JPH02167781A - Information recording medium - Google Patents

Abstract

PURPOSE:To provide a long-lived information recording medium even under the circumstances of high temperature and humidity by forming on a substrate a recording film of amorphous state which contains Au, Te100-x(2<=x<=50 atomic %) alloy as well as carbon and hydrogen, and the more amount of carbon in the part in contact with a substrate than that of the film in a mixed atmosphere of the specified amount of hydrocarbon gas and rare gas. CONSTITUTION:A recording film of amorphous state is formed on a substrate 13. This film contains Au, Te100-x(2<=x<=50 atomic %) alloy as well as carbon and hydrogen at 5<=Q<=50% or less where a flow ratio Q={X/(X+Y)}X100% and the more amount of carbon in the part in contact with the substrate than that in the film, in the flow X of a mixed hydrocarbon gas and rare gas atmosphere on the substrate. In addition, the subject medium has a long life even under circumstances of high humidity thanks to the recording film 14 provided which contains carbon and hydrogen in the AuTe alloy on the substrate. If film is formed at 5<=Q<=50% where Q is a flow rate, the optical absorption rate does not deteriorate due to a large percentage of carbon C and hydrogen H. If the film is 1,000Angstrom thick, the reflection factor becomes an extremely low value on account of a multiple interference effect. Then if the film is changed from an amorphous phase (dispersed state) to a crystal phase (flocculated state), an increase in the reflection factor is recognized as significant, and information can be recorded.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is directed to writing information by a phase change caused by irradiation with a laser beam, for example, and to change the amplitude of the laser beam due to the phase change of the component. The present invention relates to an information recording medium in which the information is read through changes in the information.

(Prior Art) As a type of information recording medium in which information is recorded by laser beam irradiation and the recorded information is reproduced, one equipped with a recording film containing Te as a main component has been developed. There is. Furthermore, a recording film containing carbon and hydrogen in addition to the Te-based recording film has been developed and put into practical use (see Japanese Patent Laid-Open No. 58-9234).

When creating this recording film, Te is sputtered in an atmosphere containing hydrocarbon gas. Then, a film of simple Te (T
A recording film (
A Te-C film (hereinafter referred to as Te-C film) is obtained. This recording film is an amorphous film containing tellurium (Te)% carbon (C) and hydrogen (H), and at least carbon (C) and hydrogen (H).
) are known to form chemical bonds.

This recording film cannot be formed by vapor deposition using tellurium (Te) and hydrocarbon as sources (without using plasma), as in the case of the Te film. This happens once the hydrocarbon gas is decomposed in the plasma.

This is because the film is formed through a chemical reaction between carbon (C) and hydrogen (H), and this is a major feature when forming an optical recording film.

(Problem to be Solved by the Invention) A recording film made of tellurium, (Te) and hydrocarbon as described above and a recording film formed of tellurium (Te) are
In comparison, under high temperature and high humidity (accelerated conditions) at -90% °C, Te film oxidizes within just one week and optical recording performance is impaired, whereas Te -C film oxidizes even after one month. The inside of the film was not oxidized and was stable. However, the recording film of the Te-C film also crystallizes at high temperatures (above about 75 degrees Celsius), resulting in a rough surface, which increases noise and has a greater effect on the reproduced signal. .

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, it is an object of the present invention to provide an information recording medium that has a long life even in a high temperature and high humidity environment.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention includes a substrate and an AuTe alloy on the substrate in a mixed atmosphere of a hydrocarbon gas and a rare gas at a flow rate of X. Flow rate ratio Q={X/(X0Y)) X10
0% is 5≦Q≦50% or less and Au x Te 100-
11. To provide an information recording medium comprising an amorphous recording film containing an alloy (2≦x≦50 at. It is something.

(Function) The information recording medium of the present invention can have a long life even in a high humidity environment by providing a recording film containing carbon and hydrogen in an AuTe alloy. Also,
Carbon (
Too much C) and hydrogen (H) do not cause a decrease in optical absorption. Furthermore, since the amount of carbon in the portion in contact with the substrate is greater than that in the interior, oxidation of the substrate/recording film interface does not occur.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing the structure of an information recording medium 18 of the present invention. The information recording medium 18 of the present invention is composed of a substrate 13 and a recording film 14 laminated on the substrate 13.

The substrate 13 is made of a material that is transparent to laser light that is irradiated onto the information recording medium for recording and reproducing information. For example, when using a laser beam with an oscillation wavelength near near infrared, polycarbonate (PC),
Polymethyl methacrylate (PMMA), glass, polyolefin, epoxy resin, etc. are used for this substrate 13.The information writing/reproducing laser beam passes through the recording film 1.
When the light is incident from the four sides, it may be made of an opaque material.

The recording film 14 is made of an Au-Te alloy containing carbon and hydrogen.

If there is a difference in the reflectance of the cluster components dispersed in the C-H matrix between aggregation and dispersion, for example, the dispersion state of the clusters can be used as a state where no information is recorded, and the state of aggregation can be used as a state where information is recorded. It is possible to record information by making it correspond to each state. This aggregation of clusters can be caused by heat generation by laser irradiation, but tellurium (Te)
In a recording film formed by a single substance, the difference in reflectance between aggregation and dispersion is not so large. However, tellurium (
When a component that can form an alloy with Te is added, a difference in reflectance may be observed. Therefore, tellurium (T
It was discovered that if 2 to 50 atomic % of gold (Au) was added to e), the difference in reflectance was significant, and it was decided to create a recording film made of an Au-Te alloy.

In the information recording medium 18 according to the present invention, recorded information is reproduced by detecting a difference in the reflectance of the recording film 14 that has undergone a phase change. This is advantageous because it becomes large when the film thickness is close to that which gives the extreme value due to interference. Therefore, the film thickness of the recording film according to the present invention is such that the interference effect decreases as the film thickness increases and converges to a certain reflectance, and that the laser power during recording increases as the film thickness increases. Taking this into consideration, the thickness is set to 5000 angstroms or less.

Example 1 A method for forming the information recording medium 18 shown in FIG. 1 will be described.

FIG. 2 is a schematic diagram of a sputtering apparatus for forming the information recording medium 18 of the present invention. First, the pulp 2 of this sputtering device is opened to the rotary pump 3 side, and the inside of the chamber 1 is set to zero.
．． It was evacuated to 2 Torr.

Next, open the pulp 2 to the cryopump 5 side and
It was evacuated to 10-5 Torr or less. At this time, since there was no need to control the displacement, the conductance valve 4 was left fully open.

Next, the pulp 6 was opened, and 1105 CC of Ar gas was introduced into the chamber 1 from the Ar gas line 7 while being controlled by a mass flow controller (not shown). Next, the pressure inside the chamber 1 was monitored with an ion gauge (not shown), and the pressure inside the chamber 1 was adjusted to 5
Adjusted to r. After confirming that this pressure does not fluctuate, the DC power supply 1
Sputter cleaning was performed by applying 0 to 100 W and performing sputter discharge for 5 minutes with the shutter 11 closed.

After stopping the supply of Ar gas and the supply of DC power, the inside of the chamber 1 was once
-'Torr or less. Then pulp 6 and 17
Open the chamber 1 and introduce Ar gas and CH4 gas into the chamber 1.
5SC each through gas line 7 and CH4 gas line 8 while adjusting with a mass flow controller (not shown).
CM and 1105CC were introduced. Then, using the conductance pulp 4, the pressure inside the chamber 1 is increased to 5×10−
It was controlled at 3 Torr. After confirming that there was no pressure fluctuation, 100 W was applied to the Au Te target 9 from the DC power supply 10. Sputter discharge was performed. After confirming that the discharge is stable, the shutter 11 is opened and a recording film 14 containing an AgTe alloy and carbon and hydrogen is placed on a polycarbonate (PC) substrate 13 that has been set in advance on the rotor 12. were laminated. The rotor is 60
Rotated at rpm.

Next, after stopping the -degree discharge and exhausting the gas, the C
H, and A "Gas was introduced by IOSCCM each. Approximately 1
After confirming that a pressure of 5 x 10-'Torr was maintained for a period of time, discharge was performed. When the film thickness reached 1000 angstroms, the shutter was closed and power supply was stopped.

Next, the conductance valve 4 is fully opened, and the inside of the chamber 1 is heated to 1×10-' Torr using the cryopump 5.
Exhausted to below. After opening the pulp 15 and introducing N2 gas into the chamber 1 from the N2 gas line 16 to return it to atmospheric pressure, the information recording medium 18 was taken out.

Recording film 1 of information recording medium 18 formed in this way
As a result of X-ray diffraction analysis, Sample No. 4 was confirmed to be an amorphous film in which no diffraction peak was observed from a specific diffraction angle. Unlike a polycrystalline film, this amorphous film does not have grain boundaries, so the reproduced laser light is not modulated at the grain boundaries and does not generate grain boundary noise.

The recording film 14 containing Au 5sTe sy, carbon (C) and hydrogen (H) obtained by the above method has a film thickness of 10
At 0.00 angstroms, as shown in FIG. 3, the reflectance reaches a minimum value due to the multiple interference effect. Therefore, when the phase is changed from amorphous (dispersed state) to crystalline state (agglomerated state) at this film thickness, a significant increase in reflectance can be observed, which indicates that information has been recorded.

By the way, in the above embodiment, the flow rate of methane gas was increased at the final stage of sputtering discharge to increase the flow rate ratio Q, but normally when sputtering is performed in a mixed atmosphere of hydrocarbon gas and rare gas, The amount of carbon produced is
Even if the flow rate of hydrocarbon gas is not increased, it may be possible to utilize the fact that the flow rate is higher at the end of discharge than at the beginning of discharge.

Example 2 By the method shown in Example 1, A u 33T e67
, the recording film 14 containing carbon (C) and hydrogen (H) was formed on the PC board 13 with a film thickness of 250 angstroms, the rotation speed was 180 Orpm, the recording frequency was 3.7 MHz,
Under conditions of recording pulse width 5 n5ec, linear velocity 5. 5
When writing with a laser power of 711W at the location corresponding to n+ /see, a good C/N of 30dB was obtained.
(Carrier/Noise) ratio was obtained.

Example 3 In the recording film 14 shown in Example 2, when the writing laser power exceeds 10 mW, not only cluster components agglomerate but also bits are formed, which may cause confusion when reading information. Therefore, in order to prevent the formation of pits, a dielectric film 20 having a thickness of 300 to 1000 angstroms is laminated on the recording film 14 formed on the substrate 13, as shown in FIG. An information recording medium 21 having the following properties was manufactured. This dielectric film 20 is made of Si
02, Sl 0. It can be formed using a material such as AN or 81N. Moreover, the film thickness of the dielectric film 20 is
If it is less than 300 angstroms, pinholes may occur, and if it is more than 1000 angstroms, it will take a long time to form the film, which is not practical.

Further, as shown in FIG. 5, the dielectric film 20 is connected to the information recording medium 1 consisting of the substrate 13 and the recording film 14 shown in FIG.
8 are bonded together via the adhesive layer 19, the recording film 14
It also serves to protect the surface from the adhesive layer 19. In addition, in this information recording medium, in order to record information by phase change, a rim (bulge) is formed around the pit.
will not occur. Therefore, it was possible to record information with narrower bit intervals, and it was possible to record information with high density.

Example 4 The reflectance of a 250 angstrom thick recording film containing Au 33T667 formed by the method of Example 1 at a flow rate ratio of Q-5 and 50% is as shown in FIG.
In an atmosphere (65℃-90
%) was extremely stable with no significant change for 1000 hours.

That is, in the information recording medium 18 of the present invention, the PC
, PMMA, etc., which are relatively permeable to oxygen and water, can be formed without using the dielectric protective film 20. The optical recording sensitivity of the information recording medium is
Forming a film on an organic resin substrate with low thermal conductivity is better and more practical than forming a film on a glass substrate. Note that the reflectance in Figure 6 is 1
It has been standardized as

Next, FIG. 7(a) shows the results of Auger electron spectroscopy (AES) in the film thickness direction of the recording film formed under Q-50%. Furthermore, as a comparative example with the present invention, FIG. 7(b) shows the results of Auger electron spectroscopy (AES) in the case of a recording film in which the amount of carbon is the same between the inside of the film and the interface between the substrate and the film. The recording film contains carbon (C), tellurium (Te), and gold (
Although hydrogen (H) is included in addition to Au), hydrogen (H) cannot be detected based on the principle of Auger electron generation.

Therefore, carbon (C), tellurium (Te) and gold (Au
) components as well as oxygen absorbed by oxidation.

AES measurement was started from the surface of the film, and sputtering with Ar" ions was performed until the organic resin substrate appeared. According to the analysis results in FIG. 7, the substrate 1 of the recording film 14 of the present invention
In the region in contact with 3, the amount of carbon (C) is greater than the amount in the film. - On the other hand, it can be seen that oxidation has not progressed because the amount of oxygen (H) is smaller than the amount in the film.

[Effects of the Invention] As explained above, according to the present invention, it is possible to provide an information recording medium with a long life even in a high temperature and high humidity environment. Furthermore, it is possible to provide an information recording medium that does not oxidize even at the interface with the substrate and has a highly sensitive recording film.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of an information recording medium according to an embodiment of the present invention, FIG. 2 is an optical recording film forming apparatus for forming the information recording medium shown in FIG. 1, and FIG. 3 is a diagram showing the effect of multiple interference. FIG. 4 and FIG. 5 are diagrams showing the structure of an information recording medium according to another embodiment of the present invention, and FIG. 6 is a diagram showing changes in playback time and reflection level. FIG. 7 is a diagram showing the results of AES analysis of the recording film. Substrate 14 Information recording medium recording film

Claims (1)

[Claims] (1) Substrate and AuTe alloy on this substrate in a mixed atmosphere of hydrocarbon gas and rare gas at flow rate X, flow rate ratio Q = {X/(X+Y)}×
100% Au_xT formed with 5≦Q≦50% or less
an amorphous recording film containing an e_1_0_0_-_x (2≦x≦50 atomic %) alloy, carbon and hydrogen, and in which the amount of carbon in the portion in contact with the substrate is greater than the amount of carbon inside the film; Characteristic information recording media.