JP4752488B2 - Laser internal scribing method - Google Patents

Description

  The present invention relates to a laser processing method used for dividing a processing object such as a silicon substrate or a glass substrate, and more particularly to a laser internal scribing method for condensing and dividing laser light inside a processing object.

2. Description of the Related Art Conventionally, a method of cutting with a dicing apparatus equipped with a disk-shaped dicing saw has been used to divide a workpiece such as a silicon substrate or a glass substrate. This cutting method has a wide and inefficient cutting width and uses cleaning water and grinding fluid, so that it is not suitable for an object to be processed on which an electronic device or the like with defects due to wetting is formed. It was. In order to cope with such problems, in recent years, processing methods using laser light have been used.
For example, there is a laser processing method in which a laser beam is irradiated with a focusing point inside a processing object, and a modified region by multiphoton absorption is formed inside the processing object along a planned division line of the processing object. It has been proposed (see Patent Document 1).

JP 2002-192370 A

  A processing method that condenses and divides a laser beam inside a workpiece, that is, a laser internal scribing method, is divided along a modified region formed by irradiating a laser beam inside the workpiece. As the interval between the modified regions arranged in parallel is narrower, it is easier to divide, and it is desirable that the modified regions be formed close to each other. In order to form a large number of modified regions close to each other, a great amount of processing time is required.

  In order to solve the above problems, the present invention condenses laser light inside a processing object such as a silicon substrate or a glass substrate so that the processing object can be easily divided and can be divided in a short time. It is an object to provide a laser internal scribing method.

  In the laser internal scribing method of the present invention, the processing object is irradiated with a laser beam with a focusing point inside the processing object, and the processing object is moved relative to the laser light along a planned dividing line, and the processing is performed. A laser internal scribing method for forming a modified region by multiphoton absorption inside an object, wherein the laser beam having a pulse width in the range of picoseconds to femtoseconds is irradiated to the inside of the object to be processed. The quality region is formed obliquely with respect to the thickness direction of the workpiece.

  According to this scribing method, a laser beam having a pulse width in the range of picoseconds to femtoseconds is irradiated with a focused point inside the object to be processed. Thus, a modified region including a hollow processing mark having a diameter of about 0.5 μm and a length of about 300 μm is formed. The workpiece is moved relative to the laser beam along the planned dividing line, and the modified region is formed obliquely with respect to the thickness direction of the workpiece, so that a slight amount of bending stress or tensile stress is generated. By applying external stress, the workpiece can be easily separated at a position along the planned dividing line with the hollow machining trace as a starting point. Further, since the width of the modified region along the planned dividing line is a minute width of about several μm, it is possible to perform division with good external dimension accuracy.

Further, in the laser internal scribing method of the present invention, the modified region formed obliquely with respect to the thickness direction of the workpiece is arranged in parallel with the oblique direction with respect to the surface of the workpiece. It is characterized by that.
According to this scribing method, the object to be processed is moved relative to the laser beam along the planned dividing line, and the modified region is inclined with respect to the surface of the object to be processed in the thickness direction of the object to be processed. By arranging in parallel in the direction, it becomes possible to continuously form a multilayer modified region corresponding to the thickness of the workpiece, and the workpiece can be divided in a short time. Also, by applying a slight external stress such as bending stress or tensile stress, the workpiece can be easily separated with good dimensional accuracy at the position along the planned dividing line, starting from the hollow processing trace. Can do.

Further, in the laser internal scribing method of the present invention, the modified region formed obliquely with respect to the thickness direction of the workpiece is formed so that the modified region itself is inclined with respect to the surface of the workpiece. And arranged side by side in the thickness direction of the workpieces.
According to this scribing method, the object to be processed is moved relative to the laser beam along the planned dividing line, the modified region is inside the thickness direction of the object to be processed, and the modified region itself is the object to be processed. By forming them obliquely with respect to the surface of the workpiece and arranging them side by side in the thickness direction of the workpiece, it becomes possible to continuously form a multilayered modified region according to the thickness of the workpiece at a time. The processing object can be divided in a short time. In addition, by applying a slight external stress such as bending stress or tensile stress, the workpiece can be easily separated with good dimensional accuracy at the position along the planned dividing line, starting from the hollow processing trace. Can do.

  Further, the laser internal scribing method of the present invention irradiates a laser beam having a pulse width in the range of picoseconds to femtoseconds inside the object to be processed, and the object to be processed is divided along a predetermined division line with respect to the laser light. A laser internal scribing method for forming a modified region by multiphoton absorption inside the workpiece, wherein a condensing point of the laser beam is inside the workpiece along the planned dividing line An adjustment step of adjusting the position of the condensing point so as to become, and irradiating the laser beam inside the workpiece in the thickness direction, and the workpiece is synchronized with the irradiation of the laser beam. And a laser irradiation / scanning step in which a large number of the modified regions are formed obliquely with respect to the thickness direction of the object to be processed.

  According to this scribing method, a laser beam having a pulse width in the range of picoseconds to femtoseconds is irradiated inside the thickness direction of the workpiece, and the workpiece is synchronized with the laser beam irradiation. By moving relative to the light and forming a large number of modified regions obliquely with respect to the thickness direction of the workpiece, the inside of the workpiece has a diameter of about 0.5 μm due to multiphoton absorption. It is possible to form a modified region including a hollow processing mark having a thickness of about 300 μm at a time in a continuous multilayer according to the thickness of the processing object, and to divide the processing object in a short time. it can. In addition, by applying a slight external stress such as bending stress or tensile stress, the workpiece can be easily separated with good dimensional accuracy at the position along the planned dividing line starting from the hollow machining trace. it can.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a quartz glass substrate will be described as an example of the processing object. In the drawings shown below, the dimensions and ratios of the constituent elements are different from actual ones for convenience of explanation.
Fig.1 (a) is a top view of the quartz glass substrate which shows the outline | summary of the laser internal scribing method, FIG.1 (b) is sectional drawing in the AA of Fig.1 (a). FIG. 2A is a cross-sectional view showing a method for separating a quartz glass substrate scribed inside a laser, and FIG. 2B is a cross-sectional view showing a state of the quartz glass substrate separated along a planned dividing line. .

  In FIG. 1A, a laser internal scribe is such that a pulsed laser beam LB (hereinafter referred to as laser beam LB) extends linearly in the Y-axis direction of one surface 2 of a quartz glass substrate 1 as a workpiece. Irradiation is performed from the surface 2 side of the quartz glass substrate 1 toward the inside while relatively moving along the planned dividing line 10 (virtual line indicated by a two-dot chain line).

  As shown in FIG. 1B, the irradiated laser beam LB is refracted on the surface 2 of the quartz glass substrate 1 and enters the inside of the quartz glass substrate 1, and a condensing point 50 inside the quartz glass substrate 1. Condensed to At the condensing point 50, the modified region 51 is formed by multiphoton absorption. The modified region 51 is a denatured region in which properties (refractive index, transmittance, light absorption rate, crystallinity, etc.) at the condensing point 50 are transformed to a state different from that of the base material.

  The quartz glass substrate 1 and the laser beam LB are repeatedly relatively moved in the thickness direction of the object to be processed according to the thickness of the object to be processed, and the thickness direction (surface 2 and surface 3 along the dividing line 10 of the quartz glass substrate 1 is determined. The multilayered modified regions 51 are arranged side by side in a continuous manner.

  The quartz glass substrate 1 in which the multilayered modified region 51 is formed in the thickness direction along the planned dividing line 10 is compared with the thickness direction along the planned dividing line 10 as shown in FIG. By applying an external stress such as a small bending stress A or a tensile stress B, the quartz glass substrate 1 can be separated along the planned dividing line 10 as shown in FIG.

When laser light in the visible region is used as the laser light LB, the laser light is transmitted without being absorbed by quartz, which is the base material of the quartz glass substrate 1, so that it is difficult to divide the quartz glass substrate 1. It is. Further, when laser light having a long pulse width of picoseconds ( ^10-12 seconds) or more is used, the laser light is absorbed into quartz and converted into thermal energy, and the quartz glass substrate 1 is melted and scattered. is there.

By condensing the pulsed laser beam LB in the range of picoseconds to femtoseconds (10 ^-15 seconds) with an extremely small pulse width inside the quartz glass substrate 1, the energy of the laser beam LB is applied to quartz in a very short time. Many photons of the concentrated and focused laser beam LB are absorbed by the interaction with the quartz electrons. A so-called multiphoton absorption phenomenon occurs.

  Multiphoton absorption is performed in an extremely short time before the energy of the laser beam LB is converted into heat, and hardly generates heat. Further, multiphoton absorption can be applied only to the inside of the quartz glass substrate 1 on which the laser beam LB is condensed, and does not affect the surfaces 2 and 3 of the quartz glass substrate 1.

Here, experimentally, laser scribing was performed on the quartz glass substrate 1 using a femtosecond laser light source. The laser internal scribe was performed by irradiating the laser beam LB from the surface 2 side of the quartz glass substrate 1 toward the inside using a laser processing apparatus 20 described later, and relatively moving along the planned dividing line 10. Then, the divided surface of the quartz glass substrate 1 divided along the planned dividing line 10 was observed.
The experiment was performed using a condensing lens with a numerical aperture of 0.8, a femtosecond laser having a wavelength of 800 nm, a pulse width of 300 fs (femtoseconds), an output of 700 mW, and a repetition rate of 1 kHz, and relatively moving at a scanning speed of 20 mm / sec. .

  As a result, a hollow processing mark having a diameter of about 0.5 μm and a length of about 300 μm was confirmed inside the quartz glass substrate 1 by the laser beam LB focused with the femtosecond laser. Further, it was confirmed that the range affected by the irradiation with the laser beam LB is at least about 2 μm.

3 and 4 show photographed images of processing marks in this experiment. In addition, the imaging | photography of the image was performed using the scanning electron microscope (SEM: Scanning Electron Microscope).
FIGS. 3A and 3B are SEM images of the split surface of the quartz glass substrate scribed inside the laser. FIG. 3A shows an image at 1000 times and FIG. 3B shows an image at 10000 times. FIG. 4 is an SEM image taken at 3000 × with a perspective view of a cut surface obtained by cutting a divided surface of a quartz glass substrate in a direction perpendicular to the divided surface. Note that the quartz glass substrate shown in FIG. 4 is coated with an inorganic layer on the divided surface scribed inside the laser for the purpose of clearly observing the divided surface.

3A and 3B, the vertical line a and the vertical line b extending in the vertical direction of the paper surface are hollow processing marks formed by the laser beam LB.
In FIG. 4, the upward direction from the substantially central portion in the vertical direction of the paper is a divided surface that is scribed inside the laser, and the downward direction from the substantially central portion indicates the cut surface. The vertical line c extending in the vertical direction of the dividing surface is a hollow processing trace, and a crack d extending from the dividing surface to the inside (cut surface) of the quartz glass substrate 1 is observed. The tip of the crack d has a depth of about 2 μm from the split surface, and the range affected by the irradiation with the laser beam LB is considered to be at least about 2 μm.
Therefore, it is estimated that the modified region 51 has a width of at least about 2 μm in the peripheral direction of the processing mark with the processing mark as a substantial center.

  In the laser internal scribing method of the present invention, the modified region 51 including the hollow processing trace formed by condensing the laser beam LB inside the quartz glass substrate 1 as the processing target is scheduled to be divided. In this processing method, the quartz glass substrate 1 is divided along the line 10 in the thickness direction of the quartz glass substrate 1 (between the surface 2 and the surface 3) and obliquely formed with respect to the surfaces 2 and 3. .

The modified region 51 formed obliquely with respect to the surfaces 2 and 3 of the quartz glass substrate 1 in the thickness direction of the quartz glass substrate 1 includes the two cases shown in FIGS. 5 (a) and 5 (b). .
FIG. 5A is a schematic view of a divided surface of a quartz glass substrate on which an oblique modified region is formed, and FIG. 5B is a diagram of the quartz glass substrate on which another oblique modified region is formed. It is a schematic diagram of a division surface. In addition, in the schematic diagram of the divided surface of the quartz glass substrate shown in FIGS. 5A and 5B and FIG. 5 and subsequent figures, the modified region 51 including the hollow processing trace is shown in an elliptical shape.

  In FIG. 5A, each modified region 51 formed inside the thickness of the quartz glass substrate 1 (between the surface 2 and the surface 3) along the planned dividing line 10 is orthogonal to the surfaces 2 and 3. A large number of modified regions 51 are formed in parallel to the surfaces 2 and 3 of the quartz glass substrate 1 in an oblique direction. In the present embodiment, a method in which a large number of such modified regions 51 are arranged in an oblique direction with respect to the surfaces 2 and 3 is referred to as a modified region oblique stacking method.

  In FIG. 5B, the modified regions 51 formed in the thickness direction (between the surface 2 and the surface 3) of the quartz glass substrate 1 along the planned dividing line 10 are the modified regions 51 themselves. The quartz glass substrate 1 is formed obliquely with respect to the surfaces 2 and 3. In the present embodiment, a region in which the modified region 51 itself is formed obliquely with respect to the surfaces 2 and 3 is referred to as an obliquely modified region 51.

  The oblique modified region 51 is formed obliquely with respect to the surfaces 2 and 3 of the quartz glass substrate 1 in the thickness direction of the quartz glass substrate 1. Each obliquely modified region 51 is formed by inclining the laser beam LB irradiated inside the quartz glass substrate 1 with respect to the incident surface 2. When the laser beam LB is incident on the quartz glass substrate 1 at an angle, the modified region 51 formed inside the quartz glass substrate 1 is formed obliquely with respect to the surfaces 2 and 3.

As a method of injecting the laser beam LB with respect to the surface 2 of the quartz glass substrate 1, a method of tilting the quartz glass substrate 1 with respect to the optical axis of the laser beam LB, or an optical axis of the laser beam LB with quartz glass. A method of tilting with respect to the substrate 1 can be used.
Since the inclination of the oblique modified region 51 is determined by the relative inclination angle between the optical axis of the laser beam LB and the quartz glass substrate 1, the cross section of the quartz glass substrate 1 when divided along the planned dividing line 10. The surface shape at can be adjusted by this inclination angle. In addition, the inclination angle with respect to the surfaces 2 and 3 of the quartz glass substrate 1 to be divided can be appropriately selected within a range of ± 45 °.

The modified region 51 formed obliquely may be a combination of these two forms, and an example is shown in FIGS. 6 (a) to (d).
FIGS. 6A to 6D are schematic views of the dividing surface of the quartz glass substrate 1 on which the oblique modified region 51 is formed. In addition, the direction of each modification area | region 51 formed is shown on the right side of the division surface of the quartz glass substrate 1 shown in each figure for reference. In addition, a large number of modified regions 51 shown in each drawing are schematic views for showing an oblique formation form, and the intervals at which the modified regions 51 are formed are different from actual ones.

  6A, in the thickness direction of the quartz glass substrate 1, there are an oblique modified region 51a having an angle of approximately 45 ° with respect to the surfaces 2 and 3, and an angle with respect to the surfaces 2 and 3. The oblique modification regions 51b inclined by −45 ° are alternately arranged in the thickness direction substantially orthogonal to the surfaces 2 and 3.

  In FIG. 6 (b), the quartz glass substrate 1 has an inner surface in the thickness direction, the oblique modified region 51a having an angle of approximately 45 ° with respect to the surfaces 2 and 3, and the surface at substantially the same position of the modified region 51a. 2 and 3 are formed so as to intersect with the oblique reforming region 51 b inclined at an angle of about −45 °, and are arranged in parallel in the thickness direction substantially orthogonal to the surfaces 2 and 3.

  6C, in the thickness direction of the quartz glass substrate 1, an oblique modified region 51b having an angle of approximately −45 ° with respect to the surfaces 2 and 3 is formed on the surfaces 2 and 3 from the surface 3 side. 3 are arranged in parallel in an oblique direction with an angle of approximately −45 °.

  In FIG. 6 (d), the quartz glass substrate 1 has an angle with respect to the surfaces 2 and 3 and the modified region 51 c formed in the direction substantially perpendicular to the surface 2 from the surface 3 side. The oblique modified region 51b inclined by approximately −45 ° is directed from the surface 3 side toward the direction substantially perpendicular to the surface 2 from the surface 3 side, and the modified region 51c, the modified region 51b, the modified region 51b, The quality regions 51c are arranged in the order.

  In addition, each modification | reformation area | region 51 (51a-51c) formed in parallel with the inside of the thickness direction of the quartz glass substrate 1 diagonally is divided along the division | segmentation planned line 10, as shown to Fig.5 (a). When the surface is viewed from the side substantially perpendicular to the surfaces 2 and 3, the overlapping amount α of the adjacent modified regions 51 is formed to be 0 (zero) or more. That is, each modified region 51 is continuously formed inside the quartz glass substrate 1 in the thickness direction.

  Thus, the quartz glass substrate 1 can be separated at a position along the planned dividing line 10 by applying external stress such as bending stress or tensile stress (see FIG. 2). Separation along the planned dividing line 10 is performed by forming hollow processing traces in a large number of modified regions 51 formed continuously in the thickness direction of the quartz glass substrate 1. It can be easily separated from the processing mark as a starting point. Moreover, since the width of the modified region 51 along the planned dividing line 10 of the quartz glass substrate 1 is a minute width of about several μm, it is possible to perform division with good external dimension accuracy.

Next, a laser internal scribing method for the quartz glass substrate 1 will be described.
First, a laser processing apparatus used for laser internal scribing will be described. FIG. 7 is a block diagram showing the configuration of the laser processing apparatus.

  In FIG. 7, the laser processing apparatus 20 includes an irradiation mechanism unit 21 that irradiates the laser light LB toward the quartz glass substrate 1 as a processing target, and a host computer 22 that controls the irradiation mechanism unit 21.

  The irradiation mechanism unit 21 includes a laser light source 24, a dichroic mirror 25, a condenser lens 26, a moving mechanism unit 27, and an imaging unit 28.

The laser light source 24 is a femtosecond laser that is a solid-state light source of titanium sapphire and emits a laser beam LB having a pulse width of femtosecond (10 ⁻¹⁵ seconds).
The dichroic mirror 25 reflects the laser light LB emitted from the laser light source 24 toward the condenser lens 26.
The condensing lens 26 is composed of, for example, an objective lens having a magnification of 100 times, a numerical aperture (NA) of 0.8, and a WD (Working Distance) of 3 mm, and condenses the laser light LB reflected by the dichroic mirror 25.

The moving mechanism unit 27 includes a mounting table 29 on which the quartz glass substrate 1 is mounted, a tilting device 30, an X-axis moving unit 31, a Y-axis moving unit 32, and a Z-axis moving unit 33.
The tilting device 30, the X-axis moving unit 31, the Y-axis moving unit 32, and the Z-axis moving unit 33 are driven by servo motors (not shown), and the mounting table 29 on which the quartz glass substrate 1 is mounted is used as the condenser lens 26. It has a function of relative movement.

  The tilting device 30 includes a spherical seat that can tilt in any direction, and has a function of tilting the mounting table 29 with respect to the optical axis of the laser beam LB. The X-axis moving unit 31 has a function of relatively moving the mounting table 29 in the X-axis direction within a plane orthogonal to the optical axis of the laser beam LB. The Y-axis moving unit 32 has a function of relatively moving the mounting table 29 in the Y-axis direction within a plane orthogonal to the optical axis of the laser beam LB.

  The Z-axis moving unit 33 moves the mounting table 29 in the Z-axis direction orthogonal to the X-axis and Y-axis directions, and the position of the condensing point of the laser beam LB is placed on the mounting table 29. 1 has a function of relative movement in the thickness direction. The Z-axis moving unit 33 is provided with a position sensor (not shown) that detects a movement position in the Z-axis direction orthogonal to the X-axis and Y-axis directions.

The imaging unit 28 includes a light source that emits visible light and a CCD (Charge Coupled Device) (both not shown), and is disposed on the opposite side of the condenser lens 26 with the dichroic mirror 25 interposed therebetween. Yes.
The light source of the imaging unit 28 emits visible light toward the condenser lens 26 and passes through the condenser lens 26 to focus. Therefore, by moving the Z-axis moving part 33 in the Z-axis direction and focusing on the surface 2 that is one surface of the quartz glass substrate 1 and the surface 3 that is the other surface, respectively, A position sensor arranged in the moving unit 33 can detect the position of each moved focal point.

The irradiation mechanism unit 21 configured as described above is controlled by the host computer 22. The host computer 22 includes a control unit 35, a display unit 42, and an input unit 43.
The control unit 35 includes an image processing unit 36 that processes image information captured by the imaging unit 28, a laser control unit 37 that controls the output, pulse width, and pulse period of the laser light source 24, and a moving mechanism unit 27 (tilting device 30). A movement control unit 38 for controlling the X-axis moving unit 31, the Y-axis moving unit 32, and the Z-axis moving unit 33).

  The control unit 35 also includes a RAM (Random Access Memory) 39 that temporarily stores data input from the input unit 43, a control program for the image processing unit 36, the laser control unit 37, the movement control unit 38, and the like. ROM (Read Only Memory) 40 and a CPU (Central Processing Unit) 41 for executing a control program stored in the ROM 40. The image processing unit 36, the laser control unit 37, the movement control unit 38, the CPU 41, the ROM 40, and the RAM 39 are connected to each other via a bus 44.

  The input unit 43 is an input unit that inputs data such as various processing conditions used in laser internal scribe processing by the laser beam LB. The display unit 42 is a display unit that displays information such as a processing state by the laser beam LB.

Next, a laser internal scribing method for the quartz glass substrate 1 using the laser processing apparatus 20 will be described.
First, the quartz glass substrate 1 divided by the laser internal scribe is placed on the placing table 29 of the laser processing apparatus 20. Then, a positioning step for relatively positioning the quartz glass substrate 1 placed on the mounting table 29 and the condenser lens 26, and a position detection step for detecting the position in the thickness direction of the surfaces 2 and 3 of the quartz glass substrate 1. A focusing point position adjusting step for adjusting the position of the focusing point 50 of the laser beam LB inside the quartz glass substrate 1, and irradiating the laser beam LB along the planned dividing line 10, and the X-axis moving unit 31, Y By the laser irradiation / scanning process in which the axis moving unit 32 and the Z axis moving unit 33 move relative to each other in the direction along the surfaces 2 and 3 and the thickness direction of the quartz glass substrate 1, A large number of modified regions 51 are formed inside.

The quartz glass substrate 1 is placed on the mounting table 29 of the laser processing apparatus 20 such that the surface 3 faces the mounting table 29 and the surface 3 is in contact with the mounting table 29.
In the positioning step, the planned dividing line 10 of the quartz glass substrate 1 is parallel to the Y-axis moving direction of the Y-axis moving unit 32, and the optical axis of the laser beam LB is positioned on the planned dividing line 10 of the quartz glass substrate 1. As described above, the X-axis moving unit 31 and the Y-axis moving unit 32 are driven in the respective moving directions based on the control signals of the movement control unit 38 and moved in the respective moving directions, so that the quartz glass substrate 1 and the condenser lens 26 are moved. And are relatively positioned.

  The position where the X-axis moving unit 31 and the Y-axis moving unit 32 move is determined by the imaging unit 28 recognizing a positioning alignment mark or the like formed on the surface 2 of the quartz glass substrate 1 via the condenser lens 26. Based on the image data of the alignment mark taken into the image processing unit 36 of the control unit 35, the coordinate to move in the control unit 35 is calculated and determined.

  In the position detection step, the Z-axis moving unit 33 moves in the thickness direction of the surfaces 2 and 3 of the quartz glass substrate 1 based on the control signal of the movement control unit 38, and the imaging unit 28 passes through the condenser lens 26 and the quartz. Positions in the thickness direction of the surface 3 and the surface 2 of the glass substrate 1 are detected. The detected position information of the surface 3 and the surface 2 in the thickness direction is output to the control unit 35 via the image processing unit 36.

  In the focal point adjustment step, the Z-axis moving unit 33 moves toward the surface 3 of the quartz glass substrate 1 based on the control signal of the movement control unit 38 based on the position information of the surface 3 input from the position detecting step. The position of the condensing point 50 of the laser beam LB by the condensing lens 26 is adjusted to the inside of the quartz glass substrate 1 by moving in the direction. The position of the condensing point 50 of the laser beam LB is set as close as possible to the surface 3 without the modified region 51 formed by irradiating the laser beam LB being exposed to the surface 3 of the quartz glass substrate 1. Is done.

In the laser irradiation / scanning process, the laser beam LB is irradiated along the planned dividing line 10 of the quartz glass substrate 1, and the quartz glass substrate 1 is irradiated with the laser beam LB (condensing lens 26) in synchronization with the irradiation timing of the laser beam LB. Move relative to.
Three specific examples of the laser irradiation / scanning process will be described. In any of the specific examples described below, the planned dividing line 10 of the quartz glass substrate 1 is positioned parallel to the Y-axis movement direction of the Y-axis movement unit 32 and is orthogonal to the surfaces 2 and 3 of the quartz glass substrate 1. In the case of the modified region oblique stacking method in which the reformed regions 51 formed in the direction are arranged along the planned dividing line 10 in an oblique direction with respect to the surfaces 2 and 3, a description will be given.

(Modified area oblique stacking method 1)
FIGS. 8A to 8E are schematic cross-sectional views of a quartz glass substrate showing an aspect of forming a modified region in a laser irradiation / scanning process. FIGS. 7B to 7E show quartz whose focal point is adjusted in order to clarify the state of scanning (relative movement) of the quartz glass substrate 1 placed on the placement table 29. The position of the glass substrate 1 is indicated by a two-dot chain line.

  In FIG. 8A, the quartz glass substrate 1 placed on the placing table 29 and subjected to positioning, position detection, and condensing point position adjustment in sequence is placed inside the quartz glass substrate 1 via the condensing lens 26. Laser light LB is irradiated. The laser beam LB irradiated with the first pulse is condensed on the condensing point 50 of the condensing lens 26. The condensing point 50 is located in the first layer in the thickness direction of the quartz glass substrate 1, and the modified region 51 is formed at the condensing point 50 by multiphoton absorption.

  Then, as shown in FIG. 8B, the quartz glass substrate 1 on which the first-layer modified region 51 is formed has a Z axis along the planned dividing line 10 while synchronizing with the irradiation timing of the laser beam LB. The moving unit 33 moves relative to the condenser lens 26 by a predetermined pitch in the −Z-axis direction, and the Y-axis moving unit 32 moves relative to the −Y-axis direction by a predetermined pitch. A second modified region 51 is formed in a diagonally upward direction with respect to the surface 3 of the modified region 51 formed in the eye.

  Then, as shown in FIG. 8C, similarly to the modified region 51 formed in the second layer, the Z-axis moving unit is moved along the planned dividing line 10 in synchronization with the irradiation timing of the laser beam LB. 33 moves relative to the condenser lens 26 in the −Z-axis direction by a predetermined pitch, and the Y-axis moving unit 32 moves relative to the −Y-axis direction by a predetermined pitch. A third-layer modified region 51 is formed in a diagonally upward direction with respect to the surface 3 of the formed modified region 51.

  Then, as shown in FIG. 8 (d), the Z-axis moving unit 33 is arranged at a predetermined pitch in the Z-axis direction with respect to the condenser lens 26 along the planned dividing line 10 in synchronization with the irradiation timing of the laser beam LB. And the Y-axis moving part 32 relatively moves by a predetermined pitch in the -Y-axis direction, and the modified region 51 is formed at the position of the first layer in the thickness direction by the fourth pulse. The

  Then, as shown in FIG. 8 (e), the Z-axis moving unit 33 is aligned with the planned dividing line 10 in synchronization with the irradiation timing of the laser beam LB, similarly to the modified region 51 formed in the second layer. The Y-axis moving unit 32 moves relative to the condenser lens 26 in the −Z-axis direction by a predetermined pitch, and the Y-axis moving unit 32 moves relative to the −Y-axis direction by a predetermined pitch. The modified region 51 is formed at a position in the thickness direction of the second layer obliquely above the surface 3 of the modified region 51 formed by a pulse.

  In synchronism with the irradiation timing of the laser beam LB applied to the inside of the quartz glass substrate 1, the relative movement of the Z-axis moving unit 33 and the Y-axis moving unit 32 is the number of passes corresponding to the thickness of the workpiece to be divided. Repeatedly, a large number of modified regions 51 arranged in parallel in the oblique direction with respect to the surfaces 2 and 3 are continuously formed in the entire area of the quartz glass substrate 1 along the planned dividing line 10. The

Note that the inclination of the modified region 51 arranged in parallel with the surfaces 2 and 3 of the quartz glass substrate 1 in an oblique direction is the scanning direction of the quartz glass substrate 1 with respect to the position of the condensing point 50 of the condenser lens 26. It depends on the scanning speed.
The number of layers of the modified region 51 formed by relative movement has been described in the case of three layers. However, after the first pulse of the laser beam LB is irradiated, the number of layers in the thickness direction of the workpiece is increased. The multilayer modified region 51 corresponding to the thickness of the workpiece may be formed at a time.

  The modified region 51 is formed using, for example, a condensing lens 26 having a numerical aperture of 0.8, a femtosecond laser having a wavelength of 800 nm, a pulse width of 300 fs (femtosecond), an output of 700 mW, and a repetition rate of 1 kHz with a scanning speed of 20 mm. / Sec, that is, processing can be performed with a laser irradiation interval of the laser beam LB of 20 μm.

(Modified area oblique stacking method 2)
FIGS. 9A to 9C are schematic cross-sectional views of a quartz glass substrate showing an aspect of forming another modified region in the laser irradiation / scanning step. In FIGS. 4B and 4C, the quartz glass substrate 1 whose focal point is adjusted is shown in order to clarify the state of movement of the quartz glass substrate 1 placed on the placing table 29. The position is indicated by a two-dot chain line.

In FIG. 9A, the quartz glass substrate 1 placed on the placement table 29 and subjected to positioning, position detection, and condensing point position adjustment in sequence is placed inside the quartz glass substrate 1 via the condensing lens 26. Laser light LB is irradiated. The laser beam LB irradiated with the first pulse is condensed on the condensing point 50 of the condensing lens 26. The condensing point 50 is located in the first layer in the thickness direction of the quartz glass substrate 1, and the first modified region 51 is formed by multiphoton absorption.
In the quartz glass substrate 1 on which the first modified region 51 is formed, the Y-axis moving unit 32 has a predetermined pitch in the −Y-axis direction along the planned dividing line 10 in synchronization with the irradiation timing of the laser beam LB. A plurality of modified regions 51 indicated by the two-dot chain line ellipse are formed in the first layer in the direction along the surface 3 of the quartz glass substrate 1 that moves relative to each other.

The quartz glass substrate 1 having a plurality of modified regions 51 formed in the first layer is scheduled to be divided by the Z-axis moving unit 33 in synchronization with the irradiation timing of the laser beam LB, as shown in FIG. 9B. Along the line 10, the Y-axis moving unit 32 moves relative to the condenser lens 26 in the -Z-axis direction by a predetermined pitch and moves in the -Y-axis direction by a predetermined pitch. The first modified region 51 of the second layer is formed in a diagonally upward direction with respect to the surface 3 of the modified region 51 formed in the above.
In the quartz glass substrate 1 on which the first modified region 51 of the second layer is formed, the Y-axis moving unit 32 is predetermined in the −Y-axis direction along the planned dividing line 10 in synchronization with the irradiation timing of the laser beam LB. The plurality of modified regions 51 in the second layer are formed in a diagonally upward direction with respect to the surface 3 of each of the plurality of modified regions 51 in the first layer that have been moved relative to the pitch.

  Then, the quartz glass substrate 1 on which the plurality of modified regions 51 of the second layer is formed, as shown in FIG. 9C, similarly to the plurality of modified regions 51 formed of the second layer, Synchronously with the irradiation timing of the light LB, the Z-axis moving unit 33 moves relative to the condenser lens 26 along the planned dividing line 10 in the −Z-axis direction by a predetermined pitch, and the Y-axis moving unit 32 −Y A plurality of modified regions 51 in the third layer are formed by relatively moving in the axial direction by a predetermined pitch.

  The relative movement of the Z-axis moving unit 33 and the Y-axis moving unit 32 is synchronized with the irradiation timing of the laser beam LB applied to the inside of the quartz glass substrate 1 in accordance with the thickness of the workpiece to be divided. A number of modified regions 51 that are arranged several times in an oblique direction with respect to the surfaces 2 and 3 are continuously formed throughout the interior of the quartz glass substrate 1 along the planned dividing line 10. Is done.

  The modified region 51 can be formed under the same conditions as the modified region oblique stacking method 1 except for the femtosecond laser repetition rate and the scanning speed. Processing can be performed with a femtosecond laser having a repetition rate of 100 Hz, a scanning speed of 20 mm / sec, or a repetition rate of 1 kHz and a scanning speed of 200 mm / sec, that is, a laser irradiation interval of the laser beam LB of 200 μm.

(Modified area oblique stacking method 3)
FIGS. 10A to 10D are schematic cross-sectional views of a quartz glass substrate showing a form of forming another modified region in the laser irradiation / scanning step. In FIGS. 4B to 4D, the quartz glass substrate 1 whose focal point has been adjusted is shown in order to clarify the state of movement of the quartz glass substrate 1 placed on the placement table 29. The position is indicated by a two-dot chain line.

  In FIG. 10A, the quartz glass substrate 1 placed on the mounting table 29 and subjected to positioning, position detection, and condensing point position adjustment in sequence is placed inside the quartz glass substrate 1 via the condensing lens 26. Laser light LB is irradiated. The laser beam LB irradiated with the first pulse is condensed on the condensing point 50 of the condensing lens 26. At the condensing point 50, the first modified region 51 is formed by multiphoton absorption.

Then, the quartz glass substrate 1 on which the first modified region 51 is formed is synchronized with the irradiation timing of the laser light LB, and the Y-axis moving unit 32 is moved along the planned dividing line 10 along the Y-axis moving unit 32. Are moved relative to each other in the -Y-axis direction at a predetermined scanning speed and irradiated with the second pulse, as shown in FIG. 10B, the surface of the first modified region 51 that has already been formed. The second modified region 51 is formed in an obliquely upward direction with respect to 3.
Similarly, in synchronization with the irradiation timing of the laser beam LB, when the Y-axis moving unit 32 relatively moves in the −Y-axis direction at a predetermined scanning speed and the third pulse is irradiated, FIG. As shown in FIG. 5, the third modified region 51 is formed in a diagonally upward direction with respect to the surface 3 of the second modified region 51 that has already been formed.

  The modified region 51 is formed in the same manner as the first pulse when the next second pulse is focused in the modified region 51 formed by the first pulse of the laser beam LB. Thus, the laser beam LB cannot be condensed. This is because the first modified region 51 that has already been formed includes not only a region where cracks have occurred, but also a modified region due to a change in refractive index and absorptivity that cannot be visually confirmed. Since the absorption rate of the laser beam LB is high and / or the refractive index is different in that region, the modified region 51 is formed at a defocused position before the condensing point 50 of the laser beam LB.

  As a result, the second modified region 51 is formed obliquely upward with respect to the surface 3 of the first modified region 51. Similarly, the third modified region 51 is formed obliquely upward with respect to the surface 3 of the second modified region 51. In this way, by controlling the irradiation interval of the laser beam LB so as to irradiate the pulse of the next laser beam LB into the modified region 51 that has already been formed, the position of the condensing point 50 is not controlled. Then, a modified region 51 composed of multiple layers is formed in parallel with the surfaces 2 and 3 of the quartz glass substrate 1 in an oblique direction.

  Then, the quartz glass substrate 1 placed on the placement table 29 is further synchronized with the irradiation timing of the laser beam LB, and the Y-axis moving unit 32 is moved along the planned dividing line 10 in the −Y-axis direction. If the laser beam LB does not exceed the laser intensity processing threshold at the defocus position of the laser beam LB after the relative movement at the scanning speed, the modified region 51 is not formed obliquely upward with the fourth pulse, and FIG. As shown in d), the quartz glass substrate 1 is formed at substantially the same position in the thickness direction as the first modified region 51 of the quartz glass substrate 1.

  Then, while adding the movement of the Z-axis moving unit 33 according to the thickness of the workpiece to be divided, the Y-axis moving unit 32 is synchronized with the irradiation timing of the laser beam LB irradiated to the inside of the quartz glass substrate 1. The relative movement is repeated, and a large number of modified regions 51 arranged in parallel obliquely with respect to the surfaces 2 and 3 are continuously formed in the entire area of the quartz glass substrate 1 along the planned dividing line 10. Formed.

  By using this method, the position of the condensing point 50 is not complicated, and the irradiation interval of the laser beam LB is controlled, so that the surface 2 and 3 of the quartz glass substrate 1 is inclined in the oblique direction. The modified region 51 arranged in parallel can be formed. Therefore, with a small number of passes, a large number of modified regions 51 arranged side by side obliquely with respect to the surfaces 2 and 3 are continuously formed in the entire area of the quartz glass substrate 1 along the planned dividing line 10. Can be formed.

  The modified region 51 is formed using, for example, a condensing lens 26 having a numerical aperture of 0.8, a wavelength of 800 nm, a pulse width of 300 fs (femtosecond), an output of 700 mW, a repetition rate of 1 kHz, a scanning speed of 2 mm / sec, or a repetition. Processing can be performed with a femtosecond laser with a rate of 10 kHz and a scanning speed of 20 mm / sec, that is, with a laser irradiation interval of the laser beam LB of 2 μm.

  In the specific examples of the three examples described above, each modified region 51 to be formed is described as being formed in a direction orthogonal to the surfaces 2 and 3 of the quartz glass substrate 1. An oblique modification region 51 (see FIG. 5B) formed obliquely with respect to the surfaces 2 and 3 of the glass substrate 1 may be used. In this case, the quartz glass substrate 1 mounted on the mounting table 29 can be formed by scanning the tilting device 30 of the irradiation mechanism unit 21 and tilting it to a predetermined tilt angle.

Further, the modified region 51 formed in multiple layers inside the quartz glass substrate 1 is not exposed to the surface 2 of the quartz glass substrate 1 and is formed as close as possible to the surface 2.
When forming the modified region 51 to a position close to the surface 2, it is detected based on position data in the thickness direction of the surface 2 and the surface 3 of the quartz glass substrate 1 detected in the position detection step and stored in the control unit 35. Thus, the movement of the Z-axis moving unit 33 is controlled.

  Then, a large number of modified regions 51 that are scribed inside the laser and are arranged in parallel in the oblique direction with respect to the surfaces 2 and 3 are formed continuously in the quartz glass substrate 1 along the planned dividing line 10. In the separation step of separating the quartz glass substrate 1 along the planned dividing line 10, an external stress such as a bending stress A or a tensile stress B is applied, so that the hollow glass contained in the many modified regions 51 is formed. They are separated along the planned dividing line 10 starting from the processing mark (see FIG. 2).

FIGS. 11A and 11B show SEM images of the divided surfaces of the quartz glass substrate 1 divided by the laser internal scribing method of the present embodiment. In the SEM image, the modified region 51 formed inside the quartz glass substrate 1 is schematically shown as an ellipse. Incidentally, the thickness of the quartz glass substrate 1 is 1 mm.
The quartz glass substrate shown in FIG. 11A is continuously formed by arranging a large number of oblique modified regions in which the modified regions themselves are inclined in the same direction with respect to the surface in the entire region in the thickness direction. ing.
In the quartz glass substrate shown in FIG. 11 (b), oblique modified regions in which the modified regions themselves are inclined in different directions with respect to the surface are alternately arranged in parallel in the thickness direction. Are formed continuously.

  According to the laser internal scribing method of the present embodiment described above, the laser beam LB having a pulse width in the range of picoseconds to femtoseconds is irradiated with the focusing point 50 inside the quartz glass substrate 1. Thus, a modified region 51 including a hollow processing mark having a diameter of about 0.5 μm and a length of about 300 μm is formed inside the quartz glass substrate 1 by multiphoton absorption. The quartz glass substrate 1 is moved relative to the laser beam LB along the planned dividing line 10, and the modified region 51 is formed obliquely with respect to the thickness direction of the quartz glass substrate 1, whereby the bending stress A or By applying a slight external stress such as a tensile stress B, the quartz glass substrate 1 can be easily separated at a position along the planned dividing line 10 starting from a hollow processing trace. Further, since the width of the modified region 51 along the planned dividing line 10 is a minute width of about several μm, it is possible to perform division with good external dimension accuracy.

  Further, the quartz glass substrate 1 is moved relative to the laser beam LB along the planned dividing line 10, and a large number of modified regions 51 are arranged in parallel obliquely with respect to the surfaces 2 and 3 (modified). Area oblique stacking method), or oblique modified regions 51 in which the modified regions 51 are formed obliquely with respect to the surfaces 2 and 3 of the quartz glass substrate 1 are formed side by side in the thickness direction of the quartz glass substrate 1. By doing so, it becomes possible to continuously form a multilayer modified region corresponding to the thickness of the quartz glass substrate 1 at a time, and to divide the workpiece into a short time.

  Further, the quartz glass substrate 1 and the laser beam LB move relative to each other in the direction along the surfaces 2 and 3 of the quartz glass substrate 1, so that the quartz glass substrate 1 and the laser beam LB are arranged in parallel obliquely with respect to the surfaces 2 and 3 of the quartz glass substrate 1. Since the plurality of modified regions 51 thus formed are formed, it is possible to control the quartz glass substrate 1 only by controlling the irradiation interval of the laser beam LB without performing a relative movement between the complicated quartz glass substrate 1 and the laser beam LB. A plurality of modified regions 51 arranged side by side with respect to the surfaces 2 and 3 in an oblique direction can be formed. Therefore, the quartz glass substrate 1 can be divided in a short time.

  The present invention is not limited to the above-described embodiment, and the following modified examples can be given.

(Modification 1)
Although the case where the quartz glass substrate 1 is used as the object to be scribed inside the laser has been described, it can be applied to a member having the transparency of the laser beam LB. Moreover, the member which has permeability | transmittance may be comprised in the multilayer.
In addition to the quartz glass substrate 1, glass substrates such as soda-lime glass, borosilicate glass, and optical glass, quartz substrates, TFT (Thin Film Transistor) displays, liquid crystal displays, various semiconductors, MEMS (Micro Electro Mechanical System) devices, etc. It may be a substrate made of formed light transmissive glass, silicon or the like. These can be divided as in the case of the quartz glass substrate 1.

(Modification 2)
The laser light source 24 of the irradiation mechanism 21 has been described in the case of a femtosecond laser using titanium sapphire as a solid light source, but is not limited to this, and the pulse width ^ranges from picoseconds ( ^10-12 seconds) to femtoseconds (10 ^-15 seconds) can be used. For example, it is possible to use a YAG laser, an excimer laser, or the like.

(Modification 3)
In the irradiation mechanism section 21 of the laser processing apparatus 20, the position of the condensing point 50 of the pulse laser beam LB is scanned by fixing the condensing lens 26 side and dividing the quartz glass substrate 1 side by X, Y, and Z axes. As described above, the quartz glass substrate 1 side is fixed, and the laser light source 24, the dichroic mirror 25, and the condenser lens 26 are integrated into the X, Y, and Z axis directions. It is good also as a structure which can be moved and inclined. Thereby, the freedom degree of design of a laser processing apparatus is expanded.

(A) is a top view of the quartz glass substrate which shows the outline | summary of the laser internal scribing method. (B) is sectional drawing in the AA of (a). (A) is sectional drawing which shows the isolation | separation method of the quartz glass substrate scribed inside the laser. (B) is sectional drawing which shows the state of the quartz glass substrate isolate | separated along the division | segmentation planned line. It is a SEM image of the split surface of the quartz glass substrate scribed inside the laser, (a) is an image at 1000 times. (B) is an image at 10,000 times. The SEM image in 3000 times which looked at the cut surface which cut the division surface of the quartz glass substrate in the orthogonal direction. (A) is a schematic diagram of the dividing surface of the quartz glass substrate in which the oblique modified region is formed. (B) is the schematic diagram of the division surface of the quartz glass substrate in which another diagonal modified area | region was formed. (A)-(d) is a schematic diagram of the division surface of the quartz glass substrate in which another diagonal modified area | region was formed. The block diagram which shows the structure of a laser processing apparatus. (A)-(e) is a schematic cross section of the quartz glass substrate which shows the aspect of formation of the modification area | region in a laser irradiation and a scanning process. (A)-(c) is a schematic cross section of the quartz glass substrate which shows the aspect of formation of another modification area | region in a laser irradiation and a scanning process. (A)-(d) is a schematic cross section of the quartz glass substrate which shows the aspect of formation of the modification area | region by irradiation of another laser beam and scanning in a laser irradiation and scanning process. (A), (b) is the SEM image of the dividing surface of the quartz glass substrate divided by the laser internal scribing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Quartz glass substrate as a processing target object, 2, 3 ... Surface, 10 ... Planned dividing line, 20 ... Laser processing apparatus, 21 ... Irradiation mechanism part, 22 ... Host computer, 25 ... Dichroic mirror, 26 ... Condensing lens , 27 ... moving mechanism part, 28 ... imaging part, 29 ... mounting table, 30 ... tilting device, 31 ... X axis moving part, 32 ... Y axis moving part, 33 ... Z axis moving part, 35 ... control part, 36 ... Image processing unit, 37... Laser control unit, 38... Movement control unit, 50... Condensing point, 51, 51 a, 51 b, 51 c ... modified region, A ... bending stress, B ... tensile stress, LB ... laser beam.

Claims (5)

Irradiating the inside of the workpiece with a laser beam to form a modified region inside the workpiece,
Moving the workpiece relative to the laser beam along a predetermined dividing line ;
A laser internal scribing method,
The modified region includes a hollow processing mark, and the hollow portion of the hollow processing mark is formed to extend obliquely with respect to the thickness direction of the processing object,
A plurality of the modified regions including the hollow processing marks are formed along the planned dividing line,
A plurality of the modified regions formed along the planned dividing line are further formed in the thickness direction of the workpiece.
A laser internal scribing method characterized by the above. The laser internal scribing method according to claim 1,
The optical axis of the laser beam is arranged obliquely with respect to the surface of the workpiece.
A laser internal scribing method characterized by the above. The laser internal scribing method according to claim 1 or 2 ,
The pulse width of the laser light ranges from picoseconds to femtoseconds.
A laser internal scribing method characterized by the above. In the laser internal scribing method according to any one of claims 1 to 3,
The workpiece is one of a silicon substrate, a glass substrate, and a quartz substrate.
A laser internal scribing method characterized by the above. The electronic device divided | segmented by the laser internal scribing method in any one of Claims 1-4.