JP2009190069A - Machining method and device for transparent substrate by laser - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device where, for the purpose of satisfactory cutting of a substrate of glass or the like, such the substrate is economically machined by using an ultra-short pulsed laser. <P>SOLUTION: According to the following method, by focusing condensing points on the surface or inside of the substrate and irradiating it with a laser beam, a plurality of, preferably continuous cavities by a self-focusing effect are formed from the front face to the back face of the substrate. The method includes: a stage (1) where a laser beam with an ultra-short pulse width having a transparent wavelength to the substrate is generated and emitted, and the emitted laser beam is divided; a stage (2) where the respective divided laser beams are condensed on a plurality of condensing points aligned so as to be separated along the scheduled cutting lines of the substrate at different intervals different from the surface (front face) of the substrate at the side on which they are made incident; and a stage (3) where the plurality of condensing points are relatively moved to the substrate along the scheduled cutting lines of the substrate. Then, the condensing point formed at the position near the surface (back face) which is the opposite side to the front face of the substrate is scanned first. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a laser processing apparatus and a processing method, and more particularly to an apparatus and method for irradiating a processing object such as a glass substrate with an ultrashort pulse laser to form a cavity due to a self-focusing effect therein.

  In the electronics industry, a transparent glass plate is used as a panel constituent material for liquid crystal display panels, plasma display panels, and the like to incorporate elements constituting pixels between substrates. In order to reduce the manufacturing cost of the display panel, the transparent glass substrate is divided into individual panels in the middle of the process using a large glass substrate and finished to the final product size. In this case, a process of cutting from a large substrate is required, and it has been proposed to use a laser as one of the methods. In the method using an ultrashort pulse, a plurality of processed portions are formed in the thickness direction of a substrate by a method of forming a plurality of spots having different focal point positions in the optical axis direction. It is described in. In the proposed method, the laser oscillator may be single or plural, and two beams are separated by a beam splitter so that a plurality of laser beams can be focused at different positions on the same optical axis by different condensing lenses. A plurality of processing points are formed in the depth direction of the substrate by matching the same axis and irradiating the substrate.

  When the thickness of the substrate is increased and the thickness of the substrate is increased accordingly, the conventional method of forming a plurality of condensing points in the depth direction is insufficient in a processing amount sufficient to divide the substrate. In other words, in order to secure the depth at two condensing points, the machining amount cannot be obtained unless the output energy of the ultrashort pulse laser is significantly increased. This causes an increase, which increases the cutting width and causes a reduction in substrate material yield. If an attempt is made to form a plurality of condensing points, a single laser beam for processing by a beam splitter unless a long optical path length to the condensing point in the substrate after the condensing lens for obtaining the plurality of condensing points is secured. It becomes difficult to bundle the beam. In order to realize this, it is difficult to increase the optical path length unless the numerical aperture of the convergent beam is reduced.

  Reducing the numerical aperture increases the beam diameter at the condensing point, thereby reducing the laser power density at the condensing point. Therefore, in order to ensure the power density threshold required for processing the transparent body A need arises to increase the incident laser energy. Therefore, increasing the number of condensing points requires that the laser oscillation output energy also increase the laser power beyond the increase factor of the number of condensing points. This has no practical advantage.

  Japanese Patent Laid-Open No. 2007-142000 discloses that a plurality of condensing points are formed inside a transparent body using a multi-grating absorption method inside a substrate, and a plurality of internal modified layers are formed in the thickness direction. Thus, it has been proposed to perform substrate separation by cleaving without forming a scribing width in the substrate separation step. When creating a plurality of condensing points, the apparatus becomes expensive because a plurality of laser light sources are used.

US Reissue Patent No. 37585 Specification JP 2006-130566 A JP 2002-205180 A JP-A-56-129340 JP 2004-111946 A Japanese Patent Laid-Open No. 2007-142000 JP 2004-337902 A

  The problem to be solved is to reduce the cost of the laser light source when providing a method and apparatus for processing a transparent body with high accuracy and efficiency from the surface using the output of an ultrashort pulse of a solid-state laser. It is in the point which aims at.

In order to solve the above problems, in the present invention,
(1) A laser processing apparatus for forming a cavity due to a self-convergence effect in a substrate by irradiating a laser beam with a focusing point on the surface or inside of the substrate,
A pulse laser light source that emits and emits laser light having a wavelength transparent to the substrate and having a pulse width of 100 ps or less, and means for dividing the laser light emitted from the laser light source;
A condensing lens that condenses each of the divided laser beams at a plurality of condensing points that are spaced apart from each other along a planned cutting line of the substrate at different distances from the substrate surface (front surface) on the incident side. When,
Relative moving means for moving the plurality of condensing points relative to the substrate while irradiating the laser beam in a pulsed manner along a planned cutting line of the substrate, When a plurality of cavities due to the self-convergence effect are simultaneously formed in the interior of the substrate with a space in the vicinity of the condensing point, and the relative movement of the condensing point by the relative moving means, The condensing point formed at a position close to the surface (back surface) opposite to the surface is scanned before the condensing point at which the condensing point is formed at a position closer to the front surface. .
(2) Further, the means for dividing the laser beam has a polarization rotation element on the incident side, and light emitted from the polarization rotation element is incident on one of the two bonded polarization prisms, and is bonded to the bonding surface. The laser beam has a structure that is split into reflected light and transmitted light to the other polarizing prism at, and the split ratio of the reflected light and transmitted light is determined depending on the rotation angle change of the polarization rotation element It is a dividing device.
(3) Also, a polarization rotation element is provided on the incident side, and light emitted from the polarization rotation element is incident on one of the two bonded polarization prisms, and the reflected light and the other polarization prism are incident on the bonding surface. And the split ratio of the reflected light and the transmitted light is determined depending on the rotation angle change of the polarization rotation element.

On the other hand, in the present invention,
(1) A laser processing method for forming a cavity due to a self-focusing effect in a substrate by irradiating a laser beam with a focusing point on the surface or inside of the substrate,
Generating and emitting laser light having a wavelength transparent to the substrate and having a pulse width of 100 ps or less of the substrate; dividing the laser light emitted from the laser light source;
Condensing each of the divided laser beams at a plurality of condensing points that are spaced apart from each other along a planned cutting line of the substrate at different distances from the incident substrate surface (front surface);
Moving the plurality of condensing points relative to the substrate while irradiating the laser light in a pulsed manner along a planned cutting line of the substrate, and condensing the light by laser light irradiation. A plurality of cavities due to the self-convergence effect are simultaneously formed in the substrate at horizontal intervals in the vicinity of the point, and a surface opposite to the front surface of the substrate (back surface) is used in the relative movement step. The condensing point formed at a position close to the surface) is scanned before the condensing point at which the condensing point is formed at a position closer to the front surface.
(2) Further, the present invention is characterized in that a cavity that reaches one or both of the front side and the back side of the substrate is formed.
(3) Further, in the step of dividing the laser light, the laser light is divided so that the intensity of the divided light that forms the cavity closest to the front or back surface of the substrate is larger than the intensity of the other divided light. Features.

A single laser light source is used to divide the laser beam, and each of the divided beams forms a cavity due to a self-focusing effect in the substrate or on the surface, so that the substrate front surface (the side on which the laser beam is incident) Since a number of cavities are formed preferably continuously from the substrate surface) to the back surface (substrate surface opposite to the front surface),
(1) Since a single laser light source is used, an economical apparatus or method is obtained.
(2) In the subsequent substrate dividing step, the force required for the division can be greatly reduced, and the yield during the division can be improved.

  In the present invention, a method of processing an object by generating a self-focusing action in the object to be processed by laser irradiation will be described first. This is because ultra-short pulse laser light with a wavelength that is transparent to a processing object such as a glass substrate is used, and a small-diameter beam is irradiated in the laser beam traveling direction over a range longer than the focal depth of the focal point. It is provided to generate a self-focusing action inside the processed object. Due to the occurrence of the self-focusing action, a condensing channel is formed over a distance longer than the beam waist in the traveling direction of the laser light, and a cavity is formed in the condensing channel portion. There is a feature that the processing distance in the traveling direction of the laser beam is remarkably increased as compared with the normal ablation processing while the processing width by the laser beam is reduced.

  The ultrashort pulse amplifies the output from the mode-locked laser oscillator to a predetermined energy with, for example, a titanium sapphire amplification medium, adjusts the power level of the pulse as necessary, and the output laser beam is a condensing optical system such as a lens. To collect light. The condensing position in the laser beam optical axis direction is set to an appropriate position on the surface or inside of the processed object such as a glass substrate.

  Here, the ultrashort pulse laser is a laser having a pulse width of 100 ps or less, and preferably has a pulse width of 500 fs to 10 ps. Further, “being transparent with respect to the object to be processed” does not necessarily mean that the object to be processed transmits 100% light, and includes cases where laser light can be transmitted to some extent. For example, when the object to be processed is a silicon substrate, it may be an infrared region having a wavelength of 1 μm to 2 μm.

  FIG. 1 shows an embodiment of a processing apparatus according to the present invention. Ultrashort pulse laser oscillator 1, splitting means 71 for splitting laser beam 2 emitted from it, condensing lens group 35 for condensing each of the split laser beams, and substrate mounting for placing a substrate 72 to be processed An XY table 49 is provided to move the table 52 and the substrate mounting table 52. The XY table 49 includes an X-direction feed table 50 and a Y-direction feed table 51 disposed below the X-direction feed table 50. The XY table 49 is scanned along a processing line while its operation is programmed by a well-known control technique and highly accurate position and speed control is performed. The substrate 72 is mounted on the XY table 49 via the substrate mounting table 52. The substrate to be processed is made of glass, for example, Corning Eagle 2000 (thickness: 700 μm) can be used.

  In the ultrashort pulse laser oscillator 1, as an example of a laser medium, in addition to a titanium sapphire crystal (central wavelength 780 nm), an erbium-doped fiber, an yttrium-doped fiber, an Nd: YAG crystal, an Nd: YVO4 crystal, an Nd: YLF crystal, etc. can give. However, when the glass substrate is an object to be processed, the laser medium is preferably a titanium sapphire crystal. The laser beam 2 is split using a beam splitting means 71.

  The beam splitting means 71 is provided for the case where the beam is reflected by the mirror 3 and passed through the polarization rotation element 4 as necessary, and the beam energy splitting ratio in the subsequent polarizing beam splitter is adjusted. The beam that has passed through the polarization rotator 4 is split into a beam 7 and a beam 8 by a beam splitter 6. The beam 7 is further split into a beam 31 and a beam 32 by a beam splitter 11, and the beam 32 is split by a beam splitter 14. The beam 25 is divided into the beam 26 and the beam 31 is divided into the beam 23 and the beam 24 by the beam splitter 18. In these optical paths, mirrors 12, 13 and 15 are used for deflection in the beam optical path direction. On the other hand, the beam 8 is similarly split into separate parallel beams 27, 28, 29 and 30 using beam splitters 16, 21 and 22 and optical path deflecting mirrors 9, 17, 19 and 20. The beam splitting means 71 generates eight parallel beams 23-30.

Eight beams of the parallel beams 23 to 30 are condensed by the condenser lenses 36 to 43 in the condenser lens group 35, respectively. These condensing lenses 36 to 43 are arranged with the height gradually increased with respect to the substrate surface. That is, the condenser lenses 36 to 43 are installed at positions along the inclined line 44. The condensing lenses 36 to 43 are preferably lenses having a large numerical aperture (NA). This is because when the numerical aperture is large, the beam spot can be reduced, and the energy density of the laser pulse can be increased.

  The condensing lens 36 is arranged so that the condensing point 46 of the beam 23 is formed at a deeper location on the substrate. This beam 23 is set to an intensity having such energy and power intensity that a cavity is formed near the back surface 74 of the substrate 72 by a self-focusing action. Accordingly, a hollow groove or a spaced hole is formed on the back surface by a self-convergence action.

  The condensing lens 37 is installed above the condensing lens 36 so that the condensing point of the beam 24 is formed at a position closer to the substrate front surface than the condensing point of the previous beam 23. The condensing lenses 38 to 43 are also positioned higher than the previous lens so that the condensing points of the corresponding beams 25 to 30 are closer to the substrate front surface 73 than the previous condensing points. Deploy. The last condensing lens 43 is arranged so that the condensing point 45 of the corresponding beam 30 is closest to the front surface 73 and is preferably on the front surface. Each of the beams 24 to 30 is also set to an intensity having such an energy and power intensity that a cavity is formed by the self-focusing action.

  As described above, the focal points of the beams 23 to 30 are from the point 46 close to the back surface 74 inside the substrate 72 to the front surface 73 or the front surface and the depth inside the front surface 73. 53-59. For this reason, the cavities 83-90 by a self-convergence effect | action are formed corresponding to the number of condensing points. These condensing points or cavities are arranged in a line along the X direction 47. The direction becomes a planned cutting line of the substrate.

  With this apparatus, the substrate 72 is moved relative to the condensing point formed by the lens group 35 along the planned cutting line. That is, the substrate 72 is scanned by the XY table 49 in the direction of the X direction arrow 47 through the movement of the substrate mounting base 52. As a result, cavities 83 to 90 are formed sequentially in the substrate 72 from a position close to the back surface 74 to a position close to the front surface 73 by self-convergence.

  Although the substrate thickness is exaggerated in the figure, the actual substrate is 1 mm or less, so that a plurality of cavities 83 to 90 can be formed close to or continuously in the substrate. Therefore, a large number of cavities 83 to 90 can be formed from the back surface 74 toward the front surface 73. Since the cavity forms a processing line by scanning the substrate, it becomes easy to separate the substrate 72 along the processing line.

  FIG. 2 shows this state. Since the moving direction of the substrate 72 is 47 by the X direction arrow and the condensing point 46 of the beam 23 by the condensing lens 36 is closest to the substrate back surface 74, the cavity 83 of the substrate back surface is formed first. As the substrate 72 moves, the cavities 84 to 90 are sequentially stacked upward. Cavity formation is repeated by the number of condensing points (8 times in this example). As a result, as shown on the right side of the substrate 72, a linear cavity extending from the front surface to the back surface is formed. As shown in this figure, it is desirable that one cavity is formed so as to be continuously connected to the cavity above or below it, but it is not always necessary to be continuous. The linear cavities are continuously formed in the X direction by scanning the substrate 72 to form a cross section for substrate separation.

  It should be noted that it is desirable to achieve either or both of the fact that the first formed cavity reaches the substrate back surface 74 and the last formed cavity reaches the substrate front surface 73. This is because if a cavity is provided on at least one of the front and back surfaces, the substrate can be divided easily and the yield can be improved.

  The beam splitter 6 in FIG. 1 can be a transparent flat plate having a dielectric multilayer film deposition mirror. Further, the beam splitter 63 can be configured by bonding two polarizing prisms 64 and 65 as shown in FIG. The polarizing prisms 64 and 65 can be made of calcite. In the beam splitter 63, incident light 60 is incident on one polarizing prism 65, and the incident light 60 is divided into two parts of transmitted light and reflected light on the bonding surface, and the other polarizing prism 64 and the original polarizing prism. Outgoing lights 62 and 62 are emitted from 65, respectively. When the incident beam 60 to the beam splitter 63 is passed through the polarization rotation element 4 in advance, the polarization direction changes depending on the rotation angle of the polarization rotation element 4, so that the ratio of transmitted light and reflected light changes. Therefore, it is possible to vary the division ratio of the outgoing lights 61 and 62 from the beam splitter 63 depending on the rotation angle of the polarization rotation element.

  Rather than equal splitting at the time of beam splitting, it is possible to determine the intensity distribution from the ease of splitting according to the work material by providing a difference in intensity between the split beams. For example, the intensity of the beam 30 or 23 forming the condensing point 45 or 46 closest to the front surface 73 and the back surface 74 can be set to be higher than that of the other beams, for example, three times the intensity. Even if the beam energy in the irradiation part inside the substrate is set to an energy level lower than the energy applied to the front surface or the back surface, it effectively acts on the substrate division. Therefore, if the difference in the beam intensity is provided in this way, the total laser beam intensity can be reduced, so that the intensity of the laser beam 2 by the laser oscillator 1 before passing through the beam splitting means 71 can be reduced. Can do.

  In the above embodiment, the processing position in the substrate is adjusted by the amount of change in the height of the condenser lens from the substrate. However, the condenser lenses 36 to 43 are arranged at the same height to be in the optical path of the plurality of parallel beams 23 to 30. It is also possible to adjust the condensing position in the substrate with the converging lens and the synthesis characteristic by giving the beam divergence angle changes to each other. In the above embodiment, the XY table 49 is moved and the substrate 72 is moved to move the focusing point and the substrate relative to each other. However, the lens group 35 and the beams 23 to 30 are also moved relative to each other. Movement is possible.

  The embodiments of the present invention have been described above. Obviously, modifications may be made to the invention without departing from the scope of the invention as set forth in the appended claims.

  The present invention can be applied to precision processing of transparent glass substrate division cutting used for display devices such as liquid crystal and plasma.

The figure for demonstrating one Example of the processing apparatus and method of this invention. The figure for showing the condition where a board | substrate is processed by the apparatus or method of FIG. An embodiment of means for dividing the laser beam will be described.

Explanation of symbols

1: Ultrashort pulse laser oscillator 2: Laser beam 3, 9, 12, 13, 15, 17, 20, 19: Mirror 4: Polarization rotating element 6, 11, 16, 18, 14, 21, 22: Beam splitter 23 -30: split beam 35: condensing lens group 36-43: condensing lens 45: condensing point 46 by beam 30: condensing point 47 by beam 23: X direction arrow 48: Y direction 49: XY table 50 : X-direction feed table 51: Y-direction feed table 52: Substrate mounting bases 53 to 59: Internal depth 60: Light incident on the beam splitter 61, 62: Light emitted from the beam splitter 63: Beam splitters 64 and 65: Calcite polarizing prism 71: beam splitting means 72: substrate 73: substrate front surface 74: substrate back surface 83-90: cavity

Claims (6)

A laser processing apparatus for forming a cavity due to a self-focusing effect in the substrate by irradiating a laser beam with a focusing point on the surface or inside of the substrate,
A pulse laser light source that emits and emits laser light having a wavelength transparent to the substrate and having a pulse width of 100 ps or less, and means for dividing the laser light emitted from the laser light source;
A condensing lens that condenses each of the divided laser beams at a plurality of condensing points that are spaced apart from each other along the planned cutting line of the substrate, which are at different distances from the substrate surface (front surface) on the incident side. When,
Relative moving means for moving the plurality of condensing points relative to the substrate while irradiating the laser beam in a pulsed manner along a planned cutting line of the substrate, In forming a plurality of cavities due to the self-convergence effect at the same time in the vicinity of the condensing point in the horizontal direction, and relatively moving the condensing point by the relative movement means, The condensing point formed at a position close to the surface (back surface) opposite to the surface is scanned before the condensing point at which the condensing point is formed at a position closer to the front surface. Laser processing equipment.   2. The laser processing apparatus according to claim 1, wherein the means for splitting the laser beam has a polarization rotation element on the incident side, and light emitted from the polarization rotation element is applied to one of the two polarizing prisms bonded together. Incident light is split into reflected light and transmitted light to the other polarizing prism at the bonding surface, and the reflected light and transmitted light are split depending on the rotation angle change of the polarization rotation element. A laser processing apparatus, which is a laser beam splitting apparatus that determines a ratio. A polarization rotation element is provided on the incident side, and light emitted from the polarization rotation element enters one of the two bonded polarization prisms, and is reflected by the bonded surface and transmitted to the other polarization prism. It has a structure to be divided, and the division ratio of the reflected light and the transmitted light is determined depending on the rotation angle change of the polarization rotation element,
Laser beam splitter. A laser processing method for forming a cavity due to a self-convergence effect in the substrate by irradiating a laser beam with a focusing point on the surface or inside of the substrate,
Generating and emitting laser light having a wavelength transparent to the substrate and having a pulse width of 100 ps or less of the substrate; dividing the laser light emitted from the laser light source;
Condensing each of the divided laser beams to a plurality of condensing points that are spaced apart from each other along a planned cutting line of the substrate at different distances from the incident substrate surface (front surface);
Moving the plurality of condensing points relative to the substrate while irradiating the laser light in a pulsed manner along a planned cutting line of the substrate, and condensing the light by laser light irradiation. A plurality of cavities due to the self-convergence effect are simultaneously formed in the substrate with a space in the horizontal direction near the point, and a surface opposite to the front surface of the substrate (back surface) during the relative movement step. A laser processing method characterized in that a condensing point formed at a position near the surface is scanned before a condensing point at which the condensing point is formed at a position closer to the front surface.   The laser processing method according to claim 4, wherein the cavity is formed so as to reach one or both of the front side and the back side of the substrate.   The step of splitting the laser light is characterized in that splitting is performed such that the intensity of the split light that forms a cavity closest to the front or back surface of the substrate is greater than the intensity of the other split light. Item 6. The laser processing method according to Item 4 or 5.

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