KR20200047591A - Method and apparatus for operation of pulse laser shutter - Google Patents

Abstract

[Task] In scan processing or step and repeat processing using a laser pulse oscillating at a repetition frequency exceeding 100 Hz, the shutter operation is started within the time window between the pulses without interfering with any of the neighboring pulses. Provided is a high-speed shutter operating method and apparatus that makes it possible to end, and to delay the arrival of life due to damage to a shutter element.
[Solution] When the time window between pulses is T, the distance across the laser beam of the shutter element at the entry / exit position of the shutter element is D, the thrust of the drive source for entry and exit is F, and the mass of the shutter element is M, respectively. The parameter satisfies the relational expression (2DM / F) ^1/2 <T, and the energy density irradiated to the shutter element is less than the damage threshold of the element. The workpiece is synchronized with the position of the placed processing stage.

Description

Method and apparatus for operation of pulse laser shutter

The present invention relates to a method and apparatus for operating a shutter that turns on, off or gating pulsed laser light used in laser processing in pulse units.

In a laser processing apparatus using pulsed laser light, there is a case in which so-called scan processing is performed on a workpiece placed on a moving processing stage by one shot without stopping the processing stage. In this case, the pulse energy of each laser pulse needs to be constant and stable.

This is the same also in the case of performing step and repeat processing in which a predetermined number of laser pulses are irradiated to the workpiece, and it is necessary to precisely control the processing depth based on the etching rate per shot.

In any processing, it is common for the pulse laser device of the light source to receive and oscillate the signal for external trigger oscillation generated based on the encoder signal output according to the position of the processing stage. The laser pulse is turned on, off, or gated by turning the external trigger signal on or off, or by opening and closing a mechanical shutter provided externally to the laser pulse train once oscillated. It is common to control the irradiation of laser pulses.

However, in the case of control by turning on or off the external trigger signal, it is known that the pulse energy of several to tens of pulses immediately after oscillation, or the pulse energy of a pulse within a predetermined time immediately after oscillation is known to be unstable. It is necessary to exclude this by mechanical shutter operation so that it is not used for processing.

In addition, the transverse mode of the laser pulse within the time between adjacent laser pulses in time (within the time window between pulses), especially when the pulsed laser is turned on, off, or gated by a mechanical shutter when the laser pulse is oscillating at a high repetition frequency. A shutter operation is required to move the area covering the distribution (beam size) at a high speed at once.

Specifically, for example, in the case of an excimer laser oscillating at 200 Hz, the time window between pulses is about 5 ms, and the length (width) of the rectangular beam in the minor axis direction is about 5 mm. Therefore, the speed required for the opening and closing operation of the shutter that can be turned on and off without interfering with any of the neighboring laser pulses is 1000 mm / s or more. However, it is not easy to realize this without involving the enlargement of the shutter device, even in the case of simple repeating operations such as scan processing, as well as in the case of step and repeat processing where it is necessary to repeat shutter opening and closing at different timings in a short time. .

In order to solve this, for example, it is conceivable to condense the width of 5 mm to 1 mm or less by using a condensing lens or the like, to shorten the distance that the shutter member must cross, but considering damage to the shutter member, , The insertion position cannot be close to the condensing point. Therefore, it is necessary to speed up the operation of the shutter member.

Patent Document 1 discloses a shutter unit mainly developed for continuous wave lasers. When this mechanism is applied to, for example, an excimer laser that oscillates at the repetition frequency of 200 Hz described above, that is, a pulse laser having a time window between pulses of about 5 ms, the response speed in rotational driving such as a reflection mirror is this. The equivalent of 5ms is not enough. In addition, even if the response speed is increased, there is a concern that damage to the reflective mirror that repeatedly operates the shutter in the beam waste is concerned.

Patent Document 2 discloses a burst mode control technique in which a predetermined number of laser pulse trains are turned on / off at a high speed by synchronously rotating two cylindrical shutter units having apertures. However, the processing time from on to off is long, and it is necessary to repeat this in a short period of time for a scan processing for a large workpiece that needs to be shuttered at a high speed when switching on / off, or at an arbitrary timing. Regarding the step and repeat processing, it cannot be said that the shutter operation by this rotating body is an appropriate configuration. In addition, although the use of a straight stage instead of a rotating body is mentioned, there is no description of a detailed method of implementation, and there is no fear of damage to the shutter unit.

Patent Document 1: Japanese Patent Publication No. 2010-264501 Patent Document 2: Japanese Patent Publication No. 2015-76537

The present invention was made in view of the problems of the above-described background in scan processing or step-and-repeat processing using (pulse) laser light whose pulse-to-pulse time window oscillates at a repetition frequency in ms, and any Provided is a high-speed shutter operation method and apparatus capable of initiating and terminating a shutter operation within a time window between pulses without interrupting any of the neighboring laser pulses, and further extending the life of the shutter element. The purpose.

The first invention is a laser processing apparatus using a laser beam having a repetition frequency exceeding 100 [Hz] and oscillating at 1 / T [Hz], which propagates toward the workpiece placed on the processing stage. A method of operating a pulsed laser shutter that turns on or off or pulses a laser pulse irradiated to a workpiece by entering and exiting a shutter element on the optical axis of the laser light and changing or blocking the overall direction thereof, at a position of the processing stage. A step of generating an external trigger signal for oscillating an arbitrary number of laser pulses based on the encoder signal according to the step, and a step of forming a lateral mode distribution shape of the laser light oscillating based on the external trigger signal by a molding optical system. , For a drive source for entering and exiting the shutter element, determining a timing of starting the operation in synchronization with the external trigger signal High, including the step of transmitting, the moving distance of the shutter element over the width of the molded laser light traversed by the shutter element at the entrance and exit position of the shutter element D [m], the thrust of the drive source F [N], when the total mass of the fixing jig for fixing the shutter element to the driving source and the shutter element is M [kg], the D, F, M and T are related formulas (2DM / F) ^1/2 It is a method of operating a pulsed laser shutter that satisfies < T and the pulse energy density of the laser pulse received by the shutter element at the entry / exit position is less than the damage threshold (threshold) of the shutter element.

In the present invention, &quot; turning on / off in pulse units &quot; means that the shutter element is moved (shutter) in part or all of the lateral mode distribution of the laser pulse without interfering with any of the adjacent laser pulses in time. Refers to switching between the passing state (opening) of the laser pulse and the blocking state (closing) including the change in the first half direction without being blocked by the opening / closing). In addition, the term "gating" means that the laser pulse therebetween is not irradiated to the workpiece by changing or blocking only a predetermined time or a fixed number of laser pulses by a combination of on and off, and changing the overall direction thereof.

"The shutter element 1 enters and exits the optical axis of the laser light", as shown in Fig. 1, is an amount shown in the horizontal mode distribution of the laser light as the shutter element 1 moves, for example, by a voice coil motor (not shown). It means that it is inserted in the direction of the arrow or removed. Then, the insertion (release) direction is perpendicular to the optical axis, making the time required until the shutter element 1 intrudes into the transverse mode distribution of laser light and blocks (receives) all of them. Direction is preferred.

The "less than the threshold of damage" not only takes into account the peak power density, but also the damage threshold by irradiation of a single pulse, as well as laser processing continuously irradiating laser pulses oscillating at a high repetition frequency, which is the application of the present invention. Refers to a criterion for determining the damage threshold value that realizes the cumulative number of shots without damage, which is expected in the apparatus.

For example, in the case of a shutter element made of synthetic quartz, even when the specifications of the pulse laser are fixed at a wavelength of 248 nm, a pulse width of 25 ns, and a repetition frequency of 200 Hz, the damage threshold values are as shown in Tables 1 and 2 below. It varies according to the expected number of shorts without damage. Therefore, in view of the pulse energy required for laser processing or the duty cycle of processing, after considering the damage threshold value at which the shutter element can receive the expected cumulative number of shots without causing damage, the optimum pulse energy density at the shutter position Will set In addition, as a criterion of damage in FIG. 2, it is assumed that the transmittance is substantially reduced to 1/2.

Energy density
[mJ / cm ² ] Cumulative number of shorts until damage occurs
[short] 50 1 × 10 ⁹ 500 3 × 10 ⁸ 5,000 2 × 10 ⁷ 10,000 5 × 10 ⁶ 15,000 2 × 10 ⁶

Further, for example, in the case of an Nd: YAG laser having a Gaussian distribution in which the lateral mode distribution of the laser light is used, an optical fiber or a lens is used in consideration of the damage threshold, and this is enlarged, so that the width of the laser light traversed by the shutter element (eg For example, the length in the short axis direction) is molded. On the other hand, in the case of an excimer laser having a large rectangular transverse mode distribution compared to an Nd: YAG laser, a lens or the like is used to reduce this to shorten its short length.

The shutter element includes, but is not limited to, changing the propagation direction using refraction like a prism, or blocking using reflection like a mirror.

The second invention is a method of operating a pulse laser shutter using a voice coil motor as a driving source in the first invention.

For the voice coil motor, one having a thrust of tens of N may be selected even if the stroke is short. By suppressing the mass of the shutter element to be driven, high-acceleration operation can be realized. For example, in the voice coil motor used in the examples of the present invention, those having a peak thrust of 38N were used.

The third invention is a method of operating a pulse laser shutter in the first or second invention, wherein the shutter element is an element made of a member transparent to the wavelength of laser light.

As the member, one having a high transmittance with respect to the wavelength of the laser light, such as an optical element such as a prism, may be selected. Further, by providing a dielectric multilayer film that prevents reflection of laser light on the irradiated surface, high transmittance can be obtained. However, it is not suitable for use in environments with low damage thresholds.

The 4th invention is a 1st or 2nd invention, The operation method of the pulsed laser shutter which is an element which a shutter element consists of a member which reflects this with respect to the wavelength of a laser beam. As the member, an optical prism or the like in which a reflective film is provided on a surface to be irradiated with laser light other than an optical mirror can be used.

A fifth aspect of the present invention is a pulsed laser shutter that turns on, off, or gates a laser pulse propagating toward a workpiece placed on a processing stage in a laser processing apparatus using the pulsed laser light, in a transverse mode of laser light. A molding optical system for forming a distribution shape, a shutter element for changing or blocking the overall direction of the laser light, a driving source for entering and exiting the shutter element from the optical path, at least a pulse laser light source, the processing stage and the operation of the driving source A timing controller that transmits and receives signals to be controlled, and the timing controller is a pulse laser shutter that transmits signals to the processing stage, the pulse laser light source, and the driving source based on an encoder signal corresponding to the position of the processing stage. .

The sixth invention is a pulse laser shutter according to the fifth invention, wherein the driving source is a voice coil motor.

In the seventh invention, in the fifth or sixth invention, the shutter element is a pulse laser shutter which is an element made of a member transparent to the wavelength of laser light.

In the eighth invention, in the fifth or sixth invention, the shutter element is a pulse laser shutter which is an element composed of a member that reflects it with respect to the wavelength of laser light.

The invention of any one of the ninth to eleventh embodiments is a pulse laser shutter using the pulse laser light source as an excimer laser according to any one of the fifth to eighth inventions.

According to the present invention, in step and repeat processing or scanning processing using a laser pulse oscillating at a high repetition frequency exceeding 100 Hz, the laser pulse within the time window between the pulses does not interfere with any of the neighboring laser pulses. It is possible to realize a long-life shutter operation for starting and ending on (or off).

1 shows the state of entry and exit of the shutter element with respect to the laser light collected by the relay lens.
2 shows the relationship between the damage threshold and the cumulative number of shots.
3 shows the state of the scan processing for the workpiece.
4 shows a laser processing device equipped with a laser shutter device.
5 shows the shape of a shutter element made of a prism.
6A shows a state in which a shutter element is mounted on a voice coil motor as a fixing jig.
Fig. 6B shows a real picture of each part of the shutter element and the fixing jig.
Fig. 7 shows a shutter element inserted into a telescope by a combination of a flat iron cylindrical lens.
8A shows a state (side) in which the shutter element is inserted into and extracted from the laser beam.
8B shows a state in which the shutter element is inserted into and removed from the laser light (another side).
9 shows a trigger timing chart.

Hereinafter, an aspect of the pulse laser shutter and the operation method thereof according to the present invention will be described in detail with reference to the drawings.

[Example]

As an embodiment of the present invention, a laser shutter to be used for one shot scan processing in the Y-axis direction at a 0.1 mm pitch is performed on the workpiece 7 placed on the X, Y, Z, and θ-axis-driven processing stages. . The basic shutter operation is an opening / closing operation for switching the laser light from an off (closed) state to an on (opened) state. In addition, as will be described later, it is common to turn the laser light on and off by turning off the external trigger signal to the laser device, and this method is also used in this embodiment.

First, the state of processing in this embodiment is shown in FIG. 3. The size of the workpiece 7 is 300 x 300 mm, and the total number of processing points is 0.1 mm pitch, and 2,000 x 2,000 = 4,000,000 points. In addition, "Y" shown in the figure is the Y-axis processing stage 6, and "X" is the direction moved by the X-axis processing stage.

4 shows a schematic configuration of the entire laser processing apparatus according to the present invention. In this example, an excimer laser 4 having an oscillation wavelength of 248 nm was used as the pulse laser light source. In addition, the repetition frequency (1 / T) when processing the above-described 0.1 mm pitch by a constant velocity motion of 20 mm / s is 200 Hz. If the pulse width of a typical excimer laser is about 25ns, the time window T between pulses is 5ms.

In addition, the shape of the lateral mode distribution of the laser beam is 5 mm in short axis and 24 mm in long axis immediately after exiting, and the beam diffusion angle is 1 × 3 mrad. As the pulsed laser light source, a Q-switched Nd: YAG laser or CO ₂ laser may be used in addition to this, but a pulsed laser light source that is an appropriate combination depends on the material of the workpiece 7, in particular, absorption characteristics for the wavelength of the laser light. You need to choose.

Next, the shutter element 1 used in this embodiment is a right angle prism made of synthetic quartz shown in Fig. 5 having a transmittance of 248 nm or more of 90% or more, and the length of each side is a = 10mm, b = 10mm, c = It is 30mm. By injecting a laser pulse to the irradiated surface 12 of this shutter element, refracting it, and changing its overall direction, on, off or gating of the laser pulse irradiated to the work 7 is realized. In addition, no coating is applied to any surface including the surface 12 to be irradiated. This is because damage caused by laser irradiation is concerned.

Moreover, this shutter element 1 was fixed to the voice coil motor 2 selected as the driving source using a fixing jig 13. The state is shown in Fig. 6A. 6B shows a real picture of the shutter element 1 and the fixing jig 13. In addition, the mass (M) of these totals is 10 g.

The specifications of the voice coil motor are shown in Table 2 below, and the specifications of the driver (amplifier) used for its control are shown in Table 3 below. Here, the peak thrust is the thrust when the instantaneous operation is performed in a low duty situation as in the present embodiment, and is larger than the rated thrust in the continuous operation. In addition, the peak thrust of the voice coil motor depends on this control driver. The peak thrust of the voice coil motor used in this example is 38N.

Specification item Shame Driving direction 1 axis (linear drive) Linear stroke 12mm + 1 / -0mm Peak thrust 38N @ 6A, 48Vdc Rated thrust 8.5N / A Encoder resolution 5 / 1.0 / 0.5 / 0.1㎛ Moving mass (max) 59g

Specification item Shame Peak current 9Adc Rated current 3Adc Peak output 1.59kW Rated power 0.53kW feedback Analog encoder (sin / cos)

The pulse energy required in one shot scan processing in this embodiment is generally 100 mJ in the step before attenuation by the reduced projection optical system or the like. In addition, the position is a position about 2 m away from the exit port of the excimer laser 4, and the beam shape in this position is generally short axis 8 mm x long axis 25 mm. Therefore, when entering and exiting the shutter element 1 at this position, the pulse energy density on the irradiated surface 12 is about 35 mJ / cm ² when considering 45 ° incidence.

The pulse energy density of this degree is equal to or less than the damage threshold value (50 mJ / cm ² ) of the right angle prism in this case, even if the expected number of undamaged accumulated shots is 1 × 10 ⁹ shots, and D is the beam shape. If 8mm, F = 38N, T = 5ms, and M = 10g, which are the same as the short axis length of (2MD / F) ^1/2 <T, the conditional expression of the present invention is satisfied ((2 × 0.01 × 0.008 / 38) ^{1 / 2} ≒ 0.0021 <0.005).

However, in this embodiment, in order to have the laser light from the blocked state (closed) to the released state (opened) with a spatial margin within the time window, the shortening direction of the beam shape is further increased from 8 mm to 5 mm described above by the forming optical system. On the other hand, on the other hand, the shutter element 1 sufficiently covers this 5 mm, and the distance D to move across is set to 10 mm, which is the same as the size (a or b) of the shutter element. Here, if the conditional expression is recalculated, (2MD / F) ^1/2 = (2 × 0.01 × 0.010 / 38) ^1/2 ≒ 0.0023 <0.005, and in this case, a combination of practical parameters with margin was obtained. .

The overall appearance of the laser light is as follows. The laser beam 41 having a rectangular lateral mode distribution emitted from the excimer laser 4 is relayed by two flat-iron lenses 3 (made of synthetic quartz) having a focal length of f = 600 mm, and a telescope at the rear end. It is general to the optical system. As shown in Fig. 1 (and Fig. 8A), in the shutter element 1, the position after the laser beam propagates 300 mm from the focal position of the first flat iron lens 3 as the entry / exit position. The beam size in this position is about 5 mm in the minor axis direction and about 15 mm in the long axis direction (all FWHM).

Thereafter, the laser light 41 that has passed through the second flat-iron lens is propagated by a homogenizer positioned at the rear end to obtain a uniform energy distribution in the lateral mode distribution. In addition, since the optical system 5 after the homogenizer is the same as a general reduced-image optical system, its details are omitted and simplified in FIG. 4.

The shutter element 1 may be installed in a telescope by a combination of two flat-cylindrical cylindrical lenses, as shown in Fig. 7, in addition to the relay lens configuration of this flat-iron lens. However, in this embodiment, as described above, the pulse energy density of the laser light 41 irradiated on the irradiated surface 12 of the shutter element is as low as 35 mJ / cm ² , and the cylindrical lens as shown in FIG. 7 is used. After forming a long elongated rectangular beam to shorten the shortening of the laser beam to be traversed, it was not made into a configuration that suppresses the pulse energy density low.

8A and 8B show the positional relationship of the shutter element 1 with respect to the laser light 41. In any of the drawings, the moving direction of the shutter element 1 is indicated by both arrows. In addition, the shutter element 1 inserted in the laser beam 41 is indicated by a solid line, and the fully removed shutter element is indicated by a dotted line. In addition, as described above, the position of insertion and extraction into the laser beam is a position after generally propagating 300 mm from the position of the beam waist portion 42 formed by the flat iron lens 3.

The lateral mode distribution of the laser light 41 at this position is a rectangle with a short axis of 5 mm and a long axis of 15 mm as described above, and in the shutter element 1, the edge portion 11 of the lateral mode distribution is shortened in the shutter element 1. Is extracted / inserted perpendicular to the optical axis. Then, in the present embodiment, this rectangular lateral mode distribution is drawn from the shutter closing state (drawing with a solid line in Fig. 8B), which is cut off with a spatial margin, and the shutter opening state (drawing with a dotted line in Fig. 8B). ), The distance to be moved in the shortest time was set to 10 mm. In addition, the dashed-dotted line in the figure represents the optical axis, the dashed-dotted line represents the normal to the irradiated surface 12, and the incident angle θ of the laser light is 45 ° from the normal. In addition, the size of the right-angle prism (shutter element 1) and the beam diffusion angle of the laser light 41 are exaggerated.

In the case of this embodiment, as shown in Fig. 8B, the time required for the instantaneous switching operation from the shutter closing to the opening for the laser light 41, that is, the time that the edge portion 11 of the shutter element moves 10 mm to the shortest. Is about 2.3 ms as described above. In addition, at this time, it is not necessary to consider the travel distance overrun by the deceleration until the shutter element stops (indicated by a gray dotted line in the drawing). This is because when the shutter is closed, the external trigger to the laser device 4 is turned off instead of performing the opposite operation when opened.

On the other hand, in contrast to the present embodiment, when it is necessary to repeatedly turn on and off the laser light by a shutter opening and closing operation in a short time, it is necessary to consider the time of acceleration and deceleration when the shutter element moves. . When the edge portion 11 of the shutter element moves 10 mm and stops, the shutter operation time is approximately 3.2 ms due to the acceleration movement of 5 mm and the deceleration movement of 5 mm (2 × 0.01 × 0.005 / 38) ^1/2 × 2. do. Also, in this case, the conditional expression (<5 ms) according to the present invention is satisfied.

Next, a more specific operation timing of the shutter will be described using transmission / reception of signals input / output to each part constituting the laser processing apparatus.

In one shot scan processing shown in Fig. 2, what is used as the Y-axis processing stage 6 is a stage for driving a DC servo motor with a linear encoder with a speed of 20 mm / s and an acceleration of 40 mm / s ² . During scan processing, the position information (signal 2) is output from the linear encoder (Y axis) to the stage motion controller as a timing controller. The stage motion controller receiving this position information generates and outputs a TTL signal (signal 3) for external trigger oscillation to the excimer laser 4 based on the arbitrary position information.

In this embodiment, the Y-axis machining stage 6 transmits the signal 3 for processing at a pitch of 0.1 mm (FIG. 3) to a excimer laser 4 over a distance of 200 mm stably performing a constant velocity motion of 20 mm / s. Output. As a result, the excimer laser 4 that received the signal 3 irradiates the laser at a repetition frequency of 200 Hz.

As described above, the time window between pulses at this time is 5 ms when the pulse width (about 25 ns) of the laser is ignored, and the shutter element 1 moves the edge portion 11 10 mm from a predetermined position to close the shutter. It can be said that it is a sufficiently long time compared with the time (2.3 ms) required for opening from. Therefore, it can be turned on, off or gated in units of laser pulses without the shutter element interfering with neighboring laser pulses.

The operation timing of each part constituting the laser processing apparatus through the whole is as follows. First, the Y-axis machining stage 6 on which the workpiece 7 is placed is moved to a standby position (indicated by "0mm" in Fig. 9) corresponding to the machining position. Next, the shutter element 1 is driven by the voice coil motor 2, where the irradiation of the laser light 41 is received near the center of the irradiated surface 12 (shown in solid lines in FIGS. 8A and 8B). When moving and inserting to the position of the shutter closing) and receiving the irradiation of the laser beam 41, the laser beam 41 is not irradiated to the workpiece 7 by refraction by the shutter element 1 (( Also, at this point in time, the signal 3 of the external trigger has not yet been transmitted to the excimer laser 4, and there is no irradiation of the laser light 41 to the shutter element 1.

Next, upon receiving an instruction to start machining (signal 1) from the operator, the Y-axis machining stage 6 starts moving at the acceleration of 40 mm / s ² from the standby position, and moves at a constant speed of 20 mm / s at a position of 5 mm movement. It becomes. The stage motion controller which received the output signal 2 from the encoder according to the position along with the movement of the Y-axis machining stage 6 starts transmission of the external trigger signal 3 to the excimer laser at this 5 mm movement time. At this time, the excimer laser 4 is ready for oscillation in an external trigger oscillation mode, and when this signal 3 is received, it is laser oscillated.

Further, in the case of a typical excimer laser, the delay time from receiving the external oscillation TTL signal (signal 3) to the actual laser pulse oscillation is about 1 µs. However, in the present embodiment, it is sufficiently short compared to 5 ms of the time window between pulses, so that it does not affect the on, off or gating operation of the laser pulse.

The Y-axis machining stage 6 also moves a distance of 5 mm with a constant velocity motion of 20 mm / s. In this embodiment, 50 pulses, which is the number of laser pulses from the excimer laser 4 oscillated in the meantime, is located in the shutter closing position (solid line position in Figs. 8A and 8B). Gating is performed (blocks). Then, the gating is released from the next 51 pulse (opening the shutter), and the pulse is used for processing.

This is, as described above, in order to obtain stable machining precision, immediately after the oscillation including the unstable laser pulse of pulse energy among the laser pulses in which the Y-axis machining stage 6 started to oscillate while changing from an acceleration movement to a constant velocity movement. The 50 pulses of is excluded by gating.

The stage motion controller is used to extract the shutter element 1 from the gating position in the time window (5 ms) between pulses between the 50th and 51st pulses with respect to the control amplifier of the voice coil motor 2. The drive signal 4 is transmitted.

The fine adjustment of the transmission time of the drive signal 4 can be performed by measuring the pulse energy after the 51th pulse. For example, when the pulse energy of the 51st pulse is lower than that of the subsequent laser pulse (52th pulse), the 51st pulsed laser light is interfering with the shutter element 1 (partly irradiated). Since it is considered, the fine adjustment of the transmission time of the drive signal 4 is performed quickly, for example, in 1 ms steps. Further, when the pulse energy of the 50th pulse is measured, fine adjustment is made similarly to delay the transmission time of the drive signal 4. In addition, the difference between the 50th and 51th pulses is the total number of pulses of the signal 3, which is an external trigger to the excimer laser, of the number of laser pulses to be used for processing (2,000 pulses in this embodiment) or the shutter element. The changed number of laser pulses (50 pulses in this embodiment) and the pulse energy of either can be easily determined from the actual number of shots.

The external oscillation trigger to the excimer laser 4 (after the Y-axis machining stage 6 moves 200 mm from the start of machining (shutter opening), i.e., when the irradiation number of laser pulses to the work piece 7 reaches 2,000 shots ( Stop signal 3). Thereafter, the X-axis and Y-axis machining stages are moved to the standby position for the next row of scan machining, and during that movement, the shutter element is again moved to the gating position. Thereafter, the same operation is repeated to perform one shot scan processing at a total of 2,000 × 2,000 locations.

It can be used in the whole laser processing apparatus using a pulsed laser light source.

1 shutter element
11 Edge
12 Irradiated surface
13 Fixing jig
2 Voice coil motor (VCM)
3 flat lens
4 excimer laser
41 Laser light
42 beam waste
5 Rear-end optical system (other than homogenizer)
6 Y-axis machining stage
7 Workpiece

Claims (11)

In a laser processing apparatus using a laser beam having a repetition frequency exceeding 100 [Hz] and oscillating at 1 / T [Hz], the shutter element enters and exits the optical axis of the laser beam propagating toward the workpiece placed on the processing stage. , As a method of operating a pulsed laser shutter that turns on or off or gating laser pulses irradiated to a workpiece by changing or blocking the overall direction thereof,
Generating an external trigger signal for oscillating an arbitrary number of laser pulses based on an encoder signal according to the position of the processing stage;
Forming a horizontal mode distribution shape of the laser light oscillating based on the external trigger signal by a molding optical system;
And a step of determining the timing of starting the operation in synchronization with the external trigger signal and transmitting the driving source for entering and exiting the shutter element,
The moving distance of the shutter element over the width of the formed laser beam traversed by the shutter element at the position of entry and exit of the shutter element is D [m], the thrust of the drive source is F [N], and the drive source is When the total mass of the fixing element for fixing the shutter element and the shutter element is M [kg], the D, F, M and T satisfy the relational expression (2DM / F) ^1/2 <T, and
A method of operating a pulsed laser shutter in which the pulse energy density of a laser pulse received by the shutter element is less than a damage threshold value of the shutter element in the position of the entry and exit. According to claim 1,
A method of operating a pulse laser shutter, wherein the driving source is a voice coil motor. The method according to claim 1 or 2,
A method of operating a pulse laser shutter, wherein the shutter element is an element made of a member transparent to the wavelength of laser light. The method according to claim 1 or 2,
A method of operating a pulsed laser shutter, wherein the shutter element is an element composed of a member that reflects it with respect to the wavelength of the laser light. In a laser processing apparatus using a pulsed laser light, as a pulsed laser shutter that turns on, off or gates a laser pulse propagating toward a workpiece placed on a processing stage in units of pulses,
A shaping optical system for shaping the transverse mode distribution of the laser light;
A shutter element that changes or blocks the overall direction of the laser light,
A driving source for entering and exiting the shutter element from the optical path;
At least, it has a pulsed laser light source and a timing controller for transmitting and receiving signals for controlling the operation of the processing stage and the driving source,
The timing controller transmits signals to the processing stage, the pulse laser light source, and the driving source based on an encoder signal corresponding to the position of the processing stage. The method of claim 5,
The pulse laser shutter is a voice coil motor. The method according to claim 5 or 6,
A pulsed laser shutter, wherein the shutter element is made of a member transparent to the wavelength of laser light. The method according to claim 5 or 6,
A pulse laser shutter, which is an element in which the shutter element is a member that reflects it with respect to the wavelength of the laser light. The method according to claim 5 or 6,
A pulse laser shutter in which the pulse laser light source is an excimer laser. The method of claim 7,
A pulse laser shutter in which the pulse laser light source is an excimer laser. The method of claim 8,
A pulse laser shutter in which the pulse laser light source is an excimer laser.

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