Laser processing auxiliary tool, laser processing device, and laser processing method

Abstract

To provide a laser processing auxiliary tool which can form a modified region in an object with good accuracy while suppressing occurrence of breakage of a plurality of function elements formed on a front surface side of the object, a laser processing device and a laser processing method.SOLUTION: A laser processing auxiliary tool 5 comprises a first sheet 51 and a second sheet 52. When a frame 15 is held by a holding part 21 so that a laser beam L is incident to an object 11 from a rear face 11b side via a tape 14 in the state that the tape 14 is bonded to the rear face 11b of the object 11 and the tape 14 is held by the frame 15, the object 11 is placed on the first sheet 51. The second sheet 52 causes a suction action of a suction table 22 on an immediate part 14c of the tape 14 at a position lower than the rear face 11b. A suction action of the suction table 22 caused on the object 11 by the first sheet 51 is weaker than a suction action of the suction table 22 caused on the intermediate part 14c by the second sheet 52.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a laser processing auxiliary tool, a laser processing apparatus, and a laser processing method. [Background technology]

[0002] A laser processing apparatus is known that irradiates a target object having a plurality of functional elements formed on its surface side with laser light to form a modified region in the target object for cutting the target into individual functional elements. In such a laser processing apparatus, a tape (so-called backgrind tape) may be attached to the surface of the target object and held by a frame, and laser light may be incident on the target object from its back side. Compared with a laser processing method in which laser light is incident on the target object from its front side, which has a plurality of functional elements formed thereon, the laser processing method in which laser light is incident on the target object from its back side has the advantages that "laser light irradiation is less affected by films and structures formed in street regions (regions between the plurality of functional elements) on the surface of the target object, and by the width of the street regions," and "the straightness of cracks from the modified region to the street regions is improved."

[0003] However, if the functional element has a fragile structure, the functional element may be damaged by attaching the tape to the surface of the object.Furthermore, on the suction table (so-called chuck table) of the laser processing device, a suction action is generated on the surface of the object via the tape, and the suction action of the suction table may also damage the functional element.

[0004] Therefore, a laser processing device has been proposed in which tape is attached to the back surface of an object and the tape is held by a frame, and the frame is held, and only the outer edge area of ​​the surface of the object on which multiple functional elements are not formed is supported (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-29927 Summary of the Invention [Problem to be solved by the invention]

[0006] However, if processing is performed while supporting only the outer edge region of the surface of the object where multiple functional elements are not formed, the deformation and positional deviation that occurs in the object may become large during processing, and it may become impossible to properly form the modified region at the desired position on the object.

[0007] The present invention aims to provide a laser processing auxiliary tool, a laser processing device, and a laser processing method that can accurately form modified areas on an object while suppressing damage to multiple functional elements formed on the surface side of the object, even if the functional elements have a fragile structure. [Means for solving the problem]

[0008] The laser processing aid of the present invention is a laser processing aid used in a laser processing device that irradiates a target object having a plurality of functional elements formed on its surface side with laser light to form modified regions in the target object along each of a plurality of lines that are set to pass between the plurality of functional elements. The laser processing device includes a support unit that supports the target object, an irradiation unit that irradiates the target object with laser light, and a control unit that controls at least one of the support unit and the irradiation unit so that the focal point of the laser light moves relatively along each of the plurality of lines. The laser processing aid of the present invention comprises: a first sheet that is placed on a suction table included in the support part and on which the object is placed when a tape that is transparent to laser light is attached to the back surface of an object and the tape is held by a frame, and the frame is held by a holding part included in the support part so that laser light is incident on the object from the back surface side through the tape; and a second sheet that is placed on the suction table in the above case and generates the suction action of the suction table on the intermediate portion of the tape between the object and the frame at a position lower than the back surface of the object placed on the first sheet, wherein the suction action of the suction table generated on the object by the first sheet is weaker than the suction action of the suction table generated on the intermediate portion by the second sheet.

[0009] In the laser processing auxiliary tool, the frame is held by the holding part so that laser light is incident on the object from the back side via the tape, and the object is placed on the first sheet with the front side of the object facing the first sheet. Then, the second sheet is positioned lower than the back side of the object, causing the suction action of the suction table to occur in the middle part of the tape. This causes the object to be pressed toward the suction table by the elastic force of the tape, thereby suppressing deformation and misalignment of the object and accurately forming a modified region in the object. In addition, there is no need to attach tape to the surface of the object, and the suction action of the suction table caused by the first sheet on the object is weaker than the suction action of the suction table caused by the second sheet on the middle part of the tape. This prevents damage to multiple functional elements formed on the front side of the object, even if the functional elements have a fragile structure. As described above, the laser processing auxiliary tool allows for accurate formation of a modified region in the object while suppressing damage to multiple functional elements formed on the front side of the object, even if the functional elements have a fragile structure.

[0010] In the laser processing aid of the present invention, the first sheet may be laminated on the second sheet so that the outer edge of the first sheet is located inside the outer edge of the second sheet. Alternatively, the second sheet may extend along the outer edge of the first sheet. This allows the laser processing aid to be easily configured.

[0011] In the laser processing aid of the present invention, the adhesive strength of the tape to the second sheet may be lower than the adhesive strength of the tape to the suction table, which makes it possible to easily peel the middle portion of the tape from the second sheet after processing.

[0012] In the laser processing aid of the present invention, each of the plurality of functional elements may be a MEMS device. In this case, a laser processing aid that can suppress damage to the plurality of functional elements formed on the surface side of the object is particularly effective.

[0013] The laser processing apparatus of the present invention is a laser processing apparatus that irradiates a laser beam onto an object having a plurality of functional elements formed on its surface side, thereby forming a modified region in the object along each of a plurality of lines that are set to pass between the plurality of functional elements. The laser processing apparatus includes: a support section that supports the object so that laser beam is incident on the object from the back side through the tape, with a tape that is transparent to laser beams attached to the back side of the object and the tape held by a frame; an irradiation section that irradiates the object with laser beams; and a control section that controls at least one of the support section and the irradiation section so that the focal point of the laser beam moves relatively along each of the plurality of lines. The support section includes a holding section that holds the frame; a placing section on which the object is placed; and a suction section that generates a suction effect on the intermediate portion of the tape between the object and the frame at a position lower than the back side of the object placed on the placing section, and the suction effect generated on the object by the placing section is weaker than the suction effect generated on the intermediate portion by the suction section.

[0014] The laser processing method of the present invention is a laser processing method used in a laser processing apparatus that irradiates a target object having a plurality of functional elements formed on its surface side with laser light to form modified regions in the target object along each of a plurality of lines that are set to pass between the plurality of functional elements. The laser processing apparatus includes a support unit that supports the target object, an irradiation unit that irradiates the target object with laser light, and a control unit that controls at least one of the support unit and the irradiation unit so that the focal point of the laser light moves relatively along each of the plurality of lines. The laser processing method of the present invention comprises: a first step in which a tape that is transparent to laser light is attached to the back surface of an object and the tape is held by a frame; a second step in which a holding portion included in a support portion holds the frame so that laser light is incident on the object from the back surface side through the tape, and the object is placed on a placing portion included in the support portion, and a suction portion included in the support portion generates a suction effect on an intermediate portion of the tape between the object and the frame at a position lower than the back surface of the object placed on the placing portion; and a third step in which a control unit controls at least one of the support portion and the irradiation portion so that the focal point moves relatively along each of a plurality of lines, and in the second step, the suction effect generated on the object by the placing portion is weaker than the suction effect generated on the intermediate portion by the suction portion.

[0015] In the laser processing apparatus and the laser processing method, the frame is held by the holding unit so that laser light is incident on the object from the back side through the tape, and the object is placed on the placing unit with the front side of the object facing the placing unit. The suction unit then applies suction to the middle portion of the tape at a position lower than the back side of the object. This allows the elastic force of the tape to press the object toward the placing unit, thereby suppressing deformation and misalignment of the object and accurately forming a modified region in the object. Furthermore, tape does not need to be attached to the surface of the object, and the suction applied to the object by the placing unit is weaker than the suction applied to the middle portion of the tape by the suction unit. This prevents damage to multiple functional elements formed on the front side of the object, even if the functional elements have a fragile structure. As described above, the laser processing apparatus and the laser processing method allow for accurate formation of a modified region in the object while suppressing damage to multiple functional elements formed on the front side of the object, even if the functional elements have a fragile structure. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a laser processing auxiliary tool, a laser processing device, and a laser processing method that can accurately form modified areas on an object while suppressing damage to multiple functional elements formed on the surface side of the object, even if the functional elements have a fragile structure. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a configuration diagram of a laser processing apparatus according to an embodiment; [Figure 2] 2 is a perspective view of an object unit attached to a support part of the laser processing apparatus shown in FIG. 1. FIG. [Figure 3] 2 is a configuration diagram of a support unit and a laser processing auxiliary tool of the laser processing apparatus shown in FIG. 1. FIG. [Figure 4] 2 is a configuration diagram of a support unit and a laser processing auxiliary tool of the laser processing apparatus shown in FIG. 1. FIG. [Figure 5] 2 is a configuration diagram of a support unit and a laser processing auxiliary tool of the laser processing apparatus shown in FIG. 1. FIG. [Figure 6] 2 is a configuration diagram of a support unit and a laser processing auxiliary tool of the laser processing apparatus shown in FIG. 1. FIG. [Figure 7] FIG. 2 is a structural diagram of a portion of an expanding device. [Figure 8] 10 is a graph showing the amount of displacement of the rear surface of an object. [Figure 9] 1 is a photograph showing the state of a modified region formed on an object. [Figure 10] FIG. 10 is a configuration diagram of a modified laser processing auxiliary tool. [Figure 11] 10A and 10B are configuration diagrams of a support portion of a modified example and a laser processing auxiliary tool of a modified example. [Figure 12] FIG. 10 is a configuration diagram of a support portion according to a modified example. [Figure 13] FIG. 10 is an exploded perspective view of a modified target unit. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and redundant explanations will be omitted. [Configuration of laser processing equipment]

[0019] As shown in FIG. 1, the laser processing apparatus 1 includes a support unit 2, an irradiation unit 3, and a control unit 4. The support unit 2 supports an object 11. In this embodiment, the support unit 2 is movable along both the X direction and the Y direction. The support unit 2 is also rotatable about an axis parallel to the Z direction. As an example, the X direction is a first horizontal direction, the Y direction is a second horizontal direction perpendicular to the first horizontal direction, and the Z direction is a vertical direction.

[0020] The irradiation unit 3 irradiates the object 11 with laser light L. The irradiation unit 3 includes a light source 31, a spatial light modulator 32, and a condenser lens 33. The light source 31 outputs laser light L that is transparent to the object 11, for example, by a pulse oscillation method. The spatial light modulator 32 modulates the laser light L output from the light source 31. The spatial light modulator 32 is, for example, a reflective liquid crystal (LCOS: Liquid Crystal on Silicon) spatial light modulator (SLM). The condenser lens 33 condenses the laser light L modulated by the spatial light modulator 32. In this embodiment, the irradiation unit 3 is movable along the Z direction. The position of the condenser lens 33 in the Z direction is fine-tuned by a piezoelectric element (not shown) based on displacement data of the laser light incident surface of the object 11 acquired by a distance measurement sensor (not shown).

[0021] When laser light L is focused inside the object 11 supported by the support part 2, the laser light L is particularly absorbed in a portion corresponding to the focusing point C of the laser light L, and a modified region M is formed inside the object 11. The modified region M is a region whose density, refractive index, mechanical strength, and other physical properties differ from those of the surrounding unmodified region. Examples of the modified region M include a melting treatment region, a crack region, a dielectric breakdown region, and a refractive index change region.

[0022] As an example, when the support part 2 is moved along the X direction and the focal point C is moved along the X direction relative to the object 11, multiple modified spots are formed so as to be lined up in a row along the X direction. One modified spot is formed by irradiating one pulse of laser light L. A row of modified regions M is a collection of multiple modified spots lined up in a row. Adjacent modified spots may be connected to each other or separated from each other depending on the relative moving speed of the focal point C with respect to the object 11 and the repetition frequency of the laser light L.

[0023] The control unit 4 controls the support unit 2, the light source 31, the spatial light modulator 32, and the condenser lens 33. The control unit 4 is configured as a computer device including a processor, a memory, a storage, a communication device, etc. In the control unit 4, software (programs) loaded into the memory, etc. are executed by the processor, and the processor controls the reading and writing of data in the memory and storage, as well as communication by the communication device. In this way, the control unit 4 realizes various functions. [Object unit configuration]

[0024] As shown in FIG. 2, the target unit 10 includes a target 11, a tape 14, and a frame 15. The target 11 includes a substrate 12 and a plurality of functional elements 13. The plurality of functional elements 13 are formed on a surface 11a of the target 11. In this embodiment, the plurality of functional elements 13 are arranged two-dimensionally (e.g., in a matrix) on the substrate 12. The substrate 12 is, for example, a semiconductor substrate such as a silicon substrate. Each functional element 13 is a MEMS (Micro Electro Mechanical Systems) device. In the laser processing apparatus 1, a plurality of lines 16 are set on the target 11 so as to pass between the plurality of functional elements 13. For example, when the plurality of functional elements 13 are arranged in a matrix, the plurality of lines 16 extend in a lattice pattern.

[0025] The tape 14 is attached to the back surface 11b (the surface opposite to the front surface 11a) of the object 11. Specifically, a central portion 14a of the tape 14 is attached to the back surface 11b of the object 11. The tape 14 is transparent to the laser light L. The tape 14 is a dicing tape, and is an expandable tape. For example, the base material of the tape 14 is polyvinyl chloride, polyolefin, polyethylene terephthalate, polypropylene, etc., and the adhesive material of the tape 14 is an acrylic resin, etc. The transmittance of the tape 14 to the laser light L is 70% or more. The expansion rate of the tape 14 is 103% or more.

[0026] The frame 15 holds the tape 14. Specifically, the frame 15 holds the tape 14 by attaching an outer edge portion 14b of the tape 14 to the frame 15. The frame 15 is formed into a ring shape, for example, from a metal plate. In the object unit 10, the object 11 is located inside the frame 15, and an intermediate portion 14c of the tape 14 between the object 11 and the frame 15 (i.e., the portion of the tape 14 between the central portion 14a and the outer edge portion 14b) is exposed to the outside. [Configuration of the support part of the laser processing device and the laser processing auxiliary tool]

[0027] As shown in FIGS. 3 and 4 , the target unit 10 is attached to the support 2 via a laser processing auxiliary tool 5. The support 2 includes a holding unit 21 and a suction table 22. The holding unit 21 holds the frame 15 of the target unit 10. The holding unit 21 is configured, for example, by a plurality of clamps. The suction table 22 generates an air suction action on a suction surface 22a. The suction table 22 is, for example, a chuck table configured such that a plurality of suction ports of a plurality of nozzles that suck air are positioned on the suction surface 22a. In this embodiment, the support 2 supports the target 11 in a state in which the target unit 10 is configured (i.e., a state in which the tape 14 is attached to the back surface 11b of the target 11 and the tape 14 is held by the frame 15) so that the laser light L is incident on the target 11 from the back surface 11b side via the tape 14.

[0028] The laser processing auxiliary tool 5 includes a first sheet 51 and a second sheet 52. The second sheet 52 is placed on the suction table 22 so as to cover the suction surface 22a. The first sheet 51 is stacked on the second sheet 52 so that the outer edge 51a of the first sheet 51 is located inside the outer edge 52a of the second sheet 52. In other words, the first sheet 51 is placed on the suction table 22 via the second sheet 52. When viewed from the Z direction, the shape of the first sheet 51 is approximately the same as the shape of the target object 11. When viewed from the Z direction, the shape of the second sheet 52 is approximately the same as the shape of the suction surface 22a, and the shape of the portion of the second sheet 52 outside the outer edge 51a of the first sheet 51 is approximately the same as the shape of the middle portion 14c of the tape 14.

[0029] The air permeability of the first sheet 51 is lower than that of the second sheet 52. In this embodiment, the second sheet 52 is a porous sheet, while the first sheet 51 is a non-porous sheet, so the air permeability of the first sheet 51 is approximately zero. The suction action of the suction table 22 that the first sheet 51 exerts on the object 11 is weaker than the suction action of the suction table 22 that the second sheet 52 exerts on the intermediate portion 14c of the tape 14. In other words, the suction force that the first sheet 51 exerts on the object 11 is weaker than the suction force that the second sheet 52 exerts on the intermediate portion 14c of the tape 14. In this embodiment, the air permeability of the first sheet 51 is approximately zero, so the suction force that the first sheet 51 exerts on the object 11 is approximately zero. The adhesive force of the tape 14 to the second sheet 52 is lower than the adhesive force of the tape 14 to the suction table 22.

[0030] "Air permeability" refers to the "volume per unit area, unit time, and unit partial pressure difference between the two sides of the sheet" of air passing through the sheet (first sheet 51 or second sheet 52) ​​under certain conditions. "Suction force" refers to the "magnitude per unit area" of the force that sucks the object to be sucked under certain conditions. "Adhesive force" refers to the "magnitude per unit area" of the force required to peel the tape 14 from the object to be adhered under certain conditions.

[0031] As an example, the material of the first sheet 51 is polyethylene terephthalate, and the material of the second sheet 52 is polyethylene. The first sheet 51 may be made of a cushioning material, or may be made of a hard material (e.g., glass) as long as it is flat. The second sheet 52 may be coated to reduce the adhesive strength of the tape 14, or may have a surface shape that reduces the adhesive strength of the tape 14. The second sheet 52 is preferably low in dust generation and is preferably antistatically treated.

[0032] With the target unit 10 configured, when the frame 15 is held by the holder 21 so that the laser light L is incident on the target 11 from the back surface 11b side via the tape 14, the target 11 is placed on the first sheet 51. In this state, the second sheet 52 causes the suction table 22 to apply suction to the middle portion 14c of the tape 14 at a position lower than the back surface 11b of the target 11 placed on the first sheet 51. As a result, the middle portion 14c of the tape 14 is sucked by the second sheet 52 and comes into contact with the second sheet 52. Note that "a position lower than the back surface 11b" refers to a position on the side where the multiple functional elements 13 are present (in this embodiment, the side where the suction table 22 is present) with respect to the surface including the back surface 11b.

[0033] In this embodiment, the suction table 22 and the laser processing auxiliary tool 5 may be integrally configured. In this case, the first sheet 51 functions as a placement section 23 on which the object 11 is placed. A portion of the second sheet 52 outside the outer edge 51a of the first sheet 51 functions as a suction section 24 that generates a suction effect on the middle portion 14c of the tape 14 at a position lower than the back surface 11b of the object 11 placed on the placement section 23. The suction effect that the placement section 23 generates on the object 11 is weaker than the suction effect that the suction section 24 generates on the middle portion 14c of the tape 14. [Laser processing method using laser processing auxiliary tools]

[0034] 3 and 4, first, tape 14 is attached to the back surface 11b of object 11 and held by frame 15, thereby forming object unit 10 (first step). Subsequently, object unit 10 is attached to support part 2 (second step). Specifically, holder 21 holds frame 15 and object 11 is placed on first sheet 51 so that laser light L is incident on object 11 from the back surface 11b side via tape 14. In this state, second sheet 52 (more specifically, the portion of second sheet 52 outside outer edge 51a of first sheet 51) generates a suction effect on middle portion 14c of tape 14 at a position lower than the back surface 11b of object 11 placed on first sheet 51.

[0035] Next, as shown in FIG. 5, the control unit 4 controls at least one of the support unit 2 and the irradiation unit 3 so that the focal point C moves relatively along each line 16 (third step). At this time, the position of the condenser lens 33 in the Z direction is fine-tuned by the piezoelectric element based on displacement data of the rear surface 11b acquired by the distance measurement sensor so that the distance from the rear surface 11b to the focal point C is constant. By irradiating the object 11 with the laser light L in this manner, modified regions M are formed in the object 11 along each line 16. Next, as shown in FIG. 6, the object unit 10 is removed from the support unit 2. Next, as shown in FIG. 7, the tape 14 is expanded by pressing the pressing member 6 against the tape 14 from the side opposite the object 11. As a result, the object 11 is cut into functional elements 13 starting from the modified regions M formed along each line 16, and the multiple semiconductor chips 110 obtained by cutting are separated from each other. Next, the tape 14 is irradiated with ultraviolet light to reduce the adhesive strength of the tape 14, and each semiconductor chip 110 is picked up.

[0036] 3 and 4, when the suction table 22 and the laser processing auxiliary tool 5 are integrally configured, the holding unit 21 holds the frame 15 and the object 11 is placed on the placing unit 23 so that the laser light L is incident on the object 11 from the back surface 11b side through the tape 14. In this state, the suction unit 24 generates a suction effect on the middle portion 14c of the tape 14 at a position lower than the back surface 11b of the object 11 placed on the placing unit 23. [Action and effect]

[0037] In the laser processing auxiliary tool 5, the frame 15 is held by the holding unit 21 so that the laser light L is incident on the object 11 from the back surface 11b side via the tape 14. The object 11 is placed on the first sheet 51 with the front surface 11a of the object 11 facing the first sheet 51. The second sheet 52 then generates a suction action of the suction table 22 on the middle portion 14c of the tape 14 at a position lower than the back surface 11b of the object 11. This causes the elastic force of the tape 14 to press the object 11 against the suction table 22, thereby suppressing deformation and misalignment of the object 11 and accurately forming the modified region M in the object 11. Furthermore, there is no need to attach the tape 14 to the front surface 11a of the object 11. Furthermore, the suction action of the suction table 22 generated on the object 11 by the first sheet 51 is weaker than the suction action of the suction table 22 generated on the middle portion 14c of the tape 14 by the second sheet 52. This makes it possible to prevent damage to the plurality of functional elements 13 formed on the surface 11a side of the object 11, even if the functional elements 13 have a fragile structure. As described above, the laser processing auxiliary tool 5 makes it possible to accurately form a modified region M in the object 11, while preventing damage to the plurality of functional elements 13 formed on the surface 11a side of the object 11, even if the functional elements 13 have a fragile structure. In this embodiment, since each functional element 13 is a MEMS device, the laser processing auxiliary tool 5, which can prevent damage to the plurality of functional elements 13 formed on the surface 11a side of the object 11, is particularly effective.

[0038] In the laser processing auxiliary tool 5, the first sheet 51 is laminated on the second sheet 52 so that the outer edge 51a of the first sheet 51 is located inside the outer edge 52a of the second sheet 52. This allows the laser processing auxiliary tool 5 to be configured simply.

[0039] In the laser processing auxiliary tool 5, the adhesive strength of the tape 14 to the second sheet 52 is lower than the adhesive strength of the tape 14 to the suction table 22. This allows the middle portion 14c of the tape 14 to be easily peeled off from the second sheet 52 after processing.

[0040] Furthermore, even when the suction table 22 and the laser processing auxiliary tool 5 are configured as an integrated unit, for the reasons described above, the laser processing apparatus 1 and the laser processing method can accurately form a modified region M in the object 11 while suppressing damage to the multiple functional elements 13 formed on the surface 11a side of the object 11, even if the functional element 13 has a fragile structure. [Experimental Results]

[0041] According to the procedure of the above-described "laser processing method using a laser processing auxiliary tool," modified regions M were formed on the target object 11 along each line 16 extending along the X direction under the following conditions. Then, the displacement of the back surface 11b of the target object 11 along the Y direction was measured. The results shown in FIG. 8 were obtained. In FIG. 8, the horizontal axis represents the position in the Y direction, and the region between the two rising edges corresponds to the target object 11. In FIG. 8, the vertical axis represents the voltage value of the signal indicating the displacement of the back surface 11b, with 1 V corresponding to approximately 8 μm. As shown in FIG. 8, after the modified regions M were formed on the target object 11 along each line 16 extending along the X direction, the "displacement of the back surface 11b along the Y direction" was within a range of approximately 8 μm. This level of displacement allows for fine adjustment of the position of the condenser lens 33 in the Z direction, enabling the modified regions M to be formed on the target object 11 along each line 16 extending along the Y direction with high precision. Object 11: Silicon wafer Diameter of object 11: 8 inches Thickness of object 11: 300 μm Diameter of suction surface 22a: 12 inches Distance between adjacent lines 16: 1mm Relative moving speed of the focal point C along each line 16: 530 mm / sec Wavelength of laser light L: 1099 nm Repetition frequency of laser light L: 80 kHz Number of columns in the modified region M per line 16: 4 columns

[0042] Following the above experiment, modified regions M were formed in the object 11 along each line 16 extending in the Y direction under the above conditions, and the object 11 was cut into multiple chips. The results shown in FIG. 9 were obtained. (a) of FIG. 9 is a photograph of the cut surface of the chip when a suction effect was applied to the surface 11a of the object 11 (Comparative Example), and (b) of FIG. 9 is a photograph of the cut surface of the chip when a suction effect was not applied to the surface 11a of the object 11 (Example) according to the procedure of the "laser processing method using a laser processing auxiliary tool" described above. As shown in (a) and (b) of FIG. 9, the Example was able to accurately form modified regions M with the same accuracy as the Comparative Example. Furthermore, the success rate of cutting the object 11 into multiple chips, the straightness of the crack on the surface 11a, and the straightness of the crack on the back surface 11b were 100%, within 3 μm, and within 5 μm, respectively, and similar results were obtained between the Example and the Comparative Example. The comparative example that generates a suction effect on the surface 11a of the object 11 is effective only from the viewpoint of forming the modified region M with high precision, but has the problem that if the functional element 13 has a fragile structure, the multiple functional elements 13 formed on the surface 11a side of the object 11 are likely to be damaged. [Variations]

[0043] The present invention is not limited to the above embodiment. For example, as shown in Fig. 10, in the laser processing auxiliary tool 5, the second sheet 52 may extend along the outer edge 51a of the first sheet 51. In this case, the laser processing auxiliary tool 5 can be easily configured. In this embodiment, the suction table 22 and the laser processing auxiliary tool 5 may be configured integrally. In this case, the first sheet 51 functions as the mounting portion 23, and the second sheet 52 functions as the suction portion 24.

[0044] 11 , when viewed from the Z direction, the shape of the first sheet 51 may be substantially the same as the shape of the suction surface 22a, and the shape of the second sheet 52 may be larger than the shape of the suction surface 22a. In this case, the laser processing auxiliary tool 5 may include a guide 53 that positions and fixes the first sheet 51 and the second sheet 52 with respect to the suction table 22. Even in this form, the suction table 22 and the laser processing auxiliary tool 5 may be configured as an integrated unit. In that case, the first sheet 51 functions as the placement portion 23, and the second sheet 52 functions as the suction portion 24.

[0045] As shown in Figure 12, the support unit 2 may be provided with a mounting unit 23 and a suction unit 24 as separate units, and the suction force of the multiple nozzles of the suction table 22 may be adjusted so that the suction action generated in the area of ​​the suction surface 22a corresponding to the object 11 is weaker than the suction action generated in the area of ​​the suction surface 22a corresponding to the middle portion 14c of the tape 14.

[0046] As shown in FIG. 13 , the adhesive strength of the tape 14 may be lower in the intermediate portion 14c than in the central portion 14a and the outer edge portion 14b. Such a tape 14 may have a release film (a protective film for the adhesive) remaining only in the intermediate portion 14c, or may have no adhesive formed only in the intermediate portion 14c. In this case, it is not necessary to consider the adhesive strength of the tape 14 to the second sheet 52. The release film remaining only in the intermediate portion 14c may be divided into multiple portions. In this case, a gap may or may not be formed between adjacent portions. Furthermore, even if the adhesive strength of the intermediate portion 14c of the tape 14 is reduced by irradiating the intermediate portion 14c of the tape 14 with ultraviolet light before the target unit 10 is removed from the support 2, it is not necessary to consider the adhesive strength of the tape 14 to the second sheet 52.

[0047] The first sheet 51 is not limited to having a shape substantially identical to that of the object 11 when viewed from the Z direction. The first sheet 51 may have a shape including multiple functional elements 13 when viewed from the Z direction. Furthermore, each functional element 13 is not limited to a MEMS device. If the functional elements 13 have a fragile structure, the laser processing auxiliary tool 5, laser processing apparatus 1, and laser processing method are effective in preventing damage to the multiple functional elements 13 formed on the surface 11a of the object 11. For example, the above-described laser processing auxiliary tool 5, laser processing apparatus 1, and laser processing method are also effective for the object 11 having multiple bumps on the surface 11a (so-called bump wafer). If a suction force is applied to the surface 11a of the object 11, warping of the object 11 may occur, potentially resulting in damage to the object 11. In this case, it may be appropriate for the first sheet 51, which will come into contact with the multiple bumps, to be made of a cushioning material. [Explanation of symbols]

[0048] 1...laser processing device, 2...support part, 3...irradiation part, 4...control part, 5...laser processing auxiliary tool, 11...object, 11a...surface, 11b...back side, 13...functional element, 14...tape, 14c...middle part, 15...frame, 16...line, 21...holding part, 22...suction table, 23...placing part, 24...suction part, 51...first sheet, 51a...outer edge, 52...second sheet, 52a...outer edge, L...laser light, C...focus point, M...modified area.

Claims

1. A laser processing device that irradiates a target object having a plurality of functional elements formed on a surface side thereof with laser light to form a modified region in the target object along each of a plurality of lines that are set to pass between the plurality of functional elements, the laser processing device comprising: a support unit that supports the target object; an irradiation unit that irradiates the target object with the laser light; and a control unit that controls at least one of the support unit and the irradiation unit so that a focal point of the laser light moves relatively along each of the plurality of lines, a first sheet on which the object is placed, the first sheet being placed on a suction table included in the support unit when the frame is held by a holding unit included in the support unit so that the laser light is incident on the object from the back side via the tape, with a tape that is transparent to the laser light being attached to the back side of the object and the tape being held by a frame; a second sheet that is placed on the suction table in the above case, and that generates a suction effect of the suction table on an intermediate portion of the tape between the object and the frame at a position lower than the back surface of the object placed on the first sheet, A laser processing auxiliary tool, wherein the suction action of the suction table that the first sheet causes on the object is weaker than the suction action of the suction table that the second sheet causes on the intermediate portion.

2. 2. The laser processing aid according to claim 1, wherein the first sheet is laminated on the second sheet such that an outer edge of the first sheet is positioned inside an outer edge of the second sheet.

3. The laser processing aid according to claim 1 , wherein the second sheet extends along an outer edge of the first sheet.

4. 4. The laser processing auxiliary tool according to claim 1, wherein the adhesive strength of the tape to the second sheet is lower than the adhesive strength of the tape to the suction table.

5. 5. The laser processing aid according to claim 1, wherein each of the plurality of functional elements is a MEMS device.

6. A laser processing apparatus that irradiates a target object having a plurality of functional elements formed on a surface side thereof with laser light to form modified regions in the target object along each of a plurality of lines that are set to pass between the plurality of functional elements, a support portion that supports the object such that a tape that is transparent to the laser light is attached to a back surface of the object and the tape is held by a frame, and the laser light is incident on the object from the back surface side via the tape; an irradiation unit that irradiates the object with the laser light; a control unit that controls at least one of the support unit and the irradiation unit so that a focal point of the laser light moves relatively along each of the plurality of lines, The support portion is a holding portion that holds the frame; a placement section on which the object is placed; a suction portion that generates a suction effect on an intermediate portion of the tape between the object and the frame at a position lower than the back surface of the object placed on the placement portion, A laser processing device, wherein the suction effect that the placing portion generates on the object is weaker than the suction effect that the suction portion generates on the intermediate portion.

7. A laser processing method for use in a laser processing apparatus that irradiates a target object having a plurality of functional elements formed on a surface side thereof with laser light to form modified regions in the target object along each of a plurality of lines that are set to pass between the plurality of functional elements, the laser processing method comprising: a support unit that supports the target object; an irradiation unit that irradiates the target object with the laser light; and a control unit that controls at least one of the support unit and the irradiation unit so that a focal point of the laser light moves relatively along each of the plurality of lines, a first step in which a tape transparent to the laser light is attached to a back surface of the object and the tape is held by a frame; a second step in which a holding portion included in the support portion holds the frame and the object is placed on a placement portion included in the support portion so that the laser light is incident on the object from the back side through the tape, and a suction portion included in the support portion generates a suction effect on an intermediate portion of the tape between the object and the frame at a position lower than the back side of the object placed on the placement portion; a third step in which the control unit controls at least one of the support unit and the irradiation unit so that the light-focusing point moves relatively along each of the plurality of lines, In the second step, the suction effect that the placing section generates on the object is weaker than the suction effect that the suction section generates on the intermediate portion.

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