Catadioptric projection lens

Abstract

The invention provides a catadioptric projection lens, and belongs to the technical field of optics, and the catadioptric projection lens comprises a first lens, a second lens and a third lens group, and the first lens, the second lens and the third lens group are sequentially arranged along an optical axis; the plane of the first lens faces the object plane and the image plane, the convex surface of the first lens faces one convex surface of the second lens, the other convex surface of the second lens faces the convex surface of the third lens group, and the concave surface of the third lens group faces the concave surface of the first reflector. The system has the advantages that the two single lenses and the combined lens are adopted, a large view field is achieved only through the spherical element, and the view field and the numerical aperture which can be achieved by an existing aspheric optical system are achieved; the lens is based on a Wynne-Dyson optical structure, the number of refractive elements contained in the lens is small, residual chromatic aberration is reduced, and the lens can support a broadband UV wave band; when the method is applied to photoetching projection, a mask pattern and a wafer pattern can be in the same direction, and the mask design process is simplified.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and particularly to a catadioptric projection lens. Background Art

[0002] An optical system based on the Wynne-Dyson structure generally consists of a lens and a concave mirror. The imaging characteristics of this concentric structure can achieve a large relative aperture and high imaging quality, so it has been widely used in fields such as spectrometers and lithographic projections.

[0003] For example, the optical structure in the paper "1:1 Stepwise Submicron Lithographic Lens" published by Academician Wang Zhijiang et al. in Acta Optica Sinica in 1988 includes a pair of TIR prisms, a pair of achromatic doublets, and an aspherical concave mirror for lithographic projection imaging; another example is that the optical structure of US Patent US9436103B2 includes a pair of TIR prisms, a pair of doublets, and two single lenses, and the mirror therein is an aspherical concave mirror, also for lithographic projection imaging. There is also Chinese Patent CN103984209B, whose optical structure consists of a mirror, three single lenses, and a concave mirror for lithographic projection illumination.

[0004] However, the field of view supported by the optical designs in existing patents and papers is relatively small, making it difficult to meet the requirements of actual products in applications. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a catadioptric projection lens.

[0006] The technical problems solved by the present invention can be achieved by the following technical solutions:

[0007] A catadioptric projection lens, comprising:

[0008] A first lens, a second lens, and a third lens group, which are arranged in sequence along the optical axis;

[0009] The plane of the first lens faces the object surface and the image surface, the convex surface of the first lens faces one of the convex surfaces of the second lens, the other convex surface of the second lens faces the convex surface of the third lens group, and the concave surface of the third lens group faces the concave surface of the first mirror.

[0010] Preferably, a second mirror is further included between the first lens and the object surface; and / or

[0011] A third mirror is further included between the first lens and the image surface.

[0012] Preferably, the first lens, the second lens, and the third lens group are all spherical lenses.

[0013] Preferably, the focal length range of the first lens is 1000 mm to 1100 mm, the refractive index is 1.4 to 1.45, the Abbe number is 94 to 95, and the effective clear aperture is greater than 170 mm.

[0014] Preferably, the focal length range of the second lens is 1800 mm to 1850 mm, the refractive index is 1.62 to 1.65, the Abbe number is 55 to 56, and the effective clear aperture is greater than 174 mm.

[0015] Preferably, the combined focal length range of the third lens group is -3000 mm to -2990 mm.

[0016] Preferably, the third lens group includes a third lens and a fourth lens, and the third lens and the fourth lens are glued together;

[0017] The refractive index of the third lens is 1.48 to 1.5, the Abbe number is 70 to 71, and the effective clear aperture is greater than 147 mm;

[0018] The refractive index of the fourth lens is 1.74 to 1.75, the Abbe number is 52 to 53, and the effective clear aperture is greater than 138 mm.

[0019] Preferably, it further includes: a diaphragm, and the diaphragm is disposed at the position where the first mirror is located.

[0020] Preferably, the magnification of the catadioptric projection lens is 1×, the field of view of the catadioptric projection lens is 62 mm, the numerical aperture is 0.1 to 0.18, and the wavelength band is 360 nm - 370 nm.

[0021] Preferably, the object plane is a mask plane, the image plane is a wafer plane, and the object plane and the image plane can be arranged in a swapable manner.

[0022] The advantages or beneficial effects of the technical solution of the present invention are as follows:

[0023] The catadioptric projection lens of the present invention uses two single lenses and one combined lens, and only uses spherical elements to achieve a large field of view, reaching the field of view and numerical aperture that can be achieved by existing aspherical optical systems; this lens is based on the Wynne-Dyson optical structure, with a small number of refractive elements, reducing the residual chromatic aberration, and can support a broadband ultraviolet wavelength band, greatly broadening its application range, enabling it to adapt to more different types of lithography processes and material requirements; when applied to lithographic projection, it can make the mask pattern and the wafer pattern in the same direction, simplifying the mask design process and reducing the complexity and workload of the design. Description of the Drawings

[0024] Figure 1 In the preferred Embodiment 1 of the present invention, it is a schematic structural diagram of a catadioptric projection lens;

[0025] Figure 2 In the preferred Embodiment 2 of the present invention, it is a schematic structural diagram of a catadioptric projection lens. Specific Embodiments

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0028] Next, the present invention will be further described in conjunction with the accompanying drawings and specific embodiments, but it is not a limitation of the present invention.

[0029] Embodiment 1

[0030] Refer to Figure 1 , in the preferred embodiment of the present invention, in view of the above problems existing in the prior art, a catadioptric projection lens is provided, including:

[0031] A first lens L1, a second lens L are sequentially arranged along the optical axis;

[0032] The plane of the first lens L1 faces the object surface S1 and the image surface S2, the convex surface of the first lens L1 faces one of the convex surfaces of the second lens L2, the other convex surface of the second lens L2 faces the convex surface of the third lens group L3, and the concave surface of the third lens group L3 faces the concave surface of the first mirror M1.

[0033] As a preferred embodiment, the first lens L1, the second lens L2, and the third lens group L3 are all spherical lenses.

[0034] In the optical system structure of the present invention, the lenses and mirrors used are all spherical elements. Compared with the existing spherical optical system structure, a larger field of view can be achieved. At the same time, by only using spherical elements, the field of view and numerical aperture (NA) indicators that can be achieved by the existing aspherical optical system can be reached.

[0035] The lens supports a relatively large field of view, which can well meet the requirements of actual products in various application scenarios. Whether it is the lithographic projection of small and precise devices or large products, it can provide stable and high-quality imaging, with strong practicability and adaptability.

[0036] In this embodiment, the first lens L1 and the second lens L2 are both spherical single lenses. The third lens group L3 is a spherical doublet lens.

[0037] As a preferred embodiment, the focal length range of the first lens L1 is 1000 mm to 1100 mm, the refractive index is 1.4 to 1.45, the Abbe number is 94 to 95, and the effective aperture is greater than 170 mm.

[0038] Specifically, in this embodiment, the focal length of the first lens L1 is f1, the refractive index of the first lens L1 is n1, the Abbe number of the first lens L1 is Vd1, and the effective aperture of the first lens L1 is D1.

[0039] The first lens L1 satisfies the following relationships:

[0040] 1000 mm < f1 < 1100 mm;

[0041] 1.4 < n1 < 1.45;

[0042] 94 < Vd1 < 95;

[0043] D1 > 170 mm.

[0044] Furthermore, the material of the first lens L1 can be selected as N-FK56 (SCHOTT) material.

[0045] As a preferred embodiment, the focal length range of the second lens L2 is 1800 mm to 1850 mm, the refractive index is 1.62 to 1.65, the Abbe number is 55 to 56, and the effective aperture is greater than 174 mm.

[0046] Specifically, in this embodiment, the focal length of the second lens L2 is f2, the refractive index of the second lens L2 is n2, the Abbe number of the second lens L2 is Vd2, and the effective aperture of the second lens L2 is D2.

[0047] The second lens L2 satisfies the following relationships:

[0048] 1800 < f2 < 185;

[0049] 1.62 < n2 < 1.65;

[0050] 55 < Vd2 < 56;

[0051] D2 > 174 mm.

[0052] Furthermore, the material of the second lens L2 can be selected as BSM18 (OHARA) material.

[0053] As a preferred embodiment, the combined focal length range of the third lens group L3 is -3000 mm to -2990 mm.

[0054] Specifically, in this embodiment, the focal length of the third lens group L3 is f3, and f3 satisfies the following relationship: -3000 < f3 < -2990.

[0055] As a preferred embodiment, the third lens group L3 includes a third lens L31 and a fourth lens L32, and the third lens L31 and the fourth lens L32 are glued together.

[0056] Specifically, since light rays of different wavelengths have different degrees of refraction when passing through a lens, when light enters the optical system, lights of different colors (i.e., different wavelengths) will be focused at different positions, resulting in phenomena such as colored fringes and blurring at the image edge, that is, chromatic aberration. This phenomenon seriously reduces the clarity and accuracy of imaging.

[0057] In this embodiment, the third lens group L3 adopts a spherical doublet lens to eliminate chromatic aberration.

[0058] The spherical doublet lens is composed of a third lens L31 and a fourth lens L32 tightly glued together. The optical properties of the third lens L31 and the fourth lens L32 complement each other. When light rays pass through these two glued lenses in sequence, the refraction and dispersion effects on light rays of different wavelengths cancel each other out, so that lights of different colors can be focused at the same position as much as possible, greatly reducing the influence of chromatic aberration, and thus significantly improving the imaging quality of the entire catadioptric projection lens.

[0059] As a preferred embodiment, the refractive index of the third lens L31 is 1.48 to 1.5, the Abbe number is 70 to 71, and the effective clear aperture is greater than 147 mm.

[0060] Specifically, the third lens L31 is a positive lens. The refractive index of the third lens L31 is n3, the Abbe number of the third lens L31 is Vd3, and the effective clear aperture of the third lens L31 is D3.

[0061] The third lens L31 satisfies the following relationships:

[0062] 1.48 < n3 < 1.5;

[0063] 70 < Vd3 < 71;

[0064] D3 > 147 mm.

[0065] Furthermore, the material of the third lens L31 can be selected as FK5 (SCHOTT) material.

[0066] As a preferred embodiment, the refractive index of the fourth lens L32 is 1.74 to 1.75, the Abbe number is 52 to 53, and the effective clear aperture is greater than 138 mm.

[0067] Specifically, the fourth lens L32 is a positive lens, the refractive index of the fourth lens L32 is n4, the Abbe number of the fourth lens L32 is Vd4, and the effective clear aperture of the fourth lens L32 is D4.

[0068] The fourth lens L32 satisfies the following relationships:

[0069] 1.74 < n4 < 1.75;

[0070] 52 < Vd4 < 53;

[0071] D4 > 138 mm.

[0072] Furthermore, the material of the fourth lens L32 can be selected as LAL61 (OHARA) material.

[0073] As a preferred embodiment, it further includes: a diaphragm, and the diaphragm is disposed at the position where the first mirror M1 is located.

[0074] Specifically, the first mirror M1 is a spherical concave mirror, and the position where it is located is also the position where the diaphragm is located.

[0075] In this embodiment, the diaphragm is preferably an aperture stop. By the aperture stop, that is, the first mirror M1 in the optical system, the numerical aperture (NA) can be controlled. For example, by reducing the effective aperture of the first mirror M1, the numerical aperture NA can be reduced; or, a diaphragm with an adjustable aperture size can also be used to flexibly adjust the numerical aperture NA.

[0076] Based on the optical principle, an optical system capable of achieving a large field of view can surely be compatible with the characteristics of a smaller field of view. The projection lens of the embodiment of the present invention can support a smaller field of view and numerical aperture NA.

[0077] As a preferred embodiment, the magnification of the catadioptric projection lens is 1×.

[0078] As a preferred embodiment, the field of view of the catadioptric projection lens is 62 mm, and the numerical aperture is 0.1 to 0.18.

[0079] As a preferred embodiment, the wavelength band of the catadioptric projection lens is 360 nm - 370 nm.

[0080] The 1X i-line catadioptric projection lens according to the embodiment of the present invention adopts a deformed optical system based on the Wynne-Dyson structure, with a magnification of 1X, capable of supporting a field of view size Φ of 62 mm, a numerical aperture NA variable between 0.1 and 0.18, and a wavelength band of 360 nm - 370 nm.

[0081] By changing the design of the lens part, a larger numerical aperture NA and field of view can be obtained. This lens contains a small number of refractive elements and has small residual chromatic aberration, can support a broadband ultraviolet (UV) band, and can make the mask pattern and the wafer pattern in the same direction in lithographic projection, simplifying the mask design.

[0082] As a preferred embodiment, the object plane is the mask plane, the image plane is the wafer plane, and the object plane and the image plane can be set in a swapped manner.

[0083] In this embodiment, the S1 plane can be used as the mask plane, and the S2 plane corresponds to the wafer plane; conversely, the S1 plane and the S2 plane can also be swapped, that is, the S1 plane is used as the wafer plane, and the S2 plane is used as the mask plane.

[0084] To ensure the transmittance of the optical system and obtain good chromatic aberration performance within a certain bandwidth, this projection lens uses a doublet lens combined with two single lenses for system aberration optimization design, and the design results can be referred to the provided parameter table 1.

[0085] Table 1 Parameters of each element of the optical system

[0086]

[0087]

[0088] In Table 1, Air 1 is the light propagation medium (i.e., air) between the first lens L1 and the second lens L2; Air2 is the air medium between the second lens L2 and the third lens L31; Air 3 is the air medium between the fourth lens L32 and the first mirror M1.

[0089] Radius 1 is the curvature radius of the surface of each optical element facing the object plane / image plane, and radius 2 is the curvature radius of the surface of each optical element facing away from the object plane / image plane. The curvature radius is a quantitative index of the surface curvature of the lens or mirror. Light propagates from left to right. Taking the intersection point of the spherical surface and the principal optical axis as the reference, if the center of the spherical surface is to the left of this point, the curvature radius is negative; conversely, if the center of the spherical surface is to the right of this point, the curvature radius is positive.

[0090] The central thickness refers to the distance between the front and back surfaces of the optical element along the optical axis. Among them, the central thickness of the air medium is also the setting distance between two adjacent optical elements.

[0091] The Clear Aperture (CA) refers to the area where all tolerances and specifications of optical functions are valid.

[0092] Referring to the lens optical parameters shown in Table 1 above, one side of the first lens L1 close to the object plane / image plane is a plane, and the side of the first lens L1 far from the object plane / image plane is a convex surface with a curvature radius of -468.273 mm, a central thickness of 64.6 mm, and an effective clear aperture of Φ347 mm; the central thickness of Air1 is 2 mm.

[0093] One side of the second lens L2 close to the object plane / image plane is a convex surface with a curvature radius of 4716.595 mm; the side of the second lens L2 far from the object plane / image plane is a convex surface with a curvature radius of -1623.527 mm, a central thickness of 176.9 mm, and an effective clear aperture of Φ347 mm. The central thickness of Air 2 is 198 mm.

[0094] One side of the third lens L31 close to the object plane / image plane is a convex surface with a curvature radius of 461.09 mm; the side of the third lens L31 far from the object plane / image plane is a convex surface with a curvature radius of -9707.328 mm, a central thickness of 75 mm, and an effective clear aperture of Φ294 mm. One side of the fourth lens L32 close to the object plane / image plane is a concave surface with a curvature radius of -9707.328 mm; the side of the fourth lens L32 far from the object plane / image plane is a concave surface with a curvature radius of 502.612 mm, a central thickness of 64 mm, and an effective clear aperture of Φ276 mm; the central thickness of Air 3 is 173 mm.

[0095] One side of the first mirror M1 close to the object plane / image plane is a concave surface with a curvature radius of -1195.255 mm, and the effective clear aperture is Φ230.4 mm.

[0096] The Strehl ratio of the projection lens according to the embodiment of the present invention reaches more than 0.98, and can provide a clearer and more accurate imaging effect for users.

[0097] Embodiment 2

[0098] In this embodiment, a mirror or a TIR prism is added between the wafer or mask and the lens L1 to deflect the optical path.

[0099] Referring to Figure 2 , taking the addition of a mirror as an example. As a preferred embodiment, between the first lens L1 and the object plane S1, there is also a second mirror M2; and / or

[0100] Between the first lens L1 and the image plane S2, there is also a third mirror M3.

[0101] Specifically, in this embodiment, a second mirror M2 and a third mirror M3 are inserted between the object / image plane and the first lens L1 to achieve light path folding and avoid interference in the vertical axis direction of the object / image plane.

[0102] Furthermore, the folding angle of the second mirror M2 or the third mirror M3 is θ, and the folding angle θ satisfies the following relationship: 45° ≤ θ ≤ 60°.

[0103] Specifically, when the folding angle θ is 45°, interference will occur with the optical system during the movement of the wafer or mask. This is because at a folding angle of 45°, the propagation path of the light overlaps or approaches the movement trajectory of the wafer or mask in space, thus affecting the normal operation of the optical system and reducing the performance and reliability of the entire catadioptric projection lens.

[0104] To effectively avoid the occurrence of such adverse situations, in this embodiment, the folding angle θ of the second mirror M2 or the third mirror M3 is further preferably non - 45°. By adjusting the folding angle, the propagation path of the light is changed, so that the transmission of the light in the optical system and the movement of the wafer or mask do not interfere with each other in space, thus avoiding interference between the wafer or mask and the optical system during the movement process.

[0105] Embodiment 3

[0106] The first mirror M1 used in this embodiment is not limited to a spherical concave mirror, and an aspherical mirror or a binary diffractive surface can also be selected.

[0107] Compared with a traditional spherical mirror, an aspherical mirror can make the light more focused during reflection, thus achieving high - quality imaging within a larger field of view, reducing the influence of aberration on the image, and enabling a qualitative improvement in the performance of the optical system.

[0108] The binary diffractive surface can design diffractive patterns according to the specific requirements of the optical system, and use micro - nano structures to diffract light to achieve specific modulation of light, such as changing the propagation direction, focusing characteristics, etc. of the light.

[0109] The base material of the mirror can be other optical glasses, and an ultraviolet reflective film can be deposited on the selected optical glass base to improve the reflectivity of the mirror to ultraviolet light, so that the mirror has better reflection performance in the ultraviolet light band, thus meeting the working requirements of a specific optical system in an ultraviolet light environment.

[0110] Embodiment 4

[0111] The lens material used for the lens in this embodiment can be other grades of glass with the same refractive index.

[0112] The advantages or beneficial effects of adopting the above technical solution are as follows: The catadioptric projection lens of the present invention uses two single lenses and a combined lens, and only spherical elements are used to achieve a large field of view, reaching the field of view and numerical aperture that can be achieved by existing aspherical optical systems; this lens is based on the Wynne-Dyson optical structure, with a small number of refractive elements, reducing the residual chromatic aberration, supporting a broadband UV band, greatly broadening its application range, and enabling it to adapt to more different types of lithography processes and material requirements; when applied to lithographic projection, it can make the mask pattern and the wafer pattern in the same direction, simplifying the mask design process and reducing the complexity and workload of the design.

[0113] The above are only the preferred embodiments of the present invention, and do not limit the implementation manners and protection scope of the present invention. For those skilled in the art, it should be realized that all the equivalent replacements and obvious changes made by using the content of this specification and the drawings should be included in the protection scope of the present invention.

Claims

1. A catadioptric projection lens, characterized in that Including: A first lens, a second lens, and a third lens group, the first lens, the second lens, and the third lens group are arranged in sequence along the optical axis; The plane of the first lens faces the object surface and the image surface, the convex surface of the first lens faces one of the convex surfaces of the second lens, the other convex surface of the second lens faces the convex surface of the third lens group, and the concave surface of the third lens group faces the concave surface of the first mirror.

2. The catadioptric projection lens according to claim 1, wherein A second mirror is further included between the first lens and the object surface; and / or A third mirror is further included between the first lens and the image surface.

3. The catadioptric projection lens according to claim 1 or 2, wherein The first lens, the second lens, and the third lens group are all spherical lenses.

4. The catadioptric projection lens according to claim 1 or 2, characterized in that, The focal length range of the first lens is 1000 mm to 1100 mm, the refractive index is 1.4 to 1.45, the Abbe number is 94 to 95, and the effective aperture is greater than 170 mm.

5. The catadioptric projection lens according to claim 1 or 2, characterized in that, The focal length range of the second lens is 1800 mm to 1850 mm, the refractive index is 1.62 to 1.65, the Abbe number is 55 to 56, and the effective aperture is greater than 174 mm.

6. The catadioptric projection lens according to claim 1 or 2, wherein The combined focal length range of the third lens group is -3000 mm to -2990 mm.

7. The catadioptric projection lens according to claim 1 or 2, characterized in that, The third lens group includes a third lens and a fourth lens, and the third lens and the fourth lens are glued together; The refractive index of the third lens is 1.48 to 1.5, the Abbe number is 70 to 71, and the effective aperture is greater than 147 mm; The refractive index of the fourth lens is 1.74 to 1.75, the Abbe number is 52 to 53, and the effective aperture is greater than 138 mm.

8. The catadioptric projection lens according to claim 1 or 2, wherein Further including: A diaphragm, and the diaphragm is arranged at the position where the first mirror is located.

9. The catadioptric projection lens according to claim 1 or 2, characterized in that, The magnification of the catadioptric projection lens is 1 times, the field of view of the catadioptric projection lens is 62 mm, the numerical aperture is 0.1 to 0.18, and the wavelength band is 360 nm - 370 nm.

10. The catadioptric projection lens according to claim 1 or 2, characterized in that, The object surface is a mask surface, the image surface is a wafer surface, and the object surface and the image surface can be set in a swapped manner.

Images