Surface scattered light collecting system

Abstract

The surface scattered light collecting system is divided into the wide-channel scattered light path and the narrow-channel scattered light path, the wide-channel scattered light negative-focal-power lens group is arranged on the wide-channel scattered light path to correct aberration, and the resolution ratio of a wide-channel scattered light focal plane is improved. Besides, a second reflecting mirror is movably arranged on a narrow channel light path reflected by the first reflecting mirror, and the second reflecting mirror reflects a focal plane of the narrow channel light to an imaging system, so that imaging observation of a target object is realized, debugging and mounting of an optical system are facilitated, and actual morphology of large-size particles or other flaws can be manually observed.

Description

Technical Field

[0001] This utility model relates to the field of wafer measurement technology, specifically to a surface scattering light collection system. Background Technology

[0002] Currently, wafer surface defect detection commonly uses laser scanning of high-speed rotating wafers. When the laser spot encounters a surface defect, scattered light is generated, scattering outwards. When the surface defect is a particle, the smaller the particle size, the lower the scattered energy. If the defect radius r satisfies 2πr / λ < 0.3 (where λ is the incident light wavelength), Rayleigh scattering occurs, and the scattered light energy tends to concentrate in the direction of the incident light and the opposite direction, which is symmetrical to the normal to the wafer surface. This is called wide-channel scattered light. For a scattered light collection system, it is necessary to collect as much wide-channel scattered light as possible to obtain sufficient light energy to identify tiny particles or other defects of similar size. This requires the optical collection system to have a large collection angle, i.e., a large numerical aperture (Na). When the particle size is large, the scattered light intensity is high, and the spatial distribution tends to be asymmetrical, usually concentrated in the direction of the normal to the wafer surface. This is called narrow-channel scattered light.

[0003] Existing technologies employ separate optical components to collect wide-channel and narrow-channel scattered light, identifying the type of surface defect by comparing the ratio of the two signal intensities to a threshold. However, achieving high focusing resolution for both wide-channel and narrow-channel scattered light with a numerical aperture greater than 0.9 on the same focal plane requires a complex optical structure, and imaging resolution affects the accuracy of defect detection. Furthermore, existing optical inspection systems in this field cannot easily acquire both the optical signal and the image of the target surface simultaneously, making it difficult to determine the actual condition of the target surface during installation, commissioning, or actual detection.

[0004] Therefore, how to design simple optical component parameters to improve the resolution of the focal plane of wide-channel scattered light and narrow-channel scattered light, and how to conveniently realize the confirmation of optical signals and their corresponding images are technical problems that need to be solved in this field. Utility Model Content

[0005] To address the aforementioned technical problems, this invention proposes a surface scattered light collection system. By combining a positive and negative optical power lens group and separating wide and narrow scattered light channels, the resolution of the focal plane of the wide-channel scattered light and the narrow-channel scattered light is improved, thereby enhancing the detection sensitivity. Simultaneously, an imaging module is added to achieve image observation of the target location.

[0006] To achieve the above objectives, the surface scattered light collection system of this invention includes a positive optical power front lens group, a rear wide-channel scattered light negative optical power lens group, a wide-channel scattered light detector, a first reflecting mirror, and a narrow-channel scattered light detector; the first reflecting mirror is located between the positive optical power front lens group and the rear wide-channel scattered light negative optical power lens group. The narrow-channel scattered light is separated from the wide-channel scattered light by the positive optical power front lens group and the first reflecting mirror, and is collected by the narrow-channel scattered light detector. Since the wide-channel collects large-angle light rays, which have significant aberrations, a rear wide-channel scattered light negative optical power lens group is additionally set in the optical path of the wide-channel scattered light to correct the aberrations, thereby improving the focal plane resolution of the wide-channel scattered light.

[0007] Another objective of this invention is to facilitate real-time manual observation of wafer surface morphology. During the installation and debugging of testing equipment, it is necessary to identify whether the wafer rotation center and the optical collection system are concentric. At this time, it is necessary to observe the wafer surface morphology, which requires an independent optical system for debugging, making the debugging process complex. In addition, in some testing processes, it is desirable to observe the actual morphology of particles or other defects, such as large particles or scratches.

[0008] To achieve the above objectives, the surface scattered light collection system of this invention further includes a second reflecting mirror and an imaging system. The second reflecting mirror is movably arranged in the narrow-channel light path reflected by the first reflecting mirror. This narrow-channel light is reflected again by the second reflecting mirror, causing the focal plane of the light beam to be reflected to the imaging system, thus enabling imaging observation of the target object. If the second reflecting mirror is moved away from the narrow-channel light path, the focal plane of the light beam falls onto the narrow-channel scattered light detector, thus enabling the detection of the narrow-channel scattered light. Preferably, the imaging system uses a separate array photodetector, such as a CCD or CMOS camera, or an imaging system composed of an optical imaging lens with a certain magnification and an array photodetector.

[0009] The technical effects of this utility model are as follows:

[0010] The surface scattering light collection system of this invention is divided into a wide-channel scattering light path and a narrow-channel scattering light path. A negative focal power lens group for the wide-channel scattering light is set in the wide-channel scattering light path to correct aberrations and improve the resolution of the focal plane of the wide-channel scattering light.

[0011] A second mirror is movably arranged in the optical path of the narrow channel light reflected by the first mirror. The second mirror reflects the focal plane of the narrow channel light to the imaging system, realizing the imaging and observation of the target object. This facilitates the debugging and installation of the optical system and the manual observation of the actual morphology of large particles or other defects. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the surface scattering light collection system in Example 1.

[0013] Figure 2 This is the MTF curve of wide-channel scattered light focal plane imaging resolution in Example 1.

[0014] Figure 3 This is the MTF curve of the focal plane imaging resolution of the narrow channel scattered light in Example 1.

[0015] Figure 4 This is a schematic diagram of the surface scattering light collection system in Example 2.

[0016] Figure 5 This is the MTF curve of wide-channel scattered light focal plane imaging resolution in Example 2.

[0017] Figure 6 This is the MTF curve of the focal plane imaging resolution of the narrow channel scattered light in Example 2. Detailed Implementation

[0018] The specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of this utility model.

[0019] A surface-scattered light collection system includes a front lens group G1 with positive optical power, a rear wide-channel negative optical power lens group G2, and a wide-channel scattered light detector D. w First reflecting mirror M1, narrow-channel scattered light detector D n And the second reflecting mirror M2.

[0020] Among them, the focal length f of the positive optical power front lens group 前 Satisfy 10mm≤f 前 ≤70mm, working distance WD satisfies 3mm≤WD≤10mm, numerical aperture is 0.9; focal length f of the back wide channel scattering negative power lens group. 后 Satisfy -50mm≤f 后 ≤-100mm; the optical distance L between the positive optical power front lens group and the rear wide-channel scattered light negative optical power lens group satisfies 30mm≤L≤100mm.

[0021] The first reflecting mirror M1 is placed between the positive optical power front lens group G1 and the rear wide-channel scattering negative optical power lens group G2. The optical axis of the positive optical power front lens group G1 passes through the center of the first reflecting mirror M1 and forms an angle of 45° with it. Part of the light beam emitted from the positive optical power front lens group G1 is reflected by the first reflecting mirror M1. The reflected light beam is equivalent to the Na of the positive optical power front lens group G1. 窄 Satisfying 0.15≤Na 窄≤0.65, this portion of the light is the narrow-channel scattered light; the remaining light not reflected by the first reflecting mirror M1, being from the edge of the beam, corresponds to the wide-channel scattered light. It enters the negative optical power lens group G2 of the wide-channel scattered light path, forming a focal plane at the wide-channel scattered light detector D. w The detection of wide-channel scattered light was achieved. The optical system, consisting of a front lens group G1 with positive optical power and a rear wide-channel scattered light negative optical power lens group G2, has a magnification M on the wafer surface, where M satisfies 10 ≤ M ≤ 30.

[0022] The second reflecting mirror M2 forms a 45° angle with the light beam. When the second reflecting mirror M2 is placed in the optical path, the narrow-channel light beam is reflected again by the second reflecting mirror M2, causing the focal plane of the beam to be reflected onto the imaging system IM, thus enabling imaging and observation of the target object. If the second reflecting mirror M2 is moved away from the narrow-channel light beam path, the focal plane of the beam falls onto the narrow-channel scattering light detector D. n It enables the detection of narrow-channel scattered light.

[0023] Furthermore, pinholes with a diameter D are provided at the focal planes of both the wide-channel and narrow-channel beams. p Satisfying 0.05mm≤D p ≤2mm, distance L between pinhole and wide / narrow channel scattered light detectors p Satisfying 1mm≤L p ≤20mm.

[0024] Example 1

[0025] See Figure 1 A surface-scattered light collection system, wherein the positive optical power front lens group G1 consists of 4 lenses, the numerical aperture Na is 0.9, and the focal length f 前 =27.24mm, working distance WD=5mm, incident light working wavelength is 266nm, field of view ±0.1mm, back wide channel scattered light negative power lens group G2 consists of 2 lenses, focal length f 后 =-55mm, the positive optical power front lens group G1 and the rear wide channel scattered light negative optical power lens group G2 have an optical interval L=41.67mm, and the magnification M of the optical system composed of the two is 20 times.

[0026] The specific parameters of the above lens group are shown in Table 1 and Table 2:

[0027] Table 1. Parameters of the positive optical power front lens group G1 and the rear wide-channel scattered light negative optical power lens group G2.

[0028]

[0029] Table 2 Aspherical parameters of lens L1

[0030]

[0031] The aforementioned first reflecting mirror M1 is positioned between the positive optical power front lens group G1 and the rear wide-channel scattered light negative optical power lens group G2. Part of the light beam emitted from the positive optical power front lens group G1 is reflected by the first reflecting mirror M1, while the other part travels from the periphery of the first reflecting mirror M1 towards the rear wide-channel scattered light negative optical power lens group G2. After refraction by the rear wide-channel scattered light negative optical power lens group G2, the light beam is focused to form a focal plane. The MTF curve of the imaging resolution on the focal plane is shown in [Figure / Image / Description]. Figure 2 The top curve is the diffraction-limited MTF curve, and the other curves are the imaging resolution MTF curves of different target objects. As can be seen from the figure, the system resolution is good and sufficient to meet the requirements of pinhole detection.

[0032] A pinhole is located at the focal plane of the wide-channel scattered light. A wide-channel scattered light detector D is placed at a distance Lp = 20 mm from the pinhole. w The light rays, located in the middle of the focal plane, pass through the pinhole and reach the wide-channel scattering light detector D. w Above, a wide-channel scattered photoelectric signal is formed.

[0033] The light beam emitted from the positive power front lens group G1 and reflected by the first reflecting mirror M1 corresponds to the object-side numerical aperture Na of the positive power front lens group G1. 窄 The value is 0.36. A movable second reflector M2 is provided in the optical path of the light reflected by the first reflector M1. When the second reflector M2 is placed in the optical path, this portion of the light is reflected again, causing the focal plane of the beam to be reflected onto the imaging system IM. The MTF curve of the imaging resolution on the focal plane is shown in [Figure number missing]. Figure 3 As shown in the figure, the MTF is close to the diffraction limit, indicating excellent imaging performance. The imaging system IM is a CCD camera, enabling imaging and observation of the target object, facilitating the debugging and installation of the optical system and manual observation of the actual morphology of large particles or other defects. When the second reflecting mirror M2 is moved out of the optical path, the light beam falls onto the narrow-channel scattering light detector D. n Above, a narrow channel of scattered photoelectric signals is formed.

[0034] A pinhole is located at the focal plane of the narrow-channel scattered light. A narrow-channel scattered light detector D is placed at a distance of 20 mm from the pinhole. n The light rays, located in the middle of the focal plane, pass through the pinhole and reach the narrow-channel scattered light detector D. w Above, a narrow channel of scattered photoelectric signals is formed.

[0035] Example 2

[0036] See Figure 4A surface-scattered light collection system, differing from Embodiment 1 in that the positive optical power front lens group G1 consists of 5 lenses, with a numerical aperture Na of 0.9 and a focal length f. 前 =48.47mm, working distance WD=9mm, incident light working wavelength is 266nm, field of view ±0.15mm, back wide channel scattered light negative power lens group G2 consists of 1 lens, focal length f 后 =-59.69mm, the positive optical power front lens group G1 and the rear wide channel scattered light negative optical power lens group G2 have an optical interval L=85mm, and the magnification M of the optical system composed of the two is 25 times.

[0037] The specific parameters of the above lens group are shown in Tables 3 and 4:

[0038] Table 3. Parameters of the positive optical power front lens group G1 and the rear wide-channel scattered light negative optical power lens group G2.

[0039]

[0040] Table 4 Aspherical parameters of lens L1

[0041]

[0042] The aforementioned first reflecting mirror M1 is positioned between the positive optical power front lens group G1 and the rear wide-channel scattered light negative optical power lens group G2. Part of the light beam emitted from the positive optical power front lens group G1 is reflected by the first reflecting mirror M1, while the other part travels from the periphery of the first reflecting mirror M1 towards the rear wide-channel scattered light negative optical power lens group G2. After refraction by the rear wide-channel scattered light negative optical power lens group G2, the light beam is focused to form a focal plane. The MTF curve of the imaging resolution on the focal plane is shown in [Figure / Image / Description]. Figure 5 As shown in the figure, this system has good resolution and can meet the requirements of pinhole detection.

[0043] There is a pinhole P at the focal plane of the wide-channel scattered light. w In relation to pinhole P w A wide-channel scattered light detector D is placed at a distance of Lp = 30 mm. w The light rays, located in the middle of the focal plane, pass through the pinhole and reach the wide-channel scattering light detector D. w Above, a wide-channel scattered photoelectric signal is formed.

[0044] The light beam emitted from the positive power front lens group G1 and reflected by the first reflecting mirror M1 corresponds to the object-side numerical aperture Na of the positive power front lens group G1. 窄The value is 0.25. A movable second reflector M2 is provided in the optical path of the light reflected by the first reflector M1. When the second reflector M2 is placed in the optical path, this portion of the light is reflected again, causing the focal plane of the beam to be reflected onto the imaging system IM. The MTF curve of the imaging resolution on the focal plane is shown in [Figure number missing]. Figure 6 As shown in the figure, the MTF is close to the diffraction limit, indicating excellent imaging performance. The imaging system IM consists of a microscope objective and a CCD camera, enabling imaging observation of the target object and facilitating the debugging and installation of the optical system, as well as manual observation of the actual morphology of large particles or other defects. When the second reflecting mirror M2 is moved out of the optical path, the light beam falls onto the narrow-channel scattering light detector D. n Above, a narrow channel of scattered photoelectric signals is formed.

[0045] There is a pinhole P at the focal plane of the narrow-channel scattered light. n In relation to pinhole P n A narrow-channel scattered light detector D is placed at a distance of 30 mm. n The light rays, located in the middle of the focal plane, pass through the pinhole and reach the narrow-channel scattered light detector D. w Above, a narrow channel of scattered photoelectric signals is formed.

[0046] The basic principles, main features, and advantages of this utility model in the explored field have been described in detail above, and some usage examples have been detailed. Finally, it should be noted that the examples given above are only for illustrative purposes and are not intended to limit this utility model. Although we have described this utility model in detail with reference to the examples, those skilled in the art can still modify the described examples and solutions, or replace related technical parts. Therefore, any modifications or equivalent substitutions made within the spirit and principles of this utility model are within the protection scope of the claims of this utility model patent.

Claims

1. A surface-scattered light collection system, comprising a front lens group with positive optical power, a rear wide-channel negative optical power lens group, a wide-channel scattered light detector, a first reflector, and a narrow-channel scattered light detector; Along the optical axis of the positive optical power front lens group, a positive optical power front lens group, a first reflecting mirror, a rear wide-channel scattered light negative optical power lens group, and a wide-channel scattered light detector are arranged sequentially; the first reflecting mirror is inclined relative to the optical axis of the positive optical power front lens group, and reflects the narrow-channel scattered light collected by the positive optical power front lens group to the narrow-channel scattered light detector. The wide-channel scattered light collected by the positive optical power front lens group is focused onto the wide-channel scattered light detector by the rear wide-channel scattered light negative optical power lens group.

2. The surface scattering light collection system as described in claim 1, characterized in that: The focal length f of the positive optical power front lens group 前 10mm≤f 前 ≤70mm; the focal length f of the rear wide-channel scattering negative optical power lens group 后 -50mm≤f 后 ≤-100mm; the optical distance L between the positive optical power front lens group and the rear wide channel scattered light negative optical power lens group is 30mm≤L≤100mm.

3. The surface scattering light collection system as described in claim 2, characterized in that: The working distance WD of the positive optical power front lens group is 3mm ≤ WD ≤ 10mm, and the numerical aperture is greater than or equal to 0.9; the narrow channel scattered light is equivalent to the numerical aperture Na of the positive optical power front lens group. 窄 0.15≤Na 窄 ≤0.

65.

4. The surface scattering light collection system as described in claim 2, characterized in that: A pinhole is provided at the focal plane of the wide-channel scattered light and the narrow-channel scattered light, and the diameter of the pinhole is D. p : 0.05mm≤D p ≤2mm, the distance L between the pinhole and the wide-channel and narrow-channel scattered light detectors p : 1mm≤L p ≤20mm.

5. The surface scattering light collection system as described in claim 1, characterized in that: The combined optical system of the positive optical power front lens group and the rear wide channel scattered light negative optical power lens group has a magnification M of 10≤M≤30 for the surface being tested.

6. The surface-scattered light collection system as described in claim 1, characterized in that: It also includes a second reflector and an imaging system, wherein the second reflector is movably located between the first reflector and the narrow-channel scattered light detector; when the second reflector moves into the narrow-channel scattered light path, the narrow-channel scattered light is reflected by the second reflector to the imaging system.

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