Method for manufacturing semiconductor device and semiconductor manufacturing apparatus

Abstract

To suppress non-uniformity of annealing occurring between an outer circumferential portion and a non-outer circumferential portion of a semiconductor wafer.SOLUTION: In laser annealing which performs heat treatment of a semiconductor wafer, when scanning a laser beam irradiated onto the semiconductor wafer, the laser beam is scanned in a first-directional positive direction, and after multiple pitches are shifted in a second direction perpendicular to a first direction at a turnaround point, the laser beam is scanned in a first-directional negative direction, and after multiple pitches are shifted in the second direction at the turnaround point, the laser beam is scanned in the first-directional positive direction, and this is repeated. The pitch is an interval between adjacent scans in the first-directional positive direction or the first-directional negative direction in the second direction.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a semiconductor device and a semiconductor manufacturing apparatus that perform laser annealing.

Background Art

[0002] Conventionally, the following laser annealing apparatus is known. That is, it includes a glass processing stage, and the front surface of a semiconductor wafer is fixed by adsorption on the wafer mounting surface of the processing stage. Then, while cooling the semiconductor wafer from the front surface side on the wafer mounting surface, a laser beam is irradiated onto the back surface side of the semiconductor wafer to perform laser annealing.

[0003] In such a laser annealing apparatus, if the size of the processing stage, in other words, the size of the wafer mounting surface, is larger than the size of the semiconductor wafer, there is a concern that vibration of the apparatus may occur. For this reason, a processing stage having a size smaller than the size of the semiconductor wafer is used. Then, since the processing stage is responsible for cooling the semiconductor wafer, a difference in the degree of annealing occurs between the outer peripheral portion and the portion other than the outer peripheral portion of the semiconductor wafer that is placed on the wafer mounting surface of the processing stage and is subjected to laser annealing.

[0004] The scanning of the laser beam irradiated on the semiconductor wafer in laser annealing is performed, for example, as follows. That is, when the plane including the back surface of the semiconductor wafer subjected to laser annealing is defined as the XY plane, the laser beam is scanned in the positive Y direction, shifted by 1 pitch position in the X direction at the turning point, then scanned in the negative Y direction, shifted by 1 pitch position in the X direction again at the turning point, and scanned in the positive Y direction again, and this is repeated.

[0005] For example, in Patent Document 1, the power of the laser beam irradiated on the semiconductor wafer is changed according to the Y-direction position of the scanned laser beam. Thereby, an attempt is made to make the annealing uniform.

Prior Art Documents

Patent Documents

[0006] Patent Document 1 Japanese Patent Application Laid-Open No. 2013-74247 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In the case of the above-described laser beam scanning, non-uniform annealing occurs between the vicinity of the turning point on the outer peripheral portion of the semiconductor wafer and other locations. This is because, in the vicinity of the turning point, the time interval between the laser irradiation in the Y positive direction scanning and the laser irradiation in the Y negative direction scanning shifted by one pitch in the X direction from the Y positive direction scanning is short, and the laser irradiation is performed in a state where the semiconductor wafer is not sufficiently cooled. This point is not considered in the technology of Patent Document 1.

[0008] An object of the present disclosure is to provide a method for manufacturing a semiconductor device and a semiconductor manufacturing apparatus that can suppress non-uniform annealing occurring between the outer peripheral portion and the portion other than the outer peripheral portion of a semiconductor wafer. MEANS FOR SOLVING THE PROBLEMS

[0009] In one aspect, a method for manufacturing a semiconductor device according to the present disclosure includes a laser annealing step of irradiating a semiconductor wafer with a laser beam to perform heat treatment on the semiconductor wafer. The laser annealing step includes a step of scanning the laser beam irradiated on the semiconductor wafer. In the scanning, the laser beam is scanned in a first direction of in the positive direction, and after shifting a plurality of pitch positions in a second direction orthogonal to the first direction at a turning point, in the first direction of in the negative direction, and after shifting a plurality of pitch positions in the second direction again at the turning point, in the first direction of in the positive direction, and this is repeated. The pitch is the interval between adjacent scans in the first direction of in the positive direction or in the first direction of in the negative direction in the second direction ri , The scanning speed of the laser beam is slower when the laser beam irradiates areas other than the outer peripheral part of the semiconductor wafer than when the laser beam irradiates the outer peripheral part of the semiconductor wafer. A method for manufacturing a semiconductor device.

[0010] Also, in one aspect, the semiconductor manufacturing apparatus of the present disclosure includes a laser annealing apparatus that irradiates a semiconductor wafer with a laser beam to perform heat treatment on the semiconductor wafer. The laser annealing apparatus includes a scanning mechanism that scans the laser beam irradiated on the semiconductor wafer. In the scanning, the laser beam is scanned in the first direction of in the positive direction, and after being shifted by a plurality of pitch positions in the second direction orthogonal to the first direction at the turning point, it is scanned in the first direction of in the negative direction, and after being shifted by a plurality of pitch positions in the second direction again at the turning point, it is scanned in the first direction of in the positive direction, and this is repeated. The pitch is the interval between adjacent scans in the first direction in the second direction of in the positive direction or the first direction of in the negative direction. ri , The scanning speed of the laser beam is slower when the laser beam irradiates areas other than the outer peripheral part of the semiconductor wafer than when the laser beam irradiates the outer peripheral part of the semiconductor wafer. It is a semiconductor manufacturing apparatus.

Effects of the Invention

[0011] According to the present disclosure, it is possible to provide a method for manufacturing a semiconductor device and a semiconductor manufacturing apparatus that can suppress the non-uniformity of annealing that occurs between the outer peripheral portion and the portion other than the outer peripheral portion of the semiconductor wafer.

Brief Description of the Drawings

[0012]

Figure 1

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Figure 8

Mode for Carrying Out the Invention

[0013] <A. Embodiment 1> <A-1. Configuration of Semiconductor Manufacturing Apparatus> FIG. 5 is a diagram conceptually showing the configuration of a laser annealing apparatus provided in the semiconductor manufacturing apparatus according to Embodiment 1.

[0014] As shown in FIG. 5, the laser annealing apparatus includes a glass stage 1, a stage base 2, a cooling unit 3, a suction line 4, and a laser oscillator 5.

[0015] The glass stage 1 mounts the semiconductor wafer 6. The semiconductor wafer 6 is suction-fixed to the mounting surface of the glass stage 1 via the suction line 4. Ion implantation of impurities is performed on the back side of the semiconductor wafer 6. The semiconductor wafer 6 is mounted with its front side facing the glass stage 1 so that the back side can be heat-treated (i.e., laser annealing treatment) by irradiation with a laser beam 7 from the laser oscillator 5. By performing the laser annealing treatment, the impurity ions implanted on the back surface of the semiconductor wafer 6 can be activated. The semiconductor wafer 6 is formed using a semiconductor material made of, for example, Si or SiC.

[0016] The stage base 2 mounts the glass stage 1 or is integrally formed with the glass stage 1. A cooling unit 3 is attached to the stage base 2 that is in contact with or integral with the glass stage 1, whereby when performing laser annealing, the semiconductor wafer 6 is cooled from the side of the front surface of the semiconductor wafer 6 (i.e., the surface in contact with the mounting surface of the glass stage 1).

[0017] <A-2. Method for manufacturing semiconductor device> Next, a method for manufacturing a semiconductor device according to Embodiment 1 using the laser annealing apparatus of FIG. 5 will be described. FIG. 6 is a flowchart showing the process of the laser annealing process in the method for manufacturing a semiconductor device using the laser annealing apparatus of FIG. 5. As shown in FIG. 6, the laser annealing process includes a preparation step S1 and a laser annealing step S2.

[0018] In the preparation step S1, a process of ion-implanting impurities is performed on the back surface side of the semiconductor wafer 6. Then, the semiconductor wafer 6 is placed on the glass stage 1 and adsorbed and fixed via the adsorption line 4. At this time, the semiconductor wafer 6 is arranged such that the front surface of the semiconductor wafer 6 faces the mounting surface of the glass stage 1 so that the back surface side of the semiconductor wafer 6 can be irradiated with the laser beam 7 from the laser oscillator 5 and heat-treated. The impurities ion-implanted into the semiconductor wafer 6 are, for example, if they are n-type impurities, phosphorus, arsenic, protons, or the like. The implanted impurities are activated by the laser annealing step S2 and become, for example, the buffer layer of an IGBT (Insulated-Gate Bipolar Transistor) or the cathode layer of a diode in a semiconductor device such as an IGBT or a diode.

[0019] In the laser annealing process S2, while cooling the semiconductor wafer 6 placed on the glass stage 1 by the cooling unit 3, annealing treatment is performed by irradiating the laser beam 7 from the laser oscillator 5. The wavelength of the laser beam 7 is, for example, from 350 nm to 600 nm. Specifically, for example, as the laser beam 7, the second harmonic of a Nd:YAG laser (the wavelength of the second harmonic is 532 nm), the second harmonic of a solid-state laser such as a Nd:YLF laser or a Nd:YVO4 laser may be used. For lasers in a wavelength band longer than the above wavelength band, such as a carbon dioxide laser (the wavelength of the carbon dioxide laser is, for example, from 9 μm to 10 μm), activation heat treatment is performed not only on the back surface but also on the front surface side of the semiconductor wafer 6. Therefore, from the relationship between the depth to be activated and the depth where heat is not desired to be transferred, it is desirable to use a laser in the above wavelength band.

[0020] As shown in FIG. 5, the laser annealing apparatus is provided with a scanning mechanism 8 for scanning the laser beam 7 irradiated onto the semiconductor wafer 6. The scanning mechanism 8 changes the irradiation position of the laser beam 7, which is irradiated from the laser oscillator 5 toward the semiconductor wafer 6 on the glass stage 1, over time. That is, the scanning mechanism 8 scans the irradiation position of the laser beam 7 with respect to the semiconductor wafer 6 on the irradiated surface of the semiconductor wafer 6 (in the case of this embodiment, the back surface of the semiconductor wafer 6). The scanning mechanism 8 may be any mechanism that can change the relative position between the laser beam 7 and the semiconductor wafer 6 over time. For example, it may be a mechanism that moves the laser beam 7 irradiated from the laser oscillator 5 over time. Also, for example, it may be a mechanism that moves the stage base 2 over time. Further, for example, it may be a mechanism that moves both the laser beam 7 and the stage base 2 over time.

[0021] FIG. 1 is a diagram for explaining the scanning of the laser beam 7 by the scanning mechanism 8. FIG. 1(a) schematically shows the conventional scanning, and FIG. 1(b) schematically shows the scanning according to the present embodiment. Here, the right direction on the paper surface is defined as the positive direction of the first direction, the left direction on the paper surface is defined as the negative direction of the first direction, and the vertical direction on the paper surface is defined as the second direction. The scanning in the positive direction of the first direction or the negative direction of the first direction is simply referred to as the scanning in the first direction, respectively. Also, the pitch p is defined as the interval between the adjacent scans in the first direction in the second direction. Further, each digit of the symbols of the scans SC1, SC2, SC3, SC4, SC5 in the first direction indicates the order of the scans. Note that, between two adjacent scans in the first direction in the second direction, the laser beam 7 may be irradiated in a state where it is overlapped by n percent. n is a variable parameter that can be set in the laser annealing apparatus.

[0022] First, the conventional scanning shown in FIG. 1(a) will be described. In the laser annealing process for heat-treating the semiconductor wafer 6, when scanning the laser beam 7 irradiated onto the semiconductor wafer 6, the laser beam 7 is scanned in the positive direction of the first direction, and after being shifted by one pitch p in the second direction orthogonal to the first direction at the turning point t, it is scanned in the negative direction of the first direction. After being shifted by one pitch p in the second direction again at the turning point t, it is scanned in the positive direction of the first direction, and this is repeated.

[0023] Thus, in the conventional scanning, the forward path (or the return path) in one first direction and the subsequent return path (or the forward path) in the same first direction are always adjacent to each other. That is, the distance in the second direction shifted at the turning point t is always the shortest one pitch p. Therefore, in the conventional scanning, the outer peripheral portion of the semiconductor wafer 6 is over-annealed, and variations occur in the sheet resistance between the outer peripheral portion and its inner portion within the plane of the semiconductor wafer 6. This is because, at the outer peripheral portion of the semiconductor wafer 6 close to the turning point t, after the irradiation of the laser beam 7 by the scanning in one first direction, before sufficient cooling is performed, the irradiation of the laser beam 7 by the subsequent scanning in the same first direction is carried out. FIG. 2 is a diagram explanatorily showing the length of time until the next irradiation of the laser beam 7 in the adjacent scanning in the first direction. In FIG. 2, the path 7a indicates the scanning path of the laser beam 7 in the vicinity of the turning point t.

[0024] Next, the scanning according to the present embodiment in FIG. 1(b) will be described. In the laser annealing step S2 for performing the heat treatment of the semiconductor wafer 6, when scanning the laser beam 7 irradiated onto the semiconductor wafer 6, the laser beam 7 is scanned in the positive direction of the first direction, and after being shifted by a plurality of pitches x·p in the second direction orthogonal to the first direction at the turning point t, it is scanned in the negative direction of the first direction. After being shifted again by a plurality of pitches x·p in the second direction at the turning point t, it is scanned in the positive direction of the first direction, and this is repeated. x is an integer and a variable that may be different for each turn, for example, a variable set in the laser annealing apparatus. Also, shifting the position by a plurality of pitches in the second direction includes the case of shifting the position by a plurality of pitches in one direction of the second direction and the case of shifting the position by a plurality of pitches in the other direction of the second direction.

[0025] Thus, according to the scanning of this embodiment, the forward path (or return path) in one first direction and the subsequent return path (or forward path) in the same first direction do not adjacent to each other. That is, the distance in the second direction shifted at the turning point t is a plurality of pitches x·p. Therefore, according to the scanning of this embodiment, over-annealing of the outer peripheral portion of the semiconductor wafer 6 is suppressed, and variation in sheet resistance between the outer peripheral portion and the inner portion thereof in the plane of the semiconductor wafer 6 is suppressed. This is because, at the outer peripheral portion of the semiconductor wafer 6 close to the turning point t, after the irradiation of the laser beam 7 by the scanning in one first direction, after ensuring the time for cooling, the irradiation of the laser beam 7 by another scanning in the first direction adjacent to the scanning in the one first direction is performed.

[0026] The method for manufacturing a semiconductor device and the semiconductor manufacturing apparatus according to this embodiment are particularly effective when the area of the mounting surface of the glass stage 1 installed on the stage base 2 having the cooling unit 3 is smaller than the area of the semiconductor wafer 6 and cooling is difficult to be performed at the outer peripheral portion of the semiconductor wafer 6.

[0027] The laser beam 7 is preferably irradiated perpendicularly to the semiconductor wafer 6. Alternatively, it is preferable to irradiate the semiconductor wafer 6 with the laser beam 7 in a direction such that the laser beam 7 is perpendicular to the glass stage 1. This is because, compared with the case where the laser beam 7 is obliquely irradiated to the semiconductor wafer 6, when irradiated perpendicularly, the depth of heat transfer in the semiconductor wafer 6 is more likely to be uniform and the heat profile is more likely to be uniform. Even when a modification such as changing the irradiation power of the laser beam 7 during scanning is performed as in the modification example described later, perpendicular incidence is more preferable than oblique incidence, thereby realizing a stable heat treatment temperature and suppressing non-uniformity in heat treatment by laser annealing between the outer peripheral portion and the portion other than the outer peripheral portion of the semiconductor wafer 6. Here, perpendicular means not only the case where the angle between the plane and the line is exactly 90 degrees, but also the case where the angle is 85 degrees or more.

[0028] <A-3. Modification Example 1> FIG. 4 is an explanatory diagram showing the scanning of the laser beam 7 according to Modification 1. In Modification 1, as shown in FIG. 4, the scanning speed of the laser beam 7 by the scanning mechanism 8 is high when the laser beam 7 is irradiated on the outer peripheral portion of the semiconductor wafer 6, and is low when the laser beam 7 is irradiated on other than the outer peripheral portion of the semiconductor wafer 6. That is, the scanning speed of the laser beam 7 is slower when the laser beam 7 is irradiated on other than the outer peripheral portion of the semiconductor wafer 6 than when the laser beam 7 is irradiated on the outer peripheral portion of the semiconductor wafer 6. By changing the scanning speed of the laser beam 7 by the scanning mechanism 8 between the outer peripheral portion and other than the outer peripheral portion according to the sheet resistance distribution of the outer peripheral portion and other than the outer peripheral portion of the semiconductor wafer 6 grasped in advance, non-uniformity of annealing can be suppressed.

[0029] For example, when the sheet resistance of other than the outer peripheral portion of the semiconductor wafer 6 grasped in advance is high, the scanning speed when irradiating the laser beam 7 on other than the outer peripheral portion of the semiconductor wafer 6 is made slow, and when the sheet resistance of the outer peripheral portion grasped in advance is low, the scanning speed when irradiating the laser beam 7 on the outer peripheral portion of the semiconductor wafer 6 is made fast. For example, when the sheet resistance is higher in other than the outer peripheral portion than in the outer peripheral portion as shown in FIG. 7 when the scanning speed of the laser beam 7 is constant, that is, when the scanning speed of the laser beam 7 does not change between the outer peripheral portion and other than the outer peripheral portion, by scanning the laser beam 7 faster in the outer peripheral portion than in other than the outer peripheral portion as shown in the scanning speed in FIG. 7, the sheet resistance is made uniform.

[0030] The change in the scanning speed of the laser beam 7 is not limited to the above-described two-stage change, and may be a change in a plurality of stages of three or more stages.

[0031] <A-4. Modification 2> FIG. 8 is an explanatory diagram showing the scanning of the laser beam 7 according to Modification 2. As shown in FIG. 8, the power of the laser beam 7 scanned by the scanning mechanism 8 is low when the laser beam 7 irradiates the outer peripheral portion of the semiconductor wafer 6, and high when the laser beam 7 irradiates other than the outer peripheral portion of the semiconductor wafer 6. That is, the power of the scanned laser beam 7 is higher when the laser beam 7 irradiates other than the outer peripheral portion of the semiconductor wafer 6 than when the laser beam 7 irradiates the outer peripheral portion of the semiconductor wafer 6. By changing the power of the laser beam 7 depending on the sheet resistance distribution of the outer peripheral portion and other than the outer peripheral portion of the semiconductor wafer 6 grasped in advance, non-uniformity of annealing can be suppressed.

[0032] For example, when the sheet resistance of other than the outer peripheral portion of the semiconductor wafer 6 grasped in advance is high, the power when irradiating other than the outer peripheral portion of the semiconductor wafer 6 with the laser beam 7 is increased, and when the sheet resistance of the outer peripheral portion of the semiconductor wafer 6 grasped in advance is low, the power when irradiating the outer peripheral portion of the semiconductor wafer 6 with the laser beam 7 is decreased.

[0033] It is desirable to change the power during scanning without stopping the scanning of the laser beam 7, whereby the throughput can be improved. Note that the change in the power of the laser beam 7 is not limited to the two-stage change described above, and may be a change in a plurality of stages of three or more stages. Further, Modification 1 and Modification 2 may be combined to perform both a change in the scanning speed and a change in the power.

[0034] <B. Embodiment 2> FIG. 3(b) is a diagram conceptually showing the configuration of a laser annealing apparatus provided in the semiconductor manufacturing apparatus according to Embodiment 2. The difference from the laser annealing apparatus of FIG. 5 according to Embodiment 1 is that, in FIG. 3(b), instead of the scanning mechanism 8 of FIG. 5, a rotational movement mechanism 9 as a scanning mechanism for scanning the laser beam 7 is provided. Since other configurations are the same, descriptions of the same components are omitted.

[0035] The rotational movement mechanism 9 as a scanning mechanism for scanning the laser beam 7 is disposed below the stage base 2 and scans the laser beam 7. In the present embodiment, for example, the irradiation position of the laser beam 7 is fixed. The rotational movement mechanism 9 rotates the stage base 2 about its central axis and moves it in the in-plane direction of the semiconductor wafer 6 (that is, the direction indicated by the dashed arrow 9a). As a result, the semiconductor wafer 6 placed on the glass stage 1 also moves in the direction indicated by the dashed arrow 9a while rotating about the central axis while being irradiated with the laser beam 7. As a result, as shown in Fig. 3(a), the laser beam 7 is scanned in a spiral shape from the outer periphery to the center of the semiconductor wafer 6 along the path 7b.

[0036] Compared with the case of the first embodiment, since the heat treatment can be performed by scanning the laser beam 7 in a spiral shape without performing the process of inverting the scanning direction of the laser beam 7 at each turning point, the throughput is improved. Further, at the outer peripheral portion of the semiconductor wafer 6, the rotational movement distance from the position of one irradiation by the laser beam 7 to the position of the next adjacent irradiation is long. At the outer peripheral portion of the semiconductor wafer 6, after the irradiation with the laser beam 7, it is sufficiently cooled and then the irradiation with the next laser beam 7 is performed. For this reason, over-annealing at the outer peripheral portion of the semiconductor wafer 6 is suppressed, and variation in the sheet resistance in the plane of the semiconductor wafer 6 between the outer peripheral portion and the inside thereof is suppressed.

[0037] For the second embodiment, the configurations described in the first modification or the second modification of the first embodiment may be combined. In this case, the change in the scanning speed or power of the laser beam 7 may be performed only once at a specific point in the spiral scanning path 7b, for example. Since the number of changes is small, the throughput is improved.

[0038] The semiconductor wafer 6 is, for example, circular with a diameter of 6 inches to 12 inches. In the case of a semiconductor wafer having a large size such as 12 inches, improvement in throughput becomes more important, and thus the present embodiment is effective.

[0039] In Embodiment 1, the number of times of the process of inverting the scanning direction of the laser beam 7 increases as the diameter of the semiconductor wafer increases. However, in this embodiment, since the process of inverting the scanning direction of the laser beam 7 is unnecessary, this embodiment is more effective for semiconductor wafers with a larger diameter.

[0040] Also, in Modification 1 or Modification 2 of Embodiment 1, as the diameter of the semiconductor wafer increases, the number of times of changing the irradiation speed or power of the laser beam 7 increases. On the other hand, when the configurations described in Modification 1 or Modification 2 of Embodiment 1 are combined in this embodiment, even if the diameter of the semiconductor wafer increases, it is not necessary to increase the number of times of changing the irradiation speed or power of the laser beam 7. Therefore, the configuration obtained by combining the configurations described in Modification 1 or Modification 2 of Embodiment 1 in this embodiment is more effective for semiconductor wafers with a larger diameter.

[0041] It should be noted that each embodiment can be freely combined, or each embodiment can be appropriately modified or omitted.

Description of Reference Numerals

[0042] 1 Glass stage, 2 Stage base, 3 Cooling unit, 4 Adsorption line, 5 Laser oscillator, 6 Semiconductor wafer, 7 Laser beam, 8 Scanning mechanism, 9 Rotary movement mechanism.

Claims

1. A method for manufacturing a semiconductor device, comprising a laser annealing step of irradiating a semiconductor wafer with a laser beam to perform heat treatment on the semiconductor wafer, wherein the laser annealing step includes a step of scanning the laser beam irradiated on the semiconductor wafer, and in the scanning, the laser beam is scanned in the positive direction of a first direction, and after being shifted by a plurality of pitch positions in a second direction orthogonal to the first direction at a turning point, the laser beam is scanned in the negative direction of the first direction, and after being shifted by a plurality of pitch positions in the second direction again at the turning point, the laser beam is scanned in the positive direction of the first direction, and this is repeated, wherein the pitch is an interval between the scans in the positive direction or the negative direction of the first direction adjacent to each other in the second direction, and the scanning speed of the laser beam is slower when the laser beam is irradiated on a portion other than the outer peripheral portion of the semiconductor wafer than when the laser beam is irradiated on the outer peripheral portion of the semiconductor wafer. A method for manufacturing a semiconductor device.

2. A method for manufacturing a semiconductor device, comprising a laser annealing step of irradiating a semiconductor wafer with a laser beam to perform heat treatment on the semiconductor wafer, wherein the laser annealing step includes a step of scanning the laser beam irradiated on the semiconductor wafer, and in the scanning, the laser beam is scanned in a spiral shape from the outer periphery to the center of the semiconductor wafer, and when the sheet resistance of a portion other than the outer peripheral portion of the semiconductor wafer becomes higher than the sheet resistance of the outer peripheral portion under the assumption that the scanning speed of the laser beam does not change between the outer peripheral portion and the portion other than the outer peripheral portion of the semiconductor wafer, the scanning speed of the laser beam is slower when the laser beam is irradiated on a portion other than the outer peripheral portion of the semiconductor wafer than when the laser beam is irradiated on the outer peripheral portion of the semiconductor wafer. A method for manufacturing a semiconductor device.

3. The method for manufacturing a semiconductor device according to claim 1 or 2, wherein the laser beam is irradiated perpendicularly to the semiconductor wafer. A method for manufacturing a semiconductor device.

4. A laser annealing apparatus for irradiating a semiconductor wafer with a laser beam to perform heat treatment on the semiconductor wafer, wherein the laser annealing apparatus includes a scanning mechanism for scanning the laser beam irradiated on the semiconductor wafer. In the scanning, the laser beam is scanned in the positive direction of the first direction, and after shifting a plurality of pitch positions in the second direction orthogonal to the first direction at the turning point, the laser beam is scanned in the negative direction of the first direction, and after shifting a plurality of pitch positions in the second direction at the turning point again, the laser beam is scanned in the positive direction of the first direction, and this is repeated. The pitch is the interval between the scans in the positive direction or the negative direction of the first direction adjacent to each other in the second direction. The scanning speed of the laser beam is slower when the laser beam is irradiated on the part other than the outer peripheral part of the semiconductor wafer than when the laser beam is irradiated on the outer peripheral part of the semiconductor wafer. Semiconductor manufacturing apparatus.

5. A laser annealing apparatus that irradiates a semiconductor wafer with a laser beam and performs heat treatment on the semiconductor wafer, The laser annealing apparatus, includes a scanning mechanism that scans the laser beam irradiated on the semiconductor wafer. In the scanning, the laser beam is scanned in a spiral shape from the outer periphery of the semiconductor wafer toward the center. When the sheet resistance of the part other than the outer peripheral part of the semiconductor wafer becomes higher than the sheet resistance of the outer peripheral part under the assumption that the scanning speed of the laser beam does not change between the outer peripheral part and the part other than the outer peripheral part of the semiconductor wafer, the scanning speed of the laser beam is slower when the laser beam is irradiated on the part other than the outer peripheral part of the semiconductor wafer than when the laser beam is irradiated on the outer peripheral part of the semiconductor wafer. Semiconductor manufacturing apparatus.

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