JP7173809B2 - Laser processing method - Google Patents

Description

The present invention relates to a laser processing apparatus and a laser processing method using the apparatus.

In recent years, in order to improve the processing performance of semiconductor chips such as ICs and LSIs, inorganic films such as SiOF and BSG (SiOB), and polymer films such as polyimide and parylene have been applied to the surface of substrates such as silicon. A semiconductor wafer in which a semiconductor device is formed by a functional layer in which a low dielectric constant insulating film (Low-k film) made of an organic film is laminated has been put into practical use.

Since the Low-k film is very fragile like mica, the Low-k film peels off when it is cut along the dividing lines with a cutting blade. Therefore, laser processing grooves are formed by removing a laminate made of a Low-k film by irradiating a laser beam along a planned division line to perform ablation processing (see, for example, Patent Document 1). ).

JP 2015-126054 A

However, when the laminate is ablated, the scattered melted material of the laminate fills the laser-processed groove, so in order to form a laser-processed groove with a sufficient width, it is necessary to irradiate the laser beam several times along the dividing line. However, there is a problem of low productivity.

The present invention has been made in consideration of such problems, and prevents the molten material scattered by ablation processing from filling back the laser-processed groove without lowering productivity, thereby forming a laser-processed groove with a sufficient width. The challenge is to create

A laser processing method according to the present invention includes a chuck table having a holding surface for holding a workpiece, and a laser beam radiating the workpiece held by the chuck table along a line to be divided to cut the workpiece. laser processing means for processing, processing feed means for relatively moving the chuck table and the laser processing means in the X-axis direction, and the chuck table in the Y-axis direction orthogonal to the X-axis direction and the holding surface direction. index feeding means for relatively moving the laser processing means , wherein the laser processing means is orthogonal to the X-axis direction and the Y-axis direction A slope that is chamfered into a flat shape so that the lower side of each side surface that constitutes a regular polygonal prism faces downward at an angle of 45 degrees with respect to the Z-axis direction. a first laser beam irradiation means for emitting a laser beam downward in the Z-axis direction; a second laser beam irradiation means for emitting a laser beam from the opposite side; a switching means for switching between the first laser beam irradiation means and the second laser beam irradiation means; and a laser beam emitted by the first laser beam irradiation means. in the first direction in the Y -axis direction to irradiate the inclined surface of the polygon mirror ; a holding step of holding the workpiece on the chuck table ; moving the chuck table in one direction in the X-axis direction with respect to the laser beam irradiation means of (1), and irradiating the polygon mirror rotating in one direction either clockwise or counterclockwise when viewed from above with a laser beam; an outward machining step of machining the workpiece by reflecting the laser beam on the slope of the polygon mirror in the Z-axis direction; a backward machining step of irradiating the polygon mirror rotating in the same direction as the forward machining step with a laser beam and reflecting the laser beam in the Z-axis direction on the slope of the polygon mirror to machine the workpiece; and a repeating step of repeating the outward machining step and the inward machining step, wherein the outward machining step and the In the backward machining step, the chuck table is positioned in the Y-axis direction so that one of the slopes of the polygon mirror is positioned directly above the dividing line and the upper side of the slope is parallel to the X-axis direction. In the repeating step, the switching means turns off either the first laser beam irradiation means or the second laser beam irradiation means when processing and feeding in one of the X-axis directions. In addition, the other laser beam irradiation means is turned on to carry out outward machining, and when processing and feeding in the other direction of the X-axis direction, the other laser beam irradiation means that was turned on during the outward machining is turned off and the One of the laser beam irradiation means is turned on to carry out reverse processing.

In the laser processing method according to the present invention, the chuck table is moved in one direction of the X-axis direction with respect to the laser beam irradiation means, the rotating polygon mirror is irradiated with the laser beam, and the laser beam is reflected in the Z-axis direction by the slope of the polygon mirror. and moving the chuck table in the other direction of the X-axis with respect to the laser beam irradiation means to irradiate a polygon mirror rotating in the same direction as in the outward machining step with the laser beam. The rotation of the polygon mirror in one direction is stopped because it consists of a return machining step in which the workpiece is machined by reflecting it in the Z-axis direction on the slope of the mirror and a repetition step in which the forward machining step and the return machining step are repeated. Machining can be continuously performed on the outward and return passes of the chuck table without any need. In addition, since the laser beam is condensed on the workpiece while reciprocating within a certain range in the X-axis direction of the workpiece, the laser beam is emitted to the same place many times without having to reciprocate the workpiece by processing feed. Because it is possible to focus light, it is possible to prevent melted material scattered by ablation processing from filling back the laser processing groove without reducing productivity, and to form a laser processing groove with a sufficient width. Become.

It is a perspective view which shows an example of a laser processing apparatus. It is a top view which shows the 1st example of a laser processing means. It is a front view which shows the 1st example of a laser processing means. It is a perspective view which shows an example of a to-be-processed object. It is a top view which shows the 1st example of the procedure of laser processing. FIG. 10 is a plan view showing a second example of the procedure of laser processing; FIG. 5 is a plan view showing a second example of laser processing means; It is a front view which shows the 2nd example of a laser processing means. FIG. 10 is a plan view showing a second example of the procedure of laser processing; FIG. 10 is a plan view showing a third example of laser processing means;

1. First Embodiment A laser processing apparatus 1 shown in FIG. A processing means 6 is provided.

The chuck table 2 has a holding surface 21 that holds a workpiece, and a frame holding portion 22 that fixes a frame that supports the workpiece on the outer peripheral side of the holding surface 21 . The holding surface 21 and the frame holding portion 22 are driven by a rotation driving portion 23 and are rotatable by a predetermined angle.

The chuck table 2 is driven by the processing feed means 3 and is movable in the X-axis direction. The processing feed means 3 includes a ball screw 31 extending in the X-axis direction, a pair of guide rails 32 arranged parallel to the ball screw 31, a motor 33 for rotating the ball screw 31, and a nut screwed onto the ball screw 31. It is composed of a moving plate 34 which is provided inside and whose bottom part is in sliding contact with the guide rail 32, and a scale 35 for recognizing the position of the moving plate 34 in the X-axis direction. When the motor 33 rotates the ball screw 31, the moving plate 34 is guided by the guide rail 32 and moves in the X-axis direction. The chuck table 2 is fixed to a moving plate 34, and when the moving plate 34 moves in the X-axis direction, the chuck table 2 also moves in the same direction.

The chuck table 2 and the processing feed means 3 are driven by the index feed means 4 and are movable in the Y-axis direction. The index feeding means 4 includes a ball screw 41 extending in the X-axis direction, a pair of guide rails 42 arranged parallel to the ball screw 41, a motor 43 for rotating the ball screw 41, and a nut screwed onto the ball screw 41. It is composed of a moving plate 44 which is provided inside and whose bottom part is in sliding contact with the guide rail 42, and a scale 45 for recognizing the position of the moving plate 44 in the Y-axis direction. When the motor 43 rotates the ball screw 41, the moving plate 44 is guided by the guide rail 42 and moves in the Y-axis direction. Further, the processing feed means 3 is arranged on a moving plate 44, and when the moving plate 44 moves in the Y-axis direction, the chuck table 2 also moves in the same direction.

It should be noted that the processing feeding means may be configured to relatively feed the chuck table 2 and the laser processing means 6 in the X-axis direction. Therefore, for example, a configuration may be adopted in which the laser processing means 6 moves in the X-axis direction and the chuck table 2 does not move in the X-axis direction. Similarly, the index feeding means may be configured to relatively feed the chuck table 2 and the laser processing means 6 in the Y-axis direction. Therefore, for example, a configuration may be adopted in which the chuck table 2 moves in the Y-axis direction and the laser processing means 6 does not move in the Y-axis direction.

As shown in FIG. 2, the laser processing means 6 has a rotating shaft 630 which is formed in a regular polygonal prism shape (a regular hexagonal prism shape in the illustrated example) and which is parallel to the Z-axis direction perpendicular to the X-axis direction and the Y-axis direction. a first laser beam irradiation means 61 for irradiating the polygon mirror 63 with a laser beam from a first horizontal direction perpendicular to the rotation axis 630; A second laser beam irradiation means 62, a first laser beam irradiation means 61, and a second laser beam irradiation means 62 for irradiating a polygon mirror 63 with a laser beam from the second direction side which is point symmetrical with respect to the first direction. and switching means 64 for switching between and. In the example of FIG. 2, the direction of rotation is the direction of arrow R1, which is the clockwise direction when viewed from above, but it can also be the counterclockwise direction when viewed from above.

As shown in FIG. 2, the laser processing means 6 includes first direction changing means 65 for directing the laser beam emitted by the first laser beam irradiation means 61 and reflected by the polygon mirror 63 in the Z-axis direction; and second direction changing means 66 for directing the laser beam emitted by the laser beam irradiation means 62 and reflected by the polygon mirror 63 in the Z-axis direction.

The spacing between the first direction changing means 65 and the second direction changing means 66 can be adjusted by the spacing adjusting means 67 . By moving at least one of the first direction changing means 65 and the second direction changing means 66 in the Y-axis direction, the space adjusting means 67 moves the first direction changing means 65 and the second direction changing means 66 Adjust the spacing between

As shown in FIG. 3, the first direction changing means 65 comprises a first mirror 651 that reflects the laser beam in the Z-axis direction. Below the first mirror 651, a first condenser 681 is provided for condensing the laser beam reflected by the first mirror 651 onto the workpiece. The second direction changing means 66 also has a second mirror 661 that reflects the laser beam in the Z-axis direction. Below the second mirror 661 is provided a second condenser 682 for condensing the laser beam reflected by the second mirror 661 onto the workpiece.

The first mirror 651 has a reflecting surface inclined 45 degrees vertically with respect to the traveling direction of the laser beam so that the laser beam reflected by the polygon mirror 63 is directed toward the workpiece held on the chuck table 2 . It is The reflecting surface of the second mirror 661 is also tilted by 45 degrees with respect to the traveling direction of the laser beam so that the laser beam reflected by the polygon mirror 63 is directed toward the workpiece held on the chuck table 2 . It is

The first laser beam irradiation means 61 is directed toward the polygon mirror 63 from one side of the X-axis direction (+X direction side) which is a predetermined distance away from the rotating shaft 630 in one direction of the Y-axis direction (-Y direction). Irradiate with a laser beam. In addition, the second laser beam irradiation means 62 emits light onto the polygon mirror 63 from the other side of the X-axis direction (−X direction), which is a predetermined distance away from the rotating shaft 630 in the other direction of the Y-axis direction (+Y direction). Shoot a laser beam at it.

The interval adjustment means 67 is controlled by control means 69 . The control means 69 can adjust the gap between the first mirror 651 and the second mirror 661 by controlling the gap adjusting means 67 .

A case will be described below in which the wafer W shown in FIG. 4 is used as a workpiece and the wafer W is processed using the laser processing apparatus 1 shown in FIGS. 1-3. Here, as shown in FIG. 4, on the front surface Wa of the wafer W, devices D are formed in regions partitioned by dividing lines L formed vertically and horizontally, and the device D is cut along the dividing lines L. Therefore, it is divided into chips for each individual device D. FIG. A low dielectric constant insulating film (Low-k film) is laminated on the front surface Wa of the wafer W. As shown in FIG.

(1) Holding Process As shown in FIG. A ring-shaped frame F is adhered to the peripheral portion of the tape T. As shown in FIG. The wafer W thus supported by the frame F via the tape T is held by suction on the chuck table 2 .

(2) Processing Step In this step, the Low-k film is removed along the dividing lines L by laser ablation processing. In addition, before the processing, the planned division line L of the wafer W is detected using an imaging means (not shown).

(2-1) Outward processing step As shown in FIG. 5(a), the laser beam is emitted from the first laser beam irradiation means 61 so as to irradiate the laser beam on the dividing line L1 to be first ablated. The laser beam is reflected by the +X side surface of the side surfaces of the polygon mirror 63, the reflected light is reflected in the -Y direction, and the center of the first mirror 651 in the Y-axis direction is positioned directly above the planned division line L1. , the position of the chuck table 2 in the Y-axis direction is adjusted. Such adjustment of the position of the chuck table 2 in the Y-axis direction is performed by the index feeding means 4 shown in FIG.

With the first mirror 651 thus positioned at a predetermined position, the polygon mirror 63 is rotated around the rotation axis 630 in the direction of arrow R2 (counterclockwise direction) as viewed from above. Note that the rotation direction of the polygon mirror 63 can also be clockwise when viewed from above. Then, while moving the chuck table 2 in, for example, the +X direction (forward feeding direction), the laser beam LB1 is emitted from the +X direction (first direction) by the first laser beam irradiation means 61 . Then, the laser beam LB1 is reflected by the side surface of the polygon mirror 63 and guided in the -Y direction, and then reflected by the first mirror 651 and guided in the -Z direction. Further, the reflected laser beam is focused on the Low-k film laminated on the surface Wa of the wafer W by the first collector 681 shown in FIG. When the laser beam is focused on the Low-k film in this manner, ablation processing is performed along the planned division line L1 in the forward direction of the chuck table 2, and the Low-k film on the planned division line L1 is removed. Then, an ablation groove (laser-processed groove) A1 is formed.

Here, since the laser beam LB1 is emitted while the polygon mirror 63 is being rotated, the laser beam reflected by one side surface 631 of the polygon mirror 63 moves in the X-axis direction within the range from the reflected laser beam LB11 to the reflected laser beam LB12. However, if the range from the laser reflected light LB11 to the laser reflected light LB12 always hits the first mirror 651, all of them can be condensed on the planned dividing line L1. Therefore, by emitting the laser beam LB1 while rotating the polygon mirror 63, the condensing position can be reciprocated at the same position on the line to be divided. In both cases, it is possible to form an ablation groove with a sufficient width while preventing backfilling of the molten material. Such processing is repeated several times to form the ablation grooves A1 along the entire length of the planned division line L1.

(2-2) Inward processing step Next, as shown in FIG. 5B, the laser beam is emitted from the second laser beam irradiation means 62 so as to irradiate the laser beam on the planned division line Lm to be ablated. The reflected laser beam is reflected by the -X side surface of the side surfaces of the polygon mirror 63, and the reflected light is reflected in the +Y direction, and the center of the second mirror 661 is positioned directly above the planned division line Lm. Adjust the position of the chuck table 2 in the Y-axis direction. Here, the position of the second mirror 661 in the Y-axis direction is adjusted in advance so that the distance in the Y-axis direction from the first mirror 651 is the distance DY between the line to be divided L1 and the line to be divided Lm. Keep Here, the interval DY is a distance obtained by multiplying the interval between the adjacent dividing lines of the wafer W by an integer of 2 or more. 2 mirror 661.

With the second mirror 661 thus positioned at a predetermined position, the polygon mirror 63 is kept rotating in the direction of the arrow R2 about the rotation axis 630, and the chuck table 2 is moved in the -X direction (return feeding direction), for example. , the first laser beam irradiation means 61 emits a laser beam LB2 from the -X direction (second direction). Then, the laser beam LB2 is reflected by the side surface of the polygon mirror 63 and guided in the +Y direction, and then reflected by the second mirror 661 and guided in the -Z direction. Further, the reflected laser beam is focused on the Low-k film laminated on the surface Wa of the wafer W by the second collector 682 shown in FIG. When the laser beam is focused on the Low-k film in this way, ablation processing is performed along the planned division line Lm in the return direction of the chuck table 2, and the Low-k film on the planned division line Lm is removed. and the ablation groove Am is formed. It is the same as the outward machining process in that the condensing position can be reciprocated at the same place on the line to be divided by rotating the polygon mirror 63 .

(2-3) Repetitive process After the return machining process, return to the forward machining process. In this case, as shown in FIG. 5(c), the line to be ablated next, for example, the line to be divided next to the line to be divided L1 on which the ablation grooves A1 are formed in the first outward processing step, is to be cut along the line to be divided L2. In order to irradiate the laser beam, the laser beam emitted from the first laser beam irradiation means 61 is reflected by the +X side surface of the side surfaces of the polygon mirror 63, the reflected light is reflected in the -Y direction, and is scheduled to be divided. The position of the chuck table 2 in the Y-axis direction is adjusted so that the center of the first mirror 651 in the Y-axis direction is located directly above the line L2. Here, the interval in the Y-axis direction between the first mirror 651 and the second mirror 661 may be maintained at the initially set interval DY. Then, similarly to the formation of the ablation grooves A1, the laser beam LB1 is emitted from the +X direction (first direction) by the first laser beam irradiation means 61 to form the ablation grooves A2 (forward processing step).

After forming the ablation grooves A2, the process returns to the backward machining step. That is, the chuck table 2 is arranged so that the center of the second mirror 661 in the Y-axis direction is positioned so that the laser beam is applied to the planned division line on the +Y side of the planned division line Lm on which the ablation groove Am is formed. position in the Y-axis direction. Here, the interval in the Y-axis direction between the first mirror 651 and the second mirror 661 may be maintained at the initially set interval DY. Then, similarly to the formation of the ablation grooves Am, the laser beam LB2 is emitted from the -X direction (second direction) by the second laser beam irradiation means 62 to form the ablation grooves (return processing step).

In this process, by repeating the forward machining process and the backward machining process as described above, ablation grooves are formed in all the lines to be divided arranged in the same direction. Further, if the chuck table 2 is rotated by 90 degrees and then similar ablation processing is performed, ablation grooves are formed in all directions on all the lines to be divided.

The order of forming the ablation grooves is not limited to the example shown in FIG. For example, as shown in FIG. 6, the odd-numbered division lines L1, L3, L5, . It can also be formed in a process. That is, as shown in FIG. 6(a), for the planned division line L3, the laser beam emitted from the first laser beam irradiation means 61 is used to form the ablation groove A3 in the outward processing step, and then the ablation groove A3 is formed as shown in FIG. As shown in b), the ablation grooves A4 are formed by the laser beam emitted from the second laser beam irradiation means 62 in the backward machining step. Next, as shown in FIG. 6(c), an ablation groove A5 is formed by a laser beam emitted from the first laser beam irradiation means 61 in the outward machining step. In this way, adjacent lines to be divided are alternately ablated in the outward machining process and the inward machining process.

In the examples shown in FIGS. 5 and 6, the switching means 64 turns on the first laser beam irradiation means 61 and turns off the second laser beam irradiation means 62 in the outward machining process. 3, the second laser beam irradiation means 62 may be turned on and the first laser beam irradiation means 61 may be turned off. In this case, in the backward processing step, the switching means 64 turns on the first laser beam irradiation means 61 and turns off the second laser beam irradiation means 62 .

2. Second Embodiment Instead of the laser processing means 6 shown in FIGS. 1-3, a laser processing means 7 shown in FIG. 7 can be used. This laser processing means 7 includes a polygon mirror 73 continuously rotating in one direction around a rotating shaft 730 parallel to the Z-axis direction perpendicular to the X-axis direction and the Y-axis direction, and a horizontal rotating shaft perpendicular to the rotating shaft 730 . A first laser beam irradiating means 71 for irradiating a polygon mirror 73 with a laser beam from the +X direction (first direction) and a -X direction (second and a second laser beam irradiation means 72 for irradiating the polygon mirror 73 with a laser beam from the direction ). Switching means for switching between the first laser beam irradiation means 71 and the second laser beam irradiation means 72 may be provided.

As shown in FIG. 8, the polygon mirror 73 is formed in a shape in which the lower sides of the side surfaces 731 forming a regular hexagonal prism are obliquely chamfered into a planar shape. Each side surface 731 is formed by an inclined surface facing downward at 45 degrees with respect to the Z-axis direction (vertical direction) so as to direct the reflected laser beam toward the wafer W below. That is, the polygon mirror 73 has a shape in which a regular hexagonal frustum is turned upside down. A first mirror 751 is arranged on one side surface 731 of the polygon mirror 73 in the -Y direction, and a second mirror 761 is arranged on another side surface 731 of the polygon mirror 73 in the +Y direction. are arranged. A first light collector 752 is arranged below the side surface 731 of the polygon mirror 73, and a second light collector 762 is arranged below another side surface 731 of the polygon mirror 73. there is

The first mirror 751 irradiates a laser beam toward the polygon mirror 73 from one Y-axis direction side (−Y direction side) of the rotation axis 730 , and the second mirror 761 uses the rotation axis 730 as a reference. , and irradiates the polygon mirror 73 with a laser beam from the other Y-axis direction side (+Y direction side) of the rotating shaft 730 . That is, the laser beam emitted in the -Z direction from the first laser beam irradiation means 71 is reflected by the first mirror 751 and guided in the +Y direction, and reflected by one side surface 731 of the polygon mirror 73 in the -Z direction. It is guided and focused onto the wafer W by the first collector 752 . On the other hand, the laser beam emitted from the second laser beam irradiation means 72 is reflected by the second mirror 761 and guided in the -Y direction, reflected by one side surface 731 of the polygon mirror 73 and guided in the -Z direction, It is focused on the wafer W by the second light collector 762 . Thus, the laser beam can be guided in the -Z direction without a mirror for guiding the laser beam in the -Z direction.

In the following, the laser processing means 7 shown in FIGS. 7 and 8 is used to perform ablation processing along the dividing line L of the wafer W shown in FIG. 4. As shown in FIG.

(1) Holding process As shown in FIG. The wafer W supported by the frame F is held by suction on the chuck table 2 .

(2) Processing Step In this step, the Low-k film is removed along the dividing lines L by laser ablation processing. In addition, before the processing, the planned division line L of the wafer W is detected using an imaging means (not shown).

(2-1) Outward processing step As shown in FIG. 9(a), the laser beam emitted from the first laser beam irradiation means 71 is irradiated onto the scheduled division line L1 to be first ablated. Adjust the position of the chuck table 2 in the Y-axis direction. Such adjustment of the position of the chuck table 2 in the Y-axis direction is performed by the index feeding means 4 shown in FIG. Here, since the side surface 731 of the polygon mirror 73 is inclined downward by 45 degrees with respect to the Z-axis direction, the laser beam LB31 emitted from the first laser beam irradiation means 71 is directed at the side surface 731 in the -Z direction. reflect to Therefore, the position of the chuck table 2 in the Y-axis direction is adjusted so that one of the side surfaces 731 is positioned directly above the planned dividing line L1 and furthermore, the side surface 731 is parallel to the X-axis direction.

After such alignment is performed, when the laser beam LB31 is emitted from the first laser beam irradiation means 71, the laser beam reflected by the side surface 731 of the polygon mirror 73 is scheduled to be split by the first condenser 752 shown in FIG. The light is condensed on the line L1, and the ablation groove A1 is formed along the line to be divided L1 by the +X-direction machining feed of the chuck table 2 . At this time, the laser beam is emitted while reciprocating within a predetermined range in the X-axis direction, as in the first embodiment.

(2-2) Inward processing step Next, as shown in FIG. 9B, a laser beam emitted from the second laser beam irradiation means 72 is irradiated onto the scheduled division line L3 to be subjected to ablation processing next. , the position of the chuck table 2 in the Y-axis direction is adjusted. Then, when the laser beam LB32 is emitted from the second laser beam irradiation means 72, the laser beam reflected by the side surface 731 of the polygon mirror 73 is collected by the second condenser 762 shown in FIG. The machining feed in the -X direction of the chuck table 2 forms an ablation groove A3 along the dividing line L1. At this time, the laser beam is emitted while reciprocating within a predetermined range in the X-axis direction, as in the first embodiment.

(2-3) Repetition process Next, as shown in FIG. 9C, the laser beam emitted from the first laser beam irradiation means 71 is projected onto the planned division line L2 to be ablated next. Then, the position of the chuck table 2 in the Y-axis direction is adjusted. Then, when the laser beam LB31 is emitted from the first laser beam irradiation means 71, the laser beam reflected by the side surface 731 of the polygon mirror 73 is collected by the second condenser 762 shown in FIG. The machining feed of the chuck table 2 in the -X direction forms the ablation grooves A2 along the dividing line L2 (forward machining step). In addition, an ablation groove is formed in the backward machining process for the planned division line L4 next to the planned division line L4 in the +Y direction.

In this way, by repeating the forward machining process and the backward machining process, ablation grooves are formed in all the lines to be divided arranged in the same direction.

3 Third Embodiment Instead of the laser processing means 6 shown in FIGS. 1-3, a laser processing means 8 shown in FIG. 10 can be used. In this laser processing means 8 , the first laser beam irradiation means 81 and the second laser beam irradiation means 82 share one oscillator 812 . The first laser beam irradiation means 81 includes a first optical component 813 in addition to the oscillator 812 . Also, the second laser beam irradiation means 82 includes a second optical component 823 in addition to the oscillation section 812 .

Switching means 83 is interposed between the oscillator 812 and the first laser beam irradiation means 81 and the second laser beam irradiation means 82 . The switching means 83 includes a half-wave plate 831 that rotates the plane of polarization of the laser beam oscillated by the oscillator 812 and a polarization beam splitter 832 that splits the laser beam that has passed through the half-wave plate 831 . The switching means 83 splits the laser beam whose plane of polarization has been rotated by the rotation of the half-wave plate 831 into an S-polarized laser beam and a P-polarized laser beam by the polarization beam splitter 832, and selectively splits each of them into a first polarized beam. It can lead to optical component 813 and second optical component 823 .

The first optical component 813 consists of two reflectors 813a, 813b that reflect the laser beam. On the other hand, the second optical component 823 is composed of three reflectors 823a, 823b, 823c that reflect the laser beam.

The laser beam whose optical path has been changed by the first optical component 813 and the laser beam whose optical path has been changed by the second optical component 823 are irradiated on different side surfaces 841 of the polygon mirror 84 facing away from each other. The polygon mirror 84 is formed in the shape of a regular hexagonal prism and is rotatable about a rotation axis 840 parallel to the Z-axis direction perpendicular to the X-axis direction and the Y-axis direction. The polygon mirror 84 has a plurality of planar side surfaces 841. As the polygon mirror 84 rotates, each side surface 841 reflects the laser beam guided by the first optical component 813 in the -Y direction. , reflect the laser beam guided by the second optical component 823 in the +Y direction.

On the −Y direction side of the side surface 841 where the laser beam guided by the first optical component 813 is reflected, a first direction changing means 85 for directing the reflected laser beam toward the −Z direction side is arranged. On the +Y direction side of the side surface 841 where the laser beam guided by the optical component 823 is reflected, a second direction changing means 86 for directing the reflected laser beam toward the -Z direction side is arranged. The first direction changing means 85 comprises a first mirror 851 that reflects the laser beam in the Z-axis direction. Below the first mirror 851, there is provided a first condenser (not shown) for condensing the laser beam reflected by the first mirror 851 onto the workpiece. The second direction changing means 86 also includes a second mirror 861 that reflects the laser beam in the Z-axis direction. Below the second mirror 861, a second condenser is provided for condensing the laser beam reflected by the second mirror 861 onto the workpiece.

The spacing between the first direction changing means 85 and the second direction changing means 86 can be adjusted by the spacing adjusting means 87 . The space adjusting means 67 moves the first direction changing means 85 or the second direction changing means 86 in the Y-axis direction so that the distance between the first direction changing means 85 and the second direction changing means 86 is increased. Adjust spacing.

The laser beam oscillated from the oscillator 812 has its plane of polarization rotated by the half-wave plate 831 and is split into an S-polarized laser beam and a P-polarized laser beam by the polarization beam splitter 832 . The laser beam guided to the first optical component 813 is reflected by the two reflectors 813 a and 813 b and directed toward the polygon mirror 84 . Then, the laser beam is reflected in the -Y direction by the side surface 841 of the polygon mirror 84, then reflected by the first mirror 851, guided in the -Z direction, and focused on the wafer by a collector (not shown). . On the other hand, the laser beam guided to the second optical component 823 is reflected by the three reflectors 823a, 823b, 823c and directed toward the polygon mirror 84. FIG. The laser beam is reflected in the +Y direction by the side surface 841 of the polygon mirror 84, then reflected by the second mirror 861, guided in the -Z direction, and focused on the wafer by a collector (not shown).

In the laser processing means 8 configured in this way, since one oscillator 812 functions as an oscillator for both the first laser beam irradiation means 81 and the second laser beam irradiation means 82, the first laser beam By sharing one oscillator 812 between the irradiation means 81 and the second laser beam irradiation means 82, the configuration can be simplified and the device cost can be reduced. Also in this laser processing means 8, an ablation groove can be formed by the procedure shown in the first and second embodiments.

1: Laser processing device 2: Chuck table 21: Holding surface 22: Frame holding unit 23: Rotation drive unit 3: Processing feed means 31: Ball screw 32: Guide rail 33: Motor 34: Moving plate 35: Scale 4: Index feed means 41: Ball screw 42: Guide rail 43: Motor 44: Moving plate 45: Scale 6: Laser processing means 61: First laser beam irradiation means 62: Second laser beam irradiation means 63: Polygon mirror 630: Rotating shaft 631: One side 64: Switching means 65: First direction changing means 651: First mirror 66: Second direction changing means 661: Second mirror 67: Distance adjusting means 681: First condenser 682: Second Concentrator 69: Control means 7: Laser processing means 71: First laser beam irradiation means 72: Second laser beam irradiation means 73: Polygon mirror 730: Rotating shaft 731: Side surface 751: First mirror 752: First mirror Condenser 761: Second mirror 762: Second condenser 8: Laser processing means 81: First laser beam irradiation means 812: Oscillator 813: First optical component 813a, 813b: Reflector 82: Second 2 laser beam irradiation means 823: second optical components 823a, 823b, 823c: reflector 83: switching means 831: half-wave plate 832: polarizing beam splitter 84: polygon mirror 840: rotating shaft 841: side surface 85: second 1 Direction Changing Means 851: First Mirror 86: Second Direction Changing Means 861: Second Mirror 87: Distance Adjusting Means W: Wafer Wa: Front Surface Wb: Back Surface L, L1 to L6, Lm: Planned Division Line D: Devices A1 to A5, Am: Ablation groove T: Tape F: Frames LB1, LB2, LB31, LB32: Laser beam

Claims (1)

A chuck table having a holding surface for holding a workpiece, laser processing means for irradiating the workpiece held on the chuck table with a laser beam along a line to be divided to process the workpiece, and the chuck processing feed means for relatively moving the table and the laser processing means in the X-axis direction; and relatively moving the chuck table and the laser processing means in the Y-axis direction orthogonal to the X-axis direction and the holding surface direction. A laser processing method using a laser processing device comprising index feeding means for moving to
The laser processing means continuously rotates in one direction about a rotation axis parallel to the Z-axis direction orthogonal to the X-axis direction and the Y-axis direction, and the lower side of each side surface constituting a regular polygonal prism is the Z-axis. a polygon mirror having a planar beveled slope facing downward at 45 degrees with respect to the axial direction ;
a first laser beam irradiation means for emitting a laser beam downward in the Z-axis direction ;
second laser beam irradiation means for emitting a laser beam downward in the Z-axis direction from the side opposite to the first laser beam irradiation means in the Y-axis direction ;
switching means for switching between the first laser beam irradiation means and the second laser beam irradiation means;
a first direction changing means for directing the laser beam emitted by the first laser beam irradiation means in the first direction of the Y -axis direction to irradiate the slope of the polygon mirror ;
second direction changing means for directing the laser beam emitted by the second laser beam irradiation means in a second direction opposite to the first direction in the Y -axis direction to irradiate the inclined surface of the polygon mirror ; with
a holding step of holding the workpiece on the chuck table;
The chuck table is moved in one direction of the X-axis direction with respect to the first laser beam irradiation means, and a laser beam is directed to the polygon mirror rotating in one direction either clockwise or counterclockwise when viewed from above. an outward machining step of irradiating the laser beam and reflecting the laser beam on the slope of the polygon mirror in the Z-axis direction to machine the workpiece;
The chuck table is moved in the other direction in the X-axis direction with respect to the second laser beam irradiation means, and the polygon mirror rotating in the same direction as the outward machining step is irradiated with the laser beam. a return machining step of machining the workpiece by reflecting it in the Z-axis direction on the slope of the mirror;
a repeating step of repeating the outward machining step and the inward machining step;
with
In the forward processing step and the backward processing step, the chuck table is positioned such that one of the slopes of the polygon mirror is positioned directly above the line to be divided, and the upper side of the slope is parallel to the X-axis direction. Adjust the Y-axis position,
In the repeating step, the switching means turns off either the first laser beam irradiation means or the second laser beam irradiation means when processing and feeding in one of the X-axis directions, and turns off the other laser beam irradiation means. A laser beam irradiation means is turned on to carry out outward machining, and when processing and feeding in the other direction of the X-axis direction, the other laser beam irradiation means that was turned on during the outward machining is turned off and the one laser beam is turned off. Turn on the irradiation means and perform the return machining
Laser processing method.

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