Double-telecentric projection objective for focus leveling

Abstract

The application provides a double-telecentric projection objective for focusing and leveling, and applies to the field of semiconductor device manufacturing technology, wherein the double-telecentric projection objective comprises an object plane, a front lens group, an aperture diaphragm, a rear lens group and an image plane arranged in sequence along an optical axis, and the front lens group and the rear lens group are symmetrically arranged along the aperture diaphragm, so that the double-telecentric projection objective adopts a refractive type and a symmetric type of object and image double-telecentric structure. The double-telecentric projection objective has the advantages of simple structure, low cost and good imaging performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor device manufacturing, in particular to a double-telecentric projection objective for focus leveling. BACKGROUND

[0002] A photolithography machine is a product of many technologies, and is used to project an integrated circuit pattern on a mask plate onto a photoresist-coated silicon wafer through a projection objective to form an image. In the photolithography machine, a wafer is adjusted to the best focal plane through a focus leveling system, so as to improve the overlaying accuracy. With the development of integrated circuits, the resolution of the photolithography machine is continuously improved, but the depth of focus of the projection objective is continuously reduced. The imaging performance of the existing projection objective is poor.

[0003] Therefore, there is a need for a new technical scheme. SUMMARY

[0004] Therefore, the present application provides a double-telecentric projection objective for focus leveling.

[0005] The present application provides the following technical scheme:

[0006] The double-telecentric projection objective for focus leveling comprises an object plane, a front lens group, an aperture diaphragm, a rear lens group and an image plane which are sequentially arranged along an optical axis, and the front lens group and the rear lens group are symmetrically arranged about the aperture diaphragm, so that the double-telecentric projection objective is of a refractive type and a symmetric type and has object and image plane double-telecentric structure.

[0007] Preferably, the plurality of lenses in the front lens group and the plurality of lenses in the rear lens group are symmetrically arranged one by one about the aperture diaphragm.

[0008] The plurality of lenses in the front lens group comprises a plurality of positive lenses and a plurality of negative lenses, and correspondingly, the plurality of lenses in the rear lens group also comprises a plurality of positive lenses and a plurality of negative lenses.

[0009] Preferably, the front lens group comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens; wherein the first lens is a convex-concave negative lens, the second lens is a double-convex positive lens, the third lens is a convex-concave positive lens, the fourth lens is a double-convex positive lens, the fifth lens is a double-concave negative lens, and the sixth lens is a concave-convex negative lens.

[0010] Correspondingly, the rear lens group comprises a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens and a twelfth lens; wherein the seventh lens is a convex-concave negative lens, the eighth lens is a double-concave negative lens, the ninth lens is a double-convex positive lens, the tenth lens is a concave-convex positive lens, the eleventh lens is a double-convex positive lens, and the twelfth lens is a concave-convex negative lens.

[0011] Preferably, at least two of the plurality of lenses in the front lens group are flint glass and at least two of the plurality of lenses in the front lens group are crown glass.

[0012] Preferably, at least two of the plurality of lenses in the rear lens group are flint glass and at least two of the plurality of lenses in the rear lens group are crown glass.

[0013] Preferably, the first lens and the sixth lens are flint glass, and the second lens and the fourth lens are crown glass.

[0014] Preferably, the seventh lens and the twelfth lens are flint glass, and the ninth lens and the eleventh lens are crown glass.

[0015] Preferably, the object-side working distance D1 of the dual-telecentric projection objective is greater than or equal to 100 mm.

[0016] Preferably, the distance D5 between the fifth lens and the sixth lens satisfies 15 mm≤D5≤40 mm.

[0017] Preferably, the distance D6 between the sixth lens and the aperture stop is greater than or equal to 30 mm.

[0018] Preferably, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens satisfy the following relationships: 2≤|f1 / f2|≤5.5; 0.8≤|f3 / f6|≤1.9; 1.0≤|f4 / f5|≤2.0.

[0019] Wherein, f1 represents the focal length of the first lens; f2 represents the focal length of the second lens; f3 represents the focal length of the third lens L3; f4 represents the focal length of the fourth lens; f5 represents the focal length of the fifth lens; and f6 represents the focal length of the sixth lens.

[0020] Preferably, the working wavelength range of the dual-telecentric projection objective is 600 nm-1000 nm.

[0021] Preferably, the numerical aperture of the dual-telecentric projection objective is 0.03.

[0022] Preferably, the object-side field diameter of the dual-telecentric projection objective is greater than 46 mm.

[0023] Preferably, the magnification of the dual-telecentric projection objective is -1.0.

[0024] Preferably, the chief ray of each field of view in the object side is incident on the first lens, and the angle between the chief ray and the optical axis is less than 0.1°; the chief ray of each field point in the image side is incident on the image plane, and the angle between the chief ray and the optical axis is less than 0.1°.

[0025] Preferably, the dual-telecentric projection objective can be used in a focus and level system in a photolithography machine.

[0026] Compared with the prior art, the at least one technical solution adopted by the embodiments of the present specification can achieve the beneficial effects at least including:

[0027] The dual-telecentric projection objective of the present application adopts a refractive structure, which is beneficial to reduce detection and adjustment difficulty and reduce cost compared with a reflective structure, and adopts a symmetrical dual-telecentric structure, which has the advantages of simple structure, low cost and good imaging performance. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0029] Figure 1 A focus and level system device schematic diagram;

[0030] Figure 2 A dual-telecentric projection objective structure schematic diagram provided by the first embodiment of the present application;

[0031] Figure 3 A field curvature, astigmatism and distortion diagram of a dual-telecentric projection objective provided by the first embodiment of the present application;

[0032] Figure 4 An MTF curve diagram of a dual-telecentric projection objective provided by the first embodiment of the present application;

[0033] Figure 5 A point column diagram of a dual-telecentric projection objective provided by the first embodiment of the present application;

[0034] Figure 6 A dual-telecentric projection objective structure schematic diagram provided by the second embodiment of the present application;

[0035] Figure 7 A field curvature, astigmatism and distortion diagram of a dual-telecentric projection objective provided by the second embodiment of the present application;

[0036] Figure 8 An MTF curve diagram of a dual-telecentric projection objective provided by the second embodiment of the present application;

[0037] Figure 9 A point column diagram of a dual-telecentric projection objective provided by the second embodiment of the present application.

[0038] Reference signs: 00, lithography objective; 10, light source module; 20, projection mark; 30, first double-telecentric projection objective; 31, first front lens group; 32, first reflecting mirror; 33, first rear lens group; 40, silicon wafer; 50, second double-telecentric projection objective; 51, second front lens group; 52, second reflecting mirror; 53, second rear lens group; 60, detection mark; 70, detection module. DETAILED DESCRIPTION

[0039] The embodiments of the present application will be described in detail below with reference to the drawings.

[0040] The above and other aspects of the present application will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:

[0041] It is to be understood that the foregoing description is that of certain examples of the application and that numerous changes in the details of construction and the combination and arrangement of parts can be made by those skilled in the art without departing from the scope of the application.

[0042] It is also to be understood that the following description is only illustrative of the aspects of the application and that changes can be made in the details and arrangement of parts by those skilled in the art without departing from the scope of the application as encompassed by the appended claims.

[0043] Furthermore, in the following description, numerous specific details are set forth in order to provide a thorough understanding of the examples. However, it will be recognized by one skilled in the art that embodiments of the application can be practiced without these specific details.

[0044] In light of this, the applicant, through in-depth research and improvement exploration of focusing and leveling systems and projection lenses, discovered that: Chinese patent documents with publication numbers CN105242501A and CN106292197A both disclose focusing and leveling systems using refractive projection lenses, but only provide schematic diagrams of the projection lenses, without specifying specific design parameters or image quality. Chinese patent document with publication number CN114690571A discloses focusing and leveling systems using reflective projection lenses, but also does not provide specific design parameters. Furthermore, compared to refractive systems, reflective lenses have stricter processing and testing requirements, are more difficult to assemble and adjust, and are more costly. Almost no patent documents provide specific solutions for projection lenses used in focusing and leveling systems.

[0045] Based on this, the technical solutions provided by the various embodiments of this application will be described below with reference to the accompanying drawings.

[0046] The first embodiment of this specification presents a dual telecentric projection lens for focusing and leveling: such as Figure 2 As shown, a focusing and leveling system for use in a lithography machine is described. This dual telecentric projection lens includes an object plane, a front lens group, an aperture stop, a rear lens group, and an image plane arranged sequentially along the optical axis. The front and rear lens groups are symmetrically arranged along the aperture stop, making the dual telecentric projection lens a refractive and symmetrical object- and image-side dual telecentric structure. The object plane and image plane can be symmetrically arranged along the aperture stop. The dual telecentric projection lens has an object- and image-side dual telecentric structure, and both are spherical lenses. Figure 2 In this context, G1 represents the front lens group and G2 represents the rear lens group.

[0047] In one embodiment, the multiple lenses in the front lens group and the multiple lenses in the rear lens group are symmetrically arranged along the aperture stop; the multiple lenses in the front lens group include multiple positive lenses and multiple negative lenses, and correspondingly, the multiple lenses in the rear lens group also include multiple positive lenses and multiple negative lenses.

[0048] For example, the front lens group includes six lenses, comprising three positive lenses and three negative lenses; the rear lens group includes six lenses, comprising three positive lenses and three negative lenses; the front and rear lens groups are symmetrical about the aperture stop. The materials, positions, and shapes of the lenses in the front lens group and the lenses in the rear lens group are symmetrically arranged along the aperture stop.

[0049] In one embodiment, the front lens group includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens, arranged in sequence; wherein the first lens is a convex-concave negative lens, the second lens is a biconvex positive lens, the third lens is a convex-concave positive lens, the fourth lens is a biconvex positive lens, the fifth lens is a biconcave negative lens, and the sixth lens is a concave-convex negative lens.

[0050] Correspondingly, the rear lens group comprises a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens and a twelfth lens, and is arranged in sequence; wherein the seventh lens is a convex-concave negative lens, the eighth lens is a double-concave negative lens, the ninth lens is a double-convex positive lens, the tenth lens is a concave-convex positive lens, the eleventh lens is a double-convex positive lens, and the twelfth lens is a concave-convex negative lens. Figure 2 L1 represents the first lens, L2 represents the second lens, L3 represents the third lens, L4 represents the fourth lens, L5 represents the fifth lens, L6 represents the sixth lens, L7 represents the seventh lens, L8 represents the eighth lens, L9 represents the ninth lens, L10 represents the tenth lens, L11 represents the eleventh lens, and L12 represents the twelfth lens.

[0051] In an embodiment, at least two of the plurality of lenses in the front lens group are flint glass material and at least two are crown glass material; and / or, at least two of the plurality of lenses in the rear lens group are flint glass material and at least two are crown glass material.

[0052] In an embodiment, the first lens and the sixth lens are flint glass material, the second lens and the fourth lens are crown glass material; and / or, the seventh lens and the twelfth lens are flint glass material, the ninth lens and the eleventh lens are crown glass material.

[0053] For example, the front lens group contains at least two flint glass material and two crown glass material, wherein the flint glass material is the convex-concave negative lens corresponding to the first lens and the concave-convex negative lens corresponding to the sixth lens, and the crown glass material is the double-convex positive lens corresponding to the second lens and the double-convex positive lens corresponding to the fourth lens. The rear lens group contains at least two flint glass material and two crown glass material, wherein the flint glass material is the convex-concave negative lens corresponding to the seventh lens and the concave-convex negative lens corresponding to the twelfth lens, and the crown glass material is the double-convex positive lens corresponding to the ninth lens and the double-convex positive lens corresponding to the eleventh lens.

[0054] Optical materials can be generally divided into two categories according to the size of refractive index and Abbe number: flint glass material and crown glass material. Flint glass material: high refractive index material low Abbe number, that is, the refractive index nd is greater than 1.60 and the Abbe number vd is less than 50; Crown glass material: low refractive index material high Abbe number, that is, the refractive index nd is less than 1.60 and the Abbe number vd is greater than 55.

[0055] In an embodiment, the object-side working distance D1 of the double-telecentric projection objective is greater than or equal to 100 mm; and / or, the distance D5 between the fifth lens and the sixth lens satisfies 15 mm≤D5≤40 mm; and / or, the distance D6 between the sixth lens and the aperture stop is greater than or equal to 30 mm.

[0056] In an embodiment, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens satisfy the following relationships: 2≤|f1 / f2|≤5.5; 0.8≤|f3 / f6|≤1.9; 1.0≤|f4 / f5|≤2.0.

[0057] wherein f1 represents a focal length of the first lens; f2 represents a focal length of the second lens; f3 represents a focal length of the third lens L3; f4 represents a focal length of the fourth lens; f5 represents a focal length of the fifth lens; and f6 represents a focal length of the sixth lens.

[0058] As shown in Figure 2 The double-telecentric projection objective lens of the embodiment comprises 12 optical lenses, one object plane, one aperture stop, and one image plane; the designed double-telecentric projection objective lens is sequentially provided with five parts of the object plane, the front lens group, the aperture stop, the rear lens group, and the image plane along the optical axis direction. The embodiment adopts a symmetrical structure, which can effectively correct aberration and improve imaging quality.

[0059] In an embodiment, the working waveband of the double-telecentric projection objective lens is 600 nm-1000 nm; and / or, the image-side numerical aperture of the double-telecentric projection objective lens is 0.03; and / or, the object-side field diameter of the double-telecentric projection objective lens is greater than 46 mm; and / or, the magnification of the double-telecentric projection objective lens is -1.0.

[0060] In an embodiment, the chief rays of each field of view on the object side are incident on the first lens, and the included angle between the chief rays and the optical axis is less than 0.1°; the chief rays of each field point on the image side are imaged on the image plane, and the included angle between the chief rays and the optical axis is less than 0.1°. Specifically, the double-telecentric projection objective lens has object-side and image-side double-telecentric structures, the chief rays of each field of view on the object side are incident on the first lens approximately parallel to the optical axis, the included angle between the chief rays and the optical axis is less than 0.1°, and the chief rays of each field point on the image side are imaged on the image plane approximately parallel to the optical axis, the included angle between the chief rays and the optical axis is less than 0.1°.

[0061] The field curvature, astigmatism, and distortion of the double-telecentric projection objective lens are as shown in Figure 3 The field curvature is within 0.025 mm, the distortion is less than 0.01%, and the astigmatism is also well corrected. Figure 3 In the figure, ASTIGMATIC FIELD CURVES represents the field curvature; DISTORTION represents the distortion; and FOCUS (MILLIMETERS) represents the focus (millimeters).

[0062] The MTF curve of the double-telecentric projection objective lens is as shown in Figure 4As shown, the horizontal coordinate is spatial frequency, and the vertical coordinate is MTF value. The MTF curve approaches the diffraction limit, and the imaging quality is good. Figure 4 In the formula, Modulation refers to MTF (Modulation Transfer Function), which is used to evaluate the imaging quality of an optical system; Spatial Frequency (cycles / mm) represents spatial frequency (line pairs per millimeter).

[0063] The spot diagram of the dual-telecentric projection objective lens is shown in FIG. 2. Figure 5 As shown, the diffraction spots are all within the Airy disk, and the imaging quality is good. Figure 5 In the formula, FIELD POSITION represents field position; and DEFOCUSING represents defocus.

[0064] The specific optical parameters of the dual-telecentric projection objective lens in this embodiment are shown in Table 1.

[0065] Table 1: Specific optical parameters of the dual-telecentric projection objective lens in the first embodiment

[0066]

[0067] In the formula, Sphere represents spherical.

[0068] In an embodiment, the dual-telecentric projection objective lens can be used in a focus and level adjustment system in a lithography machine, as shown in FIG. 3. Figure 1 As shown, the focus and level adjustment system includes a lithography objective lens 00, a light source module 10, a projection mark 20, a first dual-telecentric projection objective lens 30, a silicon wafer 40, a second dual-telecentric projection objective lens 50, a detection mark 60, and a detection module 70. The light emitted by the light source module 10 irradiates the projection mark 20, the projection mark 20 is imaged onto the silicon wafer 40 through the first dual-telecentric projection objective lens 30, and after being reflected by the surface of the silicon wafer 40, the light with the height information of the silicon wafer 40 is imaged onto the detection mark 60 through the second dual-telecentric projection objective lens 50, is received by the detection module 70, and the defocus amount of the silicon wafer 40 is obtained by calculation.

[0069] In the formula, the first dual-telecentric projection objective lens 30 can include a first front lens group 31, a first mirror 32, and a first rear lens group 33; and the second dual-telecentric projection objective lens 50 can include a second front lens group 51, a second mirror 52, and a second rear lens group 53. In addition, the first dual-telecentric projection objective lens 30 and / or the second dual-telecentric projection objective lens 50 can use the dual-telecentric projection objective lens for focus and level adjustment in any of the above embodiments.

[0070] The second embodiment of the present specification discloses a dual-telecentric projection objective lens, which can be used in a focus and level adjustment system in a lithography machine, as shown in FIG. 4. Figure 6As shown, the object plane, the front lens group G1, the aperture stop, the rear lens group G2 and the image plane are arranged in sequence along the optical axis direction; the front lens group G1 includes six lenses L1-L6, and the six lenses include three positive lenses and three negative lenses; the rear lens group includes six lenses L7-L12, and the six lenses include three positive lenses and three negative lenses; the front lens group G1 and the rear lens group G2 are symmetrical about the aperture stop.

[0071] The projection objective is a double-telecentric structure on the object and image sides and both are spherical lenses. The front lens group G1 includes: convex-concave negative lens L1, biconvex positive lens L2, convex-concave positive lens L3, biconvex positive lens L4, biconcave negative lens L5, concave-convex negative lens L6. The rear lens group G2 includes: convex-concave negative lens L7, biconcave negative lens L8, biconvex positive lens L9, concave-convex positive lens L10, biconvex positive lens L11 and concave-convex negative lens L12.

[0072] The front lens group G1 contains at least two flint glass materials and two crown glass materials, wherein the flint glass materials are the convex-concave negative lens L1 and the concave-convex negative lens L6, and the crown glass materials are the biconvex positive lens L2 and the biconvex positive lens L4; the rear lens group G2 contains at least two flint glass materials and two crown glass materials, wherein the flint glass materials are the convex-concave negative lens L7 and the concave-convex negative lens L12, and the crown glass materials are the biconvex positive lens L9 and the biconvex positive lens L11.

[0073] The object-side working distance L1 of the double-telecentric projection objective is greater than or equal to 100 mm; the distance between the fifth lens and the first lens satisfies 15 mm≤L5≤40 mm; and the distance between the sixth lens and the aperture stop is greater than or equal to 30 mm.

[0074] The first lens L1, the second lens L2, the third lens L3, the fourth lens L4 and the fifth lens L5 satisfy the following relationships: 2≤|f1 / f2|≤5.5; 0.8≤|f3 / f6|≤1.9; and 1.0≤|f4 / f5|≤2.0.

[0075] Wherein, f1: focal length of the first lens L1; f2: focal length of the second lens L2; f3: focal length of the third lens L3; f4: focal length of the fourth lens L4; f5: focal length of the fifth lens L5; and f6: focal length of the sixth lens L6.

[0076] The double-telecentric projection objective of the embodiment includes 12 optical lenses, one object plane (object), one aperture stop (aperture) and one image plane (Image); the designed double-telecentric projection objective is arranged in sequence from the light beam incidence direction as the object plane (object), the front lens group G1, the aperture stop (aperture), the rear lens group G2 and the image plane 5 parts.

[0077] The working waveband of the dual-telecentric projection objective lens of the embodiment is 600nm-1000nm; the numerical aperture on the image side of the dual-telecentric projection objective lens of the embodiment is 0.03; the field diameter on the object side of the dual-telecentric projection objective lens of the embodiment is greater than 46mm; the magnification of the dual-telecentric projection objective lens of the embodiment is -1.0; the embodiment adopts a symmetrical structure, which can effectively correct aberration and improve imaging quality.

[0078] The dual-telecentric projection objective lens of the embodiment has a dual-telecentric structure on the object and image sides, the chief rays of each field on the object side are approximately parallel to the optical axis and are incident on the first lens, the angle between the chief rays and the optical axis is less than 0.1°, and the chief rays of each field point on the image side are approximately parallel to the optical axis and are incident on the image plane, the angle between the chief rays and the optical axis is less than 0.1°.

[0079] The field curvature, astigmatism and distortion of the dual-telecentric projection objective lens of the embodiment are shown in Figure 7 , the field curvature is within 0.025mm, the distortion is less than 0.01%, and the astigmatism is also well corrected.

[0080] The MTF curve of the dual-telecentric projection objective lens of the embodiment is shown in Figure 8 , the abscissa is the spatial frequency, the ordinate is the MTF value, the MTF curve is close to the diffraction limit, and the imaging quality is good.

[0081] The spot diagram of the dual-telecentric projection objective lens of the embodiment is shown in Figure 9 , the diffraction spots are all within the Airy disk, and the imaging quality is good.

[0082] The specific optical parameters of the dual-telecentric projection objective lens of the embodiment are shown in Table 2.

[0083] Table 2: Specific optical parameters of the dual-telecentric projection objective lens of the second embodiment

[0084]

[0085] In the table, L1, L2, L3, L4, L5, L6, L7, L8, L9, L10, L11 and L12 respectively represent: convex-concave negative lens L1, double-convex positive lens L2, convex-concave positive lens L3, double-convex positive lens L4, double-concave negative lens L5, concave-convex negative lens L6, convex-concave negative lens L7, double-concave negative lens L8, double-convex positive lens L9, concave-convex positive lens L10, double-convex positive lens L11 and concave-convex negative lens L12.

[0086] The application provides a dual-telecentric projection objective lens which can be used in a focus and level adjusting system of a photoetching machine, the objective lens works in a 600nm-1000nm waveband, adopts a symmetrical dual-telecentric structure, has the advantages of simple structure, low cost and good imaging performance.

[0087] In the description, identical or similar parts between the embodiments are not repeatedly described, and each embodiment focuses on the differences from other embodiments. In particular, for the embodiments described later, the description is relatively simple, and the relevant parts refer to the part of the description of the foregoing embodiments.

[0088] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A double telecentric projection objective for focus leveling, characterized in that The double-telecentric projection objective comprises, in sequence along the optical axis, an object plane, a front lens group, an aperture diaphragm, a rear lens group, and an image plane, and the front lens group and the rear lens group are symmetrically arranged along the aperture diaphragm, so that the double-telecentric projection objective is of a refractive and symmetric object-image double-telecentric structure. The front lens group comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens; wherein the first lens is a convex-concave negative lens, the second lens is a double-convex positive lens, the third lens is a convex-concave positive lens, the fourth lens is a double-convex positive lens, the fifth lens is a double-concave negative lens, and the sixth lens is a concave-convex negative lens. Correspondingly, the rear lens group comprises a seventh lens, an eighth lens, a ninth lens, a tenth lens, an eleventh lens, and a twelfth lens; wherein the seventh lens is a convex-concave negative lens, the eighth lens is a double-concave negative lens, the ninth lens is a double-convex positive lens, the tenth lens is a concave-convex positive lens, the eleventh lens is a double-convex positive lens, and the twelfth lens is a concave-convex negative lens.

2. Double telecentric projection objective for focus and leveling according to claim 1, characterized in that The lenses in the front lens group and the lenses in the rear lens group are symmetrically arranged one by one along the aperture diaphragm.

3. Double telecentric projection objective for focus and leveling according to claim 2, characterized in that At least two of the lenses in the front lens group are made of flint glass, and at least two of the lenses are made of crown glass. At least two of the lenses in the rear lens group are made of flint glass, and at least two of the lenses are made of crown glass.

4. Double telecentric projection objective for focus and leveling according to claim 1, characterized in that The first lens and the sixth lens are made of flint glass, and the second lens and the fourth lens are made of crown glass. The seventh lens and the twelfth lens are made of flint glass, and the ninth lens and the eleventh lens are made of crown glass.

5. Double telecentric projection objective for focus and leveling according to claim 1, characterized in that The object-side working distance D1 of the double-telecentric projection objective is greater than or equal to 100 mm. The distance D5 between the fifth lens and the sixth lens satisfies 15 mm≤D5≤40 mm. The distance D6 between the sixth lens and the aperture diaphragm is greater than or equal to 30 mm.

6. Double telecentric projection objective for focus and leveling according to claim 1, characterized in that The first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens satisfy the following relationships: 2≤|f1 / f2|≤5.5; 0.8≤|f3 / f6|≤1.9; 1.0≤|f4 / f5|≤2.

0. Wherein, f1 represents the focal length of the first lens; f2 represents the focal length of the second lens; f3 represents the focal length of the third lens; f4 represents the focal length of the fourth lens; f5 represents the focal length of the fifth lens; and f6 represents the focal length of the sixth lens.

7. Double telecentric projection objective for focus and leveling according to claim 1, characterized in that The working waveband of the double-telecentric projection objective is 600 nm-1000 nm. The image-side numerical aperture of the double-telecentric projection objective is 0.

03. The object-side field diameter of the double-telecentric projection objective is greater than 46 mm. The magnification of the double-telecentric projection objective is -1.

0.

8. Double telecentric projection objective for focus and leveling according to claim 1, characterized in that The chief rays of each field of view in the object side are incident on the first lens, and the angle between the chief rays and the optical axis is less than 0.1°; the chief rays of each field point in the image side are imaged on the image plane, and the angle between the chief rays and the optical axis is less than 0.1°.

9. Double telecentric projection objective for focus and leveling according to any of claims 1 to 8, characterized in that The double-telecentric projection objective can be used in the focusing and leveling system of a lithography machine.

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