JPH0453042A - Light beam intensity adjusting method for exposing device - Google Patents

Abstract

PURPOSE:To obtain the optimum exposing amount corresponding to the thickness of respective films at an inner-most periphery, outer-most periphery and the intermediate part, to form pits with high accuracy and to improve recording density by setting the function of a curve showing optimum light beam intensity. CONSTITUTION:A driving voltage for emitting an Ar laser 13 is supplied through a driving voltage generating circuit 35, and the driving voltage generating circuit receives the data of detecting a moving amount (r) of a light beam from a feeding monitor device and controls the driving voltage. Since the driving voltage to the Ar laser is controlled so that the exposing amount becomes the secondary function of the light beam moving amount, the beam emitted from the Ar laser applies intensity corresponding to linear velocity, which is increased from the inner-most peripheral position to the outer-most periphery, and the thickness of respective films. Therefore, the optimum exposing amount can be obtained over all the face, and all the pits can be formed with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to the production of master discs for optical discs such as optical video discs and digital audio discs. Beam strength: 7'Tj! 725 Law).

Back side t &'> [i When manufacturing the master disc for the first disc, in the cutting work that is carried out in the evening, the photoresist (photosensitive agent) coated on the film on the glass disc, which is the base of the master disc, is After emitting a light beam modulated in accordance with an information signal and exposing it to light, the exposed portion of the photoresist film is dissolved and removed by a developer, thereby creating a spiral track consisting of a series of bits on the mouth. form the original form.

Conventionally, constant rotation speed (CAV: constant a
(ngularvelocity) When manufacturing a master disc for creating a disc, the glass disc is rotated at a constant number of revolutions, and the light beam of the exposure device is irradiated onto the glass disc, and the light beam is radially directed evenly in the same way as when playing a disc. It is being moved at high speed. In order to form all bits with high precision, it is necessary to make the exposure amount uniform over the entire surface of the exposed portion of the photoresist film, from the innermost circumferential position to the outermost circumferential position. , as shown by straight line A in FIG. 6, the exposure energy per unit track length is adjusted to be constant according to the linear velocity that increases linearly from the innermost circumferential position to the outermost circumferential position. The intensity of the beam is changed linearly in proportion to the amount of movement.

The intensity of the light beam can be adjusted by adjusting the drive voltage supplied to a light emitting element that emits the light beam, such as an argon ion laser (hereinafter referred to as Ar laser), using a drive voltage generation circuit shown in FIG. It will be done. That is, in FIG. 7, a constant a representing the slope of the straight line A shown in FIG.
The product ar of this and this constant a is obtained by the multiplication circuit 2, and at the same time, a constant s representing the offset amount of the straight line A is set by the constant setting circuit 1, and the sum of the above ar and this b is obtained by the addition circuit 3.
obtained by. The driving voltage supplied to the Ar laser is applied to r
If it is changed as a function of , then the exposure jlp and the light beam movement amount r will have a linear proportional relationship.

By the way, the conventional light beam intensity adjustment method described above is based on the premise that the thickness of the photoresist film provided on the surface of the glass disk before the cutting operation is uniform over the whole blood. Yes, but 17, -
7 Since the metresist film is formed by adhering liquid SOI resist to the surface of a glass plate, it is not necessarily easy to make the thickness uniform. There is a tendency for the membrane in the middle to become a dog. Therefore, simply setting the intensity of the light beam and the amount of its movement under a linear proportional relationship as described above will not allow the optimum exposure amount to be applied to the entire surface of the photoresist film to form bits with ideal precision. , α cannot be obtained, and as shown at point Q in FIG. There was an inconvenience that there was no one.

Summary of the Invention [Object of the Invention] The present invention has been made in view of the above-mentioned points, and its objective is to apply an optimal exposure amount over the entire recording area of a photoresist film. It is an object of the present invention to provide a method for adjusting the intensity of a light beam.

[Structure of the Invention] The light beam intensity adjustment method for an exposure apparatus according to the present invention determines the optimum light beam intensity at the innermost and outermost positions of the disk, and at the intermediate position between at least the innermost and outermost positions. determining the optimum light beam intensity, setting a function indicating a curve connecting the optimum light beam intensities at the innermost circumferential position, the intermediate position, and the outermost circumferential position, and adjusting the light beam intensity at each radial position according to this function; It is characterized by

[Operation of the Invention] In this light beam intensity adjustment method, the light beam applied to the photoresist film is applied to the innermost circumference, the outermost circumference, and the intermediate part of the portion of the photoresist film to be exposed. Exposure energy is applied according to each film thickness.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an exposure apparatus that implements a light beam intensity adjustment method as a first embodiment of the present invention. In addition, the exposure apparatus has a photoresist film 1.1 provided on a glass disk 11 which is a base of a master disk used for press molding of the previous disk.
．． A light beam is emitted to expose the beam to light.

As shown in FIG. 1, the exposure apparatus rotates a glass disk 1 at a constant rotation speed by an air spindle motor 12, and uses a light beam emitted from an Ar laser 13 to correspond to an information signal to be recorded. While being modulated by the optical modulator 14, the photoresist film 11a is irradiated through an objective lens (not shown) included in the moving optical system 15. Note that a reflecting mirror 17 that reflects the light beam emitted from the Ar laser 13 toward the optical modulator 14 and a reflecting mirror 18 that guides the modulated optical beam obtained through the optical modulator 14 to the moving optical system 15 are provided. It is provided. These A “lasers” 3 and the optical modulator 14
A fixed optical system 2 [] is constituted by the two reflecting mirrors] 7 and ] 8, and other necessary optical elements (not shown). While the moving optical system] 5 is movable as described below,
The fixed optical system 2 [-] remains stationary.

The optical modulator 4 included in the fixed optical system 20 has an optical wavelength of 2.
The light modulator control circuit 23 controls ON and OFF based on the limiter signal emitted from the photoresist film 11a to form the original shape of the pit on the photoresist film 11a.
r laser] modulates the light beam from 3. In addition,
Since it is well known, there will be no detailed explanation, but the signal source 22
In the case of odor, both the video and audio signals are FM modulated by an FM modulator, then combined into one fd signal by a combining circuit (adder), and this combined signal is amplitude-limited by a limiter to generate a square wave. This is then sent as a limiter signal.

A moving optical system]5 transmits the modulated light beam obtained through the above-mentioned optical modulator]4 to the photoresist films 1, 1a,
1- Focus the light as a spot light with an objective lens (
It consists of necessary optical elements such as (not shown) and is mounted on the feed table 25. The feed table 25 is capable of reciprocating in a force plane 4'4'i with respect to the main surface of the glass disk 1 mounted on the air spindle motor 2, and is applied with a driving force by the feeding mechanism 26. Please move at speed.

As mentioned above (glass disk) l is air spindle motor 1
2 at a constant rotational speed, the photoresist film 11a! ,: The original shape of the track on the spiral is formed by exposure with a modulated light beam.

The air spindle motor 12 is controlled by a spindle servo circuit 28 to keep its rotational speed constant.
Further, the operation of the feed mechanism 26 is controlled by the feed servo circuit 20 so that the feed table 25 moves at a constant speed. Regarding the moving optical system 15, since it is necessary to make the objective lens follow the vibration of the rotating glass disk 1, the objective lens is moved in the direction of its front axis.
A focus servo mechanism that supports and drives the J motion (
(not shown). By controlling the operation of this focusing mechanism by a focus servo circuit 30, the modulated light beam is focused on the resist film 1.1.
Focus on point a.

On the other hand, a linear scale 32 is provided to detect the amount of movement of the feed table 25, that is, the amount of movement of the moving optical system 15 in the radial direction of the glass plate. 33 and sent to the feed servo circuit 29, and the feed servo circuit 29 controls the operation of the feed mechanism 26 based on this signal.

Incidentally, the drive voltage for causing the Ar laser 13 to emit light is supplied through the drive voltage generation circuit 35.

The drive voltage generation circuit 35 receives detection data of the movement IR of the light beam every moment from the above-mentioned feed monitoring device 33, and controls the drive voltage as described below based on the data.

That is, as shown in FIG. 2, the relationship between the moving amount r of the light beam and the exposure amount P per unit track length, that is, the light beam intensity, is such that, for example, an upwardly convex quadratic curve B is drawn. The driving voltage is controlled. In this case, as shown in FIG. 3, the thickness of the photoresist film 1.1a is not uniform over the entire surface of the exposed portion, and is thicker than the innermost and outermost portions. Assume that the thickness of the photoresist film 11a is uneven in the middle portion of Like A
By controlling the driving voltage to the r laser 13, Ar
Corresponding to the linear velocity of the light beam emitted from the laser, which increases from the innermost circumferential position to the outermost circumferential position, and corresponding to each film thickness at the innermost circumferential position, the outermost circumferential position, and a position between them. added strength. Therefore, the optimum exposure amount can be obtained over the entire exposed portion of the photoresist film 11a, and all bits can be formed with high precision.

Here, the configuration of the drive voltage generation circuit 35 that supplies drive voltage to the Ar laser 13 will be explained in detail based on FIG. 4.

As shown in FIG. 4, the drive voltage generating circuit 35 generates a signal P-a r2+b, which is the equation of the quadratic curve B shown in FIG.
The driving voltage is controlled to satisfy r+c. That is, the circuit configuration consists of each constant a included in the chain equation,
a constant setting circuit 41 that sets b and C; multiplication circuits 42 and 43 and addition circuits 44 and 45 that perform necessary calculations regarding the data of the light beam movement amount r sent out from the above-mentioned feed monitoring device 33 and each of these constants. It consists of

In this configuration, first, a constant a is set in the constant setting circuit 41, and the product ar of the light beam movement amount r received from the feed monitoring device 33 and this constant a is obtained by the multiplier p circuit 42. Then, the second
The sum a r+b of the constant S and this ar is sent out via the adder circuit 44. Next, a obtained by the adder circuit 44
The multiplication circuit 43 multiplies r+ by the light beam movement ff1r again to obtain ar2+br. At the same time, a third constant C representing the offset amount of the quadratic curve B is set in the constant setting circuit 4], and the sum av2+br+e of the above ar2+br and this C is obtained by the addition circuit 45. That is, the driving voltage supplied to the Ar laser 13 is changed as a quadratic function of the light beam movement far.

The above-mentioned quadratic curve B is set as follows.

First, a glass plate 1 to be subjected to exposure using the above-mentioned exposure device
Prepare one sheet of 1 for curve setting.

Then, as shown at points 46 and 47 in FIG. 2, the innermost circumferential position and the outermost circumferential position of the portion of the photoresist film 11a provided on the glass disk to be exposed are experimentally exposed, Based on the results, the optimum light beam intensity at both positions, that is, the exposure ff1P+
and P2 are determined.

At the same time, as shown at point 48, at least one intermediate position between the innermost circumferential position and the outermost circumferential position is determined, and the optimum exposure amount P3 at this intermediate position is determined. In this way, three or more points 46 to 48 have been determined, so a quadratic curve connecting these points is drawn, and each constant a of the function P-a r' +b r+c representing this quadratic curve is drawn.
, b and C. Based on the function obtained in this way, the driving voltage generating circuit 35 generates the Ar laser 1 as described above.
3 to adjust the light beam intensity at each radial position of the glass disk.

FIG. 5 shows an exposure apparatus implementing a light beam intensity adjusting method as a second embodiment of the present invention. In addition, the 5th rl! Since the exposure apparatus shown in J is constructed in exactly the same manner as the exposure apparatus shown in FIG. 1 except for the parts described below, the parts other than those described below will not be described in detail.

In addition, in the following description, the same reference numerals are used for the same parts as those of the exposure apparatus shown in FIG.

As shown in FIG. 5, in the exposure apparatus, the drive voltage of the Ar tracer 3 itself is kept constant without being varied. Instead, the light beam emitted from the Ar laser [3] is modulated into a modulated light beam that flashes in response to the recording signal by the ON/OFF operation of the optical modulator]4, and then the other optical modulator 48, the intensity is adjusted.

The operation of this optical modulator 48 is controlled by an optical modulator control circuit 49. The optical modulator control circuit 49 receives data on the optical beam movement amount r from the feed monitoring device 33, and calculates the exposure amount P per unit track length, that is, the optical beam intensity, and the optical beam movement amount r, as shown in FIG. The optical modulator 48 is controlled so that the relationship with the curve B represents a quadratic curve B.

Note that the circuit configuration of the optical modulator control circuit 49 is similar to that of the drive voltage generation circuit 35 shown in FIG. 1, and therefore will not be described in detail. Further, the method of setting the quadratic curve B in FIG. 2, which is the reference for controlling the operation of the light modulation 48 by the light modulator control circuit 49, is also the same as the setting method in the exposure apparatus shown in FIG.

In addition, in each of the above-described embodiments, the photoresist film 1
1. The intensity of the light beam irradiated onto the photoresist film 1.1.a is adjusted upward by following a convex quadratic curve B, as shown in FIG. This is because the film thickness of the portion located between the innermost and outermost portions of the portion a to be exposed is smaller than that of the innermost and outermost portions. Therefore, on the contrary, if the thickness of the intermediate portion is thinner than that of the innermost and outermost portions, the light beam intensity may be changed along a downwardly convex quadratic curve. Become. In addition, since intensity adjustment based on such a quadratic curve cannot be applied depending on the mode of change in film thickness in the radial direction of the glass plate, a curve expressed by a cubic function, a higher order function, or other function is set. Then, the light beam intensity is adjusted following this curve.

Furthermore, in each of the above embodiments, read-only optical discs such as optical video discs and digital audio discs are used as discs for which the present invention manufactures master discs; It goes without saying that the present invention is also applied to the production of master discs for phase change type optical discs such as rewritable type. When manufacturing master discs for such phase change type optical discs, it is particularly effective to increase the density of information recording by creating pre-groups with narrowed or varied pitches.

Effects of the Invention As detailed above, in the light beam intensity adjustment method for an exposure apparatus according to the present invention, a function is set that represents the optimum light beam intensity at the innermost circumference, outermost circumference, and intermediate position of the disk, and this function is Adjust the forward beam intensity at each radial position accordingly.

Because of this configuration, the beam irradiated onto the photoresist film is given an intensity corresponding to the film thickness of the innermost circumferential portion, the outermost circumferential portion, and the intermediate portion of the portion of the photoresist film to be exposed. The optimum exposure amount can be obtained over the entire area to be exposed, and all pits can be formed with high precision, contributing to higher density information recording.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an exposure apparatus according to a light beam intensity adjustment method as a first embodiment of the present invention, and FIG. 2 is a quadratic curve showing a mode of adjusting the light beam intensity in the exposure apparatus shown in FIG. FIG. 3 is a partial cross-sectional view of a glass disk having a photoresist film to be exposed by the exposure device shown in FIG. 1, and FIG. 4 shows the driving voltage included in the exposure device shown in FIG. 1. FIG. 5 is a block diagram showing the circuit configuration of a generating circuit. FIG. 5 is a block diagram of an exposure apparatus according to a light beam intensity adjustment method according to a second embodiment of the present invention. FIG. 6 is a block diagram showing a light beam in a conventional light beam intensity adjustment method. FIG. 7, which shows a straight line as an intensity adjustment mode, is a block diagram of an arithmetic circuit for carrying out a conventional light beam intensity adjustment method. Explanation of symbols of main parts 11...Glass plate 1, 1g...Photoresist film 13...
...A "Laser 14.48...Light modulator 23.49...Light modulator control circuit 33
...Feed monitoring device 35... Drive voltage generation circuit

Claims (1)

[Claims] While determining the optimum light beam intensity at the innermost and outermost positions of the disk, determining the optimum light beam intensity at at least one intermediate position between the innermost and outermost positions, and determining the optimum light beam intensity at at least one intermediate position between the innermost and outermost positions, and A method of setting a function that shows a curve connecting the optimal light beam intensity at each position, and adjusting the light beam intensity at each radial position according to this function.