Manufacturing method for chips

Abstract

To provide a manufacturing method for chips that enables reliable chip formation for each functional element on a wafer.SOLUTION: The manufacturing method for chips includes dividing a wafer, which has a substrate, multiple functional elements, and functional element layers, along multiple lines to form chips. The manufacturing method for chips includes steps for: irradiating the interior of the wafer with laser light along the lines from the exposed back surface of the wafer for condensing the light to form a modified region along the lines and to form a crack extending from the modified region toward the substrate surface; grinding the back surface of the substrate after forming the modified region to thin the wafer; and radiating the laser light along the lines from the surface side of the wafer to form grooves in the functional element layer after thinning the wafer.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a chip. [Background technology]

[0002] In a wafer including multiple functional elements arranged adjacent to each other with streets interposed therebetween, insulating films (such as low-k films) and metal structures (such as metal piles and metal pads) may be formed on the surface of the streets. In such cases, if modified regions are formed inside the wafer along lines passing through the streets and cracks are propagated from the modified regions to separate the wafer into individual functional element chips, film peeling may occur along the streets, degrading the quality of the chips. Therefore, when separating the wafer into individual functional element chips, a grooving process may be performed in which the street surface is removed by irradiating the streets with laser light (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-173475 [Patent Document 2] Japanese Patent Application Publication No. 2017-011040 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described techniques, for example, depending on the extent to which a crack extends from a modified region, it may become difficult to separate the wafer into chips for each functional element.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for manufacturing chips that enables a wafer to be reliably divided into chips for each functional element. [Means for solving the problem]

[0006] The chip manufacturing method of the present invention is a method of dividing a wafer having a substrate, a plurality of functional elements, and a functional element layer along a plurality of lines to form chips, wherein each of the plurality of functional elements is formed in a region defined by a plurality of lines when viewed in the thickness direction of the wafer, and the functional element layer is formed on the surface of the substrate, and includes the steps of: irradiating laser light from the exposed back surface of the wafer along the lines so as to focus the light inside the wafer, thereby forming a modified region along the line and forming a crack extending from the modified region toward the front surface of the substrate; after the step of forming the modified region, grinding the back surface of the substrate to thin the wafer; and after the step of thinning the wafer, irradiating laser light from the front surface of the wafer along the line to form a groove in the functional element layer.

[0007] In the chip manufacturing method of the present invention, in the step of forming a groove, the groove formed may be wider in the width direction than the modified region and may be formed so as to cover a crack extending from the modified region toward the surface side of the substrate.

[0008] In the chip manufacturing method of the present invention, in the step of forming a groove, the groove may be formed so as not to completely divide the functional element layer.

[0009] In the method for manufacturing a chip of the present invention, in the step of forming the modified region, the crack extending from the modified region toward the surface side of the substrate may be formed so as not to divide the functional element layer.

[0010] In the chip manufacturing method of the present invention, in the step of forming the modified region, the crack extending from the modified region toward the front surface of the substrate may be formed so as to divide the functional element layer.

[0011] The chip manufacturing method of the present invention may further include a step of attaching tape to the back side of the substrate after the step of thinning the wafer and before the step of forming the groove, and a step of expanding the tape attached to the back side of the substrate after the step of forming the groove. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a chip manufacturing method that can reliably separate a wafer into chips for each functional element. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram illustrating the configuration of a laser processing device for forming a modified region inside a wafer. [Figure 2] FIG. 1 is a configuration diagram of a laser processing device for performing grooving processing. [Figure 3] FIG. 2 is a plan view of a wafer to be processed. [Figure 4] FIG. 4 is a cross-sectional view of a portion of the wafer shown in FIG. [Figure 5] FIG. 4 is a plan view of a portion of the street shown in FIG. 3. [Figure 6] 3 is a flowchart of a laser processing method according to the first embodiment. [Figure 7] 7(a) is a cross-sectional view of a wafer for explaining the laser processing method of the first embodiment, and FIG. 7(b) is a cross-sectional view of the wafer showing a continuation of FIG. 7(a). [Figure 8] 8(a) and 8(b) are cross-sectional views of the wafer, showing a continuation of FIG. 7(b), and FIG. 8(b) is a cross-sectional view of the wafer, showing a continuation of FIG. 8(a). [Figure 9] 9(a) is a cross-sectional view of the wafer showing a continuation of FIG. 8(b), and FIG. 9(b) is a cross-sectional view taken along line AA in FIG. 9(a). [Figure 10] 10(a) is a cross-sectional view of the wafer showing a continuation of FIG. 9(a), and FIG. 10(b) is a cross-sectional view taken along line BB in FIG. [Figure 11] FIG. 10(b) is a cross-sectional view of the wafer showing a continuation of FIG. 10(a). [Figure 12] 10 is a flowchart of a laser processing method according to a second embodiment. [Figure 13] 13(a) is a cross-sectional view of a wafer for explaining a laser processing method according to a second embodiment, and FIG. 13(b) is a cross-sectional view of a wafer showing a continuation of FIG. [Figure 14] 14(a) is a cross-sectional view of the wafer showing a continuation of FIG. 13(b), and FIG. 14(b) is a cross-sectional view of the wafer showing a continuation of FIG. 14(a). [Figure 15] 10 is a flowchart of a laser processing method according to a third embodiment. [Figure 16] 16(a) is a cross-sectional view of a wafer for explaining a laser processing method according to a third embodiment, and FIG. 16(b) is a cross-sectional view of a wafer showing a continuation of FIG. [Figure 17] 17(a) is a cross-sectional view of the wafer showing a continuation of FIG. 16(b), and FIG. 17(b) is a cross-sectional view of the wafer showing a continuation of FIG. 17(a). [Figure 18] FIG. 17(b) is a cross-sectional view of the wafer showing a continuation of FIG. [Figure 19] 10 is a flowchart of a laser processing method according to a fourth embodiment. [Figure 20] 20(a) is a cross-sectional view of a wafer for explaining a laser processing method according to a fourth embodiment, and FIG. 20(b) is a cross-sectional view of a wafer showing a continuation of FIG. 20(a). [Figure 21] FIG. 21 is a cross-sectional view of the wafer showing a continuation of FIG. 20(b). [Figure 22] 10(a) and 10(b) are cross-sectional views illustrating a laser processing method according to a modified example, the cross-sectional view corresponding to FIG. 9(b) and the laser processing method according to a modified example, respectively. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and redundant explanations will be omitted. [Configuration of laser processing equipment]

[0015] In the laser processing method of the embodiment, a modified region is formed inside the wafer. As an apparatus for forming the modified region inside the wafer, for example, a laser processing apparatus 100 shown in FIG.

[0016] 1, the laser processing apparatus 100 includes a support unit 102, a light source 103, an optical axis adjustment unit 104, a spatial light modulator 105, a focusing unit 106, an optical axis monitor unit 107, a visible light imaging unit 108A, an infrared imaging unit 108B, a movement mechanism 109, and a management unit 150. The laser processing apparatus 100 forms a modified region 11 on a wafer 20 by irradiating the wafer 20 with laser light L0. In the following description, three mutually orthogonal directions are referred to as the X direction, the Y direction, and the Z direction, respectively. As an example, the X direction is a first horizontal direction, the Y direction is a second horizontal direction perpendicular to the first horizontal direction, and the Z direction is a vertical direction.

[0017] The support unit 102 supports the wafer 20 by, for example, adsorbing the wafer 20. The support unit 102 is movable along both the X and Y directions. The support unit 102 is rotatable around a rotation axis along the Z direction. The light source 103 emits laser light L0 by, for example, a pulse oscillation method. The laser light L0 is transparent to the wafer 20. The optical axis adjustment unit 104 adjusts the optical axis of the laser light L0 emitted from the light source 103. The optical axis adjustment unit 104 is composed of, for example, multiple reflecting mirrors whose positions and angles can be adjusted.

[0018] The spatial light modulator 105 is disposed within the laser processing head H. The spatial light modulator 105 modulates the laser light L0 emitted from the light source 103. The spatial light modulator 105 is a reflective liquid crystal (LCOS: Liquid Crystal on Silicon) spatial light modulator (SLM). The spatial light modulator 105 can modulate the laser light L0 by appropriately setting a modulation pattern to be displayed on its liquid crystal layer. In this embodiment, the laser light L0 that travels downward from the optical axis adjustment unit 104 along the Z direction enters the laser processing head H, is reflected by the mirror M1, and enters the spatial light modulator 105. The spatial light modulator 105 reflects and modulates the incident laser light L0.

[0019] The focusing unit 106 is attached to the bottom wall of the laser processing head H. The focusing unit 106 focuses the laser light L0 modulated by the spatial light modulator 105 onto the wafer 20 supported by the support unit 102. In this embodiment, the laser light L0 reflected by the spatial light modulator 105 is reflected by the dichroic mirror M2 and enters the focusing unit 106. The focusing unit 106 focuses the incident laser light L0 onto the wafer 20. The focusing unit 106 is configured by attaching a focusing lens unit 161 to the bottom wall of the laser processing head H via a drive mechanism 162. The drive mechanism 162 moves the focusing lens unit 161 along the Z direction, for example, by the driving force of a piezoelectric element.

[0020] An imaging optical system (not shown) is disposed within the laser processing head H between the spatial light modulator 105 and the focusing unit 106. The imaging optical system constitutes a bilateral telecentric optical system in which the reflecting surface of the spatial light modulator 105 and the entrance pupil plane of the focusing unit 106 are in an imaging relationship. As a result, the image of the laser light L0 on the reflecting surface of the spatial light modulator 105 (the image of the laser light L0 modulated by the spatial light modulator 105) is transferred (focused) on the entrance pupil plane of the focusing unit 106. A pair of distance measurement sensors S1 and S2 are attached to the bottom wall of the laser processing head H so as to be positioned on both sides of the focusing lens unit 161 in the X direction. Each distance measurement sensor S1 and S2 emits distance measurement light (e.g., laser light) toward the laser light incident surface of the wafer 20 and detects the distance measurement light reflected from the laser light incident surface to obtain displacement data of the laser light incident surface.

[0021] The optical axis monitor unit 107 is disposed within the laser processing head H. The optical axis monitor unit 107 detects a portion of the laser light L0 that has passed through the dichroic mirror M2. The detection result by the optical axis monitor unit 107 indicates, for example, the relationship between the optical axis of the laser light L0 that is incident on the condenser lens unit 161 and the optical axis of the condenser lens unit 161. The visible light imaging unit 108A emits visible light V0 and acquires an image of the wafer 20 formed by the visible light V0 as an image. The visible light imaging unit 108A is disposed within the laser processing head H. The infrared imaging unit 108B emits infrared light and acquires an image of the wafer 20 formed by the infrared light as an infrared image. The infrared imaging unit 108B is attached to a side wall of the laser processing head H.

[0022] The movement mechanism 109 includes a mechanism for moving at least one of the laser processing head H and the support unit 102 in the X direction, Y direction, and Z direction. The movement mechanism 109 drives at least one of the laser processing head H and the support unit 102 by the driving force of a known driving device such as a motor so that the focal point C of the laser beam L0 moves in the X direction, Y direction, and Z direction. The movement mechanism 109 includes a mechanism for rotating the support unit 102. The movement mechanism 109 drives and rotates the support unit 102 by the driving force of a known driving device such as a motor.

[0023] The management unit 150 has a control unit 151, a user interface 152, and a storage unit 153. The control unit 151 controls the operation of each unit of the laser processing apparatus 100. The control unit 151 is configured as a computer device including a processor, memory, storage, communication devices, etc. In the control unit 151, the processor executes software (programs) loaded into the memory, etc., and controls reading and writing of data from and to the memory and storage, as well as communication via the communication devices. The user interface 152 displays and inputs various types of data. The user interface 152 constitutes a GUI (Graphical User Interface) with a graphics-based operating system.

[0024] The user interface 152 includes at least one of, for example, a touch panel, a keyboard, a mouse, a microphone, a tablet terminal, a monitor, etc. The user interface 152 can accept various inputs, for example, by touch input, keyboard input, mouse operation, voice input, etc. The user interface 152 can display various information on its display screen. The user interface 152 corresponds to an input accepting unit that accepts input, and a display unit that can display a setting screen based on the accepted input. The storage unit 153 is, for example, a hard disk, etc., and stores various data.

[0025] In the laser processing apparatus 100 configured as described above, when the laser light L0 is focused inside the wafer 20, the laser light L is absorbed in a portion corresponding to the focusing point C of the laser light L0 (at least a part of the focusing area), and a modified region 11 is formed inside the wafer 20. The modified region 11 is a region whose density, refractive index, mechanical strength, and other physical properties differ from those of the surrounding unmodified region. Examples of the modified region 11 include a melt-processed region, a crack region, a dielectric breakdown region, a refractive index change region, etc. The modified region 11 includes a plurality of modified spots 11s and cracks extending from the plurality of modified spots 11s.

[0026] As an example, the operation of the laser processing apparatus 100 when forming a modified region 11 inside the wafer 20 along a line 15 for cutting the wafer 20 will be described.

[0027] First, the laser processing apparatus 100 rotates the support part 102 so that the line 15 set on the wafer 20 is parallel to the X direction. Based on an image (e.g., an image of a functional element layer of the wafer 20) acquired by the infrared imaging unit 108B, the laser processing apparatus 100 moves the support part 102 in each of the X and Y directions so that the focal point C of the laser beam L0 is located on the line 15 when viewed from the Z direction. Based on an image (e.g., an image of the laser beam incident surface of the wafer 20) acquired by the visible imaging unit 108A, the laser processing apparatus 100 moves the laser processing head H (i.e., the focusing unit 106) along the Z direction so that the focal point C of the laser beam L0 is located on the laser beam incident surface (height set). Using the position of the laser processing head H as a reference, the laser processing apparatus 100 moves the laser processing head H along the Z direction so that the focal point C of the laser beam L0 is located at a predetermined depth from the laser beam incident surface.

[0028] Next, the laser processing apparatus 100 causes the light source 103 to emit laser light L0, and moves the support part 102 along the X direction so that the focal point C of the laser light L0 moves relatively along the line 15. At this time, the laser processing apparatus 100 operates the drive mechanism 162 of the focusing part 106 based on displacement data of the laser light incident surface acquired by one of the pair of distance measuring sensors S1, S2, which is located on the front side in the processing progress direction of the laser light L0, so that the focal point C of the laser light L0 is located at a predetermined depth from the laser light incident surface.

[0029] As a result of the above, a row of modified regions 11 is formed along the line 15 and at a certain depth from the laser light incident surface of the wafer 20. When the laser light L0 is emitted from the light source 103 using the pulse oscillation method, multiple modified spots 11s are formed so as to be lined up in a row along the X direction. One modified spot 11s is formed by irradiating one pulse of laser light L0. A row of modified regions 11 is a collection of multiple modified spots 11s lined up in a row. Adjacent modified spots 11s may be connected to each other or separated from each other depending on the pulse pitch of the laser light L0 (the value obtained by dividing the relative movement speed of the focal point C with respect to the wafer 20 by the repetition frequency of the laser light L0).

[0030] In the laser processing method of the embodiment, laser light is irradiated onto the streets so as to remove the surface layer of the streets of the wafer 20. As an apparatus for irradiating laser light onto the streets so as to remove the surface layer of the streets of the wafer 20, for example, a laser processing apparatus 1 shown in FIG.

[0031] 2, the laser processing device 1 includes a support unit 2, an irradiation unit 3, an imaging unit 4, and a control unit 5. The laser processing device 1 is a device that performs grooving, which removes the surface layer of the streets of the wafer 20, by irradiating the streets (details of which will be described later) of the wafer 20 with laser light L.

[0032] The support unit 2 supports the wafer 20. For example, by suctioning the wafer 20, the support unit 2 holds the wafer 20 so that the surface of the wafer 20, including the streets, faces the irradiation unit 3 and the imaging unit 4. As an example, the support unit 2 is movable along the X and Y directions, and is rotatable about an axis parallel to the Z direction.

[0033] The irradiation unit 3 irradiates the streets 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 condenser 34. The light source 31 emits the laser light L. The shaping optical system 32 conditions the laser light L emitted from the light source 31. For example, the shaping optical system 32 includes at least one of an attenuator that adjusts the output of the laser light L, a beam expander that expands the diameter of the laser light L, and a spatial light modulator that modulates 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 forms a bilateral telecentric optical system in which the modulation surface of the spatial light modulator and the entrance pupil plane of the condenser 34 are in an imaging relationship. The dichroic mirror 33 reflects the laser light L emitted from the shaping optical system 32 and makes it incident on the condenser 34. The light collecting unit 34 collects the laser light L reflected by the dichroic mirror 33 onto the street of the wafer 20 supported by the support unit 2.

[0034] 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 makes it incident on the condenser 34. The dichroic mirror 33 transmits the visible light V1 between the half mirror 36 and the condenser 34. The condenser 34 condenses the visible light V1 reflected by the half mirror 36 onto the street of the wafer 20 supported by the support 2. The image sensor 37 detects the visible light V1 reflected by the street of the wafer 20 and transmitted through the condenser 34, the dichroic mirror 33, and the half mirror 36. In the laser processing apparatus 1, the control unit 5 moves the condenser 34 along the Z direction based on the detection result by the image sensor 37, for example, so that the focal point of the laser light L is positioned on the street of the wafer 20.

[0035] The imaging unit 4 acquires image data of the streets of the wafer 20 supported by the support unit 2. The imaging unit 4 is an internal observation camera that observes the inside of the wafer 20 on which the modified region 11 has been formed by the laser processing device 100. The imaging unit 4 captures image data to acquire crack extension information regarding the extension of the crack 13 (see Figure 9(b)) extending from the modified region 11. The imaging unit 4 detects the tip of the crack 13 extending from the modified region 11. The imaging unit 4 emits infrared light to the wafer 20 and acquires an image of the wafer 20 formed by the infrared light as image data. An InGaAs camera can be used as the imaging unit 4.

[0036] The control unit 5 controls the operation of each unit of the laser processing apparatus 1. The control unit 5 includes a processing unit 51, a memory unit 52, and an input receiving unit 53. The processing unit 51 is a computer device including a processor, memory, storage, a communication device, etc. In the processing unit 51, the processor executes software (programs) loaded into the memory, etc., and controls reading and writing of data from and to the memory and storage, as well as communication via the communication device. The memory 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 an operator. As an example, the input receiving unit 53 is at least one of a keyboard, a mouse, and a GUI (Graphical User Interface).

[0037] The laser processing apparatus 1 performs grooving, removing the surface layer of each street by irradiating each street with laser light L. Specifically, the control unit 5 controls the irradiation unit 3 so that the laser light L is irradiated onto each street 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 relatively along each street. At this time, the control unit 5 irradiates the streets with the laser light L so that the surface layer of the street is removed and cracks extending from the modified region 11 reach the bottom surface of the groove (recess) formed by the removal of the surface layer of the street along a line (see FIG. 10 ) (details will be described later). [Wafer configuration]

[0038] As shown in FIGS. 3 and 4, the wafer 20 includes a semiconductor substrate 21 and a functional device 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 has a notch 21c indicating a crystal orientation. The semiconductor substrate 21 may have an orientation flat instead of the notch 21c. The functional device layer 22 is formed on the front surface 21a of the semiconductor substrate 21. The functional device layer 22 includes a plurality of functional devices 22a. The plurality of functional devices 22a are arranged two-dimensionally along the front surface 21a of the semiconductor substrate 21. Each functional device 22a is, for example, a light-receiving device such as a photodiode, a light-emitting device such as a laser diode, or a circuit device such as a memory. Each functional device 22a may be configured three-dimensionally by stacking a plurality of layers.

[0039] A plurality of streets 23 are formed on the wafer 20. The plurality of streets 23 are regions exposed to the outside between adjacent functional elements 22a. That is, the plurality of functional elements 22a are arranged adjacent to one another via the streets 23. As an example, the plurality of streets 23 extend in a lattice pattern so as to pass between adjacent functional elements 22a arranged in a matrix. As shown in FIG. 5, an insulating film 24 and a plurality of metal structures 25, 26 are formed on the surface of the streets 23. The insulating film 24 is, for example, a low-k film. Each of the metal structures 25, 26 is, for example, a metal pad. The metal structures 25 and 26 differ from each other in, for example, at least one of thickness, area, and material.

[0040] As shown in Figures 3 and 4, the wafer 20 is intended to be cut into individual functional elements 22a along each of the multiple lines 15 (i.e., to be cut into chips for each functional element 22a). When viewed in the thickness direction of the wafer 20, each line 15 passes through each street 23. As an example, when viewed in the thickness direction of the wafer 20, each line 15 extends so as to pass through the center of each street 23. Each line 15 is a virtual line set on the wafer 20 by the laser processing device 1,100. Each line 15 may also be a line that is actually drawn on the wafer 20. [Laser processing method]

[0041] A laser processing method according to the first embodiment using the laser processing apparatus 100 and the laser processing apparatus 1 will be described with reference to the flowchart shown in FIG.

[0042] First, as shown in FIG. 7(a), a wafer 20 is prepared (step S1: first process). As shown in FIG. 7(b), a grinding tape T1 is applied to the surface of the wafer 20 on the functional element 22a side. As shown in FIG. 8(a), the back surface 21b side of the semiconductor substrate 21 of the wafer 20 is ground in a grinding device having a grinding wheel BG, thereby thinning the wafer 20 to a desired thickness (step S2: grinding process). As shown in FIG. 8(b), the grinding tape T1 is replaced with a transparent dicing tape 12. The transparent dicing tape 12 is also called an expandable film.

[0043] 9(a) and 9(b), the laser processing apparatus 100 irradiates the wafer 20 with laser light L0 along each line 15, thereby forming modified regions 11 inside the wafer 20 along each line 15 (step S3: second process). Note that the upper side in FIG. 9(a) corresponds to the lower side in FIG. 9(b).

[0044] In step S3, with the transparent dicing tape 12 attached to the back surface 21b of the semiconductor substrate 21, the laser light L0 is irradiated onto the wafer 20 by aligning the focal point of the laser light L0 with the interior of the semiconductor substrate 21 via the transparent dicing tape 12. The laser light L0 is transparent to the transparent dicing tape 12 and the semiconductor substrate 21. When the laser light L0 is focused inside the semiconductor substrate 21, the laser light L0 is absorbed in a portion corresponding to the focal point of the laser light L0, and a modified region 11 is formed inside the semiconductor substrate 21. The modified region 11 has a characteristic that cracks 13 tend to extend from the modified region 11 to the incident side of the laser light L0 and the opposite side.

[0045] In step S3, the modified region 11 is formed inside the wafer 20 along the line 15 so that the crack 13 extending from the modified region 11 does not reach the street 23. The processing conditions for forming the modified region 11 in step S3 are not particularly limited and can be set based on various known findings. The processing conditions can be input as appropriate via the user interface 152 (see FIG. 1).

[0046] Next, in the laser processing apparatus 1, with the wafer 20 supported by the support part 2, the imaging part 4 acquires image data of each street 23 of the wafer 20. The control part 5 acquires crack extension information of the crack 13 based on the imaging result of the imaging part 4 (step S4: information acquisition process). The crack extension information includes information on the distance to the street 23 from the tip of the crack 13. The crack extension information may include information on whether the crack 13 has reached the street 23. The crack extension information may include information on the extension amount of the crack 13. In the crack extension information, various pieces of information on the extension of the crack 13 are associated with, for example, each position in the X direction and Y direction of each street 23. The acquired crack extension information is stored in the memory part 52 of the control part 5.

[0047] 10(a) and 10(b), the laser processing apparatus 1 performs grooving on the wafer 20 (step S5) (third process). In step S5, the control unit 5 controls the irradiation unit 3 so that the 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 relatively along each street 23. At this time, based on the crack extension information, the control unit 5 irradiates the laser light L onto the street 23 so that the surface layer of the street 23 is removed and the crack 13 reaches the bottom surface of the groove (recess) MZ formed by the removal of the surface layer of the street 23 along the line 15.

[0048] For example, in step S5, the removal depth of the surface layer of the street 23 (depth of the groove MZ) is determined based on the crack extension information so that even the crack 13 with the smallest extension amount is exposed from the bottom surface of the groove MZ. Then, the laser light L is irradiated onto the street 23 along the line 15 under processing conditions such that the surface layer of the street 23 is removed to the determined removal depth, thereby forming the groove MZ in the street 23.

[0049] For example, in step S5 shown in FIG. 9(b), the depth of the groove MZ is set based on the distance from the street 23 of the crack 13a, whose tip is farthest from the street 23 among the cracks 13a, 13b, and 13c that extend from the modified region 11 by different amounts. The depth is then set so that the crack 13a is exposed at the bottom of the groove MZ. Then, as shown in FIG. 10(b), the surface layer of the street 23 is removed to form the groove MZ with the set depth. As a result, all of the cracks 13a, 13b, and 13c reach the bottom of the groove MZ. The processing conditions for the grooving process are not particularly limited and can be set based on various known findings. The processing conditions can be input appropriately via the input receiving unit 53 (see FIG. 2).

[0050] Next, as shown in Figure 11, by expanding the transparent dicing tape 12 in an expanding device (not shown), cracks are extended in the thickness direction of the wafer 20 from the modified regions 11 formed inside the semiconductor substrate 21 along each line 15, and the wafer 20 is chipped into functional elements 22a (step S6).

[0051] As described above, in the laser processing method of this embodiment, modified regions 11 are always formed inside wafer 20 before grooving. In other words, grooving is always performed after modified regions 11 are formed inside wafer 20. That is, after modified regions 11 are formed along lines 15 inside wafer 20 in step S3, grooving is performed in step S5 to remove the surface layer of streets 23. In grooving, cracks 13 extending from modified regions 11 inside wafer 20 formed in step S3 reach the bottom surfaces of grooves MZ formed by removing the surface layer of streets 23 along lines 15. Therefore, these cracks 13 enable the wafer 20 to be reliably chipped into functional elements 22a.

[0052] In the laser processing method of this embodiment, in step S2, the wafer 20 is ground to thin it, thereby making it possible to obtain a wafer 20 with a desired thickness.

[0053] In the laser processing method of this embodiment, step S2, which is a grinding step, is performed after step S1, in which the wafer 20 is prepared, and before step S3, in which the modified region 11 is formed inside the wafer 20. For example, if the prepared wafer 20 is thicker than a certain level, it may be difficult to form the modified region 11 inside the wafer 20. In this regard, by performing the grinding step before step S3, it is possible to form the modified region 11 inside the thinned wafer 20 even if the prepared wafer 20 is thicker than a certain level, thereby making it possible to prevent difficulty in forming the modified region 11 inside the wafer 20.

[0054] The laser processing method of this embodiment includes the above-mentioned step S4 of acquiring crack extension information before performing grooving. In grooving, based on the acquired crack extension information, the street 23 is irradiated with laser light L so that the surface layer of the street 23 is removed and the crack 13 reaches the bottom surface of the groove MZ along the line 15. In this case, the crack extension information is acquired, and the grooving can be performed using the acquired crack extension information.

[0055] In the laser processing method of this embodiment, in step S4 of acquiring crack extension information, the crack extension information is acquired based on the image of the wafer 20 after step S3 in which the modified region has been formed, captured by the imaging unit 4. In this case, the crack extension information can be acquired from the image of the imaging unit 4.

[0056] In the laser processing method of this embodiment, in step S3, modified region 11 is formed inside wafer 20 along line 15 so that crack 13 does not reach street 23. For example, when wafer 20 is transported after step S3, if crack 13 reaches street 23, wafer 20 may be warped due to crack 13, and this warping may make wafer 20 more susceptible to unintended cracks. In this regard, by preventing crack 13 from reaching street 23 in step S3, it is possible to suppress the likelihood of unintended cracks occurring in wafer 20.

[0057] Next, a laser processing method according to a second embodiment using the laser processing apparatus 100 and the laser processing apparatus 1 will be described with reference to the flowchart shown in Fig. 12. In the following description, the description of the contents overlapping with the first embodiment will be omitted as appropriate.

[0058] First, a wafer 20 is prepared (step S21: first process). A grinding tape T1 is attached to the surface of the wafer 20 on the side of the functional element 22a. As shown in FIG. 13(a), in the laser processing apparatus 100, a laser beam L0 is irradiated onto the wafer 20 along each line 15, thereby forming modified regions 11 inside the wafer 20 along each line 15 (step S22: second process).

[0059] In step S22, with the grinding tape T1 attached to the functional element 22a side of the wafer 20, the laser light L0 is focused from the back surface 21b side onto the interior of the semiconductor substrate 21, and the laser light L0 is irradiated onto the wafer 20. In step S22, the modified region 11 is formed inside the wafer 20 along the line 15 so that the crack 13 extending from the modified region 11 does not reach the street 23.

[0060] 13(b), the back surface 21b of the semiconductor substrate 21 of the wafer 20 is ground in a grinding device having a grinding wheel BG to thin the wafer 20 to a desired thickness (step S23: grinding step). As shown in FIG. 14(a), the grinding tape T1 is replaced with a transparent dicing tape 12.

[0061] Next, in the laser processing apparatus 1, with the wafer 20 supported by the support part 2, the imaging part 4 acquires image data of each street 23 of the wafer 20. The control part 5 acquires crack extension information of the crack 13 based on the imaging result of the imaging part 4 (step S24: information acquisition step). As shown in FIG. 14(b), the laser processing apparatus 1 performs grooving on the wafer 20 (step S25) (third step). In step S25, based on the crack extension information, the surface layer of the street 23 is removed, and the laser light L is irradiated onto the street 23 so that the crack 13 reaches the bottom surface of the groove MZ formed by the removal of the surface layer of the street 23 along the line 15.

[0062] Next, by expanding the transparent dicing tape 12 in an expanding device, cracks are extended in the thickness direction of the wafer 20 from the modified regions 11 formed inside the semiconductor substrate 21 along each line 15, and the wafer 20 is chipped into functional elements 22a (step S26).

[0063] As described above, the laser processing method of this embodiment also achieves the same advantageous effects as the above embodiment, such as the ability to reliably divide the wafer 20 into chips for each functional element 22a. In the laser processing method of this embodiment, the grinding step S23 is performed after step S22, which forms the modified region 11 inside the wafer 20, and before step S25, which is related to grooving. For example, when transporting a wafer 20 having the modified region 11 formed therein, if the wafer 20 is thin, unintended cracks may be more likely to occur in the wafer 20. In this regard, by performing the grinding step after step S22, the wafer 20 having the modified region 11 formed therein can be transported before being thinned, making it possible to prevent unintended cracks from occurring in the wafer 20.

[0064] Next, a laser processing method according to a third embodiment using the laser processing apparatus 100 and the laser processing apparatus 1 will be described with reference to the flowchart shown in Fig. 15. In the following description, the contents that overlap with those of the first embodiment will be omitted as appropriate.

[0065] First, a wafer 20 is prepared (step S31: first process). As shown in FIG. 16(a), a laser processing apparatus 100 irradiates the wafer 20 with a laser beam L0 along each line 15, thereby forming modified regions 11 inside the wafer 20 along each line 15 (step S32: second process). In step S32, the laser beam L0 is irradiated onto the wafer 20 from the back surface 21b, with the focal point of the laser beam L0 aligned with the interior of the semiconductor substrate 21. In step S32, modified regions 11 are formed inside the wafer 20 along the lines 15 so that cracks 13 extending from the modified regions 11 do not reach the streets 23. In step S32, if the surface of the wafer 20 on the functional element 22a side is significantly uneven, for example, a tape may be attached to the surface, or the wafer 20 may be adsorbed by the support 102 that supports the wafer 20 in accordance with the unevenness.

[0066] Next, in the laser processing apparatus 1, with the wafer 20 supported by the support part 2, the imaging part 4 acquires image data of each street 23 of the wafer 20. The control part 5 acquires crack extension information of the crack 13 based on the imaging result of the imaging part 4 (step S33: information acquisition step). Next, as shown in FIG. 16(b), the laser processing apparatus 1 performs grooving on the wafer 20 (step S34) (third step). In step S34, based on the crack extension information, the surface layer of the street 23 is removed, and the street 23 is irradiated with laser light L so that the crack 13 reaches the bottom surface of the groove MZ formed by the removal of the surface layer of the street 23 along the line 15.

[0067] Next, as shown in Fig. 17(a), a grinding tape T1 is applied to the surface of the wafer 20 on the side of the functional element 22a. As shown in Fig. 17(b), the back surface 21b of the semiconductor substrate 21 of the wafer 20 is ground in a grinding device having a grinding wheel BG, and the wafer 20 is thinned to a desired thickness (step S35: grinding process). As shown in Fig. 18, the grinding tape T1 is replaced with a transparent dicing tape 12.

[0068] Next, by expanding the transparent dicing tape 12 in an expanding device, cracks are extended along each line 15 from the modified region 11 formed inside the semiconductor substrate 21 in the thickness direction of the wafer 20, and the wafer 20 is chipped into functional elements 22a (step S36).

[0069] As described above, the laser processing method of this embodiment also achieves the same advantageous effects as the above embodiment, such as being able to reliably divide the wafer 20 into chips for each functional element 22a. In the laser processing method of this embodiment, the grinding step S23 is performed after the grooving step S34. For example, when transporting the wafer 20 after grooving, if the wafer 20 is thin, unintended cracks may be more likely to occur in the wafer 20. In this regard, by performing the grinding step after step S34, the wafer 20 after grouping can be transported before being thinned, making it possible to prevent unintended cracks from occurring in the wafer 20.

[0070] Next, a laser processing method according to a fourth embodiment using the laser processing apparatus 100 and the laser processing apparatus 1 will be described with reference to the flowchart shown in Fig. 19. In the following description, the description of the contents overlapping with the third embodiment will be omitted as appropriate.

[0071] First, the wafer 20 is prepared (step S41: first process). As shown in FIG. 20(a), a protective film HM is applied to the surface on the functional element 22a side (at least on the streets 23 of the wafer 20) (step S42: protective film application process). The protective film HM is not particularly limited, and various protective films for protecting the wafer 20 can be used.

[0072] 20(b), in the laser processing apparatus 100, the wafer 20 is irradiated with laser light L0 along each line 15, thereby forming modified regions 11 inside the wafer 20 along each line 15 (step S43: second process). In step S43, with the grinding tape T1 attached to the functional element 22a side of the wafer 20, the laser light L0 is irradiated onto the wafer 20 from the back surface 21b side, with the focal point of the laser light L0 aligned with the inside of the semiconductor substrate 21. In step S43, the modified regions 11 are formed inside the wafer 20 along the lines 15 so that the cracks 13 extending from the modified regions 11 do not reach the streets 23.

[0073] Next, in the laser processing apparatus 1, with the wafer 20 supported by the support part 2, the imaging part 4 acquires image data of each street 23 of the wafer 20. The control part 5 acquires crack extension information of the crack 13 based on the imaging result of the imaging part 4 (step S44: information acquisition step). As shown in FIG. 21 , the laser processing apparatus 1 performs grooving on the wafer 20 (step S45) (third step). In step S45, based on the crack extension information, the surface layer of the street 23 is removed, and the street 23 is irradiated with laser light L so that the crack 13 reaches the bottom surface of the groove MZ formed by the removal of the surface layer of the street 23 along the line 15.

[0074] Next, the protective film HM is removed. The protective film HM may be removed at any time after step S45. A grinding tape T1 is applied to the surface of the wafer 20 on the functional element 22a side. The back surface 21b of the semiconductor substrate 21 of the wafer 20 is ground in a grinding device having a grindstone BG, and the wafer 20 is thinned to a desired thickness (step S46: grinding process). The grinding tape T1 is replaced with a transparent dicing tape 12.

[0075] Next, by expanding the transparent dicing tape 12 in an expanding device, cracks are extended in the thickness direction of the wafer 20 from the modified regions 11 formed inside the semiconductor substrate 21 along each line 15, and the wafer 20 is chipped into functional elements 22a (step S47).

[0076] As described above, the laser processing method of this embodiment also has the same advantageous effects as the above embodiment, such as being able to reliably divide the wafer 20 into chips for each functional element 22a. In the laser processing method of this embodiment, a protective film HM is applied to at least the streets 23 of the wafer 20 before step S43, which forms the modified regions 11 inside the wafer 20. In this case, the protective film HM can maintain a constant reflectance of the streets 23, making it possible to accurately obtain crack extension information in step S44. Note that the presence of the protective film HM does not affect the formation of the modified regions 11 in step S43. [Variations]

[0077] The present invention is not limited to the above-described embodiments.

[0078] In the above embodiment, as described above, the crack extension information may include information regarding whether or not the crack 13 has reached the street 23. In this case, the grooving process can be performed using the information regarding whether or not the crack 13 has reached the street 23.

[0079] For example, in the grooving process, based on crack extension information including information on whether the crack 13 has reached the street 23, the laser light L may be irradiated only to the area of ​​the street 23 where the crack 13 has not reached along the line 15, so that the surface layer of the street 23 is removed and the crack 13 reaches the bottom surface of the groove MZ along the line 15. This allows the grooving process to be performed only to the area of ​​the street 23 where the crack 13 has not reached along the line 15. The grooving process can be performed efficiently. In this case, if a protective film HM is applied as in the fourth embodiment, after the modified region 11 is formed inside the wafer 20, the crack 13 will be exposed to the street 23 through the protective film HM. The presence of the protective film HM makes the reflectance constant, making it easy to determine whether the crack 13 has reached the street 23.

[0080] In the example shown in FIG. 22(a), the crack extension information includes information that "a crack 13 that extends from the modified region 11 does not reach the street 23 along the line 15 in the first region R1, but reaches the street 23 along the line 15 in the second region R2." The first region R1 is a region in each street 23 that corresponds to the metal structure 26 (see FIG. 5), and the second region R2 is a region in each street 23 other than the first region R1. In this case, in the grooving process, the laser light L may be irradiated only onto the first region R1 of the street 23, and the laser light L may not be irradiated onto the second region R2 of the street 23. Specifically, the control unit 5 may control the irradiation unit 3 so that the output of the laser light L is turned on when the laser light L moves relatively over the first region R1, and the output of the laser light L is turned off when the laser light L moves relatively over the second region R2. As a result, as shown in the example of Figure 22(b), in the first region R1 of each street 23, the surface layer of the street 23 (i.e., the metal structure 26) is removed and the crack 13 reaches the bottom surface of the groove MZ along the line 15, while in the second region R2 of each street 23, the surface layer of the street 23 remains.

[0081] Note that "the crack 13 extending from the modified region 11 reaches the street 23 along the line 15" means "the crack 13 extending from the modified region 11 reaches the street 23, and the meandering of each of the edges 23a of the cut street 23 is within a predetermined width (a predetermined width in a direction perpendicular to the line 15)." Also, "the crack 13 extending from the modified region 11 does not reach the street 23 along the line 15" means "the crack 13 extending from the modified region 11 does not reach the street 23, or even if the crack 13 extending from the modified region 11 reaches the street 23, the meandering of each of the edges 23a of the cut street 23 exceeds the predetermined width." The predetermined width is, for example, about 10 μm.

[0082] Although the above embodiment includes an information acquisition step in which the laser processing apparatus 1 acquires crack extension information, the crack extension information may be acquired by the laser processing apparatus 100, or by another device. The above embodiment does not necessarily include the information acquisition step, in which case pre-acquired crack extension information may be stored in the memory unit 52. For example, the crack extension information may be information confirmed in advance using a test wafer. In the above embodiment, the groove MZ is formed by greasing, but a hole or a depression may be formed instead of the groove MZ; in short, it is sufficient to form a recess.

[0083] In the above embodiment, for example, since there is a certain correlation between the extension of the crack 13 and the height and light intensity of the street 23, the crack extension information may include information about the height and light intensity of the street 23. For example, the laser processing device 1 may be provided with a distance measuring unit instead of or in addition to the imaging unit 4, and the distance measuring unit may acquire information about the height of the street 23. As the distance measuring unit, for example, a laser displacement meter of a triangulation type, a spectral interference type, a multicolor confocal type, a monochromatic confocal type, or the like may be used.

[0084] In the above embodiment, the imaging unit 4 may include a camera that uses visible light to acquire image data of the streets of the wafer 20. In the above embodiment, information for controlling the irradiation conditions (laser ON / OFF control, laser power) of the laser light L in each area of ​​the streets 23 is created using an image of at least the surface layer of the streets 23 after cutting or a fluoroscopic image using infrared light, and the grooving process can be controlled based on the information. In the above embodiment, the surface layer of the streets 23 may be removed by scanning the laser light L multiple times over the streets 23. In the above embodiment, only the support unit 102 may be controlled, only the laser processing head H may be controlled, or both the support unit 102 and the laser processing head H may be controlled so that the laser light L moves relatively along each line 15. In the above embodiment, only the support unit 2 may be controlled, only the irradiation unit 3 may be controlled, or both the support unit 2 and the irradiation unit 3 may be controlled so that the laser light L moves relatively along each street 23.

[0085] In the above embodiment, the grooving process (third step) is performed so that the cracks 13 extending from the modified regions 11 reach the bottom surface of the grooves MZ along the lines 15, but this is not limiting. For example, the grooving process may be performed so that the cracks 13 do not reach the bottom surface of the grooves MZ along the lines 15 immediately after the grooving process, but reach the bottom surface of the grooves MZ along the lines 15 after the subsequent fourth step.

[0086] That is, a laser processing method according to one embodiment includes a first step of preparing a wafer 20 including a plurality of functional elements 22a arranged adjacent to one another with streets 23 interposed therebetween, a second step of forming modified regions 11 inside the wafer 20 along lines 15 passing through the streets 23 after the first step, a third step of irradiating the streets 23 with laser light L so as to remove the surface layers of the streets 23 after the second step, and a fourth step of processing the wafer 20 after the third step, wherein in the third step, the laser light L may be irradiated onto the streets 23 so that cracks 13 extending from the modified regions 11 reach the bottom surfaces of grooves MZ formed by the removal of the surface layers of the streets 23 along the lines 15 after the fourth step. Such processing can be realized by previously determining, based on actual measurement, calculation, and experience, the length of the cracks 13 after the formation of the modified regions 11 and before grooving and the amount of extension of the cracks 13 by the fourth step. The depth of the grooves MZ formed by grooving is such that the cracks 13 are exposed from the bottom surface of the grooves MZ after the fourth step.

[0087] According to this laser processing method, after the fourth step, cracks 13 extending from the modified regions 11 inside the wafer 20 reach the bottom surfaces of the grooves MZ along the lines 15. Therefore, the cracks 13 provide the same effect as above, that is, the wafer 20 can be reliably chipped into functional elements 22a. In this case, the fourth step may be a grinding step. Other examples of the fourth step include a transport step and a cleaning step.

[0088] In the above embodiment and the above modified example, "so that the crack 13 extending from the modified region 11 reaches the bottom surface of the groove MZ along the line 15" also includes the case where the crack 13 does not reach the bottom surface of the groove MZ in part of the line 15, for example, if processing is performed with the aim of dividing the wafer 20 into chips in a later step. [Explanation of symbols]

[0089] 4...imaging unit (internal observation camera), 11...modified region, 13, 13a, 13b, 13c...crack, 15...line, 20...wafer, 22a...functional element, 23...street, HM...protective film, L...laser light, MZ...groove (recess).

Claims

1. A method for dividing a wafer having a substrate, a plurality of functional elements, and a functional element layer into chips along a plurality of lines, comprising: each of the plurality of functional elements is formed in a region partitioned by the plurality of lines when viewed in a thickness direction of the wafer; the functional element layer is formed on a surface of the substrate; irradiating a laser beam from the exposed back surface of the wafer along the line so as to focus the laser beam inside the wafer, thereby forming a modified region along the line and forming a crack extending from the modified region toward the front surface of the substrate; grinding the backside of the substrate after the step of forming the modified region to thin the wafer; a step of irradiating laser light along the line from the front surface side of the wafer to form a groove in the functional element layer after the step of thinning the wafer.

2. The chip manufacturing method described in claim 1, wherein in the step of forming the groove, the groove formed is wider in the width direction than the modified region and is formed so as to cover the crack extending from the modified region toward the surface side of the substrate.

3. The chip manufacturing method according to claim 2 , wherein in the step of forming the groove, the groove is formed so as not to completely divide the functional element layer.

4. A method for manufacturing a chip described in any one of claims 1 to 3, wherein in the step of forming the modified region, the crack extending from the modified region toward the surface side of the substrate is formed so as not to separate the functional element layer.

5. A method for manufacturing a chip described in any one of claims 1 to 3, wherein in the step of forming the modified region, the crack extending from the modified region toward the surface side of the substrate is formed so as to divide the functional element layer.

6. applying a tape to the backside of the substrate after the step of thinning the wafer and before the step of forming the groove; The method for manufacturing a chip according to any one of claims 1 to 5, further comprising the step of expanding the tape attached to the back side of the substrate after the step of forming the groove.

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