JP2008218893A - Laser beam radiation method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To condense a laser beam, which has large light intensity and small unevenness of the light intensity, in a spot shape in a laser beam radiation device without enlarging the device size. <P>SOLUTION: Two laser beams La, Ld and the other laser beams Lb, Ld out of laser beams La-Ld, which were emitted from a multi-transverse mode semiconductor laser 223, are subjected to polarization multiplexing and propagated into the same optical path. The polarization multiplexed laser beam Lac and other laser beam Lbd are subjected to angle combining multiplexing so that the optical axes of all laser beams may cross with each other at a predetermined face Hp. Then, coherence on the predetermined face Hp of two wave front components, which propagate at symmetric positions with respect to each optical axis of Lac, Lbd, is reduced by using coherent reduction means 128A and 128B, and each laser beam La-Ld is made to condense in a spot shape on the predetermined face Hp by using a condensing optical system 230. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a laser beam irradiation method and apparatus for condensing laser beams emitted from three or more semiconductor lasers respectively emitting multi-lateral mode laser beams in a spot shape on a predetermined surface.

  Conventionally, in the field of thin film transistors (TFTs), scanning is performed while condensing laser light onto a spot-like (dot-like) region having a small area on an amorphous semiconductor film such as an amorphous silicon film, A laser annealing technique for polycrystallizing the semiconductor film is known.

  In addition, as a laser light source used for laser annealing, adoption of a semiconductor laser that is excellent in maintainability and handleability and can be miniaturized is being studied. Since laser annealing requires a high-power laser light source, the use of a multi-transverse mode semiconductor laser capable of obtaining a higher output has been studied.

  As a technique for condensing a high-power laser beam in the above-described dot-like region, that is, in a spot shape using a semiconductor laser, the laser beam is collimated so that the optical axes are parallel to each other. There is known a method of condensing each laser beam through a condensing lens. For example, a method is known in which each laser beam output from a plurality of semiconductor lasers is incident on a core portion of an end face of an optical fiber through a condensing lens and combined in this optical fiber to obtain a high-power laser beam. (See Patent Document 1). Here, as the number of semiconductor lasers, that is, the number of laser beams passing through the condenser lens is increased, the light intensity of the laser light condensed in a spot shape by the condenser lens can be increased.

Further, in the laser light irradiation as described above, it is important to make the light intensity distribution of the laser light uniform and free from unevenness (see Reference 2). Therefore, an apparatus using a conventional excimer laser uses an optical member such as a beam homogenizer that uniformizes the intensity distribution of laser light. It is effective to provide the beam homogenizer or the like in the optical path in order to uniformize the intensity distribution of laser light having a plurality of high-order transverse modes that oscillate simultaneously and have a relatively low spatial coherence like an excimer laser.
JP-A-56-88177 US Pat. No. 2,569,875

  By the way, a laser beam irradiation apparatus with a large output constituted by using a plurality of semiconductor lasers as described above is required to be miniaturized, and the aperture of a condensing lens that collects each laser beam is also limited. On the other hand, in order to make more laser light incident on the condenser lens in accordance with the increase in output of the laser light irradiation apparatus as described above, a semiconductor laser and a collimator lens that collimates the laser light emitted from the semiconductor laser Therefore, it is necessary to expand the space for arranging an optical member such as a reflection mirror for deflecting the optical path of the laser beam.

  Therefore, the maximum number of the laser beams when the collimated laser beams having the optical axes parallel to each other as described above are incident on the condenser lens is limited by the aperture of the condenser lens. For this reason, the light intensity of the laser light condensed in a spot shape may not reach the required light intensity, and there is a demand for obtaining a larger output without increasing the size of the laser light source. .

  In addition, multi-lateral mode laser light emitted from a multi-transverse mode semiconductor laser has a smaller number of higher-order transverse modes that oscillate simultaneously and higher spatial coherence than laser light emitted from an excimer laser. For this reason, when the laser light emitted from the multi-lateral mode semiconductor laser is condensed on a predetermined surface, unevenness of the light intensity may occur in the condensed spot. That is, in a multi-transverse mode semiconductor laser, high-order transverse mode light of the same order has two wavefront components propagating in a substantially symmetric direction with respect to the optical axis, and the light intensity is increased by interference between these two wavefront components. It is thought that unevenness occurs. This unevenness in light intensity cannot be reduced even if a beam homogenizer or the like used in the excimer laser is applied.

  The above problem is not limited to the laser light source used for laser annealing, and is generally a problem that occurs when laser beams output from three or more multi-transverse mode semiconductor lasers are condensed in a spot shape.

  The present invention has been made in view of the above circumstances, and can condense laser light having a larger light intensity and reduced light intensity unevenness in a spot shape without increasing the apparatus size. An object of the present invention is to provide a laser light irradiation method and apparatus.

  The laser light irradiation apparatus of the present invention includes three or more semiconductor lasers each emitting multi-lateral mode laser light, a collimating lens for collimating each laser light emitted from the semiconductor laser, and each collimated laser light. A laser beam irradiation apparatus including a condensing optical system that collects light in a spot shape on a predetermined surface, and propagates through different optical paths arranged in the optical path from the collimating lens to the condensing optical system. Polarization multiplexing means for combining and propagating at least two of the laser beams to the same optical path, and the laser beam combined with the polarization and other laser beams, and the optical axes of all the laser beams on the predetermined plane Interference on a predetermined plane of two wavefront components propagating at positions symmetrical with respect to the optical axis of the laser beam disposed in the optical path, and angle multiplexing means for angularly multiplexing so as to cross each other Is characterized in that a coherence reducing means for reducing the.

  The laser beam illuminating device is a state in which the polarization-combined laser beam and other laser beams are arranged in a state in which the optical axes of all the laser beams are made parallel to each other, and the interval between the optical axes of the laser beams is a semiconductor. An optical path displacing means for displacing the optical path of the laser beam so as to be incident on the condensing optical system in a state of being made smaller than the interval between the optical axes of each laser beam when emitted from the laser; can do.

  It is desirable that the angle multiplexing of the polarization combined laser beam and the other laser beam is performed in the slow axis direction.

  The optical path displacing means exchanges the optical axis of the polarization-combined laser light that has been polarization-combined by the polarization-combining means and all the optical axes of the other laser lights that propagate in the optical path different from the polarization-combined laser light. A laser that constitutes the polarization-combined laser beam corresponding to the optical axes of the polarization-combined laser beam and the optical axes of the other laser beams in a state of being parallel to each other and the optical axes of the other laser beams. In the state where the optical axis of each laser beam when the light is emitted from the semiconductor laser and the interval with respect to the optical axis when the other laser beam is emitted from the semiconductor laser are made smaller than each other, It is possible to displace at least one optical path of the polarization-combined laser beam and the other laser beam so that both the laser beam and the laser beam are incident on the condensing optical system.

  The coherence reducing means reduces, for one or more of the laser beams, the coherence on a predetermined plane of two wavefront components propagating at positions symmetrical to the optical axis of the laser beam. can do.

  The laser light illumination device can include four semiconductor lasers, and the polarization multiplexing unit can combine two laser beams out of the four laser beams emitted from the respective semiconductor lasers, and the other two laser beams. Laser light can also be polarized and multiplexed, and the optical path displacement means can displace at least one of the two polarized and multiplexed laser lights.

  The coherence reducing means may be disposed in the vicinity of a far field image formation position in laser light emitted from a semiconductor laser. The coherence reducing means separates the wavefront component of the laser light into two wavefront components that propagate symmetrically with respect to the optical axis of the laser light at the position where the far-field image is formed. Interference can be reduced.

  The coherence reducing means may be a ½ wavelength phase difference element, and the ½ wavelength phase difference element is one of two wavefront components propagating in a symmetric position with respect to the optical axis of the laser beam. Any one of the phases may be changed.

  The semiconductor laser may be hermetically sealed.

  It is desirable that the collimating lens and the condensing optical system constitute an imaging optical system that forms a near-field image of each laser beam emitted from a semiconductor laser on a predetermined surface.

  The laser light irradiation device has a predetermined surface as a region on an amorphous semiconductor film, and the amorphous semiconductor film is irradiated with the laser light according to a difference in crystal state in the amorphous semiconductor film. Assuming that the absorption rate of energy absorbed from the laser beam fluctuates, when the laser beam is scanned onto the amorphous semiconductor film, the energy of the laser beam absorbed by the amorphous semiconductor film is converted to an amorphous semiconductor. Absorption energy adjusting means for adjusting the light intensity or the scanning speed of the laser beam may be provided so as to be constant regardless of the location on the film.

  The absorption energy adjusting means may be a means for changing the irradiation light intensity by wavelength multiplexing or the like for multiplexing using the difference in wavelength of laser light. Further, the absorption energy adjusting means may be a spatial modulation element having a complex amplitude distribution of an inverse Fourier transform profile arranged in the optical path of the laser light, or a wavelength multiplexing means for multiplexing the wavelengths of the laser light. You can also.

  In the laser beam irradiation method of the present invention, each laser beam emitted from three or more semiconductor lasers respectively emitting multi-lateral mode laser beams and collimated by a collimating lens is spotted onto a predetermined surface by a condensing optical system. A laser beam irradiation method for condensing, wherein at least two laser beams propagating in mutually different optical paths from a collimating lens to a condensing optical system are polarized and combined to be propagated to the same optical path, and the polarization combining is performed. In the optical path from the collimating lens to the condensing optical system, the waved laser beam and other laser beams are angle-multiplexed so that the optical axes of all the laser beams intersect each other on the predetermined plane. The coherence on the predetermined plane of two wavefront components propagating in a symmetric position with respect to the optical axis of the laser beam is reduced.

  The laser light combined with the polarized light and the other laser light are emitted from the semiconductor laser with the optical axes of all the laser lights parallel to each other, and the interval between the optical axes of the laser lights is emitted from the semiconductor laser. The optical path of the laser beam can be displaced so that the laser beam is incident on the condensing optical system in a state of being smaller than the interval between the optical axes of each laser beam.

  The predetermined surface is a region on the amorphous semiconductor film, and the amorphous semiconductor film is irradiated from the laser light when irradiated with the laser light according to a difference in crystal state in the amorphous semiconductor film. It is assumed that the absorption rate of the energy to be absorbed fluctuates, and the laser beam energy absorbed by the amorphous semiconductor film when the laser beam is scanned onto the amorphous semiconductor film is a place on the amorphous semiconductor film. However, the light intensity or scanning speed of the laser light may be adjusted so as to be constant regardless of the case.

  The laser beam that reduces the coherence of the two wavefront components on the predetermined plane can be one or more of the laser beams emitted from the respective semiconductor lasers.

  In addition, “the state in which the interval between both optical axes of the laser beam combined with polarization and the other laser beam is made smaller than the interval between the optical axes of each laser beam when emitted from the semiconductor laser” More than the minimum interval between the optical axis of each laser beam emitted from each semiconductor laser corresponding to the laser beam combined with the polarization and the optical axis of the laser beam emitted from the semiconductor laser corresponding to the other laser beam This means a state in which the distance between the optical axes of the polarization-multiplexed laser beam and the other laser beam is made smaller.

  Note that the angle multiplexing so as to intersect with each other on the predetermined surface means that a plurality of laser beams propagating through different optical paths are transmitted to the predetermined surface so that the optical axes of the laser beams intersect with each other on the predetermined surface. This means that the light is incident on the top.

  Further, the angle multiplexing in the slow axis direction means that the optical axes of the laser beams incident on the predetermined surface are located on the same plane so as to intersect each other on the predetermined surface, and the predetermined surface This means that the laser beams intersect at a predetermined plane so that the slow axes of the laser beams incident on the plane are positioned on the plane.

  According to the laser light irradiation method and apparatus of the present invention, at least two laser beams propagating in mutually different optical paths from the collimating lens to the condensing optical system are polarized and multiplexed and propagated to the same optical path. The waved laser beam and other laser beams are angle-multiplexed so that the optical axes of all the laser beams intersect with each other on the predetermined plane, and are symmetric with respect to the optical axis of the laser beam in the optical path. Since the coherence on the predetermined plane of the two wavefront components propagating the position is reduced, the laser beam has a higher light intensity and reduced light intensity unevenness without increasing the size of the apparatus. Can be condensed in a spot shape.

  That is, by the polarization multiplexing means, the optical paths of two laser beams passing through different optical paths are made to coincide with each other, and the incident area to the condensing optical system of three or more laser lights is smaller than the conventional area. It can be. This allows laser light emitted from a larger number of semiconductor lasers to pass through the condensing optical system without increasing the size of the apparatus, so that laser light having a greater light intensity can be spot-shaped on a predetermined surface. It can be focused on the area.

  In addition, the laser beam combined with polarization and other laser beams are emitted from the semiconductor laser with the optical axes of all the laser beams parallel to each other, and the interval between the optical axes of the laser beams is emitted from the semiconductor laser. If there is provided an optical path displacing means for displacing the optical path of the laser beam so as to be incident on the condensing optical system in a state of being smaller than the interval between the optical axes of each laser beam when Since the optical path of the laser beam combined with the polarization can be made closer to the optical path of the other laser light, the incident area of the three or more laser beams into the condensing optical system can be further reduced. . Thereby, similarly to the above, laser light having a larger light intensity can be condensed on a spot-like region on the predetermined surface.

  Further, four semiconductor lasers are provided, and the polarization multiplexing unit is configured to respectively combine two laser beams of the four laser beams emitted from the semiconductor lasers and the other two laser beams, respectively. If the optical path displacing means is configured to displace at least one of the optical paths of the polarization-combined laser light, the laser light having a greater light intensity is more reliably transferred to the spot-like region on the predetermined surface. It can be condensed.

  Further, by reducing the coherence on the predetermined surface of the two wavefront components of the laser light, it is possible to reduce the unevenness of the light intensity in the spot-like region on the predetermined surface irradiated with the laser light, The spot-like region can be irradiated with a more uniform light intensity.

  Further, if the coherence reducing means is arranged at the position where the far-field image is formed in the laser light emitted from the semiconductor laser, the unevenness of the light intensity in the spot-like region can be further reliably reduced. it can.

  Here, the coherence reducing means is a half-wavelength phase difference element, and the half-wavelength phase difference element is one of two wavefront components propagating at positions symmetrical with respect to the optical axis of the laser beam. If it arrange | positions so that the phase of this may be changed, the nonuniformity of the light intensity in the said spot-like area | region can be reduced more reliably.

  Further, if the semiconductor laser is hermetically sealed, it is possible to suppress deterioration of the semiconductor laser, prevent damage due to a handling error of the semiconductor laser itself during assembly, and further improve the life of the semiconductor laser. Can be extended.

The predetermined surface is a region on the amorphous semiconductor film, and the amorphous semiconductor film is irradiated with laser light according to the difference in crystal state in the amorphous semiconductor film. When the laser beam is scanned onto the amorphous semiconductor film, the energy of the laser beam absorbed by the amorphous semiconductor film depends on the location on the amorphous semiconductor film. If the light intensity or scanning speed of the laser light is adjusted so as to be constant, the region on the amorphous semiconductor film can be changed even if there is a difference in the crystalline state in the amorphous semiconductor film. Annealing treatment can be performed uniformly Here, the absorption energy adjusting means is a spatial modulation element having a complex amplitude distribution of an inverse Fourier transform profile arranged in the optical path of the laser beam, or wavelength multiplexing for combining wavelengths As a means, amorphous half Uniform annealing treatment of the area on the conductor film can be performed more reliably.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 17 are diagrams relating to a laser annealing apparatus to which a laser beam irradiation apparatus and a multi-beam scanning optical system according to an embodiment of the present invention are applied, and laser annealing performed using this apparatus. FIG. 18 is a cross-sectional view showing a laser beam irradiation apparatus of the present invention, and FIGS. 19A and 19B are diagrams for explaining a configuration for reducing the coherence of multi-lateral mode light.

  The laser annealing apparatus shown in FIGS. 1 to 17 and the laser annealing performed using this apparatus will be described later.

  A laser beam irradiation apparatus 221 shown in FIG. 18 includes four multi transverse mode semiconductor lasers 223A to 223D (hereinafter simply referred to as semiconductor lasers 223A to 223D, or collectively, semiconductor lasers 223) that respectively emit multi transverse mode laser beams. And collimating lenses 124A to 124D (collectively referred to as collimating lenses 124) for collimating the laser beams emitted from the semiconductor lasers 223A to 223D, and the collimated laser beams to the predetermined surface Hp in a spot shape ( And a condensing lens 230 that is a condensing optical system for condensing light at one point having an area.

  In the laser light irradiation device 221, the four semiconductor lasers 223A to 223D are arranged in a line in the Y direction (up and down direction in FIG. 18). Further, laser beams La, Lb, Lc, and Ld (hereinafter collectively referred to as laser light LL) are emitted from the semiconductor lasers 223A, 223B, 223C, and 223D, respectively. The semiconductor laser 223 may be hermetically sealed.

  Further, the imaging optical system composed of the collimating lens 124 and the condenser lens 230 forms the near-field images of the laser beams La, Lb, Lc, and Ld on the predetermined surface Hp, thereby forming the spot shape. Regions are formed. That is, the imaging optical system forms a near-field image indicating the light intensity distribution of the laser beam LL on the exit surface of the laser beam LL of the semiconductor laser 223 on the predetermined plane Hp. Note that the imaging optical system composed of the collimator lens 124 and the condenser lens 230 does not necessarily form a near-field image of the laser light on the predetermined surface Hp. The light may be condensed in a spot shape.

  Further, the laser beam irradiation device 221 polarization-combines two laser beams La and Lc, which are disposed in the optical path from the collimating lens 124 to the condenser lens 230 and propagate in different optical paths, to the same optical path. Polarization combining means for polarizing and combining two laser beams Lb and Ld propagating in different optical paths and propagating them to the same optical path, and the polarization combined laser beam and another laser Angle combining means for combining light so that the optical axes of the two laser beams intersect each other on a predetermined plane, laser light Lac obtained by polarization combining the laser beams La and Lc, and other laser beams Lb, The laser beam Lbd obtained by polarization combining Ld is in a state where the optical axes of both laser beams are parallel to each other, and the interval between the optical axes is emitted from the semiconductor laser 223. Spacing between optical axes An optical path displacing means for displacing the optical paths of both laser beams, which will be described later, so as to be incident on the condensing lens 230 in a state of being made smaller, and the optical path from the collimating lens 124 to the condensing lens 230. In addition, the coherence on the predetermined plane Hp of the two wavefront components propagating symmetrically with respect to the optical axis of the laser light Lac is reduced, and the symmetrical position with respect to the optical axis of the other laser light Lbd is set. Coherence reducing means to be described later for reducing the coherence of the two wavefront components propagating on a predetermined plane.

  The four semiconductor lasers 223, the four collimating lenses 124, the polarization multiplexing unit, the optical path displacement unit, the coherence reduction unit, and the like constitute the semiconductor laser light source unit 221G.

  In other words, the laser beam irradiation device 221 is composed of the semiconductor laser light source unit 221G and the condenser lens 230 here.

  The condensing lens 230 also serves as angle multiplexing means.

  The polarization multiplexing means is a combination of PBS 126A and PBS 126B that are polarization beam splitters and a ½ wavelength plate 127 that is a ½ wavelength phase difference element. Each of the PBS 126A and PBS 126B is a cube-shaped polarization beam splitter formed by bonding two right-angle prisms. The coherence reducing means is disposed in the vicinity of the far-field image forming position indicating the light intensity distribution of the laser light LL at a distance away from the emission surface of the laser light LL in the semiconductor laser 223.

  The exit surface of the PBS 126A from which the laser beams La and Lb incident on the PBS 126A are emitted and the entrance surface of the PBS 126B on which the laser beams La and Lb emitted from the exit surface of the PBS 126A are incident or joined are arranged. . A half-wave plate 127 for rotating the polarization directions of the laser beams Lc and Ld by 90 ° is attached on the incident surface of the PBS 126B on which the laser beams Lc and Ld are incident.

  When the PBS 126A reflects, for example, the P wave component and reflects the S wave component, the laser light La and Lb incident on the PBS 126A has the S wave component transmitted through the PBS 126A and the P wave component reflected within the PBS 126A. Then, the light enters the PBS 126B. The laser beams La and Lb incident on the PBS 126A are in the direction of polarized light with many P wave components.

  In contrast to PBS 126A, PBS 126B reflects the S wave component and transmits the P wave component, and the P wave component reflected by PBS 126A passes through PBS 126B as it is.

  Each of the laser beams Lc and Ld is rotated by 90 ° by the half-wave plate 127 and then made incident on the PBS 126B, so that the direction of polarized light having a large S wave component is obtained. In the reflecting PBS 126B, the P wave component with a small amount of light passes through the PBS 126B, and the S wave with a large amount of light is reflected.

  Since the semiconductor laser has a relatively small optical output, and the optical power density necessary for high-speed scanning annealing cannot be obtained by itself, the semiconductor laser light source unit 221G includes a plurality of (here, four) semiconductor lasers 223. It is configured. Further, a laser head 120 of the laser annealing apparatus 100 described later has a configuration including a plurality (here, eight) of semiconductor laser light source units 221G.

  When the laser beams emitted from the individual semiconductor lasers 223 are combined only by the angle combination, the depth of focus becomes shallow, and the light intensity variation due to the defocus may increase. In the multi-lateral mode semiconductor laser, the radiation angle in the fast axis direction is 40 ° to 60 °, and the radiation angle in the slow axis direction is 15 ° to 25 °. In the present embodiment, the laser beams La to Ld emitted from the plurality of semiconductor lasers 223 are polarized and multiplexed in the fast axis direction, and are angularly multiplexed in the slow axis direction perpendicular to the fast axis direction. The light intensity variation due to defocusing is suppressed, and the necessary optical power density is obtained. In addition, it is desirable that the slow axis direction in which the angle is combined is a direction in which the optical path of the laser beam is displaced by the optical path displacing means.

  At the exit from which the laser beam is emitted from the semiconductor laser light source unit 221G, there is a wavefront component of the laser beam of the higher order transverse mode of each order emitted from the semiconductor laser 223 in the multi transverse mode, with respect to the optical axis. In order to reduce the coherence of the two wavefront components propagating in the substantially symmetric direction, a ½ wavelength phase difference element 128 described later is provided. The ½ wavelength phase difference element 128 rotates the polarization direction of one of the two wavefront components by 90 °. Therefore, the ½ wavelength phase difference element 128 passes only the light beam on one side of the two light beams facing each other with a straight line passing through the optical axis of the laser light and orthogonal to the optical axis in between. Is arranged.

  Here, the optical path displacing means includes reflection mirrors 125A to 125D (hereinafter collectively referred to as reflection mirror 125), a half-wave plate 127, PBS 126A, and PBS 126B.

  The optical path displacing means converts the laser beams La and Lc out of the laser beams La, Lb, Lc, and Ld, which are emitted from the semiconductor lasers 223 and reflected by the reflection mirror 125 to narrow the distance between the optical axes, into the polarized light. A laser beam Lac that is polarized and combined through the combining unit, and a laser beam Lbd that is combined with the laser beams Lb and Ld through the polarization combining unit are obtained. Each laser beam when the laser beam Lac and the laser beam Lbd are emitted from the semiconductor lasers 223A to 223D in a state where the optical axes of the two laser beams are parallel to each other and the interval between the two optical axes is emitted. One or both of the optical paths of the laser beams (the optical path of the laser beam Lac and the optical path of the laser beam Lbd) so as to be incident on the condenser lens 230 in a state of being smaller than the interval between the optical axes of the light La to Ld. Is displaced.

  Here, when the laser beams Lac and Lbd are emitted from the semiconductor lasers 223A to 223D in a state where the optical axes of the laser beams are parallel to each other, and the interval between the optical axes is emitted from the semiconductor lasers 223A to 223D, respectively. Making it enter into the condensing light lens 230 in the state made smaller than the space | interval between the optical axes of the laser beams L1-L4 means the following aspects.

  That is, when the laser beams La and Lc constituting the laser beam Lac are emitted from the semiconductor lasers 223A and 223C, the optical axes Ja and Jc are the optical axes, and the laser beams Lb and Ld constituting the laser beam Lbd are the semiconductor laser 223B. 223D are the optical axes Jb and Jd, and the optical axes of the laser beams Lac and Lbd are the optical axes Jac and Lbd, respectively. At this time, the distance between the optical axis Jac and the optical axis Lbd is smaller than the minimum distance between one optical axis among the optical axes Ja and Jc and one optical axis among the optical axes Jb and Jd. Means that the optical path displacing means displaces the optical paths of both laser beams Lac and Lbd and makes the optical axes Jac and Lbd of both laser beams Lac and Lbd parallel to each other.

  Here, the minimum distance between one of the optical axes Ja and Jc and one of the optical axes Jb and Jd when emitted from the semiconductor lasers 223A to 223D is the optical axis. Since the intervals of Ja and the optical axis Jb, the optical axis Jc and the optical axis Jb, and the optical axis Jc and the optical axis Jd are equal to each other with the value Vp, the value of the minimum interval is the value Vp. On the other hand, when the value of the interval between the optical axis Jac and the optical axis Lbd is a value Vq, the optical path displacing means has an interval Vq between the optical axes Jac and Lbd in a state where the optical axes Jac and Lbd are parallel to each other. Is made smaller than the minimum interval Vp, that is, the optical paths of both laser beams Lac and Lbd are displaced so as to satisfy the condition of the interval Vq <interval Vp.

  Further, the coherence reducing means propagates two positions which are arranged in the optical path from the collimating lens 124 to the condenser lens 230 and which are symmetrical with respect to the optical axis of the combined laser beam Lac. A 1/2 wavelength phase difference element 128A (for example, a 1/2 wavelength plate) which is an interference reduction means for reducing the interference of the wavefront component on the predetermined plane Hp, and the optical axis of the combined laser beam Lbd A half-wave phase difference element 128B (for example, a half-wave plate) that is a coherence reducing unit that reduces coherence of the two wavefront components propagating in symmetrical positions on the predetermined plane Hp. Is.

  As shown in FIG. 19, a multi-lateral mode semiconductor laser LD such as the semiconductor laser 223 oscillates a plurality of higher-order transverse modes having different orders simultaneously. As shown in FIG. 19A, the near-field image NFP (m) of high-order transverse mode light of any one order m has an intensity distribution having a plurality of peaks according to the order, and between adjacent peaks. It is an image in which the phase of is reversed. As schematically shown in FIG. 19B, the optical waveguide R of the semiconductor laser LD has two wall surfaces E1 and E2 parallel to the optical axis A. Since one order of higher-order transverse mode light is emitted after being repeatedly reflected between these two wall surfaces E1 and E2, the higher-order transverse mode light of one order is roughly about the optical axis A. A plurality of two wavefront components W1 and W2 propagating in a symmetric direction are superimposed.

  The two wavefront components W1 and W2 are roughly the same. When the wavefront component W1 is reflected by the wall surface E1, the wavefront component W2 is reflected by the wall surface E2, and when the wavefront component W1 is reflected by the wall surface E2, the wavefront component W2 is reflected by the wall surface E1. It is in the relationship reflected by. It is considered that the near-field image NFP (m) having the intensity distribution and the phase distribution is formed by the interference between the two wavefront components W1 and W2.

  Actually, since a plurality of higher-order transverse modes having different orders are simultaneously oscillated, the actual near-field image NFP is a superposition of the near-field images NFP (m) of a plurality of higher-order transverse modes having different orders. .

  If attention is paid to an arbitrary high-order transverse mode light of the order m, the two wavefront components W1 and W2 propagate in a substantially symmetric direction with respect to the optical axis A, and are substantially symmetrical with respect to the optical axis A. The far-field image FFP (m) having the characteristic intensity distributions P1 and P2 is formed.

  Even if the order of the high-order transverse mode light is different, a plurality of the two wavefront components W1 and W2 propagating in a substantially symmetrical direction with respect to the optical axis A are overlapped. However, the peak separation angle θ of the bimodal light intensity distributions P1 and P2 is determined by the stripe width and refractive index distribution of the optical waveguide R of the semiconductor laser, the oscillation wavelength, the order of the high-order transverse mode, etc. As the result, the peak separation angle θ tends to increase.

  In this figure, the far-field image FFP (m) of the high-order transverse mode light having the largest peak separation angle θ of the bimodal light intensity distributions P1 and P2 is indicated by a solid line, and the high-order transverse mode light of other orders is shown. The far field image FFP (m) is indicated by a broken line.

  Although the coherence between high-order transverse mode lights of different orders is small, the coherence between the two wavefront components W1 and W2 constituting the same-order high-order transverse mode light is large. Therefore, in the present embodiment, a half-wavelength phase difference element 128 that rotates the polarization direction of one of the two wavefront components W1 and W2 by 90 ° is provided, and these two wavefront components W1 and W2 are The intensity distribution of the emitted light from the semiconductor laser LD is made uniform.

  In the laser beam irradiation apparatus 221 configured as described above, the laser beams La, Lb, Lc, and Ld emitted from the respective semiconductor lasers 223 are passed through the collimator lens 124 and the reflection mirror 125, and further, ½ wavelength Two laser beams Lac and Lbd having optical axes parallel to each other that have been subjected to polarization multiplexing and optical path displacement are obtained through the plate 127, PBS 126A, 126B, and the like. The laser beam irradiator 221 causes the collimated laser beams Lac and Lbd whose optical axes are parallel to each other to enter the condensing lens 230, and the two laser beams Lac, The Lbd optical axes Jac and Jbd intersect each other on a predetermined surface Hp so that the light beams of the laser beams are condensed, and the two laser beams Lac and Lbd are spot-like regions on the predetermined surface Hp. To collect light.

  In the above embodiment, the case where the four laser beams La, Lb, Lc, and Ld emitted from the four semiconductor lasers 223 are focused on one spot-like point has been described. Absent.

  In the laser beam irradiation method and apparatus of the present invention, for example, each of the three laser beams emitted from each of the three semiconductor lasers is focused on one spot-like point or emitted from each of five or more semiconductor lasers. Five or more laser beams may be condensed at one spot-like point.

  For example, when the three laser beams emitted from the three semiconductor lasers are collected at one spot-like point, the light is emitted from the first and second semiconductor lasers and collimated by the polarization multiplexing means. The first and second laser beams are combined by polarization to match the optical axes to be combined into a single laser beam, and the collimated first laser beam and the third semiconductor laser are collimated by the optical path displacement means. The optical axes of the third laser beam and the third laser beam are made parallel to each other, and the first to third laser beams are made incident on the condenser lens with the optical axes closer to each other than when emitted from the semiconductor laser. Thus, the same effect as described above can be obtained.

  Here, making the optical axes closer to each other than when emitted from the semiconductor laser means that the optical axis of the third laser light emitted from the third semiconductor laser is emitted from the first semiconductor laser. Of the distance between the optical axis of the first laser light and the distance between the optical axis of the third laser light and the optical axis of the second laser light emitted from the second semiconductor laser. This means that the interval between the optical axis of the laser beam and the optical axis of the third laser beam combined by the polarization multiplexing is made smaller than the smaller interval.

  That is, for example, in the laser beam irradiation apparatus shown in FIG. 18, the three laser beams La, Lb, and Lc are emitted onto the predetermined surface Hc using only the three semiconductor lasers 223A, 223B, and 223C except the semiconductor laser 223D. Even if the light is condensed in a spot shape, the same effect as described above can be obtained.

  Next, a multi-beam scanning optical system 200, which is a laser light irradiation apparatus according to another aspect of the present invention, which is configured by applying a plurality of the laser light irradiation apparatuses 221 will be described.

  FIG. 20 is a conceptual diagram showing a schematic configuration of a multi-beam scanning optical system employing the laser beam irradiation apparatus of the present invention, and FIG. 21 is a view of the multi-beam scanning optical system viewed from the direction in which the laser beams are aligned (X direction in the figure). FIG. 22 is a conceptual diagram showing the appearance of the multi-beam scanning optical system as seen from the propagation direction of laser light (Z direction in the figure).

  In addition, the same referential mark is attached | subjected to the component equivalent to the component of the said laser beam irradiation apparatus 221, and the detailed description is abbreviate | omitted.

  Here, the multi-beam scanning optical system 200 includes eight combined semiconductor laser light sources equivalent to the semiconductor laser light source unit 221G constituting the laser light irradiation device 221, and each combined semiconductor laser light source 210 a, b, ... The laser light emitted from is condensed in a spot shape in each of eight regions arranged in one direction on the predetermined surface Hp (arrow X direction in the figure) by one condensing lens.

  20, 21, and 22, a multi-beam scanning optical system 200 includes a plurality of combined semiconductor laser light sources 210 a, 210 b,... (Hereinafter collectively referred to as combined semiconductor laser light sources arranged on the same plane Ha. 210), a near-field image of each laser beam La, Lb... Emitted from each of the combined semiconductor laser light sources 210a, 210b,. One condenser lens 230 that forms an image on a predetermined surface Hp, which is an area on the crystalline semiconductor film 249, and each of the collimated laser beams La, Lb,... Prisms 240a, 240b,..., Which are polarization optical elements that polarize the laser beams La, Lb,... So as to pass through and enter the condenser lens 230 (collectively referred to as prisms 240). It is equipped with a door.

  The amorphous semiconductor film 249 absorbs the laser light L when irradiated with the laser light L according to the difference in crystal state (difference in crystal state depending on the location) in the amorphous semiconductor film 249. The energy absorption rate fluctuates.

  When the multi-beam scanning optical system 200 scans the laser light L onto the predetermined surface Hp, which is a region on the amorphous semiconductor film 249, the energy of the laser light L absorbed by the amorphous semiconductor film 249 is increased. A spatial modulation element 245 described later, which is an absorption energy adjusting means for adjusting the light intensity or scanning speed of the laser light L so as to be constant regardless of the location on the amorphous semiconductor film 249, and a dynamic deflection means described later. A scanning speed control unit 255 is provided for controlling the above. The spatial modulation element 245 adjusts the light intensity of the laser light L, and the speed control unit 255 adjusts the scanning speed of the laser light L.

  As the dynamic deflection means, eight spot-shaped image forming points Pa, Pb, which are condensing points of the eight laser beams La, Lb,... On the predetermined surface Hp (hereinafter collectively). A galvanometer 250 that scans the imaging point P) can be employed, and the scanning speed control unit 255 controls the scanning speed of the galvanometer 250.

  The spatial modulation element 245 is a spatial modulation element having a complex amplitude distribution of an inverse Fourier transform profile arranged in the optical path of the laser light L. As the absorption energy adjusting means, a wavelength multiplexing element 246 that multiplexes the wavelengths of the laser light L may be employed.

  Here, the laser beam La emitted from the combined semiconductor laser light source 210a is composed of two collimated laser beams having mutually parallel optical axes and passing through different optical paths. Each of the laser beams Lb, Lc,... Emitted from the other combined semiconductor laser light sources 210b, 210c,... Is composed of two collimated laser beams having mutually parallel optical axes and passing through different optical paths. It is. Also, the laser beams La, Lb,... Emitted from the combined semiconductor laser light sources 210a, 210b,... Are adjusted so that their optical axes are parallel to each other.

  A diffractive optical element or the like can be employed instead of the deflecting light element.

  Further, the prism 240 which is the deflecting light element can be constituted by an individual member or can be integrated in an array.

  Further, each of the prisms 240a, 240b,... Of each laser light La, Lb,... So that each laser light La, Lb,. Deflection of the optical path. By passing each laser beam L through the rear focal point fb of the condenser lens 230, each laser beam L can be accurately imaged in each region on the predetermined plane Hp. However, even if each laser beam La, Lb,... Does not necessarily pass through the rear focal point fb, if each laser beam L passes through the entrance pupil Ir of the condenser lens 230, each laser beam L substantially Can be imaged on the predetermined plane Hp.

  The condensing lens 230 is an image-side telecentric imaging optical system, but the condensing lens 230 is not necessarily limited to an image-side telecentric imaging optical system.

  In the multi-beam scanning optical system 200, the respective laser beams La, Lb,..., The respective image formation points Pa, Pb (hereinafter collectively referred to as image formation points P) are also on the predetermined plane Hp. Each of the collimated laser beams La, Lb,... Is dynamically deflected so that the imaging points Pa, Pb,... Move in a direction intersecting with the direction in which they are arranged (the direction indicated by the arrow X in the figure). A galvanometer 250 which is a dynamic deflection means is provided. Note that a polygon mirror may be employed as the dynamic deflection unit.

  It should be noted that the imaging points Pa, Pb,... Of the laser beams La, Lb,... Imaged on the predetermined surface Hp are scanned with respect to the direction (arrow Z direction in the figure) scanned on the predetermined surface Hp. It is desirable that the direction orthogonal to each other (the direction of the arrow X in the figure) and the direction of the slow axis of each laser beam La, Lb,.

  The galvanometer 250 includes a galvanometer mirror 251 that reflects the laser beam L, a rotary shaft 252 that rotatably supports the galvanometer mirror 251, and a rotary shaft 252 that rotates the galvanometer mirror 251. And a drive motor 253.

  The position of the galvanometer 250 is determined so that the rotation axis 252J of the rotation shaft 252 passes through the rear focal point fb and the reflection surface Mh of the galvanometer mirror 251 that reflects each laser beam L.

  The multi-beam scanning optical system 200 includes a cooling unit 282 for cooling the plurality of multiplexed semiconductor laser light sources 210a, 210b,. The eight multiplexed semiconductor laser light sources 210 a, 210 b,... Are mounted on the cooling unit 282.

  The cooling unit 282 has a cooling surface 282m parallel to the plane Ha on the side of the combined semiconductor laser light source 210. The cooling surface 282m is brought into contact with the surface to be cooled 282r that is parallel to the plane Ha and is on the cooling unit 282 side of the combined semiconductor laser light source 210, so that the combined semiconductor laser light source 210a, 210b,... Are cooled. That is, each combined semiconductor laser light source 210 is cooled by the cooling unit 282.

  Next, the operation of the multi-beam scanning optical system 200 will be described.

  The combined semiconductor laser light sources 210a, 210b,... Are driven to emit each laser light L from each combined semiconductor laser light source 210 with a predetermined output, and the cooling unit 282 cools each combined semiconductor laser light source 210. To start.

  The combined semiconductor laser light source 210 generates heat with the output of the laser light L, but the temperature of the combined semiconductor laser light source 210 is maintained at a predetermined constant temperature by the cooling of the cooling unit 282.

  The parallel laser beams L collimated and emitted from the combined semiconductor laser light source 210 are incident on the prism 240. Each prism 240 deflects each of the incident laser beams L so that the laser beams L pass through the entrance pupil Ir and the rear focal point fb in the condenser lens 230.

  Each laser light L propagating toward the entrance pupil Ir and the rear focal point fb passes through the entrance pupil Ir and the rear focal point fb, and is reflected by the reflecting surface Mh of the galvano mirror 251 and enters the condenser lens 230. To do.

  Each laser beam L incident on the condenser lens 230 is condensed by the condenser lens 230 and imaged on the predetermined surface Hp.

  The image forming points Pa, Pb... Of each laser beam L imaged on the predetermined surface Hp correspond to the image forming points Pa, Pb... According to the reciprocating rotation of the galvano mirror 251. It is moved in the direction intersecting the direction aligned on the surface Hp, that is, on the amorphous semiconductor film 249 (the arrow Z direction in the figure).

  Here, the light intensity of the laser light irradiated onto the amorphous semiconductor film 249 is adjusted statically by the spatial modulation element 245 and dynamically adjusted by the speed controller 255. Thereby, the laser beam L can be irradiated onto the amorphous semiconductor film so as to cancel the fluctuation of the absorption rate of the energy of the laser beam according to the difference in crystal state in the amorphous semiconductor film 249. The energy of the laser beam L absorbed by the amorphous semiconductor film can be made constant in any region on the amorphous semiconductor film.

  In addition, the laser beam irradiation apparatus of this invention is not necessarily provided with the said coherence reduction means, The effect similar to the above can be acquired, without providing the said coherence reduction means.

  Hereinafter, a laser annealing apparatus to which the multi-beam scanning optical system can be applied and laser annealing performed using this apparatus will be described with reference to FIGS.

  Note that the same reference numerals are given to the same components as those of the laser beam irradiation apparatus 221 or the multi-beam scanning optical system 200, and detailed description thereof will be omitted.

  Here, a substrate stage 110 on which a semiconductor film to be annealed to be described later, which constitutes the laser annealing apparatus, a laser head 120 that emits laser light, and scanning that scans the laser light emitted from the laser head 120 are scanned. Of the optical system 140, the multi-beam scanning optical system 200 can be applied to the components composed of the laser head 120 and the scanning optical system 140.

"Laser annealing method"
Conventionally, it has been known that amorphous silicon (a-Si) and polycrystalline silicon (poly-Si) have different energy absorption characteristics with respect to the wavelength of laser light. Conventionally, however, granular crystalline silicon and lateral crystalline silicon are both polycrystalline silicon (poly-Si), and it has not been considered that there is a difference in energy absorption characteristics with respect to these laser beams.

  The present inventor evaluated the absorption characteristics of granular crystalline silicon and lateral crystalline silicon with respect to the wavelength of the laser beam, and found that there is a difference between these absorption characteristics. And it discovered that the irradiation conditions of the laser beam which a granular crystal part and an amorphous part melt | dissolve, and a lateral crystal part does not melt | dissolve exist. By performing laser annealing under such laser light irradiation conditions, the present inventors do not remelt the lateral crystal once generated, and select only the granular crystal part and the amorphous part without changing the crystallinity. It has been found that these materials can be melted and laterally crystallized to form lateral crystals of substantially the entire surface. Hereinafter, the evaluation performed by the present inventor will be described.

  Laser annealing was performed by using a GaN-based semiconductor laser (oscillation wavelength: 405 nm) and continuously irradiating an amorphous silicon (a-Si) film with an elongated rectangular laser beam L while relatively scanning. The substrate plane is the xy plane, the main relative scanning direction of the laser light is the x direction, and the sub relative scanning direction is the y direction.

  As shown in FIG. 1A, when the x-direction relative scanning of the laser beam L is performed once at a certain y position, a laterally grown lateral crystal extending in the main relative scanning direction x of the laser beam L is generated. A granular crystal having small crystal grains (granular poly-Si) is generated outside the crystal generation region. After the relative scanning of the laser beam L only once, granular crystals are generated on both sides of the lateral crystal growth region extending in a band shape.

  Here, a case where a granular crystal is generated at an end portion in a region directly irradiated with the laser beam L is illustrated. Depending on the laser annealing conditions, an end portion in the region directly irradiated with the laser beam L and / or a region where the laser beam L is not directly irradiated but heat is conducted (= immediately outside the region directly irradiated with the laser beam L). In this region, granular crystals are generated.

  In this specification, when a lateral crystal is grown by performing relative scanning of laser light, a region annealed when the relative scanning in the x direction of laser light L is performed once at a certain y position is referred to as “1. "Annealing region of the first laser annealing".

  In order to process the entire surface of the film, as shown in FIG. 1B, the y position is changed and the relative scanning in the x direction of the laser light L is repeatedly performed. When the x-direction relative scanning of the laser beam L is performed while changing the y position, at least a part of the granular crystal generated outside the lateral crystal before the change of the y position and the non-crystallized non-crystallized portion remain. Laser annealing is performed on a region including at least part of the crystal. At this time, the laser beam L may be irradiated so as to overlap the previously generated lateral crystal.

  As shown in the figure, when the x-direction relative scanning of the laser beam L is performed by changing the y position (when the annealing region is changed), the region to which the laser beam L is first irradiated on the semiconductor film to be annealed. It is preferable to carry out laser annealing so that the region to which the laser beam L is next irradiated partially overlaps.

  In FIG. 1A, reference numeral 20 is assigned to the semiconductor film to be annealed, reference numeral 110 is assigned to the substrate stage, and reference numeral 120 is assigned to the laser head. FIG. 1A is a diagram in the middle of performing the x-direction relative scanning of the laser light L once at a certain y position. Here, in order to facilitate visual recognition, the size of the laser head is shown larger than the film.

  FIG. 1B is an image plan view of crystallization when the x-direction relative scanning of the laser beam L is repeatedly performed while changing the y position. In the figure, a region not particularly hatched among regions irradiated with the laser beam L is a lateral crystal generation region.

For each of the lateral crystal portion (lateral poly-Si), the granular crystal portion (granular poly-Si), and the amorphous portion (a-Si), the wavelength of the measurement light is changed, and the complex refractive index n + ik (k is k) It is an extinction coefficient, and ik represents an imaginary part.). FIG. 2 shows the relationship between the wavelength and the refractive index n in each crystal state. Moreover, the relationship between the wavelength in each crystal state and the absorption coefficient α was determined based on the following formula. The results are shown in FIG. In any crystal state, it has been clarified that the absorption coefficient tends to greatly decrease around 400 nm.
Absorption coefficient α = k / 4πλ
(In the formula, k is an extinction coefficient and λ is a wavelength.)

  Next, the absorption rate of the silicon film at each wavelength was determined for lateral crystalline silicon, granular crystalline silicon, and amorphous silicon.

The energy emitted from the laser head is attenuated by the loss generated during transmission through various optical systems incorporated in the laser annealing apparatus and the loss due to Fresnel reflection on the film surface, and is absorbed by the film. The light energy absorbed by the film is expressed by the following formula.
(Light energy absorbed by the film) = (Light energy irradiated on the film) × (Ratio of the amount of light incident on the film without surface reflection) × (Ratio of the amount of light absorbed by the film)

  In the above formula, (ratio of the amount of light incident on the film without surface reflection) × (ratio of the amount of light absorbed by the film) is the absorption rate. The absorptance is the ratio of the amount of light absorbed by the film to the amount of laser light applied to the film, and is expressed as absorptance = a × b.

In the above formula, a is the ratio of the amount of light absorbed by the film, and is obtained from the following formula. The film thickness t was set to 50 nm, which is common when crystallization is performed by laser annealing to form a polysilicon TFT.
a = exp ^−αt
(Where α is the absorption coefficient and t is the film thickness)

In the above formula, b is the ratio of the amount of light incident on the film without being reflected from the surface, and is obtained from the following formula. b is an amount obtained by subtracting the loss on the film surface due to Fresnel reflection from the amount of laser light emitted from the laser head.
b = 1-((1-n) / (1 + n)) ²
(In the formula, n is a refractive index.)

  Further, at each wavelength, the ratio of the absorption ratio of granular crystalline silicon to the absorption ratio of amorphous silicon (= absorption ratio of granular poly-Si / a-Si absorption ratio), and the ratio of lateral crystalline silicon to the absorption ratio of amorphous silicon. Absorptivity ratio (= absorption rate of lateral poly-Si / absorption rate of a-Si) was determined. These absorptance ratios are the relative absorptance of granular crystalline silicon and the lateral absorptive silicon when the absorptivity of amorphous silicon is 1. The results are shown in FIG.

  Both granular crystalline silicon and lateral crystalline silicon are polycrystalline silicon (poly-Si), but FIG. 4 shows that the absorption characteristics of these laser beams differ greatly with respect to the wavelength of the laser beams.

  As shown in FIGS. 2 to 4, granular crystalline silicon (granular poly-Si) having a small particle size exhibits intermediate characteristics between amorphous silicon (a-Si) and lateral crystalline silicon (lateral poly-Si). It became clear to show. In this way, no example has been found in the past in which absorption characteristics are evaluated by dividing lateral crystalline silicon and granular crystalline silicon.

  As shown in FIG. 4, in the wavelength region of less than 350 nm, there is no significant difference in absorption characteristics between granular crystalline silicon and lateral crystalline silicon, both of which are about 0.7 to 0.9 times the absorption rate of amorphous silicon. It became clear that the high absorption rate was shown. On the other hand, in the wavelength region of 350 nm or more, both the granular crystalline silicon and the lateral crystalline silicon tend to decrease in the absorption ratio with respect to the amorphous silicon as the wavelength becomes longer. It has been clarified that the level of decrease in the absorptance ratio with respect to amorphous silicon is larger and that the decrease occurs on the shorter wavelength side. In the wavelength range of 350 to 650 nm, the difference between the absorption ratio of granular crystalline silicon to amorphous silicon and the absorption ratio of lateral crystalline silicon to amorphous silicon is large.

  FIG. 4 shows a relative absorptance ratio based on the absorptivity of amorphous silicon (a-Si). As shown in FIG. 3, the absolute absorptance is 500 nm. In the above wavelength range, all the absorptances of lateral crystalline silicon, granular crystalline silicon, and amorphous silicon are remarkably reduced. Therefore, the wavelength of the laser beam to be used can be determined within a range where the difference between the absorption rate of the lateral crystalline silicon and the absorption rate of the granular crystalline silicon is large and the absorption rate of the granular crystalline silicon and the amorphous silicon is somewhat high. preferable.

  That is, under the condition of film thickness t = 50 nm, by using a laser beam in the wavelength region of 350 to 500 nm, preferably 350 to 450 nm, the granular crystal part and the amorphous part can be melted and laterally crystallized. In addition, laser annealing that does not melt the lateral crystal portion that has already been generated can be performed.

  The excimer laser beam that is currently used for laser annealing is an ultraviolet laser beam with a wavelength of 300 nm or less. Therefore, the lateral crystal part, the granular crystal part, and the amorphous part all have high absorptance, and there is a large difference in absorption characteristics. Absent.

  Further, the visible laser light used in Patent Documents 1 to 5 mentioned in the section “Background Art” is a laser light having a wavelength region of 500 to 550 nm such as the second harmonic of a solid-state laser. In such a wavelength region, it seems that there is a large difference in the absorption characteristics between the lateral crystal part and the granular crystal part in FIG. 4, but as shown in FIG. There is no significant difference in absorption characteristics between the lateral crystal part and the granular crystal part.

  That is, conventionally, a laser beam having a wavelength region of 300 nm or less, or a wavelength region of 500 to 550 nm, which does not have a large difference in absorption characteristics between the lateral crystal portion and the granular crystal portion, has been used. And since both the lateral crystal part and the granular crystal part are polycrystalline silicon, it was thought that there was no big difference in absorption characteristics. The inventor has clarified for the first time that there exists a wavelength region in which a large difference appears in the absorption characteristics between the lateral crystal portion and the granular crystal portion.

Japanese Patent Application Laid-Open No. 2004-64066 discloses a laser annealing apparatus using a GaN-based semiconductor laser (wavelength: 350 to 450 nm). Examples of irradiation conditions include a scanning speed of 3000 mm / s and an optical power density of 600 mJ / cm ² on the surface of the amorphous silicon film (paragraph 0127). However, this document does not discuss the relationship between the crystalline state and the absorption rate.

  The melting point of single crystal silicon (c-Si) is about 1400 ° C., and the melting point of amorphous silicon (a-Si) is about 1200 ° C. Therefore, in order to melt the granular crystal part and the amorphous part, it is preferable that the surface temperature of the laser light in the granular crystal part and the amorphous part is about 1400 ° C. or higher.

  The inventor uses a GaN-based semiconductor laser (oscillation wavelength of 405 nm) and changes the amount of light emitted from the laser head on an amorphous silicon film under the condition that the relative scanning speed of the laser light is 0.01 m / s or more. Laser annealing was performed, and SEM and TEM were used to observe whether or not a lateral crystal actually grew in the central portion of the laser beam, and the surface temperature of the laser beam necessary for the lateral crystal growth was determined. there were. Moreover, it has been found from actual experiments that when the surface temperature of the laser beam reaches about 2200 ° C. or higher, partial peeling of the film may occur due to ablation. That is, in order to laterally crystallize the granular crystal part and the non-crystal part, it is preferable that the surface temperature of the laser beam in these parts is about 1700 to 2200 ° C. The surface temperature of the laser beam is an instantaneous film surface temperature when the laser beam is irradiated.

  The temperature reached by the surface is the amount of light incident on the silicon film (this amount of light is caused by the loss of the amount of light generated while passing through various optical systems incorporated in the laser annealing apparatus from the amount of light emitted from the laser head, and by Fresnel reflection on the film surface). It is calculated theoretically from the absorption rate of the silicon film.

The irradiation energy required to bring the surface temperature of the laser light to a desired temperature is conceptually expressed by the following equation. Since each energy changes with time and temperature, it cannot be simply expressed, but is shown here conceptually. In the formula, the melting energy E2 is energy required at the melting point.
(Irradiation energy E1) = (Melting energy E2) + (Energy E3 required for raising to a desired temperature) + (Heat dissipation energy E4)

  For reference, an example of calculation in an adiabatic model when a rectangular parallelepiped of 1 μm × 1 μm × 50 nm is heated is shown. Here, the calculation is performed under the condition that the desired temperature is 1400 ° C.

The melting energy E2 necessary for melting Si contained in a volume of 1 μm × 1 μm × 50 nm is calculated as follows.
E2 = (unit melting energy) × (number of moles of Si contained in a volume of 1 μm × 1 μm × 50 nm) = 46 × 10 ³ × ((2.32 g / cm ³ ) × (10 ⁻⁶ × 10 ⁻⁶ × 50 × 10 ^-9 m ³ ) / 28) = 1.9 × 10 ^-10 J

The energy E3 required to raise Si contained in a volume of 1 μm × 1 μm × 50 nm to a desired temperature (1400 ° C. = melting point in this calculation example) is calculated as follows.
E3 = (specific heat) × (mass of Si contained in a volume of 1 μm × 1 μm × 50 nm) × (desired temperature) = 770 J / kg K × (2.32 g / cm ³ × (10 ⁻⁶ × 10 ⁻⁶ × 50 × 10 ^-9 m ³ )) × 1400 ℃ ＝ 1.3 × 10 ^-10 J

  FIG. 5 shows the relationship between the energy ratio to the absorbed light energy at which the laser beam surface temperature reaches 2200 ° C. and the laser beam surface temperature. Amorphous silicon melts at about 1200 ° C. or higher, but in this figure, a region having a surface temperature of about 1400 ° C. or lower at which the lateral and granular crystals do not melt is illustrated as “non-melted”. Further, a region where the laser beam reaches a surface temperature of about 1700 to 2200 ° C. where the lateral crystal grows and a region where the laser beam reaches a surface temperature of about 2200 ° C. or more where partial film peeling occurs due to ablation are shown.

  Even when the semiconductor film 20 to be annealed is irradiated with light having a uniform light energy distribution, the amount of light energy absorbed varies depending on the crystal state, so that the surface temperature of the laser light in each crystal state changes. FIG. 5 shows that lateral crystal growth is possible under the condition that the energy ratio to the absorbed light energy at which the surface temperature of the laser light reaches 2200 ° C. is 0.82 or more, and granularity is obtained under the condition where the energy ratio is 0.70 or less. It has been shown that the crystals do not melt.

  In order to melt the granular crystal part and the non-crystalline part and laterally crystallize them, and not to melt the already produced lateral crystal part, the surface temperature of the laser beam for the granular crystal part and the non-crystalline part is low. Absorbed light energy that is about 1700 to 2200 ° C. is applied, and for the lateral crystal portion, absorbed light energy that causes the surface temperature of the laser light to be about 1400 ° C. or lower may be applied.

  When laser light is irradiated to the lateral crystal part, the granular crystal part, and the amorphous part under the same irradiation conditions, the ratio of the absorption ratio of the granular crystal silicon to the absorption ratio of the amorphous silicon (= particulate poly-Si) Absorption rate / absorption rate of a-Si) is 0.82 or more, and the ratio of absorption rate of lateral crystalline silicon to that of amorphous silicon (= absorption rate of lateral poly-Si / absorption rate of a-Si) is By selecting a wavelength that is 0.70 or less, the energy ratio absorbed by the lateral crystal part, the granular crystal part, and the amorphous part is 0.70 or less: 0.82 to 1.0: 1.0 can do.

That is, when the semiconductor film 20 to be annealed is an amorphous silicon film, the absorption rate of laser light in the lateral crystal part, the granular crystal part, and the amorphous part satisfies the relationship of the following formulas (1) and (2). It is preferable to perform laser annealing under conditions.
0.82 ≦ absorptivity of granular crystal part / absorptivity of amorphous part ≦ 1.0 (1),
Absorption rate of the lateral crystal portion / absorption rate of the non-crystalline portion ≦ 0.70 (2)

In order to stably perform laser annealing in which the granular crystal portion and the non-crystalline portion are laterally crystallized and the lateral crystal is not melted, laser annealing is performed under conditions satisfying the following expressions (1A) and (2). More preferred.
0.85 ≦ absorptivity of granular crystal part / absorptivity of amorphous part ≦ 1.0 (1A),
Absorption rate of the lateral crystal portion / absorption rate of the non-crystalline portion ≦ 0.70 (2)

  FIG. 4 shows lines with an absorptance ratio = 0.7 and an absorptance ratio = 0.82. The ratio of the absorption ratio of granular crystalline silicon to the absorption ratio of amorphous silicon (= absorption ratio of granular poly-Si / absorption ratio of a-Si) is 0.82 or more. The wavelength at which the absorptance ratio (= lateral poly-Si absorptivity / a-Si absorptivity) is 0.70 or less is a wavelength of 360 to 450 nm under the condition that the thickness t of the silicon film is 50 nm.

  The absorption rate of the laser light varies depending on the film thickness t of the silicon film. When the film thickness t (nm) is 50, 100, 200, the ratio of the absorption ratio of the lateral crystalline silicon to the absorption ratio of the laser light and the amorphous silicon (= absorption ratio of lateral poly-Si / a-Si) (Absorption rate). The results are shown in FIG.

  In FIG. 6, the wavelength at which the ratio of the absorption ratio of lateral crystalline silicon to the absorption ratio of amorphous silicon (= absorption ratio of lateral poly-Si / absorption ratio of a-Si) is 0.7 or less varies depending on the film thickness. It has been shown. Similarly, the wavelength at which the ratio of the absorption ratio of granular crystalline silicon to the absorption ratio of amorphous silicon (= absorption ratio of granular poly-Si / absorption ratio of a-Si) is 0.82 or more also varies depending on the film thickness (illustration (Omitted).

  When a polysilicon TFT is formed by crystallization by laser annealing, when the film thickness is t (nm)> 120, it is difficult to form a TFT element and the leakage current increases. When the film thickness is t (nm) <40, The active layer becomes too thin and the reliability of the device is lowered. Therefore, for TFTs, 40 ≦ film thickness t (nm) ≦ 120 nm (formula (4)) is preferable. In the case of forming a polysilicon TFT by performing crystallization by laser annealing, the film thickness t of the amorphous silicon film is most commonly about 50 nm.

  FIG. 7 shows the wavelength of the laser beam at which the surface temperature of the granular crystal portion and the non-crystalline portion is about 1700 to 2200 ° C. and the surface temperature of the lateral crystal portion is about 1400 ° C. or less with respect to the film thickness t. Indicates the range.

The wavelength at which the ratio of the absorption ratio of lateral crystalline silicon to the absorption ratio of amorphous silicon (= absorption ratio of lateral poly-Si / absorption ratio of a-Si) is 0.7 or less varies depending on the film thickness, but the film thickness t ( nm) and the laser light wavelength λ (nm) satisfy the following formula (3).
0.8t + 320 ≦ λ ≦ 0.8t + 400 (3)

  If 40 ≦ film thickness t (nm) ≦ 120, the laser beam in the wavelength region of 350 to 500 nm, preferably 350 to 490 nm is used to melt the granular crystal portion and the non-crystalline portion and laterally crystallize. It is possible to perform laser annealing that does not melt the lateral crystal portion that has already been produced.

  It has been described that in order to laterally crystallize the granular crystal part and the non-crystal part, it is necessary that the surface temperature of the laser beam in these parts be about 1700 to 2200 ° C. When the present inventor performed laser annealing while changing the conditions within the range of the surface temperature, the granular crystal had a laser beam with the granular crystals serving as nuclei at a relatively low surface temperature condition even within the above range. The lateral crystal tends to grow in a non-parallel direction with respect to the main relative scanning direction (for example, an angle direction of 5 to 45 ° with respect to the main relative scanning direction of the laser beam) and is aligned with the main relative scanning direction simultaneously. Since a lateral crystal is about to grow, a curved lateral crystal may be formed. In order to suppress variations in device characteristics of TFTs, it is preferable that the lateral crystal directions are substantially aligned over substantially the entire surface of the film.

  The present inventor performs laser annealing under the condition that the surface temperature of the laser beam in the granular crystal part and the non-crystalline part is about 2000 ± 200 ° C., so that the granular crystal is instantaneously melted and the granular crystal is nucleated. It has been found that lateral crystal growth is suppressed and the lateral crystal direction can be aligned over almost the entire surface of the film. The present inventor has found that by performing laser annealing under such conditions, the angle between the main relative scanning direction of the laser light and the lateral crystal growth direction can be made equal to or less than 5 ° over substantially the entire surface of the film.

FIG. 8 shows an absorption power density range in which the surface temperature at the amorphous portion is about 2000 ± 200 ° C. with respect to the relative scanning speed of the laser beam. As shown in this figure, the laser beam absorption power density P (MW / cm ² ) and the laser beam relative scanning speed v (m / s) in the non-crystalline portion satisfy the following formula (5). It is preferable to perform laser annealing.
0.44v ^0.34143 ≦ P ≦ 0.56v ^0.34143 (5)

Conventionally, in research in the field of SOI, it has been reported that the crystal growth rate of Si of 1 cm / s or less is expressed by the following formula.
V = V0 × exp (−Ea / kT)
(Where V is the solid phase growth rate (cm / s) from a-Si to Poly-Si, k is the Boltzmann constant, T is the annealing temperature (K), V0 is a coefficient, V0 = 2.3-3.1 × 10 ⁸ cm / s Ea is the activation energy (= equal to the vacancy formation energy in c-Si), Ea = 2.68-2.71 eV .)

  The present inventor has confirmed that the lateral crystal growth rate in the laser annealing is also expressed by the above relational expression. As described above, since the upper limit of the annealing temperature in the non-crystalline portion is about 2200 ° C., the upper limit of the lateral crystal growth rate is 8 m / s.

When irradiating a laser beam under the same irradiation condition to a lateral crystal part, a granular crystal part, and an amorphous part,
Select a wavelength at which the absorptivity ratio of granular crystalline silicon to absorptivity of amorphous silicon is 0.82 or more, and the absorptivity ratio of lateral crystalline silicon to absorptivity of amorphous silicon is 0.70 or less,
When the laser annealing is performed so that the surface temperature of the granular crystal part and the non-crystalline part is about 1700 to 2200 ° C., and the surface temperature of the lateral crystal part is about 1400 ° C. or less,
FIG. 9 shows an image diagram of the absorptivity distribution, the irradiation light intensity distribution of the laser light on the film surface, the absorption energy distribution of the laser light, and the temperature distribution in the non-crystalline part, the granular crystal part, and the lateral crystal part.

  In this figure, the temperature distribution of the film is shown instead of the surface temperature of the laser beam. This figure also shows the surface of the semiconductor film to be annealed during laser annealing, the laser beam position on the surface and the relative scanning direction of the laser beam.

  The irradiation intensity distribution of the laser light on the film surface is uniform in the non-crystalline part, granular crystal part, and lateral crystal part, but the absorption energy of each part is different, so the absorption energy of the laser light in each part is different. ing. The granular crystal part and the non-crystal part are at a melting temperature, but the lateral crystal part once generated is suppressed to a temperature at which it does not re-melt even when irradiated with laser light.

  As shown in FIG. 1A, when the x-direction relative scanning of the laser beam L is performed only once at a certain y position, granular crystals are generated on both sides of a lateral crystal growth region extending in a band shape. The In the conventional method, when the x-direction relative scanning of the laser beam L is performed for the second time by shifting the y position, granular crystals are formed on both sides of the lateral crystal growth region extending in a band shape, as in the first time. Is generated.

  However, in the above method, even if the lateral crystal portion is irradiated with the laser beam, the lateral crystal portion is not remelted, and the temperature of the portion is less than the formation temperature of the granular crystal, as shown in FIG. When the x-direction relative scanning of the laser beam L is performed for the second time by shifting the y position, granular crystals are generated only on one side of the lateral crystal growth region extending in a band shape and only on the amorphous silicon side. become. That is, in the above method, the granular crystal generated on one side is laterally crystallized out of the granular crystals generated on both sides across the region of the lateral crystal growth extending in the first band by the second laser annealing. Moreover, unnecessary granular crystals are not newly generated by the second laser annealing on the side where the laser annealing has been performed first. By repeating the same operation while changing the y position, it is possible to crystallize almost the entire surface without a joint.

  As described above, in the above method, a substantially entire lateral crystal film can be obtained. A “lateral crystal film” is a polycrystalline film composed of band-like crystal grains extending in the lateral direction (= the relative scanning direction when laser light is relatively scanned). It can be regarded as a substantially single crystal film (pseudo single crystal film). The present inventor has realized a substantially entire lateral crystal film made of crystal grains having a length in the relative scanning direction of the laser beam of about 5 μm or more and a width of 0.2 to 2 μm (see Example 1 described later). SEM / TEM surface photograph (see FIG. 14)).

  The above evaluation is an evaluation when the semiconductor film 20 to be annealed is a silicon film. However, regardless of the constituent material of the semiconductor film 20 to be annealed, the crystalline crystal part and the amorphous part melt and the lateral crystal part does not melt. By performing laser annealing under light irradiation conditions, the once generated lateral crystal is not remelted, and the crystalline and granular portions can be laterally crystallized without changing its crystallinity. It is possible to form a full lateral crystal.

That is, in the laser annealing method, a region of an annealed semiconductor film made of an amorphous semiconductor is subjected to laser annealing to irradiate a laser beam under conditions where a lateral crystal grows, thereby growing a lateral crystal.
Further, the annealing region is shifted, and laser annealing is performed again on the region including at least a part of the granular crystal generated outside the lateral crystal and at least a part of the non-crystallized remaining uncrystallized. In the laser annealing method in which the operation of lateral crystallization of the portion is performed one or more times,
Laser annealing is performed under the condition that the granular crystal portion and the amorphous portion of the semiconductor film to be annealed are melted and the lateral crystal portion of the semiconductor film to be annealed is not melted.

  The constituent material of the semiconductor film to be annealed is not particularly limited, and examples thereof include silicon, germanium, and silicon / germanium.

  In the laser annealing method, as shown in FIG. 1B, the region irradiated with laser light first and the region irradiated with laser light partially overlap the semiconductor film to be annealed. Thus, it is preferable to perform laser annealing.

  There is no particular limitation on how the laser light irradiation regions are partially overlapped. If the region irradiated with the laser beam later covers 100% of the granular crystal portion formed by the previous laser beam irradiation, the granular crystal portion is all laterally crystallized, and the lateral crystal formed by the previous irradiation The next lateral crystal region can be formed without a granular crystal region between the crystal regions.

  Depending on the application of the semiconductor film to be annealed, a granular crystal region may remain between the lateral crystal regions. Even in such a case, if the overlap between the region to which the laser light is irradiated later and the granular crystal region is 1% or more, the granular crystal region is partially laterally crystallized, so that the lateral crystal region can be widened. It is preferable that the lateral crystal region becomes wider as the rate of overlap between the region irradiated with the laser beam later and the granular crystal region increases. The overlapping ratio between the region to be irradiated with the laser beam later and the granular crystal region is preferably 50% or more.

  Depending on the laser annealing conditions, the edge within the region directly irradiated with the laser beam and / or the region that is not directly irradiated with the laser beam but conducts heat (= the region immediately outside the region directly irradiated with the laser beam). In addition, granular crystals are produced.

  In the first relative scan in the x direction, granular crystals are generated in the region where the laser beam is not directly irradiated but heat is conducted (= the region immediately outside the region directly irradiated with the laser beam), and the y position is changed. When the laser beam is directly irradiated to the granular crystal in the next relative scanning in the x direction, the region irradiated with the laser beam first and the region irradiated with the laser beam partially overlap each other. Even if not, the granular crystal can be laterally crystallized. However, considering the positional deviation between the generation region of the granular crystal and the irradiation position of the laser beam, when laser annealing is performed again with the annealing region shifted with respect to the semiconductor film to be annealed, the laser beam is first emitted. Laser annealing is preferably performed so that the irradiated region and the region irradiated with the laser beam partially overlap each other.

  In the laser annealing method, it is preferable to use a continuous wave laser beam as the laser beam. In the case of pulse laser light, time during which the laser light is not irradiated periodically even while the laser head is turned on. When continuous wave laser light is used, the laser light is continuously irradiated onto the semiconductor film to be annealed while the laser head is turned on. Large lateral crystals can be grown, which is preferable. In consideration of a wavelength range suitable for use in performing the laser annealing, it is preferable to use a semiconductor laser beam as the laser beam.

  Although the case where the laser light is relatively scanned with respect to the semiconductor film to be annealed has been described, the above method can be applied to the case where laser annealing is performed under the condition that the lateral crystal grows without performing the relative scanning with the laser light. .

  For example, by irradiating a laser beam in a rectangular shape to a certain region first, and repeatedly irradiating the laser beam multiple times while reducing the irradiation width in one direction without changing the irradiation center line, First, the temperature is cooled from the outside of the region irradiated with the laser beam, and a temperature gradient is generated between the irradiation center line and the outside, so that a lateral crystal extending outward from the irradiation center line can be grown. At this time, the generation of the granular crystal outside the lateral crystal generation region is the same as in the case where the lateral crystal is grown by relative scanning. In this case, the region that is annealed by irradiating the same region with the laser beam a plurality of times under the above conditions becomes the annealing region for one laser annealing. However, this method is inefficient because it is necessary to irradiate a laser beam a plurality of times by changing the irradiation area using a photomask or the like to one annealing region. It is also difficult to treat almost the entire surface uniformly.

  Therefore, in the laser annealing method, it is preferable to perform laser annealing by relatively scanning the laser light while partially irradiating the semiconductor film to be annealed with the laser light. In such a configuration, since the crystal grows in the relative scanning direction of the laser beam, the lateral crystal can be continuously grown, and the entire film surface can be processed efficiently. In addition, since the entire film surface can be processed continuously and densely, a substantially whole surface lateral crystal film excellent in uniformity can be obtained.

  By using the laser annealing method, a semiconductor film having high crystallinity and uniformity and suitable as an active layer of a thin film transistor (TFT) can be manufactured at low cost. By using this semiconductor film, a semiconductor device such as a TFT having excellent element characteristics (carrier mobility, etc.) and element uniformity can be manufactured.

  In this laser annealing method, a lateral crystal film having almost no granular crystal portion and almost no joint can be manufactured on almost the entire surface. Therefore, based on design information of a formation position of a semiconductor device such as a TFT, the beam end portion of the laser beam It is not necessary to devise devices such as scanning the laser beam so that the element formation region of the semiconductor device such as TFT does not overlap or selectively irradiating only the element formation region of the semiconductor device such as TFT. A semiconductor device such as a TFT having excellent characteristics (carrier mobility and the like) and element uniformity can be stably manufactured at low cost. An electro-optical device provided with such a semiconductor device such as a TFT has excellent performance such as display quality.

"Laser annealing equipment"
With reference to the drawings, the configuration of the laser annealing apparatus of the embodiment according to the laser annealing method will be described. FIG. 10 is a diagram showing the overall configuration of the laser annealing apparatus, and FIG. 11 is a diagram showing the internal configuration of one combined semiconductor laser light source 121.

  The laser annealing apparatus 100 of this embodiment includes a substrate stage 110 on which a semiconductor film 20 to be annealed such as an amorphous silicon film is placed, a laser head 120 that emits laser light L, and an emitted laser light L from the laser head 120. And a scanning optical system 140 for scanning.

  In the present embodiment, the laser light L emitted from the laser head 120 is scanned in the x direction (main relative scanning direction) by the scanning optical system 140. Further, the substrate stage 110 is movable in the y direction in the figure by a stage moving means (not shown), so that the laser light L is relatively scanned in the y direction (sub-relative scanning direction) in the figure. Yes. In this embodiment, the substrate stage 110 and the scanning optical system 140 constitute a relative scanning unit that relatively scans the laser light L with respect to the semiconductor film 20 to be annealed.

  The laser head 120 is schematically configured by a plurality of combined semiconductor laser light sources 121 arranged on the water-cooled heat sink 131 without any gap.

  Here, as described above, the multi-beam scanning optical system 200 can be applied to the components including the laser head 120 and the scanning optical system 140. As shown in FIG. 11, each multi-wavelength semiconductor laser light source 121 includes one multi-transverse mode semiconductor laser LD (broad area semiconductor laser, not shown) having a continuous wave output as a laser light oscillation source. The four LD packages 123 (123A to 123D) that are tightly sealed and the same number of collimating lenses 124 (124A) as the LD packages 123 that collimate the laser beams L1 to L4 emitted from the four LD packages 123, respectively. ˜124D) is incorporated.

  Each of the combined semiconductor laser light sources 121 further includes the same number of reflecting mirrors 125 (125A to 125D) as the LD package 123 that reflects the laser beams L1 to L4, and the laser beams L1 and L2 reflected by the reflecting mirrors 125A and 125B. Is provided, and a polarizing beam splitter 126B on which the laser beams L3 and L4 reflected by the reflecting mirrors 125C and 125D enter is provided.

  Each of the polarization beam splitters (hereinafter referred to as PBS) 126A and 126B is a cube-shaped PBS in which two right-angle prisms are bonded, and the polarization direction of the laser beams L3 and L4 is set on the light incident surface of the PBS 126B. A half-wave phase difference element 127 that is shifted by 90 ° is attached.

  For example, when the PBS 126A reflects a P-wave component, the laser beams L1 and L2 incident on the PBS 126A pass through the PBS 126A and enter the photodiodes 129A and 129B for detecting the optical output, respectively. Is reflected in the PBS 126A and enters the PBS 126B. Since the ratio of the P wave component and the S wave component can be changed by adjusting the direction of polarization of the laser beams L1 and L2, in this case, by adjusting the direction in which the P wave component increases, more Light can be used effectively.

  By making the PBS 126B have the property of reflecting (or transmitting) the component opposite to that of the PBS 126A, that is, in this case, reflecting the S wave, the P wave reflected by the PBS 126A is left as it is. Can be transmitted. On the other hand, the laser beams L3 and L4 are each shifted in polarization direction by 90 ° by the ½ wavelength phase difference element 127 and then made incident on the PBS 126B. In the PBS 126B that reflects the wave, a P-wave component with a small amount of light for light output detection passes through the PBS 126B and enters the photodiodes 129C and 129D, and an S-wave with a large amount of light is reflected.

  Therefore, in the combined semiconductor laser light source 121, the laser light L1 and the laser light L3, and the laser light L2 and the laser light L4 having different polarization components are polarized and combined in the fast axis direction in the PBS 126B, and further combined. The combined laser beams L1 and L3 and the polarized laser beams L2 and L4 are angularly combined in the slow axis direction.

  Since the laser output of the semiconductor laser LD is relatively small, and the optical power density necessary for high-speed scanning annealing cannot be obtained by itself, the laser head 120 uses the combined semiconductor laser light source 121 including a plurality of LD packages 123. It is set as the structure provided with multiple (here 8 pieces). In each combined semiconductor laser light source 121, when the emitted light from the plurality of LD packages 123 is combined only by the angle combination, the depth of focus becomes shallow, and there is a fear that the light intensity variation due to the defocus is increased. In the multi-lateral mode semiconductor laser LD, the radiation angle in the fast axis direction is 40 to 60 °, and the radiation angle in the slow axis direction is 15 to 25 °. In the present embodiment, the laser beams L1 to L4 emitted from the plurality of LD packages 123 are polarized and multiplexed in the fast axis direction and angularly multiplexed in the slow axis direction. The required optical power density is obtained.

  In the combined semiconductor laser light source 121, four LD packages 123 are formed by a collimate lens 124, a reflection mirror 125, beam splitters 126 </ b> A and 126 </ b> B, a half-wave plate 127, and half-wave phase difference elements 128 </ b> A and B. The optical system which inject | emits the laser beams L1-L4 from these collectively is comprised.

  As shown in FIG. 10, a plurality of prisms 132 a whose deflection angles are set on the light emitting surface of a laser head 120 including a plurality of combined semiconductor laser light sources 121 in accordance with the formation positions of the plurality of combined semiconductor laser light sources 121. A prism array (deflection element) 132 is attached.

  The scanning optical system 140 includes an optical scanning mirror (dynamic deflection element) 141 such as a galvano mirror and a condensing lens 142 that condenses each laser beam.

  Laser light L emitted from a plurality of combined semiconductor laser light sources 121 mounted on the laser head 120 passes through the spatial modulation element 133 serving as the absorption energy adjusting means and is deflected by the prism array 132 to be applied to the optical scanning mirror 141. Incident light is scanned in the direction of arrow x in FIG.

  The lens 142 is scanned in accordance with the optical scanning by the optical scanning mirror 141, and the laser light L deflected by the optical scanning mirror 141 enters the lens 142 and the optical axes thereof become parallel to each other.

In the present embodiment, an elongated laser beam having a longitudinal direction in the direction of the arrow y in FIG. 10 is formed by the above configuration, and scanning is performed while the semiconductor film 20 is irradiated with this laser beam. For example, the present inventor has realized a laser beam having a shape of 20 μm × 4 μm to 40 μm × 8 μm in which the irradiation light power density on the film surface of the semiconductor film 20 to be annealed is 0.5 to 2.7 W / cm ² .

  In the laser annealing apparatus 100 of the present embodiment, the irradiation condition of the laser light L is such that the granular crystal portion and the amorphous portion of the semiconductor film 20 to be annealed melt and the lateral crystal portion of the semiconductor film 20 to be annealed does not melt. Is set.

When the semiconductor film 20 to be annealed is an amorphous silicon film, the laser light L is irradiated under the following formulas (1) and (2): the laser light absorptance in the lateral crystal part, the granular crystal part, and the amorphous part. ) Is preferably set to satisfy the condition.
0.82 ≦ absorptivity of granular crystal part / absorptivity of amorphous part ≦ 1.0 (1),
Absorption rate of the lateral crystal portion / absorption rate of the non-crystalline portion ≦ 0.70 (2)

When the semiconductor film 20 to be annealed is an amorphous silicon film, the irradiation condition of the laser light L is that the film thickness t (nm) of the semiconductor film 20 to be annealed and the wavelength λ (nm) of the laser light L are expressed by the following formula (3 ) Is preferably set to satisfy the condition.
0.8t + 320 ≦ λ ≦ 0.8t + 400 (3)

  When the semiconductor film 20 to be annealed is an amorphous silicon film, the semiconductor laser (laser light oscillation source) LD mounted on the laser head 120 is preferably a semiconductor laser having an oscillation wavelength in the wavelength range of 350 to 500 nm. . As a laser that oscillates laser light in a wavelength region of 350 to 500 nm, a GaN-based semiconductor including an active layer containing one or more nitrogen-containing semiconductor compounds such as GaN, AlGaN, InGaN, InAlGaN, InGaNAs, and GANAS Examples thereof include lasers and II-VI group compound semiconductor lasers such as ZnO and ZnSe.

In the laser annealing apparatus 100 of the present embodiment, when the semiconductor film 20 to be annealed is an amorphous silicon film, the irradiation condition of the laser beam L and the relative scanning condition are the absorption power density P (MW) of the laser beam in the amorphous part. / cm ² ) and the relative scanning speed v (m / s) of the laser beam L are preferably set to satisfy the following formula (5).
0.44v ^0.34143 ≦ P ≦ 0.56v ^0.34143 (5)

  The laser annealing apparatus 100 according to the present embodiment first performs laser beam L scanning on the semiconductor film 20 to be annealed by changing the y position in the x direction (when changing the annealing region). Laser annealing is preferably performed so that the region irradiated with L and the region irradiated with laser beam L next overlap each other.

  By using the laser annealing apparatus 100 of the present embodiment having the above-described configuration, the above-described laser annealing method can be performed.

  The laser annealing apparatus 100 of the present embodiment is not limited to the above configuration, and the design can be changed as appropriate. The relative scanning of the laser light L with respect to the semiconductor film 20 to be annealed is performed by moving the substrate stage 110 and optical scanning with the scanning optical system 140. It can also be performed by mechanical scanning of the laser head 120 in the illustrated x and y directions, mechanical scanning of the substrate stage 110 in the illustrated x and y directions, or optical scanning of the laser light L in the illustrated x and y directions. Can do.

  As mentioned in this embodiment, since a high output is obtained and a long and narrow laser beam shape is obtained, the laser head 120 is equipped with a plurality of combined semiconductor laser light sources 121 each including a plurality of multi-lateral mode semiconductor lasers LD. It is preferable that Although the case where the number of LDs mounted on each combined semiconductor laser light source 121 is four has been described, the number can be designed as appropriate. The laser head 120 may include only a single combined semiconductor laser light source 121. The laser head 120 may include only a single semiconductor laser LD.

"Semiconductor films, semiconductor devices, active matrix substrates"
With reference to the drawings, a semiconductor film of the embodiment according to the laser annealing, a semiconductor device using the semiconductor film, and a manufacturing method and a configuration of an active matrix substrate including the semiconductor film will be described. In this embodiment, a top gate type pixel switching thin film transistor (pixel switching TFT) and an active matrix substrate including the same will be described as an example. FIG. 12 is a process diagram (cross-sectional view in the thickness direction of the substrate).

  First, as shown in FIG. 12A, a substrate 10 is prepared, and a semiconductor film 20 to be annealed made of an amorphous semiconductor is formed on the entire surface of the substrate 10. Here, the case where the semiconductor film 20 to be annealed is an amorphous silicon (a-Si) film is illustrated.

  The substrate 10 is not particularly limited, and has a heat resistance that can withstand heat treatment in a glass substrate (quartz glass substrate, barium borosilicate glass substrate, alumino borosilicate glass substrate, etc.), the TFT process of this embodiment, and a subsequent process of the TFT process. In addition, examples include a plastic substrate, a silicon substrate, and a metal substrate (stainless steel substrate or the like) having a heat insulating property equal to or higher than that of glass, and a substrate provided with a heat insulating property equal to or higher than that of glass.

  The semiconductor film 20 to be annealed is not directly formed on the substrate 10, but a base film (not shown) such as silicon oxide or silicon nitride is formed on the substrate 10, and then the semiconductor film 20 to be annealed is formed thereon. May be formed. The method for forming the base film and the semiconductor film 20 to be annealed is not particularly limited, and examples thereof include vapor phase growth methods such as a plasma CVD method, an LPCVD method, and a sputtering method.

  The thickness of the base film is not particularly limited, and is preferably about 200 nm, for example. The thickness of the semiconductor film 20 to be annealed is not particularly limited and is preferably 40 to 120 nm. The film thickness of the semiconductor film 20 to be annealed is preferably about 50 nm, for example.

  The to-be-annealed semiconductor film 20 formed by plasma CVD or the like usually contains a lot of hydrogen. When crystallization is performed by laser annealing while a large amount of hydrogen is contained, there is a possibility that problems such as hydrogen bumping and the film surface becoming rough, or film peeling partially due to hydrogen bumping. Therefore, it is preferable to perform a dehydrogenation process prior to laser annealing. The dehydrogenation treatment method is not particularly limited, and examples include thermal annealing treatment (for example, about 500 ° C. for about 10 minutes).

Next, as shown in FIG. 12B, the laser annealing is performed on the semiconductor film 20 to be annealed to crystallize the entire surface of the semiconductor film 20 to be annealed. In the present embodiment, substantially entire lateral crystallization is possible.
Next, as shown in FIG. 12C, the semiconductor film 21 after laser annealing is patterned by photolithography to remove regions other than the TFT element formation region. Reference numeral 22 denotes a semiconductor film after patterning.

Next, as shown in FIG. 12D, a gate insulating film 24 made of SiO ₂ or the like is formed by CVD or sputtering. The thickness of the gate insulating film 24 is not particularly limited and is preferably about 100 nm, for example.
Next, as shown in FIG. 12E, an electrode material is formed and patterned by photolithography to form a gate electrode 25 on the gate insulating film 24.

Next, as shown in FIG. 12F, an active layer 23 having a source region 23a and a drain region 23b, which are active regions, is doped with a dopant such as P and B into the semiconductor film 22 using the gate electrode 25 as a mask. Form. The case where the dopant is P is shown. In the active layer 23, a region between the source region 23a and the drain region 23b becomes a channel region 23c. The doping amount is preferably about 3.0 × 10 ¹⁵ ions / cm ² , for example. By this step, the semiconductor film 23 forming the active layer of the TFT is formed.

Next, as shown in FIG. 12G, an interlayer insulating film 26 made of SiO ₂ , SiN, or the like is formed, and further, etching such as dry etching or wet etching is performed. A contact hole 27a that communicates with the source region 23a of the film 23 and a contact hole 27b that communicates with the drain region 23b are opened.

  Further, a source electrode 28 a and a drain electrode 28 b are formed in a predetermined region on the interlayer insulating film 26. The source electrode 28a is electrically connected to the source region 23a of the semiconductor film 23 via the contact hole 27a, and the drain electrode 28b is electrically connected to the drain region 23b of the semiconductor film 23 via the contact hole 27b.

In this embodiment, the semiconductor film 21 after laser annealing and before patterning, the semiconductor film 22 after patterning and before impurity implantation, and the semiconductor film 23 after impurity implantation are all semiconductor films manufactured using the laser annealing technique. is there.
Through the above steps, the pixel switching TFT 30 of this embodiment is manufactured.

Next, as shown in FIG. 12 (h), an interlayer insulating film 31 made of SiO ₂ , SiN, or the like is formed, and etching such as dry etching or wet etching is performed to form the interlayer insulating film 31 on the source electrode 28a. A contact hole 32 is opened.

  Further, the pixel electrode 33 is formed in a predetermined region on the interlayer insulating film 31. The pixel electrode 33 is electrically connected to the source electrode 28 a of the TFT 30 through the contact hole 32.

  Only a pair of pixel electrodes 33 and TFTs 30 are shown, but in reality, a large number of pixel electrodes 33 are formed in a matrix on one substrate 10, and pixel switching is performed corresponding to each pixel electrode 33. A TFT 30 is formed.

  Usually, for a liquid crystal device, one pixel electrode 33 and one pixel switching TFT 30 are formed for one dot, and for an EL device, one pixel electrode 33 for one dot. Two pixel switching TFTs 30 are formed.

Through the above steps, the active matrix substrate 40 of the present embodiment is manufactured.
In manufacturing the active matrix substrate 40, wiring lines such as scanning lines and signal lines are formed. In some cases, the gate electrode 25 also serves as a scanning line, and in other cases, the scanning line is formed separately from the gate electrode 25. In some cases, the drain electrode 28b also serves as a signal line, and in other cases, the signal line is formed separately from the drain electrode 28b.

  In this embodiment, since the laser annealing technique is used, the semiconductor films 21 to 23 having high crystallinity and suitable as the active layer of the TFT can be manufactured. The pixel switching TFT 30 of this embodiment manufactured using these semiconductor films 21 to 23 is excellent in element characteristics (carrier mobility and the like) and element uniformity. The active matrix substrate 40 of this embodiment provided with the pixel switching TFT 30 has high performance for an electro-optical device.

  In an electro-optical device such as a liquid crystal device or an EL device, a pixel portion in which a large number of pixel electrodes and pixel switching TFTs are formed in a matrix on the same substrate, and a plurality of driving circuit TFTs that drive the pixel portion There is a case in which a driving unit including a driving circuit configured by using the above is provided. The drive circuit usually has a CMOS structure of N-type TFT and P-type TFT.

  In the laser annealing technique, since the semiconductor film 20 to be annealed can be substantially laterally crystallized, the active layer of the pixel switching TFT and the active layer of the driving circuit TFT can be formed simultaneously. With the laser annealing technique, it is possible to manufacture a driving circuit TFT having excellent element characteristics such as carrier mobility.

"Electro-optical device"
With reference to the drawings, the configuration of the electro-optical device according to the laser annealing will be described. This laser annealing can be applied to an EL device or a liquid crystal device, and an organic EL device will be described as an example. FIG. 13 is an exploded perspective view of the organic EL device.

  The organic EL device (electro-optical device) 50 according to this embodiment emits red light (R), green light (G), and blue light (B) by applying current on the active matrix substrate 40 according to the above-described embodiment. The light emitting layers 41R, 41G, and 41B to be formed are formed in a predetermined pattern, and the common electrode 42 and the sealing film 43 are sequentially stacked thereon.

  Instead of using the sealing film 43, sealing may be performed with a sealing member such as a metal can or a glass substrate. In this case, a desiccant such as calcium oxide may be included.

  The light emitting layers 41R, 41G, and 41B are formed in a pattern corresponding to the pixel electrode 33, and one pixel is composed of three dots that emit red light (R), green light (G), and blue light (B). . The common electrode 42 and the sealing film 43 are formed on substantially the entire surface of the active matrix substrate 40.

  In the organic EL device 50, one of the pixel electrode 33 and the common electrode 42 functions as an anode and the other functions as a cathode, and the light emitting layers 41R, 41G, and 41B have holes injected from the anode and electrons injected from the cathode. Light is emitted by the recombination energy.

  In order to improve the luminous efficiency, a hole injection layer and / or a hole transport layer can be provided between the light emitting layers 41R, 41G, 41B and the anode. In order to improve the light emission efficiency, an electron injection layer and / or an electron transport layer can be provided between the light emitting layers 41R, 41G, 41B and the cathode.

  Since the organic EL device (electro-optical device) 50 according to the present embodiment is configured using the active matrix substrate 40 according to the above-described embodiment, the device characteristics (such as carrier mobility) and element uniformity of the TFT 30 are excellent. Therefore, the electro-optical characteristics such as display quality are excellent.

<< Example >>
Examples and comparative examples relating to the laser annealing will be described.

(Example 1)
On the glass substrate, a base film (200 nm thickness) made of silicon oxide and an amorphous silicon film (a-Si, 50 nm thickness) were sequentially formed by plasma CVD. Thereafter, thermal annealing was performed at about 500 ° C. for about 10 minutes, and dehydrogenation treatment of the amorphous silicon film was performed.

  Laser annealing was performed on the amorphous silicon film using the laser annealing apparatus 100 (see FIGS. 10 and 11) of the above embodiment. A GaN semiconductor laser (oscillation wavelength of 405 nm) was used as the laser beam oscillation source. The shape of the laser beam on the surface of the amorphous silicon film was an elongated rectangular shape of 20 × 3 μm.

Substantially whole surface laser annealing was performed under the following conditions.
<Condition 1>
The relative scanning speed of the laser beam was 0.01 m / s, the absorption power density in the amorphous part was 0.1 MW / cm ² , and the overlap amount was 75%.

  The overlap amount of 75% means that after the x-direction relative scanning of the laser beam is performed at a certain y position, the y position is shifted by 5 μm when the x-direction relative scanning of the laser beam is performed by changing the y position. This means that laser annealing was performed so that the irradiated region overlapped by 15 μm with respect to the 20 μm wide region previously irradiated with the laser beam.

  14A and 14B show an SEM photograph and a TEM photograph of the film surface after the substantially entire surface laser annealing. As shown in the figure, under the conditions of this example, the granular crystal part and the non-crystal part melt, but the lateral crystal part once generated does not remelt even when irradiated with laser light, and is almost entirely over the surface. A lateral crystal film having almost no granular crystal part and a seamless seam was obtained. In addition, the angle between the main relative scanning direction of the laser beam and the lateral crystal growth direction can be aligned to 5 ° or less over substantially the entire surface of the film.

Even when laser annealing was carried out in the same manner by changing the laser annealing conditions to the following conditions, a lateral crystal film having almost no granular crystal portions and almost no joints was obtained on almost the entire surface.
<Condition 2>
The relative scanning speed of the laser beam is 1.0 m / s, the absorption power density in the amorphous portion is 0.5 MW / cm ² , and the overlap amount is 75%.
<Condition 3>
The relative scanning speed of the laser beam is 0.1 m / s, the absorption power density in the amorphous portion is 0.15 MW / cm ² , and the overlap amount is 75%.
<Condition 4>
The relative scanning speed of the laser beam is 0.01 m / s, the absorption power density in the amorphous portion is 0.1 MW / cm ² , and the overlap amount is 25%.

  The slower the relative scanning speed of the laser beam, the easier the heat is conducted to the surroundings, and the more likely the granular crystals are generated. However, according to the laser annealing method, the condition of the relative scanning speed of the laser beam of 0.01 m / s. In this case, the granular crystal part and the amorphous part melt, but the lateral crystal part once formed does not remelt even if it is irradiated with laser light, and there is almost no granular crystal part on the entire surface. A lateral crystal film having no carbon black was obtained.

(Comparative Example 1)
Laser annealing was performed in the same manner as in Example 1 except that laser annealing was performed under the following conditions.
<Condition 5>
The relative scanning speed of the laser beam is 0.01 m / s, the absorption power density in the amorphous part is 0.09 MW / cm ² , and the overlapping amount is 70%.
FIGS. 15A and 15B show an SEM photograph and a TEM photograph of the film surface after the substantially entire surface laser annealing. As shown in the drawing, under the conditions of this comparative example, the granular crystal portion and the lateral crystal portion were not melted again even if they were irradiated with laser light. For this reason, even when the laser beam was irradiated repeatedly, the granular crystal portion was not laterally crystallized. Further, the lateral crystal is intended to grow in the non-parallel direction (angular direction of 5 to 45 ° with respect to the scanning direction of the laser beam) with the granular crystal serving as a nucleus, and at the same time. Since the lateral crystal tries to grow so as to align in the main relative scanning direction, a curved lateral crystal was formed. The ratio of the granular crystals to the film area was 30% or more.

(Comparative Example 2)
Laser annealing was performed in the same manner as in Example 1 except that laser annealing was performed under the following conditions.
<Condition 6>
The relative scanning speed of the laser light is 0.01 m / s, the absorption power density in the amorphous portion is 0.08 MW / cm ² , and the overlapping amount is 70%.

  FIG. 16 shows a TEM photograph of the film surface after the substantially entire surface laser annealing. In this comparative example, in which the absorption power density was lower than that in comparative example 1, the non-crystalline portion was not laterally crystallized, and the obtained film was a silicon film substantially entirely composed of granular crystals.

(Evaluation of Vg-Id characteristics)
A TFT was manufactured using the silicon film obtained by laser annealing under <Condition 1> in Example 1, and the Vg-Id characteristics (relationship between the gate voltage Vg and the drain current Id) of the obtained TFT were evaluated.
Similarly, a TFT was manufactured using the silicon film obtained by laser annealing of Comparative Example 1, and its Vg-Id characteristics were evaluated. For Comparative Example 1, evaluation was performed on two TFTs (Comparative Example 1-A and Comparative Example 1-B).
The results are shown in FIG. In FIG. 17, the left and right vertical axes indicate the same Id value, but the right vertical axis is normal display and the left vertical axis is logarithmic display. As shown in the figure, the TFT obtained in Example 1 had higher carrier mobility and better device current characteristics than the TFT obtained in Comparative Example 1.

  The laser annealing apparatus can be preferably applied to the manufacture of a thin film transistor (TFT) and an electro-optical device including the same.

(A) Perspective view showing a state of generating a lateral crystal and a granular crystal when the x-direction relative scanning of the laser beam is performed once at a certain y position, and (b) is a relative view of the laser beam in the x direction when the y position is changed. Image plan view of crystallization when repeated scanning The figure which shows the relationship between the wavelength and the refractive index n in the lateral crystal part of a silicon film, a granular crystal part, and an amorphous part The figure which shows the relationship between the wavelength and the absorption coefficient in the lateral crystal part, the granular crystal part and the non-crystalline part of the silicon film The figure which shows the relationship between the wavelength of a laser beam, the absorptivity ratio of granular crystalline silicon with respect to the absorptivity of amorphous silicon, and the absorptivity ratio of lateral crystalline silicon with respect to the absorptivity of amorphous silicon The figure which shows the relationship between the energy ratio with respect to the absorbed light energy in which the surface arrival temperature of a laser beam is 2200 degreeC, the surface arrival temperature of a laser beam, and the crystal state to produce | generate The figure which shows the relationship between the wavelength of a laser beam when the film thickness t (nm) = 50,100,200 and the absorptivity ratio of the lateral crystalline silicon with respect to the absorptivity of the amorphous silicon A range of wavelengths where the surface temperature of the granular crystal portion and the non-crystalline portion is about 1700 to 2200 ° C. and the surface temperature of the lateral crystal portion is about 1400 ° C. or less with respect to the thickness t of the silicon film. Figure The figure which shows the range of the absorption power density from which the surface arrival temperature in an amorphous part becomes about 2000 +/- 200 degreeC with respect to the relative scanning speed of a laser beam. Image diagram of absorptance distribution, irradiation light intensity distribution of laser light on the film surface, absorption energy distribution of laser light, and temperature distribution in non-crystal part, granular crystal part and lateral crystal part Overall configuration of laser annealing equipment The figure which shows the internal structure of one combining semiconductor laser light source with which the laser annealing apparatus of FIG. 10 was equipped. (A)-(h) is process drawing which shows the manufacturing method of the semiconductor film of this Embodiment which concerns on laser annealing, a semiconductor device using the same, and an active matrix substrate provided with the same The figure which shows the structure of the organic electroluminescent apparatus (electro-optical apparatus) of embodiment which concerns on laser annealing (A) is a SEM surface photograph after laser annealing when laser annealing is performed under condition 1 in Example 1, and (b) is a TEM surface photograph. (A) is SEM surface photograph after laser annealing of Comparative Example 1, and (b) is TEM surface photograph. TEM surface photograph after laser annealing of Comparative Example 2 The figure which shows the evaluation result of the Vg-Id characteristic of TFT obtained in Example 1 and Comparative Example 1 Sectional drawing which shows schematic structure of the laser beam irradiation apparatus by embodiment of this invention (A), (b) is a figure explaining a mode that the coherence which multi transverse mode light has is reduced. A plan view showing a schematic configuration of a multi-beam scanning optical system to which a laser light irradiation device is applied Side view showing a multi-beam scanning optical system viewed from the direction in which collimated laser beams emitted from a semiconductor laser are aligned Front view showing a multi-beam scanning optical system as seen from the propagation direction of collimated laser light emitted from a semiconductor laser

Explanation of symbols

124 Collimating lens 128A, B 1/2 wavelength phase difference element 221 Laser light irradiation device 223 Multi transverse mode semiconductor laser 230 Condensing lens Hp Predetermined surface LL Laser light Lac, Lbd Polarization combined laser light

Claims (12)

Three or more semiconductor lasers each emitting multi-lateral mode laser light, a collimating lens for collimating each laser light emitted from the semiconductor laser, and each collimated laser light in a spot shape on a predetermined surface A laser beam irradiation device including a condensing optical system for condensing,
A polarization multiplexing unit arranged in an optical path from the collimating lens to the condensing optical system, and polarization-combining at least two laser beams propagating in different optical paths and propagating to the same optical path;
Angle multiplexing means for angularly multiplexing the polarization-multiplexed laser beam and other laser beams so that the optical axes of all the laser beams intersect each other on the predetermined plane;
Coherence reducing means for reducing the coherence on the predetermined plane of two wavefront components that are disposed in the optical path and propagate in positions symmetrical to the optical axes of the laser light. A laser beam irradiation device characterized.   The laser light combined with the polarized light and the other laser light are emitted from the semiconductor laser with the optical axes of all the laser lights parallel to each other, and the interval between the optical axes of the laser lights is emitted from the semiconductor laser. An optical path displacing means is provided for displacing the optical path of the laser beam so that the laser beam is incident on the condensing optical system in a state of being smaller than the interval between the optical axes of each laser beam. Item 2. A laser beam irradiation apparatus according to Item 1.   Four semiconductor lasers are provided, and the polarization multiplexing unit polarizes and combines two laser beams out of the four laser beams emitted from the semiconductor lasers, and also polarizes the other two laser beams. The laser beam irradiation apparatus according to claim 1, wherein the laser beam irradiation apparatus is a device for multiplexing.   4. The laser beam irradiation apparatus according to claim 1, wherein the coherence reducing means is disposed at a far field image forming position in the laser beam emitted from the semiconductor laser.   The coherence reducing means is a ½ wavelength phase difference element, and the ½ wavelength phase difference element is one of two wavefront components propagating in a symmetric position with respect to the optical axis of the laser beam. The laser beam irradiation apparatus according to claim 1, wherein the laser beam irradiation apparatus is arranged so as to change a phase of the laser beam.   6. The laser beam irradiation apparatus according to claim 1, wherein the semiconductor laser is hermetically sealed. The laser light when the predetermined surface is a region on the amorphous semiconductor film, and the amorphous semiconductor film is irradiated with the laser light according to a difference in crystal state in the amorphous semiconductor film. The absorption rate of energy from
When scanning the laser light onto the amorphous semiconductor film, the energy of the laser light absorbed by the amorphous semiconductor film is constant regardless of the location on the amorphous semiconductor film. The laser light irradiation apparatus according to claim 1, further comprising absorption energy adjusting means for adjusting light intensity or scanning speed of the laser light.   8. The laser light irradiation apparatus according to claim 7, wherein the absorption energy adjusting means is a spatial modulation element having a complex amplitude distribution of an inverse Fourier transform profile arranged in an optical path of the laser light.   8. The laser beam irradiation apparatus according to claim 7, wherein the absorption energy adjusting unit is a wavelength combining unit that combines the wavelengths of the laser beams. This is a laser beam irradiation method in which laser beams emitted from three or more semiconductor lasers each emitting multi-lateral mode laser beams and collimated by a collimator lens are focused in a spot shape on a predetermined surface by a focusing optical system. And
At least two laser beams propagating in different optical paths from the collimating lens to the condensing optical system are polarized and combined to be propagated to the same optical path, and the polarized combined laser beam and other lasers Two wavefront components that cause light to be angularly multiplexed such that the optical axes of all the laser beams intersect each other on the predetermined plane, and propagate in positions symmetrical to the optical axes of the laser beams in the optical path A method of irradiating laser light on the predetermined surface is reduced.   The laser light combined with the polarized light and the other laser light are emitted from the semiconductor laser with the optical axes of all the laser lights parallel to each other, and the interval between the optical axes of the laser lights is emitted from the semiconductor laser. 11. The laser beam according to claim 10, wherein an optical path of the laser beam is displaced so as to be incident on the condensing optical system in a state of being smaller than an interval between the optical axes of the laser beams when the laser beam is transmitted. Irradiation method. The laser light when the predetermined surface is a region on the amorphous semiconductor film, and the amorphous semiconductor film is irradiated with the laser light according to a difference in crystal state in the amorphous semiconductor film. The absorption rate of energy from
When scanning the laser light onto the amorphous semiconductor film, the energy of the laser light absorbed by the amorphous semiconductor film is constant regardless of the location on the amorphous semiconductor film. The laser light irradiation method according to claim 10 or 11, wherein the light intensity or scanning speed of the laser light is adjusted.