Method for obtaining processing conditions, and laser processing apparatus
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- HAMAMATSU PHOTONICS KK
- Filing Date
- 2022-01-26
- Publication Date
- 2026-08-03
Smart Images
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Abstract
Description
Technical Field
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[0001] The present disclosure relates to a processing condition acquisition method and a laser processing apparatus.
Background Art
[0002] [[ID=X]]Patent Document 1 describes a method of forming a weakened region along a planned cutting line on a metal film formed on the back side of a processing object by irradiating the surface of the processing object with laser light using the surface as the incident surface of the laser light. At this time, the focal point of the laser light is positioned outside the silicon wafer of the processing object.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] According to the method described in Patent Document 1, since a weakened region having a predetermined depth is formed in the metal film along the planned cutting line, it is possible to accurately cut the processing object along the planned cutting line with a relatively small external force. In particular, in recent years, in the cutting region, in order to cope with the miniaturization of device wiring, a Low-k film is adopted as an insulating film, and due to an increase in the number of stacked patterns accompanying three-dimensionalization, a plurality of films, metal wirings, and metal films may be stacked, and forming a weakened region as described above has become more effective. Along with this, a technique for obtaining suitable processing conditions when forming a weakened region is desired.
[0005] Therefore, an object of the present disclosure is to provide a processing condition acquisition method capable of obtaining suitable processing conditions when forming a weakened region and a laser processing apparatus.
Means for Solving the Problems
[0006] The processing condition acquisition method according to this disclosure is a method for acquiring laser processing conditions for forming a weakened region on a functional element layer by irradiating an object having a substrate including a first surface and a second surface opposite to the first surface, and a functional element layer provided on the second surface of the substrate, from the first surface side, and comprising: a first step of performing a first processing as multiple laser processing at different positions within the first surface while changing the focusing position of the laser beam in the Z direction intersecting the first surface within a range including the interface between the substrate and the functional element layer; a second step of acquiring an interface image by imaging the interface between the substrate and the functional element layer from the first surface side using transmitted light passing through the substrate at each of the positions within the first surface where the multiple first processings were performed; and a third step of acquiring the range of the focusing position in the Z direction of the first processing where an interface image containing laser beam damage was acquired from among the multiple interface images acquired in the second step as one of the laser processing conditions.
[0007] In this method, laser processing conditions for forming a weakened region on the functional element layer on the second surface of the substrate are obtained by irradiating the substrate from the first surface of the substrate. To achieve this, multiple laser processing passes are performed while varying the laser beam focusing position in the Z direction within a range that includes the interface between the substrate and the functional element layer. Furthermore, at each of the positions where multiple laser processing passes are performed, the interface between the substrate and the functional element layer is imaged to obtain an interface image. Depending on the focusing position, this interface image may or may not show images of damage caused by the laser beam. When the laser beam focusing position is within the range where images of damage appear in the interface image, a weakened region that allows for high-quality cutting of the substrate tends to be suitably formed. Therefore, in this method, the range of focusing positions for laser processing in which an interface image containing images of laser damage is obtained is acquired as one of the conditions for laser processing. Thus, this method makes it possible to obtain suitable processing conditions (range of focusing positions) for forming a weakened region.
[0008] In the processing condition acquisition method according to this disclosure, the range of positions in the Z direction in which the focusing position is changed in the first step may include a first range located on the first surface side of the interface and a second range located on the opposite side of the first surface from the interface and wider than the first range. Here, the range of focusing positions in which a weakened region is suitably formed is more easily obtained on the functional element layer side of the interface between the substrate and the functional element layer. Therefore, by making the range in which the focusing position is changed wider on the functional element layer side of the interface, it becomes possible to acquire this range more quickly and reliably.
[0009] The processing condition acquisition method according to this disclosure includes a fourth step after the first, second, and third steps, in which the object is cut and the surface of the functional element layer of the cut object is imaged. In the first step, laser light may be irradiated along the X direction along the first surface, and in the fourth step, the object may be cut along the X direction. In this way, by actually cutting the object and imaged on the surface of the functional element layer, it becomes possible to determine a more suitable focusing position by evaluating the cutting quality.
[0010] The processing condition acquisition method according to this disclosure may include a fifth step of performing a second processing as multiple laser processing at different positions on the first surface while changing the number of bursts of the laser light, which is pulsed light; a sixth step of acquiring a first surface image by imaging the first surface at each of the positions on the first surface where the multiple second processing was performed; and a seventh step of acquiring the number of bursts of the second processing in which a first surface image without damage to the first surface was acquired from among the multiple first surface images acquired in the sixth step, as another condition for laser processing. In this case, suitable processing conditions (number of bursts) that can form a weakened region so as not to damage the first surface, which is the incident surface of the laser light, can be acquired.
[0011] The laser processing apparatus according to this disclosure is a laser processing apparatus that obtains conditions for laser processing to form a weakened region on a functional element layer by irradiating an object having a substrate including a first surface and a second surface opposite to the first surface, and a functional element layer provided on the second surface of the substrate, from the first surface side, and comprises a support unit for supporting the object, a laser irradiation unit for irradiating the object supported by the support unit with laser light from the first surface side, an imaging unit for imaging the object supported by the support unit from the first surface side using transmitted light that passes through the substrate, and a control unit for controlling the laser irradiation unit and the imaging unit, wherein the control unit is a laser The first process involves controlling the irradiation unit to change the focusing position of the laser beam in the Z direction intersecting the first surface within a range including the interface between the substrate and the functional element layer, thereby performing multiple laser processing steps at different positions within the first surface; the second process involves controlling the imaging unit to capture an interface image of the interface between the substrate and the functional element layer from the first surface side using transmitted light at each of the positions within the first surface where multiple first processing steps were performed; and the third process involves recording each of the multiple interface images acquired in the second process in association with each of the corresponding focusing positions of the first processing steps.
[0012] This device obtains the conditions for laser processing to form a weakened region on the functional element layer on the second surface of the substrate of an object by irradiating it with laser light from the first surface of the substrate. To this end, multiple laser processing passes are performed while changing the laser beam focusing position in the Z direction within a range that includes the interface between the substrate and the functional element layer. Furthermore, at each of the positions where multiple laser processing passes are performed, the interface between the substrate and the functional element layer is imaged to obtain an interface image. As described above, depending on the focusing position, this interface image may or may not show an image of damage caused by the laser beam. When the laser beam focusing position is within the range where an image of damage appears in the interface image, a weakened region that allows for high-quality cutting of the object tends to be suitably formed. Therefore, this device records each of the multiple interface images in association with each of the corresponding laser processing focusing positions. By referring to this record, it becomes possible to obtain the range of laser processing focusing positions for which an interface image containing an image of laser damage was obtained as one of the conditions for laser processing. Thus, this device makes it possible to obtain optimal processing conditions (range of light focusing position) when forming a weakened region.
[0013] The laser processing apparatus according to this disclosure includes a display unit that displays images captured by an imaging unit, and the control unit may perform a fourth process by controlling the display unit to display each of the interface images recorded in the third process on the display unit. In this case, based on the interface images displayed on the display unit, it becomes possible to easily determine the range of the laser processing focusing position in which an interface image containing an image of laser beam damage was acquired among the multiple interface images. [Effects of the Invention]
[0014] According to this disclosure, a method for obtaining processing conditions that can obtain suitable processing conditions when forming a weakened region, and a laser processing apparatus can be provided. [Brief explanation of the drawing]
[0015] [Figure 1]FIG. 1 is a schematic diagram showing a schematic configuration of a laser processing apparatus according to the present embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view for explaining laser processing performed by the laser processing apparatus shown in FIG. 1. [Figure 3] FIG. 3 is a flowchart showing an example of a processing condition acquisition method performed by the laser processing apparatus shown in FIG. 1. [Figure 4] FIG. 9 is a schematic cross-sectional view showing one step of the processing condition acquisition method shown in FIG. 3. [Figure 5] FIG. 9 is a schematic cross-sectional view showing one step of the processing condition acquisition method shown in FIG. 3. [Figure 6] It is a graph for explaining the change in the number of bursts. [Figure 7] FIG. 7 is a diagram showing a plurality of first surface images. [Figure 8] FIG. 9 is a schematic cross-sectional view showing one step of the processing condition acquisition method shown in FIG. 3. [Figure 9] FIG. 9 is a diagram showing a plurality of interface images. [Figure 10] FIG. 10 is a schematic diagram showing a schematic configuration of a head portion according to a modified example.
BEST MODE FOR CARRYING OUT THE INVENTION
[0016] Hereinafter, an embodiment will be described with reference to the drawings. In the description of each figure, the same or corresponding elements may be denoted by the same reference numerals, and redundant descriptions may be omitted. Also, each figure may illustrate an orthogonal coordinate system defined by the X-axis, Y-axis, and Z-axis. The Z direction of the coordinate system is, for example, the vertical direction. Also, the X direction and the Y direction are, for example, two horizontal directions that intersect (are orthogonal) to each other.
[0017] FIG. 1 is a schematic diagram showing a schematic configuration of a laser processing apparatus according to the present embodiment. As shown in FIG. 1, the laser processing apparatus 1 includes a table (support portion) 10, a head portion 20, a control portion 30, an input portion 31, a display portion 33, and a recording portion 35. The table 10 is, for example, a transparent table having transparency with respect to at least visible light and near-infrared light, and supports an object 5. The object 5 includes a first surface 5a and a second surface 5b on the side opposite to the first surface 5a. The object 5 is supported on the table 10 via a tape 6 provided on the second surface 5b. The tape 6 is held by a frame portion 7 and is, for example, a transparent tape having transparency with respect to at least visible light and near-infrared light.
[0018] The table 10 may be provided with a first moving mechanism (not shown) for moving the table 10 in at least one of the X direction, the Y direction, and the Z direction. Thereby, the table 10 can be driven in at least one of the X direction, the Y direction, and the Z direction by the control portion 30 controlling the first moving mechanism.
[0019] The object 5 includes a substrate 51 and a functional element layer 52. The substrate 51 includes a first surface 5a and a second surface 51b on the side opposite to the first surface 5a. The functional element layer 52 is provided on the second surface 51b. Here, the second surface 5b of the object 5 is the surface on the side opposite to the substrate 51 in the functional element layer 52. The substrate 51 is, for example, a semiconductor substrate containing silicon or the like. The functional element layer 52 is a layer including a plurality of functional elements (semiconductor elements) arranged in the X direction and the Y direction. In the functional element layer 52, a plurality of functional elements may be stacked along the Z direction. Further, the functional element layer 52 may include an insulating film such as a metal wiring, a metal film, or a Low-k film.
[0020] The head unit 20 includes a first focusing unit 21, a first camera 23, a second camera 25, and a housing 26. The first focusing unit 21, the first camera 23, and the second camera 25 are housed within the housing 26. The first focusing unit 21 includes a lens and focuses the processing laser light L1, which is emitted from a light source outside the housing 26 and introduced into the housing 26, onto the object 5 via mirrors M1 and M2. Therefore, the head unit 20 is a laser irradiation unit that irradiates the object 5, supported on the table 10, with the laser light L1 from the first surface 5a side. The laser light L1 is penetrating to the substrate 51 of the object 5. As an example, the wavelength of the laser light L1 is about 1064 nm and the pulse width is about 9 ps.
[0021] Furthermore, the first light-gathering unit 21 receives the first observation light L2, which is emitted from a light source outside the housing 26 and introduced into the housing 26, via the mirror M2 and focuses it toward the object 5. The first camera 23 receives the reflected light of the first observation light L2 irradiated onto the object 5 via the mirrors M2, M1, and M3b and takes an image. The first observation light L2 is, for example, visible light. In this case, the first camera 23 is sensitive to visible light and near-infrared light. Thus, the head unit 20 is a first imaging unit that images the object 5 supported on the table 10 from the first surface 5a side with the first observation light L2 (acquires an image of the first surface 5a).
[0022] Furthermore, the first light-gathering unit 21 receives transmitted light L3, which is emitted from a light source outside the housing 26 and introduced into the housing 26, via mirrors M3a, M3b, M1, and M2, and focuses it toward the object 5. The second camera 25 receives the reflected light of the transmitted light L3 irradiated onto the object 5 via mirrors M2, M1, M3b, and M3a to take an image. The transmitted light L3 is, for example, near-infrared light and is penetrating to the substrate 51 of the object 5. In this case, the second camera 25 is sensitive to near-infrared light. The second camera 25 may be configured as, for example, an InGaAs camera. Thus, the head unit 20 is also a second imaging unit (imaging unit) that images the object 5 supported on the table 10 from the first surface 5a side using transmitted light L3 that passes through the substrate 51. The head unit 20 is configured so that the laser light L1, the first observation light L2, and the transmitted light L3 are irradiated onto the object 5 in a coaxial manner.
[0023] In the above example, the laser processing apparatus 1 has light sources for laser light L1, first observation light L2, and transmitted light L3 outside the head unit 20, but at least one of the light sources may be located inside the head unit 20. The head unit 20 may also be provided with a second movement mechanism (not shown) for moving the head unit 20 in at least one of the X, Y, and Z directions. As a result, the head unit 20 can be driven in at least one of the X, Y, and Z directions by the control unit 30 controlling the second movement mechanism. The movement directions of the table 10 and the movement directions of the head unit 20 can be set, at least in combination with each other, so that the object 5 can be moved relative to the irradiation position of the laser light L1, first observation light L2, and transmitted light L3 in any of the X, Y, and Z directions.
[0024] Here, the laser processing apparatus 1 includes a second light-gathering unit 27 and a third camera 29. The second light-gathering unit 27 and the third camera 29 are located on the opposite side of the head unit 20 via the table 10. The second light-gathering unit 27 includes a lens and receives the second observation light L4 emitted from a predetermined light source via the mirror M4 and focuses it toward the object 5. The third camera 29 receives the reflected light of the second observation light L4 irradiated onto the object 5 via the mirror M4 and takes an image. The second observation light L4 is, for example, visible light. In this case, the third camera 29 is sensitive to visible light and near-infrared light. Thus, the second light-gathering unit 27 and the third camera 29 are a third imaging unit that images the object 5 supported on the table 10 from the second surface 5b (the surface of the functional element layer 52) side with the second observation light L4 (acquires an image of the second surface 5b, which is the surface of the functional element layer 52).
[0025] The control unit 30 is configured as a computer device including a processor, memory, storage, and communication devices. In the control unit 30, the processor executes software (programs) loaded into memory, etc., and controls the reading and writing of data in memory and storage, as well as communication by the communication devices. The control unit 30 controls the operation of each part of the laser processing apparatus 1. The specific operation of the control unit 30 will be described later.
[0026] The input unit 31 receives input from the user and outputs the input to the control unit 30. The display unit 33 displays various types of information, such as information received by the input unit 31, information output from the control unit 30, or information recorded in the recording unit 35. The input unit 31 and the display unit 33 may be integrated and configured as a GUI (Graphical User Interface). The recording unit 35 records various types of information.
[0027] In the laser processing apparatus 1 described above, laser processing can be performed to form a weakened region J in the functional element layer 52 by irradiating the object 5 with laser light L1. Figure 2 is a schematic cross-sectional view illustrating the laser processing performed by the laser processing apparatus shown in Figure 1. As shown in Figure 2, in the laser processing apparatus 1, laser light L1 is irradiated from the first surface 5a side of the object 5, which is supported on the table 10 such that the first surface 5a faces the head unit 20 side. At this time, the focal point P (focusing position) of the laser light L1 is positioned in the vicinity of the interface B between the substrate 51 and the functional element layer 52 (in the illustrated example, inside the functional element layer 52) in the Z direction.
[0028] In other words, the laser beam L1 passes through the substrate 51 and is focused at the focusing position, and is used to process the object 5 at that focusing position. In this state, the table 10 and / or head unit 20 are driven along the X direction, causing the focusing point P of the laser beam L1 to move relative to the object 5 along the X direction. As a result, the laser beam L1 is irradiated onto the object 5 along line A along the X direction. Consequently, a weakened region J is formed in the functional element layer 52 along line A.
[0029] The weakened region J is a region in which the functional element layer 52 has been weakened. Weakening includes embrittlement. Weakening of the functional element layer 52 means that at least a portion of the functional element layer 52 (for example, a part of the functional element layer 52, and at least one of the multiple layers constituting the functional element layer 52) is affected by thermal damage such as melting and evaporation due to absorption of laser light L1, changes in chemical bonds due to laser irradiation, and the results of non-thermal processing such as cutting or ablation. Weakening of the functional element layer 52 means that, as a result, when stress such as bending stress or tensile stress is applied to the functional element layer 52, it is more prone to cutting or fracture compared to the untreated region (region that has not been weakened). The weakened region (embrittle region) J can also be described as a region where traces of laser irradiation have been made, and it is a region that is more prone to cutting or fracture compared to the untreated region. The weakened region J may be formed continuously in a linear manner in at least a portion of the functional element layer 52, or it may be formed intermittently according to the pulse pitch of the laser irradiation.
[0030] In other words, if the weakening region J is formed by the irradiation of pulsed laser light, and multiple weakening spots formed by the irradiation of one pulse of laser light are arranged in a row, then adjacent weakening spots may be continuously connected, intermittently connected, or separated and independent from each other. Furthermore, the weakening spots may be exposed on the surface (second surface 5b) of the functional element layer 52, and the exposed weakening spots may be continuously connected, intermittently connected, or separated and independent from each other.
[0031] Line A is set along the X direction so as to pass through the street region between the functional elements contained in the functional element layer 52 (in reality, multiple lines may be set in a grid pattern along the X and Y directions). Line A is the planned cutting line for cutting the object 5 for each functional element. Therefore, as described above, by forming a weakened region J in the functional element layer 52 (street region) along line A, it becomes possible to cut the object 5 accurately along line A with a relatively small external force.
[0032] In recent years, to address the miniaturization of device wiring, low-k films have been adopted as insulating films, and with the increase in the number of layered patterns due to 3D design, multiple layers of films, metal wiring, and metal films are sometimes stacked. As a result, forming a weakened region J as described above has become more effective. Accordingly, there is a need for a method to obtain suitable processing conditions for forming the weakened region J. Therefore, the laser processing apparatus 1 obtains suitable processing conditions for laser processing to form the weakened region J. The acquisition of these processing conditions will be explained below.
[0033] Figure 3 is a flowchart showing an example of a method for obtaining processing conditions performed by the laser processing apparatus shown in Figure 1. As shown in Figure 3, first, the energy of the laser beam L1 emitted from the first focusing unit 21 (objective lens) is set (step S1). As shown in Figure 4, the laser beam L1 emitted from the first focusing unit 21 is attenuated by reflection at the first surface 5a, which is the incident surface of the laser beam L1 on the object 5, and absorption at the substrate 51 before reaching the interface B between the substrate 51 and the functional element layer 52. Therefore, the energy E of the laser beam L1 emitted from the first focusing unit 21 is calculated using the formula "e = E × (1 - reflectance) × transmittance" to obtain the energy e of the laser beam L1 at interface B required to form a weakened region J in the functional element layer 52.
[0034] "Reflectance" refers to the reflectance of the first surface 5a of the laser beam L1, and is 31.9% as an example. Transmittance is the transmittance of the laser beam L1 to the substrate 51, and is calculated based on the relationship between the absorption coefficient α of the substrate 51 and the thickness t of the substrate 51, "Transmitted light amount = Incident light amount × exp(-αt)". Transmittance is 41.0% as an example. Therefore, if the energy e is 45 μJ, the above calculation formula becomes 45 μJ = E × (1 - 0.319) × (0.41), and the energy E is calculated to be approximately 160 μJ. In this step S1, the energy E of the laser beam L emitted from the first focusing unit 21 can be set at the light source by inputting the calculated value via the input unit 31. However, in this step S1, the control unit 30 may automatically calculate and set the energy E based on various conditions such as the thickness and structure of the object 5, or the type of laser processing.
[0035] Next, as shown in Figure 3, other parameters are set (step S2). Here, the pulse pitch and number of passes of the laser beam L1 are set. The number of passes is the number of times the laser beam L1 is irradiated onto a single line A while changing the focal position in the Z direction (or while maintaining the focal position in the Z direction) (number of scans). Here, as an example, the pulse pitch can be set to about 0.5 μm and the number of passes to 1 Pass. In this step S2, the settings can be made at the light source by receiving input of these parameters via the input unit 31. However, even in this step S2, the control unit 30 may automatically select and set these parameters based on various conditions such as the thickness and structure of the object 5 or the manner of laser processing.
[0036] Next, the defocus value is calculated when the focal position of the laser beam L in the Z direction is interface B (step S3). In step S3, as shown in Figure 5(a), the defocus value DB is the relative movement of the first focusing unit 21 (head unit 20) from the state where the focal position of the laser beam L (focal point P) is aligned with the first surface 5a to the focal position of the laser beam L being interface B. This value is calculated based on the thickness T5 of the substrate 51 and a coefficient based on the refractive index of the substrate 51. This coefficient is the ratio of the movement of the focal point P inside the substrate 51 to the movement of the focal point P outside the substrate 51, and in the case of the substrate 51 being silicon and this experimental system, it is approximately 4.11. The thickness T5 of the substrate 51 is, for example, approximately 730 μm. Thus, the defocus value DB is calculated as approximately 178 μm by dividing the thickness T5 by the coefficient. In step S3, the setting can be performed by inputting the value calculated in this way via the input unit 31. However, for this step S3 as well, the control unit 30 may automatically calculate and set the defocus value DB based on various conditions such as the thickness and structure of the object 5, or the type of laser processing.
[0037] Next, the burst count of the laser light L1 is set (step S4: steps 5, 6, and 7). More specifically, the laser light L1 is pulsed light as shown in Figure 6, and the number of bursts that make up each pulse (burst count) can be set. Figure 6(a) shows the case of 1 burst (i.e., no bursts) where the burst count is 1, and Figure 6(b) shows the case of 4 bursts where the burst count is 4. The pulse pitch is the same value set in step S2 (e.g., 0.5 μm) in both cases, and the period T (frequency interval) is about 5 μs, but the burst interval TP is, for example, 25 ns in the case of 4 bursts. Note that the examples of each value are for when the repetition frequency is 200 kHz.
[0038] In the case of 4 bursts, the light intensity is reduced to about 1 / 4 of that in the case of 1 burst. Therefore, changing the number of bursts changes whether or not damage occurs to the first surface 5a, which is the incident surface of the laser beam L1. For this reason, in step S4, the number of bursts is set so that no damage occurs to the first surface 5a.
[0039] To this end, in step S4, the control unit 30 first controls the first moving mechanism and / or the second moving mechanism and the laser irradiation unit to set the focusing position of the laser beam L1 in the Z direction to a predetermined position, and while changing the number of bursts of the laser beam L, it irradiates the object 5 with the laser beam L1 multiple times at different positions on the first surface 5a to perform laser processing (second processing) (fifth step). At this time, the focusing position of the laser beam L1 in the Z direction can be set to the position of interface B, for example, by using the defocus value DB set in step S3. In addition, the specific numerical value of the number of bursts for each second processing can be set to a value input via the input unit 31, for example.
[0040] Furthermore, in each second processing step, the laser beam L1 can be irradiated along one line A for each burst. In other words, in step S4, after irradiating one line A with the laser beam L1 for one burst, the focusing position of the laser beam L1 can be moved in the Y direction to a different line A, and the laser beam L1 can be irradiated along that other line A for a different burst. In this case, different positions within the first surface 5a mean different positions in the Y direction.
[0041] Subsequently, in step S4, the control unit 30 controls the first moving mechanism and / or the second moving mechanism and the first imaging unit to image the first surface 5a at each of the positions within the first surface 5a where the second processing has been performed multiple times, thereby acquiring a first surface image (sixth step). Here, for example, after imaging the first surface 5a with the first observation light L2 and the first camera 23 for one line A, the head unit 20 is moved relative to another line A, and the first surface 5a is imaged with the first observation light L2 and the first camera 23 for that other line A, thereby acquiring multiple first surface images.
[0042] Figure 7 shows multiple first-plane images. As shown in Figure 7, in the case of 4 bursts (4 bursts), 6 bursts (6 bursts), and 10 bursts (10 bursts), damage D occurs on the first plane 5a, and the first-plane images F1 to F3 contain images M of the damage D extending along the X direction. In contrast, in the case of 14 bursts (14 bursts), no damage D occurs on the first plane n5a, and the first-plane image F4 does not contain images M of the damage D. Note that the reticle image R is shown in each of the first-plane images F1 to F4 in Figure 7.
[0043] Thus, in step S4, the control unit 30 can associate the acquired multiple first surface images with the burst number corresponding to each first surface image and display them side by side on the display unit 33. At the same time, in step S4, the control unit 30 acquires the burst number of the second processing in which a first surface image in which no damage occurred to the first surface 5a was acquired (the smallest of these, which in this example is 14) as a condition for laser processing (step 7). Here, the control unit 30 may automatically acquire the burst number of the second processing corresponding to the first surface image that does not contain the image M of damage by image processing of the first surface image, or it may receive and acquire the burst number in which it is determined that no damage occurred to the first surface 5a based on the multiple first surface images displayed on the display unit 33.
[0044] Then, in step S4, the actual burst number during processing is set based on the acquired burst number (e.g., 14). Here, the acquired burst number itself may be set, or a burst number obtained by adding a predetermined margin to the acquired burst number (e.g., 16) may be set.
[0045] In the next step, the setting range for the focusing position of the laser beam L1 in the Z direction is acquired (step S5). More specifically, in step S5, as shown in Figure 8, the control unit 30 controls the first moving mechanism and / or the second moving mechanism and the laser irradiation unit to change the focusing position (focus point P) of the laser beam L1 in the Z direction within a range including the interface B, and performs multiple laser processing (first processing) at different positions within the first surface 5a (first step, first process).
[0046] Here, for example, after irradiating a laser beam L1 along one line A at one focusing position, the focusing position of the laser beam L1 can be moved in the Y direction to position it on another line A, and the laser beam L1 can then be irradiated along that other line A at the other focusing position. In this case, different positions within the first surface 5a mean different positions in the Y direction.
[0047] Furthermore, changing the focusing position within the range including interface B means that, as described above, a defocus value DB is obtained where the focusing position is interface B, and therefore the defocus value is changed before and after this defocus value DB. For example, if the defocus value DB is 178 μm, the first processing can be performed while changing the defocus value from 174 μm to 202 μm in a pitch of 2 μm. Specific numerical values such as the start and end values and pitch of these defocus values can be obtained, for example, by receiving input via the input unit 31.
[0048] Subsequently, in step S5, the control unit 30 controls the first moving mechanism and / or the second moving mechanism and the second imaging unit to capture an interface image of the interface B from the first surface 5a side using transmitted light L3 that passes through the substrate 51 at each of the positions on the first surface 5a where the first processing has been performed multiple times (second step, second processing). Here, for example, after capturing the interface B with transmitted light L3 and the second camera 25 for one line A, the head unit 20 is moved relative to another line A, and the interface B is captured with transmitted light L3 and the second camera 25 for that other line A, thereby acquiring multiple interface images.
[0049] Figure 9 shows multiple interface images. Figure 9 shows a selection of interface images D1 to D6 from among the multiple interface images acquired as described above. The defocus values corresponding to each of the interface images D1 to D6 are increased sequentially from interface image D1 to interface image D6. For example, interface image D1 corresponds to a defocus value of 178 μm, interface image D2 corresponds to a defocus value of 182 μm, interface image D3 corresponds to a defocus value of 186 μm, interface image D4 corresponds to a defocus value of 190 μm, interface image D5 corresponds to a defocus value of 194 μm, and interface image D6 corresponds to a defocus value of 198 μm. Here, among interface images D1 to D6, interface images D2 to D5 contain images N of damage caused by the laser beam L1.
[0050] Thus, depending on the focusing position (defocus value) of the laser beam L1, the interface image may or may not show an image N of damage caused by the laser beam L1. Furthermore, when the focusing position of the laser beam L1 is within the range in which the image N of damage appears in the interface image, a weakened region J that allows for high-quality cutting of the object 5 tends to be suitably formed. Here, as an example, it is considered that there exists a defocus value in the range of 182 μm to 194 μm corresponding to interface images D2 to D5 in which the weakened region J is suitably formed.
[0051] Based on these findings, in step S5, the control unit 30 then acquires, as a condition for laser processing, the range of the focusing position in the Z direction of the first processing in which interface images D2 to D6 containing the image N of damage from the laser beam L1 were acquired, as a condition for laser processing (third step). As an example, a range of defocus values (i.e., range of focusing position) of 182 μm to 194 μm corresponding to interface images D2 to D5 can be acquired. The control unit 30 may also automatically determine whether or not the image N of damage is included in a certain interface image by image processing of the interface images.
[0052] Alternatively, the control unit 30 may record each of the acquired interface images in the recording unit 35 in association with each of the corresponding focusing positions of the first processing (third process), and control the display unit 33 to display each of the interface images recorded in the recording unit 35 on the display unit 33 (fourth process). This allows the user to determine whether or not the image N of damage is included in a particular interface image based on the interface images displayed on the display unit 33.
[0053] Incidentally, the range of focal positions in which a weakened region J is suitably formed on the functional element layer 52 is more easily obtained on the functional element layer 52 side than on the interface B between the substrate 51 and the functional element layer 52. In the above example, the defocus value DB at which the focal position is at interface B was 178 μm, and by changing the defocus value in the range of 174 μm to 202 μm, interface images D2 to D6 containing the damage image N were obtained in the range of 182 μm to 194 μm.
[0054] Thus, in step S5, the range of the Z-direction position (defocus value) for changing the focusing position can include a first range located on the first surface 5a side of interface B (for example, a defocus value range of 174 μm to 178 μm) and a second range located on the second surface 5b side of interface B and wider than the first range (for example, a defocus value range of 178 μm to 202 μm).
[0055] In the next step, a more suitable focal point value is determined from the range of focal points obtained in step S5 (step S6). To this end, in step S6, first, the object 5, which in step S5 underwent the first processing to form weakened regions J at multiple focal points, is cut along each of the weakened regions J (fourth step). The weakened regions J are formed along each of the multiple lines A along the X direction. Therefore, here, the object 5 is cut along each of the multiple lines A along the X direction.
[0056] As a method for cutting the object 5, a laser beam may be irradiated onto the object 5 along each of the lines A to form a modified region and cracks extending from the modified region inside the object 5, and cutting may be performed starting from the modified region and cracks (laser dicing).
[0057] Subsequently, in step S6, the surface (second surface 5b) of the functional element layer 52 of the cut object 5 is imaged (fourth step). Based on the obtained image, the cutting quality corresponding to the first processing at each focusing position can be evaluated to determine a more suitable focusing position. When imaging the second surface 5b, the third imaging unit, which consists of the second focusing unit 27 and the third camera 29, may be used, or another imaging device may be used. Through the above, suitable processing conditions for the formation of the weakened region J are obtained.
[0058] As described above, in the processing condition acquisition method according to this embodiment, laser processing conditions for forming a weakened region J on the functional element layer 52 on the second surface 51b side of the substrate 51 are acquired by irradiating the substrate 51 of the object 5 with laser light L1 from the first surface 5a side. To this end, multiple laser processing (first processing) is performed while changing the focusing position of the laser light L1 in the Z direction within a range that includes the interface B between the substrate 51 and the functional element layer 52. Furthermore, at each of the positions where multiple laser processing is performed, the interface B between the substrate 51 and the functional element layer 52 is imaged to acquire an interface image. Then, the range of the focusing position of the laser light L1 from which an interface image containing the image N of damage from the laser light L1 is acquired is acquired as one of the conditions for laser processing. In this way, this method makes it possible to acquire suitable processing conditions (a range of focusing positions, which in the above example is a range of defocus values) for forming the weakened region J.
[0059] Furthermore, in the processing condition acquisition method according to this embodiment, the range of positions in the Z direction for changing the focusing position in step S5 includes a first range located on the side of the first surface 5a beyond the interface B, and a second range located on the opposite side of the first surface 5a (towards the second surface 5b) beyond the interface B, and which is wider than the first range. By thus extending the range for changing the focusing position to the functional element layer 52 side beyond the interface B, it becomes possible to acquire the range more quickly and reliably.
[0060] Furthermore, in the processing condition acquisition method according to this embodiment, in step S6, the object 5 is cut and the surface of the functional element layer 52 of the cut object 5 is imaged. In step S5, laser light L1 is irradiated along the X direction (line A) along the first surface 5a, and in step S6, the object 5 is cut along the X direction. In this way, by actually cutting the object 5 and imaged on the surface of the functional element layer 52, it becomes possible to determine a more suitable focusing position by evaluating the cutting quality.
[0061] Furthermore, in the processing condition acquisition method according to this embodiment, in step S4, the second processing is performed as multiple laser processing steps at different positions within the first surface 5a while changing the burst number of the pulsed laser light L1. Also in step S4, the first surface 5a is imaged at each of the positions (line A) within the first surface 5a where the multiple second processing steps have been performed, and a first surface image is acquired. Then, the burst number of the second processing step in which a first surface image without damage to the first surface 5a was acquired is acquired as another condition for laser processing. As a result, suitable processing conditions (burst number) that can form a weakened region J without damaging the first surface 5a, which is the incident surface of the laser light L1, can be acquired.
[0062] In this embodiment, the laser processing apparatus 1 obtains the conditions for laser processing to form a weakened region J on the functional element layer 52 on the second surface 51b side of the substrate 51 by irradiating the substrate 51 of the object 5 with laser light L1 from the first surface 5a side. To this end, a first processing step is performed, which is multiple laser processing steps, while changing the focusing position of the laser light L1 in the Z direction within a range that includes the interface B between the substrate 51 and the functional element layer 52. Furthermore, at each of the positions (line A) where the multiple first processing steps are performed, the interface B between the substrate 51 and the functional element layer 52 is imaged to obtain an interface image. The laser processing apparatus 1 then records each of the multiple interface images in the recording unit 35, associating each of the corresponding focusing positions. By referring to this record, it becomes possible to obtain the range of focusing positions in which an interface image containing the image N of damage from the laser light L1 was acquired as one of the conditions for laser processing. In this way, the laser processing apparatus 1 makes it possible to obtain suitable processing conditions (range of focusing positions) for forming a weakened region J.
[0063] Furthermore, the laser processing apparatus 1 according to this embodiment includes a display unit 33 that displays images captured by a second imaging unit (second camera 25), and the control unit 30 may control the display unit 33 to display each of the interface images recorded in the recording unit 35 on the display unit 33. In this case, based on the interface images displayed on the display unit 33, it becomes possible to easily grasp the range of the focusing position in which an interface image containing the image N of damage from the laser beam L was acquired among the multiple interface images.
[0064] The embodiments described above illustrate one aspect of the present disclosure. Therefore, the present disclosure is not limited to the above aspects and can be modified as appropriate.
[0065] Figure 10 is a schematic diagram showing the general configuration of a modified head unit. The head unit 20A shown in Figure 10 differs from the head unit 20 in that the optical axes of the laser beam L1 and the first observation beam L2 and the optical axis of the transmitted beam L3 are on separate axes. Therefore, in addition to the first focusing unit 21 that focuses the laser beam L1 and the first observation beam L2 toward the object 5, this head unit 20A further has a third focusing unit 22 that focuses the transmitted beam L3 toward the object 5. Thus, it is possible to arbitrarily select whether the laser beam L1, the first observation beam L2, and the transmitted beam L3 are on the same axis or on separate axes.
[0066] Furthermore, the laser processing apparatus 1 shown in Figure 1 was an example in which a transparent table 10 that is transparent to a second observation light L4 such as visible light and near-infrared light may be used. However, the use of a transparent table 10 is not essential for the laser processing apparatus 1. When the object 5 is supported by an opaque table (for example, a normal porous table), the third imaging unit, which consists of a second light-gathering unit 27 and a third camera 29, can be positioned on the same side as the head unit 20 with respect to the table. In this case, when imaging the functional element layer 52 of the object 5 with the third imaging unit, the object 5 should be repositioned so that the functional element layer 52 faces the third imaging unit.
[0067] Furthermore, in the above example, we described an example in which, in step S4 for obtaining the burst number and step S5 for obtaining the range of the focusing position, processing is performed along one line A for one burst number and one focusing position. However, processing may be performed at two or more burst numbers and two or more focusing positions at different positions on one line A. This is because it is considered sufficient to perform processing of a length of about 15 mm to determine the presence or absence of damage images M and N when evaluating a suitable burst number and focusing position.
[0068] Furthermore, after the laser processing described above, in which a laser beam L1 is incident on the object 5 from the first surface 5a side to form a weakened region J on the functional element layer 52 side, a third processing step may be performed in which a modified region and cracks extending from the modified region are formed on the substrate 51 by irradiation with laser light, and a fourth processing step may be performed in which the substrate 51 is ground from the first surface 5a side to thin it to a desired thickness. In the third processing step, while the laser beam is incident on the object 5 from the first surface 5a side, the focusing position of the laser beam is moved relative to the line A, and a modified region is formed inside the substrate 51 at the focusing position, as well as cracks extending in the Z direction from the modified region. [Explanation of symbols]
[0069] 1...Laser processing device, 5...Object, 5a...First surface, 10...Table (support part), 20...Head part (laser irradiation part, imaging part), 30...Control unit, 33...Display unit, 35...Recording unit, 51...Substrate, 51b...Second surface, 52...Functional element layer, L1...Laser light, L3...Transmitted light, J...Weakening region.
Claims
1. A method for obtaining processing conditions for laser processing to form a weakened region in a functional element layer by irradiating an object having a substrate including a first surface and a second surface opposite to the first surface, and a functional element layer provided on the second surface of the substrate, from the first surface side, A first step is to perform the first laser processing multiple times at different positions within the first surface, while changing the focusing position of the laser beam in the Z direction intersecting the first surface within a range including the interface between the substrate and the functional element layer, A second step involves acquiring an interface image by capturing the interface between the substrate and the functional element layer from the first surface side using transmitted light passing through the substrate at each of the positions within the first surface where the first processing has been performed multiple times, A third step involves obtaining, as one of the conditions for the laser processing, the range of the focusing position in the Z direction of the first processing in which the interface image containing the damage of the laser beam was obtained from among the plurality of interface images obtained in the second step, Equipped with, How to obtain processing conditions.
2. The range of positions in the Z direction for changing the focusing position in the first step includes a first range located on the first surface side of the interface, and a second range located on the opposite side of the first surface from the interface and wider than the first range. A method for obtaining processing conditions as described in claim 1.
3. The process includes a fourth step, after the first, second, and third steps, in which the object is cut and the surface of the functional element layer of the cut object is imaged. In the first step, the laser light is irradiated along the X direction along the first surface, In the fourth step, the object is cut along the X direction. A method for obtaining processing conditions according to claim 1 or 2.
4. A fifth step involves performing a second laser processing operation multiple times at different positions within the first surface while varying the number of bursts of the pulsed laser light, A sixth step involves capturing an image of the first surface at each of the positions within the first surface where the second processing has been performed multiple times, thereby acquiring a first surface image. A seventh step involves obtaining the number of bursts in the second processing in which a first surface image without damage to the first surface was obtained from among the multiple first surface images obtained in the sixth step, as another condition for the laser processing. Equipped with, A method for obtaining processing conditions according to any one of claims 1 to 3.
5. A laser processing apparatus for obtaining laser processing conditions for forming a weakened region in a functional element layer by irradiating an object having a substrate including a first surface and a second surface opposite to the first surface, and a functional element layer provided on the second surface of the substrate, from the first surface side, A support portion that supports the aforementioned object, A laser irradiation unit that irradiates the object supported by the support unit with the laser light from the first surface side, An imaging unit that images the object supported by the support portion from the first surface side using transmitted light that passes through the substrate, A control unit that controls the laser irradiation unit and the imaging unit, Equipped with, The control unit, A first process is performed in which the laser irradiation unit is controlled to change the focusing position of the laser beam in the Z direction intersecting the first surface within a range including the interface between the substrate and the functional element layer, and the first processing as laser processing is performed multiple times at different positions within the first surface. A second process is performed in which, by controlling the imaging unit, at each of the positions within the first surface where the first processing has been performed multiple times, the interface between the substrate and the functional element layer is imaged from the first surface side using transmitted light to acquire an interface image, A third process for recording each of the multiple interface images obtained in the second process in association with each of the corresponding focusing positions of the first process, Execute Laser processing equipment.
6. The imaging unit includes a display unit that displays the image captured by the imaging unit, The control unit controls the display unit to perform a fourth process, which causes each of the interface images recorded in the third process to be displayed on the display unit. The laser processing apparatus according to claim 5.