Laser processing equipment

Abstract

To provide a laser processing device that can easily monitor a state of a laser beam.SOLUTION: A laser processing device, which processes a work-piece, is provided with: a laser oscillator; a mirror that reflects a laser beam emitted from the laser oscillator; a condensing lens that condenses the laser beam reflected on the mirror to irradiate the work-piece with the beam; a detecting unit that detects leaked light of the laser beam transmitting through the mirror; and a rotatable light polarizer through which leaked light propagating from the mirror toward the detecting unit passes, which can adjust output of the leaked light received by the detecting unit within a predetermined range, by rotating the light polarizer.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a laser processing apparatus for processing a workpiece.

Background Art

[0002] In the manufacturing process of device chips, a wafer in which devices are formed in a plurality of regions partitioned by a plurality of streets (division planned lines) arranged in a grid pattern is used. By dividing this wafer along the streets and fragmenting it, device chips equipped with devices can be obtained. The device chips are incorporated into various electronic devices such as mobile phones and personal computers.

[0003] For the division of a wafer, a cutting apparatus that cuts a workpiece with an annular cutting blade is used. In recent years, the development of a process for dividing a wafer by laser processing using a laser processing apparatus has also been advanced. The laser processing apparatus includes a chuck table for holding the wafer and a laser irradiation unit for irradiating the wafer with a laser beam. The laser irradiation unit incorporates an optical system composed of various optical elements (mirrors, condenser lenses, etc.) for guiding the laser beam to the workpiece.

[0004] For example, Patent Document 1 discloses a method of condensing a laser beam having transparency with respect to a wafer inside the wafer and forming a modified layer along the streets inside the wafer. The region where the modified layer of the wafer is formed becomes more brittle than other regions. Therefore, when an external force is applied to the wafer in which the modified layer is formed along the streets, the wafer breaks along the streets and is divided into a plurality of device chips.

[0005] Furthermore, Patent Document 2 discloses a method for partially removing a low-dielectric constant insulating film (Low-k film) formed on a wafer by irradiation with a laser beam before cutting the wafer with a cutting blade. By removing the low-dielectric constant insulating film along the street, it is possible to avoid contact between the cutting blade, which rotates at high speed, and the low-dielectric constant insulating film when the cutting blade is then used to cut the wafer, thereby preventing the peeling of the low-dielectric constant insulating film.

[0006] Furthermore, when processing workpieces such as wafers with a laser processing device, the state of the laser beam irradiated onto the workpiece is sometimes monitored in order to quickly detect abnormalities in the laser beam and avoid processing defects. For example, Patent Document 3 discloses a laser processing device that irradiates a workpiece with a laser beam to perform laser processing on the workpiece, while simultaneously detecting stray light of the laser beam that has passed through the mirror of the optical system to monitor the output of the laser beam. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2002-192370 [Patent Document 2] Japanese Patent Publication No. 2003-320466 [Patent Document 3] Japanese Patent Publication No. 2021-30283 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] As described above, when monitoring stray light from a laser beam irradiated onto a workpiece, a detection unit for detecting stray light is mounted on the laser irradiation unit. However, depending on the laser beam irradiation conditions, high-power stray light may irradiate the detection unit, potentially causing damage or malfunction of the detection unit. Therefore, an ND (Neutral Density) filter is provided on the light-receiving side of the detection unit to reduce the amount of stray light. This reduces the output of stray light irradiated onto the detection unit, preventing damage or malfunction of the detection unit.

[0009] However, while ND filters have their own inherent transmittance (optical density), the irradiation conditions of the laser beam vary depending on the material of the workpiece and the type of laser processing. Therefore, even if one type of ND filter is installed alone on the light-receiving surface side of the detection unit, it is difficult to ensure that the detection unit always receives the stray light of the laser beam irradiated under various conditions at an appropriate output. For example, if the output of the laser beam is high, even with an ND filter, high-output stray light may irradiate the detection unit, and damage to the detection unit may not be completely prevented. On the other hand, if the output of the laser beam is low, the output of the stray light reaching the detection unit via the ND filter may be insufficient, making it difficult for the detection unit to detect the stray light.

[0010] Therefore, in order for the detection unit to properly detect stray light, it is necessary to select and stock multiple types of ND filters to accommodate various laser beam irradiation conditions. This increases the time and cost required to prepare the ND filters. Furthermore, if the laser beam irradiation conditions are changed while the laser processing equipment is in operation, the ND filters must be replaced accordingly. This results in prolonged interruptions in the processing of the workpiece by the laser processing equipment, reducing processing efficiency.

[0011] This invention has been made in view of the above problems, and aims to provide a laser processing apparatus that allows for easy monitoring of the state of the laser beam. [Means for solving the problem]

[0012] According to one aspect of the present invention, a laser processing apparatus for processing a workpiece comprises a laser oscillator, a mirror for reflecting a laser beam emitted from the laser oscillator, a focusing lens for focusing the laser beam reflected by the mirror and irradiating the workpiece with it, a detection unit for detecting stray light of the laser beam that has passed through the mirror, and a rotatable polarizer through which the stray light propagating from the mirror toward the detection unit passes. A rotational drive source for rotating the polarizer, and a control unit, Equipped with, The control unit outputs a control signal to the rotation drive source based on the irradiation conditions of the laser beam. A laser processing apparatus is provided in which the output of the stray light received by the detection unit can be adjusted within a predetermined range by rotating the polarizer.

[0013] Preferably, the control unit has a storage unit that stores an appropriate rotation angle indicating the appropriate rotation angle of the polarizer for each irradiation condition of the laser beam, and the control unit sets the rotation angle of the polarizer to the appropriate rotation angle by outputting a control signal to the rotation drive source based on the irradiation condition of the laser beam. Also preferably, the control unit has a storage unit that stores an appropriate output range indicating the range of output of the leaked light suitable for detection of the leaked light by the detection unit, and the control unit adjusts the rotation angle of the polarizer so that the output of the leaked light falls within the appropriate output range by outputting a control signal to the rotation drive source when the output of the leaked light measured by the detection unit is outside the appropriate output range. Preferably, the detection unit includes a position detection element. Preferably, the detection unit measures the output of the leaked light. Preferably, the detection unit measures the irradiation position and intensity distribution of the leaked light. [Effects of the Invention]

[0014] A laser processing apparatus according to one aspect of the present invention is equipped with a rotatable polarizer through which the stray light of the laser beam passes, and the output of the stray light received by the detection unit can be adjusted by rotating the polarizer. This eliminates the need to replace optical elements (such as ND filters) when adjusting the output of stray light according to the irradiation conditions of the laser beam. As a result, the time and cost required to prepare replacement optical elements are reduced, and the decrease in processing efficiency due to the replacement of optical elements is avoided. [Brief explanation of the drawing]

[0015] [Figure 1] This is a perspective view showing a laser processing machine. [Figure 2] This is a perspective view showing the workpiece. [Figure 3] This is a schematic diagram showing a chuck table and a laser irradiation unit. [Figure 4]It is a schematic diagram showing a detection unit and a polarizer.

Embodiments for Carrying out the Invention

[0016] Hereinafter, embodiments according to an aspect of the present invention will be described with reference to the accompanying drawings. First, a configuration example of the laser processing apparatus according to the present embodiment will be described. FIG. 1 is a perspective view showing a laser processing apparatus 2. In FIG. 1, the X-axis direction (processing feed direction, first horizontal direction, left-right direction), the Y-axis direction (indexing feed direction, second horizontal direction, front-back direction), and the Z-axis direction (vertical direction, height direction, up-down direction) are perpendicular to each other.

[0017] The laser processing apparatus 2 includes a base 4 that supports each component constituting the laser processing apparatus 2. The upper surface of the base 4 is a flat surface substantially parallel to the horizontal plane (XY plane), and a moving unit (moving mechanism) 6 is provided on the upper 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 moving 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 plate-shaped Y-axis moving table 12 is slidably mounted on the pair of Y-axis guide rails 10 along the Y-axis guide rails 10.

[0019] A nut portion (not shown) is provided on the back surface (lower surface) side of the Y-axis moving table 12. A Y-axis ball screw 14 arranged along the Y-axis direction is screwed into the nut portion between the pair of Y-axis guide rails 10. Further, a Y-axis pulse motor 16 for rotating the Y-axis ball screw 14 is connected to an end portion of the Y-axis ball screw 14. When the Y-axis ball screw 14 is rotated by the Y-axis pulse motor 16, the Y-axis moving table 12 moves in the Y-axis direction along the Y-axis guide rails 10.

[0020] The X-axis moving unit 18 includes a pair of X-axis guide rails 20 arranged along the X-axis direction on the surface (upper surface) side of the Y-axis moving table 12. A flat X-axis moving table 22 is slidably mounted along the X-axis guide rails 20 on the pair of X-axis guide rails 20.

[0021] On the back surface (lower surface) side of the X-axis moving table 22, a nut portion (not shown) is provided. An X-axis ball screw 24 arranged along the X-axis direction is screwed into this nut portion between the pair of X-axis guide rails 20. Further, an X-axis pulse motor 26 for rotating the X-axis ball screw 24 is connected to an end of the X-axis ball screw 24. When the X-axis ball screw 24 is rotated by the X-axis pulse motor 26, the X-axis moving table 22 moves in the X-axis direction along the X-axis guide rails 20.

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

[0023] FIG. 2 is a perspective view showing the workpiece 11. For example, the workpiece 11 is a disk-shaped wafer made of a semiconductor material such as single crystal silicon, and includes surfaces 11a and 11b that are generally parallel to each other. The workpiece 11 is partitioned into a plurality of rectangular regions by a plurality of streets (division planned lines) 13 arranged in a grid pattern so as to intersect each other. Devices 15 such as IC (Integrated Circuit), LSI (Large Scale Integration), LED (Light Emitting Diode), and MEMS (Micro Electro Mechanical Systems) devices are formed on the surface 11a side of the plurality of regions partitioned by the streets 13.

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

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

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

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

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

[0029] When the Y-axis moving table 12 is moved along the Y-axis, the chuck table 28 moves along the Y-axis. Similarly, when the X-axis moving table 22 is moved along the X-axis, the chuck table 28 moves along the X-axis. Furthermore, the chuck table 28 is connected to a rotational drive source (not shown), such as a motor, which rotates the chuck table 28 around a rotation axis that is roughly parallel to the Z-axis.

[0030] A rectangular parallelepiped support structure 32 is provided at the rear end of the base 4 (behind the Y-axis movement unit 8, the X-axis movement unit 18, and the chuck table 28). The support structure 32 is formed to protrude upward from the upper surface of the base 4, and the surface (front) of the support structure 32 is aligned with the XZ plane. A columnar support member 34 is connected to the support structure 32, protruding forward from the front surface of the support structure 32.

[0031] The laser processing apparatus 2 is equipped with a laser irradiation unit 36 ​​that irradiates a workpiece 11 with a laser beam. The laser irradiation unit 36 ​​has a laser processing head 38 attached to the tip of a support member 34. Laser processing is performed on the workpiece 11 by irradiating it with a laser beam from the laser processing head 38 onto the workpiece 11 held by the chuck table 28.

[0032] An imaging unit (not shown) may be provided at the tip of the support member 34. The imaging unit is equipped with an image sensor such as a CCD (Charged-Coupled Devices) sensor or a CMOS (Complementary Metal-Oxide-Semiconductor) sensor, and captures images of the workpiece 11 held by the chuck table 28. There are no restrictions on the type of imaging unit; for example, a visible light camera or an infrared camera can be used. Based on the image acquired by imaging the workpiece 11 with the imaging unit, the workpiece 11 and the laser processing head 38 are aligned.

[0033] The support member 34 may be connected to the support structure 32 via a Z-axis movement unit (not shown) that moves the support member 34 along the Z-axis direction. For example, a ball screw type movement mechanism may be installed on the front side of the support structure 32 as the Z-axis movement unit. In this case, the Z-axis movement unit moves (raises and lowers) the support member 34 along the Z-axis direction, thereby adjusting the height of the focal point of the laser beam emitted from the laser processing head 38 and focusing the imaging unit.

[0034] Furthermore, the laser processing apparatus 2 is equipped with a display unit (display section, display device) 40 that displays various information related to the laser processing apparatus 2. For example, a touch panel may be used as the display unit 40. In this case, the touch panel displays an operation screen for inputting information into the laser processing apparatus 2, and the operator can input information into the laser processing apparatus 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 information into the laser processing apparatus 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 40.

[0035] Furthermore, the laser processing apparatus 2 is equipped with a notification unit (notification unit, notification device) 42 that notifies the operator of information. For example, the notification unit 42 is an indicator light (warning light), which lights up or flashes when an abnormality occurs in the laser processing apparatus 2 to notify the operator of the error. However, there are no restrictions on the type of notification unit 42. For example, the notification unit 42 may be a speaker that notifies the operator of information by sound or voice.

[0036] Furthermore, the laser processing apparatus 2 includes a control unit (control unit, control device) 44 that controls the laser processing apparatus 2. The control unit 44 is connected to each component that makes up the laser processing apparatus 2 (moving unit 6, chuck table 28, clamp 30, laser irradiation unit 36, display unit 40, notification unit 42, etc.). The control unit 44 operates the laser processing apparatus 2 by outputting control signals to each component of the laser processing apparatus 2.

[0037] For example, the control unit 44 is comprised of a computer. Specifically, the control unit 44 includes a processing unit that performs calculations and other processing necessary 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 memory such as ROM (Read Only Memory) and RAM (Random Access Memory).

[0038] Figure 3 is a schematic diagram showing the chuck table 28 and the laser irradiation unit 36. When processing the workpiece 11, the workpiece 11 is first held by the chuck table 28. For example, the workpiece 11 is placed on the chuck table 28 such that the front surface 11a is exposed upwards and the back surface 11b (sheet 19 side) faces the holding surface 28a. The frame 17 (see Figure 2) is fixed by a plurality of clamps 30 (see Figure 1). In this state, when the suction force (negative pressure) of the suction source is applied to the holding surface 28a, the workpiece 11 is held by the chuck table 28 through the sheet 19.

[0039] Next, a laser beam 50 is irradiated from the laser irradiation unit 36 ​​toward the workpiece 11, and laser processing is performed on the workpiece 11. The irradiation conditions of the laser beam 50 are set appropriately according to the content of the laser processing to be performed on the workpiece 11.

[0040] For example, when dividing a workpiece 11, the irradiation conditions of the laser beam 50 are set so that the area of ​​the workpiece 11 irradiated with the laser beam 50 is modified (altered) by multiphoton absorption. Specifically, the wavelength of the laser beam 50 is set so that at least a portion of the laser beam 50 penetrates the workpiece 11. That is, the laser beam 50 is a laser beam that penetrates the workpiece 11. In addition, other irradiation conditions of the laser beam 50 are set so that the workpiece 11 is appropriately modified. For example, if the workpiece 11 is a single-crystal silicon wafer, the irradiation conditions of the laser beam 50 can be set as follows. Wavelength: 1064nm Average output: 1W Repeat frequency: 100kHz Machining feed rate: 800 mm / s

[0041] As the laser beam 50 is focused inside the workpiece 11 and the chuck table 28 is moved along the processing feed direction by the moving unit 6 (Figure 1), the chuck table 28 and the laser beam 50 move relative to each other, and the laser beam 50 is scanned along the processing feed direction. As a result, the inside of the workpiece 11 is modified (altered) by multiphoton absorption, and a modified layer is formed inside the workpiece 11 along the street 13. Thereafter, by repeating the same procedure, the laser beam 50 is irradiated along other streets 13. As a result, multiple modified layers are formed in a grid pattern inside the workpiece 11 along each street 13.

[0042] The region of the workpiece 11 where the modified layer is formed becomes more brittle than other regions of the workpiece 11. Therefore, when an external force is applied to the workpiece 11, the workpiece 11 is divided along the street 13, starting from the modified layer. In other words, the modified layer functions as a dividing point (a trigger for division).

[0043] However, there are no restrictions on the content of the laser processing. For example, the workpiece 11 may be subjected to ablation processing by irradiating it with a laser beam 50 that has absorption properties. By ablation processing, grooves are formed along the street 13 from the surface 11a to the back surface 11b of the workpiece 11, thereby dividing the workpiece 11 along the street 13.

[0044] The laser irradiation unit 36 ​​includes a laser oscillator 52 such as a YAG laser, YVO4 laser, or YLF laser, and an optical system 54 that propagates the laser beam 50 emitted from the laser oscillator 52 to the workpiece 11 held by the chuck table 28. The optical system 54 is composed of multiple optical elements and controls the direction of travel, shape, and focusing position of the laser beam 50 irradiated onto the workpiece 11.

[0045] For example, the optical system 54 includes a plurality of mirrors 56A, 56B, and 56C that reflect the laser beam 50 emitted from the laser oscillator 52, and a focusing lens 58 that focuses the laser beam 50 reflected by the mirrors 56A, 56B, and 56C and irradiates the workpiece 11 with it. Dielectric multilayer mirrors can be used as the mirrors 56A, 56B, and 56C, and a convex lens can be used as the focusing lens 58. The laser beam 50 emitted from the laser oscillator 52 is reflected sequentially by the mirrors 56A, 56B, and 56C and incident on the focusing lens 58. The laser beam 50 is then focused by the focusing lens 58 at a predetermined position (for example, the surface 11a or inside the workpiece 11).

[0046] However, there are no restrictions on the optical elements that constitute the optical system 54. For example, the optical system 54 may include other mirrors and lenses, a polarizing beam splitter (PBS), a diffractive optical element (DOE), an LCOS-SLM (Liquid Crystal On Silicon - Spatial Light Modulator), and other optical elements.

[0047] Furthermore, the laser irradiation unit 36 ​​in this embodiment is configured to monitor the state of the laser beam 50. Specifically, the laser irradiation unit 36 ​​includes a plurality of detection units 60A, 60B, and 60C for detecting leaked light from the laser beam 50.

[0048] When the laser beam 50 is reflected by the reflective surfaces of mirrors 56A, 56B, and 56C, a small portion of the laser beam 50 passes through the mirrors 56A, 56B, and 56C. Then, leaked light 50a, 50b, and 50c, corresponding to a portion of the laser beam 50, are emitted from the surfaces of mirrors 56A, 56B, and 56C opposite to the reflective surfaces.

[0049] Detection unit 60A is positioned in the optical path of the leaked light 50a and detects the leaked light 50a that has passed through mirror 56A. Detection unit 60B is positioned in the optical path of the leaked light 50b and detects the leaked light 50b that has passed through mirror 56B. Detection unit 60C is positioned in the optical path of the leaked light 50c and detects the leaked light 50c that has passed through mirror 56C.

[0050] For example, detection units 60A, 60B, and 60C are equipped with a position sensing device (PSD) that detects the irradiation position of the stray light from the laser beam 50. As the PSD, a two-dimensional PSD with a resistive layer that divides the photocurrent into four parts can be used. The PSD detects the current value (resistance value) corresponding to the position on the light-receiving surface of the PSD where the stray light from the laser beam 50 is irradiated, and outputs it as a position signal to the control unit 44 (see Figure 1).

[0051] Furthermore, detection units 60A, 60B, and 60C may measure the output of the stray light from the laser beam 50. For example, detection units 60A, 60B, and 60C are equipped with laser power meters such as thermopile power meters and photodetector power meters. The laser power meter detects the output of the stray light from the laser beam 50 and outputs it as an output signal to the control unit 44 (see Figure 1).

[0052] Furthermore, detection units 60A, 60B, and 60C may measure the irradiation position and intensity distribution of the leaked light from the laser beam 50. For example, detection units 60A, 60B, and 60C are equipped with an imaging unit (camera) that incorporates an image sensor capable of detecting the leaked light from the laser beam 50, and the leaked light is imaged on the light-receiving surface of the imaging unit. The image of the leaked light acquired by the imaging unit reflects the irradiation position and intensity distribution of the leaked light as the hue, brightness, or saturation of the image. Therefore, by imaging the leaked light with the imaging unit, information corresponding to the irradiation position and intensity distribution of the leaked light is acquired. The imaging unit then outputs the image of the leaked light acquired by imaging to the control unit 44 (see Figure 1).

[0053] Furthermore, depending on the irradiation conditions of the laser beam 50, high-power stray light 50a, 50b, 50c may irradiate the detection units 60A, 60B, 60C, potentially causing damage or malfunction of the detection units 60A, 60B, 60C. Therefore, in this embodiment, rotatable polarizers 62A, 62B, 62C are provided to adjust the light intensity (output) of the stray light 50a, 50b, 50c irradiated onto the detection units 60A, 60B, 60C.

[0054] The polarizer 62A is positioned on the optical path of the leaked light 50a (between the mirror 56A and the detection unit 60A in Figure 3) and is configured to rotate (spin) around a rotation axis parallel to the direction of propagation of the leaked light 50a. When the leaked light 50a propagating from the mirror 56A toward the detection unit 60A passes through the polarizer 62A, the amount of light in the leaked light 50a decreases by a predetermined rate. Furthermore, by rotating the polarizer 62A, the polarization direction of the leaked light 50a passing through the polarizer 62A changes, and the amount of light in the leaked light 50a reaching the detection unit 60A increases or decreases.

[0055] The polarizer 62B is positioned on the optical path of the leaked light 50b (between the mirror 56B and the detection unit 60B in Figure 3) and is configured to rotate (spin) around an axis of rotation parallel to the direction of propagation of the leaked light 50b. When the leaked light 50b propagating from the mirror 56B toward the detection unit 60B passes through the polarizer 62B, the amount of light in the leaked light 50b decreases by a predetermined rate. Furthermore, by rotating the polarizer 62B, the polarization direction of the leaked light 50b passing through the polarizer 62B changes, and the amount of light in the leaked light 50b reaching the detection unit 60B increases or decreases.

[0056] The polarizer 62C is positioned on the optical path of the leaked light 50c (between the mirror 56C and the detection unit 60C in Figure 3) and is configured to rotate (spin) around an axis of rotation parallel to the direction of propagation of the leaked light 50c. When the leaked light 50c propagating from the mirror 56C toward the detection unit 60C passes through the polarizer 62C, the amount of light in the leaked light 50c decreases by a predetermined rate. Furthermore, by rotating the polarizer 62C, the polarization direction of the leaked light 50c passing through the polarizer 62C changes, and the amount of light in the leaked light 50c reaching the detection unit 60C increases or decreases.

[0057] There are no restrictions on the types of polarizers 62A, 62B, and 62C. For example, wire grid polarizers and polarizing beam splitters can be used as polarizers 62A, 62B, and 62C.

[0058] Figure 4 is a schematic diagram showing the detection unit 60A and the polarizer 62A. The polarizer 62A is connected to a rotation drive source 64 that rotates the polarizer 62A. The rotation drive source 64 is composed of a pulse motor or the like and rotates the polarizer 62A around a rotation axis parallel to the optical axis of the polarizer 62A (the direction of propagation of the leaked light 50a).

[0059] For example, the polarizer 62A is housed in a housing, and the output shaft (rotation axis) of the rotation drive source 64 is fixed to the housing. Alternatively, the polarizer 62A may be housed in a holder (automatic polarizer holder) that integrates the housing and the rotation drive source 64. When the rotation drive source 64 is activated, the polarizer 62A rotates (spins) around the optical axis. This allows the polarizer 62A to be positioned at any rotation angle.

[0060] Leaked light 50a that has passed through mirror 56A (see Figure 3) reaches detection unit 60A via polarizer 62A, and the detection unit 60A detects the irradiation position and output of the leaked light 50a. When the detection unit 60A detects leaked light 50a, a control signal is output from control unit 44 to rotation drive source 64, and the rotation angle of polarizer 62A is adjusted. This allows the output of the leaked light 50a received by the detection unit 60A to be adjusted within a predetermined range.

[0061] Specifically, when the output of the laser beam 50 is high, the polarizer 62A is rotated in a direction that reduces the amount of leaked light 50a passing through the polarizer 62A. This prevents high-output leaked light 50a from irradiating the detection unit 60A, thus avoiding damage to or malfunction of the detection unit 60A. On the other hand, when the output of leaked light 50b is low, the polarizer 62A is rotated in a direction that increases the amount of leaked light 50a irradiated onto the detection unit 60A. This ensures that the leaked light 50a irradiates the detection unit 60A with an amount of light sufficient to detect the irradiation position and output of the leaked light 50a, allowing the detection unit 60A to properly detect the leaked light 50a.

[0062] When the detection unit 60A detects leaked light 50a, a signal corresponding to the information of the leaked light 50a (irradiation position, output value, etc.) is output to the control unit 44. The control unit 44 then monitors whether the acquired information of the leaked light 50a meets predetermined conditions. This allows for the rapid detection of abnormalities in the laser beam 50, preventing the occurrence of processing defects.

[0063] Specifically, the control unit 44 includes a storage unit 44a that stores reference information used to determine the state of the laser beam 50. The storage unit 44a pre-stores reference information such as information defining the permissible range of the irradiation position of the leaked light 50a (irradiation position reference information) and information defining the permissible range of the output value of the leaked light 50a (output reference information). For example, a threshold value (upper limit) of the distance from the reference position to the irradiation position of the leaked light 50a is stored as irradiation position reference information. In addition, threshold values ​​(upper and lower limits) of the output value of the leaked light 50a are stored as output reference information.

[0064] The control unit 44 calculates the irradiation position and output value of the leaked light 50a based on the signal input from the detection unit 60A. The control unit 44 then determines whether the irradiation position of the leaked light 50a is within an acceptable range by comparing the irradiation position of the leaked light 50a with the irradiation position reference information. The control unit 44 also determines whether the output value of the leaked light 50a is within an acceptable range by comparing the output value of the leaked light 50a with the output reference information.

[0065] If the information regarding the leaked light 50a (irradiation position, output value, etc.) is outside the acceptable range, the control unit 44 determines that the laser beam 50 is in an abnormal state. The control unit 44 then outputs a control signal to the display unit 40 (see Figure 1) and the notification unit 42 (see Figure 1) instructing them to send an error. As a result, the display unit 40 displays information (warning message, etc.) indicating that the laser beam 50 is in an abnormal state, and the notification unit 42 lights up or blinks, notifying the operator of the abnormality in the laser beam 50. The operator then performs maintenance such as adjusting the optical system 54 and replacing parts to restore the laser beam 50 to a normal state.

[0066] When the detection unit 60A detects the leaked light 50a, the rotation angle of the polarizer 62A is adjusted as described above. The rotation angle of the polarizer 62A may be adjusted manually by the operator or automatically by the laser processing device 2.

[0067] For example, the memory unit 44a stores in advance the appropriate rotation angle (optimal rotation angle) of the polarizer 62A for each irradiation condition of the laser beam 50. When the irradiation conditions of the laser beam 50 suitable for processing the workpiece 11 are set, the control unit 44 outputs a control signal to the rotation drive source 64, setting the rotation angle of the polarizer 62A to the appropriate rotation angle. As a result, the rotation angle of the polarizer 62A is automatically adjusted according to the irradiation conditions of the laser beam 50.

[0068] Furthermore, the memory unit 44a may pre-store a range of output values ​​for leaked light 50a suitable for detection by the detection unit 60A (appropriate output range). In this case, the control unit 44 determines whether the output of leaked light 50a measured by the detection unit 60A is within the appropriate output range. If the output of leaked light 50a is outside the appropriate output range, the control unit 44 outputs a control signal to the rotation drive source 64 and automatically adjusts the rotation angle of the polarizer 62A so that the output of leaked light 50a falls within the appropriate output range.

[0069] Although the details of the detection unit 60A and polarizer 62A were described above (see Figure 4), the configuration and operation of the detection units 60B and 60C (see Figure 3) are the same as those of the detection unit 60A, and the configuration and operation of the polarizers 62B and 62C (see Figure 3) are the same as those of the polarizer 62A. Furthermore, by providing multiple detection units 60A, 60B, and 60C on the laser irradiation unit 36 ​​as shown in Figure 3, it becomes easier to identify the location where an anomaly in the laser beam 50 occurs. However, the laser irradiation unit 36 ​​only needs to be equipped with at least one set of detection units and polarizers.

[0070] As described above, the laser processing apparatus 2 according to this embodiment is equipped with rotatable polarizers 62A, 62B, and 62C through which the leaked light 50a, 50b, and 50c of the laser beam 50 pass, and the output of the leaked light 50a, 50b, and 50c received by the detection units 60A, 60B, and 60C can be adjusted by rotating the polarizers 62A, 62B, and 62C. This eliminates the need to replace optical elements (such as ND filters) when adjusting the output of the leaked light 50a, 50b, and 50c according to the irradiation conditions of the laser beam 50. As a result, the effort and cost required to prepare replacement optical elements are reduced, and the decrease in processing efficiency due to the replacement of optical elements is avoided.

[0071] The configuration of the laser irradiation unit 36 ​​can be changed as appropriate, provided that the output of the leaked light 50a, 50b, 50c reaching the detection units 60A, 60B, 60C can be adjusted by the polarizers 62A, 62B, 62C. For example, the laser irradiation unit 36 ​​may be equipped with a filter (wavelength selective filter) that allows only leaked light 50a, 50b, 50c of a wavelength within a predetermined range to pass through.

[0072] Wavelength-selective filters are installed between detection unit 60A and polarizer 62A, between detection unit 60B and polarizer 62B, and between detection unit 60C and polarizer 62C. However, wavelength-selective filters may also be installed between mirror 56A and polarizer 62A, between mirror 56B and polarizer 62B, and between mirror 56C and polarizer 62C. There are no restrictions on the type of wavelength-selective filter; for example, bandpass filters, dichroic filters, long-pass filters, short-pass filters, etc., can be used.

[0073] By providing a wavelength-selective filter, it becomes possible to extract only the leakage light with wavelengths that particularly contribute to the processing of the workpiece 11 from the leakage light 50a, 50b, and 50c, and detect it with the detection units 60A, 60B, and 60C. This allows for highly accurate determination of the state of the laser beam 50 used to process the workpiece 11.

[0074] Furthermore, the structures, methods, etc., according to the above embodiments can be modified as appropriate without departing from the scope of the objectives of the present invention. [Explanation of symbols]

[0075] 11 Workpiece 11a surface 11b Back side 13th Street (planned division line) 15 devices 17 frames 17a aperture 19 seats 2. Laser processing equipment 4 base 6. Mobile Unit (Movement 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. Chuck table (holding table) 28a Holding surface 30 clamps 32 Support structure 34 Support Member 36 Laser irradiation unit 38 Laser processing heads 40 Display unit (display unit, display device) 42. Notification Unit (Notification Section, Notification Device) 44 Control Unit (Control Unit, Control Device) 44a Storage section 50 laser beams 50a, 50b, 50c Leaked light 52 Laser Oscillator 54 Optical system 56A, 56B, 56C Mirror 58 Focusing lens 60A, 60B, 60C detection unit 62A,62B,62C polarizer 64 Rotary drive source

Claims

1. A laser processing device for processing a workpiece, Laser oscillator and, A mirror that reflects the laser beam emitted from the laser oscillator, A focusing lens that concentrates the laser beam reflected by the mirror and irradiates the workpiece with it, A detection unit for detecting stray light of the laser beam that has passed through the mirror, A rotatable polarizer through which the leaked light propagating from the mirror toward the detection unit passes, A rotational drive source for rotating the polarizer, It includes a control unit, A laser processing apparatus characterized in that the control unit can adjust the output of the stray light received by the detection unit to a predetermined range by outputting a control signal to the rotation drive source based on the irradiation conditions of the laser beam and rotating the polarizer.

2. The control unit has a storage unit that stores an appropriate rotation angle indicating the appropriate rotation angle of the polarizer for each irradiation condition of the laser beam, The laser processing apparatus according to claim 1, characterized in that the control unit sets the rotation angle of the polarizer to the appropriate rotation angle by outputting a control signal to the rotation drive source based on the irradiation conditions of the laser beam.

3. The control unit has a storage unit that stores an appropriate output range indicating a range of output of the leaked light suitable for detection of the leaked light by the detection unit, The laser processing apparatus according to claim 1, characterized in that the control unit adjusts the rotation angle of the polarizer so that the output of the leaked light falls within the appropriate output range by outputting a control signal to the rotation drive source when the output of the leaked light measured by the detection unit is outside the appropriate output range.

4. The laser processing apparatus according to claim 1, characterized in that the detection unit comprises a position detection element.

5. The laser processing apparatus according to claim 1, characterized in that the detection unit measures the output of the leaked light.

6. The laser processing apparatus according to claim 1, characterized in that the detection unit measures the irradiation position and intensity distribution of the leaked light.

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