JPS5891532A - Magnetic disk storage medium - Google Patents

Abstract

PURPOSE:To reduce defective errors, and to elevate surface accuracy, head detaching and attaching resistance characteristics, productivity, etc., by using a single crystal Si wafer as a substrate, and manufacturing a gamma-Fe2O3 thin film magnetic disk. CONSTITUTION:On a single crystal Si wafer 30 whose thickness is >=0.3mm., a gamma-Fe2O3 thin film 31 whose thickness is <=0.2mum is formed by means of sputtering, etc., and also in order to make a disk have mechanical strength, a reinforcing plate 32 consisting of light metal such as Al, Ti, etc., or a light alloy such as an Al alloy, a Ti alloy, etc. is stuck to the other surface of the Si wafer 30 by an adhesive material 33, by which a magnetic disk is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultra-small and economical magnetic disk storage medium with ultra-high recording density.

Conventionally, the recording medium of magnetic disk storage devices has been a mixture of needle-shaped y-Fa Fold Os fine particles mixed with an organic binder and spin-coded onto an At-MQ alloy substrate. In order to increase the areal recording density on the surface and make the device smaller and more economical, 7-F
A magnetic disk storage medium formed with a continuous thin film of m20m,
A t-M1 reinforced with non-magnetic N (-p) as the underlayer.
Magnetic disk storage media are beginning to be used in which a C0-N1-P alloy magnetic thin film is formed on an alloy substrate by a plating method and is further coated with a 54 (H film) to protect the alloy film. The magnetization reversal region density on the top is 2
It achieves 4,000 bits/1 yctl, which is about 6 times that of spin code media.

By the way, in large processor systems, small processor systems, and even terminal devices with information processing functions,
With the development of iLSI technology, main body devices such as CPUs, main storage devices, data channels, etc. continue to rapidly achieve higher performance, smaller size, economy, and higher reliability. For this reason, in a processor system, file memory, printer.

Peripheral devices such as displays are beginning to occupy a large portion of system costs and floor space. This is because the number of elements per chip in the MO5 RAM LSI (main memory) in the processor itself has increased approximately 4,000 times over the past 10 years due to advances in miniaturization technology, but in the core of the file memory. The above-mentioned situation can be easily inferred from the fact that the increase in recording density on the medium surface of a certain magnetic disk storage device was only 10 times 710 years. After 54LSI, Ggj
s LSI and Josephson (zoaaphaas) L
As SI continues to grow, this trend will continue unabated, and it won't be long before processor system peripherals account for more than 95% of the system cost and floor space.

Therefore, rapid technological progress is desired in peripheral devices such as magnetic disk storage devices.

As is well known, the improvement in the recording density on the magnetic disk surface using the horizontal magnetization method is shown in Figure 1, which shows the principle of horizontal magnetization recording, and the annual change in the dimensions of the recording and reproducing system (medium performance index) of the magnetic disk recording device. As shown in FIG. 2, this has been achieved mainly by miniaturizing the dimensions of the recording/reproducing system. That is, the core @T of the magnetic head 1 decreases, and the magnetic head gap length 2! decrease, magnetic head flying height d decrease, magnetic disk medium surface roughness R decrease, magnetic film thickness δ decrease, magnetic thin film 2
This is an improvement in the magnetic properties (media index: z) of .

In addition, IEM2514. in FIG. IBM555
0-1. JAN3330-11, 18M354D (
IP'1NCHESTER), IEM555D,
1545 and 1545 respectively indicate disk devices manufactured by IBM.
70. 154680 indicates a disk device manufactured by Nippon Telegraph and Telephone Public Corporation. The JS4580 device in Figure 2 is γ-Fm10B.
Although it uses a thin film, compared to conventional spin code media, δ and R are significantly reduced, and 2 is significantly improved, making it an excellent medium for future improvements in areal recording density. ,
Media surface roughness R, recording signal dropout error, magnetic head take-off and landing resistance on the media.

These are problems related to the manufacturability of the γ-11!01 thin film, and all of these problems are caused by the magnetic disk substrate.

For the TS-4580 media, the ALSO layer on the substrate surface is polished to an average roughness of 0.02 per 1'rlvn pitch.
Local waviness at μ45 Joshin pitch 0.04μfi,
10tm+t pitch waviness of 0.1μ inertia and high speed magnetic head (~20m/5ac).

Although it is dealing with a low flying height (approximately ~0.25 μ), in ultra-high density recording areas, for example, the speed is ~5 Q'In1aa6
It is necessary to achieve a flying height of approximately 0.05μ. However, as an extension of the conventional technology, it is difficult to stabilize the flying of the magnetic head under the above conditions and suppress the flying height variation to approximately ±5%.

Next, the cause of signal errors in the γ-Fm30B thin film medium is the 1-20 μm diameter of the anodized At-Ml substrate.

There is a pit of regret 1-10μ deep. This is because F− in the alloy
This is because the 25i and M impurities form intermetallic compounds and do not form an A1109 layer during anodic oxidation. Measures have been taken to reduce impurities, but because anodic oxidation is a reaction in liquid, it is extremely difficult to reduce the dents any further than at present. Therefore, when using a 1w5μ magnetic head, l
Compared to the 7'W1Bμ head of 5-4580, this causes 100 times as much signal error, making it impossible to satisfy the error rate of the device.

Fifth, regarding the durability of the magnetic head when taking off and landing on the medium surface, protrusions exceeding the above-mentioned average roughness are scattered on the substrate. Although this can be avoided at present, it is extremely difficult to remove, for example, a 0.03 μm thick protrusion from an anodized At-Mf alloy substrate.

The fourth is anode conversion A for the γ-Fm@03 thin film media manufacturing method.
This is a restriction from the t-M1 alloy substrate. Since the At-M1 alloy is a low-melting alloy, recrystallization occurs at high temperatures.
The above-mentioned surface accuracy cannot be maintained. Therefore, γ-Fa
The manufacturing process for 20B thin films is strongly limited to below 320@C. In the g manufacturing process, α-Fm3 is produced by sputtering.
A 0B film is formed and then reduced to 7-F,. There is a shortage of products due to restrictions such as restrictions on the temperature of the product and the inability to use stable conditions on the high temperature side during reduction and oxidation. Therefore, if temperature constraints on the production of γ-FBO2 thin films are removed, there will be immeasurable benefits in improving productivity and magnetic properties.

The present invention overcomes the shortage of the above-mentioned γ-FHO@thin film magnetic disk medium, and achieves ultra-high recording density and small size.

It was devised to realize an economical magnetic disk storage device, and its purpose was to improve the surface accuracy of the medium and reduce defect errors by fabricating an r-FmlOj thin film magnetic disk using a single-crystal S4 wafer as a substrate. The aim is to reduce the amount of water used, improve head take-off and landing characteristics, and improve thin film productivity.

The surface precision of the commercially available S (single crystal wafer) is about one order of magnitude better than the above-mentioned anodized At-M1 alloy substrate, and since it is used for manufacturing LSIs on the order of 1 μm,
There are almost no defects beyond μCoastal. In addition, since the 5(LSI process involves heat treatment at approximately 10,006 C, it seems that the heat resistance is sufficient.Currently being manufactured.f(
The wafer diameter is approximately 7.626 m to 10.16 cm (3 to 4 inches), but the rounding process cost and reduction are approximately 12.70 cm to 15.36 cm (,5 to 6 cm).
Prototypes of inch-diameter wafers are being produced. On the other hand, the standard diameter of magnetic disk media is approximately 55.566 m (14 inches), but in recent years the diameter has become approximately 20.352 to 25.40 cm.
Small disks with a diameter of (8-10 inches) have also appeared, and floppy disks for terminals are approximately 15.566 m long.
(1, inch) diameter O type is also commercially available. Therefore, if the shortage of anodized At-M1 alloy can be overcome with S (substrate), magnetic disk media with diameters of approximately 10.16 to 12.70 cm (4 to 5 inches) can be approximately 55.560 WL (
14-inch) media, and the cost of S (wafers is estimated to be approximately 1/10 of that of anodized AL-M1 alloy substrates.) , low-cost, low-power HD
A (Hgcm -j) (# & Aaattmbly
). However, the problem with the S( substrate is its fragility, which is explained later)
This problem can be solved by reinforcing the substrate with a light metal or light alloy. The present invention was made based on this idea.
Examples will be described in detail below.

FIG. 3 is a sectional view of an embodiment of the magnetic disk storage medium of the present invention, where 30 is an S (wafer) and 31 is an r-Fan03
The thin film, S2 is a reinforcing plate, and 33 is an adhesive. Also, the fourth
This figure is an external perspective view of one embodiment of the magnetic disk storage medium of the present invention, where the same reference numerals as in FIG. 5 indicate the same parts, and 40 is a hole provided in the center of the disk.

As shown in the figure, the magnetic disk storage medium of this embodiment uses a single crystal S (wafer 50) as a disk substrate.
A γ-FazOB thin film 31 is formed thereon, and a reinforcing plate 32 made of a light metal or light alloy is attached to the other side of the S4 wafer 30 with an adhesive 3 in order to further give the disk mechanical strength.
3 was pasted together. The thickness of each part is Q, 5mtn or more for S wafer 6o.

1-Fa mushroom Os thin film 31 is 0.2 μm or less, light metal plate 3
It is preferable that 2 is 0.5 mm. The material of the light metal plate 32 is preferably a light metal such as At or 74, or a light alloy such as At alloy or 74 alloy. Further, as the adhesive 65, an organic adhesive can be used. Next, a method for manufacturing a magnetic disk storage medium according to the present invention will be explained.

First, we carefully considered the polishing method, and the thickness was 5M054.
An approximately 10.166 m wafer (hereinafter referred to as a 4-inch wafer) was prepared. When the surface accuracy of this was measured with a surface roughness needle, the average roughness at one regular pitch was 0.00254s
, the local ridge with a 3 mg pitch is O,0038 μm.

The undulation of 10 pitches is 0.01μ, just right.
It was found that an accuracy of 1/10 of that of the anodized At-M1 alloy was achieved. Incidentally, the commercially available approximately 7.626m (5
When measuring the surface accuracy of an S4 wafer with a diameter of
．． 05μ was constant. Also, approximately 55.56cm (14
The anodized At-M1 alloy substrate with a diameter of
We investigated the change in roughness of a 1 mm pitch with respect to processing temperature. The results are shown in Figure 5.As can be seen from the figure,
- In the extremely oxidized At-M1 alloy substrate, the roughness begins to increase at 520°C, and at 340°C, cracks occur over the entire A140 layer, but the surface roughness of the S1 wafer is at the experimental upper limit of soo@c There has been almost no change until now.

Next, place 1.
A 5-inch diameter hole was drilled and machined into the shape of a magnetic disk.

Next, using this as a board, Xahta 7”js, rJ+
Cog, 6 alloy target with partial pressure ratio 9ONO, -At
By reactive RF magnetron sputtering method under a mixed atmosphere of 8×10-”roff, the deposition rate was 210 j/m<s.
Then, α-(Fee
, vaTio, aICoo, os>sOs film 1050
1 was attached to one side. Although the substrate temperature during this adhesion was approximately 350° C. as measured by a heat label, no deterioration in surface accuracy was observed.

Next, α-(7#0.?4 r4s, a
t C66,6m h 08 membrane containing water vapor 25
0''C to 3506C1, preferably reduced to Fa in a H8 gas stream at about 320°C for 2 hours.

04, remove Hs gas with a rotary pump,
Air was introduced and oxidized in the atmosphere at the same temperature for 2 hours to form 'f-
FBOB thin film (r-(J'#a,ya 7'((1,I
T Coo, ones Os) was created. Film thickness is 0
．． It was 1 yen. Incidentally, in the same way, r-F Os is 5(
Formed on both sides of the square with a diamond cutter
Cut into mm x 5mm squares, r-(yss, ti
The magnetic properties of the r(+1.gll Ces, ex )s Os film were measured using a vibrating magnetometer. The result is anodized A
r-(7'@jar(1141C@I) on t-M1 alloy
, @i)! A comparison with 01 membrane is shown in the following table. However, in the following table, Bde is the residual magnetic flux density, H- is the coercive force, xr is the residual magnetization, H4 is the magnetization in an external magnetic field of 4kO-, and Mde/
M4 & is squareness ratio, S4) is core squareness, HX
is the magnetic field where the major loose is closed.

Comparison of magnetic properties of films on S(substrate and anodized At-Ml substrate)As can be seen from the table above, the medium of the present invention has a higher My/H41,5'' than the conventional medium, and a higher HX/i , is small.

In other words, the rectangularity of the hysteresis loop increases,
It can be seen that the γ-Fg90@thin film medium with the 54 substrate has characteristics for ultra-high recording density.

In addition, the Q created as described above, r-("@j47'4s, st COajl)10 with a thickness of 1 mflL
1. A 4-inch diameter wafer with a thickness of 5 mm on which a thin film was formed,
It was attached to a disk rotation system, and a magnetic head-type slider made of sapphire was levitated above the rotating medium. Then, by changing the rotation speed, the head medium spacing was adjusted from 0.04 to 0.
．． The acosat emitter attached to the head arm was changed over a range of 20 m.
Contact between the medium and the head was checked using a cmam4aaion) sensor. At this time, a lubricant was applied to the media surface to reduce the coefficient of friction. As a result, the minimum flying height of the measurement is 0,
Even at 04μ, contact between the medium and the head cannot be detected.
It was confirmed that the protrusion height of the No. 54 substrate medium was extremely low. In contrast, the medium on the anodized At-M1 alloy has 0
．． Contact between the medium and the head occurred even when the head-medium distance was less than 13/iml.

Sarani, x%-Z% Fe2ite core gap length (2g)
A magnetic head of 0.25μ, head core width (rv) of 1soμ, and coil turns (2%) of 50 turns was floated above a 54-substrate disk medium, and the head-medium spacing was 0.20μ.
Select three levels: inertia, 0゜10μs, Q, 05μs,
The spacing dependence of linear recording density was measured. The results are shown in Figure 6. As can be seen from the figure, the linear recording density at which the reproduction output decreases to 50X is 19506% at a flying height of 0.20μ.
(bitpar miLL4mater), floating height 0-10# inertia"t'S 5506pyysp-e floating.

With an amount of 0.05μ inertia, 5200&pm was obtained. The linear recording density at a flying height of 0.05 μm was about 10 times that of the current state-of-the-art magnetic disk device. On the other hand, the linear recording density of a disk using an anodized At-M1 alloy substrate was 1700b at a flying height of 0.20μ, but
With t 0.10 μm, Q, and [15 μm, recording and reproducing characteristics could not be stably measured due to contact between the medium and the head.

In addition, a 4-inch diameter wafer with a thickness of 3 mm was coated with 0.1μ normal thickness r-("L,4"0,01 COa, am)lO
The surface of the above-mentioned 54-substrate disk on which the S thin film was formed was examined using an optical microscope and a 5xHT (scanning electron microscope).
The number of substrate defects larger than normal diameter was measured, but there were none. On the other hand, the number of defects with a diameter of 1 μm or more on the anodized Al-My alloy substrate was 20 to 400 pieces/ctn. The latter medium has a practical error rate with a helad core width of 18 μm. Therefore, in the case of γ-Fm, 0.000000000000000000 using 54 substrates, almost no defect errors occur even for a core width of 5 μm.

Next, in order to give the disk mechanical strength, 54
After the above step in which the 1-Fg@0@ film was formed on one side of the substrate, a reinforcing plate made of light metals such as At and Ri or their light alloys was bonded to the other side of the substrate with an adhesive. , the thickness of the reinforcing plate using Ti is 1.2
．． Instead of 5 seaweed, S of about 10.166 jo (4 inches) diameter
(It was adhered to a substrate as described above and rotated up to a maximum of 20,000 rpm using a da cocoa motor using a rare earth magnet to examine the stability of rotation.

The stability was evaluated by measuring the acceleration of surface wobbling with a capacitive displacement sensor placed opposite the surface of S. As a result, the disk substrate lined with a reinforcing plate showed
t, regardless of the thickness of Ti, the substrate does not crack with 200QQrprni, and the acceleration is at a rotation speed of 50~/age,
1. (It was stable at less than IG.Also, even when the thickness of the 51 substrate was reduced to 1 mm, the At.

Similar results were obtained by bonding the T (plate). The results were also the same when At alloy and RT gold alloy were used. On the other hand, when the reinforcing plate was not bonded, the same result was obtained. However, there was a problem where the disc would sometimes crack and scatter while rotating.

As explained above, the present invention significantly removes the constraints derived from anodized At-M1 alloy substrates by fabricating r-#lol continuous thin film media using S (single crystal wafers as disk substrates). This makes it possible to bring out the performance of r-FfO and thin films to their limits, making it possible to achieve an areal recording density of approximately 100 times the current state-of-the-art magnetic disk. That is, approximately 10.1 (5 cm) Even if a substrate with a diameter of 4 inches is used, a magnetic disk of about 1 GEyt# can be created on one side, making it possible to significantly reduce the size and economy of magnetic disk storage devices.
00-600MEyt-capacity head-disk assembly (uni), for example 100m x 12am x
This can be achieved with a volume of 5 cm. Furthermore, not only large file systems but also file capacities of 100 fJ1yta or less in various terminals can be addressed by downsizing wafers and reducing areal recording density, so the impact will be immeasurable.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of horizontal magnetization storage, Fig. 2 is a diagram showing annual changes in the dimensions (medium performance index) of the recording/reproducing system of a magnetic disk storage device, and Figs. 5 and 4 are the invention of the present invention. A cross-sectional view and an external perspective view of an example disk storage medium, FIG. 5 is a diagram showing the processing temperature dependence of the surface roughness of the substrate, and FIG.
FIG. 2 is a diagram showing an example of measurement of recording and reproducing characteristics of a γ-PaBOB thin film medium using a substrate. 30 is S4 wafer, 31 is γ-Fe@03 thin film, 32
3 is a reinforcing plate, and 33 is an adhesive. Patent applicant Nippon Telegraph and Telephone Public Corporation Patent attorney Hisa Gobe Tamamushi (3 others) Figure 1 Figure 3 Figure 4 Figure 2 Figure 1'? 65 1970 1
975 191 JO Year Figure 5 Heat treatment temperature (・C) Figure 6 0.1 0.2 0.30.40.5 7
2 3 4 5te record 1 degree (bpm)

Claims (1)

[Claims] A continuous thin film mainly composed of 7-FazOm formed on one side of the single-crystal S4 wafer, and a continuous thin film mainly composed of 7-FazOm attached to the other side of the single-crystal S4 wafer with an adhesive. 1. A magnetic disk storage medium characterized by comprising a reinforcing plate made of a light metal or a light alloy.