Laser annealing apparatus and laser annealing method

Abstract

To provide a laser annealing apparatus that reduces a tact time until a laser annealing is executed to an amorphous silicon film and the film is modified to a crystal film.SOLUTION: A laser annealing apparatus comprises a crystallization laser beam irradiation part that irradiates an amorphous silicon film with a crystallization laser beam continuously oscillated, and modifies the amorphous silicon film to be crystallization film. The laser annealing apparatus comprises a dehydrogenation laser beam irradiation part that is relatively moved along a scanning direction against the amorphous silicon film with the crystallization laser beam irradiation part, and irradiates the amorphous silicon film with a plurality of dehydrogenation laser beams that is continuously oscillated in advance of the crystallization laser beam. In the laser annealing apparatus, a plurality of dehydrogenation laser beam spots projected to the amorphous silicon film in the plurality of dehydrogenation laser beams, and a crystallization laser beam spot are arranged so as to be a line along the scanning direction.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a laser annealing apparatus and a laser annealing method for dehydrogenating and crystallizing an amorphous silicon film in the manufacturing process of LTPS (hereinafter also referred to as low temperature polysilicon). [Background technology]

[0002] LTPS is polysilicon that is produced under low-temperature conditions. This LTPS can be produced at a temperature of about 500°C, which is the same as the production temperature of amorphous silicon. Polysilicon has a higher current driving ability (mobility) than amorphous silicon, so when applied to liquid crystal displays, it has the advantage of increasing the display speed. In addition, the thin-film transistors (hereinafter referred to as TFTs) that control the liquid crystal can also be made smaller, which allows the area of ​​the pixel apertures of the liquid crystal to be increased and the brightness to be increased. As mentioned above, LTPS is produced under low-temperature conditions, so it is possible to use inexpensive glass substrates (high strain point glass) in the same way as flat panel displays (FPDs) that use amorphous silicon as the constituent film of TFTs. This makes it possible to keep manufacturing costs low.

[0003] A laser annealing method is known that grows pseudo single crystal silicon laterally on an amorphous silicon film to increase the mobility of the channel region in a TFT. In this laser annealing method, the crystal grains of a microcrystalline silicon film formed by excimer laser annealing are used as seed crystals to grow lateral crystals in the scanning direction of a continuous wave laser beam, forming a pseudo single crystal silicon film with high mobility.

[0004] In the above-mentioned method for laser annealing an amorphous silicon film, a dehydrogenation process is required as a pre-processing step to remove hydrogen contained in the amorphous silicon film. A known device for carrying out this dehydrogenation process is one that includes a dehydrogenation furnace that houses a TFT substrate and heats it at a dehydrogenation temperature, and a current generating unit that generates a current in the gate wiring of the TFT substrate to heat the gate wiring (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-119913 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, as described above, the conventional laser annealing method has a problem that the tact time is long and the production efficiency is reduced. In the conventional laser annealing method, it is necessary to move the TFT substrate from a dehydrogenation furnace for removing hydrogen contained in the amorphous silicon film to a laser annealing device and perform laser annealing on the amorphous silicon film. In recent years, the TFT substrate of a display has become larger, so a large dehydrogenation furnace is required. Therefore, the above-mentioned laser annealing method has a problem that the tact time until the amorphous silicon film is reformed into a pseudo single crystal silicon film is long and the cost is high.

[0007] The present invention has been made in consideration of the above problems, and has an object to provide a laser annealing apparatus and a laser annealing method that shorten the takt time until an amorphous silicon film is laser annealed to convert it into a crystallized film. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, an aspect of the present invention is a laser annealing apparatus comprising a crystallization laser beam irradiation unit which irradiates a continuously oscillated crystallization laser beam toward an amorphous silicon film formed on a substrate, and a crystallization laser beam spot of the crystallization laser beam projected onto the amorphous silicon film moves along a scanning direction relative to the amorphous silicon film to modify the amorphous silicon film into a crystallized film, the laser annealing apparatus comprising a dehydrogenation laser beam irradiation unit which moves along the scanning direction relative to the amorphous silicon film together with the crystallization laser beam irradiation unit and irradiates a plurality of dehydrogenation laser beams which are continuously oscillated toward the amorphous silicon film prior to the crystallization laser beam, and a plurality of dehydrogenation laser beam spots of the dehydrogenation laser beams projected onto the amorphous silicon film and the crystallization laser beam spots are arranged in a row along the scanning direction.

[0009] In the above embodiment, it is preferable that the conditions selected from the number of the dehydrogenation laser beams, the distance between the adjacent dehydrogenation laser beams, the scan speed, and the output of the dehydrogenation laser beam are adjusted so that the multiple beam irradiation regions including the regions on the amorphous silicon film irradiated with the multiple dehydrogenation laser beam spots are within a temperature range where dehydrogenation is possible below the temperature at which hydrogen remaining in the amorphous silicon film causes a hydrogen explosion. Note that, in this embodiment, it is preferable that the distance between the adjacent dehydrogenation laser beams along the scan direction is adjusted according to at least the scan speed and the output of the dehydrogenation laser beam.

[0010] In the above-mentioned aspect, it is preferable that the crystallization laser beam irradiating unit guides laser light from a crystallization light source via a crystallization optical fiber, and the dehydrogenation laser beam irradiating unit guides laser light from each of a plurality of dehydrogenation light sources via a dehydrogenation optical fiber.

[0011] In the above aspect, it is preferable that the crystallization laser beam irradiating section and the dehydrogenation laser beam irradiating section are integrally provided.

[0012] In the above aspect, the crystallization light source and the dehydrogenation light source are preferably blue semiconductor diodes.

[0013] In the above aspect, the crystallized film is preferably a low-temperature polysilicon film or a pseudo single-crystal silicon film.

[0014] It is preferable that a plurality of dehydrogenation laser beam spots projected onto the amorphous silicon film from the plurality of dehydrogenation laser beams are set to be shifted in a direction perpendicular to the scanning direction and irradiated a plurality of times.

[0015] In the above aspect, it is preferable that the plurality of dehydrogenation laser beam spots form dehydrogenation regions on the substrate in an area wider than the width of the crystallization laser beam spot.

[0016] In the above aspect, it is preferable that the dehydrogenation laser beam spots are arranged in a row along the scanning direction, spaced a predetermined distance apart in a direction perpendicular to the scanning direction.

[0017] Another aspect of the present invention is a laser annealing method in which a continuously oscillated crystallization laser beam is irradiated toward an amorphous silicon film formed on a substrate, and a crystallization laser beam spot of the crystallization laser beam projected onto the amorphous silicon film moves along a scanning direction relative to the amorphous silicon film to modify the amorphous silicon film into a crystallized film, characterized in that a plurality of dehydrogenation laser beams are irradiated toward the amorphous silicon film prior to the crystallization laser beam, the dehydrogenation laser beam spots of the plurality of dehydrogenation laser beams projected onto the amorphous silicon film and the crystallization laser beam spots are arranged in a row along the scanning direction.

[0018] In the above embodiment, it is preferable that the conditions selected from the number of the dehydrogenation laser beams, the distance between the adjacent dehydrogenation laser beams, the scan speed, and the output of the dehydrogenation laser beam are adjusted so that the multiple beam irradiation region including the region on the amorphous silicon film irradiated with the multiple dehydrogenation laser beam spots is within a temperature range where dehydrogenation is possible below the temperature at which hydrogen remaining in the amorphous silicon film causes a hydrogen explosion. In this embodiment, it is preferable that the distance between the adjacent dehydrogenation laser beams along the scan direction is adjusted according to at least the scan speed and the output of the dehydrogenation laser beam.

[0019] In the above aspect, it is preferable that a blue semiconductor diode is used as a light source for the crystallization laser beam and the dehydrogenation laser beam, and the crystallization film is a low-temperature polysilicon film or a pseudo single crystal silicon film.

[0020] In the above aspect, it is preferable that a plurality of dehydrogenation laser beam spots projected onto the amorphous silicon film by the plurality of dehydrogenation laser beams are shifted in a direction perpendicular to the scanning direction and irradiation is performed a plurality of times.

[0021] In the above aspect, it is preferable that the plurality of dehydrogenation laser beam spots form dehydrogenation regions on the substrate in an area wider than the width of the crystallization laser beam spot.

[0022] In the above aspect, it is preferable that the dehydrogenation laser beam spots are arranged in a row along the scanning direction, the rows being shifted a predetermined distance in a direction perpendicular to the scanning direction. Effect of the Invention

[0023] The laser annealing apparatus and the laser annealing method according to the present invention have the effect of shortening the tact time until an amorphous silicon film is reformed into a crystallized film by laser annealing. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a configuration explanatory diagram showing a laser annealing apparatus according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is an explanatory side view showing a state in which the laser annealing apparatus according to the first embodiment of the present invention is operated. [Diagram 3] FIG. 3 is a plan view illustrating the crystallization laser beam irradiating section and the dehydrogenation laser beam irradiating section of the laser annealing apparatus according to the first embodiment of the present invention. [Figure 4] FIG. 4 is an explanatory plan view showing the distance between the emission ends of dehydrogenation optical fibers in the laser annealing apparatus according to the first embodiment of the present invention. [Diagram 5] FIG. 5 is a diagram showing the relationship between the number of dehydrogenation optical fibers and the scan speed in the laser annealing apparatus according to the first embodiment of the present invention. [Figure 6] FIG. 6 shows a case where the number of dehydrogenation optical fibers in the laser annealing apparatus is one, and is a diagram showing an insufficient dehydrogenation state, an appropriate dehydrogenation state, and a state where a hydrogen explosion occurs. [Figure 7] Figure 7 shows an example in which two dehydrogenation optical fibers are used in a laser annealing apparatus (solid line F) and an example in which the number is increased to two or more, and shows a state in which an area including an area irradiated with multiple dehydrogenation laser beam spots falls within the temperature range in which dehydrogenation is possible. [Figure 8] Figure 8 shows the case where two dehydrogenation optical fibers are used in a laser annealing apparatus, and shows the state in which an area where a hydrogen explosion occurs and an area where the temperature becomes insufficient for dehydrogenation appear in the area irradiated by the two dehydrogenation laser beam spots. [Figure 9] FIG. 9 is an explanatory plan view showing a state in which the crystallization laser beam irradiating unit and the dehydrogenation laser beam irradiating unit move in the scanning direction in the laser annealing apparatus according to the first embodiment of the present invention. [Figure 10] FIG. 10 is an explanatory diagram showing a substrate structure to which the laser annealing apparatus according to the first embodiment of the present invention is applied. [Figure 11] FIG. 11 is an explanatory diagram showing another substrate structure to which the laser annealing apparatus according to the first embodiment of the present invention is applied. [Figure 12] FIG. 12 is a plan view illustrating an example in which a crystallized film is formed only in a TFT formation region using the laser annealing apparatus according to the first embodiment of the present invention. [Figure 13] FIG. 13 is a plan view illustrating an example in which a crystallized film is formed in a region in which a drive circuit is formed around a substrate by using the laser annealing apparatus according to the first embodiment of the present invention. [Figure 14] FIG. 14 is a configuration explanatory diagram showing a laser annealing apparatus according to the second embodiment of the present invention. [Figure 15] FIG. 15 is an explanatory side view showing a state in which the laser annealing apparatus according to the second embodiment of the present invention is operated. [Figure 16]FIG. 16 is a plan view illustrating a crystallization laser beam irradiating section and a dehydrogenation laser beam irradiating section of a laser annealing apparatus according to the second embodiment of the present invention. [Figure 17] (a) shows the state before the dehydrogenation process used to explain the mechanism of crack occurrence in the crystallization process after the dehydrogenation process, and shows the arrangement of the dehydrogenation laser beam spot, the irradiation amount, and the correspondence with the cross section, (b) shows the state of the substrate surface in the dehydrogenation process, the irradiation amount, and the correspondence with the cross section, and (c) shows the crack occurrence state of the substrate surface after the crystallization process, the irradiation amount, and the correspondence with the cross section. [Figure 18] 1A shows modification 1, which is applied to the first and second embodiments of the present invention, in which the width dimension of the crystallization laser beam spot is shorter than the diameter dimension of the dehydrogenation laser beam spot, and shows the arrangement state of the dehydrogenation laser beam spot, its diameter, its relationship with the width dimension of the crystallization laser beam spot, the irradiation amount, and the correspondence with the cross section; (b) shows modification 1, which shows modification 1 in which the width dimension of the crystallization laser beam spot is shorter than the diameter dimension of the dehydrogenation laser beam spot, and shows the state of the substrate surface in the dehydrogenation process, the irradiation amount, and the correspondence with the cross section; and (c) shows modification 1 in which the width dimension of the crystallization laser beam spot is shorter than the diameter dimension of the dehydrogenation laser beam spot, and shows the correspondence with the state of the substrate surface in the crystallization process, the irradiation amount, and the cross section. [Figure 19]1A shows modification 2, which is applicable to the first and second embodiments of the present invention, in which the dehydrogenation laser beam spot is rectangular and the width dimension of the rectangular crystallization laser beam spot is shorter than the width dimension of the dehydrogenation laser beam spot, showing the state before the dehydrogenation process, and the diagram showing the arrangement of the dehydrogenation laser beam spot, the irradiation amount, and the correspondence with the cross section; (b) shows modification 2, which shows the dehydrogenation laser beam spot is rectangular and the width dimension of the rectangular crystallization laser beam spot is shorter than the width dimension of the dehydrogenation laser beam spot, and the diagram showing the correspondence with the state of the substrate surface in the dehydrogenation process, the irradiation amount, and the cross section; and (c) shows modification 2, which shows the dehydrogenation laser beam spot is rectangular and the width dimension of the rectangular crystallization laser beam spot is shorter than the width dimension of the dehydrogenation laser beam spot, and the diagram showing the correspondence with the state of the substrate surface after the crystallization process, the irradiation amount, and the cross section. [Figure 20] FIG. 1( a ) shows modification 3, which is applied to the first and second embodiments of the present invention, in which a row of dehydrogenation laser beam spots in the dehydrogenation process is sequentially shifted in a direction perpendicular to the scanning direction and scanned multiple times to form a dehydrogenation region wider than the crystallization laser beam spot, and shows the state of the first dehydrogenation process, the irradiation amount, and the correspondence with the cross section; FIG. 1( b ) shows modification 3, which is applied to the first and second embodiments of the present invention, in which a row of dehydrogenation laser beam spots in the dehydrogenation process is sequentially shifted in a direction perpendicular to the scanning direction and scanned multiple times to form a dehydrogenation region wider than the crystallization laser beam spot, and shows the state of the first dehydrogenation process, the irradiation amount, and the correspondence with the cross section; FIG. 13 shows variant 3 in which scanning is performed multiple times to form a dehydrogenation region wider than the crystallization laser beam spot, illustrating the state of the third dehydrogenation process, and the relationship between the arrangement of the dehydrogenation laser beam spot, the irradiation amount, and the cross section; (a) shows variant 3 in which the row of dehydrogenation laser beam spots in the dehydrogenation process is shifted sequentially in a direction perpendicular to the scanning direction to form a dehydrogenation region wider than the crystallization laser beam spot, illustrating the state of the crystallization process, and the relationship between the state of the substrate surface, the irradiation amount, and the cross section. [Figure 21]1A shows Variation 4, which is applied to the first and second embodiments of the present invention, in which the same area is scanned multiple times with a row of dehydrogenation laser beam spots in a dehydrogenation process to form a dehydrogenation area wider than the crystallization laser beam spot, and is a diagram showing the state of the first dehydrogenation process, the arrangement of the dehydrogenation laser beam spots, the irradiation amount, and the correspondence with the cross section; (b) shows Variation 4, which is applied to the first and second embodiments of the present invention, in which the same area is scanned multiple times with a row of dehydrogenation laser beam spots in a dehydrogenation process to form a dehydrogenation area wider than the crystallization laser beam spot, and is a diagram showing the state of the third dehydrogenation process, the arrangement of the dehydrogenation laser beam spots, the irradiation amount, and the correspondence with the cross section; and (c) shows Variation 3, which is applied to the first and second embodiments of the present invention, in which the same area is scanned multiple times with a row of dehydrogenation laser beam spots in a dehydrogenation process to form a dehydrogenation area wider than the crystallization laser beam spot, and is a diagram showing the state of the crystallization process, the arrangement of the dehydrogenation laser beam spots, the irradiation amount, and the correspondence with the cross section. [Figure 22] 1A is an explanatory diagram of the arrangement of dehydrogenation laser beam spots showing variant 5 in which rows of dehydrogenation laser beam spots in the dehydrogenation process applied to the first and second embodiments of the present invention are arranged alternately and in a sequential manner while being shifted in a direction perpendicular to the scanning direction, and FIG. 1B is a diagram showing a partially enlarged arrangement of dehydrogenation laser beam spots showing variant 5 in which rows of dehydrogenation laser beam spots in the dehydrogenation process are arranged alternately and in a sequential manner while being shifted in a direction perpendicular to the scanning direction, and the irradiation amount corresponding to the arrangement of the dehydrogenation laser beam spots. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The details of the laser annealing apparatus and the laser annealing method according to the embodiment of the present invention will be described below with reference to the drawings. However, it should be noted that the drawings are schematic, and the number of each member, the size of each member, the dimensional ratio, the shape, etc. are different from the actual ones. In addition, there are parts in which the dimensional relationships, ratios, and shapes are different between the drawings.

[0026] [First embodiment] (Schematic configuration of laser annealing device) As shown in Figures 1 and 2, the laser annealing apparatus 1 of the first embodiment includes a semiconductor laser array 2, a dehydrogenation laser beam irradiating unit 3, a crystallization laser beam irradiating unit 4, a stage (not shown) on which a substrate 10 is placed, and a transport means (not shown) for moving the dehydrogenation laser beam irradiating unit 3 and the crystallization laser beam irradiating unit 4 relative to the stage along a scanning direction S.

[0027] As shown in FIG. 2, the substrate 10 used in this embodiment has a glass substrate 11 as a main body. An undercoat film 12 and an amorphous silicon film 13 as a film to be laser annealed are sequentially laminated on the glass substrate 11. As shown in FIG. 10, the undercoat film 12 is composed of a silicon nitride film (Si3N4) 14 and a silicon oxide film (SiO2) 15.

[0028] (Semiconductor laser array) As shown in FIG. 1, the semiconductor laser array 2 includes a dehydrogenation light source unit 2A and a crystallization light source unit 2B.

[0029] 1, the dehydrogenation light source unit 2A includes multiple blue semiconductor lasers LD1 to LD24 as dehydrogenation light sources. In the present embodiment, the dehydrogenation light source unit 2A includes 24 blue semiconductor lasers, but the number is not limited to this as long as there is a multiple number. These blue semiconductor lasers LD1 to LD24 oscillate continuous wave laser light (CW laser light).

[0030] The dehydrogenation light source unit 2A includes coupling lenses 21, the number of which is the same as the plurality of blue semiconductor lasers LD1 to LD24. The coupling lenses 21 are connected to the emission sides of the respective blue semiconductor lasers LD1 to LD24. One end of a dehydrogenation optical fiber 22A serving as a waveguide is connected to each of the coupling lenses 21. In this embodiment, a multimode fiber is used as the dehydrogenation optical fiber 22A. Note that in the drawings, only the cores of the dehydrogenation optical fiber 22A and the crystallization optical fiber 22B are shown, and the claddings are omitted.

[0031] The crystallization light source unit 2B includes a single blue semiconductor laser LD25 and a coupling lens 21. One end of a crystallization optical fiber 22B serving as a waveguide is connected to the coupling lens 21. The blue semiconductor laser LD25 oscillates a continuous wave laser beam (CW laser beam).

[0032] Here, the continuous wave laser light (CW laser light) outputted by the blue semiconductor laser LD25 in the crystallization light source unit 2B is a concept including so-called quasi-continuous wave in which the laser light is continuously irradiated to the target area. In other words, the laser light may be a pulsed laser or a quasi-continuous wave laser in which the pulse interval is shorter than the cooling time of the silicon thin film (amorphous silicon film) after heating (the next pulse is irradiated before it solidifies).

[0033] (Dehydrogenation laser beam irradiation section and crystallization laser beam irradiation section) As shown in Fig. 2, the dehydrogenation laser beam irradiating unit 3 and the crystallization laser beam irradiating unit 4 include a long, thin, plate-like common head 5 that connects them together. As shown in Figs. 2, 3 and 4, in this embodiment, the dehydrogenation laser beam irradiating unit 3 is arranged such that the emission ends of the above-mentioned multiple dehydrogenation optical fibers 22A are arranged in a row at equal distances D along the longitudinal direction at one end side of the common head 5. In this embodiment, the longitudinal direction of the common head 5 is the same as the scanning direction S relative to the substrate 10.

[0034] A lens 7 serving as an imaging optical system is provided on the underside of the common head 5 to which the emission ends of the multiple dehydrogenation optical fibers 22A are attached. Therefore, each laser beam LB emitted from the emission end of the dehydrogenation optical fiber 22A is focused by the lens 7 to project a dehydrogenation laser beam spot BS having a predetermined diameter dimension onto the surface of the amorphous silicon film 13 of the substrate 10. In this embodiment, the multiple dehydrogenation laser beam spots BS are also set to be at equal distances. Various imaging optical system lenses such as a single lens or a compound lens can be used as the lens 7.

[0035] As shown in Figure 3, the crystallization laser beam irradiation unit 4 is arranged on the other end side of the common head 5 so that the emission side end of the crystallization optical fiber 22B is aligned with the emission side end of the dehydrogenation optical fiber 22A described above.

[0036] 2, a lens 8 as an imaging optical system is disposed on the lower surface side of the common head 5 at a position corresponding to the emission end of the crystallization optical fiber 22B. Therefore, each laser beam LB emitted from the emission end of the crystallization optical fiber 22B is condensed by the lens 8 and projects a crystallization laser beam spot BS having a predetermined diameter dimension on the surface of the amorphous silicon film 13 (13a) of the substrate 10.

[0037] The transport means (not shown) includes a mechanism for transporting the substrate 10 to be subjected to laser annealing treatment at a set speed in the scanning direction S. The transport means may fix the positions of the dehydrogenation laser beam irradiating unit 3 and the crystallization laser beam irradiating unit 4 and transport the substrate 10 in the direction opposite to the scanning direction S, or may fix the position of the substrate 10 and transport the dehydrogenation laser beam irradiating unit 3 and the crystallization laser beam irradiating unit 4 in the scanning direction S.

[0038] 2 and 9, in this embodiment, the beam spot BS of the crystallization laser beam irradiation unit 4 that irradiates the surface of the substrate 10 is disposed upstream in the scanning direction S from the beam spot BS of the dehydrogenation laser beam irradiation unit 3. In Fig. 9, a plurality of white circles indicate beam spots of the dehydrogenation laser beam LB, and a hatched circle indicates a beam spot of the crystallization laser beam. Prior to irradiation with the crystallization laser beam LB from the crystallization laser beam irradiation unit 4, the region L to be modified in the amorphous silicon film 13 on the surface of the substrate 10 is irradiated with a plurality of dehydrogenation laser beams LB from the dehydrogenation laser beam irradiation unit 3.

[0039] 2, the amorphous silicon film (undehydrogenated film) 13 is transformed into an amorphous silicon film (dehydrogenated film) 13a as hydrogen is removed from the film by the passage of the dehydrogenation laser beam irradiating section 3. Then, a polysilicon film (crystallized film) 13b is generated (modified) by the passage of the crystallization laser beam irradiating section 4.

[0040] (Setting of dehydrogenation laser beam irradiation part) In this embodiment, the multiple beam irradiation areas, including the areas in the amorphous silicon film 13 irradiated with the multiple dehydrogenation laser beam spots BS, are set to fall within a dehydrogenation temperature range below the temperature at which a hydrogen explosion occurs due to hydrogen remaining in the amorphous silicon film 13.

[0041] In order to fall within the dehydrogenation temperature range in this way, it is preferable to adjust conditions selected from the number of dehydrogenation laser beams LB, the distance between adjacent dehydrogenation laser beams LB, the scan speed, and the output of the dehydrogenation laser beam LB for the multiple dehydrogenation laser beams LB. In addition, as described above, in order to fall within the dehydrogenation temperature range, the distance between adjacent dehydrogenation laser beams LB along the scan direction S may be adjusted according to at least the scan speed and the output of the dehydrogenation laser beam LB.

[0042] The setting of the distance D between the emission side ends of the dehydrogenation optical fiber 22A is described below. The distance D between the emission side ends of the dehydrogenation optical fiber 22A is set so that the multiple beam irradiated areas including the to-be-modified area L irradiated with the multiple dehydrogenation laser beam spots BS in the amorphous silicon film 13 are within a dehydrogenation possible temperature range below the temperature at which a hydrogen explosion occurs due to hydrogen remaining in the amorphous silicon film 13. Note that instead of the distance D between the emission side ends of the dehydrogenation optical fiber 22A, the distance between the dehydrogenation laser beam spots BS may be set.

[0043] Fig. 6 shows the relationship between the substrate temperature (°C) and the scanning time (t) when only one dehydrogenation optical fiber 22A is used. In Fig. 6, the dashed line A shows the case where the substrate temperature caused by the laser beam LB emitted from one dehydrogenation optical fiber 22A is lower than the temperature region DH where dehydrogenation is possible (for example, a temperature region of about 500°C). In this case, dehydrogenation is insufficient and hydrogen remains in the amorphous silicon film 13, so that a hydrogen explosion occurs due to subsequent laser annealing by the crystallization laser beam irradiation unit 4, and an ablation state is observed.

[0044] Broken line C in FIG. 6 indicates that the substrate temperature rises sharply above the temperature region DH where dehydrogenation is possible, causing hydrogen in the amorphous silicon film 13 to escape to the outside of the film all at once, which is likely to result in a hydrogen explosion.

[0045] 6 indicates that the substrate temperature is in the temperature region DH where the amorphous silicon film 13 can be dehydrogenated, which is an appropriate condition. However, since the solid line B uses only one dehydrogenation optical fiber 22A, it takes a long time to dehydrogenate the substrate 10 having many regions L to be modified set on the surface of the amorphous silicon film 13. For this reason, a dehydrogenation furnace has conventionally been used in the dehydrogenation step of the amorphous silicon film 13, and the entire substrate 10 is placed in the dehydrogenation furnace and heated at a temperature of about 500° C. for 1 to 2 hours.

[0046] Fig. 5 shows the relationship between the number of fibers and the scan speed (mm / sec) when multiple dehydrogenation optical fibers 22A are used. This result was obtained when the dehydrogenation optical fiber 22A controlled the lighting of 24 blue semiconductor lasers LD1 to LD24. As shown in Fig. 5, a proportional relationship was observed between the number of fibers and the scan speed. In other words, if we assume that the scan speed at which dehydrogenation can be performed with one dehydrogenation optical fiber 22A is 1, it can be seen that when 24 dehydrogenation optical fibers 22A are used, the scan speed at which dehydrogenation can be performed is approximately 24 times faster.

[0047] In this way, by increasing the number of dehydrogenation optical fibers 22A, it is possible to increase the irradiation time per scan and to set a faster scan speed at which dehydrogenation can be performed, which makes it possible to significantly reduce the time required for dehydrogenation per TFT substrate (substrate 10), i.e., the tact time.

[0048] When using two laser beams, a dehydrogenation laser beam and a crystallization laser beam, simultaneously in one laser annealing device, it was difficult to align the conditions for the two, which have significantly different required outputs. It was also difficult to match the dehydrogenation process, which requires a slower scan speed to ensure dehydrogenation, with the crystallization process, which has a significantly faster scan speed.

[0049] As described below, in this embodiment, as an example, by setting the distance D between the output ends of the dehydrogenation optical fiber 22A, it is possible to efficiently use laser beams for two purposes, a dehydrogenation laser beam and a crystallization laser beam.

[0050] As described above, when the emission end portions of a large number of dehydrogenation optical fibers 22A are arranged in a row in the dehydrogenation laser beam irradiation unit 3, the distance D between the emission end portions of the dehydrogenation optical fibers 22A becomes important. Fig. 7 shows a state in which the distance D between two dehydrogenation optical fibers 22A is optimized. The solid line F shown in Fig. 7 indicates that the temperature of the substrate 10 rises rapidly, but the temperature rise between the two dehydrogenation optical fibers 22A subsides and an approximately constant equilibrium state is maintained.

[0051] By setting such a temperature equilibrium state to be the dehydrogenation temperature (temperature region DH where dehydrogenation is possible), it is possible to control the dehydrogenation state at a constant rate even if the scan speed is increased. The laser annealing apparatus 1 according to this embodiment enables good dehydrogenation at a high speed while suppressing hydrogen explosion, compared to the case where one dehydrogenation optical fiber 22A shown in Fig. 6 is used.

[0052] 7 indicates the case where the number of dehydrogenation optical fibers 22A is increased. In this way, by setting the conditions of one dehydrogenation optical fiber 22A with appropriate conditions and the adjacent dehydrogenation optical fibers 22A in the same manner, the distance D between the output side ends of the dehydrogenation optical fibers 22A may be adjusted so that the temperature of the substrate 10 in the area irradiated with the multiple dehydrogenation laser beams LB is in equilibrium.

[0053] Parameters used for such adjustment include the distance D between the emission end portions of the dehydrogenation optical fibers 22A, the scan speed, the output (energy density) of the laser beam LB, the diameter of the emission end portion of the dehydrogenation optical fiber 22A, the diameter of the beam spot BS, etc. In this embodiment, these parameters may be adjusted in a composite manner.

[0054] 8 shows a case where the distance D between the output side ends of the dehydrogenation optical fibers 22A is made larger than the distance D between the output side ends of the dehydrogenation optical fibers 22A in Fig. 7. In this case, since the distance D is longer, the temperature profile has a recess in the center E1, lowering the dehydrogenation temperature (temperature region DH where dehydrogenation is possible), resulting in a region where dehydrogenation is not possible in some areas. Furthermore, since there are regions E2 and E3 that are higher than the dehydrogenation temperature (temperature region DH), hydrogen explosions occur in some areas, and an ablation state is observed.

[0055] (Laser annealing method) In the laser annealing method according to the present embodiment, a plurality of continuously oscillated dehydrogenation laser beams LB are irradiated onto the amorphous silicon film 13 prior to the crystallization laser beam LB which moves along a scanning direction S relative to the amorphous silicon film 13 and scans at the same time.

[0056] At this time, the multiple dehydrogenation laser beam spots BS and crystallization laser beam spots BS projected onto the amorphous silicon film 13 in the multiple dehydrogenation laser beams LB are set to be arranged in a row along the scanning direction S. At the same time, the area that has undergone the dehydrogenation process is irradiated with a continuously oscillated crystallization laser beam LB, and the amorphous silicon film 13 is modified into a crystallized film such as a low-temperature polysilicon film or a pseudo single crystal silicon film by irradiating the area that has undergone the dehydrogenation process with the crystallization laser beam LB projected onto the amorphous silicon film 13 in the crystallization laser beam LB.

[0057] In this laser annealing method, the multiple beam irradiated region including the region on the amorphous silicon film 13 irradiated with the multiple dehydrogenation laser beam spots BS is set within a temperature range where dehydrogenation is possible below the temperature at which a hydrogen explosion occurs due to hydrogen remaining in the amorphous silicon film 13. Specifically, it is preferable to adjust conditions selected from the number of the multiple dehydrogenation laser beams LB, the distance between adjacent dehydrogenation laser beams LB, the scan speed, and the output of the dehydrogenation laser beam LB. More practically, the distance between adjacent dehydrogenation laser beams LB along the scan direction S may be adjusted in accordance with at least the scan speed and the output of the dehydrogenation laser beam LB.

[0058] (effect) According to the laser annealing apparatus 1 and the laser annealing method of the present embodiment having the above-mentioned configuration, it is possible to shorten the tact time required to reform the amorphous silicon film 13 into a crystallized film (low-temperature polysilicon) by laser annealing. That is, in this embodiment, the dehydrogenation process, which has a narrow processing temperature range compared to the crystallization process, which has a wide processing temperature range, can be stably performed using multiple dehydrogenation optical fibers 22A to avoid hydrogen explosion and insufficient dehydrogenation, and therefore the scanning speed can be dramatically increased as shown in FIG. 5.

[0059] Furthermore, according to the laser annealing apparatus 1 and the laser annealing method of the present embodiment, a dehydrogenation furnace is not used, so that space saving of the apparatus can be achieved.

[0060] [Second embodiment] As shown in Fig. 14 to Fig. 16, the laser annealing apparatus 1A according to the second embodiment of the present invention has a configuration in which the common head 5 according to the above embodiment is separated into a dehydrogenation head 5A and a crystallization head 5B, and other configurations are the same as those of the laser annealing apparatus 1 according to the above embodiment. A dehydrogenation optical fiber 22A is connected to the dehydrogenation head 5A. A crystallization optical fiber 22B is connected to the crystallization head 5B.

[0061] The laser annealing apparatus 1A shown in Figures 14 to 16 can set the distance between the dehydrogenation head 5A and the crystallization head 5B to any desired distance using an adjustment means (not shown), and the timing of each anneal can be adjusted when the apparatus is in use.

[0062] [Mechanism of crack generation during the crystallization process after the dehydrogenation process] In each of the above-mentioned embodiments, in order to ensure a sufficient dehydrogenation time in the dehydrogenation step, it is desirable to provide a plurality of beam spots by a plurality of dehydrogenation laser beams along the scanning direction S, but the area in the surface layer of the substrate 10 where the dehydrogenation step is performed is very narrow. As described above, since the dehydrogenation treatment with the dehydrogenation laser beam is a local modification of the film quality, depending on the film structure (layered structure) to which the dehydrogenation laser beam is irradiated, there is a risk that cracks will occur in the crystallized film (low-temperature polysilicon film or pseudo single crystal silicon film) in the annealing step by irradiation with the crystallization laser beam after the dehydrogenation step.

[0063] 17(a), 17(b), and 17(c) are diagrams of reference examples showing the cause of crack generation in the crystallization process after the above-mentioned dehydrogenation process. FIG. 17(a), 17(b), and 17(c) are diagrams in which a plan view of the substrate 10, a diagram showing the dose of the dehydrogenation laser beam in the irradiation area, and a diagram showing a cross section of the surface layer of the substrate 10 are arranged relative to one another. Here, the dose means the cumulative dose of the dose. The surface layer of the substrate 10 is composed of an undercoat film 12 made of a silicon nitride film and an amorphous silicon film 13 formed thereon. The undercoat film 12 may be composed of a silicon oxide film laminated on a silicon nitride film, but in the explanation of this mechanism, a silicon nitride film having the same hydrogen-containing properties as the amorphous silicon film 13 is used. The diagrams of the irradiation dose shown in Figures 17(a), 17(b), and 17(c) show an image of the total accumulated amount of irradiation dose before the dehydrogenation step, during the dehydrogenation step, and during the crystallization step.

[0064] The plan view of the substrate 10 in Fig. 17(a) illustrates a layout in which a plurality of circular dehydrogenation laser beam spots BS1 are arranged along the scanning direction S using a plurality of optical fibers with circular cross sections. The diameter of this dehydrogenation laser beam spot BS1 is set to W, which is set to be the same as the width dimension W of the crystallization laser beam spot BS2 shown in Fig. 17(c). Note that the irradiation amount shown in Fig. 17(a) is set to a value of 0 in the state before the start of irradiation with the dehydrogenation laser beam spot BS1 arranged as above. Note that in explaining the mechanism of crack generation, the number of dehydrogenation laser beam spots BS1 of the dehydrogenation laser beam is set to three.

[0065] FIG. 17(b) shows the state of the dehydrogenation process. In the surface layer of the substrate 10, a dehydrogenation region Adh is formed in a band shape along the scanning direction S, where dehydrogenation is performed as the dehydrogenation laser beam spot BS1 passes. The width of this dehydrogenation region Adh is equal to or slightly wider than the width (W) of the region where the diameter W of the dehydrogenation laser beam spot BS1 passes. The irradiation amount S1 in this state has a Gaussian distribution. At this time, the center M in the width direction of the dehydrogenation region Adh is in a state where dehydrogenation has progressed most, and the further away from the center M of the dehydrogenation region Adh, the less dehydrogenation has progressed. The degree of dehydrogenation corresponds to the amount of hydrogen vacancy in the surface layer of the substrate 10, so that the film density decreases toward the center M of the surface layer, as shown by the thick arrow in the figure. Therefore, stress is concentrated at the center portion M of the amorphous silicon film 13 (dehydrogenated film 13a) and the underlying base film 12 (silicon nitride film) thereunder.

[0066] In this way, when the crystallization annealing, that is, the irradiation with the crystallization laser beam spot BS2 is performed in the same trajectory as the dehydrogenation laser beam spot BS1, in the state where the stress is concentrated in the central portion M, a crystallized region Acr is formed. The irradiation amount is indicated by S2. At this time, in the process of heating by the crystallization laser beam and then cooling, the film state changes in the direction in which the above-mentioned stress is relaxed, and as a result, it is considered that a crack CR as shown in FIG. 17(c) occurs in the central portion M of the polysilicon film (crystallized film) 13b and the base film 12.

[0067] [Variation 1] 18(a), 18(b), and 18(c) show a modified example 1 that can be applied to the above-mentioned first and second embodiments of the present invention. As shown in FIG. 18(b) and FIG. 18(c), in this modified example 1, the diameter dimension of the dehydrogenation laser beam spot BS1 is set longer than that of the reference example, and the width dimension W2 of the crystallization laser beam spot BS2 is set shorter than the diameter dimension W1 of the dehydrogenation laser beam spot BS1. As shown in FIG. 18(a), this modified example 1 shows a layout in which two dehydrogenation laser beam spots BS1 are arranged along the scanning direction S. FIG. 18(a) shows a state before the dehydrogenation step is performed. The configuration of the substrate 10 in this modified example 1 is the same as that of the substrate 10 shown in FIG. 17.

[0068] FIG. 18(b) shows a state in which the dehydrogenation process is being performed. In this state, the integrated dose S3 at the position indicated by XY has a Gaussian distribution. At this time, inside the substrate 10, stress is concentrated in a central portion M near the boundary between the amorphous silicon film 13 (dehydrogenated film 13a) and the underlying film 12 (silicon nitride film) therebelow, reflecting the above-mentioned Gaussian distribution. As shown in FIG. 18(b), the region of the substrate 10 through which the dehydrogenation laser beam spot BS1 has passed becomes a dehydrogenation region Adh. This dehydrogenation region Adh is slightly wider toward the outside in the width direction than the region through which the dehydrogenation laser beam spot BS1 has passed. When the dose S3 of this dehydrogenation region Adh is compared with the dose S1 of the reference example shown in FIG. 17(b), the distribution is the same as in the reference example in that the amount of hydrogen vacancy in the central portion M is large, with a Gaussian distribution. However, the curve of the dose S3 in the central portion M is gentler than that in the reference example, and therefore the concentration of stress in the central portion M can be alleviated.

[0069] 18(c), a rectangular crystallization laser beam spot BS2 is scanned in a scanning direction S so that its center line coincides with the center line of the dehydrogenation region Adh formed in the dehydrogenation process. By performing the crystallization process in a state in which the stress concentration in the center part M of the dehydrogenation region Adh is relaxed, the occurrence of cracks CR can be suppressed.

[0070] 18(b), the curve of the region corresponding to the vicinity of the central portion M in the integrated dose S3 is relaxed to be gentle. This makes it possible to avoid stress concentration in the central portion M of the substrate 10, and suppress the occurrence of cracks CR during the heating and cooling processes associated with the crystallization process.

[0071] [Variation 2] 19(a), 19(b), and 19(c) show modified example 2, in which the dehydrogenation laser beam spot BS1 and the crystallization laser beam spot BS2 are rectangular, and the width of the crystallization laser beam spot BS2 is set shorter than the width of the dehydrogenation laser beam spot BS1. The irradiation amount in the dehydrogenation process is indicated by S5, and the irradiation amount in the crystallization process is indicated by S6.

[0072] In this modification 2, as shown in Fig. 19(b), as the dehydrogenation laser beam spot BS1 passes, the dose S5 has a dose distribution closer to a top hat shape than the dose S1 of the reference example shown in Fig. 17(b). Therefore, in the crystallization step, the degree to which the film state changes in the direction in which the stress accumulated in the dehydrogenation step is relaxed is small, so that it is possible to prevent cracks CR from occurring in the polysilicon film (crystallized film) 13b and the base film 12.

[0073] [Variation 3] 20(a), 20(b), and 20(c) show modified example 3 applied to the first and second embodiments of the present invention. In this modified example 3, the row of dehydrogenation laser beam spots BS1 in the dehydrogenation step is sequentially shifted in a direction perpendicular to the scanning direction S as shown in FIG. 20(b) to perform multiple scans (three times in this modified example) to form a dehydrogenation region Adh wider than the crystallization laser beam spot BS2. FIG. 20(a) shows the state after the first dehydrogenation step, and the dose is S7. The curve of this dose S7 has a Gaussian distribution and changes sharply in the width direction, but as shown in FIG. 20(b), it becomes the dose S7 after three scans (three rows). This dose S7 has a gentle distribution overall, and therefore, as in the above-described variant example 2, the degree to which the film state changes in the direction in which the stress accumulated in the dehydrogenation process is alleviated is small, thereby making it possible to prevent cracks CR from occurring in the polysilicon film (crystallized film) 13b and the base film 12.

[0074] [Variation 4] 21(a), 21(b), and 21(c) show a modified example 4 applied to the first and second embodiments of the present invention. In this modified example 3, the row of dehydrogenation laser beam spots BS1 in the dehydrogenation process is scanned three times along the same trajectory as shown in FIG. 20(b) to form a dehydrogenation region Adh wider than the crystallization laser beam spot BS2. FIG. 21(a) shows the state after the first dehydrogenation process, and the dose is S9. The curve of this dose S9 has a Gaussian distribution in a narrow width region (width equivalent to W) with a steep change in the width direction, but as shown in FIG. 21(b), it becomes the dose S10 after multiple scans. At this time, the width of the dehydrogenation region Adh becomes much wider than the diameter dimension W of the dehydrogenation laser beam spot BS1. This dose S10 has a gentle distribution over the entire wide width (width W of the dehydrogenation region Adh). That is, the central portion M of the substrate 10 approaches a state where almost all hydrogen has been removed (saturated state), and this saturated state also spreads to the peripheral portion. In addition, in this modification 4, as in the above-mentioned modification 1, by irradiating the crystallization laser beam spot BS2 having a narrow width dimension, the region where more hydrogen has been removed is crystallized and annealed, and the degree to which the film state changes in the direction in which the stress accumulated in the dehydrogenation process is relaxed is small. Therefore, it is possible to prevent cracks CR from occurring in the polysilicon film (crystallized film) 13b and the base film 12.

[0075] [Variation 5] 22(a) and 22(b) show a fifth modified example applied to the first and second embodiments of the present invention. In this fifth modified example, three rows of dehydrogenation laser beam spots are arranged by shifting them in a direction perpendicular to the scanning direction, and the rows are arranged alternately in sequence. As shown in FIG. 22(a), the rows of dehydrogenation laser beam spots are composed of a row of a plurality of dehydrogenation laser beam spots BS11, a row of a plurality of dehydrogenation laser beam spots BS12, and a row of a plurality of dehydrogenation laser beam spots BS13. The dehydrogenation laser beam spots in each row are arranged at a distance of d1 in the scanning direction S. Moreover, the rows of dehydrogenation laser beam spots are arranged at a distance of d2 in a direction perpendicular to the scanning direction S. Moreover, the radii of the dehydrogenation laser beam spots BS11, BS12, and BS13 are all set to the same dimension r. By appropriately adjusting these distances, the size of the overlapping portion P of the dehydrogenation laser beam spots with respect to the scanning direction S can be determined. By adjusting this overlapping portion P, it is possible to adjust the irradiation amount S12 of each portion in the dehydrogenation region. In this modification 5, the dehydrogenation process can be completed in one scan, without repeating the dehydrogenation process multiple times while shifting the row of dehydrogenation laser beam spots BS1 in a direction perpendicular to the scanning direction S as in the above-mentioned modification 3. When crystallization is to be performed in a relatively wide region, the dehydrogenation process may be repeated several times along the scanning direction S at any time while shifting in a direction perpendicular to the scanning direction S with the rows of dehydrogenation laser beam spots BS11, BS12, and 13 configured in this modification 5 combined integrally.

[0076] [Other embodiments] Although the embodiment of the present invention has been described above, the description and drawings forming a part of the disclosure of the embodiment should not be understood as limiting the present invention. From this disclosure, various alternative embodiments, examples and operating techniques will become apparent to those skilled in the art.

[0077] In the above embodiment, the blue semiconductor laser LD25 is used as the crystallization light source, but it is possible to use various lasers such as other semiconductor lasers, solid-state lasers, liquid lasers, and gas lasers.

[0078] In the above embodiment, the dehydrogenation laser beam irradiating units 3 and the crystallization laser beam irradiating units 4 are configured in one row, but such configurations may be arranged in a plurality of rows in parallel.

[0079] In the above embodiment, low-temperature polysilicon is formed as the crystallized film, but a pseudo single-crystal silicon film may be formed.

[0080] In the above embodiment, the substrate 10 having a structure applicable to a top gate type as shown in Fig. 10 is used, but a substrate 10A having a structure applicable to a bottom gate type as shown in Fig. 11 may be used. This substrate 10A has a structure in which a plurality of gate lines 16 patterned with copper (Cu), other metal wiring patterns, a silicon oxide film (SiO2) 15, a silicon nitride film (Si3N4) 14, and an amorphous silicon film 13 are sequentially laminated on a glass substrate 11. In this structure, the silicon nitride film 14 may contain a large amount of hydrogen, but the laser annealing apparatus 1 according to this embodiment makes it possible to appropriately remove hydrogen from the silicon nitride film 14 as well as from the amorphous silicon film 13.

[0081] In the above embodiment, the dehydrogenation light source unit 2A is configured to include 24 blue semiconductor lasers LD1 to LD24 as multiple dehydrogenation light sources, but several hundred blue semiconductor lasers may be arranged in a row. In recent years, TFT substrates have become larger, so it is effective to increase the number of blue semiconductor lasers in order to increase the scanning speed.

[0082] In the above embodiment, the emission side end of one crystallization optical fiber 22B is disposed in the crystallization laser beam irradiation unit 4, but the emission side end of a plurality of crystallization optical fibers 22B may be disposed in the crystallization laser beam irradiation unit 4. In addition, the shape of the emission side end of the crystallization optical fiber 22B may be rectangular.

[0083] In the above embodiment, as shown in FIG. 12, it is also possible to form low-temperature polysilicon only in the locations where TFTs are to be formed on a substrate 10B used for a backlight. In this case, there is no need to perform full-surface annealing using a conventional excimer laser device, and therefore the tact time can be reduced.

[0084] Also, like a substrate 10C shown in FIG. 13, it is possible to form low-temperature polysilicon only in drive circuit formation regions 19A and 19B on the periphery of an amorphous silicon TFT formation region 18. In FIG. [Explanation of symbols]

[0085] Adh dehydrogenation area Acr crystallization region BS Beam Spot BS1 Dehydrogenation laser beam spot BS2 Crystallization laser beam spot CR Crack D Distance L Planned modification area LB Laser Beam LD1~LD24 Blue semiconductor lasers (light source for dehydrogenation) LD25 Blue semiconductor laser (light source for crystallization) M center 1 Laser annealing equipment 2. Semiconductor laser array 2A Dehydrogenation Light Source Unit 2B Crystallization light source unit 3. Dehydrogenation laser beam irradiation section 4. Crystallization laser beam irradiation section 5 Common Head 5A Dehydrogenation Head 5B Crystallization Head 7, 8 Lenses 10, 10A, 10B, 10C Board 11 Glass substrate 12 Base film 13 Amorphous silicon film (undehydrogenated film) 13a Amorphous silicon film (dehydrogenated film) 13b Polysilicon film (crystallized film) 14 Silicon nitride film 15 Silicon oxide film 16 Gate Line 17 TFT 18 Amorphous silicon TFT formation area 19A, 19B Drive circuit formation area 21 Coupling Lens 22A Optical fiber for dehydrogenation 22B Crystallization Optical Fiber

Claims

1. A laser annealing apparatus comprising: a crystallization laser beam irradiation unit which irradiates a continuously oscillated crystallization laser beam toward an amorphous silicon film formed on a substrate; a crystallization laser beam spot of the crystallization laser beam projected onto the amorphous silicon film moves along a scanning direction relative to the amorphous silicon film to modify the amorphous silicon film into a crystallized film, a dehydrogenation laser beam irradiating unit that moves along a scanning direction relative to the amorphous silicon film together with the crystallization laser beam irradiating unit and irradiates a plurality of dehydrogenation laser beams that are continuously oscillated toward the amorphous silicon film prior to the crystallization laser beam; a plurality of dehydrogenation laser beam spots projected onto the amorphous silicon film in the plurality of dehydrogenation laser beams and the crystallization laser beam spot are arranged in a row along the scanning direction; A laser annealing apparatus comprising:

2. a plurality of beam irradiated regions including the regions irradiated with the plurality of dehydrogenation laser beam spots in the amorphous silicon film are within a temperature range in which dehydrogenation is possible, the temperature being lower than a temperature at which a hydrogen explosion occurs due to hydrogen remaining in the amorphous silicon film; For the plurality of dehydrogenation laser beams, a condition selected from the number of the dehydrogenation laser beams, the distance between adjacent dehydrogenation laser beams, the scan speed, and the output of the dehydrogenation laser beams is adjusted.

2. The laser annealing apparatus according to claim 1.

3. The crystallization laser beam irradiation unit guides laser light from a crystallization light source through a crystallization optical fiber, The dehydrogenation laser beam irradiation unit guides laser light from each of a plurality of dehydrogenation light sources via a dehydrogenation optical fiber.

2. The laser annealing apparatus according to claim 1.

4. The crystallization laser beam irradiation unit and the dehydrogenation laser beam irradiation unit are integrally provided.

2. The laser annealing apparatus according to claim 1.

5. the crystallization light source and the dehydrogenation light source are blue semiconductor diodes; 4. The laser annealing apparatus according to claim 3.

6. The crystallized film is a low-temperature polysilicon film or a pseudo single-crystalline silicon film; 2. The laser annealing apparatus according to claim 1.

7. a plurality of dehydrogenation laser beam spots projected on the amorphous silicon film by the plurality of dehydrogenation laser beams are shifted in a direction perpendicular to the scanning direction to perform irradiation a plurality of times; 2. The laser annealing apparatus according to claim 1.

8. the plurality of dehydrogenation laser beam spots form dehydrogenation regions on the substrate in an area wider than a width of the crystallization laser beam spots; 2. The laser annealing apparatus according to claim 1.

9. The dehydrogenation laser beam spots are arranged in a row along the scanning direction, the row being spaced a predetermined distance apart in a direction perpendicular to the scanning direction.

9. The laser annealing apparatus according to claim 8.

10. A laser annealing method for irradiating an amorphous silicon film formed on a substrate with a crystallization laser beam, and for modifying the amorphous silicon film into a crystallized film by moving a crystallization laser beam spot of the crystallization laser beam projected onto the amorphous silicon film along a scanning direction relative to the amorphous silicon film, comprising: a scanning direction of the amorphous silicon film along with the crystallization laser beam, and a plurality of dehydrogenation laser beams are irradiated onto the amorphous silicon film prior to the crystallization laser beam; a plurality of dehydrogenation laser beam spots projected onto the amorphous silicon film in the plurality of dehydrogenation laser beams and the crystallization laser beam spot are arranged in a row along the scanning direction; 1. A laser annealing method comprising the steps of:

11. a condition selected from the number of the dehydrogenation laser beams, the distance between adjacent dehydrogenation laser beams, the scan speed, and the output of the dehydrogenation laser beam is adjusted so that a multiple beam irradiation region including a region on the amorphous silicon film irradiated with the multiple dehydrogenation laser beam spots falls within a temperature range where dehydrogenation is possible below a temperature at which hydrogen remaining in the amorphous silicon film causes a hydrogen explosion; The laser annealing method according to claim 10.

12. A blue semiconductor diode is used as a light source of the crystallization laser beam and the dehydrogenation laser beam, and the crystallization film is a low-temperature polysilicon film or a pseudo single crystal silicon film. The laser annealing method according to claim 10.

13. a plurality of dehydrogenation laser beam spots projected onto the amorphous silicon film by the plurality of dehydrogenation laser beams are shifted in a direction perpendicular to the scanning direction and irradiated a plurality of times; The laser annealing method according to claim 10.

14. the plurality of dehydrogenation laser beam spots form dehydrogenation regions on the substrate in an area wider than a width of the crystallization laser beam spots; The laser annealing method according to claim 10.

15. The dehydrogenation laser beam spots are arranged in a row along the scanning direction, the row being shifted a predetermined distance in a direction perpendicular to the scanning direction. The laser annealing method according to claim 14.

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