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

Abstract

A laser processing device capable of monitoring the irradiation position of a laser beam on a polygon mirror. [Solution] A laser processing device comprising: a laser oscillator that emits a laser beam; a polygon mirror that has multiple reflecting surfaces and rotates to scan the laser beam; a collector that collects the laser beam scanned by the polygon mirror; an irradiation unit that irradiates measurement light incident on the reflecting surface; and a light receiving unit that receives the measurement light reflected by the reflecting surface, the measurement unit being arranged so that the amount of measurement light received by the light receiving unit changes depending on the angle between the ray of the measurement light and the reflecting surface; and a controller that identifies the irradiated surface among the multiple reflecting surfaces to be irradiated with the laser beam based on the time interval during which the amount of measurement light received by the light receiving unit after being reflected by the reflecting surface of the rotating polygon mirror reaches a predetermined reference value.

Description

[Technical Field]

[0001] The present invention relates to a laser processing device that scans a laser beam with a polygon mirror, a laser beam irradiation method that scans a laser beam with a polygon mirror and irradiates a workpiece with the laser beam, and an irradiated surface identification method that identifies an irradiated surface that is to be irradiated with the laser beam from among a plurality of reflective surfaces of a polygon mirror. [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 re-solidify 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 becomes possible to perform laser processing on the workpiece while preventing the molten material from re-solidifying, 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 rotation axis of the polygon mirror. 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 rotation axis of the polygon mirror, and there is slight variation in the angles of the reflective surfaces relative to the rotation axis of the polygon mirror. 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 an unintended area 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 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, a laser beam irradiation method, or an irradiated surface specifying 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 reflecting surfaces and rotates to scan the laser beam; a collector that collects the laser beam scanned by the polygon mirror; an irradiation unit that irradiates measurement light incident on the reflecting surface; and a light-receiving unit that receives the measurement light reflected by the reflecting surface, the measurement unit being arranged so that the amount of measurement light received by the light-receiving unit changes depending on the angle between the ray of the measurement light and the reflecting surface; and a controller that identifies an irradiated surface among the plurality of reflecting surfaces to be irradiated with the laser beam based on the time interval during which the amount of measurement light reflected by the reflecting surface of the rotating polygon mirror and received by the light-receiving unit reaches a predetermined reference value.

[0011] Preferably, the laser processing device further includes a position adjusting 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 laser beam irradiation method for scanning a laser beam with a polygon mirror having a plurality of reflecting surfaces and irradiating the laser beam onto a workpiece, the laser beam irradiation method comprising: a measurement step of irradiating measurement light toward the reflecting surface while rotating the polygon mirror, and measuring the amount of received measurement light reflected by the reflecting surface, which amount changes depending on the angle between the ray of the measurement light and the reflecting surface; an irradiation surface identification step of identifying an irradiated surface among the plurality of reflecting surfaces onto which the laser beam is to be irradiated, based on the time interval at which the amount of received light measured in the measurement step reaches a predetermined reference value; and an irradiation step of irradiating the workpiece with the laser beam by adjusting the irradiation position of the laser beam on the irradiated surface for each of the plurality of reflecting surfaces.

[0013] Furthermore, according to another aspect of the present invention, there is provided an irradiated surface identification method for identifying an irradiated surface, among a plurality of reflecting surfaces of a polygon mirror, onto which a laser beam is irradiated, the irradiated surface identification method comprising: a measurement step of irradiating measurement light toward the reflecting surface while the polygon mirror is rotated, and measuring the amount of received measurement light reflected by the reflecting surface, which amount changes depending on the angle between the ray of the measurement light and the reflecting surface; and an irradiated surface identification step of identifying the irradiated surface, among the plurality of reflecting surfaces, onto which the laser beam is irradiated, based on the time interval at which the amount of received light measured in the measurement step reaches a predetermined reference value. [Effects of the Invention]

[0014] In the laser processing device, the laser beam irradiation method, and the irradiated surface identification method according to one aspect of the present invention, the irradiated surface to be irradiated with the laser beam among a plurality of reflecting surfaces is identified based on the time interval during which the received light amount of the measurement light reflected by the reflecting surface of the rotating polygon mirror reaches a predetermined reference value, 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 a polygon mirror. [Figure 5] 10 is a flowchart showing a laser beam irradiation method. [Figure 6] FIG. 10 is a schematic diagram showing the laser processing device in a preparation step. [Figure 7] Figure 7(A) is a front view showing the measurement unit at a first time, Figure 7(B) is a front view showing the measurement unit at a second time, Figure 7(C) is a front view showing the measurement unit at a third time, and Figure 7(D) is a front view showing the measurement unit at a fourth time. [Figure 8] 10 is a graph showing the relationship between the time during which measurement light is irradiated onto a rotating polygon mirror and the amount of measurement light received. [Figure 9] FIG. 1 is a perspective view showing a laser processing device that scans a laser beam using a polygon mirror. [Figure 10] FIG. 2 is a plan view showing a part of the object to be processed. [Figure 11] FIG. 10 is a front view showing a modified example of the measurement 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 apparatus according to this embodiment will be described. FIG. 1 is a perspective view showing a laser processing apparatus 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 placed on the surface (upper surface) of the X-axis moving table 22, and holds the workpiece 11.

[0023] 2 is a perspective view showing the workpiece 11. The workpiece 11 corresponds to a workpiece to be laser processed by the laser processing device 2. 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.

[0024] The workpiece 11 is divided into a plurality of rectangular regions by a plurality of streets (planned division lines) 13 arranged in a grid pattern so as to intersect with one another. 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 surface 11a side of each of the plurality of regions divided by the streets 13.

[0025] However, there are no limitations on the type, material, shape, structure, size, etc. of the workpiece 11. For example, the 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 the devices 15, and the workpiece 11 does not necessarily have to have any devices 15 formed thereon.

[0026] When processing the workpiece 11 with the laser processing device 2 (see FIG. 1), the workpiece 11 is supported by an annular frame 17 for ease of handling (transporting, holding, etc.) the workpiece 11. The frame 17 is made of a metal such as SUS (stainless steel), and has a circular opening 17a at the center thereof that penetrates the frame 17 in the thickness direction. The diameter of the opening 17a is larger than the diameter of the workpiece 11.

[0027] 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. However, the sheet 19 may also be a thermocompression sheet that does not have an adhesive layer and can be thermocompression bonded to the workpiece 11 and the frame 17.

[0028] 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. In this way, the workpiece 11 is supported by the frame 17 via the sheet 19.

[0029] 1, the upper surface of holding table 28 is a flat surface that is roughly parallel to the horizontal plane (XY plane) and constitutes holding surface 28a that holds workpiece 11. 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 holding table 28. In addition, a plurality of clamps 30 that grip and fix frame 17 are provided around holding table 28.

[0030] 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.

[0031] 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.

[0032] 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 ​​includes a laser processing head 38 attached to the tip of the support member 34. The laser processing head 38 irradiates a laser beam onto the workpiece 11 held by the holding table 28, thereby subjecting the workpiece 11 to laser processing.

[0033] 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.

[0034] 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.

[0035] 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 position to be irradiated with 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).

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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).

[0040] When laser processing is performed on the workpiece 11, the workpiece 11 is first 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. The frame 17 is also 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.

[0041] 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 conditions for irradiating the laser beam are set appropriately depending on the content of the laser treatment to be performed on the workpiece 11.

[0042] 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

[0043] 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.

[0044] 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 including 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 a plurality of times.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] Specifically, the optical system 56 includes a position adjustment unit 58 that adjusts the irradiation position (traveling direction, light ray 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.

[0049] 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.

[0050] The polygon mirror 64 is formed in the shape of a polygonal pillar, 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. In addition, the polygon mirror 64 has a rotation axis 64a that runs along the thickness direction of the polygon mirror 64 and passes through the center of the polygon mirror 64.

[0051] 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 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 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.

[0052] 4 is a perspective view showing the polygon mirror 64. For example, the polygon mirror 64 is formed in an octagonal prism shape and has eight reflective surfaces 66 (reflective surfaces 66a to 66h). However, the shape of the polygon mirror 64 and the number of reflective surfaces 66 can be selected appropriately depending on the specifications of the laser processing device 2 and the content of the laser processing.

[0053] Any one of the reflecting surfaces 66a to 66h corresponds to the irradiated surface 66A onto which the laser beam 50 is irradiated. When the polygon mirror 64 rotates, the reflecting surfaces 66a to 66h sequentially become the irradiated surface 66A. Any one of the reflecting surfaces 66a to 66h corresponds to the irradiated surface 66B onto which light (measurement light) emitted by a measuring unit 82 (see FIG. 3) described below is irradiated. FIG. 4 shows, as an example, a case where the reflecting surface 66 corresponding to the upper surface of the polygon mirror 64 is set as the irradiated surface 66B. Details of the irradiated surface 66B will be described later.

[0054] 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 is sequentially switched among the reflecting surfaces 66a to 66h. As a result, the laser beam 50 scans the scanning area multiple times at high speed.

[0055] 3, the optical system 56 includes a condenser 70 that condenses the laser beam 50. The condenser 70 includes a condensing 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 condensing lens 72 at a predetermined position (such as the front surface 11a, rear surface 11b, or inside of the workpiece 11).

[0056] 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).

[0057] 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.

[0058] 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).

[0059] The laser processing device 2 also includes an irradiated surface specifying unit 80 that specifies an irradiated surface 66A to be irradiated with the laser beam 50 among the multiple reflective surfaces 66 of the polygon mirror 64. 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.

[0060] For example, the irradiated surface specifying unit 80 is configured by the controller 48 and a measurement unit 82 mounted on the laser irradiation unit 36. The measurement unit 82 is configured by an optical sensor that irradiates light toward the reflecting surface 66 of the polygon mirror 64 and measures the amount of light reflected by the reflecting surface 66. Then, the controller 48 specifies the irradiated surface 66A to be irradiated with the laser beam 50 based on the amount of light received measured by the measurement unit 82.

[0061] The measurement unit 82 includes an irradiation unit (light irradiation section, light projection section) 84 that irradiates measurement light 86, and a light receiving unit (light receiving section) 88 that receives the measurement light 86. For example, the irradiation unit 84 includes a light source such as an LED, and irradiates the measurement light 86 emitted from the light source to the outside. However, the irradiation unit 84 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 measurement light 86 that reaches the light receiving unit 88 into an electrical signal (voltage), and generates a signal (received light amount signal) corresponding to the amount of received measurement light 86.

[0062] The measurement light 86 emitted from the irradiation unit 84 travels (propagates) along a ray 86a and is incident on the reflecting surface 66 of the polygon mirror 64. The measurement light 86 reflected by the reflecting surface 66 is received by the light receiving unit 88, and the amount (intensity) of the measurement light 86 received is detected. The ray 86a is a line representing the travel path (propagation path) of the measurement light 86, and the energy of the measurement light 86 propagates along the ray 86a. In the measurement unit 82, the optical axis of the measurement unit 82 corresponds to the ray 86a of the measurement light 86.

[0063] The measurement unit 82 is appropriately configured so that measurement light 86 emitted from the irradiation unit 84 is reflected by the reflecting surface 66 and received by the light receiving unit 88. For example, the measurement unit 82 includes a polarizing beam splitter 90 and a lens 92.

[0064] The polarizing beam splitter 90 reflects the measurement light 86 emitted from the irradiation unit 84 toward the reflecting surface 66 of the polygon mirror 64. The lens 92 focuses the measurement light 86 reflected by the polarizing beam splitter 90 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 92. The measurement light 86 reflected by the reflecting surface 66 of the polygon mirror 64 passes through the lens 92 and the polarizing beam splitter 90 and enters the light-receiving unit 88. As a result, the measurement light 86 is received by the light-receiving unit 88.

[0065] The controller 48 is connected to the components of the laser irradiation unit 36 ​​(the laser oscillator 52, the output adjustment unit 54, the position adjustment unit 58, the rotation drive source of the polygon mirror 64, the measurement unit 82 (the irradiation unit 84 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.

[0066] When the workpiece 11 is irradiated with a laser beam 50 to perform laser processing, 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 a 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.

[0067] 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 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 fluctuate, and there is a risk that the laser beam 50 will be irradiated onto an unintended area of ​​the workpiece 11.

[0068] 4 exaggerates an example in which 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 inclined with respect to the rotation axis 64a. If the reflecting surface 66f is inclined with respect to the rotation axis 64a, the reflection direction of the laser beam 50 fluctuates when the laser beam 50 is irradiated onto the reflecting surface 66f, causing an error in the scanning position of the laser beam 50.

[0069] 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 correct 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.

[0070] Hereinafter, a specific example of a laser beam irradiation method (a method for processing a workpiece) will be described, in which a polygon mirror 64 having a plurality of reflecting surfaces 66 is used to scan the laser beam 50 and irradiate the workpiece 11. 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.

[0071] 5 is a flowchart showing a laser beam irradiation method. In the laser beam irradiation method according to this embodiment, first, a preparation step S0 is performed, and information necessary for identifying the irradiated surface 66A of the polygon mirror 64 and correcting the irradiation position of the laser beam 50 is acquired. Thereafter, a measurement step S1, an irradiated surface identification step S2, and an irradiation step S3 are performed in order, whereby the irradiation position of the laser beam 50 on the irradiated surface 66A is adjusted for each reflecting surface 66, and the laser beam 50 is irradiated onto the workpiece 11. Note that, among the above-described laser beam irradiation method, the portion including the measurement step S1 and the irradiated surface identification step S2 in particular corresponds to the irradiated surface identification method according to this embodiment.

[0072] 6 is a schematic diagram showing the laser processing device 2 in the preparation step S0. In the preparation step S0, a preliminary measurement step S01, a reflecting surface information registration step S02, and a correction amount information registration step S03 are performed in this order. Each step included in the preparation step S0 will be described in detail below.

[0073] In the laser beam irradiation method according to this embodiment, each component of the laser processing device 2 is controlled by a controller 48. The controller 48 includes a storage unit (memory) 48a that stores various information (data, programs, etc.) necessary for the operation of the laser processing device 2.

[0074] In the preparation step S0, first, a pre-measurement step S01 is performed to measure the amount of received measurement light 86 reflected by the reflecting surface 66 of the polygon mirror 64. In the pre-measurement step S01, the polygon mirror 64 is attached to the laser irradiation unit 36. Then, while the polygon mirror 64 is rotating at a predetermined speed, the measurement unit 82 is operated to irradiate the measurement light 86 toward the reflecting surface 66 of the polygon mirror 64. As a result, the measurement light 86 is irradiated sequentially onto the multiple reflecting surfaces 66, and the measurement light 86 reflected by the multiple reflecting surfaces 66 is sequentially received by the light-receiving unit 88.

[0075] Here, the measurement unit 82 is disposed so that the amount of measurement light 86 received by the light-receiving unit 88 changes depending on the angle between a ray 86a of the measurement light 86 and the reflecting surface 66. For example, the light-receiving unit 88 is disposed so that the amount of measurement light 86 received is maximized when the angle between the ray 86a of the measurement light 86 incident on the irradiated surface 66B and the irradiated surface 66B becomes perpendicular. In the light-receiving unit 88 shown in Fig. 6, the irradiation unit 84, the polarizing beam splitter 90, and the lens 92 are disposed so that the ray 86a of the measurement light 86 incident on the irradiated surface 66B is aligned along the Z-axis direction, and the light-receiving unit 88 is installed on the extension of the ray 86a of the measurement light 86 incident on the irradiated surface 66B.

[0076] When the measurement unit 82 is configured as described above, the amount of received measurement light 86 reaches a maximum each time the ray 86a of the measurement light 86 and the irradiated surface 66B of the rotating polygon mirror 64 are perpendicular to each other. Ideally, the shape of the polygon mirror 64 is a perfect regular polygonal prism, and the time interval during which the amount of received measurement light 86 reaches a maximum is also constant. For example, if the polygon mirror 64 is formed into a regular octagonal prism, the amount of received measurement light 86 reaches a maximum each time the polygon mirror 64 rotates 45°. However, in reality, it is difficult to form the polygon mirror 64 into a perfect regular polygonal prism due to the aforementioned manufacturing errors, and slight variations in the angles between the multiple reflecting surfaces 66 exist. Therefore, the time interval during which the amount of received measurement light 86 reaches a maximum is not strictly constant.

[0077] 7(A) to 7(D) show a measurement unit 82 that measures the amount of received measurement light 86. As an example, assume that there is a manufacturing error in the reflecting surface 66a, and the angle between the reflecting surface 66a and the reflecting surface 66b is larger than the angle between the reflecting surface 66a and the reflecting surface 66h. For ease of explanation, in FIGS. 7(A) to 7(D), the manufacturing error in the reflecting surface 66a is exaggerated, and the ideal reflecting surface 66a is indicated by a dashed line.

[0078] 7A is a front view showing the measurement unit 82 at a first time point. When the polygon mirror 64 is rotated and irradiated with measurement light 86, the reflecting surface 66h becomes the irradiated surface 66B at a certain timing. At this time, the measurement light 86 is irradiated onto the reflecting surface 66h, and the light-receiving unit 88 receives the measurement light 86 reflected by the reflecting surface 66h. Then, at the first time point, the ray 86a of the measurement light 86 incident on the reflecting surface 66h becomes perpendicular to the reflecting surface 66h, and the amount of measurement light 86 received by the light-receiving unit 88 becomes maximum.

[0079] 7B is a front view showing the measurement unit 82 at a second time. At a second time when the polygon mirror 64 has rotated 45° from the first time, the reflecting surface 66a becomes the irradiated surface 66B. The measuring light 86 is irradiated onto the reflecting surface 66a, and the light-receiving unit 88 receives the measuring light 86 reflected by the reflecting surface 66a. However, due to a manufacturing error of the reflecting surface 66a, the reflecting surface 66a is not perpendicular to the ray 86a of the measuring light 86 at the second time. Therefore, the measuring light 86 is reflected by the reflecting surface 66a in a direction inclined with respect to the Z-axis direction, and the amount of the measuring light 86 received by the light-receiving unit 88 is not maximized.

[0080] 7(C) is a front view showing the measurement unit 82 at a third time. At the third time when the polygon mirror 64 has rotated slightly from the second time, the ray 86a of the measurement light 86 incident on the reflecting surface 66a becomes perpendicular to the reflecting surface 66a. At this time, the amount of the measurement light 86 received by the light-receiving unit 88 becomes maximum.

[0081] 7(D) is a front view showing the measurement unit 82 at a fourth time. When the polygon mirror 64 rotates further from the third time, the reflecting surface 66b becomes the irradiated surface 66B, and at the fourth time, the light beam 86a of the measurement light 86 and the reflecting surface 66b become perpendicular to each other. At this time, the amount of the measurement light 86 received by the light-receiving unit 88 becomes maximum.

[0082] If the polygon mirror 64 were formed in an ideal regular octagonal prism shape, the amount of received measuring light 86 would be maximized every time the polygon mirror 64 rotated 45°. However, if there were manufacturing errors in the reflecting surface 66a as described above, even if the polygon mirror 64 rotated 45° from the first time point (see FIG. 7A) at which the amount of received measuring light 86 reflected by the reflecting surface 66h was maximized, the amount of received measuring light 86 reflected by the reflecting surface 66a would not be maximized (see FIG. 7B). Furthermore, the amount of received measuring light 86 reflected by the reflecting surface 66b would be maximized (see FIG. 7D) before the polygon mirror 64 rotated 45° from the third time point (see FIG. 7C) at which the amount of received measuring light 86 reflected by the reflecting surface 66a was maximized. Thus, variations occur in the intervals at which the amount of received measuring light 86 is maximized.

[0083] FIG. 8 is a graph showing the relationship between the time when the measuring light 86 is irradiated onto the rotating polygon mirror 64 and the amount of light received by the measuring light 86. In FIG. 8, the solid line shows the transition of the amount of light received when the measuring light 86 is irradiated onto a polygon mirror 64 having variations in the angle of the reflecting surface 66. On the other hand, the dashed line shows the hypothetical transition of the amount of light received when the measuring light 86 is irradiated onto a polygon mirror 64 formed in an ideal regular octagonal prism shape. Also, FIG. 8 shows the time when the predetermined reference value (threshold value) I of the amount of light received is set. ref This shows:

[0084] When the measuring light 86 is irradiated onto the reflecting surfaces 66a to 66h of the polygon mirror 64, peaks P1 to P8 appear in the amount of received measuring light 86. The amount of received measuring light 86 reaches a maximum value when the ray 86a of the measuring light 86 and the reflecting surfaces 66a to 66h, which are the irradiated surface 66B, become perpendicular to each other. Times t1 to t8 in FIG. 8 correspond to the times when the ray 86a of the measuring light 86 and the reflecting surfaces 66a to 66h become perpendicular to each other. The amount of received measuring light 86 is equal to or exceeds a reference value I during times t1 to t8 and a certain period before and after the times. ref That's all.

[0085] If the polygon mirror 64 were an ideal regular octagonal prism, the peaks in the amount of received light would appear at regular intervals (see the peaks indicated by the dashed lines in FIG. 8). However, since there is slight variation in the angle of the reflecting surface 66 of the actual polygon mirror 64, there would also be variation in the intervals between times t1 and t8 at which the amount of received light reaches its peak value. As a result, the amount of received light would not exceed the reference value I ref the time interval T 12 ~T 78 ) also varies. For convenience of explanation, in FIG. 8, the time interval T 12 ~T 78 The variability is exaggerated.

[0086] Also, the time interval T 12 ~T 78 The variation in reflectivity of the measurement light 86 can also be caused by variation in the reflectivity of the multiple reflecting surfaces 66. For example, the reflecting surface 66 of the polygon mirror 64 is configured by a laminate of multiple thin films (hafnium oxide film, silicon oxide film, etc.). However, it is difficult in the manufacturing process to make the thickness of the thin films completely uniform on all the reflecting surfaces 66, and the thickness of the thin films may vary among the reflecting surfaces 66. In this case, the reflectivity of the measurement light 86 differs slightly among the multiple reflecting surfaces 66a to 66h.

[0087] If the reflectance of the measuring light 86 differs among the reflecting surfaces 66a to 66h, the amount of the measuring light 86 reaching the light receiving unit 88 varies, and the peaks P1 to P8 of the amount of received light differ in height. As a result, the amount of received light at each of the peaks P1 to P8 is greater than the reference value I ref This causes a slight variation in the timing at which the time interval T 12 ~T 78 There will be variations in the results.

[0088] As described above, differences in the structures or characteristics among the multiple reflecting surfaces 66 are reflected in the time interval during which the amount of received measurement light 86 reaches a predetermined reference value. The light-receiving unit 88 receives the measurement light 86 and generates a signal (received light amount signal) corresponding to the amount of received measurement light 86, and outputs the received light amount signal to the controller 48. For example, the time transition of the received light amount as shown in the graph of FIG. 8 is output to the controller 48 as the received light amount signal. The controller 48 then stores the received light amount signal in the memory unit 48a.

[0089] Next, a reflecting surface information registration step S02 is performed to register information (reflecting surface information) indicating the relationship between the amount of received measuring light 86 and the plurality of reflecting surfaces 66. As described above, the interval at which the amount of received measuring light 86 reaches a predetermined reference value reflects variations in the angles of the reflecting surfaces 66a to 66h. Therefore, in the reflecting surface information registration step S02, the plurality of reflecting surfaces 66 are distinguished and identified based on the transition of the amount of received measuring light 86 (received light amount signal) measured in the preliminary measurement step S01.

[0090] Specifically, first, a time interval during which the amount of received light of the measuring light 86 reaches a predetermined reference value is calculated based on the amount of received light of the measuring light 86 measured by the light receiving unit 88. For example, as shown in FIG. ref is set, and the amount of received light reaches the reference value I ref The time interval T 12 ~T 78 is calculated.

[0091] Next, the plurality of reflecting surfaces 66 are distinguished based on the time intervals. ref The time interval between reaching 12 , T 23 , T 34 , T 45 , T 56 , T 67 , T 78 The reflecting surface 66 onto which the measurement light 86 is irradiated at the point when peak P1 appears again after the transition from the peak P1 to the reflecting surface 66a is set as the reference surface (first surface). As an example, it is assumed here that peak P1 corresponds to reflecting surface 66a, and reflecting surface 66a is set as the reference surface (first surface).

[0092] Also, after peak P1, T 12 , T 23 , T 34 , T 45 , T 56 , T 67 , T 78 The reflecting surfaces 66 onto which the measuring light 86 is irradiated at the respective times when peaks P2 to P8 appear are recognized as the second to eighth surfaces, respectively. An identification code (surface number, etc.) is then assigned to each of the first to eighth surfaces. As a result, the reflecting surfaces 66a to 66h are distinguished and identified as the first to eighth surfaces, respectively, and reflecting surface information indicating the relationship between the amount of received measuring light 86 and the reflecting surfaces 66a to 66h is obtained.

[0093] However, the method for acquiring the reflecting surface information is not limited to the above. For example, in the reflecting surface information registration step S02, the time interval (the interval between times t1 and t8) during which the amount of received light of the measuring light 86 is maximum at each of the peaks P1 to P8 may be calculated, and the reflecting surfaces 66a to 66h may be distinguished based on the time interval. In addition, when the amount of received light of the measuring light 86 is equal to or greater than the reference value I ref The time intervals at which the reflection surfaces 66a to 66h become less than the predetermined value may be calculated, and the reflection surfaces 66a to 66h may be distinguished based on the time intervals.

[0094] Furthermore, if the value of the time interval at which the amount of received measurement light 86 reaches a predetermined reference value is clearly different for each reflecting surface 66, the value of the time interval can be made to correspond one-to-one to the values ​​of the multiple reflecting surfaces 66. For example, if the time interval T 12 ~T 78 If the values ​​of are distinct, the time interval T 12 ~T 78 The reflecting surfaces 66a irradiated with the measuring light 86 at the time when the reflecting surfaces 66a are measured can be identified as the reflecting surfaces 66b to 66h, respectively. In this case, reflecting surface information that associates one reflecting surface 66 with one time interval may be acquired.

[0095] The reflective surface information acquired as described above (such as the amount of received measurement light 86 and the identification codes of the reflective surfaces 66a to 66h) is input to the controller 48 and stored in the storage unit 48a (see FIG. 6). As a result, the reflective surface information is registered in the laser processing device 2.

[0096] Next, a correction amount information registration step S03 is performed to register information (correction information) indicating the amount of correction for the irradiation position of the laser beam 50 on the irradiated surface 66A for each reflecting surface 66. The correction information is information indicating the amount of correction for the irradiation position of the laser beam 50 required to scan the laser beam 50 at a desired position for each of the multiple reflecting surfaces 66. The correction information is obtained by measuring the position of the area (irradiated area) that is actually irradiated with the laser beam 50 scanned by the polygon mirror 64, and setting the amount of correction for the irradiation position of the laser beam 50 based on the measurement results.

[0097] The position of the area irradiated with the laser beam 50 is measured by, for example, the measurement unit 42 shown in Fig. 6. As described above, the measurement unit 42 is provided on the X-axis moving table 22 of the moving unit 6 (see Fig. 1). Therefore, the position of the measurement unit 42 in the XY plane directions can be adjusted by the moving unit 6.

[0098] 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. Specifically, the measurement unit 42 includes a columnar support structure 100 connected to the moving unit 6. A moving unit (moving mechanism) 102 is provided on the front side of the support structure 100. A measuring instrument 104 that measures the intensity distribution of the laser beam 50 is connected to the moving unit 102.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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.

[0107] 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).

[0108] In correction amount information registration step S03, the measurement unit 42 measures the position of the irradiated area of ​​the laser beam 50 for each reflecting surface 66. Specifically, first, the moving unit 6 moves the measurement unit 42 along the X-axis and Y-axis directions 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 measurement unit 42.

[0109] 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 of the irradiated area of ​​the laser beam 50 (scanning position) 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 measurement light 86 is irradiated onto the reflecting surfaces 66a to 66h (first to eighth surfaces). 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.

[0110] The position of the region irradiated with the laser beam 50 measured by the measurement unit 42 is output to the controller 48. 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 region irradiated with the laser beam 50 measured by the measurement unit 42.

[0111] 4, it is assumed 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 manufacturing errors or the like. In this case, while the measurement light 86 is irradiated onto the reflecting surfaces 66b to 66h (the second to eighth surfaces) and 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 (see FIG. 9) along which it should be irradiated. On the other hand, when the measurement light 86 is irradiated onto the reflecting surface 66a (the first surface) and 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' (see FIG. 9) that is different from the linear path A along which it should be irradiated.

[0112] 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 48a, 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.

[0113] Specifically, when the measurement light 86 is irradiated onto the reflecting surfaces 66b to 66h (the second to eighth surfaces) and 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 required (correction amount = 0). On the other hand, when the measurement light 86 is irradiated onto the reflecting surface 66a (the first surface) and 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 actually be irradiated (path A). The amount of change in the irradiation position of the laser beam 50 on the reflecting surface 66f at this time corresponds to the correction amount.

[0114] As described above, in the correction amount information registration step S03, 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 storage unit 48a. As a result, the correction information is registered in the laser processing device 2.

[0115] 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 correction amount information registration step S03, 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.

[0116] 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.

[0117] 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.

[0118] 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 48a 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.

[0119] As described above, in the preparation step S0, the preliminary measurement step S01, the reflecting surface information registration step S02, and the correction amount information registration step S03 are performed. As a result, the reflecting surface information indicating the relationship between the received light amount of the measurement light 86 and the plurality of reflecting surfaces 66, and the correction information indicating the correction amount for each reflecting surface 66 at the irradiation position of the laser beam 50 on the irradiated surface 66A are registered in the laser processing device 2.

[0120] Although the above description has been given of the case where the correction amount information registration step S03 is performed after the preliminary measurement step S01 and the reflecting surface information registration step S02, there is no limitation on the timing at which the correction amount information registration step S03 is performed. For example, the correction amount information registration step S03 may be performed before the preliminary measurement step S01, or may be performed between the preliminary measurement step S01 and the reflecting surface information registration step S02. Furthermore, the preliminary measurement step S01 and the correction amount information registration step S03 may be performed simultaneously. In this case, the laser beam 50 and the measurement light 86 are irradiated onto the polygon mirror 64 simultaneously.

[0121] 9 is a perspective view showing the laser processing device 2 that scans the laser beam 50 using the polygon mirror 64. After the preparation step S0, the laser processing of the workpiece 11 is performed by the laser processing device 2. When performing laser processing on the workpiece 11, as described above, the measurement step S1, the irradiated surface specification step S2, and the irradiation step S3 are performed in this order.

[0122] When the laser processing device 2 is in operation, each component of the laser processing device 2 is controlled by a controller 48. The controller 48 includes an identification unit 48b that identifies the irradiated surface 66A of the polygon mirror 64, and an adjustment unit 48c that controls the position adjustment unit 58 to adjust the irradiation position of the laser beam 50.

[0123] When laser processing is performed on the workpiece 11, first, a control signal is input from the controller 48 to the rotation drive source 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 the mirrors 60 and 62, irradiated onto the polygon mirror 64, and scanned by the polygon mirror 64.

[0124] 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 measuring step S1 of measuring the amount of received measurement light 86 reflected by the reflecting surface 66 of the polygon mirror 64 and an irradiated surface specifying step S2 of specifying the irradiated surface 66A based on the amount of received measurement light 86 are performed.

[0125] In the measurement step S1, the measurement unit 82 is activated, and measurement light 86 is irradiated onto the polygon mirror 64. Specifically, the measurement light 86 irradiated from the irradiation unit 84 passes through a polarizing beam splitter 90 and a lens 92, enters the reflecting surface 66 of the polygon mirror 64, and is reflected by the reflecting surface 66. The measurement light 86 reflected by the reflecting surface 66 reaches the light receiving unit 88 via the lens 92 and the polarizing beam splitter 90.

[0126] The light-receiving unit 88 receives the measurement light 86 and measures the amount of received measurement light 86. This measures the amount of received measurement light 86, which changes depending on the angle between the light ray 86a (see FIG. 6, etc.) and the reflecting surface 66. The light-receiving unit 88 then generates a received-light-amount signal corresponding to the amount of received measurement light 86 and sequentially outputs it to the specifying unit 48b of the controller 48. As a result, a received-light-amount signal indicating a transition in the amount of received light, for example, as shown in FIG. 8, is input to the specifying unit 48b.

[0127] Next, the irradiated surface 66A is identified based on the interval at which the amount of received light measured in the measurement step S1 reaches a predetermined reference value (irradiated surface identification step S2). As described above, the interval at which the amount of received light of the measurement light 86 reaches a predetermined reference value reflects differences in the structures or characteristics of the multiple reflecting surfaces 66. Therefore, the identification unit 48b identifies the irradiated surface 66A based on the amount of received light of the measurement light 86 input from the light-receiving unit 88 and the reflecting surface information registered in the reflecting surface information registration step S02.

[0128] Specifically, the specifying unit 48b first calculates the time interval during which the amount of received light of the measurement light 86 reaches a predetermined reference value, based on the amount of received light of the measurement light 86 input from the light receiving unit 88. For example, the specifying unit 48b calculates the time interval during which the amount of received light of the measurement light 86 reaches a predetermined reference value I ref (See Figure 8) and calculate the time interval T 12 ~T 78 (See FIG. 8). However, the calculated time interval is not limited to the above. Other examples of the time interval are as explained in the reflecting surface information registration step S02.

[0129] Next, the specifying unit 48b reads out the reflective surface information stored in the memory unit 48a, and specifies the irradiated surface 66B of the polygon mirror 64 by applying the interval at which the amount of received measurement light 86 reaches a predetermined reference value to the reflective surface information. For example, if the time interval calculated by the specifying unit 48b is T 12 , T 23 , T 34 , T 45 , T 56 , T 67 , T 78 (see FIG. 8), and then at the point when peak P1 appears again, reflecting surface 66a is identified as being illuminated surface 66B.

[0130] Furthermore, since the positional relationship between the irradiated surface 66B irradiated with the measurement light 86 and the irradiated surface 66A irradiated with the laser beam 50 is known, once the irradiated surface 66B is identified, the irradiated surface 66A is also identified. For example, in the polygon mirror 64 shown in Fig. 9, the irradiated surface 66A is located three planes forward of the irradiated surface 66B in the rotation direction of the polygon mirror 64, so when the reflecting surface 66a is the irradiated surface 66B, the reflecting surface 66f can be identified as the irradiated surface 66A. In other words, the identifying unit 48b identifies the irradiated surface 66B based on the amount of received measurement light 86 and the reflecting surface information, thereby indirectly identifying the irradiated surface 66A.

[0131] Then, the specifying unit 48b outputs a signal (irradiated surface signal) indicating the irradiated surface 66A and / or the irradiated surface 66B to the adjusting unit 48c. For example, when it is specified that the reflecting surface 66a is the irradiated surface 66B and the reflecting surface 66f is the irradiated surface 66A, the specifying unit 48b outputs an irradiated surface signal indicating that the reflecting surface 66a is the irradiated surface 66B and the reflecting surface 66f is the irradiated surface 66A to the adjusting unit 48c.

[0132] The specifying unit 48b then sequentially outputs irradiated surface signals to the adjusting unit 48c. For example, based on the elapsed time from when the reflecting surface 66a was specified as the irradiated surface 66B and the reflecting surface 66f was specified as the irradiated surface 66A, the specifying unit 48b continuously outputs irradiated surface signals indicating which of the reflecting surfaces 66a to 66h is the irradiated surface 66A and / or which reflecting surface 66 is the irradiated surface 66B to the adjusting unit 48c in real time. Note that the timing at which the irradiated surface signals input from the specifying unit 48b to the adjusting unit 48c are switched is set based on, for example, the time interval measured in the reflecting surface information registration step S02 or the measurement step S1 described above.

[0133] After the measurement step S1 and the irradiated surface specifying step S2 are performed, the laser beam 50 is scanned by the polygon mirror 64 and irradiated onto the workpiece 11 (irradiation step S3). In the irradiation step S3, the irradiation position of the laser beam 50 on the irradiated surface 66A is adjusted for each of the multiple reflecting surfaces 66.

[0134] Specifically, in the irradiation step S3, the adjustment unit 48c sequentially receives irradiated surface signals from the identification unit 48b. The adjustment unit 48c then reads out the correction information acquired in the measurement step S1 from the storage unit 48a and sequentially outputs signals (correction signals) indicating the amount of correction for the irradiation position of the laser beam 50 on the reflecting surface 66 indicated by the irradiated surface signals to the position adjustment unit 58. For example, when the identification unit 48b inputs an irradiated surface signal indicating that the reflecting surface 66a is the irradiated surface 66B and the reflecting surface 66f is the irradiated surface 66A to the adjustment unit 48c, the adjustment unit 48c 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 adjustment unit 58.

[0135] 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 9, 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.

[0136] If the laser beam 50 is irradiated onto the vertex of the polygon mirror 64 (the connecting portion of adjacent reflecting surfaces 66), it may be difficult to accurately control the position scanned by the laser beam 50. Therefore, when the vertex of the polygon mirror 64 is positioned on the traveling path of the laser beam 50, the traveling direction of the laser beam 50 may be switched to a beam damper 74 (see FIG. 3) to temporarily stop the irradiation of the laser beam 50 onto the polygon mirror 64. This makes it possible to prevent the laser beam 50 from being irradiated onto the vertex of the polygon mirror 64.

[0137] The workpiece 11 is processed by the laser beam 50 whose irradiation position 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. At this time, the laser beam 50 is irradiated onto the reflecting surface 66 of the rotating polygon mirror 64, and is scanned along the streets 13.

[0138] 10 is a plan view showing a part of the workpiece 11. When laser processing is performed along the street 13 of the workpiece 11, for example, a path A is set at the center in the width direction of the street 13. Then, the scanning position of the laser beam 50 is set so that the focusing position P of the laser beam 50 overlaps with the path A.

[0139] However, if there is angular variation in the reflecting surface 66 of the polygon mirror 64, the focusing position P 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 position where the ablation processing is performed will be shifted, which may result in processing defects such as damage to the device 15 or variations in the dimensions of the device chip.

[0140] However, by adjusting the irradiation position of the laser beam 50 on the irradiated surface 66A as shown in Fig. 9, the focusing position P of the laser beam 50 reflected by the inclined reflecting surface 66 is corrected from on path A' to on path A. As a result, even if there is variation in the angle of the reflecting surface 66, the laser beam 50 can be scanned while maintaining the focusing position P positioned on path A. As a result, the processing accuracy is improved and the occurrence of processing defects is suppressed.

[0141] 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.

[0142] As described above, by performing the measurement step S1 to the irradiation step S3, the irradiation position of the laser beam 50 on the polygon mirror 64 can be adjusted for each of the multiple reflecting surfaces 66, while the laser beam 50 is irradiated onto the workpiece 11, thereby performing laser processing on the workpiece 11. Note that the measurement step S1 to the irradiation step S3 are realized by executing a program stored in the controller 48. Specifically, the storage unit 48a stores a program for generating control signals for operating 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 irradiation step S3.

[0143] As described above, the laser processing device 2 according to this embodiment identifies the irradiated surface 66A, among the multiple reflecting surfaces 66, onto which the laser beam 50 is irradiated, based on the interval at which the amount of received light of the measurement light 86, which is reflected by the reflecting surface 66 of the rotating polygon mirror 64 and received by the light-receiving unit 88, reaches a predetermined reference value. This makes it possible to monitor the irradiation position of the laser beam 50 on the polygon mirror 64.

[0144] 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 area of ​​the laser beam 50 caused by variations in the angle of the reflecting surface 66, etc.

[0145] In the above embodiment, the measurement unit 82 is configured so that the amount of received measurement light 86 is maximized when the reflective surface 66 of the polygon mirror 64 and the ray 86a of the measurement light 86 are perpendicular to each other (see FIG. 3, etc.). However, the configuration of the measurement unit 82 can be changed as appropriate as long as the amount of received measurement light 86 changes depending on the angle between the ray 86a of the measurement light 86 and the reflective surface 66.

[0146] 11 is a front view showing a measurement unit 82A corresponding to a modified example of the measurement unit 82. The measurement unit 82A includes an irradiation unit 84A that irradiates measurement light 86A and a light-receiving unit 88A that receives the measurement light 86A. The configurations and functions of the irradiation unit 84A and the light-receiving unit 88A are similar to those of the irradiation unit 84 and the light-receiving unit 88 of the measurement unit 82 (see FIG. 3, etc.), respectively.

[0147] The irradiation unit 84A irradiates the irradiation surface 66B of the polygon mirror 64 with the measurement light 86A in a direction inclined with respect to the Z-axis direction. That is, the beam of the measurement light 86A is set in a direction intersecting the Z-axis direction. The light receiving unit 88 is disposed so as to receive the measurement light 86A reflected by the irradiation surface 66B of the polygon mirror 64.

[0148] For example, the irradiation unit 84A and the light-receiving unit 88A are arranged so that the amount of measurement light 86A received by the light-receiving unit 88A is maximized when the irradiated surface 66B is parallel to the horizontal direction (the XY plane direction). When the light-receiving unit 88A irradiates the irradiated surface 66B with the measurement light 86A while rotating the polygon mirror 64, the amount of measurement light 86A received changes depending on the angle between the ray of measurement light 86A and the irradiated surface 66B. When the irradiated surface 66B is parallel to the horizontal direction, the measurement light 86A travels (propagates) along a ray that is non-parallel and non-perpendicular to the irradiated surface 66B, is reflected by the irradiated surface 66B, and reaches the light-receiving unit 88A.

[0149] 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]

[0150] 11 Processing object 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 Memory 48b Specific part 48c Adjustment part 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,66B Irradiated surface 68 Rod (shaft) 70 Concentrator 72 Condenser Lens 74 Beam Dumper 80 Irradiated surface identification unit 82,82A Measuring Unit 84, 84A Irradiation unit (light irradiation part, light projection part) 86,86A measurement light 86a Ray of light 88, 88A Light receiving unit (light receiving part) 90 Polarizing Beam Splitter 92 Lens 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

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 measurement unit including an irradiation unit that irradiates measurement light incident on the reflecting surface and a light receiving unit that receives the measurement light reflected by the reflecting surface, the measurement unit being arranged such that the amount of measurement light received by the light receiving unit changes depending on the angle between the ray of the measurement light and the reflecting surface; and a controller that identifies an irradiated surface among the plurality of reflecting surfaces to be irradiated with the laser beam based on the time interval during which the amount of measurement light reflected by the reflecting surface of the rotating polygon mirror and received by the light receiving unit reaches a predetermined reference value.

2. 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.

3. A laser beam irradiation method for irradiating a workpiece with a laser beam by scanning the laser beam with a polygon mirror having a plurality of reflecting surfaces, comprising: a measuring step of irradiating measurement light onto the reflecting surface while rotating the polygon mirror, and measuring the amount of the measurement light reflected by the reflecting surface, which amount changes depending on the angle between the ray of the measurement light and the reflecting surface; an irradiation surface specifying step of specifying an irradiation surface to be irradiated with the laser beam among the plurality of reflecting surfaces based on a time interval at which the amount of received light measured in the measuring step reaches a predetermined reference value; an irradiation step of irradiating the workpiece with the laser beam by adjusting the irradiation position of the laser beam on the irradiated 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 measuring step of irradiating measurement light onto the reflecting surface while rotating the polygon mirror, and measuring the amount of the measurement light reflected by the reflecting surface, which amount changes depending on the angle between the ray of the measurement light and the reflecting surface; and an irradiated surface identification step of identifying the irradiated surface to be irradiated with the laser beam among the plurality of reflecting surfaces based on the time interval at which the amount of received light measured in the measurement step reaches a predetermined reference value.

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