Laser processing method and laser processing apparatus

Abstract

To restrain degradation of chip quality.SOLUTION: A laser processing method includes a first step of preparing a wafer 20 having a first region in which a surface layer of a street 23 is configured by an insulating film 24, and a second region in which the surface layer is configured by the insulating film 24 and a metal structure 25 on the insulating film 24, a second step of irradiating the street 23 with a predetermined first laser beam L1, and a third step of irradiating the street 23 with a predetermined second laser beam L2 after the second step. The first laser beam L1 is a laser beam having processing energy which removes a part of the insulating film 24 in the first region while leaving the other portion thereof, completely removes the metal structure 25 in the second region, and removes a part of the insulating film 24 in the second region while leaving the other portion thereof. The second laser beam L2 is a laser beam having processing energy which completely removes the insulating film 24 in the first region and the insulating film 24 in the second region after the second step.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] One aspect of the present invention relates to a laser processing method and a laser processing apparatus. [Background Art]

[0002] In a wafer including a plurality of functional elements arranged adjacent to each other via streets, an insulating film (such as a Low-k film) and a metal structure (such as metal studs and metal pads) may be formed on the surface layer of the street. In such a case, if a modified region is formed inside the wafer along a line passing through the street, and a crack is extended from the modified region to divide the wafer into individual chips each including a functional element, the quality of the chips may be deteriorated, for example, film peeling occurs in a portion along the street. Accordingly, when dividing a wafer into individual chips each including a functional element, grooving processing for removing the surface layer of the street by irradiating the street with laser light may be performed.

[0003] In the technique described in Patent Document 1, multi-point branching processing of laser light is performed in order to suppress thermal damage to streets caused by laser light irradiation. By performing multi-point branching processing of laser light, the influence of thermal damage at one processing point is suppressed. [Prior Art Document] [Patent Document]

[0004] [Patent Document 1] Japanese Patent No. 6309341 [Summary of the Invention] [Problem to be Solved by the Invention]

[0005] Here, the street may include a region whose surface layer is composed of an insulating film and a metal structure on the insulating film, and a region whose surface layer is composed only of the insulating film (a region where no metal structure is formed). In such a case, if the street is irradiated with laser light under conditions that can reliably remove the metal structure, thermal damage may occur in the region of the street's surface where no metal structure is formed. Such thermal damage can degrade the quality of the chip.

[0006] Therefore, one aspect of the present invention aims to provide a laser processing method and a laser processing apparatus that can suppress the deterioration of chip quality. [Means for solving the problem]

[0007] A laser processing method according to one aspect of the present invention includes a wafer having a plurality of functional elements arranged adjacent to each other via a street, the wafer having a first region whose surface layer on the street is composed of an insulating film, and a second region whose surface layer is composed of an insulating film and a metal structure on the insulating film; a second step of irradiating the street with a predetermined first laser beam; and a third step of irradiating the street with a predetermined second laser beam after the second step, wherein the first laser beam has a processing energy that, in the irradiation range, removes a portion of the insulating film in the first region while leaving the other portion intact, completely removes the metal structure in the second region, and removes a portion of the insulating film in the second region while leaving the other portion intact; and the second laser beam has a processing energy that, in the irradiation range, completely removes the insulating film in the first region and the insulating film in the second region after the second step.

[0008] In a laser processing method according to one aspect of the present invention, a wafer is prepared having a first region whose surface layer in the street is composed of an insulating film, and a second region composed of an insulating film and a metal structure on the insulating film. The wafer is irradiated with a first laser beam in the street, and then with a second laser beam. The first laser beam has a processing energy that removes a portion of the insulating film in the first region, leaving the rest intact, and completely removes the metal structure in the second region, while also removing a portion of the insulating film in the second region, leaving the rest intact. Thus, after the street is irradiated with the first laser beam, a portion of the insulating film is removed from both the first and second regions. In this state, where a portion of the insulating film is removed by the first laser beam, the irradiated region becomes uneven (frosted glass-like). Such an uneven surface has low laser light transmittance. Therefore, even when the second laser beam irradiated after the first laser beam has processing energy that completely removes the insulating film in the first region and the insulating film in the second region, the uneven surface with low transmittance can suppress light leakage in the substrate direction of the wafer made of silicon or the like, thereby suppressing thermal damage to the wafer caused by the laser beam. As described above, according to one aspect of the present invention, thermal damage to the wafer caused by the laser beam can be suppressed and deterioration of chip quality can be suppressed.

[0009] The second laser beam may be a laser beam with processing energy that etches a portion of the substrate contained in the wafer after the second process. This allows a portion of the substrate to be etched by the second laser beam, ensuring that grooving to remove the surface layer is reliably performed while suppressing film delamination on the wafer.

[0010] The second laser beam may be a laser beam with processing energy that engraves the substrate after the second process by 4 μm or less. By limiting the engraving depth to 4 μm or less, thermal damage to the wafer caused by the laser beam can be suppressed, and degradation of chip quality can be suppressed.

[0011] The above laser processing method may further include a fourth step after the third step, in which the substrate is ground or polished so that the grooves formed in the street by irradiation with the second laser beam are exposed. With such a laser processing method, a full cut can be performed by grooving without performing a dicing step after laser grooving. This allows for rapid processing.

[0012] A laser processing method according to one aspect of the present invention includes a first step of preparing a wafer having a plurality of functional elements arranged adjacent to each other via a street, the wafer having a first region whose surface layer on the street is composed of an insulating film and a second region whose surface layer is composed of an insulating film and a metal structure on the insulating film; a second step of irradiating the street with laser light to make the insulating films of the first and second regions uneven; and a third step of completely removing the insulating films of the first and second regions by irradiating the street with laser light after the second step.

[0013] In a laser processing method according to one aspect of the present invention, a wafer is prepared having a first region whose surface layer in the street is composed of an insulating film, and a second region composed of an insulating film and a metal structure on the insulating film. Laser light is irradiated onto the street of the wafer to make the insulating films in the first and second regions uneven, and then laser light is irradiated onto the street again to completely remove the insulating films in the first and second regions. The uneven (frosted glass-like) surface of the insulating film has low transmittance of laser light. Therefore, even if the laser light irradiated thereafter has processing energy that completely removes the insulating films in the first and second regions, the uneven surface with low transmittance can suppress light leakage toward the substrate direction of the wafer, which is made of silicon or the like, and can suppress thermal damage to the wafer caused by the laser light. As described above, according to a laser processing method according to one aspect of the present invention, thermal damage to the wafer caused by laser light can be suppressed and deterioration of chip quality can be suppressed.

[0014] A laser processing apparatus according to one aspect of the present invention comprises a support unit for a wafer having a plurality of functional elements arranged adjacent to each other via a street, the first region having a surface layer composed of an insulating film on the street, and a second region having a surface layer composed of an insulating film and a metal structure on the insulating film, an irradiation unit for irradiating the street with laser light, and a control unit for controlling the irradiation unit, wherein the control unit is configured to perform a first control to control the irradiation unit so that a predetermined first laser beam is irradiated onto the street, and a second control after the first control to control the irradiation unit so that a predetermined second laser beam is irradiated onto the street, wherein the first laser beam is laser light with processing energy that, in the irradiation range, removes a part of the insulating film in the first region while leaving the other part, completely removes the metal structure in the second region, and removes a part of the insulating film in the second region while leaving the other part, and the second laser light is laser light with processing energy that, in the irradiation range, completely removes the insulating film in the first region and the insulating film in the second region after irradiation with the first laser light. In a laser processing apparatus according to one aspect of the present invention, similar to the laser processing method described above, thermal damage to the wafer caused by laser light can be suppressed, and deterioration of chip quality can be suppressed.

[0015] A laser processing apparatus according to one aspect of the present invention includes a support unit for a wafer containing a plurality of functional elements arranged adjacent to each other via a street, the wafer having a first region whose surface layer in the street is composed of an insulating film, and a second region whose surface layer is composed of an insulating film and a metal structure on the insulating film; an irradiation unit for irradiating the street with laser light; and a control unit for controlling the irradiation unit. The control unit is configured to perform a first control, which controls the irradiation unit so that laser light is irradiated onto the street so that the insulating films in the first and second regions become uneven; and a second control, which, after the first control, controls the irradiation unit so that laser light is irradiated onto the street so that the insulating films in the first and second regions are completely removed. In the laser processing apparatus according to one aspect of the present invention, similar to the laser processing method described above, thermal damage to the wafer caused by laser light can be suppressed and deterioration of chip quality can be suppressed. Effects of the Invention

[0016] According to one aspect of the present invention, degradation of chip quality can be suppressed. Brief Description of the Drawings

[0017] [Figure 1] It is a configuration diagram of a laser processing apparatus according to an embodiment. [Figure 2] It is a plan view of a wafer processed by the laser processing apparatus shown in FIG. 1. [Figure 3] It is a cross-sectional view of a part of the wafer shown in FIG. 2. [Figure 4] It is a plan view of a part of the street shown in FIG. 2. [Figure 5] It is a diagram for explaining generation of HAZ (Heat-Affected Zone) by grooving processing. [Figure 6] It is a diagram for explaining grooving processing in the present embodiment. [Figure 7] It is a diagram for explaining the principle of suppressing generation of HAZ. [Figure 8] It is a diagram for explaining an example of condition setting when a pad region is removed (dug) in one pass. [Figure 9] It is a diagram for explaining an example of condition setting when a pad region is removed (dug) in two passes. [Figure 10] It is a diagram for explaining an example of condition setting when a pad region is removed (dug) in two passes. [Figure 11] It is a diagram showing test conditions regarding the relationship between the depth of laser grooving and chip strength. [Figure 12] It is a diagram showing test conditions regarding the relationship between the depth of laser grooving and chip strength. [Figure 13] It is a diagram showing test results regarding the relationship between the depth of laser grooving and chip strength. [Figure 14] It is a flowchart of a laser processing method according to an embodiment. [Figure 15] This diagram illustrates a modified laser processing method. [Figure 16] This is a flowchart of the laser processing method for modified examples. [Figure 17] This diagram illustrates a laser processing method for other modified examples. [Modes for carrying out the invention]

[0018] Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and redundant explanations are omitted. [Configuration of the laser processing machine]

[0019] As shown in Figure 1, the laser processing apparatus 1 comprises a support unit 2, an irradiation unit 3, an imaging unit 4, and a control unit 5. The laser processing apparatus 1 is a device that performs grooving processing to remove the surface layer of the streets (details of which will be described later) of the wafer 20 by irradiating the streets of the wafer 20 with laser light L. In the following description, the three mutually orthogonal directions will be referred to as the X direction, Y direction, and Z direction, respectively. For example, the X direction is the first horizontal direction, the Y direction is the second horizontal direction perpendicular to the first horizontal direction, and the Z direction is the vertical direction.

[0020] The support unit 2 supports the wafer 20. The support unit 2 holds the wafer 20, for example, by adsorbing a film (not shown) attached to the wafer 20, so that the surface of the wafer 20, including the street, faces the irradiation unit 3 and the imaging unit 4. For example, the support unit 2 is movable along the X and Y directions and rotatable about an axis parallel to the Z direction as its centerline.

[0021] The irradiation unit 3 irradiates the street of the wafer 20 supported by the support unit 2 with laser light L. The irradiation unit 3 includes a light source 31, a shaping optical system 32, a dichroic mirror 33, and a focusing unit 34. The light source 31 emits laser light L. The shaping optical system 32 adjusts the laser light L emitted from the light source 31. As an example, the shaping optical system 32 includes at least one of an attenuator to adjust the output of the laser light L, a beam expander to increase the diameter of the laser light L, and a spatial light modulator to modulate the phase of the laser light L. If the shaping optical system 32 includes a spatial light modulator, it may also include an imaging optical system that constitutes a bilateral telecentric optical system in which the modulation plane of the spatial light modulator and the entrance pupil plane of the focusing unit 34 are in an imaging relationship. The dichroic mirror 33 reflects the laser light L emitted from the shaping optical system 32 and directs it into the focusing unit 34. The light-gathering unit 34 focuses the laser light L reflected by the dichroic mirror 33 onto the street of the wafer 20 supported by the support unit 2.

[0022] The irradiation unit 3 further includes a light source 35, a half mirror 36, and an image sensor 37. The light source 35 emits visible light V1. The half mirror 36 reflects the visible light V1 emitted from the light source 35 and directs it into the focusing unit 34. The dichroic mirror 33 transmits the visible light V1 between the half mirror 36 and the focusing unit 34. The focusing unit 34 focuses the visible light V1 reflected by the half mirror 36 onto the street of the wafer 20 supported by the support unit 2. The image sensor 37 detects the visible light V1 that has been reflected by the street of the wafer 20 and transmitted through the focusing unit 34, the dichroic mirror 33, and the half mirror 36. In the laser processing apparatus 1, the control unit 5 moves the focusing unit 34 along the Z direction, for example, so that the focusing point of the laser beam L is located on the street of the wafer 20, based on the detection result by the image sensor 37.

[0023] The imaging unit 4 acquires image data of the street of the wafer 20 supported by the support unit 2. The imaging unit 4 includes a light source 41, a half mirror 42, a light concentrator 43, and an image sensor 44. The light source 41 emits visible light V2. The half mirror 42 reflects the visible light V2 emitted from the light source 41 and causes it to enter the light concentrator 43. The light concentrator 43 focuses the visible light V2 reflected by the half mirror 42 onto the street of the wafer 20 supported by the support unit 2. The image sensor 44 detects the visible light V2 that has been reflected by the street of the wafer 20 and passed through the light concentrator 43 and the half mirror 42.

[0024] The control unit 5 controls the operation of each part of the laser processing apparatus 1. For example, the control unit 5 controls the irradiation unit 3. The control unit 5 includes a processing unit 51, a storage unit 52, and an input receiving unit 53. The processing unit 51 is a computer device including a processor, memory, storage, and communication devices. In the processing unit 51, the processor executes software (programs) loaded into memory, etc., and controls the reading and writing of data in memory and storage, as well as communication by communication devices. The storage unit 52 is, for example, a hard disk, and stores various types of data. The input receiving unit 53 is an interface unit that receives input of various types of data from the operator. As an example, the input receiving unit 53 is at least one of a keyboard, mouse, or GUI (Graphical User Interface). [Wafer composition]

[0025] As shown in Figures 2 and 3, the wafer 20 includes a semiconductor substrate 21 and a functional element layer 22. The semiconductor substrate 21 has a front surface 21a and a back surface 21b. The semiconductor substrate 21 is, for example, a silicon substrate. The semiconductor substrate 21 is provided with notches 21c indicating the crystal orientation. The semiconductor substrate 21 may also be provided with orientation flats instead of notches 21c. The functional element layer 22 is formed on the front surface 21a of the semiconductor substrate 21. The functional element layer 22 includes a plurality of functional elements 22a. The plurality of functional elements 22a are arranged two-dimensionally along the front surface 21a of the semiconductor substrate 21. Each functional element 22a is, for example, a light-receiving element such as a photodiode, a light-emitting element such as a laser diode, a circuit element such as a memory, etc. Each functional element 22a may also be configured three-dimensionally by stacking multiple layers.

[0026] Multiple streets 23 are formed on the wafer 20. The multiple streets 23 are regions exposed to the outside between adjacent functional elements 22a. In other words, the multiple functional elements 22a are arranged adjacent to each other via the streets 23. For example, the multiple streets 23 extend in a grid pattern between adjacent functional elements 22a arranged in a matrix. As shown in Figure 4, an insulating film 24 and multiple metal structures 25 are formed on the surface of the streets 23. The insulating film 24 is, for example, a low-k film. The metal structures 25 are, for example, metal pads made of aluminum or the like.

[0027] As shown in Figures 2 and 3, the wafer 20 is intended to be cut along each of several lines 15 for each functional element 22a (i.e., chipped for each functional element 22a). Each line 15 passes through each street 23 when viewed from the thickness direction of the wafer 20. For example, each line 15 extends through the center of each street 23 when viewed from the thickness direction of the wafer 20. Each line 15 is a virtual line set on the wafer 20 by the laser processing apparatus 1. Each line 15 may also be a line actually drawn on the wafer 20. [Operation of laser processing equipment and laser processing method]

[0028] The laser processing apparatus 1 performs grooving by irradiating each street 23 with laser light L to remove the surface layer of each street 23. Specifically, the control unit 5 controls the irradiation unit 3 so that laser light L is irradiated onto each street 23 of the wafer 20 supported by the support unit 2, and the control unit 5 controls the support unit 2 so that the laser light L moves relative to each street 23.

[0029] For example, in grooving processes when performing blade dicing, it is necessary to completely remove the surface layer of street 23 from the dicing line. Here, the surface layer of street 23 consists of a region composed only of the insulating film 24 (hereinafter sometimes referred to as the first region) and a region composed of the insulating film 24 and a metal structure 25 on the insulating film 24 (hereinafter sometimes referred to as the second region). For example, the surface layer of street 23 of wafer 20 shown in the left diagram of Figure 5(a) (the region of dicing street 400) consists only of the insulating film 24, which is the Low-k film 242 and the SiN / SiO2 film 241, and represents the first region. Also, the surface layer of street 23 of wafer 20 shown in the left diagram of Figure 5(b) (the region of dicing street 400) consists of the insulating film 24, which is the Low-k film 242 and the SiN / SiO2 film 241, and a metal structure 25 (metal pad) on the insulating film 24, and represents the second region. When processing a wafer 20 having a first region and a second region using common grooving conditions regardless of the region, thermal damage to the wafer 20 may become a problem.

[0030] In other words, in order to completely remove the surface layer in the street 23 in any region of the wafer 20, it is necessary to set the processing energy of the grooving laser beam L so that the laser beam is dug down to the interface of the semiconductor substrate 21 in the second region, where the surface layer is composed of an insulating film 24 and a metal structure 25 on the insulating film 24 (see the right diagram in Figure 5(b)). Since the absorption rate of the laser wavelength is greater for the metal structure 25 than for the insulating film 24, most of the energy is absorbed by the metal structure 25 in the second region. Therefore, in order to remove the insulating film 24 below the metal structure 25 as well, it is necessary to increase the processing energy of the laser beam L. However, if grooving is performed on the first region, which is composed only of the insulating film 24, with the laser beam L whose processing energy has been increased in this way, there will be an excess of energy in the first region, and as shown in the right diagram in Figure 5(a), the semiconductor substrate 21 will be dug too deeply, creating a HAZ (Heat-Affected Zone), and the reduction in the strength of the wafer 20 due to thermal damage may become a problem.

[0031] The example shown in Figure 5 illustrates the occurrence of a HAZ when the conditions for wafer 20 and laser grooving are as follows. (Conditions for wafer 20) Wafer size: 12 inches, wafer thickness: 300 μm, chip size: 5 mm, dicing street width 400: 60 μm, pattern thickness (thickness of insulating film 24): 8 μm, thickness of metal structure 25: 1 μm. (Conditions for laser grooving) For blade dicing, a 55 μm wide groove was formed; laser beam L wavelength: 515 μm, pulse width: 600 fs, focusing position: device surface, number of branches: 21 points, pulse pitch: 0.5 μm, processing energy: 9.9 μJ, Fluence / point: 0.85 J / cm 2 Number of scans: 2 passes.

[0032] Here, Fluence / point indicates the pulse energy per unit area, and the value shown is for each branched point (one point). As shown in Figure 5, the Low-k film 242, which is the insulating film 24, is provided with, for example, wiring 300.

[0033] In order to solve the above-mentioned problems, the laser processing method according to this embodiment divides the irradiation of laser light to the street 23 in grooving processing into two steps. Specifically, the laser processing method performed by the laser processing apparatus 1 includes a step of irradiating the street 23 with a predetermined first laser beam (second step), and a step of irradiating the street 23 with a predetermined second laser beam after the step of irradiating with the first laser beam (third step). In order to perform these steps, the control unit 5 is configured to perform a first control that controls the irradiation unit 3 so that the predetermined first laser beam is irradiated to the street 23, and a second control that controls the irradiation unit 3 so that the predetermined second laser beam is irradiated to the street 23 after the first control. The first laser beam is a laser beam with processing energy that, in the irradiation range, removes a part of the insulating film 24 in the first region while leaving the other part, completely removes the metal structure 25 in the second region and removes a part of the insulating film 24 in the second region while leaving the other part. Furthermore, the second laser beam is a laser beam with processing energy that completely removes the insulating film 24 in the first region and the insulating film 24 in the second region after irradiation with the first laser beam within the irradiation range.

[0034] Figure 6 illustrates the grooving process in this embodiment. Figure 6(a) shows the irradiation of the first laser beam L1 (see the center view of Figure 6(a)) and the second laser beam L2 (see the right view of Figure 6(a)) in the first region. Figure 6(b) shows the irradiation of the first laser beam L1 (see the center view of Figure 6(b)) and the second laser beam L2 (see the right view of Figure 6(b)) in the second region.

[0035] As shown in the center diagram of Figure 6(a), the first laser beam L1 has a processing energy that removes a portion of the insulating film 24 in the first region within the irradiation area, leaving the rest intact. Furthermore, as shown in the center diagram of Figure 6(b), the first laser beam L1 has a processing energy that completely removes the metal structure 25 in the second region and removes a portion of the insulating film 24 in the second region, leaving the rest intact. Here, "removing a portion of the insulating film 24 and leaving the rest intact" means removing only a portion of the insulating film 24, not the entirety, within the irradiation area, while leaving the rest intact. Also, "completely removing the metal structure 25" means removing the entire metal structure 25 within the irradiation area. Note that "completely removing the metal structure 25" may include removing almost the entire metal structure 25, even if only a small amount of the metal structure 25 remains, to the point where its function can be ignored.

[0036] As shown in the center view of Figure 6(a), in the first region after irradiation with the first laser beam L1, a portion of the insulating film 24 (in this case, a portion of the SiN / SiO2 film 241) is removed by the first laser beam L1, and the surface irradiated with the first laser beam L1 becomes an uneven (frosted glass-like) frosted glass surface 500. Also, as shown in the center view of Figure 6(b), in the second region after irradiation with the first laser beam L1, the metal structure 25 is completely removed by the first laser beam L1, and a portion of the insulating film 24 (in this case, all of the SiN / SiO2 film 241 and a portion of the Low-k film 242) is removed, and the surface irradiated with the first laser beam L1 becomes an uneven (frosted glass-like) frosted glass surface 550. Thus, the step of irradiating with the first laser beam L1 (second step) is a step of making the insulating film 24 in the first and second regions uneven by irradiating the street 23 with the first laser beam L1. In other words, the control unit 5 performs a first control to control the irradiation unit 3 so that the first laser beam L1 is irradiated onto the street 23 so that the insulating film 24 in the first and second regions becomes uneven. The frosted glass surface 500 and the frosted glass surface 550 will be described later.

[0037] As shown in the right-hand diagram of Figure 6(a), the second laser beam L2 has a processing energy that completely removes the insulating film 24 in the first region after irradiation with the first laser beam L1 within the irradiation area. Similarly, as shown in the right-hand diagram of Figure 6(b), the second laser beam L2 has a processing energy that completely removes the insulating film 24 in the second region after irradiation with the first laser beam L1 within the irradiation area. Here, "completely removing the insulating film 24" means removing the entire insulating film 24 within the irradiation area. Note that "completely removing the insulating film 24" may also include removing almost the entire insulating film 24, even if a small amount of insulating film 24 remains that is negligible in function.

[0038] As shown in the right-hand diagram of Figure 6(a) and the right-hand diagram of Figure 6(b), the second laser beam L2 is set to a processing energy that excavates a portion of the semiconductor substrate 21 of the wafer 20 after irradiation with the first laser beam L1. That is, the irradiation surface 600 of the second laser beam L2 in the first region (see Figure 6(a)) and the irradiation surface 650 of the second laser beam L2 in the second region (see Figure 6(b)) both reach the semiconductor substrate 21. Thus, the step of irradiating with the second laser beam L2 (third step) is a step of completely removing the insulating film 24 in the first and second regions by irradiating the street 23 with laser beam L2. That is, after the first control described above, the control unit 5 executes a second control to control the irradiation unit 3 so that the second laser beam L2 is irradiated onto the street 23 so that the insulating film 24 in the first and second regions is completely removed. The second laser beam L2 may be set to a processing energy that engraves the semiconductor substrate 21 of the wafer 20 by 4 μm or less after irradiation with the first laser beam L1. By setting the engraving amount to 4 μm or less in this way, thermal damage to the wafer 20 caused by the second laser beam L2 can be suppressed, and degradation of chip quality can be suppressed.

[0039] The grooving process shown in Figure 6 is performed, for example, under the following conditions for wafer 20 and laser grooving. (Conditions for wafer 20) Wafer size: 12 inches, wafer thickness: 300 μm, chip size: 5 mm, dicing street width 400: 60 μm, pattern thickness (thickness of insulating film 24): 8 μm, thickness of metal structure 25: 1 μm. (Conditions for laser grooving in the process of irradiating with the first laser beam L1 (second process)) For blade dicing, a 55 μm wide groove was formed. The wavelength of the first laser beam L1 was 515 μm, with a pulse width of 600 fs. The focal position was the device surface, with 21 branching points. The pulse pitch was 0.5 μm, the processing energy was 4.1 μJ, and the frequency / point was 0.35 J / cm. 2 Scan count: 1 pass. (Conditions for laser grooving in the process of irradiating with the second laser beam L2 (third process)) For blade dicing, a 55 μm wide groove was formed; the wavelength of the second laser beam L2 was 515 μm, the pulse width was 600 fs, the focus position was the device surface, the number of branches was 21, the pulse pitch was 0.5 μm, the processing energy was 9.9 μJ, and the fluidity / point was 0.85 J / cm. 2 Number of scans: 2 passes.

[0040] Next, the principle by which the grooving process shown in Figure 6 can suppress the generation of HAZs will be explained with reference to Figure 7. Figure 7 is a diagram illustrating the principle of suppressing the generation of HAZs. Figure 7 shows the grooving process in the first region of the wafer 20.

[0041] As shown in Figure 7(a), a first laser beam L1 with a processing energy (e.g., 4.1 μJ) is irradiated to remove a portion of the insulating film 24 in the first region, leaving the rest intact. Because the processing energy of such a first laser beam L1 is weak, the generation of HAZ in the semiconductor substrate 21 due to detached light is suppressed. Then, as shown in Figure 7(b), a portion of the insulating film 24 near the focal point (in this case, a portion of the SiN / SiO2 film 241) is removed by the first laser beam L1, and the surface irradiated by the first laser beam L1 becomes a frosted glass surface 500 with an uneven (ground glass-like) surface. Here, a frosted glass surface 500 is a geometric surface whose direction changes randomly with respect to the normal of the optical surface. On such a frosted glass surface 500, the transmittance of the laser light decreases because the light is randomly refracted or scattered. Alternatively, on such a frosted glass surface 500, the absorption rate of the laser light increases due to shape changes and discoloration. Therefore, the laser light irradiated onto the frosted glass surface 500 has difficulty reaching the semiconductor substrate 21.

[0042] Then, as shown in Figure 7(c), the frosted glass surface 500, which has already been irradiated with the first laser beam L1, is irradiated with a second laser beam L2 having a processing energy (e.g., 9.9 μJ) that completely removes the insulating film 24 in the first region. Such a second laser beam L2 would normally result in a deep etched depth in the semiconductor substrate 21, causing a HAZ (hazardous area zone) to be generated in the semiconductor substrate 21 (see Figure 5(a), right). However, since the second laser beam L2 is now irradiated onto the frosted glass surface 500, which has low laser light transmittance, excessive etching of the semiconductor substrate 21 by the second laser beam L2 and generation of a HAZ are suppressed, as shown in Figure 7(d). Specifically, the etched depth by the second laser beam L2 is set to, for example, 4 μm or less.

[0043] Here, the second region is composed of an insulating film 24 and a metal structure 25 on the insulating film 24, and differs from the first region which is composed only of the insulating film 24. However, grooving is possible using the same grooving conditions as the first region (i.e., the first laser beam L1 and the second laser beam L2). That is, when the second region is irradiated with the first laser beam L1, which has relatively weak processing energy, the metal structure 25, which has a high absorption rate even with weak processing energy, is removed relatively easily. For this reason, in the second region as well, the first laser beam L1 can be used to remove a portion of the insulating film 24 of the second region (while completely removing the metal structure 25), leaving the other portion intact, i.e., a frosted glass surface 550 (see the center view in Figure 6(b)). Then, by irradiating the frosted glass surface 550, which has already been irradiated with the first laser beam L1, with the second laser beam L2 having processing energy (e.g., 9.9 μJ) to completely remove the insulating film 24 of the second region, the insulating film 24 can be appropriately removed while suppressing the generation of HAZ, similar to the first region.

[0044] Next, the process of determining the grooving conditions will be explained in detail. Here, determining the conditions refers to setting the Fluence / point of the first laser beam L1 and the second laser beam L2. As described above, the Fluence / point of the first laser beam L1 and the second laser beam L2 are set to satisfy the conditions for grooving in both the first and second regions. That is, the Fluence / point of the first laser beam L1 is set so that in the irradiation range, a portion of the insulating film 24 in the first region is removed, leaving the rest intact, while the metal structure 25 in the second region is completely removed, and a portion of the insulating film 24 in the second region is removed, leaving the rest intact. The Fluence / point of the second laser beam L2 is set so that in the irradiation range, the insulating film 24 in both the first and second regions is completely removed, and the generation of HAZ is suppressed.

[0045] Figure 8 illustrates an example of setting the conditions for removing (excavating) a pad region on which a metal structure 25 is formed in one pass. In Figure 8, "No Si Reached" indicates a state where a portion of the insulating film 24 is removed and other parts remain; "Si Reached" indicates a state where the insulating film 24 is completely removed and no HAZ is generated; and "Si Reached (HAZ)" indicates a state where the insulating film 24 is completely removed and a HAZ is generated. Also in Figure 8, "Cannot Excavate" indicates a state where the metal structure 25 is not removed at all; "Partially Excavable" indicates a state where a portion of the metal structure 25 is removed; "Excavable" indicates a state where the metal structure 25 is completely removed, a portion of the insulating film 24 is removed and other parts remain; "Excavable, Si Reached" indicates a state where the metal structure 25 is completely removed and the insulating film 24 is completely removed and no HAZ is generated; and "Excavable, Si Reached (HAZ)" indicates a state where the metal structure 25 is completely removed and the insulating film 24 is completely removed and a HAZ is generated. Figure 8(a) illustrates the setting of the conditions for the first laser beam L1. Figure 8(b) illustrates the process of determining the conditions for the second laser beam L2.

[0046] Figure 8(a) shows the state of the first region (labeled "film-only region" in Figure 8) and the state of the second region (labeled "pad region" in Figure 8) after grooving, for each Fluence / point level of the first laser beam L1. Note that an increase in the Fluence / point level means that the Fluence / point value is larger. As described above, the Fluence / point of the first laser beam L1 is set to "remove a portion of the insulating film 24 in the first region while leaving the rest intact, and completely remove the metal structure 25 in the second region while removing a portion of the insulating film 24 in the second region while leaving the rest intact." Therefore, in the example shown in Figure 8(a), the Fluence / point level of the first laser beam L1 is set to 4.

[0047] Figure 8(b) shows the state of the first region (labeled "film-only region" in Figure 8) and the second region (labeled "pad region" in Figure 8) after grooving, for each Fluence / point level of the second laser beam L2. The results in Figure 8(b) show the state when grooving is performed on the wafer 20 after grooving has been performed with the first laser beam L1 at the Fluence / point level set based on Figure 8(a), and then grooving is performed with the second laser beam L2 at each Fluence / point level. As described above, the Fluence / point of the second laser beam L2 is set so that "the insulating film 24 of the first region and the insulating film 24 of the second region are completely removed in the irradiation range, and furthermore, the generation of HAZ is suppressed." For this reason, in the example shown in Figure 8(b), the Fluence / point level of the second laser beam L2 is set to 7. Although the desired results can be obtained even when the Fluence / point level of the second laser beam L2 is set to 8, it is preferable to select the minimum Fluence / point level.

[0048] Figures 9 and 10 illustrate an example of setting the conditions for removing (excavating) a pad region on which a metal structure 25 is formed in two passes. In Figures 9 and 10, "No Si Reached" indicates a state where a portion of the insulating film 24 is removed and other portions remain; "Si Reached" indicates a state where the insulating film 24 is completely removed and no HAZ is generated; and "Si Reached (HAZ)" indicates a state where the insulating film 24 is completely removed and a HAZ is generated. Also in Figures 9 and 10, "Cannot Excavate" indicates a state where the metal structure 25 has not been removed at all; "Partially Excavable" indicates a state where a portion of the metal structure 25 has been removed; "Excavable" indicates a state where the metal structure 25 is completely removed, a portion of the insulating film 24 is removed and other portions remain; "Excavable, Si Reached" indicates a state where the metal structure 25 is completely removed and the insulating film 24 is completely removed and no HAZ is generated; and "Excavable, Si Reached (HAZ)" indicates a state where the metal structure 25 is completely removed and the insulating film 24 is completely removed and a HAZ is generated. Figure 9(a) illustrates the setting of conditions for the first pass of the first laser beam L1, Figure 9(b) illustrates the setting of conditions for the second pass of the first laser beam L1, and Figure 10 illustrates the setting of conditions for the second laser beam L2.

[0049] Figure 9(a) shows the state of the first region (labeled "film-only region" in Figure 8) and the state of the second region (labeled "pad region" in Figure 8) after grooving, for each Fluence / point level of the first laser beam L1 in the first pass. Since the pad region is removed in two passes, in the example shown in Figure 9(a), the Fluence / point level of the first pass of the first laser beam L1 is set to 4 (removing only a portion of the metal structure 25).

[0050] Figure 9(b) shows the state of the first region (labeled "film-only region" in Figure 8) and the state of the second region (labeled "pad region" in Figure 8) after grooving, for each Fluence / point level of the second pass of the first laser beam L1. The results in Figure 9(b) show the state when grooving is performed on a wafer 20 that has been grooved with the first pass of the first laser beam L1 at the Fluence / point level set in Figure 9(a), and then grooving is performed with the second pass of the first laser beam L1 at each Fluence / point level. As described above, the Fluence / point of the first laser beam L1 is set to "remove a portion of the insulating film 24 in the first region within the irradiation range, leaving the rest intact, and completely remove the metal structure 25 in the second region, while removing a portion of the insulating film 24 in the second region and leaving the rest intact." Therefore, in the example shown in Figure 9(b), the Fluence / point level of the second pass of the first laser beam L1 is set to 5.

[0051] Figure 10 shows the state of the first region (labeled "film-only region" in Figure 8) and the second region (labeled "pad region" in Figure 8) after grooving, for each Fluence / point level of the second laser beam L2. The results in Figure 10 show the state when grooving is performed on the wafer 20 after grooving has been performed with the second pass of the first laser beam L1 at the Fluence / point level set based on Figure 9(b), and then grooving is performed with the second laser beam L2 at each Fluence / point level. As described above, the Fluence / point of the second laser beam L2 is set so that "the insulating film 24 of the first region and the insulating film 24 of the second region are completely removed in the irradiation range, and furthermore, the generation of HAZ is suppressed." For this reason, in the example shown in Figure 10, the Fluence / point level of the second laser beam L2 is set to 7. Although the desired results can be obtained even when the Fluence / point level of the second laser beam L2 is set to 8, it is preferable to select the minimum Fluence / point level.

[0052] Next, the laser processing method will be described with reference to the flowchart in Figure 14. First, a wafer 20 is prepared (step S1, first step). As described above, the wafer 20 is a wafer containing a plurality of functional elements 22a arranged adjacent to each other via a street 23, and has a first region in which the surface layer of the street 23 is composed of an insulating film 24, and a second region in which the surface layer is composed of an insulating film 24 and a metal structure 25 on the insulating film 24.

[0053] Next, the laser processing apparatus 1 irradiates the street 23 with a predetermined first laser beam L1 (step S2, second step). As described above, the first laser beam L1 is a laser beam with processing energy that, in the irradiation range, removes a portion of the insulating film 24 in the first region while leaving the rest intact, completely removes the metal structure 25 in the second region, and removes a portion of the insulating film 24 in the second region while leaving the rest intact.

[0054] Next, the laser processing apparatus 1 irradiates the street 23 with a predetermined second laser beam L2 (step S3, third step). As described above, the second laser beam L2 is a laser beam with processing energy that completely removes the insulating film 24 of the first region and the insulating film 24 of the second region in the irradiation area after the second step. The grooving process is completed by this third step.

[0055] Next, for example, a separate SD processing device (not shown) from the laser processing device 1 irradiates the wafer 20 along each line 15 with laser light, thereby forming modified regions 11 inside the wafer 20 along each line 15 (step S4). Finally, an expandable device (not shown) expands an expandable film (not shown), causing cracks to extend from the modified regions 11 formed inside the semiconductor substrate 21 along each line 15 in the thickness direction of the wafer 20, and the wafer 20 is chipped into individual functional elements 22a (step S5). [Mechanism of Action and Effects]

[0056] The laser processing method according to this embodiment includes a first step of preparing a wafer 20 having a plurality of functional elements 22a arranged adjacent to each other via a street 23, the wafer having a first region whose surface layer on the street 23 is composed of an insulating film 24, and a second region whose surface layer is composed of the insulating film 24 and a metal structure 25 on the insulating film 24; a second step of irradiating the street 23 with a predetermined first laser beam L1; and a third step of irradiating the street 23 with a predetermined second laser beam L2 after the second step, wherein the first laser beam L1 is a laser beam with processing energy that, in the irradiation range, removes a portion of the insulating film 24 in the first region while leaving the other portion, completely removes the metal structure 25 in the second region, and removes a portion of the insulating film 24 in the second region while leaving the other portion; and the second laser beam L2 is a laser beam with processing energy that, in the irradiation range, completely removes the insulating film 24 in the first region and the insulating film 24 in the second region after the second step.

[0057] In the laser processing method according to this embodiment, a wafer 20 is prepared having a first region whose surface layer in the street 23 is composed of an insulating film 24, and a second region composed of the insulating film 24 and a metal structure 25 on the insulating film 24. The wafer 20 is irradiated with a first laser beam L1 on the street 23, and then with a second laser beam L2 on the street 23. The first laser beam L1 is a laser beam with processing energy that removes a portion of the insulating film 24 in the first region, leaving the rest intact, and completely removes the metal structure 25 in the second region, while removing a portion of the insulating film 24 in the second region, leaving the rest intact. In this state, when the street 23 is irradiated with the first laser beam L1, a portion of the insulating film 24 is removed in both the first and second regions. In this state, when a portion of the insulating film 24 is removed by the first laser beam L1, the area irradiated with the first laser beam L1 becomes uneven (frosted glass-like). Such an uneven surface has low laser light transmittance. Therefore, even when the second laser beam L2 irradiated after the first laser beam L1 has processing energy sufficient to completely remove the insulating film 24 in the first region and the insulating film 24 in the second region, the uneven surface with low transmittance can suppress light leakage from the wafer 20, which is made of silicon or the like, towards the semiconductor substrate 21, thereby suppressing thermal damage to the wafer 20 caused by the laser beam. As described above, the laser processing method according to this embodiment can suppress thermal damage to the wafer 20 caused by the laser beam and suppress deterioration of chip quality.

[0058] The second laser beam L2 may be a laser beam with processing energy that etches a portion of the semiconductor substrate 21 contained in the wafer 20 after the second process. As a result, a portion of the semiconductor substrate 21 is etched by the second laser beam L2, making it possible to reliably perform grooving to remove the surface layer while suppressing the occurrence of film delamination on the wafer 20.

[0059] The second laser beam L2 may be a laser beam with processing energy that engraves the semiconductor substrate 21 after the second process by 4 μm or less. By limiting the engraving amount to 4 μm or less, thermal damage to the wafer 20 caused by the laser beam can be suppressed, and degradation of chip quality can be suppressed.

[0060] Here, we will explain the results of tests conducted to confirm the relationship between the depth of laser grooving and chip strength. Figures 11 and 12 show the test conditions for the relationship between laser grooving depth and chip strength. Figure 13 shows the results of the test for the relationship between laser grooving depth and chip strength.

[0061] In this test, wafer 20 was ground to 100 μm, then laser grooving was performed, followed by dicing to form chips. To measure the strength of the chips, a flexural strength test, as shown in Figure 11(a), was conducted. As shown in Figure 11(a), in the flexural strength test, the device surface of the chip was placed on the lower support side and the back surface of the chip was placed on the side where the force was applied, and the fracture stress σ when a force was applied to the chip was measured. When the applied force is F, the distance between the two lower supports is L2 (mm), the die width is b (mm), and the die thickness is h (mm), the fracture stress σ (Pa) is given by the following equation (1). Fracture stress σ(Pa) = 3F(L2) / 2bh 2 ...(1)

[0062] In this test, as shown in Figure 11(b), the chip thickness (die thickness): h = 0.1 mm, chip width: a = 5 mm, die width: b = 5 mm, and support width (distance between lower supports): L2 = 2 mm were set, and the test speed was 1 mm / s. The laser grooving conditions for this test were as shown in Figure 12. Specifically, the laser grooving width was set to 18 μm, and the number of branching points was set to 4, each with a different groove depth (laser grooving depth). The dicing conditions were: laser wavelength 1080 nm, processing speed: 180 mm / sec, output: 0.12 W, and pulse pitch 2.3 μm.

[0063] As shown in the test results in Figure 13, it was confirmed that the chip strength relatively decreases as the depth of grooving increases. Furthermore, by comparing the results with the required strength necessary for semiconductor manufacturing, it was found that the problem of product quality deterioration due to reduced chip strength can be solved if the depth of grooving can be limited to 3 μm. In summary, although it is necessary to groov to the semiconductor substrate 21 by laser grooving from the viewpoint of suppressing film peeling, the above test results confirmed that if grooving is excessive, the effect of HAZ becomes strong and the chip strength decreases.

[0064] The laser processing method according to this embodiment includes a second step of irradiating the street 23 with a first laser beam L1 to make the insulating film 24 of the first region and the second region uneven, and a third step of irradiating the street 23 with a second laser beam L2 after the second step to completely remove the insulating film 24 of the first region and the second region.

[0065] In the laser processing method according to this embodiment, a first laser beam L1 is irradiated onto a street 23 of the wafer 20 to make the insulating film 24 in the first and second regions uneven, and then a second laser beam L2 is irradiated onto the street 23 to completely remove the insulating film 24 in the first and second regions. The uneven (frosted glass-like) surface of the insulating film 24 has low transmittance of laser light. Therefore, even when the second laser beam L2 is set to a laser beam with processing energy that completely removes the insulating film 24 in the first and second regions, the uneven surface with low transmittance can suppress light leakage toward the semiconductor substrate 21 of the wafer 20 made of silicon or the like, and can suppress thermal damage to the wafer 20 caused by the laser beam. As described above, according to the laser processing method according to this embodiment, thermal damage to the wafer 20 caused by the laser beam can be suppressed and deterioration of chip quality can be suppressed. [Differentiation]

[0066] The present invention is not limited to the embodiments described above. For example, although the above embodiments described an example in which dicing is performed after laser grooving, the invention is not limited to this, and the dicing process may be omitted and full cutting may be performed by laser grooving. Below, with reference to Figure 15, a laser processing method in which the dicing process is omitted and full cutting is performed by laser grooving in the process of creating a bonded wafer will be described. Although a bonded wafer will be described as an example, the laser processing method in which the dicing process is omitted and full cutting is performed by laser grooving may also be performed on a single wafer other than a bonded wafer.

[0067] As shown in Figure 15(a), a bonded wafer is prepared by bonding a bottom wafer 720 and an top wafer 820 together. The semiconductor substrate 821 of wafer 820 has been ground and polished to a thickness of 10 μm or less. Also, wafer 720 is in its original thickness state. The surface of the street of wafer 720 has a region composed of an insulating film 24 and a metal structure 25 on the insulating film 24. Now, as shown in Figure 15(a), a first laser beam L1 is irradiated onto the street of wafer 720, so that the metal structure 25 is completely removed and a part of the insulating film 24 is removed. The first laser beam L1 is incident from the semiconductor substrate 821 side of wafer 820 and reaches the insulating film 24 of wafer 720.

[0068] Next, as shown in Figure 15(b), the second laser beam L2 is irradiated onto the street of wafer 720, completely removing the insulating film 24 of wafer 720. The laser beam L2 is incident from the semiconductor substrate 821 side of wafer 820 and etches a portion of the semiconductor substrate 721 of wafer 720. That is, the irradiation surface 650 of the second laser beam L2 reaches the semiconductor substrate 721. The amount of etched material in the semiconductor substrate 721 by the second laser beam L2 is set to a range in which no HAZ is generated.

[0069] Next, as shown in Figure 15(c), a protective film 900 is attached to the semiconductor substrate 821 side of wafer 820, and the semiconductor substrate 721 of wafer 720 is ground and polished so that the irradiated surface 650, which is the groove portion, is exposed.

[0070] Finally, as shown in Figure 15(d), the tape 950 is attached to the semiconductor substrate 721 side of the wafer 720 to hold the chip. If necessary, expansion processing is performed to form the chip.

[0071] Next, the laser processing method according to the above modified example will be explained with reference to the flowchart in Figure 16. First, a bonded wafer is prepared (step S11, first step).

[0072] Next, a predetermined first laser beam L1 is irradiated onto the street (step S12, second step). The first laser beam L1 is a laser beam with processing energy that, within the irradiation range, removes a portion of the insulating film 24 in the first region of the wafer 720, leaving the rest intact, and completely removes the metal structure 25 in the second region of the wafer 720, while also removing a portion of the insulating film 24 in the second region, leaving the rest intact.

[0073] Next, a predetermined second laser beam L2 is irradiated onto the street (step S13, third step). The second laser beam L2 is a laser beam with processing energy that completely removes the insulating film 24 in the first region and the insulating film 24 in the second region of the wafer 720 within the irradiation range. The grooving process is completed by this third step.

[0074] Next, a protective film 900 is attached to the semiconductor substrate 821 side of wafer 820, and the semiconductor substrate 721 of wafer 720 is ground and polished so that the irradiated surface 650, which is the groove portion, is exposed (step S14). Finally, the wafer is chipped (step S15).

[0075] As described above, the modified laser processing method further includes a fourth step of grinding or polishing the semiconductor substrate after irradiation with the second laser beam L2 so that grooves formed in the street by the irradiation of the second laser beam L2 are exposed. With such a laser processing method, full cutting can be performed by grooving without performing a dicing step after laser grooving. This allows for rapid processing.

[0076] Another variation is to perform an isolation pass using the laser processing apparatus 1 to form narrow grooves at both ends of the area to be grooved before performing the grooving process. In the example shown in Figure 17, a wafer 20 is prepared (see Figure 17(a)), narrow grooves 700 are formed at both ends of the area to be grooved (see Figure 17(b)), then a first laser beam L1 is irradiated to form a frosted glass surface 500 (see Figure 17(c)), and finally a second laser beam L2 is irradiated so that the irradiated surface 600 reaches the semiconductor substrate (see Figure 17(d)).

[0077] As described above, the steps of irradiating with the first laser beam L1 and the second laser beam L2 are processes to process the device so that the groove depth is uniform and suppress the reduction in strength due to the heat-affected zone (HAZ). However, depending on the type of device, delamination of the film may occur at both ends of the groove during laser grooving. In this regard, as in the modified example described above, fine grooves 700 are formed at both ends of the area to be grooved before laser grooving, and laser grooving is performed after the fine grooves 700 have been formed, thereby effectively suppressing delamination of the film while suppressing the HAZ.

[0078] In the isolation path described above (see Figure 17(b)), by adjusting the laser conditions, for example using burst pulses, the laser light can be absorbed by the film without excess or deficiency, suppressing film peeling and allowing for proper film removal. While the isolation path requires laser irradiation at both ends, the ends can be cut simultaneously by splitting the laser beam into two points. Furthermore, if the HAZ (Hazard Area) effect persists in the isolation path, it can be suppressed by splitting the irradiation in a nearly single-array manner. [Explanation of Symbols]

[0079] 1... Laser processing device, 2... Support unit, 3... Irradiation unit, 5... Control unit, 20... Wafer, 21... Semiconductor substrate, 23... Street, 24... Insulating film, 25... Metal structure.

Claims

1. A first step of preparing a wafer having a plurality of functional elements arranged adjacent to each other via a street, wherein the wafer has a first region in which the surface layer of the street is composed of an insulating film, and a second region in which the surface layer is composed of an insulating film and a metal structure on the insulating film, A second step involves irradiating the street with a predetermined first laser beam, The process includes, after the second step, a third step of irradiating the street with a predetermined second laser beam, The first laser beam is a laser beam with processing energy that, within the irradiation range, removes a portion of the insulating film in the first region while leaving the other portion intact, completely removes the metal structure in the second region, and removes a portion of the insulating film in the second region while leaving the other portion intact. A laser processing method wherein the second laser beam is a laser beam with processing energy that completely removes the insulating film of the first region and the insulating film of the second region after the second step in the irradiation area.

2. The laser processing method according to claim 1, wherein the second laser beam is a laser beam with processing energy for etching a portion of the substrate contained in the wafer after the second step.

3. The laser processing method according to claim 2, wherein the second laser beam is a laser beam with processing energy that engraves the substrate by 4 μm or less after the second step.

4. The laser processing method according to claim 2 or 3, further comprising a fourth step of grinding or polishing the substrate after the third step so that grooves formed in the street by irradiation with the second laser beam are exposed.

5. The laser processing method according to claim 1, wherein in the first region after the second step, the surface irradiated with the first laser light is an uneven (frosted glass-like) frosted glass surface.

6. A first step of preparing a wafer having a plurality of functional elements arranged adjacent to each other via a street, wherein the wafer has a first region in which the surface layer of the street is composed of an insulating film, and a second region in which the surface layer is composed of an insulating film and a metal structure on the insulating film, A second step involves irradiating the street with laser light to make the insulating film of the first region and the second region uneven, A laser processing method comprising a third step of completely removing the insulating films of the first and second regions by irradiating the street with laser light after the second step.

7. A wafer comprising a plurality of functional elements arranged adjacent to each other via a street, wherein the wafer has a first region in the street whose surface layer is made of an insulating film, and a second region whose surface layer is made of an insulating film and a metal structure on the insulating film, and a support portion for supporting the wafer. An irradiation unit that irradiates the street with laser light, The system comprises a control unit for controlling the irradiation unit, The control unit, A first control that controls the irradiation unit so that a predetermined first laser beam is irradiated onto the street, The system is configured to perform a second control after the first control, which controls the irradiation unit so that a predetermined second laser beam is irradiated onto the street. The first laser beam is a laser beam with processing energy that, within the irradiation range, removes a portion of the insulating film in the first region while leaving the other portion intact, completely removes the metal structure in the second region, and removes a portion of the insulating film in the second region while leaving the other portion intact. A laser processing apparatus in which the second laser beam is a laser beam with processing energy that completely removes the insulating film of the first region and the insulating film of the second region after irradiation with the first laser beam within the irradiation range.

8. A wafer comprising a plurality of functional elements arranged adjacent to each other via a street, wherein the wafer has a first region in the street whose surface layer is made of an insulating film, and a second region whose surface layer is made of an insulating film and a metal structure on the insulating film, and a support portion for supporting the wafer. An irradiation unit that irradiates the street with laser light, The system comprises a control unit for controlling the irradiation unit, The control unit, A first control that controls the irradiation unit so that laser light is irradiated onto the street such that the insulating films of the first and second regions become uneven, A laser processing apparatus configured to perform, after the first control, a second control, which controls the irradiation unit so that laser light is irradiated onto the street so that insulating films of the first and second regions are completely removed.

Images