Laser annealing system and laser annealing method

Abstract

To provide an annealing system and a method for avoiding thermal influence on a material and a structure of a lower layer even for a material having poor heat resistance without giving thermal damage to a substrate.SOLUTION: A laser annealing system 10A that anneals a thin film on a substrate by irradiating the thin film with pulsed laser light includes a laser apparatus 12 that outputs pulsed laser light, an emission optical system 70 that is an optical system that emits pulsed laser light to the thin film, and a laser annealing control processor 100 and a laser control processor 28 that are processors that control emission of pulsed laser light to the same location of the thin film by performing burst emission in which a burst period in which the pulsed laser light is continuously emitted and a suppression period in which continuous emission of the pulsed laser light is suppressed are repeated.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to a laser annealing system and a laser annealing method. [Background technology]

[0002] Indium tin oxide (ITO) is used in flat panel displays and solar cells that use glass substrates, as well as in transparent electrode films. When heat-treated (annealed), ITO crystallizes from an amorphous state, improving its electrical conductivity and carrier mobility as an electrode.

[0003] Transparent electrode films are also expected to be applied to optical integrated elements, which will enable more sophisticated devices. Optical integrated elements are realized by forming active elements such as sensors, amplifier circuits, and CMOS (Complementary Metal Oxide Semiconductor) circuits on the top layer of an integrated circuit device. Therefore, there is a demand for technology to manufacture higher quality transparent electrode films.

[0004] Furthermore, with the diversification of information terminal devices, there is a growing demand for small, lightweight, low-power-consumption, and freely bendable flexible displays, flexible computers, and flexible solar cells. This has led to a demand for the establishment of technology to form high-quality transparent electrode films on plastic substrates such as PET (Polyethylene terephthalate).

[0005] To form high-quality transparent electrode thin films on glass substrates, integrated circuits, or plastic substrates, it is necessary to crystallize the transparent electrode film without thermally damaging these substrates. While the required processing temperature for glass substrates used in displays is 400°C, for integrated circuits and PET plastic substrates, a processing temperature of 150°C or less is required.

[0006] Furthermore, in alloying metal films used in magnetic sensor elements, etc., a thin metal film is formed on a magnetic shield substrate and then annealed. However, because some magnetic shield substrates are made of materials with poor heat resistance, it is necessary to heat only the surface layer where alloying is desired.

[0007] In addition to transparent electrodes and magnetic sensor elements, annealing is also used to reduce the resistance of electrode wiring in LSIs (Large Scale Integrated circuits), restore crystallinity in semiconductor processes, and diffuse dopants, and there are processes in which it is desirable to avoid thermal effects depending on the underlying material and structure.

[0008] Laser annealing is a technique used to anneal only the surface layer without thermally damaging the underlying substrate. This method uses pulsed ultraviolet laser light that is absorbed by the upper semiconductor thin film to prevent damage to the substrate due to thermal diffusion.

[0009] When the semiconductor thin film is silicon, a XeF excimer laser with a wavelength of 351 nm, a XeCl excimer laser with a wavelength of 308 nm, a KrF excimer laser with a wavelength of 248 nm, etc. These ultraviolet gas lasers have the advantage of lower coherence of laser light compared to solid-state lasers, excellent energy uniformity on the laser light irradiated surface, and the ability to uniformly anneal a wide area with high pulse energy. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2020-202242 [Patent Document 2] U.S. Patent Application Publication No. 2022 / 0072663 Overview

[0011] A laser annealing system according to one aspect of the present disclosure is a laser annealing system that anneals a thin film on a substrate by irradiating the thin film with pulsed laser light, and includes a laser device that outputs pulsed laser light, an optical system that irradiates the thin film with the pulsed laser light, and a processor that controls the irradiation of the pulsed laser light at the same location on the thin film by performing burst irradiation that repeats a burst period in which the pulsed laser light is continuously irradiated and a suppression period in which the irradiation of the pulsed laser light is suppressed.

[0012] A laser annealing method according to another aspect of the present disclosure is a laser annealing method for annealing a thin film on a substrate by irradiating the thin film with pulsed laser light, the method including: outputting pulsed laser light from a laser device; irradiating the thin film with the pulsed laser light by an optical system; and performing burst irradiation that alternates between a burst period in which the pulsed laser light is continuously irradiated and a suppression period in which the irradiation of the pulsed laser light is suppressed, thereby irradiating the same location of the thin film with the pulsed laser light. [Brief explanation of the drawings]

[0013] Some embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 is a graph showing an example of burst operation of a laser device. [Figure 2] FIG. 2 shows a schematic diagram of an exemplary laser annealing system configuration. [Figure 3] FIG. 3 is a graph showing the pulse energy of the pulsed laser light irradiated onto the ITO thin film in the laser annealing process according to Comparative Example 1, and the transition of the temperature near the surface of the ITO thin film (thin film surface temperature) due to the laser irradiation. [Figure 4] FIG. 4 is a graph showing an example of the pulse energy of the pulsed laser light irradiated onto the ITO thin film in the laser annealing process according to Comparative Example 2, the change in the thin film surface temperature due to the laser irradiation, and the change in the temperature near the interface between the ITO film and the substrate (interface temperature). [Figure 5]FIG. 5 is a graph showing an example of burst irradiation performed by the laser annealing system according to the first embodiment, and an example of changes in the thin film surface temperature and interface temperature due to the burst irradiation. [Figure 6] FIG. 6 is a graph showing an example of burst irradiation performed by the laser annealing system according to the first modification of the first embodiment, and an example of changes in the thin film surface temperature and interface temperature during the burst irradiation. [Figure 7] FIG. 7 shows a schematic configuration of a laser annealing system according to a second modification of the first embodiment. [Figure 8] FIG. 8 is an enlarged side view of the cooling plate and the object to be irradiated shown in FIG. [Figure 9] FIG. 9 is a timing chart showing an example of control of the cooling operation. [Figure 10] FIG. 10 is a graph showing the change in the surface temperature of a thin film due to continuous irradiation with pulsed laser light. [Figure 11] FIG. 11 is an explanatory diagram that schematically shows the process of crystallization of a thin film by continuous irradiation with pulsed laser light shown in FIG. [Figure 12] FIG. 12 is a graph showing an example of a burst pattern and an example of the transition of the thin film surface temperature with burst irradiation. [Figure 13] FIG. 13 is an explanatory diagram that schematically shows the process of crystallization of a thin film by burst irradiation shown in FIG. [Figure 14] FIG. 14 shows a schematic diagram of the crystal grains produced by the burst irradiation shown in FIG. [Figure 15] FIG. 15 is a graph showing an example of burst irradiation of the laser annealing system according to the second embodiment and an example of transition of the thin film surface temperature during the burst irradiation. [Figure 16] FIG. 16 is an explanatory diagram that schematically shows the process of crystallization of a thin film by burst irradiation shown in FIG. [Figure 17] FIG. 17 shows an example of burst irradiation according to Modification 1 of Embodiment 2, and an example of the transition of the thin film surface temperature accompanying the burst irradiation. [Figure 18]FIG. 18 shows an example of burst irradiation according to Modification 2 of Embodiment 2, and an example of the transition of the thin film surface temperature accompanying the burst irradiation. [Figure 19] FIG. 19 shows a schematic configuration of a laser annealing system according to the third embodiment. [Figure 20] FIG. 20 is a perspective view showing an example of a roll-to-roll type transfer mechanism applied to a laser annealing system. [Figure 21] FIG. 21 is an explanatory diagram showing the configuration and operation of a laser annealing system according to Modification 1 of Embodiment 3. In FIG. [Figure 22] FIG. 22 schematically shows the configuration of a laser annealing system according to a second modification of the third embodiment. [Figure 23] FIG. 23 shows a schematic configuration of a laser annealing system according to the fourth embodiment. [Figure 24] FIG. 24 is a graph showing an example of burst irradiation achieved by a laser annealing system. Embodiment

[0014] -table of contents- 1. Explanation of terms 2. Example of a laser annealing system 2.1 Configuration 2.2 Operation 3. Assignment 1 4. Embodiment 1 4.1 Configuration 4.2 Operation 4.3 Actions and Effects 4.4 Modification 1 of the First Embodiment 4.4.1 Configuration 4.4.2 Operation 4.4.3 Actions and Effects 4.5 Modification 2 of Embodiment 1 4.5.1 Configuration 4.5.2 Operation 4.5.3 Actions and Effects 5. Task 2 6. Embodiment 2 6.1 Configuration 6.2 Operation 6.3 Actions and Effects 6.4 Modification 1 of Embodiment 2 6.5 Modification 2 of Embodiment 2 6.6 Other 7. Embodiment 3 7.1 Configuration 7.2 Operation 7.3 Examples of transport mechanisms 7.4 Actions and Effects 7.5 Modification 1 of Embodiment 3 7.5.1 Configuration 7.5.2 Operation 7.5.3 Actions and Effects 7.6 Modification 2 of Embodiment 3 7.6.1 Configuration 7.6.2 Operation 7.6.3 Actions and Effects 8. Embodiment 4 8.1 Configuration 8.2 Operation 8.3 Actions and Effects 9. Applications other than ITO thin films 10. About the Processor 11.Other

[0015] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below show some examples of the present disclosure and do not limit the content of the present disclosure. Furthermore, not all of the configurations and operations described in each embodiment are necessarily essential as the configurations and operations of the present disclosure. Note that the same components are given the same reference symbols, and redundant explanations will be omitted.

[0016] 1. Explanation of terms FIG. 1 is a graph showing an example of burst operation of a laser device. A laser device may output pulsed laser light by burst operation. Burst operation is an operation that alternates between burst periods during which pulsed laser light is continuously output at a constant repetition frequency for a certain period of time and pause periods during which no pulsed laser light is output for a predetermined period of time. During the burst periods, pulsed laser light is output from the laser device. During the pause periods, the output of pulsed laser light is stopped.

[0017] The burst pattern, which is a repeating pattern of burst periods and rest periods, is defined by data including one or more of the pulse energy, repetition frequency, number of pulses and length of rest periods, and number of bursts during the burst period. The burst pattern is specified by an external device such as an exposure machine or a processing machine.

[0018] The burst signal is a signal that is ON during a burst period and OFF during a pause period, and is a signal that specifies a burst operation.

[0019] 2. Example of a laser annealing system 2.1 Configuration 2 shows a schematic configuration of an exemplary laser annealing system 10. The laser annealing system 10 includes a laser device 12, an optical path 13, and a laser annealing device 14.

[0020] The laser device 12 is a laser device that outputs ultraviolet pulsed laser light. For example, the laser device 12 may be a discharge-pumped laser device that uses F2, ArF, KrF, XeCl, or XeF as a laser medium. Alternatively, the laser device 12 may be a solid-state laser device that outputs ultraviolet wavelengths.

[0021] The laser system 12 includes an oscillator 20, a monitor module 24, a shutter 26, and a laser control processor 28.

[0022] The oscillator 20 includes a chamber 30 , an optical resonator 32 , a charger 36 , and a pulsed power module (PPM) 38 .

[0023] An excimer laser gas is sealed in the chamber 30. The chamber 30 includes a pair of electrodes 43 and 44, an insulating member 45, and windows 47 and 48.

[0024] The optical resonator 32 is composed of a rear mirror 33 and an output coupler (OC) 34. The rear mirror 33 and the OC 34 each have a flat substrate coated with a highly reflective film and a partially reflective film. The chamber 30 is disposed on the optical path of the optical resonator 32.

[0025] The PPM 38 includes a switch 39 and a charging capacitor (not shown). The switch 39 is connected to a signal line that transmits a control signal from the laser control processor 28.

[0026] The charger 36 is connected to the charging capacitor of the PPM 38. The charger 36 receives charging voltage data from the laser control processor 28 and charges the charging capacitor of the PPM 38.

[0027] The monitor module 24 includes a beam splitter 50 and a light sensor 52 .

[0028] The shutter 26 is disposed on the optical path of the pulsed laser light output from the monitor module 24. The optical path of the pulsed laser light is sealed by a housing and an optical path tube 13 (not shown), and may be purged with an inert gas such as N2 gas.

[0029] The optical path tube 13 is a cover that covers the optical path of the pulsed laser light between the exit port of the laser device 12 for the pulsed laser light and the entrance port of the laser annealing device 14 .

[0030] The laser annealing apparatus 14 includes an illumination optical system 70 , a frame 72 , an XYZ stage 74 , a table 76 , and a laser annealing control processor 100 .

[0031] The illumination optical system 70 includes high-reflection mirrors 111, 112, and 113, an attenuator 120, an illumination optical system 130, a mask 140, a projection optical system 142, a window 146, and a housing 150. The illumination optical system 70 is an example of the “optical system” in this disclosure.

[0032] High-reflection mirror 111 is arranged so that the pulsed laser light that has passed through optical path pipe 13 passes through attenuator 120 and is incident on high-reflection mirror 112 .

[0033] Attenuator 120 is disposed on the optical path between high-reflection mirror 111 and high-reflection mirror 112. Attenuator 120 includes two partially reflecting mirrors 121 and 122 and rotation stages 123 and 124 that can change the angle of incidence on each mirror.

[0034] High-reflection mirror 112 is arranged so that the pulsed laser light that has passed through attenuator 120 is incident on high-reflection mirror 113. High-reflection mirror 113 is arranged so that the incident pulsed laser light is incident on fly-eye lens 134 of illumination optical system 130.

[0035] The illumination optical system 130 includes a fly's eye lens 134 and a condenser lens 136. The illumination optical system 130 is arranged to Kohler illuminate the mask 140 with a rectangular beam. The rectangular beam refers to a beam with a rectangular shape in which the light intensity distribution within the beam is uniform.

[0036] The fly-eye lens 134 is disposed, for example, such that the focal plane of the fly-eye lens 134 coincides with the front focal plane of the condenser lens 136. The condenser lens 136 is disposed such that the rear focal plane of the condenser lens 136 coincides with the position of the mask 140.

[0037] The mask 140 is, for example, a photomask in which a pattern of a metal or dielectric multilayer film is formed on a synthetic quartz substrate that transmits ultraviolet light. The mask 140 has, for example, a line and space pattern formed thereon.

[0038] The projection optical system 142 is arranged so that an image of the mask 140 is formed on the surface of the irradiation target 160 through a window 146. The projection optical system 142 is a combination of multiple lenses 143 and 144, and may be a reduction projection optical system.

[0039] The window 146 is disposed on the pulsed laser light path between the projection optical system 142 and the irradiation target 160. The window 146 is disposed in a hole provided in the housing 150 via an O-ring or the like (not shown). The window 146 is a CaF2 crystal or synthetic quartz substrate that transmits excimer laser light, and may be coated with an anti-reflection film on both sides.

[0040] The housing 150 is provided with an N2 gas inlet 152 and an outlet 154. An N2 gas supply source is connected to the inlet 152 via a pipe (not shown). The housing 150 may be sealed with an O-ring or the like to prevent outside air from entering the housing 150.

[0041] An illumination optical system 70 and an XYZ stage 74 are fixed to the frame 72. A table 76 is fixed on the XYZ stage 74. An illumination object 160 is fixed on the table 76. The table 76 is an example of a mounting table on which the illumination object 160 is placed.

[0042] The object to be irradiated 160 may be, for example, a PET substrate coated with an a-ITO thin film.

[0043] 2.2 Operation The laser annealing control processor 100 reads irradiation condition parameters for laser annealing. Specifically, the laser annealing control processor 100 reads the target fluence Fa, target pulse energy Et, number of irradiation pulses Na, and repetition frequency fa when performing laser annealing.

[0044] The laser annealing control processor 100 transmits the target pulse energy Et to the laser control processor 28, and transmits to the laser control processor 28 a light emission trigger Tr1 that corresponds to the number of irradiation pulses Na and the repetition frequency fa.

[0045] The laser control processor 28 receives the target pulse energy Et from the laser anneal control processor 100 .

[0046] The laser control processor 28 receives the light emission trigger Tr1 with the repetition frequency fa and controls the oscillator 20 to oscillate at the repetition frequency fa.

[0047] The pulsed laser light output from the oscillator 20 is sampled by a beam splitter 50 of the monitor module 24, and the pulse energy E is measured by an optical sensor 52. The laser control processor 28 controls the charging voltage of the charger 36 so that the difference ΔE between the pulse energy E and the target pulse energy Et approaches zero.

[0048] The pulsed laser light transmitted through the beam splitter 50 of the monitor module 24 enters the laser annealing device 14 via the optical path pipe 13 .

[0049] The pulsed laser light incident on the laser annealing device 14 is reflected by the high-reflection mirror 111, passes through the attenuator 120 to be attenuated, and is then reflected by the high-reflection mirror 112. At this time, the laser annealing control processor 100 controls the angles of incidence of the two partial reflection mirrors 121 and 122 by the respective rotation stages 123 and 124 so that the fluence at the position of the surface of the irradiated object 160 (the image of the mask 140) becomes the target fluence Fa.

[0050] The pulsed laser light highly reflected by the high-reflection mirrors 112 and 113 is spatially uniformized in light intensity by the illumination optical system 130 and illuminates the mask 140 .

[0051] The pulsed laser light transmitted through the mask 140 is projected onto the surface of the object 160 to be irradiated by the projection optical system 142 .

[0052] The laser annealing control processor 100 controls the XYZ stage 74 so that the image of the mask 140 transferred by the projection optical system 142 is projected at an appropriate position.

[0053] The pulsed laser light is irradiated onto the irradiation object 160 in the area where the transferred image is formed after passing through the projection optical system 142. As a result, the portion of the surface of the irradiation object 160 that is irradiated with the pulsed laser light is annealed.

[0054] An excimer laser can efficiently heat a relatively shallow surface of the irradiated material. Therefore, laser annealing using the laser device 12 can polycrystallize a thin film such as ITO formed on a substrate with a low heat resistance temperature while minimizing the impact on the substrate.

[0055] 3. Assignment 1 Below, we will explain this in detail using an ITO thin film as an example. In the field of laser annealing, there is a demand to shorten processing time and improve the processing amount per unit time (throughput). One possible way to meet this demand is to increase the laser fluence. However, increasing the laser fluence can cause laser ablation of the ITO thin film itself. Damage caused by ablation can cause the ITO thin film to lose not only its conductivity but also its transparency. Therefore, the laser fluence is limited to a value that does not cause laser ablation of the ITO thin film.

[0056] 3 is a graph showing the pulse energy of the pulsed laser light irradiated onto the ITO thin film and the change in temperature near the surface of the ITO thin film due to the laser irradiation in the laser annealing treatment according to Comparative Example 1. The comparative example is a form that the applicant recognizes as being known only by the applicant, and is not a publicly known example that the applicant acknowledges.

[0057] Fig. 3 shows an example of intermittent irradiation with a plurality of pulsed laser beams at predetermined time intervals, with three pulses shown in Fig. 3. The vertical axis of Fig. 3 represents pulse energy or temperature, and the horizontal axis represents time. The temperature Hs near the surface of the ITO thin film (hereinafter referred to as thin film surface temperature Hs) is shown by a solid line, and the pulse energy of the pulsed laser beam is schematically shown by a hatched block.

[0058] To crystallize an amorphous ITO thin film by laser annealing, the surface temperature Hs of the ITO thin film must be raised to a temperature equal to or higher than the crystallization threshold temperature Hcz, and for this purpose, the pulse energy of the pulsed laser beam must be of a certain magnitude. The crystallization threshold temperature Hcz is the temperature at which crystallization occurs and is synonymous with the crystallization temperature.

[0059] On the other hand, when a pulsed laser beam with a high fluence exceeding the ablation threshold of an ITO thin film is irradiated, the ITO thin film itself will undergo ablation. Therefore, the fluence of the pulsed laser beam is limited to a value below the ablation threshold. The ablation threshold is the lower limit of the laser fluence at which laser ablation occurs.

[0060] As shown in Figure 3, the pulse energy of the pulsed laser light irradiated onto the ITO thin film is set to a value less than the threshold energy Eab at which laser ablation does not occur. The threshold energy Eab corresponds to the ablation threshold converted into energy.

[0061] That is, in the laser annealing process according to Comparative Example 1 shown in FIG. 3, the pulse energy of the pulsed laser light is appropriately adjusted to raise the thin film surface temperature Hs to a temperature equal to or higher than the crystallization threshold temperature Hcz within the duration of each pulse, and laser irradiation is performed under fluence conditions that do not cause laser ablation.

[0062] Meanwhile, another method for improving throughput is to increase the repetition rate of laser irradiation. An example is shown in Figure 4. Figure 4 is a graph showing an example of the pulse energy of the pulsed laser light irradiated onto the ITO thin film in the laser annealing process of Comparative Example 2, the change in the thin film surface temperature Hs due to laser irradiation, and the change in the temperature Hi of the interface between the ITO thin film and the substrate (hereinafter referred to as the interface temperature Hi). The interface temperature Hi may be understood to be the substrate temperature near the interface between the ITO thin film and the substrate.

[0063] Figure 4 shows an example of irradiating a pulsed laser beam at a predetermined repetition rate for a predetermined period of time. The vertical axis of Figure 4 represents pulse energy or temperature, and the horizontal axis represents time. As shown in Figure 4, when the pulsed laser beam irradiated onto the ITO thin film is increased in repetition rate, heat accumulates in the ITO thin film, and the thin film surface temperature Hs may be maintained at or above the crystallization threshold temperature Hcz for a long period of time. If this condition continues, crystal nuclei will continue to be generated, resulting in small final crystal grains.

[0064] Furthermore, the heat accumulation effect caused by high repetition rates generates heat not only near the surface of the ITO thin film, but also at the interface between the ITO thin film and the substrate. If heat accumulation continues, the interface temperature Hi can exceed the substrate's damage threshold temperature Hbd, causing substrate damage. The damage threshold temperature Hbd is the temperature at which a substrate will suffer irreversible damage such as surface roughness and thin film peeling, and varies depending on the material.

[0065] Therefore, in addition to the fluence, the repetition frequency of the pulsed laser light is also limited, and the number of irradiations required to achieve crystallization becomes extremely large.

[0066] As described above, when polycrystallizing thin films such as ITO and IGZO films by laser annealing, the throughput was limited, which was particularly noticeable when the substrate was made of a material with low heat resistance, such as PET resin or polycarbonate (PC).

[0067] For this reason, there was a need for a laser annealing technology that would not impede crystal growth, suppress substrate damage, and improve throughput.

[0068] 4. Embodiment 1 4.1 Configuration The configuration of the laser annealing system according to the first embodiment is the same as that of the laser annealing system 10 shown in Fig. 2. In the following description of the first embodiment, the same reference numerals as those in Fig. 2 will be used.

[0069] In the laser annealing system 10 according to the first embodiment, instead of irradiating pulsed laser light at a predetermined repetition rate for a predetermined time, burst irradiation is performed in which burst periods Pb and pause periods Ps are repeated, as shown in Fig. 5. The laser annealing control processor 100 and the laser control processor 28 control the heat input to the irradiated object 16 by adjusting the repetition rate, pulse energy, and number of pulses in the burst period of the burst operation, as well as the length of the pause period.

[0070] That is, the laser annealing control processor 100 and the laser control processor 28 control the heat accumulation in the irradiated object 160 so that the temperature of the surface of the ITO thin film is maintained above the crystallization threshold temperature Hcz as much as possible, while the temperature near the substrate, including the interface between the ITO thin film and the substrate, is maintained below the damage threshold temperature Hbd.

[0071] The irradiation condition parameters of the burst irradiation related to the control of heat accumulation are adjusted depending on the materials and thicknesses of the thin film and the substrate. The laser annealing control processor 100 and the laser control processor 28 are examples of the processors in this disclosure.

[0072] In addition, in the laser annealing system 10, by providing an auxiliary cooling mechanism below the substrate, damage to the substrate due to temperature differences in the thickness direction can be reduced.

[0073] 4.2 Operation The operation of the laser annealing system 10 according to the first embodiment will be described in detail with reference to Fig. 5, focusing on differences from Fig. 4. Fig. 5 is a graph showing an example of burst irradiation performed by the laser annealing system 10 according to the first embodiment, and an example of the transition of the thin film surface temperature Hs and the interface temperature Hi due to the burst irradiation. The vertical and horizontal axes in Fig. 5 are the same as those in Fig. 4.

[0074] 5, the laser annealing system 10 performs burst irradiation in which burst periods Pb during which pulsed laser light is continuously irradiated and pause periods Ps during which the irradiation of the pulsed laser light is stopped are alternately repeated, thereby irradiating the same location of the ITO thin film with pulsed laser light during multiple burst periods. The pause periods Ps are an example of the "suppression period" of the present disclosure.

[0075] The laser annealing control processor 100 and the laser control processor 28 adjust the irradiation conditions of the burst irradiation to control the heat input and heat accumulation to the irradiated object 160, thereby controlling the thin film surface temperature Hs and the interface temperature Hi.

[0076] The irradiation conditions for burst irradiation include parameters such as the pulse energy of the pulsed laser light within the burst period Pb, the repetition frequency, the number of pulses, and the length of the pause period Ps. Note that the number of pulses within the burst period Pb is related to the length of the burst period Pb. The length of the burst period Pb may be used instead of the number of pulses. The laser fluence is set below the ablation threshold, as described in Figure 3.

[0077] As shown in FIG. 5, by continuously irradiating multiple pulses of pulsed laser light within the burst period Pb, the thin film surface temperature Hs and the interface temperature Hi gradually increase during the burst period Pb, and the thin film surface temperature Hs is maintained above the crystallization threshold temperature Hcz for a certain period of time.

[0078] Thereafter, when the pause period Ps begins, the heat input stops, and the thin film surface temperature Hs and the interface temperature Hi gradually decrease during the pause period Ps. During the pause period Ps, the thin film surface temperature Hs may fall below the crystallization threshold temperature Hcz.

[0079] The interface temperature Hi is maintained below the damage threshold temperature Hbd throughout the burst period Pb and the pause period Ps. That is, although the interface temperature Hi gradually rises during the burst period Pb, the burst period Pb ends before it reaches the damage threshold temperature Hbd, and the pause period Ps begins. Thereafter, the burst period Pb and the pause period Ps are repeated.

[0080] 4.3 Actions and Effects The burst irradiation of embodiment 1 allows the thin film surface temperature Hs to be maintained at or above the crystallization threshold temperature Hcz for the required time, minimizing the thermal impact on the substrate, which is the underlying layer. Therefore, embodiment 1 can improve the throughput of the annealing process for ITO thin films and IGZO thin films formed on substrates with low heat resistance, such as PET resin and PC.

[0081] Furthermore, according to embodiment 1, the thin film surface can be laser annealed at a temperature equal to or higher than the crystallization threshold temperature Hcz, and the vicinity of the substrate, including the interface between the ITO thin film and the substrate, can be laser annealed at a temperature lower than the damage threshold temperature Hbd. This makes it possible to efficiently generate and grow crystal nuclei while suppressing substrate damage, and is also expected to improve properties as an electrode material, such as electrical conductivity and mobility.

[0082] 4.4 Modification 1 of the First Embodiment 4.4.1 Configuration The configuration of the laser annealing system according to the first modification of the first embodiment is similar to that of the laser annealing system 10.

[0083] 5, the rest period Ps of burst irradiation is described as the period during which the pulse energy is set to zero and the laser irradiation is stopped, but the pulse energy does not have to be set to zero during the period corresponding to the rest period Ps. That is, instead of the rest period Ps, a low-power period Pd may be used in which pulse laser light adjusted to have a pulse energy lower than that of the burst period Pb is irradiated, as shown in FIG. 6. The low-power period Pd is an example of a "suppression period" in the present disclosure.

[0084] 4.4.2 Operation 6 is a graph showing an example of burst irradiation performed by the laser annealing system 10 according to the first modification of the first embodiment, and an example of the transition of the thin film surface temperature Hs and the interface temperature Hi accompanying the burst irradiation. The vertical and horizontal axes in FIG. 6 are the same as those in FIG. 3. Burst irradiation as in FIG. 6 may be adopted instead of that in FIG. 5.

[0085] 6, the laser annealing control processor 100 and the laser control processor 28 may reduce the pulse energy of the irradiated pulsed laser light in the low power period Pd, which replaces the pause period Ps, to be less than the pulse energy in the burst period Pb, thereby suppressing heat accumulation. Note that in the example of Fig. 6, the pulse energy in the low power period Pd is set so that the thin film surface temperature Hs is substantially maintained at or above the crystallization threshold temperature Hcz during the low power period Pd, but the pulse energy in the low power period Pd may be adjusted so that the thin film surface temperature Hs during the low power period Pd falls below the crystallization threshold temperature Hcz.

[0086] 4.4.3 Actions and Effects According to the first modification of the first embodiment, the degree of freedom in controlling heat accumulation in the irradiation object 160 can be improved by adjusting the pulse energy of the irradiated pulsed laser light in the low output period Pd after the burst period Pb.

[0087] 4.5 Modification 2 of Embodiment 1 4.5.1 Configuration 7 is a schematic diagram showing the configuration of a laser annealing system 10A according to Modification 2 of Embodiment 1. Differences between the configuration shown in FIG. 7 and that shown in FIG.

[0088] The laser annealing system 10A includes a cooling plate 78 on the surface of the table 76 on which the object 160 to be irradiated is placed. The cooling plate 78 may be configured to use a water-cooling system or a Peltier element. The cooling plate 78 is an example of a cooling mechanism in the present disclosure. The cooling plate 78 may be connected to a laser annealing control processor 100 so that the cooling can be turned on and off. The cooling can be turned on and off by, for example, opening and closing a valve in the case of a water-cooling system, or by turning on and off a current to a Peltier element.

[0089] 8 is an enlarged side view of the cooling plate 78 and the irradiated object 160 shown in FIG. 7. The irradiated object 160 has a layered structure of an object 160t to be heated by laser irradiation and an unheatable member 160b that should be prevented from being affected by the heat of the laser irradiation as much as possible. The object 160t to be heated is a thin film to be annealed by the laser annealing system 10A, such as an ITO thin film or an IGZO thin film. The unheatable member 160b is a substrate made of a material with poor heat resistance, such as a resin substrate made of PET resin or PC.

[0090] 4.5.2 Operation The laser annealing control processor 100 controls the ON / OFF of the cooling operation of the cooling plate 78 in synchronization with the burst operation. Fig. 9 is a timing chart showing an example of control of the cooling operation.

[0091] 9 shows the burst period Pb and pause period Ps of the burst operation, the middle graph F9B shows control example 1 of the cooling operation of the cooling plate 78, and the bottom graph F9C shows control example 2.

[0092] The timing of turning on cooling may be delayed relative to the start timing of the burst period Pb (graph F9B) or may precede it (graph F9C). The laser annealing control processor 100 adjusts the heat distribution in the thickness direction of the irradiated object 160 by turning on cooling with a delay relative to the burst period Pb or by turning on cooling earlier relative to the burst period Pb.

[0093] The length of the cooling ON period does not have to be the same as the burst period Pb. The timing at which cooling is turned ON and the length of the cooling ON period are adjusted so that the target heat distribution is obtained.

[0094] 4.5.3 Actions and Effects The cooling plate 78 can remove heat transferred to the substrate, which is the non-heatable member 160b, and therefore can more effectively prevent damage to the substrate due to thermal influence.

[0095] According to the laser annealing system 10A, the cooling operation using the cooling plate 78 has the effect of controlling the temperature gradient in the thickness direction of the irradiated object 160, making it easier to control the temperature of the thin film that is the heated object 160t while preventing the temperature of the substrate from rising.

[0096] 5. Task 2 By increasing the size of the crystal grains when ITO thin films are crystallized by laser annealing, it is easy to realize electrodes with lower resistivity and higher mobility. The energy required to crystallize from an amorphous state is thought to be in the relationship [crystal nucleus formation] > [crystal grain growth]. For this reason, a two-stage growth method for the formation of crystal nuclei and the growth of crystal grains was devised, and this method is realized in ordinary atmospheric annealing.

[0097] However, in the laser annealing process using continuous irradiation of pulsed laser light as shown in Fig. 10, the thin film surface temperature Hs continues to rise above the crystallization threshold temperature Hcz, and crystal grain growth occurs at a temperature above the crystal nucleation threshold temperature, so crystal nuclei continue to be generated and the final crystal grains become small (see Fig. 11). This is because at temperatures above the crystal nucleation threshold temperature, crystal nuclei are more likely to be formed than crystal growth.

[0098] Similar to Fig. 4, Fig. 10 shows the change in the thin film surface temperature Hs due to continuous irradiation with pulsed laser light. Fig. 11 is an explanatory diagram that schematically shows the process of crystallization of the thin film due to continuous irradiation with pulsed laser light shown in Fig. 10. Time progresses from left to right in Fig. 11. In Fig. 11, in the irradiated area ARt of the thin film, generation of crystal nuclei Cc and crystal growth occur over time.

[0099] The left diagram F11A in Figure 11 shows the generation of crystal nuclei Cc when the thin film surface temperature Hs exceeds the crystal nucleation threshold temperature. The center diagram F11B shows the increase in crystal nuclei Cc due to the generation of new crystal nuclei Cc and the growth of crystal grains. The right diagram F11C shows the further increase in crystal nuclei Cc due to the generation of new crystal nuclei Cc and the growth of crystal grains Cm from the state of the center diagram F11B.

[0100] As the number of crystal nuclei Cc increases, the crystal grains Cm cannot grow large enough, and become medium-sized crystal grains Cm. In this way, with continuous irradiation of pulsed laser light at high repetition rates, crystal grain growth occurs at a temperature above the crystal nucleation threshold temperature, so new crystal nuclei Cc continue to be generated, and the final size of each crystal grain Cm remains relatively small.

[0101] On the other hand, in the case of burst irradiation using a simple burst pulse as shown in Figure 12, new crystal nuclei are generated at the same time as the growth of crystal grains. In this case, the crystal orientations of the generated crystal grains are random, so even if adjacent grains are present, they are unlikely to merge and grow, and therefore the size of the crystal grains does not increase (see Figures 13 and 14).

[0102] 12 is a graph showing an example of a burst pattern and an example of the transition of the thin film surface temperature Hs with burst irradiation. In the burst irradiation shown in FIG. 12, the thin film surface temperature Hs rises during the burst period Pb to a state above the crystal nucleation threshold temperature Hcc, and then drops during the pause period Ps to a state below the crystal growth threshold temperature Hcg. By repeating such burst periods Pb and pause periods Ps, the thin film surface temperature Hs intermittently alternates between a state above the crystal nucleation threshold temperature Hcc and a state below the crystal growth threshold temperature Hcg, and new crystal nuclei are generated and crystal grains grow.

[0103] Figure 13 is an explanatory diagram that schematically shows the process of crystallization of a thin film by burst irradiation shown in Figure 12. In Figure 13, in the irradiated area ARt of the thin film, generation of crystal nuclei Cc and crystal growth occur over time. Regarding Figure 13, differences from Figure 11 will be explained.

[0104] 13A shows the state where crystal nuclei Cc are generated when the thin film surface temperature Hs exceeds the crystal nucleation threshold temperature Hcc. The center diagram F13B shows how the thin film surface temperature Hs intermittently exceeds the crystal nucleation threshold temperature Hcc and also exceeds the crystal growth threshold temperature Hcg, increasing the number of new crystal nuclei Cc and causing the crystal nuclei Cc to grow into crystal grains Cb.

[0105] The right diagram F13C shows how new crystal nuclei Cc are generated and crystal grains Cm and Cb grow from the state shown in the center diagram F13B.

[0106] In this way, in the burst irradiation shown in FIG. 12, the generation of new crystal nuclei Cc and the growth of crystal grains Cm and Cb occur simultaneously.

[0107] Figure 14 shows a schematic diagram of the crystal grains generated by the burst irradiation shown in Figure 12. As shown in Figure 14, the crystal grains Cb, Cm1, Cm2, Cm3, and Cm4 generated by the burst irradiation shown in Figure 12 have different crystal orientations, so even if the crystal grains are adjacent to each other, they are unlikely to merge and grow, and the final crystal grain size does not become very large.

[0108] Under these circumstances, there has been a demand for a laser annealing method that improves throughput without impeding crystal growth.

[0109] 6. Embodiment 2 6.1 Configuration The configuration of the laser annealing system according to the second embodiment is the same as that of the laser annealing system 10 shown in Fig. 2 or the laser annealing system 10A shown in Fig. 7. In the following description of the second embodiment, the same reference numerals as those in Fig. 2 will be used.

[0110] 6.2 Operation In the laser annealing system 10 according to the second embodiment, the first burst period of the burst irradiation may be irradiated with a laser beam having a higher energy level than the subsequent burst periods, thereby raising the thin film surface temperature Hs to a temperature equal to or higher than the crystal nucleation threshold temperature Hcc. In the subsequent burst periods, low-energy laser irradiation is performed to maintain the thin film surface temperature Hs below the crystal nucleation threshold temperature Hcc while achieving a temperature equal to or higher than the crystal growth threshold temperature Hcg. This allows the crystal to grow in two stages. The first burst period during which high-energy laser irradiation is performed may be a plurality of burst periods, including the first burst period.

[0111] 15 is a graph showing an example of burst irradiation in the laser annealing system 10 according to embodiment 2 and an example of the transition of the thin film surface temperature Hs accompanying the burst irradiation. The vertical and horizontal axes in FIG. 15 are the same as those in FIG.

[0112] 15, the laser annealing control processor 100 sets the pulse energy of the first burst period Pb1 in the burst operation to be higher than the pulse energy of the next burst period Pb2. The repetition frequencies in the burst periods Pb1 and Pb2 may be the same.

[0113] Laser irradiation during the first burst period Pb1 raises the thin film surface temperature Hs to a state above the crystal nucleation threshold temperature Hcc, and crystal nuclei are generated. Thereafter, the pulse energy during other burst periods, including the next (second) burst period Pb2, is set lower than the pulse energy during the first burst period Pb1, and laser irradiation is controlled so that the thin film surface temperature Hs is maintained below the crystal nucleation threshold temperature Hcc during the other burst periods while maintaining the temperature above the crystal growth threshold temperature Hcg for as long as possible. The laser irradiation conditions (pulse energy, repetition frequency, and pulse number) applied to the second and subsequent burst periods may be the same. This allows crystals to grow in two stages: crystal nucleation and grain growth.

[0114] Fig. 16 is an explanatory diagram that schematically shows the process of crystallization of a thin film by burst irradiation shown in Fig. 15. Differences between Fig. 16 and Fig. 13 will be described.

[0115] The left diagram F16A in Figure 16 shows the state in which crystal nuclei Cc are generated by laser irradiation during the first burst period Pb1. Then, as shown in the center diagram F16B, the generation of new crystal nuclei Cc is suppressed by laser irradiation during the second burst period Pb2, and the existing crystal nuclei Cc grow into crystal grains Cm. Furthermore, as shown in the right diagram F16C, the generation of new crystal nuclei Cc is suppressed by laser irradiation during the third and subsequent burst periods, and the existing crystal grains Cm grow into larger crystal grains Cb.

[0116] 6.3 Actions and Effects According to the second embodiment, the crystals can be grown in two stages, making it easier to obtain large crystals with high mobility.

[0117] 6.4 Modification 1 of Embodiment 2 The leading burst period is not limited to a mode in which the pulse energy is changed compared to the other burst periods, and for example, the leading burst period may be set to a repetition frequency different from that of the other burst periods, for example, the leading burst period may be set to a higher repetition frequency than the other burst periods (see FIG. 17).

[0118] 17 shows an example of burst irradiation according to Modification 1 of Embodiment 2, and an example of the transition of the thin film surface temperature Hs accompanying the burst irradiation. The vertical and horizontal axes in FIG. 17 are the same as those in FIG.

[0119] 17, the laser annealing control processor 100 sets the repetition frequency of the first burst period Pb1 in the burst operation higher than the repetition frequency of the next burst period Pb2. The pulse energy in each burst period Pb1, Pb2 may be the same.

[0120] Laser irradiation during the first burst period Pb1 raises the thin film surface temperature Hs to a state above the crystal nucleation threshold temperature Hcc, and crystal nuclei are generated. Thereafter, the repetition frequency during other burst periods, including the next (second) burst period Pb2, is set lower than the repetition frequency during the first burst period Pb1, and laser irradiation is controlled so that the thin film surface temperature Hs is maintained below the crystal nucleation threshold temperature Hcc during the other burst periods while maintaining the temperature above the crystal growth threshold temperature Hcg for as long as possible. The laser irradiation conditions (pulse energy, repetition frequency, and number of pulses) applied to the second and subsequent burst periods may be the same. This allows crystals to grow in two stages: crystal nucleation and grain growth.

[0121] 6.5 Modification 2 of Embodiment 2 The number of pulses (burst time) in the leading burst period may be set to be different from that in the other burst periods. For example, the number of pulses in the leading burst period may be set to be greater than that in the other burst periods (see FIG. 18). In this case, the length of the pause period after the leading burst period may be set to be different from that of the other pause periods.

[0122] 18 shows an example of burst irradiation according to Modification 2 of Embodiment 2, and an example of the transition of the thin film surface temperature Hs accompanying the burst irradiation. The vertical and horizontal axes in FIG. 18 are the same as those in FIG.

[0123] 18, the laser annealing control processor 100 may set the number of pulses in the first burst period Pb1 in a burst operation to be greater than the number of pulses in the next burst period Pb2. The pulse energy and repetition frequency in each burst period Pb1 and Pb2 may be the same.

[0124] Furthermore, the laser annealing control processor 100 may set the pause period Ps1 immediately following the first burst period Pb1 to be longer than the other pause periods Ps2.

[0125] Such burst irradiation allows the crystal to grow in two stages, as in the examples of FIGS.

[0126] 6.6 Other The second embodiment and its modifications 1 and 2 may be combined as appropriate. For example, the laser annealing control processor 100 may set the laser irradiation in the first burst period Pb1 to have higher energy and a higher repetition frequency than those in the other burst periods. Also, for example, the laser annealing control processor 100 may set the laser irradiation in the first burst period Pb1 to have higher energy but a lower repetition frequency than those in the other burst periods, or may set the laser irradiation in the first burst period Pb1 to have a higher energy but a lower repetition frequency than those in the other burst periods, or may set the laser irradiation to have a higher repetition frequency but a smaller number of pulses.

[0127] Furthermore, it is also possible to make part or all of the pause periods in the second embodiment and its first and second modifications a low output period Pd as shown in FIG.

[0128] 7. Embodiment 3 7.1 Configuration 19 is a schematic diagram showing the configuration of a laser annealing system 10B according to the third embodiment. The laser annealing system 10B is a system that performs an annealing process on a web-like irradiation target R1 by a roll-to-roll process. The irradiation target R1 may be, for example, a resin roll having a thin film formed on a resin substrate.

[0129] As shown in the central diagram F19A of Figure 19, the laser annealing system 10B includes a transport mechanism (not shown) that transports the irradiated object R1 using a roll-to-roll method, a laser device L1, and a distribution optical system including multiple beam splitters BS1, BS2, BS3, and BS4 for distributing the pulsed laser light PL1 output from the laser device L1 to multiple irradiation areas AR1, AR2, AR3, and AR4.

[0130] 19 shows a configuration including four irradiation areas AR1, AR2, AR3, and AR4, but the number of irradiation areas is not limited to this example. The number of beam splitters is changed depending on the number of irradiation areas.

[0131] The transport mechanism includes known components such as an unwinding roller, a winding roller, and a path roller.

[0132] Each of the multiple irradiation areas AR1, AR2, AR3, and AR4 is an area where pulsed laser light is irradiated onto the irradiation target R1. The pulsed laser light is distributed along the movement direction of the irradiation target R1 so that the multiple irradiation areas AR1, AR2, AR3, and AR4 are arranged at predetermined intervals. The areas between the irradiation area AR1 and the irradiation area AR2, between the irradiation area AR2 and the irradiation area AR3, and between the irradiation area AR3 and the irradiation area AR4, which are arranged at predetermined intervals, are set as intermittent areas ARs where laser irradiation is not performed.

[0133] Pulsed laser light PL1 output from laser device L1 is split by beam splitters BS1, BS2, BS3, and BS4, and enters irradiation areas AR1, AR2, AR3, and AR4, respectively. The reflectance of each beam splitter BS1, BS2, BS3, and BS4 is set so that the laser energy in each irradiation area AR1, AR2, AR3, and AR4 is equal. Note that the final beam splitter BS4 may be a reflecting mirror.

[0134] In the laser annealing system 10B, the object to be irradiated R1 moves at a low speed. The movement speed of the object to be irradiated R1 is set so that the rest period corresponds to the time it takes to pass through the intermittent area ARs. The number of irradiations per location is determined by the width of the irradiation area in the movement direction, the movement speed of the object to be irradiated R1, and the repetition frequency.

[0135] 7.2 Operation The laser device L1 continuously outputs pulsed laser light PL1 at a constant repetition rate while the irradiation object R1 is moving in a roll-to-roll manner. A graph F19B in Fig. 19 shows the pulse energy of the pulsed laser light PL1 output from the laser device L1.

[0136] 19 is an explanatory diagram showing the laser irradiation result when pulsed laser light is continuously irradiated in irradiation area AR1. In laser annealing system 10B, the position of the irradiating beam is fixed in each of irradiation areas AR1 to AR4, but since irradiated object R1 moves in the roll advancement direction (movement direction), the laser-irradiated area moves relatively, and the irradiation ranges of each beam overlap (see enlarged view F19C).

[0137] Therefore, the number of times of irradiation per one location (the same location) is determined from the beam width in the moving direction on the irradiated object R1, the moving speed (rolling speed), and the repetition frequency of the pulsed laser beam PL1. By setting a plurality of irradiation areas AR1, AR2, AR3, and AR4 and setting the areas between them as intermittent areas, each area on the irradiated object R1 is irradiated with burst pulses similar to those in the first embodiment.

[0138] Graph F19D in FIG. 19 shows an example of burst pulses of pulsed laser light irradiated onto the same location on irradiation target R1.

[0139] By dividing the irradiation area into a plurality of irradiation areas AR1, AR2, AR3, and AR4 and a plurality of intermittent areas ARs between them, each point on the irradiation target R1 is irradiated with a burst pulse as shown in graph F19D as the roll progresses. This allows for burst irradiation similar to that of the laser device 12 in embodiment 1.

[0140] The laser annealing system 10B may perform the main annealing process while the thin film is being wound onto a roll after being formed on the resin substrate.

[0141] Note that the upstream and downstream portions of each of the irradiation areas AR1, AR2, AR3, and AR4 may not be used as elements because the number of irradiations is reduced. Here, the "upstream side" refers to the upstream side in the direction of movement of the irradiated object R1, and refers to the left side in Figure 19.

[0142] 7.3 Examples of transport mechanisms FIG. 20 is a perspective view showing an example of a roll-to-roll type transport mechanism M applied to the laser annealing system 10B. The transport mechanism M includes an unwinding section 302 and a winding section 304. A film-forming section 306 and a laser annealing processing section 310 are provided between the unwinding section 302 and the winding section 304. The film-forming section 306 is a processing section for a film-forming process that forms a thin film such as ITO on a substrate fed from the unwinding section 302. The laser annealing processing section 310 is located downstream of the film-forming section 306 and is a processing section for an annealing process that performs laser irradiation in the area indicated by the arrow in FIG. 20. Although the specific configuration of the laser annealing processing section 310 is not shown in FIG. 20, the laser annealing processing section 310 includes multiple irradiation areas AR1, AR2, AR3, and AR4 described in FIG. 19. The laser annealing processing section 310 includes components such as an optical system required for laser irradiation.

[0143] With this configuration, in a roll-to-roll process, annealing can be performed while the roll is being wound up after the thin film is formed.

[0144] 7 and 8, the transport mechanism M may include cooling rollers (not shown). The cooling rollers may be disposed on the back side of the substrate in each of the irradiation areas AR1, AR2, AR3, and AR4.

[0145] 7.4 Actions and Effects According to the third embodiment, in the roll-to-roll method, the annealing treatment can be performed while the roll is being wound up, which shortens the processing time compared to annealing treatment in which the winding is stopped.

[0146] 7.5 Modification 1 of Embodiment 3 7.5.1 Configuration Fig. 21 is an explanatory diagram showing the configuration and operation of a laser annealing system 10C according to Modification 1 of Embodiment 3. Differences between the configuration shown in Fig. 21 and Fig. 19 will be described below. A schematic plan view F21A shown in the upper part of Fig. 21 shows an example of multiple irradiation areas AR1, AR2, AR3, ... in the laser annealing system 10C. Although not shown, the laser annealing system 10C, like Fig. 19, includes a laser device L1 and multiple beam splitters that direct pulsed laser light to each of the multiple irradiation areas AR1, AR2, AR3, ...

[0147] In the laser annealing system 10C, when two-stage growth is performed as in the second embodiment, an area to be irradiated with a burst pulse of high energy or high repetition frequency is arranged in the upstream part of the multiple irradiation areas AR1, AR2, AR3, etc.

[0148] 21 shows an example in which the first irradiation area AR1 is irradiated with a pulsed laser beam having a higher pulse energy than the other irradiation areas. In this case, for example, the reflectance of the upstream beam splitter may be set higher than the others to distribute more energy.

[0149] Graph F21B shown in the lower part of Figure 21 is a graph showing an example of burst irradiation by laser annealing system 10C and an example of the change in thin film surface temperature Hs due to burst irradiation. In Figure 21, the burst periods corresponding to the first irradiation area AR1 to the third irradiation area AR3 are shown, but the same is true for the burst periods corresponding to the fourth and subsequent irradiation areas. Graph F21B is the same as the graph described in Figure 15.

[0150] 7.5.2 Operation The operation of laser irradiation in the laser annealing system 10C is the same as in embodiment 3. As in embodiment 2, a crystal is grown in two stages by burst irradiation by the laser annealing system 10C.

[0151] 7.5.3 Actions and Effects The laser annealing system 10C allows crystals to be grown in two stages in a roll-to-roll process, resulting in crystals with high mobility.

[0152] 7.6 Modification 2 of Embodiment 3 7.6.1 Configuration 22 is a schematic diagram showing the configuration of a laser annealing system 10D according to Modification 2 of Embodiment 3. Differences between the configuration shown in FIG. 22 and that shown in FIG. 19 will be described.

[0153] The laser annealing system 10D includes multiple laser devices L2 and L3 instead of the laser device L1 in Fig. 19. Furthermore, the laser annealing system 10D includes a beam splitter BS5, a reflecting mirror RM1, a beam splitter BS6, and a reflecting mirror RM3 instead of the beam splitters BS1 to BS4 in Fig. 19. Other configurations may be similar to those in Fig. 19.

[0154] Depending on the width of the roll, the number of irradiation areas, or the positions of the irradiation areas, high pulse energy or a high repetition rate may be required. In such cases, as shown in Figure 22, multiple laser devices L2 and L3 may be arranged to distribute pulsed laser light to different irradiation areas AR1, AR2, AR3, and AR4, respectively.

[0155] 7.6.2 Operation The laser devices L2 and L3 are controlled to synchronously output pulsed laser beams PL2 and PL3. The pulsed laser beam PL2 output from the laser device L2 is split into two directions by a beam splitter BS5, one of which is incident on the irradiation area AR1, and the other is reflected by a reflecting mirror RM1 and incident on the irradiation area AR2. For example, the irradiation area AR1 may be configured to irradiate the irradiation area AR2 with a pulsed laser beam having a high pulse energy. Furthermore, the laser device L2 may have a higher repetition frequency than the laser device L3.

[0156] Similarly, pulsed laser beam PL3 output from laser device L3 is split into two directions by beam splitter BS6, one of which is incident on irradiation area AR3, and the other is reflected by reflecting mirror RM2 and incident on irradiation area AR4. Other operations are the same as those in FIG.

[0157] 7.6.3 Actions and Effects The laser annealing system 10D can achieve the same effects as the laser annealing system 10B. Furthermore, the laser annealing system 10D can distribute pulsed laser light with a desired pulse energy to each irradiation area. Furthermore, since multiple laser devices are used, each irradiation area can be irradiated with pulsed laser light with a desired repetition rate.

[0158] 8. Embodiment 4 8.1 Configuration 23 schematically illustrates the configuration of a laser annealing system 10E according to embodiment 4. The laser annealing system 10E includes multiple laser devices L4, L5, L6, L7, and L8 instead of the laser device 12. Each of the laser devices L4, L5, L6, L7, and L8 may have the same configuration as the laser device 12.

[0159] The laser annealing system 10E includes reflecting mirrors RMa, RMb, RMc, and RMd that guide the pulsed laser beams PL4, PL5, PL6, PL7, and PL8 output from the laser devices L4, L5, L6, L7, and L8, respectively, to the irradiation area AR12. The pulsed laser beam paths that guide the pulsed laser beams PL4, PL5, PL6, PL7, and PL8 to the irradiation area AR12 may include optical elements such as reflecting mirrors (not shown) other than the reflecting mirrors RMa, RMb, RMc, and RMd.

[0160] The irradiation area AR12 may be the area on the table 76 described in FIG. 2, or may be the irradiation areas AR1, AR2, AR3, and AR4 described in FIG.

[0161] Although FIG. 23 shows a configuration using five laser devices L4 to L8, the number of laser devices is not limited to this example.

[0162] 8.2 Operation High repetitive irradiation in the irradiation area AR12 may be achieved by performing control to delay the output timing of each pulse laser beam from the plurality of laser devices L4 to L8.

[0163] Fig. 24 is a graph showing an example of burst irradiation achieved by the laser annealing system 10E. As shown in Fig. 24, by staggering the output timings of pulsed laser beams PL4 to PL8 output from laser devices L4 to L8 and irradiating the same irradiation area AR1, burst irradiation that is substantially the same as a high-repetition burst operation is possible.

[0164] For example, when the repetition frequency of each of the laser devices L4 to L8 is 200 Hz, irradiation at a pseudo 1 kHz can be realized by irradiating the same area with the output timing of these five laser devices L4 to L8 shifted.

[0165] 8.3 Actions and Effects The laser annealing system 10E according to the fourth embodiment can realize burst irradiation at a repetition frequency higher than the repetition frequency of each of the laser devices L4 to L8.

[0166] 9. Applications other than ITO thin films The technology of the present disclosure can also be applied to the following uses.

[0167] [1] Annealing process for crystallization of channel materials such as a-Si

[0168] [2] After depositing multiple metal films on a substrate with poor heat resistance, such as a resin film, the metal materials are alloyed together through an annealing process (a process to make them magnetic).

[0169] [3] Annealing for crystal recovery after ion implantation in semiconductor processing

[0170] [4] Controlling the thermal diffusion of dopant materials into the substrate depth direction

[0171] [5] Annealing when heat-treating coating materials such as hard coatings on films

[0172] [6] Annealing treatment to reduce resistance by enlarging the crystal grains in metal wiring on semiconductor chips or printed circuit boards

[0173] 10. About the Processor Processors such as the laser control processor 28 and the laser annealing control processor 100 may be physically configured in the form of hardware to execute various processes included in the present disclosure. For example, the processor may be a computer including a memory in which a control program defining various processes is stored and a processing device that executes the control program. The control program may be stored in a single memory, or may be stored separately in multiple physically separate memories, with the various processes defined by the control program as a collection of these memories. The processing device may be a general-purpose processing device such as a CPU, or a processing device for a specific purpose such as a GPU.

[0174] The processor may be programmed in the form of software to execute various processes included in the present disclosure. For example, the processor may be a dedicated device such as an ASIC or a programmable device such as an FPGA that implements the functions of executing various processes.

[0175] The various processes included in the present disclosure may be performed by a single computer, a single dedicated device, or a single programmable device, or may be performed by cooperation of multiple physically separate computers, multiple dedicated devices, or multiple programmable devices. The various processes may be performed by a combination of at least two of one or more computers, one or more dedicated devices, and one or more programmable devices.

[0176] 11.Other The above description is intended to be illustrative rather than limiting. Thus, it will be apparent to one skilled in the art that modifications can be made to the disclosed embodiments without departing from the scope of the claims. It will also be apparent to one skilled in the art that the disclosed embodiments can be used in combination.

[0177] Terms used throughout this specification and claims should be construed as "open ended" unless expressly stated otherwise. For example, terms such as "comprise," "have," "comprise," and "equip" should be construed as meaning "without excluding the presence of elements other than those listed." In addition, the modifier "a" should be construed as meaning "at least one" or "one or more." In addition, the term "at least one of A, B, and C" should be construed as "A," "B," "C," "A+B," "A+C," "B+C," or "A+B+C." Furthermore, it should be construed as including combinations of these with elements other than "A," "B," and "C."

Claims

1. A laser annealing system that anneals a thin film on a substrate by irradiating the thin film with pulsed laser light, comprising: a laser device that outputs the pulsed laser light; an optical system that irradiates the thin film with the pulsed laser light; a processor that controls the irradiation of the pulsed laser beam at the same location on the thin film by performing burst irradiation that repeats a burst period in which the pulsed laser beam is continuously irradiated and a suppression period in which the irradiation of the pulsed laser beam is suppressed. Laser annealing system.

2. 2. The laser annealing system of claim 1, the fluence of the pulsed laser light irradiated onto the thin film is less than the ablation threshold of the thin film; Laser annealing system.

3. 2. The laser annealing system of claim 1, The processor: controlling the fluence of the pulsed laser light irradiated onto the thin film so that the fluence is less than an ablation threshold of the thin film; Laser annealing system.

4. 2. The laser annealing system of claim 1, Irradiation conditions of the burst irradiation are set so that the surface temperature of the thin film exceeds a crystallization threshold temperature of the thin film during the burst period, and the temperature of the interface between the thin film and the substrate is maintained below a damage threshold temperature of the substrate throughout the burst period and the suppression period. Laser annealing system.

5. 5. The laser annealing system according to claim 4, the irradiation conditions include at least one parameter of pulse energy, repetition frequency, number of pulses, length of the suppression period, and number of bursts of the pulsed laser beam in the burst period; Laser annealing system.

6. 2. The laser annealing system of claim 1, The processor: controlling the operation of the burst irradiation so that the surface temperature of the thin film exceeds a crystallization threshold temperature of the thin film during the burst period, and the temperature of the interface between the thin film and the substrate is maintained below a damage threshold temperature of the substrate throughout the burst period and the suppression period; Laser annealing system.

7. 2. The laser annealing system of claim 1, the laser annealing system includes a cooling mechanism for cooling the substrate. Laser annealing system.

8. 2. The laser annealing system of claim 1, the pulsed laser light in a leading burst period among the plurality of burst periods is irradiated with higher pulse energy, a higher repetition frequency, or a larger number of pulses than the pulsed laser light in other burst periods; Laser annealing system.

9. 9. The laser annealing system of claim 8, Among the plurality of suppression periods, the suppression period immediately following the first burst period is longer than the other suppression periods. Laser annealing system.

10. 9. The laser annealing system of claim 8, the irradiation conditions of the burst irradiation are set so that the surface temperature of the thin film exceeds a crystal nucleation threshold temperature of the thin film during the first burst period, the surface temperature of the thin film is maintained below the crystal nucleation threshold temperature during the other burst periods, and the surface temperature of the thin film exceeds a crystal growth threshold temperature of the thin film during the other burst periods; Laser annealing system.

11. 9. The laser annealing system of claim 8, The processor: controlling the operation of the burst irradiation so that the surface temperature of the thin film exceeds a crystal nucleation threshold temperature of the thin film during the first burst period, the surface temperature of the thin film is maintained below the crystal nucleation threshold temperature during the other burst periods, and the surface temperature of the thin film exceeds a crystal growth threshold temperature of the thin film during the other burst periods; Laser annealing system.

12. 2. The laser annealing system of claim 1, the suppression period is a rest period in which the irradiation of the pulsed laser beam is stopped, or a low-output period in which the pulsed laser beam having a pulse energy lower than that of the burst period is irradiated. Laser annealing system.

13. 2. The laser annealing system of claim 1, a transport mechanism for transporting the substrate by a roll-to-roll method, the burst irradiation is performed on the irradiation target on which the thin film has been formed while the substrate is being moved by the transport mechanism. Laser annealing system.

14. 14. The laser annealing system of claim 13, a plurality of irradiation areas for irradiating the pulsed laser light on the irradiation object are arranged at predetermined intervals along the moving direction of the irradiation object; Laser annealing system.

15. 15. The laser annealing system of claim 14, the processor controls the number of times of irradiation per one location based on the moving speed of the object to be irradiated, the width of the irradiation area, and the repetition frequency of the pulsed laser light. Laser annealing system.

16. 15. The laser annealing system of claim 14, a beam splitter that distributes the pulsed laser light output from the laser device to the plurality of irradiation areas; Laser annealing system.

17. 15. The laser annealing system of claim 14, the processor adjusts irradiation conditions such that the surface temperature of the thin film becomes equal to or higher than a crystal nucleation threshold temperature by irradiating the pulsed laser light in an upstream irradiation area among the plurality of irradiation areas. Laser annealing system.

18. 18. The laser annealing system of claim 17, the processor adjusts irradiation conditions such that the surface temperature of the thin film is equal to or higher than a crystal growth threshold temperature and is maintained below the crystal nucleation threshold temperature by irradiating the pulsed laser light in irradiation areas other than the upstream irradiation area. Laser annealing system.

19. 2. The laser annealing system of claim 1, the laser annealing system includes a plurality of the laser devices; the processor performs control to delay output timings of the pulsed laser beams from the plurality of laser devices. Laser annealing system.

20. A laser annealing method for annealing a thin film on a substrate by irradiating the thin film with pulsed laser light, comprising: outputting the pulsed laser light from a laser device; irradiating the thin film with the pulsed laser light by an optical system; and performing burst irradiation in which a burst period in which the pulsed laser beam is continuously irradiated and a suppression period in which the irradiation of the pulsed laser beam is suppressed are repeated, thereby irradiating the same location of the thin film with the pulsed laser beam. Laser annealing method.

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