JPH08190740A - Production of optical recording device - Google Patents

Abstract

PURPOSE: To regulate the refractive index of a formed dielectric layer by varying the partial pressure of nitrogen when sputtering is carried out using a silicon target in a nitrogen atmosphere. CONSTITUTION: A silicon nitride film 2 having a refractive index of 2.3 and 850Å thickness, a silicon nitride film 3 having a refractive index of 2.0 and 970Å thickness, a silicon nitride film 4 having a refractive index of 2.3 and 650Å thickness, an amorphous TbFeCo alloy film 5 having 1,000Å thickness and a silicon nitride film 6 having a refractive index of 2.0 and 500Åthickness are disposed on a glass or plastic substrate 1 to obtain the objective optical recording device. The silicon nitride films 2, 3, 4, 6 are formed by sputtering using a silicon target in a nitrogen atmosphere. The refractive index of a silicon nitride film is varied by varying the partial pressure of nitrogen at the time of sputtering. By this method, the nitride dielectric layers each having the optimum refractive index are easily formed using the single silicon target and the reproducing performance of the resultant optical recording device can be remarkably improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording device for reading information by light, recording the information by causing some change in a recording medium, and reading the information by reflected light. The present invention relates to a manufacturing method of.

[0002]

2. Description of the Related Art Conventionally, rare earth transition metal alloys (TbFe,
GdTbFe, TbFeCo, TbCo, GbTbC
o, GdCo, etc.) in magneto-optical recording using a recording medium,
Since the Kerr rotation angle is small, it is difficult to increase the signal-to-noise ratio (S / N ratio). Therefore, SiO, SiO ₂
And other oxides, AlN, Si ₃ N ₄ nitrides, ZnS and other sulfides, and MgF _{2 and} other fluorides are formed on the recording medium to increase the Kerr rotation angle as an antireflection layer and improve the reproduction performance. It was designed to raise it.

Further, an amorphous semiconductor such as As-Te-Ge system is irradiated with laser light to crystallize the amorphous semiconductor in the irradiated portion, and the reflectance of the amorphous portion and the crystallized portion is changed. Even in the case of recording by utilizing the difference, the reflectance ratio between the amorphous portion and the crystallized portion is small, and the S / N ratio is poor.
Again, the above-mentioned dielectric layer was formed on the recording medium to increase the reflectance ratio and the S / N ratio as an antireflection layer in an amorphous portion.

[0004]

However, the refractive index of the actually formed dielectric layer cannot be a perfect antireflection layer because it takes a value peculiar to the substance, so that a sufficient contrast is enhanced. It was difficult.

Therefore, the antireflection function is enhanced by laminating a plurality of antireflection layers having an optical film thickness of ¼ of the wavelength of the read light on the recording medium. For example, in the case of magneto-optical recording, It has been reported that the rotation angle is sufficiently increased (Y. Tomita, T. Yoshino, J. Op. Soc. A).
m. Vol. 1, No. 8, (1984), 809).

However, when the antireflection layer is laminated, at least two kinds of dielectric layers having different refractive indexes are required, and it is difficult to form a highly reliable dielectric material having a different refractive index, and at the same time, a vacuum is formed. In the case of forming by the vapor deposition method or the sputtering method, an apparatus equipped with a plurality of vapor deposition sources and targets is required, which leads to an increase in the size of the apparatus and cost, which is not suitable for practical use.

Since the silicon nitride film is a dense nitride film containing no oxygen, it has been reported that it is a very excellent protective film for preventing oxidation of the magneto-optical recording medium (existing). Mune, Maeda et al., IEEJ Study Group Material MAG-85-
81 (1985).

However, when a silicon nitride film is formed by a sputtering method, in the conventional method using a sintered body of siliconized ceramics as a target, oxygen contained in the sintered body target is released during the sputtering to cause a recording medium. However, there is a problem in that it is not preferable because it may be oxidized.

The present invention has been made in view of the above points, and an object thereof is to provide an optical recording device having a dielectric layer capable of sufficiently performing an antireflection function.

[0010]

In order to achieve the above object, in the present invention, sputtering is performed using a silicon target in a nitrogen atmosphere, and the partial pressure of nitrogen at that time is changed to form the film. The refractive index of the dielectric layer is adjusted.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A detailed description will be given below based on an embodiment shown in the drawings.

[0012] Figure 1 is shows the configuration of an embodiment of an optical recording device of the present invention, 1, glass or polycarbonate polymerization rest (p oly c arbonate; PC) or acrylic acid resin {e.g. Methyl methacrylate polymer ( p oly m ethyl m
eth a crylate; PMMA)}, a substrate such as an epoxy resin or other plastic substrate, 2 has a refractive index of 2.3 and a film thickness of 85
0 [Å] silicon nitride film, 3 is a silicon nitride film with a refractive index of 2.0 and a film thickness of 970 [Å], 4 is a silicon nitride film with a refractive index of 2.3 and a film thickness of 650 [Å], 5 Is 1000
The TbFeCo amorphous alloy film of [Å], 6 has a refractive index of 2.
It is a silicon nitride film having a thickness of 0 and a film thickness of 500 [Å].

Here, the silicon nitride 2, 3, 4, 6
Is formed by sputtering in a nitrogen atmosphere using a silicon (Si) target. At this time, the refractive index of the silicon nitride film is changed by changing the nitrogen partial pressure during sputtering. For example, in a high frequency bipolar magnetron sputtering device using a Si target, an incident force of 1 [k
w], the partial pressure of nitrogen in the reaction chamber was changed to 6 [mTorr] while the reactive partial sputtering was performed, and the real part of the refractive index of the silicon nitride film was measured as shown in FIG. was gotten. However, the refractive index is a value when a laser beam having a wavelength of 780 [nm] is irradiated, and when the nitrogen partial pressure is 3 × 10 ⁻⁴ [Torr] or less, the refractive index of the laser beam having a wavelength of 780 [nm] is Absorption appeared.
Here, as a material that can be used as the antireflection layer of the optical recording device, it is necessary to be transparent to the light used for recording and reading information.
Considering a film transparent to a semiconductor laser beam of 80 [nm], as shown in FIG.
By setting to 10 ⁻⁴ [Torr] and 1.5 × 10 ⁻³ [Torr], a silicon nitride film having a refractive index of 2.3 and 2.0 can be formed.

As in the above embodiment, the antireflection layer is made of Si.
When formed by reactive sputtering using a target, only one target is required to form two types of silicon nitride films having different refractive indexes, that is, a dielectric layer, preventing the sputtering apparatus from increasing in size and reducing cost. In comparison with the case where a silicon nitride sintered body target is used, there is an advantage that oxygen is not taken in and a highly reliable silicon nitride film can be formed as a protective film.

Although the TbFeCo amorphous alloy film was used as the recording medium in this embodiment, other rare earth transition metal alloys (TbFe, GdTbFe, TbCo, GdT) are used.
bCo, etc.) and recording mediums (TeGe, AsTeGe, SnTeSe, T) that perform recording / reproduction by utilizing reflectance changes.
eOx). Furthermore, the film thickness, refractive index, forming conditions, etc. of each film of the optical recording device of the present invention are not limited to those shown in the above-mentioned examples, and may be appropriately selected.

[0016]

As described above, according to the method of manufacturing an optical recording device of the present invention, the dielectric layer made of nitride having the optimum refractive index can be easily formed with a single silicon target. Further, it is possible to form an oxygen-free dielectric layer having a different refractive index, that is, an antireflection layer, and it is expected that the reproduction performance and reliability of the optical recording device will be significantly improved.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing the configuration of an embodiment of an optical recording device of the present invention.

FIG. 2 is a diagram showing a relationship between a real part of a refractive index of silicon nitride by reactive sputtering of a Si target of the present invention and a nitrogen partial pressure.

[Explanation of symbols]

 1 Glass substrate 2, 3, 4, 6 Silicon nitride film 5 TbFeCo amorphous alloy film

Claims (1)

[Claims] 1. A method of manufacturing an optical recording device comprising a substrate, a dielectric layer made of nitride, and a recording medium layer, wherein a silicon target is used when the nitride dielectric layer is formed by sputtering. A method for manufacturing an optical recording device, characterized in that the refractive index of the dielectric layer made of the nitride is adjusted by changing the partial pressure of nitrogen during sputtering.