Method for laser processing of a workpiece
By using alternating laser processing steps and protective components, the problems of device damage and incomplete segmentation caused by channel bending during semiconductor wafer processing are solved, achieving a more efficient processing procedure.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DISCO CORP
- Filing Date
- 2021-11-08
- Publication Date
- 2026-04-10
AI Technical Summary
In the laser processing of semiconductor wafers, the bending of the spacer channels leads to device damage and undivided parts, which are difficult to solve effectively with existing technologies.
Alternating laser processing steps are used to form a modified layer along the spacer starting from both ends of the wafer. Combined with the use of protective components and attraction holding steps, compressive stress is controlled to prevent bending and undivided wafers.
It effectively suppresses the bending of the spacer channel, reduces device damage and incomplete segmentation, improves processing accuracy and production efficiency, and reduces the frequency and time of alignment operations.
Smart Images
Figure CN114535839B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a laser processing method for workpieces. Background Technology
[0002] As a method for dividing a plate-shaped workpiece such as a semiconductor wafer to form a chip, a known method is to focus a laser beam that is transparent to the workpiece and irradiate the interior of the workpiece to form a modified layer, and then divide the workpiece by applying an external force (see, for example, Patent Document 1).
[0003] In this processing method, when the modified layer is formed along the spacer channel formed on the workpiece, the workpiece expands slightly in a direction perpendicular to the direction in which the spacer channel extends. As a result, a cumulative positional shift occurs in the positional relationship between the laser beam focus point and the spacer channel, thus presenting the problem that an alignment operation must be performed midway through processing to correct this positional shift, resulting in reduced productivity.
[0004] To address this issue, a laser processing method has been proposed that utilizes the phenomenon that the workpiece expands in the relatively smaller area during the formation of the modified layer or laser processing groove along the spacer, and finally processes the central area with the largest area (see Patent Document 2). Using this method, the correction (alignment operation) for positional offsets caused by the expansion of the workpiece can be reduced.
[0005] Patent Document 1: Japanese Patent No. 3408805
[0006] Patent Document 2: Japanese Patent Application Publication No. 2008-60164
[0007] However, with the miniaturization of chips in recent years, the compressive stress generated in the processed area has become a significant factor affecting the unprocessed area. Specifically, if a processing method from the outside towards the center of the workpiece is used, as in Patent Document 2, the disruption of the symmetry between the processed and unprocessed areas could cause the spacing channels in the unprocessed area to bend, potentially damaging the device during processing. Furthermore, the compressive stress applied to the central region of the workpiece hinders the formation of the modified layer, making it prone to unsegmentation in the central region. Summary of the Invention
[0008] Therefore, the object of the present invention is to provide a laser processing method for workpieces that can suppress device damage and workpiece incompleteness caused by bending of the spacer.
[0009] According to the present application, there is provided a laser processing method of a workpiece, which performs laser processing on a workpiece provided with a plurality of interval tracks on a front surface along the interval tracks using a laser processing apparatus having: a chuck table which suction-holds the workpiece; a laser beam irradiation unit which has a condenser which irradiates a laser beam on the workpiece held by the chuck table; a processing feed unit which relatively moves the chuck table and the laser beam irradiation unit in a processing feed direction; an indexing feed unit which relatively moves the chuck table and the laser beam irradiation unit in an indexing feed direction; and a control unit which controls each of the units, wherein the laser processing method of the workpiece has: a protective member attaching step of attaching a protective member on the front surface or the back surface of the workpiece; a suction-holding step of suction-holding the protective member side of the workpiece by the chuck table; a positioning step of positioning the workpiece so that a direction in which the interval tracks extend is parallel to the processing feed direction; a first laser processing step of, after the positioning step is performed, positioning a condensing point of the laser beam on an unprocessed and outermost interval track among a plurality of interval tracks provided in one half surface region from one edge to the center in the indexing feed direction of the workpiece, sequentially repeating processing feed of relatively moving the workpiece and the condensing point of the laser beam in the processing feed direction and indexing feed of relatively moving the workpiece and the condensing point of the laser beam in the indexing feed direction perpendicular to the processing feed direction, and performing laser processing on a prescribed number of interval tracks from the unprocessed and outermost interval track toward the inside among the plurality of interval tracks provided in the one half surface region; and a second laser processing step of, after the first laser processing step is performed, positioning the condensing point of the laser beam on an unprocessed and outermost interval track among a plurality of interval tracks provided in another half surface region from the other edge to the center in the indexing feed direction of the workpiece, sequentially repeating the processing feed of relatively moving the workpiece and the condensing point of the laser beam in the processing feed direction and the indexing feed of relatively moving the workpiece and the condensing point of the laser beam in the indexing feed direction perpendicular to the processing feed direction, and performing laser processing on a prescribed number of interval tracks from the unprocessed and outermost interval track toward the inside among the plurality of interval tracks provided in the other half surface region, and alternately repeating the first laser processing step and the second laser processing step to perform laser processing on all of the interval tracks provided in the workpiece.
[0010] It is preferable that the laser processing method of the workpiece further includes a suction holding release step of releasing the suction holding of the workpiece by the chuck table after the first laser processing step and the second laser processing step are performed, and releasing the compressive stress generated on the workpiece; and a re-suction holding step of again performing the suction holding of the workpiece by the chuck table after the suction holding release step.
[0011] The present application can suppress damage of a device and unseparation of a workpiece due to bending of a separation lane. BRIEF DESCRIPTION OF DRAWINGS
[0012] Figure 1 is a perspective view showing a structure example of a laser processing apparatus of the embodiment.
[0013] Figure 2 is a flowchart showing a flow of a laser processing method of the embodiment.
[0014] Figure 3 is a perspective view showing Figure 2 is a perspective view showing an example of the protection member attaching step.
[0015] Figure 4 is a perspective view showing Figure 2 is a side view showing one state of the first laser processing step.
[0016] Figure 5 is a plan view of the workpiece in Figure 4
[0017] Figure 6 is a side view showing a state after the first laser processing step. Figure 2
[0018] Figure 7 is a plan view of the workpiece in Figure 6
[0019] Figure 8 is a plan view of the workpiece in one state of the second laser processing step. Figure 2
[0020] Figure 9 is a plan view of the workpiece in a state after the second laser processing step. Figure 2
[0021] Figure 10 is a graph showing a distribution of compressive stress of a cross section of the workpiece before the suction holding release step. Figure 2
[0022] Figure 11 Figure 2 A graph showing the distribution of compressive stress of the cross section of the work after the suction holding release step.
[0023] Figure 12 is Figure 2 A plan view of the work in a state of the first laser processing step after the re-suction holding step.
[0024] Figure 13 is Figure 2 A plan view of the work in a state of the second laser processing step after the re-suction holding step.
[0025] Figure 14 is Figure 2 A plan view of the work in a state of the second laser processing step after the re-suction holding step.
[0026] Figure 15 is a plan view of a dummy wafer schematically showing a laser processing method of the 1st comparative example.
[0027] Figure 16 is a plan view of a dummy wafer schematically showing a laser processing method of the 1st comparative example. Figure 15 A graph showing the bending state of the dummy wafer.
[0028] Figure 17 is a plan view of a dummy wafer schematically showing a laser processing method of the 2nd comparative example.
[0029] Figure 18 is a plan view of a dummy wafer schematically showing a laser processing method of the 2nd comparative example. Figure 17 A graph showing the bending state of the dummy wafer.
[0030] Figure 19 is a plan view of a dummy wafer schematically showing a laser processing method of the 2nd comparative example.
[0031] Figure 20 is a plan view of a dummy wafer schematically showing a laser processing method of the 2nd comparative example. Figure 19 A graph showing the bending state of the dummy wafer.
[0032] Explanation of Reference Numerals
[0033] 1: laser processing apparatus; 10: chuck table; 20: laser beam irradiation unit; 21: laser beam; 22: condensing point; 40: processing feed unit; 50: indexing feed unit; 90: control unit; 100: work; 101: substrate; 102: front surface; 103: separation lane; 104: device; 105: back surface; 106, 107: half surface region; 110: protective member; 111: frame; 120: modified layer. DETAILED DESCRIPTION
[0034] Embodiments of the present application will be described below in detail with reference to the accompanying drawings. The present application is not limited to the contents described in the following embodiments. In addition, among the structural elements described below, there are included elements that are substantially the same as those that can be easily thought of by those skilled in the art. In addition, the structures described below can be appropriately combined. In addition, various omissions, substitutions, or alterations of the structures can be made within a scope that does not depart from the gist of the present application.
[0035] First, the structure of a laser processing apparatus 1 used in a laser processing method of an embodiment will be described with reference to the drawings. Figure 1 is a perspective view showing a structure example of the laser processing apparatus 1 of the embodiment. In the following description, the X-axis direction is one direction on a horizontal plane. The Y-axis direction is a direction perpendicular to the X-axis direction on the horizontal plane. The Z-axis direction is a direction perpendicular to the X-axis direction and the Y-axis direction. In the laser processing apparatus 1 of the embodiment, the processing feed direction is the X-axis direction, and the indexing feed direction is the Y-axis direction.
[0036] As shown in Figure 1 , the laser processing apparatus 1 has a chuck table 10, a laser beam irradiation unit 20, a processing feed unit 40, an indexing feed unit 50, a condensing point position adjustment unit 60, a photographing unit 70, a display unit 80, and a control unit 90. The laser processing apparatus 1 of the embodiment is an apparatus that processes a workpiece 100 by irradiating the workpiece 100 held by the chuck table 10 with a laser beam 21 by the laser beam irradiation unit 20. The processing of the workpiece 100 by the laser processing apparatus 1 is, for example, a modification layer formation processing that forms a modification layer inside the workpiece 100 by a stealth dicing.
[0037] The workpiece 100 is a wafer such as a semiconductor device wafer, an optical device wafer, or the like, which is a circular plate-shaped wafer having a substrate 101 (see Figure 3 ) made of silicon (Si), sapphire (Al2O3), gallium arsenide (GaAs), silicon carbide (SiC), or the like. In addition, the workpiece 100 is not limited to the embodiment, and can not be circular plate-shaped in the present application. In the embodiment, the workpiece 100 is held by the chuck table 10 in a state of being supported by a protection member 110 and a ring-shaped frame 111.
[0038] The chuck table 10 holds the workpiece 100 by a holding surface 11. The holding surface 11 is a circular plate shape formed of a porous ceramic or the like. In the embodiment, the holding surface 11 is a plane parallel to the horizontal direction. The holding surface 11 is connected to a vacuum attraction source, for example, via a vacuum attraction path. The chuck table 10 suction-holds the workpiece 100 placed on the holding surface 11. A plurality of clamping portions 12 that clamp the frame 111 supporting the workpiece 100 are arranged around the chuck table 10.
[0039] The chuck table 10 is rotated about an axis parallel to the Z-axis direction by a rotation unit 13. The rotation unit 13 is supported by an X-axis direction moving plate 14. The rotation unit 13 and the chuck table 10 are moved in the X-axis direction by a machining feed unit 40 with the aid of the X-axis direction moving plate 14. The rotation unit 13 and the chuck table 10 are moved in the Y-axis direction by an indexing feed unit 50 with the aid of the X-axis direction moving plate 14, the machining feed unit 40, and a Y-axis direction moving plate 15.
[0040] The laser beam irradiation unit 20 is a unit that irradiates the workpiece 100 held by the chuck table 10 with a pulsed laser beam 21. The laser beam irradiation unit 20 has at least a condenser that converges and irradiates the laser beam 21 to the workpiece 100 held by the chuck table 10.
[0041] The machining feed unit 40 is a unit that relatively moves the chuck table 10 and the laser beam irradiation unit 20 in the X-axis direction that is the machining feed direction. In the embodiment, the machining feed unit 40 moves the chuck table 10 in the X-axis direction. In the embodiment, the machining feed unit 40 is provided on the device main body 2 of the laser processing device 1.
[0042] The machining feed unit 40 supports the X-axis direction moving plate 14 so as to be movable in the X-axis direction. The machining feed unit 40 includes a publicly known ball screw 41, a publicly known pulse motor 42, and a publicly known guide rail 43. The ball screw 41 is provided so as to be rotatable about an axis. The pulse motor 42 rotates the ball screw 41 about the axis. The guide rail 43 supports the X-axis direction moving plate 14 so as to be movable in the X-axis direction. The guide rail 43 is fixedly provided on the Y-axis direction moving plate 15.
[0043] The indexing feed unit 50 is a unit that relatively moves the chuck table 10 and the laser beam irradiation unit 20 in the Y-axis direction that is the indexing feed direction. In the embodiment, the indexing feed unit 50 moves the chuck table 10 in the Y-axis direction. In the embodiment, the indexing feed unit 50 is provided on the device main body 2 of the laser processing device 1.
[0044] The indexing feed unit 50 supports the Y-axis direction moving plate 15 so as to be movable in the Y-axis direction. The indexing feed unit 50 includes a publicly known ball screw 51, a publicly known pulse motor 52, and a publicly known guide rail 53. The ball screw 51 is provided so as to be rotatable about an axis. The pulse motor 52 rotates the ball screw 51 about the axis. The guide rail 53 supports the Y-axis direction moving plate 15 so as to be movable in the Y-axis direction. The guide rail 53 is fixedly provided on the device main body 2.
[0045] The condensing point position adjustment unit 60 is a unit that moves the condensing point 22 of the laser beam 21 that has been condensed by the condenser of the laser beam irradiation unit 20 in the direction of the optical axis that is perpendicular to the holding surface 11 of the chuck table 10. More specifically, the condensing point position adjustment unit 60 relatively moves the chuck table 10 and the laser beam irradiation unit 20 in the Z-axis direction that is the condensing point position adjustment direction. In the embodiment, the condensing point position adjustment unit 60 moves the condenser of the laser beam irradiation unit 20 in the Z-axis direction. In the embodiment, the condensing point position adjustment unit 60 is provided to the column 3 that is provided upright from the device main body 2 of the laser processing device 1.
[0046] The condensing point position adjustment unit 60 supports at least the condenser in the laser beam irradiation unit 20 so as to be movable in the Z-axis direction. The condensing point position adjustment unit 60 includes a publicly known ball screw 61, a publicly known pulse motor 62, and a publicly known guide rail 63. The ball screw 61 is provided so as to be rotatable around an axis. The pulse motor 62 causes the ball screw 61 to rotate around the axis. The guide rail 63 supports the laser beam irradiation unit 20 so as to be movable in the Z-axis direction. The guide rail 63 is fixedly provided to the column 3.
[0047] The imaging unit 70 is configured to, for example, image the lower side from directly above the condenser of the laser beam irradiation unit 20. The imaging unit 70 includes a coaxial camera, a CCD (Charge Coupled Device) camera, or an infrared camera.
[0048] The display unit 80 is a display section configured of a liquid crystal display device or the like. The display unit 80 includes a display surface that displays an image imaged by the imaging unit 70, a setting screen of a processing condition, a state of a processing operation, and the like. In a case where the display surface includes a touch panel, the display unit 80 can also include an input section. The input section can accept various operations such as an operation of an operator to register processing content information. The input section can also be an external input device such as a keyboard. The display unit 80 switches information and images displayed on the display surface by an operation from the input section or the like. The display unit 80 can also include a notification section. The notification section notifies an operator of the laser processing device 1 of predetermined notification information by emitting at least one of sound and light. The notification section can also be an external notification device such as a speaker or a light emitting device.
[0049] The control unit 90 controls each of the above-described structural elements of the laser processing device 1 so that the laser processing device 1 performs a processing operation on the workpiece 100. The control unit 90 controls the chuck table 10, the laser beam irradiation unit 20, the processing feed unit 40, the indexing feed unit 50, the condensing point position adjustment unit 60, the imaging unit 70, and the display unit 80.
[0050] The control unit 90 is a computer including an arithmetic processing device as an arithmetic means, a storage device as a storage means, and an input / output interface device as a communication means. The arithmetic processing device includes, for example, a microprocessor such as a CPU (Central Processing Unit). The storage device has a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory). The arithmetic processing device performs various kinds of arithmetic processing in accordance with a prescribed program stored in the storage device. The arithmetic processing device outputs various kinds of control signals to the above-described structural elements via the input / output interface device in accordance with the arithmetic processing result, and performs control of the laser processing device 1.
[0051] Next, a laser processing method of the work 100 according to the embodiment will be described. Figure 2 is a flowchart showing a flow of the laser processing method according to the embodiment. The laser processing method of the work 100 includes a protective member attaching step 201, an attraction holding step 202, a positioning step 203, a first laser processing step 204, a second laser processing step 205, an attraction holding releasing step 206, an end determination step 207, and a re-attraction holding step 208.
[0052] (Protective member attaching step 201)
[0053] Figure 3 is a perspective view showing an example of the protective member attaching step 201 shown in Figure 2 The protective member attaching step 201 is a step of attaching the protective member 110 to the front surface 102 or the back surface 105 of the work 100. In the protective member attaching step 201 according to the embodiment, the protective member 110 is attached to the back surface 105 of the work 100.
[0054] First, the work 100 according to the embodiment will be described in more detail. As shown in Figure 3 The work 100 has a division 103 provided on the front surface 102 of the substrate 101 in a lattice shape and a device 104 formed on a region divided by the division 103. The device 104 is, for example, an integrated circuit such as an IC (Integrated Circuit) or an LSI (Large Scale Integration), an image sensor such as a CCD or a CMOS (Complementary Metal Oxide Semiconductor).
[0055] In the embodiment, the work 100 is formed with a modified layer 120 along the division 103 (see FIG. 1). The modified layer 120 is formed by irradiating the work 100 with laser light. The modified layer 120 is formed by irradiating the work 100 with laser light.Figure 6 ). The processed object 100 is divided into individual devices 104 along the modified layer 120 formed in the separation lane 103, thereby being singulated into chips. In addition, the processed object 100 of the embodiment has an outer diameter of 8 inches and a thickness of 100 μm. In addition, in the embodiment, the chips are square in shape, but in the present application, the chips can also be rectangular in shape.
[0056] In the protective member attaching step 201, first, the protective member 110 is attached to the back surface side of the frame 111. The frame 111 has an opening larger than the outer diameter of the processed object 100. Next, the processed object 100 is positioned at a prescribed position of the opening of the frame 111, and the back surface 105 is attached to the protective member 110. Thereby, the processed object 100 is fixed to the protective member 110 and the frame 111.
[0057] The protective member 110 includes, for example, a base material layer composed of a synthetic resin and a paste layer laminated to the base material layer and composed of a synthetic resin having adhesiveness. The protective member 110 can also have extensibility. In this case, after the modified layer 120 is formed in the processed object 100 along the separation lane 103 (refer to Figure 6 ), the protective member 110 is extended in the planar direction, whereby an external force can be imparted to the processed object 100 to divide it into individual chips.
[0058] (Suction holding step 202)
[0059] The suction holding step 202 is a step of suction holding the processed object 100 on the protective member 110 side by the chuck table 10. In the suction holding step 202 of the embodiment, first, the back surface 105 side of the processed object 100 is held with the holding surface 11 of the chuck table 10 of the laser processing apparatus 1 shown in Fig. 1 through the protective member 110. Next, the frame 111 supporting the processed object 100 is clamped by the clamping portion 12. Next, the processed object 100 placed on the holding surface 11 is suction held by the negative pressure of the vacuum suction source connected to the holding surface 11 through the vacuum suction path. Figure 1
[0060] (Positioning step 203)
[0061] The positioning step 203 is a step of positioning the direction in which the division lines 103 extend in parallel to the machining feed direction (X-axis direction). Here, the division line 103 in parallel to the machining feed direction is a division line 103 among the plurality of division lines 103 in the lattice shape provided on the front surface 102 of the workpiece 100, which forms the modification layer 120 by the machining method of the embodiment. In the embodiment, the positioning of the direction in which the division line 103 extends is performed by rotating the chuck table 10 about the vertical direction axis by the rotation unit 13. When the positioning step 203 is completed, the process shifts to the first laser machining step 204.
[0062] (First laser machining step 204)
[0063] Figure 4 is a side view showing Figure 2 one state of the first laser machining step 204. Figure 5 is Figure 4 a plan view of the workpiece 100 in Figure 6 is a side view showing Figure 2 the state after the first laser machining step 204. Figure 7 is Figure 6 a plan view of the workpiece 100 in
[0064] The first laser machining step 204 is performed after the positioning step 203 is performed. The first laser machining step 204 is a step of performing laser machining of a prescribed number of division lines 103 in one direction toward the indexing direction in parallel to the machining feed direction. In the first laser machining step 204 of the embodiment, the modification layer 120 is formed on the prescribed number of division lines 103 in parallel to the machining feed direction in one direction toward the indexing direction.
[0065] The modification layer 120 refers to a region in which the density, the refractive index, the mechanical strength, or other physical properties become in a state different from the surrounding physical properties. The modification layer 120 is, for example, a fusion-processed region, a crack region, an insulating breakdown region, a refractive index variation region, and a region in which these regions are mixed, and the like. The mechanical strength or the like of the modification layer 120 is lower than other portions of the workpiece 100.
[0066] In the first laser machining step 204, first, the workpiece 100 is imaged by the imaging unit 70, whereby the division lines 103 are detected. If the division lines 103 are detected, the alignment of positioning the division line 103-1 of the workpiece 100 and the focal point 22 of the laser beam 21 is performed as shown in Figure 5 Figure 5 The unprocessed and outermost partition 103-1 in a half-face region 106 from the upper end to the center.
[0067] In the first laser processing step 204, then, as Figure 6 As shown, a pulsed laser beam 21 is focused from the laser beam irradiation unit 20 onto the interior of the workpiece 100 for irradiation. The laser beam 21 is a laser beam with a wavelength that is transparent to the workpiece 100.
[0068] Next, the machining feed in which the workpiece 100 and the focusing point 22 of the laser beam 21 are moved relatively in the machining feed direction, and the indexing feed in which the workpiece 100 and the focusing point 22 of the laser beam 21 are moved relatively in the indexing feed direction perpendicular to the machining feed direction, are repeated sequentially. That is, while the chuck table 10 is moved relatively relative to the laser beam irradiation unit 20, the laser beam 21 is moved from the spacer channel 103-1 of the workpiece 100 toward the inward side ( Figure 5 (below) Irradiate to the interval channel 103-2 (refer to) the specified number of channels. Figure 7 The corresponding part.
[0069] Therefore, as Figure 7 As shown, laser processing is performed on a predetermined number of unprocessed spacer 103-1 located on a half-face region 106 extending from one edge to the center in the indexing feed direction of the workpiece 100, forming a modified layer 120. When the first laser processing step 204 is completed, the process proceeds to the second laser processing step 205.
[0070] (Second laser processing step 205)
[0071] Figure 8 yes Figure 2 A top view of the workpiece 100 in one state of the second laser processing step 205, as shown. Figure 9 yes Figure 2 A top view of the workpiece 100 after the second laser processing step 205, as shown.
[0072] The second laser processing step 205 is performed after the first laser processing step 204. The second laser processing step 205 is a step of performing a predetermined number of laser processing operations on the spacer 103 parallel to the processing feed direction in the opposite direction to the indexing direction. In the second laser processing step 205 of the embodiment, a modified layer 120 is formed on the spacer 103 parallel to the processing feed direction in the opposite direction to the indexing direction, in a predetermined number of directions.
[0073] In the second laser processing step 205, firstly, asFigure 8 As shown, alignment is performed by positioning the spacer 103-3 of the workpiece 100 and the focusing point 22 of the laser beam 21. The spacer 103-3 is set at another edge (in the indexing feed direction (Y-axis direction) of the workpiece 100) Figure 5 The unprocessed and outermost partition 103-3 in the multiple partitions 103 of the other half-area 107 from the lower end of the middle to the center.
[0074] In the second laser processing step 205, a pulsed laser beam 21 is then focused from the laser beam irradiation unit 20 onto the interior of the workpiece 100 for irradiation (see reference). Figure 6 (etc.). Next, the machining feed in which the workpiece 100 and the focusing point 22 of the laser beam 21 are moved relative to each other in the machining feed direction, and the indexing feed in which the workpiece 100 and the focusing point 22 of the laser beam 21 are moved relative to each other in the indexing feed direction perpendicular to the machining feed direction are repeated in sequence. That is, while the chuck table 10 is moved relative to the laser beam irradiation unit 20, the laser beam 21 is moved from the spacer 103-3 of the workpiece 100 toward the inward side ( Figure 8 (above) Irradiate to the spacer 103-4 (refer to) the specified number of channels. Figure 9 The corresponding part.
[0075] Therefore, as Figure 9 As shown, laser processing is performed on a predetermined number of unprocessed and outermost spacer 103-4 spacers 103-4 in the other half-surface region 107 located from the other edge to the center of the indexing feed direction of the workpiece 100, forming a modified layer 120. Furthermore, the number of spacers 103 processed in the second laser processing step 205 is preferably the same as the number of spacers 103 processed in the first laser processing step 204. Upon completion of the second laser processing step 205, the process proceeds to the attraction holding release step 206.
[0076] (Attraction retention release step 206)
[0077] Figure 10 It is shown Figure 2 The diagram shows the distribution of compressive stress in the cross section of the workpiece 100 before the attraction retention release step 206. Figure 11 It is shown Figure 2The diagram shows the distribution of compressive stress in the cross-section of the workpiece 100 after the attraction-hold release step 206. The attraction-hold release step 206 is performed after the first laser processing step 204 and the second laser processing step 205. The attraction-hold release step 206 is a step that releases the compressive stress generated on the workpiece 100 by releasing the attraction holding of the chuck stage 10 on the workpiece 100.
[0078] In the first laser processing step 204 and the second laser processing step 205, a modified layer 120 is formed on the spacers 103-2 and 103-4, thereby causing the workpiece 100 to expand in the indexing feed direction (Y-axis direction). Thus, as... Figure 10 As shown, in the central region 101-1 of the substrate 101 where the modified layer 120 is not formed on the spacer channel 103, the compressive stress increases.
[0079] In the suction hold release step 206, the vacuum suction source connected to the holding surface 11 of the chuck table 10 is controlled to release the suction hold of the workpiece 100 placed on the holding surface 11. Thus, as Figure 11 As shown, the compressive stress generated in the central region 101-1 of the substrate 101 where the modified layer 120 is not formed on the spacer channel 103 is released. When the attraction retention release step 206 is completed, the process proceeds to the end determination step 207.
[0080] (End of judgment step 207)
[0081] End determination step 207 is to determine whether to end. Figure 2 The flowchart illustrates the process method for determining whether the modified layer 120 has been formed in all spacer channels 103 through which the modified layer 120 is formed. If the modified layer 120 has been formed on all spacer channels 103, the process ends. Figure 2 The flowchart shown illustrates the process. If there are gaps 103 in the center of the workpiece 100 where the modified layer 120 has not been formed, the workpiece is transferred to the re-attraction and holding step 208.
[0082] (Re-attract and maintain step 208)
[0083] The re-attraction and holding step 208 is performed after the attraction and holding release step 106, when there are still gaps 103 in the center of the workpiece 100 where the modified layer 120 has not been formed. The re-attraction and holding step 208 is a step in which the workpiece 100 is attracted and held again using the chuck table 10.
[0084] In the re-attracting and holding step 208, the workpiece 100 placed on the holding surface 11 is again attracted and held by the negative pressure of the vacuum attraction source connected to the holding surface 11 of the chuck table 10 through the vacuum attraction path. When the re-attracting and holding step 208 is completed, the process returns to the first laser processing step 204. In addition, in the embodiment, the frame 111 supporting the workpiece 100 is clamped by the clamping portion 12, but in the case where the workpiece 100 is shifted in the horizontal direction with respect to the chuck table 10 in the attracting and holding releasing step 206, the process returns to the positioning step 203 and the alignment is again performed.
[0085] For example, in the case where the vacuum attraction path of the chuck table 10 is divided in accordance with a plurality of regions of the holding surface 11, the holding surface 11 can be attracted in accordance with each region. That is, it is also possible that the attracting and holding is released by the attracting and holding releasing step 206 and the attracting and holding is again performed by the re-attracting and holding step 208 only for the region of the chuck table 10 corresponding to the region in which the laser processing is performed in the first laser processing step 204 and the second laser processing step 205. According to such a method, the attracting and holding of the region including the unprocessed space lane 103 is maintained and the shift in the horizontal direction is suppressed, so that the alignment work of correcting the positional shift can be omitted.
[0086] (First laser processing step 204 after re-attracting and holding step 208)
[0087] Figure 12 is Figure 2 a plan view of the workpiece 100 in a state of the first laser processing step 204 after the re-attracting and holding step 208 shown in
[0088] In the first laser processing step 204 after the re-attracting and holding step 208, first, as shown in Figure 12 , the alignment of positioning the space lane 103-5 of the workpiece 100 and the focal point 22 of the laser beam 21 is performed. The space lane 103-5 is the unprocessed and outermost space lane 103-5 among the plurality of space lanes 103 provided to one half surface region 106 of the workpiece 100. That is, the space lane 103-5 is the space lane 103-5 one lane inward from the space lane 103-2 processed by the previous first laser processing step 204.
[0089] In the first laser processing step 204 after the re-attracted holding step 208, then, the pulsed laser beam 21 is converged from the laser beam irradiation unit 20 to the inside of the workpiece 100 and is irradiated as in the previous first laser processing step 204. Then, the processing feed in which the workpiece 100 and the condensing point 22 of the laser beam 21 are relatively moved in the processing feed direction and the indexing feed in which the workpiece 100 and the condensing point 22 of the laser beam 21 are relatively moved in the indexing feed direction perpendicular to the processing feed direction are sequentially repeated. That is, while the chuck table 10 is relatively moved with respect to the laser beam irradiation unit 20, the laser beam 21 is irradiated from the interval groove 103-5 of the workpiece 100 toward the inside (downward in Figure 12 Figure 13 ) corresponding to a prescribed number of interval grooves 103-6.
[0090] Thus, the laser processing is performed on the interval groove 103-5, which is the outermost interval groove 103-5 and is not processed, of the plurality of interval grooves 103 provided in the one half-face region 106 toward the prescribed number of interval grooves 103-6 on the inside, and the modified layer 120 is formed (refer to Figure 13 ). When the first laser processing step 204 is completed, the second laser processing step 205 is shifted to.
[0091] (Second laser processing step 205 after re-attracted holding step 208)
[0092] Figure 13 is a plan view of the workpiece 100 in a state of the second laser processing step 205 after the re-attracted holding step 208 shown in Figure 2 . Figure 14 is a plan view of the workpiece 100 in a state after the second laser processing step 205 after the re-attracted holding step 208 shown in Figure 2 .
[0093] In the second laser processing step 205 after the re-attracted holding step 208, first, as shown in Figure 13 , the alignment of the interval groove 103-7 of the workpiece 100 and the condensing point 22 of the laser beam 21 is performed. The interval groove 103-7 is the outermost interval groove 103-7 of the plurality of interval grooves 103 provided in the other half-face region 107 of the workpiece 100 and is not processed. That is, the interval groove 103-7 is the interval groove 103-7 one groove on the inside than the interval groove 103-4 processed by the previous second laser processing step 205.
[0094] In the second laser processing step 205 after the suction holding step 208, the pulsed laser beam 21 is then irradiated from the laser beam irradiation unit 20 to the inside of the workpiece 100 as in the previous second laser processing step 205. Then, the processing feed in which the workpiece 100 and the condensing point 22 of the laser beam 21 are relatively moved in the processing feed direction, and the indexing feed in which the workpiece 100 and the condensing point 22 of the laser beam 21 are relatively moved in the indexing feed direction perpendicular to the processing feed direction are sequentially repeated. That is, while the chuck table 10 is relatively moved with respect to the laser beam irradiation unit 20, the laser beam 21 is irradiated from the spacing groove 103-7 of the workpiece 100 toward the inside (upward in FIG. 6) to the portions corresponding to the prescribed number of spacing grooves 103-8. Figure 13
[0095] Thus, as shown in FIG. 6, the laser processing is performed on the spacing grooves 103-8 corresponding to the prescribed number of spacing grooves 103 from the unprocessed and outermost spacing groove 103-7 of the other half-face region 107 toward the inside, and the modification layer 120 is formed. When the second laser processing step 205 is completed, the suction holding release step 206 is again shifted to. Figure 14
[0096] Thus, in the processing method of the workpiece 100 of the embodiment, the first laser processing step 204 and the second laser processing step 205 are alternately repeated, and the laser processing is performed on all of the spacing grooves 103 of the workpiece 100. When it is determined in the end determination step 207 that the laser processing is completed on all of the spacing grooves 103, the process of the flowchart shown in FIG. 6 is ended. Figure 2
[0097] As described above, in the laser processing method of the workpiece 100 of the embodiment, the processing from one end portion side of the workpiece 100 (the first laser processing step 204) and the processing from the other end portion side (the second laser processing step 205) are alternately performed. Thus, the balance (symmetry) of the compressive stress generated from the processed spacing grooves 103 is maintained, and thus the bending of the spacing grooves 103 can be suppressed, and as a result, the damage of the device 104 can be suppressed. In addition, the spacing grooves 103 of the unprocessed region can be suppressed from being shifted in one direction, and thus the effect that the alignment work of correcting the positional shift can be omitted or the frequency of the alignment work can be reduced is exerted.
[0098] In addition, the chuck table 10 can be released from the attraction and holding of the workpiece 100, thereby releasing the compressive stress applied to the central region 101-1 of the workpiece 100, after the machining of the separation lanes 103 of the prescribed number of workpieces 100. Thus, the compressive stress that hinders the formation of the modification layer 120 can be eliminated, and thus the unseparation can be suppressed at the time of the separation into chips.
[0099] Conventionally, in order to separate the unseparated region, a work of assisting the separation of the workpiece by pressing with a squeegee or the like is performed, but by suppressing the unseparation, this work process can be omitted, and thus time saving and space saving can be achieved, and further, the generation of particles at the time of pressing with the squeegee can be suppressed.
[0100] Next, the effects of the embodiment are verified. Figure 15 is a plan view schematically showing a virtual wafer 300 of a laser machining method of a first comparative example. Figure 16 is a view showing Figure 15 the bending state of the virtual wafer 300 shown in Figure 17 is a plan view schematically showing a virtual wafer 300 of a laser machining method of a second comparative example. Figure 18 is a view showing Figure 17 the bending state of the virtual wafer 300 shown in Figure 19 is a plan view schematically showing a virtual wafer 300 of a laser machining method of the embodiment. Figure 20 is a view showing Figure 19 the bending state of the virtual wafer 300 shown in
[0101] The inventors of the present application verified the effects of the laser machining method of the embodiment by performing laser machining on the virtual wafers 300 of the first comparative example, the second comparative example, and the product of the present application shown in Figure 15 , Figure 17 and Figure 19 . The virtual wafer 300 is a wafer formed only of a substrate 301 without forming a device (for example, the device 104 of the workpiece 100 shown in Figure 3 . In the experiment, a wafer having an outer diameter of 8 inches and a thickness of 100 μm was used.
[0102] In addition, in the experiment, the bending state of the virtual wafer 300 was confirmed by measuring the positions in the Y-axis direction of each position in the machining feed direction (X-axis direction) of the front surface of the first position 400 and the second position 500. The first position 400 is one edge (edge 401) of the virtual wafer 300 in the index feed direction (Y-axis direction), and the second position 500 is the other edge (edge 502) of the virtual wafer 300 in the index feed direction (Y-axis direction). Figure 15the upper end in FIG. 8) to a position 50 mm from the other edge toward the center in the other half-face region 307, shown by a single-dot chain line in the figure. Figure 15 the lower end in FIG. 8) to a position 50 mm from the other edge toward the center in the other half-face region 307, shown by a single-dot chain line in the figure.
[0103] In addition, in the graph shown in FIG. 9, the horizontal axis indicates each position in the machining feed direction (X-axis direction), and the vertical axis indicates the position in the Y-axis direction of the front face of the virtual wafer 300. In addition, in the vertical axis, the position in the Y-axis direction of the front face of the virtual wafer 300 before laser machining is set to zero, a positive value indicates a position higher than the position before laser machining, and a negative value indicates a position lower than the position before laser machining. Figure 16 Figure 18 and Figure 20 In the graph shown in FIG. 9, the horizontal axis indicates each position in the machining feed direction (X-axis direction), and the vertical axis indicates the position in the Y-axis direction of the front face of the virtual wafer 300. In addition, in the vertical axis, the position in the Y-axis direction of the front face of the virtual wafer 300 before laser machining is set to zero, a positive value indicates a position higher than the position before laser machining, and a negative value indicates a position lower than the position before laser machining.
[0104] In the graph shown in FIG. 9, the horizontal axis indicates each position in the machining feed direction (X-axis direction), and the vertical axis indicates the position in the Y-axis direction of the front face of the virtual wafer 300. In addition, in the vertical axis, the position in the Y-axis direction of the front face of the virtual wafer 300 before laser machining is set to zero, a positive value indicates a position higher than the position before laser machining, and a negative value indicates a position lower than the position before laser machining. Figure 15 Figure 16 In the graph shown in FIG. 9, the horizontal axis indicates each position in the machining feed direction (X-axis direction), and the vertical axis indicates the position in the Y-axis direction of the front face of the virtual wafer 300. In addition, in the vertical axis, the position in the Y-axis direction of the virtual wafer 300 before laser machining is set to zero, a positive value indicates a position higher than the position before laser machining, and a negative value indicates a position lower than the position before laser machining.
[0105] In the graph shown in FIG. 9, the horizontal axis indicates each position in the machining feed direction (X-axis direction), and the vertical axis indicates the position in the Y-axis direction of the front face of the virtual wafer 300. In addition, in the vertical axis, the position in the Y-axis direction of the virtual wafer 300 before laser machining is set to zero, a positive value indicates a position higher than the position before laser machining, and a negative value indicates a position lower than the position before laser machining. Figure 17 Figure 18 In the graph shown in FIG. 9, the horizontal axis indicates each position in the machining feed direction (X-axis direction), and the vertical axis indicates the position in the Y-axis direction of the front face of the virtual wafer 300. In addition, in the vertical axis, the position in the Y-axis direction of the virtual wafer 300 before laser machining is set to zero, a positive value indicates a position higher than the position before laser machining, and a negative value indicates a position lower than the position before laser machining.
[0106] In the graph shown in FIG. 9, the horizontal axis indicates each position in the machining feed direction (X-axis direction), and the vertical axis indicates the position in the Y-axis direction of the front face of the virtual wafer 300. In addition, in the vertical axis, the position in the Y-axis direction of the virtual wafer 300 before laser machining is set to zero, a positive value indicates a position higher than the position before laser machining, and a negative value indicates a position lower than the position before laser machining. Figure 19 Figure 20 In the graph shown in FIG. 9, the horizontal axis indicates each position in the machining feed direction (X-axis direction), and the vertical axis indicates the position in the Y-axis direction of the front face of the virtual wafer 300. In addition, in the vertical axis, the position in the Y-axis direction of the virtual wafer 300 before laser machining is set to zero, a positive value indicates a position higher than the position before laser machining, and a negative value indicates a position lower than the position before laser machining.
[0107] In the graph shown in FIG. 9, the horizontal axis indicates each position in the machining feed direction (X-axis direction), and the vertical axis indicates the position in the Y-axis direction of the front face of the virtual wafer 300. In addition, in the vertical axis, the position in the Y-axis direction of the virtual wafer 300 before laser machining is set to zero, a positive value indicates a position higher than the position before laser machining, and a negative value indicates a position lower than the position before laser machining. Figure 16 In the first comparative example showing the bending state, the maximum bending amount 401 at the first position 400 is approximately 12 μm, and the maximum bending amount 501 at the second position 500 is approximately 4.5 μm. Figure 18 In the second comparative example showing the bending state, the maximum bending amount 402 at the first position 400 is about 6 μm, and the maximum bending amount 502 at the second position 500 is about 3 μm.
[0108] Compared to these first and second comparative examples, in Figure 20 In the example of the implementation showing the bending state, the maximum bending amount 403 at the first position 400 is about 3 μm, and the maximum bending amount 503 at the second position 500 is about 3 μm.
[0109] Therefore, as Figure 16 , Figure 18 and Figure 20 As shown, the following experimental results were obtained: compared with the virtual wafer 300 processed by the processing methods of each comparative example, the virtual wafer 300 processed by the processing method of the embodiment has less bending after processing. That is, it can be seen that by alternately performing processing from one end side of the workpiece 100 (first laser processing step 204) and processing from the other end side (second laser processing step 205), bending of the spacer 103 can be suppressed, and as a result, damage to the device 104 can be suppressed.
[0110] Furthermore, the present invention is not limited to the embodiments described above. That is, it can be implemented in various modifications without departing from the spirit of the present invention. For example, the attraction-holding release step 206 and the re-attraction-holding step 208 may not necessarily be included. In addition, in the figures used in the description of the embodiments, the device 104 of the workpiece 100, i.e., the divided chip, is square, but in the present invention, the divided chip may also be rectangular.
[0111] For example, the processing method of the present invention may not be used for the interval 103 with a large indexing amount in the indexing feed direction, but may be used for the interval 103 with a small indexing amount in the indexing feed direction. For example, when the chip size is 0.223mm × 10mm, the laser processing apparatus 1 may process the 10mm large indexing side in the first channel without using the processing method of the present invention, and process the 0.223mm small indexing side in the second channel using the processing method of the present invention.
[0112] In this case, in the second passage, the processing is performed by repeating the first laser processing step 204 and the second laser processing step 205 and the suction holding release step 206 of each 12.5 mm from the end of the workpiece 100, for example. Thus, it is possible to divide into individual chips only by expansion.
[0113] In addition, in a case where the processing of the remaining division tracks is performed from the other edge toward the one edge after the processing of the division tracks to the prescribed positions from one edge toward the center of the index feed direction is performed, the division rate is about 50%. In addition, in a case where the processing is performed by repeating the first laser processing step 204 and the second laser processing step 205 and the suction holding release step 206 of each 50 mm, the division rate is about 70%. In addition, in a case where the processing is performed by repeating the first laser processing step 204 and the second laser processing step 205 and the suction holding release step 206 of each 25 mm, the division rate is about 75%.
[0114] In addition, the laser processing device 1 can also be configured to process several mm in each of the first laser processing step 204 and the second laser processing step 205, that is, to automatically determine the timing of switching the processing direction by the control unit 90. The control unit 90 can also acquire the position of a target set at the center of the workpiece 100 from the imaging unit 70 or the like, for example, and perform control to switch the processing direction in a case where the target is shifted by a prescribed amount (for example, 2 μm) or more.
[0115] The target set at the center of the workpiece 100 can be an element included in the pattern surface of the front surface 102 of the workpiece 100, for example, or an element included in the front surface of the grinding mark or the protective member 110 present on the back surface 105, or the like. In a case where the target faces the chuck table 10, observation is performed from below the workpiece 100 using a visible light camera, and in a case where the surface opposite to the surface on which the target is set faces the chuck table 10, observation is performed from below the workpiece 100 using an IR (infrared) camera.
[0116] In addition, in a case where the surface opposite to the surface on which the target is set faces the chuck table 10, it is also possible to perform imaging from above the workpiece 100 using a visible light camera. In a case where imaging is performed from above the workpiece 100, it is not necessary to add an imaging unit for imaging from below the workpiece 100, and thus it is possible to contribute to cost reduction.
[0117] On the other hand, in a case where imaging is performed from below the workpiece 100, it is possible to always monitor the shift of the target while processing is performed, and thus it is not necessary to provide time for shift confirmation, and it is possible to contribute to improvement of the yield.
[0118] As described above, by automatically controlling the switching of the processing direction, the positional deviation of the work 100 can be quantitatively judged, and the processing direction can be switched at an appropriate timing. Thus, the deviation of the non-processed area interval 103 in one direction can be suppressed, and thus the alignment work of correcting the positional deviation can be omitted, or the frequency of the alignment work can be reduced.
[0119] In addition, by the automatic control of the switching of the processing direction, the correction distance in the Y-axis direction that can suppress the minimum limit of the positional deviation can be calculated. Thus, the reduction of the throughput due to the increase of the moving processing in the Y-axis direction accompanying the switching of the processing direction can be suppressed.
[0120] Further, in the mass production process, in the case where a plurality of works 100 that are wafers of the same thickness and the same chip size are sequentially processed, it can be inferred that the appropriate timing of switching the processing direction is substantially the same. Thus, the data of the switching timing calculated at the time of processing the first work 100 can also be applied to the processing of the second and subsequent works 100. Thus, the processing time can be further shortened.
Claims
1. A laser processing method of a workpiece, which performs laser processing on a workpiece provided with a plurality of interval tracks on a front surface along the interval tracks using a laser processing apparatus having: a chuck table which suction-holds the workpiece; a laser beam irradiation unit which has a condenser which irradiates a laser beam on the workpiece held by the chuck table; a processing feed unit which relatively moves the chuck table and the laser beam irradiation unit in a processing feed direction; an index feed unit which relatively moves the chuck table and the laser beam irradiation unit in an index feed direction which is perpendicular to the processing feed direction; and a control unit which controls each of the above units, wherein the laser processing method of the workpiece has the following steps: a protective member attaching step of attaching a protective member on the front surface or the back surface of the workpiece; a suction-holding step of suction-holding the protective member side of the workpiece by the chuck table; a positioning step of positioning the workpiece so that a direction in which the interval tracks extend is parallel to the processing feed direction; a first laser processing step of, after the positioning step is performed, positioning a condensing point of the laser beam on an unprocessed and outermost interval track among a plurality of interval tracks provided from one edge to a central one-half surface area in the index feed direction of the workpiece, sequentially repeating processing feed of relatively moving the workpiece and the condensing point of the laser beam in the processing feed direction and index feed of relatively moving the workpiece and the condensing point of the laser beam in the index feed direction which is perpendicular to the processing feed direction, and performing laser processing on a prescribed number of interval tracks from the unprocessed and outermost interval track toward the inside among the plurality of interval tracks provided in the one-half surface area; and a second laser processing step of, after the first laser processing step is performed, positioning the condensing point of the laser beam on an unprocessed and outermost interval track among a plurality of interval tracks provided from the other edge to the other central half surface area in the index feed direction of the workpiece, sequentially repeating the processing feed of relatively moving the workpiece and the condensing point of the laser beam in the processing feed direction and the index feed of relatively moving the workpiece and the condensing point of the laser beam in the index feed direction which is perpendicular to the processing feed direction, and performing laser processing on a prescribed number of interval tracks from the unprocessed and outermost interval track toward the inside among the plurality of interval tracks provided in the other half surface area, the first laser processing step and the second laser processing step being alternately repeated to perform laser processing on all of the interval tracks provided in the workpiece, the laser processing method of the workpiece further has the following steps: a suction-holding release step of, after the first laser processing step and the second laser processing step are performed, releasing the suction-holding of the workpiece by the chuck table and releasing a compressive stress generated on the workpiece; and a re-suction-holding step of, after the suction-holding release step, suction-holding the workpiece again by the chuck table.
Citation Information
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