Free electron laser beam shaping structure applied to integrated circuit

Abstract

The invention provides a free electron laser beam shaping structure applied to an integrated circuit. The structure comprises a beam expanding unit, a light field homogenization unit and a relay transmission unit. The beam expanding unit is used for expanding the light spot cross section size of a first light beam in a first plane and the light spot cross section size of the first light beam in a second plane to obtain a third light beam. The light field homogenization unit is used for carrying out light field homogenization treatment on the third light beam along the first plane to obtain a plurality of fourth light beams; performing light field homogenization processing on any fourth light beam along a second plane to obtain a corresponding fifth light beam; superposing the plurality of fifth light beams to obtain a sixth light beam; the relay transmission unit is used for focusing or collimating the sixth light beam to obtain a seventh light beam; reflecting the seventh light beam to obtain an eighth light beam; and focusing or collimating the eighth light beam to obtain a ninth light beam, and transmitting the ninth light beam to an optical element of the application terminal. The shaped FEL light source output light beam can be applied to the field of integrated circuit manufacturing.

Description

Technical Field

[0001] The present application relates to the technical field of optical devices, and particularly to a free electron laser beam shaping structure applied to integrated circuits. Background Art

[0002] Due to the outstanding advantages of free-electron laser (FEL) light sources, such as high brightness, short pulses, full coherence, and high purity, they have broad application and development space in many research fields such as optics, condensed matter physics, quantum physics, life science, and chemistry. In particular, the high brightness is improved by several orders of magnitude compared with the previous generation of synchrotron radiation light sources, and its higher brightness means better resolution can be obtained in dimensions such as space, energy, and time. Currently, EUV lithography technology using a 13.5 nm wavelength band is the main technical means to support smaller process nodes (such as 7 nm, 5 nm, or even more advanced nodes). Therefore, how to apply FEL light sources in the field of integrated circuit manufacturing is also the core technology that domestic and foreign researchers are focusing on.

[0003] The beam line output from the FEL light source has an extremely small spot size, such as a spot diameter in the order of dozens of micrometers or hundreds of micrometers. The FEL beam line also has an extremely narrow spectral width. Therefore, the FEL light source has ultra-high temporal coherence and spatial coherence. However, in the field of integrated circuit manufacturing, high coherence is an unfavorable factor, which will produce speckles and imaging line edge artifacts due to interference effects, reducing the imaging resolution. In addition, the beam line output from the FEL light source has ultra-high collimation, and the beam divergence is extremely small, such as dozens of micro-radians or hundreds of micro-radians, etc. At the same time, the cross-sectional light intensity distribution of the beam line presents a Gaussian-like profile distribution.

[0004] The above characteristics all make the beam line output from the FEL light source unable to meet the requirements of integrated circuit manufacturing for specific spot sizes, specific divergence characteristics (NA), and high illumination uniformity, etc., resulting in the beam line output from the FEL light source being unable to be directly used in the field of integrated circuit manufacturing. Summary of the Invention

[0005] In view of this, the present application proposes a free electron laser beam shaping structure applied to integrated circuits to solve the problem that the beam line output from the FEL light source in related technologies cannot be applied to the field of integrated circuit manufacturing because various parameters cannot meet the requirements of integrated circuit manufacturing.

[0006] The first aspect embodiment of the present application proposes a free electron laser beam shaping structure applied to integrated circuits, and the structure includes a beam expansion unit, a light field homogenization unit, and a relay transmission unit:

[0007] The beam expander unit includes a first cylindrical mirror group disposed perpendicular to the first plane and a second cylindrical mirror group disposed perpendicular to the second plane, where the first plane and the second plane are perpendicular to each other; the first cylindrical mirror group is configured to receive a first beam and broaden the spot cross-sectional dimension of the first beam in the first plane to obtain a second beam, and the second cylindrical mirror group is configured to receive the second beam and broaden the spot cross-sectional dimension of the second beam in the second plane to obtain a third beam;

[0008] The light field homogenization unit includes a first toroidal mirror, a first light homogenizer disposed perpendicular to the first plane, and a second light homogenizer disposed perpendicular to the second plane; the first light homogenizer is configured to receive the third beam, perform light field intensity homogenization processing on the third beam along the first plane to obtain a plurality of fourth beams, and emit the plurality of fourth beams; the second light homogenizer is configured to receive the plurality of fourth beams, perform light field intensity homogenization processing on any one of the fourth beams along the second plane to obtain a corresponding fifth beam, and emit the plurality of fifth beams; the first toroidal mirror is configured to receive the plurality of fifth beams and superimpose the plurality of fifth beams to obtain a sixth beam;

[0009] The relay transmission unit includes a second toroidal mirror, a third toroidal mirror, and at least one planar mirror disposed between the second toroidal mirror and the third toroidal mirror; the second toroidal mirror is configured to focus or collimate the sixth beam to obtain a seventh beam and emit the seventh beam; the at least one planar mirror is configured to reflect the seventh beam at least once to obtain an eighth beam and emit the eighth beam; the third toroidal mirror is configured to focus or collimate the eighth beam to obtain a ninth beam and emit the ninth beam onto a target optical element of the application terminal.

[0010] A free electron laser beam shaping structure applied to an integrated circuit proposed in an embodiment of the present application is conceived by combining the output beam line parameter characteristics of the FEL light source during the design process of its three core units (i.e., the beam expander unit, the light field homogenization unit, and the relay transmission unit), and is particularly suitable for FEL applications. For example: the beam expander unit can adjust and optimize the extremely small spot size of the output beam line of the FEL light source, the light field homogenization unit can adjust and optimize the Gaussian-like intensity distribution characteristics of the output beam line of the FEL light source, and the relay transmission unit can make the beam emitted from the output beam line of the FEL light source to the application terminal have a stable light field homogenization effect. Through the coordinated cooperation of the three core units, the output beam of the FEL light source shaped by the embodiment of the present application can be directly applied to the field of integrated circuit manufacturing.

[0011] In an embodiment of the present application, the first cylindrical mirror group includes a first convex cylindrical mirror and a first concave cylindrical mirror; the combination of the first convex cylindrical mirror and the first concave cylindrical mirror is used to broaden the spot cross-sectional size of the first light beam in the first plane;

[0012] The second cylindrical mirror group includes a second convex cylindrical mirror and a second concave cylindrical mirror; the combination of the second convex cylindrical mirror and the second concave cylindrical mirror is used to broaden the spot cross-sectional size of the second light beam in the second plane.

[0013] In an embodiment of the present application, the first light homogenizing element includes a first reflection array and a second reflection array arranged in parallel; the second light homogenizing element includes a third reflection array and a fourth reflection array arranged in parallel; the first reflection array and the second reflection array include a plurality of first light homogenizing units arranged in sequence; the third reflection array and the fourth reflection array include a plurality of second light homogenizing units arranged in sequence.

[0014] In an embodiment of the present application, the axis direction of each first light homogenizing unit is perpendicular to the first plane, and the axis direction of each second light homogenizing unit is perpendicular to the second plane; the arrangement direction of the plurality of first light homogenizing units is perpendicular to the arrangement direction of the plurality of second light homogenizing units.

[0015] In an embodiment of the present application, the axis directions of the first light homogenizing units in the first reflection array and the first light homogenizing units in the second reflection array are parallel; the axis directions of the second light homogenizing units in the third reflection array and the second light homogenizing units in the fourth reflection array are parallel.

[0016] In an embodiment of the present application, the structural parameters of the first reflection array and the second reflection array are the same, and the structural parameters of the third reflection array and the fourth reflection array are the same; the structural parameters include the number of light homogenizing units, the curvature radius of the light homogenizing units, and the width of the light homogenizing units.

[0017] In an embodiment of the present application, when the first plane is the yz plane in a three-dimensional coordinate system, the second plane is the xz plane in the three-dimensional coordinate system; when the first plane is the xz plane in the three-dimensional coordinate system, the second plane is the yz plane in the three-dimensional coordinate system.

[0018] In an embodiment of the present application, the first light homogenizing element includes a fifth reflection array; the fifth reflection array includes a plurality of first light homogenizing units arranged in sequence; the second light homogenizing element includes a sixth reflection array; the sixth reflection array includes a plurality of second light homogenizing units arranged in sequence; the arrangement direction of the plurality of first light homogenizing units is perpendicular to the arrangement direction of the plurality of second light homogenizing units.

[0019] In an embodiment of the present application, the first light beam is the light beam output by a free electron laser light source.

[0020] In an embodiment of the present application, the application terminal is any one of a lithography exposure device, a lithography process research device, and a defect detection device.

[0021] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be understood through the practice of the present application. Description of the Drawings

[0022] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present application. Moreover, throughout the drawings, the same reference numerals are used to represent the same components.

[0023] In the drawings:

[0024] Figure 1 A schematic structural diagram of a free electron laser beam shaping structure applied to an integrated circuit provided by an embodiment of the present application is shown;

[0025] Figure 2 A specific structural diagram of an expanding unit from a first plane perspective provided by an embodiment of the present application is shown;

[0026] Figure 3 A specific structural diagram of an expanding unit from a second plane perspective provided by an embodiment of the present application is shown;

[0027] Figure 4 A specific structural diagram of a light field homogenizing unit from a first plane perspective provided by an embodiment of the present application is shown;

[0028] Figure 5 A specific structural diagram of a light field homogenizing unit from a second plane perspective provided by an embodiment of the present application is shown;

[0029] Figure 6 A schematic diagram showing the arrangement direction of a light homogenizing unit provided by an embodiment of the present application is shown;

[0030] Figure 7 A schematic diagram showing another specific structure of a light field homogenizing unit provided by an embodiment of the present application is shown;

[0031] Figure 8 A schematic enlarged view of the structure of a fly-eye array provided by an embodiment of the present application is shown;

[0032] Figure 9The structural schematic diagram of the relay transmission unit provided by an embodiment of the present application is shown. Detailed implementation manners

[0033] Hereinafter, the exemplary embodiments of the present application will be described in more detail with reference to the accompanying drawings. Although the exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present application can be more thoroughly understood and the scope of the present application can be completely conveyed to those skilled in the art.

[0034] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in the present application should have the ordinary meanings understood by those skilled in the art to which the present application belongs.

[0035] The free electron laser beam shaping structure applied to integrated circuits provided by the embodiments of the present application can adjust and optimize parameters such as the Gaussian-like intensity distribution characteristics, high collimation characteristics, and extremely small spot size of the output beam line of accelerator light sources such as FEL, and reduce the influence of interference effects caused by coherence. The beam line after passing through the shaping optical path structure can meet the relevant application requirements in the field of integrated circuit manufacturing.

[0036] Combined with the parameter characteristics of the output beam line of the FEL light source in the EUV band and even the soft X-ray band, the embodiments of the present application propose a shaping optical path structure design that is particularly suitable for its application, which has the advantages of high processability, easy implementation, high energy utilization rate, and stable structural performance. The beam line shaping optical path structure proposed in the present application is equally applicable to other application fields other than integrated circuit manufacturing.

[0037] For ease of description, three directions are defined, namely the first direction (x-axis), the second direction (y-axis), and the third direction (z-axis) in a three-dimensional coordinate system. Among them, when the first plane is the yz plane, that is, the plane formed by the y-axis and the z-axis, the second plane is the xz plane, that is, the plane formed by the x-axis and the z-axis; conversely, when the first plane is the xz plane, that is, the plane formed by the x-axis and the z-axis, the second plane is the yz plane, that is, the plane formed by the y-axis and the z-axis.

[0038] In this embodiment, a free electron laser beam shaping structure applied to integrated circuits is provided. Figure 1 It is the structural schematic diagram of the free electron laser beam shaping structure according to the embodiment of the present application, as Figure 1 shown: The free electron laser beam shaping structure includes a beam expanding unit, a light field homogenizing unit, and a relay transmission unit. The FEL beam line passes through the shaping optical path structure and is output at the intermediate focus (IF) for subsequent terminal applications (such as lithography exposure devices, lithography process research devices, defect detection devices).

[0039] The specific structure of the beam expander unit is as Figure 2 and Figure 3 shown below: Figure 2 is a schematic diagram of the specific structure of the beam expander unit from the perspective of the first plane (for example, the yz plane), Figure 3 is a schematic diagram of the specific structure of the beam expander unit from the perspective of the second plane (for example, the xz plane). The function of the beam expander unit is to broaden the beam line of the FEL with an extremely small spot size (such as a spot diameter in the order of dozens of micrometers or hundreds of micrometers), increasing the cross-sectional size of the spot, so as to serve the subsequent optical field homogenization unit. In addition, the increased spot size after passing through the beam expander unit can also reduce the damage risk of the FEL's ultra-high power density to the subsequent optical elements and improve the service life of the subsequent optical elements.

[0040] In some specific embodiments, the beam expander unit includes a first cylindrical mirror group perpendicular to the first plane (including a first convex cylindrical mirror M1 and a first concave cylindrical mirror M2 arranged in parallel and offset, with the convex surface of M1 facing the concave surface of M2) and a second cylindrical mirror group perpendicular to the second plane (including a second convex cylindrical mirror M3 and a second concave cylindrical mirror M4 arranged in parallel and offset, with the convex surface of M3 facing the concave surface of M4). The first plane and the second plane are perpendicular to each other. The shape of the cylindrical mirror is not specifically limited in the embodiments of the present application.

[0041] During the beam propagation process, the beam output by the FEL light source is emitted to the convex side of M1, and the beam is reflected to the concave side of M2 through the convex side of M1. The convex surface of M1 diverges the beam, thus broadening the spot cross-sectional size of the beam in the first plane; the beam is then reflected from the concave side of M2 to the convex side of M3. The concave surface of M2 focuses the beam to form a collimated beam; and the beam is reflected from the convex side of M3 to the concave side of M4, and finally the concave side of M4 emits the beam to the optical field homogenization unit.

[0042] In some specific embodiments, the two sets of cylindrical mirror groups are orthogonally distributed, respectively used to broaden the spot cross-sections in two orthogonal planes, namely vertical and horizontal, as Figure 2 、 Figure 3 shown below: The combination of M1 and M2 is used to broaden the spot cross-sectional size in the yz plane, and the combination of M3 and M4 is used to broaden the spot cross-sectional size in the xz plane. In addition, M1 and M2 have no contribution to the spot magnification in the xz plane, and M3 and M4 have no contribution to the spot magnification in the yz plane.

[0043] In some specific embodiments, the incident modes of M1 to M4 are all grazing incidence, and the grazing incident angle is within 10°, or within 5°. The advantage of using grazing incidence is that a single-layer metal film can be deposited on the surface of the component to improve the reflectivity of the EUV beamline. If the incident angle is other angles than grazing incidence, a molybdenum-silicon multilayer film must be deposited on the surface of the component, which will increase the coating difficulty and cost. When the incident angles of the two components in each set of mirror groups are equal, the transmission direction of the output beam can be kept consistent with the incident beam direction.

[0044] In the embodiment of the present application, the first cylindrical mirror group is used to receive the first light beam and broaden the spot cross-sectional size of the first light beam in the first plane to obtain a second light beam, and the second cylindrical mirror group is used to receive the second light beam and broaden the spot cross-sectional size of the second light beam in the second plane to obtain a third light beam.

[0045] In the embodiment of the present application, through the first cylindrical mirror group perpendicular to the first plane and the second cylindrical mirror group perpendicular to the second plane, the "minimum spot size" parameter of the output light beam of the FEL light source can be effectively adjusted and optimized, thus providing the possibility for the output light beam of the FEL light source to meet the relevant application requirements in the field of integrated circuit manufacturing.

[0046] In some specific embodiments, the specific structure of the light field homogenization unit is as Figure 4 and Figure 5 shown: Figure 4 is a schematic structural diagram of the light field homogenization unit from the perspective of the first plane, Figure 5 is a schematic structural diagram of the light field homogenization unit from the perspective of the second plane.

[0047] As Figure 4 and Figure 5 shown: The light field homogenization unit includes a first toroidal mirror P5, a first light homogenizing member perpendicular to the first plane (including a first reflection array P1 and a second reflection array P2 arranged in parallel), and a second light homogenizing member perpendicular to the second plane (including a third reflection array P3 and a fourth reflection array P4 arranged in parallel); the first plane and the second plane are perpendicular to each other.

[0048] In the embodiment of the present application, the first reflection array P1 and the second reflection array P2 include a plurality of first light homogenizing units arranged in sequence. Each first light homogenizing unit is a concave cylindrical structure and has a radius of curvature only in one dimension. The number n of the light homogenizing units is a natural number greater than 1. All the first light homogenizing units in the first reflection array P1 are arranged adjacent to each other in sequence, for example Figure 6 a1 or a2 in

[0049] In the embodiments of the present application, the axial directions of the first light homogenizing units in the first reflection array P1 and the first light homogenizing units in the second reflection array P2 are parallel. For example Figure 4 as shown.

[0050] In the embodiments of the present application, the axial direction of each first light homogenizing unit is perpendicular to the first plane. For example Figure 4 as shown, the axial directions of the first light homogenizing units in P1 and P2 are perpendicular to the yz plane.

[0051] In the embodiments of the present application, the structural parameters of the first reflection array P1 and the second reflection array P2 are the same, and the structural parameters include the number of light homogenizing units, the curvature radius of the light homogenizing units, and the width of the light homogenizing units.

[0052] In the embodiments of the present application, the third reflection array P3 and the fourth reflection array P4 include a plurality of second light homogenizing units arranged in sequence. Each second light homogenizing unit is a concave cylindrical structure and has a curvature radius only in one dimension. The number n of light homogenizing units is a natural number greater than 1. All the second light homogenizing units in the third reflection array P3 are arranged adjacent to each other in sequence. For example Figure 6 a1 or a2 in

[0053] In the embodiments of the present application, the arrangement direction of the plurality of first light homogenizing units is perpendicular to the arrangement direction of the plurality of second light homogenizing units. For example Figure 6 as shown: when the arrangement direction of the plurality of first light homogenizing units is a1, the arrangement direction of the plurality of second light homogenizing units is a2. Conversely, when the arrangement direction of the plurality of first light homogenizing units is a2, the arrangement direction of the plurality of second light homogenizing units is a1.

[0054] In the embodiments of the present application, the axial direction of each second light homogenizing unit is perpendicular to the second plane. For example Figure 5 as shown, the axial directions of the second light homogenizing units in P3 and P4 are perpendicular to the xz plane.

[0055] In the embodiments of the present application, the axial directions of the second light homogenizing units in the third reflection array P3 and the second light homogenizing units in the fourth reflection array P4 are parallel. For example Figure 5 as shown.

[0056] In the embodiments of the present application, the structural parameters of the third reflection array and the fourth reflection array are the same, and the structural parameters include the number of light homogenizing units, the curvature radius of the light homogenizing units, and the width of the light homogenizing units.

[0057] In the embodiments of the present application, the number of the first light homogenizing units in P1 and P2 is the same, and the number of the second light homogenizing units in P3 and P4 is the same. The number of sub-units of P1 / P2 and P3 / P4 can be the same or different. As Figure 6As shown, the reflection arrays of P1 to P4 each contain 5 light homogenizing units, and the number of light homogenizing units can also be any other natural number.

[0058] The propagation of light beams in the above light field homogenizing unit is as follows:

[0059] The first light homogenizing member is configured to receive the third light beam, perform light field intensity homogenization on the third light beam along the first plane to obtain a plurality of fourth light beams, and emit the plurality of fourth light beams; the second light homogenizing member is configured to receive the plurality of fourth light beams, perform light field intensity homogenization on any one of the fourth light beams along the second plane to obtain a corresponding fifth light beam, and emit a plurality of fifth light beams; the first toroidal mirror is configured to receive the plurality of fifth light beams and superimpose the plurality of fifth light beams to obtain a sixth light beam.

[0060] In the embodiment of the present application, the first light homogenizing member perpendicular to the first plane (i.e., the yz plane) is configured to perform shaping processing on the incident beam line along the yz plane and has no contribution to the beam line in the xz plane. It can be understood that: by adjusting the distribution of light in the up-down and front-back directions (yz plane) through the first reflection array and the second reflection array, the adjusted light becomes uniform in the yz plane, but the light spot in the left-right direction (xz plane) is still non-uniform.

[0061] In the embodiment of the present application, the second light homogenizing member perpendicular to the second plane (i.e., the xz plane) is configured to perform shaping processing on the incident beam line along the xz plane and has no contribution to the beam line in the yz plane. It can be understood that: by adjusting the distribution of light in the left-right and front-back directions (xz plane) through the third reflection array and the fourth reflection array, the adjusted light becomes uniform in the xz plane, but the light spot in the up-down direction (yz plane) has already been uniform and remains unchanged.

[0062] In the embodiment of the present application, the incident collimated light (i.e., the above-mentioned third light beam) passes through P1 - P2 - P3 - P4 in sequence, and then is collected by the P5 toroidal mirror and converges on the image plane behind P5. Due to the multi-beam superposition effect, a highly uniform light field is generated on the image plane behind P5.

[0063] Among them, the collimated light is divided into several sub-beams by P1, and each sub-beam converges on the corresponding sub-unit surface of P2 after being reflected by the P1 sub-unit. The P1 reflection surface is located on the front focal plane of P2; the collimated light in the xz plane is divided into several sub-beams by P3, and the sub-beams converge on the corresponding sub-unit surface of P4 after being reflected by the P3 sub-unit. The P3 reflection surface is located on the front focal plane of P4.

[0064] P5 is used to collect several sub - beams that divide P1 to P4 and converge them on the image plane behind P5. Among them, P1 is an object in the yz plane, and P3 is an object in the xz plane. Both are imaged on the same image plane by P5. Therefore, P5 is a toroidal mirror with different curvature radii on the yz plane and the xz plane. The toroidal mirror has different beam shaping capabilities in two - dimensional orthogonal planes.

[0065] According to the object - image relationship formula of the following off - axis reflection system, parameters such as the relevant curvature radius of P5 can be calculated:

[0066] (1 / p)+(1 / q)=2 / (R t cosθ)

[0067] (1 / p)+(1 / q)=2cosθ / R S

[0068] Where p and q are the object distance and the image distance respectively, and θ is the surface incident angle.

[0069] In some specific embodiments, the surface incident angles of the reflection arrays of P1 to P4 are small - angle incidences, and the surface incident angle of P5 is a large - angle grazing incidence. In addition, other incident angles can also be adopted for P1 to P5, such as all small - angle incidences or all large - angle grazing incidences, which are not specifically limited here.

[0070] In some specific embodiments, the first reflection array P1 and the second reflection array P2 in the first light - homogenizing element are placed in parallel and misaligned, and the translation distance (i.e., the distance from P1 to P2) is a preset distance (for example, 200 mm); the incident light beam (i.e., the first light beam) forms a preset angle (for example, 45°) with the first reflection array.

[0071] The incident light beam is incident on the first reflection array P1 at an angle of 45°. The light beam is divided into multiple partial light beams by the multiple first light - homogenizing units of the first reflection array P1 and reflected respectively. After being reflected by the multiple first light - homogenizing units of the second reflection array P2, multiple light beams parallel to the incident light beam direction (i.e., the fourth light beam) are formed; each fourth light beam is reflected onto the third reflection array P3 at an angle of 45°. The fourth light beam is divided into multiple partial light beams by the multiple second light - homogenizing units of the third reflection array P3 and reflected respectively. After being reflected by the multiple second light - homogenizing units of the fourth reflection array P4, multiple light beams parallel to the fourth light beam direction (i.e., the fifth light beam) are formed. The toroidal mirror P5 receives and superimposes the multiple fifth light beams to obtain the sixth light beam.

[0072] In the embodiment of the present application, through the first light homogenizing element (i.e., the first reflection array and the second reflection array), the distribution of light in the up-down and front-back directions (yz plane) is adjusted, so that the adjusted light becomes uniform in the yz plane; and through the second light homogenizing element (i.e., the third reflection array and the fourth reflection array), the distribution of light in the left-right and front-back directions (xz plane) is adjusted, so that the adjusted light becomes uniform in the xz plane, which can effectively improve the non-uniformity of the intensity distribution of the light field in different directions; and the toroidal mirror is used to superimpose multiple third light beams to obtain a fourth light beam. Through this superimposing method, the uniformity of the light field intensity is further improved; thus, the Gaussian-like intensity distribution characteristics of the initial light spot of the FEL light source are significantly improved, and the uniformity of the illumination light field intensity is increased.

[0073] In some specific embodiments, the first light homogenizing element includes a fifth reflection array; the fifth reflection array includes a plurality of first light homogenizing units arranged in sequence; the second light homogenizing element includes a sixth reflection array; the second reflection array includes a plurality of second light homogenizing units arranged in sequence; the arrangement direction of the plurality of first light homogenizing units is perpendicular to the arrangement direction of the plurality of second light homogenizing units.

[0074] In the embodiment of the present application, the fifth reflection array is used to shape the incident beam line along the yz plane, and the distribution of light in the up-down and front-back directions (yz plane) is adjusted. The sixth reflection array is used to shape the incident beam line along the xz plane, and the distribution of light in the left-right and front-back directions (xz plane) is adjusted, which can achieve the purpose of homogenizing the light field intensity of the light beam, but its homogenizing effect is not as good as that of the above embodiment "the first light homogenizing element includes a first reflection array and a second reflection array, and the second light homogenizing element includes a third reflection array and a fourth reflection array".

[0075] In some specific embodiments, another specific structure of the light field homogenizing unit is as Figure 7 shown:

[0076] The light field homogenizing unit is composed of two reflective fly-eye arrays Q1 and Q2, and a collecting mirror Q3. Figure 8It is a schematic enlarged view of the structures of fly-eye arrays Q1 and Q2. The surface of the fly-eye array consists of n×n reflection sub-units, where n is a natural number greater than 1. All sub-units within one fly-eye array have the same radius of curvature and aperture. Q1 and Q2 can have the same structural parameters (radius of curvature, sub-unit aperture, number of sub-units, etc.) or different structural parameters. Q3 is used to collect the sub-beams split by the fly-eye array, converge and overlap the sub-beams on the rear focal plane of Q3, so as to obtain a highly uniform light field on the rear focal plane. The size and divergence of the illumination light field on the rear focal plane of Q3 are related to the following parameters: the focal lengths of Q1 and Q2, the sub-unit aperture, the distance between Q2 and Q3, the focal length of Q3, etc. In order to reduce the design difficulty of the subsequent relay transmission unit and minimize the adverse effects of aberration, it is necessary to comprehensively match the above parameters so that the size of the illumination light field at the rear focal plane of Q3 is appropriate and the divergence angle is as small as possible, such as within ±5°, or within ±2°.

[0077] In the embodiment of the present application, Figure 8 The number of sub-units of the shown fly-eye array is 5×5, and the number of sub-units can also be any other natural number greater than 1.

[0078] In the embodiment of the present application, Figure 7 The shown fly-eye array uses a small incident angle, and the collection mirror uses a large incident angle (i.e., grazing incidence). However, the three mirrors can also use other incident angles, such as all using small incident angles, or all using large grazing incidence angles.

[0079] In the embodiment of the present application, Figure 7 The shown light field homogenization unit can also be composed of a reflective fly-eye array and a collection mirror.

[0080] There are many conventional technical methods for light field homogenization, such as light pipes, micro-vibrating mirror scanning, rotating diffusers, etc. However, for the light field homogenization of the FEL beam line, the light pipe has large energy loss due to multiple reflections, the angular velocity of the micro-vibrating mirror scanning is difficult to meet the application requirements of the ultra-high frequency output of the FEL, and it is difficult to control the rotating diffuser to obtain a good scattering angle range. Therefore, the light field homogenization technical means proposed in the present application based on the fly-eye array structure is particularly suitable for FEL beam line applications, and has the advantages of high energy utilization rate, easy implementation, stable structure, etc.

[0081] In addition, combined with the coherence length characteristics of the FEL beam (the coherence length is usually a dozen or dozens of microns), on the basis of the fly-eye array structure, structural forms such as steps or wedge angles can be further superimposed. At this time, all sub-units of the fly-eye array will not be distributed on the same horizontal plane, and there will be a height difference between them, thereby reducing the probability of interference between the beams of the sub-units, reducing the adverse effects of the high coherence of the FEL on the illumination uniformity, and improving the intensity distribution uniformity on the illumination surface.

[0082] The specific structure of the relay transmission unit is as follows Figure 9 as shown: The relay transmission unit includes a second toroidal mirror P6, a third toroidal mirror P7, and at least one plane mirror disposed between the second toroidal mirror and the third toroidal mirror.

[0083] The second toroidal mirror is used to focus or collimate the sixth light beam to obtain a seventh light beam and emit the seventh light beam; the at least one plane mirror is used to reflect the seventh light beam at least once to obtain an eighth light beam and emit the eighth light beam; the third toroidal mirror is used to focus or collimate the eighth light beam to obtain a ninth light beam and emit the ninth light beam onto the target optical element of the application terminal.

[0084] In the embodiment of the present application, the second toroidal mirror P6 and the third toroidal mirror P7 have a radius of curvature and are used for beam shaping. Since the optical path is an off-axis reflective transmission, the sagittal focal length of the toroidal mirror is different from the meridional focal length. The plane mirror is used to fold the optical path, reduce the volume, and guide the beam transmission direction so that the final output light beam passes through the IF point in a specific direction.

[0085] In the embodiment of the present application, the two toroidal mirrors P6 and P7 are used for two-stage magnifying imaging. P6 images the high-uniformity light field at the rear focal plane of P5 to the intermediate image plane, and the intermediate image plane, as an object, is imaged onto the target optical element of the far-field application terminal through P7 for the second time.

[0086] In the embodiment of the present application, the number of plane mirrors disposed between the second toroidal mirror and the third toroidal mirror, as well as the setting positions of each plane mirror, can be determined according to the specific position of the target optical element of the application terminal, and no specific limitation is made here.

[0087] In the embodiment of the present application Figure 9 all elements in the shown relay transmission unit are incident at a small angle within 10°, and in addition, all elements can also adopt other incident angles.

[0088] In the embodiment of the present application, the relay transmission unit plays multiple roles: First, it images the high-uniformity light field obtained by the upstream light field homogenization unit to a specific position in the far field (such as the target optical element in the application terminal) to ensure high intensity uniformity in the far field. In addition, the relay transmission unit also needs to reduce aberration. Second, it enables the beam to pass through the IF point (the IF point can be regarded as the output port of the mechanical aperture) in accordance with the characteristic transmission direction. The cross-sectional size of the spot at the IF point should be small, such as less than 10 mm, or less than 20 mm, to ensure that the beam passes through the output port completely without energy loss. Third, at the IF point, the beam needs to have a certain divergence or numerical aperture, such as NA needs to be greater than 0.2.

[0089] In the embodiment of the present application, it is considered that the light field homogenization effect of the light beam output by P5 in the light field homogenization unit will gradually deteriorate during the subsequent transmission process, and it is impossible to ensure that the light beam emitted to the application terminal has a stable light field homogenization effect. Therefore, the embodiment of the present application provides a relay transmission unit, that is, a second toroidal mirror P6, a third toroidal mirror P7, and at least one planar mirror disposed between the second toroidal mirror and the third toroidal mirror. With this structure, the light beam emitted to the application terminal can have a stable light field homogenization effect.

[0090] A free electron laser beam shaping structure applied to integrated circuits proposed in the embodiment of the present application is conceived by combining the beam line parameter characteristics of the FEL light source output during the design of its three core units (i.e., the beam expansion unit, the light field homogenization unit, and the relay transmission unit). It is particularly suitable for FEL applications. For example, the beam expansion unit can adjust and optimize the extremely small spot size of the FEL light source output beam line; the light field homogenization unit can adjust and optimize the Gaussian-like intensity distribution characteristics of the FEL light source output beam line; and the relay transmission unit can make the light beam of the FEL light source output beam line emitted to the application terminal have a stable light field homogenization effect. In addition, the structural scheme and parameters of each core unit need to consider the parameters of adjacent upstream and downstream units. Therefore, the three units are inseparable and are sequentially distributed to form a complete overall structure.

[0091] It should be noted that:

[0092] In the specification provided herein, a large number of specific details are described. However, it can be understood that the embodiments of the present application can be practiced without these specific details. In some instances, well-known structures and technologies are not shown in detail so as not to obscure the understanding of this specification.

[0093] Similarly, it should be understood that, in order to streamline the present application and help understand one or more of the various inventive aspects, in the above description of the exemplary embodiments of the present application, the various features of the present application are sometimes grouped together into a single embodiment, figure, or description thereof. However, the disclosed method should not be construed as reflecting the following schematic: that the claimed present application requires more features than those expressly recited in each claim. Rather, as reflected by the following claims, the inventive aspect lies in less than all the features of the single foregoing disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into the detailed description, where each claim itself serves as a separate embodiment of the present application.

[0094] In addition, those skilled in the art can understand that although some of the embodiments described herein include certain features included in other embodiments rather than other features, the combination of features of different embodiments means that it is within the scope of this application and forms different embodiments. For example, in the following claims, any one of the claimed embodiments can be used in any combination.

[0095] As described above, the above are only the preferred specific embodiments of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in this application should be covered within the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the said claims.

Claims

1. A free electron laser beam shaping structure applied to an integrated circuit, characterized in that, The structure includes a beam expanding unit, a light field homogenizing unit, and a relay transmission unit: The beam expanding unit includes a first cylindrical mirror group perpendicular to the first plane and a second cylindrical mirror group perpendicular to the second plane, where the first plane and the second plane are perpendicular to each other; the first cylindrical mirror group is configured to receive a first beam and broaden the spot cross-sectional size of the first beam in the first plane to obtain a second beam, and the second cylindrical mirror group is configured to receive the second beam and broaden the spot cross-sectional size of the second beam in the second plane to obtain a third beam; The light field homogenizing unit includes a first toroidal mirror, a first light homogenizing member perpendicular to the first plane, and a second light homogenizing member perpendicular to the second plane; the first light homogenizing member is configured to receive the third beam, perform light field intensity homogenization processing on the third beam along the first plane to obtain a plurality of fourth beams, and emit the plurality of fourth beams; the second light homogenizing member is configured to receive the plurality of fourth beams, perform light field intensity homogenization processing on any one of the fourth beams along the second plane to obtain a corresponding fifth beam, and emit a plurality of fifth beams; the first toroidal mirror is configured to receive the plurality of fifth beams and superimpose the plurality of fifth beams to obtain a sixth beam; The relay transmission unit includes a second toroidal mirror, a third toroidal mirror, and at least one planar mirror disposed between the second toroidal mirror and the third toroidal mirror; the second toroidal mirror is configured to focus or collimate the sixth beam to obtain a seventh beam and emit the seventh beam; the at least one planar mirror is configured to reflect the seventh beam at least once to obtain an eighth beam and emit the eighth beam; the third toroidal mirror is configured to focus or collimate the eighth beam to obtain a ninth beam and emit the ninth beam onto a target optical element of an application terminal.

2. The beam shaping structure according to claim 1, wherein the first cylindrical mirror group includes a first convex cylindrical mirror and a first concave cylindrical mirror; the combination of the first convex cylindrical mirror and the first concave cylindrical mirror is configured to broaden the spot cross-sectional size of the first beam in the first plane; the second cylindrical mirror group includes a second convex cylindrical mirror and a second concave cylindrical mirror; the combination of the second convex cylindrical mirror and the second concave cylindrical mirror is configured to broaden the spot cross-sectional size of the second beam in the second plane.

3. The beam shaping structure according to claim 1 or 2, characterized in that, The first light homogenizing member includes a first reflection array and a second reflection array arranged in parallel; the second light homogenizing member includes a third reflection array and a fourth reflection array arranged in parallel; the first reflection array and the second reflection array include a plurality of first light homogenizing units arranged in sequence; the third reflection array and the fourth reflection array include a plurality of second light homogenizing units arranged in sequence.

4. The beam shaping structure according to claim 3, wherein The axial direction of each first light homogenizing unit is perpendicular to the first plane, and the axial direction of each second light homogenizing unit is perpendicular to the second plane; the arrangement direction of the plurality of first light homogenizing units is perpendicular to the arrangement direction of the plurality of second light homogenizing units.

5. The beam shaping structure according to claim 3, characterized in that The axial directions of the first light homogenizing units in the first reflection array and the first light homogenizing units in the second reflection array are parallel; the axial directions of the second light homogenizing units in the third reflection array and the second light homogenizing units in the fourth reflection array are parallel.

6. The beam shaping structure according to claim 3, wherein The structural parameters of the first reflection array and the second reflection array are the same, and the structural parameters of the third reflection array and the fourth reflection array are the same; the structural parameters include the number of light homogenizing units, the radius of curvature of the light homogenizing units, and the width of the light homogenizing units.

7. The beam shaping structure according to claim 1, characterized in that When the first plane is the yz plane in the three-dimensional coordinate system, the second plane is the xz plane in the three-dimensional coordinate system; when the first plane is the xz plane in the three-dimensional coordinate system, the second plane is the yz plane in the three-dimensional coordinate system.

8. The beam shaping structure according to claim 1, characterized in that, The first light homogenizing member includes a fifth reflection array; the fifth reflection array includes a plurality of first light homogenizing units arranged in sequence; the second light homogenizing member includes a sixth reflection array; the sixth reflection array includes a plurality of second light homogenizing units arranged in sequence; the arrangement direction of the plurality of first light homogenizing units is perpendicular to the arrangement direction of the plurality of second light homogenizing units.

9. The beam shaping structure according to claim 1, wherein The first light beam is the light beam output by a free electron laser light source.

10. The beam shaping structure according to claim 1, characterized in that, The application terminal is any one of a lithography exposure device, a lithography process research device, and a defect detection device.

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