CN110703564B - Optical system film analysis method, device and storage medium - Google Patents
Optical system film analysis method, device and storage medium Download PDFInfo
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- 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
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- G03F7/70591—Testing optical components
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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
- G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
- G03F7/70491—Information management, e.g. software; Active and passive control, e.g. details of controlling exposure processes or exposure tool monitoring processes
Abstract
The application discloses an optical system thin film analysis method, equipment and a storage medium, wherein the method comprises the following steps: designing and adding corresponding extreme ultraviolet multilayer films according to the angle distribution on different surface type elements in an optical system without films; establishing an equivalent reflection point for the transmission process of each incident ray in the extreme ultraviolet multilayer film by utilizing space ray tracing, calculating the coordinate of the equivalent reflection point, and calculating the coordinate of an emergent ray formed by the incident ray after being reflected by the equivalent reflection point on the surface of the film; tracing the optical system after being coated with the film one by one until reaching an exit pupil surface; the imaging quality of the filmed optical system was calculated at the exit pupil and evaluated. Therefore, the reflection process of a single light ray in the multilayer film is converted into the reflection at an equivalent reflection point, the defect that the concept of average incidence angle fails at a large incidence angle is overcome, the complex physical optical process of the light in the multilayer film can be converted into geometric optical content, and the analysis, evaluation and optimization of a film-coating optical system are accurately used.
Description
Technical Field
The invention relates to the technical field of extreme ultraviolet lithography, in particular to an optical system film analysis method, optical system film analysis equipment and a storage medium.
Background
Extreme Ultraviolet Lithography (EUVL) is a projection Lithography technology that uses Extreme Ultraviolet light with a wavelength of 13.5nm as a working wavelength, has a natural advantage of reducing the exposure wavelength by one order of magnitude, can well release the limitation on the numerical aperture NA and process factors of an objective lens, makes the objective lens become a next-generation Lithography technology, and is a preferred technology for realizing the industrialization of a 7nm and below technology node integrated circuit. Because the extreme ultraviolet light almost has extremely strong absorption to all optical materials, the extreme ultraviolet lithography adopts a reflective element, and utilizes an optical thin film technology to carry out film system design to obtain high reflectivity, thereby improving the lithography yield. Currently, as shown in fig. 1, the euv multilayer film is mainly formed by alternately depositing two materials, i.e., Mo/Si (molybdenum/silicon), and the period of the multilayer film is about 7nm, the period is about 40 to 60, and the total thickness reaches about 300 nm. The theoretical incident reflectance peak at a wavelength of 13.5nm can reach 74%, and the film thickness-to-wavelength ratio is greater than 20, which introduces additional wave aberration. When a coated optical system is processed, the displacement of the coated optical system as a whole of a bare lens cannot be simply understood, and the aberration and the imaging position deviation introduced by the thin film can jointly influence the wave aberration of the system, reduce the imaging quality of the objective optical system and finally influence the photoetching performance, so the influence of the thin film on the optical system is considered in the design process of the objective optical system, and the coated optical system is quantitatively evaluated.
At present, the influence analysis of the extreme ultraviolet lithography objective lens film introduction is mainly divided into two ideas. One method is to mainly analyze the polarization aberration introduced by the thin film, the thought is mainly to analyze the polarization aberration by adopting polarized light ray tracing, introduce the two-way attenuation and the phase delay caused by the multilayer film into the polarization tracing, and analyze the polarization influence by using a Jones matrix or a Mueller matrix. Russell A.Chipman and Thiago S.Jota analyzed the effect of film polarization on lithography contrast and resolution for trapezoidal films in extreme ultraviolet lithography. However, polarization tracking does not take into account the physical thickness of the multilayer film and therefore cannot handle ray traversing and bending due to the physical thickness of the multilayer film. For this reason, j.wesner and m.f.bal have established an effective incident depth model, addressing the above problem through an equivalent interface. The initial stage of the equivalent interface calculation is to derive and build an effective incident depth model from the angle of the film introduced phase change, the depth being a function of the light incident angle and the film parameters, proportional to the second order partial derivative of the film introduced phase shift to the light incident angle. Because the derivation adopts the low-order approximation of cosine function, neglects high-order terms of 4 orders and above, and the inconsistency of the phase change of p light and s light in the film under the condition of large angle, the model may have some discomfort when the incident angle is large, such as large separation of the effective incident depth of the p light and the effective incident depth of the s light, or negative value, etc. For this reason, m.f.bal at DELFT university of the netherlands and wanjun at vinpocetine institute of chinese academy of sciences have proposed different methods to solve the above problems, respectively. The M.F.Bal adopts a method of weighting and averaging based on the ratio of the reflection energy of interfaces with different depths, firstly, the ratio of the energy reflected by the light energy at each interface with different depths of the multilayer film to the total reflection energy is calculated, then the weighted average value of the depths of each reflection interface is calculated by taking the ratio as the weight, and the average value is the effective incident depth. The Wanjun adopts the concept of energy conservation, namely, firstly, the multiple transmission and reflection of a light beam in the multilayer film are equivalent to the single reflection on an equivalent interface and the energy attenuation of an incident light beam and a reflected light beam, the light intensity of a transmission part does not change after entering a virtual substrate, then the relation between the attenuation coefficient of the light beam in the multilayer film and the reflectivity and transmittance of the multilayer film is deduced according to the law of energy conservation, and finally, the attenuation coefficient is corrected by considering the multiple reflection of the light beam in the multilayer film and the effective incident depth is calculated in a reverse mode. The equivalent interface converts a complex physical optical process in the multilayer film into a simple geometric optical process, constructs an equivalent system and utilizes the existing optical design software to evaluate the imaging quality of the system. It should be noted that, as the average incident angle gradually increases, the multilayer film reflection amplitude and phase gradually increase with the change of the incident angle, and the difference between different polarization states gradually increases, and the equivalent interface is an average interface, so the effectiveness of this method gradually loses with the increase of the incident angle. Therefore, the imaging quality of the high-NA large-incidence-angle optical system added with the optical film cannot be reasonably evaluated, and the problem that the optical system processed according to the design cannot be compatible with the optical film is caused.
Therefore, a technical problem to be solved by those skilled in the art is how to solve the problem that the designed optical system is incompatible with the extreme ultraviolet multilayer film because the existing equivalent interface model cannot effectively evaluate the imaging quality of the optical system after adding a film under the off-axis high NA large incident angle.
Disclosure of Invention
In view of the above, the present invention provides a method, an apparatus and a storage medium for analyzing a thin film of an optical system, which can overcome the defect that the concept of average incident angle fails at a large incident angle. The specific scheme is as follows:
an optical system thin film analysis method comprising:
designing and adding corresponding extreme ultraviolet multilayer films according to the angle distribution on different surface type elements in an optical system without films;
establishing an equivalent reflection point for the transmission process of each incident ray in the extreme ultraviolet multilayer film by utilizing space ray tracing, and calculating the coordinate of the equivalent reflection point;
calculating the coordinate of the emergent ray formed by the incident ray after being reflected by the equivalent reflection point on the surface of the extreme ultraviolet multilayer film according to the coordinate of the equivalent reflection point;
tracing the optical system after the film is added to the exit pupil surface one by one;
and calculating the imaging quality of the optical system after the film is added at the exit pupil and carrying out image quality evaluation.
Preferably, in the method for analyzing a thin film in an optical system provided in an embodiment of the present invention, designing and adding corresponding euv multilayer films according to angle distributions on different surface-type elements in an optical system without adding a film specifically includes:
setting a field sampling point by using optical design software according to the structural parameters of an optical system without a film;
obtaining the incident angle distribution of incident light rays in effective clear apertures on the surfaces of different bare lenses in the optical system according to the set field sampling points;
and adding a corresponding extreme ultraviolet multilayer film on the surface of each bare lens according to the obtained incident angle distribution.
Preferably, in the above method for analyzing a thin film of an optical system according to an embodiment of the present invention, before calculating the coordinates of the equivalent reflection point, the method further includes:
fitting a surface equation of the surface of the extreme ultraviolet multilayer film according to the film system parameters of the extreme ultraviolet multilayer film;
and calculating the coordinate of the incident ray on the surface of the extreme ultraviolet multilayer film by utilizing space ray tracing according to the fitted surface equation of the surface of the extreme ultraviolet multilayer film.
Preferably, in the method for analyzing a thin film of an optical system according to an embodiment of the present invention, calculating coordinates of the equivalent reflection point specifically includes:
calculating the effective depth of the equivalent reflection point by an energy weighted average method;
fitting a surface equation of the surface where the equivalent reflection points are located by using the calculated effective depth of the equivalent reflection points;
and calculating the coordinate of the equivalent reflection point according to the calculated coordinate of the incident ray on the surface of the extreme ultraviolet multilayer film and the fitted surface equation of the surface where the equivalent reflection point is located.
Preferably, in the method for analyzing a thin film of an optical system according to an embodiment of the present invention, calculating the effective depth of the equivalent reflection point by using an energy weighted average method specifically includes:
calculating the light intensity of the incident light on each layer of film interface in the extreme ultraviolet multilayer film and the distance between each layer of film interface and the surface of the extreme ultraviolet multilayer film by a Fresnel formula and an optical thin film characteristic matrix method;
and calculating the effective depth of the equivalent reflection point by an energy weighted average method according to the calculated light intensity and distance.
Preferably, in the method for analyzing a thin film of an optical system provided in an embodiment of the present invention, calculating the imaging quality of the optical system after the film is added at the exit pupil, and performing image quality evaluation specifically includes:
calculating the imaging quality of the optical system after the addition of the film at the exit pupil; the imaging quality comprises exit pupil wave aberration and MTF;
if the calculated imaging quality meets the requirement, judging that the extreme ultraviolet multilayer film can be compatible with the optical system; if the requirements are not met, optimizing by taking the object-image distance and the mirror distance as optimization variables;
if the optimized imaging quality meets the requirements, judging that the optimized extreme ultraviolet multilayer film can be compatible with the optical system; and if the optimized extreme ultraviolet multilayer film does not meet the requirements, redesigning the extreme ultraviolet multilayer film.
The embodiment of the invention also provides optical system thin film analysis equipment which comprises a processor and a memory, wherein the processor executes a computer program stored in the memory to realize the optical system thin film analysis method provided by the embodiment of the invention.
Embodiments of the present invention further provide a computer-readable storage medium for storing a computer program, where the computer program is executed by a processor to implement the above optical system thin film analysis method provided by the embodiments of the present invention.
It can be seen from the above technical solutions that, the method, the apparatus and the storage medium for analyzing a thin film of an optical system provided by the present invention include: designing and adding corresponding extreme ultraviolet multilayer films according to the angle distribution on different surface type elements in an optical system without films; establishing an equivalent reflection point for the transmission process of each incident ray in the extreme ultraviolet multilayer film by utilizing space ray tracing, and calculating the coordinate of the equivalent reflection point; calculating the coordinate of the emergent ray formed by the incident ray after being reflected by the equivalent reflection point on the surface of the extreme ultraviolet multilayer film according to the coordinate of the equivalent reflection point; tracing the optical system after being coated with the film one by one until reaching an exit pupil surface; the imaging quality of the optical system after the addition of the film was calculated at the exit pupil and image quality evaluation was performed.
According to the invention, through ray tracing, an average incident angle concept is not adopted, but the relation between the incident coordinate and the emergent coordinate of each ray on the film surface is established, namely an equivalent reflection point is established in the propagation process of each ray in the extreme ultraviolet multilayer film to obtain the equivalent reflection point coordinate, then the emergent ray coordinate is calculated by using the equivalent reflection point, tracing is carried out on different surfaces of a subsequent optical system on the basis until reaching the exit pupil surface, and finally image quality evaluation is carried out at the exit pupil. The optical system with the optical film added under the high off-axis NA large incident angle is analyzed and optimized by utilizing the space ray tracing, the method is suitable for a coated reflective structure, the reflection process of a single ray in the multilayer film is converted into reflection at an equivalent reflection point, the defect that the average incident angle concept fails at the large incident angle is overcome, the problem that the imaging quality of the optical system cannot be effectively evaluated after the film is added under the high off-axis NA large incident angle by using the conventional equivalent interface model is solved, the complicated physical optical process of light in the extreme ultraviolet multilayer film can be converted into geometric optical content, and the method can be accurately used for analyzing, evaluating and optimizing the coated optical system.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a schematic structural diagram of a conventional optical film after being coated on a substrate;
FIG. 2 is a flow chart of a method for analyzing a thin film of an optical system according to an embodiment of the present invention;
FIG. 3 is a flowchart illustrating a step S102 of a method for analyzing a thin film in an optical system according to an embodiment of the present invention;
fig. 4 is a schematic diagram of light subjected to coordinate transformation of an equivalent reflection point according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a method for analyzing a thin film of an optical system, which comprises the following steps as shown in figure 2:
s101, designing and adding corresponding extreme ultraviolet multilayer films according to angle distribution on different surface type elements in an optical system without films;
in practical application, a bare lens optical system without a film is designed, a bare base surface type equation is given, angle analysis of each surface type element on the element is given, and on the basis, corresponding film system design of the extreme ultraviolet multilayer film is carried out according to the angle distribution on different elements;
s102, establishing an equivalent reflection point for the transmission process of each incident ray in the extreme ultraviolet multilayer film by utilizing space ray tracing, and calculating the coordinate of the equivalent reflection point;
s103, calculating the coordinate of an emergent ray formed by the incident ray after being reflected by the equivalent reflection point on the surface of the extreme ultraviolet multilayer film according to the coordinate of the equivalent reflection point;
it should be understood that for an euv lithography system, which is a reflective structure, the energy at the substrate is 0, regardless of the angle of incidence, and the light will be totally reflected back into the vacuum environment at a certain depth from the film surface. In the prior art, the processing of optical design software (such as Code V software) on a thin film is to consider only the influence of the thin film on the transmittance and polarization of the system, and the imaging compatibility evaluation of the optical thin film cannot be reasonably and effectively carried out by using a bare lens optical system as a working surface when the imaging quality evaluation is carried out. Therefore, the invention provides an optical system film analysis method based on equivalent reflection points, which is characterized in that the reflection process of a single light ray in a multilayer film is converted into reflection at the equivalent reflection points, and the coordinates of the incident light ray on the film surface after being reflected by the equivalent reflection points are calculated;
s104, tracing the optical system after the film is added to the exit pupil surface one by one;
in practical applications, the optical system comprises six faces, so that each face thereof needs to be subjected to ray tracing;
and S105, calculating the imaging quality of the optical system after the film is added at the exit pupil and evaluating the image quality.
In the method for analyzing the optical system thin film provided by the embodiment of the invention, a set of space ray tracing program optimized for analysis of the off-axis high-NA large-incidence-angle optical system is established, and a relation between an incident coordinate and an emergent coordinate of each ray on a film surface is established without adopting an average incidence angle concept, namely, an equivalent reflection point is established in the propagation process of each ray in the extreme ultraviolet multilayer film to obtain an equivalent reflection point coordinate, then the emergent ray coordinate is calculated by using the equivalent reflection point, on the basis, tracing is performed on different surfaces of a subsequent optical system until reaching an exit pupil surface, and finally, image quality evaluation is performed at the exit pupil. The optical system with the optical film added under the off-axis high-NA large incident angle is analyzed and optimized by utilizing the space ray tracing, the method is suitable for a coated reflective structure, the reflection process of a single ray in the multilayer film is equivalently converted into single reflection at an equivalent reflection point, the defect that the concept of the average incident angle fails at the large incident angle is overcome, the problem that the imaging quality of the optical system cannot be evaluated after the film is effectively added under the off-axis high-NA large incident angle by using the conventional equivalent interface model is solved, not only can the complicated physical optical process of light in the extreme ultraviolet multilayer film be converted into concise geometric optical content, but also the method can be accurately used for analyzing, evaluating and optimizing the coated optical system.
In specific implementation, in the method for analyzing a thin film in an optical system provided in an embodiment of the present invention, step S101 is to design and add corresponding euv multilayer films according to an angle distribution on different surface-type elements in an optical system without adding a film, and specifically may include: firstly, setting a field sampling point by using optical design software (such as Code V software) according to the structural parameters of an optical system without a film; then according to the set field sampling points, obtaining the incident angle distribution of the incident light in the effective clear aperture of the surface of different bare lenses in the optical system; and finally, adding a corresponding extreme ultraviolet multilayer film on the surface of each bare lens according to the obtained incident angle distribution.
It should be noted that the average incident angle, i.e. the average incident angle of each point of the incident light within the effective clear aperture of the different bare mirror surfaces in the optical system, is mainly considered here. And (4) according to the average incident angle distribution, combining with optical design software, designing and obtaining corresponding film system parameters of the extreme ultraviolet multilayer film.
In specific implementation, in the method for analyzing a thin film of an optical system according to an embodiment of the present invention, as shown in fig. 3, before the step S102 is executed to calculate the coordinates of the equivalent reflection point, the method may further include the following steps:
s201, fitting a surface equation of the surface of the extreme ultraviolet multilayer film according to film system parameters of the extreme ultraviolet multilayer film;
s202, calculating coordinates of incident light on the surface of the extreme ultraviolet multilayer film by utilizing space light tracing according to the fitted surface equation of the surface of the extreme ultraviolet multilayer film.
Further, the step S102 of calculating the coordinates of the equivalent reflection point may specifically include the following steps:
s203, calculating the effective depth of the equivalent reflection point by an energy weighted average method;
in practical application, before the effective depth is calculated, energy distribution of the light at different incident depths under different angles is calculated by using thin film calculation analysis software; on the basis, the effective depth of the image is calculated by utilizing the concept of energy weighted average;
s204, fitting a surface equation of the surface where the equivalent reflection points are located by using the calculated effective depth of the equivalent reflection points; the surface equation mainly comprises a curvature radius R and a high-order aspheric surface description;
and S205, calculating the coordinate of the equivalent reflection point according to the calculated coordinate of the incident light on the surface of the extreme ultraviolet multilayer film and the fitted surface equation of the surface where the equivalent reflection point is located.
Further, in a specific implementation, in the method for analyzing a thin film of an optical system provided in the embodiment of the present invention, the step S203 may specifically include calculating an effective depth of the equivalent reflection point by an energy weighted average method, and the method may specifically include: firstly, calculating the light intensity of incident light on each layer of film interface in the extreme ultraviolet multilayer film and the distance between each layer of film interface and the surface of the extreme ultraviolet multilayer film by a Fresnel formula and an optical thin film characteristic matrix method; and then, calculating the effective depth of the equivalent reflection point by an energy weighted average method according to the calculated light intensity and distance.
Specifically, as shown in fig. 4, a surface equation of the surface a of the euv multilayer film is fitted according to the film system parameters of the euv multilayer film, and then the coordinates of the incident light on the surface a of the euv multilayer film can be calculated according to the ray tracing, using { x, y, z, θ [ ]iRepresents it. The coordinates of the incident ray on the bare mirror surface B in FIG. 4 are given by { x0,y0,z0,θ0Represents it. Then, according to the concept of energy weighted average, the incident light ray { x, y, z, theta [ ]iMultiple reflection in the extreme ultraviolet multilayer film is equivalent to reflection at an equivalent reflection point, and the coordinate of the equivalent reflection point on a plane C where the equivalent reflection point is located is calculated to be { x ', y', z ', theta' }, and the maximum value isThen calculating the coordinate { x) of the emergent ray on the surface A of the extreme ultraviolet multilayer film1,y1,z1,θ1}。
Coordinates { x ', y ', z ', theta ' } of the equivalent reflection point and coordinates { x, y, z, theta ' } of incident light on the extreme ultraviolet multilayer film surface AiThere is the following relationship between:
where α is the angle between the incident ray and the meridian plane, D is the spatial distance between the incident ray and the equivalent reflection point and the effective depth of the equivalent reflection point, and θnThe included angle of the normal direction of the equivalent reflection point in the meridian direction is shown.
It should be noted that the surfaces of the equivalent reflection points corresponding to each ray in the drawing are different, because the coordinates of the incident rays are different, the positions of the equivalent reflection points are different, the effective depth values are also different, and the rays are difficult to fit by using one surface, so that the equivalent reflection points based on ray tracing are accurately solved, and the light intensity of the incident rays is assumed to be I0Then, the light intensity I of the light on each interface j can be calculated by using the Fresnel formula and the optical film characteristic matrixjAnd the distance D of the interface from the surface of the filmjThen, the effective depth D of the equivalent reflection point can be calculated by using the energy weighted average:
after the effective depth is determined, fitting the plane C where the equivalent reflection point corresponding to the ray is located, calculating the coordinate of the equivalent reflection point, and then calculating the coordinate of the emergent ray.
Further, in a specific implementation, in the method for analyzing a thin film of an optical system provided in the embodiment of the present invention, the step S105 of calculating the imaging quality of the optical system after the film is added at the exit pupil and performing image quality evaluation may specifically include: calculating the imaging quality of the optical system after the film is added at the exit pupil; the imaging quality comprises exit pupil wave aberration and MTF; if the calculated imaging quality meets the requirements, judging that the extreme ultraviolet multilayer film can be compatible with the optical system; if the requirements are not met, optimizing by taking the object-image distance and the mirror distance as optimization variables; if the optimized imaging quality meets the requirements, the optimized extreme ultraviolet multilayer film is judged to be compatible with the optical system; and if the requirements are not met after optimization, redesigning the extreme ultraviolet multilayer film.
Specifically, if the imaging quality of the film-added optical system meets the requirements, the optimization design is finished, and the structural parameters are output, which indicates that the naked lens optical system can meet the imaging compatibility by adding the currently designed extreme ultraviolet multilayer film. And if the imaging quality of the optimized film-added optical system meets the requirements, ending the optimized design, outputting optimized structural parameters, and indicating that the naked lens optical system can meet the imaging compatibility after being optimized and adjusted by adding the currently designed extreme ultraviolet multilayer film. If not, redesigning the membrane system and carrying out iterative design until the membrane system can meet the requirements.
Correspondingly, the embodiment of the invention also discloses optical system thin film analysis equipment, which comprises a processor and a memory; wherein, the processor implements the thin film analysis method of the optical system disclosed in the foregoing embodiments when executing the computer program stored in the memory.
For more specific processes of the above method, reference may be made to corresponding contents disclosed in the foregoing embodiments, and details are not repeated here.
Further, the present invention also discloses a computer readable storage medium for storing a computer program; the computer program when executed by a processor implements the optical system thin film analysis method disclosed above.
For more specific processes of the above method, reference may be made to corresponding contents disclosed in the foregoing embodiments, and details are not repeated here.
The embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same or similar parts among the embodiments are referred to each other. The device and the storage medium disclosed by the embodiment correspond to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
The embodiment of the invention provides an optical system film analysis method, equipment and a storage medium, wherein the optical system film analysis method comprises the following steps: designing and adding corresponding extreme ultraviolet multilayer films according to the angle distribution on different surface type elements in an optical system without films; establishing an equivalent reflection point for the transmission process of each incident ray in the extreme ultraviolet multilayer film by utilizing space ray tracing, and calculating the coordinate of the equivalent reflection point; calculating the coordinate of the emergent ray formed by the incident ray after being reflected by the equivalent reflection point on the surface of the extreme ultraviolet multilayer film according to the coordinate of the equivalent reflection point; tracing the optical system after being coated with the film one by one until reaching an exit pupil surface; the imaging quality of the optical system after the addition of the film was calculated at the exit pupil and image quality evaluation was performed. The optical system with the optical film added under the high off-axis NA large incident angle is analyzed and optimized by utilizing the space ray tracing, the method is suitable for a coated reflective structure, the reflection process of a single ray in the multilayer film is converted into reflection at an equivalent reflection point, the defect that the average incident angle concept fails at the large incident angle is overcome, the problem that the imaging quality of the optical system cannot be effectively evaluated after the film is added under the high off-axis NA large incident angle by using the conventional equivalent interface model is solved, the complicated physical optical process of light in the extreme ultraviolet multilayer film can be converted into geometric optical content, and the method can be accurately used for analyzing, evaluating and optimizing the coated optical system.
Finally, it should also be noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The above detailed description of the method, apparatus and storage medium for analyzing thin films of an optical system provided by the present invention is provided, and the principle and embodiments of the present invention are described herein by using specific examples, and the above descriptions of the examples are only used to help understanding the method and core ideas of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
Claims (8)
1. An optical system thin film analysis method, comprising:
designing and adding corresponding extreme ultraviolet multilayer films according to the angle distribution on different surface type elements in an optical system without films;
establishing an equivalent reflection point for the transmission process of each incident ray in the extreme ultraviolet multilayer film by utilizing space ray tracing, and calculating the coordinate of the equivalent reflection point;
calculating the coordinate of the emergent ray formed by the incident ray after being reflected by the equivalent reflection point on the surface of the extreme ultraviolet multilayer film according to the coordinate of the equivalent reflection point;
tracing the optical system after the film is added to the exit pupil surface one by one;
and calculating the imaging quality of the optical system after the film is added at the exit pupil and carrying out image quality evaluation.
2. The method for analyzing a thin film in an optical system according to claim 1, wherein designing and adding corresponding extreme ultraviolet multilayer films according to the angle distribution on different surface-type elements in the optical system without adding the films specifically comprises:
setting a field sampling point by using optical design software according to the structural parameters of an optical system without a film;
obtaining the incident angle distribution of incident light rays in effective clear apertures on the surfaces of different bare lenses in the optical system according to the set field sampling points;
and adding a corresponding extreme ultraviolet multilayer film on the surface of each bare lens according to the obtained incident angle distribution.
3. The optical system thin film analysis method according to claim 2, further comprising, before calculating the coordinates of the equivalent reflection point:
fitting a surface equation of the surface of the extreme ultraviolet multilayer film according to the film system parameters of the extreme ultraviolet multilayer film;
and calculating the coordinate of the incident ray on the surface of the extreme ultraviolet multilayer film by utilizing space ray tracing according to the fitted surface equation of the surface of the extreme ultraviolet multilayer film.
4. The method for analyzing optical system films according to claim 3, wherein calculating the coordinates of the equivalent reflection point specifically comprises:
calculating the effective depth of the equivalent reflection point by an energy weighted average method;
fitting a surface equation of the surface where the equivalent reflection points are located by using the calculated effective depth of the equivalent reflection points;
and calculating the coordinate of the equivalent reflection point according to the calculated coordinate of the incident ray on the surface of the extreme ultraviolet multilayer film and the fitted surface equation of the surface where the equivalent reflection point is located.
5. The method for analyzing optical system thin films according to claim 4, wherein calculating the effective depth of the equivalent reflection point by an energy weighted average method specifically comprises:
calculating the light intensity of the incident light on each layer of film interface in the extreme ultraviolet multilayer film and the distance between each layer of film interface and the surface of the extreme ultraviolet multilayer film by a Fresnel formula and an optical thin film characteristic matrix method;
and calculating the effective depth of the equivalent reflection point by an energy weighted average method according to the calculated light intensity and distance.
6. The method for analyzing a thin film of an optical system according to claim 1, wherein the step of calculating the imaging quality of the optical system after the addition of the film at the exit pupil and performing image quality evaluation comprises:
calculating the imaging quality of the optical system after the addition of the film at the exit pupil; the imaging quality comprises exit pupil wave aberration and MTF;
if the calculated imaging quality meets the requirement, judging that the extreme ultraviolet multilayer film can be compatible with the optical system; if the requirements are not met, optimizing by taking the object-image distance and the mirror distance as optimization variables;
if the optimized imaging quality meets the requirements, judging that the optimized extreme ultraviolet multilayer film can be compatible with the optical system; and if the optimized extreme ultraviolet multilayer film does not meet the requirements, redesigning the extreme ultraviolet multilayer film.
7. An optical system thin film analysis apparatus comprising a processor and a memory, wherein the processor implements the optical system thin film analysis method according to any one of claims 1 to 6 when executing a computer program stored in the memory.
8. A computer-readable storage medium for storing a computer program, wherein the computer program when executed by a processor implements the optical system thin film analysis method according to any one of claims 1 to 6.
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