PROCESSING METHODS

Abstract

Machining method for a workpiece (10) having a necessary area (62) and a non-necessary area (64), the machining method comprising: a protective wall forming step of irradiating an area defining a boundary between the necessary area (62) and the unnecessary area (64) with a laser beam having a wavelength having transmittability with respect to the workpiece (10), and forming a plurality of shielding tunnels (102, 104) formed of a fine pore (130) and a modified tube (140) surrounding the fine pore (130), thereby forming a protective wall (110), wherein the protective wall forming step comprises a first protective wall forming step of successively forming the shielding tunnels (102) in a planned dividing line (14) with interposition of at least one of the shielding tunnels (102, 104) at corresponding intervals, and a second protective wall forming step of successively forming the shielding tunnels (104) in regions where the distances therebetween are arranged in the planned dividing line (14); and an unnecessary portion (64) removing step of removing the unnecessary portion (64) after performing the protective wall forming step.

Description

BACKGROUND OF THE INVENTIONField of the invention

[0001] The present invention relates to a machining method for a workpiece having a necessary area and an unnecessary area. Description of the state of the art

[0002] A wafer in which a plurality of devices such as integrated circuits (ICs) and large-scale integration (LSI) circuits are formed on a front surface so as to be divided by a plurality of planned dividing lines that intersect each other is divided into individual device chips by a dividing device or a laser processing device, and the device chips obtained by the division are used for electrical devices such as mobile phones and PCs.

[0003] The laser processing apparatus is essentially composed of a chuck table that holds a wafer, an imaging unit that images the wafer held by the chuck table and detects a region to be processed, a laser beam irradiation unit that detects the wafer held by the chuck table with a laser beam, and a processing feed mechanism that performs relative processing feed of the chuck table and the laser beam irradiation unit and can process the wafer with high processing accuracy (see, for example, Japanese Patent Application Laid-Open No. JP 2015-85347 A

[0004] As types of the laser beam irradiation unit, there are a type that irradiates a laser beam having a wavelength with an absorbance with respect to a wafer to perform ablation processing (see, for example, Japanese Patent Application Laid-Open No. 2004-188475); a type that irradiates a laser beam having a wavelength with a transmittance with respect to a wafer to perform internal processing by which a modified layer is formed inside the wafer (see, for example, Japanese Patent Application Laid-Open No. 3408805B2);and a type that performs irradiation with a laser beam having a wavelength having a transmittance with respect to a wafer in such a manner that a value obtained by dividing the numerical aperture (NA) of a light collector by the refractive index (N) of the wafer is in a range of 0.05 to 0.2 and forms shielding tunnels configured of a fine pore and a modified tube surrounding the fine pore inside the wafer (see, for example, Japanese Patent Application Laid-Open No. 2014-221483).

[0005] Further information helpful for understanding the present invention can be found in the following documents: DE 10 2017 212 858 A1 relates to a method for processing a substrate having a first surface and a second surface opposite the first surface, wherein the substrate has on the first surface a component region with a plurality of components which is divided by a plurality of dividing lines.

[0006] JP 2017-41 472 A relates to a method for processing a composite substrate in which two semiconductor substrates are separated along a planned dividing line. DESCRIPTION OF THE INVENTION

[0007] However, in the case where a workpiece is a wafer, for example, in which a plurality of components are formed on a front surface so as to be delimited by planned dividing lines, and a metal layer called a test element group (TEG), which is designed to perform evaluation and organization of the components, is formed on the planned dividing lines, irradiation with a high-set power of a laser beam must be performed when irradiating and processing the planned dividing lines with the laser beam. This raises a problem in that a crack due to the laser beam irradiation develops in a necessary region where the component is formed outside the planned dividing lines, resulting in damage to the component.

[0008] The situation in which the above-described problem occurs is not necessarily limited to the case where the TEG is arranged along the planned division lines. Even if the TEG is not formed along the planned division lines, in some cases, due to the crystal structure of the material constituting a wafer, a crack is likely to be generated in a region outside the planned division line when the planned division line is irradiated with a laser beam. Furthermore, the above-described crack problem may also occur when a wafer is divided into individual device chips by cutting the wafer along the planned division lines with a rotatably held cutting blade.Furthermore, the situation in which such a problem occurs is not limited to the case where laser processing is performed along the planned dividing lines of a wafer in which a plurality of components are formed on a front surface so as to be delimited by the planned dividing lines. Also, when dividing a required region of a specific shape from a plate-shaped workpiece by removing an unnecessary region, a problem may occur in that a crack develops from the unnecessary region side to the necessary region side, and a desired processing result is not obtained.

[0009] Therefore, it is an object of the present invention to provide a machining method by which a desired machining result is achieved without causing a crack to develop to a particular side of the necessary area when machining is performed on a workpiece in which an unnecessary area is removed from the workpiece to obtain the necessary area.

[0010] According to one aspect of the present invention, there is provided a machining method for a workpiece having a necessary region and an unnecessary region. The machining method includes a protective wall forming step of irradiating a region defining a boundary between the necessary region and the unnecessary region with a laser beam having a wavelength having transmissibility with respect to the workpiece, and forming a plurality of shielding tunnels formed of a fine pore and a modified tube surrounding the fine pore, thereby forming a protective wall, and an unnecessary region removing step of removing the unnecessary region after performing the protective wall forming step.

[0011] Preferably, the shielding tunnels formed in the shielding wall forming step are formed such that the modified tubes of the adjacent shielding tunnels are in contact with each other. The shielding wall forming step includes a first shielding wall forming step of sequentially forming the shielding tunnels in a planned parting line with intervals corresponding to at least one of the shielding tunnels therebetween, and a second shielding wall forming step of sequentially forming the shielding tunnels in regions where the intervals are arranged therebetween in the planned parting line. Preferably, the shielding tunnels formed in the first shielding wall forming step and the shielding tunnels formed in the second shielding wall forming step are formed such that steps are alternately performed in a thickness direction of the workpiece.Preferably, the shielding tunnels are layered in the thickness direction in the protective wall formation step.

[0012] Preferably, the protective wall forming step includes a third protective wall forming step of forming shielding tunnels over the shielding tunnels formed in the first protective wall forming step, and a fourth protective wall forming step of forming shielding tunnels over the shielding tunnels formed in the second protective wall forming step when the shielding tunnels are layered in the thickness direction. Preferably, in the protective wall forming step, when the shielding tunnels are layered in the thickness direction, the shielding tunnels of an upper part are layered so as not to contact the shielding tunnels of a lower part.

[0013] Preferably, the workpiece is a wafer in which a plurality of components are formed on a front surface so as to be divided by a plurality of planned division lines that intersect each other, and the necessary region is a region in which the component is formed, and the unnecessary region is a region in which the planned division line is formed. Further, in the protective wall forming step, the protective wall is formed on each of opposite sides of the planned division line defining the width of the planned division line, and in the unnecessary region removing step, a planned division line removal processing is performed to remove the planned division line, which is the unnecessary region encompassed by the pair of protective walls.Preferably, the removal processing of the planned parting line is laser processing by irradiation with a laser beam or cutting processing performed by a cutting blade. Preferably, the wavelength of the laser beam with which the irradiation is performed in the protective wall forming step is 532 nm, and the energy per pulse is 2.0 to 4.0 10 . -5 J and the distance between focal points is 10 to 15 µm.

[0014] The necessary region in the present invention is a region that is used in another step as it is after being divided from the workpiece by laser processing, cutting, or the like, and the unnecessary region is a region that is not used as it is after the processing is performed. For example, the unnecessary region is a discarded region or a region that is subject to recycling in some cases.

[0015] According to the present invention, even if the unnecessary portion is broken by irradiation with the high-power laser beam or by the cutting blade to be removed, generation of a crack in the necessary portion is prevented by the protective wall, and the problem that the necessary portion to be divided is damaged is eliminated.

[0016] The above and other objects, features and advantages of the present invention, as well as the modes of carrying them into effect, will best become apparent and the invention itself will be best understood by studying the following description and appended claims, with reference to the accompanying drawings which illustrate some preferred embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an overall perspective view of a laser machining apparatus capable of performing a machining method according to an embodiment of the present invention; Fig. 2 is a perspective view of a wafer which is a workpiece of the present embodiment; Fig. 3A is a perspective view illustrating a protective wall forming step; Fig. 3B is a perspective view of a wafer unit for which the protective wall forming step is completed; Fig. 3C is a plan view in which a part of the wafer for which the protective wall forming step was performed is enlarged; Fig. 3D is a sectional view in which a part of the wafer for which the first and second protective wall forming steps have been completed is enlarged; Fig. 3E is a schematic perspective view of a shielding tunnel; Fig. 4A is a perspective view of a mold in which a step of removing the unnecessary portion by laser processing is performed; Fig. 4B is a perspective view of the wafer unit for which the step of removing the unnecessary portion is completed; Fig. 5 is a perspective view illustrating a mode in which the step of removing the unnecessary portion is carried out by cutting processing; Fig. 6 is a partially enlarged sectional view illustrating another embodiment of the protective wall forming step; and Fig. 7 is a plan view illustrating another embodiment of the workpiece. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] A laser machining apparatus capable of carrying out a machining method of an embodiment of the present invention will be described below with reference to the accompanying drawings, and thereafter, the machining method of the present embodiment will be described.

[0018] In Fig. 1 shows a perspective overall view of a laser processing device 1. The laser processing device 1 has a holding unit 3 which is arranged above a base 2 and which holds a wafer 10 (see Fig. 2) described later, a moving mechanism 4 that moves the holding unit 3 in an X-axis direction and a Y-axis direction, an imaging unit 6 that images the wafer 10 held by the holding unit 3, and a laser beam irradiation unit 7 that irradiates the wafer 10 held by the holding unit 3 with a laser beam to perform the desired processing. Further, the laser processing apparatus 1 includes a frame body 5 configured from a vertical wall part 5a uprightly disposed on a lateral side of the moving mechanism 4 and a horizontal wall part 5b extending from an upper end part of the vertical wall part 5a in the horizontal direction. The imaging unit 6 and the laser beam irradiation unit 7 are housed and held inside the horizontal wall part 5b.

[0019] As in Fig. 1, the holding unit 3 includes a rectangular X-axis movable platen 31 mounted above the base 2 for movement in the X-axis direction, a rectangular Y-axis movable platen 32 mounted above the X-axis movable platen 31 for movement in the Y-axis direction, a circular cylindrical support column 33 fixed to an upper surface of the Y-axis movable platen 32, and a rectangular cover plate 34 fixed to an upper end of the support column 33. A chuck table 35 is disposed above the cover plate 34 and extends upward through an elongated hole formed on the cover plate 34.The chuck table 35 is a means that holds the wafer 10 using an XY plane, identified based on an X coordinate and a Y coordinate, as a holding surface and is configured to rotate by a rotation drive means housed in the support column 33 and not shown. On an upper surface of the chuck table 35, a suction-adhering chuck 36 is arranged, which forms the holding surface and is made of a porous material having gas permeability. The suction-adhering chuck 36 is connected to suction means (not shown) via a path passing through the support column 33. Four clamps 37 are arranged at equal intervals around the suction-adhering chuck 36, which are used when the wafer 10, to be described later, is held on the chuck table 35.By actuating the suction means, the wafer 10 can be held under suction by the suction-adhering chuck 36.

[0020] The movement mechanism 4 includes an X-axis movement mechanism 4a that moves the above-described chuck table 35 in the X-axis direction, and a Y-axis movement mechanism 4b that moves the chuck table 35 in the Y-axis direction. The X-axis movement mechanism 4a converts a rotary motion of a motor 42a into a linear motion via a ball screw 42b and transmits the linear motion to the X-axis movable platen 31 to move the X-axis movable platen 31 in the X-axis direction along a pair of guide rails 2A arranged along the X-axis direction on the base 2.The Y-axis movement mechanism 4b converts a rotary motion of a motor 44a into a linear motion via a ball screw 44b and transmits the linear motion to the Y-axis movable plate 32 to move the Y-axis movable plate 32 in the Y-axis direction along a pair of guide rails 31a arranged along the Y-axis direction on the X-axis movable plate 31.

[0021] The laser processing apparatus 1 described above is controlled by a controller (not shown). The controller is configured by a computer and includes a central processing unit (CPU) that executes calculation processing according to a control program, a read-only memory (ROM) that stores the control program, etc., a read-write random access memory (RAM) for temporarily storing a detection value obtained by detection, a calculation result, etc., an input interface, and an output interface (a schematic illustration of details is omitted). The imaging unit 6, the laser beam irradiation unit 7, the X-axis moving mechanism 4a and the Y-axis moving mechanism 4b that configure the moving mechanism 4, and so on are connected to and controlled by the controller.

[0022] A workpiece that is machined using the machining method based on the invention is, for example, the one shown in Fig. 2. The wafer 10 has a thickness of about 100 μm, for example, and is a SiC wafer in which a plurality of components 12 are formed on a front surface 10a such that they are divided by a plurality of planned dividing lines 14 that intersect each other. When processed by the laser processing apparatus 1 described above, the wafer 10 is supported via an adhesive tape T by a ring frame F having an opening part Fa that can accommodate the wafer 10, and is loaded into the laser processing apparatus 1 as a unit wafer 13.

[0023] In Fig. 2 is a perspective view in which a portion of the wafer 10 is enlarged. As can be seen from the enlarged perspective view, a TEG 16, which is a metal layer for performing evaluation and organization of the components 12, is disposed on the planned dividing lines 14 formed on the front surface 10a of the wafer 10 of the present embodiment.

[0024] In the processing method of the present embodiment, by performing processing of the wafer 10 as described below, the planned dividing lines 14, which are unnecessary regions in the wafer 10, are removed, and the regions in which the devices 12 are formed as necessary regions are divided into individual chips.

[0025] In the processing method of the present embodiment, first, a protective wall forming step is performed in which regions defining the boundary between the region where the device 12 is formed, which is the necessary region, and the planned dividing line 14, which is the unnecessary region, are irradiated with a laser beam having a wavelength having a transmittance with respect to the wafer 10, and a plurality of shielding tunnels configured from a fine pore and a modified tube surrounding the fine pore are formed, thereby forming protective walls. A method for performing the protective wall forming step in the present embodiment will be described in more detail.

[0026] In carrying out the protective wall forming step, after the wafer 10 described above has been prepared, the wafer 10 is placed over the chuck table 35 of the Fig. 1 and held under suction, and the frame F is clamped and fixed by the clamps 37. Thereafter, the above-described moving mechanism 4 is actuated, and the wafer 10 is positioned directly under the imaging unit 6 and is imaged to detect positional information regarding the components 12 and the planned dividing lines 14 of the wafer 10. Furthermore, based on the positional information, the moving mechanism 4, etc., are actuated, and the predetermined planned dividing line 14 extending in a first direction of the wafer 10 is aligned with the X-axis direction.

[0027] Next, as in Fig. 3A, the wafer 10 is positioned directly under a light collector 71 of the laser beam irradiation unit 7. Then, while the X-axis moving mechanism 4a is actuated to perform processing feed of the wafer 10 in the X-axis direction based on the position information detected by the imaging unit 6, the areas defining the boundary between the device 12 and the planned dividing line 14 are irradiated with a laser beam LB1. Consequently, two strips of protective walls 100 are formed, as shown in Fig. 3C, in which a part of the planned dividing line 14 is shown enlarged. In the present embodiment, the regions defining the boundary between the component 12 and the planned dividing line 14 are regions on both sides of the planned dividing line 14, which define the width of the planned dividing line 14, which is the unnecessary region, as can be seen from Fig. 3C can be seen.

[0028] When irradiating the above-described laser beam LB1, the numerical aperture (NA) of a converging lens constituting the light collector 71 of the laser beam irradiation unit 7 of the present embodiment is set so that a value obtained by dividing the NA by the refractive index (N) of the wafer 10 falls within a range of, for example, 0.05 to 0.2. Further, the wavelength of the laser beam LB1 is set to 532 nm, which is a wavelength having transmittance with respect to the wafer 10. The average output power is set to 0.2 to 0.4 W, and the repetition frequency is set to 10 kHz. The energy per pulse is set to 2.0 to 4.0.10 -5J, and the distance between the focal points is set to 10 to 15 µm. By positioning the focal points on the inside of the wafer 10 and performing irradiation with the laser beam LB1 based on such a laser processing condition, shielding tunnels 102 and 104 are formed as shown in Fig. 3D. As in Fig. 3E, the shielding tunnels 102 and 104 are configured from a fine pore 130 and a modified tube 140 surrounding the fine pore 130. For example, the diameter of the fine pore 130 is about 1 μm, and the diameter of the modified tube 140 is about 10 μm. The above-described protective walls 100 are formed along the planned dividing line 14 by sequentially forming the shielding tunnels 102 and 104 adjacent to each other. The energy per pulse of the laser beam LB1 used for irradiation in forming the protective walls 100 is set to a value high enough so that the protective walls 100 do not become starting points of division when the wafer 10 is divided along the planned dividing lines 14.

[0029] In the training of those in the Fig. 3C and Fig. For example, in the protective walls 100 shown in FIG. 3D, a first protective wall forming step is first performed, in which the shielding tunnels 102 are successively formed with intervals corresponding to at least one shielding tunnel (approximately 10 to 13 µm) interposed along the above-described regions defining the boundary between the component 12 and the planned parting line 14. Thereafter, a second protective wall forming step is performed, in which the shielding tunnels 104 are sequentially formed for the regions where the intervals lie therebetween. That is, the shielding tunnels 102 and the shielding tunnels 104 are alternately formed along the X-axis direction to form the protective walls 100.By performing the first shielding wall forming step and the second shielding wall forming step with interposition of a time interval in the formation of the shielding walls 100 as stated above, the influence of a hot spot caused when irradiation of the laser beam LB1 is carried out to sequentially form adjacent shielding tunnels is avoided, and development of a crack in the required region (region where the device 12 is formed) caused in the formation of the shielding tunnels 102 and 104 can be avoided.

[0030] The purpose of performing the first shielding wall forming step and the second shielding wall forming step with a time interval in the above-described embodiment is to avoid the influence of a hot spot as described above. This is because if only the first shielding wall forming step is performed with the shortened pitch of the shielding tunnels 102, the diffusion of heat generated during the formation of the shielding tunnels 102 is insufficient, and it is impossible to prevent the development of a crack in the required region (region where the device 12 is formed). Preferably, the laser processing condition is the same between the first shielding wall forming step and the second shielding wall forming step. However, other laser processing conditions may be used.

[0031] After two strips of the protective walls 100 formed from the shielding tunnels 102 and 104 are formed along the predetermined planned dividing line 14 in the first direction as described above, the index feed of the wafer 10 is performed in the Y-axis direction, and the planned dividing line 14 adjacent in the Y-axis direction, which has not yet been processed and which extends in the first direction, is positioned directly under the light collector 71. Then, the focus points of the laser beam LB1 are positioned at the inner side of the regions defining the width of the planned dividing line 14 of the wafer 10, and irradiation is performed similarly to the above description to sequentially perform the above-described first protective wall forming step and the second protective wall forming step.

[0032] As a result, the shielding tunnels 102 and 104 are formed to form two strips of the protective walls 100. Similarly, the processing feeding and index feeding of the wafer 10 are performed in the X-axis direction and the Y-axis direction, and two strips of the protective walls 100 are formed along all the planned dividing lines 14 extending in the first direction. Thereafter, the wafer 10 is rotated 90 degrees in a direction indicated by an arrow R1, and the planned dividing lines 14 extending in a second direction orthogonal to the planned dividing lines 14 along which the protective walls 100 have already been formed are aligned in the X-axis direction.Then, the focus points of the laser beam LB1 are positioned and irradiation is carried out in a similar manner as described above also for the inside of the areas defining the boundaries between the remaining components 12 and the planned dividing lines 14, and, as shown in . Fig. 3B, the protective walls 100 are formed corresponding to all the planned parting lines 14 formed on the front surface 10a of the wafer 10. This completes the protective wall forming step of the present embodiment.

[0033] After the above-described protective wall forming step is performed, an unnecessary region removing step is performed in which the planned dividing lines 14, which are the unnecessary regions, are removed. Specifically, the wafer 10 in which the above-described protective walls 100 corresponding to all the planned dividing lines 14 have been formed is conveyed to a laser processing apparatus 20 located in Fig. 4A (only a part of which is shown). The laser processing apparatus 20 includes a holding unit (not shown), a laser beam irradiation unit 21 that irradiates the wafer 10 held by the holding unit with a laser beam LB2, X-axis feeding means that performs processing feeding of the holding unit and the laser beam irradiation unit 21 relatively in the X-axis direction, Y-axis feeding means that performs index feeding of the holding unit and the laser beam irradiation unit 21 relatively in the Y-axis direction orthogonal to the X-axis direction, and rotation driving means that rotates the holding unit (none of which is shown).

[0034] For the wafer 10 conveyed to the laser processing apparatus 20 and held by the holding unit, an alignment step is performed using an alignment means (not shown) arranged in the laser processing apparatus 20, and the position of the planned dividing lines 14 formed on the front surface 10a is detected. In addition, the wafer 10 is rotated by the rotation drive means, and the planned dividing lines 14 in the first direction are aligned with the X-axis direction. Information about the detected position of the planned dividing lines 14 is stored in a controller (not shown).

[0035] Based on the position information regarding the planned dividing lines 14 detected by the above-described alignment step, a light collector 22 of the laser beam irradiation unit 21 is positioned at a processing start position of the predetermined planned dividing line 14 extending in the first direction. Then, the focal point of the laser beam LB2 is positioned on the front surface 10a of the wafer 10, irradiation is performed, and processing feed of the wafer 10 together with the holding unit is performed in the X-axis direction to perform ablation processing along the predetermined planned dividing line 14 extending in the first direction. As a result, a removal groove 200 is formed that divides the wafer 10 along the planned dividing line 14. As shown on the right side of Fig. As shown in FIG. 4A, which shows a part of the wafer 10 in an enlarged view, the removal groove 200 is formed to remove the unnecessary area enclosed by the protective walls 100 formed on both sides, which define the width of the planned dividing line 14. The laser beam LB2 emitted from the laser beam irradiation unit 21 is a laser beam having a wavelength (for example, 355 nm) that has an absorbability with respect to, for example, SiC that configures the wafer 10.

[0036] After the removal groove 200 is formed along the predetermined projected dividing line 14 extending in the first direction as described above, index feeding of the wafer 10 is performed in the Y-axis direction by the pitch of the projected dividing lines 14, and the projected dividing line 14, which is located adjacent to the predetermined projected dividing line 14 in the Y-axis direction and which has not yet been processed, is positioned directly under the light collector 22. Then, the focal point of the laser beam LB2 is positioned on a front surface of the projected dividing line 14 of the wafer 10, and irradiation is performed similarly to the above, and processing feeding of the wafer 10 is performed in the X-axis direction to form the removal groove 200.Similarly, machining feeding and index feeding of the wafer 10 are performed in the X-axis direction and in the Y-axis direction, and the removal grooves 200 are formed along the planned dividing lines 14 extending in the first direction.

[0037] Thereafter, the wafer 10 is rotated 90 degrees in a direction indicated by an arrow R2, and the planned dividing lines 14 extending in a second direction, which is a direction orthogonal to the planned dividing lines 14 in the first direction, in which the removal grooves 200 have already been formed and in which the removal grooves 200 have not yet been formed, are aligned with the X-axis direction. Then, the focal point of the laser beam LB2 is positioned, and irradiation similar to the above description is also performed for the remaining planned dividing lines 14. As a result, the processing of the planned dividing lines to form the removal grooves 200 is carried out along all the planned dividing lines 14 formed in the wafer 10, as shown in Fig. 4B. This separates the components 12 from the wafer 10, and the step of removing the unnecessary area is completed.

[0038] The step of removing the unnecessary portion performed in the present invention is not limited to laser processing by irradiation with the above-described laser beam LB2. For example, the wafer 10 in which the protective walls 100 are formed in all the planned parting lines 14 could be processed into a Fig. 5 (only a part of which is shown), and the step of removing the unnecessary portion could be carried out by the cutting device 50.

[0039] The cutting device 50 includes a chuck table (not shown) that holds the wafer 10 under suction, and a cutting unit 52 that cuts the wafer 10 held under suction by the chuck table. The chuck table is rotatable and includes a moving mechanism (not shown) that moves a processing feed of the chuck table in a Fig. 5 by an arrow X. Furthermore, the cutting unit 52 has a spindle 54 which is rotatably supported by a spindle housing 53 arranged in the Y-axis direction indicated by an arrow Y in Fig. 5, and an annular cutting blade 56 supported by the tip of the spindle 54, and has a Y-axis moving mechanism (not shown) that performs index feeding of the cutting blade 56 in the Y-axis direction. The spindle 54 is rotatably driven by a spindle motor (not shown).

[0040] When performing the unnecessary portion removal step, the wafer 10 is first placed over the chuck table of the cutting device 50 and held under suction with the front surface 10a of the wafer 10 facing upward, and the planned dividing lines 14 extending in the first direction of the wafer 10 are aligned with the X-axis direction. In addition, positional alignment is performed with the cutting blade 56. Thereafter, the cutting blade 56, rotated at high speed, is positioned in the planned dividing lines 14 aligned with the X-axis direction, at the unnecessary portion encompassed by the protective walls 100 formed on both sides and defining the width of the planned dividing line 14, and is caused to cut into the wafer 10 from the front surface 10a side.In addition, machining feed of the chuck table is performed in the X-axis direction to form a removal groove 220 that divides the wafer 10. Furthermore, index feeding of the cutting blade 56 of the cutting unit 52 is performed on the planned dividing line 14 located adjacent in the Y-axis direction to the planned dividing line 14 in which the removal groove 220 has been formed and which does not have the removal groove 220 formed therein, and cutting processing for forming the removal groove 220 is performed similarly to the above. By repeating this, the removal grooves 220 are formed along all the planned dividing lines 14 along the X-axis direction.

[0041] Thereafter, the chuck table is rotated 90 degrees in a direction indicated by an arrow R3, and the second direction orthogonal to the first direction in which the removal grooves 220 were first formed is aligned with the X-axis direction. Then, the above-described cutting processing is performed for all the planned division lines 14 newly aligned with the X-axis direction to form the removal grooves 220 along all the planned division lines 14 formed in the wafer 10. The cutting step is performed in this way, and the removal processing of the planned division line to divide the wafer 10 into component chips of each component 12 along the planned division lines 14 is performed, and the unnecessary region removal step is completed, so that the components 12, which are the necessary regions, are formed similarly to the Fig. 4B shown wafer 10 can be divided.

[0042] As described above, in the present embodiment, before performing the unnecessary region removing step in which the planned dividing lines 14 constituting the unnecessary regions are removed, the regions defining the boundary between the necessary region in which the device 12 is formed and the unnecessary region in which the planned dividing line 14 is formed are irradiated with the laser beam having a wavelength having a transmittance with respect to the wafer 10, and the shielding tunnels 102 and 104 configured from the fine pore and the modified tube surrounding the fine pore are formed to form the protective walls 100.Thus, even if the planned dividing lines 14 are broken to be removed by irradiation with the laser beam having a high power or by the cutting blade, development of a crack in the region where the component 12 is formed, which is the necessary region, is prevented by the protective walls 100, and the problem that damage to the components 12 occurs to be divided individually is eliminated.

[0043] The present invention is not limited to the above-described embodiment. In forming the shielding tunnels in the above-described protective wall forming step, the shielding tunnels may be formed so as to be layered by shifting the position of the focal point in the up-down direction when irradiating the laser beam LB1 in the thickness direction of the wafer 10. For example, in the protective wall forming step performed for the wafer 10 having a thickness of 500 µm, as shown in Fig. 6, the first protective wall forming step of successively forming shielding tunnels 111 in the planned dividing line 14 aligned with the X-axis direction of the wafer 10 is carried out with at least intervals corresponding to one shielding tunnel interposed therebetween, and the second protective wall forming step of successively forming shielding tunnels 112 in the regions where the intervals in the planned dividing line 14 are interposed therebetween is carried out. Thereafter, a third protective wall forming step of forming shielding tunnels 113 may be carried out over the formed shielding tunnels 111, and a fourth protective wall forming step of forming shielding tunnels 114 may be carried out over the shielding tunnels 112 formed in the second protective wall forming step. Fig. In the embodiment illustrated in FIG. 6, a protective wall 110 is formed by performing fifth and sixth protective wall forming steps for forming shielding tunnels 115 and 116 further layered over the shielding tunnels 113 and 114, in addition to the first to fourth protective wall forming steps described above. Further, when irradiating the laser beam LB1 to form the shielding tunnels 111 to 116, the focal point is positioned to be shifted in the up-down direction, and the shielding tunnels 111 to 116 are layered in the thickness direction. In this way, the protective walls 110 that prevent crack development can be effectively formed even in a thick workpiece.

[0044] In the Fig. In the embodiment shown in Fig. 6, when performing the second protective wall forming step after performing the first protective wall forming step, the shielding tunnels 111 formed in the first protective wall forming step and the shielding tunnels 112 formed in the second protective wall forming step are formed so that steps are alternately taken in the thickness direction of the wafer 10. Thereby, when performing processing on a thick workpiece to remove the unnecessary region, the influence of a hot spot is more effectively avoided, and development of a crack in the necessary region is prevented by the protective walls 110. In the present embodiment, steps are alternately performed in the thickness direction even when the shielding tunnels 113 to 116 are formed in the third to sixth protective wall forming steps.When the shielding tunnels are layered in the thickness direction in the first to sixth protective wall forming steps described above, the shielding tunnels of the upper part are layered so that they do not contact the shielding tunnels of the lower part. This can reduce the occurrence of a crack in a case where the shielding tunnels of the upper part are formed to contact the shielding tunnels of the lower part. Furthermore, if the shielding tunnels are formed so that the modified tubes of adjacent shielding tunnels contact each other in the protective wall forming step, the development of a crack from the unnecessary region to the necessary region can be effectively prevented when the unnecessary region removal step is performed.

[0045] Moreover, in the above-described embodiment, the case was described where the workpiece is the wafer 10 in which the plurality of components 12 are formed on the front surface 10a so as to be divided by the plurality of planned dividing lines 14 intersecting each other. However, the present invention is not limited to this. For example, the workpiece may be a circular plate-shaped member 60 made of SiC, which is composed of a necessary region 62 having a substantially rectangular shape in the center, which is located on the left side of Fig. 7, and an unnecessary region 64 on the outer peripheral side surrounding the necessary region 62. When processing the plate-shaped member 60 by the processing method according to the invention, the plate-shaped member 60 is held by an unillustrated ring frame through an adhesive tape and conveyed to the laser processing apparatus 1 described above.Thereafter, the protective wall forming step is performed, in which the focal point of a laser beam having a wavelength, for example, 532 nm, which is transmissible to the plate-shaped member 60 is positioned at the inner side of a region defining the boundary between the necessary region 62 and the unnecessary region 64, irradiation is performed, and the shielding tunnels formed from the fine pore and the modified tube surrounding the fine pore are formed to form a protective wall 120 along the outer periphery of the necessary region 62. A detailed description of this protective wall forming step will be omitted because it is a step performed under similar conditions to the protective walls 100 and 110 of the protective wall forming steps described above.

[0046] After the protective wall 120 is formed as described above, the unnecessary region removing step is performed, in which the unnecessary region 64 surrounding the necessary region 62 is removed along the protective wall 120. The unnecessary region removing step is performed, for example, by laser processing with the laser processing device 20 described above. As shown on the right side of Fig.As shown in Fig. 7, in which a part of the plate-shaped member 60 is enlarged, irradiation with the above-described laser beam LB2 having a wavelength having an absorbance with respect to the plate-shaped member 60 is performed along the outer side of the protective wall 120, and a first removal groove 130 is formed that divides the plate-shaped member 60. Further, a plurality of second removal grooves 132 are formed, extending radially from the above-described first removal groove 130 to the outer peripheral edge of the plate-shaped member 60. By forming the first removal groove 130 and the second removal grooves 132 in this way, the unnecessary region 64 of the plate-shaped member 60 is removed, and only the necessary region 62 can be obtained.At this time, a problem that a crack develops from the unnecessary area 64 to the necessary area 62 and the necessary area 62 is damaged does not occur.

Claims

[1] Machining method for a workpiece (10) having a necessary area (62) and a non-necessary area (64), the machining method comprising: a protective wall forming step of irradiating an area defining a boundary between the necessary area (62) and the unnecessary area (64) with a laser beam having a wavelength having transmittance with respect to the workpiece (10), and forming a plurality of shielding tunnels (102, 104) formed from a fine pore (130) and a modified tube (140) surrounding the fine pore (130), thereby forming a protective wall (110), wherein the protective wall forming step comprises a first protective wall forming step of successively forming the shielding tunnels (102) in a planned dividing line (14) with interposition of at least one of the shielding tunnels (102, 104) at corresponding intervals, and a second protective wall forming step of successively forming the shielding tunnels (104) in regions where the distances therebetween are arranged in the planned dividing line (14); and an unnecessary region (64) removing step of removing the unnecessary region (64) after performing the protective wall forming step. [2] The machining method according to claim 1, wherein the shielding tunnels (102, 104) formed in the protective wall forming step are formed such that the modified tubes (140) of the adjacent shielding tunnels (102, 104) are in contact with each other. [3] The machining method according to claim 1 or 2, wherein the shielding tunnels (102) formed in the first shielding wall forming step and the shielding tunnels (104) formed in the second shielding wall forming step are formed by alternately performing steps in a thickness direction of the workpiece (10). [4] A processing method according to any preceding claim, wherein the shielding tunnels (102, 104) are layered in a thickness direction in the shielding wall forming step. [5] The machining method according to any one of the preceding claims, wherein the shielding wall forming step comprises a third shielding wall forming step of forming shielding tunnels over the shielding tunnels formed in the first shielding wall forming step and a fourth shielding wall forming step of forming shielding tunnels over the shielding tunnels formed in the second shielding wall forming step when the shielding tunnels are layered in the thickness direction. [6] A machining method according to any one of the preceding claims, wherein in the shielding wall forming step, when the shielding tunnels are layered in the thickness direction, the shielding tunnels of an upper part are layered so as not to be in contact with the shielding tunnels of a lower part. [7] A machining method according to any one of the preceding claims, wherein the workpiece (10) is a wafer in which a plurality of components are formed on a front surface so as to be divided by a plurality of planned dividing lines (14) intersecting each other, the necessary area (62) is an area in which the component is formed, and the unnecessary area (64) is an area in which the planned parting line (14) is formed, in the protective wall forming step, the protective wall (110) is formed on each of opposite sides of the planned dividing line (14) defining a width of the planned dividing line (14), and, in the unnecessary area removal step (64), a planned dividing line (14) removal processing is carried out to remove the planned dividing line (14) which is the unnecessary area (64) encompassed by the pair of protective walls. [8] A machining method according to claim 7, wherein the removal machining of the planned parting line (14) is laser machining by irradiation of a laser beam or cutting machining performed by a cutting blade. [9] A machining method according to any one of the preceding claims, wherein the wavelength of the laser beam with which the irradiation is carried out in the protective wall forming step is 532 nm, an energy per pulse is 2.0 to 4.0 10 -5 J and a distance between focal points of 10 to 15 µm.

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