JPS6358634A - Information recording medium and its production - Google Patents

Abstract

PURPOSE:To increase a change in reflectivity by the phase transformation of crystal and to prevent the change in recording characteristic even after repeated recordings and erasures by projecting a light beam locally to a recording film formed of an In-Sb alloy to change the optical characteristic thereof. CONSTITUTION:The recording layer 3 sandwiched by dielectric films 2 and 6 on a substrate 1 is formed by alternately laminating In layers 4 and Sb layers 5 to 5-50Angstrom thickness by simultaneous binary sputtering of In and Sb. An alloy uniformly mixed with In and Sb is formed when the laser light 10 stopped down by a lens 9 is projected to recording bits 8 to heat the same. 45-50atom% indium is thereby formed with <=+ or -1% dispersion, by which the change in the reflectivity by the phase transformation of the crystal is increased and the recording signal quality is increased. The change in the recording characteristic is decreased even after the repeated recordings and erasures. The life is extended by the stronger bond of In and Sb.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Industrial Application Field) This invention relates to an information recording medium in which information is recorded by causing crystal phase transformation in a recording layer using a light beam, and a method for manufacturing the same.

(Prior Art) Conventional optical discs include those shown in FIGS. 4 to 6. The optical disc shown in FIG. 4 is produced by forming a thin film 2 of a low-melting point material on a substrate 1, and spot-irradiating this thin film 2 with a laser beam to locally melt and evaporate the thin film 2, forming minute sixes 3. .

Information is recorded by forming this hole 3.

In addition, in the optical disc shown in FIG. 5, when two or more thin films 6 and 7 are laminated on the substrate 4 and spot irradiated with a laser beam, bubbles are generated from the base film 6 and the thin film 7 has a bulge 8. form and record information. However, in the optical disk shown in FIG. 4 or FIG. 5, irreversible changes are made to the recording portion (hole 3, bulge 8), so although recording is possible, erasing is not possible.

In the optical disc shown in FIG. 6, a thin film 10 is formed on a substrate 9 using a material whose structure changes depending on temperature, and a local part 11 of the thin film 10 is heated by spot irradiation with a laser beam to change the structure to a structure having different light reflectance. It is used to record information by changing the In this case, recording and erasing becomes possible if the thin film 10 is formed of a material whose optical properties change reversibly depending on temperature.

Such materials include semiconductor materials such as Ge5Te or GeTe. They selectively take two states, a crystalline phase and an amorphous phase, depending on the temperature, and since the complex refractive index differs in each state, these two states can be reversibly changed by heat treatment with a laser beam. (J, of' Non-Crystal
line 5 solid 41 (1970) and Mf
3talurgiCal Transaction
s 2841 (1971)).

However, the aforementioned semiconductor materials have problems in that they are chemically unstable and have low durability, making it difficult to put them into practical use. That is, when a semiconductor such as Ge, Te or GeTe is heated to a molten state and cooled at a high speed, it becomes amorphous, and when it is heated to a temperature lower than its melting point and cooled at a low speed, it becomes crystalline. The amorphous phase and the crystalline phase each have a complex refractive index expressed as n-1k (where n is the refractive index, k is the extinction coefficient,
i is an imaginary unit). This makes it possible to write and read information, but when these semiconductors are made into thin films, they have low chemical stability and gradually corrode and deteriorate in the atmosphere. For this reason, it is difficult to put it to practical use as a material for optical disks for recording and reproducing information.

Therefore, instead of chalcogen-based semiconductors such as Te, Ge or GeTe, indium (In)-antimony (S b)
alloys are attracting attention as information recording media. This In
In the -3b alloy, t-th transformation of the crystal phase occurs when irradiated with a light beam, and the alloy changes reversibly between the crystal phase and other crystal phases. In other words, among the In 100-x S b alloy systems, those having a composition in which X is 50 to 70 have reflectance changes due to this phase transformation between crystals. Furthermore, unlike chalcogen-based semiconductors, this alloy is chemically stable and is thought to have a long life.

(Problems to be solved by the invention) However, the conventional InSb alloy 100
The thin film of -x x is created by vapor deposition of an ingot, and it is extremely difficult to control the composition within ±2 atomic percent using this method. Furthermore, information recording media having recording films made of this alloy have a problem in that their compositions vary widely during mass production. Due to this variation in composition, the magnitude of change in reflectance due to phase transformation varies, making it less practical.

This invention was made in view of such circumstances, and
The purpose of the present invention is to provide an information recording medium that can control the composition of an In-Sb alloy to a predetermined value with high precision, has excellent mass productivity, and has improved characteristics as an optical memory, and a method for manufacturing the same. do.

[Structure of the Invention] (Means for Solving the Problems) An information recording medium according to the present invention has a recording film formed of an indium-antimony alloy obtained by simultaneously sputtering an indium target and an antimony target. , is characterized in that information is recorded by locally irradiating the recording film with a light beam to change its optical characteristics.

Further, another information recording medium according to the present invention is an indium-based medium having an indium content of 45 to 50% in atomic percent.
It has a recording film made of an antimony alloy, and is characterized in that information is recorded by locally irradiating the recording film with a light beam to change its optical characteristics.

Further, in the method for manufacturing an information recording medium according to the present invention, in the method for manufacturing an information recording medium in which information is recorded by irradiating a recording film on a substrate with a light beam to change its optical characteristics, an indium target and an indium target are used. A recording film of an indium-antimony alloy is formed on a substrate by dual simultaneous sputtering of an antimony target.

(Function) As a result of experimental research on the relationship between the composition and the amount of change in reflectance for In-Sb alloys, the inventors found that
-Sb alloy system, 100-x
x Reflectance changes greatly in In50Sb5Q to I
It has been found that the alloy is n45Sb55 (that is, X is in the range of 50 to 55). When the composition is outside this range, the amount of change in reflectance becomes significantly small. For example, like In52Sb48 and In45Sb55,
A difference in composition of 2% in atomic percent makes the amount of change in reflectance extremely small.

Therefore, it is necessary to form the In--Sb alloy recording film so that the In content is within the range of 45 to 50 atomic %. In order to control the alloy composition within this range with high precision, in the present invention, the In target and the SB target are formed by dual simultaneous sputtering. According to the two-component simultaneous sputtering method, the composition of the In-Sb alloy can be controlled within ±0.5 at. Can be formed stably.

(Embodiments) Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. 1 and 2 are cross-sectional views showing an information recording medium according to an embodiment of the present invention. A dielectric film 2 is formed on a resinous substrate 1 made of polycarbonate or the like, and a recording 1143 is formed on this dielectric film 2. A dielectric film 6 is formed on the recording film 3, and a protective film 7 made of ultraviolet curing resin or the like is provided on the dielectric film 6. The dielectric film 2.6 is
This is provided to prevent evaporation of the recording film 3 due to laser beam irradiation. The protective film 7 prevents handling flaws from occurring on the information recording medium.

As will be described later, the recording film 3 is formed by a binary simultaneous sputtering method using an indium (In) target and an antimony (Sb) target, and immediately after film formation, as shown in FIG. This is a laminate in which human In layers 4 and SB layers 5 are alternately laminated. By heating the entire recording layer 3 in the form of a laminate, or by irradiating a laser beam 10 focused by a lens 9 onto a predetermined recording bit 8 as shown in FIG. By heating, as shown in FIG.
and sb are uniformly mixed to produce an IN-Sb alloy. In this way, by heating the laminate consisting of the In layer 4 and the SB layer 5, both layers are uniformly mixed and initialized.

FIG. 3 shows a sputtering film forming apparatus for forming this information recording medium. The chamber 10 has a gas exhaust port 11
The gas exhaust boat 11 is connected to a suitable exhaust device (not shown) to exhaust the inside of the chamber 10 through the exhaust port 11, and the gas introduction port 12 is connected to an appropriate exhaust device (not shown) to exhaust the inside of the chamber 10. The introduction boat 12 is connected to a supply source (not shown) to supply Ar gas to the chamber 1.
It is designed to be introduced within 0.

The substrate 1 (polycarbonate plate) is supported with its surface horizontally at the upper part of the chamber 10 by a support device 13, and the support device 13 rotates the substrate 1 during film formation. A flat electrode 14.1 faces the substrate 1.
5 is installed in the chamber 10, and this electrode 14.
15 are connected to high frequency power sources 16 and 17, respectively. An In target 18 and an SB target 19 are placed on the electrodes 14 and 15, respectively. Shutters 20.degree. 21 are arranged between the electrodes 14.degree. 15 and the substrate 1, respectively.

According to this film forming apparatus, first, the inside of the chamber 10 is evacuated to a vacuum of, for example, 10''6 torr using an exhaust device. Ar gas is then introduced into the chamber 10 from an Ar gas source at a flow rate of, for example, 20 SCCM, and the gas pressure within the chamber 10 is adjusted to, for example, 5 millitorr (m torr).

Then, the polycarbonate substrate 1 is heated, for example, at 60 r
While rotating at pa+, high frequency power was applied to the SiO2 dielectric target (not shown), and 5i02
The dielectric film 2 is formed to have a thickness of, for example, 1000 mm.

Next, with the shutters 20 and 21 closed, the In target 18 and the sb shutter are
High frequency power of 50 W and 45 W is applied to the nets 19, respectively. After pre-sputtering for a predetermined time, the shutter 2
0.21 and sputtering In and sb onto the substrate 1.

If this sputtering is continued for about 1 minute and 30 seconds, a laminate of, for example, 1000 In layers and sb layers is formed. Next, turn off the high frequency power supply 16.17, and turn off the SiO2
By applying high frequency power to the target, for example, about 500
A SiO2 dielectric film 6 is formed. Next, the sample after the film formation is removed from the support device 13, and outside the chamber 10, the ultraviolet curable resin is applied with a spinner to a thickness of about 3 μm, for example.
The protective film 7 is formed by applying the resin and curing it with ultraviolet rays.

In this dual-component simultaneous sputtering, the sputtering speed of In and sb is measured individually using a film thickness meter such as a crystal oscillator, and the film formation speed is controlled by feeding back the measurement results to the high-frequency power applied to each target. Variations in the composition ratio of In and sb in the recording layer formed under highly accurate control can be easily reduced to ±1% or less. By the way, when the inventors of this application formed a film of In-5b alloy under the above film-forming conditions, the target composition was In50 sbs O
On the other hand, an alloy having a composition of In49.5Sb50.5 could be obtained.

While rotating the optical disc on which the In-8b alloy recording film formed in this way was coated at 600 rpm, first,
This optical disk was irradiated with a semiconductor laser beam with a continuous output of 11 mW to initialize its recording bit 8 (FIG. 2). Next, a semiconductor laser beam with a wavelength of 830 nta was applied with a power of 15 mW and a pulse width of 100 ns.
The signal was recorded upon irradiation to cause a phase transformation of the crystal. A signal component approximately twice as large as the DC component of the reflected light was obtained from this recording section. A similar signal recording experiment was conducted on an optical disk having an In-5b recording film formed by vapor deposition, but the signal amount in this case was about 1.3 times the DC component.

Furthermore, when this recording section was irradiated with a laser beam using the same semiconductor laser with an output of 5 mW and a pulse width of 300 ns, the signal was erased and no residual erasure was observed.

When recording and erasing signals was repeated under the above-mentioned semiconductor laser beam irradiation conditions, in the recording medium according to the embodiment of the present invention, no change was observed in the amount of recorded signals even after approximately 104 repetitions, and no erased signal remained. was also not recognized. However, in a conventional recording medium having a recording film formed by vapor deposition, the signal remains largely unerased after approximately 100 recording/erasing repetition tests, and the S/N ratio disappears after 103 repetitions.

As described above, in the present invention, since the change in reflectance due to the phase transformation of the crystal is large, the amount of recorded signal is large, and even if recording and erasing are repeated, there is little change in the recording characteristics, and the life is long. Since the In-Sb alloy film is formed using a dual-component simultaneous sputtering method, the composition ratio of In and sb can be controlled with high precision. This is considered to be because the In layers 4 and the sb layers 5 are alternately stacked, so that a compound with a strong bond between In and sb is formed after initialization by heating such as laser irradiation. As described above, since the bond between In and sb is strong, crystal-to-crystal transition occurs quickly upon subsequent erasing of recording by a laser pulse.

Therefore, the In--Sb alloy film formed by this dual-component sputtering method is suitable as a phase-change erasable optical disk material.

[Effects of the Invention] In this invention, since the change in reflectance due to the phase transformation of the In-Sb alloy crystal is large, the amount of recorded signal is large;
Further, even if recording and erasing are repeated, the recording characteristics do not change much and the lifespan is long.

[Brief explanation of drawings]

1 and 2 are cross-sectional views showing an information recording medium according to an embodiment of the present invention, and FIG. 3 is a schematic view showing a film forming apparatus thereof.
4 to 6 are cross-sectional views showing conventional information recording media. 1: Substrate, 2, 6: Dielectric film, 3: Recording film, 4HIn layer, 5USB layer, 18: In target, 19, Sb target. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Commissioner of the Patent Office Kuro 1) Akio Yu 1, Indication of case Patent application No. 1983-203349 2, Invention name information recording medium and its manufacturing method 3, relationship with the case of the person making the amendment Patent applicant (307) Toshiba Corporation 4, agent 5, voluntary amendment 7, content of amendment (1) Specification page 14 In the 10th line, "300 ns" is corrected to "l'-1300 ns".

Claims (8)

[Claims] (1) It has a recording film made of an indium-antimony alloy obtained by simultaneously sputtering an indium target and an antimony target, and changes its optical characteristics by locally irradiating this recording film with a light beam. An information recording medium characterized by recording information by. (2) A patent characterized in that a recording layer of an indium-antimony alloy is obtained by alternately forming multiple layers of indium films and antimony films by dual-component simultaneous sputtering, and then uniformizing the indium and antimony layers. An information recording medium according to claim 1. (3) Claim 1, characterized in that indium and antimony are made uniform by heating the laminate of the indium film and antimony film with a laser beam.
or the information recording medium described in paragraph 2. (4) The information recording medium according to claim 1, wherein the composition of the indium-antimony alloy is 45 to 50% in atomic percent of indium. (5) It has a recording film made of an indium-antimony alloy with an indium content of 45 to 50 atomic percent, and the optical characteristics are changed by locally irradiating this recording film with a light beam. An information recording medium that records information by (6) In a method of manufacturing an information recording medium in which information is recorded by irradiating a recording film on a substrate with a light beam to change its optical properties, the method of manufacturing an information recording medium in which information is recorded by irradiating a recording film on a substrate with a light beam to change its optical properties, is to form a film on a substrate by simultaneous dual sputtering of an indium target and an antimony target. A method of manufacturing an information recording medium, comprising forming a recording film of an indium-antimony alloy. (7) A patent characterized in that a recording film of an indium-antimony alloy is obtained by alternately forming multiple layers of indium films and antimony films by dual-component simultaneous sputtering, and then uniformizing the indium and antimony layers. A method for manufacturing an information recording medium according to claim 6. (8) The method for manufacturing an information recording medium according to claim 6, wherein the composition of the indium-antimony alloy is 45 to 50% by atomic percent of indium.