JP2718695B2 - Magneto-optical recording member and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording member for recording, reproducing, and erasing information using light and a method for manufacturing the same, and particularly to a member having high reliability. And a long-life magneto-optical recording member and a method of manufacturing the same.

[Conventional technology]

With the progress of the advanced information society, the need for a high-density, large-capacity and rewritable file memory is increasing. An optical disk has been paid attention to satisfying this requirement, and among them, magneto-optical recording is at the stage closest to practical use.

By the way, TbFeCo is used as a recording material for magneto-optical recording.
An amorphous alloy system composed of a rare earth element and an iron group element, including a system, and a Heusler alloy system mainly composed of PtMnSb, etc., are known, all of which are active against oxygen and water in the atmosphere. Easily corrodes to form hydroxides and oxides. As a result, various characteristics of the disk have been reduced with the passage of time, recorded information cannot be retained, and the life of the disk or the reliability of the disk has been reduced. To prevent this, Cr, Mo, W, etc. may be added to a CoTb alloy in JP-A-61-51806, and Cr, Ti, etc. may be added to an alloy comprising CoFe and a rare earth element in JP-A-61-87306. Is described.

[Problems to be solved by the invention]

The above-mentioned prior art does not consider that the magneto-optical recording film simultaneously suppresses corrosion caused by water and the like in the atmosphere and pitting caused locally, and the reliability of the magneto-optical recording member is not sufficient. There was a problem that was not.

An object of the present invention is to provide a magneto-optical recording member having high reliability and a method for manufacturing the same.

[Means for solving the problem]

In order to achieve the above object, the magneto-optical recording member of the present invention has a magneto-optical recording film for recording, reproducing, and erasing information by light, which contains Cr, and which is bonded to Cr in a portion near at least one interface. Nitrogen is present, and the central portion in the thickness direction is substantially free of nitrogen.

In order to achieve the above object, a magneto-optical recording member according to the present invention is characterized in that a magneto-optical recording film for recording, reproducing, and erasing information by light contains Cr, and has Cr and The structure is such that bonded nitrogen is present and the Cr concentration is increased near the interface.

Still further, in order to achieve the above object, the method for producing a magneto-optical recording member of the present invention includes the steps of: forming a Cr-containing magneto-optical recording film on a substrate by sputtering or electron beam evaporation; At the beginning and / or the end of the formation of the magneto-optical recording film, sputtering or electron beam evaporation is performed in an atmosphere containing nitrogen, and nitrogen bonded with Cr is present in the vicinity of at least one interface of the magneto-optical recording film. It is like that.

The magneto-optical recording film used in the present invention may have any composition as long as it has perpendicular magnetic anisotropy and contains Cr. For example, it is composed of rare earth elements and iron group elements,
A material containing Cr is used. Furthermore, Pt, Au, P
It is preferable to use at least one element selected from d and Rh and further use at least one element selected from Nb, Ti, Ta and Al. Usually, the total amount of the rare earth element and the iron group element is preferably at least 85 at%. In addition to such an alloy system, a Heusler alloy containing Cr or the like is used, and in this case, an alloy further containing Pt is preferable.

It is preferable that Cr is present at 0.5 at% or more near the interface of the recording film. The composition of the element may be changed in the thickness direction of the recording film.
It may be set to 0 at%. The bonding layer of Cr and N (hereinafter referred to as oxygen diffusion preventing layer) is 20 to
It is preferably present at a thickness of 200 mm. If less than 20 mm, the effect is not remarkable. Although the upper limit of the thickness may exceed 200 °, it is not preferable to increase the thickness unnecessarily since formation of this layer takes a long time.

In the oxygen diffusion preventing layer, N is preferably 0.1 to 4 at%, more preferably 0.2 to 3 at%. 0.
If less than 1 at%, the effect is not remarkable. Although the amount of N may exceed 4 at%, it is difficult to contain a large amount of N by a usual method.

[Action]

By providing a nitrogen layer bonded to Cr near the interface of the magneto-optical recording film, diffusion of oxygen and the like into the recording film is prevented, so that corrosion of the recording film can be suppressed.

〔Example〕

Hereinafter, the details of the present invention will be described in detail using examples.

Example 1 FIG. 1 shows a schematic diagram of a cross-sectional structure of a magneto-optical disk manufactured by the following method. On a substrate 1 having a guide groove, a silicon nitride base film 2 is formed by sputtering to a thickness of 600.
Was formed. The refractive index of the produced film was 2.5. Subsequently, a magneto-optical recording film 3 having a composition of Tb ₂₆ Fe ₄₄ Co ₂₀ Cr ₃ Pt ₇ was formed by a sputtering method. A TbFeCoPt alloy and Cr were used for the target, and Ar was used for the discharge gas. The film was formed by a dual simultaneous sputtering method. That is, first, RF power is applied to both targets at the same
A 0 ° film was formed. Then, the discharge gas was switched to N ₂ and the sputtering was continued without stopping the discharge to form an oxygen diffusion preventing layer 4 of about 200 °, thereby producing a magneto-optical disk.

The characteristics of the disk manufactured in this manner are as follows: carrier-to-noise ratio (C / N) 58 dB (pulse width: 500 nsec, frequency: 1 MHz, externally applied magnetic field: 400 Oe, N _A = 0.5, laser power 8 mW, rotation speed 1
20 rpm). The change with time of the error rate when this disk was left in 60 ° C.-90% RH was examined, and the results are shown in FIG. As a comparative example, a disk in which all the films were formed using only Ar was used. As a result, when the disk is left in this environment, using the disk of this embodiment
Even if left for 00 hours, the error rate does not increase and 2 × 10
^-6 (case / bit), while using the film of the comparative example, it increased about 3 times to 6 × 10 ^-6 (case / bit) after 3000 hours.

By the way, when the state analysis of nitrogen in the surface layer was performed by using XPS, Cr was not present as a simple substance but in a bonded state. In addition, a result suggesting the binding of Cr and nitrogen was obtained from the measurement by Mossbauer. The amount of nitrogen in the oxygen diffusion preventing layer is about 0.
It is 5 to 1 at%. The reason why the error rate is not increased as described above is that Cr nitride exists.
On the other hand, in the comparative example having no oxygen diffusion preventing layer,
Although the progress of corrosion is suppressed by the effect of the added element, it is insufficient. It can be seen that this is due to the difference in the density of the passive film mainly composed of Cr.

Embodiment 2 In this embodiment, a disk is manufactured using an ion beam sputtering apparatus, and a schematic view of the apparatus is shown in FIG. The apparatus shown in FIG. 4 is a schematic diagram of the cross-sectional structure of the manufactured disk, which is of a load lock type. In the figure, the main part for performing sputtering is shown. In normal sputtering, argon gas is introduced into the depot gun (gun for ionization), ionized, accelerated,
The alloy target Tb ₁₉ Nd ₅ Fe ₃₇ Co ₂₈ Cr ₄ Pt ₇ ) and its ions collide with each other to perform sputtering. To make a disc,
Prior to the formation of the recording film, nitrogen ions were emitted from a milling gun to clarify the surface of the substrate 1 with guide grooves. Then, while the milling gun is operated, the depot gun is also operated at the same time, a film is formed while milling is performed, and the oxygen diffusion preventing layer 4 is provided. Forming a film 3;
When the thickness reached 800 mm, milling was performed again, and a 200-degree oxygen diffusion preventing layer 4 was formed thereon to obtain a desired magneto-optical disk. As a comparative example, a magneto-optical disk in which a 1100 ° film was formed only by a depot gun without using a milling gun was used.

When the characteristics of this disk were evaluated, C / N = 52dB
(Frequency: 1 MHz, pulse width: 500 ns, external applied magnetic field: 400 O _e , N _A
= 0.5, recording laser power 10mW, readout laser power
1.5 mW). The magnetic characteristics of the recording film are as follows: Curie temperature: Tc = 250 ° C., compensation temperature: Tcomp = 90 ° C., force-rotation angle:
theta _{K =} 0.34 °, coercive force: was H _C = 9KO _e.

Next, FIG. 5 shows the results of the change over time of the error rate when the disk was left in 60 ° C.-90% RH. From this figure, the error rate of the disk manufactured according to the present invention is
2 x 10
^-6 (events / bit), but then increased gradually, reaching 3 × 10 ^-6 (events / bit) after 3000 hours. On the other hand, in the comparative example not using the present invention, 2 ×
The error rate, which was 10 ^-6 (cases / bit), gradually increased after 1000 hours, and 1 × 10 ^-5 after 3000 hours
(Cases / bit). Thus, it can be seen that the use of the present invention can significantly suppress the occurrence of errors.

By the way, the combination of Auger electron spectroscopy and Mossbauer spectrum was used to examine the bonding state between the metal material and nitrogen on the surface of the recording film, and it was found that mainly Cr and nitrogen in the material were strongly bonded. . In addition to Cr, Fe also partially bound to nitrogen. Since the compound of Cr and nitrogen is stable and dense and has a remarkably high protective effect, it may be provided not only as a surface layer but also as a protective film. The amount of nitrogen in the oxygen diffusion preventing layer was about 0.5 to 1 at%.

Example 3 The structure of the magneto-optical disk manufactured in this example is as follows.
As shown in FIG. 4 as in the second embodiment. The production of the disk was performed by a DC binary simultaneous sputtering method. FIG. 6 shows a schematic diagram of the apparatus. The equipment used was a deposition source
It consisted of a TbFeCoPT alloy target, two Cr targets, and an N ₂ plasma source. The discharge gas consisted mainly of Ar, and N ₂ for nitriding turned into suitable plasma. The disc was prepared by irradiating the surface of the substrate 1 with a guide groove with plasma from an N ₂ plasma gun and then discharging the Cr target to form a film of about 50 °.
As the current flowing to the target gradually decreases, Tb
The recording layer 3 was formed by discharging the FeCoPt target. Here, when the film thickness reached 100 °, the irradiation with nitrogen plasma was stopped. Then, when the total film thickness reaches 800 mm, T
The current applied to bFeCoPt was gradually reduced, and stopped completely when the total film thickness reached 900 °. Conversely, the current flowing through the Cr target was gradually increased, and the dose of N ₂ plasma was increased. Then, when the total film thickness reached 1100 °, the film formation was stopped. The composition of the recording layer is Tb ₂₆ Fe
₄₄ Co ₂₀ Cr ₃ Pt ₇ , the composition of the oxygen diffusion preventing layer is the same as that of the recording layer on the side in contact with the recording layer, with the amount of Cr increasing outward and the amount of other metal elements decreasing. , And the metal element is only Cr on the surface.

The C / N of the disc thus manufactured was 53 dB when measured under the same recording and reproduction conditions as in Example 2. A life test was performed using this disk, and the results are as shown in FIG. As a comparative example, one manufactured without irradiation with N ₂ plasma was used. As the test method, 60 as in Example 1
The change with time of the error rate when the disk was left in a temperature of -90% RH was measured. As a result, the disc manufactured without using the present invention had an error rate of 2 × 10 ^{-6 at the} initial stage of manufacture.
(Cases / bit) began to increase gradually after the elapse of 1000 hours, and reached 8 × 10 ^-6 (cases / bit) after 3000 hours. On the other hand, the error rate of the disk manufactured by using the present invention was 2 × 10 ⁻⁶ (items / bit) without any change both at the initial stage of the production and after leaving for 3000 hours.

When the bonding state of nitrogen and Cr on the surface layer of this disk was examined by XPS and Mossbauer, a result suggesting that Cr and nitrogen were also bonded was obtained. In addition, of the elements constituting the recording film of the disk manufactured in this example,
FIG. 8 shows the results of examining the distributions of Cr, N and O.
Oxygen exists only in the vicinity of the surface of the recording layer, and Cr has a composition gradient from the surface to the inside of the film, thereby further strengthening the bond with nitrogen and suppressing the peeling of the layer. A great protection effect was obtained. Incidentally, the amount of nitrogen in the oxygen diffusion preventing layer is about 0.5 to 1
at%.

Example 4 The structure of the manufactured disk is the same as that of Example 2, as shown in FIG. The production of the disk was performed by an electron beam (EB) vapor deposition apparatus. A PtMnSb alloy and Cr were used as the source of the evaporation. First, maintaining the disc substrate having a guide groove to 300 ° C., on this, C in an N ₂ atmosphere
When the r layer is stacked about 50mm, switch to Ar atmosphere
When tMnSb and Cr were simultaneously vapor-deposited and the film thickness became 900 °, the atmosphere was changed again to a N ₂ atmosphere and only Cr was vapor-deposited until 1100 °.

The life test of this disk was performed under the same environmental conditions as in Example 1. The life was evaluated based on the result of measuring the change in the thickness of the oxide layer on the surface by ellipsometry. The result is as shown in FIG. Here, as a comparative example, a disk in which all the films were formed in an Ar atmosphere was used. As a result, when the present invention was used, the film thickness of the surface layer was greatly increased up to 300 hours at first, but no growth of the surface layer was observed at all up to 3000 hours thereafter. On the other hand, in the comparative example in which the film was not formed in the N ₂ atmosphere, the film thickness of the surface layer changed greatly in 300 hours immediately after being left in the environment, and thereafter, the film thickness gradually increased. . This indicates that the corrosion has progressed over time. It was found that the progress of corrosion can be greatly suppressed by providing a bonding layer of Cr and N as seen in this example. The composition of the recording film was Pt ₃₀ Mn ₂₅ Sb ₃₈ Cr ₇ , and the amount of nitrogen in the oxygen diffusion preventing layer was about 1 to 1.5 at%.
It is.

As described above, the present invention does not depend on the type of the magnetic material and does not depend on the manufacturing method, and the compound layer in which Cr and N are bonded is present near the interface of the recording film, thereby improving the corrosion resistance. There is.

〔The invention's effect〕

According to the present invention, the presence of the compound layer in which Cr and N are bonded near the interface of the magneto-optical recording film has the effect of greatly improving the corrosion resistance without changing the magnetic characteristics. In addition, when the surface layer is formed easily by mainly changing the preparation atmosphere and a continuous film can be formed, a strong protective layer can be formed without peeling or cracking. Furthermore, the produced nitride layer, especially the compound of Cr and N, has remarkably high hardness and high mechanical protection performance.

[Brief description of the drawings]

FIG. 1 is a schematic view of a cross-sectional structure of a magneto-optical disk according to one embodiment of the present invention, FIGS. 2, 5, and 7 are diagrams showing a change with time of an error rate for explaining the present invention. 3 is a schematic view of an ion beam sputtering apparatus, FIG. 4 is a schematic view of a cross-sectional structure of a magneto-optical disk according to another embodiment of the present invention, and FIG.
FIG. 8 is a schematic view of a DC binary simultaneous sputtering apparatus, FIG. 8 is a view showing an analysis result of a magneto-optical disk according to another embodiment of the present invention, and FIG. 9 is an explanatory view for explaining the present invention. DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Underlayer 3 ... Magneto-optical recording film 4 ... Oxygen diffusion preventing layer

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Norio Ota 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo Inside Central Research Laboratory, Hitachi, Ltd. (56) References JP-A-62-14349 (JP, A)

Claims (4)

(57) [Claims] 1. A magneto-optical recording member having a perpendicular magnetic anisotropy and having a magneto-optical recording film for recording, reproducing and erasing information by light, wherein the magneto-optical recording film contains Cr,
A magneto-optical recording member characterized in that nitrogen bonded to Cr exists in at least one portion near the interface, and that the central portion in the thickness direction of the magneto-optical recording film contains substantially no nitrogen. 2. The magneto-optical recording method according to claim 1, wherein the composition of the magneto-optical recording film changes in the film thickness direction, and the Cr concentration increases near the interface of the magneto-optical recording film. Parts. 3. A magneto-optical recording member having a perpendicular magnetic anisotropy and having a magneto-optical recording film for recording, reproducing and erasing information by light, wherein the magneto-optical recording film contains Cr,
A magneto-optical recording member characterized in that nitrogen bonded to Cr is present in the vicinity of at least one interface, and the Cr concentration is increased in the vicinity of the interface. 4. Manufacture of a magneto-optical recording member for forming a magneto-optical recording film on a substrate having perpendicular magnetic anisotropy by sputtering or electron beam evaporation and capable of recording, reproducing and erasing information by light. The method wherein the magneto-optical recording film is Cr
And sputtering or electron beam evaporation is performed in an atmosphere containing nitrogen at the initial or final stage or both of the formation of the magneto-optical recording film, and at least one interface near the interface of the magneto-optical recording film contains Cr and A method for producing a member for magneto-optical recording, wherein bonded nitrogen is present.