Method for processing a workpiece

Abstract

The present application provides a method for processing a workpiece, which inhibits the return of a laser beam to a laser oscillator and uses the laser beam to remove a region of the workpiece that includes a chamfered portion. The method for processing a workpiece is a method for processing a workpiece that is disc-shaped, and has the following steps: a tape attaching step in which a tape is attached to one face of the workpiece and the workpiece is integrated with a frame by means of the tape; a holding step in which, after the tape attaching step, the workpiece is held by a holding unit across the tape; and a laser beam irradiation step in which, after the holding step, a pulsed laser beam having a wavelength that is absorbed by the workpiece is irradiated from the other face, which is opposite the one face, of the workpiece toward the one face, and in the laser beam irradiation step, the laser beam is irradiated in a ring shape on the one face in a state in which the orientation of the laser beam is adjusted so as to have an incident angle that is inclined at a prescribed angle with respect to a normal to the other face of the workpiece.

Description

Technical Field

[0001] This invention relates to a method for processing a workpiece, which uses a pulsed laser beam having a wavelength absorbed by the workpiece to process a disk-shaped workpiece. Background Technology

[0002] With the miniaturization and weight reduction of electronic devices in recent years, the thinning of device chips has been continuously developing. In order to manufacture thin device chips, for example, the back side of a workpiece such as a semiconductor wafer on which devices such as IC (Integrated Circuit) and LSI (Large Scale Integration) are formed is ground to a thickness of 20μm to 100μm (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., chamfered portions are formed). Therefore, when the back side of the workpiece is ground to less than half its thickness, a so-called cutting edge (also known as a sharp edge) is formed on the outer periphery of the workpiece. When a cutting edge is formed, the following problem exists: during the grinding or transport of the workpiece, chipping or damage occurs on the outer periphery of the workpiece.

[0004] To solve this problem, a process for removing the chamfered outer periphery using a cutting device has been proposed (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 tool positioned at a predetermined distance inward from the outer periphery of the workpiece is inserted into the back side of the workpiece. In this state, the chuck table is rotated.

[0005] However, when a cutting tool, which typically cuts along a straight path, cuts along a curved path corresponding to the outer periphery of the workpiece, the workpiece may sometimes break due to stress. Furthermore, cutting along a curved path with a cutting tool takes time, resulting in lower productivity.

[0006] Therefore, the following method is proposed: instead of a cutting tool, a pulsed laser beam with a wavelength absorbed by the workpiece is used to remove the outer periphery of the workpiece with a chamfered portion, and then grinding is performed on the back side (for example, see Patent Document 3).

[0007] Patent Document 1: Japanese Patent Application Publication No. 2004-319885

[0008] Patent Document 2: Japanese Patent Application Publication No. 2003-273053

[0009] Patent Document 3: Japanese Patent Application Publication No. 2006-108532

[0010] However, when the laser beam is irradiated roughly perpendicularly to one side of the workpiece, the laser beam reflected from that side returns to the laser oscillator, causing the laser oscillator to become unstable and potentially resulting in poor processing. Summary of the Invention

[0011] The present invention was made in view of this problem, and its purpose is to suppress the laser beam from returning to the laser oscillator and to use the laser beam to remove the area of ​​the workpiece containing the chamfer.

[0012] According to one aspect of the present invention, a method for processing a workpiece is provided, the workpiece being disc-shaped, wherein the method comprises the following steps: a tape-adhering step, wherein a tape is adhered to one surface of the workpiece, and the workpiece is integrated with a frame by means of the tape; a holding step, wherein after the tape-adhering step, the workpiece is held by a holding unit across the tape; and a laser beam irradiation step, wherein after the holding step, a pulsed laser beam having a wavelength absorbed by the workpiece is irradiated from another surface of the workpiece located opposite to the first surface toward the second surface, wherein the laser beam is irradiated in a ring shape on the second surface with the orientation of the laser beam adjusted to have an incident angle inclined at a predetermined angle relative to the normal of the second surface of the workpiece.

[0013] Preferably, in the holding step, the workpiece is held in the other downward exposed state, and in the laser beam irradiation step, the laser beam is irradiated from below to above.

[0014] In addition, preferably during the laser beam irradiation step, a processing groove with a predetermined diameter is formed on the other side of the workpiece at a position inside the outer periphery, thereby separating the workpiece by the processing groove.

[0015] In addition, preferably, the workpiece has a device area on the other side where multiple devices are formed and an outer peripheral remaining area surrounding the device area. The range of the outer peripheral remaining area extends from the outer periphery of the workpiece to the inner side of a predetermined distance. Furthermore, the workpiece has a circular recess on the other side corresponding to the device area and an annular protrusion surrounding the outer side of the circular recess and corresponding to the outer peripheral remaining area. In the laser beam irradiation step, the laser beam is irradiated at the boundary between the device area and the outer peripheral remaining area on the other side.

[0016] Additionally, preferably, the workpiece has a device area on the other side where multiple devices are formed, and an outer peripheral remaining area surrounding the device area. The range of the outer peripheral remaining area extends from the outer periphery of the workpiece to the inner side at a predetermined distance. Furthermore, the workpiece has a circular recess corresponding to the device area on one side and an annular protrusion surrounding the outer side of the circular recess and corresponding to the outer peripheral remaining area. In the laser beam irradiation step, the laser beam is irradiated onto the outer peripheral remaining area extending from the outer periphery to the inner side at a predetermined distance from the outer periphery, thereby ablating and removing the portion of the workpiece corresponding to the outer peripheral remaining area in the thickness direction.

[0017] In addition, preferably, in the laser beam irradiation step, the laser beam is irradiated onto the other surface while the incident surface of the laser beam is perpendicular to the imaginary surface, and the imaginary surface passes through the center of the other surface and the focal point of the laser beam and is perpendicular to the other surface.

[0018] Alternatively, it is preferable to rotate the holding unit relative to the focal point of the laser beam during the laser beam irradiation step, thereby forming a processing groove perpendicular to the other surface.

[0019] In addition, preferably, in the laser beam irradiation step, with the incident surface of the laser beam parallel to the imaginary surface, the laser beam is irradiated obliquely from the center of the other surface toward the outside of the other surface, and the imaginary surface passes through the center of the other surface and the focal point of the laser beam and is perpendicular to the other surface.

[0020] In addition, it is preferable that in the laser beam irradiation step, the irradiation position of the laser beam is controlled by a current scanner arranged in a manner facing the other surface, thereby irradiating the laser beam in a state in which the incident surface of the laser beam is parallel to the imaginary surface.

[0021] In addition, preferably, in the laser beam irradiation step, a processing groove is formed on the workpiece by the laser beam, and the laser beam irradiation step includes the following detection step: when the processing groove penetrates the workpiece, the laser beam that has passed through the processing groove is detected by a photodetector unit.

[0022] One aspect of the present invention provides a workpiece processing method comprising a laser beam irradiation step, wherein a pulsed laser beam having a wavelength absorbed by the workpiece is irradiated toward another surface of the workpiece. In the laser beam irradiation step, the laser beam is irradiated in a ring shape on the other surface while the orientation of the laser beam is adjusted to have an incident angle tilted at a predetermined angle relative to the normal of the other surface of the workpiece.

[0023] During the laser beam irradiation step, the incident angle of the laser beam is tilted at a specified angle relative to the normal of the other surface of the workpiece. Therefore, even if the laser beam is reflected from the other surface, it can be prevented from returning to the laser oscillator. Consequently, the state of the laser oscillator is less likely to become unstable, thus reducing the possibility of processing defects in laser processing. Attached Figure Description

[0024] Figure 1 It is a flowchart of the processing method.

[0025] Figure 2 (A) is a three-dimensional view of the front side of the workpiece. Figure 2 (B) is a three-dimensional view of the back side of the workpiece.

[0026] Figure 3 This is a diagram showing the pasting steps.

[0027] Figure 4 It is a three-dimensional view of the workpiece unit.

[0028] Figure 5 This is a diagram illustrating the holding steps.

[0029] Figure 6 This is a three-dimensional diagram illustrating one method of laser beam irradiation.

[0030] Figure 7 yes Figure 6 A rough sketch.

[0031] Figure 8 (A) is a diagram showing the formation of the machining groove. Figure 8 (B) is a diagram showing the detection steps.

[0032] Figure 9 (A) is a three-dimensional view of the workpiece in the first modified example. Figure 9 (B) is a cross-sectional view of the workpiece in the first modified example.

[0033] Figure 10 This is a three-dimensional view of the workpiece in the second variation.

[0034] Figure 11 This is a diagram illustrating the laser beam irradiation steps of the third modified example.

[0035] Figure 12 yes Figure 11 A rough sketch.

[0036] Figure 13 This is a diagram illustrating the laser beam irradiation steps of the fourth modified example.

[0037] Figure 14 This is a diagram illustrating the detection steps of the second embodiment.

[0038] Figure 15 Figure (A) is an example of the laser beam irradiation step of the third embodiment. Figure 15 (B) is a diagram illustrating another example of the laser beam irradiation step of the third embodiment.

[0039] Figure 16 This is a partial cross-sectional side view showing the laser processing apparatus of the fourth embodiment.

[0040] Label Explanation

[0041] 2, 32, 42: Laser processing device; 4: Chuck table (holding unit); 4a: Holding surface; 4b: Through-hole; 6: Frame; 8: Perforated plate; 10: Rotation mechanism; 10a: Rotation axis; 11, 31, 41, 43: Workpiece; 11a: Front side (another side); 11b: Back side (one side); 11c: Outer perimeter; 11d: Circular recess; 11e: Annular protrusion; 11f: Normal; 11g: Processing groove; 12: Clamping mechanism; 14: Optical detection unit; 13: Pre-division line; 15: Device; 16: Laser beam irradiation unit Element; 18: Concentrator; 17a: Device area; 17b: Remaining peripheral area; 17c: Boundary; 19: Cutout; 20, 24: Imaginary surfaces; 22, 26: Incident surfaces; 21: Belt; 23: Frame; 25: Workpiece unit; 27: Debris; 28: Current scanner; 34: Holding ring (holding unit); 34a: Rotation axis; 36: Housing; 38: Clamping mechanism; 40: Light source; A1: Center; A2: Concentration 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. Detailed Implementation

[0042] An embodiment of one aspect of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a flowchart of the processing method according to the first embodiment. First, the disc-shaped workpiece 11, which is the object of processing in this embodiment, will be described.

[0043] Figure 2 (A) is a perspective view of the front (other side) 11a side of the workpiece 11. Figure 2 (B) is a perspective view of the back side (one side) 11b of the workpiece 11 located on the opposite side of the front side 11a.

[0044] like Figure 2 As shown in (A), multiple pre-defined dividing lines (spacers) 13 are arranged in a grid pattern on the front side 11a of the workpiece 11, and IC, LSI and other devices 15 are formed in multiple regions divided by the multiple pre-defined dividing lines 13.

[0045] In this embodiment, the workpiece 11 is a silicon wafer, but there are no limitations on the material, structure, size, etc. of the workpiece 11. The workpiece 11 can also be a wafer formed from other semiconductor materials. Similarly, there are no limitations on the type, number, shape, structure, size, etc. of the devices 15.

[0046] A circular device region 17a containing multiple devices 15 exists in the center of the front side 11a. Around the device region 17a, there is an outer peripheral remaining region 17b that does not have any devices 15 formed and is roughly flat compared to the device region 17a.

[0047] The peripheral remaining area 17b is a range on the front side 11a from the outer periphery 11c of the workpiece 11 (excluding the notch 19) to the inner side. For example, in the case of a wafer with a diameter of 12 inches (about 300 mm), the range about 3 mm from the outer periphery 11c is called the peripheral remaining area 17b.

[0048] exist Figure 2 In (A), the boundary 17c between device region 17a and the remaining peripheral region 17b is shown by a single-dotted line. For example... Figure 2 As shown in (B), in the workpiece 11 of this embodiment, there is a circular recess 11d in the center of the back surface 11b side, which is formed by thinning the back surface 11b side to a predetermined thickness.

[0049] The circular recess 11d is the region corresponding to the device region 17a in the thickness direction of the workpiece 11. An annular protrusion 11e is formed on the outside of the circular recess 11d in a manner surrounding the circular recess 11d.

[0050] The annular protrusion 11e is the region corresponding to the remaining outer peripheral region 17b in the thickness direction of the workpiece 11. Additionally, as... Figure 3 As shown, chamfered portions are formed on the outer periphery of both the front side 11a and the back side 11b.

[0051] When processing the workpiece 11, the back side 11b of the workpiece 11 is attached to the center of the circular strip 21, and a metal ring-shaped frame 23 (see reference) is attached to the outer periphery of the strip 21. Figure 3 , Figure 4 (with pasting step S10).

[0052] Figure 3 This diagram illustrates the bonding step S10. The tape 21 has a resin-based substrate layer and an adhesive layer (paste layer) disposed on one entire surface of the substrate layer. The adhesive layer is, for example, formed of a UV-curable resin.

[0053] In the tape pasting step S10, for example, the workpiece 11 is first arranged with the back side 11b facing upwards, and then the frame 23 is arranged on the outer side of the outer periphery of the workpiece 11. Then, the adhesive layer side of the tape 21 is pasted onto the back side 11b of the workpiece 11 and one side of the frame 23.

[0054] Thus, a workpiece unit 25 is formed, which integrates the workpiece 11 and the frame 23 by means of the belt 21 (see reference). Figure 4 ). Figure 4 This is a three-dimensional view of the workpiece unit 25.

[0055] After the pasting step S10, the workpiece unit 25 is attracted and held by the disc-shaped chuck stage (holding unit) 4 provided in the laser processing device 2 (holding step S20) (see reference). Figure 5 ). Figure 5 This is a diagram illustrating step S20.

[0056] Here, the structure of the laser processing apparatus 2 will be described. The chuck table 4 described above is arranged with the holding surface 4a facing downwards. The chuck table 4 has a disc-shaped frame 6 made of metal. A disc-shaped recess is formed in the lower part of the frame 6.

[0057] A disc-shaped porous plate 8 made of porous ceramic 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 on the same plane, forming a generally flat retaining surface 4a.

[0058] A flow path (not shown) is formed in the frame 6. One end of the flow path is connected to an attraction source (not shown) such as an injector, and the other end of the flow path is connected to a perforated plate 8. When the attraction source is activated, negative pressure is transmitted to the holding surface 4a.

[0059] A cylindrical transparent portion 4b is provided in a part of the frame 6 and the perforated plate 8. The transparent portion 4b is formed of a material (e.g., optical glass) that is transparent or light-transmitting to the laser beam L described later.

[0060] The through-hole 4b extends from the lower surface of the perforated plate 8 to the upper surface of the frame 6. In this embodiment, only one through-hole 4b is provided, but multiple through-holes 4b may also be provided discretely along the radial direction of the chuck table 4.

[0061] The upper part of the frame 6 is connected to the output shaft of a rotating mechanism 10, which includes a motor. The rotating mechanism 10 enables the chuck table 4 to rotate around the rotating axis 10a. A horizontal moving mechanism (not shown) is connected to the upper part of the rotating mechanism 10 for moving the rotating mechanism 10 in the X-axis and Y-axis directions.

[0062] A light detection unit 14 is arranged above the chuck stage 4 and on the side of the rotary mechanism 10. The light detection unit 14 is a power meter, a power sensor, a camera with a light reduction filter, etc., and is capable of detecting the laser beam L that has passed through the transmission part 4b.

[0063] Multiple 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 circumference of the chuck table 4. Furthermore, in Figure 5 The image shows two clamping mechanisms 12.

[0064] When the workpiece unit 25 is held by the holding surface 4a with the front side 11a exposed downwards, the back side 11b of the workpiece 11 is held by the holding surface 4a through the belt 21. In addition, the frame 23 is held by the clamping mechanism 12.

[0065] A laser beam irradiation unit 16 is configured below the chuck worktable 4 (see reference). Figure 6 The laser beam irradiation unit 16 includes a laser oscillator (not shown) for generating a pulsed laser beam having a wavelength absorbed by the workpiece 11.

[0066] The laser beam emitted from the laser oscillator is directed upwards toward the holding surface 4a via a defined optical system from the condenser 18, which has a focusing lens. In addition, the condenser 18 is connected to a Z-axis moving mechanism (not shown) that moves the condenser 18 along the Z-axis direction, and an angle adjustment unit (not shown) that adjusts the incident angle of the laser beam.

[0067] The laser processing device 2 is equipped with a control unit (not shown) that controls the movement of the chuck table 4, the laser beam irradiation unit 16, the horizontal movement mechanism (not shown), the Z-axis movement mechanism (not shown), the angle adjustment unit, etc.

[0068] The control unit may be composed of a computer, which includes a processor (processing device) represented by a CPU (Central Processing Unit); main storage devices such as DRAM (Dynamic Random Access Memory), SRAM (Static Random Access Memory), and ROM (Read Only Memory); and auxiliary storage devices such as flash memory, hard disk drives, and solid-state drives.

[0069] The auxiliary storage device stores software containing a prescribed program. Following this software, the processing device and other components operate, thereby realizing the function of the control unit. Next, refer to... Figure 6 and Figure 7 The laser beam irradiation step S30 after holding step S20 will be explained.

[0070] Figure 6 This is a perspective view showing one method of laser beam irradiation step S30. Figure 7 yes Figure 6 A rough sketch. Additionally... Figure 7 With Figure 6 Depicting from different perspectives, in Figure 6 and Figure 7 For ease of explanation, components such as the chuck worktable 4, belt 21, and frame 23 are omitted.

[0071] In the laser beam irradiation step S30, a laser beam L is irradiated onto the front surface 11a of the workpiece 11 from the concentrator 18 located below the workpiece unit 25 (i.e., from the front surface 11a side). That is, the laser beam L is irradiated from below to above.

[0072] 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 the imaginary surface 20 (see reference). Figure 7 The imaginary surface 20 passes through the center A1 of the front surface 11a and the focusing point A2 of the laser beam L and is perpendicular to the front surface 11a.

[0073] In addition, the laser beam L is oriented according to an incident angle α (acute angle) that is tilted at a predetermined angle relative to the normal 11f of the front 11a, and the focusing point A2 is positioned at a point in the boundary portion 17c (annular region).

[0074] In this state, the chuck table 4 is rotated around the rotation axis 10a, thereby irradiating the front surface 11a with a laser beam L, and performing ablation processing along the outer periphery 11c, thereby forming a processing groove 11g in a ring shape along the boundary portion 17c, perpendicular to the front surface 11a (see reference). Figure 8 (A)).

[0075] Figure 8 Figure (A) shows the formation of the processing groove 11g. For example, when the thickness of the workpiece 11 in the device region 17a is 100 μm, the laser processing conditions are as follows.

[0076] Laser medium for laser oscillator: Yb-added optical fiber

[0077] Wavelength: Above 1059nm and below 1065nm

[0078] Repetition frequency: 50kHz

[0079] Average output: 17W

[0080] Machining feed rate: 163 rpm

[0081] Focused light spot diameter: 25μm

[0082] As laser processing progresses, the processing groove 11g gradually deepens. When the processing groove 11g penetrates the workpiece 11, the workpiece 11 is separated into the device region 17a and the outer peripheral remaining region 17b, with the processing groove 11g as the boundary (see reference). Figure 8 (B)

[0083] In the laser beam irradiation step S30 of this embodiment, the laser beam L is irradiated onto the front surface 11a at an incident angle α that is tilted at a predetermined angle relative to the normal 11f of the front surface 11a of the workpiece 11. Therefore, even if the laser beam L is reflected on the front surface 11a, it is reflected at the reflection angle α, which can suppress the laser beam L from returning to the laser oscillator.

[0084] Therefore, the state of the laser oscillator is less prone to instability, thus reducing the possibility of defects in laser processing. Furthermore, by incident the laser beam L at an angle α, the debris 27 is scattered along the travel direction B1 of the laser beam L at the reflection angle α (see reference). Figure 6 , Figure 7 Therefore, it is possible to reduce the adhesion of debris 27 to the condenser lens.

[0085] Furthermore, during laser processing, an air jet nozzle (not shown) can be positioned directly below the center A1 of the front surface 11a to jet air from the center A1 toward the focusing point A2. This more reliably prevents debris 27 generated during ablation from adhering to the device area 17a.

[0086] In addition, the laser beam irradiation step S30 of this embodiment includes the following detection step S35: when the workpiece 11 is penetrated by the processing groove 11g, the laser beam L that has passed through the processing groove 11g is detected by the light detection unit 14. Figure 8 (B) is a diagram showing the detection step S35.

[0087] When the light detection unit 14 receives light of an intensity exceeding a specified value, it sends a specified light-receiving signal to the control unit. Therefore, the light detection unit 14 can automatically detect whether the processing groove 11g is through. After detecting that it is through, the irradiation of the laser beam L is stopped.

[0088] Alternatively, after detection step S35 and before the laser beam L stops irradiating, the following cleaning step can be performed: the laser beam L is made to have a low output compared to the laser processing conditions described above, and the debris attached to the vicinity of the processing tank 11g is removed.

[0089] After laser beam irradiation step S30, the peripheral remaining region 17b, which is separated from the device region 17a in a ring shape, is removed from the belt 21 (removal step S40). For example, at multiple circumferential locations of the peripheral remaining region 17b, the chuck stage 4 is rotated while a wedge (not shown) is inserted between the belt 21 and the back surface 11b. As a result, the peripheral remaining region 17b falls off the belt 21.

[0090] In the removal step S40, instead of a wedge, the claw (not shown) can be lowered at multiple circumferential locations of the remaining outer peripheral region 17b, so that the remaining outer peripheral region 17b falls off the belt 21 while the claw is inserted between the belt 21 and the back surface 11b.

[0091] (First Modification) Next, various modifications of the first embodiment will be described. Figure 9 (A) is a perspective view of the workpiece 31 in the first modified example. Figure 9 (B) is a cross-sectional view of the workpiece 31 of the first modified example.

[0092] In the first modified example, the workpiece 31 does not have a circular recess 11d formed on the back side 11b, which is different from the workpiece 11 described above. The workpiece 31 is similarly subjected to the pasting step S10 to the removal step S40, thereby removing the area including the chamfered portion formed on the outer periphery of the workpiece 31.

[0093] (Second variation) Figure 10 This is a perspective view of the workpiece 41 in the second modified example. No device 15 is formed on the workpiece 41. For example, a processing groove 11g is formed along a predetermined diameter having a diameter smaller than that of the workpiece 41, thereby enabling the formation of a workpiece 43 with a diameter smaller than that of the workpiece 41 from the workpiece 41.

[0094] (3rd Modification) Next, a modification of the laser beam irradiation step S30 will be described. Figure 11 This is a diagram showing the laser beam irradiation step S30 of the third modified example. Figure 12 yes Figure 11 A rough sketch.

[0095] In the laser beam irradiation step S30 of the third variation, the incident surface 26 of the laser beam L is made parallel to the imaginary surface 24, which passes through the center A1 of the front surface 11a and the focusing point A2 of the laser beam L and is perpendicular to the front surface 11a.

[0096] In addition, the laser beam L is oriented according to an incident angle β (acute angle) that is tilted at a predetermined angle relative to the normal 11f of the front 11a, and the focusing point A2 is positioned at a point in the boundary portion 17c (annular region).

[0097] In this state, the chuck table 4 is rotated around the rotation axis 10a, thereby irradiating the laser beam L obliquely from the center A1 of the front face 11a toward the outside of the front face 11a, and performing ablation processing along the outer periphery 11c.

[0098] The laser processing conditions can be the same as those described above. As the laser processing proceeds, the processing groove 11g gradually deepens. When the processing groove 11g penetrates the workpiece 11, the workpiece 11 is separated into the device region 17a and the remaining outer peripheral region 17b with the processing groove 11g as the boundary.

[0099] At this time, the workpiece 11 on the device region 17a side becomes an inverted frustum shape, thus having the following advantages: in the removal step S40, the inner peripheral side surface of the remaining outer peripheral region 17b is less likely to interfere with the outer peripheral side surface of the device region 17a.

[0100] In the laser beam irradiation step S30 of the third variation, the laser beam L is irradiated onto the front surface 11a at an incident angle β that is tilted at a predetermined angle relative to the normal 11f of the front surface 11a of the workpiece 11. Therefore, even if the laser beam L is reflected on the front surface 11a, it is reflected at the reflection angle β, which can suppress the laser beam L from returning to the laser oscillator.

[0101] Therefore, the state of the laser oscillator is less prone to instability, thus reducing the possibility of processing defects in laser machining. Furthermore, by setting the laser beam L to an incident angle β, the debris 27 disperses approximately along the travel direction B2 of the laser beam L at the reflection angle β. Therefore, the adhesion of the debris 27 to the focusing lens can be reduced.

[0102] Furthermore, during laser processing, an air jet nozzle (not shown) can be positioned directly below the center A1 of the front surface 11a to jet air from the center A1 toward the focusing point A2. Additionally, in the third modified example, a detection step S35 can be performed. By performing the detection step S35, it is possible to automatically detect whether the processing groove 11g is through.

[0103] (4th Modification) Next, the 4th modification obtained by modifying the 3rd modification will be explained. Figure 13 This is a diagram showing the laser beam irradiation step S30 of the fourth modification example. In the fourth modification example, similarly to the third modification example, with the incident surface 26 parallel to the imaginary surface 24, the laser beam L is irradiated onto the boundary portion 17c of the front surface 11a. The imaginary surface 24 passes through the center A1 and the focusing point A2 and is perpendicular to the front surface 11a.

[0104] However, in the fourth modification, with the chuck stage 4 stationary and not rotating, a current scanner 28, configured to face the holding surface 4a (i.e., the front surface 11a), is used to control the irradiation position of the laser beam L by scanning the focusing point A2 along the boundary portion 17c. In the fourth modification, the same effect as in the third modification can be achieved. Alternatively, the photodetector unit 14 can be used to perform the detection step S35.

[0105] Next, refer to Figure 14 The second embodiment will be described. In the second embodiment, the laser processing apparatus 32 replaces the chuck stage 4 with a retaining ring (retaining unit) 34. The retaining ring 34 has an annular housing 36 and a plurality of clamping mechanisms 38 discretely disposed around the housing 36.

[0106] The retaining ring 34 is connected to the same rotating mechanism (not shown) as the chuck table 4, and is rotatable about a rotating axis 34a passing through the center of the housing 36. A laser beam irradiation unit 16 is arranged below the retaining ring 34 so as to irradiate the laser beam L upwards.

[0107] The aforementioned light detection unit 14 is arranged on the side opposite to the concentrator 18 of the laser beam irradiation unit 16. The concentrator 18 of the laser beam irradiation unit 16 and the light detection unit 14 are arranged such that the rotation axis 34a is sandwiched in the middle in the horizontal direction. A light source 40 irradiating downwards is arranged above the light detection unit 14.

[0108] The light source 40 is, for example, a laser diode. The laser beam from the light source 40 has a wavelength (e.g., a wavelength in the ultraviolet band) that is difficult to penetrate the workpiece 11 but can pass through the band 21, and has a low output compared to the laser beam L used to process the workpiece 11.

[0109] More specifically, the output of the laser beam from the light source 40 is so small that it does not process the workpiece 11 (i.e., below the processing threshold of the workpiece 11). The laser beam from the light source 40 is directed toward the photodetector unit 14.

[0110] In the second embodiment, when processing the workpiece 11, the tape-attaching step S10 to the removal step S40 are performed sequentially. After the workpiece unit 25 is formed using the tape-attaching step S10, the frame 23 is held by the retaining ring 34, thereby holding the workpiece 11 through the tape 21 (holding step S20).

[0111] Next, similar to the first embodiment, with the incident surface 22 of the laser beam L perpendicular to the imaginary surface 20 (see reference...) Figure 7The laser beam L is oriented according to an incident angle α (acute angle) that is tilted at a predetermined angle relative to the normal 11f of the front face 11a, and the focusing point A2 is positioned at a point on the boundary portion 17c (annular region) (see reference). Figure 6 , Figure 7 ).

[0112] In addition, the retaining ring 34 is rotated around the rotation axis 34a, thereby performing ablation processing along the outer periphery 11c, thereby forming a processing groove 11g in a ring shape along the boundary portion 17c, perpendicular to the front surface 11a.

[0113] Of course, in the second embodiment, the return of the laser beam L to the laser oscillator can also be suppressed, so the state of the laser oscillator is less likely to become unstable. Therefore, the possibility of processing defects in laser processing can be reduced.

[0114] 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, thereby detecting whether the processing groove 11g penetrates the workpiece 11. Figure 14 This is a diagram illustrating the detection step S35 of the second embodiment.

[0115] In this embodiment, a low-output light source 40 can be used for the detection step S35. Therefore, there is no need to configure a light-reducing filter or the like in the light detection unit 14, thus reducing costs. In addition, it is less likely to cause burning in the sensor elements, filters, etc., thus reducing the likelihood of malfunctions in the light detection unit 14.

[0116] Furthermore, in the subsequent removal step S40, a light-shielding plate (not shown) with approximately the same diameter as the circular recess 11d is placed on the belt 21, and then ultraviolet light is irradiated onto the entire back side 11b of the workpiece 11. This reduces the adhesion between the annular protrusion 11e and the belt 21, and the remaining peripheral area 17b, which is separated annularly from the circular recess 11d, is removed from the belt 21 using the aforementioned claws or similar means (removal step S40).

[0117] In addition, in the removal step S40, the remaining peripheral area 17b is removed from the tape 21 after the adhesive force of the tape 21 is reduced, so the device area 17a can be stably attached to the tape 21 and the remaining peripheral area 17b can be easily removed.

[0118] In addition, the same configuration and structure as in the first embodiment can achieve the same effect. Furthermore, the first to fourth variations can be applied to the second embodiment. Next, the third embodiment will be described.

[0119] In the laser beam irradiation step S30 of the third embodiment, the portion corresponding to the remaining peripheral region 17b in the thickness direction of the workpiece 11 is ablated and removed, which is different from the first and second embodiments.

[0120] Figure 15 Figure (A) is an example of the laser beam irradiation step S30 of the third embodiment. Figure 15 In (A), for ease of explanation, the chuck worktable 4, belt 21, frame 23, etc. are omitted.

[0121] exist Figure 15 In the example shown in (A), as in the first embodiment (see reference 1), Figures 6 to 8 In the manner described in (B), with the incident surface 22 of the laser beam L perpendicular to the imaginary surface 20, the laser beam L is irradiated at an incident angle α (acute angle) that is tilted at a predetermined angle relative to the normal 11f of the front surface 11a.

[0122] Thus, the focusing point A2 is positioned at the outer periphery 11c. Furthermore, while rotating the chuck stage 4 around the rotation axis 10a, the rotation axis 10a is slowly moved closer to the focusing point A2 as indicated by arrow C1. Additionally, the height of the focusing point A2 of the laser beam L can be adjusted appropriately.

[0123] Furthermore, the focusing point A2 can be moved from an inner position at a predetermined distance from the outer perimeter 11c to the outer perimeter 11c, allowing the chuck table 4 to rotate instead of move horizontally, and the laser beam irradiation unit 16 to move horizontally. Additionally, if the spot diameter of the focusing point A2 is sufficiently large, the chuck table 4 can be rotated instead of moving horizontally.

[0124] A laser beam L is irradiated onto the remaining peripheral region 17b, extending to a position inside the outer perimeter 11c at a predetermined distance. This removes the portion of the workpiece 11 corresponding to the remaining peripheral region 17b in the thickness direction. Therefore, the removal step S40 can be omitted.

[0125] Furthermore, in the laser beam irradiation step S30, the incident surface 22 of the laser beam L can be made parallel to the imaginary surface 20, thus as in the third modification of the first embodiment (see the following). Figure 11 , Figure 12 In this way, the portion corresponding to the remaining peripheral region 17b in the thickness direction of the workpiece 11 is removed by ablation.

[0126] Figure 15 Figure (B) is a diagram illustrating another example of the laser beam irradiation step S30 of the third embodiment. Figure 15 In (B), for ease of explanation, the chuck worktable 4, etc., are omitted.

[0127] exist Figure 15 In the example shown in (B), such as Figures 11 to 13 In this way, with the incident surface 22 of the laser beam L parallel to the imaginary surface 20, the laser beam L is irradiated at an incident angle β (acute angle) that is tilted at a predetermined angle relative to the normal 11f of the front surface 11a.

[0128] Thus, the focusing point A2 is positioned at the outer periphery 11c. Furthermore, while rotating the chuck stage 4 around the rotation axis 10a, the rotation axis 10a is slowly moved closer to the focusing point A2 as shown by arrow C1. Additionally, the height of the focusing point A2 of the laser beam L can be adjusted appropriately.

[0129] In the third embodiment, it can be as follows Figure 15 As described in (A), by moving the focusing point A2 from the inside to the outside of the workpiece 11, the chuck table 4 can rotate instead of moving horizontally, while the laser beam irradiation unit 16 moves horizontally. Furthermore, if the spot diameter of the focusing point A2 is sufficiently large, the chuck table 4 can rotate instead of moving horizontally.

[0130] A laser beam L is irradiated onto the remaining peripheral region 17b, extending to a position within a predetermined distance from the outer periphery 11c. This allows the portion of the workpiece 11 corresponding to the remaining peripheral region 17b in the thickness direction to be removed. Alternatively, a fourth modification of the first embodiment (see also...) can be performed... Figure 13 Apply the current scanner 28 as described above.

[0131] Next, the fourth embodiment will be described. Figure 16 This is a partial cross-sectional side view showing the laser processing apparatus 42 of the fourth embodiment. In the laser processing apparatus 42, a chuck stage 4 is arranged with the holding surface 4a facing upwards, and a laser beam irradiation unit 16 is arranged above the holding surface 4a.

[0132] In the fourth embodiment, it is also possible to work with the first embodiment (see reference). Figures 6 to 8 (B) of the first embodiment, and the third variation thereof (see reference). Figure 11 , Figure 12 ) or the fourth variation of the first embodiment (see Figure 13 Similarly, a processing groove 11g is formed at the boundary 17c.

[0133] Of course, the workpiece 31 of the first modification of the first embodiment (refer to) can be modified. Figure 9 (A) Figure 9(B)) can be processed to form a workpiece 43 with a smaller diameter from the workpiece 41 of the second modification of the first embodiment (see reference). Figure 10 ).

[0134] Alternatively, the chuck worktable 4 can be replaced as in the second embodiment (see [reference]). Figure 14 Using a retaining ring 34, as in the third embodiment (see embodiment 3), can replace the forming of the machining groove 11g. Figure 15 (A) Figure 15 In the manner described in (B), the portion corresponding to the remaining peripheral region 17b of the workpiece 11 in the thickness direction is removed by ablation.

[0135] In addition, the structure and method of the above embodiments can be appropriately modified and implemented as long as they do not depart from the scope of the purpose of the present invention.

Claims

1. A processing method of a workpiece, the workpiece being in a disc shape, the workpiece being a semiconductor wafer, characterized by comprising: a processing method of the workpiece having steps of: a tape attaching step of attaching a tape to one face of the workpiece and integrating the workpiece with a frame by means of the tape; a holding step of holding the workpiece with a holding unit through the tape after the tape attaching step; and a laser beam irradiation step of irradiating a pulsed laser beam having a wavelength absorbed by the workpiece from the other face side of the workpiece located opposite to the one face to the other face after the holding step, wherein the semiconductor wafer is subjected to ablation processing in the laser beam irradiation step, wherein the laser beam is irradiated in a ring shape on the other face in a state where the orientation of the laser beam is adjusted in such a manner that the incident angle thereof is inclined at a prescribed angle with respect to a normal line of the other face of the workpiece.

2. The processing method of the workpiece according to claim 1, characterized in that, in the holding step, the workpiece is held in a state where the other face is exposed downward, and in the laser beam irradiation step, the laser beam is irradiated from the lower side toward the upper side.

3. The processing method of the workpiece according to claim 1 or 2, characterized in that, in the laser beam irradiation step, a processing groove having a prescribed diameter on the other face side is formed at a position inside the workpiece than the outer periphery, whereby the workpiece is separated with the processing groove as a boundary.

4. The processing method of the workpiece according to claim 1 or 2, characterized in that, the workpiece has a device region in which a plurality of devices are formed on the other face side and an outer peripheral remaining region which surrounds the device region, the outer peripheral remaining region ranging from the outer periphery of the workpiece to a position inside by a prescribed distance, and the workpiece has a circular recess corresponding to the device region and an annular protrusion which surrounds the outer side of the circular recess and corresponds to the outer peripheral remaining region on the one face side, and in the laser beam irradiation step, the laser beam is irradiated to a boundary portion of the device region and the outer peripheral remaining region on the other face side.

5. The processing method of the workpiece according to claim 1 or 2, characterized in that, the workpiece has a device region in which a plurality of devices are formed on the other face side and an outer periphery remaining region which surrounds the device region, the outer periphery remaining region ranging from the outer periphery of the workpiece to a position inside by a prescribed, distance, and the workpiece has a circular recess corresponding to the device region and an annular, protrusion which surrounds the outer side of the circular recess and corresponds to the outer peripheral remaining region, on the one face side, and in the laser beam irradiation step, the laser beam is, irradiated to the outer peripheral remaining region from the outer periphery to a position inside by a prescribed distance from the outer periphery, whereby a portion corresponding to the outer peripheral remaining region in the thickness direction of the workpiece is ablated and removed.

6. The processing method of the workpiece according to claim 1 or 2, characterized in ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ In the laser beam irradiation step, the laser beam is irradiated to the other surface in a state in which an incident plane of the laser beam is perpendicular to an imaginary plane passing through a center of the other surface and a focal point of the laser beam and being perpendicular to the other surface.

7. The method according to claim 6, wherein In the laser beam irradiation step, the holding unit is rotated with respect to the focal point of the laser beam, thereby forming a processing groove perpendicular to the other surface.

8. The method according to claim 1 or 2, wherein In the laser beam irradiation step, the laser beam is obliquely irradiated to the other surface from a center of the other surface toward an outer side of the other surface in a state in which an incident plane of the laser beam is parallel to an imaginary plane passing through the center of the other surface and the focal point of the laser beam and being perpendicular to the other surface.

9. The method according to claim 8, wherein In the laser beam irradiation step, the irradiation position of the laser beam is controlled by a galvanometer scanner arranged so as to face the other surface, thereby irradiating the laser beam in a state in which an incident plane of the laser beam is parallel to the imaginary plane.

10. The method according to claim 1 or 2, wherein In the laser beam irradiation step, a processing groove is formed on the work by the laser beam, and the laser beam irradiation step includes a detection step of detecting the laser beam that has passed through the processing groove by a light detection unit when the processing groove has passed through the work.

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