Method of configuring extreme ultraviolet (EUV) source and EUV exposure method using EUV source

Abstract

Provided are a method of configuring an extreme ultraviolet (EUV) source capable of improving optical performance prior to an exposure process, and an EUV exposure method using the EUV source. A method of configuring an EUV source includes: generating an object spectrum for a layout of a mask pattern; generating a pupil image corresponding to the object spectrogram; and configuring the EUV illumination mode by: selecting a mirror in at least a portion of a first region of the pupil map that satisfies a specific condition; and applying a pole equilibrium perturbation to the plurality of mirrors.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based upon and claims the benefit of priority from Korean Patent Application No. 10-2024-0022003 filed on February 15, 2024, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. Technical Field

[0003] The present invention relates to an extreme ultraviolet (EUV) light source, and more particularly, to a method of configuring an EUV source in relation to optimizing an EUV illumination mode, and an EUV exposure method using the EUV source. Background Art

[0004] Recently, as semiconductor circuit linewidths have become increasingly thinner, light sources with shorter wavelengths are becoming increasingly necessary. For example, EUV (European UV) is being used as an exposure light source, and the number of semiconductor device layers exposed using EUV has increased. Due to the absorption characteristics of EUV, reflective EUV masks are often used during EUV exposure. Furthermore, the illumination optics used to transmit EUV light to the EUV mask and the projection optics used to project EUV light reflected from the EUV mask onto the exposure target can include multiple mirrors. Summary of the Invention

[0005] One or more aspects of the present disclosure provide a method of configuring an extreme ultraviolet (EUV) light source that improves optical performance before an exposure process, and an EUV exposure method using the EUV source.

[0006] According to one aspect of the present disclosure, a method for configuring an extreme ultraviolet (EUV) source is provided, the method comprising: generating a target spectral map for a layout of a mask pattern; generating a pupil map corresponding to the target spectral map; and configuring an EUV illumination mode by: selecting a plurality of mirrors in a first region of the pupil map based on satisfying a first condition, and applying a pole balance perturbation to the plurality of mirrors.

[0007] According to another aspect of the present disclosure, a method for configuring an extreme ultraviolet (EUV) source is provided, the method comprising: generating a target spectral map for a layout of a mask pattern; generating a pupil map corresponding to the target spectral map; and configuring an EUV illumination pattern based on one of a maximum overlap area where a maximum number of beams overlap in the pupil map or a next maximum overlap area where a next maximum number of beams overlap is greater than or equal to an area where an illumination efficiency is 1 by: selecting a plurality of mirrors in at least a portion of a first area including the maximum overlap area or the next maximum overlap area, and applying a pole balance perturbation to introduce asymmetry in the pupil map.

[0008] According to another aspect of the present disclosure, an extreme ultraviolet (EUV) exposure method is provided, including: obtaining a target pattern; configuring an EUV mask and an EUV source corresponding to the target pattern; and performing EUV exposure on a wafer using the EUV source and the EUV mask, wherein configuring the EUV source includes: generating a target spectrum map for a layout of a mask pattern on the EUV mask; generating a pupil map corresponding to the target spectrum map; and configuring an EUV illumination pattern based on one of a maximum overlap area where a maximum number of beams overlap in the pupil map or a next maximum overlap area where a next maximum number of beams overlap is greater than or equal to an area where an illumination efficiency is 1, by the following operations: selecting a plurality of mirrors in at least a portion of a first area including the maximum overlap area or the next maximum overlap area, and applying a pole balance perturbation to introduce asymmetry in the pupil map. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The embodiments will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0010] Figure 1 is a flow chart schematically illustrating a method of configuring an extreme ultraviolet (EUV) light source according to an embodiment;

[0011] Figure 2A and Figure 2B yes Figure 1 A conceptual diagram of an object spectrum diagram in a method for configuring an EUV source;

[0012] Figure 3 is with Figure 1 A conceptual diagram of a pupil diagram related to a method of configuring an EUV source;

[0013] Figures 4A to 4E It is through Figure 1 A conceptual diagram of various EUV illumination modes configured by applying pole balance perturbation in a method for configuring an EUV source and a layout of mask patterns corresponding to the various EUV illumination modes;

[0014] Figure 5A is a conceptual diagram of a scanning electron microscope (SEM) image of a cross-pole illumination mode and a target pattern according to a comparative example, and Figure 5B is a conceptual diagram of a Y-dipole illumination pattern and a scanning electron microscope (SEM) image of a target pattern based on a method of configuring an EUV source according to an embodiment;

[0015] Figures 6A to 6C is shown with Figure 1 A conceptual diagram of the concepts of mask pattern layout, aerial image, and Normalized Image Logarithmic Slope (NILS) related to a method of configuring an EUV source; and

[0016] Figure 7is a flowchart schematically illustrating an EUV exposure method using an EUV source according to an embodiment. DETAILED DESCRIPTION

[0017] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. The same components in the drawings are denoted by the same reference numerals, and redundant descriptions thereof will be omitted.

[0018] Figure 1 is a flow chart schematically illustrating a method of configuring an extreme ultraviolet (EUV) source according to an embodiment.

[0019] In reference Figure 1 Before describing the method for configuring an EUV source according to an embodiment, the EUV facility will be briefly described. The EUV facility may include an EUV light source, a first optical system, a second optical system, an EUV mask, and a wafer. The EUV light source may generate and output EUV light with high energy density. For example, the EUV light may be in the wavelength range of approximately 5 nm to approximately 50 nm. For example, the EUV light source may generate and output high-energy-density EUV light with a wavelength of or approximately 13.5 nm. The EUV light source may be a plasma-based light source or a synchrotron radiation light source. Here, a plasma-based light source refers to a light source that generates plasma and utilizes light emitted by the plasma. For example, a plasma-based light source may include, but is not limited to, a laser-produced plasma (LPP) light source or a discharge-produced plasma (DPP) light source.

[0020] The first optical system may include a plurality of mirrors Mr. The first optical system may be referred to as an EUV illumination optical system or an EUV illumination mode. According to an embodiment, in the method of configuring an EUV source, the EUV source may include an EUV light source, a first optical system, and a second optical system. However, the present disclosure is not limited thereto, and therefore, in some embodiments, the EUV source may be the same as the EUV illumination mode.

[0021] The first optical system can transmit EUV light from an EUV light source to an EUV mask. For example, the EUV light from the EUV light source can be reflected by a mirror in the first optical system and incident on the EUV mask on the mask stage. According to embodiments, the first optical system can shape the EUV light into a curved slit shape and cause the EUV light to be incident on the EUV mask. Here, the curved slit shape of the EUV light can be a parabolic two-dimensional curve in the xy plane.

[0022] The EUV mask can be a reflective mask having reflective regions, non-reflective regions, and / or intermediate reflective regions. The EUV mask can include a substrate, a reflective multilayer film on the substrate, and an absorber layer formed on the reflective multilayer film. For example, the substrate can include a low thermal expansion coefficient material (LTEM), such as quartz. The reflective multilayer film can reflect EUV light. For example, the reflective multilayer film can have a structure in which molybdenum (Mo) layers and silicon (Si) layers are alternately stacked in multiple layers. Depending on the embodiment, the absorber layer can include, for example, TaN, TaNO, TaBO, Ni, Au, Ag, C, Te, Pt, Pd, Cr, etc. However, the materials of the reflective multilayer film and the absorber layer are not limited to the above-mentioned materials. Here, the absorber layer portion can correspond to the non-reflective region and / or intermediate reflective region described above.

[0023] The EUV mask reflects EUV light from the first optical system so that it is incident on the second optical system. For example, the EUV mask structures the EUV light according to the pattern shape formed by the reflective multilayer film and the absorption layer on the substrate, so that the EUV light reflected on the optical system is structured EUV light. The EUV light can be structured to include at least one secondary diffraction light based on the pattern on the EUV mask. The structured EUV light can be incident on the second optical system while retaining the information in the form of the pattern on the EUV mask, and can be projected onto the EUV exposure target through the second optical system. The EUV exposure target can be a wafer, and the second optical system can be called an EUV projection optical system. The second optical system can include multiple mirrors.

[0024] The EUV mask can be placed on a mask stage. The EUV mask can be moved in the x-direction, y-direction, or z-direction by moving the mask stage, and can also be rotated around the x-axis, y-axis, or z-axis. For example, the movement in the x-direction or y-direction can be horizontal movement, and the movement in the z-direction can be vertical movement. The wafer for EUV exposure can be located on the wafer stage. The wafer can be moved in the x-direction, y-direction, or z-direction by moving the wafer stage. In addition, the wafer W can also be rotated around the x-axis, y-axis, or z-axis by rotating the wafer stage.

[0025] According to an embodiment, in operation S110, the method of configuring the EUV source may include generating an object spectrum map for the layout of the mask pattern. According to an embodiment, the method may include obtaining information about the mask pattern. For example, the method may include obtaining information about the mask pattern before generating the object spectrum map for the layout of the mask pattern. In the example case where the mask pattern is a repeating pattern, the information about the mask pattern may include, but is not limited to, the spacing of the repeating pattern, the target critical dimension (CD), characteristics, and the gauge of the mask pattern. Here, the characteristics may include optical properties such as the aspect ratio (or long / short ratio) of CD, dose, local CD uniformity (LCDU), normalized image log slope (NILS), point uniformity (IPU), mask error enhancement factor (MEEF), and depth of focus (DoF). However, the characteristics are not limited to the above-mentioned optical properties. For reference, the specification is a 1D line extracted with respect to the optical performance of the optimization target, and may generally refer to the cutting lines of the x-axis and y-axis of the mask pattern. NILS refers to an optical performance that exhibits the following characteristics: as the NILS value increases, the CD varies less with process variations. Reference will be made below to Figures 6A to 6C The cutting lines and NILS for the x-axis and y-axis are described in more detail. In some embodiments, a characteristic may be referred to as a constraint or condition.

[0026] The object spectrogram can be generated based on the layout of the mask pattern. The object spectrogram can be generated in an automated manner to a certain extent. For example, when the layout of the mask pattern is received, the shape of the layout can be parameterized, and the object spectrogram can be automatically generated by a graph generation tool based on the parameters. Figure 2A and Figure 2B Describe the object spectrogram in more detail.

[0027] In operation S120, the method may include generating a pupil map corresponding to the object spectrogram. For example, after generating the object spectrogram, generating the pupil map corresponding to the object spectrogram. The pupil map may be generated by convolving a 2D fast Fourier transform (FFT) of a mask pattern with the pupil. For example, the mask pattern may be normalized, and a pupil with a 100% pupil fill rate (PFR) may be used. PFR may refer to a ratio of an area of a pupil surface to an area of the pupil surface. The pupil map may appear in the form of a 2D FFT image, such as Figure 3 The following will refer to Figure 3 The pupil diagram is described in more detail.

[0028] The pupil map can be used to define the first region described below. Furthermore, the pupil map can be used to generate a top-hat. For example, a top-hat can be generated to exclude unnecessary EUV point sources in the EUV illumination pattern. By excluding unnecessary EUV point sources in the EUV illumination pattern through a top-hat operation before calculating the aerial image of all EUV point sources, the time required to calculate the aerial image of the EUV point sources can be significantly reduced.

[0029] Here, the EUV point source is the smallest unit that can be turned on / off individually and can be generated by segmenting the EUV illumination pattern. Each EUV point source can have incoherence. In other words, the light originating from EUV point sources at different positions can have the characteristic of not interfering with each other. Therefore, each EUV point source can be processed independently of each other. In addition, the entire EUV illumination pattern can be configured by summing the EUV point sources. For example, the entire EUV illumination pattern can be configured by adding all EUV point sources. The following uses the concept of EUV mapping to describe in more detail how to configure the EUV illumination pattern by segmenting the EUV point source or summing the EUV point sources.

[0030] According to an embodiment, an aerial image of a point source may be calculated by optical simulation. The aerial image may refer to a point source displayed as an intensity distribution on the x-axis and y-axis, such as Figure 6B As shown in the figure. According to an embodiment, optical simulation refers to the process of accurately calculating the light intensity from a light source in two or one dimensions, and can be performed using a rigorous simulation tool. In the method of configuring an EUV source according to an embodiment, optical simulation is not limited to a specific software tool and can be performed using any type of software tool as long as the intensity of light can be accurately calculated in two or one dimensions. Here, by generating a top hat based on a drawing method to exclude unnecessary EUV point sources, the time required to calculate the aerial image of the EUV point source can be significantly reduced.

[0031] In operation S130, the method may include configuring an EUV illumination mode based on a pupil diagram. For example, after calculating the pupil diagram, the EUV illumination mode may be configured by selecting a mirror in at least a portion of a first region of the pupil diagram that satisfies a condition. The condition may be one or more predetermined conditions. Here, the mirror may refer to a pupil plane mirror (PFM). In the first region of the pupil diagram, a maximum overlap region where a maximum number of light beams in the pupil diagram overlap through the mirror may be defined as a corresponding maximum overlap region, which is equal to or greater than an area where an illumination efficiency of 1 is achieved. The area where an illumination efficiency of 1 is achieved may be referred to as "an area of illumination efficiency 1". In the example case where the maximum overlap region is less than an area of illumination efficiency 1, the first region of the pupil diagram may include the next maximum overlap region until the maximum overlap region is equal to or greater than an area of illumination efficiency 1. For example, the first region of the pupil diagram may include an area where the next maximum number of light beams overlap, and has an area equal to or greater than an area of illumination efficiency 1. According to an embodiment, illumination efficiency 1 may refer to a state where all point sources are used. Reference will be made below to Figure 2A 、 Figure 2B and Figure 3 The first region of the pupil diagram and the illumination efficiency 1 are described in more detail.

[0032] According to an embodiment, in a method for configuring an EUV source, operation S130 of configuring an EUV illumination pattern may include applying a pole balance perturbation. Here, pole balance perturbation may refer to the process of changing a selected mirror combination without significantly altering the overall EUV illumination pattern. Furthermore, pole balance perturbation may refer to finding a mirror combination that disrupts pole balance. Therefore, in the method for configuring an EUV source according to an embodiment, pole balance perturbation may be used to disrupt pole balance and may also introduce asymmetry in the pupil diagram.

[0033] According to an embodiment, in a method for configuring an EUV source, the perturbation of the pole balance in operation S130 of configuring an EUV illumination pattern can be applied to certain processes in a general source and mask optimization (SMO) tool, or independently applied to EUV illumination pattern optimization, independent of the SMO tool. For reference, to briefly describe an SMO tool, the SMO tool may primarily include pre-processing operations, illumination pattern optimization operations, and post-processing operations. Pre-processing operations may primarily perform processing related to depth of focus. Illumination pattern optimization operations may include a series of processes for optimizing the illumination pattern. Post-processing operations may include, for example, dose optimization and mask optimization.

[0034] According to embodiments, pole-balanced perturbations can be applied to an illumination pattern optimization operation. For example, pole-balanced perturbations can be applied to at least one of the free-form source (FFS) and mask optimization process, the EUV source rendering process, and the separate mirror and mask optimization process included in the illumination pattern optimization operation. The FFS and mask optimization process can correspond to a process for configuring the mask optical proximity correction (OPC) and the shape of the corresponding coarse illumination pattern in response to a target pattern. The EUV source rendering process can correspond to a process for converting illumination pattern intensity information into mirror-related information. In other words, the EUV source rendering process can correspond to a process for determining a mirror combination selected in response to the pupil map. The separate mirror and mask optimization process can correspond to a process for further optimizing the illumination pattern by changing the positions of the selected mirrors. According to embodiments, the application of pole-balanced perturbations can be automated using a SMO tool. For example, pole-balanced perturbations can be automated by parameterizing the pupil map in at least one of the three aforementioned processes and parameterizing the arrangement ratio of the mirrors selected for each pole position.

[0035] In the example case of applying a perturbation of the pole balance to optimize EUV illumination modes independent of the SMO tool, mirrors can be selected within at least a portion of a first region of the pupil diagram, and the arrangement ratio of the selected mirrors can be reflected differently for each pole position. For example, through optical simulation, mirrors can be selected for each pole position so that the aspect ratio of the CD of the after-development inspection (ADI) under each illumination mode is targeted. Furthermore, mirrors can be selected by pole position to improve optical performance, for example, reducing LCDU and / or increasing NILS.

[0036] According to embodiments, applying the pole balance perturbation to the optimization of the EUV illumination pattern independent of the SMO tool can also be automated. For example, this can be automated by parameterizing the pupil diagram and determining the mirror placement ratio selected for each pole position using the parameters. Furthermore, this can be automated by arbitrarily dividing the pupil diagram into regions without regard to the poles of the pupil diagram and determining the mirror placement ratio selected for each region.

[0037] According to an embodiment, a method for configuring an EUV source may include configuring an EUV illumination mode by selecting a mirror in at least a portion of a first region of a pupil diagram that satisfies a specific condition. Furthermore, during the configuration of the EUV illumination mode, optical performance of the EUV illumination mode may be improved prior to an exposure process by applying a perturbation to the extreme point balance. For example, the method for configuring an EUV source according to an embodiment may minimize LCDU, increase NILS, and reduce dose by perturbation to the extreme point balance. As described above, in the first region of the pupil diagram, a maximum overlap region where the maximum number of beams overlap due to the mirror is defined as a corresponding maximum overlap region equal to or greater than an area of illumination efficiency 1. In the example case where the maximum overlap region is less than an area of illumination efficiency 1, the first region of the pupil diagram may include the next maximum overlap region, until the maximum overlap region equals or exceeds an area of illumination efficiency 1. For example, the first region of the pupil diagram may include a region where the next maximum number of beams overlap, and have an area equal to or greater than an area of illumination efficiency 1.

[0038] With respect to EUV mapping, the EUV light from the EUV source focused within the first optical system before the EUV light is focused on the EUV mask is referred to as intermediate focused light. According to embodiments, the first optical system may cause the intermediate focused light to be incident on the EUV mask. The intermediate focused light transmitted through the first optical system may correspond to a field facet mirror (FFM) and a PFM. For example, the FFM may represent the form of the electromagnetic field of the EUV light transmitted through the first optical system, and the PFM may represent the form of the electromagnetic field of the EUV light on the pupil surface of the EUV mask. Typically, in EUV facilities, there may be restrictions when selecting an optical path from M (a positive integer) FFMs to N (an integer greater than M) PFMs. According to embodiments, such restrictions may correspond to EUV mapping when selecting an optical path from the FFM to the PFM.

[0039] At the same time, countless PFM combinations are possible through EUV mapping. According to embodiments, EUV mapping can be performed so that one FFM selects one of a limited number of PFMs. Therefore, the PFM combinations can be configured in a two-dimensional matrix form. In other words, one of a limited number of PFMs can be selected to correspond to each of the FFMs.

[0040] Figure 2A and Figure 2B yes Figure 1 A conceptual diagram of an object spectrum diagram in a method of configuring an EUV source. Figure 2A shows a spectrum of an object with a crosspole illumination pattern, and Figure 2BThe spectrum of an object with Y-dipole illumination mode is shown. Figure 1 Description given.

[0041] refer to Figure 2A and Figure 2B , an object spectrum map can be generated to correspond to the layout of the mask pattern. The object spectrum map can be generated in an automated manner to a certain extent. In other words, in the example case of inputting the layout of the mask pattern, the shape of the layout can be parameterized, and the object spectrum map can be automatically generated by the map generation tool based on the parameters. Figure 2A and Figure 2B In the figure, the relatively large light gray points (D1-D5) within the circle and the dark gray points (OD) outside the circle may correspond to the poles of the object spectrum diagram. Specifically, point D1 in the exact center of the circle may be the pole caused by the 0th order diffraction light, while the four outermost points (D2-D5) in the diagonal direction within the circle and the dark gray points (OD) outside the circle may be the poles caused by the 1st order diffraction light. According to an embodiment, the small circle within the circle may correspond to the selected mirror Mr corresponding to the EUV point source. According to an embodiment, in Figure 2A and Figure 2B The intensity of the pole due to the 0th order diffracted light in the center is shown together with the intensity of the pole due to the 1st order diffracted light outside the circle in the x and y directions. Figure 2A and Figure 2B It can be seen that the intensities of the other poles are similar, but Figure 2B In the figure, the intensities of the two extreme points outside the circle in the y direction appear relatively large.

[0042] exist Figure 2A In the object spectrum diagram, the mirrors can be densely arranged in the upper, lower, left and right parts of the circle. Figure 2A The EUV illumination mode shown together in FIG may correspond to a cross-pole illumination mode. For reference, according to an embodiment, a cross-pole may also be referred to as a 4-pole pole. In contrast, in Figure 2B In the object spectrum diagram, the mirrors can be densely arranged in the upper and lower parts of the circle. Figure 2B The EUV illumination pattern shown may correspond to a Y-dipole illumination pattern.

[0043] According to an embodiment, Figure 2A and Figure 2B The upper left pattern (MP) of may correspond to the layout of the mask pattern corresponding to the cross-polar illumination mode and the Y-dipole illumination mode, respectively. Figure 2A The layout of the mask pattern in Figure 2BThe layout of the mask pattern in the x-direction can have a relatively large major axis. Therefore, for a target pattern with a large major axis in the x-direction, the EUV illumination pattern can be optimized by configuring a Y-dipole illumination pattern instead of a cross-pole illumination pattern.

[0044] Figure 3 is with Figure 1 A conceptual diagram of a pupil diagram related to a method of configuring an EUV source is shown. Figures 1 to 2B Description given.

[0045] refer to Figure 3 As described above, a pupil map can be generated by convolving the 2D FFT of the mask pattern with the pupil. Because the pupil map corresponds to overlapping diffracted light, it can also be called an overlapping diffraction order map. Furthermore, because the pupil map corresponds to interference in the object spectrum, it can also be called an object spectral interferogram.

[0046] The pupil map can be used to define the first region described below. Furthermore, the pupil map can be used to generate a top-hat. For example, a top-hat can be generated to exclude unnecessary EUV point sources in the EUV illumination pattern. Before calculating the aerial image of all EUV point sources, the top-hat operation can be used to exclude unnecessary EUV point sources in the EUV illumination pattern, significantly reducing the time required to calculate the aerial image of the EUV point sources.

[0047] In the following, refer to Figure 2A and Figure 2B The first region of the pupil diagram is described. Figure 3 In the pupil diagram of , the light gray portion in the center corresponds to the pole based on 5-beam imaging, and ①, ②, ③, and ④ on the top, bottom, left, and right sides may correspond to the poles based on 4-beam imaging. Here, 5-beam imaging may refer to imaging using 5 spectra within the pupil, and 4-beam imaging may refer to imaging using 4 spectra.

[0048] Specifically, the central pole is imaged using the 0th-order diffracted light arranged in the center and four 1st-order diffracted lights arranged along two diagonal directions. According to the embodiment, ①, ②, ③, and ④ are each imaged using the central 0th-order diffracted light and the three 1st-order diffracted lights surrounding it. For example, the pole of ① is imaged using the central 0th-order diffracted light and the 1st-order diffracted lights in the north, northwest, and northeast directions.

[0049] In the first region of the pupil diagram, the maximum overlap region in which the maximum number of light beams overlap through the mirrors in the pupil diagram is defined as the corresponding maximum overlap region having an area equal to or greater than the area of the illumination efficiency 1. In the example case where the maximum overlap region is smaller than the area of the illumination efficiency 1, the first region of the pupil diagram may include the next maximum overlap region until the maximum overlap region is equal to or greater than the area of the illumination efficiency 1. For example, the first region of the pupil diagram may include the region in which the next maximum number of light beams overlap, and has an area equal to or greater than the area of the illumination efficiency 1. Here, as described above, the illumination efficiency 1 may refer to a state in which all point sources are used, that is, a state in which all mirrors corresponding to all point sources are selected. In addition, the area of the illumination efficiency 1 may correspond to, for example, Figure 2A The area occupied by the selected mirror (i.e., the small circle) in . Figure 3 In , the central 5-beam imaging pole region may be smaller than the area of illumination efficiency 1, and therefore, the 4-beam imaging region, i.e., the ①, ②, ③, ④ pole regions, must be included to be larger than the area of illumination efficiency 1. Therefore, in Figure 3 In the pupil diagram of , the first region of the pupil diagram may correspond to a region occupied by the central 5-beam imaging pole region and all 4-beam imaging poles ①, ②, ③, and ④.

[0050] In the example case of implementing an EUV illumination mode by uniformly selecting mirrors throughout the first region based on the first region of the pupil diagram, the pole balance of the cross-pole form and the symmetry of the pupil diagram can be maintained. However, the EUV illumination mode that maintains the pole balance of the cross-pole form and the symmetry of the pupil diagram may have poor optical performance.

[0051] Therefore, in the method for configuring an EUV source according to an embodiment, when configuring an EUV illumination pattern, not only is a cross-pole EUV illumination pattern achieved by uniformly selecting mirrors across the pole regions ①, ②, ③, and ④, but also a dipole-like EUV illumination pattern achieved by selecting mirrors in the pole regions of ① and ② or in the pole regions of ③ and ④, thereby improving optical performance. For reference, achieving an EUV illumination pattern by selecting mirrors in only a portion of the first region may result in a perturbation of the pole balance. This perturbation of the pole balance may cause the pole balance to be disrupted and also introduce asymmetry into the pupil diagram.

[0052] Figures 4A to 4E It is through Figure 1 A conceptual diagram of various EUV illumination modes configured by applying extreme point balance perturbation in the method of configuring EUV source, and the layout of mask patterns corresponding to various EUV illumination modes. Briefly give or omit the above referenced Figures 1 to 3 Description given.

[0053] refer to Figure 4A , shows that by selecting Figure 3 The EUV illumination mode is configured with most of the mirrors in the extreme areas ③ and ④ of the pupil diagram. Therefore, Figure 2A The EUV illumination mode can correspond to an X-dipole or X-dipole-like illumination mode. As can be seen from the layout of the mask pattern on the right, the X-dipole illumination mode corresponds to an almost circular mask pattern. Figure 4B , by selecting Figure 3 The EUV illumination mode is configured by selecting mirrors in the extreme regions ①, ②, ③ and ④ in the pupil diagram of FIG. , that is, by selecting a relatively large number of mirrors in the extreme regions ③ and ④, and selecting a smaller number of mirrors in the extreme regions ① and ②. Figure 4B The EUV illumination mode may correspond to a cross-pole illumination mode in which the x-axis pole is enhanced (hereinafter referred to as "X-axis enhanced cross-pole illumination mode"). As can be seen from the layout of the mask pattern on the right, the X-axis enhanced cross-pole illumination mode may correspond to an elliptical mask pattern. Figure 4C , by selecting Figure 3 The EUV illumination pattern is configured by selecting mirrors uniformly over the entire pole regions ①, ②, ③ and ④ in the pupil diagram of FIG. Figure 4C The EUV illumination mode can correspond to the pole-balanced cross-pole illumination mode. As can be seen from the layout of the mask pattern on the right, the pole-balanced cross-pole illumination mode can also correspond to the elliptical mask pattern. Figure 4D , by selecting Figure 3 The EUV illumination system is configured by selecting mirrors in the extreme regions ①, ②, ③ and ④ in the pupil diagram of FIG, i.e., by selecting a relatively larger number of mirrors in the extreme regions ① and ② and a smaller number of mirrors in the extreme regions ③ and ④. Figure 4D The EUV illumination mode may correspond to a cross-pole illumination mode in which the y-axis pole is enhanced (hereinafter referred to as "Y-axis enhanced cross-pole illumination mode"). As can be seen from the layout of the mask pattern on the right, the Y-axis enhanced cross-pole illumination mode may correspond to an elliptical mask pattern. Figure 4E , by selecting Figure 3 The EUV illumination mode is configured by using most of the mirrors in the extreme regions ① and ② in the pupil diagram. Figure 4E The EUV illumination pattern can correspond to a Y-dipole or Y-dipole-like illumination pattern. From the layout of the mask pattern on the right, it can be seen that the Y-dipole illumination pattern can correspond to an elliptical mask pattern. Based on the NILS value, it can be predicted that Figure 4E The Y-dipole illumination mode corresponds to the optimal EUV illumination mode. For example, in the case of the Y-dipole illumination mode, NILS can be increased by 7% or more compared to the cross-pole illumination mode.

[0054] Figure 5A is a conceptual diagram of a scanning electron microscope (SEM) image of a cross-pole illumination mode and a target pattern according to a comparative example, and Figure 5B is a conceptual diagram of a scanning electron microscope (SEM) image of a Y-dipole illumination pattern and a target pattern based on a method of configuring an EUV source according to an embodiment.

[0055] refer to Figure 5A and Figure 5B , when compared Figure 5A Comparison example of the cross-pole lighting mode and Figure 5B When using the Y-dipole illumination mode according to the embodiment, the LCDU can be improved by 9% and the effective dose can be increased by 25%. In addition, the SEM image on the right shows that the uniformity of the pattern is improved.

[0056] Figures 6A to 6C is shown with Figure 1 A conceptual diagram of the mask pattern layout, aerial image, and NILS concepts related to the method of configuring an EUV source.

[0057] Figure 6A The cutting lines of the major and minor axes defined on the layout of the mask pattern are shown to calculate the aerial image. Figure 6A , the dotted square on the layout of the mask pattern is a simulation box, the solid line of the major axis in the solid line in the cross inside the square corresponds to the x-axis cutting line, and the solid line of the minor axis corresponds to the y-axis cutting line. Figure 6B The intensity of an EUV point source on the x-axis (graph G1) and y-axis (graph G2) is shown. Figure 6B In the two diagrams G1 and G2 in FIG, the horizontal axis is the position on the x-axis and y-axis, and the unit is arbitrary units, and the vertical axis is the intensity, and the unit is also arbitrary units. In this way, an aerial image can be calculated for each point source.

[0058] Generally, a target CD can be calculated by CD targeting. CD targeting may refer to setting a level of a threshold intensity TH for an aerial image so that a pattern with a desired CD value can be patterned. According to an embodiment, in CD targeting, the CD of the aerial image has an offset relative to the actual patterned ADI CD, but the offset value is constant within a given CD range, and therefore, the target CD value can be determined by taking this into consideration. Figure 6C In FIG, the target CD calculated by CD positioning on the x-axis is indicated by a double arrow. That is, the target CD can be calculated by setting the threshold intensity TH on the x-axis.

[0059] NILS can be defined on the x-axis as CDx*{dln(I) / dx}, or (CDx / I)*(dI / dx). That is, NILS can be defined by the CD value CDx, the intensity value I at the point in the spatial image that defines the CD value, and the differential value (dI / dx) of the intensity at the point that defines the CD value. NILS can be defined on the y-axis using the same concept. Figure 6C In the figure, the differential value of intensity, i.e., the slope of intensity, is shown as a dotted line at the point where the CD value is defined. As mentioned above, NILS is an optical performance characteristic in which the CD value changes less with process variations such as dose and focus as the NILS value increases. Therefore, as the NILS value increases, it can be determined that the performance of the EUV illumination mode or EUV source is more optimized.

[0060] Figure 7 1 is a flow chart schematically illustrating an EUV exposure method (hereinafter referred to as “EUV exposure method”) using an EUV source according to an embodiment. Figures 1 to 6C Description given.

[0061] refer to Figure 7 In operation S210, an EUV exposure method according to an embodiment may include receiving a layout of a target pattern. Here, the target pattern may refer to a pattern to be formed on a silicon (Si) substrate (e.g., a wafer). For example, the pattern on a mask may be transferred to a substrate through an exposure process to form the target pattern on the substrate. According to embodiments, the pattern on the mask is typically reduced in size and projected onto the wafer, and the pattern on the mask may be larger than the target pattern on the substrate.

[0062] In operation S230, the EUV exposure method may include configuring an EUV mask and an EUV source based on a target pattern. For example, after receiving a layout of the target pattern, the EUV mask and EUV source may be configured corresponding to the target pattern. Configuring the EUV mask may include an OPC process and an EUV mask manufacturing process. According to embodiments, when configuring the EUV mask, the OPC process may be performed in conjunction with configuring the EUV source.

[0063] According to an embodiment, configuring the EUV source may include Figure 1 The method of configuring EUV source in Figure 1 Various operations described in the description of the method for configuring an EUV source in the EUV exposure method can achieve an optimal EUV source. According to an embodiment, in the EUV exposure method, configuring the EUV source may include configuring the entire EUV optical system.

[0064] After configuring an EUV mask and an EUV source, EUV exposure is performed on the wafer using the EUV source and EUV mask ( S250 ). EUV exposure may involve projecting EUV light onto an EUV photoresist (PR) layer on the wafer using the EUV source and EUV mask. In some embodiments, the EUV exposure may include a development process for the PR layer. This development process may form a PR pattern.

[0065] The EUV exposure method according to the embodiment includes, in the operation (S230) of configuring an EUV mask and an EUV source, Figure 1 The present invention provides a method for configuring an EUV source, thereby realizing an EUV source with optimized optical performance. Furthermore, an optimal EUV exposure can be performed based on the optimized EUV source. As a result, a PR pattern that optimally meets the required patterning performance indicators can be formed on the wafer.

[0066] While the present disclosure has been particularly shown and described with reference to embodiments thereof, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope of the appended claims.

Claims

1. A method for configuring an extreme ultraviolet (EUV) source, the method comprising: generating an object spectrum map for the layout of the mask pattern; generating a pupil map corresponding to the object spectral map; as well as To configure EUV illumination mode, do the following: selecting a plurality of mirrors in a first region of the pupil map based on a first condition being satisfied, and A pole-balancing perturbation is applied to the plurality of mirrors.

2. The method according to claim 1, wherein In the first region, a maximum overlap region in the pupil diagram where a maximum number of light beams overlap by the plurality of mirrors is defined as a corresponding maximum overlap region, the corresponding maximum overlap region being equal to or greater than an area where an illumination efficiency of 1 is obtained, where an illumination efficiency of 1 refers to a state where all field facet mirrors corresponding to an EUV point source are selected, and Based on the maximum overlapping area being smaller than the area where the lighting efficiency is 1, the first area includes a next maximum overlapping area, in which the next maximum number of light beams overlap, and the area of the next maximum overlapping area is equal to or larger than the area where the lighting efficiency is 1.

3. The method according to claim 2, wherein: Configuring the EUV illumination mode includes arranging the plurality of mirrors in a manner such that the extreme balance is disrupted.

4. The method according to claim 2, wherein: Configuring the EUV illumination pattern includes arranging the mirrors to form a dipole-like illumination pattern.

5. The method according to claim 2, further comprising: A tool for optimizing the EUV source is used, applying a mask, to search for a combination of the plurality of mirrors in which the extreme balance is destroyed.

6. The method according to claim 5, wherein: searching for the combination of the plurality of mirrors in at least one of a free form source FFS and mask optimization process, an EUV source rendering process, or a separate mirror and mask optimization process included in the tool, and In the combination of the plurality of mirrors, an arrangement ratio of the plurality of mirrors selected for each pole position is determined by a parameter.

7. The method according to claim 2, further comprising: searching for a combination of the plurality of mirrors in which the pole balance is destroyed, Among them, in the combination of the plurality of mirrors, the arrangement ratio of the plurality of mirrors selected for each pole position is determined by parameters.

8. The method according to claim 2, wherein: Based on the pupil diagram being circular, the 0th-order diffraction light is located at the center of the circle, and a plurality of 1st-order diffraction lights are located inside or outside the circle, The first area is defined by the 0th order diffraction light and the plurality of 1st order diffraction lights within the circle, and When configuring the EUV illumination mode, the plurality of mirrors are selected to reflect an extreme point ratio in the first region.

9. The method according to claim 2, wherein: The plurality of mirrors are selected so that an aspect ratio of a critical dimension CD of a post-development inspection ADI corresponding to the mask pattern becomes a target.

10. The method according to claim 2, wherein: The plurality of mirrors is selected to increase the normalized image log slope NILS.

11. A method for configuring an extreme ultraviolet (EUV) source, the method comprising: generating an object spectrum map for the layout of the mask pattern; generating a pupil map corresponding to the object spectral map; as well as To configure EUV illumination mode, do the following: A plurality of mirrors are selected in at least a portion of a first region and a pole-balancing perturbation is applied to introduce asymmetry in the pupil diagram, wherein the first region is greater than or equal to an area where an illumination efficiency is 1 and the first region includes a maximum overlap region where a maximum number of beams overlap in the pupil diagram, or a sum of the maximum overlap region and a next maximum overlap region where a next maximum number of beams overlap.

12. The method according to claim 11, wherein Configuring the EUV illumination pattern includes arranging the plurality of mirrors to form a dipole-like illumination pattern.

13. The method according to claim 11, further comprising: applying a mask to search for a combination of the plurality of mirrors for which the pole balance is destroyed, wherein the EUV mask is applied using a tool optimized for the mask or independently of the tool, and Among them, in the combination of the plurality of mirrors, the arrangement ratio of the plurality of mirrors selected for each pole position is determined by parameters.

14. The method according to claim 11, wherein Based on the pupil diagram being circular, the 0th-order diffraction light is located at the center of the circle, and a plurality of 1st-order diffraction lights are located inside or outside the circle, The first area is defined by the 0th order diffraction light and the plurality of 1st order diffraction lights within the circle, and In configuring the EUV illumination mode, the plurality of mirrors are selected to reflect various extreme point ratios in the first region.

15. The method according to claim 11, wherein The plurality of mirrors are selected so that an aspect ratio of a critical dimension CD of a post-development inspection ADI corresponding to the mask pattern is targeted and a normalized image logarithmic slope NILS increases.

16. An extreme ultraviolet (EUV) exposure method, comprising: Obtaining a target pattern; configuring an EUV source and an EUV mask corresponding to the target pattern; as well as performing EUV exposure on a wafer using the EUV source and the EUV mask, Wherein, configuring the EUV source includes: generating an object spectrum map for a layout of a mask pattern on the EUV mask; generating a pupil map corresponding to the subject spectral map; and To configure EUV illumination mode, do the following: selecting a plurality of mirrors in at least a portion of the first region and applying a pole-balancing perturbation to introduce an asymmetry in the pupil diagram, The first area is greater than or equal to an area with an illumination efficiency of 1, and includes a maximum overlapping area where a maximum number of light beams overlap in the pupil diagram, or a sum of the maximum overlapping area and a next maximum overlapping area where a next maximum number of light beams overlap.

17. The method according to claim 16, wherein: Configuring the EUV illumination pattern includes arranging the plurality of mirrors to form a dipole-like illumination pattern.

18. The method according to claim 16, further comprising: applying a mask to search for a combination of the plurality of mirrors for which the pole balance is destroyed, wherein the EUV mask is applied using a tool optimized for the mask or independently of the tool, and Among them, in the combination of the plurality of mirrors, the arrangement ratio of the plurality of mirrors selected for each pole position is determined by parameters.

19. The method according to claim 16, wherein Based on the pupil diagram being circular, the 0th-order diffraction light is located at the center of the circle, and a plurality of 1st-order diffraction lights are located inside or outside the circle, The first area is defined by the 0th order diffraction light and the plurality of 1st order diffraction lights within the circle, and In configuring the EUV illumination mode, the plurality of mirrors are selected to reflect various extreme point ratios in the first region.

20. The method according to claim 16, wherein The plurality of mirrors are selected so that an aspect ratio of a critical dimension CD of a post-development inspection ADI corresponding to the mask pattern is determined and a normalized image logarithmic slope NILS increases.

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