Manufacturing method of individualized chips, liquid ejection head, and stealth dicing method

Abstract

To provide a stealth dicing method of a wafer having hollow portions, capable of improving dimensional accuracy of singulated chips and reducing a possibility of processing failures occurrence.SOLUTION: One embodiment of the present disclosure is a stealth dicing method performed on a wafer having a first substrate, a second substrate, and hollow portions, the second substrate being thinner than the first substrate in a region defining each of the hollow portions. The stealth dicing method includes: a first step of performing laser application on the second substrate to form a modified region in the second substrate; and a second step of performing laser application on the first substrate after the first step to form a modified region in the first substrate. In either the first or second step, multiple modified regions are formed, arranged in a Z-direction at positions corresponding to both sides of the hollow portion in a Y-direction, and in the other step, multiple modified regions are formed, arranged in the Z-direction at a position corresponding to one side of the hollow portion in the Y-direction.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present disclosure relates to a wafer dicing method and a liquid ejection head. [Background technology]

[0002] One method for dicing a wafer is stealth dicing, which uses a laser. Stealth dicing is a method in which a laser beam is focused to form a modified region as a weak area along a specified dicing line, and a dicing tape is stretched to cut through the modified region, thereby dividing the wafer into individual chips.

[0003] According to Patent Document 1, the problem of multi-layer wafers made of different materials, that is, wafers made of multiple substrates, can be solved by irradiating each surface with a laser according to the wavelength of the material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-177537 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the technology of Patent Document 1 does not take into consideration that the laser light refracts in a direction different from the specified direction at the material interface, and therefore cannot deal with processing defects such as the generation of cracks in the wafer or failure to cut it properly during stealth dicing of a wafer with a hollow portion.

[0006] In view of the above problems, the present disclosure aims to improve the dimensional accuracy of individual chips and reduce the possibility of processing defects in stealth dicing of a wafer having a hollow portion. [Means for solving the problem]

[0007] One embodiment of the present invention is a stealth dicing method for a wafer having a first substrate, a second substrate bonded to the first substrate, and a hollow portion between the first substrate and the second substrate, wherein the thickness of the second substrate is thinner than the thickness of the first substrate in a region defining the hollow portion, the stealth dicing method comprising: a first step of forming a modified region in the second substrate by irradiating the second substrate with a laser to serve as a region for cleaving having low crystal strength; and a second step of forming a modified region in the first substrate by irradiating the first substrate with a laser after the first step, wherein, when the direction in which the hollow portion extends is the X direction, the thickness direction of the wafer is the Z direction, and the direction perpendicular to the X and Z directions is the Y direction, in either the first step or the second step, a plurality of modified regions arranged in the Z direction are formed at positions corresponding to both sides of the hollow portion in the Y direction, and in the other step, a plurality of modified regions arranged in the Z direction are formed at positions corresponding to one side of the hollow portion in the Y direction. Effect of the Invention

[0008] According to the present disclosure, in stealth dicing of a wafer having a hollow portion, the dimensional accuracy of the individual chips can be improved, thereby reducing the possibility of processing defects. [Brief description of the drawings]

[0009] [Figure 1] Schematic diagram of a wafer having a hollow portion to which the technical idea of ​​the present disclosure can be applied. [Diagram 2] Schematic diagram showing crack generation, which is a problem of the present disclosure. [Diagram 3] Schematic diagram of a wafer to which the technical idea of ​​the present disclosure can be applied. [Figure 4] Schematic diagram of a multi-layered wafer structure to which the technical concept of the present disclosure can be applied. [Diagram 5] FIG. 1 is a perspective view showing a chip structure obtained by dicing a wafer. [Figure 6] Flowchart of a dicing method according to a first embodiment [Figure 7] Schematic diagram showing a stealth dicing process in the first embodiment. [Figure 8] Schematic diagram showing a dicing method in the first embodiment. [Figure 9] Schematic diagram showing an expanding process in the first embodiment. [Figure 10] Flowchart of a dicing method according to a second embodiment [Figure 11] FIG. 13 is a schematic diagram showing a stealth dicing process in the second embodiment; [Figure 12] FIG. 13 is a schematic diagram showing a dicing method according to a second embodiment; [Figure 13] Schematic diagram showing an expanding process in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. The following description is not intended to limit the scope of the claims more than necessary. In addition, in the following description, the wafer has a two-layer structure with terminals arranged on the inner surface of the hollow portion, but this structure is merely an example. The method according to the present disclosure is also applicable to wafers with three or more layers and wafers without terminals. Furthermore, in the following description, a chip for inkjet recording is used as the chip, but the contents of the present disclosure can also be applied to chips other than those for inkjet recording.

[0011] <Explanation of the problem to be solved by this disclosure> The following is a supplementary explanation of the above-mentioned problem. In a multi-layered wafer made up of multiple substrates, the refractive index of each substrate is different before lamination, and the laser light is refracted in a direction different from the specified direction at the material interface. This is not taken into consideration in Patent Document 1. As a result, the light cannot be focused on a specified area, so a modified area cannot be formed, and the wafer cannot be divided even by applying an external force, making dicing difficult.

[0012] One possible solution to this problem is to provide a laser suitable for the material of each substrate, and to have each surface of the wafer (i.e., the front and back) irradiated with the laser to form a modified region on each surface of the substrate. This allows for predetermined dicing and facilitates processing. However, in order to focus the laser light at a predetermined position, the laser light must pass through layers with different refractive indices, making it difficult to process wafers with three or more layers.

[0013] By the way, by bonding multiple substrates, it is possible to provide a space between the substrates that make up the wafer. This space is defined as the "hollow portion" between the substrates of the wafer. When irradiating a laser from only one side of a wafer with a hollow portion, the laser irradiated from the irradiation device is irradiated and focused toward one point from the same wide plane, but when passing through a layer with a different refractive index, it is difficult to focus the laser light at the desired depth. Therefore, in stealth dicing of a wafer with a hollow portion, since processing from only one side is difficult, processing from both sides is generally performed.

[0014] 1, when the laser 40 advances in the Z-axis direction and, at a certain position in the Z-axis direction, the hollow portion 22 occupies half of the X-direction region irradiated with the laser 40, the refraction effects are different between the substrate portion and the hollow portion, and the optical paths differ on the left and right sides of the central axis, which prevents light from being focused. In other words, the refractive index of the substrate portion is greater than 1, while the refractive index of the air in the hollow portion is approximately 1, which prevents light from being focused, and therefore it is necessary to perform processing in which the laser is incident from both sides of the substrate.

[0015] In addition, in the processing for obtaining an L-shaped structure in which a hollow portion is exposed on one side of the chip as shown in FIG. 5, a total of three dicing lines must be provided, including one dicing line from the first surface of the wafer and two dicing lines from the second surface opposite to the first surface. The case of providing three dicing lines will be described later with reference to FIG. 8(a) and FIG. 8(b). In this case, if the dicing lines are processed arbitrarily (i.e., without considering the order in which the dicing lines are provided), the strain and stress may be concentrated in a certain area, and the dicing tape may not be able to withstand the tension constantly applied thereto, which may cause cracks in the wafer. FIG. 2 shows an example in which a crack 82 occurs during the formation of multiple modified regions 42 in a silicon substrate 80.

[0016] Stealth dicing is a method of reducing the strength of a substrate against cleavage at a dicing line by forming a modified region by laser irradiation, and since the thickness of a substrate with a hollow portion is smaller than that of a substrate without a hollow portion, such a substrate is weak against cleavage. Therefore, in the process of forming the modified region, it is important to form the modified region while maintaining the appropriate strength required to realize precise cleavage.

[0017] The mechanism by which the above-mentioned cracks occur is that when the strength of the entire substrate decreases as the process of forming the modified region progresses, the strength may fall below the appropriate strength for cleavage. If the strength of the substrate falls below the stress at the cross section caused by the tension of the dicing tape, unintended cleavage of the wafer occurs. Conditions that make unintended cleavage likely include when the thickness is thin and stress is concentrated at a specific point, when the laser output is too strong for the thickness, or when the number of modified regions formed is large. Patent Document 1 cannot deal with processing defects such as the above-mentioned cleavage defects.

[0018] <Wafer structure> Fig. 3 is a schematic diagram of a circular plate wafer 10 to which the present disclosure can be applied. Fig. 4 is a schematic diagram showing the structure of a chip 11 obtained when the wafer 10 is divided into individual chips.

[0019] Figure 5 is a schematic diagram of an example of a chip obtained after singulation. In detail, Figure 5(a) shows a chip 12 (L-shaped) with terminals on one side obtained by setting the laser irradiation position in the hollow part to be the same for each chip. Also, Figure 5(b) shows a chip 13 (inverted T-shaped) with terminals on both sides obtained by setting the laser irradiation position in the hollow part to be line-symmetric for each chip.

[0020] 3 to 5, the extending direction of hollow portion 22 and the direction in which multiple terminals 23 are arranged is defined as the X direction, the thickness direction of wafer 10 (chip) which is a laminated wafer is defined as the Z direction, and the direction perpendicular to the X direction and the Z direction is defined as the Y direction. In the drawings from FIG. 3 onwards, such coordinate axes are used.

[0021] In an embodiment of the present disclosure, a wafer 10 is used in which two or more substrates are bonded face to face. The substrates constituting the wafer 10 include, for example, a first substrate having a recess or a hollow portion and a second substrate having no recess or hollow portion, and the first substrate and the second substrate are bonded together. By providing a space between the first substrate and the second substrate to be bonded together, the wafer 10 has a hollow portion 22 (see FIG. 4, etc.). As shown in the figure, the first substrate having the recess or hollow portion is thicker (has a longer length in the Z direction) than the second substrate.

[0022] In the following, a stealth dicing method will be described in which a laser is irradiated from both sides of the wafer 10, which is a bonded wafer, toward the hollow portion 22 described above, to expose the hollow portion 22 and separate it into chips.

[0023] First, stealth dicing will be described. In stealth dicing, a laser beam is focused by an objective lens optical system, and the laser is irradiated onto the wafer 10 along a predetermined dicing line to form a modified region as a region with low crystal strength in the material layer on the dicing line. Then, starting from the modified region thus formed, an external force is applied by an expanding process or the like to break the wafer 10. Note that "low crystal strength" here means that the crystal strength is relatively low compared to the surrounding region that is not irradiated with the focused laser beam.

[0024] The process of forming the modified region will be described below. A "modified region" is formed, which is a region with reduced crystal strength, by irradiating the wafer with a laser so that the laser light is concentrated at a predetermined depth from the wafer surface. The wafer 10 of this embodiment is capable of movement in a direction perpendicular to the irradiation axis of the laser light (Z-axis), that is, movement on the XY plane. The wafer 10 can also be rotated. In other words, the wafer 10 can be rotated by θ around the Z axis.

[0025] By performing laser irradiation scanning at a predetermined cycle on the wafer moving relative to the irradiation device at a predetermined speed, a layer of modified regions can be formed along a scanning line at a predetermined depth from the wafer surface. When forming the layer of modified regions, the focal length of the laser is changed, and irradiation or scanning is performed so that the laser light is concentrated at each of a plurality of predetermined depths, so that a layer of modified regions can be formed at each of a plurality of positions in the Z direction perpendicular to the wafer surface.

[0026] The more layers in the modified region, the more times the irradiation or scanning is required, but the more the precision and cleavability in the expansion can be improved. The number of layers in the modified region and the intensity of the laser can be appropriately adjusted according to various factors, including the thickness of the object to be cut. When the modified region is formed along a predetermined dicing line and a force is applied from the outside to divide it, it is possible to cleave along the dicing line starting from the point where the force is applied. In addition, since stealth dicing is performed without contacting the wafer, it is a method that can reduce contamination and damage to the wafer caused by cutting powder and cutting water compared to blade dicing, which is known as another dicing method.

[0027] [First embodiment] Hereinafter, a first embodiment according to the present disclosure will be described with reference to Fig. 6 to Fig. 9. Fig. 6 is a flowchart of a dicing method in this embodiment. This dicing method includes steps S60 to S68. Fig. 7 is a schematic diagram showing a stealth dicing process of a wafer 10 in this embodiment.

[0028] Fig. 8(a) is a cross-sectional view of the wafer 10 of this embodiment. As shown in Fig. 8(a), in the wafer 10, the recess of the first substrate 20 and the second substrate 21 are joined to form a hollow portion 22. In the hollow portion 22 formed by the recess of the first substrate 20, a terminal 23 for electrical connection is provided on the surface of the second substrate 21.

[0029] Moreover, since the first substrate 20 and the second substrate 21 are joined by an adhesive, there is an adhesive layer 25 between the first substrate 20 and the second substrate 21. As for the thickness (length in the Z direction) of the first substrate 20, as described above, the thickness of the region where the recess for the hollow portion 22 is not provided is greater than the thickness of the second substrate 21 (i.e., the length between the interface of the second substrate 21 and the hollow portion 22). Moreover, the thickness of the region where the recess for the hollow portion 22 is provided may be approximately the same as the thickness of the second substrate 21, or may be greater or smaller than the thickness.

[0030] In order to expose the terminals 23, it is necessary to form a cutting line by irradiating the first substrate 20 with two lasers 40 and the second substrate 21 with one laser 40. At that time, a part of the first substrate 20 becomes waste material, so a dicing tape 24 for waste material recovery is affixed to the surface from which the waste material will be generated.

[0031] Step S60 in Fig. 6 is a process of attaching the dicing tape 24 to the first substrate 20 of the wafer 10. The dicing tape 24 is attached and fixed to a general dicing frame (not shown) that is larger than the outer periphery of the wafer 10, and then the fixed dicing tape 24 is attached to the wafer 10. Note that it is preferable to use a tape that is easily permeable to a laser 40 used in the stealth dicing method described below as the dicing tape 24. Note that hereinafter, "Step S~" will be abbreviated to "S~".

[0032] In S61, the second substrate 21 above the hollow portion 22 is irradiated with or scanned with a laser along the dicing line 60. In this step, as shown in Fig. 7(b), the laser is irradiated from the surface of the second substrate 21 to which the dicing tape 24 is not attached. The reason for this is that in this example, the length from the surface on the second substrate 21 side to the hollow portion 22 is shorter than the length from the surface on the first substrate 20 side to which the dicing tape 24 is attached to the hollow portion 22.

[0033] In addition, in a configuration different from this example (FIG. 7), that is, in a configuration in which the length from the surface on the first substrate 20 side to the hollow portion 22 is shorter than the length from the surface on the second substrate 21 side to the hollow portion 22, the laser is irradiated from the surface on the first substrate 20 side. In other words, the processing of the first substrate 20 is performed prior to the processing of the second substrate 21.

[0034] For the substrate having a shorter length between the outer surface and the hollow portion 22, i.e., a substrate that is relatively thin in the region where the hollow portion 22 is provided, the cross-sectional area of ​​the substrate in the region of the hollow portion 22 is smaller than that of the relatively thick substrate. Also, for the relatively thin substrate, the limit strength against cleavage in the x-axis direction (or y-axis direction) perpendicular to the wafer surface is also smaller than that of the relatively thick substrate. Furthermore, at the time of the subsequent laser irradiation in S65, not only does the limit strength against cleavage in the x-axis direction or y-axis direction decrease with the increase in the modified region formed, but stress is concentrated in the remaining region to be modified. Furthermore, the change in limit strength due to the increase in the modified region is also large, specifically, the limit strength decreases rapidly.

[0035] Due to the various factors mentioned above, there is a possibility that the wafer 10 will not be able to withstand the tension constantly applied by the dicing tape 24. Therefore, it is effective to prevent unintended cracks from occurring on the surface of the relatively thin substrate by not applying the dicing tape 24. It is also effective to process the relatively thin substrate before processing the relatively thick substrate, in other words, not to process the relatively thin substrate as a process immediately before expanding.

[0036] According to the stealth dicing method, the laser light irradiation depth of the laser 40 is adjusted between the outer surface (interface) on the second substrate 21 side and the boundary surface of the hollow portion 22 (the lower surface of the second substrate 21 in FIG. 7(b)), and the laser is scanned at the adjusted laser light irradiation depth. This forms a plurality of modified regions 42 along a predetermined dicing line 60 (see FIG. 4, etc., specifically along the X direction) and at different Z direction positions. At this time, the modified regions are formed preferentially from deeper positions using the surface on the side where the laser is irradiated as a reference.

[0037] A method of irradiating the laser 40 to form a modified region preferentially from a deep position will be described. In general, if the laser 40 is irradiated in order from a shallow position to a deep position, the modified region 42 formed in the shallow position makes it difficult for the laser 40 to reach the deep position. Therefore, it is necessary to irradiate the laser from a position close to the hollow portion 22, which is a deep position. Here, the irradiation position in the stealth dicing method of this embodiment will be described with reference to FIG. 8. FIG. 8 is a schematic diagram showing the hollow portion dicing method in this embodiment. In detail, FIG. 8(a) shows the relationship between the dicing line on the surface on the second substrate side and the laser irradiation position, and FIG. 8(b) shows the relationship between the dicing line on the surface on the first substrate side and the laser irradiation position.

[0038] In FIG. 8(a), the laser 40 is incident from the outer surface of the second substrate side 21, but with regard to the Y-direction position, it is irradiated from a position slightly shifted toward the center of the hollow portion 22 from the dicing line 60 so as to reach the inside of the XY plane, which is the boundary surface that defines the hollow portion 22. If the laser is not irradiated so as to reach the inside of the XY plane, which is the boundary surface that defines the hollow portion 22, the second substrate 21 may not be cleaved later, or a predetermined dicing line shape may not be obtained. Therefore, the laser 40 is irradiated while taking into consideration the tolerance of the device so that the laser focusing part 41 is surely within the XY plane, which is the boundary surface that defines the hollow portion 22, near the predetermined dicing line. At that time, the irradiation position is adjusted so as to be within the allowable tolerance of the chip and the product.

[0039] Returning to the explanation of Fig. 6, in S62, the wafer 10 is rotated 90° around the Z axis.

[0040] In S63, the second substrate 21 above the hollow portion 22 is irradiated or scanned with a laser along the dicing line 61. Specifically, as shown in FIG. 7(c), the laser light irradiation depth of the laser 40 is adjusted between the outer surface (interface) on the second substrate 21 side and the adhesive layer 25 according to the stealth dicing method, and the laser is scanned at the adjusted laser light irradiation depth. This forms a plurality of modified regions 42 along a predetermined dicing line 61 (see FIG. 4, etc., specifically along the Y direction) and at different Z direction positions. At this time, the modified regions are formed preferentially from positions farther away (i.e., deeper positions) from the outer surface (interface) on the side where the laser is irradiated.

[0041] In S64, the wafer 10 is turned upside down and rotated 90 degrees. As a result of this step, the surface that can be irradiated with laser becomes the surface on the first substrate 20 side (see FIG. 7(d)).

[0042] In S65, the first substrate 20, which has a hollow portion 22 and is thicker than the second substrate 21, is irradiated with or scanned with a laser along the dicing lines 62 and 63 (see FIG. 4 and FIG. 7(d)). In this step, modified regions 42 are formed in the first substrate 20 through the dicing tape 24 so that the first substrate 20 can be fractured after stealth dicing.

[0043] In S65, first, modified regions are formed along the dicing lines 62. Specifically, the laser light irradiation depth of the laser 40 is adjusted between the XY plane of the first substrate 20 that defines the hollow portion 22 and the surface of the first substrate 20 to which the dicing tape 24 is attached. Then, laser scanning is performed along the dicing lines 62 at the adjusted laser light irradiation depth. Such laser scanning is performed multiple times while changing the laser light irradiation depth. As a result, multiple modified regions 42 are formed along the predetermined dicing lines 62 (along the X direction) and at different Z direction positions.

[0044] As the control of the irradiation or scanning of the laser 40 in S65, the irradiation or scanning of the laser 40 using the dicing line 62, which is irradiated after the dicing line 60 and before the dicing line 63, will be described. In forming the modified region corresponding to the dicing line 62, stress is likely to concentrate on the remaining part during modification. Therefore, the laser output used for the dicing line 62 is set to be equal to or lower than the output used for the dicing line 60. In addition, when the dicing line 62 and the dicing line 63 processed thereafter are compared, the laser light irradiation depth to the hollow portion 22 is the same, but the number of irradiations for the dicing line 62 is made smaller than the number of irradiations for the dicing line 63. The reason for this is that when the dicing line 62 is processed by irradiating the laser 40, stress is concentrated on the dicing line 62, and thus distortion is concentrated on the dicing line 62.

[0045] On the other hand, since stress is less likely to concentrate on the dicing line 63, which is irradiated after the dicing line 62, even if a modified region equivalent to the dicing line 62 is formed, the dicing line 63 is in a state where it is difficult to break. Therefore, compared to the dicing line 62, the output of the laser 40 is increased to lower the crystal strength of the modified region, or the number of times the laser is irradiated or scanned is increased to increase the number of modified regions formed in the depth direction of the first substrate 20. This makes it possible to achieve a breakability on the dicing line 63 equivalent to that of the dicing line 62.

[0046] In the above embodiment, the laser 40 is irradiated in the order of the dicing line 62 and the dicing line 63, but the order of irradiation in S65 can be changed. However, the laser output used for the dicing line irradiated first must be equal to or lower than the laser output used for the dicing line 60 in the previous process. In addition, when forming the modified region in the dicing line irradiated later, the number of scans is increased or the output of the laser 40 is increased compared to when forming the modified region in the dicing line irradiated earlier, thereby lowering the crystal strength of the modified region. In this way, it is possible to form the modified region in any order.

[0047] In S66, the wafer 10 is rotated 90 degrees around the Z axis.

[0048] In S67, the first substrate 20 is irradiated or scanned with a laser along the dicing line 64 of the first substrate 20. Specifically, as shown in FIG. 7(e), the laser light irradiation depth of the laser 40 is adjusted according to the stealth dicing method, and the laser is scanned at the adjusted laser light irradiation depth. This forms a plurality of modified regions 42 along a predetermined dicing line 64 (see FIG. 4, etc., specifically along the Y direction) and at different Z direction positions. At this time, the modified regions 42 are formed preferentially from a position farther away (i.e., a deeper position) from the outer surface (interface) on the side where the laser is irradiated. In this embodiment, as shown in FIG. 7(e), the laser 40 is irradiated from the first substrate 20 side according to the stealth dicing method.

[0049] In S68, the wafer 10 is cleaved by performing an expanding process. By expanding the dicing tape with a predetermined force, a crack is generated starting from the modified region, and the generated crack is completely connected to the entire thickness direction of the wafer, and the wafer is cleaved and divided into individual pieces. As described above, the Y direction position of the modified region formed using the dicing line 60 and the Y direction position of the modified region formed using the dicing line 63 are approximately the same. In this step, a cleavage surface that communicates with the first substrate and the second substrate is formed at the approximately same position. The method of expanding is not particularly limited. For example, the wafer can be cleaved by stretching the dicing tape using an expander.

[0050] FIG. 9 is a schematic diagram showing the expanding process in this embodiment. As shown in FIG. 9, by expanding the dicing tape 24 with a predetermined force, the wafer 10 is divided and singulated starting from the modified regions 42. At the same time as the singulation, the terminals 23 installed on the second substrate 21 are exposed. Due to such exposure, the region of the first substrate 20 sandwiched between the lines of the multiple modified regions 42 formed using the laser 40 becomes unnecessary waste material 43. The waste material 43 is held by the dicing tape 24 and does not fall. Therefore, the first substrate 20 and the terminals 23 can be exposed to singulate the chips 11 while preventing the first substrate 20 and the terminals 23 from being soiled or damaged.

[0051] In cases where three or more layers of wafers are stacked, it is desirable to appropriately adjust the depth of the laser boundary when scanning the laser 40 from above and below while taking into consideration the attenuation effect of the laser. In addition, by changing the cutting position of the second substrate relative to the hollow portion, it is possible to separate the chips into the shape of an L-shaped one-side terminal chip 12 as shown in FIG. 5(a) or the shape of an inverted T-shaped two-side terminal chip 13 as shown in FIG. 5(b). In addition, the present disclosure is not limited to the above-mentioned form, but can also be applied to other shapes including a shape in which the hollow portion is exposed. The one-side terminal chip 12 and the two-side terminal chip 13 are used as components of a liquid ejection head in a printer such as an inkjet recording device.

[0052] In this embodiment, the first substrate 20 is an ink flow path substrate in which an ink flow path is formed. The second substrate 21 is a composite substrate of an energy generating element substrate including energy generating elements for ejecting ink from ejection ports, and an ejection port substrate in which ink ejection ports are formed. In addition, the first substrate 20 and the second substrate 21 each include a wafer material made of silicon crystal. However, the substrates to which the present disclosure can be applied are not limited to these substrates.

[0053] <Effects of this embodiment> As described above, in this embodiment, the first laser processes the second substrate 21 along the dicing line 60. The second laser processes the first substrate 20 along the dicing line 62, and the third laser processes the first substrate 20 along the dicing line 63. At this time, the processing is performed so that the Y-direction position of the modified region formed in the second substrate 21 by irradiation with the first laser and the Y-direction position of the modified region formed in the first substrate 20 by irradiation with the third laser are substantially the same.

[0054] According to this embodiment, in stealth dicing of a bonded wafer consisting of multiple layers and having a hollow portion, the strength on the dicing line is prevented from suddenly decreasing before expanding, and the dimensional accuracy of the chip is improved by controlling the stress concentration caused by the increase in the modified region. Therefore, it is possible to prevent cleavage failures such as unexpected cleavage and non-cleavage.

[0055] [Second embodiment] A second embodiment according to the present disclosure will be described below with reference to Fig. 10 to Fig. 13. Fig. 10 is a flowchart of a dicing method according to the present embodiment, and the dicing method includes steps S100 to S108. Fig. 11 is a schematic diagram showing a stealth dicing process of a wafer 10 according to the present embodiment.

[0056] 11(a) is a cross-sectional view of wafer 10 of this embodiment, showing the state immediately after S100 described below. As shown in Fig. 11(a), in wafer 10, the recess of first substrate 20 and the flat surface of second substrate 21 are joined to form hollow portion 22, and terminal 23 for electrical connection is provided on the bottom surface of the recess of first substrate 20. Regarding the thickness (length in Z direction) of first substrate 20, the thickness of the region where the recess for hollow portion 22 is provided is equal to or greater than the thickness of second substrate 21.

[0057] In order to expose the terminals 23, it is necessary to form a plurality of modified regions 42 in each substrate by irradiating the second substrate 21 with two lasers 40 and irradiating the first substrate 20 with one laser 40. At that time, a part of the second substrate 21 becomes waste material, so a dicing tape 24 for waste material recovery is attached to the second substrate 21 on the surface from which the waste material will be generated.

[0058] 10 is a process of attaching the dicing tape 24 to the second substrate 21 of the wafer 10. The dicing tape 24 is attached to and fixed on a general dicing frame (not shown) that is larger than the outer periphery of the wafer 10, and then the fixed dicing tape 24 is attached to the wafer 10.

[0059] In S101, the second substrate 21 above the hollow portion 22 is irradiated with or scanned with a laser along the dicing line 72 and the dicing line 73. In this step, as shown in FIG. 11(b), the laser 40 is incident on the surface to which the dicing tape 24 is attached. Note that in this embodiment, unlike the first embodiment (dicing line 62 and dicing line 63 in FIG. 4), two dicing lines (dicing line 72 and dicing line 73) are set on the second substrate 21.

[0060] In S101, first, modified regions are formed along the dicing lines 73. Specifically, the laser light irradiation depth of the laser 40 is adjusted between the lower surface of the second substrate 21 that defines the hollow portion 22 and the upper surface of the second substrate 21 to which the dicing tape 24 is attached. Then, laser scanning is performed along the dicing lines 73 at the adjusted laser light irradiation depth. Such laser scanning is performed multiple times while changing the laser light irradiation depth, giving priority to the deeper positions. In this way, multiple modified regions 42 are formed along the predetermined dicing lines 73 (along the X direction) and at different Z direction positions.

[0061] Thereafter, modified regions are formed along the dicing lines 72. Specifically, the laser light irradiation depth of the laser 40 is adjusted between the lower surface of the second substrate 21 that defines the hollow portion 22 and the upper surface of the second substrate 21 to which the dicing tape 24 is attached. Then, laser scanning is performed along the dicing lines 72 at the adjusted laser light irradiation depth. Such laser scanning is performed multiple times while changing the laser light irradiation depth, giving priority to the deeper positions. In this way, multiple modified regions 42 are formed along the predetermined dicing lines 72 (along the X direction) and at different Z direction positions.

[0062] Fig. 12 is a schematic diagram showing a hollow portion dicing method in this embodiment. In detail, Fig. 12(a) shows the relationship between the dicing line position on the surface on the second substrate 21 side and the laser irradiation position, and Fig. 12(b) shows the relationship between the dicing line position on the surface on the first substrate 20 side and the laser irradiation position.

[0063] 12(a), the two lasers 40 are each incident from the surface of the dicing tape 24 attached to the second substrate 21. The incident position of the laser 40 in the Y direction is irradiated from a point slightly shifted toward the center of the hollow portion 22 from the dicing line 72 or dicing line 73 so as to reach the inside of the XY plane, which is the boundary surface that defines the hollow portion 22. At that time, the irradiation position is adjusted so that the cleavage falls within the allowable tolerance of the chip and the product.

[0064] For scanning and irradiation along dicing lines 72, the laser light irradiation depth is adjusted between the lower surface of second substrate 21 that defines hollow portion 22 and the upper surface of second substrate 21, and scanning is preferentially performed from a position farther from the upper surface, i.e., a deeper position, along dicing lines 72. This forms a plurality of modified regions 42 along dicing lines 72. Note that scanning and irradiation along dicing lines 73 is similar to that for dicing lines 72.

[0065] Regarding the control of the two lasers 40, the output of the laser used in the modified region of dicing line 73, which is irradiated first, is set to be smaller than the output of the laser used in dicing line 72. Also, in order to reduce the number of layers in the modified region, the number of times of scanning irradiation is set to be smaller in forming the modified region by dicing line 73 than for dicing line 72. Note that, in the above-described embodiment, the laser 40 is irradiated in the order of dicing line 73 and then dicing line 72, but the order of irradiation can be changed (however, the contents of the items related to irradiation need to be changed as appropriate).

[0066] Returning to the explanation of Fig. 10, in S102, the wafer 10 is rotated 90° around the Z axis.

[0067] In S103, the second substrate 21 is irradiated or scanned with a laser along the dicing line of the second substrate 21. Specifically, as shown in FIG. 11(c), the laser light irradiation depth of the laser 40 is adjusted between the upper and lower surfaces of the second substrate 21 according to the stealth dicing method, and the laser is scanned at the adjusted laser light irradiation depth. This forms a plurality of modified regions 42 along a predetermined dicing line and at different positions in the Z direction. At this time, the modified regions are formed preferentially from deeper positions.

[0068] In S104, the wafer 10 is turned upside down and rotated 90 degrees. As a result of this step, the surface that can be irradiated with laser becomes the interface (outer surface) on the first substrate 20 side (see FIG. 11(d)).

[0069] In S105, the first substrate 20, which is thicker than the second substrate 21, is irradiated with or scanned with a laser along the dicing line 70 (see FIG. 12(b)). In this step, a modified region is formed in the first substrate 20 so that the substrate can be cut after stealth dicing. Note that the output of the laser 40 used for the dicing line 70 in the processing of this step need only be equal to or greater than the output of the laser 40 used for the dicing line 73.

[0070] In S106, the wafer 10 is rotated 90 degrees around the Z axis.

[0071] In S107, the first substrate 20 is irradiated with laser light, or the first substrate 20 is scanned with laser light along the dicing line. Specifically, as shown in FIG. 11(e), the laser light irradiation depth of the laser 40 is adjusted according to the stealth dicing method, and laser scanning is performed at the adjusted laser light irradiation depth. This forms a plurality of modified regions 42 along a predetermined dicing line (along the Y direction) and at different Z direction positions. At this time, the modified regions are formed preferentially from deeper positions. In this embodiment, as shown in FIG. 11(e), the laser 40 is irradiated from the interface (outer surface) on the first substrate 20 side according to the stealth dicing method.

[0072] In S108, the wafer 10 is cleaved by an expanding process. By expanding the dicing tape with a predetermined force, cracks are generated starting from the modified regions, and the generated cracks are completely connected throughout the entire thickness direction of the wafer, and the wafer is cleaved and divided into individual pieces. The method of expanding is not particularly limited. For example, the wafer can be cleaved by stretching the dicing tape using an expander.

[0073] FIG. 13 is a schematic diagram showing the expanding process in this embodiment. As shown in FIG. 13, by expanding the dicing tape 24 with a predetermined force, the wafer 10 is divided and singulated starting from the modified regions 42. At the same time as the singulation, the terminals 23 installed on the first substrate 20 are exposed. Due to such exposure, the region of the second substrate 21 sandwiched between the lines of the multiple modified regions 42 formed using the laser 40 becomes unnecessary waste material 43. The waste material 43 is held by the dicing tape 24 and does not fall. Therefore, the second substrate 21 and the terminals 23 can be exposed to singulate the chips 11 while preventing the second substrate 21 and the terminals 23 from being soiled or damaged.

[0074] <Effects of this embodiment> According to this embodiment, in stealth dicing of a bonded wafer consisting of multiple layers and having a hollow portion, the strength on the dicing line is prevented from suddenly decreasing before expanding, and the dimensional accuracy of the chip is improved by controlling the stress concentration caused by the increase in the modified region. Therefore, it is possible to prevent cleavage failures such as unexpected cleavage and non-cleavage.

[0075] [Technical Features of the Disclosure] The present disclosure includes the following configurations.

[0076] (Configuration 1) A stealth dicing method for a wafer having a first substrate, a second substrate bonded to the first substrate, and a hollow portion between the first substrate and the second substrate, the second substrate being thinner than the first substrate in a region defining the hollow portion, the stealth dicing method comprising: a first step of forming a modified region in the second substrate by irradiating the second substrate with a laser to serve as a region for cleaving having low crystal strength; and a second step of forming a modified region in the first substrate by irradiating the first substrate with a laser after the first step, the modified region being formed in the first substrate by irradiating the first substrate with a laser, the first step being characterized in that, when the direction in which the hollow portion extends is the X direction, the thickness direction of the wafer is the Z direction, and the direction perpendicular to the X direction and the Z direction is the Y direction, in either the first step or the second step, a plurality of modified regions arranged in the Z direction are formed at positions corresponding to both sides of the hollow portion in the Y direction, and the other step is characterized in that a plurality of modified regions arranged in the Z direction are formed at positions corresponding to one side of the hollow portion in the Y direction.

[0077] (Structure 2) The stealth dicing method described in Structure 1, characterized in that the first step forms a plurality of modified regions arranged in the Z direction by irradiating a position corresponding to one side of the hollow portion of the second substrate in the Y direction with a first laser, and the second step forms a plurality of modified regions arranged in the Z direction by irradiating a position corresponding to one side of the hollow portion of the first substrate in the Y direction with a second laser, and further forms a plurality of modified regions arranged in the Z direction by irradiating a position corresponding to the other side of the hollow portion in the Y direction with a third laser.

[0078] (Configuration 3) The stealth dicing method according to configuration 1 or 2, characterized in that the output of the second laser is equal to or lower than the output of the first laser.

[0079] (Structure 4) A stealth dicing method described in any one of structures 1 to 3, characterized in that in the second step, the output of the third laser is greater than the output of the second laser, and in the second step, the number of times the third laser is irradiated or scanned is greater than the number of times the second laser is irradiated or scanned.

[0080] (Configuration 5) A stealth dicing method as described in Configuration 4, characterized in that the Y-direction position of the modified region formed on the second substrate by irradiation with the first laser is approximately identical to the Y-direction position of the modified region formed on the first substrate by irradiation with the third laser.

[0081] (Structure 6) A stealth dicing method as described in Structure 4, characterized in that the Y-direction position of the modified region formed on the second substrate by irradiation with the first laser is approximately identical to the Y-direction position of the modified region formed on the first substrate by irradiation with the second laser.

[0082] (Structure 7) A stealth dicing method according to any one of Structures 1 to 6, further comprising a step of performing an expanding process, wherein when the expanding process is performed, a fracture surface is formed that connects the first substrate and the second substrate at approximately the same position.

[0083] (Structure 8) A stealth dicing method described in any one of structures 1 to 7, characterized in that the first substrate has a recess on a surface that joins with the flat surface of the second substrate, and the hollow portion is realized by the recess of the first substrate and the flat surface of the second substrate.

[0084] (Configuration 9) A stealth dicing method according to any one of configurations 1 to 8, characterized in that a plurality of terminals arranged in the X direction are provided on the second substrate in the hollow portion.

[0085] (Structure 10) A stealth dicing method described in any one of Structures 1 to 9, further comprising a step of attaching a dicing tape to the second substrate, wherein the expanding process causes a portion of the second substrate to be retained by the dicing tape as waste material.

[0086] (Configuration 11) A stealth dicing method according to any one of configurations 1 to 10, characterized in that the first substrate and the second substrate each comprise a wafer material made of silicon crystal.

[0087] (Structure 12) A stealth dicing method described in any one of structures 1 to 11, characterized in that the first step forms a plurality of modified regions arranged in the Z direction by irradiating a position corresponding to one side of the hollow portion of the second substrate in the Y direction with a first laser, and further forms a plurality of modified regions arranged in the Z direction by irradiating a position corresponding to the other side of the hollow portion of the first substrate in the Y direction with a second laser, and the second step forms a plurality of modified regions arranged in the Z direction by irradiating a position corresponding to one side of the hollow portion of the first substrate in the Y direction with a third laser.

[0088] (Configuration 13) A stealth dicing method according to any one of configurations 1 to 12, characterized in that in the hollow portion, a plurality of terminals arranged in the X direction are provided on the first substrate.

[0089] (Configuration 14) A liquid ejection head having chips obtained by dividing a wafer by a stealth dicing method, the wafer having a first substrate as an ink flow path substrate having an ink flow path formed therein, a second substrate as an energy generating element substrate including an energy generating element for ejecting ink from an ejection port, and a hollow portion between the first substrate and the second substrate bonded to the first substrate, the thickness of the second substrate being thinner than the thickness of the first substrate in a region defining the hollow portion, and the stealth dicing method is such that a region for cutting having low crystal strength is formed in the second substrate by irradiating a laser onto the second substrate. A liquid ejection head comprising: a first step of forming a modified region; and a second step of forming a modified region in the first substrate by irradiating the first substrate with a laser after the first step, wherein when the direction in which the hollow portion extends is defined as the X direction, the thickness direction of the wafer is defined as the Z direction, and the direction perpendicular to the X and Z directions is defined as the Y direction, in either the first or second step, a plurality of modified regions arranged in the Z direction are formed at positions corresponding to both sides of the hollow portion in the Y direction, and in the other step, a plurality of modified regions arranged in the Z direction are formed at positions corresponding to one side of the hollow portion in the Y direction. [Explanation of symbols]

[0090] 10 Wafers 11 Chips 12 Chip with terminal on one side 13 Double-Terminated Chip 20 First board 21 Second board 22 Hollow part 23 Terminal 24 Dicing tape 25 Adhesive layer 40 Laser 41 Laser focusing unit 42 Modification Area 43 Scrap materials 60~64 Dicing lines 70 Dicing Line 72 Dicing Line 73 Dicing Line 80 Silicon Substrate 82 Crack

Claims

1. a first substrate, a second substrate bonded to the first substrate, and a hollow portion between the first substrate and the second substrate; In a region defining the hollow portion, the thickness of the second substrate is thinner than the thickness of the first substrate.

1. A method for manufacturing singulated chips using a wafer, comprising: a first step of forming a modified region in the second substrate by irradiating the second substrate with a laser, the modified region being a region for cleaving having low crystal strength; a second step of forming a modified region in the first substrate by irradiating the first substrate with a laser after the first step; and When the direction in which the hollow portion extends is defined as the X direction, the thickness direction of the wafer is defined as the Z direction, and the direction perpendicular to the X and Z directions is defined as the Y direction, in either the first step or the second step, a plurality of modified regions are formed in the Z direction at positions corresponding to both sides of the hollow portion in the Y direction, and in the other step, a plurality of modified regions are formed in the Z direction at positions corresponding to one side of the hollow portion in the Y direction.

1. A method for producing individualized chips, comprising:

2. the first step includes irradiating a first laser beam to a position of the second substrate corresponding to one side of the hollow portion in the Y direction, thereby forming a plurality of modified regions arranged in the Z direction; The second step forms a plurality of modified regions arranged in the Z direction by irradiating a second laser beam onto a position corresponding to one side of the hollow portion of the first substrate in the Y direction, and further forms a plurality of modified regions arranged in the Z direction by irradiating a third laser beam onto a position corresponding to the other side of the hollow portion in the Y direction.

2. The method for manufacturing singulated chips according to claim 1.

3. The output of the second laser is equal to or less than the output of the first laser.

3. The method for manufacturing individual chips according to claim 2.

4. In the second step, the output of the third laser is greater than the output of the second laser; In the second step, the number of times of irradiation or scanning with the third laser is greater than the number of times of irradiation or scanning with the second laser.

4. The method for manufacturing individual chips according to claim 3.

5. a Y-direction position of a modified region formed on the second substrate by irradiation with the first laser is substantially the same as a Y-direction position of a modified region formed on the first substrate by irradiation with the third laser; 5. The method for producing individual chips according to claim 4.

6. a Y-direction position of a modified region formed on the second substrate by irradiation with the first laser is substantially the same as a Y-direction position of a modified region formed on the first substrate by irradiation with the second laser; 5. The method for producing individual chips according to claim 4.

7. Further comprising the step of performing an expanding process; When the expanding process is performed, a fractured surface that communicates with the first substrate and the second substrate is formed at the substantially same position.

7. The method for manufacturing individual chips according to claim 5 or 6.

8. the first substrate has a recess on a surface that is bonded to the flat surface of the second substrate; the hollow portion is realized by the recess of the first substrate and the flat surface of the second substrate. The method for producing singulated chips according to claim 7 .

9. In the hollow portion, a plurality of terminals arranged in an X direction are provided on the second substrate.

9. The method for producing singulated chips according to claim 8.

10. The method further includes a step of attaching a dicing tape to the second substrate; By the expanding process, a portion of the second substrate is held by the dicing tape as a waste material.

10. The method for producing singulated chips according to claim 9.

11. the first substrate and the second substrate each include a wafer material made of crystalline silicon; The method for manufacturing singulated chips according to claim 10 .

12. the first step includes irradiating a first laser beam onto a position corresponding to one side of the hollow portion of the second substrate in the Y direction, thereby forming a plurality of modified regions arranged in the Z direction, and further irradiating a second laser beam onto a position corresponding to the other side of the hollow portion in the Y direction, thereby forming a plurality of modified regions arranged in the Z direction; the second step irradiates a third laser beam onto a position of the first substrate corresponding to one side of the hollow portion in the Y direction, thereby forming a plurality of modified regions arranged in the Z direction; 2. The method for manufacturing singulated chips according to claim 1.

13. In the hollow portion, a plurality of terminals arranged in an X direction are provided on the first substrate.

13. The method for producing singulated chips according to claim 12.

14. A liquid ejection head having chips obtained by dividing a wafer by a stealth dicing method, The wafer is a first substrate as an ink flow path substrate in which an ink flow path is formed; a second substrate serving as an energy generating element substrate including energy generating elements for ejecting ink from the ejection ports; a hollow portion between the first substrate and the second substrate joined to the first substrate; and a thickness of the second substrate is smaller than a thickness of the first substrate in a region defining the hollow portion; The stealth dicing method includes: a first step of forming a modified region in the second substrate by irradiating the second substrate with a laser, the modified region being a region for cleaving having low crystal strength; a second step of forming a modified region in the first substrate by irradiating the first substrate with a laser after the first step; and When the direction in which the hollow portion extends is defined as the X direction, the thickness direction of the wafer is defined as the Z direction, and the direction perpendicular to the X and Z directions is defined as the Y direction, in either the first step or the second step, a plurality of modified regions are formed in the Z direction at positions corresponding to both sides of the hollow portion in the Y direction, and in the other step, a plurality of modified regions are formed in the Z direction at positions corresponding to one side of the hollow portion in the Y direction. A liquid ejection head characterized by:

15. A semiconductor device comprising: a first substrate; a second substrate joined to the first substrate; and a hollow portion between the first substrate and the second substrate; In a region defining the hollow portion, the thickness of the second substrate is thinner than the thickness of the first substrate. A stealth dicing method for a wafer, comprising: a first step of forming a modified region in the second substrate by irradiating the second substrate with a laser, the modified region being a region for cleaving having low crystal strength; a second step of forming a modified region in the first substrate by irradiating the first substrate with a laser after the first step; and When the direction in which the hollow portion extends is defined as the X direction, the thickness direction of the wafer is defined as the Z direction, and the direction perpendicular to the X and Z directions is defined as the Y direction, in either the first step or the second step, a plurality of modified regions are formed in the Z direction at positions corresponding to both sides of the hollow portion in the Y direction, and in the other step, a plurality of modified regions are formed in the Z direction at positions corresponding to one side of the hollow portion in the Y direction. A stealth dicing method characterized by:

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