JP2002352482A - Fine pattern forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method to form a fine pattern on a base plate by forming a mixed layer narrower than the light beam spot diameter on the boundary surface of a mask layer and a metal layer. SOLUTION: This invention is to form a mask layer on a base plate, and a metal film on the mask layer. Condensing and radiating an optical beam from above the metal film at a predetermined position, a mixed layer of the mask layer and the metal layer is formed on the boundary plane of the mask layer and the metal layer heated higher than prescribed. This invention is characterized in that the mask layer is selectively etched where there is no mixed layer to leave the mixed layer after removing the metal layer selectively.

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. About.

[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 reduce the track pitch of a light beam spot in order to reduce the track pitch of a guide groove or a pre-pit of an optical disk, the wavelength λ of a laser beam is reduced.
Is shortened, and the numerical aperture NA of the objective lens is increased.

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

[0005] 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 the exposure, the positive photoresist 6 is developed to form a positive photoresist pattern corresponding to the spiral guide groove and the prepit.

FIG. 2 shows a standardized light intensity distribution with respect to a spot diameter of a light beam converged on a positive photoresist 6 in the related art. This indicates an almost Gaussian light intensity distribution. It has a substantially 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 decreases due to light absorption, and a wide latent image 9 is formed on the positive resist surface, which is narrow on the glass substrate surface.

FIG. 4 shows the state of formation of the latent image 9 when exposing adjacent guide grooves at a track pitch TP substantially equal to the light beam spot diameter BS. For example, 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.

As shown in FIG. 6, the light beam spot diameter B
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 a positive optical photoresist 6 applied directly on a glass substrate is used for manufacturing an optical disk master, the track pitch is reduced while maintaining stable tracking performance. It turned out that realization was difficult.

[0015]

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 layer having a narrow width on the surface of a substrate 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 light beam spot diameter.

[0017]

According to the present invention, a mask layer is formed on a substrate, and a metal film is formed on the mask layer.
At the interface between the mask layer and the metal film, which has been heated to a predetermined temperature or higher by condensing and irradiating a light beam to a predetermined position from above the metal film, a mixed layer in which the mask layer and the metal film are mixed is formed. Forming a metal pattern, selectively removing the metal film, and selectively etching a mask layer in a region where the mixed film is not formed to leave the mixed layer, thereby providing a method of forming a fine pattern. Things. Thereby, a fine pattern having pre-pits and guide grooves smaller than the light beam spot diameter can be formed.

The substrate may be selectively etched simultaneously with the etching of the mask layer or after the etching of the mask layer. Furthermore, a transparent film may be formed on the metal film after forming the metal layer and before condensing and irradiating the light beam.

Here, it is preferable that the mixed layer is formed in a region smaller than the spot diameter of the concentratedly irradiated light beam. In particular, the metal film and the transparent film are subjected to condensing irradiation. It is preferable to have an anti-reflection structure for the reflected light beam. The substrate having the fine pattern thus formed can be used as an optical disk master or the like. Further, the remaining mixed layer may be removed by sputter etching. In this case, a substrate having a smoother surface can be formed.

Further, if so-called transfer is performed using an optical disk master having such a fine pattern, a stamper for an optical disk can be manufactured. Further, if the resin injection molding and the formation of the recording layer of the recording medium and the like are performed using the optical disk stamper, an optical disk can be manufactured. Also, by forming an electroformed film using the optical disk stamper as an electrode and peeling the electroformed film from the optical disk stamper, it is possible to manufacture an optical disk work stamper whose surface unevenness is reversed. Can be used to manufacture an optical disk.

The mask layer is made of Si, SiN or SiO ₂ , and the metal film is made of Al, Co, Fe, N
i, Pd or Ti can be used, but is not limited thereto. As the substrate, glass, silicon, plastic, or the like can be used. Further, AlN can be used for the transparent film.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 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. conventionally,
In the present invention, a mask in which a mask layer 12, a metal film 13, and a transparent film 14 are formed in this order on a glass substrate 7 is used. .

The present invention is characterized in that an optical disk master having a fine pattern is manufactured by the following method. In the following embodiments, for a fine pattern formed on a substrate surface, a single track is formed by a pair of concave portions and convex portions, and a land recording method or a groove recording method in which information is recorded only in either the concave portions or the convex portions. Target optical disks. 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 a master optical disc, a mask layer 12 made of, for example, SiO ₂ having a thickness of 40 is formed on a substrate 7 made of glass (quartz) or silicon by sputtering.
It is formed on the order of nm. Next, a metal film 13 made of, for example, Al is formed on the mask layer 12 by sputtering.
Is formed to a thickness of about 400 nm. Furthermore, this metal film 1
3, a transparent film 14 made of, for example, AlN
It is formed to a thickness of about 4 nm. The transparent film 14 is preferably formed on the metal film 13 in order to prevent reflection of the irradiated laser beam and adjust the laser power sensitivity. However, the transparent film 14 is not indispensable. Layer 15 can be formed.

Here, the thickness of the transparent film 14 needs to be set so as to exhibit an antireflection effect with respect to the laser beam 2 used for exposure. For example, assuming that the wavelength of the laser beam 2 is λ and the refractive index of the transparent film 14 is n, a desirable thickness w of the transparent film 14 can be expressed by w = (mλ) / (4n). Here, m is an odd number. This transparent film 1
4 can be AlN.

As described above, by forming the transparent film 14 formed on the metal film 13 into an anti-reflection structure, the light beam 2
Is absorbed by the mask layer 12, the metal film 13, and the transparent film 14. When the light beam is absorbed by the metal film 13, the metal film 13
, A Gaussian temperature distribution corresponding to the intensity distribution of the light beam 2 is formed. FIG. 9 shows an embodiment of the temperature distribution with respect to the diameter of the light beam spot irradiated on the metal film 13.

The metal film 13 is irradiated with the light beam 2, and a mixed layer 15 in which the metal film 13 and the mask layer 12 are mixed is formed at the interface between the metal film 13 and the mask layer 12 which have been heated to a predetermined temperature or higher. The formation of the mixed layer 15 can be confirmed by an electron microscope. In the temperature distribution shown in FIG.
When the light beam spot diameter BS is 300 nm, the temperature peak of the heat-sensitive multilayer film 12 is about 1000 ° C.
The width of the region whose temperature has risen to 0 ° C. or more, that is, the mixed layer 15
Is about 120 nm, which is smaller than the light beam spot diameter. Here, the lower limit temperature (700 ° C. in FIG. 9) at which the mixed layer 15 is formed is referred to as a mixed layer forming temperature or an alloy forming temperature. Using the mixed layer 15 thus formed as a mask, portions of the mask layer 12 and the metal film 13 other than the mixed layer 15 are removed by etching in a later step.

FIG. 10 shows a cross-sectional shape when an adjacent track is exposed at a track pitch TP (= 300 nm) having a width substantially equal to the light beam spot diameter BS. In this case, the width of the region whose temperature has risen above the mixed layer formation temperature (= 1)
50 nm) is the light beam spot diameter BS (= 300 n)
m), the mixed layer 15 is formed spaced apart in the track direction.

FIG. 11 shows a cross-sectional shape after such laser cutting is continuously performed and spiral laser cutting is performed. According to FIG. 11, at the interface between the metal film 13 and the mask layer 12, in the track direction,
The mixed layers 15 separated by the track pitch TP are arranged. This continuous cutting is performed by gradually moving the rising mirror 3-3 and the objective lens 5 shown in FIG.

FIG. 12 shows a cross-sectional shape after the transparent film 14 and the metal film 13 are etched after the above-described laser cutting. Here, the etching can be performed using wet etching or dry etching, but a wet etching solution or dry etching that can etch the transparent film 14 and the metal film 13 and leave the mixed layer 15 and the mask layer 12 can be used. This is performed using gas. The solution and the dry etching gas in the wet etching here differ depending on the material such as the metal film 13. Next, using the mixed layer 15 as a mask, the mask layer 12 in a region where there is no mixed layer 15 is etched.

FIG. 13 shows a cross-sectional shape after removing the mask layer 12 other than the region where the mixed layer 15 exists. In order to leave the mixed layer 15 and remove the mask layer 12, wet etching or dry etching can be used. The wet etching solution and the dry etching gas differ depending on the material of the mask layer 12. According to FIG. 13, a substrate having a structure in which the mixed layers 15 arranged at an interval of about 300 nm track pitch TP is arranged on the substrate 7 is formed. The substrate having the structure shown in FIG. 13 can be used as an optical disk master.

Next, in the state shown in FIG. 13, the substrate 7 is etched to a depth of about 40 nm using the mixed layer 15 as a mask. For this etching, wet etching or dry etching can be used. This FIG.
Can be used as an optical disk master.

Further, when the mask layer 12 and the mixed layer 15 are etched by dry etching, a substrate 7 having an uneven shape on the surface as shown in FIG. 15 is formed.
Further, instead of the dry etching in the state shown in FIG. 13, the substrate 7 and the mixed layer 15 may be sputter-etched. FIG. 22 shows a cross-sectional structure of the substrate 7 after sputter-etching the surfaces of the substrate 7 and the mixed layer 15 of FIG. 13 in the present invention. This sputter etching makes the surface roughness of the substrate 7 smoother. The substrate shown in FIG. 22 can also be used as an optical disk master.

Next, a process of manufacturing an optical disk from the optical disk master completed by the above manufacturing process will be described. Here, a process of manufacturing an optical disk using the optical disk master shown in FIG. 15 will be described. 16 shows an electrode film forming step, FIG. 17 shows a Ni electroforming step, FIG. 18 shows a stamper forming step by peeling, FIG. 19 shows a resin optical disk substrate forming step, FIG. 20 shows an optical disk substrate completing step, and FIG. 21 shows a recording medium. FIG. 6 is a diagram showing a cross-sectional state of the disk after each of the forming steps is performed.

First, as shown in FIG. 16, an electrode film 16 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 16 in the subsequent stamper peeling step, the surface of the electrode film is oxidized by ashing or the like.

Next, as shown in FIG. 17, using the electrode film 16 as an electrode, Ni electroforming is performed to form a Ni electroformed film 17. Then, as shown in FIG. 18, after the Ni electroformed film 17 is peeled from the electrode film 16, the back surface of the Ni electroformed film 17 (FIG.
6) is polished. The polished Ni electroformed film 17 becomes the stamper 18.

Next, as shown in FIG.
Is mounted on an injection molding machine, and a resin such as polycarbonate is injection-formed to form a resin optical disk substrate 19 as shown in FIG.

Finally, as shown in FIG. 21, an optical disk is completed by forming a recording medium 20 on a guide track forming surface (an uneven surface of the substrate) of an optical disk substrate 19. Here, the recording medium 20 is a constituent layer composed of a plurality of layers for recording data, for example,
A transparent dielectric layer, a recording layer, a transparent dielectric layer, and a reflective layer are laminated in this order.

The optical disk manufactured in this manner 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. 21) 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) Si was formed on a glass substrate 7 as a mask layer 12 to a thickness of 40 nm, and a metal film 13 was formed.
Al is formed to a thickness of 40 nm, and the transparent film 1
As No. 4, AlN was formed with a film thickness of 44 nm. Next, K
r laser light 2 having a wavelength of 351 nm from a laser light source 1
The surface of the transparent film 14 was condensed and irradiated with the objective lens 5 having an aperture NA of 0.95, and laser cutting was performed. Here, the light beam spot diameter BS of the focused laser light 2
Was approximately 300 nm. Laser cutting was performed with a track pitch TP of 300 nm and a laser power of 20 mW. Here, the metal film 13
The transparent film 14 has an antireflection structure for a laser beam having a wavelength of 351 nm. By the above steps, FIG.
The mixed layer 15 as shown in FIG.

Next, when the AlN transparent film 14 and the Al metal film 13 were removed by wet etching using a sodium hydroxide solution, as shown in FIG.
And Si mixed layer 15 remained. Here, when the remaining mixed layer 15 was observed using an electron microscope, the pattern width was about 120 nm. The interval T of the mixed layer 15
P is about 300 nm. That is, the mixed layer pattern 15 having the same track pitch TP as the light beam spot diameter BS and having a pattern width smaller than the light beam spot diameter BS was able to be realized.

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

Next, using the mixed layer pattern 15 as a mask, the glass substrate 7 is placed in a dry etching apparatus,
A Cl ₂ etching gas (flow rate 150 sccm) was introduced, the gas pressure during etching was set to 50 mTorr, and 40
By applying a high-frequency power of 0 W, dry etching of the Si mask layer 12 was performed. Under these etching conditions, in the mixed layer pattern 15, Al is alloyed with Si, so that the etching hardly proceeds,
Etching of only the Si mask layer 12 proceeded. Thus, a substrate as shown in FIG. 13 was formed.

Next, a flow rate of 20 s was applied to the etching apparatus.
Introduce CF ₄ gas at ccm and gas pressure 10mTorr
Then, dry etching of the glass substrate 7 was performed by applying a high-frequency power of 500 W. The above mixed layer pattern 1
In No. 5, since Al was alloyed with Si, the etching hardly proceeded, and only the glass substrate 7 proceeded. As a result, as shown in FIG.
The glass substrate 7 etched to a depth of about nm was formed.

Next, a flow rate of 70 s was supplied to the etching apparatus.
Ar gas was introduced at ccm, the gas pressure was set to 10 mTorr, and high frequency power of 500 W was applied to remove the mixed layer pattern 15 by sputter etching. Next, a Cl ₂ etching gas (flow rate 150 sccm) is introduced into the etching apparatus, a gas pressure at the time of etching is set to 50 mTorr, a high frequency power of 400 W is applied, and the Si mask layer 12 is removed by etching. 1
The fine pattern of the master optical disk shown in FIG. 5 was formed.

The Ni electrode film 16 is formed on the optical disk master.
Is formed by sputtering, and the surface of the Ni electrode film 16 is oxidized by oxygen plasma.
Is formed by electroforming, a stamper 18 is manufactured, and a recording medium 20 including a transparent dielectric layer, a recording layer, a transparent dielectric layer, and a reflective layer is formed on an optical disk substrate 19 manufactured by injection molding.
Were sequentially formed to form a protective coat layer made of an ultraviolet curable resin. The recording layer 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 a magneto-optical recording material, a phase change material, or the like can be used. An optical disk as shown in FIG. 21 was manufactured by the above steps.

(Embodiment 2) In the method for forming a fine pattern of an optical disk master described in the first embodiment, a fine pattern is formed by etching up to the substrate 7. It is also possible to form a pattern. Here, an embodiment in which a fine pattern is formed by etching the mask layer 12 will be described.

First, in the same manner as in Example 1, an Si mask layer 12, an Al metal film 13, and an AlN transparent film 14 are formed in this order, and laser cutting is performed.
A mixed layer 15 of 1 and Si is formed. Next, after the AlN transparent film 14 and the Al metal film 13 are sequentially removed, Al and Si are removed.
Dry etching is performed using the mixed layer 15 as a mask.
For dry etching, use a Cl ₂ etching gas (flow rate 15
0 sccm) and the gas pressure at the time of etching is 50
mTorr, and 400 W of high frequency power was applied. Under these etching conditions, in the mixed layer pattern 15, since Al was mixed with Si, the etching hardly proceeded, and only the Si mask layer 12 proceeded (FIG. 13).

Next, an Ar gas (flow rate 70 sccm) was introduced, a gas pressure was set to 10 mTorr, and a high-frequency power of 500 W was applied to remove the mixed layer pattern 15 by sputter etching. It was possible to form a fine pattern of the optical disk master having similar irregularities (FIG. 22).

In Embodiment 2 described above, in FIG. 13, the mixed layer pattern 15 was removed by sputter etching to obtain an optical disk master. However, even when the mixed layer pattern 15 remains, it can be used as an optical disk master. is there. However, it is desirable to perform sputter etching in order to reduce the noise of the optical disk. As a result of measuring the surface roughness in each state using an atomic force microscope, when the sputter etching was not performed, the surface roughness of the glass substrate 7 was 0.27 nm, and the surface roughness of the mixed layer pattern 15 was When sputter etching is performed, the surface roughness of the glass substrate 7 is 0.21 nm, and the surface roughness of the Si mask layer 12 where the mixed layer pattern 15 is removed is 0. .2
The thickness is 8 nm, so that the surface roughness of the optical disk master can be reduced, and the noise of the optical disk can be reduced.

(Embodiment 3) In the method of forming a fine pattern described in Embodiment 1, the case where Si is used as the mask layer 12 is described. However, a mask layer other than Si can be used. Here, an embodiment in which SiO ₂ is used as the mask layer 12 will be described.

First, in the same manner as in Example 1, a glass substrate
7, a mask layer 12 of SiO2 having a thickness of 40 nm
Then, the Al metal film 13 and the AlN transparent film 14 are
By forming and performing laser cutting, Al and
SiO_TwoIs formed. Next, the AlN transparent film
14 and the Al metal film 13 are sequentially removed, and then Al and Si are removed.
O _TwoDry etching using the mixed layer 15 of
U.

The dry etching was performed by introducing a CF4 etching gas (flow rate: 20 sccm), setting the gas pressure at the time of etching to 10 mTorr, and applying a high frequency power of 400 W. Under these etching conditions, since Al was mixed with SiO ₂ in the mixed layer pattern 15, the etching hardly proceeded, and only the SiO ₂ mask layer 12 proceeded (FIG. 13).

Next, an Ar gas (flow rate 70 sccm) was introduced, a gas pressure was set to 10 mTorr, a high frequency power of 500 W was applied, and the mixed layer pattern 15 was removed by sputter etching. It was possible to form a fine pattern of the optical disk master having similar irregularities (FIG. 22). Also, instead of SiO ₂ ,
Even if SiN is used as the mask layer 12, a fine pattern of the master optical disc can be formed.

(Embodiment 4) In the method for forming a fine pattern of a master optical disc described in Embodiments 1 to 3,
Although the case where Al is used as the metal film 13 is described, a metal other than Al may be used. For example, when Co is used, a master optical disc can be prepared by the following steps.

When Co is used as the metal film 13, the actual
Co and Si by laser cutting at the same time as Example 1
Was formed (FIG. 11).
Next, wet etching using sodium hydroxide solution
To remove the AlN transparent film 14 and rinse with pure water.
The sodium hydroxide solution was further removed, and (3HCl / H _Two
O_Two) The Co metal film 13 can be removed using an aqueous solution.
For example, similarly to the first embodiment, as shown in FIG.
The mixed layer 15 of i remained.

Next, using the mixed layer pattern 15 as a mask, the glass substrate 7 is placed in a dry etching apparatus,
The flow rate of the Cl ₂ etching gas was set to 150 sccm, the gas pressure at the time of etching was set to 50 mTorr, and high-frequency power of 400 W was applied to dry-etch the Si mask layer 12. Under these etching conditions, since the mixed layer pattern 15 contains Si mixed with Co, the etching hardly progresses, and the Si mask layer 1
Etching of only 2 proceeded (FIG. 13).

Further, the same manufacturing steps as in Example 1 (FIG. 1)
4, FIG. 15), a fine pattern of the master optical disc as shown in FIG. 15 could be formed.
Instead of Co, the same 3d transition metals Fe and N
Even if i is used, a fine pattern of the master optical disc can be formed by the same process.

(Embodiment 5) Metal film 13 in Embodiment 1
May be used as Pd. In this case, the mixed layer pattern 15 composed of Pd and Si is formed by laser cutting.
Is formed. Further, after removing the AlN transparent film 14 by wet etching using a sodium hydroxide solution, the sodium hydroxide solution is removed by pure water rinsing, and the Pd metal film 13 is removed by using a (KI / I ₂ ) aqueous solution. Is removed, a mixed layer 15 of Pd and Si remains as shown in FIG.

Next, if dry etching of the Si mask layer 12 is performed under the same conditions as those of the fourth embodiment, the mixed layer pattern 15 hardly progresses etching because Pd is mixed with Si. Etching of only the mask layer 12 proceeded (FIG. 13). Further, by performing the same manufacturing steps (FIGS. 14 and 15) as in Example 1, FIG.
The fine pattern of the master optical disc shown in FIG.

(Embodiment 6) Metal film 13 in Embodiment 1
May be used as Ti. In this case, the laser cutter
Layer pattern 15 composed of Ti and Si by
Is formed. In addition, using sodium hydroxide solution
The AlN transparent film 14 is removed by wet etching.
After that, remove the sodium hydroxide solution with pure water rinse
And (NH _FourOH / H_TwoO_Two) Ti metal using aqueous solution
If the film 13 is removed, as shown in FIG.
Thus, the mixed layer 15 of Ti and Si remained.

Next, if dry etching of the Si mask layer 12 is performed under the same conditions as in the fourth embodiment, the mixed layer pattern 15 hardly etches because Ti is mixed with Si, Etching of only the mask layer 12 proceeded (FIG. 13). Further, by performing the same manufacturing steps (FIGS. 14 and 15) as in Example 1, FIG.
The fine pattern of the master optical disc shown in FIG.

(Example 7) The fine pattern of the optical disc master manufactured according to the present invention has the concavo-convex shape reversed from that of the conventional optical disc master. The shape will be reversed. The seventh embodiment corrects the reversal. Hereinafter, correction of the inversion of the uneven shape will be described. Here, the stamper 18 formed after the peeling step shown in FIG. 19 is used.

First, the surface of the stamper 18 on which the guide tracks are formed is oxidized by oxygen plasma. Thereafter, a Ni electroformed film 17 'is formed on the guide track forming surface using the stamper 18 as an electrode. This Ni
The uneven surface of the electroformed film 17 'is obtained by reversing the unevenness of the Ni electroformed film 17 formed in FIG.

Next, the Ni electroformed film 17 ′ is
Then, if the back surface is polished, a work stamper 18 ′ in which the irregularities are reversed with respect to the stamper 18 is formed. When an optical disk substrate is manufactured by injection molding using the work stamper 18 ', the pre-pits and the guide grooves (= 150 nm) having the same concavo-convex structure as the conventional one and smaller than the light beam spot diameter (= about 300 nm). The optical disk substrate having the above can be manufactured.

According to the method for forming a fine pattern of the present invention, in addition to a land recording method or a groove recording method in which information is recorded only in a concave portion or a convex portion of a fine pattern, information is recorded in both a concave portion and a convex portion. Also in the land-groove recording method for recording, a substrate having a fine pattern having a width smaller than the diameter of the light beam spot can be manufactured.

[0067]

According to the present invention, a mask layer and a metal film are formed on a substrate in this order, and a light beam is condensed and radiated to a portion of the center of the light beam spot where the temperature is raised to a predetermined temperature or higher. In addition, since the mixed layer is formed at the interface between the mask layer and the metal film, it is possible to manufacture a substrate having a fine pattern including prepits and guide grooves smaller than the light beam spot diameter. Further, by using a substrate having such a fine pattern, an optical disk master, an optical disk stamper, an optical disk work stamper, and an optical disk having a narrow track pitch 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 of a metal film 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 transparent film and a metal film are removed in the present invention.

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

FIG. 14 is a cross-sectional view illustrating a state where a substrate surface in a region where a mixed layer is not formed is etched in the present invention.

FIG. 15 is a completed view of an optical disc master completed by the manufacturing process of the present invention.

FIG. 16 is a cross-sectional view illustrating a state where an electrode film is formed on the master optical disc of the present invention.

FIG. 17 is a cross-sectional view illustrating a state in which a Ni electroformed film is formed on the optical disk master of the present invention.

FIG. 18 is a cross-sectional view illustrating a state where a Ni electroformed film is peeled off from the optical disk master according to the present invention.

FIG. 19 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. 20 is a completed view of a molded optical disk substrate in the present invention.

FIG. 21 is a cross-sectional view illustrating a state where a recording medium is formed on an optical disk substrate in the present invention.

FIG. 22 is a cross-sectional view of the concavo-convex pattern in a state where the mixed layer is etched after the mask layer is etched 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 Mask layer 13 Metal film 14 Transparent film 15 Mixed layer 16 Electrode film 17 Ni electroformed film 18 Stamper 19 Resin optical disk substrate 20 Recording medium

Continued on the front page (72) Inventor Junji Hirokane 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka F-term (reference) 5D121 BB14 BB18 BB25 BB33 BB34 GG04 GG14

Claims (12)

[Claims] 1. A mask layer is formed on a substrate, a metal film is formed on the mask layer, and a light beam is condensed and radiated to a predetermined position from above the metal film to raise the temperature to a predetermined temperature or higher. At the interface between the raised mask layer and the metal film, a mixed layer in which the mask layer and the metal film are mixed is formed, and after selectively removing the metal film, the mask layer in a region without the mixed film is removed. A method for forming a fine pattern, characterized by selectively etching to leave the mixed layer. 2. The method for forming a fine pattern according to claim 1, wherein the substrate is selectively etched simultaneously with the etching of the mask layer or after the etching of the mask layer. 3. The method for forming a fine pattern according to claim 1, wherein the mixed layer is formed in a region smaller than a spot diameter of the light beam condensed and irradiated. 4. The method according to claim 1, wherein a transparent film is formed on the metal film after forming the metal layer and before condensing and irradiating the light beam. A method for forming a fine pattern. 5. The method for forming a fine pattern according to claim 4, wherein the metal film and the transparent film have an anti-reflection structure for a light beam condensed and irradiated. 6. The method according to claim 4, wherein the transparent film is made of AlN. 7. The method according to claim 7, wherein the mask layer is made of Si, SiN or Si.
O ₂ , wherein the metal film is made of Al, Co, Fe, Ni,
7. The method for forming a fine pattern according to claim 1, comprising Pd or Ti. 8. The method according to claim 1, wherein the remaining mixed layer is removed by sputter etching.
The method for forming a fine pattern according to any one of the above. 9. An optical disk master manufactured by using the method for forming a fine pattern according to claim 1. 10. An optical disk stamper manufactured by using the optical disk master according to claim 9. 11. An optical disk work stamper manufactured by forming an electroformed film using the optical disk stamper of claim 10 as an electrode and peeling the electroformed film from the optical disk stamper. 12. An optical disk manufactured by using the optical disk stamper according to claim 10 or the optical disk work stamper according to claim 11.