CN112415870B - Prism assembly, optical system, photoetching equipment and light field rotation method - Google Patents
Prism assembly, optical system, photoetching equipment and light field rotation method Download PDFInfo
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- CN112415870B CN112415870B CN201910786560.7A CN201910786560A CN112415870B CN 112415870 B CN112415870 B CN 112415870B CN 201910786560 A CN201910786560 A CN 201910786560A CN 112415870 B CN112415870 B CN 112415870B
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F9/00—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically
- G03F9/70—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically for microlithography
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
- G03F7/70—Microphotolithographic exposure; Apparatus therefor
- G03F7/70058—Mask illumination systems
- G03F7/70141—Illumination system adjustment, e.g. adjustments during exposure or alignment during assembly of illumination system
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
- G03F9/00—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically
- G03F9/70—Registration or positioning of originals, masks, frames, photographic sheets or textured or patterned surfaces, e.g. automatically for microlithography
- G03F9/7065—Production of alignment light, e.g. light source, control of coherence, polarization, pulse length, wavelength
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Abstract
The invention relates to a prism assembly, an optical system, a photoetching device and a light field rotating method, wherein the prism assembly comprises an incident surface, a light splitting surface, a plurality of first internal reflection surfaces, a plurality of second internal reflection surfaces and a light combining surface, light beams enter the prism assembly from the incident surface and are split on the light splitting surface to obtain orthogonal S polarized light and P polarized light, then the S polarized light is reflected on the first internal reflection surfaces for multiple times and then is transmitted on the light combining surface to obtain first emergent light, meanwhile, the P polarized light is reflected on the second internal reflection surfaces and the light combining surface for multiple times to obtain second emergent light, the first emergent light and the second emergent light are overlapped, and the incident direction and the emergent direction of the light beams are mutually vertical during each reflection. The invention has the advantage that the condition that the polarization state of the light beam is changed in the reflection process can be avoided without arranging dielectric films on all the reflecting surfaces of the prism assembly.
Description
Technical Field
The invention relates to the technical field of integrated circuit manufacturing, in particular to a prism assembly, an optical system, photoetching equipment and a light field rotating method.
Background
Prior art lithographic apparatus are primarily used in the manufacture of integrated circuits IC or other microdevices. The key step in the fabrication of Integrated Circuits (ICs) using lithographic apparatus is the alignment of the reticle with the wafer, most of the current alignment methods are grating alignment. The grating alignment means that the uniform illumination light beam irradiates on the light beam alignment mark to be diffracted, the diffracted emergent light carries all information about the alignment mark, then the light field of the emergent light is separated, rotated and overlapped, and the alignment center position is finally determined through the photoelectric detector and signal processing.
At present, there is a grating alignment method, which generates two alignment mark images overlapped by rotating ± 90 degrees (relatively rotating 180 degrees) by a self-reference interferometer, then detects interference signals of overlapped diffraction orders on a pupil plane, and then obtains alignment position information according to a relative phase change of each diffraction order during mark scanning. The self-referencing interferometer used in the alignment method uses a prism having a plurality of internal reflection surfaces, and diffracted light is reflected by the prism a plurality of times and then emitted for alignment. In this method, each reflecting surface of the prism needs to be coated with a dielectric film to eliminate the polarization in different directions generated when the diffracted light is reflected and transmitted, thereby ensuring the alignment effect, but this method has the disadvantages of high cost and complex process.
Disclosure of Invention
The invention aims to provide a prism assembly, an optical system, a photoetching device and a light field rotating method, so that the production cost of the prism assembly is reduced while the alignment effect is ensured.
To achieve the above object, the present invention provides a prism assembly, comprising: an incident surface; a splitting plane; a plurality of first internal reflection surfaces; a plurality of second internal reflection surfaces; and a light converging surface;
a light beam enters the prism assembly from the incident surface and is split at the splitting surface to obtain orthogonal S polarized light and P polarized light, then the S polarized light is transmitted at the light combining surface after being reflected by the first internal reflection surfaces in sequence to obtain first emergent light, meanwhile, the P polarized light is reflected by the second internal reflection surfaces and the light combining surface in sequence to obtain second emergent light, the first emergent light and the second emergent light are overlapped, and the incident direction and the emergent direction of the light beam are vertical during each reflection.
Optionally, the light field of the second outgoing light and the first outgoing light is rotated by 180 ° relatively.
Optionally, the number of the first internal reflection faces is equal to the number of the second internal reflection faces.
Optionally, the number of the first internal reflection surface and the second internal reflection surface is 3.
Optionally, the P-polarized light is n-th i The emitting direction after secondary reflection and the n-th polarized light i The exit directions after-1 reflection are the same, n i Is a positive integer greater than or equal to 2.
Optionally, the emission direction of the P polarized light after the first reflection is opposite to the propagation direction of the S polarized light when the S polarized light is not reflected.
Optionally, the one beam splitting surface, the plurality of first internal reflection surfaces, the plurality of second internal reflection surfaces and the one light combining surface are arranged according to a cartesian coordinate system, so that the propagation direction of the light beam in the prism assembly is parallel or perpendicular to any coordinate axis of the cartesian coordinate system.
Optionally, the prism assembly includes at least a first prism and a second prism glued to each other, the first prism including a plurality of the first internal reflection surfaces, and the second prism including a plurality of the second internal reflection surfaces.
Optionally, the prism assembly comprises a polarization splitting prism, a first prism and a second prism;
the polarization beam splitter prism is provided with the beam splitting surface and the light combining surface, and the beam splitting surface is superposed with the light combining surface;
the first prism comprises a plurality of the first internal reflection surfaces, and the second prism comprises a plurality of the second internal reflection surfaces;
the first prism and the second prism are respectively arranged on two adjacent sides of the polarization splitting prism and positioned on two sides of the splitting surface.
To achieve the above object, the present invention further provides an optical system comprising the prism assembly as described above.
Optionally, the optical system is an interferometer.
To achieve the above object, the present invention also provides a lithographic apparatus comprising an optical system as described above.
In order to achieve the above object, the present invention further provides a light field rotation method, including:
providing a light beam;
splitting the light beam to obtain orthogonal S polarized light and P polarized light;
reflecting the S polarized light for m times and then transmitting to obtain first emergent light; and the number of the first and second groups,
performing n-time reflection on the P polarized light to obtain second emergent light, wherein the second emergent light is superposed with the first emergent light;
the incident direction and the emergent direction of the light beam are vertical during each reflection, and m and n are positive integers which are more than or equal to 3.
Optionally, the light field of the second outgoing light and the first outgoing light is rotated 180 ° relatively.
Compared with the prior art, the prism assembly, the optical system, the photoetching equipment and the light field rotating method have the advantages that:
the prism assembly provided by the invention comprises an incident surface, a splitting surface, a plurality of first reflecting surfaces, a plurality of second reflecting surfaces and a light combining surface, wherein a light beam is incident into the prism assembly from the incident surface and then split by the splitting surface to obtain orthogonal P polarized light and S polarized light, the P polarized light and the S polarized light are respectively reflected for multiple times and then superposed on the light combining surface again, and the incident direction and the emergent direction of any light beam during each reflection are perpendicular to each other, so that the polarization in other directions (namely the polarization in different directions generated during the reflection and propagation of diffracted light) can not occur during each reflection of the P polarized light and the S polarized light, a dielectric film is not required to be arranged on each reflecting surface of the prism assembly, the occurrence of the polarization state change of the emergent light beam can be avoided, and the production cost of the prism assembly is reduced while the alignment effect is ensured.
Drawings
Fig. 1 is a schematic structural diagram of a prism assembly provided by the present invention according to a first embodiment;
FIG. 2 is a schematic view of a first prism in the prism assembly shown in FIG. 1;
FIG. 3 is a schematic diagram of the propagation of light rays in the first prism shown in FIG. 2;
FIG. 4 is a schematic diagram of a second prism in the prism assembly of FIG. 1;
FIG. 5 is a schematic diagram of the propagation of light rays in the second prism shown in FIG. 4;
FIG. 6 is a schematic view of the propagation of light in the prism assembly of FIG. 1;
FIG. 7 is a schematic diagram showing the state of the light field of the light rays after propagating through the prism assembly shown in FIG. 1, wherein a is a schematic diagram showing the state of the light field of the first emergent light, and b is a schematic diagram showing the state of the light field of the second emergent light;
FIG. 8 is a schematic view of a prism assembly provided in accordance with a second embodiment of the present invention;
FIG. 9 is a schematic view of a first prism in the prism assembly shown in FIG. 8;
FIG. 10 is a schematic representation of the propagation of light in the first prism shown in FIG. 9;
FIG. 11 is a schematic view of a second prism in the prism assembly shown in FIG. 8;
FIG. 12 is a schematic diagram of light propagating in the second prism shown in FIG. 11;
FIG. 13 is a schematic diagram of light propagating in the prism assembly shown in FIG. 8;
FIG. 14 is a schematic diagram of the state of the light field of the light rays after propagating in the prism assembly shown in FIG. 8, in which a is a schematic diagram of the state of the light field of the first emergent light, and b is a schematic diagram of the state of the light field of the second emergent light;
fig. 15 is a schematic structural diagram of a prism assembly provided by the present invention according to a third embodiment.
In the figure:
100-an incident plane;
200-a light splitting surface;
300-a first internal reflection face;
400-a second internal reflection face;
500-light combining surface.
Detailed Description
A core idea of the present invention is to provide a prism assembly for rotating a light field of a light beam, comprising: an incident surface; a light splitting surface; a plurality of first internal reflection surfaces; a plurality of second internal reflection surfaces; and a light converging surface;
a light beam enters the prism assembly from the incident surface and is split at the splitting surface to obtain orthogonal S polarized light and P polarized light, the S polarized light is transmitted at the light combining surface after being reflected by the first internal reflection surfaces in sequence to obtain first emergent light, the P polarized light is reflected by the second internal reflection surfaces and the light combining surface in sequence to obtain second emergent light, the first emergent light and the second emergent light are overlapped, and the incident direction and the emergent direction of the light beam are vertical during each reflection.
The direction of each reflecting surface in the prism assembly is controlled, so that the incident direction and the emergent direction of the light beam are perpendicular to each other when the light beam is reflected each time. In this way, the beam does not experience polarization in other directions as it propagates through the prism assembly, thereby ensuring that the polarization state of the beam is unchanged. And this prism subassembly need not all to set up the dielectric film on every plane of reflection, has reduced prism subassembly's manufacturing cost.
To further clarify the objects, advantages and features of the present invention, a more particular description of the invention will be rendered by reference to the appended drawings. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is provided for the purpose of facilitating and clearly illustrating embodiments of the present invention.
As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents, and the plural forms "a plurality" includes more than two referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally employed in its sense including "and/or" unless the content clearly dictates otherwise, and the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either fixedly connected, detachably connected, or integrally connected. Either mechanically or electrically. They may be directly connected or indirectly connected through intervening media, or may be connected through the use of two elements or the interaction of two elements. The specific meanings of the above terms in the present invention can be understood according to specific situations by those of ordinary skill in the art. The same or similar reference numbers in the drawings identify the same or similar elements.
Example one
Referring to fig. 1, fig. 1 is a schematic structural diagram of a prism assembly according to an embodiment of the present invention, in which lines with arrows indicate light beams. As shown in fig. 1, the prism assembly includes an incident surface 100, a beam splitting surface 200, a plurality of first internal reflection surfaces 300, a plurality of second internal reflection surfaces 400, and a light combining surface 500. In practical application, incident light enters the prism assembly from the incident plane 100 and is split on the splitting plane 200 to obtain orthogonal S-polarized light and P-polarized light, that is, at the splitting plane 200, a part of the incident light is reflected to obtain S-polarized light, and another part of the incident light is transmitted to obtain P-polarized light; and then the S polarized light is reflected for multiple times in the prism assembly and then transmitted to obtain first emergent light, meanwhile, the P polarized light is also reflected for multiple times in the prism assembly to obtain second emergent light, and the first emergent light and the second emergent light are recombined into a beam of emergent light and then emitted out of the prism assembly.
Specifically, the S-polarized light is reflected by the first internal reflection surfaces 300 for multiple times, and then the S-polarized light is transmitted through the light combining surface 500 to obtain the first outgoing light. In the process, the incident direction and the emergent direction of the S polarized light are vertical to each other when the S polarized light is reflected each time. Meanwhile, the P-polarized light is reflected by the second reflection surfaces 300 for multiple times, and then the P-polarized light is reflected from the light combining surface 500 to obtain the second outgoing light, and the incident direction and the outgoing direction of the P-polarized light during each reflection are perpendicular to each other in the process. And the second emergent light is superposed with the first emergent light at the light-combining surface 500 to form a bundle of emergent light, and finally the emergent light is emitted out of the prism assembly.
For example, where the prism assembly is employed in an optical system, such as an interferometer of an alignment system on a lithographic apparatus, the light field of the first outgoing light may be rotated +90 ° relative to the light field of the incoming light, and the light field of the second outgoing light may be rotated-90 ° relative to the light field of the incoming light. In this way, the optical fields of the first emergent light and the second emergent light relatively rotate by 180 degrees to achieve the aim of aligning the interferometer, so that the alignment of the mask and the wafer is achieved. Of course, the light field of the first outgoing light may also rotate by-90 ° with respect to the light field of the incident light, while the light field of the second outgoing light may rotate by +90 ° with respect to the light field of the incident light, and the same effect may also be achieved.
Further, a Polarization Beam Splitter (PBS) may be disposed on one surface of the prism assembly to form the light splitting surface 200. Further, the light combining surface 500 can also be formed by disposing a PBS film on one surface of the prism assembly. In some embodiments, the light splitting surface 200 and the light combining surface 500 may be overlapped, that is, the light splitting surface 200 and the light combining surface 500 are the same surface; in other embodiments, the light splitting surface 200 and the light combining surface 500 are two surfaces separated from each other.
Referring to fig. 1, according to practical requirements, the number of the first internal reflection surfaces 300 and the number of the second internal reflection surfaces 400 may be equal, for example, the number of the first internal reflection surfaces 300 and the number of the second internal reflection surfaces 400 may be three. That is, the S-polarized light is reflected three times in the prism assembly and then transmitted from the light-combining surface 500; the P-polarized light is reflected four times within the prism assembly before exiting the prism assembly (i.e., the P-polarized light is reflected once at each of the three second internal reflection surfaces 200 and then reflected once again at the light-combining surface 500).
When the light fields of the first emergent light and the second emergent light need to rotate 180 degrees relatively, the polarization light of P is n i The emitting direction after secondary reflection can be the nth direction of the S polarized light i The exit directions after 1 reflection are the same, wherein n i Is a positive integer greater than or equal to 2. Preferably, the exit direction of the P polarized light after the first reflection is opposite to the propagation direction of the S polarized light when the light is not reflected, so that the structure of the prism assembly is simpler. In addition, the optical paths of the P-polarized light and the S-polarized light propagating in the prism assembly may be equal.
Next, the propagation of the light beam in the prism assembly will be described in detail with reference to the accompanying drawings. In the following embodiments, the light field of the first outgoing light and the light field of the second outgoing light are described as an example of being rotated by 180 ° relative to each other, but the present invention should not be limited thereto.
With continued reference to fig. 1, the prism assembly of the present embodiment may be formed by gluing two prisms, which are a first prism (not labeled) and a second prism (not labeled), respectively. The structure of the first prism is shown in fig. 2, the structure of the second prism is shown in fig. 4, and the light-splitting surface 200 is located on the surface of the first prism glued to the second prism, or the light-splitting surface 200 is located on the surface of the second prism glued to the first prism, although PBS films can be disposed on both the surface of the first prism and the surface of the second prism to form the light-splitting surface 200.
The incident surface 100 may be disposed on any one of the prisms, for example, on the first prism. Preferably, the incident plane 100 and the splitting plane 200 form an angle of 45 °, so that when the incident light enters the prism assembly in a direction perpendicular to the incident plane 100, the incident light can be split by the splitting plane 200 to obtain P-polarized light and S-polarized light.
In this embodiment, the first prism has a plurality of the first internal reflection surfaces 300, and the second prism has a plurality of the second internal reflection surfaces 400, that is, the P-polarized light is reflected in the first prism a plurality of times to rotate the P-polarized light field, and the S-polarized light is reflected in the second prism a plurality of times to rotate the S-polarized light field. In this embodiment, the number of the first internal reflection surface 300 and the second internal reflection surface 400 is three.
The prism assembly comprises a first prism, a second prism, a light splitting surface, a light converging surface, a first internal reflection surface, a second internal reflection surface, a light splitting surface and a light converging surface, wherein the surfaces of the prism assembly (including the first internal reflection surface, the second internal reflection surface, the light splitting surface and the light converging surface) are arranged according to a Cartesian coordinate system, so that the propagation direction of light beams in the prism assembly is parallel or vertical to any coordinate axis of the Cartesian coordinate system, and a schematic propagation principle diagram of the light beams in the first prism, the second prism and the prism assembly is drawn according to the Cartesian coordinate system. Fig. 3 shows a schematic diagram of the P-polarized light propagating in the first prism, fig. 5 shows a schematic diagram of the S-polarized light propagating in the second prism, and fig. 7 shows a schematic diagram of the incident light entering the prism assembly and exiting after propagating in the prism assembly.
Referring to FIG. 3, a cube is provided to illustrate the light propagation principles of the prism assembly of the present invention through the cube. In particular, each side of the cube is made parallel or perpendicular to any coordinate axis of the cartesian coordinate system, and the apex of the cube may correspond to a point on each face of the prism assembly. In detail, O 1 The point is a point on the incident surface 100, A 1 The point is a point on the light splitting surface 200, B 1 Dots, C 1 Dots and D 1 The points are sequentially points on the three first internal reflection surfaces 300, E 1 The points are points on the light combining surface 500.
An incident light from the O 1 Spot-incident on the prism assembly and then at A 1 At a point the incident light is split to obtain P-polarized light (not shown) and S-polarized light, which then propagates along the sides of the cube, along the path a 1 B 1 →B 1 C 1 →C 1 D 1 →D 1 E 1 . That is, S polarization is in turn at B 1 Dots, C 1 Dots and D 1 The point is reflected, and the incident direction and the emergent direction of the S polarized light are vertical during each reflection. Then, S-polarized light is polarized from E 1 The point transmits and then emits out of the prism assembly (i.e. the S polarized light transmits on the light combining surface and then emits out of the prism assembly) to obtain a first emergent light E 1 F 1 . In the process, the light beams (including the incident light beams and the emergent light beams in each reflection) always form an included angle of 45 degrees with the normal lines of the corresponding reflection surfaces, the light beams are transmitted along the positive direction or the negative direction of the coordinate axis of the Cartesian coordinate system, polarization in other directions cannot be generated, and therefore the polarization state of the S-polarized light in the first prism cannot be changed. In the illustration, a, b, c, d represent four different orientations of the light field of the light beam in the respective plane. It can be seen from fig. 1 that the light field of S polarization is rotated by +90 ° with respect to the light field of the incident light (the positive direction here means the clockwise direction).
Referring to fig. 5, a cube is also provided, such that each side of the cube is parallel or perpendicular to any coordinate axis of the cartesian coordinate system, and the vertex of the cube can correspond to a point on each face of the prism assembly. In detail, A 2 The point is located at a point on the splitting plane 200, B 2 Dots, C 2 Dots and D 2 Points are located on three second internal reflection surfaces 200 in sequence, E 2 A point is located on the light combining surface 500, and A 2 B 2 Perpendicular to the entrance face 100.
An incident light at A 2 The point is split into P-polarized light and S-polarized light (not shown), the P-polarized light propagates along the side of the cube, and the propagation path is A 2 B 2 →B 2 C 2 →C 2 D 2 →D 2 E 2 . That is, P polarized light is in turn at B 2 Dots, C 2 Dots and D 2 The point is reflected, and the incident direction and the emergent direction of the P polarized light are vertical during each reflection. Then, P is polarized at E 2 Point-reflected light is emitted out of the prism assembly to obtain second emergent light E 2 F 2 . In the process, the light beams (including the incident light beams and the emergent light beams in each reflection) always form an included angle of 45 degrees with the normal line of the corresponding reflection surface and are transmitted along the positive direction or the negative direction of the coordinate axis of the Cartesian coordinate system, and polarization in other directions cannot be generated, so that the polarization state of the P polarized light in the first prism cannot be changed. In the illustration, a, b, c, d represent four different orientations of the light field of the light beam in the respective plane. It can be seen from fig. 1 that the P-polarized light field is rotated by-90 deg. with respect to the incident light field (negative direction here means counterclockwise).
Combining the cubes shown in fig. 3 and 5, overlapping the point A1 and the point A2, and marking the overlapped point as a point a; at the same time make A 1 B 1 And A 2 B 2 Perpendicular to, and then respectively extended by D 1 E 1 And D 2 E 2 The two are made to intersect at point E, resulting in a schematic representation of the beam propagation in the complete prism assembly, the result being shown in fig. 6. In fig. 6, point O is a point on the incident surface 100, point a is a point on the spectroscopic surface 200, and point B 1 Dot, C 1 Dots and D 1 The points are sequentially points on three first internal reflection surfaces 300, B 2 Dots, C 2 Dots and D 2 The points are sequentially points on the three second internal reflection surfaces 400, and the point E is a point on the light combining surface 500. In fact, in this embodiment, the light splitting surface 200 and the light combining surface 500 are overlapped to form the same surface.
An incident light OA is incident on the prism assembly, and the angle between the incident light and the beam splitting surface 200 is 45 °. The light beam OA is split at the point A on the splitting plane 200 to obtain S-polarized light sumP-polarized light, then S-polarized light along AB 1 →B 1 C 1 →C 1 D 1 →D 1 E → EF propagation while P polarization is along AB 2 →B 2 C 2 →C 2 D 2 →D 2 E → EF propagation, wherein the light beam EF is obtained by the coincidence of the first emergent light and the second emergent light.
As can be seen from the above analysis process, in the process of obtaining the first outgoing light from the incident light in the present embodiment, the light beam is reflected by four times: incident light is reflected at the spectroscopic surface 200 to obtain S-polarized light, and the S-polarized light is sequentially reflected once on each of the three first internal reflection surfaces 300 in the first prism. Similarly, in the process of obtaining the second outgoing light from the incident light, the light beam is also reflected four times: the P polarized light is reflected once on each of the three second internal reflection surfaces 400 in the second prism in turn, and the P polarized light is reflected once on the light combining surface 500.
For each reflecting surface (including the splitting surface 200, the first internal reflecting surface 300, the second internal reflecting surface 400, and the light combining surface 500), there is a reflection matrix:
wherein i is a positive integer of 1 or more, and n is x 、n y 、n z The component values of the normal vector of the corresponding reflecting surface on the x-axis, the y-axis and the z-axis in the cartesian coordinate system are respectively.
Therefore, when the incident light undergoes four reflections to obtain the first emergent light, the reflection matrix of the prism assembly is as follows:
N＝N 4 *N 3 *N 2 *N 1
in the formula, N 1 Is the reflection matrix of the light beam on the splitting plane 200, N 2 、N 3 、N 4 A reflection matrix (i.e., N) of three first internal reflection surfaces 300 in sequence 2 Is B 1 Reflection matrix of the first internal reflection surface 300 where the dots are located, N 3 Is C 1 Reflection matrix of the first internal reflection surface 300 where the dots are located, N 4 Is D 1 At which point is locatedA reflective matrix of the first internal reflection surface 300).
If the side length of the cube is 1, the following components are present:
N＝N 4 *N 3 *N 2 *N 1
the light field states of the incident light are: a _ in = [1;0;0], b _ in = [0;1;0], c _ in = [ -1;0;0], d _ in = [0; -1;0], OA _ in = [0;0;1];
thus, the light field state of the first outgoing light (EF _ out _ 1) is:
a_out_1＝N*a_in＝[0；0；1]
b_out_1＝N*b_in＝[-1；0；0]
c_out_1＝N*c_in＝[0；0；-1]
d_out_1＝N*d_in＝[1；0；0]
EF_out_1＝N*OA_in＝[0；-1；0]
similarly, when the incident light undergoes four reflections to obtain the second emergent light, the reflection matrix of the prism assembly is:
in the formula, N 1 ′、N 2 ′、N 3 ' A reflection matrix of three second internal reflection faces 400 in order (i.e., N) 1 ' is B 2 Reflection matrix, N, of the second internal reflection surface 400 where the dots are located 2 ' is C 2 Reflection matrix, N, of the second internal reflection surface 400 where the dots are located 3 ' is D 2 Reflection matrix of the second internal reflection surface 400 where the dots are located), N 4 ' reflection matrix of the light-combining surface 500.
The light field state of the second emergent light (EF _ out _ 2) is as follows:
a_out_2＝N′*a_in＝[0；0；-1]
b_out_2＝N′*b_in＝[1；0；0]
c_out_2＝N′*c_in＝[0；0；1]
d_out_2＝N′*d_in＝[-1；0；0]
EF_out_2＝N′*OA_in＝[0；-1；0]
the light field states of the first emergent light and the second emergent light are visually represented in fig. 7, wherein a is a schematic diagram of the light field state of the first emergent light, and b is a schematic diagram of the light field state of the second emergent light. As is clear from fig. 7, the light fields of the first outgoing light and the second outgoing light are rotated by 180 ° with respect to each other.
In fact, when the light beam enters the prism assembly from the light combining surface 500 and propagates in the direction of the above-described embodiment and then exits from the light splitting surface 200, two outgoing light beams with their light fields relatively rotated by 180 ° can be obtained, and the two outgoing light beams can be overlapped.
Example two
The structure and the using method of the prism assembly provided in this embodiment are substantially the same as those of the first embodiment, and only different points are described below. Fig. 8 shows a schematic structural diagram of a prism assembly provided by the second embodiment, which can also be formed by gluing a first prism and a second prism. Fig. 9 shows a schematic structural diagram of the first prism having the first internal reflection surface 300, and fig. 10 shows a schematic principle diagram of the light beam propagating in the first prism. Fig. 11 shows a schematic view of the structure of a second prism having said second internal reflection surface 400, fig. 12 shows a schematic view of the principle of light beam propagation in the second prism, and fig. 13 shows a schematic view of the principle of light beam propagation in the prism assembly. For clarity, fig. 10, 12 and 13 show the light field states of the light beams as a, b, c and d.
As shown in fig. 8, the prism assembly of the present embodiment has a light splitting surface 200, three first internal reflection surfaces 300, three second internal reflection surfaces 400 and a light combining surface 500.
Referring to fig. 9 and 10, a cube is provided such that the sides of the cube are parallel or perpendicular to any coordinate axis of the cartesian coordinate system, and then the vertices of the cube are mapped to points on each side of the prism assembly. Specifically, O 3 A point on the incident surface 100, A 3 The point is a point on the splitting plane 200, B 3 Dot, C 3 Point and D 3 The points are in turn points on three first internal reflection surfaces 300, E 3 The points are points on the light combining surface 500. The S-polarized light obtained by splitting the incident light at the splitting plane 200 propagates in the first prism along the path A 3 B 3 →B 3 C 3 →C 3 D 3 →D 3 E 3 Then, S polarized light is polarized from E 3 The point is transmitted and then emits out of the prism component to obtain a first emergent light E 3 F 3 。
Similarly, referring to FIG. 11 and FIG. 12, A 4 The point is a point on the splitting plane 200, B 4 Dots, C 4 Dots and D 4 The points are sequentially points on the three second internal reflection surfaces 200, E 4 The point is a point on the light combining surface 500, and A 4 B 4 Perpendicular to the entrance face 100. A P polarized light obtained by splitting an incident light at the splitting plane 200 propagates in the second prism, and the propagation route is A 4 B 4 →B 4 C 4 →C 4 D 4 →D 4 E 4 Then, P is polarized at E 4 Point-reflected light is emitted out of the prism assembly to obtain second emergent light E 4 F 4 。
Next, the cubes shown in FIG. 10 and FIG. 12 are combined to form A 3 Point sum A 4 Point coincidence and marking the coincident points as A' points; at the same time make A 3 B 3 And A 4 B 4 Perpendicular to, and then respectively extended by D 3 E 3 And D 4 E 4 The two are made to intersect at point E' to obtain a schematic representation of the beam propagation in the complete prism assembly, the result is shown in fig. 13. In fig. 13, point O 'is located on the incident surface 100, point a' is located on the splitting surface 200, and point B 3 Dots, C 3 Dots and D 3 Points are located on three first internal reflection surfaces 300 in sequence, B 4 Dots, C 4 Dots and D 4 Points are sequentially located on the three second internal reflection surfaces 400, and the point E' is located on the light combining surface 500.
Emitting an incident light O' AAnd the incident light forms an angle of 45 degrees with the light splitting surface 200. The beam O 'A' is split at the point A 'on the splitting plane 200 to obtain S-polarized light and P-polarized light, and then the S-polarized light follows the point A' B 3 →B 3 C 3 →C 3 D 3 →D 3 E '→ E' F 'propagation while P polarization is along A' B 4 →B 4 C 4 →C 4 D 4 →D 4 E ' → E ' F ' propagation, light beam E ' F ' resulting from the coincidence of the first outgoing light and the second outgoing light.
When the incident light propagates in the prism assembly to obtain a first emergent light, the reflection matrix of the prism assembly is:
in the formula, N 1 "is the reflection matrix of the beam splitting surface 200, N 2 ″、N 2 "and N 2 "in turn, a reflection matrix of three first internal reflection surfaces 300 (i.e., N) 2 Is "B 3 A reflection matrix of the first internal reflection surface 300, N 3 Is "as C 3 A reflection matrix of the first internal reflection surface 300, N 4 Is "D 3 The reflective matrix of the first internal reflection surface 300).
The light field state of the incident light is: a _ in = [1;0;0], b _ in = [0;1;0], c _ in = [ -1;0;0], d _ in = [0; -1;0], O 'a' _ in = [0;0;1],
the light field state of the first outgoing light (E 'F' _ out _ 1) is:
a_out_1＝N″*a_in＝[0；0；1]
b_out_1＝N″*b_in＝[1；0；0]
c_out_1＝N″*c_in＝[0；0；-1]
d_out_1＝N″*d_in＝[-1；0；0]
E′F′_out_1＝N″*O′A′_in＝[0；1；0]
similarly, when the incident light propagates in the prism assembly to obtain the second emergent light, the reflection matrix of the prism is:
in the formula, N 1 ″′、N 2 ″′、N 3 "' is a reflection matrix of three second internal reflection faces 400 in that order (i.e., N 1 Is' B 4 Reflection matrix, N, of the second internal reflection surface 400 where the dots are located 2 "' is C 4 Reflection matrix, N, of the second internal reflection surface 400 where the dots are located 3 "' is D 4 Reflection matrix of the second internal reflection surface 400 where the dots are located), N 4 "" is the reflection matrix of the x-ray surface 500.
The light field state of the second outgoing light (E 'F' _ out _ 2) is:
a_out_2＝N″′*a_in＝[0；0；-1]
b_out_2＝N″′*b_in＝[-1；0；0]
c_out_2＝N″′*c_in＝[0；0；1]
d_out_2＝N″′*d_in＝[1；0；0]
E′F′_out_2＝N″′*O′A′_in＝[0；1；0]
the light field states of the first outgoing light and the second outgoing light are visually represented in fig. 14, where a is a schematic view of the light field state of the first outgoing light, and b is a schematic view of the light field state of the second outgoing light. As is clear from fig. 14, the light fields of the first outgoing light and the second outgoing light are rotated by 180 ° with respect to each other.
The prism assembly in the present embodiment differs from that of the first embodiment in that the propagation direction of the S-polarized light before reflection is opposite to that of the first embodiment, and the light field of the first exiting light is rotated by-90 ° with respect to the incident light. And the exit direction of the P-polarized light after the first reflection in the present embodiment is opposite to the exit direction of the P-polarized light after the first reflection in the first embodiment, and the light field of the second exit light is rotated by +90 ° with respect to the incident light.
EXAMPLE III
The structure and the using method of the prism assembly provided in this embodiment are substantially the same as those of the first embodiment, and only different points are described below.
Fig. 15 shows a schematic structural diagram of a prism assembly provided in a third embodiment, referring to fig. 15, the prism assembly in this embodiment can be composed of a first prism, a polarization splitting prism (PBS prism), and a second prism. Specifically, referring to fig. 15, the PBS prism is formed by gluing a first right-angle prism and a second right-angle prism, wherein at least one of the right-angle prisms has a PBS film coated on its bevel, and the bevel serves as both the light splitting plane 200 and the light combining plane 500. The first prism has three first internal reflection surfaces 300, and the first prism is disposed at one side of one right-angle surface of the first right-angle prism. The second prism has three second internal reflection surfaces 400, and the second prism is disposed at one side of a right-angle surface of the second right-angle prism, and the second prism and the first prism are disposed adjacently. In this embodiment, the first prism and the second prism may be spaced apart from the PBS prism, or the first prism and the second prism may be glued to the PBS prism.
In the present embodiment, the traveling path of the light beam is as shown in fig. 15, and the three first internal reflection surfaces 300 of the first prism may be arranged in the same manner as the three first internal reflection surfaces 300 of the first embodiment, so that the reflection matrix N of the first prism is
Similarly, the three second internal reflection surfaces 400 of the second prism in this embodiment are arranged in the same manner as the three second internal reflection surfaces 400 of the first embodiment, so the reflection matrix N of the second prism is:
the prism assembly provided by the above embodiment can be used not only in an interferometer of an alignment system in a lithography apparatus, but also in other occasions where a light field of a light beam needs to be rotated, and the rotation angles of the first outgoing light and the second outgoing light can be controlled by adjusting the number and the orientation of the first internal reflection surface 300 and the second internal reflection surface 400 according to practical application occasions.
Further, based on the prism assembly provided in the foregoing embodiments, the present invention also provides an optical system including the prism assembly, including but not limited to an interferometer in an alignment system of a lithographic apparatus. If the optical system is an interferometer, the interferometer can enable the first emergent light and the second emergent light to rotate 180 degrees relatively, so that the interferometer can be applied to grating alignment to generate two alignment mark images which rotate 180 degrees relatively and overlap, and alignment of a mask and a wafer in the manufacturing process of an Integrated Circuit (IC) is further achieved. In addition, the interferometer is different from the interferometer in the prior art only in the prism assembly, and other structures can be completely the same, and are not described in detail here because they are not related to the improvement point of the present invention.
Further, embodiments of the present invention also provide a lithographic apparatus including the optical system.
In addition, the invention also provides an optical field rotation method, which specifically comprises the following steps:
providing a light beam;
splitting the light beam to obtain orthogonal S polarized light and P polarized light;
reflecting the S polarized light for m times and then transmitting to obtain first emergent light; and the number of the first and second groups,
performing n-time reflection on the P polarized light to obtain second emergent light, wherein the second emergent light is superposed with the first emergent light;
the incident direction and the emergent direction of the light beam are vertical during each reflection; and m and n are positive integers greater than or equal to 3.
Optionally, the light field of the second outgoing light and the first outgoing light is rotated by 180 ° relatively.
Although the present invention is disclosed above, it is not limited thereto. Various modifications and alterations of this invention may be made by those skilled in the art without departing from the spirit and scope of this invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (14)
1. A prism assembly, comprising: an incident surface; a splitting plane; a plurality of first internal reflection surfaces; a plurality of second internal reflection surfaces; and a light converging surface;
a light beam enters the prism assembly from the incident surface and is split at the splitting surface to obtain orthogonal S polarized light and P polarized light, wherein the reflecting part is the S polarized light, the transmitting part is the P polarized light, then the S polarized light is transmitted at the light combining surface after being reflected by the first internal reflecting surfaces in sequence to obtain first emergent light, meanwhile, the P polarized light is reflected by the second internal reflecting surfaces and the light combining surface in sequence to obtain second emergent light, the first emergent light and the second emergent light are overlapped, and the incident direction and the emergent direction of the light beam are vertical during each reflection and always form an included angle of 45 degrees with the normal line of the corresponding reflecting surface.
2. The prism assembly of claim 1 wherein the optical field of the second exiting light is rotated 180 ° relative to the optical field of the first exiting light.
3. The prism assembly according to claim 2, wherein the number of the first internal reflection surfaces is equal to the number of the second internal reflection surfaces.
4. The prism assembly according to claim 3, wherein the number of the first internal reflection faces and the second internal reflection faces is 3.
5. The prism assembly according to any one of claims 2 to 4, wherein the P-polarized light is n i The emitting direction after secondary reflection and the n-th polarized light i The exit directions after 1 reflection are the same, n i Is a positive integer greater than or equal to 2.
6. The prism assembly according to claim 5, wherein the exit direction of the P-polarized light after first reflection is opposite to the propagation direction of the S-polarized light when not reflected.
7. The prism assembly according to any one of claims 1 to 4, wherein the one beam splitting surface, the plurality of first internal reflection surfaces, the plurality of second internal reflection surfaces and the one light combining surface are arranged in a Cartesian coordinate system such that a propagation direction of the light beam in the prism assembly is parallel or perpendicular to any coordinate axis of the Cartesian coordinate system.
8. The prism assembly of any one of claims 1 to 4 wherein the prism assembly comprises at least a first prism and a second prism glued to each other, the first prism comprising a plurality of the first internal reflecting surfaces and the second prism comprising a plurality of the second internal reflecting surfaces.
9. The prism assembly of any one of claims 1 to 4 wherein the prism assembly comprises a polarizing beam splitting prism, a first prism, and a second prism;
the polarization beam splitter prism is provided with the beam splitting surface and the light combining surface, and the beam splitting surface is superposed with the light combining surface;
the first prism comprises a plurality of the first internal reflection surfaces, and the second prism comprises a plurality of the second internal reflection surfaces;
the first prism and the second prism are respectively arranged on two adjacent sides of the polarization splitting prism and positioned on two sides of the splitting surface.
10. An optical system comprising a prism assembly according to any one of claims 1 to 9.
11. The optical system of claim 10, wherein the optical system is an interferometer.
12. A lithographic apparatus comprising an optical system according to claim 10 or 11.
13. A method of rotating a light field, comprising:
providing a light beam;
splitting the light beam to obtain orthogonal S polarized light and P polarized light;
reflecting the S polarized light for m times and then transmitting to obtain first emergent light; and the number of the first and second groups,
performing n-time reflection on the P polarized light to obtain second emergent light, wherein the second emergent light is superposed with the first emergent light;
the incident direction and the emergent direction of the light beam are vertical during each reflection and always form an included angle of 45 degrees with the normal line of the corresponding reflection surface; m and n are positive integers greater than or equal to 3.
14. The light field rotation method of claim 13, wherein the light field of the second outgoing light is rotated 180 ° relative to the light field of the first outgoing light.
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| JP6743398B2 (en) * | 2016-01-28 | 2020-08-19 | リコーイメージング株式会社 | Observation optics and prism |
| CN110095880B (en) * | 2018-01-31 | 2020-08-07 | 上海微电子装备（集团）股份有限公司 | Self-referencing interferometer, alignment system and lithographic apparatus |
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| US6628406B1 (en) * | 2000-04-20 | 2003-09-30 | Justin L. Kreuzer | Self referencing mark independent alignment sensor |
| CN1949087A (en) * | 2006-11-03 | 2007-04-18 | 上海微电子装备有限公司 | Aligning system of photoetching apparatus and steping combined system of said aligning system thereof |
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