JP2023035534A - Optical modulator, method for optical modulation, laser processor, and method for processing laser - Google Patents

Abstract

To provide an optical modulator, a method for optical modulation, a laser processor, and a method for laser processing that can precisely cut off a workpiece along a cut-scheduled line.SOLUTION: An optical modulator (10) includes: a spatial optical modulator (28); and control means (50) for setting a hologram pattern to present in the spatial optical modulator, to be a striped Fresnel pattern including a first rectangular region and a second rectangular region, the first rectangular region including an optical axis of an incident light and at least two second rectangular regions located with the first rectangular region in between and having different curvatures from each other, and collectively emitting light modulated by the first rectangular region and the second rectangular region, to different light collection positions.SELECTED DRAWING: Figure 2

Description

The present invention relates to a light modulating device and method for irradiating a plurality of condensing points inside a work with laser light, and in particular, the light modulating device and method irradiate the inside of the work with laser light to obtain a laser processing area. It relates to a laser processing apparatus and method for forming.

2. Description of the Related Art Conventionally, there has been known a laser processing apparatus that forms a laser processing region inside a work along a planned cutting line of the work by irradiating a laser beam with a focal point aligned with the inside of the work (for example, See Patent Document 1).

In the laser processing apparatus described in Patent Document 1, when the workpiece is irradiated with the laser beam and relatively moved along the planned cutting line, the relative movement direction of the laser beam is different in the thickness direction in the workpiece. A pair of laser processing regions are simultaneously formed by simultaneously focusing the laser beams at two positions separated along the . As a result, it is possible to form two rows of laser-processed regions inside the workpiece in one scan for one line to be cut.

JP 2011-051011 A

However, in the laser processing apparatus described in Patent Document 1, as described above, when simultaneously forming a pair of laser processing regions, the thickness direction in the work is different from each other, and along the relative movement direction of the laser beam In order to simultaneously focus the laser beams on two distant positions, the two laser-processed regions aligned in the thickness direction within the workpiece are formed at mutually different timings. Therefore, there is a problem that the cracks generated from the two laser-processed regions arranged in the thickness direction are difficult to connect with each other, and the cutting accuracy of the work is not good.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical modulation device and method, and a laser processing device and method that can accurately cut a workpiece along a planned cutting line. .

In order to achieve the above object, a light modulation device according to a first aspect of the present invention includes a spatial light modulator, and a hologram pattern to be presented by the spatial light modulator in a first rectangular area including the optical axis of incident light. and a striped Fresnel pattern composed of at least two second rectangular regions arranged so as to sandwich the first rectangular region, the Fresnel patterns having mutually different curvatures, the first rectangular region and the second rectangular region and control means for condensing and irradiating the light modulated by the regions to different condensing positions.

In the light modulation device according to a second aspect of the present invention, in the first aspect, the control means adjusts the second The area ratio of the first rectangular area and the second rectangular area is changed.

In the light modulation device according to the third aspect of the present invention, in the first aspect or the second aspect, the control means sets the Fresnel pattern to be set in at least one of the first rectangular area and the second rectangular area so that the major axis direction is An elliptical or oval shape parallel to the longitudinal direction of the first rectangular area and the second rectangular area is formed.

In any one of the first to third aspects of the light modulation device according to the fourth aspect of the present invention, the control means sets a random pattern in at least one of the first rectangular area and the second rectangular area.

A laser processing apparatus according to a fifth aspect of the present invention comprises a laser light source that outputs a laser beam, an optical modulator according to any one of the first to fourth aspects, and a laser beam modulated by the optical modulator. A condensing lens for condensing and irradiating the inside of the work is provided.

In the laser processing apparatus according to the sixth aspect of the present invention, in the fifth aspect, the longitudinal directions of the first rectangular area and the second rectangular area are perpendicular to the processing direction of the laser processing apparatus.

A laser processing apparatus according to a seventh aspect of the present invention is, in the fifth or sixth aspect, provided with a correction ring for correcting aberration of laser light generated inside the work.

According to a laser processing apparatus according to an eighth aspect of the present invention, in any one of the fifth to seventh aspects, the controller controls the aberration correction hologram pattern for correcting the aberration of the laser beam generated inside the workpiece. Superimposed on the hologram pattern.

According to a ninth aspect of the present invention, there is provided a laser processing apparatus according to any one of the fifth to eighth aspects, wherein the control means changes the wavefront distortion correction hologram pattern for correcting the wavefront distortion of the laser beam to a hologram pattern. superimposed on

A light modulation method according to a tenth aspect of the present invention is characterized in that a hologram pattern to be presented by a spatial light modulator is composed of a first rectangular area including the optical axis of incident light and at least two rectangular areas arranged to sandwich the first rectangular area. A striped Fresnel pattern consisting of two second rectangular regions, which are set to Fresnel patterns with mutually different curvatures, and the light modulated by the first rectangular region and the second rectangular region are respectively focused at different condensing positions. Irradiate with light.

A laser processing method according to an eleventh aspect of the present invention modulates laser light from a laser light source by the light modulation method according to the tenth aspect, and condenses and irradiates the modulated laser light into the interior of the work.

ADVANTAGE OF THE INVENTION According to this invention, a to-be-processed object can be cut|disconnected accurately along a line to cut.

FIG. 1 is a configuration diagram showing an outline of a laser processing apparatus equipped with an optical modulation device according to one embodiment of the present invention. FIG. 2 is a diagram showing an example of a hologram pattern. FIG. 3 is a simplified diagram showing a laser beam modulated by a hologram pattern according to this embodiment. FIG. 4 is a diagram for explaining a laser processing method according to one embodiment of the present invention. FIG. 5 is a diagram for explaining a laser processing method according to one embodiment of the present invention. FIG. 6 is a diagram for explaining a laser processing method according to one embodiment of the present invention. FIG. 7 is a perspective view schematically showing the shape of laser light after modulation. FIG. 8 is a plan view showing an example of a pattern presented in a rectangular area of the hologram pattern. 9 is a plan view showing a hologram pattern according to Modification 1. FIG. 10 is a plan view showing a hologram pattern according to Modification 2. FIG. FIG. 11 is a diagram showing condensing points of laser light modulated by a hologram pattern according to Modification 2. As shown in FIG. FIG. 12 is a plan view showing another example of the hologram pattern according to Modification 2. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of an optical modulation device and method and a laser processing device and method according to the present invention will be described with reference to the accompanying drawings.

[Laser processing equipment]
FIG. 1 is a configuration diagram showing an outline of a laser processing apparatus equipped with an optical modulation device according to one embodiment of the present invention. As shown in FIG. 1, the laser processing apparatus 1 according to this embodiment includes a stage 11, a laser engine (optical system unit) 20, and a controller 50. As shown in FIG. In this embodiment, the laser engine 20 and the controller 50 are configured separately, but the configuration is not limited to this, and the laser engine 20 may include part or all of the controller 50 .

The stage 11 holds the work by suction. The stage 11 includes a stage moving mechanism (not shown), and is configured to be movable in the XYZθ directions by the stage moving mechanism. As the stage moving mechanism, for example, various mechanisms such as a ball screw mechanism and a linear motor mechanism can be used. In FIG. 1, three XYZ directions are orthogonal to each other, of which the X and Y directions are horizontal, and the Z direction is vertical. The θ direction is the direction of rotation about the vertical axis (Z axis). The stage 11 is an example of relative movement means of the present invention.

In this embodiment, a semiconductor wafer (hereinafter referred to as "wafer") W such as a silicon wafer is applied as the work. The wafer W is partitioned into a plurality of regions by cutting lines arranged in a grid pattern, and various devices constituting semiconductor chips are formed in each partitioned region. In this embodiment, a case where a wafer W is applied as a work will be described, but the present invention is not limited to this, and for example, a glass substrate, a piezoelectric ceramic substrate, a glass substrate, etc. can also be applied. can.

A back grind tape (hereinafter referred to as BG tape) having an adhesive material is attached to the surface (device surface) on which devices are formed, and the wafer W is placed on the stage 11 so that the back surface faces upward. The thickness of the wafer W is not particularly limited, but is, for example, 700 μm or more or 700 μm to 800 μm.

The wafer W may be mounted on the stage 11 in a state in which a dicing tape having an adhesive material is attached to one surface thereof and integrated with the frame via the dicing tape.

The laser engine 20 includes a laser light source 22, a spatial light modulator 28, a condenser lens 38, and the like. The light modulation device 10 according to this embodiment includes a spatial light modulator 28 and a controller 50 .

A laser light source (IR (Infrared) laser light source) 22 outputs processing laser light L for forming a laser processing region inside the wafer W under the control of the control unit 50 . As for the conditions of the laser beam L, for example, the light source is a semiconductor laser-excited Nd:YAG (Neodym: Yttrium Aluminum Garnet) laser, the wavelength is 1.1 μm, and the cross-sectional area of the laser beam spot is 3.14×10 ⁻⁸ cm ^{2 .} , the oscillation mode is a Q-switch pulse, the repetition frequency is 80 kHz to 200 kHz, the pulse width is 180 ns to 370 ns, and the output is 8 W.

The spatial light modulator 28 is of a phase modulation type, receives the laser light L (incident light) output from the laser light source 22, and modulates the phase of the laser light L in each of a plurality of two-dimensionally arranged pixels. A predetermined hologram pattern is presented, and the phase-modulated laser beam L is output. As a result, as will be described later in detail, when the laser beam L is irradiated and relatively moved along the planned cutting line, the thickness direction inside the wafer W is different from each other, and the relative movement direction of the laser beam L is different from each other. The laser light L is condensed at two equal positions at the same time.

As the spatial light modulator 28, for example, a reflective liquid crystal (LCOS: Liquid Crystal on Silicon) spatial light modulator (SLM: Spatial Light Modulator) is used. The operation of the spatial light modulator 28 and the hologram pattern presented by the spatial light modulator 28 are controlled by the controller 50 . Here, the control unit 50 is an example of control means of the present invention.

The condensing lens 38 is an objective lens (infrared objective lens) that converges the laser light L inside the wafer W. As shown in FIG. The numerical aperture (NA) of this condenser lens 38 is, for example, 0.65.

The condenser lens 38 has a correction ring 40 for correcting the aberration of the laser light L occurring inside the wafer W. As shown in FIG. The corrector ring 40 is manually rotatable. When the corrector ring 40 is rotated in a predetermined direction, the interval between the lens groups constituting the condenser lens 38 is changed, and the laser beam irradiation surface of the wafer W is changed. Aberration can be corrected so that the aberration of the laser beam L is less than or equal to a predetermined aberration at a predetermined depth position from (back surface).

Note that the correction ring 40 may be configured to be electrically rotated by a correction ring drive section (not shown). In this case, the control unit 50 controls the operation of the correction ring drive unit to rotate the correction ring 40, thereby correcting the aberration of the laser beam L to a desired state.

The laser engine 20 includes a beam expander 24, a λ/2 wavelength plate 26, a reducing optical system 36, and the like.

The beam expander 24 expands the laser light L output from the laser light source 22 to a beam diameter suitable for the spatial light modulator 28 . The λ/2 wavelength plate 26 adjusts the plane of polarization of laser light incident on the spatial light modulator 28 . The reduction optical system 36 is an afocal optical system (both-side telecentric optical system) consisting of a first lens 36a and a second lens 36b. projected down to

Although not shown, the laser engine 20 includes an alignment optical system for alignment with the wafer W, an autofocus system for keeping the distance (working distance) between the wafer W and the condenser lens 38 constant. units are provided.

The control unit 50 is a control device that controls the operation of each part of the laser processing apparatus 1, and includes a CPU (Central Processing Unit) that functions as a controller that executes various processes, and a RAM (Random Access Memory) that functions as a memory that stores various information. Memory) and ROM (Read Only Memory). The control unit 50 controls the operation of each part (the stage 11, the laser engine 20, etc.) of the laser processing apparatus 1 based on the processing information (processing conditions, etc.) specified by the operator, thereby performing laser processing inside the wafer W. It controls the operation for forming the area.

The controller 50 also controls the operation of the spatial light modulator 28 to cause the spatial light modulator 28 to present a predetermined hologram pattern.

The laser processing apparatus 1 includes wafer transfer means, an operation panel, a television monitor, indicator lamps, and the like (none of which are shown).

Switches and a display device for operating each part of the laser processing apparatus 1 are attached to the operation plate. The television monitor displays an image of the wafer W captured by a CCD (Charge Coupled Device) camera (not shown), program contents, various messages, and the like. The indicator lamp indicates the operating status of the laser processing apparatus 1, such as during processing, processing end, emergency stop, and the like.

Next, a laser processing method according to one embodiment of the present invention will be described. This laser processing method is carried out using the laser processing apparatus 1 of the present embodiment described above.

First, by manually (or electrically) rotating the corrector ring 40 provided in the condenser lens 38, the laser beam L is focused at a position (processing depth of the laser processing area) inside the wafer W where the laser beam L is focused. The aberration correction amount is adjusted so that the L aberration is equal to or less than a predetermined aberration. In this specification, the "aberration correction amount" is a value converted into the depth from the laser beam irradiation surface (rear surface) of the wafer W. As shown in FIG. That is, for example, when the aberration correction amount is 500 μm, it means that the aberration of the laser beam is minimized at a position near the depth of 500 μm from the laser beam irradiation surface of the wafer W. For example, when the thickness (initial thickness) of the wafer W is 775 μm, the amount of aberration correction by the correction ring 40 is preferably set to 500 μm.

In this manner, the correction ring 40 of the condenser lens 38 is used to correct the aberration at the position where the focal point of the laser beam L is aligned so that it is less than or equal to a predetermined aberration. It is possible to efficiently focus the laser light L at a deep position of the wafer W in the thickness direction. The reason why it is effective to correct aberrations using the correction ring 40 and other means for correcting aberrations are described in detail in Japanese Patent Laid-Open No. 2016-011315 filed by the applicant of the present application. We omit the explanation here.

In this embodiment, the correction ring 40 is used for aberration correction, but the present invention is not limited to this. For example, the correction ring 40 may not be used for aberration correction. In this case, the spatial light modulator 28 may be used for aberration correction. Also, the spatial light modulator 28 and the correction ring 40 may be used together to correct aberrations.

Next, after mounting the wafer W to be processed on the stage 11, alignment of the wafer W is performed using an alignment optical system (not shown).

Next, while irradiating the wafer W with the laser light L, the wafer W is relatively moved along the planned cutting line. The relative movement of the laser beam L is performed by moving the stage 11 holding the wafer W by suction in the X direction.

At this time, the beam diameter of the laser light L output from the laser light source 22 is expanded by the beam expander 24, reflected by the first mirror 30, the polarization direction is changed by the λ/2 wavelength plate 26, and spatial light modulation is performed. incident on the device 28 .

A luminous flux of laser light L incident on the spatial light modulator 28 is modulated by the hologram pattern presented on the spatial light modulator 28 . The hologram pattern PA1 (see FIG. 2) according to the present embodiment modulates the laser light L so that the light flux of the laser light L is condensed and irradiated to two condensing points inside the wafer W, as will be described later. .

The laser light L emitted from the spatial light modulator 28 in this manner is sequentially reflected by the second mirror 31 and the third mirror 32, passes through the first lens 36a, and further passes through the fourth mirror 33 and the third mirror 36a. It is reflected by the 5-mirror 34, passes through the second lens 36b, and enters the condenser lens 38. FIG. As a result, the laser light L emitted from the spatial light modulator 28 is reduced and projected onto the condenser lens 38 by the reduction optical system 36 consisting of the first lens 36a and the second lens 36b. The laser light L incident on the condenser lens 38 is condensed at two different condensing positions inside the wafer W by the condenser lens 38 .

[Example of hologram pattern]
FIG. 2 is a diagram showing an example of a hologram pattern.

As shown in FIG. 2, the hologram pattern PA1 according to this embodiment is a combination of two types of Fresnel patterns FL1 and FL2. The Fresnel patterns FL1 and FL2 are Fresnel patterns having different curvatures, and the hologram pattern PA1 is a pattern obtained by dividing the Fresnel patterns FL1 and FL2 into rectangular regions (regions K1 to Kn and regions L1 to Ln, where n is an integer of 2 or more, and in the example shown in FIG.

As shown in FIG. 2, in the hologram pattern PA, the central area K1 (first rectangular area) of the Fresnel pattern FL1 is arranged at the center, that is, at the position of the optical axis AX of the laser beam L, and its X direction (processing direction ), regions L2, K3, L4, and K5 (second rectangular regions) are arranged in stripes in order so as to sandwich region K1.

Although n=5 in the example shown in FIG. 2, the present invention is not limited to this. That is, the hologram pattern PA1 according to this embodiment can be realized by combining at least three striped patterns of the central region K1 and the regions L2 arranged on both sides thereof.

FIG. 3 is a simplified diagram showing the laser light L modulated by the hologram pattern PA1 according to this embodiment.

In the example shown in FIG. 3, of the laser light L, the component modulated by the pattern FL1 (areas K1, K3 and K5) is condensed at the condensing point FP1 and modulated by the pattern FL2 (areas L2 and L4). The component is focused on the focal point FP2.

As described above, when the laser beam L is modulated by the hologram pattern PA1, which is a combination of two types of Fresnel patterns FL1 and FL2 having different curvatures, two focal points FP1 and FP2 inside the wafer W are formed as shown in FIG. can be condensed and irradiated with the laser light L at the same time.

In the example shown in FIG. 3, the focal point FP1 is closer to the front surface of the wafer W than the focal point FP2 (lower side in FIG. 3), but the present invention is not limited to this. By adjusting the curvatures of the Fresnel patterns FL1 and FL2, it is possible to make the focal point FP2 closer to the front surface of the wafer W than the focal point FP1.

Also, in the example shown in FIG. 2, the regions K1, L2, K3, L4 and K5 are arranged adjacent to each other without gaps, but the present invention is not limited to this. For example, there may be gaps between regions K1, L2, K3, L4 and K5.

Furthermore, in this embodiment, it is possible to control (attenuate) the power of the laser light L at the focal points FP1 and FP2 by arranging a random pattern between any of the regions K1, L2, K3, L4 and K5. can. In this case, it is possible to control (attenuate) the power of the laser light L at the focal points FP1 and FP2 while keeping the Gaussian distribution specific to the laser light L common.

[Laser processing method]
4 to 6 are diagrams for explaining the laser processing method according to one embodiment of the present invention. 4 is a diagram showing a state in which the laser light L is condensed inside the wafer W. As shown in FIG. FIG. 5 is a diagram showing a state in which a laser processing area is formed at the condensing position of the laser beam L shown in FIG. FIG. 6 is a diagram showing a state in which two rows of laser-processed regions are formed inside the wafer W along the planned cutting line.

As shown in FIG. 4, the laser light L modulated by the spatial light modulator 28 is located at two different positions in the thickness direction inside the wafer W and equal to each other in the relative movement direction M of the laser light L (second position). The light is condensed simultaneously by the condensing lens 38 at the first condensing position FP1 and the second condensing position FP2). As a result, as shown in FIG. 5, a pair of laser processing regions P1 and P2 are formed in the vicinity of the two condensing positions FP1 and FP2. Further, when the pair of laser-processed regions P1 and P2 are formed, cracks Ki1 and Ki2 extending in the thickness direction of the wafer W are formed starting from the respective laser-processed regions P1 and P2. Therefore, when one scan along the planned cutting line is performed, two rows of laser processing regions P1 and P2 can be formed inside the wafer W as shown in FIG. As an example, the interval in the thickness direction between the two condensing positions FP1 and FP2 inside the wafer W is set to 50 μm to 80 μm.

In this way, when two rows of laser processing regions P1 and P2 are formed inside the wafer W by one scan along the planned cutting line, the stage 11 is indexed and fed by one pitch in the Y direction, and the next step is performed. Similarly, laser processing regions P1 and P2 are formed on the line to be cut.

When the laser processing areas P1 and P2 are formed along all of the planned cutting lines parallel to the X direction, the stage 11 is rotated by 90°, and the lines perpendicular to the previous lines are similarly all laser processed areas P1 and P2. P2 is formed. Thereby, laser processing regions P1 and P2 are formed along all the lines to be cut.

After the laser-processed regions P1 and P2 are formed along the planned cutting lines as described above, the back surface of the wafer W is ground using a grinding device (not shown) to obtain the thickness (initial thickness) T1 of the wafer W. is processed to a predetermined thickness (final thickness) T2 (for example, 30 μm to 50 μm).

After the back surface grinding process, an expanding tape (dicing tape) is attached to the back surface of the wafer W, and after the BG tape attached to the front surface of the wafer W is peeled off, the expanding tape attached to the back surface of the wafer W is tensioned. An expanding step is performed by adding and stretching.

As a result, the wafer W is cut starting from the crack extending to the device surface (front surface) side of the wafer W. As shown in FIG. That is, the wafer W is cut along the planned cutting lines and divided into a plurality of chips.

As described above, in the present embodiment, when the wafer W is irradiated with the laser beam L and relatively moved along the planned cutting line, the relative movement of the laser beam L is different in the thickness direction inside the wafer W. The laser processing areas P1 and P2 are simultaneously formed by condensing the laser light L at two condensing positions FP1 and FP2 which are equal to each other in the direction M by the condensing lens 38 at the same time. Therefore, the two laser processing regions P1 and P2 aligned in the thickness direction inside the wafer W are formed at substantially the same timing. As a result, when forming two rows of laser processing regions P1 and P2 inside the wafer W in one scan along the planned cutting line, the laser processing regions P1 and P2 formed at substantially the same timing are generated from the laser processing regions P1 and P2. Since the cracks are formed continuously in the thickness direction of the wafer W, compared to the case where the laser processing regions P1 and P2 arranged in the thickness direction are formed at different timings, the cracks generated from the laser processing regions P1 and P2 has good linearity, and cracks generated inside the wafer W can be extended efficiently and with high accuracy.

[Aspect of Condensing Laser Light L]
FIG. 7 is a perspective view schematically showing the shape of the laser beam L after modulation.

As shown in FIG. 7, the hologram pattern PA1 according to the present embodiment is a combination of a plurality of rectangular patterns. is shaped into a rectangle whose longitudinal direction is perpendicular to the processing direction (X direction).

The rectangular shaped laser beam L becomes a rectangle with the processing direction as the longitudinal direction when condensed by the condensing lens 38 . Therefore, in this embodiment, by shaping the laser beam L into a rectangle, astigmatism can be generated and the directionality of the cracks Ki1 and Ki2 can be given. In this way, since the cracks can be extended along the processing direction from the laser processing regions P1 and P2 as starting points, it is possible to improve the connectivity of the cracks in the processing direction along the planned cutting line.

FIG. 8 is a plan view showing an example of a pattern presented in the rectangular area of the hologram pattern PA1.

The area K1-1 shown in FIG. 8 shows an example of a perfect circular Fresnel pattern, and the area K1-2 shows an elliptical Fresnel pattern having a major axis direction (major axis direction) perpendicular to the processing direction. shows an example.

As shown in the region K1-2, by making the Fresnel pattern an elliptical shape with the direction perpendicular to the processing direction as the major axis direction, it is possible to further improve crack growth performance and connectivity. Note that the Fresnel pattern is not limited to an elliptical shape, and may be an oval shape, for example.

In this embodiment, the laser beam L is condensed simultaneously by the condensing lens 38 to two condensing points FP1 and FP2 which are mutually different in the thickness direction inside the wafer W, and the laser processing regions P1 and P2 are simultaneously condensed. After performing the two-stage processing for forming, the back surface grinding process of grinding the back surface of the wafer W is performed to divide the wafer W into individual chips. For example, the laser processing may be performed multiple times while changing the position (processing depth of the laser processing region) where the laser light L is condensed inside the wafer W as necessary. At that time, according to the processing depth of the laser processing region, the hologram pattern presented by the spatial light modulator 28 is a correction pattern for correcting the aberration inside the wafer W (aberration correction hologram pattern. , a pattern in the direction of canceling the correction by the correction ring 40), it is possible to perform appropriate aberration correction even for a relatively shallow portion of the wafer W from the laser beam irradiation surface.

Further, a wavefront distortion correction hologram pattern for correcting the wavefront distortion of the laser beam may be superimposed on the hologram pattern.

[Modification 1]
9 is a plan view showing a hologram pattern according to Modification 1. FIG.

As shown in FIG. 9, in the hologram pattern PA1 according to the above embodiment, the regions K1, L2, K3, L4 and K5 have the same width Δ in the processing direction (Δ=500 pixels in one example), In the hologram pattern PA2 according to Modification 1, the width Δ1 of the regions K1, K3 and K5 is longer than the width Δ2 of the regions L2 and L4. where Δ1=560 pixels and Δ2=440 pixels or Δ1=600 pixels and Δ2=400 pixels. By doing so, it is possible to increase the intensity and convergence of the laser light L at the condensing point FP1 rather than at the condensing point FP2.

For example, by adjusting the size (area ratio) of the regions K1, K3 and K5 and the regions L2 and L4 according to the positional relationship (distance) between the surface of the wafer W and the focal points FP1 and FP2, It becomes possible to adjust the intensity and convergence degree of the laser light L at the focal points FP1 and FP2. For example, when the distance between the surface of the wafer W and the focal point FP1 is long, the width Δ1 of the regions K1, K3, and K5 is increased to increase the intensity and convergence at the focal point FP1. As a result, the crack Ki1 extending from the focal point FP1 can be lengthened and reach the surface of the wafer W. FIG. Further, when the distance between the surface of the wafer W and the focal point FP1 is short and the distance between the focal points FP1 and FP2 is long, by setting Δ1<Δ2, the focal point FP1 and The connectivity of cracks with FP2 can be improved.

[Modification 2]
10 is a plan view showing a hologram pattern according to Modification 2, and FIG. 11 is a diagram showing condensing points of laser light modulated by the hologram pattern according to Modification 2. As shown in FIG.

In the hologram pattern P3 shown in FIG. 10, the Fresnel pattern curvatures of the regions K1, L2, M3, N4 and O5 are different from each other. By configuring in this way, the laser light L modulated by each region can be condensed on different condensing points FP1 to FP5.

Furthermore, as shown in FIG. 12, by changing the widths (area ratios) of the regions K1, L2, M3, N4, and O5, the mutual positional relationship (distance ), it is possible to adjust the intensity and convergence degree of the laser light L at the condensing points FP1 to FP5.

[Modification 3]
In the above embodiment, the longitudinal direction of the regions of the hologram patterns PA1 to PA3 (regions K1, L2, K3, L4 and K5, or regions K1, L2, M3, N4 and O5) is the processing direction of the laser processing apparatus 1 ( X direction), but the present invention is not limited to this. For example, the longitudinal direction of the regions of the hologram patterns PA1 to PA3 (regions K1, L2, K3, L4 and K5, or regions K1, L2, M3, N4 and O5) is the direction parallel to the processing direction of the laser processing apparatus 1. It is also possible to

In this case, the pattern presented in the rectangular area of the hologram pattern may be an elliptical or oval Fresnel pattern with the longitudinal direction of each area being the major axis direction, as in the example shown in FIG.

[Modification 4]
In each of the above-described embodiments, within the wafer W, the position in the thickness direction of the wafer W is different, and the position along the processing direction (X direction) of the laser processing apparatus 1 is the same. Although described by way of example, the invention is not so limited. For example, when the position in the thickness direction of the wafer W is the same and the laser beam L is condensed and irradiated at different positions along the processing direction of the laser processing apparatus 1, or the thickness direction of the wafer W The present invention can also be applied to a case where the laser beam L is condensed and radiated to condensed positions at different positions along the processing direction of the laser processing apparatus 1 .

In this embodiment, a reflective spatial light modulator (LCOS-SLM) is used as the spatial light modulator 28, but the present invention is not limited to this, and MEMS-SLM (Micro Electro Mechanical System-SLM) or DMD (Deformable Mirror Device) or the like. Moreover, the spatial light modulator 28 is not limited to a reflective type, and may be a transmissive type. Further, the spatial light modulator 28 may be of liquid crystal cell type or LCD (Liquid Crystal Display) type.

DESCRIPTION OF SYMBOLS 1... Laser processing apparatus, 10... Optical modulation apparatus, 11... Stage, 20... Laser engine, 22... Laser light source, 24... Beam expander, 26... λ/2 wavelength plate, 28... Spatial light modulator, 36... Reduction optics System 38 Condensing lens 40 Correction ring 50 Control unit

Claims (11)

a spatial light modulator;
The hologram pattern to be presented by the spatial light modulator is a striped fresnel consisting of a first rectangular area including the optical axis of the incident light and at least two second rectangular areas arranged to sandwich the first rectangular area. Control means for setting Fresnel patterns having mutually different curvatures, and focusing and irradiating the light modulated by the first rectangular area and the second rectangular area to different condensing positions, respectively;
A light modulating device comprising: The control means changes the area ratio of the first rectangular area and the second rectangular area according to the positional relationship between the condensing positions of the light modulated by the first rectangular area and the second rectangular area. The optical modulation device according to claim 1. The control means sets the Fresnel pattern to be set in at least one of the first rectangular region and the second rectangular region as an ellipse or a long ellipse whose major axis direction is parallel to the longitudinal direction of the first rectangular region and the second rectangular region. 3. The light modulating device according to claim 1, wherein the light modulating device has a circular shape. 4. The light modulation device according to claim 1, wherein said control means sets a random pattern in at least one of said first rectangular area and said second rectangular area. a laser light source that outputs laser light;
an optical modulation device according to any one of claims 1 to 4;
a condensing lens for condensing and irradiating the inside of the workpiece with the laser light modulated by the light modulation device;
A laser processing device with a 6. The laser processing apparatus according to claim 5, wherein longitudinal directions of said first rectangular area and said second rectangular area are orthogonal to a processing direction of said laser processing apparatus. 7. The laser processing apparatus according to claim 5, further comprising a correction ring for correcting aberration of said laser light generated inside said work. 8. The laser processing apparatus according to any one of claims 5 to 7, wherein said control means superimposes an aberration correction hologram pattern for correcting aberration of said laser beam generated inside said work on said hologram pattern. . 9. The laser processing apparatus according to claim 5, wherein said control means superimposes a wavefront distortion correction hologram pattern for correcting wavefront distortion of said laser beam on said hologram pattern. The hologram pattern to be presented by the spatial light modulator is a striped Fresnel pattern consisting of a first rectangular area including the optical axis of the incident light and at least two second rectangular areas arranged to sandwich the first rectangular area. and are set to Fresnel patterns with mutually different curvatures,
A light modulating method, wherein the light modulated by the first rectangular region and the second rectangular region are condensed and irradiated to different condensing positions. modulating the laser light from the laser light source by the light modulation method according to claim 10,
A laser processing method in which a modulated laser beam is condensed and irradiated to the inside of a workpiece.

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