Laser processing apparatus and laser processing method

Abstract

To provide a laser processing device that can prevent dirt from adhering to optical elements. [Solution] The laser processing apparatus 2 includes a holding means 4 for holding a workpiece, a laser beam irradiation means 6 equipped with a light concentrator for irradiating the workpiece held by the holding means 4 with a laser beam, an X-axis feed means 8 for feeding the holding means 4 and the light concentrator relatively in the X-axis direction, and a Y-axis feed means 10 for feeding the holding means 4 and the light concentrator relatively in the Y-axis direction which is perpendicular to the X-axis direction. The laser beam irradiation means 6 includes a non-magnetic chamber having a first end for receiving light and a second end for sending out light, a holder for holding an optical element housed in the chamber, a first magnetic coupling connected to the holder, a second magnetic coupling disposed outside the chamber and interlocking with the first magnetic coupling, and a drive shaft connected to the second magnetic coupling, and includes an optical component in which the optical element is driven by the rotation of the drive shaft.

Description

Technical Field

[0001] The present invention relates to a laser processing apparatus and a laser processing method.

Background Art

[0002] A wafer on which a plurality of devices such as ICs and LSIs are formed on the surface partitioned by a dicing line is thinned by grinding the back surface and then diced into individual device chips by a dicing apparatus or a laser processing apparatus, and the diced device chips are used in electric devices such as mobile phones and personal computers.

[0003] A laser processing apparatus includes a chuck table for holding a wafer, a laser beam irradiation unit including a condenser for irradiating a laser beam onto the wafer held by the chuck table, and a feed unit for relatively feeding the chuck table and the condenser, and can process the wafer with high precision (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The laser beam irradiation unit of the laser processing apparatus includes an oscillator that oscillates a laser beam, an attenuator that adjusts the output of the laser beam oscillated by the oscillator, a beam expander that adjusts the beam diameter, and an optical axis adjustment unit that adjusts the optical axis of the laser beam whose output is adjusted by the attenuator.

[0006] However, if dust and dirt adhere to optical elements such as half-wave plates, quarter-wave plates, mirrors, lenses, beam splitters, prisms, diffraction gratings, and polarizing elements that make up attenuators, beam expanders, and optical axis adjustment means, or if dirt from grease splashes from surrounding structures adheres to them, it can lead to a decrease in the transmittance, reflectance, and light intensity of the optical elements, as well as vignetting caused by the adhering substances, resulting in a decrease in the performance of the optical elements. This phenomenon of dirt accumulation is particularly pronounced in areas where high-power-density light, such as laser beams, is irradiated, and the dirt reduces the transmittance, reflectance, and light intensity of the optical elements, thus degrading their performance.

[0007] The object of the present invention is to provide a laser processing apparatus and a laser processing method that can prevent dirt from adhering to optical elements. [Means for solving the problem]

[0008] According to the present invention, the following laser processing apparatus is provided that solves the above problems. That is, "A laser processing device, The system includes a holding means for holding a workpiece, a laser beam irradiation means equipped with a light concentrator for irradiating the workpiece held by the holding means with a laser beam, an X-axis feeding means for feeding the holding means and the light concentrator relative to each other in the X-axis direction, and a Y-axis feeding means for feeding the holding means and the light concentrator relative to each other in the Y-axis direction which is perpendicular to the X-axis direction. The laser beam irradiation means is A laser processing apparatus is provided which includes an optical component comprising: a non-magnetic chamber having a first end for receiving light and a second end for sending out light; a holder for holding an optical element housed in the chamber; a first magnetic coupling connected to the holder; a second magnetic coupling disposed outside the chamber and interlocking with the first magnetic coupling; and a drive shaft connected to the second magnetic coupling, wherein the optical element is driven by the rotation of the drive shaft.

[0009] Preferably, the drive shaft is equipped with a motor. The non-magnetic material may include aluminum, stainless steel, copper, brass, resin, glass, or ceramics. The chamber may be filled with or depressurized with dry air or an inert gas including nitrogen. Preferably, the first and second ends of the chamber are connected to each other by a connecting portion.

[0010] Furthermore, the present invention provides the following laser processing method that solves the above problems. That is, "A laser processing method for dividing a wafer of a workpiece into individual chips, The preparation process for preparing the laser processing apparatus described above, A holding step of holding the wafer in the holding means, A laser processing step in which a laser beam is irradiated onto a wafer held by the holding means to divide the wafer into individual chips, A laser processing method including is provided. [Effects of the Invention]

[0011] The laser processing apparatus of the present invention is The system includes a holding means for holding a workpiece, a laser beam irradiation means equipped with a light concentrator for irradiating the workpiece held by the holding means with a laser beam, an X-axis feeding means for feeding the holding means and the light concentrator relative to each other in the X-axis direction, and a Y-axis feeding means for feeding the holding means and the light concentrator relative to each other in the Y-axis direction which is perpendicular to the X-axis direction. The laser beam irradiation means is The laser processing apparatus of the present invention includes a non-magnetic chamber having a first end for receiving light and a second end for sending out light, a holder for holding an optical element housed in the chamber, a first magnetic coupling connected to the holder, a second magnetic coupling disposed outside the chamber and linked to the first magnetic coupling, and a drive shaft connected to the second magnetic coupling, wherein the optical element is driven by the rotation of the drive shaft. As a result, the optical element is isolated from the external environment, preventing dirt from adhering to it. Therefore, the problem of reduced performance of the optical element is eliminated. Furthermore, since the laser processing apparatus of the present invention does not suffer from reduced performance of the optical element, it is less prone to failure and has a long lifespan.

[0012] The laser processing method of the present invention is A laser processing method for dividing a wafer of a workpiece into individual chips, The preparation process for preparing the laser processing apparatus described above, A holding step of holding the wafer in the holding means, A laser processing step in which a laser beam is irradiated onto a wafer held by the holding means to divide the wafer into individual chips, Because it includes this feature, the optical elements are shielded from the external environment, preventing dirt from adhering to them. Therefore, wafer processing can be performed stably without the problem of reduced performance of the optical elements. In addition, the aforementioned laser processing equipment is less prone to failure and has a long lifespan, which helps to reduce the unit cost of the chips. [Brief explanation of the drawing]

[0013] [Figure 1] A perspective view of the laser processing apparatus according to the present invention. [Figure 2] Figure 1 is a perspective view of the laser beam irradiation means of the laser processing apparatus shown in Figure 1. [Figure 3] (a) Exploded perspective view of the first optical component shown in Figure 2, (b) Perspective view of the first optical component shown in (a). [Figure 4](a) Exploded perspective view of an attenuator including the second optical component shown in FIG. 2, (b) Perspective view of the attenuator shown in (a). [Figure 5] (a) Exploded perspective view of the second optical component shown in FIG. 2, (b) Perspective view of the second optical component shown in (a). [Figure 6] Cross-sectional view of the second optical component shown in FIG. 2. [Figure 7] (a) Exploded perspective view of the third optical component shown in FIG. 2, (b) Perspective view of the third optical component shown in (a). [Figure 8] (a) Exploded perspective view of the fourth optical component shown in FIG. 2, (b) Perspective view of the fourth optical component shown in (a).

Embodiments for Carrying Out the Invention

[0014] First, a preferred embodiment of the laser processing apparatus according to the present invention will be described with reference to the drawings.

[0015] (Laser processing apparatus 2) As shown in FIG. 1, the laser processing apparatus 2 includes holding means 4 for holding a workpiece, laser beam irradiation means 6 provided with a condenser for irradiating the workpiece held by the holding means 4 with a laser beam, X-axis feed means 8 for relatively machining and feeding the holding means 4 and the condenser in the X-axis direction, and Y-axis feed means 10 for relatively machining and feeding the holding means 4 and the condenser in the Y-axis direction. The X-axis direction is the direction indicated by arrow X in FIG. 1, the Y-axis direction is the direction indicated by arrow Y in FIG. 1 and is perpendicular to the X-axis direction, and the XY plane defined by the X-axis direction and the Y-axis direction is substantially horizontal. Also, the Z-axis direction indicated by arrow Z in FIG. 1 is the vertical direction perpendicular to the X-axis direction and the Y-axis direction. Note that the dimensions, shapes, etc. of the members in the drawings are exaggerated for the convenience of explanation.

[0016] (Holding means 4 of the laser processing apparatus 2) The holding means 4 includes an X-axis movable plate 14 supported on the upper surface of the base 12 of the laser processing device 2 so as to be movable in the X-axis direction, a Y-axis movable plate 16 supported on the upper surface of the X-axis movable plate 14 so as to be movable in the Y-axis direction, a support column 18 fixed to the upper surface of the Y-axis movable plate 16, and a cover plate 20 fixed to the upper end of the support column 18. The cover plate 20 has an elongated hole 20a extending in the Y-axis direction, and a chuck table 22 extending upward through the elongated hole 20a is rotatably mounted on the upper end of the support column 18.

[0017] A disc-shaped suction chuck 24 is positioned at the upper end of the chuck table 22 of the holding means 4. The suction chuck 24 is made of a porous material such as porous ceramics and is connected to a suction means (not shown). The chuck table 22 generates a suction force on the upper surface of the suction chuck 24 using the suction means, and holds the workpiece placed on the upper surface of the suction chuck 24 by suction. Multiple clamps 26 are positioned around the periphery of the chuck table 22 at intervals in the circumferential direction.

[0018] (Laser beam irradiation means 6 of the laser processing device 2) The laser beam irradiation means 6 has a housing 28 that extends upward from the upper surface of the base 12 and then substantially horizontally. As shown in Figure 2, the housing 28 contains a laser oscillator 30, a first optical component 32 (beam expander), an attenuator 34 including a second optical component, a third optical component 36 (angle adjuster), and a fourth optical component 38 (focuser). Also, as shown in Figure 1, an imaging means 40 for imaging the workpiece and detecting the area to be laser processed is mounted on the lower tip of the housing 28, spaced apart in the X-axis direction from the fourth optical component 38 (focuser).

[0019] (Laser oscillator 30 of laser beam irradiation means 6) The laser oscillator 30 includes a laser light source (not shown) that emits a laser beam LB, and a chamber 44 that covers the laser light source and shields it from the external environment. The chamber 44 is equipped with a feed end 44a that sends out the laser beam LB emitted by the laser light source. The feed end 44a is provided with a connecting portion 44b, which may be composed of, for example, an annular flange.

[0020] (First optical component 32 of the laser beam irradiation means 6) The first optical component 32 is configured as a beam expander that adjusts the beam diameter of the laser beam LB oscillated by the laser oscillator 30. As shown in Figures 3(a) and 3(b), the first optical component 32 includes a chamber 48, a holder 50, a housing 54 that houses a first magnetic coupling 52 and a second magnetic coupling (not shown), and a drive shaft 56.

[0021] (Chamber 48 of the first optical component 32) The chamber 48 comprises a first end 48a that receives light and a second end 48b that emits light. The chamber 48 is cylindrical and made of a non-magnetic material. The non-magnetic material forming the chamber 48 may include, for example, aluminum, stainless steel, copper, brass, resin, glass, or ceramics. The optical path within the chamber 48 is defined along the axial direction (Y-axis direction) of the chamber 48 from the first end 48a to the second end 48b. The first end 48a and the second end 48b are provided with a connecting part 48c that can be connected to the connecting part 44b of the laser oscillator 30 via appropriate fastening members such as bolts or clamp bands. A sealing member (not shown) such as an O-ring or gasket is provided between the connecting part 44b and the connecting part 48c. In addition, a pair of guide grooves (not shown) extending in the Y-axis direction are formed on the inner circumferential surface of the chamber 48, and a lens 48d is fixed to the second end 48b side.

[0022] (Holder 50 for the first optical component 32) The holder 50 holds the optical element 58 housed within the chamber 48. The holder 50 is cylindrical and made of a non-magnetic material. The optical element 58 is a lens (movable lens) that works in cooperation with the lens 48d (fixed lens) of the chamber 48 to adjust the beam diameter of the laser beam LB, and is fixed inside the holder 50. The holder 50 is also housed within the chamber 48 so as to be movable in the Y-axis direction via a non-magnetic guide bearing 60. The guide bearing 60 is mounted on the outer circumferential surface of the holder 50 and slidably fits into one of the guide grooves of the chamber 48.

[0023] (First magnetic coupling 52 of the first optical component 32) The first magnetic coupling 52 is connected to the holder 50. The first magnetic coupling 52 is rectangular in shape and extends in the Y-axis direction, and is slidably fitted into the other guide groove of the chamber 48. The first magnetic coupling 52 comprises a non-magnetic substrate 52a mounted on the outer circumferential surface of the holder 50, and a magnet 52b mounted on the outer surface of the substrate 52a. The magnet 52b is magnetized alternately with north and south poles in the Y-axis direction. Note that the magnet 52b may be in a configuration in which multiple magnets are aligned in the Y-axis direction.

[0024] (Second magnetic coupling of the first optical component 32) The second magnetic coupling is positioned outside the chamber 48 and is interlocked with the first magnetic coupling 52. The second magnetic coupling is cylindrical and is housed in a non-magnetic housing 54 so as to be rotatable about an axis Ax extending along the X-axis. The north and south poles of the magnets of the second magnetic coupling are arranged alternately in the circumferential direction. The housing 54 is mounted on the outer surface of the chamber 48, and a partition member (not shown) is provided between the housing 54 and the chamber 48. This partition member prevents foreign matter from entering from the second magnetic coupling side to the first magnetic coupling 52 side (inside the chamber 48).

[0025] (Drive shaft 56 of the first optical component 32) The drive shaft 56 is connected to a second magnetic coupling. The drive shaft 56 is non-magnetic. The drive shaft 56 may be equipped with a motor (for example, a pulse motor) that rotates the drive shaft 56. Alternatively, the drive shaft 56 may be rotated manually around axis Ax.

[0026] In the first optical component 32, the drive shaft 56 rotates about the axis Ax, causing the second magnetic coupling connected to the drive shaft 56 to rotate about the axis Ax. As a result, the attraction and repulsion between the magnet of the second magnetic coupling and the magnet 52b of the first magnetic coupling 52 causes the first magnetic coupling 52 to move in the Y-axis direction. This causes the holder 50 connected to the first magnetic coupling 52 and the optical element 58 held in the holder 50 to move in the Y-axis direction. Consequently, the beam diameter of the laser beam LB, which enters from the first end 48a of the chamber 48 and is discharged from the second end 48b, is adjusted. In other words, in the first optical component 32, even if the optical element 58 is isolated from the external environment by the chamber 48, the beam diameter of the laser beam LB can be adjusted by rotating the drive shaft 56 to move the optical element 58 in the Y-axis direction.

[0027] (Attenuator 34 of laser beam irradiation means 6) The attenuator 34 adjusts the output of the laser beam LB, whose beam diameter has been adjusted by the first optical component 32. As shown in Figures 4(a) and 4(b), the attenuator 34 includes a second optical component 62 and an additional optical component 63.

[0028] (Second optical component 62 of attenuator 34) Referring to Figures 5(a), 5(b), and 6, the second optical component 62 includes a chamber 64, a holder 66, a first magnetic coupling 68, a second magnetic coupling 70, and a drive shaft 72.

[0029] (Chamber 64 of the second optical component 62) The chamber 64 comprises a first end 64a that receives light and a second end 64b that emits light. The chamber 64 is cylindrical and made of a non-magnetic material. The optical path within the chamber 64 is defined along the axial direction (Y-axis direction) of the chamber 64 from the first end 64a to the second end 64b. The first end 64a and the second end 64b of the chamber 64 are provided with connecting parts 64c that can be connected to the connecting part 48c of the first optical component 32. A sealing member such as an O-ring or gasket (not shown) is provided between the connecting part 48c and the connecting part 64c. In addition, as shown in Figure 6, the inner diameter of the chamber 64 is approximately constant, but an annular projection 64d projecting radially inward is formed on the inner circumferential surface of the chamber 64 on the second end 64b side.

[0030] The outer surface of the chamber 64 is provided with a positioning section 64e into which the second magnetic coupling 70 is positioned. The positioning section 64e comprises a circular partition wall 64f arranged on the outer circumferential surface of the chamber 64 and an annular side wall 64g protruding from the periphery of the partition wall 64f. The positioning section 64e is hermetically sealed to prevent foreign matter from entering the interior of the chamber 64 through the positioning section 64e.

[0031] (Holder 66 for the second optical component 62) The holder 66 holds the optical element 74 housed in the chamber 64. The holder 66 is cylindrical and made of a non-magnetic material. The optical element 74 is fixed to one axial end of the holder 66. In this embodiment, a half-wave plate is fixed as the optical element 74, but the optical element 74 is not limited to a half-wave plate and may be, for example, a quarter-wave plate, a polarizer, a diffraction grating, a wedge prism, etc. The holder 66 has a first portion 66a to which the optical element 74 is fixed, a second portion 66b with a smaller diameter than the first portion 66a, and a third portion 66c with a smaller diameter than the second portion 66b. A male screw 66d is formed at the tip of the third portion 66c (the end opposite to the end to which the optical element 74 is fixed) (see Figure 5(a)). As the holder 66 is housed in the chamber 64, as shown in Figure 6, the first portion 66a of the holder 66 and the annular projection 64d of the chamber 64 come into contact, positioning the holder 66 in a predetermined position within the chamber 64.

[0032] The holder 66 is housed in the chamber 64 via a non-magnetic bearing 76 so as to be rotatable about an axis Ay (see Figure 6) extending along the Y-axis. The bearing 76 may be a sliding bearing or a rolling bearing. As shown in Figure 6, the Y-axis position of the bearing 76 is defined by the contact between the Y-axis end of the bearing 76 (the left end in Figure 6) and the second portion 66b of the holder 66. In addition, there is a gap of several micrometers between the bearing 76 and the annular projection 64d of the chamber 64 in the Y-axis direction.

[0033] (First magnetic coupling 68 of the second optical component 62) The first magnetic coupling 68 is connected to the holder 66. The first magnetic coupling 68 comprises a cylindrical fitting portion 68a made of a non-magnetic material and a cylindrical magnet 68b mounted on the outer circumferential surface of the fitting portion 68a. The magnet 68b is magnetized alternately with north and south poles in the circumferential direction. Alternatively, the magnet 68b may be in a form in which multiple magnets are aligned in the circumferential direction and mounted on the fitting portion 68a. When connecting the first magnetic coupling 68 to the holder 66, the inner circumferential surface of the fitting portion 68a is fitted to the outer circumferential surface of the holder 66, and then the annular leaf spring 78 and the cylindrical fastener 80 are attached to the holder 66. As a result, the bearing 76 and the first magnetic coupling 68 are brought into close contact by the annular leaf spring 78, and the end of the bearing 76 is brought into close contact with the side surface of the second portion 66b of the holder 66. Furthermore, a female thread 80a is formed on the inner circumferential surface of the cylindrical fastener 80, and the fastener 80 is attached to the holder 66 by the engagement of the female thread 80a of the fastener 80 with the male thread 66d of the holder 66. The leaf spring 78 and the fastener 80 are non-magnetic materials.

[0034] (Second magnetic coupling 70 of the second optical component 62) The second magnetic coupling 70 is positioned outside the chamber 64 and is interlocked with the first magnetic coupling 68. The second magnetic coupling 70 comprises a circular substrate 70a made of a non-magnetic material and a disc-shaped magnet 70b mounted on the lower surface of the substrate 70a. The north and south poles of the magnet 70b extend radially from the center of the magnet 70b and are arranged alternately in the circumferential direction. The second magnetic coupling 70 is supported by appropriate brackets (not shown) so as to be rotatable about an axis Az extending along the Z-axis direction, and is positioned in the positioning section 64e of the chamber 64. The second magnetic coupling 70 positioned in the positioning section 64e is covered by a non-magnetic cover 82. A through hole 82a for passing the drive shaft 72 is provided in the center of the cover 82.

[0035] Furthermore, the first and second magnetic couplings 68 and 70 are not limited to the above-described forms and various configurations can be adopted. For example, regarding the relationship between the axes of the first and second magnetic couplings 68 and 70, in this embodiment, the axis Ay of the first magnetic coupling 68 and the axis Az of the second magnetic coupling 70 are orthogonal, but the axes of the first and second magnetic couplings 68 and 70 may be parallel. Also, regarding the shape of the second magnetic coupling 70, in this embodiment it is disc-shaped, but it may be cylindrical with alternating N and S poles magnetized in the circumferential direction.

[0036] (Drive shaft 72 of the second optical component 62) The drive shaft 72 is connected to the second magnetic coupling 70. Specifically, the drive shaft 72 is fixed to the upper surface of the substrate 70a of the second magnetic coupling 70. Although not shown in the figures, the drive shaft 72 may be equipped with a motor (for example, a pulse motor) to rotate it. Alternatively, the drive shaft 72 may be rotated manually around axis Az. The drive shaft 72 is made of a non-magnetic material.

[0037] In the second optical component 62, the drive shaft 72 rotates around axis Az, causing the second magnetic coupling 70 connected to the drive shaft 72 to rotate around axis Az. As a result, the attraction and repulsion between the magnet 70b of the second magnetic coupling 70 and the magnet 68b of the first magnetic coupling 68 causes the first magnetic coupling 68 to rotate around axis Ay. This causes the holder 66 connected to the first magnetic coupling 68 and the optical element 74 held by the holder 66 to rotate around axis Ay. Consequently, the rotation angle of the optical element 74 through which the laser beam LB passes is adjusted. Thus, in the second optical component 62, even if the optical element 74 is isolated from the external environment by the chamber 64, the rotation of the drive shaft 72 around axis Az allows the optical element 74 to be rotated around axis Ay.

[0038] (Additional optical component 63 of attenuator 34) As shown in Figures 4(a) and 4(b), the chamber 84 of the additional optical component 63 comprises a first end 84a that receives light and a second end 84b that sends out light. The first end 84a and the second end 84b are provided with connecting portions 84c that can be connected to the connecting portion 64c of the second optical component 62. A sealing member (not shown), such as an O-ring or gasket, is provided between the connecting portions 64c and 84c. Inside the chamber 84 are a damper (not shown) that absorbs light and a beam splitter (not shown) that branches the light incident from the first end 84a and guides it to the second end 84b and also to the damper. The beam splitter may be of plate type or cube type.

[0039] The laser beam LB, incident from the first end 64a into the chamber 64 of the second optical component 62, is then incident from the first end 84a into the chamber 84 of the additional optical component 63 after the amount of P-polarized and S-polarized light is adjusted in the optical element 74 (half-wave plate) for the beam splitter of the additional optical component 63. Of the laser beam LB incident on the additional optical component 63, the P-polarized light is transmitted through the beam splitter and sent out from the second end 84b of the chamber 84, while the S-polarized light is reflected by the beam splitter, guided to the damper, and absorbed. The attenuator 34 is configured to rotate the optical element 74 (half-wave plate) by rotating the drive shaft 72 of the second optical component 62, thereby adjusting the ratio of P-polarized light (the ratio sent out from the second end 84b). In this way, the attenuator 34 adjusts the output of the laser beam LB incident on the second optical component 62 and sends it out from the additional optical component 63.

[0040] Although not shown in the diagram, the chamber 84 of the additional optical component 63 may be provided with a third end for sending out S-polarized light reflected by the beam splitter, instead of a damper. This allows the laser beam LB incident on the second optical component 62 to be split into P-polarized and S-polarized light in an appropriate ratio, sending out P-polarized light from the second end 84b of the chamber 84 of the additional optical component 63 and S-polarized light from the third end of the chamber 84. In other words, it can be configured not as an attenuator 34 for adjusting the output of the laser beam LB, but as a branching means for splitting the laser beam LB in any ratio.

[0041] (Third optical component 36 of the laser beam irradiation means 6) The third optical component 36 is configured as an angle adjuster that adjusts the angle of the optical path of the laser beam LB whose output has been adjusted by the attenuator 34. As shown in Figures 7(a) and 7(b), the third optical component 36 includes a chamber 86, a holder 88, a housing 92 that houses a first magnetic coupling 90 and a second magnetic coupling (not shown), and a drive shaft 94.

[0042] (Chamber 86 of the third optical component 36) The chamber 86 has a non-magnetic upper chamber 86a and a non-magnetic lower chamber 86b connected to the lower surface of the upper chamber 86a.

[0043] (Upper chamber 86a) The upper chamber 86a comprises a first end 86c for receiving light and a second end 86d for sending out light. The optical path within the upper chamber 86a is defined such that a laser beam LB incident from the first end 86c along the Y-axis direction is emitted from the second end 86d along the X-axis direction. The first end 86c and the second end 86d are also provided with a connecting portion 86e that can be connected to a connecting portion 84c of an additional optical component 63 of the attenuator 34. A sealing member such as an O-ring or gasket (not shown) is provided between the connecting portion 84c and the connecting portion 86e.

[0044] (Lower chamber 86b) The lower chamber 86b is airtightly connected to the lower surface of the upper chamber 86a. This prevents foreign matter from entering the interior of the chamber 86 from between the upper chamber 86a and the lower chamber 86b. As shown in Figure 7(a), the upper surface of the lower chamber 86b is provided with a housing hole 86f for housing the first magnetic coupling 90. A second magnetic coupling is also connected to the lower chamber 86b, as will be described later, and a partition member (not shown) is provided between the second magnetic coupling and the first magnetic coupling 90. The partition member of the lower chamber 86b prevents foreign matter from entering from the second magnetic coupling side to the first magnetic coupling 90 side (inside the chamber 86).

[0045] (Holder 88 for the third optical component 36) The holder 88 holds the optical element 96 housed in the upper chamber 86a. The holder 88, made of a non-magnetic material, has a disc-shaped main portion 88a and a cylindrical portion (not shown) extending downward from the lower surface of the main portion 88a. The optical element 96 is a prism mirror that reflects the laser beam LB incident on the upper chamber 86a from a first end 86c and guides it to a second end 86d, and is fixed to the upper surface of the main portion 88a of the holder 88. The optical element 96 may also be a plate-shaped mirror. The holder 88 is housed in the chamber 86 so as to be rotatable about an axis Az extending along the Z-axis direction, via a non-magnetic bearing 98. The bearing 98 is mounted on the cylindrical portion of the holder 88 and rotatably fits into a housing hole 86f of the lower chamber 86b.

[0046] (First magnetic coupling 90 of the third optical component 36) The first magnetic coupling 90 is connected to the holder 88. The first magnetic coupling 90 comprises a cylindrical connecting portion (not shown) fixed to the cylindrical part of the holder 88, and a cylindrical magnet 90a mounted on the outer surface of the connecting portion. The magnet 90a is magnetized alternately with north and south poles in the circumferential direction. Alternatively, the magnet 90a may be configured as multiple magnets aligned in the circumferential direction and mounted on the connecting portion.

[0047] (Second magnetic coupling of the third optical component 36) The second magnetic coupling is positioned outside the upper chamber 86a and is interlocked with the first magnetic coupling 90. The second magnetic coupling is cylindrical or disc-shaped and is housed in a non-magnetic housing 92 so as to be rotatable about an axis Ay extending along the Y-axis. The north and south poles of the magnets of the second magnetic coupling are arranged alternately in the circumferential direction. The housing 92 is mounted on the lower chamber 86b.

[0048] Furthermore, the first magnetic coupling 90 and the second magnetic coupling are not limited to the above-described forms and various configurations can be adopted. For example, regarding the relationship between the axes of the first magnetic coupling 90 and the second magnetic coupling, in the fourth embodiment, the axis Az of the first magnetic coupling 90 and the axis Ay of the second magnetic coupling are orthogonal, but the axes of the first magnetic coupling 90 and the second magnetic coupling may be parallel.

[0049] (Drive shaft 94 of the third optical component 36) The drive shaft 94 is connected to a second magnetic coupling. Although not shown, the drive shaft 94 may be equipped with a motor (for example, a pulse motor) to rotate it. Alternatively, the drive shaft 94 may be manually rotated around axis Az. The drive shaft 94 is made of a non-magnetic material.

[0050] In the third optical component 36, the drive shaft 94 rotates around the axis Ay, causing the second magnetic coupling connected to the drive shaft 94 to rotate around the axis Ay. As a result, the attraction and repulsion between the magnet of the second magnetic coupling and the magnet 90a of the first magnetic coupling 90 causes the first magnetic coupling 90 to rotate around the axis Az. This causes the holder 88 connected to the first magnetic coupling 90 and the optical element 96 held by the holder 88 to rotate around the axis Az. Consequently, the angle of the optical path of the laser beam LB, which enters from the first end 86c of the upper chamber 86a and exits from the second end 86d, is adjusted. In other words, in the third optical component 36, even if the optical element 96 is isolated from the external environment by the chamber 86, the angle of the optical path of the laser beam LB can be adjusted by rotating the drive shaft 94 around the axis Ay, thereby rotating the optical element 96 around the axis Az.

[0051] (Fourth optical component 38 of the laser beam irradiation means 6) The fourth optical component 38 is configured as a focuser that concentrates the laser beam LB, whose optical path angle has been adjusted by the third optical component 36. As shown in Figures 8(a) and 8(b), the fourth optical component 38 includes a chamber 100, a holder 102, a housing 106 that houses a first magnetic coupling 104 and a second magnetic coupling (not shown), and a drive shaft 108.

[0052] (Chamber 100 of the fourth optical component 38) Chamber 100 comprises a first end 100a for receiving light and a second end 100b for sending out light. Chamber 100 is cylindrical and made of a non-magnetic material. The optical path within Chamber 100 is defined along the axial direction (Z-axis direction) of Chamber 100 from the first end 100a to the second end 100b. The first end 100a is provided with a connecting portion 100c that can be connected to a connecting portion 86e of the third optical component 36. A sealing member (not shown) such as an O-ring or gasket is provided between the connecting portion 86e and the connecting portion 100c. On the other hand, the second end 100b does not have a connecting portion, but a cover glass 100d is fitted to prevent foreign matter from entering the chamber 100. In addition, a pair of guide grooves 100e extending in the Z-axis direction are formed on the inner circumferential surface of Chamber 100.

[0053] (Holder 102 for the fourth optical component 38) The holder 102 holds the optical element 110 housed within the chamber 100. The holder 102 is cylindrical and made of a non-magnetic material. The optical element 110 is a set of lenses (lens assembly) that focus the laser beam LB, and is fixed inside the holder 102. Figure 8(a) shows two lenses as a simplified representation of the optical element 110, but the number of lenses in the optical element 110 can be arbitrarily set. The holder 102 is housed within the chamber 100 so as to be movable (up and down) in the Z-axis direction via a non-magnetic guide bearing 112. The guide bearing 112 is mounted on the outer circumferential surface of the holder 102 and slidably fits into one of the guide grooves 100e of the chamber 100.

[0054] (First magnetic coupling 104 of the fourth optical component 38) The first magnetic coupling 104 is connected to the holder 102. The first magnetic coupling 104 is rectangular in shape and extends in the Z-axis direction, and is slidably fitted into the other guide groove 100e of the chamber 100. The first magnetic coupling 104 comprises a non-magnetic substrate 104a mounted on the outer circumferential surface of the holder 102, and a magnet 104b mounted on the outer surface of the substrate 104a. The magnet 104b is magnetized alternately with north and south poles in the Z-axis direction. Note that the magnet 104b may be in a configuration in which multiple magnets are aligned in the Z-axis direction.

[0055] (Second magnetic coupling of the fourth optical component 38) The second magnetic coupling is positioned outside the chamber 100 and is interlocked with the first magnetic coupling 104. The second magnetic coupling is cylindrical and is housed in a non-magnetic housing 106 so as to be rotatable about an axis Ax extending along the X-axis. The north and south poles of the magnets in the second magnetic coupling are arranged alternately in the circumferential direction. The housing 106 is mounted on the outer surface of the chamber 100, and a partition member (not shown) is provided between the housing 106 and the chamber 100. This partition member prevents foreign matter from entering the inside of the chamber 100.

[0056] (Drive shaft 108 of the fourth optical component 38) The drive shaft 108 is connected to a second magnetic coupling. Although not shown, the drive shaft 108 may be equipped with a motor (for example, a pulse motor) to rotate it. Alternatively, the drive shaft 108 may be manually rotated around axis Ax. The drive shaft 108 is made of a non-magnetic material.

[0057] In the fourth optical component 38, the drive shaft 108 rotates about axis Ax, causing the second magnetic coupling connected to the drive shaft 108 to rotate about axis Ax. As a result, the first magnetic coupling 104 moves in the Z-axis direction due to the attraction and repulsion between the magnet of the second magnetic coupling and the magnet 104b of the first magnetic coupling 104. This causes the holder 102 connected to the first magnetic coupling 104 and the optical element 110 held by the holder 102 to move in the Z-axis direction. Consequently, the Z-axis position of the focal point of the laser beam LB, which enters from the first end 100a of the chamber 100 and exits from the second end 100b, is adjusted. In other words, in the fourth optical component 38, even if the optical element 110 is isolated from the external environment by the chamber 100, the focal point of the laser beam LB can be adjusted by raising and lowering the optical element 110 by rotating the drive shaft 108.

[0058] Referring to Figure 2, in the laser beam irradiation means 6 which can be configured as described above, the laser beam LB emitted from the laser oscillator 30 along the Y-axis is first adjusted in beam diameter by a first optical component 32 (beam expander), and then its output is adjusted by an attenuator 34 including a second optical component 62. The laser beam LB with adjusted output is first converted from the Y-axis direction to the X-axis direction by a first third optical component 36 (angle adjuster), and then converted from the X-axis direction to the Z-axis direction by a second third optical component 36 (angle adjuster). The laser beam LB with the converted Z-axis direction is then focused by a fourth optical component 38 (focuser) and irradiated onto the workpiece held by the holding means 4.

[0059] (X-axis feed means 8 of laser processing device 2) As shown in Figure 1, the X-axis feed mechanism 8 includes a ball screw 114 connected to the X-axis movable plate 14 and extending in the X-axis direction, and a motor 116 that rotates the ball screw 114. The X-axis feed mechanism 8 converts the rotational motion of the motor 116 into linear motion using the ball screw 114 and transmits it to the X-axis movable plate 14, moving the X-axis movable plate 14 along the guide rail 12a on the base 12 in the X-axis direction. As a result, the chuck table 22 of the holding mechanism 4 is machine-feeded in the X-axis direction relative to the fourth optical component 38 (concentrator).

[0060] (Y-axis feed mechanism 10 of laser processing device 2) The Y-axis feed mechanism 10 includes a ball screw 118 connected to the Y-axis movable plate 16 and extending in the Y-axis direction, and a motor 120 that rotates the ball screw 118. The Y-axis feed mechanism 10 converts the rotational motion of the motor 120 into linear motion using the ball screw 118 and transmits it to the Y-axis movable plate 16, moving the Y-axis movable plate 16 in the Y-axis direction along the guide rail 14a on the X-axis movable plate 14. As a result, the chuck table 22 of the holding mechanism 4 is machine-feeded in the Y-axis direction relative to the fourth optical component 38 (concentrator).

[0061] (Workpiece) Figure 1 also shows a disc-shaped wafer 122 as a workpiece that can be processed by the laser processing apparatus 2. The wafer 122 may be formed from a semiconductor material such as silicon. The surface 122a of the wafer 122 is divided into a plurality of rectangular regions by grid-like division lines 124. A device 126 such as an IC or LSI is formed in each of the plurality of rectangular regions. The wafer 122 is also supported on an annular frame 130 via a tape 128. Figure 1 shows an example in which the back surface 122b of the wafer 122 is attached to the tape 128, but the surface 122a of the wafer 122 may also be attached to the tape 128.

[0062] (Laser processing method) Next, preferred embodiments of the laser processing method according to the present invention will be described.

[0063] (preparation process) In this embodiment, first, the laser processing apparatus 2 described above is prepared.

[0064] (holding process) After the preparation process is carried out, a holding process is performed in which the wafer 122 is held by the holding means 4. In the holding process, first, the wafer 122 is placed on the upper surface of the chuck table 22 of the holding means 4. Next, a suction force is generated in the suction chuck 24 by the suction means, and the wafer 122 is held by suction on the upper surface of the chuck table 22. In addition, the annular frame 130 is fixed with multiple clamps 26.

[0065] (Laser processing process) After the holding process is performed, a laser processing process is carried out in which a laser beam LB is irradiated onto the wafer 122 held by the holding means 4 to divide the wafer 122 into individual chips. In the laser processing process, first, the focal point of the laser beam LB is positioned on the division line 124 of the wafer 122. At this time, the wafer 122 is imaged by the imaging means 40, and the division line 124 of the wafer 122 is aligned in the X-axis direction by rotating the chuck table 22 as appropriate based on the image of the wafer 122 captured by the imaging means 40. Then, the focal point of the laser beam LB is positioned on the division line 124 aligned in the X-axis direction. The vertical position of the focal point can be arbitrary.

[0066] In the laser processing process, once the focal point of the laser beam LB is positioned at the required location, the laser beam LB is irradiated onto the wafer 122 along the planned division line 124 to perform laser processing. For example, by irradiating the wafer 122 with a laser beam LB of a wavelength that is transparent to the wafer 122 from the fourth optical component 38 (concentrator) while feeding the chuck table 22 in the X-axis direction, a starting point for division can be formed inside the planned division line 124. Alternatively, by irradiating the wafer 122 with a laser beam LB of a wavelength that is absorbed by the wafer 122 from the fourth optical component 38 (concentrator) while feeding the chuck table 22 in the X-axis direction, ablation processing can be performed along the planned division line 124 to form a division groove. Then, the chuck table 22 is repeatedly irradiated with the laser beam LB while indexing and feeding it in the Y-axis direction by the amount of the spacing of the division lines 124 in the Y-axis direction, thereby performing laser processing on all of the division lines 124 aligned in the X-axis direction. Furthermore, the chuck table 22 is rotated 90 degrees, and the irradiation of the laser beam LB and indexing and feeding are repeated alternately, thereby performing laser processing on all of the division lines 124 that are orthogonal to the division lines 124 that have been laser processed earlier. If a starting point for division has been formed, the wafer 122 can be divided into individual chips along the starting point by applying an external force to the wafer 122.

[0067] As described above, in the laser beam irradiation means 6 of this embodiment, the optical elements 58, 74, 96, 110 and lens 48d of the first to fourth optical components 32, 62, 36, 38 are isolated from the external environment by chambers 48, 64, 86, 100. In addition, the laser light source of the laser oscillator 30 is also isolated from the external environment by chamber 44. Therefore, with the laser processing apparatus 2, it is possible to prevent dirt from adhering to the optical elements 58, 74, 96, 110 and lens 48d, and the problem of reduced performance of the optical elements 58, 74, 96, 110 and lens 48d is eliminated. Furthermore, since the laser processing apparatus 2 of this embodiment does not have the problem of reduced performance of the optical elements 58, 74, 96, 110 and lens 48d, it is less prone to failure and has a long lifespan.

[0068] According to the laser processing method of this embodiment, since the laser processing apparatus 2 is used, the optical elements 58, 74, 96, 110 and the lens 48d are shielded from the external environment, preventing dirt from adhering to the optical elements 58, 74, 96, 110 and the lens 48d. Therefore, the wafer 122 can be processed stably without the problem of performance degradation of the optical elements 58, 74, 96, 110 and the lens 48d. In addition, since the laser processing apparatus 2 is less prone to failure and has a long lifespan, the unit cost of the chips can be reduced.

[0069] Furthermore, it is preferable that the chambers 48, 64, 86, and 100 of the first to fourth optical components 32, 62, 36, and 38, the chamber 44 of the laser oscillator 30, and the chamber 84 of the additional optical component 63 are filled with dry air or an inert gas (e.g., nitrogen gas) at a pressure slightly higher than atmospheric pressure, as this more effectively prevents foreign matter from entering the interiors of the first to fourth optical components 32, 62, 36, and 38. In this case, although not shown, a communication hole is provided to connect the interiors of the chambers, and a supply port connected to a supply means for supplying dry air or an inert gas is provided in one of the chambers. When dry air or an inert gas is supplied from the supply port, it spreads throughout the interiors of the chambers via the communication hole.

[0070] Alternatively, the chambers 48, 64, 86, and 100 of the first to fourth optical components 32, 62, 36, and 38, the chamber 44 of the laser oscillator 30, and the chamber 84 of the additional optical component 63 may be reduced in pressure to a substantially vacuum state. When the chambers are substantially vacuum state, obstruction of the laser beam LB within the chambers can be suppressed. In this case, although not shown, communication holes are provided to connect the interiors of the chambers, and a suction port connected to a suction means is provided in one of the chambers. When the suction means is activated, the pressure inside the chambers is reduced through the suction port and the communication holes.

[0071] The configuration of the laser beam irradiation means 6 is not limited to the configuration described above. For example, a second optical component 62 having a quarter-wave plate as an optical element 74 may be provided downstream of the attenuator 34 (between the third optical component 36 as the first angle adjuster and the third optical component 36 as the next angle adjuster). This converts the linearly polarized laser beam LB (P-polarization component) sent from the attenuator 34 into circularly polarized light by the quarter-wave plate. By converting the laser beam LB into circularly polarized light, the influence of the polarization plane on laser processing can be reduced. [Explanation of Symbols]

[0072] 2: Laser processing equipment 4: Holding means 6: Laser beam irradiation means 8: X-axis feed mechanism 10: Y-axis feed mechanism 32: First optical component 34: Attenuator 36: The third optical component 38: The fourth optical component 48: Chamber 48a: First end 48b: Second end 48c: Connection part 50: Holder 52: First Magnet Coupling 56: Drive shaft 58: Optical elements 62: Second optical component 64: Chamber 64a: First end 64b: Second end 64c: Connection part 66: Holder 68: First Magnet Coupling 70: Second Magnet Coupling 72: Drive shaft 74: Optical elements 86: Chamber 86a: Upper chamber 86b: Lower chamber 86c: First end 86d: Second end 86e: Connecting part 88: Holder 90: First magnetic coupling 94: Drive shaft 96: Optical elements 100: Chamber 100a: First end 100b: Second end 100c: Connection part 102: Holder 104: First Magnet Coupling 108: Drive shaft 110: Optical element

Claims

1. A laser processing device, The system includes a holding means for holding a workpiece, a laser beam irradiation means equipped with a light concentrator for irradiating the workpiece held by the holding means with a laser beam, an X-axis feeding means for feeding the holding means and the light concentrator relative to each other in the X-axis direction, and a Y-axis feeding means for feeding the holding means and the light concentrator relative to each other in the Y-axis direction which is perpendicular to the X-axis direction. The laser beam irradiation means is A laser processing apparatus comprising an optical component, comprising: a non-magnetic chamber having a first end for receiving light and a second end for sending out light; a holder for holding an optical element housed in the chamber; a first magnetic coupling connected to the holder; a second magnetic coupling disposed outside the chamber and interlocked with the first magnetic coupling; and a drive shaft connected to the second magnetic coupling, wherein the optical element is driven by the rotation of the drive shaft.

2. The laser processing apparatus according to claim 1, wherein the drive shaft is equipped with a motor.

3. The laser processing apparatus according to claim 1, wherein the non-magnetic material includes aluminum, stainless steel, copper, brass, resin, glass, or ceramics.

4. The laser processing apparatus according to claim 1, wherein the chamber is filled with dry air or an inert gas containing nitrogen gas, or the pressure is reduced.

5. The laser processing apparatus according to claim 1, wherein the first end and the second end of the chamber are connected to each other by a connecting portion.

6. A laser processing method for dividing a wafer of a workpiece into individual chips, A preparation step for preparing the laser processing apparatus according to claim 1, A holding step of holding the wafer in the holding means, A laser processing step in which a laser beam is irradiated onto a wafer held by the holding means to divide the wafer into individual chips, A laser processing method including [specific type of laser processing].

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