JPS60191451A - Manufacture of photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To improve durability by etching the surface of a substrate by sputtering before the sputtering of a magnetic thin film is carried out. CONSTITUTION:The glass substrate 1 is held by the substrate holder of a bipolar RF sputtering device, and a target (several 10X10mm.<2> terbium chips 3 arranged uniformly on 100mm.phi cobalt disk 2; Tb0.27C0.73) is placed on a packing plate or copper. Then, vacuum frost is discharged and gaseous Ar is admitted; and the glass substrate 1 is etched by sputtering for >=10min with a shutter 5 closed. Then, the shutter is opened to perform primary sputtering. When an angle thetak of Kerr rotation and an angle thetaF of Faraday rotation are measured while the film thickness of a Tb-Co amorphous alloy film after sputter etching is performed for 60min is varied, an ineffective layer having no photomagnetic effect is obtained below 60Angstrom film thickness. Therefore, the film thickness of a Tb-Co amorphous alloy recording layer should be at least >=60Angstrom . Consequently, the Tb-Co amorphous alloy recording layer formed on the sputter-etched substrate has high acid resistance.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a magneto-optical recording medium using a compensated temperature recording method, and in particular to the production of a magneto-optical recording medium having a magnetic recording layer made of a terbium-cobalt amorphous alloy. It is about the method.

(Prior art) Erasable and rewritable so-called E-IJR, AW recording media are used for video discs, audio discs, document file discs, internal and external memories of computers, and various research and development efforts are underway on these media. There is.

There are various types of E-DRAW recording systems, but when a magneto-optical recording system is used, an amorphous alloy of dilute transition metals is mainly used for the recording medium and j-.

Many combinations of this amorphous alloy are already known, including G (l-Co, G d-F e, T
b −F e , G d −T l) −F e
, T b -P e -Co, etc. are mainly studied. Depending on the recording method, these magneto-optical recording media are classified into Curie temperature recording and compensated temperature recording.
In either method, the magnetization t of the amorphous alloy described in -
It is necessary to align perpendicularly to the i-plane, and this perpendicularly magnetizable film can be formed by vapor deposition, sputtering, or the like.

Oxidation stability is currently a particular problem in perpendicularly magnetizable films of these rare earth-transition metal amorphous alloys. That is, these amorphous alloys are oxidized by particles in the air and lose their perpendicular magnetization characteristics, so there is a problem that they cannot be put to practical use with recording media that require long-term storage stability.

As a result of continuing research on amorphous alloys that do not contain Fe, which are susceptible to oxidation, the inventor discovered that an amorphous alloy of Tb-〇〇 has excellent oxidation resistance stability, and completed the present invention. .

Conventionally, Qd-Co systems have been mainly studied as perpendicularly magnetizable films of rare 10m-transition metals that do not contain Fe.
There are few studies on the T b -Co system, and although there are some similarities in the properties and single action of the two, it is possible that the two types of alloys exhibit unpredictable single action depending on the difference in alloy system, just as in the case of general alloys. be.

T b -Co amorphous alloy has perpendicular magnetization characteristics and the composition region where it has perpendicular magnetization is T
It is already known that when l~, expressed as bxCo+-x, ), pp. 70-72).

However, even if T b -Cof of this composition is simply formed into a thin film by well-known vapor deposition or sputtering, it is not possible to obtain a perpendicularly magnetizable film that is stable over a long period of time. () cannot be done. The present inventor discovered that an ineffective layer that does not function for perpendicular magnetization exists in a TI)-Co amorphous alloy film,
Furthermore, we discovered a method to improve this oxidation resistance function1.
7.

(Object of the Invention) Therefore, an object of the present invention is to provide a method for manufacturing a vertically magnetizable T b -Co amorphous alloy film that has excellent durability.

(Structure of the Invention) The present invention provides a method for manufacturing a magneto-optical recording medium by forming an a-type thin film of a terbium-cobalt amorphous alloy having a compensated temperature recording composition on a substrate by a sputtering method. The method is characterized in that the surface of the substrate is subjected to sputter etching before performing the tsuttering.

Generally, a glass plate is used as the above-mentioned substrate, but it is not limited to glass as long as it is made of a material that can be splattered and swayed. Metal plates such as aluminum and stainless steel, or metal plates such as polymethyl methacrylate and polycarbonate can also be used. It may be a plastic plate, or a tape or sheet such as polyester.

T I) The composition ratio of
= 0.2 to 0.35, and in the case of Suba Tsutaring, x = about 0.15 to 032. Generally, the compensation temperature has a strong dependence on the composition, but the composition ratio can be determined according to the desired compensation temperature.

=5- The above TbC0 amorphous film is preferably made by sputtering. Preferably, this sputtering uses bias sputtering that applies a bias to the substrate. This bias sputtering is described in detail in J, J, A, , P, 1.9 (19so) 1807 by the present inventors.

Since the following is already known matter and does not form part of the present invention, details will be omitted. If necessary, please refer to the above-mentioned documents.

(A-bed of the invention) A feature of the present invention is that the surface of the substrate is sputter-etched before sputtering the thin film.

This sputter etching of the substrate surface can be carried out by introducing Ar gas into the sputtering apparatus, and then subjecting the substrate to sputter etching with Ar gas while the shutter is closed.

The durability of the perpendicularly magnetizable film of the T b -Co-based amorphous alloy is improved by this sputter etching. That is, by etching the substrate with Ar using the spatter 6, impurities adsorbed on the substrate, such as oxygen and oil, are removed, and the surface of the substrate is purified.

It is preferable that the time for performing the sputter etching described above is 10 minutes or more. Sufficient purification cannot be achieved in less than 10 minutes. Furthermore, there is no significant difference in the results even if the test is carried out for more than 10 minutes.

By performing this spacing notching, the Kerr rotation angle increases from 0.16 in the case where it is not performed to 0.27, approximately 1.7 times.

The effect of this suba-tsuta etching is particularly remarkable in the case of Tb-(2) amorphous alloy;
There is almost no effect with b-P e amorphous metal.

The present inventor formed a T b -Co amorphous alloy with varying film thickness on a sputter-etched substrate by sputtering, and measured the magneto-optical effect (Kerr rotation angle θk and Faraday rotation angle θF) [ As a result, it was found that there was a film thickness in which no magneto-optical effect could be obtained, that is, an ineffective layer, and that the film thickness of this ineffective layer was 60A. Therefore, the thickness of the Tb--Co amorphous alloy recording layer must be at least 60A or more.

The Tb-(:,o amorphous alloy recording layer formed on a sputter-etched 17 substrate according to the present invention exhibits extremely high oxidation resistance or stability, i.e., 110
Even when the above-mentioned recording layer was annealed in the atmosphere at a temperature raised to 1°C, no oxidation deterioration was observed on the side of the substrate to which the notching was performed. On the other hand, on the side exposed to the atmosphere, the thickness of the ineffective layer was about 120A, but the oxidation deterioration of J2 could not be alleviated even after long-term annealing.

The present invention will be explained below using examples.

Embodiment The well-known bipolar pole 11 shown in FIG. F sputtering equipment (UL
VAC8B R-] 104 E )+7) Hold the glass substrate (1) in a substrate holter and place a target (1007 nm cobalt disk (2) on a 1.OX 10 rnrn," terbium chip ( 3) Several sheets evenly arranged; T b
O, 27CO, 73) were placed.

After evacuating the vacuum chamber to 5×1O-7 TOrr, introduce Ar gas and set the A and r gas pressures to 10 mTOrr.
With the shutter (5) closed, move the glass substrate (1) to A.
Sputter etching was performed using r gas.

The relationship between the time (minutes) of conosputter etching and the force/rotation angle θk (degrees) of the glass substrate with the finally obtained Tb-C0 amorphous alloy recording layer with a film thickness of 12μ is shown in Figure 2. It is. It can be seen that when the suba/vine etching time is increased to 10 minutes or more, θk measured from the glass side is greatly improved.

For comparison, the measurement results of a Tb-Pe amorphous alloy formed in the same manner are also shown in FIG. It is clearly seen that the effect of sputter etching when using Co is more significant than that of Fe, which is easily oxidized.

Incidentally, when performing the above-mentioned subasotae notching, the contacts of the matching circuits 6 and 7 may both be set to E.

Next, the shutter was opened and main sputtering was performed. The Kerr rotation angle 01 ((degree)) and the Faraday rotation angle OF(
The results of measuring the temperature are shown in Figure 3.

In this Figure 3, Ok(G) is from the glass substrate side,
Still, θk(F) is a value measured from the Tl)-CO pupil side. It can be seen from FIG. 3 that a film thickness of 60 Å or less becomes an ineffective layer with no magneto-optical effect.

Further, FIG. 4 shows the values of saturation magnetization (M s ) and perpendicular coercive force (Hc) for each film thickness.

As the film thickness decreases, Ms increases and I-1c decreases, so in the above invalid layer, Tb is selectively oxidized and shifts to CO-ch 11111, which deviates from the range of perpendicular magnetization composition. This is expected to occur.

In order to investigate the oxidation stability of the Tb-C0 amorphous alloy recording layer by sputter etching according to the present invention, 1
Figure 5 shows the measurement of the change in the magneto-optical effect of the recording layer in the atmosphere as the temperature rose to 00°C.

FIG. 5 was taken for a recording layer with a film thickness of 800 Å, and θk (G) is the value measured from the glass substrate side, and -10-θk (F) is the value measured from the amorphous alloy layer side. As can be seen from this figure, θk(G
) is extremely stable over time, and θk(P) on the amorphous alloy layer side is still saturated at approximately 0.12. The thickness of the oxide layer at this time (1) can be estimated to be approximately 12 OA from FIG. 3 above. This value rarely changes after that.

Although the present invention has been described above with reference to special embodiments, the present invention is not limited thereto.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of a well-known R,F sputtering apparatus used in the present invention. FIG. 2 is a diagram showing the effect of the notching according to the present invention, where the curve A id T b is the relationship between the Kerr rotation angle (degrees) and the notching time (minutes) when read from the glass plate side of the Co film. The relationship is shown for the curve BidTb-Fe. Figure 3 shows the Kerr rotation angle (θk(G
) Value read from the glass plate side, θk(F): T I)-
Co value read from the clear side) and Faraday rotation angle (θ
A diagram showing each relationship with F). Fig. 4 is a diagram showing the relationship between saturation magnetization (Ms) and perpendicular coercive force (t(c)) with respect to the Tb-Co film thickness.
This is a diagram showing the relationship between the annealing time (minutes) and the Kerr rotation angle when annealing is performed in the atmosphere of C, and the calculated oxide layer thickness (π: unit A) is also shown. (Code in the diagram)

Claims (1)

[Claims] 1) A method for manufacturing a magneto-optical recording medium by forming a magnetic thin film of a terbium-cobalt amorphous alloy having a compensated temperature recording composition on a substrate by a sputtering method, in which sputtering of the magnetic thin film is carried out. A method characterized in that the surface of the substrate is previously notched. 2) J: The method according to claim 1, wherein the time for performing the spa notae notching is 10 minutes or more. 3) The method according to claim 1, wherein the magnetic film is formed by bias spacing. 4) The method according to claim 1, wherein the magnetic film has a thickness of 60A or more.