Control device for annealing device, annealing device, and annealing method

Abstract

This invention provides a control device, an annealing apparatus, and an annealing method for an annealing apparatus capable of further suppressing temperature rise on the side opposite to the laser irradiation surface. A beam-shaping optical element shapes the beam point of a pulsed laser beam output from a laser source onto the surface of the object to be annealed into a shape that is elongated in one direction. A moving mechanism moves the beam point relative to the object to be annealed. The control device controls the laser source and the moving mechanism to perform a sweeping motion that simultaneously incident the pulsed laser beam onto the object to be annealed and moves the beam point relative to the object to be annealed along the length direction of the beam point, thereby performing annealing.

Description

Technical Field

[0001] This invention relates to a control device for an annealing apparatus, an annealing apparatus, and an annealing method. Background Technology

[0002] To activate dopants doped into planar annealed materials such as silicon wafers, the materials need to be heated (annealed). In the manufacturing process of insulated-gate bipolar transistors (IGBTs), after forming circuit elements on one side of a semiconductor wafer, impurities are doped on the other side and then annealed. During annealing, a resin protective tape is attached to the circuit formation surface. To prevent the protective tape from melting, it is ideal to suppress the temperature rise of the circuit formation surface.

[0003] To adequately heat the surface opposite to the circuit formation surface and suppress temperature rise on the circuit formation surface, laser annealing is used, where a laser is irradiated onto the surface opposite to the circuit formation surface (e.g., Patent Document 1, etc.). In the annealing technique described in Patent Document 1, after one laser pulse is incident, the next cycle of laser pulse is incident on a portion of the cooling process following a temperature rise. This allows for efficient utilization of the laser pulse's energy, thus reducing the amount of energy required to be applied to the semiconductor wafer. By reducing the amount of energy applied, temperature rise on the surface opposite to the laser irradiation surface can be suppressed.

[0004] [Existing technical documents]

[0005] [Patent Literature]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2020-202242 Summary of the Invention

[0007] [The problem the invention aims to solve]

[0008] If the object to be annealed, such as a semiconductor wafer, becomes thinner, the temperature of the side opposite to the laser irradiation surface tends to rise. The purpose of this invention is to provide a control device, an annealing apparatus, and an annealing method for an annealing apparatus that can further suppress the temperature rise of the side opposite to the laser irradiation surface.

[0009] [Technical means to solve the problem]

[0010] According to one aspect of the present invention, a control device is provided that controls an annealing apparatus, wherein the annealing apparatus comprises:

[0011] Laser source, outputting pulsed laser beam;

[0012] A beam-shaping optical element shapes the spot of the pulsed laser beam output from the laser source onto the surface of the annealed object into a shape that is elongated in one direction; and

[0013] A moving mechanism moves the beam point relative to the annealing object, and in the control device,

[0014] The laser source and the moving mechanism are controlled to perform a sweeping motion in which the pulsed laser beam is incident on the annealing object while the beam point moves relative to the annealing object in the length direction of the beam point, thereby performing annealing.

[0015] According to another aspect of the present invention, an annealing apparatus is provided, the annealing apparatus comprising:

[0016] Laser source, outputting pulsed laser beam;

[0017] A beam-shaping optical element shapes the beam spot of the pulsed laser beam output from the laser source onto the surface of the annealed object into a shape that is elongated in one direction.

[0018] A moving mechanism scans the pulsed laser beam, causing the beam point to move along the length direction of the beam point; and

[0019] The control device controls the laser source and the moving mechanism.

[0020] The control device is

[0021] Annealing is performed by sweeping a pulsed laser beam onto the object to be annealed while moving the beam point relative to the object in the length direction of the beam point.

[0022] According to another aspect of the present invention, an annealing method is provided in which a pulsed laser beam is incident on the surface of the object to be annealed, and annealing is performed while the beam point is moved. In this annealing method,

[0023] The beam point has a shape that is elongated in one direction.

[0024] The annealing is performed by a sweeping motion that moves the beam point along its length.

[0025] [The effects of the invention]

[0026] By sweeping the beam point along its length, the temperature rise of the side of the annealing object opposite to the laser irradiation surface can be suppressed under the same pulse energy density. Attached Figure Description

[0027] Figure 1 This is a schematic perspective view of the annealing apparatus based on the embodiment.

[0028] Figure 2 This is a schematic diagram of the laser annealing apparatus based on this embodiment.

[0029] Figure 3 It is a graph showing the calculated changes in surface temperature T over time when a single pulsed laser beam is incident on a silicon wafer.

[0030] Figure 4 It is a cross-sectional view of the annealed object incident on a pulsed laser beam.

[0031] Figure 5A and Figure 5B This is a graph representing an example of the calculated temperature distribution within a cross-section of an annealed object.

[0032] Figure 6 This is a flowchart illustrating the annealing method based on an embodiment.

[0033] Figure 7A and Figure 7B This is a schematic diagram showing the trajectory of the beam point when annealing is performed using the annealing methods based on the embodiments and comparative examples, respectively.

[0034] Figure 8 It is a graph showing the relationship between the sweeping speed of the beam spot and the activation rate, and the relationship between the sweeping speed of the beam spot and the highest temperature reached on the back side of the annealed object.

[0035] Figure 9 It is a graph showing the relationship between the aspect ratio of the beam point, the maximum temperature reached on the back side of the annealed object, and the activation rate.

[0036] Figure 10 It is a graph showing the relationship between the sweep speed, the maximum temperature reached on the back side of the annealed object, and the activation rate when the aspect ratio of the beam point is 1.

[0037] [Explanation of Symbols]

[0038] 10: Laser source

[0039] 11: Beam Expander

[0040] 12: Beam shaping optical elements

[0041] 13, 14: Retroreflector

[0042] 15: Beam Scanner

[0043] 15A: Current Mirror

[0044] 15B: Motor

[0045] 16: fθ lens

[0046] 17: Movable platform

[0047] 18: Chuck mechanism

[0048] 20: Mobile organization

[0049] 30: Laser Diode

[0050] 31: Gain Fiber

[0051] 32: Incident-side optical fiber

[0052] 33: Fiber Bragg Grating

[0053] 34: Output side optical fiber

[0054] 35: Fiber Bragg grating

[0055] 36: Wavelength conversion element

[0056] 37: Driver

[0057] 39: Beam point

[0058] 40: Control device

[0059] 50: Chamber

[0060] 51: Laser through the window

[0061] 60: Annealing material

[0062] Pf: Heat source

[0063] Pr: The location on the back side directly below the heat source Pf.

[0064] h: Thickness of the annealed object (60 mm)

[0065] S1~S3: Steps

[0066] Lx: Dimension in the x-direction of beam point 39

[0067] Ly: Dimension of beam point 39 in the y-direction

[0068] Wx: The distance that beam point 39 moves in the x-direction.

[0069] Wy: The distance that beam point 39 moves in the y-direction. Detailed Implementation

[0070] Reference Figures 1-10 An annealing apparatus and annealing method based on one embodiment will be described.

[0071] Figure 1 This is a schematic perspective view of the annealing apparatus based on the embodiment. A laser source 10 outputs a pulsed laser beam. The pulsed laser beam output from the laser source 10 is incident on the laser irradiation surface of the object to be annealed 60 via a beam expander 11, a beam shaping optics 12, a reflecting mirror 13, a reflecting mirror 14, a beam scanner 15, and an fθ lens 16. The object to be annealed 60 is, for example, a semiconductor wafer with ion-implanted dopant.

[0072] The object to be annealed 60 is held in place by a chuck mechanism 18 supported by a movable platform 17. The movable platform 17 allows the chuck mechanism 18 to move in two directions within the horizontal plane. The object to be annealed 60 moves as a result of the movement of the chuck mechanism 18. For example, an XY platform can be used as the movable platform 17.

[0073] The beam expander 11 adjusts the beam size (diameter of the beam profile) at the incident position of the laser beam on the beam shaping optics 12. The beam shaping optics 12 shapes the beam spot on the beam irradiation surface of the annealed object 60 into a shape that is elongated in one direction and homogenizes the intensity distribution. For example, a diffractive optical element is used as the beam shaping optics 12. The beam scanner 15 includes a galvano mirror 15A and a motor 15B. The motor 15B rotates the galvano mirror 15A within a range located in the oblique direction, thereby scanning the pulsed laser beam in one dimension. Through this scanning, the beam spot moves along its length direction on the surface of the annealed object 60. The fθ lens 16 focuses the pulsed laser beam scanned by the beam scanner 15 onto the laser irradiation surface of the annealed object 60.

[0074] Figure 2 This is a schematic diagram of the laser annealing apparatus based on this embodiment. For... Figure 1 Repeated content in the description is omitted.

[0075] A fiber laser oscillator is used as the laser source 10. An input-side fiber 32 is connected to one end of a gain fiber 31 doped with a laser-active medium, and an output-side fiber 34 is connected to the other end. A high-reflectivity fiber Bragg grating 33 is formed on the input-side fiber 32, and a low-reflectivity fiber Bragg grating 35 is formed on the output-side fiber 34. The high-reflectivity fiber Bragg grating 33 and the low-reflectivity fiber Bragg grating 35 constitute an optical resonator.

[0076] The excitation light output from the laser diode 30 is guided into the gain fiber 31 via the input fiber 32. The laser-active medium doped in the gain fiber 31 is excited by the excitation light. Stimulated emission occurs when the laser-active medium migrates to a low-energy state, generating laser light. The laser light generated by the gain fiber 31 is incident on the wavelength conversion element 36 via the output fiber 34. The laser beam, whose wavelength has been converted by the wavelength conversion element 36, is incident on the annealing object 60 via the beam expander 11, the beam shaping optics 12, the folding mirror 13, the folding mirror 14, the beam scanner 15, and the fθ lens 16. For example, the gain fiber 31 outputs laser light in the infrared region, and the wavelength conversion element 36 converts the infrared laser light into laser light in the green wavelength region.

[0077] The driver 37 drives the laser diode 30 based on instructions received from the control device 40. The instructions received from the control device 40 include information specifying the repetition frequency of the laser pulses output from the laser diode 30. The driver 37 causes the excitation laser to be output from the laser diode 30 at the repetition frequency of the laser pulses indicated by the control device 40. As a result, a pulsed laser beam is output from the laser source 10 at the instructed repetition frequency.

[0078] A movable platform 17 and a chuck mechanism 18 are disposed within a chamber 50. A laser transmission window 51 is installed on the wall of the chamber 50 above the annealing object 60 held by the chuck mechanism 18. A pulsed laser beam passing through an fθ lens 16 passes through the laser transmission window 51 and is incident on the laser irradiation surface of the annealing object 60. The laser annealing apparatus based on this embodiment is used, for example, to perform activation annealing of dopants doped in the annealing object 60. The annealing object 60 is, for example, a silicon wafer.

[0079] The control device 40 includes a user-operated console. The user operates the console to input information about the repetition frequency of the pulses in the specified pulsed laser beam. The control device 40 provides the input pulse repetition frequency information to the driver 37.

[0080] The control device 40 also controls the beam scanner 15 and the movable platform 17 to move the beam point on the laser irradiation surface of the annealed object 60. An xyz rectangular coordinate system is defined, wherein the direction in which the beam point moves by scanning the pulsed laser beam using the beam scanner 15 is defined as the x-direction, and the direction orthogonal to the x-direction within the laser irradiation surface is defined as the y-direction. The beam point of the pulsed laser beam has a shape that is elongated in the x-direction.

[0081] The action of moving the beam point in the x-direction by operating the beam scanner 15 is called a "sweeping action". If the control device 40 controls the movable platform 17 to move the annealing object 60 in the y-direction, the position of the beam point on the surface of the annealing object 60 will be shifted (offset) in the y-direction. The action of shifting the position of the beam point in the y-direction is called a "stepping action".

[0082] Thus, by driving either the beam scanner 15 or the movable platform 17, the beam point can be moved in the x or y direction on the surface of the annealed object 60. The beam scanner 15 and the movable platform 17 constitute a moving mechanism 20 that moves the beam point in a two-dimensional direction on the surface of the annealed object 60.

[0083] The maximum length for sweeping the beam point in the x-direction depends on the swing angle of the pulsed laser beam based on the beam scanner 15 and the performance of the fθ lens 16. When the maximum sweep length is shorter than the size of the object to be annealed 60, the sweeping and stepping actions are repeatedly performed to shift the object to be annealed 60 in the x-direction and execute the annealing procedure for a portion of the x-direction multiple times, thereby annealing approximately the entire area of ​​the object to be annealed 60.

[0084] Next, refer to Figure 3 The time-varying surface temperature of the object being annealed is explained when a pulsed laser beam is incident on it at 60°C.

[0085] For simplicity, the case of a laser pulse with uniform power density P incident on the annealing object 60 will be described. The surface temperature T of the laser-irradiated surface of the annealing object 60 can be expressed by the following formula.

[0086] [Formula 1]

[0087]

[0088] Here, t represents the elapsed time since heating began, C represents the specific heat of the annealed material 60, ρ represents the density of the annealed material 60, and λ represents the thermal conductivity of the annealed material 60. For example, the unit of surface temperature T is "K", and the unit of power density P is "W / cm³". 2 The unit for time t is "seconds", the unit for specific heat C is "J / g·K", and the unit for density ρ is "g / cm³". 3 The unit of thermal conductivity λ is “W / cm·K”.

[0089] If the pulse width of the pulsed laser beam is denoted as t0, then the highest temperature reached by the laser-irradiated surface is T. a It is expressed by the following formula.

[0090] [Formula 2]

[0091]

[0092] If the highest temperature T reached by the laser irradiation surface is determined... a If the target value is determined, then the power density P and pulse width t0 required to raise the temperature to this target value are determined.

[0093] Figure 3 This is a graph showing the calculated changes in surface temperature T over time when a single pulsed laser beam is incident on a silicon wafer. The horizontal axis represents the elapsed time t from the rise time of the laser pulse in "ns", the left vertical axis represents the surface temperature T of the annealed object at 60°C in "°C", and the right vertical axis represents the surface temperature T in "MW / cm²". 2 "" represents the power density P of the pulsed laser beam. The dashed line in the graph represents the time variation of the power density P of the pulsed laser beam, and the solid line represents the time variation of the surface temperature T of the annealed object at 60°C. The pulse width of the pulsed laser beam is t0, and the peak power density is 5 MW / cm². 2 .

[0094] During the incident period of the laser pulse (0≦t≦t0), the surface temperature T rises according to equation (1). The surface temperature T at the moment when the pulse width t0 has elapsed since the rise of the laser pulse (t=t0) is equal to the highest temperature T reached. a After the laser pulse decreases (t≧t0), the surface temperature T gradually decreases.

[0095] Next, refer to Figures 4-5B The temperature rise of the side opposite to the laser irradiation surface (hereinafter referred to as the back side) of the annealed object 60 will be explained.

[0096] Figure 4 This is a cross-sectional view of the annealed object 60 incident on a pulsed laser beam. The incident position 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 the position Pr on the back side directly below the heat source Pf is expressed by the following formula.

[0097] [Formula 3]

[0098]

[0099] Here, Q represents the heat input from the heat source Pf to the annealed object 60, h represents the thickness of the annealed object 60, v represents the sweeping velocity of the heat source Pf, and k represents the thermal diffusivity of the annealed object 60. For example, the unit of heat input Q is "W", the unit of thickness h of the annealed object 60 is "cm", the unit of sweeping velocity v is "cm / s", and the unit of thermal diffusivity k is "cm". 2 / s".

[0100] As can be seen from equation (3), the slower the sweeping speed v of the heat source Pf, the greater the temperature rise ΔT at point Pr on the back side. Especially when the thickness h of the annealed object 60 is thin, the increase in temperature rise ΔT becomes significant.

[0101] Figure 5A and Figure 5B This is a chart illustrating an example of the calculated temperature distribution within a cross-section of the annealed object 60. Furthermore, Figure 5A and Figure 5B This represents the cross-sectional temperature distribution of an annealed object 60 with a finite thickness and its back side under heat insulation conditions. The horizontal axis represents the position of the sweeping direction of the heat source Pf. 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 surface irradiated by the beam in "μm". Figure 5A and Figure 5B This represents the temperature distribution under different sweep velocities v of the heat source Pf. Figure 5B Indicates and Figure 5A Temperature distribution when the sweep rate v of the heat source Pf is faster than that of the heat source. The curves in the graph represent isotherms, and the values ​​for each curve are expressed in °C.

[0102] It can be seen that the sweeping speed v is slow ( Figure 5A ) and fast situations ( Figure 5B Compared to the previous case, the temperature gradient along the thickness direction is gentler. That is, with a slow sweeping speed v, the temperature rise ΔT on the back side is greater than with a fast sweeping speed v. In other words, by increasing the sweeping speed v, the temperature rise ΔT on the back side can be reduced.

[0103] Next, refer to Figure 6 An annealing method based on an embodiment will be described. Figure 6 This is a flowchart illustrating the annealing method based on an embodiment. First, the control device 40 ( Figure 1 , Figure 2 The laser source 10 and the beam scanner 15 are controlled to perform a sweeping action (step S1) in which the pulsed laser beam is incident on the annealing object 60 while the beam point is moved in its length direction.

[0104] If a sweeping action is completed, the control device 40 controls the movable platform 17 to perform a stepping action that causes the annealed object 60 to shift in a direction intersecting the length direction of the beam point (step S2). The sweeping action of step S1 and the stepping action of step S2 are repeated until approximately the entire surface area of ​​the annealed object 60 is annealed (step S3).

[0105] Next, refer to Figure 7A and Figure 7B The superior effects of the embodiments are illustrated by comparing them with comparative examples. Figure 7A and Figure 7B This is a schematic diagram showing the trajectory of the beam point 39 when annealing is performed using the annealing methods based on the embodiments and comparative examples, respectively. Figure 7A and Figure 7B The hollow arrow indicates the direction of movement of beam point 39 relative to the annealed object 60.

[0106] In either the embodiment or the comparative example, the sweeping direction of the beam spot 39 is parallel to the x-direction. This is achieved by making the beam scanner 15 ( Figure 1 , Figure 2 The beam point 39 is swept using the following operation. At the end of each sweep, a stepping motion is performed to shift the beam point 39 in the y-direction. Annealing is performed by alternating and repeating the sweeping and stepping motions.

[0107] The dimension of beam point 39 in the x-direction is denoted as Lx, and the dimension in the y-direction is denoted as Ly. The distance that beam point 39 moves in the x-direction during one cycle of the pulsed laser beam is denoted as Wx. The distance that beam point 39 moves in the y-direction during one step is denoted as Wy. The overlap ratio OVx in the x-direction and the overlap ratio OVy in the y-direction are expressed by the following formula.

[0108] [Formula 4]

[0109]

[0110]

[0111] In one embodiment, the dimension Lx of the beam point 39 in the x-direction is larger than the dimension Ly in the y-direction. In this embodiment, the beam point 39 is swept along its length direction. In a comparative example, conversely, the dimension Ly in the y-direction is larger than the dimension Lx in the x-direction. In this comparative example, the beam point 39 is swept in a direction orthogonal to its length direction.

[0112] The following situation was examined: the dimensions Lx in the x-direction and Ly in the y-direction of the beam point 39 based on the embodiment are equal to the dimensions Ly in the y-direction and Lx in the x-direction of the beam point 39 based on the comparative example, respectively. That is, the beam point 39 based on the embodiment and the beam point 39 based on the comparative example have the same size and shape. In addition, the overlap rate OVx in the x-direction and the overlap rate OVy in the y-direction are the same in both the embodiment and the comparative example.

[0113] Under the stated conditions, the number of pulses required to anneal approximately the entire area of ​​the object 60 is approximately the same in both the embodiment and the comparative example. Furthermore, the pulse energy density is the same in both the embodiment and the comparative example. Therefore, as... Figure 3As shown, the highest temperature reached on the surface of the annealed object 60 is approximately the same in both the embodiment and the comparative example. Therefore, the activation rate is also approximately the same when the annealed object 60 is subjected to activation annealing.

[0114] In the embodiment and the comparative example, since the size of the beam spot 39 and the overlap rate OVx in the x-direction are the same, the sweeping speed of the beam spot 39 in the embodiment is faster than that in the comparative example. Therefore, as referred to Figure 5A and Figure 5B As explained, compared to the comparative example, the highest temperature reached on the back side of the annealed object 60 in this embodiment is lower. Thus, when annealing is performed under conditions where the number of pulsed laser beams emitted and the activation rate are the same, in this embodiment, compared to the comparative example, the temperature rise on the back side of the annealed object 60 can be suppressed.

[0115] To confirm the superior performance of this embodiment, the sweeping speed of the beam spot 39, the activation rate, and the maximum reaching temperature of the back surface of the annealed object 60 were calculated. Hereinafter, refer to... Figure 8 The calculation results are explained.

[0116] Figure 8 This is a graph showing the relationship between the sweeping speed of the beam spot 39 and the activation rate, and the relationship between the sweeping speed of the beam spot 39 and the highest temperature reached on the back side of the annealed object 60. The horizontal axis represents the sweeping speed of the beam spot, the vertical axis of the upper graph represents the activation rate in "%", and the vertical axis of the lower graph represents the highest temperature reached on the back side of the annealed object 60. The thick and thin solid lines in the graphs respectively represent the results of the embodiment (…). Figure 7A ) and comparative examples ( Figure 7B The calculation results when annealing using the method of )

[0117] In the embodiment, the dimension Lx of the beam point 39 in the x-direction is set to twice the dimension Ly in the y-direction. In the comparative example, the dimension Ly of the beam point 39 in the y-direction is set to twice the dimension Lx in the x-direction. Furthermore, the pulse repetition frequency and pulse energy density are the same in both the embodiment and the comparative example. In either the embodiment or the comparative example, as the sweeping speed of the beam point 39 increases, the activation rate decreases, and the maximum temperature reached on the back side of the annealed object 60 also decreases.

[0118] It is evident that when sweeping is performed under conditions where the activation rate is 80%, the maximum temperature reached on the back side of the annealed object 60 is lower when using the annealing method based on the embodiment than when using the annealing method based on the comparative example. Thus, by employing the annealing method based on this embodiment, the maximum temperature reached on the back side can be suppressed to a low level, and the desired activation rate can be achieved.

[0119] Next, refer to Figure 9 For beam point 39 ( Figure 7A The preferred shape is described. Figure 9 This is a graph showing the relationship between the aspect ratio of the beam point 39, the maximum temperature reached on the back side of the annealed object 60, and the activation rate. Here, the aspect ratio is defined as the ratio of the dimension Lx in the x-direction of the beam point 39 to the dimension Ly in the y-direction. Figure 9 The horizontal axis of the chart shows the aspect ratio, the left vertical axis represents the highest temperature reached on the back side of the annealed object 60 in "°C", and the right vertical axis represents the activation rate in "%". Figure 9 The solid line in the graph represents the highest temperature reached on the back side of the annealed object 60, and the dashed line represents the activation rate.

[0120] Figure 9 The chart shown was obtained through calculation. As a prerequisite for the calculation, the annealed object 60 was set as a silicon wafer with a thickness of 50 μm, and the repetition frequency of the pulsed laser beam was set to 800 kHz. Phosphorus ions were used as the dopant, and the acceleration energy during ion implantation was set to 2.5 MeV. Even if the aspect ratio of the beam spot 39 was changed, the area of ​​the beam spot 39 and the overlap ratio OVx (Equation (4)) of the sweep direction were kept constant.

[0121] As the aspect ratio increases, the maximum temperature reached on the back side of the annealed object 60 decreases slowly. This is because the sweeping speed increases. The activation rate decreases sharply when the aspect ratio exceeds approximately 3. Preferably, the aspect ratio of the beam point 39 is less than the point where the activation rate begins to decrease sharply. Figure 9 In the example shown, the aspect ratio is preferably set to 3 or less, and more preferably to 2.5 or less.

[0122] In addition, in order to achieve sufficient suppression of the rise in the highest temperature reached on the back side of the annealed object 60 compared to the case where the aspect ratio is 1, i.e., the beam point 39 is a square, it is preferable to set the aspect ratio to 1.5 or higher.

[0123] Next, refer to Figure 10 The relationship between the sweeping speed of beam point 39, the maximum temperature reached on the back side of the annealed object 60, and the activation rate is explained. Figure 10 This is a graph showing the sweeping speed at an aspect ratio of 1 for beam point 39, the maximum temperature reached on the back side of the annealed object 60, and the relationship with the activation rate. Figure 10 The horizontal axis of the graph shown represents the sweeping speed in units of [m / s], the left vertical axis represents the highest temperature reached on the back side of the annealed object 60 in units of "℃", and the right vertical axis represents the activation rate in units of "%". Figure 10 The solid line in the graph represents the highest temperature reached on the back side of the annealed object 60, and the dashed line represents the activation rate.

[0124] As the sweeping speed increases, the maximum temperature reached on the back side of the annealed object 60 decreases, and the activation rate also decreases. Figure 10 In the example shown, where the maximum allowable temperature on the back side of the annealed object 60 is 200°C, the sweeping speed must be set to 4 m / s or higher. According to... Figure 9 The calculation results show that if the aspect ratio is increased from 1 to 2.5, the maximum temperature reached on the back side of the annealed object 60 decreases by approximately 100°C. Figure 10 In the example shown, if the aspect ratio of beam point 39 is set to approximately 2.5, the maximum temperature reached on the back side can be expected to decrease by about 100°C. Thus, even if the sweep speed is reduced to 2 m / s, the maximum temperature reached on the back side can be suppressed to around 200°C.

[0125] Thus, by optimizing the aspect ratio of beam point 39, the range of selectable sweep speeds can be expanded. In the described embodiment, by optimizing the aspect ratio of beam scanner 15 ( Figure 2 ) operates to perform beam point 39 ( Figure 7A The sweeping is performed in the x-direction. Therefore, compared to the case where the movable platform 17 is operated to move the annealed object 60 in the x-direction for sweeping, the sweeping speed can be increased.

[0126] To reduce the temperature rise ΔT on the back side of the annealed object 60, it is known from equation (3) that it is preferable to increase the sweep speed v as much as possible. However, if the repetition frequency of the pulses of the pulsed laser beam and the beam point 39 ( Figure 7A If the dimension Lx in the x-direction is fixed and the sweeping speed v is increased, then the overlap rate OVx in the x-direction will decrease or there will be no overlap.

[0127] 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 of the surface of the annealed object 60 decreases. To maintain the maximum arrival temperature T of the laser-irradiated surface under the condition of reduced power density P... a Therefore, the pulse width t0 must be increased. If the pulse width t0 is increased, the heat transfer along the thickness direction during the laser pulse incidence period increases. As a result, the temperature of the irradiated surface increases. Therefore, the dimension Lx cannot be increased unconditionally.

[0128] To maintain a sufficient overlap ratio OVx without increasing the size Lx, it is sufficient to simply increase the pulse repetition frequency f. For example, to suppress excessive temperature rise on the back side of a semiconductor wafer with a thickness of 100 μm or less, it is preferable to set the pulse repetition frequency f to 15 kHz or more, and more preferably to 100 kHz or more.

[0129] The embodiments described are examples, and the present invention is not limited to the embodiments described. For example, it will be apparent to those skilled in the art that various changes, improvements, combinations, etc., can be made.

Claims

1. A control device for controlling an annealing apparatus, wherein the annealing apparatus comprises: Laser source, outputting pulsed laser beam; A beam-shaping optical element shapes the beam spot of the pulsed laser beam output from the laser source onto the surface of the annealed object into a shape that is longer in one direction with an aspect ratio of 1.5 or more and 2.5 or less. as well as A moving mechanism that moves the beam point relative to the annealing object, and a control device, The laser source and the moving mechanism are controlled to perform a sweeping motion in which the pulsed laser beam is incident on the annealing object while the beam point moves relative to the annealing object in the length direction of the beam point, thereby performing annealing.

2. The control device according to claim 1, wherein, After one of the sweeping actions is completed, a stepping action is performed to shift the beam point relative to the annealed object in a direction intersecting the length direction of the beam point. The annealing is performed by repeating the sweeping and stepping actions.

3. The control device according to claim 1 or 2, wherein, During the sweeping motion, the laser source is controlled to output a pulsed laser beam with a pulse repetition frequency of 100 kHz or higher.

4. An annealing apparatus, comprising: Laser source, outputting pulsed laser beam; A beam-shaping optical element shapes the beam spot of the pulsed laser beam output from the laser source onto the surface of the annealed object into a shape that is longer in one direction with an aspect ratio of 1.5 or more and 2.5 or less. The moving mechanism scans the pulsed laser beam, causing the beam point to move along the length direction of the beam point; as well as The control device controls the laser source and the moving mechanism. The control device is Annealing is performed by sweeping a pulsed laser beam onto the object to be annealed while moving the beam point relative to the object in the length direction of the beam point.

5. The annealing apparatus according to claim 4, wherein, The moving mechanism has the function of moving the beam point in a direction that intersects the length direction of the beam point. The control device then After one of the sweeping actions is completed, a stepping action is performed to shift the beam point relative to the annealed object in a direction intersecting the length direction of the beam point. The annealing is performed by repeatedly performing the sweeping and stepping actions.

6. The annealing apparatus according to claim 4 or 5, wherein, The control device controls the laser source during the sweeping action, so that the repetition frequency of the pulsed laser beam is above 100 kHz.

7. An annealing method comprising incident a pulsed laser beam onto the surface of an object to be annealed, and performing annealing while moving the beam spot, wherein, The beam point has a shape that is elongated in one direction with an aspect ratio of 1.5 or higher and 2.5 or lower. The annealing is performed by a sweeping motion that moves the beam point along its length.

8. The annealing method according to claim 7, wherein, After one of the sweeping actions is completed, a stepping action is performed to shift the beam point relative to the annealed object in a direction intersecting the length direction of the beam point. The annealing is performed by repeatedly performing the sweeping and stepping actions.

9. The annealing method according to claim 7 or 8, wherein, During the sweeping action, the pulse repetition frequency of the pulsed laser beam incident on the annealing object is 100 kHz or higher.

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