Laser processing apparatus and laser processing method

Abstract

The laser processing apparatus of the present application is a laser processing apparatus that performs laser processing of an object composed of a birefringent material, and includes: a light source that outputs laser light; a spatial light modulator that modulates the laser light output from the light source; a condenser lens that condenses the laser light toward the object; and a polarization component control section that functions as the spatial light modulator, which controls a polarization component of the laser light in such a manner that the laser light is condensed at one point in the Z direction (the direction of the optical axis) of the object.

Description

Technical Field

[0001] One aspect of the present invention relates to a laser processing apparatus and a laser processing method. Background Technology

[0002] A known processing method involves irradiating a semiconductor object, such as a semiconductor ingot, with a laser to form a modified region inside the semiconductor object, and causing cracks extending from the modified region to develop, thereby cutting out a semiconductor component, such as a semiconductor wafer, from the semiconductor object (for example, see Patent Documents 1 and 2).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-183600

[0006] Patent Document 2: Japanese Patent Application Publication No. 2017-057103 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In this case, for example, when focusing a laser beam onto a semiconductor object made of a birefringent material such as a gallium nitride (GaN) ingot, the refractive indices of the P-polarized and S-polarized components of the incident light are different. Furthermore, this incident light splits into ordinary and extraordinary rays, with the extraordinary ray not obeying Snell's law and propagating at a different angle of refraction than the ordinary ray. For these reasons, the P-polarized and S-polarized components focus at different positions along the depth direction of the semiconductor object. As described above, because the focusing point branches along the depth direction, multiple dents are unintentionally formed in the semiconductor object, and undesirable cracks are produced. Therefore, the processing quality, such as in slicing, may be reduced.

[0009] One aspect of the present invention is made in view of the above-mentioned facts, and its object is to improve the quality of laser processing of semiconductor objects made of birefringent materials.

[0010] means for solving problems

[0011] One aspect of the laser processing apparatus of the present invention is a laser processing apparatus for irradiating a semiconductor object made of a birefringent material with a laser and performing laser processing on the semiconductor object, and includes: a laser output unit that outputs laser light; a spatial light modulator that modulates the laser light output from the laser output unit; a focusing lens that focuses the laser light toward the semiconductor object; and a polarization component control unit that controls the polarization component of the laser light at a point on the semiconductor object in the direction of the optical axis.

[0012] In one aspect of the laser processing apparatus of the present invention, the laser output from the laser output unit is modulated by a spatial light modulator and focused onto a semiconductor object by a focusing lens. Furthermore, in this laser processing apparatus, the polarization component of the laser is controlled by a polarization component control unit to focus the laser onto a single point on the semiconductor object. Typically, when focusing a laser onto a semiconductor object made of a birefringent material, the refractive indices of the P-polarized component and the S-polarized component of the incident light are different. Additionally, this incident light is divided into ordinary ray and extraordinary ray, where the extraordinary ray does not follow Snell's law and propagates at a different angle of refraction than the ordinary ray. For these reasons, in the depth direction of the semiconductor object, the P-polarized component and the S-polarized component are focused at different positions (the focusing point becomes two points). Thus, multiple scratches may be unintentionally formed on the semiconductor object, and undesirable cracks may occur, potentially reducing the processing quality of slicing, etc. To address this issue, as in one embodiment of the laser processing apparatus of the present invention, the polarization component of the laser is controlled by a polarization component control unit to focus the laser beam onto a single point on the semiconductor workpiece. This ensures that the focusing point is only a single point, and since only one notch is formed on the semiconductor workpiece, the generation of unintended (inappropriate) cracks in the semiconductor workpiece can be suppressed. Thus, the reduction in processing quality, such as during slicing, can be prevented. As described above, the laser processing apparatus according to one embodiment of the present invention can improve the quality of laser processing on semiconductor workpieces made of birefringent materials.

[0013] In the aforementioned laser processing apparatus, the laser output unit outputs linearly polarized laser light, and the polarization component control unit unifies the polarization component of the laser light, which is focused by a lens and irradiates the object, into either P-polarized or S-polarized light. As described above, when the incident light contains both P-polarized and S-polarized components, and these components are focused at different positions, the polarization component control unit unifies the laser polarization component into either P-polarized or S-polarized light, thereby ensuring that the focusing point is appropriately a single point.

[0014] In the aforementioned laser processing apparatus, the polarization component control unit may include a conversion element that converts linearly polarized light into radially polarized light or angularly polarized light. Radially polarized light (radial polarization) is incident on the semiconductor object as P-polarized light. Angularly polarized light, on the semiconductor object, is incident on the semiconductor object as S-polarized light. Therefore, by converting linearly polarized light into radially polarized light or angularly polarized light, the polarization component of the laser can be appropriately unified into either P-polarized light or S-polarized light, and the focusing point can be appropriately made a single point.

[0015] In the aforementioned laser processing apparatus, the polarization component control unit may also include a slit portion that blocks either P-polarized or S-polarized laser light. By blocking either P-polarized or S-polarized light, the polarization component of the laser can be appropriately unified into either P-polarized or S-polarized light, and the focusing point can be appropriately made into a single point.

[0016] In the aforementioned laser processing apparatus, the slit can also be a slit pattern set as the modulation pattern of a spatial light modulator. By setting the slit pattern as the modulation pattern of the spatial light modulator, a physical slit is not required, and the focusing point can be appropriately made into a single point through a simple structure.

[0017] In the aforementioned laser processing apparatus, the birefringent material can also be a uniaxial crystal material with a plane orientation of 001. Therefore, by unifying the polarization composition of the laser to either P-polarized or S-polarized light, the quality of laser processing can be effectively improved.

[0018] One aspect of the laser processing method of the present invention is a laser processing method for irradiating a semiconductor object made of a birefringent material with a laser and performing laser processing on the semiconductor object, and includes: a step of placing the semiconductor object on a stage; a step of setting a polarization component control unit, the polarization component control unit controlling the polarization component of the laser in such a way that the laser is focused on a point in the optical axis direction on the semiconductor object; and a step of outputting the laser.

[0019] In the laser processing method described above, it is also possible that, in the process of outputting the laser, the laser is output as linearly polarized light, and in the process of setting the polarization component control unit, a conversion element is installed to convert linearly polarized light into radially polarized light or angularly polarized light.

[0020] In the above-mentioned laser processing method, it is also possible that, in the process of setting the polarization component control unit, the slit pattern of the P-polarized or S-polarized light that blocks the laser is set as the modulation pattern of the spatial light modulator that modulates the laser.

[0021] The effects of the invention

[0022] According to one aspect of the present invention, the quality of laser processing of semiconductor objects made of birefringent materials can be improved. Attached Figure Description

[0023] Figure 1 This is a structural diagram of the laser processing apparatus according to the first embodiment of the present invention.

[0024] Figure 2 This is a side view of the object of the laser processing method and semiconductor component manufacturing method of the first embodiment, namely a GaN ingot.

[0025] Figure 3 yes Figure 2The top view of the GaN ingot shown.

[0026] Figure 4 This is a longitudinal cross-sectional view of a portion of a GaN ingot during a process in a semiconductor component manufacturing method using a laser processing apparatus.

[0027] Figure 5 This is a cross-sectional view of a portion of a GaN ingot during a process in a semiconductor component manufacturing method using a laser processing apparatus.

[0028] Figure 6 This is a side view of a GaN ingot during a process in a semiconductor component manufacturing method using a laser processing apparatus.

[0029] Figure 7 This is a side view of a GaN ingot during a process in a semiconductor component manufacturing method using a laser processing apparatus.

[0030] Figure 8 This is a diagram showing the modulation pattern (including the slit pattern) of a spatial light modulator.

[0031] Figure 9 This is a diagram showing the focal point when using a slit pattern.

[0032] Figure 10 This is a flowchart illustrating each step of the laser processing method according to the first embodiment.

[0033] Figure 11 This is a diagram showing the difference in the focusing point between the comparative example and this embodiment.

[0034] Figure 12 This is a structural diagram of the laser processing apparatus according to the second embodiment of the present invention.

[0035] Figure 13 It is a diagram illustrating the modulation of the polarization distribution by an axisymmetric polarizing element.

[0036] Figure 14 This is a flowchart illustrating each step of the laser processing method according to the second embodiment. Detailed Implementation

[0037] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, in each drawing, the same or equivalent parts are given the same reference numerals, and repeated descriptions are omitted.

[0038] [First Implementation]

[0039] [Basic Structure of Laser Processing Equipment]

[0040] like Figure 1As shown, the laser processing apparatus 1 of the first embodiment includes: a stage 2, a light source 3, a spatial light modulator 4, a focusing lens 5, and a control unit 6. The laser processing apparatus 1 is an apparatus for irradiating a semiconductor object 11, i.e., an object 11, made of a birefringent material, with a laser L and performing laser processing on the object 11. The birefringent material is, for example, a uniaxial crystal material with anisotropic surface orientation (001). The birefringent material may also be a biaxial crystal material. The laser processing apparatus 1 forms a modified region 12 on the object 11 by irradiating it with the laser L. The laser processing apparatus 1 may also be a laser slicing apparatus, which is mainly described in this embodiment, a laser dicing apparatus, an internal laser marking apparatus, or a laser structuring apparatus. Hereinafter, the first horizontal direction will be referred to as the X direction, and the second horizontal direction perpendicular to the first horizontal direction will be referred to as the Y direction. Furthermore, the vertical direction will be referred to as the Z direction.

[0041] The stage 2 supports the object 11, for example, by adsorbing and attaching a thin film to it. In this embodiment, the stage 2 can move along both the X and Y directions. Furthermore, the stage 2 can rotate about an axis parallel to the Z direction.

[0042] Light source 3 is a laser output unit that outputs laser light L that is transmissible to object 11, for example, through pulse oscillation. Light source 3 outputs laser light L, for example, as linearly polarized light. The laser light L output from light source 3 is adjusted by, for example, an attenuator (not shown), and its beam diameter is enlarged by one or more lens systems (not shown). Spatial light modulator 4 modulates the laser light L output from light source 3. Spatial light modulator 4 is, for example, a spatial light modulator (SLM) of reflective liquid crystal on silicon (LCOS). In this embodiment, spatial light modulator 4 also functions as a polarization component control unit (described later) for controlling the polarization component of laser light L. Condensing lens 5 focuses the laser light L modulated by spatial light modulator 4 toward object 11. In this embodiment, spatial light modulator 4 and condensing lens 5 can move along the Z-direction.

[0043] When laser L is focused inside the object 11 supported on the stage 2, the laser L is specifically absorbed at the point C corresponding to the focus point C, thus forming a modified region 12 inside the object 11. The modified region 12 is a region whose density, refractive index, mechanical strength, and other physical properties differ from the surrounding unmodified region. Examples of modified regions 12 include: melt-processed regions, cracked regions, insulation failure regions, and regions with refractive index changes.

[0044] As an example, if the stage 2 is moved along the X direction and the focusing point C is moved relative to the object 11 along the X direction, multiple modification points 13 are formed in a row along the X direction. Each modification point 13 is formed by irradiation with a single pulse of laser L. A row of modification regions 12 is a collection of multiple modification points 13 arranged in a row. Adjacent modification points 13 may be connected or separated depending on the relative movement speed of the focusing point C relative to the object 11 and the repetition frequency of the laser L.

[0045] The control unit 6 controls the stage 2, the light source 3, the spatial light modulator 4, and the condenser lens 5. The control unit 6 is configured as a computer device including a processor, memory, storage devices, and communication devices. In the control unit 6, software (programs) loaded into memory are executed by the processor, and the reading and writing of data in memory and storage devices, as well as communication via the communication devices, are controlled by the processor. Thus, the control unit 6 performs various functions.

[0046] [An example of a semiconductor component manufacturing method using laser processing equipment]

[0047] Next, as an example of a semiconductor component manufacturing method using laser processing apparatus 1, the GaN ingot 20 (refer to) of object 11 is processed. Figure 2 and Figure 3 ) Slice and obtain multiple GaN wafers 30 (refer to) Figure 2 and Figure 3 The process of () will be described. In this embodiment, the object 11 is as follows: Figure 2 and Figure 3 As shown, a GaN ingot (semiconductor ingot, semiconductor object) 20 is formed, for example, in a disc shape from gallium nitride (GaN). As an example, the GaN ingot 20 has a diameter of 2 inches and a thickness of 2 mm. As an example, the GaN wafer 30 has a diameter of 2 inches and a thickness of 100 μm.

[0048] First, the laser processing apparatus 1 forms a plurality of modification points 13 along each of the plurality of virtual surfaces 15. Each of the plurality of virtual surfaces 15 is a surface inside the GaN ingot 20 opposite to the surface 20a of the GaN ingot 20, and is arranged in a direction opposite to the surface 20a. In this embodiment, each of the plurality of virtual surfaces 15 is a surface parallel to the surface 20a, for example, in a circular shape. Each of the plurality of virtual surfaces 15 is arranged to overlap each other when viewed from the surface 20a side. In the GaN ingot 20, a plurality of peripheral regions 16 are provided in a manner that surrounds each of the plurality of virtual surfaces 15. That is, each of the plurality of virtual surfaces 15 does not reach the side surface 20b of the GaN ingot 20. As an example, the distance between adjacent virtual surfaces 15 is 100 μm, and the width of the peripheral region 16 (in this embodiment, the distance between the outer edge of the virtual surface 15 and the side surface 20b) is 30 μm or more.

[0049] The formation of multiple modification points 13 is performed sequentially on each virtual surface 15 from the opposite side of surface 20a by irradiating it with a laser L having a wavelength of, for example, 532 nm. Since the formation of the multiple modification points 13 is identical in each of the multiple virtual surfaces 15, the following describes the formation of multiple modification points 13 along the virtual surface 15 closest to surface 20a, with reference to... Figure 4 and Figure 5 Please provide an explanation. Furthermore, in Figure 5 In the image, the arrow represents the trajectory of the focusing point C of the laser L.

[0050] First, laser processing device 1, such as Figure 4 and Figure 5 As shown, by directing the laser L from the surface 20a into the interior of the GaN ingot 20, a plurality of modification points 13 are formed along the virtual surface 15 (e.g., arranged in a two-dimensional manner along the entire virtual surface 15). At this time, the laser processing apparatus 1 can form the plurality of modification points 13 either in a manner where the plurality of cracks 14 extending from the plurality of modification points 13 are not connected to each other, or in a manner where the plurality of cracks 14 extending from the plurality of modification points 13 are connected to each other. Furthermore, the laser processing apparatus 1 forms multiple rows of modification points 13 by moving the focusing point C of the pulsed laser L along the virtual surface 15. Moreover, in Figure 4 and Figure 5 In the diagram, modification point 13 is indicated by white space (no shading), and the extent of the crack 14 is indicated by dashed lines.

[0051] In this embodiment, the pulsed laser L is modulated by a spatial light modulator 4 to focus light onto a plurality of focusing points C arranged in the Y direction. Furthermore, the plurality of focusing points C are moved relative to each other along the X direction on the virtual surface 15. As an example, the pulse pitch of the laser L (i.e., the relative movement speed of the plurality of focusing points C divided by the repetition frequency of the laser L) is 10 μm. Additionally, the pulse energy of the laser L at each focusing point C (hereinafter referred to as "pulse energy of the laser L") is 0.33 μJ.

[0052] Next, a heating device equipped with a heater or the like heats the GaN ingot 20, and in each of the plurality of virtual surfaces 15, the plurality of cracks 14 extending from the plurality of modification points 13 are connected to each other, thereby achieving the desired effect. Figure 6 As shown, in each of the plurality of virtual surfaces 15, a crack 17 (hereinafter referred to as "crack 17") is formed across the virtual surface 15. Figure 6 In the diagram, the areas containing multiple modification points 13, multiple cracks 14, and cracks 17 are represented by dashed lines. Alternatively, cracks 14 can be connected to each other to form cracks 17 by applying a force to the GaN ingot 20 using methods other than heating. Furthermore, multiple modification points 13 can be formed along the virtual surface 15 to connect multiple cracks 14 to each other, thus forming cracks 17.

[0053] Here, nitrogen gas is generated within multiple cracks 14 extending from multiple modification points 13 in the GaN ingot 20. Therefore, by heating the GaN ingot 20 to expand the nitrogen gas, the pressure (internal pressure) of the nitrogen gas can be used to form cracks 17. Furthermore, since the peripheral region 16 hinders the development of the multiple cracks 14 towards the outside of the virtual surface 15 surrounded by the peripheral region 16 (e.g., the side surface 20b of the GaN ingot 20), the leakage of nitrogen gas generated within the multiple cracks 14 to the outside of the virtual surface 15 can be suppressed. That is, the peripheral region 16 is an unmodified region that does not contain modification points 13, and when cracks 17 are formed on the virtual surface 15 surrounded by the peripheral region 16, it is a region that hinders the development of the multiple cracks 14 towards the outside of the virtual surface 15 surrounded by the peripheral region 16. Therefore, the width of the peripheral region 16 can be set to 30 μm or more.

[0054] Next, the grinding device grinds (polishes) the portions of the GaN ingot 20 corresponding to the plurality of peripheral regions 16 and the plurality of virtual surfaces 15, thereby achieving the desired effect. Figure 7 As shown, multiple GaN wafers 30 are obtained from GaN ingot 20 with each of the multiple cracks 17 as boundaries. As described above, GaN ingot 20 is cut along each of the multiple virtual surfaces 15. In addition, in this process, portions of GaN ingot 20 corresponding to the multiple peripheral regions 16 can also be removed by machining other than grinding, laser processing, etc.

[0055] [Structure of a laser processing device with polarization composition control]

[0056] The spatial light modulator 4 functions as a polarization component control unit, which controls the polarization component of the laser L by focusing the light onto the object 11 at a point along the optical axis (Z direction, the depth direction of the object 11). Typically, when focusing the laser onto an object 11 made of a birefringent material such as a GaN ingot 20, because the refractive indices of the P-polarized (extraordinary) and S-polarized (ordinary) components of the incident light are different, and because the light propagates at different angles of refraction for the ordinary and extraordinary rays, the P-polarized and S-polarized components focus at different positions along the Z direction of the object 11, resulting in two focusing points FP (see reference). Figure 11 (a)). For this reason, multiple scratches are formed on the object 11 and inappropriate cracks are generated, which may reduce the processing quality of the GaN wafer 30 slices, etc. In this embodiment, the spatial light modulator 4 functions as a polarization component control unit to form a focusing point FP (see reference) in the Z direction of the object 11. Figure 11 (b) controls the polarization component of laser L in a manner that controls the polarization component of laser L.

[0057] The spatial light modulator 4 functions as a slit that blocks either the P-polarized or S-polarized light of the laser L, thereby unifying the polarization component of the laser L into either P-polarized or S-polarized light and making the focusing point FP a single point. Furthermore, "unifying the polarization component of the laser L into either P-polarized or S-polarized light" not only means completely restricting the polarization component of the laser L to either P-polarized or S-polarized light, but also includes including the polarization component of the laser L containing the blocked polarization component within a range where the focusing point FP does not become two or more points. The slit that functions as the spatial light modulator 4 is a slit pattern set as the modulation pattern of the spatial light modulator 4. In the spatial light modulator 4, by appropriately setting the modulation pattern displayed on the liquid crystal layer, the laser L can be modulated (e.g., modulating the intensity, amplitude, phase, polarization, etc. of the laser L). The modulation pattern is a hologram pattern to which modulation is applied, including the slit pattern.

[0058] Figure 8 This is a diagram showing the modulation pattern (including the slit pattern) displayed on the liquid crystal layer of the spatial light modulator 4. Figure 8 The "light-blocking area" shown refers to the area blocked by the slit pattern SP1 or slit pattern SP2 described later. Additionally, Figure 8 The arrows shown indicate the direction of linear polarization. Figure 8(a) The modulation pattern MP1 shown includes a slit pattern SP1 and an aberration correction pattern CP. The aberration correction pattern refers to the correction pattern for spherical aberration, astigmatism, distortion, coma, etc. Figure 8 In the example shown in (a), the slit pattern SP1 is set such that light outside the slit portion, formed in the linear polarization direction, is blocked. In this case, the S-polarized light of laser L is blocked, and the polarization component of laser L is unified (restricted) to P-polarized light. Furthermore, in Figure 8 (b) The modulation pattern MP2 shown contains a slit pattern SP2 and an aberration correction pattern CP. Figure 8 In the example shown in (b), the slit pattern SP2 is set such that light outside the slit portion, formed in a direction orthogonal to the linear polarization direction, is blocked. In this case, the P-polarized light of the laser is blocked, and the polarization component of the laser L is uniformly (restricted) to S-polarized light.

[0059] Figure 9 (a) is a diagram showing the spotlight FP when using slit pattern SP1. Figure 9 (b) is a diagram showing the focal point FP when using the slit pattern SP2. Figure 9 (a) and Figure 9 (b) In each case, the left figure represents the XZ plane, and the right figure represents the YZ plane. For example... Figure 9 As shown in (a), when using the slit pattern SP1, referring to either the XZ plane or the YZ plane, it can be confirmed that the focusing point FP is only one point in the Z direction (optical axis direction). Similarly, as Figure 9 As shown in (b), when using the slit pattern SP2, it can be confirmed by referring to either the XZ plane or the YZ plane that the focusing point FP is only one point in the Z direction (optical axis direction). Furthermore, when using the slit pattern SP2, when the P-polarized light is blocked and unified into the S-polarized light component, the focusing property is better because the refractive index is the same regardless of the incident angle in S-polarized light.

[0060] [An example of laser processing methods]

[0061] Next, regarding an example of laser processing methods, refer to... Figure 10 Please provide an explanation. Figure 10 This diagram illustrates the various steps of the laser processing method according to the first embodiment. This laser processing method involves irradiating a workpiece 11 (e.g., a GaN ingot 20) made of a birefringent material with a laser L and performing laser processing on the workpiece 11.

[0062] like Figure 10As shown, in the laser processing method of the first embodiment, firstly, the object 11 is set (placed) on the stage 2 (step S1, the process of placing the semiconductor object).

[0063] Next, in the spatial light modulator 4, a modulation pattern (including a slit pattern) is set to be displayed on the liquid crystal layer (step S2, the process of setting the polarization component control unit). The modulation pattern here refers to, for example... Figure 8 The modulation pattern MP1 shown in (a) includes a slit pattern SP1 that blocks the S-polarized light of the laser L and unifies (restricts) the polarization component into P-polarized light. Alternatively, the modulation pattern refers to, for example... Figure 8 (b) The modulation pattern MP2 shown includes a slit pattern SP2 that blocks the P-polarized light of the laser L, thereby unifying (restricting) the polarization component into S-polarized light. As described above, in step S2 (the process of setting the polarization component control unit), the slit pattern SP1 or SP2 that blocks the P-polarized or S-polarized light of the laser L is set as the modulation pattern of the spatial light modulator 4. Furthermore, the slit pattern and the aberration correction pattern can also be displayed on the liquid crystal layer of the spatial light modulator 4.

[0064] Next, the laser processing conditions are input and set (step S3). The laser processing conditions refer to conditions such as the energy of the laser L and the pulse interval. Finally, the laser processing device 1 forms multiple modification points 13 along each of the multiple virtual surfaces 15, and laser processing is performed (step S4, laser output process).

[0065] [Effects]

[0066] Next, the effects of the laser processing apparatus 1 in this embodiment will be explained.

[0067] The laser processing apparatus 1 of this embodiment is a laser processing apparatus for laser processing an object 11 made of birefringent material, and includes: a light source 3 that outputs laser L; a spatial light modulator 4 that modulates the laser L output from the light source 3; a focusing lens 5 that focuses the laser L toward the object 11; and a polarization component control unit that controls the polarization component of the laser L at a point on the object 11 in the Z direction (optical axis direction) and functions as the spatial light modulator 4.

[0068] In the laser processing apparatus 1 of this embodiment, the laser light output from the light source 3 is modulated by the spatial light modulator 4 and focused onto the object 11 by the condenser lens 5. Furthermore, in this laser processing apparatus 1, the polarization component of the laser light L is controlled by a polarization component control unit that functions as the spatial light modulator 4, so that the light is focused onto a single point on the object 11. Typically, when focusing a laser light onto a semiconductor object made of a birefringent material, since the refractive indices of the P-polarized component and the S-polarized component of the incident light are different, therefore, as... Figure 11 As shown in (a), in the depth direction of the semiconductor object, the P-polarized component and the S-polarized component are focused at different positions (the focusing point FP becomes two points). This can unintentionally create multiple scratches on the semiconductor object, causing undesirable cracks and potentially reducing the processing quality of slices, etc. To address this, as in the laser processing apparatus 1 of this embodiment, the polarization component control unit, which functions as a spatial light modulator 4, focuses the light at the focusing point FP (refer to...). Figure 11 (b) By controlling the polarization component of the laser at a single point on the object 11, only one scratch is formed on the object 11, thus suppressing the generation of unintended (inappropriate) cracks on the object 11. This helps to prevent a decrease in processing quality, such as when slicing. As described above, the laser processing apparatus 1 according to this embodiment can improve the quality of laser processing on semiconductor objects made of birefringent materials.

[0069] In the laser processing apparatus 1, the light source 3 outputs a linearly polarized laser L. A polarization component control unit, functioning as a spatial light modulator 4, unifies the polarization component of the laser L into either P-polarized or S-polarized light. As described above, when the incident light contains both P-polarized and S-polarized components, and these components are focused at different positions, the polarization component control unit unifies the polarization component of the laser L into either P-polarized or S-polarized light, thereby ensuring that the focusing point FP is appropriately made a single point.

[0070] In the laser processing apparatus 1, the polarization component control unit, which functions as the spatial light modulator 4, may also have a slit portion that blocks either the P-polarized or S-polarized light of the laser. By blocking either the P-polarized or S-polarized light, the polarization component of the laser can be unified into either P-polarized or S-polarized light, and the focusing point can be appropriately made into a single point.

[0071] In the laser processing apparatus 1, the aforementioned slit portion can also be a slit pattern SP1 or a slit pattern SP2 set as the modulation pattern of the spatial light modulator 4 (see reference). Figure 8 By setting the slit pattern to the modulation pattern of the spatial light modulator 4, a physical slit is not required, and the focal point can be appropriately made into a single point with a minimal and simple structure. Furthermore, in the laser processing apparatus 1, a physical slit can be provided instead of the slit pattern of the spatial light modulator 4 to block the P-polarized or S-polarized laser light.

[0072] [Second Implementation]

[0073] The following is for reference Figures 12-14The laser processing apparatus 100 and laser processing method according to the second embodiment of the present invention will be described below. Furthermore, the differences from the first embodiment will be mainly described below, and descriptions that are repeated in the first embodiment will be omitted.

[0074] Figure 12 This is a structural diagram of the laser processing apparatus 100 according to the second embodiment. The laser processing apparatus 100 has a basic structure that is substantially the same as that of the laser processing apparatus 1 of the first embodiment, except that in addition to the structure of the laser processing apparatus 1, it also includes an axisymmetric polarizing element 150 (conversion element).

[0075] Axisymmetric polarizing element 150, such as Figure 12 As shown, it is configured in the optical path, specifically downstream of the spatial light modulator 4 and upstream of the condenser lens 5. Because linearly polarized light needs to be input to the spatial light modulator 4, the axisymmetric polarizing element 150 must be configured further downstream than the spatial light modulator 4. The axisymmetric polarizing element 150 functions as a polarization component control unit and is a conversion element (polarizer) that converts the linearly polarized light of the laser L into radially polarized light (radial polarization) or angularly polarized light (concentric polarization).

[0076] Figure 13 This is a diagram illustrating the modulation of the polarization distribution caused by the axisymmetric polarizing element 150. Figure 13 In the example shown, axisymmetric polarizing element 150a and axisymmetric polarizing element 150b are shown as examples of axisymmetric polarizing elements 150. Axisymmetric polarizing element 150a is used to linearly polarize laser light L (…). Figure 13 The input shown is converted into radial polarized light ( Figure 13 The conversion element shown in the upper diagram of the output is an axisymmetric polarizing element 150b, which converts the linearly polarized light of laser L (as shown in the upper diagram of the upper diagram of the lower diagram of the upper ... Figure 13 The input shown is converted into angularly polarized light. Figure 13 The conversion element (shown in the diagram below) is used as the axisymmetric polarizing element 150. A conventionally known structure can be used, for example, a component with half-wavelength plates of different axial orientations at 15-degree intervals on a quartz plate. By rotating the axisymmetric polarizing element 150 by 90 degrees, the conversion between radial polarization and angular polarization can be switched.

[0077] For an example of a laser processing method using the laser processing apparatus 100 described above, refer to Figure 14 Please provide an explanation. Figure 14 This is a diagram illustrating each step of the laser processing method according to the second embodiment.

[0078] like Figure 14As shown, in the laser processing method of the second embodiment, firstly, the object 11 is set (placed) on the stage 2 (step S11, the process of placing the semiconductor object).

[0079] Next, at a predetermined position in the optical path (downstream of the spatial light modulator 4 and upstream of the condenser lens 5), an axisymmetric polarizing element 150 is installed to convert linear polarized light into radial polarized light or angular polarized light (step S12, process of setting the polarization component control unit).

[0080] Next, an aberration correction pattern is displayed on the liquid crystal layer of the spatial light modulator 4, and laser processing conditions are input and set (step S13). Finally, laser processing is performed by forming multiple modification points 13 along each of the multiple virtual surfaces 15 using the laser processing apparatus 1 (step S14, laser output process).

[0081] According to the laser processing apparatus 100 described above, the linearly polarized light of the laser L is converted into radially polarized light or angularly polarized light by the axisymmetric polarizing element 150. The radially polarized light is incident on the object 11 as P-polarized light. In addition, the angularly polarized light is incident on the object 11 as S-polarized light. Therefore, by converting the linearly polarized light into radially polarized light or angularly polarized light, the polarization component of the laser L can be appropriately unified into P-polarized light or S-polarized light, and the focusing point can be appropriately made into a single point.

[0082] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments. For example, the polarization component control unit only needs to control the polarization component of the laser by focusing the light at a point in the optical axis direction, and it is not necessary to unify the polarization component of the laser into either P-polarized or S-polarized light.

[0083] Symbol Explanation

[0084] 1, 100… Laser processing device; 2… Stage; 3… Light source (laser output unit); 4… Spatial light modulator; 5… Condenser lens; 11… Object (semiconductor object); 150… Axisymmetric polarizing element (conversion element); L… Laser; SP1, SP2: Slit pattern.

Claims

1. A laser processing apparatus, wherein, It is a laser processing apparatus that irradiates a semiconductor object made of birefringent material with a laser and performs laser processing on the semiconductor object. The laser processing apparatus includes: A laser output unit that outputs the laser; A spatial light modulator based on a reflective liquid crystal method, which modulates the laser output from the laser output unit; A focusing lens that directs the laser beam toward the semiconductor object; and The polarization component control unit controls the polarization component of the laser light in a manner that focuses the light onto the semiconductor object at a point along the optical axis. The laser output unit outputs laser light as linearly polarized light. The polarization component control unit unifies the polarization component of the laser into either P-polarized or S-polarized light. The polarization component control unit includes a slit portion that blocks the P-polarized or S-polarized light of the laser. The slit portion is a slit pattern configured as the modulation pattern of the spatial light modulator.

2. The laser processing apparatus according to claim 1, wherein, The birefringent material is a uniaxial crystal material with a plane orientation of 001.

3. A laser processing method, wherein, This is a laser processing method that irradiates a semiconductor object made of birefringent material with a laser and performs laser processing on the semiconductor object. The laser processing method includes: The process of placing the semiconductor object on a stage; The process of setting a polarization component control unit, wherein the polarization component control unit controls the polarization component of the laser in such a way that the laser beam is focused onto a semiconductor object at a point along the optical axis; and The process of outputting the laser, In the process of setting the polarization component control unit, the slit pattern that blocks the P-polarized or S-polarized light of the laser is set as the modulation pattern of a spatial light modulator of reflective liquid crystal type that modulates the laser.

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