JP2748894B2 - Exposure equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus, and more particularly, to an exposure apparatus for a master for producing an optical recording medium.

[0002]

2. Description of the Related Art When manufacturing an optical recording medium for recording / reproducing information by changing optical characteristics by irradiating a light beam, a method for manufacturing an optical recording medium in which a concave / convex pattern of information pits and guide grooves to be recorded is formed in advance. Optical recording media for recording / reproducing information based on the master are manufactured in large quantities. The master for producing the optical recording medium is conventionally produced by an exposure apparatus (for example, see Japanese Patent Laid-Open No. 4-49).
No. 527, JP-A-4-205722).

FIG. 2 is a block diagram showing an example of the above-described conventional exposure apparatus. This exposure apparatus includes a laser oscillator 2 that oscillates a laser beam 1, a power control unit 3 that controls the power of the laser beam 1, an optical modulator 4 that performs optical modulation corresponding to an exposure pattern, A head 16 including an expander lens 5 for enlarging the beam diameter of the laser beam 1, a folding mirror 14 for changing the direction of the laser beam 1 in the vertical direction, and an objective lens for condensing the laser beam 1 and a focusing laser beam 15 And a rotating mechanism 18 to which a photoresist disk 17 to which the focused laser beam is irradiated is fixed, and a focusing laser beam 15 reflected by the photoresist disk 17 is detected. Are maintained at the same distance from each other by a focus servo actuator 19.

When the light modulator 4 is always turned on, the guide groove is exposed on the photoresist board 17, and when the light modulator 4 is modulated on / off, the pits are exposed on the photoresist board 17. For example, the rotating mechanism 18 to which the photoresist board 17 is fixed is rotated at a constant rotation speed, and the moving optical system 20 including the expander lens 5, the folding mirror 14, and the head 16 is moved at a constant speed, thereby forming a spiral. The guide groove can be exposed from the inner periphery to the outer periphery.

[0005]

However, in the above-described conventional exposure apparatus, the optical axis of the laser beam 1 oscillated by the laser oscillator 2 may fluctuate depending on the state of the laser. This fluctuation of the optical axis changes the point of incidence of the head 16 on the objective lens.
When the optical axis fluctuates, the intensity of the laser beam 1 changes.

Further, since the moving optical system 20 is moved during exposure, the incident point of the head 16 on the objective lens changes by a small angle between the moving axis of the moving optical system 20 and the optical axis of the laser beam. As a result, the incident point gradually changes during exposure, so that the intensity of the laser beam changes.

Further, the head 16 and the photoresist board 17
Is designed to keep a certain distance by the focus servo, so that the exposure may gradually deviate from the focal depth of the focused laser beam. There is a drawback that it changes with the.

[0008] The present invention has been made in view of the above points,
An object of the present invention is to provide an exposure apparatus capable of keeping a laser beam incident point on an objective lens constant during exposure.

[0009]

In order to achieve the above object, the present invention provides a light source for emitting a laser beam, a photoresist disk having a surface coated with a photoresist, and a rotating mechanism for rotating the photoresist disk. A branching unit for branching a part of the laser beam from the light source to the photoresist board, a sensor unit for detecting an optical axis position shift of the laser beam branched by the branching unit, and a laser beam passing through the branching unit. A head having an objective lens for focusing on a resist board, an operation unit for calculating a displacement amount based on an output displacement detection signal of a sensor unit, and an optical path of a laser beam between the light source and the branching unit. And a correcting means for correcting the displacement of the optical axis of the laser beam based on the displacement result of the computing unit.

Here, the correcting means in the present invention comprises a first mirror for changing the optical path of the laser beam emitted from the light source, and a second mirror for changing the optical path of the laser beam reflected by the first mirror again. A mirror, and a first mirror driving unit that drives the first mirror so as to correct one of a horizontal direction component and a vertical direction component of the optical axis correction amount based on an output position shift amount calculation result of the calculation unit; A second mirror driving unit that drives the second mirror so as to correct the other of the optical axis correction amount in the horizontal direction and the vertical direction based on the output position shift amount calculation result of the calculation unit. Features.

The present invention also provides a modulator for modulating the intensity of a laser beam emitted from a light source in accordance with information to be exposed, and a focus servo means for controlling a distance between a head and a photoresist disk surface to be kept constant. And the branching means, the sensor section, and the head constitute a moving optical system, and move in the radial direction of the photoresist disc during exposure.

In the present invention, the optical axis of the laser beam from the light source to the photoresist board is detected by the sensor unit in the optical system whose optical axis has been adjusted in advance, and the arithmetic unit detects the positional deviation based on the positional deviation detection signal. Since the amount is calculated and the optical axis position shift of the laser beam is corrected by the correction means and returned to the optical axis position shift, the optical axis of the laser beam emitted from the light source fluctuates depending on the state of the light source. Can also correct the fluctuation and keep the laser beam incident point on the objective lens of the head constant.

[0013]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration diagram of an embodiment of the present invention. 2, the same components as those in FIG. 2 are denoted by the same reference numerals. In FIG. 1, mirrors 10 and 12 are provided in the optical path of the laser beam 1 between the light modulator 4 and the expander lens 5.
A beam splitter 7 is provided in an optical path of the laser beam 1 between the laser beam 1 and the return mirror 14. Further, a sensor unit 8 that monitors a part of the light split by the beam splitter 7 and an output signal of the sensor unit 8 are used. It is characterized in that an operation unit 9 for executing a predetermined operation and mirror driving units 11 and 13 are newly provided.

The power control unit 3 is provided with an EO (Electro
Optic), and sets and controls a voltage at which a desired power is obtained. Also, the optical modulator 4
Is an EO modulator or AO (Acoustic Opti)
c) It consists of a modulator. The sensor section 8 is composed of a four-division photodetector.

The expander lens 5, the beam splitter 7, the sensor unit 8, the folding mirror 14, and the head 16 constitute a moving optical system 25 that moves above the photoresist board 17 in the radial direction of the photoresist board 17. The head 16 is provided with a focus servo actuator 19
Is controlled in the vertical direction with respect to the surface of the photoresist board 17 by the output signal of FIG.

Next, the operation of this embodiment will be described. A laser beam 1 adjusted to an appropriate position in advance is emitted from a laser oscillator 2, this laser beam 1 is power-controlled by a power control unit 3, and then enters a light modulator 4 to perform light modulation corresponding to an exposure pattern. Receive. The laser beam 1 emitted after being modulated by the optical modulator 4 is
The mirror 10 corrects the horizontal direction of the optical axis correction amount to change the optical path, and further enters the mirror 12 to change the optical path so that the vertical direction amount of the optical axis correction amount is corrected. The beam diameter is expanded by the lens 5 and is incident on the beam splitter 7, where a part is transmitted and the rest is reflected.

A part of the laser beam transmitted through the beam splitter 7 is turned in the vertical direction by a folding mirror 14 and is moved by an objective lens in a head 16 together with a focusing laser beam 15 from a light source (not shown) on a photoresist disk. The light is condensed on the surface 17. Focusing laser beam 15 reflected by photoresist disk 17
Is detected by the focus servo actuator 19 and always keeps the photoresist disc 17 and the head 16 at the same distance.

The photoresist disk 17 has a surface coated with a photoresist, and is rotated by a rotation mechanism 18, so that the portion irradiated with the laser beam 1 is exposed. After the photoresist disk 17 is developed thereafter, it becomes a basis for forming a stamper disk.

On the other hand, the remaining laser beam 1 (monitor light 6) reflected by the beam splitter 7 is a four-divided photodetector composed of four divided light receiving units A, B, C and D as shown in FIG. After being incident on the sensor unit 8 and converted into an optical axis position shift detection signal a having a level corresponding to the shift of the optical axis position, the signal is supplied to the arithmetic unit 9. Here, the positions of the mirrors 10 and 12 are adjusted in advance so that the monitor light 6 is applied to the center position of the four-divided photodetector constituting the sensor unit 8 when the optical axis position of the laser beam 1 is the best. ing.

That is, when the monitor light 6 is shifted upward from the center of the sensor section 8 in the figure, it means that the monitor light 6 is shifted to the right when the head 16 is overlooked. Similarly, the monitor light 6 is shifted downward. When the monitor light 6 is shifted to the right (left) direction when the head 16 is overlooked, it is shifted to the front (rear) side when the head 16 is overlooked.

The level of electric signals obtained by the photoelectric conversion in the light receiving sections A, B, C and D is also indicated by A, B, C and D in the sensor section 8 as follows: (AB) And (C-D) are monitored as an optical axis position shift detection signal a which is a voltage signal.

The calculating unit 9 calculates the optical axis position shift amount and the optical axis correction amount based on the optical axis position shift detection signal a obtained by converting the light amount displacement due to the optical axis position shift of the monitor light 6 into a voltage displacement, A correction signal b corresponding to the horizontal portion of the optical axis correction amount and a correction signal c corresponding to the vertical portion of the optical axis correction amount are generated and output.

For example, the arithmetic unit 9 calculates (A−B) = k ×
y, (CD) = m × z (where k and m are constants, y is the driving amount of the mirror 12, and z is the driving amount of the mirror 10). ) Indicates a positive voltage value, the mirror 12 is driven rightward in the figure, and when (AB) indicates a negative voltage value, the mirror 12 is driven leftward in the figure. The signal c is generated and output. When (C-D) indicates a positive voltage value, the mirror 10 is driven forward in the figure, and (C-D)
When D) indicates a negative voltage value, a correction signal b for driving the mirror 10 backward in the figure is generated and output.

As described above, the horizontal direction correction signal b is supplied to the mirror driving unit 11 to drive the mirror 10 in the moving amount and the moving direction so as to eliminate the horizontal position shift amount of the optical axis. At the same time, the vertical direction correction signal c is supplied to the mirror driving unit 13 to drive the mirror 12 in the moving amount and the moving direction so as to eliminate the vertical position shift amount of the optical axis.

As a result, the optical axis of the monitor light 6 is controlled so as not to be displaced, and as a result, the optical axis of the laser beam 1 is controlled so as not to be displaced. The point of incidence of the laser beam on the objective lens in the head 16 can be kept constant.
As a result, the intensity of the laser beam focused on the photoresist board 17 becomes constant, and the laser beam is exposed stably within the depth of focus of the focused laser beam, and the desired guide groove or pit shape is stabilized, and , Accurately obtained.

[0026]

As described above, according to the present invention,
Even if the optical axis of the laser beam emitted from the light source fluctuates depending on the state of the light source, the fluctuation can be corrected and the point of incidence of the laser beam on the objective lens of the head can be kept constant. The intensity of the focused laser beam can be made constant, the exposure can be performed stably within the depth of focus of the focused laser beam, and the desired guide groove or pit shape can be obtained stably by the exposure. The branching unit, the sensor unit, and the head constitute a moving optical system, so that exposure can be performed stably even when moving in the radial direction of the photoresist disk during exposure.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of an example of a conventional device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser beam 2 laser oscillator 3 power control unit 4 optical modulator 5 expander lens 7 beam splitter 8 sensor unit 9 calculation unit 10 first mirror 11 first mirror drive unit 12 second mirror 13 second mirror drive Unit 14 Folding mirror 16 Head 17 Photoresist board 18 Rotating mechanism unit 19 Focus servo actuator 25 Moving optical system

Claims (2)

(57) [Claims] A light source for emitting a laser beam; a photoresist disk having a surface coated with a photoresist; a rotation mechanism for rotating the photoresist disk; and a laser beam from the light source to the photoresist disk. Branching means for branching a part of the laser beam; a sensor unit for detecting an optical axis displacement of the laser beam branched by the branching means; and focusing the laser beam passing through the branching means on the photoresist board. A head provided with an objective lens that performs the calculation, a calculation unit that calculates a displacement amount based on an output displacement detection signal of the sensor unit, provided in an optical path of the laser beam between the light source and the branching unit; based on the positional deviation amount calculation result of the arithmetic unit, have a correction means for correcting the optical axis positional deviation of the laser beam, as the correction means, said It is emitted from the source
A first mirror for changing an optical path of the laser beam,
The optical path of the laser beam reflected by the first mirror
The second mirror that changes again and the output position shift of the arithmetic unit
The horizontal and vertical optical axis correction amounts are calculated based on the amount calculation results.
Driving the first mirror to correct one of the directions
The first mirror drive unit and the output position shift of the arithmetic unit
Based on the amount calculation result, the horizontal axis amount of the optical axis correction amount and
The second mirror so as to correct the other part in the vertical direction.
And a second mirror driving unit for driving.
And to the exposure device. 2. A modulator for modulating the intensity of the laser beam emitted from the light source in accordance with information to be exposed, and a focus servo means for controlling a distance between the head and the photoresist disk surface to be kept constant. the a, the branch unit, the sensor unit and the head constitute a movable optical system, according to claim 1 Symbol placement of an exposure apparatus, wherein the moving in the radial direction of the photoresist plate during exposure.