Laser irradiation apparatus, laser irradiation method, and method for manufacturing semiconductor device

Abstract

A laser irradiation apparatus includes: a laser light source configured to emit linearly polarized pulsed laser light; a first half-wave plate rotatably provided in an optical path of the pulsed laser light; a first polarization beam splitter configured to branch the pulsed laser light from the first half-wave plate into first pulsed light and second pulsed light; a second polarization beam splitter configured to combine the first pulsed light and the second pulsed light, the second pulsed light being delayed with respect to the first pulsed light by using a difference in optical path length between the first pulsed light and the second pulsed light; and a first wave plate rotatably provided in an optical path of combined pulsed light generated by combining the first pulsed light and the second pulsed light at the second polarization beam splitter.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a laser irradiation apparatus, a laser irradiation method, and a method for manufacturing a semiconductor device. BACKGROUND

[0002] Japanese Patent No. 6706155 discloses a laser annealing apparatus for forming a polycrystalline silicon thin film. In Japanese Patent No. 6706155, a solid-state laser apparatus emits linearly polarized laser light. The linearly polarized laser beam is incident on a polarization beam splitter through a half wave plate. The polarization beam splitter divides the laser light into two beams. The two beams divided by the polarization beam splitter are combined with each other at a second polarization beam splitter. SUMMARY

[0003] In such a laser irradiation apparatus, it is desirable to irradiate a subject with laser light having an appropriate polarization state.

[0004] Other problems and novel features will be clarified from the description of this specification and the drawings.

[0005] According to an embodiment, a laser irradiation apparatus includes: a laser light source configured to emit pulsed laser light that is linearly polarized; a first half wave plate rotatably disposed in an optical path of the pulsed laser light; a first polarization beam splitter configured to branch the pulsed laser light from the first half wave plate into first pulsed light and second pulsed light; a second polarization beam splitter configured to combine the first pulsed light with the second pulsed light, the second pulsed light being delayed relative to the first pulsed light by utilizing a difference in optical path length between the first pulsed light and the second pulsed light; and a first wave plate rotatably disposed in an optical path of combined pulsed light, the combined pulsed light being generated by combining the first pulsed light with the second pulsed light at the second polarization beam splitter.

[0006] According to an embodiment, a laser irradiation method includes: (a) emitting pulsed laser light that is linearly polarized; (b) causing the pulsed laser light to be incident on a first half wave plate that is rotatably disposed; (c) branching the pulsed laser light from the first half wave plate into first pulsed light and second pulsed light; (d) combining the first pulsed light with the second pulsed light, the second pulsed light being delayed relative to the first pulsed light by utilizing a difference in optical path length between the first pulsed light and the second pulsed light; and (e) causing combined pulsed light to be incident on a first wave plate that is rotatably disposed in an optical path of the combined pulsed light, the combined pulsed light being generated by combining the first pulsed light with the second pulsed light at a second polarization beam splitter.

[0007] According to one embodiment, a method for manufacturing a semiconductor device includes the steps of: (S1) forming an amorphous film on a substrate; and (S2) annealing the amorphous film, thereby crystallizing the amorphous film and further forming a crystallized film, wherein the annealing (S2) includes the steps of: (A) emitting a linearly polarized pulsed laser; (B) making the pulsed laser incident on a first half-wave plate placed rotatably; (C) branching the pulsed laser from the first half-wave plate into first pulsed light and second pulsed light; (D) combining the first pulsed light with the second pulsed light, the second pulsed light being delayed with respect to the first pulsed light by using a difference in optical path length between the first pulsed light and the second pulsed light; (E) making the combined pulsed laser incident on a first wave plate rotatably provided in an optical path of the combined pulsed laser, the combined pulsed laser being generated by combining the first pulsed light with the second pulsed light at a second polarization beam splitter.

[0008] According to this embodiment, laser light having a suitable polarization state can be irradiated to an object.

[0009] The above and other objects, features and advantages of the present disclosure will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, which are to be considered illustrative only, and not to be considered as restricting the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 An optical system of a laser annealing apparatus according to the present embodiment is shown;

[0011] Figure 2 An optical system of a laser annealing apparatus is shown;

[0012] Figure 3 Laser light split by a polarization beam splitter 33 is shown;

[0013] Figure 4 A time waveform of laser light combined by a polarization beam splitter 61 is shown;

[0014] Figure 5 A polarization state of laser light synthesized by a polarization beam splitter 61 is depicted;

[0015] Figure 6 is a simplified sectional view of the configuration of an organic EL (electroluminescence) display;

[0016] Figure 7 is a sectional view showing a process in a method for manufacturing a semiconductor device according to this embodiment; and

[0017] Figure 8 is a sectional view showing a process in a method for manufacturing a semiconductor device according to this embodiment. DETAILED DESCRIPTION

[0018] The laser irradiation apparatus according to this embodiment is, for example, a laser annealing apparatus for forming LTPS (low-temperature polycrystalline silicon) films. The laser irradiation apparatus, laser annealing method, and method for manufacturing semiconductor devices according to this embodiment will now be described with reference to the accompanying drawings.

[0019] (Optical system of laser irradiation equipment)

[0020] Reference Figure 1 The structure of the laser irradiation device according to this embodiment is described. Figure 1 The optical system of the laser irradiation device 1 is schematically shown. A silicon film 101 is formed on the upper surface (main surface) of a substrate 100. The laser irradiation device 1 uses a laser L1 to irradiate the silicon film 101 formed on the substrate 100. In this way, an amorphous silicon film (a-Si film) 101 can be converted into a polycrystalline silicon film (p-Si film) 101. The substrate 100 is, for example, a transparent substrate, such as a glass substrate. The substrate 100 is the object to be irradiated by the laser beam.

[0021] Note that in Figure 1 A three-dimensional orthogonal coordinate system (XYZ) is shown for clarity. The Z-direction is vertical and perpendicular to the substrate 100. The XY plane is a plane parallel to the surface on which the silicon film 101 is formed on the substrate 100. The X-direction is the longitudinal direction of the rectangular substrate 100, while the Y-direction is the transverse direction of the substrate 100. Furthermore, in the laser irradiation apparatus 1, the laser is transported by a conveying mechanism (not in...) Figure 1 (As shown in the diagram) While transporting the substrate 100 along the positive X-axis, the silicon film 101 is irradiated with a laser L1. Note that in Figure 1 In the middle, the silicon film 101 that has not yet been irradiated by laser L1 is called amorphous silicon film 101a, while the silicon film 101 that has been irradiated by laser L1 is called polycrystalline silicon film 101b.

[0022] The laser irradiation device 1 includes a stage 10, a laser source 21, an optical system 20, and a detection unit 22. The substrate 100 is positioned above the stage 10. The stage 10 is a floating stage (floating unit) that levitates (i.e., suspends) the substrate 100 by jetting air. However, the stage 10 is not limited to a floating stage. For example, the stage 10 can be a vacuum chuck type stage. The stage 10 jets gas from below the substrate 100 towards the substrate 100.

[0023] Therefore, with a tiny gas gap formed between the stage 10 and the substrate 100, the substrate 100 is transported along the positive X-axis.

[0024] The optical system 20 is an optical system for irradiating the silicon film 101 with the laser light Ll to crystallize the amorphous silicon film 101a. The optical system 20 includes a polarization control unit 30 for controlling a polarization state of the laser beam Ll. The polarization control unit 30 controls the polarization state of the laser beam Ll. The detailed configuration of the optical system 20 will be described later.

[0025] The optical system 20 is disposed above the substrate 100 (on the positive side of the Z axis of the substrate 100). The laser light source 21 is a pulsed laser light source that generates pulsed laser light. The laser light source 21 is, for example, a solid-state laser device such as a Nd:YAG laser device. Further, the laser light source 21 emits pulsed laser light Ll. The laser light source 21 emits linearly polarized laser light Ll. The laser light source 21 is not limited to a solid-state laser device, but can also be a semiconductor laser device.

[0026] The optical system 20 includes a homogenizer for homogenizing the laser beam Ll, a condenser lens for converging the laser beam Ll, and the like. The laser light Ll forms a linear irradiation region on the substrate 100. The irradiation region has a linear shape in which the Y direction is the longitudinal direction and the X direction is the lateral direction.

[0027] The optical system 20 guides the laser light Ll emitted from the laser light source 21 to the substrate 100. The laser light incident on the substrate 100 from the optical system 20 is referred to as laser light L2. The amorphous silicon film 101a is crystallized by irradiation with the laser light L2. The silicon film 101 is irradiated with the laser light L2 while changing the portion of the substrate 100 to which the laser light L2 is applied. By transporting the substrate 100 in the positive direction of the X axis by the transport mechanism of the stage 10, a uniform polycrystalline silicon film 101b is formed on the substrate 100. Needless to say, the laser light source 21 and the optical system 20 can be moved instead of transporting the substrate 100. That is, as long as the irradiation region is scanned with the laser light L2 by moving the substrate 100 and the annealing optical system 20 relative to each other, any configuration or the like can be used.

[0028] Further, a detection unit 22 is disposed above the substrate 100. The detection unit 22 is provided so as to photograph (i.e., take an image of) the crystallized polysilicon film 101b. The detection unit 22 includes, for example, a camera for taking an image of the polysilicon film 101b. Alternatively, the detection unit 22 can include a spectrometer for measuring a spectrum of reflected light reflected by the polysilicon film 101b. Further, the detection unit 22 can include an illumination light source for illuminating the substrate 100. By way of example, the illumination light source generates illumination light for illuminating a region irradiated with the laser beam L2. The camera detects reflected light from the region illuminated by the illumination light. Since the detection unit 22 can photograph the region irradiated with the laser beam L2, the crystalline state of the polysilicon film 101b can be evaluated. It is possible to evaluate the uniformity and non-uniformity of the crystalline state of the polysilicon film 101b.

[0029] The polarization control unit 30 controls the polarization state of the laser beam LI and adjusts the pulse waveform. Specifically, the polarization control unit 30 controls the temporal waveform of the pulsed laser beam by delaying a portion of the pulsed laser beam. Figure 2 is a schematic view showing the configuration of the polarization control unit 30. The polarization control unit 30 includes a half-wave plate 31, a mirror 32, a polarization beam splitter 33, a polarization beam splitter 61, and a wave plate 62.

[0030] The half-wave plate 31 is rotatably disposed in the optical path of the laser beam LI. By rotating the half-wave plate 31 about the optical axis of the laser beam LI, the polarization direction of the laser beam LI can be adjusted. That is, the linear polarization direction is rotated according to the rotation angle of the half-wave plate 31.

[0031] The laser beam LI is incident on the mirror 32 through the half-wave plate 31. The mirror 32 reflects the laser beam LI toward the polarization beam splitter 33. The laser beam LI reflected by the mirror 32 is incident on the polarization beam splitter 33.

[0032] The polarization beam splitter 33 branches the laser beam LI into two pulsed beams L31, L32. The polarization beam splitter 33 branches incident light according to the polarization state. Specifically, the polarization beam splitter 33 transmits the P-polarization component and reflects the S-polarization component. Thus, the pulsed light L31 transmitted through the polarization beam splitter 33 becomes linearly polarized light of P-polarization. The pulsed light L32 reflected by the polarization beam splitter 33 becomes linearly polarized light of S-polarization.

[0033] The pulsed light L31 and the pulsed light L32 are combined at a later stage by a polarization beam splitter 61. Two optical paths are provided between the polarization beam splitter 33 and the polarization beam splitter 61. The pulsed beam L31 propagates from the polarization beam splitter 33 to the polarization beam splitter 61 in one optical path, and the pulsed beam L32 propagates from the polarization beam splitter 33 to the polarization beam splitter 61 in the other optical path. An optical path length difference is created between the two optical paths so as to delay the pulsed light L32 with respect to the pulsed light L31.

[0034] Between the polarization beam splitter 33 and the polarization beam splitter 61, the optical path through which the pulsed light L31 propagates is referred to as an advance optical path 40, and the optical path through which the pulsed light L32 propagates is referred to as a delay optical path 50. The optical path length of the delay optical path 50 is longer than the optical path length of the advance optical path 40. The pulsed light L31 is defined as advance pulsed light, and the pulsed light L32 is defined as delay pulsed light.

[0035] A wave plate 41 is disposed in the advance optical path 40. The pulsed light L31 from the polarization beam splitter 33 travels through the wave plate 41 and then enters the polarization beam splitter 61.

[0036] A mirror 51, a mirror 52, and a wave plate 53 are disposed in the delay optical path 50. The pulsed light L32 from the polarization beam splitter 33 is reflected by the mirror 51 and the mirror 52. The pulsed light L32 reflected by the mirror 52 is incident on the wave plate 53. The pulsed light L32 travels through the wave plate 53 and enters the polarization beam splitter 61. Since the mirror 51 and the mirror 52 are disposed in the delay optical path 50, the optical path length becomes longer than the length of the advance optical path 40. Therefore, the pulsed light L32 entering the polarization beam splitter 61 is more delayed than the pulsed light L31.

[0037] In Figure 2 In the delay optical path 50, two mirrors 51 and 52 are provided, but the arrangement and the number of the mirrors 51 and 52 can be adjusted according to the optical path length difference. Of course, optical elements other than mirrors can be used to create the optical path length difference. The delay time can be adjusted by adjusting the positions of the mirrors 51 and 52.

[0038] The polarization beam splitter 61 combines the pulsed light L31 and the pulsed light L32. The polarization beam splitter 61 transmits the pulsed light L31 and reflects the pulsed light L32. Therefore, the pulsed light L31 and the pulsed light L32 propagate along the same optical axis. The pulsed light L31 and the pulsed light L32 are combined with each other in a state in which the pulsed light L32 is delayed with respect to the pulsed light L31 by the optical path length difference.

[0039] For example, each of the wave plate 41 and the wave plate 53 is a half wave plate. The wave plate 41 can be a third half wave plate, and the wave plate 53 can be a fourth half wave plate. In the pre-pulse light path 40, the wave plate 41 is rotatably arranged. The rotation axis of the wave plate 41 is parallel to the optical axis of the pulsed light L31. In the delayed light path 50, the wave plate 53 is rotatably arranged. The rotation axis of the wave plate 53 is parallel to the optical axis of the pulsed light L32.

[0040] The wave plates 41 and 53 are provided to reduce the light loss at the polarization beam splitter 61. For example, the polarization beam splitter 61 transmits a P-polarization component and reflects an S-polarization component. The wave plate 41 is arranged to maximize the amount of transmitted light of the pulsed light L31 at the polarization beam splitter 61. That is, the wave plate 41 is arranged at a rotation angle such that the pulsed light L31 incident on the polarization beam splitter 61 becomes P-polarized.

[0041] The wave plate 53 is arranged to maximize the amount of reflected light of the pulsed light L32 at the polarization beam splitter 61. That is, the wave plate 53 is arranged at a rotation angle such that the pulsed light L32 incident on the polarization beam splitter 61 becomes S-polarized. For example, the reflection by the mirrors 51 and 52 can cause the rotation of the polarization direction of the pulsed light L32. Even in this case, the loss of the pulsed light L32 in the polarization beam splitter 61 can be prevented by rotating the wave plate 53. The wave plates 41 and 53 can be omitted.

[0042] As described above, the polarization beam splitter 61 combines the pulsed light L31 with the pulsed light L32. Therefore, the pre-pulse light and the delayed pulsed light propagate coaxially. Here, the pulsed light L31 and the pulsed light L32 combined by the polarization beam splitter 61 are set as a combined pulsed light L60. The combined pulsed light L60 includes the pre-pulse light and the delayed pulsed light.

[0043] The light amounts of the pulsed light L31 and the pulsed light L32 will now be described. As shown in FIG. 6, the pulsed light L31 and the pulsed light L32 are linearly polarized lights orthogonal to each other. Here, the half wave plate 31 is disposed in the light path from the laser light source 21 to the polarization beam splitter 33. Then, by rotating the half wave plate 31, the ratio of the pulsed light L31 to the pulsed light L32 can be adjusted. By rotating the half wave plate 31, the polarization direction of the laser beam L1 is changed. Figure 3

[0044] Therefore, the intensity ratio of the pre-pulse light to the delayed pulsed light can be changed according to the rotation angle of the half wave plate 31. Figure 4 FIG. 7 is a schematic view schematically showing the time waveform of the combined pulsed light L60 including the pre-pulse light P1 and the delayed pulsed light P2. In FIG. 7, the time axis is shown on the horizontal axis, and the intensity axis is shown on the vertical axis. Figure 4 In FIG. 7, three examples at the angle change of the half wave plate 31 are shown.

[0045] Figure 4 ​The upper portion shows the time waveform when the intensity of the leading pulse P1 is set higher than the intensity of the delayed pulse P2. Figure 4 The middle part shows the time waveform when the intensity of the leading pulse P1 is equal to the intensity of the delayed pulse P2. Figure 4 The lower portion shows the time waveform when the intensity of the leading pulse P1 is set lower than that of the delayed pulse P2. By changing the rotation angle of the half-wave plate 31, the intensity ratio of the leading pulse P1 and the delayed pulse P2 can be any ratio. Therefore, the time waveform of the combined pulse L60 can be adjusted. Since the attenuator does not block the laser beam, the intensity of the laser beam can be maintained.

[0046] refer to Figure 2 The embodiment will be described again. A combined pulse light L60 from the polarization beam splitter 61 enters a waveplate 62. Waveplate 62 is a second half-waveplate. Waveplate 62 is rotatably disposed in the optical path of the combined pulse light L60. The polarization direction of the combined pulse light L60 can be adjusted by rotating waveplate 62 around the optical axis of the combined pulse light L60. That is, the linear polarization direction rotates according to the rotation angle of waveplate 62.

[0047] The combined pulse light L60, which is transmitted through the waveplate 62, is reflected by the reflector 63. The combined pulse light L60 reflected by the reflector 63 is sequentially incident on the lens 64, the beam equalizer 65, the beam equalizer 66, and the lens 67.

[0048] Lens 64 converges the combined pulsed light L60. Beam equalizers 65 and 66 homogenize the spatial distribution of the combined pulsed light L60. Beam equalizer 65 is a combination of an array of lenses for splitting the beam along the X-direction and an array of lenses for splitting the beam along the Y-direction. Beam equalizer 66 is a combination of an array of lenses for transmitting the X-direction-splitting beam to the condenser lens constituting lens 67 and an array of lenses for transmitting the Y-direction-splitting beam to the condenser lens constituting lens 67. The condenser lens is mounted such that the beam becomes a flat-top beam at the aperture stage. The magnification is then changed by the objective lens. Lens 67 converges the combined pulsed light L60.

[0049] Although not shown in the figure, the optical system 20 transmits the light beam in such a manner that the light beam is repeatedly focused and collimated from the light source 11 to the homogenizer 65. The combined pulsed light L60 can be amplified so that the light beam is split before reaching the homogenizer 65. For example, the lens 64 can be a combination of a lens that amplifies the light beam and a lens that collimates the amplified light beam, specifically, a telescopic lens. The lens 67 is a condenser lens for converging the light beam, and a slit (an aperture) is arranged on the downstream side of the lens 67. An epi-illumination mirror for irradiating the substrate with the light beam can be placed downstream of the slit. An objective lens can be placed downstream of the epi-illumination mirror.

[0050] The combined pulsed light L60 is applied to the substrate 100 as Figure 1 laser light L2. The laser beam L2 forms a linear irradiation region on the substrate 100. The laser beam L2 is not limited to a line beam. For example, the laser beam L2 can have a flat spatial distribution in both the X direction and the Y direction. The spot shape of the laser beam L2 on the substrate 100 can be a square of 1 mm. Thus, the substrate 100 can be irradiated with a line beam having a uniform spatial distribution.

[0051] Referring to Figure 5 the polarization state of the laser beam L2 applied to the substrate 100 is described. Figure 5 is a schematic diagram that schematically shows the polarization state of the laser beam L2 including the preceding pulse beam Pl and the delayed pulse beam P2. Figure 5 Three examples are shown in which the wave plate 62 angle is changed.

[0052] As shown in Figure 5 by changing the angle of the wave plate 62 with respect to the substrate 100, the preceding pulse light Pl can be made into first linearly polarized light (e.g., S-polarization), and the delayed pulse light P2 can be made into second linearly polarized light (e.g., P-polarization). Alternatively, by changing the angle of the wave plate 62 with respect to the substrate 100, the preceding pulse light Pl can be made into second linearly polarized light, and the delayed pulse light P2 can be made into first linearly polarized light. That is, the polarization states of the preceding pulse light Pl and the delayed pulse light P2 can be exchanged. Furthermore, the preceding pulse light Pl and the delayed pulse light P2 can be linearly polarized light that is tilted, for example, 45 degrees with respect to the first linearly polarized light. Of course, the rotation angle of the wave plate 62 is not limited to 45 degrees.

[0053] Thus, by adjusting the rotation angle of the wave plate 62, a desired polarization state can be achieved. Therefore, according to the laser irradiation process, a pulsed laser beam in an appropriate polarization state can be applied to the substrate 100. Furthermore, according to the laser irradiation process, a pulsed laser beam having an appropriate temporal waveform can be applied to the substrate 100.

[0054] Note that the mirror 63 can be a partially transmissive mirror that transmits a part of the combined pulse light L60. For example, the mirror 63 reflects 99% of the combined pulse light L60, and transmits 1% of the combined pulse light L60. The combined pulse light L60 that is transmitted through the mirror 63 enters the light detector 70. Of course, there is no specific limitation on the transmittance and reflectance of the mirror 63. Furthermore, the mirror 63 can have 100% reflectance when detection by the light detector 70 is not performed.

[0055] The light detector 70 detects the combined pulse light L60 that is transmitted through the mirror 63. The rotation angle of the half-wave plate 31 can be adjusted in accordance with the detection result of the light detector 70. The light detector 70 detects the temporal waveform of the combined pulse light L60. In accordance with the detection result of the light detector 70, the rotation angle of the half-wave plate 31 can be changed so that the light amounts of the leading pulse light Pl and the delayed pulse light P2 become a desired ratio.

[0056] The rotation angle of the wave plate 62 when the light detector 70 detects the combined pulse light L60 is described. The optical characteristics of the mirror 63 can depend on the polarization state of incident light. For example, assume that the transmittance of the mirror 63 for S-polarization is lower than the transmittance of the mirror 63 for P-polarization. In this case, the ratio of the detected light amounts of the leading pulse light Pl and the delayed pulse light P2 detected by the light detector 70 deviates from the actual light amounts of the leading pulse light Pl and the delayed pulse light P2. For example, when the leading pulse light Pl is S-polarized and the delayed pulse light P2 is P-polarized, the light detector 70 detects the combined pulse light L60 to have a light amount ratio in which the light amount of the delayed pulse light P2 having P-polarization is high.

[0057] Therefore, in the present embodiment, the rotation angle of the wave plate 62 is adjusted so that the S-polarized component and the P-polarized component in the leading pulse light Pl become equal to each other, and the S-polarized component and the P-polarized component in the delayed pulse light P2 become equal to each other. Specifically, the optical axis of the wave plate 62 is arranged to be inclined by 22.5 degrees with respect to the linearly polarized light of the leading pulse light Pl. Therefore, when the leading pulse light Pl travels through the wave plate 62, the linearly polarized light of the leading pulse light Pl is rotated by 45 degrees.

[0058] The delayed pulse light P2 is linearly polarized light that is orthogonal to the leading pulse light Pl. Therefore, when the delayed pulse light P2 travels through the wave plate 62, the linearly polarized light of the delayed pulse light P2 is also rotated by 45 degrees. Thus, it is possible to make the polarization ratio of the leading pulse light Pl incident on the mirror 63 equal to the polarization ratio of the delayed pulse light P2. Therefore, the light detector 70 can more accurately detect the combined pulse light L60. Since the temporal waveform of the combined pulse light L60 can be accurately measured, the polarization state can be more appropriately adjusted. After the adjustment of the rotation angle of the half-wave plate 31 is completed, the rotation angle of the wave plate 62 can be adjusted.

[0059] Further, the rotation angle of the wave plate 41 or the wave plate 53 can be adjusted based on the detection result of the light detector 70. The rotation angle of the wave plate 41 is changed so that the amount of light detected by the light detector 70 becomes maximum. Then, the rotation angle of the wave plate 53 is changed so that the amount of light detected by the light detector 70 becomes maximum. Thus, the loss of the laser beam in the polarization beam splitter 61 can be reduced. After the adjustment of the rotation angles of the half wave plate 31, the wave plate 41, and the wave plate 53 is completed, the wave plate 62 can be adjusted.

[0060] Further, the wave plate 62 can be a quarter wave plate. For example, in the process in which the substrate 100 is irradiated with the laser beam of circular polarization, the quarter wave plate can be used as the wave plate 62 instead of the half wave plate.

[0061] The wave plate 41 and the wave plate 53 can be omitted. The wave plate 41 or the wave plate 53 can be a quarter wave plate, respectively.

[0062] The polarization state can be controlled according to the evaluation result of the crystal state of the polysilicon film 101b. For example, Figure 1 The detection unit 22 shown in FIG. 2 detects the crystal state of the polysilicon film 101b. The rotation angles of the half wave plate 31 and the wave plate 62 are adjusted according to the detection result of the detection unit 22. Thus, the polarization state suitable for various process conditions can be generated. For example, the polarization state can be optimized according to factors such as the output power of the laser beam, the type of the substrate 100, the thickness of the silicon film 101, the conveyance speed of the substrate 100, and the like. For example, the polarization state is controlled so that the change in the crystal state of the polysilicon becomes small. Thus, the laser beam L2 in the polarization state suitable for the annealing process can be irradiated to the substrate 100.

[0063] By using the polarization beam splitter 33 and the polarization beam splitter 61, the loss of the laser can be reduced. The combined pulse light L60 in the desired polarization state can be efficiently generated. That is, since no polarizer or the like is used, the absorption of the laser beam can be prevented, and the laser beam can be efficiently utilized.

[0064] The laser annealing method according to the present embodiment includes the steps of: (a) emitting a linearly polarized pulsed laser; (b) causing the pulsed laser to be incident on a first rotatable half-wave plate; (c) splitting the pulsed laser from the first half-wave plate into first pulsed light and second pulsed light; (d) combining the first pulsed light with the second pulsed light, the second pulsed light being delayed relative to the first pulsed light by utilizing a difference in optical path length between the first pulsed light and the second pulsed light; and (e) causing the combined pulsed laser to be incident on a first wave plate rotatably provided in an optical path of the combined pulsed laser, the combined pulsed laser being generated by combining the first pulsed light with the second pulsed light at a second polarization beam splitter. By rotating the first half-wave plate and the first wave plate, a laser beam in a proper polarization state can be generated.

[0065] The polarization state of the laser beam affects the grain size and orientation of the crystal.

[0066] In the present embodiment, the laser beam can be controlled to be in an arbitrary polarization state. Therefore, the polarization state can be controlled to improve the quality of the crystal, such as uniformity, periodicity, and directionality. By controlling the microcrystal state, adjustment can be performed under conditions in which non-uniformity hardly occurs.

[0067] Further, for the stage 10, it is preferable to use a floatation conveyance stage for conveying the substrate 100 while floating the substrate 100. Specifically, the floatation conveyance stage is more advantageous in conveying a large substrate. When annealing a large substrate, it is necessary to reduce the cost per product. When annealing a large substrate using a floatation conveyance stage, the laser beam is irradiated to the substrate 100 after being converted to a proper polarization state. Therefore, proper annealing can be performed. Further, by controlling the polarization state based on the evaluation result of the crystal state by the detection unit 22, a high-quality crystal can be produced at a high production rate.

[0068] The polarization control unit 30 can be applied to other laser irradiation apparatuses other than the laser annealing apparatus. For example, the polarization control unit 30 can be incorporated in a laser irradiation apparatus of a laser processing apparatus or a laser lift-off apparatus. The laser irradiation apparatus according to the present embodiment is not limited to the above-described examples.

[0069] For example, in a laser processing process such as drilling, it can irradiate a circularly polarized laser beam to an object. In this case, a quarter-wave plate can be used as the wave plate 62. The laser light source 21 generates an ultrashort pulse of laser light LI, and the polarization controller 30 sets the combined pulsed light L60 to be a single pulse having a desired pulse width. In a laser lift-off apparatus, an ultrashort pulse of a laser beam can be circularly polarized and used to irradiate an object.

[0070] (Organic EL Display)

[0071] The semiconductor device having the above-described polysilicon film is suitable for a thin film transistor (TFT) array substrate for an organic electroluminescence (EL) display. That is, the polysilicon film is used as a semiconductor layer having a source region, a channel region, and a drain region of a TFT.

[0072] A structure in which the semiconductor device according to the present embodiment is applied to an organic EL display is described below. Figure 6 FIG. 1 is a cross-sectional view of a pixel circuit of an organic EL display device, which is depicted in a simplified manner. Figure 6 An organic EL display device 300 shown in FIG. 3 is a display device of an active matrix type in which TFTs are provided in respective pixels PX.

[0073] The organic EL display device 300 includes a substrate 310, a TFT layer 311, an organic layer 312, a color filter layer 313, and a sealing substrate 314. Figure 6 An organic EL display device of a top emission type in which the sealing substrate 314 side is located on the viewing side is shown. Note that the following description is given in order to show an example of the structure of an organic EL display device, and the present embodiment is not limited to the structure described below. For example, the semiconductor device according to the present embodiment can be used for an organic EL display device of a bottom emission type.

[0074] The substrate 310 is a glass substrate or a metal substrate. The TFT layer 311 is provided over the substrate 310. The TFT layer 311 includes a TFT 311a provided in each pixel PX. Further, the TFT layer 311 includes a wiring line (not shown) connected to the TFT 311a, and the like. The TFT 311a, the wiring line, and the like constitute a pixel circuit.

[0075] The organic layer 312 is provided over the TFT layer 311. The organic layer 312 includes an organic EL light-emitting element 312a provided in each pixel PX. Further, in the organic layer 312, a partition wall 312b for partitioning the organic EL light-emitting element 312a is provided between the pixels PX.

[0076] The color filter layer 313 is provided over the organic layer 312. The color filter layer 313 includes a color filter portion 313a for performing color display. That is, in each pixel PX, a resin layer colored in R (red), G (green), or B (blue) is provided as the color filter portion 313a.

[0077] The sealing substrate 314 is provided over the color filter layer 313. The sealing substrate 314 is a transparent substrate such as a glass substrate, and is provided for preventing degradation of the organic EL light-emitting element of the organic layer 312.

[0078] The current flowing through the organic EL light emitting element 312a of the organic layer 312 is varied in accordance with a display signal supplied to the pixel circuit. Therefore, by supplying a display signal corresponding to a display image to each pixel PX, the amount of light emitted in each pixel PX can be controlled. As a result, a desired image can be displayed.

[0079] In an active matrix display device such as an organic EL display, one pixel PX is provided with one or more TFTs (for example, a switching TFT and a driving TFT). Also, the TFT of each pixel PX is provided with a semiconductor layer having a source region, a channel region, and a drain region. The polycrystalline silicon film according to the present embodiment is suitable for the semiconductor layer of the TFT. That is, by using the polycrystalline silicon film manufactured by the manufacturing method for the semiconductor layer of the TFT array substrate described above, the in-plane unevenness as a characteristic of the TFT can be suppressed. Therefore, a display device having excellent display characteristics can be manufactured at a high production rate.

[0080] (Method for manufacturing semiconductor device)

[0081] The method for manufacturing a semiconductor device using the ELA apparatus according to the present embodiment is suitable for manufacturing a TFT array substrate. Reference is made to Figure 7 and Figure 8 describing a method for manufacturing a semiconductor device including a TFT. Figure 7 and Figure 8 are cross-sectional views showing processes for manufacturing a semiconductor device. In the following description, a method for manufacturing a semiconductor device having an inverse stagger type (reverse stagger) TFT is described. Figure 7 and Figure 8 showing a step for forming a polycrystalline silicon film in the method for manufacturing a semiconductor device. Note that, as the manufacturing step, a publicly known method other than the formation of the polycrystalline silicon film can also be used, and the description of the publicly known method is omitted here.

[0082] As shown in Figure 7 , a gate electrode 402 is formed on a glass substrate 401. A gate insulating film 403 is formed on the gate electrode 402. An amorphous silicon film 404 is formed on the gate insulating film 403. The amorphous silicon film 404 is arranged so as to overlap with the gate electrode 402 interposed by the gate insulating film 403. For example, the gate insulating film 403 and the amorphous silicon film 404 are formed continuously by a chemical vapor deposition (CVD) method.

[0083] Then, the amorphous silicon film 404 is irradiated with a laser L2, and further a polycrystalline silicon film 405 is formed as shown in Figure 8 . That is, by Figure 1The ELA apparatus 1 and the like shown causes the amorphous silicon film 404 to be crystallized. Thus, a polysilicon film 405 having crystallized silicon is formed on the gate insulating film 403. The polysilicon film 405 corresponds to the above-described polysilicon film 101b.

[0084] Further, although in the above description, it has been described that the laser annealing apparatus according to the present embodiment irradiates an amorphous silicon film with a laser to form a polysilicon film, the laser annealing apparatus can also irradiate an amorphous silicon film with a laser to form a microcrystalline silicon film. Further, the laser used to perform annealing is not limited to an Nd:YAG laser. Further, the method according to the present embodiment can be applied to a laser annealing apparatus that crystallizes a thin film other than a silicon film. That is, as long as a laser annealing apparatus irradiates an amorphous film with a laser to form a crystallized film, the method according to the present embodiment can be applied. With the laser annealing apparatus according to the present embodiment, a substrate having a crystallized film can be appropriately inspected.

[0085] From the foregoing description, it will be apparent that embodiments of the present disclosure can be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the claims.

Claims

1. A laser irradiation apparatus comprising: a laser light source configured to emit linearly polarized pulsed laser light; a first half-wave plate rotatably provided in an optical path of the pulsed laser light; a first polarization beam splitter configured to branch the pulsed laser light from the first half-wave plate into first pulsed light and second pulsed light; a second polarization beam splitter configured to combine the first pulsed light and the second pulsed light, the second pulsed light being delayed with respect to the first pulsed light by using a difference in optical path length between the first pulsed light and the second pulsed light; a first wave plate rotatably provided in an optical path of combined pulsed light generated by combining the first pulsed light and the second pulsed light at the second polarization beam splitter; a second wave plate rotatably provided in an optical path of the first pulsed light from the first polarization beam splitter to the second polarization beam splitter; a third wave plate rotatably provided in an optical path of the second pulsed light from the first polarization beam splitter to the second polarization beam splitter; a partially transmissive mirror configured to extract a portion of the combined pulsed light that is transmitted through the first wave plate; and a photodetector configured to detect the combined pulsed light from the partially transmissive mirror, the first wave plate is a half-wave plate or a quarter-wave plate, wherein one of the second wave plate and the third wave plate is a half-wave plate, and the other of the second wave plate and the third wave plate is a quarter-wave plate or a half-wave plate, and wherein the rotation angles of the second wave plate and the third wave plate are adjustable so that a detected light amount detected by the photodetector becomes maximum, and after adjustment of the rotation angles of the second wave plate and the third wave plate is completed, the rotation angle of the first wave plate is adjustable. the combined pulsed light forms a linear irradiation region on an object along a first direction.

2. The laser irradiation apparatus according to claim 1, wherein forming an amorphous film on the object; and 3. The laser irradiation apparatus according to claim 2, wherein crystallizing the amorphous film by the combined pulsed light.

4. The laser irradiation apparatus according to claim 2 or 3, further comprising a floating conveyance stage for conveying the object while floating the object to be irradiated, thereby scanning a region of the object irradiated by the combined pulsed light.

5. The laser irradiation apparatus according to claim 2 or 3, further comprising a detection unit having an illumination light source for illuminating the object and a camera for detecting reflected light from a region of the object illuminated by the illumination light source, thereby enabling evaluation of a crystalline state of a crystallized film of the object and adjustment of the rotation angle of the first wave plate in accordance with the evaluated crystalline state.

6. A laser irradiation method comprising the steps of: (a) emitting linearly polarized pulsed laser light; (b) causing the pulsed laser light to be incident on a rotatably placed first half-wave plate; (c) branching the pulsed laser light from the first half-wave plate into first pulsed light and second pulsed light; ​ (d) combining the first pulsed light with the second pulsed light, the second pulsed light being delayed relative to the first pulsed light by using a difference in optical path length between the first pulsed light and the second pulsed light; and (e) causing the combined pulsed light to be incident on a first wave plate rotatably provided in an optical path of the combined pulsed light, the combined pulsed light being generated by combining the first pulsed light with the second pulsed light at a second polarization beam splitter, The laser irradiation method further includes the steps of: causing the first pulsed light to be incident on a second wave plate rotatably provided in an optical path of the first pulsed light from a first polarization beam splitter to the second polarization beam splitter; causing the second pulsed light to be incident on a third wave plate rotatably provided in an optical path of the second pulsed light from the first polarization beam splitter to the second polarization beam splitter; causing the combined pulsed light transmitted through the first wave plate to be incident on a partially transmitting mirror, and extracting a portion of the combined pulsed light; and detecting the combined pulsed light from the partially transmitting mirror by a light detector, wherein the first wave plate is a half wave plate or a quarter wave plate, wherein one of the second wave plate and the third wave plate is a half wave plate, and the other of the second wave plate and the third wave plate is a quarter wave plate or a half wave plate, and wherein the rotation angles of the second wave plate and the third wave plate are adjusted so that an amount of detected light detected by the light detector becomes maximum, and after the adjustment of the rotation angles of the second wave plate and the third wave plate is completed, the rotation angle of the first wave plate is adjusted.

7. The laser irradiation method according to claim 6, wherein The combined pulsed light forms a linear irradiation region on the object along a first direction.

8. The laser irradiation method according to claim 7, wherein forming an amorphous film on the object; and crystallizing the amorphous film by the combined pulsed light.

9. The laser irradiation method according to claim 7 or 8, the laser irradiation method including the steps of: illuminating the object by illumination light from an illumination light source; detecting, by a detector, reflected light from the object illuminated by the illumination light source, thereby evaluating a crystal state of the crystallized film; adjusting the rotation angle of the first wave plate in accordance with the evaluated crystal state.

10. The laser irradiation method according to claim 7 or 8, the laser irradiation method including the steps of: floating and transporting the object by a floating transport stage, thereby scanning a region of the object irradiated by the combined pulsed light.

11. A method for manufacturing a semiconductor device, the method including the steps of: (S1) forming an amorphous film on a substrate; and (S2) annealing the amorphous film to crystallize the amorphous film and further form a crystallized film, wherein the annealing step (S2) includes the steps of: (A) emitting pulsed laser light of linear polarization; (B) causing the pulsed laser light to be incident on a first half wave plate rotatably placed; (C) branching the pulsed laser light from the first half wave plate into first pulsed light and second pulsed light; (D) combining the first pulsed light with the second pulsed light by using a difference in optical path length between the first pulsed light and the second pulsed light; and (E) causing the combined pulsed light to be incident on a second half wave plate rotatably provided in an optical path of the combined pulsed light. (D) combining the first pulsed light with the second pulsed light that is delayed relative to the first pulsed light by using a difference in optical path length between the first pulsed light and the second pulsed light; and (E) causing the combined pulsed light to be incident on a first wave plate rotatably provided in an optical path of the combined pulsed light that is generated by combining the first pulsed light with the second pulsed light at a second polarizing beam splitter, The method further includes the steps of: causing the first pulsed light to be incident on a second wave plate rotatably provided in an optical path of the first pulsed light from a first polarizing beam splitter to the second polarizing beam splitter; causing the second pulsed light to be incident on a third wave plate rotatably provided in an optical path of the second pulsed light from the first polarizing beam splitter to the second polarizing beam splitter; extracting a portion of the combined pulsed light by causing the combined pulsed light transmitted through the first wave plate to be incident on a partially transmissive mirror; and detecting the combined pulsed light from the partially transmissive mirror by a light detector, wherein the first wave plate is a half wave plate or a quarter wave plate, wherein one of the second wave plate and the third wave plate is a half wave plate, and the other of the second wave plate and the third wave plate is a quarter wave plate or a half wave plate, and wherein the rotation angles of the second wave plate and the third wave plate are adjusted so that an amount of detected light detected by the light detector becomes maximum, and the rotation angle of the first wave plate is adjusted after the adjustment of the rotation angles of the second wave plate and the third wave plate is completed.

12. The method for manufacturing a semiconductor device according to claim 11, the method comprising the steps of: illuminating the substrate by illumination light from an illumination light source; detecting reflected light from the substrate illuminated by the illumination light source by a detector, thereby evaluating a crystal state of the crystallized film, adjusting the rotation angle of the first wave plate according to the evaluated crystal state.

13. The method for manufacturing a semiconductor device according to claim 12, wherein the substrate is floated and transported by a floatation transport stage, thereby scanning an area of the substrate irradiated by the combined pulsed light.

14. The method for manufacturing a semiconductor device according to any one of claims 9 to 13, wherein, the combined pulsed light forms a linear irradiation area on the substrate along a first direction. the combined pulsed light forms a linear irradiation area on the substrate along a first direction.

Images