Design method and device for gradient Mo / Si multilayer film of large-caliber collecting mirror and medium

Abstract

The invention provides a design method and device for a gradient Mo / Si multilayer film of a large-diameter collecting mirror and a medium, and the method comprises the steps: forming the gradient Mo / Si multilayer film through an extreme ultraviolet period reflection gradient Mo / Si multilayer film, a protective cap layer and an isolation layer, covering the top of the extreme ultraviolet period reflection gradient multilayer film with the protective cap layer, and arranging the isolation layer between Mo / Si layers; the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film is of a periodic multilayer film structure with the layer thickness changing in a gradient mode, the layer thickness and the incidence angle change in a gradient mode, and the quadratic function relation is met. Fitting optimization is carried out on the layer thickness of each layer of thin film of the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film based on the quadratic function relation to match the incident angle, and the gradient Mo / Si multilayer film of the large-caliber collecting mirror is obtained, so that the problem that the reflectivity requirement in the large incident angle range when the large-caliber collecting mirror of an extreme ultraviolet lithography optical system works cannot be met is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of precision photolithography component research, and in particular to a design method, equipment and medium for a gradient Mo / Si multilayer film of a large-aperture collecting mirror. Background Art

[0002] The collector mirror is a key component in extreme ultraviolet (EUV) lithography optical systems. Its manufacturing precision and surface quality directly affect the reflection and focusing capabilities of EUV radiation, as well as the diffraction efficiency of infrared light, which in turn determines the output power and stability of the EUV lithography light source. These factors ultimately affect the throughput, resolution, manufacturing cost, and reliability of the EUV lithography tool.

[0003] The wavelength of extreme ultraviolet light ranges from 10nm to 121nm. In the EUV band, the refractive index of most materials is close to 1. Traditional anti-reflection coatings have low reflectivity in the EUV band, limiting the light-collecting performance of the collector mirror. To improve reflectivity, EUV periodic multilayer coatings are typically formed by alternating materials with high and low refractive indices. These include uniform multilayer coating structures and gradient multilayer coating structures. Uniform multilayer coatings can only achieve high reflectivity within a specific, narrow incident angle range of approximately 5°. Because the incident angle range of light is wide when operating in large-aperture collector mirrors in EUV lithography optical systems—for example, the incident angle range for a 650mm collector mirror is approximately 5 to 36°—traditional uniform multilayer coatings cannot meet the reflectivity requirements within this wide incident angle range. Gradient multilayer coating structures, on the other hand, vary in film thickness at different collector mirror apertures, achieving high reflectivity across a wide range of incident angles. Currently, the most common gradient multilayer coating structure is suitable for collector mirrors with apertures of 300mm or less, with fewer multilayer coating structures suitable for larger apertures.

[0004] Therefore, it is urgent to propose a design method for a gradient Mo / Si multilayer film for a large-aperture collecting mirror to solve the technical problem of not being able to meet the reflectivity requirements within a large incident angle range when the large-aperture collecting mirror of the extreme ultraviolet lithography optical system works. Summary of the Invention

[0005] In order to overcome the problems existing in the related art, the present disclosure provides a design method, equipment and medium for a gradient Mo / Si multilayer film of a large-aperture collecting mirror, so as to solve the technical problem in the related art that the reflectivity requirements within a large incident angle range cannot be met when the large-aperture collecting mirror of the extreme ultraviolet lithography optical system is working.

[0006] One or more embodiments of the present specification provide a method for designing a gradient Mo / Si multilayer film for a large-aperture collecting mirror, wherein the gradient Mo / Si multilayer film is composed of an extreme ultraviolet periodic reflection gradient Mo / Si multilayer film, a protective cap layer, and an isolation layer, wherein the protective cap layer is covered on top of the extreme ultraviolet periodic reflection gradient multilayer film, and an isolation layer is provided between the Mo / Si layers;

[0007] The extreme ultraviolet periodic reflection gradient Mo / Si multilayer film is a periodic multilayer thin film structure with a gradient change in layer thickness, and the layer thickness and the incident angle change in a gradient manner, satisfying a quadratic function relationship;

[0008] Based on the quadratic function relationship, the thickness of each layer of the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film is fitted and optimized to match the incident angle, thereby obtaining a gradient Mo / Si multilayer film for a large-aperture collecting mirror.

[0009] Preferably, the initial layer thickness of the extreme ultraviolet periodic reflective gradient Mo / Si multilayer film is determined by a genetic algorithm, and the layer thickness at the optimal reflectivity value at near normal incidence is obtained by a simplex optimization algorithm.

[0010] Preferably, the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film is composed of alternating absorption layers and spacer layers, and the absorption layers and the spacer layers are two high and low atomic number Z materials with different refractive indices in the extreme ultraviolet band. The high Z material can be Mo or Ru, and the low Z material can be Si or B4C.

[0011] Preferably, the absorption layer is Mo, the isolation layer is a Si layer, the protective cap layer is a single layer of Ru, and the isolation layer is a single layer of B4C.

[0012] Preferably, the absorption layer and the isolation layer constitute one period of the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film, and one periodic structure is B4C-Si-B4C-Mo.

[0013] Preferably, the period thickness of the one periodic structure satisfies Bragg's law.

[0014] Preferably, the periodic thickness of the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film is between 6nm and 8nm, the thickness of the Mo layer is between 2.11nm and 2.66nm, the thickness of the Si layer is between 4.17nm and 5.19nm, the thickness of the B4C layer is between 0.25nm and 0.5nm, and the thickness of the Ru layer is between 1.7nm and 2.2nm.

[0015] Preferably, the layer thickness of the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film and its position on the collecting mirror are expressed as a quadratic function relationship. Under the condition that the two sides of the film are symmetrical about the optical axis, the translation amount in the vertical axis direction affects the thickness change. The layer thickness change of the gradient film of the collecting mirror and the translation amount satisfy a quadratic function relationship, and are directly proportional to the initial layer thickness of the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film.

[0016] One or more embodiments of the present specification provide a computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, a method for designing a gradient Mo / Si multilayer film for a large-aperture collecting mirror as described above is implemented.

[0017] One or more embodiments of the present specification provide a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of the method for designing a gradient Mo / Si multilayer film for a large-aperture collecting mirror as described above.

[0018] The present disclosure provides a design method, device and medium for a gradient Mo / Si multilayer film of a large-aperture collecting mirror, which has the advantages that the gradient Mo / Si multilayer film is composed of an extreme ultraviolet periodic reflection gradient Mo / Si multilayer film, a protective cap layer and an isolation layer. The gradient structure can broaden the effective reflection angle range and is suitable for wide-angle incident scenes of extreme ultraviolet light. The protective cap layer is covered on the top of the extreme ultraviolet periodic reflection gradient multilayer film to prevent the surface of the multilayer film from being oxidized, contaminated or scratched. The isolation layer is provided between the Mo / Si layers to block the mutual diffusion of Mo and Si, avoid the formation of an amorphous state or compound phase at the interface, and maintain the ideal optical constants of the multilayer film. The extreme ultraviolet periodic reflection gradient Mo / Si multilayer film has the advantages of broadening the effective reflection angle range and being suitable for wide-angle incident scenes of extreme ultraviolet light. The protective cap layer is covered on the top of the extreme ultraviolet periodic reflection gradient multilayer film to prevent the surface of the multilayer film from being oxidized, contaminated or scratched. The isolation layer is provided between the Mo / Si layers to block the mutual diffusion of Mo and Si, avoid the formation of an amorphous state or compound phase at the interface, and maintain the ideal optical constants of the multilayer film. The Si multilayer film is a periodic multilayer thin film structure with a gradient change in layer thickness. The layer thickness changes gradiently with the incident angle, satisfying a quadratic function relationship, which can avoid the decrease in reflectivity of traditional uniform multilayer films due to angle deviation; based on the quadratic function relationship, the layer thickness of each layer of the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film is fitted and optimized to match the incident angle, and the gradient Mo / Si multilayer film of the large-aperture collecting mirror is obtained. Using the quadratic function model, for the optical design of a specific large-aperture collecting mirror, the optimal thickness of each layer of Mo and Si is calculated through a numerical optimization algorithm, so that the entire mirror surface has the highest reflectivity and the best uniformity within the working wavelength and the designed incident angle range. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate one or more embodiments of this specification or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 A schematic flow chart of a design method for a gradient Mo / Si multilayer film for a large-aperture collecting mirror provided in one or more embodiments of this specification;

[0021] Figure 2 A graph of thickness variation of a gradient multilayer film provided for one or more embodiments of this specification;

[0022] Figure 3 A multilayer film design flow chart for one or more embodiments of this specification;

[0023] Figure 4 The designed reflectivity of the film system provided in one or more embodiments of this specification;

[0024] Figure 5 Theoretical fitting reflectivity of the film system provided for one or more embodiments of this specification;

[0025] Figure 6 A cross-sectional view of a multilayer film structure provided for one or more embodiments of this specification;

[0026] Figure 7 A schematic diagram of a gradient multilayer film structure provided for one or more embodiments of this specification;

[0027] Figure 8 A schematic diagram of the structure of a computer device provided in one or more embodiments of this specification. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solutions in one or more embodiments of this specification, the technical solutions in one or more embodiments of this specification will be clearly and completely described below in conjunction with the drawings in one or more embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on one or more embodiments of this specification, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this invention document.

[0029] The present invention will be described in detail below with reference to specific implementation methods and the accompanying drawings.

[0030] Method Example

[0031] According to an embodiment of the present invention, a design method for a gradient Mo / Si multilayer film of a large-aperture collecting mirror is provided, such as Figure 1 FIG. 1 is a flow chart of a method for designing a gradient Mo / Si multilayer film for a large-aperture collecting mirror provided in this embodiment. The method for designing a gradient Mo / Si multilayer film for a large-aperture collecting mirror according to an embodiment of the present invention comprises the following steps:

[0032] S110. Design the initial structure of the multilayer film, which is composed of an extreme ultraviolet periodic reflection gradient Mo / Si multilayer film, a protective cap layer and an isolation layer to form a gradient Mo / Si multilayer film, wherein the protective cap layer is covered on the top of the extreme ultraviolet periodic reflection gradient multilayer film and the isolation layer is set between the Mo / Si layers.

[0033] S120, the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film is a periodic multilayer thin film structure with a gradient change in layer thickness. The initial layer thickness of the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film is determined by a genetic algorithm, and the layer thickness at the optimal value of reflectivity at near normal incidence is obtained by a simplex optimization algorithm. The layer thickness d varies with the incident angle θ in a gradient manner, satisfying a quadratic function relationship, which is similar to the fitting relationship between the uniform film thickness and the incident angle for achieving high reflectivity at a single incident angle. Figure 2 As shown in FIG, a thickness variation diagram of the gradient multilayer film provided in this embodiment.

[0034] The quadratic function relationship is expressed as:

[0035] d(θ)=K2θ 2 +K1θ+K0;

[0036] Among them, K2, K1, K0 are polynomial coefficients.

[0037] S130. Based on the quadratic function relationship, the layer thickness d of each layer of the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film is fitted and optimized to match the incident angle θ, thereby obtaining the gradient Mo / Si multilayer film of the large-aperture collecting mirror.

[0038] like Figure 3 The figure shows the multilayer film design flow chart provided in this embodiment. Based on the reflectivity results obtained, the reflectivity vs. incident angle curve fitting results were verified. After verification, the quadratic goodness of fit between reflectivity and incident angle was greater than 0.998. Outliers that did not conform to the fitting results were further optimized to match the corresponding incident angle reflectivity peaks, and the optimization process was repeated.

[0039] The design reflective film system provided in this embodiment has a theoretical reflectivity calculated by simulation as follows: Figure 4 、 Figure 5 As shown, Figure 4 As shown, the reflectivity of the film system provided in this embodiment is designed, as shown in FIG. Figure 5 As shown, the theoretical fitting reflectivity of the film system provided in this embodiment achieves a high reflectivity of Rs>67% within the angle range of 5 to 35 degrees.

[0040] The method provided in this embodiment comprises an extreme ultraviolet periodic reflection gradient Mo / Si multilayer film, a protective cap layer and an isolation layer to form a gradient Mo / Si multilayer film. The gradient structure can broaden the effective reflection angle range and is suitable for wide-angle incident scenes of extreme ultraviolet light. The protective cap layer is covered on the top of the extreme ultraviolet periodic reflection gradient multilayer film to prevent the surface of the multilayer film from being oxidized, contaminated or scratched. An isolation layer is provided between the Mo / Si layers to block the mutual diffusion of Mo and Si, avoid the formation of an amorphous state or compound phase at the interface, and maintain the ideal optical constants of the multilayer film. The extreme ultraviolet periodic reflection gradient Mo / Si multilayer film is a periodic multilayer film with a gradient change in layer thickness. The invention discloses a thin film structure with a layer thickness d, wherein the layer thickness d varies with the incident angle θ in a gradient manner, satisfying a quadratic function relationship, and avoiding the decrease in reflectivity of the traditional uniform multilayer film due to angular deviation. Based on the quadratic function relationship, the layer thickness d of each layer of the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film is fitted and optimized to match the incident angle θ, thereby obtaining a gradient Mo / Si multilayer film for a large-aperture collecting mirror. The quadratic function model is used to calculate the optimal thickness of each layer of Mo and Si through a numerical optimization algorithm for the optical design of a specific large-aperture collecting mirror, so that the entire mirror surface has the highest reflectivity and the best uniformity within the working wavelength and the designed incident angle range.

[0041] In one embodiment, the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film is composed of alternating absorption layers and spacer layers. The absorption layer and the spacer layer are two high and low atomic number Z materials with different refractive indices in the extreme ultraviolet band. The high Z material can be Mo or Ru, and the low Z material can be Si or B4C. The absorption layer is Mo, and the isolation layer is a Si layer. Considering factors such as diffusion between Mo / Si layers and oxidation corrosion of the film, the protective cap layer is a single layer of Ru, and the isolation layer is a single layer of B4C. The absorption layer and the isolation layer constitute one period of the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film. The number of film pairs of the periodic multilayer film is 50 pairs, and one periodic structure is B4C-Si-B4C-Mo. Figure 6 , which is a cross-sectional view of the multilayer film structure provided in this embodiment.

[0042] In one embodiment, the high-Z material and the low-Z material constitute one period of the extreme ultraviolet periodic multilayer film, and the layer thickness of one periodic structure satisfies the Bragg law, so that the crest of the standing wave is located in the spacer layer region of the multilayer film, and the trough of the standing wave is located in the absorption layer region of the multilayer film.

[0043] Bragg's law for layer thickness: mλ = 2dsinθ;

[0044] In one embodiment, the periodic thickness of the extreme ultraviolet periodic reflective gradient Mo / Si multilayer film is between 6nm and 8nm, the Mo layer thickness is between 2.11nm and 2.66nm, the Si layer thickness is between 4.17nm and 5.19nm, the B4C thickness is between 0.25nm and 0.5nm, and the Ru layer thickness is between 1.7nm and 2.2nm.

[0045] In one embodiment, Figure 7 As shown, it is a schematic diagram of the gradient multilayer film structure provided in this embodiment. The layer thickness of the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film and the position on the collecting mirror are expressed as a quadratic function relationship. Under the condition that the two sides of the film are symmetrical about the optical axis, the translation amount in the vertical axis direction affects the thickness change. The layer thickness change of the gradient film of the collecting mirror and the translation amount satisfy the quadratic function relationship and are proportional to the initial layer thickness.

[0046] like Figure 8 As shown, the present invention also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the design method of the gradient Mo / Si multilayer film of the large-aperture collecting mirror in the above-mentioned embodiment, or, when executed by a processor, implements the design method of the gradient Mo / Si multilayer film of the large-aperture collecting mirror in the above-mentioned embodiment.

[0047] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in various forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0048] Each embodiment in this specification is described in a progressive manner. The same or similar parts between the embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the device or system embodiments, since they are basically similar to the method embodiments, the description is relatively simple. For the relevant parts, refer to the partial description of the method embodiments. The device and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the scheme of this embodiment. A person of ordinary skill in the art can understand and implement it without making any creative efforts.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and the contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A design method for a gradient Mo / Si multilayer film for a large-aperture collecting mirror, characterized in that: The following steps are involved: The gradient Mo / Si multilayer film is composed of an extreme ultraviolet periodic reflection gradient Mo / Si multilayer film, a protective cap layer and an isolation layer, wherein the protective cap layer is covered on the top of the extreme ultraviolet periodic reflection gradient multilayer film and the isolation layer is set between the Mo / Si layers; The extreme ultraviolet periodic reflection gradient Mo / Si multilayer film is a periodic multilayer thin film structure with a gradient change in layer thickness, and the layer thickness and the incident angle change in a gradient manner, satisfying a quadratic function relationship; Based on the quadratic function relationship, the thickness of each layer of the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film is fitted and optimized to match the incident angle, thereby obtaining a gradient Mo / Si multilayer film for a large-aperture collecting mirror.

2. The design method of the gradient Mo / Si multilayer film for the large-aperture collecting mirror according to claim 1, characterized in that: The initial layer thickness of the extreme ultraviolet periodic reflective gradient Mo / Si multilayer film is determined by a genetic algorithm, and the layer thickness at the optimal reflectivity value at near normal incidence is obtained by a simplex optimization algorithm.

3. The design method of the gradient Mo / Si multilayer film for the large-aperture collecting mirror according to claim 1, characterized in that: The extreme ultraviolet periodic reflection gradient Mo / Si multilayer film is composed of alternating absorption layers and spacer layers. The absorption layers and the spacer layers are two high and low atomic number Z materials with different refractive indices in the extreme ultraviolet band. The high Z material can be Mo or Ru, and the low Z material can be Si or B4C.

4. The design method of the gradient Mo / Si multilayer film for the large-aperture collecting mirror according to claim 3, characterized in that: The absorption layer is Mo, the isolation layer is a Si layer, the protective cap layer is a single layer of Ru, and the isolation layer is a single layer of B4C.

5. The design method of the gradient Mo / Si multilayer film for the large-aperture collecting mirror according to claim 4, characterized in that: The absorption layer and the isolation layer constitute one period of the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film, and one periodic structure is B4C-Si-B4C-Mo.

6. The design method of the gradient Mo / Si multilayer film for the large-aperture collecting mirror according to claim 5, characterized in that: The layer thickness of one periodic structure satisfies Bragg's law.

7. The design method of the gradient Mo / Si multilayer film for the large-aperture collecting mirror according to claim 1, characterized in that: The periodic thickness of the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film is between 6nm and 8nm, the Mo layer thickness is between 2.11nm and 2.66nm, the Si layer thickness is between 4.17nm and 5.19nm, the B4C thickness is between 0.25nm and 0.5nm, and the Ru layer thickness is between 1.7nm and 2.2nm.

8. The design method of the gradient Mo / Si multilayer film for the large-aperture collecting mirror according to claim 1, characterized in that: The layer thickness of the extreme ultraviolet periodic reflection gradient Mo / Si multilayer film and its position on the collecting mirror are expressed as a quadratic function relationship. Under the condition that the two sides of the film are symmetrical about the optical axis, the translation amount in the vertical axis direction affects the thickness change. The layer thickness change of the gradient film of the collecting mirror and the translation amount satisfy a quadratic function relationship and are proportional to the initial layer thickness.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the method for designing the gradient Mo / Si multilayer film of the large-aperture collecting mirror according to any one of claims 1 to 8 is implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method for designing a gradient Mo / Si multilayer film for a large-aperture collecting mirror as claimed in any one of claims 1 to 8 are implemented.

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