JPH0798891A - Optical base disk exposure device - Google Patents

Abstract

PURPOSE:To accurately form fine pits and to remarkably improve the production by using the extreme ultraviolet radiation transparent optical member for the optical parts through which the emitting light passes. CONSTITUTION:In a light intensity modulating device 11 and in an optical system 12, the synthesized quartz or fluorite is used as the ultraviolet radiation transparent member for the optical parts through which the emitting light passes. The light emitted from an ultraviolet laser light source emitting part 10 is sent to the modulator 11 and the light is modulated according to the pit recording signal sent from the formatter of a terminal 13. The modulated light is irradiated through autofocusing optical system 14 and through an objective lens 17a to an optical disk 17b. The laser light is rotated and scanned on the disk by a disk rotating mechanism. At the same time, the optical system 12 including the objective lens is moved in the radial direction from the center of the disk. Thus, the beam is scanned spirally on the disk and the photo resist is exposed to form the pit with high density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk master exposure apparatus that irradiates a master of an optical disk coated with a photoresist with an exposure pattern using light from an exposure light source to expose the master.

[0002]

2. Description of the Related Art A conventional mastering device for cutting a master disc of an optical disk is a laser beam having a wavelength of about 400 nm emitted from an exposure light source, for example, a Kr laser (λ = 413n).
m) or Ar laser (λ = 351 nm) continuous wave gas laser in the ultraviolet wavelength range is used to expose the disc on which the resist is applied through the objective lens by narrowing it down to a diffraction-limited micro-spot. It is carried out.

[0003]

By the way, in the optical disc, the processing size of the pits must be miniaturized as the density of the optical disc is increased. When the processing size of this pit is required to be 0.25 μm or less, even if the condenser lens has a numerical aperture NA close to 1 at the wavelength of the gas laser used in the above-mentioned mastering device, the laser light will be sufficient. It becomes impossible to narrow down to. For this reason,
It is extremely difficult to accurately machine a master of an optical disc to a dimension of 0.25 μm or less.

Although the output power of these gas lasers at the exposure wavelength is about several hundred mW, the light intensity irradiated on the optical disk master is reduced to about 1 mW due to the loss in the optical system of the mastering device. Resulting in. Due to this loss and the restriction on the sensitivity of the photoresist, the mastering device has a problem that the exposure time becomes long and the characteristics are deteriorated.

Therefore, the present invention has been made in view of the above situation, and provides an optical disk master exposure apparatus capable of forming fine pits with high accuracy and greatly improving productivity. To aim.

[0006]

An optical disk master exposure apparatus according to the present invention controls a rotation speed of the optical disk master when forming an optical disk master by forming a pattern according to data with light from an exposure light source. While rotating with
In an optical disk master exposure apparatus that moves a spot focused by a moving unit in a radial direction from a rotation center, laser light emitted by diode laser excitation is wavelength-converted inside a first resonator, and the laser is emitted from the first resonator. Light source means for extracting the light whose wavelength is converted by the external resonance type second resonator, and the output light from the light source means is switched at high speed by an electric pulse signal according to the data supplied. A light source for modulating light intensity, and an optical system for converging the light modulated by the light modulator to a diffraction-limited spot size and irradiating the light on a disk master coated with a photoresist. The means and the optical system are characterized by using a far-ultraviolet transmitting optical material for an optical component that transmits outgoing light.

Here, the light source means does not transmit the optical transmission characteristics on the emission side of at least the pair of reflecting means by the emission wavelength of the second resonator, but emits light by the first resonator. It is also configured to transmit light having a wavelength.

The first resonator of the light source means has a laser medium and a first non-linear optical element provided inside the resonator, and the laser medium is, for example, Nd: YAG, the first nonlinear optical element.
KTP is used for the non-linear optical element. Further, the second resonator of the light source means is provided with a second nonlinear optical element between at least a pair of reflecting means, and at least one reflecting means of the pair of reflecting means is moved in the optical axis direction. have. The second nonlinear optical element that converts the wavelength of the light emitted from the first resonator is, for example, BBO.
Is used. Further, between the first resonator and the second resonator in the light source means, there is provided a phase modulating means for phase modulating the fundamental wave laser light emitted from the first resonator.

The above wavelength conversion includes sum frequency mixing, second harmonic generation, fourth harmonic generation, etc., and as a laser medium,
Not limited to Nd: YAG, but Nd: YV
There are O ₄ , Nd: BEL, LNP and the like. In addition to KTP and BBO, nonlinear crystal optical elements include LN, QPM LN,
There are LBO, KN, etc. The controlled unit of the control unit is composed of an electromagnetic actuator having at least one coil, one or more magnets and a yoke made of a magnetic material, such as a voice coil motor, and servo control is performed.

Further, the far-ultraviolet transmitting optical material uses synthetic quartz or fluorite.

[0011]

In the optical disc master exposure apparatus according to the present invention, the laser light emitted by the diode laser excitation from the light source means is sequentially wavelength-converted by the inside of the first resonator and the outside resonance type second resonator. An optical system that uses a far-ultraviolet transmitting optical material for the optical component that emits laser light and transmits the light modulated by the modulation means that modulates the light intensity is focused to a diffraction-limited spot size and coated with photoresist. By irradiating the disc master with light having a short wavelength, it is possible to irradiate the light with a sufficient emission power for exposure.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical disk master exposure apparatus according to the present invention will be described below with reference to the drawings.

The optical disk master exposure apparatus of the present invention will be described with reference to FIG. The optical disk master exposure apparatus is an apparatus for forming an optical disk master by forming a pattern according to data with light from an exposure light source. For example, as shown in FIG. 1, the optical disc master exposure apparatus wavelength-converts laser light emitted by diode laser excitation inside a first resonator, and emits light from the first resonator into an external resonance type. An ultraviolet laser light source emitting section 10 as a light source means for extracting the light whose wavelength has been converted by the second resonator, and an electric pulse signal corresponding to the data supplied with the emitted light from the ultraviolet laser light source emitting section 10. A light intensity modulator 11 as a modulation means for switching at high speed to perform light intensity modulation;
An optical system 12 for converging the light modulated by the light intensity modulator 11 to a diffraction-limited spot size and irradiating it on a disk master coated with a photoresist.

Here, the light intensity modulator 11 and the optical system 12 use synthetic quartz or fluorite as an optical material for transmitting far-ultraviolet rays in an optical component through which outgoing light is transmitted. The optical system 12 may be considered to constitute an optical system including the light intensity modulator 11.

The ultraviolet laser light source emitting section 10 emits light having a wavelength λ = 266 nm of the fourth harmonic of a YAG laser which is excited and emitted by a semiconductor laser at a level of several tens mW, as will be described later in detail. The emitted light is reflected by the mirror 10a by 90 ° and sent to the light intensity modulator 11. Data to be recorded on the optical disc master is supplied to the light intensity modulator 11 as a pit recording signal from a so-called formatter that generates an electrical pulse signal via the input terminal 13. The light is modulated according to this data. The light intensity modulator 11 is preferably a modulation element that utilizes the acousto-optic effect using Black diffraction or the Pockels effect.

The light modulated by the mirror 10c is 90
Reflected beam expander 15 and focus detection control system 14 such as a polarization beam splitter (hereinafter, PBS)
14A, 1/4 wavelength plate 16, and after being reflected at 90 ° by the mirror 10d, it is transmitted through the objective lens 17a having a high numerical aperture NA and is irradiated onto the optical disc master 17b coated with a photoresist in advance. It At this time, as the objective lens 17a, an incident light, for example, a lens having a high numerical aperture NA value which is aberration-corrected for the wavelength λ = 266 nm is used, and the beam is focused and irradiated to the diffraction limit. The objective lens 17a is made of synthetic quartz, fluorite, or the like whose material sufficiently transmits light in this wavelength range. The optical disk master 17b is placed on a mounting table 19 that rotates in accordance with the rotation of the spindle motor 18 in the direction of arrow R.

On the other hand, the ultraviolet laser light source emitting section 10 emits light of wavelength λ = 266 nm and simultaneously emits light of wavelength λ = 532 nm of the second harmonic of the YAG laser. The route of this light is also an optical path that passes through each of the above-mentioned optical elements, and is irradiated onto the optical disc master 17b. Optical disc master 17
In b, this light is reflected and the return light is the objective lens 17a,
PBS 14A through mirror 10c and quarter wave plate 16
Is supplied to. Here, this return light is a quarter wavelength plate 1
Since it has passed 6 twice, it is reflected by the PBS 14A. As a result, the PBS 14A of the autofocus optical system 14 sends the return light to the focus error amount detection element 14C via the wavelength selection element 14B. The use of the wavelength selection element 14B allows the light of the fourth harmonic, which is the exposure wavelength, to be emitted from the PB.
Since a considerable amount of light is reflected at S14A, the light of the exposure wavelength is blocked by using a multilayer interference film or the like.

In the focus error amount detecting element 14C, the light for exposure is used for the optical disc master 1 by using, for example, the astigmatism method.
The amount of displacement from the best focus position when focusing on 7b is optically detected, and this detected amount is converted into an electric signal. The detected electric signal is supplied to the drive control unit 14D forming a part of the autofocus servo system 14.

Here, the above-mentioned astigmatism method is a method in which the cylindrical lens is arranged behind the detection lens and the astigmatism is positively utilized for detection by the photodetector. Since this cylindrical lens has only the same function as a parallel plate with respect to the direction orthogonal to the above-mentioned single direction in the lens only in the single direction of the cylindrical lens, it does not converge at a position other than the focus position of the detection lens and this cylindrical lens The focus error signal is detected by forming a narrow beam image. By controlling the focus error signal to be zero, the focus of the objective lens is maintained at the optimum position.

The drive control unit 11c generates a drive signal for correcting the positional deviation based on the electric signal to generate the objective lens 1
Electromagnetic actuator 17c for slightly moving 2a up and down, 1
Output to 7d. Electromagnetic actuator 17c, 17d
Is the drive signal to move the objective lens 12a up and down (direction of arrow A)
By slightly moving the optical disc master 17b, the focus position of the optical disc master 17b can be automatically adjusted to the best position and exposure can be performed while suppressing loss.

Here, for example, when an aplanatic lens with a numerical aperture NA = 0.9 is used as the objective lens for the spot size of laser light, it is used as an airy disc.
It can be narrowed down to 0.36 μm.

The laser beam thus formed is rotated and scanned on the disk by the disk rotating mechanism, and at the same time, the optical system including the objective lens is moved in the radial direction from the center of the disk, so that the beam is spirally scanned on the disk. Then, the photoresist can be exposed to form high density pits.

Next, the optical disk master exposure apparatus of the present invention
Principle and Basics of Ultraviolet Laser Light Source Emitting Section 10 Used in
This configuration will be described in detail with reference to FIGS. 2 and 3.
The description will be made with reference to FIG. Laser in Figure 2
The light source 111 uses an SHG (second harmonic wave generation), which will be described later.
Raw) Laser light source device and emits fundamental laser light
To be done. This fundamental wave laser light is a so-called EO (electrical light).
Phase modulator 1 using a science element or an AO (acousto-optic) element
Phase modulation is applied at 12, and the reflection for detecting the reflected light from the resonator is performed.
Through the surface 113, through the condenser lens 114,
The light is incident on the partial resonator 115. Out of this
The partial resonator 115 includes a concave mirror (reflection surface) 116 and a plane mirror.
The non-linear optical crystal element 11 is formed between (the reflection surface of) 117 and
8 are arranged and configured. The external resonator 115 is
Between the pair of reflecting surfaces 116 and 117 of the resonator 115,
Optical path length L _RBecomes a predetermined length and the optical path phase difference Δ is an integer of 2π
Resonates when doubled, and the reflectance and the reflection position near the resonance phase
The phase changes greatly. A pair of reflecting surfaces 11 of the resonator 115
At least one of 6, 117, for example, the reflecting surface 117,
It is driven in the optical axis direction by the electromagnetic actuator 119.
It is like this.

SH is used as the laser light source 111.
When a single mode laser beam is generated and input to the external resonator 115 by using the G laser light source device, for example, BBO (barium borate) is used as the nonlinear optical crystal element 118 inside the resonator 115, and the nonlinear optical thereof is used. The second harmonic (incident light is SHG
In the case of a laser, a laser beam of the fourth harmonic) is generated. In this case, the reflection surface 11 of the concave mirror of the external resonator 115
Reference numeral 6 denotes a dichroic mirror that reflects almost all incident light, and the reflecting surface 117 of the plane mirror reflects most of the incident light and transmits most of the emitted light that has been shortened to half the wavelength of the incident light. Is.

The oscillator 121 outputs a modulation signal for driving the optical phase modulator 112, and this modulation signal is sent to the phase modulator 112 via a driver (driving circuit) 122a. The reflected light (return light) of the laser light sent to the resonator 115 is detected by the photodetector 123 such as a photodiode via the reflecting surface 113, and the reflected light detection signal is sent to the synchronous detection circuit 122b. The modulated signal from the oscillator 121 is supplied to the synchronous detection circuit 122b (with waveform shaping, phase delay, etc. if necessary), and is multiplied by the reflected light detection signal to perform synchronous detection. . The detection output signal from the synchronous detection circuit 122b becomes an error signal of the resonator optical path length by passing through the LPF (low pass filter) 122c. This error signal is sent to the driver 122d, and the driver 122d
The electromagnetic actuator 119 is driven by the drive signal from d.
Is driven to move the reflecting surface 117 in the optical axis direction and perform servo to make the error signal zero, whereby the optical path length L _R of the external resonator 115 is the minimum point (resonance point) of the reflectance. Is controlled by the length.

A so-called voice coil drive type actuator can be used as the electromagnetic actuator 119, and the multiple resonance frequency of the servo loop can be brought to several tens of kHz to 100 kHz or more. Due to the reduction, the cut-off frequency of the servo band can be expanded, and the drive current can be reduced, so that the circuit configuration can be simplified. As a result, the change of the resonator length L _R of the external resonance circuit 115 is reduced to 1/1 of the wavelength.
000 to 1/10000, that is, a system that suppresses extremely stably to 1 angstrom or less can be configured at low cost.

The external resonator 115 uses a so-called Fabry-Perot resonator. This resonator resonates when the optical path phase difference Δ is an integral multiple of 2π, and the reflection phase largely changes near the resonance phase. Using the phase change to control the frequency of the resonator is called RWPDreve as Drever Locking.
r, et al. “Laser Phase and Frequency Stabilization
Using an Optical Resonator ”, Applied Physics B 3
1. External resonator 11 disclosed in 97-105 (1983).
5 utilizes this technique.

Since the optical disk master device of the present invention requires ultraviolet light of a short wavelength, the structure shown in FIG. 3 is adopted as the laser light source. Here, the laser light source 21 is an SHG laser oscillator. As shown in FIG. 3, the laser light source 111 of the ultraviolet laser light source emitting unit 10 includes a laser medium 24 such as Nd: YAG and KTP (KTiOPO ₄ ) between a pair of reflecting surfaces 22 and 23 of a resonator 21, for example. And the non-linear optical crystal element 25 of FIG. The SHG laser light is generated and sent to the external resonator 26 by causing the fundamental wave laser of the wavelength from the laser medium 24 to pass through the nonlinear optical crystal element 25 and resonate. One of the pair of reflecting surfaces 27, 28 of the external resonator 26, for example, the reflecting surface 27 is driven and controlled by the electromagnetic actuator 29 in the optical axis direction. In the external resonator 26, a nonlinear optical crystal element 30 such as BBO built therein generates a second harmonic of the incident laser light, that is, a laser light that is a fourth harmonic as viewed from the original fundamental laser, and the external resonator 26 It is taken out from 26.

As a specific example of this, an ultraviolet laser light source emitting section 1
0 is configured as shown in FIG. 4, for example. Here, parts common to those in FIG. 2 and FIG. 3 described above are denoted by the same reference numerals and description thereof is omitted, and the laser wavelength and the like will be described by giving specific numerical values. The laser diode 110, which is a semiconductor laser, sends laser light having a wavelength of 810 nm to the laser light source 111. The laser light source 111 uses a laser medium Nd: YAG, and resonates a fundamental wave laser light having a wavelength of 1064 nm at the KTP 25 to generate a second harmonic wave having a wavelength of 532 nm, which is half the above wavelength, and an electro-optic phase modulator (EOM) 112. Emit to. The frequency f _c of the laser light source 111 (for example, about 50
Phase modulation of the frequency f _m (for example, 10 MHz) is performed on the laser light of 0 to 600 THz) by the phase modulator 112, and side bands f _c ± f _m are established. The signal of the carrier frequency of this phase modulation is supplied from the signal source (oscillator) 121.

The resonance frequency is f₀From the external resonator 26
Frequency f of the incoming light_c, F _c± f_mBeat between
By the FM sideband method to detect
Is detected by the photodetector 123, and the reflectance of the resonator is extremely low.
A position error detection signal with a polarity for a small position
Voice coil, which is one of the electromagnetic actuators to detect
The reflection surface 27 is moved in the optical axis direction by the motor 29, and
The difference detection signal is controlled to be zero. Highly accurate position
The synchronous detection circuit 122b, L of FIG.
Consists of a PF 122c and drivers 122a and 122d
The error signal is taken out by the locking circuit 122.

The optical path length is set to L _R so that the error signal becomes zero.
To output the second harmonic through the BBO 30 in the external resonator 26.
The laser light having an ultraviolet wavelength of 266 nm is emitted from the dichroic mirror 28.

The laser medium is Nd: YAG.
It is not limited to Nd: YVO ₄ , Nd: BE
L, LNP, etc. For non-linear crystal optical elements, KTP
And BBO, LN, QPM LN, LBO, KN, etc.

With the above-mentioned structure, fine wavelength pits can be formed with high precision by irradiating light with a short wavelength with an emission power sufficient for exposure, and by increasing the number of rotations during exposure, The productivity can be greatly improved.

The exposure apparatus of the present invention is not limited to the projection exposure apparatus using the refraction-type optical system as in the above-described embodiments, and may be, for example, a reflection-type optical system or a proximity exposure apparatus. Can also be applied.

[0035]

In the optical disk master exposure apparatus according to the present invention, the laser light emitted from the light source means by the diode laser excitation is sequentially wavelength-converted in the first resonator and in the second resonator of the external resonance type. The far-ultraviolet transmitting optical material is used as an optical component that emits the laser light emitted and transmits the light modulated by the modulation means that modulates the light intensity. By irradiating the coated disc master with light with a wavelength shortened with an emission power sufficient for exposure, fine pits can be formed with high accuracy, and by increasing the number of rotations during exposure, The productivity can be greatly improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of an optical disk master exposure apparatus according to the present invention.

FIG. 2 is a diagram illustrating a basic principle for generating an ultraviolet laser used in the above block diagram.

FIG. 3 is a block diagram showing a basic configuration for generating a fourth harmonic when an SHG laser is used.

FIG. 4 is a block circuit diagram showing a configuration of an ultraviolet laser light source emitting unit of the optical disk master exposure apparatus according to the present invention.

[Explanation of symbols]

 10 ... ・ ・ ・ UV laser light source emitting section 10a, 10c, 10d ・ ・ ・ Mirror 11 ・ ・ ・ ・ ・ ・ Light intensity modulator 12 ・ ・ ・ ・ ・ ・ Optical system 13 ・ ・ ・ ・Input terminal 14 Autofocus optical system 14A Polarizing beam splitter 14B Wavelength selection element 14C・ Focus error amount detection element 14D ・ ・ ・ ・ Drive control unit 15 ・ ・ ・ ・ ・ ・ Beam expander 16 ・ ・ ・ ・ ・ ・ 1/4 wavelength plate 17a ・ ・ ・ ・· Objective lens 17b ··· Optical disc master 17c, 17d · · Electromagnetic actuator 18 ··· Mounting table 19 ··· · Spindle motor

Claims (3)

[Claims] 1. When the optical disc master is formed by forming a pattern according to data with light from an exposure light source, the optical disc master is rotated at a controlled rotation speed while rotating a spot condensed by a moving means. In an optical disk master exposure device that moves in the radial direction from the center, laser light emitted by diode laser excitation
And a light source means for extracting the light emitted from the first resonator and having the wavelength converted by the external resonance type second resonator, and the light emitted from the light source means. Modulation means for performing high-speed light intensity modulation by switching with an electrical pulse signal according to the data to be recorded, and the light modulated by the modulation means is condensed to a diffraction-limited spot size to apply a photoresist. And an optical system for irradiating onto a disc master, wherein the modulating means and the optical system use a far-ultraviolet transmitting optical material for an optical component through which outgoing light is transmitted. 2. The optical disk master exposure apparatus according to claim 1, wherein the far-ultraviolet transmitting optical material is synthetic quartz. 3. The optical disc master exposure apparatus according to claim 1, wherein the far ultraviolet ray transmitting optical material uses fluorite.