JP2548697B2 - Method for manufacturing magneto-optical storage element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a magneto-optical storage element for recording / reproducing / erasing information with a laser beam.

[Conventional technology]

In recent years, research and development of an optical memory device capable of satisfying various requirements such as high density, large capacity, and high speed access have been actively promoted. Among various optical memory devices, a magneto-optical memory device using a perpendicularly magnetized film as a memory material is particularly attracting attention because it can erase unnecessary information and re-record new information.

However, while having the above-mentioned advantages, the magneto-optical storage device has a drawback that the reproduction signal level is low. In particular, in the so-called Kerr effect reproduction system for reproducing information by using the reflected light from the magneto-optical storage element, the Kerr rotation S / because the corner is small
It was difficult to raise N. Therefore, the magnetic material, which is a recording medium in the past, was improved, or
The idea was to increase the Kerr rotation angle by forming a Sio or Sio ₂ dielectric film. Then, as an example of the latter, by forming a Sio film on the MnBi magnetic film, the Kerr rotation angle is
It has been reported that the temperature increased from 0.7 degrees to 3.6 degrees. (J
(App1.Phys ・ Vol.45No.8August.1974) However, this Kerr rotation angle increasing effect utilizes multiple reflections of light in the dielectric film, so in order to bring out the effective effect, refraction of the dielectric film The rate and film thickness must be tightly controlled.

By the way, in the case of an oxide-based dielectric film such as Sio or Sio _2, there is a risk of causing oxidation, which is deterioration of the magnetic material, and therefore a dielectric material containing no oxygen such as silicon nitride (Si ₃ N ₄ ) is proposed.

[Problems to be solved by the invention]

However, the silicon nitride film is
_When formed by the sputtering method using ₃ N ₄ ) as a target and argon gas, it was difficult to make the refractive index stable and reproducible.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for manufacturing a magneto-optical storage element capable of adjusting the refractive index of a silicon nitride dielectric film.

[Means for solving problems]

In the method of manufacturing a magneto-optical memory device according to the present invention, the target is silicon, and the mixing ratio of the nitrogen gas and the inert gas is nitrogen gas / (inert gas + nitrogen gas) (%) = 10.
The steps of forming a silicon nitride dielectric film on a transparent substrate by reaction sputtering with a mixed gas, forming a magnetic film having an easy axis of perpendicular magnetization on the dielectric film, and forming a protective film on the magnetic film. Is to be applied.

[Action]

When the reaction sputtering method is used, the refractive index of the dielectric film can be changed by changing the mixing ratio of the inert gas and the nitrogen gas. That is, as shown in FIG. 3, when the mixing ratio of nitrogen gas is 0, the refractive index of the produced dielectric film shows the value of silicon alone, and the composition of the dielectric film is the composition of silicon alone. When the ratio of nitrogen gas is gradually increased, the refractive index of the resulting dielectric film changes continuously, changing the composition of the dielectric film from silicon alone to a mixture of various compositions. Is changing.

Therefore, while performing monitoring by an appropriate means, the introduction ratio of the inert gas and the nitrogen gas into the sputter device, that is, the mixing ratio of the nitrogen gas and the inert gas, is set to the nitrogen gas /
By adjusting and controlling (inert gas + nitrogen gas) (%) = 10 or less, the refractive index of the dielectric film can be adjusted in a wide range.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, (1) is a transparent substrate made of glass or synthetic resin, and in this case, glass (2) is a transparent substrate by reaction sputtering with a mixed gas of 90% argon gas and 10% nitrogen gas using a Si target. It is a silicon nitride dielectric film formed in (1). (3) is formed on the silicon nitride dielectric film by the sputtering method, and contains GdCo, TbFe, and GdTb.
Co, GdTbFe, or the like, in this case, is an amorphous magnetic film made of a rare metal of GdCo and a transition metal, and has an easy axis of perpendicular magnetization. (4) is a protective film formed on the magnetic film (3) and is a silicon nitride film. The refractive index of the silicon nitride dielectric film obtained by the reaction sputtering method as described above was 1.9, and a stable one was obtained.

FIG. 2 is a characteristic diagram showing the relationship between the film thickness of the silicon nitride dielectric film and the Kerr rotation angle when the GdCo film as the magnetic film has a constant thickness of 200 nm. Silicon nitride dielectric film thickness 70nm
In this case, the Kerr rotation angle is about 1.7 times larger than that without the silicon nitride dielectric film. The Kerr rotation angle is normalized by the value when the thickness of the silicon nitride dielectric film is 0 nm.

Furthermore, as shown in FIG. 3, the refractive index of the dielectric film produced by adjusting the mixing ratio of the inert gas and the nitrogen gas continuously changes due to the change of the mixing ratio.
Not only the dielectric having a refractive index of 1.9 shown in FIG. 2 but also dielectrics having other refractive indexes, the characteristics of film thickness and Kerr rotation angle having the same tendency as in FIG. 2 can be obtained.

If the refractive index of the silicon nitride dielectric film can be adjusted, the following effects can be obtained. For example, if the sputtering power and time are constant, the film thickness of the silicon nitride dielectric film should be constant, but in practice it is possible to avoid changing the film thickness of the dielectric film due to various process differences. At the same time, the Kerr rotation angle of the dielectric film also changes accordingly. In this case, if the sputtering power or time is adjusted in order to obtain a dielectric film having a given Kerr rotation angle while keeping the film thickness of the dielectric film constant, the change of the film thickness of the device or the influence on the subsequent process is affected. However, in the present invention, as described above, the dielectric film having a predetermined Kerr rotation angle can be obtained by adjusting the mixing ratio of the mixed gas to adjust the refractive index of the dielectric film. That is, if a characteristic diagram such as that shown in FIG. 2 is obtained for the dielectric film of each refractive index, the predetermined dielectric film thickness can be maintained and the desired nitrogen gas amount can be adjusted. The refractive index of the dielectric film can be adjusted so as to have the rotation angle.

〔The invention's effect〕

As described above, according to the present invention, reaction sputtering using silicon as a target and mixing ratio of nitrogen gas and inert gas is nitrogen gas / (inert gas + nitrogen gas) (%) = 10 or less. The steps of forming a silicon nitride dielectric film on a transparent substrate, forming a magnetic film having an easy axis of perpendicular magnetization on this dielectric film, and forming a protective film on this magnetic film are performed by There is an effect that a silicon nitride dielectric film having a controlled index can be obtained, and thus a method of manufacturing a magneto-optical storage element having a stable and increased Kerr rotation angle can be obtained.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view showing the structure of a magneto-optical storage element obtained according to an embodiment of the present invention, and FIG. 2 is a silicon nitride dielectric in a magneto-optical storage element according to an embodiment of the present invention. FIG. 3 is a characteristic diagram showing the relationship between the film thickness of the film and the Kerr rotation angle, and FIG. 3 is a characteristic diagram showing the relationship between the mixing ratio of the inert gas and the nitrogen gas and the refractive index in the reaction sputtering method according to the present invention. . In the figure, (1) is a transparent substrate, (2) is a silicon nitride dielectric film, (3) is a magnetic film, and (4) is a protective film.

Claims (1)

(57) [Claims] 1. A silicon nitride target on a transparent substrate by reactive sputtering with a mixed gas of nitrogen gas and an inert gas in which the mixing ratio is nitrogen gas / (inert gas + nitrogen gas) (%) = 10 or less. A method of manufacturing a magneto-optical storage element, which comprises a step of forming a dielectric film, a step of forming a magnetic film having an easy axis of perpendicular magnetization on the dielectric film, and a step of forming a protective film on the magnetic film.