Wafer processing method and laser processing device

Abstract

To provide a processing method for wafer and a laser processing device that reduce remaining of glue at an outer peripheral part of a reverse side of a chip when an adhesive tape is expanded.SOLUTION: A processing method for wafer has: a sticking step for sticking a wafer 100 on an adhesive tape 111 having an adhesive layer 116 decreasing in adhesive strength with ultraviolet rays; an adhesive strength decreasing step for irradiating the adhesive layer 116 with a laser beam 78 having a wavelength corresponding to that of ultraviolet rays along a predetermined division line 102 so as to decrease the adhesive strength of the adhesive layer 116 equivalent to the predetermined division line 102; a modified layer forming step for irradiating the wafer 100 along the predetermined division line 102 with a laser beam having a wavelength of penetration while gathered into the wafer 100 so as to form a modified layer inside the wafer 100; and a tape expanding step for expanding the adhesive tape 111 to split the wafer 100 at the modified layer as a starting point.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to a wafer processing method and a laser processing apparatus for dividing a wafer by expanding a tape. [Background technology]

[0002] A process is known in which a modified layer is formed inside a wafer such as a semiconductor substrate, and then an adhesive tape to which the wafer is attached is expanded to divide the wafer at the modified layer (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2002-192370 A [Patent Document 2] JP 2007-123658 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the process of expanding the adhesive tape attached to the back surface of the wafer and dividing it starting from a modified layer formed inside the wafer, there was a problem in that the area corresponding to the intended division line was prone to stretching when the adhesive tape was expanded, causing the adhesive layer in the area corresponding to the intended division line to rub against the outer periphery of the back surface of the chip, reducing the adhesive strength of the adhesive tape and leaving glue residue on the outer periphery of the back surface of the chip when it was picked up.

[0005] The present invention has been made in consideration of such problems, and its object is to provide a wafer processing method and laser processing apparatus that reduce the occurrence of glue residue on the outer periphery of the back surface of a chip when the adhesive tape is expanded. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the wafer processing method of the present invention is a wafer processing method for dividing a wafer along a plurality of planned division lines formed in a first direction and a second direction intersecting the first direction, the method comprising the steps of: attaching the wafer to an adhesive tape that is larger than the wafer and has an adhesive layer whose adhesive strength is reduced by ultraviolet light; From the surface of the wafer opposite to the surface to which the adhesive tape is attached, The method is characterized by having an adhesive strength reducing step of irradiating the adhesive layer with a laser beam of a wavelength corresponding to ultraviolet light along the planned division line to reduce the adhesive strength of the adhesive layer corresponding to the planned division line, a modified layer forming step of irradiating a laser beam of a wavelength that is transparent to the wafer along the planned division line while focusing the laser beam inside the wafer, to form a modified layer inside the wafer, and a tape expanding step of expanding the adhesive tape to divide the wafer starting from the modified layer.

[0007] The wafer may be semi-transparent or transparent, and the adhesion reducing step may involve irradiating the wafer with a laser beam having a wavelength corresponding to ultraviolet light through the wafer. In the adhesive strength reducing step, the adhesive strength of the adhesive layer may be reduced in a width wider than the modified layer formed in the modified layer forming step.

[0008] In order to solve the above-mentioned problems and achieve the object, the laser processing apparatus of the present invention is a laser processing apparatus for processing a wafer, the laser processing apparatus comprising a holding table for holding a wafer, a laser beam application unit for irradiating a laser beam onto the wafer held on the holding table, and a processing feed unit for relatively moving the holding table and the laser beam application unit in a processing feed direction, the laser beam application unit comprising a first laser beam oscillation unit for oscillating a laser beam having a wavelength that is transparent to the wafer, a second laser beam oscillation unit for oscillating a laser beam having a wavelength corresponding to ultraviolet light onto an adhesive layer of an adhesive tape to which the wafer is attached, a first condenser for collecting the laser beam oscillated from the first laser beam oscillation unit and irradiating the wafer with the laser beam, and a second condenser for collecting the laser beam oscillated from the second laser beam oscillation unit and irradiating the wafer with the laser beam. From the surface of the wafer opposite to the surface to which the adhesive tape is attachedand a second collector which irradiates a laser beam onto the adhesive layer corresponding to the planned dividing line of the wafer, thereby reducing the adhesive strength, and the first laser beam emitting unit focuses the laser beam inside the wafer corresponding to the planned dividing line, thereby forming a modified layer. The second laser beam oscillating unit may reduce the adhesive strength of the adhesive layer in a width wider than the modified layer formed by the first laser beam oscillating unit. Effect of the Invention

[0009] The present invention can reduce the occurrence of adhesive residue on the outer periphery of the back surface of a chip when the adhesive tape is expanded. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing an example of the configuration of a laser processing device according to an embodiment. [Diagram 2] FIG. 2 is a perspective view showing an example of a wafer to be processed by the laser processing apparatus according to the embodiment. [Diagram 3] FIG. 3 is a cross-sectional view showing the adhesive tape of FIG. [Figure 4] FIG. 4 is a diagram illustrating a schematic view of a main part of the laser processing apparatus of FIG. [Diagram 5] FIG. 5 is a flowchart showing an example of a processing procedure of the wafer processing method according to the embodiment. [Figure 6] FIG. 6 is a cross-sectional view illustrating the adhesive strength reducing step of FIG. [Figure 7] FIG. 7 is a cross-sectional view illustrating the modified layer forming step of FIG. [Figure 8] FIG. 8 is a perspective view showing a tape expanding apparatus for carrying out the tape expanding step of FIG. [Figure 9] FIG. 9 is a cross-sectional view illustrating the tape expanding step of FIG. [Figure 10] FIG. 10 is a cross-sectional view illustrating the tape expanding step of FIG. [Figure 11] FIG. 11 is a cross-sectional view illustrating the ultraviolet ray irradiation step of FIG. [Figure 12]FIG. 12 is a cross-sectional view illustrating the pick-up step of FIG. [Figure 13] FIG. 13 is a diagram for explaining the function and effect of the laser processing apparatus and the wafer processing method according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The form (embodiment) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiment. Furthermore, the components described below include those that a person skilled in the art can easily imagine and those that are substantially the same. Furthermore, the configurations described below can be appropriately combined. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the gist of the present invention.

[0012] [Embodiment] A laser processing apparatus 1 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a configuration example of the laser processing apparatus 1 according to the embodiment. FIG. 2 is a perspective view showing an example of a wafer 100 which is an object to be processed by the laser processing apparatus 1 according to the embodiment. FIG. 3 is a cross-sectional view showing an adhesive tape 111 of FIG. 2. FIG. 4 is a diagram showing a schematic view of a main part of the laser processing apparatus 1 of FIG. 1. As shown in FIG. 1, the laser processing apparatus 1 according to the embodiment includes a holding table 10, a laser beam application unit 20, an imaging unit 30, a processing feed unit 41, an indexing feed unit 42, and a control unit 50.

[0013] In this embodiment, the wafer 100, which is the processing target to be processed by the laser processing apparatus 1, is made of, for example, silicon, sapphire, silicon carbide (SiC), gallium arsenide, lithium tantalate (LiTaO 3, LT), a disk-shaped semiconductor substrate wafer (semiconductor wafer) using glass or the like as a base material, or an optical device substrate wafer (optical device wafer). As shown in FIG. 2, the wafer 100 has a flat surface 101, and chip regions 103 are formed in regions partitioned by a plurality of planned division lines 102 formed along a first direction and a second direction intersecting the first direction. In the present embodiment, the wafer 100 further has a plurality of planned division lines 102 formed in a lattice shape with the first direction and the second direction perpendicular to each other, but the present invention is not limited to this. In the present embodiment, the wafer 100 has a device formed in each chip region 103, but the present invention is not limited to this, and the device may not be formed.

[0014] In this embodiment, as shown in FIG. 2, the wafer 100 has a functional film 105 formed on the back surface 104 behind the front surface 101, but the present invention is not limited to this, and the functional film 105 may not be formed. The functional film 105 is a metal film or a dielectric film provided to control, for example, the reflectance or transmittance of light depending on the function of the semiconductor device (chip 109 (see FIG. 10)) to be produced. The metal film of the functional film 105 is, for example, a film of a metal such as Al (aluminum), Au (gold), or Cr (chromium). The dielectric film of the functional film 105 is, for example, a film of TiO 2 , Ta 2 O 5 , Al 2 O 3 , SiO 2 , MgF 2 The functional film 105 is a dielectric film such as a dielectric film, etc. The functional film 105 is not shown in FIG.

[0015] As shown by the arrow in Fig. 2, the wafer 100 has an adhesive tape 111 attached to the back surface 104 via a functional film 105, and an annular frame 112 attached to the outer edge of the adhesive tape 111. As shown in Fig. 3, the adhesive tape 111 has a base layer 115 made of synthetic resin that is larger than the wafer 100 in the surface direction of the wafer 100, and an adhesive layer 116 made of synthetic resin that is laminated on the entire surface of one surface of the base layer 115 and has adhesiveness. The adhesive layer 116 side of the adhesive tape 111 is attached to the back surface 104 of the wafer 100 via the functional film 105. The adhesive strength of the adhesive layer 116 of the adhesive tape 111 is reduced by irradiation with ultraviolet light 148 (see Fig. 11) or a laser beam 78 (see Fig. 4) having a wavelength corresponding to ultraviolet light (for example, 355 nm in this embodiment).

[0016] The base material of the wafer 100 is as follows: silicon is black and transmits almost no ultraviolet light, sapphire is whitish translucent or transparent and transmits about 80% of ultraviolet light, silicon carbide is green to black and its transparency and transmittance to ultraviolet light increases depending on the manufacturing conditions and purity, gallium arsenide is gray to black and transmits almost no ultraviolet light, LT is yellowish translucent or transparent and transmits about 70% of ultraviolet light, and glass has a different color depending on the composition but is translucent or transparent and transmits about 70% of ultraviolet light. Therefore, the laser processing apparatus 1 according to the embodiment can irradiate the adhesive layer 116 of the adhesive tape 111 with ultraviolet light 148 or a laser beam 78 having a wavelength corresponding to ultraviolet light through the wafer 100 when the base material of the wafer 100 is translucent or transparent and has a predetermined transmittance to ultraviolet light (for example, 50%) or more, specifically, when the base material is sapphire, a part of silicon carbide, LT, or a part of glass.

[0017] The hardness of the base material of the wafer 100 is as follows: silicon is equivalent to a modified Mohs hardness of 7, sapphire is equivalent to a modified Mohs hardness of 12, silicon carbide is equivalent to a modified Mohs hardness of 13, gallium arsenide is equivalent to a modified Mohs hardness of 4.5, LT is equivalent to a modified Mohs hardness of about 5.5 to 6, and glass varies depending on the composition and is equivalent to a modified Mohs hardness of about 5 to 8. In the present invention, the hardness is determined by any one of Brinell hardness, Vickers hardness, Knoop hardness, Rockwell hardness, superficial hardness, Mayer hardness, durometer hardness, Barcol hardness, monotron hardness, Martens hardness, Shore hardness, Mohs hardness, and modified Mohs hardness. In this embodiment, when the wafer 100 is made of a base material having a harder property than silicon, specifically, when sapphire, silicon carbide, or hard glass having a harder property than silicon (glass having a modified Mohs hardness of 7 or more), an adhesive tape 111 is used in which an adhesive layer 116 having a stronger adhesive force than an adhesive tape with a DAF (Die Attach Film) that is generally used for wafers made of silicon is formed in order to reduce peeling of the wafer 100 (chip 109) due to warping and to increase the division rate when dividing the wafer 100 by expanding the adhesive tape 111.

[0018] The holding table 10 includes a disk-shaped frame body with a recess formed therein, and a disk-shaped suction part fitted into the recess. The suction part of the holding table 10 is formed of a porous ceramic or the like with a large number of porous holes, and is connected to a vacuum suction source (not shown) via a vacuum suction path (not shown). The upper surface of the suction part of the holding table 10 is a holding surface 11 on which the wafer 100 is placed and which suction-holds the placed wafer 100. In this embodiment, the holding surface 11 is a holding surface on which the wafer 100 is placed with the front surface 101 facing upward, and suction-holds the placed wafer 100 from the back surface 104 side via an adhesive tape 111. The holding surface 11 and the upper surface of the frame body of the holding table 10 are arranged on the same plane, and are formed parallel to the XY plane, which is a horizontal plane.

[0019] As shown in FIG. 1, the laser beam application unit 20 is fixed to the base 2 of the laser processing device 1, and includes a first laser beam application unit 21 and a second laser beam application unit 22. As shown in FIG. 4, the laser beam application unit 20 performs laser processing by irradiating the wafer 100 held on the holding table 10 with a laser beam 68 having a wavelength (for example, 1064 nm, 532 nm, etc. in this embodiment) that is transparent to the wafer 100 by the first laser beam application unit 21, and irradiating the wafer 100 with a laser beam 78 having a wavelength corresponding to ultraviolet light that reduces the adhesive force of the adhesive layer 116 by the second laser beam application unit 22. As shown in FIG. 1, in this embodiment, the irradiation port of the laser beam 68 of the first laser beam application unit 21 and the irradiation port of the laser beam 78 of the second laser beam application unit 22 are arranged adjacent to each other along the processing feed direction (X-axis direction in FIG. 1).

[0020] As shown in Fig. 4, the first laser beam application unit 21 has a first laser beam oscillation unit 61 and a first condenser 62. The first laser beam oscillation unit 61 oscillates a laser beam 68 having a wavelength that is transparent to the wafer 100. In this embodiment, the first laser beam oscillation unit 61 oscillates a pulsed laser beam 68, but the present invention is not limited to this. The first condenser 62 is disposed on the optical path of the laser beam 68 oscillated by the first laser beam oscillation unit 61, condenses the laser beam 68 to form a condensed region 69, and irradiates the condensed laser beam 68 toward the wafer 100 held on the holding table 10. In this embodiment, the first collector 62 has a reflecting mirror 63 that reflects the laser beam 68 emitted by the first laser beam oscillation unit 61 and guides it to a focusing lens 64, and a focusing lens 64 that focuses the laser beam 68 guided from the reflecting mirror 63 to an arbitrary height to form a focusing area 69 and irradiates the focused laser beam 68 toward the wafer 100 held on the holding table 10, but the present invention is not limited to this and may have other optical systems.

[0021] The first laser beam application unit 21 focuses a laser beam 68 oscillated by the first laser beam oscillation unit 61 by a first collector 62 inside the wafer 100 corresponding to the planned dividing lines 102 to form a focusing region 69, and irradiates the laser beam 68 toward the wafer 100 held on the holding table 10 to form a modified layer 300 in the focusing region 69 inside the wafer 100. In this embodiment, the first laser beam application unit 21 forms a focusing region 69 having a width equal to or narrower than the planned dividing lines 102 inside the wafer 100 to form a modified layer 300 having a width equal to or narrower than the planned dividing lines 102.

[0022] As shown in FIG. 4, the second laser beam application unit 22 has a second laser beam oscillation unit 71 and a second condenser 72. The second laser beam oscillation unit 71 oscillates a laser beam 78 having a wavelength corresponding to ultraviolet light that reduces the adhesive strength of the adhesive layer 116. In this embodiment, the second laser beam oscillation unit 71 oscillates a pulsed laser beam 78, but the present invention is not limited to this. The second condenser 72 is disposed on the optical path of the laser beam 78 oscillated by the second laser beam oscillation unit 71, condenses the laser beam 78 to form a condensed region 79, and irradiates the condensed laser beam 78 toward the wafer 100 held on the holding table 10. In this embodiment, the second collector 72 has a reflecting mirror 73 that reflects the laser beam 78 oscillated by the second laser beam oscillation unit 71 and guides it to a focusing lens 74, and a focusing lens 74 that focuses the laser beam 78 guided from the reflecting mirror 73 at an arbitrary height to form a focusing area 79 and irradiates the focused laser beam 78 toward the wafer 100 held on the holding table 10, but the present invention is not limited to this and may have other optical systems.

[0023] The second laser beam application unit 22 focuses the laser beam 78 oscillated by the second laser beam oscillation unit 71 on the adhesive layer 116 of the adhesive tape 111 corresponding to the planned division line 102 by the second condenser 72 to form a focused region 79, and irradiates the laser beam 78 toward the wafer 100 held on the holding table 10, and forms a reduced adhesive force region 200 in which the adhesive force of the adhesive layer 116 is reduced in the focused region 79 of the adhesive layer 116. In this embodiment, the second laser beam application unit 22 may form a focused region 79 in the adhesive layer 116 of the adhesive tape 111 that is wider than the focused region 69 formed by the first laser beam application unit 21 at least inside the wafer 100, to form a reduced adhesive force region 200 that is wider than at least the modified layer 300.

[0024] The modified layer 300 is formed narrower than the dividing line 102 so as to fit within the dividing line 102. The modified layer 300 is preferable because the width of the dividing line 102 can be designed to be narrower by narrowing the width, and the amount of chip 109 that can be taken is increased. On the other hand, the adhesive strength reduction region 200 is formed at least wider than the modified layer 300, so that the adhesive strength of the region where the outer periphery of the chip 109 rubs when the adhesive tape 111 is expanded can be reduced over a wide range, and adhesive residue on the outer periphery of the back surface 104 of the chip 109 can be prevented. The adhesive strength reduction region 200 may be formed to be equal to the dividing line 102 or wider than the dividing line 102, straddling the dividing line 102.

[0025] The imaging unit 30 is fixed to the laser beam application unit 20. In this embodiment, as shown in Fig. 1, the imaging unit 30 is disposed adjacent to an application port of the laser beam 68 of the first laser beam application unit 21 and an application port of the laser beam 78 of the second laser beam application unit 22 along the processing feed direction (the X-axis direction in Fig. 1).

[0026] The imaging unit 30 includes an imaging element for imaging a surface 101 and a planned dividing line 102 of the wafer 100 before laser processing held on the holding table 10. The imaging element is, for example, a CCD (Charge-Coupled Device) imaging element or a CMOS (Complementary MOS) imaging element. The imaging unit 30 images the surface 101 and the like of the wafer 100 before laser processing held on the holding table 10 to obtain an image for performing alignment between the wafer 100 and the irradiation position of the laser beam 68 by the first laser beam application unit 21 of the laser beam application unit 20 and the irradiation position of the laser beam 78 by the second laser beam application unit 22, and outputs the obtained image to the control unit 50.

[0027] The processing feed unit 41 moves the holding table 10 in the processing feed direction, thereby moving the holding table 10 and the laser beam application unit 20 relatively in the processing feed direction. Here, the processing feed direction is one horizontal direction, the X-axis direction shown in Fig. 1, in this embodiment. The indexing feed unit 42 moves the holding table 10 in the indexing feed direction, thereby moving the holding table 10 and the laser beam application unit 20 relatively in the indexing feed direction. Here, the processing feed direction is another horizontal direction, the Y-axis direction shown in Fig. 1, which is perpendicular to the X-axis direction, in this embodiment.

[0028] The control unit 50 controls the operation of various components of the laser processing apparatus 1 to cause the laser processing apparatus 1 to perform laser processing of the wafer 100. The control unit 50 controls the first laser beam oscillation unit 61 to control optical properties such as the phase, polarization plane, amplitude, intensity, and propagation direction of the laser beam 68. The control unit 50 controls the first condenser 62 to control the height (position in the thickness direction of the wafer 100) and width of the focusing area 69 where the laser beam 68 is focused. The control unit 50 controls the second laser beam oscillation unit 71 to control optical properties such as the phase, polarization plane, amplitude, intensity, and propagation direction of the laser beam 78. The control unit 50 controls the second condenser 72 to control the height (position in the thickness direction of the wafer 100) and width of the focusing area 79 where the laser beam 78 is focused.

[0029] The control unit 50 acquires an image for performing alignment captured by the imaging unit 30, and performs alignment based on this image. The control unit 50 controls the indexing feed unit 42 according to the result of performing alignment, and aligns the positions of the irradiation position of the laser beam 68 by the first laser beam application unit 21 and the irradiation position of the laser beam 78 by the second laser beam application unit 22 in the indexing feed direction (Y-axis direction) to positions corresponding to the planned dividing line 102 of the wafer 100 held on the holding table 10. The control unit 50 controls the processing feed unit 41 according to the result of performing alignment, and moves the position of the irradiation position of the laser beam 68 of the first laser beam application unit 21 or the irradiation position of the laser beam 78 of the second laser beam application unit 22 in the processing feed direction (X-axis direction) along the planned dividing line 102 relative to the wafer 100 held on the holding table 10.

[0030] In this embodiment, the control unit 50 includes a computer system. The computer system included in the control unit 50 includes an arithmetic processing device having a microprocessor such as a CPU (Central Processing Unit), a storage device having a memory such as a ROM (Read Only Memory) or a RAM (Random Access Memory), and an input / output interface device. The arithmetic processing device of the control unit 50 performs arithmetic processing according to a computer program stored in the storage device of the control unit 50, and outputs a control signal for controlling the laser processing device 1 to each component of the laser processing device 1 via the input / output interface device of the control unit 50.

[0031] Next, this specification will explain a wafer processing method according to an embodiment based on the drawings. The wafer processing method according to the embodiment is a method for dividing a wafer 100 along a planned dividing line 102, and is carried out using a laser processing apparatus 1 according to the embodiment. FIG. 5 is a flow chart showing an example of a processing procedure of the wafer processing method according to the embodiment. As shown in FIG. 5, the wafer processing method according to the embodiment includes a bonding step 1001, an adhesive strength reducing step 1002, a modified layer forming step 1003, a tape expanding step 1004, an ultraviolet ray irradiation step 1005, and a pick-up step 1006.

[0032] 2, the bonding step 1001 is a step of bonding the back surface 104 of the wafer 100 to the adhesive layer 116 side of the adhesive tape 111. In the bonding step 1001, a ring-shaped frame 112 is further bonded to the outer edge portion of the adhesive layer 116 side of the adhesive tape 111 bonded to the back surface 104 of the wafer 100.

[0033] The adhesive strength reducing step 1002 is carried out after the bonding step 1001, and is a step in which the second laser beam application unit 22 of the laser processing apparatus 1 irradiates the adhesive layer 116 with a laser beam 78 having a wavelength corresponding to ultraviolet light along the planned division line 102, thereby reducing the adhesive strength of the adhesive layer 116 corresponding to the planned division line 102.

[0034] Fig. 6 is a cross-sectional view for explaining the adhesive force reducing step 1002 in Fig. 5. Specifically, in the adhesive force reducing step 1002, the wafer 100 having the adhesive tape 111 attached to the back surface 104 in the attaching step 1001 is placed on the holding surface 11 of the holding table 10 with the front surface 101 facing upward, and is suction-held on the holding surface 11 from the back surface 104 side via the adhesive tape 111, as shown in Fig. 6. In the adhesive force reducing step 1002, the control unit 50 then executes an alignment process and controls the indexing feed unit 42 to align the position of the irradiation position of the laser beam 78 of the second laser beam application unit 22 in the indexing feed direction (Y-axis direction) to a position corresponding to the planned dividing line 102 of the wafer 100 held on the holding table 10.

[0035] In the adhesive strength reduction step 1002, the control unit 50 then controls the second laser beam oscillation unit 71 to adjust the optical properties of the laser beam 78, and controls the second collector 72 as shown in FIG. 6 to adjust the height of the focusing area 79 for focusing the laser beam 78 to match the adhesive layer 116 of the adhesive tape 111 attached to the wafer 100 held on the holding table 10, and adjusts the width of the focusing area 79 to be at least wider than the modified layer 300 formed in the modified layer formation step 1003 which is performed subsequently. In the adhesive force reducing step 1002, after these adjustments, the control unit 50, as shown in FIG. 6, causes the second laser beam application unit 22 to apply the laser beam 78 while moving the application position of the laser beam 78 by the processing feed unit 41 along the division line 102 relative to the wafer 100 held on the holding table 10, to form an adhesive force reducing region 200 having a width at least wider than the modified layer 300 in the region corresponding to the division line 102 of the adhesive layer 116 of the adhesive tape 111 or in the region spanning the region corresponding to the division line 102. In the adhesive force reducing step 1002, the width of the light collecting region 79 may be formed to be equal to or wider than the division line 102. In the adhesive force reducing step 1002, the laser beam 78 is applied to all the division lines 102 one by one to form an adhesive force reducing region 200 along the division line 102.

[0036] In addition, when the base material of the wafer 100 is sapphire, silicon carbide, or hard glass, an adhesive tape 111 is used in which an adhesive layer 116 having stronger adhesive strength than an adhesive tape with a DAF is formed, but such an adhesive tape 111 may contain a substance that does not sufficiently transmit or scatters the laser beam 78 having a wavelength corresponding to ultraviolet light. Even in such a case, in the adhesive strength reducing step 1002, if the base material of the wafer 100, sapphire, silicon carbide, or hard glass, is translucent or transparent and has a predetermined transmittance (for example, 50%) or more for ultraviolet light, the adhesive strength reducing region 200 can be favorably formed by irradiating the adhesive layer 116 of the adhesive tape 111 through the wafer 100 from the front surface 101 side of the wafer 100 as shown in FIG. 6. On the other hand, in the adhesive strength reduction step 1002, if the base material of the wafer 100 is not translucent or transparent and has a predetermined transmittance to ultraviolet light (e.g., 50%) (e.g., a part of silicon), an adhesive tape 111 that does not contain any substance that sufficiently transmits or scatters the laser beam 78 of a wavelength corresponding to ultraviolet light is used, and the laser beam 78 of a wavelength corresponding to ultraviolet light is irradiated from the adhesive tape 111 side to the adhesive layer 116 to form an adhesive strength reduction region 200.

[0037] The modified layer forming step 1003 is a step in which a laser beam 68 having a wavelength that is transparent to the wafer 100 is irradiated along the planned division lines 102 in a state in which the laser beam 68 is focused inside the wafer 100 by the first laser beam application unit 21 of the laser processing apparatus 1, thereby forming a modified layer 300 inside the wafer 100. In this embodiment, the modified layer forming step 1003 is performed after the adhesive strength reducing step 1002, but the present invention is not limited to this, and may be performed before the adhesive strength reducing step 1002.

[0038] Fig. 7 is a cross-sectional view for explaining the modified layer forming step 1003 in Fig. 5. In the modified layer forming step 1003, first, similarly to the adhesive strength reducing step 1002, the wafer 100 is suction-held by the holding surface 11 and brought into a state in which an alignment process has been executed. In the modified layer forming step 1003, the control unit 50 then controls the indexing feed unit 42 to align the position of the irradiation position of the laser beam 68 of the first laser beam application unit 21 in the indexing feed direction (Y-axis direction) to a position corresponding to the planned division line 102 of the wafer 100 held on the holding table 10.

[0039] In the modified layer formation step 1003, the control unit 50 then controls the first laser beam oscillation unit 61 to adjust the optical properties of the laser beam 68, and controls the first collector 62 as shown in FIG. 7 to adjust the height of the focusing area 69 for focusing the laser beam 68 to a predetermined height inside the wafer 100 held on the holding table 10, and adjusts the width of the focusing area 79 to be equal to or narrower than the planned dividing lines 102. In the modified layer forming step 1003, after these adjustments, the control unit 50, as shown in Fig. 7, causes the first laser beam application unit 21 to apply the laser beam 68 while moving the application position of the laser beam 68 by the processing feed unit 41 along the dividing lines 102 relative to the wafer 100 held on the holding table 10, thereby forming modified layers 300 having a width equal to or narrower than the dividing lines 102 in the area corresponding to the dividing lines 102 inside the wafer 100. In the modified layer forming step 1003, the laser beam 68 is applied to all the dividing lines 102 one by one to form modified layers 300 along the dividing lines 102. The modified layers 300 are formed narrower than the dividing lines 102 so as to fit within the dividing lines 102. Furthermore, in the modified layer forming step 1003, by narrowing the width of the modified layer 300 as much as possible, the width of the intended dividing lines 102 can be designed to be narrow, which is preferable because it increases the amount of chips 109 that can be removed.

[0040] The tape expansion step 1004 is performed after the adhesive strength reduction step 1002 and the modified layer formation step 1003, and is a step in which the adhesive tape 111 is expanded using the tape expansion device 130 shown in Figure 8, thereby dividing the wafer 100 along the intended division line 102 starting from the modified layer 300.

[0041] FIG. 8 is a perspective view showing the tape expanding device 130 which performs the tape expanding step 1004 of FIG. 5. As shown in FIG. 8, the tape expanding device 130 which performs the tape expanding step 1004 includes a cylindrical frame holding part 131, a plurality of clamp parts 132, a disk-shaped holding table 133, and an air cylinder 134. The frame holding part 131 holds the annular frame 112 placed thereon with its annular upper surface. The clamp parts 132 are arranged in a circular pattern along the outer periphery of the frame holding part 131, and sandwich the annular frame 112 placed on the frame holding part 131 to fix the wafer 100 to which the frame 112 is attached via the adhesive tape 111. The holding table 133 has a smaller diameter than the inner periphery of the frame holding part 131 and is provided on the inner periphery side of the frame holding part 131, and suction-holds the wafer 100 via the adhesive tape 111 from the back surface 104 side. The air cylinder 134 is attached below the holding table 133 and moves the holding table 133 up and down relative to the frame holding portion 131 and the clamp portion 132 .

[0042] Fig. 9 is a cross-sectional view for explaining the tape expanding step 1004 in Fig. 5. Fig. 10 is a cross-sectional view for explaining the tape expanding step 1004 in Fig. 5. In the tape expanding step 1004, first, as shown in Fig. 9, an adhesive layer 116 of an affixed adhesive tape 111 has a reduced adhesive strength region 200 formed along a planned division line 102, and an annular frame 112 attached to a wafer 100 having a modified layer 300 formed therein is placed on a frame holding portion 131 and fixed by a clamp portion 132. In the tape expansion step 1004, next, as shown in FIG. 10, the air cylinder 134 moves the holding table 133 upward to a position where the holding surface of the holding table 133 is sufficiently higher than the holding surface of the frame holding portion 131, thereby raising the wafer 100 and the portion of the adhesive tape 111 attached to the wafer 100 to a position sufficiently higher than the frame 112 and the portion of the adhesive tape 111 attached to the frame 112, thereby expanding the adhesive tape 111 radially outward, and dividing the wafer 100 along the planned division lines 102 starting from the modified layer 300 to form chips 109 (devices).

[0043] Fig. 11 is a cross-sectional view for explaining the ultraviolet ray irradiation step 1005 in Fig. 5. The ultraviolet ray irradiation step 1005 is carried out after the tape expanding step 1004, and is a step in which ultraviolet rays 148 are irradiated onto the entire surface of the adhesive layer 116 from the adhesive tape 111 side by a plurality of ultraviolet ray irradiation lamps 141 of an ultraviolet ray irradiation device 140 arranged in a plane facing the adhesive tape 111, thereby reducing the adhesive strength of the adhesive layer 116 over the entire surface.

[0044] FIG. 12 is a cross-sectional view for explaining the pick-up step 1006 in FIG. 5. The pick-up step 1006 is performed after the ultraviolet irradiation step 1005, and as shown in FIG. 12, the pick-up device 150 picks up the chips 109 obtained by dividing the wafer 100 along the division lines 102 by the suction unit 151 provided at the lower end thereof, and picks up the chips 109 by suction from above. Here, in this embodiment, the suction unit 151 suctions and holds the chips 109 from above by the negative pressure introduced from a suction source (not shown) on the lower surface. In the pick-up step 1006, in this embodiment, the chips 109 are peeled off and picked up for each chip region 103, and all the chips 109 formed from the wafer 100 are obtained by dividing them into individual chips.

[0045] The laser processing apparatus 1 and wafer processing method of the embodiment having the above-mentioned configuration irradiates a laser beam 78 having a wavelength corresponding to ultraviolet light onto an area of ​​the adhesive tape 111 corresponding to the planned division line 102 to reduce the adhesive force of the adhesive layer 116, and then expands the adhesive tape 111 to divide the wafer 100 along the planned division line 102, starting from the modified layer 300. Therefore, the laser processing apparatus 1 and wafer processing method of the embodiment reduce the adhesive strength of the adhesive layer 116 in the area of ​​the adhesive tape 111 corresponding to the planned division line 102 that is more likely to spread when the adhesive tape 111 is expanded and divided, thereby achieving the effective effect of reducing the occurrence of glue residue on the outer periphery of the back surface 104 of the chip 109 due to the adhesive layer 116 in that area rubbing against the outer periphery of the back surface 104 of the chip 109 when the adhesive tape 111 is expanded, and the occurrence of peeling off of the functional film 105 on the outer periphery of the back surface 104 of the chip 109 due to the adhesive layer 116 in that area rubbing against the functional film 105 on the outer periphery of the back surface 104 of the chip 109.

[0046] Conventionally, it has been considered to irradiate the entire surface of the adhesive tape with ultraviolet light and then expand the adhesive tape to divide the wafer along the planned division lines, but with this method, the adhesive strength of the entire surface of the adhesive tape is reduced when the adhesive tape is expanded, which may cause the chips to move and come into contact with each other, resulting in chipping. On the other hand, in the laser processing apparatus 1 and wafer processing method according to the embodiment, the adhesive tape 111 forms a modified layer 300 and serves as a starting point for expanding the space between the chips 109, so that the adhesive tape 111 is likely to expand, and friction between the adhesive tape 111 and the chips 109 is likely to occur. Laser beam 78 having a wavelength corresponding to ultraviolet light is irradiated to the area of ​​the adhesive tape 111 corresponding to the planned division lines 102, thereby reducing the adhesive strength of the adhesive layer 116, while the adhesive tape corresponding to the chip region 103 (or the area excluding the outer periphery of the chip region 103) is irradiated to the area of ​​the adhesive tape 111 corresponding to the chip region 103 (or the area excluding the outer periphery of the chip region 103). The adhesive tape 111 is expanded to divide the wafer 100 along the planned division lines 102 without irradiating the area of ​​the chip 111 with ultraviolet light or laser light 78 of a wavelength corresponding to ultraviolet light and without reducing the adhesive strength of the adhesive layer 116. Therefore, the movement of the chips 109 is restricted by the area of ​​the adhesive tape 111 where the adhesive strength of the adhesive layer 116 has not been reduced. This reduces glue residue on the back surface 104 of the chips 109 while reducing the risk of the chips 109 moving and coming into contact with each other, resulting in chipping.

[0047] In addition, when a functional film 105 is formed on the back surface 104, conventional methods not only tend to leave glue residue, but also have the problem of the functional film on the back surface of the outer periphery of the chip peeling off due to rubbing between the adhesive tape and the chip. However, the laser processing apparatus 1 and wafer processing method of the embodiment are also effective in preventing peeling of the functional film 105 of the wafer 100 (chip 109) on which the functional film 105 is formed.

[0048] Furthermore, the laser processing apparatus 1 and the wafer processing method according to the embodiment further irradiate a laser beam 78 having a wavelength corresponding to ultraviolet light to an area spanning the area of ​​the adhesive tape 111 corresponding to the division lines 102, i.e., an area wider than the division lines 102, to reduce the adhesive strength of the adhesive layer 116. Therefore, the laser processing apparatus 1 and the wafer processing method according to the embodiment reduce the adhesive strength of the adhesive layer 116 in an area corresponding to the outer periphery of the chip area 103 adjacent to the division lines 102 (the outer periphery of the chip 109) in addition to the area of ​​the adhesive tape 111 corresponding to the division lines 102, so that the occurrence of glue residue on the outer periphery of the back surface 104 of the chip 109 and peeling of the functional film 105 can be further reduced.

[0049] Furthermore, the laser processing apparatus 1 and wafer processing method according to the embodiment are even more effective when the base material of the wafer 100 is hard, translucent or transparent, such as sapphire, silicon carbide, or hard glass, and has a predetermined transmittance (e.g., 50%) or more against ultraviolet light. In such a case, the laser processing apparatus 1 and wafer processing method according to the embodiment use an adhesive tape 111 with a high fixing power having an adhesive layer 116 with stronger adhesive power, which makes it easy for glue residue to occur on the back surface 104 of the chip 109. However, by irradiating a laser beam 78 having a wavelength corresponding to ultraviolet light through the wafer 100 from the front surface 101 side of the wafer 100 in the adhesive strength reduction step 1002, the adhesive strength of the adhesive layer 116 in the area of ​​the adhesive tape 111 corresponding to the planned division line 102 can be effectively reduced without being affected by the substances contained in the adhesive tape 111, and the occurrence of glue residue on the outer periphery of the back surface 104 of the chip 109 and peeling off of the functional film 105 can be reduced.

[0050] Next, the inventors of the present invention confirmed the effects of the laser processing apparatus 1 and the wafer processing method according to the embodiment. Figure 13 is a diagram for explaining the effects of the laser processing apparatus 1 and the wafer processing method according to the embodiment. Figure 13 shows the results obtained when confirming the effects.

[0051] The right column of "Example" in Fig. 13 shows a schematic diagram of the appearance of the back surface 104 of the chip 109, which shows the result of the occurrence of adhesive residue on the outer periphery of the back surface 104 of the chip 109, obtained when the wafer processing method according to the embodiment is performed using the laser processing apparatus 1 according to the embodiment on the wafer 100 without the functional film 105. In the "Example" in Fig. 13, in the adhesive strength reducing step 1002, an adhesive strength reducing region 200 having a width equivalent to the dividing line 102 is formed in the region corresponding to the dividing line 102 of the adhesive layer 116 of the adhesive tape 111, and in the modified layer forming step 1003, a modified layer 300 having a width equivalent to the dividing line 102 is formed in the region corresponding to the dividing line 102 inside the wafer 100. The right column of "Comparative Example" in Figure 13 shows a schematic diagram of the appearance of the back surface of a chip, which shows the result of forming a modified layer on a wafer placed on a holding table using a conventional laser processing apparatus in which the second laser beam application unit 22 has been removed from the laser processing apparatus 1 of the embodiment, for a wafer 100 without a functional film 105, and then expanding the adhesive tape to divide the wafer, resulting in the occurrence of glue residue on the outer periphery of the back surface of the chip.

[0052] As shown in Fig. 13, when the wafer processing method according to the embodiment is carried out using the laser processing apparatus 1 according to the embodiment, no glue residue was observed on the outer periphery of the back surface 104 of the chip 109, whereas when a modified layer is formed and divided using a conventional laser processing apparatus, glue residue was observed on the entire periphery of the back surface of the chip. As a result, in the embodiment shown in Fig. 13, it was revealed that the occurrence of glue residue on the outer periphery of the back surface 104 of the chip 109 can be reduced by irradiating the region of the adhesive tape 111 corresponding to the division line 102 with a laser beam 78 having a wavelength corresponding to ultraviolet light by the second laser beam irradiation unit 22 to reduce the adhesive force of the adhesive layer 116.

[0053] It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. [Explanation of symbols]

[0054] 1 Laser processing equipment 10 Holding table 20 Laser beam irradiation unit 41 Processing feed unit 61 First Laser Beam Oscillation Unit 62 First Concentrator 68,78 Laser beam 71 Second Laser Oscillation Unit 72 Secondary Concentrator 100 wafers 102 Division line 111 Adhesive Tape 116 Adhesive layer 148 UV rays 300 Modification layer

Claims

1. A wafer processing method for dividing a wafer along a plurality of dividing lines formed in a first direction and a second direction intersecting the first direction, comprising: a bonding step of bonding the wafer to an adhesive tape having an adhesive layer that is larger than the wafer and has an adhesive strength that is reduced by ultraviolet light; an adhesive strength reducing step of irradiating the adhesive layer with a laser beam having a wavelength corresponding to ultraviolet light along the planned dividing line from a surface of the wafer opposite to the surface to which the adhesive tape is attached, thereby reducing the adhesive strength of the adhesive layer corresponding to the planned dividing line; a modified layer forming step of irradiating a laser beam having a wavelength that is transparent to the wafer along the intended dividing lines while the laser beam is focused inside the wafer, thereby forming a modified layer inside the wafer; a tape expanding step of expanding the adhesive tape to divide the wafer starting from the modified layer; A wafer processing method comprising the steps of:

2. The wafer is translucent or transparent; 2. The method for processing a wafer according to claim 1, wherein the adhesive strength reducing step comprises irradiating a laser beam having a wavelength corresponding to ultraviolet light through the wafer.

3. A wafer processing method for dividing a wafer along a plurality of planned division lines formed in a first direction and a second direction intersecting the first direction, comprising: a bonding step of bonding the wafer to an adhesive tape having an adhesive layer that is larger than the wafer and has an adhesive strength that is reduced by ultraviolet light; an adhesive strength reducing step of irradiating the adhesive layer with a laser beam having a wavelength corresponding to ultraviolet light along the intended division line to reduce the adhesive strength of the adhesive layer corresponding to the intended division line; a modified layer forming step of irradiating a laser beam having a wavelength that is transparent to the wafer along the intended dividing lines while the laser beam is focused inside the wafer, thereby forming a modified layer inside the wafer; a tape expanding step of expanding the adhesive tape to divide the wafer starting from the modified layer; having The method for processing a wafer, wherein in the adhesive strength reducing step, the adhesive strength of the adhesive layer is reduced in a width wider than the modified layer formed in the modified layer forming step.

4. A laser processing apparatus for processing a wafer, comprising: A holding table for holding a wafer; a laser beam application unit that applies a laser beam to the wafer held on the holding table; a processing feed unit that relatively moves the holding table and the laser beam application unit in a processing feed direction; A laser processing apparatus comprising: The laser beam irradiation unit includes: a first laser beam oscillation unit that oscillates a laser beam having a wavelength that is transparent to the wafer; a second laser beam oscillation unit that oscillates a laser beam having a wavelength corresponding to ultraviolet light onto the adhesive layer of the adhesive tape to which the wafer is attached; a first condenser that condenses the laser beam oscillated from the first laser beam oscillation unit and irradiates the wafer with the laser beam; a second condenser for condensing the laser beam oscillated from the second laser beam oscillation unit and irradiating the surface of the wafer opposite to the surface to which the adhesive tape is affixed; and having irradiating the adhesive layer with a laser beam corresponding to the planned dividing line of the wafer by the second laser beam emitting unit to reduce adhesive strength; A laser processing apparatus characterized in that the first laser beam oscillation unit focuses light inside the wafer corresponding to the intended dividing lines to form a modified layer.

5. A laser processing apparatus for processing a wafer, comprising: A holding table for holding a wafer; a laser beam application unit that applies a laser beam to the wafer held on the holding table; a processing feed unit that relatively moves the holding table and the laser beam application unit in a processing feed direction; A laser processing apparatus comprising: The laser beam irradiation unit includes: a first laser beam oscillation unit that oscillates a laser beam having a wavelength that is transparent to the wafer; a second laser beam oscillation unit that oscillates a laser beam having a wavelength corresponding to ultraviolet light onto the adhesive layer of the adhesive tape to which the wafer is attached; a first condenser that condenses the laser beam oscillated from the first laser beam oscillation unit and irradiates the wafer with the laser beam; a second condenser that condenses the laser beam oscillated from the second laser beam oscillation unit and irradiates the wafer with the laser beam; having irradiating the adhesive layer with a laser beam corresponding to the planned dividing line of the wafer by the second laser beam emitting unit to reduce adhesive strength; The first laser beam oscillation unit is used to focus light inside the wafer corresponding to the planned dividing line, thereby forming a modified layer; A laser processing apparatus characterized in that the second laser beam oscillation unit reduces the adhesive strength of the adhesive layer in a width wider than the modified layer formed by the first laser beam oscillation unit.

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