JP4585684B2 - Acousto-optic device stationary system in laser beam lithography system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to the stabilization of an acousto-optic element used for modulating a laser beam of a laser beam drawing apparatus.
[0002]
[Prior art]
In a conventional laser beam drawing apparatus, in order to draw a two-dimensional image on a drawing surface, an acousto-optic element (hereinafter referred to as AOM (acousto--) that diffracts incident light from a laser beam emitted from a light source depending on whether or not an ultrasonic wave is applied. optic modulator) is used to modulate an on state in which drawing is performed and an off state in which drawing is not performed, and is deflected by deflecting means such as a polygon mirror to scan the drawing surface in a predetermined direction.
[0003]
FIG. 1 shows a state of light modulation in the laser beam drawing apparatus. First, the control unit 4 generates a modulation signal based on drawing data corresponding to drawing contents. The driver 5 receives the modulated signal transmitted from the control unit 4. The driver 5 applies an ultrasonic wave to the AOM 3 corresponding to the modulation signal. The laser beam incident on the AOM 3 is emitted from the AOM 3 as zero-order light that travels straight without being diffracted when no ultrasonic wave is applied. The laser beam is emitted from the AOM 3 as first-order diffracted light diffracted in a predetermined direction in the AOM 3 when an ultrasonic wave is applied. In a conventional laser beam drawing apparatus, first-order diffracted light is used as drawing light for exposing the drawing object, that is, drawing.
[0004]
In the present specification, only the first-order diffracted light and the 0th-order light among the light generated by the diffraction action of the AOM are considered, and the other multi-order diffracted light having low power is not considered.
[0005]
An AOM that modulates a laser beam has a feature of generating heat when an ultrasonic wave is applied. Furthermore, with the change in temperature of the AOM, a phenomenon occurs in which the direction of diffraction of the first-order diffracted light is displaced from a predetermined direction (see arrow p in FIG. 1). If this phenomenon is left unattended, the incident position of the laser beam on the deflecting means located downstream of the AOM on the optical path will deviate from the predetermined position. That is, the laser beam cannot scan on a predetermined scanning line of the drawing object placed on the drawing surface when the temperature of the AOM changes. Also, a predetermined beam spot shape cannot be obtained due to the deviation of the incident position with respect to the deflecting means. That is, drawing with high accuracy and high drawing quality cannot be performed.
[0006]
[Problems to be solved by the invention]
Therefore, in view of the above circumstances, the present invention provides an acoustooptic device steadying system that stabilizes the diffraction direction of the first-order diffracted light so that the laser beam emitted from the acoustooptic device scans a predetermined scanning line on the drawing surface. The purpose is to do.
[0007]
[Means for Solving the Problems]
For this reason, the acoustooptic element steadying system in the laser beam drawing apparatus according to claim 1 includes an acoustooptic element that is driven by application of ultrasonic waves and diffracts the incident laser beam, and is in the sub-scanning direction. Applied to a laser beam drawing apparatus that performs predetermined drawing on the drawing object placed on the drawing surface by scanning the diffracted light emitted from the acousto-optic element in the main scanning direction on the drawing surface moving to Is done. The system is provided between a light source for irradiating a laser beam, a light control means for adjusting the laser beam, and a laser beam for a drawing operation and a laser for a non-drawing operation. Control means for controlling the drive of the dimming means so as to block the beam and always controlling the drive of the acousto-optic element by a predetermined modulation signal regardless of whether or not the drawing object is being drawn. Features.
[0008]
According to the first aspect, even during the non-drawing operation, the AOM applies ultrasonic waves corresponding to the modulation signal having substantially the same duty ratio as the modulation signal generated by the drawing data during the drawing operation , and the temperature rises in advance. Therefore, it is possible to provide an AOM in a steady state in which the diffraction direction of the first-order diffracted light does not change even when the temperature is changed by applying ultrasonic waves during the drawing operation.
[0009]
According to a second aspect, the system further includes storage means for storing drive data for forcibly driving the acousto-optic element. In this case, during the drawing operation, the control means converts the drawing data corresponding to the predetermined drawing content into a modulation signal so that the object to be drawn corresponding to the predetermined drawing content is exposed or not exposed in each scan. Thus, the acousto-optic element can be driven and controlled, and the drive data read from the storage means can be converted into a modulation signal during the non-drawing operation to control the acousto-optic element.
[0010]
The drive data may be completely independent of the drawing data, but the duty ratio of the modulation signal obtained by converting the drive data is substantially the same as the duty ratio of the modulation signal obtained by converting the drawing data. It is desirable to be. Even during the non-drawing operation, if the drive control is performed with the modulation signal having the same duty ratio as the modulation signal given during the drawing operation, an unnecessary burden is not imposed on the AOM. It is possible to shorten the life of the AOM accompanying the useless temperature change and to reduce the influence on other members.
[0011]
Moreover, the acousto-optic constant system can modulate a plurality of laser beams can be applied to a so-called multi-channel type AOM.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
First, the laser beam drawing apparatus 100 equipped with the AOM steadying system according to the present invention will be described. FIG. 2 is a schematic configuration diagram of the laser beam drawing apparatus 100. The laser beam drawing apparatus 100 includes a polygon mirror 7, an fθ lens 8, a drawing table 9, and a mirror 10 in addition to an AOM steadying system 50 including a light source 1, a mechanical shutter 2, an AOM 3, a control unit 4, a driver 5, and a memory 6. , And a photodetector 11. A drawing object D is placed on the drawing table 9.
[0013]
Note that the AOM 3, the control unit 4, and the driver 5 in the present embodiment are the same as those provided in the above-described conventional laser beam drawing apparatus, and are therefore given the same reference numerals as in FIG.
[0014]
Conventionally, the drawing operation on the drawing object D is performed as follows. In the following text, for convenience of description, drawing a predetermined drawing pattern on one drawing object D is called drawing operation, and a laser beam modulated during one scan enters the drawing object D. (Drawing) is called exposure, and not entering (not drawing) is called non-exposure. A laser beam (arrow line in FIG. 2) emitted from the light source 1 enters the AOM 3 via the shutter 2. Since the light source 1 is in a state of continuously irradiating the laser beam until the power is turned off when the power of the laser beam drawing apparatus 100 is turned on, the light source 1 is configured to be shielded by the shutter 2 except during the drawing operation. The shutter 2 is driven and controlled by the control unit 4.
[0015]
When drawing data corresponding to predetermined drawing content is input by an external input unit (not shown), the control unit 4 generates a modulation signal based on the drawing data and transmits the modulation signal to the driver 5. , AOM3 is driven and controlled.
[0016]
Since the operation of the driver 5 and the AOM 3 has already been described in the section of the prior art, description thereof is omitted here (see FIG. 1). The first-order diffracted light that exposes the drawing object D is guided to the polygon mirror 7.
[0017]
The polygon mirror 7 has a plurality of deflection surfaces. The polygon mirror 7 is rotated in a certain direction by driving a motor (not shown), and deflects an incident laser beam (first-order diffracted light).
[0018]
The laser beam deflected by each deflection surface of the polygon mirror 7 scans the drawing object D in the main scanning direction via the fθ lens 8. While the laser beam scans over the drawing object D, the drawing table 9 moves in a direction perpendicular to the main scanning direction (direction perpendicular to the paper surface of FIG. 2), thereby drawing a two-dimensional image. It is drawn on the body D.
[0019]
The laser beam incident on the mirror 10 disposed outside the drawing area via the fθ lens 8 is received by the photodetector 11. When the photodetector 11 receives light, the photodetector 11 transmits a predetermined signal to the control unit 4. The control unit 4 specifies the exposure start position for each scan based on the signal from the photodetector 11 and adjusts the transmission timing of the modulation signal.
[0020]
Thus, conventionally, the AOM 3 is driven only during the drawing operation. Here, AOM3 has the following properties. FIG. 3 shows a change in the diffraction direction of the first-order diffracted light when an ultrasonic wave is continuously applied to a specific AOM 3. The horizontal axis represents the ultrasonic application time, that is, the temperature change of the AOM 3, and the vertical axis represents the diffraction direction. Indicates displacement (unit: mrad). As shown in FIG. 3, when the ultrasonic wave is continuously applied to the AOM 3, the diffraction direction of the first-order diffracted light continues to change with heat generation, and eventually becomes substantially stable at a predetermined position. After stabilization, the diffraction direction does not change because the temperature is in equilibrium even if ultrasonic waves are continuously applied.
[0021]
In the following text, a state in which the diffraction direction of the first-order diffracted light continues to change is referred to as a transient state, and a state in which the diffraction direction of the first-order diffracted light is substantially stable at a predetermined position is referred to as a steady state. Although there are individual differences in the AOMs mounted on the laser beam drawing apparatus, any AOM has properties as shown in FIG. The time in the transient state is also approximately equal to the time for drawing one drawing object D, although there are individual differences for each AOM mounted.
[0022]
If the diffraction direction of the primary diffracted light is not stable, the drawing object D cannot be drawn with high accuracy. Therefore, the AOM 3 must always be above a predetermined temperature, that is, in a steady state. However, as described above, conventionally, since the AOM 3 is driven only when the drawing operation is actually performed, a temperature change occurs during the drawing operation, and the drawing operation ends before the AOM 3 becomes a steady state. That is, since the object D is scanned in a state where the diffraction direction of the first-order diffracted light is changed, a high-definition drawing result according to the drawing data cannot be obtained. After the drawing operation is completed, the AOM 3 is not driven until the next drawing operation is performed, and is naturally cooled. Therefore, when the next drawing object D is drawn, the AOM 3 is still in a transient state and the diffraction direction due to the temperature change. Changes will occur.
[0023]
Therefore, according to the present invention, when the power of the laser beam drawing apparatus 100 is in an on state, the AOM 3 is driven and controlled by the control unit 4 via the driver 5 regardless of the drawing operation. AOM3 is maintained in a steady state.
[0024]
Specifically, at the time of the drawing operation, the control unit 4 generates a modulation signal based on the drawing data as in the past, and drives and controls the AOM 3 with the modulation signal. Further, the control unit 4 applies an appropriate ultrasonic wave to the AOM 3 even when the drawing operation is not performed (during the non-drawing operation) so that the AOM 3 is not in a transient state. During the non-drawing operation, the drawing object 9 is conveyed to the drawing table 9 after the drawing object D is drawn after the power is turned on until the drawing operation is performed on the first drawing object D. It means the time until it is placed.
[0025]
In this embodiment, drive data is stored in a non-volatile memory 6 such as an EEPROM in order to generate a modulation signal during a non-drawing operation. The drive data is data irrelevant to the drawing data and is data for forcibly driving the AOM 3.
[0026]
If the AOM 3 is simply maintained in a steady state, the drive data may be data that always applies an ultrasonic wave to the AOM 3. However, if ultrasonic waves are continuously applied to the AOM 3, excessive heat generation will cause the AOM 3 itself to malfunction or adversely affect other members, leading to a reduction in drawing accuracy. In general, the drawing pattern drawn on the drawing object D is generally determined for each laser beam drawing apparatus 100. Therefore, drive data that can generate a modulation signal having substantially the same duty ratio as the modulation signal generated by the drawing data that is most frequently used in each laser beam drawing apparatus 100 is set as an initial setting when the laser beam drawing apparatus 100 is shipped. Is stored in the memory 6.
[0027]
During the non-drawing operation, the control unit 4 generates a modulation signal based on the drive data read from the memory 6. By transmitting the modulation signal to the driver 5, the AOM 3 is driven and controlled even during the non-drawing operation. As described above, since the modulation signal has substantially the same duty ratio as that of the modulation signal used at the time of drawing, an appropriate ultrasonic wave can be applied to the AOM 3 without applying an excessive load and the steady state can be obtained.
[0028]
FIG. 4 is a timing chart showing drive control of the AOM 3 of the control unit 4 described above. As shown in FIG. 4, while the laser beam drawing apparatus 100 is powered on (FIG. 4 (1)), during the drawing operation, according to the modulation signal generated based on the drawing data (FIG. 4 (3)), During the non-drawing operation, the AOM 3 is always driven and controlled (FIG. 4 (5)) according to the modulation signal generated based on the drive data (FIG. 4 (4)).
[0029]
The AOM 3 is always driven and controlled, but only when the drawing operation is executed (only when the AOM 3 is driven by the modulation signal based on the drawing data), the shutter 2 is opened by the control of the control unit 4 and the laser beam is emitted. Since the light enters the AOM 3 (FIG. 4B), the laser beam does not enter the AOM 3 that is modulated and controlled based on the drive data. That is, the laser beam does not enter the drawing table 9 even if the AOM 3 is driven during the non-drawing operation. Therefore, there is no possibility that unnecessary exposure is performed on the drawing object D during conveyance or placement.
[0030]
Here, FIGS. 4 (3) and 4 (4) do not show the waveform of the modulated signal itself, but show the timing at which the modulated signal is transmitted from the control unit 4 to the driver 5. That is, it means that a modulated signal having a waveform that vibrates finely based on drawing data or the like is transmitted to the driver 5 when it is within the block surrounded by the diagonal lines in FIGS. 4 (3) and 4 (4). . Similarly, FIG. 4 (6) also shows the timing at which the drawing operation is executed. That is, when the laser beam modulated based on the modulation signal shown in FIG. 4 (3) scans the drawing object D when it is in the block surrounded by the oblique lines in FIG. 4 (6), exposure / non-exposure is performed. By repeating, a predetermined drawing pattern is obtained.
[0031]
The above is the embodiment of the present invention. The present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the present invention.
[0032]
For example, in the above-described embodiment, a drawing apparatus that performs drawing with a single laser beam has been described. However, the laser beam emitted from the light source 1 is divided into a plurality of parallel beams using a beam splitter or the like, and the plurality of the plurality of beams are divided. The present invention can also be applied to an AOM mounted on a drawing apparatus (multi-beam drawing apparatus) that performs predetermined drawing on a non-drawing object D using a beam.
[0033]
Furthermore, in the above embodiment, the drive control of the AOM 3 during the non-drawing operation is performed based on the drive data. However, the drive control of the AOM 3 can be performed without using the drive data. For example, instead of the drive data stored in the memory 6 in the above embodiment, the drawing data used in the previous drawing operation is stored in the memory 6 and the AOM 3 during the non-drawing operation is stored based on the drawing data. The drive control may be performed.
[0034]
In addition, a temperature detection sensor for detecting the temperature of the AOM 3 can be provided to stabilize the AOM 3 from the actual temperature of the AOM 3. A temperature detection sensor disposed in the vicinity of the AOM 3 detects the temperature of the AOM 3 and transmits a detection result to the control unit 4. In this modified example, the control unit 4 is preliminarily provided with the temperature at which the mounted AOM 3 is stabilized in a steady state as data. The control unit 4 automatically generates a modulation signal that brings the detection result from the temperature detection sensor to a temperature that stabilizes in a steady state, and applies an ultrasonic wave to the AOM 3 as necessary, thereby performing a non-drawing operation. The drive control of the AOM 3 is performed. In this modification, the control unit 4 determines whether the AOM 3 is actually in a steady state based on temperature detection. Therefore, it is possible to display the determination result on the display unit of the laser beam drawing apparatus 100 so that the user can visually confirm the steady state of the AOM 3.
[0035]
【The invention's effect】
As described above, according to the present invention, the first-order diffracted light that becomes the drawing light during the drawing operation can be controlled by controlling the driving of the AOM with the modulation signal based on the drive data even during the non-drawing operation and maintaining the AOM in a steady state. The diffraction direction in the AOM can be always stabilized, and a high-definition and high-quality drawing result can be obtained.
[0036]
In the multi-beam drawing apparatus, a higher-definition drawing pattern can be drawn as the intervals between the divided beams, that is, the intervals between the beam spots formed on the non-drawing body D are more uniform. . Therefore, by applying the present invention to a multi-beam drawing apparatus, the diffraction directions of a plurality of first-order diffracted lights emitted from the AOM can always be stabilized, and a higher-definition drawing result can be obtained.
[Brief description of the drawings]
FIG. 1 shows the operation of an AOM.
FIG. 2 is a schematic configuration diagram of a laser beam drawing apparatus equipped with the AOM steadying system of the embodiment of the present invention.
FIG. 3 is a graph showing the properties of AOM.
FIG. 4 is a timing chart showing AOM drive control according to the embodiment of the present invention.
[Explanation of symbols]
1 Light source 2 Mechanical shutter 3 AOM
4 Controller 5 Driver 6 Memory 50 AOM Steady System

Claims (5)

It has an acousto-optic element that is driven by applying ultrasonic waves and diffracts the incident laser beam, and diffracted light emitted from the acousto-optic element on the drawing surface that moves in the sub-scanning direction In the laser beam drawing apparatus that performs predetermined drawing on the drawing object placed on the drawing surface by scanning,
A light source for irradiating the laser beam;
A dimming means provided between the light source and the acoustooptic device for dimming the laser beam;
During the drawing operation and the translucent said laser beam, together with the time of non-drawing operation for driving and controlling the light control means such that shields the laser beam, regardless of whether it is in drawing operation, always drawn during the drawing operation Control means for driving and controlling the acousto-optic element with a modulation signal having a duty ratio substantially the same as the modulation signal generated by the data ;
An acousto-optic element steadying system in a laser beam drawing apparatus. In the acousto-optic element stationary system in the laser beam drawing apparatus according to claim 1,
Storage means for storing drive data for forcibly driving the acousto-optic element;
The control means converts drawing data corresponding to predetermined drawing contents into the modulation signal so that exposure and non-exposure to the drawing object corresponding to the predetermined drawing contents are performed in each scanning during the drawing operation. Then, the acousto-optic device is driven and controlled, and the drive data read from the storage means is converted into the modulation signal and the acousto-optic device is driven and controlled during non-drawing operation. Acousto-optic element stationary system in apparatus. In the acousto-optic element stationary system in the laser beam drawing apparatus according to claim 2 ,
The control means stores the drawing data in the storage means at the time of drawing, and uses the drawing data stored in the storage means as the driving data at the time of non-drawing. Optical element stationary system. In the acoustooptic device stationary system in the laser beam drawing apparatus according to any one of claims 1 to 3 ,
The acoustooptic device modulates a plurality of laser beams during a drawing operation,
The laser beam drawing apparatus performs drawing by simultaneously scanning a plurality of diffracted lights emitted from the acoustooptic element on a drawing object, and making the acoustooptic element steady in the laser beam drawing apparatus system. In the acousto-optic element stationary system in the laser beam drawing apparatus according to claim 1,
A temperature detecting means for detecting the temperature of the acoustooptic device;
The control means converts drawing data corresponding to predetermined drawing contents into the modulation signal so that exposure and non-exposure to the drawing object corresponding to the predetermined drawing contents are performed in each scanning during the drawing operation. and said acousto-optic device is driven and controlled by, at the time of non-writing operation, the actual temperature detected by said temperature detecting means such that said acousto-optic device matches a predetermined temperature when a steady state, the modulation An acoustooptic element steadying system characterized by automatically generating a signal and drivingly controlling the acoustooptic element.

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