Laser processing equipment

Abstract

To provide a laser processing device which allows a user to correctly confirm a state of a processing groove formed on a surface of a wafer.SOLUTION: A laser processing device comprises: a chuck table which holds a wafer 10; laser irradiation means which performs laser processing by irradiating the wafer held by the chuck table with a laser beam; feeding means which relatively feeds the chuck table and the laser beam; main imaging means which images a processing region; auxiliary imaging means 7B; and display means 8. The auxiliary imaging means comprises: an objective lens 71; a camera 72 which generates an image via the objective lens; a half mirror 73; a light source 74 which illuminates the wafer 10; a first polarizing plate 75 between the camera and the half mirror; and a second polarizing plate 76 between the light source and the half mirror. The second polarizing plate is arranged such that a polarizing axis of light irradiated with from the light source and reflected by the half mirror through the second polarizing plate is rotated at a required angle with respect to a polarizing axis of the first polarizing plate.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a laser processing apparatus that performs laser processing by irradiating a wafer held on a chuck table with a laser beam. [Background technology]

[0002] Wafers, on whose surface devices such as ICs and LSIs are formed along dividing lines, are then separated into individual device chips using a dicing machine or laser processing machine, and these are used in electrical equipment such as mobile phones and personal computers.

[0003] The laser processing apparatus at least comprises a chuck table for holding a wafer, a laser irradiation means for irradiating the wafer held on the chuck table with a laser beam to perform laser processing, a feeding means for feeding the chuck table and the laser irradiation means relatively for processing, an imaging means for imaging the area to be laser processed, and a display means, and is capable of laser processing the wafer with high precision (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2004-188475 A Summary of the Invention [Problem to be solved by the invention]

[0005] When forming a groove on the surface of a wafer by ablation processing using the above-mentioned laser processing device, it is necessary to set the laser processing conditions appropriately according to the material and thickness of the wafer, and in order to check whether the settings are appropriate, the state of the groove actually formed on the surface of the wafer may be checked. If the state of this groove is imaged using a conventional imaging means used in the alignment process originally provided in the laser processing device, there is a problem that the groove cannot be distinguished from the debris generated by the ablation processing because the debris adheres to both sides of the groove, and the condition of the groove cannot be accurately grasped.

[0006] The present invention has been made in consideration of the above-mentioned facts, and its main technical objective is to provide a laser processing apparatus that can accurately check the state of a processing groove formed on the surface of a wafer. [Means for solving the problem]

[0007] In order to solve the above-mentioned main technical problem, according to the present invention, there is provided a laser processing apparatus comprising at least a chuck table for holding a wafer, a laser irradiation means for irradiating a laser beam onto the wafer held on the chuck table to perform laser processing, a feeding means for relatively feeding the chuck table and the laser beam, a main imaging means for imaging an area to be laser processed, an auxiliary imaging means, and a display means, wherein the auxiliary imaging means comprises an objective lens, a camera for generating an image via the objective lens, a half mirror disposed between the camera and the objective lens, a light source for illuminating the wafer held on the chuck table via the half mirror and the objective lens, a first polarizing plate disposed between the camera and the half mirror, and a second polarizing plate disposed between the light source and the half mirror, and the second polarizing plate is disposed so that the polarization axis of light irradiated from the light source, passing through the second polarizing plate and reflected by the half mirror is rotated by a required angle with respect to the polarization axis of the first polarizing plate.

[0008] The auxiliary imaging means is preferably configured to image the laser-machined area of ​​the wafer held on the chuck table and to image the grooves and debris formed by the laser machining. The first polarizing plate and the second polarizing plate constituting the auxiliary imaging means may be selectively positionable between an active position and a non-active position, and may be positioned at the non-active position to constitute the main imaging means. Furthermore, it is preferable that the required angle is 90 degrees. Effect of the Invention

[0009] The laser processing apparatus of the present invention comprises at least a chuck table for holding a wafer, a laser irradiation means for irradiating a laser beam onto the wafer held on the chuck table to perform laser processing, a feed means for relatively feeding the chuck table and the laser beam, a main imaging means for imaging an area to be laser processed, an auxiliary imaging means, and a display means, the auxiliary imaging means including an objective lens, a camera for generating an image via the objective lens, a half mirror disposed between the camera and the objective lens, and a display means for displaying an image of the half mirror and the objective lens. The laser processing system includes a light source that illuminates the wafer held on the chuck table via a first polarizing plate disposed between the camera and the half mirror, and a second polarizing plate disposed between the light source and the half mirror. The second polarizing plate is disposed so that the polarization axis of light irradiated from the light source, passing through the second polarizing plate and reflected by the half mirror is rotated by a required angle with respect to the polarization axis of the first polarizing plate. This makes it possible to clearly contrast the processed grooves formed by laser processing with the debris, thereby making it possible to clearly check the quality of the processed grooves. [Brief description of the drawings]

[0010] [Figure 1] FIG. 2 is an overall perspective view of the laser processing device. [Diagram 2] 2 is a perspective view showing a state in which an imaging means attached to the laser processing apparatus shown in FIG. 1 functions as a main imaging means. FIG. [Diagram 3] FIG. 1 is a perspective view illustrating an embodiment of a laser processing step. [Figure 4] 3 is a perspective view showing a state in which the imaging means shown in FIG. 2 functions as an auxiliary imaging means. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a laser processing apparatus configured based on the present invention will be described in detail with reference to the accompanying drawings.

[0012] 1 shows an overall perspective view of a laser processing apparatus 2 according to this embodiment. As shown in the figure, a workpiece to be processed by the laser processing apparatus 2 of this embodiment is a disk-shaped wafer 10, which is held on an annular frame F via an adhesive tape T.

[0013] The laser processing apparatus 2 is equipped with a chuck table 25 that holds the wafer 10, a laser irradiation means 6 that irradiates the wafer 10 held on the chuck table 25 with a laser beam to perform laser processing, a feeding means 30 that relatively feeds the chuck table 25 and the laser beam irradiated from the laser irradiation means 6 for processing, an imaging means 7 that also serves as a main imaging means for imaging the area to be laser processed and an auxiliary imaging means for imaging the processing grooves and debris formed by laser processing, and a display means 8.

[0014] The holding means 20 including the chuck table 25 includes a rectangular X-axis direction movable plate 21 mounted on the base 3 so as to be movable in the X-axis direction, a rectangular Y-axis direction movable plate 22 mounted so as to be movable in the Y-axis direction along the guide rails 21a, 21a on the X-axis direction movable plate 21, a cylindrical support 23 fixed to the upper surface of the Y-axis direction movable plate 22, and a rectangular cover plate 26 fixed to the upper end of the support 23. The chuck table 25 is a circular member extending upward through an elongated hole formed on the cover plate 26, and is configured to be rotatable by a rotation drive means (not shown). The chuck table 25 has a holding surface 25a formed of a porous material having air permeability and defined by the X-axis direction and the Y-axis direction. The holding surface 25a is connected to a suction means (not shown) by a flow path passing through the support 23. The X-axis direction is the direction indicated by the arrow X in FIG. 1, and the Y-axis direction is the direction indicated by the arrow Y, which is perpendicular to the X-axis direction. The plane defined by the X-axis direction and the Y-axis direction is substantially horizontal.

[0015] The feed means 30 includes an X-axis moving means 31 that moves the chuck table 25 of the holding means 20 and the laser beam emitted from the laser irradiation means 6 relatively in the X-axis direction to feed the work, and a Y-axis moving means 32 that moves the chuck table 25 and the laser beam emitted from the laser irradiation means 6 relatively in the Y-axis direction. The X-axis moving means 31 includes a ball screw 34 that extends in the X-axis direction on the base 3, and a motor 33 connected to one end of the ball screw 34. A nut portion (not shown) of the ball screw 34 is formed on the lower surface of the X-axis direction movable plate 21. The X-axis moving means 31 converts the rotational motion of the motor 33 into linear motion by the ball screw 34 and transmits it to the X-axis direction movable plate 21, and moves the X-axis direction movable plate 21 forward and backward in the X-axis direction along the guide rails 3a, 3a on the base 3. The Y-axis moving means 32 has a ball screw 36 extending in the Y-axis direction on the X-axis movable plate 21, and a motor 35 connected to one end of the ball screw 36. A nut portion (not shown) of the ball screw 36 is formed on the lower surface of the Y-axis movable plate 22. The Y-axis moving means 32 converts the rotational motion of the motor 35 into linear motion by the ball screw 36 and transmits it to the Y-axis movable plate 22, and moves the Y-axis movable plate 22 forward and backward in the Y-axis direction along the guide rails 21a, 21a on the X-axis movable plate 21.

[0016] A frame 37 is erected at the back of the holding means 20, and includes a vertical wall 37a extending upward (in the Z-axis direction) from the top surface of the base 3, and a horizontal wall 37b extending horizontally. The horizontal wall 37b houses the optical system of the laser irradiation means 6 and the imaging means 7. A condenser 61 constituting the laser irradiation means 6 is disposed on the lower surface of the tip of the horizontal wall 37b, and an objective lens 71 of the imaging means 7 is disposed at a position spaced apart from the condenser 61 in the X-axis direction. The above-mentioned laser irradiation means 6 is a means for irradiating a laser beam having a wavelength that is absorbed by the wafer 10, and is set to a laser processing condition for performing ablation processing on the surface of the wafer 10. The objective lens 71 shown in the figure indicates an objective lens housed in a cylindrical case. A display means 8 is disposed above the horizontal wall 37b. The above-mentioned laser irradiation means 6, imaging means 7, display means 8, moving means 30, etc. are electrically connected to a control means described later, and are controlled based on instruction signals sent from the control means, so that laser processing of the wafer 10 is performed.

[0017] The imaging means 7 of this embodiment will be described with reference to Fig. 2. Fig. 2 shows the optical system of the imaging means 7 housed in the horizontal wall portion 37b of the frame body 37, which is omitted for convenience of explanation. As described above, the imaging means 7 of this embodiment serves both as the main imaging means 7A that images the area to be laser processed and the auxiliary imaging means 7B (see Fig. 4) that images the grooves and debris formed by the laser processing, as will be described later, and Fig. 2 shows the state in which the imaging means 7 functions as the main imaging means 7A that images the area to be laser processed.

[0018] As shown in Fig. 2, the imaging means 7 includes an objective lens 71, a camera 72 that generates an image through the objective lens 71, a half mirror 73 arranged between the camera 72 and the objective lens 71, a light source 74 that illuminates the wafer 10 held on the chuck table 25 through the half mirror 73 and the objective lens 71, a first polarizing plate 75 arranged between the camera 72 and the half mirror 73, and a second polarizing plate 76 arranged between the light source 74 and the half mirror 73. The light source 74 is a light source that irradiates visible light L1, for example. The first polarizing plate 75 is a polarizing plate whose polarization axis is set in a predetermined direction (Y-axis direction in this embodiment), and is a polarizing plate that transmits only light vibrating in the Y-axis direction when light passes through the first polarizing plate 75. On the other hand, in the embodiment shown in FIG. 2, the second polarizing plate 76 is arranged so that the polarization axis of the light irradiated from the light source 74, passing through the second polarizing plate 76, and reflected by the half mirror 73 is rotated by 90 degrees with respect to the polarization axis of the first polarizing plate 75, that is, in the X-axis direction perpendicular to the Y-axis direction. The camera 72 is connected to the control means 100, and an image transmitted from the camera 72 to the control means 100 is displayed on the display means 8. In the above embodiment, the visible light L1 irradiated from the light source 74 is arranged so that the polarization axis of the light after passing through the second polarizing plate 76 and reflecting by the half mirror 73 is rotated by 90 degrees with respect to the polarization axis of the first polarizing plate 75, but the present invention is not limited to this. It is sufficient that the polarization axis of the light after passing through the second polarizing plate 76 and reflecting by the half mirror 73 is appropriately rotated with respect to the polarization axis of the first polarizing plate 75 according to the state of the surface of the wafer 10. In other words, it is sufficient that the polarization axis of the second polarizing plate 76 is rotated by a required angle relative to the polarization axis of the first polarizing plate 75, and is not limited to being set along the X-axis or Y-axis direction.

[0019] Further, the first polarizing plate 75 of the imaging means 7 of this embodiment is held by a first polarizing plate holding plate 77, and the second polarizing plate 76 is held by a second polarizing plate holding plate 78. The first polarizing plate holding plate 77 and the second polarizing plate holding plate 78 are held by a holding mechanism (not shown) and are configured to be movable in the horizontal direction. Further, an opening 77a is formed in the first polarizing plate holding plate 77, and by moving the first polarizing plate holding plate 77 in the direction indicated by the arrow R1, when the wafer 10 held on the chuck table 25 is imaged by the camera 72, the first polarizing plate 75 can be selectively moved from an operating position where the first polarizing plate 75 operates to a non-operating position where the first polarizing plate 75 does not operate. Similarly, an opening 78a is formed in the second polarizing plate holding plate 78, and by moving the second polarizing plate holding plate 78 in the direction indicated by the arrow R2, the plate can be selectively moved from an operating position where the light L1 emitted from the light source 74 passes through the second polarizing plate 76 to a non-operating position where the second polarizing plate 76 does not operate. In the imaging means 7 shown in Fig. 2, both the first polarizing plate holding plate 77 and the second polarizing plate holding plate 78 are moved to the non-operating positions. As a result, the imaging means 7 is set to a state where it functions as the main imaging means 7A that images the area to be laser processed by the camera 72.

[0020] The laser processing device 2 of this embodiment has roughly the configuration described above, and the functions and actions of this embodiment will be described below.

[0021] When performing laser processing using the laser processing device 2 of this embodiment, first, as shown in FIG. 1, the wafer 10 is transported to the laser processing device 2, placed on the chuck table 25 of the holding means 20, and held by suction. As shown in the figure, the wafer 10 has a surface on which a plurality of devices 12 are formed, which is partitioned by the division lines 14. Next, the above-mentioned feed means 30 is operated to position the wafer 10 held on the chuck table 25 directly under the objective lens 71 of the imaging means 7. At this time, as described based on FIG. 2, the imaging means 7 positions the first polarizing plate holding plate and the second polarizing plate holding plate 78 in the non-operating position, and is in a state of functioning as the main imaging means 7A for imaging the area to be laser processed. Next, as shown in FIG. 2, the visible light L1 irradiated from the light source 74 is reflected by the reflecting surface 73b of the half mirror 73 through the opening 78a of the second polarizing plate holding plate 78 in the non-operating position, as shown by the arrow R3, and is guided to the objective lens 71 side. The visible light L1 reflected by the reflecting surface 73b of the half mirror 73 is reflected by the wafer 10 held on the chuck table 25 to become reflected light L2, which is guided to the half mirror 73 via the objective lens 71 and passes through the reflecting surface 73b and the upper surface 73a of the half mirror 73 (a part of the reflected light L2 is reflected toward the light source 74). Furthermore, the reflected light L2 passes through the opening 77a of the first polarizing plate holding plate 77 and is guided to the camera 72 as shown by the arrow R4. As a result, the camera 72 generates an image and displays it on the display means 8 via the control means 100. As shown in FIG. 2, the image generated by the camera 72 includes the division lines 14, which are areas where processing grooves should be formed by laser processing, and the position of the division lines 14 is detected. Next, the chuck table 25 is rotated by the above-mentioned rotation drive means to align the division lines 14 in the X-axis direction, and the position of the area to be processed is stored in the control means 100, completing the alignment process. Once the alignment step has been performed, the laser processing step is carried out, which will be described below with reference to FIG.

[0022] Based on the position information of the dividing lines 14 detected by the above-mentioned alignment step, the chuck table 25 is moved to position the condenser 61 of the laser beam application means 6 directly above the processing start position of the dividing lines 14 in the predetermined direction, and the focal point of the laser beam LB is positioned on the dividing lines 14 of the wafer 10 and irradiated, and the wafer 10 is processed and fed in the X-axis direction together with the chuck table 25 to perform ablation processing along the predetermined dividing lines 14 of the wafer 10 to form a processed groove 110. After the processed groove 110 is formed along the predetermined dividing lines 14, the wafer 10 is indexed and fed in the Y-axis direction by the interval of the dividing lines 14, and the unprocessed dividing lines 14 adjacent in the Y-axis direction are positioned directly below the condenser 61. Then, in the same manner as described above, the focal point of the laser beam LB is positioned on the dividing lines 14 of the wafer 10 and irradiated, and the wafer 10 is processed and fed in the X-axis direction to form the processed groove 110. Similarly, the wafer 10 is machined and fed in the X-axis direction and the Y-axis direction to form grooves 110 along all of the dividing lines 14 along the X-axis direction. Next, the wafer 10 is rotated 90 degrees to align the unmachined dividing lines 14 perpendicular to the dividing lines 14 along which the grooves 110 have already been formed, with the X-axis direction. Then, the remaining dividing lines 14 are irradiated with the laser beam LB by positioning the focusing point in the same manner as described above to form grooves 110 along all of the dividing lines 14 formed on the surface of the wafer 10, completing the laser machining process.

[0023] As described above, when the laser processing step is completed, a processing groove checking step described below is performed to check the condition of the processing groove 110. When performing the processing groove checking step, the above-mentioned feed means 30 is operated to move the chuck table 25, and the wafer 10 is positioned directly under the objective lens 71 of the imaging means 7. At this time, as shown in FIG. 4, the imaging means 7 moves the first polarizing plate holding plate 77 in the direction indicated by the arrow R5 to the working position, and moves the second polarizing plate holding plate 78 in the direction indicated by the arrow R6 to the working position. As a result, the imaging means 7 is brought into a state where it functions as an auxiliary imaging means 7B suitable for imaging the laser-processed area of ​​the wafer 10 held on the chuck table 25, i.e., the area where the processing groove 110 is formed, and imaging the processing groove 110 formed by the laser processing and the debris attached to both sides of it, which will be described later.

[0024] As described above, when the wafer 10 on which the machined groove 110 is formed is positioned directly under the objective lens 71 of the imaging means 7 serving as the auxiliary imaging means 7B, the light source 74 irradiates the wafer 10 with visible light L1. This visible light L1 passes through the second polarizing plate 76, and only the light L3, which is a component vibrating in the vertical direction, travels in the direction indicated by the arrow R7, is guided to and reflected by the reflecting surface 73b of the half mirror 73, and is irradiated via the objective lens 71 to the area on the wafer 10 on which the machined groove 110 is formed. The light L3 irradiated to the area on the wafer 10 on which the machined groove 110 is formed is reflected by the area on the wafer 10 on which the machined groove 110 is formed to become reflected light L4, which travels in the direction indicated by the arrow R8 via the objective lens 71 and passes through the half mirror 73 (part of which is reflected by the reflecting surface 73b). The reflected light L4 that passes through the half mirror 73 is guided to the first polarizing plate 75, and of the reflected light L4, only the transmitted light L5 that passes through the first polarizing plate 75 travels in the direction indicated by the arrow R9, and an image is generated by the camera 72 and displayed on the display means 8 via the control means 100.

[0025] Here, the above-mentioned passing light L5 will be described in more detail. As described above, the light L1 irradiated from the light source 74 passes through the second polarizing plate 76 whose polarization axis is set in the vertical direction (Z-axis direction), so that the polarization axis of the light L3 reflected by the half mirror 73 is rotated by 90 degrees with respect to the polarization axis of the first polarizing plate 75, that is, in the X-axis direction. When this light L3 is reflected on the wafer 10, if it is regularly reflected on the wafer 10, the direction of the polarization axis of the reflected light does not change and it is reflected in the X-axis direction. On the other hand, when it is reflected on the wafer 10, if it is reflected on a part of the wafer 10 that has a fine uneven surface, etc., the uneven surface causes diffuse reflection, resulting in reflected light containing polarization axes in various directions. Here, when the component of the reflected light L4 specularly reflected on the wafer 10 of this embodiment is guided to the first polarizing plate 75, the polarization axis of the first polarizing plate 75 faces the Y-axis direction, so the component of the reflected light L4 whose polarization axis is in the X-axis direction is blocked by the first polarizing plate 75 and cannot pass through. In contrast, if the reflected light L4 contains a component that is diffusely reflected on the wafer 10, when it is guided to the first polarizing plate 75, it contains light components in the direction of the polarization axis of the first polarizing plate 75 (the Y-axis direction) and light components with polarization axes close to the Y-axis direction, so that these reflected lights pass through the first polarizing plate 75 and reach the camera 72 to generate an image.

[0026] As shown in FIG. 4, when the light L3 is irradiated to an area where the groove 110 is properly formed, the light L3 is mainly reflected in the area, forming a reflected light with little diffuse reflection. In contrast, the debris formed on both sides of the groove 110 includes fine uneven surfaces, so the light L3 irradiated to this area is diffused and forms a reflected light containing light with polarization axes in various directions. When the reflected light L4 generated by the specular reflection and the diffuse reflection is guided to the first polarizing plate 75, the reflected light component generated by the specular reflection is blocked, and only the light whose polarization axis is in the Y-axis direction and close to the Y-axis direction among the reflected light generated by the diffuse reflection at the debris is transmitted to form the transmitted light L5. The transmitted light L5 thus formed is guided to the camera 72 to generate an image and display it on the display means 8 (groove confirmation process). As a result, as shown in FIG. 4, the contrast between the groove 110 and the debris 120 becomes clear, and it becomes possible to properly check the condition of the groove 110. For ease of explanation, the image displayed on the display means 8 in FIG. 4 is an image in which black and white are inverted.

[0027] In this embodiment, the first polarizing plate 75 and the second polarizing plate 76 are held by a first polarizing plate holding plate 77 and a second polarizing plate holding plate 78, and are configured so that they can be selectively positioned between an operative position and a non-operative position. By configuring them as a single imaging means 7 that serves as both the main imaging means 7A and the auxiliary imaging means 7B, it is possible to prevent the space required for arranging the imaging means from becoming excessive.

[0028] In the above-described embodiment, one imaging means 7 is configured to function as both the main imaging means 7A and the auxiliary imaging means 7B, but the present invention is not limited to this. The main imaging means 7A and the auxiliary imaging means 7B may be configured as independent and separate means, and the above-described alignment process and processing groove confirmation process may be performed by the separately configured main imaging means 7A and auxiliary imaging means 7B.

[0029] In the above embodiment, an example was shown in which laser processing was performed using a wafer 10 having a surface partitioned by a plurality of planned division lines 14 on which a plurality of devices 12 were formed, but the present invention is not limited to this, and a so-called dummy wafer on which no devices 12 were formed may also be used. Furthermore, in the above embodiment, an example was shown in which the polarization axis of the second polarizing plate 76 was rotated 90 degrees with respect to the polarization axis of the first polarizing plate 75, but as long as it is rotated by a required angle, i.e., greater than 0 degrees, the effect of blocking reflected light specularly reflected on the surface of the wafer 10 can be obtained. [Explanation of symbols]

[0030] 2: Laser processing equipment 3: Base 6: Laser irradiation means 61: Concentrator 7: Imaging means 71: Objective lens 72: Camera 73: Half mirror 74:Light source 75: First polarizing plate 76: Second polarizing plate 77: First polarizing plate holding plate 77a: Opening 78: Second polarizing plate holding plate 78a: Opening 10: Wafer 12: Device 14: Planned division line 20: Holding means 21:X-axis movable plate 22: Y-axis direction movable plate 25: Chuck table 30:Transportation means 31:X-axis movement means 32: Y-axis movement means 37:Frame body 37a: Vertical wall 37b:Horizontal wall part 100: Control means 110: Machining groove 120: Debris

Claims

1. The laser processing apparatus includes at least a chuck table for holding a wafer, a laser irradiation means for irradiating a laser beam onto the wafer held on the chuck table to perform laser processing, a feed means for relatively feeding the chuck table and the laser beam for processing, a main imaging means for imaging an area to be laser processed, an auxiliary imaging means, and a display means, the auxiliary imaging means includes an objective lens, a camera that generates an image through the objective lens, a half mirror disposed between the camera and the objective lens, a light source that illuminates the wafer held on the chuck table through the half mirror and the objective lens, a first polarizing plate disposed between the camera and the half mirror, and a second polarizing plate disposed between the light source and the half mirror; A laser processing apparatus in which the second polarizing plate is arranged so that the polarization axis of light irradiated from the light source, passing through the second polarizing plate, and reflected by the half mirror is rotated by a required angle relative to the polarization axis of the first polarizing plate.

2. 2. The laser processing apparatus according to claim 1, wherein the auxiliary imaging means is configured to be able to image a laser-processed area on the wafer held on the chuck table and to image a processing groove and debris formed by the laser processing.

3. The laser processing apparatus of claim 1, wherein the first polarizing plate and the second polarizing plate constituting the auxiliary imaging means can be selectively positioned between an operative position and a non-operative position, and when positioned in the non-operative position constitute the main imaging means.

4. 2. The laser processing apparatus according to claim 1, wherein the required angle is 90 degrees.

Images