Observation methods for laser processing equipment and laser beam

Abstract

This invention provides a laser processing apparatus and a method for observing a laser beam, which can suppress contamination of optical components and allows for easy adjustment. The laser processing apparatus includes: a laser oscillator that oscillates laser light; a first concentrator that focuses the laser beam emitted from the laser oscillator onto a workpiece held on a chuck table; and an observation unit that simulates the state of the focusing point of the laser beam irradiating the workpiece. The observation unit includes: a second concentrator that focuses the laser beam in a direction different from the holding surface of the chuck table; a microscope that magnifies the laser beam focused by the second concentrator; and an imaging element that observes the focusing point of the laser beam magnified by the microscope.

Description

Technical Field

[0001] This invention relates to a laser processing apparatus and a method for observing a laser beam. Background Technology

[0002] To dicing and chip-forming workpieces such as semiconductor wafers, a laser processing apparatus (see, for example, Patent Document 1) is used, which includes a laser beam irradiation unit that focuses a laser beam onto the workpiece. The laser beam irradiation unit is typically configured such that a laser beam emitted from a laser oscillator is guided and focused onto the workpiece using various optical components that control the beam size, shape, etc., to process the workpiece on its front side or inside. Therefore, in order to obtain the desired processing result when processing the workpiece, the optical component assembly of the laser beam irradiation unit must be adjusted.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2007-275912

[0004] Furthermore, to determine whether the desired processing result can be obtained, processing must be attempted. Therefore, the mainstream method is to adjust the optical components while processing the workpiece. However, this method requires actual preparation of the workpiece before processing, thus incurring costs for workpiece preparation and processing time. In addition, in laser beam irradiation units, the optical component assembly is usually arranged in a closed (shielded) space, but it becomes open during adjustment. Therefore, debris (processing chips) generated from the workpiece during processing may adhere to the optical components during adjustment. Summary of the Invention

[0005] Therefore, the object of the present invention is to provide a laser processing apparatus and a method for observing a laser beam that can suppress contamination of optical components and can be easily adjusted.

[0006] According to one aspect of the present invention, a laser processing apparatus is provided, comprising: a chuck stage having a holding surface for holding a workpiece; a laser oscillator oscillating a laser beam; a first concentrator concentrating the laser beam emitted from the laser oscillator onto the workpiece held by the chuck stage; and an observation unit simulating the state of the focal point of the laser beam irradiating the workpiece, the observation unit comprising: a second concentrator concentrating the laser beam in a direction different from the holding surface of the chuck stage; a microscope magnifying the laser beam concentrated by the second concentrator; and an imaging element observing the focal point of the laser beam magnified by the microscope.

[0007] Preferably, the observation unit is configured to be detachable.

[0008] According to another aspect of the present invention, a method for observing a laser beam is provided, wherein the state of a laser beam irradiating a workpiece is simulatedly observed in a laser processing apparatus, the laser processing apparatus comprising: a chuck stage having a holding surface for holding the workpiece; a laser oscillator oscillating a laser beam; and a first concentrator converging the laser beam emitted from the laser oscillator to irradiate the workpiece held by the chuck stage, wherein the laser beam observation method comprises the following steps: a preparation step, preparing an observation unit, the observation unit... The unit includes a second condenser, a microscope, and an imaging element. The second condenser focuses the laser beam in a direction different from the holding surface of the chuck stage. The microscope magnifies the laser beam focused by the second condenser. The imaging element observes the focal point of the magnified laser beam by the microscope. The unit is configured in a position that can receive the laser beam emitted from the laser oscillator. The unit is also configured to observe the state of the focal point of the laser beam emitted from the laser oscillator and incident on the imaging element.

[0009] The preferred method for observing a laser beam also includes the following judgment step: judging whether the state of the focusing point of the laser beam observed through this observation step is qualified.

[0010] The invention of this application can suppress contamination of optical components and can easily adjust optical components. Attached Figure Description

[0011] Figure 1 This is a perspective view showing an example of the structure of a laser processing apparatus according to an embodiment.

[0012] Figure 2 It is shown schematically. Figure 1 The diagram shows the structure of the laser beam irradiation unit and the observation unit of the laser processing device.

[0013] Figure 3 It is shown Figure 2 A three-dimensional diagram of the structure of the laser beam irradiation unit and the observation unit.

[0014] Figure 4 This is a flowchart illustrating the process of observing a laser beam according to an embodiment.

[0015] Figure 5 This is a schematic diagram illustrating the structure of the laser beam irradiation unit and the observation unit of a modified laser processing apparatus.

[0016] Label Explanation

[0017] 1, 1-2: Laser processing device; 10: Chuck worktable; 11: Holding surface; 20, 20-2: Laser beam irradiation unit; 21: Laser beam; 22: Laser oscillator; 23, 24, 28: Reflector; 25: Adjustment lens; 26: Mounting plate; 29: First condenser; 30, 30-2: Observation unit; 31, 31-2: Direction conversion mirror; 32: Housing; 33: Second condenser; 34: Microscope; 35: Imaging element; 100: Workpiece. Detailed Implementation

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the constituent elements described below include contents that are readily conceived by those skilled in the art and substantially the same. Additionally, the structures described below can be appropriately combined. Furthermore, various omissions, substitutions, or modifications to the structure can be made without departing from the spirit of the present invention.

[0019] First, the structure of the laser processing apparatus 1 according to an embodiment of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a perspective view showing a structural example of the laser processing apparatus 1 according to the embodiment. Figure 2 It is shown schematically. Figure 1 A schematic diagram of the structure of the laser beam irradiation unit 20 and the observation unit 30 of the laser processing apparatus 1 shown. Figure 3 It is shown Figure 2 A perspective view of the structure of the laser beam irradiation unit 20 and the observation unit 30. In the following description, the X-axis direction is a direction on the horizontal plane. The Y-axis direction is a direction perpendicular to the X-axis direction on the horizontal plane. The Z-axis direction is a direction perpendicular to both the X-axis and Y-axis directions. In the laser processing apparatus 1 of the embodiment, the processing feed direction is the X-axis direction, and the indexing feed direction is the Y-axis direction.

[0020] like Figure 1 and Figure 2 As shown, the laser processing apparatus 1 includes a chuck table 10, a laser beam irradiation unit 20, an observation unit 30, an X-axis movement unit 40, a Y-axis movement unit 50, a Z-axis movement unit 60, an imaging unit 70, and a display unit 80. The laser processing apparatus 1 of this embodiment is a device that processes a workpiece 100 held on the chuck table 10 by irradiating it with a laser beam 21 through the laser beam irradiation unit 20. The processing of the workpiece 100 by the laser processing apparatus 1 includes, for example, modifying layer formation processing to form a modified layer inside the workpiece 100 through stealth cutting; groove processing to form a groove on the front surface of the workpiece 100; or cutting processing to cut the workpiece 100 along a predetermined dividing line; and so on.

[0021] The workpiece 100 is a wafer, such as a semiconductor device wafer or optical device wafer, with a substrate such as silicon (Si), sapphire (Al2O3), gallium arsenide (GaAs), or silicon carbide (SiC). However, the workpiece 100 is not limited to any particular embodiment; in this invention, it may not be in a circular shape. For example, a strip 111 with a diameter larger than the outer diameter of the workpiece 100 and attached to an annular frame 110 may be attached to the back surface of the workpiece 100 and supported within the opening of the annular frame 110.

[0022] The chuck stage 10 holds the workpiece 100 using a holding surface 11. The holding surface 11 is a circular plate shape formed of porous ceramic or the like. In this embodiment, the holding surface 11 is a plane parallel to the horizontal direction. The holding surface 11 is connected to a vacuum suction source, for example, via a vacuum suction path. The chuck stage 10 attracts and holds the workpiece 100 placed on the holding surface 11. A plurality of clamping parts 12 are arranged around the chuck stage 10 to clamp the annular frame 110 supporting the workpiece 100.

[0023] The chuck table 10 rotates about an axis parallel to the Z-axis via a rotary unit 13. The rotary unit 13 is supported by an X-axis moving plate 14. The rotary unit 13 and the chuck table 10 move in the X-axis direction via the X-axis moving plate 14 and the X-axis moving unit 40. The rotary unit 13 and the chuck table 10 move in the Y-axis direction via the X-axis moving plate 14, the X-axis moving unit 40, and the Y-axis moving plate 15 and the Y-axis moving unit 50.

[0024] The laser beam irradiation unit 20 is a unit that irradiates the workpiece 100 held by the chuck table 10 with a pulsed laser beam 21. For example... Figure 2 and Figure 3 As shown, the laser beam irradiation unit 20 includes a laser oscillator 22, a reflector 23, 24, an adjustment lens 25, a mounting plate 26, a first condenser 29, and a direction conversion mirror 31.

[0025] The laser oscillator 22 oscillates to produce a laser with a specified wavelength for processing the workpiece 100. The laser beam 21 irradiated by the laser beam irradiation unit 20 has a wavelength that is either transmissible or absorptive to the workpiece 100.

[0026] Reflector 23 reflects the laser beam 21 emitted from laser oscillator 22 toward reflector 24. Reflector 24 further reflects the laser beam 21 reflected by reflector 23 toward observation unit 30. In the case that the laser beam 21 emitted from laser oscillator 22 is UV (ultraviolet), a reflective film for reflecting UV is formed on reflectors 23 and 24.

[0027] The adjustment lens 25 is positioned in the optical path of the laser beam 21 between the laser oscillator 22 and the reflector 24. The adjustment lens 25 propagates the laser beam 21 emitted from the laser oscillator 22 towards the observation unit 30 or the processing point of the workpiece 100. In this embodiment, the adjustment lens 25 is composed of multiple lenses. Figure 3 As shown, in this embodiment, the adjustment target lenses 25 are mounted on the mounting plate 26 in a state where they are housed in the support 251. The support 251 supports the outer edge of each lens in the adjustment target lenses 25, leaving the central part of the lens exposed.

[0028] Mounting plate 26 includes a flat plate body 261 and a plurality of fixing parts 262. The fixing parts 262 are provided on the plate body 261 and detachably fix the adjustment lens 25 and the direction conversion mirror 31 (described later). In one embodiment, the fixing part 262 is a threaded hole (not shown) for screws to be threaded into a through hole 252 of the through support 251, but this is not a limitation in the present invention. In one embodiment, a plurality of fixing parts 262 are provided at intervals along the optical path of the laser beam 21 between the laser oscillator 22 and the reflector 23, and also at intervals along a vertical direction perpendicular to the optical path.

[0029] The first condenser 29 focuses the laser beam 21 reflected by the direction conversion mirror 31 (described later) onto the workpiece 100 held on the chuck table 10 for focused irradiation. That is, the first condenser 29 is a focusing lens for machining. In this embodiment, the first condenser 29 is a biconvex single lens. At least the first condenser 29 in the laser beam irradiation unit 20 is supported on the Z-axis direction moving unit 60 (see reference 1). Figure 1 The Z-axis moving unit 60 is mounted on a column 3 that is erected from the main body 2 of the laser processing device 1.

[0030] The direction-changing mirror 31 is detachably disposed in the optical path of the laser beam 21 between the laser oscillator 22 and the second condenser 33 of the observation unit 30 (described later). In this embodiment, the direction-changing mirror 31 is detachably disposed in the optical path of the laser beam 21 between the adjustment target lens 25 and the second condenser 33. Figure 3 As shown, in this embodiment, the outer edge of the direction conversion mirror 31 is supported by a support 311. The support 311 is mounted on a mounting plate 26. Thus, the direction conversion mirror 31 is mounted on the mounting plate 26. When the laser beam 21 emitted from the laser oscillator 22 is UV, a reflective film that reflects UV light is formed on the direction conversion mirror 31.

[0031] The observation unit 30 is a unit used to simulate the state of the focusing point of the laser beam 21 irradiating the workpiece 100. In an embodiment, the observation unit 30 includes a housing 32, a second condenser 33, a microscope 34, and an imaging element 35.

[0032] When the direction-changing mirror 31 is positioned in the optical path of the laser beam 21 between the laser oscillator 22 and the second condenser 33, it reflects the laser beam 21 propagating from the adjustment lens 25 towards the workpiece 100 held by the holding surface 11 of the chuck stage 10. When the direction-changing mirror 31 is removed from the optical path of the laser beam 21 between the laser oscillator 22 and the second condenser 33, the laser beam 21, having passed through the adjustment lens 25, is incident on the imaging element 35 via the second condenser 33 and the microscope 34.

[0033] The housing 32 internally houses a second condenser 33, a microscope 34, and an imaging element 35. For example... Figure 3 As shown, the housing 32 is mounted on the mounting plate 26. That is, the observation unit 30 in this embodiment is configured to be detachable from the mounting plate 26. With the direction conversion mirror 31 removed from the optical path of the laser beam 21 between the laser oscillator 22 and the second condenser 33, the laser beam 21 emitted from the laser oscillator 22 enters the housing 32.

[0034] The second condenser 33 focuses the laser beam 21 in a direction different from the holding surface 11 of the chuck stage 10. In the observation unit 30, the laser beam 21, focused in a direction different from that during processing, is observed via a direction-conversion mirror 31. That is, the second condenser 33 is a simulated focusing lens. In this embodiment, the second condenser 33 is a biconvex single lens. The focal distance of the second condenser 33 is the same as that of the first condenser 29. That is, the focusing point of the laser beam 21 focused by the second condenser 33 is a simulated processing point. In this embodiment, the focal distance of the second condenser 33 is 50 mm. In this embodiment, the second condenser 33 focuses the laser beam 21 incident on the housing 32 and guides it towards the microscope 34.

[0035] The microscope 34 magnifies the laser beam 21 that has been focused by the second condenser 33. The magnification of the microscope 34 is set, for example, to be more than 10x and less than 30x, and in this embodiment, it is set to 20x. When the laser beam 21 oscillating from the laser oscillator 22 is UV, the microscope 34 includes a UV-compatible microscope lens that is resistant to UV.

[0036] The imaging element 35 observes the focal point of the laser beam 21 magnified by the microscope 34. The imaging element 35 captures images within a defined field of view, specifically the focal point of the laser beam 21 within that field of view. The imaging element 35 may include, for example, a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor). The focal distance of the second condenser 33 is the same as that of the first condenser 29; therefore, the imaging element 35 can simulate the focal point of the laser beam 21 reflected by the direction-converting mirror 31 during processing. The operator can adjust optical components such as the object lens 25 while observing the simulated processing point image captured by the imaging element 35.

[0037] The observation unit 30 can be removed after adjustment, or it can remain in place after adjustment to observe the light leakage of the laser beam 21 transmitted through the direction conversion mirror 31.

[0038] like Figure 1 As shown, the X-axis moving unit 40 is a unit that moves the chuck stage 10 and the laser beam irradiation unit 20 relative to each other in the X-axis direction, which is the processing feed direction. In this embodiment, the X-axis moving unit 40 moves the chuck stage 10 in the X-axis direction. In this embodiment, the X-axis moving unit 40 is provided on the device body 2 of the laser processing apparatus 1.

[0039] The X-axis moving unit 40 supports the X-axis moving plate 14 for free movement in the X-axis direction. The X-axis moving unit 40 includes a known ball screw 41, a known pulse motor 42, and a known guide rail 43. The ball screw 41 is configured to rotate freely about an axis. The pulse motor 42 rotates the ball screw 41 about its axis. The guide rail 43 supports the X-axis moving plate 14 for free movement in the X-axis direction. The guide rail 43 is fixedly mounted on the Y-axis moving plate 15.

[0040] The Y-axis moving unit 50 is a unit that moves the chuck table 10 and the laser beam irradiation unit 20 relative to each other in the Y-axis direction, which is the indexing feed direction. In this embodiment, the Y-axis moving unit 50 moves the chuck table 10 in the Y-axis direction. In this embodiment, the Y-axis moving unit 50 is provided on the device body 2 of the laser processing apparatus 1.

[0041] The Y-axis moving unit 50 supports the Y-axis moving plate 15 for free movement in the Y-axis direction. The Y-axis moving unit 50 includes a known ball screw 51, a known pulse motor 52, and a known guide rail 53. The ball screw 51 is configured to rotate freely about an axis. The pulse motor 52 rotates the ball screw 51 about its axis. The guide rail 53 supports the Y-axis moving plate 15 for free movement in the Y-axis direction. The guide rail 53 is fixedly mounted on the device body 2.

[0042] The Z-axis moving unit 60 is a unit that moves the focusing point of the laser beam 21, which is focused by the first concentrator 29 of the laser beam irradiation unit 20, in a direction perpendicular to the optical axis of the holding surface 11 of the chuck table 10. More specifically, the Z-axis moving unit 60 moves the chuck table 10 and the laser beam irradiation unit 20 relative to each other in the Z-axis direction, which is the direction for adjusting the position of the focusing point. In this embodiment, the Z-axis moving unit 60 moves the laser beam irradiation unit 20 in the Z-axis direction. In this embodiment, the Z-axis moving unit 60 is mounted on a column 3 erected from the device body 2 of the laser processing apparatus 1.

[0043] The Z-axis moving unit 60 irradiates at least the first concentrator 29 in the laser beam 20 (see reference). Figure 2 The support is movable in the Z-axis direction. The Z-axis movement unit 60 includes a known ball screw 61, a known pulse motor 62, and a known guide rail 63. The ball screw 61 is configured to rotate freely about an axis. The pulse motor 62 rotates the ball screw 61 about an axis. The guide rail 63 supports the laser beam irradiation unit 20 for movable in the Z-axis direction. The guide rail 63 is fixedly mounted on the column 3.

[0044] The imaging unit 70 is configured, for example, to capture images from directly above the first condenser 29 of the laser beam irradiation unit 20. The imaging unit 70 includes a coaxial camera, a CCD camera, or an infrared camera.

[0045] The display unit 80 is a display section composed of a liquid crystal display device or the like. The display unit 80 displays, for example, a setting screen for processing conditions, the state of the workpiece 100 captured by the imaging unit 70, and the state of the processing operation on the display surface. The display unit 80 also displays, for example, an image of the focal point of the laser beam 21 captured by the imaging element 35 on the display surface.

[0046] When the display surface of the display unit 80 includes a touch panel, the display unit 80 may include an input section. The input section can accept various operations from the operator, such as registering processing content information. The input section may be an external input device such as a keyboard. The display unit 80 switches the information and images displayed on the display surface through operations from the input section, etc. The display unit 80 may include a notification section. The notification section emits at least one of sound and light to notify the operator of the laser processing apparatus 1 of pre-set notification information. The notification section may be an external notification device such as a speaker or a light-emitting device.

[0047] Next, the observation method of the laser beam 21 in the embodiment will be described. Figure 4 This is a flowchart illustrating the observation method of the laser beam 21 according to the embodiment. The observation method of the laser beam 21 includes a preparation step 201, an arrangement step 202, an observation step 203, and a determination step 204.

[0048] Preparation step 201 is the step of preparing the observation unit 30. That is, in preparation step 201, the observation unit 30 is prepared as follows: the observation unit 30 has: a second condenser 33 that focuses the laser beam 21 in a direction different from the holding surface 11 of the chuck stage 10; a microscope 34 that magnifies the laser beam 21 focused by the second condenser 33; and an imaging element 35 that observes the focusing point of the laser beam 21 magnified by the microscope 34.

[0049] The placement step 202 involves placing the observation unit 30, prepared in preparation step 201, at a position capable of receiving the laser beam 21 emitted from the laser oscillator 22. In placement step 202 of this embodiment, the observation unit 30 is placed in the optical path of the laser beam 21, which is reflected by the mirror 24 and passes through the adjustment lens 25, with the second condenser 33, microscope 34, and imaging element 35 arranged side by side. At this time, the direction conversion mirror 31 is removed beforehand from the optical path between the mirror 24 and the second condenser 33.

[0050] Observation step 203 is a step of observing the state of the focusing point of the laser beam 21 emitted from the laser oscillator 22 and incident on the imaging element 35. In observation step 203, the laser beam 21 is irradiated toward the observation unit 30, which is configured in configuration step 202. For the laser beam 21 incident on the housing 32 of the observation unit 30, the focusing point, which is converged by the second concentrator 33, is magnified by the microscope 34 and photographed by the imaging element 35. The image of the focusing point of the laser beam 21 photographed by the imaging element 35 is displayed, for example, on the display surface of the display unit 8 so that the operator can confirm it.

[0051] Determination step 204 is a step of determining whether the state of the focusing point of the laser beam 21 observed in observation step 203 is acceptable. In determination step 204, for example, the beam shape and luminous intensity distribution at the processing point of the laser beam 21 are determined based on the shape and brightness distribution of the focusing point in the captured image. The determination in determination step 204 can, for example, be performed by the control unit of the laser processing apparatus 1. The control unit can, for example, determine whether the state of the focusing point of the laser beam 21 is acceptable by determining whether the shape and brightness distribution of the focusing point in the captured image are within a preset range.

[0052] In judgment step 204, if the result is deemed unqualified, adjustments are made to optical components such as the object lens 25 while reviewing the image captured by the imaging element 35 of the focal point of the laser beam 21. In judgment step 204, if the result is deemed qualified, the adjustment process ends.

[0053] [Variation Example]

[0054] Next, the structure of the modified laser processing apparatus 1-2 will be described with reference to the accompanying drawings. Figure 5 This is a schematic diagram illustrating the structure of the laser beam irradiation unit 20-2 and the observation unit 30-2 of the modified laser processing apparatus 1-2. Compared with the laser processing apparatus 1 of the embodiment, the modified laser processing apparatus 1-2 differs in that it has a laser beam irradiation unit 20-2 and an observation unit 30-2 instead of a laser beam irradiation unit 20 and an observation unit 30.

[0055] Compared to the laser beam irradiation unit 20 of the embodiment, the modified laser beam irradiation unit 20-2 differs in that it does not include the direction conversion mirror 31, but includes the reflector 28. Furthermore, compared to the observation unit 30 of the embodiment, the modified observation unit 30-2 differs in that it also includes the direction conversion mirror 31-2.

[0056] The direction conversion mirror 31-2 is detachably disposed in the optical path of the laser beam 21 between the laser oscillator 22 and the reflector 28. In a modified example, the direction conversion mirror 31-2 is detachably disposed in the optical path of the laser beam 21 between the adjustment lens 25 and the reflector 28. In a modified example, the direction conversion mirror 31-2 is installed inside the housing 32.

[0057] When the direction-changing mirror 31-2 is positioned in the optical path of the laser beam 21 between the laser oscillator 22 and the reflector 28, it reflects the laser beam 21 that has passed through the adjustment lens 25, causing the laser beam 21 to pass through the second condenser 33 and the microscope 34 and then onto the imaging element 35. When the direction-changing mirror 31-2 is removed from the optical path of the laser beam 21 between the laser oscillator 22 and the reflector 28, the laser beam 21 that has passed through the adjustment lens 25 is then incident on the reflector 28.

[0058] The reflector 28 causes the laser beam 21, which is reflected by the reflector 24 and passes through the adjustment lens 25, to be reflected toward the workpiece 100 held by the holding surface 11 of the chuck stage 10. In addition, when the direction conversion mirror 31-2 is removed from the optical path of the laser beam 21 between the laser oscillator 22 and the reflector 28, the laser beam 21 is incident on the reflector 28.

[0059] As explained above, in the laser processing apparatuses 1 and 1-2 of the embodiments and modifications, by means of a replica concentrator (second concentrator 33) and an optical system that amplifies and observes the laser beam 21 focused by the replica concentrator, it is possible to observe the laser beam 21 in the same state as the processing point without performing processing. Therefore, the time spent preparing the workpiece 100 for adjustment and the processing time can be reduced. In addition, it is possible to suppress the adhesion of debris generated from the workpiece 100 during processing to the optical components during adjustment. Furthermore, by observing the laser beam 21 while performing adjustment, abnormalities in the laser beam 21 can be noticed during the adjustment stage, thus preventing rework.

[0060] Furthermore, the present invention is not limited to the embodiments described above. That is, various modifications and implementations can be made without departing from the spirit of the present invention.

Claims

1. A laser processing apparatus, wherein the laser processing apparatus has: a chuck table having a holding surface that holds a workpiece; a laser oscillator that oscillates laser light; a direction conversion mirror; a first condenser that condenses a laser beam emitted from the laser oscillator and reflected by the direction conversion mirror and irradiates the workpiece held by the chuck table; and an observation unit that observationally observes a state of a condensing point of the laser beam irradiated to the workpiece, the observation unit includes: a second condenser that condenses the laser beam in a direction different from the holding surface of the chuck table; a microscope that magnifies the laser beam condensed by the second condenser; and a photographing element that observes a condensing point of the laser beam magnified by the microscope, the direction conversion mirror is detachably disposed on an optical path between the laser oscillator and the second condenser, in a state in which the direction conversion mirror is disposed on the optical path, the direction conversion mirror reflects the laser beam toward the first condenser and transmits a leakage light of the laser beam, in a state in which the direction conversion mirror is removed from the optical path, the laser beam is transmitted through the second condenser and the microscope and is incident on the photographing element.

2. The laser processing apparatus according to claim 1, wherein the observation unit is configured to be detachable.

3. An observation method of a laser beam that observationally observes a state of a laser beam irradiated to a workpiece in a laser processing apparatus having: a chuck table having a holding surface that holds the workpiece; a laser oscillator that oscillates laser light; a direction conversion mirror; and a first condenser that condenses the laser beam emitted from the laser oscillator and reflected by the direction conversion mirror and irradiates the workpiece held by the chuck table, wherein, the observation method of the laser beam includes steps of: a preparation step of preparing an observation unit having a second condenser that condenses the laser beam in a direction different from the holding surface of the chuck table, a microscope that magnifies the laser beam condensed by the second condenser, and a photographing element that observes a condensing point of the laser beam magnified by the microscope; a disposition step of disposing the observation unit at a position at which the laser beam emitted from the laser oscillator is received and removing the direction conversion mirror from an optical path between the laser oscillator and the second condenser; and an observation step of observing a state of a condensing point of the laser beam emitted from the laser oscillator and incident on the photographing element, the observation method of the laser beam further includes: in a state in which the direction conversion mirror is disposed on the optical path, the observation unit observes a leakage light of the laser beam that is not reflected toward the first condenser but is transmitted.

4. The observation method of the laser beam according to claim 3, wherein the observation method of the laser beam further includes a determination step of determining whether or not a state of the condensing point of the laser beam observed by the observation step is acceptable.

Images