Control Apparatus for Annealing Apparatus, Annealing Apparatus and Annealing Method

Abstract

The present invention provides a control device for an annealing apparatus capable of further suppressing the temperature rise on the surface opposite to the laser irradiation surface. A beam spot of a pulsed laser beam output from a laser light source on the surface of an annealing target is shaped into an elongated shape in one direction by a beam shaping optical element. A moving mechanism moves the beam spot relative to the annealing target. The control device performs annealing by controlling the laser light source and the moving mechanism to incident a pulsed laser beam on the annealing target while performing a sweeping operation that moves the beam spot relative to the annealing target along the length of the beam spot.

Description

Technology 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 a dopant doped in a planar annealing target such as a silicon wafer, it is necessary to heat (anneal) the annealing target. In the manufacturing process of insulated gate bipolar transistors (IGBTs), circuit elements are formed on one side of a semiconductor wafer, and then impurities are doped into the other side to perform annealing. When annealing, a protective tape made of resin is attached to the circuit-forming surface. To prevent the protective tape from melting, it is desired to suppress the temperature rise of the circuit-forming surface.

[0003] Laser annealing is used to sufficiently heat the side opposite to the circuit forming surface while suppressing the temperature rise of the circuit forming surface (e.g., Patent Document 1, etc.). In the annealing technique described in Patent Document 1, after a single laser pulse is incident, the next cycle of laser pulse is incident on a position that is in the cooling process after the temperature rise. As a result, the energy of the laser pulse can be effectively utilized, thereby reducing the amount of energy that must be supplied to the semiconductor wafer. By reducing the amount of energy supplied, the temperature rise of the side opposite to the laser-irradiated surface can be suppressed. Prior art literature

[0004] Japanese Patent Publication No. 2020-202242 The problem to be solved

[0005] When an annealing target such as a semiconductor wafer becomes thin, the temperature of the side opposite to the laser irradiation surface is prone to rising. The objective of the present invention is to provide a control device for an annealing device, an annealing device, and an annealing method that can further suppress the temperature rise of the side opposite to the laser irradiation surface. means of solving the problem

[0006] According to one aspect of the present invention,

[0007] A laser light source that outputs a pulsed laser beam;

[0008] A beam shaping optical element that shapes the beam spot on the surface of the annealing target, of the pulsed laser beam output from the laser light source, into a long shape in one direction;

[0009] A control device for controlling an annealing device having a moving mechanism for moving the beam spot with respect to the annealing target,

[0010] A control device is provided that performs annealing by controlling the laser light source and the moving mechanism, thereby causing the pulsed laser beam to be incident on the annealing target, and performing a sweeping operation to move the beam spot in the longitudinal direction of the beam spot with respect to the annealing target.

[0011] According to another aspect of the present invention,

[0012] A laser light source that outputs a pulsed laser beam;

[0013] A beam shaping optical element that shapes the beam spot on the surface of an annealing target, of the pulsed laser beam output from the above laser light source, into a long shape in one direction;

[0014] A moving mechanism that scans the pulsed laser beam and moves the beam spot along the length of the beam spot;

[0015] A control device for controlling the above laser light source and the above moving mechanism; is provided,

[0016] The above control device is,

[0017] An annealing device is provided that performs annealing by incidenting the above pulsed laser beam on the annealing target and performing a sweeping operation to move the beam spot in the longitudinal direction of the beam spot with respect to the annealing target.

[0018] According to another aspect of the present invention,

[0019] In an annealing method in which a pulsed laser beam is incident on the surface of an annealing target and annealing is performed while moving the beam spot,

[0020] The above beam spot has a long shape in one direction, and

[0021] An annealing method is provided by performing an annealing by moving the beam spot in the longitudinal direction of the beam spot. Effects of the invention

[0022] By sweeping the beam spot along the length of the beam spot, the temperature rise on the side opposite to the laser irradiation surface of the annealing target can be suppressed under conditions of the same pulse energy density. Brief explanation of the drawing

[0023] FIG. 1 is a schematic perspective view of an annealing device according to an embodiment. FIG. 2 is a schematic diagram of a laser annealing device according to the present embodiment. Figure 3 is a graph showing the calculated value of the change in surface temperature (T) over time when one shot of pulsed laser beam is incident on a silicon wafer. Figure 4 is a cross-sectional view of an annealing object into which a pulsed laser beam is incident. Figures 5A and 5B are graphs showing an example of the calculation results of the temperature distribution within a cross-section of an annealing object. FIG. 6 is a flowchart showing the sequence of an annealing method according to an embodiment. FIGS. 7A and FIGS. 7B are schematic diagrams showing the trajectory of a beam spot when annealing is performed by an annealing method according to an example and a comparative example, respectively. Figure 8 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 maximum temperature reached on the back side of the annealing target. Figure 9 is a graph showing the relationship between the aspect ratio of the beam spot, the maximum temperature reached on the back side of the annealing target, and the activation rate. Figure 10 is a graph showing the relationship between the sweeping speed, the maximum temperature reached on the back side of the annealing target, and the activation rate when the aspect ratio of the beam spot is 1. Specific details for implementing the invention

[0024] Referring to FIGS. 1 to 10, an annealing apparatus and an annealing method according to one embodiment will be described.

[0025] FIG. 1 is a schematic perspective view of an annealing device 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), a folding mirror (13, 14), a beam scanner (15), and an fθ lens (16) and is incident on the laser irradiation surface of an annealing target (60). The annealing target (60) is, for example, a semiconductor wafer in which a dopant has been ion-implanted.

[0026] The annealing object (60) is held within a chuck mechanism (18) supported by a movable stage (17). The movable stage (17) moves the chuck mechanism (18) in two directions within a horizontal plane. As the chuck mechanism (18) moves, the annealing object (60) moves. For example, an XY stage is used as the movable stage (17).

[0027] The beam expander (11) adjusts the beam size (diameter of the beam cross-section) at the position where the laser beam is incident on the beam shaping optical element (12). The beam shaping optical element (12) shapes the beam spot on the beam irradiation surface of the annealing object (60) into a long shape in one direction while simultaneously making the intensity distribution uniform. For example, a diffractive optical element 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) scans the pulsed laser beam in a one-dimensional direction by rotating the galvanometer mirror (15A) within a range in the low-angle direction. Through this scanning, the beam spot on the surface of the annealing object (60) moves along its length. The fθ lens (16) focuses the pulsed laser beam scanned by the beam scanner (15) onto the laser irradiation surface of the annealing object (60).

[0028] FIG. 2 is a schematic diagram of a laser annealing device according to the present embodiment. Descriptions of content that overlap with the description of FIG. 1 are omitted.

[0029] A fiber laser oscillator is used as a laser light source (10). An input optical fiber (32) is connected to one end of a gain optical 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 on the input optical fiber (32), and a low-reflectivity fiber Bragg grating (35) is formed on the output optical fiber (34). An optical resonator is configured with the high-reflectivity fiber Bragg grating (33) and the low-reflectivity fiber Bragg grating (35).

[0030] Excitation light output from the laser diode (30) passes through the input optical fiber (32) and is introduced into the gain optical fiber (31). The laser active medium doped in the gain optical fiber (31) is excited by the excitation light. When the laser active medium transitions to a low-energy state, stimulated emission occurs, and laser light is generated. The laser light generated in the gain optical fiber (31) passes through the output optical fiber (34) and is incident on the wavelength conversion element (36). The laser beam, whose wavelength is converted by the wavelength conversion element (36), passes through the beam expander (11), beam shaping optical element (12), folding mirror (13, 14), beam scanner (15), and fθ lens (16) and is incident on the annealing target (60). For example, the gain optical fiber (31) outputs laser light in the infrared region, and the wavelength conversion element (36) converts the laser light in the infrared region into laser light in the green wavelength region.

[0031] 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 pulse output from the laser diode (30). The driver (37) causes the laser diode (30) to output excitation laser light at the repetition frequency of the laser pulse 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.

[0032] A movable stage (17) and a chuck mechanism (18) are arranged within a chamber (50). A laser transmission window (51) is mounted on the wall of the chamber (50) above the annealing target (60) held by the chuck mechanism (18). A pulsed laser beam passing through the fθ lens (16) passes through the laser transmission window (51) and is incident on the laser irradiation surface of the annealing target (60). The laser annealing device according to the present embodiment performs, for example, activation annealing of a dopant doped in the annealing target (60). The annealing target (60) is, for example, a silicon wafer.

[0033] The control device (40) includes a console operated by a user. The user operates the console to input information specifying the repetition frequency of the pulses of the pulse laser beam. The control device (40) provides the information specifying the repetition frequency of the input pulses to the driver (37).

[0034] Additionally, the control device (40) moves the beam spot on the laser irradiation surface of the annealing target (60) by controlling the beam scanner (15) and the operating stage (17). By scanning the pulsed laser beam with the beam scanner (15), an xyz orthogonal coordinate system is defined in which the direction in which the beam spot moves is the x direction, and the direction orthogonal to the x direction within the laser irradiation surface is the y direction. The beam spot of the pulsed laser beam has an elongated shape in the x direction.

[0035] The operation of moving the beam spot in the x direction by operating the beam scanner (15) is to be called a "sweeping operation." When the control device (40) controls the operating stage (17) to move the annealing target (60) in the y direction, the position of the beam spot on the surface of the annealing target (60) is displaced in the y direction (displaced in the y direction). The operation of displaced the position of the beam spot in the y direction is to be called a "stepping operation."

[0036] 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 annealing object (60). The beam scanner (15) and the movable stage (17) constitute a moving mechanism (20) that moves the beam spot in a two-dimensional direction on the surface of the annealing object (60).

[0037] The maximum length for which the beam spot can be swept in the x-direction depends on the swing angle of the pulsed laser beam by the beam scanner (15) and the performance of the Fθ lens (16). If the maximum length of the sweeping is shorter than the dimensions of the annealing target (60), the annealing target (60) can be annealed almost the entire area of ​​the annealing target (60) by repeating the sweeping and stepping operations to anneale a portion of the x-direction range multiple times while shifting the annealing target (60) in the x-direction.

[0038] Next, with reference to FIG. 3, the time change of the surface temperature when a pulsed laser beam is incident on an annealing target (60) will be described.

[0039] For simplicity, the case where a laser pulse of uniform power density (P) is incident on an annealing target (60) is described. The surface temperature (T) of the laser irradiation surface of the annealing target (60) can be expressed by the following formula.

[0040]

[0041] Here, t is the elapsed time from the start of heating, C is the specific heat of the annealing object (60), ρ is the density of the annealing object (60), and λ is the thermal conductivity of the annealing object (60). For example, the unit of surface temperature (T) is "K", the unit of power density (P) is "W / cm²", the unit of elapsed time (t) is "seconds", the unit of specific heat (c) is "J / g·K", the unit of density (ρ) is "g / cm³", and the unit of thermal conductivity (λ) is "W / cm·K".

[0042] If the pulse width of the pulsed laser beam is denoted as t0, the maximum temperature reached on the laser-irradiated surface (T a ) is expressed by the following formula.

[0043]

[0044] Maximum temperature reached on the laser irradiation surface (T a Once the target value of ) is determined, the power density (P) and pulse width (t0) required to raise the temperature to that target value are determined.

[0045] FIG. 3 is a graph showing the calculated values ​​for the time change of the surface temperature (T) when a single shot of pulsed laser beam is incident on a silicon wafer. The horizontal axis represents the elapsed time (t) from the rising point of the laser pulse in units of "ns", the left vertical axis represents the surface temperature (T) of the annealing target (60) in units of "°C", and the right vertical axis represents the power density (P) of the pulsed laser beam in units of "MW / cm²". In the graph, the dotted line represents the time change of the power density (P) of the pulsed laser beam, and the solid line represents the time change of the surface temperature (T) of the annealing target (60). The pulse width of the pulsed laser beam is t0, and the peak power density is 5 MW / cm².

[0046] During the period (0 ≤ t ≤ t0) in which the laser pulse is incident, the surface temperature (T) rises according to Equation (1). The surface temperature (T) at the point (t=t0) after a time equivalent to the pulse width (t0) has elapsed from the point of the laser pulse rise is the maximum reached temperature (T a It is the same as ). After the laser pulse descends (t≥t0), the surface temperature (T) gradually decreases.

[0047] Next, with reference to FIGS. 4 to 5B, the temperature rise of the side opposite to the laser irradiation surface of the annealing target (60) (hereinafter referred to as the back side) will be explained.

[0048] FIG. 4 is a cross-sectional view of an annealing target (60) into which a pulsed laser beam is incident. The incident position of the laser beam becomes the heat source (Pf). For simplicity, considering 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) is expressed by the following formula.

[0049]

[0050] Here, Q is the heat input from the heat source (Pf) to the annealing object (60), h is the thickness of the annealing object (60), v is the sweeping speed of the heat source (Pf), and k is the heat diffusivity of the annealing object (60). For example, the unit of the heat input (Q) is "W", the unit of the thickness (h) of the annealing object (60) is "cm", the unit of the sweeping speed (v) is "cm / s", and the unit of the heat diffusivity (k) is "cm² / s".

[0051] From equation (3), it can be seen that as the sweeping speed (v) of the heat source (Pf) slows down, the amount of temperature rise (ΔT) at the point (Pr) on the back surface increases. In particular, when the thickness (h) of the annealing target (60) is thin, the increase in the amount of temperature rise (ΔT) becomes significant.

[0052] FIGS. 5A and 5B are graphs showing an example of the calculated result of the temperature distribution within the cross-section of an annealing target (60). FIGS. 5A and 5B also illustrate the temperature distribution within the cross-section of an annealing target (60) under conditions where the thickness is finite and the back surface is insulated. The horizontal axis represents the position of the heat source (Pf) in the sweeping 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 "㎛". FIGS. 5A and 5B show the temperature distribution when the sweeping speed (v) of the heat source (Pf) is different. FIG. 5B shows the temperature distribution when the sweeping speed (v) of the heat source (Pf) is faster than in FIG. 5A. The curves in the graphs represent isotherms, and the numerical values ​​attached to each curve represent the temperature in units of "℃".

[0053] It can be seen that when the sweeping speed (v) is slow (Fig. 5A), the temperature gradient in the thickness direction is gentler compared to when it is fast (Fig. 5B). That is, when the sweeping speed (v) is slow, the temperature rise (ΔT) on the back side is greater than when it is fast. In other words, by increasing the sweeping speed (v), the temperature rise (ΔT) on the back side can be reduced.

[0054] Next, an annealing method according to an embodiment will be described with reference to FIG. 6. FIG. 6 is a flowchart showing the sequence of an annealing method according to an embodiment. First, a control device (40) (Fig. 1, Fig. 2) controls a laser light source (10) and a beam scanner (15) to induce a pulsed laser beam on an annealing target (60) and performs a sweeping operation to move the beam spot in the longitudinal direction (step S1).

[0055] When one sweeping operation is completed, the control device (40) controls the operating stage (17) to execute a stepping operation that moves the annealing target (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 area of ​​the annealing target (60) is annealed (step S3).

[0056] Next, with reference to FIGS. 7A and 7B, the superior effects of the embodiment are explained in comparison with the comparative example. FIGS. 7A and 7B are schematic diagrams showing the trajectory of the beam spot (39) when annealing is performed using the annealing method according to the embodiment and the comparative example, respectively. The white arrows in FIGS. 7A and 7B indicate the direction of movement of the beam spot (39) relative to the annealing target (60).

[0057] In both the example and the comparative example, the sweeping direction of the beam spot (39) is parallel to the x-direction. Sweeping of the beam spot (39) is performed by operating the beam scanner (15) (Fig. 1, Fig. 2). When one sweeping operation is completed, a stepping operation is performed to shift the beam spot (39) in the y-direction. Annealing is performed by alternately repeating the sweeping operation and the stepping operation.

[0058] The x-direction dimension of the beam spot (39) is denoted as Lx, and the y-direction dimension is denoted as Ly. The distance the beam spot (39) moves in the x-direction during one cycle of the pulsed laser beam is denoted as Wx. The distance the beam spot (39) moves in the y-direction during one stepping motion is denoted as Wy. The overlap rate in the x-direction (OVx) and the overlap rate in the y-direction (OVy) are expressed by the following equations.

[0059]

[0060] In the embodiment, the x-direction dimension (Lx) of the beam spot (39) is larger than the y-direction dimension (Ly). In the embodiment, the beam spot (39) is swept along its length. In the comparative example, conversely, the y-direction dimension (Ly) is larger than the x-direction dimension (Lx). In the comparative example, the beam spot (39) is swept in a direction orthogonal to its length.

[0061] We examine the case where the x-direction dimension (Lx) and y-direction dimension (Ly) of the beam spot (39) according to the embodiment are the same as the y-direction dimension (Ly) and x-direction dimension (Lx) of the beam spot (39) according to the comparative example, respectively. That is, the beam spot (39) according to the embodiment and the beam spot (39) according to the comparative example have the same size and shape. In addition, the overlap ratio (OVx) in the x-direction and the overlap ratio (OVy) in the y-direction are the same in the embodiment and the comparative example.

[0062] Under these conditions, the number of shots required to anneale almost the entire area of ​​the annealing target (60) is nearly 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 target (60) is also nearly the same in the example and the comparative example. Consequently, when performing activation annealing of the annealing target (60), the activation rate is also nearly the same.

[0063] In the example 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) is faster in the example than in the comparative example. Therefore, as described with reference to FIGS. 5A and 5B, the maximum temperature reached on the back side of the annealing target (60) is lower in the example than in the comparative example. Thus, when annealing is performed under conditions where the number of shots of the pulsed laser beam and the activation rate are the same, the temperature rise on the back side of the annealing target (60) can be suppressed in this example compared to the comparative example.

[0064] To confirm the excellent effects of this embodiment, the sweeping speed of the beam spot (39), the activation rate, and the maximum temperature reached on the back side of the annealing target (60) were calculated. The results of the calculation will be explained below with reference to FIG. 8.

[0065] FIG. 8 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 maximum temperature reached on the back side of the annealing target (60). The horizontal axis represents the sweeping 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 side of the annealing target (60). The thick solid line and the thin solid line in the graph represent the calculated results when annealing is performed according to the method of the example (Fig. 7A) and the comparative example (Fig. 7B), respectively.

[0066] In the example, the x-direction dimension (Lx) of the beam spot (39) is twice the y-direction dimension (Ly), and in the comparative example, the y-direction dimension (Ly) of the beam spot (39) is twice the x-direction dimension (Lx). In addition, the pulse repetition frequency and pulse energy density are the same in the example and the comparative example. In both the example and the comparative example, as the sweeping speed of the beam spot (39) increases, the activation rate decreases, and the maximum temperature reached on the back side of the annealing target (60) also decreases.

[0067] When sweeping under conditions where the activation rate is 80%, it can be seen that the maximum temperature reached on the back side of the annealing target (60) is lower when the annealing method according to the embodiment is adopted than when the annealing method according to the comparative example is adopted. In this way, by adopting the annealing method according to the present embodiment, it is possible to achieve the desired activation rate while keeping the maximum temperature reached on the back side low.

[0068] Next, the preferred shape of the beam spot (39) (Fig. 7A) is 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) to the y-direction dimension (Ly) of the beam spot (39). 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 units of "°C", and the right vertical axis represents the activation rate in units of "%". The solid line of the graph shown in Fig. 9 represents the maximum temperature reached on the back surface of the annealing object (60), and the dotted line represents the activation rate.

[0069] The graph shown in FIG. 9 was obtained by calculation. As a prerequisite for the calculation, the annealing target (60) was set to a silicon wafer with a thickness of 50 μm, and the pulse repetition frequency of the pulse 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 when the aspect ratio of the beam spot (39) was changed, the area of ​​the beam spot (39) and the overlap rate (OVx) (Equation (4)) in the sweeping direction were kept constant.

[0070] As the aspect ratio increases, the maximum temperature reached on the back side of the annealing target (60) decreases gradually. This is because the sweeping speed increases. The activation rate decreases rapidly when the aspect ratio exceeds about 3. It is desirable to make the aspect ratio of the beam spot (39) smaller than the point where the activation rate begins to decrease rapidly. In the example illustrated in FIG. 9, it is desirable to make the aspect ratio 3 or less, and more desirable to make it 2.5 or less.

[0071] In addition, compared to the case where the aspect ratio is 1, that is, the beam spot (39) is square, it is preferable to make the aspect ratio 1.5 or higher to obtain a sufficient effect of suppressing the rise in the maximum temperature reached on the back side of the annealing target (60).

[0072] Next, with reference to FIG. 10, the relationship between the sweeping speed of the beam spot (39), the maximum temperature reached on the back side of the annealing target (60), and the activation rate will be explained. FIG. 10 is a graph showing the relationship between the sweeping speed, the maximum temperature reached on the back side of the annealing target (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 sweeping speed in units [m / s], the left vertical axis represents the maximum temperature reached on the back side of the annealing target (60) in units "°C", and the right vertical axis represents the activation rate in units "%". The solid line of the graph shown in FIG. 10 represents the maximum temperature reached on the back side of the annealing target (60), and the dotted line represents the activation rate.

[0073] As the sweeping speed increases, the maximum temperature reached on the back side of the annealing target (60) decreases, and the activation rate also decreases. In the example illustrated in FIG. 10, when the allowable upper limit of the maximum temperature reached on the back side of the annealing target (60) is 200°C, the sweeping speed must be 4 m / s or more. From the calculation results illustrated in FIG. 9, it can be seen that if the aspect ratio is increased from 1 to 2.5, the maximum temperature reached on the back side of the annealing target (60) decreases by about 100°C. In the example illustrated in FIG. 10 as well, if the aspect ratio of the beam spot (39) is set to about 2.5, it is expected that the maximum temperature reached on the back side will decrease by about 100°C. Then, even if the sweeping speed is reduced to 2 m / s, it is possible to suppress the maximum temperature reached on the back side to about 200°C.

[0074] In this way, by optimizing the aspect ratio of the beam spot (39), the selectable range of the sweeping speed can be expanded. In the above embodiment, sweeping in the x-direction of the beam spot (39) (Fig. 7A) is performed by operating the beam scanner (15) (Fig. 2). Therefore, compared to the case where the annealing target (60) is moved in the x-direction by operating the movable stage (17) to sweep, the sweeping speed can be increased.

[0075] In order to reduce the temperature rise (ΔT) on the back side of the annealing target (60), as can be seen from Equation (3), it is desirable to make the sweeping speed (v) as fast as possible. However, if the sweeping speed (v) is made fast under conditions where the pulse repetition frequency of the pulse laser beam and the x-direction dimension (Lx) of the beam spot (39) (Fig. 7A) are constant, the overlap rate (OVx) in the x-direction becomes smaller or does not overlap.

[0076] In order to maintain the overlap rate (OVx) when the sweeping speed (v) is increased, if the x-direction dimension (Lx) of the beam spot (39) is increased, the power density (P) on the surface of the annealing target (60) is reduced. Under conditions where the power density (P) is reduced, the maximum temperature (T) reached on the laser irradiation surface a In order to maintain ), the pulse width (t0) must be increased. If the pulse width (t0) is increased, the amount of heat conducted in the thickness direction during the period when the laser pulse is incident increases. As a result, the temperature of the irradiated surface rises. Therefore, the dimension (Lx) cannot be increased indefinitely.

[0077] In order to maintain a sufficient overlap rate (OVx) without increasing the dimensions (Lx), the pulse repetition frequency (f) can be increased. For example, to suppress an excessive rise in temperature on the back side of a semiconductor wafer with a thickness of 100 μm or less, it is desirable to set the pulse repetition frequency (f) to 15 kHz or higher, and more desirable to set it to 100 kHz or higher.

[0078] The embodiments described above are examples, and 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, combinations, etc., are possible. Explanation of the symbols

[0079] 10: Laser light source 11: Beam expander 12: Beam shaping optical element 13, 14: Folding mirror 15: Beam Scanner 15A: Galvano Mirror 15B: Motor 16: fθ lens 17: Movable stage 18: Chuck mechanism 30: Gain optical fiber 32: Input optical fiber 33: Fiber Bragg grating 34: Output fiber 35: Fiber optic Bragg grating 36: Wavelength conversion device 37: Driver 39: Beam Spot 40: Control unit 50: Chamber 51: Laser transmission window 60: Annealing object

Claims

Claim 1 A control device for controlling an annealing device comprising: a laser light source for outputting a pulsed laser beam; a beam shaping optical element for shaping a beam spot on the surface of an annealing target, of the pulsed laser beam output from the laser light source, into a shape long in one direction with an aspect ratio of 1.5 or more and 2.5 or less; and a moving mechanism for moving the beam spot relative to the annealing target; wherein the control device controls the laser light source and the moving mechanism to perform annealing by performing a sweeping operation that moves the beam spot relative to the annealing target in the longitudinal direction of the beam spot while incidenting the pulsed laser beam onto the annealing target. Claim 2 A control device according to claim 1, wherein when one of the sweeping operations is terminated, a stepping operation is performed to offset the beam spot with respect to the annealing target in a direction intersecting the longitudinal direction of the beam spot, and the annealing is performed by repeating the sweeping operation and the stepping operation. Claim 3 A control device according to claim 1 or 2, which controls the laser light source during the period of the sweeping operation to output the pulsed laser beam having a pulse repetition frequency of 100 kHz or more. Claim 4 An annealing device comprising: a laser light source that outputs a pulsed laser beam; a beam shaping optical element that shapes a beam spot on the surface of an annealing target, of the pulsed laser beam output from the laser light source, into a shape long in one direction with an aspect ratio of 1.5 or more and 2.5 or less; a moving mechanism that scans the pulsed laser beam and moves the beam spot in the longitudinal direction of the beam spot; and a control device that controls the laser light source and the moving mechanism; wherein the control device performs annealing by performing a sweeping operation that moves the beam spot in the longitudinal direction of the beam spot with respect to the annealing target while incidenting the pulsed laser beam on the annealing target. Claim 5 An annealing device according to claim 4, wherein the moving mechanism has the function of moving the beam spot in a direction intersecting the longitudinal direction of the beam spot, and the control device additionally performs a stepping operation to offset the beam spot in a direction intersecting the longitudinal direction of the beam spot with respect to the annealing target when one of the sweeping operations is completed, and performs the annealing by repeating the sweeping operation and the stepping operation. Claim 6 An annealing device according to claim 4 or 5, wherein the control device controls the laser light source during the period of the sweeping operation to make the repetition frequency of the pulse of the pulse laser beam 100 kHz or higher. Claim 7 An annealing method in which a pulsed laser beam is incident on the surface of an object to be annealed and annealing is performed while moving a beam spot, wherein the beam spot has a shape that is long in one direction with an aspect ratio of 1.5 or more and 2.5 or less, and annealing is performed by performing a sweeping operation that moves the beam spot along the length direction of the beam spot. Claim 8 An annealing method according to claim 7, wherein when one of the sweeping operations is completed, a stepping operation is performed to offset the beam spot with respect to the annealing target in a direction intersecting the longitudinal direction of the beam spot, and the annealing is performed by repeating the sweeping operation and the stepping operation. Claim 9 An annealing method according to claim 7 or 8, wherein the repetition frequency of the pulse of the pulse laser beam incident on the annealing target during the period of the sweeping operation is 100 kHz or higher.

Images