JP2003196892A - Method and apparatus for manufacturing optical disk - Google Patents

Abstract

(57) [Summary] [PROBLEMS] An optical disc having excellent recording, erasing, and reproducing characteristics in all areas from the inner circumference to the outer circumference when used at a constant angular velocity, and such an optical disc can be formed stably and at high speed. And methods. SOLUTION: The recording film composition of the optical disk is Ge, Sb,
It contains three elements of Te, and the ratio of Ge, Sb, and Te is in a range surrounded by A, B, C, and D in FIG. 1. The composition ratio of Ge and Te is the same in the entire region of the optical disk. The Sb amount is reduced from the periphery to the outer periphery. In addition, as a manufacturing method, the substrate is opposed to a plurality of ring-shaped targets having a common central axis, and the substrate and the target are installed so as to coincide with each other, and the compositions of the plurality of ring-shaped targets are different. Then, a recording film is formed by simultaneous sputtering from a plurality of ring targets.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc for recording, reproducing or rewriting information at high density and high speed by using an optical means such as a laser beam and a method for manufacturing the same.

[0002]

2. Description of the Related Art A technique for recording and reproducing high-density information on an optical disk by using light such as a laser beam is known, and is currently applied to document files, still image files, external memory for computers, etc. It is being appreciated.

Recently, a rewritable type has been put into practical use, and particularly in a phase change optical disk utilizing reversible state change between an amorphous state and a crystalline state of a recording film, a laser spot passes through a signal track only once. In this regard, so-called overwriting is possible, in which a new signal is recorded while an old signal is erased. The recording film composition of such a phase change optical disc includes Ge, Te, Sb,
Alloys such as Se are mainly used.

In a general overwrite method for a phase change optical disk, laser power is modulated between a recording power and an erasing power by a recording signal and a track is irradiated with the modulated laser power. The area irradiated with the recording power is cooled after the recording film reaches the melting point and is cooled, so that a new signal is recorded by amorphization regardless of the presence or absence of old recording marks, and the area irradiated with the erasing power is the recording film. Is heated above the crystallization temperature, the old signal in the amorphous state is crystallized and erased.

Therefore, in the phase change optical disk, the crystallization speed is an important parameter. In other words, if the crystallization speed is too slow (that is, the crystallization time is too long), the laser spot is not sufficiently crystallized and the unerased residue occurs. On the other hand, if the crystallization speed is too fast (that is, the crystallization time is too short), even if the recording film is cooled after melting when recording a signal, it will not be completely amorphized but recrystallized sufficiently. Recording marks are not obtained, or the shape of the recording marks is distorted. That is, there is an optimum crystallization speed according to the linear speed (relative speed between the laser spot and the optical disk).

There are mainly two methods for rotating an optical disk. One is a method of rotating at a constant linear velocity in the entire area of the optical disc, and the other is a method of rotating at a constant angular velocity (that is, a constant number of rotations). According to the latter, for example, even when the optical head moves from the inner circumference to the outer circumference to access necessary information, it is not necessary to adjust the rotation speed,
It has the advantage of being fast.

By the way, when an optical disc is rotated at a constant angular velocity, the linear velocity is different between the inner circumference and the outer circumference. Inner circumference is slow and outer circumference is fast. At this time, if the crystallization speed is optimized according to the linear velocity of the inner circumference, crystallization will be insufficient at the outer circumference and unerased residue will occur. Conversely, if it is optimized according to the linear velocity of the outer circumference, the melted portion at the inner circumference will In some cases, a large recording mark could not be obtained due to the progress of recrystallization.

As a method for solving this, Japanese Patent Laid-Open No. 1-1
In Japanese Patent No. 84510, the composition of the recording film is changed in the radial direction,
An optical disc has been proposed in which the crystallization time is shortened toward the outer circumference. Specifically, a method is disclosed in which, in an optical disc made of an alloy of GeTe and Sb ₂ Te ₃ , the inner circumference is made GeTe rich to slow down the crystallization speed, and the outer circumference is made to be Sb ₂ Te ₃ rich to speed up the crystallization speed. ing. According to this method, good erasing characteristics can be obtained from the inner circumference to the outer circumference.

Further, in the above-mentioned Japanese Patent Application, as a method of manufacturing such an optical disc, as shown in FIG. 12, while rotating the substrate 9, a position eccentric to the center of rotation is provided.
Providing two or more evaporation sources 22 or sputter sources,
Further, a method of providing a partition plate 23 between the substrate and the source to change the composition in the radial direction of the disk is disclosed.

[0010]

[Patent Document 1] JP-A-1-184510

[0011]

However, as a result of further investigations by the inventors, in the above inner circumference, GeT
e-rich to slow down the crystallization speed, and Sb ₂ T
It has been found that the amplitude of the reproduced signal may differ between the inner circumference and the outer circumference of the optical disc that is made e ₃ rich and has a high crystallization speed. It is considered that this is because when the ratio of GeTe and Sb ₂ Te ₃ is changed, not only the crystallization speed of the recording film but also the complex refractive index is significantly changed.

The reproduction of a signal on a phase change optical disk is
Generally, this is performed by irradiating the signal track with a reproduction laser power and detecting the difference in reflectance between the crystalline state and the amorphous state. When the complex refractive index changes between the inner circumference and the outer circumference, the reflectivity between the amorphous state and the crystalline state also changes,
As a result, the amplitude of the reproduced signal is different between the inner circumference and the outer circumference, which makes it impossible to obtain uniform reproduced signal quality in the entire recording area of the optical disc.

The optical disk manufacturing method described in the above-mentioned Japanese Patent Application also has the following problems.

First, since two or more evaporation sources or sputter sources are provided at positions eccentric to the center of rotation of the substrate, they must be rotated at a high speed to achieve the same composition in the circumferential direction, or they must be rotated. It is necessary to slow down the membrane rate.
In any case, unless the substrate is rotated a sufficient number of times from the start to the end of film formation, the composition in the circumferential direction and the film thickness become non-uniform. This is a big problem when producing a large number of optical disks at high speed.

In the above-mentioned Japanese Patent Application, a vacuum vapor deposition method is mentioned as one of the film forming methods. However, the vacuum vapor deposition method has a smaller adhesion strength of a thin film than the sputtering method, and a vapor deposition source at the time of film formation. There is also a problem that foreign matter is likely to be formed on the substrate due to bumping or the like.

The present invention solves the above problems and provides an optical disk in which the crystallization speed increases from the inner circumference to the outer circumference, but the signal reproduction characteristics do not change, and such an optical disk can be stably and rapidly deposited. It is intended to provide a new device.

[0017]

In order to achieve the above object, the manufacturing method of the present invention is a manufacturing method of an optical disc having a recording film which changes between optically distinguishable states by irradiation of light. A plurality of ring-shaped targets each having the same constituent element and different compositions of the constituent elements are arranged concentrically, and the central axes of the plurality of ring-shaped targets are aligned with the central axis of the substrate. When the recording film is formed on the substrate, the sputtering power to be applied to each of the plurality of ring-shaped targets is independently controlled so that the film formation rate on the substrate becomes uniform. The feature is that sputtering is performed.

Another manufacturing method of the present invention is a manufacturing method of an optical disc having a recording film that changes between optically distinguishable states by irradiation of light, each of which contains the same constituent element. A disk-shaped target and a ring-shaped target having different elemental compositions are arranged concentrically, and the substrate is placed so that the central axis of the disk-shaped target coincides with the central axis of the substrate, and the recording film is formed on the substrate. In the case of depositing a film, it is characterized in that sputtering is performed by independently controlling the sputtering power supplied to each of the disk-shaped target and the ring-shaped target so that the film formation rate on the substrate becomes uniform. There is.

Further, the manufacturing apparatus of the present invention is a manufacturing apparatus of an optical disc having a recording film on a substrate which changes between optically distinguishable states by irradiation of light, each of which includes the same constituent element. When a plurality of ring-shaped targets having different elemental compositions and the recording film is formed on the substrate by sputtering, each of the plurality of ring-shaped targets is formed so that the film formation rate on the substrate becomes uniform. And a control means for independently controlling the sputtering power input to the.

Further, another manufacturing apparatus of the present invention is an optical disk manufacturing apparatus having a recording film on a substrate which changes between optically distinguishable states by irradiation of light, each of which has the same constituent element. A disk-shaped target and a ring-shaped target having different compositions of the constituent elements, and the disk-shaped target so that the film formation rate on the substrate becomes uniform when the recording film is formed on the substrate by sputtering. A target and a control unit for independently controlling the sputtering power applied to each of the ring-shaped targets.

In the above-mentioned manufacturing method and manufacturing apparatus, the plurality of ring-shaped targets, or the disk-shaped target and the ring-shaped target are Ge,
One of the features of the present invention is that it contains three elements of Sb and Te, the composition ratio of Ge and Te is the same, the Te amount is larger than the Ge amount, and the Sb amount is smaller as the target is placed outside. Is.

Another feature of the present invention is that the plurality of ring-shaped targets, or the disk-shaped target and the ring-shaped target have a composition ratio of Ge and Te of 2: 5.

Furthermore, the plurality of ring-shaped targets,
Alternatively, the disc-shaped target and the ring-shaped target include an additive element other than the three elements, and a target arranged outside is more preferable than a target arranged inside,
It is one of the features of the present invention that the amount of the additional element added is small. Also, if the additive element is Pd, Co, N
At least one of i, Tl, Se, In, Au, Ag, and Cr is also one of the features of the present invention.

In the optical disc manufactured by the manufacturing method and the manufacturing apparatus of the present invention, the crystallization speed is fast from the inner circumference to the outer circumference, and the reproduction amplitude is almost the same on the inner circumference and the outer circumference. Recording and erasing and reproducing characteristics can be obtained.

Further, according to the optical disk manufacturing method and manufacturing apparatus of the present invention, it becomes possible to manufacture an optical disk having a high crystallization speed from the inner circumference to the outer circumference with good reproducibility and at high speed.

[0026]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the drawings.

FIG. 2 shows a sectional view of an example of an optical disk according to the present invention. A substrate 1 is generally made of transparent glass, quartz, polycarbonate, polymethylmethacrylate, or the like.

On the substrate 1, a first dielectric layer 2, a recording film 3, a second dielectric layer 4 and a reflective film 5 are laminated in this order. Further, if necessary, a protective cover 6 may be provided to protect the thin film layer.

First dielectric layer 2 and second dielectric layer 4
Is preferably a transparent and thermally stable substance, and examples thereof include oxides, nitrides, chalcogenides, fluorides, carbides of metals and semimetals, and mixtures thereof, and specifically, SiO ₂ , SiO ₂ . , Al ₂ O ₃ , GeO ₂ , In ₂ O ₃ , Ta
₂ O ₅ , TeO ₂ , TiO ₂ , MoO ₃ , WO ₃ , ZrO ₂ ,
Si ₃ N ₄ , AlN, BN, TiN, ZnS, CdS, C
dSe, ZnSe, ZnTe, AgF, PbF ₂ , Mn
It is a simple substance such as F ₂ , NiF ₂ , or SiC, or a mixture thereof.

The reflective layer 5 is composed of a metal film, and as a material thereof, a simple substance such as Au, Al, Ti, Ni, Cu, Cr or the like or an alloy thereof can be used.

Incidentally, the first dielectric layer 2, the recording film 3, the second
By appropriately designing the film thickness of the dielectric layer 4, the structure without the reflective layer 5 is possible.

Further, even when the thin film structure of the optical disk is further different, it is included in the present invention as long as it satisfies the gist of the present invention.

The characteristics of the optical disk of the present invention are that the crystallization speed of the recording film 3 is faster on the outer circumference than on the inner circumference, and the composition of the recording film contains at least three elements of Ge, Sb and Te. Including, the ratio of Ge, Sb, Te is A in FIG.
It is in the range surrounded by B, C, and D, and the composition ratio of Ge and Te is almost the same in the entire area of the optical disc, and the amount of Sb is reduced from the inner periphery to the outer periphery of the optical disc.

Alternatively, the recording film composition of the optical disk is set to G
e, Sb, and Te, Pd, Co, Ni, Tl,
One or more elements such as Se, In, Au, Ag, and Cr are added, and the amount of the added element decreases from the inner circumference to the outer circumference of the optical disk.

In order to obtain good recording and erasing characteristics from the inner circumference to the outer circumference of the optical disk, it is desirable that the crystallization speed of the recording film is faster on the outer circumference than on the inner circumference. In the above-mentioned Japanese Patent Application No. 1-184510, GeSb is used as the recording film.
Using a ternary alloy of Te, GeTe and Sb _{2 on the} inner and outer circumferences
Optical discs with different Te ₃ ratios have been proposed.

GeSbTe ternary alloy is well known as a recording film for phase change optical disks, and it has been reported that the crystallization rate of the thin film is as shown in FIG. 13 (Japa
neseJournal of Applied Physics, Vol.26 (1987) Supple
ment26-4, p61).

That is, the crystallization rate is G of stoichiometric composition.
Change on the line connecting eTe and Sb ₂ Te ₃ ,
When rich, the crystallization speed is slow, and when Sb ₂ Te ₃ rich, the crystallization speed is fast. The above-mentioned Japanese patent application is such a GeS
It is an invention made by utilizing the characteristics of the ternary alloy of bTe.

However, as a result of further study by the inventors, the crystallization rate is changed between the inner circumference and the outer circumference of the optical disk by adopting any two compositions having different crystallization speeds (the constituent elements may be different). If you do this easily,
In some cases, it has been found that the reproduced signal quality (particularly the reproduced amplitude) is different between the inner circumference and the outer circumference of the optical disc because the complex refractive index differs greatly between the inner circumference composition and the outer circumference composition.

For example, between point E and point F on the line connecting GeTe and Sb ₂ Te ₃ in FIG. 3, the composition of point F has a crystallization speed about twice as fast, but a large complex refractive index. Therefore, when the thin film structure of the optical disk is used, for example, the wavelength λ =
At 780 nm, at point E, the reflectance difference ΔR between the amorphous state and the crystalline state is about 30%, but at point F, ΔR
R was about 10% (see Example 1 below for details).

Since the phase-change optical disk mainly reproduces the recorded signal by detecting the difference in reflectance between the amorphous state and the crystalline state, the difference in reflectance difference ΔR between the points E and F results in It will be the difference in playback amplitude between the inner and outer circumferences,
It turns out that this is a practical problem. Note that FIG. 3 is an enlarged view of a region near Sb in the ternary composition diagram of Ge, Sb, and Te shown in FIG. Further, composition points A to M in FIG.
Specific compositions corresponding to are listed at the end of the examples.

On the other hand, in the present invention, the recording film composition is G
Any point on the line of eTe and Sb ₂ Te ₃ and Sb10
It is changed on the line connecting the 0% point. For example, between point G and point H in FIG. 3, the composition of point G has a crystallization speed about twice as fast, but the difference in complex refractive index is small, so when the optical disk is formed into a thin film, the wavelength λ = 780 nm. At the point G, the reflectance difference ΔR is about 24.5%, while at the point H, the difference ΔR is about 24%, and the difference is small. As a result, the reproduction amplitudes at the inner and outer circumferences are small. The difference is small,
It turns out that there is no problem in practice.

Also in the Te-rich composition region from the GeTe and Sb ₂ Te ₃ lines (the composition region on the Te side of the straight line AB in FIG. 1), the crystallization rate changes depending on the composition, but the signal repetition It was found that the deterioration of signal quality due to recording was severe.

Further, a Ge-rich composition region from the line connecting GeTe and Sb100% (from the straight line DA in FIG.
In the e-side composition region), the crystallization time is longer than 1 μs. The time of 1 μs corresponds to the time required for a laser spot having a diameter of 1 μm to pass through one point on the optical disc at a linear velocity of 1 m / s, for example.

Since the linear velocity is generally used at a velocity higher than 1 m / s, if the crystallization time is longer than that (that is, the crystallization velocity is slow), it is not practical as a recording film material for optical discs. . Further, since the melting point is high in this region, a large recording power is required, and therefore it cannot be used for the recording film of the optical disc.

In the composition region in which Te is smaller than that of the straight line CD in FIG. 1, the crystallization time is longer than 1 μs, and the crystallization speed becomes too slow to be practical. The Te amount is preferably 45% or more.

Further, the composition ratio of Ge and Te is Ge: Te.
In the case where the composition of the limited region of the present invention is set to be near 2: 5 (on the straight line connecting the point G and the point M in FIG. 3), the overwrite repetitive characteristic becomes very good, and 1 million times Overwriting can be achieved.

Further, in the present invention, the three elements Ge, Sb and Te are indispensable as the recording film composition, but other elements may be contained to the extent that the gist of the present invention is not impaired.

Generally, when other elements are added to the Ge.Sb.Te alloy, the crystallization rate is lowered in most cases. That is, it is possible to control the crystallization rate by utilizing this characteristic to change the concentration of the additive element between the inner circumference and the outer circumference.

Particularly, as additional elements, Pd, Co, Ni,
When at least one of Tl, Se, In, Au, Ag, and Cr is selected, the crystallization speed is lowered and the change in complex refractive index is small, so that the reflectance change amount Δ of the optical disc is decreased.
It was found that R was almost constant and that the crystallization temperature did not decrease. The addition amount is preferably 20% or less. If it is more than this range, the crystallization rate may be sharply reduced or the complex refractive index may be greatly changed.

The optical disk of the present invention in which the crystallization speed of the recording film is faster on the outer circumference than on the inner circumference can be manufactured by an apparatus as shown in the sectional view of FIG. 5 is a sketch showing the positional relationship between the target and the substrate shown in FIG.

The ring-shaped inner target 7 and the outer target 8 share a central axis 10, and the substrate 9 faces the targets 7 and 8 with the central axis 10 further common. By changing the composition of the two targets 7 and 8, an optical disk whose composition changes from the inner circumference to the outer circumference can be manufactured.

FIG. 6 shows a radial film formation rate distribution at the substrate position when a film is formed from each target, and a total film formation rate distribution of both. Note that the film forming rate in FIG. 6 is standardized and shown by the maximum value of the total film forming rate. Further, although the recording film thickness should originally be made uniform from the inner circumference to the outer circumference of the optical disk, it can be seen that it can be made substantially uniform by adjusting the film forming rates of the inner circumference target and the outer circumference target as shown in FIG.

At this time, in order to change the composition of the recording film from the inner circumference to the outer circumference from point H to point G in FIG.
The composition of the point I, which is Sb poor from the point G, is selected as the composition of 1) and the peripheral target composition. The distribution of the recording film composition at this time in the radial direction of the disk is shown in FIG. Composition point I, G, H, J
Are on the straight line of Ge amount: Te amount = 2: 5, respectively, and the Sb amount changes. Therefore, in FIG. 7, the recording film composition is represented by the Sb amount. The recording area of this optical disc has a radius of 25 mm at the innermost circumference and a radius of 6 at the outermost circumference.
When it is 0 mm, the composition of the point H is approximately 25 mm at the innermost radius, the composition of the point G is approximately 60 mm at the outermost radius, and the Sb amount gradually decreases from the inner periphery to the outer periphery. I understand.

The relationship between the recording film composition and the target composition is as follows: target shape, TS distance (distance between target and substrate),
Although it depends on the size of the substrate and the like, the composition of the recording film is set to a range surrounded by A, B, C, and D in FIG. 1 which is a ternary composition diagram of Ge, Sb, and Te. In order that the composition ratio of Ge and Te is almost the same in the entire region and the amount of Sb is reduced from the inner circumference to the outer circumference of the optical disc, the ring-shaped target composition is also Ge.
The composition ratios of Te and Te are substantially the same, the Te content is larger than the Ge content, and the Sb content may be reduced from the inner peripheral target to the outer peripheral target. However, the target composition may be outside the region surrounded by A, B, C, and D in FIG. 1 as in the above embodiment.

Although the number of ring-shaped targets is two in FIG. 5, it may be three or more. In this case, the intermediate target composition is between the composition of the inner target and the composition of the outer target. In this way, the crystallization rate of the recording film formed by using three or more targets can be continuously increased from the inner circumference to the outer circumference.

When the number of ring-shaped targets is increased, it is possible to obtain a uniform film thickness distribution without increasing the TS distance even if the substrate size is increased. Therefore, the attachment rate of the sputtered atoms to the substrate is increased, and the target material can be effectively used.

Although the inner target is also ring-shaped in FIG. 5, the center target may be a disc-shaped target 14 instead of the ring-shaped target as shown in FIG. The method of selecting the target composition in this case is the same as the case of using all the ring-shaped targets described above. The number of ring-shaped targets 15 may be two or more,
When the number of ring-shaped targets is increased, a uniform film thickness distribution can be obtained without increasing the TS distance even if the substrate size is increased, and the target material can be effectively used.

Further, as shown in FIG. 9, for example, one target 16 is composed of targets which are concentrically divided into a plurality of regions having different compositions, and an inner region 17 and an outer region 1 are formed.
It is also possible to manufacture a disk having a higher crystallization rate from the inner circumference to the outer circumference of the optical disk by changing the composition with 8 and.

The merit of this manufacturing method is that the film can be formed by a conventional sputtering apparatus using a general disc-shaped target. That is, with a simple device, it is possible to manufacture an optical disc in which the crystallization speed increases from the inner side to the outer side.

It should be noted that the target may be divided into any number as long as it is divided into two or more regions, but in consideration of manufacturing the target, the division into two is preferable. The method of selecting the target composition in this case is based on the case where all the ring-shaped targets are used.

The advantage of the manufacturing method of FIGS. 5 and 8 over the manufacturing method of FIG. 9 is that the target manufacturing method is easy. For example, as shown in FIG. 9, when one target is divided into two or more, the boundary is created. If a gap or the like is formed at this boundary, it will cause an abnormal discharge, so a high-level target manufacturing technique is required. On the other hand, for example, in the manufacturing method shown in FIGS. 5 and 8, the targets have a single composition, so that there is no fear of abnormal discharge.

Further, the recording film is made of Ge / Sb / Te alloy,
In the case of a composition in which another additional element is added, the amount of the additional element may be increased toward the inner target. For example, in FIG. 5, the amount of added elements in the inner target 7 is larger than that in the outer target 8, and in FIG.
5, the disk-shaped target 14 has a larger amount of added elements, and in FIG. 9, the amount of added elements in the inner region 17 is larger than that in the outer region 18, a disk having a higher crystallization speed from the inner circumference to the outer circumference is obtained. It is possible to make.

The substrate may be rotated (rotated) on the target during film formation. However, since the target structure is rotationally symmetric with respect to the central axis and the substrate shares the central axis with the target, the composition and film thickness on the substrate are also isotropic with respect to the center. Therefore, the substrate may be stationary facing the target, and in this case, the rotation mechanism of the optical disk is not required, and the device configuration is simplified.

When a plurality of independent targets are used as in the manufacturing method having the configuration of FIG. 5 or FIG. 8, it is desirable that the targets have the same life. In other words, if the number of film-depositable optical disks is the same, the target replacement time can always be the same, so that the stop period of the film-forming apparatus can be shortened and therefore the operating rate of the film-forming apparatus can be improved.

The required film formation rate from each target differs depending on the substrate shape, the TS distance, the target shape, and the like. Therefore, in order to make both the number of film formations of the optical disk the same (make the life of the target the same), the thickness of the target may be adjusted according to each film formation speed.

By the multi-source vacuum deposition method, for example, as shown in FIG.
It is also possible to install a vapor deposition source and a substrate as shown in FIG. For example, the composition material at the point J in FIG. 3 is placed in the vapor deposition source 19 at the center, and the composition material at the point I is placed at the vapor deposition source 20 distant from the center. It is possible to manufacture an optical disc in which the delay is delayed.

However, as described above, in addition to the problems that the vacuum vapor deposition method has a lower adhesion strength of the thin film than the sputtering method and that foreign substances are easily formed on the substrate due to bumping or the like at the vapor deposition source during film formation, The vapor deposition source is generally a point, and it is necessary to rotate the substrate to make the composition and film thickness on the substrate isotropic with respect to the center. In particular, when a film is formed in a short time during mass production, high speed rotation is required, which is not practical.

In the case of evaporating an alloy composed of a plurality of elements from one evaporation source by the evaporation method, the ratio of the elements to be formed may be different from the composition of the evaporation source due to the difference in melting point and vapor pressure depending on the elements. It may change over time and is impractical also in this respect.

Example 1 Before producing the optical disc according to the present invention, the relationship between the recording film composition and the reflectance of the optical disc was determined.

The reflectance in the case of the optical disc configuration is 1
A film having the same structure as that shown in FIG. 2 was formed on a 2 × 18 mm glass substrate, and reflectances Ra and 3 in an amorphous state immediately after the film formation were measured.
The reflectance Rc in the crystalline state which was heat-treated at 00 ° C. for 5 minutes was measured to obtain the reflectance difference ΔR = Rc−Ra.

The material of the dielectric layer is the first dielectric layer and the second dielectric layer.
Zn with 20 mol% of SiO ₂ added to both dielectric layers
S, and the material of the reflective layer is Al. Each film thickness is
The first dielectric layer is 174 nm, the recording film thickness is 30 nm, the second dielectric layer is 23 nm, and the reflective layer thickness is 100 nm. The measurement wavelength is 780 nm.

Thus, the recording film composition is changed in the vicinity of the area surrounded by A, B, C, and D in FIG. 1 with the same thin film structure, and the recording film composition and the reflectance of the optical disk are changed. Sought a relationship. Note that all film formation was performed by a sputtering method.

FIG. 11 shows the result. In the figure, the contour line shows the composition ratio dependence of the reflectance difference ΔR when the optical disc structure is formed. In FIG. 13 described above, GeTe and Sb ₂ Te _{3 are used.}
Although it is shown that the crystallization speed changes when the composition is changed on the line connecting the and, it can be seen from FIG. 11 that the reflectance change amount ΔR of the optical disc also largely changes.

On the other hand, when Sb is further added to the composition at an arbitrary point on the line connecting GeTe and Sb ₂ Te ₃ , ΔR hardly changes. That is, it is possible to change only the crystallization speed as shown in FIG. 13 without changing ΔR.

However, if the amount of Sb is too large, as can be seen from FIG. 13, the crystallization time becomes long. Japanese mentioned above
Journal of Applied Physics, Vol.26 (1987) Suppl
As a result of measuring the crystallization rate by the same method as described in ement 26-4, p61, the crystallization time is 1 μs in the area on the right side of the straight line CD in FIG. 1, that is, the area where Te is less than 45%. It has been found that it exceeds the limit and is unsuitable as a recording material for optical discs.

In FIG. 11, ΔR is small in the composition near Sb ₂ Te _3, but this is because the thin film structure does not match the change in the complex refractive index of the recording film. That is, by optimizing the film thickness of each thin film, it is possible to make ΔR a large value of, for example, 20% or more (in this case, Ge).
ΔR becomes smaller in the composition near Te). That is, for example, even when the composition is changed from the point B to the point C where Sb is further added, if the optical disc configuration is optimized, ΔR can be set to 20% or more in the entire region of the optical disc, and good signal quality can be obtained.

From the inner circumference to the outer circumference, GeTe and S
Even when the composition is changed on the line connecting b ₂ Te ₃ to change the crystallization rate, if the film thickness of the thin film is also changed from the inner circumference to the outer circumference, a large reflectance change can be obtained in the entire region. It is difficult to change the film thickness of the thin film within one optical disk in view of mass productivity.

Further, as can be seen from FIG. 13, the crystallization rate becomes slower as the distance from the composition on the line between GeTe and Sb ₂ Te ₃ increases. Therefore, even if the composition ratio of Ge and Sb is made the same from an arbitrary composition point on the line of GeTe and Sb ₂ Te ₃ and the concentration of Te is changed between the inner circumference and the outer circumference of the optical disk, The crystallization rate can be changed. However, in this case, as shown in FIG.
This is not good because the optical constant changes greatly due to the density change, and the reflectance changes greatly between the inner circumference and the outer circumference.

(Example 2) Next, in the case where another element was added to the GeSbTe ternary alloy, the relationship between the amount of the added element, the reflectance difference ΔR, and the crystallization time was determined. The sample configuration and the measuring method for obtaining ΔR are the same as in Example 1, and the method for obtaining the crystallization time is as described above in Japanese Journal of Applied Physics, Vol. 26 (19).
87) Same as the method described in Supplement 26-4, p61.

Table 1 shows the results when the composition of point H in FIG. 3 was selected as the composition of the GeSbTe ternary alloy and other elements were added to it. As you can see from the table, GeS
It can be seen that the addition of Pd, Co, and Se to the bTe ternary alloy slows down the crystallization rate in all cases. However, if the addition amount exceeds 20%, the crystallization time exceeds 1 μs,
Alternatively, since the reflectance difference ΔR may be small, the addition amount is preferably 20% or less.

Incidentally, as additional elements, other elements such as Ni, Tl,
Similar results were obtained using In, Au, Cr and Ag. Also, a plurality of elements may be added at the same time.

Further, as the composition of Ge, Sb, and Te, the point H
It has been found that the crystallization speed can be slowed with almost no change in the reflectance difference ΔR by using other compositions in the region surrounded by A, B, C, and D in FIG. 1 other than the above.

[0083]

[Table 1]

(Embodiment 3) An optical disk was produced by the sputtering apparatus having the structure shown in FIG. 4 and the recording / erasing characteristics were measured. Inner target size is outer diameter 66mm (diameter), inner diameter 3
4 mm, thickness 6 mm, outer target size is outer diameter 1
42 mm, inner diameter 108 mm, and thickness 6 mm. The inside of the target composition is the composition of point J in FIG. 3, and the outside is the composition of point I in FIG. The sputtering power of the inner target and the outer target can be controlled independently.

The substrate is a polycarbonate substrate having a diameter of 123 mm provided with a signal recording track, and is stationary and opposed at a position of 35 mm above the target. On the substrate, ZnS—SiO _{2 as} a dielectric layer is formed in advance with a thickness of 174 nm.

After exhausting the inside of the vacuum chamber 11 to 3 × 10 ^-7 Torr by the exhaust system 13, Ar gas is introduced from the gas inlet 12 and simultaneous sputtering from two targets is performed under a gas pressure of 3 mTorr. Thus, a recording film having a thickness of 30 nm was formed on the substrate. After that, ZnS-SiO ₂ is added to 2
A film having a thickness of 3 nm and Al having a thickness of 100 nm was formed as a reflective layer. Further, a UV resin was overcoated thereon to form an optical disc. Since the recording film was in an amorphous state after sputtering, the entire surface was crystallized by laser irradiation to initialize the optical disk. This is an optical disc 1.

When the composition of the recording film is formed under the same conditions as those of the optical disk 1, the composition at the point H in FIG. 3 is around the radius 25 mm which is the innermost peripheral area of the signal recording, and the radius is around 60 mm which is the outermost peripheral area. ICP that the composition of point G in FIG.
Confirmed by analytical method.

As comparative examples, three types of optical discs having the same structure as the above-mentioned optical disc 1 but having different recording film compositions were produced. The optical disc 2 has a recording film composition in the entire region at the same point H as the innermost circumference of the optical disc 1, and the optical disc 3 has the recording film composition in the entire region in the optical disc 1
The composition of the point G is the same as that of the outermost circumference. Also, the optical disc 4
Is the composition at point K, which is intermediate between the composition at point H and the composition at point G in the entire area of the recording film composition.

The produced optical discs 1 to 4 were recorded at a wavelength of 780n.
The recording / reproducing characteristics were measured with a recording / reproducing apparatus having an objective lens numerical aperture (NA) of 0.55.

The recording / reproducing evaluation of signals was carried out by the following procedure. The optical disk was installed in a recording / reproducing apparatus, the spindle motor was rotated at 1800 rpm constant, and a light beam from a semiconductor laser was irradiated to a recording thin film layer as a minute light spot by an optical system to perform focus and tracking control.

First, at a position with a radius of 25 mm, the frequency f1
Both the signals of (0.785 MHz) and f2 (0.589 MHz) are alternately overwritten 20 times with a duty of 50%, and the CNR (signal to noise ratio) of f1 and f2 are overwritten on f1. In this case, the erasing rate of the f1 component was calculated. The measurement was performed with the recording power at which the CNR was saturated and the erasing power at which the maximum erasing rate was obtained.
The linear velocity at this time is 4.71 m / s, and the recording mark length is 3.0 μm at f1 and 4.0 μm at f2.

Next, at a position with a radius of 60 mm, the frequency f3
(1.885 MHz) and f4 (1.414 MHz) signals are alternately overwritten 20 times with a duty of 50% to erase the CNR of f3 and the f3 component when f4 is overwritten on f3. I asked for the rate. The linear velocity at this time is 11.31 m / s, the recording mark length is 3.0 μm at f3 and 4.0 μm at f4, which is the same as the case of the radius of 25 mm.

The measurement results are shown in (Table 2). In the optical disc 1 according to the present invention, good recording is achieved on both the innermost circumference and the outermost circumference.
It can be seen that erase characteristics can be obtained. On the other hand, it is understood that the optical disk 2 has a slow crystallization rate, and thus a sufficient erasing rate cannot be obtained at the outer periphery. In the optical disc 3, the CNR is very small in the inner circumference. It is considered that this is because the crystallization speed is high, and thus an amorphous recording mark of a sufficient size cannot be obtained at the inner circumference where the linear velocity is low.
In addition, the crystallization speed of the optical disk 4 is too high at the inner circumference,
Since the outer circumference is too slow, a decrease in CNR on the inner circumference and insufficient erasure on the outer circumference are observed.

That is, it is understood that the optical disc according to the present invention can obtain good recording / erasing characteristics from the innermost circumference to the outermost circumference for the first time.

Since the difference in the complex refractive index of the recording film between the inner circumference and the outer circumference is small, the reflected light change ΔR is substantially the same, and as a result, good CNR is obtained for both the inner circumference and the outer circumference.

[0096]

[Table 2]

Example 4 A substrate and a target are shown in FIG.
An optical disk was produced by the sputtering apparatus having the configuration shown in and the recording / erasing characteristics were measured.

The target size is 200 mm in diameter, and is divided into two concentric circles at a diameter of 80 mm. The inside of the target composition is the composition of the point M in FIG. 3, and the outside is the composition of the point L in FIG. At the time of sputtering, since the erosion region due to discharge covers both the inside and outside regions of the target, the respective compositions are simultaneously sputtered from the inside region and outside region of the target.

The substrate shape of the optical disk, the thin film structure other than the recording film composition, the film thickness of each thin film, the film forming conditions, and the initialization method were all the same as in Example 3. Further, in the case of recording film formation, the substrate is stationary and opposed at a position of 40 mm above the target. This optical disk according to the present invention will be referred to as an optical disk 5.

When the composition of the recording film is formed under the same conditions as the optical disk 5, the composition of the point H in FIG. 3 is around the radius of 25 mm which is the innermost peripheral area of the signal recording, and the radius of around 60 mm is the outermost area. ICP that the composition of point G in FIG.
Confirmed by analytical method.

The recording / erasing characteristics of the optical disk 5 thus produced are
The measurement was performed using the same evaluation device and evaluation conditions as in Example 3. As a result, the optical disk 5 has a CNR of 59.8d at the innermost circumference.
B, the erasure rate is -31.9 dB, and C is the outermost circumference.
The NR was 60.5 dB and the erasing rate was -31.0 dB. That is, like the optical disc 1, it can be seen that good recording / erasing characteristics can be obtained at both the innermost circumference and the outermost circumference.

Example 5 As a comparative example with the present invention, an optical disk 6 having the composition of point E in FIG. 3 on the inner circumference and the composition of point F in FIG. 3 on the outer circumference was produced. The substrate and thin film structure of the optical disk are the same as those in the third embodiment.

The evaluation method of the manufactured optical disc is described in Example 3.
However, since the optical disc 6 has a faster crystallization speed of the recording film than the optical disc 1, the optical disc rotation speed is 24
The rotation speed was set to 00 rpm, and rotation was performed at about 1.33 in the case of Example 3. The frequencies f1 to f4 are also multiplied by 1.33 to make the recorded mark length the same as in the third embodiment.

As a result of the measurement, the optical disc 6 has a C at the innermost circumference.
NR is 62.5 dB, erasure rate is -32.7 dB,
At the outermost circumference, the CNR is 52.3 dB and the erase rate is -3.
It became 1.1 dB. Since the crystallization speed increases from the inner circumference to the outer circumference, good erasing characteristics can be obtained at both the innermost circumference and the outermost circumference. However, it can be seen that the CNR is good at the innermost circumference, but is small at the outermost circumference. As a result of microscopic observation, a sufficiently large amorphous recording mark was formed even at the outermost periphery. Therefore, C at the outermost circumference
It is considered that the reason why the NR is small is that the reflectance change ΔR is small.

A representing each composition used in the present specification
The specific composition represented by at% of each point of ~ M is: A: (Ge, Sb, Te) = (50, 0, 50) B: (Ge, Sb, Te) = (0, 40, 60) C: (Ge, Sb, Te) = (0, 55, 45) D: (Ge, Sb, Te) = (45, 10, 45) E: (Ge, Sb, Te) = (35, 12, 53) ) F: (Ge, Sb, Te) = (7, 35, 58) G: (Ge, Sb, Te) = (22, 22, 56) H: (Ge, Sb, Te) = (20, 29, 51) I: (Ge, Sb, Te) = (23,20,57) J: (Ge, Sb, Te) = (19,34,47) K: (Ge, Sb, Te) = (21,26) , 53) L: (Ge, Sb, Te) = (23, 19, 58) M: (Ge, Sb, Te) = (18, 36, 46).

[0106]

As described above, the optical disk produced by the manufacturing method and the manufacturing apparatus of the present invention has a high crystallization speed from the inner circumference to the outer circumference, and the reproduction amplitudes are almost the same on the inner circumference and the outer circumference, so that the angular velocity is constant. Even in this case, good recording / erasing and reproducing characteristics can be obtained in the entire area of the optical disc. Therefore,
It is possible to easily provide an optical disc capable of high-quality signal recording over the entire area and realizing high-speed access.

Further, according to the optical disk manufacturing method and manufacturing apparatus of the present invention, it becomes possible to manufacture the above high performance optical disk with good reproducibility and at high speed.

[Brief description of drawings]

FIG. 1 is a Ge, Sb, Te ternary alloy composition diagram showing a region of a recording film composition of an optical disc of the present invention.

FIG. 2 is a diagram showing a cross-sectional structure of an optical disc of the present invention.

FIG. 3 is a Ge, Sb, Te ternary alloy composition diagram showing the composition of the target and the recording film adopted in the examples.

FIG. 4 is a configuration diagram of an example of a sputtering apparatus that realizes the optical disc manufacturing method according to the present invention.

5 is a schematic diagram showing a positional relationship between a substrate and a target of the sputtering apparatus of FIG.

FIG. 6 is a diagram showing a distribution of film formation rates when a film is formed by the sputtering apparatus of FIG.

7 is a diagram showing the composition distribution in the radial direction of the optical disc when a film is formed by the sputtering apparatus of FIG.

FIG. 8 is a schematic diagram showing a positional relationship between a substrate and a target of a sputtering apparatus of a different mode for realizing the optical disc manufacturing method according to the present invention.

FIG. 9 is a schematic diagram showing a positional relationship between a substrate and a target of a sputtering apparatus of still another aspect for realizing the optical disc manufacturing method according to the present invention.

FIG. 10 is a diagram showing a vapor deposition apparatus when an optical disc according to the present invention is manufactured by a simultaneous vapor deposition method.

FIG. 11 is a diagram showing a relationship between a reflectance change ΔR of an optical disc and a recording film composition.

FIG. 12 is a diagram showing a method for manufacturing an optical disc in Japanese Patent Application No. 1-184510.

FIG. 13 is a diagram showing the relationship between the composition of a recording film made of a ternary alloy of Ge, Sb, and Te and the crystallization rate.

[Explanation of symbols]

1 substrate 2 First dielectric layer 3 recording film 4 Second dielectric layer 5 Reflective film 6 Protective cover 7 Inside target 8 outer target 9 substrates 10 central axis 11 vacuum chamber 12 gas inlet 13 Exhaust system 14 Disc target 15 ring target

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G11B 7/24 522 B41M 5/26 X (72) Inventor Kenichi Nagata 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. (72) Nobuo Akabira No. 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Masahide Yokoyama 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Person Hiroshi Hayada 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 2H111 EA04 EA23 FB05 FB09 FB12 FB15 FB16 FB17 FB21 FB23 4K029 BA21 BB02 BC07 BD12 CA05 DC04 DC15 5D029 JA01 J18 A01 J18A5 EE18 EE19 EE30

Claims (14)

[Claims] 1. A method for manufacturing an optical disc having a recording film that changes between optically distinguishable states by irradiation with light, wherein a plurality of ring-shaped optical elements each containing the same constituent element and different in composition of the constituent element. The targets are arranged concentrically, and the substrates are set so that the central axes of the plurality of ring-shaped targets coincide with the central axes of the substrates, and the substrate is formed when the recording film is formed on the substrates. A method for manufacturing an optical disk, characterized in that sputtering is performed by independently controlling the sputtering power supplied to each of the plurality of ring-shaped targets so that the above film formation rate becomes uniform. 2. The plurality of ring-shaped targets each include three elements of Ge, Sb, and Te, have the same composition ratio of Ge and Te, and have a larger amount of Te than the amount of Ge and are arranged outside. The optical disc manufacturing method according to claim 1, wherein the target has a smaller amount of Sb. 3. The method of manufacturing an optical disk according to claim 2, wherein the composition ratio of Ge and Te of the plurality of ring-shaped targets is 2: 5. 4. The plurality of ring-shaped targets are the three targets.
2. The method of manufacturing an optical disc according to claim 1, wherein a target that includes an additional element other than the element and that is disposed outside the target that is disposed inside has a smaller amount of the additive element added. 5. The additive element is Pd, Co, Ni, T
5. The method for manufacturing an optical disc according to claim 4, wherein the method is at least one of 1, Se, In, Au, Ag, and Cr. 6. A method of manufacturing an optical disc having a recording film which changes between optically distinguishable states by irradiation of light, comprising a disk-shaped target each containing the same constituent element and different in composition of the constituent element. A ring-shaped target is arranged concentrically, the central axis of the disk-shaped target is placed on the substrate so as to match the central axis of the substrate, and the substrate is formed when the recording film is formed on the substrate. A method for manufacturing an optical disk, wherein sputtering is performed by independently controlling the sputtering power supplied to each of the disk-shaped target and the ring-shaped target so that the above film formation rate becomes uniform. 7. The disk-shaped target and the ring-shaped target each contain three elements of Ge, Sb, and Te, and have the same composition ratio of Ge and Te, and the Te content is higher than the Te content.
7. The method for manufacturing an optical disc according to claim 6, wherein the amount of Sb is larger and the Sb amount is smaller as the target is arranged outside. 8. The method of manufacturing an optical disk according to claim 7, wherein the composition ratio of Ge and Te of the disk-shaped target and the ring-shaped target is 2: 5. 9. The disk-shaped target and the ring-shaped target contain an additive element other than the three elements, and the target placed outside has a smaller addition amount of the additive element than the target placed inside. 7. The method for manufacturing an optical disc according to claim 6, wherein the optical disc is manufactured. 10. The additive element is Pd, Co, Ni,
10. The method for manufacturing an optical disc according to claim 9, wherein the optical disc is at least one of Tl, Se, In, Au, Ag, and Cr. 11. A manufacturing apparatus for an optical disc having a recording film on a substrate, which changes between optically distinguishable states by irradiation of light, wherein a plurality of optical discs each contain the same constituent element and have different compositions of the constituent elements. And a sputtering power applied to each of the plurality of ring-shaped targets so that the film formation rate on the substrate becomes uniform when the recording film is formed on the substrate by sputtering. An optical disk manufacturing apparatus comprising: a control unit that independently controls the optical disk. 12. The plurality of ring-shaped targets each include three elements of Ge, Sb, and Te, have the same composition ratio of Ge and Te, and have a larger amount of Te than the amount of Ge and are arranged outside. The optical disk manufacturing apparatus according to claim 11, wherein the target has a smaller amount of Sb. 13. A manufacturing apparatus of an optical disc having a recording film on a substrate which changes between optically distinguishable states by irradiation of light, wherein the disks each contain the same constituent element and the composition of the constituent element is different. A ring-shaped target and a ring-shaped target, and when the recording film is formed on the substrate by sputtering, the disk-shaped target and the ring-shaped target are formed so that the film formation rate on the substrate becomes uniform. An optical disc manufacturing apparatus comprising: a control unit that independently controls the sputtering power that is input. 14. The disk-shaped target and the ring-shaped target each contain three elements of Ge, Sb, and Te, and have the same composition ratio of Ge and Te, and the Te content is larger than the Ge content and is outside. 14. The optical disk manufacturing apparatus according to claim 13, wherein the Sb amount is smaller as the targets are arranged closer to each other.