JP5117806B2 - Laser processing method and laser processing apparatus - Google Patents

Description

  The present invention relates to a laser processing method and a laser processing apparatus for cutting a plate-like processing object along a scheduled cutting line.

  As a technique for cutting a plate-like workpiece along a cutting scheduled line, there is a technique called a blade dicing method (see, for example, Patent Document 1). In the blade dicing method, a plate-like workpiece is pasted on an expandable sheet stretched on an annular frame, this is fixed on a mounting table, and the workpiece is placed on a planned cutting line with a cutting blade that rotates at high speed. Cut along. At this time, in order to prevent damage to the frame surrounding the workpiece, the cutting blade is moved relative to the workpiece only in the area inside the frame.

  On the other hand, as a laser processing method for cutting a plate-like workpiece along a scheduled cutting line, the plate-like workpiece is pasted on an expandable sheet stretched on an annular frame, and this is placed on a mounting table By fixing the focusing point with the condensing lens and irradiating the processing laser light inside the processing object, the modified region that is the starting point of cutting is cut along the planned cutting line. (See, for example, Patent Document 2).

In such a laser processing method, unlike the blade dicing method, it is necessary to move the condensing lens relative to the processing target including the region outside the frame. The reason is as follows. That is, in order to irradiate the processing object with the processing laser beam in a state where the relative moving speed of the condensing lens with respect to the processing object is constant, the relative position of the condensing lens with respect to the processing object This is because it is necessary to add an acceleration distance until the relative moving speed becomes constant speed to a long moving distance. Furthermore, for example, by extending the expandable sheet to the periphery, the modified region may be cut along the planned cutting line using the modified region as a starting point of cutting, but in order to achieve reliable cutting, This is because it is necessary to make the frame as small as possible with respect to the workpiece.
JP 2006-13312 A JP 2004-273895 A

  Incidentally, the laser processing method as described above has the following problems. For example, when the laser beam for measurement is condensed by a condensing lens, the amount of reflected light of the laser beam for measurement is detected, and when the amount of light exceeds a predetermined threshold, the modified region is processed. In some cases, the processing laser light is condensed by a condensing lens. At this time, since the condensing lens is moved relative to the object to be processed, including the region outside the frame, a frame having a high reflectance as the object to be processed is erroneously recognized as the object to be processed. The frame may be irradiated with a processing laser beam to damage the frame, and eventually the workpiece may be damaged.

  Therefore, the present invention has been made in view of such circumstances, and in forming a modified region inside a plate-like workpiece attached to an expandable sheet stretched on an annular frame. An object of the present invention is to provide a laser processing method and a laser processing apparatus capable of preventing damage to the frame by irradiating the processing laser beam on the frame.

  In order to achieve the above object, the laser processing method according to the present invention provides a condensing point with a condensing lens inside a plate-like workpiece attached to an expandable sheet stretched on an annular frame. A laser processing method for forming a modified region that is a starting point of cutting inside a processing object along a planned cutting line of the processing object by irradiating a processing laser beam together. And a step of setting a processing region having an outer shape between the frame and the frame, and relatively moving at least one of the condensing lens and the object to be processed along a line including a cutting scheduled line, When the laser beam for measurement is focused on the processing region by the condensing lens and reflected from the laser light irradiation surface of the processing object when positioned on the processing region, By detecting Processing the processing laser light with the condensing lens while adjusting the distance between the laser light irradiating surface and the condensing lens so that the condensing point of the light matches a predetermined position with respect to the laser light irradiating surface And condensing toward the object to form a modified region inside the object to be processed.

  The laser processing method according to the present invention also includes a processing laser beam in which a condensing point is aligned with a condensing lens inside a plate-like processing object attached to an expandable sheet stretched on an annular frame. Is a laser processing method for forming a modified region, which is a starting point of cutting, along the planned cutting line of the processing object inside the processing object, between the processing object and the frame. A step of setting a processing region having an outer shape, and relatively moving at least one of the condensing lens and the object to be processed along a line including a planned cutting line, and the condensing lens is positioned on the processing region; When the laser beam for measurement is condensed toward the processing region by the condensing lens and the reflected light of the laser beam for measurement reflected by the laser light irradiation surface of the workpiece is detected, The focusing point of the processing laser beam is Adjusting the distance between the laser light irradiation surface and the condensing lens so as to match a predetermined position with the light irradiation surface as a reference, obtaining adjustment information regarding the adjustment, and along the line including the planned cutting line When at least one of the condensing lens and the object to be processed is relatively moved, and the condensing lens is positioned on the processing area, the laser light irradiation surface and the condensing lens are adjusted based on the adjustment information. And a step of condensing the processing laser beam toward the object to be processed by the condensing lens while adjusting the distance to the object, and forming a modified region inside the object to be processed. To do.

  In these laser processing methods, at least one of the condensing lens and the processing object is relatively moved along a line including the line to be cut of the processing object, and an outer shape is formed between the processing object and the frame. When the condensing lens is positioned on the processing area, the measurement laser light is condensed toward the processing area by the condensing lens and reflected by the laser light irradiation surface of the workpiece. The reflected light of the laser beam is detected. Then, based on the detection result of the reflected light of the measurement laser light, the laser light irradiation surface and the condensing lens so that the condensing point of the processing laser light is in a predetermined position with respect to the laser light irradiation surface While adjusting the distance, the processing laser light is condensed toward the object to be processed by the condensing lens, and the modified region is formed inside the object to be processed. As described above, in these laser processing methods, when the condensing lens is positioned on the processing region having the outer shape between the workpiece and the frame, the processing laser light is transmitted by the condensing lens. Condensing light toward the object to be processed to form a modified region inside the object to be processed. Therefore, even if the condensing lens including the region outside the frame is moved relative to the object to be processed, the frame is mistakenly recognized as the object to be processed, and the processing laser light is irradiated to the frame. It is possible to prevent the frame from being damaged.

  The modified region is formed by causing multi-photon absorption or other light absorption inside the processing object by irradiating the processing object with a laser beam with a focusing point aligned.

  In the laser processing method according to the present invention, when the condensing lens is positioned on the processing region, the measuring laser light is condensed toward the processing region by the condensing lens and reflected by the processing region. The amount of reflected light of the measured laser beam is detected, and when the amount of light exceeds a predetermined threshold, the focusing point of the processing laser beam is adjusted to a predetermined position with reference to the laser beam irradiation surface It is preferable to adjust the distance between the laser light irradiation surface and the condensing lens. As a result, the modified region can be accurately formed at a predetermined position with reference to the laser light irradiation surface.

  In the laser processing method according to the present invention, when the condensing lens is positioned on the processing region, the measuring laser light is condensed toward the processing region by the condensing lens and reflected by the processing region. The amount of reflected light of the measured laser beam is detected, and when the amount of light exceeds a predetermined threshold, the condensed image of the reflected light of the measuring laser beam to which astigmatism is added is constant. In addition, it is preferable to adjust the distance between the laser light irradiation surface and the condensing lens. Thereby, even if the laser beam irradiation surface of the workpiece has surface deflection, the modified region can be accurately formed at a position at a certain distance from the laser beam irradiation surface.

  In the laser processing method according to the present invention, it is preferable that the object to be processed is cut along the scheduled cutting line with the modified region as the starting point of cutting. As a result, the workpiece can be accurately cut along the scheduled cutting line.

  In the laser processing method according to the present invention, the workpiece may include a semiconductor substrate, and the modified region may include a melt processing region.

  According to the present invention, when the modified region is formed inside the plate-like workpiece attached to the expandable sheet stretched on the annular frame, the frame is irradiated with the processing laser light. Damage can be prevented.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the laser processing method of the present embodiment, a phenomenon called multiphoton absorption is used in order to form a modified region inside the workpiece. Therefore, first, a laser processing method for forming a modified region by multiphoton absorption will be described.

Photon energy hν is smaller than the band gap E _G of absorption of the material becomes transparent. Therefore, a condition under which absorption occurs in the material is hv> E _G. However, even when optically transparent, increasing the intensity of the laser beam very Nhnyu> of _{E G} condition (n = 2,3,4, ···) the intensity of laser light becomes very high. This phenomenon is called multiphoton absorption. In the case of a pulse wave, the intensity of the laser beam is determined by the peak power density (W / cm ² ) at the condensing point of the laser beam. For example, the multiphoton is obtained under conditions where the peak power density is 1 × 10 ⁸ (W / cm ² ) or more. Absorption occurs. The peak power density is determined by (energy per pulse of laser light at the condensing point) / (laser beam cross-sectional area of laser light × pulse width). In the case of a continuous wave, the intensity of the laser beam is determined by the electric field intensity (W / cm ² ) at the condensing point of the laser beam.

  The principle of the laser processing method according to this embodiment using such multiphoton absorption will be described with reference to FIGS. As shown in FIG. 1, there is a planned cutting line 5 for cutting the workpiece 1 on the surface 3 of the wafer-like (plate-like) workpiece 1. The planned cutting line 5 is a virtual line extending linearly. In the laser processing method according to the present embodiment, as shown in FIG. 2, the modified region 7 is formed by irradiating the laser beam L with the focusing point P inside the processing object 1 under the condition that multiphoton absorption occurs. Form. In addition, the condensing point P is a location where the laser light L is condensed. Further, the planned cutting line 5 is not limited to a straight line but may be a curved line, or may be a line actually drawn on the workpiece 1 without being limited to a virtual line.

  Then, the condensing point P is moved along the planned cutting line 5 by relatively moving the laser light L along the planned cutting line 5 (that is, in the direction of arrow A in FIG. 1). Thereby, as shown in FIGS. 3 to 5, the modified region 7 is formed inside the workpiece 1 along the planned cutting line 5, and this modified region 7 becomes the cutting start region 8. Here, the cutting starting point region 8 means a region that becomes a starting point of cutting (cracking) when the workpiece 1 is cut. The cutting starting point region 8 may be formed by continuously forming the modified region 7 or may be formed by intermittently forming the modified region 7.

  In the laser processing method according to the present embodiment, the laser beam L is hardly absorbed by the surface 3 of the workpiece 1, so that the surface 3 of the workpiece 1 is not melted.

  If the cutting start region 8 is formed inside the processing target 1, cracks are likely to occur from the cutting start region 8, so that the processing target 1 is cut with a relatively small force as shown in FIG. 6. be able to. Therefore, the processing object 1 can be cut with high accuracy without causing unnecessary cracks on the surface 3 of the processing object 1.

  The following two types of cutting of the workpiece 1 starting from the cutting start region 8 are conceivable. First, after the cutting start region 8 is formed, when the artificial force is applied to the processing target 1, the processing target 1 is broken starting from the cutting start region 8 and the processing target 1 is cut. It is. This is, for example, cutting when the workpiece 1 is thick. The artificial force is applied by, for example, applying bending stress or shear stress to the workpiece 1 along the cutting start region 8 of the workpiece 1 or giving a temperature difference to the workpiece 1. It is to generate thermal stress. The other one forms the cutting start region 8 so that it is naturally cracked from the cutting start region 8 in the cross-sectional direction (thickness direction) of the processing target 1, and as a result, the processing target 1 is formed. This is the case when it is disconnected. This is possible, for example, when the thickness of the workpiece 1 is small, and the cutting start region 8 is formed by one row of the modified region 7, and when the thickness of the workpiece 1 is large. This is made possible by forming the cutting start region 8 by the modified region 7 formed in a plurality of rows in the thickness direction. Even in the case of natural cracking, cracks do not run on the surface 3 of the portion corresponding to the portion where the cutting start region 8 is not formed in the portion to be cut, and the portion where the cutting start region 8 is formed. Since only the corresponding part can be cleaved, the cleaving can be controlled well. In recent years, since the thickness of the workpiece 1 such as a silicon wafer tends to be thin, such a cleaving method with good controllability is very effective.

  In the laser processing method according to the present embodiment, there are the following cases (1) to (3) as modified regions formed by multiphoton absorption.

(1) In the case where the modified region is a crack region including one or a plurality of cracks, the focusing point is set inside the object to be processed (for example, a piezoelectric material made of glass or LiTaO ₃ ), and the electric field strength at the focusing point is Irradiation with laser light is performed under conditions of 1 × 10 ⁸ (W / cm ² ) or more and a pulse width of 1 μs or less. The magnitude of this pulse width is a condition that allows a crack region to be formed only inside the workpiece without causing extra damage to the surface of the workpiece while causing multiphoton absorption. As a result, a phenomenon of optical damage due to multiphoton absorption occurs inside the workpiece. This optical damage induces thermal strain inside the workpiece, thereby forming a crack region inside the workpiece. The upper limit value of the electric field strength is, for example, 1 × 10 ¹² (W / cm ² ). The pulse width is preferably 1 ns to 200 ns, for example. The formation of the crack region by multiphoton absorption is described in, for example, “Inside of glass substrate by solid-state laser harmonics” on pages 23-28 of the 45th Laser Thermal Processing Research Papers (December 1998) It is described in “Marking”.

  The inventor obtained the relationship between the electric field strength and the size of the cracks by experiment. The experimental conditions are as follows.

(A) Workpiece: Pyrex (registered trademark) glass (thickness 700 μm)
(B) Laser
Light source: Semiconductor laser pumped Nd: YAG laser
Wavelength: 1064nm
Laser light spot cross-sectional area: 3.14 × 10 ⁻⁸ cm ²
Oscillation form: Q switch pulse
Repeat frequency: 100 kHz
Pulse width: 30ns
Output: Output <1mJ / pulse
Laser light quality: TEM ₀₀
Polarization characteristics: Linearly polarized light (C) Condensing lens
Transmittance with respect to laser beam wavelength: 60% (D) Moving speed of mounting table on which workpiece is mounted: 100 mm / second

Note that the laser light quality TEM ₀₀ means that the light condensing performance is high and the light can be condensed up to the wavelength of the laser light.

FIG. 7 is a graph showing the results of the experiment. The horizontal axis represents the peak power density. Since the laser beam is a pulsed laser beam, the electric field strength is represented by the peak power density. The vertical axis represents the size of a crack portion (crack spot) formed inside the workpiece by one pulse of laser light. Crack spots gather to form a crack region. The size of the crack spot is the size of the portion having the maximum length in the shape of the crack spot. Data indicated by black circles in the graph is for the case where the magnification of the condenser lens (C) is 100 times and the numerical aperture (NA) is 0.80. On the other hand, the data indicated by the white circles in the graph is when the magnification of the condenser lens (C) is 50 times and the numerical aperture (NA) is 0.55. From the peak power density of about 10 ¹¹ (W / cm ² ), it can be seen that a crack spot is generated inside the workpiece, and the crack spot increases as the peak power density increases.

  Next, the mechanism of cutting the workpiece by forming the crack region will be described with reference to FIGS. As shown in FIG. 8, under the condition that multiphoton absorption occurs, the converging point P is aligned with the inside of the workpiece 1 and the laser beam L is irradiated to form a crack region 9 along the planned cutting line. The crack region 9 is a region including one or more cracks. The crack region 9 thus formed becomes a cutting start region. As shown in FIG. 9, the crack further grows from the crack region 9 (that is, from the cutting start region), and the crack is formed on the front surface 3 and the back surface 21 of the workpiece 1 as shown in FIG. 10. As shown in FIG. 11, the workpiece 1 is broken and the workpiece 1 is cut. A crack that reaches the front surface 3 and the back surface 21 of the workpiece 1 may grow naturally, or may grow when a force is applied to the workpiece 1.

(2) When the reforming region is a melt processing region The focusing point is set inside the object to be processed (for example, a semiconductor material such as silicon), and the electric field strength at the focusing point is 1 × 10 ⁸ (W / cm ^2). ) Irradiation with laser light is performed under the above conditions with a pulse width of 1 μs or less. As a result, the inside of the workpiece is locally heated by multiphoton absorption. By this heating, a melt processing region is formed inside the workpiece. The melt treatment region is a region once solidified after melting, a region in a molten state, or a region re-solidified from a molten state, and can also be referred to as a phase-changed region or a region in which the crystal structure has changed. The melt treatment region can also be said to be a region in which one structure is changed to another structure in a single crystal structure, an amorphous structure, or a polycrystalline structure. In other words, for example, a region changed from a single crystal structure to an amorphous structure, a region changed from a single crystal structure to a polycrystalline structure, or a region changed from a single crystal structure to a structure including an amorphous structure and a polycrystalline structure. To do. When the object to be processed has a silicon single crystal structure, the melt processing region has, for example, an amorphous silicon structure. The upper limit value of the electric field strength is, for example, 1 × 10 ¹² (W / cm ² ). The pulse width is preferably 1 ns to 200 ns, for example.

  The inventor has confirmed through experiments that a melt-processed region is formed inside a silicon wafer. The experimental conditions are as follows.

(A) Workpiece: silicon wafer (thickness 350 μm, outer diameter 4 inches)
(B) Laser
Light source: Semiconductor laser pumped Nd: YAG laser
Wavelength: 1064nm
Laser light spot cross-sectional area: 3.14 × 10 ⁻⁸ cm ²
Oscillation form: Q switch pulse
Repeat frequency: 100 kHz
Pulse width: 30ns
Output: 20μJ / pulse
Laser light quality: TEM ₀₀
Polarization characteristics: Linearly polarized light (C) Condensing lens
Magnification: 50 times
N. A. : 0.55
Transmittance with respect to laser beam wavelength: 60% (D) Moving speed of mounting table on which workpiece is mounted: 100 mm / second

  FIG. 12 is a view showing a photograph of a cross section of a part of a silicon wafer cut by laser processing under the above conditions. A melt processing region 13 is formed inside the silicon wafer 11. The size in the thickness direction of the melt processing region 13 formed under the above conditions is about 100 μm.

  The fact that the melt processing region 13 is formed by multiphoton absorption will be described. FIG. 13 is a graph showing the relationship between the wavelength of the laser beam and the transmittance inside the silicon substrate. However, the reflection components on the front side and the back side of the silicon substrate are removed to show the transmittance only inside. The above relationship was shown for each of the thickness t of the silicon substrate of 50 μm, 100 μm, 200 μm, 500 μm, and 1000 μm.

  For example, when the thickness of the silicon substrate is 500 μm or less at the wavelength of the Nd: YAG laser of 1064 nm, it can be seen that the laser light is transmitted by 80% or more inside the silicon substrate. Since the thickness of the silicon wafer 11 shown in FIG. 12 is 350 μm, the melt processing region 13 by multiphoton absorption is formed near the center of the silicon wafer 11, that is, at a portion of 175 μm from the surface. In this case, the transmittance is 90% or more with reference to a silicon wafer having a thickness of 200 μm. Therefore, the laser beam is hardly absorbed inside the silicon wafer 11 and almost all is transmitted. This is not because the laser beam is absorbed inside the silicon wafer 11 and the melt processing region 13 is formed inside the silicon wafer 11 (that is, the melt processing region is formed by normal heating with laser light) It means that the melt processing region 13 is formed by multiphoton absorption. The formation of the melt-processed region by multiphoton absorption is described in, for example, “Evaluation of processing characteristics of silicon by picosecond pulse laser” on pages 72 to 73 of the 66th Annual Meeting of the Japan Welding Society (April 2000). Have been described.

  Note that a silicon wafer is cracked as a result of generating cracks in the cross-sectional direction starting from the cutting start region formed by the melt processing region and reaching the front and back surfaces of the silicon wafer. The The cracks that reach the front and back surfaces of the silicon wafer may grow naturally or may grow by applying force to the silicon wafer. And when a crack naturally grows from the cutting start region to the front and back surfaces of the silicon wafer, the case where the crack grows from a state where the melt treatment region forming the cutting starting region is melted, and the cutting starting region There are both cases where cracks grow when the solidified region is melted from the molten state. However, in either case, the melt processing region is formed only inside the silicon wafer, and the melt processing region is formed only inside the cut surface after cutting as shown in FIG. In this way, when the cutting start region is formed by the melt processing region inside the workpiece, unnecessary cracking off the cutting start region line is unlikely to occur during cleaving, so that cleaving control is facilitated. Incidentally, the formation of the melted region is not only caused by multiphoton absorption, but may also be caused by other absorption effects.

(3) When the modified region is a refractive index changing region The focusing point is set inside the object to be processed (for example, glass), and the electric field intensity at the focusing point is 1 × 10 ⁸ (W / cm ² ) or more. Laser light is irradiated under the condition that the pulse width is 1 ns or less. When the pulse width is made extremely short and multiphoton absorption occurs inside the workpiece, the energy due to the multiphoton absorption is not converted into thermal energy, and the ion valence change and crystallization occur inside the workpiece. Alternatively, a permanent structural change such as polarization orientation is induced to form a refractive index change region. The upper limit value of the electric field strength is, for example, 1 × 10 ¹² (W / cm ² ). For example, the pulse width is preferably 1 ns or less, and more preferably 1 ps or less. The formation of the refractive index changing region by multiphoton absorption is described in, for example, “The Femtosecond Laser Irradiation to the Inside of Glass” on pages 105 to 111 of the 42nd Laser Thermal Processing Research Institute Proceedings (November 1997). Photo-induced structure formation ”.

  As described above, the cases of (1) to (3) have been described as the modified regions formed by multiphoton absorption. However, considering the crystal structure of the wafer-like workpiece and its cleavage property, the cutting origin region is described below. If it forms in this way, it will become possible to cut | disconnect a process target object with much smaller force from the cutting | disconnection starting point area | region as a starting point, and still more accurately.

That is, in the case of a substrate made of a single crystal semiconductor having a diamond structure such as silicon, the cutting start region is formed in a direction along the (111) plane (first cleavage plane) or the (110) plane (second cleavage plane). Is preferred. In the case of a substrate made of a zinc-blende-type III-V group compound semiconductor such as GaAs, it is preferable to form the cutting start region in the direction along the (110) plane. Further, in the case of a substrate having a hexagonal crystal structure such as sapphire (Al ₂ O ₃ ), the (1120) plane (A plane) or (1100) plane ( It is preferable to form the cutting start region in a direction along the (M plane).

  Note that the orientation flat is formed on the substrate along the direction in which the above-described cutting start region is to be formed (for example, the direction along the (111) plane in the single crystal silicon substrate) or the direction perpendicular to the direction in which the cutting start region is to be formed. By using the orientation flat as a reference, it is possible to easily and accurately form the cutting start area along the direction in which the cutting start area is to be formed on the substrate.

  Next, a preferred embodiment of the present invention will be described.

  As shown in FIGS. 14 and 15, a workpiece 1 includes a functional element layer formed on a surface 11 a of a silicon wafer 11 including a silicon wafer (semiconductor substrate) 11 having a thickness of 100 μm and a plurality of functional elements 15. 16. The functional element 15 is, for example, a semiconductor operation layer formed by crystal growth, a light receiving element such as a photodiode, a light emitting element such as a laser diode, or a circuit element formed as a circuit, and the orientation flat 6 of the silicon wafer 11. Are formed in a matrix form in a direction parallel to and perpendicular to.

  The workpiece 1 configured as described above is cut for each functional element 15 as follows. First, as shown in FIG. 16, the back surface 21 of the workpiece 1 is pasted on an expanding tape (expandable sheet) 23 stretched on an annular frame 22. Then, the surface 22 of the workpiece 1 is directed upward, and the frame 22 and the expanded tape 23 holding the workpiece 1 are fixed on the mounting table 101 of the laser processing apparatus 100. Subsequently, the cutting lines 5 are set in a lattice shape so as to pass between the adjacent functional elements 15 (see FIG. 14). Then, using the surface 3 of the workpiece 1 as a laser beam incident surface, the processing laser beam L1 is irradiated with the focusing point P inside the silicon wafer 11, and the melting process is performed along each scheduled cutting line 5. Region 13 is formed inside silicon wafer 11. Subsequently, the frame 22 holding the workpiece 1 and the expanded tape 23 are attached to an expanded tape expansion device (not shown), and the expanded tape 23 is expanded to the surroundings, so that the melting region 13 is the starting point of cutting. The workpiece 1 is cut along the scheduled cutting line 5 and a large number of semiconductor chips obtained by the cutting are separated from each other. As described above, the workpiece 1 can be accurately cut along the scheduled cutting line 5. Note that cracks may be mixed in the melt processing region 13.

  Here, the laser processing apparatus 100 will be described. As shown in FIG. 16, the laser processing apparatus 100 includes a mounting table 101 on which the workpiece 1 is mounted horizontally, a laser unit 102, and a movement control unit connected to each of the mounting table 101 and the laser unit 102. 103. The movement control unit 103 moves the mounting table 101 in the horizontal direction (X-axis direction and Y-axis direction) and moves the laser unit 102 in the vertical direction (Z-axis direction).

  The laser unit 102 includes a processing laser light source 104 that pulsates the processing laser light L1. The processing laser light L1 emitted from the processing laser light source 104 sequentially passes through a shutter 105 that selectively passes and blocks the processing laser light L1 and a beam expander 106 that expands the beam size, and is then dichroic. After passing through the mirror 107, the light is condensed by the condensing lens 108 and irradiated onto the workpiece 1. Note that a piezo element 109 for finely adjusting the position in the Z-axis direction is attached to the condensing lens 108.

  Further, the laser unit 102 includes a measurement laser light source 111 that emits measurement laser light L2 for irradiating a processing region 30 described later. The measurement laser light L2 emitted from the measurement laser light source 111 is sequentially reflected by the mirror 112, the half mirror 113, and the dichroic mirror 107, and travels downward on the optical axis of the processing laser light L1. Then, the light is condensed by the condensing lens 108 and irradiated to the processing region 30.

  The measurement laser light L2 irradiated to the processing region 30 is reflected by the processing region 30, and the reflected light L3 of the measurement laser light is incident again on the condensing lens 108 and the optical axis of the processing laser light L1. After traveling upward, it is reflected by the dichroic mirror 107 and passes through the half mirror 113. The reflected light L3 of the measurement laser light transmitted through the half mirror 113 is added with astigmatism by a shaping optical system 114 including a cylindrical lens and a plano-convex lens, and is divided into four equal parts. The light is condensed on the light receiving surface 115. As described above, a condensed image of the reflected light L3 of the measurement laser beam to which astigmatism is added is formed on the light receiving surface of the four-divided photodiode 115. It changes with the position of the condensing point of the laser beam L2 for measurement with respect to the surface (laser beam irradiation surface) 3 of the workpiece 1 located in the position.

  A condensing lens control unit 116 connected to the piezo element 109 is connected to the quadrant photodiode 115. The condensing lens control unit 116 detects the light amount of the reflected light L3 of the measurement laser light reflected by the processing region 30, and when the light amount exceeds a predetermined threshold, the light received by the quadrant photodiode 115 is received. The condensed image formed on the surface is acquired as a voltage value, and the piezo element 109 is driven so that the voltage value becomes constant (that is, the condensed image becomes constant), so that the workpiece 1 is processed. The distance between the front surface 3 and the condensing lens 108 is adjusted to be substantially constant, and the drive signal of the piezo element 109 at that time is recorded.

  The formation of the melt processing region 13 by the laser processing apparatus 100 configured as described above will be described in more detail.

  First, as shown in FIG. 17, the back surface 21 of the workpiece 1 is pasted on an expanding tape 23 stretched around an annular frame 22. Then, the surface 22 of the workpiece 1 is directed upward, and the frame 22 and the expanded tape 23 holding the workpiece 1 are fixed on the mounting table 101 of the laser processing apparatus 100. Subsequently, as shown in FIG. 18, the cutting scheduled lines 5 are set in a lattice shape so as to pass between the adjacent functional elements 15, 15, and the processing target is based on at least one of the processing target 1 and the frame 22. A machining region 30 having an outer diameter larger than the outer diameter of the object 1 and smaller than the inner diameter of the frame 22 is set. That is, the processing region 30 has an outer shape between the processing object 1 and the frame 22.

  Subsequently, as shown in FIG. 19, the coordinates of the intersection point between each line 50 including the planned cutting line 5 parallel to the orientation flat 6 and the outer shape of the processing region 30 are acquired. In addition, when forming the melting process area | region 13 along the scheduled cutting line 5 perpendicular | vertical to the orientation flat 6, it is the same as the case where the melting process area 13 is formed along the scheduled cutting line 5 parallel to the orientation flat 6. Therefore, the description thereof is omitted below.

  Subsequently, as shown in FIG. 20, by moving the mounting table 101 in the direction in which the planned cutting line 5 parallel to the orientation flat 6 extends, the condensing lens 108 is moved to the processing object 1 by the arrow B. Move relative to the direction. At this time, the condensing lens 108 is moved relative to the workpiece 1 including the region outside the frame 22 for the following reason. That is, in order to irradiate the processing target object 1 with the processing laser beam L1 in a state where the relative moving speed of the condensing lens 108 with respect to the processing target object 1 is constant, the condensing of the processing target object 1 is focused. This is because it is necessary to add an acceleration distance until the relative moving speed becomes equal to the relative moving distance of the lens 108 for use. Further, by expanding the expanding tape 23 to the periphery, in order to reliably cut the workpiece 1 along the scheduled cutting line 5 with the melt processing region 13 as a starting point of cutting, a frame is attached to the workpiece 1. This is because it is necessary to make 22 as small as possible.

  When the condensing lens 108 reaches one intersection α1 between the line 50 including the planned cutting line 5 and the outer shape of the processing region 30 due to the relative movement of the condensing lens 108 with respect to the workpiece 1, FIG. As shown in (a), the control signal of the measurement laser light source 111 is changed from “OFF” to “ON”, and the measurement laser light L2 is emitted from the measurement laser light source 111 and condensed by the condensing lens 108. The At this time, the measurement laser beam L2 is reflected by the expanded tape 23. Since the expanded tape 23 has a lower reflectance than the surface 3 of the workpiece 1, the measurement laser beam L2 is measured as shown in FIG. The amount of reflected light L3 of the laser beam for use does not reach the threshold value T. At this time, as shown in FIG. 20C, the drive signal of the piezo element 109 is “OFF”, and the condensing lens 108 is held at a predetermined position.

  Subsequently, when the condensing lens 108 reaches one intersection β1 between the line 50 including the planned cutting line 5 and the outer edge of the workpiece 1, the measurement laser beam L2 is reflected by the surface 3 of the workpiece 1 Therefore, as shown in FIG. 20B, the amount of the reflected light L3 of the measurement laser light exceeds the threshold T. As a result, as shown in FIG. 20C, the driving signal of the piezo element 109 is changed from “OFF” to “ON”, and the reflected light L3 of the measurement laser beam is formed on the light receiving surface of the four-division photodiode 115. The piezo element 109 is driven so that the voltage value based on the optical image is constant, and the distance between the surface 3 of the workpiece 1 and the condensing lens 108 is adjusted to be substantially constant.

  At the same time, as shown in FIG. 20D, the control signal of the shutter 105 is changed from “OFF” to “ON”, and the processing laser light L 1 emitted from the processing laser light source 104 passes through the shutter 105 and is condensed. The light is collected by the lens 108 for use. As a result, even if the surface 3 of the workpiece 1 has runout, it melts along the planned cutting line 5 to a position at a certain distance from the surface 3 of the workpiece 1 (inside the silicon wafer 11). The processing region 13 can be formed with high accuracy. The timing at which the control signal of the shutter 105 is changed from “OFF” to “ON” and the processing laser beam L1 is applied to the object 1 is changed from “OFF” to “ON”. The timing may be substantially the same as or a little later than that timing.

  Subsequently, when the condensing lens 108 reaches the other intersection β2 between the line 50 including the planned cutting line 5 and the outer edge of the workpiece 1, the measurement laser beam L2 is reflected by the expanded tape 23. As shown in FIG. 20B, the amount of reflected light L3 of the measurement laser light is below the threshold T. As a result, as shown in FIG. 20C, the drive signal of the piezo element 109 is changed from “ON” to “OFF”, and the condensing lens 108 is held at a predetermined position. At the same time, as shown in FIG. 20D, the control signal of the shutter 105 is changed from “ON” to “OFF”, and the processing laser light L1 emitted from the processing laser light source 104 is blocked.

  Subsequently, when the condensing lens 108 reaches the other intersection α2 of the line 50 including the planned cutting line 5 and the outer shape of the processing region 30, as shown in FIG. The control signal is changed from “ON” to “OFF”, and the emission of the measurement laser light L2 from the measurement laser light source 111 is stopped.

  As described above, in the laser processing method of the present embodiment, the condensing lens 108 is moved relative to the processing object 1 along the line 50 including the scheduled cutting line 5 of the processing object 1. When the condensing lens 108 is positioned on the processing region 30 having an outer shape between the workpiece 1 and the frame 22, the measuring laser beam L 2 is directed to the processing region 30 by the condensing lens 108. And the reflected light L3 of the measurement laser light reflected by the surface 3 of the workpiece 1 is detected. By detecting the reflected light L3 of the laser beam for measurement, the surface 3 of the processing object 1 and the focusing point P of the processing laser light L1 are positioned at a certain distance from the surface 3 of the processing object 1. While adjusting the distance from the condensing lens 108 to be substantially constant, the processing laser light L1 is condensed toward the processing object 1 by the condensing lens 108, and the melting processing region 13 of the processing object 1 is focused. Form inside. Thus, in the laser processing method of the present embodiment, when the condensing lens 108 is positioned on the processing region 30 having the outer shape between the processing target 1 and the frame 22, the processing laser light L1. Is condensed toward the processing object 1 by the condensing lens 108, and the melting treatment region 13 is formed inside the processing object 1. Therefore, even if the condensing lens 108 is moved relative to the workpiece 1 including the region outside the frame 22, the frame 22 is erroneously recognized as the workpiece, and the processing laser is applied to the frame 22. It is possible to prevent the frame 22 from being damaged by irradiating the light L1.

  The present invention is not limited to the above embodiment.

  For example, when relatively moving at least one of the condensing lens 108 and the workpiece 1 along the line 50 that crosses the frame 22, the measurement laser beam L2 is irradiated as follows. You may implement control in the laser processing apparatus 100. FIG. That is, the distance between the surface 3 of the workpiece 1 and the condensing lens 108 is adjusted until the condensing lens 108 reaches one intersection α1 between the line 50 and the outer shape of the processing region 30 from one side. Calculation processing based on the amount of reflected light L3 of the measurement laser light (hereinafter referred to as “autofocus calculation processing”) is stopped, and the condensing lens 108 is placed at a fixed position in the thickness direction of the workpiece 1. Fix and stop irradiation of the processing laser beam L1. Then, autofocus calculation processing is performed until the condensing lens 108 reaches one intersection point β1 between the line 50 and the outer edge of the workpiece 1 from above one intersection point α1, and the thickness direction of the workpiece 1 is determined. , The condenser lens 108 is fixed at a fixed position, and the irradiation of the processing laser beam L1 is stopped. Here, even when the autofocus calculation process is performed, the condensing lens 108 is fixed at a fixed position in the thickness direction of the workpiece 1 because the amount of the reflected light L3 of the measurement laser light is predetermined. This is because the threshold value is not exceeded. Then, autofocus calculation processing is performed until the condensing lens 108 reaches the other intersection β2 between the line 50 and the outer edge of the workpiece 1 from the one intersection β1, and the surface 3 of the workpiece 1 is The distance to the condensing lens 108 is adjusted, and the processing laser beam L1 is irradiated.

  In addition, after setting the processing region 30 having the outer shape between the processing object 1 and the frame 22, the melt processing region 13 may be formed inside the processing object 1 as follows.

  That is, first, the condensing lens 108 is moved relative to the workpiece 1 along the line 50 including the planned cutting line 5, and the condensing lens 108 is positioned on the processing region 30. At this time, the measurement laser beam L2 is condensed toward the processing region 30 by the condensing lens 108, and the reflected light L3 of the measurement laser beam reflected by the surface 3 of the workpiece 1 is detected. The piezo element 109 is driven so that the condensing point P of the processing laser light L1 is positioned at a certain distance from the surface 3 of the processing object 1, and the surface 3 of the processing object 1 and the condensing lens are driven. The distance between the piezoelectric element 109 and the drive signal (adjustment information) of the piezo element 109 is recorded.

  Subsequently, when the condensing lens 108 is moved relative to the workpiece 1 along the line 50 including the planned cutting line 5, and the condensing lens 108 is positioned on the processing region 30. Then, the recorded drive signal is reproduced to drive the piezo element 109, and the processing laser beam L1 is collected while the distance between the surface 3 of the workpiece 1 and the focusing lens 108 is adjusted to be substantially constant. The lens 108 is focused toward the workpiece 1 to form the melt processing region 13 inside the workpiece 1. The timing at which the control signal of the shutter 105 is changed from “OFF” to “ON” and the processing laser beam L1 is applied to the object 1 is changed from “OFF” to “ON”. The timing may be substantially the same as or a little earlier than that timing.

  The formation of the melt processing region 13 as described above is such that the workpiece 1 is relatively thick and a plurality of rows of the melt processing regions 13 are arranged in the thickness direction of the workpiece 1 with respect to one cutting scheduled line. It is effective when forming.

  Further, in the above embodiment, the surface 3 of the processing object 1 and the condensing lens 108 are arranged so that the condensing point P of the processing laser light L1 is at a certain distance from the surface 3 of the processing object 1. The surface 3 of the processing object 1 and the condensing lens 108 are adjusted so that the condensing point P of the processing laser light L1 matches a predetermined position with respect to the surface 3 of the processing object 1. The distance may be adjusted. In this case, it is possible to accurately form the melt processing region 13 at a predetermined position with respect to the surface 3 of the processing object 1, and the melting processing region 13 and the wavy line in which the distance from the surface 3 of the processing object 1 changes midway. It becomes possible to form the melt processing region 13 and the like in the shape of the cutting line 5.

  Moreover, in the said embodiment, although the reflected light L3 of the laser beam for a measurement reflected on the surface 3 of the process target object 1 was detected, it reflected on other laser beam irradiation surfaces, such as the back surface 21 of the process target object 1. The reflected light L3 of the measurement laser beam may be detected.

  Moreover, in the said embodiment, although the fusion | melting process area | region 13 was formed in the inside of the silicon wafer 11 of the workpiece 1, a crack area | region and a refractive index change area | region are formed in the wafer which consists of other materials, such as glass and a piezoelectric material. For example, other modified regions may be formed.

It is a top view of the processing target object during laser processing by the laser processing method concerning this embodiment. It is sectional drawing along the II-II line of the workpiece shown in FIG. It is a top view of the processing target after laser processing by the laser processing method concerning this embodiment. It is sectional drawing along the IV-IV line of the workpiece shown in FIG. It is sectional drawing along the VV line of the workpiece shown in FIG. It is a top view of the processed object cut | disconnected by the laser processing method which concerns on this embodiment. It is a graph which shows the relationship between the peak power density and the magnitude | size of a crack spot in the laser processing method which concerns on this embodiment. It is sectional drawing of the process target object in the 1st process of the laser processing method which concerns on this embodiment. It is sectional drawing of the process target object in the 2nd process of the laser processing method which concerns on this embodiment. It is sectional drawing of the process target object in the 3rd process of the laser processing method which concerns on this embodiment. It is sectional drawing of the process target object in the 4th process of the laser processing method which concerns on this embodiment. It is a figure showing the photograph of the section in the part of silicon wafer cut by the laser processing method concerning this embodiment. It is a graph which shows the relationship between the wavelength of the laser beam and the internal transmittance | permeability of a silicon substrate in the laser processing method which concerns on this embodiment. It is a top view of the processing target used as the object of the laser processing method of this embodiment. It is a fragmentary sectional view along the XV-XV line shown in FIG. It is a block diagram of the laser processing apparatus with which the laser processing method of this embodiment is implemented. It is explanatory drawing of the laser processing method of this embodiment. It is explanatory drawing of the laser processing method of this embodiment following FIG. It is explanatory drawing of the laser processing method of this embodiment following FIG. It is explanatory drawing of the laser processing method of this embodiment following FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Processing object, 3 ... Surface (laser beam incident surface), 5 ... Planned cutting line, 11 ... Silicon wafer (semiconductor substrate), 13 ... Melting process area | region (modification area | region), 22 ... Frame, 23 ... Expanding tape (Expandable sheet), 50 ... line, 108 ... condensing lens, L1 ... processing laser beam, L2 ... measuring laser beam, L3 ... reflected light of measuring laser beam, P ... condensing point.

Claims (17)

By irradiating a processing laser beam with a condensing point aligned with a condensing lens inside a plate-like processing object attached to an expandable sheet stretched on an annular frame, the processing object A laser processing method for forming a modified region that is a starting point of cutting along the planned cutting line inside the workpiece,
Setting a processing region having an outer shape between the processing object and the frame;
Measurement is performed when at least one of the condensing lens and the object to be processed is relatively moved along a line including the planned cutting line, and the condensing lens is positioned on the processing region. The processing laser beam is condensed toward the processing region by the condensing lens and the reflected light of the measurement laser beam reflected by the laser light irradiation surface of the processing object is detected, thereby the processing Adjusting the distance between the laser light irradiation surface and the condensing lens so that the condensing point of the laser light is aligned with a predetermined position with respect to the laser light irradiation surface. And a step of condensing light toward the object to be processed by a condensing lens, and forming the modified region inside the object to be processed. By irradiating a processing laser beam with a condensing point aligned with a condensing lens inside a plate-like processing object attached to an expandable sheet stretched on an annular frame, the processing object A laser processing method for forming a modified region that is a starting point of cutting along the planned cutting line inside the workpiece,
Setting a processing region having an outer shape between the processing object and the frame;
Measurement is performed when at least one of the condensing lens and the object to be processed is relatively moved along a line including the planned cutting line, and the condensing lens is positioned on the processing region. The processing laser beam is condensed toward the processing region by the condensing lens and the reflected light of the measurement laser beam reflected by the laser light irradiation surface of the processing object is detected, thereby the processing The distance between the laser light irradiation surface and the condensing lens is adjusted so that the condensing point of the laser light is aligned with a predetermined position with reference to the laser light irradiation surface, and adjustment information relating to the adjustment is acquired. Process,
When at least one of the condensing lens and the object to be processed is relatively moved along a line including the planned cutting line, and when the condensing lens is positioned on the processing region, Based on the adjustment information, while adjusting the distance between the laser light irradiation surface and the condensing lens, the processing laser light is condensed toward the processing object by the condensing lens, Forming a modified region inside the object to be processed.   When the condensing lens is positioned on the processing region, the measurement laser light is condensed toward the processing region by the condensing lens and reflected by the processing region. When the amount of reflected light of the processing laser beam is detected and the amount of light exceeds a predetermined threshold, the focusing point of the processing laser beam is adjusted to a predetermined position with reference to the laser light irradiation surface The laser processing method according to claim 1, wherein a distance between the laser light irradiation surface and the condensing lens is adjusted.   When the condensing lens is positioned on the processing region, the measurement laser light is condensed toward the processing region by the condensing lens and reflected by the processing region. When the amount of reflected light of the measuring laser beam is detected and the amount of light exceeds a predetermined threshold value, the condensed image of the reflected light of the measuring laser beam to which astigmatism is added is constant. The laser processing method according to claim 1, wherein a distance between the laser light irradiation surface and the condensing lens is adjusted.   The laser processing method according to claim 1, wherein the workpiece is cut along the scheduled cutting line with the modified region as a starting point of cutting.   The laser processing method according to claim 1, wherein the object to be processed includes a semiconductor substrate, and the modified region includes a melt processing region. Relatively moving at least one of the condenser lens and the object to be processed along the line crossing the frame;
The measurement for adjusting the distance between the laser light irradiation surface and the condensing lens until the condensing lens reaches one intersection of the line and the outer shape of the processing region from one side Stop arithmetic processing based on the amount of reflected light of the laser light, fix the condensing lens at a fixed position in the thickness direction of the workpiece, and stop the irradiation of the processing laser light,
The amount of reflected light of the laser beam for measurement from one intersection point of the line and the outer shape of the processing area until the condensing lens reaches one intersection point of the line and the outer edge of the workpiece The calculation processing based on is performed, the condenser lens is fixed at a fixed position in the thickness direction of the workpiece, and the irradiation of the processing laser beam is stopped,
Until the condensing lens reaches the intersection of the line and the outer edge of the object to be processed from one intersection of the line and the outer edge of the object to be processed, The calculation processing based on the light quantity is performed, the distance between the laser light irradiation surface and the condensing lens is adjusted, and the processing laser light irradiation is performed. A laser processing method according to claim 1. By aligning a condensing point inside the plate-like object to be processed and irradiating a processing laser beam, a modified region that becomes a starting point of cutting along the scheduled cutting line of the object to be processed is defined as the object to be processed. A laser processing apparatus to be formed inside,
A mounting table on which the processing object pasted on an expandable sheet stretched on an annular frame is mounted;
A processing laser light source for emitting the processing laser light, and a laser unit having a measurement laser light source for emitting the measurement laser light;
A condensing lens for condensing the processing laser light and the measurement laser light,
Set a machining area having an outer shape between the workpiece and the frame;
Acquire the coordinates of one intersection and the other intersection of the line including the planned cutting line and the outer shape of the processing region,
The at least one of the condensing lens and the object to be processed is relatively moved along the line, and after the condensing lens reaches the one intersection, the condensing is performed on the other intersection. Until the lens for reaching, when the condensing lens is located on the processing region, the measurement laser light is condensed toward the processing region by the condensing lens, By detecting the reflected light of the measurement laser light reflected by the laser light irradiation surface of the workpiece, the focusing point of the processing laser light is aligned with a predetermined position with respect to the laser light irradiation surface. As described above, while adjusting the distance between the laser light irradiation surface and the condensing lens, the processing laser light is condensed toward the object to be processed by the condensing lens, and the modified region Is formed inside the workpiece. The laser processing apparatus according to claim.   When the condensing lens is positioned on the processing region, the measurement laser light is condensed toward the processing region by the condensing lens and reflected by the processing region. When the amount of reflected light of the processing laser beam is detected and the amount of light exceeds a predetermined threshold, the focusing point of the processing laser beam is adjusted to a predetermined position with reference to the laser light irradiation surface The laser processing apparatus according to claim 8, wherein a distance between the laser light irradiation surface and the condensing lens is adjusted.   When the condensing lens is positioned on the processing region, the measurement laser light is condensed toward the processing region by the condensing lens and reflected by the processing region. When the amount of reflected light of the measuring laser beam is detected and the amount of light exceeds a predetermined threshold value, the condensed image of the reflected light of the measuring laser beam to which astigmatism is added is constant. The laser processing apparatus according to claim 8, wherein a distance between the laser light irradiation surface and the condensing lens is adjusted. Relatively moving at least one of the condenser lens and the object to be processed along the line crossing the frame;
The measurement for adjusting the distance between the laser light irradiation surface and the condensing lens until the condensing lens reaches one intersection of the line and the outer shape of the processing region from one side Stop arithmetic processing based on the amount of reflected light of the laser light, fix the condensing lens at a fixed position in the thickness direction of the workpiece, and stop the irradiation of the processing laser light,
The amount of reflected light of the laser beam for measurement from one intersection point of the line and the outer shape of the processing area until the condensing lens reaches one intersection point of the line and the outer edge of the workpiece The calculation processing based on is performed, the condenser lens is fixed at a fixed position in the thickness direction of the workpiece, and the irradiation of the processing laser beam is stopped,
From when the condensing lens reaches one intersection of the line and the outer edge of the object to be processed, until the condensing lens reaches the other intersection of the line and the outer edge of the object to be processed In the meantime, arithmetic processing based on the amount of reflected light of the measurement laser light is performed, the distance between the laser light irradiation surface and the condenser lens is adjusted, and the processing laser light is irradiated. The laser processing apparatus according to any one of claims 8 to 10, wherein:   When at least one of the condensing lens and the workpiece is relatively moved along the line, the measurement laser light is emitted when the condensing lens reaches the one intersection. 11. The laser processing apparatus according to claim 8, wherein when the condensing lens reaches the other intersection point, emission of the measurement laser beam is stopped. . By aligning a condensing point inside the plate-like object to be processed and irradiating a processing laser beam, a modified region that becomes a starting point of cutting along the scheduled cutting line of the object to be processed is defined as the object to be processed. A laser processing apparatus to be formed inside,
A mounting table on which the processing object pasted on an expandable sheet stretched on an annular frame is mounted;
A processing laser light source for emitting the processing laser light, and a laser unit having a measurement laser light source for emitting the measurement laser light;
A condensing lens for condensing the processing laser light and the measurement laser light,
Set a machining area having an outer shape between the workpiece and the frame;
Acquire the coordinates of one intersection and the other intersection of the line including the planned cutting line and the outer shape of the processing region,
The at least one of the condensing lens and the object to be processed is relatively moved along the line, and after the condensing lens reaches the one intersection, the condensing is performed on the other intersection. Until the lens for reaching, when the condensing lens is located on the processing region, the measurement laser light is condensed toward the processing region by the condensing lens, By detecting the reflected light of the measurement laser light reflected by the laser light irradiation surface of the workpiece, the focusing point of the processing laser light is aligned with a predetermined position with respect to the laser light irradiation surface. So as to adjust the distance between the laser light irradiation surface and the condensing lens, and obtain adjustment information related to the adjustment,
When at least one of the condensing lens and the object to be processed is relatively moved along the line, and the condensing lens is positioned on the processing region, based on the adjustment information And adjusting the distance between the laser light irradiation surface and the condensing lens while condensing the processing laser light toward the object to be processed by the condensing lens, A laser processing apparatus, wherein the laser processing apparatus is formed inside a workpiece.   When the condensing lens is positioned on the processing region, the measurement laser light is condensed toward the processing region by the condensing lens and reflected by the processing region. When the amount of reflected light of the processing laser beam is detected and the amount of light exceeds a predetermined threshold, the focusing point of the processing laser beam is adjusted to a predetermined position with reference to the laser light irradiation surface The laser processing apparatus according to claim 13, wherein a distance between the laser light irradiation surface and the condensing lens is adjusted.   When the condensing lens is positioned on the processing region, the measurement laser light is condensed toward the processing region by the condensing lens and reflected by the processing region. When the amount of reflected light of the measuring laser beam is detected and the amount of light exceeds a predetermined threshold value, the condensed image of the reflected light of the measuring laser beam to which astigmatism is added is constant. The laser processing apparatus according to claim 13, wherein a distance between the laser light irradiation surface and the condensing lens is adjusted. Relatively moving at least one of the condenser lens and the object to be processed along the line crossing the frame;
The measurement for adjusting the distance between the laser light irradiation surface and the condensing lens until the condensing lens reaches one intersection of the line and the outer shape of the processing region from one side Stop arithmetic processing based on the amount of reflected light of the laser light, fix the condensing lens at a fixed position in the thickness direction of the workpiece, and stop the irradiation of the processing laser light,
The amount of reflected light of the laser beam for measurement from one intersection point of the line and the outer shape of the processing area until the condensing lens reaches one intersection point of the line and the outer edge of the workpiece The calculation processing based on is performed, the condenser lens is fixed at a fixed position in the thickness direction of the workpiece, and the irradiation of the processing laser beam is stopped,
From when the condensing lens reaches one intersection of the line and the outer edge of the object to be processed, until the condensing lens reaches the other intersection of the line and the outer edge of the object to be processed In the meantime, arithmetic processing based on the amount of reflected light of the measurement laser light is performed, the distance between the laser light irradiation surface and the condenser lens is adjusted, and the processing laser light is irradiated. The laser processing apparatus according to any one of claims 13 to 15, wherein   When at least one of the condensing lens and the workpiece is relatively moved along the line, the measurement laser light is emitted when the condensing lens reaches the one intersection. The laser processing apparatus according to claim 13, wherein when the condensing lens reaches the other intersection, emission of the measurement laser light is stopped. .

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