JP5598801B2 - Laser dicing method, chip manufacturing method, and laser processing apparatus - Google Patents

Description

  The present invention relates to a laser dicing method and a chip manufacturing method for dividing a crystal substrate by irradiating a laser beam. The present invention also relates to a laser processing apparatus for forming damage for dividing a crystal substrate by irradiating the crystal substrate with laser light.

  In recent years, a laser dicing method has been proposed as a new technique for dividing a substrate. In the laser dicing method, the substrate is divided by irradiating the substrate with laser light to form damage. When two scheduled division lines intersect on a substrate, it has been proposed to perform processing in a predetermined procedure for the purpose of improving processing accuracy (see, for example, Patent Documents 1 to 3).

  Patent Document 1 discloses a laser dicing method in which a brittle substrate is divided by forming preliminary residual stress lines on both sides of a scribe region and then irradiating the brittle substrate with laser light to form a crack. In this technique, a preliminary residual stress line is formed before the substrate is irradiated with laser light, thereby preventing splashing at the end of the scribe area and leaving the scribe area after division. Examples of the preliminary residual stress line include a minute deformation formed by pressing with a pressure terminal ball, a minute alteration formed by laser light irradiation, and a minute groove formed by etching.

  Patent Document 2 discloses a first step of forming a first scribe line composed of vertical cracks on a brittle substrate by irradiating a laser beam along a first division planned line and further spraying a cooling medium, and a first division schedule. A second step of irradiating the brittle substrate by irradiating a laser beam along the second division line intersecting the line and further blowing a cooling medium, and again irradiating the laser beam along the first scribe line A laser dicing method is disclosed that includes a third step of cleaving a brittle substrate by extending a crack. In this technique, a brittle substrate such as a glass substrate is used as an object to be processed in order to develop a crack. Moreover, the crack extended in the 2nd direction formed in the 2nd process, and the crack extended in the 1st direction formed in the 3rd process by making the irradiation width of the laser beam in the 3rd process 1.0 mm or less The occurrence of chipping near the intersection is suppressed.

  Patent Document 3 discloses a first step of forming a half-cut first crack on a brittle substrate by irradiating a laser beam along a first division planned line and further spraying a cooling medium; A second step of forming a full-cut second crack on the brittle substrate by irradiating a laser beam along the intersecting second division planned line and spraying a cooling medium, and a laser along the half-cut first crack A laser dicing method including a third step of irradiating light again to make a full cut is disclosed. In this technique, a brittle substrate such as a glass substrate is used as an object to be processed in order to develop a crack.

  In the techniques described in Patent Documents 2 and 3, if the brittle substrate is completely divided along the first division planned line in the first step, the crack is propagated beyond the division point in the subsequent steps. The brittle substrate cannot be divided along the second scheduled division line. For this reason, it is essential to form a half-cut crack in the first step.

JP-A-9-260310 JP 2010-184457 A JP 2007-301806 A

  In the technique described in Patent Document 1, it is necessary to form at least two preliminary residual stress lines for one division planned line. For this reason, the technique described in Patent Document 1 has a problem that the number of processing steps increases at least three times. Further, in the techniques of Patent Documents 2 and 3, in order of processing along the first division planned line, processing along the second division planned line, and processing along the first division planned line again, The stage must be rotated at least twice. For this reason, the techniques disclosed in Patent Documents 2 and 3 have a problem that the process is complicated and the processing line is easily shifted, so that it is difficult to ensure the processing accuracy.

  The present invention has been made in view of the above point, and is a laser dicing method for dividing a crystal substrate by irradiating a laser beam along a planned division line, which is more easily performed than a conventional technique. It is an object of the present invention to provide a laser dicing method that can suppress the occurrence of cracks in the vicinity and that can be divided with high accuracy. Another object of the present invention is to provide a chip manufacturing method using the laser dicing method and a laser processing apparatus used in the laser dicing method.

  The present inventor has found that the above problem can be solved by irradiating laser light in a predetermined order when irradiating the crystal substrate with the laser beam along the division lines intersecting each other. Completed the invention.

That is, the present invention relates to the following laser dicing method and chip manufacturing method.
[1] A crystal substrate is irradiated with laser light along a first division planned line and a second division planned line that intersect each other, and the crystal substrate is applied along the first division planned line and the second planned division line. A damage forming step for forming damage, and an expanding step for applying a tensile force to the crystal substrate irradiated with the laser beam, wherein the damage forming step is applied to the crystal substrate along the first division line. A first step of irradiating laser light to form damage on the crystal substrate along the first planned division line, and laser light on the crystal substrate along the second planned division line after the first step. A second step of forming damage on the crystal substrate along the second division line, and a laser on the crystal substrate along the second division line after the second step. , And a third step of forming again damage to the crystal substrate along the second scheduled division line, and the depth of damage formed in the second step is the first step and The laser dicing method, wherein the crystal substrate is divided in the damage forming step or the expanding step, which is shallower than the depth of damage formed in the third step.
[2] The depth of damage formed in the second step is in the range of 5 to 50% of the thickness of the crystal substrate, and the depth of damage formed in the first step and the third step is: The laser dicing method according to [1], which is 70% or more of the thickness of the crystal substrate.
[3] The laser dicing method according to [1] or [2], wherein the crystal substrate is divided in the damage forming step.
[4] The laser dicing method according to [1] or [2], wherein the crystal substrate is divided in the expanding step.
[5] Any one of [1] to [4], which does not include a break step for dividing the crystal substrate by applying a bending force to the crystal substrate between the damage forming step and the expanding step. The laser dicing method described in 1.
[6] The crystal substrate is irradiated with a laser beam along the first scheduled division line and the second scheduled division line that intersect each other, and the crystal substrate is applied along the first scheduled division line and the second scheduled line. A damage forming step for forming damage, and an expanding step for applying a tensile force to the crystal substrate irradiated with the laser beam, wherein the damage forming step is applied to the crystal substrate along the first division line. A first step of irradiating laser light to form damage on the crystal substrate along the first planned division line, and laser light on the crystal substrate along the second planned division line after the first step. A second step of forming damage on the crystal substrate along the second division line, and a laser on the crystal substrate along the second division line after the second step. A third step of again damaging the crystal substrate along the second scheduled division line, and in the second step, the condensing point of the laser beam is the crystal substrate In the range of 100 μm above the surface of the crystal substrate, and in the first step and the third step, the condensing point of the laser light is located below the surface of the crystal substrate, The laser dicing method, wherein the crystal substrate is divided in the damage forming step or the expanding step.
[7] The laser beam is a pulsed laser beam, and the peak power density of the laser beam in the second step is in the range of 1.6 × 10 ^{8 to} 1.6 × 10 ⁹ W / cm ² . The laser dicing method according to [6], wherein the peak power density of the laser light in the first step and the third step is 2.0 × 10 ⁹ W / cm ² or more.
[8] The laser dicing method according to [6] or [7], wherein the crystal substrate is divided in the damage formation step.
[9] The laser dicing method according to [6] or [7], wherein the crystal substrate is divided in the expanding step.
[10] Any one of [6] to [9], which does not include a break step for dividing the crystal substrate by applying a bending force to the crystal substrate between the damage forming step and the expanding step. The laser dicing method described in 1.
[11] A chip manufacturing method in which a chip is manufactured by dividing a crystal substrate using the laser dicing method according to any one of [1] to [10].

The present invention also relates to the following laser processing apparatus.
[12] A laser light source that emits laser light, an optical system that irradiates the crystal substrate with the laser light, and at least one of the optical system and the crystal substrate is moved so that the optical system and the crystal substrate are relatively And moving the laser beam to the crystal substrate along a first division planned line and a second division planned line intersecting each other, and driving the first division planned line and the second division line. A laser processing apparatus for forming damage on the crystal substrate along a planned division line, wherein the crystal substrate is irradiated with laser light along the first planned division line, and then along the first planned division line. A first step of forming damage to the crystal substrate, and irradiating the crystal substrate with laser light along the second division line after the first step, and along the second division line. A second step of forming damage to the crystal substrate; and after the second step, irradiating the crystal substrate again with the laser beam along the second division line, and along the second division line. And a third step of forming damage again in the crystal substrate. The damage is formed in the crystal substrate by a damage forming step, and the depth of damage formed in the second step is the first step and the third step. Laser processing equipment, shallower than the depth of damage to be formed in.
[13] A laser light source that emits laser light, an optical system that irradiates the crystal substrate with the laser light, and at least one of the optical system and the crystal substrate is moved so that the optical system and the crystal substrate are relatively And moving the laser beam to the crystal substrate along a first division planned line and a second division planned line intersecting each other, and driving the first division planned line and the second division line. A laser processing apparatus for forming damage on the crystal substrate along a planned division line, wherein the crystal substrate is irradiated with laser light along the first planned division line, and then along the first planned division line. A first step of forming damage to the crystal substrate, and irradiating the crystal substrate with laser light along the second division line after the first step, and along the second division line. A second step of forming damage to the crystal substrate; and after the second step, irradiating the crystal substrate again with the laser beam along the second division line, and along the second division line. A damage forming step including a third step of forming damage again on the crystal substrate, and in the second step, the condensing point of the laser beam is from the surface of the crystal substrate to the surface of the crystal substrate. A laser processing apparatus, which is located within a range of 100 μm above the surface of the crystal substrate, and in the first step and the third step, the condensing point of the laser light is located below the surface of the crystal substrate.

  According to the present invention, it is possible to divide a crystal substrate with high accuracy while suppressing generation of cracks with fewer steps than in the prior art. Therefore, according to the present invention, chips can be obtained from the crystal substrate with a high yield.

1A to 1C are schematic views showing a crystal substrate dividing step using a laser dicing method according to the present invention. 2A to 2D are schematic views for explaining a laser beam irradiation procedure in the laser dicing method according to the present invention. It is a schematic diagram for demonstrating the mechanism in which generation | occurrence | production of a crack is suppressed. It is a schematic diagram which shows an example of the laser processing apparatus which concerns on one embodiment of this invention. FIGS. 5A to 5C are schematic views for explaining the procedures of processing examples 1, 3, 5, and 6. FIG. 6A and 6B are schematic diagrams for explaining the procedures of processing examples 2 and 4. FIG. FIG. 7A is a photograph of a cross section of the SiC substrate showing damage formed by the processing under processing condition 2 . FIG. 7B is a photograph of a cross section of the SiC substrate showing damage formed by the processing under processing condition 1 . FIG. 8A is a photograph of the SiC substrate divided by the procedure of Processing Example 1. FIG. 8B is a photograph of the SiC substrate divided by the procedure of Processing Example 2. FIG. 9A is an enlarged photograph in the vicinity of the intersection of the planned division lines of the SiC substrate divided in the procedure of Processing Example 1. 9B and 9C are enlarged photographs of the vicinity of the intersection of the planned dividing lines of the SiC substrate divided by the procedure of Processing Example 2. FIG. FIG. 10A is a photograph of a cross-section of the sapphire substrate showing damage formed by processing under processing condition 4 . FIG. 10B is a photograph of a cross section of the sapphire substrate showing the damage formed by the processing under the processing condition 3 . FIG. 11A is a photograph of the sapphire substrate divided by the procedure of Processing Example 3. FIG. 11B is a photograph of the sapphire substrate divided by the procedure of Processing Example 4. FIG. 12A is an enlarged photograph of the vicinity of the intersection of the planned division lines of the sapphire substrate divided by the procedure of Processing Example 3. FIG. 12B is an enlarged photograph near the intersection of the planned division lines of the sapphire substrate divided by the procedure of Processing Example 2. FIG. 13A is a photograph of a SiC substrate divided by the procedure of Processing Example 5 by irradiating a pulse laser beam with a pulse energy of 5 μJ. FIG. 13B is a photograph of the SiC substrate divided by the procedure of Processing Example 5 by irradiating a pulse laser beam with a pulse energy of 10 μJ. FIG. 13C is a photograph of the SiC substrate divided by the procedure of Processing Example 5 by irradiating a pulse laser beam having a pulse energy of 100 μJ. FIG. 14A is an enlarged photograph of the vicinity of the intersection of the planned dividing lines of the SiC substrate divided by the procedure of Processing Example 5 by irradiating a pulse laser beam having a pulse energy of 5 μJ. FIG. 14B is an enlarged photograph of the vicinity of the intersection of the planned dividing lines of the SiC substrate divided by the procedure of Processing Example 5 by irradiating a pulse laser beam having a pulse energy of 10 μJ. FIG. 14C is an enlarged photograph of the vicinity of the intersection of the planned division lines of the SiC substrate divided by the procedure of Processing Example 5 by irradiating a pulse laser beam with a pulse energy of 100 μJ.

1. Laser dicing method and chip manufacturing method A laser dicing method according to the present invention includes a damage forming step of irradiating a crystal substrate with laser light along division lines that intersect each other to form damage on the crystal substrate, And an expanding step of applying a tensile force to the irradiated crystal substrate. The crystal substrate is divided in either the damage forming process or the expanding process. As will be described later, the laser dicing method according to the present invention is characterized in that laser light is irradiated in a predetermined order in the damage forming step.

The type of the substrate to be processed is not particularly limited as long as it is a crystalline substrate, and may be a single crystal substrate or a polycrystalline substrate. Examples of the crystal substrate include a silicon carbide (SiC) substrate, a sapphire (Al ₂ O ₃ ) substrate, a silicon (Si) substrate, a gallium nitride (GaN) substrate, a zinc oxide (ZnO) substrate, and a gallium oxide (Ga ₂ O _3). ) Substrate, diamond substrate and the like. A thin film such as an epitaxial layer may be formed on the surface of the crystal substrate.

  FIG. 1 is a schematic view showing an example of dividing a crystal substrate using the laser dicing method according to the present invention. As shown in FIG. 1A, the relative position between the laser beam 100 and the crystal substrate 110 is changed while the crystal substrate 110 is irradiated with the laser beam 100. At this time, the condensing point of the laser beam 100 is located outside, on the surface, or inside the crystal substrate 110 and moves along the division line 120 of the crystal substrate 110. By scanning the laser beam 100 once or twice (described later) in this way, as shown in FIG. 1B, the damage 130 having a depth of 70% or more of the thickness of the crystal substrate 110 along the planned dividing line 120. Can be formed (damage formation step). At this time, the damage 130 is considered to be formed by a phenomenon such as thermal expansion, melting, decomposition, or volume explosion caused by the crystal substrate 110 absorbing the laser light 100 (one-photon absorption or multiphoton absorption). Thereafter, as shown in FIG. 1C, a tensile force is applied to the crystal substrate 110 on which the damage 130 is formed (expanding process). With the above procedure, the crystal substrate 110 can be easily divided along the division line 120.

  In the laser dicing method according to the present invention, it is possible to immediately move to the expanding step (see FIG. 1C) after the damage forming step (see FIGS. 1A and 1B). That is, in the laser dicing method according to the present invention, it is not necessary to perform a break process between the damage forming process and the expanding process. Here, the “break process” means that a force (bending force) in a direction substantially perpendicular to the substrate surface is applied to the substrate to cause damage formed on the surface of the substrate to reach the back surface of the substrate. It means the process of dividing. On the other hand, the “expanding process” means a process of dividing the substrate starting from damage formed on the substrate by applying a force (tensile force) in a direction substantially parallel to the substrate surface to the substrate (FIG. 1C). reference).

  Hereinafter, the damage forming process and the expanding process will be described.

[Damage formation process]
In the damage formation step, the crystal substrate is irradiated with laser light along the first division planned line and the second division planned line intersecting each other, and the crystal substrate is damaged along the first division planned line and the second division planned line. (See FIG. 1A and FIG. 1B).

  FIG. 2A is a diagram illustrating an example of division planned lines set on the crystal substrate 110. In the example shown in FIG. 2A, a plurality of first division planned lines 120a extending in the X-axis direction and a plurality of second division planned lines 120b extending in the Y-axis direction are set. In this example, the first scheduled division line 120a and the second scheduled division line 120b intersect each other at a right angle, but the angle at which the first scheduled division line 120a and the second scheduled division line 120b intersect is not particularly limited. Further, in this example, the pitch of the first scheduled division line 120a and the pitch of the second scheduled division line 120b are all the same, but these pitches may not be constant.

  In the laser dicing method according to the present invention, the laser beam is irradiated along the first division planned line and the second division planned line in a predetermined order. That is, first, as shown in FIG. 2B, the crystal substrate 110 is irradiated with laser light along the first planned division line 120a, and the crystal substrate 110 is deeply damaged 130a (described later) along the first planned division line 120a. ) Is formed (first step). Next, as shown in FIG. 2C, the crystal substrate 110 is irradiated with laser light along the second scheduled division line 120b, and shallow damage 130b (described later) is applied to the crystalline substrate 110 along the second scheduled division line 120b. Form (second step). Finally, as shown in FIG. 2D, the crystal substrate 110 is again irradiated with the laser light along the second scheduled division line 120b, and the crystal substrate 110 is deeply damaged 130c (described later) along the second scheduled division line 120b. ) Is formed (third step).

  Thus, in the laser dicing method according to the present invention, (1) deep damage 130a along the first division planned line 120a, (2) shallow damage 130b along the second division planned line 120b, and (3) second division planned. Damage 130 is formed in the order of shallow damage 130b along line 120b. Here, “deep damage” and “shallow damage” are relative expressions of depth. That is, the depth of the damage 130b formed in the second step is shallower than the depth of the damage 130a formed in the first step and the damage 130c formed in the third step. The depth of the damage 130a formed in the first step and the depth of the damage 130c formed in the third step may be the same or different.

  From the viewpoint of suppressing the occurrence of cracks in the vicinity of the intersection of the first planned dividing line 120a and the second planned divided line 120b, the depth of the shallow damage 130b formed in the second step is 5 to 50 of the thickness of the crystal substrate 110. % Is preferable. From the viewpoint of reliably dividing the crystal substrate 110, the depth of the deep damage 130a formed in the first step and the deep damage 130c formed in the third step is 70% or more of the thickness of the crystal substrate 110. Is preferred. As will be described later, the depth of damage can be controlled by adjusting the position of the laser beam condensing point (position in the Z-axis direction), the peak power density of the laser beam, and the like.

  As described above, in the laser dicing method according to the present invention, after the deep damage 130a is formed along the first division planned line 120a (after the first step), the deep damage 130c along the second division planned line 120b is formed. Before forming (before the third step), a shallow damage 130b is formed along the second division planned line 120b, so that cracks in the vicinity of the intersection of the first division planned line 120a and the second planned division line 120b are formed. Suppresses the occurrence. Here, the inferred mechanism will be described with respect to the point at which the occurrence of cracks in the vicinity of the intersection of the first scheduled division line 120a and the second scheduled division line 120b is suppressed. It is not limited to.

  FIG. 3 is a schematic diagram for explaining a mechanism in which the occurrence of cracks is suppressed. 3A and 3B are diagrams showing a procedure of a conventional general laser dicing method, and FIGS. 3C to 3E are diagrams showing a procedure of a laser dicing method according to the present invention. Arrowheads attached to the damages 130a, 130b, and 130c indicate the scanning direction of the laser light.

  In the conventional general laser dicing method, as shown in FIG. 3A, after deep damage 130a is formed along the first division planned line 120a, the second division planned line 120b is formed as shown in FIG. 3B. A deep damage 130c is formed along. In this way, when the deep damage 130a is formed along the second division planned line 120b in the state where the deep damage 130a is formed along the first division planned line 120a, the laser indicated by the arrow in FIG. 3B. Thermal stress generated by irradiation concentrates toward the damage 130a, and a crack 140 is generated at the end of each chip.

  On the other hand, in the laser dicing method according to the present invention, as shown in FIG. 3C, after deep damage 130a is formed along the first division planned line 120a, the second division is scheduled as shown in FIG. 3D. Shallow damage 130b is formed along line 120b. Thereafter, as shown in FIG. 3E, a deep damage 130c is formed along the second division planned line 120b. As described above, when a deeper damage 130c is formed along the second division planned line 120b in a state where the shallow damage 130b is formed along the second divided division line 120b, thermal stress generated by laser irradiation is generated. Can be released to the space caused by the shallow damage 130b, and the occurrence of cracks due to the concentration of thermal stress is suppressed.

  The wavelength of the laser light is not particularly limited as long as damage can be formed on the crystal substrate. The wavelength of the laser light is appropriately selected according to the type of crystal substrate. For example, when processing a SiC substrate, it is preferable to irradiate a laser beam having a wavelength of 500 nm or more. Moreover, when processing a sapphire board | substrate, it is preferable to irradiate the laser beam with a wavelength of 300-600 nm.

  In the laser dicing method according to the present invention, the type of laser used as the laser light source is not particularly limited, and is appropriately selected according to the type of crystal substrate. Examples of the laser include Ho laser, Er laser, Yb laser, various semiconductor lasers, and the like. The oscillating laser beam may be a pulsed laser beam or a continuous wave (CW) laser beam.

  In the second step of forming shallow damage, it is preferable that the condensing point of the laser light is located within a range of 100 μm from the surface to the upper side of the crystal substrate. By doing so, the depth of the shallow damage 130b formed in the second step can be within a range of 5 to 50% of the thickness of the crystal substrate 110. Here, “the position of the laser beam condensing point” means the position of the condensing point (lens offset) when it is assumed that the refractive index of the crystal substrate is the same as that of air. Further, “above the surface” means a direction perpendicular to the substrate surface and toward the outside. On the other hand, in the first step and the third step for forming deep damage, it is preferable that the condensing point of the laser light is located below the surface of the crystal substrate. By doing in this way, the depth of the deep damage 130a, 130c formed in the first step and the third step can be 70% or more of the thickness of the crystal substrate 110.

When the laser beam is a pulsed laser beam, the peak power density of the pulsed laser beam is within the range of 1.6 × 10 ^{8 to} 1.6 × 10 ⁹ W / cm ² in the second step of forming shallow damage. Preferably there is. By doing so, the depth of the shallow damage 130b formed in the second step can be within a range of 5 to 50% of the thickness of the crystal substrate 110. On the other hand, in the first step and the third step for forming deep damage, the peak power density of the pulse laser beam is preferably 2.0 × 10 ⁹ W / cm ² or more. By doing in this way, the depth of the deep damage 130a, 130c formed in the first step and the third step can be 70% or more of the thickness of the crystal substrate 110.

  As described above, in the laser dicing method according to the present invention, the crystal substrate is divided in either the damage forming step or the expanding step. In the former case, the crystal substrate is divided by spontaneously forming a dividing surface that reaches the back surface from the surface of the crystal substrate, triggered by the formation of damage by laser light irradiation. Whether or not the crystal substrate is divided in the damage formation step can be confirmed by observing the vicinity of the division planned line from the front surface side using a microscope with light applied from the back surface side of the crystal substrate. That is, when the crystal substrate is divided, light passes along the planned division line, so that it can be confirmed that the crystal substrate is divided.

[Expanding process]
In the expanding process, a tensile force is applied to the crystal substrate that has been damaged in the damage forming process (see FIG. 1C). As described above, “applying a tensile force” means applying a force in a direction substantially parallel to the substrate surface. When the crystal substrate is divided in the damage forming process, the space between the divided chips is expanded by the expanding process. On the other hand, when the crystal substrate is not divided in the damage forming step, the crystal substrate is divided from the damage by the expanding step, and at the same time, the interval between the divided chips is expanded.

  The method for applying a tensile force to the crystal substrate is not particularly limited. For example, a dicing tape may be attached to the back surface of the crystal substrate and the dicing tape may be stretched. In this case, a dicing tape may be affixed before the damage formation step, or a dicing tape may be affixed after the damage formation step.

  As described above, the laser dicing method according to the present invention suppresses the generation of cracks by irradiating the laser light in a predetermined order when irradiating the crystal substrate with the laser light along the division lines that intersect each other. However, damage with a high aspect ratio (a depth of 70% or more of the thickness of the crystal substrate) can be formed on the surface of the crystal substrate with high accuracy and high speed. Therefore, the laser dicing method according to the present invention can divide the crystal substrate with high accuracy and at high speed while suppressing the generation of cracks only by the expanding process without performing the breaking process.

  By using the laser dicing method according to the present invention, for example, a crystal substrate can be divided to manufacture a chip or an electronic device.

  Means for carrying out the laser dicing method according to the present invention is not particularly limited. For example, the laser dicing method according to the present invention can be implemented using a laser processing apparatus according to the present invention described below.

2. Laser processing apparatus The laser processing apparatus according to the present invention is an apparatus used in the damage forming step of the laser dicing method according to the present invention. That is, the laser processing apparatus according to the present invention irradiates the crystal substrate with laser light along the first scheduled division line and the second scheduled division line that intersect each other, and the first divided planned line and the second scheduled division line are irradiated. A device that forms damage to the crystal substrate along the line.

  A laser processing apparatus according to the present invention includes at least a laser light source that emits laser light, an optical system that irradiates the crystal substrate with laser light emitted from the laser light source, and an optical system (laser light) and the crystal substrate that are relatively And a drive unit that is moved automatically. Hereinafter, each component will be described.

  The laser light source emits laser light that irradiates the crystal substrate. As described above, the type of laser used as the laser light source is not particularly limited, and is appropriately selected according to the type of crystal substrate. Examples of the laser include Ho laser, Er laser, Yb laser, various semiconductor lasers, and the like. The oscillating laser beam may be a pulsed laser beam or a continuous wave (CW) laser beam.

  The optical system irradiates the crystal substrate with laser light emitted from the laser light source so that the focal point is located at a desired position. Usually, the optical system includes a telescope optical system that optimizes the beam diameter of laser light, a condensing lens that condenses the laser light at a desired position, and the like.

  The drive unit moves at least one of the optical system (laser light) and the crystal substrate to relatively move the optical system and the crystal substrate. Thereby, a laser beam can be irradiated along the division | segmentation scheduled line of a crystal substrate. As a result, damage with a high aspect ratio can be formed along the planned dividing line of the crystal substrate. The drive unit may move the stage on which the crystal substrate is placed, may move the optical system, or may move both the stage and the optical system.

  The laser processing apparatus according to the present invention irradiates a crystal substrate with laser light along a first division planned line and a second division planned line that intersect each other, and along the first division planned line and the second division planned line. Damage is formed in the crystal substrate. At this time, the laser processing apparatus according to the present invention irradiates the crystal substrate with laser light along the first division line, and forms damage on the crystal substrate along the first division line (first step). . Next, the laser processing apparatus according to the present invention irradiates the crystal substrate with laser light along the second division planned line, and forms damage on the crystal substrate along the second division planned line (second step). Finally, the laser processing apparatus according to the present invention irradiates the crystal substrate again with the laser beam along the second scheduled division line, and forms damage again on the crystal substrate along the second scheduled line (third). Process). As described above, the depth of damage formed in the second step is shallower than the depth of damage formed in the first step and the third step.

  In addition, the laser processing apparatus may include a stage on which a crystal substrate to be processed is placed, an automatic aiming system for positioning a condensing point at a desired position, and the like.

  FIG. 4 is a schematic diagram showing a laser processing apparatus according to an embodiment of the present invention. As shown in FIG. 4, the laser processing apparatus 200 includes a laser light source 210, a telescope optical system 220, a condenser lens 230, a stage 240, an AF camera 250, an XY stage controller 260, a Z controller 270, and a computer 280.

  The laser light source 210 emits laser light having a predetermined wavelength. As described above, the type of laser used as the laser light source is appropriately selected according to the type of crystal substrate to be processed.

  The telescope optical system 220 optimizes the beam diameter of the laser light emitted from the laser light source 210 in order to obtain a preferable processing shape.

  The condensing lens 230 condenses the laser light that has passed through the telescope optical system 220. For example, the condensing lens 230 is an objective lens for a microscope.

  The stage 240 includes a mounting table on which the crystal substrate 110 to be processed is mounted, and a drive mechanism that can move the mounting table. The drive mechanism can move the mounting table in the X-axis or Y-axis direction or rotate the X-axis or Y-axis as a center. The crystal substrate 110 on the stage 240 is moved in the XY axis direction along the planned division line by this drive mechanism.

  The AF camera 250 is a camera for acquiring a surface profile of a processed part of the crystal substrate 110. The acquired profile is output to the computer 280.

  Based on an instruction from the computer 280, the XY stage controller 260 moves the stage 240 in the XY axis direction so that the condensing position of the laser light is along the planned division line of the crystal substrate 110.

  Based on an instruction from the computer 280, the Z controller 270 moves the condensing lens 230 in the Z-axis direction so that the condensing position of the laser light matches a desired position.

  The computer 280 is connected to the laser light source 210, the AF camera 250, the XY stage controller 260, and the Z controller 270, and comprehensively controls these units. For example, the computer 280 controls the AF camera 250 and the XY stage controller 260 to acquire the surface profile of the crystal substrate 110. In addition, the computer 280 controls the XY stage controller 260 and the Z controller 270 to scan the laser light along the planned division line of the crystal substrate 110.

  Next, a procedure for dividing the crystal substrate 110 using the laser processing apparatus 200 will be described.

  First, damage from the surface to the inside is formed in the crystal substrate 110 by the laser processing apparatus 200 shown in FIG. 4 (damage formation step). Specifically, first, the crystal substrate 110 with the dicing tape 150 attached to the back surface is placed on the stage 240 and the surface profile of the crystal substrate 110 is acquired by the AF camera 250 and the XY stage controller 260. Next, laser light is emitted from the laser light source 210 to irradiate the crystal substrate 110 with the laser light. At this time, based on the surface profile acquired in advance, the stage 240 is moved in the XY axis direction (horizontal direction) to scan the division planned line with the laser light (see FIG. 1A). Further, deep damage 130a is formed along the first planned division line 120a (first step), then shallow damage 130b is formed along the second planned division line 120b (second step), and finally the second division is performed. Laser light is scanned so as to form deep damage 130c along the planned line 120b (third step) (see FIG. 2). At this time, the condensing point of the laser beam is positioned within the range of 100 μm above the surface of the crystal substrate 110 to the surface of the crystal substrate 110 in the second step, and the surface of the crystal substrate 110 in the first step and the third step. It is preferable to position it below. As a result, it is possible to form a damage having a depth of 70% or more of the thickness of the crystal substrate 110 while suppressing the generation of cracks along the division line of the crystal substrate 110 (see FIG. 1B).

  In the laser dicing method according to the present invention, after forming the deep damage 130a along the first division planned line 120a (first step), the shallow damage 130b and the deep damage 130c are formed along the second planned division line 120b. (Second step and third step). Therefore, the stage may be rotated once between the first process and the second process. Thus, since the stage is not rotated between the second step and the third step, it is possible to prevent the shallow damage 130b formed in the second step from being shifted from the deep damage 130c formed in the third step. .

  Next, the dicing tape 150 is stretched by an expanding device (not shown), and a tensile force is applied to the damaged crystal substrate 110 (expanding process). When the crystal substrate 110 is divided in the damage forming process, the space between the divided chips is expanded by the expanding process. On the other hand, when the crystal substrate 110 is not divided in the damage formation process, the expansion process divides the crystal substrate 110 starting from the damage, and widens the interval between the divided chips simultaneously (see FIG. 1C).

  By the above procedure, the crystal substrate can be divided (diced) only by the damage forming step and the expanding step without interposing the break step.

  FIG. 4 shows an example in which the stage 240 is moved to irradiate the laser beam along the planned division line. However, the means for irradiating the laser beam along the planned division line is a laser beam. If the condensing point of this and a crystal substrate can be moved relatively, it will not specifically limit. For example, instead of the stage 240, the optical system (the telescope optical system 220 and the condenser lens 230) may be moved, or both the stage 240 and the optical system may be moved.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail with reference to an Example, this invention is not limited by these Examples.

[Example 1]
In Example 1, it is shown that the SiC substrate can be divided only by the damage forming step and the expanding step while suppressing the generation of cracks by the laser dicing method according to the present invention.

  A square SiC single crystal substrate (length 10 mm × width 10 mm × thickness 150 μm) was prepared as a workpiece. In the present embodiment, this SiC substrate is divided into 2 mm vertical and horizontal lines to obtain 25 square chips (vertical 2 mm × width 2 mm × thickness 150 μm). In the following description, the planned division line in the horizontal direction (X-axis direction) is defined as a first planned division line, and the planned division line in the vertical direction (Y-axis direction) is defined as a second scheduled division line.

  A SiC substrate with a dicing tape attached to the back surface is placed on the stage, and a pulse laser beam (wavelength 1064 nm, pulse width 200 nanoseconds, spot diameter 6.2 μm at the focal point) is irradiated onto the SiC substrate from the front side of the SiC substrate. Thus, damage from the surface toward the inside was formed in the SiC substrate (damage formation step). At this time, the stage was moved in the XY axis direction (horizontal direction), and damage was formed along the planned dividing line of the SiC substrate. Next, the dicing tape affixed to the back surface of the SiC substrate was evenly stretched to divide (chip) the SiC substrate along the planned division line (expanding process).

  The processing conditions in the damage formation process were selected from two processing conditions 1 and 2 shown in Table 1 according to the processing process. The processing condition 1 is intended to form a shallower damage than the processing condition 2.

(Processing example 1)
In Processing Example 1, the SiC substrate was divided by the procedure shown in FIG. First, pulse laser light was irradiated under the processing condition 2 along four first division planned lines parallel to each other (see FIG. 5A). As a result, deep damage having an apparent width of 45 μm and a depth of 150 μm (100% with respect to the substrate thickness) was formed along the first division line (see FIG. 7A). Next, pulsed laser light was irradiated under the processing condition 1 along four second planned division lines that are orthogonal to the first planned division line and parallel to each other (see FIG. 5B). As a result, shallow damage having an apparent width of 15 μm and a depth of 60 μm (40% with respect to the substrate thickness) was formed along the second division line (see FIG. 7B). Next, the pulse laser beam was irradiated again along the second division planned line under the processing condition 2 (see FIG. 5C). As a result, deep damage having an apparent width of 45 μm and a depth of 150 μm (100% with respect to the substrate thickness) was formed along the second division line (see FIG. 7A). Finally, the dicing tape affixed to the back surface of the SiC substrate was evenly stretched, and the SiC substrate was divided (made into chips) along the planned division line. The “appearance width” in the above description means the width of a line (including damage and debris around the damage) that appears black when the processed substrate is viewed in plan. Therefore, the numerical value of the “appearance width” does not coincide with the damage width in the photographs shown in FIGS. 7A and 7B.

(Processing example 2)
In Processing Example 2, the SiC substrate was divided by the procedure shown in FIG. First, pulsed laser light was irradiated under the processing condition 2 along four first division planned lines parallel to each other (see FIG. 6A). As a result, deep damage having an apparent width of 45 μm and a depth of 150 μm (100% with respect to the substrate thickness) was formed along the first division line (see FIG. 7A). Next, pulsed laser light was irradiated under the processing condition 2 along the four second division lines parallel to each other perpendicular to the first division line (see FIG. 6B). As a result, deep damage having an apparent width of 45 μm and a depth of 150 μm (100% with respect to the substrate thickness) was formed along the second division line (see FIG. 7A). Finally, the dicing tape affixed to the back surface of the SiC substrate was evenly stretched, and the SiC substrate was divided (made into chips) along the planned division line.

  8A is a photograph of the SiC substrate after the expanding step in Processing Example 1. FIG. FIG. 8B is a photograph of the SiC substrate after the expanding step in Processing Example 2. As shown in these photographs, 25 square chips were obtained (expand success rate 100%) in any of the processing examples.

  Further, the presence or absence of cracks in the 25 chips obtained in Processing Example 1 and the 25 chips obtained in Processing Example 2 were examined. FIG. 9A is an enlarged photograph in the vicinity of the intersection of the planned division lines of the SiC substrate divided in the procedure of Processing Example 1. 9B and 9C are enlarged photographs of the vicinity of the intersection of the planned dividing lines of the SiC substrate divided by the procedure of Processing Example 2. FIG. As shown in FIG. 9A, no cracks were observed in the 25 chips obtained in Processing Example 1. On the other hand, as shown in FIGS. 9B and 9C, in 6 chips out of 25 obtained in Processing Example 2, cracks were recognized near the intersections of the planned dividing lines (crack defect rate: 24%, divided). (Maximum reach distance of cracks from the planned line: 100 μm from the second scheduled line in the X-axis direction × 400 μm from the first scheduled line in the Y-axis direction).

  From the above results, it can be seen that by the laser dicing method according to the present invention, the SiC substrate can be divided only by the damage forming step and the expanding step while suppressing the generation of cracks. Similar results can be obtained by using a SiC polycrystalline substrate instead of the SiC single crystal substrate.

[Example 2]
In Example 2, the laser dicing method according to the present invention shows that the sapphire substrate can be divided only by the damage forming step and the expanding step while suppressing the generation of cracks.

  A square sapphire single crystal substrate (length 10 mm × width 10 mm × thickness 85 μm) was prepared as a processing object. In this embodiment, this sapphire substrate is divided into 2 mm intervals in the vertical and horizontal directions to obtain 25 square chips (vertical 2 mm × horizontal 2 mm × thickness 85 μm). In the following description, the planned division line in the horizontal direction (X-axis direction) is defined as a first planned division line, and the planned division line in the vertical direction (Y-axis direction) is defined as a second scheduled division line.

  A sapphire substrate with a dicing tape attached to the back surface is placed on the stage, and a sapphire substrate is irradiated with pulsed laser light (wavelength 355 nm, pulse width 20 nanoseconds, spot diameter 2.2 μm at the focal point) from the surface side of the sapphire substrate. Then, damage from the surface toward the inside was formed in the sapphire substrate (damage formation step). At this time, the stage was moved in the XY axis direction (horizontal direction), and damage was formed along the planned division line of the sapphire substrate. Next, the dicing tape affixed to the back surface of the sapphire substrate was evenly stretched to divide (chip) the sapphire substrate along the planned division line (expanding process).

  The processing conditions in the damage formation process were selected from two processing conditions 3 and 4 shown in Table 2 according to the processing process. Processing condition 3 is intended to form a shallower damage than processing condition 4.

(Processing example 3)
In Processing Example 3, the sapphire substrate was divided by the procedure shown in FIG. First, pulse laser light was irradiated under the processing condition 4 along four first division planned lines parallel to each other (see FIG. 5A). As a result, deep damage having an apparent width of 12 μm and a depth of 85 μm (100% with respect to the substrate thickness) was formed along the first division line (see FIG. 10A). Next, the pulse laser beam was irradiated under the processing condition 3 along the four second division lines parallel to each other perpendicular to the first division line (see FIG. 5B). As a result, shallow damage having an apparent width of 10 μm and a depth of 20 μm (24% with respect to the substrate thickness) was formed along the second division line (see FIG. 10B). Next, the pulse laser beam was irradiated again along the second division planned line under the processing condition 4 (see FIG. 5C). As a result, deep damage having an apparent width of 12 μm and a depth of 85 μm (100% with respect to the substrate thickness) was formed along the second division line (see FIG. 10A). Finally, the dicing tape affixed to the back surface of the sapphire substrate was evenly stretched, and the sapphire substrate was divided (made into chips) along the planned division line.

(Processing example 4)
In Processing Example 4, the sapphire substrate was divided by the procedure shown in FIG. First, pulse laser light was irradiated under the processing condition 4 along four first division planned lines parallel to each other (see FIG. 6A). As a result, deep damage having an apparent width of 12 μm and a depth of 85 μm (100% with respect to the substrate thickness) was formed along the first division line (see FIG. 10A). Next, pulsed laser light was irradiated under the processing condition 4 along four second scheduled division lines that are orthogonal to the first scheduled division line and parallel to each other (see FIG. 6A). As a result, deep damage having an apparent width of 12 μm and a depth of 85 μm (100% with respect to the substrate thickness) was formed along the second division line (see FIG. 10A). Finally, the dicing tape affixed to the back surface of the sapphire substrate was evenly stretched, and the sapphire substrate was divided (made into chips) along the planned division line.

  FIG. 11A is a photograph of the sapphire substrate after the expanding step in Processing Example 3. FIG. 11B is a photograph of the sapphire substrate after the expanding step in Processing Example 4. As shown in these photographs, 25 square chips were obtained (expand success rate 100%) in any of the processing examples.

  Further, the presence or absence of cracks in the 25 chips obtained in Processing Example 3 and the 25 chips obtained in Processing Example 4 were examined. FIG. 12A is an enlarged photograph of the vicinity of the intersection of the planned division lines of the sapphire substrate divided by the procedure of Processing Example 3. FIG. 12B is an enlarged photograph of the vicinity of the intersection of the planned division lines of the sapphire substrate divided by the procedure of Processing Example 4. As shown in FIG. 12A, no cracks were observed in the 25 chips obtained in Processing Example 3. On the other hand, as shown in FIG. 12B, cracks were observed in 9 chips out of 25 chips obtained in Processing Example 4 (crack defect rate: 36%, maximum reach distance of cracks from the division planned line) : 60 μm from the second planned division line in the X-axis direction × 400 μm from the first planned division line in the Y-axis direction).

  From the above results, it can be seen that by the laser dicing method according to the present invention, the sapphire substrate can be divided only by the damage forming step and the expanding step while suppressing the generation of cracks. Similar results can be obtained by using a sapphire polycrystalline substrate instead of the sapphire single crystal substrate.

[Example 3]
Example 3 shows the results of examining the relationship between the depth of damage in shallow processing and the crack generation rate in the laser dicing method according to the present invention.

  The same square SiC single crystal substrate (length 10 mm × width 10 mm × thickness 150 μm) as in Example 1 was prepared as a processing object. This embodiment also aims to obtain 25 square chips by dividing the SiC substrate into a straight line at intervals of 2 mm in each of the vertical and horizontal directions.

(Processing example 5)
By irradiating the SiC substrate with pulsed laser light (wavelength 1064 nm, pulse width 200 nanoseconds, spot diameter 6.2 μm at the focal point) in the same procedure as in Working Example 1 (see FIG. 5) of Example 1, Damage from the surface toward the inside was formed on the SiC substrate (damage formation step). That is, the pulse laser beam was irradiated along the first division planned line under the processing condition 6 (deep processing) shown in Table 3 (see FIG. 5A). Next, pulsed laser light was irradiated along the second division planned line under the processing condition 5 (shallow processing) (see FIG. 5B). In the processing condition 5, the depth of damage to be formed is changed by changing the pulse energy in five stages. Next, the pulse laser beam was irradiated again along the second division line under the processing condition 6 (deep processing) (see FIG. 5C). Finally, the dicing tape affixed to the back surface of the SiC substrate was evenly stretched to divide (chip) the SiC substrate along the planned division line (expanding process).

  FIG. 13A is a photograph of a SiC substrate (after the expanding process) irradiated with pulsed laser light having a pulse energy of 5 μJ under processing condition 5 (shallow processing). FIG. 13B is a photograph of the SiC substrate (after the expansion process) irradiated with a pulse laser beam having a pulse energy of 10 μJ. FIG. 13C is a photograph of the SiC substrate (after the expansion process) irradiated with a pulse laser beam with a pulse energy of 100 μJ. As shown in these photographs, 25 square chips were obtained (expand success rate 100%) in any of the processing examples.

  Moreover, the presence or absence of the generation | occurrence | production of a crack was investigated about 25 chips | tips obtained by each processing example. FIG. 14A is an enlarged photograph of the vicinity of the intersection of the planned division lines of the SiC substrate irradiated with a pulse laser beam having a pulse energy of 5 μJ under the processing condition 5 (shallow processing). FIG. 14B is an enlarged photograph of the vicinity of the intersection of the planned division lines of the SiC substrate irradiated with a pulse laser beam having a pulse energy of 10 μJ. FIG. 14C is an enlarged photograph of the vicinity of the intersection of the lines to be divided of the SiC substrate irradiated with a pulse laser beam having a pulse energy of 100 μJ. As shown in FIGS. 14B and 14C, no cracks were observed when pulsed laser light having a pulse energy of 10 to 100 μJ was applied under the processing condition 5 (shallow processing). On the other hand, as shown in FIG. 14A, when a pulse laser beam with a pulse energy of 5 μJ was irradiated under the processing condition 5, a small number of small cracks were observed near the intersection of the planned division lines (crack defect rate: 8%). .

  Table 4 shows the relationship between the pulse energy of the pulse laser beam irradiated under the processing condition 5 (shallow processing), the size of the formed groove, the expansion success rate, and the crack failure rate.

From the above results, in the laser dicing method according to the present invention, the depth of damage formed in shallow processing is within a range of 5 to 50% with respect to the thickness of the substrate, thereby more reliably generating cracks. It turns out that it can suppress. Further, it can be seen that in shallow processing, the generation of cracks can be more reliably suppressed by setting the peak power density of the pulsed laser light within the range of 1.6 × 10 ⁸ to 1.6 × 10 ⁹ W / cm ^2. .

[Example 4]
Example 4 shows the result of examining the relationship between the depth of damage in deep processing and the expansion success rate in the laser dicing method according to the present invention.

  The same square SiC single crystal substrate (length 10 mm × width 10 mm × thickness 150 μm) as in Example 1 was prepared as a processing object. This embodiment also aims to obtain 25 square chips by dividing the SiC substrate into a straight line at intervals of 2 mm in each of the vertical and horizontal directions.

(Processing example 6)
By irradiating the SiC substrate with pulsed laser light (wavelength 1064 nm, pulse width 200 nanoseconds, spot diameter 6.2 μm at the focal point) in the same procedure as in Working Example 1 (see FIG. 5) of Example 1, Damage from the surface toward the inside was formed on the SiC substrate (damage formation step). That is, the pulse laser beam was irradiated along the first division planned line under the processing condition 8 (deep processing) shown in Table 5 (see FIG. 5A). In the processing condition 8, the depth of damage to be formed is changed by changing the pulse energy in five stages. Next, pulsed laser light was irradiated along the second scheduled division line under the processing condition 7 (shallow processing) (see FIG. 5B). Next, the pulse laser beam was irradiated again along the second division planned line under the processing condition 8 (deep processing) (see FIG. 5C). As described above, in the processing condition 8, the depth of damage to be formed is changed by changing the pulse energy in five stages. Finally, the dicing tape affixed to the back surface of the SiC substrate was evenly stretched to divide (chip) the SiC substrate along the planned division line (expanding process).

  Table 6 shows the relationship between the pulse energy of the pulse laser beam irradiated under the processing condition 8 (deep processing), the size of the formed groove, the expansion success rate, and the crack failure rate.

From the above results, in the laser dicing method according to the present invention, the expansion success rate can be improved more reliably by setting the depth of damage formed in deep processing to 70% or more with respect to the thickness of the substrate. I understand. It can also be seen that the expansion success rate can be improved more reliably by setting the peak power density of the pulse laser beam to 2.0 × 10 ⁹ W / cm ² or more in shallow processing. In this example, even if the depth of damage formed by shallow processing was changed within a range of 10 to 60 μm, the results shown in Table 6 were not changed.

  The laser dicing method according to the present invention can divide a crystal substrate without performing a break process while suppressing the generation of cracks. For example, by using the laser dicing method according to the present invention, it is possible to simplify the manufacturing process of the semiconductor element, reduce the manufacturing cost of the semiconductor element, and the like.

100 Laser beam 110 Crystal substrate 120 Scheduled division line (first division planned line or second planned division line)
120a First scheduled division line 120b Second divided division line 130 Damage 130a Deep damage formed along the first divided division line 130b Shallow damage formed along the second divided division line 130c Along the second divided division line 140 Deep crack 140 Dicing tape 200 Laser processing device 210 Laser light source 220 Telescope optical system 230 Condensing lens 240 Stage 250 AF camera 260 XY stage controller 270 Z controller 280 Computer

Claims (13)

The crystal substrate is irradiated with laser light along a first planned division line and a second planned division line that intersect each other, and the crystal substrate is internally exposed from the surface along the first planned division line and the second planned division line. A damage formation process for forming damage extending to
An expanding step of applying a tensile force to the crystal substrate irradiated with the laser beam;
Including
The damage forming step irradiates the crystal substrate with a laser beam along the first planned division line to form a damage extending from the surface to the inside along the first planned division line. And irradiating the crystal substrate with the laser beam along the second planned division line after the first step, and forming damage extending from the surface to the inside along the second planned division line A second step, and after the second step, the laser beam is again irradiated to the crystal substrate along the second scheduled division line, and the crystal substrate is re- introduced from the surface along the second planned division line. A third step of forming damage extending to
The depth of damage formed in the second step is shallower than the depth of damage formed in the first step and the third step.
The crystal substrate is divided in the damage forming step or the expanding step.
Laser dicing method. The depth of damage formed in the second step is in the range of 5 to 50% of the thickness of the crystal substrate,
The depth of damage formed in the first step and the third step is 70% or more of the thickness of the crystal substrate.
The laser dicing method according to claim 1.   The laser dicing method according to claim 1, wherein the crystal substrate is divided in the damage forming step.   The laser dicing method according to claim 1, wherein the crystal substrate is divided in the expanding step.   The laser dicing as described in any one of Claims 1-4 which does not include the break process which applies a bending force to the said crystal substrate and divides | segments the said crystal substrate between the said damage formation process and the said expand process. Method. The crystal substrate is irradiated with laser light along a first planned division line and a second planned division line that intersect each other, and the crystal substrate is internally exposed from the surface along the first planned division line and the second planned division line. A damage formation process for forming damage extending to
An expanding step of applying a tensile force to the crystal substrate irradiated with the laser beam;
Including
The damage forming step irradiates the crystal substrate with a laser beam along the first planned division line to form a damage extending from the surface to the inside along the first planned division line. And irradiating the crystal substrate with the laser beam along the second planned division line after the first step, and forming damage extending from the surface to the inside along the second planned division line A second step, and after the second step, the laser beam is again irradiated to the crystal substrate along the second scheduled division line, and the crystal substrate is re- introduced from the surface along the second planned division line. A third step of forming damage extending to
In the second step, the condensing point of the laser light is located within a range of 100 μm above the surface of the crystal substrate to the surface of the crystal substrate,
In the first step and the third step, the condensing point of the laser light is located below the surface of the crystal substrate,
The crystal substrate is divided in the damage forming step or the expanding step.
Laser dicing method. The laser beam is a pulsed laser beam,
The peak power density of the laser beam in the second step is in the range of 1.6 × 10 ^{8 to} 1.6 × 10 ⁹ W / cm ² ,
The peak power density of the laser beam in the first step and the third step is 2.0 × 10 ⁹ W / cm ² or more.
The laser dicing method according to claim 6.   The laser dicing method according to claim 6, wherein the crystal substrate is divided in the damage forming step.   The laser dicing method according to claim 6 or 7, wherein the crystal substrate is divided in the expanding step.   The laser dicing according to any one of claims 6 to 9, which does not include a break step of dividing the crystal substrate by applying a bending force to the crystal substrate between the damage forming step and the expanding step. Method.   A chip manufacturing method in which a chip is manufactured by dividing a crystal substrate using the laser dicing method according to claim 1. A laser light source for emitting laser light;
An optical system for irradiating the crystal substrate with the laser beam;
A drive unit that moves at least one of the optical system and the crystal substrate to relatively move the optical system and the crystal substrate;
The crystal substrate is irradiated with a laser beam along a first division planned line and a second division planned line intersecting each other, and the crystal substrate is projected from the surface along the first division planned line and the second planned division line. A laser processing device that forms damage that extends inside ,
A first step of irradiating the crystal substrate along the first planned division line with laser light to form damage extending from the surface to the inside of the crystal substrate along the first planned division line; A second step of irradiating the crystal substrate with laser light along the second scheduled division line after the step to form damage extending from the surface to the inside along the second scheduled division line; After the second step, the crystal substrate is again irradiated with laser light along the second division line, and damage extending from the surface to the inside is formed again on the crystal substrate along the second division line. Forming a damage extending from the surface to the inside of the crystal substrate by a damage forming step including a third step;
The depth of damage formed in the second step is shallower than the depth of damage formed in the first step and the third step.
Laser processing equipment. A laser light source for emitting laser light;
An optical system for irradiating the crystal substrate with the laser beam;
A drive unit that moves at least one of the optical system and the crystal substrate to relatively move the optical system and the crystal substrate;
The crystal substrate is irradiated with a laser beam along a first division planned line and a second division planned line intersecting each other, and the crystal substrate is projected from the surface along the first division planned line and the second planned division line. A laser processing device that forms damage that extends inside ,
A first step of irradiating the crystal substrate along the first planned division line with laser light to form damage extending from the surface to the inside of the crystal substrate along the first planned division line; A second step of irradiating the crystal substrate with laser light along the second scheduled division line after the step to form damage extending from the surface to the inside along the second scheduled division line; After the second step, the crystal substrate is again irradiated with laser light along the second division line, and damage extending from the surface to the inside is formed again on the crystal substrate along the second division line. Forming a damage extending from the surface to the inside of the crystal substrate by a damage forming step including a third step;
In the second step, the condensing point of the laser light is located within a range of 100 μm above the surface of the crystal substrate to the surface of the crystal substrate,
In the first step and the third step, the condensing point of the laser light is located below the surface of the crystal substrate,
Laser processing equipment.