JP4721293B2 - Laser processing method - Google Patents

Description

  The present invention relates to a laser processing method for performing processing by irradiating a workpiece with a laser beam.

  FIG. 9 is a schematic view showing a conventional laser processing apparatus for forming grooves.

  For example, a pulse laser beam is emitted from the laser light source 51 at a frequency of 1 kHz. The laser beam is made uniform (top flat) by the homogenizer 52 and the pulse energy density of the beam cross section is made uniform (top flat), and then the cross section is shaped into a circle by a mask 53 having a circular through hole, for example. The light is reflected by the reflection mirror 54 and enters the substrate 56 through the condenser lens 55. The substrate 56 is, for example, a substrate in which an ITO film is formed on a glass base material. The laser beam is incident on the ITO film of the substrate 56. The beam spot of the laser beam on the ITO film surface is, for example, a circle having a diameter of 0.2 mm. The substrate 56 is placed on the XY stage 57. The XY stage 57 can move the incident position of the pulse laser beam in the surface on the substrate 56 by moving the substrate 56 in a two-dimensional plane.

  First, the XY stage 57 is moved so that the pulsed laser beam is irradiated onto the substrate 56 at a 50% overlap rate, and a groove is formed in the ITO film of the substrate 56. Here, the overlapping rate means the ratio of the moving distance in the radial direction of the circle per shot of the laser beam with respect to the diameter of the circle.

  FIG. 10A is a schematic plan view of a substrate 56 in which continuous holes are formed by a laser beam irradiated at a 50% overlap rate and grooves are formed in the ITO film. The opening of the groove is indicated by a bold line. Grooves are formed as a result of continuously drilling holes having a shape depending on the beam spot of the laser beam incident on the ITO film. For this reason, the edge of the opening along the length direction of the groove has irregularities due to a part of the outer periphery of the circular beam spot. When the frequency of the irradiated laser beam is 1 kHz and the beam spot of the laser beam on the ITO film of the substrate 56 is a circle having a diameter of 0.2 mm, the processing speed is 100 mm / s. Mainly determined by the operating speed of the XY stage 57 and making the machining speed higher than this cannot be adopted in view of the uniformity of the machining shape.

  In order to bring the edge of the opening of the groove formed in the ITO film close to a straight line, a method of increasing the overlapping rate is used. For example, the XY stage 57 is moved on the ITO film of the substrate 56 so that the pulse laser beam is irradiated at a 90% overlap rate, thereby forming a groove.

  FIG. 10B is a schematic plan view of the substrate 56 in which continuous holes are formed by a laser beam irradiated at a 90% overlap rate and grooves are formed in the ITO film. Similar to FIG. 10A, the opening of the groove is indicated by a bold line. The edge of the opening along the length direction of the groove approaches a straight line. However, since the laser beam is irradiated at an overlap rate of 90%, the processing speed is one fifth of that when the overlap rate is 50%, that is, 20 mm / s. Although the shape of the opening can be improved, the time efficiency of processing deteriorates.

  FIG. 11 is a schematic cross-sectional view of the substrate 56 taken along the line PQ in FIG. 10A. Grooves are formed in the ITO film formed on the glass substrate. The side surface of the groove is inclined with respect to the surface of the substrate 56. It is desirable that the groove has a more side face shape.

  An object of the present invention is to provide a laser processing method capable of performing high-quality processing in a time-efficient manner.

According to one aspect of the present invention, waving the traveling direction of the adjusted laser beam to have a spread angle of Jo Tokoro, disposed in a position parallel spaced from the surface by a predetermined distance and the workpiece surface The proximity mask having a through hole is irradiated with the laser beam, and the laser beam that has passed through the through hole is incident on the surface of the object to be processed, so that the shape of the through hole is formed on the surface of the object to be processed. A step of transferring, the predetermined spread angle and the predetermined distance within a range in which the predetermined distance is 0.5 mm or less and the predetermined spread angle is 0.5 mrad or less; And a step of setting the predetermined divergence angle within a range of 0.1 mrad or less and greater than 5 mm and 2.0 mm or less .
According to another aspect of the present invention, the laser beam adjusted to have a predetermined divergence angle is moved in a direction parallel to the surface of the workpiece and separated from the surface by a predetermined distance. The proximity mask having a through hole is irradiated with the laser beam, and the laser beam that has passed through the through hole is incident on the surface of the object to be processed, so that the shape of the through hole is formed on the surface of the object to be processed. Transferring, at least one of the predetermined divergence angle and the predetermined distance, the accuracy with which the shape of the through hole is transferred to the surface of the workpiece, the divergence angle of the laser beam, and the proximity mask And a step of setting based on a relationship obtained in advance with respect to the distance to the surface of the workpiece.

  High-precision processing can be performed at high speed by performing laser processing using a proximity mask using a beam scanner that changes the traveling direction of the laser beam. Further, based on the numerical relationship that the transfer accuracy, the laser beam divergence angle and the proximity gap must satisfy, the proximity gap and the divergence angle are determined when processing is performed with the desired transfer accuracy. It can be easily selected.

  FIG. 1 is a schematic view of a laser processing apparatus for performing a laser processing method according to a first embodiment of the present invention.

  A third harmonic (wavelength 355 nm) of an Nd: YAG laser is emitted from a laser light source 1, for example, an Nd: YAG laser oscillator including a wavelength conversion unit, with a pulse energy of 1 mJ / pulse and a pulse width of 50 ns. The laser beam is incident on the conical optical system 4 through a variable attenuator 2 that adjusts the pulse energy and an expander 3 that expands the beam diameter and emits it as parallel light. The conical optical system 4 includes a pair of conical lenses 4a and 4b. The pair of conical lenses 4a and 4b are of the same type, for example, and are arranged so that the bottom surfaces face each other. The laser beam is incident on the conical lens 4a from the axial direction of the right cone so that the center of the beam section overlaps the apex of the right cone portion, and is emitted from the conical lens 4b. The conical optical system 4 converts the beam profile of the incident laser beam so that the intensity is weak at the center of the beam cross section and strong at the periphery. This will be described in detail later. For the conical optical system 4, a convex lens can be used instead of the conical lens 4b on the laser beam emission side.

  The laser beam emitted from the conical optical system 4 passes through, for example, a mask 5 having a rectangular through hole and an objective lens 6 that forms an image of the rectangular through hole of the mask 5 on the substrate 12. The mask 5 and the objective lens 6 can be moved in a direction parallel to the traveling direction of the laser beam by voice coil mechanisms 9 and 10 (which can be replaced by a driving mechanism such as a piezo driving mechanism), respectively. The movement by the voice coil mechanisms 9 and 10 is performed by a signal transmitted from the controller 11. The substrate 12 is placed on the holding table 8.

  The laser beam condensed by the objective lens 6 enters the galvano scanner 7. The galvano scanner 7 includes an X scanner 7a and a Y scanner 7b, and scans a laser beam in a two-dimensional direction at high speed. The X scanner 7a and the Y scanner 7b are both configured to include a swingable reflecting mirror. When the X direction and the Y direction orthogonal to each other are defined on the substrate 12 held by the holding table 8, the X scanner 7a and the Y scanner 7b each of the laser beams condensed by the objective lens 6 are used. The laser beam is scanned so that the incident point moves on the surface of the substrate 12 in the X direction and the Y direction. The galvano scanner 7 can scan the laser beam in a two-dimensional direction by combining the X scanner 7a and the Y scanner 7b.

The substrate 12 that is the object to be processed is, for example, a substrate in which an ITO film is formed on a glass base, and the laser beam is incident on the ITO film of the substrate 12 at a processing energy of about 1 J / cm ² .

  FIG. 2 is a schematic diagram showing an optical path of a laser beam that scans the substrate 12 through the mask 5, the objective lens 6, and the galvano scanner 7.

When the laser beam is incident on the incident position M on the substrate 12, the through hole of the mask 5 is imaged on M. Further, when the optical path length from the mask 5 to the objective lens 6 is a, the optical path length from the objective lens 6 to the incident position on the substrate 12 is b, and the focal length of the objective lens 6 is f, the through hole of the mask is the substrate 12. In order to form an image above, the relational expression (1 / a) + (1 / b) = 1 / f (1)
Must be met.

  The operation position of the galvano scanner 7 changes the incident position of the laser beam from the incident position M on the substrate 12 to N. If the incident angle to the incident position M is different from the incident angle to the incident position N, and the mask 5 and the objective lens 6 remain fixed, the optical path length from the objective lens 6 to the incident position M and the objective lens 6 Therefore, the through-hole of the mask 5 does not form an image on N.

  In the laser processing apparatus shown in FIG. 1, the controller 11 sends signals for moving the mask 5 and the objective lens 6 to the voice coil mechanisms 9 and 10 in synchronization with the operation of the galvano scanner 7. This signal moves, for example, the mask 5 and the objective lens 6 so that the optical path length a from the mask 5 to the objective lens 6 and the optical path length b from the objective lens 6 to the incident position on the substrate 12 are both kept constant. It is a signal to make. The voice coil mechanisms 9 and 10 receive a signal from the controller 11 and move the mask 5 and the objective lens 6 in directions parallel to the traveling direction of the laser beam, respectively.

  As shown in FIG. 2, when the incident position changes from M to N, the distance that the mask 5 and the objective lens 6 are moved by the voice coil mechanisms 9 and 10 is Δb. The mask 5 and the objective lens 6 are displaced by the same distance Δb in the same direction. By doing so, the above equation (1) is satisfied, and the through hole of the mask 5 is imaged at the incident position N.

  The optical path length a from the mask 5 to the objective lens 6 and the optical path length from the objective lens 6 to the incident position on the substrate 12, for example, always during scanning of the laser beam as well as at the two incident positions M and N. If b is kept constant, the through hole of the mask 5 is always imaged on the surface of the substrate 12. The mask 5 and the objective lens 6 are moved in synchronization with the scanning of the laser beam by the galvano scanner 7 so that the optical path length a and the optical path length b are always constant. In this case, the imaging magnification (reduction ratio) of the through hole of the mask 5 is always constant.

  For example, the focal length f of the objective lens 6 is 833 mm, the optical path length a from the mask 5 to the objective lens 6 is 5000 mm, and the optical path length b from the objective lens 6 to the incident position on the substrate 12 is kept constant at 1000 mm. In this case, the imaging magnification (reduction ratio) of the through hole of the mask 5 is 1/5.

  FIG. 3A is a schematic plan view of the substrate 12 on which a pulse laser beam is irradiated by one shot so as to form an image of the rectangular through hole of the mask 5 on the surface, and a hole is formed at the image formation position. On the substrate 12, a rectangular beam spot formed with an image of the through hole is formed, and a hole is opened in the ITO film at that position.

  FIG. 3B shows the irradiation position by moving the incident position of the beam while irradiating with a 4-shot pulse laser beam while forming an image of the rectangular through-hole of the mask 5 at a constant imaging magnification (reduction ratio). It is a top view of the board | substrate 12 which formed the groove | channel in FIG. The galvano scanner 7 scans the pulse laser beam in the long side direction of the beam spot formed in a rectangular shape. Further, a beam is irradiated at an overlap rate of 50%, and a hole is formed in each shot to form a groove.

  By forming a rectangular beam spot of a certain size and scanning the laser beam in a direction parallel to a pair of parallel sides (long sides in FIG. 3B), a groove with a constant width can be formed. it can. When a pulse laser beam is used as in this embodiment, a part of a pair of parallel sides of the beam spot (long side in FIG. 3B) is a part of a pair of parallel sides of the beam spot of the previous shot. The laser beam is scanned so as to overlap the part. Since the edge of the opening of the groove is formed by the straight portion of the rectangular beam spot, it becomes a straight shape having no irregularities.

  From the viewpoint of ease of control, etc., it is desirable to form the beam spot on the substrate 12 so that the direction of a pair of parallel sides of the beam spot is parallel to the X direction or the Y direction.

  The through hole of the mask 5 that forms an image on the substrate 12 may not be rectangular. If a beam spot is formed in a shape having a pair of parallel sides, and a laser beam is scanned in a direction parallel to the pair of parallel sides, a groove having a constant width without irregularities on the edge of the opening is processed. be able to.

  FIG. 4A is a diagram illustrating an example of the through hole of the mask 5. The through hole of the mask 5 is formed in a shape having a pair of parallel sides. The other pair of sides connecting the pair of sides is curved inward. When the cross section of the laser beam is shaped using a mask having such a through hole, a beam spot having a shape having a pair of parallel sides can be formed on the substrate 12.

  FIG. 4B is a schematic diagram illustrating a hole that is formed in the substrate 12 when the through hole illustrated in FIG. 4A is imaged on the substrate 12. By continuously forming holes having the same shape as this hole in a direction parallel to a pair of parallel sides, a groove having a certain width and having no irregularities on the edge of the opening can be processed. Furthermore, since the accumulated energy density of the laser beam incident near the edge of the groove is larger than the accumulated energy density of the laser beam incident on the center of the groove, the side surface of the groove can be made more vertical.

  In addition, when only a groove extending in one direction as shown in FIG. 3B is laser processed, a one-dimensional galvano scanner or polygon scanner having one oscillating reflector may be used. At this time, the scanning direction of the scanner and the direction of a pair of parallel sides of the beam spot may be matched.

  The conical optical system 4 will be described with reference to FIGS. As described above, the conical optical system 4 converts the beam profile of the incident laser beam so that it is weak at the center of the beam cross section and strong at the periphery.

  FIG. 5A is a schematic graph showing the energy density per pulse in the cross section of the pulse laser beam emitted from the laser light source 1. The pulse laser beam generally has a high pulse energy density at the center of the cross section, and the pulse energy density decreases toward the periphery. The conical optical system 4 inverts and emits the central portion and the peripheral portion of the incident laser beam by the two conical lenses 4a and 4b. Therefore, the beam profile of the laser beam emitted from the conical optical system 4 has a weak distribution at the center of the beam cross section and a strong distribution at the periphery.

  FIG. 5B is a schematic graph showing the energy density per pulse in the cross section of the pulse laser beam emitted from the conical optical system 4 and shaped by the mask 5. The beam has a weak pulse energy density distribution at the center and a strong pulse energy density at the periphery.

  FIG. 5C is a schematic cross-sectional view of the substrate 12 taken along the line C5-C5 of FIG. 3B. A laser beam having the beam profile shown in FIG. 5B is condensed by the objective lens 6 and is incident on the substrate 12, whereby the side surface inclination angle of the ITO film of the substrate 12 can be close to 90 °. Therefore, the groove shown in FIG. 3B is a groove having a steep side wall in addition to the edge of the opening being formed in a straight line.

  In addition, in synchronization with the operation of the galvano scanner 7, the pulse energy of the pulse laser beam can be adjusted to perform higher quality processing. As the incident angle of the laser beam incident on the substrate 12 increases, the area of the beam spot at the incident position increases. Therefore, when the pulse energy of the laser beam scanned by the galvano scanner 7 is fixed to a constant value, the pulse energy density of the laser beam at the incident position decreases as the incident angle increases, and the workability changes. In order to maintain a constant workability, it may be necessary to keep the pulse energy density of the laser beam constant at the incident position.

  The variable attenuator 2 changes the pulse energy of the laser beam emitted from the laser light source 1 in synchronization with the operation of the galvano scanner 7. When the laser beam is incident on the substrate 12 at a large incident angle based on the synchronization signal transmitted from the controller 11, the pulse energy attenuation rate is decreased and the pulse energy of the beam emitted from the variable attenuator 2 is increased. . By doing so, the pulse energy density at the incident position of the laser beam can be kept constant even during the scanning of the beam.

  Even if it is not kept constant, when the incident angle of the laser beam to the substrate 12 varies, the attenuation factor of the pulse energy by the variable attenuator 2 is varied so as to reduce the variation of the pulse energy density at the incident position. Then, the quality of processing can be improved.

  When the laser beam is incident on the substrate 12 and scanned, the imaging magnification (reduction ratio) of the through hole of the mask 5 is changed in synchronization with the operation of the galvano scanner 7 while the laser beam is incident on the substrate 12. The pulse energy density can also be kept constant.

Δ ₂ = f ² × Δ ₁ / (b−f−Δ ₁ ) / (b−f) (2)
[(A + Δ ₂ ) / (b−Δ ₂ )] ² = (a / b) ² / cos θ (3)
Δ ₁ and Δ ₂ are determined according to the incident angle θ of the laser beam on the substrate 12 (the angle formed by the normal of the substrate 12 and the incident light) so as to satisfy the relationship between the two equations. The mask 5 and the objective lens 6 are moved in correspondence with the incident angle θ so that the optical path length to the lens 6 is a + Δ ₂ and the optical path length from the objective lens 6 to the incident position on the substrate 12 is b−Δ _1. You can do it. Here, a and b are the optical path length from the mask 5 to the objective lens 6 and the optical path length from the objective lens 6 to the incident position on the substrate 12 when θ is 0, respectively. F is the focal length of the objective lens 6. Even if the expressions (2) and (3) are not strictly satisfied, the quality of laser processing can be improved by changing the imaging magnification so as to reduce the fluctuation of the area of the beam spot when the incident angle changes. Can be improved. As the incident angle increases, the imaging magnification (reduction ratio) may be reduced.

  FIG. 6 is a schematic view of a laser processing apparatus according to a modification of the first embodiment, which includes an optical path adjustment mechanism 20 that changes the optical path length b from the objective lens 6 to the incident position on the substrate 12. The voice coil mechanisms 9 and 10 are removed from the laser processing apparatus shown in FIG. 1, and an optical path adjusting mechanism 20 is added. Other configurations are the same as those of the laser processing apparatus shown in FIG. In the laser processing apparatus shown in FIG. 6, the optical path length a from the mask 5 to the objective lens 6 is constant. The optical path adjustment mechanism 20 can always keep the optical path length b from the objective lens 6 to the incident position on the substrate 12 constant during scanning of the laser beam in synchronization with the operation of the galvano scanner 7, for example. By doing so, the through-hole of the mask 5 is always imaged on the substrate 12 at a constant imaging magnification (reduction ratio), and the groove as shown in FIG. 3B can be processed.

  FIG. 7 is a schematic diagram of the optical path adjustment mechanism 20. The optical path adjusting mechanism 20 includes, for example, four reflecting mirrors 21a to 21d. Each of the four reflecting mirrors changes the traveling direction of the incident laser beam by 90 °, for example, and the optical path adjusting mechanism 20 emits the laser beam in a direction parallel to the traveling direction of the incident laser beam. Two of the reflection mirrors 21 a and 21 b form the moving part 22. The moving part 22 can move in the direction of the arrow in the figure. The optical path length b from the objective lens 6 to the substrate 12 is adjusted by displacing the moving unit 22. When the incident angle of the laser beam on the substrate 12 increases, the moving unit 22 moves upward in FIG. 7, and shortens the optical path length of the laser beam in the optical path adjusting mechanism 20, thereby making the optical path length b constant. keep. The moving unit 22 is moved in response to a signal from the controller 11. The controller 11 keeps the optical path length b from the objective lens 6 to the substrate 12 shown in FIG. 6 constant by synchronizing the operation of the galvano scanner 7 and the movement of the moving unit 22.

  In the laser processing apparatus shown in FIG. 6, the optical path adjusting mechanism 20 is added to adjust the optical path length b, but is further inserted between the mask 5 and the objective lens 6 in order to adjust the optical path a. You can also. By using the two optical path adjusting mechanisms 20, the optical path length a and the optical path length b can be adjusted so as to satisfy, for example, the relational expression (1) even during scanning of the laser beam.

  Further, depending on the processing to be performed, only one of the mask 5 and the objective lens 6 may be moved to adjust the optical path length a or the optical path length b. For example, the objective lens 6 can be fixed and only the mask 5 can be moved so as to satisfy the relational expression (1).

  Although the board | substrate with which the ITO film | membrane was formed on the glass base material was considered as a processing target object, you may process a polyimide film | membrane part using the board | substrate with which the polyimide film | membrane was formed on the silicon substrate. These are used as a solar cell substrate or a liquid crystal substrate. Further, a touch panel in which an ITO film is formed on a polyimide film, a semiconductor film, and the like can be processed. Moreover, a film-like workpiece can be processed.

  FIG. 8A is a schematic diagram of a transport mechanism 31 that transports the film 30. The film 30 is transported by the transport mechanism 31. The vacuum chuck 32 fixes a predetermined processing position on the conveyed film 30 and defines a processing surface. The laser beam scanned by the galvano scanner 7 is incident on the film 30 fixed by the vacuum chuck 32, whereby processing at a predetermined processing position is performed. When the processing at the predetermined position is completed, the transport mechanism 31 transports the film 30, and another processing position is fixed by the vacuum chuck 32, and processing is performed.

  Conventionally, the film 30 fixed by the vacuum chuck 32 is moved by an XY stage, and processing is performed by irradiating a beam using a fixed optical system. In the present embodiment, since the processing is performed by scanning the beam with the galvano scanner 7 and making the beam enter the processing position, the processing speed can be increased.

  FIG. 8B is a schematic diagram of the transport mechanism 31 including the rotary encoder 33. The rotary encoder 33 detects the speed of the film 30 transported by the transport mechanism 31. The detection result is sent to the controller 11, and the controller 11 obtains the transport amount of the film 30 from the transport speed of the film 30. A control signal created from the transport speed and transport amount of the film 30 and data of a predetermined processing position defined on the film 30 is transmitted from the controller 11 to the galvano scanner 7. The galvano scanner 7 receives the control signal, scans the laser beam, and performs processing by irradiating the beam on a predetermined processing position on the film 30.

  Since the XY stage is not required and the film 30 can be processed while being conveyed, the processing speed can be increased.

  Focus processing can be performed by using a laser processing apparatus in which the conical optical system 4, the mask 5, and the voice coil mechanism 9 are removed from the laser processing apparatus shown in FIG. The laser beam is focused on the substrate 12 by the objective lens 6 so as to be focused. When the laser beam scans on the substrate 12 by the operation of the galvano scanner 7 and the incident position of the beam on the substrate 12 changes, the objective lens 6 is moved from the objective lens 6 to the substrate 12 by the voice coil mechanism 10. Is moved in a direction parallel to the traveling direction of the beam passing through the objective lens so that the optical path length b is kept constant. By this movement, the laser beam is always focused on the substrate 12. For this reason, high quality processing can be realized.

In this embodiment, a pulsed laser beam is used, but a continuous wave laser beam may be used depending on the processing to be performed. Further, an Nd: YAG laser oscillator including a wavelength conversion unit is used as the laser light source, and the third harmonic of the Nd: YAG laser is emitted. However, the fundamental wave to the fifth harmonic of the solid laser can be used. It is also possible to use a CO ₂ laser or the like.

  In this embodiment, the galvano scanner is used as the high-speed scanning optical system. However, a high-speed scanning optical system using a polygon mirror may be used. By moving the object to be processed on the XY stage, the laser beam is scanned using a high-speed scanning optical system instead of changing the incident position of the laser beam, and the incident position of the laser beam is changed, so that the processing speed can be improved. it can.

  In the focus processing method described above, the laser beam is always focused on the substrate surface. Next, a method for performing high quality processing by adjusting the positional relationship between the focal point of the laser beam and the substrate surface according to the incident position of the laser beam on the substrate surface will be described.

  The laser processing apparatus according to the second embodiment shown in FIG. 12A is obtained by removing the conical optical system 4, the mask 5 and the voice coil mechanism 9 from the laser processing apparatus shown in FIG. An aperture 5 a that has a circular through hole and adjusts the beam diameter is disposed between the expander 3 and the objective lens 6. It is not necessary to image the through hole of the aperture 5a on the surface of the substrate 12.

  By using the voice coil mechanism 10, the objective lens 6 is moved in parallel with the traveling direction of the laser beam passing through the objective lens 6, and the focal point of the laser beam is moved closer to or away from the surface of the substrate 12. The pulse energy density of the laser beam applied to the laser beam is adjusted.

  In response to the control signal transmitted from the controller 11, the galvano scanner 7 swings the laser beam in a desired traveling direction at a desired timing. By operating the voice coil mechanism 10 in synchronization with the galvano scanner 7 in accordance with a control signal transmitted from the controller 11, the substrate 12 is irradiated with a laser with a desired pulse energy density according to the incident position of the laser beam. Can do.

  An example of a laser processing method using the laser processing apparatus of FIG. 12A will be described with reference to FIG. The upper side of FIG. 13 schematically shows an optical path of a pulsed laser beam that scans the substrate 12 through the objective lens 6 and the galvano scanner 7.

  The laser beam L1b is incident on the incident position M1 perpendicular to the substrate surface. Laser beams L1a and L1c are incident on incident positions N1a and N1c, respectively, at an incident angle α1. The incident position M1 is located at the midpoint of the line segment having the incident positions N1a and N1c at both ends.

  The lower side of FIG. 13 shows the substrate surface as viewed from the galvano scanner 7 side. Beam spots 91a, 91b, and 91c indicate beam spots on the substrate surface of the laser beams L1a, L1b, and L1c (that is, at the incident positions N1a, M1, and N1c), respectively.

  Pulsed laser beam irradiation was repeated while changing the traveling direction of the laser beam from the optical path of the laser beam L1a toward the optical path of the laser beam L1c, and formed at each laser irradiation position in the same manner as shown in FIGS. 10A and 10B. Grooves 101 are formed on the substrate surface so that the holes are continuous.

  First, when the laser beam L1a forming the starting point of the groove 101 is irradiated, the position of the objective lens 6 is set so that the laser beam L1a is focused at the incident position N1a. The point where the size of the beam spot is minimized is called the focus of the laser beam.

  When the laser beam L1c forming the end point of the groove 101 is irradiated, the position of the objective lens 6 is set so that the laser beam L1c is focused at the incident position N1c. Since the optical path lengths from the objective lens 6 to the incident positions N1a and N1c are substantially equal, the position of the objective lens 6 may be considered to be the same at the start and end of grooving. The laser beams L1a and L1c have the same incident angle, and the beam spots 91a and 91c may be considered to have the same area.

  Here, first, a description will be given of what kind of problem occurs when a groove is formed by scanning a laser beam with the objective lens 6 fixed at this position.

  A laser whose traveling direction is swung by the galvano scanner 7 when the objective lens 6 is fixed at a position where the laser beam L1a is focused at the incident position N1a (or the laser beam L1c is focused at the incident position N1c). A virtual surface drawn by the locus of the focal point of the beam is defined as a condensing surface 81a. A point R on the condensing surface 81a indicates the focal position of the laser beam L1b.

  At incident positions on the groove 101 other than the incident positions N1a and N1c, the laser beam is incident on the substrate while being focused on the focal point. As the distance from the incident position to the focal point becomes longer, the beam diameter at the incident position becomes larger than the beam diameter at the focal point. The distance between the incident position and the focal point is maximum with respect to the laser beam L1b irradiated to the center of the groove.

  The pulse energy density of the laser beam is usually higher at the center than near the outer periphery of the beam cross section. As the beam diameter increases, the pulse energy density at each position in the beam cross section decreases. Therefore, even if the beam diameter is increased, the region where the pulse energy density is equal to or higher than the threshold for processing the substrate is limited to the vicinity of the center of the beam section.

  In the vicinity of the incident positions N1a and N1c, which are the ends of the groove 101, a laser beam having a small beam diameter but having a pulse energy density equal to or higher than a processing threshold is irradiated at a high pulse energy density to the vicinity of the outer periphery of the beam cross section. A thick groove is formed. On the other hand, in the vicinity of the incident position M1, which is the center of the groove, a laser beam having a large beam diameter but having a pulse energy density greater than or equal to the processing threshold only in a narrow region at the center of the beam cross section is irradiated with a low pulse energy density. A narrow groove is formed. Thus, the width of the groove varies depending on the location.

  In addition, the distance from the incident position M1 of the laser beam L1b to the point R on the condensing surface 81a becomes longer as the incident angle α1 increases. Therefore, as the incident angle α1 increases, the difference between the beam diameter of the laser applied to the incident positions N1a and N1c and the beam diameter of the laser applied to the incident position M1 increases. That is, the difference in the width between the end and the center of the groove becomes significant. Since the incident angle α1 is the incident angle of the laser beam that forms the end of the groove, the incident angle α1 increases when, for example, a long groove is to be formed on a large substrate.

  Next, a method for forming a groove by moving the position of the objective lens 6 to scan the laser beam while adjusting the focal position will be described. When the focal position of the laser beam is adjusted, the beam diameter of the laser beam applied to the substrate is adjusted, and the pulse energy density on the substrate surface is adjusted.

  Consider where to focus the laser beam L1b incident on the incident position M1. By setting the focal point to a position closer to the incident position M1 than the point R on the condensing surface 81a, the beam diameter can be reduced and correction can be made to increase the pulse energy density at the incident position M1. However, when the focal point is brought close to the incident position M1, the pulse energy density at the incident position M1 becomes higher than the pulse energy density at the incident positions N1a and N1c.

  Since the laser beam L1b is perpendicularly incident on the substrate surface, the beam spot is circular when the focal point is set at the incident position M1. On the other hand, since the laser beams L1a and L1c are incident on the substrate surface at an angle of incidence α1, the beam spots 91a and 91c have an elliptical shape. That is, the pulse energy density at the beam spot 91b when the laser beam L1b is focused at the incident position M1 is higher than the pulse energy density at the beam spots 91a and 91c.

  Therefore, the focal point of the laser beam L1b is adjusted to a position slightly deeper than the incident position M1 (far from the incident position M1 toward the inside of the substrate), and the area of the beam spot 91b is the area of the beam spots 91a and 91c at the incident position N1a. To be equal to In this way, processing can be performed by irradiating the laser with a pulse energy density equal to the incident position N1a or N1c and M1.

  Processing may be performed by aligning the pulse energy density so that the area of the beam spot is kept constant at other incident positions on the groove 101. A focal locus when the groove 101 is scanned under a condition that does not change the area of the beam spot is the light condensing surface 81b. The focal position of the laser beam L1b is a point Q on the condensing surface 81b.

  A description will be given of how to adjust the position of the objective lens 6 when the focal point is moved along the condensing surface 81b. First, when the laser beam L1a is irradiated, the objective lens 6 is set at a position that focuses at the incident position N1a. This position is called a reference position.

  When the laser beam is scanned from the incident position N1a toward M1, the objective lens 6 is gradually moved from the reference position toward the laser light source so that the focal point is closer to the substrate surface than the condensing surface 81a. It is moved along the surface 81b to suppress an increase in the area of the beam spot and a decrease in pulse energy density. The moving distance from the reference position of the objective lens is zero for the laser beam L1a incident on the incident position N1a, increased as the laser moves toward the incident position M1, and maximum for the laser beam L1b incident on the incident position M1.

  Subsequently, when scanning the laser beam from the incident position M1 toward N1c, the objective lens 6 may be gradually brought closer to the reference position. The moving distance of the objective lens from the reference position is decreased as the laser moves toward the incident position N1c, and is zero for the laser beam L1c incident on the incident position N1c.

  In this way, by scanning the laser while adjusting the position of the objective lens 6 so that the focal point of the laser beam irradiated to each incident position moves along the condensing surface 81b, the width varies depending on the location. The groove 101 can be formed while suppressing the fluctuation.

  Summarize how to move the objective lens. If scanning continues without moving the position of the objective lens, if the pulse energy density on the substrate surface decreases, the objective lens is moved so that the focal point of the laser beam approaches the incident position. Try to suppress the decline. If scanning continues without moving the position of the objective lens, if the pulse energy density on the substrate surface increases, the objective lens is moved so that the focal position of the laser beam is far from the incident position. What is necessary is just to suppress an increase in pulse energy density.

  As an example of processing, the method of focusing on the substrate surface at the incident positions at both ends of the groove has been described, but the focusing may be performed at another incident position. If the beam spot at each incident position is maintained in a substantially constant area, the processing can be performed with the same pulse energy density, so that a constant workability can be maintained at any incident position.

  It should be noted that even if the pulse energy density of the irradiated laser beam is not strictly kept constant at each incident position, the fluctuation of the pulse energy density at the incident position is suppressed when the incident position changes. Then, processing can be performed satisfactorily.

  Although grooving (scribing) has been described as an example, drilling or the like may be performed. Although an example in which the galvano scanner is scanned in the one-dimensional direction has been described, the scanning may be performed in the two-dimensional direction so that the entire surface of the substrate is processed. Although processing using a pulse laser beam has been described as an example, the laser beam may be a continuous wave. When processing is performed with a continuous wave laser beam, the power density on the processing surface is prevented from changing for each incident position.

  Instead of moving the objective lens 6, the pulse energy density of the laser beam applied to the substrate can be adjusted using a variable attenuator.

  A variable attenuator 2 is added to the laser processing apparatus shown in FIG. 12A in the laser processing apparatus according to the modification of the second embodiment shown in FIG. 12B. The variable attenuator 2 can attenuate the power of the pulsed laser beam applied to the substrate 12 at a desired attenuation rate in synchronization with the operation of the galvano scanner 7 based on the control signal transmitted from the controller 11.

  An example of a laser processing method using a variable attenuator will be described with reference to FIG. FIG. 14 schematically shows an optical path of a pulsed laser beam that scans the substrate 12 through the objective lens 6 and the galvano scanner 7 in the laser processing apparatus shown in FIG. 12B.

  The laser beam L2b is incident on the incident position M2 perpendicular to the substrate surface. Laser beams L2a and L2c are incident on incident positions N2a and N2c at an incident angle α2, respectively. The incident position M2 is located at the midpoint of the line segment having the incident positions N2a and N2c at both ends.

  The objective lens 6 is fixed at a position where the laser beam L2b is focused at the incident position M2. A virtual surface drawn by the locus of the focal point of the laser beam whose traveling direction is swung by the galvano scanner 7 is defined as a condensing surface 82.

  In the same manner as described with reference to FIG. 13, the irradiation of the pulse laser beam is repeated while changing the traveling direction of the laser beam from the optical path of the laser beam L2a toward the optical path of the laser beam L2c. Form.

  As the incident position of the laser beam moves away from the incident position M2, the distance from when the laser beam is focused until it enters the substrate becomes longer. Since the laser beam after passing through the focal point becomes a divergent beam, the beam spot on the substrate surface increases as the distance from the focal point to the incident position increases.

  Further, as the incident position moves away from the incident position M2, the incident angle of the laser beam on the substrate increases. Even when a laser beam having the same beam diameter is irradiated, the beam spot on the substrate surface increases as the incident angle increases.

  As described with reference to FIG. 13, the pulse energy density in a large beam spot decreases over the entire beam cross section, and it is limited only to the vicinity of the center of the beam cross section that is equal to or greater than a threshold at which the substrate can be processed. For this reason, the width of the groove formed by irradiation with a large beam spot becomes narrow.

  When a groove is formed by irradiating a laser with a constant pulse energy at any incident position, the width near the center of the groove is formed thick, and the end of the groove is formed narrow.

  Therefore, the power is adjusted by the variable attenuator 2 in accordance with the incident position so that the pulse energy density on the substrate surface is constant at any incident position. The amount of power attenuation is minimized when the end of the groove is processed, increased as it goes toward the center of the groove, and maximized when the incident position M2, which is the center of the groove, is irradiated. In this way, the groove can be formed while suppressing the width from varying depending on the location.

  In order to make the pulse energy density of the laser beam irradiated to the substrate uniform, the focal point is moved by moving the objective lens 6 by the voice coil mechanism 10 and the power of the pulse laser beam is changed by the variable attenuator 2. A combination of attenuation may be used.

  The laser beam may be a continuous wave. When processing with a continuous wave laser beam, the power of the continuous wave laser beam is adjusted with a variable attenuator so as to suppress the power density on the processing surface from fluctuating for each incident position.

  Now, for example, in the processing of a glass substrate having an ITO film formed on the surface, the substrate size tends to increase. When the substrate becomes large and the region to be processed becomes wide, the amount of movement of the objective lens 6 is large in the processing performed by moving the objective lens 6 according to the incident position of the laser beam as described with reference to FIG. The case that becomes. From the viewpoint of ease of control, it is preferable that the amount of movement of the objective lens 6 can be reduced.

  Next, with reference to FIG. 15A, a description will be given of a laser processing apparatus according to the third embodiment that can increase the movement distance of the focal position of the laser beam while keeping the movement of the objective lens 6 at a short distance.

  In the laser processing apparatus shown in FIG. 15A, a secondary condenser lens 71 is added between the objective lens 6 and the galvano scanner 7 of the laser processing apparatus shown in FIG. 12A. In the description of FIG. 15A, the objective lens 6 is referred to as a primary condenser lens 6.

  The laser beam emitted from the aperture 5 a is incident on the primary condenser lens 6. The primary condensing lens 6 condenses the laser beam on the virtual primary condensing surface 83. The laser beam that has passed through the primary condensing surface 83 becomes a divergent beam and enters the secondary condensing lens 71. The laser beam focused by the secondary condenser lens 71 is moved in the traveling direction by the galvano scanner 7 and enters the substrate 12.

Next, the movement amount of the primary condenser lens 6 will be described. When the primary condensing surface 83 is brought close to the secondary condensing lens 71, the focal position of the laser beam focused by the secondary condensing lens 71 moves in the direction in which the laser beam travels. The moving distance of the primary condensing surface 83 is d1, and the moving distance of the focal point of the laser beam is d2. Further, the numerical aperture of the secondary condenser lens 71 with respect to the laser beam incident on the secondary condenser lens 71 is NA2, and the numerical aperture of the secondary condenser lens 71 with respect to the focused beam that has passed through the secondary condenser lens 71 is NA2. To do. The magnification P is
P = NA1 / NA2
Defined as
d2 = d1 × P ²
Is established.

  As can be seen from the above equation, if the magnification P is increased, the moving distance d2 of the focal point can be increased even if the moving distance d1 of the primary condensing surface 83 is shortened. For example, when the magnification P is 2, the focal point of the laser beam can be moved in the traveling direction of the 8 mm laser beam by bringing the primary condensing surface 83 closer to the 2 mm secondary condensing lens.

  The primary condensing surface 83 is moved by moving the primary condensing lens 6 in the optical axis direction. When the laser beam incident on the primary condensing lens 6 is a parallel light beam, the moving distance of the primary condensing lens 6 and the moving distance of the primary condensing surface 83 are equal. If the distance for moving the primary condenser lens 6 is about 2 mm or less, a linear motion mechanism using a piezo drive mechanism can be used. By using a linear motion mechanism that uses a piezo drive mechanism instead of the voice coil mechanism 10, the primary condenser lens 6 can be moved at high speed and with high accuracy.

  FIG. 16 shows a configuration example of the secondary condenser lens 71. The secondary condenser lens 71 is composed of a plurality of lenses. The object point So and the image point Si are in a conjugate relationship. This object point So corresponds to the position of the beam spot on the primary condensing surface 83 shown in FIG. 15A. This imaging optical system is considered as an infinitely conjugate optical system. The secondary condenser lens 71 is divided into a front lens group 71a and a rear lens group 71b. The light beam emitted from the object point So is converted into a parallel light beam by the front lens group 71a. This parallel light beam is focused on the image point Si by the rear lens group 71b. Although there are cases where the secondary condenser lens 71 cannot be physically divided, it is assumed here that it is virtually divided.

The front focal length of the front lens group 71a is Ff, and the rear focal length of the rear lens group 71b is Fr. At this time, the magnification P defined by the above equation is
P = Fr / Ff
It is expressed.

  In the laser processing apparatus shown in FIG. 15A, the primary condenser lens 6 is a convex lens, but may be a concave lens 6a as shown in FIG. 15B. At this time, the primary condensing surface 83a becomes a virtual image and appears closer to the laser light source than the concave lens 6a.

  Thus, by increasing the magnification P, it is possible to greatly change the focal position of the laser beam applied to the substrate while keeping the moving distance of the primary condenser lens 6 short. In order to produce a significant effect, the magnification P is preferably 2 or more, and more preferably 4 or more.

  The beam spots 91a and 91c shown in FIG. 13 are elliptical because they are laser beam beam spots incident on the substrate at an angle. On the other hand, the beam spot 91b has a circular shape because it is a laser beam spot incident perpendicularly to the substrate. Thus, the incident angle varies depending on the incident position of the laser beam, and the beam spot shape on the substrate varies.

  The opening of the hole to be processed is elliptical if the beam spot is elliptical, and circular if the beam spot is circular. However, there is a case where it is desired that the hole opening has the same shape (for example, a circle) at any incident position.

  Next, with reference to FIG. 17, a laser processing apparatus according to a fourth embodiment capable of correcting the shape of the beam spot according to the incident position will be described.

  In the laser processing apparatus shown in FIG. 17, the laser processing apparatus shown in FIG. 12A has an aperture tilt mechanism 60a that rotates the aperture 5a around an axis perpendicular to the optical axis of the laser beam, and the aperture 5a is a laser beam light. An aperture rotation mechanism 61a that rotates around an axis parallel to the axis is added.

  The aperture rotation mechanism 61a is a mechanism similar to that of the mask rotation mechanism included in the laser processing apparatus described later with reference to FIG. 22A, and rotates the mask. The aperture 5a is an axis parallel to the optical axis of the laser beam. Rotate around.

  The aperture tilt mechanism 60a and the aperture rotation mechanism 61a are each tilted around the axis perpendicular to the optical axis of the laser beam in synchronization with the operation of the galvano scanner 7 based on the control signal transmitted from the controller 11. The angle and the rotation angle about an axis parallel to the optical axis of the laser beam are changed.

  The beam cross-sectional shape perpendicular to the optical axis when the laser beam is incident on the substrate surface obliquely is compared with the beam cross-sectional shape on the substrate surface. The beam cross-sectional shape on the substrate surface is a shape in which the beam cross-sectional shape perpendicular to the optical axis is stretched in the direction of the intersection of the substrate surface and the incident surface. For example, if a laser beam having a circular cross section is incident on the substrate surface obliquely, the beam cross section on the substrate surface becomes an ellipse that is long in the direction of the line of intersection between the substrate surface and the incident surface. Note that the larger the incident angle, the longer the beam spot on the substrate surface is in the intersecting direction.

  Therefore, a laser beam whose cross section perpendicular to the optical axis is shaped into an ellipse with an appropriate ratio of the major axis to the minor axis is oblique to the substrate surface so that the major axis direction of the ellipse is perpendicular to the incident surface. The beam spot on the substrate surface could be made circular.

  FIG. 18A schematically shows a view of the aperture 5a rotated about the axis perpendicular to the optical axis of the laser beam by the aperture tilt mechanism 60a along the direction of the rotation axis of the aperture tilt mechanism 60a. The laser beam lb incident from the left side of the figure is shaped by the aperture 5a and emitted to the right side of the figure.

  As shown in FIG. 18B, the circular through hole 62a of the aperture 5a rotated by the aperture tilting mechanism 60a looks elliptical when viewed from the line of sight along the optical axis of the laser beam. That is, the cross section of the laser beam is shaped into an ellipse.

  In addition, when the surface where two different diameters of the circular through hole of the aperture 5a extend is orthogonal to the optical axis of the laser beam, the cross section of the laser beam is shaped into a circle. As the aperture 5a is inclined and the angle formed by the rotation center axis of the circular through hole and the optical axis of the laser beam increases, the elliptical short axis of the shaped beam cross section becomes shorter. In this manner, the aperture tilt mechanism 60a can change the aspect ratio of the beam cross section after shaping.

  As shown in FIG. 18C, the aperture 5a is further rotated around an axis parallel to the optical axis of the laser beam by using the aperture rotation mechanism 61a.

  The beam cross-sectional shape at the position where the beam spot of the laser beam is minimized (referred to as the focal point of the laser beam) is elliptical. The long axis direction of the beam cross section at the focal point corresponds to the short axis direction of the beam cross section at the position of the through hole of the aperture 5a.

  Therefore, the aperture 5a is rotated by the aperture rotation mechanism 61a so that the major axis direction of the ellipse of the beam cross section at the position of the through hole coincides with the intersecting line direction. In this way, the shape of the beam spot on the substrate can be kept circular for any incident position.

  Although the processing by the condensing method that does not require the through-hole of the aperture to be imaged on the substrate surface has been described, even when the processing by the mask projection method that forms the image of the through-hole on the substrate surface is performed, The shape of the beam spot can be corrected. In the mask projection method, the long axis direction of the image of the through hole formed on the substrate surface corresponds to the long axis direction of the beam cross section at the position of the through hole of the mask.

  It is the same to incline a mask having a circular through-hole around an axis perpendicular to the optical axis of the laser beam. However, when the mask is further rotated around an axis parallel to the optical axis of the laser beam, the short axis direction of the elliptical shape of the beam cross-section when exiting the through hole is the direction of the line of intersection between the incident surface and the substrate surface Rotate to match.

  Although the case where the shape of the through hole is a circle has been described, the beam spot shape of the laser beam shaped by the through hole of another shape can be corrected.

  Next, with reference to FIG. 19, a laser processing apparatus according to a fifth embodiment for performing a laser processing method using a proximity mask will be described. In the laser processing apparatus shown in FIG. 19, a proximity mask 63 is added to the laser processing apparatus shown in FIG. 12A.

  The proximity mask 63 is held by the proximity mask holding mechanism 64 and is disposed immediately above the substrate 12 in parallel with the surface of the substrate 12. A through hole having the same shape as the shape to be processed on the substrate surface is formed in the proximity mask 63. The distance (proximity gap) dg between the proximity mask 63 and the surface of the substrate 12 can be adjusted by the proximity mask holding mechanism 64.

  The expander 3 expands the beam diameter of the laser beam emitted from the laser light source 1 and emits a parallel laser beam. The laser beam emitted from the expander 3 has a divergence angle β. When the beam diameter of the laser beam is expanded by, for example, 10 times by the expander 3, the divergence angle is reduced to 1/10. The expander 3 can adjust the divergence angle of the laser beam.

  While the proximity mask 63 is scanned by the galvano scanner 7, the laser beam is irradiated. In the through hole of the proximity mask 63, the laser beam passes and enters the substrate 12, and the substrate 12 is processed. In portions other than the through holes, the laser beam does not pass and the substrate 12 is not processed. Thus, the substrate surface can be processed so as to transfer the shape of the through hole of the proximity mask 63.

  At this time, even if the incident position of the laser beam changes, the position of the objective lens 6 is moved according to the incident position of the laser beam on the substrate so that the fluctuation of the pulse energy density on the substrate surface is suppressed. However, laser irradiation can be performed. The laser light source 1 may emit a continuous wave laser beam. In that case, the fluctuation of the power density on the substrate surface is suppressed.

  In order to perform high-precision processing, the shape of the through hole of the proximity mask 63 needs to be accurately transferred to the substrate. The accuracy of the transfer depends on the proximity gap dg and the divergence angle of the laser beam applied to the proximity mask 63. The divergence angle of the laser beam applied to the proximity mask may be considered to be equal to the divergence angle β of the laser beam when passing through the expander.

  FIG. 20 shows a simulation result of how the transfer accuracy changes depending on the proximity gap and the divergence angle of the laser beam for the proximity mask having a T-shaped through hole. An image 97 of T-shaped through holes when the proximity gap and the divergence angle of the laser beam are variously changed is shown side by side. In each figure, the divergence angle of the laser beam is smaller as it is arranged on the right side, and the proximity gap is smaller as it is arranged on the lower side.

  The clearer the edge of the image 97, the higher the transfer accuracy. As can be seen from the figure, the transfer accuracy deteriorates as the proximity gap increases at the same spread angle. Further, when the gap is the same, the transfer accuracy deteriorates as the divergence angle increases. As both the proximity gap and the divergence angle are reduced, the transfer accuracy can be increased.

  FIG. 21 schematically shows a graph of the relationship that the proximity gap and the divergence angle of the laser beam must satisfy when trying to ensure certain transfer accuracy. When trying to ensure the accuracy of a certain transfer, if the proximity gap increases, the divergence angle must be reduced, and if the expansion angle increases, the proximity gap must be reduced.

  If the relationship that the proximity gap and the divergence angle of the laser beam have to satisfy as shown in FIG. 21 is obtained in advance for various transfer accuracies, when processing is performed with a desired transfer accuracy, The proximity gap and the divergence angle can be easily selected.

  The laser processing method using the proximity mask has an advantage that processing can be performed with high transfer accuracy by setting the proximity gap and the divergence angle small. Further, by positioning the through hole of the proximity mask immediately above the processing position of the substrate and performing processing, high positioning accuracy can be obtained. Since the proximity mask covers the surface of the substrate except for the processing position, there is an advantage that scattered objects generated when the substrate is shaved during processing are difficult to adhere to the surface of the substrate.

  In addition, when performing processing to irradiate the substrate with the laser beam that has passed through the through hole of the proximity mask, by moving the incident position of the laser beam on the substrate by changing the traveling direction of the laser beam with a galvano scanner, The processing speed can be increased as compared with the case where the incident position is moved by moving the XY stage on which the substrate is placed.

  Next, with reference to FIG. 22A, a laser processing apparatus according to a sixth embodiment having a laser light source that oscillates a continuous wave laser beam will be described. As the laser light source 1 that oscillates a continuous wave laser beam, for example, a semiconductor laser that oscillates a laser beam having a wavelength in the infrared region can be used.

  The laser beam lb0 emitted from the laser light source 1 enters the sorting optical system 65. The sorting optical system 65 converts the laser beam lb0 into a laser beam lb1 that travels along a certain optical axis in a certain time zone, and a laser beam lb2 that travels along another optical axis in another time zone. Distribute.

  The sorting optical system 65 includes, for example, a half-wave plate 65a, an electro-optical element 65b exhibiting a Pockels effect, and a polarizing plate 65c. The half-wave plate 65a converts the laser beam lb0 emitted from the laser light source 1 into linearly polarized light that becomes a P wave with respect to the polarizing plate 65c. This P wave enters the electro-optic element 65b.

  The electro-optic element 65b rotates the polarization axis of the laser beam based on the trigger signal sig sent from the controller 11. When the electro-optic element 65b is not applied with a voltage, the incident P wave is emitted as it is. When the electro-optic element 65b is in a voltage application state, the electro-optic element 65b rotates the polarization plane of the P wave by 90 degrees. Accordingly, the laser beam emitted from the electro-optic element 65b becomes an S wave with respect to the polarizing plate 65c.

  The polarizing plate 65c transmits the P wave as it is and reflects the S wave. The laser beam lb1 that is the S wave reflected by the polarizing plate 65c is incident on the beam damper 66 that is the end of the laser beam lb1. The laser beam lb2 which is a P wave transmitted through the polarizing plate 65c is incident on the expander 3.

  The laser beam lb2 whose beam diameter has been expanded by the expander 3 to be parallel light is incident on the mask 5 having a rectangular through hole. Here, processing by the mask projection method will be described as an example. That is, processing is performed by forming an image of the through hole of the mask 5 on the surface of the substrate 12.

  A mask rotation mechanism 61 is used to rotate the mask 5 around an axis parallel to the optical axis of the laser beam. The mask rotation mechanism 61 includes, for example, a goniometer, and rotates the mask by a desired angle at a desired timing based on a control signal sent from the controller 11. Details of the mask rotation mechanism 61 will be described later. The voice coil mechanism 9 moves the position of the mask 5 in parallel with the traveling direction of the laser beam.

  The laser beam lb2 emitted from the mask 5 is focused by the objective lens 6. The voice coil mechanism 10 moves the position of the objective lens 6 in parallel with the traveling direction of the laser beam. The laser beam emitted from the objective lens 6 passes through the galvano scanner 7 and then enters the surface of the substrate 12.

  With reference to FIG. 22B, the board | substrate 12 which is a process target object is demonstrated. A transfer layer 111 is present on the surface of the underlayer 110. The transfer layer 111 has a property of being bonded to the surface of the base layer 110 when heat is applied.

  For example, a part 111 a of the transfer layer 111 is heated by laser irradiation and bonded to the base layer 110. When the unheated portion 111b of the transfer layer 111 is removed, only the heated portion 111a remains on the surface of the base layer 110. This is similar to, for example, that the ink in the heated portion of the ink ribbon is transferred to paper when performing thermal transfer printing.

  Returning to FIG. 22A, the description will be continued. The XY stage 8 a is used as a holding table for the substrate 12. The XY stage 8 a can move the substrate 12 in a two-dimensional plane parallel to the surface of the substrate 12. The controller 11 controls the XY stage 8a to move the substrate 12 to a desired position at a desired timing.

  In the example of the laser processing method described here, the X scanner 7a and the Y scanner 7b of the galvano scanner 7 are fixed at a position where the laser beam emitted from the galvano scanner 7 enters the substrate 12 perpendicularly. Yes. By moving the substrate 12 with the XY stage 8a, the incident position of the laser beam on the substrate 12 is moved.

  Using the voice coil mechanisms 9 and 10, the optical path length from the mask 5 to the objective lens 6 and the optical path length from the objective lens 6 to the incident position of the laser beam on the substrate 12 are as follows. It is set so that an image is formed on the surface at a desired imaging magnification (reduction ratio).

  With reference to FIG. 23, a control method of the sorting optical system will be described. FIG. 23 shows an example of a timing chart of the trigger signal sig and the laser beams lb0, lb1, and lb2. At time t0, emission of the laser beam lb0 is started.

  From time t0 to time t1, the trigger signal sig is not sent from the controller. During this time, no voltage is applied to the electro-optic element, and the laser beam lb2 is always emitted from the sorting optical system. The laser beam lb1 is not emitted. During this time, the laser beam lb2 is a continuous wave.

  From time t1 to time t2, a voltage is applied to the electro-optical element of the sorting optical system in synchronization with the trigger signal sig that is periodically transmitted by the controller.

  While the trigger signal sig is sent, the electro-optical element is in a voltage application state, and the laser beam lb0 is distributed to the laser beam lb1. On the other hand, while the trigger signal sig is not sent, the electro-optic element is in a voltage-free state, and the laser beam lb0 is distributed to the laser beam lb2. The laser beam lb2 from time t1 to time t2 is a laser beam that is periodically oscillated and stopped.

  In the intermittently emitted laser beam lb2, the pulse width w1 and the period w2 can be set to arbitrary lengths by adjusting the trigger signal sig. For example, the pulse width w1 is 10 μs to several tens of μs, and the period w2 is several hundreds of μs.

  As described above, when the trigger signal is not input to the sorting optical system, the laser beam lb2 that is continuously emitted is obtained, and when the trigger signal is intermittently input to the sorting optical system, the pulse laser beam lb2 that is intermittently emitted is obtained. Is obtained.

  Since the laser beam lb2 emitted continuously can be irradiated onto the substrate continuously, it is suitable for, for example, processing for forming a line (processing for leaving the transfer layer in a line shape on the base layer). On the other hand, the laser beam lb2 emitted intermittently can be irradiated onto the substrate intermittently, and is suitable for, for example, processing for forming dots (processing for leaving the transfer layer on the base layer in the form of dots).

  A line processing method will be described with reference to FIG. 24A. Laser processing on the substrate 12 is started, and processing is started. At the start of processing, first, a region on the entire width of one end of the line 103 is irradiated with a rectangular beam spot 93. Thereafter, the XY stage is moved in one direction so that the beam spot is directed toward the other end of the line 103 while continuously irradiating the laser. The moving direction of the XY stage is parallel to the side where the rectangular beam spot 93 is located. The direction of movement of the beam spot on the substrate is indicated by an arrow.

  When the beam spot reaches the other end of the line 103, the laser irradiation to the substrate is stopped and the processing is finished. In this way, the line-shaped region on the substrate surface is heated by laser irradiation, thereby forming a line 103 in which the transfer layer remains in a line shape on the surface of the underlayer.

  The outer shape of the formed line 103 is a rectangle in which the side in the length direction is parallel to the side where the beam spot 93 is present and the side in the width direction is parallel to the side orthogonal to the side where the beam spot 93 is located. The width of the line 103 is equal to the length of the side perpendicular to the side where the beam spot 93 is located.

  A dot processing method will be described with reference to FIG. 24B. In dot processing, the XY stage is moved in one direction while intermittently irradiating the substrate 12 with a laser beam. The moving direction of the XY stage is parallel to a side (referred to as side p) where the rectangular beam spot 94a is located.

  First, at the start of laser irradiation of the first pulse, a region on the entire width of one end of the dot 104a is irradiated with a rectangular beam spot 94a. Since the XY stage is moving, the beam spot moves on the substrate until the laser irradiation of the first pulse is completed. The direction of movement of the beam spot is indicated by an arrow.

  In this manner, the dot-like region on the substrate surface is heated by laser irradiation, and the dots 104a are formed in which the transfer layer remains in the form of dots on the surface of the underlayer.

  Thereafter, similarly, dots 104b, 104c, 104d, and 104e are formed by laser irradiation of the second, third, fourth, and fifth pulses, respectively. The substrate surface area irradiated with the beam spots 94b, 94c, 94d, and 94e at the start of irradiation of the second, third, fourth, and fifth pulses is different from the area of the substrate surface irradiated with the beam spot 94a. It corresponds to the area moved parallel to the direction. Each dot is arranged on a straight line parallel to the moving direction of the XY stage.

  The outer shape of each dot is a rectangle having a side parallel to the side p of the beam spot 94a and a side parallel to a side orthogonal to the side p of the beam spot 94a (referred to as side q).

  The length of the side perpendicular to the moving direction of the XY stage of each dot is equal to the length of the side q. For example, when the length of the side q is 20 μm, the length is 20 μm.

  The length of the side of each dot parallel to the moving direction of the XY stage depends on the length of the side p of the beam spot, the moving speed of the XY stage, and the pulse irradiation time (pulse width).

  For example, it is assumed that the length of the side p of the beam spot is 12 μm, the moving speed of the XY stage is 800 mm / s, and the pulse width is 10 μs. Since the distance that the XY stage moves during the pulse width of 10 μs (that is, the distance that the substrate moves) is 8 μm, the length of the side of the dot parallel to the moving direction of the XY stage is the length of the side p of the beam spot. This is 20 μm, which is 12 μm in length plus 8 μm of moving distance.

  The pitch d between adjacent dots coincides with the distance that the XY stage moves during one pulse period. For example, when the pulse period is 375 μs and the moving speed of the XY stage is 800 mm / s, the pitch d is 300 μm.

  In summary, the size of the beam spot is set to 12 μm in the length of side p and 20 μm in length to the side q, the laser beam is oscillated with a pulse width of 10 μs and a period of 375 μs, and the XY stage is moved at 800 mm / s. In this case, 20 μm square dots can be formed at a 300 μm pitch.

  In some cases, it is desired to process a plurality of lines having different directions on the substrate. However, if lines in different directions are formed while the direction of the beam spot on the substrate is kept constant, there arises a problem that the line width changes depending on the direction of the lines.

  An example of such a situation will be described with reference to FIG. First, the line 109a is formed by the method described with reference to FIG. 24A. Next, a line 109b having a direction different from the line 109a is formed without changing the direction of the beam spot. At the start of laser irradiation, a beam spot 99 is irradiated to one end of the line 109b. While moving the XY stage in the length direction of the line 109b, the beam spot is moved to the other end of the line 109b to form the line 109b.

  As shown in the figure, the width of the line 109a is equal to the length of the long side of the beam spot 99, but the width of the line 109b is not necessarily equal to the length of the long side. Further, the end side of the line 109b cannot be formed so as to be orthogonal to the length direction of the line. Such a problem can be avoided by using the mask rotation mechanism 61 shown in FIG. 22A.

  FIG. 25 is a schematic view showing a mask rotation mechanism 61 holding a mask 5 having a rectangular through hole 62. The surface where the two diagonal lines of the rectangular through-hole 62 extend is perpendicular to the optical axis of the laser beam. The mask rotation mechanism 61 rotates the mask 5 around an axis parallel to the optical axis of the laser beam, with the intersection of the rectangular diagonal lines of the through hole 62 as the rotation center.

  Corresponding to the rotation of the mask 5, the image of the through hole 62 rotates within the surface of the substrate 12. The side of the rectangular image of the through hole 62 on the substrate can be parallel to any direction within the substrate surface.

  As will be described below, the mask 5 can be rotated by the mask rotating mechanism 61 before changing the moving direction of the incident position of the laser beam on the substrate in order to change the direction of the line to be processed.

  With reference to FIG. 26, the processing method of the line using a mask rotation mechanism is demonstrated. The line 103a is formed by the method described with reference to FIG. 24A. It is assumed that the length of the long side of the beam spot 93a is equal to the width of the line 103a, and the direction of the short side of the beam spot 93a is parallel to the length direction of the line 103a.

  Before starting the processing of the line 103b having a direction different from the line 103a, the mask is rotated by the mask rotation mechanism so that the short side of the beam spot 93b is parallel to the length direction of the line 103b. Then, the substrate is moved by the XY stage so that the beam spot is irradiated on the entire width of one end of the line 103b.

  Laser beam irradiation is started, and the line 103b is formed by moving the XY stage in the length direction of the line 103b by the same process as described with reference to FIG. 24A. The width of the line 103b is equal to the length of the long side of the beam spot 93b. In addition, the side in the width direction and the side in the length direction of the line 103b are orthogonal to each other.

  In this way, a plurality of lines having different directions can be formed to have the same width. A mask rotation mechanism can also be used to form a plurality of dots having different directions without changing the size and shape.

  Although the example in which the sorting optical system is controlled by the periodic trigger signal and the laser beam is pulsed has been described, the trigger signal may not be periodic. For example, when it is desired to form a plurality of dots at unequal pitches, a non-periodic trigger signal can be used. Further, the pulse width of the laser beam need not be constant. What is necessary is just to set suitably according to the size etc. of the dot to form.

  By changing the shape and size of the beam spot on the substrate, the line width, dot size, and the like can be adjusted. By changing the mask, the shape and size of the beam spot can be changed. Also, the size of the beam spot can be changed by changing the imaging magnification (reduction ratio).

  Although the processing in which the transfer layer remains on the surface of the substrate in the form of lines or dots has been described as an example, the processing may be such that the surface of the substrate is dug into a shape of lines or dots by laser irradiation.

  The shape of the through hole of the mask is not limited to a rectangle, and may be appropriately selected according to the shape of a dot or line to be formed.

  Although the example in which the incident position of the laser beam on the substrate is moved by the XY stage has been described, the incident position can also be moved by shaking the traveling direction of the laser beam with a galvano scanner.

  Next, referring to FIG. 27A, the seventh embodiment has two laser light sources, one laser light source emits a pulsed laser beam, and the other laser light source emits a continuous wave laser beam. A laser processing apparatus will be described.

  The laser light source 1a is, for example, an Nd: YAG laser oscillator including a wavelength conversion unit, and emits a pulse laser beam of the fourth harmonic (wavelength 266 nm) of the Nd: YAG laser. The pulse width is 10 ns, for example. The pulse laser beam emitted from the laser light source 1 a is incident on the half-wave plate 69 a and is linearly polarized so as to be a P wave with respect to the polarizing plate 67.

  The laser light source 1b is a semiconductor laser oscillator, for example, and emits a continuous wave laser beam having a wavelength of 808 nm. The continuous wave laser beam emitted from the laser light source 1 b enters the half-wave plate 69 b and is linearly polarized so as to be an S wave with respect to the polarizing plate 67.

  The pulsed laser beam emitted from the half-wave plate 69 a passes through the expander 3 a that expands the beam diameter to parallel light and the mask 5 having, for example, a rectangular through hole, and is incident on the front surface of the polarizing plate 67. Incident at an angle of 45 °.

  The continuous wave laser beam emitted from the half-wave plate 69 b passes through the expander 3 b that expands the beam diameter to be parallel light, is reflected by the folding mirror 68, and is incident on the back surface of the polarizing plate 67 at an incident angle of 45 °. Incident.

  The polarizing plate 67 transmits a pulsed laser beam that is a P wave and reflects a continuous wave laser beam that is an S wave. By the polarizing plate 67, the pulse laser beam emitted from the laser light source 1a and the continuous wave laser beam emitted from the laser light source 1b are superimposed on the same optical axis.

  The pulse laser beam passing through the polarizing plate 67 and the continuous wave laser beam reflected by the polarizing plate 67 are focused by the objective lens 6, pass through the galvano scanner 7, and enter the substrate 12.

  An XY stage 8 a used as a holding table for the substrate 12 can move the substrate 12 in a two-dimensional plane parallel to the surface of the substrate 12. The controller 11 controls the XY stage 8a to move the substrate 12 to a desired position at a desired timing.

  In the example of the laser processing method described here, the X scanner 7a and the Y scanner 7b of the galvano scanner 7 are fixed at a position where the laser beam emitted from the galvano scanner 7 enters the substrate 12 perpendicularly. Yes. By moving the substrate 12 with the XY stage 8a, the incident position of the laser beam on the substrate 12 is moved.

  The voice coil mechanisms 9 and 10 respectively move the positions of the mask 5 and the objective lens 6 in parallel with the traveling direction of the pulse laser beam emitted from the laser light source 1a. The image of the through hole of the mask 5 is imaged on the surface of the substrate 12 at a desired imaging magnification (reduction ratio) by adjusting the positions of the mask 5 and the objective lens 6.

  With reference to FIG. 27B, the board | substrate 12 which is a process target object is demonstrated. A surface layer 121 is formed on the surface of the foundation layer 120. The underlayer 120 is, for example, a color filter of a liquid crystal display device, and is a resin layer made of polyimide resin, acrylic resin, or the like having a thickness of 1 μm. The surface layer 121 is, for example, an ITO film having a thickness of 0.5 μm.

  When only the surface layer 121 is removed by laser irradiation, it is difficult to process only the surface layer 121 because the underlayer 120 is more easily processed than the surface layer 121. For example, when the substrate is irradiated with a laser, the ground layer 120 explodes due to the effect of heat transmitted to the ground layer 120 before the surface layer 121 is directly processed, and the surface layer 121 is blown away accordingly. Things happen.

  The present inventor has found that it is easy to process only the surface layer 121 by performing laser irradiation after preheating the substrate. In the laser processing apparatus shown in FIG. 27A, the substrate 12 is preheated by the continuous wave laser beam emitted from the laser light source 1b, and holes and the like are processed by the pulse laser beam emitted from the laser light source 1a.

  Next, with reference to FIGS. 28A to 28C, an example of a method of forming holes by irradiating a pulsed laser after preheating a processing point on a substrate with a continuous wave laser will be described.

  As shown in FIG. 28A, processed points 105a, 105b, and 105c are defined on the surface of the substrate 12 irradiated with a continuous wave laser beam (indicated by a circular beam spot 95). The center of the beam spot 95 is located on a straight line connecting the processing points 105a to 105c. The XY stage is moved in parallel with the straight line, and the processing points 105 a to 105 c are moved toward the beam spot 95.

  As shown in FIG. 28B, when the processing point 105a reaches the edge of the beam spot 95, the processing point 105a is irradiated with a continuous wave laser and supply of preheating is started.

  As shown in FIG. 28C, when the processing point 105 a reaches the center of the beam spot 95, one-shot pulse laser irradiation is performed on the center of the beam spot 95. The beam spot of the pulse laser is indicated by a beam spot 96.

  The workpiece point 105 a is preheated while moving from the edge to the center of the beam spot 95. By irradiating the preheated processing point 105a with a pulse laser, it is possible to suppress the processing of the base layer and to form a hole in the surface layer of the substrate.

  The substrate 12 is continuously moved to form holes in the processing points 105b and 105c as well as the processing point 105a.

The irradiation conditions of the continuous wave laser beam used for preheating are, for example, a beam spot having a circular shape with a diameter of 20 mm, and a power density on the substrate surface of 0.1 W / cm ² . The irradiation condition of the pulse laser beam used for processing is, for example, that the beam spot is a 20 μm square and the pulse energy density on the substrate surface is 0.1 to 0.4 J / cm ² .

  Note that the time during which the workpiece point is preheated is approximately equal to the time during which the workpiece point moves by the length of the radius of the beam spot of the continuous wave laser. For example, when the radius of the beam spot is 10 mm and the moving speed of the XY stage is 800 mm / s, this time is about 0.13 seconds. By irradiating the center of the beam spot of the continuous wave laser beam with the pulse laser, it becomes easy to perform processing with the same preheating time even if the moving direction of the XY stage is changed variously.

  Since the preheating applied to the substrate surface by the irradiation of the continuous wave laser is transmitted to the base layer, the base layer is processed if too much preheating is applied. Therefore, it is necessary to supply the preheating so that the temperature of the underlayer remains below the temperature at which the underlayer is not processed. For example, it is necessary to keep the temperature of the underlayer below the melting point of the material of the underlayer.

  The ITO film is transparent to visible light, but the absorption coefficient for near infrared rays having a wavelength of 808 nm, for example, is not zero. Therefore, light of this wavelength can be used for preheating the ITO film. If light having a larger ITO absorption coefficient (for example, a wavelength in the vicinity of 1064 nm) is used, an improvement in preheating efficiency is expected.

  The example in which the pulse laser beam and the continuous wave laser beam are superimposed on the same optical axis to irradiate the substrate has been described. However, both laser beams may not be on the same optical axis. If the beam spot of the pulsed laser beam is included in the beam spot of the continuous wave laser beam and both laser beams are irradiated onto the substrate, the processing point reaches the edge of the beam spot of the continuous wave laser beam. Until the position of the beam spot of the pulse laser is reached, preheating can be supplied to the processing point.

  However, in order to give preheating, it is necessary that the processing point reaches the irradiation position of the pulse laser beam after passing through the inside of the beam spot of the continuous wave laser beam. Therefore, it is necessary that the irradiation position of the pulse laser beam does not coincide with the position of the processing point when the processing point comes into contact with the outer periphery of the beam spot of the continuous wave laser beam.

  Although an example in which holes are formed has been described, a plurality of holes may be formed continuously to form grooves.

  Although the example in which the incident position of the laser beam on the substrate is moved by the XY stage has been described, the incident position can also be moved by shaking the traveling direction of the laser beam with a galvano scanner.

  As mentioned above, although this invention was demonstrated along the Example, this invention is not limited to these. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

FIG. 1 is a schematic view of a laser processing apparatus for performing a laser processing method according to a first embodiment of the present invention. FIG. 2 is a schematic view showing an optical path of a laser beam in the laser processing apparatus for performing the laser processing method according to the first embodiment. 3A and 3B are plan views schematically showing the substrate processed by laser beam irradiation. FIG. 4A is an example of a through hole of a mask, and FIG. 4B is a schematic view showing a hole that can be opened in the substrate when the through hole shown in FIG. 4A is imaged on the substrate. FIG. 5A is a schematic graph showing energy density per pulse in a cross section of a pulse laser beam emitted from a laser light source, and FIG. 5B is a pulse laser in which a pulse energy density distribution is converted by a cone optical system. 5C is a schematic graph showing energy density per pulse in a cross section of the beam, and FIG. 5C is a schematic cross sectional view of a hole machined by a pulsed laser beam having a pulse energy density distribution shown in FIG. 5B. . FIG. 6 is a schematic diagram of a laser processing apparatus that performs a laser processing method according to a modification of the first embodiment. FIG. 7 is a schematic view showing an optical path adjusting mechanism. 8A and 8B are schematic views showing the transport mechanism. FIG. 9 is a schematic view of a conventional laser scribing apparatus. 10A and 10B are schematic plan views of a substrate processed by a conventional laser scribing apparatus. FIG. 11 is a schematic cross-sectional view of a substrate processed by a conventional laser scribing apparatus. FIG. 12A is a schematic view of a laser processing apparatus that performs a laser processing method according to the second embodiment, and FIG. 12B is a schematic view of a laser processing apparatus that performs a laser processing method according to a modification of the second embodiment. . FIG. 13 is a schematic view showing an optical path of a laser beam in a laser processing apparatus that performs the laser processing method according to the second embodiment. FIG. 14 is a schematic view showing an optical path of a laser beam in a laser processing apparatus that performs a laser processing method according to a modification of the second embodiment. FIG. 15A is a schematic diagram of a laser processing apparatus that performs the laser processing method according to the third embodiment, and FIG. 15B is a schematic diagram illustrating another configuration example of the primary condenser lens. FIG. 16 is a schematic diagram illustrating a configuration example of a secondary condenser lens. FIG. 17 is a schematic view of a laser processing apparatus for performing the laser processing method according to the fourth embodiment. FIG. 18A is a schematic view of the aperture rotated by the aperture tilt mechanism as seen from the direction of the rotation axis of the aperture tilt mechanism, and FIG. 18B shows the aperture rotated by the aperture tilt mechanism from the optical axis direction of the laser beam. FIG. 18C is a schematic view of the aperture rotated by the aperture tilt mechanism and the aperture rotation mechanism, as viewed from the optical axis direction of the laser beam. FIG. 19 is a schematic view of a laser processing apparatus for performing the laser processing method according to the fifth embodiment. FIG. 20 is a plan view of a substrate on which an image of a through hole is projected, showing a result of a simulation regarding transfer accuracy in a laser processing method using a proximity mask. FIG. 21 is a graph schematically showing the relationship between the divergence angle of the laser beam and the proximity gap when processing is performed with a certain transfer accuracy. FIG. 22A is a schematic view of a laser processing apparatus for performing a laser processing method according to the sixth embodiment, and FIG. 22B is a schematic cross-sectional view of a substrate. FIG. 23 is an example of an opportunity signal and a laser beam timing chart when performing laser processing using the laser processing apparatus according to the sixth embodiment. FIG. 24A is a schematic plan view of the substrate on which lines are formed, and FIG. 24B is a schematic plan view of the substrate on which dots are formed. FIG. 25 is a schematic view showing a mask rotation mechanism holding a mask. FIG. 26 is a schematic plan view of a substrate on which lines are formed using a mask rotation mechanism. FIG. 27A is a schematic view of a laser processing apparatus for performing a laser processing method according to the seventh embodiment, and FIG. 27B is a schematic cross-sectional view of a substrate. FIG. 28A, FIG. 28B, and FIG. 28C are plan views of the substrate for explaining the positional relationship between the processing point and the beam spot. FIG. 29 is a schematic plan view of a substrate on which lines are formed without using a mask rotation mechanism.

Claims (2)

Waving the traveling direction of the adjusted laser beam to have a spread angle of Jo Tokoro, disposed from the surface parallel to the surface of the object positioned at a predetermined distance, a proximity mask having through holes Irradiating the laser beam, causing the laser beam that has passed through the through hole to enter the surface of the workpiece, and transferring the shape of the through hole to the surface of the workpiece;
1. The predetermined spread angle and the predetermined distance are within a range where the predetermined distance is 0.5 mm or less and the predetermined spread angle is 0.5 mrad or less, or the predetermined distance is greater than 0.5 mm. A step of setting the predetermined divergence angle within a range of 0.1 mrad or less at 0 mm or less . Waving the traveling direction of the adjusted laser beam to have a spread angle of Jo Tokoro, disposed from the surface parallel to the surface of the object positioned at a predetermined distance, a proximity mask having through holes Irradiating the laser beam, causing the laser beam that has passed through the through hole to enter the surface of the workpiece, and transferring the shape of the through hole to the surface of the workpiece;
At least one of the predetermined divergence angle and the predetermined distance, the accuracy with which the shape of the through-hole is transferred to the surface of the workpiece, the divergence angle of the laser beam, the proximity mask and the workpiece And a step of setting based on a relationship obtained in advance with respect to the distance to the surface.