Workpiece holding device, laser processing device, and laser annealing method

Abstract

The present invention provides a workpiece holding device that enables processing by irradiating the edges of workpieces such as semiconductor wafers with a laser beam. [Solution] The workpiece to be laser-processed is held in a workpiece holding device. The workpiece holding device comprises a first surface for holding the workpiece and a second surface located lower than the first surface. When the first surface is viewed from above, the first surface is encompassed by the workpiece held on the first surface, and the second surface extends outward from the workpiece held on the first surface.

Description

Technical Field

[0005]

[0001] The present invention relates to a workpiece holding device, a laser processing device, and a laser annealing method.

Background Art

[0002] As an annealing method for activating dopants doped in a semiconductor wafer, laser annealing is known in which a pulsed laser beam is incident on the wafer and the beam spot is moved within the wafer surface. If the beam spot protrudes from the wafer during laser annealing, the stage that adsorbs the wafer is damaged. In order to prevent damage to the stage, an irradiation prohibited area is defined at the peripheral edge of the wafer (Patent Document 1). The beam spot is moved within a circular irradiation permitted area surrounded by this irradiation prohibited area. As an example, an area within about several millimeters from the edge of the semiconductor wafer is set as the irradiation prohibited area.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] On the wafer surface of a semiconductor wafer, a plurality of chip regions in the shape of a square or a rectangle are defined. Depending on the width of the irradiation prohibited area, the laser beam is not incident on the chip region near the edge of the semiconductor wafer. For this reason, the number of chips that can be cut out from one semiconductor wafer is reduced. An object of the present invention is to provide a workpiece holding device, a laser processing device, and a laser annealing method capable of performing processing by irradiating a laser beam even in the vicinity of the edge of a workpiece such as a semiconductor wafer.

Means for Solving the Problems

[0006] According to another aspect of the present invention, The aforementioned workpiece holding device, A laser optical system that incidents a laser beam onto the surface of the workpiece held on the first surface A laser processing apparatus equipped with [a specific feature] is provided.

[0007] According to yet another aspect of the present invention, The workpiece is held on the first surface of the workpiece holding device, A laser annealing method in which a laser beam is incident on the upper surface of a workpiece held on the first surface, and the beam spot is moved while annealing is performed, A laser annealing method is provided in which, for a portion of the period during which the beam spot is moved, at least a portion of the beam spot is incident on the outside of the workpiece held on the first surface. [Effects of the Invention]

[0008] If at least a portion of the laser beam spot moves away from the workpiece, the detached portion of the laser beam is incident on the second surface. Since the second surface is located at a lower position than the first surface, the beam spot on the second surface becomes larger, and the energy density of the laser beam decreases. Therefore, even if the laser beam is incident near the edge of the workpiece and at least a portion of the beam spot moves away from the workpiece, damage to the workpiece holder is less likely to occur. This makes it possible to perform processing by incidenting the laser beam near the edge of the workpiece. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a block diagram of a laser processing apparatus according to the first embodiment. [Figure 2] Figure 2A is a plan view of the workpiece holding device 10 according to the first embodiment, and Figure 2B is a cross-sectional view taken along the dashed line 2B-2B in Figure 2A. [Figure 3] Figure 3 is a schematic partial plan view showing an example of the movement path of beam spot 65. [Figure 4] Figure 4 is a schematic diagram showing the beam spots 65 and 65A when the laser beam 68 is incident on the edge of the workpiece 60. [Figure 5] Figure 5 is a flowchart showing the procedure for the laser annealing method according to the first embodiment. [Figure 6] Figure 6 is a schematic partial plan view showing an example of the movement path of the beam spot 65 when annealing is performed using the annealing method according to the comparative example. [Figure 7] Figure 7A is a schematic plan view showing the positional relationship between the first surface 11A of the workpiece holding device according to the second embodiment and the workpiece 60, while Figures 7B and 7C are schematic plan views showing the shape of the first surface 11A of the workpiece holding device and the workpiece 60 in a plan view according to a modified version of the second embodiment. [Figure 8] Figure 8 is a cross-sectional view of the workpiece holding device 10 according to the third embodiment. [Figure 9]FIG. 9 is a cross-sectional view of the workpiece holding device 10 according to the fourth embodiment.

Mode for Carrying Out the Invention

[0010] Referring to FIGS. 1 to 6, a workpiece holding device, a laser processing device, and a laser annealing method according to the first embodiment will be described.

[0011] FIG. 1 is a block diagram of a laser processing device according to the first embodiment. A pulsed laser beam output from the laser optical system 50 is incident on the workpiece 60. By the incidence of the pulsed laser beam, the workpiece 60 is processed. For example, the workpiece 60 is a semiconductor wafer into which a dopant has been ion-implanted. By irradiating the semiconductor wafer with a pulsed laser beam, annealing for activating the dopant is performed.

[0012] The laser optical system 50 includes a laser oscillator 51, a beam expander 52, a beam shaping optical element 53, and a folding mirror 54. The laser oscillator 51 outputs a pulsed laser beam. The pulsed laser beam output from the laser oscillator 51 is incident on the workpiece 60 via the beam expander 52, the beam shaping optical element 53, and the folding mirror 54. In addition, an aperture, a lens, etc. may be arranged as necessary.

[0013] As the laser oscillator 51, for example, a fiber laser oscillator, a laser diode, a solid laser oscillator, etc. can be used. The beam expander 52 adjusts the beam size at the incident position of the laser beam to the beam shaping optical element 53. The beam shaping optical element 53 shapes the beam spot on the surface of the workpiece 60 and equalizes the intensity distribution. The beam shaping optical element 53 includes, for example, an imaging lens and images the beam cross-sectional shape at a predetermined location on the upper surface of the workpiece 60.

[0014] The object to be processed 60 is held on the upper surface of the object holding device 10. The object holding device 10 will be described in detail later with reference to FIGS. 2A and 2B. The object to be processed 60 is held horizontally, for example.

[0015] The object holding device 10 is supported by the drive mechanism 40. The drive mechanism 40 moves the object holding device 10 in two directions parallel to the horizontal plane and perpendicular to each other according to a command from the control device 70. Due to the movement of the object holding device 10, the object to be processed 60 moves in two directions parallel to the horizontal plane and perpendicular to each other. For example, an XY stage is used as the drive mechanism 40.

[0016] The control device 70 controls the drive mechanism 40 and the laser oscillator 51. For example, the control device 70 controls the drive mechanism 40 so that the pulsed laser beam is incident on the target position on the upper surface of the object to be processed 60. Further, the output timing of the pulsed laser beam from the laser oscillator 51 is controlled.

[0017] Figure 2A is a plan view of the workpiece holding device 10 according to the first embodiment, and Figure 2B is a cross-sectional view along the dashed line 2B-2B in Figure 2A. The workpiece holding device 10 includes a chuck table 11 and a ceramic plate 20. The chuck table 11 has an upward-facing first surface 11A and a second surface 11B that is continuous with the first surface 11A via a step 11C. The second surface 11B is positioned lower than the first surface 11A. When the first surface 11A is viewed from above (hereinafter sometimes simply referred to as "in a plan view"), the first surface 11A is encompassed by the workpiece 60 held by the first surface 11A. For example, the outer circumference of the first surface 11A coincides with the outer circumference of the workpiece 60. The shape of the first surface 11A and the workpiece 60 in a plan view is circular. In plan view, the second surface 11B extends beyond the workpiece 60 held by the first surface 11A. In Figure 2B, the member with the first surface 11A and the member with the second surface 11B are depicted as a single continuous member, but it is not necessary to provide the first surface 11A and the second surface 11B on a single member. For example, a structure in which the member with the first surface 11A and another member with the second surface 11B are interconnected may be used.

[0018] The first surface 11A, the step 11C, and the second surface 11B are made of metal, such as aluminum. A ceramic plate 20 is placed between the first surface 11A and the workpiece 60 held on the first surface 11A. The ceramic plate 20 has the function of preventing metal elements from penetrating the workpiece 60. Furthermore, placing the ceramic plate 20 provides a flatter surface for holding the workpiece 60. Note that if the penetration of metal elements into the workpiece 60 is not a problem, the placement of the ceramic plate 20 is not essential, and the workpiece 60 may be placed directly on the metal first surface 11A.

[0019] A suction passage 12 is provided within the chuck table 11. The suction passage 12 opens to the bottom of a groove 13, for example, arranged concentrically on the first surface 11A. The other end of the suction passage 12 opens to the side surface of the chuck table 11. The ceramic plate 20 is provided with a plurality of suction holes 21 that penetrate in the thickness direction. In a plan view, the plurality of suction holes 21 are arranged along the groove 13 provided on the first surface 11A. By drawing suction through the suction passage 12 from the side surface of the chuck table 11, the workpiece 60 can be vacuum-adsorbed onto the upper surface of the ceramic plate 20.

[0020] Next, with reference to Figure 3, an example of the beam spot's movement path on the upper surface (annealed surface) of the workpiece 60 will be described. Figure 3 is a schematic partial plan view showing an example of the beam spot 65's movement path. Mutually orthogonal x and y axes are defined on the upper surface of the workpiece 60. In Figure 3, the left-right direction is the x-axis, the up-down direction is the y-axis, and downward is defined as the positive direction of the y-axis. The shape of the beam spot 65 is, for example, a rectangle that is long in the y-axis direction. In Figure 3, the beam spot 65 of the first shot is hatched upwards to the right.

[0021] During annealing, the workpiece 60 is moved in the x-axis and y-axis directions relative to the laser beam path, thereby moving the beam spot 65 relative to the workpiece 60. Hereinafter, the relative movement between the workpiece 60 and the beam spot 65 will be expressed as the beam spot 65 moving relative to the workpiece 60.

[0022] For example, by alternately repeating a main scan, which moves the beam spot 65 in the x-axis direction while overlapping it, and a sub-scan, which displaces the beam spot 65 in the y-axis direction, the upper surface of the workpiece 60 is annealed. Here, "overlap" means a state in which two beam spots 65 from two temporally adjacent laser pulses partially overlap each other. The region into which the pulsed laser beam is incident in one main scan is called the main scan region 66.

[0023] Focusing on a specific location on the upper surface of the workpiece 60, a predetermined number of laser pulses are incident on that location during one main scan. For example, if the overlap rate in the x-axis direction is 50%, two laser pulses are incident on any location, and if the overlap rate in the x-axis direction is 2 / 3 (approximately 66%), three laser pulses are incident on any location. Near both ends of the main scan area 66, which is long in the x-axis direction, there are areas where the predetermined number of laser pulses are not incident. The range of the main scan in the x-axis direction is set so that the predetermined number of laser pulses are incident on the upper surface of the workpiece 60 from one end in the x-axis direction to the other within one main scan area 66.

[0024] The displacement of the beam spot 65 per sub-scan is such that the beam spot 65 partially overlaps in the y-axis direction before and after the sub-scan. For example, the displacement of the sub-scan is half the dimension of the beam spot 65 in the y-axis direction. In Figure 3, the area where the two main scan regions 66 before and after the sub-scan overlap and where a predetermined number of laser pulses are incident during the main scan is hatched downwards to the right.

[0025] For example, in the first scan, a portion of the main scanning region 66 of the beam spot 65 on the positive side of the y-axis overlaps with a portion of the main scanning region 66 of the beam spot 65 in the second scan. Similarly, a portion of the i-th main scanning region 66 on the positive side of the y-axis overlaps with a portion of the main scanning region 66 of the beam spot 65 in the (i+1)-th scan. The sub-scan range is set such that this overlapping region extends continuously from one end to the other on the upper surface of the workpiece 60 with respect to the y-axis.

[0026] By setting the main scanning range in the x-axis direction and the sub-scanning range in the y-axis direction in this way, a predetermined number of laser pulses will be incident on the entire upper surface of the workpiece 60. As a result, the entire upper surface of the workpiece 60 can be annealed uniformly.

[0027] When a pulsed laser beam is incident on the edge of the workpiece 60, the edge of the workpiece 60 passes through the inside of the beam spot 65. As a result, a portion of the beam spot 65 is located outside the workpiece 60.

[0028] Next, the size of the laser beam spot will be explained with reference to Figure 4. Figure 4 is a schematic diagram showing the beam spots 65 and 65A when the laser beam 68 is incident on the edge of the workpiece 60. A ceramic plate 20 is held on the first surface 11A of the workpiece holding device 10, and the workpiece 60 is held on top of the ceramic plate 20. The laser beam 68 output from the laser optical system 50 (Figure 1) is focused on the upper surface 61 of the workpiece 60, and the beam spot 65 is formed.

[0029] The laser beam 68 that passes over the upper surface 61 of the workpiece 60 becomes a divergent beam, causing blurring on the second surface 11B and enlarging the beam spot 65A. As the beam spot 65A enlarges, the pulse energy density decreases. For example, if the focal length of the objective lens of the laser optical system 50 is 100 mm and the height from the second surface 11B to the upper surface 61 of the workpiece 60 is 50 mm, the area of ​​the beam spot 65A will be approximately 600 times the area of ​​the beam spot 65. It is preferable to set the height difference between the first surface 11A and the second surface 11B so that the area of ​​the beam spot 65A is 50 times or more the area of ​​the beam spot 65.

[0030] Next, the laser annealing method according to the first embodiment will be described. Figure 5 is a flowchart showing the procedure of the laser annealing method according to the first embodiment. First, the workpiece 60 is held on the ceramic plate 20 placed on the first surface 11A of the workpiece holding device 10 and vacuum-adsorbed (step S1). The control device 70 (Figure 1) controls the laser oscillator 51 to start the incidence of a pulsed laser beam from the laser optical system 50 onto the workpiece 60 (step S2).

[0031] The control device 70 moves the workpiece holding device 10 by controlling the drive mechanism 40 (Figure 1) at the same time as the pulse laser beam is started to be injected, thereby moving the beam spot 65 (Figure 3) on the upper surface of the workpiece 60 (Step S3). For example, as explained with reference to Figure 3, the main scan and sub scan of the beam spot 65 are repeated alternately. During a portion of the time the beam spot 65 is moving, at least a portion of the beam spot 65 is injected outside the workpiece 60 held on the first surface 11A. The movement of the beam spot 65 continues until the pulse laser beam is injected over the entire upper surface of the workpiece 60 for a predetermined number of shots (Step S4).

[0032] When the pulsed laser beam has been incident on the entire upper surface of the workpiece 60 for a predetermined number of shots, the movement of the beam spot 65 and the incidence of the pulsed laser beam are terminated (step S5). After that, the workpiece 60 is removed from the workpiece holding device 10 (step S6).

[0033] Next, the excellent effects of the first embodiment will be described. In the first embodiment, as shown in Figure 4, in a plan view, the second surface 11B, which extends outward from the workpiece 60, is located at a lower position than the first surface 11A. As a result, the pulse energy density on the second surface 11B is lower than the pulse energy density at the upper surface of the ceramic plate 20 and at the position of the first surface 11A.

[0034] If the ceramic plate 20 or the first surface 11A extends outside the workpiece 60, a portion of the pulsed laser beam incident on the edge of the workpiece 60 will be incident on the ceramic plate 20 or the first surface 11A. Because the height difference between the top surface of the ceramic plate 20 or the first surface 11A and the top surface of the workpiece 60 is small, a high pulse energy density is maintained on the top surface of the ceramic plate 20 or the first surface 11A. As a result, the ceramic plate 20 or the first surface 11A is damaged by the incident pulsed laser beam.

[0035] In the first embodiment, the ceramic plate 20 and the first surface 11A are included within the workpiece 60 in a plan view, so the laser beam does not incident on the ceramic plate 20 or the first surface 11A. On the second surface 11B, where the laser beam may incident, the pulse energy density is low, so damage to the second surface 11B is suppressed. Thus, in the first embodiment, even when a pulsed laser beam is incident on the outside of the workpiece 60, the excellent effect of making the workpiece holding device 10 less susceptible to damage is obtained.

[0036] In order to obtain a sufficient effect that the workpiece 60 is less likely to be damaged, it is preferable to make the height difference between the first surface 11A and the second surface 11B 10 mm or more, and more preferable to make it 20 mm or more.

[0037] Next, we will explain the superior effects of the first embodiment in comparison with the comparative example shown in Figure 6. Figure 6 is a schematic partial plan view showing an example of the movement path of the beam spot 65 when annealing is performed using the comparative example annealing method. In the comparative example, in order to prevent damage to the ceramic plate 20 (Figure 4) and the first surface 11A (Figure 4), the main scan and sub-scan are performed under conditions that the beam spot 65 does not move outside the workpiece 60. As a result, the area in which the laser pulse is incident for a predetermined number of shots (the area with downward-sloping hatching in Figure 6) becomes narrower.

[0038] In particular, it becomes impossible to inject a predetermined number of laser pulses into the region near the edge of the workpiece 60. Since the operation of the electronic circuits in the chip region where the predetermined number of laser pulses were not injected cannot be guaranteed, the number of chips that can be cut from a single semiconductor wafer decreases.

[0039] In contrast, in the first embodiment, as explained with reference to Figure 3, a pulsed laser beam can be incident on the entire upper surface of the workpiece 60 for a predetermined number of shots. Therefore, the chip region can be placed close to the edge of the workpiece 60. As a result, the number of chips that can be cut from a single semiconductor wafer can be increased.

[0040] Next, a modified example of the first embodiment will be described. In the first embodiment, the edge of the first surface 11A was aligned with the edge of the workpiece 60 in a plan view, but the edge of the first surface 11A may be set back from the edge of the workpiece 60. In this case, the edge of the ceramic plate 20 is aligned with the edge of the first surface 11A.

[0041] Next, the amount of recession of the edge of the first surface 11A will be explained. Of the workpiece 60, the area outside the edge of the first surface 11A is not in contact with the ceramic plate 20, so the thermal history during annealing may differ from that of other areas. If the thermal history during annealing differs, the target annealing effect cannot be obtained. Therefore, it is preferable not to place the chip area in the area outside the edge of the first surface 11A. In other words, it is preferable to set the recession amount such that the condition is met that the edge of the first surface 11A is located outside the area where the chip area is placed.

[0042] Next, other modifications of the first embodiment will be described. In the first embodiment, the first surface 11A and the second surface 11B are parallel, but they do not necessarily have to be parallel. For example, it is sufficient if the first surface 11A and the second surface 11B are positioned to face the same direction. Here, two surfaces facing the same direction means that the angle between the normal vector of any position on one surface and the normal vector of any position on the other surface is less than 90°.

[0043] In the first embodiment, the second surface 11B is a flat surface, but it may be other than a flat surface. For example, it may be a stepped surface or a curved surface. Any configuration that can receive the laser beam passing outside the workpiece 60 is acceptable. Also, in the first embodiment, the angle between the first surface 11A and the step 11C is a right angle, but it may be an acute angle. If the angle between the first surface 11A and the step 11C is an acute angle, the laser beam passing outside the workpiece 60 will not enter the step 11C but will enter the second surface 11B.

[0044] Next, with reference to Figure 7A, the workpiece holding device according to the second embodiment will be described. The following description will omit details of components common to the workpiece holding device according to the first embodiment, which was described with reference to Figures 1 to 6.

[0045] Figure 7A is a schematic plan view showing the positional relationship between the first surface 11A of the workpiece holding device according to the second embodiment and the workpiece 60. The workpiece 60 is a semiconductor wafer having a notch 60N. That is, in plan view, the workpiece 60 has a shape in which a V-shaped or U-shaped notch is provided in a part of a circle. The notch 60N is used as a mark to indicate the crystal orientation of the workpiece 60, which is a semiconductor wafer. In plan view, the shape of the first surface 11A and the ceramic plate 20 is equal to the maximum inscribed circle of the workpiece 60 having the notch 60N. In Figure 7A, the edge of the first surface 11A is shown by a dashed line.

[0046] Similar to the first embodiment, a groove 13 is provided on the first surface 11A, and a suction hole 21 is provided in the ceramic plate 20. The workpiece 60 is held in the workpiece holding device with the center point of its circular portion slightly offset from the center point of the first surface 11A in the direction in which the notch 60N is provided.

[0047] Next, we will describe the excellent effects of the second embodiment. In the second embodiment, as in the first embodiment, the first surface 11A is included within the workpiece 60 in a plan view. Therefore, even when the pulsed laser beam is irradiated outside the workpiece 60, damage to the workpiece holder is suppressed. The same effect can be obtained even if the first surface 11A is slightly smaller than the maximum inscribed circle of the workpiece 60. It is preferable not to place a chip area in the area of ​​the workpiece 60 that is located outside the first surface 11A. When a ceramic plate 20 (Figure 2B) is placed between the first surface 11A and the workpiece 60, it is preferable that the edge of the ceramic plate 20 is shaped to coincide with the edge of the first surface 11A in a plan view.

[0048] Next, a modified workpiece holding device according to the second embodiment will be described with reference to Figures 7B and 7C. Figures 7B and 7C are schematic plan views showing the shape of the first surface 11A and the workpiece 60 of the modified workpiece holding device according to the second embodiment in a plan view. In Figures 7B and 7C, the workpiece 60 is shown on the left and the first surface 11A is shown on the right.

[0049] In the modified example shown in Figure 7B, similar to the second embodiment (Figure 7A), the workpiece 60 is a semiconductor wafer having a notch 60N. In the modified example shown in Figure 7C, an orientation flat 60F is provided instead of a notch to indicate the crystal orientation of the semiconductor wafer. In the modified examples shown in Figures 7B and 7C, the planar shapes of the first surface 11A and the ceramic plate 20 match the planar shapes of the workpiece 60. That is, notches are provided that align with the notch 60N or the orientation flat 60F.

[0050] As shown in Figures 7B and 7C, in plan view, the first surface 11A may have a circular shape in which the portion corresponding to the notch 60N or orientation flat 60F of the workpiece 60 held on the first surface 11A is missing.

[0051] Next, a workpiece holding device according to the third embodiment will be described with reference to Figure 8. The following description will omit explanations of components common to the workpiece holding device according to the first embodiment, which was described with reference to Figures 1 to 6.

[0052] Figure 8 is a cross-sectional view of the workpiece holding device 10 according to the third embodiment. In the third embodiment, the second surface 11B has the property of absorbing laser light. For example, it is possible to place a laser light absorbing material 15 on the surface of a metal member and use the upper surface of the laser light absorbing material 15 as the second surface 11B. It is preferable to use a material with low reflectivity at the wavelength of the laser light used for processing as the laser light absorbing material 15. For example, nickel with a black surface treatment can be used.

[0053] Next, we will describe the excellent effects of the third embodiment. If the second surface 11B has the property of reflecting the laser beam, the laser beam incident on the second surface 11B may be reflected and incident on other parts in the laser processing device. In the third embodiment, since the second surface 11B absorbs the laser light, the situation in which the laser beam is incident on an unexpected location becomes less likely.

[0054] Next, a workpiece holding device according to the fourth embodiment will be described with reference to Figure 9. The following description will omit explanations of components common to the workpiece holding device according to the first embodiment, which was described with reference to Figures 1 to 6.

[0055] Figure 9 is a cross-sectional view of the workpiece holding device 10 according to the fourth embodiment. In the first embodiment (Figure 2B), the second surface 11B is parallel to the first surface 11A. That is, the laser beam is incident on the second surface 11B almost perpendicularly. In contrast, in the fourth embodiment, the second surface 11B is inclined with respect to the first surface 11A such that the normal vector N at any point on the second surface 11B is away from the first surface 11A. Furthermore, a beam damper 18 that absorbs the laser beam is positioned at a location that intersects with the normal vector N of the second surface 11B. The beam damper 18 is positioned so as not to block the path of the laser beam 68 incident on the workpiece 60.

[0056] The laser beam incident on the second surface 11B is reflected by the second surface 11B in the direction of the normal vector N. This reflected light is incident on the beam damper 18 and absorbed by the beam damper 18.

[0057] Next, the superior effects of the fourth embodiment will be described. In the fourth embodiment, since the laser beam incident on the second surface 11B is absorbed by the beam damper 18, it becomes less likely that the laser beam will be incident on an unexpected location. Furthermore, since the second surface 11B reflects the laser beam, the temperature rise of the chuck table 11 due to the incidence of the laser beam is suppressed.

[0058] The embodiments described above are illustrative, and it goes without saying that partial substitution or combination of the configurations shown in different embodiments is possible. Similar effects and benefits from similar configurations in multiple embodiments will not be mentioned sequentially for each embodiment. Furthermore, the present invention is not limited to the embodiments described above. For example, it will be obvious to those skilled in the art that various modifications, improvements, and combinations are possible. [Explanation of Symbols]

[0059] 10. Workpiece holding device 11 Chuck Table 11A 1st page 11B 2nd side 11C step 12 Suction path 13 Groove 15. Laser light absorbing material 18 Beam damper 20 Ceramic Plates 21 Suction hole 40 Drive mechanism 50 Laser Optics 51 Laser Oscillator 52 Beam Expander 53 Beam shaping optical elements 54 Folding mirror 60. Object to be processed (semiconductor wafer) 60F Orientation Flat 60N Notch 61 Top surface of the workpiece 65 Beam Spot 65A Beam spot on the second surface 66 Main scanning area 68 Laser beams 70 Control device

Claims

1. A workpiece holding device for holding a workpiece to be processed by laser, The first surface that holds the workpiece, A second surface is provided at a lower position than the first surface. Equipped with, A workpiece holding device wherein, when the first surface is viewed from above, the first surface is encompassed by the workpiece held on the first surface, and the second surface extends beyond the workpiece held on the first surface.

2. The workpiece held on the first surface is a semiconductor wafer having a notch. The workpiece holding device according to claim 1, wherein, when the first surface is viewed from above, the first surface is equal to or smaller than the maximum inscribed circle of the workpiece, which is a semiconductor wafer having a notch.

3. The workpiece held on the first surface is a semiconductor wafer having a notch or orientation flat. The workpiece holding device according to claim 1, wherein, when the first surface is viewed from above, the first surface has a circular shape with a portion corresponding to a notch or orientation flat of the semiconductor wafer held on the first surface missing.

4. The second surface has the property of absorbing a laser beam, as described in any one of claims 1 to 3.

5. The second surface is inclined such that the normal vector at any point on the second surface moves away from the first surface. Furthermore, the workpiece holding device according to any one of claims 1 to 3, wherein a beam damper that absorbs the laser beam is arranged at a position intersecting the normal vector of the second surface.

6. The first surface is made of metal, Furthermore, the workpiece holding device according to any one of claims 1 to 3, further comprising a ceramic plate disposed between the first surface and the workpiece held on the first surface.

7. A workpiece holding device according to any one of claims 1 to 3, A laser optical system that incidents a laser beam onto the surface of the workpiece held on the first surface A laser processing device equipped with laser processing equipment.

8. Furthermore, the laser processing apparatus according to claim 7, further comprising a drive mechanism for moving the workpiece holding device in a direction parallel to the first surface.

9. The workpiece holding device according to any one of claims 1 to 3 holds the workpiece on its first surface, A laser annealing method in which a laser beam is incident on the upper surface of a workpiece held on the first surface, and the beam spot is moved while annealing is performed, A laser annealing method in which, for a portion of the period during which the beam spot is moved, at least a portion of the beam spot is incident on the outside of the workpiece held on the first surface.

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