JPH06274944A - Fine pattern forming device - Google Patents

Abstract

PURPOSE:To make a forming pit and groove thin in width at the time of forming plural replicas from a master disk in which fine patterns modulated into, photosensitive materials by laser exposure are recorded. CONSTITUTION:A converged laser beam constituted of two preceding beam 4 and succeeding beam 5 whose positions are shifted back-and-front and right- and-left is used for an object to be exposed, the transmittance of a light fading layer 3 is increased by the preceding beam 4, and the part of a resist 2 at which the succeeding beam 5 and the preceding beam 4 are overlapped is irradiated to a resist photosensitive level by the beams 4 and 5. Then, the forming bit and groove can be made thin, and the plural replicas can be formed without depending on the wavelength of a using light source or the number of the openings of an objective lens.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine pattern forming apparatus using a laser beam for narrowing the line width in the formation of pits in a read-only ROM type optical disc or in the formation of tracking grooves in a recordable optical disc (hereinafter referred to as a master. It is called a writer).

[0002]

2. Description of the Related Art Due to the progress of information society, the amount of data handled by both organizations and individuals is increasing dramatically. Among them, as the optical disc, a read-only ROM medium or a recordable type such as a write-once type and a rewritable type has been developed and is being used in various fields. There is a growing demand for higher densities even in optical disks that are said to have a large capacity. Especially when image information is handled, it becomes a huge amount of data.
0MB (130mm write-once, rewritable disc for information),
One side 540MB (CD), one side 600MB (CD-RO
The optical disk described as M) has a shortage of capacity.

Therefore, it is required to increase the capacity per one side of the disk, but in order to achieve this, it is necessary to narrow the width of the pit or groove itself to be formed. Regarding the miniaturization of the pattern formed on such an optical disc, the method disclosed in Japanese Patent Laid-Open No. 1-098142 “Optical disc mastering device” is performed by using a light source with a wavelength shortened by using a non-linear optical element. , Patent Publication No. 1
-317241 "Optical disc mastering method" shows the problem of the photobleaching layer. As a process improvement method, the photoresist film surface is exposed to a developer before exposure to form a sparingly soluble layer on the surface of the pit. Is trying to miniaturize. The miniaturization only by the process makes it difficult to control the temperature and time involved in the exposure and development, but cannot cope with further miniaturization. Further, the method of shortening the wavelength by using a non-linear element has a problem that the optical system becomes complicated and adjustment is difficult.

Next, a conventional master writer will be described with reference to the drawings.

FIG. 4 is a block diagram of a conventional master writer, and FIG. 5 is a sectional view of a substrate showing an example of a method for forming a fine pattern using a photobleaching layer by the master writer of FIG.

In FIG. 4, in this master writer, an Ar gas laser 11 (λ: 457.9) which is a light source is used.
The laser light emitted from (nm) passes through the diaphragm 12, the automatic laser control 13, the diaphragm 14, the wave plate 15, and the polarization beam splitter 16b to split the beam into two systems. That is, the sub beam system passes through the E / O modulator 21b for power control, the diaphragm 22b, and the shutter 23'b,
The main beam system is connected to the beam splitter 24b and the λ / 4 plate 25 by the E / O modulator 17 for main beam modulation.
b, ND filter 18b, mirror 19b, diaphragm 22
b, shutter 23b, beam splitter 24b
Then, it is re-combined with the sub-beam system and expanded as collimated light by the collimator lens 26, and enters the optical head 28 having a condenser lens (objective lens) 28a through a shutter 27. The object to be exposed (resist, glass master with a photobleachable layer) on the spindle 31 is irradiated from the optical head 28, but the focus servo uses a He-Ne laser (wavelength: 633n) deviating from the photosensitive wavelength of the resist.
m) 30. The rear beam system (main beam system) and the preceding beam system (sub beam system) are arranged in parallel in the radial direction of the disk, which is the object to be exposed, without being in contact with each other.

In FIG. 5, a resist 2 and a photobleaching layer 3 are provided on a glass substrate 1 by a coating method centering on spin coating. This is modulated laser beam 5 '
The resist 2 is exposed through the photobleachable layer 3. A resist photosensitive region 33 is formed by transmitting a light amount necessary for resist exposure in the transmittance increasing region 32. After removal of the photobleachable layer 3, this is developed and dried to form pits and grooves. By using the photobleachable layer 3, the edges of the pits or grooves formed on the resist 2 are sharper than those without the photobleachable layer 3 and good modulation can be obtained. Since the width itself is determined by the wavelength of the light source and the numerical aperture of the objective lens used, there is a limit to making it narrow.

[0008]

If the optical disc produced by using the above-mentioned conventional master writer is used to increase its density, it will face some major technical problems. That is, increasing the recording density means writing more data in a unit area. If the conventional pit width and groove width are increased to increase the density, theoretically, the amount of data per unit area increases while the pit width or groove width is narrower than the track pitch, but higher density cannot be expected. . In fact, since the track error signal is drastically reduced, the characteristics of the disk cannot be secured even if the pit width and the groove width are smaller than the track pitch.

Basically, it is desired to miniaturize the beam diameter registered on the master writer used for exposure. Since the exposure beam diameter (wavelength λ / numerical aperture NA) may be reduced, NA may be increased or λ may be shortened. NA (NA ≦ 1) has already exceeded 0.9 in the current mastering, and the extent of improvement is
small. In addition, the depth of focus of the focus servo tends to become more severe. Therefore, it is desirable to reduce λ, but the current mastering light source is a single-mode laser that can continuously oscillate and can be sufficiently narrowed down. It is a laser that solves problems such as lifetime, stability, and noise. As a result, λ cannot help but use the near-ultraviolet region. It is difficult to use light with a wavelength in the near-ultraviolet region as well because it is used in the air with a large NA, and when it goes out of the visible region, the beam itself cannot be seen, which causes trouble in adjusting the optical system.

Further, the shortening of the wavelength of the light source is naturally limited because it is not a means for advancing infinitely.

[0011]

An object of the present invention is to form finer pits or grooves using the existing optical system.

Therefore, the master writer of the present invention is
Uses two focused laser beams that are displaced to the front, back, left, and right with respect to the traveling direction, and the preceding beam raises the transmittance of the photobleaching layer, and the portion overlapping the preceding beam of the rear beam is irradiated to the resist exposure level. It is characterized by doing. Further, in the master writer of the present invention, when writing is performed on the rotating substrate, the preceding beam is installed at a position closer to the inner circumference side than the backward beam, and only the portion where the preceding beam and the backward beam overlap by continuous irradiation is continuous. Grooves or continuous protrusions. Further, it is characterized in that fine concave pits or convex pits are formed by continuous irradiation of one of the preceding beam and the rear beam and pulse irradiation of the other.

Further, the continuous groove and the concave pit shown here are exposed by forming a photobleaching layer on the positive resist, and the continuous protrusion and the convex pit are formed by forming the photobleaching layer on the negative resist. It is characterized by forming.

The photobleaching layer provided on the resist is made of a nitrone compound material and is set to have an optical density and a film thickness such that the initial transmittance is 10% or less. A water-soluble diffusion-preventing layer containing polyvinyl alcohol as a main material is provided between the resist and the photobleaching layer. After exposure, the layer is removed with pure water or a dedicated solvent and then developed.

[0015]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of a master writer according to the present invention, and FIG. 2 is a sectional view of a substrate showing an example of a method for forming a fine pattern using a photobleachable layer by the master writer of FIG. .

In FIG. 1, the operation of the master writer of this embodiment is almost the same as the operation of the conventional master writer, and the diagram for explaining the operation is the same as that of FIG. Ar gas laser 11 (λ: 457.
The laser light emitted from (9 nm) passes through the diaphragm 12, the automatic laser control 13, the diaphragm 14, the wave plate 15, and the polarization beam splitter 16a to split the beam into two systems.
That is, the sub-beam system goes through the E / O modulator 21a for power control, the diaphragm 22a, and the shutter 23'a to the beam splitter 24a and the λ / 4 plate 25, and the main beam system is the E / O modulator for main beam modulation. 17a, ND filter 18a, mirror 19a, diaphragm 2
2a, shutter 23a, beam splitter 24
The collimator lens 26 is recombined with the sub-beam system at a.
The parallel light magnified in (1) is passed through the shutter 27 and is incident on the optical head 28 having a condenser lens (objective lens) 28a. The exposed object (resist,
The optical head 28 irradiates the glass master with a photobleachable layer, but the focus servo is a He-Ne laser (wavelength: 633) deviating from the photosensitive wavelength of the resist.
nm) 30.

A major difference from the conventional example is that the leading beam and the trailing beam are arranged so as to form adjacent focal points on the object to be exposed to form an overlapping portion.

In FIG. 2, a substrate 1 is a substrate having a reduced surface roughness used for mastering exposure, glass is used here, and a photoresist 2 is applied onto the substrate 1 mainly by a spin coating method. It is formed by the method. The pit depth needs to be determined by the light source and the tracking method, but since the resist film thickness directly controls it, it is necessary to manage it sufficiently. Both positive and negative resists can be used, but a novolak-based negative resist is easy to use. The photobleachable layer 3 is provided on the resist 2 by a coating method centered on the spin coating method. The photobleachable layer 3 has a transmittance that varies depending on the wavelength of the light source used, but basically the transmittance is low in the unexposed portion, and the transmittance rapidly increases after exposure. Further, in the process of increasing the transmittance, the transmittance changes depending on the irradiation amount. The photobleachable layer 3 is made of a nitrone compound material and is set to have an optical density and a film thickness such that the initial transmittance is 10% or less. A water-soluble diffusion-preventing layer containing polyvinyl alcohol as a main material is provided between the resist and the photobleaching layer. After exposure, the layer is removed with pure water or a dedicated solvent and then developed.

On such an object to be exposed, the preceding beam 4 is first irradiated onto the photobleaching layer 3 to form a fading region 6 due to the preceding beam. On the other hand, the rear beam 5 forms a fading area 7. The overlapping portion 8 of the fading area 6 due to the preceding beam and the fading area 7 due to the rear beam has undergone photobleaching more than the areas 6 and 7 which are irradiated only once by beam irradiation twice. Therefore, the resist exposure region 9 is formed by adjusting the irradiation power. Since this is an overlapping region of the front beam and the rear beam, it is theoretically possible to form infinitely narrow grooves or pits.

FIG. 3 is a diagram for conceptually explaining the exposure power and the resist exposure region in FIG. 2, and FIG. 3A is a graph showing the relationship between the transmittance required for resist exposure and the photobleaching performance transmittance. 3 (b) is a front view of the substrate showing the exposure power and resist exposure area of FIG.

In FIG. 2A, the preceding beam intensity 4'is lower than the transmittance intensity 10 required for resist exposure. On the other hand, the rear beam intensity 5'is also the same, but in the overlapping region, it becomes higher than the transmittance intensity required for resist exposure. Therefore, in FIG. 2B, a trace 9 ′ is formed in the overlapping region of the preceding beam trace 4 ″ and the backward beam trace 5 ″. After exposure using these master writers, the photobleachable layer 3 is removed, and after a development and drying process, pits or grooves are formed in the overlapping region.

[0023]

As described above, in the master writer according to the present invention, the resist exposure is performed by controlling the photobleaching layer transmittance in the region where the preceding beam and the backward beam are superposed, and the conventional optical Even if the system is used, it is possible to form infinitely thin pits and grooves without being influenced by the numerical aperture and the wavelength of the light source used.

Further, in the master writer of the present invention, the pit edge formed is basically sharp due to the use of the photobleaching layer, and even after forming very fine pits and grooves, subsequent stamper formation and injection. It is possible to reduce transfer defects during molding.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a master writer according to the present invention.

FIG. 2 is a cross-sectional view of a substrate showing an example of a method of forming a fine pattern using a photobleachable layer by the master writer of FIG.

FIG. 3 is a diagram for conceptually explaining the exposure power and the resist exposure area of FIG. FIG. 3A is a graph showing the relationship between the transmittance required for resist exposure and the light fading performance transmittance. FIG. 3B is a front view of the substrate showing the exposure power and the resist exposure area of FIG.

FIG. 4 is a configuration diagram of a conventional master writer.

5 is a sectional view of a substrate showing an example of a method for forming a fine pattern using a photobleaching layer by the master writer of FIG.

[Explanation of symbols]

1 substrate 2 resist 3 photobleaching layer 4 preceding beam 4'photobleaching transmittance due to preceding beam 4 "transmissivity change area due to preceding beam 5 back beam 5 'photobleaching transmittance due to rear beam 5" transmittance change due to rear beam Area 6 Fading area due to preceding beam 7 Fading area due to rear beam 8 Area where fading is advanced due to overlap of preceding and backward beams 9 Resist photosensitive area 9 ′ Resist sensitive area due to overlap of preceding and posterior beams 10 Transmissivity change area 10 Resist Transmittance required for photosensitization 11 Ar gas laser 12 Aperture 13 Auto laser control 14 Aperture 15 Wave plate 16a, 16b Polarizing beam splitter 17a, 17b E / O modulator 18a, 18b ND filter 19a, 19b Mirror 20a, 20b Aperture 21a, 21b E / O module 22a, 22b diaphragm 23a, 23b shutter 23'a, 23'b shutter 24a, 24b beam splitter 25 λ / 4 plate 26 collimator lens 27 shutter 28 optical head 28a condenser lens (objective lens) 29 mirror 30 He- Ne laser 31 Spindle 32 Transmittance increasing area 33 Resist photosensitive area

Claims (5)

[Claims] 1. A front beam and a rear beam which are positioned rearward and rearward with respect to an object to be exposed and which are rearward.
And a means for directly writing on the resist by irradiating the focused laser beam and the preceding beam to increase the transmittance of the photobleaching layer, and irradiating the overlapping portion of the preceding beam and the backward beam to the resist photosensitive level. , A means for irradiating the overlapping portions on the resist to the resist exposure level with these beams to draw directly on the resist. 2. When recording from the inner periphery in a spiral shape on a rotating substrate forming a fine pattern from the inner periphery, the preceding beam is positioned on the inner periphery side of the rear beam when drawing is performed on the rotating substrate. The fine pattern forming apparatus according to claim 1, wherein 3. The continuous groove or the continuous protrusion is formed only in a portion where the preceding beam and the rear beam overlap each other by continuous irradiation.
The fine pattern forming apparatus described. 4. A fine concave pit or a convex pit is formed by performing continuous irradiation on one of the preceding beam and the rear beam and performing pulse irradiation on the other one of them. Alternatively, the fine pattern forming apparatus according to claim 3. 5. The continuous groove and the concave pit are exposed by forming a photobleaching layer on the positive resist, and the continuous protrusion and the convex pit are formed by forming the photobleaching layer on the negative resist. The fine pattern forming apparatus according to claim 3 or 4, which is characterized in that.