CN117381202A

CN117381202A - Laser processing device

Info

Publication number: CN117381202A
Application number: CN202310838418.9A
Authority: CN
Inventors: 荻原孝文; 近藤裕太; 山田丈史
Original assignee: Hamamatsu Photonics KK
Current assignee: Hamamatsu Photonics KK
Priority date: 2022-07-11
Filing date: 2023-07-10
Publication date: 2024-01-12
Also published as: KR20240008246A; JP2024009576A

Abstract

A laser processing device (1) is provided with: a laser light source unit (3) that outputs laser light (L); a spatial light modulator (51) that includes a modulation surface (51 a) on which the laser light (L) output from the laser light source unit (3) is incident, and that modulates the laser light (L) according to a modulation pattern by displaying the modulation pattern on the modulation surface (51 a) and outputs the modulated laser light; a condensing lens (54) for condensing the laser light (L) emitted from the spatial light modulator (51) inside the object (11); a shutter (55) that blocks a part of the laser light (L) between the spatial light modulator (51) and the condenser lens (54); and a control unit (9). A control unit (9) performs a switching process for switching a modulation pattern including a diffraction pattern (MP 3). A baffle (55) blocks diffracted light (Lg) generated by a diffraction pattern (MP 3) in the laser light (L) from entering the condensing lens (54).

Description

Laser processing device

Technical Field

The present invention relates to a laser processing apparatus.

Background

Patent document 1 (japanese patent application laid-open No. 2015-223620) describes a laser processing apparatus. The laser processing device includes a spatial light modulator for modulating laser light emitted from a light source. In the spatial light modulator, a laser beam is modulated by displaying a modulation pattern on the liquid crystal layer according to a voltage applied to the liquid crystal layer. In the laser processing apparatus, as an example of laser processing, laser internal processing is cited. In this laser internal processing, when a modified region is formed in the object, the laser beam is relatively moved along a line while the converging point is aligned with the interior of the object. Thereby, the modified region is formed inside the object along the line.

Disclosure of Invention

However, in the laser internal processing described above, when the Beam profile (Beam profile) of the laser Beam is, for example, gaussian, there is a possibility that a damage (damage) such as surface ablation (absorption) occurs in a region where a central portion of the Gaussian Beam (Gaussian Beam) having a high peak intensity is incident on the incident surface of the laser Beam of the object.

In particular, when the modified region is formed by locating the converging point at a position closer to the incident surface of the laser beam of the object, the beam diameter at the incident surface of the laser beam is smaller than that in the case of locating the converging point of the laser beam farther from the incident surface, and therefore the damage is liable to occur (example 1). In addition, even when a grinding mark, a film or a tape (tape) is left on the incident surface of the laser beam of the object and the incident surface is in a state where the laser beam is easily absorbed, the damage is easily generated (example 2). Further, for example, as in the case of forming a weakened region (details of the weakened region will be described later) in the object, such damage is likely to occur even when a laser having a shorter pulse width is used than in the case of forming a modified region (example 3).

In order to suppress such damage, for example, it is conceivable to suppress the peak intensity of the laser light by modulating the laser light using a spatial light modulator as described in patent document 1. However, in example 1 described above, in the processing in which the converging point of the laser beam is located in the vicinity of the incident surface, it is desirable to suppress the peak intensity and suppress the damage, and in the processing in which the converging point of the laser beam is located at a position farther from the incident surface, it is difficult to generate the damage, and in addition, in some cases, it is undesirable to suppress the peak intensity in order to perform appropriate processing for securing energy at the processing point.

In addition, in the above example 3, in the processing for forming the weakened region by using the laser having a short pulse width, it is desirable to suppress the peak intensity and suppress the damage, but in the processing for forming the modified region by using the laser having a long pulse width, it is relatively difficult to generate the damage, and therefore, in some cases, it is not necessarily desirable to suppress the peak intensity in order to properly form the modified region. Further, in the case of example 2 described above, depending on the state of the incidence surface of the laser beam on the object, it is preferable that the peak intensity be suppressed or the necessity of suppressing the peak intensity be low.

In this way, in the above-described technical field, it is required to both suppress damage to the incident surface of the laser beam of the object and to appropriately process the object.

Accordingly, an object of the present invention is to provide a laser processing apparatus capable of achieving both suppression of damage to a laser light incident surface and appropriate processing.

The laser processing device of the invention comprises: a laser light source that outputs laser light; a spatial light modulator that includes a modulation surface on which the laser light output from the laser light source is incident, and that modulates the laser light according to a modulation pattern by displaying the modulation pattern on the modulation surface and emits the modulated laser light; a condensing lens for condensing the laser light emitted from the spatial light modulator into the object; a shutter (damper) disposed between the spatial light modulator and the condenser lens, for blocking a part of the laser light emitted from the spatial light modulator so as not to be incident on the condenser lens; a moving unit for relatively moving a converging point of the laser beam with respect to the object; and a control section that controls the laser light source, the spatial light modulator, and the moving section, the control section performing: a 1 st processing step of irradiating the object with the laser light while controlling the laser light source and the moving unit so that the position of the converging point in the Z direction intersecting the incident surface of the laser light of the object is set to be the 1 st position and the converging point is relatively moved in the X direction along the incident surface, thereby forming a modified region in the object; and a 2 nd processing step of forming a modified region in the object by controlling the laser light source and the moving unit to irradiate the object with the laser light while setting the position of the converging point in the Z direction to be a 2 nd position closer to the incident surface than the 1 st position and relatively moving the converging point in the X direction, wherein the control unit further controls the spatial light modulator so that a diffraction pattern having a higher diffraction efficiency from a region having a low intensity of the laser light in the modulation surface is displayed on the modulation surface when the 2 nd processing step is performed and so that the diffraction pattern is not displayed on the modulation surface when the 1 st processing step is performed, and the barrier blocks the diffraction light generated by the diffraction pattern from the laser light from being incident on the converging lens by switching the modulation pattern between the 1 st processing step and the 2 nd processing step.

In this processing apparatus, the 1 st processing and the 2 nd processing are performed. In the 1 st processing, the laser beam is irradiated to the object while the position of the converging point in the Z direction intersecting the incident surface of the laser beam on the object is set to the 1 st position and the converging point is relatively moved in the X direction, whereby a modified region is formed in the object. In the 2 nd processing, the modified region is formed in the same manner as in the 1 st processing, but the position of the converging point in the Z direction is set to be 2 nd position closer to the incident surface side than the 1 st position in the 1 st processing. Therefore, in the processing 2, the converging point of the laser beam is located closer to the incident surface than in the processing 1, and therefore, the incident surface is easily damaged such as surface ablation. Therefore, in the processing apparatus, a diffraction pattern is displayed on the spatial light modulator so that the diffraction efficiency increases from the region where the intensity of the laser light is low to the region where the intensity is high when the processing apparatus 2 is executed, and a switching process is performed to switch the modulation pattern between the processing 1 and the processing 2 so that the diffraction pattern is not displayed on the spatial light modulator when the processing 1 is executed. The diffracted light generated by the diffraction pattern in the laser light is blocked by the shutter so as not to be incident on the condenser lens. As a result, the peak intensity of the laser beam is suppressed by the diffraction pattern and the shutter in the 2 nd processing in which damage is relatively easy to occur, and such control of the peak intensity is not performed in the 1 st processing in which damage is relatively difficult to occur. Therefore, it is possible to achieve both suppression of damage to the laser light incident surface in the 2 nd processing and appropriate processing in the 1 st processing.

In the laser processing apparatus according to the present invention, the control unit may execute: and a 3 rd processing step of forming a modified region in the object by controlling the laser light source and the moving unit so that the position of the converging point in the Z direction is set to a 3 rd position closer to the incident surface than the 2 nd position and the converging point is moved relatively in the X direction, and thereby irradiating the object with the laser light, wherein the control unit controls the spatial light modulator so that a diffraction pattern having a higher diffraction efficiency from a region having a low intensity of the laser light in the modulation surface toward a region having a high diffraction efficiency is displayed on the modulation surface when the 3 rd processing step is performed, and the diffraction efficiency of at least 1 region in the modulation surface of the diffraction pattern in the 3 rd processing step is higher than the diffraction efficiency of a corresponding region in the modulation surface of the diffraction pattern in the 2 nd processing step. In this case, it is possible to suppress the damage of the laser light incident surface in the 2 nd processing and the 3 rd processing and to properly process in the 1 st processing.

The laser processing device of the invention comprises: a laser light source that outputs laser light; a spatial light modulator that includes a modulation surface on which the laser light output from the laser light source is incident, and that modulates the laser light according to a modulation pattern by displaying the modulation pattern on the modulation surface and emits the modulated laser light; a condensing lens for condensing the laser light emitted from the spatial light modulator into the object; a baffle plate disposed between the spatial light modulator and the condenser lens, and configured to intercept a part of the laser beam emitted from the spatial light modulator so as not to be incident on the condenser lens; a moving unit for relatively moving a converging point of the laser beam with respect to the object; and a control section that controls the laser light source, the spatial light modulator, and the moving section, the control section performing: a 1 st processing step of forming a modified region in the object by controlling the laser light source and the moving unit, and irradiating the object with the laser light while positioning the converging point inside the object through an incidence plane having an absorptivity of the laser light of 1 st absorptivity and relatively moving the converging point along an X direction along the incidence plane; and a 2 nd processing step of forming a modified region in the object by controlling the laser light source and the moving unit to irradiate the object with the laser light while the converging point is positioned inside the object and the converging point is relatively moved along the X direction along the incident surface through an incident surface having a 2 nd absorptivity higher than a 1 st absorptivity, wherein the control unit further controls the spatial light modulator to display a diffraction pattern having a higher diffraction efficiency from a region having a low intensity of the laser light in the modulation surface to a region having a high diffraction efficiency in the 2 nd processing step, and to switch the modulation pattern between the 1 st processing step and the 2 nd processing step so that the diffraction pattern is not displayed on the modulation surface in the 1 st processing step and the diffraction pattern is not displayed on the modulation surface in the 1 st processing step, and to block the diffraction pattern generated by the diffraction pattern in the laser light in the barrier so that the diffraction pattern is not displayed on the modulation surface in the 1 st processing step.

In this processing apparatus, the 1 st processing and the 2 nd processing are performed. In the 1 st processing, the laser beam is irradiated to the object while the converging point is positioned inside the object via the incidence plane of which the absorptivity of the laser beam is 1 st absorptivity and the converging point is relatively moved in the X direction, whereby a modified region is formed in the object. In the 2 nd processing, the modified region is formed in the same manner as in the 1 st processing, but the absorptivity of the laser light on the incident surface of the object is higher than in the 1 st processing. Therefore, the 2 nd processing is more likely to absorb laser light on the incident surface than the 1 st processing, and therefore, the incident surface is more likely to be damaged such as surface ablation. Therefore, in the processing apparatus, a diffraction pattern is displayed on the spatial light modulator so that the diffraction efficiency increases from the region where the intensity of the laser light is low to the region where the intensity is high when the processing apparatus 2 is executed, and a switching process is performed to switch the modulation pattern between the processing 1 and the processing 2 so that the diffraction pattern is not displayed on the spatial light modulator when the processing 1 is executed. The diffracted light generated by the diffraction pattern in the laser light is blocked by the shutter so as not to be incident on the condenser lens. As a result, the peak intensity of the laser beam is suppressed by the diffraction pattern and the shutter in the 2 nd processing in which damage is relatively easy to occur, and such control of the peak intensity is not performed in the 1 st processing in which damage is relatively difficult to occur. Therefore, it is possible to achieve both suppression of damage to the laser light incident surface in the 2 nd processing and appropriate processing in the 1 st processing.

The laser processing device of the invention comprises: a laser light source including a 1 st laser that outputs a 1 st laser light as a laser light, and a 2 nd laser that outputs a 2 nd laser light having a shorter pulse width than the 1 st laser light as the laser light; a spatial light modulator that includes a modulation surface on which the laser light output from the laser light source is incident, and that modulates the laser light according to a modulation pattern by displaying the modulation pattern on the modulation surface and emits the modulated laser light; a condensing lens for condensing the laser light emitted from the spatial light modulator into the object; a baffle plate disposed between the spatial light modulator and the condenser lens, and configured to intercept a part of the laser beam emitted from the spatial light modulator so as not to be incident on the condenser lens; a moving unit for relatively moving a converging point of the laser beam with respect to the object; a laser switching mechanism for switching the laser beam incident on the modulation surface between the 1 st laser beam and the 2 nd laser beam; and a control section that controls the laser light source, the spatial light modulator, and the moving section, the control section performing: a 1 st processing step of irradiating the object with the 1 st laser beam while relatively moving the converging point of the 1 st laser beam in an X direction along an incidence plane of the 1 st laser beam of the object while positioning the converging point inside the object by controlling the laser light source, the laser light switching mechanism, and the moving unit, thereby forming a modified region in the object; and a 2 nd processing step of forming a weakened region in the object by controlling the laser light source, the laser switching means, and the moving unit to irradiate the 2 nd laser light onto the object while relatively moving the converging point of the 2 nd laser light along an X direction along an incident surface of the 2 nd laser light of the object, wherein the control unit further controls the spatial light modulator to display a diffraction pattern having a diffraction efficiency that increases from a region having a low intensity of the laser light in the modulation surface to a region having a high diffraction efficiency in the 2 nd processing step on the modulation surface, and to switch the modulation pattern between the 1 st processing step and the 2 nd processing step so that the diffraction pattern is not displayed on the modulation surface in the case of performing the 1 st processing step, and to block the diffraction light generated by the diffraction pattern in the laser light from being incident on the condensing lens.

In this processing apparatus, the 1 st processing and the 2 nd processing are performed. In the 1 st processing, the 1 st laser beam is irradiated to the object while the converging point of the 1 st laser beam is positioned inside the object and the converging point is relatively moved in the X direction, so that a modified region is formed in the object. In the 2 nd processing, unlike the 1 st processing, the 2 nd laser having a shorter pulse width than the 1 st laser is used. That is, in the 2 nd processing, the weakened region is formed in the object by irradiating the object with the 2 nd laser light while locating the converging point of the 2 nd laser light having a relatively short pulse width inside the object and relatively moving the converging point in the X direction. Therefore, since the 2 nd processing uses a laser having a short pulse width as compared with the 1 st processing, damage to the incident surface such as surface ablation is likely to occur. Therefore, in the processing apparatus, a diffraction pattern is displayed on the spatial light modulator so that the diffraction efficiency increases from the region where the intensity of the laser light is low to the region where the intensity is high when the processing apparatus 2 is executed, and a switching process is performed to switch the modulation pattern between the processing 1 and the processing 2 so that the diffraction pattern is not displayed on the spatial light modulator when the processing 1 is executed. The diffracted light generated by the diffraction pattern in the laser light is blocked by the shutter so as not to be incident on the condenser lens. As a result, the peak intensity of the laser beam is suppressed by the diffraction pattern and the shutter in the 2 nd processing in which damage is relatively easy to occur, and such control of the peak intensity is not performed in the 1 st processing in which damage is relatively difficult to occur. Therefore, it is possible to achieve both suppression of damage to the laser light incident surface in the 2 nd processing and appropriate processing in the 1 st processing.

In the laser processing apparatus according to the present invention, the laser switching mechanism may include: a 1 st mirror for reflecting the 1 st laser light output from the 1 st laser toward the modulation surface; a 2 nd mirror for reflecting the 2 nd laser light output from the 2 nd laser toward the modulation surface; and a mirror driving unit that drives the 2 nd mirror so as to be inserted into and removed from an optical path of the 1 st laser beam from the 1 st mirror toward the modulation surface. In this case, even when the wavelength of the 1 st laser beam is close to the wavelength of the 2 nd laser beam, the switching of the laser beam which is output from the laser light source and is incident on the spatial light modulator can be reliably performed.

In the laser processing apparatus according to the present invention, the beam profile of the laser beam on the modulation surface may have a gaussian distribution, and the control unit may generate the diffraction pattern so that the diffraction efficiency increases from the outside of the modulation surface toward the center. In this case, in the processing using the laser beam having the gaussian distribution, both suppression of damage to the laser light incident surface and appropriate processing can be easily and reliably achieved.

In the laser processing apparatus according to the present invention, the control unit may generate the diffraction pattern so that the diffraction efficiency changes in at least 2 steps. In this case, the beam profile of the laser beam incident on the condenser lens and the object can be formed into a more desirable shape.

According to the present invention, it is possible to provide a laser processing apparatus capable of suppressing damage to a laser light incident surface and performing appropriate processing.

Drawings

Fig. 1 is a schematic view showing a laser processing apparatus according to the present embodiment.

Fig. 2 is a schematic diagram showing a laser processing apparatus according to the present embodiment.

Fig. 3 is a diagram showing the imaging optical system shown in fig. 1 and 2.

Fig. 4 is a schematic cross-sectional view showing the spatial light modulator shown in fig. 1 and 2.

Fig. 5 is a diagram for explaining modulation of laser light using a spatial light modulator.

Fig. 6 is a schematic diagram for explaining a relationship between a beam profile of a laser and a damage threshold.

Fig. 7 is a schematic diagram for explaining an example of the diffraction pattern.

Fig. 8 is a diagram for explaining the 1 st processing example of the laser processing apparatus.

Fig. 9 is a diagram for explaining the 1 st processing example of the laser processing apparatus.

Fig. 10 is a diagram for explaining the 1 st processing example of the laser processing apparatus.

Fig. 11 is a diagram for explaining a 2 nd working example of the laser processing apparatus.

Fig. 12 is a diagram for explaining a 2 nd working example of the laser processing apparatus.

Fig. 13 is a diagram for explaining a 3 rd processing example of the laser processing apparatus.

Fig. 14 is a diagram for explaining a 3 rd processing example of the laser processing apparatus.

Fig. 15 is a schematic view showing a laser processing apparatus according to a modification.

Detailed Description

An embodiment will be described below with reference to the drawings. In the description of each drawing, the same or corresponding portions are denoted by the same reference numerals, and overlapping description is omitted. In each of the drawings, an orthogonal coordinate system is shown which is constituted by an X axis showing an X direction, a Y axis showing a Y direction, and a Z axis showing a Z direction. As an example, the X direction is the 1 st horizontal direction, the Y direction is the 2 nd horizontal direction intersecting the X direction, and the Z direction is the vertical direction intersecting the X direction and the Y direction.

[ laser processing device ]

Fig. 1 and 2 are schematic views showing a laser processing apparatus according to the present embodiment. As shown in fig. 1 and 2, the laser processing apparatus 1 includes a stage 2, a laser light source unit 3, a 1 st moving mechanism (moving unit) 4, a laser irradiation unit 5, a 2 nd moving mechanism (moving unit) 7, and a control unit 9.

The stage 2 supports the object 11 so that the surface 11a of the object 11 is orthogonal to the Z direction by, for example, attaching a film (not shown) to the object 11. Here, the object 11 is supported on the stage 2 with the surface 11a facing the laser irradiation section 5. The stage 2 is movable in each of the X direction and the Y direction, and is rotatable about an axis parallel to the Z direction as a center line.

The laser light source unit (laser light source) 3 outputs laser light L by, for example, a pulse oscillation system. The laser light L has, for example, permeability to the object 11. The laser light source unit 3 includes a 1 st laser 31, a 2 nd laser 32, attenuators 33 and 36, beam expanders 34 and 37, a 1 st mirror 35, a 2 nd mirror 38, and a mirror driving unit 39.

The 1 st laser 31 outputs the 1 st laser light L1 as the laser light L. The attenuator 33 and the beam expander 34 are disposed in this order on the optical path of the 1 st laser light L1. The attenuator 33 receives the 1 st laser beam L1 emitted from the 1 st laser 31, adjusts the output of the 1 st laser beam L1, and emits the 1 st laser beam. The beam expander 34 expands the diameter of the 1 st laser beam L1 outputted by the attenuator 33. The 1 st mirror 35 reflects the 1 st laser beam L1 emitted from the beam expander 34 toward the laser irradiation section 5 (a modulation surface 51a of the spatial light modulator 51 described below).

The 2 nd laser 32 outputs the 2 nd laser light L2 as the laser light L. The attenuator 36 and the beam expander 37 are disposed in this order on the optical path of the 2 nd laser light L2. The attenuator 36 receives the 2 nd laser beam L2 emitted from the 2 nd laser 32, adjusts the output of the 2 nd laser beam L2, and emits the 2 nd laser beam. The beam expander 37 expands the diameter of the 2 nd laser beam L2 outputted by the attenuator 36. The 2 nd mirror 38 reflects the 2 nd laser light L2 emitted from the beam expander 37 toward the laser light irradiation section 5 (the modulation surface 51a of the spatial light modulator 51 described below).

The mirror driving section 39 drives the 2 nd mirror 38 using, for example, a cylinder (air cylinder) or the like. More specifically, the mirror driving unit 39 drives the 2 nd mirror 38 so as to insert and withdraw the 2 nd mirror 38 with respect to the optical path of the 1 st laser light L1 from the 1 st mirror 35 toward the modulation surface 51 a. The position of the 2 nd mirror 38 is determined by being pushed against a preset member when driven by the mirror driving section 39. Therefore, it is difficult to generate an optical axis shift. Fig. 1 shows a state in which the 2 nd mirror 38 is pulled out from the optical path of the 1 st laser beam L1, and fig. 2 shows a state in which the 2 nd mirror 38 is inserted into the optical path of the 1 st laser beam L1.

As a result, the laser light source unit 3 can switch between a state in which the 1 st laser light L1 is output (a state in which the 2 nd mirror 38 is removed from the optical path of the 1 st laser light L1) and a state in which the 2 nd laser light L2 is output (a state in which the 2 nd mirror 38 is disposed on the optical path of the 1 st laser light L1). That is, the laser processing apparatus 1 is configured to switch between processing using the 1 st laser beam L1 and processing using the 2 nd laser beam L2. The 1 st mirror 35, the 2 nd mirror 38, and the mirror driving section 39 constitute a laser switching mechanism. The 1 st mirror 35 and the 2 nd mirror 38 are aligned so that the optical axis of the 1 st laser light L1 and the optical axis of the 2 nd laser light L2 coincide.

The combination of the 1 st laser 31 and the 2 nd laser 32 may be arbitrarily set according to the required processing mode. One example of a combination of the 1 st laser 31 and the 2 nd laser 32 is as follows. SD means processing for forming a modified region in the object 11, and SG means processing for forming a weakened region in the object 11.

EXAMPLE 1 various glass processing

No. 1 laser 31:1030nm (pulse width: fs)

2 nd laser 32:532nm (pulse width: ps)

EXAMPLE 2 dissimilar material SD (example: glass/Si)

1 st laser 31:532nm (pulse width: ps)

2 nd laser 32:1099nm (pulse width: ns)

Example 3: heterogeneous treatment (SG/SD)

1 st laser 31:1099nm (pulse width: ns)

2 nd laser 32:1064nm (pulse width: ps)

Example 4 Si (thin)/Si (thick)

1 st laser 31:1064nm (pulse width: ns)

2 nd laser 32:1099nm (pulse width: ns)

Reference is next made to fig. 1, 2. The laser irradiation unit 5 irradiates the object 11 with the laser light L having transparency to the object 11 by condensing the laser light L. When the laser light L is condensed in the object 11 supported by the stage 2, the laser light L is absorbed particularly in a portion corresponding to the condensed point C of the laser light L, and the modified region 12 (or a weakened region 22 described below) is formed in the object 11.

The modified region 12 is a region having a density, refractive index, mechanical strength, and other physical properties different from those of the surrounding non-modified region. Examples of the modified region 12 include a melt-processed region, a crack region, an insulation-damaged region, and a refractive index change region. The modified region 12 may be formed such that a crack extends from the modified region 12 to the incident side and the opposite side of the laser light L. Such modified regions 12 and cracks are used for cutting the object 11, for example.

The 1 st movement mechanism 4 includes: a 1 st moving unit 41 that moves the stage 2 in one direction in a plane intersecting (orthogonal to) the Z direction; and a 2 nd moving unit 42 for moving the stage 2 in the other direction in the plane intersecting (orthogonal to) the Z direction. As an example, the 1 st moving unit 41 moves the stage 2 in the X direction, and the 2 nd moving unit 42 moves the stage 2 in the Y direction. The 1 st moving mechanism 4 may include a moving portion that rotates the stage 2 about an axis parallel to the Z direction as a rotation axis. The 2 nd moving mechanism 7 moves the laser irradiation section 5 at least in the Z direction (may also move in the X direction and the Y direction).

As an example, when the stage 2 is moved in the X direction and the converging point C is moved relative to the object 11 in the X direction, the plurality of modified spots 12s are formed so as to be aligned in 1 line in the X direction. 1 modified dot 12s is formed by irradiation of 1 pulse of laser light L. The modified regions 12 of 1 row are a set of modified spots 12s arranged in 1 row. The adjacent modified spots 12s may be connected to each other or separated from each other depending on the relative movement speed of the converging spot C with respect to the object 11 and the repetition frequency of the laser beam L. Thus, the 1 st moving mechanism 4 and the 2 nd moving mechanism 7 are moving parts for moving the converging point C of the laser beam L relative to the object 11.

The laser irradiation section 5 includes a spatial light modulator 51, an imaging optical system 52, a mirror 53, and a condenser lens 54. The spatial light modulator 51 receives the laser beam L output from the laser light source unit 3, modulates the laser beam L, and outputs the modulated laser beam L. The mirror 53 reflects the laser light L emitted from the spatial light modulator 51 toward the condenser lens 54. The condensing lens 54 condenses the laser light L toward the object 11. The imaging optical system 52 is interposed between the spatial light modulator 51 and a condenser lens 54 (here, a mirror 53).

Fig. 3 is a diagram showing the imaging optical system shown in fig. 1 and 2. As shown in fig. 3, the imaging optical system 52 includes a pair of lenses 52A, 52B constituting a 4f lens unit. The pair of lenses 52A and 52B constitute a two-sided telecentric (telecentric) optical system in which the modulation surface 51a of the spatial light modulator 51 and the entrance pupil surface 33a of the condenser lens 54 are in imaging relation. Thus, the image of the laser light on the modulation surface 51a of the spatial light modulator 51 (the image of the laser light L modulated on the spatial light modulator 51) is converted (imaged) on the entrance pupil surface 54a of the condenser lens 54. In addition, fs in the figure shows fourier surfaces. The laser irradiation section 5 further includes a shutter 55 disposed on the fourier surface Fs.

Fig. 4 is a schematic cross-sectional view showing the spatial light modulator shown in fig. 1 and 2. As shown in FIG. 4, the spatial light modulator 51 is a spatial light modulator (SLM: spatial Light Modulator) of a reflective liquid crystal (LCOS: liquid Crystal on Silicon). The spatial light modulator 51 is formed by sequentially stacking a driving circuit layer 512, a pixel electrode layer 513, a reflective film 514, an alignment film 515, a liquid crystal layer 516, an alignment film 517, a transparent conductive film 518, and a transparent substrate 519 on a semiconductor substrate 511.

The semiconductor substrate 511 is, for example, a silicon substrate. The driving circuit layer 512 constitutes an active matrix (active matrix) circuit on the semiconductor substrate 511. The pixel electrode layer 513 includes a plurality of pixel electrodes 513a arranged in a matrix along the surface of the semiconductor substrate 511. Each pixel electrode 513a is formed of a metal material such as aluminum, for example. A voltage is applied to each pixel electrode 513a through the driving circuit layer 512.

The reflective film 514 is, for example, a dielectric multilayer film. The alignment film 515 is provided on the surface of the liquid crystal layer 516 on the side of the reflection film 514, and the alignment film 517 is provided on the surface of the liquid crystal layer 516 on the opposite side of the reflection film 514. The alignment films 515 and 517 are formed of a polymer material such as polyimide, for example, and rubbing (rubbing) treatment is performed on the surfaces of the alignment films 515 and 517 in contact with the liquid crystal layer 516, for example. The alignment films 515 and 517 align the liquid crystal molecules 516a included in the liquid crystal layer 516 in a predetermined direction.

The transparent conductive film 518 is provided on the surface of the transparent substrate 519 on the alignment film 517 side, and faces the pixel electrode layer 513 through the liquid crystal layer 516 and the like. The transparent substrate 519 is, for example, a glass substrate. The transparent conductive film 518 is made of a light-transmitting and conductive material such as ITO. The transparent substrate 519 and the transparent conductive film 518 transmit the laser light L.

In the spatial light modulator 51 having the above-described configuration, when a signal indicating a modulation pattern is input from the control unit 9 to the driving circuit layer 512, a voltage corresponding to the signal is applied to each pixel electrode 513a, and an electric field is formed between each pixel electrode 513a and the transparent conductive film 518. When the electric field is formed, in the liquid crystal layer 516, the arrangement direction of the liquid crystal molecules 516a changes for each region (pixel 51 p) corresponding to each pixel electrode 513a, and the refractive index changes for each region corresponding to each pixel electrode 513 a. This state is a state in which a modulation pattern is displayed on the liquid crystal layer 516. The modulation pattern is used to modulate the laser light L.

That is, when the laser light L is incident on the liquid crystal layer 516 from the outside through the transparent substrate 519 and the transparent conductive film 518 while the liquid crystal layer 516 is displaying a modulation pattern, the laser light L is reflected by the reflective film 514 and is emitted from the liquid crystal layer 516 to the outside through the transparent conductive film 518 and the transparent substrate 519, and the laser light L is modulated according to the modulation pattern displayed on the liquid crystal layer 516. In this way, the modulation pattern displayed on the liquid crystal layer 516 is appropriately set according to the spatial light modulator 51, so that the laser light L can be modulated (for example, the intensity, amplitude, phase, polarization, and the like of the laser light L are modulated).

The modulation surface 51a shown in fig. 3 and the like is, for example, a liquid crystal layer 516. Accordingly, the spatial light modulator 51 includes a modulation surface 51a on which the laser light L output from the laser light source unit 3 is incident, and is configured to modulate the laser light L according to a modulation pattern by displaying the modulation pattern on the modulation surface 51 a. As the modulation pattern, various patterns such as a distortion correction pattern and an aberration correction pattern can be used, and here, a case of using a diffraction pattern including a diffraction lattice for diffracting the laser light L is exemplified.

Fig. 5 is a diagram for explaining modulation of laser light using a spatial light modulator. Fig. 5 (a) shows a state in which the modulation pattern MP1 including no diffraction pattern is displayed on the modulation surface 51a (i.e., no diffraction pattern is displayed), and fig. 5 (b) shows a state in which the diffraction pattern MP2 is displayed on the modulation surface 51 a. In the state shown in fig. 5 (a), the laser light L output from the laser light source unit 3 and incident on the modulation surface 51a is reflected on the modulation surface 51a without diffraction, and is emitted from the spatial light modulator 51. Therefore, the substantially entire laser beam L passes through the baffle 55 and is incident on the condenser lens 54 (entrance pupil plane 54 a) via the imaging optical system 52, and is condensed toward the object 11.

On the other hand, in the state shown in fig. 5 (b), the laser beam L output from the laser light source unit 3 and incident on the modulation surface 51a is diffracted according to the diffraction pattern MP2 displayed on the modulation surface 51a, and is branched into diffracted light Lg and non-diffracted light Ln, and is emitted from the spatial light modulator 51. The non-diffracted light Ln passes through the baffle 55 without being deflected and is incident on the condenser lens 54 (entrance pupil plane 54 a) via the imaging optical system 52, and is condensed toward the object 11, as in the state of fig. 5 (a).

On the other hand, the diffracted light Lg is emitted at an angle corresponding to the diffraction pattern MP2, and is blocked by the shutter 55. Therefore, the diffracted light Lg does not enter the condenser lens 54 (entrance pupil plane 54 a) and does not reach the object 11. That is, the shutter 55 is disposed between the spatial light modulator 51 and the condenser lens 54, and blocks a part of the laser light L emitted from the spatial light modulator 51 from entering the condenser lens 54. More specifically, the shutter 55 blocks the diffracted light Lg generated by the diffraction pattern MP2 in the laser light L so as not to be incident on the condenser lens 54.

At this time, by adjusting the period of the grating (graining) of the diffraction pattern MP2, the branching distance of the diffracted light Lg can be set so that the diffracted light Lg is blocked by the shutter 55. Further, by adjusting the gradation value (gradation difference of 2 values) of the diffraction pattern MP2, the ratio (diffraction efficiency) of the diffracted light Lg can be adjusted. That is, for example, when the diffraction pattern MP2 having a half diffraction efficiency of a gradation value is used for the entire surface of the modulation surface 51a, the ratio of the diffracted light Lg to the non-diffracted light Ln is 50:50, and half of the laser light L reaches the object 11 through the baffle 55.

When the diffraction pattern MP2 having the highest diffraction efficiency and having the highest gradation value is used for the entire modulation surface 51a, the ratio of the diffracted light Lg to the non-diffracted light Ln is 100:0, and all of the laser light L is blocked by the shutter 55. In this way, in the laser processing apparatus 1, the ratio of the laser beam L reaching the object 11 for processing can be adjusted by adjusting the diffraction pattern MP2 displayed on the spatial light modulator 51.

Here, as shown in fig. 6 (a), when the beam profile Pf of the laser beam L has a gaussian distribution and its peak intensity (peak energy) is lower than the damage threshold Th of the incident surface (here, the surface 11 a) of the laser beam L of the object 11, damage such as surface ablation is not generated, and laser internal processing of the object 11 can be performed. On the other hand, as shown in fig. 6 (b), if the damage threshold Th of the incident surface of the object 11 is lowered, there is a possibility that damage will occur in the area of the incident surface where the center portion of the gaussian beam having high peak intensity is incident. Therefore, as shown in fig. 6 (c), it is desirable to suppress the peak intensity and to suppress the damage of the incident surface and to perform processing.

Accordingly, in the laser processing apparatus 1, as shown in fig. 7, the diffraction pattern MP3 having a high diffraction efficiency is displayed from the low intensity region of the laser light L in the modulation surface 51a toward the high region with respect to the modulation surface 51a of the spatial light modulator 51, so that the laser light L having the beam profile Pf2 with suppressed peak intensity is formed on the entrance pupil surface 54a of the condenser lens 54.

In the example of fig. 7, the laser light L has a gaussian beam profile pf1 on the modulation surface 51a, and the intensity increases from the region R1 to the region R3 of the modulation surface 51 a. That is, the region R3 of the modulation surface 51a is located at, for example, the center of the modulation surface 51a, and is the region where the intensity of the laser light L is highest. The region R1 is a ring-shaped region outside the region R3, and is a region where the intensity of the laser light L is the lowest. The region R2 is a ring-shaped region between the region R1 and the region R3, and is a region in which the intensity of the laser light L is intermediate.

Therefore, in this example, the diffraction pattern MP3 displayed on the modulation surface 51a is a pattern in which the diffraction efficiency increases stepwise (2 steps in this case) from the outside (region R1) of the modulation surface 51a toward the center (region R3). As an example, the diffraction efficiency in the region R1 of the diffraction pattern MP3 may be 0%, the diffraction efficiency in the region R2 of the diffraction pattern MP3 may be 30%, and the diffraction efficiency in the region R3 of the diffraction pattern MP3 may be 50%.

As a result, the proportion of diffracted light Lg is maximized (i.e., the proportion of the laser light L blocked by the shutter 55 is maximized) at the portion of the laser light L incident on the region R3. In addition, the proportion of diffracted light Lg in the laser light L decreases (that is, it is difficult to block the laser light by the baffle plate 55) in the order of the portion of the laser light L that is incident on the region R2 and the portion that is incident on the region R1. As a result, the laser beam L having the flat (flat) beam profile pf2 as a whole is formed with the peak intensity suppressed at the entrance pupil plane 54a of the condenser lens 54.

In the laser processing apparatus 1, the same effect can be obtained by adjusting the diffraction pattern MP3 so that the diffraction efficiency increases from the region where the intensity of the laser light L on the modulation surface 51a is relatively low to the region where the intensity of the laser light L is high, not limited to the case where the beam profile of the laser light L has a gaussian distribution.

[ working example 1 ]

Next, a description will be given of a 1 st processing example of laser processing by the laser processing apparatus 1 including various processes performed under the control of the control unit 9. In this processing example 1, laser light is irradiated to the object 11 at a plurality of positions in the Z direction intersecting the surface 11a along the line a extending in the X direction along the surface 11a, to form the modified region 12. The control unit 9 is configured as a computer device including a processor, a memory, a storage, a communication device, and the like. The control unit 9 executes software (program) read into a memory or the like by a processor, and controls reading and writing of data from and to the memory and the storage, and communication by a communication device, thereby executing various processes.

In the 1 st working example, first, preparation for working is performed. In preparation for machining, first, as shown in fig. 8, the object 11 is supported by the stage 2, and the machining conditions are set. The object 11 of the 1 st processing example is, for example, a semiconductor wafer such as a silicon wafer. The object 11 includes a front surface 11a and a rear surface 11b opposite to the front surface 11 a. The object 11 is supported on the stage 2 with the surface 11a facing the laser irradiation section 5. Thus, the surface 11a of the object 11 serves as an incident surface of the laser light L.

Here, it is possible to set which of the irradiation (scanning) of the laser light L at a plurality of positions different in the Z direction is used in the diffraction pattern MP3 described above. For example, among the plurality of scans at different positions in the Z direction, a setting using the diffraction pattern MP3 is performed at the time of scanning at the position closest to the surface 11a and at the time of scanning at the position closest to the surface 11 a. Thereafter, generation and calibration (calibration) of a modulation pattern including the diffraction pattern MP3 are actually performed.

Next, in preparation for processing, alignment (alignment) and height setting (height set) are performed. As an example, here, based on images of the object 11 and the laser light L taken by a camera not shown, the irradiation positions of the laser light L in the X direction and the Y direction (the direction along the surface 11 a) are determined as alignment, and the position of the focal point C of the laser light L in the Z direction is adjusted as height setting. After that, the processing is actually performed.

That is, in the laser processing apparatus 1, the control unit 9 executes the processing (1 st processing) S11 of forming the modified region 12 in the object 11 by irradiating the object 11 with the laser light L while setting the position of the converging point C of the laser light L in the Z direction to the 1 st position Z1 and relatively moving the converging point C in the X direction by controlling the laser light source unit 3, the 1 st moving mechanism 4, and the 2 nd moving mechanism 7.

At this time, the control unit 9 controls the laser oscillation of any one of the 1 st laser 31 and the 2 nd laser 32, and controls the mirror driving unit 39 as necessary, whereby any one of the 1 st laser L1 and the 2 nd laser L2 can be output as the laser light L from the laser light source unit 3. The control unit 9 may execute the processing S11 with respect to 2 or more 1 st positions Z1 different from each other.

In the processing S11, the control unit 9 controls the spatial light modulator 51 so that the diffraction pattern MP3 having a higher diffraction efficiency is not displayed on the modulation surface 51a from the region (for example, the region R1) having a low intensity of the laser light L in the modulation surface 51a toward the region (for example, the region R3) (so that the modulation pattern MP1 not including the diffraction pattern MP3 is displayed on the modulation surface 51 a).

Next, as shown in fig. 9, in the laser processing apparatus 1, the control unit 9 executes a processing (S) (2) S12 of forming the modified region 12 in the object 11 by controlling the laser light source unit 3, the 1 st movement mechanism 4, and the 2 nd movement mechanism 7, while setting the position of the converging point C in the Z direction to a 2 nd position Z2 on the front surface 11a side of the 1 st position Z1, and relatively moving the converging point C in the X direction and irradiating the object 11 with the laser light L.

At this time, the control unit 9 may control the laser light source unit 3 so that one of the 1 st laser light L1 and the 2 nd laser light L2, which is used in the processing S11, is output as the laser light L from the laser light source unit 3. That is, the same laser light L may be used in the processing S11 and the processing S12. In this case, the laser processing apparatus 1 may be provided with one of the 1 st laser 31 and the 2 nd laser 32, and the laser switching mechanism is not required.

In the processing S12, the control unit 9 controls the spatial light modulator 51 so that the diffraction pattern MP3 is displayed on the modulation surface 51 a. In this way, the control unit 9 further executes the switching process S13 (see fig. 8 and 9) of switching the modulation pattern between the process S11 and the process S12 so that the diffraction pattern MP3 is displayed on the modulation surface 51a when the process S12 is executed and the diffraction pattern MP3 is not displayed on the modulation surface 51a when the process S11 is executed.

As described above, in the processing example 1, the processing S11 and the processing S12 are performed. In the processing S11, the laser beam L is irradiated onto the object 11 while the position of the converging point C of the laser beam in the Z direction is set to the 1 st position Z1 and the converging point C is relatively moved in the X direction, so that the modified region 12 is formed in the object 11. In the processing S12, the modified region 12 is formed in the same manner as in the processing S11, but the position of the converging point C in the Z direction is set to the 2 nd position Z2 on the incident surface side than the 1 st position Z1.

Therefore, since the converging point C of the laser light L is located closer to the incident surface in the processing S12 than in the processing S11, the beam diameter of the laser light L on the incident surface becomes smaller, and damage to the incident surface such as surface ablation is likely to occur. Therefore, in the laser processing apparatus 1, the switching process for switching the modulation pattern is performed such that the diffraction pattern MP3 having higher diffraction efficiency from the region where the intensity of the laser light L is low toward the region where the intensity is high is displayed on the spatial light modulator 51 when the processing process S12 is performed, and such that the diffraction pattern MP3 is not displayed on the spatial light modulator 51 when the processing process S11 is performed.

The diffraction light Lg generated by the diffraction pattern MP3 in the laser light L is blocked by the shutter 55 so as not to be incident on the condenser lens 54. As a result, when the processing S12 in which damage is relatively easy to occur is performed, the peak intensity of the laser beam L is suppressed by the diffraction pattern MP3 and the shutter 55, and when the processing S11 in which damage is relatively difficult to occur is performed, such control of the peak intensity is not performed. Therefore, both suppression of damage to the laser light incident surface in the processing step S12 and appropriate processing in the processing step S11 can be achieved.

Next, as shown in fig. 10, in the laser processing apparatus 1, the control unit 9 performs a processing (processing 3) S14 of forming the modified region 12 in the object 11 by controlling the laser light source unit 3, the 1 st moving mechanism 4, and the 2 nd moving mechanism 7, while setting the position of the converging point C in the Z direction to a third position Z3 closer to the surface 11a than the 2 nd position Z2, and relatively moving the converging point C in the X direction and irradiating the object 11 with the laser light L.

At this time, the control unit 9 may control the laser light source unit 3 so that one of the 1 st laser light L1 and the 2 nd laser light L2, which is used in the processing steps S11 and S12, is output as the laser light L from the laser light source unit 3. That is, the same laser light L may be used in the processing steps S11, S12 and S14. In this case, the laser processing apparatus 1 may be provided with one of the 1 st laser 31 and the 2 nd laser 32, and the laser switching mechanism is not required.

In the 1 st working example, the scan in the working process S14 is a scan at a position closest to the surface 11a among scans at a plurality of positions different in the Z direction. Therefore, the control unit 9 controls the spatial light modulator 51 so that the diffraction pattern is displayed on the modulation surface 51a in the processing step S14. In the processing S14, the modified region 12 is formed similarly to the processing S12, but the position of the converging point C in the Z direction is set to a 3 rd position Z3 on the incident surface side than the 2 nd position Z2.

Therefore, since the converging point C of the laser light L is located closer to the incident surface in the processing S14 than in the processing S12, the beam diameter of the laser light L on the incident surface becomes smaller, and damage to the incident surface such as surface ablation is more likely to occur. Therefore, in the laser processing apparatus 1, when the processing S14 is performed, the diffraction pattern MP4 having a higher diffraction efficiency from the region where the intensity of the laser light L is low toward the region where the intensity is high is displayed on the spatial light modulator 51. In particular, at least a part of the regions R1 to R3 in the modulation surface 51a of the diffraction pattern MP4 has a higher diffraction efficiency than the corresponding regions R1 to R3 in the modulation surface 51a of the diffraction pattern MP3 of the processing S12.

As an example, when the diffraction efficiency in the region R1 of the diffraction pattern MP3 in the processing S12 is 0%, the diffraction efficiency in the region R2 of the diffraction pattern MP3 is 15%, and the diffraction efficiency in the region R3 of the diffraction pattern MP3 is 25%, the diffraction efficiency in the region R1 of the diffraction pattern MP4 in the processing S14 can be 0%, the diffraction efficiency in the region R2 of the diffraction pattern MP4 is 30%, and the diffraction efficiency in the region R3 of the diffraction pattern MP4 is 50%. That is, the diffraction efficiency of each of the regions R1 to R3 of the diffraction pattern MP4 is equal to or higher than the diffraction efficiency of the corresponding region R1 to R3 of the diffraction pattern MP3 of the processing S12, and in particular, the diffraction efficiency of the regions R2, R3 of the diffraction pattern MP4 is higher than the diffraction efficiency of the regions R2, R3 of the diffraction pattern MP 3. As a result, when the processing S14 is performed, in which damage is more likely to occur, the peak intensity of the laser light L is suppressed to be lower than in the case of the processing S12 by the diffraction pattern MP4 and the shutter 55.

In the laser processing apparatus 1, the beam profile Pf1 of the laser beam L on the modulation surface 51a may have a gaussian distribution, and the control unit 9 may generate the diffraction patterns MP3 and MP4 so that the diffraction efficiency increases from the outside of the modulation surface 51a toward the center. In this case, in the processing using the laser light L having the gaussian distribution, both suppression of damage to the laser light incident surface and appropriate processing can be easily and reliably achieved.

In the laser processing apparatus 1, the control unit 9 may generate the diffraction patterns MP3 and MP4 so that the diffraction efficiency changes in at least 2 steps. In this case, the beam profile of the laser beam L incident on the condenser lens 54 and the object 11 can be formed into a more desirable shape.

In addition, in all irradiation (scanning) of the laser light L at a plurality of positions different in the Z direction, diffraction patterns MP3, MP4 having higher diffraction efficiency from a region where the intensity of the laser light L is low toward a region where the intensity is high may be used. As an example, in the processing S11 in which the converging point C of the laser light L is located at the 1 st position Z1 relatively far from the incident surface of the laser light L, the diffraction pattern MP3 having relatively low diffraction efficiency may be used, and in the processing S12 in which the converging point C of the laser light L is located at the 2 nd position Z2 relatively close to the incident surface of the laser light L, the processing S14 in which the converging point C of the laser light L is located at the 3 rd position Z3, the diffraction pattern MP4 having relatively high diffraction efficiency may be used. That is, the control unit 9 may perform processing to display a diffraction pattern having high diffraction efficiency on the spatial light modulator 51 as the position of the converging point C of the laser light L in the Z direction approaches the incidence plane.

[ working example 2 ]

Next, a description will be given of a processing example 2 of the laser processing apparatus 1 including various processes performed under the control of the control unit 9. In this processing example 2, the object 11 is irradiated with the laser light L along a line a extending along the X direction along the surface 11a to form the modified region 12 and the weakened region 22. In the processing example 2, first, processing preparation is performed. In preparation for machining, first, as shown in fig. 11, machining conditions are set as a state in which the object 11 is supported on the stage 2.

Object 11 of processing example 2 includes substrate 16 and functional element layer 17 formed on substrate 16. The substrate 16 includes a surface 11a, and the functional element layer 17 includes a back surface 11b. The substrate 16 is, for example, a semiconductor substrate including silicon or the like. The functional element layer 17 is a layer including a plurality of functional elements (semiconductor elements) arranged along the X direction and the Y direction. In the functional element layer 17, a plurality of functional elements may be stacked in the Z direction. In addition, the functional element layer 17 may include an insulating film such as a metal wiring, a metal film, or a Low-k film. The object 11 is supported on the stage 2 via a belt T provided on the rear surface 11b so that the front surface 11a faces the laser irradiation section 5. Thus, the surface 11a of the object 11 is set as the incident surface of the laser light L.

Here, it is possible to set which of the irradiation (scanning) of the laser light L for forming the modified region 12 and the irradiation (scanning) of the laser light L for forming the weakened region 22 is used in the diffraction pattern MP3 described above. Here, the setting is performed such that the diffraction pattern MP3 is used in the scanning for forming the weakened region 22 and the diffraction pattern MP3 is not used in the scanning for forming the modified region 12. Thereafter, generation and calibration of a modulation pattern including the diffraction pattern MP3 are actually performed.

Next, in preparation for processing, alignment and height setting are performed. As an example, here, based on images of the object 11 and the laser light L taken by a camera not shown, the irradiation positions of the laser light L in the X direction and the Y direction (the direction along the surface 11 a) are determined as alignment, and the position of the focal point C of the laser light L in the Z direction is adjusted as height setting. After that, the processing is actually performed.

That is, in the laser processing apparatus 1, the control unit 9 performs the processing (processing of the 2 nd) S21 of forming the weakened region 22 in the object 11 by controlling the laser light source unit 3, the 1 st moving mechanism 4, and the 2 nd moving mechanism 7 so that the converging point C of the 2 nd laser light L2 is positioned inside the object 11 and the converging point C is relatively moved in the X direction and so that the 2 nd laser light L2 is irradiated to the object 11. In the processing S21, the control unit 9 controls the spatial light modulator 51 so that the diffraction pattern MP3 is displayed on the modulation surface 51 a.

At this time, the control section 9 controls the laser oscillation of the 2 nd laser 32 out of the 1 st laser 31 and the 2 nd laser 32, and controls the mirror driving section 39 to drive the 2 nd mirror 38, thereby outputting the 2 nd laser light L2 as the laser light L from the laser light source section 3. The pulse width of the 2 nd laser beam L2 is set to be shorter than the pulse width of the 1 st laser beam L1 used in the processing step S22 described below (for specific examples of the wavelength and the pulse width, refer to the above-mentioned [ example 3: heterogeneous processing (SG/SD) ]). The converging point C of the 2 nd laser beam L2 is located near the interface between the substrate 16 and the functional element layer 17 (in the illustrated example, inside the functional element layer 17) in the Z direction.

Weakened region 22 is a region where functional element layer 17 is weakened. Weakening includes embrittlement. The weakening of the functional element layer 17 refers to thermal damage such as melting and evaporation due to absorption of the 2 nd laser light L2, change in chemical bonds due to laser light irradiation, and results of non-thermal processing such as cutting or ablation processing in a region of at least a part of the functional element layer 17 (for example, a part of the functional element layer 17, at least one layer among the layers constituting the functional element layer 17, and the like).

The weakening of the functional element layer 17 means that when stress such as bending stress or tensile stress is applied to the functional element layer 17 as a result, a state is brought about in which cutting or breaking is likely to occur, as compared with a non-treated region (a region not weakened). The weakened region (embrittlement region) 22 is a region where a trace is generated by laser irradiation, and is a region which is easily cut or broken as compared with the untreated region. The weakened region 22 may be formed continuously in a linear shape in at least a part of the functional element layer 17, or may be formed intermittently according to the pulse pitch of laser irradiation.

That is, when the weakened region 22 is formed by arranging a plurality of 1 weakened points formed by the irradiation of the 2 nd laser light L2 as the pulse light, the adjacent weakened points may be continuously connected, intermittently connected, or separated from each other. The weakened points may be exposed on the front surface (back surface 11 b) of the functional element layer 17, and the exposed weakened points may be continuously connected, intermittently connected, or independently separated from each other. In recent years, in order to cope with the miniaturization of wiring of devices, it has become more effective to form the weakened region 22 as described above by using a Low-k film as an insulating film, by stacking a plurality of films, metal wiring, or metal film in accordance with an increase in the number of stacked patterns in three dimensions, or the like.

Next, as shown in fig. 12, in the laser processing apparatus 1, the control unit 9 executes a processing (1 st processing) S22 of forming the modified region 12 in the object 11 by controlling the laser light source unit 3, the 1 st moving mechanism 4, and the 2 nd moving mechanism 7, and irradiating the object 11 with the 1 st laser light L1 while relatively moving the 1 st laser light L1 converging point C in the X direction, thereby positioning the 1 st laser light L1 converging point C inside the object 11.

At this time, the control unit 9 controls the laser oscillation of the 1 st laser 31 out of the 1 st laser 31 and the 2 nd laser 32, and controls the mirror driving unit 39 to drive the 1 st laser L1 as the laser light L by pulling out the 2 nd mirror 38 from the optical path of the 1 st laser L1. The converging point C of the 1 st laser beam L1 is located closer to the surface 11a than the weakened region 22 in the Z direction.

In the processing S22, the control unit 9 controls the spatial light modulator 51 so that the diffraction pattern MP3 is not displayed on the modulation surface 51a (so that the modulation pattern MP1 including no diffraction pattern MP3 is displayed on the modulation surface 51 a). In this way, the control unit 9 further executes the switching process S23 (see fig. 11 and 12) of switching the modulation pattern between the process S21 and the process S22 so that the diffraction pattern MP3 is displayed on the modulation surface 51a when the process S21 is executed and the diffraction pattern MP3 is not displayed on the modulation surface 51a when the process S22 is executed.

In the processing example 2, different lasers L are used in the processing S21 and the processing S22. Thus, it is possible to perform generation and calibration of the modulation pattern in preparation for processing each laser, i.e., each of the 1 st laser light L1 and the 2 nd laser light L2, and record information of the attenuators 33, 36. In addition, setting (output measurement range) of a power meter (power meter) may be switched for each laser as needed.

As described above, in processing example 2, processing S21 and processing S22 are performed. In the processing S22, the 1 st laser beam L1 is irradiated onto the object 11 while the converging point C of the 1 st laser beam L1 is positioned inside the object 11 and the converging point C is relatively moved in the X direction, so that the modified region 12 is formed in the object 11. In the processing S21, unlike the processing S22, the 2 nd laser light L2 having a shorter pulse width than the 1 st laser light L1 is used. That is, in the processing S21, the weakened region 22 is formed in the object 11 by irradiating the object 11 with the 2 nd laser light L2 while locating the converging point C of the 2 nd laser light L2 of a relatively short pulse width inside the object 11 and relatively moving the converging point C in the X direction.

Therefore, since a laser having a short pulse width is used in the processing step S21, damage to the incident surface such as surface ablation is likely to occur, as compared with the processing step S22. Therefore, in the laser processing apparatus 1, a switching process is performed to switch the modulation pattern between the processing S21 and the processing S22 so that the diffraction pattern MP3 having a higher diffraction efficiency from the low intensity region of the laser light L (the 2 nd laser light L2) to the high region is displayed on the spatial light modulator 51 when the processing S21 is performed, and so that the diffraction pattern MP3 is not displayed on the spatial light modulator 51 when the processing S22 is performed.

The diffraction light Lg generated by the diffraction pattern MP3 in the laser light L (the 2 nd laser light L2) is blocked by the baffle 55 so as not to be incident on the condenser lens 54. As a result, when the processing S21 is relatively likely to be damaged, the diffraction pattern MP3 and the shutter 55 suppress the peak intensity of the laser beam L (the 2 nd laser beam L2), and when the processing S22 is relatively unlikely to be damaged, such peak intensity control is not performed. Therefore, both suppression of damage to the laser light incident surface in the processing step S21 and appropriate processing in the processing step S22 can be achieved.

The laser processing device 1 further includes: a 1 st mirror 35 for reflecting the 1 st laser light L1 output from the 1 st laser 31 toward the modulation surface 51 a; a 2 nd mirror 38 for reflecting the 2 nd laser light L2 output from the 2 nd laser 32 toward the modulation surface 51 a; and a mirror driving unit 39 for driving the 2 nd mirror 38 so as to be inserted into and removed from the 2 nd mirror 38 with respect to the optical path of the 1 st laser beam L1 directed from the 1 st mirror 35 to the modulation surface 51 a. Therefore, even when the wavelength of the 1 st laser beam L1 is close to the wavelength of the 2 nd laser beam L2 (for example, 1064nm and 1099nm as in the above example), the laser beam L (incident on the spatial light modulator 51) output from the laser light source unit 3 can be reliably switched.

[ working example 3 ]

Next, a description will be given of a processing example 3 of the laser processing apparatus 1 including various processes performed under the control of the control unit 9. In this processing example 3, 2 objects 11 having different states of incidence surfaces of the laser light L are irradiated with the laser light L along lines a extending along X directions along the surfaces 11aA and 11aB (described below), respectively, to form modified regions 12. In this processing example 3, modified regions 12 are formed for each of a plurality of (2 in this case) objects 11A and 11B. In this processing example 3, processing preparation is first performed. In preparation for machining, first, as shown in fig. 13, machining conditions are set as a state in which the object 11A is supported by the stage 2.

Object 11A includes surface 11aA. The object 11A is a semiconductor wafer such as a silicon wafer, and the surface 11aA is a 1 st absorption rate surface of the laser light L such as a mirror surface, for example. The object 11A is supported on the stage 2 with the surface 11aA facing the laser irradiation section 5 side. Thus, the surface 11aA of the object 11A is set as the incident surface of the laser light L.

On the other hand, the object 11B includes a surface 11aB (see fig. 14). The object 11B is, for example, a semiconductor wafer such as a silicon wafer, and the surface 11aB thereof has a 2 nd absorption rate higher than the absorption rate of the laser light L of the surface 11aA (i.e., the laser light L is absorbed more easily than the surface 11 aA) by, for example, generating grinding marks or providing a film or a tape.

Here, it is possible to set which of the scans of the irradiation (scanning) of the laser light L to the objects 11A, 11B having the surfaces 11aA, 11aB different from each other is used in the above-described diffraction pattern MP3. Here, the setting is made such that the diffraction pattern MP3 is used when scanning the object 11B having the surface 11aB that is relatively easy to absorb the laser light L. Thereafter, generation and calibration of a modulation pattern including the diffraction pattern MP3 are actually performed.

Next, in preparation for processing, alignment and height setting are performed. As an example, here, based on images of the object 11A and the laser light L taken by a camera not shown, the irradiation positions of the laser light L in the X direction and the Y direction (the direction along the surface 11 aA) are determined as alignment, and the position of the focal point C of the laser light L in the Z direction is adjusted as height setting. After that, the processing is actually performed.

That is, in the laser processing apparatus 1, the control unit 9 performs the processing (processing 1 st processing) S31 of forming the modified region 12 in the object 11A by controlling the laser light source unit 3, the 1 st moving mechanism 4, and the 2 nd moving mechanism 7 so that the converging point C of the laser light L is positioned inside the object 11A via the incidence surface (the surface 11 aA) where the absorptivity of the laser light L is the 1 st absorptivity, and so that the converging point C is relatively moved in the X direction and the laser light L is irradiated to the object 11A.

At this time, the control unit 9 controls the laser oscillation of any one of the 1 st laser 31 and the 2 nd laser 32, and controls the mirror driving unit 39 as necessary, whereby any one of the 1 st laser L1 and the 2 nd laser L2 can be output as the laser light L from the laser light source unit 3. The control unit 9 may execute the processing S31 at 2 or more different Z-direction positions.

In the processing S31, the control unit 9 controls the spatial light modulator 51 so that the diffraction pattern MP3 having higher diffraction efficiency from the low intensity region to the high intensity region of the laser light L in the modulation surface 51a is not displayed on the modulation surface 51a (so that the modulation pattern MP1 not including the diffraction pattern MP3 is displayed on the modulation surface 51 a).

Next, as shown in fig. 14, in the laser processing apparatus 1, the object 11B is supported by the stage 2. The object 11B is supported on the stage 2 with the surface 11aB facing the laser irradiation section 5. Thus, the surface 11aB of the object 11B serves as an incident surface of the laser light L.

Next, alignment and height setting are performed. As an example, here, based on images of the object 11B and the laser light L taken by a camera not shown, the irradiation positions of the laser light L in the X direction and the Y direction (the direction along the surface 11 aB) are determined as alignment, and the position of the focal point C of the laser light L in the Z direction is adjusted as height setting. After that, the processing is actually performed.

That is, the control unit 9 performs the processing (processing 2) S32 of forming the modified region 12 in the object 11B by controlling the laser light source unit 3, the 1 st moving mechanism 4, and the 2 nd moving mechanism 7 so that the converging point C is located inside the object 11B via the incidence surface (surface 11 aB) of the laser light L having the 2 nd absorptivity higher than the 1 st absorptivity and the converging point C is relatively moved in the X direction and irradiating the object 11B with the laser light L.

At this time, the control unit 9 may control the laser light source unit 3 so that one of the 1 st laser light L1 and the 2 nd laser light L2, which is used in the processing S31, is output as the laser light L from the laser light source unit 3. That is, the same laser light L may be used in the processing S31 and the processing S32. In this case, the laser processing apparatus 1 may be provided with one of the 1 st laser 31 and the 2 nd laser 32, and the laser switching mechanism is not required. The 1 st absorption rate and the 2 nd absorption rate of the surfaces 11aA and 11aB do not need to be actual values, and can be determined based on the presence or absence of grinding marks or bands.

In the processing step S32, the control unit 9 controls the spatial light modulator 51 so that the diffraction pattern MP3 is displayed on the modulation surface 51 a. In this way, the control unit 9 further executes the switching process S33 (see fig. 12 and 13) of switching the modulation pattern between the process S31 and the process S32 so that the diffraction pattern MP3 is displayed on the modulation surface 51a when the process S32 is executed and the diffraction pattern MP3 is not displayed on the modulation surface 51a when the process S31 is executed.

As described above, in processing example 3, processing S31 and processing S32 are performed. In the processing S31, the laser light L is irradiated onto the object 11A while the converging point C is positioned inside the object 11A via the incidence plane of the laser light L having the 1 st absorptivity and the converging point C is relatively moved in the X direction, so that the modified region 12 is formed in the object 11A. In the processing step S32, the modified region 12 is formed in the same manner as in the processing step a31, and the laser beam L on the incidence surface of the object 11B is higher in absorptivity than in the processing step S31. Therefore, in the processing S32, the laser light L is absorbed more easily on the incident surface than in the processing S31, and therefore, damage to the incident surface such as surface ablation is liable to occur.

Therefore, in the laser processing apparatus 1, a switching process is performed to switch the modulation pattern between the processing S31 and the processing S32 such that the diffraction pattern MP3 having a higher diffraction efficiency from the low intensity region of the laser light L toward the high intensity region is displayed on the spatial light modulator 51 when the processing S32 is performed, and such that the diffraction pattern MP3 is not displayed on the spatial light modulator 51 when the processing S31 is performed.

The diffraction light Lg generated by the diffraction pattern MP3 in the laser light L is blocked by the shutter 55 so as not to be incident on the condenser lens 54. As a result, the peak intensity of the laser beam L is suppressed by the diffraction pattern MP3 and the shutter 55 when the processing S32 is relatively likely to be damaged, and such control of the peak intensity is not performed when the processing S31 is relatively unlikely to be damaged. Therefore, both suppression of damage to the laser light incident surface in the processing step S32 and appropriate processing in the processing step S31 can be achieved.

In the case where the processing S32 is performed at a plurality of positions in the Z direction, the control unit 9 may use the diffraction patterns MP3 and MP4 separately as in the processing S12 and the processing S14 of the processing example 1. That is, in the case where the processing S32 is performed at a plurality of Z-direction positions, the diffraction pattern MP3 having relatively low diffraction efficiency can be used when the converging point C is located relatively far from the incident surface of the laser light L, and the diffraction pattern MP4 having relatively high diffraction efficiency can be used when the converging point C is located relatively close to the incident surface of the laser light L.

In addition, in both the processing S31 for the object 11A and the processing S32 for the object 11B, a diffraction pattern having a higher diffraction efficiency from a region where the intensity of the laser light L is low to a region where the intensity of the laser light L is high may be used. As an example, in the processing S31 in the case where the absorptivity of the laser light L at the incident surface of the laser light L is relatively low, the diffraction pattern MP3 having relatively low diffraction efficiency may be used, and in the processing S32 in the case where the absorptivity of the laser light L at the incident surface of the laser light L is relatively high, the diffraction pattern MP4 having relatively high diffraction efficiency may be used. That is, the control unit 9 may perform processing in which the higher the absorptivity of the laser light L to the incidence surface of the laser light L is, the higher the diffraction efficiency is, the higher the diffraction pattern is displayed on the spatial light modulator 51.

[ Pattern adjustment ]

In the laser processing apparatus 1, the modulation pattern may be adjusted as a condition in addition to the processing as described above. In this pattern adjustment, first, in the state where the object 11 is supported on the stage 2, the alignment and the height setting are performed, and then the processing conditions are set, as in the processing example described above, and the generation and the calibration of the modulation pattern are performed.

Then, the object 11 is irradiated with the laser beam L, and the object 11 is laser-machined. Next, by observing and evaluating the object 11, a determination is made as to whether processing (for example, whether the modified region 12 is formed) can be performed at a desired Z-direction position of the object 11 and/or whether damage is not generated on the incident surface. As a result of this determination, when processing cannot be performed at a desired position of the object 11 and/or when damage occurs to the incident surface, the spatial light modulator 51 is controlled so that the diffraction pattern MP3 in which the predetermined diffraction efficiency (the blocking ratio of the laser light L) and the predetermined regions R1 to R3 are set is displayed on the modulation surface 51 a.

After that, the laser processing of the object 11 is performed after setting the processing conditions, generating the modulation pattern, and calibrating the modulation pattern again. Then, the observation and evaluation of the object 11 are performed again. Then, a determination is again made as to whether processing can be performed at a desired Z-direction position of the object 11 (for example, whether the modified region 12 is formed) and/or whether damage is not generated on the incident surface. As a result of this determination, when processing cannot be performed at a desired position of the object 11 and/or when damage occurs to the incident surface, the spatial light modulator 51 is controlled so that the diffraction efficiency or the settings of the regions R1 to R3 are changed and the diffraction pattern MP3 is displayed on the modulation surface 51 a.

As described above, the adjustment of the diffraction pattern MP3, the processing of the object 11, the observation, and the evaluation are repeatedly performed until the object 11 is subjected to a desired processing while suppressing the damage of the incident surface, thereby determining an appropriate modulation pattern.

Modification example

The above embodiment illustrates an aspect of the present invention. Therefore, the present invention is not limited to the laser processing apparatus 1 described above, and can be arbitrarily modified.

Fig. 15 is a schematic view showing a laser processing apparatus according to a modification. The laser processing apparatus 1A shown in fig. 15 is different from the laser processing apparatus 1 of the above embodiment in that the laser light source section 3 has a dichroic mirror 38A instead of the 2 nd mirror 38; and does not have the mirror driving portion 39. The dichroic mirror 38A is disposed on the optical path of the 1 st laser beam L1 from the 1 st mirror 35 toward the modulation surface 51 a. The dichroic mirror 38A reflects the 2 nd laser light L2 toward the modulation surface 51 a.

On the other hand, the dichroic mirror 38A has a transmittance with respect to the wavelength of the 1 st laser light L1. Therefore, the dichroic mirror 38A functions as a simple transmission window for the 1 st laser beam L1. In the laser processing apparatus 1A, the 1 st laser beam L1 transmitted through the dichroic mirror 38A is adjusted so as to match the optical path of the 2 nd laser beam L2 reflected by the dichroic mirror 38A and output.

The laser processing apparatus 1A can also achieve the same processing and effects as the laser processing apparatus 1. In addition, according to the laser processing apparatus 1A, when the 1 st laser light L1 and the 2 nd laser light L2 are switched, no optical axis shift occurs. In the laser processing apparatus 1A, the 1 st laser beam L1 may be aligned by the 1 st mirror 35, and the 2 nd laser beam L2 may be aligned by the dichroic mirror 38A. That is, the alignment of the 1 st laser light L1 and the 2 nd laser light L2 is separated.

In addition, the above-described processing examples 1, 2, and 3 are each subjected to a characteristic modulation pattern switching process, but these switching processes may be performed in combination with each other.

For example, in the processing example 3, when the object 11A having the surface 11aA that is relatively difficult to absorb the laser light L is processed S31, and the modified region 12 is formed by irradiating (scanning) the laser light L while locating the converging point C at a plurality of positions in the Z direction, as described above, the control unit 9 may display the diffraction pattern MP3 on the modulation surface 51 at the time of scanning at a position close to the incident surface (the surface 11 aA) among the plurality of positions in the Z direction, and may display the diffraction pattern MP4 at the time of scanning at a position closer to the incident surface (the surface 11 aA), as described above, in the processing example 1, so that the diffraction pattern MP3 is not displayed on the modulation surface 51A at the time of scanning at other positions.

Similarly, in the processing example 2, when the processing S22 is performed using the 1 st laser beam L1 having a relatively long pulse width, in the case where the modified region 12 is formed by irradiating (scanning) the laser beam L while locating the converging point C at a plurality of positions in the Z direction, the control unit 9 may display the diffraction pattern MP3 on the modulation surface 51a at the time of scanning at a position close to the incident surface (the surface 11 a) among the plurality of positions in the Z direction, and may display the diffraction pattern MP4 at the time of scanning at a position closer to the incident surface, as in the processing example 1, so that the diffraction pattern MP3 is not displayed on the modulation surface 51a at the time of scanning at other positions.

In each processing example, when the peak intensity of the laser beam is suppressed by the diffraction pattern MP3, the control unit 9 may perform a process of increasing the output of the laser beam L from the laser light source unit 3 to increase the input energy to the object 11. The diffraction pattern MP3 may be configured such that the diffraction efficiency varies in 1 stage, or may be configured such that the diffraction efficiency varies in 3 stages or more.

Claims

1. A laser processing apparatus, wherein,

The device is provided with:

a laser light source that outputs laser light;

a spatial light modulator that includes a modulation surface on which the laser light output from the laser light source is incident, and that modulates the laser light according to a modulation pattern by displaying the modulation pattern on the modulation surface and emits the modulated laser light;

a condensing lens for condensing the laser light emitted from the spatial light modulator into the object;

a baffle plate disposed between the spatial light modulator and the condenser lens, and configured to intercept a part of the laser light emitted from the spatial light modulator so as not to be incident on the condenser lens;

a moving unit for relatively moving a converging point of the laser beam with respect to the object; and

a control unit that controls the laser light source, the spatial light modulator, and the moving unit,

the control section performs:

a 1 st processing step of irradiating the object with the laser light while controlling the laser light source and the moving unit so that the position of the converging point in the Z direction intersecting the incident surface of the laser light of the object is set to be the 1 st position and the converging point is relatively moved in the X direction along the incident surface, thereby forming a modified region in the object; and

A 2 nd processing step of forming a modified region in the object by irradiating the object with the laser light while controlling the laser light source and the moving unit so that the position of the converging point in the Z direction is set to a 2 nd position on the incident surface side than the 1 st position and the converging point is relatively moved in the X direction,

the control unit further controls the spatial light modulator to display a diffraction pattern having a diffraction efficiency that increases from a region of low intensity to a region of high intensity of the laser light in the modulation plane on the modulation plane when the 2 nd processing is performed, and to switch the modulation pattern between the 1 st processing and the 2 nd processing without displaying the diffraction pattern on the modulation plane when the 1 st processing is performed,

the shutter blocks the diffracted light generated by the diffraction pattern in the laser light so as not to be incident on the condenser lens.

2. The laser processing apparatus according to claim 1, wherein,

the control section performs: a 3 rd processing step of forming a modified region in the object by irradiating the object with the laser light while controlling the laser light source and the moving unit so that the position of the converging point in the Z direction is set to a 3 rd position on the incident surface side than the 2 nd position and the converging point is relatively moved in the X direction,

The control unit controls the spatial light modulator so that a diffraction pattern having a high diffraction efficiency is displayed on the modulation surface from a region having a low intensity of the laser light in the modulation surface when the 3 rd processing is performed,

at least 1 region within the modulation plane of the diffraction pattern of the 3 rd process has a diffraction efficiency higher than a diffraction efficiency of a corresponding region within the modulation plane of the diffraction pattern of the 2 nd process.

3. A laser processing apparatus, wherein,

the device is provided with:

a laser light source that outputs laser light;

the control section performs:

a 1 st processing step of forming a modified region in the object by controlling the laser light source and the moving unit so that the converging point is located inside the object through an incidence plane in which the absorptivity of the laser light is 1 st, and the converging point is relatively moved in an X direction along the incidence plane, and irradiating the object with the laser light; and

a 2 nd processing step of irradiating the object with the laser light while relatively moving the converging point along the X direction along the incidence plane with respect to the object through the incidence plane in which the absorptivity of the laser light is 2 nd higher than the 1 st absorptivity by controlling the laser light source and the moving unit, thereby forming a modified region in the object,

4. A laser processing apparatus, wherein,

the device is provided with:

a laser light source including a 1 st laser that outputs a 1 st laser light as a laser light, and a 2 nd laser that outputs a 2 nd laser light having a shorter pulse width than the 1 st laser light as the laser light;

a moving unit for relatively moving a converging point of the laser beam with respect to the object;

a laser switching mechanism for switching the laser beam incident on the modulation surface between the 1 st laser beam and the 2 nd laser beam; and

the control section performs:

a 1 st processing step of irradiating the object with the 1 st laser beam while relatively moving the converging point of the 1 st laser beam in an X direction along an incidence plane of the 1 st laser beam of the object while positioning the converging point inside the object by controlling the laser light source, the laser light switching mechanism, and the moving unit, thereby forming a modified region in the object; and

a 2 nd processing step of forming a weakened region in the object by irradiating the object with the 2 nd laser light while relatively moving the converging point of the 2 nd laser light along an X direction along an incidence plane of the 2 nd laser light of the object while controlling the laser light source, the laser light switching mechanism, and the moving unit,

5. The laser processing apparatus according to claim 4, wherein,

the laser switching mechanism includes:

a 1 st mirror for reflecting the 1 st laser light output from the 1 st laser toward the modulation surface;

a 2 nd mirror for reflecting the 2 nd laser light output from the 2 nd laser toward the modulation surface; and

and a mirror driving unit configured to drive the 2 nd mirror so as to be inserted into and removed from an optical path of the 1 st laser beam from the 1 st mirror toward the modulation surface.

6. The laser processing apparatus according to any one of claims 1 to 5, wherein,

the beam profile of the laser light on the modulation surface has a gaussian distribution,

the control unit generates the diffraction pattern so that diffraction efficiency increases from the outside of the modulation plane toward the center.

7. The laser processing apparatus according to any one of claims 1 to 6, wherein,

the control unit generates the diffraction pattern such that the diffraction efficiency changes in at least 2 steps.