Chip manufacturing method

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 chip manufacturing method. [Background Art]

[0002] In a wafer including a plurality of functional elements arranged adjacent to each other via streets, an insulating film (such as a low-k film) and a metal structure (such as metal studs or metal pads) may be formed on the surface layer of the streets. In such cases, if a modified region is formed inside the wafer along a line passing through the streets, and cracks are propagated from the modified region to singulate the wafer into individual chips each including one functional element, chip quality may be degraded, such as film peeling occurring at portions along the streets. Accordingly, when singulating a wafer into chips each including a functional element, grooving processing for removing the surface layer of the streets by irradiating the streets with laser light may be performed (see, for example, Patent Documents 1 and 2). [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 2007-173475 [Patent Document 2] Japanese Unexamined Patent Publication No. 2017-011040 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] With the technology described above, it may be difficult to singulate a wafer into chips each including one functional element, for example, depending on the magnitude of the propagation amount of cracks from the modified region.

[0005] Accordingly, an object of the present invention is to provide a chip manufacturing method that enables reliable singulation of a wafer into chips each including one functional element. [Means for Solving the Problem]

[0006] The present invention provides a method for manufacturing a chip, comprising dividing a wafer having a substrate, a plurality of functional elements, and a functional element layer along a plurality of lines to form a chip, wherein each of the plurality of functional elements is formed in a region partitioned by a plurality of lines when viewed from the thickness direction of the wafer, and the functional element layer is formed on the surface of the substrate, and the method comprises the steps of: irradiating a laser beam from the back surface exposed on the wafer along the lines to focus it into the interior of the wafer, thereby forming a modified region along the lines and forming cracks extending from the modified region toward the surface side of the substrate; thinning the wafer by grinding the back surface of the substrate after the step of forming the modified region; and forming grooves in the functional element layer by irradiating a laser beam from the surface side of the wafer along the lines after the step of thinning the wafer.

[0007] In the chip manufacturing method of the present invention, in the step of forming a groove, the formed groove may be wider than the modified region in the width direction and may be formed to cover cracks that extend 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 grooves, the grooves to be formed may be formed so as not to completely separate the functional element layer.

[0009] In the chip manufacturing method of the present invention, in the step of forming a modified region, cracks extending from the modified region toward the substrate surface may be formed in such a way as not to interrupt the functional element layer.

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

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

[0012] According to the present invention, it is possible to provide a chip manufacturing method that can reliably form chips from wafers, with each functional element being a separate chip. [Brief explanation of the drawing]

[0013] [Figure 1] This is a diagram showing the configuration of a laser processing apparatus that forms a modified region inside a wafer. [Figure 2] This is a diagram showing the configuration of a laser processing machine used for grooving. [Figure 3] This is a plan view of the wafer to be processed. [Figure 4] Figure 3 is a cross-sectional view of a portion of the wafer shown. [Figure 5] Figure 3 is a plan view of a portion of the street shown. [Figure 6] This is a flowchart of the laser processing method according to the first embodiment. [Figure 7] (a) is a cross-sectional view of a wafer illustrating the laser processing method of the first embodiment. (b) is a cross-sectional view of a wafer, continuing from Figure 7(a). [Figure 8] (a) is a cross-sectional view of the wafer, continuing from Figure 7(b). (b) is a cross-sectional view of the wafer, continuing from Figure 8(a). [Figure 9] (a) is a cross-sectional view of the wafer, continuing from Figure 8(b). (b) is a cross-sectional view along line AA in Figure 9(a). [Figure 10] (a) is a cross-sectional view of the wafer, continuing from Figure 9(a). (b) is a cross-sectional view along line BB in Figure 10(a). [Figure 11] This is a cross-sectional view of the wafer, continuing from Figure 10(a). [Figure 12] This is a flowchart of the laser processing method according to the second embodiment. [Figure 13] (a) is a cross-sectional view of a wafer illustrating the laser processing method of the second embodiment. (b) is a cross-sectional view of a wafer, continuing from Figure 13(a). [Figure 14] Fig. 13(a) is a cross-sectional view of a wafer showing a continuation of Fig. 13(b). Fig. 13(b) is a cross-sectional view of a wafer showing a continuation of Fig. 14(a). [Figure 15] It is a flowchart of the laser processing method according to the third embodiment. [Figure 16] Fig. 16(a) is a cross-sectional view of a wafer for explaining the laser processing method according to the third embodiment. Fig. 16(b) is a cross-sectional view of a wafer showing a continuation of Fig. 16(a). [Figure 17] Fig. 17(a) is a cross-sectional view of a wafer showing a continuation of Fig. 16(b). Fig. 17(b) is a cross-sectional view of a wafer showing a continuation of Fig. 17(a). [Figure 18] It is a cross-sectional view of a wafer showing a continuation of Fig. 17(b). [Figure 19] It is a flowchart of the laser processing method according to the fourth embodiment. [Figure 20] Fig. 20(a) is a cross-sectional view of a wafer for explaining the laser processing method according to the fourth embodiment. Fig. 20(b) is a cross-sectional view of a wafer showing a continuation of Fig. 20(a). [Figure 21] It is a cross-sectional view of a wafer showing a continuation of Fig. 20(b). [Figure 22] Fig. 23(a) is a cross-sectional view corresponding to Fig. 9(b) for explaining a laser processing method according to a modification. Fig. 23(b) is a cross-sectional view corresponding to Fig. 10(b) for explaining a laser processing method according to a modification. DETAILED DESCRIPTION OF EMBODIMENTS

[0014] Hereinafter, modes for carrying out the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and overlapping descriptions will be omitted. [Configuration of Laser Processing Apparatus]

[0015] In the laser processing method of the embodiment, a modified region is formed inside a wafer. As an apparatus for forming a modified region inside a wafer, for example, the laser processing apparatus 100 shown in Fig. 1 can be used.

[0016] As shown in Figure 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 moving mechanism 109, and a management unit 150. The laser processing apparatus 100 is a device that forms a modified region 11 on a wafer 20 by irradiating the wafer 20 with laser light L0. In the following description, the three mutually orthogonal directions are referred to as the X direction, Y direction, and Z direction, respectively. For example, the X direction is the first horizontal direction, the Y direction is the second horizontal direction perpendicular to the first horizontal direction, and the Z direction is the vertical direction.

[0017] The support unit 102 supports the wafer 20, for example, by adsorbing the wafer 20. The support unit 102 is movable along the X and Y directions. The support unit 102 is rotatable about a rotation axis along the Z direction. The light source 103 emits laser light L0, for example, by 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, a plurality of reflective mirrors whose position and angle can be adjusted.

[0018] The spatial light modulator 105 is located inside 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 on silicon (LCOS) spatial light modulator (SLM). The spatial light modulator 105 can modulate the laser light L0 by appropriately setting the modulation pattern displayed on its liquid crystal layer. In this embodiment, the laser light L0 that travels downward along the Z direction from the optical axis adjustment unit 104 enters the laser processing head H, is reflected by the mirror M1, and enters the spatial light modulator 105. The spatial light modulator 105 modulates the laser light L0 that has entered in this manner while reflecting it.

[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 incident on the focusing unit 106. The focusing unit 106 focuses the incident laser light L0 onto the wafer 20. The focusing unit 106 is configured such that a focusing lens unit 161 is attached 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] Within the laser processing head H, an imaging optical system (not shown) is positioned between the spatial light modulator 105 and the focusing unit 106. The imaging optical system constitutes a bilateral telecentric optical system in which the reflective surface of the spatial light modulator 105 and the entrance pupil surface of the focusing unit 106 are in an imaging relationship. As a result, the image of the laser light L0 on the reflective surface of the spatial light modulator 105 (the image of the laser light L0 modulated by the spatial light modulator 105) is transferred (imaged) onto the entrance pupil surface of the focusing unit 106. A pair of distance measuring sensors S1 and S2 are mounted on 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 measuring sensor S1 and S2 emits distance measuring light (e.g., laser light) toward the laser light incident surface of the wafer 20 and acquires displacement data of the laser light incident surface by detecting the distance measuring light reflected from the laser light incident surface.

[0021] The optical axis monitor unit 107 is located inside 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 shows, for example, the relationship between the optical axis of the laser light L0 incident on the focusing lens unit 161 and the optical axis of the focusing lens unit 161. The visible light imaging unit 108A emits visible light V0 and acquires an image of the wafer 20 as a visible light V0 image. The visible light imaging unit 108A is located inside the laser processing head H. The infrared imaging unit 108B emits infrared light and acquires an infrared image of the wafer 20 as an infrared light image. The infrared imaging unit 108B is attached to the side wall of the laser processing head H.

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

[0023] The management unit 150 includes a control unit 151, a user interface 152, and a storage unit 153. The control unit 151 controls the operation of each part of the laser processing apparatus 100. The control unit 151 is configured as a computer device including a processor, memory, storage, and communication devices. In the control unit 151, the processor executes software (programs) loaded into memory, etc., and controls the reading and writing of data in memory and storage, as well as communication by 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 the following: a touch panel, keyboard, mouse, microphone, tablet terminal, monitor, etc. The user interface 152 can accept various types of input, such as touch input, keyboard input, mouse operation, and voice input. The user interface 152 can display various types of information on its display screen. The user interface 152 corresponds to an input receiving unit that accepts input and a display unit that can display a settings screen based on the received input. The storage unit 153 is, for example, a hard disk and stores various types of data.

[0025] In the laser processing apparatus 100 configured as described above, when laser light L0 is focused into the wafer 20, the laser light L is absorbed in the portion corresponding to the focal point (at least a part of the focal area) C of the laser light L0, 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 the surrounding unmodified region. Examples of modified regions 11 include melting regions, crack regions, dielectric breakdown regions, refractive index change regions, 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 will be described when a modified region 11 is formed inside the wafer 20 along a line 15 for cutting the wafer 20.

[0027] First, the laser processing apparatus 100 rotates the support unit 102 so that the line 15 set on the wafer 20 is parallel to the X direction. Based on the image acquired by the infrared imaging unit 108B (for example, an image of the functional element layer on the wafer 20), the laser processing apparatus 100 moves the support unit 102 along 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 the image acquired by the visible imaging unit 108A (for example, an image of the laser beam incident surface of the wafer 20), 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 setting). Using that position 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 emits laser light L0 from the light source 103 and moves the support part 102 along the X direction so that the focal point C of the laser light L0 moves relative to the line 15. At this time, the laser processing apparatus 100 operates the drive mechanism 162 of the focusing part 106 so that the focal point C of the laser light L0 is located at a predetermined depth from the laser light incident surface, based on the displacement data of the laser light incident surface acquired by one of the pair of distance measuring sensors S1 and S2, which is located on the front side in the processing direction of the laser light L0.

[0029] As a result, a row of modified regions 11 is formed along line 15 and at a certain depth from the laser light incident surface of wafer 20. When laser light L0 is emitted from light source 103 by pulse oscillation, multiple modified spots 11s are formed so as to be aligned in a row along the X direction. Each modified spot 11s is formed by irradiation with one pulse of laser light L0. A row of modified regions 11 is a collection of multiple modified spots 11s aligned 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 wafer 20 by the repetition frequency of the laser light L0).

[0030] In the laser processing method of this embodiment, laser light is irradiated onto the streets of the wafer 20 so as to remove the surface layer of the streets. As an apparatus for irradiating the streets of the wafer 20 with laser light so as to remove the surface layer of the streets, for example, the laser processing apparatus 1 shown in Figure 2 can be used.

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

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

[0033] The irradiation unit 3 irradiates the street of the wafer 20 supported by the support unit 2 with laser light L. The irradiation unit 3 includes a light source 31, a shaping optical system 32, a dichroic mirror 33, and a focusing unit 34. The light source 31 emits laser light L. The shaping optical system 32 adjusts the laser light L emitted from the light source 31. As an example, the shaping optical system 32 includes at least one of an attenuator to adjust the output of the laser light L, a beam expander to increase the diameter of the laser light L, and a spatial light modulator to modulate the phase of the laser light L. If the shaping optical system 32 includes a spatial light modulator, it may also include an imaging optical system that constitutes a bilateral telecentric optical system in which the modulation plane of the spatial light modulator and the entrance pupil plane of the focusing unit 34 are in an imaging relationship. The dichroic mirror 33 reflects the laser light L emitted from the shaping optical system 32 and directs it into the focusing unit 34. The light-gathering unit 34 focuses the laser light L reflected by the dichroic mirror 33 onto the street of the wafer 20 supported by the support unit 2.

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

[0035] The imaging unit 4 acquires street image data 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 in which the modified region 11 has been formed by the laser processing apparatus 100. The imaging unit 4 captures image data to acquire crack propagation information regarding the propagation of cracks 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 onto the wafer 20 and acquires an image of the wafer 20 using 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 part of the laser processing apparatus 1. The control unit 5 includes a processing unit 51, a storage unit 52, and an input receiving unit 53. The processing unit 51 is a computer device including a processor, memory, storage, and communication devices. In the processing unit 51, the processor executes software (programs) loaded into memory, etc., and controls the reading and writing of data in memory and storage, as well as communication by the communication devices. The storage unit 52 is, for example, a hard disk, and stores various types of data. The input receiving unit 53 is an interface unit that receives input of various types of data from the operator. As an example, the input receiving unit 53 is at least one of a keyboard, mouse, or GUI (Graphical User Interface).

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

[0038] As shown in Figures 3 and 4, the wafer 20 includes a semiconductor substrate 21 and a functional element layer 22. The semiconductor substrate 21 has a front surface 21a and a back surface 21b. The semiconductor substrate 21 is, for example, a silicon substrate. The semiconductor substrate 21 is provided with notches 21c indicating the crystal orientation. The semiconductor substrate 21 may also be provided with orientation flats instead of notches 21c. The functional element layer 22 is formed on the front surface 21a of the semiconductor substrate 21. The functional element layer 22 includes a plurality of functional elements 22a. The plurality of functional elements 22a are arranged two-dimensionally along the front surface 21a of the semiconductor substrate 21. Each functional element 22a is, for example, a light-receiving element such as a photodiode, a light-emitting element such as a laser diode, a circuit element such as a memory, etc. Each functional element 22a may also be configured three-dimensionally by stacking multiple layers.

[0039] Multiple streets 23 are formed on the wafer 20. The multiple streets 23 are regions exposed to the outside between adjacent functional elements 22a. In other words, the multiple functional elements 22a are arranged adjacent to each other via the streets 23. For example, the multiple streets 23 extend in a grid pattern between adjacent functional elements 22a arranged in a matrix. As shown in Figure 5, an insulating film 24 and multiple 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 metal structure 25, 26 is, for example, a metal pad. Metal structures 25 and 26 differ from each other in at least one of the following respects: thickness, area, or material.

[0040] As shown in Figures 3 and 4, the wafer 20 is intended to be cut along each of several lines 15 for each functional element 22a (i.e., chipped for each functional element 22a). Each line 15 passes through each street 23 when viewed from the thickness direction of the wafer 20. For example, each line 15 extends through the center of each street 23 when viewed from the thickness direction of the wafer 20. Each line 15 is a virtual line set on the wafer 20 by the laser processing apparatus 1,100. Each line 15 may also be a line 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 Figure 6.

[0042] First, a wafer 20 is prepared as shown in Figure 7(a) (Step S1: First step). A grinding tape T1 is attached to the surface of the wafer 20 on the functional element 22a side, as shown in Figure 7(b). As shown in Figure 8(a), the back surface 21b side of the semiconductor substrate 21 of the wafer 20 is ground in a grinding apparatus having a grinding wheel BG to thin the wafer 20 to the desired thickness (Step S2: Grinding step). As shown in Figure 8(b), the grinding tape T1 is replaced with a transparent dicing tape 12. The transparent dicing tape 12 is also called an expanded film.

[0043] Next, as shown in Figures 9(a) and 9(b), the laser processing apparatus 100 irradiates the wafer 20 with laser light L0 along each line 15 to form modified regions 11 inside the wafer 20 along each line 15 (Step S3: Second step). Note that the upper part of Figure 9(a) corresponds to the lower part of Figure 9(b).

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

[0045] In step S3 described above, 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. These processing conditions can be appropriately input via the user interface 152 (see Figure 1).

[0046] Next, in the laser processing apparatus 1, with the wafer 20 supported by the support unit 2, the imaging unit 4 acquires image data of each street 23 of the wafer 20. The control unit 5 acquires crack propagation information of the crack 13 based on the imaging results of the imaging unit 4 (step S4: information acquisition step). The crack propagation information includes information about the distance of the tip of the crack 13 to the street 23. The crack propagation information may also include information about whether or not the crack 13 has reached the street 23. The crack propagation information may also include information about the amount of crack propagation of the crack 13. In the crack propagation information, various pieces of information about the propagation of the crack 13 are associated, for example, with each position in the X and Y directions of each street 23. The acquired crack propagation information is stored in the storage unit 52 of the control unit 5.

[0047] Next, as shown in Figures 10(a) and 10(b), the laser processing apparatus 1 performs grooving on the wafer 20 (step S5) (third step). In step S5, the control unit 5 controls the irradiation unit 3 so that laser light L is irradiated onto each street 23 of the wafer 20 supported by the support unit 2, and the control unit 5 controls the support unit 2 so that the laser light L moves relative to each street 23. At this time, based on crack propagation information, the control unit 5 irradiates the street 23 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 (recess) MZ formed by the removal of the surface layer of the street 23 along the line 15.

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

[0049] For example, in step S5 above, in the example shown in Figure 9(b), the depth of the groove MZ is set such that crack 13a is exposed at the bottom surface of the groove MZ, based on the distance from street 23 of crack 13a, which has the furthest tip from street 23 among cracks 13a, 13b, and 13c, which have different amounts of extension from the modified region 11. Then, as shown in Figure 10(b), the surface layer of street 23 is removed so that a groove MZ of the set depth is formed. As a result, all cracks 13a, 13b, and 13c reach the bottom surface of the groove MZ. The processing conditions for grooving are not particularly limited and can be set based on various known findings. These processing conditions can be appropriately input via the input receiving unit 53 (see Figure 2).

[0050] Next, as shown in Figure 11, the transparent dicing tape 12 is expanded in an expanding apparatus (not shown) to extend cracks in the thickness direction of the wafer 20 from the modified regions 11 formed inside the semiconductor substrate 21 along each line 15, thereby chipping the wafer 20 into individual functional elements 22a (step S6).

[0051] As described above, in the laser processing method of this embodiment, a modified region 11 is always formed inside the wafer 20 before grooving. In other words, grooving is always performed after the modified region 11 is formed inside the wafer 20. That is, after the modified region 11 is formed inside the wafer 20 along the line 15 in step S3, grooving is performed in step S5 to remove the surface layer of the street 23. In grooving, cracks 13 extending from the modified region 11 inside the wafer 20 formed in step S3 reach the bottom surface of the groove MZ formed by removing the surface layer of the street 23 along the line 15. Therefore, these cracks 13 make it possible to reliably chip the wafer 20 into individual functional elements 22a.

[0052] In the laser processing method of this embodiment, the wafer 20 is thinned by grinding in step S2. This makes it possible to obtain a wafer 20 of the 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 thickness, it may become difficult to form the modified region 11 inside the wafer 20. In this regard, by performing the grinding step before step S3, even if the prepared wafer 20 is thicker than a certain thickness, the modified region 11 can be formed inside the thinned wafer 20, thereby suppressing the difficulty in forming the modified region 11 inside the wafer 20.

[0054] The laser processing method of this embodiment includes step S4 above, in which crack propagation information is acquired before performing grooving. In grooving, based on the acquired crack propagation information, laser light L is irradiated 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 MZ along the line 15. In this case, crack propagation information can be acquired and used to perform grooving.

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

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

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

[0058] First, a wafer 20 is prepared (Step S21: First step). A grinding tape T1 is attached to the surface of the wafer 20 on the functional element 22a side. As shown in Figure 13(a), in the laser processing apparatus 100, laser light L0 is irradiated onto the wafer 20 along each line 15 to form a modified region 11 inside the wafer 20 along each line 15 (Step S22: Second step).

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

[0060] Next, as shown in Figure 13(b), the back surface 21b of the semiconductor substrate 21 of the wafer 20 is ground in a grinding apparatus equipped with a grinding wheel BG to thin the wafer 20 to the desired thickness (Step S23: Grinding process). As shown in Figure 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 unit 2, the imaging unit 4 acquires image data of each street 23 of the wafer 20. The control unit 5 acquires crack propagation information of the cracks 13 based on the imaging results of the imaging unit 4 (step S24: information acquisition step). As shown in Figure 14(b), the laser processing apparatus 1 performs grooving on the wafer 20 (step S25) (third step). In step S25, based on the crack propagation information, the surface layer of the street 23 is removed, and 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, in the expanding apparatus, the transparent dicing tape 12 is expanded to extend cracks in the thickness direction of the wafer 20 from the modified regions 11 formed inside the semiconductor substrate 21 along each line 15, thereby chipping the wafer 20 into individual functional elements 22a (step S26).

[0063] As described above, the laser processing method of this embodiment also provides the same advantages as the above embodiment, such as being able to reliably chip the wafer 20 into individual functional elements 22a. In the laser processing method of this embodiment, step S23, which is a grinding process, is performed after step S22, which forms the modified region 11 inside the wafer 20, and before step S25, which is a grooving process. For example, when transporting a wafer 20 in which a modified region 11 has been formed inside, if the wafer is thin, there is a possibility that unintended cracks may occur in the wafer 20. In this regard, by performing the grinding process after step S22, the wafer 20 in which the modified region 11 has been formed inside can be transported before it is thinned, and it is possible to suppress the likelihood of unintended cracks occurring in the wafer 20.

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

[0065] First, a wafer 20 is prepared (Step S31: First step). As shown in Figure 16(a), in the laser processing apparatus 100, a laser beam L0 is irradiated onto the wafer 20 along each line 15 to form a modified region 11 inside the wafer 20 along each line 15 (Step S32: Second step). In Step S32, the focal point of the laser beam L0 is aligned with the inside of the semiconductor substrate 21 from the back surface 21b side, and the laser beam L0 is irradiated onto the wafer 20. In Step S32, the modified region 11 is formed inside the wafer 20 along the line 15 so that cracks 13 extending from the modified region 11 do not reach the street 23. In Step S32, for example, if the surface of the wafer 20 on the functional element 22a side is uneven, tape material may be attached to that surface, or the wafer 20 may be adsorbed by the support part 102 that supports the wafer 20 according to the unevenness.

[0066] Next, in the laser processing apparatus 1, with the wafer 20 supported by the support unit 2, the imaging unit 4 acquires image data of each street 23 of the wafer 20. The control unit 5 acquires crack propagation information of the cracks 13 based on the imaging results of the imaging unit 4 (step S33: information acquisition step). Subsequently, as shown in Figure 16(b), the laser processing apparatus 1 performs grooving on the wafer 20 (step S34) (third step). In step S34, based on the crack propagation information, the surface layer of the street 23 is removed, and 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.

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

[0068] Next, in the expanding apparatus, the transparent dicing tape 12 is expanded to extend cracks in the thickness direction of the wafer 20 from the modified regions 11 formed inside the semiconductor substrate 21 along each line 15, thereby chipping the wafer 20 into individual functional elements 22a (step S36).

[0069] As described above, the laser processing method of this embodiment also provides the same advantages as the above embodiment, such as being able to reliably chip the wafer 20 into individual functional elements 22a. In the laser processing method of this embodiment, step S23, which is a grinding process, is performed after step S34, which is related to grooving. For example, when transporting the wafer 20 after grooving, if its thickness is thin, there is a possibility that unintended cracks may occur in the wafer 20. In this regard, by performing the grinding process after step S34, the wafer 20 can be transported before it is thinned after grooving, and it is possible to suppress the likelihood of unintended cracks occurring in the wafer 20.

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

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

[0072] As shown in Figure 20(b), in the laser processing apparatus 100, a modified region 11 is formed inside the wafer 20 along each line 15 by irradiating the wafer 20 with laser light L0 along each line 15 (step S43: second step). In step S43, 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 side 21b side into the interior of the semiconductor substrate 21 and irradiated onto the wafer 20 with laser light L0. In step S43, the modified region 11 is formed inside the wafer 20 along the line 15 so that cracks 13 extending from the modified region 11 do not reach the street 23.

[0073] Next, in the laser processing apparatus 1, with the wafer 20 supported by the support unit 2, the imaging unit 4 acquires image data of each street 23 of the wafer 20. The control unit 5 acquires crack propagation information of the cracks 13 based on the imaging results of the imaging unit 4 (step S44: information acquisition step). As shown in Figure 21, the laser processing apparatus 1 performs grooving on the wafer 20 (step S45) (third step). In step S45, based on the crack propagation information, the surface layer of the street 23 is removed, and 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.

[0074] Next, the protective film HM is removed. The timing of removing the protective film HM can be any timing after step S45 described above. A grinding tape T1 is attached to the surface of the wafer 20 on the functional element 22a side. The back surface 21b side of the semiconductor substrate 21 of the wafer 20 is ground in a grinding apparatus having a grinding wheel BG to thin the wafer 20 to the desired thickness (step S46: grinding process). The grinding tape T1 is replaced with a transparent dicing tape 12.

[0075] Next, in the expanding apparatus, the transparent dicing tape 12 is expanded to extend cracks in the thickness direction of the wafer 20 from the modified regions 11 formed inside the semiconductor substrate 21 along each line 15, thereby chipping the wafer 20 into individual functional elements 22a (step S47).

[0076] As described above, the laser processing method of this embodiment also provides the same advantages as the above embodiment, such as being able to reliably chip the wafer 20 into functional elements 22a. In the laser processing method of this embodiment, a protective film HM is applied to at least the streets 23 on the wafer 20 before step S43 in which the modified region 11 is formed inside the wafer 20. In this case, the reflectivity of the streets 23 can be kept constant by the protective film HM, so that crack propagation information can be acquired with high accuracy in step S44. Note that the formation of the modified region 11 by step S43 is not affected by the presence of the protective film HM. [Differentiation]

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

[0078] In the above embodiment, the crack propagation information may include information as described above 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 grooving, based on crack propagation information including whether or not the crack 13 has reached street 23, laser light L may be irradiated only in the areas of street 23 where the crack 13 has not reached line 15, so that the surface layer of street 23 is removed and the crack 13 reaches line 15 at the bottom surface of the groove MZ. This ensures that grooving is performed only in the areas of street 23 where the crack 13 has not reached line 15, allowing for efficient grooving. In this case, if a protective film HM is applied as in the fourth embodiment described above, the crack 13 will be exposed to street 23 through the protective film HM after the modified region 11 has been formed inside the wafer 20. The presence of the protective film HM makes it easier to determine whether or not the crack 13 has reached street 23 because the reflectivity remains constant.

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

[0081] Furthermore, "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 severed street 23 is within a predetermined width (a predetermined width in the 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 "Either 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 severed street 23 exceeds a predetermined width." The predetermined width is, for example, about 10 μm.

[0082] The above embodiment includes an information acquisition step for acquiring crack propagation information in the laser processing apparatus 1, but the crack propagation information may be acquired in the laser processing apparatus 100, or by other devices. The above embodiment does not have to include an information acquisition step, in which case the previously acquired crack propagation information may be stored in the storage unit 52. For example, the crack propagation information may be information that has been previously confirmed on a test wafer. In the above embodiment, grooves MZ were formed by griving, but holes or depressions may be formed instead of grooves MZ; the point is to form a recess.

[0083] In the above embodiment, for example, since there is a certain correlation between the height and light intensity of the street 23 and the propagation of the crack 13, the crack propagation information may include information regarding the height and light intensity of the street 23. For example, the laser processing apparatus 1 may be equipped with a distance measuring unit in place of or in addition to the imaging unit 4, and the distance measuring unit may acquire information regarding the height of the street 23. As the distance measuring unit, for example, a laser displacement meter such as a triangulation type, spectral interference type, multicolor confocal type, or monocolor confocal type can be used.

[0084] In the above embodiment, the imaging unit 4 may include a camera that acquires image data of the streets of the wafer 20 using visible light. In the above embodiment, information can be created to control the irradiation conditions of the laser beam L in each region of the street 23 (laser ON / OFF control, laser power) using an image of at least the surface layer of the street 23 after cutting, or a see-through image using infrared light, and the grooving process can be controlled based on that information. In the above embodiment, the surface layer of the street 23 may be removed by scanning the street 23 with the laser beam L multiple times. 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 beam L0 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 beam L moves relatively along each street 23.

[0085] In the above embodiment, grooving (third step) is performed so that the crack 13 extending from the modified region 11 reaches the bottom surface of the groove MZ along the line 15, but the embodiment is not limited to this. For example, the grooving may be performed so that the crack 13 does not reach the bottom surface of the groove MZ along the line 15 immediately afterward, but after the subsequent fourth step, the crack 13 reaches the bottom surface of the groove MZ along the line 15.

[0086] In other words, a laser processing method according to one embodiment includes: a first step of preparing a wafer 20 containing a plurality of functional elements 22a arranged adjacent to each other via a street 23; a second step of forming a modified region 11 inside the wafer 20 along a line 15 passing through the street 23 after the first step; a third step of irradiating the street 23 with laser light L after the second step so that the surface layer of the street 23 is removed; and a fourth step of processing the wafer 20 after the third step. In the third step, the laser light L may be irradiated onto the street 23 so that cracks 13 extending from the modified region 11 reach the bottom surface of the groove MZ formed by the removal of the surface layer of the street 23 along the line 15 after the fourth step. Such processing can be achieved by knowing in advance, based on actual measurements, calculations, and experience, the length of the cracks 13 after the formation of the modified region 11 and before grooving, and the amount of extension of the cracks 13 by the fourth step. The depth of the groove MZ formed by the grooving process is the depth to which the crack 13 becomes exposed from the bottom surface of the groove MZ after the fourth step.

[0087] According to this laser processing method, after the fourth step, cracks 13 extending from the modified region 11 inside the wafer 20 reach the bottom surface of the groove MZ along the line 15. Therefore, the same effect as described above is achieved, in which the wafer 20 can be reliably chipped into individual functional elements 22a by the cracks 13. In this case, the fourth step may be a grinding step. Other possible fourth steps include, for example, a transport step and a cleaning step.

[0088] In the above embodiment and 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 cases where the crack 13 does not reach the bottom surface of the groove MZ in a part of the line 15, for example, if processing is performed in a later step for the purpose of chipping the wafer 20. [Explanation of Symbols]

[0089] 4...Imaging unit (internal observation camera), 11...Modified area, 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, multiple functional elements, and a functional element layer along multiple lines to form chips, Each of the multiple functional elements is formed in each region demarcated by the multiple lines when viewed from the thickness direction of the wafer. The functional element layer is formed on the surface of the substrate, The steps include: irradiating the wafer with laser light from the exposed back surface along the line so as to focus the light into the wafer, thereby forming a modified region along the line and forming a crack extending from the modified region toward the surface side of the substrate; After the step of forming the modified region, the back surface of the substrate is ground to thin the wafer, The step of thinning the wafer, followed by the step of irradiating the wafer with laser light from the surface side along the line to form grooves in the functional element layer, A method for manufacturing a chip, wherein in the step of forming the groove, the crack extending from the modified region reaches the bottom surface of the groove along the line.

2. The method for manufacturing a chip according to claim 1, wherein in the step of forming the groove, the formed groove is wider in the width direction than the modified region and is formed to cover the crack that extends from the modified region toward the surface side of the substrate.

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

4. The method for manufacturing a chip according to any one of claims 1 to 3, wherein in the step of forming the modified region, the cracks extending from the modified region toward the surface side of the substrate are formed in such a way as not to interrupt the functional element layer.

5. The method for manufacturing a chip according to 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 to divide the functional element layer.

6. After the step of thinning the wafer and before the step of forming the groove, the step of attaching the tape to the back side of the substrate, A 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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