Processing method for wafer

Abstract

To provide a processing method for a wafer that can align a position of a processing groove formed on a surface of a wafer with a position of a modified layer formed in the wafer.SOLUTION: A processing method for a wafer 10 comprises: a processing groove forming step of forming a processing groove 17 that does not completely divide the wafer, from a front surface 12 side of the wafer; a first position memorizing step of photographing the processing groove and a predetermined pattern 31 formed thereby and memorizing a positional relation between the predetermined pattern and the processing groove; a first processing position detecting step of photographing the front surface of the wafer from a rear surface 13 side of the wafer, detecting the predetermined pattern from a photographed image 42 of the wafer, and detecting a position at which the processing groove is formed, on the basis of the positional relation memorized in the first position memorizing step, from the predetermined pattern; and a modified layer forming step of emitting a laser light beam to the position detected in the first processing position detecting step to form a modified layer, inside the wafer corresponding to the processing groove 17.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a wafer processing method. [Background technology]

[0002] In a wafer processing method, when dividing a wafer having a functional layer laminated on the surface of a substrate into multiple chips, the functional layer is first removed from the surface side of the wafer to form a processed groove. Then, a laser beam is irradiated from the back side of the wafer to form a modified layer inside the wafer corresponding to the processed groove. Then, an external force is applied starting from this modified layer to divide the wafer. (See, for example, Patent Document 1.) [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-039014 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional technology, when forming a modified layer on the back side of the wafer, it may be difficult to image and detect the processed groove formed on the front side of the wafer. Therefore, the position of the processed groove and the position of the modified layer may be misaligned, which may lead to defective division of the chip. Therefore, there is a problem to be solved, which is to provide a wafer processing method that can align the position of the processed groove formed on the front side of the wafer with the position of the modified layer formed inside.

[0005] The present invention has been made in consideration of the above points, and aims to provide a wafer processing method that can align the position of a processing groove formed on the front surface side of the wafer with a modified layer formed inside. [Means for solving the problem]

[0006] The wafer processing method of the present invention is a wafer processing method for processing a wafer having at least one pattern formed in an area partitioned by a plurality of planned dividing lines on the front side of a substrate along the planned dividing lines, the method including a groove forming step of holding the rear side of the wafer on a first holding table and forming a groove that does not completely divide the wafer from the front side of the wafer, a first position storing step of imaging the groove and the pattern formed around the groove and storing the positional relationship between the pattern and the groove, and a step of storing the positional relationship between the pattern and the groove after the first position storing step. the back side of the wafer is held on a second holding table, the front side of the wafer is imaged from the back side of the wafer, the pattern is detected from the imaged image, and the position at which the processed groove is formed is detected from the pattern based on the positional relationship stored in the first position storage step; a modified layer forming step of irradiating a laser beam to the position detected in the first processed position detection step to form a modified layer inside the wafer corresponding to the processed groove; and a dividing step of applying an external force to the wafer to divide the wafer along the modified layer into a plurality of chips.

[0007] The wafer processing method of the present invention is a wafer processing method for processing a wafer having a plurality of planned dividing lines on a front surface side of a substrate along the planned dividing lines, the method including: a processing groove forming step of holding the back surface side of the wafer on a first holding table and forming a processing groove that does not completely divide the wafer from the front surface side of the wafer; a first center calculation step of calculating a center position of the wafer while the wafer is held on the first holding table; a second position storage step of storing a positional relationship between the center position calculated in the first center calculation step and the processing groove; a second processing position detection step of detecting a position at which the processing groove is formed based on the positional relationship stored in the second position storage step from the center position calculated in the second center calculation step; a modified layer formation step of irradiating a laser beam to the position detected in the second processing position detection step to form a modified layer inside the wafer corresponding to the processing groove; and a division step of applying an external force to the wafer to divide the wafer along the modified layer into a plurality of chips. Effect of the Invention

[0008] According to the present invention, it is possible to provide a wafer processing method capable of aligning a processed groove formed on the front surface side of a wafer with a modified layer formed therein. [Brief description of the drawings]

[0009] [Figure 1] 1 is a perspective view of a wafer to be processed by a processing method according to an embodiment of the present invention. [Diagram 2] FIG. 1 is a diagram showing an example of a processing apparatus for performing a wafer processing method. [Diagram 3] 11A to 11C are diagrams illustrating an example of a processed groove forming step. [Figure 4] FIG. 11 is a diagram showing an example of a first position storage step. [Diagram 5] FIG. 11 is a diagram illustrating an example of a first processing position detection step. [Figure 6]11A to 11C are diagrams illustrating an example of a modified layer forming step. [Figure 7] FIG. 11 is a diagram illustrating an example of a division step. [Figure 8] FIG. 11 is a diagram illustrating an example of a second position storage step. [Figure 9] FIG. 11 is a diagram illustrating an example of a second processing position detection step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the wafer processing method according to the present embodiment will be described with reference to the accompanying drawings. FIG. 1 is a perspective view of a wafer processed by the processing method according to the present embodiment. FIG. 2 is a diagram showing an example of a processing apparatus for carrying out the wafer processing method. FIG. 3 is a diagram showing an example of a processed groove forming step. FIG. 4 is a diagram showing an example of a first position storing step. FIG. 5 is a diagram showing an example of a first processed position detecting step. FIG. 6 is a diagram showing an example of a modified layer forming step. FIG. 7 is a diagram showing an example of a division step. FIG. 8 is a diagram showing an example of a second position storing step. FIG. 9 is a diagram showing an example of a second processed position detecting step.

[0011] First Embodiment The wafer processing method according to the first embodiment includes a processed groove forming step, a first position storing step, a first processed position detecting step, a modified layer forming step, and a dividing step.

[0012] The X-axis, Y-axis, and Z-axis directions shown in each figure are perpendicular to each other. The X-axis and Y-axis directions are approximately horizontal, and the Z-axis direction is up-down (vertical). In each figure, of the two arrows indicating the X-axis direction, the +X side is the left, and the -X side is the right. Of the two arrows indicating the Y-axis direction, the +Y side is the front, and the -Y side is the rear. Of the two arrows indicating the Z-axis direction, the +Z side is the up, and the -Z side is the down.

[0013] The wafer 10 shown in FIG. 1 is a disk-shaped semiconductor workpiece having a substrate 11 made of, for example, silicon. The substrate 11 has a front surface 12 and a back surface 13. On the front surface 12 side of the substrate 11, chips 15, which are electronic devices, are formed in a plurality of regions defined by a plurality of lattice-like dividing lines 14. In FIG. 1, only some of the lattice-like dividing lines 14 are shown. Note that the wafer 10 to which the present invention is applied is not limited to a semiconductor workpiece. At least one or more patterns, which will be described later, are formed in the region defined by the plurality of dividing lines 14. The wafer is not limited to the configuration shown in FIG. 1 as long as it has a configuration capable of implementing the wafer processing method of the present embodiment.

[0014] A functional layer 16 is provided on the surface 12 of a substrate 11 constituting a wafer 10. The functional layer 16 constitutes the surface 12 side of the chip 15. A processed groove 17 is formed on the surface 12 side of the wafer 10 along the intended division lines 14. The processed groove 17 is a groove that penetrates the functional layer 16 and has a shape recessed from the surface 12 of the wafer 10 (recessed from the surface 12).

[0015] The functional layer 16 includes a low dielectric constant insulating film (hereinafter referred to as a low-k film) made of an inorganic film such as SiOF, BSG (Borosilicate Glass) (SiOB), or an organic film such as a polymer film of a polyimide system or a parylene system, and a conductor film made of a conductive metal. The low-k film is laminated with the conductor film to form the chip 15. The conductor film forms the circuit of the chip 15. For this purpose, the chip 15 is composed of the low-k films laminated on each other and the conductor film laminated between the low-k films. The functional layer 16 of the planned division line 14 is composed of the low-k film and does not include a conductor film.

[0016] A central portion of a tape (support member) T is attached to the wafer 10, and a ring-shaped frame 25 (see FIG. 7 described later) is attached to the outer periphery of the tape T. The wafer 10 is carried into the processing device 1 while being supported by the frame 25 via the tape T.

[0017] As shown in FIG. 2, the processing apparatus 1 includes at least a first laser beam application unit 20, a second laser beam application unit 21, a first holding table 23, a second holding table 24, a first imaging unit 27, a second imaging unit 28, and an expansion unit 29. The processing apparatus 1 is not limited to the configuration shown in FIG. 2. A control unit 100 is connected to the processing apparatus 1. The processing apparatus 1 is configured to relatively move the first laser beam application unit 20 that applies a laser beam and the first holding table 23 that holds the wafer 10 to form a processed groove 17 by laser processing the wafer 10. The processing apparatus 1 is also configured to relatively move the second laser beam application unit 21 that applies a laser beam and the second holding table 24 that holds the wafer 10 to form a modified layer 18 by laser processing the wafer 10.

[0018] The first laser beam application unit 20 irradiates a laser beam (pulse laser) oscillated from an oscillator (not shown) toward the wafer 10 held on the first holding table 23. The laser beam irradiated from the first laser beam application unit 20 has a wavelength that is absorbed by the wafer 10, and the laser beam is focused on the surface 12 of the wafer 10 to form a processing groove 17.

[0019] The first laser beam application unit 20 performs ablation processing on the wafer 10 on the first holding table 23. The first laser beam application unit 20 forms a processing groove 17 by concentrating a laser beam of an absorptive wavelength along the division line 14 of the wafer 10. Note that ablation refers to a phenomenon in which, when the irradiation intensity of a laser beam reaches a predetermined processing threshold or more, the laser beam is converted into electronic, thermal, optical, and mechanical energy on a solid surface, resulting in the explosive release of neutral atoms, molecules, positive and negative ions, radicals, clusters, electrons, and light, and the solid surface is sublimated and etched. In the processing device 1, the first holding table 23 is moved in the processing feed direction relative to the first laser beam application unit 20, thereby performing ablation processing along the division line 14 of the wafer 10.

[0020] A first imaging unit 27 that captures an image of the front surface 12 of the wafer 10 is provided on the side of the first laser beam application unit 20. Based on the image captured by the first imaging unit 27, a processing head (not shown) of the first laser beam application unit 20 and the wafer 10 are aligned.

[0021] The second laser beam application unit 21 irradiates a laser beam (pulse laser) oscillated from an oscillator (not shown) toward the wafer 10 held on the second holding table 24. The laser beam irradiated from the second laser beam application unit 21 has a wavelength that is transparent to the wafer 10, and the laser beam is focused inside the wafer 10 to form a pulse mark.

[0022] Inside the wafer 10, pulse marks are continuously formed along the dividing lines 14, forming modified layers 18 that serve as dividing starting points on the wafer 10. That is, dividing starting points that are processed grooves 17 or modified layers 18 formed inside the wafer 10 are formed along the dividing lines 14. The dividing lines 14 are formed in a lattice pattern on the surface 12 of the wafer 10, and chips 15 are formed in each area partitioned by the dividing lines 14. The modified layer 18 is formed, for example, by irradiating the wafer 10 along the dividing lines 14 with a laser beam that has a wavelength that transmits the wafer 10 and has a focal point positioned inside the wafer 10. The modified layer 18 refers to a region in which the density, refractive index, mechanical strength, and other physical properties inside the wafer 10 are different from those of the surrounding area due to irradiation with a laser beam, and the strength is lower than that of the surrounding area. The modified layer 18 may be, for example, a melting process area, a crack area, an insulation breakdown area, a refractive index change area, or a mixture of these.

[0023] The processing apparatus 1 is controlled by a control unit 100. The control unit 100 has a processing unit 101 (processor) that generates signals for controlling each part of the processing apparatus 1, and a storage unit 102 that stores various information used in the processing unit 101. The storage unit 102 is composed of one or more storage media such as a ROM (Read Only Memory) and a RAM (Random Access Memory) depending on the application. A program for executing a processing method for the wafer 10 is stored in the storage unit 102. The processing unit 101 executes the processing method for the wafer 10 by reading and executing the program stored in the storage unit 102.

[0024] An optical system of the processing device 1 is provided in the first laser beam application unit 20. Note that the optical system of the processing device 1 is not limited to the configuration formed in the first laser beam application unit 20.

[0025] First Embodiment A description will now be given of a first embodiment of a wafer processing method using the processing apparatus 1 configured as above. The first embodiment of the wafer processing method includes a processing groove forming step, a first position storing step, a first processing position detecting step, a modified layer forming step, and a dividing step.

[0026] (Groove formation step) The groove forming step according to the first embodiment will be described with reference to Fig. 3. The groove forming step is performed by the control unit 100 controlling the first laser beam application unit 20. As shown in Fig. 3, in the groove forming step, the back surface 13 of the wafer 10 is held on the first holding table 23 with the back surface 13 facing downward and the front surface 12 facing upward. The first holding table 23 can stably hold the wafer 10 by suction or the like.

[0027] Then, the first laser beam application unit 20 located above the first holding table 23 applies a laser beam La having a wavelength that is absorbent to the wafer 10. The focal point of the laser beam La is set at a predetermined position on the front surface 12 side of the wafer 10. In the area irradiated with the laser beam La, the functional layer 16 (Low-k film) of the wafer 10 is removed by ablation, and as a result, a laser grooving (LG) groove is formed. This laser grooving groove becomes the processed groove 17. As a result, the processed groove 17 is formed at a depth that does not completely divide the wafer 10 from the front surface 12 side of the wafer 10. The depth that does not completely divide the wafer 10 means a depth that does not penetrate the wafer 10. The relative positions of the first holding table 23 and the first laser beam application unit 20 are changed in the horizontal direction, and the processed groove forming step is completed when the processed grooves 17 are formed along all the planned division lines 14.

[0028] (First position storage step) The first position storage step will be described with reference to Fig. 4. The first position storage step is performed by the control unit 100 controlling the first imaging unit 27. Fig. 4(1) shows a cross-sectional view of the wafer 10 in the first position storage step, Fig. 4(2) shows a wafer image 32 of the wafer 10 acquired by the first imaging unit 27 in the first position storage step, and Fig. 4(3) shows a top view of the wafer 10 in the first position storage step. The wafer image 32 corresponds to the image.

[0029] 4(1), in the first position memorizing step of the first embodiment, similarly to the machining groove forming step, the back surface 13 of the wafer 10 is held on a first holding table 23 with the back surface 13 facing downward and the front surface 12 facing upward. The first holding table 23 can stably hold the wafer 10 by suction or the like.

[0030] A predetermined target pattern (31 in FIG. 4) is formed on the front surface 12 of the wafer 10. The shape of the pattern is an example, and has a characteristic shape that serves as a key pattern of planar shape and color that can be detected and identified in the wafer image 32 captured by the first imaging unit 27. In the first position storage step, the pattern formed on the wafer 10 serves as a mark for forming the processing grooves 17 along the planned division lines 14. In this embodiment, the pattern is formed in a cross shape.

[0031] Then, as shown in Fig. 4(2), in the first position storage step according to the first embodiment, the control unit 100 controls the first imaging unit 27 arranged above the first holding table 23 to capture an image of the front surface 12 side of the wafer 10 and acquire a wafer image 32. The wafer image 32 includes the groove 17 and a pattern 31 corresponding to the cross pattern formed around the groove 17. Then, the control unit 100 stores the pattern 31 formed on the wafer 10 and the positional relationship between the pattern 31 and the groove 17 in the storage unit 102 based on the wafer image 32 acquired by the first imaging unit 27.

[0032] In the first position storage step, the control unit 100 captures an image of the front surface 12 side of the wafer 10 with the first imaging unit 27 to obtain a wafer image 32. Then, the control unit 100 performs pattern matching based on the obtained wafer image 32 to detect a predetermined pattern 31 that is to be a target.

[0033] A process (teaching operation) is performed to register the position information of the groove 17 in the control unit 100 based on the detected pattern 31. In the teaching operation, an image of the pattern 31 is stored in the memory unit 102 of the control unit 100 as pattern information. In addition, the control unit 100 stores the distance information from the pattern 31 to the groove 17 in the memory unit 102. As shown in FIG. 4(2), the control unit 100 detects the distance Ra from the pattern 31 to the groove 17 as a positional relationship through the teaching operation in the first position storage step. Then, the control unit 100 stores the distance Ra between the pattern 31 formed on the wafer 10 and the planned division line 14 as information on the positional relationship in the memory unit 102 based on the detected distance from the pattern 31 to the groove 17. The teaching operation determines the positional relationship of the groove 17 to the pattern 31 formed on the wafer 10. That is, by locating the pattern 31 on the wafer 10 by the first imaging unit 27, the processing device 1 can recognize the position of the processing groove 17 on the wafer 10 to be processed, as shown in Fig. 4 (3). In the first position storage step, the first imaging unit 27 captures an image of the front surface 12 side of the wafer 10, and a wafer image 32 is acquired. As a result, the acquired wafer image 32 clearly shows the processing groove 17 formed on the front surface 12 side.

[0034] (First processing position detection step) The first processing position detection step will be described with reference to Fig. 5. The first processing position detection step is performed by the control unit 100 controlling the second imaging unit 28. Fig. 5(1) shows a cross-sectional view of the wafer 10 in the first processing position detection step, Fig. 5(2) shows a wafer image 42 of the wafer 10 acquired by the second imaging unit 28 in the first processing position detection step, and Fig. 5(3) shows a bottom view of the wafer 10 in the first processing position detection step. The wafer image 42 corresponds to the image.

[0035] 5(1), in the first processing position detection step according to the first embodiment, after the first position storage step, the wafer 10 is transported by a transport arm (not shown) or the like, and the front surface 12 of the wafer 10 is held on the second holding table 24 with the front surface 12 of the wafer 10 facing downward and the back surface 13 facing upward. The second holding table 24 can stably hold the wafer 10 by suction or the like. In this case, the processing groove 17 formed in the wafer 10 is disposed downward.

[0036] A predetermined target pattern 31 is formed on the front surface 12 of the wafer 10. In the first processing position detection step, the pattern 31 formed on the wafer 10 serves as a mark for forming the modified layer 18 along the intended dividing lines 14.

[0037] 5(2), in the first processing position detection step according to the first embodiment, the control unit 100 controls the second imaging unit 28 arranged above the second holding table 24 to capture an image of the back surface 13 side of the wafer 10 and acquire a wafer image 42. The wafer image 42 includes the processed groove 17 and the pattern 31 formed around the processed groove 17. The control unit 100 detects the pattern 31 formed on the wafer 10 based on the wafer image 42 acquired by the second imaging unit 28.

[0038] In the first processing position detection step, the control unit 100 captures an image of the back surface 13 side of the wafer 10 with the second imaging unit 28 to obtain a wafer image 42. Then, the control unit 100 performs pattern matching on the wafer image 42 captured and obtained by the second imaging unit 28 to detect the pattern 31 formed on the wafer 10.

[0039] In the first processing position detection step, the second imaging unit 28 captures an image of the back surface 13 of the wafer 10, and a wafer image 42 is obtained. The pattern 31 formed on the wafer 10 is made of a material that does not transmit light, such as metal. Therefore, even when the second imaging unit 28, which is made of an infrared camera or the like, captures an image from the back surface 13 of the wafer 10, the pattern 31 formed on the front surface 12 is clearly reflected in the wafer image 42. On the other hand, since the processed groove 17 is shallowly formed, when the wafer 10 is captured from the back surface 13, the processed groove 17 formed on the front surface 12 of the wafer 10 is only faintly reflected in the wafer image 42. For this reason, when the front surface 12 of the wafer 10 is held on the second holding table 24 with the front surface 12 of the wafer 10 facing downward and the back surface 13 facing upward in order to form the modified layer 18 in the modified layer formation step described later, the position of the processed groove 17 cannot be accurately recognized. Although the processed groove 17 is processed by irradiating a laser beam at a position a predetermined distance away from the pattern 31 set by the teaching operation, some positional deviation occurs depending on the positioning accuracy of the first holding table 23 and the second laser beam application unit 21, so if alignment is performed based on the pattern 31, there is a risk that the position of the modified layer 18 will be misaligned with respect to the processed groove 17.

[0040] Therefore, the control unit 100 detects the position where the processed groove 17 is formed, based on the pattern 31 detected in the first processing position detection step, using information on the positional relationship between the pattern 31 and the processed groove 17 that is actually measured after the formation of the processed groove 17 and that is stored in the first position storage step. As shown in Fig. 5 (2), the pattern 31 formed on the wafer 10 is clearly reflected in the wafer image 42 captured from the front surface 12 side of the wafer 10. Therefore, in the first processing position detection step, the control unit 100 detects the position where the processed groove 17 is formed (processing position) based on this clear pattern 31 and the distance Ra, which is the information on the positional relationship that is stored in the first position storage step.

[0041] In the first processing position detection step, after detecting the processing position where a processing groove 17 corresponding to one planned division line 14 is formed, the processing position where a processing groove 17 corresponding to another planned division line 14 is formed may be calculated based on the size of the chip 15 (chip size).

[0042] Specifically, in the first position storage step, the control unit 100 first detects the machining position of the machining groove 17 corresponding to the reference division line 14. Thereafter, when the second holding table 24 is moved in the X-axis direction relative to the second imaging unit 28, the size of the chip 15 in the X-axis direction is added to this detected machining position. This makes it possible to detect the machining position of the machining groove 17 corresponding to the division line 14 adjacent in the X-axis direction to the reference division line 14. In addition, by adding the size of the chip 15 in the X-axis direction to the machining position of the adjacent division line 14, it is possible to detect the machining position of the further adjacent division line 14.

[0043] Similarly, when the second holding table 24 is moved in the Y-axis direction relative to the second imaging unit 28, the size of the chip 15 in the Y-axis direction is added to this detected processing position. This makes it possible to detect the processing position of the planned division line 14 adjacent in the Y-axis direction to the reference planned division line 14. Moreover, by adding the size of the chip 15 in the Y-axis direction to the processing position of the adjacent planned division line 14, it is possible to detect the processing position of the further adjacent planned division line 14.

[0044] In this case, since it is not necessary to store information on the positional relationship between the pattern 31 and the processing groove 17 for each of the planned dividing lines 14, it is possible to improve the processing speed of the processing method and reduce the amount of data stored in the memory unit 102. In addition, in the first position storage step, the processing position of the processing groove 17 corresponding to the reference planned dividing line 14 is frequently detected, so that the positional deviation of the processing groove 17 can be minimized. As a result, the processing groove 17 formed on the front surface 12 side and the modified layer 18 formed inside the wafer 10 can be accurately aligned, and the modified layer 18 can be formed with higher accuracy.

[0045] (Modified layer formation step) The modified layer forming step will be described with reference to Fig. 6. The modified layer forming step is performed by the control unit 100 controlling the second laser beam application unit 21.

[0046] As shown in Fig. 6, in the modified layer forming step, a laser beam is irradiated to the position detected in the first processing position detecting step to form a modified layer 18 inside the wafer 10 corresponding to the processing groove 17. Specifically, as shown in Fig. 6, in the processing groove forming step, the front surface 12 of the wafer 10 is held on a second holding table 24 with the front surface 12 facing downward and the back surface 13 facing upward. The second holding table 24 can stably hold the wafer 10 by suction or the like. Then, a laser beam Lb having a wavelength that is transparent to the substrate 11 of the wafer 10 irradiated with the laser beam La in the processing groove forming step is irradiated from the back surface 13 side of the wafer 10.

[0047] 6, in the wafer 10 irradiated with the laser beam Lb from the back surface 13, cracks 19 are formed from each modified layer 18 toward the front surface 12. The direction in which the cracks 19 are formed can be controlled by appropriately setting the focal point position of the laser beam Lb in the thickness direction of the wafer 10. For example, when the modified layer 18 is formed at a position closer to the front surface 12 in the thickness direction of the wafer 10, the cracks 19 are mainly formed toward the front surface 12 close to the modified layer 18.

[0048] (split step) The dividing step will be described with reference to Fig. 7. The dividing step is performed by the control unit controlling the expansion unit 29. As shown in Fig. 7, in the dividing step of the first embodiment, after the modified layer forming step, an external force is applied to the wafer 10 to divide the wafer 10 into a plurality of chips 15 along the modified layer 18. The dividing step is performed by controlling the expansion unit 29 of the control unit 100.

[0049] 7(1) shows a cross-sectional view of the expansion unit 29 before expansion, and Fig. 7(2) shows a cross-sectional view of the expansion unit 29 after expansion. The expansion unit 29 expands the tape T of the wafer 10.

[0050] The expansion unit 29 includes a base 210, a frame pressing portion 220, a frame support portion 221, an expansion drum 230, a third holding table 232 that is installed inside the expansion drum 230 and has a pressing surface 233 at approximately the same height as the upper surface of the expansion drum 230, and a lifting unit 240 that raises and lowers the expansion drum 230 and the third holding table 232. The base 210 is formed in a cylindrical shape and supports the expansion drum 230 and the lifting unit 240. The third holding table 232 is formed in a disk shape and is disposed inside the expansion drum 230. The third holding table 232 presses the wafer 10 with the pressing surface 233 via the tape T. In addition, the third holding table 232 serves to suction and hold the wafer 10 in order to maintain the spacing between the chips after expansion.

[0051] The expansion drum 230 is arranged in a circular opening of the frame support part 221 so as to be movable up and down. A plurality of expansion rollers 231 are attached to the outer periphery of the upper end of the expansion drum 230. The expansion rollers 231 are rotatably fixed to the outer periphery of the third holding table 232. Therefore, the expansion rollers 231 are raised and lowered in the vertical direction (Z-axis direction) together with the third holding table 232 by the lifting unit 240. The frame support part 221 is formed of a metal material such as SUS. The expansion rollers 231 function as a pressing unit. The expansion rollers 231 expand the tape T with the expansion rollers 231 in a state in which the frame 25 of the wafer 10 is sandwiched between the frame support part 221 and the frame pressing part 220. As a result, the wafer 10 can be suction-held by the third holding table 232 to maintain the interval (chip interval) of the chips 15.

[0052] The expansion drum 230 is disposed on the base 210 and is formed in a cylindrical shape. The expansion drum 230 is disposed inside the frame pressing part 220 and in a position coaxial with the frame pressing part 220. The inner and outer diameters of the expansion drum 230 are smaller than the inner diameters of the frame 25 and the frame pressing part 220, and larger than the outer diameter of the wafer 10.

[0053] The lifting unit 240 moves the frame support part 221 and the expansion drum 230 relatively along the vertical direction (Z-axis direction). The lifting unit 240 raises and lowers the expansion drum 230 between a position where the upper surface of the frame support part 221 is located on the same plane as the lower end of the expansion drum 230, and a position where the upper surface of the frame support part 221 is lower than the lower end of the expansion drum 230. The lifting unit 240 is provided at approximately the center of the base 210. The lifting unit 240 is composed of a motor and a ball screw (not shown), and may be formed to be freely expandable and contractible in the vertical direction.

[0054] The division step in this embodiment involves expanding the tape T of the wafer 10, which has a division starting point formed along the planned division line 14, with an expansion unit 29 to apply an external force to the wafer 10, thereby dividing the wafer 10 into multiple chips 15 along the modified layer 18.

[0055] In the processing method of the wafer 10 of the first embodiment, a pattern that can be accurately imaged whether it is imaged from the front surface 12 side or the back surface 13 side of the wafer 10 is used as the reference position. Then, in the first processing position detection step, the control unit 100 detects the processing position where the processing groove 17 is formed based on this clearly imageable pattern and the distance Ra, which is the information of the positional relationship stored in the first position storage step. As a result, it is possible to accurately align the processing groove 17 formed on the front surface 12 side of the wafer 10 with the modified layer 18 formed inside the wafer 10, and it becomes possible to form the modified layer 18 with higher precision.

[0056] Second Embodiment The wafer processing method according to the second embodiment is executed by a processing groove forming step, a first center calculation step, a second position storage step, a second center calculation step, a second processing position detection step, a modified layer forming step, and a division step. The wafer may have a configuration capable of implementing the wafer processing method of this embodiment, and is not limited to the configuration shown in FIG. 1. In the wafer processing method according to the second embodiment, the processing groove forming step, the modified layer forming step, and the division step are the same as those in the wafer processing method according to the first embodiment, and therefore the description will be omitted. Hereinafter, only the steps different from the wafer processing method according to the first embodiment will be described. Note that the wafer 10 according to the second embodiment does not need to have a pattern formed thereon.

[0057] (First center calculation step) The first center calculation step is performed by the control unit 100 controlling the first imaging unit 27. In the first center calculation step, similarly to the machined groove formation step, the back surface 13 of the wafer 10 is held on the first holding table 23 with the back surface 13 facing downward and the front surface 12 facing upward. The first holding table 23 can stably hold the wafer 10 by suction or the like.

[0058] In the first center calculation step according to the second embodiment, the control unit 100 controls the first imaging unit 27 disposed above the first holding table 23 to capture an image of the front surface 12 side of the wafer 10 to obtain a wafer image. Then, the control unit 100 calculates the center position 51 (see FIGS. 8 and 9) of the wafer 10 based on the wafer image acquired by the first imaging unit 27.

[0059] The control unit 100 calculates the center position 51 by the following algorithm. First, the control unit 100 refers to the wafer image, captures images of at least three locations on the edge of the wafer 10, and detects the coordinates of each edge. The control unit 100 draws perpendicular bisectors for three straight lines connecting two points on the detected edge, and calculates the point where the three perpendicular bisectors intersect as the center position 51 of the wafer 10.

[0060] (Second position storage step) The second position storage step will be described with reference to Fig. 8. The second position storage step is performed by the control unit 100 controlling the first imaging unit 27. Fig. 8 shows a top view of the wafer 10 in the second position storage step.

[0061] In the second position memorizing step of the second embodiment, similarly to the machined groove forming step, the back surface 13 of the wafer 10 is held on the first holding table 23 with the back surface 13 facing downward and the front surface 12 facing upward. The first holding table 23 can stably hold the wafer 10 by suction or the like.

[0062] In a second position storage step according to the second embodiment, the control unit 100 controls the first imaging unit 27 arranged above the first holding table 23 to capture an image of the front surface 12 side of the wafer 10 to obtain a wafer image. The wafer image includes the processing groove 17. In the second position storage step, in a state in which the planned dividing line 14 is positioned so as to be parallel to the X coordinate (i.e., θ alignment is completed), the distance Rc in the Y-axis direction between the center position 51 calculated in the first center calculation step and the processing groove 17 is stored in the storage unit 102 as a positional relationship.

[0063] (Second center calculation step) The second center calculation step is performed by the control unit 100 controlling the second imaging unit 28. In the second center calculation step according to the second embodiment, after the second position storage step, the wafer 10 is transported by a transport arm (not shown) or the like, and the front surface 12 of the wafer 10 is held on the second holding table 24 with the front surface 12 of the wafer 10 facing downward and the back surface 13 facing upward. The second holding table 24 can stably hold the wafer 10 by suction or the like. In this case, the machined groove 17 formed in the wafer 10 is disposed downward.

[0064] In the second center calculation step, the control unit 100 controls the second imaging unit 28 disposed above the second holding table 24 to capture an image of the back surface 13 of the wafer 10 to obtain a wafer image. Then, the control unit 100 calculates the center position 51 (see FIGS. 8 and 9) of the wafer 10 based on the wafer image acquired by the first imaging unit 27.

[0065] The calculation of the center position 51 in the control unit 100 is performed by the following algorithm. First, the control unit 100 refers to the wafer image, captures images of at least three edges of the wafer 10, and detects the coordinates of each edge. The control unit 100 draws perpendicular bisectors for three straight lines connecting two points of the detected edges, and calculates the point where the three perpendicular bisectors intersect as the center position 51 of the wafer 10. In the second center calculation step, the center position 51 can be calculated based on the edges of the wafer image, so that the coordinates serving as the base point of the wafer 10 can be accurately recognized.

[0066] (Second processing position detection step) The second processing position detection step will be described with reference to Fig. 9. The second processing position detection step is performed by the control unit 100 controlling the second imaging unit .

[0067] In the second processing position detection step according to the second embodiment, after the second center calculation step, the front surface 12 of the wafer 10 is held on the second holding table 24 with the front surface 12 facing downward and the back surface 13 facing upward. The second holding table 24 can stably hold the wafer 10 by suction or the like. In this case, the processing groove 17 formed in the wafer 10 is disposed downward.

[0068] The control unit 100 controls the second imaging unit 28 arranged above the second holding table 24 to capture an image of the back surface 13 side of the wafer 10 to obtain a wafer image. The wafer image includes the processing groove 17. Then, based on the wafer image acquired by the second imaging unit 28, the control unit 100 detects the position where the processing groove 17 is formed based on the positional relationship stored in the second position storage step from the center position 51 calculated in the second center calculation step. Specifically, after calculating the center position 51, the control unit 100 detects a position away from the center position 51 by the distance Rd in the Y-axis direction as the processing position.

[0069] In the second processing position detection step, the second imaging unit 28 captures an image of the back surface 13 of the wafer 10, and a wafer image is acquired. Since the processing groove 17 is shallow, when the back surface 13 of the wafer 10 is imaged, the processing groove 17 formed on the front surface 12 of the wafer 10 is only faintly reflected in the wafer image. For this reason, when the front surface 12 of the wafer 10 is held on the second holding table 24 with the front surface 12 of the wafer 10 facing downward and the back surface 13 facing upward in order to form the modified layer 18 in the modified layer formation step described later, the position of the processing groove 17 cannot be accurately recognized. As a result, when alignment is performed based on the pattern 41 or the center position of the wafer, the position of the modified layer 18 may be shifted with respect to the processing groove 17.

[0070] Therefore, based on the center position 51 detected in the first center calculation step, the control unit 100 detects the position where the processed groove 17 is formed using the information on the positional relationship between the center position 51 and the processed groove 17 stored in the second position storage step. Since the center position 51 can be accurately calculated whether the image is captured from the front surface 12 side or the back surface 13 side, in the second processed position detection step, the control unit 100 detects the position where the processed groove 17 is formed (processed position) based on the accurately calculated center position 51 and the distance Rc, which is the information on the positional relationship stored in the first position storage step.

[0071] In the processing method of the wafer 10 according to the second embodiment, the center position 51 that can be accurately calculated whether the image is captured from the front surface 12 side or the back surface 13 side is used as the reference position. In the second processing position detection step, the control unit 100 detects the processing position where the processing groove 17 is formed based on the accurately calculated center position 51 and the distance Rc, which is the information on the positional relationship stored in the first position storage step. As a result, the processing groove 17 formed on the front surface 12 side and the modified layer 18 formed inside the wafer 10 can be accurately aligned, and the modified layer 18 can be formed with higher accuracy. In addition, in the processing method of the wafer 10 according to the second embodiment, it is not necessary for a pattern suitable for alignment to be formed on the wafer 10. Therefore, the processing method of this embodiment can be applied to various wafers 10, and the variation of the wafer 10 can be increased.

[0072] In the above embodiment, the processed groove 17 is formed by laser processing in the processed groove forming step, but it is also possible to form the processed groove 17 by cutting processing using a cutting blade or the like. In this case, the holding table provided for the cutting processing may be the first holding table, and the holding table provided for the laser processing device may be the second holding table.

[0073] The embodiments of the present invention are not limited to the above-mentioned embodiments and modifications, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea of ​​the present invention. Furthermore, if the technical idea of ​​the present invention can be realized in a different way due to technological progress or a derived technology, the present invention may be implemented using that method. Therefore, the claims cover all embodiments that may be included within the scope of the technical idea of ​​the present invention. [Industrial Applicability]

[0074] As described above, the method for processing the wafer 10 using the processing apparatus 1 of the present invention can align the processed groove formed on the front surface side with the modified layer formed inside. Therefore, it is particularly useful in fields where alignment between the processed groove and the modified layer is required. [Explanation of symbols]

[0075] 1: processing device, 10: wafer, 11: substrate, 12: front surface, 13: back surface, 14: planned division line, 15: chip, 16: functional layer, 17: machined groove, 18: modified layer, 19: crack; 20: first laser beam irradiation unit; 21: second laser beam application unit, 23: first holding table, 24: second holding table, 27: first imaging unit, 28: second imaging unit, 29: Expansion unit, 100: Control unit

Claims

1. A wafer processing method for processing a wafer having at least one pattern formed in an area defined by a plurality of dividing lines on a front surface side of a substrate along the dividing lines, comprising: The back side of the wafer is held on a first holding table, A groove forming step of forming a groove that does not completely divide the wafer from the front surface side of the wafer; Taking an image of the processed groove and the pattern formed around the processed groove; a first position storing step of storing a positional relationship between the pattern and the processed groove; After the first position storage step, The back side of the wafer is held on a second holding table, a first processing position detection step of imaging the front side of the wafer from the back side of the wafer, detecting the pattern from the captured image, and detecting the position where the processing groove is formed from the pattern based on the positional relationship stored in the first position storage step; Irradiating a laser beam onto the position detected in the first processing position detection step; a modified layer forming step of forming a modified layer inside the wafer corresponding to the processed groove; a dividing step of dividing the wafer into a plurality of chips along the modified layer by applying an external force to the wafer; A wafer processing method comprising the steps of:

2. A wafer processing method for processing a wafer having a plurality of planned dividing lines on a front surface side of a substrate along the planned dividing lines, comprising: The back side of the wafer is held on a first holding table, A groove forming step of forming a groove that does not completely divide the wafer from the front surface side of the wafer; In a state where the image forming apparatus is held on the first holding table, a first center calculation step of calculating a center position of a wafer; The positional relationship between the center position calculated in the first center calculation step and the machining groove is stored. A second position storage step; The back side of the wafer is held on a second holding table, a second center calculation step of calculating the center position of the wafer; From the center position calculated in the second center calculation step, a second machining position detection step of detecting a position where the machined groove is formed based on the positional relationship stored in the second position storage step; Irradiating a laser beam onto the position detected in the second processing position detection step; a modified layer forming step of forming a modified layer inside the wafer corresponding to the processed groove; a dividing step of dividing the wafer into a plurality of chips along the modified layer by applying an external force to the wafer; A wafer processing method comprising the steps of:

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