Illumination optics system and method of forming laser beam using the same

Abstract

Provided are an illumination optical system and a method of forming a laser beam using the same. The illumination optical system comprises a lens array unit configured to receive a plurality of laser beams provided from one side, a spatial light modulator configured to control phases of the plurality of laser beams passing through the lens array unit, and a condensing lens configured to overlap the plurality of laser beams passing through the spatial light modulator to form a flat-top beam, wherein the plurality of laser beams includes a first laser beam and a second laser beam passing through two adjacent lenses, and wherein the spatial light modulator is configured to control the first laser beam and the second laser beam to have different phases.

Description

ILLUMINATION OPTICS SYSTEM AND METHOD OF FORMING LASER BEAM USING THE SAME

[0001] This disclosure relates to an illumination optical system and a method of forming a laser beam using the same.

[0002] Laser annealing refers to a processing method that partially heat-treats the surface of a workpiece (for example, a wafer) through a laser. Laser annealing requires a high-intensity flat-top beam.

[0003] As part of an effort to obtain a flat-top beam, as shown in Fig. 1, there was an attempt to obtain a high-power flat-top beam by using a lens (17) to overlap laser beams (11, 12, 13, 14) that have passed through lens arrays (15, 16). However, according to this method, interference patterns occurred due to interference between laser beams (11, 12, 13, 14), making it difficult to obtain a flat-top beam.

[0004] Therefore, there is a need for a technology that may obtain a high-power flat-top beam while preventing interference between laser beams.

[0005] One technical problem to be solved by the present disclosure is to provide an illumination optical system capable of obtaining a flat-top beam by minimizing interference between adjacent laser beams.

[0006] The technical problems to be solved by the present disclosure are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

[0007] According to one embodiment of the present disclosure, there is provided an illumination optical system comprising: a lens array unit configured to receive a plurality of laser beams provided from one side; a spatial light modulator configured to control phases of the plurality of laser beams passing through the lens array unit; a polarizer configured to adjust a polarization direction of at least some of the plurality of laser beams passing through the spatial light modulator; and a condensing lens configured to focus the plurality of laser beams passing through the polarizer, wherein the plurality of laser beams includes a first laser beam and a second laser beam passing through two adjacent lenses, and wherein the spatial light modulator is configured to control the first laser beam and the second laser beam to have orthogonal phases.

[0008] The polarizer may adjust the polarization directions of the first laser beam and the second laser beam to be orthogonal to each other.

[0009] The spatial light modulator may include a liquid crystal layer including a plurality of liquid crystals, and may control the phase of the first laser beam or the second laser beam by individually adjusting the refractive index of the plurality of liquid crystals based on the thickness of the lens included in the lens array unit.

[0010] The plurality of liquid crystals may include a plurality of first liquid crystals corresponding to a first lens that outputs the first laser beam, and a plurality of second liquid crystals corresponding to a second lens that outputs the second laser beam, and the first laser beam passing through the plurality of first liquid crystals and the second laser beam passing through the plurality of second liquid crystals may have uniform phase distributions.

[0011] At least some of the plurality of laser beams passing through the spatial light modulator may have non-uniform phase distributions.

[0012] The spatial light modulator may control the phases of the plurality of laser beams based on a Hadamard matrix.

[0013] The illumination optical system may further include a first lens unit that reduces the size of the plurality of laser beams passing through the lens array unit and transfers them to the spatial light modulator; and a second lens unit that enlarges the size of the plurality of laser beams passing through the spatial light modulator and transfers them to the polarizer.

[0014] The polarizer may include a plurality of half-wave plates arranged at predetermined intervals.

[0015] According to another embodiment of the present disclosure, there is provided a method of forming a laser beam using an illumination optical system including a lens array unit, a spatial light modulator, a polarizer, and a condensing lens, the method comprising: irradiating a plurality of laser beams provided from one side onto the spatial light modulator using the lens array unit; controlling phases of the plurality of laser beams using the spatial light modulator; adjusting a polarization direction of at least some of the plurality of laser beams passing through the spatial light modulator using the polarizer; and forming a flat-top beam by overlapping the plurality of laser beams using the condensing lens, wherein the plurality of laser beams includes a first laser beam and a second laser beam passing through two adjacent lenses, and wherein the spatial light modulator controls the first laser beam and the second laser beam to have orthogonal phases.

[0016] According to another embodiment of the present disclosure, there is provided a laser annealing apparatus comprising: a light source unit configured to provide a plurality of laser beams; a transfer optical system configured to align the plurality of laser beams; an illumination optical system configured to form a flat-top beam from the plurality of laser beams transferred from the transfer optical system; and an imaging optical system configured to image the flat-top beam onto a workpiece, wherein the illumination optical system includes: a lens array unit configured to receive the plurality of laser beams; a spatial light modulator configured to control phases of the plurality of laser beams passing through the lens array unit; a polarizer configured to adjust a polarization direction of at least some of the plurality of laser beams passing through the spatial light modulator; and a condensing lens configured to focus the plurality of laser beams passing through the polarizer, wherein the plurality of laser beams includes a first laser beam and a second laser beam passing through two adjacent lenses, and wherein the spatial light modulator is configured to control the first laser beam and the second laser beam to have orthogonal phases.

[0017] The above exemplary embodiments and other exemplary embodiments will be described or clarified by the detailed description to be read below in connection with the accompanying drawings.

[0018] The above content of the disclosure does not include a complete list of all aspects of the disclosure. It should be understood that the disclosure includes all possible methods, apparatuses, and systems that may be implemented from all appropriate combinations of the various aspects disclosed below in the detailed description and claims, as well as those summarized above. In addition, effects that may be obtained or predicted due to embodiments of this disclosure will be directly or implicitly disclosed in the detailed description of the embodiments of this disclosure. For example, various effects expected according to embodiments of this disclosure will be disclosed within the detailed description to be described later.

[0019] The disclosed technology may have the following effects. However, this does not mean that a particular embodiment must include all of the following effects or only the following effects, and the scope of the disclosed technology should not be understood as being limited thereto.

[0020] According to one embodiment of the present disclosure, a flat-top beam with improved energy distribution may be obtained. Accordingly, annealing quality may be improved.

[0021] The aspects, features, and advantages of certain embodiments of the disclosure will become clearer through the following description referring to the accompanying drawings.

[0022] Fig. 1 is a schematic diagram illustrating a conventional beam formation method.

[0023] Fig. 2 is a block diagram illustrating the configuration of a laser annealing apparatus (1000) according to one embodiment of the present disclosure.

[0024] Fig. 3 is a schematic diagram of an illumination optical system (300) according to one embodiment of the present disclosure.

[0025] Fig. 4 is a schematic diagram of an illumination optical system (300) according to another embodiment of the present disclosure.

[0026] Fig. 5A shows a phase distribution corresponding to a Hadamard matrix.

[0027] Fig. 5B shows a method of controlling the phase of a laser beam using a spatial light modulator (330) set based on a Hadamard matrix.

[0028] Fig. 5C shows a beam formation method using an illumination optical system (300) including a spatial light modulator (330) set based on a Hadamard matrix.

[0029] Terminology used in the present specification will be briefly described first, and then the present disclosure will be described in detail.

[0030] As terms used herein, general terms currently used as widely as possible will be selected in consideration of functionality in the present disclosure, but may vary depending on the intent of those of ordinary skill in the art, precedents, the advent of new technology, and the like. In particular, a term may be arbitrarily selected by the applicant. In this case, the meaning of the term will be explained in detail through the relevant description of the disclosure. Therefore, the terms used herein should be defined on the basis of their meanings and the overall content of the present disclosure rather than their names.

[0031] The present disclosure may be modified in various ways and have various embodiments, and specific embodiments will be illustrated in the drawings and described in detail. However, this does not intend to limit the present disclosure to specific embodiments, and it is to be understood that the present disclosure includes all modifications, equivalents, and substitutions within the disclosed spirit and technical scope. In describing embodiments, a detailed description of relevant known technology will be omitted when determined to obscure the subject matter of the present disclosure.

[0032] Terms such as "first," "second," and the like may be used to describe various components, but components are not limited by the terms. The terms are only used for the purpose of distinguishing one component from others.

[0033] Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "include," "have," and the like indicate the presence of features, integers, steps, operations, components, parts, or combinations thereof described in the present specification and do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

[0034] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the technical field to which the present disclosure pertains may easily implement the present disclosure. However, the present disclosure may be implemented in many different forms and is not limited to the embodiments described herein. In order to clearly describe the present disclosure, parts irrelevant to the description are omitted from the drawings for clarity.

[0035]

[0036] Fig. 2 is a block diagram illustrating the configuration of a laser annealing apparatus (1000) according to one embodiment of the present disclosure.

[0037] Referring to Fig. 2, the laser annealing apparatus (1000) (abbreviated as annealing apparatus) may include a light source unit (100), a transfer optical system (200), an illumination optical system (300), a mask (400), and an imaging optical system (500).

[0038] The light source unit (100) may generate laser beams and provide them to the transfer optical system (200). Each of the laser beams may include a continuous laser beam or a pulsed laser beam. The light source unit (100) may include a plurality of laser devices. Each laser device may output a laser beam of the same intensity or the same output power and provide it to the transfer optical system (200).

[0039] The transfer optical system (200) may be arranged between the light source unit (100) and the illumination optical system (300). The transfer optical system (200) may transfer laser beams to the illumination optical system (300). The transfer optical system (200) may align the laser beams. The transfer optical system (200) may adjust the diameter or phase of each laser beam. The transfer optical system (200) may include a plurality of mirrors. The transfer optical system (200) may include at least one of an attenuator, a beam expander, and a phase shifter.

[0040] The illumination optical system (300) may form a flat-top beam with a uniform intensity distribution based on the laser beams transferred from the transfer optical system (200). The illumination optical system (300) may irradiate the flat-top beam onto the mask (400). The illumination optical system (300) may control the phase or polarization direction of some of the laser beams. For example, the illumination optical system (300) may control the adjacent laser beams to have orthogonal phases. Alternatively, the illumination optical system (300) may adjust the polarization direction of the laser beams so that the polarization directions of adjacent laser beams are orthogonal. Accordingly, the interference noise of the laser beams may be reduced.

[0041] The mask (400) may be arranged between the illumination optical system (300) and the imaging optical system (500). The mask (400) may transmit only a portion of the laser beam received from the illumination optical system (300). For example, the mask (400) may transmit only the part where the illumination area intensity is uniform.

[0042] The imaging optical system (500) may image the laser beam passing through the mask (400) onto a workpiece (W). The imaging optical system (500) may image a flat-top beam onto the workpiece (W). The imaging optical system (500) may adjust the size of the laser beam to be imaged on the workpiece (W). The imaging optical system (500) may include an eyepiece. The workpiece (W) may include a wafer.

[0043] Fig. 3 is a schematic diagram of an illumination optical system (300) according to one embodiment of the present disclosure.

[0044] Referring to Fig. 3, the illumination optical system (300) may include a lens array unit (310), a first lens unit (320), a spatial light modulator (330), a second lens unit (340), a polarizer (350), and a condensing lens (360). The optical path shown by the solid line represents the actual optical path of the laser beam, and the optical path shown by the dotted line represents the imaging optical path defined based on the spatial light modulator (330).

[0045] The lens array unit (310) may include a first lens array (311) and a second lens array (312). The lens array unit (310) may receive laser beams (L1, L2, L3, L4) provided from one side. The lens array unit (310) may adjust the distance between the laser beams (L1, L2, L3, L4). For example, the lens array unit (310) may increase the distance between the laser beams (L1, L2, L3, L4) to separate the laser beams (L1, L2, L3, L4) from each other. The lens array unit (310) may adjust the size of the laser beams (L1, L2, L3, L4). For example, the lens array unit (310) may reduce the size of the laser beams (L1, L2, L3, L4). The size of the laser beams (L1, L2, L3, L4) may refer to the spot size of each beam.

[0046] Referring to Fig. 3, the illumination optical system (300) may include a lens array unit (310), a first lens unit (320), a spatial light modulator (330), a second lens unit (340), a polarizer (350), and a condensing lens (360). The optical path shown by the solid line represents the actual optical path of the laser beam, and the optical path shown by the dotted line represents the imaging optical path defined based on the spatial light modulator (330).

[0047] The lens array unit (310) may include a first lens array (311) and a second lens array (312). The lens array unit (310) may receive laser beams (L1, L2, L3, L4) provided from one side. The lens array unit (310) may adjust the distance between the laser beams (L1, L2, L3, L4). For example, the lens array unit (310) may increase the distance between the laser beams (L1, L2, L3, L4) to separate the laser beams (L1, L2, L3, L4) from each other. The lens array unit (310) may adjust the size of the laser beams (L1, L2, L3, L4). For example, the lens array unit (310) may reduce the size of the laser beams (L1, L2, L3, L4). The size of the laser beams (L1, L2, L3, L4) may refer to the spot size of each beam.

[0048] The spatial light modulator (330) may control the phase of the first laser beam (L1) and / or the second laser beam (L2) so that the phases of the first laser beam (L1) and the second laser beam (L2) are orthogonal. For example, the spatial light modulator (330) may delay the phase of the first laser beam (L1) so that the phase of the first laser beam (L1) is 90 degrees later than the phase of the second laser beam (L2). Also, the spatial light modulator (330) may control one laser beam to have different phases by region. That is, the spatial light modulator (330) may control the laser beam to have a non-uniform phase distribution.

[0049] The spatial light modulator (330) may include a liquid crystal layer including a plurality of liquid crystals. The spatial light modulator (330) may control the phase of the laser beam by individually adjusting the refractive index of the plurality of liquid crystals.

[0050] Meanwhile, among the lenses included in the lens array unit (310), there may be lenses with different thicknesses due to manufacturing errors. Conventional phase shift masks have a fixed form, so if the size or position of the incident beam is changed due to lens thickness errors, there was a limitation that the phase shift does not occur as much as originally intended. In contrast, the spatial light modulator (330) according to this disclosure may control the refractive index of liquid crystals by reflecting the thickness error of individual lenses, so even if there is a lens thickness error, it may delay the phase of the laser beam as intended. For example, the spatial light modulator (330) may control the refractive index of liquid crystals based on the characteristics (e.g., phase or intensity distribution) of the laser beams (L1, L2, L3, L4) at the input plane (P). Therefore, the spatial light modulator (330) may compensate for lens thickness errors.

[0051] The second lens unit (340) may transfer the laser beams (L1, L2, L3, L4) passing through the spatial light modulator (330) to the polarizer (350). The second lens unit (340) may be a 4F system including two lenses. The second lens unit (340) may relay the image output by the spatial light modulator (330) to the polarizer (350). The image passing through the second lens unit (340) may be formed on the spatial light modulator (350). In addition, the second lens unit (340) may enlarge the size of the laser beams (L1, L2, L3, L4).

[0052] The polarizer (350) may adjust the polarization direction of at least some of the laser beams (L1, L2, L3, L4) passing through the spatial light modulator (330). The polarizer (350) may adjust the polarization directions of the first laser beam (L1) and the second laser beam (L2) to be orthogonal to each other. For example, if the polarization directions of the incident first laser beam (L1) and second laser beam (L2) are the same, the polarizer (350) may adjust the polarization direction of the first laser beam (L1) to be orthogonal to the polarization direction of the second laser beam (L2). The polarizer (350) may include a plurality of wave plates arranged at predetermined intervals. The wave plate may be a half-wave plate.

[0053] The condensing lens (360) may overlap the laser beams (L1, L2, L3, L4) to form a flat-top beam. When overlapping a plurality of laser beams, interference noise is generally generated. However, since the illumination optical system (300) according to this disclosure controls the phases of the laser beams (L1, L2, L3, L4) using the spatial light modulator (330), interference noise may be minimized. In addition, the illumination optical system (300) may minimize interference noise by controlling the polarization directions of the laser beams (L1, L2, L3, L4) using the polarizer (350).

[0054] The condensing lens (360) may image the flat-top beam onto the mask (400). Although not shown, a plurality of condensing lenses may be arranged between the illumination optical system (300) and the mask (400). In addition, the illumination optical system (300) may further include a field lens.

[0055] Meanwhile, the illumination optical system (300) does not necessarily have to be implemented in a form that includes all of the above-described components. For example, the illumination optical system (300) may not include the polarizer (350). In this case, the illumination optical system (300) may still generate a flat-top beam by controlling the phases of the laser beams (L1, L2, L3, L4) using the spatial light modulator (330).

[0056] In the following, embodiments utilizing the spatial light modulator (330) and the polarizer (350) will be described. For convenience of explanation, the description of other components of the illumination optical system (300) will be omitted, and the embodiments will be described focusing on the spatial light modulator (330) and the polarizer (350).

[0057] Fig. 4 is a schematic diagram of an illumination optical system (300) according to another embodiment of the present disclosure.

[0058] Referring to Fig. 4, the laser beams (L1, L2, L3, L4, L5, L6, L7, L8) may propagate in the x-axis direction. The lines shown in the y-axis direction represent the wavefronts of the laser beams (L1, L2, L3, L4, L5, L6, L7, L8). The double-headed arrows indicate the polarization directions of the laser beams (L1, L2, L3, L4, L5, L6, L7, L8). The laser beams (L1, L2, L3, L4, L5, L6, L7, L8) passing through the lens array unit (310) may have the same phase and polarization direction.

[0059] The spatial light modulator (330) may control the phases of the laser beams (L1, L2, L3, L4, L5, L6, L7, L8). The spatial light modulator (330) may control the phases of the laser beams (L1, L2, L5, L6) and the laser beams (L3, L4, L7, L8) to differ by a predetermined angle (e.g., 90 degrees). For example, the phases of the laser beams (L1, L2, L5, L6) passing through the spatial light modulator (330) may be 90 degrees later than the phases of the laser beams (L3, L4, L7, L8). The phases of the laser beams (L1, L2, L5, L6) may be orthogonal to the phases of the laser beams (L3, L4, L7, L8). As another example, the spatial light modulator (330) may control the phases of the laser beams (L1, L2, L5, L6) and the laser beams (L3, L4, L7, L8) to differ by 180 degrees.

[0060] The spatial light modulator (330) may include a plurality of regions (S1, S2, S3, S4) containing a plurality of liquid crystals. In one embodiment, the spatial light modulator (330) may delay the phases of the laser beams (L1, L2, L5, L6) by a predetermined angle. In this case, the spatial light modulator (330) may control the refractive indices of the liquid crystals corresponding to the first region (S1) and the third region (S3) so that the phases of the laser beams (L1, L2, L5, L6) are delayed. In another embodiment, the spatial light modulator (330) may adjust the phases of the laser beams (L1, L2, L3, L4, L5, L6, L7, L8), but may control them so that the phases of the laser beams (L1, L2, L5, L6) and the laser beams (L3, L4, L7, L8) differ by a predetermined angle.

[0061] The polarizer (350) may control the polarization directions of the laser beams (L1, L2, L3, L4, L5, L6, L7, L8) passing through the spatial light modulator (330). The polarizer (350) may control the polarization directions of the odd-numbered laser beams (L1, L3, L5, L7) and the even-numbered laser beams (L2, L4, L6, L8) to be orthogonal. For example, the polarizer (350) may change the polarization directions of the odd-numbered laser beams (L1, L3, L5, L7) to the y-axis direction.

[0062] The polarizer (350) may include regions (A1, A2, A3, A4, A5, A6, A7, A8) defined in an array form. Wave plates may be arranged in at least some of the regions (A1, A2, A3, A4, A5, A6, A7, A8). In one embodiment, half-wave plates may be arranged in regions (A1, A3, A5, A7), and half-wave plates may not be arranged in regions (A2, A4, A6, A8). In another embodiment, it is also possible that half-wave plates are not arranged in regions (A1, A3, A5, A7), and half-wave plates are arranged in regions (A2, A4, A6, A8). The half-wave plates may be arranged at predetermined intervals.

[0063] When overlapping laser beams, if adjacent beams have orthogonal phases, or if the polarization directions of adjacent beams are orthogonal, the interference noise between the beams may be reduced. The illumination optical system (300) may reduce the interference noise between the laser beams (L1, L2, L3, L4, L5, L6, L7, L8) using the spatial light modulator (330) and the polarizer (350). Specifically, since the first laser beam (L1) and the second laser beam (L2) have orthogonal polarization directions, they may not interfere even when overlapped. The first laser beam (L1) and the third laser beam (L3) have orthogonal phases, so they may not interfere even when overlapped. The first laser beam (L1) and the fourth laser beam (L4) have orthogonal phases and orthogonal polarization directions, so they may not interfere even when overlapped.

[0064] Meanwhile, the regions (S1, S2, S3, S4) of the spatial light modulator (330) and the regions (A1, A2, A3, A4, A5, A6, A7, A8) of the polarizer (350) are expressed as one-dimensional arrays in Fig. 4, but they may have a two-dimensional array form.

[0065] Figs. 5A to 5B are diagrams for explaining an illumination optical system (300) according to yet another embodiment of the present disclosure.

[0066] Fig. 5A shows a phase distribution corresponding to a Hadamard matrix.

[0067] Referring to Fig. 5a, the Hadamard matrix (M) may include a first row (r1), a second row (r2), a third row (r3), and a fourth row (r4). Each row of the Hadamard matrix (M) may be orthogonal to each other. For example, the first row (r1) may be orthogonal to the second row (r2). Therefore, if the spatial light modulator (330) controls a plurality of laser beams to have a phase distribution based on the Hadamard matrix (M), interference noise may not occur even when the plurality of laser beams passing through the spatial light modulator (330) are overlapped.

[0068] Fig. 5B shows a method of controlling the phase of a laser beam using a spatial light modulator (330) set based on a Hadamard matrix.

[0069] Referring to Fig. 5B, the spatial light modulator (330) may include a first region (S1) corresponding to the first laser beam (L1), a second region (S2) corresponding to the second laser beam (L2), a third region (S3) corresponding to the third laser beam (L3), and a fourth region (S4) corresponding to the fourth laser beam (L4).

[0070] The spatial light modulator (330) may control the refractive indices of liquid crystals located in the regions (S1, S2, S3, S4) so that the laser beams (L1, L2, L3, L4) have phases that are orthogonal to each other. Specifically, the refractive indices of liquid crystals located in the first region (S1) may be set to output a laser beam having a phase distribution the same as the first row (r1) of the Hadamard matrix (H). Therefore, the first laser beam (L1) passing through the first region (S1) may have a phase distribution the same as the first row (r1).

[0071] The refractive indices of liquid crystals located in the second region (S2) may be set to output a laser beam having a phase distribution the same as the second row (r2) of the Hadamard matrix (H). Therefore, the second laser beam (L2) passing through the second region (S2) may have a phase distribution the same as the second row (r2).

[0072] The refractive indices of liquid crystals located in the third region (S3) may be set to output a laser beam having a phase distribution the same as the third row (r3) of the Hadamard matrix (H). Therefore, the third laser beam (L3) passing through the third region (S3) may have a phase distribution the same as the third row (r3).

[0073] The refractive indices of liquid crystals located in the fourth region (S4) may be set to output a laser beam having a phase distribution the same as the fourth row (r4) of the Hadamard matrix (H). Therefore, the fourth laser beam (L4) passing through the fourth region (S4) may have a phase distribution the same as the fourth row (r4).

[0074] The laser beams (L1, L2, L3, L4) passing through the spatial light modulator (330) may have phase distributions that are orthogonal to each other. Meanwhile, the first laser beam (L1) passing through the spatial light modulator (330) may have a uniform phase distribution. On the other hand, the laser beams (L2, L3, L4) passing through the spatial light modulator (330) may have non-uniform phase distributions.

[0075] Fig. 5C shows a method of beam formation using an illumination optical system (300) including a spatial light modulator (330) set based on a Hadamard matrix.

[0076] Referring to Fig. 5C, the laser beams (L1, L2, L3, L4, L5, L6, L7, L8) may propagate in the x-axis direction. The double-headed arrows indicate the polarization directions of the laser beams (L1, L2, L3, L4, L5, L6, L7, L8). The laser beams (L1, L2, L3, L4, L5, L6, L7, L8) passing through the lens array unit (310) may have the same phase and polarization direction.

[0077] The spatial light modulator (330) may include a first region (S1) corresponding to the first laser beam (L1), a second region (S2) corresponding to the second laser beam (L2), a third region (S3) corresponding to the third laser beam (L3), a fourth region (S4) corresponding to the fourth laser beam (L4), a fifth region (S5) corresponding to the fifth laser beam (L5), a sixth region (S6) corresponding to the sixth laser beam (L6), a seventh region (S7) corresponding to the seventh laser beam (L7), and an eighth region (S8) corresponding to the eighth laser beam (L8).

[0078] The refractive indices of liquid crystals located in the first region (S1) and the fifth region (S5) may be set to output a laser beam having a phase distribution the same as the first row (r1) of the Hadamard matrix (H). Therefore, the first laser beam (L1) and the fifth laser beam (L5) passing through the spatial light modulator (330) may have a phase distribution the same as the first row (r1). That is, the first laser beam (L1) and the fifth laser beam (L5) may have a uniform phase distribution.

[0079] The refractive indices of liquid crystals located in the second region (S2) and the sixth region (S6) may be set to output a laser beam having a phase distribution the same as the second row (r2) of the Hadamard matrix (H). Therefore, the second laser beam (L2) and the sixth laser beam (L6) passing through the spatial light modulator (330) may have a phase distribution the same as the second row (r2). That is, the second laser beam (L2) and the sixth laser beam (L6) may have a non-uniform phase distribution.

[0080] The refractive indices of liquid crystals located in the third region (S3) and the seventh region (S7) may be set to output a laser beam having a phase distribution the same as the third row (r3) of the Hadamard matrix (H). Therefore, the third laser beam (L3) and the seventh laser beam (L7) passing through the spatial light modulator (330) may have a phase distribution the same as the third row (r3). The third laser beam (L3) and the seventh laser beam (L7) may have a non-uniform phase distribution.

[0081] The refractive indices of liquid crystals located in the fourth region (S4) and the eighth region (S8) may be set to output a laser beam having a phase distribution the same as the fourth row (r4) of the Hadamard matrix (H). Therefore, the fourth laser beam (L4) and the eighth laser beam (L8) passing through the spatial light modulator (330) may have a phase distribution the same as the fourth row (r4). The fourth laser beam (L4) and the eighth laser beam (L8) may have a non-uniform phase distribution.

[0082] The polarizer (350) may be configured to adjust the polarization directions of the laser beams (L1, L2, L3, L4, L5, L6, L7, L8) passing through the spatial light modulator (330). For example, the polarizer (350) may adjust the polarization directions of the laser beams (L1, L2, L3, L4) to be in the y-axis direction. The polarizer (350) may adjust the polarization directions of the laser beams (L5, L6, L7, L8) to be in the x-axis direction. Therefore, the laser beams (L1, L2, L3, L4) and the laser beams (L5, L6, L7, L8) passing through the polarizer (350) may have orthogonal polarization directions to each other.

[0083] The polarizer (350) may include regions (A1, A2, A3, A4, A5, A6, A7, A8) respectively corresponding to the regions (S1, S2, S3, S4, S5, S6, S7, S8) of the spatial light modulator (330). At least one wave plate may be disposed in at least some of the regions (A1, A2, A3, A4, A5, A6, A7, A8). In one embodiment, at least one half-wave plate may be disposed in the regions (A1, A2, A3, A4), and no half-wave plates may be disposed in the regions (A5, A6, A7, A8). In another embodiment, no half-wave plates may be disposed in the regions (A1, A2, A3, A4), and at least one half-wave plate may be disposed in the regions (A5, A6, A7, A8).

[0084] The laser beams (L1, L2, L3, L4) passing through the polarizer (350) may have the same polarization direction, but since they have mutually orthogonal phases, interference may not occur even if they are overlapped. The laser beams (L5, L6, L7, L8) passing through the polarizer (350) may have the same polarization direction, but since they have mutually orthogonal phases, interference may not occur even if they are overlapped.

[0085] The first laser beam (L1) passing through the polarizer (350) may have the same phase as the fifth laser beam (L5), but since they have mutually orthogonal polarization directions, interference may not occur even if they are overlapped. The second laser beam (L2) passing through the polarizer (350) may have the same phase as the sixth laser beam (L6), but since they have mutually orthogonal polarization directions, interference may not occur even if they are overlapped. The third laser beam (L3) passing through the polarizer (350) may have the same phase as the seventh laser beam (L7), but since they have mutually orthogonal polarization directions, interference may not occur even if they are overlapped. The fourth laser beam (L4) passing through the polarizer (350) may have the same phase as the eighth laser beam (L8), but since they have mutually orthogonal polarization directions, interference may not occur even if they are overlapped.

[0086] As such, the illumination optical system (300) may prevent coherence noise between laser beams to be overlapped by controlling the phases and polarization directions of the laser beams.

[0087] Accordingly, the illumination optical system (300) may obtain a flat-top beam without coherence noise by allowing the laser beams (L1, L2, L3, L4, L5, L6, L7, L8) to be overlapped.

[0088] While the preferred embodiments of the present disclosure have been described and illustrated above, the present disclosure is not limited to the specific embodiments described above. Various modifications may be made by those of ordinary skill in the art without departing from the scope of the claims, and such modifications should not be construed as departing from the technical spirit or prospect of the present disclosure.

Claims

1.An illumination optical system comprising:a lens array unit configured to receive a plurality of laser beams provided from one side;a spatial light modulator configured to control phases of the plurality of laser beams passing through the lens array unit; anda condensing lens configured to overlap the plurality of laser beams passing through the spatial light modulator to form a flat-top beam,wherein the plurality of laser beams includes a first laser beam and a second laser beam passing through two adjacent lenses, andwherein the spatial light modulator is configured to control the first laser beam and the second laser beam to have different phases.2.The illumination optical system of claim 1, further comprising:a polarizer configured to adjust a polarization direction of at least some of the plurality of laser beams passing through the spatial light modulator,wherein the polarizer is configured to adjust the polarization directions of the first laser beam and the second laser beam to be orthogonal to each other.3.The illumination optical system of claim 1, wherein the spatial light modulator comprises:a liquid crystal layer including a plurality of liquid crystals, andwherein the spatial light modulator is configured to control the phase of the first laser beam or the second laser beam by individually adjusting refractive indices of the plurality of liquid crystals based on thicknesses of lenses included in the lens array unit.4.The illumination optical system of claim 3, wherein the plurality of liquid crystals comprises:a plurality of first liquid crystals corresponding to a first lens through which the first laser beam passes, anda plurality of second liquid crystals corresponding to a second lens through which the second laser beam passes, andwherein the first laser beam passing through the plurality of first liquid crystals and the second laser beam passing through the plurality of second liquid crystals have uniform phase distributions.5.The illumination optical system of claim 1, wherein at least some of the plurality of laser beams passing through the spatial light modulator have non-uniform phase distributions.6.The illumination optical system of claim 1, wherein the spatial light modulator is configured to control the phases of the plurality of laser beams based on a Hadamard matrix.7.The illumination optical system of claim 2, further comprising:a first lens unit configured to reduce a size of the plurality of laser beams passing through the lens array unit and transfer them to the spatial light modulator; anda second lens unit configured to enlarge a size of the plurality of laser beams passing through the spatial light modulator and transfer them to the polarizer.8.The illumination optical system of claim 2, wherein the polarizer comprises a plurality of half-wave plates arranged at predetermined intervals.9.A method of forming a laser beam using an illumination optical system including a lens array unit, a spatial light modulator, a polarizer, and a condensing lens, the method comprising:irradiating a plurality of laser beams provided from one side onto the spatial light modulator using the lens array unit;controlling phases of the plurality of laser beams using the spatial light modulator; andforming a flat-top beam by overlapping the plurality of laser beams passing through the spatial light modulator using the condensing lens,wherein the plurality of laser beams includes a first laser beam and a second laser beam passing through two adjacent lenses, andwherein the spatial light modulator controls the first laser beam and the second laser beam to have different phases.10.The method of claim 9, further comprising:adjusting a polarization direction of at least some of the plurality of laser beams passing through the spatial light modulator using the polarizer,wherein the polarizer adjusts the polarization directions of the first laser beam and the second laser beam to be orthogonal to each other.11.The method of claim 9, wherein the spatial light modulator comprises:a liquid crystal layer including a plurality of liquid crystals, andwherein the spatial light modulator controls the phase of the first laser beam or the second laser beam by individually adjusting refractive indices of the plurality of liquid crystals based on thicknesses of lenses included in the lens array unit.12.The method of claim 11, wherein the plurality of liquid crystals comprises:a plurality of first liquid crystals corresponding to a first lens through which the first laser beam passes, anda plurality of second liquid crystals corresponding to a second lens through which the second laser beam passes, andwherein the first laser beam passing through the plurality of first liquid crystals and the second laser beam passing through the plurality of second liquid crystals have uniform phase distributions.13.The method of claim 9, wherein the spatial light modulator controls the phases of the plurality of laser beams based on a Hadamard matrix.14.The method of claim 9, wherein the illumination optical system further comprises a first lens unit and a second lens unit, the method further comprising:reducing a size of the plurality of laser beams passing through the lens array unit and transferring them to the spatial light modulator using the first lens unit; andenlarging a size of the plurality of laser beams passing through the spatial light modulator and transferring them to the polarizer using the second lens unit.15.A laser annealing apparatus comprising:a light source unit configured to provide a plurality of laser beams;a transfer optical system configured to align the plurality of laser beams;an illumination optical system configured to form a flat-top beam from the plurality of laser beams transferred from the transfer optical system; andan imaging optical system configured to image the flat-top beam onto a workpiece,wherein the illumination optical system comprises:a lens array unit configured to receive the plurality of laser beams;a spatial light modulator configured to control phases of the plurality of laser beams passing through the lens array unit; anda condensing lens configured to overlap the plurality of laser beams passing through the spatial light modulator to form the flat-top beam,wherein the plurality of laser beams includes a first laser beam and a second laser beam passing through two adjacent lenses, andwherein the spatial light modulator is configured to control the first laser beam and the second laser beam to have different phases.

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