JPH02167779A - Information recording medium - Google Patents

Abstract

PURPOSE:To provide a long-lived data recording medium even under circumstances at high temperature and humidity by forming a recording film of amorphous state which contains Cu, Te100-x(5<=x<=45 atomic %) alloy as well as carbon and hydrogen in a specific flow of a mixed hydrocarbon and rare gas atmosphere with the more amount of carbon in the part in contact with the substrate than that in the film, on the substrate. CONSTITUTION:A recording film 14 of amorphous state is provided on a substrate 13. This film contains an AuTe alloy in the flow X of a mixed hydrocarbon gas and rare gas atmosphere on a substrate and Cu, Te100-x(5<=x<=45 atomic %) alloy as well as carbon and hydrogen at less than 5<=Q<=50 % where Q={X/(X+Y)}X100%. The film also contains the more amount of carbon in the part in contact with the substrate than that of the film. If a film is formed at less than 5<=Q<=50 % (Q = flow rate), an optical absorption rate does not deteriorate due to the excessive amount of carbon C and hydrogen H. A recording film 14 reaches the minimum value of reflection factor due to a multiple interference effect, if the film is 1,000Angstrom thick. If the film is changed from an amorphous phase (dispersed state) to a crystal phase (flocculated state) at that thickness, the reflection factor becomes significant and data can be recorded accordingly.

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, information is recorded by irradiation with laser light and the recorded information is reproduced.
A device equipped with a recording film containing Te as a main component has been developed. 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 and contains 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. After hydrocarbon gas is once decomposed in plasma, carbon (C) and hydrogen (H
) is formed through a chemical reaction, and this is a major feature when forming an optical recording film.

(Problem 8 to be solved by the invention) A recording film made of tellurium (Te) and a hydrocarbon as described above and a recording film formed of tellurium (Te) are
When compared under high temperature and high humidity (accelerated conditions) at -90% °C, the Te film oxidizes within just one week and optical recording performance is impaired, whereas the Te-C film oxidizes after one month. The inside of the membrane was not oxidized and remained 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/(X+Y)) x10
0% is 5≦Q≦50% or less and Cu s Te too-
*(5≦x≦45 atomic %) An information recording medium comprising an amorphous recording film containing an 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. 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 a CuTe 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 having an oscillation wavelength near near infrared, polycarbonate (PC), polymethyl methacrylate (PMMA), glass, polyolefin, epoxy resin, etc. are used. Note that this substrate 13 is such that the information writing/reproducing laser beam is connected to the recording film 14.
When the light is incident from the surface side, it may be made of an opaque material.

The recording film 14 is made of a Cu-Te alloy containing carbon and water.

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 due to laser irradiation, but in a recording film formed of a single Te, the difference in reflectance between aggregation and dispersion is not so large. However, when a component that can form an alloy with Te is added, a difference in reflectance may be observed. Therefore, in the present invention, Tel:Cu is
It was discovered that if ~45 atomic % was added, the difference in reflectance was significant, and it was decided to create a recording film made of a Cu-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, open the valve 2 of this sputtering device to the rotary pump 3 side, and make the inside of the chamber 1 zero.
, evacuated to 2 Torr.

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

Next, the valve 6 was opened, and IOSCCM was introduced into the chamber 1 while adjusting Ar gas from the Ar gas line 7 using 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.

A: After stopping the gas supply and DC power supply, use the cryopump 5 to temporarily pump the inside of the chamber 1 to I
-'Torr or less. Then valves 6 and 17
Open the A gas and CH4 gas in 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 IO5CCM were introduced. Next, the pressure inside the chamber 1 is reduced to 5X10-'T using the conductance valve 4.
It was controlled to orr. After confirming that there is no pressure fluctuation, connect the DC power supply 10 to the Cu Te target 9.
100W was applied from After confirming that the sputter discharge is stable, open the shutter 11,
The polycarbonate (
PC) A recording film 14 containing a CuTe alloy and carbon and hydrogen was laminated on a substrate 13. rotor is 60 rpm
I rotated it. Next, after stopping the -degree discharge and exhausting the gas, IOSCCM of each CH4 and A gas was introduced. It was confirmed that the pressure of 5 X 10 '' Torr was maintained for about 1 minute. After that, discharge was caused. When the film thickness reached 1000 angstroms, the shutter was closed and power supply was stopped.

Next, the conductance valve 4 was fully opened, and the inside of the chamber 1 was evacuated to below I×10 −′ Torr using the cryopump 5 . After opening the valve 15 and introducing N2 gas into the chamber 1 from the N2 gas line 16 to return the pressure 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 Cu53Te67, 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, at this film thickness, it changes from amorphous (dispersed state) to crystalline state (agglomerated state).
When the phase is changed to , a significant increase in reflectance can be observed, indicating 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, Cu 3iTe 67,
The film thickness of the recording film 14 containing carbon (C) and hydrogen (H) is 2
A film with a thickness of 50 angstroms was formed on a PC board 13 at a rotation speed of 180 Orpm and a recording frequency of 3.7 MH2.
, recording pulse width 5 n5ec, linear velocity 5.
When writing with a laser power of 7mW at a location equivalent to 5m/see, a good C/N of 30dB was obtained.
(Carrier/Nolse) ratio was obtained.

Example 3 In the recording film 14 shown in Example 2, when the writing laser power exceeds 10a+W, not only cluster components aggregate but also pits 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. As this dielectric film 20, S
It can be formed using materials such as l 02, Si 01AII, and SiN. Furthermore, if the thickness of the dielectric film 20 is less than 300 angstroms, pinholes may occur, and if it is more than 1000 angstroms, the film formation time will be longer, 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 a single adhesive layer. Furthermore, in this information recording medium, since information is recorded by phase change, a rim (bulge) that is formed around the pit does not occur. Therefore, it was possible to record information with narrower pit intervals, and it was possible to record information with high density.

Example 4 The reflectance of a 250 angstrom thick recording film containing Cu 5sTe 67 formed by the method of Example 1 at a flow rate ratio of Q-5 and 50% is T as shown in FIG.
In an atmosphere where the reflectance of e single film and Cu Te single film (Q-○) decreases due to rapid oxidation (65℃
Even at 0%), it 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 copper (
Although hydrogen (H) is included in addition to Cu ), hydrogen (H) cannot be detected based on the principle of Auger electron generation.

Therefore, carbon (C), tellurium (Te) and copper (Cu)
) 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 shown 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 that has a long life even in a high temperature 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 CuTe 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% Cu_xT formed with 5≦Q≦50% or less
an amorphous recording film containing an e_1_0_0_-_x (5≦x≦45 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.