JP2002245686A - Method of forming fine pattern - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a master optical disk which has high reliability and high tracking performance in a method of forming a fine pattern by forming a mixed film smaller than the diameter of a light beam spot at the boundary between a substrate and a metallic film and forming a pattern having a guide groove of a rectangular shape. SOLUTION: A metallic film is formed on the surface of the substrate and the mixed film consisting of the metallic film and the substrate is formed at the boundary of the metallic film and the substrate heated up to a prescribed temperature or above by condensing and irradiating the prescribed position of the metallic film with the light beam from above the metallic film, by which only the metallic film is selectively removed. The substrate of the regions where the mixed films are not formed is etched by a prescribed amount in such a manner that the mixed film and the substrate below the same are made to remain.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a fine pattern, and more particularly to a method for forming a fine pattern required when manufacturing an optical disk master for manufacturing an optical disk or the like for recording information at high density. .

[0002]

2. Description of the Related Art Today, in order to realize a higher density of an optical disk, a track pitch of a guide groove and a prepit of the optical disk have been reduced. The formation of the guide grooves and prepits is generally performed by a so-called mastering process in which a photoresist applied to a glass substrate is condensed and irradiated with a laser beam, and the photoresist is exposed and developed to produce an optical disc master. Will be here,
Assuming that the wavelength of the laser light is λ and the numerical aperture of the objective lens for condensing the laser light is NA, the light beam spot diameter of the condensed laser light is approximately 0.8λ / NA. Conventionally,
In order to narrow the track pitch of the guide grooves and pre-pits of the optical disk, the wavelength λ of the laser beam is reduced and the numerical aperture NA of the objective lens is increased in order to reduce the diameter of the light beam spot. Have been done.

A description will be given of laser cutting of a conventional optical disc master coated with a positive photoresist 6 which is conventionally used. FIG. 1 shows a schematic configuration diagram of a conventional laser cutting device. In FIG. 1, a laser beam 2 emitted from a laser light source 1 is reflected by mirrors 3-1 and 1-2. After light intensity control is performed by a light modulator 4, the laser beam 2 is reflected by a falling mirror 3-3. By passing through the objective lens 5, the positive photoresist 6 applied on the glass substrate 7 is focused and irradiated.

The glass substrate 7 is mounted on a spindle motor 8. The falling mirror 3-3 is synchronized with the rotation of the glass substrate 7 accompanying the rotation of the spindle motor.
The exposure corresponding to the spiral guide groove and the pre-pit is performed on the positive photoresist 6 by moving the and the objective lens 5. After exposure, the positive photoresist 6 is developed to form a positive photoresist pattern corresponding to the spiral guide groove and the pre-pit.

FIG. 2 shows a standardized light intensity distribution with respect to a spot diameter of a light beam condensed on a conventional positive photoresist 6. This indicates an almost Gaussian light intensity distribution.

Generally, the light beam spot diameter BS is defined by a range where the light intensity is 1 / e ² of the maximum light intensity. The light beam spot diameter BS is determined by the wavelength λ of the laser light 2 to be used and the numerical aperture NA of the objective lens 5 for condensing the laser light 2, and the light beam spot diameter BS is approximately 0.8 × λ / NA. Can be approximated by For example, as the laser light 2, a laser light having a wavelength of 351 nm from the Kr laser light source 1 is used, and the numerical aperture NA is 0.95.
In the case where the objective lens is used, the light beam spot diameter BS becomes 296 nm.

FIG. 3 shows that a positive photoresist 6 on a glass substrate 7 is irradiated with the light beam 2 having the light beam spot diameter BS.
Shows the state of formation of the latent image 9 when is exposed. As the light beam 2 passes through the positive photoresist 6, the light intensity becomes weaker due to light absorption, and a latent image 9 which is narrow on the glass substrate surface but wide on the positive resist surface is formed. In FIG.
Track pitch T approximately equal to light beam spot diameter BS
P indicates the state of formation of the latent image 9 when the adjacent guide groove is exposed. For example, if the light beam spot diameter BS is 296
nm, and the track pitch TP is 300 nm.
The position of the latent image 9 corresponds to a guide groove.

FIG. 5 shows a state of the latent image 9 formed on the positive photoresist 6 after such spiral guide grooves are continuously formed. FIG. 6 shows the latent image 9 shown in FIG.
2 shows the positive photoresist pattern 10 after the development.

[0009] As shown in FIG.
Since S and the track pitch TP are almost equal, the guide groove 1
It was found that only a small amount of the positive type photoresist pattern 10 remained during 1 and that the pattern did not become a rectangular pattern. In such a state, a slight change in the light beam intensity at the time of cutting or a track pitch change due to an external vibration causes the positive photoresist pattern 1 to change.
It was confirmed that the shape of No. 0 was remarkably changed, and in the worst case, the positive type photoresist pattern 10 was missing and stable tracking became difficult.

In order to avoid such a situation, it is necessary to make the width of the positive photoresist pattern 10 wider. Therefore, an attempt was made to form a wider positive photoresist pattern 10 by weakening the intensity of the laser beam 2 when exposing the positive photoresist 6.

FIG. 7 shows a state of the latent image when the intensity of the laser beam is reduced. As shown in FIG. 7, when the intensity of the laser beam 2 at the time of exposure is reduced, a V-groove latent image 9 corresponding to the light intensity distribution of the light beam spot is formed. In this case, too, a rectangular positive photoresist pattern is formed. Was not formed. Further, in order to obtain a rectangular pattern, the trough pitch TP is larger than the light beam spot diameter BS and needs to be about twice.

As described above, when the optical disk master is manufactured by applying a positive type photoresist 6 on a glass substrate, the track pitch can be reduced while maintaining stable tracking performance. Has proved difficult to achieve.

[0013]

At present, the numerical aperture NA of the objective lens has already been used near the limit, and the wavelength of the laser light also uses the ultraviolet laser light. Therefore, it is difficult to further shorten the wavelength. For example, an objective lens having a numerical aperture NA of 0.95 is used, and a Kr laser having a wavelength of 351 nm is used as a light source. In this case, the light beam spot diameter is about 0.3 μm, and it is impossible to realize a track pitch of 0.3 μm or less.

The present invention has been made in view of the above circumstances, and has been achieved by forming a mixed film having a narrow width on the substrate surface using the same objective lens and laser light as in the prior art. It is another object of the present invention to provide a method for forming a fine pattern having a guide groove smaller than a spot diameter of a light beam on a substrate.

[0015]

According to the present invention, a metal film is formed on a surface of a substrate, and a light beam is condensed and irradiated on a predetermined position of the metal film from above the metal film. At the interface between the metal film and the substrate whose temperature has been raised to
A mixed film composed of a metal film and a substrate is formed, and only the metal film is selectively removed, and the substrate in a region where the mixed film is not formed is formed so as to leave the mixed film and a substrate thereunder. An object of the present invention is to provide a method for forming a fine pattern, characterized in that etching is performed by a fixed amount. This allows
A fine pattern having pre-pits and guide grooves smaller than the light beam spot diameter can be formed.

Further, a metal film is formed on the surface of the substrate, a transparent film is formed on the metal film, and a light beam is condensed and radiated to a predetermined position from above the transparent film so as to have a predetermined temperature. At the interface between the metal film and the substrate raised above, a mixed film composed of the metal film and the substrate is formed, the metal film and the transparent film are selectively removed, and the mixed film and the substrate thereunder are removed. An object of the present invention is to provide a method for forming a fine pattern, which comprises etching a predetermined amount of a substrate in a region where a mixed film is not formed so as to remain. further,
After the substrate in the region without the mixed film is etched by a predetermined amount, the remaining mixed film may be selectively removed by sputter etching. According to this, the roughness of the substrate surface can be improved.

[0017]

In the present invention, it is preferable that the mixed film is formed in an area smaller than the diameter of a light beam spot of a concentratedly irradiated light beam.
In particular, when the transparent film is formed, it is preferable that the transparent film has an anti-reflection structure with respect to the condensed and irradiated light beam. The anti-reflection structure refers to a structure capable of absorbing the light beam condensed and irradiated as efficiently as possible. In order for the transparent film to exhibit an anti-reflection effect, it is necessary to select the thickness of the transparent film in relation to the wavelength of the light beam.

As the material of the transparent film, any material having a transparent property may be used, but a transparent resin, a transparent dielectric film or the like can be used. For example, AlN can be used. As a material of the substrate, glass, Si or SiO ₂ can be used, but other plastics, compound semiconductors, or the like may be used. As the material of the metal film, besides metals such as Al, Co or Pd,
Metals having melting points lower than these metals can be used.

By using the method for forming a fine pattern as described above, it is possible to manufacture an optical disk master having pre-pits and guide grooves smaller than the light beam spot diameter.

If Ni electroforming is further performed using this optical disk master, a stamper for optical disks can be manufactured by so-called transfer. Further, an optical disk can be manufactured by performing injection molding of a resin and formation of a recording layer of a recording medium using the stamper for an optical disk.

To efficiently form a mixed film in a region smaller than the light beam spot diameter by irradiating the light beam,
As described above, in addition to the transparent film having the antireflection structure, it is preferable that the metal film also has the antireflection structure. Here, in order for the transparent film or the like to have an antireflection structure, in other words, to exhibit an antireflection effect, it is necessary to select an appropriate thickness of the transparent film or the like in relation to the wavelength of the light beam. For example, the thickness w of the transparent film is given by w = (mλ) /
(4n), where m: odd number, λ: wavelength of light beam, n:
What is necessary is just to make it the refractive index of a transparent film.

The predetermined temperature for forming a mixed film (hereinafter referred to as a mixed film forming temperature) means that a metal film reacts with a substrate to form a solid solution, a eutectic compound, or an intermetallic compound. Temperature at which an alloy composed of both materials is formed at the interface between the metal film and the substrate. For example, when the substrate material is Si and the metal film is Al, the mixed film formation temperature is 5
A mixed film in which Al is mixed with Si is formed in the interface region where the temperature is about 00 ° C. or higher and the temperature is higher than this temperature.

Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. Note that the present invention is not limited to this. The conventional laser cutting device shown in FIG. 1 is also a laser cutting device used for manufacturing the optical disc master of the present invention. In the conventional case, a glass substrate 7 as shown in FIG.
Although the one coated with the positive type photoresist 6 on it is used, the present invention uses the one formed by forming a metal film on a glass substrate. The present invention is characterized in that a master optical disc is manufactured by the following method in order to reduce the track pitch of the master optical disc.

In the following embodiment, in a fine pattern formed on the surface of a substrate, one track is constituted by a pair of concave portions and convex portions, and land recording for recording information only in either the concave portions or the convex portions. The method is intended for optical disks of the group type or group recording type. In this method, the length obtained by adding the width of the pair of concave portions and convex portions is the track pitch TP.

FIG. 8 is a schematic explanatory view of laser cutting in the method of manufacturing an optical disk master according to the present invention.

As the optical disk master, glass (quartz) is used.
Alternatively, a metal film 12 is formed on a substrate 7 made of silicon or the like.
(For example, aluminum) and a transparent film 13 (for example, aluminum nitride: AlN) formed in this order are used. First, a mixed film 14 is formed by irradiating a light beam having a predetermined beam spot diameter BS from above the transparent film 13 of the master. As shown in FIG. 8, the mixed film 14 is formed only at the interface between the metal film 12 and the substrate 7 and only in the region where the temperature of the metal film 12 has risen to a temperature higher than the mixed film forming temperature.

Here, when the mixed film is formed by the aluminum metal film 12 and the silicon substrate 7, the mixed film forming temperature is, for example, about 500 ° C. The thickness of the transparent film 13 is such that the laser beam 2 used for exposure is
It is desirable to set so as to exhibit an anti-reflection effect so that the light is incident on the surface. For example, assuming that the wavelength of the laser beam 2 is λ and the refractive index of the transparent film 13 is n, a desirable thickness w of the transparent film 13 can be expressed by w = (mλ) / (4n). Here, m is an odd number.

As described above, by forming the transparent film 13 formed on the metal film 12 into an anti-reflection structure, the light beam 2
Is absorbed by the metal film 12 and the transparent film 13. When the light beam 2 is absorbed by the metal film 12, the Gaussian-like temperature distribution corresponding to the intensity distribution of the light beam 2 is efficiently formed on the metal film 12.

FIG. 9 shows an embodiment of the temperature distribution with respect to the diameter of the light beam spot irradiated on the metal film 12. In the temperature distribution shown in FIG.
m, the peak of the interface temperature of the metal film 12 is 700
° C, the width of the formed mixed film 14 is about 100 nm, which indicates that the forming temperature of the mixed film 14 is 500 ° C or more.

According to this distribution, the metal film 12 is formed in an area having a width smaller than the beam spot diameter BS of the light beam 2 having a temperature (here, 500 ° C.) required for forming the mixed film.
It can be seen that a mixed film 14 made of the material of the substrate 7 is formed. The formation of such a mixed film having a width smaller than the beam spot diameter BS was confirmed by detecting fluorescent X-rays from a focused electron beam with a scanning electron microscope. In FIG. 8, the mixed film 14 is replaced with the metal film 12.
Between the metal film 12 and the substrate 7 is formed as a thin film at the interface between the metal film 12 and the substrate 7. .

FIG. 10 shows a cross-sectional shape when an adjacent track is exposed at a track pitch TP substantially equal to the light beam spot diameter BS. In this case, since the region where the temperature of the metal film 12 has risen above the mixed film forming temperature is smaller than the light beam spot diameter BS, the mixed film 14 is formed separated in the track direction.

FIG. 11 shows the cross-sectional shape after such laser cutting is continuously performed and spiral laser cutting is performed. Metal film 12 and substrate 7
The mixed films 14 are arranged at a track pitch TP at the interface with the. This continuous laser cutting is performed by gradually moving the falling mirror 3-3 and the objective lens 5 shown in FIG.

As described above, the mixed film 14 (width of about 150 nm) having a width smaller than the track pitch TP (for example, 300 nm) is formed at intervals of the track pitch TP, and thus corresponds to a concave portion between the mixed films. The guide groove 11 can be formed with a width smaller than the track pitch.

After such laser cutting, the transparent film 13 and the metal film 12 are removed by wet etching or dry etching.
Only leave. FIG. 12 shows the transparent film 13 and the metal film 1.
2 shows a cross-sectional state in which 2 is removed by etching and only the mixed film 14 remains. Here, when wet etching is used, it may be performed using an acid aqueous solution, an alkaline aqueous solution, or the like. When dry etching is used, CF ₄
Or CCl ₄ gas.

Next, using the mixed film 14 as a mask, the exposed portion of the substrate 7 where the mixed film 14 is not formed is
Etch. This etching can be performed using wet etching or dry etching. FIG. 13 shows a sectional state of the substrate 7 after the etching. As shown in FIG. 13, both the mixed film 14 having a convex portion having a width of 150 nm and the guide groove 11 having a concave portion having a width of 150 nm have a rectangular shape, and are formed at a track pitch TP of about 300 nm.

Although the state shown in FIG. 13 can be used as an optical disk master, it is preferable to etch the surface of the mixed film 14 and the substrate 7 from the viewpoint of improving the surface roughness. That is, if the substrate 7 and the mixed film 14 are etched by a predetermined amount by sputter etching as shown in FIG. 14, an optical disk master with improved surface roughness is completed.

In the master optical disk completed in this manner, a convex portion to be a guide track is formed in a rectangular shape, and the pitch thereof is formed with a track pitch TP as narrow as the light beam spot diameter BS. So
By using this optical disk master, it is possible to manufacture an optical disk suitable for high-density recording and having more stable tracking performance.

Next, a process for manufacturing an optical disk from the optical disk master completed by the above manufacturing process will be described. 15 shows an electrode film forming step, FIG. 16 shows a Ni electroforming step, FIG. 17 shows a stamper forming step by peeling, and FIG.
8 is a diagram showing a sectional state of the disc after a resin optical disc substrate forming step, FIG. 19 is a completed optical disc substrate step, and FIG. 20 is a recording medium forming step.

First, as shown in FIG. 15, an electrode film 15 serving as an electrode for electroforming is formed on the surface of the master optical disc by sputtering or the like. Ni, Ni,
Metals such as Ta and stainless steel are desirable. In order to facilitate the peeling of the stamper from the electrode film 15 in the subsequent stamper peeling step, the surface of the electrode film is oxidized by ashing or the like.

Next, as shown in FIG. 16, using the electrode film 15 as an electrode, Ni electroforming is performed to form a Ni electroformed film 16. Then, as shown in FIG. 17, after the Ni electroformed film is peeled off from the electrode film 15, the back surface of the Ni electroformed film 16 (the surface on the uneven side in FIG. 17) is polished. This polished Ni electroformed film 16 becomes the stamper 17.

Next, as shown in FIG.
Is mounted on an injection molding machine, and a resin such as polycarbonate is injection-molded to form a resin optical disk substrate 18 as shown in FIG.

Finally, as shown in FIG. 20, the optical disk is completed by forming the recording medium 19 on the guide track forming surface (the uneven surface of the substrate) of the optical disk substrate 18. Here, the recording medium is a constituent layer composed of a plurality of layers for recording so-called data, and is, for example, a laminate of a transparent dielectric layer, a recording layer, a transparent dielectric layer, and a reflective layer in this order.

The optical disk manufactured as described above has a light beam spot diameter B used for laser cutting.
A track pitch TP (for example, 300 n
m), a rectangular guide track (a convex portion on the disk surface in FIG. 20) is formed. Since a rectangular guide track can be formed, an optical disk having a narrow track pitch suitable for high-density recording and capable of stable tracking can be accurately formed by using an optical disk master manufactured using the manufacturing method of the present invention. be able to. Next, an embodiment of a method for manufacturing an optical disk master and an optical disk master according to the present invention will be described.

Example 1 A metal film 12 was formed on a Si substrate 7.
Al is formed to a thickness of 40 nm, and the transparent film 1
As No. 3, AlN was formed with a film thickness of 44 nm. These thin films can be formed using a reactive sputtering method.

Next, the wavelength 351 from the Kr laser light source 1 will be described.
The laser beam 2 of nm was focused and irradiated on the surface of the transparent film 13 by an objective lens 5 having a numerical aperture NA of 0.95, and laser cutting was performed. Here, the light beam spot diameter BS of the condensed laser light 2 was about 300 nm. Also, assuming that the track pitch TP is 300 nm, 20 mW
Laser cutting was performed with a laser power of the following intensity. The metal film 12 and the transparent film 13 having the above-mentioned thickness are
It has an anti-reflection structure for laser light having a wavelength of 351 nm. Through the above steps, the mixed film 14 having the structure as shown in FIG. 11 was formed.

Next, the AlN transparent film 13 and the Al metal film 12 were removed by wet etching using a sodium hydroxide solution. As a result, a mixed film 14 of Al and Si remained as shown in FIG. Here, when the formed mixed film 14 is observed using fluorescent X-rays of an electron microscope, the pattern width of the remaining mixed film 14 is 120 nm.
Met. That is, the mixed film 14 having the same track pitch TP (300 nm) as the light beam spot diameter BS and having a pattern width smaller than the light beam spot diameter BS was formed.

Next, using the mixed film 14 as a mask, S
The i-substrate 7 is placed in a dry etching apparatus, and a CF ₄ etching gas (flow rate 50 sccm) and an O ₂ gas (flow rate 30)
(sccm) was introduced into the apparatus, the gas pressure during etching was set to 30 mTorr, and high-frequency power of 400 W was applied to dry-etch the Si substrate 7.

Under these etching conditions, since Si and Al were mixed in the mixed film pattern 14, the etching of the mixed film hardly proceeded, and the etching of only the Si substrate 7 proceeded (see FIG. 13). For example, 1
After the dry etching for about a minute, the Si substrate 7 in the region where the mixed film 14 was not formed was etched to a depth of about 400 nm, and a rectangular concave portion was formed. The width of the recess formed at this time, that is, the width of the guide groove 11 in the left-right direction on the paper surface is about 150 nm. That is, the guide groove 11 having a width smaller than the light beam spot diameter could be formed.

In the above-described conventional manufacturing method, the track pitch TP needs to be about twice as large as the beam spot diameter BS in order to obtain a rectangular concavo-convex pattern. Even when the track pitch TP is substantially equal to the beam spot diameter BS, a rectangular concavo-convex pattern can be formed.

Next, a flow rate of 70 s
Ar gas was introduced at ccm, the gas pressure was set to 10 mTorr, and high frequency power of 500 W was applied to the mixed film 1.
4 was removed by sputter etching. This allows
The surface roughness is improved, and an optical disc master as shown in FIG. 14 is completed.

Next, as shown in FIG. 15, a Ni electrode film 15 was formed on the optical disk master by sputtering. Then, after the surface of the Ni electrode film 15 was oxidized by oxygen plasma, a Ni electroformed film 16 was formed by electroforming (see FIG. 16). Then, the stamper 17 was formed by peeling the optical disc master from the Ni electroformed film 16 and polishing the back surface of the Ni electroformed film 16 (FIG. 17).

Next, the polycarbonate was added to the stamper 17.
An optical disk substrate 18 made of resin was formed by injection molding on the concave and convex surface of the resin and peeling it off from the stamper 17.
8, see FIG. 19).

Further, a recording medium 19 composed of a transparent dielectric layer, a recording layer, another transparent dielectric layer, and a reflective layer is formed on the optical disk substrate 18 in this order, and a protective coat layer made of an ultraviolet curable resin is formed thereon. Was formed. The recording layer,
It is made of a material on which information can be recorded by a laser beam focused and irradiated by an optical pickup of an optical disk drive, and various commercially available magneto-optical recording materials and phase change materials can be used. Through the above steps, an optical disk as shown in FIG. 20 was manufactured.

In the first embodiment, in FIG. 14, the mixed film 14 is removed by sputter etching to use the optical disk as a master, but the mixed disk 14 can be used as a master for an optical disk even when the mixed film 14 remains. .

However, in order to reduce the noise of the optical disk, it is desirable to perform sputter etching as described above. The surface roughness in each state was measured using an atomic force microscope. As a result, when the sputter etching was not performed, the surface roughness of the etched surface of the Si substrate 7 was 0.
29 nm, and the surface roughness of the mixed film 14 is 0.88 nm.
On the other hand, by performing sputter etching, the surface roughness of the etched surface of the Si substrate 7 is 0.23 n
m, and the surface roughness of the portion of the Si substrate 7 where the mixed film 14 has been removed becomes 0.27 nm. That is, the surface roughness of the optical disk master can be reduced by sputter etching, and the noise of the optical disk can be reduced.

(Embodiment 2) In the method for manufacturing an optical disk master described in Embodiment 1, a Si substrate is used as the substrate 7, but a substrate other than the Si substrate may be used. Here, an embodiment in which a quartz substrate is used as the substrate 7 will be described.

First, as in the first embodiment, an Al metal film 12 and an AlN transparent film 13 are formed, and laser cutting is performed to form a mixed film 14 of Al and SiO ₂ . Next, after the AlN transparent film 13 and the Al metal film 12 are sequentially removed, dry etching is performed using the mixed film 14 of Al and SiO ₂ as a mask. Dry etching is
A CF ₄ etching gas (flow rate 100 sccm) was introduced, the gas pressure during etching was set to 30 mTorr,
The test was performed by supplying 0 W high frequency power.

Under these etching conditions, since the mixed film 14 is a mixture of Al and SiO ₂ , the etching of the mixed film hardly proceeds, and the SiO ₂ substrate in the region where no mixed film is formed is formed. Etching of only 7 proceeded. Finally, by performing sputter etching, an optical disc master having the same irregularities as in Example 1 could be produced.

(Embodiment 3) In the method of manufacturing an optical disk master described in Embodiment 1, Al is used for the metal film 12, but a metal other than Al, for example, Co, can be used.

When Co is used as the metal film 12 shown in FIG. 8, a mixed film 14 of Co and SiO ₂ is formed.

After removing the AlN transparent film 13 by wet etching using a sodium hydroxide solution,
The sodium hydroxide solution was removed by pure water rinsing, and (3
HCl / H ₂ O ₂ ) aqueous solution was used to remove the Co metal film 12. As a result, a mixed film 14 of Co and SiO ₂ remained as shown in FIG.

Next, using the mixed film 14 as a mask, the quartz substrate 7 is placed in a dry etching apparatus, the flow rate of the CF ₄ etching gas is set to 100 sccm, the gas pressure at the time of etching is set to 30 mTorr, and high-frequency power of 400 W is applied. Then, dry etching of the quartz substrate 7 was performed.

Under these etching conditions, since the mixed film 14 contains Co ₂ mixed with SiO ₂ , the etching of the mixed film hardly proceeds, and only the quartz substrate 7 in the region where no mixed film is formed is formed. Etching progressed. Next, if the same sputter etching as in the first embodiment is performed, the master optical disc is completed. As the metal film 12,
Instead of Co, the same 3d transition metals Fe and N
i can also be used.

(Embodiment 4) Here, a case where Pd is used as the metal film 12 will be described. In this case, by irradiating a light beam from above the transparent film 13 as shown in FIG. 8, a mixed film 14 composed of Pd and SiO ₂ is formed.

After removing the AlN transparent film 13 by wet etching using a sodium hydroxide solution,
The sodium hydroxide solution was removed by pure water rinsing, and (K
I / I ₂ ) The Pd metal film 12 was removed using an aqueous solution. As a result, as shown in FIG.
_{The two} mixed films 14 remained.

Next, using the mixed film 14 as a mask, the quartz substrate 7 is placed in a dry etching apparatus, the flow rate of the CF ₄ etching gas is set to 100 sccm, the gas pressure at the time of etching is set to 30 mTorr, and high frequency power of 400 W is applied. Then, dry etching of the quartz substrate 7 was performed.
Under this etching condition, the mixed film 14
Since Pd was mixed with SiO ₂ , etching of the mixed film hardly proceeded, and etching of only the quartz substrate 7 proceeded. Next, if the same sputter etching as in the first embodiment is performed, the master optical disc is completed.

(Embodiment 5) The optical disk master shown in FIG. 14 manufactured according to the present invention is different from the conventional optical disk master in that the concavo-convex shape is reversed. Therefore, even in the optical disk finally manufactured as shown in FIG. 20, the concavo-convex shape is reversed. Thus, in a fifth embodiment, a description will be given of correcting the reverse of the unevenness.
Here, a stamper 17 formed after the peeling step shown in FIG. 17 is used.

First, the uneven surface on which the guide tracks of the stamper 17 are formed is oxidized by oxygen plasma. Thereafter, the Ni electroformed film 16 'is formed on the uneven surface using the stamper 17 as an electrode. The uneven surface of the Ni electroformed film 16 'is obtained by reversing the unevenness of the Ni electroformed film 16 formed in FIG.

Next, the Ni electroformed film 16 ′ is
If the back surface is polished after peeling off from the stamper 7, a work stamper 17 'in which the irregularities are reversed with respect to the stamper 17 is formed. If an optical disk substrate is manufactured using this work stamper 17 ', an optical disk substrate having a concavo-convex structure similar to the conventional one and having pre-pits and guide grooves (= about 150 nm) smaller than the light beam spot diameter (= about 300 nm). Can be manufactured. In the present invention, the land recording method or the group recording method for recording information only on either the concave portion or the convex portion of the fine pattern, the manufacturing of a substrate having a fine pattern smaller than the light beam spot diameter is described. Similarly, in a land group recording method in which information is recorded in both a concave portion and a convex portion, a substrate having a fine pattern with a narrow width can be manufactured.

[0070]

According to the present invention, a mixed film having a diameter smaller than the light beam spot diameter is formed by condensing and irradiating a light beam onto a substrate having a metal film formed on its surface. Thus, a substrate having a fine pattern consisting of prepits and guide grooves smaller than the light beam spot diameter can be manufactured. Further, by using a substrate having such a fine pattern, an optical disk master having a narrow track pitch, an optical disk stamper, and an optical disk can be manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a laser cutting device used for manufacturing an optical disc master in the present invention.

FIG. 2 is an explanatory diagram of a normalized light intensity distribution with respect to the diameter of a focused light beam spot.

FIG. 3 is a cross-sectional view illustrating a conventional laser cutting exposure process.

FIG. 4 is a cross-sectional view illustrating a conventional laser cutting exposure process.

FIG. 5 is a cross-sectional view illustrating a conventional laser cutting exposure process.

FIG. 6 is a cross-sectional view of a positive photoresist pattern formed by conventional laser cutting.

FIG. 7 is a cross-sectional view illustrating a conventional laser cutting exposure process.

FIG. 8 is a cross-sectional view illustrating an exposure process according to an embodiment of the method of manufacturing an optical disc master according to the present invention.

FIG. 9 is an explanatory diagram of an interface temperature distribution with respect to a light beam spot diameter in the present invention.

FIG. 10 is a cross-sectional view illustrating an exposure process according to an embodiment of the method of manufacturing an optical disc master of the present invention.

FIG. 11 is a cross-sectional view illustrating an exposure process according to an embodiment of the method of manufacturing an optical disc master of the present invention.

FIG. 12 is a cross-sectional view illustrating a state after a metal film and a transparent film are removed in the present invention.

FIG. 13 is a cross-sectional view illustrating a state where a substrate surface in a region where a mixed film is not formed is etched in the present invention.

FIG. 14 is a completed view of an optical disc master completed by the manufacturing process of the present invention.

FIG. 15 is a cross-sectional view illustrating a state in which an electrode film is formed on the master optical disc of the present invention.

FIG. 16 is a cross-sectional view illustrating a state in which a Ni electroformed film is formed on the master optical disc of the present invention.

FIG. 17 is a cross-sectional view illustrating a state where a Ni electroformed film is peeled off from the master optical disc of the present invention.

FIG. 18 is a cross-sectional view illustrating a state in which a resin optical disc substrate is molded from a stamper in the present invention.

FIG. 19 is a completed view of a molded optical disk substrate in the present invention.

FIG. 20 is a cross-sectional view illustrating a state in which a recording medium is formed on an optical disk substrate in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser light source 2 Laser light (light beam) 3-1 Mirror 3-2 Mirror 3-3 Falling mirror 4 Optical modulator 5 Objective lens 6 Positive photoresist 7 Glass substrate 8 Spindle motor 9 Latent image 10 Positive photoresist Pattern 11 Guide groove 12 Metal film 13 Transparent film 14 Mixed film 15 Electrode film 16 Ni electroformed film 17 Stamper 18 Resin optical disk substrate 19 Recording medium

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Rishin Nobue 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka F-term in Sharp Corporation (reference) 4K057 DA11 DB06 DB17 DC10 DD03 DE08 DN03 WA11 WB01 WB03 WB05 WB17 WB17 WB20 WC10 WE01 WE08 WE22 WN04 5D121 AA02 BA01 BA05 BB14 BB18 BB33 BB34 GG04

Claims (10)

[Claims] 1. A metal film formed on a surface of a substrate, wherein the metal film is heated to a predetermined temperature or higher by condensing and irradiating a light beam onto a predetermined position of the metal film from above the metal film. A mixed film formed of a metal film and a substrate at an interface between the metal film and the substrate, selectively removing only the metal film, and leaving the mixed film and a substrate therebelow to form a mixed film. A method of forming a fine pattern, characterized by etching a predetermined amount of a substrate in an unexposed region. 2. A method of forming a metal film on a surface of a substrate, forming a transparent film on the metal film, and condensing and irradiating a light beam to a predetermined position from above the transparent film to obtain a predetermined temperature. At the interface between the metal film and the substrate raised above, a mixed film composed of the metal film and the substrate is formed, the metal film and the transparent film are selectively removed, and the mixed film and the substrate thereunder are removed. A method of forming a fine pattern, characterized by etching a predetermined amount of a substrate in a region where a mixed film is not formed so as to remain. 3. The fine pattern according to claim 1, wherein after etching the substrate in a region where the mixed film is not formed by a predetermined amount, the remaining mixed film is selectively removed by sputter etching. Formation method. 4. The method for forming a fine pattern according to claim 1, wherein said mixed film is formed in an area smaller than a spot diameter of a light beam intensively irradiated. 5. The method for forming a fine pattern according to claim 2, wherein said transparent film has an anti-reflection structure for a light beam condensed and irradiated. 6. The method according to claim 5, wherein the transparent film is made of AlN. 7. The formation of a fine pattern according to claim 1, wherein the substrate is made of Si or SiO ₂ and the metal film is made of Al, Co or Pd. Method. 8. A master optical disc manufactured by using the method for forming a fine pattern according to claim 1. 9. An optical disk stamper manufactured by using the optical disk master according to claim 8. 10. An optical disk manufactured by using the optical disk stamper according to claim 9.