Laser processing device

Abstract

To provide a laser processing device capable of improving efficiency of processing and cleaning of a workpiece.SOLUTION: A laser processing device 1 includes: a workpiece holding part 10 that holds a workpiece W; a processing head 20 including a laser output part that outputs laser LB for processing the workpiece W and a cleaning nozzle 34 that discharges liquid jet LJ to a surface of the workpiece W; a movement mechanism that moves the processing head 20 and the workpiece holding part 10 relatively to each other and thereby, changing an irradiation position of the laser LB and a discharge position of the liquid jet LJ in the workpiece W; and a control part 50 that controls output of the laser LB and discharge of the liquid jet LJ. The control part 50 switches between a processing mode of outputting the laser LB and controlling processing of the workpiece W and a cleaning mode of discharging the liquid jet LJ while stopping output of the laser LB and cleaning the workpiece W, according to a processing step of the workpiece W.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a laser processing apparatus that processes a workpiece using a laser. [Background technology]

[0002] Wafers on which numerous devices have been formed in the pre-processing of semiconductor manufacturing are divided into multiple chips for each device in the dicing process. Multiple devices are formed on the front surface of the wafer, and each device is separated by planned separation lines called streets. To prevent the chips from falling apart, adhesive tape (hereafter also referred to as "dicing tape") is attached to the back surface of the wafer prior to dicing. In the dicing process, cuts are made along the streets from the front side of the wafer, separating the devices.

[0003] Dicing methods include blade dicing, which cuts the wafer by pressing a dicing blade against it, and laser dicing, which separates the wafer surface using laser light. Laser dicing generally produces a smaller kerf width than blade dicing, which has the advantage of reducing street width and increasing the yield of chips that can be removed from the wafer.

[0004] A laser dicing method has also been proposed in which a laser is output using a liquid jet as a light guide (see Patent Document 1). This method can achieve high-precision processing while preventing thermal damage to the wafer during processing and adhesion of debris generated during processing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6688979 Summary of the Invention [Problem to be solved by the invention]

[0006] However, even when the dicing process of Patent Document 1 is adopted, debris generated by the laser processing can adhere to the wall surface of the kerf. In addition, because the edge of the kerf is brittle, a layer that is about to peel off can occur, and the peeled pieces from the edge become new debris. If this debris adheres to the device, it may cause defects in subsequent processes (such as the wire bonding process).

[0007] For this reason, it is necessary to perform spin cleaning or other procedures after dicing to remove debris remaining in the kerf. In this case, the wafer must be moved from the processing area after dicing to the cleaning area for cleaning, which leaves room for improvement in terms of manufacturing efficiency. Note that this problem is not limited to dicing machines used in semiconductor manufacturing, but can occur in any equipment that requires high-precision cleaning after laser processing of the workpiece.

[0008] The present invention has been made in view of the above circumstances, and one of its objects is to provide a laser processing apparatus that can improve the efficiency of processing and cleaning a workpiece. [Means for solving the problem]

[0009] A laser processing apparatus according to one aspect of the present invention includes a processing head including a workpiece holder for holding a workpiece, a laser output unit for outputting a laser for processing the workpiece, and a cleaning nozzle for discharging a liquid jet toward the surface of the workpiece, a movement mechanism for changing the laser irradiation position on the workpiece and the liquid jet discharge position by moving the processing head and the workpiece holder relatively, and a control unit for controlling the laser output and the liquid jet discharge. The control unit switches between a processing mode in which the laser is output to control processing of the workpiece and a cleaning mode in which the laser output is stopped while the liquid jet is discharged to clean the workpiece, depending on the processing step of the workpiece. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a laser processing device that can improve the efficiency of processing and cleaning a workpiece. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating a schematic configuration of a laser processing device according to a first embodiment. [Figure 2] FIG. 1 is a diagram schematically illustrating a system configuration of a laser processing apparatus. [Figure 3] FIG. 2 is a diagram schematically illustrating the configuration of a cleaning liquid supply unit and a gas supply unit. [Figure 4] FIG. 2 is a diagram schematically illustrating a laser beam guided by a liquid jet. [Figure 5] FIG. 2 is a perspective view showing the structure of a wafer after dicing. [Figure 6] FIG. 2 is a plan view of a wafer. [Figure 7] 1A to 1C are diagrams schematically illustrating processing and cleaning methods in a dicing process. [Figure 8] 1A to 1C are diagrams schematically illustrating processing and cleaning methods in a dicing process. [Figure 9] 10 is a flowchart showing an outline of a processing process. [Figure 10] 10 is a flowchart showing an outline of a cleaning process. [Figure 11] FIG. 4 is a diagram schematically illustrating the configuration of a laser processing device according to a second embodiment. [Figure 12] FIG. 1 is a diagram schematically illustrating a system configuration including a fine bubble mixing section. [Figure 13] 10 is a flowchart showing an outline of a processing process. [Figure 14] 10 is a flowchart showing an outline of a cleaning process. [Figure 15] FIG. 10 is a diagram schematically illustrating the configuration of a laser processing device according to a third embodiment. [Figure 16] FIG. 2 is a diagram schematically illustrating a system configuration including a cleaning unit. [Figure 17] FIG. 2 is a diagram schematically illustrating the configuration of a cleaning unit. [Figure 18] FIG. 10 is a diagram schematically illustrating the configuration of a laser processing device according to a modified example. [Figure 19] 10A and 10B are diagrams schematically illustrating specific examples of angle adjustment mechanisms. [Figure 20] FIG. 10 is a diagram schematically illustrating the configuration of a fine bubble mixing section according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the following embodiment and its modifications, substantially the same components are designated by the same reference numerals, and the description thereof will be omitted as appropriate.

[0013] [First embodiment] The laser processing device of this embodiment is used in the dicing process of semiconductor manufacturing. This laser processing device performs dicing along streets set on the surface of a semiconductor wafer (an example of a workpiece, also simply called a "wafer"), and then cleans the wafer to remove debris adhering to the kerf. Because the width of the kerf is small, on the microscale, a cleaning liquid is supplied in the form of a liquid jet, which allows the cleaning liquid to spread throughout the kerf.

[0014] In this laser processing device, the processing head has an integrated laser output unit and cleaning nozzle, and switches between a processing mode in which a laser is output using a liquid jet as a light guide, and a cleaning mode in which a liquid jet is ejected while the laser output is stopped, depending on the wafer processing step. That is, in this embodiment, the laser processing device also functions as a cleaning device, and the cleaning step can be performed after dicing while the wafer remains in the processing area. Alternatively, the cleaning step can be performed as part of the dicing step. Details of this will be explained below.

[0015] FIG. 1 is a diagram showing a schematic configuration of a laser processing device according to a first embodiment. For convenience of explanation, the following description will be given assuming that the front-rear direction, left-right direction, and up-down direction when viewing the laser processing apparatus from the front are the X direction, Y direction, and Z direction, respectively. The laser processing device 1 includes a workpiece holder 10 that holds a wafer W, and a processing head 20 that can output a laser and a liquid jet toward the wafer W, and functions as a dicing device.

[0016] The wafer W undergoes a dicing process to form a kerf. Note that in this embodiment, a laser dicing method is adopted. Laser dicing methods include a laser ablation method in which the wafer is separated by sublimation and evaporation using a laser, and a laser internal processing method in which a modified layer is formed inside the wafer using a laser and then the wafer is separated by tension (for example, the technology described in Japanese Patent No. 3408805). The laser processing device 1 uses the laser ablation method.

[0017] The workpiece holding unit 10 includes a work table 12, a rotary table 14, an X table 16, and a Y table 18. The work table 12 has a holding surface 12a that holds the wafer W by suction. The holding surface 12a is provided with a plurality of suction holes through which a vacuum is drawn to hold the back surface of the wafer W by suction. By driving a vacuum suction source (not shown), the wafer W can be sucked and fixed to the holding surface 12a.

[0018] A pair of guide rails 22 extending in the Y direction are provided on the base 2 of the laser processing apparatus 1. The Y table 18 is installed horizontally so that it can move in the Y direction along the guide rails 22. The Y table 18 is driven by a Y movement mechanism 24. A pair of guide rails 26 extending in the X direction are provided on the upper surface of the Y table 18. The X table 16 is installed horizontally so that it can move in the X direction along the guide rails 26. The X table 16 is driven by an X movement mechanism 28. In this embodiment, each movement mechanism is realized by a linear motor, but may also be realized by a screw feed mechanism and a servo motor that drives it.

[0019] The rotary table 14 is rotatably supported by the X-table 16, and the work table 12 is fixed to the upper surface of the rotary table 14. The rotary table 14 can be rotated around its own axis (in the θ direction around an axis L extending in the Z direction) by a rotation mechanism 30. The rotation mechanism 30 is realized by, for example, a spindle motor. With this configuration, the work table 12 can move in each of the X direction, Y direction, and θ direction.

[0020] Meanwhile, a Z-table 32 is disposed on a column 4 erected on the base 2, and the processing head 20 is supported by the Z-table 32. The processing head 20 includes a cleaning nozzle 34 that converts the cleaning liquid into a liquid jet and discharges it toward the wafer W. The cleaning nozzle 34 also functions as a "laser output unit" that outputs a processing laser (described in detail later).

[0021] A pair of guide rails 36 extending in the Z direction are provided on the front surface of the column 4. The Z table 32 is installed so as to be movable in the Z direction along the guide rails 36. The Z table 32 is driven by a Z movement mechanism 38. The Z movement mechanism 38 is realized, for example, by a screw feed mechanism and a servo motor that drives it. The Z table 32 is provided with an angle adjustment mechanism 37 that can adjust the inclination angle of the cleaning nozzle 34 with respect to the surface of the wafer W (described in detail later).

[0022] In the above configuration, the X movement mechanism 28, the Y movement mechanism 24, the Z movement mechanism 38, and the rotation mechanism 30 function as a "movement mechanism" that moves the machining head 20 and the work table 12 relative to each other.

[0023] FIG. 2 is a diagram schematically showing the system configuration of the laser processing device 1. As shown in FIG. In addition to the workpiece holder 10 and processing head 20 described above, the laser processing apparatus 1 includes a laser unit 100, a cleaning liquid supply unit 40, a gas supply unit 42, and a control unit 50. The laser unit 100 includes a laser oscillator 102, an optical mechanism 104, and a condenser lens 106. The optical mechanism 104 is composed of optical elements such as a mirror. The laser LB (laser light) output from the laser oscillator 102 is reflected by the mirror and guided to the processing head 20 via the condenser lens 106. The condenser lens 106 condenses the incident laser LB toward the inside of the processing head 20.

[0024] In this embodiment, the laser LB uses laser light in a wavelength range that is not easily absorbed by the liquid jet LJ. When water is used as the liquid jet LJ, the preferable conditions for the laser LB are a wavelength in the UV wavelength range (less than 400 nm), a pulse width of 1 μs or less, a repetition frequency of more than 1 kHz, an average output of 0.1 to 10 W, and a spot diameter at the focal point of 0.23 to 10 μm.

[0025] A chamber 60 into which a cleaning liquid is introduced is formed inside the processing head 20. An inlet port 62 communicating with the chamber 60 is provided on the side wall of the processing head 20, and a liquid supply channel 41 is connected to the inlet port 62. A window 110 is provided above the chamber 60. The window 110 is made of an optically transparent material and allows the laser beam LB to pass through while sealing the chamber 60. Therefore, the laser beam LB passing through the focusing lens 106 passes through the window 110, enters the chamber 60, and is focused on the cleaning nozzle 34. The optical mechanism 104 may include a galvanometer mirror and its driving mechanism. By controlling the angle of the galvanometer mirror, it is possible to change the incident angle and incident position of the laser beam LB relative to the liquid jet LJ. Although a galvanometer mirror is used in this embodiment, an acousto-optical element (AOM) may also be used.

[0026] The cleaning liquid supply unit 40 is connected to the processing head 20 via a liquid supply path 41, and supplies pressurized cleaning liquid (e.g., pressurized water) to the processing head 20. The gas supply unit 42 is connected to the processing head 20 via a gas supply path 43, and supplies gas to the processing head 20 to stabilize the liquid jet LJ.

[0027] FIG. 3 is a diagram schematically illustrating the configuration of the cleaning liquid supply unit 40 and the gas supply unit 42. As shown in FIG. The cleaning liquid supply unit 40 includes a liquid supply source 44, a pump 46, and a flow control valve 48. The pump 46 and the flow control valve 48 are provided, from upstream, in a liquid supply path 41 that connects the liquid supply source 44 and the machining head 20. The liquid supply source 44 has a tank that stores cleaning liquid. By driving the pump 46, cleaning liquid can be drawn up from the liquid supply source 44 and supplied to the machining head 20. Pressurized cleaning liquid is supplied to the machining head 20. The flow control valve 48 controls the flow rate of the cleaning liquid supplied to the machining head 20. In this embodiment, the flow control valve 48 consists of a motor-driven electric valve, but it may also be a solenoid-driven electromagnetic valve.

[0028] The gas supply unit 42 includes a gas supply source 52 and an on-off valve 54. The on-off valve 54 is provided in a gas supply path 43 that connects the gas supply source 52 and the processing head 20. The gas supply source 52 has a tank that stores pressurized gas. The on-off valve 54 is an electromagnetic valve, and gas can be supplied from the gas supply path 43 to the processing head 20 by opening the on-off valve 54.

[0029] Returning to FIG. 2, the processing head 20 includes a cleaning nozzle 34 and an air nozzle 35. The cleaning nozzle 34 discharges the cleaning liquid supplied from the cleaning liquid supply unit 40 as a liquid jet LJ. The air nozzle 35 is provided coaxially downstream of the cleaning nozzle 34. A chamber 64 is formed between the cleaning nozzle 34 and the air nozzle 35. An inlet port 66 communicating with the chamber 64 is provided in the side wall of the processing head 20, and a gas supply path 43 is connected to the inlet port 66.

[0030] The gas introduced from the inlet port 66 is guided to the air nozzle 35 while swirling around the liquid jet LJ, and is then discharged from the air nozzle 35 as a gas jet GJ. This gas flow (swirling flow) acts as a guide wall to suppress the spread of the liquid jet LJ. In other words, the liquid jet LJ travels straight without diffusing. Therefore, the diameter of the liquid jet LJ that strikes the wafer W is approximately equal to the diameter of the discharge port 34a of the cleaning nozzle 34.

[0031] The air nozzle 35 discharges the gas jet GJ so as to surround the liquid jet LJ. By coaxially surrounding the liquid jet LJ with the gas jet GJ, the liquid jet LJ can be stably discharged in a straight line. The diameter of the liquid jet LJ discharged from the cleaning nozzle 34 toward the wafer W can be kept almost constant. This can be achieved, for example, by using the technology described in Japanese Patent No. 5437578.

[0032] The control unit 50 is a general-purpose computer and includes a CPU that executes various arithmetic processes, memory or storage that stores control programs, etc., memory used as a work area for data storage and program execution, an input / output interface, a user interface, etc. The user interface accepts operation inputs as user instructions. The control unit 50 controls the operation of the laser unit 100, cleaning liquid supply unit 40, gas supply unit 42, and each movement mechanism in accordance with the control program. Note that, although the control unit 50 controls each part of the laser processing apparatus 1 in this embodiment, each part may be provided with its own control unit.

[0033] FIG. 4 is a diagram schematically illustrating how a laser beam is guided by a liquid jet. The liquid jet LJ has a function similar to that of an optical fiber. The laser beam LB is focused by the focusing lens 106 and enters the liquid jet LJ coaxially with the central axis L1. The laser beam LB is guided along the central axis L1 while being totally reflected within the liquid jet LJ. In other words, the liquid jet LJ functions as a light guide path for the laser beam LB.

[0034] Therefore, the outlet 34a is not only an outlet for the liquid jet LJ but also a laser output unit 80 that outputs a laser from the processing head 20. That is, the cleaning nozzle 34 and the laser output unit 80 are provided in the processing head 20 so that the central axis L1 of the liquid jet LJ and the optical axis L2 of the laser LB are coaxial.

[0035] As mentioned above, the gas jet GJ acts as a guide wall, keeping the diameter of the liquid jet LJ almost constant. The laser LB travels straight through the liquid jet LJ, ensuring its directivity. Because the liquid jet LJ functions as a light guide, laser processing is possible regardless of the focal length of the laser LB. The liquid jet LJ also makes it possible to cool the processing point and remove debris.

[0036] Next, the kerf cleaning method according to this embodiment will be described in detail. FIG. 5 is a perspective view showing the structure of the wafer W after dicing. The wafer W undergoes a dicing process, forming grid-like kerfs K (kerfs) surrounding each of the devices D. A dicing tape 70 is attached to the back surface of the wafer W, and the peripheral edge of the dicing tape 70 is fixed to an annular frame 72. The wafer W is fixed to the work table 12 via the frame 72 (see FIG. 1).

[0037] FIG. 6 is a plan view of the wafer W. FIG. 6(A) shows the wafer W before dicing, and FIG. 6(B) shows the wafer W after dicing. FIG. 6(C) is an enlarged view of part A in FIG. 6(B). Note that this is a schematic diagram for ease of understanding, and chips and other components provided on the wafer W are depicted larger than they actually are.

[0038] As shown in Figure 6(A), streets S1 and S2 that are perpendicular to each other are set as planned division lines on the surface of the wafer W. Street S1 extends in the X direction, and street S2 extends in the Y direction. A plurality of these streets S1 and S2 are set on the surface of the wafer W and arranged in a grid pattern. Devices D are formed within areas defined by these streets S1 and S2.

[0039] 6(B), dicing is performed along these streets S1 and S2, and a kerf K is formed so as to pass through the center of each street S1 and S2 in the width direction. In this embodiment, the widths of the streets S1 and S2 are the same, and therefore, when there is no need to distinguish between them, they are collectively referred to as "street S."

[0040] As shown in FIG. 6(C), the street S is a boundary that separates adjacent devices D, and the kerf K is formed within the range of the street S. In this embodiment, the width of the kerf K (kerf width Wk) is several tens of μm, which is smaller than the width of the street S (street width Ws). Because the kerf width Wk is extremely small, it is necessary to increase the cleaning strength (liquid pressure) in order to spread the cleaning liquid throughout the kerf K.

[0041] On the other hand, if the high-pressure cleaning liquid hits the device D, it may damage the device D. Therefore, in this embodiment, the diameter of the liquid jet discharged toward the kerf K is set to be approximately the same as the kerf width Wk, or at least smaller than the street width Ws. Note that the diameter of the liquid jet may also be smaller than the kerf width Wk (details will be described later).

[0042] 7 and 8 are diagrams showing the processing and cleaning methods in the dicing process. Fig. 7(A) shows the processing mode, and Fig. 7(B) shows the cleaning mode. Fig. 7(C) is an enlarged view of part B in Fig. 7(B). The outline arrows in the figures indicate the relative movement direction of the processing head 20 with respect to the wafer W.

[0043] 7(A), in the processing mode, the control unit 50 controls the driving of the laser unit 100, the cleaning liquid supply unit 40, the gas supply unit 42, and each movement mechanism to perform laser dicing along the street S. That is, the control unit 50 outputs the laser beam LB to control the dicing process of the wafer W. At this time, the laser beam LB is output toward the wafer W using the liquid jet LJ discharged from the cleaning nozzle 34 as a light guide path. By driving the X movement mechanism 28 to move the cleaning nozzle 34 and the wafer W relatively in the X direction, the laser beam LB can be moved in the longitudinal direction of the street S.

[0044] At this time, the laser beam LB is output while the cleaning nozzle 34 (processing head 20) is moved relative to the wafer W along a vertical plane Fv including the center of the street S in the width direction. By moving the processing head 20 and the work table 12 relatively, the irradiation position of the laser beam LB on the wafer W and the discharge position of the liquid jet LJ can be changed. This irradiation of the laser beam LB forms a kerf K along the street S on the surface of the wafer W.

[0045] As shown in FIG. 7(B), in the cleaning mode, the control unit 50 stops driving the laser unit 100 and stops the output of the laser LB. Meanwhile, the control unit 50 controls the driving of the cleaning liquid supply unit 40, the gas supply unit 42, and each moving mechanism. That is, the control unit 50 discharges the liquid jet LJ while stopping the output of the laser LB, and performs jet cleaning along the kerf K. By driving the X-movement mechanism 28, the liquid jet LJ can be moved in the longitudinal direction of the kerf K. At this time, the liquid jet LJ is discharged while the cleaning nozzle 34 (processing head 20) is moved relative to the wafer W along a vertical plane Fv including the kerf K.

[0046] As shown in FIG. 7(C), the width Wk and depth h of the kerf K are several tens of μm, but fine debris d adheres to the inner wall surface of the kerf K immediately after machining. Also, peeling pieces f may occur at the edge of the kerf K. The liquid jet LJ has a liquid pressure sufficient to wash away these debris. In this embodiment, the diameter of the discharge port 34a of the cleaning nozzle 34 is set to several tens of μm, which is approximately the same as the kerf width Wk. Furthermore, the liquid pressure (discharge pressure) of the liquid jet LJ is set sufficiently high, for example, in the range of 100 to 600 bar. Therefore, the liquid pressure acting on the position where the liquid jet LJ hits is also approximately the same, allowing the liquid jet LJ to be sufficiently distributed within the kerf K.

[0047] 8(A) is a cross-sectional view taken along the vertical plane Fv in FIG. 7(B), and FIG. 8(B) is a view seen in the direction of the arrow C in FIG. 8(A). 8(A), in the cleaning mode, the cleaning nozzle 34 (more specifically, the axis L1 of the discharge port 34a) is set to form a predetermined inclination angle θ1 (e.g., 45 degrees) with respect to the surface of the wafer W. The laser processing apparatus 1 is equipped with the angle adjustment mechanism 37 described above (see FIG. 1), and can appropriately adjust the inclination angle θ1 of the cleaning nozzle 34 with respect to the surface of the wafer W (i.e., the discharge angle of the liquid jet LJ with respect to the surface of the wafer W).

[0048] In this embodiment, the angle adjustment mechanism 37 includes a goniostage (not shown) or the like, and can manually adjust the angle of the machining head 20 relative to the work table 12. In a modified example, the angle adjustment mechanism 37 may include a stepping motor that rotates the machining head 20 about a horizontal axis. The control unit 50 may control the motor to automatically adjust the angle.

[0049] The cleaning nozzle 34 discharges the liquid jet LJ obliquely downward toward the front of the wafer W in the direction of travel relative to the wafer W. This allows the cleaning liquid discharged earlier to be expelled from the kerf K by pushing it forward together with debris. As shown in FIG. 8(B), cleaning is performed efficiently with the liquid jet LJ contained within the kerf K. After cleaning the kerf K along the street S1, the rotation mechanism 30 rotates the work table 12 by 90 degrees, allowing the kerf K along the street S2 to be cleaned (see FIG. 6(B)).

[0050] Regarding the tilt angle θ1, a correspondence relationship that provides good cleaning performance may be set in advance based on experiments or the like between cleaning conditions such as the discharge pressure and discharge flow rate of the liquid jet LJ and the tilt angle of the cleaning nozzle 34 relative to the wafer W. Other cleaning conditions may include the type of dicing, the presence or absence of a liquid film (third embodiment) described later, and the like.

[0051] In this embodiment, the tilt angle θ1 is set to 90 degrees in the processing mode, and the laser LB is applied perpendicularly to the surface of the wafer W. In a modified example, the tilt angle θ1 may be appropriately set within a range of less than 90 degrees even in the processing mode.

[0052] FIG. 9 is a flowchart showing an outline of the processing. When the user switches to the processing mode, the control unit 50 discharges the liquid jet LJ and the gas jet GJ at processing settings (set flow rate, set pressure) (S10), and starts processing control (dicing processing control) together with the output of the laser LB (S12).

[0053] FIG. 10 is a flowchart showing an outline of the cleaning process. When the user switches to the cleaning mode, the control unit 50 stops the output of the laser LB (S20), discharges the liquid jet LJ and the gas jet GJ at the settings for cleaning (set flow rate, set pressure) (S22), and starts cleaning control using the liquid jet LJ (S24).

[0054] As described above, in this embodiment, the processing head 20 integrally includes the laser output unit 80 and the cleaning nozzle 34. The control unit 50 then switches between a processing mode in which the laser LB is output using the liquid jet LJ as a light guide, and a cleaning mode in which the liquid jet LJ is ejected while the output of the laser LB is stopped. In other words, the laser processing apparatus 1 also functions as a cleaning device, and the cleaning process can be performed while the wafer W remains in the processing area, thereby improving the efficiency of the entire dicing process. The processing mode and cleaning mode can be easily switched on and off by turning the laser drive on and off. Since there is no need to provide a separate jet cleaning device, the system can be implemented at low cost.

[0055] Furthermore, by setting the diameter of the discharge port 34a of the cleaning nozzle 34 to be equal to or smaller than the kerf width Wk, the diameter of the liquid jet LJ can be made approximately the same as the kerf width Wk. This makes it easy to achieve jet cleaning that is targeted at the kerf K. Since the liquid jet LJ is prevented from directly hitting the device D, the liquid pressure can be set high. This ensures sufficient cleaning strength required for kerf cleaning, improving cleaning efficiency.

[0056] In the present embodiment, the laser processing apparatus 1 is described as having an angle adjustment mechanism 37 that can adjust the tilt angles of the processing head 20 and the cleaning nozzle 34, but the laser processing apparatus 1 does not have to have the angle adjustment mechanism 37. For example, the laser processing apparatus 1 may be configured to eject the laser LB and / or the liquid jet LJ perpendicular to the wafer W and switch between the processing mode and the cleaning mode. Furthermore, the laser processing apparatus 1 may have the processing head 20 and the cleaning nozzle 34 as separate entities.

[0057] [Second embodiment] The laser processing apparatus of this embodiment differs from the first embodiment in that fine bubbles (microscopic air bubbles) are mixed into the liquid jet discharged from the cleaning nozzle. FIG. 11 is a diagram schematically illustrating the configuration of a laser processing apparatus according to the second embodiment. In the laser processing apparatus 201, the cleaning liquid supply unit 240 includes a fine bubble mixing unit 210. The fine bubble mixing unit 210 mixes microbubbles or nanobubbles into the cleaning liquid upstream of the cleaning nozzle 34. Hereinafter, microbubbles or nanobubbles will be collectively referred to as "fine bubbles" as appropriate.

[0058] FIG. 12 is a diagram showing a schematic diagram of a system configuration including the fine bubble mixing section 210. In this embodiment, a branch path 45 is provided that branches off from the gas supply path 43. The branch path 45 is connected to the liquid supply path 41 on the upstream side of the processing head 20. That is, the gas from the gas supply source 52 is also supplied to the liquid supply path 41 via the branch path 45.

[0059] The fine bubble mixing section 210 generates fine bubbles by injection, and includes, from the upstream side of the branching path 45, a pressure booster valve 212, a pressure booster tank 214, a flow control valve 216, and an injector 218. A portion of the gas supplied from the gas supply source 52 is boosted in pressure by the pressure booster valve 212 and stored in the pressure booster tank 214. The supply amount of the boosted gas is controlled by adjusting the aperture of the flow control valve 216. In this embodiment, the flow control valve 216 is an electrically operated valve, but it may also be an electromagnetic valve.

[0060] The pressurized gas is injected from the nozzle of the injector 218 into the liquid supply path 41 and mixed into the cleaning liquid as fine bubbles. More specifically, by injecting pressurized gas into the pressurized cleaning liquid, a gas-liquid mixed flow containing microbubbles or nanobubbles is generated. Each part of the fine bubble mixing unit 210 is controlled by the control unit 50. The control unit 50 controls the flow control valve 48 and the flow control valve 216, respectively, to adjust whether or not fine bubbles are mixed into the cleaning liquid and the amount of fine bubbles to be mixed in.

[0061] In addition to the injection method, there are various other methods for generating fine bubbles in the cleaning liquid, such as the cavitation method, in which gas is sucked into a swirling flow of pressurized cleaning liquid and pulverized to generate fine bubbles; the gas-liquid agitation method, in which gas is supplied to the pressurized cleaning liquid and agitated at high speed to generate fine bubbles by breaking down the air bubbles present in the cleaning liquid; and the gas dispersion method, in which fine bubbles are generated by passing gas through a porous body immersed in the cleaning liquid (see, for example, JP 2008-253893 A). Any of these methods may be used, but the fine bubbles to be mixed in should have a diameter sufficiently smaller than that of the liquid jet LJ, i.e., sufficiently smaller than the diameter of the discharge port 34a.

[0062] 11, the control unit 50 can operate the fine bubble mixing unit 210 to mix fine bubbles into the cleaning liquid and discharge the liquid as a liquid jet LJ from the cleaning nozzle 34. According to this embodiment, the fine bubbles in the cleaning liquid can adsorb debris and wash it away, thereby further improving the cleaning efficiency of the calf K.

[0063] FIG. 13 is a flowchart showing an outline of the processing. When the processing mode is entered, the control unit 50 stops driving the fine bubble mixing unit 210 to stop mixing fine bubbles into the cleaning liquid (S210). Next, as a preparation step before processing, the liquid jet LJ is discharged at a set pressure (S212).

[0064] This preparation process is to discharge any microscopic bubbles remaining in the cleaning nozzle 34 prior to laser processing. This prevents the presence of bubbles from degrading the laser LB light guiding performance of the liquid jet LJ. In this embodiment, the set pressure is set to a pressure higher than the pressure during processing and cleaning, but it may also be set to the same pressure as either the processing or cleaning. Alternatively, it may also be set to a pressure lower than the pressure during processing and cleaning.

[0065] When a predetermined time has elapsed since the start of the preparation step (Y in S214), the control unit 50 starts discharging the liquid jet LJ and the gas jet GJ with settings for processing (S216), and then starts processing control together with the output of the laser LB (S218).

[0066] FIG. 14 is a flowchart showing an outline of the cleaning process. When the mode is switched to the cleaning mode, the control unit 50 stops the output of the laser LB (S230), starts discharging the liquid jet LJ and the gas jet GJ with the settings for cleaning (S232), and activates the fine bubble mixing unit 210 to start mixing fine bubbles into the cleaning liquid (S234). Then, cleaning control using the liquid jet LJ is started (S236).

[0067] The size and density of the fine bubbles can be adjusted by controlling the opening of the pressure booster valve 212 and the flow control valve 216 in the fine bubble mixing section 210. Therefore, the control values for these are set in advance so that fine bubbles suitable for cleaning can be obtained.

[0068] According to this embodiment, in the cleaning mode, the debris can be adsorbed by the fine bubbles in the cleaning liquid and washed away, thereby further improving the cleaning efficiency of the calf K.

[0069] [Third embodiment] The laser processing apparatus of this embodiment differs from the first embodiment in that a liquid film is formed on the surface of the wafer W and a liquid jet LJ is supplied from above the liquid film. FIG. 15 is a diagram schematically illustrating the configuration of a laser processing apparatus according to the third embodiment. The laser processing apparatus 301 includes a cleaning unit 310 that supplies a cleaning liquid so that a liquid film Lm is formed on the surface of the wafer W, in addition to the jet cleaning performed by the processing head 20. The processing head 20 functions as a "first cleaning unit," and the cleaning unit 310 functions as a "second cleaning unit."

[0070] In this embodiment, the cleaning unit 310 is provided integrally with the work table 12, but in a modified example, it may be provided as a cleaning device independent of the workpiece holder 10. A liquid supply path 47 is provided that connects the cleaning liquid supply unit 40 and the cleaning unit 310, and cleaning liquid is supplied from the cleaning liquid supply unit 40 to the cleaning unit 310. Low-pressure cleaning liquid is supplied from the cleaning unit 310 in the form of a sprinkler, rather than a liquid jet.

[0071] FIG. 16 is a diagram showing a schematic diagram of a system configuration including the cleaning unit 310. As shown in FIG. A liquid supply path 47 is provided so as to branch off from the liquid supply path 41 downstream of the pump 46, and is connected to the cleaning unit 310. A flow control valve 312 is provided in the liquid supply path 47. The cleaning liquid is also supplied to the liquid supply path 47 when the pump 46 is driven. The flow control valve 312 controls the flow rate of the cleaning liquid supplied to the cleaning unit 310. In this embodiment, the flow control valve 312 is an electric valve, but it may also be an electromagnetic valve.

[0072] FIG. 17 is a diagram showing a schematic configuration of the cleaning unit 310. As shown in FIG. The cleaning section 310 has a block 320 fixed to the work table 12 and a nozzle unit 322 attached to the block 320. The nozzle unit 322 includes a chamber 324 that communicates with the liquid supply path 47 and a plurality of liquid supply holes 326 that communicate with the chamber 324. The nozzle unit 322 has an arc-shaped side surface facing the wafer W, and a plurality of liquid supply holes 326 are arranged on the side surface. All of the liquid supply holes 326 open toward the wafer W side.

[0073] The cleaning liquid supplied through the liquid supply path 47 is stored in the chamber 324 and is discharged from each liquid supply hole 326 toward the surface of the wafer W. This cleaning liquid flows over the surface of the wafer W in a direction away from the cleaning nozzle 34 while forming a liquid film on the surface of the wafer W, and is led to a drainage path (not shown). That is, on the surface of the wafer W, the flow direction of the cleaning liquid discharged from the cleaning nozzle 34 and the flow direction of the cleaning liquid discharged from the nozzle unit 322 are the same.

[0074] According to this embodiment, by forming a thin liquid film Lm that covers the entire surface of the wafer W, it is possible to prevent or suppress the re-adhesion of debris contained in the cleaning liquid (waste liquid) to surrounding devices after jet cleaning. This further improves the quality of the cleaning. Because the liquid jet has high liquid pressure, the liquid film does not interfere with jet cleaning. By creating a flow in the liquid film itself, it is possible to guide debris detached from the kerf by jet cleaning to the discharge path, further improving the cleaning effect.

[0075] In this embodiment, as in the second embodiment, the cleaning liquid supply unit 40 may be configured to include a fine bubble mixing unit 210 (see FIG. 11). The fine bubble mixing unit 210 may supply cleaning liquid mixed with fine bubbles to the processing head 20. The fine bubble mixing unit 210 may supply cleaning liquid mixed with fine bubbles to the cleaning unit 310. By mixing fine bubbles into the liquid film as well, the debris removal effect can be improved.

[0076] Although the preferred embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to this specific embodiment, and various modifications are possible within the scope of the technical concept of the present invention.

[0077] [Variations] FIG. 18 is a diagram schematically illustrating the configuration of a laser processing device according to a modified example. Although not mentioned in the above embodiment, the wafer W may be held so as to be tilted relative to the horizontal plane. In this modification, in the configuration of the third embodiment, the work table 12 is tilted so as to be lower in the X direction. In the illustrated example, the upper surface of the X table 356 of the workpiece holder 350 is tilted, but the upper surface of the Y table 18 may also be tilted.

[0078] As a result, the axis L of the turntable 14 is inclined with respect to the vertical axis (axis in the Z direction). This configuration can promote the flow of the liquid film in the X direction, and keep the surface of the wafer W clean. Note that an angle adjustment mechanism may be provided that can adjust the inclination angle of the work table 12, for example, by making the turntable 14 oscillating about a horizontal axis.

[0079] 19A to 19C are diagrams showing a schematic view of a specific example of the angle adjustment mechanism. In the above embodiment, as shown in FIG. 19(A), the angle adjustment mechanism 37 is assumed to be a mechanism for tilting the entire head unit 150 in which the laser unit 100 and the processing head 20 are integrated.

[0080] 19(B), a flexible optical fiber 152 may be used to guide the laser LB output from the laser oscillator 102 to the condenser lens 106. The condenser lens 106 may be provided as part of the processing head 20, and may be realized as a mechanism for tilting a head unit 154 including the tip of the optical fiber 152 and the processing head 20.

[0081] 19(C), it may be realized as a mechanism that tilts only the processing head 20 that does not include the condenser lens 106. In that case, when executing the processing mode, the arrangement of the optical system and the like will be adjusted separately.

[0082] FIG. 20 is a diagram schematically illustrating the configuration of a fine bubble mixing section according to a modified example. In the above embodiment, as shown in FIG. 12, an example was shown in which a cleaning liquid is supplied in a single phase (liquid phase) from the liquid supply source 44, and gas is supplied from the gas supply source 52 to mix fine bubbles, thereby ejecting a two-phase gas-liquid cleaning jet.

[0083] In a modified example, as shown in Figure 20(A), a fine bubble mixer 162 may be incorporated into a tank 160 serving as a liquid supply source. The fine bubble mixer 162 has a circulation path 163 that returns the cleaning liquid drawn out from the tank 160 back to the tank 160. A pump 164 and a fine bubble generating nozzle 166 are provided in the circulation path 163.

[0084] A pump 164 draws up the cleaning liquid in the tank 160 and passes it through a fine bubble generating nozzle 166, generating fine bubbles. The fine bubble generating nozzle 166 may take in air from the outside, or may introduce gas from a gas supply source. In this modification, the bubble density and bubble diameter of the cleaning liquid stored in the tank 160 can be adjusted by controlling the flow rate and pressure of the cleaning liquid by adjusting the aperture of the fine bubble generating nozzle 166 during the cleaning liquid circulation process.

[0085] The tank 160 is connected to the processing head 20 via a liquid supply path 41. The control unit 50 drives the pump 46 and controls the flow control valve 48, so that the cleaning liquid containing fine bubbles can be supplied to the processing head 20.

[0086] In another modification, as shown in Figure 20(B), the fine bubble mixing section 170 may be provided with a fine bubble tank 172 that stores a cleaning liquid with fine bubbles mixed in, separate from the liquid supply source 44. The liquid supply source 44 is a single-phase tank that stores a cleaning liquid that is only in the liquid phase. As in the above modification, the fine bubble mixing section 170 has a circulation path 163 that returns the cleaning liquid drawn from the fine bubble tank 172 back to the fine bubble tank 172. A pump 164 and a fine bubble generating nozzle 166 are provided in the circulation path 163.

[0087] A supply path 49 extending from the fine bubble tank 172 is connected to the liquid supply path 41. A three-way control valve 180 is provided at the confluence of supply path 49 and liquid supply path 41. With this configuration, the single-phase cleaning liquid supplied from liquid supply source 44 (single-phase tank) and the gas-liquid two-phase cleaning liquid supplied from fine bubble tank 172 are mixed. The control unit 50 controls the three-way control valve 180 to adjust the mixing ratio.

[0088] The fine bubble tank 172 is connected to the liquid supply path 41 via a supply path 49. A pump 56 is provided in the supply path 49. The control unit 50 drives the pumps 46 and 56 and controls the three-way control valve 180, thereby supplying the cleaning liquid containing fine bubbles to the processing head 20.

[0089] [Other variations] In the above embodiment, the laser processing is exemplified as laser grooving, which forms a kerf on the surface of the wafer W. However, the laser processing apparatus 1 can also be applied to edge trimming of the wafer W. That is, when a wafer is ultra-thinned, backside grinding is performed. However, if the outer periphery of the wafer is ground while retaining its rounded shape, edge chipping occurs, which may lead to cracks. Therefore, to prevent such cracks, edge trimming is sometimes performed to remove the rounded shape of the outer periphery in advance. The laser processing apparatus of the above embodiment can also be applied to such edge trimming.

[0090] In the above embodiment, an example has been shown in which the laser processing apparatus 1 is used sequentially for processing and cleaning wafers. In a modified example, the laser processing apparatus 1 may be used only as a processing apparatus. Alternatively, it may be used only as a cleaning apparatus. Since the laser processing apparatus 1 has both a processing function and a cleaning function, these functions can be used selectively as needed.

[0091] In the above embodiment, as shown in Figures 13 and 14, an example was shown in which the incorporation of fine bubbles into the liquid jet is stopped in the processing mode and is incorporated in the cleaning mode. In a modified example, fine bubbles may be incorporated into the liquid jet even in the processing mode. Whether or not fine bubbles are incorporated may be determined based on whether or not the change in laser intensity distribution caused by light scattering by fine bubbles and the reduction in laser processing point output are at an acceptable level for processing. The control unit 50 controls the fine bubble incorporation unit to ensure laser light guidance by the liquid jet in the processing mode.

[0092] In the above embodiment, as shown in Fig. 13, an example was shown in which a liquid jet is discharged for a predetermined time (set time) in the preparation step before processing. In a modified example, the preparation step may be set not by the liquid jet discharge time but by the number of discharges. The preparation step may be determined to be complete when the number of liquid jet discharges (number of shots) reaches the set number.

[0093] Alternatively, a sensor may be provided to detect air bubbles when they are present inside the cleaning nozzle 34. When air bubbles are no longer detected due to the ejection of the liquid jet in the preparation step, it may be determined that the preparation step is complete.

[0094] In the above embodiment, as shown in Figures 2 and 4, the configuration in which the outlet 34a is both the outlet for the liquid jet LJ and the laser output unit 80, i.e., the liquid jet LJ serves as the light guide path for the laser LB, has been exemplified. In a modified example, a configuration in which the liquid jet does not serve as the light guide path for the laser may be adopted. In this case, although the cleaning nozzle and the laser output unit are provided in the processing head, they are independent of each other. Even with this configuration, by integrating the laser processing function and the cleaning function into a single processing head, the device configuration can be simplified and compact. The processing mode and the cleaning mode can be performed in the processing area.

[0095] In the above embodiment, an example has been shown in which the work table 12 is configured to be movable in the X, Y, and θ directions, and the machining head 20 is configured to be movable in the Z direction. In a modified example, the work table 12 may be configured to be movable in the X and θ directions, and the machining head 20 may be configured to be movable in the Y and Z directions. Alternatively, the work table 12 may be configured to be movable only in the θ direction, and the machining head 20 may be configured to be movable in the X, Y, and Z directions. Other configurations may be adopted as long as the work table 12 and the machining head 20 can move relatively in the X, Y, Z, and θ directions.

[0096] In the above embodiment, the diameter of the discharge port of the cleaning nozzle 34 is set smaller than the street width, specifically, to be approximately the same as the kerf width, so that the diameter of the liquid jet is approximately the same as the kerf width. In a modified example, the diameter of the discharge port may be set equal to or smaller than the kerf width. This makes it easier to achieve jet cleaning that is targeted at debris within the kerf. It also makes it easier to suppress the liquid jet from bouncing around the kerf, stabilizing cleaning. Alternatively, the diameter of the discharge port may be set larger than the kerf width but smaller than the street width.

[0097] In the above embodiment, an example was shown in which a gas jet was simultaneously ejected to stabilize the liquid jet, but if the liquid jet is sufficiently stable, the supply of the gas jet may be omitted. Alternatively, the control unit may switch whether or not to eject the gas jet depending on the cleaning location and cleaning state on the wafer. Also, the flow rate of the gas jet may be changed depending on the cleaning location and cleaning state. In the preparation process before laser processing, the supply of the gas jet may be omitted.

[0098] Although not mentioned in the above embodiment, jet cleaning and spin cleaning may be used in combination in the cleaning process of the wafer W. A cleaning liquid supply unit for performing spin cleaning may be provided, and spin cleaning may be performed at least either before or after jet cleaning.

[0099] In the above embodiment, an example has been shown in which the wafer W is fixed and held on the work table 12. In a modified example, the wafer W may be held in a manner in which it is held by a gripping device (not shown). For example, the peripheral edge of the wafer W may be held by an arm of the gripping device.

[0100] In the above embodiment, a wafer (substrate) is used as an example of the workpiece, but the above embodiment and modifications can be applied to any object to be laser processed, including any laser processing device that requires high-precision cleaning after laser processing of the workpiece.

[0101] Although not mentioned in the above embodiment, the mere act of mixing fine bubbles into the liquid jet that serves as the laser light guide path is expected to have the effect of facilitating the removal of debris during laser processing. Such a laser processing device can be expressed, for example, as follows.

[0102] a workpiece holder that holds the workpiece; a processing head including a laser output unit that outputs a laser for processing the workpiece and a cleaning nozzle that ejects a liquid jet toward the surface of the workpiece, the processing head ejecting the liquid jet as a light guide path for the laser; a movement mechanism that changes the laser irradiation position on the workpiece and the liquid jet ejection position by moving the processing head and the workpiece holder relatively; a fine bubble mixing unit for mixing microbubbles or nanobubbles into the cleaning liquid discharged as the liquid jet; A laser processing device comprising:

[0103] Such a laser processing device can solve the problem of improving the efficiency of debris removal during laser processing in which a laser is output using a liquid jet as a light guide path.

[0104] The present invention is not limited to the above-described embodiments and modifications, and the components can be modified without departing from the spirit of the invention. Various inventions can be formed by appropriately combining multiple components disclosed in the above-described embodiments and modifications. Furthermore, some components can be omitted from all the components shown in the above-described embodiments and modifications. [Explanation of symbols]

[0105] 1 laser processing device, 10 workpiece holder, 12 work table, 14 rotary table, 16 X table, 18 Y table, 20 processing head, 24 Y movement mechanism, 28 X movement mechanism, 30 rotation mechanism, 32 Z table, 34 cleaning nozzle, 34a discharge port, 35 air nozzle, 37 angle adjustment mechanism, 38 Z movement mechanism, 40 cleaning liquid supply unit, 41 liquid supply path, 42 gas supply unit, 43 gas supply path, 44 liquid supply source, 45 branch path, 46 pump, 47 liquid supply path, 48 flow control valve, 50 control unit, 52 gas supply source, 54 opening / closing valve, 60 chamber, 62 inlet port, 64 chamber, 66 inlet port, 70 dicing tape, 72 frame, 80 laser output unit, 100 laser unit, 102 laser oscillator, 104 optical mechanism, 106 Focusing lens, 110 window section, 150 head unit, 152 optical fiber, 154 head unit, 160 tank, 162 fine bubble mixing section, 163 circulation path, 164 pump, 166 fine bubble generating nozzle, 170 fine bubble mixing section, 172 fine bubble tank, 174 supply path, 180 three-way control valve, 201 laser processing device, 210 fine bubble mixing section, 216 flow control valve, 218 injector, 240 cleaning liquid supply section, 301 laser processing device, 310 cleaning section, 312 flow control valve, 320 block, 322 nozzle unit, 324 chamber, 326 liquid supply hole, 350 workpiece holding section, 356 X table, D device, GJ gas jet, K kerf, LB laser, LJ liquid jet, Lm liquid film, S street, W Wafer.

Claims

1. a workpiece holder that holds the workpiece; a processing head including a laser output unit that outputs a laser for processing the workpiece and a cleaning nozzle that ejects a liquid jet toward the surface of the workpiece; a movement mechanism that changes the laser irradiation position on the workpiece and the liquid jet ejection position by moving the processing head and the workpiece holder relatively; a control unit for controlling the output of the laser and the ejection of the liquid jet; Equipped with The control unit switches between a processing mode in which the laser is output to control processing of the workpiece, and a cleaning mode in which the liquid jet is ejected to clean the workpiece while stopping the output of the laser, depending on the processing process of the workpiece.

2. The laser processing device according to claim 1 , wherein the control unit ejects the liquid jet as a light guide path for the laser in the processing mode.

3. 3. The laser processing device according to claim 2, wherein the cleaning nozzle and the laser output unit are provided on the processing head so that a central axis of the liquid jet and an optical axis of the laser are coaxial.

4. The laser processing device according to claim 2 , further comprising an angle adjustment mechanism that adjusts the inclination angle of the cleaning nozzle relative to the surface of the workpiece.

5. a first cleaning unit including the cleaning nozzle and configured to eject the liquid jet; A second cleaning unit that supplies a cleaning liquid to form a liquid film on the surface of the workpiece separately from the liquid jet; The laser processing device according to claim 2 , comprising:

6. 6. The laser processing apparatus according to claim 5, further comprising a fine bubble mixing unit for mixing microbubbles or nanobubbles into the cleaning liquid supplied to form the liquid film.

7. 7. The laser processing device according to claim 5, wherein the flow of the liquid film is formed by holding the workpiece with the workpiece holder so that the surface of the workpiece is inclined with respect to a horizontal plane.

8. a fine bubble mixing unit for mixing microbubbles or nanobubbles into the cleaning liquid discharged as the liquid jet; The laser processing apparatus according to claim 2 , wherein the control unit activates the fine bubble mixing unit in the cleaning mode.

9. a fine bubble mixing unit for mixing microbubbles or nanobubbles into the cleaning liquid discharged as the liquid jet; The fine bubble mixing unit is capable of adjusting the size and density of the microbubbles or nanobubbles, The laser processing apparatus according to claim 2 , wherein the control unit controls the fine bubble mixing unit to ensure that the laser is guided by the liquid jet in the processing mode.

10. The laser processing apparatus according to claim 9, wherein the control unit executes a preparation step of ejecting the liquid jet with the fine bubble mixing unit stopped prior to execution of the processing mode.

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