Wafer detection scattered light acquisition objective lens and wafer detection equipment

Abstract

The invention discloses a wafer detection scattered light collection objective lens, and relates to the technical field of optical imaging. The scattered light collecting lens is applied to wafer defect detection, the scattered light collecting lens sequentially comprises a first lens group, a second lens group, a third lens group and a fourth lens group from an object plane to an image plane in the optical axis direction of the lens, twelve lenses and an aperture diaphragm, and the twelve lenses and the aperture diaphragm are coaxially arranged; the first lens group is a catadioptric lens group, has positive focal power, and is used for imaging an object plane to an intermediate image plane through two times of reflection. The numerical aperture of the acquisition objective lens provided by the invention is equal to 0.9, the field of view is equal to 2.6 mm, the acquisition objective lens has the characteristics of large field of view, large numerical aperture and small center shielding, the capability of detecting scattered light of defects can be greatly improved, chromatic aberration is corrected by adopting a refraction and reflection mode, and a wider laser bandwidth can be realized compared with a general refraction mode of combining CaF2 and fused quartz.

Description

Technical Field

[0001] The present invention relates to the field of optical imaging technology, and in particular to a wafer detection scattered light collection objective lens and wafer detection equipment. Background Art

[0002] Wafer defect detection is the key to improving the yield of semiconductor processes. Using optics, especially lasers, to detect defects on the wafer surface is a common technical route. Due to the limitation of optical resolution, it is necessary to collect the scattered light of the defects, especially nano-level defects, to detect defects. In order to improve the signal-to-noise ratio, a lens with a high numerical aperture is required. In order to take into account production capacity, the scanning field of view needs to be as large as possible, so a large field of view objective is required. Laser light source is a common wafer detection light source. In order to achieve high power, quasi-continuous (QCW) deep ultraviolet DUV laser is often used. The bandwidth of QCW laser is generally greater than 50pm. For large numerical aperture objectives, this bandwidth must be taken into account. In the deep ultraviolet DUV region, the transmittance of ordinary optical materials is extremely low, and there are very few materials that can be used, which makes it very difficult to correct chromatic aberration.

[0003] The existing patent (publication number: CN117348201) discloses a folding reflective objective lens. Although the wavelength of the objective lens is very wide and the numerical aperture can reach 0.9, the wavelength can only reach the ultraviolet band, not the deep ultraviolet band, and the scanning field of view is 1mm, which has limitations in use. Therefore, we propose a wafer detection scattered light collection objective lens and wafer detection equipment. Summary of the invention

[0004] The purpose of the present invention is to provide a wafer detection scattered light collection objective lens and a wafer detection device, with a numerical aperture equal to 0.9 and a field of view equal to 2.6mm, which can greatly improve the detection capability of scattered light of defects.

[0005] To achieve the above-mentioned object, the present invention provides the following technical solutions: a wafer inspection scattered light collection objective lens, which is applied to wafer defect detection, wherein the scattered light collection lens includes a first lens group, a second lens group, a third lens group, and a fourth lens group in sequence along its optical axis from the object plane to the image plane, a total of twelve lenses and an aperture stop, and the twelve lenses and the aperture stop are coaxially arranged;

[0006] The first lens group is a catadioptric lens group with positive optical power, and is used to image the object plane onto the intermediate image plane through two reflections;

[0007] The second lens group includes four lenses with positive optical power, and is used to collimate the intermediate image into quasi-parallel light;

[0008] The third lens group includes three lenses with negative optical power, which are used to adjust the incident height of quasi-parallel light;

[0009] The fourth lens group includes two lenses with positive focal length, and is used to collimate the adjusted light to convert the divergent light into collimated light.

[0010] Furthermore, the first lens group includes a first lens, a second lens and a third lens, wherein the first lens, the second lens and the third lens are coaxially distributed in sequence along the optical axis from the object plane to the image plane.

[0011] Furthermore, the first lens is a positive meniscus lens, the first surface of the first lens away from the second lens is a convex surface, the central transmission area is circular, and the central transmission area occupies less than 10% of the area of ​​the entire first surface, and the remaining area is a reflection surface area;

[0012] The second surface of the first lens facing the second lens is a plane or a convex surface or a concave surface, and has a large radius of curvature, |R|≥1000;

[0013] The second lens is a negative meniscus lens, which is bent toward the object plane. The third lens is a reflective surface. The third lens is set to be a concave surface, and a hole is dug in the central area of ​​the third lens for transmission. The central hole area is circular and occupies less than 5% of the total area of ​​the reflective surface.

[0014] Furthermore, the second lens group includes a fourth lens, a fifth lens, a sixth lens, a seventh lens and an aperture stop, and the fourth lens, the fifth lens, the sixth lens, the seventh lens and the aperture stop are coaxially distributed in sequence along the optical axis from the object plane to the image plane.

[0015] Further, the fourth lens is a meniscus negative lens, which is bent toward the image plane; the fifth lens is a biconvex positive lens; the sixth lens is a plano-convex positive lens, a biconvex positive lens or a meniscus positive lens;

[0016] The seventh lens is a positive meniscus lens, which is bent toward the image plane, and the aperture stop is installed on the side of the seventh lens facing the image plane.

[0017] Furthermore, the third lens group includes an eighth lens, a ninth lens and a tenth lens, and the eighth lens, the ninth lens and the tenth lens are coaxially distributed in sequence along the optical axis from the object plane to the image plane.

[0018] Furthermore, the eighth lens is configured as a negative meniscus lens, which is bent toward the image plane; the ninth lens is configured as a double convex positive lens; and the tenth lens is configured as a negative meniscus lens, which is bent toward the object plane.

[0019] Furthermore, the fourth lens group includes an eleventh lens and a twelfth lens, and the eleventh lens and the twelfth lens are coaxially distributed in sequence along the optical axis from the object plane to the image plane.

[0020] Furthermore, the eleventh lens is configured as a meniscus negative lens, bent toward the image plane, and the twelfth lens is configured as a plano-convex positive lens, a bi-convex positive lens or a meniscus positive lens.

[0021] According to a second aspect of the present invention, the present invention provides a wafer inspection device, comprising the above-mentioned wafer inspection scattered light collection objective lens.

[0022] The present invention has at least the following beneficial effects:

[0023] 1. Large numerical aperture: The numerical aperture can reach 0.9, achieving a scattered light cone angle of less than 64°.

[0024] 2. Large field of view: The field of view can reach 2.6mm, which greatly improves the detection efficiency compared with the scanning field of view of about 0.5mm of common microscopes or about 1mm of existing technologies.

[0025] 3. The present invention uses only twelve lenses to achieve good aberration correction for large numerical aperture and large field of view. The number of lenses is small, which reduces production costs and assembly difficulty.

[0026] 4. The present invention adopts a catadioptric method to correct chromatic aberration, which can achieve a wider laser bandwidth than the general refraction method using a combination of CaF2 and fused quartz, and the cost is lower when all fused quartz materials are used.

[0027] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic diagram of the structure of a scattered light collection objective lens for wafer inspection provided by an embodiment of the present invention;

[0029] Figure 2 A spot diagram of a scattered light collection objective lens for wafer inspection provided by an embodiment of the present invention;

[0030] Figure 3 A transfer function MTF diagram of a wafer detection scattered light collection objective lens provided in an embodiment of the present invention;

[0031] Figure 4 A field curvature and distortion diagram of a scattered light collection objective lens for wafer inspection provided in an embodiment of the present invention.

[0032] Reference numerals:

[0033] 1. The first lens; 2. The second lens; 3. The third lens; 4. The fourth lens; 5. The fifth lens; 6. The sixth lens; 7. The seventh lens; 8. The aperture stop; 9. The eighth lens; 10. The ninth lens; 11. The tenth lens; 12. The eleventh lens; 13. The twelfth lens; G1. The first lens group; G2. The second lens group; G3. The third lens group; G4. The fourth lens group. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0035] See also Figure 1-Figure 4 The present invention provides a technical solution: a wafer detection scattered light collection objective lens, which is applied to wafer defect detection. The scattered light collection lens includes a first lens group G1, a second lens group G2, a third lens group G3, and a fourth lens group G4 in sequence along its optical axis from the object plane to the image plane, a total of twelve lenses and an aperture stop 8, and the twelve lenses and the aperture stop 8 are coaxially arranged;

[0036] The first lens group G1 is a catadioptric lens group with positive optical power, and is used to image the object plane onto the intermediate image plane through two reflections;

[0037] The second lens group G2 includes four lenses with positive refractive power, which are used to collimate the intermediate image into quasi-parallel light;

[0038] The third lens group G3 includes three lenses with negative optical power, which are used to adjust the incident height of quasi-parallel light;

[0039] The fourth lens group G4 includes two lenses with positive optical power, and is used to collimate the adjusted light, thereby converting the divergent light into collimated light.

[0040] According to the technical solution of this embodiment, the first lens group G1 includes a first lens 1, a second lens 2 and a third lens 3, wherein the first lens 1, the second lens 2 and the third lens 3 are coaxially distributed in sequence along the optical axis from the object plane to the image plane. Specifically, the first lens 1 is a positive meniscus lens, the first surface of the first lens 1 away from the second lens 2 is a convex surface, the central transmission area is circular, and the central transmission area occupies less than 10% of the area of ​​the entire first surface, and the remaining area is a reflection surface area;

[0041] The second surface of the first lens 1 facing the second lens 2 is a plane or a convex surface or a concave surface, and has a large radius of curvature, |R|≥1000;

[0042] The second lens 2 is a negative meniscus lens, which is bent toward the object plane. The third lens 3 is a reflective surface. The third lens 3 is set to be a concave surface, and the central area of ​​the third lens 3 is dug for transmission. The central dug hole area is circular and occupies less than 5% of the total area of ​​the reflective surface.

[0043] According to the technical solution of this embodiment, the second lens group G2 includes a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7 and an aperture stop 8, and the fourth lens 4, the fifth lens 5, the sixth lens 6, the seventh lens 7 and the aperture stop 8 are coaxially distributed in sequence along the optical axis from the object plane to the image plane. Specifically, the fourth lens 4 is a meniscus negative lens, which is bent toward the image plane; the fifth lens 5 is a biconvex positive lens; the sixth lens 6 can be set to a plano-convex positive lens, a biconvex positive lens or a meniscus positive lens, which is not specifically limited in this embodiment and can be selected according to actual conditions;

[0044] The seventh lens 7 is a meniscus positive lens, which is bent toward the image plane. The aperture stop 8 is installed on the side of the seventh lens 7 facing the image plane. The aperture stop is set inside the lens group, which is beneficial to controlling the lens size of the overall optical path system. In addition, the aperture stop is close to the image plane, that is, on the right side of the lens 7, close to the concave surface, which is beneficial to correct off-axis aberrations and achieve good imaging effects in each field of view.

[0045] According to the technical solution of this embodiment, the third lens group G3 includes an eighth lens 9, a ninth lens 10 and a tenth lens 11. The eighth lens 9, the ninth lens 10 and the tenth lens 11 are coaxially distributed in sequence along the optical axis from the object plane to the image plane. Specifically, the eighth lens 9 is configured as a meniscus negative lens, which is bent toward the image plane; the ninth lens 10 is configured as a double convex positive lens; and the tenth lens 11 is configured as a meniscus negative lens, which is bent toward the object plane.

[0046] With respect to the technical solution of this embodiment, the fourth lens group G4 includes an eleventh lens 12 and a twelfth lens 13, and the eleventh lens 12 and the twelfth lens 13 are coaxially distributed in sequence along the optical axis from the object plane to the image plane. Specifically, the eleventh lens 12 is configured as a meniscus negative lens, bent toward the image plane, and the twelfth lens 13 is configured as a plano-convex positive lens, a bi-convex positive lens or a meniscus positive lens. This embodiment is not specifically limited here and can be selected according to actual conditions.

[0047] It should be noted that in this embodiment, all lenses are set to spherical surfaces. The spherical surface design can make the light as parallel as possible before entering the lens, thereby reducing the influence of aberrations, and all lenses are made of fused quartz material. The refractive index of fused quartz material is very high, which can reach between 3.4 and 3.9. This slows down the propagation speed of light inside the lens, thereby making the outgoing light more concentrated, which is beneficial to improving the quality of imaging.

[0048] Furthermore, the objective lens described in this embodiment has a numerical aperture of 0.9 and a field of view of 2.6 mm.

[0049] The component parameters are as follows:

[0050]

[0051]

[0052] Figure 2 The spot diagram of the objective is given, and it can be seen that the spot size of each field of view within the spectral bandwidth is close to the diffraction limit, with a maximum field of view of +-1.3mm; Figure 3 The transfer function of the objective lens is given, and each wavelength and field of view are close to the diffraction limit. The 3000lp / mm MTF exceeds 0.2, achieving a very high resolution. Figure 4 The field curvature and distortion diagrams are given. The field curvature at each wavelength is basically corrected and is smaller than the focal depth. Apart from this, the distortion is within 1%.

[0053] To summarize, the light on the object plane is converged by the first lens 1 and then emitted to the second lens 2. It is slightly diverged by the second lens 2 and then incident on the third lens 3 at a suitable angle for reflection. The reflected light enters the second lens 2 and the first lens 1 in sequence. After being reflected on the reflection surface of the first lens 1, it is focused on the intermediate image plane by the first lens 1 and the second lens 2. The intermediate image then passes through the second lens group G2, the third lens group G3 and the fourth lens group G4 to emit parallel light. The intermediate image is formed by the refraction and reflection method of the first lens group G1, which reduces the aperture angle of the subsequent optical path, further reduces the size of the optical path lens, and is conducive to correcting spherical aberration, ultimately forming a more complete imaging effect.

[0054] Embodiment 2:

[0055] This embodiment provides a wafer inspection device, including a wafer inspection scattered light collection objective lens described in the first embodiment.

[0056] It should be noted that the wafer detection scattered light collection objective lens and other parts of a wafer detection device provided by the present application can be designed, manufactured and sold separately, or they can be assembled together and then sold as a whole. Regardless of the monomers formed before the combination or the whole formed after the combination, they all fall within the protection scope of the present application.

[0057] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0058] For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances. When an element is referred to as being "assembled on", "installed on", "fixed on" or "set on" another element, it can be directly on the other element or there can also be a centered element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be a centered element at the same time. The terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used herein are only for illustrative purposes and are not intended to be the only implementation method.

[0059] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

[0060] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

Claims

1. A wafer detection scattered light collection objective lens, applied to wafer defect detection, characterized in that: The scattered light collection lens comprises a first lens group (G1), a second lens group (G2), a third lens group (G3), and a fourth lens group (G4) in sequence from the object plane to the image plane along the optical axis direction, a total of twelve lenses and an aperture stop (8), and the twelve lenses and the aperture stop (8) are coaxially arranged; The first lens group (G1) is a catadioptric lens group with positive optical power, and is used to image the object plane onto the intermediate image plane through two reflections; The second lens group (G2) comprises four lenses with positive optical power, and is used to collimate the intermediate image into quasi-parallel light; The third lens group (G3) includes three lenses with negative optical power, which are used to adjust the incident height of quasi-parallel light; The fourth lens group (G4) comprises two lenses with positive focal length and is used to collimate the adjusted light and convert the divergent light into collimated light.

2. The scattered light collection objective lens for wafer inspection according to claim 1, characterized in that: The first lens group (G1) comprises a first lens (1), a second lens (2) and a third lens (3), wherein the first lens (1), the second lens (2) and the third lens (3) are coaxially distributed in sequence along the optical axis from the object plane to the image plane.

3. The scattered light collection objective lens for wafer inspection according to claim 2, characterized in that: The first lens (1) is a positive meniscus lens, the first surface of the first lens (1) away from the second lens (2) is a convex surface, the central transmission area is circular, and the central transmission area occupies less than 10% of the area of ​​the entire first surface, and the remaining area is a reflection surface area; The second surface of the first lens (1) facing the second lens (2) is a plane or a convex surface or a concave surface, and has a relatively large radius of curvature, |R|≥1000; The second lens (2) is a negative meniscus lens, which is bent toward the object plane. The third lens (3) is a reflective surface. The third lens (3) is set as a concave surface, and a hole is dug in the central area of ​​the third lens (3) for transmission. The central hole area is circular and occupies less than 5% of the total area of ​​the reflective surface.

4. The scattered light collection objective lens for wafer inspection according to claim 2, characterized in that: The second lens group (G2) comprises a fourth lens (4), a fifth lens (5), a sixth lens (6), a seventh lens (7) and an aperture stop (8), and the fourth lens (4), the fifth lens (5), the sixth lens (6), the seventh lens (7) and the aperture stop (8) are coaxially distributed in sequence along the optical axis from the object plane to the image plane.

5. The scattered light collection objective lens for wafer inspection according to claim 4, characterized in that: The fourth lens (4) is a meniscus negative lens, which is bent towards the image plane; the fifth lens (5) is a biconvex positive lens; the sixth lens (6) is a planoconvex positive lens, a biconvex positive lens or a meniscus positive lens; The seventh lens (7) is a positive meniscus lens, which is bent toward the image plane, and the aperture stop (8) is installed on the side of the seventh lens (7) facing the image plane.

6. The wafer inspection scattered light collection objective lens according to claim 4, characterized in that: The third lens group (G3) comprises an eighth lens (9), a ninth lens (10) and a tenth lens (11), and the eighth lens (9), the ninth lens (10) and the tenth lens (11) are coaxially distributed in sequence along the optical axis from the object plane to the image plane.

7. The wafer inspection scattered light collection objective lens according to claim 6, characterized in that: The eighth lens (9) is configured as a negative meniscus lens, which is bent towards the image plane; the ninth lens (10) is configured as a double convex positive lens; and the tenth lens (11) is configured as a negative meniscus lens, which is bent towards the object plane.

8. The scattered light collection objective lens for wafer inspection according to claim 7, characterized in that: The fourth lens group (G4) comprises an eleventh lens (12) and a twelfth lens (13), and the eleventh lens (12) and the twelfth lens (13) are coaxially distributed in sequence along the optical axis from the object plane to the image plane.

9. The wafer inspection scattered light collection objective lens according to claim 8, characterized in that: The eleventh lens (12) is configured as a meniscus negative lens, which is bent toward the image plane, and the twelfth lens (13) is configured as a plano-convex positive lens, a bi-convex positive lens or a meniscus positive lens.

10. A wafer inspection device, characterized in that: A wafer detection scattered light collection objective lens comprising any one of claims 1 to 9.

Images