JPH11149670A - Exposing method, and exposing device, master disk and optical disk using the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exposing method capable of increasing capacity of an optical recording medium and increasing recording density without shortening a recording light wavelength and increasing NA (opening coefficient) of an object lens and to provide an exposing device, a master disk and an optical disk using the method. SOLUTION: A deflection section 15 deflecting luminous flux emitted from a light source 12 for recording using a light deflection element such as AOD, EOD, and the like is arranged between a modulation section 14 and a beam expander section 16, while a recording signal supply section 18 generating a modulation signal supplied to the modulation section 14 and a scanning signal supplied to the deflection section 15 is arranged, supplies a modulation signal to the modulation section 14, while supplies a scanning signal synchronizing with the modulation signal to the deflection section 15, and an exposure pattern is formed on a photo-resist film 9 scanning an exposure spot in the tangential direction of an optical original disk 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method, an exposure apparatus using the same, and a master and an optical disk.
More specifically, a photoresist film formed on a master such as an optical disk master is exposed by irradiating an exposure spot with an exposure spot,
The present invention relates to an exposure method for forming pits or grooves, an exposure apparatus using the same, an original master and an optical disk.

[0002]

2. Description of the Related Art An optical disk, which is an example of an optical recording medium,
As shown in a schematic perspective view of FIG. 6, a signal recording area 3 is formed on at least one surface of a disk substrate 2 made of optically transparent plastic or the like. FIG. 7 is an enlarged schematic view of the signal recording area 3 in FIG. 6 in the signal recording area 3 of a ROM (Read Only Memory) type optical disc 1 typified by a CD (product name, Compact Disc). a) or a RAM (Random Ac) represented by a phase-change disk or a magneto-optical disk.
A groove 6 as shown in FIG. 7 (b), which is a similar schematic enlarged view, is formed in a signal recording area 3 of the optical disc 1 of a (Memory) type in a spiral shape at a predetermined track pitch of, for example, 1 to 2 μm. Have been.

In the ROM type optical disk 1 in which the pits 5 are formed, data is constituted by a plurality of pits 5 formed in the tangential direction of the signal recording area 3, and the pits 5 can be used as a tracking diffraction grating. Used. Then, a light reflecting layer (not shown) is formed on the surface of the signal recording area 3 where the pits 5 are formed. In the RAM type optical disc 1 in which the groove 6 is formed, data is recorded on one of the concavities and convexities in the signal recording area 3, for example, the land 7 which is the convex side in FIG. 7B, and the groove 6 which is the other concave side. Is generally used for tracking. Although not shown, a phase change film or a magnetic film is formed on the surface of the signal recording area 3 where the groove 6 and the land 7 are formed. A light reflection layer is further formed on the film. Also, a ROM area and a RAM are stored in the RAM type optical disc 1 and the signal recording area 3.
Also in the partial ROM type optical disk 1 sharing a region, data such as disk-specific information and addresses are generally formed by pits 5 in advance.

Although not shown, these optical discs 1 emit a light beam emitted from a light source such as a semiconductor laser constituting an optical pickup device and condensed using an objective lens from the reading surface 4 side, thereby obtaining a RAM type optical disk. In the case of the optical disc 1, for example, a signal is recorded on the land 7 or a signal recorded on the land 7 is read. Tracking in this case is performed by detecting reflected light diffracted by the groove 6. Further, in the case of the ROM type optical disk 1, similarly, a light beam emitted from a light source and condensed by using an objective lens is irradiated from the reading surface 4 side, reflected light diffracted by the pits 5 is detected, and a signal Readout and tracking are performed. As described above, since the shape and dimensional accuracy of the pits 5 and the grooves 6 formed in the signal recording area 3 of the optical disk 1 affect the performance of the optical disk 1, high-precision formation is required.

FIG. 9 is a schematic process explanatory view following FIGS. 8 (a) to 8 (c) and FIG. 8 (c), which are schematic process explanatory drawings, in the order of processes from the production of the optical disc master to the production of the optical disc 1. This will be described with reference to (a) to (c). FIG. 9A is a schematic enlarged perspective view in which the groove 6 and the land 7 formed on the optical disk master 8 are enlarged, and FIG. 9B is the groove 6 and the land 7 formed on the optical disk master 8. FIG. 9 is a schematic sectional view of a portion of FIG.
(C) is the disk substrate 2 transferred from the optical disk master 8
FIG.

First, as shown in FIG. 8A, after the surface of an optical disk master 8 is polished sufficiently flat, it is sufficiently cleaned.

[0008] Next, as shown in FIG. 8 (b), a photoresist film 9 that changes to alkali-soluble by, for example, exposure processing is applied to the optical disk master 8 to a thickness of about 0.1 μm. Generally, this coating step is performed by a spin coating method.

Next, as shown in FIG. 8C, a photoresist film 9 is exposed by irradiating a focused exposure spot with an objective lens 17 constituting an exposure optical system of an exposure apparatus to be described later. . At this time, by moving the exposure spot in the radial direction at a predetermined track pitch per rotation while rotating the optical disk master 8, FIG.
As shown in (c), the latent image 10 of the spiral groove 6 on the photoresist film 9 or the latent image 10 of the pit 5 on the photoresist film 9 by intermittently irradiating the exposure spot at this time. Form.

Next, by developing the latent image 10 formed on the photoresist film 9 with, for example, an alkaline developing solution to remove the exposed portion, that is, the photosensitive portion of the photoresist film 9, a ROM type optical disk can be obtained. Optical disc master 8 for 1
As shown in FIG. 9A, a groove 6 and a land 7 which are continuous grooves are formed on a photoresist film 9 in the radial direction on the optical disk master 8 for the RAM type optical disk 1. Are formed alternately.

[0010] Next, as shown in FIG. 9 (b), a nickel plating or the like is applied to the master optical disc 8 on which the grooves 6 and the lands 7 or the pits 5 are formed on the photoresist film 9 by the development processing to form a stamper. The precursor 11a is formed. Then, by removing the stamper precursor 11a, the stamper 11 in which the groove 6 and the land 7 or the pit 5 of the photoresist film 9 are transferred is produced.

Next, as shown in FIG. 9 (c), the concave and convex shape of the stamper 11 is transferred to a plastic material as a substrate material of the optical disk 1 by injection molding or the like, and the groove 6 is formed.
Then, the disk substrate 2 as a replica on which the lands 7 are formed is manufactured. Then, after manufacturing the disk substrate 2,
If a recording film, a reflective film and a protective film are formed on the uneven surface on which the grooves 6 and the lands 7 are formed or on the surface on which the pits 5 are formed, that is, on the surface of the signal recording area 3, The manufacture of the optical disc 1 as a recording medium is completed.

FIG. 10 is a schematic diagram showing the configuration of an exposure apparatus and an exposure optical system for forming the latent image 10 of the groove 6 and the lands 7 or the pits 5 on the optical disk master 8 described above. Reference numeral 12 denotes a recording light source such as a Kr ion laser having a wavelength of 413 nm. Reference numeral 13 removes the instability of the output of the light flux emitted from the recording light source 12 and controls the final recording light intensity. And a recording light intensity control unit composed of an EO (electro-optic crystal element) or the like. Reference numeral 14 denotes a modulation unit having modulation means for forming a pit having a length corresponding to the modulation signal. The modulator constituting the modulation unit 14 is required to have a performance capable of being used in a band of several tens of MHz. Specifically, EOM (electro-optic crystal element modulator) or AOM (acousto-optic crystal element modulator) is used. Reference numeral 16 denotes a beam expander unit having an optical system for expanding the diameter of a recording light beam, and the beam expander unit 1
The diameter of the exposure spot condensed on the photoresist film 9 of the optical disk master 8 using the objective lens 17 is controlled by the enlargement ratio in 6. With such a configuration, if the exposure spot is moved at a predetermined track pitch per rotation in the radial direction while rotating the optical disk master 8 at a predetermined rotation speed, the latent image 10 of the groove 6 or the latent image 10 of the pit 5 is formed. It can be formed in a spiral at a predetermined track pitch.

In recent years, a DVD (trade name, Digital Vers) having a recording density about five times that of a conventional CD has been developed.
atile Disc) etc. are commercialized, and the optical disc 1
In the field, there is a tendency for higher density recording. For this reason,
There is a need for an exposure technique that enables the formation of smaller grooves 6 and pits 5 by means such as reducing the exposure spot diameter. The exposure spot diameter φ is a diffraction limit (φ = 1 .1) from the recording light wavelength λ and the numerical aperture NA of the objective lens 17.
22 × (λ / NA)). Therefore, in order to make the exposure spot diameter φ smaller, the objective lens 1
7, a large numerical aperture NA, a small recording light wavelength λ,
Alternatively, it is necessary to increase the numerical aperture NA of the objective lens 17 and decrease the recording light wavelength λ.

However, the numerical aperture NA of the objective lens 17 used in the exposure apparatus is generally in the range of 0.9 to 0.95 which is almost equal to 1 which is the theoretical maximum value of the numerical aperture NA. in use. As for the recording light wavelength λ, the use of ultraviolet light having a wavelength of about 350 nm has begun to be put into practical use. However, when a wavelength of 200 nm, which is a shorter wavelength, is to be used, the conventional process such as the photoresist film 9 is required. However, there are problems such as the necessity of a significant change, difficulty in securing optical components corresponding to this wavelength, and adverse effects on the human body in this wavelength range. For the above reasons, it is currently difficult to obtain a smaller-diameter exposure spot, and means for forming a smaller-diameter exposure spot other than the above-described means are required. Even if it is possible to form an exposure spot with a smaller diameter than the current one, it is presumed that a technique for obtaining the maximum recording density within a possible range by using the spot is naturally required.

By the way, when the recording density is considered separately in the tangential direction and the radial direction, there is room for improvement in the tangential direction even in the conventional exposure method, in order to further increase the recording density. That is, in the ROM type optical disc 1 such as a CD or a DVD, the ratio between the track pitch and the shortest pit period (shortest pit length × 2) is approximately 1: 1.
It is assumed that this ratio will not change significantly in the future (CD: track pitch 1.6 μm, shortest pit period 1.67 μm, DVD: track pitch 0.74 μm, shortest pit period 0.80 μm) . Therefore, if the recording density is increased while keeping this ratio at 1: 1, for example, in the step of exposing and developing the latent image 10 of the pits 5, the period of the pits 5 that can be separated and formed is generally in the radial direction. As compared with the tangential direction, the pits 5 are larger in the tangential direction than in the radial direction.

The reason why the formation of the pits 5 in the tangential direction is first difficult will be described with reference to FIGS. 11 (a) to 11 (c) which are schematic state diagrams of condensed spots applied to the photoresist film 9. FIG. This will be described in further detail.
A modulation signal voltage level is "1", a time exposure spot on the photoresist film 9 is irradiated with the t, if a tangential direction of the relative velocity of the exposure spot and V _t, the moving distance L of the exposure spot It will be L = V _t × _t. A V _r = 0 When V _r in the radial direction of the relative velocity of the exposure spot for this. Although the planar shape of the exposure spot irradiated on the photoresist film 9 of the optical disk master 8 is substantially circular, it is considered that the actual shape of the exposure spot extends by the moving distance L of the exposure spot. Accordingly, with respect to the separation and formation of the pits 5 with a shorter period, the tangential direction is disadvantageous by the moving distance L of the exposure spot. For example, the recording light wavelength λ
= 351 nm, NA = 0.90 for the objective lens 17 and a commercially available i-line photoresist film 9 (film thickness d =
In the case of exposing about 100 nm), in the radial direction, a groove 6 could be formed completely separated from an adjacent track up to a track pitch of 0.30 μm, but in the tangential direction, the shortest pit 5 could be formed. The period was up to 0.36 μm (the moving distance L of the exposure spot at this time was 0.18 μm).

This means that if the recording method of the pits 5 is improved, it is possible to record in the tangential direction at the same cycle of the pits 5 as in the radial direction. Specifically, it can be realized by a as small as possible a movement distance L of the exposure spot, when V _t is constant from the moving distance L = V _t × t of the exposure spots above the photoresist film 9 The time t during which the exposure spot is irradiated may be made shorter. Here pit 5
The period of the P _l, the time length of the modulation signal corresponding to this set to t _0, pulses photoresist film 9 to the exposure spot is represented by the ratio t / t ₀ the time t and t ₀ being irradiated If the duty is D (D = t / t ₀ ), the cycle is P _l
In the exposure of the pit 5, the pulse duty D of the recording signal is made as close to 0 as possible,
The period P _l can be the minimum of.

However, if the moving distance L of the exposure spot is reduced without changing the intensity of the recording light, there is a problem that it is difficult to secure the size (width, length) of the pit 5. In other words, the intensity distribution of the luminous flux of the exposure spot has a uniform diameter φ.
11 (a) to 11 (c) assuming that the circle has
Indicated in orthogonal coordinates consisting of xy axis as, in response to the travel distance L of the exposure spot the center point of the exposure spot S ₀ to (((-L / 2), 0) from (L / 2 ,
Suppose that the pit 5 is formed by moving along the x-axis to 0). At this time, the origin of the coordinates is the center of the pit 5,
The exposure amount (integrated exposure amount) Q at this point is proportional to the passing distance of the exposure spot, and is shown in FIGS. 11 (a) and 11 (b).
The moving distance L of the exposure spot shown in FIG.
In the state (1), the exposure amount (integrated exposure amount) Q does not change with respect to the change in the movement distance L of the exposure spot, and remains constant, and the movement distance L of the exposure spot shown in FIG.
<In the state of the exposure spot diameter φ, the movement distance L of the exposure spot becomes large and the exposure amount (integrated exposure amount)
Q also has a large proportional relationship. FIG. 12 shows this in a graph. The exposure amount Q in a state where the exposure spot moving distance L <the exposure spot diameter φ is smaller in proportion to the smaller the exposure spot moving distance L. I understand. Incidentally, the actual exposure spot has a Gaussian distribution in which the intensity decreases from the center of the light beam toward the periphery, and as shown in FIG. 13, the pits 5 are formed with a movement distance L smaller than the exposure spot diameter φ. Exposure amount Q
As a result, it may be difficult to form a pit 5 having a sufficient size, or it may be difficult to develop the latent image 10 of the pit 5 formed in the photoresist film 9. From such a pit 5, the amplitude of the reproduced signal cannot be sufficiently obtained, which leads to an increase in the error rate.

As means for solving the above-mentioned problem using the prior art, for a pit 5 whose length in the tangential direction is small, the insufficient exposure amount Q is changed in accordance with the length of the pit 5. It is conceivable to achieve optimization by doing so. That is, this is a method of optimizing the recording light intensity at the modulation signal voltage level. This will be described with reference to FIG. For example, when a random pit pattern is formed on the photoresist film 9 of the optical disk master 8, a modulation signal is supplied to the modulator of the modulation unit 14 in the exposure apparatus of the example shown in FIG. 10 and recording using, for example, EO What is necessary is just to supply a light intensity control signal synchronized with the modulation signal to the light intensity control unit 13 so that a desired exposure intensity is obtained for each pit 5. Alternatively, when EOM or AOM is used for the modulator of the modulation section 14, a similar result can be obtained by changing the modulation signal voltage level "1" for each pit 5.

However, in the above-described means, the smaller the moving distance L of the exposure spot, the higher the recording light intensity of the exposure spot must be. For example, when the moving distance L of the exposure spot is 0, the necessary recording light intensity of the exposure spot becomes infinite, which is difficult to realize with the current recording light source 12 having a limited output.
The limit for reducing the moving distance L of the exposure spot is limited to the output value of the recording light source 12. Therefore, considering the output of the recording light source 12 used in the current exposure apparatus, the light amount loss of the exposure optical system, the sensitivity of the material of the photoresist film 9, the durability of the optical elements constituting the exposure optical system, etc. It is difficult to make the moving distance L of the exposure spot smaller by the means described above.

In order to reduce the required maximum intensity of the recording light of the exposure spot, a method of reducing the relative speed of the exposure spot in the tangential direction can be considered. The relationship between the recording light intensity I and the tangential direction of the relative velocity of the exposure spot, the tangential direction of the relative velocity of the exposure spot was V _t as a parameter, FIG. 15
FIG. 15B shows a case where the relationship is as shown in FIG. 15A (recording light intensity I = constant) and the recording light intensity linear density is _Iv .
(Recording light intensity I∝relative velocity in the tangential direction of the exposure spot V _t (I _v (n) = I _n )
/ V, n = 1, 2, 3 I _v (1) <I _v (2) <I _v
(3)) for the case in perform exposure and development of the groove 6, as a result of a tangential direction of the relative velocity of the exposure spots were compared width W of the groove 6 relative to V _t, 1
As shown in FIG. 5A, when the recording light intensity I is constant, the relative velocity V of the exposure spot in the tangential direction is obtained.
_t is is the width of the groove 6 with becomes large is small, as shown in FIG. 15 (b), if the relationship of the recording light intensity Iα exposure spot in the tangential direction of the relative velocity V _t is the groove width W of 6 is not changed with respect to the tangential direction of the relative velocity V _t of the exposure spot, I _V = I _n
The greater the value of / V, the greater the width W of the groove 6.
Therefore, the indicative of the actual recording light intensity I is a value based on the recording light intensity I in the tangential direction of the relative velocity V _t of the exposure spot, as it were recorded light intensity line density I _V
It can be seen that it is.

If the moving distance L of the exposure spot is L = 0, it is necessary to make the recording light intensity linear density _IV almost infinite.
Therefore it may be zero relative speed V _t of the tangential direction of the exposure spots instead of the recording light intensity I infinite in. However, this has the following disadvantages. 1. Even when the pits 5 are formed by simply exposing only the pits 5 of a single length, the rotation speed of the turntable for driving the optical disk master 8 (usually 150 rpm to 200 rpm) capable of guaranteeing accuracy in an actual exposure apparatus. since there is a lower limit to the minimum value in the tangential direction of the relative velocity V _t of the exposure spot it is difficult to be zero.
2. In the case of forming a random pit pattern, but must be small tangential direction of the relative velocity V _t of the exposure spot only when the length of the tangential direction to form a pit 5 is small, this number Hundred rp
The maximum number of rotations of the optical disk master 8 rotating at m is a few MHz.
And it is difficult to realize.

As described above, in the current exposure technology, the recording light intensity linear density _IV is limited to a finite value. Therefore, the moving distance L of the exposure spot is small enough to contribute to the improvement of the recording density in the tangential direction. It is more difficult to set the moving distance L of the exposure spot to L = 0.

[0024]

The recording density can be reduced without using a means for shortening the recording light wavelength and increasing the objective lens NA, or using a means for increasing the recording lens wavelength and increasing the objective lens NA. An object of the present invention is to provide an exposure method for increasing the capacity of an optical recording medium, an exposure apparatus using the same, and a master and an optical disk.

[0025]

In order to solve the above-mentioned problems, according to the exposure method of the present invention, a light beam emitted from a recording light source is modulated based on a modulation signal supplied to a modulation means, and the modulated light beam is modulated. The light beam is deflected by a deflecting device using an optical deflecting element such as an AOD or an EOD, and the deflected light beam is condensed using an objective lens to form an exposure spot. In an exposure method of irradiating a resist film to form an exposure pattern based on a modulation signal, while supplying a scanning signal for scanning the exposure spot in substantially the same direction as the rotation direction of the master in synchronization with the modulation signal to the deflecting means, An exposure pattern is formed on the photoresist film. Further, the present invention is characterized by a master manufactured by this exposure method and an optical disk manufactured by using the master.

In the exposure apparatus of the present invention, at least a recording light source, a modulating means for modulating a light beam emitted from the recording light source, and a light beam modulated by the modulating means are converted by using an optical deflection element such as an AOD or an EOD. Deflecting means for deflecting the light, the light beam deflected by the deflecting means is condensed using an objective lens to form an exposure spot, and the condensed spot is irradiated on a photoresist film formed on the master. In an exposure apparatus that forms an exposure pattern, a recording signal that supplies a modulation signal supplied to a modulation unit and a scanning signal that scans an exposure spot in substantially the same direction as the rotation of the master in synchronization with the modulation signal to the deflection unit. It has a supply means, and forms an exposure pattern smaller than the diameter of the exposure spot on the photoresist film. Further, the present invention is characterized by a master produced by the exposure apparatus and an optical disc produced by using the master.

According to the above-described means, effective recording can be performed without manipulating the modulation signal for modulating the light beam emitted from the recording light source and without controlling the moving speed of the exposure spot by the exposure device. Since the signal pulse can be set to almost 0, pits smaller in diameter than the exposure spot diameter can be formed, and the recording light intensity linear density increases in inverse proportion to the recording signal pulse length. The amount is automatically compensated, and it is possible to provide an exposure method and an exposure apparatus capable of obtaining a sufficient reproduction signal amplitude from the formed pit. Therefore, by using the exposure method and the exposure apparatus, it is possible to provide a master such as an optical disk master corresponding to high density, and further, to use this master, it is possible to provide an optical disk corresponding to high density.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An exposure method and an exposure apparatus using the same according to the present invention provide a tangential exposure spot between a modulator and a beam expander constituting an exposure apparatus using an objective lens. A deflection unit composed of an optical deflecting element such as an AOD or an EOD for scanning in the medial direction is provided, and a recording signal supply unit for supplying a modulation signal to the modulation unit and a scanning signal to the deflection unit is provided to be supplied to the deflection unit. The exposure spot is scanned in the tangential direction by a scanning signal. This scanning direction can be easily performed by adjusting an installation angle in a plane perpendicular to the optical axis of an optical deflection element such as an AOD or an EOD. Hereinafter, an embodiment of the present invention will be described with reference to FIGS. Note that components in the figure that have the same structure as the conventional technology are denoted by the same reference numerals.

FIG. 1 is a schematic explanatory view for explaining that a pit having a smaller diameter than the exposure spot diameter can be formed by reducing the relative speed of the exposure spot in the tangential direction, and FIG. FIG. 1B is a schematic explanatory view showing a state in which the photoresist film 9 of the master 8 is exposed by irradiating a condensing exposure spot by using an objective lens 17 constituting an exposure optical system, and FIG. The method is shown in FIG.
(C) shows the exposure method of the present invention. In the conventional exposure method and apparatus, the relative speed V _t of the tangential direction in the photoresist film 9 of exposure spots they were given only the linear velocity V _g generated by the rotation of the optical disc master 8. Therefore, as shown in FIG. 1B, in the conventional exposure method and the conventional exposure apparatus, the exposure in the tangential direction of the pits formed by exposure during the time t (from Point A to Point B) during which the exposure spot is irradiated is performed. The distance L is L = V _g × t. In contrast, in the present invention, as shown in FIG. 1 ((c), the speed of the line of the exposure spot is scanned in the tangential direction to the linear velocity V _g in the same direction caused by the rotation of the optical disc master 8 Speed V _s
Because it gives a relative speed V _t of the tangential direction in the photoresist film 9 exposed spot V _t = V _g
The -V _s. Therefore, the exposure time t (Point A from Point A to Point B before Point B) is irradiated.
Exposure distance L in the tangential direction of the pits formed by exposure to C) is L = (V _g −V _s ) × t. That is, by controlling the scanning amplitude of the exposure spot in the tangential direction, it is possible to form a pit smaller in diameter than the exposure spot diameter φ. And
If V _g = V _s , V _t = 0, and it is possible to form a pit whose length in the tangential direction is extremely small.

Hereinafter, in the procedure for forming a pit having a very small length in the tangential direction, the period of the recording signal in the exposure of a single periodic pit is represented by T ₀ ,
FIG. 2 is a diagram schematically illustrating a case where the time of the modulation signal voltage level “1” is T, and the position of the exposure spot on the objective lens 17 before the modulation signal voltage level is “1” is the initial position (Point A). This will be described with reference to (a) to (d).

First, as shown in FIGS. 2A and 2B, the light beam emitted from the recording light source at the time of the modulation signal voltage level "1" is focused by using the objective lens 17 on the exposure spot. , it is scanned between (from t ₁ t ₂₎ the time T in the optical disc master velocity V _g in the same direction as the tangential direction in the exposure spot velocity V _s of. The length of the latent image of the pit formed by this is: the exposure distance L in the tangential direction from Point A to Point C = (V _g −V _s ) ×
It becomes T.

Next, as shown in FIGS. 2C to 2D, the modulation signal voltage level at which light emission from the recording light source is stopped (modulation signal voltage level "0") is "0". utilizing certain time (t ₂ from t _3), the exposure spot apparent, scanned at the master optical disk velocity V _g and reverse the tangential direction to the exposure spot velocity V _s, the objective lens 1
7 is returned to the position where the exposure spot becomes the initial position (Point B). Then, by repeating the procedures of FIGS. 2A to 2D, pits having a very small length in the tangential direction, such as pits having a smaller diameter than the exposure spot diameter φ, can be formed.

The method of the above case can be applied to the formation of a random pit pattern because the amount of exposure is insufficient to form a sufficient pit size, and the exposure spot diameter φ
In this case, a pit is formed at an exposure spot moving distance L smaller than the pit. At present, a digital signal is generally used as a modulation signal used for recording on the optical disk 1, and the pit length (modulation signal pulse width) of the modulation signal pattern is limited to a finite number. For example, in a signal called EFM + used for DVD, 3T, 4T, 5
.., 14T (1T represents a reference clock length). Of these, the pit length to be subjected to recording compensation is at most one or two from the smallest one, so the exposure method in the above case may be applied to only one or two of these. Since the pit length is known in advance for these one or two signals, it is easy to obtain an appropriate compensation amount (scanning speed V _{s of the} exposure spot) from several trials. As a result, pits that were difficult to form in a sufficient size with the conventional exposure method and the exposure apparatus using the pits have been replaced with pits having a substantially ideal size in which a sufficient reproduction signal amplitude can be obtained even in a random pit pattern. Can be formed. Further, it is possible to form a pit having a small cycle in the tangential direction, which has conventionally been difficult to separate and form. From the above, the present invention is not limited to the mastering of the ROM and RAM type optical disk masters, but can be applied to the recording of data in the RAM type such as a magneto-optical disk and a phase change optical disk.

An embodiment to which the present invention is applied will be described below with reference to FIGS. Note that, as in the case of the embodiment, components having the same structure as that of the conventional technology are denoted by the same reference numerals in the drawings.

[0035]

FIG. 3 is a schematic diagram showing the structure of an exposure apparatus and an exposure optical system. Reference numeral 12 indicates that the wavelength is 41, for example.
Reference numeral 13 denotes a recording light source such as a 3 nm Kr ion laser, which removes the instability of the output of the light beam emitted from the recording light source 12 and controls the final recording light intensity;
It is a recording light intensity control unit composed of an EO (electro-optic crystal element) or the like. Reference numeral 14 denotes a modulation unit having modulation means for forming a pit having a length corresponding to the modulation signal. The modulator constituting the modulation unit 14 is required to have a performance capable of being used in a band of several tens of MHz. Specifically, EOM (electro-optic crystal element modulator) or AOM (acousto-optic crystal element modulator) is used. Reference numeral 15 denotes a deflecting unit having deflecting means.
It is composed of a light deflecting element such as an OD (acousto-optic crystal light deflecting element). The deflection unit 15 allows the optical disk master 8
Of the exposure spot irradiated on the photoresist film 9 in the tangential direction. Reference numeral 16 denotes a beam expander unit having an optical system for expanding the diameter of a recording light beam, and an exposure spot condensed on the photoresist film 9 of the optical disk master 8 using an objective lens 17 according to the magnification in the beam expander unit 16. Is controlled. A modulation signal for modulating a light beam emitted from the recording light source 12 is supplied from a recording signal supply unit 18 to a modulator constituting the modulation unit 14, and the exposure spot is scanned in the tangential direction in synchronization with the modulation signal. The scanning signal is supplied to the deflection unit 15. With such a configuration, if the exposure spot is moved at a predetermined track pitch per rotation in the radial direction while rotating the optical disk master 8 at a predetermined rotation speed, the latent image of the groove 6 or the latent image of the pits 5 can be changed to the predetermined position. It can be formed spirally at a track pitch.

The light deflecting element constituting the above-mentioned deflecting unit 15 has an EOD whose scanning frequency can correspond to several tens of MHz, which is equivalent to the recording light modulation frequency at the time of pit formation, rather than AOD.
Is desirable.

FIG. 4 shows the relationship between the modulation signal supplied to the modulation section 14 and the scanning signal supplied to the deflection section 15.
FIG. 4 is a schematic explanatory diagram illustrating a case where a pit having a single cycle is formed. The modulation signal may be a normal rectangular wave, and the pulse duty can be changed in the effective value according to the present invention without any particular problem. Then, the scanning signal synchronized with the modulation signal is supplied to the driving device of the optical deflecting element constituting the deflecting unit 15, and the supplied voltage E and the displacement ΔX of the exposure spot have a relationship of the following equation 1.

ΔX = α × E (1) (where α is a proportional constant)

The displacement of the exposure spot is ΔX = 0 at the initial position when the pulse of the modulation signal rises, becomes almost the maximum displacement ΔX _max at the fall, and returns to the initial position at the next rise of the pulse. Becomes Then, the moving velocity V _s of the exposure spot for the time T of the modulated signal voltage level "1" can be represented by the formula 2 below.

V _s = ΔX _max / T (2)

As a signal pattern for scanning an exposure spot as described above, a triangular wave as shown in a scanning signal example 1 in FIG. 4 is generally used. When the peak voltage of the triangular wave is E _top and the peak of the triangular wave of the scanning signal coincides with the fall timing of the pulse of the modulation signal,
From Equations 1 and 2 above, Equation 3 below is derived.

V _s = (α × E _top ) / T (3) From this equation 3, it can be seen that the moving speed V _s of the exposure spot can be controlled by the peak voltage value E _top of the scanning signal. However,
The positive or negative of the peak voltage E _top is the moving speed V of the exposure spot
the linear velocity V _g generated by the rotation of the _s and the optical disc master 8 is made to be the same direction. The path until the exposure spot returns to the initial position is arbitrary. Therefore, the voltage of the scanning signal only needs to be 0 at the rise of the pulse of the next modulation signal. For example, as shown in the scanning signal example 2 in FIG. Such a sawtooth signal pattern may be used.

FIG. 5 shows the relationship between the modulation signal supplied to the modulation unit 14 and the scanning signal supplied to the deflection unit 15.
FIG. 4 is a schematic explanatory diagram illustrating a case where a random pit pattern is formed. When a random pit pattern is formed, a waveform such as a triangular wave or a sawtooth wave synchronized with the modulation signal may be supplied from the recording signal supply unit 18 to the deflecting unit 15 only for pits having a length that requires recording compensation. That is, the compensation amount corresponding to the pits of each length can be controlled by the peak voltage value E _top of the scanning signal, as in the case of forming the pits of a single cycle.

[0044]

According to the exposure method of the present invention and the exposure apparatus using the same, the wavelength of the recording light can be reduced and the objective lens NA can be reduced.
It is possible to provide a master such as an optical disc master corresponding to high density without using a means for increasing the recording light wavelength or shortening the recording light wavelength and increasing the objective lens NA. Therefore, by using this master, it is possible to provide an optical disk compatible with high density.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view for explaining that a pit having a smaller diameter than an exposure spot diameter can be formed by reducing the relative speed of an exposure spot in the tangential direction according to the present invention; It is a schematic explanatory view of a state where a photoresist film is exposed by irradiating an exposure spot, (b) shows a conventional exposure method, and (c) shows an exposure method of the present invention.

FIGS. 2A and 2B illustrate an embodiment of the present invention, and FIGS.
(D) is a schematic explanatory view showing a procedure for forming a pit having a small length in the tangential direction.

FIG. 3 is a schematic configuration diagram of an exposure apparatus and an exposure optical system of the present invention.

FIG. 4 is a schematic diagram illustrating a relationship between a modulation signal supplied to a modulation unit of the present invention and a scanning signal supplied to a deflecting unit when a pit having a single period is formed.

FIG. 5 is a schematic diagram illustrating a relationship between a modulation signal supplied to a modulation unit of the present invention and a scanning signal supplied to a deflection unit when a random pit pattern is formed.

FIG. 6 is a schematic external perspective view of a conventional optical disc.

FIGS. 7 (a) and 7 (b) are schematic enlarged views in which a signal recording area in FIG. 6 is enlarged.

8 (a) to 8 (c) are schematic process explanatory views for manufacturing an optical disk from a conventional optical disk master.

FIG. 9 is a schematic process explanatory view following FIG. 8 (c),
(A) is a schematic enlarged perspective view in which the groove and land portions formed on the optical disk master are enlarged, (b) is a schematic cross-sectional view of the groove and land portions formed on the optical disk master, (c) 1 is a schematic sectional view of a disk substrate transferred from an optical disk master.

FIG. 10 is a schematic configuration diagram of a conventional exposure apparatus and an exposure optical system.

FIGS. 11A to 11C are schematic explanatory diagrams showing why it is difficult to secure a pit size in a conventional tangential direction.

FIG. 12 is a graph showing a conventional relationship between an exposure amount and a moving distance of an exposure spot.

FIG. 13 is a schematic explanatory view of a conventional relationship between an exposure amount and a pit shape to be formed.

FIG. 14 is a schematic explanatory diagram of a relationship between a conventional modulation signal voltage level and a pit shape formed.

15A and 15B show a relationship between a relative speed of an exposure spot in a tangential direction and a groove width, in which FIG. 15A is a graph when the recording light intensity is constant, and FIG. It is a graph at the time of the relative speed of an exposure spot in the tangential direction.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Disk board, 3 ... Signal recording area, 4 ... Reading surface, 5 ... Pit, 6 ... Groove, 7 ...
Land, 8: optical disk master, 9: photoresist film,
DESCRIPTION OF SYMBOLS 10 ... Latent image, 11 ... Stamper, 11a ... Stamper precursor, 12 ... Recording light source, 13 ... Recording light intensity control part, 14
... Modulating section, 15 deflecting section, 16 beam expander section, 17 objective lens, 18 recording signal supply section

Claims (10)

[Claims] 1. A light beam emitted from a recording light source is modulated based on a modulation signal supplied to a modulation device, and the light beam modulated by the modulation device is deflected by a deflection device. The light flux deflected by the above is condensed using an objective lens to form an exposure spot, and the exposure spot is irradiated on a photoresist film formed on a master to form an exposure pattern based on the modulation signal. In the exposure method, the exposure pattern is formed on the photoresist film while supplying a scanning signal for scanning the exposure spot in substantially the same direction as the rotation direction of the master in synchronization with the modulation signal to the deflection unit. An exposure method comprising: 2. The exposure method according to claim 1, wherein an optical deflecting element is used as said deflecting means. 3. The exposure method according to claim 2, wherein the light deflection element is an electro-optic crystal light deflection element. 4. The exposure method according to claim 1, wherein the master is an optical disk master. 5. A master produced by the exposure method according to claim 1. 6. An optical disk manufactured using the master manufactured by the exposure method according to claim 1. 7. At least a recording light source; a modulating unit for modulating a light beam emitted from the recording light source; and a deflecting unit for deflecting the light beam modulated by the modulating unit. An exposure apparatus that forms an exposure spot by condensing the deflected light beam using an objective lens and irradiates the exposure spot to a photoresist film formed on a master to form an exposure pattern, A recording signal supply unit for generating a modulation signal to be supplied to the unit and a scanning signal to be supplied to the deflecting unit; supplying the modulation signal to the modulation unit; and synchronizing the scanning signal with the modulation signal. Supplying the deflecting means to form the exposure pattern on the photoresist film while scanning the exposure spot in substantially the same direction as the rotation direction of the master. Exposure apparatus according to claim. 8. The exposure apparatus according to claim 7, wherein the master is an optical disk master. 9. An original master produced by the exposure apparatus according to claim 7. 10. An optical disk manufactured using an original master manufactured by the exposure apparatus according to claim 7.