JP2011119419A - Laser processing apparatus, and laser processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser processing apparatus reducing an area where a laser process is not performed. <P>SOLUTION: A mask that makes the beam cross section of a laser beam into a long shape whose length is variable is positioned on the optical path of the laser beam emitted from a light source. The subject to be processed is held on a holding stand. The beam cross section shaped by the mask forms an image on the surface of the subject to be processed. A stage or the like moves so that a beam incidence area on which the laser beam is incident moves over the surface of the subject to be processed in a direction perpendicular to the longitudinal direction of the beam incidence area. An illumination inhibition area and an illumination permission area are defined on the holding surface of the holding stand. A control device stores the position information of a boundary line between the illumination prohibition area and the illumination permission area, and varies the length of the beam cross section shaped by the mask, based on the positional relationship between the subject to be processed and the beam incidence area and the position information of the boundary line, so that the illumination prohibition area will not be illuminated with the laser beam. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an apparatus and a method for performing laser processing while causing a laser beam to enter a processing target and moving the incident position of the laser beam on the processing target.

  For example, a long beam having a long beam cross section in one direction on the surface of the semiconductor wafer is used for laser annealing for activating impurities implanted into the semiconductor wafer. By scanning the long beam in a direction perpendicular to the length direction, the band-shaped region of the semiconductor wafer can be annealed. By performing the raster scan, a plurality of band-like regions can be annealed.

  In order to form a long beam, for example, a mask having a long transmission region and an imaging optical system that forms an image on the semiconductor wafer are used. Patent Document 1 discloses an apparatus that scans an exposure pattern by individually driving a mask and a stage that holds a semiconductor wafer.

JP 2007-19529 A

  When raster scanning is performed using a long beam on the surface of a circular semiconductor wafer, the edge of the annealed region becomes stepped. For this reason, an area where laser processing is not performed (an area that is not annealed) occurs near the edge of the semiconductor wafer. If the laser beam is scanned to the outside of the edge of the semiconductor wafer, almost the entire region can be laser processed. However, in this method, there is a concern that the stage on which the semiconductor wafer is placed is irradiated with a laser beam, and the stage is damaged or particles are generated.

  An object of the present invention is to provide a laser processing apparatus and a laser processing method for reducing an area where laser processing is not performed.

According to one aspect of the invention,
A light source that emits a laser beam;
A mask which is arranged on the optical path of the laser beam emitted from the light source and makes the beam cross section of the laser beam variable in length, and
A holding table for holding a processing object;
An optical system that forms an image of the beam section shaped by the mask on the surface of the object to be processed held by the holding table;
The light source, the mask, the imaging optical system, so that a beam incident region on which the laser beam is incident moves on the surface of the processing object in a direction intersecting the length direction of the beam incident region, And a moving mechanism for moving at least one of the stages;
A control device for controlling the mask and the moving mechanism;
When the object to be processed is held on the holding table, an irradiation prohibited area where laser beam irradiation is prohibited and an irradiation allowable area where laser beam irradiation is allowed are defined on the holding surface of the holding table,
The control device stores the positional information of the boundary line between the irradiation prohibited area and the irradiation allowable area, and is based on the positional relationship between the processing object and the beam incident area and the positional information of the boundary line. There is provided a laser processing apparatus that changes the length of the beam cross section of the laser beam shaped by the mask so that the laser beam is not irradiated to the irradiation prohibited region.

According to another aspect of the invention,
A first transmission region that is long in one direction uses an optical system that forms an image on the surface of a semiconductor wafer having at least a part of an outer peripheral line along the circumference. A laser beam is incident on the surface of the semiconductor wafer, and laser A method of laser processing the semiconductor wafer by moving the laser beam or the semiconductor wafer so that an incident position of the beam moves in a direction intersecting a length direction of the image of the first transmission region. ,
Laser processing that shields a part of the first transmission region so that the laser beam does not enter the region outside the semiconductor wafer when the image of the first transmission region straddles the outer peripheral line of the semiconductor wafer. A method is provided.

According to yet another aspect of the invention,
A light source that emits a laser beam;
A mask that is disposed on the optical path of the laser beam emitted from the light source, has a transmission region that is long in one direction, and the outside of the transmission region is a region that shields the laser beam;
An imaging optical system for forming an image of a transmission region of the mask;
A stage for holding a processing object at a position where a transmission region of the mask is imaged by the imaging optical system;
A moving mechanism that moves at least one of the light source, the mask, the imaging optical system, and the stage so that the incident position of the laser beam moves on the surface of the processing target;
The upper surface of the stage includes a placement area for placing the processing object and a side area surrounding the placement area in plan view, and the side area is lower than the placement area and has a height thereof. The difference is that the laser processing apparatus is set such that the upper surface of the side region is out of the focal depth when the transmission region of the mask is imaged on the surface of the processing object held in the mounting region. Is provided.

According to yet another aspect of the invention,
A light source that emits a laser beam;
A stage for holding the object to be processed at a position where the laser beam emitted from the light source enters;
A moving mechanism for moving at least one of the light source and the stage so that the incident position of the laser beam moves on the surface of the processing object;
The laser beam is disposed on the surface of the processing object held on the stage, shields the laser beam from entering at least a part of the first region on the outer peripheral side of the surface of the processing object, and the first Two light-shielding plates that are provided with an opening so that a laser beam is incident on the second region inside the one region, the relative position with respect to the object to be processed is fixed, and are spaced apart from each other When,
There is provided a laser processing apparatus having an exhaust device for exhausting the space between the two light shielding plates.

  By changing the length of the transmission region of the mask, it is possible to reduce the region that is not irradiated with the laser that occurs in the vicinity of the edge even when the outer shape of the object to be processed is circular or the like.

(1A) is a schematic view of a laser processing apparatus according to Example 1, (1B) is a plan view of a fixed mask, and (1C) is a plan view of a movable mask. (2A) is a plan view of a semiconductor wafer as a processing object, and (2B) shows the relationship between the shape of the laser incident area when the laser irradiation is performed near the edge of the processing object and the processing object. It is a top view. (3A)-(3C) are top views which show the positional relationship of both when a fixed mask and a movable mask are piled up. 6 is a plan sectional view showing another configuration example of a mask used in the laser processing apparatus according to Embodiment 1. FIG. 6 is a schematic view of a laser processing apparatus according to Embodiment 2. FIG. (6A) is a cross-sectional view showing the positional relationship between the XY stage, the processing object, and the laser beam when the laser is incident on the processing object using the laser processing apparatus according to Example 2, and (6B) And (6C) are cross-sectional views taken along one-dot chain lines 6B-6B and 6C-6C, respectively (6A). 6 is a schematic diagram of a laser processing apparatus according to Embodiment 3. FIG. (8A) is a sectional view of the aperture, and (8B) is a plan view of the aperture.

  Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 1A shows a schematic diagram of a laser processing apparatus according to the first embodiment. The light source 10 emits a laser beam. The light source 10 includes, for example, a laser oscillator, a shutter, a diversion lens, a uniformizing optical system, a condenser lens, and the like. A mask 17 is disposed on the optical path of the laser beam emitted from the light source 10. The mask 17 includes a fixed mask 15 and a movable mask 16 that are arranged with a minute gap therebetween. An xyz orthogonal coordinate system is defined in which the traveling direction of the laser beam is the negative direction of the z axis.

  FIG. 1B shows a plan view of the fixed mask 15, and FIG. 1C shows a plan view of the movable mask 16. The fixed mask 15 includes a transmission region 15A that is long in the y direction. The transmission region 15A transmits the laser beam. The region (light shielding region) 15B other than the transmission region 15A shields the laser beam. The movable mask 16 includes a light shielding region 16B that is long in the y direction. The light shielding region 16B shields the laser beam. The region (transmission region) 16A other than the light shielding region 16B transmits the laser beam. As the fixed mask 15 and the movable mask 16, for example, a transparent substrate with Ni plating is used. Ni plating is applied to the light shielding regions 15B and 16B.

  The light shielding area 16B is thicker and longer than the transmission area 15A. For this reason, it is possible to overlap the movable mask 16 with the fixed mask 15 so that the light shielding region 16B completely includes the transmission region 15A.

  Returning to FIG. 1A, the description will be continued. The fixed mask 15 and the movable mask 16 are arranged with a small gap so that the surfaces plated with Ni face each other. With respect to the x direction, the transmissive region 15A is disposed inside the light shielding region 16B.

  The fixed mask 15 is fixed with respect to the path of the laser beam. The movable mask 16 is supported by the moving mechanism 18 so as to be movable in the y direction. When the movable mask 16 is moved in the y direction, the length of the portion where the transmission region 15A and the light shielding region 16B overlap is changed. For this reason, the dimension in the x direction of the region through which the laser beam is transmitted (portion where the transmission region 15A and the transmission region 16A overlap) changes. A portion where the transmission region 15A and the transmission region 16A overlap is referred to as a “composite transmission region”.

  The laser beam that has passed through the combined transmission region of the mask 17 enters the surface of the processing object 30 via the lens (imaging optical system) 20. The processing object 30 is held on the holding table 21 by a vacuum chuck or an electrostatic chuck. The holding table 21 moves the holding table 21 in the x direction and the y direction by the moving mechanism 23.

  The imaging optical system 20 images the combined transmission area of the mask 17 on the surface of the processing object 30. The Ni-plated surfaces of the fixed mask 15 and the mask 16 are within the depth of field of the imaging optical system 20. For this reason, both the edge of the transmission region 15 </ b> A of the fixed mask 15 and the edge of the light shielding region 16 </ b> B of the movable mask 16 clearly form an image (focus) on the surface of the processing object 30. The control device 22 controls the moving mechanism 18 and the moving mechanism 23.

  FIG. 2A shows a plan view of the processing object 30. The processing object 30 is, for example, a semiconductor wafer, and a notch 30A is formed at a circumferential edge. An image (hereinafter referred to as a laser incident region) 31 of the combined transmission region is formed on the surface of the processing object 30.

  By driving the moving mechanism 23 shown in FIG. 1A, the surface of the processing object 30 is raster scanned by the beam incident area 31. The beam incident area 31 has an elongated shape that is long in the y direction, the main scanning direction corresponds to the x direction, and the sub scanning direction corresponds to the y direction.

  FIG. 2B shows how the shape of the laser incident area 31 changes during main scanning. It is not necessary to irradiate a laser beam to an annular region having a width of about 2 mm in contact with the circumferential edge of the surface of the processing object 30. Note that laser beam irradiation may be performed. The laser beam must be irradiated to the inner area. The region outside the processing target 30 should not be irradiated with a laser beam. Hereinafter, the area outside the processing object 30 is referred to as an irradiation prohibited area 37. A region inside the outer periphery of the processing object 30 is referred to as an irradiation allowable region 36. A region inside the annular region having a width of about 2 mm in contact with the circumferential edge is referred to as an irradiation target region 35.

  An image 32 (a region 32 indicated by a broken line in FIG. 2B) of the transmission region 15A (FIG. 1B) of the fixed mask 15 straddles the boundary line (the edge of the processing object 30) between the irradiation allowable region 36 and the irradiation prohibited region 37. At this time, the combined transmission region is shortened so that the laser incident region 31 (the region 31 indicated by the solid line in FIG. 2B) does not enter the irradiation prohibited region 37. However, the length of the combined transmission region is set so that the region where the irradiation target region 35 and the image 32 of the transmission region 15A overlap is irradiated with the laser beam. Specifically, the light-shielded area of the image 32 of the transmission area 15 </ b> A is prevented from entering the irradiation target area 35.

  3A to 3C are plan views showing a state where the fixed mask 15 and the movable mask 16 overlap each other.

  FIG. 3A shows a state in which the transmissive region 15A is completely enclosed in the light shielding region 16B. At this time, the composite transmission region does not exist. This state corresponds to a state where the image 32 of the transmission region 15A (FIG. 1B) does not overlap with the irradiation target region 35, as indicated by a broken line 3A in FIG. 2B.

  FIG. 3B shows a state where the movable mask 16 is shifted in the y direction and the combined transmission region 33 appears. In this state, as shown by a broken line and a solid line 3B in FIG. 2B, the image 32 of the transmission region 15A straddles the boundary line between the irradiation prohibited region 37 and the irradiation allowable region 36 and enters the irradiation target region 35. Corresponds to the state of being out. Of the image 32 in the transmission area 15A, the area overlapping the irradiation prohibited area 37 is shielded from light by the light shielding area 16B. At this time, a region overlapping the irradiation target region 35 in the image 32 of the transmission region 15A is not shielded by the light shielding region 16B. That is, in the image 32 of the transmission region 15A, the boundary between the region shielded by the light shielding region 16B and the region not shielded from light is the region within the irradiation allowable region 36 and the region outside the irradiation target region 35. To position.

  FIG. 3C shows a state in which the movable mask 16 is further shifted in the y direction so that the light shielding region 16B does not overlap with the transmission region 15A. At this time, the combined transmission region 33 is equal to the transmission region 15A. This state corresponds to a state where the image 32 of the transmission region 15A does not overlap the irradiation prohibited region 37, as indicated by the solid line 3C in FIG. 2B.

  When the length of the laser incident area 31 is fixed, the image 32 of the transmission area 15A straddles the boundary line between the irradiation prohibited area 37 and the irradiation allowable area 36, as indicated by a broken line and a solid line 3B in FIG. 2B. In some cases, laser irradiation could not be performed. In the laser processing apparatus according to the first embodiment, since the length of the laser incident area 31 can be changed, the irradiation forbidden area 37 and the irradiation target area 35 are irradiated with laser without irradiating the irradiation prohibited area 37 with laser. It can be carried out. For this reason, the area | region which cannot irradiate a laser among the surfaces of the process target object 30 can be reduced.

  The case where the planar shape of the image 32 of the transmissive region 15A of the fixed mask 15 is, for example, a rectangle having a length of 2.5 mm and a width of 250 μm is compared with a case of a rectangle having a length of 5 mm and a width of 125 μm. Since the areas of both the images 32 are equal, the light intensity on the surface of the processing object 30 is also equal. Therefore, it is possible to perform the same laser treatment using any mask.

  Increasing the length of the image 32 can reduce the number of sub-scans when the surface of the processing device 30 is raster scanned. In general, the acceleration / deceleration time of the holding table 21 is required when scanning one row shown in FIG. 2A and shifting to the next row scanning. For this reason, an increase in the number of sub-scans leads to an increase in laser processing time.

  When the length of the laser incident region 31 is unchanged, if the image 32 is lengthened, the region that is not irradiated with the laser spreads. In the first embodiment, even if the image 32 is lengthened, the actual laser incident area 31 can be shortened, so that the area not irradiated with the laser does not spread. For this reason, it is possible to shorten the laser processing time by lengthening the image 32 and reducing the number of sub-scans.

  In the first embodiment, the image of the synthetic transmission region 33 is moved in the direction intersecting the length direction on the surface of the processing object 30 by moving the holding table 21. Instead of moving the holding table 21, the light source 10, the mask 17, and the imaging optical system 20 may be moved. Further, the light emitted from the light source 10 may be propagated to the mask 17 by an optical fiber. In this case, the light source 10 and the incident end of the optical fiber may be stationary, and the output end of the optical fiber, the mask 17, and the imaging optical system 20 may be moved.

  Further, the light source 10, the mask 17, and the imaging optical system 20 may be moved in the y-axis direction, and the holding base 21 may be moved in the x-axis direction. Conversely, the light source 10, the mask 17, and the imaging optical system 20 may be moved in the x-axis direction, and the holding base 21 may be moved in the y-axis direction.

  FIG. 4A shows a plan sectional view of a mask 17 according to a modification of the first embodiment. In the modification, the mask 17 is composed of one light shielding plate 17B. A parallelogram opening 17A is formed in the light shielding plate 17B. The opening 17A has a pair of edges parallel to the x-axis. The other edge is inclined with respect to the y-axis. The beam cross section 19 of the laser beam at the position where the mask 17 is disposed has a long shape in the y-axis direction. The shape of the beam cross section is obtained by a homogenizing optical system or the like constituting the light source 10 shown in FIG. 1A.

  The beam cross section 19 is longer than the dimension of the opening 17A in the y-axis direction. For this reason, the light shielding plate 17 </ b> B shields a region having a certain length from the end of the beam cross section 19. A beam cross section of the laser beam transmitted through the opening 17A is imaged on the surface of the processing object 30. When the beam cross section 19 intersects both of a pair of edges parallel to the x axis of the opening 17A, the beam cross section on the surface of the processing target 30 is the longest.

  As shown in FIG. 4B, when the mask 17 is moved in the x direction, a state in which the beam cross section 19 intersects an oblique edge with respect to the y axis of the opening 17A is obtained. At this time, in the beam cross section 19, the region shielded by the light shielding plate 17B becomes longer, and the beam cross section of the laser beam transmitted through the mask 17 becomes shorter than in the case of FIG. 4A. Thereby, the beam incident area on the surface of the processing object 30 is also shortened. By controlling the positional relationship between the beam cross section 19 and the mask 17, the length of the beam cross section of the laser beam transmitted through the mask 17 can be changed. Thereby, the length of the beam incident area | region in the surface of the process target object 30 can be adjusted.

  FIG. 5 is a schematic diagram of a laser processing apparatus according to the second embodiment. Hereinafter, differences from the laser processing apparatus according to the first embodiment illustrated in FIG. 1A will be described. In the second embodiment, the movable mask 16 of FIG. 1A is not disposed, and the mask 17 is configured only by the fixed mask 15. The upper surface of the holding table 21 is divided into a placement area 21A and a side area 21B. In a plan view, the side region 21B surrounds the placement region 21A. The side area 21B is lower than the placement area 21A. The processing object 30 is placed on the placement area 21A.

  In plan view, the placement area 21 </ b> A is completely contained in the processing object 30. For this reason, when the processing object 30 is observed from above the holding table 21, the placement area 21A cannot be viewed, and only the side area 21B is visible.

  FIG. 6A shows an example of a cross section parallel to the yz plane between the holding table 21 and the laser beam path. The incident area of the laser beam straddles the edge of the processing object 30. That is, a part of the laser beam is incident on the processing object 30 and the remaining part is incident on the side region 21 </ b> B of the holding table 21.

  6B is a cross-sectional view taken along one-dot chain line 6B-6B in FIG. 6A. The transmission region of the mask 17 forms an image (focuss) on the surface of the processing object 30.

  6C is a cross-sectional view taken along one-dot chain line 6C-6C in FIG. 6A. The laser beam is once focused at the same height as the surface of the processing object 30, and then diverges and enters the side region 21B. The difference in height between the placement area 21A and the side area 21B is that the upper surface of the side area 21B is formed when the transmission area of the mask 17 is imaged on the surface of the processing object 30 held in the placement area 21A. Is set to a dimension that deviates from the depth of focus.

  Since the laser beam is out of focus on the side region 21B, the light intensity (power density) of the laser beam on the surface of the side region 21B is weaker than the light intensity on the surface of the processing object 30. Become. For this reason, the side region 21B is not easily damaged by the laser beam, and generation of particles is also suppressed.

  In the second embodiment, as shown in FIG. 6A, laser irradiation can be performed even when the incident region of the laser beam straddles the edge of the processing object 30. For this reason, laser irradiation can be performed on almost the entire area of the processing object 30.

  FIG. 7 shows a schematic diagram of a laser processing apparatus according to the third embodiment. Hereinafter, differences from the laser processing apparatus according to the first embodiment illustrated in FIG. 1A will be described. In the third embodiment, the movable mask 16 of FIG. 1A is not disposed, and the mask 17 is configured by only the fixed mask 15. A light shielding plate (aperture) 40 having an opening is disposed above (in front of) the holding table 21.

  8A shows a sectional view of the aperture 40, and FIG. 8B shows a plan view of the aperture 40. As shown in FIG. A cross-sectional view taken along one-dot chain line 8A-8A in FIG. 8B corresponds to FIG. 8A. The aperture 40 includes two light shielding plates 41 and 42 arranged with a gap therebetween. Of the two light shielding plates 41 and 42, the light shielding plate 41 arranged on the processing object 30 side is provided with an opening 46 smaller than the processing object 30. The other light shielding plate 42 is provided with an opening 47 larger than the opening 46. In plan view, the openings 46 and 47 and the processing object 30 are arranged substantially concentrically. The light shielding plate 41 shields the laser beam so that the laser beam does not enter a partial region on the outer peripheral side of the surface of the processing target 30. The laser beam that has passed through the openings 46 and 47 enters the processing object 30.

  A through hole 44 is provided in the light shielding plate 42. The exhaust device 49 exhausts the inside of the gap 43 between the light shielding plate 41 and the light shielding plate 42 through the through hole 44.

  For example, aluminum is used for the light shielding plate 41 and the light shielding plate 42. The upper surface of the light shielding plate 41 (the surface on which the laser beam is incident) is roughened. As a result, the incident laser beam is scattered and the intensity of the regular reflection light is reduced.

  When the incident region of the laser beam straddles the edge of the opening 46, a part of the laser beam is incident on the processing object 30 and the remaining laser beam is incident on the light shielding plate 41. The upper opening 47 is set to a size such that the laser beam does not enter the upper light shielding plate 42 when the incident region of the laser beam straddles the edge of the opening 46. Specifically, in plan view, the distance from the edge of the opening 46 to the edge of the upper opening 47 may be longer than the length of the laser beam incident area.

  Particles generated when the laser beam is incident on the light shielding plate 41 are discharged to the outside through the gap 43 and the through hole 44. For this reason, the adhesion of particles to the processing object 30 can be suppressed.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

DESCRIPTION OF SYMBOLS 10 Light source 15 Fixed mask 15A Transmission area 15B Light shielding area 16 Movable mask 16A Transmission area 16B Light shielding area 17 Mask 17A Opening part 17B Light shielding plate 18 Moving mechanism 20 Imaging optical system 21 XY stage 21A Mounting area 21B Side area 22 Control device 30 Processing Object 31 Laser Incidence Area 32 Fixed Mask Transmission Area Image 33 Composite Transmission Area 35 Irradiation Target Area 36 Irradiation Allowed Area 37 Irradiation Prohibited Area 40 Light-shielding plate (aperture) having an opening
41, 42 Light shielding plate 43 Gap 44 Through hole 46, 47 Opening 49 Exhaust device

Claims (7)

A light source that emits a laser beam;
A mask which is arranged on the optical path of the laser beam emitted from the light source and makes the beam cross section of the laser beam variable in length, and
A holding table for holding a processing object;
An optical system that forms an image of the beam section shaped by the mask on the surface of the object to be processed held by the holding table;
The light source, the mask, the imaging optical system, so that a beam incident region on which the laser beam is incident moves on the surface of the processing object in a direction intersecting the length direction of the beam incident region, And a moving mechanism for moving at least one of the stages;
A control device for controlling the mask and the moving mechanism;
When the object to be processed is held on the holding table, an irradiation prohibited area where laser beam irradiation is prohibited and an irradiation allowable area where laser beam irradiation is allowed are defined on the holding surface of the holding table,
The control device stores the positional information of the boundary line between the irradiation prohibited area and the irradiation allowable area, and is based on the positional relationship between the processing object and the beam incident area and the positional information of the boundary line. A laser processing apparatus for changing a length of a beam cross section of the laser beam shaped by the mask so that the irradiation prohibited area is not irradiated with the laser beam. The mask is
A fixed mask that includes a first transmission region that is long in one direction and has a fixed size, the position of which is fixed with respect to the optical path of the laser beam emitted from the light source;
A movable mask that overlaps the fixed mask, shields a part or the entire region in the length direction of the first transmission region, and can change the length of the light shielding part;
The control device moves the movable mask so that the laser beam does not enter the irradiation prohibited area when the image of the first transmission area on the holding table enters the irradiation prohibited area. The laser processing apparatus according to claim 1, wherein a part of the first transmission region is shielded from light. An irradiation target region to be irradiated with a laser beam is defined in the irradiation allowable region of the processing target object held on the holding table,
The laser processing apparatus according to claim 2, wherein the control device moves the movable mask so that the laser beam incident on the irradiation target region is not shielded when the movable mask is moved. The light source has an elongated beam cross section at the position of the mask,
The mask includes a light shielding plate that shields a region of a certain length from an end of the beam cross section, and the length of the light shielded region when the light shielding plate moves in a direction crossing the longitudinal direction of the beam cross section. The laser processing apparatus according to claim 1, wherein the angle changes. A first transmission region that is long in one direction uses an optical system that forms an image on the surface of a semiconductor wafer having at least a part of an outer peripheral line along the circumference. A laser beam is incident on the surface of the semiconductor wafer, and laser A method of laser processing the semiconductor wafer by moving the laser beam or the semiconductor wafer so that an incident position of the beam moves in a direction intersecting a length direction of the image of the first transmission region. ,
Laser processing that shields a part of the first transmission region so that the laser beam does not enter the region outside the semiconductor wafer when the image of the first transmission region straddles the outer peripheral line of the semiconductor wafer. Method. A light source that emits a laser beam;
A mask that is disposed on the optical path of the laser beam emitted from the light source, has a transmission region that is long in one direction, and the outside of the transmission region is a region that shields the laser beam;
An imaging optical system for forming an image of a transmission region of the mask;
A stage for holding a processing object at a position where a transmission region of the mask is imaged by the imaging optical system;
A moving mechanism that moves at least one of the light source, the mask, the imaging optical system, and the stage so that the incident position of the laser beam moves on the surface of the processing target;
The upper surface of the stage includes a placement area for placing the processing object and a side area surrounding the placement area in plan view, and the side area is lower than the placement area and has a height thereof. The difference is that the laser processing apparatus is set such that the upper surface of the side region deviates from the depth of focus when the transmission region of the mask is imaged on the surface of the processing object held in the mounting region. . A light source that emits a laser beam;
A stage for holding the object to be processed at a position where the laser beam emitted from the light source enters;
A moving mechanism for moving at least one of the light source and the stage so that the incident position of the laser beam moves on the surface of the processing object;
The laser beam is disposed on the surface of the processing object held on the stage, shields the laser beam from entering at least a part of the first region on the outer peripheral side of the surface of the processing object, and the first Two light-shielding plates that are provided with an opening so that a laser beam is incident on the second region inside the region 1, the relative position with respect to the object to be processed is fixed, and are spaced apart from each other When,
A laser processing apparatus having an exhaust device for exhausting a space between the two light shielding plates.

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