JP2008132500A - Laser beam machining apparatus, laser beam machining method, method of manufacturing substrate and method of manufacturing electo-optical apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining apparatus, a laser beam machining method, a method of manufacturing a substrate and a method of manufacturing an electro-optical apparatus by which the drop of processing speed is suppressed by decreasing the number of stages for forming property modification zone to form a property modification zone corresponding to one cross section. <P>SOLUTION: This laser beam machining apparatus is provided with: a laser beam source for emitting a laser beam; an optical element for condensing the laser beam in the vicinity of one point in an object to be machined by condensing the laser beam and emitting onto the object to be machined; a stage having a placing plane on which the object to be machined is placed; a moving device for relatively moving the optical element and the stage in the direction parallel to the placing plane; and an optical axis varying device for varying the position of the one point in the thickness direction of the object to be machined by varying the incident angle of the laser beam to the object to be machined in the direction parallel to the relatively moving direction and the facial direction perpendicular to the facial direction of the object to be machined. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser processing apparatus, a laser processing method, a laser processing apparatus or a substrate manufacturing method using the laser processing method, and an electric power using the laser processing apparatus or laser processing method. The present invention relates to a method for manufacturing an optical device.

  Conventionally, as a technique for cutting a workpiece such as a substrate or a wafer along an arbitrary cutting line, a modified region by multiphoton absorption is formed along the planned cutting line inside the workpiece, and the modification is performed. A technique of cutting using a quality region is known. In Patent Document 1, a modified region inside a workpiece is formed by irradiating the workpiece with a pulse laser beam using a laser processing apparatus and condensing the pulse laser beam on a portion to be modified. A laser processing method is disclosed. According to this technique, the object to be processed can be cut from the modified region as a starting point by applying a slight force. This technique is suitable for fine processing because cutting scraps are not easily generated.

  In Patent Document 2, when the thickness of the workpiece is larger than the width of the modified region in the thickness direction of the workpiece, the thickness direction of the workpiece is about one cutting scheduled line. By executing the modified region forming process a plurality of times while changing the position of the condensing point, the modified region is stacked in the thickness direction of the workpiece, and the modified region in the planar direction of the workpiece is A method of forming a modified region over the entire thickness direction without increasing the area is disclosed.

JP 2002-192367 A JP 2002-205180 A

  However, since the modified region forming step is performed a plurality of times, there is a problem that the processing time increases and the processing speed per processing object decreases.

  The present invention solves the above-described problem, and can reduce the number of modified region forming steps for forming a modified region corresponding to one cut surface, thereby suppressing a decrease in processing speed. It is an object to realize a laser processing apparatus, a laser processing method, a substrate manufacturing method, and an electro-optical device manufacturing method.

  A laser processing apparatus according to the present invention includes a laser light source that emits laser light, an optical element that condenses the laser light in the vicinity of one point in the processing target, and a stage on which the processing target is mounted. A moving device that relatively moves the optical element and the stage in a direction parallel to the mounting surface, and an incident angle of the laser beam to the workpiece is parallel to the relative movement direction, and the surface of the workpiece And an optical axis changing device that changes the position in the thickness direction of one workpiece to be processed by changing in a plane direction perpendicular to the direction.

  According to the laser processing apparatus of the present invention, the modified region is formed in the vicinity of the one point by emitting the laser beam from the laser light source and condensing it in the vicinity of the one point in the processing object by the optical element. The In a state where light is focused on one point in the processing object placed on the stage, the optical element and the stage are moved relative to each other by the moving device, so that the modified region has a continuous or small interval in the processing object. A modified layer is formed that is spaced apart.

  At this time, by changing the incident angle of the laser beam to the workpiece by the optical axis fluctuation device in a plane direction parallel to the relative movement direction and perpendicular to the plane direction of the workpiece, the laser beam is The thickness direction of the object to be processed is changed by changing the condensing position, that is, the position where the modified region is formed in the surface direction perpendicular to the surface direction of the object to be processed, that is, in the thickness direction of the object to be processed. A modified layer having a undulating shape can be formed.

  The modified region is a region where a microcrack is formed or a region where a refractive index change occurs due to a permanent structural change such as crystallization or polarization orientation. The object to be processed can be divided using the modified layer connecting the modified regions as a trigger. It has been confirmed by the inventors of the present invention that even a modified layer having a wave shape in the thickness direction of the object to be processed functions sufficiently as a trigger for division.

  Since the modified layer has a wave shape in the thickness direction of the workpiece, the dimension of the modified layer in the thickness direction of the workpiece can be increased. If the thickness of the workpiece is larger than the dimension of the modified layer in the thickness direction of the workpiece, the modified layer is stacked in the thickness direction of the workpiece. By increasing the dimension of the modified layer in the vertical direction, the number of stacked layers can be suppressed. Therefore, it is possible to reduce the number of times the modified layer is formed, and to suppress a decrease in the processing speed for forming the modified layer over the entire thickness direction of the workpiece.

  In the present invention, it is preferable that the laser processing apparatus is an optical lens in which the optical element has a curvature of field, and the optical axis fluctuation device is provided between the laser light source and the optical lens.

  According to this laser processing apparatus, since the optical axis changing device is provided between the laser light source and the optical lens, the incident angle of the laser light to the optical lens can be changed. In general, in an optical lens having a curvature of field, light having different incident angles has a different focal position, that is, a focal position, in the axial direction of the optical lens. According to this laser processing apparatus, since the optical lens has a curvature of field, by changing the incident angle of the laser light to the optical lens, the processing of the position where the laser light is condensed in the processing object is performed. The position in the thickness direction of the object can be changed.

  In the present invention, in the laser processing apparatus, it is preferable that the optical axis fluctuation device is provided between the optical element and the stage.

  In general, the distance from the optical element to the focal point is constant when parallel light parallel to the optical axis of the optical element is collected by the optical element. Therefore, if the distance between the optical element and the optical axis varying device is fixed, the distance from the optical axis varying device to the focal point is constant. By changing the incident angle to the workpiece by the optical axis fluctuation device, that is, by changing the direction of the laser beam traveling from the optical axis fluctuation device to the workpiece, the optical axis fluctuation device in the thickness direction of the workpiece is changed. The distance to the focal point varies. According to this laser processing apparatus, by changing the incident angle to the processing object while keeping the distance between the optical element and the optical axis changing apparatus, the optical axis changing apparatus and the processing object constant, The position in the thickness direction of the workpiece can be changed at the position where the laser beam is condensed in the object.

  The laser processing method according to the present invention condenses the laser beam emitted from the laser irradiation device inside the processing object to form a modified region, and the processing object and the laser irradiation device are arranged in the plane direction of the processing object. And a scanning step for forming a modified layer in which the modified regions are continuously or spaced apart from each other, and in parallel with the scanning step, the incident angle of the laser beam to the workpiece Is changed in a plane direction parallel to the relative movement direction and perpendicular to the plane direction of the workpiece, thereby changing the position of the modified region in the thickness direction of the workpiece.

  According to the laser processing method of the present invention, in parallel with the scanning step, the incident angle of the laser beam to the processing object is parallel to the relative movement direction and is a surface direction perpendicular to the surface direction of the processing object. The position of the modified region in the thickness direction of the workpiece is changed by changing in step. Thereby, it is possible to form a modified layer having a wave shape in the surface direction perpendicular to the surface direction of the workpiece, that is, in the thickness direction of the workpiece. Since the modified layer has a wave shape in the thickness direction of the workpiece, the dimension of the modified layer in the thickness direction of the workpiece can be increased. If the thickness of the workpiece is larger than the dimension of the modified layer in the thickness direction of the workpiece, the modified layer is stacked in the thickness direction of the workpiece. By increasing the dimension of the modified layer in the vertical direction, the number of stacked layers can be suppressed. Therefore, it is possible to reduce the number of times the modified layer is formed, and to suppress a decrease in the processing speed for forming the modified layer over the entire thickness direction of the workpiece.

  In the present invention, the laser processing method condenses the laser light using an optical lens having a curvature of field, and changes the incident angle of the laser light incident on the optical lens, so that the laser light on the object to be processed is changed. It is preferable to vary the incident angle.

  In an optical lens having a curvature of field, light having different incident angles has a different focal position, that is, a focal position, in the axial direction of the optical lens. According to this laser processing method, since the optical lens has a curvature of field, by changing the incident angle to the optical lens, the position of the processing target at the position where the laser light is condensed in the processing target is determined. The position in the surface direction perpendicular to the surface direction, that is, the thickness direction of the workpiece can be changed.

  In this case, in the laser processing method, it is preferable to change the incident angle of the laser light on the workpiece by changing the traveling direction of the laser light emitted from the optical lens that collects the laser light.

  In general, the optical path length from the optical lens to the focal point is constant when parallel light parallel to the optical axis of the optical lens is collected by the optical lens. Since the optical path length is constant, the focal angle from the optical lens in the thickness direction of the workpiece is changed by changing the incident angle to the workpiece, that is, by changing the direction of the laser light traveling from the optical lens to the workpiece. The distance to fluctuates. According to this laser processing method, the laser beam is condensed in the processing target by changing the incident angle to the processing target while keeping the distance between the optical lens and the processing target constant. The position in the thickness direction of the workpiece can be changed.

  In the present invention, the laser processing method is an operation for changing the incident angle of the laser beam to the processing object when the position where the modified region is formed is closer to the surface of the processing object than a predetermined distance. It is preferable to carry out a scanning step that does not involve.

  When the position where the modified region is formed is close to the surface of the object to be processed, there is a possibility that the position where the modified region is formed varies from the inside of the object to be processed. According to this laser processing method, when the position where the modified region is formed is closer to the surface of the object to be processed than a predetermined distance, the scanning step without the operation of changing the incident angle is executed. Thus, it is possible to suppress the useless scanning step in which the position where the modified region is formed deviates from the inside of the workpiece.

  A substrate manufacturing method according to the present invention is characterized in that a mother substrate in which a plurality of substrates are partitioned is divided into individual substrates using the laser processing method described above.

  According to the substrate manufacturing method of the present invention, the number of times of forming the modified layer can be reduced, and the laser capable of suppressing the decrease in the processing speed for forming the modified layer over the entire thickness direction of the workpiece. By dividing the mother substrate using the processing method, the mother substrate can be efficiently divided to manufacture the substrate.

  A method of manufacturing an electro-optical device according to the present invention is characterized in that a mother electro-optical device substrate in which a plurality of electro-optical devices are partitioned is divided into individual electro-optical devices using the laser processing method described above.

  According to the method for manufacturing an electro-optical device according to the present invention, the number of times of forming the modified layer can be reduced, and the decrease in the processing speed for forming the modified layer over the entire thickness direction of the workpiece can be suppressed. By dividing the mother electro-optical device substrate using a laser processing method that can be performed, the mother electro-optical device substrate can be efficiently divided to manufacture the electro-optical device.

  A substrate manufacturing method according to the present invention is characterized in that a mother substrate in which a plurality of substrates are partitioned is divided into individual substrates using the laser processing apparatus described above.

  According to the substrate manufacturing method of the present invention, the number of times of forming the modified layer can be reduced, and the laser capable of suppressing the decrease in the processing speed for forming the modified layer over the entire thickness direction of the workpiece. By dividing the mother substrate using the processing apparatus, the mother substrate can be efficiently divided to manufacture the substrate.

  A method of manufacturing an electro-optical device according to the present invention is characterized in that a mother electro-optical device substrate on which a plurality of electro-optical devices are partitioned is divided into individual electro-optical devices using the laser processing apparatus described above.

  According to the method for manufacturing an electro-optical device according to the present invention, the number of times of forming the modified layer can be reduced, and the decrease in the processing speed for forming the modified layer over the entire thickness direction of the workpiece can be suppressed. By dividing the mother electro-optical device substrate using a laser processing apparatus capable of dividing the mother electro-optical device substrate, the electro-optical device can be efficiently manufactured by dividing the mother electro-optical device substrate efficiently.

  A method of manufacturing an electro-optical device according to the present invention is characterized in that a mother substrate on which a plurality of substrates constituting the electro-optical device are formed is divided into individual substrates using the laser processing apparatus described above.

  According to the method for manufacturing an electro-optical device according to the present invention, the number of times of forming the modified layer can be reduced, and the decrease in the processing speed for forming the modified layer over the entire thickness direction of the workpiece can be suppressed. By dividing the mother substrate using a laser processing apparatus capable of dividing the mother substrate efficiently and manufacturing the substrate constituting the electro-optical device efficiently, the electro-optical device can be efficiently manufactured. .

  An embodiment of a laser processing apparatus, a laser processing method, a substrate manufacturing method, and an electro-optical device manufacturing method according to the present invention will be described below with reference to the drawings. According to an embodiment of the present invention, in a process of manufacturing a liquid crystal display panel constituting a liquid crystal display device that is an example of an electro-optical device, a mother substrate on which the liquid crystal display panel is partitioned is cut to form individual liquid crystal display panels. A laser processing method and a laser processing apparatus used in the dividing step will be described as an example.

(First embodiment)
<Configuration of LCD panel>
First, a liquid crystal display panel will be described. FIG. 1 is a schematic diagram showing the structure of a liquid crystal display panel. FIG. 1A is a plan view of the liquid crystal display panel as viewed from the counter substrate side together with each component, and FIG. 1B is a cross-sectional shape taken along line AA in FIG. It is a schematic sectional drawing which shows. In each drawing used in the following description, the scale is different for each layer and each member so that each layer and each member can be recognized on the drawing.

  As shown in FIGS. 1A and 1B, a liquid crystal display panel 10 is bonded to an element substrate 1 having a TFT (Thin Film Transistor) element 3, a counter substrate 2 having a counter electrode 6, and a sealing material 4. And a liquid crystal 5 filled in a gap between the element substrate 1 and the counter substrate 2. The outer shape of the element substrate 1 is slightly larger than the counter substrate 2 and is in a state of protruding in a frame shape.

  The element substrate 1 uses a quartz glass substrate having a thickness of about 1.2 mm, and has a pixel electrode (not shown) constituting a pixel on its surface and a TFT in which one of three terminals is connected to the pixel electrode. Element 3 is formed. The remaining two terminals of the TFT element 3 are connected to a data line (not shown) and a scanning line (not shown) which are arranged in a grid pattern so as to surround the pixel electrode and are insulated from each other. The data line is drawn out in the Y-axis direction and connected to the data line driving circuit unit 9a at the terminal unit 16. The scanning lines are drawn out in the X-axis direction and are individually connected to two scanning line driving circuit units 9b formed in the left and right frame regions. The input side wirings of each data line driving circuit unit 9 a and scanning line driving circuit unit 9 b are connected to the mounting terminals 11 arranged along the terminal unit 16, respectively. In the frame region opposite to the terminal portion 16, a wiring 12 that connects the two scanning line driving circuit portions 9b is provided.

  The counter substrate 2 is a transparent quartz glass substrate having a thickness of approximately 1.0 mm, and is provided with a counter electrode 6 as a common electrode. The counter electrode 6 is electrically connected to the wiring provided on the element substrate 1 side through the vertical conduction parts 14 provided at the four corners of the counter substrate 2, and the wiring is also connected to the mounting terminal 11 provided in the terminal part 16. It is connected.

  An alignment film 7 and an alignment film 8 are formed on the surface of the element substrate 1 facing the liquid crystal 5 and the surface of the counter substrate 2, respectively.

  In the liquid crystal display panel 10, a relay substrate that is electrically connected to an external drive circuit is connected to the mounting terminal 11. An input signal from the external drive circuit is input to each data line drive circuit unit 9a and scan line drive circuit unit 9b, whereby the TFT element 3 is switched for each pixel electrode, and the pixel electrode and the counter electrode 6 are switched. In the meantime, a drive voltage is applied to display.

  Although not shown in FIG. 1, polarizing plates are provided on the front and back surfaces of the liquid crystal display panel 10 to polarize incoming and outgoing light, respectively.

<LCD panel mother board>
Next, a mother substrate 10A in which the liquid crystal display panel 10 is partitioned will be described with reference to FIG. FIG. 2 is a schematic view showing a mother substrate on which a liquid crystal display panel is partitioned. 2A is a schematic plan view of the mother substrate, and FIG. 2B is a schematic cross-sectional view showing a cross-sectional shape in a cross section indicated by BB in FIG. 2A. In addition, in FIG.2 (b), the sealing material 4 is abbreviate | omitting illustration. Although the thickness of the sealing material 4 and the liquid crystal 5 with respect to the thickness of the mother element substrate 1A and the like is very small, in FIG. 1B described above, the liquid crystal 5 and the like are shown thickly.

  As shown in FIG. 2A, in the mother substrate 10A, a plurality of element substrates 1 corresponding to one liquid crystal display panel 10 are formed in a wafer-like mother element substrate 1A. Then, as shown in FIG. 2B, the counter substrate 2 is bonded to the element substrate 1 that is partitioned and formed individually. One liquid crystal display panel 10 is taken out from the mother substrate 10A by cutting the planned cutting positions along the partition regions Dx and Dy. In this case, the mother element substrate 1A is a quartz glass substrate having a thickness of 1.2 mm and a diameter of 12 inches. On the mother substrate 10A, 200 liquid crystal display panels 10 are partitioned and formed.

<Laser processing equipment>
Next, the laser processing apparatus used in this embodiment will be described. FIG. 3 is a schematic diagram showing the configuration of the laser processing apparatus.

  As shown in FIG. 3, the laser processing apparatus 100 includes a laser light source 21, a reflecting mirror 22, a condenser lens 23, a Z-axis slide mechanism 24, a reflecting mirror rotating device 29, a stage 20, and a rotating mechanism. A mechanism 25, an X-axis slide mechanism 27, a Y-axis slide mechanism 26, and a machine base 28 are provided.

  The laser light source 21 is a so-called Nd: YAG laser using, for example, a crystal obtained by doping yttrium-aluminum-garnet with neodymium as a laser medium. The excitation method of the laser light source 21 is, for example, LD excitation. In order to form the modified layer on the mother element substrate 1A made of quartz glass, the laser beam is used by oscillating Nd: YAG-THG (third harmonic).

  The laser light emitted from the laser light source 21 is reflected by the reflecting mirror 22 and condensed by the condenser lens 23. The workpiece W is placed on the stage 20 so that the focal point on which the laser light is collected by the condenser lens 23 is located inside the workpiece W. The condenser lens 23 is supported by a slide arm 24 a extending from the Z-axis slide mechanism 24, and the Z-axis slide mechanism 24 moves the condenser lens 23 relative to the workpiece W placed on the stage 20. Is moved in the thickness direction of the workpiece W (Z-axis direction in FIG. 3). The reflecting mirror rotating device 29 supports the reflecting mirror 22 so as to be rotatable, and changes the optical axis direction of the laser light reflected by the reflecting mirror 22 by changing the angle of the reflecting mirror 22.

  The machine base 28 is a frame that supports each mechanism constituting the laser processing apparatus 100. An X-axis slide base 27b constituting the X-axis slide mechanism 27 is fixed to the machine base 28, and the X-axis slider 27a constituting the X-axis slide mechanism 27 is slidable and fixable in the X-axis direction. The slide base 27b is engaged. The Y-axis slide base 26b constituting the Y-axis slide mechanism 26 is fixed to the X-axis slider 27a, and the Y-axis slider 26a constituting the Y-axis slide mechanism 26 is slidable and fixable in the Y-axis direction. The shaft slide base 26b is engaged. A rotation mechanism base 25b constituting the rotation mechanism 25 is fixed to the Y-axis slider 26a, and the rotation table 25a constituting the rotation mechanism 25 is rotatable about the Z axis so as to be rotatable. The base 25b is engaged. The X-axis slider 27a, the Y-axis slider 26a, and the rotation table 25a are driven by a servo motor (not shown) configured between the X-axis slide base 27b, the Y-axis slide base 26b, and the rotation mechanism base 25b, respectively. The

  The stage 20 is fixed to the rotary table 25a and is used for placing the workpiece W. The workpiece W placed on the stage 20 is sucked by, for example, a suction device configured on the stage 20 and fixed to the stage 20. The workpiece W fixed to the stage 20 can be rotated around the Z axis by the rotation mechanism 25, and the posture of the condenser lens 23 in the direction parallel to the X axis and the Y axis (plane direction) is set. Adjusted. Further, the workpiece W fixed to the stage 20 is moved in a plane direction parallel to the X axis and the Y axis by the X axis slide mechanism 27 and the Y axis slide mechanism 26, and the workpiece W is arbitrarily selected. Is moved to a position facing the condenser lens 23. The X-axis slide mechanism 27 and the Y-axis slide mechanism 26 correspond to a traveling device. The thickness direction of the workpiece W placed and fixed on the stage 20 is the Z-axis direction.

  The laser processing apparatus 100 includes a main computer 30 as a control unit that controls each of the above components. The main computer 30 has a CPU and various memories.

  A laser control unit 31, a lens control unit 32, a stage control unit 33, a reflecting mirror control unit 34, an input unit 35, and a display unit 36 are connected to the main computer 30. The input unit 35 is used to input data on various processing conditions used during laser processing, and the display unit 36 is used to display various information during laser processing. The laser control unit 31 controls the output, pulse width, and pulse period of the laser light source 21. The lens control unit 32 drives the Z-axis slide mechanism 24 to control the position of the condenser lens 23 in the Z-axis direction. The stage control unit 33 controls a servo motor (not shown) that drives the rotation mechanism 25, the X-axis slide mechanism 27, and the Y-axis slide mechanism 26. The reflecting mirror rotating device 29 supports the reflecting mirror 22 in a rotatable manner, and the reflecting mirror control unit 34 controls the reflecting mirror rotating device 29 to change the angle of the reflecting mirror 22. The optical axis direction of the laser beam reflected by the reflecting mirror 22 is changed.

  The Z-axis slide mechanism 24 that moves the condensing lens 23 in the Z-axis direction has a built-in position sensor capable of detecting the moving distance, and the lens control unit 32 detects the output of the position sensor and collects the light. The position of the lens 23 in the Z-axis direction can be controlled. Therefore, the condensing position of the condensing lens 23 can be adjusted to an arbitrary position from the surface of the workpiece W. In addition, the lens group which comprises the condensing lens 23 has not corrected the curvature of field, and the condensing lens 23 has a curvature of field.

<Formation of modified region>
Here, formation of the modified region by multiphoton absorption will be described. Even if the workpiece W is made of a material that is transparent to the light applied thereto, absorption occurs when the photon energy hν is much larger than the absorption band gap Eg of the material. This absorption is called multiphoton absorption. When multiphoton absorption is caused to occur inside the workpiece W, the energy of the multiphoton absorption is converted into thermal energy, so that microcracks are formed inside the workpiece W. Alternatively, when the pulse width of the laser beam is made extremely short to cause multiphoton absorption to occur inside the workpiece W, the energy of the multiphoton absorption is not converted into thermal energy, but the ionic valence change and crystallization. Alternatively, a permanent structural change such as polarization orientation is induced to form a refractive index change region. In the present embodiment, the region where these micro cracks are formed or the refractive index change region is referred to as a modified region 40 (see FIG. 4).

  In the case of forming a modified region with pulsed laser light, one modified region is formed with one pulse of laser light. By forming the modified region while moving the condensing position in the plane direction of the workpiece W, the modified region is arranged continuously or at a slight interval in the plane direction of the workpiece W. Form a row. This row of the modified region is hereinafter referred to as a modified layer 42 (see FIG. 5). The condensing position is moved in the thickness direction of the workpiece W, and a new modified layer 42 is formed at a position overlapping the formed modified layer 42 and the workpiece W in the plane direction. The modified layer 44 (see FIG. 5) is formed by stacking the quality layers 42 and the modified regions 40 arranged in a plane.

<Conversion in optical axis direction>
Next, the relationship between the direction of the optical axis incident on the workpiece W and the focal position of the focal point F where the light is collected will be described with reference to FIG. FIG. 4 is a schematic diagram showing the relationship between the optical axis direction and the focal position. As described above, in the laser processing apparatus 100, the laser light emitted from the laser light source 21 (see FIG. 3) is reflected by the reflecting mirror 22, changes its direction, and enters the condenser lens 23. The laser light emitted from the condenser lens 23 is condensed at the focal position. As described above, the angle of the reflecting mirror 22 in the plane direction parallel to the Y axis and the Z axis can be changed by the reflecting mirror rotating device 29.

  As shown in FIG. 4, the laser light L <b> 1 emitted in parallel with the Y-axis direction from the laser light source 21 is reflected by the reflecting mirror 22 so as to enter the condenser lens 23. The laser beam L11 that is incident upon and reflected by the reflecting mirror 221 indicated by the solid line at the incident angle θ1 is substantially parallel to the Z-axis direction and is incident on the condenser lens 23 at an incident angle of approximately 0 degrees. . The laser beam L12 from which the incident laser beam L11 is emitted from the condenser lens 23 is collected at the focal point F1. The laser beam L21 incident on the reflecting mirror 222 indicated by the two-dot chain line at the incident angle θ2 and reflected is inclined with respect to the Z-axis direction, and the laser beam L1 is condensed on the condenser lens 23. Incident light is incident at an incident angle inclined with respect to the optical axis of the lens 23. The laser beam L22 emitted from the incident laser beam L21 from the condenser lens 23 is collected at the focal point F2. The focal point F3 is a focal point on which the laser light is condensed when the reflecting mirror 22 is tilted to the side opposite to the reflecting mirror 222 with respect to the reflecting mirror 221.

  Since the condensing lens 23 has field curvature, the image plane F0 is curved, and the focal point F1, the focal point F2, or the focal point F3 have different positions in the Z-axis direction. Therefore, the modified region 401, the modified region 402, and the modified region 403 that are formed by the laser light focused on the focal point F1, the focal point F2, and the focal point F3 are located in the processing object W. The workpiece W is different in the thickness direction. Since the reflecting mirror rotating device 29 can change the angle of the reflecting mirror 22 in the Y-axis and Z-axis plane directions, the focal point F1, the focal point F2, and the focal point F3 are on substantially the same plane parallel to the Y-axis and the Z-axis. Exists. Accordingly, the modified region 401, the modified region 402, and the modified region 403 are formed on substantially the same plane.

<Separation of LCD panel>
Next, a process of cutting the mother substrate 10A by a laser scribing method using the laser processing apparatus 100 and separating it into individual liquid crystal display panels 10 will be described. As described above, in the mother substrate 10A, a plurality of element substrates 1 corresponding to one liquid crystal display panel 10 are formed on the mother element substrate 1A, and the counter substrate 2 is bonded to the element substrate 1 that is individually formed. Has been. A liquid crystal display panel is formed by forming a modified band at the boundary of the element substrate 1 formed on the mother element substrate 1A, and applying a weak bending force or tensile force in the vicinity of the modified band to separate the modified band portion. 10 is separated. The mother substrate 10A corresponds to a workpiece.

  In order to prevent a part of the liquid crystal display panel 10 from being separated and becoming difficult to handle in a state where the modified zone is formed, a protective film 39 (FIG. 6) covering the whole mother substrate 10A in advance. Is attached on the counter substrate 2 in advance. It should be noted that if the laser light incident surface has irregularities or bends, the condensing property of the laser light within the substrate is impaired, and the modified region 40 (modified layer 42) may not be formed. The laser light incident surface must be a smooth surface. Therefore, when the laser light is incident from the protective film 39 side, the protective film 39 is attached using a film having a substantially mirror surface so that the flatness of the surface is not impaired.

  Next, the process of forming the modified zone 44 on the mother element substrate 1A will be described with reference to FIG. FIGS. 5A, 5B, 5C, and 5D are schematic cross-sectional views of a mother element substrate showing a process in which a modified zone is formed on the substrate. In FIG. 5, the counter substrate 2 other than the mother element substrate 1A is not shown.

  As a preparation stage for forming the modified zone 44, first, the mother substrate 10 </ b> A is fixed to the stage 20. Next, the stage 20 is rotated around the Z-axis by the rotation mechanism 25, and one extending direction of the boundary of the element substrate 1 formed on the mother element substrate 1A coincides with, for example, the Y-axis direction in FIG. Let Next, the mother substrate 10A fixed to the stage 20 is moved in the X-axis direction by the X-axis slide mechanism 27, and one of the boundaries where the extending direction of the element substrate 1 coincides with the Y-axis direction is condensed. Set on the optical axis of the lens 23. Next, the modified zone 44 is formed along the boundary set on the optical axis of the condenser lens 23.

  First, as shown in FIG. 5A, the laser light emitted from the condensing lens 23 is condensed by condensing it in the vicinity of the surface opposite to the laser light incident surface of the mother element substrate 1A. A quality region 40 is formed. In parallel with the formation of the modified region 40, the Y-axis slide mechanism 26 moves the mother element substrate 1A in the direction of arrow a to form a modified layer 421 in which the modified regions 40 are continuous or continuous. . As described above, the laser light source 21 that is the light source of the laser light L1 is an LD-excited Nd: YAG laser. In the present embodiment, a third harmonic having a wavelength of 355 nm is used. The modified region by the laser beam having a wavelength of 355 nm is a micro crack formation region in which micro cracks are formed.

  Next, as shown in FIG. 5B, in parallel with the formation of the modified region 40, the mother element substrate 1 </ b> A is moved in the direction of the arrow “a” and the emission angle of the laser light from the condenser lens 23. That is, the modified layer 426 is formed by changing the incident angle of the laser beam on the mother element substrate 1A. As described above, the angle of the reflecting mirror 22 in the plane direction parallel to the Y axis and the Z axis can be changed by the reflecting mirror rotating device 29. By changing the angle of the reflecting mirror 22, the incident angle of the laser light to the condenser lens 23 is changed, thereby changing the emission angle of the laser light from the condenser lens 23. The reflecting mirror 22 and the reflecting mirror rotating device 29 correspond to an optical axis changing device.

  The process of forming the modified layer 426 will be described in more detail. While the position of the condensing lens 23 moves from the position of the condensing lens 231 shown in FIG. 5B to the position of the condensing lens 232, the emission angle of the laser light L is changed as indicated by an arrow b. While the position of the condenser lens 23 moves from the position of the condenser lens 231 to the position of the condenser lens 232, the position of the focal point F of the laser light moves from the focal point F4 to the focal point F5 shown in FIG. To do. As a result, the modified layer 422 curved upward in FIG. 5B is formed.

  Subsequently, while the condenser lens 23 moves from the position of the condenser lens 232 to the position of the condenser lens 233, the emission angle of the laser light L is changed as indicated by an arrow c. While the condenser lens 23 moves from the position of the condenser lens 232 to the position of the condenser lens 233, the position of the focal point F of the laser light moves from the focal point F5 to the focal point F6. Thereby, a substantially U-shaped modified layer 423 is formed.

  Subsequently, while the condenser lens 23 moves from the position of the condenser lens 233 to the position of the condenser lens 234, the emission angle of the laser light L is changed as indicated by an arrow b. While the condenser lens 23 moves from the position of the condenser lens 233 to the position of the condenser lens 234, the position of the focal point F of the laser light moves from the focal point F6 to the focal point F7. As a result, the modified layer 424 having a shape that is formed by extending the substantially U-shape into a horizontally long shape is formed. Thereafter, similarly, the modified layer 423 and the modified layer 424 are continuously formed to form the modified layer 426.

  Next, as shown in FIG. 5C, the modified region 40 is formed by condensing the laser light emitted from the condenser lens 23 in the vicinity of the laser light incident surface of the mother element substrate 1A. To do. In parallel with the formation of the reforming region 40, the mother element substrate 1A is moved in the direction of arrow a by the Y-axis slide mechanism 26, so that the reforming layer 427 in which the reforming regions 40 are continuous or continuous is changed to the mother. It is formed in the vicinity of the laser beam incident surface of the element substrate 1A.

  In this way, by forming the modified layer 421, the modified layer 426, and the modified layer 427, a modified zone 441 as shown in FIG. 5D is formed.

  When the formation of the modified band 44 (modified band 441) is completed at the boundary of all the element substrates 1 formed on the mother element substrate 1A, the mother substrate 10A is separated into individual liquid crystal display panels 10. FIG. 6 is a schematic diagram showing a state in which the mother substrate is divided at the portion where the modified zone is formed. By applying a force so as to separate both sides sandwiching the reforming zone 44, the portion of the reforming zone 44 is divided. For example, as shown in FIG. 6A, the pressing jig 50 is pressed on a straight line on which the modified band 441 is formed to apply stress to the vicinity of the mother element substrate 1A where the modified band 441 is formed. As shown in FIG. 6B, the mother element substrate 1A subjected to stress is divided by the surface on which the modified band 441 is formed as a result of the modified band 441 as a trigger. Separated into individual liquid crystal display panels 10.

<Example of shape of reforming zone>
Next, an example of the reforming zone 44 having a shape different from that of the above-described reforming zone 441 will be described with reference to FIG. FIGS. 7A, 7B, 7C, and 7D are schematic cross-sectional views each showing an example of the shape of the reforming zone. The modified zone 442 shown in FIG. 7A is composed of only one layer of the above-described modified layer 426 (see FIG. 5). This is applied when the thickness of the workpiece 61 is small and the modified layer 426 can be formed over substantially the entire surface in the thickness direction by a single scan.

  A modified zone 443 shown in FIG. 7B includes a modified layer 428 and the above-described modified layer 421 and modified layer 427 (see FIG. 5). Similar to the above-described modified layer 426, the modified layer 428 is formed by changing the laser light emission angle while relatively moving the condenser lens 23 and the workpiece 62. When the relative movement speed between the focal point F and the object to be processed 62 by changing the emission angle of the laser beam is larger than the relative movement speed between the condenser lens 23 and the object to be processed 62, the modified layer 426 is used. The modified layer 42 having a proper shape is formed. When the modified layer 42 is small, the modified layer 42 having a shape like the modified layer 428 is formed.

  The modified zone 444 shown in FIG. 7C is formed by stacking two modified layers 428 in the thickness direction of the workpiece 63. The modified zone 446 shown in FIG. 7D includes the modified layer 421, the modified layer 426, the other modified layer 426, and the modified layer 427 described above, which are the workpiece 64. Are laminated in the thickness direction.

<Division of counter substrate 2>
As described above, the counter substrate 2 is individually attached to each of the element substrates 1 partitioned on the mother element substrate 1A. Similar to the element substrate 1, the counter substrate 2 is partitioned and formed on the mother counter substrate. The mother counter substrate is divided into the above-described mother element substrate 1A by dividing the mother substrate 10A into the liquid crystal display panel 10 and dividing the mother substrate 10A to form the individual counter substrate 2 by dividing the mother substrate 10A. To do.

The effects of the first embodiment will be described below. According to the first embodiment, the following effects can be obtained.
(1) By providing the reflecting mirror 22 and the reflecting mirror rotating device 29 corresponding to the optical axis varying device between the laser light source 21 and the condensing lens 23, the incident angle to the condensing lens 23 is fluctuated. Can be made. Further, the laser light emitted from the laser light source 21 is parallel light having directivity, and even if the distance between the laser light source 21 and the condenser lens 23 changes, there is almost no influence such as light loss. Therefore, by providing the reflecting mirror 22 and the reflecting mirror rotating device 29 at this position, the influence on the optical system can be suppressed and the optical axis changing device can be provided.

  (2) Since the condensing lens 23 has a curvature of field, by changing the angle of incidence on the condensing lens 23, the mother element substrate at the focal point F where the laser light is condensed in the mother element substrate 1A. The position in the thickness direction of 1A can be changed.

  (3) By changing the position of the focal point F in the thickness direction of the mother element substrate 1A, the width of the formed modified layer 426 and the modified layer 428 in the thickness direction of the mother element substrate 1A can be increased. . The width in the thickness direction of the mother element substrate 1A of the modified layer that can be formed by one scan is widened, thereby reducing the number of scans for forming the modified band 44 over substantially the entire surface in the thickness direction of the mother element substrate 1A. be able to. Therefore, the processing time for forming the modified zone 44 can be shortened.

(Second embodiment)
Next, a second embodiment of the laser processing apparatus, the laser processing method, the substrate manufacturing method, and the electro-optical device manufacturing method according to the present invention will be described. The laser processing apparatus of this embodiment is substantially the same as the laser processing apparatus 100 described in the first embodiment. Only the configuration and operation of the laser light transmission path different from the first embodiment will be described.

<Configuration of laser light transmission path>
First, the configuration of the laser beam transmission path of the laser processing apparatus used in this embodiment will be described. FIG. 8 is a schematic diagram showing a configuration of a laser beam transmission path of the laser processing apparatus.

  As shown in FIG. 8, the laser beam transmission path of the laser processing apparatus includes a first reflecting mirror 322, a condenser lens 323, a second reflecting mirror 324, a third reflecting mirror 325, and a third reflecting mirror rotating. And a device 329.

  Laser light emitted from the laser light source 21 (see FIG. 3) is reflected by the first reflecting mirror 322 and collected by the condenser lens 323. The condenser lens 323 is supported by a Z-axis slide mechanism 24 (see FIG. 3), and the Z-axis slide mechanism 24 is a condenser lens with respect to the workpiece W placed on the stage 20 (see FIG. 3). The position of condensing the laser beam is moved in the thickness direction of the workpiece W by relatively moving the H.323. The laser light emitted from the condenser lens 323 is reflected by the second reflecting mirror 324 and further reflected by the third reflecting mirror 325 to be condensed inside the workpiece W. The third reflecting mirror rotating device 329 supports the third reflecting mirror 325 so that the third reflecting mirror 325 can rotate, and the angle of the third reflecting mirror 325 in the plane direction parallel to the Y axis and the Z axis can be changed. it can. The third reflecting mirror rotating device 329 changes the optical axis direction of the laser light reflected by the third reflecting mirror 325 by changing the angle of the third reflecting mirror 325. The third reflecting mirror rotating device 329 and the third reflecting mirror 325 correspond to an optical axis changing device.

<Conversion in optical axis direction>
Next, the relationship between the direction of the optical axis that is incident on the workpiece W and the focal position of the focal point F where the light is collected will be described with reference to FIG. 8 as with the configuration of the laser light transmission path. As described above, the laser light emitted from the laser light source 21 (see FIG. 3) is collected by the condensing lens 323 and is condensed at the focal position inside the workpiece W.

  As shown in FIG. 8, the laser light L <b> 3 emitted in parallel with the Y-axis direction from the laser light source 21 is reflected by the first reflecting mirror 322 so as to enter the condenser lens 323. The angle of the first reflecting mirror 322 is fixed, and the direction of the laser light L31 from which the laser light L3 is reflected by the first reflecting mirror 322 is substantially parallel to the Z-axis direction and is substantially incident on the condenser lens 323. Incident at an angle of 0 degrees.

  The laser light L31 incident on the condenser lens 323 is condensed by the condenser lens 323, and the laser light L32 whose optical axis direction is substantially parallel to the Z-axis direction is emitted. The laser beam L32 reflected by the second reflecting mirror 324 and substantially parallel to the optical axis direction Y-axis direction is denoted as laser beam L33. The laser beam L34 reflected by the third reflecting mirror 325 is incident on the workpiece W.

  The laser beam L33 (laser beam L34) reflected by the laser beam L33 incident on the third reflecting mirror 326 indicated by the solid line at an incident angle θ3 is substantially parallel to the Z-axis direction and is to be processed. It enters the object W at an incident angle of approximately 0 degrees. The laser beam L36 incident on the workpiece W is collected at the focal point F21. The laser beam L37 (laser beam L34) reflected when the laser beam L33 is incident on the third reflecting mirror 327 indicated by a two-dot chain line at an incident angle θ4 and reflected is inclined with respect to the Z-axis direction. It enters the object W at an incident angle inclined with respect to the Z-axis direction. The laser beam L37 incident on the workpiece W is collected at the focal point F22. The focal point F23 is a focal point on which laser light is condensed when the third reflecting mirror 325 is tilted to the opposite side of the third reflecting mirror 327 with respect to the third reflecting mirror 326.

  When parallel light parallel to the optical axis of the condenser lens 323 is condensed by the condenser lens 323, the distance from the condenser lens 323 to the focal point F is constant. Since the distance to the focal point F does not change even if it is reflected halfway, the focal point F21, the focal point F22, and the focal point F23 are arc-shaped around the point where the optical axis of the laser beam L33 is reflected by the third reflecting mirror 325. Located on the image plane F0. Therefore, the modified region 431, the modified region 432, and the modified region 433 that are formed by the laser light focused on the focal point F21, the focal point F22, and the focal point F23 in the processing object W are formed at positions where they are formed. The workpiece W is different in the thickness direction. Since the third reflecting mirror rotating device 329 can change the angle of the third reflecting mirror 326 in the Y-axis Z-axis plane direction, the focus F21, the focus F22, and the focus F23 are parallel to the Y-axis and the Z-axis. Exists on substantially the same plane. Therefore, the modified region 431, the modified region 432, and the modified region 433 are formed on substantially the same plane.

<Separation of LCD panel>
As described above, the laser processing apparatus of the present embodiment forms the modified region 40 by changing the angle of the third reflecting mirror 326 in the Y-axis Z-axis plane direction by the third reflecting mirror rotating device 329. The position to be processed can be changed in the thickness direction of the workpiece W. Using this laser processing apparatus, in the first embodiment, a process similar to the process of forming the modified zone 44 on the mother element substrate 1A described with reference to FIG. The reforming zone 44 similar to the reforming zone 441 and the reforming zone 443 shown in FIG. Subsequently, in the first embodiment, similarly to the method described with reference to FIG. 6, the mother substrate 10 </ b> A is divided into individual liquid crystal display panels 10 by dividing the surface on which the modified zone 44 is formed. To separate.

Hereinafter, effects of the second embodiment will be described. According to the second embodiment, the following effects similar to or different from the effects of the first embodiment described above can be obtained.
(1) By providing the third reflecting mirror 326 and the third reflecting mirror rotating device 329 corresponding to the optical axis changing device, the incident angle of the laser beam to the workpiece W is changed to be formed. The positions where the modified regions 40 such as the quality region 431, the modified region 432, and the modified region 433 are formed can be changed in the thickness direction of the workpiece W.

  (2) A third reflecting mirror 326 and a third reflecting mirror rotating device 329 corresponding to the optical axis changing device are provided between the condenser lens 323 and the workpiece W (stage 20 (see FIG. 3)). ing. Thereby, since it is not necessary to change the incident angle of the laser light incident on the condensing lens 323, the effective diameter of the condensing lens 323 does not need to be large so that the incident light can pass through an inclination, The condenser lens 323 can be reduced in size.

  (3) By changing the position of the focal point F in the thickness direction of the workpiece W (mother element substrate 1A), the width of the formed modified layer 42 in the thickness direction of the mother element substrate 1A can be increased. it can. Since the width in the thickness direction of the mother element substrate 1A of the modified layer that can be formed by one scan is widened, the number of scans for forming the modified band 44 over substantially the entire surface in the thickness direction of the mother element substrate 1A is reduced. be able to. Therefore, the processing time for forming the modified zone 44 can be shortened.

  As mentioned above, although preferred embodiment which concerns on this invention was described referring an accompanying drawing, embodiment of this invention is not restricted to the said embodiment. The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention, and can be implemented as follows.

  (Modification 1) In the above embodiment, the position adjustment of the condensing point with respect to the mother substrate 10A in the Z-axis direction is performed by moving the condensing lens 23 or the condensing lens 323 by the Z-axis slide mechanism 24. However, it is not essential to move the condenser lens 23 or the condenser lens 323. The position adjustment of the condensing point with respect to the mother substrate 10A in the Z-axis direction may be adjusted by moving the stage 20 in the Z-axis direction. The laser light irradiation device including the laser light source 21 and the condensing lens 23 does not need to have an adjustment device, and the entire laser light irradiation device can be made lighter and smaller than when the laser light irradiation device has an adjustment device.

  (Modification 2) In the above embodiment, the modified layer formed by connecting the modified regions so as to be substantially connected to each other has been described as an example. However, the modified regions constituting the modified layer are substantially connected. That is not essential. As long as it can be divided by applying a small stress, the modified regions may be connected to each other at an interval. By separating the interval, the relative movement speed can be increased compared to the configuration in which the modified regions are substantially connected, and the processing speed when forming the modified layer can be increased. On the other hand, the modified region having a configuration in which the modified regions are connected so as to be substantially connected to each other as in the above-described embodiment is more easily divided than the configuration in which the intervals are separated.

  (Modification 3) In the above-described embodiment, the modified zone having the configuration in which the modified layers are stacked with an interval therebetween has been described as an example, but it is not essential that the modified layers are stacked with an interval. As long as it can be divided by applying a small stress, the modified layers may be laminated so as to be substantially connected to each other even if the modified layers are laminated with a space therebetween. By laminating the modified layers so as to be substantially connected to each other, the modified layers are easily divided as compared with the configuration in which the intervals are separated. On the other hand, by separating the intervals as in the above-described embodiment, the time required for forming the modified zone can be shortened as compared with the configuration in which the modified layers are substantially connected.

  (Modification 4) In the above embodiment, the stage 20 is moved in the direction orthogonal to the Z axis with respect to the condenser lens 23 to move the condenser lens 23 and the mother substrate 10A relative to each other. It is not essential to move the stage 20 side. The relative movement of the condenser lens 23 and the mother substrate 10A may be performed by moving the condenser lens 23 side.

  (Modification 5) In the embodiment described above, the scanning direction of each scan forming the modified region is the same direction, but it is not essential that the scanning direction of each scan is the same direction. The scanning direction may be changed for each modified layer to be stacked. By forming the modified layer by scanning in both reciprocating directions, the time for forming the modified zone can be shortened compared to the case where the scanning direction of each scan is a single direction.

  (Modification 6) In the above-described embodiment, the substrate to be processed is a quartz glass substrate. However, the present invention is not limited to a silicon substrate such as a semiconductor, a quartz substrate made of quartz, Pyrex (registered trademark), or neoceram. (Registered trademark) and a substrate made of OA-10 can also be applied.

  (Modification 7) In the above-described embodiment, the laser light source 21 is an Nd: YAG laser that uses a yttrium-aluminum-garnet-doped neodymium crystal as a laser medium. However, the laser light source uses another laser medium. It may be a laser light source. For example, another YAG laser, YLF laser, YVO4 laser, or the like can be used. In addition to the third harmonic, the Nd: YAG fundamental wave can also be used for the Nd: YAG laser. Note that it is preferable to select an appropriate laser medium or laser light to be oscillated according to the material to be processed.

  (Modification 8) In the above embodiment, the liquid crystal display panel of the liquid crystal display device as the electro-optical device has been described. However, the present invention can also be applied to the manufacture of an electro-optical device other than the liquid crystal display device. For example, the present invention can be applied to the manufacture of an organic EL (electroluminescence) display device.

  (Modification 9) In the above embodiment, by using the condensing lens 23 having a large effective diameter, even if the angle of the laser beam from the reflecting mirror 22 fluctuates, the incident position on the condensing lens 23 fluctuates. However, it is not essential to use a large-diameter condenser lens. A configuration in which the position of the reflecting mirror is also changed in synchronization with the change of the position of the reflecting mirror so that the incident angle changes or the laser light is incident near the center of the condenser lens may be employed.

  (Modification 10) In the above embodiment, the angle of incidence on the workpiece W is varied by varying the angles of the reflecting mirror 22 and the third reflecting mirror 326. As a means, it is not essential to change the angle of the reflecting mirror. Other methods such as rotating the condenser lens may be used.

  In the above-described embodiment, the mother substrate on which the liquid crystal display panel is formed has been described as an example of the processing target. However, the laser processing apparatus and the laser processing method according to the present invention are various processing target processing apparatuses and processing methods. Available as For example, a glass substrate dividing apparatus and method used for cutting a glass substrate as in a liquid crystal display panel, a crystal substrate dividing apparatus and method used for cutting a crystal substrate such as a crystal oscillator, and a silicon substrate dividing apparatus and method such as an integrated circuit It can be used as a piezoelectric element dividing apparatus and method such as a piezoelectric element, a plastic plate dividing apparatus and method, and the like.

The schematic diagram which shows the structure of a liquid crystal display panel. Schematic which shows the mother board | substrate with which the liquid crystal display panel was dividedly formed. The schematic diagram which shows the structure of a laser processing apparatus. The schematic diagram which shows the relationship between an optical axis direction and a focus position. FIG. 4 is a schematic cross-sectional view of a mother element substrate showing a process in which a modified zone is formed on the substrate. The schematic diagram which shows a mode that a mother board | substrate is parted in the part in which the modification | reformation zone was formed. The schematic cross section which shows the example of a shape of a modification zone. The schematic diagram which shows the structure of the laser beam transmission path | route of a laser processing apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Element board | substrate, 1A ... Mother element board | substrate, 2 ... Counter substrate, 10 ... Liquid crystal display panel, 10A ... Mother board | substrate, 20 ... Stage, 22, 221, 222 ... Reflection mirror, 23, 323 ... Condensing lens, 24 ... Z axis slide mechanism, 25 ... rotation mechanism, 26 ... Y axis slide mechanism, 27 ... X axis slide mechanism, 29 ... reflecting mirror rotation device, 40 ... modified region, 42 ... modified layer, 44 ... modified zone , 100 ... Laser processing device, 322 ... First reflecting mirror, 324 ... Second reflecting mirror, 325, 326, 327 ... Third reflecting mirror, 329 ... Third reflecting mirror rotating device, 401, 402, 403, 431 432, 433 ... modified region, 421, 422, 423, 424, 426, 427, 428 ... modified layer, 441, 442, 443, 444, 446 ... modified zone, F ... focus, W ... workpiece.

Claims (12)

A laser light source for emitting laser light;
An optical element for condensing the laser beam in the vicinity of one point in the workpiece;
A stage having a placement surface on which the workpiece is placed;
A moving device that relatively moves the optical element and the stage in a direction parallel to the mounting surface;
By changing the incident angle of the laser beam to the workpiece in a plane direction that is parallel to the relative movement direction and perpendicular to the plane direction of the workpiece, An optical axis varying device that varies the position in the thickness direction. The optical element is an optical lens having a field curvature,
The laser processing apparatus according to claim 1, wherein the optical axis fluctuation device is provided between the laser light source and the optical lens.   The laser processing apparatus according to claim 1, wherein the optical axis fluctuation device is provided between the optical element and the stage. The laser beam emitted from the laser irradiation apparatus is condensed inside the processing object to form a modified region, and the processing object and the laser irradiation apparatus are relatively moved in the plane direction of the processing object. And having a scanning step of forming a modified layer in which the modified regions are continuously or spaced apart from each other,
In parallel with the scanning step, by changing the incident angle of the laser beam to the workpiece in a plane direction parallel to the relative movement direction and perpendicular to the plane direction of the workpiece, A laser processing method, wherein a position of the modified region in a thickness direction of the workpiece is changed.   The laser light is condensed using an optical lens having a curvature of field, and the incident angle of the laser light to be incident on the optical lens is changed to change the incident angle of the laser light on the workpiece. The laser processing method according to claim 4, wherein the laser processing method is varied.   5. The incident angle of the laser beam on the workpiece is changed by changing a traveling direction of the laser beam emitted from an optical lens that collects the laser beam. Laser processing method.   When the position where the modified region is formed is closer to the surface of the object to be processed than a predetermined distance, the scanning without an operation for changing the incident angle of the laser beam to the object to be processed The laser processing method according to claim 4, wherein a step is executed.   A method for manufacturing a substrate, comprising: dividing a mother substrate on which a plurality of substrates are partitioned into individual substrates using the laser processing method according to claim 4.   A mother electro-optical device substrate in which a plurality of electro-optical devices are partitioned is divided into the individual electro-optical devices by using the laser processing method according to claim 4. Manufacturing method of electro-optical device.   A method for manufacturing a substrate, comprising: dividing a mother substrate, on which a plurality of substrates are partitioned, into individual substrates using the laser processing apparatus according to claim 1.   A mother electro-optical device substrate in which a plurality of electro-optical devices are partitioned is divided into the individual electro-optical devices using the laser processing device according to claim 1. Manufacturing method of electro-optical device.   4. The electro-optical device using the laser processing apparatus according to claim 1, wherein a mother substrate on which a plurality of substrates constituting the electro-optical device are formed is divided into individual substrates. Device manufacturing method.

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