Laser processing device, irradiation target surface identification method, and laser beam irradiation method

Abstract

To provide a laser processing device capable of monitoring an irradiation position of a laser beam on a polygon mirror.SOLUTION: A laser processing device comprises: a laser oscillator which emits a laser beam; a polygon mirror which has a plurality of reflection surfaces and scans the laser beam by rotation; a condenser which condenses the laser beam scanned by the polygon mirror; a detection target portion which rotates together with the polygon mirror; and a sensor which does not rotate together with the polygon mirror and detects the detection target portion. The laser processing device identifies an irradiation target surface to which the laser beam is irradiated among the plurality of reflection surfaces on the basis of detection of the detection target portion by the sensor.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a laser processing device that scans a laser beam with a polygon mirror, an irradiation surface specifying method that specifies an irradiation surface to be irradiated with a laser beam among a plurality of reflective surfaces of a polygon mirror, and a laser beam irradiation method that irradiates a plurality of reflective surfaces of a polygon mirror with a laser beam. [Background technology]

[0002] The device chip manufacturing process uses a wafer in which devices are formed in multiple regions defined by multiple streets (planned division lines) arranged in a grid pattern. Device chips equipped with devices are manufactured by dividing the wafer along the streets into individual pieces. Device chips are incorporated into various electronic devices such as mobile phones and personal computers.

[0003] Wafer division is achieved using a cutting device that cuts the workpiece with an annular cutting blade. Recently, development has also been underway for a process of dividing wafers by laser processing using a laser processing device. The laser processing device includes a holding table that holds the workpiece and a laser irradiation unit that irradiates the workpiece with a laser beam. The laser irradiation unit incorporates an optical system comprised of various optical elements (mirrors, lenses, etc.), and the laser beam is guided to the workpiece by the optical system. For example, by irradiating the workpiece with a laser beam that is absorbed by the workpiece, ablation processing is performed on the workpiece, resulting in division of the workpiece.

[0004] When a workpiece is irradiated with a laser beam, molten material (debris) is generated in the area irradiated with the laser beam (irradiated area). The molten material may then resolidify in the irradiated area (backfilling, recasting), hindering efficient laser processing. To address this issue, a method has been proposed in which a polygon mirror is installed in the optical system of a laser irradiation unit and the polygon mirror scans the laser beam multiple times at high speed (see Patent Document 1). Using this method, it is possible to perform laser processing on the workpiece while preventing the molten material from resolidifying, thereby improving processing efficiency. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-51536 Summary of the Invention [Problem to be solved by the invention]

[0006] The polygon mirror mounted in the optical system of the laser irradiation unit of the laser processing device is formed in a polygonal prism shape with multiple reflecting surfaces (mirror surfaces). When a laser beam is irradiated onto the polygon mirror rotating at high speed, the laser beam is reflected by the reflecting surfaces whose angles change continuously, causing scanning. Furthermore, as the polygon mirror rotates, the laser beam is incident on the multiple reflecting surfaces in sequence, causing repeated scanning of the laser beam.

[0007] Ideally, a polygon mirror is formed into a regular polygonal prism so that all of its reflective surfaces are parallel to the polygon mirror's axis of rotation. However, in reality, due to errors in the manufacturing process and other factors, it is difficult to perfectly align the angles of all of the reflective surfaces with the polygon mirror's axis of rotation, and there is slight variation in the angles of the reflective surfaces relative to the polygon mirror's axis of rotation. This causes the reflection direction of the laser beam to vary for each reflective surface of the polygon mirror, which can result in the laser beam being irradiated onto unintended areas of the workpiece.

[0008] One possible method for suppressing fluctuations in the laser beam irradiation position due to variations in the angle of the polygon mirror's reflecting surfaces is to correct the laser beam's irradiation position on each reflecting surface. However, because the laser processing device does not perform processing to monitor in real time which reflecting surface of the polygon mirror the laser beam is irradiating during laser processing, it is difficult to achieve control that adjusts the laser beam's irradiation position for each reflecting surface.

[0009] The present invention has been made in view of the above problems, and has as its object to provide a laser processing device, an irradiated surface specifying method, or a laser beam irradiation method that are capable of monitoring the irradiation position of a laser beam on a polygon mirror. [Means for solving the problem]

[0010] According to one aspect of the present invention, there is provided a laser processing device comprising: a laser oscillator that emits a laser beam; a polygon mirror that has a plurality of reflective surfaces and rotates to scan the laser beam; a collector that collects the laser beam scanned by the polygon mirror; a detectable part that rotates together with the polygon mirror; and a sensor that does not rotate together with the polygon mirror and is capable of detecting the detectable part, and based on detection of the detectable part by the sensor, a laser processing device is provided that identifies an irradiated surface among the plurality of reflective surfaces onto which the laser beam is irradiated.

[0011] Preferably, the detection portion is disposed at a position other than the plurality of reflecting surfaces. Also, preferably, the laser processing device further includes a position adjustment unit that adjusts the irradiation position of the laser beam on the irradiated surface for each of the plurality of reflecting surfaces.

[0012] According to another aspect of the present invention, there is provided a method for identifying an irradiated surface among a plurality of reflecting surfaces of a polygon mirror, the method comprising: a detection step of detecting a detectable portion that rotates together with the polygon mirror by a sensor that does not rotate together with the polygon mirror; and a identification step of identifying the irradiated surface among the plurality of reflecting surfaces that is irradiated by the laser beam based on the detection of the detectable portion by the sensor.

[0013] Furthermore, according to another aspect of the present invention, there is provided a laser beam irradiation method for irradiating a laser beam onto a plurality of reflecting surfaces of a polygon mirror, the laser beam irradiation method comprising: a detection step for detecting a detection part that rotates together with the polygon mirror by a sensor that does not rotate together with the polygon mirror; an identification step for identifying an irradiated surface among the plurality of reflecting surfaces onto which the laser beam is to be irradiated based on the detection of the detection part by the sensor; and a laser irradiation step for irradiating the laser beam onto the plurality of reflecting surfaces while adjusting the irradiation position of the laser beam on the irradiated surface for each of the plurality of reflecting surfaces. [Effects of the Invention]

[0014] In the laser processing device, the irradiated surface specifying method, and the laser beam irradiation method according to one aspect of the present invention, the irradiated surface to be irradiated with the laser beam is specified among the multiple reflecting surfaces of the polygon mirror based on the result of detection by a sensor of a detection part that rotates together with the polygon mirror, thereby making it possible to monitor the irradiation position of the laser beam on the polygon mirror. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view showing a laser processing apparatus. [Figure 2] FIG. [Figure 3] FIG. 2 is a schematic diagram showing a laser irradiation unit. [Figure 4] FIG. 2 is a perspective view showing an example of a polygon mirror and an irradiation surface specifying unit. [Figure 5] FIG. 10 is a perspective view showing another example of the polygon mirror and the irradiation surface specifying unit. [Figure 6] FIG. 2 is a front view showing a laser irradiation unit and a measurement unit. [Figure 7] 10 is a flowchart showing a laser beam irradiation method. [Figure 8] FIG. 1 is a perspective view showing a laser processing apparatus when a laser beam irradiation method is performed. [Figure 9] FIG. 10 is a perspective view showing a modified example of the irradiation surface specifying unit. DETAILED DESCRIPTION OF THE INVENTION

[0016] An embodiment according to one aspect of the present invention will be described below with reference to the accompanying drawings. First, a configuration example of a laser processing device according to this embodiment will be described. FIG. 1 is a perspective view showing a laser processing device 2 that performs laser processing on a workpiece 11. In FIG. 1, the X-axis direction (processing feed direction, first horizontal direction, left-right direction) and the Y-axis direction (indexing feed direction, second horizontal direction, front-rear direction) are perpendicular to each other. Furthermore, the Z-axis direction (up-down direction, height direction, vertical direction) is perpendicular to the X-axis direction and the Y-axis direction.

[0017] The laser processing device 2 includes a base 4 that supports each of the components that make up the laser processing device 2. The top surface of the base 4 is a flat surface that is roughly parallel to the horizontal plane (XY plane), and a moving unit (moving mechanism) 6 is provided on the top surface of the base 4. The moving unit 6 includes a Y-axis moving unit (Y-axis moving mechanism) 8 and an X-axis moving unit (X-axis moving mechanism) 18.

[0018] The Y-axis movement unit 8 includes a pair of Y-axis guide rails 10 arranged along the Y-axis direction on the upper surface of the base 4. A flat Y-axis movement table 12 is mounted on the pair of Y-axis guide rails 10 so as to be slidable along the Y-axis guide rails 10.

[0019] A nut portion (not shown) is provided on the rear surface (lower surface) side of the Y-axis moving table 12. A Y-axis ball screw 14, which is disposed along the Y-axis direction between a pair of Y-axis guide rails 10, is threadedly engaged with this nut portion. A Y-axis pulse motor 16 is also connected to the end of the Y-axis ball screw 14. When the Y-axis pulse motor 16 rotates the Y-axis ball screw 14, the Y-axis moving table 12 moves in the Y-axis direction along the Y-axis guide rails 10.

[0020] The X-axis movement unit 18 includes a pair of X-axis guide rails 20 arranged along the X-axis direction on the front (upper) surface side of the Y-axis movement table 12. A flat X-axis movement table 22 is mounted on the pair of X-axis guide rails 20 so as to be slidable along the X-axis guide rails 20.

[0021] A nut portion (not shown) is provided on the rear surface (lower surface) side of the X-axis moving table 22. An X-axis ball screw 24, which is disposed along the X-axis direction between a pair of X-axis guide rails 20, is threadedly engaged with this nut portion. An X-axis pulse motor 26 is connected to the end of the X-axis ball screw 24. When the X-axis pulse motor 26 rotates the X-axis ball screw 24, the X-axis moving table 22 moves in the X-axis direction along the X-axis guide rails 20.

[0022] A holding table (chuck table) 28 is connected to the moving unit 6. The holding table 28 is installed on the surface (upper surface) of the X-axis moving table 22, and holds the workpiece 11 that is the target of laser processing by the laser processing device 2.

[0023] 2 is a perspective view showing a workpiece 11. For example, the workpiece 11 is a disk-shaped wafer made of a semiconductor material such as single crystal silicon, and has a front surface 11a and a back surface 11b that are generally parallel to each other. The workpiece 11 is divided into a plurality of rectangular regions by a plurality of streets (planned division lines) 13 that are arranged in a grid pattern so as to intersect with each other. Devices 15, such as ICs (Integrated Circuits), LSIs (Large Scale Integration), LEDs (Light Emitting Diodes), and MEMS (Micro Electro Mechanical Systems) devices, are formed on the front surface 11a side of each of the plurality of regions divided by the streets 13.

[0024] However, there are no limitations on the type, material, shape, structure, size, etc. of workpiece 11. For example, workpiece 11 may be a substrate (wafer) made of a semiconductor other than silicon (GaAs, InP, GaN, SiC, etc.), sapphire, glass, ceramics, resin, metal, etc. Furthermore, there are no limitations on the type, number, shape, structure, size, arrangement, etc. of devices 15, and workpiece 11 does not necessarily have to have devices 15 formed thereon.

[0025] When processing workpiece 11 with laser processing device 2 (see FIG. 1), workpiece 11 is supported by an annular frame 17 for ease of handling (transporting, holding, etc.) of workpiece 11. Frame 17 is made of metal such as SUS (stainless steel), and has a circular opening 17a at the center thereof that penetrates frame 17 in the thickness direction. The diameter of opening 17a is larger than the diameter of workpiece 11.

[0026] A circular sheet 19 is fixed to the workpiece 11 and the frame 17. For example, the sheet 19 may be a tape including a circular film-like substrate and an adhesive layer (glue layer) provided on the substrate. The substrate is made of a resin such as polyolefin, polyvinyl chloride, or polyethylene terephthalate. The adhesive layer is made of an epoxy-based, acrylic-based, or rubber-based adhesive. The adhesive layer may be made of an ultraviolet-curable resin.

[0027] With the workpiece 11 placed inside the opening 17a of the frame 17, the center of the sheet 19 is attached to the back surface 11b of the workpiece 11, and the outer periphery of the sheet 19 is attached to the frame 17. As a result, the workpiece 11 is supported by the frame 17 via the sheet 19.

[0028] 1, the upper surface of the holding table 28 is a flat surface that is roughly parallel to the horizontal plane (XY plane) and constitutes a holding surface 28a that holds the workpiece 11. The holding surface 28a is connected to a suction source (not shown) such as an ejector via a flow path (not shown), a valve (not shown), and the like formed inside the holding table 28. In addition, a plurality of clamps 30 that grip and fix the frame 17 are provided around the periphery of the holding table 28.

[0029] When the Y-axis moving table 12 is moved along the Y-axis direction, the holding table 28 is moved along the Y-axis direction. When the X-axis moving table 22 is moved along the X-axis direction, the holding table 28 is moved along the X-axis direction. Furthermore, a rotation drive source (not shown), such as a motor, is connected to the holding table 28 to rotate the holding table 28 around a rotation axis that is roughly parallel to the Z-axis direction.

[0030] A rectangular parallelepiped support structure 32 is provided at the rear end of the base 4 (rear of the moving unit 6 and the holding table 28). The support structure 32 is formed so as to protrude upward from the upper surface of the base 4, and the surface (front surface) of the support structure 32 is disposed along the XZ plane. A columnar support member 34 protruding forward from the surface of the support structure 32 is connected to the support structure 32.

[0031] The laser processing device 2 is equipped with a laser irradiation unit 36 ​​that irradiates a laser beam onto the workpiece 11. The laser irradiation unit 36 ​​has a laser processing head 38 attached to the tip of the support member 34. The workpiece 11 held by the holding table 28 is irradiated with a laser beam from the laser processing head 38, thereby subjecting the workpiece 11 to laser processing.

[0032] An imaging unit 40 that captures an image of a subject is provided at the tip of the support member 34. The imaging unit 40 includes an image sensor such as a CCD (Charged-Coupled Devices) sensor or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor, and captures an image of the workpiece 11 held by the holding table 28. There is no limitation on the type of imaging unit 40, and for example, a visible light camera or an infrared camera is used. Based on the image acquired by capturing an image of the workpiece 11 with the imaging unit 40, the alignment of the workpiece 11 with the laser processing head 38, confirmation of the state of the workpiece 11, evaluation of the processing of the workpiece 11, etc. are performed.

[0033] The support member 34 may be connected to the support structure 32 via a Z-axis movement unit (not shown) that moves the support member 34 along the Z-axis direction. For example, a ball screw type movement mechanism is installed as the Z-axis movement unit on the front side of the support structure 32. In this case, by moving (raising and lowering) the support member 34 along the Z-axis direction with the Z-axis movement unit, it is possible to adjust the height position of the focal point of the laser beam emitted from the laser processing head 38, focus the imaging unit 40, etc.

[0034] The laser processing device 2 also includes a measurement unit 42 that measures the position of an area (irradiated area) to be irradiated with the laser beam. The measurement unit 42 receives the laser beam irradiated from the laser irradiation unit 36 ​​and detects the irradiation position of the laser beam. For example, the measurement unit 42 is installed on the X-axis moving table 22 and connected to the moving unit 6 (the Y-axis moving unit 8 and the X-axis moving unit 18). This allows the measurement unit 42 to be moved along the X-axis and Y-axis directions by the moving unit 6. The configuration, function, and use of the measurement unit 42 will be described in detail later (see FIG. 6).

[0035] The laser processing device 2 also includes a display unit (display section, display device) 44 that displays various types of information related to the laser processing device 2. For example, a touch panel is used as the display unit 44. In this case, an operation screen for inputting information into the laser processing device 2 is displayed on the touch panel, and an operator can input information into the laser processing device 2 by touching the touch panel. In other words, the touch panel also functions as an input unit (input section, input device) for inputting various types of information into the laser processing device 2, and is used as a user interface. However, the input unit may be an input device such as a mouse or keyboard that is provided separately and independently from the display unit 44.

[0036] The laser processing device 2 also includes an alarm unit (alarm section, alarm device) 46 that notifies the operator of information. For example, the alarm unit 46 is an indicator light (warning light), which lights up or flashes when an abnormality occurs in the laser processing device 2 to notify the operator of the error. However, there is no limitation on the type of the alarm unit 46. For example, the alarm unit 46 may be a speaker that notifies the operator of information by sound or voice, or may be a transmitter that transmits information to the outside of the laser processing device 2.

[0037] Furthermore, the laser processing device 2 includes a controller (control unit, control section, control device) 48 that controls the laser processing device 2. The controller 48 is connected to each component (movement unit 6, holding table 28, clamp 30, laser irradiation unit 36, imaging unit 40, measurement unit 42, display unit 44, notification unit 46, etc.) that constitutes the laser processing device 2. The controller 48 operates the laser processing device 2 by outputting control signals to each component of the laser processing device 2.

[0038] For example, the controller 48 is configured by a computer. Specifically, the controller 48 includes a processing unit that executes processes such as calculations required for the operation of the laser processing device 2, and a storage unit that stores various information (data, programs, etc.) used for the operation of the laser processing device 2. The processing unit includes a processor such as a CPU (Central Processing Unit). The storage unit includes memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory).

[0039] When laser processing is performed on the workpiece 11, first, the workpiece 11 is held by the holding table 28. For example, the workpiece 11 is placed on the holding table 28 so that the front surface 11a is exposed upward and the back surface 11b (the sheet 19 side) faces the holding surface 28a. In addition, the frame 17 is fixed by a plurality of clamps 30. In this state, when the suction force (negative pressure) of the suction source is applied to the holding surface 28a, the workpiece 11 is sucked and held by the holding table 28 via the sheet 19.

[0040] Next, the laser irradiation unit 36 ​​is activated, and a laser beam is irradiated from the laser processing head 38 onto the workpiece 11. This performs a predetermined laser treatment on the workpiece 11. The irradiation conditions of the laser beam are set appropriately depending on the content of the laser treatment to be performed on the workpiece 11.

[0041] For example, the irradiation conditions of the laser beam are set so that ablation processing is performed on the workpiece 11. Specifically, the wavelength of the laser beam is set so that at least a portion of the laser beam is absorbed by the workpiece 11. In other words, the laser beam is absorbent by the workpiece 11. In addition, other irradiation conditions of the laser beam are also set appropriately so that appropriate ablation processing is performed on the workpiece 11. For example, when the workpiece 11 is a single crystal silicon wafer, the irradiation conditions of the laser beam can be set as follows: Wavelength: 355nm Average output: 2W Repetition frequency: 200kHz Processing feed rate: 400mm / s

[0042] When irradiating the workpiece 11 with a laser beam, the holding table 28 holding the workpiece 11 is rotated to align the length direction of a predetermined street 13 with the X-axis direction. Furthermore, the position of the holding table 28 in the Y-axis direction is adjusted so that the focusing position of the laser beam coincides with the position of the predetermined street 13 in the Y-axis direction. Then, while irradiating the laser beam from the laser processing head 38, the holding table 28 is moved along the X-axis direction (processing feed). As a result, the holding table 28 and the laser processing head 38 move relatively along the X-axis direction, and the laser beam is irradiated along the street 13. Thereafter, by repeating the same procedure, the laser beam is irradiated along all of the streets 13.

[0043] When the laser beam is irradiated onto the workpiece 11 as described above, ablation processing is performed along the streets 13 of the workpiece 11, and laser-processed grooves extending from the front surface 11a to the back surface 11b of the workpiece 11 are formed along the streets 13. This divides the workpiece 11 into a plurality of device chips, each of which includes a device 15 (see FIG. 2). Note that if it is difficult to divide the workpiece 11 by irradiating it with a laser beam once, the laser beam may be irradiated along each street 13 multiple times.

[0044] However, there is no limitation on the type of laser processing performed on the workpiece 11. For example, by irradiating the workpiece 11 with a laser beam, a laser-processed groove having a depth less than the thickness of the workpiece 11 may be formed in the workpiece 11, or a hole may be drilled in the workpiece 11.

[0045] Next, a description will be given of the details of the laser irradiation unit 36. Fig. 3 is a schematic diagram showing the laser irradiation unit 36. The laser irradiation unit 36 ​​irradiates the workpiece 11 with a laser beam 50, thereby performing laser processing such as ablation processing on the workpiece 11.

[0046] The laser irradiation unit 36 ​​includes a laser oscillator 52 such as a YAG laser, a YVO4 laser, or a YLF laser that emits a pulsed laser beam 50, and an output adjustment unit 54 such as an attenuator that adjusts the output of the laser beam 50 emitted from the laser oscillator 52. The laser irradiation unit 36 ​​also includes an optical system 56 that guides the laser beam 50 to the workpiece 11 held by the holding table 28. The optical system 56 includes a plurality of optical elements, and controls the traveling direction, shape, focusing position, etc. of the laser beam 50.

[0047] Specifically, the optical system 56 includes a position adjustment unit 58 that adjusts the irradiation position (traveling direction) of the laser beam 50. The position adjustment unit 58 changes the traveling direction of the laser beam 50, which is emitted from the laser oscillator 52 and has its output adjusted by the output adjustment unit 54, and adjusts the irradiation position on a polygon mirror 64, which will be described later. For example, the position adjustment unit 58 is configured with an acousto-optic deflector (AOD), an electro-optic deflector (EOD), a galvanometer scanner, an optical MEMS, or the like. However, there are no limitations on the configuration of the position adjustment unit 58 as long as it is possible to adjust the traveling direction of the laser beam 50.

[0048] The optical system 56 also includes mirrors 60 and 62 and a polygon mirror 64 that reflect the laser beam 50. For example, dielectric multilayer mirrors are used as the mirrors 60 and 62. The laser beam 50 emitted from the position adjustment unit 58 is reflected by the reflecting surfaces of the mirrors 60 and 62 and is incident on the polygon mirror 64.

[0049] The polygon mirror 64 is formed in a polygonal prism shape, and the side surfaces (outer peripheral surfaces) of the polygon mirror 64 form a plurality of flat reflecting surfaces (mirror surfaces) 66 that reflect the laser beam 50. Each of the reflecting surfaces 66 is connected to an adjacent pair of reflecting surfaces 66, and the connecting portions of the reflecting surfaces 66 form the vertices of the polygon mirror 64.

[0050] A rotary drive source such as a motor that rotates the polygon mirror 64 is connected to the polygon mirror 64. The rotary drive source has a columnar rod (shaft) 68 that corresponds to an output shaft. The rod 68 is arranged along the height direction (thickness direction) of the polygon mirror 64, and the tip of the rod 68 is fixed to the center of the polygon mirror 64. The polygon mirror 64 and the rotary drive source are installed so that a rotation axis 64a of the polygon mirror 64 is along the Y-axis direction. When the rotary drive source is driven, the polygon mirror 64 and the rod 68 rotate around the rotation axis 64a.

[0051] As shown in Fig. 4, for example, the polygon mirror 64 is formed in an octagonal prism shape and has eight reflecting surfaces 66 (reflecting surfaces 66a to 66h). Any one of the reflecting surfaces 66a to 66h corresponds to the irradiated surface 66A onto which the laser beam 50 is irradiated (reflecting surface 66f in Fig. 4). When the polygon mirror 64 rotates, the reflecting surfaces 66a to 66h successively become the irradiated surface 66A. However, the shape of the polygon mirror 64 and the number of reflecting surfaces 66 can be changed as appropriate depending on the specifications of the laser processing device 2, the content of the laser processing, etc.

[0052] When the polygon mirror 64 is rotated around the rotation axis 64a and the laser beam 50 is irradiated onto the polygon mirror 64, the laser beam 50 is reflected by the irradiated surface 66A. Furthermore, the rotation of the polygon mirror 64 changes the angle of the irradiated surface 66A. As a result, the traveling direction of the laser beam 50 changes continuously, and the laser beam 50 scans (disperses) a predetermined scanning area (dispersion area). Then, as the polygon mirror 64 rotates multiple times at high speed, the irradiated surface 66A switches between the reflecting surfaces 66a to 66h in this order. As a result, the laser beam 50 scans the scanning area multiple times at high speed.

[0053] 3, the optical system 56 includes a condenser 70 that condenses the laser beam 50. The condenser 70 includes a condenser lens 72, such as an fθ lens, that condenses the laser beam 50 scanned by the polygon mirror 64 and irradiates the workpiece 11. The laser beam 50 reflected by the irradiated surface 66A of the polygon mirror 64 enters the condenser 70 and is condensed by the condenser lens 72 at a predetermined position (such as the front surface 11a of the workpiece 11, the back surface 11b of the workpiece 11, or the inside of the workpiece 11).

[0054] The position adjustment unit 58 adjusts the irradiation position of the laser beam 50 on the irradiated surface 66A by changing the traveling direction of the laser beam 50. This allows the laser beam 50 to be irradiated at any position on the irradiated surface 66A. Furthermore, by using the position adjustment unit 58 to deflect the traveling direction of the laser beam 50 away from the mirror 60, the irradiation of the laser beam 50 on the irradiated surface 66A is stopped. In other words, the position adjustment unit 58 can also switch whether or not the laser beam 50 is irradiated on the irradiated surface 66A (turning the laser beam 50 on and off).

[0055] It is preferable that the optical system 56 includes a beam damper 74 that blocks the laser beam 50 emitted from the position adjustment unit 58. When stopping the irradiation of the laser beam 50 onto the irradiated surface 66A, the position adjustment unit 58 adjusts the traveling direction of the laser beam 50 so that the laser beam 50 is incident on the beam damper 74. This safely stops the irradiation of the laser beam 50 onto the irradiated surface 66A.

[0056] The optical system 56 that guides the laser beam 50 to the workpiece 11 is configured by the various optical elements described above. However, there are no limitations on the optical elements that configure the optical system 56. For example, the optical system 56 may further include optical elements such as other mirrors and lenses, a polarizing beam splitter (PBS), a diffractive optical element (DOE), and an LCOS-SLM (Liquid Crystal on Silicon - Spatial Light Modulator).

[0057] The laser processing device 2 also includes an irradiated surface specifying unit 80 that specifies an irradiated surface 66A, among the multiple reflective surfaces 66 of the polygon mirror 64, onto which the laser beam 50 is irradiated. For example, the irradiated surface specifying unit 80 includes the controller 48, a detection target 82 that rotates together with the polygon mirror 64, and a sensor 84 that does not rotate together with the polygon mirror 64 but can detect the detection target 82. Note that detection of the detection target 82 by the sensor 84 includes not only cases in which the sensor 84 directly or actively detects the detection target 82, but also cases in which the sensor 84 indirectly or passively detects the detection target 82 by directly or actively detecting an area other than the detection target 82. The irradiated surface specifying unit 80 monitors in real time which reflective surface 66 of the polygon mirror 64 is irradiated with the laser beam 50.

[0058] 4 is a perspective view showing an example of the polygon mirror 64 and the irradiated surface specifying unit 80. For example, the detected portion 82 corresponds to a part of the side surface of the rod 68 connected to the polygon mirror 64. The sensor 84 also includes a light irradiating unit (light irradiating portion, light projecting portion) 86 that irradiates light (detection light) 86a, and a light receiving unit (light receiving portion) 88 that receives the light 86a. The light irradiating unit 86 and the light receiving unit 88 are installed in a state where they are supported by a predetermined support member (not shown) that is independent of the polygon mirror 64, and do not rotate together with the polygon mirror 64.

[0059] For example, the light emitting unit 86 includes a light source such as an LED, and emits light 86a emitted from the light source to the outside. However, the light emitting unit 86 may be connected to the light source via an optical fiber or the like. The light receiving unit 88 includes a photoelectric conversion element that converts the light 86a that has reached the light receiving unit 88 into an electric signal (voltage), and generates a signal (received light amount signal) corresponding to the amount of light received by the light receiving unit 88.

[0060] Light 86a emitted from light irradiation unit 86 is irradiated onto rod 68 and reflected by the side surface of rod 68. Then, light 86a reflected by the side surface of rod 68 reaches light receiving unit 88, and the intensity (amount of received light) of light 86a incident on light receiving unit 88 is detected by light receiving unit 88.

[0061] Here, the detectable portion 82 is configured so that the reflection characteristics of the light 86a for the area where the detectable portion 82 is provided differ from the reflection characteristics of the light 86a for the area where the detectable portion 82 is not provided. For example, the detectable portion 82 is formed so that the reflectance of the light 86a irradiated onto the detectable portion 82 is lower than the reflectance of the light 86a irradiated onto the part of the rod 68 where the detectable portion 82 is not provided.

[0062] When the sensor 84 is operated while the polygon mirror 64 and the rod 68 are rotated around the rotation axis 64a, the light irradiation unit 86 irradiates the side surface of the rod 68 with light 86a while the detected part 82 is rotating together with the polygon mirror 64 and the rod 68. The light 86a reflected by the side surface of the rod 68 is then received by the light receiving unit 88.

[0063] At this time, the intensity of the light 86a received by the light receiving unit 88 differs depending on whether or not the light 86a is irradiated onto the detection target portion 82. Specifically, while the light 86a is irradiated onto the detection target portion 82, the light 86a is less likely to be reflected by the side surface of the rod 68 than when the light 86a is irradiated onto a portion of the rod 68 where the detection target portion 82 is not provided. As a result, the amount of light 86a that reaches the light receiving unit 88 decreases, and the amount of light received by the light receiving unit 88 also decreases.

[0064] When the detected part 82 and the sensor 84 are configured as described above, it becomes possible to identify the position (rotation angle) of the detected part 82 based on a change in the amount of light received by the light-receiving unit 88. For example, by comparing the amount of light received by the light-receiving unit 88 with a predetermined reference value (reference value) that has been set in advance, it is possible to determine whether the detected part 82 is positioned at a predetermined position (the upper end of the rod 68 in FIG. 4).

[0065] The specific configuration of the detection target portion 82 is not limited as long as it is possible to create a difference in the reflection characteristics of light 86a between an area where the detection target portion 82 is provided and an area where the detection target portion 82 is not provided. Furthermore, the detection target portion 82 may be configured to be detachable from the rod 68, or may be formed on the rod 68 itself.

[0066] For example, the detected portion 82 is formed of a black sticker that absorbs light 86a and is attached to a part of the side surface of the rod 68. This reduces the amount of light received by the light-receiving unit 88 only while the detected portion 82 is being irradiated with light 86a. Furthermore, the detected portion 82 may be minute irregularities formed on the side surface of the rod 68, or may be a member having minute irregularities fixed to the side surface of the rod 68. In this case, when the light 86a is irradiated onto the detected portion 82, the light 86a scatters, making it difficult for the light 86a to reach the light-receiving unit 88, and the amount of light received by the light-receiving unit 88 decreases.

[0067] In order to clearly distinguish whether or not the light 86a is irradiated onto the detection target 82, it is preferable to ensure a certain level of difference between the reflectance R1 of the light 86a for the area where the detection target 82 is provided and the reflectance R2 of the light 86a for the area where the detection target 82 is not provided. For example, the detection target 82 is configured so that the reflectance R1 is 50% or less of the reflectance R2, and preferably 30% or less.

[0068] The position of the detected portion 82 is set so that the irradiated surface 66A of the polygon mirror 64 and the detected portion 82 have a predetermined positional relationship. For example, the detected portion 82 is provided on a portion of the side surface of the rod 68 that faces the reflective surface 66a of the polygon mirror 64. The sensor 84 is also positioned so that the light 86a is irradiated onto the upper end of the rod 68.

[0069] When the positions of the detection target portion 82 and the sensor 84 are set as described above, the detection target portion 82 is positioned at the upper end of the rod 68 and detected by the sensor 84 at the moment when the reflecting surface 66a becomes the upper surface of the polygon mirror 64 and the reflecting surface 66f becomes the irradiated surface 66A. This makes it possible to identify the irradiated surface 66A based on the detection of the detection target portion 82 by the sensor 84.

[0070] However, the positions of the detected portion 82 and the sensor 84 are not limited to those described above. For example, the detected portion 82 may be detected by the sensor 84 at the timing when any one of the reflecting surfaces 66a to 66e, 66g, and 66h becomes the irradiated surface 66A. Furthermore, the detected portion 82 may be provided so as to face any one of the reflecting surfaces 66b to 66h, or may be provided at a position on the tip surface of the rod 68 away from the rotation axis 64a.

[0071] Fig. 5 is a perspective view showing another example of the polygon mirror 64 and the irradiated surface specifying unit 80. As shown in Fig. 5, the detected portion 82 can also be provided on the side surface of the polygon mirror 64. In this case, the detected portion 82 is configured so that the reflection characteristics (reflectance, etc.) of the light 86a irradiated to the detected portion 82 differ from the reflection characteristics (reflectance, etc.) of the light 86a irradiated to a portion of the polygon mirror 64 where the detected portion 82 is not provided.

[0072] For example, the detected portion 82 is provided on a portion of the side surface of the polygon mirror 64 adjacent to the reflective surface 66a of the polygon mirror 64. The sensor 84 is positioned so that the light 86a is irradiated onto the upper end of the side surface of the polygon mirror 64. In this case, the detected portion 82 is detected by the sensor 84 at the moment when the reflective surface 66a becomes the upper surface of the polygon mirror 64 and the reflective surface 66f becomes the irradiated surface 66A.

[0073] In this way, the detection target 82 rotating together with the polygon mirror 64 is detected by the sensor 84. Then, the sensor 84 outputs a signal (received light amount signal) corresponding to the amount of light received by the light receiving unit 88 (intensity of the light 86a) to the controller 48 (see FIG. 3).

[0074] Although the above description has been given of the case where the detected part 82 is provided on the side surface of the rod 68 (see FIG. 4) or the side surface of the polygon mirror 64 (see FIG. 5), there are no restrictions on where the detected part 82 is provided as long as it is a place that rotates together with the polygon mirror 64. For example, the detected part 82 may be provided on the reflective surface 66 of the polygon mirror 64, or on another member (other than the rod 68) connected to the polygon mirror 64. Furthermore, the detected part 82 may be provided on a rotating member that is installed independently of the polygon mirror 64 and rotates at the same rotation speed (angular velocity) as the polygon mirror 64.

[0075] However, it is particularly preferable to place the detected portion 82 at a position other than the reflecting surface 66 of the polygon mirror 64. In this case, the reflection characteristics of the light 86a on the reflecting surface 66 do not matter, and therefore the reflecting surface 66 of the polygon mirror 64 can be configured by taking into consideration only the reflection characteristics of the laser beam 50 on the reflecting surface 66. This makes it easier to design and implement the polygon mirror 64.

[0076] 3, the laser processing device 2 includes a measurement unit 42 that measures the position of an area (irradiated area) irradiated with the laser beam 50 scanned by the polygon mirror 64. For example, the measurement unit 42 is provided on the X-axis moving table 22 adjacent to the holding table 28.

[0077] For example, the measurement unit 42 is configured by a beam profiler capable of measuring the spatial intensity distribution of the laser beam 50. In this case, the intensity distribution of the laser beam 50 scanned by the polygon mirror 64 is measured by the measurement unit 42.

[0078] 6 is a front view showing the laser irradiation unit 36 ​​and the measurement unit 42. For example, the measurement unit 42 includes a columnar support structure 100 connected to a moving unit 6. A moving unit (moving mechanism) 102 is provided on the front side of the support structure 100. A measuring device 104 that measures the intensity distribution of the laser beam 50 is connected to the moving unit 102.

[0079] The moving unit 102 is configured by a ball screw type moving mechanism, for example, similar to the Y-axis moving unit 8 and the X-axis moving unit 18 (see FIG. 1), and moves (lifts and lowers) the measuring device 104 along the Z-axis direction. By lifting and lowering the measuring device 104, the positional relationship between the polygon mirror 64 and the measuring device 104 can be adjusted.

[0080] The measuring instrument 104 includes a housing 106 that houses the components of the measuring instrument 104. A microscope 108 that magnifies the laser beam 50 is provided at the top end of the housing 106. The magnification of the microscope 108 is set appropriately depending on the diameter, shape, etc. of the laser beam 50, and is, for example, between 5x and 100x. The housing 106 also houses an attenuation optical system 110 that attenuates the laser beam 50, and an imaging unit 112 that receives and images the laser beam 50.

[0081] The attenuation optical system 110 guides the laser beam 50 to the imaging unit 112 while attenuating the intensity of the laser beam 50 expanded by the microscope 108. For example, the attenuation optical system 110 is configured with an ND (Neutral Density) filter that reduces the amount of light in the laser beam 50. However, there are no limitations on the type and configuration of the attenuation optical system 110, and for example, an attenuator configured to include multiple prisms can also be used.

[0082] The imaging unit 112 detects and images the laser beam 50 that has been magnified by the microscope 108 and attenuated by the attenuation optical system 110. Specifically, the imaging unit 112 is configured to include an optical sensor such as a CMOS sensor, and has a light-receiving surface 112a that receives the laser beam 50. The imaging unit 112 then measures the intensity distribution of the laser beam 50 received by the light-receiving surface 112a using the optical sensor.

[0083] With the measurement unit 42 positioned directly below the polygon mirror 64, the polygon mirror 64 is rotated while the laser beam 50 is irradiated onto the polygon mirror 64, and the laser beam 50 scanned by the polygon mirror 64 is irradiated onto the measurement unit 42. The laser beam 50 then enters the microscope 108 and is magnified, and is attenuated by the attenuation optical system 110, after which it reaches the imaging unit 112 and is detected by the imaging unit 112.

[0084] When the imaging unit 112 detects the laser beam 50, the intensity of the laser beam 50 is measured in an area (irradiated area) of the light-receiving surface 112a that is irradiated with the laser beam 50. This identifies the position of the area irradiated with the laser beam 50. For example, an area of ​​the light-receiving surface 112a where the intensity of the laser beam 50 is detected or an area where the intensity of the laser beam 50 is equal to or greater than a predetermined threshold corresponds to the area irradiated with the laser beam 50.

[0085] As described above, the position of the region irradiated by the laser beam 50 can be extracted from the intensity distribution of the laser beam 50 measured by the measurement unit 42 (beam profiler). However, there are no limitations on the type of measurement unit 42 as long as it is possible to identify the position of the region irradiated by the laser beam 50. For example, the measurement unit 42 may be a wavefront sensor that is capable of detecting the wavefront of the laser beam 50 and generating a phase distribution of the wavefront of the laser beam 50. In this case, the region irradiated by the laser beam 50 is reflected in the phase distribution of the wavefront, and the position of the region irradiated by the laser beam 50 can be extracted from the phase distribution of the wavefront of the laser beam 50.

[0086] When the measurement unit 42 is mounted on the laser processing device 2, the position of the irradiated area of ​​the laser beam 50 scanned by the polygon mirror 64 can be identified by the measurement unit 42. This eliminates the need for a complicated process, such as experimentally processing a test sample with the laser beam 50 and identifying the position of the irradiated area of ​​the laser beam 50 from the positions of the laser processing marks formed on the sample. As a result, the task of checking the position of the irradiated area of ​​the laser beam 50 is simplified.

[0087] 6 has been described as an example in which the laser beam 50 that has passed through the condenser 70 is measured by the measurement unit 42. However, the device configuration for identifying the position of the irradiated area of ​​the laser beam 50 scanned by the polygon mirror 64 is not limited to the above. For example, the laser processing device 2 may be provided with a measurement unit that measures the position of the irradiated area of ​​the laser beam 50 between the polygon mirror 64 and the condenser 70, instead of the measurement unit 42.

[0088] The measurement unit is configured to be movable, for example, between a measurement position located on the path of the laser beam 50 between the polygon mirror 64 and the condenser 70 and a retracted position off the path of the laser beam 50. When measuring the intensity distribution of the laser beam 50, the measurement unit is positioned at the measurement position and measures the position of the irradiated area of ​​the laser beam 50 between the polygon mirror 64 and the condenser 70. In this way, the measurement unit can be installed at any position on the side of the polygon mirror 64 in the traveling direction of the laser beam 50 (downstream side).

[0089] 3 is connected to the components of the laser irradiation unit 36 ​​(the measurement unit 42, the laser oscillator 52, the output adjustment unit 54, the position adjustment unit 58, the rotation drive source of the polygon mirror 64, the sensor 84 (the light irradiation unit 86 and the light receiving unit 88), etc.). The controller 48 outputs control signals to the components of the laser irradiation unit 36 ​​to control the operation of each component, thereby processing the workpiece 11 with the laser beam 50.

[0090] When laser processing is performed by irradiating the workpiece 11 with the laser beam 50, molten material (debris) is generated in the area irradiated with the laser beam 50 (the irradiated area). If the molten material resolidifies in the irradiated area (backfilling, recasting), efficient laser processing is hindered. However, by irradiating the laser beam 50 onto the polygon mirror 64 rotating at high speed and scanning the laser beam 50 multiple times at high speed, it becomes possible to perform laser processing on the workpiece 11 while preventing the molten material from resolidifying.

[0091] Ideally, the polygon mirror 64 is formed in the shape of a regular polygonal prism so that all of the reflecting surfaces 66 are parallel to the rotation axis 64a of the polygon mirror 64. However, in reality, it is difficult to align the angles of all of the reflecting surfaces 66 with the rotation axis 64a due to errors in the manufacturing process, etc., and there is slight variation in the angles of the reflecting surfaces 66 with respect to the rotation axis 64a of the polygon mirror 64. If a reflecting surface 66 that is slightly inclined with respect to the rotation axis 64a of the polygon mirror 64 and is not parallel to the rotation axis 64a becomes the irradiated surface 66A, the focusing position of the laser beam 50 will vary, and there is a risk that the laser beam 50 will be irradiated onto an unintended area of ​​the workpiece 11.

[0092] Therefore, in this embodiment, the irradiated surface specifying unit 80 specifies the irradiated surface 66A, among the multiple reflective surfaces 66 of the polygon mirror 64, onto which the laser beam 50 is irradiated. This makes it possible to monitor in real time which reflective surface 66 of the polygon mirror 64 is irradiated with the laser beam 50 during laser processing, and to adjust the irradiation position of the laser beam 50 on the irradiated surface 66A for each reflective surface 66. As a result, fluctuations in the focusing position of the laser beam 50 due to variations in the angle of the reflective surface 66 are suppressed, and it is possible to prevent the laser beam 50 from irradiating an unintended area of ​​the workpiece 11.

[0093] Below, we will explain a specific example of a laser beam irradiation method (a method for processing a workpiece) in which the laser beam 50 is irradiated onto a plurality of reflecting surfaces 66 provided on the polygon mirror 64. In this embodiment, the laser beam 50 is scanned by the polygon mirror 64 while adjusting the irradiation position of the laser beam 50 on the irradiated surface 66A for each of the plurality of reflecting surfaces 66.

[0094] FIG. 7 is a flowchart showing a laser beam irradiation method. FIG. 8 is a perspective view showing the laser processing device 2 when the laser beam irradiation method is being performed. The laser beam irradiation method according to this embodiment is realized by sequentially performing a measurement step S1, a detection step S2, an identification step S3, and a laser irradiation step S4. Of the above-described laser beam irradiation method, the process particularly including the detection step S2 and the identification step S3 corresponds to an irradiation surface identification method that identifies an irradiation surface 66A to be irradiated with the laser beam 50. Hereinafter, the irradiation surface identification method and the laser beam irradiation method according to this embodiment will be described in detail, mainly with reference to FIGS. 7 and 8.

[0095] In the above-described irradiated surface specifying method and laser beam irradiation method, each component of the laser processing device 2 is controlled by a controller 48. As shown in Fig. 8, the controller 48 includes an specifying unit 48a that specifies the irradiated surface 66A of the polygon mirror 64, and an adjusting unit 48b that controls the position adjusting unit 58 to adjust the irradiation position of the laser beam 50. The controller 48 also includes a storage unit (memory) 48c that can store various information (data, programs, etc.) used in the processing in the specifying unit 48a and the adjusting unit 48b.

[0096] The storage unit 48c stores in advance information (irradiated surface information) indicating the relationship between the detection of the detection target portion 82 by the sensor 84 and the irradiated surface 66A of the polygon mirror 64. Specifically, the irradiated surface information indicates the reflective surface 66 that becomes the irradiated surface 66A when the detection target portion 82 is detected by the sensor 84. For example, if the polygon mirror 64 and the irradiated surface specifying unit 80 are configured as shown in FIG. 8, the irradiated surface information indicates that the reflective surface 66f becomes the irradiated surface 66A when the detection target portion 82 is detected by the sensor 84. The irradiated surface information may be set by an operator and input to the controller 48, or may be generated by the controller 48.

[0097] In the laser beam irradiation method according to this embodiment, first, the position of the irradiated area to be irradiated with the laser beam 50 scanned by the polygon mirror 64 is measured for each of the plurality of reflecting surfaces 66 (measurement step S1). In measurement step S1, the position of the irradiated area of ​​the laser beam 50 is measured for each of the reflecting surfaces 66 by the measurement unit 42 shown in Fig. 6. Then, information (correction information) indicating the amount of correction for the irradiation position of the laser beam 50 on the irradiated surface 66A for each of the reflecting surfaces 66 is stored in the storage unit 48c.

[0098] 6, the measuring unit 42 is moved along the X-axis and Y-axis directions by the moving unit 6 until it is positioned directly below the polygon mirror 64. Then, the laser beam 50 is irradiated onto the rotating polygon mirror 64, and the laser beam 50 is scanned by the polygon mirror 64. As a result, the laser beam 50 scanned by the polygon mirror 64 is irradiated onto the measuring unit 42.

[0099] The measurement unit 42 measures the position of the irradiated area of ​​the laser beam 50 scanned by the polygon mirror 64. Specifically, as described above, the measurement unit 42 measures the intensity distribution of the laser beam 50 and extracts the position (scanning position) of the irradiated area of ​​the laser beam 50 from the intensity distribution of the laser beam 50. The measurement unit 42 also measures the position of the irradiated area of ​​the laser beam 50 when the laser beam 50 is irradiated onto the reflecting surfaces 66a to 66h. In this way, the position of the irradiated area of ​​the laser beam 50 is measured for each of the plurality of reflecting surfaces 66.

[0100] The position of the irradiated area of ​​the laser beam 50 measured by the measurement unit 42 is output to the controller 48 (see FIG. 8). The controller 48 then calculates, for each of the reflecting surfaces 66a to 66h, the amount of correction to the irradiation position of the laser beam 50 required to scan the laser beam 50 at a desired position. This correction amount corresponds to the difference between the position where the laser beam 50 should originally be irradiated and the position of the irradiated area of ​​the laser beam 50 measured by the measurement unit 42.

[0101] For example, assume that the reflecting surfaces 66a to 66e, 66g, and 66h are parallel to the rotation axis 64a of the polygon mirror 64, and the reflecting surface 66f is slightly tilted with respect to the rotation axis 64a due to an error in the manufacturing process or the like. In this case, while the laser beam 50 is irradiated onto the reflecting surfaces 66a to 66e, 66g, and 66h, the laser beam 50 scans normally along the linear path A along which it should be irradiated. On the other hand, when the laser beam 50 is irradiated onto the reflecting surface 66f, the tilt of the reflecting surface 66f causes the reflection direction of the laser beam 50 to fluctuate, and the laser beam 50 scans along a path A' that is different from the linear path A along which it should be irradiated.

[0102] In the above case, the controller 48 calculates the difference (error) in the positions in the Y-axis direction between the path A and the path A'. For example, the coordinates of the path A are stored in advance in the memory unit 48c, and the controller 48 calculates the difference between the coordinates of the path A and the coordinates of the area to be irradiated with the laser beam 50 (the coordinates of the path A') measured by the measurement unit 42. Then, the controller 48 determines the amount of correction for the irradiation position of the laser beam 50 on the irradiated surface 66A for each of the reflecting surfaces 66a to 66h so that the position to be irradiated with the laser beam 50 coincides with the position that should originally be processed.

[0103] Specifically, when the laser beam 50 is irradiated onto the reflecting surfaces 66a to 66e, 66g, and 66h, the position where the laser beam 50 should be irradiated and the position where the laser beam 50 is actually irradiated coincide with each other. Therefore, correction of the irradiation position of the laser beam 50 is not necessary (correction amount = 0). On the other hand, when the laser beam 50 is irradiated onto the reflecting surface 66f, it is necessary to adjust the irradiation position of the laser beam 50 on the reflecting surface 66f so that the position where the laser beam 50 is actually irradiated (path A') coincides with the position where the laser beam 50 should originally be irradiated (path A). The amount of variation in the irradiation position of the laser beam 50 on the reflecting surface 66f at this time corresponds to the correction amount.

[0104] As described above, in the measurement step S1, the position of the irradiated area of ​​the laser beam 50 scanned by the polygon mirror 64 is measured by the measurement unit 42 for each of the plurality of reflecting surfaces 66. Then, the controller 48 stores the correction amount for each of the plurality of reflecting surfaces 66 as correction information in the memory unit 48c.

[0105] However, the method for measuring the position of the region irradiated with the laser beam 50 is not limited to measurement by the measurement unit 42. For example, in the measurement step S1, a test sample may be experimentally processed using the polygon mirror 64, and the position of the region irradiated with the laser beam 50 may be identified based on the processing results. In this case, the measurement unit 42 can be omitted from the laser processing device 2.

[0106] Specifically, first, the sample is held on the holding table 28 (see FIGS. 1 and 3). Then, the sample is irradiated with a laser beam 50 while being scanned by a polygon mirror 64. As a result, the sample is processed by the laser beam 50, and a linear processing mark is formed on the sample. The position where this processing mark is formed corresponds to the position of the area irradiated with the laser beam 50. Thereafter, the sample is imaged, for example, by the imaging unit 40 (see FIG. 1), and an image of the processing mark formed on the sample is acquired. Then, the controller 48 identifies the position of the processing mark, i.e., the position of the area irradiated with the laser beam 50, based on the image of the processing mark.

[0107] It is also possible to measure the tilt of the multiple reflecting surfaces 66 of the polygon mirror 64 and identify the position of the area to be irradiated with the laser beam 50 based on the tilt of the reflecting surfaces 66. For example, a tilt measuring device (not shown) that measures the tilt of the multiple reflecting surfaces 66 of the polygon mirror 64 is installed near the polygon mirror 64. An autocollimator, for example, can be used as the tilt measuring device. The tilt measuring device measures the tilt of the reflecting surfaces 66a-66h with respect to the rotation axis 64a of the polygon mirror 64 and outputs the measured tilt to the controller 48. Then, the controller 48 calculates the position of the area to be irradiated with the laser beam 50 for each of the reflecting surfaces 66a-66h based on the tilt of the reflecting surfaces 66a-66h measured by the tilt measuring device.

[0108] Furthermore, the inclinations of the multiple reflecting surfaces 66 of the polygon mirror 64 may be measured and recorded before the polygon mirror 64 is mounted on the laser processing device 2. In this case, the position of the region to be irradiated with the laser beam 50 and the amount of correction are calculated based on the previously recorded inclinations of the reflecting surfaces 66 and stored in the storage unit 48c of the controller 48. The position of the region to be irradiated with the laser beam 50 and the amount of correction may be calculated outside the laser processing device 2 and then input to the controller 48 by an operator, or the controller 48 may calculate them based on the inclinations of the reflecting surfaces 66.

[0109] Next, laser processing of the workpiece 11 is carried out by the laser processing device 2. First, a control signal is input from the controller 48 to a rotation drive source (not shown) connected to the polygon mirror 64, causing the polygon mirror 64 to rotate at high speed together with the rod 68. There is no limit to the rotation speed of the polygon mirror 64, and it is set to, for example, about 500 rotations per second. In addition, the laser beam 50 emitted from the position adjustment unit 58 is reflected by mirrors 60 and 62, irradiated onto the polygon mirror 64, and scanned by the polygon mirror 64.

[0110] At this time, the irradiated surface specifying method according to the present embodiment specifies an irradiated surface 66A to be irradiated with the laser beam 50 among the multiple reflecting surfaces 66 of the polygon mirror 64. Specifically, a detection step S2 in which the sensor 84 detects the detection target portion 82, and a specifying step S3 in which the irradiated surface 66A is specified based on the detection of the detection target portion 82 by the sensor 84 are performed.

[0111] In the detection step S2, the sensor 84 is activated to detect the detection target portion 82. Specifically, light 86a emitted from the light irradiation unit 86 is irradiated onto the rod 68, which rotates together with the polygon mirror 64. The light 86a reflected by the rod 68 reaches the light receiving unit 88 and is received by the light receiving unit 88. The light receiving unit 88 generates an electrical signal corresponding to the amount of light 86a received, and outputs the electrical signal to the identification unit 48a of the controller 48.

[0112] As described above, the reflection characteristics of the light 86a differ depending on whether the light 86a is irradiated onto the detection target portion 82 provided on the rod 68, and the amount of light received by the light-receiving unit 88 also differs. Therefore, the identifying unit 48a determines whether the detection target portion 82 has been detected by the sensor 84 based on the signal (amount of received light) input from the light-receiving unit 88. For example, the identifying unit 48a determines whether the detection target portion 82 has been detected by the sensor 84 by comparing the amount of light received by the light-receiving unit 88 with a predetermined reference value (threshold value) stored in advance in the memory unit 48c.

[0113] In the identifying step S3, an irradiated surface 66A of the plurality of reflecting surfaces 66 that is irradiated with the laser beam 50 is identified based on the detection of the detection target portion 82 by the sensor 84. Specifically, when it is determined that the detection target portion 82 has been detected by the sensor 84, the identifying unit 48a refers to the irradiated surface information stored in the storage unit 48c and identifies the irradiated surface 66A of the plurality of reflecting surfaces 66 that is irradiated with the laser beam 50. The identifying unit 48a then outputs a signal (irradiated surface signal) indicating the irradiated surface 66A to the adjusting unit 48b. For example, when the sensor 84 shown in FIG. 8 detects the detection target portion 82, the identifying unit 48a refers to the irradiated surface information and identifies the reflective surface 66f as the irradiated surface 66A, and outputs an irradiated surface signal indicating that the reflective surface 66f is the irradiated surface 66A to the adjusting unit 48b.

[0114] After the irradiated surface specifying method (detection step S2 and specification step S3) is performed as described above, the laser beam 50 is irradiated onto the plurality of reflecting surfaces 66 of the polygon mirror 64. At this time, based on the position of the irradiated area of ​​the laser beam 50 measured by the measurement unit 42 in the measurement step S1, the irradiation position of the laser beam 50 on the irradiated surface 66A is adjusted for each of the plurality of reflecting surfaces 66 (laser irradiation step S4).

[0115] In the laser irradiation step S4, irradiated surface signals are sequentially input from the identification unit 48a to the adjustment unit 48b. For example, the identification unit 48a continuously outputs irradiated surface signals indicating which of the reflecting surfaces 66a-66h is the irradiated surface 66A to the adjustment unit 48b in real time, based on the rotation angle of the polygon mirror 64 and the elapsed time since the sensor 84 detected the detection target portion 82. Specifically, the irradiated surface signal input from the identification unit 48a to the adjustment unit 48b is switched every time the polygon mirror 64 rotates 45°.

[0116] The adjuster 48b accesses the storage unit 48c and reads out the correction information acquired in the measurement step S1. Then, the adjuster 48b refers to the correction information and sequentially outputs to the position adjustment unit 58 a signal (correction signal) indicating the amount of correction for the irradiation position of the laser beam 50 on the reflecting surface 66 indicated by the irradiated surface signal. For example, when the identifier 48a inputs an irradiated surface signal indicating that the reflecting surface 66f is the irradiated surface 66A to the adjuster 48b, the adjuster 48b refers to the correction information and outputs to the position adjustment unit 58 the amount of correction for the irradiation position of the laser beam 50 on the reflecting surface 66f.

[0117] Then, at the timing when the laser beam 50 actually irradiates the reflecting surface 66, the position adjustment unit 58 corrects the irradiation position of the laser beam 50 on the reflecting surface 66. In this way, the irradiation position of the laser beam 50 on the irradiated surface 66A is adjusted for each of the multiple reflecting surfaces 66. As a result, the focusing position of the laser beam 50 is corrected during scanning with the laser beam 50, and the laser beam 50 scans along the path A along which it should originally be irradiated. In Figure 8, the path of the laser beam 50 before the irradiation position is corrected is shown by a dashed line, and the path of the laser beam 50 after the irradiation position is corrected is shown by a solid line.

[0118] The workpiece 11 is machined by the laser beam 50, the irradiation position of which has been adjusted as described above. For example, by irradiating the laser beam 50 along the streets 13 (see FIG. 2 ) of the workpiece 11 as described above, the workpiece 11 is subjected to ablation processing, and the workpiece 11 is divided along the streets 13. In this case, path A is set at the center of the street 13 in the width direction, and the laser beam 50 is scanned by the polygon mirror 64 so that the focusing position of the laser beam 50 is positioned on path A.

[0119] If there is angular variation in the reflecting surface 66 of the polygon mirror 64, the focusing position of the laser beam 50 will be positioned on path A', which is shifted from path A. If the laser beam 50 is scanned in this state, the ablation processing position will be shifted, which may result in processing defects such as damage to the device 15 or dimensional variations in the device chip. However, as shown in FIG. 8 , by adjusting the irradiation position of the laser beam 50 on the irradiated surface 66A, the focusing position of the laser beam 50 reflected by the inclined reflecting surface 66 is corrected from path A' to path A. This allows the laser beam 50 to scan while maintaining the focusing position positioned on path A, even if there is variation in the angle of the reflecting surface 66. As a result, processing accuracy is improved and processing defects are suppressed.

[0120] The irradiation position of the laser beam 50 in the X-axis direction can also be adjusted by changing the timing at which the laser beam 50 irradiates the polygon mirror 64 (the on / off timing of the laser beam 50). Specifically, the irradiation position of the laser beam 50 in the X-axis direction can be adjusted by controlling the timing at which the irradiation destination of the laser beam 50 emitted from the position adjustment unit 58 is switched from the mirror 60 to the beam damper 74 (see FIG. 3) and the timing at which the irradiation destination is switched from the beam damper 74 to the mirror 60.

[0121] As described above, by sequentially performing the measurement step S1 to the laser irradiation step S4, the laser beam 50 can be irradiated onto the workpiece 11 while adjusting the irradiation position of the laser beam 50 on the polygon mirror 64 for each of the multiple reflecting surfaces 66, thereby performing laser processing on the workpiece 11. Note that the measurement step S1 to the laser irradiation step S4 are realized by executing a program stored in the controller 48. Specifically, the storage unit 48c stores a program for generating control signals that operate each component of the laser irradiation unit 36 ​​according to the above procedure. The controller 48 then reads and executes the program, thereby automatically executing the measurement step S1 to the laser irradiation step S4.

[0122] As described above, the laser processing device 2 according to this embodiment identifies the irradiated surface 66A, among the multiple reflecting surfaces 66 of the polygon mirror 64, onto which the laser beam 50 is irradiated, based on the result of detection by the sensor 84 of the detection target portion 82 that rotates together with the polygon mirror 64. This makes it possible to monitor the irradiation position of the laser beam 50 on the polygon mirror 64. Furthermore, the laser processing device 2 according to this embodiment includes a position adjustment unit 58 that adjusts the irradiation position of the laser beam 50 on the irradiated surface 66A for each reflecting surface 66. This makes it possible to suppress fluctuations in the position of the irradiated region of the laser beam 50 due to variations in the angle of the reflecting surfaces 66, etc.

[0123] In the above embodiment, an example has been described in which the detection target 82 detected by the sensor 84 is disposed at a position other than the reflecting surface 66 of the polygon mirror 64 (see FIGS. 4 and 5, etc.). However, if there is no problem with the design of the polygon mirror 64 or if there are circumstances that make it difficult to provide the detection target 82 at a position other than the reflecting surface 66, any of the multiple reflecting surfaces 66 can be used as the detection target.

[0124] 9 is a perspective view showing an irradiated surface specifying unit 80A which is a modified example of the irradiated surface specifying unit 80. The irradiated surface specifying unit 80A is made up of a controller 48 and a sensor 120 mounted on the laser irradiation unit .

[0125] At least one of the multiple reflecting surfaces 66 of the polygon mirror is set as a detected surface (detected portion) 66B that is detected by the sensor 120. As an example, the following describes a case where the reflecting surface 66a is the detected surface 66B.

[0126] The sensor 120 detects the detection surface 66B from among the multiple reflecting surfaces 66 provided on the polygon mirror 64. Then, the controller 48 identifies the irradiation surface 66A to be irradiated with the laser beam 50 based on the detection of the detection surface 66B by the sensor 120.

[0127] Specifically, the sensor 120 includes a light emitting unit (light emitting section, light projecting section) 122 that emits light (detection light) 122a, and a light receiving unit (light receiving section) 124 that receives the light 122a. The configurations, functions, etc. of the light emitting unit 122 and the light receiving unit 124 are similar to those of the light emitting unit 86 and the light receiving unit 88 (see FIG. 8, etc.), respectively. The light 122a emitted from the light emitting unit 122 is irradiated onto and reflected by the reflecting surface 66 of the polygon mirror 64. The light 122a reflected by the reflecting surface 66 is then received by the light receiving unit 124, and the intensity (amount of received light) of the light 122a is detected by the light receiving unit 124.

[0128] The optical system of the sensor 120 is appropriately designed so that light 122a emitted from the light emitting unit 122 is reflected by the reflecting surface 66 and received by the light receiving unit 124. For example, the sensor 120 includes a polarizing beam splitter 126 and a lens 128.

[0129] The polarizing beam splitter 126 reflects the light 122a emitted from the light irradiation unit 122 toward the reflecting surface 66 of the polygon mirror 64. Furthermore, the lens 128 focuses the light 122a reflected by the polarizing beam splitter 126 and causes it to travel toward the reflecting surface 66 of the polygon mirror 64. A collimator lens, for example, is used as the lens 128. The light 122a reflected by the reflecting surface 66 of the polygon mirror 64 passes through the lens 128 and the polarizing beam splitter 126 and enters the light receiving unit 124. As a result, the light 122a is received by the light receiving unit 124.

[0130] The detection surface 66B of the polygon mirror 64 is configured so that the reflection characteristics of the light 122a incident on the detection surface 66B differ from the reflection characteristics of the light 122a incident on the reflecting surfaces 66 other than the detection surface 66B. As an example, the reflectance of the light 122a incident on the detection surface 66B is higher than the reflectance of the light 122a incident on the reflecting surfaces 66 other than the detection surface 66B.

[0131] For example, the reflective surface of the polygon mirror 64 is configured by a laminate of multiple thin films (hafnium oxide film, silicon oxide film, etc.). In this case, by employing different laminate structures (thickness, number of layers, material, etc. of thin films) for the reflective surface 66 that becomes the detection surface 66B and the other reflective surfaces 66, it is possible to make the reflectance of the light 122a incident on the detection surface 66B different from the reflectance of the light 122a incident on the reflective surfaces 66 other than the detection surface 66B.

[0132] When the multiple reflecting surfaces 66 of the polygon mirror 64 are configured as described above, the intensity of the light 122a received by the light receiving unit 124 differs depending on whether the reflecting surface 66 irradiated with the light 122a is the detection surface 66B or not. This makes it possible to detect the detection surface 66B based on the amount of light received by the light receiving unit 124.

[0133] In order to clearly distinguish between the detection surface 66B and the other reflecting surfaces 66 based on the amount of light received by the light receiving unit 124, it is preferable to ensure a certain level of difference between the reflectance R1' of the light 122a with respect to the detection surface 66B and the reflectance R2' of the light 122a with respect to the other reflecting surfaces 66. For example, the polygon mirror 64 is configured so that one of the reflectance R1' and the reflectance R2' is at least two times, preferably at least three times, the other.

[0134] The light receiving unit 124 outputs a signal (light receiving amount signal) corresponding to the amount of light received by the light receiving unit 124 (the intensity of the light 86a) to the controller 48. The memory section 48c of the controller 48 also stores information (irradiated surface information) indicating the positional relationship of the irradiated surface 66A with respect to the detected surface 66B.

[0135] The irradiated surface information indicates the reflecting surface 66 that becomes the irradiated surface 66A when the detected surface 66B is detected by the sensor 120. For example, when the polygon mirror 64 and the irradiated surface specifying unit 80A are configured as shown in Fig. 9, the irradiated surface information indicates that the reflecting surface 66 located three planes ahead of the detected surface 66B in the rotation direction of the polygon mirror 64 is the irradiated surface 66A. More specifically, when the reflecting surface 66a is set as the detected surface 66B, the irradiated surface information indicates that the reflecting surface 66f is the irradiated surface 66A.

[0136] When the laser processing device 2 performs laser processing on the workpiece 11, the laser beam 50 is irradiated onto the irradiated surface 66A of the polygon mirror 64 and scanned by the polygon mirror 64. The sensor 120 is also activated to detect the detected surface 66B of the polygon mirror 64. Specifically, light 122a irradiated from the light irradiation unit 122 passes through the polarizing beam splitter 126 and the lens 128 and is incident on the reflecting surface 66 of the polygon mirror 64, and is reflected by the reflecting surface 66. Then, at the timing when the traveling direction of the light 122a incident on the reflecting surface 66 becomes approximately perpendicular to the reflecting surface 66, the light 122a reaches the light receiving unit 124 via the lens 128 and the polarizing beam splitter 126 and is received by the light receiving unit 124. The light receiving unit 124 generates an electrical signal corresponding to the amount of light 122a received and outputs the electrical signal to the identification unit 48a of the controller 48.

[0137] As described above, the reflection characteristics of the light 122a and the amount of light received by the light receiving unit 124 differ depending on whether the reflecting surface 66 onto which the light 122a emitted from the light emitting unit 122 is incident is the detection surface 66B. Therefore, the identification unit 48a determines whether the reflecting surface 66 detected by the sensor 120 is the detection surface 66B based on the signal (amount of received light) input from the light receiving unit 124. For example, the identification unit 48a compares the amount of light received by the light receiving unit 124 with a predetermined reference value (threshold value) stored in advance in the storage unit 48c to determine whether the reflecting surface 66 onto which the light 122a is incident is the detection surface 66B (detection step S2).

[0138] When the reflecting surface 66 detected by the sensor 120 is determined to be the detected surface 66B, the identifying unit 48a refers to the irradiated surface information stored in the storage unit 48c and identifies the irradiated surface 66A, among the multiple reflecting surfaces 66, that is irradiated with the laser beam 50 (identification step S3). The identifying unit 48a then outputs a signal (irradiated surface signal) indicating the irradiated surface 66A to the adjusting unit 48b. For example, when the sensor 120 shown in FIG. 9 detects the reflecting surface 66a, the identifying unit 48a refers to the irradiated surface information and identifies the reflecting surface 66f as the irradiated surface 66A, and outputs an irradiated surface signal indicating that the reflecting surface 66f is the irradiated surface 66A to the adjusting unit 48b.

[0139] The adjuster 48b refers to the correction information stored in the memory 48c and sequentially outputs to the position adjuster 58 (see FIG. 8 ) a signal (correction signal) indicating the amount of correction for the irradiation position of the laser beam 50 on the reflecting surface 66 indicated by the irradiated surface signal. For example, when the identifier 48a inputs an irradiated surface signal indicating that the reflecting surface 66f is the irradiated surface 66A to the adjuster 48b, the adjuster 48b refers to the correction information and outputs the amount of correction for the irradiation position of the laser beam 50 on the reflecting surface 66f to the position adjuster 58. Then, at the timing when the laser beam 50 actually irradiates the reflecting surface 66, the position adjuster 58 corrects the irradiation position of the laser beam 50 on the reflecting surface 66. As a result, the irradiation position of the laser beam 50 on the irradiated surface 66A is adjusted for each of the multiple reflecting surfaces 66 (laser irradiation step S4).

[0140] Although the above description has been given of a case where one of the multiple reflective surfaces 66 of the polygon mirror 64 is set as the detection surface 66B, the configuration of the polygon mirror 64 is not limited to this. For example, instead of setting the detection surface 66B, the multiple reflective surfaces 66 may be configured so that the reflection characteristics (reflectance, etc.) of the light 122a are different for all of the reflective surfaces 66. In this case, the amount of light received by the light receiving unit 124 differs for each reflective surface 66 onto which the light 122a is irradiated. Therefore, the identification unit 48a can identify the reflective surface 66a onto which the light 122a is incident based on the amount of light received by the light receiving unit 124.

[0141] In addition, the structures, methods, etc. according to the above-described embodiments can be modified as appropriate without departing from the scope of the object of the present invention. [Explanation of symbols]

[0142] 11 Workpiece 11a surface 11b Back side 13th Street (Planned division line) 15 devices 17 frames 17a aperture 19 sheets 2. Laser processing equipment 4 Foundation 6. Mobile unit (mobile mechanism) 8 Y-axis movement unit (Y-axis movement mechanism) 10 Y-axis guide rail 12 Y-axis moving table 14 Y-axis ball screw 16 Y-axis pulse motor 18 X-axis movement unit (X-axis movement mechanism) 20 X-axis guide rail 22 X-axis moving table 24 X-axis ball screw 26 X-axis pulse motor 28 Holding table (chuck table) 28a Holding surface 30 Clamp 32 Support structure 34 Support member 36 Laser irradiation unit 38 Laser processing head 40 Imaging unit 42 Measuring Unit 44 Display unit (display unit, display device) 46 Alarm unit (alarm unit, alarm device) 48 Controller (control unit, control section, control device) 48a Specific part 48b Adjustment part 48c Memory 50 Laser Beam 52 Laser oscillator 54 Output Adjustment Unit 56 Optical system 58 Position adjustment unit 60,62 mirror 64 Polygon Mirror 64a Rotation axis 66, 66a to 66h Reflective surface (mirror surface) 66A Irradiated surface 66B Detected surface (detected part) 68 Rod (shaft) 70 Concentrator 72 Condenser Lens 74 Beam Dumper 80,80A Irradiation surface identification unit 82 Detected part 84 sensors 86 Light irradiation unit (light irradiation part, light projection part) 86a Light (detection light) 88 Light receiving unit (light receiving part) 100 Support structure 102 Mobile unit (mobile mechanism) 104 Measuring instruments 106 Case 108 Microscope 110 Attenuation Optical System 112 Imaging unit 112a Photosensitive surface 120 sensors 122 Light irradiation unit (light irradiation part, light projection part) 122a Light (detection light) 124 Light receiving unit (light receiving part) 126 Polarizing Beam Splitter 128 Lens

Claims

1. a laser oscillator that emits a laser beam; a polygon mirror having a plurality of reflecting surfaces and rotating to scan the laser beam; a condenser that condenses the laser beam scanned by the polygon mirror; a detection target portion that rotates together with the polygon mirror; a sensor that does not rotate together with the polygon mirror and is capable of detecting the detection portion, The laser processing device specifies the irradiated surface to be irradiated with the laser beam among the plurality of reflecting surfaces based on the detection of the detection portion by the sensor.

2. The laser processing apparatus according to claim 1 , wherein the detection target is disposed at a position other than the plurality of reflecting surfaces.

3. 3. The laser processing apparatus according to claim 1, further comprising a position adjustment unit that adjusts the irradiation position of the laser beam on the irradiation surface for each of the plurality of reflecting surfaces.

4. A method for identifying an irradiated surface to be irradiated with a laser beam among a plurality of reflecting surfaces of a polygon mirror, the method comprising: a detecting step of detecting the detection target portion that rotates together with the polygon mirror by a sensor that does not rotate together with the polygon mirror; and a specifying step of specifying the irradiated surface to be irradiated with the laser beam among the plurality of reflecting surfaces based on the detection of the detection portion by the sensor.

5. A laser beam irradiation method for irradiating a laser beam onto a plurality of reflecting surfaces of a polygon mirror, comprising: a detecting step of detecting the detection target portion that rotates together with the polygon mirror by a sensor that does not rotate together with the polygon mirror; a step of identifying an irradiated surface to be irradiated with the laser beam among the plurality of reflecting surfaces based on the detection of the detection portion by the sensor; a laser irradiation step of irradiating the laser beam onto the plurality of reflecting surfaces and adjusting the irradiation position of the laser beam on the irradiated surface for each of the plurality of reflecting surfaces.

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