JP2748900B2 - Exposure equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an exposure apparatus, and more particularly, to an exposure apparatus for a master for manufacturing an optical recording medium (a master optical disc).

[0002]

2. Description of the Related Art In the manufacture of an optical recording medium for recording and reproducing information by changing optical characteristics by irradiating a light beam, a concave / convex pattern of information pits and guide grooves is recorded in advance on an optical disk master. Conventionally, the recording of the information pits and the concavo-convex pattern of the guide groove has been described in, for example,
No. 28, JP-A-4-26941, JP-A-63
An exposure apparatus described in JP-A-231737 or the like was used. The general configuration of these conventional exposure apparatuses will be described with reference to FIG.

In FIG. 1, a conventional exposure apparatus includes a laser oscillator 2 for oscillating a laser beam 1 whose optical axis has been adjusted to an appropriate position in advance, a power control unit 3 for controlling the power of the laser beam 1, and a laser beam. A variable polarization beam splitter 6 for dividing the laser beam 1 into a guide groove forming laser beam 4 and a pit forming laser beam 5 having different deflecting surfaces; a mirror 7 for making the laser beam 4 and the laser beam 5 parallel; AO (A) that performs light modulation corresponding to the pattern
(Cost Optic) modulators 8 and 9 and expander lenses 10 and 11 for expanding the beam diameters of the laser beams 4 and 5.

A conventional exposure apparatus uses a laser beam 4
A mirror 12 for setting a desired interval between the laser beam 5 and the laser beam 5;
The beam splitter 13, a folding mirror 21 that changes the direction in the vertical direction, a head 23 including an objective lens for focusing the folded laser beam on a photoresist board 24, and the focused laser beam is irradiated. Rotating mechanism 25 for fixing and rotating photoresist disc 24
And a focus servo unit 26 that detects the focusing laser beam 22 reflected by the photoresist board 24, sends an actuator drive signal a to the head 23, and always keeps the photoresist board 17 and the head 23 at the same distance. It is composed of

In such a configuration, if the AO modulator 8 is always turned on, the guide groove is exposed on the photoresist disc 24, and the preformatted pits are exposed on the photoresist disc 24 by turning the modulator 9 on and off. The rotating optical system 27 including the expander lenses 10 and 11, the mirror 12, the beam splitter 13, the folding mirror 21, and the head 23 is rotated while rotating the rotation mechanism 25 to which the photoresist board 24 is fixed at a constant rotation speed. By moving the preformat pits at a constant speed, the preformat pits can be exposed from the inner circumference to the outer circumference with the spiral guide groove and the on-land.

However, when exposing a master having a narrow track pitch, interference between two laser beams becomes a problem. For this reason, when the modulator 9 for the preformat pit is turned on, the modulation level of the AO modulator 8 for the guide groove is reduced to, for example, 80% of the modulation level when only the guide groove is formed. When the modulator 9 for the preformat pit is turned off, the modulation level of the AO modulator 8 for the guide groove is made the same as the modulation level when only the guide groove is formed.

By doing so, it is possible to adjust the interference between the two laser beams at the exposure power level to make the guide groove and the preformat pit shape desired. As described above, in order to form the guide groove and the preformat pit shape into a desired shape, the modulator for the preformat pit is so exposed that the two laser beams are uniformly exposed on the photoresist disc 24 in the radial direction. 9 and AO for guide groove
It is important to control the modulator 8.

If the moving optical system 27 is moved at the time of exposure, the displacement of the optical axes of the two laser beams by a small angle changes the incident point of the head 23 with respect to the objective lens. . By changing gradually during exposure, 2
A change in the distance between the two laser beams occurs, and a shift amount in the rotation direction on the photoresist disc occurs between the two laser beams. As a result, the shape of the guide groove and the shape of the preformat pit at the displaced portion may change, and the shape of the guide groove and the shape of the preformat pit may differ between the inner circumference and the outer circumference.

As a known technique for solving this problem, there is a technique disclosed in Japanese Patent Application Laid-Open No. 4-117636. This is a device for condensing two beams and exposing the same to an optical disk master, monitors the two beams by using reflected light from the optical disk master, and feeds back the feedback to the distance between the two laser beams, that is, The beam interval is kept constant.

[0010]

In the exposure apparatus described in the above-mentioned patent publication, the interval between the two beams is kept constant by using the reflected light from the master optical disc. However, the amount of reflected light is considered to be affected by the type of glass, the type of photoresist, the film thickness, the ambient temperature, the humidity, and the like, but is at most about 3 to 8%. For this reason, there are many noises, and it is difficult to monitor a beam using reflected light.

Further, the reflected light is affected by the roughness of the surface of the photoresist coating surface, and the beam interval is accurately monitored by the inclination of the master, the uniformity of the photoresist film thickness, and the effects of defects. May not be possible.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art, and an object of the present invention is to provide an exposure apparatus capable of accurately monitoring the interval between two beams and keeping the interval between the two beams constant. To provide.

[0013]

According to the present invention, there is provided an exposure apparatus for converting a beam from the same light source into a first beam and a second beam substantially parallel to the beam, and a second beam after the conversion. A light condensing means for converging the first and second beams on the surface of the master optical disc, wherein
The first and second beams before focusing by means
Beam splitter for extracting monitor light from the
The monitor light extracted by the
And a sensor for detecting a change in the irradiation position.
By the light condensing means according to the irradiation position detected by
From the first beam to the second beam before focusing
Error detection to detect the error of the distance to the predetermined distance value
Output means and the error detection means.
Diffraction means for diffracting the second beam .

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the present invention is as follows.

A beam from the same light source is converted into a first beam and a second beam substantially parallel to the first beam. The converted first and second beams are focused on the surface of the optical disk master. An error of the distance from the first beam to the second beam before the focusing with respect to a predetermined distance value is detected.
By diffracting the second beam according to this detection result, the interval between both beams is kept constant.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of an exposure apparatus according to the present invention, and the same parts as those in FIG. 4 are denoted by the same reference numerals. In the figure, an exposure apparatus according to an embodiment of the present invention has a beam splitter 15 for dividing laser beams 4 and 5 into monitor light 14 in the configuration of the apparatus of FIG.
A polarization beam splitter 16 that divides the monitor light 14 into two, a sensor unit 17 and a sensor unit 18 that monitor an optical axis position shift of the monitor light 14, an operation unit 19 that calculates an optical axis correction amount, and an operation An AO modulator driving unit 20 driven by the optimum position signal b calculated by the unit 19 is added. The modulator driving section 20 may use a Bragg diffraction type acousto-optic diffraction grating or the like.

The moving optical system 27 in the present embodiment includes the expander lenses 10 and 11, the mirror 12, the polarization beam splitters 13 and 16, the beam splitter 15,
It comprises the sensor units 17 and 18, a folding mirror 21, and a head 23.

The power control unit 3 has EO (Ele)
Using a (ctro optic) modulator, a voltage at which a desired power is obtained is set and controlled. Further, as the modulator 9, an EO modulator or an AO modulator is used.

For the sensor units 17 and 18, for example, a four-divided photodetector is used, and a laser beam for a guide groove,
Adjustment is made so that the two laser beams of the preformat pit laser beam have the best optical axis at the center of the 4-split photodetector. Thereby, the displacement of the optical axis position of the monitor light can be detected as a light amount displacement to the four-divided photodetector, and can be monitored as a voltage displacement.

That is, as shown in FIG. 2A, a four-part photodetector divided into four parts A to D is used for the sensor unit 17. If the optical axis of the laser beam is located at the center position of the sensor unit 17, the difference between the detection voltage in the part A and the detection voltage in the part B and the difference between the detection voltage in the part C and the detection voltage in the part D are: Both become 0 [V]. If the optical axis of the laser beam deviates even slightly from the center position of the sensor unit 17, the difference between these detected voltages is not 0 [V], and a voltage displacement amount corresponding to the deviation amount is output. Therefore, the difference between these detected voltages is monitored as the position shift signal c.

Also, as shown in FIG.
The sensor unit 18 also uses a four-divided photodetector divided into four parts A to D. Then, similarly, the difference between the detected voltages is monitored as the position shift signal d.

The arithmetic section 19 includes a position shift signal c from the sensor section 17, a position shift signal d from the sensor section 18, a spindle speed signal e monitored by the rotation mechanism section 25,
Photoresist disc 2 monitoring position of moving optical system 27
4, a photoresist disk 2 for both laser beams for guide grooves and preformat pits based on the radius signal f
4 to calculate the amount of displacement in the rotation direction.

Here, the spindle speed signal e is a signal corresponding to the spindle speed obtained by monitoring the rotation of the spindle contained in the rotation mechanism 25 by a rotary encoder (not shown) or the like. Also, the radius signal f
Is a signal corresponding to the relative position of the laser beam passing through the head 23 from the rotation center of the photoresist disc 24, and is obtained by monitoring the amount of positional displacement of the moving optical system 27 by a linear encoder (not shown). .

FIG. 3 shows a schematic configuration of the photoresist board 24. Now, it is assumed that the rotation center position of the rotation mechanism unit 25 and the rotation center position of the photoresist board 24 match, and the laser beams 4 and 5 emitted from the head 23 by the movement of the moving optical system 27 It passes through the center of rotation of the board 24. And
Photoresist disk 2 of laser beam 4 and laser beam 5
4, the moving distances in the X-axis direction and the Y-axis direction are B4x, B4
y, B5x, and B5y, and the components cx, cy, dx, and d of the position shift signal c and the position shift signal d in the X-axis direction and the Y-axis direction.
y. Then, the moving distance B4 in the X-axis direction and the Y-axis direction
x, B4y, B5x, and B5y can be represented by the following equations.

B4x = k · dx · 2 (f + Δf) π / e (1) B4y = m · dy (2) B5x = n · cx · 2fπ / e (3) B5y = p · cy (4) Note that, in equations (1) to (4), k, m, n, and p
Is a constant.

As shown in FIG. 3, the amount of displacement in the rotation direction is represented by | B4y-B5y |.

Next, the modulation timing shift amount corresponding to the rotation direction shift amount is calculated by the following equation.

T = r | B4x-B5x | / e (5) In equation (5), r is a constant. Furthermore, A
The moving amount Δx of the O modulator 8 in the direction perpendicular to the optical axis of the laser beam 4 is calculated by the following equation.

Δx = v × t (6) In Equation (6), v is the sound speed in the crystal of the AO modulator 8, and is a fixed value depending on the type of the crystal.

Returning to FIG. 1, the AO modulator driving unit 20 uses the movement amount Δx obtained by the equation (6) as the optimum position signal b.
Send to As a result, the AO modulator driving unit 20 moves the AO by a moving amount Δx in the direction perpendicular to the optical axis of the laser beam 4.
The modulator 8 is driven.

In short, the present apparatus detects an error of a distance between beams before focusing on the surface of the master optical disc with respect to a predetermined distance value, and diffracts the beam according to the detection result to cancel the error. The beam interval is kept constant. And 2 with beam splitter
The monitor light is extracted from the two beams, and the sensor to which the extracted monitor light is irradiated detects a change in the irradiation position and detects an error.

As described above, in this apparatus, in the optical system whose optical axis has been adjusted in advance, the sensor unit monitors the optical axis position deviation of the laser beam, and the calculation unit returns the positional deviation amount and the original optical axis position. Is calculated, and the AO modulator is driven by the correction amount to sequentially correct the positional deviation. By doing this,
There is no deviation in the rotation direction of both the guide groove and preformat laser beams on the photoresist disc during exposure, and an optical disc disc having a desired guide groove shape and a desired preformat pit shape can be stably obtained. It is.

Since the present apparatus monitors the beam before condensing on the master, instead of monitoring the reflected light from the master, improvement in monitoring accuracy can be expected.
By improving the monitoring accuracy, the interval between the two beams can be controlled with high accuracy. Further, although the interval between the two beams is about 0.7 to 0.8 microns, the interval tends to be narrower in the future, so that the problem of the influence of the two beams is inevitable. In other words, the closer the interval (pitch) becomes, the more important the two-beam interval (particularly the modulation timing of the two beams) becomes. However, according to the present apparatus, the two-beam interval can be kept constant with high accuracy. It is.

[0035]

As described above, the present invention detects an error of a distance between beams before focusing on a master with respect to a predetermined distance value, and diffracts one of the beams according to the detection result. There is an effect that the interval between both beams can be kept constant.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an exposure apparatus according to an embodiment of the present invention.

FIG. 2A is a schematic configuration diagram of a sensor unit 17 in FIG. 1;
FIG. 2B is a schematic configuration diagram of the sensor unit 18 in FIG.

FIG. 3 is a diagram showing a relationship between a photoresist disc 24 in FIG. 1 and a beam irradiation position.

FIG. 4 is a block diagram illustrating a configuration of a conventional exposure apparatus.

[Explanation of symbols]

 Reference Signs List 2 laser oscillator 3 power control unit 6 variable polarization beam splitter 7, 12 mirror 8, 9 modulator 10, 11 expander lens 13, 15 beam splitter 16 polarization beam splitter 17, 18 sensor unit 19 arithmetic unit 20 AO modulator drive unit DESCRIPTION OF SYMBOLS 21 Folding mirror 23 Head 24 Photoresist board 25 Rotation mechanism part 26 Focus servo part 27 Moving optical system

Claims (3)

(57) [Claims] 1. A conversion means for converting a beam from the same light source into a first beam and a second beam substantially parallel to the beam, and converting the converted first and second beams onto a surface of an optical disk master. A light condensing means for converging light to the first and second light sources, wherein the first and second light sources are not condensed by the light condensing means .
A beam splitter that extracts monitor light from the beam,
Monitor light extracted by the beam splitter is directly irradiated
And a sensor for detecting a change in the irradiation position.
The light collector according to the irradiation position detected by the sensor
The second beam from the first beam before focusing by the step
Error of the distance to a given beam with respect to a predetermined distance value
Error detecting means, and the second window according to a detection result by the error detecting means.
An exposure apparatus, comprising: a diffraction unit for diffracting a beam . 2. The sensor is a four-segment photodetector.
The monitor light with respect to the center position divided into four
2. The exposure apparatus according to claim 1, wherein the error is detected based on the irradiation position . 3. The exposure apparatus according to claim 1, wherein the diffraction unit includes an acousto-optic diffraction unit that diffracts the second beam according to the detection result.