Laser processing method, laser processing device, and method for producing semiconductor device

Abstract

Provided is a laser processing method for irradiating a target with laser light to perform processing along a virtual surface inside the target which is along a laser light incidence surface of the target, said laser processing method comprising: a first processing step for forming a plurality of modification regions along the virtual surface in a first portion, which is part of the target when viewed from a Z direction that intersects the incidence surface, by irradiating the first portion of the target with laser light along the virtual surface; and a second processing step for, after the first processing step, forming a plurality of modification regions along the virtual surface in a second portion, which is another part of the target when viewed from Z direction, by irradiating the second portion of the target with laser light along the virtual surface.

Description

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

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

[0002] Patent Document 1 describes a laser processing apparatus that forms a modified region along a virtual plane inside an object by irradiating the object with laser light. The laser processing apparatus includes a first processing process of irradiating a first portion of the object with laser light under a first processing condition, and a second processing process of irradiating a second portion inside the first portion of the object with laser light under a second processing condition different from the first processing condition after the first processing process.

[0003] Republished Patent No. 2020 / 090929

[0004] Currently, in peeling processing for peeling an object along a virtual plane, as in the laser processing apparatus described in Patent Document 1, it is known to perform laser processing under different processing conditions on one part and another part of the object.

[0005] In particular, according to the findings of the present inventor, in a first portion that is a part of the object, with respect to the processing progress direction that is the moving direction of the focus point of the laser light, the entire plurality of modified regions are connected by cracks, and with respect to the index feed direction that intersects the processing progress direction, after forming a state (first reference state) in which the plurality of modified regions are not connected by cracks, in a second portion that is another part of the object, with respect to both the processing progress direction and the index feed direction, by forming a state (second reference state) in which the entire plurality of modified regions are connected by cracks, it is possible to cause cracks to progress throughout the virtual plane that is the planned peeling surface.

[0006] In this case, since it is not necessary to connect the modified regions with cracks in the index feed direction in the first part, the processing interval in the index feed direction (for example, the interval between lines when the laser focusing point is moved relative to multiple concentric lines) can be made wider than the processing interval in the index feed direction in the second part. As a result, cycle time is increased compared to the case where a second reference state is formed in both the first and second parts. However, according to the inventor's knowledge, in this case there is room for improvement in the processing quality regarding the unevenness of the peeled surface when the object is peeled from the peeled surface (virtual surface).

[0007] Therefore, the purpose of this disclosure is to provide a laser processing method, a laser processing apparatus, and a method for manufacturing semiconductor devices that can improve processing quality while increasing cycle time.

[0008] The laser processing method according to the present disclosure is a laser processing method for processing an object by irradiating the object with laser light, wherein the method comprises: a first processing step of irradiating a first portion of the object, which is a part of the object when viewed from a Z direction intersecting the incident surface, with the laser light along the virtual surface to form a plurality of modified regions along the virtual surface on the first portion; and after the first processing step, irradiating a second portion of the object, which is another part of the object when viewed from a Z direction, with the laser light along the virtual surface to form a plurality of modified regions along the virtual surface on the second portion. A laser processing method comprising: a second processing step, wherein in the first processing step, the laser beam is irradiated onto the object in the first part under first processing conditions such that at least a portion of the plurality of modified regions are in a first state in which the modified regions are not connected to each other due to cracks that occur as a result of the formation of the modified regions; and in the second processing step, the laser beam is irradiated onto the object in the second part under second processing conditions such that the entire plurality of modified regions are in a second state in which the modified regions are connected to each other due to the cracks, thereby propagating the cracks so that the modified regions are connected to each other via the cracks across both the first and second parts.

[0009] The laser processing apparatus according to the present disclosure is a laser processing apparatus for processing an object along a virtual plane inside the object along the incident surface of the laser beam by irradiating the object with laser light, comprising: a support part for supporting the object; an irradiation part for irradiating the object supported by the support part with laser light; a moving part for moving at least one of the support part and the irradiation part so that the focal point of the laser beam moves along the virtual plane; and a control unit for controlling the support part, the irradiation part and the moving part, wherein the control unit controls the irradiation part and the moving part to irradiate the object with laser light along the virtual plane to a first part which is a part of the object when viewed from the Z direction intersecting the incident surface, and to form a plurality of modified regions along the virtual plane to the first part, and to control the irradiation part and the moving part after the first processing. The laser processing apparatus performs a second processing process in which, with respect to a second part which is another part of the object when viewed from the Z direction, the laser beam is irradiated onto the object along the virtual plane to form a plurality of modified regions along the virtual plane on the second part, wherein in the first processing process, the laser beam is irradiated onto the object in the first part under first processing conditions such that at least a portion of the plurality of modified regions are in a first state in which the modified regions are not connected to each other through cracks that occur as a result of the formation of the modified regions, and in the second processing process, the laser beam is irradiated onto the object in the second part under second processing conditions such that the entire plurality of modified regions are in a second state in which the modified regions are connected to each other through cracks, thereby propagating the cracks so that the modified regions are connected to each other through cracks across both the first and second parts.

[0010] In this laser processing method and laser processing apparatus, a laser beam is irradiated onto an object to process it along a virtual plane inside the object that is aligned with the incident surface of the laser beam. Specifically, a first part of the object is irradiated with laser beam along the virtual plane to form multiple modified regions in the first part, and then a second part of the object is irradiated with laser beam along the virtual plane to form multiple modified regions in the second part. When forming modified regions in the first part, the laser beam is irradiated under first processing conditions such that at least some of the modified regions are in a first state where they are not connected to each other due to cracks that occur as the modified regions are formed. When forming modified regions in the second part, the laser beam is irradiated under second processing conditions such that all of the modified regions are in a second state where they are connected to each other due to cracks. As a result, after forming modified regions in the second part, cracks are propagated so that the modified regions are connected to each other via cracks across both the first and second parts. This makes it possible to peel the object along the virtual plane. In particular, this method improves cycle time compared to the case where the second state is formed in both the first and second parts, suppresses unevenness on the peeled surface of the object, and improves processing quality.

[0011] The laser processing method according to the present disclosure may also be [2] "the laser processing method according to [1] above, wherein the first part and the second part have outer edges that are concentric with each other when viewed from the Z direction, and in the first processing step and the second processing step, spiral processing is performed in which the laser beam is irradiated onto the object while the focal point of the laser beam is moved relative to the object in a spiral shape when viewed from the Z direction, or concentric processing is performed in which the laser beam is irradiated onto the object while the focal point of the laser beam is moved relative to the object in a concentric shape when viewed from the Z direction." In this case, it becomes possible to efficiently perform the laser processing of the first part and the laser processing of the second part, and further improvements in cycle time can be achieved.

[0012] The laser processing method according to the present disclosure may also be [3] "the laser processing method according to [2] above, wherein the second part is a circular part that includes the center of the object when viewed from the Z direction, and the first part is an annular part that surrounds the second part when viewed from the Z direction." In this case, of the first and second parts arranged concentrically, the second part is on the central side (inside). Therefore, the pitch of the modified region in the second part may be smaller than that of the first part, so that the second state can be formed easily and reliably.

[0013] The laser processing method according to this disclosure may also be [4] "the laser processing method according to [2] or [3] above, wherein when spiral processing is performed in the first and second processing steps, the direction of relative movement of the focal point is kept constant across the first and second processing steps, and when concentric circle processing is performed in the first and second processing steps, the direction in which the position of the focal point is moved from one concentric circle to another concentric circle is kept constant across the first and second processing steps." In this case, processing can be carried out in the same direction in the first and second parts, thereby further improving cycle time.

[0014] The laser processing method according to the present disclosure may also be [5] "a laser processing method according to any of [1] to [4] above, comprising a first condition acquisition step for acquiring first processing conditions by irradiating a sample with the laser light along a line before the first processing step, wherein the first condition acquisition step has a first step, the first step being a third processing step for forming a plurality of modified regions on the sample by irradiating the sample with the laser light along a line with candidate conditions for the first processing conditions, a first determination step for determining whether the modified regions formed on the sample are in a first state after the third processing step, and a first correction step for correcting the candidate conditions if, as a result of the determination in the first determination step, the modified regions formed on the sample are not in a first state, wherein the first condition acquisition step is repeated until it is determined in the first determination step that the modified regions formed on the sample are in a first state." In this case, it becomes possible to efficiently acquire first processing conditions for making the state of the modified region in the first part a first state.

[0015] The laser processing method according to the present disclosure may be [6] "the laser processing method according to [5] above, wherein the first condition acquisition step has a second step following the first step, and the second step includes a fourth processing step of irradiating the sample with laser light along the line if, in the determination of the first determination step, it is determined that the modified region formed on the sample is in a first state; a second determination step of determining whether or not the modified region formed on the sample is in a second state after the fourth processing step; and a second correction step of correcting the candidate conditions if, as a result of the second determination step, the modified region formed on the sample is not in a second state, and in the first condition acquisition step, the first step and the second step are repeatedly performed until it is determined in the second determination step that the modified region formed on the sample is in a second state, and the candidate conditions when it is determined in the second determination step that the modified region formed on the sample is in a second state are acquired as the first processing conditions." In this case, it becomes possible to efficiently and reliably obtain the first processing conditions for setting the state of the modified region in the first part to the first state.

[0016] The laser processing method according to the present disclosure may also be [7] "the laser processing method according to any one of [1] to [4] above, comprising a second condition acquisition step for acquiring the first processing conditions by irradiating a sample with laser light before the first processing step, wherein the sample includes a substrate having a surface which is the incident surface of the laser light and a back surface opposite to the surface, and a film provided on the back surface, and the second condition acquisition step includes a fifth processing step of irradiating the sample with laser light multiple times while changing the output so that a first damage state is formed in which the film is damaged by the laser light, a second damage state is formed in which the film is damaged by the laser light and the output is set to a second output which is greater than the first output, and the film is damaged, and a third damage state is formed in which the output is set to a third output which is between the first output and the second output, and the film is not damaged, and in the second condition acquisition step, the conditions including the third output in which the third damage state is formed are acquired as the first processing conditions." In this case, it becomes possible to efficiently obtain the first processing conditions for setting the state of the modified region in the first part to the first state.

[0017] The laser processing method according to the present disclosure may also be [8] "the laser processing method according to [7] above, wherein in the fifth processing step, the third damage state is formed at a plurality of third outputs that are different from each other, and in the second condition acquisition step, a condition including the third output between the smallest third output and the largest third output among the plurality of third outputs is acquired as the first processing condition." In this case, it becomes possible to acquire the first processing condition for making the state of the modified region in the first part a first state more efficiently and appropriately.

[0018] The method for manufacturing a semiconductor device according to this disclosure is

[10] "a method for manufacturing a semiconductor device comprising: a first processing step and a second processing step included in the laser processing method described in any of [1] to [8] above; a peeling step performed after the second processing step to peel the object along the virtual surface; and a cutting step performed after the peeling step to cut the object into multiple chips for each of the multiple functional elements." According to this manufacturing method, the above laser processing method is performed, making it possible to improve processing quality while increasing cycle time.

[0019] According to this disclosure, it is possible to provide a laser processing method and a laser processing apparatus that can improve processing quality while increasing cycle time.

[0020] Figure 1 is a schematic diagram showing the configuration of a laser processing apparatus according to one embodiment. Figure 2 is a schematic diagram showing the configuration of the irradiation unit shown in Figure 1. Figure 3 is a diagram showing one step of the laser processing method according to this embodiment. Figure 4 is a diagram showing one step of the laser processing method according to this embodiment. Figure 5 is a diagram showing the workpiece of the laser processing method according to this embodiment. Figure 6 is a diagram showing one step of the laser processing method according to this embodiment. Figure 7 is a diagram showing one step of the laser processing method according to this embodiment. Figure 8 is a diagram showing the modified region and the crack formation state. Figure 9 is a diagram showing one step of the laser processing method according to this embodiment. Figure 10 is a diagram showing one step of the laser processing method according to this embodiment. Figure 11 is a diagram showing the modified region and the crack formation state. Figure 12 is a diagram for explaining the process of manufacturing a semiconductor device. Figure 13 is a flowchart showing an example of the processing condition acquisition process. Figure 14 is a diagram showing one step included in the first condition acquisition process. Figure 15 is a diagram showing one step included in the first condition acquisition process. Figure 16 is a diagram showing one step included in the first condition acquisition process. Figure 17 is a diagram showing a sample according to a modified example. Figure 18 is a flowchart showing another example of the processing condition acquisition process. Figure 19 shows one step included in the second condition acquisition process. Figure 20 shows an object related to a modified example. Figure 21 shows an object related to a modified example.

[0021] An embodiment will be described below with reference to the drawings. In each drawing, the same or corresponding parts will be denoted by the same reference numerals, and redundant explanations may be omitted. In addition, each drawing may show a Cartesian coordinate system defined by the X, Y, and Z axes.

[0022] Figure 1 is a schematic diagram showing the configuration of a laser processing apparatus according to one embodiment. As shown in Figure 1, the laser processing apparatus 1 comprises a stage (support unit) 2, an irradiation unit 3, moving units 4 and 5, and a control unit 6. The laser processing apparatus 1 is a device for forming a modified region 12 on an object 11 by irradiating the object 11 with laser light L. More specifically, the laser processing apparatus 1 is for processing the object 11 along a virtual surface inside the object 11 that is aligned with the incident surface of the laser light L on the object 11 by irradiating the object 11 with laser light L.

[0023] Stage 2 supports the object 11, for example, by holding a film attached to the object 11. Stage 2 is rotatable about an axis parallel to the Z direction. Stage 2 may also be movable along the X and Y directions. The X and Y directions are the first and second horizontal directions, which intersect (are orthogonal to each other), and the Z direction is the vertical direction.

[0024] The irradiation unit 3 is for irradiating the object 11 supported on the stage 2 with laser light L. The irradiation unit 3 focuses the laser light L, which is penetrating to the object 11, and irradiates the object 11 with it. When the laser light L is focused inside the object 11 supported on the stage 2, the laser light L is particularly absorbed in the portion corresponding to the focal point C of the laser light L, and a modified region 12 is formed inside the object 11.

[0025] The modified region 12 is a region whose density, refractive index, mechanical strength, and other physical properties differ from those of the surrounding unmodified region. Examples of modified regions 12 include melting regions, crack regions, dielectric breakdown regions, and refractive index change regions. The modified region 12 may be formed such that cracks extend from the modified region 12 toward the incident side of the laser beam L and the opposite side. Such modified regions 12 and cracks can be used, for example, to cut the object 11. Alternatively, the modified region 12 may be formed such that cracks extend from the modified region 12 into the plane of the object 11 along the incident surface of the laser beam L. Such modified regions 12 and cracks can be used to delaminate the object 11.

[0026] As an example, when stage 2 is moved along the X direction and the focal point C is moved relative to the object 11 along the X direction, multiple modified spots 12s are formed in a line along the X direction. Each modified spot 12s is formed by irradiation with one pulse of laser light L. A row of modified regions 12 is a collection of multiple modified spots 12s arranged in a line. Adjacent modified spots 12s may be connected to each other or separated from each other, depending on the relative movement speed of the focal point C with respect to the object 11 and the repetition frequency of the laser light L.

[0027] The moving unit 4 includes a first moving unit 41 that moves the stage 2 in one direction within a plane intersecting (orthogonal to) the Z direction, and a second moving unit 42 that moves the stage 2 in another direction within the plane intersecting (orthogonal to) the Z direction. For example, the first moving unit 41 moves the stage 2 along the X direction, and the second moving unit 42 moves the stage 2 along the Y direction. The moving unit 4 also rotates the stage 2 around an axis parallel to the Z direction. The moving unit 5 supports the irradiation unit 3. The moving unit 5 moves the irradiation unit 3 along the X, Y, and Z directions. When the stage 2 and / or the irradiation unit 3 are moved while the focal point C of the laser beam L is formed, the focal point C is moved relative to the object 11. That is, the moving units 4 and 5 move at least one of the stage 2 and the irradiation unit 3 in order to move the focal point C of the laser beam L relative to the object 11.

[0028] The control unit 6 controls the operation of the stage 2, the irradiation unit 3, and the moving units 4 and 5. The control unit 6 has a processing unit, a storage unit, and an input receiving unit (not shown). 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 constitutes a GUI (Graphical User Interface).

[0029] Figure 2 is a schematic diagram showing the configuration of the irradiation unit shown in Figure 1. Figure 2 shows a hypothetical line A indicating the planned laser processing. As shown in Figure 2, the irradiation unit 3 includes a light source 31, a spatial light modulator 7, and a focusing lens (focusing unit) 33. The light source 31 outputs laser light L, for example, by a pulse oscillation method. The irradiation unit 3 may also be configured to not have a light source 31, and to introduce laser light L from outside the irradiation unit 3. The spatial light modulator 7 modulates the laser light L output from the light source 31. The focusing lens 33 focuses the laser light L modulated by the spatial light modulator 7 and output from the spatial light modulator 7 (i.e., the laser light that has passed through the spatial light modulator 7) toward the object 11.

[0030] In the spatial light modulator 7, when a signal indicating a modulation pattern is input from the control unit 6, the modulation pattern is displayed according to the signal. The modulation pattern is for modulating the laser light L. In the spatial light modulator 7, when the modulation pattern is displayed and laser light L is incident from the outside, reflected, and emitted to the outside, the laser light L is modulated according to the displayed modulation pattern. In this way, the spatial light modulator 7 makes it possible to modulate the laser light L (for example, modulating the intensity, amplitude, phase, polarization, etc. of the laser light L) by appropriately setting the displayed modulation pattern.

[0031] As described above, the laser light L output from the light source 31 is incident on the focusing lens 33 via the spatial light modulator 7, and is focused into the object 11 by the focusing lens 33, thereby forming a modified region 12 and cracks extending from the modified region 12 in the object 11 at the focusing point C. Furthermore, by controlling the movement units 4 and 5 of the control unit 6, the focusing point C is moved relative to the object 11, thereby forming the modified region 12 and cracks along the direction of movement of the focusing point C.

[0032] Next, a laser processing method according to one embodiment will be described. The laser processing method according to this embodiment is carried out by the laser processing apparatus 1 described above. Therefore, the laser processing method described below is also an example of the processing performed by the laser processing apparatus 1. That is, here, the control unit 6 controls the moving units 4 and 5 to move at least one of the stage 2 and the irradiation unit 3, thereby moving the focal point C of the laser beam L relative to the object 11 and irradiating the object 11 with the laser beam L to perform laser processing to form a modified region 12 on the object 11. More specifically, in this laser processing method, by irradiating the object 11 with the laser beam L, processing is performed along a virtual surface inside the object 11 that is aligned with the incident surface of the laser beam L on the object 11.

[0033] Figure 3 is a diagram showing one step of the laser processing method according to this embodiment. Here, first, object 11 is formed from object 11A (step S101). That is, in step S101, object 11A, which will be the basis for object 11, is prepared, and object 11 is formed by laser processing of object 11A. Object 11A is, for example, a silicon wafer. Object 11A includes a first surface 11a and a second surface 11b opposite to the first surface 11a. A device layer including a plurality of functional elements is formed on the second surface 11b of object 11A. Object 11A is supported on stage 2 such that the first surface 11a faces the irradiation unit 3 side (i.e., the second surface 11b faces the stage 2 side).

[0034] The object 11A includes an effective region R and a removal region E. The effective region R is the portion containing the semiconductor device to be acquired. The effective region R is also the portion that constitutes the object 11. Here, the effective region R is a disc-shaped portion that includes the center of the object 11A when viewed from the thickness direction of the object 11A, i.e., the Z direction which intersects the first surface 11a, which is the incident surface of the laser beam L. The removal region E is the region of the object 11A located outside the effective region R. In this embodiment, the removal region E is the outer edge portion of the object 11A other than the effective region R. Here, the removal region E is the annular portion surrounding the effective region R. The removal region E includes the peripheral edge (outer bevel portion) of the object 11A when viewed from the Z direction.

[0035] A virtual surface M1 is set on the object 11A as the surface to be peeled off. The virtual surface M1 is the surface on which the modified region 12 is to be formed. The virtual surface M1 is a surface along the first surface 11a, which is the incident surface of the laser beam L on the object 11A. The virtual surface M1 is a surface parallel to the first surface 11a and, when viewed from the Z direction, exhibits a circular shape, for example. The virtual surface M1 is a virtual region and is not limited to a plane, but may be a curved surface or a three-dimensional surface. The setting of the effective region R, the removal region E, and the virtual surface M1 can be done in the control unit 6. The effective region R, the removal region E, and the virtual surface M1 may be specified by coordinates.

[0036] Furthermore, a line M3 is set on the object 11A as a trimming line. Line M3 is the line where the modified region 12 is planned to be formed. Line M3 extends in an annular shape inside the outer edge of the object 11A. Here, line M3 extends in an annular shape. Line M3 is set at the boundary between the effective region R and the removal region E of the object 11A. The setting of line M3 can be done in the control unit 6. Line M3 is a virtual line, but it may also be an actually drawn line. Line M3 may also be specified by coordinates.

[0037] In step S101, trimming is performed first. That is, in step S101, as shown in Figure 4, a laser beam L is irradiated along line M3 to form a modified region 12. Here, the modified region 12 is formed over the entire thickness of the object 11A in the Z direction.

[0038] More specifically, in step S101, the control unit 6 controls the moving units 4 and 5 to move the irradiation unit 3 and / or stage 2 so that the focal point C of the laser beam L is located on line M3 and at a predetermined depth (position in the Z direction) from the first surface 11a of the object 11. In this state, the control unit 6 controls the moving unit 4 to rotate the stage 2 around an axis parallel to the Z direction and controls the light source 31 to start irradiating with the laser beam L, thereby moving the focal point C of the laser beam L relative to the object 11. As a result, a ring-shaped modified region 12 is formed inside the object 11 along the circular line M3. In step S101, the above irradiation of the laser beam L is performed multiple times, while sequentially changing the position of the focal point C in the Z direction, for example, from the second surface 11b side to the first surface 11a side.

[0039] Next, in step S101, by applying an external force to the object 11A, for example, the modified region 12 formed along line M3 and the cracks extending from the modified region 12 are used to remove the removal region E from the object 11A. As a result, the object 11 (effective region R) is obtained, as shown in Figure 5. The object 11 has a first surface 11a and a second surface 11b. A virtual surface M1 is set on the object 11, and a plurality of lines A are set on it. The plurality of lines A are circular in shape when viewed from the Z direction and are arranged concentrically from the center of the object 11. The lines A are lines on which the laser beam L is irradiated to form the modified region 12 by moving the focal point C of the laser beam L.

[0040] Furthermore, as described above, the object 11 is formed by removing the removal region E, which is a bevel portion, from the object 11A, and therefore exhibits a cylindrical (disc-shaped) form that is rectangular in side view. The object 11 includes a first portion 111, which is a part of the object 11, and a second portion 112, which is another part of the object 11. In this embodiment, the object 11 consists of the first portion 111 and the second portion 112.

[0041] Therefore, the first part 111 is a part of the object 11, and the second part 112 is the remainder of the object 11. The first part 111 and the second part 112 have outer edges that are concentric circles when viewed from the Z direction. Here, the second part 112 is a circular part that includes the center of the object 11 when viewed from the Z direction, and the first part 111 is an annular part that surrounds the second part 112 when viewed from the Z direction.

[0042] In the subsequent step, as shown in Figures 6 and 7, a laser beam L is irradiated onto the object 11, which is a part of the object 11 when viewed from the Z direction, along the virtual plane M1, thereby forming a plurality of modified regions 12 on the first part 111 along the virtual plane M1 (step S102, first processing step). In other words, in step S102, the control unit 6 controls the irradiation unit 3 and the moving units 4 and 5 to irradiate the object 11, which is a part of the object 11 when viewed from the Z direction, with a laser beam L along the virtual plane M, thereby executing a first processing operation in which a plurality of modified regions 12 are formed on the first part 111 along the virtual plane M1.

[0043] Specifically, in step S102, first, as shown in FIG. 6, the control unit 6 controls the moving units 4 and 5 to align the position of the condensing point C of the laser beam L in the Z direction with the virtual plane M1, and to align the position of the condensing point C in the directions intersecting with the Z direction (for example, the X direction and the Y direction (the same hereinafter)) with one of the plurality of lines A set in the first portion 111, and the irradiation unit 3 and / or the stage 2 are moved. In this state, the control unit 6 controls the moving unit 4 to rotate the stage 2 about an axis parallel to the Z direction as the rotation axis, and controls the light source 31 to start irradiating the laser beam L, and relatively moves the condensing point C of the laser beam L with respect to the object 11.

[0044] As a result, as shown in FIG. 7, when viewed from the Z direction, a plurality of modified regions 12 arranged in a circular shape while being spaced apart from each other are formed on the one line A. These plurality of modified regions 12 are formed on the virtual plane M1 when viewed from the direction intersecting with the Z direction. In step S102, the control unit 6 controls the moving units 4 and 5 to sequentially change the position of the condensing point C of the laser beam L in the direction intersecting with the Z direction over all the lines A set in the first portion 111, and repeats the same laser processing. As a result, a plurality of modified regions 12 arranged while being spaced apart from each other over the first portion 111 are formed.

[0045] Thus, in step S102, as an example, concentric circle processing is performed in which the laser beam L is irradiated to the object 11 while relatively moving the condensing point C of the laser beam L in a concentric circle shape when viewed from the Z direction. Further, in step S102, as an example, the direction (hereinafter referred to as the "index feed direction") in which the position of the condensing point C is moved from one line A (concentric circle) to another line A (concentric circle) is made constant. The index feed direction is, for example, the direction from the outer side in the radial direction to the inner side in the radial direction of the first portion 111.

[0046] Here, Figure 8 is a diagram showing the formation state of the modified regions and cracks. Figure 8(a) shows one example of the formation state, and Figure 8(b) shows another example of the formation state. In Figure 8, the X direction is the processing progress direction, which is the direction in which the focal point C of the laser beam L moves, and the Y direction is the index feed direction. As shown in Figure 8(a), one example of the formation state of the modified regions 12 and cracks 13 is the first state SST, in which at least some of the modified regions 12 among the multiple modified regions 12 are in a state in which the modified regions 12 are not connected to each other by cracks 13 that occur as a result of the formation of the modified regions 12 (for example, extending from the modified regions 12).

[0047] In the first state SST of the illustrated example, in both the machining direction and the index feed direction, most (or part) of the multiple modified regions 12 are modified regions 121 that are not connected to other modified regions 12 by cracks 13. On the other hand, in the first state SST of the illustrated example, some (or the remaining) of the multiple modified regions 12 are modified regions 122 that are connected to other modified regions 12 by cracks 13 in the machining direction. That is, in the first state SST, modified regions 121 that are not connected to other modified regions 12 by cracks 13 are dominant (for example, they make up the majority) of the multiple modified regions 12. However, in the first state SST of the illustrated example, no modified regions 12 that are connected to other modified regions 12 by cracks 13 occur in the index feed direction. Furthermore, the first state SST includes a state in which all of the multiple modified regions 12 are not connected to each other by cracks 13 (i.e., a state in which all modified regions 12 are modified regions 121).

[0048] As another example of the formation states of the modified regions 12 and the cracks 13, there is a third state SHC in which most of the plurality of modified regions 12 are connected to each other by the cracks 13 only in one of the processing progress direction and the index feed direction (here, the processing progress direction). In the third state SHC of the illustrated example, most of the plurality of modified regions 12 have become modified regions 122 that are connected to other modified regions 12 by the cracks 13 in the processing progress direction. That is, in the third state SHC, among the plurality of modified regions 12, the modified regions 122 that are connected to other modified regions 12 by the cracks 13 in one of the processing progress direction and the index feed direction are dominant (for example, they account for the majority). However, in the third state SHC of the illustrated example, there are no modified regions 12 that are connected to other modified regions 12 by the cracks 13 in the index feed direction.

[0049] In the step S102 (first processing), the laser beam L is irradiated onto the object 11 under the first processing conditions in which at least some of the plurality of modified regions 12 are in the above-described first state SST in which the modified regions 12 are not connected to each other by the cracks 13 generated along with the formation of the modified regions 12. The first processing conditions include various conditions such as the interval in the index feed direction of the line A, the focusing correction of the laser beam L, the spherical aberration, the pulse pitch, the pulse energy, the pulse width, the output, and the like.

[0050] Note that by further adjusting the output, the focusing correction, etc. of the laser beam L with respect to the first processing conditions to strengthen the formation of the modified regions 12, the formation states of the modified regions 12 and the cracks 13 can be changed from the first state SST to the third state SHC. In other words, by keeping the strength of the formation of the modified regions at a certain level, the formation states of the modified regions 12 and the cracks 13 can be made the first state SST so that they do not become the third state SHC.

[0051] In the subsequent step, as shown in Figures 9 and 10, a laser beam L is irradiated onto the object 11 along a virtual plane M1 to form a plurality of modified regions 12 on the second part 112, which is another part of the object 11 when viewed from the Z direction (step S103, second processing step). In other words, in step S103, the control unit 6 controls the irradiation unit 3 and the moving units 4 and 5 to irradiate the object 11 with a laser beam L along a virtual plane M1 to form a plurality of modified regions 12 on the second part 112, which is another part of the object 11 when viewed from the Z direction, and executes a second processing process in which a plurality of modified regions 12 are formed on the second part 112 along a virtual plane M1.

[0052] Specifically, in step S103, first, as shown in Figure 9, the control unit 6 controls the moving units 4 and 5 to move the irradiation unit 3 and / or stage 2 so that the position of the focal point C of the laser beam L in the Z direction is aligned with the virtual plane M1, and the position of the focal point C in the direction intersecting the Z direction is aligned with one of the multiple lines A set in the second part 112. In this state, the control unit 6 controls the moving unit 4 to rotate the stage 2 around an axis parallel to the Z direction, and controls the light source 31 to start irradiating with the laser beam L, thereby moving the focal point C of the laser beam L relative to the object 11.

[0053] As a result, as shown in Figure 10, multiple modified regions 12 are formed on a circular line A, spaced apart from each other when viewed from the Z direction. These multiple modified regions 12 are formed on a virtual plane M1 when viewed from a direction intersecting the Z direction. In step S103, the control unit 6 controls the moving units 4 and 5 to sequentially change the position of the focal point C of the laser beam L in the direction intersecting the Z direction across all lines A set in the second section 112, and the same laser processing is repeated. As a result, multiple modified regions 12 are formed across the second section 112, spaced apart from each other.

[0054] Thus, in step S103, as an example, concentric machining is performed by irradiating the object 11 with the laser beam L while relatively moving the focal point C of the laser beam L in a concentric circle when viewed from the Z direction. Furthermore, in step S103, as an example, the index feed direction is kept constant. The index feed direction is, for example, the direction from the radially outside to the radially inside of the second part 112. In this case, the index feed direction remains constant throughout steps S102 and S103.

[0055] Here, Figure 11 is a diagram showing the formation state of the modified region and cracks. Figure 11 shows yet another example of the formation state. In Figure 11, the X direction is the processing direction and the Y direction is the index feed direction. As shown in Figure 11, another example of the formation state of the modified region 12 and crack 13 is the second state SFC, in which all of the multiple modified regions 12 are connected to each other by cracks 13.

[0056] In the second state SFC shown in the illustrated example, in both the processing direction and the index feed direction, all of the multiple modified regions 12 are modified regions 123 in which they are connected to other modified regions 12 by cracks 13. In the second state SFC, as shown in Figures 10 and 11, the cracks 13 can propagate two-dimensionally over almost the entire second portion 112, resulting in a state where the modified regions 12 are connected to each other by cracks 13. Furthermore, the second state SFC can be changed from the third state SHC to the second state SFC by adjusting the output of the laser beam L, focusing correction, etc., to further strengthen the formation of the modified regions 12 for the third state SHC.

[0057] Thus, in step S103 (second processing), laser light L is irradiated onto the object 11 in the second part 112 under second processing conditions such that the entirety of the multiple modified regions 12 are in a second state SFC, where the modified regions 12 are connected to each other by cracks 13. As a result, in step S103, cracks 13 are propagated along the virtual plane M1 throughout the entirety of the first part 111 and the second part 112 so that the modified regions 12 are connected to each other via cracks 13. As a result, it becomes possible to peel off the object 11 along the virtual plane M1 by utilizing the modified regions 12 and cracks 13 formed along the virtual plane M1.

[0058] Therefore, in the subsequent step, as shown in Figure 12(a), the modified region 12 and the crack 13 are used to peel off the object 11 along the virtual surface M1 (step S104: peeling step). As described above, a device layer containing multiple functional elements is formed on the second surface 11b of the object 11. Therefore, here, a new object 11T including the second surface 11b of the object 11 is formed by peeling off the portion including the first surface 11a of the object 11. After that, as shown in Figure 12(b), the object 11T is cut into multiple chips 200 for each of the multiple functional elements (step S105: cutting step). This gives rise to multiple chips 200 (i.e., semiconductor devices). Thus, the method comprising steps S104 and S105 in addition to steps S101 to S103 of the laser processing method according to this embodiment is a method for manufacturing semiconductor devices according to this embodiment. In addition, any method can be used to cut the object 11T in step S105, such as laser dicing, blade dicing, and plasma dicing.

[0059] Herein, the laser processing method according to this embodiment further comprises a processing condition acquisition step for acquiring first processing conditions to be used in step S102. This step may be performed at least before carrying out step S102.

[0060] Figure 13 is a flowchart showing an example of a processing condition acquisition process. Figure 13 shows one of several processing condition acquisition processes (the first condition acquisition process). Here, first, a sample 11B is prepared as shown in Figure 13. Sample 11B is, for example, a silicon wafer, and may be the same as object 11 or object 11A, but may also be at least different in shape from object 11 or object 11A. Multiple linear lines A are set on sample 11B. In this case, lines A extend along the X direction and are arranged along the Y direction.

[0061] In the first condition acquisition step, the first processing conditions are acquired by irradiating the sample 11B with laser light L along line A (first step). That is, the processing conditions of the sample 11B using laser light L are first set as candidate conditions for the first processing conditions, and then, under these candidate conditions, the laser light L is irradiated onto the sample 11B along line A to form multiple modified regions 12 in the sample 11B (step S201, third processing step).

[0062] Specifically, in step S201, as shown in Figure 14(a), the control unit 6 controls the moving units 4 and 5 to move the irradiation unit 3 and / or stage 2 so that the position of the focal point C in a direction intersecting the Z direction is aligned with one of the multiple lines A set on the sample 11B. At this time, the position of the focal point C of the laser beam L in the Z direction may be the same as, for example, the position in the Z direction where the virtual plane M1 on the object 11 is set. In this state, the control unit 6 controls the moving unit 5 to move the irradiation unit 3 in the X direction and controls the light source 31 to start irradiating with the laser beam L, thereby moving the focal point C of the laser beam L relative to the object 11 along the X direction.

[0063] As a result, as shown in Figure 14(b), multiple modified regions 12 are formed, arranged on the linear line A, spaced apart from each other when viewed from the Z direction. In step S201, the control unit 6 controls, for example, the moving unit 5, to sequentially change the position of the focal point C of the laser beam L in a direction intersecting the Z direction across all lines A, and repeatedly performs the same laser processing. As a result, multiple modified regions 12 are formed, spaced apart from each other across all lines A.

[0064] In a subsequent step, for example, the control unit 6 controls an imaging device (not shown) of the laser processing apparatus 1 to image the sample 11B, thereby determining whether the modified region 12 (formation state of the modified region 12) formed in the sample 11B is in the first state SST (step S202, first determination step). As an example, the imaging device can acquire an image including images of the modified region 12 and cracks 13 inside the sample 11B by imaging the sample 11B with light transmitted through the sample 11B, and in step S202, a determination may be made based on this image.

[0065] If the result of the determination in step S202 is that the modified region 12 formed on sample 11B is not in the first state SST (step S202: No), the candidate conditions are corrected (step S203, first correction step). More specifically, if the result of the determination in step S202 is that the state of the modified region 12 formed on sample 11B is the third state SHC or the second state SFC, the formation of the modified region 12 is too strong, so the candidate conditions are corrected to optimize various conditions such as output, pulse pitch, focusing correction, astigmatism, and the spacing in the index feed direction of line A in order to weaken the formation of the modified region 12. In this case, optimization may include, for example, weakening the output, widening the pulse pitch, strengthening the focusing correction, optimizing the astigmatism correction value, or widening the spacing in the index feed direction of line A.

[0066] Subsequently, the process returns to step S201, and either sample 11B is replaced with another sample 11B, or the unprocessed portion of sample 11B is used, and the above processing in step S201 is performed again under the candidate conditions corrected in step S203, and the determination is made again in step S202. In other words, if steps S201, S202, and S203 are considered the first steps of the first condition acquisition process, then the first steps will be repeatedly performed until the modified region 12 formed in sample 11B in step S202 is determined to be the first state SST.

[0067] Then, if the result of the determination in step S202 is determined to be the first state SST, then, as shown in Figure 15(a), the sample 11B with the modified region 12 formed, which was subjected to determination in step S202, is irradiated again with laser light L along line A (step S204, fourth processing step).

[0068] In step S204, laser light L is irradiated onto a portion of line A that has been processed in step S201, among a plurality of lines A. For example, in step S204, when viewed from the Z direction, a portion of one side of sample 11B in the Y direction is designated as the first portion B1, and another portion of sample 11B in the Y direction is designated as the second portion B2. Laser light L is irradiated along the processed line A set in the second portion B2. Here, the first portion B1 and the second portion B2 are continuous in the Y direction.

[0069] Specifically, in step S204, the control unit 6 controls the moving units 4 and 5 to move the irradiation unit 3 and / or stage 2 so that the position of the focal point C in a direction intersecting the Z direction is aligned with one of the multiple lines A set in the second part B2. At this time, the position of the focal point C of the laser beam L in the Z direction may be the same as, for example, the position in the Z direction where the virtual plane M1 on the object 11 is set. In this state, the control unit 6 controls the moving unit 5 to move the irradiation unit 3 in the X direction and controls the light source 31 to start irradiating with the laser beam L, thereby moving the focal point C of the laser beam L relative to the object 11 along the X direction.

[0070] As a result, as shown in Figure 15(b), a plurality of modified regions 12 (modified regions 12 schematically shown as triangular in the illustration) are formed, arranged on the linear line A, spaced apart from each other when viewed from the Z direction. In step S204, the control unit 6 controls, for example, the moving unit 5, to sequentially change the position of the focal point C of the laser beam L in a direction intersecting the Z direction across all lines A set in the second part B2, and repeats the same laser processing. In the illustrated example, the position in the direction intersecting the Z direction where the focal point C is aligned in step 204 is the same as the position where the focal point C was aligned in step S201. Therefore, in step S204, modified regions 12 are formed again so as to overlap with the modified regions 12 formed in step S201 when viewed from the Z direction.

[0071] The processing conditions in step S204 may be the same as those in step S201, which result in the modified region 12 formed in sample 11B being in the first state SST, or they may be different. If the processing conditions in step S204 are the same as those in step S201, which result in the modified region 12 being in the first state SST, then it is ensured that the modified region 12 formed by the execution of step S204 is at least in the first state SST, thereby suppressing the occurrence of a situation where the formation of the modified region 12 is too weak.

[0072] In the next step, it is determined whether the modified region 12 formed in sample 11B is in the second state SFC (step S205, second determination step). That is, in step S205, it is determined whether the crack 13 has propagated throughout the entire first part B1 and second part B2 so that all of the multiple modified regions 12 formed in step S204 are connected to each other by cracks 13 (second state SFC), as shown in Figure 16, and the modified regions 12 are connected to each other via cracks 13 throughout both the first part B1 and the second part B2. The determination in step S205 can be performed, for example, by the same method as the determination in step S202.

[0073] Next, if the result of the judgment in step S205 is that the modified region 12 formed on sample 11B is not in the second state SFC (step S205: No), the candidate conditions are corrected (step S206, second correction step). More specifically, if the result of the judgment in step S205 is that the state of the modified region 12 formed on sample 11B is the first state SST or the third state SHC, the formation of the modified region 12 in step S201, which is the first stage of laser processing, is too weak. Therefore, the candidate conditions are corrected to optimize various conditions such as output, pulse pitch, focusing correction, astigmatism, and the spacing in the index feed direction of line A in order to strengthen the formation of the modified region 12 in step S201. In this case, optimization may include increasing the output, narrowing the pulse pitch, weakening the focusing correction, optimizing the astigmatism correction value, or narrowing the spacing in the index feed direction of line A.

[0074] Subsequently, the process returns to step S201, and either sample 11B is replaced with another sample 11B, or the unprocessed portion of sample 11B is used, and the above processing in step S201 is performed again under the candidate conditions corrected in step S206, and steps S202 to S205 are performed again. In other words, if steps S204, S205, and S206 are considered the second steps of the first condition acquisition process, the first and second steps will be repeatedly performed until the modified region 12 formed in sample 11B in step S205 is determined to be the second state SFC.

[0075] Then, if the result of the determination in step S205 determines that the modified region 12 formed in sample 11B is in the second state SFC (step S205: Yes), the candidate conditions for that case are acquired as the first processing conditions (step S207), and the series of steps is completed.

[0076] As described above, in the laser processing method and laser processing apparatus 1 according to this embodiment, processing is performed along a virtual surface M1 inside the object 11 that is aligned with the incident surface of the laser beam L on the object 11 by irradiating the object 11 with laser light L. Specifically, a first part 111, which is a part of the object 11, is irradiated with laser light L along the virtual surface M1 to form a plurality of modified regions 12 in the first part 111, and then a second part 112, which is another part of the object 11, is irradiated with laser light L along the virtual surface M1 to form a plurality of modified regions 12 in the second part 112.

[0077] When forming a modified region 12 in the first portion 111, laser light L is irradiated under first processing conditions such that at least some of the modified regions 12 are in a first state SST, where the modified regions 12 are not connected to each other due to cracks 13 that occur as a result of the formation of the modified regions 12. When forming a modified region 12 in the second portion 112, laser light L is irradiated under second processing conditions such that all of the modified regions 12 are in a second state SFC, where the modified regions 12 are connected to each other due to cracks 13. As a result, after forming a modified region 12 in the second portion 112, the cracks 13 are propagated so that the modified regions 12 are connected to each other via the cracks 13 across both the first portion 111 and the second portion 112. This makes it possible to peel off the object 11 along the virtual surface M1. In particular, this method improves cycle time compared to the case where a second state SFC is formed in both the first portion 111 and the second portion 112, and also suppresses unevenness on the peeled surface of the object 11, thereby improving processing quality.

[0078] In the laser processing method according to this embodiment, the first portion 111 and the second portion 112 have outer edges that are concentric with each other when viewed from the Z direction, and in steps S102 and S103, concentric processing is performed by irradiating the object 11 with laser light L while relatively moving the focal point C of the laser light L in a concentric manner when viewed from the Z direction. This makes it possible to efficiently perform laser processing of the first portion 111 and the second portion 112, thereby further improving cycle time.

[0079] Furthermore, in the laser processing method according to this embodiment, the second portion 112 is a circular portion that includes the center of the object 11 when viewed from the Z direction, and the first portion 111 is an annular portion that surrounds the second portion 112 when viewed from the Z direction. That is, of the first portion 111 and the second portion 112 which are arranged concentrically, the second portion 112 is on the central side (inside). Therefore, in the second portion 112, the pitch of the modified region 12 can be smaller compared to the first portion 111, so that the second state SFC can be formed easily and reliably.

[0080] Furthermore, in the laser processing method according to this embodiment, when concentric circle processing is performed in steps S102 and S103, the direction in which the position of the focusing point C is moved from one concentric circle (line A) to another concentric circle (line A) is kept constant throughout steps S102 and S103. As a result, processing can be carried out in the same direction in the first part 111 and the second part 112, thereby further improving the cycle time.

[0081] Furthermore, the laser processing method according to this embodiment includes a first condition acquisition step for acquiring first processing conditions by irradiating the sample 11B with laser light L along line A before step S102. The first condition acquisition step has a first step. The first step includes step S201, in which a plurality of modified regions 12 are formed on the sample 11B by irradiating the sample 11B with laser light L along line A under candidate conditions for the first processing conditions; step S202, after step S201, in which a determination is made as to whether or not the modified regions 12 formed on the sample 11B are in a first state SST; and step S203, if, as a result of the determination in step S202, the modified regions 12 formed on the sample 11B are not in a first state SST, in which case the candidate conditions are corrected. The first condition acquisition step is repeated until it is determined in step S202 that the modified regions 12 formed on the sample 11B are in a first state SST. Therefore, it becomes possible to efficiently obtain the first processing conditions for setting the state of the modified region 12 in the first part 111 to the first state SST.

[0082] Furthermore, in the laser processing method according to this embodiment, the first condition acquisition step includes a second step following the first step. The second step includes, if, in the determination in step S202, the modified region 12 formed on the sample 11B is determined to be in the first state SST, step S204, irradiating the sample 11B with laser light L along line A; step S205, after step S204, determining whether or not the modified region 12 formed on the sample 11B is in the second state SFC; and step S206, if, as a result of step S205, the modified region 12 formed on the sample 11B is not in the second state SFC, correcting the candidate conditions. Then, in the first condition acquisition step, the first and second steps are repeatedly performed until it is determined that the modified region 12 formed in the sample 11B in step S205 is in the second state SFC. At the same time, the candidate conditions at which it is determined that the modified region 12 formed in the sample 11B in step S205 is in the second state SFC are acquired as the first processing conditions. This makes it possible to efficiently and reliably acquire the first processing conditions for making the state of the modified region in the first part the first state.

[0083] Furthermore, the semiconductor device manufacturing method according to this embodiment includes the above-described steps S102 and S103, a step S104 in which the object T is peeled off along the virtual surface M1 after step S103, and a step S105 in which the object 11T is cut into multiple chips 200 for each of the multiple functional elements after step S104. According to the semiconductor device manufacturing method according to this embodiment, the laser processing method according to this embodiment is implemented, making it possible to improve processing quality while increasing cycle time.

[0084] The embodiments described above illustrate one aspect of the present disclosure. Therefore, the present disclosure is not limited to the embodiments described above and can be modified as appropriate. Modifications will be described next.

[0085] In the above embodiment, an example was described in which, when irradiating the processed line A with laser light L in step S204 of the first condition acquisition process, the position of the focal point C in the direction intersecting the Z direction is the same as the position where the focal point C was aligned in step S201 (an example of overlapping irradiation). However, as shown in Figure 17(a), when irradiating the processed line A with laser light L in step S204 of the first condition acquisition process, the position of the focal point C in the direction intersecting the Z direction may be shifted in the processing direction (X direction) relative to the position where the focal point C was aligned in step S201. In this case, the modified region 12 formed in step S204 may or may not partially overlap the modified region 12 formed in step S201.

[0086] Furthermore, as shown in Figure 17(b), when irradiating the processed line A with laser light L in step S204 of the first condition acquisition step, the position of the focal point C in the direction intersecting the Z direction may be shifted in the index feed direction (Y direction) relative to the position where the focal point C was aligned in step S201. In this case, the modified region 12 formed in step S204 may or may not partially overlap the modified region 12 formed in step S201.

[0087] Furthermore, as shown in Figure 17(c), when irradiating the processed line A with laser light L in step S204 of the first condition acquisition step, the position of the focal point C in the direction intersecting the Z direction may be shifted in both the processing direction (X direction) and the index feed direction (Y direction) relative to the position where the focal point C was aligned in step S201. In this case, the modified region 12 formed in step S204 may or may not partially overlap the modified region 12 formed in step S201.

[0088] Furthermore, in the above embodiment, the first condition acquisition step was described as an example of a process for acquiring the first processing conditions. However, the process for acquiring the first processing conditions may be another example (second condition acquisition step) described below.

[0089] Figure 18 is a flowchart showing another example of the processing condition acquisition process. The second condition acquisition process shown in Figure 18 can be performed at least before process S102. The second condition acquisition process is for acquiring the first processing conditions by irradiating the sample 11C with laser light L. Therefore, in the second condition acquisition process, first, the sample 11C shown in Figure 19 is prepared. The sample 11C includes a substrate 150 having a surface 150a that is the incident surface of the laser light L and a back surface 150b opposite to the surface 150a, and a film 160 provided on the back surface 150b of the substrate 150. The substrate 150 is, for example, a silicon wafer. The film 160 is, for example, a metal film such as tin (Sn).

[0090] Next, in the second condition acquisition step, the surface 150a of the substrate 150 is used as the incident surface for the laser beam L, and the output of the laser beam L is changed while irradiating multiple locations on the sample 11C with the laser beam L to form multiple modified regions 12 on the sample 11C (step S301, fifth processing step). For example, in step S301, with the focal point C of the laser beam L located inside the substrate 150 of the sample 11C, the output of the laser beam L is gradually increased, for example, from output C0 to output C5, while irradiating multiple locations on the sample 11C with the laser beam L.

[0091] Next, it is determined whether or not damage 14 has occurred to the film 160 of sample 11C due to the lapse of the laser beam L (step S302). Here, when the output of the laser beam L is set to output C0, no modified region 12 is formed on the substrate 150, and no damage 14 due to the lapse of the laser beam L occurs on the film 160. Also, when the output of the laser beam L is set to output C1, no modified region 12 is formed on the substrate 150, and damage 14 occurs on the film 160.

[0092] Furthermore, when the output of the laser beam L is set to output C2 to C4, a modified region 12 is formed on the substrate 150, and no damage 14 occurs on the film 160. When the output of the laser beam L is set to output C5, a modified region 12 is formed on the substrate 150, and damage 14 occurs on the film 160. According to the inventor's findings, the output of the laser beam L for the first processing condition in which the modified region 12 formed by laser processing of the object 11 is in the first state SST is an output in which a modified region 12 is formed on the substrate 150, and no damage 14 occurs on the film 160. Therefore, the candidate outputs of the laser beam L for the first processing condition are output C2 to C4.

[0093] Therefore, in the subsequent step, a condition is obtained as the first processing condition that includes output C3, which is between the smallest output C2 and the largest output C4 among outputs C2 to C4 (step S303).

[0094] As described above, in the second condition acquisition step, the laser beam L is irradiated onto the sample 11C multiple times while changing the output so that the following conditions are formed: a first damage state Ds1 in which the output of the laser beam L is set to a first output (output C1) and damage 14 occurs to the film 160 due to the laser beam L; a second damage state Ds2 in which the output of the laser beam L is set to a second output (output C5) which is greater than the first output (output C1) and damage 14 occurs to the film 160; and a third damage state Ds3 in which the output of the laser beam L is set to a third output (output C2 to C4) which is between the first output (output C1) and the second output (output C5) and no damage 14 occurs to the film 160.

[0095] Then, in the second condition acquisition step, conditions including the third output (outputs C2 to C4) that form the third damage state Ds3 are acquired as the first processing conditions. This makes it possible to efficiently acquire the first processing conditions for setting the state of the modified region 12 in the first part 111 of the object 11 to the first state SST. In particular, in the second condition acquisition step, conditions including the third output (output C3) between the smallest third output (output C2) and the largest third output (output C4) among the multiple third outputs (outputs C2 to C4) are acquired as the first processing conditions. This makes it possible to acquire the first processing conditions more efficiently and appropriately.

[0096] In the above embodiment, a case was described in which a plurality of concentric lines A are set on the object 11, and in step S102, concentric processing is performed in which the laser beam L is irradiated onto the object 11 while the focal point C of the laser beam L is moved relative to it in a concentric manner when viewed from the Z direction. However, as shown in Figure 20, spiral processing may also be performed in which spiral lines A are set on the object 11, and the laser beam L is irradiated onto the object 11 while the focal point C of the laser beam L is moved relative to it in a spiral manner when viewed from the Z direction. In this case, it becomes possible to efficiently perform the laser processing of the first part and the laser processing of the second part, and further improvement in cycle time can be achieved.

[0097] When performing spiral machining in this manner, the direction of relative movement of the focusing point C may be kept constant throughout processes S102 and S103 (for example, from the outside to the inside of the object 11). In this case, machining can be carried out in the same direction in the first part 111 and the second part 112, thereby further improving the cycle time.

[0098] Furthermore, in the above embodiment, an example was described in which a single object 11 is prepared by removing the bevel portion (removal area E) of an object 11A, which is a single wafer, and then performing a delamination process. However, as shown in Figure 21, the object 11 may be included in a bonded wafer. Specifically, the object 11 is included in the object 11A as an effective area R and is bonded to an object 11D, which is a silicon wafer, for example, via a device layer 170 formed on the second surface 12b of the object 11.

[0099] Thus, when the object 11 is included in the bonded wafer, the virtual surface M1, which is the surface to be peeled off, can be set at a deeper position on the object 11 (a position farther from the first surface 11a). Therefore, the crack 13 formed along the virtual surface M1 extends from the virtual surface M1 to the second surface 11b, making it possible to peel off the object 11 without removing the bevel portion (removal area E).

[0100] Furthermore, in the above embodiment, an example was described in which the index feed direction was kept constant across processes S102 and S103. However, the index feed direction may be different for processes S102 and S103. For example, the index feed direction for process S102 may be set to move from the radially outside to the radially inside of the first portion 111, while the index feed direction for process S103 may be set to move from the radially inside to the radially outside of the second portion 112. Alternatively, the index feed direction for process S102 may be set to move from the radially inside to the radially outside of the first portion 111, while the index feed direction for process S103 may be set to move from the radially outside to the radially inside of the second portion 112.

[0101] Furthermore, even in the example where the index feed direction is kept constant across processes S102 and S103, the index feed direction may be from the radially inside to the radially outside of the object 11 in both processes S102 and S103.

[0102] Furthermore, the above embodiment has described the case in which the first portion 111, in which the modified region 12 is in the first state SST, is on the outside, and the second portion 112, in which the modified region 12 is in the second state SFC, is on the inside. However, the first portion 111, in which the modified region 12 is in the first state SST, may be the inner portion including the center of the object 11, and the second portion 112, in which the modified region 12 is in the second state SFC, may be the outer portion surrounding the first portion 111.

[0103] Furthermore, the first part 111 and the second part 112 are not limited to being arranged concentrically with respect to each other.

[0104] 1... Laser processing device, 2... Stage (support part), 3... Irradiation part, 4, 5... Moving part, 6... Control unit, 11... Object, 11B, 11C... Sample, 12... Modified area, 13... Crack, 14... Damage, 111... First part, 112... Second part, A... Line, C... Focusing point, L... Laser beam.

Claims

1. A laser processing method for processing an object by irradiating the object with laser light, wherein the laser light is irradiated onto a first portion of the object, which is a part of the object as viewed from the Z direction intersecting the incident surface, along the virtual surface, thereby forming a plurality of modified regions on the first portion of the object along the virtual surface; and a second processing step, after the first processing step, irradiating onto a second portion of the object, which is another part of the object as viewed from the Z direction, along the virtual surface, thereby forming a plurality of modified regions on the second portion of the object along the virtual surface, wherein in the first processing step, the laser light is irradiated onto the first portion of the object under first processing conditions such that at least some of the plurality of modified regions are in a first state in which the modified regions are not connected to each other due to cracks that occur as a result of the formation of the modified regions. A laser processing method comprising: in the second processing step, irradiating the object with laser light in the second portion under second processing conditions such that the entire plurality of modified regions are in a second state in which the modified regions are connected to each other by the cracks, thereby propagating the cracks so that the modified regions are connected to each other through the cracks across both the first and second portions.

2. The laser processing method according to claim 1, wherein the first and second parts have outer edges that are concentric with each other when viewed from the Z direction, and in the first and second processing steps, spiral processing is performed in which the laser beam is irradiated onto the object while the focal point of the laser beam is moved relative to the object in a spiral shape when viewed from the Z direction, or concentric processing is performed in which the laser beam is irradiated onto the object while the focal point of the laser beam is moved relative to the object in a concentric shape when viewed from the Z direction.

3. The laser processing method according to claim 2, wherein the second portion is a circular portion that includes the center of the object when viewed from the Z direction, and the first portion is an annular portion that surrounds the second portion when viewed from the Z direction.

4. The laser processing method according to claim 2 or 3, wherein when spiral processing is performed in the first and second processing steps, the direction of relative movement of the focal point is kept constant across the first and second processing steps, and when concentric circle processing is performed in the first and second processing steps, the direction in which the position of the focal point is moved from one concentric circle to another concentric circle is kept constant across the first and second processing steps.

5. A laser processing method according to any one of claims 1 to 4, comprising a first condition acquisition step for acquiring the first processing conditions by irradiating the sample with the laser light along the line before the first processing step, wherein the first condition acquisition step comprises a first step, the first step comprising: a third processing step for forming a plurality of modified regions on the sample by irradiating the sample with the laser light along the line according to candidate conditions for the first processing conditions; a first determination step for determining whether the modified regions formed on the sample are in a first state after the third processing step; and a first correction step for correcting the candidate conditions if, as a result of the determination in the first determination step, the modified regions formed on the sample are not in a first state, wherein the first condition acquisition step is repeated until it is determined in the first determination step that the modified regions formed on the sample are in a first state.

6. The laser processing method according to claim 5, wherein the first condition acquisition step comprises a second step following the first step, the second step comprising: a fourth processing step of irradiating the sample with the laser light along the line if, in the determination of the first determination step, it is determined that the modified region formed on the sample is in the first state; a second determination step of determining whether or not the modified region formed on the sample is in the second state after the fourth processing step; and a second correction step of correcting the candidate condition if, as a result of the second determination step, the modified region formed on the sample is not in the second state, the first condition acquisition step repeatedly performs the first and second steps until it is determined in the second determination step that the modified region formed on the sample is in the second state, and acquires the candidate condition when it is determined in the second determination step that the modified region formed on the sample is in the second state as the first processing condition.

7. A laser processing method according to any one of claims 1 to 4, comprising a second condition acquisition step for acquiring the first processing conditions by irradiating a sample with laser light before the first processing step, wherein the sample includes a substrate having a surface which is the incident surface of the laser light and a back surface opposite to the surface, and a film provided on the back surface, and the second condition acquisition step includes a fifth processing step of irradiating the sample with laser light multiple times while changing the output so that a first damage state is formed in which the film is damaged by the laser light, a second damage state is formed in which the film is damaged by the laser light and the output is set to a second output which is greater than the first output, and the film is damaged, and a third damage state is formed in which the film is not damaged, and in the second condition acquisition step, conditions including the third output which forms the third damage state are acquired as the first processing conditions.

8. The laser processing method according to claim 7, wherein in the fifth processing step, the third damage state is formed at a plurality of third outputs that are different from each other, and in the second condition acquisition step, a condition is acquired as the first processing condition that includes the third output between the smallest third output and the largest third output among the plurality of third outputs.

9. A laser processing apparatus for processing an object by irradiating the object with laser light, wherein the apparatus comprises: a support unit for supporting the object; an irradiation unit for irradiating the object supported by the support unit with laser light; a moving unit for moving at least one of the support unit and the irradiation unit so that the focal point of the laser light moves along the virtual surface; and a control unit for controlling the support unit, the irradiation unit and the moving unit, wherein the control unit controls the irradiation unit and the moving unit to irradiate a first portion of the object, which is a part of the object as viewed from the Z direction intersecting the incident surface, with laser light along the virtual surface, and to form a plurality of modified regions along the virtual surface on the first portion, A laser processing apparatus that, after the first processing process, controls the irradiation unit and the moving unit to irradiate the object with the laser light along the virtual plane to a second part, which is another part of the object as viewed from the Z direction, thereby forming a plurality of modified regions along the virtual plane on the second part, wherein in the first processing process, the laser light is irradiated onto the object in the first part under first processing conditions such that at least some of the plurality of modified regions are in a first state in which the modified regions are not connected to each other through cracks that occur as a result of the formation of the modified regions, and in the second processing process, the laser light is irradiated onto the object in the second part under second processing conditions such that the entire plurality of modified regions are in a second state in which the modified regions are connected to each other through cracks, thereby propagating the cracks so that the modified regions are connected to each other through cracks across both the first and second parts.

10. A method for manufacturing a semiconductor device comprising: a first processing step and a second processing step included in the laser processing method according to any one of claims 1 to 8; a peeling step performed after the second processing step to peel the object along the virtual surface; and a cutting step performed after the peeling step to cut the object into a plurality of chips for each of the plurality of functional elements.

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