JP2000339760A - Optical information recording medium and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase change type optical information recording medium having a light absorbing layer and a reflective layer, in order to improve characteristics by suppressing crosstalk, etc. Provided is a configuration capable of easily increasing the accompanying change in reflectance (difference between reflectance Rc in a crystalline state and reflectance Ra in an amorphous state; Rc-Ra). SOLUTION: On a substrate 1, a first dielectric layer 2, a phase change recording film 3, a second dielectric layer 6, a light absorption layer 7, and a reflection layer 8 are formed in this order. The refractive index of the first dielectric layer is made larger than the refractive index of the second dielectric layer, and for example, Rc is set to 15%.
As described above, Ra is set to 2% or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium, and more particularly to a phase change type optical information recording medium capable of recording, reproducing and rewriting information.

[0002]

2. Description of the Related Art FIG. 4 shows a typical layer structure of a conventional optical information recording medium. The substrate 101 is made of, for example, a resin such as polycarbonate or polymethyl methacrylate (hereinafter, PMMA), glass, or the like, and has a guide groove for guiding a laser beam. The recording layer 104 has a state in which the optical characteristics are different, and is made of a substance that can change reversibly between the states. In the case of a rewritable phase change recording material, a so-called chalcogenide-based material containing Te or Se as a material of the recording layer 104, or a material containing Sb, for example, Te
-Sb-Ge, Te-Sn-Ge, Te-Sb-Ge-
Se, Te-Sn-Ge-Au, Ag-In-Sb-T
Materials including e, In-Sb-Se, In-Te-Se, and the like are generally used.

The dielectric layers 109 and 110 have a function of protecting the recording layer 104 such as preventing oxidation, evaporation and deformation of the material of the recording layer 4. Further, by adjusting the film thickness of the dielectric layers 109 and 110, the absorptance of the optical information recording medium,
Since the difference in reflectance between the recording unit and the erasing unit can be adjusted, it also has a function of adjusting the optical characteristics of the medium. Dielectric layer 109,
The conditions for the material constituting 110 are not only to satisfy the above-mentioned purpose, but also to have good adhesion to the recording material and the substrate 1, and to make the dielectric layers 109 and 110 themselves a film having good weather resistance which does not cause cracks. It is required that there be. When these dielectric layers 9 and 10 are used in contact with the recording layer, they must be materials that do not impair the optical change of the recording material. As a material of the dielectric layers 109 and 110,
Sulfides such as ZnS, oxides such as SiO ₂ , Ta ₂ O ₅ and Al ₂ O ₃ , nitrides such as GeN, Si ₃ N ₄ and AlN, GeO
N, SiON, nitrides such as AlON, other carbides,
A dielectric such as a fluoride or an appropriate combination thereof has been proposed. In general it is often used ZnS-SiO _2. Also, usually, the dielectric layers 109 and 110
Both use the same material, manufacturing method, film quality, and the like.

The reflective layer 8 is generally made of Au, Ag, Al, C
It is made of a metal such as r or an alloy of these metals, and is provided for the purpose of a heat radiation effect and effective light absorption of the recording thin film, but is not an essential layer and may not be formed.

[0005] The light absorbing layer 107 is a layer provided for the purpose of improving the recording and reproducing characteristics. For example, Japanese Patent Application Laid-Open No. 5-1
No. 59360 proposes to improve the overwrite erasing rate by providing a light absorbing layer to suppress the difference in the light absorption between crystalline and amorphous recording films. For example,
Japanese Patent Application Laid-Open No. 5-325261 proposes that this layer is referred to as a thermal expansion alleviating layer to reduce a change in the film thickness of the recording layer due to repeated recording and erasing many times. For example, JP-A-8-115536 and JP-A-8-190733
Japanese Patent Application Laid-Open No. 8-190734 discloses that a light absorbing layer is provided to improve overwrite characteristics, and that the thickness of a dielectric layer provided between the light absorbing layer and the recording film is 1 nm or more. It has been proposed to improve the jitter characteristics by setting the recording film to a quenching structure with a thickness of 50 nm or less.

Although not shown in the drawing, in order to prevent the optical information recording medium from being oxidized, corroded, adhered to dust, etc., a structure using an overcoat layer on the reflective layer 108 or an ultraviolet-ray resin is used. A configuration in which a dummy substrate is used as an adhesive is generally known.

[0007]

In a phase change type recording medium, in order to improve recording / reproducing characteristics, the reflectance (hereinafter sometimes abbreviated as "Rc") from the crystal portion of the recording film and the ratio from the amorphous portion to the amorphous portion. It is desired to increase the difference from the reflectance (hereinafter, may be abbreviated as “Ra”). A general phase change type recording medium has a configuration in which Rc is increased and Ra is decreased. For example, it is desired that Rc is about 15% or more. Further, in order to improve the recording / reproducing characteristics, Rc and Ra are used.
It is better that the difference from the design is as large as possible. In a phase-change recording medium employing the land-groove recording method, when reading a signal from a certain track, a signal from an adjacent track is read. In order to suppress crosstalk, it is considered that Ra should be as low as possible in design, and specifically, it is desired that Ra be about 2% or less.

However, in a phase-change recording medium having a light absorbing layer between the recording layer and the reflective layer, Rc is adjusted to 15% or more and Ra to 2% or less by adjusting the thickness of the dielectric layer. Has a very narrow dielectric film thickness margin,
There is a problem that it is difficult to stably secure the above-mentioned reflectance during mass production.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and has an optical information recording medium having a structure having a reflective layer and a light absorbing layer, and capable of stably realizing characteristics of a large Rc and a small Ra. It is intended to provide a manufacturing method.

[0010]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
The optical information recording medium of the present invention comprises a substrate,
Wherein the multilayer film is formed on the substrate.
From the side closer to the first dielectric layer and the laser light irradiation.
Reversible state between amorphous and crystalline phases upon irradiation
Recording layer capable of changing state, second dielectric layer, and light absorbing layer
And a reflective layer, and the refractive index n of the first dielectric layer₁
And the refractive index n of the second dielectric layer_TwoAnd n ₁> N_Twoconnection of
Is satisfied.

According to the optical information recording medium of the present invention, Rc
Large and small Ra can be stably realized.

In the optical information recording medium of the present invention, the refractive index n
₁ is preferably 2.1 or more, more preferably 2.3 or more. Further, the refractive index n ₂ is preferably 2.2 or less, and 1.8.
The following are more preferred.

The thickness of the first dielectric layer is 15 × λ / (64 × n ₁ ) or more, where λ is the wavelength of the laser beam.
It is preferable that the thickness be 0 · λ / (64 · n ₁ ) or less, and the thickness of the second dielectric layer be 10 nm or more and 70 nm or less.

It is preferable that the first dielectric layer is made of any one of the following. A zinc-containing compound, an oxide, nitride, fluoride, carbide, sulfide or a mixture thereof containing at least one selected from Al, Ga, In, Tl, Si, Ti, Zr, Hf and Cu. mixture. On the other hand, the second dielectric layer is preferably made of any of the following. A mixture with a zinc-containing compound, an oxide, a nitride, a fluoride, a carbide, a sulfide containing at least one selected from Si, Ge, Sn, Be, Mg, Ca and Ba, or a mixture thereof.

Further, in the optical information recording medium of the present invention, n
To satisfy _1> n ₂ relations, a first dielectric layer and second dielectric layer is composed of the same kinds of elements, and arrangement ratio of the element (content ratio) is preferably different . Further, it is preferable that the first dielectric layer and the second dielectric layer are a mixture of the same type of dielectrics, and the mixing ratio of the dielectrics is different. Furthermore, it is preferable that at least one selected from an oxygen concentration, a nitrogen concentration, and a fluorine concentration is different between the first dielectric layer and the second dielectric layer. According to these preferred examples, the relationship of n ₁ > n ₂ can be realized without preparing completely different materials.

According to the optical information recording medium of the present invention,
Ra of 0% or less can be easily realized. Ra is 2.
Rc can be set to 15.0% or more while being set to 0% or less. Further, Rc [%] is larger than Ra [%].
It is easy to increase by 14 points or more in% display.

Further, the optical information recording medium of the present invention preferably further comprises a diffusion preventing layer formed so as to be in contact with the recording layer. It is preferable that the diffusion prevention layers are arranged on both sides of the recording layer.

Further, a first method of manufacturing an optical information recording medium according to the present invention includes a substrate and a multilayer film formed on the substrate, wherein the multilayer film is formed in a first order from a side closer to the substrate. A recording layer capable of reversibly changing its state between an amorphous phase and a crystalline phase by irradiation with a laser beam,
A method for manufacturing an optical information recording medium including a second dielectric layer, a light absorbing layer, and a reflective layer, wherein the first dielectric layer and the second dielectric layer are Formed by co-sputtering using a plurality of targets having different refractive indices, and, when forming the first dielectric layer and the second dielectric layer in the co-sputtering, the refractive index of the refractive index n ₁ of the first dielectric layer at the wavelength of the laser beam the second dielectric layer n ₂ and is n ₁
> N ₂ , the ratio of the power supplied to the plurality of targets is changed.

Further, a second method of manufacturing an optical information recording medium according to the present invention includes a substrate and a multilayer film formed on the substrate, wherein the multilayer film is formed in a first order from a side close to the substrate. A recording layer capable of reversibly changing its state between an amorphous phase and a crystalline phase by irradiation with a laser beam,
A method for manufacturing an optical information recording medium including a second dielectric layer, a light absorbing layer, and a reflective layer, wherein the first dielectric layer and the second dielectric layer are formed by a reactive gas. deposited in a gas atmosphere that contains, and the refractive index n ₂ of the second dielectric layer and the refractive index n ₁ of the first dielectric layer at a wavelength of the laser light is n _1> n ₂ So that the concentration of the reactive gas when forming the first dielectric layer is set to be equal to or less than the concentration of the reactive gas when forming the second dielectric layer. I do.

According to the production method of the present invention, Rc is stably
An optical information recording medium that realizes a characteristic having a large Ra and a small Ra can be manufactured without complicating a conventional process or apparatus.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. One embodiment of the optical information recording medium shown in FIG. 1 includes a first dielectric layer 2 on a substrate 1,
It has a configuration in which a recording layer 4, a second dielectric layer 6, a light absorption layer 7, and a reflection layer 8 are stacked in this order. Another embodiment of the optical information recording medium shown in FIG. 2 is that a first dielectric layer 2, a first diffusion prevention layer 3, a recording layer 4, a second diffusion prevention layer 5, It has a configuration in which a second dielectric layer 6, a light absorbing layer 7, and a reflecting layer 8 are stacked in this order.

However, the present invention is not limited to the above configuration, and two or more dielectric layers are provided between the substrate 1 and the recording layer 4 and between the recording layer 4 and the light absorbing layer 7, respectively. May be formed. When the dielectric layer has a multilayer structure, the refractive index of the dielectric layer refers to the refractive index when the dielectric layer having the multilayer structure is regarded as one layer.

As a material of the substrate 1, a resin such as polycarbonate or PMMA, glass or the like is used, and it is preferable that a guide groove for guiding a laser beam is provided.

The material of the first dielectric layer 2 is, for example, ZnS, ZnSe, ZnTe, ZnPo, ZnC, ZnSi, ZnGe, ZnSn, ZnP, ZnA.
Examples include zinc-containing compounds such as s, ZnSb, and ZnBi. Preferred zinc-containing compounds are ZnS or ZnSe. Also, A
Examples include at least one oxide, nitride, fluoride, carbide, sulfide or a mixture thereof selected from l, Ga, In, Tl, Si, Ti, Zr, Hf and Cu. Among the metals used as these oxides and the like, a preferred metal is Si. The first dielectric layer 2 is preferably made of a thermally stable material having a large refractive index at the wavelength of the reading light laser.

The film thickness of the first dielectric layer 2 is at _least 15 · λ / (64 · n ₁ ) with respect to the wavelength λ of the readout laser and the refractive index n _{1 of} the first dielectric layer (40 · n ₁ ). λ) / (64
n ₁ ) The following are preferred. This is because it is easy to reduce Ra while increasing Rc.

As the material of the second dielectric layer 6, for example, ZnS, ZnSe, ZnTe, ZnPo, ZnC, ZnSi, ZnGe, ZnSn, ZnP, ZnA
Examples include zinc-containing compounds such as s, ZnSb, and ZnBi. Preferred zinc-containing compounds are ZnS or ZnSe. Also, S
oxides, nitrides, fluorides, etc. of i, Ge, Sn, Be, Mg, Ca, Ba, etc.
Examples thereof include carbides, sulfides, and mixtures thereof.
Among the metals used as these oxides and the like, a preferred metal is Si. The second dielectric layer 6 is preferably made of a thermally stable material having a small refractive index at the wavelength of the reading light laser.

The thickness of the second dielectric layer 6 is 10 nm or more and 7
It is preferably 0 nm or less, more preferably 20 nm or more and 50 nm or less. If the thickness of the second dielectric layer is less than 10 nm, the recording film is too close to the light absorbing layer, and when a track to be recorded is irradiated with a light laser, the heat of the light absorbing layer causes a signal in an adjacent track to be disturbed. The so-called cross-erase may be remarkable. On the other hand, the second
If the thickness of the dielectric layer is more than 70 nm, the recording film is gradually cooled and coarse crystals are likely to be formed around recording marks, so that jitter may be deteriorated.

It is preferable that the first dielectric layer 2 and the second dielectric layer 6 are made of the same kind of metal element. In this case, the composition ratio of the metal element is adjusted in order to satisfy the relationship of the refractive indexes (n ₁ > n ₂ ). Also, the same type of dielectric may be mixed so as to have different ratios to form both dielectric layers 2 and 6, so that n ₁ > n ₂ .

When the dielectric layers 2 and 6 made of the same kind of metal element or the same kind of dielectric are formed as described above, these layers can be formed from the same material source (for example, a sputtering target).

For example, the dielectric layers 2 and 6 can be formed by co-sputtering using two or more targets made of materials having different refractive indexes and changing the ratio of power applied to these two or more targets. . In particular,
A target made of a low-refractive-index material is prepared on one side, and a target made of a high-refractive-index material is prepared on the other side. By controlling the input power to these two targets, the refractive index of the dielectric layers 2 and 6 becomes a predetermined value. Control.

However, the two dielectric layers whose constituent ratios are adjusted as described above can be formed not by co-sputtering but also by sputtering using a single target. In this case, two targets having different refractive indexes are prepared. Targets having different refractive indices may be prepared by changing the mixing ratio of the high refractive index material and the low refractive index material.

The dielectric layers 2 and 6 can be formed from a single target by adjusting the atmosphere at the time of film formation.
The film can be formed so as to satisfy the relationship of the refractive indexes (n ₁ > n ₂ ). Specifically, the refractive index can be adjusted by adding a reactive gas to an inert gas (rare gas). Generally, the addition of a reactive gas reduces the refractive index of the layer.
Therefore, when the dielectric layers 2 and 6 are formed using the same target, the reactive gas concentration when forming the first dielectric layer 2 is set to the same value as when forming the second dielectric layer 6. It is preferable that the concentration be less than or equal to the reactive gas concentration. Examples of the reactive gas include nitrogen, oxygen, and fluorine. The reactive gas is preferably at least one selected from nitrogen and oxygen.

The method of changing the concentration of the reactive gas may be used together with the co-sputtering described above, which involves controlling the power applied to the two targets.

The diffusion preventing layers 3 and 5 have a role of protecting the recording layer such as preventing oxidation, corrosion and deformation of the recording layer 4, and also have a function of diffusing or migrating atoms between the recording layer 4 and the dielectric layer 2. (Hereinafter simply referred to as “atom diffusion”). The diffusion preventing layers 3 and 5 are preferably formed when sulfur or sulfide is contained in the dielectric layer. Even if the diffusion preventing layer is formed so as to be in contact with only one of the recording layers 4, it is effective for preventing atom diffusion, but for preventing it more effectively, the diffusion preventing layer is in contact with both sides of the recording layer 4. It is preferable to form it. The material of the diffusion prevention layers 3 and 5 is not particularly limited as long as the above-mentioned atomic diffusion is suppressed. For example, nitrides such as GeN, GeCrN, CrN and SiN, GeON,
GeCrON, CrON, nitrides such as SiON, carbides, fluorides,
These mixtures can be used.

The thickness of the diffusion preventing layers 3 and 5 is not particularly limited, but is preferably 1 nm or more and 15 nm or less.

For the recording layer 4, a material whose optical characteristics change reversibly is used. In the case of a phase change recording medium, it is preferable to use a chalcogenide-based material containing Sb or Te or Se. As such a material, for example, Te-Se-G
e, Te-Sn-Ge, Te-Sb-Ge-Se, Te-Sn-Ge-Au, Ag-In-Sb-T
e, In-Sb-Se, and In-Te-Se. The recording layer 4
Some include sputtering gas components such as Ar and Kr, H, C,
A small amount (for example, about 10 atomic% or less) of impurities such as H ₂ O and other materials added for various purposes may be contained.

The thickness of the recording layer 4 is preferably 3 nm or more and 25 nm or less. If the film thickness is less than 3 nm, the recording material does not easily form a layer, and if it exceeds 25 nm, thermal diffusion in the recording layer surface becomes large, and adjacent erasure is likely to occur when recording is performed at high density. is there.

The light absorbing layer 7 is made of a metal such as Si, Ge, Sn, Pb, etc.
Alternatively, it is formed of an alloy of an appropriately selected metal. The thickness of the light absorption layer 7 is not particularly limited, but is 10 nm or more and 80 nm or more.
nm or less is preferred. The reflection layer 8 is made of Au, Ag, Cu, A
It is formed of a metal such as l, Cr, Ni, or an alloy of a suitably selected metal. The thickness of the reflective layer 8 is not particularly limited, but is preferably 40 nm or more and 300 nm or less.

Hereinafter, recording and erasing of signals using the optical information recording medium of the present invention will be briefly described. The recording medium that is being rotated by the rotation control device is irradiated with laser light that has been narrowed down to minute spots by the optical system. Reversible and localized partly reversible amorphous state generating power levels can vary from a crystalline state to an amorphous state of the recording layer by laser light irradiation to P _1, also from an amorphous state to a crystalline state by irradiation of a laser beam the crystalline state generates a power level as P ₂ which may change,
By modulating the laser power between P ₁ and P ₂ , a recording mark is generated or erased, and information is recorded, erased, or overwritten. Although not particularly limited, when irradiating at least a laser beam of power level P ₁ is composed of a pulse train, it is preferable that a so-called multi-pulse.

Further, the power of the recording mark is lower than any of the power levels P ₁ and P ₂ , and the optical state of the recording mark is not affected by the irradiation of the laser beam at that power level, and the reproduction of the recording mark from the recording medium is not affected. Therefore, a signal from a recording medium obtained by irradiating a laser beam having a power level (reproducing power level P ₃ ) at which a sufficient reflectance can be obtained is read by a detector, and an information signal is reproduced.

Various conditions are as follows, for example. The wavelength of the laser beam is 650 nm, the numerical aperture of the objective lens used is 0.60, the signal system is the EFM modulation system, the shortest bit length is 0.28 μm, and the scanning speed of the laser beam in the track direction is 8 m / s. Using a substrate on which tracks called grooves and lands (between grooves) are alternately formed, signals are recorded on both the grooves and the lands. The track pitch is 0.60 μm. Of course, substrates having different width ratios between the groove and the land may be used.

Next, an apparatus for manufacturing an optical information recording medium will be described. The method for producing the multilayer film constituting the optical information recording medium is not limited to the sputtering method, and a vapor deposition method such as a vacuum evaporation method and a CVD method can be applied. Here, the sputtering method is used. FIG. 3 shows an example of a film forming apparatus.

A vacuum pump (not shown) is connected to the vacuum vessel 11 through an exhaust port 12 so that the inside of the vacuum vessel can be maintained at a high vacuum. The vacuum pump includes a cryopump, a mechanical booster pump, and a rotary pump, and can be used as appropriate. The gas supply port 13 can supply a constant flow of an inert gas, a reactive gas such as nitrogen or oxygen, or a mixed gas thereof. In the figure, reference numeral 14 denotes a substrate, which is attached to a driving device 15 for revolving the substrate on its own axis. In the figure, reference numeral 17 denotes a sputtering target, which is connected to the cathode 18. The cathode 18 is omitted in the figure, but is connected to a DC power source or an RF
Connected to power. Further, a shutter 19 is provided above the target to prevent contamination on the target. The vacuum vessel 11 and the shutter 1
9 is connected to the ground.

Hereinafter, an example in which an optical information recording medium having the structure shown in FIG. 2 is manufactured using the apparatus shown in FIG. 4 will be described. Here, the substrate 1 has a thickness of 0.6 mm and a diameter of 1 mm.
A 20 mm disc-shaped polycarbonate resin was used.

The first dielectric layer 2 was formed by co-sputtering using a target made of ZnSe and a target made of SiO ₂ . The first dielectric layer 2 is formed on a ZnSe target by RF in an Ar gas atmosphere.
Put the power of 5.10W / cm ^2, the SiO ₂ target was put the power of RF0~1.80W / cm ^2, to form a thin film while adjusting the mixing ratio of ZnSe and SiO _2.

The second dielectric layer 6 was formed by co-sputtering using a target made of ZnS and a target made of SiO ₂ . The second dielectric layer 6 is formed on a ZnS target by RF5.1 while appropriately mixing oxygen and / or nitrogen in an Ar gas atmosphere.
Put the power of the 0W / cm ^2, the SiO ₂ target to put the power of the RF1.0~10.2W / cm ^2,
It was formed as a mixed thin film of ZnS and SiO ₂ in which O and N were appropriately mixed.

The thicknesses of the dielectric layers 2 and 6 were adjusted so that the reflectance from the recording medium was optimal (so that Rc was large and Ra was small).

The target material for forming the diffusion preventing layers 3 and 5 was Ge. The sputtering gas is a mixed gas of argon and nitrogen, and the sputtering gas pressure is 10 mT.
orr, the nitrogen partial pressure in the sputtering gas is 40% by volume, the sputtering power density is 6.4 W / cm ² , and the film thickness is 5
nm was common.

When forming the recording layer 4, nitrogen is added to Ar at 3%.
The mixed gas is supplied at a constant flow rate such that the total pressure becomes 1 mTorr, and DC 1.27 W / cm ² ,
RF 5.10 W / cm ² power was applied, and the film thickness was 12 nm.

The light absorbing layer 7 is formed by using a mixed target of Si and W, supplying Ar gas at a total pressure of 2.0 mTorr, applying a power of 4.45 W / cm ² DC, and setting the film thickness to 50 nm. And

The reflective layer 8 is made of Au, and Ar gas is supplied at a total pressure of 2.
0 mTorr and DC 4.45 W / cm ²
And the film thickness was set to 200 nm.

As the inert gas in the sputtering gas, a gas that can be sputtered such as Kr may be used in addition to Ar.

Various recording media were manufactured while the refractive indices of the first dielectric layer 2 and the second dielectric layer 6 were variously adjusted according to the above film forming conditions.

The refractive indices of the produced dielectric layers 2 and 6 were measured using a single layer film formed on a quartz substrate under the same conditions using an optical spectrometer. Specifically, the refractive index is a refractive index at a reading wavelength (650 nm) of a laser beam.

The characteristics of the samples prepared as described above were evaluated as follows. The recording signal system was an EFM modulation system, and the wavelength of the laser used was 650.
nm, and the numerical aperture of the objective lens was 0.60. The shortest mark length is 0.42 μm and the disk rotation speed is 8.2 m linear velocity
/ S. The groove pitch is 1.20 μm, ie 0.60 μm
A substrate in which groove portions and land portions were alternately formed every m was used.

In order to evaluate the characteristics, the reflectance from the portion where the recording layer was in the amorphous state and the reflectance from the portion where the recording layer was initialized to be in the crystalline state were measured. Also, a jitter value J ₁ when a random signal at intervals of 1T from 3T to 11T is recorded on each track of the groove and the land.
And 1T from 3T to 11T in the order of a, e, b, d, c on five consecutive tracks (a, b, c, d, e)
After recording a random signal in increments, to evaluate the jitter value J ₂ tracks c, to evaluate the difference between J ₁ and J ₂ as a cross-talk. Also, a mark having a length of 3T was recorded on each track of the land and the groove, and the ratio of the reproduced signal to the noise signal was measured as the C / N ratio (dB).

Table 1 shows the refractive index and the thickness of the dielectric layers 2 and 6 for each sample. Table 2 shows Rc and Ra of each sample, crosstalk between land and groove, and average value of C / N ratio. In the table, when the crosstalk was less than 1.0% in jitter value,
1.0% or more and less than 2.0%, Δ, 2.0%
What was above is rated as x. Also, the C / N ratio is 51d.
B was less than B, Δ was 51 dB or more and less than 53 dB, and ５３ was 53 dB or more.

(Table 1) Sample First protective layer Second protective layer Refractive index Film thickness (nm) Refractive index Film thickness (nm) ―――――――――――――――――――――――――――― Comparative Example 1 2.4 110 2 0.435 Comparative Example 2 2.1 128 2.1 40 Comparative Example 3 1.8 150 1.8 45 Comparative Example 4 1.8 160 2.1 40 Comparative Example 5 2.1 120 2.3 35- ――――――――――――――――――――――――――― Example 1 2.1 128 1.9 45 Example 2 2.2 120 2.0 45 Example 3 2.2 128 1.9 45 Example 4 2.3 115 1.9 45 Example 5 2.3 130 1.8 48 Example 6 2.3 125 1.7 50 Example 7 2.4 110 2.2 38 Example 8 2.4 120 2.0 45 Example 9 2.4 130 1.8 48 Example 10 2.4 130 1.6 50 Example 11 2.5 115 2.2 38 Example 12 2.5 125 2.0 45 Example 13 2.5 125 1.8 48 Example 14 2.5 130 1.6 50 Example 15 2.5 130 1.5 55 55 ―――――――――――― ――――――――――――――――――

(Table 2) ―――――――――――――――――――――――――――――――――― Sample Rc Ra Rc-Ra Crosstalk C / N ratio ―――――――――――――――――――――――――――――――― Comparative Example 1 18.4 2.6 15.8 × Δ Comparative Example 2 17.7 2.1 15.6 × Δ Comparative Example 3 14.2 2.3 11.9 × × Comparative Example 4 13.9 2.1 11.8 × × Comparative Example 5 15.3 2 0.4 12.9 × × ―――――――――――――――――――――――――――――――― Example 1 16.8 1.9 14.9 △ △ Example 2 16.4 1.8 14.6 △ △ Example 3 17.2 1.3 15.9 △ △ Example 4 17.6 1.7 15.9 △ △ Example 5 17.2 1.0 16.2 ○ ○ Example 6 17.3 1.0 6.3 ○ Example 7 17.4 1.9 15.5 ○ Example 8 16.0 0.9 15.1 ○ Example 9 17.5 1.0 16.5 ○ Example 10 17.3 0.7 16.6 ○ ○ Example 11 17.1 1.6 15.5 △ △ Example 12 16.5 1.2 15.3 △ △ Example 13 17.7 0.9 16. 8 ○ ○ Example 14 16.9 0.7 16.2 ○ ○ Example 15 16.6 0.6 16.0 ○ ○ ――――――――――――――――――― ―――――――――――――――

As shown in Comparative Examples 1 and 2, when the refractive indices of the first dielectric layer 2 and the second dielectric layer 6 are both equal to or greater than 2.1 and equal, Rc increases but Ra decreases. No crosstalk was observed, and the crosstalk was as high as 2% or more in any of the samples. When the refractive index of the dielectric layer 2 is equal to the refractive index of the dielectric layer 6 as shown in Comparative Example 3, neither Rc nor Ra can be increased, and the crosstalk and C / N Both ratios resulted in poor results. As shown in Comparative Examples 4 and 5, when the refractive index of the dielectric layer 2 was equal to or less than the refractive index of the dielectric layer 6, both the crosstalk and the C / N ratio were poor.

As shown in Examples 1 to 15, good characteristics were obtained for the samples in which the refractive index of the dielectric layer 2 was higher than that of the dielectric layer 6. The film thickness of the first dielectric layer 2 of the sample shown in the example is 15 · λ / (64 · n) with respect to the wavelength λ of the readout laser and the refractive index n _{1 of} the first dielectric layer. ₁ ) More than (40 • λ) / (64 •
n ₁ ) The following range. In the above example, the crosstalk and the C / N ratio could be improved for both the first dielectric layer 2 and the second dielectric layer 6 without strictly controlling the film thickness.

In particular, for a sample in which the refractive index of the first dielectric layer 2 is 2.3 or more and the refractive index of the dielectric layer 6 is 1.8 or less, Ra is 1% or less, The difference between Rc and Ra could be set to 16 points or more in% display, and significant improvement was observed in both crosstalk and C / N ratio. Thus, increasing Rc and decreasing Ra to increase the difference between Rc and Ra is an effective means for suppressing crosstalk and improving the C / N ratio.

[0063]

As described above, according to the present invention,
In a phase change recording medium comprising at least five layers including a light absorbing layer and a reflecting layer, the refractive index n ₁ of the dielectric layer between the substrate and the recording layer is determined by the dielectric constant between the recording layer and the light absorbing layer. By making the refractive index n ₂ larger than the refractive index of the body layer, the difference in reflectance between the recorded portion and the erased portion in the recording layer can be enlarged, and the recording / reproducing characteristics can be improved. INDUSTRIAL APPLICABILITY The optical information recording medium of the present invention has excellent recording / reproducing characteristics at high density and is suitable for a land-groove recording method.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of one embodiment of the optical information recording medium of the present invention.

FIG. 2 is a sectional view of another embodiment of the optical information recording medium of the present invention.

FIG. 3 is a diagram showing an example of an optical information recording medium manufacturing apparatus of the present invention.

FIG. 4 is a sectional view of a conventional optical information recording medium.

[Explanation of symbols]

 Reference Signs List 1 substrate 2 first dielectric layer 3 first diffusion prevention layer 4 recording layer 5 second diffusion prevention layer 6 second dielectric layer 7 light absorption layer 8 reflection layer 11 vacuum container 12 exhaust port 13 gas supply port 14 Substrate 15 Drive 16 Substrate holder 17 Sputtering target 18 Cathode 19 Shutter

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H111 EA03 EA04 EA23 EA37 EA43 FA01 FA11 FA12 FA21 FA23 FA25 FA26 FA27 FA28 GA01 GA03 5D029 JC02 LA14 LA15 LA16 LA17 LB07 LC06 5D121 AA03 EE03 EE09 EE17

Claims (16)

[Claims] 1. A semiconductor device comprising: a substrate; and a multilayer film formed on the substrate, wherein the multilayer film is arranged in order from a side closer to the substrate.
A first dielectric layer, a recording layer capable of reversibly changing its state between an amorphous phase and a crystalline phase by irradiation with a laser beam, a second dielectric layer, a light absorbing layer, and a reflecting layer. hints, the first optical information recording medium in which the refractive index of the dielectric layer n ₁ and the refractive index n ₂ of the second dielectric layer is characterized by satisfying the relation of n _1> n _2. 2. The method according to claim 1, wherein the refractive index n ₁ is 2.1 or more.
An optical information recording medium according to claim 1. 3. The method according to claim 1, wherein the refractive index n ₂ is 2.2 or less.
Or the optical information recording medium according to 2. 4. The film thickness of the first dielectric layer is not less than 15 · λ / (64 · n ₁ ) and 40 · 40, where λ is the wavelength of the laser beam.
The optical information recording medium according to claim ₁ , wherein λ / (64 · n ₁ ) or less. 5. The optical information recording medium according to claim 1, wherein the thickness of the second dielectric layer is 10 nm or more and 70 nm or less. 6. The optical information recording medium according to claim 1, wherein the first dielectric layer comprises any of the following. Zinc-containing compound, Al, Ga, In, Tl, Si, Ti, Zr, oxide containing at least one selected from Hf and Cu, nitride, fluoride, carbide,
Sulfides or mixtures thereof, and mixtures with 7. The optical information recording medium according to claim 1, wherein the second dielectric layer comprises one of the following: A mixture with a zinc-containing compound, an oxide, a nitride, a fluoride, a carbide, a sulfide containing at least one selected from Si, Ge, Sn, Be, Mg, Ca and Ba, or a mixture thereof. 8. The first dielectric layer and the second dielectric layer,
The optical information recording medium according to any one of claims 1 to 7, wherein the optical information recording medium is composed of the same kind of element and has a different composition ratio of the element. 9. The first dielectric layer and the second dielectric layer,
The optical information recording medium according to any one of claims 1 to 8, wherein the mixture is a mixture of the same type of dielectrics, and the mixture ratio of the dielectrics is different. 10. The optical information recording according to claim 1, wherein at least one selected from an oxygen concentration, a nitrogen concentration, and a fluorine concentration is different between the first dielectric layer and the second dielectric layer. Medium. 11. The reflectance Ra of laser light when the recording layer is in an amorphous phase is 2.0% or less.
11. The optical information recording medium according to any one of items 10 to 10. 12. The optical information recording medium according to claim 11, wherein the reflectance Rc of the laser light when the recording layer is in a crystalline phase is 15.0% or more. 13. The reflectance Rc [%] of laser light when the recording layer is in a crystalline phase is 14 points or more larger than the reflectance Ra [%] of laser light when the recording layer is in an amorphous phase. The optical information recording medium according to claim 11. 14. The optical information recording medium according to claim 1, further comprising a diffusion preventing layer formed so as to be in contact with the recording layer. 15. A semiconductor device comprising: a substrate; and a multilayer film formed on the substrate, wherein the multilayer film includes, in order from a side closer to the substrate, a first dielectric layer, and an amorphous phase formed by laser light irradiation. A method for manufacturing an optical information recording medium including a recording layer capable of reversibly changing state with a crystalline phase, a second dielectric layer, a light absorbing layer, and a reflecting layer, Together with the second dielectric layer,
A film is formed by co-sputtering using a plurality of targets made of materials having mutually different refractive indices, and, when forming the first dielectric layer and the second dielectric layer in the co-sputtering, refractive index n ₂ and the n ₁ of the second dielectric layer and the refractive index n ₁ of the first dielectric layer
> N ₂ , wherein the ratio of the power applied to the plurality of targets is changed so as to satisfy n2. 16. A semiconductor device comprising: a substrate; and a multilayer film formed on the substrate, wherein the multilayer film sequentially forms a first dielectric layer and an amorphous phase by irradiation with a laser beam from a side closer to the substrate. A method for manufacturing an optical information recording medium including a recording layer capable of reversibly changing state with a crystalline phase, a second dielectric layer, a light absorbing layer, and a reflecting layer, Together with the second dielectric layer,
Deposited in a gas atmosphere containing reactive gas and the refractive index n ₂ of the second dielectric layer and the refractive index n ₁ of the first dielectric layer at a wavelength of the laser light is n ₁ > N ₂
So that the concentration of the reactive gas when forming the first dielectric layer is set to be equal to or less than the concentration of the reactive gas when forming the second dielectric layer. Of manufacturing an optical information recording medium.