JP2008087026A - Laser beam machining method and laser beam machining apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining method and a laser beam machining apparatus that can suppress deviation of a quality modification region to be formed, from a planned cutting line. <P>SOLUTION: A laser beam is emitted with a converging point focused on the inside of a workpiece 1, so that the quality modification region to be a cutting starting point is formed inside the workpiece 1 along the plurality of planned cutting lines set in the workpiece 1. Then, in the workpiece 1, in order of a region Z1 on the near side, a region Z2 on the deep side, and a region Z3 in the center, the quality modification region is formed along the planned cutting lines extending in these regions. Consequently, this can reduce the effect of the moving workpiece during the laser beam machining, compared with the machining on the machining order of general planned cutting lines,. <P>COPYRIGHT: (C)2008,JPO&INPIT

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 conventional laser processing method, by aligning a condensing point inside a plate-shaped workpiece and irradiating laser light, along the plurality of scheduled cutting lines set on the workpiece, There is known a method of forming a modified region to be formed inside a workpiece (for example, see Patent Document 1).
JP 2004-343008 A

  By the way, in the laser processing method as described above, the cutting schedule set on the one end portion side of the workpiece in the direction in which the line to be cut extends in the workpiece and the direction substantially orthogonal to the thickness direction of the workpiece. In general, the modified region is formed along the planned cutting line in an order from the line toward the planned cutting line set on the other end side of the workpiece. However, when the workpieces are processed in such a general order, there is a problem that the modified region to be formed shifts from the planned cutting line and the shift amount gradually increases as the processing progresses. This problem is particularly noticeable when processing a chip having a very small chip size and a large number of lines to be cut set as a workpiece, such as a μ-chip wafer.

  Then, this invention makes it a subject to provide the laser processing method and laser processing apparatus which can suppress that the modification | reformation area | region formed changes from the cutting scheduled line.

  In order to achieve the above object, a laser processing method according to the present invention includes a plurality of cuts set on a processing object by irradiating a laser beam with a focusing point inside the plate-shaped processing object. A laser processing method for forming a modified region, which is a starting point of cutting, inside a workpiece along a planned line, and is modified along the planned cutting line extending in a predetermined direction in the predetermined region. Along the scheduled cutting line extending in the predetermined direction in the step of forming the quality region and the region located on one side of the predetermined region in the predetermined direction and the direction intersecting the thickness direction of the workpiece Forming a modified region and a cutting line extending in a predetermined direction in a region located on the other side of the predetermined region in a direction intersecting the predetermined direction and the thickness direction of the workpiece Forming a modified region along the line; Including, a step of forming a modified region in a region located on one side of the predetermined region, a step of forming a modified region in a region located on the other side of the predetermined region, and a predetermined region The step of forming the modified region is performed in this order.

  Further, the laser processing apparatus according to the present invention irradiates a laser beam with a focusing point inside the plate-like processing object, along a plurality of scheduled cutting lines set on the processing object, A laser processing apparatus for forming a modified region that is a starting point of cutting inside a workpiece, a mounting table on which the processing target is mounted, a laser light source that emits laser light, and a mounting table A condensing lens for condensing the laser light emitted from the laser light source, and a control means for controlling the behavior of at least one of the mounting table and the condensing lens inside the processed object. The means controls the operation of at least one of the mounting table and the condensing lens in order to form the modified region along the planned cutting line extending in the predetermined direction in the predetermined region, and the predetermined direction. Intersect with the thickness direction of the workpiece Operate at least one of the mounting table and the condensing lens to form the modified region along the planned cutting line extending in the predetermined direction in the region located on one side of the predetermined region in the direction And a modified region along a predetermined cutting line extending in a predetermined direction in a region located on the other side of the predetermined region in a predetermined direction and a direction intersecting the thickness direction of the workpiece. In order to form a modified region in a region located on one side of a predetermined region, control for operating at least one of the mounting table and the condensing lens is performed. The control for forming the modified region in the region located on the other side of the predetermined region, and the control for forming the modified region in the predetermined region in this order. Features.

  Thus, according to the present invention, first, the modified region is formed along the planned cutting line set in the region located on one side of the predetermined region in the workpiece. Thereafter, a modified region is formed along a scheduled cutting line set in a region located on the other side of the predetermined region in the workpiece. Finally, a modified region is formed along a scheduled cutting line set in a predetermined region in the workpiece. In this way, the modified region along the planned cutting line set in each region in the order of the region located on one side of the predetermined region, the region located on the other side of the predetermined region, and the predetermined region By forming, the influence of the processing object moving during laser processing can be reduced as compared with the case where the processing object is processed in the general order described above. That is, for example, a crack (half cut) that extends to the front surface or the back surface of the workpiece is generated, and when the half cut is opened, the workpiece is pushed and the influence of movement of the workpiece can be reduced. It becomes. Therefore, according to the present invention, it is possible to suppress the formed modified region from deviating from the planned cutting line.

  Further, in each of the steps of forming the modified region, the center portion of the processing object from the scheduled cutting line set on the end side of the processing object in the predetermined direction and the direction intersecting the thickness direction of the processing object It is preferable to form the modified regions along the planned cutting line in the order of the planned cutting line set on the side. In this case, the influence of the movement of the processing object accompanying laser processing can be further reduced as compared with the case of processing the processing object in the general order described above. Therefore, it is possible to further suppress the formed modified region from deviating from the planned cutting line.

  In some cases, the object to be processed includes a semiconductor substrate, and the modified region includes a melt processing region.

  Moreover, it is preferable to include the process of cut | disconnecting a process target object along a scheduled cutting line by making a modification | reformation area | region into the starting point of cutting | disconnection. As a result, the workpiece can be accurately cut along the scheduled cutting line.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to suppress that the modification | reformation area | region formed falls off from a cutting plan line.

  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 pulsed waves, the intensity of laser light is determined by the peak power density of the focus point of the laser beam (W / cm ^2), for example, the peak power density multiphoton at ^{1 × 10 8 (W / cm} 2) or more conditions Absorption occurs. The peak power density is obtained by (energy per one pulse of laser light at a 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.

  The laser processing method according to the present embodiment does not form the modified region 7 by causing the workpiece 1 to generate heat when the workpiece 1 absorbs the laser beam L. The modified region 7 is formed by transmitting the laser beam L through the workpiece 1 and generating multiphoton absorption inside the workpiece 1. Therefore, since the laser beam L is hardly absorbed by the surface 3 of the workpiece 1, 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. For example, when the thickness of the workpiece 1 is small, the cutting start region 8 is formed by the one row of the modified region 7, and when the thickness of the workpiece 1 is large, for example. 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 at 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, the modified regions formed by multiphoton absorption include the following cases (1) to (3).

(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, the laser beam L is irradiated with the focusing point P inside the workpiece 1 under the condition that multiphoton absorption occurs, and a crack region 9 is formed inside 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 processing region is a region once solidified after melting, a region in a molten state, a region in which the material is 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 referred to as 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, and 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 (semiconductor substrate). 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). Are listed.

  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.
[First embodiment]

  A first embodiment of the present invention will be described. As shown in FIGS. 14 and 15, the workpiece 1 includes a silicon wafer 11 which is a Si bare wafer having a thickness of 150 μm and 6 inches, and a function formed on the surface 11 a of the silicon wafer 11 including a plurality of functional elements 15. And an element layer 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 in the direction of the arrow H parallel to the direction of the arrow B and the direction of the arrow B perpendicular to the direction. A plurality of scheduled cutting lines 5 are set in a grid pattern on the workpiece 1 so as to pass between adjacent functional elements. Specifically, the workpiece 1 includes a planned cutting line 5 a extending in the direction of arrow H parallel to the orientation flat 6 and a planned cutting line 5 b extending in the direction of arrow B perpendicular to the orientation flat 6. Is set. Here, the planned cutting line 5a is 584 lines, and the planned cutting line 5b is 584 lines. Such a workpiece 1 is cut along the planned cutting line 5 and becomes a discrete device or the like which is a microchip having a chip size of 0.25 mm × 0.25 mm, for example.

  As shown in FIG. 16, the laser processing apparatus 100 irradiates the laser beam L with the condensing point P inside the plate-shaped processing target 1, thereby cutting a plurality of cuts set on the processing target 1. It is an apparatus that forms a modified region that is a starting point of cutting inside the workpiece 1 along the planned line 5.

  The laser processing apparatus 100 includes a laser light source 101 that pulsates laser light L, a laser light source control unit 102 that controls the laser light source 101 in order to adjust the output and pulse width of the laser light L, and the reflection of the laser light L. A dichroic mirror 103 having a function and arranged to change the direction of the optical axis of the laser light L by 90 °, and a condensing lens 105 for condensing the laser light L reflected by the dichroic mirror 103. ing. Further, the laser processing apparatus 100 moves the mounting table 107 on which the processing object 1 irradiated with the laser beam L collected by the condensing lens 105 is placed, and the mounting table 107 in the X-axis direction (left and right direction on the paper surface). ), An Y-axis stage 111 for moving the mounting table 107 in the Y-axis direction (perpendicular to the paper surface) orthogonal to the X-axis direction, and the mounting table 107 for the X-axis and Y-axis A Z-axis stage 113 for moving in the Z-axis direction (up and down direction on the paper surface) orthogonal to the direction, and a stage control unit (control means) 115 for controlling the movement of the stages 109, 111, 113.

  The stage control unit 115 operates each stage 109, 111, 113 in a predetermined region of the workpiece 1 to form a modified region along the planned cutting line 5 extending in a predetermined direction. Control and modification along a predetermined cutting line 5 extending in a predetermined direction in a region located on one side of the predetermined region in a direction substantially orthogonal to the predetermined direction and the thickness direction of the workpiece. In order to form the region, in the region located on the other side of the predetermined region in the predetermined direction and in the direction substantially orthogonal to the thickness direction of the workpiece, the stage 109, 111, 113 is operated. In order to form the modified region along the planned cutting line 5 extending in a predetermined direction, control for operating each of the stages 109, 111, and 113 is executed. Then, the stage control unit 115 performs control for forming the modified region in the region located on one side of the predetermined region, and forms the modified region in the region located on the other side of the predetermined region. And control for forming a modified region in a predetermined region are executed in this order.

  That is, as shown in FIG. 17A, the stage control unit 115 is viewed from the surface 3 of the workpiece 1 when the modified region is formed along the cutting line 5a (see FIG. 15), for example. A control circuit for forming a modified region in the region Z1 on the front side when the entire region of the workpiece 1 is divided into three in the direction of arrow H with the lower side on the front side and the upper side on the paper side as the back. A control circuit for forming a modified region in the region Z2 and a control circuit for forming a modified region in the central region Z3, and these circuits are executed in this order (in detail) Later).

  When cutting the workpiece 1 using the laser processing apparatus 100, first, for example, an expanded tape is attached to the back surface 21 of the workpiece 1. Subsequently, the laser light source controller 102 irradiates the laser light L from the laser light source 101 with the focusing point from the surface 3 of the workpiece 1 to the inside of the silicon wafer 11, and follows each scheduled cutting line 5 a (5 b). Thus, a modified region serving as a starting point of cutting is formed. Subsequently, the laser light source controller 102 irradiates the laser light L from the laser light source 101 with the focusing point from the surface 3 of the workpiece 1 to the inside of the silicon wafer 11, and follows each scheduled cutting line 5 b (5 a). Thus, a modified region serving as a starting point for cutting is formed. Then, the expanded tape is expanded. As a result, the workpiece 1 is accurately cut for each functional element 15 along the scheduled cutting line 5 using the modified region as a starting point of cutting, and the plurality of semiconductor chips are separated from each other. Note that the modified region may include a crack region or the like in addition to the melt processing region.

  Next, the formation of the modified region along each of the planned cutting lines 5 will be described in detail. Here, as an example, the formation of the modified region along the planned cutting line 5a will be described.

  First, as shown in FIG. 17A, the processing object 1 is irradiated with the laser light L with the focusing point inside the silicon wafer 11. At the same time, the stage controller 115 relatively moves the condensing point along the planned cutting line 5a extending in the direction of the arrow H in the region Z1 of the workpiece 1. Specifically, in the region Z1 on the near side of the workpiece 1, the stage controller 115 relatively moves the condensing point along the scheduled cutting line 5a, and the arrow C1 is a direction from the near side to the far side. The mounting table 107 is sent in the direction of. By repeating these steps, a modified region is formed in the workpiece 1 sequentially, for example, 200 lines in the direction of the arrow C1 along the planned cutting line 5a set in the region Z1. In other words, in the region Z1 located on the front side (one side) of the region Z3 in the direction of the arrow B which is the direction in which the planned cutting line 5a extends and the direction of the thickness of the workpiece 1 is crossed, the arrow The modified region is formed along the planned cutting line 5a extending in the H direction.

  Next, as shown in FIG. 17 (b), the processing object 1 is irradiated with the laser beam L with the focusing point inside the silicon wafer 11. At the same time, the stage control unit 115 relatively moves the condensing point along the planned cutting line 5a extending in the arrow H direction in the region Z2 of the workpiece 1. Specifically, in the area Z2 on the back side of the workpiece 1, the stage controller 115 relatively moves the condensing point along the planned cutting line 5a, and the arrow C2 is a direction from the near side to the back side. The mounting table 107 is sent in the direction of. By repeating these steps, a modified region is formed inside the workpiece 1 sequentially, for example, 200 lines in the direction of the arrow C2 along the planned cutting line 5a set in the region Z2. In other words, in the region Z2 located on the far side (the other side) of the region Z3 in the direction of the arrow B which is the direction in which the planned cutting line 5a extends and the direction of the thickness of the workpiece 1 is crossed, the arrow The modified region is formed along the planned cutting line 5a extending in the H direction.

  Then, as shown in FIG. 17 (c), the processing object 1 is irradiated with the laser light L with the condensing point set inside the silicon wafer 11. At the same time, the stage controller 115 relatively moves the condensing point along the planned cutting line 5a extending in the direction of the arrow H in the region Z3 of the workpiece 1. Specifically, in the center region Z3 of the workpiece 1, the stage controller 115 relatively moves the condensing point along the planned cutting line 5a, and the arrow C that is the direction from the front toward the back The mounting table 107 is sent in the direction. By repeating these steps, a modified region is formed inside the workpiece 1 sequentially, for example, by 184 lines in the direction of the arrow C1 along the planned cutting line 5a set in the region Z3. In other words, along the planned cutting line 5a extending in the arrow H direction in the region Z3 in the direction of the arrow B which is the direction in which the planned cutting line 5a extends and the direction of the thickness of the workpiece 1 is intersected. A modified region is formed.

  As a result, a modified region serving as a starting point for cutting is formed along the planned cutting line 5a (see FIG. 15). Note that, regarding the formation of the modified region along the planned cutting line 5b (see FIG. 15), the workpiece 1 is 90 ° with respect to the Z axis as a base axis with respect to the formation of the modified region along the planned cutting line 5a. It is the same except that it is mounted on the mounting table 107 in a rotated state. In this case, when the stage control unit 115 divides the entire region of the processing object 1 into three in the direction of the arrow B with the right side of the drawing as viewed from the front surface 3 of the processing target 1 and the left side of the drawing as the back. A control circuit for forming the modified region in the front region, a control circuit for forming the modified region in the rear region, and a control circuit for forming the modified region in the central region, These circuits are executed in this order.

  By the way, in the conventional laser processing method, as shown in FIG. 22, in the case where the modified region is formed along the plurality of planned cutting lines 5 extending in the direction parallel to the orientation flat 6 in the workpiece 1, Along each cutting scheduled line 5 in the order of the arrow C0 from the scheduled cutting line 5 set on one end (lower side of the sheet) of the workpiece 1 to the scheduled cutting line 5 set on the other end (upper side of the sheet). In general, a modified region is formed. However, if the workpiece 1 is machined in the order of the arrow C0, the modified region to be formed may deviate from the planned cutting line 5 and the deviation amount may gradually increase as the machining progresses.

  On the other hand, if the modified region to be formed is deviated from the planned cutting line 5 and the amount of deviation is more than a certain value (for example, the amount of deviation is about 5 μm or more when the interval between adjacent cutting scheduled lines is 20 μm), the quality is poor. It becomes. Therefore, it is necessary to perform so-called index correction in the laser processing method. Index correction refers to, for example, monitoring the surface of a workpiece with a monitoring camera or the like, and monitoring the amount of deviation. When the amount of deviation exceeds a certain level, the laser beam is irradiated accurately along the planned cutting line. The correction means that the position of the workpiece is finely corrected by moving the mounting table.

  Therefore, as described above, in the conventional laser processing method, as the processing progresses, the modified region formed shifts from the planned cutting line 5 and the shift amount gradually increases. The correction must be performed at a frequency of performing one index correction after processing. Therefore, a great deal of labor and time is spent.

  Therefore, as a result of intensive studies, the present inventors have found that the phenomenon that the modified region formed as the processing progresses shifts from the planned cutting line 5 and the shift amount gradually increases is due to the following phenomenon. I found out.

  That is, for example, when a crack (half cut) extending to the front surface 3 or the back surface 21 of the workpiece 1 or a crack extending to the front surface 3 and the back surface 21 (full cut) occurs in laser processing, the crack is opened. The workpiece 1 may open at the crack. In other words, the workpiece 1 is pushed in the direction of opening the crack at the boundary of the crack, and the workpiece 1 moves. This opening differs depending on the shape and size of the workpiece, the total number of cutting lines, the position, etc. As an example, for example, when the half cut opens about 0.4 μm, the back side goes to the back with the half cut as the boundary. The front side is moved by 0.2 μm toward the front.

  Also, for example, when a modified region formed by laser processing includes a melt processing region, the back side moves to the back and the near side moves to the front due to the expansion of the melt processing region. It is.

  Therefore, in view of the above phenomenon, in the present embodiment, as described above, in the workpiece 1, the cutting that extends to each region in the order of the near side region Z1, the far side region Z2, and the central region Z3. A modified region is formed along the planned line 5a. Thereby, compared with the case where it processes in the order of the arrow C0 of the conventional cutting scheduled line, the influence which the workpiece 1 moves in the case of laser processing can be reduced.

  The reason is considered as follows. That is, the shift of the modified region from the planned cutting line 5 is caused by the above movement. This movement depends on the relationship between the size and mass of each part of the workpiece 1 with the scheduled cutting line 5 as a boundary. That is, the area Z1 on the near side and the area Z2 on the back side are easily affected by the movement, whereas the center area Z3 is hardly affected by the movement. On the other hand, the region where the processing order is later is more affected by the movement due to processing in other regions. Therefore, the area Z1 and the area Z2 that are easily affected by the movement are processed before the influence of the movement, so that the influence can be suppressed.

  Furthermore, as described above, after forming the region Z1 on one side with respect to the region Z3, the modified region is formed in the region Z2 on the other side with respect to the region Z3. That is, the modified regions are formed in order in regions Z1 and Z2 that are symmetrical via the region Z3. This is because the influence of the movement due to the formation of the modified region in the area Z1 and the influence of the movement due to the formation of the modified area in the area Z2 effectively act in the direction of canceling each other. .

  Therefore, according to the present embodiment, it is possible to suppress the formed modified region from being displaced from the planned cutting line 5. As a result, the frequency of the index correction amount can be greatly reduced, the tact time in laser processing can be shortened, and the processing efficiency can be improved. Incidentally, since the movement of the mounting table 107 without the irradiation of the laser beam L for performing the processing of the region Z2 after the processing of the region Z1 occurs, it can be considered that the tact time increases at first glance, but the laser of this embodiment The processing method can further shorten the tact time by reducing the index correction frequency.

  Here, along the plurality of planned cutting lines 5a in the plurality of regions, for example, two rows of modified regions are simultaneously formed along each of the planned cutting lines 5a extending to the region Z1 and the region Z2. It is also possible to form a plurality of rows simultaneously. However, in this case, the movement toward the center in each of the region Z1 and the region Z2 occurs at the same time, and thus there is a possibility that a compressive stress is generated in the central region Z3 sandwiched between them. As a result, the workpiece 1 is warped or the degree of warpage is increased. For example, when the workpiece is thin, the workpiece 1 may be broken. That is, it is not preferable to form a plurality of rows of modified regions at the same time along the scheduled cutting lines in the plurality of regions.

  On the other hand, in the present embodiment, the modified regions are not formed in a plurality of rows at the same time, but are sequentially formed along the planned cutting line 5a as described above. Thereby, the stress by the said movement of the workpiece 1 is released each time by the said movement, Therefore The curvature in the workpiece 1 and the possibility of a fracture | rupture can be reduced. In the present embodiment, as described above, the workpiece 1 is attached to the expanded tape and placed on the placing table 107, and the expanded tape also extends due to its elasticity along with the movement.

  In the present embodiment, the processing object 1 is a so-called μ chip wafer as described above. As described above, when using a chip having a very small chip size and a large number of planned cutting lines 5, the effect of the present embodiment is particularly effective since the shift of the modified region from the planned cutting line 5 is significant. Is demonstrated.

As described above, as a result of processing the workpiece 1 by each of the laser processing method of the present embodiment described above and the conventional laser processing method, in the conventional processing method, the total number of index corrections was 60 times, In the processing method of the present embodiment, the total number of index corrections is 50. Thereby, it was possible to suppress the above-described effect, that is, the effect that the modified region to be formed is deviated from the planned cutting line 5, the tact time in the laser processing is shortened, and the processing efficiency is improved. .
[Second Embodiment]

  Next, a second embodiment of the present invention will be described. Here, the description which overlaps with the said 1st Embodiment is abbreviate | omitted, and only a different point is demonstrated.

  The laser processing apparatus of the second embodiment is different from the laser processing apparatus 100 of the first embodiment in that a stage control unit 215 is provided instead of the stage control unit 115 as shown in FIG. The stage control unit 215 controls movement of the X-axis stage 109, the Y-axis stage 111, and the Z-axis stage 113, respectively.

  Specifically, as illustrated in FIG. 18A, the stage control unit 215, for example, forms a modified region along the planned cutting line 5a, and is below the paper surface as viewed from the surface 3 of the workpiece 1. Is the front side, the upper side of the drawing is the back, and the entire region of the workpiece 1 is divided into five in the direction of the arrow H, a control circuit for forming a modified region in the foremost region Z4, A control circuit for forming a reforming region in the region Z5, a control circuit for forming a reforming region in a region Z6 adjacent to the region Z4 on the foremost side and positioned on the back side of the region Z4, A control circuit for forming a modified region in a region Z7 adjacent to the region Z5 and located on the front side of the region Z5, and a control circuit for forming a modified region in the central region Z8, and Are executed in this order. ).

  The case where the modified region is formed along the planned cutting line 5 using this laser processing apparatus will be described in more detail. Here, as an example, the formation of the modified region along the planned cutting line 5a will be described.

  First, as shown in FIG. 18A, the processing object 1 is irradiated with the laser light L with the focusing point inside the silicon wafer 11. At the same time, the stage controller 215 relatively moves the condensing point along the planned cutting line 5a extending in the direction of arrow H in the region Z4 of the workpiece 1. Specifically, in the foremost region Z5 of the workpiece 1, the stage controller 215 relatively moves the condensing point along the planned cutting line 5a extending in the arrow H direction, and from the near side. The mounting table 107 is sent in the direction of arrow C4, which is the direction toward the back. By repeating these steps, a modified region is formed inside the workpiece 1 sequentially, for example, by 100 lines in the direction of the arrow C4 along the planned cutting line 5a set in the region Z4.

  Next, as shown in FIG. 18 (b), the processing object 1 is irradiated with the laser light L with the condensing point set inside the silicon wafer 11. At the same time, the stage control unit 215 relatively moves the condensing point along the planned cutting line 5 a extending in the direction of the arrow H in the region Z <b> 5 of the workpiece 1. Specifically, in the deepest region Z5 of the workpiece 1, the stage controller 215 relatively moves the condensing point along the planned cutting line extending in the direction of the arrow H, and from the front to the back. The mounting table 107 is sent in the direction of the arrow C5, which is the direction toward. By repeating these steps, a modified region is formed inside the workpiece 1 in order, for example, by 100 lines in the direction of the arrow C5 along the planned cutting line 5a set in the region Z5.

  Next, as shown in FIG. 18 (c), the processing object 1 is irradiated with the laser light L with the focusing point set inside the silicon wafer 11. At the same time, the stage controller 215 relatively moves the condensing point along the planned cutting line 5a extending in the direction of the arrow H in the region Z6 of the workpiece 1. Specifically, in a region Z6 adjacent to the foremost region Z4 of the workpiece 1 and positioned on the far side of the region Z4, the stage control unit 215 applies a cutting scheduled line extending in the arrow H direction. The condensing point is relatively moved along, and the mounting table 107 is sent in the direction of arrow C6, which is the direction from the front to the back. By repeating these steps, a modified region is formed inside the workpiece 1 sequentially, for example, 100 lines in the direction of the arrow C6 along the planned cutting line 5a set in the region Z6.

  Next, as shown in FIG. 19A, the processing object 1 is irradiated with the laser light L with the focusing point inside the silicon wafer 11. At the same time, the stage control unit 215 relatively moves the condensing point along the planned cutting line 5a extending in the arrow H direction in the region Z7 of the workpiece 1. Specifically, in the region Z7 adjacent to the farthest region Z5 of the workpiece 1 and positioned on the near side of the region Z5, the stage control unit 215 plans to cut the cutting line 5a extending in the arrow H direction. The condensing point is relatively moved along the direction and the mounting table 107 is sent in the direction of the arrow C7, which is the direction from the front to the back. By repeating these steps, a modified region is formed inside the workpiece 1 sequentially, for example, by 100 lines in the direction of the arrow C7 along the planned cutting line 5a set in the region Z7.

  Then, as shown in FIG. 19 (b), the processing object 1 is irradiated with the laser beam L with the condensing point aligned with the inside of the silicon wafer 11. At the same time, the stage control unit 215 relatively moves the condensing point along the planned cutting line 5a extending in the arrow H direction in the region Z8 of the workpiece 1. Specifically, in the center region Z8 of the workpiece 1, the stage controller 215 relatively moves the condensing point along the planned cutting line 5a extending in the direction of the arrow H, and from the front to the back. The mounting table 107 is sent in the direction of the arrow C8, which is the direction toward. By repeating these steps, a modified region is formed inside the workpiece 1 sequentially, for example, by 184 lines in the direction of the arrow C8 along the planned cutting line 5a set in the region Z8.

  As a result, a modified region serving as a starting point for cutting is formed along the planned cutting line 5a (see FIG. 15). Note that, regarding the formation of the modified region along the planned cutting line 5b (see FIG. 15), the workpiece 1 is 90 ° with respect to the Z axis as a base axis with respect to the formation of the modified region along the planned cutting line 5a. It is the same except that it is mounted on the mounting table 107 in a rotated state. In this case, when the stage control unit 215 divides the entire region of the processing object 1 into five in the arrow B direction with the right side of the drawing as viewed from the front surface 3 of the processing target 1 and the left side of the drawing as the back. A control circuit for forming a reformed region in the foremost region, a control circuit for forming a reformed region in the farthest region, located adjacent to the foremost region and on the far side of the region A control circuit for forming a modified region in a region to be processed, a control circuit for forming a modified region in a region adjacent to the innermost region and positioned on the front side of the region, and reformed to a central region A control circuit for forming the region is provided, and these circuits are executed in this order.

  According to this embodiment, in the workpiece 1, the foremost area Z4, the farthest area Z5, the area Z4, and the area Z4, the area Z6, the area Z5, and the area Z5 are adjacent. The modified region is formed along the planned cutting line 5a extending in each region in the order of the rear region Z7 and the central region Z8. As a result, it is possible to suppress the same effect as the above effect, that is, the modified region to be formed is deviated from the planned cutting line 5, and as a result, the frequency of the index correction amount can be greatly reduced. The tact time can be shortened, and the processing efficiency can be improved.

As described above, as a result of processing the workpiece 1 by each of the laser processing method of the present embodiment described above and the conventional laser processing method, in the conventional processing method, the total number of index corrections was 60 times, In the processing method of this embodiment, the total number of index corrections is 30. Thereby, it was possible to suppress the above-described effect, that is, the effect that the modified region to be formed is deviated from the planned cutting line 5, the tact time in the laser processing is shortened, and the processing efficiency is improved. .
[Third Embodiment]

  Next, a third embodiment of the present invention will be described. Here, the description which overlaps with the said 1st Embodiment is abbreviate | omitted, and only a different point is demonstrated.

  The laser processing apparatus of the third embodiment is different from the laser processing apparatus 100 of the first embodiment in that a stage control unit 315 is provided instead of the stage control unit 115 as shown in FIG. The stage control unit 315 controls movement of the X-axis stage 109, the Y-axis stage 111, and the Z-axis stage 113, respectively.

  Specifically, as shown in FIG. 20A, the stage control unit 315 starts from the surface 11a of the object to be processed, for example, when the modified region is formed along the planned cutting line 5b (see FIG. 15). A control circuit for forming a modified region in the foremost region Z9 when the entire region of the object to be processed is divided into six in the direction of arrow B with the lower side of the paper as viewed and the upper side as viewed in the back. A control circuit for forming a reforming region in the rear region Z10, a control circuit for forming a reforming region in a region Z11 adjacent to the frontmost region Z9 and positioned on the far side of the region Z9, A control circuit for forming a modified region in a region Z12 that is adjacent to the region Z10 on the back side and located on the front side of the region Z10, and a modified region is formed in the region Z13 on the front side of the two regions located in the center Control circuit, and center Control circuitry for forming a modified region on the far side of the area Z14 of the second region, has a, and executes these circuits in this order. In particular, the stage control unit 315 moves the mounting table 107 in a direction toward the center when forming the modified region along a plurality of scheduled cutting lines extending to each region, and moves the plurality of planned cutting lines to the center. The stages 109, 111, and 113 are respectively controlled so as to form the modified regions along the direction toward the planned cutting line (details will be described later).

  The case where the modified region is formed along the planned cutting line 5 using this laser processing apparatus will be described in more detail. Here, as an example, the formation of the modified region along the planned cutting line 5b will be described.

  First, as shown in FIG. 20A, the processing object 1 is irradiated with the laser light L with the focusing point inside the silicon wafer 11. At the same time, the stage control unit 315 relatively moves the condensing point along the planned cutting line 5b extending in the arrow B direction in the region Z9 of the workpiece 1. Specifically, in the foremost region Z9 of the workpiece 1, the stage controller 315 relatively moves the condensing point along the planned cutting line 5b extending in the arrow B direction, and from the near side. The mounting table 107 is sent in the direction of arrow C9, which is the direction toward the center. By repeating these steps, a modified region is formed inside the workpiece 1 sequentially, for example, by 100 lines in the direction of the arrow C9 along the planned cutting line 5b set in the region Z9.

  Next, as shown in FIG. 20B, the processing object 1 is irradiated with the laser beam L with the focusing point inside the silicon wafer 11. At the same time, the stage control unit 315 relatively moves the condensing point along the planned cutting line 5b extending in the arrow B direction in the region Z10 of the workpiece 1. Specifically, in the deepest region Z10 of the workpiece 1, the stage controller 315 relatively moves the condensing point along the planned cutting line 5b extending in the arrow B direction, and from the back. The mounting table 107 is sent in the direction of arrow C10, which is the direction toward the center. By repeating these steps, a modified region is formed inside the workpiece 1 sequentially, for example, by 100 lines in the direction of the arrow C10 along the scheduled cutting line 5b set in the region Z10.

  Next, as shown in FIG. 20 (c), the processing object 1 is irradiated with the laser light L with the focusing point set inside the silicon wafer 11. At the same time, the stage control unit 315 relatively moves the condensing point along the planned cutting line 5b extending in the arrow B direction in the region Z11 of the workpiece 1. Specifically, in a region Z11 that is adjacent to the region Z9 that is the foremost side of the workpiece 1 and is located on the far side of the region Z9, the planned cutting line 5b that extends in the arrow B direction by the stage control unit 315. The condensing point is relatively moved along the direction and the mounting table 107 is sent in the direction of arrow C11 which is a direction from the front toward the center. By repeating these steps, a modified region is formed inside the workpiece 1 sequentially, for example, 100 lines in the direction of the arrow C11 along the planned cutting line 5b set in the region Z11.

  Next, as shown in FIG. 21A, the processing object 1 is irradiated with the laser beam L with the focusing point inside the silicon wafer 11. At the same time, the stage control unit 315 relatively moves the condensing point along the planned cutting line 5b extending in the arrow B direction in the region Z12 of the workpiece 1. Specifically, in a region Z12 that is adjacent to the deepest region Z10 of the workpiece 1 and is located on the deep side of the region Z10, the stage control unit 315 extends the planned cutting line 5b that extends in the arrow B direction. The focusing point 107 is moved in the direction of arrow C12 which is a direction from the back to the center while relatively moving the condensing point. As a result, a modified region is formed inside the workpiece 1 sequentially, for example, by 100 lines in the direction of the arrow C12 along the planned cutting line 5b set in the region Z12.

  Next, as shown in FIG. 21 (b), the processing object 1 is irradiated with the laser beam L with the focusing point inside the silicon wafer 11. At the same time, the stage control unit 315 relatively moves the condensing point along the planned cutting line 5b extending in the arrow B direction in the region Z13 of the workpiece 1. Specifically, in the region Z13 located on the near side of the center of the workpiece 1, the stage controller 315 relatively moves the condensing point along the planned cutting line 5b extending in the arrow B direction. Further, the mounting table 107 is sent in the direction of the arrow C13 which is the direction from the front toward the center. As a result, a modified region is formed inside the workpiece 1 by, for example, 92 lines sequentially in the direction of the arrow C13 along the planned cutting line 5b set in the region Z13.

  Then, as shown in FIG. 21 (c), the processing object 1 is irradiated with the laser beam L with the condensing point aligned inside the silicon wafer 11. At the same time, the stage controller 315 relatively moves the condensing point along the planned cutting line 5b extending in the direction of arrow B in the region Z14 of the workpiece 1. Specifically, in the region Z14 located at the center back side of the workpiece 1, the stage controller 315 relatively moves the condensing point along the planned cutting line 5b extending in the arrow B direction. Further, the mounting table 107 is sent in the direction of the arrow C14 which is a direction from the back to the center. As a result, a modified region is formed inside the workpiece 1 by, for example, 92 lines sequentially in the direction of the arrow C14 along the planned cutting line 5b set in the region Z14.

  As a result, a modified region serving as a starting point for cutting is formed along the planned cutting line 5b (see FIG. 15). In addition, regarding the formation of the modified region along the planned cutting line 5a (see FIG. 15), the workpiece 1 is 90 ° with respect to the Z axis as a base axis with respect to the formation of the modified region along the planned cutting line 5b. It is the same except that it is mounted on the mounting table 107 in a rotated state. In this case, when the stage control unit 315 divides the entire region of the processing object into six in the direction of arrow B with the right side of the drawing as viewed from the front surface 3 of the processing target and the left side of the drawing as the back, A control circuit for forming a modified region in the front region, a control circuit for forming a modified region in the farthest region, a region adjacent to the farthest region and located on the far side of the region A control circuit for forming a reforming region, a control circuit for forming a reforming region in a region adjacent to the innermost region and positioned in front of the region, and the front of the two regions located in the center A control circuit for forming the reforming region in the region on the side, and a control circuit for forming the reforming region in the back region of the two regions located in the center, and these circuits are arranged in this order Will be executed.

  According to this embodiment, in the workpiece 1, the foremost area Z9, the farthest area Z10, the area Z9, and the area Z9, the area Z11, the area Z10, and the area Z10 are adjacent to the area Z10. The modified region is formed along the planned cutting line 5b extending to each region in the order of the region Z12 on the near side, the region Z13 on the near side of the center, and the region Z14 on the far side of the center. As a result, it is possible to suppress the same effect as the above effect, that is, the modified region to be formed is deviated from the planned cutting line 5, and as a result, the frequency of the index correction amount can be greatly reduced. The tact time can be shortened, and the processing efficiency can be improved.

  Furthermore, in the present embodiment, as described above, when forming the modified region in each region, the arrow H that intersects the direction of the arrow B that is the extending direction of the planned cutting line 5b and the thickness direction of the workpiece 1 is as follows. In the direction, the modified region extends along the planned cutting line 5b in the order from the planned cutting line 5b set on the end side of the workpiece 1 to the planned cutting line 5b set on the center side of the processing target. It is formed. That is, when forming the modified region along the plurality of planned cutting lines 5b extending to the respective regions Z9 to Z14, the stage 107 is moved in the direction toward the center by the stage control unit 315, and the central planned cutting line Processing is sequentially performed in the directions of arrows C9 to C14 toward 5b. Thereby, it becomes possible to further suppress the formed modified region from being displaced from the planned cutting line 5. As a result, the frequency of the index correction amount can be greatly reduced, the tact time in laser processing can be further shortened, and the processing efficiency can be further improved.

  The reason is considered as follows. That is, as described above, the shift of the modified region from the planned cutting line 5 is caused by the above movement, and this movement is the size and mass of each part of the workpiece 1 with the planned cutting line 5 as a boundary. Depends on the relationship. Therefore, the regions located on the near side and the far side are more susceptible to the above movement. On the other hand, as described above, the region whose processing order is later is more affected by the movement due to processing in other regions. Of course, even if the above movement affects the area where the machining has already been performed, the machining has already been completed, so that there is no problem. Therefore, it is possible to minimize the influence by processing the areas located on the near side and the back side that are easily affected by the movement before the influence of the movement. is there.

  Further, in each of the regions that are symmetric with respect to the predetermined region, one of the plurality of scheduled cutting lines 5 is sequentially formed so as to be symmetric with respect to the center of the workpiece 1, This is because the influence of the movement due to the formation of the modified region in the region and the influence of the movement due to the formation of the modified region in the other region act more effectively in the direction of canceling each other.

  Accordingly, it is possible to further suppress the formed modified region from being shifted from the scheduled cutting line 5, and as a result, the frequency of the index correction amount can be greatly reduced, and the tact time in laser processing can be further reduced. As a result, the processing efficiency can be further improved.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to the above embodiment.

  For example, in the above embodiment, the entire region of the processing object 1 is divided into three, five, and six when viewed from the surface 3 of the processing object 1 in laser processing, but the entire region is divided into four. Processing may be performed, and processing may be performed by dividing into seven or more. Even in these cases, the same effects as described above can be obtained by performing processing on each region in the same order of the regions as in the above embodiment.

  Further, instead of the silicon wafer 11, for example, a semiconductor compound material such as gallium arsenide, a piezoelectric material, a crystalline material such as sapphire may be used. In the present embodiment, the laser light irradiation conditions are not limited by the pulse pitch width, output, and the like, and can be various irradiation conditions.

It is a top view of the processing target object during the laser processing by the laser processing device 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 device 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 apparatus which concerns on this embodiment. It is a graph which shows the relationship between the electric field strength and the magnitude | size of a crack spot in the laser processing apparatus which concerns on this embodiment. It is sectional drawing of the process target object in the 1st process of the laser processing apparatus which concerns on this embodiment. It is sectional drawing of the process target object in the 2nd process of the laser processing apparatus which concerns on this embodiment. It is sectional drawing of the process target object in the 3rd process of the laser processing apparatus which concerns on this embodiment. It is sectional drawing of the processing target object in the 4th process of the laser processing apparatus which concerns on this embodiment. It is a figure showing the photograph of the cross section in a part of silicon wafer cut | disconnected by the laser processing apparatus which concerns on this embodiment. It is a graph which shows the relationship between the wavelength of the laser beam in the laser processing apparatus which concerns on this embodiment, and the transmittance | permeability inside a silicon substrate. It is a front view which shows a process target object. It is a fragmentary sectional view in alignment with the XVI-XVI line in FIG. It is a schematic block diagram which shows the laser processing apparatus which concerns on 1st Embodiment of this invention. It is a figure for demonstrating the laser processing method which concerns on 1st Embodiment of this invention. It is a figure for demonstrating the laser processing method which concerns on 2nd Embodiment of this invention. It is a figure for demonstrating the continuation of the laser processing method shown in FIG. It is a figure for demonstrating the laser processing method which concerns on 3rd Embodiment of this invention. It is a figure for demonstrating the continuation of the laser processing method shown in FIG. It is a figure for demonstrating the conventional laser processing method.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Processing object, 5, 5a, 5b ... Planned cutting line, 101 ... Laser light source, 105 ... Condensing lens, 107 ... Mounting stage, 115 ... Stage control part (control means), L ... Laser beam, P ... Condensing point.

Claims (5)

By aligning a condensing point inside the plate-like workpiece and irradiating the laser beam, the modified region serving as a starting point for cutting is formed along the plurality of scheduled cutting lines set on the workpiece. A laser processing method for forming inside a workpiece,
Forming the modified region along the planned cutting line extending in a predetermined direction in a predetermined region;
In the region located on one side of the predetermined region in the predetermined direction and the direction intersecting the thickness direction of the workpiece, the modification is performed along the scheduled cutting line extending in the predetermined direction. Forming a quality region;
In the region located on the other side of the predetermined region in the predetermined direction and the direction intersecting the thickness direction of the workpiece, the modification is performed along the planned cutting line extending in the predetermined direction. Forming a quality region, and
Forming the modified region in a region located on one side of the predetermined region, forming the modified region in a region located on the other side of the predetermined region, and the predetermined Forming the modified region in the region in this order.   In each of the steps of forming the modified region, the object to be processed from the scheduled cutting line set on the end side of the object to be processed in a direction intersecting the predetermined direction and the thickness direction of the object to be processed. 2. The laser processing method according to claim 1, wherein the modified region is formed along the planned cutting line in an order toward the planned cutting line set on the center side of the object.   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.   The laser processing method according to any one of claims 1 to 3, further comprising a step of cutting the workpiece along the scheduled cutting line with the modified region as a starting point of cutting. By aligning a condensing point inside the plate-like workpiece and irradiating the laser beam, the modified region serving as a starting point for cutting is formed along the plurality of scheduled cutting lines set on the workpiece. A laser processing apparatus for forming inside a workpiece,
A mounting table on which the workpiece is mounted;
A laser light source for emitting the laser light;
A condensing lens that condenses the laser light emitted from the laser light source inside the processing object placed on the mounting table,
Control means for controlling the behavior of at least one of the mounting table and the condensing lens,
The control means includes
Control for operating at least one of the mounting table and the condensing lens to form the modified region along the planned cutting line extending in a predetermined direction in a predetermined region;
In the region located on one side of the predetermined region in the predetermined direction and the direction intersecting the thickness direction of the workpiece, the modification is performed along the scheduled cutting line extending in the predetermined direction. A control for operating at least one of the mounting table and the condensing lens to form a quality region;
In the region located on the other side of the predetermined region in the predetermined direction and the direction intersecting the thickness direction of the workpiece, the modification is performed along the planned cutting line extending in the predetermined direction. In order to form the quality region, the control for operating at least one of the mounting table and the condensing lens is performed,
Control for forming the modified region in a region located on one side of the predetermined region, control for forming the modified region in a region located on the other side of the predetermined region, And a control for forming the modified region in the predetermined region in this order.

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