JPH06101151B2 - Method for manufacturing optical information recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing an optical information recording medium in which information is recorded by causing an optical change by irradiation with a laser beam.

[Technical background of the invention and its problems]

Information recording using a laser beam has features such as a remarkably high recording density and real-time recording, and research and development have been conducted in recent years. As an optical information recording medium, a medium in which a chalcogenide thin film such as Te or a dye thin film is formed on a transparent resin substrate has been conventionally proposed. However, such an information recording medium has a serious problem that it deteriorates due to the influence of oxygen, moisture, or ultraviolet rays in the air during storage, which hinders the recording and reproduction of information.

Japanese Unexamined Patent Publication (Kokai) No. 57-165292 proposes a medium in which Te is mixed with carbon in order to eliminate the drawbacks of the prior art. One method for producing a recording film containing Te and carbon is a method of sputtering a Te target with plasma of hydrocarbon gas. However, sputtering is
Conventionally, it has been used as a method for forming a thin film of the metal by sputtering a metal target with plasma of a rare gas such as Ar. There are very few examples in which the combination of the target and the plasma gas having a high possibility of reaction, or the sputtering using a dissociative gas such as hydrocarbon is practically used.
Therefore, when carrying out such sputtering on an industrial level, detailed film forming conditions are often unknown. For example, when a dissociative gas is used, the dissociation process changes depending on the power applied to the target, the pressure at the time of forming the film, the flow rate of the gas to be introduced, and the characteristics of the formed film change. Moreover, the above-mentioned various condition values to be set at the time of film formation vary depending on the sputtering apparatus. Therefore, there is an inconvenience that the optimum film forming conditions must be set by conducting a large number of experiments for each individual apparatus.

[Object of the Invention]

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to manufacture an optical information recording medium having a recording film with well-controlled recording and reproducing characteristics in sputtering using a gas containing a dissociative hydrocarbon. To provide a method.

[Outline of Invention]

In the method for producing an optical information recording medium of the present invention, various forming condition fluctuation factors that occur in the process of forming a recording film by sputtering a metal target with plasma of a gas containing hydrocarbon mainly discharge the hydrocarbon. It was found that it was caused by the dissociation phenomenon associated with, and the partial pressure of the second hydrocarbon generated by the dissociation phenomenon from the introduced hydrocarbon was set within the range of 2 to 12 with respect to the partial pressure before the start of discharge. It is characterized in that the recording film is formed under control.

〔The invention's effect〕

According to the present invention, a film formation of a recording film which shows excellent recording / reproducing characteristics as an optical information recording medium in any sputtering apparatus and which satisfies the industrial need for a high recording film forming speed. There is an extremely great effect that the condition can be set in advance without repeating many experiments.

Example of Invention

 Hereinafter, the present invention will be described in detail based on examples.

FIG. 1 is an example of a sputtering apparatus for carrying out the present invention. In the figure, 1 is a vacuum container, 2 is an exhaust port connected to a vacuum pump (not shown), 3 is a gas inlet containing a dissociative gas, 4 is a metal target, 5 is a power application terminal,
A counter electrode 6 is grounded and also serves as a substrate holder.
7 is a partial pressure gauge.

When manufacturing an optical information recording medium, a substrate made of a transparent organic resin or glass is placed on the substrate holder 6, and the vacuum container 1 is evacuated to about 10 ⁻⁶ Torr. After that, a gas containing a dissociative gas is introduced from the gas inlet, and a valve (not shown) is opened and closed to adjust the gas flow rate and the exhaust amount to the vacuum pump so that the inside of the vacuum container 1 has a predetermined pressure. Control the amount. The pressure in the vacuum vessel is preferably in the range of 10 ⁻³ Torr to 10 ⁻² Torr. If it is below 10 ⁻⁴ Torr, it is difficult to obtain stable discharge. If it is higher than 10 ^-1 Torr, stable sputtering is difficult. After the vacuum container 1 reaches a predetermined pressure, electric power is applied between the target 4 and the counter electrode 6 via the power terminal 5 to cause discharge. The target 3 is sputtered by the plasma containing the hydrocarbon generated by the discharge, and the recording film is formed on the substrate.

Hydrocarbons dissociate by discharge. Various active species generated by dissociation include those involved in sputtering, those that react with a target, and those that deposit on a substrate. Therefore, the type, quantity, and energy of the active species have a significant influence on the recording / reproducing characteristics of the recording film and the deposition rate on the substrate. The most important factors affecting the dissociation process are the average residence time of the dissociative gas in the discharge space and the applied power density. The dissociation reaction is promoted as the average residence time is longer and the applied power density is higher. The average stay time is defined by the following formula.

That is, the target area usually takes a constant value for each sputtering apparatus, but even if the discharge pressure, the distance between the electrodes, and the applied power device are fixed, the average residence time of the dissociative gas changes if the flow rate of the dissociative gas changes. Therefore, the progress of the dissociation reaction changes, and the formation process of the recording film changes. Even if the flow rate of the dissociative gas is changed, it is possible to keep the pressure in the vacuum container constant by changing the exhaust speed of the vacuum pump. This change in the dissociation process is the main cause of complicating the process of forming the recording film by sputtering the gas containing hydrocarbon.

To further elaborate on this point, in sputtering using a dissociative gas, the pressure in the vacuum container, the flow rate of the dissociative gas, and the appropriate value of the applied power density differ depending on the sputtering apparatus, and once these values become appropriate. Even if it is set, if the value fluctuates during film formation, it is not possible to form a recording film exhibiting good recording / reproducing characteristics at a high forming speed. However, when forming a recording film by sputtering using a dissociative gas, the change in film forming conditions due to the dissociation phenomenon of the dissociative gas was not considered at all, so the recording / reproducing characteristics of the recording film and the substrate Had a significant effect on the deposition rate of P. Therefore, the applicants have further researched the influence of such fluctuations in the film forming conditions on the film formation, and the particular problem is that after introducing the dissociative gas until the pressure in the vacuum container becomes stable, the discharge We have found that it is the change in pressure inside the vacuum container that occurs when power is turned on at the start.

That is, in sputtering using a dissociative gas, the pressure of the dissociative gas in the vacuum container is usually sharply reduced when power is applied at the start of discharge. For this reason, conventionally, the average residence time of the dissociative gas in the discharge space defined by the above equation is reduced, the dissociative reaction of the dissociative gas is suppressed, and as a result, it is set when the dissociative gas is introduced. The initial film formation conditions were lost during film formation, making it difficult to control the recording / reproducing characteristics of the recording film and the deposition rate on the substrate. On the other hand, in the present invention, as described above, the recording / reproducing characteristics of the recording film,
The average residence time of the dissociative gas in the discharge space and the applied power density, which are important factors for the deposition rate on the substrate,
By resetting to an appropriate range immediately after the start of discharge, it is possible in principle to avoid problems caused by fluctuations in film forming conditions. More specifically, for example, while controlling the exhaust rate of the vacuum pump so that the pressure of the dissociative gas does not change again, the flow rate of the dissociative gas is suppressed and the average residence time of the dissociative gas in the discharge space is reduced. The dissociation reaction of the dissociative gas may be promoted by a method of correcting the value.

Here, the applicants confirmed by various experiments that the second hydrocarbon such as C ₂ H ₂ and C ₂ H ₄ is mainly produced by the dissociation of the introduced hydrocarbon by the discharge, and as described above. If the film forming conditions are appropriately adjusted immediately after the discharge is started and the partial pressure of C ₂ H ₂ and C ₂ H ₄ at the time of forming the recording film is controlled within a predetermined range compared to the partial pressure before the start of discharge, the sputtering device It was found that it is possible to form a recording film with controlled characteristics.

FIG. 2 is a diagram for forming a recording film by sputtering a gas containing hydrocarbon. In the figure,
11 is the upper limit of the applied power density, which does not depend on the device, so that the substrate and the recording film are not damaged by the heating by the discharge. The value is usually about ² W / cm ² . 12 is the lower limit of the applied power density, which does not depend on the device, for maintaining stable discharge. The value is usually about 0.01 W / cm ² . 13 is the lower limit of the hydrocarbon flow rate for maintaining the pressure required for discharge. In the case of an ordinary device, the value is about 1 to 10 cm ³ / min. 14 is the upper limit of the hydrocarbon flow rate for maintaining the pressure required for discharge. In the case of a normal device, it is about 100 to 500 cm ³ / min.

In FIG. 2, the hatched region I surrounded by the straight lines 11 and 13 and the curve 15 is a region where the dissociation reaction proceeds excessively because the average residence time of hydrocarbons in the discharge space is long and the applied power density is large. Is. When the recording film is formed in the region I, the action of the active species generated by dissociation and the substrate is too intense, the recording film is not formed, and the powder of the active species is deposited or the recording film is not formed. Even if formed, the surface flatness is remarkably impaired.

In FIG. 2, the hatched region III surrounded by the straight lines 12 and 14 and the curve 16 is a region in which the average residence time of hydrocarbons is short and the applied power density is small, so that the dissociation reaction does not proceed sufficiently. Therefore, the deposition rate of the recording film becomes extremely slow. This is an area unsuitable for forming a recording film on an industrial level.

Due to the above, the area surrounded by straight lines 11, 12, 13, 14 and curves 15, 16
If the recording film is formed in II, a medium having excellent recording / reproducing characteristics can be manufactured, and at the same time, an industrial advantage that the film forming speed is high can be held.

Example 1 In an RF bipolar electrode sputtering apparatus equipped with a circular Te target having a diameter of 20 cm, the distance between electrodes was set to 7 cm, and CH ₄ was introduced as a hydrocarbon to 2 × 10 ⁻² Torr. Introduce CH ₄
While keeping the flow rate constant, the applied power density was variously changed to perform sputtering to form a recording film. Introducing CH ₄ was measured C ₂ H ₂ partial pressure P ₁ at the time of partial pressure P ₂ and the recording layer formed of C ₂ H ₂ in the state of not performing discharge potentiometer. A quadrupole mass spectrometer was used as the partial pressure meter. The relationship between the value of P ₁ / P ₂ and the recording film deposition rate is shown in FIG. In the figure, a is CH ₄
The flow rate is 10 cm ³ / min and b is a curve when the flow rate is constant at 20 cm ³ / min. C ₂ H ₂ is generated immediately with the start of discharge and P ₁ / P ₂
The value of was increased, and a deposition rate greater than 2 was observed. As the applied power increased, the value of P ₁ / P ₂ further increased, and at the same time, the deposition rate also increased.

The curve indicated by c in FIG. 3 shows the relationship between the reflectance of the information recording medium manufactured in this example and the value of P ₁ / P ₂ when the recording film is formed.

The reflectance value changes depending on the refractive index of the recording film,
Usually, about 40% or more is preferable.

The substrate is an acrylic plate with a thickness of 1.5 mm, and the thickness of the recording film is 600Å. The reflectance was measured using a semiconductor laser (wavelength 8300Å). When the value of P ₁ / P ₂ exceeds 12, the reflectance value is rapidly lowered because the flatness of the recording film surface is impaired.

Excellent recording that the medium manufactured in the range of P ₁ / P ₂ is larger than 2 and smaller than 12 has a signal recorded by irradiation with a semiconductor laser beam of 5 mW × 200 nsec, and the modulation of the reproduced signal shows 60%. Reproduction characteristics are shown.

The Te target in the same manner as in Example -2 Example -1 was performed to form the recording layer by sputtering in a plasma of CH _4. Discharge pressure is 2 × 10
^-2 Torr. Introducing CH ₄ was measured partial pressure P _4, and C ₂ H ₄ partial pressure at the time of recording film of C ₂ H ₄ in a state of not performing discharge. The relationship between the value of P ₃ / P ₄ and the deposition rate is shown in Fig. 4 a, b,
Shown in c. a is CH ₄ flow rate 30cm ³ / min, b is 50cm ³ / min, c is
The case is 70 cm ³ / min. With the start of discharge, C ₂ H ₄ is immediately generated and the value of P ₃ / P ₄ increases, and when it exceeds 2, it becomes 100.
A large deposition rate of Å / min or more was obtained. The value of P ₃ / P ₄ further increased with the increase of the applied power, and at the same time, the deposition rate also increased. Under the film forming conditions in which the value of P ₃ / P ₄ was larger than ₂ , the value of the partial pressure ratio P ₁ / P ₂ of C ₂ H ₂ which was measured at the same time was similarly larger than 2. Similarly, when P ₃ / P ₄ was smaller than 12, P ₁ / P ₂ was also 12 or less.

The curve d in FIG. 4 represents the reflectance of the medium manufactured in this example.
It shows the relationship with the values of P ₃ / P ₄ . The substrate is a 1.5 mm acrylic plate, and the thickness of the recording film is 600Å. The reflectance was measured using a semiconductor laser (wavelength 8300Å). The reflectance was decreased rapidly when the value of P ₂ / P ₄ exceeds 12. The flatness of the recording film surface was significantly impaired.

Example 3 In a RF planar magnetron sputtering apparatus equipped with a circular Ag target having a diameter of 15 cm, a mixed gas of CH ₄ and Ar was introduced so as to have a concentration of 5 × 10 ⁻³ Torr. The partial pressure ratio between CH ₄ and Ar was 3/1. The recording film was formed by changing the power density from 0.01 to 0.5 W / cm ² while keeping the mixed gas flow rate constant at 10 cm ³ / min. In parallel, P ₁ and P ₂ were measured. When the partial pressure ratio P ₁ / P ₂ of C ₂ H ₂ is 2, the deposition rate is 150Å / min.
_It was about 7 times larger than the value of 20Å / min when ₁ / P ₂ = 1.8.

Example 4 In a DC planar magnetron sputtering apparatus equipped with a circular Sb target having a diameter of 12 cm, C ₂ H ₆ was introduced at 5 × 10 ⁻³ Torr.

Was performed in the formation of the recording film by the C ₂ H ₆ flow rate varied between power density 0.5~1W / cm ² as 5 cm ³ / min constant. Concurrent with C ₂ H ₄
The partial pressures P ₃ and P ₄ were measured. The surface of the recording film formed in the range where the P ₃ / P ₄ value is smaller than 12 is flat and is 5 mW × 250 ns.
It showed good recording and reproducing characteristics with a recording sensitivity of ec and a modulation of 50%. On the other hand, when the value of P ₃ / P ₄ was 15, the recording film was not formed and the black powdery polymer was deposited on the substrate. P ₃ /
When the value of P ₄ is less than 12, the partial pressure ratio of C ₂ H ₂ P ₁ /
The value of P ₂ was 12 or less.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of an apparatus for carrying out the manufacturing method of the present invention, FIG. 2 is an explanatory diagram relating to the manufacturing method of the present invention, and FIGS. 3 and 4 are recording media manufactured by the present invention. FIG. 3 is a diagram showing a relationship between a deposition rate of a recording film, a medium reflectance, and a hydrocarbon partial pressure ratio at the time of forming the recording film. 1 ... vacuum container, 2 ... exhaust port, 3 ... gas inlet port, 4
...... Target, 5 ...... Power application terminal, 6 ...... Substrate holder, 7 ...... Voltage meter.

Claims (7)

[Claims] 1. A metal target is sputtered with a plasma of a gas containing hydrocarbon to obtain at least metal, carbon,
In the method of forming a recording film containing hydrogen, the partial pressure of the second hydrocarbon different from the introduced hydrocarbon generated from the hydrocarbon introduced by discharge in the process of forming the recording film is set.
Let P ₁ be the second hydrocarbon partial pressure when the hydrocarbon is introduced but the discharge is not performed be P _2, and the value of P ₁ / P ₂ should be in the range of 2 to 12 so that the discharge is performed. And a method for manufacturing an optical information recording medium. 2. The hydrocarbon introduced for forming a recording film is CH ₄
The method for manufacturing an optical information recording medium according to claim 1, wherein 3. The method for producing an optical information recording medium according to claim 1, wherein the second hydrocarbon produced from the introduced hydrocarbon when forming the recording film is C ₂ H _2. . 4. The method for producing an optical information recording medium according to claim 1, wherein the second hydrocarbon produced from the introduced hydrocarbon at the time of forming the recording film is C ₂ H _4. . 5. The optical information recording medium according to claim 1, wherein the introduced hydrocarbon flow rate, discharge pressure, and applied power density are controlled so that the value of P ₁ / P ₂ falls within the range of 2 to 12. Manufacturing method. 6. The optical information according to claim 1, wherein the plasma is a mixed gas of hydrocarbon and a rare gas, and the partial pressure of the introduced hydrocarbon is higher than the partial pressure of the rare gas at the time of introduction. Recording medium manufacturing method. 7. A metal target containing at least one of Te, Sb, and Ag, as set forth in claim 1.
A method for manufacturing the optical information recording medium according to the item 1.