Laser processing apparatus and laser processing method

Abstract

A laser processing apparatus includes an irradiation section and a control section. The irradiation section has a spatial light modulator and a condensing section that condenses laser light modulated by the spatial light modulator on an object. The control section performs first control that modulates the laser light with the spatial light modulator to split the laser light into a plurality of beams of processing light, and a plurality of condensing points of the plurality of beams of processing light are located at different positions from each other in a direction perpendicular to an irradiation direction of the laser light. In the first control, the laser light is modulated so that, in the irradiation direction, between a condensing point of unmodulated light of the laser light and an opposite surface of the object on a side opposite to a surface of incidence of the laser light, there is a crack that extends from a plurality of modified points constituting a modified region and is connected along an imaginary surface.

Description

TECHNICAL FIELD

[0001] The present application relates to a laser processing apparatus and a laser processing method. BACKGROUND

[0002] Patent Document 1 describes a laser processing apparatus including a holding mechanism that holds a workpiece, and a laser irradiation mechanism that irradiates the workpiece held by the holding mechanism with laser light. The laser processing apparatus described in Patent Document 1 is configured such that the laser irradiation mechanism having a condenser lens is fixed with respect to a base, and the workpiece is moved by the holding mechanism in a direction perpendicular to an optical axis of the condenser lens.

[0003] [Related Art Documents]

[0004] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent No. 5456510 SUMMARY

[0006] [Problems to be Solved by the Invention]

[0007] In the laser processing apparatus described above, sometimes a modified region is formed inside an object along an imaginary plane by irradiating the object with laser light. In this case, a portion of the object is peeled off with the modified region extending over the imaginary plane and a crack extending from the modified region as boundaries. In such a peeling process, sometimes so-called multi-focus laser processing is performed, that is, the laser light is modulated to split the laser light into a plurality of beams of processing light to perform processing. However, the peeling process that performs the multi-focus laser processing has a problem that damage of a portion of the object on the side opposite to the laser light incident side (for example, a functional element layer) by unmodulated light of the laser light becomes significant.

[0008] Therefore, it is a technical problem of the present application to provide a laser processing apparatus and a laser processing method that can suppress damage of a portion of an object on the side opposite to the laser light incident side.

[0009] [Means of Solving the Technical Problem]

[0010] The laser processing apparatus of one embodiment of the present application forms a modified region along an imaginary surface inside an object by irradiating laser light on the object, and includes a support portion that supports the object, an irradiation portion that irradiates laser light on the object supported by the support portion, a moving mechanism that moves at least one of the support portion and the irradiation portion, and a control portion that controls the irradiation portion and the moving mechanism. The irradiation portion includes a spatial light modulator that modulates laser light and a condensing portion that condenses the laser light modulated by the spatial light modulator on the object. The control portion performs first control in which the laser light is modulated by the spatial light modulator so that the laser light is split into a plurality of beam processing lights, and a plurality of focal points of the plurality of beam processing lights are located at different positions from each other in a direction perpendicular to an irradiation direction of the laser light. In the first control, the laser light is modulated so that a crack that extends from a plurality of modified points that constitute the modified region and is connected in a manner of extending along the imaginary surface exists between a side opposite to a surface on which the laser light is incident and an opposite surface of the object in the irradiation direction of the laser light.

[0011] In the laser processing apparatus, the laser light is split into the plurality of beam processing lights, and the plurality of focal points of the plurality of beam processing lights are located at different positions from each other in the direction perpendicular to the irradiation direction. At this time, the crack that extends from the plurality of modified points that constitute the modified region and is connected in the manner of extending along the imaginary surface exists between the focal point of the non-modulated light of the laser light and the opposite surface of the object on the side opposite to the surface on which the laser light is incident. With the crack, the non-modulated light of the laser light can be blocked from reaching the side opposite to the laser light incident side of the object. Thus, it is possible to inhibit an occurrence of damage on the opposite side of the object due to the non-modulated light of the laser light. That is, it is possible to inhibit damage of the side opposite to the laser light incident side of the object.

[0012] In the laser processing apparatus of one embodiment of the present application, the crack that extends from the plurality of modified points can be connected in a manner of extending in a planar shape along the imaginary surface. With such a crack, the non-modulated light of the laser light can be effectively blocked.

[0013] In the laser processing apparatus of one embodiment of the present application, the object can include a substrate and a functional element layer provided on the side opposite to the laser light incident side of the substrate. In this case, since the functional element layer is provided on the opposite side of the object, the above effect of inhibiting damage of the opposite side of the object is particularly effective.

[0014] In the laser processing apparatus of one embodiment of the present application, the control portion can perform second control in which at least one of the support portion and the irradiation portion is moved by the moving mechanism so that the positions of the focal points of the plurality of beam processing lights are moved along the imaginary surface. By moving the positions of the focal points of the plurality of beam processing lights along the imaginary surface, the modified region along the imaginary surface can be formed in detail.

[0015] In the laser processing apparatus of one embodiment of the present application, in the first control, the plurality of focal points of the plurality of beams of processing light can be moved in a direction perpendicular to the direction of irradiation of the laser light so that a crack exists between the focal point of the non-modulated light of the laser light and the opposite surface in the direction of irradiation. Thus, the crack can be reliably formed between the focal point of the non-modulated light of the laser light and the opposite surface of the laser light incident surface in the direction of irradiation of the laser light.

[0016] In the laser processing apparatus of one embodiment of the present application, in the second control, at least one of the support portion and the irradiation portion can be moved so that the positions of the focal points of the plurality of beams of processing light are moved along the processing line, and cracks extending from the plurality of modified points and connected to each other in a direction along the processing line and a direction intersecting the processing line are stretched. With such cracks, the non-modulated light of the laser light can be effectively blocked.

[0017] In the laser processing apparatus of one embodiment of the present application, in the first control, the laser light can be modulated so that in the direction of irradiation, each focal point of the plurality of beams of processing light is located on the opposite side to the ideal focal point of the processing light from the focal point of the non-modulated light of the laser light, or each focal point of the plurality of beams of processing light is located on the opposite side to the ideal focal point of the processing light from the focal point of the non-modulated light. Thus, as a result, the focal point of the non-modulated light of the laser light can be moved away from the side of the object opposite to the laser light incident side. Thus, the case where damage is caused on the opposite side of the object by the focal point of the non-modulated light of the laser light can be prevented.

[0018] In the laser processing apparatus of one embodiment of the present application, in the first control, the laser light can be modulated so that in the direction of irradiation, a modified region exists between the focal point of the non-modulated light of the laser light and the opposite surface of the object. In this case, with the modified region, the non-modulated light of the laser light can be blocked from reaching the side of the object opposite to the laser light incident side. Thus, the case where damage is caused on the opposite side of the object by the non-modulated light of the laser light can be prevented.

[0019] The laser processing method of one embodiment of the present application forms a modified region along a virtual surface in the inside of an object by irradiating the object with laser light, and includes a step of splitting the laser light into a plurality of beams of processing light and moving a plurality of focal points of the plurality of beams of processing light to different positions in a direction perpendicular to the direction of irradiation of the laser light, in which step a crack extending from a plurality of modified points constituting the modified region and connected to each other in a direction along the virtual surface exists between the focal point of the non-modulated light of the laser light and the opposite surface of the object on the side opposite to the laser light incident surface in the direction of irradiation.

[0020] With this laser processing method, the non-modulated light of the laser can be blocked by the crack present between the condensing point of the non-modulated light and the opposite surface of the object, so that the non-modulated light of the laser does not reach the opposite side of the object. Therefore, the non-modulated light of the laser can be prevented from causing damage to the opposite side of the object. That is, the damage to the opposite side of the object from the laser incident side can be prevented.

[0021] [Effects of Invention]

[0022] According to the present application, a laser processing apparatus and a laser processing method that can prevent damage to the opposite side of the object from the laser incident side can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a structural view of the laser processing apparatus of the first embodiment.

[0024] Figure 2 is a cross-sectional view of a part of the spatial light modulator shown in Figure 1

[0025] Figure 3 (a) is a plan view of the object. Figure 3 (b) is a cross-sectional view of the object.

[0026] Figure 4 is a schematic plane for explaining the splitting of the laser.

[0027] Figure 5 is a side cross-sectional view of the object for explaining the multi-focal point processing control of the first embodiment.

[0028] Figure 6 is a side cross-sectional view of the object for explaining the multi-focal point processing control of the first embodiment.

[0029] Figure 7 is a graph showing the results of the evaluation test for evaluating the peeling processing of the first embodiment.

[0030] Figure 8 is a graph showing a display example of the input accepting section of the first embodiment.

[0031] Figure 9 is a side cross-sectional view of the object for explaining the multi-focal point processing control of the first embodiment.

[0032] Figure 10 is a side cross-sectional view of the object for explaining the multi-focal point processing control of the second embodiment.

[0033] Figure 11 is a graph showing the results of the evaluation test for evaluating the peeling processing of the second embodiment. ​

[0034] Figure 12 It is a side cross-sectional view of an object for explaining multi-focus processing control according to a modification of the second embodiment.

[0035] Figure 13 It is a side cross-sectional view of an object for explaining multi-focus processing control according to another modified example of the second embodiment.

[0036] Figure 14 It is a side cross-sectional view of an object for explaining multi-focus processing control according to the third embodiment.

[0037] Figure 15 This is a top cross-sectional view of an object for explaining cracks in the third embodiment.

[0038] Figure 16 It is a figure which shows the result of the evaluation test which evaluated the peeling process of 3rd Embodiment. DETAILED DESCRIPTION

[0039] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. In each drawing, the same or corresponding parts are given the same reference numerals, and repeated descriptions are omitted.

[0040] [First embodiment]

[0041] The first embodiment is described. Figure 1 As shown, a laser processing apparatus 1 includes a support unit 2, a light source 3, an optical axis adjustment unit 4, a spatial light modulator 5, a focusing unit 6, an optical axis monitoring unit 7, a visible light imaging unit 8A, an infrared light imaging unit 8B, a moving mechanism 9, and a control unit 10. The laser processing apparatus 1 forms a modified region 12 on an object 11 by irradiating the object 11 with laser light L. In the following description, three mutually orthogonal directions are referred to as the X-direction, the Y-direction, and the Z-direction. In this embodiment, the X-direction is a first horizontal direction, the Y-direction is a second horizontal direction perpendicular to the first horizontal direction, and the Z-direction is a vertical direction.

[0042] The support portion 2 supports the object 11, for example, by adsorbing a thin film (not shown) attached to the object 11, so that the surface 11a and back surface 11b of the object 11 are perpendicular to the Z direction. The support portion 2 is movable in both the X and Y directions. In the support portion 2 of this embodiment, the object 11 is placed with the back surface 11b of the object 11 on the laser incident side, i.e., on the upper side (with the surface 11a on the side of the support portion 2, i.e., on the lower side). The support portion 2 has a rotation axis 2R extending in the Z direction. The support portion 2 is rotatable about the rotation axis 2R.

[0043] The light source 3 emits laser light L, for example, by a pulse oscillation method. The laser light L has a penetrating property (projecting property) with respect to the object 11. The optical axis adjusting section 4 adjusts the optical axis of the laser light L emitted from the light source 3. In the present embodiment, the optical axis adjusting section 4 adjusts the optical axis of the laser light L while changing the traveling direction of the laser light L emitted from the light source 3 so as to be along the Z direction. The optical axis adjusting section 4 is configured, for example, by a plurality of mirrors whose position and angle are adjustable.

[0044] The spatial light modulator 5 is disposed in the laser processing head H. The spatial light modulator 5 modulates the laser light L emitted from the light source 3. In the present embodiment, the laser light L traveling downward along the Z direction from the optical axis adjusting section 4 is incident into the laser processing head H, the laser light L incident into the laser processing head H is reflected horizontally by the mirror Hl so as to have an angle with respect to the Y direction, and the laser light L reflected by the mirror Hl is incident into the spatial light modulator 5. The spatial light modulator 5 reflects and modulates the laser light L thus incident along the Y direction horizontally.

[0045] The condensing section 6 is installed in the bottom wall of the laser processing head H. The condensing section 6 condenses the laser light L modulated by the spatial light modulator 5 to the object 11 supported by the supporting section 2. In the present embodiment, the laser light L reflected horizontally along the Y direction by the spatial light modulator 5 is reflected by the dichroic mirror H2 to the lower side along the Z direction, and the laser light L reflected by the dichroic mirror H2 is incident into the condensing section 6. The condensing section 6 condenses the laser light L thus incident to the object 11. The condensing section 6 is configured such that a condensing lens unit 61 is installed in the bottom wall of the laser processing head H by (with the aid of) a driving mechanism 62. The driving mechanism 62 moves the condensing lens unit 61 along the Z direction using, for example, the driving force of a piezoelectric element.

[0046] Further, in the laser processing head H, between the spatial light modulator 5 and the condensing section 6, an imaging optical system (omitted from illustration) is disposed. The imaging optical system configures a two-side telecentric optical system in which the reflecting surface of the spatial light modulator 5 and the entrance pupil surface of the condensing section 6 are in an imaging relationship. Thereby, the image of the laser light L on the reflecting surface of the spatial light modulator 5 (the image of the laser light L modulated by the spatial light modulator 5) is imaged on the entrance pupil surface of the condensing section 6. On the bottom wall of the laser processing head H, a pair of distance measuring sensors S1, S2 is installed which are located on both sides of the condensing lens unit 61 in the X direction. Each distance measuring sensor S1, S2 emits light (for example, laser light) for distance measurement with respect to the back surface 11b of the object 11, detects the light for distance measurement reflected by the back surface 11b, and thereby acquires displacement data of the back surface 11b. The laser processing head H configures an irradiation section.

[0047] The optical axis monitoring section 7 is arranged in the laser processing head H. The optical axis monitoring section 7 detects a part of the laser L that has passed through the dichroic mirror H2. The detection result of the optical axis monitoring section 7 indicates, for example, the relationship between the optical axis of the laser L that has entered the condenser lens unit 61 and the optical axis of the condenser lens unit 61. The visible light camera 8A is arranged in the laser processing head H. The visible light camera 8A emits visible light V and acquires an image of the object 11 caused by the visible light V. In the present embodiment, the visible light V emitted from the visible light camera 8A is irradiated to the back surface lib of the object 11 via the dichroic mirror H2 and the condenser section 6, and the visible light V reflected from the back surface lib is detected by the visible light camera 8A via the condenser section 6 and the dichroic mirror H2. The infrared light camera 8B is attached to a side wall of the laser processing head H. The infrared light camera 8B emits infrared light and acquires an infrared image of the object 11 caused by the infrared light.

[0048] The moving mechanism 9 includes a mechanism that moves the laser processing head H in the X direction, the Y direction, and the Z direction. The moving mechanism 9 drives the laser processing head H by the driving force of a known driving device such as a motor, to move the condensing point C of the laser L in the X direction, the Y direction, and the Z direction. In addition, the moving mechanism 9 includes a mechanism that rotates the support section 2 about the rotation axis 2R. The moving mechanism 9 rotationally drives the support section 2 by the driving force of a known driving device such as a motor, to move the condensing point C of the laser L in the θ direction about the rotation axis 2R.

[0049] The control section 10 controls the operation of each section of the laser processing apparatus 1. The control section 10 controls at least the spatial light modulator 5 and the moving mechanism 9. The control section 10 has a processing section 101, a storage section 102, and an input accepting section 103. The processing section 101 is configured as a computer device including a processor, a memory (a storage), a storage section, and a communication device, and the like. In the processing section 101, the processor executes software (a program) read to the memory or the like, and controls the reading and writing of data of the memory and the storage section, and the communication of the communication device.

[0050] The storage section 102 is, for example, a hard disk or the like, and stores various data. The input accepting section 103 is an interface section that accepts the input of various data from an operator. In the present embodiment, the input accepting section 103 configures a GUI (Graphical User Interface). The input accepting section 103 accepts the input of a slicing position and a Z direction offset as described later.

[0051] In the laser processing apparatus 1 configured as described above, when the laser L is condensed inside the object 11, the laser L is absorbed at a portion corresponding to the condensing point C of the laser L, and a modified region 12 is formed inside the object 11. The modified region 12 is a region in which physical properties such as density, refractive index, and mechanical strength are different from those of a non-modified region around the modified region 12. As the modified region 12, for example, there are a fusion-processed region, a crack region, an insulation-destroyed region, a refractive index- changed region, and the like. The modified region 12 includes a plurality of modified points 12s and cracks extending from the plurality of modified points 12s.

[0052] The spatial light modulator 5 will be described in detail. The spatial light modulator 5 is a spatial light modulator (SLM) of a reflective type liquid crystal on silicon (LCOS). As shown in FIG. 6, the spatial light modulator 5 is configured by sequentially stacking a drive circuit layer 52, a pixel electrode layer 53, a reflective film 54, an orientation film 55, a liquid crystal layer 56, an orientation film 57, a transparent conductive film 58, and a transparent substrate 59 on a semiconductor substrate 51. Figure 2

[0053] The semiconductor substrate 51 is, for example, a silicon substrate. The drive circuit layer 52 configures an active matrix circuit on the semiconductor substrate 51. The pixel electrode layer 53 includes a plurality of pixel electrodes 53a arranged in a matrix shape along a surface of the semiconductor substrate 51. Each pixel electrode 53a is formed of, for example, a metal material such as aluminum. A voltage can be applied to each pixel electrode 53a by the drive circuit layer 52.

[0054] The reflective film 54 is, for example, a dielectric multilayer film. The orientation film 55 is provided on a surface of the liquid crystal layer 56 on the reflective film 54 side, and the orientation film 57 is provided on a surface of the liquid crystal layer 56 on the opposite side from the reflective film 54. Each of the orientation films 55 and 57 is formed of, for example, a high molecular material such as polyimide, and a rubbing process is applied to a surface of each of the orientation films 55 and 57 that contacts the liquid crystal layer 56. The orientation films 55 and 57 align liquid crystal molecules 56a contained in the liquid crystal layer 56 in a certain direction.

[0055] The transparent conductive film 58 is provided on a surface of the transparent substrate 59 on the orientation film 57 side, and opposes the pixel electrode layer 53 via the liquid crystal layer 56 and the like. The transparent substrate 59 is, for example, a glass substrate. The transparent conductive film 58 is formed of, for example, a material that is optically transmissive and electrically conductive such as ITO. The transparent substrate 59 and the transparent conductive film 58 transmit the laser L.

[0056] ​In the spatial light modulator 5 configured as described above, when a signal representing a modulation pattern is input from the control unit 10 to the drive circuit layer 52, a voltage corresponding to the signal is applied to each pixel electrode 53a, forming an electric field between each pixel electrode 53a and the transparent conductive film 58. When this electric field is formed, the arrangement direction of the liquid crystal molecules 56a in each region corresponding to each pixel electrode 53a in the liquid crystal layer 56 changes, causing the refractive index in each region corresponding to each pixel electrode 53a to change. This state indicates that the modulation pattern is displayed in the liquid crystal layer 56.

[0057] When the liquid crystal layer 56 displays a modulation pattern, laser light L is incident on the liquid crystal layer 56 from the outside through the transparent substrate 59 and the transparent conductive film 58, is reflected by the reflective film 54, and is emitted (emitted) from the liquid crystal layer 56 through the transparent conductive film 58 and the transparent substrate 59 to the outside. In this manner, the laser light L is modulated according to the modulation pattern displayed on the liquid crystal layer 56. Thus, according to the spatial light modulator 5, by appropriately setting the modulation pattern displayed on the liquid crystal layer 56, it is possible to modulate the laser light L (e.g., modulate the intensity, amplitude, phase, polarization (polarization), etc. of the laser light L).

[0058] The structure of the object 11 will be described in detail. The object 11 of this embodiment is as follows. Figure 3 (a) and Figure 3 (b) shows a wafer formed into a circular plate shape. The object 11 has a surface (first surface) 11a and a back surface (second surface) 11b opposite to the surface 11a. The object 11 includes a substrate 21 and a device layer (functional element layer) 22 provided on the side of the substrate 21 opposite to the laser incident surface. The object 11 is constructed by stacking the device layer 22 on the substrate 21.

[0059] The substrate 21 is, for example, a semiconductor substrate such as a silicon substrate. The substrate 21 may also be provided with a notch or an orientation flat indicating the crystal orientation. The device layer 22 is provided on the surface 11a side of the object 11. The device layer 22 includes a plurality of functional elements arranged in a matrix along the main surface of the substrate 21. The device layer 22 includes metal layers such as a Ti (titanium) layer and a Sn (tin) layer vapor-deposited on the substrate 21. Each functional element is, for example, a light-receiving element such as a photodiode, a light-emitting element such as a laser diode, a circuit element such as a memory, etc. Each functional element is sometimes three-dimensionally constructed by stacking multiple layers.

[0060] An imaginary surface Ml is set in the object 11 as a peeling intended surface. The imaginary surface Ml is a surface in which the modified region 12 is intended to be formed. The imaginary surface Ml is a surface opposite to the laser incidence surface, that is, the back surface lib of the object 11. The imaginary surface Ml is a surface parallel to the back surface lib, for example, a circular shape. The imaginary surface (virtual surface) Ml is an imaginary region, and is not limited to a flat surface, but can be a curved surface or even a three-dimensional surface.

[0061] Further, a processing line 15 is set in the object 11. The processing line 15 is a line in which the modified region 12 is intended to be formed. The processing line 15 extends in a spiral shape from the outer periphery side to the inner side in the object 11. In other words, the processing line 15 extends in a spiral shape (involute) with the position of the rotation axis 2R (see FIG. 2) of the support portion 2 as the center. The processing line 15 is an imaginary line, but can also be an actually drawn line. The imaginary surface Ml and the processing line 15 can be set by the control portion 10. The imaginary surface Ml and the processing line 15 can be obtained by performing coordinate designation. Either one of the imaginary surface Ml and the processing line 15 can be set. Figure 1 ) of the support portion 2 as the center. The processing line 15 is an imaginary line, but can also be an actually drawn line. The imaginary surface Ml and the processing line 15 can be set by the control portion 10. The imaginary surface Ml and the processing line 15 can be obtained by performing coordinate designation. Either one of the imaginary surface Ml and the processing line 15 can be set.

[0062] The laser processing apparatus 1 of the present embodiment forms the modified region 12 inside the object 11 along the imaginary surface Ml by focusing the condensing point (at least a part of the condensing region) C of the laser L on the object 11, and irradiating the laser L. The laser processing apparatus 1 performs laser processing including peeling processing on the object 11, and obtains (manufactures) a semiconductor element. The peeling processing is processing for peeling a part of the object 11.

[0063] The control portion 10 performs multi-focal point processing control (1st control) for modulating the laser L by the spatial light modulator 5 so that the laser L is split into a plurality of processing lights, and a plurality of condensing points of the plurality of processing lights are located at different positions from each other in a direction perpendicular to the irradiation direction of the laser L. For example, in the multi-focal point processing control, the spatial light modulator 5 is controlled so that the liquid crystal layer 56 of the spatial light modulator 5 displays a prescribed modulation pattern (a modulation pattern including a diffraction pattern, etc.). In this state, the laser L is emitted from the light source 3, and is condensed on the object 11 from the back surface lib side by the condensing portion 6. That is, the laser L is modulated by the spatial light modulator 5, and the modulated laser L is condensed on the object 11 by the condensing portion 6 with the back surface lib as the laser incidence surface. Thus, the laser L is split (diffracted) into two processing lights LI, L2, and the condensing points CI, C2 of the two processing lights LI, L2 are located at different positions from each other in the X direction and / or the Y direction.

[0064] In the present embodiment, the laser processing apparatus 1 is configured to perform the multi-focal point processing control (1st control) and the peeling processing control (2nd control) described above. Figure 4In the example shown, the laser light L is split into two processing lights L1, L2 so that two modified points 12s arranged in a line in an oblique direction K2 oblique with respect to a processing direction K1 (an extension direction of the processing line 15) are formed on the virtual plane M1. The processing light L1 is -1st order light, and the processing light corresponds to +1st order light. With respect to the plurality of modified points 12s formed at the same time, the interval in the X direction is a split interval BPx, and the interval in the Y direction is a split interval BPy. With respect to a pair of modified points 12s formed by irradiation of the laser light L by two continuous pulses, the interval in the processing direction K1 is a pulse interval PP. The angle between the processing direction K1 and the oblique direction K2 is a split angle a.

[0065] In the multi-focal point processing control, as shown in Figure 5 The laser light L is modulated so that the focal points C1, C2 of the respective plurality of processing lights L1, L2 in the Z direction are shifted to the device layer 22 side with respect to the ideal focal points C10, C20 by a prescribed amount (i.e., a Z direction shift amount). Specifically, in the multi-focal point processing control, the laser light L is modulated by the spatial light modulator 5 so that the focal points C1, C2 of the respective plurality of processing lights L1, L2 in the Z direction are shifted to the device layer 22 side with respect to the ideal focal points C10, C20 by a prescribed amount (i.e., a Z direction shift amount).

[0066] The ideal focal point of the processing light is the focal point assuming that there is no spherical aberration and the processing light is focused in a point in the object 11. The non-modulated light L0 of the laser light L is light of the laser light L incident to the spatial light modulator 5 that is emitted from the spatial light modulator 5 without being modulated by the spatial light modulator 5. For example, light of the laser light L incident to the spatial light modulator 5 that is reflected by the outer side surface (a surface on the side opposite the transparent conductive film 58) of the transparent substrate 59 is the non-modulated light L0. The focal point C0 of the non-modulated light L0 corresponds to the focal position of the condenser lens unit 61. When the non-modulated light L0 is located inside the object 11, or is located on the side opposite the incident side by the object 11 (refer to FIG. 6), although the focal region extends in the Z direction due to the influence of spherical aberration and the like, the point that is most affected by the damage, i.e., the point with the strongest intensity, is defined as the focal point C0. Figure 9

[0067] ​In the multi-focal point machining control, the spatial light modulator 5 is used to modulate the laser light L so that the condensing point CO of the non-modulated light L0 is located inside the object 11 on the laser light incident side (back surface 1 lb side) in the Z direction. In the multi-focal point machining control, based on the cutting position and the Z direction offset amount accepted by the input accepting section 103, the condensing points CI, C2 of the respective plural beams of machining light LI, L2 are offset from the ideal condensing points CIO, C20 of the machining light LI, L2 to positions along the imaginary plane Ml. Such offset of the condensing points CI, C2 of the machining light LI, L2 can be achieved by appropriately controlling the modulation pattern displayed by the liquid crystal layer 56 of the spatial light modulator 5.

[0068] The control section 10 performs, together with irradiation of the laser light L from the laser machining head H, movement control (2nd control) that moves at least one of the support section 2 and the laser machining head H by the movement mechanism 9 so that the positions of the condensing points CI, C2 of the plural beams of machining light LI, L2 are moved along the imaginary plane Ml. In the movement control, at least one of the support section 2 and the laser machining head H is moved so that the positions of the condensing points CI, C2 of the plural beams of machining light LI, L2 are moved along the machining line 15. In the movement control, the movement of the laser machining head H (condensing points CI, C2) in the X direction is controlled while the support section 2 is rotated.

[0069] The control section 10 can perform various controls based on rotation information (hereinafter referred to as "θ information") about the amount of rotation of the support section 2. The θ information can be acquired from the amount of driving of the movement mechanism 9 that rotates the support section 2, or can be acquired by other sensors or the like. The θ information can be acquired by various methods known per se. The control section 10 controls the display of the input accepting section 103. The control section 10 performs peeling machining based on various settings input from the input accepting section 103.

[0070] Next, a laser machining method of the laser machining device 1 will be described. Here, an example of performing peeling machining on the object 11 using the laser machining device 1 will be described.

[0071] First, the object 11 is placed on the support section 2 in a state where the back surface 1 lb is on the laser light incident surface side. The surface 1 la side of the object 11 on which the device layer 22 is mounted is protected by being bonded to a support substrate or the like or by a tape material. Next, height setting (Height set) is performed in which the laser machining head H (i.e., the condensing section 6) is moved in the Z direction so that the condensing point C of the laser light L is located on the back surface 1 lb, based on an image (e.g., an image of the back surface 1 lb of the object 11) acquired by the visible light camera 8A. The laser machining head H is moved in the Z direction so that the condensing point C of the laser light L is located at a prescribed depth from the back surface 1 lb, with reference to the position of the height set.

[0072] Hereinafter, the position of the condensing section 6 after the laser machining head H has been moved from the position set by the height in the Z direction will be referred to as the "defocus position". Here, the defocus position is a parameter that becomes more negative (negative side) as the condensing section 6 is closer to the object 11, with the position at the time of height setting as the reference (defocus position = 0). The prescribed depth is the depth at which a modified region 12 can be formed along the imaginary surface Ml of the object 11.

[0073] Next, while rotating the support section 2 at a certain rotational speed, laser light L is irradiated from the light source 3, and the laser machining head H is moved in the X direction to move the condensing point C in the X direction from the outer edge side to the inner side of the imaginary surface Ml. Thereby, a modified region 12 extending in a spiral shape with the position of the rotational axis 2R (refer to FIG. 2) as the center is formed along the machining line 15 on the imaginary surface Ml of the object 11. Figure 1 ) of the object 11.

[0074] In forming the modified region 12, multi-focal machining control is performed to split the laser light L into a plurality of beams of machining light Ll, L2, and to position a plurality of condensing points Cl, C2 of the plurality of beams of machining light Ll, L2 at different positions from each other in the X direction and / or the Y direction. Also, the positions of the condensing points Cl, C2 of the plurality of beams of machining light Ll, L2 are relatively moved along the imaginary surface Ml. Thereby, a plurality of modified points 12s can be formed along the imaginary surface Ml. At this time, based on the displacement data of the back surface lib obtained by the distance measuring sensor located on the front side of the machining direction Kl among the pair of distance measuring sensors S l, S2, the drive mechanism 62 of the condensing section 6 is operated to cause the condensing point C of the laser light L to follow the back surface lib.

[0075] The modified region 12 formed includes a plurality of modified points 12s. One modified point 12s is formed by irradiation of one pulse of laser light L. The modified region 12 is a collection of a plurality of modified points 12s. Adjacent modified points 12s are connected to each other in some cases, and are separated from each other in some cases, depending on the pulse pitch PP of the laser light L (a value obtained by dividing the relative movement speed of the condensing point C with respect to the object 11 by the repetition frequency of the laser light L).

[0076] Next, a portion of the object 11 is peeled off with the modified region 12 extending over the imaginary surface Ml and the cracks extending from the modified points 12s of the modified region 12 as boundaries. The peeling of the object 11 can be performed using, for example, a suction jig (jig). The peeling of the object 11 can be performed on the support section 2, or can be performed by moving to a region dedicated to peeling. The peeling of the object 11 can also be performed using air blowing or adhesive tape. In a case where the object 11 cannot be peeled off only by external stress, an etching liquid (KOH or TMAH, etc.) that reacts with the object 11 can be used to selectively etch the modified region 12. Thereby, the object 11 can be easily peeled off.

[0077] In the above manner, although the support portion 2 is caused to rotate at a certain rotational speed, the rotational speed can also be varied. For example, the rotational speed of the support portion 2 can also be varied so that the pulse pitch PP of the modified points 12s is a certain interval. As for the peeling surface of the object 11, finishing lapping or lapping using a lapping material such as an emery stone can also be performed. In the case where the object 11 is peeled by etching, the lapping can also be simplified.

[0078] However, the conventional multi-focal point machining control in general, such as Figure 6 is configured so that the respective condensing points Cl, C2 of the multiple machining lights Ll, L2 coincide with the ideal condensing points CIO, C20 thereof, as shown. In this case, there is a problem in that the device layer 22 is damaged due to the influence of the leakage light (light that is not absorbed by the object 11) of the non-modulated light LO of the laser light L. In particular, in the peeling machining, this problem becomes significant. This is because, in the peeling machining, the laser light L also irradiates the active region of the device layer 22, and thus the leakage light of the non-modulated light LO easily causes damage directly below the device layer 22, and even easily causes deterioration of the device characteristics.

[0079] In this regard, according to the multi-focal point machining control of the present embodiment, the respective condensing points Cl, C2 of the multiple machining lights Ll, L2 are located on the side opposite to the condensing point CO of the non-modulated light LO of the laser light L with respect to the ideal condensing points CIO, C20 of the machining lights Ll, L2 in the Z direction. Specifically, the respective condensing points Cl, C2 of the multiple machining lights Ll, L2 are located at positions closer to the device layer 22 by a Z-direction offset amount with respect to the ideal condensing points CIO, C20. Compared to the case where the ideal condensing points CIO, C20 are located at positions along the imaginary surface Ml (refer to the comparative example described later), the defocus positions are located on the side away from the device layer 22 by the Z-direction offset amount. Compared to the case where the ideal condensing points CIO, C20 are located at positions along the imaginary surface Ml, the condensing point CO of the non-modulated light LO is located on the side away from the device layer 22 by the Z-direction offset amount.

[0080] Accordingly, according to the laser machining device 1 and the laser machining method, the condensing point CO of the non-modulated light LO of the laser light L is distanced from the device layer 22 of the object 11 as a result. The energy density of the leakage light that reaches the device layer 22 can be suppressed. The adverse effects of the condensing of the non-modulated light LO on the device layer 22 can be reduced. The occurrence of damage to the device layer 22 of the object 11 by the condensing of the non-modulated light LO can be suppressed. That is, the damage to the device layer 22 (the side opposite to the laser light incidence side) of the object 11 can be suppressed.

[0081] In the multi-focal processing control of the laser processing apparatus 1, the laser L is modulated by the spatial light modulator 5 so that the condensing point CO of the non-modulated light LO is located inside the object 11 on the laser incidence side (the back surface lib side) in the Z direction. In other words, in the laser processing method, the condensing point CO of the non-modulated light LO is located inside the object 11 on the laser incidence side in the Z direction. Thereby, the condensing point CO of the non-modulated light LO can be effectively distanced from the device layer 22 of the object 11.

[0082] In the laser processing apparatus 1 and the laser processing method, the object 11 includes the substrate 21 and the device layer 22. Since the device layer 22 is provided on the side of the object 11 opposite to the laser incidence side, as an effect of suppressing damage to the side of the object 11 opposite to the laser incidence side, an effect of suppressing damage to the device layer 22 of the object 11 can be exerted. This effect is particularly effective.

[0083] In the laser processing apparatus 1 and the laser processing method, at least one of the support 2 and the laser processing head H is moved by the moving mechanism 9 so that the positions of the condensing points CI, C2 of the multiple beams of processing light LI, L2 are moved along the virtual plane Ml. By thus moving the positions of the condensing points CI, C2 of the multiple beams of processing light LI, L2 along the virtual plane Ml, the modified region 12 along the virtual plane Ml can be specifically formed.

[0084] Further, in the multi-focal processing control of the laser processing apparatus 1, it can also be that the laser L is modulated by the spatial light modulator 5 so that the condensing point CO of the non-modulated light LO is located outside the object 11 and on the condensing portion 6 side than the object 11 in the Z direction. In other words, in the laser processing method, it can also be that the condensing point CO of the non-modulated light LO is located outside the object 11 and on the condensing portion 6 side than the object 11 in the Z direction. Thereby, the condensing point CO of the non-modulated light LO can be effectively distanced from the device layer 22 of the object 11.

[0085] Figure 7 is a graph showing the results of evaluation tests for evaluating the peeling processing of the first embodiment.

[0086] In the graph, the comparative example is, for example Figure 6Examples of the peeling processing of the general multi-focus processing control are shown. Embodiment 1 is an example of the peeling processing of the multi-focus processing control of the first embodiment described above. The Z-direction offset amount indicates an absolute value. The damage evaluation photograph is a photograph of the object 11 (device layer 22) after the laser processing, viewed from the surface 11a. As the common processing conditions, the beam splitting pitch BPX is 100 μm, the beam splitting pitch BPy is 60 μm, the output (power) of the laser L is 3.7 W, the pulse energy (converted value assuming a loss of 20% due to beam splitting) is 18.5 μJ, the pulse pitch PP is 6.25 μm, the frequency is 80 kHz, and the pulse width is 700 ns. The object 11 is a wafer in which the surface 11a and the back surface 11b have a face orientation of

[100] . In the photograph in the drawing, the laser L is scanned along the processing line extending left and right.

[0087] As shown in Figure 7 , it is known that, in the comparative example, damage due to leakage of the non-modulated light L0 is intermittently exhibited along the processing line in the device layer 22 (refer to the dotted line in the drawing). In Embodiment 1, it is known that this damage can be avoided. Furthermore, it is also known that when the Z-direction offset amount is 5 μm, 10 μm, and 15 μm, it is difficult to avoid the occurrence of damage.

[0088] Figure 8 is a drawing showing an example of the display of the input accepting section 103. As shown in Figure 8 , the input accepting section 103 accepts input of various data from an operator. In the drawing, "SS1" indicates the processing light L1, and "SS2" indicates the processing light L2. The operator can input "beam splitting number" and "offset direction", and numerical values and the like regarding each processing light L1, L2, through the input accepting section 103.

[0089] In the example shown in Figure 8 , "2" is input in "beam splitting number", and "Z-direction" is input in "offset direction". That is, the laser processing method of the Z-direction offset in which the laser L is beam split into two processing lights L1, L2 is selected. The laser processing method of the Z-direction offset is, as described above, a laser processing method in which the focal points C1, C2 of the respective multiple processing lights L1, L2 are located at positions closer to the device layer 22 by the Z-direction offset amount with respect to the ideal focal points C10, C20.

[0090] The cutting position indicates the position (distance from the back surface 11b) of the virtual plane Ml in the object 11. The cutting position corresponds to the first data. The Z-direction offset amount indicates the distance of the respective condensing points Cl, C2 of the machining lights Ll, L2 from the ideal condensing points CIO, C20. The Z-direction offset amount corresponds to the second data. The "reference" input to the "spherical aberration" indicates the correction amount of the spherical aberration of the respective machining lights Ll, L2, L3. Further, in the input accepting section 103, the input of the Z-direction offset amount can also be limited so as to be a certain value or more.

[0091] Thus, in the laser processing apparatus 1, based on the various data including the cutting position and the Z-direction offset amount accepted by the input accepting section 103, it is possible to cause the condensing points Cl, C2 of the multiple machining lights Ll, L2 to be offset from the ideal condensing points CIO, C20. In this case, the operator can at least set the cutting position and the Z-direction offset amount as desired.

[0092] Figure 9 is a side sectional view of the object 11 to explain the multi-focal processing control of the first embodiment. As shown in Figure 9 In the multi-focal processing control, the laser light L can also be modulated so that the condensing points Cl, C2 of the respective machining lights Ll, L2 in the Z-direction are located on the side opposite to the ideal condensing points CIO, C20 from the condensing point CO of the non-modulated light L0. In the multi-focal processing control of this variant, the laser light L is modulated by the spatial light modulator 5 so that the condensing points Cl, C2 of the respective machining lights Ll, L2 in the Z-direction are located at positions closer to the condensing section 6 side by the Z-direction offset amount from the ideal condensing points CIO, C20.

[0093] In this variant as well, as a result, it is possible to cause the condensing point CO of the non-modulated light L0 to be distanced from the device layer 22 of the object 11. It is possible to suppress the energy density of the leakage light of the non-modulated light L0 reaching the device layer 22, and to suppress the damage to the device layer 22 (the side opposite to the laser light incidence side) in the object 11.

[0094] In the multi-focal processing control of the variant, the laser light L is modulated by the spatial light modulator 5 so that the condensing point CO of the non-modulated light L0 is located outside the object 11 and further on the side opposite to the condensing section 6 side from the object 11 in the Z-direction. In other words, in the laser processing method of the variant, the condensing point CO of the non-modulated light L0 is located outside the object 11 and further on the side opposite to the condensing section 6 side from the object 11 in the Z-direction. Thereby, it is possible to effectively cause the condensing point CO of the non-modulated light L0 to be distanced from the device layer 22 of the object 11.

[0095] [Second Embodiment]

[0096] The second embodiment will be described. In the description of the second embodiment, differences from the first embodiment will be described, and duplicate descriptions will be omitted.

[0097] In the second embodiment, the multi-focus processing control is as follows: Figure 10 As shown, the laser light L is modulated by the spatial light modulator 5, splitting (diffracting) the laser light L into three processing lights L1, L2, and L3, with their respective focal points C1, C2, and C3 located at different positions in the X and / or Y directions. Processing light L3 is zero-order light.

[0098] During multi-focus processing control, the spatial light modulator 5 modulates the laser light L so that a modified region 12 (modified spot 12m) resulting from the convergence of the processing light L3 exists between the focal point C0 of the non-modulated light L0 of the laser light L in the Z direction and the surface 11a (the surface opposite to the laser incident surface). Specifically, during multi-focus processing control, the modified spot 12m is formed by the convergence of the processing lights L1 and L2 of the processing lights L1 to L3 formed by the splitting of the laser light L. Simultaneously, the modified spot 12m is formed between the focal point C0 of the non-modulated light L0 in the Z direction and the surface 11a (directly below the focal point C0) by the convergence of the processing light L3, which is zero-order light.

[0099] The output of 0th-order processing light L3 is the smallest among the outputs of processing lights L1 to L3. Modified spot 12m, resulting from the convergence of 0th-order processing light L3, is smaller than modified spot 12s, resulting from the convergence of processing lights L1 and L2. Modified spot 12m contributes less to delamination along imaginary surface M1 of object 11 than modified spot 12s. For example, the output (energy) of processing lights L1 and L2 at modified spot 12s is 18.5 μJ, while the output (energy) of processing light L3 at modified spot 12m, which is smaller than this, is 8 μJ.

[0100] As described above, in the laser processing apparatus and laser processing method of the second embodiment, laser light L is split into multiple processing light beams L1 to L3, and the multiple light convergence points C1 to C3 of the multiple processing light beams L1 to L3 are positioned at different positions in the X and / or Y directions. In this case, a modified region 12 exists between the light convergence point C0 of the non-modulated light L0 and the surface 11a (device layer 22) of the object 11. This modified region 12 blocks the non-modulated light L0 from reaching the device layer 22 on the surface 11a side of the object 11. For example, from the point (time) when the temperature of the light convergence point C3 of the processing light L3 and its surrounding area rises and absorption begins, leakage of the non-modulated light L0 is also absorbed at the light convergence point C3 and its surrounding area. This reduces the amount of non-modulated light L0 leaking into the device layer 22 to a level that does not affect it. This prevents damage to the device layer 22 caused by the non-modulated light L0. In other words, damage to the device layer 22 of the object 11 can be suppressed.

[0101] In the laser processing apparatus and laser processing method of the second embodiment, the convergence of the zero-order processing light L3 included in the multiple processing lights L1 to L3 forms a modified spot 12m between the focal point C0 of the non-modulated light L0 in the Z direction and the surface 11a. This allows the modified spot 12m, formed simultaneously with the modified spot 12s, to block the non-modulated light L0 from reaching the device layer 22 of the object 11.

[0102] In the laser processing apparatus and laser processing method of the second embodiment, the output of processing light L3, which is zero-order light, is the smallest among the outputs of the multiple processing light beams L1 to L3. This makes it possible to reduce the likelihood of delamination of the object 11 along the imaginary plane M1 in the modified region 12 caused by the focusing of processing light L3, which is zero-order light.

[0103] Figure 11 : is a graph showing the results of the evaluation test for evaluating the peeling process of the second embodiment. Figure 6 The example of the conventional multi-focus processing control peeling process shown in the figure. Example 2 is an example of the multi-focus processing control peeling process of the second embodiment described above. The infrared image is an image of the position of the imaginary surface M1 obtained by the infrared light shooting unit 8B. The damage evaluation photograph is a photograph of the object 11 (device layer 22) after laser processing viewed from the surface 11a. In the image and photograph in the figure, the laser L is scanned along the processing line extending to the left and right. As Figure 11 As shown, in the comparative example, damage caused by light leakage of the non-modulated light L0 appears intermittently on the device layer 22 along the processing line (see the dotted line). However, in Example 2, it is found that this damage can be avoided.

[0104] Figure 121 is a side sectional view of an object 11 for explaining multi-focus machining control according to a modified example of the second embodiment. Figure 11 As shown, in multi-focus processing control, the output of zero-order processing light L3 can be made equal to the output of processing lights L1 and L2 (at least one of the multiple processing light beams L1 to L3, excluding zero-order processing light L3). This allows the modified region 12 (modified point 12m) formed by focusing zero-order processing light L3 to be used for debonding the object 11 along the imaginary plane M1.

[0105] Figure 13 1 is a side sectional view of an object 11 for explaining another modified example of the second embodiment of the multi-focus processing control. Figure 11 As shown, in multi-focus processing control, the spatial light modulator 5 can also be used to modulate the laser L, so that the focal points C1 and C2 of the processing light L1 and L2 move in a direction perpendicular to the irradiation direction of the laser L, so that the modified area 12 that has been formed (the modified point 12r in the example shown in the figure) is located between the focal point C0 of the non-modulated light L0 in the Z direction and the surface 11a.

[0106] For example, in multi-focus processing control, when laser light L is split into two beams and pulsed with processing lights L1 and L2, the spatial light modulator 5 may be used to move the focal points C1 and C2 of processing lights L1 and L2 in the X and / or Y directions so that the focal point C0 of the non-modulated light L0 is located directly above the modified region 12 formed by the previous pulsed irradiation of processing light L1 (or processing light L2). In this way, the non-modulated light L0 can be physically blocked by the formed modified region 12, preventing it from reaching the device layer 22.

[0107] The laser processing apparatus 1 and laser processing method of the second embodiment may also include the laser processing apparatus 1 and laser processing method of the first embodiment. Specifically, in the second embodiment, the light-converging points C1 and C2 of the processing lights L1 and L2 may be positioned opposite the light-converging point C0 of the non-modulated light L0 relative to the ideal light-converging points C10 and C20 in the Z direction, or may be positioned opposite the light-converging point C0 of the non-modulated light L0 relative to the ideal light-converging points C10 and C20. Consequently, the light-converging point C0 of the non-modulated light L0 may be positioned away from the device layer 22 (on the side opposite to the laser incident side).

[0108] [Third embodiment]

[0109] The third embodiment will be described. In the description of the third embodiment, differences from the first embodiment will be described, and duplicate descriptions will be omitted.

[0110] In the multi-focus processing control of the third embodiment, as Figure 14As shown, the laser light L is modulated so that the cracks FC extending from the modification points 12s and connected to each other along the imaginary surface Ml are located between the focal point C0 of the non-modulated light L0 in the Z direction and the surface 11a of the object 11 (the opposite surface of the laser light incidence surface).

[0111] The cracks FC extend in two dimensions (planarly) along the imaginary surface Ml and are connected to each other (see Figure 15 ). The cracks FC extend in the direction along the machining line 15 and the direction intersecting (orthogonal to) the machining line 15 and are connected. The cracks FC are peeling cracks. The cracks FC extend in the up-down-left-right directions at the position of the imaginary surface Ml in the infrared image taken by the infrared light imaging section 8B, and are connected across multiple machining lines 15. The cracks FC can be achieved in a case where the machining state is a full cutting state. The full cutting state is a state where the cracks FC extend from the modification points 12s, and is a state where the modification points 12s cannot be confirmed on the infrared image (the space formed by the cracks FC or even the gap can be confirmed) (see the infrared image of Example 3 of Figure 16 ).

[0112] The machining conditions in which such cracks FC can be achieved are conditions (full cutting conditions) in which various machining parameters are appropriately set based on known techniques so that the machining state is a full cutting (slicing full cut) state. As the full cutting conditions, for example, the output of the laser light L is 3.7 W, the pulse energy (assuming a converted value in which 20% is lost due to beam splitting) is 18.5 μJ, the pulse width is 700 ns, the beam splitting pitch BPx, BPy is 10 μ to 30 μm (in particular, the beam splitting pitch BPy is 30 μm), the machining speed is 800 mm / s, the pulse pitch PP is 10 μm, and the pulse width is 700 ns. In the multi-focal point machining control, laser machining is performed such that the full cutting conditions are the machining conditions.

[0113] As described above, in the laser machining device and the laser machining method of the third embodiment, the laser light L is split into the multiple beams of machining light L1 to L3, and the multiple focal points C1 to C3 of the multiple beams of machining light L1 to L3 are located at different positions from each other in the X direction and / or the Y direction. At this time, between the focal point C0 of the non-modulated light L0 of the laser light L and the surface 11a of the object 11, there are the cracks FC extending from the modification points 12s and connected to each other along the imaginary surface Ml. With the cracks FC, it is possible to block the non-modulated light L0 so as not to reach the device layer 22 on the surface 11a side of the object 11. Thus, it is possible to suppress the occurrence of damage (injury) in the device layer 22 of the object 11 due to the non-modulated light L0. That is, it is possible to suppress the damage of the device layer 22 of the object 11.

[0114] In the laser processing apparatus and laser processing method of the third embodiment, cracks FC extending from the plurality of modified points 12s are connected so as to extend two-dimensionally (planarly) along the imaginary plane M1. Such cracks FC can effectively block the non-modulated light L0.

[0115] In the laser processing apparatus and laser processing method of the third embodiment, cracks FC extending from the plurality of modified points 12s extend and connect in a direction along the processing line 15 and in a direction intersecting the processing line 15. Such cracks FC can effectively block the non-modulated light L0.

[0116] In the third embodiment, as long as the crack FC extends within the range (see Figure 15 If the translucent range is not specified, the spatial light modulator 5 can be used to move the focal points C1 and C2 of the processing lights L1 and L2 in the X and / or Y directions so that the focal point C0 of the non-modulated light L0 is located at any position directly above the crack FC. In other words, the focal points C1 and C2 of the processing lights L1 and L2 can be moved in a direction perpendicular to the irradiation direction of the laser light L so that the crack FC exists between the focal point C0 of the non-modulated light L0 in the Z direction and the surface 11a. In this way, the crack FC can be reliably located between the focal point C0 of the non-modulated light L0 in the Z direction and the surface 11a.

[0117] Figure 16 : is a graph showing the results of the evaluation test for evaluating the peeling process of the third embodiment. Figure 6 The example of the conventional multi-focus processing control peeling process shown in the figure. Example 3 is an example of the multi-focus processing control peeling process of the third embodiment described above. The infrared image is an image of the position of the imaginary surface M1 obtained by the infrared light shooting unit 8B. The damage evaluation photograph is a photograph of the object 11 (device layer 22) after laser processing when viewed from the surface 11a. In the image and photograph in the figure, the laser L is scanned along the processing line extending in the left and right directions. As Figure 16 As shown, in the comparative example, damage caused by light leakage of the non-modulated light L0 appears intermittently on the device layer 22 along the processing line (see the dotted line in the figure). However, in Example 3, this damage can be avoided.

[0118] The laser processing apparatus and the laser processing method of the third embodiment can also include the laser processing apparatus 1 and the laser processing method of the first embodiment described above. That is, in the third embodiment, it is also possible that the condensing points Cl, C2 of the processing lights Ll, L2 are located on the side opposite to the condensing point Co of the non-modulated light L0 in the Z direction with respect to the ideal condensing points ClO, C20, as a result, the condensing point Co of the non-modulated light L0 is distanced from the device layer 22 (the side opposite to the laser light incident side). Alternatively or additionally, the laser processing apparatus and the laser processing method of the third embodiment include the laser processing apparatus and the laser processing method of the second embodiment described above. That is, in the third embodiment, the modified region 12 is present between the condensing point Co of the non-modulated light L0 and the surface 11a of the object 11 (the device layer 22).

[0119] [Modified Example]

[0120] The present application is not limited to the above-described embodiments.

[0121] In the above-described embodiments, the number of split beams of the laser light L (the number of processing lights) is not limited to the above-described two split beams and three split beams, and can be four or more. In the above-described embodiments, the intervals of the condensing points of the multiple processing lights can be equal or can be different. In the above-described embodiments, both the laser processing head H and the support portion 2 are moved by the moving mechanism 9, but at least one of the laser processing head H and the support portion 2 can be moved by the moving mechanism 9.

[0122] In the above-described embodiments, the effect of suppressing damage to the device layer 22 on the side opposite to the laser light incident side of the object 11 can be exhibited, but is not limited to the effect of suppressing damage to the device layer 22. According to the above-described embodiments, damage to the surface 11a, which is the surface opposite to the laser light incident surface of the object 11, can be suppressed. According to the above-described embodiments, damage to the portion on the surface 11a side of the object 11 can be suppressed. In summary, according to the above-described embodiments, damage to the side opposite to the laser light incident side of the object 11 can be suppressed.

[0123] In the above-described embodiments, the processing line is not limited to a spiral shape, and various shapes of processing lines can be set in the object 11. The processing line can also include, for example, multiple straight lines arranged side by side in a predetermined direction. Some or all of the multiple straight lines can be connected or can not be connected. The above-described embodiments can include multiple laser processing heads as the irradiation portion. In the above-described embodiments, the spatial light modulator 5 is not limited to a reflection-type spatial light modulator, and a transmission-type spatial light modulator can also be used.

[0124] The kind of the object 11, the shape of the object 11, the size of the object 11, the number and the direction of the crystal orientation possessed by the object 11, and the face orientation of the main surface of the object 11 are not particularly limited in the above-described embodiments. In the above-described embodiments, the object 11 can be formed of a crystalline material having a crystal structure, or can be formed of a non-crystalline material having a non-crystalline structure (amorphous structure) instead of or in addition to the crystalline material. The crystalline material can be either of an anisotropic crystal and an isotropic crystal. For example, the object 11 can include a substrate formed of at least any one of gallium nitride (GaN), silicon (Si), silicon carbide (SiC), LiTaO3, diamond, GaOx, sapphire (Al2O3), gallium arsenide, indium phosphide, glass, and an alkali-free glass.

[0125] In the above-described embodiments, the modified region 12 is, for example, a crystal region, a recrystallized region, or a gettered region formed in the inside of the object 11. The crystal region is a region that maintains the structure before processing of the object 11. The recrystallized region is a region that is solidified as a single crystal or a polycrystal when evaporated, plasmaized, or melted and then solidified. The gettered region is a region that exhibits a gettering effect of collecting impurities such as heavy metals, and can be formed continuously or intermittently. The above-described embodiments can also be applied to processing such as ablation.

[0126] In the above-described first embodiment, the Z-direction offset of the respective condensing points C1, C2 of the plurality of beams of processing light L1, L2 toward the device layer 22 with respect to the ideal condensing points C10, C20 by the Z-direction offset amount is performed, and as a result, the condensing point CO of the non-modulated light LO in the Z-direction is located on the laser light incident side of the inside of the object 11, but is not limited thereto. As a result of the Z-direction offset, the condensing point CO of the non-modulated light LO in the Z-direction can also be located at the central portion of the inside of the object 11.

[0127] Each structure of the above-described embodiments and modified examples is not limited to the above-described materials and shapes, and various materials and shapes can be applied. Furthermore, each structure of the above-described embodiments or modified examples can be arbitrarily applied to each structure of other embodiments or modified examples.

[0128] [Explanation of Reference Signs]

[0129] 1: laser processing apparatus

[0130] 2: support portion

[0131] 5: spatial light modulator

[0132] 6: condensing portion

[0133] 9: moving mechanism

[0134] 10: control section

[0135] 11: object

[0136] 11a: surface (surface opposite to laser incidence surface)

[0137] 11b: back surface (laser incidence surface)

[0138] 12: modified region

[0139] 12s, 12m, 12r: modified point

[0140] 15: machining line

[0141] 21: substrate

[0142] 22: device layer (functional element layer)

[0143] 103: input acceptance section

[0144] C0: condensing point of non-modulated light

[0145] C1, C2, C3: condensing points of machining light

[0146] C10, C20: ideal condensing points

[0147] FC: crack

[0148] H: laser machining head

[0149] L: laser

[0150] L0: non-modulated light

[0151] L1, L2: machining light

[0152] L3: machining light (0th order light)

[0153] M1: imaginary surface

Claims

1. A laser processing apparatus that forms a modified region inside an object along an imaginary plane by irradiating a laser to the object, characterized by comprising: a support portion that supports the object; an irradiation portion that irradiates the laser to the object supported by the support portion; a moving mechanism that moves at least one of the support portion and the irradiation portion; and a control portion that controls the irradiation portion and the moving mechanism, wherein the irradiation portion has a spatial light modulator that modulates the laser, and a condensing portion that condenses the laser modulated by the spatial light modulator to the object, the control portion performs first control that modulates the laser by the spatial light modulator to split the laser into a plurality of processing lights, and a plurality of condensing points of the plurality of processing lights are located at different positions from each other in a direction perpendicular to an irradiation direction of the laser, in the first control, the laser is modulated so that there is a crack that extends from a plurality of modified points constituting the modified region and is connected along the imaginary plane between a condensing point of unmodulated light of the laser located directly above the crack and an opposite surface of the object on a side opposite to a surface on which the laser is incident.

2. The laser processing apparatus according to claim 1, wherein the crack that extends from the plurality of modified points is connected in a manner that expands in a planar shape along the imaginary plane.

3. The laser processing apparatus according to claim 1, wherein the object includes a substrate and a functional element layer provided on a side of the substrate opposite to a side on which the laser is incident.

4. The laser processing apparatus according to claim 2, wherein the object includes a substrate and a functional element layer provided on a side of the substrate opposite to a side on which the laser is incident.

5. The laser processing apparatus according to claim 1, wherein in the first control, the plurality of condensing points of the plurality of processing lights are moved in the direction perpendicular to the irradiation direction of the laser so that the crack is present between the condensing point of the unmodulated light of the laser and the opposite surface in the irradiation direction.

6. The laser processing apparatus according to claim 2, wherein in the first control, the plurality of condensing points of the plurality of processing lights are moved in the direction perpendicular to the irradiation direction of the laser so that the crack is present between the condensing point of the unmodulated light of the laser and the opposite surface in the irradiation direction.

7. The laser processing apparatus according to claim 3, wherein in the first control, the plurality of condensing points of the plurality of processing lights are moved in the direction perpendicular to the irradiation direction of the laser so that the crack is present between the condensing point of the unmodulated light of the laser and the opposite surface in the irradiation direction.

8. The laser processing apparatus according to claim 4, wherein ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ In the first control, a plurality of focal points of a plurality of beams of the machining light are caused to move in a direction perpendicular to an irradiation direction of the laser light, so that the crack exists between the focal point of the non-modulated light of the laser light and the opposite surface in the irradiation direction.

9. The laser processing apparatus according to any one of claims 1 to 8, wherein: the control section executes second control for causing at least one of the support section and the irradiation section to move by the movement mechanism, so that the positions of the focal points of the plurality of beams of the machining light move along the imaginary surface.

10. The laser processing apparatus according to claim 9, wherein: in the second control, at least one of the support section and the irradiation section is caused to move, so that the positions of the focal points of the plurality of beams of the machining light move along a machining line, the cracks extending from the plurality of modified points are connected by extending in a direction along the machining line and a direction intersecting the machining line.

11. The laser processing apparatus according to any one of claims 1 to 8, wherein: in the first control, the laser light is modulated so that the respective focal points of the plurality of beams of the machining light are located on the opposite side from the focal point of the non-modulated light of the laser light with respect to the ideal focal point of the machining light in the irradiation direction.

12. A laser processing method of forming a modified region along an imaginary surface in the inside of an object by irradiating laser light to the object, the laser processing method comprising: a process of causing the laser light to split into a plurality of beams of machining light by a spatial light modulator that modulates the laser light, and causing a plurality of focal points of the plurality of beams of the machining light to be located at different positions from each other in a direction perpendicular to an irradiation direction of the laser light, in the process, the crack extending from a plurality of modified points constituting the modified region and connected by extending along the imaginary surface exists between the focal point of the non-modulated light of the laser light located directly above the crack and an opposite surface on the opposite side from the laser light incident surface of the object in the irradiation direction.

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