Annealing device control device, annealing device, and annealing method

Abstract

To provide an annealing device controller capable of further suppressing the temperature rise of the surface opposite to a laser irradiation surface.SOLUTION: A beam spot on the surface of an object to be annealed of a pulsed laser beam output from a laser light source is shaped into a shape elongated in one direction by a beam shaping optical element. A moving mechanism moves the beam spot relative to the object to be annealed. A controller controls the laser light source and the moving mechanism to perform sweeping operation of moving the beam spot on the object to be annealed in the longitudinal direction of the beam spot while making the pulsed laser beam incident on the object to be annealed.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a control device for an annealing device, an annealing device, and an annealing method. [Background technology]

[0002] In order to activate dopants doped into a flat annealing target such as a silicon wafer, the target must be heated (annealed). In the manufacturing process of insulated gate bipolar transistors (IGBTs), for example, circuit elements are formed on one side of a semiconductor wafer, and then impurities are doped onto the other side, followed by annealing. During annealing, a resin protective tape is attached to the circuit-formed surface. To prevent the protective tape from melting, it is desirable to suppress the temperature rise of the circuit-formed surface.

[0003] In order to sufficiently heat the surface opposite the circuit formation surface and suppress a temperature rise on the circuit formation surface, laser annealing is used, in which laser light is irradiated onto the surface opposite the circuit formation surface (for example, Patent Document 1, etc.). In the annealing technology described in Patent Document 1, one laser pulse is applied, and then the next laser pulse is applied to a location that is in the cooling process after the temperature rise. This allows the energy of the laser pulse to be used effectively, thereby reducing the amount of energy that needs to be input to the semiconductor wafer. By reducing the amount of energy input, it is possible to suppress a temperature rise on the surface opposite the laser irradiated surface. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-202242 Summary of the Invention [Problem to be solved by the invention]

[0005] As an object to be annealed, such as a semiconductor wafer, becomes thinner, the temperature of the surface opposite to the laser-irradiated surface tends to rise. An object of the present invention is to provide an annealing device control device, an annealing device, and an annealing method that can further suppress the temperature rise of the surface opposite to the laser-irradiated surface. [Means for solving the problem]

[0006] According to one aspect of the present invention, a laser light source that outputs a pulsed laser beam; a beam shaping optical element that shapes the beam spot of the pulsed laser beam output from the laser light source on the surface of an object to be annealed into a shape that is elongated in one direction and has an aspect ratio of 1.5 to 2.5; a movement mechanism that moves the beam spot relative to the object to be annealed; A control device for controlling an annealing device comprising: The laser light source and the moving mechanism are controlled to direct the pulsed laser beam onto the object to be annealed while moving the beam spot on the object to be annealed. , in the longitudinal direction of the beam spot Perform a sweeping motion to move the object. After one sweep operation is completed, a step operation is performed to shift the beam spot relative to the object to be annealed in a direction intersecting the longitudinal direction of the beam spot. This provides a control system for performing annealing.

[0007] According to another aspect of the present invention, a laser light source that outputs a pulsed laser beam; a beam shaping optical element that shapes the beam spot of the pulsed laser beam output from the laser light source on the surface of an object to be annealed into a shape that is elongated in one direction and has an aspect ratio of 1.5 to 2.5; The pulse laser beam is scanned to form a beam spot in the longitudinal direction and the A direction intersecting the longitudinal direction of the beam spot a moving mechanism for moving the beam spot; a control device that controls the laser light source and the moving mechanism; Equipped with The control device controls the pulse laser beam to be incident on the object to be annealed, and controls the beam spot on the object to be annealed. In the longitudinal direction of the beam spot Perform a sweeping motion to move the object. After one sweep operation is completed, a step operation is performed to shift the beam spot relative to the object to be annealed in a direction intersecting the longitudinal direction of the beam spot. By doing so, an annealing apparatus for performing annealing is provided.

[0008] According to yet another aspect of the present invention, An annealing method in which a pulsed laser beam is incident on a surface of an object to be annealed and annealing is performed while moving the beam spot, comprising: the beam spot has an aspect ratio of 1.5 or more and 2.5 or less and is elongated in one direction, A sweeping operation is performed to move the beam spot in the longitudinal direction of the beam spot. After one sweep operation is completed, a step operation is performed to shift the beam spot relative to the object to be annealed in a direction intersecting the longitudinal direction of the beam spot. By performing the above-mentioned annealing, an annealing method is provided. [Effects of the Invention]

[0009] By sweeping the beam spot in the longitudinal direction of the beam spot, it is possible to suppress a temperature rise on the surface of the object to be annealed opposite to the laser irradiated surface under the same pulse energy density conditions. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic perspective view of an annealing apparatus according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram of the laser annealing apparatus according to this embodiment. [Figure 3] FIG. 3 is a graph showing calculated values ​​of the change in surface temperature T over time when one shot of a pulsed laser beam is incident on a silicon wafer. [Figure 4] FIG. 4 is a cross-sectional view of an object to be annealed onto which a pulsed laser beam is incident. [Figure 5] 5A and 5B are graphs showing an example of calculation results of temperature distribution in a cross section of an object to be annealed. [Figure 6]FIG. 6 is a flowchart showing the procedure of the annealing method according to the embodiment. [Figure 7] 7A and 7B are schematic diagrams showing the trajectories of the beam spot when annealing is performed by the annealing methods according to the embodiment and the modified example, respectively. [Figure 8] FIG. 8 is a graph showing the relationship between the sweep speed of the beam spot and the activation rate, and the relationship between the sweep speed of the beam spot and the maximum temperature reached on the back surface of the object to be annealed. [Figure 9] FIG. 9 is a graph showing the relationship between the aspect ratio of the beam spot, the maximum temperature reached on the back surface of the object to be annealed, and the activation rate. [Figure 10] FIG. 10 is a graph showing the relationship between the sweep speed, the maximum temperature reached on the back surface of the object to be annealed, and the activation rate when the aspect ratio of the beam spot is 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] An annealing apparatus and an annealing method according to one embodiment will be described with reference to FIGS.

[0012] 1 is a schematic perspective view of an annealing apparatus according to an embodiment. A laser light source 10 outputs a pulsed laser beam. The pulsed laser beam output from the laser light source 10 passes through a beam expander 11, a beam shaping optical element 12, folding mirrors 13 and 14, a beam scanner 15, and an fθ lens 16 and is incident on the laser irradiation surface of an object to be annealed 60. The object to be annealed 60 is, for example, a semiconductor wafer into which dopant ions have been implanted.

[0013] The object to be annealed 60 is held by a chuck mechanism 18 supported by a movable stage 17. The movable stage 17 moves the chuck mechanism 18 in two directions in a horizontal plane. The movement of the chuck mechanism 18 moves the object to be annealed 60. For example, an XY stage is used as the movable stage 17.

[0014] The beam expander 11 adjusts the beam size (beam cross-sectional diameter) of the laser beam at the incident position on the beam shaping optical element 12. The beam shaping optical element 12 shapes the beam spot on the beam irradiation surface of the object to be annealed 60 into a shape that is elongated in one direction and homogenizes the intensity distribution. A diffractive optical element, for example, is used as the beam shaping optical element 12. The beam scanner 15 includes a galvanometer mirror 15A and a motor 15B. The motor 15B rotates the galvanometer mirror 15A within a certain range in the tilt direction, thereby scanning the pulsed laser beam in a one-dimensional direction. This scanning moves the beam spot in the longitudinal direction on the surface of the object to be annealed 60. The fθ lens 16 focuses the pulsed laser beam scanned by the beam scanner 15 onto the laser irradiation surface of the object to be annealed 60.

[0015] 2 is a schematic diagram of a laser annealing apparatus according to this embodiment. Explanation of the contents that overlap with the explanation of FIG. 1 will be omitted.

[0016] A fiber laser oscillator is used as the laser light source 10. An input optical fiber 32 is connected to one end of a gain fiber 31 doped with a laser active medium, and an output optical fiber 34 is connected to the other end. A high-reflectivity fiber Bragg grating 33 is formed in the input optical fiber 32, and a low-reflectivity fiber Bragg grating 35 is formed in the output optical fiber 34. The high-reflectivity fiber Bragg grating 33 and the low-reflectivity fiber Bragg grating 35 form an optical resonator.

[0017] Pumping light output from the laser diode 30 is introduced into the gain fiber 31 through the input optical fiber 32. The laser active medium doped in the gain fiber 31 is excited by the pumping light. When the laser active medium transitions to a low energy state, stimulated emission occurs, generating laser light. The laser light generated in the gain fiber 31 passes through the output optical fiber 34 and enters the wavelength conversion element 36. The laser beam wavelength-converted by the wavelength conversion element 36 passes through the beam expander 11, the beam shaping optical element 12, the folding mirrors 13 and 14, the beam scanner 15, and the fθ lens 16 and is then incident on the object to be annealed 60. The gain fiber 31 outputs laser light, for example, in the infrared region, and the wavelength conversion element 36 converts the infrared laser light into laser light in the green wavelength region.

[0018] The driver 37 drives the laser diode 30 based on a command from the control device 40. The command received from the control device 40 includes information specifying the repetition frequency of the laser pulses output from the laser diode 30. The driver 37 causes the laser diode 30 to output an excitation laser beam at the repetition frequency of the laser pulses commanded by the control device 40. As a result, a pulsed laser beam is output from the laser light source 10 at the commanded repetition frequency.

[0019] A movable stage 17 and a chuck mechanism 18 are disposed in a chamber 50. A laser transmission window 51 is attached to the wall of the chamber 50 above an object to be annealed 60 held by the chuck mechanism 18. The pulsed laser beam transmitted through the fθ lens 16 passes through the laser transmission window 51 and is incident on the laser irradiation surface of the object to be annealed 60. The laser annealing apparatus according to this embodiment performs activation annealing of a dopant doped in the object to be annealed 60, for example. The object to be annealed 60 is, for example, a silicon wafer.

[0020] The control device 40 includes a console operated by a user. The user operates the console to input information specifying the pulse repetition frequency of the pulse laser beam. The control device 40 then provides the input information specifying the pulse repetition frequency to the driver 37.

[0021] The control device 40 further controls the beam scanner 15 and the movable stage 17 to move the beam spot on the laser irradiation surface of the annealing object 60. An xyz Cartesian coordinate system is defined in which the direction in which the beam spot moves as a result of scanning the pulsed laser beam with the beam scanner 15 is the x direction, and the direction orthogonal to the x direction in the laser irradiation surface is the y direction. The beam spot of the pulsed laser beam has a shape that is elongated in the x direction.

[0022] The operation of operating the beam scanner 15 to move the beam spot in the x direction is referred to as the "sweeping operation." When the control device 40 controls the movable stage 17 to move the object to be annealed 60 in the y direction, the position of the beam spot is displaced in the y direction on the surface of the object to be annealed 60 (shifted in the y direction). The operation of displacing the position of the beam spot in the y direction is referred to as the "stepping operation."

[0023] In this way, by driving either the beam scanner 15 or the movable stage 17, the beam spot can be moved in the x-direction or the y-direction on the surface of the object to be annealed 60. The beam scanner 15 and the movable stage 17 constitute a movement mechanism 20 that moves the beam spot in two-dimensional directions on the surface of the object to be annealed 60.

[0024] The maximum length over which the beam spot can be swept in the x direction depends on the deflection angle of the pulsed laser beam by the beam scanner 15 and the performance of the fθ lens 16. If the maximum sweep length is shorter than the dimensions of the object to be annealed 60, the procedure of annealing a partial range in the x direction by repeating the sweeping operation and stepping operation multiple times while shifting the object to be annealed 60 in the x direction makes it possible to anneal almost the entire area of ​​the object to be annealed 60.

[0025] Next, with reference to FIG. 3, the change in surface temperature over time when a pulsed laser beam is incident on the object 60 to be annealed will be described.

[0026] For simplicity, a case will be described in which a laser pulse with a uniform power density P is incident on the to-be-annealed object 60. The surface temperature T of the laser-irradiated surface of the to-be-annealed object 60 can be expressed by the following equation.

number

[0027] If the pulse width of the pulsed laser beam is denoted as t0, the maximum temperature that can be reached on the laser irradiated surface is T a is expressed by the following formula:

number

[0028] Maximum temperature reached on the laser irradiated surface T a Once the target value of is determined, the power density P and pulse width t0 required to raise the temperature to the target value are determined.

[0029] Figure 3 is a graph showing calculated values ​​of the change in surface temperature T over time when one shot of a pulsed laser beam is incident on a silicon wafer. The horizontal axis represents the elapsed time t from the rising edge of the laser pulse in the unit of "ns", the left vertical axis represents the surface temperature T of the annealing target 60 in the unit of "°C", and the right vertical axis represents the power density P of the pulsed laser beam in the unit of "MW / cm". 2The dashed line in the graph indicates the change over time in the power density P of the pulsed laser beam, and the solid line indicates the change over time in the surface temperature T of the object 60 to be annealed. The pulse width of the pulsed laser beam is t0, and the peak power density is 5 MW / cm 2 is.

[0030] During the laser pulse irradiation period (0≦t≦t0), the surface temperature T rises according to formula (1). The surface temperature T at the time when the time equivalent to the pulse width t0 has elapsed from the rising edge of the laser pulse (t=t0) is the maximum temperature T a After the laser pulse falls (t≧t0), the surface temperature T gradually decreases.

[0031] Next, the temperature rise of the surface of the object 60 to be annealed opposite to the laser irradiated surface (hereinafter referred to as the back surface) will be described with reference to FIGS. 4 to 5B.

[0032] 4 is a cross-sectional view of an annealing object 60 onto which a pulsed laser beam is incident. The position of incidence of the laser beam is the heat source Pf. For simplicity, if we consider the temperature distribution directly below the heat source of an infinitely thick plate, the temperature rise ΔT at a position Pr on the back surface directly below the heat source Pf can be expressed by the following equation:

number

[0033] From equation (3), it can be seen that the slower the sweep speed v of the heat source Pf, the larger the temperature rise ΔT at point Pr on the back surface. In particular, when the thickness h of the annealing object 60 is thin, the increase in the temperature rise ΔT becomes significant.

[0034] 5A and 5B are graphs showing an example of the calculation results of the temperature distribution within the cross section of the annealing object 60. Note that FIGS. 5A and 5B show the temperature distribution within the cross section of the annealing object 60 with a finite thickness and a thermally insulated back surface. The horizontal axis represents the position of the heat source Pf in the sweep direction. The current position of the heat source Pf is set as the origin of the horizontal axis, and the direction of movement of the heat source is set as positive. The vertical axis represents the depth from the beam irradiation surface in units of μm. FIGS. 5A and 5B show the temperature distribution when the sweep speed v of the heat source Pf is different. FIG. 5B shows the temperature distribution when the sweep speed v of the heat source Pf is faster than that of FIG. 5A. The curves in the graphs represent isotherms, and the numbers attached to each curve represent the temperature in units of °C.

[0035] It can be seen that when the sweep speed v is slow (FIG. 5A), the temperature gradient in the thickness direction is gentler than when it is fast (FIG. 5B). That is, when the sweep speed v is slow, the temperature rise ΔT on the backside is larger than when it is fast. In other words, by increasing the sweep speed v, the temperature rise ΔT on the backside can be reduced.

[0036] Next, an annealing method according to an embodiment will be described with reference to Fig. 6. Fig. 6 is a flowchart showing the procedure of the annealing method according to the embodiment. First, the control device 40 (Figs. 1 and 2) controls the laser light source 10 and the beam scanner 15 to perform a sweeping operation in which the pulsed laser beam is incident on the annealing object 60 while moving the beam spot in its longitudinal direction (step S1).

[0037] After one sweeping operation is completed, the control device 40 controls the movable stage 17 to perform a stepping operation to shift the object to be annealed 60 in a direction intersecting the longitudinal direction of the beam spot (step S2). The sweeping operation of step S1 and the stepping operation of step S2 are repeated until almost the entire surface of the object to be annealed 60 is annealed (step S3).

[0038] Next, the excellent effects of the embodiment will be described in comparison with a comparative example with reference to Figures 7A and 7B. Figures 7A and 7B are schematic diagrams showing the trajectory of the beam spot 39 when annealing is performed by the annealing method according to the embodiment and the modified example, respectively. The white arrows in Figures 7A and 7B indicate the direction of movement of the beam spot 39 relative to the annealing target 60.

[0039] In both the example and the comparative example, the sweep direction of the beam spot 39 is parallel to the x direction. The beam spot 39 is swept by operating the beam scanner 15 (FIGS. 1 and 2). After one sweep is completed, a step operation is performed to shift the beam spot 39 in the y direction. Annealing is performed by alternately repeating the sweep operation and the step operation.

[0040] The dimension of the beam spot 39 in the x direction is denoted by Lx, and the dimension in the y direction is denoted by Ly. The distance that the beam spot 39 moves in the x direction during one period of the pulsed laser beam is denoted by Wx. The distance that the beam spot 39 moves in the y direction during one step operation is denoted by Wy. The overlap ratio OVx in the x direction and the overlap ratio OVy in the y direction are expressed by the following equations.

number

[0041] In the embodiment, the dimension Lx in the x direction of the beam spot 39 is larger than the dimension Ly in the y direction. In the embodiment, the beam spot 39 is swept in its longitudinal direction. In the comparative example, conversely, the dimension Ly in the y direction is larger than the dimension Lx in the x direction. In the comparative example, the beam spot 39 is swept in a direction perpendicular to its longitudinal direction.

[0042] Consider the case where the x-direction dimension Lx and the y-direction dimension Ly of the beam spot 39 according to the example are equal to the y-direction dimension Ly and the x-direction dimension Lx of the beam spot 39 according to the comparative example. That is, the beam spot 39 according to the example and the beam spot 39 according to the comparative example have the same size and shape. Furthermore, the overlap ratio OVx in the x direction and the overlap ratio OVy in the y direction are the same in the example and the comparative example.

[0043] Under these conditions, the number of shots required to anneal almost the entire area of ​​the annealing object 60 is almost the same in the example and the comparative example. In addition, the pulse energy density is the same in the example and the comparative example. Therefore, as shown in FIG. 3, the maximum temperature reached on the surface of the annealing object 60 is also almost the same in the example and the comparative example. Therefore, when activation annealing is performed on the annealing object 60, the activation rate is also almost the same.

[0044] Since the size of the beam spot 39 and the overlap rate OVx in the x direction are the same in the example and the comparative example, the sweep speed of the beam spot 39 is faster in the example than in the comparative example. Therefore, as described with reference to Figures 5A and 5B, the maximum temperature reached on the rear surface of the annealing object 60 is lower in the example than in the comparative example. As such, when annealing is performed under conditions where the number of pulsed laser beam shots and activation rate are approximately the same, the example can suppress the temperature rise on the rear surface of the annealing object 60 compared to the comparative example.

[0045] In order to confirm the excellent effects of this embodiment, the sweep speed of the beam spot 39, the activation rate, and the maximum temperature reached on the back surface of the annealing object 60 were calculated. The calculation results will be explained below with reference to FIG.

[0046] 8 is a graph showing the relationship between the sweep speed of the beam spot 39 and the activation rate, and the relationship between the sweep speed of the beam spot 39 and the maximum temperature reached on the back surface of the annealing object 60. The horizontal axis represents the sweep speed of the beam spot, the vertical axis of the upper graph represents the activation rate in units of % and the vertical axis of the lower graph represents the maximum temperature reached on the back surface of the annealing object 60. The thick solid line and thin solid line in the graph represent the calculation results when annealing is performed by the methods according to the example (FIG. 7A) and the comparative example (FIG. 7B), respectively.

[0047] In the example, the x-direction dimension Lx of the beam spot 39 was twice the y-direction dimension Ly, and in the comparative example, the y-direction dimension Ly of the beam spot 39 was twice the x-direction dimension Lx. The pulse repetition frequency and pulse energy density were the same in the example and the comparative example. In both the example and the comparative example, as the sweep speed of the beam spot 39 increases, the activation rate decreases and the maximum temperature reached on the back surface of the annealing object 60 also decreases.

[0048] When swept under conditions that result in an activation rate of 80%, it can be seen that the maximum temperature reached on the back surface of the annealing object 60 when the annealing method according to the embodiment is employed is lower than when the annealing method according to the comparative example is employed. Thus, by employing the annealing method according to the embodiment, it is possible to achieve a desired activation rate while keeping the maximum temperature reached on the back surface low.

[0049] Next, a preferred shape of the beam spot 39 (FIG. 7A) will be described with reference to FIG. 9. FIG. 9 is a graph showing the relationship between the aspect ratio of the beam spot 39, the maximum temperature reached on the back surface of the annealing object 60, and the activation rate. Here, the aspect ratio is defined as the ratio of the x-direction dimension Lx of the beam spot 39 to the y-direction dimension Ly. The horizontal axis of the graph shown in FIG. 9 represents the aspect ratio, the left vertical axis represents the maximum temperature reached on the back surface of the annealing object 60 in °C, and the right vertical axis represents the activation rate in %. The solid line in the graph shown in FIG. 9 represents the maximum temperature reached on the back surface of the annealing object 60, and the dashed line represents the activation rate.

[0050] The graph shown in Figure 9 was obtained by calculation. As a prerequisite for the calculation, the annealing target 60 was a silicon wafer with a thickness of 50 µm, and the pulse repetition frequency of the pulse laser beam was 800 kHz. Phosphorus ions were used as the dopant, and the acceleration energy during ion implantation was 2.5 MeV. Even when the aspect ratio of the beam spot 39 was changed, the area of ​​the beam spot 39 and the overlap rate OVx in the sweep direction (Equation (4)) were kept constant.

[0051] As the aspect ratio increases, the maximum temperature reached on the backside of the annealing object 60 gradually decreases. This is due to the faster sweep speed. The activation rate drops sharply when the aspect ratio exceeds approximately 3. It is preferable to set the aspect ratio of the beam spot 39 smaller than the point at which the activation rate starts to drop sharply. In the example shown in FIG. 9, the aspect ratio is preferably set to 3 or less, and more preferably 2.5 or less.

[0052] Furthermore, in order to obtain a sufficient effect of suppressing the increase in the maximum temperature reached on the rear surface of the object to be annealed 60 compared to when the aspect ratio is 1, i.e., when the beam spot 39 is square, it is preferable that the aspect ratio be 1.5 or more.

[0053] Next, with reference to FIG. 10, the relationship between the sweep speed of the beam spot 39, the maximum temperature reached on the back surface of the annealing object 60, and the activation rate will be described. FIG. 10 is a graph showing the relationship between the sweep speed, the maximum temperature reached on the back surface of the annealing object 60, and the activation rate when the aspect ratio of the beam spot 39 is 1. The horizontal axis of the graph shown in FIG. 10 represents the sweep speed in units of m / s, the left vertical axis represents the maximum temperature reached on the back surface of the annealing object 60 in units of °C, and the right vertical axis represents the activation rate in units of %. The solid line in the graph shown in FIG. 10 indicates the maximum temperature reached on the back surface of the annealing object 60, and the dashed line indicates the activation rate.

[0054] As the sweep speed increases, the maximum temperature of the rear surface of the annealing object 60 decreases, and the activation rate also decreases. In the example shown in FIG. 10, if the allowable upper limit of the maximum temperature of the rear surface of the annealing object 60 is 200°C, the sweep speed must be 4 m / s or greater. The calculation results shown in FIG. 9 indicate that increasing the aspect ratio from 1 to 2.5 reduces the maximum temperature of the rear surface of the annealing object 60 by approximately 100°C. In the example shown in FIG. 10, if the aspect ratio of the beam spot 39 is increased to approximately 2.5, the maximum temperature of the rear surface is expected to decrease by approximately 100°C. Therefore, even if the sweep speed is reduced to 2 m / s, the maximum temperature of the rear surface can be suppressed to approximately 200°C.

[0055] In this way, the range of selectable sweep speeds can be expanded by optimizing the aspect ratio of the beam spot 39. In the above embodiment, the beam spot 39 (FIG. 7A) is swept in the x direction by operating the beam scanner 15 (FIG. 2). Therefore, it is possible to increase the sweep speed compared to when the movable stage 17 is operated to move the annealing object 60 in the x direction to perform the sweep.

[0056] As can be seen from equation (3), it is preferable to make the sweep speed v as fast as possible in order to reduce the temperature rise ΔT of the rear surface of the to-be-annealed object 60. However, if the sweep speed v is increased under the condition that the pulse repetition frequency of the pulsed laser beam and the dimension Lx in the x direction of the beam spot 39 (FIG. 7A) are constant, the overlap ratio OVx in the x direction will become smaller or will not overlap at all.

[0057] If the x-direction dimension Lx of the beam spot 39 is increased to maintain the overlap ratio OVx when the sweep speed v is increased, the power density P on the surface of the object to be annealed 60 will decrease. To maintain the maximum temperature Ta of the laser-irradiated surface under conditions where the power density P is reduced, the pulse width t0 must be increased. As the pulse width t0 increases, the amount of heat transferred in the thickness direction during the laser pulse irradiation period increases. As a result, the temperature of the irradiated surface will increase. Therefore, the dimension Lx cannot be increased unconditionally.

[0058] To maintain a sufficient overlap ratio OVx without increasing the dimension Lx, the pulse repetition frequency f should be increased. For example, to prevent an excessive rise in the temperature of the backside of a semiconductor wafer with a thickness of 100 μm or less, the pulse repetition frequency f is preferably set to 15 kHz or higher, and more preferably set to 100 kHz or higher.

[0059] The above-described embodiments are merely examples, and the present invention is not limited to the above-described embodiments. For example, it will be obvious to those skilled in the art that various modifications, improvements, combinations, etc. are possible. [Explanation of symbols]

[0060] 10 Laser light source 11 Beam Expander 12 Beam shaping optical elements 13, 14 Folding mirror 15 Beam Scanner 15A Galvanometer Mirror 15B motor 16 fθ lens 17 Movable stage 18 Chuck mechanism 20 Moving mechanism 30 Laser Diode 31 Gain fiber 32 Input optical fiber 33 Fiber Bragg Grating 34 Output optical fiber 35 Fiber Bragg Grating 36 Wavelength conversion element 37 Drivers 39 beam spots 40 Control device 50 Chambers 51 Laser transmission window 60 Annealing object

Claims

1. a laser light source that outputs a pulsed laser beam; a beam shaping optical element that shapes the beam spot of the pulsed laser beam output from the laser light source on the surface of an object to be annealed into a shape that is elongated in one direction and has an aspect ratio of 1.5 to 2.5; a movement mechanism that moves the beam spot relative to the object to be annealed; A control device for controlling an annealing device comprising: A control device that controls the laser light source and the moving mechanism to irradiate the pulsed laser beam onto the object to be annealed, performs a sweeping operation to move the beam spot relative to the object to be annealed in the longitudinal direction of the beam spot, and when one sweeping operation is completed, performs a stepping operation to shift the beam spot relative to the object to be annealed in a direction intersecting the longitudinal direction of the beam spot, thereby performing annealing.

2. 2. The control device according to claim 1, wherein the annealing is performed by repeating the sweeping operation and the stepping operation, and the stepping operation is performed so that the area annealed by the sweeping operation before the stepping operation and the area annealed by the sweeping operation after the stepping operation overlap in a direction intersecting the longitudinal direction of the beam spot.

3. 3. The control device according to claim 1, wherein the laser light source is controlled to output the pulse laser beam having a pulse repetition frequency of 100 kHz or more during the sweeping operation.

4. a laser light source that outputs a pulsed laser beam; a beam shaping optical element that shapes the beam spot of the pulsed laser beam output from the laser light source on the surface of an object to be annealed into a shape that is elongated in one direction and has an aspect ratio of 1.5 to 2.5; a moving mechanism that scans the pulsed laser beam to move the beam spot in a longitudinal direction of the beam spot and in a direction intersecting the longitudinal direction of the beam spot; a control device that controls the laser light source and the moving mechanism; Equipped with The control device performs a sweeping operation to move the beam spot relative to the annealing object in the longitudinal direction of the beam spot while irradiating the pulsed laser beam onto the annealing object, and after completing one sweeping operation, performs a stepping operation to shift the beam spot relative to the annealing object in a direction intersecting the longitudinal direction of the beam spot, thereby performing annealing.

5. 5. The annealing apparatus of claim 4, wherein the control device performs the annealing by repeating the sweeping operation and the stepping operation, and performs the stepping operation so that the area annealed by the sweeping operation before the stepping operation and the area annealed by the sweeping operation after the stepping operation overlap in a direction intersecting the longitudinal direction of the beam spot.

6. 6. The annealing apparatus according to claim 4, wherein the control device controls the laser light source during the sweeping operation to set the pulse repetition frequency of the pulse laser beam to 100 kHz or higher.

7. An annealing method in which a pulsed laser beam is incident on a surface of an object to be annealed and annealing is performed while moving the beam spot, comprising: the beam spot has an aspect ratio of 1.5 or more and 2.5 or less, and is elongated in one direction; An annealing method in which the annealing is performed by performing a sweeping operation to move the beam spot in the longitudinal direction of the beam spot, and when one sweeping operation is completed, performing a stepping operation to shift the beam spot relative to the object to be annealed in a direction intersecting the longitudinal direction of the beam spot.

8. 8. The annealing method according to claim 7, wherein the annealing is performed by repeating the sweeping operation and the stepping operation, and the stepping operation is performed so that the region annealed by the sweeping operation before the stepping operation and the region annealed by the sweeping operation after the stepping operation overlap in a direction intersecting the longitudinal direction of the beam spot.

9. 9. The annealing method according to claim 7, wherein the pulse repetition frequency of the pulse laser beam incident on the object to be annealed during the sweeping operation is 100 kHz or higher.

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