Deep ultraviolet objectives and optical systems

Abstract

The embodiment of the present application provides a deep ultraviolet objective and an optical system. The deep ultraviolet objective comprises a front group lens and a rear group lens; the front group lens is arranged close to an object plane, and the front group lens has a positive refractive power; and the rear group lens has a negative refractive power. The front group lens comprises a refractive lens and at least one diffractive optical element, so as to eliminate chromatic aberration.

Description

Technical Field

[0001] This application relates to the field of optical technology, specifically to a deep ultraviolet objective lens and optical system. Background Technology

[0002] In the field of deep ultraviolet (DUV) objectives, the dispersion curves of commonly used materials change at a faster rate than in the visible light domain. For example, with fused silica, a 1 nm change in wavelength corresponds to a 0.0016 nm change in refractive index, which is equivalent to a 38 nm change in wavelength near 532 nm, resulting in significant chromatic aberration. This chromatic aberration affects the imaging quality of DUV objectives. Summary of the Invention

[0003] The purpose of this application is to provide a deep ultraviolet objective lens and optical system that can reduce chromatic aberration to improve image quality.

[0004] To achieve the objectives of this application, the following technical solution is provided:

[0005] In a first aspect, one embodiment of this application provides a deep ultraviolet objective lens, which includes a front lens group and a rear lens group. The front lens group has positive refractive power; the rear lens group has negative refractive power. The front lens group includes a refractive lens and at least one diffractive optical element.

[0006] The deep ultraviolet objective lens provided in this application achieves achromaticity due to the complementarity between the diffractive optical elements and other refractive lenses in the deep ultraviolet objective lens, which is beneficial to improving the imaging quality and resolution of the deep ultraviolet objective lens.

[0007] According to the first aspect, in some possible implementations of this application, the diffractive optical element includes a first surface and a second surface disposed opposite to each other in the optical axis direction of the deep ultraviolet objective, the first surface being disposed away from the rear lens group, at least one of the first surface and the second surface being a diffraction surface, the diffraction surface forming a plurality of diffraction bands, the surface of the diffraction bands including at least four steps.

[0008] Diffractive optical elements can be stepped diffractive optical elements. The diffraction band includes at least four steps. The more steps there are, the better the diffraction efficiency of the diffractive optical element can be improved, the less light energy loss can be reduced, and the higher the energy utilization rate can be increased.

[0009] The diffractive optical element includes a first surface and a second surface disposed opposite to each other in the optical axis direction of the deep ultraviolet objective lens. The first surface is disposed away from the rear lens group. At least one of the first surface and the second surface is a diffraction surface. The diffraction surface includes a blazed grating surface and forms a plurality of diffraction bands. The surface of the diffraction bands in the optical axis direction is a continuous surface.

[0010] The diffraction surface includes the blazed grating surface. Because diffractive optical elements are continuous, the diffraction band is a continuous surface, facilitating fabrication.

[0011] According to the first aspect, in some possible implementations of this application, the diffraction surface is a harmonic diffraction surface, and the harmonic diffraction order of the harmonic diffraction surface is at least 2.

[0012] In this possible implementation, the etching depth of the microstructure on the surface of a common diffraction element is increased, and its phase modulation function is changed so that the phase difference between adjacent rings is equal to an integer multiple of 2π.

[0013] According to the first aspect, in some possible implementations of this application, in the optical axis direction, the largest diameter refractive lens in the front group lens is disposed on the side of the front group lens closest to the rear group lens, and at least one of the diffractive optical elements is provided on at least one of the sides of the largest diameter refractive lens in the front group lens facing away from the rear group lens.

[0014] In this possible implementation, placing the diffractive optical element on the side of the seventh lens with the largest optical path aperture in the front lens group helps to reduce the incident angle of light to the diffractive optical element, thereby improving the diffraction efficiency of the diffractive optical element.

[0015] According to the first aspect, in some possible implementations of this application, the rear lens group includes at least one refractive lens and an aperture stop, the aperture stop and the refractive lens of the rear lens group being arranged along the optical axis of the deep ultraviolet objective.

[0016] In this possible implementation, the aperture is used to define the size of the light beam.

[0017] According to the first aspect, in some possible implementations of this application, at least one refractive lens of the rear lens group includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens. Along the optical axis of the deep ultraviolet objective, the second lens is located between the first lens and the third lens, the third lens is located between the second lens and the fourth lens, the fourth lens is located between the third lens and the aperture stop, the aperture stop is located between the fourth lens and the fifth lens, and the fifth lens is located between the fourth lens and the sixth lens.

[0018] According to the first aspect, in some possible implementations of this application, the first lens, the fourth lens, and the sixth lens are positive lenses, and the second lens and the third lens are negative lenses.

[0019] According to the first aspect, in some possible implementations of this application, the refractive lens of the rear lens group is a spherical lens. Since spherical lenses have a uniform shape and a relatively simple manufacturing process, their production cost is low.

[0020] According to the first aspect, in some possible implementations of this application, the refractive lens in the front lens group is a positive spherical lens.

[0021] According to the first aspect, in some possible implementations of this application, the refractive lenses in the front lens group include a seventh lens, an eighth lens, a ninth lens, and a tenth lens. Along the optical axis of the deep ultraviolet objective, the seventh lens is disposed on the side of the front lens group closest to the rear lens group; the eighth lens is located between the seventh lens and the ninth lens; the ninth lens is located between the eighth lens and the tenth lens; and at least one of the seventh lens facing the rear lens group and the lens between the seventh lens and the eighth lens is provided with the diffractive optical element.

[0022] According to the first aspect, in some possible implementations of this application, the diffractive optical element is provided between the seventh lens and the eighth lens, and the surface parameters of the deep ultraviolet objective are as follows:

[0023]

[0024] In this possible implementation, at least one of the diffractive optical elements is provided on the side of the seventh lens facing the rear lens group, and the above-described surface design is used to improve imaging quality while reducing energy loss.

[0025] According to the first aspect, in some possible implementations of this application, at least one diffractive optical element is provided on the side of the seventh lens facing the rear lens group and between the seventh lens and the eighth lens, and the surface parameters of the deep ultraviolet objective are as follows:

[0026]

[0027] In this possible implementation, at least one diffractive optical element is provided on the side of the seventh lens facing the rear lens group and between the seventh lens and the eighth lens. Through the above-described surface design, the image quality is improved while the energy loss is reduced.

[0028] According to the first aspect, in some possible implementations of this application, the material of the diffractive optical element is fused silica.

[0029] According to the first aspect, in some possible implementations of this application, the numerical aperture NA of the deep ultraviolet objective is... 0.88.

[0030] In this possible implementation, the larger the numerical aperture NA of the deep ultraviolet objective, the better its optical resolution k*λ / NA.

[0031] According to the first aspect, in some possible implementations of this application, the working distance of the deep ultraviolet objective is... 7.8mm.

[0032] In this possible implementation, when the sample is a photomask, the distance between the photomask and the maskpellicle is typically approximately 7.5 mm. Working distance of deep ultraviolet objectives. 7.8mm means that the working distance of the deep ultraviolet objective is greater than the distance between the photomask and the photomask protective film. Due to the high optical resolution of the deep ultraviolet objective, it is suitable for inspecting photomasks.

[0033] According to the first aspect, in some possible implementations of this application, the operating bandwidth of the deep ultraviolet objective is... 10 pm.

[0034] According to the first aspect, in some possible implementations of this application, the wavefront aberration of the deep ultraviolet objective... 0.02λ, where λ is the working wavelength of the deep ultraviolet objective, is beneficial to improving the imaging quality and imaging effect of the deep ultraviolet objective.

[0035] According to the first aspect, in some possible implementations of this application, the operating wavelength range of the deep ultraviolet objective is [193.358nm, 193.378nm].

[0036] In a second aspect, this application provides an optical system comprising a housing and a deep ultraviolet objective lens, wherein the deep ultraviolet objective lens is the deep ultraviolet objective lens provided in the first aspect, and the deep ultraviolet objective lens is mounted on the housing. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of an optical system provided in one embodiment of this application;

[0038] Figure 2 This is a schematic diagram of the structure of the deep ultraviolet objective lens provided in the first embodiment of this application;

[0039] Figure 3 This is a three-dimensional schematic diagram of a diffractive optical element provided in one embodiment of this application;

[0040] Figure 4 yes Figure 3 A cross-sectional schematic diagram of a portion of the structure of the diffractive optical element shown;

[0041] Figure 5 This is a schematic diagram of a step diffraction optical element provided in one embodiment of this application;

[0042] Figure 6 and Figure 7 This is a schematic diagram of the imaging optics simulation of the deep ultraviolet objective lens provided in the first embodiment within a working temperature range of approximately 23°C.

[0043] Figure 8 This is a schematic diagram of the structure of the deep ultraviolet objective lens provided in the second embodiment of this application;

[0044] Figure 9 and Figure 10 This is a schematic diagram of the imaging optics simulation of the deep ultraviolet objective lens provided in the second embodiment, operating at a temperature range of approximately 23°C.

[0045] Explanation of reference numerals in the attached figures:

[0046] 100. Optical System; 10. Housing; 20. Imaging Module; 30. Deep Ultraviolet Objective; 31. Rear Lens Group; L1. First Lens; L2. Second Lens; L3. Third Lens; L4. Fourth Lens; L5. Fifth Lens; L6. Sixth Lens; 401. Aperture Stop; 33. Front Lens Group; L7. Seventh Lens; L8. Eighth Lens; L9. Ninth Lens; L10. Tenth Lens; 201. Diffractive Optical Element; 301. Diffraction Band; 3011. Step; 2011. First Diffractive Optical Element; 2012. Second Diffractive Optical Element; S0-S28. Surface; 40. Optical Path Switching Module; 60. Illumination Module. Detailed Implementation

[0047] Defects in the semiconductor integrated circuit manufacturing process have an increasingly significant impact on the performance and yield of integrated circuits. Effective defect control is crucial for ensuring yield and performance within the semiconductor integrated circuit process flow. Optical imaging inspection is the primary and fastest method for defect detection. Semiconductor inspection equipment typically uses objective lenses to detect defects in integrated circuits. Semiconductor inspection equipment can also inspect masks and other materials.

[0048] In the field of deep ultraviolet objectives, the dispersion curves of commonly used materials change at a faster rate than in the visible light field. Taking fused silica as an example, a 1nm change in wavelength near 193nm corresponds to a 0.0016 change in refractive index, which is equivalent to a 38nm change in wavelength near 532nm, resulting in significant chromatic aberration. Chromatic aberration affects the resolution of the objective lens.

[0049] In addition, in the deep ultraviolet field, the bandwidth of the light source is generally around 8 to 20 pm. The additional bandwidth narrowing process will cause a decrease in power and an increase in coherence. Therefore, in the field of objectives, achieving achromaticity is of great significance to improving the resolution of objectives.

[0050] Based on this, this application provides a deep ultraviolet objective lens and its related optical system to reduce chromatic aberration and improve image quality. The deep ultraviolet objective lens includes a front lens group and a rear lens group. The front lens group has positive refractive power; the rear lens group has negative refractive power. The front lens group includes at least one diffractive optical element (DOE).

[0051] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of an optical system 100 provided in one embodiment of this application. The optical system 100 can be used to detect defects in a sample. The sample can be a wafer or a photomask, etc., and this application does not limit the type of sample.

[0052] The optical system 100 includes a housing 10, an imaging module 20, a deep ultraviolet objective lens 30, an optical path switching module 40, and an illumination module 60. The housing 10 can be a sealed structure, enclosing and forming an inner cavity. The illumination module 60, imaging module 20, optical path switching module 40, and objective lens 30 are all housed within this inner cavity. The deep ultraviolet objective lens 30 can be mounted on and pass through the housing 10. The illumination module 60 emits an illumination beam. The optical path switching module 40 switches the illumination beam to the deep ultraviolet objective lens 30 and illuminates the imaging module 20 with an imaging beam, which is formed by the illumination beam passing through the deep ultraviolet objective lens 30 and being reflected by the sample. The imaging module 20 may include an image sensor. The imaging module 20 performs microscopic imaging based on the imaging beam.

[0053] The optical system 100 can also be a semiconductor detection device or a microscope, etc.

[0054] It is understood that this application does not limit the specific architecture of the optical system 100. For example, the optical system 100 may omit the imaging module 20, the optical path switching module 40, and the illumination module 60; or, the optical system 100 may include an eyepiece and a deep ultraviolet objective lens 30, wherein the eyepiece is used to form an upright, magnified virtual image from the inverted real image formed by the deep ultraviolet objective lens 30.

[0055] Please see Figure 2 The first embodiment of this application provides a deep ultraviolet objective lens 30, which includes a front lens group 33 and a rear lens group 31. This deep ultraviolet objective lens 30 can be used for... Figure 1 In the optical system 100 shown.

[0056] In this embodiment, the front lens group 33 is positioned close to the object surface (object plane) S26, and the light beam is incident from the surface S0 side, i.e., surface S0 can be considered as the incident surface, and surface S25 can be considered as the exit surface of the deep ultraviolet objective lens 30. The distance between surface S25 and object plane S26 can be the working distance (WD) of the deep ultraviolet objective lens 30. In other embodiments, the rear lens group 31 can also be positioned close to the object plane S26. The front lens group 33 has positive refractive power. The rear lens group 31 has negative refractive power. The rear lens group 31 includes a refractive lens. The front lens group 33 includes a refractive lens and at least one diffractive optical element 201. The refractive lens and diffractive optical element 201 of the front lens group 33 are arranged along the optical axis of the deep ultraviolet objective lens 30.

[0057] Please refer to the color difference elimination formula (1):

[0058] (1)

[0059] in, It is the 30th deep ultraviolet objective lens. i Focal power of each element It is the 30th deep ultraviolet objective lens. i Abbe number of each component.

[0060] According to formula (1), to achieve achromatic optical system 100, i.e., to achieve dispersion-free optical system 100, the diffractive optical element 201 needs to be complementary to the other refractive lenses in the deep ultraviolet objective lens 30. The dispersion of the diffractive optical element 201 is independent of the material of the diffractive optical element 201, and is related to the wavelength. The Abbe number of the diffractive optical element 201 is negative, i.e., the Abbe number of the diffractive optical element 201 is opposite to that of the refractive lens, thus achieving complementarity between the diffractive optical element and the refractive lens.

[0061] The deep ultraviolet objective lens 30 provided in this application is a hybrid lens of diffractive optical element 201 and refractive lens. Since the diffractive optical element 201 and other refractive lenses in the deep ultraviolet objective lens 30 complement each other to achieve achromatic aberration, it is beneficial to improve the imaging quality and resolution of the deep ultraviolet objective lens 30.

[0062] In some embodiments of this application, the operating wavelength λ of the deep ultraviolet objective 30 is in the ultraviolet region between 100 nm and 400 nm, that is, the operating wavelength λ range of the deep ultraviolet objective 30 is [100 nm, 400 nm]. For example, the operating wavelength λ range can be [193.358 nm, 193.378 nm]. The numerical aperture (NA) of the deep ultraviolet objective 30 is also specified. 0.88. Working distance of the deep ultraviolet objective lens (30°). 7.8mm. Working bandwidth of the deep ultraviolet objective lens 30. 10pm. Wavelength aberration of deep ultraviolet objective lens 30. 0.02λ. The working distance refers to the distance from the deep ultraviolet objective lens 30 to the surface of the sample to be inspected.

[0063] The optical resolution formula for the deep ultraviolet objective 30 is: k*λ / NA, where k is the process factor, and theoretically, the minimum limit for exposure k is approximately 0.25. A larger numerical aperture NA results in better optical resolution. The numerical aperture NA of the deep ultraviolet objective 30 is... 0.88, so that the deep ultraviolet objective 30 can achieve high optical resolution.

[0064] Wavefront aberration refers to the distortion of the wavefront of light in an optical system. The smaller the wavefront aberration, the higher the image quality. The deep ultraviolet objective 30 provided in this application exhibits wavefront aberration... A value of 0.02λ can improve the imaging effect and quality of the deep ultraviolet objective 30.

[0065] When the sample is a photomask, the distance between the photomask and the photomask pellicle is typically approximately 7.5 mm. The working distance of a deep ultraviolet objective lens 30 is... 7.8 mm, meaning the working distance of the deep ultraviolet objective 30 is greater than the distance between it and the protective film of the photomask. Because the deep ultraviolet objective 30 can eliminate chromatic aberration by incorporating the diffractive optical element 201, it achieves high optical resolution and is suitable for inspecting photomasks.

[0066] It is understood that this application does not limit the numerical aperture range of the deep ultraviolet objective 30, does not limit the working distance range of the deep ultraviolet objective 30, and does not limit the working bandwidth range of the deep ultraviolet objective 30.

[0067] It is understood that the technical solution provided in this application can also be applied to other objectives, such as microscope objectives. This application does not limit the working wavelength of the deep ultraviolet objective. In this embodiment, the diffractive optical element 201 is made of fused silica material, and other refractive lenses in the deep ultraviolet objective 30 can be made of fused silica or calcium fluoride material.

[0068] The diffractive optical element 201 includes a first surface S18 and a second surface S17 disposed opposite to each other along the optical axis of the deep ultraviolet objective lens 30. The first surface S18 is disposed away from the rear lens group 31. The first surface S18 is a diffractive surface.

[0069] In some embodiments of this application, the diffractive optical element 201 can be used as a binary (diffractive) optical element (BINARY2), and the surface shape of the diffraction surface can be called BINARY2. A binary (diffractive) optical element is a multi-order phase structure. The ideal continuous phase profile is approximated in a stepped manner with a quantization multiple of 2, hence the name binary (diffractive) optical element. Binary (diffractive) optical elements are characterized by small size, light weight, ease of array integration, and mass reproduction. For details, please refer to... Figure 3 and Figure 4 The diffraction surface forms multiple diffraction bands 301, and the diffraction optical element 201 can be a stepped diffraction optical element. The diffraction band 301 includes at least four steps 3011. The more steps 3011 there are, the higher the diffraction efficiency of the diffraction optical element 201. For example, the efficiency can reach up to 95% with 8 steps 3011, and up to 99% with 16 steps 3011.

[0070] In some embodiments of this application, the diffraction surface of the diffractive optical element 201 can be a blazed grating surface, the outer surface of the diffraction band 301 is a non-stepped structure, and the outer surface of the diffraction band 301 in the optical axis direction is a continuous surface. In this case, the diffractive optical element 201 can be called a continuous diffractive optical element. A blazed grating, also known as a small echelle grating, is a specific reflective or projective diffraction grating structure that produces maximum diffraction efficiency at a specific diffraction order. This means that the optical power is concentrated as much as possible at the preset diffraction order, while the loss of optical power at other orders (especially the zero order) is minimized. Figure 5 The x-axis represents the radius of the diffractive optical element. Figure 5 The vertical axis represents the phase (0 to 2). ), Figure 5 The radius and phase in the figure are exemplary and do not constitute a limitation on this application.

[0071] The diffraction plane satisfies the phase function represented by the following formula (2):

[0072] , (2)

[0073] in, M These are diffraction orders, typically... 1. Ai is the phase coefficient, and ρ is the normalized radius coefficient, specifically the actual radius of the diffractive optical element 201 / normalized radius. In this embodiment, as shown in Table 1, they represent the coefficient values ​​of the 2nd, 4th, and 6th order terms, respectively.

[0074] Table 1

[0075]

[0076] It is understandable that the second surface S17 can also be set as a diffraction surface.

[0077] In some embodiments of this application, the diffractive optical element 201 may be a harmonic diffractive optical element (HDOE), and at least one of the first surface S18 and the second surface S17 forms a harmonic diffraction surface with a harmonic diffraction order of at least 2.

[0078] Diffractive optical elements can be stepped or continuous surface diffractive optical elements, in order to Figure 4 or Figure 5 The diffractive optical element shown in the example is a typical diffractive optical element. Let the height of the diffraction band of the typical diffractive optical element be... Let the distance between the diffraction band closest to the center of a conventional diffractive optical element and the center be . The diffraction surface of a harmonic diffraction optical element may include a diffraction band, which may include at least four steps. Alternatively, the diffraction surface may be a continuous surface. When the diffraction optical element 201 employs a harmonic diffraction optical element, the height of the diffraction band (diffraction band) of the harmonic diffraction optical element is set to... Let the distance between the annulus closest to the center of the resonant diffraction optical element and the center be . R 01 , = ; R 01 = ， It is a positive integer.

[0079] Harmonic diffraction elements can achieve higher diffraction efficiency than ordinary diffraction optical elements by increasing the etching depth of the microstructure on the surface of ordinary diffraction elements and changing their phase modulation function.

[0080] Please refer to it again. Figure 2The rear lens group 31 includes at least one refractive lens and an aperture stop 401. The aperture stop 401 is used to limit the size of the light beam. In one embodiment, the refractive lens of the rear lens group 31 includes a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, and a sixth lens L6. Along the optical axis of the deep ultraviolet objective lens 30, the first lens L1 is located on the side of the rear lens group 31 furthest from the front lens group 33, and the first lens L1, second lens L2, third lens L3, fourth lens L4, aperture stop 401, fifth lens L5, and sixth lens L6 are arranged sequentially. That is, along the optical axis of the deep ultraviolet objective lens 30, the second lens L2 is located between the first lens L1 and the third lens L3, the third lens L3 is located between the second lens L2 and the fourth lens L4, the fourth lens L4 is located between the third lens L3 and the aperture stop, the aperture stop is located between the fourth lens L4 and the fifth lens L5, and the fifth lens L5 is located between the fourth lens L4 and the sixth lens L6. Lenses L1, L4, and L6 are positive lenses, while L2 and L3 are negative lenses. Lenses L1, L2, L3, L4, L5, and L6 are all spherical lenses. A spherical lens is a lens whose front and back surfaces are both parts of a sphere, and the curvature of the sphere is fixed. Because spherical lenses have a uniform shape, their manufacturing process is relatively simple, resulting in lower production costs.

[0081] It is understood that this application does not limit the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 to spherical lenses, and each of the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, and the sixth lens L6 can be either a spherical lens or an aspherical lens.

[0082] It is understood that this application does not limit the number of refractive lenses in the rear lens group 31. The rear lens group 31 may include at least one refractive lens, and the rear lens group 31 only needs to have negative refractive power.

[0083] In one embodiment, the refractive lenses of the front lens group 33 include a seventh lens L7, an eighth lens L8, a ninth lens L9, and a tenth lens L10. Optionally, along the optical axis of the deep ultraviolet objective lens 30, the seventh lens L7 is disposed on the side of the front lens group 33 closest to the rear lens group 31, and the seventh lens L7, the diffractive optical element 201, the eighth lens L8, the ninth lens L9, and the tenth lens L10 are arranged sequentially. The seventh lens L7, the eighth lens L8, the ninth lens L9, and the tenth lens L10 are all spherical lenses. The seventh lens L7, the eighth lens L8, the ninth lens L9, and the tenth lens L10 are all positive lenses.

[0084] It is understood that this application does not limit the seventh lens L7, the eighth lens L8, the ninth lens L9 and the tenth lens L10 to be spherical lenses, and each of the seventh lens L7, the eighth lens L8, the ninth lens L9 and the tenth lens L10 can be either a spherical lens or an aspherical lens.

[0085] In this embodiment, the seventh lens L7 is the largest diameter refractive lens in the rear lens group 31. Positioning the diffractive optical element 201 on the side of the seventh lens L7, which has the largest optical path aperture in the front lens group 33, helps to reduce the incident angle of the light beam onto the diffractive optical element 201, thereby improving the diffraction efficiency of the diffractive optical element 201. In this embodiment, the diameter of the diffractive optical element 201 is also larger than the diameters of the eighth lens L8, the ninth lens L9, and the tenth lens L10.

[0086] It is understandable that the diffractive optical element 201 can also be set on the side of the seventh lens L7 facing the rear lens group 31.

[0087] It is understood that this application does not limit the height at which the light beam is incident on the diffractive optical element 201.

[0088] It is understood that this application does not limit the specific architecture of the front lens group 33, as long as the front lens group 33 includes at least one diffractive optical element 201.

[0089] It is understood that the number of refractive lenses in the front lens group 33 can be one. In some embodiments, the refractive lens with the largest height in the front lens group 33 is located on the side of the front lens group 33 closest to the rear lens group 31, and the side of the refractive lens with the largest height in the front lens group 33 facing or away from the rear lens group 31 is provided with a diffractive optical element 201.

[0090] In some embodiments of this application, the lens design parameters in the deep ultraviolet objective 30 are shown in Table 2. The material of the diffractive optical element 201 is fused silica, and NIFS-V in Table 2 represents fused silica. STANDARD refers to a standard surface type, which can be a plane or a sphere. Surfaces S0-S26 are the surfaces of various lenses, etc., in the deep ultraviolet objective 30, and S0, S1, S25, and S26 can be virtual surfaces. See Table 2 below for details. In Table 2, along the optical axis of the deep ultraviolet objective 30, the front surface is the surface of the optical element away from the object surface, and the rear surface of the deep ultraviolet objective 30 is the surface of the optical element facing the object surface.

[0091] Table 2

[0092]

[0093] Please see Figure 6 and Figure 7 , Figure 6The horizontal axis in the figure represents the field of view value (+Y Field Degrees). Figure 8 The vertical axis represents the root mean square wavefront error in waves. Figure 6 The combined wavelet aberration of the deep ultraviolet objective lens 30 at an operating temperature of approximately 23°C is given. A, B, C, D, E, and F represent the wavelet aberrations of ultraviolet wavelengths 193.358 / 193.362 / combined / 193.368 / 193.378 / 193.374 within the operating temperature range of 23°C, respectively. The combined wavelet aberration is the average of the RMS wavelet aberrations of the other five wavelengths. Figure 7 In the diagram, IMA represents the exit surface position, and OBJ represents the incident angle. According to simulation results, the deep ultraviolet objective 30 achieves comprehensive wave aberration reduction within the wavelength range of 193.358nm / 193.362 / 193.368 / 193.374 / 193.378nm at an operating temperature of approximately 23℃. As can be seen from 0.01λ, the deep ultraviolet objective 30 of this application can still achieve a low overall wavefront aberration value at a long working distance of not less than 7.8 mm and a working bandwidth of not less than 10 pm, which is beneficial to improving imaging quality and imaging effect.

[0094] Please see Figure 8 The second embodiment of this application provides a deep ultraviolet objective lens 30. The difference between the deep ultraviolet objective lens 30 provided in the second embodiment and the deep ultraviolet objective lens 30 provided in the first embodiment is that diffractive optical elements are provided on both sides of the seventh lens L7 in the optical axis direction, that is, diffractive optical elements are provided between the sixth lens L6 and the seventh lens L7, and between the seventh lens L7 and the eighth lens L8. The two diffractive optical elements include a first diffractive optical element 2011 (labeled as DOE1 in Table 4) and a second diffractive optical element 2012 (labeled as DOE2 in Table 4). The first surfaces of the first diffractive optical element 2011 and the second diffractive optical element 2012 are both diffractive surfaces. The diffractive surfaces satisfy the phase function characterized by formula (2).

[0095] In this embodiment, as shown in Table 3, the coefficients represent the coefficients of the 2nd, 4th, and 6th order terms, respectively.

[0096] Table 3

[0097]

[0098] In some embodiments of this application, multiple diffraction bands are concentrically arranged around the center of the diffraction surface on the diffraction plane of the diffraction optical element. The more diffraction bands there are, the smaller the minimum annular band width becomes, making the diffraction optical element more difficult to manufacture. Setting up two diffraction optical elements is equivalent to separating multiple diffraction bands on one diffraction plane of one diffraction optical element and setting them on the diffraction planes of the two diffraction optical elements. In this way, the minimum annular band width increases with the increase of the number of diffraction elements used, making it easier to manufacture.

[0099] It is understandable that the number of diffractive optical elements can be kept to one. The first and second surfaces of the diffractive optical element are both diffraction surfaces. This is equivalent to setting multiple diffraction bands on one diffraction surface of a diffractive optical element separately on two diffraction surfaces of the same diffractive optical element. In this way, the minimum ring width will increase with the increase of diffractive elements used, making it easier to process.

[0100] It is understood that at least one of the first surface and the second surface is set as a diffraction surface.

[0101] It is understood that this application does not limit the number of refractive lenses in the front lens group 33. In the optical axis direction, the refractive lens with the largest diameter in the front lens group 33 is located on the side of the front lens group 33 closest to the rear lens group 31. At least one of the orientation of the refractive lens with the largest diameter in the front lens group 33 and the side away from the rear lens group 31 is provided with a diffractive optical element.

[0102] In some embodiments of this application, the design parameters of the deep ultraviolet objective lens 30 are shown in Table 4. Surfaces S0-S28 are the surfaces of each lens, etc., of the deep ultraviolet objective lens 30. S0, S1, S27, and S28 can be virtual surfaces. In Table 4, along the optical axis direction of the deep ultraviolet objective lens 30, the front surface is the surface of the deep ultraviolet objective lens 30 away from the object surface, and the rear surface is the surface of the deep ultraviolet objective lens 30 facing the object surface.

[0103] Table 4

[0104]

[0105] Please see Figure 9 and Figure 10 , Figure 9 The horizontal axis in the figure represents the field of view value (+Y Field Degrees). Figure 10 The vertical axis represents the RMS wavefront error in waves. Figure 9The combined wavelet aberration of the deep ultraviolet objective 30 at an operating temperature of approximately 23°C is given. A, B, C, D, E, and F represent the wavelet aberrations of ultraviolet wavelengths 193.358 / 193.362 / combined / 193.368 / 193.378 / 193.3749 within the operating temperature range of 23°C, respectively. The combined wavelet aberration is the average of the RMS wavelet aberrations of the other five wavelengths. Figure 10 In the diagram, IMA represents the exit surface position, and OBJ represents the incident angle. According to simulation results, the deep ultraviolet objective 30 achieves a comprehensive wavefront aberration ≤0.02λ within a working temperature range of 23℃ and a wavelength range of 193.358nm / 193.362 / 193.368 / 193.374 / 193.378nm. This demonstrates that the deep ultraviolet objective 30 of this application can still achieve a low comprehensive wavefront aberration value even with a working distance of not less than 7.8mm and a working bandwidth of not less than 10pm, which is beneficial for improving imaging quality and imaging effect.

[0106] In the description of the embodiments of this application, it should be noted that the orientation or positional relationship of the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and other indicators are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0107] It should be noted that when a component is said to be "fixed" to another component, it can be directly on the other component or it can be in a middle component. When a component is said to be "connected" to another component, it can be directly connected to the other component or it may be in a middle component.

[0108] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items.

[0109] The above-disclosed embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art can understand that all or part of the processes for implementing the above embodiments, and equivalent variations made in accordance with the claims of this application, still fall within the scope of this application.

Claims

1. A deep-UV objective (30), characterized by The deep ultraviolet objective (30) comprises a front group lens (33) and a rear group lens (31); the front group lens (33) has a positive refractive power; the rear group lens (31) has a negative refractive power; The front group lens (33) comprises a refractive lens and at least one diffractive optical element (201); The rear group lens (31) comprises at least one refractive lens and a diaphragm (401), the diaphragm (401) and the refractive lens of the rear group lens (31) are arranged along the optical axis of the deep ultraviolet objective (30), at least one refractive lens of the rear group lens (31) comprises a first lens (L1), a second lens (L2), a third lens (L3), a fourth lens (L4), a fifth lens (L5) and a sixth lens (L6), along the direction of the optical axis of the deep ultraviolet objective (30), the second lens (L2) is located between the first lens (L1) and the third lens (L3), the third lens (L3) is located between the second lens (L2) and the fourth lens (L4), the fourth lens (L4) is located between the third lens (L3) and the diaphragm (401), the diaphragm (401) is located between the fourth lens (L4) and the fifth lens (L5), and the fifth lens (L5) is located between the fourth lens (L4) and the sixth lens (L6); The refractive lens in the front group lens (33) comprises a seventh lens (L7), an eighth lens (L8), a ninth lens (L9) and a tenth lens (L10); Along the direction of the optical axis of the deep ultraviolet objective (30), the seventh lens (L7) is arranged on the side of the front group lens (33) closest to the rear group lens (31), the eighth lens (L8) is located between the seventh lens (L7) and the ninth lens (L9), and the ninth lens (L9) is located between the eighth lens (L8) and the tenth lens (L10); the deep ultraviolet objective (30) has a refractive power of 10 pieces of refractive lens; Wherein, the diffractive optical element (201) is arranged between the seventh lens (L7) and the eighth lens (L8), and the surface parameters of the deep ultraviolet objective (30) are as follows: ， Alternatively, at least one diffractive optical element (201) is arranged on the side of the seventh lens (L7) facing the rear group lens (31) and between the seventh lens (L7) and the eighth lens (L8), and the surface parameters of the deep ultraviolet objective (30) are as follows: 。 2. The DUV objective (30) of claim 1, characterized in that The diffractive optical element (201) comprises a first surface and a second surface arranged oppositely in the direction of the optical axis of the deep ultraviolet objective (30), the first surface is arranged away from the rear group lens (31), at least one of the first surface and the second surface is a diffractive surface, the diffractive surface forms a plurality of diffraction zones (301), and the surface of the diffraction zone (301) comprises at least four steps (3011).

3. The DUV objective (30) of claim 1, characterized in that The diffractive optical element (201) comprises a first surface and a second surface arranged opposite in the direction of the optical axis of the deep ultraviolet objective (30), the first surface is arranged away from the rear group of lenses (31), at least one of the first surface and the second surface is a diffractive surface, the diffractive surface comprises a blazed grating surface, the diffractive surface forms a plurality of diffraction zones (301), the surface of the diffraction zone (301) in the direction of the optical axis is a continuous surface.

4. The deep-UV objective (30) according to claim 2 or 3, characterized in that The diffractive surface is a harmonic diffractive surface, and the harmonic diffractive order of the harmonic diffractive surface is at least 2.

5. The DUV objective (30) according to any of claims 1 to 4, characterized in that In the direction of the optical axis, the largest diameter refractive lens in the front group of lenses (33) is arranged on the side of the front group of lenses (33) closest to the rear group of lenses (31), and at least one of the side facing away from the rear group of lenses (31) of the largest diameter refractive lens of the front group of lenses (33) is provided with at least one diffractive optical element (201).

6. The DUV objective (30) of claim 1, characterized in that The first lens (L1), the fourth lens (L4), and the sixth lens (L6) are positive lenses, and the second lens (L2) and the third lens (L3) are negative lenses.

7. The DUV objective (30) according to any of claims 1 to 6, characterized in that The refractive lens in the front group of lenses (33) is a positive spherical lens.

8. The DUV objective (30) according to any one of claims 1 to 7, characterized in that The material of the diffractive optical element (201) is fused quartz.

9. The DUV objective (30) according to any of claims 1 to 8, characterized in that The numerical aperture NA of the deep-UV objective (30) 0.

88.

10. The DUV objective (30) of claim 9, characterized in that Working distance of the deep-UV objective (30) 7.8 mm.

11. The DUV objective (30) according to any of claims 1 to 10, characterized in that The working bandwidth of the deep ultraviolet objective (30) 10 pm.

12. The DUV objective (30) according to any of claims 1 to 11, characterized in that wavefront aberration of the deep-ultraviolet objective (30) 0.02λ, λ being the working wavelength of the deep-ultraviolet objective (30).

13. The deep-UV objective (30) according to any one of claims 1 to 12, characterized in that The working wavelength range of the deep ultraviolet objective (30) is [193.358nm, 193.378nm].

14. An optical system (100), characterized in that The optical system (100) comprises a housing and a deep ultraviolet objective (30), the deep ultraviolet objective (30) is the deep ultraviolet objective (30) according to any one of claims 1-13, and the deep ultraviolet objective (30) is installed in the housing (10).

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