of the mesh parameter cannot be done in parallel on the surface of the ferrimagnetic layer.
  • the layers of ferrimagnetic garnet are manufactured so as to have a negative magnetostriction coefficient.
  • a compressive stress obtained by ion implantation, induces a magnetic anisotropy in the plane of the implanted surface layer which is greater than the growth anisotropy of the starting material, i.e. material not implanted.
  • this magnetostriction mechanism has its limits which depend on the importance of the growth anisotropy of the material (growth by epitaxy) as well as on its negative magnetostriction coefficient. Indeed, one cannot increase the dose of implanted ions indefinitely, because beyond a certain threshold of defects, the magnetism of the implanted surface layer is canceled and one can no longer move the bubbles along the patterns propagation, notably not implanted.
  • the subject of the present invention is precisely another method of manufacturing a layer having a strong planar magnetic anisotropy in a ferrimagnetic garnet enabling the various drawbacks given above to be remedied.
  • the step of heating the entire structure, in the presence of a reducing agent makes it possible to greatly increase the magnetic anisotropy of the ferrimagnetic garnet layer.
  • the reducing agent is a gas.
  • this gas is hydrogen.
  • the implanted ions are neon ions.
  • the method of manufacturing a ferrimagnetic garnet layer of high planar magnetic anisotropy in accordance with the invention advantageously applies to the production of a bubble memory with non-implanted propagation patterns.
  • the first step of the process consists in forming in a known manner by epitaxy on a non-magnetic substrate, such as gadolinium gallate (Gd 3 Ga 5 0 12 ) a layer of ferrimagnetic garnet whose magnetization vector is oriented perpendicular to the surface of said layer .
  • a non-magnetic substrate such as gadolinium gallate (Gd 3 Ga 5 0 12 ) a layer of ferrimagnetic garnet whose magnetization vector is oriented perpendicular to the surface of said layer .
  • a non-magnetic substrate such as gadolinium gallate (Gd 3 Ga 5 0 12 ) a layer of ferrimagnetic garnet whose magnetization vector is oriented perpendicular to the surface of said layer .
  • this ferrima- layer gndov q ue with a thickness of the order of 1000 nm, magnetic bubbles may exist in the presence of a polarizing field.
  • ferrimagnetic garnet As ferrimagnetic garnet, one can use a material well known to those skilled in the art, corresponding to the following formula (YSmLuCa) 3 ( F e Ge ) 5 0 12 '
  • the orientation of the magnetization vectors in the ferrimagnetic garnet layer is due to an anisotropy of growth of the materials, anisotropy obtained by a judicious choice of the operating conditions of the epitaxy. These operating conditions are well known to those skilled in the art.
  • the next step of the method consists in carrying out an ion implantation in the upper ferrimagnetic layer in order to form defects in the upper part of said layer over a thickness of the order of 300 nm.
  • This ion implantation can be carried out with different types of ions such as hydrogen, neon, nitrogen, oxygen, argon, etc. at a high dose without making the ferrimagnetic material constituting the implanted part of the epitaxial layer amorphous, that is to say depriving this material of its magnetic properties.
  • an implantation of neon ions can be carried out at a dose less than or equal to 10 15 atoms / cm 2 and at an energy of 200 keV.
  • the ion implantation in addition to the creation of defects in the upper part of the ferrimagnetic layer allows the formation in said part, using an appropriate mask, of the non-implanted propagation patterns of the magnetic bubbles.
  • a reducing agent can be a solid, a liquid or a gas.
  • a gaseous reducing agent such as hydrogen sulfide (H 2 S), hydrogen phosphide (PH 3 ), hydrogen antimonide (SbH 3 ), hydrogen arsenide (AsH 3 ) and hydrogen.
  • H 2 S hydrogen sulfide
  • PH 3 hydrogen phosphide
  • SbH 3 hydrogen antimonide
  • AsH 3 hydrogen arsenide
  • hydrogen will be used.
  • the heating in the presence of the reducing agent is carried out at a temperature between 250 and 450 ° C.
  • the use of a temperature lower than 250 ° C would involve a too long duration of heating and a temperature above 450 ° C would be harmful to obtain a strong plane magnetic anisotropy in the upper part of the layer of ferrimagnetic garnet.
  • the heating time depends on the heating temperature. In fact, the higher the heating temperature, the shorter the duration of this heating.
  • the heating of the structure, in the presence of the reducing agent can be carried out in one or more stages.
  • the reduction of the implanted part results in a large variation in magnetic anisotropy, which results in the formation of a plane magnetization layer in said implanted layer.
  • This plane magnetization layer is used in particular to stabilize the underlying bubbles.
  • a second heating of the structure was then carried out in the presence of hydrogen at a temperature of 292 ° C. for a period of 95 hours, the hydrogen pressure being of the order of 1 atm., Then a further measurement was made. times the variation of the magnetic anisotropy field between the anisotropy field of the implanted virgin ferrimagnetic layer and the anisotropy field of the layer thus treated.
  • the magnetic anisotropy of the implanted ferrimagnetic layer has more than doubled.
  • This variation in anisotropy can only be due to a reduction in the surface layer of the implanted layer, apparently leading to migration towards the surface of this layer of oxygen, entering into the composition of this layer, this oxygen from defects caused during ion implantation.
  • the migration of oxygen to the surface of the implanted magnetic layer causes an oxygen depletion thereof, resulting in a reduction of Fe 3+ ions to Fe 2+ ions responsible for magnetic anisotropy.
  • the purpose of the third vacuum heating is to show that the increase in magnetic anisotropy is not due to a diffusion of hydrogen inside the upper ferrimagnetic layer. Indeed, if this were the case, we should observe a decrease in the variation of magnetic anisotropy, during this vacuum annealing; the hydrogen being very mobile at this temperature would partially leave the structure. However, there is rather an increase in the variation of magnetic anisotropy, which would tend to think that a migration of oxygen towards the surface of the implanted layer has still taken place.
  • the part of the non-implanted ferrimagnetic layer containing the magnetic bubbles is in no way modified by the heating stages, in the presence of a reducing agent, of the structure.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Thin Magnetic Films (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Physical Vapour Deposition (AREA)

Abstract

Dans le cadre de l'élaboration d'une mémoire à bulles, le procédé de l'invention consiste à former une couche de grenat ferrimagnétique par épitaxie à partir du substrat amagnétique, à implanter des ions dans la partie supérieure de la couche de grenat ferrimagnétique afin de créer des défauts dans ladite partie et de former les motifs de propagation, et à chauffer l'ensemble, en présence d'un agent réducteur à une température comprise entre 250 et 450°C.In the context of the development of a bubble memory, the method of the invention consists in forming a ferrimagnetic garnet layer by epitaxy from the non-magnetic substrate, in implanting ions in the upper part of the ferrimagnetic garnet layer in order to create defects in said part and to form the propagation patterns, and to heat the assembly, in the presence of a reducing agent at a temperature between 250 and 450 ° C.

Description

La présente invention a pour objet un procédé de fabrication d'une couche ayant une forte anisotropie magnétique plane dans un grenat ferrimagnétique. Elle s'applique en particulier dans le domaine de l'élaboration des mémoires à bulles magnétiques et notamment dans l'élaboration des mémoires à bulles à disques non implantés, mais aussi dans le domaine de l'élaboration de matériau semi-conducteur ou magnéto-optique.The present invention relates to a method of manufacturing a layer having a strong planar magnetic anisotropy in a ferrimagnetic garnet. It applies in particular in the field of the development of magnetic bubble memories and in particular in the development of bubble memories with non-implanted discs, but also in the field of the production of semiconductor or magneto- material. optical.

De façon générale, l'élaboration d'une mémoire à bullés consiste, tout d'abord, à épitaxier une couche de grenat ferrimagnétique à anisotropie de croissance perpendiculaire à la couche sur un substrat amagnétique, principalement un grenat. On rappelle que les bulles magnétiques sont des petits domaines magnétiques dont l'aimantation, dirigée perpendiculairement à sa surface, est inversée par rapport à celle du matériau contenant les bulles. Ensuite, on implante des ions dans la couche épitaxiée.In general, the development of a bubble memory is, firstly, to e p itaxier a ferrimagnetic garnet layer growth anisotropy perpendicular to the layer on an amagnetic substrate, primarily a garnet. It is recalled that the magnetic bubbles are small magnetic domains whose magnetization, directed perpendicular to its surface, is reversed compared to that of the material containing the bubbles. Next, ions are implanted in the epitaxial layer.

Cette implantation ionique permet la création en surface de la couche de grenat ferrimagnétique, d'une couche à aimantation plane, c'est-à-dire, d'une couche dont l'aimantation est parallèle à la surface de ladite couche. Cette couche à aimantation plane a notamment pour but d'augmenter la stabilité des bulles magnétiques. Cette implantation ionique permet de réaliser des couches à aimantation plane sur une épaisseur de l'ordre de 0,5 µm.This ion implantation allows the creation on the surface of the ferrimagnetic garnet layer, of a plane magnetization layer, that is to say, of a layer whose magnetization is parallel to the surface of said layer. The purpose of this plane magnetization layer is in particular to increase the stability of the magnetic bubbles. This ion implantation makes it possible to produce layers with plane magnetization over a thickness of the order of 0.5 μm.

En utilisant un masque d'implantation approprié, on peut par ailleurs définir, dans le cas de mémoires à bulles à motifs non implantés, les motifs de propagation, qui sont des motifs contigus, ayant la forme de disque, de losange, etc. ; étant donné que l'implantation ionique n'est effectuée qu'autour de ces motifs, ces motifs sont appelés des motifs non implantés.By using an appropriate implantation mask, it is also possible to define, in the case of bubble memories with non-implanted patterns, the propagation patterns, which are contiguous patterns, having the disc, diamond shape, etc. ; since ion implantation is only performed around these patterns, these patterns are called non-implanted patterns.

Dans le cas de mémoires à bulles à motifs à base de fer et de nickel, l'implantation ionique sert, en plus de la formation de la couche superficielle à aimantation plane, à supprimer les bulles "dures", c'est-à-dire les bulles ayant des structures de parois complexes.In the case of bubble memories with patterns based on iron and nickel, the ion implantation serves, in addition to the formation of the surface layer with plane magnetization, to remove the "hard" bubbles, that is to say say bubbles with complex wall structures.

La propagation des bulles magnétiques le long des motifs de propagation est réalisée en appliquant un champ continu tournant suivant une direction parallèle à la surface de la couche ferrimagnétique. Les bulles se trouvant au-dessous de la couche Superficielle à aimantation plane sont collées aux motifs de propagation non implantés par l'intermédiaire d'un puits de potentiel dû au champ des contraintes entre les zones implantées et non implantées.The propagation of the magnetic bubbles along the propagation patterns is carried out by applying a continuous field rotating in a direction parallel to the surface of the ferrimagnetic layer. The bubbles located below the surface layer with plane magnetization are bonded to the non-implanted propagation patterns via a potential well due to the stress field between the implanted and non-implanted areas.

Le déplacement des bulles magnétiques le long. des motifs de propagation provient de l'action du champ tournant qui crée une paroi chargée mobile entraînant les bulles.Moving the magnetic bubbles along. propagation patterns comes from the action of the rotating field which creates a moving charged wall causing the bubbles.

Pendant longtemps, on a utilisé les propriétés de magnétostriction des couches de grenat ferrimagnétique pour obtenir cette anisotropie magnétique de la couche superficielle. En effet, le bombardement ionique crée à la surface de la couche de grenat épitaxiée des défauts entraînant ainsi une déformation du paramètre de maille dans la direction perpendiculaire à ladite couche de grenat ferrimagnétique. Ces défauts introduisent dans la couche de grenat de fortes contraintes mécaniques, orientées parallèlement à la surface de ladite couche ; il a été prouvé qu'une dilatation du paramètre de maille ne pouvait se faire parallèlement à la surface de la couche ferrimagnétique.For a long time, the magnetostriction properties of the ferrimagnetic garnet layers have been used to obtain this magnetic anisotropy of the surface layer. In fact, the ion bombardment creates defects on the surface of the epitaxial garnet layer, thus causing a deformation of the mesh parameter in the direction perpendicular to said ferrimagnetic garnet layer. These defects introduce into the garnet layer strong mechanical stresses, oriented parallel to the surface of said layer; it has been proven that a dilation of the mesh parameter cannot be done in parallel on the surface of the ferrimagnetic layer.

Les couches de grenat ferrimagnétique sont fabriquées de manière à présenter un coefficient de magnétostriction négatif. Dans ce cas, une contrainte en compression, obtenue par l'implantation ionique, induit une anisotropie magnétique dans le plan de la couche superficielle implantée qui est supérieure à l'anisotropie de croissance du matériau de départ, c'est-à-dire du matériau non implanté.The layers of ferrimagnetic garnet are manufactured so as to have a negative magnetostriction coefficient. In this case, a compressive stress, obtained by ion implantation, induces a magnetic anisotropy in the plane of the implanted surface layer which is greater than the growth anisotropy of the starting material, i.e. material not implanted.

Malheureusement, ce mécanisme de magnétostriction a ses limites qui dépendent de l'importance de l'anisotropie de croissance du matériau (croissance par épitaxie) ainsi que de son coefficient négatif de magnétostriction. En effet, on ne peut pas augmenter la dose d'ions implantés indéfiniment, car au-delà d'un certain seuil de défauts, le magnétisme de la couche superficielle implantée s'annule et on ne peut plus déplacer les bulles le long des motifs de propagation notamment non implantés.Unfortunately, this magnetostriction mechanism has its limits which depend on the importance of the growth anisotropy of the material (growth by epitaxy) as well as on its negative magnetostriction coefficient. Indeed, one cannot increase the dose of implanted ions indefinitely, because beyond a certain threshold of defects, the magnetism of the implanted surface layer is canceled and one can no longer move the bubbles along the patterns propagation, notably not implanted.

Or, étant donné que les nouvelles générations de mémoires à bulles magnétiques et en particulier de mémoires à motifs non implantés, tendent à mémoriser des densités d'informations de plus en plus élevées, il est nécessaire que les bulles magnétiques soient de plus en plus petites, ce qui ne peut être réalisé qu'au moyen d'un matériau ayant une grande anisotropie de croissance. Malheureusement, avec de tels matériaux, il n'est plus possible d'obtenir une aimantation plane dans la couche implantée par un simple mécanisme de magnétostriction.However, since the new generations of magnetic bubble memories and in particular memories with non-implanted patterns, tend to memorize increasingly higher information densities, it is necessary that the magnetic bubbles are smaller and smaller , which can only be achieved with a material having a large growth anisotropy. Unfortunately, with such materials, it is no longer possible to obtain a plane magnetization in the implanted layer by a simple magnetostriction mechanism.

Afin d'augmenter l'anisotropie magnétique de la couche implantée et ce, quelle que soit l'anisotropie de croissance du matériau de départ, il a été récemment envisagé d'effectuer dans cette couche implantée une pulvérisation inverse,d'ions d'argon. Celle-ci est réalisée en soumettant l'échantillon et à un chauffage supérieur à 100°C. Ce procédé a été décrit dans un article intitulé "Magnetic and crystalline properties of ion-implanted garnet fibers with plasma exposure" de K. Betsui et al., paru à la Conférence "Intermag" Hambourg (1984).In order to increase the magnetic anisotropy of the implanted layer and this, whatever the growth anisotropy of the starting material, it has recently been envisaged to perform in this implanted layer a reverse spraying, of argon ions . This is carried out by subjecting the sample and to heating above 100 ° C. This process was described in an article entitled "Magnetic and crystalline properties of ion-implanted garnet fibers with plasma exposure" by K. Betsui et al., Published at the "Intermag" Conference Hamburg (1984).

La présente invention a justement pour objet un autre procédé de fabrication d'une couche ayant une forte anisotropie magnétique plane dans un grenat ferrimagnétique permettant de remédier aux différents inconvénients donnés précédemment.The subject of the present invention is precisely another method of manufacturing a layer having a strong planar magnetic anisotropy in a ferrimagnetic garnet enabling the various drawbacks given above to be remedied.

De façon plus précise, l'invention a pour objet un procédé de fabrication d'une couche de grenat ferrimagnétique, présentant une forte anisotropie plane magnétique, sur un substrat amagnétique, se caractérisant en ce qu'il comprend les étapes suivantes :'

  • - formation d'au moins une couche de grenat ferrimagnétique par épitaxie à partir du substrat amagnétique,
  • - implantation d'ions à forte dose dans la couche de grenat ferrimagnétique afin de créer des défauts dans ladite couche, et
  • - chauffage de l'ensemble, en présence d'un agent réducteur, à une température comprise entre 250 et 450°C.
More specifically, the subject of the invention is a method for manufacturing a layer of ferrimagnetic garnet, having a strong plane magnetic anisotropy, on a non-magnetic substrate, characterized in that it comprises the following steps:
  • - formation of at least one layer of ferrimagnetic garnet by epitaxy from the non-magnetic substrate,
  • implantation of ions at high dose in the ferrimagnetic garnet layer in order to create defects in said layer, and
  • - Heating the assembly, in the presence of a reducing agent, to a temperature between 250 and 450 ° C.

Conformément à l'invention, l'étape de chauffage de l'ensemble de la structure, en présence d'un agent réducteur, permet d'augmenter très fortement l'anisotropie magnétique de la couche de grenat ferrimagnétique.According to the invention, the step of heating the entire structure, in the presence of a reducing agent, makes it possible to greatly increase the magnetic anisotropy of the ferrimagnetic garnet layer.

Cette augmentation de l'anisotropie magnétique peut semble-t-il s'expliquer par une réduction en surface de la couche ferrimagnétique implantée.This increase in magnetic anisotropy may seem to be explained by a reduction in the surface of the ferrimagnetic layer implanted.

Selon un mode préféré de mise en oeuvre du procédé selon l'invention, l'agent réducteur est un gaz. De préférence, ce gaz est de l'hydrogène.According to a preferred embodiment of the method according to the invention, the reducing agent is a gas. Preferably, this gas is hydrogen.

Selon un autre mode préféré de mise en oeuvre du procédé selon l'invention, les ions implantés sont des ions de néon.According to another preferred embodiment of the method according to the invention, the implanted ions are neon ions.

Le procédé de fabrication d'une couche de grenat ferrimagnétique de forte anisotropie magnétique plane conformément à l'invention s'applique avantageusement à la fabrication d'une mémoire à bulles à motifs de propagation non implantés.The method of manufacturing a ferrimagnetic garnet layer of high planar magnetic anisotropy in accordance with the invention advantageously applies to the production of a bubble memory with non-implanted propagation patterns.

Dans une telle application, le procédé selon l'invention comprend les étapes suivantes :

  • - formation d'une couche de grenat ferrimagnétique par épitaxie à partir du substrat amagnétique,
  • - implantation d'ions dans la partie supérieure de la couche de grenat ferrimagnétique afin de créer des défauts dans ladite partie et de former les motifs de propagation, et
  • - chauffage de l'ensemble, en présence d'un agent réducteur, à une température comprise entre 250 et 450°C.
In such an application, the method according to the invention comprises the following steps:
  • - formation of a ferrimagnetic garnet layer by epitaxy from the non-magnetic substrate,
  • implantation of ions in the upper part of the ferrimagnetic garnet layer in order to create defects in said part and to form the propagation patterns, and
  • - Heating the assembly, in the presence of a reducing agent, to a temperature between 250 and 450 ° C.

D'autres caractéristiques et avantages de l'invention ressortiront mieux de la description qui va suivre, donnée à titre illustratif mais nullement limitatif.Other characteristics and advantages of the invention will emerge more clearly from the description which follows, given by way of illustration but in no way limiting.

Cette description est faite dans le cadre de la fabrication des mémoires à bulles à disques non implantés, mais bien entendu, comme on l'a indiqué plus haut, l'invention est d'application beaucoup plus générale.This description is made in the context of the manufacture of bubble memories with non-implanted disks, but of course, as indicated above, the invention is of much more general application.

La première étape du procédé consiste à former de façon connue par épitaxie sur un substrat amagnétique, tel que du gallate de gadolinium (Gd3 Ga5 012) une couche de grenat ferrimagnétique dont le vecteur aimantation est orienté perpendiculairement à la surface de ladite couche. Dans cette couche ferrima- gnétique,d'une épaisseur de l'ordre de 1 000 nm, pourront exister des bulles magnétiques, en présence d'un champ polarisant.The first step of the process consists in forming in a known manner by epitaxy on a non-magnetic substrate, such as gadolinium gallate (Gd 3 Ga 5 0 12 ) a layer of ferrimagnetic garnet whose magnetization vector is oriented perpendicular to the surface of said layer . In this ferrima- layer gnéti q ue, with a thickness of the order of 1000 nm, magnetic bubbles may exist in the presence of a polarizing field.

Comme grenat ferrimagnétique, on peut utiliser un matériau bien connu de l'homme du métier, répondant à la formule suivante (YSmLuCa)3 (FeGe)5 0 12' As ferrimagnetic garnet, one can use a material well known to those skilled in the art, corresponding to the following formula (YSmLuCa) 3 ( F e Ge ) 5 0 12 '

L'orientation des vecteurs aimantation dans la couche de grenat ferrimagnétique est due à une anisotropie de croissance des matériaux, anisotropie obtenue par un choix judicieux des conditions opératoires de l'épitaxie. Ces conditions opératoires sont bien connues de l'homme du métier.The orientation of the magnetization vectors in the ferrimagnetic garnet layer is due to an anisotropy of growth of the materials, anisotropy obtained by a judicious choice of the operating conditions of the epitaxy. These operating conditions are well known to those skilled in the art.

L'étape suivante du procédé consiste à réaliser une implantation ionique dans la couche supérieure ferrimagnétique afin de former des défauts dans la partie supérieure de ladite couche sur une épaisseur de l'ordre de 300 nm. Cette implantation ionique peut être réalisée avec différents types d'ions tels que des ions d'hydrogène, de néon, d'azote, d'oxygène, d'argon, etc. à une forte dose sans pour autant rendre amorphe le matériau ferrimagnétique constituant la partie implantée de la couche épitaxiée, c'est-à-dire démunir ce matériau de ses propriétés magnétiques. Par exemple, on peut effectuer une implantation d'ions de néon à une dose inférieure ou égale à 1015 atomes/cm2 et à une énergie de 200 keV.The next step of the method consists in carrying out an ion implantation in the upper ferrimagnetic layer in order to form defects in the upper part of said layer over a thickness of the order of 300 nm. This ion implantation can be carried out with different types of ions such as hydrogen, neon, nitrogen, oxygen, argon, etc. at a high dose without making the ferrimagnetic material constituting the implanted part of the epitaxial layer amorphous, that is to say depriving this material of its magnetic properties. For example, an implantation of neon ions can be carried out at a dose less than or equal to 10 15 atoms / cm 2 and at an energy of 200 keV.

L'implantation ionique en plus de la création des défauts dans la partie supérieure de la couche ferrimagnétique permet la formation dans ladite partie, en utilisant un masque approprié, des motifs de propagation non implantés des bulles magnétiques.The ion implantation in addition to the creation of defects in the upper part of the ferrimagnetic layer allows the formation in said part, using an appropriate mask, of the non-implanted propagation patterns of the magnetic bubbles.

Après cette implantation ionique, on soumet l'ensemble de la structure à un chauffage en présence d'un agent réducteur. Cet agent réducteur peut être un solide, un liquide ou un gaz. De préférence, on utilisera un réducteur gazeux tel que du sulfure d'hydrogène (H2S), du phosphure d'hydrogène (PH3), de l'antimoniure d'hydrogène (SbH3), de l'arséniure d'hydrogène (AsH3) et de l'hydrogène. De façon avantageuse, on utilisera de l'hydrogène.After this ion implantation, the entire structure is subjected to heating in the presence of a reducing agent. This reducing agent can be a solid, a liquid or a gas. Preferably, we will use a gaseous reducing agent such as hydrogen sulfide (H 2 S), hydrogen phosphide (PH 3 ), hydrogen antimonide (SbH 3 ), hydrogen arsenide (AsH 3 ) and hydrogen. Advantageously, hydrogen will be used.

Le chauffage en présence de l'agent réducteur est effectué à une température comprise entre 250 et 450°C. L'utilisation d'une température inférieure à 250°C entraînerait une durée trop longue de chauffage et une température au-dessus de 450°C serait néfaste à l'obtention d'une forte anisotropie magnétique plane dans la partie supérieure de la couche de grenat ferrimagnétique.The heating in the presence of the reducing agent is carried out at a temperature between 250 and 450 ° C. The use of a temperature lower than 250 ° C would involve a too long duration of heating and a temperature above 450 ° C would be harmful to obtain a strong plane magnetic anisotropy in the upper part of the layer of ferrimagnetic garnet.

En effet, une température trop élevée entraînerait la guérison des défauts créés dans cette couche lors de l'implantation ionique.Indeed, too high a temperature would cure the defects created in this layer during ion implantation.

La durée de chauffage est fonction de la température de chauffage. En effet, plus la température de chauffage est élevée, plus la durée de ce chauffage sera courte.The heating time depends on the heating temperature. In fact, the higher the heating temperature, the shorter the duration of this heating.

Le chauffage de la structure, en présence de l'agent réducteur peut être effectué en une ou plusieurs étapes.The heating of the structure, in the presence of the reducing agent can be carried out in one or more stages.

La réduction de la partie implantée entraîne une forte variation d'anisotropie magnétique, ce qui se traduit par la formation d'une couche à aimantation plane dans ladite couche implantée. Cette couche à aimantation plane sert notamment à stabiliser les bulles sous-jacentes.The reduction of the implanted part results in a large variation in magnetic anisotropy, which results in the formation of a plane magnetization layer in said implanted layer. This plane magnetization layer is used in particular to stabilize the underlying bubbles.

L'exemple de mise en oeuvre du procédé de l'invention ci-dessous va permettre d'illustrer l'augmentation obtenue de façon importante de l'aniso tropie magnétique de la partie de la couche ferrimagnétique implantée, contenant notamment les motifs de propagation non implantés, des bulles magnétiques,The example of implementation of the process of the invention below will make it possible to illustrate the increase obtained in a significant manner in the magnetic anisotropy of the part of the implanted ferrimagnetic layer, containing in particular the non-propagating patterns. implanted, magnetic bubbles,

Après avoir implanté dans une couche de grenat ferrimagnétique en (YSmLuCa)3 (FeGe)5 012, des ions de néon à une dose de 10 15 atomes/cm' et à une énergie de 200 keV, on a déterminé la variation d'anisotropie entre l'anisotropie du matériau ferrimagnétique vierge et du matériau ferrimagnétique implanté, par mesure de la variation du champ magnétique d'anisotropie ΔHK (en A/m). Ensuite, on a effectué un premier chauffage de la structure en présence d'hydrogène pendant 28 heures à une température de 292°C, dans un four, la pression d'hydrogène étant de l'ordre de 1 atm. (105 Pa). On a alors effectué une seconde mesure de la variation d'anisotropie magnétique entre l'anisotropie de la couche magnétique implantée et recuite et l'anisotropie de la couche vierge.After having implanted in a layer of ferrimagnetic garnet in (YSmLuCa) 3 (FeGe) 5 0 12 , neon ions at a dose of 10 15 atoms / cm 'and at an energy of 200 keV, the variation of anisotropy between the anisotropy of the virgin ferrimagnetic material and of the implanted ferrimagnetic material, by measuring the variation of the anisotropy magnetic field ΔH K (in A / m). Then, a first heating of the structure was carried out in the presence of hydrogen for 28 hours at a temperature of 292 ° C, in an oven, the hydrogen pressure being of the order of 1 atm. (10 5 Pa). A second measurement of the variation in magnetic anisotropy between the anisotropy of the implanted and annealed magnetic layer and the anisotropy of the virgin layer was then carried out.

On a ensuite effectué un deuxième chauffage de la structure en présence d'hydrogène à une température de 292°C pendant une durée de 95 heures, la pression d'hydrogène étant de l'ordre de 1 atm., puis on a mesuré encore une fois la variation du champ d'anisotropie magnétique entre le champ d'anisotropie de la couche ferrimagnétique vierge implantée et le champ d'anisotropie de la couche ainsi traitée.A second heating of the structure was then carried out in the presence of hydrogen at a temperature of 292 ° C. for a period of 95 hours, the hydrogen pressure being of the order of 1 atm., Then a further measurement was made. times the variation of the magnetic anisotropy field between the anisotropy field of the implanted virgin ferrimagnetic layer and the anisotropy field of the layer thus treated.

Enfin, un troisième chauffage sous vide à une température de 200°C pendant environ 1 heure, a été effectué. On a à nouveau mesuré la variation du champ d'anisotropie magnétique ainsi que déterminé par réactions nucléaires avec des ions de bore, la quantité d'hydrogène ayant pu diffuser à l'intérieur de la couche supérieure implantée.Finally, a third heating under vacuum at a temperature of 200 ° C for about 1 hour was carried out. The variation in the magnetic anisotropy field was again measured as determined by nuclear reactions with boron ions, the quantity of hydrogen having been able to diffuse inside the implanted upper layer.

Les résultats des différentes mesures sont donnés dans le tableau ci-après.The results of the various measurements are given in the table below.

Comme le montre ce tableau, l'anisotropie magnétique de la couche ferrimagnétique implantée, grâce au procédé de l'invention, a fait plus que doubler. Cette variation d'anisotropie ne peut être due qu'à une réduction de la couche superficielle de la couche implantée entraînant semble-t-il une migration vers la surface de cette couche de l'oxygène, entrant dans la composition de cette couche, cet oxygène provenant des défauts causés lors de l'implantation ionique. La migration de l'oxygène vers la surface de la couche magnétique implantée provoque un appauvrissement en oxygène de celle-ci, entraînant une réduction des ions Fe3+ en ions Fe2+ responsable de l'anisotropie magnétique.As this table shows, the magnetic anisotropy of the implanted ferrimagnetic layer, thanks to the process of the invention, has more than doubled. This variation in anisotropy can only be due to a reduction in the surface layer of the implanted layer, apparently leading to migration towards the surface of this layer of oxygen, entering into the composition of this layer, this oxygen from defects caused during ion implantation. The migration of oxygen to the surface of the implanted magnetic layer causes an oxygen depletion thereof, resulting in a reduction of Fe 3+ ions to Fe 2+ ions responsible for magnetic anisotropy.

Le troisième chauffage sous vide a pour but de montrer que l'augmentation de l'anisotropie magnétique n'est pas due à une diffusion d'hydrogène à l'intérieur de la couche ferrimagnétique supérieure. En effet, si tel était le cas, on devrait observer une diminution de la variation d'anisotropie magnétique, lors de ce recuit sous vide ; l'hydrogène étant très mobile à cette température sortirait partiellement de la structure. Or, on observe plutôt une augmentation de la variation d'anisotropie magnétique, ce qui tendrait à penser qu'une migration d'oxygène vers la surface de la couche implantée a encore eu lieu.The purpose of the third vacuum heating is to show that the increase in magnetic anisotropy is not due to a diffusion of hydrogen inside the upper ferrimagnetic layer. Indeed, if this were the case, we should observe a decrease in the variation of magnetic anisotropy, during this vacuum annealing; the hydrogen being very mobile at this temperature would partially leave the structure. However, there is rather an increase in the variation of magnetic anisotropy, which would tend to think that a migration of oxygen towards the surface of the implanted layer has still taken place.

Il est à noter que la partie de la couche ferrimagnétique non implantée, contenant les bulles magnétiques, n'est nullement modifiée par les étapes de chauffage, en présence d'un agent réducteur, de la structure.

Figure imgb0001
It should be noted that the part of the non-implanted ferrimagnetic layer containing the magnetic bubbles is in no way modified by the heating stages, in the presence of a reducing agent, of the structure.
Figure imgb0001

Claims (5)

1. Procédé de fabrication d'une couche de grenat ferrimagnétique présentant une forte anisotropie magnétique, sur un substrat amagnétique, caractérisé en ce qu'il comprend les étapes suivantes : - formation d'au moins une couche de grenat ferrimagnétique par épitaxie à partir du substrat amagnétique, - implantation d'ions à forte dose dans la couche de grenat ferrimagnétique afin de créer des défauts dans ladite couche, et - chauffage de l'ensemble, en présence d'un agent réducteur, à une température comprise entre 250 et 450°C. 1. Method for manufacturing a ferrimagnetic garnet layer having a strong magnetic anisotropy, on a non-magnetic substrate, characterized in that it comprises the following steps: - formation of at least one layer of ferrimagnetic garnet by epitaxy from the non-magnetic substrate, implantation of ions at high dose in the ferrimagnetic garnet layer in order to create defects in said layer, and - Heating the assembly, in the presence of a reducing agent, to a temperature between 250 and 450 ° C. 2. Procédé selon la revendication 1, caractérisé en ce que l'agent réducteur est un gaz.2. Method according to claim 1, characterized in that the reducing agent is a gas. 3. Procédé selon la revendication 2, caractérisé en ce que l'agent réducteur est de l'hydrogène.3. Method according to claim 2, characterized in that the reducing agent is hydrogen. 4. Procédé selon l'une quelconque des revendications 1 à 3, caractérisé en ce que les ions implantés sont des ions de néon.4. Method according to any one of claims 1 to 3, characterized in that the implanted ions are neon ions. 5. Procédé de fabrication d'une couche de grenat ferrimagnétique, présentant une forte anisotropie magnétique plane sur un substrat amegnétique selon l'une quelconque des revendications 1 à 4, appliqué à la fabrication d'une mémoire à bulles à motifs de propagation non implantés, caractérisé en ce qu'il comprend les étapes suivantes : - formation d'une couche de grenat ferrimagnétique par épitaxie à partir du substrat amagnétique, - implantation d'ions dans la partie supérieure de la couche de grenat ferrimagnétique afin de créer des défauts dans ladite partie et de former les motifs de propagation, et - chauffage de l'ensemble, en présence d'un agent réducteur, à une température comprise entre 250 et 450°C. 5. A method of manufacturing a ferrimagnetic garnet layer, having a strong plane magnetic anisotropy on an amegnetic substrate according to any one of claims 1 to 4, applied to the production of a bubble memory with non-implanted propagation patterns , characterized in that it comprises the following stages: - formation of a ferrimagnetic garnet layer by epitaxy from the non-magnetic substrate, implantation of ions in the upper part of the ferrimagnetic garnet layer in order to create defects in said part and to form the propagation patterns, and - Heating the assembly, in the presence of a reducing agent, to a temperature between 250 and 450 ° C.
EP85402149A 1984-11-12 1985-11-07 Method of producing a layer having a strong magnetic anisotropy in a ferrimagnetic garnet Expired - Lifetime EP0186531B1 (en)

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