JP4329741B2 - Laser irradiation apparatus and laser scribing method - Google Patents

Description

  The present invention relates to a laser irradiation apparatus and a laser scribing method for a substrate such as a semiconductor using the laser irradiation apparatus.

  A laser irradiation apparatus that forms a divided region for irradiating a substrate such as a semiconductor to cut or divide the substrate includes a laser light source that emits a laser beam having a pulse width of 1 μs or less, and an emitted laser beam. A laser processing apparatus provided with a condensing lens for condensing light is known (Patent Document 1).

A laser processing method (laser scribing method) using this laser processing apparatus irradiates a laser beam with a condensing part inside the object to be processed, and forms a modified region by multiphoton absorption inside the object to be processed. To do. A line to be cut is formed in a region that is constituted by the modified region and is spaced a predetermined distance inward from the surface on the laser light incident surface side of the workpiece. Thereafter, when a stress is applied to the workpiece from the outside, the workpiece is cracked starting from the planned cutting line. Further, the laser beam is condensed so that the peak power density at the condensing point is 1 × 10 ⁸ (W / cm ² ) or more.

  In this laser processing method, since the modified region is formed by aligning the light converging part inside the processing object, even if there is a wiring or the like constituting a circuit on the laser light incident surface side surface of the processing object The processing object can be divided in the thickness direction along the planned cutting line without causing thermal damage to these wirings.

Further, in the laser processing method using this laser processing apparatus, the size of the modified region formed inside the object to be processed or the crack portion (crack spot) formed from this is determined by the characteristics of the condensing lens. And depends on the peak power density of the laser beam. For example, in the embodiment in which the glass (thickness 700 μm) disclosed in Patent Document 1 is cut using a YAG laser, the peak power density is about 1 × 10 ¹¹ when the numerical aperture of the condenser lens is 0.55. In (W / cm ² ), the size of the crack spot is approximately 100 μm. Further, when the peak power density is about 5 × 10 ¹¹ (W / cm ² ), it is about 250 μm.

JP 2002-192370 A

  However, when the thickness of the workpiece is considerably larger than the size of the crack spot, it is difficult to break the workpiece without deforming the fracture surface after forming the line to be cut. When external stress is applied, there is a problem that the growth direction of the crack starting from the modified region is shifted and the outer shape defect is generated without cracking along the planned cutting line. In order to improve such a problem, a method of repeatedly irradiating a laser beam so that the modified region is continuous in the thickness direction corresponding to the thickness of the workpiece can be considered, but the laser beam is irradiated. There is a problem that the processing time becomes long and the productivity decreases.

  The present invention has been made in consideration of the above problems, and a laser irradiation apparatus capable of enlarging the size of a modified region formed by one laser irradiation and scribing a workpiece with high productivity. An object of the present invention is to provide a laser scribing method using this laser irradiation apparatus.

  The laser irradiation apparatus of the present invention adjusts the position of a laser light source that emits pulsed laser light having wavelength dispersion characteristics, a condensing unit that condenses the pulsed laser light, and a focused point of the pulsed laser light with respect to the workpiece. Possible adjusting means, moving means capable of moving the workpiece relative to the light collecting means in a plane substantially perpendicular to the optical axis of the pulse laser light, and a light collecting area where the pulse laser light is condensed Is adjusted at a predetermined position in the thickness direction of the workpiece, and the moving means is controlled so that the light collection region moves relatively along the planned cutting position of the workpiece. And an axial chromatic aberration enlarging unit having a refractive index larger than 1 on the optical axis between the condensing unit and the object to be processed.

  According to this configuration, the control unit controls the adjusting means to adjust the position of the condensing point so that the condensing region of the pulsed laser light is arranged at a predetermined position in the thickness direction of the object to be processed. If the moving means is controlled so that the condensing region moves relatively along the intended cutting position of the object, the modified region is formed in the condensing region by the multi-photon absorption of the pulse laser beam by the processing object. Can be formed in the thickness direction of the workpiece. Since the axial chromatic aberration enlarging means having a refractive index larger than 1 is provided on the optical axis between the condensing means and the object to be processed, the pulse laser beam condensed by the condensing means In FIG. 3, the axial chromatic aberration due to wavelength dispersion is expanded. Therefore, the modified region formed in the thickness direction of the workpiece can be further expanded. That is, the size of the modified region formed by one laser irradiation can be enlarged, and the modified region can be formed in the thickness direction of the workpiece with a smaller number of irradiations, so that high productivity is achieved. Thus, it is possible to provide a laser irradiation apparatus capable of scribing a workpiece.

  The axial chromatic aberration enlarging means further includes an inserting means that can be inserted so as to be substantially orthogonal to the optical axis, and the control unit controls the inserting means so that the axial chromatic aberration enlarging means is connected to the condensing means and the object to be processed. It is preferable to insert between them.

  According to this configuration, since the control unit can control the insertion unit to insert the axial chromatic aberration expansion unit between the condensing unit and the processing target, the axis in the condensing region of the pulsed laser light The width of the upper chromatic aberration can be changed by inserting the axial chromatic aberration expanding means. If the width of the condensing region is changed, the width of the modified region formed by multi-photon absorption of the pulse laser beam by the workpiece can be changed. Therefore, the width of the modified region to be formed is changed by inserting the axial chromatic aberration enlarging means between the light condensing means and the object to be processed according to the thickness of the object to be processed, and changing the width of the light condensing area. In other words, the workpiece can be scribed while the productivity is higher.

  The laser scribing method of the present invention is formed by irradiating a processing object with focused pulsed laser light having wavelength dispersion characteristics using the laser irradiation apparatus described in the above invention, and the processing object absorbs multiphotons. A laser scribing method for forming a modified region to be processed in a thickness direction along a planned cutting position of a workpiece, and collecting so that an optical axis of a pulsed laser beam is positioned on a line of the planned cutting position of the workpiece. A positioning step for relatively positioning the light means and the object to be processed, and an axial chromatic aberration enlarging means are disposed between the light collecting means and the object to be processed, so that at least a part of the condensing region of the pulse laser beam is An adjustment process for adjusting the position of the condensing point by the adjusting means so that it is applied to the surface opposite to the incident surface of the pulse laser beam of the processing object, and a cutting schedule while moving the processing object relative to the condensing means Along the position The first scanning step of irradiating the pulsed laser beam to form the first modified region and the adjusting unit shifts the condensing region in the thickness direction of the processing object, and the processing object is moved with respect to the condensing unit. The second modified region is formed so as to be continuous with the first modified region formed in the first scanning step in the thickness direction by irradiating the pulse laser beam along the planned cutting position while relatively moving. And a second scanning step.

  According to this method, the optical axis of the pulsed laser beam and the intended cutting position of the workpiece are positioned in the positioning step, and in the adjusting step, the focusing region of the pulsed laser beam in the thickness direction of the workpiece is adjusted by the adjusting means. The position of the condensing point is adjusted so that at least a part of the light is applied to the surface of the workpiece opposite to the incident surface of the pulse laser beam. In the first scanning step, the axial chromatic aberration enlarging means is arranged between the condensing means and the object to be processed, and laser irradiation is performed in a state where the axial chromatic aberration is enlarged in the condensing region. A first modified region is formed in the thickness direction along the planned cutting position of the object. In the second scanning step, the condensing region is shifted in the thickness direction of the object to be processed by the adjusting means, and laser irradiation is performed in the same manner as in the first scanning step, and the first modified region continues in the thickness direction. Thus, the second modified region is formed. Therefore, compared with the case where the axial chromatic aberration enlarging means is not disposed between the condensing means and the object to be processed, the modified area formed by multiphoton absorption is enlarged in the condensing area where the axial chromatic aberration is enlarged. Therefore, the number of scans of laser irradiation for continuously forming the modified region across the thickness direction of the workpiece can be reduced. Therefore, it is possible to provide a laser scribing method capable of scribing a workpiece with high productivity.

  Further, another laser scribing method of the present invention uses a laser irradiation apparatus according to claim 2 to irradiate a focused pulsed laser beam having a wavelength dispersion characteristic onto a processing target, thereby causing many processing targets. A laser scribing method in which a modified region formed by photon absorption is formed in a thickness direction along a planned cutting position of a workpiece, and the optical axis of the pulsed laser beam is on the line of the planned cutting position of the workpiece. A positioning step for relatively positioning the focusing means and the workpiece so as to be positioned, and at least a part of the focusing area of the pulsed laser beam on the surface opposite to the incident surface of the pulsed laser beam on the workpiece An adjustment step for adjusting the position of the condensing point so as to be applied, and forming a first modified region by irradiating the laser beam along the planned cutting position while moving the object to be processed relative to the condensing means First scan Then, the axial chromatic aberration enlarging means is inserted between the condensing means and the object to be processed by the inserting means, and the condensing region is shifted in the thickness direction of the object to be processed by the adjusting means, and the object to be processed is The second modified region is formed so as to be continuous with the first modified region formed in the first scanning step in the thickness direction by irradiating a pulse laser beam along the planned cutting position while relatively moving And a second scanning step.

  According to this method, in the first scanning step, the first modification is performed in a state where the axial chromatic aberration expanding means is not inserted between the light collecting means and the object to be processed and the axial chromatic aberration is small in the light collecting region. A quality region is formed. In the second scanning step, the second modification is performed in a state where the axial chromatic aberration enlarging means is inserted between the condensing means and the object to be processed, that is, in a state where the axial chromatic aberration is enlarged as compared with the first scanning step. A quality region is continuously formed in the thickness direction in the first modified region. Therefore, the first modified region is formed in a state where the width in the thickness direction is narrower than that of the second modified region, that is, in a state in which the modified density is high. When cutting with, it is easily cut from the surface side where the first modified region is formed. That is, it is possible to reduce the occurrence of a defect in the outer shape of the fractured surface due to the cutting to the second modified region side triggered by the first modified region.

  An embodiment of the present invention uses a laser irradiation device used in a step of cutting a mother substrate on which a liquid crystal display panel is partitioned in a step of manufacturing a liquid crystal display panel constituting a liquid crystal display device, and uses this laser irradiation device. The laser scribing method used will be described as an example.

(LCD panel)
First, the liquid crystal display panel will be described. FIG. 1 is a schematic view showing the structure of a liquid crystal display panel. The figure (a) is a schematic front view, The figure (b) is the schematic sectional drawing cut | disconnected by the AA line of the figure (a).

  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 the liquid crystal 5 filled in the gap between the two substrates 1 and 2. The element substrate 1 protrudes in a frame shape that is slightly larger than the counter substrate 2.

  The element substrate 1 uses a quartz glass substrate having a thickness of about 1.2 mm, and on its surface, a pixel electrode (not shown) constituting a pixel and a TFT element in which one of three terminals is connected to the pixel electrode. 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 in the Y-axis direction and connected to the data line driving circuit unit 9 at the terminal unit 1a. The scanning lines are drawn out in the X-axis direction and are individually connected to two scanning line drive circuit units 13 and 13 formed in the left and right frame regions. The input side wirings of the data line driving circuit unit 9 and the scanning line driving circuit unit 13 are connected to the mounting terminals 11 arranged along the terminal unit 1a. In the frame region opposite to the terminal portion 1a, a wiring 12 that connects the two scanning line driving circuit portions 13 and 13 is provided.

  The counter substrate 2 is a transparent 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 1a. It is connected.

  Alignment films 7 and 8 are respectively formed on the surface of the element substrate 1 facing the liquid crystal 5 and the surface of the counter substrate 2.

  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 9 and the scan line drive circuit unit 13, 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 for deflecting incoming and outgoing light are provided on the front and back surfaces of the liquid crystal display panel 10, respectively.

  FIG. 2 is a schematic view showing a mother substrate on which a liquid crystal display panel is partitioned. FIG. 4A is a schematic plan view, and FIG. 4B is a schematic cross-sectional view taken along the line BB in FIG.

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

  In this embodiment, each counter substrate 2 is bonded to the substrate W. However, another mother substrate in which a plurality of counter substrates 2 are formed in a wafer-like substrate is bonded to the substrate W. The liquid crystal display panel 10 may be taken out by cutting the opposite mother substrate.

(Laser irradiation device)
Next, a laser irradiation apparatus to which the present invention is applied will be described. FIG. 3 is a schematic diagram showing the configuration of the laser irradiation apparatus.

  As shown in FIG. 3, a laser irradiation apparatus 100 includes a laser light source 101 that emits pulsed laser light, a dichroic mirror 102 that reflects the emitted pulsed laser light, and a condensing unit that collects the reflected pulsed laser light. As a condensing lens 103. Also, a stage 107 on which a substrate W as a processing target is placed, and an X-axis slide unit 110 and a Y-axis slide unit 108 as moving means for moving the stage 107 in the X and Y axis directions with respect to the condenser lens 103. And. Further, a Z-axis slide mechanism 104 serving as an adjustment unit that adjusts the position of the condensing point of the pulse laser beam by changing the position of the condensing lens 103 in the Z-axis direction with respect to the substrate W placed on the stage 107; And a quartz glass plate 106 as an axial chromatic aberration enlarging means arranged so as to be orthogonal to the optical axis 101a between the condenser lens 103 and the substrate W. Furthermore, an imaging device 112 is provided that is located on the opposite side of the condenser lens 103 with the dichroic mirror 102 interposed therebetween.

  The laser irradiation apparatus 100 includes a main computer 120 that controls each of the above components. The main computer 120 includes an image processing unit 124 that processes image information captured by the imaging apparatus 112 in addition to a CPU and various memories. is doing. The imaging device 112 incorporates a coaxial incident light source and a CCD (solid-state imaging device). Visible light emitted from the coaxial incident light source passes through the condenser lens 103 and is focused.

  Connected to the main computer 120 are an input unit 125 for inputting data of various processing conditions used in laser processing and a display unit 126 for displaying various information at the time of laser processing. In addition, a laser control unit 121 that controls the output, pulse width, and pulse period of the laser light source 101, and a lens control unit 122 that drives the Z-axis slide mechanism 104 to control the position of the condenser lens 103 in the Z-axis direction. It is connected. Further, a stage control unit 123 that drives a servo motor (not shown) that moves the X-axis slide unit 110 and the Y-axis slide unit 108 along the rails 109 and 111, respectively, is connected.

  The Z-axis slide mechanism 104 that moves the condensing lens 103 in the Z-axis direction has a built-in position sensor capable of detecting the moving distance, and the lens control unit 122 detects the output of the position sensor and collects the light. The position of the lens 103 in the Z-axis direction can be controlled. Therefore, the thickness of the substrate W can be measured by moving the condenser lens 103 in the Z-axis direction so that the focus of the visible light emitted from the coaxial incident light source of the imaging device 112 is aligned with the surface of the substrate W. It is.

  The laser light source 101 is a so-called femtosecond laser that emits laser light having, for example, titanium sapphire as a solid light source with a femtosecond pulse width. In this case, the pulsed laser light has wavelength dispersion characteristics, the center wavelength is 800 nm, and the half width is about 10 nm. The pulse width is about 300 fs (femtosecond), the pulse period is 1 kHz, and the output is about 700 mW.

  In this case, the condensing lens 103 is an objective lens having a magnification of 100 times, a numerical aperture (NA) of 0.8, and a WD (Working Distance) of 3 mm. The condenser lens 103 is supported by a slide arm 104 a extending from the Z-axis slide mechanism 104. A quartz glass plate 106 is supported on the end of a rotating arm 105 a extending from a motor 105 that moves together with the Z-axis slide mechanism 104. The lens control unit 122 drives the Z-axis slide mechanism 104 and also drives the motor 105 to rotate the rotary arm 105a about the Z-axis as a rotation axis. Thereby, the quartz glass plate 106 can be inserted in front of the opening 103 a of the condenser lens 103.

  In this embodiment, the stage 107 is supported by the Y-axis slide unit 108, but is supported by the X-axis slide unit 110 by reversing the positional relationship between the X-axis slide unit 110 and the Y-axis slide unit 108. It is good also as a form. Moreover, it is preferable to support the stage 107 on the Y-axis slide part 108 via the θ table. According to this, it is possible to make the substrate W more perpendicular to the optical axis 101a.

  FIG. 4 is a schematic diagram showing an enlarged state of longitudinal chromatic aberration. FIG. 6A shows the condensing state of the pulsed laser light when the axial chromatic aberration enlarging means is not inserted, and FIG. 5B shows the condensing state of the pulsed laser light when the axial chromatic aberration enlarging means is inserted. It is shown. The quartz glass plate 106 as the axial chromatic aberration expanding means has a thickness of 2 mm and a refractive index of about 1.46.

  As shown in FIG. 4A, when the quartz glass plate 106 is not inserted, the pulse laser beam 113 collected by the condenser lens 103 is incident on the substrate W having a refractive index larger than 1 and refracted. Then, the condensing point from the short-wavelength side pulse laser beam 114 to the long-wavelength side pulse laser beam 115 is focused on the condensing region 116 shifted on the optical axis 101a. The condensing region 116 has a so-called axial chromatic aberration.

  As shown in FIG. 4B, when the quartz glass plate 106 is inserted, the pulsed laser light collected by the condenser lens 103 is refracted through the quartz glass plate 106 having a refractive index larger than 1. . Therefore, the short-wavelength side pulse laser beam 114 and the long-wavelength side pulse laser beam 115 are incident on the substrate W in a state where the focal points are shifted. Then, the light is further refracted after being incident, and is condensed in a condensing region 117 whose focal point is shifted on the optical axis 101 a from the short-wavelength pulse laser beam 114 to the long-wavelength pulse laser beam 115. That is, the light condensing region 117 is further expanded in axial chromatic aberration.

  Here, the formation of the modified region by multiphoton absorption will be described. Even if the object to be processed is a transparent material, absorption occurs when the photon energy hν is much larger than the absorption band gap Eg of the material. This is called multiphoton absorption. When the pulse width of the laser beam is made extremely short and multiphoton absorption is caused to occur inside the workpiece, the energy of the multiphoton absorption is not converted into thermal energy, and the ionic valence. Permanent structural changes such as change, crystallization or polarization orientation are induced to form a refractive index change region. In the present embodiment, this refractive index change region is called a modified region.

  FIG. 5 is a photograph showing a modified region formed by multiphoton absorption. FIG. 4A shows a modified region corresponding to FIG. 4A, and FIG. 4B shows a modified region corresponding to FIG. Both are cross-sectional photographs of the substrate W.

As shown in FIG. 5A, when the substrate W is irradiated with the pulse laser beam 113 without inserting the quartz glass plate 106, the modified region 20 formed in the light condensing region 116 of the pulse laser beam 113 is When viewed from the cross section of the substrate W, it has a width of about 300 μm in the thickness direction of the substrate W. In this case, the peak power density in the condensing region 116 is 8 × 10 ¹² W / cm ² . Further, as the position of the condensing region 116 approaches the incident surface Wa of the pulse laser beam 113, the optical path difference between the short wavelength side pulse laser beam 114 and the long wavelength side pulse laser beam 115 decreases, and the incident surface Wa. In the vicinity of, the width of the modified region 20 is approximately 50 μm.

  As shown in FIG. 5B, when the quartz glass plate 106 is inserted and the substrate W is irradiated with the pulse laser beam, the modified region 21 formed in the condensing region 117 of the pulse laser beam is When viewed from the cross section, the substrate W has a width of about 700 μm in the thickness direction. That is, it is possible to expand the axial chromatic aberration and expand the width of the modified region by inserting the quartz glass plate 106 using the characteristics of the pulsed laser light having wavelength dispersion characteristics.

  As the irradiation conditions of the pulse laser beam 113 for forming such modified regions 20 and 21, it is necessary to set the output of the pulse laser beam, the pulse width, the pulse period, the laser scan speed, etc. depending on the object to be processed. Needless to say. In particular, it is necessary to consider that the output of the laser light source 101 is attenuated by absorption by a transmissive material disposed on the optical axis 101a such as the dichroic mirror 102, the condenser lens 103, and the quartz glass plate 106. Therefore, it is desirable to carry out a preliminary test using an actual processing object to derive the optimum irradiation conditions.

(Laser scribing method)
Next, a laser scribing method to which the present invention is applied will be described. FIG. 6 is a flowchart showing a laser scribing method.

  As shown in FIG. 6, the laser scribing method of the present embodiment uses a laser irradiation apparatus 100, and the condensing lens 103 and the substrate so that the optical axis 101 a of the pulse laser beam is positioned on the line of the planned cutting position of the substrate W. Positioning step (step S1) for relatively positioning W and the position of the condensing point so that the condensing region of the pulse laser beam is located at a predetermined position in the thickness direction (Z-axis direction) of the substrate W Adjusting step (step S3). In addition, a primary laser scan (first scanning step) for forming a first modified region by irradiating a pulsed laser beam along a planned cutting position while moving the substrate W relative to the condenser lens 103. Step S4) is provided. Further, the focusing region is shifted in the Z-axis direction by the Z-axis slide mechanism 104, and the primary laser scan is performed by irradiating the laser beam along the planned cutting position while moving the substrate W relative to the focusing lens 103. A secondary laser scan (step S5) is provided as a second scanning process for forming the second modified region so as to be continuous with the first modified region formed in step Z in the Z-axis direction.

  Step S1 in FIG. 6 is a positioning process. In step S <b> 1, the substrate W illustrated in FIG. 2 is placed so that the counter substrate 2 side is in contact with the surface of the stage 107. Then, the substrate W is positioned so that the partition region Dx is parallel to the X-axis direction. In addition, the stage controller 123 drives the servo motor so that the optical axis 101a of the pulsed laser beam is positioned on the line of the planned cutting positions of the arbitrary partitioned regions Dx and Dy of the substrate W, and the X-axis slide unit 110 and Y The shaft slide part 108 is moved. In this case, if an orientation flat or the like for defining the direction is formed on the wafer-like substrate W, positioning can be performed relatively easily. Then, the process proceeds to step S2.

  Step S2 in FIG. 6 is a step of measuring the thickness of the substrate W. In step S <b> 2, the operator operates the main computer 120 to measure the thickness of the substrate W. The image captured by the imaging device 112 is displayed on the display unit 126, and the imaging device 112 is displayed on the incident surface Wa (see FIG. 4) of the pulse laser beam of the substrate W and the other surface Wb (see FIG. 4) on the other side. The main computer 120 calculates the thickness of the substrate W from the output of the position sensor of the Z-axis slide mechanism 104 by performing the operation of focusing the visible light emitted from the Z-axis slide mechanism 104. The calculation result is stored in the storage unit of the main computer 120 as coordinates in the Z-axis direction. Then, the process proceeds to step S3.

  Step S3 in FIG. 6 is an adjustment process for adjusting the position of the condensing point of the pulse laser beam. As described above, when the quartz glass plate 106 is inserted, the light condensing region 117 in which the longitudinal chromatic aberration is widened. The positional relationship in the Z-axis direction between the focus of visible light captured by the imaging device 112 and the light condensing region 117 is obtained in advance from the result of a preliminary test for laser irradiation and input as data. Based on this data and the thickness data (coordinates in the Z-axis direction) of the substrate W obtained in step S2, in step S3, the lens control unit 122 drives the motor 105 to move the quartz glass plate 106 to the condenser lens. 103 is inserted in front of the opening 103a. Then, as shown in FIG. 4B, the lens control unit 122 drives the Z-axis slide mechanism 104 so that at least a part of the condensing region 117 is on the side opposite to the incident surface Wa of the pulsed laser light of the substrate W. The condenser lens 103 is moved in the Z-axis direction so as to be placed on the surface Wb. Then, the process proceeds to step S4.

  Step S4 in FIG. 6 is a primary laser scanning process. In step S <b> 4, the first modified region is formed by irradiating the laser beam along the planned cutting position while moving the substrate W relative to the condenser lens 103. In this case, as shown in FIG. 2, a plurality (200) of liquid crystal display panels 10 are partitioned on the substrate W, and a laser scan that crosses the substrate W in the X-axis direction corresponding to the partitioned region Dx is performed. Do it once. Subsequently, a laser scan is performed 15 times across the substrate W in the Y-axis direction corresponding to the partition region Dy. Naturally, each laser scan is performed while shifting in the X-axis or Y-axis direction at a predetermined pitch corresponding to the partition arrangement on the substrate W of the liquid crystal display panel 10. Since the scheduled cutting position is input as data in advance, the main computer 120 sends a control signal based on this data to the stage control unit 123. The stage control unit 123 moves the substrate W relative to the condenser lens 103 by moving the X-axis slide unit 110 and the Y-axis slide unit 108 based on the control signal. In this case, the speed at which the substrate W is moved corresponding to the irradiation of the pulsed laser beam, that is, the laser scanning speed is approximately 20 mm / second. Accordingly, the time required for the laser scanning 19 times in the X-axis direction and 15 times in the Y-axis direction is approximately 9 minutes because the wafer size of the substrate W is 12 inches (300 mm). Then, the process proceeds to step S5.

  Step S5 in FIG. 6 is a secondary laser scanning process. In step S5, the lens control unit 122 drives the Z-axis slide mechanism 104 to shift the condensing region 117 in the Z-axis direction. Then, the laser beam is irradiated along the planned cutting position while moving the substrate W relative to the condensing lens 103, and continuously in the Z-axis direction to the first modified region formed by the primary laser scan. Thus, the second modified region is formed. The laser scanning method is the same as in step S4. In this case, since the width of the modified region 21 formed in the condensing region 117 is about 700 μm, if the position of the condensing region 117 is shifted about 500 μm in the Z-axis direction, the width of the substrate W having a thickness of 1.2 mm The reformed region 21 is continuously formed inside. If the thickness of the substrate W is less than 700 μm, only the primary laser scan in step S4 is required. Further, if the thickness of the substrate W is 700 μm or more, the laser scan with the condensing region 117 shifted in the Z-axis direction according to the thickness may be repeated. Then, the process proceeds to step S6.

  Step S6 in FIG. 6 is a step of dividing (breaking) the substrate W along the formed modified region. FIG. 7 is a schematic sectional view showing a breaking method. FIG. 4A is a cross-sectional view showing how to apply external stress, and FIG. 4B is a cross-sectional view after breaking. In step S6, for example, as shown in FIG. 7A, external stress is applied in the C or D direction to the modified region Rc continuously formed in the thickness direction of the substrate W by steps S4 and S5. Add. As a result, the substrate W is divided at the modified region Rc as shown in FIG. FIG. 8 is a cross-sectional photograph of the substrate after division. As shown in FIG. 8, the modified region Rc is formed over the entire region in the thickness direction of the substrate W. In this case, the width of the modified region Rc (the width in the direction orthogonal to the Z-axis direction) is approximately 10 to 20 μm.

  According to the laser scribing method described above, the modified region Rc is continuously formed in the thickness direction of the substrate W, and therefore can be cut accurately and easily. In addition, it is difficult for external defects to occur on the fracture surface. Further, when the modified region Rc continuous in the thickness direction of the substrate W is formed without inserting the quartz glass plate 106, the condensing region 116 of the pulse laser beam 113 has axial chromatic aberration as it approaches the incident surface Wa. Less. As a result, the width of the modified region 20 is reduced, and in order to form the modified region Rc that is continuous in the thickness direction of the substrate W having a thickness of 1.2 mm, approximately 10 (about 90 minutes) laser scanning steps are required. become. In the laser scribing method according to the present embodiment, two laser scanning steps (about 18 minutes) are sufficient, and the time required for laser processing can be greatly reduced.

The effect of the said embodiment is as follows.
(1) Since the laser irradiation apparatus 100 of the above embodiment has a configuration in which the quartz glass plate 106 can be inserted in front of the opening 103 a of the condenser lens 103, the pulse transmitted through the condenser lens 103. By refracting the laser light, the pulsed laser light can be condensed on the condensing region 117 where the longitudinal chromatic aberration is widened. Therefore, if a pulsed laser beam having such wavelength dispersion characteristics is irradiated so as to form a condensing point inside a substrate W made of a quartz glass substrate, a modification formed by multiphoton absorption in the condensing region 117. The region 21 can be enlarged as compared with the modified region 20 formed without inserting the quartz glass plate 106. Therefore, it is possible to provide the laser irradiation apparatus 100 that can scribe the substrate W with high productivity by increasing the size of the modified region formed by one laser irradiation.

  (2) In the laser irradiation apparatus 100 of the above-described embodiment, the lens control unit 122 can drive the motor 105 as insertion means to insert the quartz glass plate 106 between the condenser lens 103 and the substrate W. . Therefore, the width of the longitudinal chromatic aberration in the condensing region of the pulse laser beam can be changed by inserting the quartz glass plate 106. If the width of the condensing region is changed, the width of the modified region formed by the substrate W by multiphoton absorption of the pulse laser beam can be changed. Accordingly, by inserting the quartz glass plate 106 between the condensing lens 103 and the substrate W according to the thickness of the substrate W and changing the width of the condensing region, the width of the modified region to be formed is changed. The workpiece can be scribed in a state where the productivity is higher.

  (3) In the laser scribing method of the above embodiment, the laser irradiation apparatus 100 is used, and the quartz glass plate 106 is inserted, and at least a part of the condensing region 117 of the pulse laser beam is incident on the incident surface Wa of the pulse laser beam. An adjustment step of adjusting the position of the light condensing point so as to be applied to the surface Wb on the opposite side is provided. In addition, a primary laser scanning step of forming a first modified region by irradiating pulse laser light along a planned cutting position while moving the substrate W relative to the condenser lens 103 is provided. Further, by driving the Z-axis slide mechanism 104 and moving the condensing lens 103 in the Z-axis direction, the condensing region 117 is shifted in the Z-axis direction, and the pulse laser beam is irradiated again along the planned cutting position. A secondary laser scanning step is provided in which the second modified region is formed so as to be continuous with the first modified region formed in the primary laser scanning step in the Z-axis direction. Therefore, it is possible to form a modified region Rc that is continuous along the thickness direction of the substrate W. If an external stress that divides the modified region Rc is applied, it is possible to reduce the occurrence of an external defect on the fracture surface. The substrate W can be cut accurately and easily. Further, since the size of the modified region 21 formed by one laser irradiation is enlarged as compared with the case where the quartz glass plate 106 is not inserted, the thickness direction of the substrate W can be reduced with a smaller number of laser scanning steps. A continuous modified region Rc can be formed. That is, a laser scribing method having high productivity can be provided.

Modifications other than the above embodiment are as follows.
(Modification 1) In the laser irradiation apparatus 100 of the above embodiment, the motor 105 is provided as an insertion means into which the quartz glass plate 106 can be inserted. However, the present invention is not limited to this. The quartz glass plate 106 may be fixedly disposed on the opening 103 a side of the condenser lens 103.

  (Modification 2) In the laser irradiation apparatus 100 of the above embodiment, the axial chromatic aberration expanding means is not limited to the quartz glass plate 106. For example, the same effect can be obtained by using a member capable of adjusting the refractive index, such as a diffraction grating or a diffraction lens. In addition, a method of coating the refractive index adjusting material on the surface so that the axial chromatic aberration spreads the refractive index of the condensing lens 103 may be used. Further, the liquid is not limited to a solid such as the quartz glass plate 106, but may be a liquid filled with a liquid having a refractive index larger than 1 in a container that transmits laser light.

  (Modification 3) In the laser irradiation apparatus 100 of the above-described embodiment, the structure of the adjusting means for adjusting the position of the condensing point of the pulse laser light and the moving means for moving the substrate W relative to the condensing lens 103 Is not limited to this. For example, the condensing lens 103 may be fixed and the substrate W side may be movable in the X, Y, and Z axis directions. Alternatively, the substrate W side may be fixed, and the laser light source 101, the dichroic mirror 102, and the condenser lens 103 may be integrally movable in the X, Y, and Z axis directions.

  (Modification 4) The laser scribing method of the above embodiment is not limited to this. For example, in the primary laser scanning step, laser scanning is performed without inserting the quartz glass plate 106 to form a first modified region having a narrow width (corresponding to the modified region 20 in FIG. 5A). . Subsequently, in the secondary laser scanning step, the quartz glass plate 106 is inserted, and the second modified region having a large width (corresponding to the modified region 21 in FIG. 5B) is continued to the first modified region. You may form as follows. According to this, the first modified region is formed in a state where the axial chromatic aberration is small and the electric field strength or the peak power density is higher in the condensing region, that is, in the state where the modified density is high. In this case, when an external stress is applied, the cutting can proceed in the direction in which the second modified region is formed with the first modified region as a trigger. Therefore, the modified region Rc continuous in the thickness direction of the substrate W can be formed so as to be more easily cut.

  (Modification 5) In the laser scribing method of the above embodiment, the object to be processed is not limited to the substrate W made of quartz glass. The laser scribing method of the present invention can be applied to any object to be processed that is transparent to laser light. For example, it can be used for scribing a semiconductor wafer made of low alkali glass, soda glass, silicon, or the like. Can do.

  (Modification 6) In the laser scribing method of the above embodiment, the routing is not limited to this. For example, when the primary laser scanning process is finished, the substrate W is inverted and placed on the stage 107, and the position of the condensing point is adjusted again by the positioning process and the adjusting process of the substrate W. Then, a secondary laser scanning process is performed. In this way, the modified region can be formed with substantially the same width in the thickness direction of the condensing region in the primary and secondary laser scanning steps. That is, the modified region formed from the front and back surfaces of the substrate W toward the inside can be formed with substantially the same density regardless of the distance from the front and back surfaces.

Schematic 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. Schematic which shows the structure of a laser irradiation apparatus. Schematic which shows the expansion state of axial chromatic aberration. A photograph showing a modified region formed by multiphoton absorption. The flowchart which shows the laser scribing method. The schematic sectional drawing which shows the breaking method. Cross-sectional photograph of the substrate after cutting.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 ... Modified | denatured area | region, 21 ... Enlarged modified | denatured area | region, 100 ... Laser irradiation apparatus, 101 ... Laser light source, 101a ... Optical axis, 103 ... Condensing lens as a condensing means, 104 ... Z axis as an adjusting means Slide mechanism 105 ... Motor as insertion means 106 ... Quartz glass plate as axial chromatic aberration enlargement means 108 ... X-axis slide part as movement means 110 ... Y-axis slide part as movement means 113 ... Pulse laser Light, 116, 117 ... Condensing region, 120 ... Main computer as control unit, W ... Substrate as object to be processed, Wa ... Incident surface of pulse laser beam, Wb ... Surface opposite to incident surface of pulse laser beam .

Claims (4)

A laser light source that emits pulsed laser light having wavelength dispersion characteristics;
Condensing means for condensing the pulse laser beam;
Adjustment means capable of adjusting the position of the focused point of the pulsed laser light with respect to the workpiece;
Moving means capable of moving the workpiece relative to the condensing means in a plane substantially perpendicular to the optical axis of the pulsed laser light;
The adjustment means is controlled so that a condensing region where the pulse laser beam is condensed is arranged at a predetermined position in the thickness direction of the workpiece, and the cutting object is cut along the planned cutting position. A control unit that controls the moving means so that the light collection region moves relatively,
An on-axis chromatic aberration enlarging unit having a refractive index larger than 1 is provided on the optical axis between the condensing unit and the workpiece. Further comprising an insertion means capable of inserting the longitudinal chromatic aberration expanding means so as to be substantially orthogonal to the optical axis,
The laser irradiation apparatus according to claim 1, wherein the control unit controls the insertion unit to insert the axial chromatic aberration expansion unit between the condensing unit and the object to be processed. Modification using the laser irradiation apparatus according to claim 1 or 2, wherein the object to be processed is irradiated with a focused pulsed laser beam having wavelength dispersion characteristics, and the object to be processed is absorbed by multiphotons. A laser scribing method for forming a region in a thickness direction along a planned cutting position of the workpiece,
A positioning step of relatively positioning the condensing means and the processing object so that an optical axis of the pulse laser beam is positioned on a line of the planned cutting position of the processing object;
The axial chromatic aberration enlarging means is disposed between the condensing means and the object to be processed, and at least a part of the condensing region of the pulsed laser light is an incident surface of the pulsed laser light of the object to be processed. An adjustment step of adjusting the position of the condensing point by the adjusting means so as to be on the opposite surface;
A first scanning step of forming a first modified region by irradiating the pulsed laser light along the planned cutting position while moving the workpiece relative to the condensing means;
The adjustment means shifts the condensing region in the thickness direction of the object to be processed, and irradiates the pulse laser beam along the planned cutting position while moving the object to be processed relative to the condensing means. And a second scanning step of forming a second modified region so as to be continuous in the thickness direction with the first modified region formed in the first scanning step. Scribe method. A modified region formed by irradiating a processing object with a focused pulsed laser beam having wavelength dispersion characteristics using the laser irradiation apparatus according to claim 2 and absorbing the multiphoton by the processing object. A laser scribing method for forming in a thickness direction along a planned cutting position of the workpiece,
A positioning step of relatively positioning the condensing means and the processing object so that an optical axis of the pulse laser beam is positioned on a line of the planned cutting position of the processing object;
An adjustment step of adjusting the position of the condensing point so that at least a part of the condensing region of the pulsed laser light is applied to the surface of the workpiece opposite to the incident surface of the pulsed laser light;
A first scanning step of forming a first modified region by irradiating the pulsed laser light along the planned cutting position while moving the workpiece relative to the condensing means;
The axial chromatic aberration enlarging means is inserted between the condensing means and the object to be processed by the inserting means, and the condensing region is shifted in the thickness direction of the object to be processed by the adjusting means, and the condensing means In the thickness direction, the first modified region formed in the first scanning step is irradiated with the pulse laser beam along the planned cutting position while relatively moving the object to be processed. And a second scanning step for forming the second modified region so as to be continuous.