JP7579760B2 - Laser processing device and laser processing method - Google Patents

Description

The present invention relates to a laser processing device and a laser processing method.

Laser processing devices are known that form modified regions in an object by irradiating the object with laser light (see, for example, Patent Document 1). Such laser processing devices may include a support section that supports the object, a light source that emits laser light, a spatial light modulator that modulates the laser light emitted from the light source, and a focusing section that focuses the laser light modulated by the spatial light modulator.

JP 2011-051011 A

In the laser processing apparatus as described above, a modified region may be formed on the glass substrate along each of the multiple lines by irradiating the object including the glass substrate with laser light along each of the multiple lines. In such a case, it is important that sufficient flexural strength is ensured for the multiple chips obtained by cutting the object including the glass substrate along each of the multiple lines. However, even if the laser processing conditions can ensure sufficient flexural strength for a certain laser processing apparatus, when the laser processing conditions are applied to another laser processing apparatus having the same specifications as the laser processing apparatus, sufficient flexural strength may not be ensured.

The present invention aims to provide a laser processing device and a laser processing method that can ensure sufficient flexural strength for multiple chips obtained by cutting an object, including a glass substrate.

The laser processing device of the present invention is a laser processing device that forms a modified region on a glass substrate by irradiating a laser beam on an object including a glass substrate, and includes a support section that supports the object, a light source that emits laser beam, a first optical section that imparts astigmatism to the laser beam emitted from the light source, a second optical section that focuses the laser beam imparted with astigmatism by the first optical section on a first region in a first direction perpendicular to the optical axis of the laser beam and on a second region downstream of the first region in the traveling direction of the laser beam in a second direction perpendicular to the optical axis and the first direction, a moving section that moves the second optical section relatively to the support section, an imaging section that acquires an image of the modified region, and a control section that controls the first optical section so that each of a plurality of different astigmatisms is imparted to the laser beam as astigmatism, controls the moving section so that the first region on the glass substrate moves relatively along the second direction, and outputs the image of the modified region acquired by the imaging section in association with each of the plurality of astigmatisms.

In this laser processing device, each of a plurality of different astigmatisms is sequentially imparted to the laser light, and an image of the modified region formed on the glass substrate by irradiation of the laser light is outputted linked to each of the plurality of astigmatisms. Here, when the first region of the laser light focused in the first direction is moved relatively along the second direction on the glass substrate, the direction of the crack extending from the modified region tends to stabilize. Also, when the direction of the crack extending from the modified region is along the second direction, it is easy to ensure sufficient bending strength for the plurality of chips obtained by cutting the object. Therefore, by imparting astigmatism linked to the image of the modified region in which the crack direction is along the second direction to the laser light, it is possible to realize laser processing conditions that can ensure stable and sufficient bending strength. Therefore, this laser processing device makes it possible to ensure sufficient bending strength for the plurality of chips obtained by cutting the object including the glass substrate.

In the laser processing device of the present invention, the first optical unit may be a spatial light modulator, and the control unit may input a signal indicating each of a plurality of astigmatism patterns corresponding to each of the plurality of astigmatisms to the spatial light modulator. This makes it possible to easily and reliably impart each of the plurality of different astigmatisms to the laser light.

In the laser processing device of the present invention, each of the multiple astigmatism patterns may be an astigmatism pattern in which the value obtained by dividing the width of the first region in the second direction by the width of the first region in the first direction is different from each other. This makes it possible to easily and reliably impart each of the multiple different astigmatisms to the laser light.

In the laser processing device of the present invention, the control unit may have a display unit that displays images of the modified area acquired by the imaging unit in association with each of the multiple astigmatisms. This allows the operator to objectively recognize the relationship between the astigmatism and the modified area.

In the laser processing device of the present invention, the control unit may have an input receiving unit that receives input of one of multiple astigmatisms as a laser processing condition. This allows the operator to set an appropriate astigmatism as a laser processing condition.

The laser processing method of the present invention is a laser processing method for forming a modified region on a glass substrate by irradiating a laser beam on an object including the glass substrate, and includes a first step of sequentially imparting a plurality of different astigmatisms to the laser beam and acquiring an image of the modified region formed on the glass substrate by irradiating the laser beam to which each of the plurality of astigmatisms has been imparted, and a second step of linking the image of the modified region to each of the plurality of astigmatisms. In the first step, the laser beam to which each of the plurality of astigmatisms has been imparted is focused on a first region in a first direction perpendicular to the optical axis of the laser beam, and is focused on a second region downstream of the first region in the traveling direction of the laser beam in a second direction perpendicular to the optical axis and the first direction, and the first region is moved relatively along the second direction on the glass substrate.

In this laser processing method, for the same reason as in the laser processing device described above, by imparting astigmatism linked to an image of a modified region in which the crack direction is along the second direction to the laser light, it is possible to realize laser processing conditions that can stably ensure sufficient flexural strength. Therefore, this laser processing method makes it possible to ensure sufficient flexural strength for multiple chips obtained by cutting an object including a glass substrate. The laser processing method of the present invention may further include a third step of setting one of the multiple astigmatisms linked to the image of the modified region as a laser processing condition.

The present invention provides a laser processing device and a laser processing method that can ensure sufficient flexural strength for multiple chips obtained by cutting an object including a glass substrate.

1 is a configuration diagram of a laser processing apparatus according to an embodiment; 2 is a cross-sectional view of a portion of the spatial light modulator shown in FIG. 1. FIG. 1 is a plan view of a glass substrate which is an object of an embodiment. 2 is a diagram showing an astigmatism pattern displayed on the spatial light modulator shown in FIG. 1. 2 is a diagram showing the optical path of laser light to which astigmatism has been imparted by the spatial light modulator shown in FIG. 1 . 2 is a diagram showing the shape of a first region of laser light to which astigmatism has been imparted by the spatial light modulator shown in FIG. 1 . 2A and 2B are diagrams showing a display state and an input receiving state of the interface unit shown in FIG. 1 . FIG. 1 shows an image of a modified region formed on a glass substrate. FIG. 13 is a diagram showing the bending strength of a plurality of chips obtained by cutting the glass substrate. 11A and 11B are diagrams illustrating the relationship between astigmatism for each condenser lens unit and an image of a modified region. 11A and 11B are diagrams showing the relationship between astigmatism and images of modified regions for each laser processing device. 11A and 11B are diagrams illustrating the relationship between astigmatism and images of modified regions for each glass material.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and duplicated explanations will be omitted.
[Configuration of laser processing device]

As shown in FIG. 1, the laser processing device 1 includes a support unit 2, a light source 3, an optical axis adjustment unit 4, a spatial light modulator (first optical unit) 5, a focusing unit (second optical unit) 6, a moving unit 7, a visible imaging unit (imaging unit) 8, an infrared imaging unit 9, and a control unit 10. The laser processing device 1 is a device that forms a modified region 12 in an object 11 by irradiating the object 11 with laser light L. In the following description, the three mutually orthogonal directions are referred to as the X direction, the Y direction, and the Z direction, respectively. In this embodiment, the X direction is the first horizontal direction, the Y direction is the second horizontal direction perpendicular to the first horizontal direction, and the Z direction is the vertical direction.

The support unit 2 supports the object 11. As an example, the support unit 2 adheres to a film (not shown) attached to the object 11, thereby supporting the object 11 so that the surface 11a of the object 11 is perpendicular to the Z direction. The support unit 2 is movable along both the X direction and the Y direction, and is rotatable about an axis parallel to the Z direction.

The light source 3 emits laser light L. As an example, the light source 3 emits the laser light L by a pulse oscillation method. The laser light L is transparent to the object 11.

The optical axis adjustment unit 4 adjusts the optical axis of the laser light L emitted from the light source 3. In this embodiment, the optical axis adjustment unit 4 adjusts the optical axis of the laser light L while changing the traveling direction of the laser light L emitted from the light source 3 to be along the Z direction. The optical axis adjustment unit 4 is composed of, for example, multiple reflecting mirrors whose positions and angles can be adjusted.

The spatial light modulator 5 is disposed in the housing H. The spatial light modulator 5 modulates the laser light L emitted from the light source 3. In this embodiment, the laser light L traveling downward from the optical axis adjustment unit 4 along the Z direction enters the housing H, and the laser light L that enters the housing H is reflected horizontally by the mirror M1 so as to form an angle with the Y direction, and the laser light L reflected by the mirror M1 enters the spatial light modulator 5. The spatial light modulator 5 modulates the laser light L thus entered while reflecting it horizontally along the Y direction.

The focusing unit 6 is attached to the bottom wall of the housing H. The focusing unit 6 focuses the laser light L modulated by the spatial light modulator 5 on the object 11 supported by the support unit 2. In this embodiment, the laser light L reflected horizontally along the Y direction by the spatial light modulator 5 is reflected downward along the Z direction by the dichroic mirror M2, and the laser light L reflected by the dichroic mirror M2 enters the focusing unit 6. The focusing unit 6 focuses the incident laser light L from the surface 11a side along the Z direction onto the object 11. In this embodiment, the focusing unit 6 is configured by attaching a focusing lens unit 61 to the bottom wall of the housing H via a driving mechanism 62. The focusing lens unit 61 has the function of focusing parallel light to a point on the optical axis. The driving mechanism 62 moves the focusing lens unit 61 along the Z direction, for example, by the driving force of a piezoelectric element.

In addition, an imaging optical system (not shown) is arranged between the spatial light modulator 5 and the focusing unit 6 inside the housing H. The imaging optical system constitutes a double-telecentric optical system in which the reflecting surface of the spatial light modulator 5 and the entrance pupil plane of the focusing unit 6 are in an imaging relationship. As a result, the image of the laser light L on the reflecting surface of the spatial light modulator 5 (the image of the laser light L modulated by the spatial light modulator 5) is transferred (imaged) similarly on the entrance pupil plane of the focusing unit 6.

A pair of distance measurement sensors S1, S2 are attached to the bottom wall of the housing H, positioned on either side of the focusing lens unit 61 in the X direction. Each distance measurement sensor S1, S2 emits distance measurement light (e.g., laser light) to the surface 11a of the object 11, and obtains displacement data of the surface 11a by detecting the distance measurement light reflected by the surface 11a.

The moving unit 7 moves the light collecting unit 6 relative to the support unit 2. The moving unit 7 is a moving mechanism (including a driving source such as an actuator or a motor) that moves at least one of the housing H and the support unit 2 to move the light collecting unit 6 relative to the support unit 2. In this embodiment, the moving unit 7 moves the support unit 2 along each of the X and Y directions, rotates the support unit 2 about an axis parallel to the Z direction as a center line, and moves the housing H along the Z direction.

The visible imaging unit 8 is disposed within the housing H. The visible imaging unit 8 emits visible light V and obtains an image of the object 11 using the visible light V. In this embodiment, the visible light V emitted from the visible imaging unit 8 is irradiated onto the surface 11a of the object 11 via the dichroic mirror M2 and the light collecting unit 6, and the visible light V reflected by the surface 11a is detected by the visible imaging unit 8 via the light collecting unit 6 and the dichroic mirror M2.

The infrared imaging unit 9 is attached to the side wall of the housing H. The infrared imaging unit 9 emits infrared light and captures an image of the object 11 using the infrared light. In this embodiment, the housing H and the infrared imaging unit 9 can move together in the Z direction.

The control unit 10 controls the operation of each part of the laser processing device 1. The control unit 10 has a processing unit 101, a memory unit 102, and an interface unit (display unit, input reception unit) 103. The processing unit 101 is configured as a computer device including a processor, memory, storage, and communication devices. In the processing unit 101, the processor executes software (programs) loaded into the memory, etc., and controls reading and writing of data in the memory and storage, as well as communication by the communication device. The memory unit 102 is, for example, a hard disk, and stores various data. The interface unit 103 displays various data to the operator and receives input of various data from the operator. In this embodiment, the interface unit 103 constitutes a GUI (Graphical User Interface).

In the laser processing device 1 configured as described above, when the laser light L is focused inside the object 11, the laser light L is absorbed in a portion corresponding to the focusing point C of the laser light L, and a modified region 12 is formed inside the object 11. The modified region 12 is a region whose density, refractive index, mechanical strength, and other physical properties are different from those of the surrounding non-modified region. Examples of the modified region 12 include a melting process region, a crack region, an insulation breakdown region, and a refractive index change region. The modified region 12 has a characteristic that cracks tend to extend from the modified region 12 to the incident side of the laser light L and the opposite side. Such a characteristic of the modified region 12 is utilized to cut the object 11.

As an example, we will explain the operation of the laser processing device 1 when forming a modified region 12 inside the object 11 along a line 15 for cutting the object 11.

First, the laser processing device 1 rotates the support part 2 about an axis parallel to the Z direction so that the line 15 set on the object 11 is parallel to the X direction. Next, the laser processing device 1 moves the support part 2 along each of the X and Y directions based on an image (e.g., an image of a functional element layer of the object 11) acquired by the infrared imaging unit 9 so that the focal point C of the laser light L is located on the line 15 when viewed from the Z direction.

Then, based on the image (e.g., an image of the surface 11a of the object 11) acquired by the visible imaging unit 8, the laser processing device 1 moves the housing H (i.e., the focusing unit 6) along the Z direction so that the focal point C of the laser light L is located on the surface 11a. Next, based on that position, the laser processing device 1 moves the housing H (i.e., the focusing unit 6) along the Z direction so that the focal point C of the laser light L is located at a predetermined depth from the surface 11a.

Then, the laser processing device 1 emits the laser light L from the light source 3 and moves the support part 2 along the X direction so that the focal point C of the laser light L moves relatively along the line 15. At this time, the laser processing device 1 operates the drive mechanism 62 of the focusing part 6 so that the focal point C of the laser light L is located at a predetermined depth from the surface 11a based on the displacement data of the surface 11a acquired by the distance measuring sensor located at the front side (the front side in the relative movement direction of the laser light L with respect to the object 11) of the pair of distance measuring sensors S1, S2.

As a result, a row of modified regions 12 is formed along the line 15 and at a certain depth from the surface 11a of the object 11. When the laser light L is emitted from the light source 3 by the pulse oscillation method, multiple modified spots 12s are formed so as to be lined up in a row along the X direction. One modified spot 12s is formed by irradiation with one pulse of laser light L. A row of modified regions 12 is a collection of multiple modified spots 12s lined up in a row. Adjacent modified spots 12s may be connected to each other or separated from each other depending on the pulse pitch of the laser light L (the value obtained by dividing the relative moving speed of the focal point C with respect to the object 11 by the repetition frequency of the laser light L).
[Configuration of spatial light modulator]

The spatial light modulator 5 of this embodiment is a reflective liquid crystal (LCOS: Liquid Crystal on Silicon) spatial light modulator (SLM: Spatial Light Modulator). As shown in FIG. 2, the spatial light modulator 5 is configured by stacking a drive circuit layer 52, a pixel electrode layer 53, a reflective film 54, an alignment film 55, a liquid crystal layer 56, an alignment film 57, a transparent conductive film 58, and a transparent substrate 59 in this order on a semiconductor substrate 51.

The semiconductor substrate 51 is, for example, a silicon substrate. The drive circuit layer 52 forms an active matrix circuit on the semiconductor substrate 51. The pixel electrode layer 53 includes a plurality of pixel electrodes 53a arranged in a matrix along the surface of the semiconductor substrate 51. Each pixel electrode 53a is formed of, for example, a metal material such as aluminum. A voltage is applied to each pixel electrode 53a by the drive circuit layer 52.

The reflective film 54 is, for example, a dielectric multilayer film. The alignment film 55 is provided on the surface of the liquid crystal layer 56 facing the reflective film 54, and the alignment film 57 is provided on the surface of the liquid crystal layer 56 opposite the reflective film 54. Each alignment film 55, 57 is formed of, for example, a polymeric material such as polyimide, and the contact surface of each alignment film 55, 57 with the liquid crystal layer 56 is subjected to, for example, a rubbing treatment. The alignment films 55, 57 align the liquid crystal molecules 56a contained in the liquid crystal layer 56 in a fixed direction.

The transparent conductive film 58 is provided on the surface of the transparent substrate 59 on the alignment film 57 side, and faces the pixel electrode layer 53 with the liquid crystal layer 56 and the like sandwiched therebetween. The transparent substrate 59 is, for example, a glass substrate. The transparent conductive film 58 is formed of, for example, a light-transmitting and conductive material such as ITO. The transparent substrate 59 and the transparent conductive film 58 transmit the laser light L.

In the spatial light modulator 5 configured as described above, when a signal indicating a modulation pattern is input from the control unit 10 to the drive circuit layer 52, a voltage corresponding to the signal is applied to each pixel electrode 53a, and an electric field is formed between each pixel electrode 53a and the transparent conductive film 58. When this electric field is formed, the arrangement direction of the liquid crystal molecules 216a in the liquid crystal layer 56 changes for each region corresponding to each pixel electrode 53a, and the refractive index changes for each region corresponding to each pixel electrode 53a. This state is the state in which the modulation pattern is displayed in the liquid crystal layer 56.

With the modulation pattern displayed on the liquid crystal layer 56, when laser light L enters the liquid crystal layer 56 from the outside through the transparent substrate 59 and the transparent conductive film 58, is reflected by the reflective film 54, and is emitted from the liquid crystal layer 56 to the outside through the transparent conductive film 58 and the transparent substrate 59, the laser light L is modulated according to the modulation pattern displayed on the liquid crystal layer 56. In this way, with the spatial light modulator 5, by appropriately setting the modulation pattern to be displayed on the liquid crystal layer 56, it is possible to modulate the laser light L (for example, modulate the intensity, amplitude, phase, polarization, etc. of the laser light L).
[Configuration of the object]

The object 11 of this embodiment is a glass substrate 20, as shown in FIG. 3. As an example, the glass substrate 20 is formed into a rectangular plate shape from synthetic quartz glass, alkali-free glass, borosilicate glass, or the like. Note that the object 11 of this embodiment may further include, in addition to the glass substrate 20, other layers (e.g., a film formed on at least one of the main surfaces of the glass substrate 20, etc.).

The glass substrate 20 is irradiated with laser light L along each of the multiple lines 15. As a result, modified regions 12 are formed on the glass substrate 20 along each of the multiple lines 15. In this embodiment, the modified regions 12 are formed on the glass substrate 20 such that the entire modified regions 12 are located inside the glass substrate 20. Note that the modified regions 12 may also be formed on the glass substrate 20 such that a portion of the modified regions 12 is exposed to the outside.

The glass substrate 20 on which the modified region 12 is formed is cut into a plurality of chips along each of the plurality of lines 15 as cracks extend from the modified region 12 to the incident side of the laser light L and the opposite side. In this embodiment, the plurality of lines 15 are set in a lattice pattern when viewed from the thickness direction of the glass substrate 20. Each line 15 is a virtual line set on the glass substrate 20 by the laser processing device 1. Note that each line 15 may be a line that is actually drawn on the glass substrate 20.
[Functions of the control unit]

The control unit 10 inputs a signal indicating the astigmatism pattern AS to the spatial light modulator 5, as shown in FIG. 4. This causes the astigmatism pattern AS to be displayed on the liquid crystal layer 56 of the spatial light modulator 5, and astigmatism is imparted to the laser light L incident on the focusing unit 6. In this embodiment, the laser light L is oscillated by a burst pulse of an ultrashort pulse laser from the light source 3.

When the laser light L to which astigmatism has been imparted by the spatial light modulator 5 enters the focusing unit 6, as shown in FIG. 5, the laser light L is focused by the focusing lens unit 61 in the Y direction (first direction perpendicular to the optical axis of the laser light L) to a first region R1, and in the X direction (second direction perpendicular to the optical axis of the laser light L and the first direction) to a second region R2. The second region R2 is located downstream of the first region R1 in the traveling direction of the laser light L. Note that optical components disposed between the spatial light modulator 5 and the focusing unit 6 are not shown in FIG. 5.

In this state, the control unit 10 controls the moving unit 7 so that the first region R1 moves relatively along the X direction on the glass substrate 20. As a result, a modified region 12 is formed on the glass substrate 20 along the X direction. Next, the control unit 10 controls the visible imaging unit 8 to acquire an image of the modified region 12 formed on the glass substrate 20.

Based on the above, the control unit 10 functions as follows in the laser processing condition determination mode. The laser processing condition determination mode is a mode for determining the laser processing conditions for forming a modified region 12 suitable for cutting the glass substrate 20 into multiple chips. Note that the laser processing method performed in the laser processing condition determination mode corresponds to the laser processing method of this embodiment.

First, the control unit 10 controls the spatial light modulator 5 so that each of the multiple different astigmatisms is sequentially imparted to the laser light L, and controls the visible imaging unit 8 so that an image of the modified region 12 formed on the glass substrate 20 by irradiation with the laser light L to which each of the multiple astigmatisms has been imparted is acquired (first step). In each state in which each of the multiple astigmatisms has been imparted to the laser light L, the control unit 10 controls the moving unit 7 so that the first region R1 on the glass substrate 20 moves relatively along the X direction. As a result, a modified region 12 corresponding to the astigmatism is formed on the glass substrate 20.

In the first step, the control unit 10 inputs signals indicating each of the multiple astigmatism patterns AS corresponding to each of the multiple astigmatisms to the spatial light modulator 5. As shown in FIG. 6, each of the multiple astigmatism patterns AS is an astigmatism pattern that makes the value (hereinafter referred to as "ellipticity") obtained by dividing the width of the first region R1 in the X direction (left-right direction in FIG. 6) by the width of the first region R1 in the Y direction (up-down direction in FIG. 6) different from each other. When the ellipticity of the first region R1 is 1, the astigmatism pattern AS is not input to the spatial light modulator 5, that is, when astigmatism is not imparted to the laser light L. In FIG. 6, the diameter of the first region R1 when the ellipticity is 1 is, for example, about 1 μm. Note that the shape of the first region R1 of the laser light L to which astigmatism is imparted is not limited to a perfect ellipse, and may be, for example, a flattened circle, an oval, or the like.

After the first step, the control unit 10 links (in other words, associates) the image of the modified region 12 acquired by the visible imaging unit 8 to each of the multiple astigmatisms (second step), and after the second step, the control unit 10 sets one of the multiple astigmatisms to which the image of the modified region 12 is linked as a laser processing condition (third step). In this embodiment, as shown in FIG. 7, the interface unit 103 displays the image of the modified region 12 acquired by the visible imaging unit 8 (the image of the modified region 12 when viewed from the thickness direction of the glass substrate 20) linked to each of the multiple astigmatisms (ellipticity in FIG. 7), and accepts input of one of the multiple astigmatisms (ellipticity in FIG. 7) as a laser processing condition.

In the example shown in FIG. 7, the larger the ellipticity of the first region R1 (in other words, the stronger the astigmatism imparted to the laser light L), the more the direction of the crack extending from the modified region 12 tends to be along the X direction (the left-right direction in FIG. 7). In the example shown in FIG. 7, the black dot-like region corresponds to the modified spot, and the black linear region extending from the modified spot corresponds to the crack. If the direction of the crack extending from the modified region 12 is along the X direction (i.e., if the direction of the crack is along the direction in which the line 15 extends), it is easy to ensure sufficient bending strength for the multiple chips obtained by cutting the glass substrate 20. For this reason, the operator selects an image of the modified region 12 in which the crack direction is along the X direction, and inputs the astigmatism (ellipticity in FIG. 7) associated with the image into the control unit 10 as a laser processing condition. The bending strength is the fracture stress (stress when the chip is broken) obtained by the bending strength measurement test. The flexural strength measurement test is a test (four-point bending test) in which a chip is placed on two first cylinders arranged in parallel, and in that state, an external force is applied downward to the chip using two second cylinders arranged in parallel with a narrower gap between them than the two first cylinders, and the stress at which the chip breaks is measured.
[Action and Effects]

In the laser processing apparatus 1 and the laser processing method performed by the laser processing apparatus 1, each of a plurality of different astigmatisms is sequentially imparted to the laser light L, and an image of the modified region 12 formed on the glass substrate 20 by irradiation of the laser light L is outputted linked to each of the plurality of astigmatisms. Here, when the first region R1 of the laser light L focused in the Y direction is moved relatively along the X direction on the glass substrate 20, the direction of the crack extending from the modified region 12 tends to be stabilized. In addition, when the direction of the crack extending from the modified region 12 is along the X direction, it is easy to ensure sufficient bending strength for the plurality of chips obtained by cutting the glass substrate 20. Therefore, by imparting astigmatism linked to the image of the modified region 12 whose crack direction is along the X direction to the laser light L, it is possible to realize laser processing conditions that can ensure stable and sufficient bending strength. Therefore, the laser processing device 1 and the laser processing method performed by the laser processing device 1 make it possible to ensure sufficient flexural strength for the multiple chips obtained by cutting the glass substrate 20. Note that outputting the images of the modified region 12 in association with each of the multiple astigmatisms is not limited to displaying them on the interface unit 103, but also includes storing them in a storage device such as a memory.

In the laser processing device 1, the control unit 10 inputs signals indicating each of the multiple astigmatism patterns AS corresponding to each of the multiple astigmatisms to the spatial light modulator 5. This makes it possible to easily and reliably impart each of the multiple different astigmatisms to the laser light L.

In the laser processing device 1, each of the multiple astigmatism patterns AS is an astigmatism pattern that differs from one another in the value obtained by dividing the width of the first region R1 in the X direction by the width of the first region R1 in the Y direction. This makes it possible to easily and reliably impart each of the multiple different astigmatisms to the laser light L.

In the laser processing device 1, the control unit 10 has an interface unit 103 that displays the image of the modified region 12 acquired by the visible imaging unit 8, linked to each of the multiple astigmatisms. This allows the operator to objectively recognize the relationship between the astigmatism and the modified region 12.

In the laser processing apparatus 1, the control unit 10 has an interface unit 103 that receives input of any one of a plurality of astigmatisms as a laser processing condition, thereby allowing an operator to set an appropriate astigmatism as a laser processing condition.
[Experimental Results]

FIG. 8(a) is an image of a modified region formed on a 500 μm thick glass substrate made of alkali-free glass by irradiation with laser light to which no astigmatism is imparted (image of the modified region when viewed from the thickness direction of the glass substrate). FIG. 8(b) is an image of a modified region formed on a 500 μm thick glass substrate made of alkali-free glass by irradiation with laser light to which astigmatism with an ellipticity of 1.61 is imparted (image of the modified region when viewed from the thickness direction of the glass substrate). In FIG. 8(a) and FIG. 8(b), the laser processing conditions were the same as follows, except for whether or not astigmatism was imparted to the laser light. From the results of FIG. 8(a) and FIG. 8(b), it was found that when the laser light to which astigmatism is imparted is focused on the first region in the Y direction (the vertical direction in FIG. 8), and the first region is relatively moved along the X direction (the horizontal direction in FIG. 8) on the glass substrate, the direction of the crack extending from the modified region is stabilized along the X direction. The laser processing conditions are as follows:
Laser light wavelength: 1028 nm
Laser light pulse width: 300 fs
Repetition frequency of laser light: 50 kHz
Relative moving speed of the laser beam with respect to the glass substrate: 500 mm/s
Laser light energy: 2 μJ
Distance from the laser light incident surface of the glass substrate to the modified region: 80 μm

FIG. 9(a) is a diagram showing the bending strength of a plurality of chips obtained when a modified region is formed on a 200 μm thick glass substrate made of fluorophosphate glass by irradiation with laser light to which no astigmatism is imparted. FIG. 9(b) is a diagram showing the bending strength of a plurality of chips obtained when a modified region is formed on a 200 μm thick glass substrate made of fluorophosphate glass by irradiation with laser light to which an astigmatism of ellipticity of 1.61 is imparted. In FIG. 9(a) and FIG. 9(b), the laser processing conditions are the same as shown below, except for whether or not astigmatism is imparted to the laser light, and the chip size when viewed from the thickness direction is also the same at 5 mm×7 mm. In FIG. 9(a) and FIG. 9(b), "incident surface pressing" indicates that a load is applied to the chip from the surface (incident surface) of the chip on the side where the laser light is incident, and "reverse surface pressing" indicates that a load is applied to the chip from the reverse surface (surface opposite to the incident surface) of the chip. 9(a) and (b), it was found that when a modified region is formed on a glass substrate by irradiation with a laser beam not imparted with astigmatism, the fracture stress indicating the bending strength varies, whereas when a modified region is formed on a glass substrate by irradiation with a laser beam imparted with astigmatism, the fracture stress indicating the bending strength stabilizes at a high value. The laser processing conditions are as follows:
Laser light wavelength: 1028 nm
Laser light pulse width: 300 fs
Repetition frequency of laser light: 50 kHz
Relative moving speed of the laser beam with respect to the glass substrate: 400 mm/s
Laser light energy: 7 μJ
Distance from the laser light incident surface of the glass substrate to the modified region: 100 μm

Figure 10 shows the relationship between the astigmatism for each focusing lens unit and the image of the modified region (the image of the modified region when viewed from the thickness direction of the glass substrate). From the results in Figure 10, it was found that for modified regions formed on a glass substrate by irradiation with laser light without astigmatism (irradiation of laser light with an ellipticity of 1), the direction of cracks extending from the modified region varies depending on the focusing lens unit, whereas for modified regions formed on a glass substrate by irradiation with laser light with an astigmatism of 1.03 to 1.08, the closer the ellipticity is to 1.08, the more stable the direction of cracks extending from the modified region becomes along the X direction (the left-right direction in Figure 10).

Figure 11 shows the relationship between the astigmatism for each laser processing device and the image of the modified region (the image of the modified region when viewed from the thickness direction of the glass substrate). From the results in Figure 11, it was found that for modified regions formed on a glass substrate by irradiation with laser light without astigmatism (irradiation of laser light with an ellipticity of 1), the direction of the cracks extending from the modified region varies depending on the laser processing device, whereas for modified regions formed on a glass substrate by irradiation with laser light with an astigmatism of 1.08 to 1.6, the closer the ellipticity approaches 1.6, the more stable the direction of the cracks extending from the modified region becomes along the X direction (the left-right direction in Figure 11).

Fig. 12 is a diagram showing the relationship between the astigmatism for each glass material and the image of the modified region (the image of the modified region when viewed from the thickness direction of the glass substrate). From the results of Fig. 12, it was found that for the modified region formed on the glass substrate by irradiation with laser light without astigmatism (irradiation with laser light with ellipticity of 1), the direction of the crack extending from the modified region varies for each glass material, whereas for the modified region formed on the glass substrate by irradiation with laser light with astigmatism of 1.04 to 1.6, the closer the ellipticity is to 1.6, the more stable the direction of the crack extending from the modified region becomes along the X direction (the left-right direction in Fig. 12).
[Modification]

The present invention is not limited to the above embodiment. For example, the first optical unit that imparts astigmatism to the laser light L emitted from the light source 3 is not limited to the spatial light modulator 5. As an example, the first optical unit may be an optical system including a cylindrical lens that can move along the optical axis direction. However, it is difficult to stabilize the direction of the crack extending from the modified region 12 simply by displaying a slit pattern on the spatial light modulator 5 or arranging a mechanical slit to make the cross-sectional shape of the laser light L perpendicular to the optical axis elongated in the focusing region.

The display unit that displays the image of the modified region 12 in association with each of the multiple astigmatisms is not limited to the interface unit 103, but may be a display or the like provided separately from the control unit 10. The input receiving unit that receives input of any of the multiple astigmatisms as a laser processing condition is not limited to the interface unit 103, but may be a mouse, keyboard, or the like provided separately from the control unit 10.

In the above embodiment, the X direction is the first horizontal direction, the Y direction is the second horizontal direction perpendicular to the first horizontal direction, and the Z direction is the vertical direction, but the X direction, Y direction, and Z direction are not limited to these respective directions. For example, the Z direction may be a direction that intersects with the vertical direction.

1...laser processing device, 2...support section, 3...light source, 5...spatial light modulator (first optical section), 6...light collecting section (second optical section), 7...moving section, 8...visible imaging section (imaging section), 10...control section, 11...object, 12...modified region, 20...glass substrate, 103...interface section (display section, input receiving section), AS...astigmatism pattern, L...laser light, R1...first region, R2...second region.

Claims (7)

A laser processing apparatus for forming a modified region on a glass substrate by irradiating a target object including the glass substrate with laser light, comprising:
A support portion that supports the object;
a light source that emits the laser light;
a first optical unit that imparts astigmatism to the laser light emitted from the light source;
a second optical unit that focuses the laser light to which the astigmatism has been imparted by the first optical unit onto a first region in a first direction perpendicular to an optical axis of the laser light, and focuses the laser light onto a second region downstream of the first region in a traveling direction of the laser light, in a second direction perpendicular to the optical axis and the first direction;
A moving unit that moves the second optical unit relative to the support unit;
An imaging unit for acquiring an image of the modified region;
a control unit that controls the first optical unit so that each of a plurality of different astigmatisms is imparted to the laser light as the astigmatism, controls the moving unit so that the first region of the glass substrate moves relatively along the second direction, and outputs the image of the modified region acquired by the imaging unit in association with each of the plurality of astigmatisms. the first optical unit is a spatial light modulator;
The laser processing apparatus according to claim 1 , wherein the control unit inputs, to the spatial light modulator, signals indicating a plurality of astigmatism patterns corresponding to the plurality of astigmatisms, respectively. The laser processing device according to claim 2, wherein each of the plurality of astigmatism patterns is an astigmatism pattern in which the value obtained by dividing the width of the first region in the second direction by the width of the first region in the first direction is different from each other. The laser processing device according to any one of claims 1 to 3, wherein the control unit has a display unit that displays the image of the modified region acquired by the imaging unit in association with each of the multiple astigmatisms. The laser processing device according to any one of claims 1 to 4, wherein the control unit has an input receiving unit that receives input of any one of the multiple astigmatisms as a laser processing condition. A laser processing method for forming a modified region on a glass substrate by irradiating a target object including the glass substrate with laser light, comprising:
a first step of sequentially imparting a plurality of different astigmatisms to the laser light and acquiring an image of the modified region formed on the glass substrate by irradiation of the laser light to which each of the plurality of astigmatisms has been imparted;
a second step of associating the image of the modified region with each of the plurality of astigmatisms;
a first region in a first direction perpendicular to an optical axis of the laser light, and a second region downstream of the first region in a traveling direction of the laser light, the second region being perpendicular to the optical axis and the first direction; and a first region being relatively moved along the second direction on the glass substrate. The laser processing method according to claim 6, further comprising a third step of setting one of the multiple astigmatisms associated with the image of the modified region as a laser processing condition.

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