Microobjective optical system, microscope objective and wafer detection microscope

Abstract

The embodiment of the invention discloses a microscope objective optical system, a microscope objective and a wafer detection microscope, and relates to the field of optics. The system is sequentially provided with a first lens group, a second lens group and a third lens group along the same optical axis from an image space to an object space; wherein the third lens group has positive focal power and is used for collecting light beams; the second lens group has negative focal power, the first lens group has positive focal power, the second lens group and the third lens group are used for correcting and compensating the optical system, and the second lens group comprises at least two lenses made of materials with different dispersion coefficients. The second lens group and the third lens group with correction and compensation functions are arranged, so that the optical system can meet the microscopic requirement of an ultra-wide working spectrum range, and the imaging quality is ensured.

Description

Technical Field

[0001] The present application relates to the field of optical technology, and in particular to a microscope objective optical system, a microscope objective and a wafer inspection microscope. Background Art

[0002] The third-generation semiconductors are suitable for making high-temperature, high-frequency, high-power and radiation-resistant electronic devices. They are widely used in semiconductor lighting, 5G communications, satellite communications, optical communications, power electronics, aerospace and other fields. They are the new driving force for the development of the electronics industry today. Improving the quality of third-generation semiconductor manufacturing devices is very important for third-generation semiconductor manufacturers because it directly determines the performance of the device and thus the production cost. Therefore, fast, high-precision and non-destructive detection technology plays an important role in the third-generation semiconductor production line.

[0003] At present, one of the core hardware that affects the detection resolution in the quality inspection method of semiconductor manufacturing devices is the microscope objective optical system. Due to different surface feature detection requirements, the required working wavelengths are also different. However, the working spectrum of traditional microscope objective lenses is relatively narrow. Therefore, when the working wavelength band required for detection is relatively wide, multiple objective lenses with different spectrum bands are required to meet different surface feature detection requirements. Summary of the invention

[0004] The present application provides a microscope objective optical system, a microscope objective and a wafer inspection microscope, which are used to meet the inspection requirements of a wide spectral band.

[0005] This application provides the following solutions:

[0006] In a first aspect, a microscope objective optical system is provided, wherein a first lens group, a second lens group and a third lens group are sequentially arranged along the same optical axis from the image side to the object side; wherein the third lens group has positive focal power and is used for light beam collection; the second lens group has negative focal power, the first lens group has positive focal power, and the second lens group and the first lens group are used to correct and compensate the optical system; the second lens group includes at least two lenses made of materials with different dispersion coefficients.

[0007] According to an achievable method in an embodiment of the present application, the second lens group includes a lens with a material dispersion coefficient between 55 and 65 and a lens with a material dispersion coefficient between 95 and 98.

[0008] According to an implementable manner in the embodiment of the present application, the optical power of the first lens group is smaller than the optical power of the third lens group.

[0009] According to an implementable manner in the embodiment of the present application, the first lens group includes, from the image side to the object side along the optical axis direction thereof, in sequence: a first lens having negative optical power, a second lens having negative optical power, a third lens having positive optical power, and a fourth lens having positive optical power; and / or,

[0010] The second lens group includes, from the image side to the object side along the optical axis direction thereof, a fifth lens having negative optical power, a sixth lens having positive optical power, a seventh lens having negative optical power, an eighth lens having negative optical power and a ninth lens having positive optical power; and / or,

[0011] The third lens group includes, from the image side to the object side along the optical axis direction, a tenth lens with positive focal power, an eleventh lens with negative focal power, a twelfth lens with positive focal power, a thirteenth lens with negative focal power, a fourteenth lens with positive focal power and a fifteenth lens with positive focal power.

[0012] According to an achievable manner in an embodiment of the present application, the first lens, the second lens, the seventh lens and the eleventh lens are negative meniscus lenses;

[0013] The third lens and the fifteenth lens are positive meniscus lenses;

[0014] The fourth lens, the sixth lens, the ninth lens, the tenth lens, the twelfth lens and the fourteenth lens are biconvex lenses;

[0015] The fifth lens, the eighth lens and the eleventh lens are biconcave lenses.

[0016] According to an achievable manner in an embodiment of the present application, the first lens, the fourth lens, and the thirteenth lens are made of fused quartz glass;

[0017] The second lens, the third lens, the sixth lens, the seventh lens, the ninth lens, the tenth lens, the twelfth lens, the fourteenth lens and the fifteenth lens are made of calcium fluoride glass;

[0018] The material of the fifth lens and the eighth lens is barium crown glass;

[0019] The material of the eleventh lens is double crown glass.

[0020] According to an achievable manner in an embodiment of the present application, the microscope objective optical system further includes an aperture stop, and the aperture stop is located between the first lens group and the second lens group; the aperture stop is coaxially arranged with the first lens group and the second lens group.

[0021] According to an achievable method in an embodiment of the present application, the focal length of the microscope objective optical system is 15 mm, the apertures of the lenses included in the first lens group, the second lens group and the third lens group are less than or equal to 25 mm, and the overall length of the microscope objective optical system is less than 100 mm.

[0022] In a second aspect, a microscope objective is provided, wherein the microscope objective comprises the optical system as described in the first aspect above.

[0023] In a third aspect, a wafer inspection microscope is provided, wherein the wafer inspection microscope comprises the microscope objective lens as described in the second aspect above.

[0024] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0025] 1) In the microscope objective optical system of the present application, the light beam is collected by the third lens group, and the second lens group corrects and compensates the light beam passing through the third lens group by setting lenses with different dispersion coefficient glasses, thereby eliminating the chromatic aberration effect of a wide spectrum. The first lens group further corrects and compensates the light beam, so that the microscope objective optical system can operate in a wide frequency band without using multiple objective lenses with different spectrum bands.

[0026] 2) The third lens group of the objective lens system of the present invention has the largest positive focal power, has a large collection angle, and realizes high-efficiency energy collection. The second lens group has negative focal power, and corrects and compensates for the spherical aberration and chromatic aberration of the third lens group. The first lens group has a weaker positive focal power, and compensates for the residual high-order aberrations of the third lens group and the second lens group, and realizes near-diffraction-limited imaging.

[0027] 3) The objective lens system of the present invention adopts fused quartz, calcium fluoride, heavy crown and barium crown materials, which have high transmittance, so that the optical system of the present application has high transmittance in the deep ultraviolet to near infrared spectrum. In addition, the refractive index of heavy crown and barium crown glass is low, which can correct the aberration of the optical system of the present application, so that the optical system of the present application can achieve good imaging with a large field of view and a long working distance.

[0028] 4) All lenses of the objective lens of the present invention are designed with spherical surfaces, avoiding the problem of manufacturing difficulties caused by introducing aspherical surfaces or free-form surfaces.

[0029] 5) Through the structural design of the microscope objective optical system, the working distance of the optical system of the present application is greater than 10mm, the working wavelength bandwidth range can reach 320nm~900nm, the numerical aperture NA is greater than 0.4, the maximum object field radius is 0.6mm, and it can have high-resolution imaging from deep ultraviolet to near-infrared spectrum, while taking into account large field of view and long working distance. In addition, the optical system of the present application emits parallel light, the maximum beam aperture is 20mm, and the objective lens exit pupil has the characteristic of infinity, which is easy to combine with other microscope objective optical systems such as subsequent tube lenses.

[0030] Of course, any product implementing the present application does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 This is a diagram of the optical system architecture of a microscope objective lens applicable to the embodiments of the present application;

[0033] Figure 2 A schematic diagram of the structure of a microscope objective optical system applicable to another embodiment of the present application;

[0034] Figure 3 A schematic diagram of the optical path of a microscope objective optical system applicable to an embodiment of the present application;

[0035] Figure 4 The imaging point diagrams of different spectral bands of the microscope objective optical system applicable to the embodiments of the present application;

[0036] Figure 5a The MTF diagram of the imaging in the 320nm-400nm spectrum of the microscope objective optical system applicable to the embodiment of the present application;

[0037] Figure 5b The MTF diagram of the imaging in the 385nm-410nm spectral range of the microscope objective optical system applicable to the embodiment of the present application;

[0038] Figure 5c The MTF diagram of the imaging in the 400nm-700nm spectrum of the microscope objective optical system applicable to the embodiment of the present application;

[0039] Figure 5d The imaging MTF diagram of the microscope objective optical system applicable to the embodiment of the present application in the 700nm to 900nm spectral range;

[0040] Figure 6 This is a vignetting curve diagram of the microscope objective optical system applicable to the embodiment of the present application. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application belong to the scope of protection of this application.

[0042] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0043] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0044] The directions or positional relationships such as "upper", "lower", "front", "back", "left", and "right" involved in the embodiments of the present application are only for the convenience of describing the present application, and are not intended to limit the devices or components of the present disclosure to have specific directions or positions. It should be understood that the expressions of these directions or positional relationships are all relative. Any modifications, equivalent substitutions, improvements, etc. made within the scope of the present disclosure shall be included in the protection scope of the present disclosure.

[0045] At present, there are some microscope objective technologies, which mainly use two groups of lenses, one group of lenses is used for focusing, and the other group of lenses is used for light compensation, so as to magnify the object and produce a clear image. However, this type of microscope objective can only work in a smaller wavelength range such as the ultraviolet spectrum, the visible spectrum or the near-infrared spectrum. When the wavelength range required for surface detection is larger, this type of microscope objective cannot meet the detection requirements of broadband.

[0046] In view of this, in order to achieve an ultra-wide spectral band operating wavelength, the present application provides a microscope objective optical system. In order to facilitate the understanding of the present application, the system architecture on which the present application is based is first described. Figure 1 The system architecture diagram of the microscope objective optical system applicable to the embodiment of the present application is as follows: Figure 1As shown, the left side is the image side, i.e., the position where the image is formed, and the right side is the object side. The laser enters the optical system from the right side along the optical axis. In the optical system, from the image side along the optical axis, it includes a first lens group with positive refractive power, a second lens group with negative refractive power, and a third lens group with positive refractive power.

[0047] When the optical system is working, the laser is first focused by the third lens group. The third lens group bears the largest positive optical power, that is, the optical power of the third lens group is greater than that of the first lens group, and has a large collection angle, achieving efficient energy collection. After that, the laser passes through the second lens group. The second lens group corrects and compensates the laser by setting lenses with different dispersion coefficient glasses, especially the spherical aberration and chromatic aberration caused by the laser passing through the third lens group, eliminating the chromatic aberration effect in a wide spectrum. Finally, the laser is emitted after passing through the first lens group, and the first lens group further compensates and corrects the laser, especially the residual high-order aberrations. After the laser passes through the first lens group, the objective exit pupil has the characteristic of infinity, and can be combined with other microscope objective optical systems such as tube lenses in the future.

[0048] In the optical system of the present application, the three lens groups can be directly realized by a single lens that meets the refractive power requirements and can achieve the required functions, or by a combination of multiple lenses. For example, the first lens group can be realized by only one lens with positive focal power, or by a combination of multiple lenses, and only the refractive power of the combination of the multiple lenses is required to be compensated and corrected.

[0049] As a preferred embodiment, the first lens group includes, from the image side along the optical axis direction, a first lens with negative power, a second lens with negative power, a third lens with positive power, and a fourth lens with positive power. The second lens group includes, in sequence, a fifth lens with negative power, a sixth lens with positive power, a seventh lens with negative power, an eighth lens with negative power, and a ninth lens with positive power. The third lens group includes, in sequence, a tenth lens with positive power, an eleventh lens with negative power, a twelfth lens with positive power, a thirteenth lens with negative power, a fourteenth lens with positive power, and a fifteenth lens with positive power.

[0050] The first lens to the fifteenth lens can be implemented by various types of lenses that meet the focal power requirements. For example, a lens with positive focal power can be set as a biconvex type lens, or can be set as a positive meniscus type lens.

[0051] As a preferred embodiment, the first lens, the second lens, the seventh lens, and the eleventh lens can be set as negative meniscus lenses, and the concave surface of the negative meniscus lenses faces the image side. The third lens and the fifteenth lens are positive meniscus lenses, and the convex surface of the positive meniscus lenses faces the object side. The fourth lens, the sixth lens, the ninth lens, the tenth lens, the twelfth lens, and the fourteenth lens are double convex lenses. The fifth lens, the eighth lens, and the eleventh lens are double concave lenses. This embodiment adopts a spherical design for all lenses, which can avoid the problem of manufacturing difficulties caused by the introduction of aspherical or free-form surface lenses.

[0052] During the operation of the optical system of the present application, the material of the lens can be flexibly selected. The lens of the present application can be made of materials such as fused quartz and calcium fluoride conventional in the optical field, or can be selected in a targeted manner according to the function of each lens group and the characteristics of the lens material. For example, in particular, along the direction of laser incidence, the spot size formed by the front lens is smaller, the laser power density is larger, and it is more easily damaged by the laser. In order to ensure that the lens is not damaged by the laser, a material with strong radiation resistance, such as magnesium fluoride, calcium fluoride, etc., can be used for the third lens group. Materials such as fused quartz glass, barium crown glass, and heavy crown glass have certain differences in refractive index and dispersion from calcium fluoride glass, and can correct a certain degree of chromatic aberration, and can be used for the first lens group and the second lens group.

[0053] As a preferred embodiment, in the present application, the first lens, the fourth lens and the thirteenth lens are made of high-transmittance fused silica glass, with a refractive index of 1.46>Nd>1.45 and an dispersion coefficient of 68.2>Vd>67.8; the second lens, the third lens, the sixth lens, the seventh lens, the ninth lens, the tenth lens, the twelfth lens, the fourteenth lens and the fifteenth lens are made of high-transmittance calcium fluoride glass, with a refractive index of 1.45>Nd>1.43 and an dispersion coefficient of 98>Vd>95; the fifth lens and the eighth lens are made of barium crown glass, with a refractive index of 1.60>Nd>1.52 and an dispersion coefficient of 65>Vd>55; the eleventh lens is made of double crown glass, with a refractive index of 1.65>Nd>1.58 and an dispersion coefficient of 60>Vd>52.

[0054] Furthermore, the optical system of the present application may further include an aperture, which is located between the first lens group and the second lens group and is used to limit the size of the imaging beam. By setting the aperture, it is possible to ensure that the numerical aperture NA is greater than 0.4. According to the Rayleigh resolution formula:

[0055]

[0056] Where λ is the operating wavelength. At a typical wavelength of 370 nm, the characteristic resolution σ of the objective lens is better than 560 nm.

[0057] In order to ensure the working quality of the system, an optimal parameter setting method is given: the overall length of the optical system is less than 100mm, the maximum aperture of the lens is 25mm, and the focal length of the objective lens is 15mm. When the working wavelength is 320nm~900nm, it can be achieved that after the object side is imaged by the objective lens, it can be emitted as parallel light on the image side, the maximum beam diameter is 20mm, the numerical aperture NA is greater than 0.4, and the maximum field of view radius can reach 0.6mm. Furthermore, the apertures of the second lens, the third lens and the fourth lens are 25mm.

[0058] A specific embodiment of the present application is given below:

[0059] Figure 2 FIG. 1 is a schematic diagram of a microscope objective optical system structure applicable to another embodiment of the present application, such as Figure 2 As shown, the image side is defined as the left and the object side is defined as the right. The objective lens includes, from the image side along its optical axis, a first lens group G1 with positive refractive power, a second lens group G2 with negative refractive power, an objective lens stop and a third lens group G3 with positive refractive power.

[0060] The first lens group includes, from the image side along the optical axis, a first lens 1 with negative power, a second lens 2 with negative power, a third lens 3 with positive power, and a fourth lens 4 with positive power. The second lens group includes, from the image side along the optical axis, a fifth lens 5 with negative power, a sixth lens 6 with positive power, a seventh lens 7 with negative power, an eighth lens 8 with negative power, and a ninth lens 9 with positive power. The third lens group includes, from the image side along the optical axis, a tenth lens 10 with positive power, an eleventh lens 11 with negative power, a twelfth lens 12 with positive power, a thirteenth lens 13 with negative power, a fourteenth lens 14 with positive power, and a fifteenth lens 15 with positive power.

[0061] The first lens 1, the second lens 2, the seventh lens 7, and the eleventh lens 11 are all negative meniscus lenses; the third lens 3 and the fifteenth lens 15 are all positive meniscus lenses; the fourth lens 4, the sixth lens 6, the ninth lens 9, the tenth lens 10, the twelfth lens 12, and the fourteenth lens 14 are all biconvex lenses; the fifth lens 5, the eighth lens 8, and the eleventh lens 11 are all biconcave lenses. The specific parameters of each lens in this embodiment are shown in Table 1 below:

[0062] Table 1

[0063]

[0064]

[0065] In the above table, the two curvature radii corresponding to each lens are the curvature radii of the left and right curved surfaces of the lens respectively; the lens thickness is the center thickness of the lens on the optical axis; the air gap is the distance between the lens and the lens on the right, and the air gap of the fifteenth lens 15 refers to the working distance of the lens. The specific parameters of the above lenses can be fine-tuned in actual operation to meet the parameter requirements of different systems.

[0066] The first lens 1, the fourth lens 4, and the thirteenth lens 13 use high-transmittance fused silica glass, with a refractive index Nd=1.4585 and an dispersion coefficient Vd=67.795; the second lens 2, the third lens 3, the sixth lens 6, the seventh lens 7, the ninth lens 9, the tenth lens 10, the twelfth lens 12, the fourteenth lens 14 and the fifteenth lens 15 use high-transmittance calcium fluoride glass, with a refractive index Nd=1.4338 and an dispersion coefficient Vd=94.996; the fifth lens 5 and the eighth lens 8 use barium crown glass, with a refractive index Nd=1.52 and an dispersion coefficient Vd=59.724. The barium crown glass has the advantages of high refractive index and relatively low dispersion, and plays an important role in wide-spectrum chromatic aberration correction; the eleventh lens 11 uses heavy crown glass, with a refractive index Nd=1.6074 and an dispersion coefficient Vd=56.655.

[0067] For this embodiment, the present application has conducted an effect test. The test light path diagram is as follows Figure 3 As shown in the figure, the colored lines represent the light path. The specific evaluation indicators are as follows:

[0068] 1. Imaging diffuse spots

[0069] The intensity distribution of the diffraction image formed by a point light source on different sections before and after the image plane after passing through the optical system is called a diffuse spot. When an ideal star point is imaged, the light intensity before and after the image plane is symmetrically distributed and varies with the field of view. However, when an actual optical system is imaged, this symmetry will be destroyed due to defects such as aberrations. The distribution of diffuse spot energy can very sensitively reflect optical aberrations and defects. Quantitative measurement of diffuse spot parameters is an important means to control the imaging quality of the optical system.

[0070] Figure 4 The imaging point diagrams of different spectral bands of the microscope objective optical system applicable to the embodiment of the present application are as follows: Figure 4 As shown, the objective lens system of this embodiment has an imaging diffuse spot close to the Airy disk size in a wide spectral range of 320nm to 900nm under different imaging fields of view, indicating that the imaging quality of this embodiment is good.

[0071] 2. Optical Modulation Transfer Function (MTF)

[0072] Modulation Transfer Function (MTF) is an important parameter used to describe the performance of optical systems, imaging systems or display systems. The value range of MTF is usually between 0 and 1, which indicates the transfer efficiency of the system at a specific spatial frequency. The modulation transfer function MTF (ν) fully reflects the transfer characteristics of components from low frequency to high frequency. MTF (ν) = 1 means that any imaging system will always respond to a uniform bright field (zero frequency). The images formed by slowly changing backgrounds and coarse objects through the system are relatively clear, and the low-frequency modulation transfer function of the system is relatively high. The higher the spatial frequency, the smaller the modulation transfer function, indicating that the smaller the object, the lower the resolution of the optical system, and the details of objects with MTF (ν) ≈ 0 will become very blurred or even disappear in the image intensity distribution through the system.

[0073] Figures 5a to 5d The MTF diagram of the imaging of the spectral range of 320nm-400nm, 385nm-410nm, 400nm-700nm, and 700nm-900nm for the microscope objective optical system applicable to the embodiment of the present application. In the figure, the horizontal axis is the spatial frequency, the unit is lp / mm, the higher the spatial frequency, the smaller the size of the corresponding target; the vertical axis is the MTF value, the higher the MTF, the clearer the imaging. Figures 5a to 5d The different colored curves in the figure represent different imaging fields of view, where the blue curve is the central field of view 0.00mm. As shown in FIG5 , the objective lens system of this embodiment has an MTF greater than 0.27 in the deep ultraviolet 320nm to 400nm band when the spatial frequency is 1000lp / mm; in the visible light 400 to 700nm band when the spatial frequency is 500lp / mm, the MTF is greater than 0.22; in the near infrared 700 to 900nm band when the spatial frequency is 500lp / mm, the central field of view MTF is greater than 0.2, and the surface imaging quality is excellent.

[0074] 3. Vignetting Curve

[0075] The vignetting curve usually describes the illumination uniformity of the optical system, showing the proportion of unobstructed light in the optical system at different field angles. By analyzing this curve, the illumination uniformity of the optical system at different field angles can be evaluated, that is, whether the light can evenly cover the entire imaging plane. This is very important for many optical applications, especially when it is necessary to ensure image quality and reduce optical system errors.

[0076] Figure 6 This is a vignetting curve diagram of the microscope objective optical system applicable to the embodiment of the present application. The horizontal axis is the field angle, in millimeters; the vertical axis is the proportion of unblocked light. Figure 6It can be seen that in the optical system of this embodiment, no light is blocked in the entire field of view, that is, the optical system of this embodiment has no vignetting in the entire field of view and has uniform illumination.

[0077] The above method provided in the embodiment of the present application can be applied to a variety of application scenarios, including but not limited to:

[0078] The microscope objective optical system provided in the embodiment of the present application can be used in the manufacturing process of the third-generation semiconductor, such as for detecting and analyzing defects on the surface of semiconductor chips, such as impurities, cracks, etc., and can also perform detailed analysis of the chip structure, including crystal structure, device layout, connection method, etc., so as to help engineers optimize the design and manufacturing process. Specifically, it can be used for wafer surface defect detection. Improving wafer quality is very important for third-generation semiconductor manufacturers because it directly determines the performance of the device and thus determines the production cost. Using the solution of the present application, the wafer can be detected at a long working distance with an ultra-wide spectrum, thereby improving the quality of the produced wafer.

[0079] According to another embodiment, a microscope objective lens is provided. The microscope objective lens comprises Figure 1 The microscope objective optical system shown. The microscope objective may also include a barrel, threads, and a rear focal plane. The barrel is the physical housing of the microscope objective, and may be made of materials such as brass. The threads are used to mount the objective onto the microscope nosepiece, and their specifications are usually in accordance with the Royal Microscopical Society standards. The rear focal plane is the hole or opening through which light enters the objective.

[0080] According to another embodiment, a wafer inspection microscope is provided. The optical part of the wafer inspection microscope includes the aforementioned microscope objective lens, which is mounted on a rotator at the lower end of the lens barrel. The microscope objective lens may include Figure 1The optical system of the microscope objective lens shown in FIG. The optical part of the wafer inspection microscope can also include an eyepiece for transmitting the magnified image to the observer's eyes. The mechanical part of the wafer inspection microscope is the basic support part of the microscope, which mainly includes a mirror base, a mirror column and a mirror arm. The mirror base is the base of the wafer inspection microscope, which is used to support the entire mirror body; the mirror column connects the mirror base and the mirror arm. The mirror arm is the part that is held by hand when taking and placing the wafer inspection microscope. The lighting part of the wafer inspection microscope is located below the stage, including a reflector and a light collector. The reflector can be rotated in any direction and has a flat and concave surface, which are suitable for environments with strong and weak light, respectively. The light collector consists of a condenser and an aperture, which can focus light on the object to be observed. The focusing part of the wafer inspection microscope includes a coarse adjuster and a fine adjuster. The coarse adjuster is used to quickly adjust the distance between the microscope objective lens and the object. The fine adjuster is used to obtain a clearer image when using a high-power microscope objective lens. Wafer inspection microscopes can also include a stage, which is a platform under the microscope for placing the object under observation. The stage is generally made of metal or glass and can be moved left and right to observe different parts of the object.

[0081] The technical solution provided by the present application is described in detail above. The principle and implementation method of the present application are described in detail using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present application. At the same time, for those skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as limiting the present application.

Claims

1. A microscope objective optical system, characterized in that: A first lens group, a second lens group and a third lens group are arranged in sequence along the same optical axis from the image side to the object side; wherein the third lens group has positive focal power and is used for light beam collection; the second lens group has negative focal power, the first lens group has positive focal power, and the second lens group and the first lens group are used to correct and compensate the optical system; the second lens group includes at least two lenses made of materials with different dispersion coefficients.

2. The microscope objective optical system according to claim 1, characterized in that: The second lens group includes a lens with a material Abbe coefficient between 55 and 65 and a lens with a material Abbe coefficient between 95 and 98.

3. The microscope objective optical system according to claim 1, characterized in that: The optical power of the first lens group is smaller than that of the third lens group.

4. The microscope objective optical system according to claim 1, characterized in that: The first lens group includes, from the image side to the object side along the optical axis direction thereof, a first lens having negative optical power, a second lens having negative optical power, a third lens having positive optical power and a fourth lens having positive optical power; and / or, The second lens group includes, from the image side to the object side along the optical axis direction thereof, a fifth lens having negative optical power, a sixth lens having positive optical power, a seventh lens having negative optical power, an eighth lens having negative optical power and a ninth lens having positive optical power; and / or, The third lens group includes, from the image side to the object side along the optical axis direction, a tenth lens with positive focal power, an eleventh lens with negative focal power, a twelfth lens with positive focal power, a thirteenth lens with negative focal power, a fourteenth lens with positive focal power and a fifteenth lens with positive focal power.

5. The microscope objective optical system according to claim 4, characterized in that: The first lens, the second lens, the seventh lens and the eleventh lens are negative meniscus lenses; The third lens and the fifteenth lens are positive meniscus lenses; The fourth lens, the sixth lens, the ninth lens, the tenth lens, the twelfth lens and the fourteenth lens are biconvex lenses; The fifth lens, the eighth lens and the eleventh lens are biconcave lenses.

6. The microscope objective optical system according to claim 4, characterized in that: The first lens, the fourth lens and the thirteenth lens are made of fused quartz glass; The second lens, the third lens, the sixth lens, the seventh lens, the ninth lens, the tenth lens, the twelfth lens, the fourteenth lens and the fifteenth lens are made of calcium fluoride glass; The material of the fifth lens and the eighth lens is barium crown glass; The material of the eleventh lens is double crown glass.

7. The microscope objective optical system according to claim 1, characterized in that: The microscope objective optical system further comprises an aperture stop, wherein the aperture stop is located between the first lens group and the second lens group; the aperture stop is coaxially arranged with the first lens group and the second lens group.

8. The microscope objective optical system according to claim 1, characterized in that: The focal length of the microscope objective optical system is 15 mm, the apertures of the lenses included in the first lens group, the second lens group and the third lens group are less than or equal to 25 mm, and the overall length of the microscope objective optical system is less than 100 mm.

9. A microscope objective lens, characterized in that: The microscope objective comprises an optical system as claimed in any one of claims 1 to 8.

10. A wafer inspection microscope, characterized in that: The wafer inspection microscope comprises the microscope objective lens as claimed in claim 9.

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