Method for processing wafers and method for dividing wafers

Abstract

To suppress the adverse effects caused by the scattering of debris when a laser beam is irradiated. [Solution] The present invention relates to a method for forming grooves extending along a street of a wafer (100) having a functional layer (120) on its surface (101) and forming a street (104) with a plurality of devices (105). The method comprises a protective film formation step of forming a protective film on the surface of the wafer, a fine groove formation step of forming a plurality of fine grooves (151) extending along the street by irradiating a first laser beam (LB1) that is divided into a plurality of parts in the width direction within the width of the street of the wafer held on a chuck table (34), a wide bottom groove formation step of eliminating the plurality of fine grooves and forming a bottom groove (152) of a predetermined width by irradiating a second laser beam (LB2) with a predetermined width less than or equal to the width of the street, and a protective film removal step of removing the protective film.

Description

Technical Field

[0001] The present invention relates to a method for processing a bonded wafer that transfers devices from one wafer to another wafer.

Background Art

[0002] Patent Document 1 discloses a method of dividing a wafer by irradiating the surface of a wafer having a plurality of devices and streets with a laser beam. In this method, along the streets in the wafer, a laser beam having an absorbable wavelength with respect to the wafer is irradiated, and ablation processing for removing the surface of the wafer is performed.

[0003] A protective film may be formed on the surface of the wafer processed by the above method. In this case, when cutting and dividing the wafer along the streets, by irradiating a laser beam from the protective film side of the wafer as in Patent Document 1, the formation of two grooves along the streets and the formation of a wide groove between the two grooves are performed. At this time, due to the formation of the wide groove, metal components such as TEGs and wirings arranged on the streets are removed by ablation processing. Further, even if debris such as a melt of a metal component is generated by the irradiation of the laser beam, the protective film protects the devices on the surface of the wafer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when forming wide grooves by laser beam irradiation, the amount of debris increases with the groove width, which presents a problem as the protective film may not adequately protect the device. While increasing the thickness of the protective film can protect the device from debris, it also increases the amount of resin material required to form the protective film and increases the time required for its formation, thus reducing productivity.

[0006] This invention has been made in view of the above, and one of its objectives is to provide a wafer processing method and a wafer splitting method that can suppress adverse effects caused by the scattering of debris when a laser beam is irradiated. [Means for solving the problem]

[0007] A wafer processing method according to one aspect of the present invention is a wafer processing method for which a laser beam is irradiated along a street of a wafer having an insulating film on its surface and forming a street with a plurality of devices, thereby forming grooves extending along the street, comprising: a protective film forming step of forming a protective film on the surface of the wafer; a fine groove forming step of irradiating a first laser beam, which is divided into a plurality of parts in the width direction within the width of the street of the wafer held on a chuck table, to form a plurality of fine grooves extending along the street; a wide bottomed groove forming step of irradiating a second laser beam with a predetermined width less than or equal to the width of the street to remove the plurality of fine grooves and form a bottomed groove of a predetermined width; and a protective film removal step of removing the protective film.

[0008] Furthermore, a wafer processing method according to one aspect of the present invention is a wafer processing method for which a laser beam is irradiated along a street of a wafer having an insulating film on its surface and forming a street with a plurality of devices, thereby forming grooves extending along the street, comprising: a protective film forming step of forming a protective film on the surface of the wafer; a wide bottomed groove forming step of irradiating the wafer, held on a chuck table, with a first laser beam divided into a plurality of parts in the width direction within the width of the street and a second laser beam having a predetermined width less than or equal to the width of the street, to form a bottomed groove of a predetermined width; and a protective film removal step of removing the protective film.

[0009] A wafer splitting method according to one aspect of the present invention is a wafer splitting method comprising: irradiating a laser beam along the streets of a wafer having an insulating film on its surface and forming a street with a plurality of devices, thereby forming grooves along the streets, and then splitting the wafer, comprising: a protective film forming step of forming a protective film on the surface of the wafer; a fine groove forming step of irradiating a wafer held on a chuck table with a first laser beam divided into a plurality of parts in the width direction within the width of the street to form a plurality of fine grooves extending along the street; a wide bottom groove forming step of irradiating a second laser beam with a predetermined width less than or equal to the width of the street to remove the plurality of fine grooves and form a bottom groove of a predetermined width; a protective film removal step of removing the protective film; and a splitting step of splitting the wafer along the bottom grooves formed on the wafer.

[0010] Furthermore, a wafer splitting method according to one aspect of the present invention is a wafer splitting method comprising: irradiating a laser beam along the streets of a wafer having an insulating film on its surface and forming streets with a plurality of devices to form grooves along the streets, and then splitting the wafer, comprising: a protective film forming step of forming a protective film on the surface of the wafer; a wide bottomed groove forming step of irradiating a wafer held on a chuck table with a first laser beam divided into a plurality of parts in the width direction within the width of the streets and a second laser beam with a predetermined width less than or equal to the width of the streets, to form bottomed grooves of a predetermined width; a protective film removal step of removing the protective film; and a splitting step of splitting the wafer along the bottomed grooves formed on the wafer. [Effects of the Invention]

[0011] According to the present invention, a first laser beam, which is divided into multiple beams, is used to reduce the size of, for example, metal parts on the street, and a second laser beam, which is relatively wider, is used to form a bottomed groove. By reducing the size of the metal parts in this way, the amount of debris scattered onto the protective film can be reduced, and the protective film can protect the device from damage caused by the debris. This eliminates the need to form a thick protective film, reduces the amount of resin material used for the protective film, shortens the formation time of the protective film, increases productivity, and suppresses the adverse effects of debris scattering when the laser beam is irradiated. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1A is a perspective view showing the appearance of a wafer used in the wafer splitting method in the embodiment, and Figure 1B is a partial cross-sectional view of the wafer. [Figure 2] This is an explanatory diagram of the protective film formation process. [Figure 3] This is a schematic perspective view of a laser processing device. [Figure 4] Figures 4A and 4B illustrate the process of forming narrow grooves. [Figure 5] Figures 5A and 5B illustrate the process of forming wide, bottomed grooves. [Figure 6] This is a schematic diagram illustrating the laser irradiation flow in the narrow groove formation process and the wide bottom groove formation process. Figures 6A and 6B show embodiments, Figure 6C shows a modified example, and Figure 6D shows another modified example. [Figure 7] This is a description of the protective film removal process. [Figure 8] This is an explanatory diagram showing an example of a division process. [Figure 9] Figures 9A and 9B are explanatory diagrams showing another example of the splitting process. [Figure 10] Figures 10A and 10B are explanatory diagrams showing another example of the splitting process. [Modes for carrying out the invention]

[0013] Hereinafter, a wafer splitting method including a wafer processing method according to an embodiment will be described with reference to the accompanying drawings. In the wafer splitting method according to the embodiment, a protective film forming step, a narrow groove forming step, a wide-bottomed groove forming step, a protective film removing step, and a splitting step are performed in this order. Note that the steps shown in each figure in the embodiment are merely examples and are not limited to this configuration.

[0014] FIG. 1A is a perspective view showing the appearance of a wafer used in the wafer splitting method according to the embodiment. FIG. 1B is a partial cross-sectional view of the wafer. As shown in FIG. 1A, the wafer 100 includes, for example, a disk-shaped substrate 110 having a circular surface (first surface) 111 and a circular back surface (second surface) 112 on the opposite side of the surface 101. The substrate 110 is typically made of a semiconductor such as silicon (Si).

[0015] On the surface 111 side of the substrate 110, a functional layer 120 composed of at least one film is laminated. Specifically, the functional layer 120 is composed of metal parts or metal films that serve as wiring, an insulating film (including a Low-k film) that insulates between wirings, a semiconductor film, and the like. Representative examples of the Low-k film used for the functional layer 120 include inorganic insulating films made of inorganic materials such as SiOF and SiOB, and organic insulating films made of polymers such as polyimide and parylene.

[0016] The back surface 112 of the substrate 110 described above becomes the back surface 102 of the wafer 100, and the surface 121 of the functional layer 120 becomes the surface 101 of the wafer 100. The back surface 122 of the functional layer 120 is laminated on the surface 111 of the substrate 110. The surface 101 side of the wafer 100 is partitioned into a plurality of small regions by a plurality of linear streets 104 (predetermined splitting lines) having a predetermined width, and in each small region, a device 105 such as an IC (Integrated Circuit) including the functional layer 120 as a component is provided. Therefore, the wafer 100 forms a plurality of streets 104 and a plurality of devices 105. The functional layer 120 is also formed on the streets 104, and metal parts and the like are provided in the streets 104.

[0017] In this embodiment, the substrate 110 of the wafer 100 is made of a semiconductor such as silicon. However, there are no restrictions on the material, shape, structure, size, etc. of the substrate 110. For example, a wafer 100 including a substrate 110 made of other materials such as semiconductors, ceramics, resins, metals, etc. may be used. Similarly, there are no restrictions on the type, quantity, shape, structure, size, arrangement, etc. of the devices 105.

[0018] Before the implementation of the protective film forming process described later, as shown in FIG. 1A, a tape T is adhered to the back surface 102 of the wafer 100, and the wafer 100 is supported by an annular frame F through this tape T. Therefore, in the state supported by the frame F, the front surface 101 of the wafer 100 is exposed upward. In this embodiment, each process is implemented in the state where the wafer 100 is supported through the tape T and the frame F, but each process may also be implemented in the state without the tape T and the frame F. Also, tapes T with different materials and functions may be used according to the processing and treatment in each process.

[0019] [Protective Film Forming Process] FIG. 2 is an explanatory diagram of the protective film forming process. As shown in FIG. 2, first, the protective film forming process is implemented in a protective film forming apparatus (not shown). In the protective film forming process, the wafer 100 is sucked and held by a holding table 11 through the tape T. Four clamp portions 12 (two are not shown) are provided around the holding table 11, and the frame F is clamped and fixed from all directions by each clamp portion 12. A water-soluble resin nozzle 13 is provided above the holding table 11, and the water-soluble resin is dropped onto the wafer 100 from the tip of the water-soluble resin nozzle 13.

[0020] When a pool of water is formed in the center of the wafer 100 surface by the dropped water-soluble resin, the supply of water-soluble resin is stopped, and the holding table 11 that holds the wafer 100 is rotated. Due to the centrifugal force accompanying the rotation of the holding table 11, the entire surface 101 of the wafer 100 is covered with water-soluble resin. Then, as the water-soluble resin solidifies, a protective film 140 is uniformly formed on the surface 121 (top surface) of the functional layer 120 that becomes the surface 101 of the wafer 100. The protective film 140 prevents debris from adhering to the device 105 during laser processing, which will be described later. Examples of water-soluble resins include polyvinyl alcohol (PVA) and polyethylene glycol (PEG).

[0021] After the protective film formation process is performed, the laser processing apparatus 20 sequentially performs the fine groove formation process and the wide low groove formation process. Before describing these processes, the laser processing apparatus 20 will be described with reference to Figure 3. Figure 3 is a schematic perspective view of the laser processing apparatus. Note that the laser processing apparatus is not limited to the configuration shown in Figure 3, as long as it is capable of performing the laser processing steps of this embodiment.

[0022] As shown in Figure 3, the laser processing apparatus 20 is configured to laser process the wafer 100 by relatively moving the laser irradiation unit 40, which irradiates a first laser beam LB1 (see Figure 4A) and a second laser beam LB2 (see Figure 4B), and the chuck table 34 that holds the wafer 100.

[0023] A moving mechanism 22 for moving the chuck table 34 in the X-axis and Y-axis directions is provided on the base 21 of the laser processing apparatus 20. The moving mechanism 22 has a pair of guide rails 23 arranged on the base 21 and parallel to the X-axis direction, and a motor-driven X-axis table 24 that is slidably mounted on the pair of guide rails 23. The moving mechanism 22 also has a pair of guide rails 25 arranged on the upper surface of the X-axis table 24 and parallel to the Y-axis direction, and a motor-driven Y-axis table 26 that is slidably mounted on the pair of guide rails 25.

[0024] Nut portions (not shown) are formed on the back sides of the X-axis table 24 and the Y-axis table 26, respectively, and ball screws 27 and 28 are screwed into these nuts. Drive motors 29 and 30, connected to one end of the ball screws 27 and 28, are rotationally driven, causing the chuck table 34 to move along the guide rails 23 and 25 in the X-axis and Y-axis directions.

[0025] Furthermore, the moving mechanism 22 further includes a rotating mechanism 31 provided on the Y-axis table 26. The rotating mechanism 31 supports the chuck table 34 from below, and the rotating mechanism 31 and the chuck table 34 move together with the Y-axis table 26 in the X-axis and Y-axis directions. The rotating mechanism 31 also includes a drive motor and pulley mechanism (not shown), which rotate the chuck table 34 around the Z-axis.

[0026] Four clamping sections 36 are provided around the chuck table 34, and the frame F is clamped and fixed from all four sides by each clamping section 36. A holding surface 35 for suction holding the wafer 100 is formed on the upper surface of the chuck table 34. The holding surface 35 is connected to a suction source (not shown), such as an ejector, via a flow path (not shown) or a valve (not shown) provided inside the chuck table 34.

[0027] An arm portion 38 is provided protruding from the rear vertical wall portion 37 of the chuck table 34, and a laser irradiation unit 40 and an imaging camera 41 are provided at the tip of the arm portion 38 so as to face the chuck table 34 in the vertical direction. The imaging camera 41 is provided to the side of the laser irradiation unit 40 and images the surface 101 of the wafer 100 held by the chuck table 34.

[0028] The laser irradiation unit 40 irradiates the wafer 100 held on the chuck table 34 with a first laser beam LB1 and a second laser beam LB2 emitted from a laser oscillator (not shown). The laser oscillator contains, for example, a laser medium such as Nd:YAG suitable for laser oscillation, and generates pulsed laser beams LB1 and LB2 with wavelengths absorbed by the wafer 100 (functional layer 120) at a predetermined repetition frequency.

[0029] The laser irradiation unit 40 is equipped with optical systems such as mirrors and lenses that guide the pulsed first laser beam LB1 and second laser beam LB2 emitted from the laser oscillator to the wafer 100. The laser irradiation unit 40 focuses the first laser beam LB1 and second laser beam LB2 to a predetermined height position (a position along the Z-axis) above the chuck table 34. The functional layer 120 of the wafer 100 is ablated by the first laser beam LB1 and second laser beam LB2 irradiated from the laser irradiation unit 40. Ablation is a phenomenon in which, when the irradiation intensity of each laser beam LB1 and LB2 exceeds a predetermined processing threshold, it is converted into electronic, thermal, photochemical, and mechanical energy on the solid surface, resulting in the explosive emission of neutral atoms, molecules, positive and negative ions, radicals, clusters, electrons, and light, and etching of the solid surface.

[0030] [Narrow groove forming process] Using the laser processing apparatus 20, the fine groove formation process shown in Figures 4A and 4B is performed. Figures 4A and 4B illustrate the fine groove formation process; Figure 4A is a cross-sectional view showing the wafer being irradiated with the first laser beam, and Figure 4B is a cross-sectional view of the wafer after laser processing with the first laser beam. In the fine groove formation process, the first laser beam LB1 (laser beam), which is divided into multiple parts in the width direction within the width of the street 104 of the wafer 100 held in the chuck table 34, is irradiated to form multiple fine grooves 151 (grooves) extending along the street 104. In other words, multiple fine grooves 151 are formed in one street 104 after one processing feed. Multiple fine grooves 151 may be formed by performing multiple processing feeds (X-axis direction feeds). In this case, the first laser beam LB1 does not have to be divided into multiple parts.

[0031] In the groove formation process, first, the wafer 100 is transported to the chuck table 34 via a transport mechanism (not shown). At this time, the wafer 100 is placed on the chuck table 34 so that the side with the protective film 140 formed on the wafer 100 faces upward. In this state, negative pressure (suction force) generated by a suction source is applied to the upper surface of the chuck table 34, and the wafer 100 is held on the chuck table 34 via the tape T.

[0032] Next, the orientation of the chuck table 34 around the Z axis is adjusted by the rotation mechanism 31 so that the extension direction of the street 104, which will be the processing area of ​​the wafer 100, is parallel to the X axis. Then, the position of the chuck table 34 in the Y axis direction is adjusted by the movement mechanism 22 so that the laser irradiation unit 40 is positioned above the extension line in the extension direction of the street 104. In addition, the optical system of the laser irradiation unit 40 is adjusted so that the first laser beam LB1 is focused at a height suitable for processing the wafer 100, and the first laser beam LB1 is divided into multiple beams in the width direction within the width of the street 104.

[0033] Subsequently, while irradiating the wafer 100, which has been divided into multiple parts from the laser irradiation unit 40, the moving mechanism 22 moves the chuck table 34 along the X-axis at a predetermined speed (processing feed rate). As a result, the wafer 100 held on the chuck table 34 and the focal point of the first laser beam LB1 move relative to each other in the X-axis direction.

[0034] As a result, as shown in Figure 4A, the first laser beam LB1 is irradiated from the protective film 140 side formed on the wafer 100 along the street 104, and the portion of the functional layer 120 irradiated by the first laser beam LB1 is removed by ablation. This creates a plurality of fine grooves 151 extending along the street 104, as shown in Figure 4B. These multiple fine grooves 151 divide and reduce the size of metal parts and the like formed on the street 104.

[0035] At the bottom of the multiple narrow grooves 151, there is a high probability that the substrate 110 will be exposed, but the substrate 110 does not necessarily have to be exposed at the bottom of the multiple narrow grooves 151. The multiple narrow grooves 151 may or may not reach the back surface 122 of the functional layer 120.

[0036] The conditions for irradiating with the first laser beam LB1 are adjusted to a range in which multiple narrow grooves 151, spaced apart from each other in the width direction of the street 104, are appropriately formed. For example, the first laser beam LB1 is branched and divided so as to be focused at multiple points spaced apart from each other in the width direction of the street 104 (i.e., multiple points spaced apart along the Y-axis). Therefore, multiple narrow grooves 151 are formed simultaneously with a single movement of the chuck table 34 (scanning of the first laser beam LB1). However, the specific conditions and irradiation methods for irradiating with the first laser beam LB1 are not limited to these.

[0037] [Wide bottomed groove forming process] After the completion of the narrow groove formation process, the wide-bottomed groove formation process shown in Figures 5A and 5B is performed. Figures 5A and 5B illustrate the wide-bottomed groove formation process; Figure 5A is a cross-sectional view showing the wafer being irradiated with the second laser beam, and Figure 5B is a cross-sectional view of the wafer after laser processing by the second laser beam.

[0038] In the wide-bottomed groove formation process, a second laser beam LB2 (laser beam) with a predetermined width less than or equal to the width of the street 104 of the wafer 100 held on the chuck table 34 is irradiated to eliminate the multiple narrow grooves 151 shown in Figure 4B and form a bottomed groove 152 (groove) of a predetermined width. When forming the bottomed groove 152 in the wide-bottomed groove formation process, for example, the same or similar laser processing apparatus as the laser processing apparatus 20 described above is used, and the processing procedure is carried out in the same way as in the narrow groove formation process, except that the laser beams LB1 and LB2 used for irradiation are different.

[0039] In the wide-bottomed groove formation process, when the laser processing apparatus 20 described above is used, the optical system of the laser irradiation unit 40 is adjusted to allow simultaneous irradiation of the second laser beam LB2 in a predetermined width less than or equal to the width of the street 104, while simultaneously branching or shaping it. This second laser beam LB2 is irradiated along the street 104 where multiple fine grooves 151 have been formed, using the same procedure as in the fine groove formation process. As a result, in the areas of the street 104 where multiple fine grooves 151 have been formed, the portion of the functional layer 120 irradiated by the second laser beam LB2 is removed by ablation. As a result, as shown in Figure 5B, the multiple fine grooves 151 are left unformed, and a wide-bottomed groove 152 extending along the street 104 is formed. Since the metal parts formed on the street 104 by the multiple fine grooves 151 are smaller, the debris caused by the metal parts generated during the formation of the bottomed groove 152 is also smaller.

[0040] At the bottom of the wide closed groove 152, there is a high possibility that the substrate 110 will be exposed, but the substrate 110 does not necessarily have to be exposed at the bottom. The wide closed groove 152 may or may not reach the back surface 122 of the functional layer 120.

[0041] The conditions for irradiating with the second laser beam LB2 are adjusted within a range that appropriately forms a bottomed groove 152 of a predetermined width in the width direction of the street 104. Therefore, one movement of the chuck table 34 (scanning of the second laser beam LB2) forms one bottomed groove 152 of a predetermined width. However, the specific conditions and irradiation methods for irradiating with the second laser beam LB2 are not limited to these.

[0042] Figures 6A and 6B are schematic explanatory diagrams showing the laser irradiation flow for the narrow groove formation process and the wide bottomed groove formation process in the embodiment. As shown in Figure 6A, in this embodiment, the narrow groove formation process, in which the first laser beam LB1 is irradiated onto the street 104, is performed first, and the wide bottomed groove formation process, in which the second laser beam LB2 is irradiated, is performed later, at different timings. Therefore, for example, on any wafer 100, after forming narrow grooves 151 by performing the narrow groove formation process on all streets 104 from which the functional layer 120 is to be removed, the bottomed grooves 152 are formed by performing the wide bottomed groove formation process.

[0043] [Protective film removal process] After the wide-bottomed groove formation process is performed, a protective film removal process is carried out to remove the protective film 140 formed on the wafer 100, as shown in Figure 7. Figure 7 illustrates the protective film removal process. In the protective film removal process, cleaning water is supplied from the water supply nozzle 45 toward the upper surface of the wafer 100, and the protective film 140 formed on the wafer 100 is removed. Since the protective film 140 is made of a water-soluble resin, it can be easily washed away with the cleaning water, and at this time, debris generated in the previously performed narrow groove formation process and wide-bottomed groove formation process is also washed away along with the protective film 140.

[0044] [Dividing process] Figure 8 is an explanatory diagram showing an example of the splitting process. Figures 9 and 10 are explanatory diagrams showing other examples of the splitting process. After the protective film removal process is performed, a splitting process is carried out to split the wafer 100 along the bottomed groove 152 formed in the wafer 100, as shown in Figures 8, 9, and 10. Various methods can be employed for the splitting process, as long as the wafer 100 can be split along the bottomed groove 152 of the wafer 100.

[0045] The splitting process shown in Figure 8 involves holding the wafer 100 via tape T on a chuck table (not shown) of a cutting device, and then cutting the wafer 100 along the street 104 with a rotating cutting blade 48. As a result, as shown in Figure 8, cutting grooves 154 are formed along the entire thickness direction of the wafer 100 and up to the top surface of the tape T, splitting the wafer 100 and forming device chips containing one device 105 each.

[0046] In the dicing process shown in Figure 9, the wafer 100 is held via tape T on a chuck table (not shown) in a laser processing apparatus for stealth dicing (registered trademark). Then, as shown in Figure 9A, a laser beam with a wavelength that is transparent to the wafer 100 is irradiated from the processing head 51 of the laser processing apparatus, and a processing mark is formed by the focusing of the laser beam inside the wafer 100.

[0047] As these processing marks are continuously formed along the bottomed groove 152 (street 104), a modified layer 156, which serves as the starting point for splitting, is formed on the wafer 100. Note that processing marks refer to cracks extending from the laser spot. The modified layer 156 refers to a region where the density, refractive index, mechanical strength, and other physical properties inside the wafer 100 differ from the surrounding area due to laser irradiation, resulting in a lower strength compared to the surrounding area. As shown in Figure 9B, after the modified layer 156 is formed on the wafer 100, expanding the tape T divides the wafer 100 into individual devices 105 along the modified layer 156 (bottomed groove 152, street 104).

[0048] In the splitting process, the tape T can be expanded using an expander 60, as shown in Figure 10. After the modified layer 156 is formed on the wafer 100, the wafer 100 is held on the table 61 of the expander 60 via the tape T. Multiple clamping parts 62 are provided around the table 61, and the frame F is clamped and fixed by each clamping part 62. Then, each clamping part 62 is lowered, separating the table 61 from each clamping part 62. As a result, the tape T is expanded radially, and an external force acts on the modified layer 156, which has reduced strength, causing the wafer 100 to be split into individual devices 105 starting from the modified layer 156.

[0049] The wafer 100 is divided along the bottomed groove 152 by the division process, and a device chip including the device 105 is formed. The method for dividing the wafer 100 in this embodiment has been described above, but the processing method for the wafer 100 involves at least each of the above-described steps other than the division process.

[0050] According to the above embodiment, by forming a narrow groove 151 in the street 104 during the narrow groove formation process, metal parts on the street 104 can be divided into smaller pieces. Therefore, even if debris including metal parts is generated during the removal of the functional layer 120 in the street 104 during the wide bottom groove formation process, the amount of debris scattered onto the protective film 140 can be reduced. As a result, even if the protective film 140 is formed thinly or the amount of resin material for the protective film 140 is reduced, the device 105 can be protected by the protective film 140 from damage caused by debris. In other words, since it is not necessary to form a thick protective film 140, the amount of resin material for the protective film 140 can be reduced, the formation time of the protective film 140 can be shortened, and the decrease in productivity can be suppressed, and the adverse effects of debris scattering when irradiated with laser beams LB1 and LB2 can be suppressed.

[0051] Furthermore, the present invention is not limited to the embodiments described above, and can be implemented with various modifications. In the embodiments described above, the size, shape, etc., shown in the accompanying drawings are not limited thereto, and can be appropriately modified within the scope that allows the present invention to exert its effects. In addition, the present invention can be implemented with appropriate modifications as long as it does not deviate from the scope of its objectives.

[0052] In the above embodiment, after the completion of the narrow groove formation process by irradiating with the first laser beam LB1, the wide bottomed groove formation process by irradiating with the second laser beam LB2 was performed, but the embodiment is not limited to this. In the above embodiment, the narrow groove formation process may be omitted, and in the wide bottomed groove formation process, both the first laser beam LB1 and the second laser beam LB2 may be irradiated, and the first laser beam LB1, which has been divided into multiple parts in the width direction within the width of the street 104, and the second laser beam LB2, which has a predetermined width less than or equal to the width of the street 104, may be superimposed and irradiated to form a bottomed groove 152 of a predetermined width.

[0053] For example, as shown in the modified example in Figure 6C, two laser irradiation units (not shown) may be placed side by side at a predetermined distance apart in the extending direction of the street 104, and the second laser beam LB2 may be superimposed immediately after the first laser beam LB1 is irradiated. Alternatively, as shown in another modified example in Figure 6D, the irradiation positions of the first laser beam LB1 and the second laser beam LB2 may be overlapped, and the first laser beam LB1 and the second laser beam LB2 may be repeatedly irradiated alternately in a short period of time. [Industrial applicability]

[0054] As described above, the present invention has the effect of reducing debris by irradiating metal parts on the street with a first laser beam that is divided into multiple parts, thereby eliminating the need to form a thick protective film and improving productivity. [Explanation of Symbols]

[0055] 34: Chuck Table 100: Wafer 101: Surface 104: Street 105: Device 120: Functional layer (insulating film) 140:Protective film 151: Narrow groove (groove) 152: Bottomed groove (groove) LB1: First laser beam (laser beam) LB2: Second laser beam (laser beam)

Claims

1. A wafer processing method comprising irradiating a laser beam along a street of a wafer having an insulating film on its surface and forming a street with a plurality of devices, thereby forming grooves extending along the street, A protective film formation step in which a protective film is formed on the surface of the wafer, A groove forming step involves irradiating the wafer, held on a chuck table, with a first laser beam divided into multiple segments in the width direction within the width of the street to form a plurality of narrow grooves extending along the street, A wide-bottomed groove forming step involves irradiating the street with a second laser beam of a predetermined width less than or equal to the street width to eliminate the multiple narrow grooves and form a bottomed groove of a predetermined width, A wafer processing method comprising a protective film removal step of removing the protective film.

2. A wafer processing method comprising irradiating a laser beam along a street of a wafer having an insulating film on its surface and forming a street with a plurality of devices, thereby forming grooves extending along the street, A protective film formation step in which a protective film is formed on the surface of the wafer, A wide-bottomed groove forming step involves irradiating a wafer held on a chuck table with a first laser beam divided into multiple sections in the width direction within the width of the street, and a second laser beam with a predetermined width less than or equal to the width of the street, thereby forming a bottomed groove of a predetermined width. A wafer processing method comprising a protective film removal step of removing the protective film.

3. A method for dividing a wafer, comprising irradiating a laser beam along the streets of a wafer having an insulating film on its surface and forming streets with a plurality of devices, to form grooves along the streets, and then dividing the wafer, A protective film formation step in which a protective film is formed on the surface of the wafer, A groove forming step involves irradiating the wafer, held on a chuck table, with a first laser beam divided into multiple segments in the width direction within the width of the street to form a plurality of narrow grooves extending along the street, A wide-bottomed groove forming step involves irradiating the street with a second laser beam of a predetermined width less than or equal to the street width to eliminate the multiple narrow grooves and form a bottomed groove of a predetermined width, A protective film removal step to remove the protective film, A method for dividing a wafer, comprising: a dividing step of dividing the wafer along a bottomed groove formed on the wafer.

4. A method for dividing a wafer, comprising irradiating a laser beam along the streets of a wafer having an insulating film on its surface and forming streets with a plurality of devices, to form grooves along the streets, and then dividing the wafer, A protective film formation step in which a protective film is formed on the surface of the wafer, A wide-bottomed groove forming step involves irradiating a wafer held on a chuck table with a first laser beam divided into multiple sections in the width direction within the width of the street, and a second laser beam with a predetermined width less than or equal to the width of the street, thereby forming a bottomed groove of a predetermined width. A protective film removal step to remove the protective film, A method for dividing a wafer, comprising: a dividing step of dividing the wafer along a bottomed groove formed on the wafer.

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