Laser processing apparatus and inspection method
By adjusting the laser beam width to fit the structure of the cutting path and adjacent functional components, the problem of laser obstruction in laser processing devices was solved, achieving highly efficient laser processing results.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HAMAMATSU PHOTONICS KK
- Filing Date
- 2021-03-04
- Publication Date
- 2026-06-09
Smart Images
Figure CN115348912B_ABST
Abstract
Description
Technical Field
[0001] One aspect of the present invention relates to a laser processing apparatus and an inspection method. Background Technology
[0002] Laser processing apparatuses are known to form multiple rows of modified regions within the semiconductor substrate along multiple lines by irradiating the wafer with a laser from the other side of the semiconductor substrate, thereby cutting the wafer along multiple lines. Patent Document 1 describes a laser processing apparatus equipped with an infrared camera, which allows observation from the back side of the semiconductor substrate of the modified regions formed within the semiconductor substrate, processing damage to the functional element layer, etc.
[0003] Existing technical documents
[0004] Patent documents
[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-64746 Summary of the Invention
[0006] The technical problem the invention aims to solve
[0007] As described in the laser processing apparatus, there are cases where a laser is irradiated onto the wafer from the side where the functional element layer is formed, creating a modified region inside the semiconductor substrate. When the laser is irradiated from the side where the functional element layer is formed, in order to prevent the laser from irradiating the functional elements, the laser must be confined to the region between adjacent functional elements, i.e., within the dicing channel. Conventionally, the laser width has been controlled by using slits or the like, thereby confining the laser within the dicing channel.
[0008] Here, the structures that constitute the functional elements may have a certain thickness (height). Because of this, even if the laser can be confined within the cutting path, there is still a possibility that the laser may be blocked by a part of the structure with height, preventing the desired laser irradiation.
[0009] One aspect of the present invention is made in view of the above-mentioned actual situation, and its purpose is to suppress the blocking of laser by structures such as circuits and to achieve the desired laser irradiation.
[0010] means of solving technical problems
[0011] According to one aspect of the present invention, a laser processing apparatus comprises: a stage supporting a wafer having a first surface and a second surface opposite to the first surface, wherein a plurality of elements are formed on the first surface and cleavage extends through adjacent elements; an irradiation unit that forms one or more modified regions inside the wafer by irradiating the wafer with a laser from the first surface side; a beam width adjustment unit that adjusts the beam width of the laser; and a control unit that controls the beam width adjustment unit to adjust the beam width of the laser to a target beam width corresponding to surface information, wherein the surface information includes the width of the cleavage and the position and height of structures constituting elements adjacent to the cleavage.
[0012] In one aspect of the laser processing apparatus of the present invention, in a configuration that irradiates a wafer with laser light from a first surface on which multiple elements are formed, the laser beam width is adjusted to be less than or equal to a target beam width corresponding to the width of the kerf on the first surface and the position and height of the structures constituting the elements. By adjusting the laser beam width to be less than or equal to a target beam width that takes into account not only the width of the kerf but also the position and height of the structures constituting the elements, the laser beam width can be adjusted to be not only limited to the width of the kerf but also not obstructed by the structures. This suppresses laser obstruction by structures such as circuits and enables desired laser irradiation (laser irradiation limited to the width of the kerf and not obstructed by structures). In other words, the laser processing apparatus according to one aspect of the present invention can suppress the reduction in laser output inside the wafer caused by laser obstruction by structures. Furthermore, when the laser irradiates structures such as circuits, it is considered that interference may cause unwanted beams to enter the interior of the wafer, leading to deterioration of processing quality. Regarding this, by suppressing laser obstruction by structures (or irradiation of structures) as described above, such deterioration of processing quality can be prevented. Furthermore, depending on the type of structure, laser irradiation may cause dissolution or other damage. In this regard, by suppressing laser beams from being blocked by the structure (or from irradiating the structure) as described above, the effects of the laser on the structure (such as dissolution) can be avoided.
[0013] Alternatively, the beam width adjustment unit may have a slit portion that adjusts the beam width by blocking a portion of the laser. The control unit determines the slit width of the slit portion in relation to the penetration area of the laser based on surface information and sets this slit width in the slit portion. With this configuration, the beam width can be adjusted easily and reliably.
[0014] Alternatively, if the derived slit width is less than the threshold value for forming a modified region, the control unit outputs information indicating that the material is unprocessable. This avoids processing despite the unprocessable state where a modified region cannot be formed (unnecessary processing), thus enabling efficient processing.
[0015] Alternatively, if the derived slit width is such that it worsens the length of cracks extending from the modified region, the control unit outputs information urging a change in processing conditions. Thus, in situations where suitable processing cannot be performed, a change in processing conditions can be prompted, enabling smooth processing.
[0016] Alternatively, the control unit can further consider the laser processing depth within the wafer to derive the slit width. Even with the same surface information, different processing depths will result in different suitable slit widths. In this regard, deriving the slit width by considering the processing depth allows for a more suitable slit width to be derived, effectively suppressing laser obstruction by the structure.
[0017] Alternatively, when multiple modified regions are formed at different depths within the wafer by irradiating the wafer with a laser, the control unit derives the slit width based on a combination of surface information and laser processing depth for each region. By deriving the slit width from each different processing depth and surface information, a more suitable slit width can be derived, and laser obstruction by the structure can be more effectively suppressed.
[0018] Alternatively, the control unit can further consider the offset of the laser incident position on the first surface during processing to control the beam width adjustment unit. It is assumed that the processing line will gradually shift as processing progresses. To address this, by pre-determining this offset and controlling the beam width adjustment unit accordingly, laser obstruction by the structure can be suppressed even if processing line shift occurs.
[0019] One aspect of the inspection method of the present invention includes the following steps: a step of setting a wafer having a first surface and a second surface opposite to the first surface, wherein a plurality of elements are formed on the first surface and cleavage extends through adjacent elements; a step of receiving surface information input, the surface information including the width of the cleavage and the position and height of the structure constituting the element adjacent to the cleavage; a step of controlling a beam width adjustment unit for adjusting the beam width of a laser to a target beam width corresponding to the surface information; and a step of controlling an irradiation unit for irradiating the wafer with a laser from the first surface side.
[0020] [The effects of the invention]
[0021] According to one aspect of the present invention, laser beams can be suppressed from being blocked by structures such as circuits and the desired laser irradiation can be achieved. Attached Figure Description
[0022] [ Figure 1 [Illustration of a laser processing apparatus according to one embodiment]
[0023] [ Figure 2 [Image] is a top view of a wafer in one embodiment.
[0024] [ Figure 3 ]yes Figure 2 A cross-sectional view of a portion of the wafer shown.
[0025] [ Figure 4 ]yes Figure 1 The diagram shows the structure of the laser irradiation unit.
[0026] [ Figure 5 ]yes Figure 1 The diagram shown is a structural diagram of the inspection camera unit.
[0027] [ Figure 6 ]yes Figure 1 The diagram shows the structure of the camera unit used for alignment correction.
[0028] [ Figure 7 ] is used to explain based on Figure 5 The image shown is a cross-sectional view of the wafer based on the imaging principle of the inspection camera unit, and images of various locations obtained by the inspection camera unit.
[0029] [ Figure 8 ] is used to explain based on Figure 5 The image shown is a cross-sectional view of the wafer based on the imaging principle of the inspection camera unit, and images of various locations obtained by the inspection camera unit.
[0030] [ Figure 9 [This is a SEM image of the modified region and cracks formed inside the semiconductor substrate.]
[0031] [ Figure 10 [Image] is a SEM image of the modified region and cracks formed inside the semiconductor substrate.
[0032] [ Figure 11 ] is used to explain based on Figure 5 The diagram shows the optical path of the inspection camera unit and the schematic diagram showing the image at the focal point obtained by the inspection camera unit.
[0033] [ Figure 12 ] is used to explain based on Figure 5 The diagram shows the optical path of the inspection camera unit and the schematic diagram showing the image at the focal point obtained by the inspection camera unit.
[0034] [ Figure 13 [This is a diagram illustrating the adjustment of the beam width.]
[0035] [ Figure 14[This is a diagram illustrating the adjustment of the beam width.]
[0036] [ Figure 15 This diagram illustrates the adjustment of the beam width using a slit pattern.
[0037] [ Figure 16 ] is a program that displays the slit width export process.
[0038] [ Figure 17 ] is a program that displays the slit width export process.
[0039] [ Figure 18 The diagram illustrates the offset of the laser incident position.
[0040] [ Figure 19 [ ] is a flowchart of the beam width adjustment process.
[0041] [ Figure 20 [This is a schematic diagram of the slit width export processing.]
[0042] Symbol Explanation
[0043] 1…laser processing apparatus, 2…stage, 8…control unit, 20…wafer, 21a…surface (first surface), 21b…back side (second surface), 22a…functional element (component), 22x…structure, 23…cutting kerf area (cutting kerf), 31…light source (irradiation unit), 32…spatial light modulator (beam width adjustment unit). Detailed Implementation
[0044] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Furthermore, the same or equivalent parts are given the same symbol in each drawing, and repeated descriptions are omitted.
[0045] [Composition of Laser Processing Equipment]
[0046] like Figure 1 As shown, the laser processing apparatus 1 includes: a stage 2, a laser irradiation unit 3, multiple camera units 4, 5, and 6, a drive unit 7, a control unit 8, and a display 150. The laser processing apparatus 1 is a device that forms a modified region 12 on an object 11 by irradiating the object 11 with a laser L.
[0047] The stage 2 supports the object 11, for example, by adsorbing and adhering a film to it. The stage 2 can move along the X and Y directions respectively, and can rotate about an axis parallel to the Z direction. In addition, the X and Y directions are mutually perpendicular first and second horizontal directions, and the Z direction is a vertical direction.
[0048] The laser irradiation unit 3 focuses the penetrating laser L onto the object 11. If the laser L is focused inside the object 11 supported by the stage 2, the laser L is specifically absorbed at the point corresponding to the focusing point C of the laser L, and a modified region 12 is formed inside the object 11.
[0049] 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. The modified region 12 has the characteristic that it readily allows cracks to extend from the modified region 12 toward the incident side of the laser L and to the opposite side. This characteristic of the modified region 12 can be used for cutting the object 11.
[0050] 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 modified particles 12s will be formed in a row along the X direction. Each modified particle 12s is formed by irradiation with a single pulse of laser L. A row of modified regions 12 is a collection of multiple modified particles 12s arranged in a row. Adjacent modified particles 12s 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.
[0051] The camera unit 4 captures images of the modified region 12 formed on the object 11 and the front end of the crack extending from the modified region 12.
[0052] Under the control of the control unit 8, camera units 5 and 6 use light transmitted through the object 11 to capture images of the object 11 supported by the platform 2. The images obtained by camera units 5 and 6 are, for example, provided to the alignment position of the laser L.
[0053] The drive unit 7 supports the laser irradiation unit 3 and multiple camera units 4, 5, and 6. The drive unit 7 moves the laser irradiation unit 3 and the multiple camera units 4, 5, and 6 along the Z direction.
[0054] The control unit 8 controls the operation of the stage 2, the laser irradiation unit 3, the multiple camera units 4, 5, and 6, and the drive unit 7. The control unit 8 is configured as a computer device including a processor, memory, storage devices, and communication devices. In the control unit 8, the processor executes software (programs) loaded into memory, etc., and controls the reading and writing of data in memory and storage devices, as well as communication via the communication devices.
[0055] The display 150 has the functions of an input section for receiving information from the user and a display section for displaying information to the user.
[0056] [The composition of objects]
[0057] like Figure 2 and Figure 3 As shown, the object 11 in this embodiment is a wafer 20. The wafer 20 includes a semiconductor substrate 21 and a functional element layer 22. The semiconductor substrate 21 has a surface 21a (first surface) and a back surface 21b (second surface). The semiconductor substrate 21 is, for example, a silicon substrate. The functional element layer 22 is formed on the surface 21a of the semiconductor substrate 21. The functional element layer 22 includes a plurality of functional elements 22a (elements) arranged in two dimensions along the surface 21a. The functional elements 22a are, for example, light-receiving elements such as photodiodes, light-emitting elements such as laser diodes, and circuit elements such as memory. The functional elements 22a are sometimes stacked in multiple layers and configured in a three-dimensional structure. In addition, a notch 21c indicating the crystal orientation is provided on the semiconductor substrate 21, but an orientation flat may be provided instead of the notch 21c.
[0058] Along each of the plurality of lines 15, the wafer 20 is cut into each functional element 22a. Viewed from the thickness direction of the wafer 20, the plurality of lines 15 pass between each of the plurality of functional elements 22a. More specifically, viewed from the thickness direction of the wafer 20, the lines 15 pass through the center (center in the width direction) of the cleavage region 23 (cleavage). In the functional element layer 22, the cleavage region 23 extends through the spaces between adjacent functional elements 22a. In this embodiment, the plurality of functional elements 22a are arranged in a matrix along the surface 21a, and the plurality of lines 15 are set in a grid pattern. The lines 15 are hypothetical lines, but can also be actual drawn lines. As described above, the wafer 20 has a surface 21a (refer to...). Figure 2 ) and the back surface 21b opposite to surface 21a (refer to Figure 3 The wafer has multiple functional elements 22a formed on its surface 21a, and the dicing region 23 extends through the space between adjacent functional elements 22a.
[0059] [Composition of the laser irradiation unit]
[0060] like Figure 4As shown, the laser irradiation unit 3 includes a light source 31 (irradiation section), a spatial light modulator 32 (beam width adjustment section), and a focusing lens 33. The light source 31 outputs laser light L using, for example, a pulse oscillation method. By irradiating the wafer 20 with laser light from the surface 21a side, the light source 31 forms multiple (in this case, two rows) modified regions 12a, 12b inside the wafer 20. The spatial light modulator 32 modulates the laser light L output from the light source 31. The spatial light modulator 32 functions as a slit (specifically described later), adjusting the beam width of the laser by partially blocking it. The slit, which functions as the spatial light modulator 32, is a slit pattern set as the modulation pattern of the spatial light modulator 32. In the spatial light modulator 32, by appropriately setting the modulation pattern displayed on the liquid crystal layer, the laser light L can be modulated (e.g., the intensity, amplitude, phase, polarization, etc. of the laser light L can be modulated). The modulation pattern refers to a holographic pattern imparted for modulation, and includes the slit pattern. The spatial light modulator 32 is, for example, a spatial light modulator (SLM) of a reflective liquid crystal on silicon (LCOS). The condenser lens 33 focuses the laser L modulated by the spatial light modulator 32. Alternatively, the condenser lens 33 can also be a correction ring lens.
[0061] In this embodiment, the laser irradiation unit 3 irradiates the wafer 20 with laser L from the surface 21a side of the semiconductor substrate 21 along each of the plurality of lines 15, thereby forming two rows of modified regions 12a and 12b inside the semiconductor substrate 21 along each of the plurality of lines 15. Modified region 12a is the modified region closest to the back surface 21b among the two rows of modified regions 12a and 12b. Modified region 12b is the modified region closest to modified region 12a among the two rows of modified regions 12a and 12b, and is also the modified region closest to the surface 21a.
[0062] Two rows of modified regions 12a and 12b are adjacent in the thickness direction (Z direction) of wafer 20. These two rows of modified regions 12a and 12b are formed by moving two focusing points C1 and C2 along line 15 relative to the semiconductor substrate 21. For example, focusing point C2 is positioned behind focusing point C1 in the travel direction and on the incident side of laser L, and laser L is modulated by spatial light modulator 32. Furthermore, the formation of the modified regions can be single-focus or multi-focus, and can be single-pass or multi-pass.
[0063] The laser irradiation unit 3 irradiates the wafer 20 with laser L from the surface 21a side of the semiconductor substrate 21 along multiple lines 15. As an example, this is applied to a single-crystal silicon substrate with a thickness of 400 μm. <100> The semiconductor substrate 21 of the substrate has two focusing points C1 and C2 aligned with positions 54 μm and 128 μm away from the back surface 21b, respectively, so that laser L is irradiated onto the wafer 20 from the surface 21a side of the semiconductor substrate 21 along multiple lines 15. For example, under the condition that the cracks 14 passing through the two rows of modified regions 12a and 12b reach the back surface 21b of the semiconductor substrate 21, the wavelength of laser L is set to 1099 nm, the pulse width to 700 nm, and the repetition frequency to 120 kHz. Furthermore, the output of laser L at focusing point C1 is set to 2.7 W, the output of laser L at focusing point C2 is set to 2.7 W, and the moving speed of the two focusing points C1 and C2 relative to the semiconductor substrate 21 is set to 800 mm / s. Alternatively, laser L can be irradiated under the condition that the cracks 14 passing through the two rows of modified regions 12a and 12b do not reach the back surface 21b of the semiconductor substrate 21. That is, in subsequent processes, for example by grinding the back side 21b of the semiconductor substrate 21, the semiconductor substrate 21 can be thinned and the cracks 14 can be exposed on the back side 21b, and the wafer 20 can be cut into multiple semiconductor devices along each of the multiple lines 15.
[0064] [The structure of the inspection camera unit]
[0065] like Figure 5 As shown, the imaging unit 4 includes a light source 41, a reflector 42, an objective lens 43, and a light detection unit 44. The imaging unit 4 captures images of the wafer 20. The light source 41 outputs light I1 that is transparent to the semiconductor substrate 21. The light source 41 is, for example, composed of a halogen lamp and a filter, and outputs light I1 in the near-infrared region. The light I1 output from the light source 41 is reflected by the reflector 42 and passes through the objective lens 43, illuminating the wafer 20 from the surface 21a side of the semiconductor substrate 21. At this time, the stage 2 supports the wafer 20, on which two rows of modified regions 12a and 12b are formed, as described above.
[0066] Objective lens 43 allows light I1 reflected from the back surface 21b of semiconductor substrate 21 to pass through. That is, objective lens 43 allows light I1 propagating within semiconductor substrate 21 to pass through. The numerical aperture (NA) of objective lens 43 is, for example, 0.45 or greater. Objective lens 43 has a correction ring 43a. The correction ring 43a corrects aberrations generated by light I1 within semiconductor substrate 21, for example, by adjusting the distance between the multiple lenses constituting objective lens 43. Furthermore, the means of correcting aberrations is not limited to correction ring 43a; other correction means such as spatial light modulators can also be used. Light detection unit 44 detects light I1 transmitted through objective lens 43 and mirror 42. Light detection unit 44 is, for example, composed of an InGaAs camera, and detects light I1 in the near-infrared region. Furthermore, the means of detecting (image) light I1 in the near-infrared region is not limited to an InGaAs camera; other imaging means capable of transmission imaging, such as a transmission confocal microscope, can also be used.
[0067] Camera unit 4 can capture images of each of the two modified regions 12a and 12b, and the front ends of each of the multiple cracks 14a, 14b, 14c, and 14d. Crack 14a extends from modified region 12a toward the back side 21b. Crack 14b extends from modified region 12a toward the surface 21a. Crack 14c extends from modified region 12b toward the back side 21b. Crack 14d extends from modified region 12b toward the surface 21a.
[0068] [Composition of the camera unit for alignment correction]
[0069] like Figure 6 As shown, the imaging unit 5 includes a light source 51, a reflector 52, a lens 53, and a light detection unit 54. The light source 51 outputs light I2 that is permeable to the semiconductor substrate 21. The light source 51 is, for example, composed of a halogen lamp and a filter, and outputs light I2 in the near-infrared region. The light source 51 can be common to the light source 41 of the imaging unit 4. The light I2 output from the light source 51 is reflected by the reflector 52 and passes through the lens 53, and illuminates the wafer 20 from the surface 21a side of the semiconductor substrate 21.
[0070] Lens 53 allows light I2 reflected from the back surface 21b of semiconductor substrate 21 to pass through. That is, lens 53 allows light I2 propagating within semiconductor substrate 21 to pass through. The numerical aperture of lens 53 is 0.3 or less. That is, the numerical aperture of the objective lens 43 of imaging unit 4 is larger than the numerical aperture of lens 53. Light detection unit 54 detects the light I2 passing through lens 53 and mirror 52. Light detection unit 54 is, for example, constructed using an InGaAs camera, and detects light I2 in the near-infrared region.
[0071] Under the control of the control unit 8, the imaging unit 5 illuminates the wafer 20 with light I2 from the surface 21a side and detects the light I2 returning from the back side 21b side, thereby capturing an image of the back side 21b. Similarly, under the control of the control unit 8, the imaging unit 5 illuminates the wafer 20 with light I2 from the surface 21a side and detects the light I2 returning from the formation locations of the modified regions 12a and 12b in the semiconductor substrate 21, thereby acquiring an image of the region including the modified regions 12a and 12b. These images are used for alignment of the irradiation location of the laser L. The imaging unit 6 has the same configuration as the imaging unit 5, except that the lens 53 has a lower magnification (e.g., 6x in imaging unit 5, 1.5x in imaging unit 6), and is used for alignment in the same way.
[0072] [Based on the camera principle of the inspection camera unit]
[0073] use Figure 5 The camera unit 4 shown is as follows: Figure 7 As shown, relative to the semiconductor substrate 21 reaching the back surface 21b from the crack 14 that traverses the two rows of modified regions 12a and 12b, the focal point F (the focal point of the objective lens 43) is moved from the surface 21a side toward the back surface 21b side. In this case, if the focal point F is aligned with the tip 14e of the crack 14 extending from the modified region 12b toward the surface 21a side from the surface 21a side, the tip 14e ( Figure 7 (Image on the right). However, even when focusing F on the crack 14 itself and the front end 14e of the crack 14 reaching the back surface 21b from the surface 21a side, they cannot be identified. Figure 7 (The image on the left in the image).
[0074] Other uses Figure 5 The camera unit 4 shown is as follows: Figure 8 As shown, the focus F is moved from the surface 21a side toward the back surface 21b of the semiconductor substrate 21, relative to the crack 14 that traverses the two modified regions 12a and 12b. In this case, even if the focus F is aligned with the tip 14e of the crack 14 extending from the modified region 12a toward the back surface 21b from the surface 21a side, it is still impossible to confirm the tip 14e. Figure 8 (Image on the left in the image). However, if the focal point F is aligned with the region opposite to the back surface 21b from the surface 21a side, so that the imaginary focal point Fv, which is symmetrical to the focal point F with respect to the back surface 21b, is located at the front end 14e, then the front end 14e can be confirmed ( Figure 8 (Image on the right side of the image). Additionally, the hypothetical focal point Fv is a point symmetrical about the back surface 21b with respect to the focal point F, which takes into account the refractive index of the semiconductor substrate 21.
[0075] The reason why the crack 14 itself cannot be confirmed as described above can be imagined as being because the width of the crack 14 is smaller than the wavelength of the light I1 that serves as illumination. Figure 9 and Figure 10 These are SEM (Scanning Electron Microscope) images of the modified region 12 and cracks 14 formed inside the semiconductor substrate 21, which serves as a silicon substrate. Figure 9 (b) is Figure 9 A magnified image of region A1 shown in (a), Figure 10 (a) is Figure 9 A magnified image of region A2 shown in (b). Figure 10 (b) is Figure 10 A magnified image of region A3 shown in (a). Thus, the width of the crack 14 is about 120 nm, which is smaller than the wavelength of light I1 in the near-infrared region (e.g., 1.1–1.2 μm).
[0076] The camera principle envisioned based on the above is as follows. Figure 11 As shown in (a), if the focal point F is placed in the air, a black image is obtained because light I1 will not return. Figure 11 (The image on the right in (a)). Figure 11 As shown in (b), if the focal point F is located inside the semiconductor substrate 21, a white image is obtained because the light I1 reflected from the surface 21a returns. Figure 11 (The image on the right in (b)). Figure 11 As shown in (c), if the focal point F is aligned with the modified region 12 from the surface 21a side, the modified region 12 absorbs and scatters a portion of the light I1 reflected back from the back surface 21b, thus obtaining an image in which the modified region 12 appears black against a white background. Figure 11 (The image on the right in (c)).
[0077] like Figure 12 As shown in (a) and (b), if the focal point F is aligned from the surface 21a side with the tip 14e of the crack 14, then due to optical specificities (stress concentration, strain, atomic density discontinuities, etc.) and light blocking caused near the tip 14e, a portion of the light I1 reflected from the back surface 21b will undergo scattering, reflection, interference, absorption, etc., thus obtaining an image in which the tip 14e appears black against a white background. Figure 12 (Images on the right in (a) and (b)). Figure 12 As shown in (c), if the focal point F is aligned with the portion of the crack 14 other than the front end 14e from the surface 21a side, a white image is obtained because at least a portion of the light I1 reflected from the back surface 21b will return. Figure 12 (The image on the right in (c)).
[0078] [Laser beam width adjustment processing]
[0079] The following describes the laser beam width adjustment process performed when forming a modified region for purposes such as dicing wafer 20. Alternatively, the beam width adjustment process can be performed independently of the modified region formation process (without being linked to it).
[0080] First, refer to Figure 13 and Figure 14 Explain why the laser beam width must be adjusted. Figure 13 and Figure 14 This diagram illustrates the adjustment of the beam width. Additionally, in Figure 13 and Figure 14 In the accompanying figures, "DF" indicates the laser-based processing position (focusing position), and "Cutting Position" indicates the cutting position when the back side 21b is ground and the wafer 20 is cut into multiple semiconductor devices in subsequent processes. Figure 13 As shown, in this embodiment, a plurality of functional elements 22a are formed on the incident surface 21a, i.e., the surface of the laser L on the wafer 20. For example... Figure 13 As shown in (a), when the beam width of the laser L is large, the laser L incident on surface 21a may extend beyond the kerf region 23 and reach the functional element 22a, causing a portion of the laser L to be unable to focus inside the wafer 20 (being blocked by the functional element 22a). When the kerf region 23 is narrow or the processing position (focusing position) is deep, the laser L is more likely to be blocked by the functional element 22a. When the laser L is blocked by the functional element 22a, because a portion of the laser L cannot focus inside the wafer 20, the output of the laser L inside the wafer 20 is reduced. Furthermore, due to the interference between the laser L and the functional element 22a, there is a concern that unwanted beams may enter the interior of the wafer 20, causing deterioration in processing quality. Additionally, depending on the type of structure 22x constituting the functional element 22a, there is a concern that it may be dissolved by irradiation from the laser L.
[0081] To prevent the laser L from being blocked by the functional element 22a, the beam width of the laser L must be adjusted. For example, the laser L can be cut to an arbitrary width using the slit portion of the spatial light modulator 32 (a slit pattern set as the modulation pattern) (details to follow). Figure 13As shown in (b), the laser L incident toward surface 21a can be confined to the width of the kerf region 23. That is, by cutting off a portion of the laser L (the laser cutoff portion LC), the laser L incident toward surface 21a can be confined to the width of the kerf region 23.
[0082] Here, the structure 22x constituting the functional element 22a has a certain height t (thickness t). Thus, even if the laser L can be confined within the cutting channel region 23 as described above, there is still a concern that the laser L might be partially blocked by a portion of the structure 22x with height t. For example, in... Figure 14 In the example shown in (a), the beam width Wt0 of the laser L incident on the surface of the cutting channel region 23 is controlled to be narrower than the width of the cutting channel region 23. However, structures 22x, 22x of height t are provided at positions X away from both ends of the cutting channel region 23 (position X). Because the beam width Wt of the laser L at this height t position is larger than the separation distance of the structures 22x, 22x, the laser L is partially blocked by a portion of the structure 22x of height t.
[0083] On the other hand, for example Figure 14 As shown in (b), when the height t of structure 22x is greater than the above Figure 14 When the height t of structures 22x, 22x shown in (a) is sufficiently low, even if the beam width Wt0 of the laser L and the distance X of structures 22x, 22x from the end of the cutting channel region 23, etc., are the same as those conditions... Figure 14 The configuration shown in (a) is the same, and the laser L will not be blocked by the structure 22x constituting the functional element 22a. For example... Figure 14 As shown in (c), the distance X from the end of structure 22x, 22x to the cutting channel region 23 is greater than that described above. Figure 14 When the distance X from the end of the structure 22x, 22x to the cutting channel region 23 shown in (a) is sufficiently large, even if the beam width Wt0 of the laser L and the height t of the structure 22x, 22x, etc. are the same as those conditions, Figure 14 The configuration shown in (a) is the same, and the laser L will not be blocked by the structure 22x that constitutes the functional element 22a.
[0084] As shown above, in order to suppress the situation where the laser L is blocked by the structure 22x constituting the functional element 22a, in addition to the width of the cutting track region 23, the position and height of the structure 22x constituting the functional element 22a adjacent to the cutting track region 23 must also be considered, and the beam width of the laser L is adjusted accordingly. The detailed functions of the control unit 8 related to the laser beam width adjustment are explained below.
[0085] The control unit 8 controls the spatial light modulator 32 (beam width adjustment unit) by adjusting the laser beam width to below the target beam width corresponding to the surface information, which includes the width of the kerf region 23 and the position and height of the structure 22x constituting the functional element 22a adjacent to the kerf region 23. The control unit 8, for example, controls the spatial light modulator 32 (beam width adjustment unit) based on a setting screen displayed on the display 150 (see...). Figure 20 In (b)), surface information is obtained from user input. This surface information includes the width W of the kerf region 23, and the position X and height t of the structure 22x constituting the functional element 22a adjacent to the kerf region 23. The position X of the structure 22x is the separation distance X from the end of the kerf region 23 to the structure 22x. The target beam width includes a value at surface 21a and a value at height t of the structure 22x. The target beam width at surface 21a is, for example, the width W of the kerf region 23. The target beam width at height t of the structure 22x is, for example, the separation distance between the structures 22x and 22x adjacent to the kerf region 23, and is a value obtained by adding the width W of the kerf region 23, the position X of one structure 22x, and the position X of the other structure 22x (W+X+X). By controlling the laser beam width at surface 21a to be below the target beam width at surface 21a, and by controlling the laser beam width at height t to be below the target beam width at height t, the laser can be reliably confined within the cutting channel region 23, and the situation where the laser L is blocked by the structure 22x constituting the functional element 22a can be avoided.
[0086] Based on the surface information described above, the control unit 8 derives the slit width (specifically described later) of the spatial light modulator 32, which functions as a slit section, in relation to the laser penetration area, and sets a slit pattern corresponding to the slit width in the spatial light modulator 32. Figure 15 This diagram illustrates the adjustment of the beam width using the slit pattern SP. Figure 15 The slit pattern SP shown in (a) is a modulation pattern displayed on the liquid crystal layer of the spatial light modulator 32. The slit pattern SP includes a blocking region CE that blocks the laser L and a penetrating region TE that allows the laser L to pass through. The penetrating region TE is set to a size corresponding to the slit width. The slit pattern SP is set in such a way that the smaller the slit width, the smaller the penetrating region TE becomes (the larger the blocking region CE becomes), and the larger the laser cutoff portion LC becomes. Figure 15 In the slit pattern SP of (a), to reduce the beam width of laser L, the two ends of laser L in the width direction become the blocking region CE, and the central region becomes the penetration region TE. For example... Figure 15As shown in (a), by passing the laser through the slit pattern SP, the two ends (laser cutoff portion LC) of the laser L in the width direction can be cut off, and the beam width of the laser L becomes less than the target beam width.
[0087] The control unit 8 can also further consider the processing depth of the laser L on the wafer 20 and derive the slit width. Figure 15 (b) shows the machining depth (position of “DF”) compared to the above. Figure 15 (a) A shallow example. In Figure 15 (a) and Figure 15 In (b), other conditions such as surface information are the same. In this case, control unit 8 is more sensitive to shallow machining depths. Figure 15 (b) The slit pattern SP, compared to the processing depth Figure 15 The slit pattern SP in (a) reduces the blocking area CE and increases the penetration area TE. That is, the control unit 8 can also be controlled such that the deeper the processing depth of the laser L, the larger the blocking area CE in the slit pattern SP. In this way, considering not only surface information but also processing depth, the slit pattern SP can be set more appropriately. The control unit 8 can also be, for example, Figure 4 As shown, when multiple (2 columns) modified regions 12a, 12b are formed inside the semiconductor substrate 21 at different depths, the slit width is derived for each combination of surface information and the processing depth of laser L.
[0088] Figure 16 and Figure 17 This diagram illustrates an example of a specific slit width derivation process. Control unit 8 derives the slit width, for example, by performing calculations according to procedures 1 to 4 below. Furthermore, as will be stated later, the calculation procedure based on control unit 8 is not limited to the following.
[0089] like Figure 16 As shown in (a), the width of the dicing region 23 of wafer 20 is set as W, the position of structures 22x, 22x (the separation distance between the ends of the dicing region 23) is set as X, the height of structure 22x is set as t, and the processing depth of laser L is set as DF. The processing depth refers to the processing depth measured from surface 21a.
[0090] In program 1, such as Figure 16 (b) and Figure 16 As shown in (c), the control unit 8 ignores the presence of the structure 22x and calculates the slit width in such a way that the laser beam width is less than or equal to the target beam width (width W of the cutting area 23) on the surface 21a. The slit width is derived from the following equation (1).
[0091]
[0092] In equation (1) above, “SLIT” is the slit width, Z is a fixed value depending on the type of spatial light modulator 32, n is the refractive index depending on the material of the workpiece, and a is a constant (dz rate) taking into account the refractive index of the material of the workpiece. Now, let’s set n = 3.6, a = 4.8, Z = 480, the width W of the cutting track region 23 = 20 μm, and the processing depth DF = 50 μm. In this case, the slit width SLITstreet = 72 μm is derived in program 1 based on the width of the cutting track region 23.
[0093] Next, in program 2, such as Figure 16 As shown in (d), the control unit 8 calculates the beam amplification distance Xt from the surface 21a to the height t of the structure 22x when the slit width SLITstreet = 72 μm obtained in program 1 is used. The distance Xt is derived by the following equation (2) which is derived from equation (1). Now, the height t of the structure 22x is set to 40 μm. In this case, substituting the slit width SLITstreet = 72 μm into SLIT in equation (2), the distance Xt = 8 μm is derived.
[0094]
[0095] Next, in program 3, control unit 8 compares the distance Xt = 8 μm derived in program 2 with the position X of structure 22x (the separation distance from the end of the cutting channel region 23). Control unit 8, for example, as follows... Figure 17 As shown in (a), when the position X is larger than the distance Xt (position X is greater than 8 μm), it is determined that even if a slit width SLITstreet = 72 μm is used, the laser will not be blocked by the structure 22x, and the slit width SLITstreet is determined to be the final slit width. On the other hand, the control unit 8, for example, Figure 17 As shown in (b), when the position X is smaller than the distance Xt (position X is less than 8 μm), it is determined that if the slit width SLITstreet = 72 μm is used, the laser will be blocked by the structure 22x. Therefore, it is decided not to use the slit width SLITstreet, and the final slit width considering the position and height of the structure 22x is recalculated.
[0096] Procedure 4 is performed only if, in Procedure 3, it is decided to recalculate the final slit width taking into account the position and height of structure 22x. In Procedure 4, the control unit 8... Figure 17As shown in (c), the slit width is calculated by taking into account the position and height of structure 22x, so that the laser beam width is below the target beam width at the height t of structure 22x. The slit width is derived from the following equation (3). Now, the position of structure 22x (the separation distance from the end of the cutting channel region 23) is set to X = 4 μm. In this case, the final slit width SLIT structure = 56 μm is derived, taking into account the position and height of structure 22x.
[0097]
[0098] Furthermore, in the above calculation procedure, after initially calculating the slit width ignoring the existence of structure 22x, it is determined whether the laser will be blocked by structure 22x under that slit width, and the final slit width is derived. However, the calculation procedure is not limited to this. The control unit 8 may also, for example, derive both the slit width SLITstreet derived by equation (1) and the slit width SLIT structure derived by equation (3), and then decide to use the smaller slit width as the final slit width.
[0099] The control unit 8 can also be configured to further consider the offset of the incident position of the laser on the surface 21a during processing, and control the spatial light modulator 32 that sets the slit pattern. For example... Figure 18 As shown, when laser light is continuously irradiated onto the cutting track region 23 of multiple processing lines l1 to l3, gaps are created between the chips, causing the positions of processing lines l1 to l3 to gradually shift. Figure 18 In the example, compared to the initial processing line l1, the position of the next processing line l2 will shift to the left, and compared to processing line l2, the position of the next processing line l3 will shift to the left. Although it is possible to consider performing a correction process every few processing lines, each processing line must be corrected to eliminate the position shift. However, considering the processing time, it is impractical to correct each processing line. In this embodiment, the control unit 8 confirms the incident position shift of the laser during processing (processing position shift margin value) in advance, and when using the above formula (1) or (3) to derive the slit width, the width W of the cutting track region 23 is set to take into account the processing position shift margin value. For example, the control unit 8 can set the value of the width W of the cutting track region 23 minus the processing position shift margin value as the corrected width W of the cutting track region 23, and derive the slit width. Furthermore, the control unit 8 controls the spatial light modulator 32 by setting the slit pattern based on the slit width derived from the processing position offset margin value.
[0100] The control unit 8 may also control the display 150 to show information indicating that the engine is not suitable for processing when the derived slit width is less than the limit slit value, which is the boundary value that can form the modified region. The limit slit value is, for example, a value set for each engine based on prior processing experiments.
[0101] The control unit 8 can also control the display 150 to display information prompting changes to various processing conditions when the derived slit width is a slit width that worsens the crack length extending from the modified region 12. Processing conditions include, for example: number of laser beams processed, ZH (Z-height), VD, number of focal points, pulse energy, focusing parameters, processing speed, frequency, pulse width, etc. ZH represents the processing depth (height) during laser processing.
[0102] Next, refer to Figure 19 This section explains the beam width adjustment process implemented by the 8th control unit.
[0103] The control unit 8 initially receives input related to processing conditions (process parameters (recipe)) (step S1). The control unit 8 receives information input from the user, for example, via a setting screen displayed on the display 150. Specifically, the control unit 8, as... Figure 20 As shown in (a), multiple modified regions 12 are received (in Figure 20 The input of the Z-height (ZH1, ZH2, ZH3) of the machining positions (SD1, SD2, SD3). Additionally, the control unit 8... Figure 20 As shown in (c), the control unit 8 receives inputs of the width W of the cutting channel region 23, the height t of the structure 22x, the position X of the structure 22x, and the material of the workpiece (e.g., silicon). Furthermore, the control unit 8 acquires preset fixed values that are not input by the user. Specifically, the control unit 8... Figure 20 As shown in (b), the following values are obtained: a fixed value N based on the material (e.g., a fixed value corresponding to n and a in equation (1)), the critical slit width (limit slit value), and the machining position offset allowance Y. These values may or may not be displayed on the display 150. Alternatively, when these values are displayed on the display 150, they may be values set by user input.
[0104] Next, the control unit 8 selects a processing position from the processing positions of the multiple modified regions 12 (SD1, SD2, SD3) before the slit width calculation (step S2). Then, the control unit 8 calculates the slit width at the selected processing position (step S3). Specifically, the control unit 8 calculates the slit width at the selected processing position, for example, using the procedures 1 to 4 described above.
[0105] Next, the control unit 8 determines whether the derived slit width is appropriate (step S4). Specifically, the control unit 8 determines whether the derived slit width is less than the critical slit width (limit slit value). Furthermore, the control unit 8 may also determine whether the derived slit width is a slit width that worsens the length of the crack extending from the modified region 12.
[0106] In step S4, if it is determined that the slit width is inappropriate, the control unit 8 controls the display 150 to display an alarm (step S5). Displaying an alarm means, for example, displaying information indicating that the material is unprocessable when the slit width is at a critical slit width. Alternatively, displaying an alarm means, for example, displaying information urging a change in processing conditions when the slit width is a slit width that worsens the length of the crack.
[0107] In step S4, if the slit width is determined to be appropriate, the control unit 8 determines the slit width of the selected processing position based on the derived slit width (step S6). Next, the control unit 8 determines whether there are any unselected processing positions (step S7). If there are still unselected processing positions, the process starts again from step S2. On the other hand, if there are no unselected processing positions (the slit width has been determined for all processing positions), the control unit 8 sets the slit pattern corresponding to the derived slit width on the spatial light modulator 32 for each processing position and starts processing (step S8). The above is the beam width adjustment process.
[0108] Next, the effects of the laser processing apparatus 1 in this embodiment will be explained.
[0109] The laser processing apparatus 1 of this embodiment includes a stage 2, a light source 31, a spatial light modulator 32, and a control unit 8. The stage 2 supports a wafer 20 having a surface 21a and a back surface 21b opposite to the surface 21a. Multiple functional elements 22a are formed on the surface 21a, and the kerf region 23 extends through adjacent functional elements 22a. The light source 31 forms one or more modified regions 12 inside the wafer 20 by irradiating the wafer 20 with laser light from the surface 21a side. The spatial light modulator 32 serves as a beam width adjustment unit for adjusting the beam width of the laser. The control unit 8 controls the spatial light modulator 32 to adjust the beam width of the laser to be below a target beam width corresponding to surface information, which includes the width of the kerf region 23 and the position and height of the structure 22x constituting the functional element 22a adjacent to the kerf region 23.
[0110] In the laser processing apparatus 1, in a configuration where laser light is irradiated onto the wafer 20 from the surface 21a on which multiple functional elements 22a are formed, the laser beam width is adjusted to be below the target beam width, which corresponds to the width of the kerf region 23 of the surface 21a and the position and height of the structure 22x constituting the functional elements 22a. Therefore, by adjusting the laser beam width to be below the target beam width, which takes into account not only the width of the kerf region 23 but also the position and height of the structure 22x constituting the functional elements 22a, the laser beam width can be adjusted to be not only limited to the width of the kerf region 23 but also not obstructed by the structure 22x. Thus, laser obstruction by the structure 22x, such as circuitry, can be suppressed, and the desired laser irradiation (laser irradiation limited to the width of the kerf region 23 and not obstructed by the structure 22x) can be achieved.
[0111] That is, the laser processing apparatus 1 of this embodiment can suppress the reduction of laser output inside the wafer 20 caused by the laser being blocked by the structure 22x. Furthermore, when the laser irradiates the structure 22x, such as circuitry, it is believed that interference may cause unwanted beams to enter the interior of the wafer 20, leading to deterioration of processing quality. Regarding this, by suppressing the laser from being blocked by the structure 22x (or irradiating the structure 22x) as described above, such deterioration of processing quality can be prevented. Additionally, depending on the type of structure 22x, there are concerns that it may dissolve due to laser irradiation. Regarding this, by suppressing the laser from being blocked by the structure 22x (or irradiating the structure 22x) as described above, the influence of the laser on the structure 22x (e.g., dissolution of the structure 22x) can be avoided.
[0112] Alternatively, the spatial light modulator 32 can function as a slit portion that adjusts the beam width by blocking part of the laser, and the control unit 8 can derive the slit width of the slit portion related to the laser penetration area based on surface information, and set the slit width in the slit portion. With this configuration, the beam width can be easily and reliably adjusted.
[0113] Alternatively, when the derived slit width is less than the threshold value that allows the formation of a modified region, the control unit 8 outputs information indicating that the material is not processable. This avoids processing despite the material being in a state where a modified region cannot be formed (unnecessary processing), and enables efficient processing.
[0114] Alternatively, if the derived slit width is such that it worsens the length of the cracks extending from the modified region, the control unit 8 outputs information urging a change in processing conditions. Thus, in situations where suitable processing cannot be performed, a change in processing conditions can be urged, enabling smooth processing.
[0115] Alternatively, the control unit 8 can further consider the laser processing depth on the wafer 20 to derive the slit width. Even with the same surface information, the appropriate slit width will differ depending on the processing depth. In this regard, by considering the processing depth to derive the slit width, a more suitable slit width can be derived, and the laser being blocked by the structure 22x can be appropriately suppressed.
[0116] Alternatively, when multiple modified regions 12 are formed at different depths inside the wafer 20 by irradiating the interior of the wafer 20 with a laser, the control unit 8 derives the slit width for each combination of surface information and laser processing depth. In this way, by deriving the slit width for each combination of different processing depths and surface information, a more suitable slit width can be derived, and the blocking of the laser by the structure 22x can be more appropriately suppressed.
[0117] Alternatively, the control unit 8 can further consider the offset of the laser incident position on the surface 21a during processing, thereby controlling the spatial light modulator 32. It is assumed that the processing line will gradually shift as processing progresses. In response to this, by pre-determining such an offset, the spatial light modulator 32 is controlled in consideration of the offset (setting the slit pattern), so that even if the processing line shift occurs, the laser can still be suppressed from being blocked by the structure 22x.
[0118] The above description pertains to embodiments of the present invention, but the present invention is not limited to the above embodiments. For example, although it has been described that the control unit 8 adjusts the beam width of the laser by setting the slit pattern of the spatial light modulator 32, the method of adjusting the beam width is not limited to this. For example, instead of setting a slit pattern, a physical slit may be set to adjust the beam width. Alternatively, the beam width may be adjusted by adjusting the ellipticity of the laser in the spatial light modulator 32.
Claims
1. A laser processing apparatus, wherein, have: A stage that supports a wafer having a first surface and a second surface opposite to the first surface, wherein a plurality of elements are formed on the first surface and cleavage extends through the space between adjacent elements. An irradiation section forms one or more modified regions inside the wafer by irradiating the wafer with a laser from the first surface side; A beam width adjustment unit that adjusts the beam width of the laser; as well as The control unit controls the beam width adjustment unit to adjust the beam width of the laser to a target beam width corresponding to the surface information, wherein the surface information includes the width of the cutting path and the position and height of the structures constituting the elements adjacent to the cutting path. The beam width adjustment section has a slit portion that adjusts the beam width by blocking a portion of the laser. The control unit derives the final slit width of the slit portion related to the penetration area of the laser based on the slit width based on the width of the cutting path and the slit width taking into account the position and height of the structure, and sets the final slit width of the slit portion, wherein the slit width based on the width of the cutting path is calculated by the following formula (1). ……（1） (1) In the formula, SLIT is the slit width based on the width of the cutting track, Z is a fixed value depending on the type of spatial light modulator, n is the refractive index depending on the material of the workpiece, a is a constant considering the refractive index of the material of the workpiece, W is the width of the cutting track, and DF is the processing depth. The slit width, which takes into account the position and height of the structure, is the slit width SLIT calculated by the following equation (3). ……（3） (3) In the formula, Z is a fixed value that depends on the type of spatial light modulator; n is the refractive index that depends on the material of the object being processed; a is a constant that takes into account the refractive index of the material of the object being processed; W is the width of the cutting channel; DF is the processing depth; X is the position of the structure, which is the separation distance between the structure and the end of the cutting channel; t is the height of the structure. In the process of deriving the final slit width related to the laser penetration area of the slit portion based on the slit width of the cutting path and the slit width taking into account the position and height of the structure, the smaller of the two slit widths is determined as the final slit width. If the derived final slit width is a slit width that worsens the length of the cracks extending from the modified region, the control unit outputs information to the outside urging a change in processing conditions.
2. A laser processing apparatus, wherein, have: A stage that supports a wafer having a first surface and a second surface opposite to the first surface, wherein a plurality of elements are formed on the first surface and cleavage extends through the space between adjacent elements. An irradiation section forms one or more modified regions inside the wafer by irradiating the wafer with a laser from the first surface side; A beam width adjustment unit that adjusts the beam width of the laser; as well as The control unit controls the beam width adjustment unit to adjust the beam width of the laser to a target beam width corresponding to the surface information, wherein the surface information includes the width of the cutting path and the position and height of the structures constituting the elements adjacent to the cutting path. The beam width adjustment section has a slit portion that adjusts the beam width by blocking a portion of the laser. The control unit derives the final slit width of the slit portion related to the penetration area of the laser based on the slit width based on the width of the cutting path and the slit width taking into account the position and height of the structure, and sets the final slit width of the slit portion, wherein the slit width based on the width of the cutting path is calculated by the following formula (1). ……（1） (1) In the formula, SLIT is the slit width based on the width of the cutting track, Z is a fixed value depending on the type of spatial light modulator, n is the refractive index depending on the material of the workpiece, a is a constant considering the refractive index of the material of the workpiece, W is the width of the cutting track, and DF is the processing depth. The slit width, which takes into account the position and height of the structure, is the slit width SLIT calculated by the following equation (3). ……（3） (3) In the formula, Z is a fixed value that depends on the type of spatial light modulator; n is the refractive index that depends on the material of the object being processed; a is a constant that takes into account the refractive index of the material of the object being processed; W is the width of the cutting channel; DF is the processing depth; X is the position of the structure, which is the separation distance between the structure and the end of the cutting channel; t is the height of the structure. The final slit width related to the laser penetration area is derived from the slit width based on the width of the cutting path and the slit width taking into account the position and height of the structure. The distance Xt by which the laser beam expands from the first surface to the height of the structure when the slit width based on the width of the cutting path is used, and the position X of the structure are compared. When the position X is greater than the distance Xt, the slit width based on the width of the cutting path is determined as the final slit width; When the position X is smaller than the distance Xt, the slit width that takes into account the position and height of the structure is determined as the final slit width; When the slit width based on the width of the cutting channel is adopted, the distance Xt by which the laser beam expands from the first surface to the height of the structure is calculated according to the following formula (2) based on the slit width based on the width of the cutting channel; the position X of the structure is the separation distance of the structure from the end of the cutting channel. ……（2） (2) In the formula, a is a constant that takes into account the refractive index of the material being processed; t is the height of the structure; SLIT is the slit width based on the width of the cutting path; Z is a fixed value that depends on the type of spatial light modulator; n is the refractive index that depends on the material being processed. If the derived final slit width is a slit width that worsens the length of the cracks extending from the modified region, the control unit outputs information to the outside urging a change in processing conditions.
3. The laser processing apparatus as described in claim 1 or 2, wherein, If the final slit width derived is less than the threshold value that can form the modified region, the control unit outputs information to the outside indicating that it is not processable.
4. The laser processing apparatus as described in claim 1 or 2, wherein, In the case where multiple modified regions are formed at different depths inside the wafer by irradiating the interior of the wafer with the laser, the control unit derives the final slit width from a combination of each surface information and the processing depth of the laser.
5. The laser processing apparatus as described in claim 1 or 2, wherein, The control unit further considers the laser incident position offset on the first surface during processing to control the beam width adjustment unit.
6. The laser processing apparatus as described in claim 3, wherein, The control unit further considers the laser incident position offset on the first surface during processing to control the beam width adjustment unit.
7. The laser processing apparatus as described in claim 4, wherein, The control unit further considers the laser incident position offset on the first surface during processing to control the beam width adjustment unit.
8. An inspection method, wherein, It includes the following processes: A process of setting up a wafer having a first surface and a second surface opposite to the first surface, wherein a plurality of elements are formed on the first surface and cleavage extends through the space between adjacent elements. The process of receiving surface information input, which includes the width of the cutting track and the position and height of the structure constituting the element adjacent to the cutting track; The process of controlling the beam width adjustment section to adjust the laser beam width to a level below the target beam width corresponding to the surface information; and The process of controlling the irradiation section of the laser in a manner that irradiates the wafer from the first surface side to form one or more modified regions inside the wafer. The beam width adjustment section has a slit portion that adjusts the beam width by blocking a portion of the laser. The final slit width of the slit portion related to the laser penetration area is derived based on the slit width based on the width of the cutting path and the slit width taking into account the position and height of the structure, and this final slit width is set in the slit portion, wherein the slit width based on the width of the cutting path is calculated by the following equation (1). ……（1） (1) In the formula, SLIT is the slit width based on the width of the cutting track, Z is a fixed value depending on the type of spatial light modulator, n is the refractive index depending on the material of the workpiece, a is a constant considering the refractive index of the material of the workpiece, W is the width of the cutting track, and DF is the processing depth. The slit width, which takes into account the position and height of the structure, is the slit width SLIT calculated by the following equation (3). ……（3） (3) In the formula, Z is a fixed value that depends on the type of spatial light modulator; n is the refractive index that depends on the material of the object being processed; a is a constant that takes into account the refractive index of the material of the object being processed; W is the width of the cutting channel; DF is the processing depth; X is the position of the structure, which is the separation distance between the structure and the end of the cutting channel; t is the height of the structure. In the process of deriving the final slit width related to the laser penetration area of the slit portion based on the slit width of the cutting path and the slit width taking into account the position and height of the structure, the smaller of the two slit widths is determined as the final slit width. If the derived final slit width is a slit width that worsens the length of the cracks extending from the modified region, information urging a change in processing conditions is output externally.
9. An inspection method, wherein, It includes the following processes: A process of setting up a wafer having a first surface and a second surface opposite to the first surface, wherein a plurality of elements are formed on the first surface and cleavage extends through the space between adjacent elements. The process of receiving surface information input, which includes the width of the cutting track and the position and height of the structure constituting the element adjacent to the cutting track; The process of controlling the beam width adjustment section to adjust the laser beam width to a level below the target beam width corresponding to the surface information; and The process of controlling the irradiation section of the laser in a manner that irradiates the wafer from the first surface side to form one or more modified regions inside the wafer. The beam width adjustment section has a slit portion that adjusts the beam width by blocking a portion of the laser. The final slit width of the slit portion related to the laser penetration area is derived based on the slit width based on the width of the cutting path and the slit width taking into account the position and height of the structure, and this final slit width is set in the slit portion, wherein the slit width based on the width of the cutting path is calculated by the following equation (1). ……（1） (1) In the formula, SLIT is the slit width based on the width of the cutting track, Z is a fixed value depending on the type of spatial light modulator, n is the refractive index depending on the material of the workpiece, a is a constant considering the refractive index of the material of the workpiece, W is the width of the cutting track, and DF is the processing depth. The slit width, which takes into account the position and height of the structure, is the slit width SLIT calculated by the following equation (3). ……（3） (3) In the formula, Z is a fixed value that depends on the type of spatial light modulator; n is the refractive index that depends on the material of the object being processed; a is a constant that takes into account the refractive index of the material of the object being processed; W is the width of the cutting channel; DF is the processing depth; X is the position of the structure, which is the separation distance between the structure and the end of the cutting channel; t is the height of the structure. The final slit width related to the laser penetration area is derived from the slit width based on the width of the cutting path and the slit width taking into account the position and height of the structure. The distance Xt by which the laser beam expands from the first surface to the height of the structure when the slit width based on the width of the cutting path is used, and the position X of the structure are compared. When the position X is greater than the distance Xt, the slit width based on the width of the cutting path is determined as the final slit width; When the position X is smaller than the distance Xt, the slit width that takes into account the position and height of the structure is determined as the final slit width; When the slit width based on the width of the cutting channel is adopted, the distance Xt by which the laser beam expands from the first surface to the height of the structure is calculated according to the following formula (2) based on the slit width based on the width of the cutting channel; the position X of the structure is the separation distance of the structure from the end of the cutting channel. ……（2） (2) In the formula, a is a constant that takes into account the refractive index of the material being processed; t is the height of the structure; SLIT is the slit width based on the width of the cutting path; Z is a fixed value that depends on the type of spatial light modulator; n is the refractive index that depends on the material being processed. If the derived final slit width is a slit width that worsens the length of the cracks extending from the modified region, information urging a change in processing conditions is output externally.