WO1988002033A1 - Method for making an amorphous aluminum-nitrogen alloy layer - Google Patents
Method for making an amorphous aluminum-nitrogen alloy layer Download PDFInfo
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- WO1988002033A1 WO1988002033A1 PCT/US1987/002193 US8702193W WO8802033A1 WO 1988002033 A1 WO1988002033 A1 WO 1988002033A1 US 8702193 W US8702193 W US 8702193W WO 8802033 A1 WO8802033 A1 WO 8802033A1
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
- G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
- G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
- G11B11/10582—Record carriers characterised by the selection of the material or by the structure or form
- G11B11/10586—Record carriers characterised by the selection of the material or by the structure or form characterised by the selection of the material
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/0021—Reactive sputtering or evaporation
- C23C14/0036—Reactive sputtering
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
- C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
- C23C14/0641—Nitrides
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/0009—Materials therefor
- G02F1/0036—Magneto-optical materials
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B11/00—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor
- G11B11/10—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field
- G11B11/105—Recording on or reproducing from the same record carrier wherein for these two operations the methods are covered by different main groups of groups G11B3/00 - G11B7/00 or by different subgroups of group G11B9/00; Record carriers therefor using recording by magnetic means or other means for magnetisation or demagnetisation of a record carrier, e.g. light induced spin magnetisation; Demagnetisation by thermal or stress means in the presence or not of an orienting magnetic field using a beam of light or a magnetic field for recording by change of magnetisation and a beam of light for reproducing, i.e. magneto-optical, e.g. light-induced thermomagnetic recording, spin magnetisation recording, Kerr or Faraday effect reproducing
- G11B11/10582—Record carriers characterised by the selection of the material or by the structure or form
- G11B11/10586—Record carriers characterised by the selection of the material or by the structure or form characterised by the selection of the material
- G11B11/10589—Details
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/72—Protective coatings, e.g. anti-static or antifriction
- G11B5/726—Two or more protective coatings
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers
- G11B5/851—Coating a support with a magnetic layer by sputtering
Definitions
- This invention relates to the field of magneto-optic (MO) recording and, more particularly, to methods for producing aluminum nitride layers for use in magneto-optic recording elements.
- magnetic-optic recording element refers to a multilayer structure used in the magneto-optic write/read process for selectively modifying the characteristic of an incident polarized light beam in accordance with a magnetization pattern formed in a magneto-optic recording layer which forms part of such structure.
- such recording element includes a substrate, a magneto-optic recording layer (e.g. amorphous alloys of rare earth and transition metals) and one or more corrosion-preventing, anti-reflection layers of a dielectric or semi-conductive material.
- a so-called "bi-layer” recording element comprises a magneto-optic layer having a single anti-reflection layer disposed on one surface thereof, the opposite surface of the magneto-optic layer being contiguous with the supporting substrate (which is not counted in determining the number of layers).
- a "tri-layer” structure would include a second protective layer disposed between the substrate and the MO layer.
- a primary function of the anti-reflection protective layer in an MO recording element is to enhance the magneto-optic rotation angle ⁇ K caused by the well-known Kerr effect (in reflective systems) and Faraday effect (in transmission systems).
- ⁇ K magneto-optic rotation angle
- some of the more desirable MO materials exhibit a ⁇ K of well less than 0.5°, and, without enhancement, the signal-to-noise ratio of the read-out signal, is marginal, at best.
- Another equally important function of the antireflection layer is to prevent corrosion of the contiguous MO layer. It is well known that some of the most promising MO layers (e.g. the aforementioned rare earth-transition metal (RE-TM) alloys) are environmentally unstable. That is, they exihibit little resistance to corrosion and oxidation which, of course, dramatically alters their magneto-optic properties.
- RE-TM rare earth-transition metal
- K. Ohta et al disclose a tri-layer recording element in which a rare earth-transition metal (RE-TM) thin film is sandwiched between a pair of corrosion-preventing layers made of crystalline aluminum nitride (AlN). These layers are supported by a glass substrate, and the exposed AlN layer is overcoated with a reflective layer (e.g. copper).
- RE-TM rare earth-transition metal
- AlN crystalline aluminum nitride
- An object of the invention is to provide a method for making the M0 recording elements of the invention.
- amorphous films of aluminum nitride particularly those having a stoichiometry of Al 1-x N x , where x is between about 0.30 and 0.45, give rise to a substantially greater ⁇ K , and corrosion resistance than do the crystalline A5.N layers of the prior art.
- a method for producing such films comprises a reactive sputtering step in which deposition rate, the nitrogen-to-inert gas ratio, the substrate temperature, the sputter power, the nitrogen flow rate, and the total pressure are precisely controlled.
- FIGS. 1A and 1B are cross-sectional views of magneto-optic recording elements
- FIGS. 2 and 3 are Kerr hysteresis loops of a magneto-optic recording element (FIG. 1A) with and without an amorphous antireflection layer, respectively;
- FIG. 4 illustrates the manner in which recording element reflectivity and magneto-optic rotation angle vary with thickness of the anti-reflective coating
- FIG. 5 schematically illustrates a reactive sputtering apparatus of the type used for carrying out the method of the invention
- FIG. 6 is a transmission electron micrograph (TEM) at 250,000 X of an amorphous aluminum-nitrogen alloy thin film made in accordance with the method of the invention
- FIG. 7 is an electron beam diffraction pattern of a selected portion of the thin film shown in FIG. 6; and FIG. 8 is a graph illustrating the corrosion resistance properties of amorphous and crystalline aluminum nitride layers.
- FIG. 1A is a cross-sectional view of a bi-layer magneto-optic recording element.
- a substrate 10 which may, if desired, be a transparent material made of, for example, glass, polycarbonate, acetate or acrylic resin.
- a magneto-optic thin-film layer 12 which may comprise any material which imparts a Kerr or Faraday effect to incident polarized light.
- recording layer 12 comprises a ternary alloy including a rare earth and transition metal.
- a particularly preferred MO media is a terbium-iron-cobalt (TbFeCo).
- Disposed atop recording layer 12 is an anti-reflection, corrosion—preventing layer 14 of aluminum-nitrogen alloy (Al 1-x N x ) thin film.
- the Al 1-x N x layer, of the FIG. 1A recording element is amorphous in character, that is, it is substantially free of any crystalline structure, as is evident in the photo micrograph and electron diffraction pattern of FIGS. 6 and 7. As such, there are no grain boundaries which would act as fast diffusion paths through which ambient gases can reach and react with the MO layer. Also, the absence of grain boundaries, has the effect of eliminating grain boundary noise which tends to reduce the performance (i.e., signal/noise ratio) of the recording element.
- the compositional formula or stoichiometry of this amorphous layer can be represented by the formula Al 1-x N x , where x is between about 0.30 and 0.45.
- this material is distinct from stoichiometric crystalline compound, AlN, with respect to its optical properties.
- the refractive index of a thin (e.g. 60 nanometer) Al 1-x N x film on a Si substrate at 633 nm. wavelength is about 1.85, compared to about 2.05 for crystalline AlN.
- an optimum match i.e. to achieve the maximum antireflection condition
- the refractive index of the overlayer is equal to the square root of the refractive index of the MO layer.
- FIGS. 2 and 3 the Kerr hysteresis loop of an amorphous Al 1-x N x coated TbFeCo bi-layer recording element is shown in FIG. 2, while that of an uncoated TbFeCo is shown in FIG. 3.
- the thickness of the Al 1-x N x overlayer is optimized by maximizing the aforementioned figure of merit, ⁇ K ⁇ R.
- amorphous aluminum nitride thin films are prepared in a RF planar magnetron system by reactively sputtering an aluminum target (e.g. 99.9995% purity) in an argon-nitrogen atmosphere.
- the general configuration for RF magnetron sputtering is shown in FIG. 5.
- argon and nitrogen gases are premixed in mixing chamber 20 before admission into a vacuum chamber 22.
- the substrate S which is to receive the Al 1-x N x film, is positioned on a substrate holder H which, in turn, is positioned in thermal contact with a water-cooled copper block B.
- the aluminum target T is spaced from substrate S by about 5 cm.
- the target is supported by a conventional planar magnetron (e.g. disclosed in U.S. Patent No. 4,324,631) and is operatively coupled to the negative terminal of a two kilowatt A.C. power source RF.
- the power applied to the target is controlled by a variable impedance Z.
- the vacuum chamber is pumped below 1x10 -7 Torr before backfilling with ultrahigh purity argon and nitrogen.
- the properties of the deposited Al 1-x N x films depend upon certain parameters of the RF sputtering system.
- One important parameter is the deposition rate which, of course, depends on the RF input power, target to substrate distance, substrate temperature, total sputtering pressure and the partial pressure of nitrogen, etc.
- the following other parameters need be controlled to produce amorphous films: a) the ratio of nitrogen to argon, b) substrate temperature, c) the sputtering power, d) the reactive gas (N 2 ) flow rate, and e) the total pressure.
- the following conditions have been found to give rise to amorphous Al 1-x N x films: N 2 :Ar Ratio - 30-50%
- the best films, insofar as optical structure and corrosion resistance are concerned, were produced using an N 2 :Ar ratio of about 50%, a sputter power of about 600 watts, a nitrogen flow of 3 seem, a total sputtering pressure of 5 mTorr, a substrate temperature of 75°C and a deposition rate of 16 nm/min.
- the film consists substantially of polycrystalline aluminum, and when the N 2 :Ar ratio exceeded 50%, the films obtained are of microcrystalline aluminum-nitride.
- the desired stoichiometry mentioned above i.e., Al 1-x N x films where x is between about 0.30 to 0.45) is achieved when the N 2 :Ar ratio is between about 30% and 50%, and the other parameters are met.
- Target to substrate distance - 5 cm.
- amorphous Al 1-x N x films can be advantageously used in more complex recording elements, such as the tri-layer structure shown in Fig. 1B.
- the magneto-optic layer When positioned on opposite sides of the magneto-optic layer, the latter is protected from corrosion from both sides.
- the amorphous Al 1-x N x intermediate layer 16 prevents any absorbed water or impurities in the substrate 10 from migrating to the MO layer 12 causing the formation of metal hydroxides or oxides.
- FIG. 8 shows the absorbance change in the immersion test.
- the TbFeCo film with crystalline aluminum nitride coating shows (curve A) a marked decrease in absorbance in short term.
- curve B shows the amorphous aluminum nitride coating.
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Abstract
Method for producing an amorphous aluminum nitride layer having a desired stoichiometry. Such method involves the steps of disposing a substrate in close proximity to an aluminum target in a low pressure atmosphere of nitrogen and an inert gas, and reactive sputtering an aluminum nitride layer onto the substrate at a certain minimum deposition rate while maintaining certain parameters (i.e. nitrogen-to-inert gas ratio, substrate temperature, sputtering power, nitrogen flow rate and sputtering pressure) within certain limits.
Description
METHOD FOR MAKING AN AMORPHOUS ALUMINUM-NITROGEN ALLOY LAYER BACKGROUND OF THE INVENTION This invention relates to the field of magneto-optic (MO) recording and, more particularly, to methods for producing aluminum nitride layers for use in magneto-optic recording elements.
As used herein, "magneto-optic recording element" refers to a multilayer structure used in the magneto-optic write/read process for selectively modifying the characteristic of an incident polarized light beam in accordance with a magnetization pattern formed in a magneto-optic recording layer which forms part of such structure. Typically, such recording element includes a substrate, a magneto-optic recording layer (e.g. amorphous alloys of rare earth and transition metals) and one or more corrosion-preventing, anti-reflection layers of a dielectric or semi-conductive material. A so-called "bi-layer" recording element comprises a magneto-optic layer having a single anti-reflection layer disposed on one surface thereof, the opposite surface of the magneto-optic layer being contiguous with the supporting substrate (which is not counted in determining the number of layers). A "tri-layer" structure would include a second protective layer disposed between the substrate and the MO layer.
A primary function of the anti-reflection protective layer in an MO recording element is to enhance the magneto-optic rotation angle θK caused by the well-known Kerr effect (in reflective systems) and Faraday effect (in transmission systems). As is well known, some of the more desirable MO materials exhibit a θK of well less than 0.5°, and, without enhancement, the signal-to-noise ratio of the read-out signal, is marginal, at best. Another equally important
function of the antireflection layer is to prevent corrosion of the contiguous MO layer. It is well known that some of the most promising MO layers (e.g. the aforementioned rare earth-transition metal (RE-TM) alloys) are environmentally unstable. That is, they exihibit little resistance to corrosion and oxidation which, of course, dramatically alters their magneto-optic properties.
In a 1984 article published in the Japanese Journal of Applied Electronics, Vol. 8, No. 2, pp. 93-96, entitled "Study on High Reliability of a Magneto-optic Medium with a Multilayer Structure," K. Ohta et al disclose a tri-layer recording element in which a rare earth-transition metal (RE-TM) thin film is sandwiched between a pair of corrosion-preventing layers made of crystalline aluminum nitride (AlN). These layers are supported by a glass substrate, and the exposed AlN layer is overcoated with a reflective layer (e.g. copper). As a result of this multilayer arrangement, the magneto-optic rotation angle, θK, increased to 1.2 degrees, and the coercive force of the MO layer was relatively stable over time. While this enhanced value of θk produces a relatively high figure of merit, θK√R, (where R is the power reflectivity of the recording element), the manufacture of such an element is relatively time-consuming and, hence, costly. Moreover, the environmental stability of such elements is still far less than desirable. SUMMARY OF THE INVENTION
An object of the invention is to provide a method for making the M0 recording elements of the invention.
It has been discovered that amorphous films of aluminum nitride, particularly those having a stoichiometry of Al1-xNx, where x is between about 0.30 and 0.45, give rise to a substantially
greater θK, and corrosion resistance than do the crystalline A5.N layers of the prior art. According to the invention, there is provided a method for producing such films. Such method comprises a reactive sputtering step in which deposition rate, the nitrogen-to-inert gas ratio, the substrate temperature, the sputter power, the nitrogen flow rate, and the total pressure are precisely controlled. The invention will be better understood from the ensuing detailed description of preferred embodiments, reference being made to the accompanying drawings wherein like reference characters denote like parts.
BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A and 1B are cross-sectional views of magneto-optic recording elements;
FIGS. 2 and 3 are Kerr hysteresis loops of a magneto-optic recording element (FIG. 1A) with and without an amorphous antireflection layer, respectively;
FIG. 4 illustrates the manner in which recording element reflectivity and magneto-optic rotation angle vary with thickness of the anti-reflective coating; FIG. 5 schematically illustrates a reactive sputtering apparatus of the type used for carrying out the method of the invention;
FIG. 6 is a transmission electron micrograph (TEM) at 250,000 X of an amorphous aluminum-nitrogen alloy thin film made in accordance with the method of the invention;
FIG. 7 is an electron beam diffraction pattern of a selected portion of the thin film shown in FIG. 6; and FIG. 8 is a graph illustrating the corrosion resistance properties of amorphous and crystalline aluminum nitride layers.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring now to the drawings, FIG. 1A is a cross-sectional view of a bi-layer magneto-optic recording element. Such recording comprises a substrate 10 which may, if desired, be a transparent material made of, for example, glass, polycarbonate, acetate or acrylic resin. Disposed atop substrate 10 is a magneto-optic thin-film layer 12 which may comprise any material which imparts a Kerr or Faraday effect to incident polarized light. Preferably, however, recording layer 12 comprises a ternary alloy including a rare earth and transition metal. A particularly preferred MO media is a terbium-iron-cobalt (TbFeCo). Disposed atop recording layer 12 is an anti-reflection, corrosion—preventing layer 14 of aluminum-nitrogen alloy (Al1-xNx) thin film.
The Al1-xNx layer, of the FIG. 1A recording element is amorphous in character, that is, it is substantially free of any crystalline structure, as is evident in the photo micrograph and electron diffraction pattern of FIGS. 6 and 7. As such, there are no grain boundaries which would act as fast diffusion paths through which ambient gases can reach and react with the MO layer. Also, the absence of grain boundaries, has the effect of eliminating grain boundary noise which tends to reduce the performance (i.e., signal/noise ratio) of the recording element. The compositional formula or stoichiometry of this amorphous layer can be represented by the formula Al1-xNx, where x is between about 0.30 and 0.45. It should be noted that this material is distinct from stoichiometric crystalline compound, AlN, with respect to its optical properties. For example, the refractive index of a thin (e.g. 60 nanometer) Al1-xNx film on a Si substrate at
633 nm. wavelength is about 1.85, compared to about 2.05 for crystalline AlN. When using the recording element of FIG. 1A in a front surface write/read mode, the index 1.85 is a better match to typical MO media (n
3.2) than the index (n = 2.05) of crystalline AJIN for antireflection effects. Assuming a front surface write/read mode in which incident medium is air, an optimum match (i.e. to achieve the maximum antireflection condition) is achieved when the refractive index of the overlayer is equal to the square root of the refractive index of the MO layer.
Referring to FIGS. 2 and 3, the Kerr hysteresis loop of an amorphous Al1-xNx coated TbFeCo bi-layer recording element is shown in FIG. 2, while that of an uncoated TbFeCo is shown in FIG. 3.
Note, with no applied field, 2θK is approximately
2.33 degrees with the amorphous Al1-xNx coated recording element, whereas 2θK for the uncoated element is only about 0.28 degrees. This overall enhancement by a factor of more than eight is believed to be the highest Kerr rotation enhancement observed so far in a simple bi-layer recording element. It is quite comparable to that achieved in more complicated multilayer structures, such as reported in the aforementioned article by Ohta et al. The manner in which the reflectivity and Kerr enhancement vary with thickness of the Al1-xNx layer is shown in FIG. 4. Here, the Kerr enhancement factor is represented by θK/θKO, where θKO and θK are Kerr rotation angles of an uncoated and coated recording element respectively.
Preferably, the thickness of the Al1-xNx overlayer is optimized by maximizing the aforementioned figure of merit, ΘK√R.
According to a preferred embodiment of this invention, amorphous aluminum nitride thin films are prepared in a RF planar magnetron system by
reactively sputtering an aluminum target (e.g. 99.9995% purity) in an argon-nitrogen atmosphere. The general configuration for RF magnetron sputtering is shown in FIG. 5. As shown, argon and nitrogen gases are premixed in mixing chamber 20 before admission into a vacuum chamber 22. The substrate S, which is to receive the Al1-xNx film, is positioned on a substrate holder H which, in turn, is positioned in thermal contact with a water-cooled copper block B. The aluminum target T is spaced from substrate S by about 5 cm. The target is supported by a conventional planar magnetron (e.g. disclosed in U.S. Patent No. 4,324,631) and is operatively coupled to the negative terminal of a two kilowatt A.C. power source RF. The power applied to the target is controlled by a variable impedance Z. The vacuum chamber is pumped below 1x10-7 Torr before backfilling with ultrahigh purity argon and nitrogen. la order to minimize contamination in the deposited film, it is preferable to sputter clean the target in a conventional manner, while a shutter S' protects the substrate S from deposition. Such cleaning is carried out in two steps, first sputtering in a pure argon atmosphere for about 15 minutes, and then sputtering for 30 minutes in the desired gas mixture.
It has been found that the properties of the deposited Al1-xNx films depend upon certain parameters of the RF sputtering system. One important parameter is the deposition rate which, of course, depends on the RF input power, target to substrate distance, substrate temperature, total sputtering pressure and the partial pressure of nitrogen, etc. In addition to the deposition rate, the following other parameters need be controlled to produce amorphous films: a) the ratio of nitrogen to argon, b) substrate temperature, c) the sputtering
power, d) the reactive gas (N2) flow rate, and e) the total pressure. The following conditions have been found to give rise to amorphous Al1-xNx films: N2:Ar Ratio - 30-50%
Substrate Temperature - < 80°C Deposition Rate - > 15 nanometer/minute Sputter Power - 600-1000 Watts Nitrogen Flow Rate - 3-6 seem Total Sputtering Pressure - 1-15 mTorr.
The best films, insofar as optical structure and corrosion resistance are concerned, were produced using an N2:Ar ratio of about 50%, a sputter power of about 600 watts, a nitrogen flow of 3 seem, a total sputtering pressure of 5 mTorr, a substrate temperature of 75°C and a deposition rate of 16 nm/min.
When the N2.:Ar ratio was less than 20%, the film consists substantially of polycrystalline aluminum, and when the N2:Ar ratio exceeded 50%, the films obtained are of microcrystalline aluminum-nitride. The desired stoichiometry mentioned above (i.e., Al1-xNx films where x is between about 0.30 to 0.45) is achieved when the N2:Ar ratio is between about 30% and 50%, and the other parameters are met.
During RF sputtering, the following general conditions were met: Sputtering power - 300-2000 Watts
Sputtering gas pressure - 1-30 mTorr Background pressure - 1x10 Torr N2 flow rate - 3-6 seem
Target to substrate distance - 5 cm.
As indicated above, amorphous Al1-xNx films can be advantageously used in more complex recording elements, such as the tri-layer structure
shown in Fig. 1B. When positioned on opposite sides of the magneto-optic layer, the latter is protected from corrosion from both sides. The amorphous Al1-xNx intermediate layer 16 prevents any absorbed water or impurities in the substrate 10 from migrating to the MO layer 12 causing the formation of metal hydroxides or oxides.
To illustrate the more corrosion resistance provided by the amorphous Al1-xNx coatings over the crystalline films electrochemical corrosion tests were performed on two different TbFeCo films (100 nm thick), one coated with 100 nm of amorphous Al1-xNx and the other coated with a 100 nm layer of crystalline AS.N. These specimens were immersed in a 0.1 Molar chloroacetate/KCl buffer aqueous solution and their changes in light absorbance or transmittance were measured with light at 632 nm. Corrosion causes the growth of pin holes in the film. In order to express quantitatively, the degree of oxidation or corrosion, a measurement of the total area of pin holes is the best way. However, since the accurate measurement of pin hole area is difficult and time consuming, the optical absorbance/transmittance through the film provide an indirect measure of the total area of corrosion pits. FIG. 8 shows the absorbance change in the immersion test. The TbFeCo film with crystalline aluminum nitride coating shows (curve A) a marked decrease in absorbance in short term. During the immersion time of 24 hours, there was a absorbance decrease of more than 60% with crystalline coating while during the same period of time in the same conditions there was a decrease of absorbance by only 20% with the amorphous aluminum nitride coating (curve B). Thus it indicates that the TbFeCo media with amorphous aluminum nitride coating has better corrosion resistance. Similar results were obtained
from potentio-dynamic polarization experiments carried out in the same solution. It was found that the amorphous aluminum nitride coating has corrosion resistance more than two times that of the crystalline aluminum nitride coating.
Since Al, is very reactive to oxygen as it is possible that trace amounts of oxygen present in the sputtering chamber during film deposition may find its way into the Al1-xNx film. Such modifications, if it occurs in these films, whether or not beneficial, is intended to be covered by this invention.
While the invention has been disclosed with particular reference to a preferred embodiment, it will be apparent to those skilled in the art that modifications may be made without departing from the spirit and scope of the invention, as defined by the following claims.
Claims
1. A method for producing an amorphous layer of an aluminum-nitrogen alloy on a substrate, said method comprising the steps of: a) disposing said substrate in close proximity to an aluminum target in a low pressure atmosphere of nitrogen and an inert gas; b) reactive sputtering an aluminum-nitrogen alloy onto said substrate at a rate exceeding 15 nanometers/min. while maintaining (i) the nitrogen-to-inert gas ratio between about 30 and 50%, (ii) the substrate temperature at less than about 80°C, (iii) the sputtering power between about 600 and 1000 Watts, (iv) the nitrogen flow rate between about 3 and 6 seem, and (v) the total sputtering pressure between about 1 and 15 mTorr.
2. The method according to claim 1 herein the nitrogen-to-inert gas ratio is maintained at about 50%, the substrate temperature is maintained at about 75°C, the sputtering power is maintained at about 3 seem, and the total sputtering pressure is maintained at about 5 mTorr.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE8787905896T DE3772036D1 (en) | 1986-09-17 | 1987-09-03 | METHOD FOR PRODUCING AN AMORPHOUS ALUMINUM NITRIDE LAYER. |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US06/908,365 US4719154A (en) | 1986-09-17 | 1986-09-17 | Magneto-optic recording element with amorphous aluminum-nitrogen alloy layer |
US908,365 | 1986-09-17 | ||
US067,758 | 1987-06-29 | ||
US07/067,758 US4959136A (en) | 1986-09-17 | 1987-06-29 | Method for making an amorphous aluminum-nitrogen alloy layer |
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Publication Number | Publication Date |
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WO1988002033A1 true WO1988002033A1 (en) | 1988-03-24 |
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Family Applications (1)
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PCT/US1987/002193 WO1988002033A1 (en) | 1986-09-17 | 1987-09-03 | Method for making an amorphous aluminum-nitrogen alloy layer |
Country Status (5)
Country | Link |
---|---|
US (1) | US4959136A (en) |
EP (1) | EP0282527B1 (en) |
JP (1) | JPH01501072A (en) |
DE (1) | DE3772036D1 (en) |
WO (1) | WO1988002033A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6905962B2 (en) | 1999-04-20 | 2005-06-14 | Trikon Technologies Limited | Method of depositing a layer |
Families Citing this family (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH03173958A (en) * | 1989-12-01 | 1991-07-29 | Pioneer Electron Corp | Magneto-optical disk |
US5407548A (en) * | 1990-10-26 | 1995-04-18 | Leybold Aktiengesellschaft | Method for coating a substrate of low resistance to corrosion |
KR930009690B1 (en) * | 1991-03-05 | 1993-10-08 | 주식회사 에스.케이.씨 | Manufacturing method of recording materials |
US5342681A (en) * | 1992-08-28 | 1994-08-30 | Texas Instruments Incorporated | Absorbing, low reflecting coating for visible and infrared light |
JPH07109573A (en) * | 1993-10-12 | 1995-04-25 | Semiconductor Energy Lab Co Ltd | Glass substrate and heat treatment |
JPH09501612A (en) * | 1994-04-08 | 1997-02-18 | マーク エー. レイ, | Selective plasma growth |
US6312568B2 (en) * | 1999-12-07 | 2001-11-06 | Applied Materials, Inc. | Two-step AIN-PVD for improved film properties |
WO2002043466A2 (en) | 2000-11-30 | 2002-06-06 | North Carolina State University | Non-thermionic sputter material transport device, methods of use, and materials produced thereby |
US6784085B2 (en) | 2000-11-30 | 2004-08-31 | North Carolina State University | MIIIN based materials and methods and apparatus for producing same |
GB0116688D0 (en) * | 2001-07-07 | 2001-08-29 | Trikon Holdings Ltd | Method of depositing aluminium nitride |
US20090071371A1 (en) * | 2007-09-18 | 2009-03-19 | College Of William And Mary | Silicon Oxynitride Coating Compositions |
KR101281684B1 (en) * | 2008-01-25 | 2013-07-05 | 성균관대학교산학협력단 | Fabrication method of nitride semiconductor substrate |
JP6445901B2 (en) * | 2015-03-10 | 2018-12-26 | 株式会社神戸製鋼所 | Light absorbing conductive film and sputtering target for forming light absorbing conductive film |
CN104862659B (en) * | 2015-05-22 | 2017-09-26 | 电子科技大学 | A kind of medium frequency magnetron reaction sputtering method of aluminium nitride film |
CN111206213B (en) * | 2020-02-25 | 2021-08-13 | 西安交通大学 | AlN amorphous film and preparation method thereof |
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DE2634412A1 (en) * | 1975-08-01 | 1977-02-10 | Fuji Photo Film Co Ltd | LITHOGRAPHIC PRINTING PLATE |
US4125446A (en) * | 1977-08-15 | 1978-11-14 | Airco, Inc. | Controlled reflectance of sputtered aluminum layers |
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US3461054A (en) * | 1966-03-24 | 1969-08-12 | Bell Telephone Labor Inc | Cathodic sputtering from a cathodically biased target electrode having an rf potential superimposed on the cathodic bias |
US3600218A (en) * | 1968-05-15 | 1971-08-17 | Ibm | Method for depositing insulating films of silicon nitride and aluminum nitride |
JPS5940227B2 (en) * | 1980-06-24 | 1984-09-28 | 富士通株式会社 | Reactive sputtering method |
-
1987
- 1987-06-29 US US07/067,758 patent/US4959136A/en not_active Expired - Fee Related
- 1987-09-03 WO PCT/US1987/002193 patent/WO1988002033A1/en active IP Right Grant
- 1987-09-03 EP EP87905896A patent/EP0282527B1/en not_active Expired - Lifetime
- 1987-09-03 JP JP62505501A patent/JPH01501072A/en active Pending
- 1987-09-03 DE DE8787905896T patent/DE3772036D1/en not_active Expired - Fee Related
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE2634412A1 (en) * | 1975-08-01 | 1977-02-10 | Fuji Photo Film Co Ltd | LITHOGRAPHIC PRINTING PLATE |
US4125446A (en) * | 1977-08-15 | 1978-11-14 | Airco, Inc. | Controlled reflectance of sputtered aluminum layers |
Non-Patent Citations (7)
Title |
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Applied Physics Letters, Volume 36, No. 8, April 1980, American Institute of Physics, (New York, US), T. SHIOSAKI et al.: "Low-Temperature Growth of Piezoelectric AIN Film by rf Reactive Planar Magnetron Sputtering", pages 643-645 see the whole document * |
Applied Physics Letters, Volume 39, No. 8, October 1981, (New York, US), S. ONISHI et al.: "Colorless, Transparent, C-Oriented Aluminum Nitride Films Grown at low Temperature by a Modified Sputter Gun", pages 643-645 see the whole document * |
Journal of Applied Physics, Volume 43, No. 3, March 1972, (New York, US), H.F. WINTERS et al.: "Influence of Surface Absorption Characteristics on Reactively Sputtered Films Grown in the Biased and Unbiased Modes", pages 794-800 see page 794, point II; page 796, left-hand column, last line * |
Le Vide; Les Couches Minces, Volume 40, No. 225, January/February 1985, (Paris, FR), J.J. HANTZPERQUE et al.: "Kinetics and Aluminium by Ions N2+ and Ar+", pages 13-32, see page 14, point 2 * |
Thin Solid Films, Volume 139, No. 3, 2 June 1986, Elsevier Sequoia, (Lausanne, CH), L. XINJIAO et al.: "On the Properties of AIN thin Films Grown by low Temperature Reactive R.F. Sputtering", pages 261-274 see page 262, table I * |
Thin Solid Films, Volume 65, No. 2, January 1980, Elsevier Sequoia S.A., (Lausanne, CH), H.J. ERLER et al.: "Nitride Film Deposition by Reactive Ion Beam Sputtering", pages 233-245 see abstract; page 236, table i; page 241, table III * |
Thin Solid Films, Volume 8. No. 1, July 1971, Elsevier Sequoia S.A, (Lausanne, CH), J. Duchene: "Radiofrequency Reactive Sputtering for Deposition of Aluminium Nitride thin Films", pages 69-79 see page 70, point 2; page 71, line 5; page 75, point 5 * |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6905962B2 (en) | 1999-04-20 | 2005-06-14 | Trikon Technologies Limited | Method of depositing a layer |
Also Published As
Publication number | Publication date |
---|---|
JPH01501072A (en) | 1989-04-13 |
DE3772036D1 (en) | 1991-09-12 |
EP0282527B1 (en) | 1991-08-07 |
US4959136A (en) | 1990-09-25 |
EP0282527A1 (en) | 1988-09-21 |
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