JPH0237545A - Production of magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To stably form a composite film having a compsn. in which an oxygen content is well compounded with one evaporating source by gradually increasing the electric power for film formation form low to high electric power in forming a dielectric layer consisting of an oxide and nitride on a substrate. CONSTITUTION:Low electric power sputtering is executed in a gaseous mixture atmosphere composed of N2 and Ar after evacuation to a prescribed degree of vacuum at the time of forming the dielectric layer 22 consisting of an AlN film by a reactive sputtering method on the polycarbonate substrate 21. The substrate 21 having the high oxygen content and the aluminum nitride layer 22a having the good adhesiveness to the substrate 21 are formed in this way. The oxidation is suppressed and the aluminum nitride layer 22b having a high nitrogen content is formed when the electric power for the film formation is gradually increased. An intermediate layer 22c in which the oxygen concn. decrease gradually in thus formed between the layers 22a and 22b. The recording layer 23 and a protective layer 24 are provided on the layer 22. The stable film formation is stably executed with the one evaporating source in this way and the recording medium having the high reliability is obtd.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for manufacturing a magneto-optical recording medium for recording and reproducing information using laser light or the like, and more specifically to a method for manufacturing a magneto-optical recording medium for recording and reproducing information using a laser beam or the like. The present invention relates to a method for manufacturing a magneto-optical recording medium characterized by a method for forming a film.

<Prior Art> Optical recording media have attracted attention in recent years as a medium capable of high-density, large-volume recording.

For example, magneto-optical recording media are one of them. Magnetic materials used for the recording layer of magneto-optical recording media include GdFe,
TbFe, TbFeCo, QdTb
Fe, TbCo, Ndoy
FeCo, NdFeGdCo, etc.
Amorphous magnetic alloy films of rare earths and transition metals are seen as promising.

However, since rare earth elements such as Tb have poor corrosion resistance, it is necessary to prevent oxidation after forming the recording layer. As a method for preventing this oxidation, AJIN and s+o are applied above and below the recording layer.

Sf Oz, S! 3N4, TiN, or the like, or the recording layer is subjected to nitriding, carbonizing, hydrogenating, or fluoriding treatment, or pt, 1. It has been reported that it is effective to use a magnetic material to which Al or the like is added.

Among the methods described above, the method of subjecting the recording layer to various treatments or adding various metals causes a decrease in the Kerr rotation angle etc. at the initial stage of film formation, and there is room for further study in the future.

On the other hand, the method of providing a protective layer has good corrosion resistance and a thin film.

Optimization of the refractive index also has the effect of enhancing the Kerr rotation angle, and is an effective method for preventing oxidation of the recording layer after film formation.

However, while investigating the changes in characteristics of magneto-optical recording media with a protective layer over time, such as during weather tests, it was discovered that 5tO
Although the initial characteristics of oxide-based films such as z were good, abnormalities occurred in coercive force and Kerr rotation angle over time. The cause of this is presumed to be the generation of free oxygen from the oxide film.

Furthermore, when non-oxide-based materials such as SiN, AfN, ZnS, etc. are used as a protective layer, the adhesion to the substrate is poor, and even if the adhesion is good, cracks may occur, leaving room for further study. Ta.

Therefore, a composite film was devised, consisting of an oxide film with good adhesion on the substrate side and a nitride film with good corrosion resistance on the medium side, which realized a highly reliable optical recording medium with stable recording and reproducing characteristics. It has been reported (Japanese Unexamined Patent Publication No. 62-298037).

<Problems to be Solved by the Invention> However, conventional methods for creating such composite films require the use of dual evaporation equipment, gas exchange during film formation, etc., which are not stable in terms of cost. The situation was disadvantageous from the viewpoint of film formation as well.

In view of the above problems, the present invention provides a method for manufacturing a magneto-optical recording medium that makes it possible to form a protective layer of a stable composite film (all dielectric layers ideal for magneto-optical recording media) using a single evaporation source. It is something to do.

<Means for solving the problem> The above object is achieved by the present invention as described below. That is,
In the present invention, a dielectric layer and a recording layer made of an amorphous rare earth-transition metal alloy film are sequentially formed on a polymer substrate, and the dielectric layer has a high oxygen content on the substrate side and a recording layer on the recording side. When forming the dielectric layer of a magneto-optical recording medium made of a low dielectric material, a reactive vapor phase thin film formation method with one evaporation source is used, and after evacuation to a predetermined ultimate vacuum, a predetermined reactive gas is introduced. The method of manufacturing a magneto-optical recording medium is characterized in that the dielectric film is formed in the reactive gas atmosphere while adjusting the film-forming power so that the oxygen content becomes the same.

The present invention was made by focusing on the dependence of the film composition of a dielectric film on the formation power. That is, when performing reactive sputtering in a nitrogen atmosphere, for example, a film formed with low power is severely oxidized by residual gas contained in the chamber, substrate, etc., resulting in a film with good substrate adhesion and high oxygen content. This is used on the substrate side. On the other hand, selective oxidation is suppressed in films formed using high power, resulting in a film with a high nitrogen content. This is used for the recording layer side.

The film formation power depends on the film formation method and chamber volume.

Although there is no particular limitation as it varies depending on the pretreatment method of the substrate, the pumping speed of the vacuum system, etc., for example, an RF magnetron sputtered layer is used and the ultimate vacuum degree is 2 x 10'.
When forming a film by introducing nitrogen gas into the Torr after exhausting it, on the low power side, the lower the power, the better the oxidation progresses, but taking into consideration the relationship with the film forming speed, the
On the high power side, the higher the power, the lower the oxygen content of the film and the more nitriding progresses, but considering the influence of radiant heat from the target on the substrate, it is preferably about 12 W/cIi. In addition,
The oxygen content of the film depends on the amount of gas remaining after evacuation, in other words, the degree of vacuum achieved during evacuation. The degree of vacuum reached at this point is 10
6 T orr or less is preferable from a practical standpoint.

By the way, the thin film forming method in the present invention is not particularly limited as long as it is a vapor phase thin film forming method in which III is deposited on the substrate from the gas phase, as typified by the above-mentioned sputtering method, and vacuum evaporation methods may be used in addition to the sputtering method.

Known vapor phase thin film forming methods such as the EB method, CVD method, and ECR method can also be applied. Note that reactivity refers to the formation of a predetermined compound thin film while introducing a predetermined reactive gas and causing a reaction in these vapor phase thin film forming methods.

Moreover, the evaporation source is Si constituting the dielectric layer, which will be described later.
Even if it is made of metals such as AfL, Ti, In, Si A, semimetals, or alloys thereof, compounds such as nitrides, carbides, fluorides, sulfides, etc., depending on the composition of the dielectric layer. It may be a fired body. The reactive gas used for forming the film may be a reactive gas depending on the structure of the dielectric layer, such as a nitride containing nitrogen gas.

Incidentally, the magneto-optical recording medium to which the present invention is applied may be one in which a dielectric layer and a recording layer are formed on a substrate, and a metal layer, a protective layer, a protective flat plate, etc. may be further provided thereon as necessary. Needless to say, it is okay.

The dielectric layer may be a dielectric material having a high oxygen content on the substrate side and a low oxygen content layer on the recording layer side.

Well-known metals and semimetals are used as dielectrics.

or nitrides, carbides, and fluorides of these alloys.

Examples include sulfides. As examples of metals, semimetals, and alloys thereof, Si, Al, and SiAl nitrides are preferably used from the viewpoint of durability and enhancement effect.

Oxygen is mainly contained in the form of oxides of metals, semimetals, or alloys thereof constituting the above-mentioned dielectric, but the form in which it is contained is not particularly limited. Further, the pattern of change in the content of 1 in the layer thickness direction is not particularly limited, but it is preferable from the viewpoint of the characteristics of the entire layer that at least in the change portion, the change is not step-like but gradually decreases. The oxygen content on the substrate side is preferably at least 10-odd atomic percent or more, and on the recording layer side, the lower the oxygen content is, the better, but it is preferably several atomic percent or less.

The recording layer may be made of an amorphous alloy film of rare earth metals and transition metals, and the above-mentioned known materials can be used.

Examples of the substrate include polymer resin substrates such as PMMA, polycarbonate, and epoxy, and glass substrates, but polycarbonate is particularly preferably used because it is inexpensive and has good temperature characteristics and dimensional stability.

<Function> With the dielectric film forming method described above, a composite film of oxide and nitride, which has good adhesion to the substrate and can prevent deterioration of the recording layer due to oxidation, is created using a single evaporation source. It becomes possible to form a film stably, and a highly reliable magneto-optical recording medium with stable recording and reproducing characteristics can be obtained at low cost.

<Example> Hereinafter, an example of the present invention will be described with reference to the drawings.

Figure 1 shows a known two-pronged RF device with a substrate and a target placed opposite each other.
AuN11 film formed using magnetron sputtering equipment
This figure shows the dependence of the film composition on the film formation power. 1st
In the figure, (1) is the aluminum content layer, (2) is the nitrogen content, and (3) is the oxygen content.

The above A1Ni1 film formation method uses A! L (5N
) is a reactive sputtering method in a mixed gas atmosphere with a mixing ratio of Nz/Ar = 1.0 (7), the sputtering gas pressure is 2 x 10-3 T Orr, and the distance between the substrate and target is 11α , the ultimate vacuum is 4 x 10'
It was set as Torr. Further, film composition analysis was performed using AES. As shown in Figure 1, the oxygen-containing layer is 3
It was confirmed that it exceeds 0 at (atomic) % and becomes almost Qat % in the case of At cassata. It was also confirmed that the nitrogen content had a tendency opposite to that of oxygen.

FIG. 2 is a sectional view showing the structure of a magneto-optical recording medium according to an embodiment of the present invention. In FIG. 2, (21) is a polycarbonate substrate, (22a).

(22b) is the low power (1,
2W/ail) aluminum nitride layer (approximately 400 people)
and Aluminum nitride II (approximately 400 people) formed by high power (6.0 W/cd') film formation, (23) is Record 1 consisting of an amorphous alloy of Tb23Feg6COu (subscripts are atomic %) formed by the same sputtering method. 400 people), (
24) is the protective layer T formed by the same sputtering method.
+ 11 (1000 people).

Here, when increasing the power from low power to high power in forming the dielectric layer (22), the power was gradually increased in the discharge state without stopping the discharge. If you do this (22a
) and (22b), it was revealed from the AES results that an intermediate III (22c) was formed in which the consistent oxygen content gradually decreased by 81 degrees.

FIG. 3 shows the results of a weather resistance test at 70° C. and 90% RH for the magneto-optical recording medium of the above embodiment according to the present invention. When the magnetic material of Normal Recording II (23) is oxidized, the coercive force and Kerr rotation angle decrease, but as shown in FIG. No cracks or deterioration of coercive force or Kerr rotation angle were observed after 1000 hours.

For comparison, FIG. 4 shows the change over time in the coercive force of a magneto-optical recording medium in which the dielectric layer (22) shown in FIG. 2 was entirely replaced with a low-electrical scattering film (800 layers). Although no cracks were observed in the medium, deterioration of characteristics was confirmed after about 50 hours as shown in FIG.

Similarly, all of the dielectric layer (22) in FIG. 2 was sputtered at high power! ! A weather test was also conducted on the magneto-optical medium that had been replaced by the same person (800 people), but cracks appeared in the medium after just 10 hours.

Note that the sputtering gas pressure is high (10″2T orr level).
When forming a dielectric protective film by sputtering with low power, it is possible to obtain a film with a similar composition to that of a film sputtered with low power, that is, a film with a high oxygen content, but it has been confirmed that the film is sparse and has poor durability. There is.

<Effects of the Invention> As described above, according to the present invention, the structure is simple and the productivity is high, and a composite film suitable for a magneto-optical recording medium can be stably formed using a single evaporation source, and the durability is improved. An excellent magneto-optical recording medium can be obtained. In this way, the present invention makes a significant contribution to the practical application of magneto-optical recording media.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the film formation power dependence of the film composition of the aluminum nitride film of the example, FIG. 2 is a side cross-sectional view showing the structure of the magneto-optical recording medium of the example, and FIG. FIG. 4 is a graph of changes over time in characteristics indicating durability of a magneto-optical recording medium prepared as a comparative example. 21: Substrate 22: Dielectric layer 23: Recording layer 24: Protective layer

Claims (1)

[Claims] 1. A dielectric layer and a recording layer made of a rare earth-transition metal amorphous alloy film are sequentially formed on a polymer substrate, and the dielectric layer has a high oxygen content on the substrate side. When forming a dielectric layer of a magneto-optical recording medium consisting of a low dielectric material on the recording side, a reactive vapor phase thin film formation method using one of the evaporation sources is used, and after evacuation to a predetermined ultimate vacuum, a predetermined reactivity is applied. A method for manufacturing a magneto-optical recording medium, characterized in that the dielectric film is formed by introducing a gas and adjusting the film-forming power to the oxygen content in the reaction gas atmosphere. 2. The method of manufacturing a magneto-optical recording medium according to claim 1, wherein the reactive gas is nitrogen gas to form a dielectric made of oxygen-containing nitride. 3. The method for manufacturing a magneto-optical recording medium according to claim 1 or 2, wherein the vapor phase thin film forming method is a sputtering method. 4. The method for manufacturing a magneto-optical recording medium according to claim 3, wherein the ultimate degree of vacuum is 10^-^5 Torr or less. 5. The method for manufacturing a magneto-optical recording medium according to claim 2, wherein the dielectric layer is Si, Al, Ti, or an oxygen-containing nitride of Si and Al.