JP2007021557A - Laser beam irradiation apparatus and laser beam scribing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam irradiation apparatus capable of scribing a work with high productivity, and a laser beam scribing method using the laser beam irradiation apparatus. <P>SOLUTION: The laser beam irradiation apparatus 100 comprises a laser beam source 101, a condensing lens 103 for condensing laser beams, a Z-axis slide mechanism 104 capable of moving the condensing lens 103 in the Z-axis direction, an X-axis slide part 108 and a Y-axis slide part 106 capable of moving a stage 105 with a substrate W placed thereon in a plane substantially orthogonal to the optical axis 101a, a lens control part 122 for controlling the Z-axis slide mechanism 104, a stage control part 123 for controlling the X-axis slide part 108 and the Y-axis slide part 106, and a main computer 120 for integrally controlling a laser beam control part 121, the lens control part 122 and the stage control part 123 with each other. By oscillating the condensing lens 103 in the Z-axis direction, the laser beam condensing area is oscillated in the thickness direction of the substrate W to irradiate laser beams. <P>COPYRIGHT: (C)2007,JPO&INPIT

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 the laser beam so that the modified region is continuous in the thickness direction corresponding to the workpiece can be considered. However, there is a problem that the processing time for irradiating the laser beam becomes long and the productivity is lowered.

  The present invention has been made in consideration of the above problems, and an object thereof is to provide a laser irradiation apparatus capable of scribing a workpiece with high productivity and a laser scribing method using the laser irradiation apparatus. .

  The laser irradiation apparatus of the present invention includes a laser light source that emits laser light, a condensing unit that condenses the laser light, and a condensing region of the laser light by moving the condensing unit relative to the workpiece. The first moving means that can change the position of the workpiece in the thickness direction of the workpiece, and the second that can move the workpiece relative to the light collecting means in a plane substantially perpendicular to the optical axis of the laser beam. And a control unit for controlling the laser light source, the first moving unit, and the second moving unit, the control unit with respect to the incident surface or the incident surface in the thickness direction of the workpiece of the laser light The position of the condensing means is set by controlling the first moving means so that the end of the condensing region of the laser light is applied to the surface on the opposite side, and the laser light is applied along the planned cutting position of the workpiece. The first moving hand so that the first scanning to irradiate and the condensing region of the laser light vibrate. , The laser beam is irradiated along the planned cutting position of the processing object, and the processing object is formed by multiphoton absorption by the first scanning as viewed from the direction along the planned cutting position. And a second scan for forming a second modified region continuous in the thickness direction in the modified region.

  According to this configuration, the control unit controls the first moving unit and the second moving unit to perform the first scanning that irradiates the laser beam along the planned cutting position of the workpiece. As a result, a first modified region that is continuous in the thickness direction is formed on the incident surface of the laser beam or the surface opposite to the incident surface. Further, the first moving means is controlled so that the condensing region of the laser beam vibrates, and the second scanning is performed to irradiate the laser beam along the planned cutting position of the workpiece. As a result, a second modified region continuous in the thickness direction is formed in the first modified region formed by multiphoton absorption of the workpiece by the first scanning as viewed from the direction along the planned cutting position. Is done. Therefore, as compared with the case where the modified region continuous in the thickness direction is formed by irradiating the laser beam while sequentially shifting the condensing region of the laser beam in the thickness direction of the workpiece along the planned cutting position, the second The modified region is formed by the laser light condensing region being vibrated by the first moving means, so that it is possible to reduce the number of times the laser light is scanned to form the modified region continuous in the thickness direction. it can. Then, if stress is applied to the workpiece from the outside so that the second modified region is cut starting from the first modified region, the workpiece can be cut at the planned cutting position. That is, even when the thickness of the workpiece is increased, the laser processing time can be shortened, and a laser irradiation apparatus capable of scribing the workpiece with high productivity can be provided.

  Further, the control unit controls the first moving means so that the end of the laser beam condensing region is placed on the surface opposite to the incident surface in the thickness direction of the laser beam workpiece. Setting the position of the condensing means, controlling the first moving means so as to vibrate the condensing area of the laser light, and the first scanning for irradiating the laser light along the planned cutting position of the workpiece; A first modified region formed by irradiating a laser beam along the planned cutting position of the workpiece and absorbing the multiphoton by the first scan as viewed from the direction along the planned cutting position. And a second scan for forming a second modified region continuous in the thickness direction, and an end surface of the laser beam condensing region on the incident surface in the thickness direction of the workpiece of the laser beam. The position of the light collecting means is set by controlling the moving means, and the cutting target position of the workpiece is set. Thus, it is preferable to perform a third scan that irradiates the laser beam and forms a third modified region continuous in the thickness direction in the second modified region as viewed from the direction along the planned cutting position. .

  According to this configuration, the control unit controls the first moving unit to set the position of the condensing unit so that the end of the condensing region of the laser beam is applied to the incident surface of the laser beam, and the workpiece A third scan for irradiating the laser beam along the scheduled cutting position is performed. As a result, a third modified region is formed which is continuous with the second modified region in the thickness direction as viewed from the direction along the planned cutting position and along the laser light incident surface. Therefore, when viewed from the direction along the planned cutting position, the first modified region, the second modified region, and the third modified region are continuous in the thickness direction of the workpiece. A first modified region is formed along the surface opposite to the laser light incident surface, and a third modified region is formed along the incident surface. In other words, laser irradiation that can cut a workpiece by reducing the occurrence of a defective shape that is shifted from the planned cutting position after cutting is formed along the front and back surfaces of the cutting position of the workpiece. An apparatus can be provided.

  In addition, the control unit controls the first moving unit so that the condensing region of the laser beam vibrates, irradiates the laser beam along the planned cutting position of the workpiece, and follows the planned cutting position. It is preferable to further perform a fourth scan for forming a fourth modified region continuous in the thickness direction with respect to at least the second modified region as viewed from the direction.

  According to this configuration, the control unit controls the first moving unit so that the condensing region of the laser beam vibrates, and performs the fourth scan for irradiating the laser beam along the planned cutting position of the workpiece. Do. As a result, a fourth modified region that is continuous in the thickness direction with respect to at least the second modified region as viewed from the direction along the planned cutting position is formed. Therefore, the laser processing time is extended by performing the fourth scan, but by forming the fourth modified region in the thickness direction of the planned cutting position where the processing target is to be cut, the laser processing time is further increased. If a modified region is formed and an external stress is applied, it is possible to provide a laser irradiation apparatus that can easily cut a workpiece at a planned cutting position.

  The laser scribing method of the present invention uses the laser irradiation apparatus of the present invention to irradiate a focused laser beam, and to cut the modified region formed by the multi-photon absorption of the processing object. A laser scribing method for forming in a thickness direction along the position, wherein the second moving means causes the light converging means and the processing object to be positioned so that the optical axis of the laser light is on the line of the planned cutting position of the processing object. Positioning step of relatively positioning the focusing point by the first moving means so that the end of the focusing region of the laser beam is placed on the surface opposite to the laser beam incident surface of the workpiece A first adjustment step for adjusting the position, and a first scan for forming a first modified region by irradiating a laser beam along the planned cutting position while relatively moving the workpiece by the second moving means Process and processing pair by second moving means Corresponding to the relative movement of the object, the first moving means oscillates the condensing region in the thickness direction of the object to be processed, and irradiates the laser beam along the planned cutting position, and from the direction along the planned cutting position. And a second scanning step of forming a second modified region so as to be continuous with the first modified region formed in the first scanning step in the thickness direction.

  According to this method, in the positioning step, the processing object is moved relative to the light collecting means by the second moving means, and the optical axis of the laser beam is positioned on the line of the planned cutting position of the processing object. Position to do. In the first adjustment step, the position of the condensing point is set by the first moving means so that the end of the condensing region of the laser light is placed on the surface opposite to the laser light incident surface of the workpiece. To do. In the first scanning step, the first modified region is formed by irradiating the laser beam along the planned cutting position while relatively moving the workpiece by the second moving means. Thus, the first modified region is formed along the surface opposite to the laser light incident surface. In the second scanning step, by irradiating the laser beam along the planned cutting position while vibrating the condensing region in the thickness direction of the object to be processed by the first moving unit, from the direction along the planned cutting position. As seen, the second modified region is formed in the first modified region so as to be continuous in the thickness direction. Therefore, compared with the case of irradiating laser light while sequentially shifting the position of the laser light condensing point in the thickness direction of the workpiece along the planned cutting position, to form a modified region continuous in the thickness direction, In the second scanning step, the second modified region that is continuous with the first modified region and oscillated in the thickness direction is formed. Therefore, the laser beam that forms the modified region continuous in the thickness direction is formed. The number of scans can be reduced. Then, if stress is applied to the workpiece from the outside so that the second modified region is cut starting from the first modified region, the workpiece can be cut at the planned cutting position. That is, it is possible to provide a laser scribing method capable of shortening the laser processing time and scribing the workpiece with high productivity.

  A second adjustment step of adjusting the position of the condensing point by the first moving means so that the end of the condensing region of the laser light is placed on the laser light incident surface of the workpiece; It is preferable to further include a third scanning step of forming a third modified region by irradiating a laser beam along a planned cutting position while relatively moving the workpiece by the moving means.

  According to this method, in the second adjustment step, the position of the condensing point is adjusted by the first moving unit so that the end of the condensing region of the laser light is applied to the laser light incident surface of the workpiece. . In the third scanning step, the laser beam is irradiated along the planned cutting position while the workpiece is relatively moved by the second moving means. As a result, a third modified region is formed along the laser light incident surface. In other words, since the modified regions are formed along the front and back surfaces of the cutting target position of the workpiece, it is possible to reduce the occurrence of an external defect that is deviated from the cutting target position after cutting, and to achieve high yield and high productivity. A laser scribing method capable of cutting an object can be provided.

  Further, in response to the relative movement of the object to be processed by the second moving means, the first moving means vibrates the condensing region in the thickness direction, and irradiates the laser beam along the planned cutting position to cut. It is preferable to further include a fourth scanning step of forming a fourth modified region that is continuous in the thickness direction with respect to at least the second modified region as viewed from the direction along the planned position.

  According to this method, in the fourth scanning step, laser light is irradiated while vibrating the condensing region in the thickness direction by the first moving means in the same manner as in the second scanning step, and along the planned cutting position. A fourth modified region that is continuous in the thickness direction with respect to at least the second modified region as viewed from the direction is formed. Therefore, although the laser processing time is extended by performing the fourth scanning step, the laser processing time is increased by forming the fourth modified region in the thickness direction of the planned cutting position where the workpiece is to be cut. Thus, a laser scribing method can be provided in which a modified region is formed and an object to be cut can be easily cut at an intended cutting position by applying external stress. In this case, since it is desirable that the fourth modified region has as few portions as possible to overlap the second modified region in the thickness direction of the workpiece, for example, the phase is shifted from the second modified region. The fourth modified region may be formed in a state in which it has been removed.

  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, the laser irradiation apparatus 100 includes a laser light source 101 that emits laser light, a dichroic mirror 102 that reflects the emitted laser light, and a collection unit that collects the reflected laser light. And an optical lens 103. Further, a stage 105 on which a substrate W as a processing target is placed, and a second movement that can move the stage 105 relative to the condensing lens 103 in a plane substantially orthogonal to the optical axis 101a of the laser beam. An X-axis slide part 108 and a Y-axis slide part 106 are provided as means. Further, as a first moving means that can move the condensing lens 103 relative to the substrate W placed on the stage 105 to change the position of the condensing region of the laser light in the thickness direction of the substrate W. A Z-axis slide mechanism 104 is provided. Furthermore, an imaging device 110 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 as a control unit that controls each of the above components. In addition to the CPU and various memories, the main computer 120 includes an image processing unit 124 that processes image information captured by the imaging device 110. The imaging device 110 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.

  The main computer 120 is connected to an input unit 125 for inputting data of various processing conditions used during laser processing and a display unit 126 for displaying various information during laser processing. A laser controller 121 that controls the output, pulse width, and pulse period of the laser light source 101 and a lens that drives the Z-axis slide mechanism 104 to control the position, vibration speed, and amplitude of the condenser lens 103 in the Z-axis direction. A control unit 122 is connected. Further, a stage control unit 123 is connected to drive a servo motor (not shown) that moves the X-axis slide unit 108 and the Y-axis slide unit 106 along the rails 107 and 109, respectively.

  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 condensing 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 110 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 laser beam 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.

  In this embodiment, the stage 105 is supported by the Y-axis slide unit 106, but is supported by the X-axis slide unit 108 by reversing the positional relationship between the X-axis slide unit 108 and the Y-axis slide unit 106. It is good also as a form. Further, it is preferable to support the stage 105 on the Y-axis slide unit 106 via a 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 cross-sectional view showing a state in which the position of the laser beam condensing region is varied in the thickness direction of the workpiece. FIG. 6A is a schematic cross-sectional view showing a state in which the end of the laser light condensing region is positioned so as to be on the surface Wb opposite to the laser light incident surface Wa, and FIG. It is a schematic sectional drawing which shows the state from which the condensing area | region gradually approached the entrance plane Wa.

  As shown in FIG. 4A, the laser beam 113 condensed by the condensing lens 103 has a wavelength dispersion characteristic. Therefore, when the laser beam 113 is incident on the substrate W having a refractive index of about 1.46, a short wavelength is obtained. The condensing points from the laser beam 114 on the side to the laser beam 115 on the long wavelength side are focused on a condensing region 116 shifted on the optical axis 101a. The condensing region 116 has a so-called axial chromatic aberration. In this case, since the condensing point of the laser light 115 on the long wavelength side of the condensing region 116 is close to the surface Wb, the optical path difference between the laser light 114 on the short wavelength side and the laser light 115 on the long wavelength side is the largest. It is getting bigger. That is, the width of the light collection region 116 in the thickness direction of the substrate W is the maximum.

  As shown in FIG. 4B, when the condensing lens 103 is moved in the Z-axis direction by driving the Z-axis slide mechanism 104 so that the position of the condensing region 116 approaches the incident surface Wa side, The optical path difference between the laser light 114 on the short wavelength side and the laser light 115 on the long wavelength side is gradually reduced. Accordingly, the width of the substrate W in the thickness direction gradually changes from the condensing region 117 where the width is gradually reduced to the condensing region 118. Of course, when the Z-axis slide mechanism 104 is driven so that the condensing region approaches the surface Wb from the vicinity of the incident surface Wa and the condensing lens 103 is moved in the Z-axis direction, the condensing region 118 collects light. The width in the thickness direction of the substrate W gradually increases toward the region 116.

  If a laser light source 101 having a small wavelength dispersion characteristic, that is, a half-width is very narrow and a chromatic aberration of the condensing lens 103 is small or corrected, the position of the condensing point in the thickness direction of the substrate W is used. It is possible to suppress the amount of change in which the width of the light collection region changes.

  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.

  Based on the irradiation characteristics of the laser beam 113 with respect to the substrate W, the main computer 120 of the laser irradiation apparatus 100 is configured such that the end of the condensing region of the laser beam 113 is the surface opposite to the incident surface Wa of the laser beam 113. The position of the condensing lens 103 is set by the Z-axis slide mechanism 104 so as to be applied to Wb, and the first scanning is performed to irradiate the laser beam 113 along the planned cutting positions along the partition areas Dx and Dy of the substrate W. Do. Further, the first scanning is performed by irradiating the laser beam 113 along the planned cutting position of the substrate W while vibrating the condensing region of the laser beam 113 by the Z-axis slide mechanism 104 and viewing from the direction along the planned cutting position. As a result, a second scan is performed to form a second modified region continuous with the first modified region formed by the substrate W absorbing multiphotons. Further, the position of the condensing lens 103 is set by the Z-axis slide mechanism 104 so that the end of the condensing region of the laser beam 113 is placed on the incident surface Wa of the laser beam 113, and the partitioned regions Dx and Dy of the substrate W are set. A third scan is performed to irradiate the laser beam 113 along the planned cutting position along the line to form a third modified region continuous in the thickness direction in the second modified region. Furthermore, the laser beam 113 is irradiated along the planned cutting position of the substrate W while vibrating the condensing region of the laser beam 113 by the Z-axis slide mechanism 104, and at least the second is seen from the direction along the planned cutting position. A fourth scan is performed to form a fourth modified region continuous in the thickness direction with respect to the modified region.

  According to such a laser irradiation apparatus 100, the laser beam is irradiated by sequentially shifting the position of the condensing point of the laser beam 113 in the thickness direction of the substrate W, and the modification is continuously performed in the thickness direction along the planned cutting position. Compared with the case where the region is formed, the second modified region is formed with the condensing region of the laser beam 113 being oscillated. Therefore, the scanning of the laser beam 113 that forms the modified region continuous in the thickness direction is performed. It is possible to reduce the number of times. In addition, since the first modified region and the third modified region are formed along the front and back surfaces of the planned cutting position of the substrate W, when the substrate W is cut by applying external stress, the first modified region is formed. Cutting is performed starting from the region or the third modified region. Therefore, it is possible to reduce the occurrence of external defects on the fracture surface.

  If the modified region can be continuously formed in the thickness direction of the planned cutting position, the third or fourth scan, and the third and fourth scans are not necessarily performed.

(Laser scribing method)
Next, a laser scribing method to which the present invention is applied will be described. FIG. 5 is a flowchart showing a laser scribing method.

  As shown in FIG. 5, the laser scribing method of the present embodiment uses the laser irradiation apparatus 100 to relatively position the condenser lens 103 and the substrate W placed on the stage 105 (step S1). And a first adjustment step (step S3) in which the position of the condensing point of the laser beam 113 is adjusted by the Z-axis slide mechanism 104. Further, as a first scanning process of forming a first modified region by irradiating the laser beam 113 along the planned cutting position while relatively moving the substrate W by the X-axis slide portion 108 and the Y-axis slide portion 106. A primary laser scanning process (step S4) is provided. Then, while moving the substrate W relatively and vibrating the condensing region in the thickness direction of the substrate W by the Z-axis slide mechanism 104, the laser beam 113 is irradiated along the planned cutting position, and the direction along the planned cutting position. A secondary laser scanning step (step S5) as a second scanning step for forming the second modified region so as to be continuous with the first modified region formed in the primary laser scanning step in the thickness direction as viewed from the top. ). Further, a second adjustment step of adjusting the position of the condensing point by the Z-axis slide mechanism 104 so that the end of the condensing region of the laser beam 113 is placed on the incident surface Wa of the laser beam 113 of the substrate W (step S6). It has. A third laser scanning process (step S7) is provided as a third scanning process in which the third modified region is formed by irradiating the laser beam 113 along the planned cutting position while relatively moving the substrate W. Yes. Further, the substrate W is relatively moved and the condensing region is vibrated in the thickness direction of the substrate W by the Z-axis slide mechanism 104, and the laser beam 113 is irradiated along the planned cutting position. A fourth laser scanning step (fourth scanning step) for forming the fourth modified region so as to be continuous in the thickness direction with respect to the second modified region formed in the secondary laser scanning step as viewed from (4) Step S8) is provided.

  Step S1 in FIG. 5 is a step of positioning the substrate W. In step S 1, the substrate W shown in FIG. 2 is placed so that the counter substrate 2 side is in contact with the surface of the stage 105. Then, the substrate W is positioned so that the partition region Dx is parallel to the X-axis direction. Further, the stage control unit 123 drives the servo motor so that the optical axis 101a of the laser beam 113 is positioned on the line of the planned cutting position of the arbitrary divided regions Dx and Dy of the substrate W, and the X-axis slide unit 108 and the Y-axis slide unit 108 are driven. The shaft slide part 106 is moved. In this case, an alignment mark for positioning is formed on the wafer-like substrate W, the alignment mark is recognized by the imaging device 110, and coordinates are calculated based on the image data captured by the image processing unit 124. Thus, the substrate W is positioned. Then, the process proceeds to step S2.

  Step S2 in FIG. 5 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 110 is displayed on the display unit 126, and the laser beam incident surface Wa (see FIG. 4) and the other surface Wb (see FIG. 4) on the other side of the substrate W from the imaging device 110. 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 emitted visible light. 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. 5 is a first adjustment step of adjusting the position of the condensing point of the laser beam 113. In step S3, the positional relationship in the Z-axis direction between the focal point of the visible light captured by the imaging device 110 and the condensing region 116 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, as shown in FIG. 104 is driven, and the condensing lens 103 is moved in the Z-axis direction so that the end of the condensing region 116 is applied to the surface Wb of the substrate W opposite to the incident surface Wa of the laser light 113. Then, the process proceeds to step S4.

Step S4 in FIG. 5 is a primary laser scanning process. FIG. 6 is a schematic cross-sectional view showing a state in which the first modified region is formed. In step S4, the first modified region 21 is formed by irradiating the laser beam 113 along the planned cutting position while moving the substrate W relative to the condenser lens 103 as shown in FIG. 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 108 and the Y-axis slide unit 106 based on the control signal. In this case, the speed at which the substrate W is moved corresponding to the irradiation of the laser beam 113, 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). In this case, the peak power density in the condensing region 116 is 8 × 10 ¹² W / cm ² . Thus, the width of the first modified region 21 formed by the substrate W by multiphoton absorption of the laser beam 113 is approximately 200 to 300 μm. Then, the process proceeds to step S5.

  Step S5 in FIG. 5 is a secondary laser scanning process. FIG. 7 is a schematic cross-sectional view showing a state in which the second modified region is formed. In step S5, as in step S4, the main computer 120 controls the stage control unit 123 to drive the X-axis slide unit 108 and the Y-axis slide unit 106 so that the partition regions Dx and Dy are at the planned cutting positions. Correspondingly, laser scanning is performed 19 times in the X-axis direction and 15 times in the Y-axis direction. Further, the condenser lens 103 is vibrated in the Z-axis direction by the Z-axis slide mechanism 104 in synchronization with these laser scans. That is, the condensing point of the laser beam 113 vibrates in the thickness direction of the substrate W, and changes between the condensing region 117 and the condensing region 118. Then, as shown in FIG. 7, a second modified region 22 that is continuous in the thickness direction is formed in the first modified region 21 when viewed from the direction along the planned cutting position (scanning direction). In this case, the amplitude of the second modified region is approximately 700 to 800 μm. The vibration speed of the Z-axis slide mechanism 104 controlled by the lens control unit 122 is approximately 1.5 mm / second. Therefore, the vibration is performed once in approximately one second, and the laser scanning speed is 20 mm / second, so that the vibration period is also approximately 20 mm. Then, the process proceeds to step S6.

  Step S6 in FIG. 5 is a second adjustment process for adjusting the position of the condensing point of the laser beam 113. In step S <b> 6, as shown in FIG. 4B, the lens control unit 122 drives the Z-axis slide mechanism 104 so that the end of the condensing region 118 is applied to the incident surface Wa of the laser beam 113 of the substrate W. Then, the condenser lens 103 is moved in the Z-axis direction. Then, the process proceeds to step S7.

  Step S7 in FIG. 5 is a tertiary laser scanning process. FIG. 8 is a schematic cross-sectional view showing a state in which the third modified region is formed. In step S7, as in step S4, the main computer 120 controls the stage control unit 123 to drive the X-axis slide unit 108 and the Y-axis slide unit 106 to correspond to the planned cutting positions of the partition areas Dx and Dy. The laser scan is performed 19 times in the X-axis direction and 15 times in the Y-axis direction. As a result, as shown in FIG. 8, the third modified region 23 that overlaps the maximum amplitude of the second modified region 22 is formed in the thickness direction along the planned cutting position of the incident surface Wa of the substrate W. Is done. That is, a third modified region 23 that is continuous in the thickness direction is formed in the second modified region 22 when viewed from the scanning direction. In this case, the width of the third modified region 23 is approximately 50 μm because the condensing region becomes smaller as it approaches the incident surface Wa. Then, the process proceeds to step S8.

  Step S8 in FIG. 5 is a quaternary laser scanning process. FIG. 9 is a schematic cross-sectional view showing a state where the fourth modified region is formed. In step S8, similarly to step S5, the main computer 120 controls the stage control unit 123 to drive the X-axis slide unit 108 and the Y-axis slide unit 106 to correspond to the planned cutting positions of the partition areas Dx and Dy. The laser scan is performed 19 times in the X-axis direction and 15 times in the Y-axis direction. Further, the condenser lens 103 is vibrated in the Z-axis direction by the Z-axis slide mechanism 104 in synchronization with these laser scans. In this case, the lens control unit 122 controls the vibration of the condensing lens 103 by the Z-axis slide mechanism 104 so that the phase is shifted with respect to the second modified region 22 formed in the previous secondary laser scanning process. As a result, as shown in FIG. 9, a fourth modified region 24 partially overlapping each modified region 21, 22, 23 is formed in the thickness direction along the planned cutting position. If at least the second modified region 22 and the fourth modified region 24 partially overlap, the first modified region 21 and the third modified region 23 do not overlap. May be. According to this, it is possible to increase the density of the modified region formed between the first modified region 21 and the third modified region 23. That is, it becomes possible to facilitate cutting in the subsequent break process (step S9). Then, the process proceeds to step S9.

  Step S9 in FIG. 5 is a breaking process for cutting the substrate W at the planned cutting position. FIG. 10 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 S9, for example, as shown in FIG. 10A, the modified region Rc continuously formed in the thickness direction of the substrate W by step S4, step S5, step S7, and step S8 is changed to C or External stress is applied in the D direction. As a result, the substrate W is divided at the modified region Rc as shown in FIG. In addition, since the first modified region 21 and the third modified region 23 are formed in the thickness direction along the incident surface Wa and the front surface Wb of the substrate W, that is, the planned cutting positions of the front and back surfaces, It is possible to reduce the occurrence of the appearance defect on the fractured surface due to the cutting progressed from this point. Therefore, cutting with high accuracy is possible. 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.

  Such a laser scribing method is the second method compared to the case where the condensing point of the laser beam 113 is sequentially shifted in the thickness direction of the substrate W and the laser beam 113 is irradiated to form a modified region continuous in the thickness direction. Since the modified region 22 and the fourth modified region 24 are formed in a vibrating state, the number of laser scans can be reduced. Further, if the thickness of the substrate W is reduced to, for example, about 600 μm, the substrate W can be cut even if the third laser scanning step, the fourth laser scanning step, or the third and fourth laser scanning steps are omitted. It is.

The effect of the said embodiment is as follows.
(1) In the laser irradiation apparatus and laser scribing method of the above-described embodiment, the main computer 120 controls the laser light source 101, the Z-axis slide mechanism 104, the X-axis slide unit 108, and the Y-axis slide unit 106, respectively, to perform the primary operation. Perform quaternary laser scan. As a result, the first modified region 21 and the third modified region 23 are formed in the thickness direction along the planned cutting position of the front and back surfaces of the substrate W (the surface Wb opposite to the incident surface Wa of the laser beam 113). It is formed. Further, the second modified region 22 and the fourth modified region 24 are formed in such a state that the first modified region 21 and the third modified region 23 are vibrated so as to be continuous when viewed from the scanning direction. Is done. That is, since the modified region Rc continuous in the thickness direction of the substrate W is formed, if an external stress is applied to the substrate W in the breaking process, the first modified region 21 or the third modified region at the planned cutting position. The substrate W can be cut accurately and easily with 23 as a starting point. Further, it is possible to provide a laser irradiation apparatus 100 and a laser scribing method capable of scribing the substrate W with high productivity by reducing the number of laser scans for forming the modified region Rc continuous in the thickness direction of the substrate W.

Modifications other than the above embodiment are as follows.
(Modification 1) In the laser irradiation apparatus 100 and the laser scribing method of the above embodiment, the second modified region 22 meandered by vibrating the condenser lens 103 by the Z-axis slide mechanism 104 as the first moving means. The method of forming the fourth modified region 24 is not limited to this. FIG. 11 is a schematic cross-sectional view showing a modified region formed in a modified example. For example, as shown in FIG. 11A, the lens controller 122 may control the Z-axis slide mechanism 104 so that the second modified region 22 is formed in a triangular wave shape (fourth modified). The same applies to the region 24). According to this, since the vibration control of the Z-axis slide mechanism 104 may be a constant speed, complicated control is not required. In the case of meandering, the control has a constant speed region and an acceleration region in the thickness direction.

  (Modification 2) In the laser irradiation apparatus 100 and the laser scribing method of the above-described embodiment, the first modification region 21 and the third modification region 23 are vibrated in the thickness direction while oscillating when viewed from the scanning direction. The method for forming the continuous second modified region 22 or the fourth modified region 24 is not limited to this. For example, as shown in FIG. 11B, when the thickness of the substrate W is further increased, the modified region 35 is formed on the incident surface Wa side of the laser beam 113 when viewed from the scanning direction, and the opposite side is formed. The modified region 31 is formed on the surface Wb side. Then, a modified region 32 that is vibrated so as to be continuous in the thickness direction is formed in the modified region 31. Similarly, the modified region 34 is formed in the modified region 35 so as to vibrate continuously in the thickness direction. And you may form the modification | reformation area | region 33 of the state oscillated so that between the modification | reformation area | regions 32 and 34 may continue in the thickness direction. In this way, the width of vibration of the condenser lens 103 by the Z-axis slide mechanism 104 can be reduced. That is, it is not necessary to increase the width of vibration of the condenser lens 103 in accordance with the thickness of the substrate W, and it is possible to improve durability quality such as a failure of the apparatus due to vibration of the Z-axis slide mechanism 104.

  (Modification 3) In the laser irradiation apparatus 100 of the above embodiment, the laser light source 101 is a femtosecond laser using titanium sapphire as a solid light source, but is not limited thereto. For example, if the object to be processed is a substrate made of silicon or the like like a semiconductor wafer, a YAG laser can be used.

  (Modification 4) 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 5) In the laser scribing method of the above embodiment, the order and method of laser processing are not limited to this. For example, the primary and tertiary laser scanning steps may be performed first, and then the secondary and quaternary laser scanning steps may be performed. When the secondary laser scanning process is finished, the substrate W is inverted and placed on the stage 105, and the position of the condensing point is adjusted again in the positioning process of the substrate W and the second adjustment process. Then, a tertiary and quaternary laser scanning process is performed. In this way, the width in the thickness direction of the third modified region 23 formed in the tertiary laser scanning process is substantially equal to the width of the first modified region 21. Further, the shape of the fourth modified region 24 formed in the quaternary laser scanning process can be a state in which the second modified region 22 is inverted. That is, the modified regions formed from the front and back surfaces to the inside of the substrate W can be formed with substantially the same distribution regardless of the distance from the front and back surfaces. Therefore, it becomes possible to break easily regardless of the direction of external stress applied in the breaking process.

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. The schematic sectional drawing which shows the state which varied the position of the condensing area | region of the laser beam in the thickness direction of the workpiece. The flowchart which shows the laser scribing method. The schematic sectional drawing which shows the state in which the 1st modification area | region was formed. The schematic sectional drawing which shows the state in which the 2nd modification area | region was formed. The schematic sectional drawing which shows the state in which the 3rd modification area | region was formed. The schematic sectional drawing which shows the state in which the 4th modification area | region was formed. The schematic sectional drawing which shows the breaking method. The schematic sectional drawing which shows the formation state of the modification area | region of a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 ... 1st modification area | region, 22 ... 2nd modification area | region, 23 ... 3rd modification area | region, 24 ... 4th modification area | region, 100 ... Laser irradiation apparatus, 101 ... Laser light source, 101a ... Light Numeral 103: Condensing lens as condensing means 104: Z-axis sliding mechanism as first moving means 106: Y-axis sliding portion as second moving means 108: As second moving means X axis slide part, 113 ... laser light, 116, 117, 118 ... condensing area, 120 ... main computer as control part, W ... substrate as workpiece, Wa ... incident surface of laser light, Wb ... incident surface Opposite surface.

Claims (6)

A laser light source for emitting laser light;
Condensing means for condensing the laser light;
A first moving means capable of moving the light condensing means relative to the processing object to change the position of the condensing region of the laser light in the thickness direction of the processing object;
Second moving means capable of moving the workpiece relative to the light collecting means in a plane substantially perpendicular to the optical axis of the laser beam;
A controller for controlling the laser light source and the first moving means and the second moving means;
The control unit is configured so that an end of the laser beam condensing region is applied to an incident surface of the laser beam in a thickness direction of the workpiece or a surface opposite to the incident surface. The position of the condensing means is set by controlling the moving means so that the first scanning that irradiates the laser light along the planned cutting position of the workpiece and the condensing area of the laser light vibrate. The first moving means is controlled to irradiate the laser beam along the planned cutting position of the processing object, and the processing object is processed by the first scanning as viewed from the direction along the planned cutting position. And a second scanning for forming a second modified region continuous in the thickness direction in the first modified region formed by multiphoton absorption of an object.   The control unit controls the first moving unit so that an end portion of the laser beam condensing region is applied to a surface opposite to the incident surface of the laser beam in the thickness direction of the workpiece. Then, the position of the condensing means is set, and the first scanning for irradiating the laser light along the planned cutting position of the workpiece, and the first condensing area of the laser light vibrate. , The laser beam is irradiated along the scheduled cutting position of the workpiece, and the workpiece is multiphoton by the first scanning as viewed from the direction along the scheduled cutting position. A second scan for forming a second modified region continuous in the thickness direction in the first modified region formed by absorption; and an incident surface of the laser beam in the thickness direction of the workpiece, The first shift is performed so that the end of the laser beam condensing region is covered. The position of the condensing means is set by controlling the means, the laser beam is irradiated along the planned cutting position of the workpiece, and the second modification is seen from the direction along the planned cutting position. The laser irradiation apparatus according to claim 1, wherein a third scan for forming a third modified region continuous in the thickness direction is performed on the quality region.   The control unit controls the first moving unit so that a condensing region of the laser beam vibrates, irradiates the laser beam along a planned cutting position of the workpiece, and the planned cutting position 3. The fourth scan for forming a fourth modified region that is continuous in the thickness direction with respect to at least the second modified region as viewed from the direction along the line. 4. Laser irradiation device. Using the laser irradiation apparatus according to any one of claims 1 to 3, irradiating a focused laser beam to form a modified region formed by multi-photon absorption of the workpiece to be processed. A laser scribing method for forming in a thickness direction along a planned cutting position of an object,
A positioning step of relatively positioning the condensing unit and the processing object by the second moving unit so that an optical axis of the laser beam is positioned on a line of the planned cutting position of the processing object;
The first moving means adjusts the position of the condensing point so that the end of the condensing region of the laser light is placed on the surface of the workpiece opposite to the laser light incident surface. The adjustment process of
A first scanning step of forming a first modified region by irradiating the laser beam along the planned cutting position while relatively moving the workpiece by the second moving means;
Corresponding to the relative movement of the object to be processed by the second moving means, the first moving means vibrates the light collecting region in the thickness direction of the object to be processed, along the planned cutting position. A second modified region is irradiated with the laser beam so as to be continuous with the first modified region formed in the first scanning step in the thickness direction when viewed from the direction along the planned cutting position. And a second scanning step for forming a laser scribing method. A second adjusting step of adjusting a position of a condensing point by the first moving means so that an end of the condensing region of the laser light is applied to the laser light incident surface of the workpiece;
And a third scanning step of forming a third modified region by irradiating the laser beam along the planned cutting position while relatively moving the object to be processed by the second moving means. The laser scribing method according to claim 4. Corresponding to the relative movement of the object to be processed by the second moving means, the laser light is irradiated along the scheduled cutting position while the first moving means vibrates the condensing region in the thickness direction. And a fourth scanning step of forming a fourth modified region continuous in the thickness direction with respect to at least the second modified region as viewed from the direction along the planned cutting position. The laser scribing method according to claim 5.

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