Laser processing device

Abstract

To provide a processing apparatus capable of solving the problem of being uneconomical because two laser processing devices having different wavelengths have to be prepared.SOLUTION: A laser processing device includes: holding means for holding a wafer; laser beam application means 7 of applying a pulse laser beam to the wafer held by the holding means; and processing feeding means for feeding the holding means and the laser beam applying means 7 relatively to each other. The laser beam application means 7 includes: an oscillator 70 for oscillating a pulsed laser beam LB1; a branching part 73 for branching the pulsed laser beam LB1 oscillated by the oscillator 70 into a first optical path L1 and a second optical path L2; a first capacitor 71 disposed in the first optical path L1 for condensing the pulsed laser beam LB1 on the wafer held by the holding means; a wavelength converter 82 disposed in the second optical path L2 for converting the wavelength of the pulsed laser beam LB1 oscillated by the oscillator 70; and a second capacitor 81 for condensing a pulse laser beam LB2 whose the wavelength has been converted onto the wafer held by the holding means.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a laser processing apparatus for irradiating a wafer with a pulsed laser beam. [Background technology]

[0002] Wafers with multiple devices such as ICs and LSIs formed on their surface along planned dividing lines are then separated into individual device chips using dicing equipment and laser processing equipment, and are used in electrical devices such as mobile phones and personal computers.

[0003] Furthermore, when a low-dielectric-constant insulating film known as a low-k film is laminated on the surface of a wafer, cutting the wafer with a cutting blade can cause the low-k film to peel off like mica, and this peeling can reach the device from the planned dividing line, resulting in a decrease in the quality of the device.

[0004] Therefore, the applicant has proposed a technology in which a laser beam is irradiated on both sides of the planned dividing line to form two grooves, and then a cutting blade is used to cut between the two grooves, so that peeling of the insulating film does not reach the device even when the planned dividing line is cut with a cutting blade (see Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-064230 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when a low-k film (for example, 10 μm thick) is made by stacking transparent films including SiO2 films on a silicon substrate, the leakage of the laser beam can cause peeling at the interface between the low-k film and the silicon substrate, reducing the quality of the devices that are individually separated from the wafer, and improvements were needed.

[0007] Furthermore, if a laser beam is irradiated on both sides of the planned dividing line to form two grooves, the low-k film will remain in the area between the two grooves, and cutting the planned dividing line with a cutting blade will be unstable in the width direction, making frequent cutting impossible.Therefore, one possible method is to irradiate the low-k film in the area between the two grooves with a laser beam to completely remove it.However, the wavelength of the laser beam suitable for forming the two grooves is different from the wavelength of the laser beam suitable for removing the low-k film in the area between the two grooves, which requires the preparation of two laser processing machines with different wavelengths, which is uneconomical.

[0008] The present invention has been made in consideration of the above facts, and its main technical object is to provide a processing device that can suppress the leakage of laser beams, even when a low-k film (for example, 10 μm thick) is formed on a silicon substrate by laminating transparent films including an SiO2 film, thereby solving the problem of peeling occurring at the interface between the low-k film and the silicon substrate, which reduces the quality of the devices that are individually separated from the wafer, and that can properly form two grooves and remove the low-k film in the area between the two grooves using a single laser processing device, thereby solving the uneconomical problem of having to prepare two laser processing devices with different wavelengths. [Means for solving the problem]

[0009] In order to solve the above-mentioned main technical problems, according to the present invention, there is provided a laser processing apparatus comprising: holding means for holding a wafer; laser beam application means for irradiating a pulsed laser beam onto the wafer held by the holding means; and processing feed means for relatively feeding the holding means and the laser beam application means, wherein the laser beam application means comprises: an oscillator for oscillating a pulsed laser beam; a branching section for branching the pulsed laser beam oscillated by the oscillator into a first optical path and a second optical path; a first condenser disposed on the first optical path for focusing the pulsed laser beam on the wafer held by the holding means; a wavelength converter disposed on the second optical path for converting the wavelength of the pulsed laser beam oscillated by the oscillator; and a second condenser for focusing the wavelength-converted pulsed laser beam on the wafer held by the holding means.

[0010] The wavelength converter preferably converts the wavelength of the pulsed laser beam oscillated by the oscillator into a deep-ultraviolet pulsed laser beam, and the repetition frequency of the pulsed laser beam oscillated by the oscillator is preferably set to a value such that the deep-ultraviolet pulsed laser beam is irradiated onto the wafer at a time interval shorter than the thermal diffusion time in a transparent film, including an SiO2 film, laminated on the upper surface of the silicon substrate. Furthermore, the second optical path preferably includes a separator that separates the spot of the wavelength-converted pulsed laser beam into two spots in a Y-axis direction perpendicular to the X-axis direction when the processing feed direction is the X-axis direction, and a beam expander that adjusts the spacing between the spots separated by the separator. Furthermore, the first optical path preferably includes a beam width setting unit that sets the beam width of the pulsed laser beam in the Y-axis direction between the branching unit and the first condenser, and the beam width of the pulsed laser beam is set to correspond to the spacing between the two spots separated by the separator.

[0011] The branching unit preferably comprises a half-wave plate and a polarizing beam splitter, and the half-wave plate is rotated to adjust the power ratio of the pulsed laser beam guided to the first optical path and the second optical path. The branching unit may comprise a mirror unit and a positioning means for positioning the mirror unit between an active position and an inactive position, and may be configured such that the pulsed laser beam is guided to the second optical path when the mirror unit is in the active position and the pulsed laser beam is guided to the first optical path when the mirror unit is in the inactive position. A beam expander may be disposed between the oscillator and the branching unit to reduce the power density of the pulsed laser beam and thereby reduce the load on the branching unit. The first and second condensers may be configured as a common condenser. Furthermore, the repetition frequency of the pulsed laser beam oscillated by the oscillator is preferably set to a value exceeding 1 MHz so that the time interval between irradiation of the pulsed laser beam is less than 1.0 μs, which is the thermal diffusion time in a SiO2 film. Preferably, the wavelength of the pulsed laser beam oscillated by the oscillator is 515 to 532 nm, and the wavelength converted by the wavelength converter is 257 to 266 nm. [Effects of the Invention]

[0012] The laser processing apparatus of the present invention comprises holding means for holding a wafer, laser beam application means for applying a pulsed laser beam to the wafer held by the holding means, and processing feed means for relatively feeding the holding means and the laser beam application means, the laser beam application means comprising an oscillator for emitting a pulsed laser beam, a branching section for branching the pulsed laser beam oscillated by the oscillator into a first optical path and a second optical path, a first condenser disposed in the first optical path for focusing the pulsed laser beam on the wafer held by the holding means, a wavelength converter disposed in the second optical path for converting the wavelength of the pulsed laser beam oscillated by the oscillator, and a wavelength converter disposed in the second optical path for converting the wavelength of the pulsed laser beam oscillated by the oscillator. and a second condenser that condenses the pulsed laser beam whose wavelength has been converted to a wavelength of 10 μm. This prevents laser beam leakage, eliminating the problem of peeling at the interface between the low-k film and the silicon substrate, which reduces the quality of the devices that are individually separated from the wafer, even if a low-k film (for example, 10 μm thick) is formed on a silicon substrate by laminating transparent films including an SiO2 film. This also makes it possible to properly form two grooves and remove the low-k film in the area between the two grooves using a single laser processing device, eliminating the uneconomical problem of having to prepare two laser processing devices with different wavelengths. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is an overall perspective view of a laser processing apparatus according to an embodiment of the present invention; [Figure 2] 2 is a block diagram showing the configuration of an optical system of a laser beam application means disposed in the laser processing apparatus shown in FIG. 1. FIG. [Figure 3] (a) is a perspective view showing how laser processing is performed to form two grooves on a wafer using the laser processing device shown in Figure 1; (b) is a partially enlarged cross-sectional view showing how two grooves are formed by the laser processing shown in (a); and (c) is a plan view showing the two grooves shown in (b). [Figure 4](a) is a perspective view showing how laser processing is performed by the laser processing device shown in Figure 1 to remove the low-k film between the two grooves; (b) is a partially enlarged cross-sectional view showing how the removed area is formed by the laser processing shown in (a); and (c) is a plan view showing the removed area shown in (b). DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a processing apparatus configured based on the present invention will be described in detail with reference to the accompanying drawings.

[0015] 1 shows a laser processing apparatus 1 of this embodiment. Using this laser processing apparatus 1, laser processing is performed on a wafer 10 held by an annular frame F as shown in the figure via a protective tape T. The wafer 10 is a wafer having a low-k film 16 formed on the upper surface of a silicon substrate by laminating transparent films including an SiO2 film.

[0016] The laser processing device 1 includes a holding means 3 for holding a wafer 10, a laser beam application means 7 for applying a laser beam to the wafer 10 held by the holding means 3, and a processing feed means 4 for feeding the holding means 3 and the laser beam application means 7 in the X-axis direction.

[0017] In addition to the above-described configuration, the laser processing apparatus 1 of this embodiment is equipped with an alignment means 6 that takes an image of the wafer 10 held by the holding means 3 and performs alignment, a frame body 5 consisting of a vertical wall portion 5a erected on the side of the processing feed means 4 and a horizontal wall portion 5b extending horizontally from the upper end of the vertical wall portion 5a, and a control means (not shown) that controls each operating part.

[0018] The holding means 3 is a means for holding the wafer 10 using an XY plane, defined by X and Y coordinates, as a holding surface. As shown in FIG. 1 , the holding means 3 includes a rectangular X-axis movable plate 31 mounted on the base 2 so as to be movable in the X-axis direction, a rectangular Y-axis movable plate 32 mounted on the X-axis movable plate 31 so as to be movable in the Y-axis direction, a cylindrical support 33 fixed to the upper surface of the Y-axis movable plate 32, and a rectangular cover plate 34 fixed to the upper end of the support 33. A chuck table 35 is disposed on the cover plate 34 and extends upward through an elongated hole formed in the cover plate 34. The chuck table 35 is rotatable by a rotation drive means (not shown) housed in the support 33. A circular suction chuck 36, made of a porous material with air permeability and having an XY plane, defined by X and Y coordinates, as a holding surface, is disposed on the upper surface of the chuck table 35. The suction chuck 36 is connected to a suction means (not shown) by a flow path passing through the support 33, and four clamps 37 are arranged at equal intervals around the suction chuck 36 to grip the frame F when holding the wafer 10 on the chuck table 35.

[0019] The processing feed means 4 includes an X-axis moving means 4a that moves the holding means 3 in the X-axis direction, and a Y-axis moving means 4b that moves the holding means 3 in the Y-axis direction. The X-axis moving means 4a converts the rotational motion of the motor 42a into linear motion via a ball screw 42b and transmits the linear motion to the X-axis movable plate 31, moving the X-axis movable plate 31 in the X-axis direction along a pair of guide rails 2A, 2A arranged on the base 2 along the X-axis direction. The Y-axis moving means 4b converts the rotational motion of the motor 44a into linear motion via a ball screw 44b and transmits the linear motion to the Y-axis movable plate 32, moving the Y-axis movable plate 32 in the Y-axis direction along a pair of guide rails 31a, 31a arranged on the X-axis movable plate 31 along the Y-axis direction.

[0020] The horizontal wall 5b of the frame 5 accommodates an optical system constituting the laser beam application means 7 and the alignment means 6. A first condenser 71 constituting part of the laser beam application means 7 and a second condenser 81 adjacent to the first condenser 71 in the X-axis direction indicated by the arrow X in the figure are disposed on the underside of the tip of the horizontal wall 5b (details will be explained later). The alignment means 6 is an imaging means that captures an image of the wafer 10 held on the chuck table 35 of the holding means 3 to detect the position and orientation of the wafer 10, the laser processing position to be irradiated with the laser beam, etc., and is disposed in a position adjacent to the first condenser 71 and second condenser 81 in the X-axis direction.

[0021] 2 is a block diagram showing an outline of the optical system of the laser beam application means 7 constructed according to the present invention. The laser beam application means 7 includes an oscillator 70 that oscillates a pulsed laser beam LB1 having a predetermined wavelength and repetition frequency, a branching unit 73 that branches the pulsed laser beam LB1 oscillated by the oscillator 70 into a first optical path L1 and a second optical path L2, a first condenser 71 that is disposed on the first optical path L1 and focuses the pulsed laser beam LB1 on the wafer 10 held by the holding means 3, a wavelength converter 82 that is disposed on the second optical path L2 and converts the wavelength of the pulsed laser beam LB1 oscillated by the oscillator 70, and a second condenser 81 that focuses the pulsed laser beam LB2, the wavelength of which has been converted by the wavelength converter 82, on the wafer 10 held by the holding means 3.

[0022] The splitter 73 is composed of, for example, a half-wave plate 73a and a polarizing beam splitter 73b. By rotating the half-wave plate 73a and appropriately adjusting the rotation angle of the half-wave plate 73a, it is possible to adjust the power ratio between the p-polarized light that is transmitted through the polarizing beam splitter 73b and guided to the first optical path L1 and the s-polarized light that is reflected by the polarizing beam splitter and guided to the second optical path L2.

[0023] The wavelength converter 82 disposed on the second optical path L2 converts the wavelength of the pulsed laser beam LB1 oscillated by the oscillator 70, for example, into a pulsed laser beam LB2 having a different wavelength. More specifically, if the pulsed laser beam LB1 oscillated by the oscillator 70 is green light with a wavelength of 515 to 532 nm, the wavelength converter 82 converts the wavelength into deep ultraviolet light with a wavelength of 257 to 266 nm. The wavelength converter 82 is configured to include, for example, a BBO crystal or a CLBO crystal.

[0024] Furthermore, the repetition frequency of the pulsed laser beam LB1 oscillated by the oscillator 70 is set to a value that allows irradiation at time intervals shorter than the thermal diffusion time of the transparent films, including SiO2 films, that make up the Low-k film 16 laminated on the top surface of the silicon substrate that makes up the wafer 10. More specifically, the Low-k film 16 laminated on the top surface of the wafer 10 is formed by laminating transparent films, including SiO2 films, and since the thermal diffusion time of SiO2 is 1.0 μs, in order to prevent peeling from occurring at the interface between the Low-k film 16 and the silicon substrate, the repetition frequency of the pulsed laser beam irradiated onto the Low-k film 16 is set to a repetition frequency that exceeds 1 MHz, which is a repetition frequency that makes the pulse interval shorter than the thermal diffusion time. It has been confirmed that peeling of the low-k film 16 is more effectively suppressed when the pulse interval of the laser beam LB1 is less than 1.0 μs, which is the thermal diffusion time of an SiO2 film, and therefore the pulse interval of the pulsed laser beam LB1 oscillated by the oscillator 70 is set to preferably less than 0.5 μs, more preferably less than 0.25 μs. In other words, the repetition frequency of the pulsed laser beam LB1 is preferably set to greater than 2 MHz, and more preferably greater than 4 MHz.

[0025] The laser beam application means 7 of this embodiment will be described in more detail with reference to Fig. 2. A beam expander 72 is disposed between the oscillator 70 and the branching unit 73. The beam expander 72 adjusts the spot diameter of the pulsed laser beam LB1 to lower the power density and reduce the load on the branching unit 73.

[0026] In the second optical path L2, when the processing feed direction of the wafer 10 held on the chuck table 35 is the X-axis direction, there are disposed a separator 83 that separates the spot of the pulsed laser beam LB2, whose wavelength has been converted by the wavelength converter 82, into two spots in the Y-axis direction, and a beam expander 84 that adjusts the spacing in the Y-axis direction of the spots separated by the separator 83. As the separator 83, it is preferable to employ, for example, a birefringent beam splitter.

[0027] A beam width setting unit 74 is disposed on the first optical path L1 between the branching unit 73 and the first condenser 71, and sets the beam width of the pulsed laser beam LB1 in the Y-axis direction to correspond to the spacing between the two spots separated by the separation unit 83 on the second optical path L2. The beam width setting unit 74 is composed of, for example, a beam expander 74a and a cylindrical lens 74b. The beam expander 74a adjusts the spot diameter of the pulsed laser beam LB1, and the cylindrical lens 74b adjusts the beam width of the pulsed laser beam LB1. The beam width setting unit 74 may be a mask means having an opening corresponding to the spacing between the two spots separated by the separation unit 83.

[0028] In addition to the above-described configuration, an attenuator may be provided in each of the first optical path L1 and the second optical path L2, and the outputs of the pulsed laser beams LB1 and LB2 branched by the branching unit 73 may be individually adjusted. Furthermore, the first optical path L1 and the second optical path L2 are appropriately provided with reflecting mirrors 75, 85, etc. that guide the pulsed laser beams LB1 and LB2 to the first condenser 71 and the second condenser 81.

[0029] The control means (not shown) is configured by a computer and includes a central processing unit (CPU) that performs calculations according to a control program, a read-only memory (ROM) that stores the control program, etc., a readable and writable random access memory (RAM) that temporarily stores detected values, calculation results, etc., an input interface, and an output interface (details not shown). Each operating part of the laser processing device 1 described above is appropriately controlled by this control means.

[0030] The laser processing apparatus 1 of this embodiment has roughly the configuration as described above, and the laser processing performed by the laser processing apparatus 1 will be described below.

[0031] 3(a), the wafer 10 to be processed in this embodiment is supported on an annular frame F via adhesive tape T. The wafer 10 is a wafer having a surface 10a on which a plurality of devices 12 are formed by dividing the wafer 10 along dividing lines 14, and a low-k film 16 formed by laminating SiO2 films is disposed on the upper surface of the silicon substrate. The low-k film 16 has a thickness of, for example, 10 μm, and the total thickness of the wafer 10 is 700 μm (for convenience of explanation, the actual dimensions are not shown).

[0032] When laser processing is performed on the wafer 10 described above, the wafer 10 is transported to the laser processing apparatus 1 described with reference to Fig. 1, placed on the chuck table 35 of the holding means 3 and held by suction, and the frame F is fixed by the clamps 37. Next, the wafer 10 held by the holding means 3 is transported by the processing feed means 4 to just below the alignment means 6 and imaged, and the positions of the planned dividing lines 14 formed on the surface 10a are detected, and the chuck table 35 is rotated by the rotation drive means described above to align the planned dividing lines 14 in a predetermined direction of the wafer 10 with the X-axis direction. Position information of the detected planned dividing lines 14 is stored in the control means described above.

[0033] Based on the position information detected by the alignment means 6, the second condenser 81 of the laser beam application means 7 is positioned at a predetermined processing start position of the dividing line 14 aligned in the X-axis direction. In the laser processing of this embodiment, first, to form two grooves along both sides of the dividing line 14 in the Y-axis direction, a pulsed laser beam LB2 converted to a wavelength of deep ultraviolet light (e.g., 266 nm) is applied in the second optical path L2 of the laser beam application means 7, as shown in FIG. 3(a). The pulsed laser beam LB2 is composed of two spots set at a predetermined distance in the Y-axis direction within the width of the dividing line 14. As shown in FIG. 3(b), the focal points of the pulsed laser beam LB2 are positioned on both sides of the dividing line 14 formed on the front surface 10a of the wafer 10 and applied, and the X-axis moving means 4a is operated to feed the wafer 10 together with the holding means 3 in the X-axis direction indicated by the arrow X in FIG. 3(a). As a result, two grooves 100a and 100b are formed on both sides of the dividing line 14, as shown in FIGS. 3(b) and 3(c).

[0034] As described above, in the laser beam application means 7 of this embodiment, the beam width setting unit 74 is disposed on the first optical path L1, and sets the beam width of the pulsed laser beam LB1 corresponding to the interval between the two spots of the pulsed laser beam LB2 separated by the separation unit 83 on the second optical path L2. Then, at the division line 14 along which the two grooves 100a, 100b are formed, the first condenser 71 irradiates the pulsed laser beam LB1 having a wavelength (e.g., 532 nm) oscillated by the oscillator 70 with the focal point positioned at the center of the two grooves 100a, 100b so as to follow the pulsed laser beam LB2 that has been irradiated earlier, thereby removing the low-k film 16 remaining between the two grooves 100a, 100b and forming a removed region 100c, as shown in FIGS. 4(b) and 4(c). Although the second collector 81 is omitted in Figure 4(a), the second collector 81 is arranged adjacent to the first collector 71 in the X-axis direction, and a removal area 100c can be formed in conjunction with the formation of two grooves 100a, 100b at a predetermined planned division line 14.

[0035] After two grooves 100a, 100b are formed along both sides of a predetermined dividing line 14 of the wafer 10 and the low-k film 16 remaining between the two grooves 100a, 100b is removed to form a removal region 100c, the wafer 10 is indexed and fed in the Y-axis direction indicated by the arrow Y in the figure, so that the adjacent unprocessed dividing line 14 in the Y-axis direction is positioned directly below the second collector 81. Then, using the same procedure as described above, the wafer 10 is processed and fed in the X-axis direction to form the grooves 100a, 100b and removal region 100c. Similarly, the wafer 10 is processed and fed in the X-axis and Y-axis directions to form the grooves 100a, 100b and removal region 100c along all of the dividing lines 14 along the X-axis direction.

[0036] Next, the wafer 10 is rotated 90 degrees to align the unprocessed dividing lines 14 in the direction perpendicular to the dividing lines 14 on which the grooves 100a, 100b and removal regions 100c have already been formed, in the X-axis direction. Laser processing is then performed on each of the remaining dividing lines 14 using the same procedure as described above, to form two grooves 100a, 100b and removal regions 100c along all of the dividing lines 14 formed on the front surface 10a of the wafer 10.

[0037] The laser processing conditions when carrying out the laser processing of this embodiment are set, for example, as follows. Wavelength: Pulse laser beam LB1 = 532 nm Pulse laser beam LB2=266nm Repetition frequency: 4MHz Average power: 0.8W Pulse width: 200fs Processing feed rate: 400mm / s Condenser lens numerical aperture (NA): 0.068

[0038] The power ratio when the pulsed laser beam LB1 is branched by the branching section 73 described above is set according to the area of ​​the processed region when forming the two grooves 100a, 100b and the area of ​​the processed region when forming the removal region 100c, and in this embodiment, the ratio of the pulsed laser beam LB1 branched to the second optical path L2 side that forms the two grooves 100a, 100b is low (e.g., 30%), and the ratio of the pulsed laser beam LB1 branched to the first optical path L1 side that forms the removal region 100c is high (e.g., 70%).

[0039] According to the above-described embodiment, even if the low-k film 16 (e.g., 10 μm thick) is formed by laminating transparent films including SiO2 films, the wavelength converter 82 can convert the pulsed laser beam LB2 to a pulsed laser beam LB2 of a desired wavelength. Therefore, the pulsed laser beam LB1 branched by the wavelength converter 82 can be converted to a pulsed laser beam LB2 of a deep ultraviolet wavelength. This suppresses light leakage during the formation of the two grooves 100a, 100b, thereby enabling laser processing that eliminates the problem of peeling at the interface between the low-k film 16 and the silicon substrate. Furthermore, the wavelength of the pulsed laser beam LB1 emitted by the oscillator 70 can be adjusted to a wavelength suitable for removing the low-k film 16 remaining between the two grooves. This makes it possible to form the two grooves 100a, 100b and efficiently remove the low-k film 16 remaining between the two grooves using a single laser processing apparatus 1.

[0040] The present invention is not limited to the above-described embodiment. For example, the splitter 73 described above includes a half-wave plate 73a and a polarizing beam splitter 73b. However, instead of the half-wave plate 73a and the polarizing beam splitter 73b, a splitter 73c shown on the left side of FIG. 2 may be provided. The splitter 73c includes a mirror 733 and a positioning means 731. The mirror 733 includes a reflecting surface 734. The positioning means 731 includes an elevating rod 732 having the mirror 733 attached to its tip. By operating the positioning means 731, the elevating rod 732 can be raised and lowered in the direction indicated by arrow R1. According to this branching portion 73c, the mirror portion 733 can be positioned at an operational position P1 where the pulsed laser beam LB1 oscillated by the oscillator 70 is guided to the second optical path L2, and at a non-operational position P2 where the pulsed laser beam LB2 is guided to the first optical path L1.

[0041] When laser processing is performed by disposing the branching unit 73c in place of the branching unit 73 described above in the laser beam application means 7, the positioning means 731 is operated to move the mirror unit 733 to the operating position P1, the pulsed laser beam LB1 is reflected by the reflecting surface 734 of the mirror unit 733 and guided to the second optical path L2, and the pulsed laser beam LB2, which has been converted to a wavelength of deep ultraviolet light by the wavelength converter 82, is separated into two spots by the separating unit 83 and the focal point of the pulsed laser beam LB2 is positioned in the width direction of the dividing lines 14 of the wafer 10, and is irradiated from the second collector 81. Thereby, two grooves 100a, 100b are formed on the dividing lines 14 formed on the front surface 10a of the wafer 10, as described with reference to FIG. Next, the positioning means 731 is operated to position the mirror part 733 at the non-operating position P2, and the pulsed laser beam LB1 is guided to the first optical path L1. The pulsed laser beam LB1, whose width in the Y-axis direction is set corresponding to the spacing between the two spots (i.e., the spacing between the two grooves 100a and 100b) from the first condenser 71, is positioned at the center of the planned dividing line 14 of the wafer 10, and laser processing is performed. As a result, as described with reference to FIG. 4 , the low-k film 16 remaining between the two grooves 100a and 100b is removed to form the removed region 100c. When laser processing is performed using the branching part 73c in this manner, it is preferable to provide attenuators in each of the first optical path L1 and the second optical path L2 to individually adjust the output of the pulsed laser beam LB2 that forms the two grooves 100a and 100b and the output of the pulsed laser beam LB1 that forms the removed region 100c.

[0042] Furthermore, in the above-described embodiment, the first collector 71 and the second collector 81 are arranged as separate collectors, but they are not necessarily arranged as separate collectors, and one collector may serve as both the first collector 71 and the second collector 81. For example, in the second optical path L2 shown in Fig. 2, instead of the optical path L2a from the beam expander 84 to the second collector 81, an optical path L2b including reflecting mirrors 86 and 87 that guide the pulsed laser beam LB2 from the beam expander 84 to the first collector 71 is arranged, whereby the first collector 71 can also function as the second collector 81. In this configuration, the pulsed laser beam LB2 having two spots generated by the second optical path L2 is advanced (for example, by 1 mm) ahead of the spot position of the pulsed laser beam LB1 guided by the first optical path L1, and following the formation of two grooves 100a, 100b along the dividing line 14 of the wafer 10 by the pulsed laser beam LB2 converted to a wavelength of deep ultraviolet light (266 nm), the pulsed laser beam LB1 set to a wide width by the first optical path L1 is irradiated between the two grooves 100a, 100b, thereby forming the removal region 100c described with reference to Fig. 4. With this configuration, it is possible to appropriately remove the low-k film 16 formed by stacking transparent films including an SiO2 film from the dividing line 14, as in the embodiment described above.

[0043] In the above-described embodiment, the separating unit 83 is provided in the second optical path L2, and the spot of the wavelength-converted pulsed laser beam LB2 is separated into two spots in the Y-axis direction to simultaneously form two grooves 100a, 100b on the division line 14. However, the separating unit 83 may be omitted. When the laser beam application means 7 does not include the separating unit 83, the branching unit of the present invention is configured with the above-described branching unit 73c, and the pulsed laser beam LB1 oscillated by the oscillator 70 is guided to the second optical path L2 by setting the branching unit 73c in its operative position, and one spot is positioned on one side of the division line 14 in the width direction by the second condenser 81, and laser processing is performed in the same manner as described above to form the groove 100a, and then one spot is positioned on the other side of the division line 14 in the width direction to form the groove 100b by laser processing. Thereafter, the branching portion 73c is set to the inactive position, and the pulsed laser beam LB1 oscillated by the oscillator 70 is guided to the first optical path L1 and irradiated from the first condenser 71 to the area between the grooves 100a and 100b, thereby forming the removal region 100c. With this configuration and processing procedure, it is possible to appropriately remove the low-k film 16 formed by laminating transparent films including an SiO2 film from the intended dividing line 14, as in the previously described embodiment. [Explanation of symbols]

[0044] 1: Laser processing equipment 2: Base 3: Holding means 35: Chuck table 4: Processing feed means 4a: X-axis feed means 4b: Y-axis feed means 5:Frame body 6: Alignment means 7: Laser beam irradiation means 70: Oscillator 71: First Concentrator 72: Beam expander 73: Branch 73a: 1 / 2 wavelength plate 73b: Polarizing beam splitter 74: Beam width setting unit 74a: Beam expander 74b: Cylindrical lens 75: Reflective mirror 81: Second concentrator 82: Wavelength converter 83: Separation part 84: Beam Expander 85: Reflective mirror 10: Wafer 12: Device 14: Planned division line 16:Low-k film 100a, 100b: Groove 100c: Removal area L1: First optical path L2: Second optical path LB1, LB2: Pulse laser beam

Claims

1. The wafer processing apparatus comprises: a holding means for holding a wafer; a laser beam application means for applying a pulsed laser beam to the wafer held by the holding means; and a processing feed means for relatively feeding the holding means and the laser beam application means, The laser beam application means is a laser processing apparatus comprising: an oscillator that oscillates a pulsed laser beam; a branching section that branches the pulsed laser beam oscillated by the oscillator into a first optical path and a second optical path; a first condenser that is disposed on the first optical path and focuses the pulsed laser beam on the wafer held by the holding means; a wavelength converter that is disposed on the second optical path and converts the wavelength of the pulsed laser beam oscillated by the oscillator; and a second condenser that focuses the pulsed laser beam whose wavelength has been converted on the wafer held by the holding means.

2. the wavelength converter converts the wavelength of the pulsed laser beam oscillated by the oscillator into a pulsed laser beam of deep ultraviolet light; The repetition frequency of the pulsed laser beam oscillated by the oscillator is controlled by the SiO ２ 2. The laser processing apparatus according to claim 1, wherein the pulsed laser beam of deep ultraviolet light is set to a value at which the wafer is irradiated at a time interval shorter than the thermal diffusion time in the transparent film including the film.

3. 2. The laser processing apparatus according to claim 1, further comprising: a separator configured to separate a spot of the wavelength-converted pulsed laser beam into two spots in a Y-axis direction perpendicular to the X-axis direction when the processing feed direction is an X-axis direction; and a beam expander configured to adjust the spacing between the spots separated by the separator.

4. 4. The laser processing apparatus according to claim 3, wherein a beam width setting unit is disposed in the first optical path between the branching unit and the first condenser, for setting the beam width of the pulsed laser beam in the Y-axis direction, and the beam width of the pulsed laser beam is set in accordance with the interval between the two spots separated by the separating unit.

5. 2. The laser processing apparatus according to claim 1, wherein the branching section is composed of a half-wave plate and a polarizing beam splitter, and the half-wave plate is rotated to adjust the power ratio of the pulsed laser beam guided to the first optical path and the second optical path.

6. 2. The laser processing apparatus according to claim 1, wherein the branching section comprises a mirror section and positioning means for positioning the mirror section at an operating position and a non-operating position, and the pulsed laser beam is guided to the second optical path when the mirror section is positioned at the operating position, and the pulsed laser beam is guided to the first optical path when the mirror section is positioned at the non-operating position.

7. 2. The laser processing device according to claim 1, wherein a beam expander is disposed between the oscillator and the branching portion, and the power density of the pulsed laser beam is reduced to reduce the load on the branching portion.

8. 2. The laser processing apparatus according to claim 1, wherein the first condenser and the second condenser are configured as a common condenser.

9. The repetition frequency of the pulsed laser beam oscillated by the oscillator is determined by the time interval between irradiation of the pulsed laser beam. ２ 3. The laser processing apparatus according to claim 2, wherein the frequency is set to a value exceeding 1 MHz so as to be less than 1.0 μs, which is the thermal diffusion time in the film.

10. 2. The laser processing apparatus according to claim 1, wherein the wavelength of the pulsed laser beam oscillated by said oscillator is 515 to 532 nm, and the wavelength converted by said wavelength converter is 257 to 266 nm.

Images