Laser processing method, method for manufacturing semiconductor device, and laser processing apparatus

Abstract

This laser processing method comprises: a preparation step for preparing an object; a first formation step for forming a first modified region inside a substrate along a line by causing laser light to be incident on the substrate from a second surface of the object; and a second formation step for forming a second modified region inside the substrate along the line by causing laser light to be incident on the substrate from the second surface. In the second formation step, a second modified region is formed between the first modified region and the second surface such that a crack reaches the second surface from the first modified region at a first portion of the line.

Description

Laser processing method, method for manufacturing a semiconductor device, and laser processing apparatus

[0001] The present disclosure relates to a laser processing method, a method for manufacturing a semiconductor device, and a laser processing apparatus.

[0002] An object having a substrate and a functional element layer including a plurality of functional elements two-dimensionally arranged on the substrate is prepared, and laser light is made incident on the substrate from the surface on the substrate side of the object, so that a modified region is formed inside the substrate along a line for cutting the object for each of the plurality of functional elements (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2020-027924

[0004] In the laser processing method as described above, if a portion corresponding to a part of the line in the functional element layer has a structure that is difficult to crack (for example, a crack-resistant TEG (Test Element Group), a crack-resistant film), the cutting quality of the object may deteriorate in a part of the line. On the other hand, in order to suppress the deterioration of the cutting quality of the object in a part of the line, if the number of columns of the modified regions arranged in the thickness direction of the substrate along the line is increased, the object may crack along the line just by applying a slight external force to the object, and it may be difficult to transport the object to a subsequent process device (for example, a device for grinding the substrate after forming the modified region).

[0005] An object of the present disclosure is to provide a laser processing method, a method for manufacturing a semiconductor device, and a laser processing apparatus that can improve the cutting quality of an object along a line and enable the transport of the object after forming a modified region for an object having a structure in which a portion corresponding to a part of the line in the functional element layer is difficult to crack.

[0006] A laser processing method according to one aspect of the present disclosure is: [1] "A laser processing method comprising: a preparation step of preparing an object having a substrate and a functional element layer having a plurality of functional elements arranged two-dimensionally on the first surface side of the substrate, having a first surface and a second surface facing each other; a first forming step of forming a first modified region inside the substrate along a line for cutting the object for each of the plurality of functional elements by injecting a first laser beam from the second surface into the substrate after the preparation step; and a second forming step of forming a second modified region inside the substrate along the line by injecting a second laser beam from the second surface into the substrate after the first forming step, wherein in the second forming step, the energy of the second laser beam is set to be equal to or greater than a processing threshold in a first portion of the line, and the energy of the second laser beam is set to be less than the processing threshold in a second portion of the line different from the first portion, so that in the first portion, a crack extends from the first modified region to the second surface, and the second modified region is formed between the first modified region and the second surface."

[0007] In the above laser processing method, after a first modified region is formed inside the substrate along the line, a second modified region is formed between the first modified region and the second surface in the first part of the line, such that cracks reach from the first modified region to the second surface on the substrate side of the object. As a result, in the first part of the line, cracks originating from the first and second modified regions are more likely to reach the first surface on the functional element layer side of the object. Therefore, even if the functional element layer has a structure that makes it difficult for the part corresponding to the first part of the line to crack, a decrease in the cutting quality of the object in that first part is suppressed. Furthermore, in the second part of the line, cracks originating from the first modified region are less likely to reach the second surface of the substrate. Therefore, even if only a slight external force is applied to the object, it is suppressed that the object will crack along the line. Thus, according to the above laser processing method, for objects in which the functional element layer has a structure that makes it difficult for the part corresponding to a part of the line to crack, it is possible to improve the cutting quality of the object along the line and to transport the object after the formation of the modified region.

[0008] A laser processing method in one aspect of the present disclosure may also be [2] "the laser processing method according to [1] above, further comprising: preparing another object corresponding to the object, forming a third modified region corresponding to the first modified region on the other object under the same conditions as the first forming step, and identifying the first portion by confirming the state of cracks arising from the third modified region." According to this, the first portion of the line can be reliably set for the portion of the functional element layer that is less prone to cracking.

[0009] A laser processing method according to one aspect of this disclosure may be [3] "the laser processing method according to [2] above, wherein in the specific step, the position of the tip of the crack originating from the third modified region on the side opposite to the incident side of the laser light is confirmed." The amount by which a crack originating from the third modified region extends on the side opposite to the incident side of the laser light tends to be shorter in the part of the functional element layer that is less prone to cracking compared to the amount by which a crack originating from the third modified region extends on the side opposite to the incident side of the laser light. Therefore, by confirming the position of the tip of the crack originating from the third modified region on the side opposite to the incident side of the laser light, the first part of the line can be reliably set for the part of the functional element layer that is less prone to cracking.

[0010] A laser processing method in one aspect of the present disclosure may be [4] "the laser processing method according to [2] above, wherein in the specific step, the position of the tip on the incident side of the laser beam in the crack originating from the third modified region is confirmed." The position of the tip on the incident side of the laser beam in the crack originating from the third modified region is a position that is easy to confirm while the influence of the functional element layer is suppressed. Therefore, by confirming the position of the tip on the incident side of the laser beam in the crack originating from the third modified region, the first part of the line can be reliably set for the part of the functional element layer that is less prone to cracking.

[0011] A laser processing method according to one aspect of the present disclosure may be [5] "the laser processing method according to any one of [2] to [4] above, wherein in the specific step, the third modified region is formed such that the crack originating from the third modified region reaches the first surface of the other object." In this case, both the amount by which the crack originating from the third modified region extends to the side opposite to the incident side of the laser light, and the amount by which the crack originating from the third modified region extends to the incident side of the laser light, tend to be shorter in the part of the functional element layer that is less prone to cracking. Therefore, the first part of the line can be set more reliably with respect to the part of the functional element layer that is less prone to cracking.

[0012] A laser processing method according to one aspect of the present disclosure may be [6] "the laser processing method according to [1], further comprising a selection step of identifying a first portion by confirming the state of cracks arising from the first modified region after the first forming step and before the second forming step." According to this, the first portion of the line can be reliably set for a portion of the functional element layer that is less prone to cracking.

[0013] A laser processing method in one aspect of the present disclosure may be [7] "the laser processing method according to [6] above, wherein in the specific step, the position of the tip of the crack originating from the first modified region on the side opposite to the incident side of the laser light is confirmed." The amount by which a crack originating from the first modified region extends on the side opposite to the incident side of the laser light tends to be shorter in the part of the functional element layer that is less prone to cracking compared to the amount by which a crack originating from the first modified region extends on the incident side of the laser light. Therefore, by confirming the position of the tip of the crack originating from the first modified region on the side opposite to the incident side of the laser light, the first part of the line can be reliably set for the part of the functional element layer that is less prone to cracking.

[0014] One aspect of the laser processing method of this disclosure may be [8] "the laser processing method according to [6] above, wherein in the specific step, the position of the tip on the incident side of the laser beam in the crack originating from the first modified region is confirmed." The position of the tip on the incident side of the laser beam in the crack originating from the first modified region is a position that is easy to confirm while the influence of the functional element layer is suppressed. Therefore, by confirming the position of the tip on the incident side of the laser beam in the crack originating from the first modified region, the first portion of the line can be reliably set for the part of the functional element layer that is less prone to cracking.

[0015] A laser processing method according to one aspect of the present disclosure may be [9] "the laser processing method according to any one of [6] to [8] above, wherein in the first forming step, the first modified region is formed such that the crack generated from the first modified region reaches the first surface of the object." In this case, both the amount by which the crack generated from the first modified region extends to the side opposite to the incident side of the laser light, and the amount by which the crack generated from the first modified region extends to the incident side of the laser light, tend to be shorter in the part of the functional element layer that is less prone to cracking. Therefore, the first part of the line can be set more reliably with respect to the part of the functional element layer that is less prone to cracking.

[0016] A laser processing method according to one aspect of the present disclosure may be

[10] "the laser processing method according to any one of [1] to [9] above, wherein in the second forming step, the second modified region is formed between the first modified region and the second surface such that the crack extends from the first modified region to the first surface in the first portion." According to this, even when the portion of the functional element layer corresponding to the first portion of the line is configured to be less prone to cracking, it is possible to more reliably suppress a decrease in the cutting quality of the object in the first portion.

[0017] A laser processing method according to one aspect of the present disclosure may be

[11] "a laser processing method according to any one of [1] to

[10] , further comprising a grinding step of grinding the substrate from the second surface side after the second forming step." In this case, the cracking of the object along the line before grinding the substrate is suppressed, so that the substrate can be reliably ground.

[0018] A laser processing method according to one aspect of the present disclosure may be

[12] "the laser processing method according to

[11] above, wherein in the grinding step, the substrate is ground from the second surface side so that the first modified region and the second modified region are removed." In this case, since the first modified region and the second modified region do not remain on the chip obtained by cutting the object, the strength of the chip can be improved.

[0019] A laser processing method according to one aspect of the present disclosure may be

[13] "the laser processing method according to any one of [1] to

[12] above, wherein in the second forming step, the second laser light is pulsed in the first part and the oscillation of the second laser light is stopped in the second part." This makes it possible to reliably switch the energy of the second laser light to be above the processing threshold in the first part of the line and below the processing threshold in the second part of the line.

[0020] A laser processing method according to one aspect of the present disclosure may be

[14] "the laser processing method according to any one of [1] to

[12] above, wherein in the second forming step, the second laser light is pulsed in the first part and the second part." This makes it possible to reliably switch the energy of the second laser light to be above the processing threshold in the first part of the line and below the processing threshold in the second part of the line.

[0021] A laser processing method according to one aspect of the present disclosure may be

[15] "the laser processing method according to any one of [1] to

[12] above, wherein in the second forming step, the second laser light is pulsed in the first part and continuously oscillated in the second part." This makes it possible to reliably switch the energy of the second laser light to be above the processing threshold in the first part of the line and below the processing threshold in the second part of the line.

[0022] A laser processing method according to one aspect of the present disclosure may be

[16] "the laser processing method according to any one of [1] to

[15] above, wherein the configuration of the portion corresponding to the first portion in the functional element layer is different from the configuration of the portion corresponding to the second portion in the functional element layer." Even with such an object, it becomes possible to improve the cutting quality of the object along the line and to transport the object after the formation of the modified region.

[0023] A method for manufacturing a semiconductor device according to one aspect of the present disclosure is

[17] "a method for manufacturing a semiconductor device comprising the preparation step, the first forming step and the second forming step described in [1] above, and a cutting step after the second forming step in which the object is cut along the line for each of the plurality of functional elements."

[0024] According to the above semiconductor device manufacturing method, a semiconductor device cut with high precision can be obtained.

[0025] A laser processing apparatus according to one aspect of the present disclosure comprises:

[18] a support unit for supporting an object having a substrate and a functional element layer having a plurality of functional elements arranged two-dimensionally on the first surface side of the substrate, having a first surface and a second surface facing each other; an irradiation unit for irradiating the object with a first laser beam and a second laser beam, respectively; and a control unit for controlling at least the irradiation unit, wherein the control unit controls at least the irradiation unit such that the first laser beam is incident on the substrate from the second surface so that a first modification region is formed inside the substrate along a line for cutting the object for each of the plurality of functional elements. The laser processing apparatus controls the irradiation section such that, after the first modified region is formed, the second laser beam is incident on the substrate from the second surface so that the second modified region is formed inside the substrate along the line, and so that the second modified region is formed between the first modified region and the second surface, and so that in the first portion of the line the energy of the second laser beam is greater than or equal to a processing threshold, and in the second portion of the line different from the first portion the energy of the second laser beam is less than the processing threshold, so that a crack extends from the first modified region to the second surface.

[0026] According to the above-described laser processing apparatus, for the same reasons as described above for the laser processing method, it becomes possible to improve the cutting quality of objects along the line, and to transport the object after the formation of the modified region, for objects in which the functional element layer has a structure that makes it difficult for a part corresponding to a part of the line to crack, and for objects in which the line is less likely to crack.

[0027] According to this disclosure, it is possible to provide a laser processing method, a semiconductor device manufacturing method, and a laser processing apparatus that enable improved cutting quality of objects along lines and transport of objects after the formation of modified regions, for objects in which a portion corresponding to a part of the line in the functional element layer is less prone to cracking.

[0028] Figure 1 is a configuration diagram of an example laser processing apparatus. Figure 2 is a configuration diagram of the irradiation unit shown in Figure 1. Figure 3 is a configuration diagram of the imaging unit shown in Figure 1. Figure 4 is a plan view of an example object. Figure 5 is a cross-sectional view of a part of the object shown in Figure 4. Figure 6 is a cross-sectional view of a part of the object in which a modified region has been formed. Figure 7 is a table showing the crack state in relation to the formation conditions of the first and second modified regions. Figure 8 is a table showing the crack state in relation to the length of the first part in the line. Figure 9 is a cross-sectional view of a part of the object in which a modified region has been formed. Figure 10 is a cross-sectional view of a part of the object in which a modified region has been formed. Figure 11 is a cross-sectional view of a part of the object after the first forming process. Figure 12 is a cross-sectional view of a part of the object after the second forming process. Figure 13 is a cross-sectional view of a part of the object after the grinding process. Figure 14 is a flowchart of the first example laser processing method. Figure 15 is a flowchart of the second example laser processing method. Figure 16 is a cross-sectional view of a part of the object after the first forming process. Figure 17 is a cross-sectional view of a portion of the object after the first forming process.

[0029] The embodiments of this disclosure will be described in detail below with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and redundant descriptions are omitted. [Configuration of the laser processing apparatus]

[0030] As shown in Figure 1, the laser processing apparatus 1 comprises a support unit 2, an irradiation unit 3, an imaging unit 4, a plurality of drive units 5 and 6, and a control unit 7. The laser processing apparatus 1 irradiates the object 10 with laser light L to form a modified region M on the object 10. For example, the object 10 is a wafer containing a plurality of semiconductor devices. In this case, the wafer is cut into a plurality of chips to obtain a plurality of semiconductor devices.

[0031] The support part 2 supports the object 10, for example, by adsorbing a film attached to the object 10. In this example, the support part 2 is movable in the X and Y directions and rotatable about an axis parallel to the Z direction as its centerline. For example, the X and Y directions are the first and second horizontal directions, which are perpendicular to each other, and the Z direction is the vertical direction.

[0032] The irradiation unit 3 focuses a laser beam L that is penetrating to the object 10 and irradiates the object 10 with it. In this example, the irradiation unit 3 is movable in the Z direction. When the laser beam L is focused inside the object 10 supported by the support unit 2, the laser beam L is particularly absorbed in the portion corresponding to the focused spot C of the laser beam L, and a modified region M is formed inside the object 10. The focused spot C is also referred to as the focused region or focus point.

[0033] The modified region M is a region whose density, refractive index, mechanical strength, and other physical properties differ from the surrounding unmodified region. Examples of modified regions M include melting regions, crack regions, dielectric breakdown regions, and refractive index change regions. Cracks F are generated in the modified region M on both the side of the laser beam L incident and the opposite side. The modified region M and cracks F are used to cut the object 10.

[0034] As an example, when a focused spot C is moved relative to an object 10 along a line A parallel to the X direction, multiple modified spots Ms are formed in a line along line A. Each modified spot Ms is formed by irradiation with one pulse of laser light L. A row of modified regions M is a collection of multiple modified spots Ms arranged in a line. Adjacent modified spots Ms may be connected to each other or separated from each other, depending on the relative movement speed of the focused spot C with respect to the object 10 and the repetition frequency of the laser light L.

[0035] The imaging unit 4 images the modified region M and cracks F formed on the object 10 by irradiation with laser light L. The imaging unit 4 can image the tip of the crack F on the side where the laser light L was incident, and the tip of the crack F on the opposite side of the side where the laser light L was incident. This makes it possible to confirm the position of the tip of the crack F on the side where the laser light L was incident, and the position of the tip of the crack F on the opposite side of the side where the laser light L was incident.

[0036] The drive unit 5 supports the support unit 2 and drives the support unit 2. In this example, the drive unit 5 moves the support unit 2 in the X and Y directions, and rotates the support unit 2 with an axis parallel to the Z direction as its centerline. The drive unit 6 supports the irradiation unit 3 and the imaging unit 4 and drives the irradiation unit 3 and the imaging unit 4. In this example, the drive unit 6 moves the irradiation unit 3 and the imaging unit 4 in the Z direction.

[0037] As an example, the drive unit 5 rotates the support unit 2 so that line A is parallel to the X direction, and moves the support unit 2 in the Y direction so that the focusing spot C is located on line A. The drive unit 6 moves the irradiation unit 3 in the Z direction so that the focusing spot C is located inside the object 10. In this state, the drive unit 5 moves the support unit 2 in the X direction so that the focusing spot C moves relatively along line A.

[0038] The control unit 7 controls the support unit 2, the irradiation unit 3, the imaging unit 4, and the respective drive units 5 and 6. The control unit 7 has a processing unit, a storage unit, and an input receiving unit. The processing unit is configured as a computer device including a processor, memory, storage, and communication devices. In the processing unit, the processor executes software (programs) loaded into memory, etc., and controls the reading and writing of data in memory and storage, as well as communication by the communication devices. The storage unit is, for example, a hard disk, and stores various types of data. The input receiving unit is an interface unit that displays various types of information and accepts input of various types of information from the user. The input receiving unit is, for example, a GUI (Graphical User Interface).

[0039] As shown in Figure 2, the illumination unit 3 includes a light source 31, a spatial light modulator 32, a focusing unit 33, and a 4f lens unit 34. The light source 31 emits laser light L, for example, by a pulse oscillation method. The spatial light modulator 32 modulates the laser light L emitted from the light source 31 by displaying a modulation pattern. The spatial light modulator 32 is, for example, a reflective liquid crystal (LCOS) spatial light modulator. The focusing unit 33 is composed of at least one lens and focuses the laser light L modulated by the spatial light modulator 32 onto the object 10. The 4f lens unit 34 projects the image of the laser light L on the modulation plane of the spatial light modulator 32 onto the entrance pupil plane of the focusing unit 33.

[0040] The irradiation unit 3 does not necessarily have a light source 31. For example, laser light L may be guided to the irradiation unit 3 from a light source 31 located outside the irradiation unit 3. The irradiation unit 3 may also have other optical systems. For example, an attenuator and / or a beam expander may be placed in the optical path between the light source 31 and the spatial light modulator 32.

[0041] As shown in Figure 3, the imaging unit 4 includes a light source 41, a mirror 42, an objective lens 43, and an image sensor 44. The light source 41 emits light L1 that is transparent to the object 10. For example, the light source 41 is composed of a halogen lamp and a filter, and emits light L1 in the near-infrared region. The light L1 emitted from the light source 41 is reflected by the mirror 42, passes through the objective lens 43, and irradiates the object 10. The light L1 reflected by the object 10 passes through the objective lens 43 and the mirror 42 and enters the image sensor 44. The image sensor 44 detects the light L1 that has been reflected by the object 10 and transmitted through the objective lens 43 and the mirror 42. For example, the image sensor 44 is composed of an InGaAs sensor, and detects light L1 in the near-infrared region. [Configuration of the object]

[0042] As shown in FIGS. 4 and 5, the object 10 has a first surface 10a and a second surface 10b that face each other. The object 10 includes a substrate 11 and a functional element layer 12 disposed on the side of the first surface 10a of the substrate 11. The functional element layer 12 includes a plurality of functional elements 12a two-dimensionally arranged on the side of the first surface 10a of the substrate 11. As an example, the substrate 11 is a semiconductor substrate such as a silicon substrate, and the functional element 12a is a light receiving element such as a photodiode, a light emitting element such as a laser diode, or a circuit element such as a memory. The functional element 12a may be an element three-dimensionally configured by stacking a plurality of layers. Note that a notch 11c indicating the crystal orientation is provided on the substrate 11. An orientation flat may be provided on the substrate 11 instead of the notch 11c.

[0043] The object 10 is cut for each of the plurality of functional elements 12a along each of the plurality of lines A. Each line A passes between adjacent functional elements 12a when viewed in the thickness direction of the substrate 11. In this example, the plurality of functional elements 12a are arranged in a matrix along the first surface 10a, and the plurality of lines A extend in a grid pattern. Note that the line A is a virtual line set by the laser processing apparatus 1. The line A may be a line actually drawn on the object 10. [Functions of the First Modified Region and the Second Modified Region]

[0044] FIG. 6(a) is a cross-sectional view of a part of the object 10 in which the first modified region M1 and the second modified region M2 are formed under Condition 1. FIG. 6(b) is a cross-sectional view of a part of the object 10 in which the first modified region M1 and the second modified region M2 are formed under Condition 2. FIG. 6(c) is a cross-sectional view of a part of the object 10 in which the first modified region M1 and the second modified region M2 are formed under Condition 3.

[0045] First, in conditions 1, 2, and 3, objects 10 with the same specifications were prepared, and laser light L was incident on the substrate 11 from the second surface 10b under the same conditions, so that five rows of first modified regions M1 aligned in the thickness direction of the substrate 11 were formed inside the substrate 11 along line A. At the time when the five rows of first modified regions M1 were formed inside the substrate 11, the cracks F originating from the first modified regions M1 did not reach either the first surface 10a or the second surface 10b.

[0046] Next, under conditions 1, 2, and 3, laser light L was incident on the substrate 11 from the second surface 10b under different conditions, thereby forming three rows of second modified regions M2 aligned in the thickness direction of the substrate 11 along line A inside the substrate 11. At this time, in the first portion A1 of line A, the energy of the laser light L was set to be above the processing threshold, and in the second portion A2 of line A, which is different from the first portion A1, the energy of the laser light L was set to be below the processing threshold, thereby forming three rows of second modified regions M2 inside the substrate 11 along the first portion A1. Here, the length of the first portion A1 was set to 3 mm.

[0047] In condition 1, three rows of second modified regions M2 were formed along the first portion A1 so that cracks F originating from each second modified region M2 did not connect to one another. In condition 2, three rows of second modified regions M2 were formed along the first portion A1 so that cracks F originating from each first modified region M1 and each second modified region M2 connected to one another, and these cracks F did not reach the second surface 10b. In condition 3, three rows of second modified regions M2 were formed along the first portion A1 so that cracks F originating from each first modified region M1 and each second modified region M2 connected to one another, and these cracks F reached the second surface 10b.

[0048] Figure 7 is a table showing the state of crack F with respect to the formation conditions (i.e., Condition 1, Condition 2, and Condition 3) of the first modification region M1 and the second modification region M2. In this table, the "state of the crack during adsorption" means the state of crack F before the adsorption of the object 10 by the support portion 2 of the laser processing apparatus 1 is released, and the "state of the crack after adsorption release" means the state of crack F after the adsorption of the object 10 by the support portion 2 of the laser processing apparatus 1 is released. Also, "ST" means a state where crack F does not reach both the first surface 10a and the second surface 10b, and "HC" means a state where crack F reaches only the second surface 10b. Further, the "length of the crack on the first surface side" means the length of crack F extending from the first modification region M1 closest to the first surface 10a toward the first surface 10a side.

[0049] As shown in Figure 7, in the case of Condition 1, the "length of the crack on the first surface side" in the first portion A1 hardly increases with respect to the "length of the crack on the first surface side" in the second portion A2. From this, it was found that if the cracks F generated from each second modification region M2 do not connect to each other, in the first portion A1, hardly any effect of the crack F generated from the first modification region M1 extending toward the first surface 10a side can be obtained.

[0050] On the other hand, in the case of Condition 2 and Condition 3, the "length of the crack on the first surface side" in the first portion A1 increases with respect to the "length of the crack on the first surface side" in the second portion A2. From this, it was found that if the cracks F generated from each first modification region M1 and each second modification region M2 are connected to each other, in the first portion A1, a sufficient effect of the crack F generated from the first modification region M1 extending toward the first surface 10a side can be obtained. Particularly in the case of Condition 3, the "length of the crack on the first surface side" in the first portion A1 significantly increases with respect to the "length of the crack on the first surface side" in the second portion A2. From this, it was found that if the second modification region M2 is formed inside the substrate 11 along the first portion A1 so that crack F reaches the second surface 10b from the first modification region M1, in the first portion A1, a large effect of the crack F generated from the first modification region M1 extending toward the first surface 10a side can be obtained.

[0051] Furthermore, even under condition 3, the state in the second part A2 where the crack F does not reach both the first surface 10a and the second surface 10b is maintained even after the suction is released. From this, it was found that even under condition 3, it is possible to suppress the cracking of the object 10 along line A with only a slight external force acting on the object 10, that is, it is possible to transport the object 10 to the equipment for the next process.

[0052] Figure 8 is a table showing the state of crack F with respect to the length of the first portion A1 in line A. In this table, "BHC" means that the crack F has reached only the first surface 10a, and "FC" means that the crack F is connected inside the object 10 and has reached both the first surface 10a and the second surface 10b. The meanings of the other terms are as described above.

[0053] As shown in Figure 8, even when the length of the first portion A1 is 1 mm, the "length of the crack on the first surface" in the first portion A1 is significantly greater than the "length of the crack on the first surface" in the second portion A2. From this, it was found that even if the length of the first portion A1 is about 1 mm, if the second modified region M2 is formed inside the substrate 11 along the first portion A1 so that the crack F extends from the first modified region M1 to the second surface 10b, the effect of the crack F originating from the first modified region M1 extending significantly towards the first surface 10a in the first portion A1 can be obtained. It was also found that this effect improves as the length of the first portion A1 increases.

[0054] Furthermore, when the length of the first portion A1 is 5 mm, in the first portion A1, the crack F reaches both the first surface 10a and the second surface 10b after the adsorption is released, while in the second portion A2, the crack F reaches only the first surface 10a after the adsorption is released. From this, it was found that if the second modified region M2 is formed inside the substrate 11 along the first portion A1 such that the crack F reaches both the first surface 10a and the second surface 10b from the first modified region M1, then in the second portion A2, the crack F originating from the first modified region M1 can be extended toward the first surface 10a. In this case as well, it was found that in the second portion A2, the crack F does not reach the second surface 10b even after the adsorption is released, making it possible to transport the object 10 to the equipment for the subsequent process.

[0055] As shown in Figures 9 and 10, we will consider the case where the portion 12b corresponding to the first portion A1 of line A in the functional element layer 12 is configured to be resistant to cracking (for example, a crack-resistant TEG or a crack-resistant film), and the substrate 11 is ground from the second surface 10b side after the formation of the modified region M. In Figures 9 and 10, the grinding completion position (the position of the second surface 10b of the object 10 after grinding) is indicated by a dashed line, assuming that the thickness of the object 10 after grinding is 100 μm or more.

[0056] As shown in Figure 9(a), when multiple rows of first modified regions M1 aligned in the thickness direction of the substrate 11 are formed along line A between the grinding completion position and the second surface 10b, cracks F originating from the first modified regions M1 do not reach both the first surface 10a and the second surface 10b along the entire line A, making it easier to transport the object 10 to the grinding apparatus for the substrate 11. In this case, when the object 10 is ground from the second surface 10b side to the grinding completion position, and then cut along line A, although the first modified regions M1 do not remain on the cut object 10, meandering occurs in the crack-resistant portion 12b.

[0057] As shown in Figure 9(b), when multiple rows of first modified regions M1 aligned in the thickness direction of the substrate 11 are formed along line A between the grinding completion position and the second surface 10b, and further, when multiple rows of second modified regions M2 aligned in the thickness direction of the substrate 11 are formed along line A between the first modified region M1 and the second surface 10b, cracks F originating from the first modified regions M1 and the second modified regions M2 reach both the first surface 10a and the second surface 10b along the entire line A, making it difficult to transport the object 10 to the grinding apparatus for the substrate 11. In that case, when the object 10 is ground from the second surface 10b side to the grinding completion position, and then the object 10 is cut along line A, the first modified regions M1 do not remain on the object 10 after cutting, and meandering does not occur in the crack-resistant portion 12b.

[0058] As shown in Figure 10(a), when multiple rows of first modified regions M1 aligned in the thickness direction of the substrate 11 are formed inside the substrate 11 so as to straddle the grinding completion position along line A, cracks F originating from the first modified regions M1 reach the first surface 10a along the entire line A but not the second surface 10b, making it easier to transport the object 10 to the grinding apparatus for the substrate 11. In this case, when the object 10 is ground from the second surface 10b side to the grinding completion position, and then cut along line A, meandering did not occur in the crack-resistant portion 12b, but the first modified regions M1 remained on the object 10 after cutting.

[0059] As shown in Figure 10(b), when multiple rows of first modified regions M1 aligned in the thickness direction of the substrate 11 are formed along line A between the grinding completion position and the second surface 10b, and further, when multiple rows of second modified regions M2 aligned in the thickness direction of the substrate 11 are formed along the first portion A1 of line A between the first modified region M1 and the second surface 10b, cracks F originating from the first modified regions M1 and M2 reach both the first surface 10a and the second surface 10b in the first portion A1 of line A, while cracks F originating from the first modified region M1 do not reach both the first surface 10a and the second surface 10b in the second portion A2 of line A, thereby facilitating the transport of the object 10 to the apparatus for grinding the substrate 11. Furthermore, in that case, when the object 10 is ground from the second surface 10b side to the grinding completion position, and then the object 10 is cut along line A, the first modified region M1 does not remain on the object 10 after cutting, and meandering does not occur in the crack-resistant portion 12b.

[0060] From the above considerations, it was found that when the portion 12b corresponding to the first portion A1 of line A in the functional element layer 12 is configured to be resistant to cracking, and when the substrate 11 is ground from the second surface 10b side after the formation of the modified region M, even when the thickness of the object 10 after grinding is 100 μm or more, the first modified region M1 and the second modified region M2 are formed as shown in Figure 10(b), making it easier to transport the object 10 to the apparatus for grinding the substrate 11, the first modified region M1 does not remain on the object 10 after cutting, and meandering is less likely to occur in the portion 12b which is configured to be resistant to cracking. [Laser processing method and method for manufacturing semiconductor devices]

[0061] Based on the above considerations, the laser processing method and semiconductor device manufacturing method will be described with reference to Figures 11, 12, and 13. The following laser processing method and semiconductor device manufacturing method are implemented when the portion 12b corresponding to each first portion A1 of each line A in the functional element layer 12 is configured to be resistant to cracking, and when the substrate 11 is ground from the second surface 10b side after the formation of the modified region M. In other words, as a premise, the configuration of the portion 12b corresponding to each first portion A1 of each line A in the functional element layer 12 is different from the configuration of the portion corresponding to each second portion A2 of each line A in the functional element layer 12. Specifically, the portion 12b corresponding to each first portion A1 of each line A in the functional element layer 12 has the characteristic of being less prone to cracking F (i.e., less prone to cracking) compared to the portion corresponding to each second portion A2 of each line A in the functional element layer 12. In Figures 11 and 12, the grinding completion position (the position of the second surface 10b of the object 10 after grinding) is indicated by a dashed line.

[0062] First, as shown in Figure 11, the object 10 is prepared (preparation step), and after the preparation step, multiple rows of first modified regions M1 aligned in the thickness direction of the substrate 11 are formed along each line A between the grinding completion position and the second surface 10b (first formation step). The multiple rows of first modified regions M1 are formed inside the substrate 11 along each line A by irradiating the substrate 11 with laser light (first laser light) L from the second surface 10b, so that cracks F generated from the first modified region M1 in each line A do not reach both the first surface 10a and the second surface 10b. The formation of multiple rows of first modified regions M1 for each line A may be carried out by modulating the laser light L emitted from the light source 31 with multiple focused spots C by a spatial light modulator 32, or by moving the focused spots C relative to each line A multiple times.

[0063] After the first forming step, as shown in Figure 12, multiple rows of second modified regions M2 aligned in the thickness direction of the substrate 11 are formed between the first modified region M1 and the second surface 10b along each first portion A1 of each line A (second forming step). The multiple rows of second modified regions M2 are formed inside the substrate 11 along each first portion A1 of each line A by injecting laser light (second laser light) L from the second surface 10b into the substrate 11, so that cracks F extend from the first modified region M1 to the second surface 10b in each first portion A1 of each line A, and cracks F extend from the first modified region M1 to the first surface 10a in each first portion A1 of each line A. In other words, in this example, multiple rows of second modified regions M2 are formed inside the substrate 11 along each first portion A1 of each line A, such that cracks F originating from the first modified region M1 and the second modified region M2 in each first portion A1 of each line A reach both the first surface 10a and the second surface 10b. The formation of multiple rows of second modified regions M2 for each line A may be carried out by modulating the laser light L emitted from the light source 31 with a spatial light modulator 32 so that it has multiple focused spots C, or by moving the focused spots C relative to each line A multiple times.

[0064] In the second forming step, the energy of the laser light L is set to be above the processing threshold in each first portion A1 of each line A, and below the processing threshold in each second portion A2 of each line A, thereby forming multiple rows of second modified regions M2 inside the substrate 11 along each first portion A1 of each line A. At this time, the laser light L may be pulsed in each first portion A1 of each line A and stopped in each second portion A2 of each line A, or it may be pulsed in each first portion A1 and each second portion A2 of each line A, or the laser light L may be pulsed in each first portion A1 of each line A and continuously in each second portion A2 of each line A.

[0065] After the second forming step, as shown in Figure 13, the substrate 11 is ground from the second surface 10b side, thereby removing the first modified region M1 and the second modified region M2 (grinding step). After the grinding step, the object 10 is cut along each line A for each of the multiple functional elements 12a (see Figures 4 and 5), thereby obtaining multiple semiconductor devices (cutting step). In this example, the preparation step to the grinding step corresponds to the laser processing method, and the preparation step to the cutting step corresponds to the semiconductor device manufacturing method. The first forming step and the second forming step are carried out by the control unit 7 controlling at least the irradiation unit 3 in the laser processing apparatus 1 described above.

[0066] The identification step for identifying the first part A1 in the object 10 will now be described. Figure 14 is a flowchart of a first example of a laser processing method that includes an identification step. In the first example of a laser processing method, the identification step is performed first (step S01 in Figure 14). In this identification step, as shown in Figures 16 and 17, another object 10A corresponding to the object 10 is prepared, and a third modified region M3 corresponding to the first modified region M1 is formed on the other object 10A under the same conditions as the first forming step, and the state of the crack F generated from the third modified region M3 is confirmed (details of the confirmation will be described later), thereby identifying the first part A1 (i.e., the first part A1 is determined). The other object 10A is an object for determining conditions that has the same specifications as the object 10.

[0067] Next, the preparation process is carried out (step S02 in Figure 14), and in the laser processing apparatus 1, alignment and height setting are performed in this order (steps S03, S04 in Figure 14). During alignment, the laser beam focusing spot C (or a representative focusing spot C if the laser beam L is modulated by the spatial light modulator 32 to have multiple focusing spots C) is positioned above the processing start position of the object 10 supported by the support part 2, and during height setting, the focusing spot C is positioned on the second surface 10b of the object 10. However, the laser beam L is not actually emitted during alignment and height setting. Subsequently, the first forming process, the second forming process, the grinding process, and the cutting process are carried out as described above (steps S05, S06, S07, S08 in Figure 14). At this time, the second forming process is carried out based on the information of the first part A1 identified in the specific process.

[0068] In a specific step of the first example of the laser processing method, as shown in Figures 16(a) and (b), a third modified region M3 corresponding to the first modified region M1 is formed inside the substrate 11 along line A, and the state of the crack F originating from the third modified region M3 is confirmed. In this example, the third modified region M3 is formed inside the substrate 11 along line A such that the crack F originating from the third modified region M3 in the portion of the functional element layer 12 other than portion 12b reaches the first surface 10a of another object 10A. When confirming the state of the crack F, the position of the tip F1 on the first surface 10a side (i.e., the side opposite to the incident side of the laser light L) of the crack F originating from the third modified region M3 may be confirmed, or the position of the tip F2 on the second surface 10b side (i.e., the side on which the laser light L was incident) of the crack F originating from the third modified region M3 may be confirmed.

[0069] As shown in Figure 16(a), the position of the tip F1 of the crack F in portion 12b is located on the third modified region M3 side than the position of the tip F1 of the crack F in the portion of the functional element layer 12 other than portion 12b. In other words, the amount by which the crack F extends toward the first surface 10a in portion 12b is smaller than the amount by which the crack F extends toward the first surface 10a in the portion of the functional element layer 12 other than portion 12b. In the laser processing apparatus 1, the tip F1 of the crack F is imaged by the imaging unit 4, and the position information of the portion of the crack F tip F1 that has not reached the first surface 10a is stored as position information of the first portion A1. As an example, imaging of the tip F1 of the crack F by the imaging unit 4 is performed by positioning the focal point of the light L1 from the imaging unit 4 at the interface between the substrate 11 and the functional element layer 12, and moving the focal point along line A. In this case, the position information of the portion where the tip F1 of the crack F was imaged is stored as the position information of the second portion A2, and the position information of the portion where the tip F1 of the crack F was not imaged is stored as the position information of the first portion A1. In order to image the tip F1 of the crack F in the portion where the tip F1 of the crack F was not imaged, the focal point of the light L1 reflected at the interface between the substrate 11 and the functional element layer 12 should be moved in the thickness direction of the substrate 11.

[0070] Furthermore, as shown in Figure 16(b), the position of the tip F2 of the crack F in portion 12b is located on the third modified region M3 side than the position of the tip F2 of the crack F in the portion of the functional element layer 12 other than portion 12b. In other words, the amount by which the crack F extends toward the second surface 10b in portion 12b is smaller than the amount by which the crack F extends toward the second surface 10b in the portion of the functional element layer 12 other than portion 12b. In the laser processing apparatus 1, the tip F2 of the crack F is imaged by the imaging unit 4, and the position information of the portion where the tip F2 of the crack F is located at a predetermined distance or more from the second surface 10b is stored as the position information of the first portion A1. As an example, imaging of the tip F2 of the crack F by the imaging unit 4 is performed by positioning the focal point of the light L1 from the imaging unit 4 at a depth of a predetermined distance from the second surface 10b, while the focal point is moved along line A. In this case, the position information of the portion where the tip F2 of the crack F is imaged is stored as the position information of the second portion A2, and the position information of the portion where the tip F2 of the crack F is not imaged is stored as the position information of the first portion A1. In order to image the tip F2 of the crack F in the portion where the tip F2 of the crack F is not imaged, the focal point of the light L1 from the imaging unit 4 should be moved in the thickness direction of the substrate 11.

[0071] As shown in Figure 17, a third modified region M3 corresponding to the first modified region M1 may be formed inside the substrate 11 along line A so that cracks F originating from the third modified region M3 do not reach the first surface 10a of another object 10A, and the state of cracks F originating from the third modified region M3 may be confirmed. However, in that case, there is likely to be a difference in the position of the tip F1 of the crack F between portion 12b and the portion of the functional element layer 12 other than portion 12b, but there is unlikely to be a difference in the position of the tip F2 of the crack F. Therefore, if a third modified region M3 corresponding to the first modified region M1 is formed inside the substrate 11 along line A so that cracks F originating from the third modified region M3 do not reach the first surface 10a of another object 10A, it is preferable that the tip F1 of the crack F is imaged by the imaging unit 4, and the position information of the portion where the tip F1 of the crack F is at least a predetermined distance from the first surface 10a is stored as the position information of the first portion A1.

[0072] Figure 15 is a flowchart of a second example of a laser processing method that includes a specific step. In the second example of the laser processing method, first, a preparation step is performed (step S11 in Figure 15). Next, alignment and height setting are performed in this order (steps S12 and S13 in Figure 15). Then, the first forming step is performed as described above (step S14 in Figure 15). Next, the specific step is performed (step S15 in Figure 15). In this specific step, as shown in Figures 16 and 17, the state of the crack F originating from the first modified region M1 in the object 10 is confirmed (details of the confirmation will be described later), and the first part A1 is identified (i.e., the first part A1 is determined). Next, the second forming step, grinding step, and cutting step are performed as described above (steps S16, S17, and S18 in Figure 15). At this time, the second forming step is performed based on the information of the first part A1 identified in the specific step.

[0073] In a specific step of the second example of the laser processing method, as shown in Figures 16(a) and 16(b), a first modified region M1 is formed inside the substrate 11 along line A, and the state of the crack F originating from the first modified region M1 is confirmed. In this example, the first modified region M1 is formed inside the substrate 11 along line A such that the crack F originating from the first modified region M1 in the functional element layer 12, excluding portion 12b, reaches the first surface 10a of the object 10. When confirming the state of the crack F, the position of the tip F1 on the first surface 10a side (i.e., the side opposite to the incident side of the laser light L) of the crack F originating from the first modified region M1 may be confirmed, or the position of the tip F2 on the second surface 10b side (i.e., the side on which the laser light L was incident) of the crack F originating from the first modified region M1 may be confirmed.

[0074] As shown in Figure 16(a), the position of the tip F1 of the crack F in portion 12b is located closer to the first modified region M1 than the position of the tip F1 of the crack F in the portion of the functional element layer 12 other than portion 12b. In other words, the amount by which the crack F extends toward the first surface 10a in portion 12b is smaller than the amount by which the crack F extends toward the first surface 10a in the portion of the functional element layer 12 other than portion 12b. In the laser processing apparatus 1, the tip F1 of the crack F is imaged by the imaging unit 4, and the position information of the portion of the crack F tip F1 that has not reached the first surface 10a is stored as position information of the first portion A1. As an example, imaging of the tip F1 of the crack F by the imaging unit 4 is performed by positioning the focal point of the light L1 from the imaging unit 4 at the interface between the substrate 11 and the functional element layer 12, while moving the focal point along line A. In this case, the position information of the portion where the tip F1 of the crack F was imaged is stored as the position information of the second portion A2, and the position information of the portion where the tip F1 of the crack F was not imaged is stored as the position information of the first portion A1. In order to image the tip F1 of the crack F in the portion where the tip F1 of the crack F was not imaged, the focal point of the light L1 reflected at the interface between the substrate 11 and the functional element layer 12 should be moved in the thickness direction of the substrate 11.

[0075] Furthermore, as shown in Figure 16(b), the position of the tip F2 of the crack F in portion 12b is located closer to the first modified region M1 than the position of the tip F2 of the crack F in the portion of the functional element layer 12 other than portion 12b. In other words, the amount by which the crack F extends toward the second surface 10b in portion 12b is smaller than the amount by which the crack F extends toward the second surface 10b in the portion of the functional element layer 12 other than portion 12b. In the laser processing apparatus 1, the tip F2 of the crack F is imaged by the imaging unit 4, and the position information of the portion where the tip F2 of the crack F is located at a predetermined distance or more from the second surface 10b is stored as the position information of the first portion A1. As an example, imaging of the tip F2 of the crack F by the imaging unit 4 is performed by positioning the focal point of the light L1 from the imaging unit 4 at a depth of a predetermined distance from the second surface 10b, while the focal point is moved along line A. In this case, the position information of the portion where the tip F2 of the crack F is imaged is stored as the position information of the second portion A2, and the position information of the portion where the tip F2 of the crack F is not imaged is stored as the position information of the first portion A1. In order to image the tip F2 of the crack F in the portion where the tip F2 of the crack F is not imaged, the focal point of the light L1 from the imaging unit 4 should be moved in the thickness direction of the substrate 11.

[0076] As shown in Figure 17, the first modified region M1 may be formed inside the substrate 11 along line A so that cracks F originating from the first modified region M1 do not reach the first surface 10a of the object 10, and the state of cracks F originating from the first modified region M1 may be confirmed. However, in that case, there is likely to be a difference in the position of the tip F1 of the crack F between portion 12b and the portion of the functional element layer 12 other than portion 12b, but there is less likely to be a difference in the position of the tip F2 of the crack F. Therefore, when the first modified region M1 is formed inside the substrate 11 along line A so that cracks F originating from the first modified region M1 do not reach the first surface 10a of the object 10, it is preferable that the tip F1 of the crack F is imaged by the imaging unit 4, and the position information of the portion where the tip F1 of the crack F is more than a predetermined distance from the first surface 10a is stored as the position information of the first portion A1. [Operation and Effects]

[0077] In the laser processing method described above, after a first modified region M1 is formed inside the substrate 11 along line A, a second modified region M2 is formed between the first modified region M1 and the second surface 10b in the first portion A1 of line A, such that cracks F reach from the first modified region M1 to the second surface 10b on the substrate 11 side of the object 10. As a result, in the first portion A1 of line A, cracks F generated from the first modified region M1 and the second modified region M2 are more likely to reach the first surface 10a on the functional element layer 12 side of the object 10. Therefore, even if the portion 12b of the functional element layer 12 corresponding to the first portion A1 of line A is configured to be less prone to cracking, a decrease in the cutting quality of the object 10 in the first portion A1 is suppressed. Furthermore, in the second portion A2 of line A, cracks F originating from the first modified region M1 are less likely to reach the second surface 10b of the substrate 11. This suppresses the cracking of the object 10 along line A even with slight external force applied to it. Therefore, according to the laser processing method described above, for an object 10 in which a portion 12b corresponding to a part of line A in the functional element layer 12 is less prone to cracking, it becomes possible to improve the cutting quality of the object 10 along line A, and to transport the object 10 after the formation of the modified region M.

[0078] In the laser processing method described above, the configuration of portion 12b corresponding to the first portion A1 in the functional element layer 12 is different from the configuration of portion 12b corresponding to the second portion A2 in the functional element layer 12. Even with such an object 10, it is possible to improve the cutting quality of the object 10 along line A, and it is also possible to transport the object 10 after the formation of the modified region M.

[0079] In the second forming step, a second modified region M2 is formed between the first modified region M1 and the second surface 10b such that a crack F extends from the first modified region M1 to the first surface 10a in the first portion A1. This makes it possible to more reliably suppress a decrease in the cutting quality of the object 10 in the first portion A1, even when the portion 12b corresponding to the first portion A1 of line A in the functional element layer 12 is configured to be less prone to cracking.

[0080] In the grinding process, after the second forming process, the substrate 11 is ground from the second surface 10b side. In this case, the cracking of the object 10 along line A before grinding of the substrate 11 is suppressed, so that the substrate 11 can be ground reliably.

[0081] In the grinding process, the substrate 11 is ground from the second surface 10b side, thereby removing the first modified region M1 and the second modified region M2. In this case, since the first modified region M1 and the second modified region M2 do not remain on the chip obtained by cutting the object 10, the strength of the chip can be improved.

[0082] In the second forming step, the laser beam L may be pulsed in the first part A1 and stopped in the second part A2. Alternatively, in the second forming step, the laser beam L may be pulsed in both the first part A1 and the second part A2. Alternatively, in the second forming step, the laser beam L may be pulsed in the first part A1 and continuously in the second part A2. In any case, it is possible to reliably switch the energy of the laser beam L in the first part A1 of line A to be above the processing threshold and the energy of the laser beam L in the second part A2 of line A to be below the processing threshold.

[0083] In a specific step of the first example of laser processing method, another object 10A corresponding to the object 10 is prepared, and under the same conditions as the first forming step, a third modified region M3 corresponding to the first modified region M1 is formed on the other object 10A, and the state of the crack F generated from the third modified region M3 is confirmed, thereby identifying the first portion A1. This makes it possible to reliably set the first portion A1 of line A to the portion 12b of the functional element layer 12 that is less prone to cracking.

[0084] In a specific step of the first example of the laser processing method, the position of the tip F1 on the side opposite to the incident side of the laser beam L in the crack F originating from the third modified region M3 may be confirmed. The amount by which the crack F originating from the third modified region M3 extends on the side opposite to the incident side of the laser beam L tends to be particularly short in the portion 12b of the functional element layer 12 that is less prone to cracking, compared to the amount by which the crack F originating from the third modified region M3 extends towards the incident side of the laser beam L. Therefore, by confirming the position of the tip F1 on the side opposite to the incident side of the laser beam L in the crack F originating from the third modified region M3, the first portion A1 of line A can be reliably set for the portion 12b of the functional element layer 12 that is less prone to cracking.

[0085] In a specific step of the first example of the laser processing method, the position of the incident tip F2 of the laser beam L in the crack F originating from the third modified region M3 may be confirmed. The position of the incident tip F2 of the laser beam L in the crack F originating from the third modified region M3 is a position that is easy to confirm while the influence of the functional element layer 12 is suppressed. Therefore, by confirming the position of the incident tip F2 of the laser beam L in the crack F originating from the third modified region M3, the first portion A1 of line A can be reliably set for the portion 12b of the functional element layer 12 that is less prone to cracking.

[0086] In a specific step of the first example of the laser processing method, the third modified region M3 may be formed such that a crack F originating from the third modified region M3 reaches the first surface 10a of another object 10A. In this case, both the amount by which the crack F originating from the third modified region M3 extends to the side opposite to the incident side of the laser light L, and the amount by which the crack F originating from the third modified region M3 extends to the incident side of the laser light L, tend to be shorter in the portion 12b of the functional element layer 12 that is less prone to cracking. Therefore, the first portion A1 of line A can be set more reliably with respect to the portion 12b of the functional element layer 12 that is less prone to cracking.

[0087] In the specific step of the second example laser processing method, the state of the crack F originating from the first modified region M1 is confirmed after the first forming step and before the second forming step, thereby identifying the first portion A1. This makes it possible to reliably set the first portion A1 of line A to the portion 12b of the functional element layer 12 that is less prone to cracking.

[0088] In a specific step of the second example of the laser processing method, the position of the tip F1 of the crack F originating from the first modified region M1 on the side opposite to the incident side of the laser beam L may be confirmed. The amount by which the crack F originating from the first modified region M1 extends on the side opposite to the incident side of the laser beam L tends to be particularly short in the portion 12b of the functional element layer 12 that is less prone to cracking, compared to the amount by which the crack F originating from the first modified region M1 extends on the incident side of the laser beam L. Therefore, by confirming the position of the tip F1 of the crack F originating from the first modified region M1 on the side opposite to the incident side of the laser beam L, the first portion A1 of line A can be reliably set for the portion 12b of the functional element layer 12 that is less prone to cracking.

[0089] In a specific step of the second example of the laser processing method, the position of the incident tip F2 of the laser beam L in the crack F originating from the first modified region M1 may be confirmed. The position of the incident tip F2 of the laser beam L in the crack F originating from the first modified region M1 is a position that is easy to confirm while the influence of the functional element layer 12 is suppressed. Therefore, by confirming the position of the incident tip F2 of the laser beam L in the crack F originating from the first modified region M1, the first portion A1 of line A can be reliably set for the portion 12b of the functional element layer 12 that is less prone to cracking.

[0090] In the first forming step of the second example of the laser processing method, the first modified region M1 is formed such that cracks F originating from the first modified region M1 reach the first surface 10a of the object 10. In this case, both the amount by which the cracks F originating from the first modified region M1 extend to the side opposite to the incident side of the laser light L, and the amount by which the cracks F originating from the first modified region M1 extend to the incident side of the laser light L, tend to be shorter in the portion 12b of the functional element layer 12 that is less prone to cracking. Therefore, the first portion A1 of line A can be set more reliably with respect to the portion 12b of the functional element layer 12 that is less prone to cracking.

[0091] In the semiconductor device manufacturing method described above, after the preparation step, first forming step, and second forming step of the laser processing method described above are performed, the object 10 is cut along line A for each of the multiple functional elements 12a. This makes it possible to obtain a semiconductor device that has been cut with high precision.

[0092] In the laser processing apparatus 1 described above, the control unit 7 sets the energy of the laser light L in the first part A1 of line A to be above the processing threshold, and the energy of the laser light L in the second part A2 of line A to be below the processing threshold, so that a crack F reaches from the first modified region M1 to the second surface 10b in the first part A1 of line A, as a second modified region M2 is formed between the first modified region M1 and the second surface 10b. According to the laser processing apparatus 1 described above, for the same reasons as the laser processing method described above, it is possible to improve the cutting quality of the object 10 along line A for an object 10 in which a portion 12b corresponding to a part of line A in the functional element layer 12 is less prone to cracking, and it is also possible to transport the object 10 after the formation of the modified region M. [Modification]

[0093] This disclosure is not limited to the embodiments described above. In the laser processing method described above, multiple rows of first modified regions M1 are formed inside the substrate 11 along each line A in the first forming step, but in the first forming step, it is sufficient that at least one row of first modified regions M1 is formed inside the substrate 11 along each line A. Also, in the laser processing method described above, multiple rows of second modified regions M2 are formed inside the substrate 11 along each line A in the second forming step, but in the second forming step, it is sufficient that at least one row of second modified regions M2 is formed inside the substrate 11 along line A.

[0094] In the laser processing method described above, in the second forming step, multiple rows of second modified regions M2 are formed inside the substrate 11 along each first portion A1 of each line A so that cracks F originating from the first modified region M1 and the second modified region M2 in each first portion A1 of each line A reach both the first surface 10a and the second surface 10b. However, in the second forming step, it is sufficient that at least one row of second modified regions M2 is formed between the first modified region M1 and the second surface 10b along each first portion A1 of each line A so that cracks F extend from the first modified region M1 to the second surface 10b in each first portion A1 of each line A.

[0095] In the second forming step, it is sufficient for the crack F to extend from the first modified region M1 to the second surface 10b in at least a portion of the first portion A1. That is, the crack F may extend from the first modified region M1 to the second surface 10b in the entire first portion A1, or in only a portion of the first portion A1, or in a wider portion of line A that includes the entire first portion A1. Furthermore, in the laser processing method described above, the first portion A1 of line A is set to a portion 12b in the functional element layer 12 that is less prone to cracking, but the first portion A1 of line A may be set to the intersection of lines A that intersect each other. More specifically, if a modified region M is formed along one of two intersecting lines A, and then a modified region M is formed along the other of the two intersecting lines A, the first portion A1 may be set at the intersection of the other line A with the one line A. In such a case, cracks F are less likely to extend from the modified region M at the intersection of the other line A with the one line A.

[0096] In the laser processing apparatus 1, the spatial light modulator 32 was of the reflective type, but the spatial light modulator 32 may also be of the transmissive type. Also, in the laser processing apparatus 1, the drive unit 5 drives the support unit 2, and the drive unit 6 drives the irradiation unit 3, which in turn drives the focusing unit 33, but the laser processing apparatus 1 only needs to have a drive unit that drives at least one of the support unit and the irradiation unit 3. As an example, the laser processing apparatus 1 may have a drive unit that moves the support unit 2 in the Z, X, and Y directions and rotates the support unit 2 with an axis parallel to the Z direction as the center line. Alternatively, the laser processing apparatus 1 may have a drive unit that moves the focusing unit 33 (or irradiation unit 3) in the Z, X, and Y directions and rotates the focusing unit 33 (or irradiation unit 3) with an axis parallel to the Z direction as the center line.

[0097] 1... Laser processing device, 2... Support unit, 3... Irradiation unit, 7... Control unit, 10... Object, 10A... Another object, 10a... First surface, 10b... Second surface, 11... Substrate, 12... Functional element layer, 12a... Functional element, 12b... Part, A... Line, A1... First part, A2... Second part, F... Crack, F1, F2... Tip, L... Laser light (First laser light, Second laser light), M1... First modified region, M2... Second modified region, M3... Third modified region.

Claims

1. A laser processing method comprising: a preparation step of preparing an object comprising a substrate having a first surface and a second surface facing each other, and a functional element layer including a plurality of functional elements arranged two-dimensionally on the first surface side of the substrate; a first forming step of forming a first modified region inside the substrate along a line for cutting the object for each of the plurality of functional elements by injecting a first laser beam from the second surface into the substrate after the preparation step; and a second forming step of forming a second modified region inside the substrate along the line by injecting a second laser beam from the second surface into the substrate after the first forming step, wherein in the second forming step, the energy of the second laser beam is set to be equal to or greater than a processing threshold in a first portion of the line, and the energy of the second laser beam is set to be less than the processing threshold in a second portion of the line different from the first portion, so that a crack extends from the first modified region to the second surface in the first portion, thereby forming the second modified region between the first modified region and the second surface.

2. The laser processing method according to claim 1, further comprising: a selection step of preparing another object corresponding to the object, forming a third modified region corresponding to the first modified region on the other object under the same conditions as the first forming step, and identifying the first portion by confirming the state of cracks arising from the third modified region.

3. The laser processing method according to claim 2, wherein in the specified step, the position of the tip of the crack originating from the third modified region on the side opposite to the laser beam incidence side is confirmed.

4. The laser processing method according to claim 2, wherein in the specified step, the position of the tip on the incident side of the laser beam in the crack originating from the third modified region is confirmed.

5. The laser processing method according to any one of claims 2 to 4, wherein in the specific step, the third modified region is formed such that the crack originating from the third modified region reaches the first surface of the other object.

6. The laser processing method according to claim 1, further comprising: a identification step of identifying a first portion by confirming the state of cracks arising from the first modified region after the first forming step and before the second forming step.

7. The laser processing method according to claim 6, wherein in the specified step, the position of the tip of the crack originating from the first modified region on the side opposite to the laser beam incidence side is confirmed.

8. The laser processing method according to claim 6, wherein in the specified step, the position of the tip on the incident side of the laser beam in the crack generated from the first modified region is confirmed.

9. The laser processing method according to any one of claims 6 to 8, wherein in the first forming step, the first modified region is formed such that the cracks originating from the first modified region reach the first surface of the object.

10. The laser processing method according to any one of claims 1 to 9, wherein in the second forming step, a second modified region is formed between the first modified region and the second surface such that the crack extends from the first modified region to the first surface in the first portion.

11. The laser processing method according to any one of claims 1 to 10, further comprising a grinding step of grinding the substrate from the second surface side after the second forming step.

12. The laser processing method according to claim 11, wherein in the grinding step, the substrate is ground from the second surface side, thereby removing the first modified region and the second modified region.

13. The laser processing method according to any one of claims 1 to 12, wherein in the second forming step, the second laser light is pulsed in the first portion and the oscillation of the second laser light is stopped in the second portion.

14. The laser processing method according to any one of claims 1 to 12, wherein in the second forming step, the second laser light is pulsed in the first portion and the second portion.

15. The laser processing method according to any one of claims 1 to 12, wherein in the second forming step, the second laser light is pulsed in the first portion and continuously oscillated in the second portion.

16. The laser processing method according to any one of claims 1 to 15, wherein the configuration of the portion corresponding to the first portion in the functional element layer is different from the configuration of the portion corresponding to the second portion in the functional element layer.

17. A method for manufacturing a semiconductor device, comprising the preparation step, the first forming step, and the second forming step described in claim 1, and a cutting step, after the second forming step, of cutting the object along the line for each of the plurality of functional elements.

18. A support portion for supporting an object comprising a substrate having a first surface and a second surface facing each other, and a functional element layer including a plurality of functional elements arranged two-dimensionally on the first surface side of the substrate; an irradiation portion for irradiating the object with a first laser beam and a second laser beam, respectively; and a control portion for controlling at least the irradiation portion, wherein the control portion controls at least the irradiation portion such that the first laser beam is incident on the substrate from the second surface so that a first modification region is formed inside the substrate along a line for cutting the object for each of the plurality of functional elements, and after the first modification region is formed, the irradiation portion controls at least the irradiation portion such that the second laser beam is incident on the substrate from the second surface so that a second modification region is formed inside the substrate along the line, A laser processing apparatus in which the second modified region is formed between the first modified region and the second surface, and the energy of the second laser beam is set to be above a processing threshold in the first portion of the line, and below the processing threshold in the second portion of the line, which is different from the first portion, so that a crack extends from the first modified region to the second surface in the first portion of the line.

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