Wafer processing method

Abstract

To provide a wafer processing method that is unlikely to leave damaged areas.SOLUTION: A wafer processing method is for processing a wafer on which a functional layer is stacked on a substrate. The wafer processing method includes: a functional layer processing step 102 for irradiating the functional layer with a laser beam along a scheduled division line to form a laser processed groove in the functional layer; a damage removal step 104 for removing a damage area on the periphery of the laser-processed groove modified by the functional layer processing step 102 with a cutting blade after execution of the functional layer processing step 102.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for processing a wafer having a functional layer. [Background technology]

[0002] When forming grooves along the planned dividing line in a wafer having a functional layer formed on the surface of a silicon (Si) substrate or the like, in which a low-k film such as a nitride film, an oxide film, or a polyimide film, and a wiring layer are stacked, if the functional layer is processed using a cutting blade, peeling of the film is likely to occur. Therefore, it is common to form laser-processed grooves by irradiating a laser beam onto the functional layer (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-064231 Summary of the Invention [Problem to be solved by the invention]

[0004] However, there is a problem that the functional layer can be damaged by the heat generated when the functional layer is irradiated with a laser beam for processing. Previously, methods have been developed to remove damage caused by laser processing of silicon substrates, etc.

[0005] In recent years, functional layers have become thicker, and it has been discovered that damage to the functional layers, which had not previously been noticed, affects the die strength of the chips when the wafer is divided into chips.

[0006] An object of the present invention is to provide a wafer processing method that is less likely to leave damaged areas. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the wafer processing method of the present invention is a wafer processing method for processing a wafer having a functional layer stacked on a substrate, and is characterized by comprising a functional layer processing step of irradiating the functional layer with a laser beam along a planned dividing line to form a laser-processed groove in the functional layer, and a damage removal step of removing, after the functional layer processing step, a damaged area around the laser-processed groove that has been modified by the functional layer processing step with a cutting blade.

[0008] In the wafer processing method, in the damage removal step, the cutting depth of the cutting blade may be shallower than the laser-processed groove.

[0009] The wafer processing method may further include a substrate dividing step of dividing the substrate along the planned dividing lines. [Effects of the Invention]

[0010] In the present invention, the cutting blade removes at least a portion of the damaged area, including the side and edge of the laser-processed groove modified in the functional layer processing step, thereby reducing the damaged area remaining in the functional layer, thereby achieving the effect of reducing the amount of damage remaining in the wafer after processing. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view of a wafer to be processed by the wafer processing method according to the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically showing a main part of the wafer shown in FIG. [Figure 3] FIG. 3 is a flowchart showing the flow of the wafer processing method according to the first embodiment. [Figure 4] FIG. 4 is a side view, partly in section, schematically showing the protective film coating step of the wafer processing method shown in FIG. [Figure 5]FIG. 5 is a cross-sectional view schematically showing a main part of the wafer after the protective film coating step of the wafer processing method shown in FIG. [Figure 6] FIG. 6 is a side view, partly in section, schematically showing the functional layer processing step of the wafer processing method shown in FIG. [Figure 7] FIG. 7 is a cross-sectional view of a main part of a wafer, schematically showing a functional layer processing step of the wafer processing method shown in FIG. [Figure 8] FIG. 8 is a side view, partly in section, schematically showing the cleaning step of the wafer processing method shown in FIG. [Figure 9] FIG. 9 is a cross-sectional view schematically showing a main part of the wafer after the cleaning step of the wafer processing method shown in FIG. [Figure 10] FIG. 10 is a side view, partially in section, schematically showing the damage removal step of the wafer processing method shown in FIG. [Figure 11] FIG. 11 is a cross-sectional view schematically showing a main part of a wafer in a damage removing step of the wafer processing method shown in FIG. [Figure 12] FIG. 12 is a cross-sectional view schematically showing a main part of the wafer after the damage removal step of the wafer processing method shown in FIG. [Figure 13] FIG. 13 is a cross-sectional view schematically showing a main part of a wafer in a state where a modified layer is formed inside the substrate in the substrate dividing step of the wafer processing method shown in FIG. [Figure 14] FIG. 14 is a side view, partly in section, schematically showing a state in which the substrate is divided in the substrate dividing step of the wafer processing method shown in FIG. [Figure 15] FIG. 15 is a cross-sectional view schematically showing a main part of the wafer after the substrate dividing step in the wafer processing method shown in FIG. [Figure 16] FIG. 16 is a side view, partially in section, schematically showing a part of the damage removing step in the wafer processing method according to a modified example of the first embodiment. [Figure 17]FIG. 17 is a side view, partially in section, schematically showing the remaining part of the damage removing step in the wafer processing method according to the modified example of the first embodiment. [Figure 18] FIG. 18 is a cross-sectional view schematically showing a main part of a wafer after two laser-processed grooves have been formed in the functional layer processing step of the wafer processing method according to the second embodiment. [Figure 19] FIG. 19 is a cross-sectional view schematically showing a main part of a wafer in a state where the functional layer between two laser-processed grooves has been removed in the functional layer processing step of the wafer processing method according to the second embodiment. [Figure 20] FIG. 20 is a cross-sectional view schematically showing a main part of a wafer after the protective film cleaning step in the wafer processing method according to the second embodiment. [Figure 21] FIG. 21 is a side view, partially in section, schematically showing the damage removing step of the wafer processing method according to the second embodiment. [Figure 22] FIG. 22 is a cross-sectional view schematically showing a main part of a wafer after the damage removing step in the wafer processing method according to the second embodiment. [Figure 23] FIG. 23 is a side view, partially in section, schematically showing a part of the damage removing step in the wafer processing method according to a modified example of the second embodiment. [Figure 24] FIG. 24 is a side view, partially in section, schematically showing the remaining part of the damage removing step in the wafer processing method according to a modified example of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Modes (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the configuration can be made within the scope of the gist of the present invention.

[0013] [Embodiment 1] A wafer processing method according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view of a wafer to be processed by the wafer processing method according to the first embodiment. Fig. 2 is a cross-sectional view schematically showing a main part of the wafer shown in Fig. 1. Fig. 3 is a flowchart showing the flow of the wafer processing method according to the first embodiment.

[0014] The wafer 1 to be processed by the wafer processing method according to the first embodiment is a disk-shaped semiconductor wafer, an optical device wafer, or the like, having a substrate 2 made of silicon, sapphire, gallium arsenide, SiC (silicon carbide), or the like. The wafer 1 has devices 5 formed in each of the regions partitioned by a plurality of planned dividing lines 4 formed in a lattice pattern on the surface 3.

[0015] The device 5 is, for example, an integrated circuit such as an IC (Integrated Circuit) or an LSI (Large Scale Integration), an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), or a memory (semiconductor storage device).

[0016] 1 and 2, the wafer 1 has a functional layer 6 laminated on the surface of the substrate 2. The functional layer 6 includes a low-dielectric-constant insulating film (hereinafter referred to as a low-k film) made of an inorganic film such as a nitride film, an oxide film, SiOF, or BSG (SiOB), or an organic film such as a polyimide-based or parylene-based polymer film, and a conductor film made of a conductive metal.

[0017] The device 5 is composed of a low-k film and a conductive film laminated between the low-k films. The conductive film forms the wiring pattern of the device 5. The functional layer 6 along the planned dividing lines 4 also includes a TEG (Test Element Group), which is an evaluation element for identifying design or manufacturing problems that may occur in the device 5.

[0018] 1, the back surface 7 of the wafer 1, which is the back side of the front surface 3, is attached to the center of a disk-shaped adhesive tape 10, an annular frame 11 is attached to the outer edge of the adhesive tape 10, and the wafer 1 is supported in an opening of the frame 11 via the adhesive tape 10. In the first embodiment, the frame 11 is formed in an annular shape and has an inner diameter larger than the outer diameter of the wafer 1. In the first embodiment, the adhesive tape 10 has an outer diameter larger than the outer diameter of the wafer 1 and the inner diameter of the opening, and smaller than the outer diameter of the frame 11.

[0019] In addition, in the first embodiment, the adhesive tape 10 may be an adhesive tape having a flexible and non-adhesive base layer and a flexible and adhesive adhesive layer laminated on the base layer, or may be a sheet made of a thermoplastic resin without an adhesive layer. In the case of a non-adhesive sheet, the material is preferably a polyolefin sheet, a polyethylene sheet, a polypropylene sheet, or a polystyrene sheet, and it is attached to the frame 11 or the wafer 1 by thermocompression bonding.

[0020] In the first embodiment, as shown in FIG. 2 , the thickness 13 of the functional layer 6 of the wafer 1 is greater than the thickness 12 of the substrate 2. In the first embodiment, the thickness 12 of the substrate 2 of the wafer 1 is, for example, 10 μm, and the thickness 13 of the functional layer 6 of the wafer 1 is, for example, 20 μm or more and 30 μm or less. In the present invention, the thickness of the substrate 2 may be greater than the thickness 13 of the functional layer 6 in at least one of the functional layer processing step 102, the damage removal step 104, and the substrate division step 105. Also included is a configuration in which a grinding step is performed after the functional layer processing step and the damage removal step, and the thickness of the functional layer 6 is thinner than the thickness 13 of the functional layer 6 when the chip is thinned to its final thickness by the grinding step. In other words, the wafer 1 is processed so that the thickness 13 of the functional layer 6 is thicker than the thickness 12 of the substrate 2 when the device chip is thinned to its final thickness.

[0021] (Wafer Processing Method) The wafer processing method according to the first embodiment is a method for processing a wafer 1 having a functional layer 6 stacked on the aforementioned substrate 2. As shown in Fig. 3, the wafer processing method according to the first embodiment includes a protective film application step 101, a functional layer processing step 102, a protective film cleaning step 103, a damage removal step 104, and a substrate division step 105.

[0022] (Protective film application step) Fig. 4 is a side view, partially in cross section, schematically showing the protective film coating step of the wafer processing method shown in Fig. 3. Fig. 5 is a cross-sectional view schematically showing a main part of the wafer after the protective film coating step of the wafer processing method shown in Fig. 3. The protective film coating step 101 is a step of forming a protective film 26 (shown in Fig. 5) on the front surface 3 of the wafer 1.

[0023] In the first embodiment, in the protective film coating step 101, the protective film coating device 20 suction-holds the back surface 7 side of the wafer 1 to the holding surface 22 of the spinner table 21 via the adhesive tape 10, and clamps the frame 11 with the clamps 23 provided around the periphery of the spinner table 21. In the protective film coating step 101, the protective film coating device 20 rotates the spinner table 21 around its axis and drops the water-soluble resin 25 from the water-soluble resin supply nozzle 24 onto the center of the front surface 3 of the wafer 1, as shown in FIG.

[0024] The dropped water-soluble resin 25 flows from the center to the outer periphery on the surface 3 of the wafer 1 due to the centrifugal force generated by the rotation of the spinner table 21, and is applied to the entire surface 3 of the wafer 1.

[0025] The water-soluble resin 25 is, for example, a water-soluble resin such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP). In the protective film application step 101, the water-soluble resin 25 applied to the entire surface of the front surface 3 of the wafer 1 is dried to form a water-soluble protective film 26 that covers the entire surface of the front surface 3 of the wafer 1, as shown in Fig. 5. If the volume of the functional layer 6 removed in the functional layer processing step 102 is small and the adhesion of processing debris does not affect quality, the protective film application step 101 does not need to be performed.

[0026] (Functional layer processing step) Figure 6 is a side view, partially in cross section, schematically showing the functional layer processing step of the wafer processing method shown in Figure 3. Figure 7 is a cross-sectional view of a main part of the wafer, schematically showing the functional layer processing step of the wafer processing method shown in Figure 3. The functional layer processing step 102 is a step of irradiating the functional layer 6 with a laser beam 34 (shown in Figure 6) along the planned dividing lines 4 to form laser grooves 14 (shown in Figure 7) in the functional layer 6.

[0027] In the functional layer processing step 102, as shown in Fig. 6, the laser processing device 30 suction-holds the back surface 7 of the wafer 1 to the holding surface 32 of the holding table 31 via adhesive tape 10, and clamps the frame 11 with clamps 33 provided around the holding table 31. In the functional layer processing step 102, as shown in Fig. 6, the laser processing device 30 positions a focal point 35 of a laser beam 34 having a wavelength absorbed by the functional layer 6 on the front surface 3, and irradiates the wafer 1 with the pulsed laser beam 34 along the planned dividing lines 4 from the front surface 3 side of the wafer 1 along the planned dividing lines 4 at the center in the width direction of the planned dividing lines 4 while relatively moving the holding table 31 and the laser beam application unit 36 ​​along the planned dividing lines 4 from the position indicated by the dashed lines in Fig. 6 to the position indicated by the solid lines.

[0028] Then, since the wavelength of the laser beam 34 is absorbed by the functional layer 6, the functional layer 6 on the dividing lines 4 of the wafer 1 is subjected to ablation, and the protective film 26 and the functional layer 6 on the dividing lines 4 are removed. Since the functional layer processing step 102 aims to remove the functional layer 6, a laser groove 14 is formed to a depth at which the substrate 2 is exposed. Therefore, the surface layer of the substrate 2 is also removed. The wavelength of the laser beam 34 irradiated in the functional layer processing step 102 may also be absorbed by the substrate 2. In the functional layer processing step 102, as shown in FIG. 7 , the laser groove 14 exposing the substrate 2 is formed along the dividing lines 4 of the wafer 1 at the center of the dividing lines 4 in the width direction. Furthermore, as shown in FIG. 7 , a damaged region 15 modified by the heat of the laser beam 34 is formed around the laser groove 14, including at least the side surface 141 and edge 142 of the laser groove 14. Because heat generated by laser processing rises, damage is more likely to occur near the surface of the functional layer 6 than near the bottom of the laser-processed grooves 14. Therefore, in embodiment 1, a damaged area 15 with greater damage is formed particularly at the end of the functional layer 6 on the surface 3 side. In the functional layer processing step 102, the laser processing device 30 forms laser-processed grooves 14 on all of the planned division lines 4.

[0029] (Protection film cleaning step) Fig. 8 is a side view, partially in cross section, schematically showing the cleaning step of the wafer processing method shown in Fig. 3. Fig. 9 is a cross-sectional view schematically showing the main part of the wafer after the cleaning step of the wafer processing method shown in Fig. 3. The protective film cleaning step 103 is a step for cleaning the wafer 1 on which the functional layer processing step 102 has been performed.

[0030] In protective film cleaning step 103, cleaning device 40 suction-holds back surface 7 of wafer 1 to holding surface 42 of spinner table 41 via adhesive tape 10, and clamps frame 11 with clamps 43 provided around spinner table 41. In protective film cleaning step 103, cleaning device 40 rotates spinner table 41 around its axis and supplies cleaning water 45 (pure water in the first embodiment) from cleaning nozzle 44 to the center of front surface 3 of wafer 1, as shown in FIG.

[0031] Then, the supplied cleaning water 84 flows from the center to the outer periphery over the front surface 3 of the wafer 1 due to centrifugal force generated by the rotation of the spinner table 81, cleaning the entire front surface 3 of the wafer 1 and dissolving the protective film 26 so that the cleaning water 84 flows over the front surface 3. In the protective film cleaning step 103, the cleaning device 40 removes foreign matter from the front surface 3 of the wafer 1 and also removes the protective film 26 from the front surface 3 as shown in FIG.

[0032] (Damage removal step) Fig. 10 is a side view, partially in section, schematically showing the damage removal step of the wafer processing method shown in Fig. 3. Fig. 11 is a cross-sectional view schematically showing the main part of the wafer in the damage removal step of the wafer processing method shown in Fig. 3. Fig. 12 is a cross-sectional view schematically showing the main part of the wafer after the damage removal step of the wafer processing method shown in Fig. 3.

[0033] The damage removal step 104 is a step in which, after the functional layer processing step 102, a cutting blade 54 is used to remove the damaged area 15 on the inner surface of the laser-processed groove 14 that has been modified by the functional layer processing step 102. In the damage removal step 104, the cutting device 50 suction-holds the back surface 7 of the wafer 1 to the holding surface 52 of the holding table 51 via the adhesive tape 10, as shown in FIG. In the damage removal step 104, as shown in Figures 10 and 11, the cutting device 50 moves the holding table 51 and the cutting blade 54 relatively along the planned dividing line 4, and cuts the cutting edge 56 of the cutting blade 54, which has a blade thickness 55 greater than the width 16 of the laser-machined groove 14, from the surface 3 of the wafer 1 along the planned dividing line 4 into an area including both edges 142 of the laser-machined groove 14, thereby forming a cutting groove 17 including the edges 142 of the laser-machined groove 14 and removing at least a portion of the damage area 15 formed on the side 141 and edge 142 of the laser-machined groove 14.

[0034] In the damage removal step 104 in the first embodiment, as shown in Fig. 11, the depth to which the cutting device 50 cuts with the cutting blade 54 is shallower than the depth 18 of the laser-processed groove 14, which in the first embodiment is shallower than the thickness 13 of the functional layer 6. In the damage removal step 104, the cutting device 50 removes at least a portion of the damage areas 15 on the side surfaces 141 and edges 142 of the laser-processed grooves 14 formed on all of the planned division lines 4, as shown in Fig. 12.

[0035] (Substrate division step) Fig. 13 is a cross-sectional view schematically showing a main part of a wafer in a state where a modified layer is formed inside the substrate in the substrate dividing step of the wafer processing method shown in Fig. 3. Fig. 14 is a side view, partially in cross section, schematically showing a state where the substrate is divided in the substrate dividing step of the wafer processing method shown in Fig. 3. Fig. 15 is a cross-sectional view schematically showing a main part of a wafer after the substrate dividing step of the wafer processing method shown in Fig. 3.

[0036] The substrate dividing step 105 is a step of dividing the substrate 2 along the dividing lines 4. In the first embodiment, in the substrate dividing step 105, the laser processing device 60 peels off the adhesive tape 10, suction-holds the front surface 3 side of the wafer 1 on the holding surface of the holding table, and clamps the frame 11 with clamps provided around the holding table. In the substrate dividing step 105, as shown in FIG. 13 , the laser processing device 60 positions a focal point 62 of a laser beam 61 having a wavelength that is transparent to the substrate 2 inside the substrate 2, and irradiates the wafer 1 with a pulsed laser beam 61 from the back surface 7 side of the wafer 1 along the dividing lines 4 while moving the holding table and the laser beam application unit 63 relatively along the dividing lines 4.

[0037] Then, since the wavelength of the laser beam 61 is a wavelength that is transparent to the wafer 1, modified layers 19 are formed inside the substrate 2 along the planned dividing lines 4. In the first embodiment, in the substrate dividing step 105, the laser processing device 30 irradiates the laser beam 61 from the back surface 7 side of the wafer 1 along all the planned dividing lines 4, and forms modified layers 19 inside the substrate 2 along all the planned dividing lines 4.

[0038] The modified layer 19 refers to a region in which the density, refractive index, mechanical strength, or other physical properties are different from those of the surrounding area, and examples thereof include a melting treatment region, a crack region, a dielectric breakdown region, a refractive index change region, and a region in which these regions are mixed, etc. The gas strength of the modified layer 19 is lower than the mechanical strength of the other portions of the substrate 2 other than the modified layer 19.

[0039] In addition, in embodiment 1, the laser beam 61 that forms the modified layer 19 on the substrate 2 is a laser beam with a shorter pulse width than the laser beam 34 that forms the laser-processed groove 14.As a result, the laser beam 34 that forms the laser-processed groove 14 is a laser beam with a longer pulse width than the laser beam 61 that forms the modified layer 19, so the thermal impact is greater and damaged areas 15 are more likely to occur in the functional layer 6.

[0040] In the substrate dividing step 105, a protective member 191 is attached to the front surface 3 of the wafer 1, and the grinding device 70 suction-holds the front surface 3 side of the wafer 1 on the holding surface 72 of the holding table 71 via the protective member 191. In the substrate dividing step 105, as shown in FIG. 14 , the grinding device 70 rotates the grinding wheel 74 about its axis using the spindle 73 and rotates the holding table 71 about its axis, and while supplying grinding water (not shown), such as pure water, the grinding stone 75 of the grinding wheel 74 is brought into contact with the back surface 7 and moved toward the holding table 71 at a predetermined feed rate, thereby grinding the wafer 1 with the grinding stone 75 to thin the wafer 1 to a predetermined finishing thickness. Note that the wafer 1 thinned to the finishing thickness has a functional layer 6 thinner than the substrate 2. In the first embodiment, the wafer 1 thinned to the finishing thickness has all of the modified layer 19 removed in the substrate dividing step 105.

[0041] In the first embodiment, in the substrate dividing step 105, the wafer 1 is pressed by the grinding stone 75 of the grinding wheel 74, so that, as shown in Fig. 15, cracks 192 extend from the modified layer 19 to the groove bottoms of the laser-processed grooves 14 and the back surface 7, and the substrate 2 and functional layer 6 are divided along the planned dividing lines 4. Note that Fig. 14 shows the cracks 192 without showing the modified layer 19.

[0042] In the wafer processing method according to the first embodiment described above, after forming the laser-processed groove 14 that exposes the substrate 2 by removing the functional layer 6 in the functional layer processing step 102, at least a portion of the damaged area 15 including the side surface 141 and edge 142 of the laser-processed groove 14 modified in the functional layer processing step 102 is removed by the cutting blade 54, thereby reducing the damaged area 15 remaining in the functional layer 6. As a result, the wafer processing method according to the first embodiment has the effect of making it difficult for the damaged area 15 to remain in the wafer 1 after processing.

[0043] In the wafer processing method according to the first embodiment, when the functional layer 6 is removed with the laser beam 34 in the functional layer processing step 102, the heat from the laser beam 34 causes a damaged area 15 in the functional layer 6. Since the cutting blade 54 is less affected by heat than the laser beam 34, the wafer processing method according to the first embodiment can remove the damaged area 15 on the inner surface of the laser-processed groove 14 while preventing new damage from being formed around the cut groove.

[0044] If the functional layer 6 is to be removed using only the cutting blade 54, the processing load is high and there is a problem that the functional layer 6 is pulled by the cutting blade 54 and peeled off. However, in the wafer processing method of embodiment 1, the functional layer 6 is removed with the laser beam 34, and then only the edge 142 of the laser-processed groove 14 is cut with the cutting blade 54. This reduces the volume of the functional layer 6 to be cut, keeps the processing load low, and prevents the functional layer 6 from peeling off from the substrate 2.

[0045] To further prevent peeling of the functional layer 6 from the substrate 2 by the cutting blade 54, it is preferable to remove as little of the functional layer 6 as possible by the cutting blade 54. Because heat from the laser beam 34 rises, a damaged area 15 is more likely to occur near the surface 3 than around the bottom of the laser-processed groove 14. Therefore, in the wafer processing method according to embodiment 1, the cutting blade 54 is caused to cut into the laser-processed groove 14 that exposes the substrate 2 to a depth that does not reach the substrate 2, thereby removing the damaged area 15. As a result, in the wafer processing method according to embodiment 1, the amount of functional layer 6 removed by the cutting blade 54 in the depth direction is limited, so the cutting load is kept low and peeling of the functional layer 6 from the substrate 2 can be prevented.

[0046] In the wafer processing method according to the first embodiment, damage to the substrate 2 also affects the flexural strength of the individually divided device chips, but if the processing involves forming a modified layer 19 and grinding the modified layer 19 to remove it, the damaged area 15 caused by the irradiation of the laser beam 34 is removed by grinding. Furthermore, since the wafer 1 is processed in which the functional layer 6 is thicker than the substrate 2, the damaged area 15 of the functional layer 6 has a greater effect on the flexural strength of such a wafer 1.

[0047] In the first embodiment, the laser beam 34 that forms the laser processed groove 14 has a longer pulse width than the laser beam 34 that forms the modified layer 19, and therefore the thermal effect is greater, making the damaged region 15 more likely to occur in the functional layer 6. However, the wafer processing method according to the first embodiment has the effect of removing the damaged region 15 in the functional layer 6, making it less likely that the damaged region 15 will remain in the wafer 1 after processing.

[0048] [Modification] A wafer processing method according to a modified example of the first embodiment of the present invention will be described with reference to the drawings. Fig. 16 is a side view, partially in cross section, schematically showing a portion of the damage removal step of the wafer processing method according to a modified example of the first embodiment. Fig. 17 is a side view, partially in cross section, schematically showing a portion of the remaining damage removal step of the wafer processing method according to a modified example of the first embodiment. In Figs. 16 and 17, the same parts as those in the first embodiment are designated by the same reference numerals, and their description will be omitted.

[0049] The wafer processing method according to the modification of the first embodiment is the same as that of the first embodiment, except for the damage removal step 104. In the modification of the first embodiment, as shown in Fig. 16, the cutting device 50 moves the holding table 51 and the cutting blade 54 relative to each other along the dividing line 4, and causes the cutting edge 56-1 of the cutting blade 54-1, which has a blade thickness 55-1 thinner than the width 16 of the laser-processed groove 14, to cut into one inner edge of the laser-processed groove 14 from the front surface 3 of the wafer 1 along the dividing line 4, and as shown in Fig. 17, causes the cutting edge 56-1 of the cutting blade 52-1 to cut into the other edge 142 of the laser-processed groove 14 from the front surface 3 of the wafer 1 along the dividing line 4, thereby forming a cut groove 17 including the edge 142 of the laser-processed groove 14 and removing at least a part of the damaged area 15 formed on the side surface 141 and edge 142 of the laser-processed groove 14.

[0050] In the modification of the first embodiment, in the damage removal step 104 , the cutting depth of the cutting device 50 with the cutting blade 54 is shallower than the depth of the laser-processed groove 14 and shallower than the thickness 13 of the functional layer 6 .

[0051] In the wafer processing method according to the modified example of the first embodiment, after forming the laser processed groove 14 that removes the functional layer 6 and exposes the substrate 2 in the functional layer processing step 102, at least a part of the damaged area 15 on the inner surface of the functional layer 6 modified in the functional layer processing step 102 is removed by the cutting blade 54, thereby making it possible to suppress the damaged area 15 remaining in the functional layer 6. As a result, the wafer processing method according to the first embodiment has the effect of making it difficult for the damaged area 15 to remain in the wafer 1.

[0052] [Embodiment 2] A wafer processing method according to the second embodiment will be described with reference to the drawings. FIG. 18 is a cross-sectional view schematically showing a main part of a wafer after two laser-processed grooves have been formed in the functional layer processing step of the wafer processing method according to the second embodiment. FIG. 19 is a cross-sectional view schematically showing a main part of a wafer in a state in which the functional layer between the two laser-processed grooves has been removed in the functional layer processing step of the wafer processing method according to the second embodiment. FIG. 20 is a cross-sectional view schematically showing a main part of a wafer after a protective film cleaning step of the wafer processing method according to the second embodiment. FIG. 21 is a side view, partially in cross section, schematically showing a damage removal step of the wafer processing method according to the second embodiment. FIG. 22 is a cross-sectional view schematically showing a main part of a wafer after a damage removal step of the wafer processing method according to the second embodiment. In FIGS. 18, 19, 20, 21, and 22, the same parts as those in the second embodiment are designated by the same reference numerals, and description thereof will be omitted.

[0053] The wafer processing method according to the second embodiment is the same as that according to the first embodiment, except for the functional layer processing step 102 and the damage removal step 104. In the second embodiment, in the functional layer processing step 102, the laser processing device 30 positions the focal point 35 of the laser beam 34, which has a wavelength absorbed by the functional layer 6, on the surface 3, and irradiates the wafer 1 with the pulsed laser beam 34 at one end of the width direction of the dividing line 4 from the surface 3 side of the wafer 1 while moving the holding table 51 and the laser beam application unit 36 ​​relatively along the dividing line 4, as shown in Fig. 18, to form a laser-processed groove 14-2 at one end, and then irradiates the wafer 1 with the pulsed laser beam 34 at the other end of the width direction of the dividing line 4 to form a laser-processed groove 14-2 at the other end.

[0054] In the second embodiment, in the functional layer processing step 102, the laser processing device 30 forms a laser groove 14-2 at both ends of each planned division line 4 in the width direction, and then removes the functional layer 6 between the two laser grooves 14-2, as shown in Fig. 19, to form a laser groove 14 in each planned division line 4 that is wider than that in the first embodiment. Thereafter, in the protective film cleaning step 103, as shown in Fig. 20, the protective film 26 is removed from the wafer 1. Note that in the second embodiment, a laser beam 34 having a beam diameter larger than the two laser grooves 14-2 is irradiated, but in the present invention, a laser beam 34 having a smaller beam diameter may be irradiated multiple times, or the functional layer 6 between the two laser grooves 14-2 may be removed with a cutting blade.

[0055] In embodiment 2, in the damage removal step 104, as shown in Figure 21, the cutting device 50 moves the holding table 51 and the cutting blade 54 relatively along the planned dividing line 4, and cuts the cutting edge 56 of the cutting blade 54, which has a blade thickness 55 thicker than the width 16 of the laser-machined groove 14, from the surface 3 of the wafer 1 along the planned dividing line 4 into an area including both edges 142 of the laser-machined groove 14, to form a cutting groove 17 and remove at least a portion of the damage area 15 formed on the side 141 and edge 142 of the laser-machined groove 14.

[0056] In the second embodiment, in the damage removal step 104, as shown in Fig. 22, the cutting depth of the cutting device 50 with the cutting blade 54 is shallower than the depth 18 of the laser-processed groove 14 and shallower than the thickness 13 of the functional layer 6. In the damage removal step 104, the cutting device 50 removes at least a portion of the damaged area 15 on the inner surface of the laser-processed groove 14 formed along all of the planned division lines 4, as shown in Fig. 12.

[0057] In the wafer processing method according to the second embodiment, after forming the laser processed groove 14 that removes the functional layer 6 and exposes the substrate 2 in the functional layer processing step 102, at least a part of the damaged area 15 on the inner surface of the functional layer 6 modified in the functional layer processing step 102 is removed by the cutting blade 54, thereby making it possible to suppress the damaged area 15 remaining in the functional layer 6. As a result, the wafer processing method according to the first embodiment has the effect of making it difficult for the damaged area 15 to remain in the wafer 1.

[0058] [Modification] A wafer processing method according to a modified example of the second embodiment of the present invention will be described with reference to the drawings. Fig. 23 is a side view, partially in cross section, schematically showing a portion of the damage removal step of the wafer processing method according to a modified example of the second embodiment. Fig. 24 is a side view, partially in cross section, schematically showing a portion of the remaining damage removal step of the wafer processing method according to a modified example of the second embodiment. In Figs. 23 and 24, the same parts as those in the second embodiment are designated by the same reference numerals, and their description will be omitted.

[0059] The wafer processing method according to the modified example of the second embodiment is the same as that of the second embodiment, except for the damage removal step 104. In the modified example of the second embodiment, as shown in Fig. 23, the cutting device 50 moves the holding table 51 and the cutting blade 54 relative to each other along the dividing line 4, and causes the cutting edge 56-1 of the cutting blade 54-1, which has a blade thickness 55-1 thinner than the width 16 of the laser-processed groove 14, to cut from the front surface 3 of the wafer 1 along the dividing line 4 into a region including one edge 142 of the laser-processed groove 14, and as shown in Fig. 24, causes the cutting edge 56 of the cutting blade 54 to cut from the front surface 3 of the wafer 1 along the dividing line 4 into a region including the other edge 142 of the laser-processed groove 14, thereby forming the cut groove 17 and removing at least a part of the damaged region 15 formed on the inner surface of the laser-processed groove 14.

[0060] In the modification of the second embodiment, in the damage removal step 104 , the cutting depth of the cutting device 50 with the cutting blade 54 - 1 is shallower than the depth 18 of the laser-processed groove 14 and shallower than the thickness 13 of the functional layer 6 .

[0061] In the wafer processing method according to the modified example of the second embodiment, after forming the laser processed groove 14 that removes the functional layer 6 and exposes the substrate 2 in the functional layer processing step 102, at least a part of the damaged area 15 on the inner surface of the functional layer 6 modified in the functional layer processing step 102 is removed by the cutting blade 54, thereby making it possible to suppress the damaged area 15 remaining in the functional layer 6. As a result, the wafer processing method according to the first embodiment has the effect of making it difficult for the damaged area 15 to remain in the wafer 1.

[0062] The present invention is not limited to the above-described embodiment. In other words, various modifications can be made without departing from the gist of the present invention. In the present invention, the protective film application step 101 and the protective film cleaning step 103 are not essential and may not be performed. [Explanation of symbols]

[0063] 1 wafer 2 boards 4 Planned division line 6 Functional Layers 14 Laser-machined grooves 15 Damage Area 34 Laser beam 54,54-1 Cutting blade 101 Protective film application step 102 Functional layer processing step 104 Damage Elimination Step 105 PCB division steps

Claims

1. A wafer processing method for processing a wafer in which a functional layer is stacked on a substrate, comprising: a functional layer processing step of irradiating the functional layer with a laser beam along the planned division line to form a laser processed groove in the functional layer; A wafer processing method characterized by comprising, after the functional layer processing step, a damage removal step of removing, with a cutting blade, the damaged area around the laser-processed groove modified by the functional layer processing step.

2. 2. The wafer processing method according to claim 1, wherein in the damage removal step, the cutting depth of the cutting blade is shallower than the laser-processed groove.

3. 3. The wafer processing method according to claim 1, further comprising a substrate dividing step of dividing the substrate along the planned dividing lines.

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