JP3916734B2 - Laser processing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser processing apparatus using a laser.
[0002]
[Prior art]
Because laser light has good coherence, it is easy to control the beam shape, it is possible to emit light in a single wavelength region, and light emission with high energy density from the infrared region to the ultraviolet region by selecting the laser medium In recent years, it has become widely used regardless of fields such as machining and semiconductor processing. For example, in semiconductor processing, a laser processing apparatus is used as an annealing apparatus, a surface modification apparatus, an exposure apparatus, or the like.
[0003]
Recently, gas lasers such as excimer lasers have been widely used because they are simple in constructing laser media, as high-efficiency light emission in the ultraviolet region and high-power lasers in the infrared region. For example, in an excimer laser, pumping is performed by forming excited species such as excimer, which is a metastable compound of a rare gas and a halogen gas, by performing high-pressure glow discharge on a gas filled in a reaction vessel.
[0004]
In order to obtain a large laser output, it is necessary to generate more molecules in an excited state in the reaction vessel. For that purpose, a large output can be obtained by increasing the reaction vessel or increasing the gas pressure in the vessel. However, since the oscillation intensity of the laser light source is insufficient to process a large area with an actual laser processing machine, the workpiece is fixed to the stage and the laser is oscillated in synchronization with the movement of the stage. Therefore, laser processing of a large area is often performed.
[0005]
[Problems to be solved by the invention]
However, when the reaction vessel is enlarged, there is a problem that the space for laser action becomes large, so that the coherence due to resonance deteriorates and the laser characteristics change with time. Further, even when the gas pressure is increased, there is a problem that the laser output and the beam shape change with time due to the temperature rise accompanying discharge and the history of the electrode surface. For example, in the case of an excimer laser which is a pulse laser, it is generally recognized that the stability of the beam intensity and waveform shape for each pulse is a problem.
[0006]
For this reason, if laser irradiation is performed while moving the workpiece placed on the stage, the degree of processing changes due to fluctuations in beam intensity and waveform shape, so that processing by laser cannot be performed uniformly. was there.
[0007]
An object of the present invention is to provide a laser processing apparatus which can perform uniform processing while avoiding the influence on processing due to instability of laser output.
[0008]
[Means for Solving the Problems]
A laser processing apparatus according to the present invention includes a stage for supporting a workpiece, a laser light source for processing the workpiece, detection means for detecting the intensity of laser light emitted from the laser light source, and the detection and a control means for controlling the stage on the basis of the output means. Preferably, the laser light source is an excimer laser.
[0009]
In the above configuration, the intensity of the laser light emitted from the laser light source can be monitored through the detecting means, and it can be detected that the effective intensity is lowered or increased due to the change in the intensity distribution of the oscillation light. Therefore, for example, when the intensity of the laser beam emitted from the laser light source decreases, the movement of the stage is suppressed and laser irradiation is performed again at that position to compensate for the reduction in the degree of processing. In this way, uniform processing can be performed by the laser.
[0010]
The following configurations can be adopted together with the above configuration.
[0011]
The laser light source is a first laser light source, and further includes a second laser light source, and the first laser light source is excited by the second laser light source. Thereby, the first laser light source can be controlled more appropriately.
[0012]
The optical path of the laser light incident on the first laser light source from the second laser light source and the optical path of the laser light emitted from the first laser light source are arranged so as to be approximately parallel, and the laser light is A second control means is provided for weakening the oscillation output of the first laser light source when it deviates from the optical path. As a result, the first laser light source can emit laser light having a uniform beam shape and output direction.
[0013]
The second control means of the present invention uses the intensity of the non-parallel component of the laser light incident from the second laser light source to the first laser light source as a control signal, and uses the intensity of the non-parallel component to generate the first laser. It has the means to weaken the output of a light source, It is characterized by the above-mentioned . Thereby, the first laser light source can be easily and reliably controlled.
[0014]
In the case where the second control means is a shielding plate installed so as to shield the non-parallel component of the laser light incident on the first laser light source from the second laser light source, the second control is performed. The means can be configured easily.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a principle diagram according to a reference example of the present invention. The laser processing apparatus 10 includes a laser light source 14 including a laser medium 12, a half mirror 16, and a stage 20 that supports the workpiece 18 and moves the workpiece 18. The half mirror 16 functions to change the path of the laser light 22 emitted from the laser light source 14 to guide the laser light 22 to the workpiece 18 and to transmit a part of the light 24 and irradiate the sensor 26. The sensor 26 can detect the intensity of the laser light 22 emitted from the laser light source 14. The stage 20 is driven by a stage driving device 28. The stage driving device 28 includes a control device 30. The output of the sensor 26 is sent to the control device 30, and the control device 30 feedback-controls the stage 20 based on the output of the sensor 26.
[0016]
The laser processing apparatus 10 normally performs processing while scanning the workpiece 18 with the laser beam 22 while operating the stage 18. In this case, since the moving speed of the stage 20 is not strictly constant due to mechanical play, friction, etc., the amount of movement of the stage 20 is controlled with respect to the laser, and in the case of a continuous wave laser, the laser irradiation energy intensity is modulated. In the case of a pulse laser, a trigger is given.
[0017]
However, if there is instability such as a change with time of the laser itself, a change in the laser output will appear as a change in the processing state of the workpiece 18 as it is. Therefore, in the present invention, the intensity of the laser beam 22 emitted from the laser light source 14 is monitored through the sensor 26, and it is detected that the intensity distribution of the laser beam 22 has changed and the effective intensity has dropped. In this case, the movement of the stage 20 is suppressed (speed is reduced or stopped), and laser irradiation is performed again at that position to compensate for a decrease in the degree of processing. For this reason, even when a change such as a decrease in the laser intensity is shown, the work of the large-area work 18 is performed in order to keep the intensity of the laser light 22 incident on the work 18 substantially constant. However, it is possible to perform laser processing with a certain quality.
[0018]
FIG. 2 is a diagram showing a basic configuration of the present invention. As shown in the principle diagram of FIG. 1, the laser processing apparatus 10 includes a laser light source 14 including a laser medium 12, a half mirror 16, and a stage that supports the workpiece 18 and moves the workpiece 18. 20, a sensor 26, and a control device 30. Further, in FIG. 2, the laser processing apparatus 10 includes a second laser light source 34 including a laser medium 32. The laser light source 14 described above is referred to as a first laser light source.
[0019]
The first laser light source 14 is excited by the second laser light source 34. That is, the laser light 36 emitted from the second laser light source 34 is directed to the delay circuit 42 through the half mirror 38 and the mirror 40, passes through the delay circuit 42, and then passes through the mirror 44 to the laser of the first laser light source 14. Guided to medium 12. Accordingly, the laser medium 12 of the first laser light source 14 is excited and further amplified by the laser light 36 emitted from the second laser light source 34. Laser light 22 emitted from the first laser light source 14 irradiates the workpiece 18 on the stage 20 from the first laser light source 14.
[0020]
A part of the laser light 24 emitted from the first laser light source 14 enters a sensor 26 that detects the intensity of the laser light 22 emitted from the laser light source 14, and the output of the sensor 26 is sent to the control device 30. . The output of the sensor 26 is one of the stage control signals. A part of the laser light 46 emitted from the second laser light source 34 is guided to the sensor 48 by the half mirror 38. The output of the sensor 48 is input to the control circuit 50 of the first laser light source 14 and is one of the control signals.
[0021]
The operation of the configuration shown in FIG. 2 will be described with reference to FIG. In the figure, the horizontal axis represents time, and the vertical axis schematically represents laser energy. In the case of performing processing with an annealing apparatus, for example, a case of performing crystallization of amorphous silicon with an excimer laser will be described as an example. In order to crystallize amorphous silicon, a certain peak output is required. On the other hand, if excessive energy is applied, the silicon evaporates and becomes defective.
[0022]
FIG. 3A shows an ideal machining state. In this case, the pulse laser output is within the set upper limit A and lower limit B, and processing can proceed without problems.
[0023]
However, in practice, as shown in FIG. 3B, the pulse laser output may exceed the upper limit A or the lower limit B of the energy because of energy fluctuation. In such a case, if processing is performed while moving the workpiece 18 at a constant speed, the history of fluctuations in the energy of the laser oscillation light remains in the processing state of the workpiece 18. For example, sufficient processing may not be performed with the pulse laser output of a, excessive processing may be performed with the pulse laser output of b, or silicon may be evaporated.
[0024]
Therefore, as shown in FIG. 3C, when the sensor 26 detects that the energy of the output of the first laser light source 14 is insufficient, the scanning of the stage 20 is stopped and re-irradiation is performed. It does not cause processing defects with insufficient energy as shown. Further, since the first laser light source 14 is excited by the second laser light source 34, when the sensor 48 detects that the laser light 36 is excessive or insufficient, the delay by the delay circuit 42 is caused. Within a period of time, the control circuit 50 of the first laser light source 14 stops the oscillation of the first laser light source 14, and the laser is re-attacked for both excess and deficiency of excitation light, resulting in a defect. There is no.
[0025]
FIG. 4 is a diagram showing a reference example of the present invention. FIG. 4 includes a first laser light source 14 and a second laser light source 34 similar to the previous configuration . The output of the first laser light source 14 is monitored by a sensor (not shown). Among high-power lasers, gas lasers tend to shift the output direction of oscillating laser light, and in particular, excimer lasers are known to change the energy distribution of the beam. This is because the pumping in the laser medium is performed by corona discharge, so that the distribution of excited species in the chamber is uneven.
[0026]
Therefore, in this reference example, the apparatus is arranged such that the laser beam 36 excited by the laser medium 32 of the second laser light source 34 is incident on the laser medium 12 of the first laser light source 14 as parallel as possible. Thus, a shielding plate 52 for removing the non-parallel component of the laser beam 36 is provided at the entrance of the laser medium 12 of the first laser light source 14. Accordingly, since the excitation of the laser medium 12 of the first laser light source 14 is partially performed by the excitation light of the second laser light source 34, the output direction of the laser light of the second laser light source 34 is indicated by a broken line. Even if there is a deviation, only the component having a constant beam shape and output direction among the excitation laser light 36 oscillated from the second laser light source 34 can enter the laser medium 12 of the first laser light source 14. For this reason, pumping and stimulated emission of the first laser light source 14 are performed with laser light having a constant beam shape and a constant output direction. Therefore, the output laser light 22 of the first laser light source 14 has a beam shape and an output direction. Will oscillate as well-equipped light.
[0027]
Further, when the beam shape or the output direction of the excitation laser beam of the second laser light source 34 is abnormal, the output of the first laser light source 14 is greatly reduced, taking the structure described above, always Only uniform oscillation laser light can be used for processing.
[0028]
FIG. 5 is a diagram showing an embodiment of the present invention. In this embodiment, in addition to the above reference example, the output laser beam 36 of the second laser light source 34 is configured to detect the non-parallel component of the laser beam 36 by the sensor 54 provided on the shielding plate 52. Compared to the above reference example, when the output of the non-parallel component is detected and the non-parallel component is generated, the output of the first laser light source 34 can be stopped, so that excitation by the non-parallel component can be further suppressed. It becomes. Further, since the output of the sensor 54 is used as a monitor signal of the stage movement control device 30, it can be used in place of the signal from the sensor 26 of the previous embodiment. Therefore, it is not necessary to directly monitor the excitation laser beam 22 of the first laser light source 14 having a large output.
[0029]
In the embodiments described above, the gas laser such as an excimer laser is used for explanation. However, the present invention is not limited to this, and a YAG laser, a semiconductor laser, or the like may be used. In particular, as the second laser, it is also possible to use oscillation of high-order harmonics such as a YAG laser.
[0030]
【The invention's effect】
As described above , according to the present invention, uniform processing can be performed regardless of the laser output, which greatly contributes to improving the reliability of the laser processing apparatus.
[Brief description of the drawings]
FIG. 1 is a principle diagram according to a reference example of the present invention.
FIG. 2 is a diagram showing a basic configuration of the present invention.
FIG. 3 is a diagram for explaining the operation of the configuration of FIG. 2;
FIG. 4 is a diagram showing a reference example of the present invention.
FIG. 5 is a diagram showing an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Laser processing apparatus 12 1st laser light source 16 Half mirror 18 Workpiece 20 Stage 26 Sensor 30 Control apparatus 34 2nd laser light source 38 Half mirror 40, 44 Mirror 46 Delay circuit 48 Sensor 50 Control circuit 52 Shielding plate 54 Sensor

Claims (2)

Based on a stage for supporting the workpiece, a first laser light source for processing the workpiece, a detection means for detecting the intensity of the laser light emitted from the laser light source, and an output of the detection means And a control means for controlling the stage,
The laser light source is a first laser light source, and further includes a second laser light source, and the first laser light source is excited by the second laser light source,
The optical path of the laser light incident on the first laser light source from the second laser light source and the optical path of the laser light emitted from the first laser light source are arranged so as to be approximately parallel, and the laser light is A second control means for weakening the oscillation output of the first laser light source when deviating from the optical path;
The second control means uses the intensity of the non-parallel component of the laser light incident on the first laser light source from the second laser light source as a control signal, and determines the intensity of the first laser light source based on the intensity of the non-parallel component. A laser processing apparatus comprising means for weakening output. A first laser light source for processing the workpiece;
A second laser light source for exciting the first laser light source;
The optical path of the laser light incident on the first laser light source from the second laser light source and the optical path of the laser light emitted from the first laser light source are arranged so as to be approximately parallel, and the second And a control means for using the intensity of the non-parallel component of the laser light incident from the laser light source to the first laser light source as a control signal and weakening the output of the first laser light source by the intensity of the non-parallel component. Laser processing equipment.

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