JP2001056973A - Production of optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress residual stress based on difference in thermal expansion coefficient and to lessen warpage of a substrate by setting the gas pressure at the time of film-forming a lower dielectric body layer which come into contact with the substrate of phase transition recording layer by sputtering higher than the gas pressure at the time of film-forming the other layer. SOLUTION: The sputtering device is provided with six film-forming chambers and the substrate successively passes through the same. The lower dielectric body layer consisting of ZnS-SiO2 is formed in all of the first, second, third and fifth film-forming chambers, and a recording layer and a reflecting layer and a heat radiating layer are respectively formed in fourth and sixth chambers. In the step of sputtering process, the warpage is generated in the substrate based on the difference in thermal expansion coefficient between the substrate and the lower dielectric body layer. For example, the pressure of Ar gas in the second, third and fifth film-forming chambers is set to be 2 mTorr and the pressure of Ar gas in the first film-forming chamber is set to be 10 mTorr. Further, the density of the dielectric body layer of the lowermost layer being in contact with the substrate is lowered to 2.2 g/cm3 and, thereby, the warpage of the substrate is reduced to 1.6 deg.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical disk, and more particularly to a DVD (Digital Versatile Disc) -RW.
The present invention relates to a method for manufacturing an optical disc which eliminates warpage of a substrate in a manufacturing process of an optical recording medium such as (Rewritable).

[0002]

2. Description of the Related Art An optical disk having a phase change recording layer is manufactured or sold as an optical disk for a digital signal recording medium. For example, CD-RW, DVD-R
W and CD-RAM (Random Access Memory) correspond to this. These are generally plastic substrates / ZnS-Si
O ₂ / chalcogen phase change recording medium / ZnS—SiO ₂ /
It has a four-layer film structure such as an Al-based alloy. An optical disc having such a phase-change type recording layer irradiates a crystal layer of a recording material with light to change a light-irradiated portion to an amorphous layer, and performs recording. Therefore, the recording layer must be a crystalline layer in an initial state (a state where optical recording is possible). Since this recording layer is generally formed at a temperature of about 100 ° C. by sputtering or the like, it is an amorphous layer at the stage of manufacture, and requires initial crystallization for crystallizing the entire recording layer.

In the manufacturing process of an optical disk, the temperature of the entire surface of the substrate is raised to about 100 ° C. during film formation by sputtering, and in the manufacture of a phase change recording disk, the temperature of the laser spot size is further increased to 100 ° C. or more during the initial crystallization process. I do. When an inexpensive plastic substrate is used as the optical recording disk, the substrate is greatly warped due to the temperature difference between the front and back surfaces of the substrate during sputtering deposition and high temperature processing during the initial crystallization process for the phase change recording disk. In the case of a DVD-RW substrate with a high recording density, the thickness is
This is a more serious problem because the thickness is 0.6 mm, which is １ ／ of the thickness of the RW. Therefore, Japanese Patent Application Laid-Open No. 8-287527
In the publication, an initial crystallization process is performed after a 0.6 mm substrate is bonded and corrected to a flat state.

[0004]

However, this conventional method is effective when the warpage of the substrate after film formation is small, but it is difficult to correct by warping when the warp after film formation is about twice. become. In the first place, the warpage of the substrate is caused by a large difference in the coefficient of thermal expansion between the substrate and the dielectric thin film. Since there is a difference in thermal expansion coefficient between the two,
When cooling from a high temperature of about ° C. to room temperature, a residual stress always occurs, and the stress warps the substrate. That is, the fact that the substrate expands more at high temperatures is caused by the warpage.

SUMMARY OF THE INVENTION The present invention has been made to solve this problem, and a dielectric layer in contact with a substrate so that residual stress caused by a difference in thermal expansion between the substrate and a dielectric thin film is reduced as much as possible. It is an object of the present invention to provide an optical disk manufacturing method in which the density of a substrate is made smaller than that of other portions to eliminate the warpage of a substrate.

[0006]

In order to solve the above-mentioned problems, a method of manufacturing an optical disk having a phase-change recording layer according to the present invention is directed to a method for forming a lower dielectric layer in contact with a substrate by sputtering. It is characterized in that sputtering is performed with a gas pressure higher than a gas pressure at the time of forming another layer. Therefore, since the gas pressure during film formation is high, energy particles such as film formation gas that collide with the thin film being formed are frequently scattered, so that the density of the lower dielectric layer in contact with the substrate decreases, and accordingly, the substrate Residual stress caused by a difference in thermal expansion coefficient between the substrate and the lower dielectric layer is reduced, and the amount of warpage of the substrate after the initial liquid crystal conversion can be reduced.

Further, when the thermal expansion coefficient of the lower dielectric layer is smaller than the thermal expansion coefficient of the substrate, the density of the lower dielectric layer is lower than that of the other layers, and the thermal expansion coefficient of the lower dielectric layer is lower than that of the substrate. If the coefficient is larger than the coefficient, the density of the lower dielectric layer is higher than that of the other layers, so that in any case, the residual stress caused by the difference in thermal expansion coefficient between the substrate and the lower dielectric layer is reduced, and after the initial liquid crystal conversion, Of the substrate can be reduced.

When the lower dielectric layer is formed by sputtering, by mixing diatomic molecules into the gas, the density of the formed lower dielectric layer is reduced. Therefore, the amount of warpage of the substrate after the initial liquid crystal conversion can be reduced.

Further, when sputtering the lower dielectric layer, sputtering with diatomic molecules and sputtering with an inert gas are alternately performed. Further, since the diatomic molecules are N ₂ and the inert gas is Ar, a collision is caused. In this case, the stress at the portion where the film is formed can be reduced by diatomic molecules whose elastic constant is smaller than that of the inert gas, so that the amount of warpage of the optical disk can be reduced.

[0010] In addition, when the lower dielectric layer in contact with the substrate is formed by sputtering, the thickness of the lower dielectric layer is made larger than the thickness of the other layers when the film is formed. Subsequent warpage of the substrate can be reduced.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a method for manufacturing an optical disk having a phase-change recording layer, a lower dielectric layer is formed by sputtering to reduce the density of a lower dielectric layer in contact with a substrate as compared with the density of the substrate. The sputtering is performed with the gas pressure at that time higher than the gas pressure at the time of forming the other layers.

[0012]

FIG. 1 is a plan view showing a schematic configuration of a sputtering apparatus by a manufacturing method according to one embodiment of the present invention. Although the sputtering apparatus shown in FIG. 1 has six film-forming chambers 1 to 6 and a substrate introducing section 7, the number of film-forming chambers does not need to be six and three or more film-forming chambers can be produced. The details of the film formation are shown below.

Deposition chamber 1 (hereinafter referred to as PC1): ZnS—SiO ₂ (lower dielectric layer) Deposition chamber 2 (hereinafter referred to as PC2): ZnS—SiO ₂ (lower dielectric layer) Deposition chamber 3 ( hereinafter referred to as PC3): referred to as ZnS-SiO ₂ (lower dielectric layer) deposition chamber 4 (hereinafter PC 4): AgInSbTe (referred to as recording layer) deposition chamber 5 (hereinafter PC5): ZnS-SiO ₂ (lower dielectric Body layer) Film forming chamber 6 (hereinafter referred to as PC6): Al (reflective heat dissipation layer)

Next, a comparative example and an experimental example according to the present embodiment will be described.

[Comparative Example] A diameter of 120c was obtained by injection molding.
m, a PC board having a thickness of 0.6 mm is formed. On PC1,
A ZnS—SiO ₂ film is formed under the following conditions. Input power: RF 4 kW / 8 inch target, Gas pressure: 2 mTorr Gas type: Ar Film thickness: 63 nm

In PC2 and PC3, Z
forming the nS-SiO ₂ film. Input power: RF 4 kW / 8 inch target, Gas pressure: 2 mTorr Gas type: Ar Film thickness: 63 nm

In the PC4, AgInSb was used under the following conditions.
A Te film is formed. Input power: DC 0.4 kW / 8 inch target, Gas pressure: 2 mTorr Gas type: Ar Film thickness: 20 nm

In the PC5, ZnS-Si is formed under the following conditions.
An O ₂ film is formed. Input power: RF 4 kW / 8 inch target, gas pressure: 2 mTorr Gas type: Ar Film thickness: 20 nm

On the PC 6, an Al film is formed under the following conditions. Input power: DC 5 kW / 8 inch target, gas pressure: 2 mTorr Gas type: Ar Film thickness: 140 nm

Then, after applying the UV curable resin,
Irradiate light. Thereafter, the AgInSbTe recording layer is irradiated with a laser beam focused at a size of 1 μm × 96 μm to crystallize the AgInSbTe. The crystallization conditions were as follows: a linear rotation speed of 4 m / s and a laser feed speed of 5 m / s.
0 μm / rotation, laser input power is 800 mW.

[Experimental Example 1] A diameter of 120c was obtained by injection molding.
m, polycarbonate substrate with a thickness of 0.6 mm (hereinafter referred to as PC
(Referred to as a substrate). On the PC1, a ZnS—SiO ₂ film is formed under the following conditions. Input power: RF 4 kW / 8 inch target, gas pressure: 10 mTorr Gas type: Ar Film thickness: 90 nm

In PC2 and PC3, Z
forming the nS-SiO ₂ film. Input power: RF 4 kW / 8 inch target, gas pressure: 2 mTorr Gas type: Ar Film thickness: 50 nm

In the PC4, AgInSb was used under the following conditions.
A Te film is formed. Input power: DC 0.4 kW / 8 inch target, Gas pressure: 2 mTorr Gas type: Ar Film thickness: 20 nm

In the PC5, ZnS-Si is formed under the following conditions.
An O ₂ film is formed. Input power: RF 4 kW / 8 inch target, gas pressure: 2 mTorr Gas type: Ar Film thickness: 20 nm

On the PC 6, an Al film is formed under the following conditions. Input power: DC 5 kW / 8 inch target, gas pressure: 2 mTorr Gas type: Ar Film thickness: 140 nm

Then, after applying the UV curing resin,
Irradiate light. Thereafter, the AgInSbTe recording layer is irradiated with a laser beam focused at a size of 1 μm × 96 μm to crystallize the AgInSbTe. The crystallization conditions are as follows: a linear rotation speed of 4 m / s, a laser feed speed of 0 μm / rotation, and a laser input power of 800 mW.

FIG. 2 shows the relationship between the film forming pressure and the density when forming a film of ZnS-SiO ₂ . As shown in FIG. 2, ZnS—SiO _{2 formed} at a gas pressure of 10 mTorr on PC1 has a density of 2.2 g / cm ³ , PC2, P
ZnS-S deposited at C3 at a gas pressure of 2 mTorr
iO ₂ has a density of 3.3 g / cm ³ . In addition, a film thickness formed by the PC1, that is, a ZnS— film having a density of 2.2 g / cm ³ .
FIG. 3 shows the relationship between the SiO ₂ film thickness and the disk warpage angle after the initial crystallization. The warpage of Experimental Example 1 was 1.6 deg, compared to the warpage of 2.2 deg of the above-described comparative example, and the effect of reducing the density of the portion in contact with the substrate was obtained. Further, even if the film thickness of the low-density portion is 10 nm, the effect of reducing the amount of warpage is observed. This is because the density of the lower dielectric layer in contact with the substrate was lowered because the gas pressure during film formation was high, and the energy particles such as film formation gas that collided with the thin film being formed were frequently scattered. It is.

[Experimental Example 2] Injection molding was performed to obtain a diameter of 120c.
m, a PC board having a thickness of 0.6 mm is formed. On PC1,
A ZnS—SiO ₂ film is formed under the following conditions. Input power: RF 4 kW / 8 inch target, gas pressure: 2 mTorr Gas type: Ar and N ₂ (gas flow ratio 1: 1) Film thickness: 63 nm

In PC2 and PC3, Z
forming the nS-SiO ₂ film. Input power: RF 4 kW / 8 inch target, gas pressure: 2 mTorr Gas type: Ar and N ₂ (gas flow ratio 1: 1) Film thickness: 63 nm

In PC4, AgInSb was used under the following conditions.
A Te film is formed. Input power: DC 0.4 kW / 8 inch target, Gas pressure: 2 mTorr Gas type: Ar Film thickness: 20 nm

In the PC5, ZnS-Si was formed under the following conditions.
An O ₂ film is formed. Input power: RF 4 kW / 8 inch target, gas pressure: 2 mTorr Gas type: Ar Film thickness: 20 nm

On the PC 6, an Al film is formed under the following conditions. Input power: DC 5 kW / 8 inch target, gas pressure: 2 mTorr Gas type: Ar Film thickness: 140 nm

At this time, the portion of the ZnS—SiO ₂ thin film formed by using the N ₂ gas contains N atoms.

After applying the UV curable resin,
Irradiate light. Thereafter, the AgInSbTe recording layer is irradiated with a laser beam focused at a size of 1 μm × 96 μm to crystallize the AgInSbTe. The crystallization conditions were as follows: a linear rotation speed of 4 m / s, and a laser feed speed of 5 m / s.
0 μm / rotation, laser input power is 800 mW.

FIG. 4 shows the relationship between the gas flow ratio and the film density. FIG. 5 shows the relationship between the gas flow ratio and the warpage angle after the initial crystallization. As can be seen from both figures, the warp angle of the comparative example is 2.2 deg, whereas the warp angle of the experimental example 2 is 1.4 deg.
This has the effect of reducing the density of ZnS—SiO ₂ .

[Experimental Example 3] Diameter 120c by injection molding
m, a PC board having a thickness of 0.6 mm is formed. On PC1,
A ZnS—SiO ₂ film is formed under the following conditions. Input power: RF 4 kW / 8 inch target, gas pressure: 2 mTorr Gas type: N ₂ film thickness: 90 nm

In PC2 and PC3, Z
forming the nS-SiO ₂ film. Input power: RF 4 kW / 8 inch target, gas pressure: 2 mTorr Gas type: Ar Film thickness: 50 nm

On the PC4, AgInSb was used under the following conditions.
A Te film is formed. Input power: DC 0.4 kW / 8 inch target, Gas pressure: 2 mTorr Gas type: Ar Film thickness: 20 nm

In the PC5, ZnS-Si was formed under the following conditions.
An O ₂ film is formed. Input power: RF 4 kW / 8 inch target, gas pressure: 2 mTorr Gas type: Ar Film thickness: 20 nm

An Al film is formed on the PC 6 under the following conditions. Input power: DC 5 kW / 8 inch target, gas pressure: 2 mTorr Gas type: Ar Film thickness: 140 nm

At this time, the portion of the ZnS-SiO ₂ thin film formed by using the N ₂ gas contains N atoms.

Then, after applying the UV curable resin,
Irradiate light. Thereafter, the AgInSbTe recording layer is irradiated with a laser beam focused at a size of 1 μm × 96 μm to crystallize the AgInSbTe. The crystallization conditions were as follows: a linear rotation speed of 4 m / s, and a laser feed speed of 5 m / s.
0 μm / rotation, laser input power is 800 mW.

FIG. 6 shows the relationship between the film thickness formed by the PC 1, that is, the film thickness formed by the N ₂ gas, and the warp angle after the initial crystallization. The warp angle of Experimental Example 3 was 1.0 deg, compared to the warp angle of 2.2 deg of the above-described comparative example, and the effect of reducing the density of ZnS—SiO ₂ in contact with the substrate was obtained. The effect is obtained even when the film thickness formed by the N ₂ gas is 10 nm.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications and substitutions can be made within the scope of the claims.

[0045]

As described above, the method for manufacturing an optical disk having a phase-change recording layer according to the present invention is intended to reduce the density of the lower dielectric layer in contact with the substrate in comparison with the density of the substrate. It is characterized in that sputtering is performed with the gas pressure at the time of forming the lower dielectric layer by sputtering higher than the gas pressure at the time of forming the other layers. Therefore, the density of the lower dielectric layer in contact with the substrate is reduced due to a high frequency of scattering of energy particles such as a deposition gas that collide with the thin film being formed due to a high gas pressure at the time of film formation. Residual stress caused by a difference in thermal expansion coefficient between the substrate and the lower dielectric layer is reduced, and the amount of warpage of the substrate after the initial liquid crystal conversion can be reduced.

Further, when the thermal expansion coefficient of the lower dielectric layer is smaller than the thermal expansion coefficient of the substrate, the density of the lower dielectric layer is lower than that of the other layers, and the thermal expansion coefficient of the lower dielectric layer is lower than that of the substrate. If the coefficient is larger than the coefficient, the density of the lower dielectric layer is higher than that of the other layers, so that in any case, the residual stress caused by the difference in thermal expansion coefficient between the substrate and the lower dielectric layer is reduced, and after the initial liquid crystal conversion, Of the substrate can be reduced.

When the lower dielectric layer is formed by sputtering, by mixing diatomic molecules into the gas, the density of the formed lower dielectric layer is reduced. Therefore, the amount of warpage of the substrate after the initial liquid crystal conversion can be reduced.

Further, when sputtering the lower dielectric layer, sputtering with diatomic molecules and sputtering with an inert gas are alternately performed. Further, since the diatomic molecules are N ₂ and the inert gas is Ar, a collision is prevented. In this case, the stress at the portion where the film is formed can be reduced by diatomic molecules whose elastic constant is smaller than that of the inert gas, so that the amount of warpage of the optical disk can be reduced.

Further, in order to make the density of the lower dielectric layer in contact with the substrate smaller than the density of the substrate, the thickness of the lower dielectric layer when the lower dielectric layer is formed by sputtering is made different from that of the other layers. By performing sputtering with a thickness larger than the film thickness at the time of film formation, the amount of warpage of the substrate after the initial liquid crystalization can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan view showing a schematic configuration of a sputtering apparatus according to a method for manufacturing an optical disk according to one embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between gas pressure and density in the present embodiment.

FIG. 3 is a diagram showing a relationship between a film thickness and a warp angle in the present embodiment.

FIG. 4 is a diagram showing a relationship between a gas flow ratio and a film density in the present embodiment.

FIG. 5 is a diagram showing a relationship between a gas flow ratio and a warpage angle in the present embodiment.

FIG. 6 is a diagram showing a relationship between a film thickness and a warp angle in the present embodiment.

[Explanation of symbols]

 1 to 6: film formation chamber, 7: substrate introduction part.

Claims (6)

[Claims] 1. A method for manufacturing an optical disk having a phase-change recording layer, wherein the lower dielectric layer in contact with the substrate is sputtered by setting the gas pressure at the time of sputtering to be higher than the gas pressure at the time of forming the other layers. A method for manufacturing an optical disk, comprising: 2. When the coefficient of thermal expansion of the lower dielectric layer is smaller than the coefficient of thermal expansion of the substrate, the density of the lower dielectric layer is lower than that of the other layers, and the coefficient of thermal expansion of the lower dielectric layer is lower than the substrate. 2. The method according to claim 1, wherein the density of the lower dielectric layer is higher than that of the other layers when the coefficient of thermal expansion of the lower dielectric layer is larger than that of the other layers. 3. The method according to claim 1, wherein when the lower dielectric layer is formed by sputtering, diatomic molecules are mixed in the gas.
3. The method for manufacturing an optical disk according to claim 1. 4. The method for manufacturing an optical disk according to claim 1, wherein when sputtering the lower dielectric layer, sputtering using diatomic molecules and sputtering using an inert gas are alternately performed. 5. The method according to claim 4, wherein the diatomic molecule is N ₂ and the inert gas is Ar. 6. The sputtering method according to claim 1, wherein said lower dielectric layer is formed by sputtering with a film thickness of said lower dielectric layer being larger than a film thickness of other layers when said lower dielectric layer is formed by sputtering. Or a method for manufacturing an optical disk.