JPH0785520A - Production of magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a magneto-optical recording medium with a small tilt as well as to attain a high rate of film formation, to unnecessitate a gas diffusion preventing mechanism between chambers in the case of production in a multi- chamber sputtering device and to enhance the throughput of production. CONSTITUTION:At least a magneto-optical recording layer and a dielectric layer are formed on a substrate. In the resulting magneto-optical recording medium, the dielectric layer is formed from an SiC target having <=0.05OMEGAcm resistivity and each of the constituent layers of the recording medium are formed by DC sputtering with only gaseous Ar.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium and its manufacturing method. More specifically, it relates to a highly productive magneto-optical recording medium.

[0002]

2. Description of the Related Art Among optical recording media, rewritable types that can be written and erased are conventionally known as phase change type, photochromic type, magneto-optical type and the like. Among these rewritable types, the magneto-optical type is now becoming popular because it is excellent in writing speed and repetition resistance. As a material for the magneto-optical recording film (MO film) used in this magneto-optical recording medium, a rare earth-transition metal alloy film (RE
TM film) is often used.

This RETM film has a problem that it is inferior in corrosion resistance and the car rotation angle is small. Therefore, in order to solve the problem, a dielectric layer has been conventionally provided to improve the corrosion resistance, and at the same time, the interference is caused by light interference. The method of increasing the rotation angle and adjusting the reflectance has been used.

As the MO film, in addition to the RETM film, Pt /
An artificial lattice film such as Co has also been proposed. Also in a magneto-optical recording medium using this artificial lattice film, a method of providing a dielectric layer to increase the car rotation angle and adjusting the reflectance is used.

Transparent and highly chemically stable silicon nitride is often used as the material for the dielectric layer. As an example of the structure of a magneto-optical recording medium using silicon nitride, the refractive index of silicon nitride is set to about 2.0 to 2.2, and substrate / silicon nitride (about 80 to 120 nm) / RETM (20 to 30 n
m) / silicon nitride (about 15 to 35 nm) / metal reflective film (about 30 to 100 nm). Each layer is usually formed by a multi-chamber sputtering apparatus having a plurality of chambers according to the layer to be formed.

[0006]

At this time, the dielectric layer made of silicon nitride is usually formed by high frequency reactive sputtering using a silicon target in a mixed gas of argon gas and nitrogen gas. In order to use a mixed gas,
It was difficult to form a film having a high film formation rate and a small stress, such as DC sputtering. Further, when a plurality of types of films are formed by a multi-chamber sputtering apparatus, the characteristics of the RETM film deteriorate when nitrogen is mixed therein. There was a problem that it had to be prevented. In addition, there is a problem in that it takes time to transfer the disk due to this partition, and the productivity is reduced.

Further, since the deposition rate of the silicon nitride film is lower than the deposition rate of the RETM film and the metal reflection film,
The formation of a silicon nitride film has been the rate limiting factor for mass production throughput. Therefore, a method has been used in which the silicon nitride film is formed in a plurality of chambers so that the film forming time in each chamber is made uniform to increase the throughput.

[0008]

In view of the above-mentioned situation, the inventors of the present invention have conducted intensive studies and, as a result, formed a dielectric layer of a magneto-optical recording medium from a SiC target having a resistivity of 0.05 Ωcm or less, In addition, productivity is improved by forming each layer constituting the magneto-optical recording medium by sputtering with only argon gas, and when a multi-chamber sputtering apparatus is used, a partition between chambers is not required. This has led to the completion of the present invention.

That is, according to the present invention, in a method of manufacturing a magneto-optical recording medium in which at least a magneto-optical recording layer and a dielectric layer are formed on a substrate by sputtering, the dielectric layer has a resistivity of 0.05 Ωcm or less. The present invention relates to a method of manufacturing a magneto-optical recording medium, which is composed of a target and each layer constituting the magneto-optical recording medium is formed by DC sputtering using only argon gas.

The present invention will be described in detail below.

The structure of each layer of the magneto-optical recording medium of the present invention is not particularly limited as long as it has at least a magneto-optical recording layer and a dielectric layer, but the magneto-optical recording layer is protected and the magneto-optical recording medium is protected. In order to improve the characteristics of (1), it is preferable to adopt a structure of substrate / dielectric layer / magneto-optical recording layer / dielectric layer / reflection layer. Further, an overcoat layer and / or a hard coat layer may be provided, and these media may be laminated.

Examples of the substrate of the present invention include transparent resins such as glass, polycarbonate, acrylic resins represented by polymethyl (meth) acrylate, and olefin resins.

The dielectric layer in the present invention can be formed from a SiC target by DC sputtering. The atomic ratio of Si to C is 47/53 to 53 /.
47, preferably 50/50, and the resistivity of the SiC target is 0.05 Ωcm or less, preferably 0.02 Ω.
cm or less. If the resistivity exceeds 0.05 Ωcm, abnormal discharge is likely to occur or the discharge is likely to be interrupted, which is not preferable. Those containing impurities such as boron can be used as these targets.

Examples of the magneto-optical recording layer in the present invention include TbFe, TbCo, TbFeCo, DyCo,
DyFeCo, GdFe, GdFeCo, TbFeN
It is possible to use an alloy composed of a rare earth metal such as i and GdTbFeCo and an iron group transition metal. Further Cr, T
It may contain additives such as i, Al, Ta, Mo, Bi, and Cu, or may contain other impurities.

When a reflective layer is provided, Al, Cr, A
It is possible to use a single element such as g, Ti, or Mo, or a metal composed of a plurality of elements.

In the present invention, each layer as described above is formed by DC sputtering with only argon gas. Through such a manufacturing method, not only the productivity is improved, but also in a multi-chamber sputtering apparatus which does not have a mechanism for preventing gas diffusion between the chambers in a sputtering apparatus including a plurality of chambers. It becomes possible to manufacture a magnetic recording medium. Of course, even in an apparatus having a gas diffusion preventing mechanism, the present invention can be carried out by forming a film with a gate valve normally provided for preventing gas diffusion being opened.

Further, since DC sputtering is possible, a high film forming rate can be obtained, and the stress of the obtained film is lowered, so that a magneto-optical recording medium having a small tilt can be manufactured.

[0018]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited thereto.

Reference Example 1 As the sputtering apparatus, a multi-chamber sputtering apparatus capable of partitioning the chambers with a gate valve was used. The chamber is composed of a load chamber, a load chamber, a vacuum storage chamber, a first dielectric layer deposition chamber, a magneto-optical recording layer deposition chamber, a second dielectric layer deposition chamber, and a reflection chamber. It consists of seven layers, a layer deposition chamber and an unloading chamber. SiC (Si: 50 atomic%, C:
A target of 50 at%, resistivity: 1.5 × 10 ^-2 Ωcm) was installed. In the RETM film forming chamber, Tb and FeCo (F
Two targets of e: ₉₂ atomic% and Co: 8 atomic% were set. An Al target was installed in the reflection film forming chamber.

Before manufacturing the magneto-optical recording medium, a SiC film was formed on the glass substrate by DC sputtering in the first dielectric layer forming chamber, and the film forming rate was obtained. The film forming conditions were Ar gas only and gas pressure was 0.5 P.
a, input power was 1000 W. Also under the same conditions
A SiC film was formed on glass and the stress of the film was determined. The results are shown in Table 1.

Reference Example 2 The same procedure as in Reference Example 1 was performed except that RF sputtering was used instead of DC sputtering in the first dielectric layer film forming chamber, and the film forming rate and film stress were measured. The results are shown in Table 1.

Reference Example 3 In the first dielectric layer deposition chamber of the apparatus of Reference Example 1, an attempt was made to deposit a SiN film by performing DC sputtering and RF sputtering on a glass substrate. The film forming conditions were an argon / nitrogen mixed gas, a gas pressure of 0.5 Pa, and an input power of 1000 W.

In DC sputtering, the discharge was unstable and continuous discharge was impossible, so the deposition rate was determined only for RF sputtering. A SiN film was formed on the cover glass by RF sputtering under the same conditions, and the film stress was determined. The results are shown in Table 1.

[0024]

[Table 1]

Example 1 Using the sputtering apparatus used in Reference Example 1, 1.6 μ
A magneto-optical recording medium was formed by DC sputtering using a polycarbonate substrate having a diameter of 86 mm and having guide grooves of m pitch. The medium is composed of a substrate / SiC dielectric layer (80 nm) / TbFeCo magneto-optical recording layer (23 nm).
/ SiC dielectric layer (30 nm) / Al reflective layer (50 n
m), the composition of the magneto-optical recording layer is Tb ₂₀ (Fe ₉₂ Co ₈ )
₈₀ . The sputtering gas is Ar in all layers
Gas was used, the gas pressure was 0.5 Pa, and the input power at the time of forming the dielectric layer was 1000 W.

For film formation, gas is introduced into all of the first dielectric layer film forming chamber, the magneto-optical recording layer film forming chamber, the second dielectric layer film forming chamber, and the reflective layer film forming chamber, and discharge is continued at a predetermined power. In this state, with all the gate valves between the chambers open, the substrate was moved from the first dielectric layer film forming chamber to the reflective layer film forming chamber to sequentially form each layer. That is, even when the first dielectric layer was formed, the other film forming chambers were also discharged. The same applies to film formation other than the first dielectric. However, while the sputtering of one layer was completed and the substrate was transferred to the next film forming chamber, the gas was continuously introduced into each sputtering chamber, but the discharge was stopped.

The recording / reproducing characteristics and tilt of the obtained magneto-optical recording medium were measured. Recording / reproduction characteristics have a wavelength of 780 nm, N
Marker length 0.75 μm with an optical system evaluator with A = 0.53.
The carrier-to-noise ratio (CNR) was determined under the following condition. The tilt was obtained by sampling at an angle of 5 degrees in the circumferential direction and at an interval of 4 mm in the radial direction with an evaluation system of an optical system having a wavelength of 780 nm and NA = 0.53. The results are shown in Table 2.

Comparative Example 1 Recording and reproducing characteristics and tilt of the obtained magneto-optical recording medium were measured in the same manner as in Example 1 except that RF sputtering was used instead of DC sputtering. The results are shown in Table 2.

Comparative Example 2 1.6 μm was obtained by the sputtering apparatus used in Reference Example 1.
A magneto-optical recording medium was formed by RF sputtering using a 86 mm diameter polycarbonate substrate having m-pitch guide grooves. The medium is composed of a substrate / SiN dielectric layer (100 nm) / TbFeCo magneto-optical recording layer (23 n
m) / SiN dielectric layer (30 nm) / Al reflective layer (50
nm), the composition of the magneto-optical recording layer is Tb ₂₀ (Fe ₉₂ C
o ₈ ) ₈₀ . Note that film formation was performed with all the gate valves closed, gas was introduced only in the sputtering chamber, and no gas was introduced or discharged in the other sputtering chambers. The SiN dielectric layer was sputtered with Ar / nitrogen mixed gas in the first and second dielectric layer deposition chambers, and the layers other than the SiN dielectric layer were sputtered with argon gas only. The gas pressure was 0.5 Pa and the input power was 1000 W.

Table 2 shows the results of measuring the characteristics and tilt of the obtained magneto-optical recording medium by the same method as in Example 2.

Comparative Example 3 In Comparative Example 2, all the gate valves were opened and sputtering was performed. While opening the gate valve,
Each layer was formed in a state where gas was introduced into all sputtering chambers and discharge was continued. Note that the gas was continuously introduced into each sputtering chamber, but the discharge was stopped, while the sputtering of each layer was completed and the substrate was transported.

The results of measuring the characteristics and tilt of the obtained magneto-optical recording medium by the same method as in Example 2 are shown in Table 2.

[0033]

[Table 2]

[0034]

According to the present invention, a magneto-optical recording medium having a high film formation rate and a small tilt can be obtained. Furthermore,
When a multi-chamber sputtering apparatus is used for production, a mechanism for preventing gas diffusion between the chambers is not required, so that the production throughput can be improved.

[0035]

Claims (1)

[Claims] 1. A method for manufacturing a magneto-optical recording medium comprising a substrate on which at least a magneto-optical recording layer and a dielectric layer are formed by sputtering, wherein the dielectric layer has a resistivity of 0.05Ω.
A method of manufacturing a magneto-optical recording medium, comprising a SiC target having a size of 1 cm or less, and each layer constituting the magneto-optical recording medium is formed by DC sputtering using only argon gas.