JP2002100071A - Phase change type recording medium, method for producing the same, and method for inspecting the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phase change type recording medium capable of recording and reproducing information with light and adaptable particularly to a CAV (constant angular velocity) system in which the angular velocity of rotation of an optical disk is constant and to provide a method for producing the medium at a low production cost and a method for easily inspecting the medium. SOLUTION: In the phase change type recording medium obtained by stacking two or more recording layers on a substrate 201, the constituent components of each of the recording layers 203, 204 are at least two principal elements selected from the group comprising Sb, Te, In, Ag and Ge and one or more additive elements, the recording layers are different from each other in the kinds and amounts of the additive elements and the recording layer on the interior side to the direction of light incidence has a lower rate of crystallization.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phase change recording medium, and more particularly, to a CAV in which information can be recorded / reproduced by light, and in particular, the angular velocity of rotation of an optical disk is constant.
The present invention relates to a phase change type recording medium corresponding to the method, a manufacturing method thereof, and a method of inspecting the phase change type recording medium.

[0002]

2. Description of the Related Art As an optical recording medium (optical disk) for recording / reproducing information by laser light, there is a rewritable recording medium using a phase change material for a recording layer. This phase-change type recording medium uses a material in which an amorphous phase-a crystalline phase changes reversibly by light irradiation as a recording layer, and can record / erase with a simple optical system, and can record information already recorded. This is a recording medium on which new information can be recorded while erasing information.

Generally, an amorphous state in a recording layer is a recording state, and a crystalline state is an erasing state.
Information recording was performed by irradiating a laser beam at the recording level and heating to a temperature equal to or higher than the melting point, and then quenching to form an amorphous mark, and erasing was performed by irradiating a laser beam at the erasing level to raise the temperature to the crystallization temperature. The mark is crystallized by slow cooling later. The recording mark is for reproducing by detecting a change in the amount of reflected light due to a reflectance difference or a phase difference between the amorphous phase and the crystalline phase.

[0004] Recording media are classified into two systems, CLV and CAV, depending on the rotation system. The CLV method is a method of rotating at a constant linear velocity, and the CAV method is a method of rotating at a constant angular velocity.

[0005] This CLV system requires control of the number of revolutions in particular, and is not suitable for high-speed access. Therefore, in recent years, CA where the linear velocity on the outer circumference of the recording medium is faster than the inner circumference is
In fact, the V method is often used.

Therefore, as a phase change type recording medium corresponding to such a system, for example, Japanese Patent Laid-Open No. Hei 10-199039
In Japanese Patent Application Laid-Open Publication No. H11-139, there is described a technique in which the composition of the recording layer on the inner periphery and the outer periphery of the recording medium is changed by bonding. Further, Japanese Patent Application Laid-Open No. 08-77600 describes a method of changing the composition of the inner and outer peripheries of a recording medium by masking during film formation.

[0007]

In a phase change type recording medium under the above-mentioned situation, a uniform amorphous mark is conventionally formed over the entire area of the recording medium in order to obtain good recording / reproducing characteristics. It was necessary to form it stably. However, in the case of the above-described CVL method, the trailing edge of the rear end of the amorphous mark becomes conspicuous at the outer periphery where the linear velocity is high. In the case of phase change recording, a predetermined mark length is formed by modulating a laser power from a recording level to an erasing level and erasing a trailing portion of the mark. Therefore, at this time, at the outer periphery where the linear velocity becomes faster and the time for the laser beam to pass one point of the track becomes shorter, the crystallization of the trailing end of the mark becomes insufficient, and the tail tends to be longer than the target. is there.

[0008] Such fluctuations in the mark shape cause reproduction jitter. Further, when the linear velocity is out of the margin of the recording layer material, the trailing edge of the mark usually becomes unclear and the trailing edge cannot be reproduced. This may cause problems such as disappearance.

Therefore, an object of the present invention is to solve such a conventional problem, and CVL
Even when the method is used, the structure of a phase change type recording medium for forming an amorphous mark stably over the entire area of the recording medium, a method of inspecting the recording medium, and a method of manufacturing a recording medium capable of reducing the manufacturing cost are described. To provide.

[0010]

In view of the above-mentioned problems, the present inventors have conducted intensive studies and as a result, have found that the constituent elements for forming the recording layer laminated on the substrate and the formation of the constituent elements are described. By focusing on the method, a phase change type recording medium capable of forming a uniform amorphous mark on both the inner and outer circumferences of the recording medium, a manufacturing method which has excellent repetitive recording characteristics and does not require an initialization step, and the like, have been found. Was completed. That is, according to the present invention, in a phase change recording medium in which at least two recording layers are laminated on a substrate, the components of each recording layer are Sb, Te, I
a main element of at least two elements selected from the group consisting of n, Ag and Ge, and at least one or more other additional elements different from the main element, and the types of the additional elements and A phase-change recording medium, wherein the amount of addition differs for each of the recording layers, and further, each of the recording layers is provided with a recording layer having a low crystallization speed on the back side with respect to the light incident direction. I will provide a.

According to the present invention, in a phase-change recording medium having a recording layer on a substrate and a layer serving as a diffusion source for introducing an additional element into the recording layer at initialization, the recording layer is , Sb, Te, In, Ag, and Ge as at least two elements selected from the group consisting of main components, and the layer serving as the diffusion source is provided in contact with the recording layer. A phase change recording medium is provided.

Thus, a phase-change recording medium can be formed in which a uniform amorphous mark can be formed on both the inner and outer circumferences of the recording medium.

Further, according to the present invention, there is provided a method for manufacturing a phase-change recording layer provided with a layer serving as a diffusion source as described above, that is, when a recording layer is initialized on a substrate, In a method for manufacturing a phase-change recording medium having a layer serving as a diffusion source for introducing an element, the recording layer containing at least two elements selected from the group consisting of Sb, Te, In, Ag and Ge as a main element is provided. Wherein the layer serving as the diffusion source is provided in contact with the recording layer, and the layer serving as the diffusion source is provided with a thickness difference to control the concentration distribution of the additional element in the plane of the recording medium. Provided is a method for manufacturing a phase change recording medium. By this manufacturing method, it is possible to manufacture a phase change type recording medium capable of improving the repetitive recording characteristics of the recording medium.

According to the present invention, in the method for manufacturing a phase-change recording medium according to the present invention described above, when forming a recording layer by a sputtering method, The present invention provides a method for manufacturing a phase change type recording medium, characterized in that different targets are used for forming a film. By this manufacturing method, a film suitable for the recording medium in the present invention can be formed.

Further, according to the present invention, in the inspection method for a phase change recording medium, the laser power is modulated in two stages of a recording level and an erasing level while the medium is stationary, and the mark erasing time is measured. In addition, the present invention provides an inspection method for a phase change type recording medium, characterized in that the characteristic of the medium is determined by comparing with a standard value. Thereby, the recording / reproducing medium can be inspected by a simple method.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the phase change recording medium according to the present invention, there are several methods for modulating the crystallization speed of a phase change material. For example, the method changes depending on the type of element added to SbTe. Therefore, Table 1 to be described later shows the mark erasing time examined by the inspection method according to the present invention shown in the fifth embodiment. For example, the main component of the recording layer is SbTe
A phase change material containing Ge, Si, and B as additional elements;
When compared with gInSbTe, GeSbTe is A
gInSbTe, and then SiSbT
It is shown that the erasing time becomes shorter in the order of e and BSbTe.

FIG. 1 shows a laser power modulation method for recording a mark and a mark shape by the modulation. That is, in FIG. 1, the laser power is modulated in three steps of the recording level 101, the erasing level 102, and the bottom level 103, and the linear density is 0.27 (μm / b).
It), a single-period mark of 50% duty was recorded.
The distance between the front end 105 and the rear end 106 of the mark 104 is
Measured as the mark length 107, the resulting mark lengths are compared and are shown in Table 2.

As a result, even when the recording is performed under the same conditions, the erasing time corresponding to the crystallization speed is short.
e and BSbTe form short marks. In the case of GeSbTe having a low crystallization speed, the rear end of the mark cannot be sufficiently erased, and the mark is long. On the other hand, in the case of SiSbTe or BSbTe having a high crystallization speed, the rear end of the mark is erased and the mark length is reduced. As described above, when recording is performed at the same linear velocity, it can be seen that the crystallization rate changes depending on the type of the added element, and the mark length changes. Therefore, CAV
When the linear velocity changes between the inner and outer circumferences of the disk as in the system, a uniform mark can be formed over the entire recording medium by adjusting the type of the added element and the amount of addition in accordance with the linear velocity.

In the present invention, as described above, a preferable medium configuration for modulating the type and amount of the additional element in the surface of the recording medium, a method for manufacturing the same, and the like are provided. As the substrate, polycarbonate, polyolefin, acryl, glass, or the like can be used. Further, as the dielectric layer, B, Al, Si, Ca, Ti,
Examples thereof include oxides, nitrides, sulfides, and carbides of Zn, Ge, Ta, and the like, which can be used alone or as a mixture thereof. In addition, as the recording layer, for example, AgInSbTe, AgInTe, GeS
Examples include bTe and SbTe, which can be used as appropriate. Further, as an additional element, for example, B, C, Mg, Al, S
i, P, Cu, Ga, Ge, In, Sn, Ba, La,
Bi, Gd and the like can be mentioned, and the element can be used as a single substance or a compound composed of a plurality of elements. Moreover, Ag, AgPd, AgPd
Cu, AgTiCu, AgTiCu, AlTi, AlC
r and the like.

As described above, the embodiments of the phase change recording medium according to the present invention will be further described below, as already described above. Therefore, in the present invention, it is preferable to provide a seed layer in contact with the recording layer surface having a low crystallization rate, which has already been described above, and as the seed layer or the recording layer on the substrate, which has already been described above. At the time of initialization, in a method for manufacturing a phase change recording medium in which a layer serving as a diffusion source for introducing an additional element into a recording layer is provided, a method for manufacturing Sb, Te, I
As a diffusion source layer provided in contact with a recording layer containing at least two elements selected from the group consisting of n, Ag, and Ge as main components, Bi or Bi ₂ Te ₃ is suitably suitable. Thereby, in the phase change recording medium according to the present invention in which the recording layer is laminated on the substrate in at least two or more layers, and the phase change type recording medium according to the present invention in which a layer (or a seed layer) serving as a diffusion source is provided In the recording medium, the initialization step can be omitted, and the manufacturing cost can be reduced.

Further, in the present invention, in a phase change type recording medium in which at least two recording layers are laminated on a substrate, preferably the main component element and the A layer for preventing interdiffusion with an additional element can be provided as appropriate. Thereby, the repetitive recording characteristics of the recording medium can be improved, and as a layer for preventing such mutual diffusion, for example, B,
Examples thereof include oxides such as Al, Si, Ca, Ti, Zn, Ge, and Ta, nitrides, sulfides, and carbides. In the present invention, a single substance thereof and a mixture thereof can be used.

In the present invention, the phase-change recording medium provided with a layer serving as a diffusion source, or the phase-change recording medium provided with Bi or Bi ₂ Te ₃ as a layer serving as a diffusion source, as described above. Inspection method, that is, the recording level and the erasing level of 2 when the above-described recording medium is stationary.
In the inspection method of modulating the laser power at the stage, measuring the disappearance time of the mark, and determining the characteristics of the medium by comparing with the standard value, preferably, the erasing time of the mark obtained by using this inspection method is as follows: formula _{(I), Tx / T 1 ≦ R 1} / Rx (I) ( wherein, represents an erase time T ₁ of the innermost circumference R _1, is. an erase time Tx at any measurement position Rx) in It is preferable to satisfy the relationship expressed. Thereby, the inspection of the recording / reproducing medium is simplified.

[0023]

The present invention will be further described below with reference to examples, but the present invention is not limited to these examples.

(Example 1) An example of a phase-change type recording medium according to the present invention having two recording layers will be described below with reference to FIGS. First, on the polycarbonate substrate 201
And a ZnS / SiO ₂ 202 film having a thickness of 70
nm. Next, a first recording layer of BSbTe203 was laminated on the lower dielectric with a thickness of 10 nm. Next, GeSbTe 204 as a second recording layer is formed thereon.
Was deposited in a thickness of 10 nm. A ZnS.SiO ₂ 205 as a lower dielectric layer was laminated thereon with a thickness of 20 nm. Further, Ag 206 is used as a reflective layer to a thickness of 120 nm.
Was laminated. After a thin film of each of these layers was formed by a sputtering method, it was initialized as a recording medium to crystallize the recording layer.

A mark was simultaneously recorded on the first and second recording layers having the above-mentioned layer structure. FIG. 3 shows the recorded mark shape.

FIG. 3 shows the mark shape when recording is performed by the CAV method from the innermost circumference A to the outermost circumference B of the recording medium 301, and the linear velocity increases from A to B. FIG. 3A shows a conventional example in which the recording layer is a single GeSbTe layer, and FIG. 3B shows a case where the recording layer according to the present embodiment is BSbT.
2 shows a two-layer structure of e and GeSbTe. Conventional GeS
In the bTe single layer, when the recording layer composition matches the low linear velocity on the inner circumference (302), the trailing edge of the mark extends toward the outer circumference as the linear velocity increases. As the linear velocity increases further,
The rear end cannot be erased and becomes unclear (30
3).

On the other hand, BSbTe and GeSbTe of the present invention
In the two-layer structure of GeSbTe, GeSbTe
Mark 305 becomes the target length, and the BSbTe mark 304 becomes shorter than the target. In the high linear velocity region on the outer periphery, the rear end of the GeSbTe mark 307 is unclear, and the BSbTe mark 306 has a target length. In the vicinity of the inner periphery, the BSbTe mark falls below the reproduction limit, so that a reproduction signal can be obtained with the GeSbTe mark. In the vicinity of the outer periphery, a reproduced signal is obtained with the BSbTe mark because the rear end of the GeSbTe mark becomes unclear. Therefore, according to the present invention, an apparently constant reproduction signal is obtained from the innermost circumference to the outermost circumference, and the reproduction jitter can be reduced.

(Embodiment 2) In the recording medium shown in Embodiment 1, the GeSbT of the recording layer on the back side with respect to the light incident direction
An example of a phase-change recording medium in which Bi ₂ Te ₃ is provided as a seed layer in contact with the e-plane is shown with reference to FIG. Ag 402 serving as a reflective layer was formed to a thickness of 120 nm on a polycarbonate substrate 401. Next, Z as the lower dielectric
nS.SiO ₂ 403 was formed to a thickness of 20 nm. Next, Bi ₂ Te ₃ 404 as a seed layer is deposited to a thickness of 3 nm.
Was formed. Next, GeSbTe405 of the first recording layer is used.
Is formed to a film thickness of 10 nm, and the second recording layer BSbT
e406 was laminated with a thickness of 10 nm. On this, ZnS.SiO ₂ 407 as an upper dielectric layer was laminated with a film thickness of 20 nm. A thin film of each of these layers was formed by a sputtering method. The seed layer is in a crystalline state, and GeSbTe is crystallized at the film formation stage following the seed layer. In addition, BSbTe is crystallized at the film formation stage, following the crystallized GeSbTe. Therefore, the initialization step becomes unnecessary. In addition,
Recording and reproduction were performed in the same manner as in Example 1.

(Embodiment 3) In the recording medium of Embodiment 1, if repetitive recording is performed, mutual diffusion occurs between the first and second recording layers, and the characteristics fluctuate. No Thus, FIG. 5 shows a configuration in which the recording medium shown in the first embodiment is configured as a rewritable type. In Example 1, a barrier layer was inserted between the first and second recording layers to form a film. Ta ₂ O ₅ 508 as the barrier layer is formed to a thickness of ₅ n.
m were similarly laminated by a sputtering method, and recording and reproduction were performed in the same manner as in Example 1.

With respect to the obtained recording medium, the amount of increase in jitter due to repetitive recording was compared with that in Example 1, and an EFM modulation pattern having a linear density of 0.27 (μm / bit) was recorded. FIG. 6 shows the increase from the initial jitter in the inner and outer peripheries of the recording medium No. 3. As a result, FIG.
As is clear from the above, in the layer configuration of the recording medium of Example 1, interdiffusion occurs between the first and second recording layers with repetitive recording, and the crystallization speed becomes an intermediate speed. In both cases, the jitter has increased. On the other hand, in Example 3, since the interdiffusion is suppressed by the barrier layer, it is understood that no remarkable fluctuation of the jitter is observed up to 1000 repetitions.

Embodiment 4 FIG. 7A shows a recording medium in which a layer serving as a diffusion source for introducing an additional element into the recording layer at the time of initialization is provided in contact with the recording layer. On a polycarbonate substrate 701, ZnS.SiO ₂ 702 as a lower dielectric was formed to a thickness of 70 nm. Next, the recording layer GeS
bTe703 was laminated to a thickness of 15 nm. Next, Si707 as an additive element was stacked with a thickness of 5 nm. Thereon, a ZnS · SiO ₂ 704 to the lower dielectric layer was laminated in a thickness of 20 nm, further, a reflective layer Ag70
5 was laminated to a thickness of 120 nm. Similarly, a thin film of each layer was formed by a sputtering method.

FIG. 7B shows the layer structure after initialization. Here, initialization is performed from the inner circumference to the outer circumference. At this time, the laser power is modulated in two stages. At the inner peripheral position, the laser power is set to the laser power at which GeSbTe is crystallized, and at the outer peripheral position, the laser power is set to cause the crystallization of GeSbTe and the diffusion of Si into GeSbTe. The inner peripheral portion 72 is made of crystalline GeS.
This is a stacked structure of bTe 703 and Si 707, and the outer peripheral portion 71 is GeSbTe 708 in a crystalline state.

FIG. 8 shows the result of measuring the mark length by the method shown in FIG. The horizontal axis is the radial position of the disk, with 21 mm being the innermost circumference and 59 mm being the outermost circumference. In the case of GeSbTe having a low crystallization speed, the target mark length is obtained near the inner periphery, but the mark length is longer than the target length when the thickness is 40 nm or more. In GeSbTe in which Si is introduced into the recording layer by the initialization and the crystallization speed is increased,
At 40 nm or more where the linear velocity increases, the target mark length is obtained. Therefore, by setting the laser power switching position at the time of initialization to a radius of 40 mm, 40 nm
The outer peripheral portion becomes GeSbTe, and the mark length can be made uniform from the innermost periphery to the outermost periphery.

(Embodiment 5) In the case of the configuration of Embodiment 4, if recording is repeated, Si diffuses into the recording layer even at the inner periphery and the characteristics fluctuate, so that it is not suitable for a rewritable recording medium. Therefore, FIG. 9 shows a configuration in which the recording medium shown in the fourth embodiment is configured as a rewritable type.

FIG. 9 shows the layer structure after film formation. ZnS.SiO serving as a lower dielectric on a polycarbonate substrate 901
₂ 902 was deposited to a thickness of 70nm. Next, GeSbTe903 as a recording layer was laminated with a thickness of 15 nm.
Next, Si904 as an additional element of the recording layer is laminated.

FIG. 10 shows the relationship between the target and the substrate during Si film formation.
2 shows a layout. To center of Si target 1001
The center of the substrate 1002 is eccentric to rotate the substrate. This
According to the method described above, the inner peripheral portion is thinner and the outer peripheral portion is
Can membrane. The film thickness is 1 nm at the innermost circumference and 5 nm at the outermost circumference.
is there. On top of that, ZnS.SiO as a lower dielectric layer _Two
905 with a thickness of 20 nm. In addition, a reflective layer
Ag906 was formed to a thickness of 120 nm.

Next, the recording layer is initialized. Unlike the third embodiment, the initialization condition is set to a condition in which Si diffuses into the recording layer over the entire surface of the medium. All Si is taken into GeSbTe, and the Si concentration in GeSbTe increases from the inner circumference to the outer circumference corresponding to the film thickness, and the crystallization speed increases. Unlike the configuration of the fourth embodiment (FIG. 7B), there is no single Si layer. Therefore, even if the recording is repeatedly performed, the interdiffusion between the layers does not occur, so that the fluctuation of the characteristics is avoided.

(Embodiment 6) FIG. 11 shows a layer structure of a recording medium in which the diffusion source layer is Bi ₂ Te ₃ in Embodiment 5.

Ag 1102 as a reflective layer was formed on a polycarbonate substrate 1101 to a thickness of 120 nm. Next, ZnS.SiO ₂ 1103 as a lower dielectric was formed to a thickness of 20 nm. Next, Bi ₂ T as a seed layer
e ₃ 1104 was formed. As in the case of forming the Si layer shown in FIG. 10, the center of the substrate is decentered with respect to the center of the Bi ₂ Te ₃ target, and the substrate is rotated. According to this method, the film can be formed such that the inner peripheral portion 112 is thin and the outer peripheral portion 111 is thick.
The film thickness is 2 nm at the innermost periphery and 10 nm at the outermost periphery. Next, GeSbTe as a recording layer is formed to a thickness of 10 nm. ZnS.SiO ₂ 11 as an upper dielectric layer thereon
06 with a thickness of 20 nm. The seed layer is in a crystalline state, and BiSbTe is crystallized at the film formation stage, following the seed layer. Along with the crystallization, interdiffusion of the seed layer and the recording layer occurs, and the Bi concentration of the recording layer becomes lower on the inner periphery and increases on the outer periphery corresponding to the film thickness distribution. As the Bi concentration increases, Bi
The crystallization speed of SbTe increases. Therefore, the trailing of the rear end of the mark at the outer peripheral position can be suppressed, and a uniform mark can be formed over the inner and outer peripheries by the CVA method. Furthermore, an initialization step is not required in the method of the fifth embodiment, and the manufacturing cost can be reduced.

(Embodiment 7) The thickness of the composition control layer in Examples 4 to 6 is determined by measuring the erasing time of the amorphous mark by the following inspection method. In addition, it is used as an in-line monitor, and the composition and the film thickness are inspected for variations.

FIG. 12 shows the measuring method. With the disc stationary, a single laser pulse is applied. FIG.
As shown in FIG. 2 (a), the laser power is at recording level 1
201 modulates in two stages of reproduction and erasure levels 1202. The pulse width of the recording level is 180 nsec, and the board power is 15 mW. The reproduction level is 2.2 mW at which erasing of the amorphous mark occurs. FIG.
(B) shows a temporal change of the reflected light intensity. The area of the formed amorphous mark is reduced, that is, erased, by reproducing it with the power of the erasing level. The reflected light intensity is
The crystal level is reduced from the crystal level 1203 to the amorphous level 1204, and returns to the crystal level again. The time when the reflected light intensity increases by 50% from the amorphous level is defined as an erasing time 1205. This erasing time changes according to the crystallization speed of each material. In addition, by setting a reference value of the erasing time and monitoring a change from the reference value, a change between lots in the composition and the film thickness can be inspected easily in a short time.

The mark erasing time obtained by the above-described inspection method is, assuming that the erasing time T ₁ at the innermost circumference R ₁ and the erasing time Tx at an arbitrary measurement position Rx, Tx / T ₁ ≦ R
_{The 1} / Rx relationship is inspected by the above-described inspection method. This means that when the medium is rotated at a constant angular velocity,
Since the linear velocity at each point will increase in proportion to the radius,
This means increasing the crystallization rate accordingly.
For example, the innermost circumference (R ₁ ) of the recording media of Examples 4 to 6 is 2
1 mm, and the outermost circumference (R ₂ ) is 59 mm. Outer circumference 21
Assuming that the erasing time obtained in mm is 1, the erasing time at the outermost circumference of 59 mm is 0.35 (1 × 21 mm / 59 mm).
Check that: As described above, Table 1 shows the change of the mark erasing time by the added element, and Table 2 shows the change of the mark length by the added element.

[0043]

[Table 1]

[0044]

[Table 2]

Thus, the characteristics of the phase change recording medium according to the present invention can be inspected nondestructively in a short time. Example 4
In the medium, the crystallization speed is increased by increasing the Si concentration in GeSbTe from the inner circumference to the outer circumference. In such a recording medium, the Si concentration distribution can be determined by composition analysis using X-rays or the like in the conventional method, but the recording layer is as thin as 15 nm, and it takes time to obtain sufficient signal intensity. In addition, it is difficult to separate Si in Zn.SiO ₂ and Si in the recording layer, and there is a problem in measurement accuracy. On the other hand, it is understood that the inspection method for measuring the erasing time according to the method of the present invention can easily inspect the characteristics of the recording medium as shown in the embodiment.

(Embodiment 8) In the method of manufacturing a recording medium described in Embodiments 1 to 6, a method for forming a recording layer target is as follows. SbTe as a main component is composed of Sb and Te.
Mixed and sintered at a ratio of Sb / Te = 75/25
Use a Te target. Ge or B, which is an additional element, is obtained by sintering each powder to obtain a Ge or B target. GeSbTe is formed by combining SbTe and a Ge target, and BSbTe is formed by simultaneous deposition of SbTe and a B target. As a result, unlike the conventional method, when a multi-material was formed on a single target, the sputter rate fluctuated due to the erosion shape, and the composition fluctuation due to the target life became a problem. Rate is the most important factor. It is necessary to adjust the composition variation according to the target usage time. By forming the main component and the additional element of the recording layer with different targets, the composition can be easily adjusted.

[0047]

As described above, according to the present invention, in the phase change type recording medium, the recording layer materials having different crystallization speeds are laminated in two or more layers, so that the inner peripheral region having a low linear velocity has a low crystallinity. A target mark length can be formed in a layer with a low
Further, in the outer peripheral region at a high linear velocity exceeding the margin of this layer, the target mark length can be formed in the layer having a high crystallization speed, so that even when the recording is performed by the CAV method, the fluctuation of the mark length can be suppressed over the entire substrate. Jitter can be reduced. This also eliminates the need for a recording medium initialization step, reduces manufacturing costs, and provides a phase-change recording medium with improved repetitive recording characteristics by providing a mutual diffusion preventing layer between the recording layers. Further, in connection with the improvement of the repetitive recording characteristics of the medium provided with the interdiffusion preventing layer, an example of composition modulation in two zones in which the composition can be modulated at a target position in the medium plane was described. , It is also possible to divide the data into smaller zones. Further, according to the inspection method for measuring the erasing time according to the present invention, it is possible to provide an inspection method for a phase change type recording medium in which the characteristics of the recording medium are non-destructive, the measurement accuracy is excellent, and the inspection can be performed in a short time.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a laser power modulation method and a mark shape.

FIG. 2 is a diagram showing a layer configuration of a recording medium according to Embodiment 1 of the present invention.

FIG. 3 is a diagram illustrating a mark shape according to the first embodiment. (A)
(B) shows the case where the conventional recording layer is a GeSbTe single layer,
Is a case where the recording layer of the present invention is two layers of BSbTe / GeSbTe.

FIG. 4 is a diagram showing a layer configuration of a recording medium according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a layer configuration of a recording medium according to a third embodiment of the present invention.

FIG. 6 is a diagram showing an increase in jitter due to repetitive recording (comparison between Example 3 and Example 1).

FIG. 7 is a diagram showing a layer configuration of a recording medium according to Embodiment 4 of the present invention. (A) shows the layer configuration after film formation, (b)
Indicates the layer configuration after initialization.

FIG. 8 is a diagram illustrating a change in 3T mark length depending on the composition of a recording layer.

FIG. 9 is a diagram showing a layer configuration of a recording medium according to Embodiment 5 of the present invention.

FIG. 10 is a conceptual diagram showing a method for forming a Si layer in Example 5.

FIG. 11 is a diagram showing a layer configuration of a recording medium according to Embodiment 6 of the present invention.

FIG. 12 is a diagram illustrating a method for inspecting a recording medium described in a seventh embodiment. It is a figure showing (a) laser modulation method and (b) change of reflected light intensity.

[Explanation of symbols]

103 Bottom level 104 Phase change mark 105 Mark leading end 106 Mark trailing end 107 Mark length 301 Disc top view A Innermost circumference B Outermost circumference 302 Innermost mark 303 Extension of mark trailing edge at outermost circumference 304 Innermost BSbTe mark of the mark 305 innermost of the mark 306 outermost GeSbTe marks 307 outermost BSbTe of _{GeSbTe 203,406,503 BSbTe 508 Ta 2 O 5} 707,904,1001 Si target 1002 substrate 201,401,501, 701,901,1101
Polycarbonate substrate 207, 402, 506, 705, 906, 1102
Ag 202, 205, 403, 407, 502, 505, 7
02,704,902,905,1103,1106
ZnS.SiO ₂ 204, 404, 1104 BiTe ₃ 405, 504, 703, 903, 1105 GeSb
Te 71, 91, 111 Outer circumference 72, 92, 112 Inner circumference 207, 706, 507, 907 Protective layer 101, 1201 Recording level 102, 1202 Reproduction / erase level 1203 Crystal level 1204 Amorphous level 1205 Erasure time

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G11B 7/26 531 C23C 14/34 A // C23C 14/34 B41M 5/26 X F term (Reference) 2H111 EA12 EA23 EA31 EA37 FA02 FA11 FA23 FB05 FB09 FB12 FB17 FB21 GA03 4K029 AA09 AA11 BA21 BA22 BB02 BD12 CA05 DC16 5D029 HA05 HA07 JA01 JB03 JB05 5D090 AA01 BB05 BB12 CC02 DD03 JJ11 EE11A01EEG

Claims (9)

[Claims] 1. A phase-change recording medium having at least two recording layers laminated on a substrate, wherein the constituent components of each recording layer are selected from the group consisting of Sb, Te, In, Ag and Ge. The recording layer includes at least two selected main component elements and at least one or more other additional elements different from the main component element, and the type of the additional element and the amount of the additional element are different from each other. A phase-change recording medium, wherein each of the recording layers is provided as a recording layer having a low crystallization speed on the back side in the light incident direction. 2. The phase-change recording medium according to claim 1, wherein a seed layer of Bi or Bi ₂ Te ₃ is provided in contact with the surface of the recording layer having a low crystallization rate. 3. The phase change type recording according to claim 1, wherein a layer for preventing mutual diffusion between the main component element and the additional element is provided between the recording layers. Medium. 4. A phase-change recording medium having a recording layer on a substrate and a layer serving as a diffusion source for introducing an additional element into the recording layer during initialization, wherein the recording layer is made of Sb, Te, In or A phase change recording medium comprising at least two elements selected from the group consisting of Ag, Ge and Ge as main elements, and wherein the layer serving as the diffusion source is provided in contact with the recording layer. 5. A method for manufacturing a phase-change recording medium, comprising: forming a recording layer on a substrate and a layer serving as a diffusion source for introducing an additional element into the recording layer at the time of initialization, wherein Sb, Te, In, Ag and Ge are provided. Providing the recording layer containing at least two elements selected from the group consisting of the main components, contacting the layer serving as the diffusion source with the recording layer, and providing the layer serving as the diffusion source with a film thickness step. A method for manufacturing a phase-change recording medium, comprising controlling the concentration distribution of the additive element in the plane of the recording medium. 6. The method according to claim 1, wherein the diffusion source layer is Bi or Bi ₂ T.
method of manufacturing a phase-change recording medium according to claim 5, characterized in that the e _3. 7. A method for manufacturing a phase-change recording medium according to claim 1, or a method for manufacturing a phase-change recording medium obtained by the method according to claim 5. A method for manufacturing a phase change recording medium, wherein a target for forming the main component element and a target for forming the additional element are different from each other when forming by a sputtering method. 8. A method for inspecting a phase change type recording medium, comprising measuring a mark erasing time by modulating laser power in two stages of a recording level and an erasing level while the recording medium is stationary. A method for inspecting a phase change type recording medium, wherein characteristics of the recording medium are determined by comparison measurement with a standard value. 9. A phase-change recording medium according to claim 4,
Alternatively, the mark erasing time obtained by using the phase change type recording medium obtained by the manufacturing method according to claim 5 or 6 by using the inspection method according to claim 7 is expressed by the following formula (I): Tx / T ₁ ≦ R ₁ / Rx (I) (where the erase time T ₁ at the innermost circumference R ₁ and the erase time Tx at an arbitrary measurement position Rx are satisfied). A method for inspecting a phase change recording medium, which is a feature.