Laser cutting method, laser cutting device and chip

Abstract

The invention provides a laser cutting method, a laser cutting device and a chip, and relates to the technical field of semiconductors. The method is used for solving the problems of material layering, cracks and other defects in the cutting process of the semiconductor device. The laser cutting method comprises the steps that a wafer is provided, and cutting lines are arranged on the surface of the wafer; and the laser beams bend and move in the extending direction of the cutting line so as to cut the wafer. According to the laser cutting method, the risks of material layering and cracks of the chip can be reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor technology, and in particular to a laser cutting method, a laser cutting device and a chip. BACKGROUND

[0002] In the manufacturing process of semiconductor devices, there is a cutting process step, for example, laser cutting. Due to the different manufacturing materials of semiconductor devices, defects such as material delamination and cracks may occur during cutting, affecting the yield of products. SUMMARY

[0003] Embodiments of the present application provide a laser cutting method, a laser cutting device and a chip, which are used to solve the problem that defects such as material delamination and cracks may occur in the cutting process of semiconductor devices.

[0004] To achieve the above-mentioned purpose, embodiments of the present application adopt the following technical solutions:

[0005] In a first aspect, a laser cutting method is provided, which includes providing a wafer, the surface of the wafer having a cutting line. A laser beam is bent and moved along the extension direction of the cutting line to cut the wafer.

[0006] The laser cutting method provided by the first aspect of the present application can increase the diameter size of the keyhole formed during laser cutting, that is, it is beneficial to increase the width of the cutting groove formed on the wafer, thereby reducing the probability of blockage caused by the collapse of the keyhole, and improving the quality of laser cutting.

[0007] In a possible implementation manner of the first aspect of the present application, the amplitude of the bending movement of the laser beam is greater than or equal to 1 μm and less than or equal to 10 μm, and the frequency of the laser beam is greater than or equal to 10 Hz and less than or equal to 100 Hz. Within this parameter range, the keyhole can be stabilized to stabilize the flow of molten material in the molten pool, thereby improving the cutting quality.

[0008] In a possible implementation manner of the first aspect of the present application, the amplitude of the bending movement of the laser beam is greater than or equal to 2 μm and less than or equal to 5 μm, and the frequency of the laser beam is greater than or equal to 10 Hz and less than or equal to 50 Hz. Within this range, the cutting quality can be further improved.

[0009] In a possible implementation manner of the first aspect of the present application, the method of bending and moving the laser beam along the extension direction of the cutting line includes periodically bending and moving the laser beam along the extension direction of the cutting line. In this way, the periodic bending and movement of the laser beam, that is, the repeated movement of the laser beam according to a certain rule, can improve the cutting quality while reducing the control difficulty.

[0010] In a possible implementation of the first aspect of the present application, the movement track of the periodic bending movement comprises a plurality of track lines, two adjacent track lines are connected end to end, and at least one intersection exists between the two adjacent track lines. In this way, part of the movement track of the laser beam can move in the opposite direction of the extension direction of the cutting line, that is, the partial area can be heated twice, thereby facilitating further improvement of the cutting quality.

[0011] In a possible implementation of the first aspect of the present application, part of the line segment of the two adjacent track lines coincides with each other. In this structure, the track can be cut at least twice, thereby increasing the heating area and facilitating further improvement of the cutting quality.

[0012] In a possible implementation of the first aspect of the present application, the track line comprises a first arc segment and a second arc segment, the first arc segment and the second arc segment are located on two sides of the cutting line respectively, the end point of the first arc segment is connected to the start point of the second arc segment, and the end point of the second arc segment is connected to the start point of the first arc segment of another adjacent track line. In this way, the movement track of the laser beam forms a track similar to a spiral line, thereby repeatedly moving on both sides of the cutting line on the wafer, increasing the width of the cutting groove, and improving the cutting quality.

[0013] In a possible implementation of the first aspect of the present application, the second arc segments of the two adjacent track lines intersect. That is, when the laser beam starts to move from the start point of a track line, it first moves a certain distance in the direction of the previous track line, and then moves in the extension direction of the cutting line, thereby heating the partial area twice.

[0014] In a possible implementation of the first aspect of the present application, the track line comprises a plurality of ring segments, and at least one intersection exists between two adjacent ring segments. In this structure, the track line can form a structure similar to an "8" character, and when the laser beam moves, the partial area can be heated repeatedly, thereby facilitating further reduction of the risk of collapse blockage of the keyhole.

[0015] In a possible implementation of the first aspect of the present application, the shape of the ring segment is circular or elliptical.

[0016] In a possible implementation of the first aspect of the present application, the track line comprises a first straight line segment and a second straight line segment, the end point of the first straight line segment is connected to the start point of the second straight line segment, and the start point of the second straight line segment is connected to the start point of the first straight line segment of another adjacent track line. In this structure, the track line forms an extension structure similar to a sawtooth, and the laser beam can move along the plurality of straight line segments to form the track line, thereby facilitating reduction of the control difficulty.

[0017] In one possible implementation of the first aspect of this application, both the first and second straight line segments intersect the cutting line. That is, the laser beam moves repeatedly on both sides of the cutting line, thereby increasing the width of the cutting groove.

[0018] In one possible implementation of the first aspect of this application, the included angle between the first straight line segment and the second straight line segment is an acute angle. This structure increases the number of trajectory lines per unit length of the cutting line, thereby increasing the density of laser cutting and improving cutting quality.

[0019] In one possible implementation of the first aspect of this application, the trajectory line includes multiple third straight line segments and multiple fourth straight line segments, which are alternately distributed and connected end-to-end. The third straight line segments intersect the cutting line, and two adjacent fourth straight line segments are located on either side of the cutting line. This structure is advantageous for increasing the length of the laser beam's trajectory, thereby increasing the area covered by the cutting trajectory and improving the cutting quality.

[0020] In one possible implementation of the first aspect of this application, the third straight segment is perpendicular to the cutting line. This structure reduces the number of directions of laser motion, which helps to simplify control.

[0021] In one possible implementation of the first aspect of this application, the fourth straight line segment is parallel to the cutting line. This structure reduces the number of directions of laser motion, which helps to simplify control.

[0022] In a second aspect, a laser cutting device is provided for cutting a device to be cut, the device having a cutting line. The laser cutting device includes a controller, a drive mechanism, and a laser emitter. The controller is electrically connected to the drive mechanism, and the controller controls the drive mechanism to drive the laser emitter to move along a motion trajectory, the motion trajectory bending and extending along the extension direction of the cutting line.

[0023] In addition, the laser cutting device may also include components such as a frame and a reflector. The frame is used to support or fix the aforementioned orifice, drive mechanism, and laser emitter. The reflector can control the propagation path of the laser, thereby increasing the overall structural reliability.

[0024] Thirdly, a chip is provided in which the edges are bent and extended.

[0025] The chip provided in the third aspect of this application is obtained by laser cutting along the aforementioned bending and extending motion trajectory. This reduces the risk of material delamination and cracks in the chip, while also improving the chip's fracture strength.

[0026] In one possible implementation of the third aspect of this application, the chip material includes a low dielectric constant material.

[0027] In one possible implementation of the third aspect of this application, multiple grooves are formed along the edge of the chip, and these grooves are distributed sequentially along the edge of the chip. That is, the laser beam bends along the extension direction of the cutting line, so that the edge of the chip forms a structure that matches the trajectory of the laser beam.

[0028] In one possible implementation of the third aspect of this application, the groove is an arc-shaped structure in a plane parallel to the chip surface.

[0029] In one possible implementation of the third aspect of this application, the groove is a triangular structure in a plane parallel to the chip surface.

[0030] In one possible implementation of the third aspect of this application, the groove is a rectangular structure in a plane parallel to the chip surface. Attached Figure Description

[0031] Figure 1 A structural diagram of a chip provided in an embodiment of this application;

[0032] Figure 2 This is a structural diagram of a wafer provided in an embodiment of this application;

[0033] Figure 3 for Figure 2 The provided cross-sectional simulation image of the wafer during the dicing process;

[0034] Figure 4 A cross-sectional view of a chip provided in an embodiment of this application;

[0035] Figure 5 A cross-sectional view of another chip provided in an embodiment of this application;

[0036] Figure 6 A cross-sectional view of another chip provided in an embodiment of this application;

[0037] Figure 7 A schematic diagram of the cross-sectional structure of a wafer during the laser cutting process provided in this application embodiment;

[0038] Figure 8 A schematic diagram of a motion trajectory for laser cutting provided in an embodiment of this application;

[0039] Figure 9 A simulation diagram of the laser's point of action at different times during the laser's linear motion, provided as an embodiment of this application.

[0040] Figure 10 A simulation diagram of the temperature gradient at different times during the linear motion of a laser, provided as an embodiment of this application.

[0041] Figure 11A schematic diagram of another motion trajectory for laser cutting provided in an embodiment of this application;

[0042] Figure 12 The laser edge provided in the embodiments of this application Figure 11 The diagram shows a simulation of the temperature gradient at different times during the motion trajectory shown.

[0043] Figure 13 Simulation curves of keyhole depth formed under different amplitudes when a laser beam moving along a bending trajectory cuts a wafer, as provided in the embodiments of this application;

[0044] Figure 14 Simulation curves of keyhole depth formed at different frequencies when a laser beam moving along a bending trajectory cuts a wafer, as provided in the embodiments of this application;

[0045] Figure 15 Simulation curves of the keyhole radius formed by a laser beam moving along a bending trajectory cutting a wafer under different amplitudes, provided in the embodiments of this application;

[0046] Figure 16 Simulation curves of the keyhole radius formed at different frequencies when a laser beam moving along a bending trajectory cuts a wafer, as provided in the embodiments of this application.

[0047] Figure 17 A bar chart showing the test results of temperature gradients at different amplitudes when a laser beam moving along a bending trajectory cuts a wafer, as provided in the embodiments of this application.

[0048] Figure 18 A bar chart showing the test results of temperature gradient at different frequencies when a laser beam moving along a bending trajectory cuts a wafer, as provided in the embodiments of this application.

[0049] Figure 19 The test structure diagram of the flow rate in the molten pool at different amplitudes when a laser beam moving along a bending trajectory cuts a wafer, as provided in the embodiments of this application;

[0050] Figure 20 The test structure diagram of the flow velocity in the molten pool at different frequencies when a laser beam moving along a bending trajectory cuts a wafer, as provided in the embodiments of this application;

[0051] Figure 21 A velocity curve of a laser beam moving along a bending trajectory cutting at different amplitudes, provided in an embodiment of this application;

[0052] Figure 22 A velocity curve of a laser beam moving along a bending trajectory cutting at different frequencies, provided in an embodiment of this application;

[0053] Figure 23A schematic diagram showing the test results of the stirring Reynolds number at different frequencies and amplitudes when a laser beam moves along a bending trajectory to cut a wafer, as provided in the embodiments of this application.

[0054] Figure 24 This is a structural diagram of another chip provided in an embodiment of this application;

[0055] Figure 25 A schematic diagram of another trajectory line provided in an embodiment of this application;

[0056] Figure 26 A schematic diagram of yet another trajectory line provided in the embodiments of this application;

[0057] Figure 27 For along Figure 26 The structural diagram of the chip formed after cutting the provided trajectory lines;

[0058] Figure 28 A schematic diagram of another trajectory line provided in the embodiments of this application;

[0059] Figure 29 For along Figure 28 The structural diagram of the chip formed after cutting the provided trajectory lines;

[0060] Figure 30 This is a structural diagram of a laser cutting device provided in an embodiment of this application.

[0061] Reference numerals: 100-Wafer; 110-Cutting line; 200-Chip; 210-Groove; 300-Laser cutting device; 310-Rack; 320-Laser emitter; 330-Controller; 340-Nozzle; 350-Support surface; 360-Drive mechanism; 400-Trajectory line; 410-First arc segment; 411-First sub-segment; 412-Second sub-segment; 420-Second arc segment; 421-Third sub-segment; 422-Fourth sub-segment; 430-Annular segment; 440-First straight segment; 450-Second straight segment; 460-Third straight segment; 470-Fourth straight segment. Detailed Implementation

[0062] The technical solutions of the embodiments of this application will be described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0063] Hereinafter, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature.

[0064] Furthermore, in this application, directional terms such as "upper" and "lower" are defined relative to the orientation of the components shown in the accompanying drawings. It should be understood that these directional terms are relative concepts, used for relative description and clarification, and can change accordingly depending on the orientation of the components in the accompanying drawings.

[0065] In this application, unless otherwise expressly specified and limited, the term "connection" shall be interpreted broadly. For example, "connection" may be a fixed connection, a detachable connection, or an integral part; it may be a direct connection or an indirect connection through an intermediate medium.

[0066] Please see Figure 1 , Figure 1 This is a structural diagram of a chip 200 provided in an embodiment of this application. The chip 200 can realize functions such as control, data processing, and storage. Figure 1 The circles shown can represent solder joints or solder balls on chip 200. For example, chip 200 can be a control chip 200 (e.g., a system-on-chip, SOC), a graphics processing unit (GPU), or other types of chip 200.

[0067] The aforementioned chip 200 can be applied to electronic devices, such as mobile phones, tablet computers, laptop computers, personal digital assistants (PDAs), monitors, cameras, personal computers, laptops, wearable devices, etc.

[0068] In the manufacturing process of chip 200, it can be formed by dicing wafer 100. Please refer to [link / reference]. Figure 2 and Figure 3 , Figure 2 This is a structural diagram of the wafer 100 provided in an embodiment of this application. Figure 3 for Figure 2 The provided cross-sectional simulation diagram of the wafer 100 during the dicing process, wherein the chip 200 obtained after dicing the wafer 100 can also be referred to as a die. In some embodiments, the chip 200 formed by dicing the wafer 100 can also undergo a packaging process. Therefore, the embodiments of this application do not impose special limitations on this, and in the following embodiments, the chip 200 without the packaging process is used as an example for description.

[0069] Conductive circuits are formed on wafer 100 by process methods (e.g., chemical vapor deposition, grinding, etching, etc.), and then the chip 200 is formed by dicing process, and the chip 200 has integrated circuits.

[0070] To reduce leakage current in integrated circuits, reduce capacitance between wires forming integrated circuits, and reduce heat generation in integrated circuits, the aforementioned chip 200 can be made of a low-dielectric-constant material (also known as low-K material). That is, the aforementioned wafer 100 is fabricated using a low-dielectric-constant material, and then the chip 200 is formed through a dicing process.

[0071] Because low dielectric constant materials are inherently brittle, laser cutting is generally used to cut wafer 100. Therefore, please continue reading... Figure 2 and Figure 3 During the process of cutting the wafer 100 with a laser, the laser beam moves along the cutting line 110 (i.e., the cutting path) on the wafer 100, that is, the laser beam moves in a straight line, thereby completing the cutting of the wafer 100 to form the chip 200.

[0072] However, during laser cutting, the laser beam has high energy, resulting in significant energy penetration into the wafer 100 and high heat in the cutting area. Since the coefficients of thermal expansion of the low-dielectric-constant material are different from those of adjacent materials, the stress caused by thermal expansion differs between the low-dielectric-constant material and its neighbors under the influence of heat. Consequently, defects such as delamination and cracks exist between the low-dielectric-constant material and its neighbors in the chip 200 formed after laser cutting, affecting the yield rate of the chip 200.

[0073] Please see Figure 4 , Figure 5 and Figure 6 , Figure 4 This is a cross-sectional view of a chip 200 provided in an embodiment of this application. Figure 5 A cross-sectional view of another chip 200 provided in an embodiment of this application. Figure 6 This is a cross-sectional view of another chip 200 provided in an embodiment of this application. Wherein, Figure 4-6 The area indicated by the square box represents the region where chip 200 exhibits delamination and cracks.

[0074] In related technologies, reducing laser energy is generally used to decrease the energy injected into the wafer 100, thereby reducing the stress difference between the dielectric constant material and adjacent materials, which can lead to delamination and cracking. However, reducing laser energy may result in the cutting depth not meeting the cutting requirements. Therefore, this method does not improve the cutting quality of the wafer 100.

[0075] Based on this, research has found that, please refer toFigure 7 , Figure 7 This is a schematic diagram of the cross-sectional structure of the wafer 100 provided in the embodiments of this application during the laser cutting process. Figure 7 The triangle in the image represents a laser beam. Laser cutting refers to using a high-power-density laser beam to irradiate the material to be cut (i.e., wafer 100), heating the material to its vaporization temperature and causing it to evaporate, forming a hole (also known as a keyhole). Figure 7 As shown in region A), as the laser beam moves relative to the material being cut, a very narrow kerf (also known as a cutting groove) is continuously formed in the hole. Figure 7 (not shown in the image), thus completing the cutting.

[0076] During laser cutting, the material around the keyhole formed by the laser beam on the wafer 100 is in a molten state; the area where the molten material is located is called the molten pool. Figure 7 (As shown in region B). Figure 7 Region C is the vaporization zone, also known as the cutting zone. Within this molten pool, forces such as recoil pressure, surface tension, and buoyancy exist, resulting in complex forces acting on the molten material and causing it to continuously flow within the pool.

[0077] When the flow of molten material in the molten pool is unstable, it may cause collapse within the keyhole. This means that solid material from the surrounding area enters the keyhole, causing blockage and preventing the laser from completely cutting the wafer, resulting in lower cutting quality. Conversely, the more stable the flow of molten material in the molten pool, the lower the probability of collapse within the keyhole, and the better the laser cutting quality.

[0078] Specifically, the lower the flow velocity of the molten material within the molten pool, the more stable the flow of the molten material within the molten pool. Furthermore, the lower the temperature gradient around the cutting groove, the more stable the flow of the molten material within the molten pool.

[0079] Based on this, this application provides a laser cutting method that causes a laser beam to bend along the extension direction of the cutting line 110 on the wafer 100 to cut the wafer 100. Specifically, the laser beam bends along the extension direction of the cutting line 110 in the regions on both sides of the cutting line 110, resulting in a curved trajectory for the laser beam. Please refer to [link to relevant documentation]. Figure 8 , Figure 8 This is a schematic diagram of a motion trajectory for laser cutting provided in an embodiment of this application.

[0080] In some embodiments, the laser beam can undergo periodic bending motion along the extension direction of the cutting line 110. The trajectory of the laser beam can include multiple trajectory lines 400, with adjacent trajectory lines 400 connected end-to-end. Furthermore, adjacent trajectory lines 400 can have at least one intersection point.

[0081] This increases the width of the dicing groove formed by the laser beam on the surface of wafer 100 (i.e., Figure 8 The width of the trajectory line 400 along the direction perpendicular to the cutting line 110, thus making Figure 7 The radial dimension of the keyhole is increased, that is, the width of the keyhole is increased, which reduces the probability of keyhole blockage when it collapses, thereby improving the quality of laser cutting.

[0082] Furthermore, since there can be at least one intersection between two adjacent trajectories on the trajectory of the laser beam, the laser beam can move a certain distance in the opposite direction of the extension direction of the cutting line 110, so that a part of the cutting groove on the wafer 100 can be heated a second time, which helps to further reduce the probability of blockage caused by collapse in the keyhole and further improve the quality of laser cutting.

[0083] For example, please continue reading Figure 8 The aforementioned trajectory line 400 may include a first arc segment 410 and a second arc segment 420. The first arc segment 410 and the second arc segment 420 are located on both sides of the cutting line 110, respectively. The end of the first arc segment 410 is connected to the starting point of the second arc segment 420, and the end of the second arc segment 420 is connected to the starting point of the first arc segment 410 of the next trajectory line 400. The laser beam moves in a cyclical manner along multiple trajectory lines 400 in sequence.

[0084] Furthermore, the second arc segments 420 of two adjacent trajectory lines 400 intersect, that is, there is an intersection point between them, so that after the laser beam moves to the end point along the second arc segment 420 of one trajectory line 400, it moves a certain distance in the opposite direction along the first arc segment 410 of the next trajectory line 400, thereby enabling secondary heating of a part of the cutting groove to improve the cutting quality.

[0085] Based on this, the following simulation tests are conducted on the process of cutting with a laser beam moving in a straight line (i.e., along the cutting line 110 on the wafer 100) and the process of cutting with a laser beam moving along the aforementioned bent trajectory.

[0086] Please see Figure 9 and Figure 10 , Figure 9 This is a simulation diagram showing the laser's point of application at different times during the laser's linear motion, as provided in an embodiment of this application.Figure 10 This is a simulation diagram illustrating the temperature gradient at different times during the linear motion of a laser, as provided in an embodiment of this application. Figure 9 and Figure 10 Figures (a), (b), (c), (d), (e), and (f) in the figure represent six moments in the laser cutting process.

[0087] Depend on Figure 9 and Figure 10 It can be seen that the laser beam moves along a straight line (i.e., Figure 8 During the cutting process (the direction of the cutting line 110) in the middle, at 1.003 seconds... Figure 9 and Figure 10 As shown in Figure (c), the first keyhole collapse occurred at 1.004 seconds. Figure 9 and Figure 10 As shown in Figure (d), the keyhole was reopened, meaning the collapse occurred in a short time. During the cutting process, the frequency of collapses was relatively high.

[0088] Please see Figure 11 and Figure 12 , Figure 11 This is a schematic diagram of another motion trajectory for laser cutting provided in an embodiment of this application. Figure 12 The laser edge provided in the embodiments of this application Figure 11 The diagram shows a simulation of the temperature gradient at different times during the motion trajectory.

[0089] In this example, the first arc segment 410 of the aforementioned trajectory line 400 may include a first sub-segment 411 and a second sub-segment 412, and the second arc segment 420 may include a third sub-segment 421 and a fourth sub-segment 422. The endpoint of the first sub-segment 411 is connected to the starting point of the second sub-segment 412, the endpoint of the second sub-segment 412 is connected to the starting point of the third sub-segment 421, the endpoint of the third sub-segment 421 is connected to the starting point of the fourth sub-segment 422, and the endpoint of the fourth sub-segment 422 is connected to the starting point of the first sub-segment 411 of an adjacent trajectory line 400.

[0090] Among them, the first sub-segment 411 corresponds to Figure 12 The first row of the simulation diagram corresponds to the second sub-segment 412. Figure 12 The second row of the simulation diagram corresponds to the third sub-segment 421. Figure 12 The third row of the simulation diagram corresponds to the fourth sub-segment 422. Figure 12 The fourth row is a simulation diagram.

[0091] Depend on Figure 12 It can be seen that during the process of the laser beam cutting wafer 100 along the bent trajectory, the first collapse occurred after 0.0175 seconds.Figure 12 As shown in the third image of the second row (in the middle), a second collapse occurred after 0.02 seconds. Figure 12 (As shown in the first image of the fourth row).

[0092] Therefore, it can be seen that cutting along a curved trajectory with a laser beam results in fewer collapses and a lower frequency of collapses compared to cutting along a straight trajectory. Thus, a laser beam moving along a curved trajectory is beneficial for improving the cutting quality of wafer 100.

[0093] Furthermore, by Figure 12 It can be seen that when the laser beam moves along the curved trajectory, the width of the keyhole increases significantly (compared to...). Figure 9 and Figure 10 (as shown in the keyhole diagram), thereby reducing the risk of keyhole blockage due to collapse, and further improving the cutting quality of wafer 100.

[0094] Based on this, different parameters were tested on the cutting process of the laser beam moving along the bending trajectory. For example, the keyhole depth and keyhole diameter (i.e., keyhole width) formed when the laser beam cuts wafer 100 at different amplitudes and frequencies could be tested.

[0095] Please see Figure 13 , Figure 13 The simulation curves of the keyhole depth formed by a laser beam moving along a bending trajectory cutting a wafer 100 at different amplitudes are provided in the embodiments of this application. Figure 13 Figure (b) is Figure 13 A magnified view of (a) over a period of time. From Figure 13 It can be seen that when the laser amplitude is 0, there are more peaks on the curve. As the amplitude gradually increases, that is, when the amplitude is 1μm, 3μm and 5μm, the peaks on the corresponding curves decrease.

[0096] Please see Figure 14 , Figure 14 The simulation curves of the keyhole depth formed at different frequencies when a laser beam moving along a bending trajectory cuts a wafer 100, provided in the embodiments of this application, are shown. Figure 14 Figure (b) is Figure 14 The image (a) is an enlarged view of a period of time. As can be seen from the figure, when the laser frequency is 0, there are more peaks on the curve. As the amplitude gradually increases, that is, when the amplitude is 10Hz, 20Hz and 30Hz, the peaks on the corresponding curves decrease.

[0097] Please see Figure 15 , Figure 15Simulation curves of the keyhole radius formed when a laser beam moving along a bending trajectory cuts a wafer 100, as provided in this application embodiment, at different amplitudes. Figure 15 It can be seen that when the laser amplitude is 0, there are more peaks on the curve. As the amplitude gradually increases, that is, when the amplitude is 1μm, 3μm and 5μm, the peaks on the corresponding curves decrease.

[0098] Please see Figure 16 , Figure 16 Simulation curves of the keyhole radius formed at different frequencies when a laser beam moving along a bending trajectory cuts a wafer 100, as provided in the embodiments of this application. Figure 16 It can be seen that when the laser frequency is 0, there are more peaks on the curve. As the amplitude gradually increases, that is, when the frequency is 10Hz, 20Hz and 30Hz, the peaks on the corresponding curves decrease.

[0099] It should be noted that the curve shown in the figure contains multiple peaks, and each peak represents a sequential keyhole collapse. Therefore, increasing the laser amplitude and frequency can reduce the number of peaks in the curve, thus reducing the frequency of keyhole collapses during the cutting process.

[0100] Furthermore, the temperature gradient and flow rate in the molten pool were tested when the laser beam cut at different amplitudes and frequencies.

[0101] Please see Figure 17 , Figure 17 A bar chart showing the test results of temperature gradient σ at different amplitudes when a laser beam moving along a bending trajectory cuts wafer 100, as provided in an embodiment of this application. Figure 17 It can be seen that when the amplitude and frequency of the laser increase, the temperature gradient of the molten pool decreases significantly.

[0102] Please see Figure 18 , Figure 18 A bar chart showing the test results of the temperature gradient σ at different frequencies when a laser beam moving along a bending trajectory cuts wafer 100, as provided in an embodiment of this application. Figure 18 It can be seen that when the amplitude and frequency of the laser increase, the flow velocity of the molten pool decreases significantly.

[0103] Please see Figure 19 , Figure 19 This is a test structure diagram showing the flow velocity in the molten pool at different amplitudes when a laser beam moving along a bending trajectory cuts wafer 100, as provided in an embodiment of this application. Figure 19 It can be seen that as the amplitude of the laser increases, the percentage of the maximum flow velocity in the molten pool gradually decreases.

[0104] Please see Figure 20 ,Figure 20 This is a test structure diagram showing the flow velocity in the molten pool at different frequencies when a laser beam moving along a bending trajectory cuts wafer 100, as provided in an embodiment of this application. Figure 20 It can be seen that as the frequency of the laser increases, the percentage of the maximum flow velocity in the molten pool gradually decreases.

[0105] It should be noted that the maximum flow velocity in the molten pool refers to... Figure 19 and Figure 20 In the bar chart, the flow velocity gradually increases from bottom to top. The E4 region at the top represents the maximum flow velocity. As the amplitude and frequency of the laser increase, the proportion of the maximum flow velocity gradually decreases, meaning that the flow velocity of the molten pool gradually decreases.

[0106] As discussed above, lower temperature gradients and flow rates in the molten pool are more conducive to pool stability, thus improving cutting quality. Therefore, higher laser amplitude and frequency are more beneficial for improving the cutting quality of wafer 100.

[0107] Based on this, during the laser's movement along the aforementioned curved trajectory, the laser's motion can be divided into two directions, with speeds of Vx and Vy, respectively. Where Vx represents the velocity of the laser beam along the extension direction of the cutting line 110 (including the left and right directions in the figure), Vy represents the velocity of the laser beam in the direction perpendicular to the cutting line 110, V0 represents the velocity of the laser beam along the extension direction of the cutting line 110 (i.e., when moving in a straight line), A represents the amplitude of the laser beam's bending motion, and f represents the laser frequency. This indicates the phase angle along the direction of extension of the cutting line 110. This indicates the phase angle along the direction perpendicular to the cutting line 110.

[0108] The total velocity of the laser can be calculated from the above formula. Since a higher laser velocity (i.e., keyhole velocity) results in a more stable keyhole, and consequently a more stable molten pool, a keyhole is more stable when Vr > V0. Because of the laser's bending motion, its velocity Vr also fluctuates dynamically. Therefore, a keyhole stability can be guaranteed when the minimum value of Vr, i.e., (Vr)min > V0.

[0109] Based on this, it can be deduced from the above formula that... That is, when πAf > V0, the keyhole is more stable. Therefore, it can be concluded that during the cutting process of the laser beam along the curved trajectory, the greater the amplitude and frequency of the laser, the better.

[0110] Please see Figure 21 and Figure 22 , Figure 21The image provided in this application shows the velocity curves of a laser beam moving along a bending trajectory cutting at different amplitudes, according to an embodiment of the application. Figure 22 The velocity curves of a laser beam moving along a bending trajectory at different frequencies provided in the embodiments of this application are shown. Figure 21 and Figure 22 The vertical axis shown represents the total velocity Vr of the laser beam. Figure 21 and Figure 22 It can be seen that the greater the amplitude and frequency of the laser, the greater the total velocity Vr of the laser, which is more conducive to improving the quality of laser cutting.

[0111] Furthermore, the stirring Reynolds number is a dimensionless number characterizing fluid flow; the smaller the stirring Reynolds number, the more stable the flow within the molten pool. The stirring Reynolds number Re = ρND 2 / μ=ρf(2A) 2 / μ≤2500, where ρ represents density, N represents stirring power, D represents diameter, f represents laser frequency, A represents laser amplitude, and μ represents fluid viscosity. When the stirring Reynolds number is less than or equal to 2500, the flow within the molten pool can remain stable.

[0112] Please see Figure 23 , Figure 23 This is a schematic diagram illustrating the test results of the stirring Reynolds number at different frequencies and amplitudes when a laser beam moving along a bending trajectory cuts a wafer 100, as provided in an embodiment of this application. Figure 23 It is understood that when the laser cuts along the aforementioned curved trajectory, the laser amplitude and frequency must maintain a certain upper limit, i.e., the stirring Reynolds number must be avoided to exceed 2500. Therefore, in the laser cutting method provided in this application embodiment, the laser amplitude can be greater than or equal to 1 μm and less than or equal to 10 μm. The laser frequency can be greater than or equal to 10 Hz and less than or equal to 100 Hz.

[0113] In some embodiments, the amplitude of the laser can be greater than or equal to 2 μm and less than or equal to 5 μm. Furthermore, the frequency of the laser can be greater than or equal to 10 Hz and less than or equal to 50 Hz. For example, the amplitude can be 2.5 μm, 2.7 μm, 3 μm, 3.2 μm, 3.5 μm, 3.6 μm, 3.9 μm, 4 μm, 4.3 μm, 4.5 μm, 4.8 μm, etc. Furthermore, the frequency can be 12 Hz, 15 Hz, 18 Hz, 20 Hz, 22 Hz, 25 Hz, 30 Hz, 35 Hz, 40 Hz, 42 Hz, 45 Hz, 48 Hz, etc. Therefore, this application does not impose any special limitations on the amplitude and frequency of the laser.

[0114] Based on the above embodiments, since the laser cuts the wafer 100 with a bending motion trajectory, the edge of the chip 200 obtained after cutting also forms a bending and extending structure, that is, the edge of the chip 200 forms an uneven structure.

[0115] For example, please refer to Figure 24 , Figure 24 This is a structural diagram of another chip 200 provided in an embodiment of this application. Multiple grooves 210 are formed along the edge of the chip 200, and the multiple grooves 210 are distributed sequentially along the edge of the chip 200, thereby creating a bent and extended structure along the edge of the chip 200.

[0116] Furthermore, since the trajectory line 400 of the aforementioned motion trajectory is arc-shaped, the edge of the chip 200 forms an arc-shaped groove 210 in a plane parallel to the surface of the chip 200, that is, the groove 210 is an arc-shaped groove structure.

[0117] In the above embodiments, the laser cuts along an arc-shaped trajectory. However, the trajectory line 400 of the laser's bending motion is not unique; the structures of other possible trajectory lines 400 are described below.

[0118] In some embodiments, please refer to Figure 25 , Figure 25 This is a schematic diagram of another trajectory line 400 provided in an embodiment of this application. The laser trajectory line 400 described above may include multiple annular segments 430, with at least one intersection point between adjacent annular segments 430. For example, the trajectory line 400 may include two annular segments 430 that are tangent to each other, i.e., they have one intersection point. Furthermore, any point on the annular segment 430 can serve as the starting point of the trajectory line 400, meaning the laser can move continuously with this structure.

[0119] In this case, the trajectory line 400 forms an "8" shape. As the laser moves along this trajectory line 400, it repeatedly moves in the extension direction of the cutting line 110, allowing some areas to be heated a second time. Therefore, some segments of two adjacent trajectory lines 400 can overlap, meaning that the laser can repeatedly pass through the same segment during its movement, further increasing the area for secondary heating and improving the cutting quality.

[0120] Furthermore, after cutting based on the aforementioned trajectory line 400, the edge of the chip 200 can still form an arc-shaped groove structure, differing from the previous embodiment only in the central angle of the arc. Therefore, this will not be described again.

[0121] In other embodiments, please refer to Figure 26 and Figure 27 ,Figure 26 This is a schematic diagram of yet another trajectory line 400 provided in an embodiment of this application. Figure 27 For along Figure 26 The provided trajectory line 400, after being cut, forms the structure of the chip 200. The trajectory line 400 can also extend in a bent, straight-segment structure. Specifically, the trajectory line 400 may include a first straight segment 440 and a second straight segment 450. The end of the first straight segment 440 is connected to the starting point of the second straight segment 450, and the starting point of the second straight segment 450 is connected to the starting point of the first straight segment 440 of an adjacent trajectory line 400. In this way, the first straight segment 440 and the second straight segment 450 can extend in different directions, thus forming an approximately sawtooth-shaped bent motion trajectory for the trajectory line 400.

[0122] Furthermore, the first straight line segment 440 and the second straight line segment 450 can both intersect with the dicing line 110 on the wafer 100, so that the trajectory line 400 can move repeatedly on both sides of the dicing line 110, thereby increasing the radial dimension of the keyhole, that is, increasing the width of the keyhole.

[0123] Since the first straight line segment 440 and the second straight line segment 450 intersect, an angle is formed between them. In some examples, the angle between the first straight line segment 440 and the second straight line segment 450 can be an acute angle. With this structure, the number of trajectory lines 400 along the extension direction of the cutting line 110 can be increased; that is, within a certain length range on the cutting line 110, the number of trajectory lines 400 increases, and the distance between adjacent first straight line segments 440 and second straight line segments 450 decreases, thereby improving the range of laser cutting and thus enhancing cutting quality.

[0124] Furthermore, after the laser beam moves along the aforementioned trajectory line 400 to cut the wafer 100, the edge of the resulting chip 200 can form an approximately sawtooth-shaped bending structure, that is, the cross-section of the aforementioned groove 210 forms a triangular shape. The sawtooth-shaped bending structure of the chip 200 helps to improve the fracture strength of the chip 200, thereby improving the quality of the chip 200.

[0125] In some other embodiments, please refer to Figure 28 and Figure 29 , Figure 28 This is a schematic diagram of another trajectory line 400 provided in an embodiment of this application. Figure 29 For along Figure 28The provided trajectory line 400, after being cut, forms the structure of the chip 200. The trajectory line 400 may further include multiple third straight line segments 460 and multiple fourth straight line segments 470. These segments alternate sequentially and are connected end-to-end. The third straight line segment 460 intersects the cutting line 110, and two adjacent fourth straight line segments 470 are located on either side of the cutting line 110. The trajectory line 400 forms a structure of multiple straight line segments that bend and extend sequentially.

[0126] In some examples, the third straight segment 460 can be perpendicular to the cutting line 110, and the fourth straight segment 470 can be parallel to the cutting line 110. In this way, the laser's movement direction only includes two directions: parallel to the cutting line 110 and perpendicular to the cutting line 110, which helps to reduce the difficulty of control and improve cutting efficiency.

[0127] Furthermore, in this case, the edge of the chip 200 obtained by cutting forms a groove 210, forming a polygonal structure in a plane parallel to the surface of the chip 200. For example, when the third straight line segment 460 is perpendicular to the cutting line 110 and the fourth straight line segment 470 is parallel to the cutting line 110, the groove 210 forms a rectangular structure.

[0128] In other possible embodiments, the laser's trajectory may also form other zigzag patterns, such as an approximately wavy zigzag pattern. Alternatively, the laser's trajectory may extend in an irregular, zigzag pattern. Therefore, this application does not impose any particular limitation on this.

[0129] Based on this, please refer to Figure 30 , Figure 30 This is a structural diagram of a laser cutting apparatus 300 provided in an embodiment of this application. The laser cutting apparatus 300 may include a frame 310, a laser emitter 320, a controller 330, a nozzle 340, a support surface 350, and a drive mechanism 360. The laser emitter 320, controller 330, nozzle 340, and drive mechanism 360 are all mounted on the frame 310. The laser emitter 320 and drive mechanism 360 are both electrically connected to the controller 330. The nozzle 340 is connected to the laser emitter 320 and is used to emit a laser beam. The drive mechanism 360 can drive the nozzle 340, or drive the laser emitter 320 and nozzle 340 to move along the aforementioned bent and extended motion trajectory. The support surface 350 is used to place a wafer 100, so that the laser beam can cut the wafer 100.

[0130] Furthermore, the laser cutting apparatus 300 described above only schematically shows some components and does not constitute any limitation on the actual structure of the laser cutting apparatus 300. For example, the laser cutting apparatus 300 may also include multiple reflectors, which may be located between the laser emitter 320 and the nozzle 340, thereby enabling control of the propagation path of the laser beam. Therefore, this application does not impose any special limitations in this regard.

[0131] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0132] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A laser cutting method, characterized by, The application relates to a method for cutting a wafer, and a wafer cutting device. A wafer is provided, and a surface of the wafer has a cutting line; A laser beam is moved along an extension direction of the cutting line in a bending mode to cut the wafer.

2. The laser cutting method according to claim 1, characterized in that, The amplitude of the bending mode of the laser beam is greater than or equal to 1 mu m and less than or equal to 10 mu m, and the frequency of the laser beam is greater than or equal to 10 Hz and less than or equal to 100 Hz.

3. The laser cutting method according to claim 2, characterized in that, The amplitude of the bending mode of the laser beam is greater than or equal to 2 mu m and less than or equal to 5 mu m, and the frequency of the laser beam is greater than or equal to 10 Hz and less than or equal to 50 Hz.

4. The laser cutting method according to any one of claims 1 to 3, characterized in that, The method for moving the laser beam along the extension direction of the cutting line in a bending mode comprises the following steps. The laser beam is moved along the extension direction of the cutting line in a periodic bending mode.

5. The laser cutting method of claim 4, wherein, The movement track of the periodic bending mode comprises a plurality of track lines, and two adjacent track lines are connected end to end, and at least one intersection exists between the two adjacent track lines.

6. The laser cutting method of claim 5, wherein, Portions of the two adjacent track lines are overlapped.

7. The laser cutting method according to any one of claims 4 to 6, characterized in that, The track line comprises a first arc segment and a second arc segment, the first arc segment and the second arc segment are located on two sides of the cutting line respectively, the end point of the first arc segment is connected with the start point of the second arc segment, and the end point of the second arc segment is connected with the start point of the first arc segment of another adjacent track line.

8. The laser cutting method of claim 7, wherein, The second arc segments of two adjacent track lines intersect.

9. The laser cutting method according to any one of claims 4-6, characterized in that, The track line comprises a plurality of ring segments, and at least one intersection exists between two adjacent ring segments.

10. The laser cutting method of claim 9, wherein, The shape of the ring segment is circular or elliptical.

11. The laser cutting method according to any one of claims 4-6, characterized in that, The track line comprises a first straight line segment and a second straight line segment, the end point of the first straight line segment is connected with the start point of the second straight line segment, and the start point of the second straight line segment is connected with the start point of the first straight line segment of another adjacent track line.

12. The laser cutting method of claim 11, wherein, The first straight line segment and the second straight line segment both intersect with the cutting line.

13. The laser cutting method according to claim 11 or 12, characterized in that, The included angle formed between the first straight line segment and the second straight line segment is an acute angle.

14. The laser cutting method according to any one of claims 4-6, characterized in that, The track line comprises a plurality of third straight line segments and a plurality of fourth straight line segments, the plurality of third straight line segments and the plurality of fourth straight line segments are alternately distributed and connected end to end, the third straight line segment intersects with the cutting line, and two adjacent fourth straight line segments are located on two sides of the cutting line.

15. The laser cutting method of claim 14, wherein, The third straight line segment is perpendicular to the cutting line.

16. The laser cutting method according to claim 14 or 15, characterized in that, The fourth straight line segment is parallel to the cutting line.

17. A laser cutting apparatus for cutting a device to be cut, said device to be cut having a cutting line thereon, characterized in that, The device comprises a controller, a driving mechanism and a laser emitter, the controller is electrically connected with the driving mechanism, the controller controls the driving mechanism to drive the laser emitter to move along a movement track, and the movement track is bent and extended along the extension direction of the cutting line.

18. A chip, characterized by The edge of the chip is bent and extended.

19. The chip of claim 18, wherein, The material of the chip comprises a low dielectric constant material.

20. The chip according to claim 18 or 19, characterized in that The edge of the chip is formed with a plurality of grooves, and the plurality of grooves are sequentially distributed along the edge of the chip.

21. The chip of claim 20, wherein, In a plane parallel to the surface of the chip, the groove is an arc structure.

22. The chip of claim 20, wherein, In a plane parallel to the surface of the chip, the groove is a triangular structure.

23. The chip of claim 20, wherein, In a plane parallel to the surface of the chip, the groove is a rectangular structure.

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