Processing method of the workpiece

Abstract

To provide a processing method which removes an area, including the chamfering part of a workpiece, using a laser beam while suppressing the return of the laser beam to a laser oscillator.SOLUTION: A processing method of a disc-like workpiece 11 in a laser machining device 2 includes: a tape pasting step which pastes a tape to one surfaces 11d of a workpiece to integrate the workpiece and a frame through the tape; a holding step which holds the workpiece by the holding unit through the tape; and a laser beam radiation step which radiates a pulse-shaped laser beam L, having a wavelength to be absorbed by the workpiece, from the other surface 11a of the workpiece, which is located opposite to one surfaces, to the other surface. In the laser beam radiation step, the laser beam L is radiated annularly on the other surface in a state that the orientation of the laser beam L is adjusted to have an incidence angle α which is inclined by a predetermined angle with respect to a normal line 11f of the other surface of the workpiece.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a method for processing a workpiece, in which a disk-shaped workpiece is processed with a pulsed laser beam having a wavelength that is absorbed by the workpiece. [Background technology]

[0002] In recent years, device chips have become thinner as electronic devices become smaller and lighter. To manufacture thin device chips, for example, the back side of a workpiece such as a semiconductor wafer having devices such as ICs (Integrated Circuits) and LSIs (Large Scale Integration) formed on the front side is ground to a thickness of 20 μm to 100 μm (see, for example, Patent Document 1), and then the workpiece is divided into individual device chips.

[0003] However, the outer periphery of the front and back sides of the workpiece is usually chamfered (i.e., a bevel portion is formed). Therefore, when the back side of the workpiece is ground to half its thickness or less, a so-called knife edge (also called a sharp edge) is formed on the outer periphery of the workpiece. When a knife edge is formed, there is a problem that cracks or chips occur on the outer periphery of the workpiece during grinding or transportation.

[0004] In order to solve this problem, a process has been proposed in which the outer periphery where the chamfer is formed is removed by a cutting device (see, for example, Patent Document 2). Specifically, the front side of the workpiece is held by a chuck table, and the lower end of a cutting blade positioned a predetermined distance inward from the outer periphery of the workpiece is cut into the back side of the workpiece, while the chuck table is rotated.

[0005] However, when a cutting blade that normally cuts a workpiece along a straight line cuts a workpiece along a curved path that corresponds to the periphery of the workpiece, the workpiece is subjected to stress and may be damaged. Furthermore, cutting a workpiece along a curved path with a cutting blade takes time, resulting in a problem of relatively low productivity.

[0006] Therefore, a method has been proposed in which, instead of using a cutting blade, a pulsed laser beam having a wavelength that is absorbed by the workpiece is used to remove the outer periphery of the workpiece where the chamfer is formed, and then the back side is ground (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2004-319885 A [Patent Document 2] JP 2003-273053 A [Patent Document 3] JP 2006-108532 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, when a laser beam is irradiated approximately perpendicularly to one surface of a workpiece, the laser beam reflected by the surface may return to the laser oscillator, causing the state of the laser oscillator to become unstable, which may result in processing defects.

[0009] The present invention has been made in consideration of these problems, and has an object to remove an area including a chamfered portion of a workpiece using a laser beam while suppressing the return of the laser beam to the laser oscillator. [Means for solving the problem]

[0010] According to one aspect of the present invention, a method for processing a disk-shaped workpiece includes a tape application step of applying a tape to one surface of the workpiece and integrating the workpiece and a frame via the tape, a holding step of holding the workpiece with a holding unit via the tape after the tape application step, and a laser beam irradiation step of irradiating a pulsed laser beam having a wavelength absorbed by the workpiece from the other surface of the workpiece located opposite to the one surface to the other surface after the holding step, wherein the direction of the laser beam is adjusted so that the laser beam has an incident angle inclined by a predetermined angle with respect to a normal to the other surface of the workpiece. At the same time, the incidence plane of the laser beam is made perpendicular to a virtual plane that passes through the center of the other surface and the focal point of the laser beam and is perpendicular to the other surface. In this state, the other surface is annularly irradiated with the laser beam.

[0011] Preferably, in the holding step, the workpiece is held with the other surface exposed downward, and in the laser beam applying step, the laser beam is applied upward from below.

[0012] In addition, preferably, in the laser beam irradiation step, a groove having a predetermined diameter is formed on the other surface side, inside the outer periphery of the workpiece, thereby separating the workpieces at the groove.

[0013] In addition, preferably, the workpiece has, on the other surface side, a device area in which a plurality of devices are formed, and a peripheral surplus area surrounding the device area and ranging from the outer periphery of the workpiece to a position a predetermined distance inward, and also has, on the one surface side, a circular recess corresponding to the device area, and an annular convex portion surrounding the outside of the circular recess and corresponding to the peripheral surplus area, and in the laser beam irradiation step, the laser beam is irradiated to the boundary between the device area on the other surface side and the peripheral surplus area.

[0014] In addition, preferably, the workpiece has, on the other surface side, a device region in which a plurality of devices are formed, and a peripheral excess region surrounding the device region and ranging from an outer circumferential edge of the workpiece to a position a predetermined distance inward, and has, on the one surface side, a circular recess corresponding to the device region, and an annular convex portion surrounding the outside of the circular recess and corresponding to the peripheral excess region, and in the laser beam irradiation step, the laser beam is irradiated to the peripheral excess region from the outer circumferential edge to a predetermined distance inward from the outer circumferential edge, thereby ablating and removing the portion corresponding to the peripheral excess region in the thickness direction of the workpiece.

[0017] According to another aspect of the present invention, there is provided a method for processing a disk-shaped workpiece, the method comprising: a tape adhering step of adhering a tape to one surface of the workpiece and integrating the workpiece and a frame via the tape; a holding step of holding the workpiece with a holding unit via the tape after the tape adhering step; and a laser beam irradiating step of irradiating a pulsed laser beam having a wavelength that is absorbed by the workpiece from the other surface of the workpiece located opposite to the one surface to the other surface after the holding step, the laser beam being adjusted to have an incident angle that is inclined by a predetermined angle with respect to a normal to the other surface of the workpiece, and irradiating the other surface with the laser beam in an annular shape. The laser beam is irradiated obliquely from the center of the other surface toward the outside of the other surface with the incidence surface of the laser beam parallel to a virtual plane that passes through the center of the other surface and the focal point of the laser beam and is perpendicular to the other surface. A method for processing a workpiece is provided. .

[0018] Also, preferably, in the laser beam irradiation step, the laser beam is irradiated with the incident plane of the laser beam parallel to the virtual plane by controlling the irradiation position of the laser beam with a galvanometer scanner arranged to face the other surface.

[0019] According to yet another aspect of the present invention, there is provided a method for processing a disk-shaped workpiece, comprising: a tape adhering step of adhering a tape to one surface of the workpiece and integrating the workpiece and a frame via the tape; a holding step of holding the workpiece with a holding unit via the tape after the tape adhering step; and a laser beam irradiating step of irradiating a pulsed laser beam having a wavelength that is absorbed by the workpiece from the other surface of the workpiece located opposite to the one surface to the other surface after the holding step, wherein in the laser beam irradiating step, the laser beam is irradiated in an annular shape on the other surface while adjusting the direction of the laser beam to have an incident angle inclined by a predetermined angle with respect to a normal to the other surface of the workpiece, The laser beam irradiation step forms a groove in the workpiece by the laser beam, and when the groove penetrates the workpiece, a laser beam passes through the groove. Light A detection step of detecting the A method for processing a workpiece is provided. . Preferably, in the detection step, a light source that irradiates light having an output lower than the processing threshold of the workpiece and the light detection unit are arranged to sandwich the workpiece in the thickness direction of the workpiece, and the light from the light source that passes through the processing groove is detected by the light detection unit.

[0020] A method for processing a workpiece according to one aspect of the present invention includes a laser beam irradiation step of irradiating the other surface of the workpiece with a pulsed laser beam having a wavelength that is absorbed by the workpiece. In the laser beam irradiation step, the laser beam is irradiated in an annular shape on the other surface while the direction of the laser beam is adjusted so that the laser beam has an incident angle that is inclined by a predetermined angle with respect to a normal line of the other surface of the workpiece.

[0021] In the laser beam irradiation step, the incident angle of the laser beam is inclined at a predetermined angle with respect to the normal line of the other surface of the workpiece, so that even if the laser beam is reflected by the other surface, the laser beam can be prevented from returning to the laser oscillator. Therefore, the state of the laser oscillator is less likely to become unstable, and the possibility of processing defects in the laser processing can be reduced. [Brief description of the drawings]

[0022] [Figure 1] FIG. [Diagram 2] FIG. 2(A) is a perspective view of the front side of the workpiece, and FIG. 2(B) is a perspective view of the back side of the workpiece. [Diagram 3] FIG. 13 is a diagram showing a tape application step. [Figure 4] FIG. [Diagram 5] FIG. [Figure 6] FIG. 11 is a perspective view showing one aspect of a laser beam irradiation step. [Figure 7] FIG. 7 is a schematic diagram of FIG. [Figure 8] FIG. 8(A) is a diagram showing how a machined groove is formed, and FIG. 8(B) is a diagram showing a detection step. [Figure 9] FIG. 9(A) is a perspective view of a workpiece according to a first modified example, and FIG. 9(B) is a cross-sectional view of the workpiece according to the first modified example. [Figure 10] FIG. 11 is a perspective view of a workpiece according to a second modified example. [Figure 11]FIG. 13 is a diagram showing a laser beam irradiation step according to a third modified example. [Figure 12] FIG. 12 is a schematic diagram of FIG. [Figure 13] FIG. 13 is a diagram showing a laser beam irradiation step according to a fourth modified example. [Figure 14] FIG. 11 is a diagram showing a detection step according to the second embodiment. [Figure 15] FIG. 15(A) is a diagram showing an example of a laser beam irradiation step according to the third embodiment, and FIG. 15(B) is a diagram showing another example of a laser beam irradiation step according to the third embodiment. [Figure 16] FIG. 11 is a partial cross-sectional side view showing a laser processing apparatus according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] An embodiment according to one aspect of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a flow diagram of a processing method according to a first embodiment. First, a disk-shaped workpiece 11 to be processed in this embodiment will be described.

[0024] FIG. 2(A) is a perspective view of the front surface (other surface) 11a of the workpiece 11, and FIG. 2(B) is a perspective view of the back surface (one surface) 11b of the workpiece 11 located opposite the front surface 11a.

[0025] As shown in FIG. 2(A), a plurality of planned division lines (streets) 13 are set in a lattice pattern on the front surface 11a of the workpiece 11, and devices 15 such as ICs and LSIs are formed in each of a plurality of areas partitioned by the plurality of planned division lines 13.

[0026] In this embodiment, the workpiece 11 is a silicon wafer, but there is no limitation on the material, structure, size, etc. of the workpiece 11. The workpiece 11 may be a wafer made of other semiconductor materials. Similarly, there is no limitation on the type, number, shape, structure, size, etc. of the device 15.

[0027] At the center of the front surface 11a side, there is a circular device region 17a including a plurality of devices 15. Around the device region 17a, there is a peripheral surplus region 17b where no devices 15 are formed and which is generally flat compared to the device region 17a.

[0028] The peripheral surplus region 17b is a range on the surface 11a from the peripheral edge 11c of the workpiece 11 excluding the notch 19 to a position a predetermined distance inward. For example, in the case of a wafer having a diameter of 12 inches (about 300 mm), the peripheral surplus region 17b is a range of about 3 mm from the peripheral edge 11c.

[0029] In Fig. 2A, the boundary 17c between the device region 17a and the peripheral surplus region 17b is indicated by a dashed line. As shown in Fig. 2B, in the workpiece 11 of this embodiment, a circular recess 11d is present in the center of the back surface 11b by thinning the back surface 11b by a predetermined thickness.

[0030] The circular recess 11d is a region that corresponds to the device region 17a in the thickness direction of the workpiece 11. An annular protrusion 11e is formed outside the circular recess 11d so as to surround the circular recess 11d.

[0031] The annular protrusion 11e is a region that corresponds to the outer peripheral excess region 17b in the thickness direction of the workpiece 11. In addition, a chamfer is formed on each outer periphery on the front surface 11a side and the back surface 11b side as shown in FIG.

[0032] When processing the workpiece 11, the back surface 11b of the workpiece 11 is attached to the center of a circular tape 21, and a metal ring-shaped frame 23 (see Figures 3 and 4) is attached to the outer periphery of the tape 21 (tape attachment step S10).

[0033] 3 is a diagram showing a tape application step S10. The tape 21 has a resin base layer and an adhesive layer (glue layer) provided on one entire surface of the base layer. The adhesive layer is formed of, for example, an ultraviolet-curable resin.

[0034] In the tape application step S10, for example, first, the workpiece 11 is placed so that the back surface 11b faces upward, and then the frame 23 is placed around the outer periphery of the workpiece 11. Thereafter, the adhesive layer side of the tape 21 is applied to the back surface 11b of the workpiece 11 and one surface of the frame 23.

[0035] As a result, workpiece unit 25 (see FIG. 4) is formed in which workpiece 11 and frame 23 are integrated via tape 21. FIG.

[0036] After the tape application step S10, the workpiece unit 25 is suction-held by a disk-shaped chuck table (holding unit) 4 provided in the laser processing device 2 (holding step S20) (see FIG. 5). FIG. 5 is a diagram showing the holding step S20.

[0037] Here, the configuration of the laser processing device 2 will be described. The above-mentioned chuck table 4 is arranged so that the holding surface 4a faces downward. The chuck table 4 has a disk-shaped frame 6 made of metal. A disk-shaped recess is formed in the lower part of the frame 6.

[0038] A disk-shaped porous plate 8 made of porous ceramics is fixed in the recess of the frame 6. The lower surface of the frame 6 and the lower surface of the porous plate 8 are flush with each other and form a substantially flat holding surface 4a.

[0039] A flow path (not shown) is formed in the frame 6. One end of the flow path is connected to a suction source (not shown) such as an ejector, and the other end of the flow path is connected to a porous plate 8. When the suction source is operated, a negative pressure is transmitted to the holding surface 4a.

[0040] A cylindrical transmitting portion 4b is provided on a part of the frame 6 and the porous plate 8. The transmitting portion 4b is made of a material (for example, optical glass) that is transparent or translucent to the laser beam L described later.

[0041] The transmitting portion 4b penetrates from the lower surface of the porous plate 8 to the upper surface of the frame 6. In this embodiment, only one transmitting portion 4b is provided, but a plurality of transmitting portions 4b may be provided discretely along the radial direction of the chuck table 4.

[0042] An output shaft of a rotation mechanism 10 having a motor or the like is connected to the upper part of the frame 6. The rotation mechanism 10 can rotate the chuck table 4 around a rotation shaft 10a. A horizontal movement mechanism (not shown) for moving the rotation mechanism 10 in the X-axis and Y-axis directions is connected to the upper part of the rotation mechanism 10.

[0043] An optical detection unit 14 is disposed above the chuck table 4 and on the side of the rotation mechanism 10. The optical detection unit 14 is a power meter, a power sensor, a camera with a neutral density filter, or the like, and is capable of detecting the laser beam L that has passed through the transmitting portion 4b.

[0044] A plurality of clamping mechanisms 12 are provided on the side of the rotating mechanism 10. In this embodiment, four clamping mechanisms 12 are discretely arranged along the circumferential direction of the chuck table 4. Note that two clamping mechanisms 12 are shown in FIG.

[0045] When the workpiece unit 25 is sucked and held by the holding surface 4a with the front surface 11a exposed downward, the back surface 11b of the workpiece 11 is held by the holding surface 4a via the tape 21. In addition, the frame 23 is clamped by the clamp mechanism 12.

[0046] A laser beam irradiation unit 16 is disposed below the chuck table 4 (see FIG. 6). The laser beam irradiation unit 16 includes a laser oscillator (not shown) for generating a pulsed laser beam having a wavelength that is absorbed by the workpiece 11.

[0047] The laser beam emitted from the laser oscillator passes through a predetermined optical system and is irradiated upward from a condenser 18 equipped with a focusing lens toward the holding surface 4a. The condenser 18 is connected to a Z-axis movement mechanism (not shown) that moves the condenser 18 along the Z-axis direction, and an angle adjustment unit (not shown) that adjusts the incidence angle of the laser beam.

[0048] The laser processing device 2 is provided with a control unit (not shown) that controls the operations of the chuck table 4, the laser beam irradiation unit 16, a horizontal movement mechanism (not shown), a Z-axis movement mechanism (not shown), an angle adjustment unit, and the like.

[0049] The control unit is composed of a computer including, for example, a processor (processing device) represented by a CPU (Central Processing Unit), a main memory device such as a DRAM (Dynamic Random Access Memory), a SRAM (Static Random Access Memory), or a ROM (Read Only Memory), and an auxiliary memory device such as a flash memory, a hard disk drive, or a solid state drive.

[0050] The auxiliary storage device stores software including a predetermined program. The functions of the control unit are realized by operating the processing device and the like according to this software. Next, the laser beam irradiation step S30 after the holding step S20 will be described with reference to Figs. 6 and 7.

[0051] Fig. 6 is a perspective view showing one embodiment of the laser beam irradiation step S30, and Fig. 7 is a schematic diagram of Fig. 6. Note that Fig. 7 is drawn from a different perspective than Fig. 6, and for convenience, the chuck table 4, tape 21, frame 23, etc. are omitted in Figs. 6 and 7.

[0052] In the laser beam irradiation step S30, the laser beam L is irradiated onto the surface 11a of the workpiece 11 from the condenser 18 located below the workpiece unit 25 (i.e., from the surface 11a side). In other words, the laser beam L is irradiated from below to above.

[0053] In particular, in the laser beam irradiation step S30 of this embodiment, the incident surface 22 of the laser beam L is made perpendicular to a virtual surface 20 that passes through the center A1 of the surface 11a and the focal point A2 of the laser beam L and is perpendicular to the surface 11a (see FIG. 7).

[0054] Furthermore, the direction of the laser beam L is adjusted so that it has an incident angle α (acute angle) inclined at a predetermined angle with respect to the normal 11f of the surface 11a, and the focal point A2 is positioned at a point on the boundary portion 17c (annular region).

[0055] In this state, the chuck table 4 is rotated around the rotation axis 10a, whereby the laser beam L is irradiated onto the surface 11a and ablation processing is performed along the outer peripheral edge 11c, thereby forming a ring-shaped processed groove 11g along the boundary portion 17c in an aspect perpendicular to the surface 11a (see Figure 8 (A)).

[0056] 8A is a diagram showing how the processed groove 11g is formed. For example, when the thickness of the device region 17a is 100 μm, the laser processing conditions are as follows:

[0057] Laser medium of the laser oscillator: Yb-doped fiber Wavelength: 1059nm or more and 1065nm or less Repetition frequency: 50kHz Average power output: 17W Machining feed speed: 163 rpm Focused spot diameter: 25μm

[0058] As the laser processing progresses, the processing groove 11g gradually becomes deeper, and when the processing groove 11g penetrates the workpiece 11, the workpiece 11 is separated by the processing groove 11g into a device region 17a and an outer peripheral excess region 17b (see Figure 8 (B)).

[0059] In the laser beam irradiation step S30 of this embodiment, the laser beam L is irradiated onto the surface 11a of the workpiece 11 so as to have an incident angle α inclined at a predetermined angle with respect to the normal 11f of the surface 11a. Therefore, even if the laser beam L is reflected by the surface 11a, it is reflected at a reflection angle α, and the return of the laser beam L to the laser oscillator can be suppressed.

[0060] Therefore, the state of the laser oscillator is less likely to become unstable, reducing the possibility of defective laser processing. In addition, by making the laser beam L incident at an incident angle α, the debris 27 scatters along the traveling direction B1 of the laser beam L at a reflection angle α (see Figs. 6 and 7). Therefore, the adhesion of the debris 27 to the focusing lens can be reduced.

[0061] During the laser processing, an air injection nozzle (not shown) may be placed directly under the center A1 of the surface 11a to inject air from the center A1 toward the focal point A2. This makes it possible to more reliably prevent the debris 27 generated during the ablation processing from adhering to the device region 17a.

[0062] Incidentally, the laser beam irradiation step S30 of this embodiment includes a detection step S35 in which, when the processed groove 11g penetrates the workpiece 11, the laser beam L that has passed through the processed groove 11g is detected by the light detection unit 14. Fig. 8(B) is a diagram showing the detection step S35.

[0063] When the light detection unit 14 receives light having an intensity equal to or greater than a predetermined value, it transmits a predetermined light reception signal to the control unit. Therefore, it is possible to automatically detect whether the processed groove 11g has penetrated or not by using the light detection unit 14. After it is detected that the groove has penetrated, the irradiation of the laser beam L is stopped.

[0064] After the detection step S35 and before the irradiation of the laser beam L is stopped, a cleaning step may be performed in which the output of the laser beam L is reduced compared to the laser processing conditions described above, and debris adhering to the vicinity of the processed groove 11g is removed.

[0065] After the laser beam irradiation step S30, the outer circumferential surplus region 17b separated in a ring shape from the device region 17a is removed from the tape 21 (removal step S40). For example, the chuck table 4 is rotated in a state where wedges (not shown) are inserted between the tape 21 and the back surface 11b at multiple points in the circumferential direction of the outer circumferential surplus region 17b. This causes the outer circumferential surplus region 17b to fall from the tape 21.

[0066] In the removal step S40, instead of wedges, a claw portion (not shown) may be inserted between the tape 21 and the back surface 11b at multiple points around the circumferential edge of the outer circumferential edge 17b, and the claw portion may be pulled down to cause the outer circumferential edge 17b to fall off the tape 21.

[0067] (First Modification) Next, various modifications of the first embodiment will be described. Fig. 9(A) is a perspective view of a workpiece 31 according to a first modification, and Fig. 9(B) is a cross-sectional view of the workpiece 31 according to the first modification.

[0068] The workpiece 31 of the first modification is different from the above-described workpiece 11 in that the circular recess 11d is not formed on the back surface 11b side. By similarly carrying out the tape application step S10 to the removal step S40 on the workpiece 31, the area including the chamfered portion formed on the outer periphery of the workpiece 31 can be removed.

[0069] 10 is a perspective view of a workpiece 41 according to a second modified example. The workpiece 41 does not have a device 15 formed thereon. For example, by forming a groove 11g along a predetermined diameter smaller than the diameter of the workpiece 41, a workpiece 43 having a smaller diameter than the workpiece 41 can be formed from the workpiece 41.

[0070] (Third Modification) Next, a modification of the laser beam irradiation step S30 will be described. Fig. 11 is a diagram showing the laser beam irradiation step S30 according to the third modification. Fig. 12 is a schematic diagram of Fig. 11.

[0071] In the laser beam irradiation step S30 of the third modified example, the incident plane 26 of the laser beam L is made parallel to a virtual plane 24 that passes through the center A1 of the surface 11a and the focal point A2 of the laser beam L and is perpendicular to the surface 11a.

[0072] Furthermore, the direction of the laser beam L is adjusted so that it has an incident angle β (acute angle) inclined at a predetermined angle with respect to the normal 11f of the surface 11a, and the focal point A2 is positioned at a point on the boundary portion 17c (annular region).

[0073] In this state, the chuck table 4 is rotated around the rotation axis 10a, whereby the laser beam L is irradiated obliquely from the center A1 of the surface 11a toward the outside of the surface 11a, and ablation processing is performed along the outer circumferential edge 11c.

[0074] The laser processing conditions may be the same as those described above. As the laser processing proceeds, the groove 11g gradually becomes deeper, and when the groove 11g penetrates the workpiece 11, the workpiece 11 is divided into the device region 17a and the peripheral excess region 17b at the boundary of the groove 11g.

[0075] At this time, the workpiece 11 on the device region 17a side has an inverted truncated cone shape, which has the advantage that the inner peripheral side surface of the outer peripheral excess region 17b is less likely to interfere with the outer peripheral side surface of the device region 17a in the removal step S40.

[0076] In the laser beam irradiation step S30 according to the third modified example, the laser beam L is irradiated onto the surface 11a of the workpiece 11 so as to have an incident angle β inclined at a predetermined angle with respect to the normal 11f of the surface 11a. Therefore, even if the laser beam L is reflected by the surface 11a, it is reflected at a reflection angle β, and the return of the laser beam L to the laser oscillator can be suppressed.

[0077] Therefore, the state of the laser oscillator is less likely to become unstable, and the possibility of processing defects in laser processing can be reduced. In addition, by setting the incident angle β of the laser beam L, the debris 27 scatters approximately along the traveling direction B2 of the laser beam L at the reflection angle β. Therefore, the adhesion of the debris 27 to the condenser lens can be reduced.

[0078] During laser processing, an air injection nozzle (not shown) may be disposed directly under the center A1 of the surface 11a to inject air from the center A1 toward the focal point A2. In the third modified example, a detection step S35 may be performed. By performing the detection step S35, it is possible to automatically detect whether the processed groove 11g has penetrated the workpiece.

[0079] (Fourth Modification) Next, a fourth modification obtained by modifying the third modification will be described. Fig. 13 is a diagram showing a laser beam irradiation step S30 according to the fourth modification. In the fourth modification, similarly to the third modification, a laser beam L is irradiated onto the boundary portion 17c of the surface 11a with the incidence surface 26 parallel to the imaginary surface 24 that passes through the center A1 and the focal point A2 and is perpendicular to the surface 11a.

[0080] However, in the fourth modified example, the chuck table 4 is kept stationary without being rotated, and the galvano scanner 28 arranged to face the holding surface 4a (i.e., the surface 11a) is used to control the irradiation position of the laser beam L while scanning the focal point A2 along the boundary portion 17c. The fourth modified example can also achieve the same effect as the third modified example. Of course, the detection step S35 may be performed using the light detection unit 14.

[0081] Next, a second embodiment will be described with reference to Fig. 14. A laser processing apparatus 32 of the second embodiment includes a holding ring (holding unit) 34 instead of the chuck table 4. The holding ring 34 has a ring-shaped housing 36 and a plurality of clamp mechanisms 38 provided discretely around the periphery of the housing 36.

[0082] The retaining ring 34 is connected to a rotation mechanism (not shown) similar to that of the chuck table 4, and is rotatable around a rotation axis 34a passing through the center position of the housing 36. Below the retaining ring 34, a laser beam irradiation unit 16 is disposed in a manner capable of irradiating the laser beam L upward.

[0083] The above-mentioned light detection unit 14 is disposed on the opposite side of the laser beam irradiation unit 16 from the condenser 18, with the rotation axis 34a sandwiched between them in the horizontal direction. A light source 40 that irradiates light downward is disposed above the light detection unit 14.

[0084] The light source 40 is, for example, a laser diode. The laser beam from the light source 40 has a wavelength that is difficult to transmit through the workpiece 11 and transmits through the tape 21 (for example, a wavelength in the ultraviolet range), and has a lower output than the laser beam L that processes the workpiece 11.

[0085] More specifically, the output of the laser beam from the light source 40 is small enough not to process the workpiece 11 (i.e., lower than the processing threshold of the workpiece 11). The laser beam from the light source 40 is irradiated toward the light detection unit 14.

[0086] In the second embodiment, when processing the workpiece 11, the steps from the tape application step S10 to the removal step S40 are performed in sequence. After the workpiece unit 25 is formed in the tape application step S10, the frame 23 is attached to the holding ring 3. 4 The workpiece 11 is held via the tape 21 by holding it with the tape 21 (holding step S20).

[0087] Next, as in the first embodiment, with the incident surface 22 of the laser beam L perpendicular to the virtual surface 20 (see FIG. 7), the direction of the laser beam L is adjusted so that it has an incident angle α (acute angle) inclined at a predetermined angle with respect to the normal 11f of the surface 11a, and the focal point A2 is positioned at a point on the boundary portion 17c (annular region) (see FIGS. 6 and 7).

[0088] Furthermore, the retaining ring 3 4 By rotating the tool around the rotation axis 34a, ablation processing is performed along the outer circumferential edge 11c, and a processed groove 11g perpendicular to the surface 11a is formed in a ring shape along the boundary portion 17c.

[0089] Of course, in the second embodiment, the return of the laser beam L to the laser oscillator can be suppressed, so the state of the laser oscillator is less likely to become unstable, and therefore the possibility of processing defects in laser processing can be reduced.

[0090] However, in the detection step S35 of the second embodiment, the laser beam irradiated from the light source 40 is detected by the light detection unit 14 to detect whether or not the processed groove 11g penetrates the workpiece 11. Fig. 14 is a diagram showing the detection step S35 according to the second embodiment.

[0091] In this embodiment, the detection step S35 can be performed using a low-output light source 40. Therefore, it is not necessary to provide a neutral density filter or the like in the light detection unit 14, which reduces costs. In addition, there is an advantage that the sensor element, filter, etc. are less likely to burn, making it less likely for problems such as failure of the light detection unit 14 to occur.

[0092] Furthermore, in the subsequent removal step S40, a light shielding plate (not shown) having approximately the same diameter as the circular recess 11d is placed on the tape 21, and ultraviolet light is irradiated onto the entire back surface 11b side of the workpiece 11. This reduces the adhesive force between the annular protrusion 11e and the tape 21, and then the outer peripheral excess region 17b separated into a ring shape from the circular recess 11d is removed from the tape 21 using the above-mentioned claw or the like (removal step S40).

[0093] Furthermore, in the removal step S40, the adhesive force of the tape 21 is reduced before the outer circumferential excess region 17b is removed from the tape 21, so that the device region 17a can be stably attached to the tape 21 and the outer circumferential excess region 17b can be easily removed.

[0094] In addition, the same effects can be achieved based on the same arrangement, configuration, etc. as the first embodiment. In addition, the first to fourth modified examples may be applied to the second embodiment. Next, the third embodiment will be described.

[0095] The third embodiment differs from the first and second embodiments in that the laser beam irradiation step S30 removes a portion of the workpiece 11 in the thickness direction thereof that corresponds to the outer circumferential excess region 17b by ablation.

[0096] Fig. 15(A) is a diagram showing an example of the laser beam irradiation step S30 according to the third embodiment. For convenience, the chuck table 4, the tape 21, the frame 23, etc. are omitted in Fig. 15(A).

[0097] In the example shown in Figure 15(A), as in the first embodiment (see Figures 6 to 8(B)), the laser beam L is irradiated so as to have an incident angle α (acute angle) inclined at a predetermined angle with respect to the normal 11f of the surface 11a, with the incident surface 22 of the laser beam L being perpendicular to the virtual surface 20.

[0098] In this way, the focal point A2 is positioned at the outer circumferential edge 11c. Then, while rotating the chuck table 4 around the rotation axis 10a, the rotation axis 10a is gradually brought closer to the focal point A2 as shown by the arrow C1. The height position of the focal point A2 of the laser beam L may be adjusted as appropriate.

[0099] Also, the focal point A2 may be moved from a position a predetermined distance inside the outer circumferential edge 11c to the outer circumferential edge 11c, or the chuck table 4 may be rotated without moving it horizontally and the laser beam irradiation unit 16 may be moved horizontally. Furthermore, when the spot diameter of the focal point A2 is sufficiently large, the chuck table 4 may be rotated without moving the chuck table 4 and the laser beam irradiation unit 16 horizontally.

[0100] By irradiating the laser beam L to the outer circumferential surplus region 17b from the outer circumferential edge 11c to a position a predetermined distance inward, it is possible to remove the portion corresponding to the outer circumferential surplus region 17b in the thickness direction of the workpiece 11. Therefore, the removal step S40 can be omitted.

[0101] Furthermore, in the laser beam irradiation step S30, the incident surface 22 of the laser beam L may be made parallel to the virtual surface 20, so that the portion corresponding to the outer peripheral excess region 17b in the thickness direction of the workpiece 11 may be removed by ablation, as in the third variant of the first embodiment (see Figures 11 and 12).

[0102] Fig. 15(B) is a diagram showing another example of the laser beam irradiation step S30 according to the third embodiment. In Fig. 15(B) as well, the chuck table 4 and the like are omitted for the sake of convenience.

[0103] In the example shown in Figure 15(B), as in Figures 11 to 13, the laser beam L is irradiated so that the incident surface 22 of the laser beam L is parallel to the virtual surface 20 and has an incident angle β (acute angle) inclined at a predetermined angle with respect to the normal 11f of the surface 11a.

[0104] In this way, the focal point A2 is positioned at the outer circumferential edge 11c. Then, while rotating the chuck table 4 around the rotation axis 10a, the rotation axis 10a is gradually brought closer to the focal point A2 as shown by the arrow C1. The height position of the focal point A2 of the laser beam L may be adjusted as appropriate.

[0105] 15(A), in the third embodiment, the focal point A2 may be moved from the inside to the outside of the workpiece 11, or the chuck table 4 may be rotated without moving it horizontally and the laser beam application unit 16 may be moved horizontally. Furthermore, if the spot diameter of the focal point A2 is sufficiently large, the chuck table 4 may be rotated without moving the chuck table 4 and the laser beam application unit 16 horizontally.

[0106] By irradiating the laser beam L to the peripheral surplus region 17b from the outer circumferential edge 11c to a position a predetermined distance inward, it is possible to remove a portion corresponding to the peripheral surplus region 17b in the thickness direction of the workpiece 11. Note that a galvano scanner 28 can also be applied as in the fourth modified example of the first embodiment (see FIG. 13).

[0107] Next, a fourth embodiment will be described. Fig. 16 is a partial cross-sectional side view showing a laser processing apparatus 42 according to the fourth embodiment. In the laser processing apparatus 42, the chuck table 4 is arranged so that the holding surface 4a faces upward, and a laser beam irradiation unit 16 is arranged above the holding surface 4a.

[0108] In the fourth embodiment, a processing groove 11g can be formed in the boundary portion 17c in a manner similar to that of the first embodiment (see Figures 6 to 8(B)), the third variant of the first embodiment (see Figures 11 and 12), or the fourth variant of the first embodiment (see Figure 13).

[0109] Of course, a workpiece 31 according to a first modified example of the first embodiment (see Figures 9(A) and 9(B)) may be machined, or a workpiece 43 having a smaller diameter may be formed from a workpiece 41 according to a second modified example of the first embodiment (see Figure 10).

[0110] Also, instead of the chuck table 4, a holding ring 3 is used as in the second embodiment (see FIG. 14). 4Alternatively, instead of forming the machining groove 11g, the portion of the workpiece 11 in the thickness direction corresponding to the outer peripheral excess region 17b may be removed by ablation as in the third embodiment (see Figures 15(A) and 15(B)).

[0111] In addition, the structures, methods, etc. according to the above-described embodiments can be modified as appropriate without departing from the scope of the object of the present invention. [Explanation of symbols]

[0112] 2, 32, 42: Laser processing device, 4: Chuck table (holding unit) 4a: Holding surface, 4b: Transmission part 6: frame, 8: porous plate, 10: rotation mechanism, 10a: rotation shaft 11,31,41,43: Workpiece, 11a: front surface (other side), 11b: back surface (one side) 11c: outer periphery, 11d: circular recess, 11e: annular protrusion, 11f: normal line, 11g: machined groove 12: Clamp mechanism 14: Light detection unit 13: Planned division line, 15: Device 16: laser beam irradiation unit, 18: condenser 17a: device region, 17b: peripheral excess region, 17c: boundary portion, 19: notch 20, 24: Virtual surface, 22, 26: Incident surface 21: tape, 23: frame, 25: workpiece unit, 27: debris 28: Galvano scanner 34: retaining ring (retaining unit), 34a: rotating shaft 36: Housing, 38: Clamp mechanism, 40: Light source A1: Center, A2: Focus point, B1, B2: Direction of travel, C1: Arrow L: laser beam, α: angle of incidence, angle of reflection, β: angle of incidence, angle of reflection

Claims

1. A method for processing a disk-shaped workpiece, comprising the steps of: a tape adhering step of adhering a tape to one surface of the workpiece and integrating the workpiece and a frame via the tape; a holding step of holding the workpiece with a holding unit via the tape after the tape application step; and a laser beam irradiation step of irradiating a pulsed laser beam having a wavelength that is absorbed by the workpiece from a side of the other surface of the workpiece located opposite to the one surface, after the holding step, to the other surface, a laser beam irradiation step of adjusting a direction of the laser beam so that the laser beam has an incident angle inclined at a predetermined angle with respect to the normal to the other surface of the workpiece, and irradiating the laser beam in a ring shape on the other surface with the incident plane of the laser beam perpendicular to a virtual plane that passes through the center of the other surface and the focal point of the laser beam and is perpendicular to the other surface.

2. In the holding step, the workpiece is held in a state where the other surface is exposed downward, 2. The method for processing a workpiece according to claim 1, wherein in the laser beam applying step, the laser beam is applied from below to above.

3. The method for processing a workpiece as described in claim 1 or 2, characterized in that in the laser beam irradiation step, a groove having a predetermined diameter is formed on the other surface side, inside the outer periphery of the workpiece, thereby separating the workpiece at the groove.

4. The workpiece is The other surface has a device region in which a plurality of devices are formed, and a peripheral excess region surrounding the device region and ranging from an outer peripheral edge of the workpiece to a position a predetermined distance inward, and a circular recess on the one surface corresponding to the device region, and an annular protrusion surrounding the circular recess and corresponding to the outer circumferential excess region; 4. The method for processing a workpiece according to claim 1, wherein in the laser beam irradiation step, the laser beam is irradiated onto the boundary between the device region on the other surface side and the outer peripheral excess region.

5. The workpiece is The other surface has a device region in which a plurality of devices are formed, and a peripheral excess region surrounding the device region and ranging from an outer peripheral edge of the workpiece to a position a predetermined distance inward, and a circular recess on the one surface corresponding to the device region, and an annular protrusion surrounding the circular recess and corresponding to the outer circumferential excess region; A method for processing a workpiece as described in any one of claims 1 to 3, characterized in that in the laser beam irradiation step, the laser beam is irradiated to the outer peripheral surplus region from the outer peripheral edge to a predetermined distance inward from the outer peripheral edge, thereby ablating and removing the portion corresponding to the outer peripheral surplus region in the thickness direction of the workpiece.

6. A method for machining a disk-shaped workpiece, comprising the steps of: a tape adhering step of adhering a tape to one surface of the workpiece and integrating the workpiece and a frame via the tape; a holding step of holding the workpiece with a holding unit via the tape after the tape application step; and a laser beam irradiation step of irradiating a pulsed laser beam having a wavelength that is absorbed by the workpiece from a side of the other surface of the workpiece located opposite to the one surface, after the holding step, to the other surface, In the laser beam irradiation step, irradiating the other surface with the laser beam in a ring shape while adjusting the direction of the laser beam so that the laser beam has an incident angle inclined by a predetermined angle with respect to a normal to the other surface of the workpiece; a laser beam is irradiated obliquely from the center of the other surface toward the outside of the other surface with the incident surface of the laser beam parallel to a virtual plane that passes through the center of the other surface and the focal point of the laser beam and is perpendicular to the other surface.

7. 7. The method for processing a workpiece according to claim 6, wherein in the laser beam irradiation step, the laser beam is irradiated with the incident plane of the laser beam parallel to the virtual plane by controlling the irradiation position of the laser beam with a galvanometer scanner arranged to face the other surface.

8. A method for machining a disk-shaped workpiece, comprising the steps of: a tape adhering step of adhering a tape to one surface of the workpiece and integrating the workpiece and a frame via the tape; a holding step of holding the workpiece with a holding unit via the tape after the tape application step; and a laser beam irradiation step of irradiating a pulsed laser beam having a wavelength that is absorbed by the workpiece from a side of the other surface of the workpiece located opposite to the one surface, after the holding step, to the other surface, In the laser beam irradiation step, the laser beam is irradiated in a ring shape on the other surface of the workpiece while adjusting the direction of the laser beam so that the laser beam has an incident angle inclined by a predetermined angle with respect to a normal line of the other surface of the workpiece; The method for processing a workpiece is characterized in that the laser beam irradiation step includes a detection step of forming a groove in the workpiece by the laser beam, and detecting light passing through the groove with an optical detection unit when the groove penetrates the workpiece.

9. A method for processing a workpiece as described in claim 8, characterized in that in the detection step, a light source that irradiates light having an output lower than the processing threshold of the workpiece and the light detection unit are arranged to sandwich the workpiece in the thickness direction of the workpiece, and the light from the light source that passes through the processing groove is detected by the light detection unit.

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