JP2023135423A - Wafer processing method - Google Patents

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

The present invention relates to a method for processing a wafer including a functional layer.

Machining grooves are formed along the planned dividing line on a wafer in which a functional layer is formed by laminating a low-k film such as a nitride film, an oxide film, a polyimide film, and a wiring layer on the surface of a Si (silicon) substrate, etc. When forming a functional layer, if the functional layer is processed with a cutting blade, the film tends to peel off, so it is common to irradiate the functional layer with a laser beam to form laser-processed grooves (for example, Patent Document 1 reference).

Japanese Patent Application Publication No. 2005-064231

However, there is a problem in that the functional layer is damaged due to the influence of heat when the functional layer is processed by irradiating it with a laser beam. Conventionally, methods have been developed to remove damage caused by laser processing on silicon substrates and the like.

In recent years, functional layers have become thicker, and it has been found that damage to the functional layers, which had not received attention until now, affects the bending strength of chips when a wafer is divided into chips.

An object of the present invention is to provide a wafer processing method that is less likely to leave damaged areas.

In order to solve the above-mentioned problems and achieve the objects, the wafer processing method of the present invention is a wafer processing method for processing a wafer in which a functional layer is laminated on a substrate. A functional layer processing step of irradiating the functional layer with a laser beam to form a laser processing groove in the functional layer, and after performing the functional layer processing step, the laser processing groove modified by the functional layer processing step. The present invention is characterized by comprising a damage removal step of removing surrounding damaged areas with a cutting blade.

In the wafer processing method, the depth to which the cutting blade cuts in the damage removal step may be shallower than the laser processing groove.

The wafer processing method may further include a substrate dividing step of dividing the substrate along the planned dividing line.

In the present invention, at least a portion of the damaged area including the side surfaces and edges of the laser-processed groove modified in the functional layer processing step is removed using a cutting blade, so that the damaged area remaining in the functional layer can be reduced. As a result, the wafer after processing is less likely to be damaged.

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 essential parts of the wafer shown in FIG. FIG. 3 is a flowchart showing the flow of the wafer processing method according to the first embodiment. FIG. 4 is a side view schematically showing, partially in cross section, the protective film coating step of the wafer processing method shown in FIG. 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. FIG. 6 is a side view schematically showing, partially in cross section, the functional layer processing step of the wafer processing method shown in FIG. FIG. 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 FIG. FIG. 8 is a side view schematically showing, partially in cross section, the cleaning step of the wafer processing method shown in FIG. 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. FIG. 10 is a side view schematically showing, partially in cross section, the damage removal step of the wafer processing method shown in FIG. FIG. 11 is a cross-sectional view schematically showing a main part of the wafer in the damage removal step of the wafer processing method shown in FIG. 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. FIG. 13 is a cross-sectional view schematically showing a main part of the wafer in which a modified layer is formed inside the substrate in the substrate dividing step of the wafer processing method shown in FIG. FIG. 14 is a side view schematically showing, partially in cross section, a state in which the substrate is divided in the substrate dividing step of the wafer processing method shown in FIG. FIG. 15 is a cross-sectional view schematically showing a main part of the wafer after the substrate dividing step of the wafer processing method shown in FIG. FIG. 16 is a side view schematically showing a part of the damage removal step of the wafer processing method according to the modified example of the first embodiment, with a partial cross section. FIG. 17 is a side view schematically showing, partially in cross section, the remaining part of the damage removal step of the wafer processing method according to the modification of the first embodiment. FIG. 18 is a cross-sectional view schematically showing a main part of the wafer after two laser processing grooves are 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 the main part of the wafer after removing the functional layer between two laser-processed grooves 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 the main part of the wafer after the protective film cleaning step of the wafer processing method according to the second embodiment. FIG. 21 is a side view schematically showing, partially in cross section, 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 the wafer after the damage removal step of the wafer processing method according to the second embodiment. FIG. 23 is a side view schematically showing a part of the damage removal step of the wafer processing method according to a modification of the second embodiment, with a portion in cross section. FIG. 24 is a side view schematically showing, partially in cross section, the remaining part of the damage removal step of the wafer processing method according to a modification of the second embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 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. Further, the constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Further, various omissions, substitutions, or changes in the configuration can be made without departing from the gist of the present invention.

[Embodiment 1]
A wafer processing method according to Embodiment 1 of the present invention will be explained based on 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 essential parts of the wafer shown in FIG. FIG. 3 is a flowchart showing the flow of the wafer processing method according to the first embodiment.

The wafer 1 to be processed in the wafer processing method according to the first embodiment is a disk-shaped semiconductor wafer, an optical device wafer, etc. whose substrate 2 is silicon, sapphire, gallium arsenide, SiC (silicon carbide), or the like. . On the wafer 1, devices 5 are formed in each area defined by a plurality of dividing lines 4 formed in a lattice shape on the surface 3.

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). ) etc.

In the first embodiment, the wafer 1 has a functional layer 6 laminated on the surface of the substrate 2, as shown in FIGS. 1 and 2. The functional layer 6 is a low dielectric constant insulating 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 polymer film such as a polyimide film or a parylene film). (hereinafter referred to as a Low-k film) and a conductive film made of a conductive metal.

The device 5 is composed of a low-k film and a conductor film laminated between the low-k films. The conductor film constitutes the wiring pattern of the device 5. Note that the functional layer 6 of the planned dividing line 4 also includes a TEG (Test Element Group), which is an element for evaluation to find out design and manufacturing problems that occur in the device 5.

In the embodiment, as shown in FIG. 1, the wafer 1 has a back surface 7 behind the front surface 3 attached to the center of a disc-shaped adhesive tape 10, and an annular frame 11 attached to the outer edge of the adhesive tape 10. and is supported in the opening of the frame 11 via the adhesive tape 10. In the first embodiment, the frame 11 is formed into an annular shape, and the inner diameter is 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.

Further, in the first embodiment, the adhesive tape 10 may be an adhesive tape having a base material layer having flexibility and non-adhesiveness, and an adhesive layer laminated on the base material layer and having flexibility and adhesiveness. Alternatively, a sheet made of thermoplastic resin without an adhesive layer may be used. In the case of a non-adhesive sheet, the polyolefin sheet is preferably a polyethylene sheet, a polypropylene sheet, or a polystyrene sheet, and is adhered to the frame 11 or the wafer 1 by thermocompression bonding.

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

(Wafer processing method)
The wafer processing method according to the first embodiment is a method of processing the wafer 1 in which the functional layer 6 is laminated on the substrate 2 described above. As shown in FIG. 3, the wafer processing method according to the first embodiment includes a protective film coating step 101, a functional layer processing step 102, a protective film cleaning step 103, a damage removal step 104, and a substrate dividing step 105. Equipped with

(Protective film application step)
FIG. 4 is a side view schematically showing, partially in cross section, the protective film coating step of the wafer processing method shown in FIG. 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. The protective film coating step 101 is a step of forming a protective film 26 (shown in FIG. 5) on the surface 3 of the wafer 1.

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 on the holding surface 22 of the spinner table 21 via the adhesive tape 10, and the frame 11 is attached to the spinner table 21. It is clamped with a clamp part 23 provided around the . In the protective film coating step 101, the protective film coating device 20 rotates the spinner table 21 around its axis as shown in FIG. Drip into the center of the bottle.

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

Note that the water-soluble resin 25 is, for example, a water-soluble resin such as polyvinyl alcohol (PVA) or polyvinylpyrrolidone (PVP). In the protective film coating step 101, by drying the water-soluble resin 25 applied to the entire surface 3 of the wafer 1, a water-soluble protective film covering the entire surface 3 of the wafer 1 is formed, as shown in FIG. Form 26. Note that 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 the quality, the protective film coating step 101 may not be performed.

(Functional layer processing step)
FIG. 6 is a side view schematically showing, partially in cross section, the functional layer processing step of the wafer processing method shown in FIG. FIG. 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 FIG. The functional layer processing step 102 is a step of irradiating the functional layer 6 with a laser beam 34 (shown in FIG. 6) along the planned dividing line 4 to form a laser processing groove 14 (shown in FIG. 7) in the functional layer 6. It is.

In the functional layer processing step 102, as shown in FIG. 6, the laser processing device 30 suction-holds the back surface 7 side of the wafer 1 on the holding surface 32 of the holding table 31 via the adhesive tape 10, and holds the frame 11 on the holding surface 32 of the holding table 31. 31 is clamped by a clamp part 33 provided around it. In the functional layer processing step 102, as shown in FIG. The wafer 1 is divided into the wafer 1 from the surface 3 side of the wafer 1 while relatively moving the laser beam irradiation unit 36 along the dividing line 4 from the position shown by the broken line in FIG. 6 to the position shown by the solid line. 4, a pulsed laser beam 34 is irradiated onto the center of the planned dividing line 4 in the width direction.

Then, since the wavelength of the laser beam 34 of the wafer 1 is absorptive to the functional layer 6, the functional layer 6 on the dividing line 4 is ablated, and the functional layer 6 on the dividing line 4 is ablated. The protective film 26 and functional layer 6 are removed. Note that since the purpose of the functional layer processing step 102 is to remove the functional layer 6, the laser processing groove 14 is formed to a depth where the substrate 2 is exposed. Therefore, the surface layer of the substrate 2 is also removed. Further, the wavelength of the laser beam 34 irradiated in the functional layer processing step 102 may also be absorbent to the substrate 2. In the functional layer processing step 102, as shown in FIG. 7, the wafer 1 is formed along the dividing line 4 with a laser processing groove 14 in which the substrate 2 is exposed at the center in the width direction of the dividing line 4. Further, as shown in FIG. 7, in the wafer 1, a damaged region 15 modified by the heat of the laser beam 34 is formed around the laser-processed groove 14, including at least the side surface 141 and the edge 142 of the laser-processed groove 14. be done. Since the heat generated by laser processing rises upward, damage is more likely to occur near the surface of the functional layer 6 than near the bottom of the laser processed groove 14. Therefore, in the first embodiment, a damaged region 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 processing grooves 14 on all the planned dividing lines 4.

(Protective film cleaning step)
FIG. 8 is a side view schematically showing, partially in cross section, the cleaning step of the wafer processing method shown in FIG. 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. The protective film cleaning step 103 is a step of cleaning the wafer 1 on which the functional layer processing step 102 has been performed.

In the protective film cleaning step 103, the cleaning device 40 suction-holds the back side 7 of the wafer 1 to the holding surface 42 of the spinner table 41 via the adhesive tape 10, and the frame 11 is attached to a clamp provided around the spinner table 41. Clamp at section 43. In the protective film cleaning step 103, the cleaning device 40 rotates the spinner table 41 around its axis as shown in FIG. to the center of the surface 3.

Then, the supplied cleaning water 84 flows over the surface 3 of the wafer 1 from the center side toward the outer circumference due to the centrifugal force generated by the rotation of the spinner table 81, thereby cleaning the entire surface 3 of the wafer 1. The protective film 26 is melted and poured over the surface 3. In the protective film cleaning step 103, the cleaning device 40 removes foreign matter from the surface 3 of the wafer 1, and also removes the protective film 26 from the surface 3, as shown in FIG.

(Damage removal step)
FIG. 10 is a side view schematically showing, partially in cross section, the damage removal step of the wafer processing method shown in FIG. FIG. 11 is a cross-sectional view schematically showing a main part of the wafer in the damage removal step of the wafer processing method shown in FIG. 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.

The damage removal step 104 is a step in which, after the functional layer processing step 102 is performed, the damaged region 15 on the inner surface of the laser processing groove 14 modified by the functional layer processing step 102 is removed using the cutting blade 54 . In the damage removal step 104, as shown in FIG. It is clamped by a clamp part 53 provided around the periphery. In the damage removal step 104, the cutting device 50 moves the holding table 51 and the cutting blade 54 relatively along the dividing line 4, as shown in FIGS. The cutting blade 56 of the cutting blade 54, which has a thicker blade thickness 55 than The cutting groove 17 including the edge 142 is formed to remove at least a portion of the damaged area 15 formed on the side surface 141 and edge 142 of the laser-processed groove 14.

In the first embodiment, in the damage removal step 104, as shown in FIG. It is shallower than the thickness 13 of layer 6. In the damage removal step 104, the cutting device 50 removes at least a portion of the damaged area 15 between the side surfaces 141 and edges 142 of the laser processing grooves 14 formed on all the planned dividing lines 4, as shown in FIG. .

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

The substrate dividing step 105 is a step of dividing the substrate 2 along the planned dividing line 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 sets the frame 11 around the holding table. Clamp with the clamp part that has been fixed. In the substrate dividing step 105, the laser processing device 60 positions the condensing point 62 of the laser beam 61 having a wavelength that is transparent to the substrate 2 inside the substrate 2, as shown in FIG. A pulsed laser beam 61 is irradiated onto the wafer 1 from the back surface 7 side of the wafer 1 along the planned dividing line 4 while moving the laser beam irradiation unit 63 relatively along the planned dividing line 4.

Then, in the wafer 1, since the wavelength of the laser beam 61 is transparent to the wafer 1, a modified layer 19 is formed inside the substrate 2 along the dividing line 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, thereby cutting the substrate along all the planned dividing lines 4. A modified layer 19 is formed inside the substrate 2.

Note that the modified layer 19 refers to a region whose density, refractive index, mechanical strength, and other physical properties are different from those of the surrounding area, and includes a melt-treated region, a crack region, and a dielectric breakdown region. , a refractive index change region, and a region in which these regions are mixed. Note that the gas strength of the modified layer 19 is lower than the mechanical strength of the parts of the substrate 2 other than the modified layer 19.

Note that in the first embodiment, the laser beam 61 that forms the modified layer 19 on the substrate 2 uses a laser beam that has a shorter pulse width than the laser beam 34 that forms the laser processed groove 14. Since the laser beam 34 that forms the laser-processed groove 14 has a longer pulse width than the laser beam 61 that forms the modified layer 19, the thermal effect is greater and damage areas 15 are more likely to occur in the functional layer 6. .

In the substrate dividing step 105, a protection 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 to the holding surface 72 of the holding table 71 via the protection member 191. In the substrate dividing step 105, the grinding device 70 rotates the grinding wheel 74 around the axis by the spindle 73 and rotates the holding table 71 around the axis, as shown in FIG. While supplying water, the grinding wheel 74 is brought into contact with the back surface 7 and brought close to the holding table 71 at a predetermined feed speed, and the wafer 1 is ground by the grinding wheel 75 to give the wafer 1 a predetermined finish. Thin to thickness. Note that in the wafer 1 that has been thinned to the final thickness, the functional layer 6 is thinner than the substrate 2. Further, in the first embodiment, the entire modified layer 19 of the wafer 1 that has been thinned to the final thickness is removed in the substrate dividing step 105.

In the first embodiment, in the substrate dividing step 105, the wafer 1 is pressed by the grinding wheel 75 of the grinding wheel 74, so that the wafer 1 has cracks 192 from the modified layer 19 at the bottom of the laser processing groove 14, as shown in FIG. Then, the substrate 2 and the functional layer 6 are divided along the dividing line 4 extending to the back surface 7 . Note that FIG. 14 omits the modified layer 19 and shows the cracks 192.

In the wafer processing method according to the first embodiment described above, in the functional layer processing step 102, the functional layer 6 is removed to form the laser processing groove 14 that exposes the substrate 2, and then the functional layer is modified in the functional layer processing step 102. Since at least a portion of the damaged region 15 including the side surfaces 141 and edges 142 of the laser-processed groove 14 is removed by the cutting blade 54, the damaged region 15 remaining in the functional layer 6 can be reduced. As a result, the wafer processing method according to the first embodiment has the effect that it is difficult to leave damaged areas 15 on the wafer 1 after processing.

In the wafer processing method according to the first embodiment, in the functional layer processing step 102, when the functional layer 6 is removed using the laser beam 34, a damaged region 15 is generated in the functional layer 6 due to the heat generated by the laser beam 34. Since the cutting blade 54 is less affected by heat than the laser beam 34, the wafer processing method according to the first embodiment prevents the formation of new damage around the cutting groove, and also improves the laser processing groove 14. The damaged area 15 on the inner surface can be removed.

Note that if the functional layer 6 is attempted to be removed using only the cutting blade 54, there is a problem that the processing load is high and the functional layer 6 is pulled by the cutting blade 54 and peeled off.However, the wafer processing method according to the first embodiment Since only the edge 142 of the laser-processed groove 14 is cut with the cutting blade 54 while the functional layer 6 is removed by the laser beam 34, the volume of the functional layer 6 to be cut is reduced, the processing load is kept low, and the functionality is improved. Peeling of the layer 6 from the substrate 2 can be prevented.

In order to further prevent separation of the functional layer 6 from the substrate 2 by the cutting blade 54, it is preferable that the amount of functional layer 6 removed by the cutting blade 54 is small. Since the heat generated by the laser beam 34 rises upward, the damaged region 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 the first embodiment, the damaged region 15 is removed by cutting the laser processing groove 14 that exposes the substrate 2 with the cutting blade 54 to a depth that does not reach the substrate 2. As a result, in the wafer processing method according to the first embodiment, since the removal amount of the functional layer 6 by the cutting blade 54 is limited in the depth direction, the cutting load can be kept low, and the peeling of the functional layer 6 from the substrate 2 can be suppressed. can be prevented.

In the wafer processing method according to the first embodiment, damage caused to the substrate 2 also affects the bending strength of the individually divided device chips, but the modified layer 19 is formed and removed by grinding the modified layer 19. In the case of cutting, the damaged region 15 caused by the laser beam 34 irradiation 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 region 15 of the functional layer 6 affects the flexural strength of such a wafer 1.

In the first embodiment, since 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, the thermal effect is greater and the laser beam 34 forms the functional layer 6. However, a damaged area 15 is likely to occur. However, since the wafer processing method according to the first embodiment removes the damaged region 15 of the functional layer 6, the wafer processing method has the effect that it is difficult to leave the damaged region 15 on the wafer 1 after processing.

[Modified example]
A wafer processing method according to a modification of Embodiment 1 of the present invention will be described based on the drawings. FIG. 16 is a side view schematically showing a part of the damage removal step of the wafer processing method according to the modified example of the first embodiment, with a partial cross section. FIG. 17 is a side view schematically showing, partially in cross section, the remaining part of the damage removal step of the wafer processing method according to the modification of the first embodiment. In addition, in FIGS. 16 and 17, the same parts as in Embodiment 1 are denoted by the same reference numerals, and the description thereof will be omitted.

The wafer processing method according to the modification of Embodiment 1 is the same as Embodiment 1 except that the damage removal step 104 is different. In a modification of the first embodiment, as shown in FIG. 16, the cutting device 50 cuts the width 16 of the laser-processed groove 14 while relatively moving the holding table 51 and the cutting blade 54 along the planned dividing line 4. The cutting blade 56-1 of the cutting blade 54-1 with a thin blade thickness 55-1 is cut into one inner edge of the laser processing groove 14 from the surface 3 of the wafer 1 along the dividing line 4, as shown in FIG. As shown in FIG. A cutting groove 17 is formed, and at least a part of the damaged area 15 formed on the side surface 141 and the edge 142 of the laser-processed groove 14 is removed.

Also in the modified example of the first embodiment, the depth that the cutting device 50 cuts with the cutting blade 54 in the damage removal step 104 is shallower than the depth of the laser-processed groove 14 and shallower than the thickness 13 of the functional layer 6.

In the wafer processing method according to the modification of the first embodiment, in a functional layer processing step 102, the functional layer 6 is removed to form a laser processing groove 14 that exposes the substrate 2, and then in the functional layer processing step 102, modification is performed. Since at least a part of the damaged area 15 on the inner surface of the functional layer 6 that has been removed is removed by the cutting blade 54, the damaged area 15 remaining on the functional layer 6 can be suppressed. As a result, the wafer processing method according to the first embodiment has the effect that damaged areas 15 are less likely to be left on the wafer 1.

[Embodiment 2]
A wafer processing method according to the second embodiment will be explained based on the drawings. FIG. 18 is a cross-sectional view schematically showing a main part of the wafer after two laser processing grooves are 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 the main part of the wafer after removing the functional layer between two laser-processed grooves 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 the main part of the wafer after the protective film cleaning step of the wafer processing method according to the second embodiment. FIG. 21 is a side view schematically showing, partially in cross section, 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 the wafer after the damage removal step of the wafer processing method according to the second embodiment. 18, FIG. 19, FIG. 20, FIG. 21, and FIG. 22, the same parts as in the second embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

The wafer processing method according to the second embodiment is the same as that of the first embodiment except that the functional layer processing step 102 and the damage removal step 104 are different. In the second embodiment, in the functional layer processing step 102, the laser processing device 30 positions the condensing point 35 of the laser beam 34 having a wavelength that is absorbent to the functional layer 6 on the surface 3, as shown in FIG. While relatively moving the holding table 51 and the laser beam irradiation unit 36 along the planned dividing line 4, a pulse pattern is applied to the wafer 1 from the front surface 3 side of the wafer 1 to one end in the width direction of the planned dividing line 4. After irradiating the wafer 1 with a laser beam 34 to form a laser processing groove 14-2 at one end, irradiating the wafer 1 with a pulsed laser beam 34 at the other end in the width direction of the dividing line 4, A laser-processed groove 14-2 is formed at the other end.

In the second embodiment, in the functional layer processing step 102, the laser processing device 30 forms two laser processing grooves 14-2 at both ends of each planned dividing line 4 in the width direction, and then forms two grooves 14-2 as shown in FIG. The functional layer 6 between the laser-processed grooves 14-2 is removed to form a laser-processed groove 14 wider than that in the first embodiment at each dividing line 4. Thereafter, the protective film 26 of the wafer 1 is removed in a protective film cleaning step 103, as shown in FIG. In addition, in the second embodiment, the laser beam 34 with a beam diameter larger than the two laser processing grooves 14-2 is irradiated, but in the present invention, the laser beam 34 with a small beam diameter is irradiated multiple times. Alternatively, the functional layer 6 between the two laser-processed grooves 14-2 may be removed using a cutting blade.

In the second embodiment, in the damage removal step 104, the cutting device 50 removes the laser-processed groove 14 while relatively moving the holding table 51 and the cutting blade 54 along the planned dividing line 4, as shown in FIG. The cutting blade 56 of the cutting blade 54, which has a blade thickness 55 thicker than the width 16, is cut into a region including both edges 142 of the laser processing groove 14 from the surface 3 of the wafer 1 along the planned dividing line 4 to form a cutting groove. 17 to remove at least a portion of the damaged region 15 formed on the side surface 141 and edge 142 of the laser-processed groove 14.

In the second embodiment, in the damage removal step 104, as shown in FIG. 22, the cutting device 50 cuts the depth with the cutting blade 54, which is shallower than the depth 18 of the laser-processed groove 14, and the thickness 13 of the functional layer 6. shallower than 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 processing groove 14 formed on all the planned dividing lines 4, as shown in FIG.

In the wafer processing method according to the second embodiment, in a functional layer processing step 102, the functional layer 6 is removed to form a laser processing groove 14 that exposes the substrate 2, and then the modified function is removed in the functional layer processing step 102. Since at least a portion of the damaged area 15 on the inner surface of the layer 6 is removed by the cutting blade 54, the damaged area 15 remaining on the functional layer 6 can be suppressed. As a result, the wafer processing method according to the first embodiment has the effect that damaged areas 15 are less likely to be left on the wafer 1.

[Modified example]
A wafer processing method according to a modification of the second embodiment of the present invention will be described based on the drawings. FIG. 23 is a side view schematically showing a part of the damage removal step of the wafer processing method according to a modification of the second embodiment, with a portion in cross section. FIG. 24 is a side view schematically showing, partially in cross section, the remaining part of the damage removal step of the wafer processing method according to a modification of the second embodiment. In addition, in FIGS. 23 and 24, the same parts as in Embodiment 2 are denoted by the same reference numerals, and the description thereof will be omitted.

The wafer processing method according to the modification of the second embodiment is the same as the second embodiment except that the damage removal step 104 is different. In a modification of the second embodiment, as shown in FIG. 23, the cutting device 50 cuts the width 16 of the laser-processed groove 14 while relatively moving the holding table 51 and the cutting blade 54 along the planned dividing line 4. Also, the cutting blade 56-1 of the cutting blade 54-1 with a thin blade thickness 55-1 is cut into a region including one edge 142 of the laser processing groove 14 from the surface 3 of the wafer 1 along the dividing line 4, As shown in FIG. 24, the cutting edge 56 of the cutting blade 54 is cut into the area including the other edge 142 of the laser processing groove 14 along the dividing line 4 from the surface 3 of the wafer 1 to form the cutting groove 17. At least a portion of the damaged region 15 formed on the inner surface of the laser-processed groove 14 is removed.

Also in the modified example of the second embodiment, the depth that the cutting device 50 cuts with the cutting blade 54-1 in the damage removal step 104 is shallower than the depth 18 of the laser-processed groove 14 and smaller than the thickness 13 of the functional layer 6. Also shallow.

In the wafer processing method according to the modification of the second embodiment, in the functional layer processing step 102, the functional layer 6 is removed to form a laser processing groove 14 exposing the substrate 2, and then the functional layer processing step 102 is performed to form a laser processing groove 14 for exposing the substrate 2. Since at least a part of the damaged area 15 on the inner surface of the functional layer 6 that has been removed is removed by the cutting blade 54, the damaged area 15 remaining on the functional layer 6 can be suppressed. As a result, the wafer processing method according to the first embodiment has the effect that damaged areas 15 are less likely to be left on the wafer 1.

Note that the present invention is not limited to the above embodiments. That is, various modifications can be made without departing from the gist of the invention. Note that in the present invention, the protective film coating step 101 and the protective film cleaning step 103 are not essential and may not be performed.

1 Wafer 2 Substrate 4 Planned dividing line 6 Functional layer 14 Laser processing groove 15 Damaged area 34 Laser beam 54, 54-1 Cutting blade 101 Protective film coating step 102 Functional layer processing step 104 Damage removal step 105 Substrate dividing step

Claims (3)

A wafer processing method for processing a wafer having a functional layer laminated on a substrate, the method comprising:
a functional layer processing step of irradiating the functional layer with a laser beam along the planned dividing line to form a laser processing groove in the functional layer;
Processing of a wafer, comprising, after performing the functional layer processing step, a damage removal step of removing, with a cutting blade, a damaged area around the laser processing groove modified by the functional layer processing step. Method. 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 processing groove. 3. The wafer processing method according to claim 1, further comprising a substrate dividing step of dividing the substrate along the planned dividing line.

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