Optical detection device

Abstract

According to the optical detection device provided by the invention, the focus detection light beam enters the reflecting piece through the first mask, the incident focus detection light beam is reflected by the periphery of the reflecting piece and then is imaged on the surface of the to-be-detected wafer through the objective lens, and the to-be-detected wafer reflects the image and enters the beam splitter through the objective lens and the reflecting piece; an image reflected by the beam splitter is acquired by the first detection unit, an image transmitted by the beam splitter enters the second mask, and a light beam transmitted by the second mask is acquired by the second detection unit; an illumination light beam penetrates through the hollow position of the reflection piece to generate an intermediate image, the intermediate image is imaged on the surface of a wafer to be detected through the objective lens, and then the intermediate image is obtained by the imaging unit through the objective lens, and the reflection piece in a special shape or position is used in a light path, so that the illumination light beam and the focus detection light beam are in the same wave band; the imaging light beam and the focusing light beam both pass through the objective lens, that is, the objective lens only uses one wave band and has no requirement on the working distance, so that the design and processing difficulty and the manufacturing cost of the objective lens are reduced.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to an optical detection device. Background Art

[0002] In semiconductor inspection equipment, the inspection imaging system uses an objective lens with a large numerical aperture, and the focal depth of the objective lens is often at the sub-micron level. However, the mobile platform for inspecting wafers has certain irregular movements, the fixture for fixing wafers has certain warping, and the silicon wafer itself has a geometric structure in the vertical direction, which makes it easy for the inspection plane to exceed the focal depth of the objective lens. In order to enable the inspection system to perform real-time inspection within the focal depth range, a real-time autofocus system is essential.

[0003] The existing technology mainly includes coaxial detection. In the coaxial detection scheme, both the detection imaging beam and the automatic focusing beam will pass through the objective lens, and the working band of the detection imaging system and the working band of the automatic focusing system are two bands that are far apart. The imaging beam and the automatic focusing beam are combined and split through a dichroic mirror. The working band of the detection imaging system is a band with a shorter wavelength, which is beneficial to improving the imaging resolution of the system, while the band of the automatic focusing system is usually longer, which is convenient for isolation from the imaging band. This requires the objective lens to be designed and coated for the two bands during design, which increases the difficulty of objective lens design and processing as well as manufacturing cost. Summary of the invention

[0004] In view of this, the present invention provides an optical detection device to reduce the design, processing difficulty and manufacturing cost of the objective lens.

[0005] To solve the above problems, this application adopts the following technical solutions:

[0006] One of the purposes of the present application is to provide an optical detection device, comprising:

[0007] An automatic focusing system (100), the automatic focusing system (100) comprising a light source module (110), a first mask (7), a reflector (10), an objective lens (13), a beam splitter (16), a second mask (17), a first detection unit (120) and a second detection unit (130), the light source module (110) being used to emit a focused light beam, and the reflector (10) being hollow in the middle;

[0008] A detection imaging system (200), the detection imaging system (200) comprising an illumination light source (22), the objective lens (13) and an imaging unit (210), the illumination light source (22) being used to emit an illumination light beam, the focused light beam having the same wavelength as the illumination light beam;

[0009] The focused light beam enters the reflective element (10) through the first mask (7), the periphery of the reflective element (10) reflects the incident focused light beam, and then forms an image on the surface (14) of the wafer to be detected through the objective lens (13), the surface (14) of the wafer to be detected reflects the image, and then enters the beam splitter (16) through the objective lens (13) and the reflective element (10), the image reflected by the beam splitter (16) is acquired by the first detection unit (120), the image transmitted by the beam splitter (16) enters the second mask (17), and the light beam transmitted by the second mask (17) is acquired by the second detection unit (130);

[0010] The illumination light beam passes through the hollowed-out position of the reflector (10) to generate an intermediate image, and the intermediate image is imaged on the surface of the wafer (14) to be inspected through the objective lens (13), and then acquired by the imaging unit (210) through the objective lens (13).

[0011] In some of the embodiments, the autofocus system (100) further comprises a rotatable scatterer (3), and the focused light beam enters the first mask (7) through the scatterer (3).

[0012] In some of the embodiments, the light source module (110) comprises a focusing light source (1) and a converging lens group (2), and a focusing light beam emitted by the focusing light source is incident on the scatterer (3) through the converging lens group (2).

[0013] In some of the embodiments, the light source module (110) includes two light sources, and the two light sources can alternately flash into the scatterer (3), and the light spots of the two light sources at the position of the diffuser (3) are conjugate with the entrance pupil of the objective lens (13), and each light source only occupies half of the entrance pupil of the objective lens (13).

[0014] In some of the embodiments, the autofocus system (100) further comprises a coupling lens group (4) and a light homogenizing device (5), and the focused light beam passing through the scatterer (3) enters the light homogenizing device (5) through the coupling lens group (4) to generate an illumination spot.

[0015] In some of the embodiments, the light homogenizer (5) is a light homogenizer rod, and the light homogenizer rod is located at the image plane of the coupling lens group (4); or the light homogenizer (5) is a microlens array, and the microlens array is located at the aperture stop of the coupling lens group (4).

[0016] In some of the embodiments, the reflector (10) is a single reflector, the middle of the single reflector is hollowed out, and the shape of the hollowed out middle is consistent with the shape of the illumination spot; or the reflector (10) is two reflectors, and the middle of the two reflectors do not overlap to form a hollow, and the illumination spot passes through the middle of the two reflectors.

[0017] In some of the embodiments, the autofocus system (100) further comprises an illumination lens group (6), and the illumination spot enters the first mask (7) through the illumination lens group (6).

[0018] In some of the embodiments, in the optical path from the focused light beam to the first mask (7), an aperture stop (25) is also provided at the position of the aperture stop (25) to block the light beam entering the pupil of the objective lens (13), and the aperture stop is a semicircular, small hole or rectangular hole with a fixed shape and is symmetrically distributed at the aperture stop, and the symmetry axis of the aperture stop passes through the center of the pupil and is perpendicular to the periodic change direction of the first mask (7).

[0019] In some of the embodiments, a light switch is also provided at the position of the aperture diaphragm, and the light switch can periodically block the diaphragm, and only blocks one of the symmetrical structures of the diaphragm at the same time, so that the light beam entering the pupil of the objective lens (13) is only located on one side of the pupil of the objective lens (13), and the light beam entering the objective lens (13) from this side is focused on the surface of the wafer (14) to be inspected, and returns along the original path from the other side of the objective lens (13).

[0020] In some embodiments, the second mask (17) is a detection grating module, and the detection grating module includes a polarizer (171), a spectroscopic crystal (172) and a detection grating (173) arranged in sequence along the propagation direction of the light beam. The polarizer (171) makes the incident light become linearly polarized light. The spectroscopic crystal (172) separates the projected grating image into o light and e light with polarization directions perpendicular to each other, and the two polarized images are offset by half a grating period in a direction perpendicular to the detection grating (173). The angle between the light transmission axis of the polarizer (171) and the optical axis of the spectroscopic crystal (172) is adjusted so that when the wafer to be inspected is at a reference zero height, the light intensities of the o light and the e light are equal.

[0021] In some of the embodiments, a beam splitter prism (26) is further included. The light beam passing through the detection grating (173) is incident on the beam splitter prism (26), and two moiré fringes of different polarization states are formed by the beam splitter prism (26) and are completely separated in space.

[0022] In some embodiments, the second detection unit (130) comprises a second converging lens group (18) and a second detector (19), and there are two second detectors (19). The moiré fringes of two different polarization states passing through the beam splitter prism (26) are imaged on the two second detectors (19) respectively through the second converging lens group (18).

[0023] This application adopts the above technical solution, and its beneficial effects are as follows:

[0024] The optical detection device provided by the present application comprises a focused light beam entering the reflective element (10) through the first mask (7), the periphery of the reflective element (10) reflects the incident focused light beam, and then forms an image on the surface of a wafer (14) to be detected through the objective lens (13), the surface of the wafer (14) to be detected reflects the image and then enters a beam splitter (16) through the objective lens (13) and the reflective element (10), the image reflected by the beam splitter (16) is acquired by a first detection unit (120), the image transmitted through the beam splitter enters the second mask (17), and is transmitted by the second mask (17). The light beam is acquired by the second detection unit (130); the illumination light beam passes through the hollow position of the reflector (10) to generate an intermediate image, the intermediate image is imaged on the surface of the wafer (14) to be detected through the objective lens (13), and then acquired by the imaging unit (210) through the objective lens (13). The present application uses a reflector with a special shape or position in the optical path, so that the imaging light beam and the focusing light beam are in the same band. Since both the imaging light beam and the focusing light beam pass through the objective lens, that is, the objective lens only uses one band and has no requirements for its working distance, the design and processing difficulty and manufacturing cost of the objective lens are reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application or the description of the prior art 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 any creative work.

[0026] Figure 1 This is a schematic diagram of the structure of the optical detection device provided in Example 1 of the present application.

[0027] Figure 2 It is a structural schematic diagram of the light homogenizing device provided in Example 1 of the present application.

[0028] Figure 3 This is another structural schematic diagram of the light homogenizing device provided in Example 1 of the present application.

[0029] Figure 4It is a schematic diagram of the structure of the reflector provided in Example 1 of the present application.

[0030] Figure 5 It is a schematic diagram of the structure of the reflector provided in Example 1 of the present application.

[0031] Figure 6 It is a schematic diagram of the structure of the aperture provided in Example 1 of the present application.

[0032] Figure 7 It is a structural schematic diagram of the reflected image displacement when the wafer to be inspected moves upward or downward provided in Example 1 of the present application.

[0033] Figure 8 It is a schematic diagram of the principle that the light beam reflected by the wafer to be inspected overlaps the image of the first mask on the surface of the second mask provided in Example 1 of the present application.

[0034] Fig. 9 This is the working signal acquisition principle diagram provided in Example 1 of the present application.

[0035] Fig.10 It is a schematic diagram of the structure of the optical detection device provided in Example 2 of the present application.

[0036] Fig.11 It is a schematic diagram of the structure of the optical detection device provided in Example 3 of the present application.

[0037] Fig.12 It is a schematic diagram of the structure of the second mask provided in Example 3 of the present application.

[0038] Fig.13 It is a schematic diagram of the morphology of moiré fringes with two different polarization states formed by a beam splitter prism provided in Example 3 of the present application. DETAILED DESCRIPTION

[0039] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0040] In the description of the present application, it should be understood that the terms "upper", "lower", "horizontal", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0041] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0042] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0043] Example 1

[0044] See also Figure 1 , is a schematic diagram of the structure of the optical detection device provided in Example 1 of the present application, which includes: an automatic focusing system 100 and a detection imaging system 200. The specific implementation methods of each component and their mutual connection relationships are described in detail below.

[0045] The automatic focusing system 100 comprises a light source module 110, a first mask 7, a reflector 10, an objective lens 13, a beam splitter 16, a second mask 17, a first detection unit 120 and a second detection unit 130. The light source module 110 is used to emit a focused light beam. The reflector 10 is hollow in the middle.

[0046] The detection imaging system 200 comprises an illumination light source 22, an objective lens 13 and an imaging unit 210. The illumination light source 22 is used to emit an illumination light beam, and the wavelength of the focused light beam is the same as that of the illumination light beam.

[0047] The optical detection device provided in this application works as follows:

[0048] The focused light beam enters the reflective element 10 through the first mask 7, and the surrounding of the reflective element 10 reflects the incident focused light beam, and then forms an image on the surface of the wafer 14 to be detected through the objective lens 13. The surface of the wafer 14 to be detected reflects the image and then enters the beam splitter 16 through the objective lens 13 and the reflective element 10. The image reflected by the beam splitter 16 is acquired by the first detection unit 120, and the image transmitted by the beam splitter 16 enters the second mask 17. The light beam blocked by the second mask 17 is acquired by the first detection unit 120, and the light beam transmitted by the second mask 17 is acquired by the second detection unit 130.

[0049] The illumination light beam passes through the hollowed-out position of the reflector 10 to generate an intermediate image. The intermediate image is imaged on the surface of the wafer 14 to be inspected through the objective lens 13 and then acquired by the imaging unit 210 through the objective lens 13 .

[0050] It can be understood that the above-mentioned optical detection device uses a reflective member 10 with a hollow middle in the optical path. The illumination light beam can directly pass through the middle of the reflective member 10, and the focusing light beam of the automatic focusing system is reflected from the periphery of the reflective member 10. The transmitted and reflected two light beams then enter the objective lens 13, so that the imaging light beam and the focusing light beam are in the same band. Since both the imaging light beam and the focusing light beam will pass through the objective lens, that is, the objective lens only uses one band and has no requirements for its working distance, the design and processing difficulty and manufacturing cost of the objective lens are reduced.

[0051] Please refer to Figure 1 The light source module 110 includes a focusing light source 1 and a converging lens group 2. The focusing light beam emitted by the focusing light source enters the scatterer 3 through the converging lens group 2, and then enters the first mask 7 through the scatterer 3. Since the scatterer 3 can rotate at a high speed, the speckle effect generated by the coherent light source is eliminated.

[0052] Please refer to Figure 1 The automatic focusing system 100 further includes a coupling lens group 4 and a light homogenizing device 5. The focusing light beam passing through the scatterer 3 enters the light homogenizing device 5 through the coupling lens group 4 to generate an illumination spot.

[0053] See also Figure 2 , is a schematic diagram of the structure of the light homogenizing device 5 provided in Example 1.

[0054] In this embodiment, the light homogenizing device 5 is a microlens array structure, which adopts Köhler illumination (that is, the light homogenizing device is located in the pupil), and the microlens array is located at the middle pupil of the coupling mirror group 4. The microlens array is used when the system has a smaller divergence angle to better meet the actual application requirements.

[0055] See also Figure 3 , is another structural schematic diagram of the light homogenizing device 5 provided in Example 1.

[0056] In this embodiment, the homogenizer 5 is a homogenizer rod, which uses critical illumination (the homogenizer is located in the field of view). The homogenizer rod is located at the image plane of the coupling lens group 4. The homogenizer rod is used when the system has a larger divergence angle to better meet actual application requirements.

[0057] It can be understood that in this embodiment 1, a light homogenizing device 5 is arranged in the light path, so as to better ensure the uniformity of the light spot illuminating the first mask 7 .

[0058] See also Figure 4 , is a structural schematic diagram of the reflector 10 provided in this embodiment 1.

[0059] In this embodiment, the reflector 10 is a single reflector, and the middle of the single reflector is hollowed out, and the shape of the hollowed out middle is consistent with the shape of the illumination spot. For example, when the light homogenizing device 5 is a rectangular light homogenizing rod, a rectangular illumination spot can be formed, and then the hollowed out middle part of the single reflector is also rectangular.

[0060] See also Figure 5 , is another structural schematic diagram of the reflector 10 provided in this embodiment 1.

[0061] In this embodiment, the reflector 10 may also be two reflectors, and the middle of the two reflectors do not overlap to form a hollow, and the illumination spot may also pass through the middle of the two reflectors.

[0062] Please refer to Figure 1 The automatic focusing system 100 further includes an illumination lens group 6 , and the illumination spot enters the first mask 7 through the illumination lens group 6 .

[0063] It should be noted that, in the autofocus system, the light source module 110 is in the optical path from the light source to the first mask 7. Here, in order to make the incident light beam enter the objective lens 13 from the pupil side, an aperture stop is used at the position of the aperture stop 25 of the illuminating light beam to block its pupil. For example, the aperture stop 25 can be set in the optical path passing through the illumination lens group 6.

[0064] See also Figure 6 , is a schematic structural diagram of the aperture stop 25 provided in this embodiment.

[0065] In this embodiment, the aperture may be of a fixed shape such as a semicircle, a small hole, a rectangle, etc., and is symmetrically distributed on the aperture aperture, with the symmetry axis of the aperture passing through the pupil center and perpendicular to the periodic variation direction of the first mask 7 .

[0066] Furthermore, a light switch is provided at the aperture stop position, and the function of the light switch is to periodically block the semicircles, small holes, and rectangles distributed on the aperture stop, and only block one of the symmetrical structures at the same time, so that the light beam shining into the pupil of the objective lens 13 is only located on one side of the pupil of the objective lens 13, and the light beam entering the objective lens from one side of the pupil is focused on the surface of the wafer 14 to be detected. When the wafer 14 to be detected moves up or down, it will cause the reflected image to shift (the image refers to the image formed by the first mask 7 on the surface of the wafer to be detected), and return along the original path from the other side of the objective lens 13, please refer to Figure 8 .

[0067] Please refer to Figure 1The first detection unit 120 includes a first focusing lens group 20 and a first detector 21. The first detection unit 130 includes a second focusing lens group 18 and a second detector 19. The first focusing lens group 20 and the second focusing lens group 18 are used to focus the corresponding light beams and detect them by the first detector 21 and the second detector 19 respectively.

[0068] It can be understood that in the optical detection device provided in the above-mentioned embodiment 1, the focused light beam emitted by the light source module 110 passes through the scatterer 3, the coupling lens group 4, the homogenizing device 5, the illumination lens group 6, and the aperture stop 25 to illuminate the first mask plate 7, and then passes through the first relay lens group 8, the first semi-transparent and semi-reflective mirror 9, the reflector 10, the second relay lens group 11, and the second semi-transparent and semi-reflective mirror 12 to image the aperture stop on one side of the pupil of the objective lens 13, and then the objective lens 13 images the first mask plate 7 on the surface of the sample to be detected 14, and the image of the first mask plate is reflected by the surface of the sample to be detected 14 and passes through the objective lens 13 again and is reflected from the pupil of the objective lens The light beam is emitted from the other side, passes through the second semi-transparent and semi-reflective mirror 12, the second relay lens group 11, the reflector 10, the first semi-transparent and semi-reflective mirror 9, and the third relay lens group 15, and enters the third semi-transparent and semi-reflective mirror 16. A part of the light beam is reflected by the third semi-transparent and semi-reflective mirror 16, converged by the first converging lens group 20, and then obtained by the first detector 21; another part of the light beam is transmitted through the third semi-transparent and semi-reflective mirror 16, enters the second mask 17, and is imaged onto the surface of the second mask plate 17, wherein a part of the light beam is blocked by the second mask 17, and another part of the light beam is transmitted by the second mask 17, and then converged by the second converging lens group 18, and then obtained by the second detector 19.

[0069] It can be understood that the up and down movement of the sample 14 to be inspected may cause the image of the first mask plate 7 on the second mask plate 17 to shift left and right.

[0070] See also Figure 8 , which is a schematic diagram of the principle that the light beam reflected by the wafer 14 to be inspected overlaps the image of the first mask 7 on the surface of the second mask 17 provided in this embodiment.

[0071] In this embodiment, the light beam reflected from the surface of the wafer 14 to be detected overlaps the image of the first mask 7 on the surface of the second mask 17. When the wafer 14 to be detected is in focus, it corresponds to CASE1. At this time, the light beam reflected from the wafer 14 to be detected is acquired by the second detection unit 130 after passing through the second mask 17. At this time, the light beam is recorded as Light intensity2; when the wafer 14 to be detected is defocused upward, the light reflected from the wafer 14 to be detected is converged by the second converging lens group 18 after passing through the second mask 17 and acquired by the second detector 19. At this time, the light beam is recorded as Light intensity1; when the wafer 14 to be detected is defocused upward, the light reflected from the wafer 14 to be detected is converged by the second converging lens group 18 after passing through the second mask 17 and acquired by the second detector 19. At this time, the light beam is recorded as Light intensity3.

[0072] See also Fig. 9 , is a schematic diagram of the working signal acquisition principle provided in this embodiment 1. The first detector 21 receives the Normal signal, i.e., the signal that has not passed through the second mask plate 17, and the second detector 19 receives the Focus signal, i.e., the signal that has passed through the second mask plate. Channel A is the signal detected by the detector when one channel is blocked (i.e., the apertures distributed on the aperture are blocked by optical switching), and Channel B is the signal detected by the detector when another channel is blocked, as follows:

[0073] FA = Focus Channel A

[0074] Fa=Focus Channel A Background Offset

[0075] FB=Focus Channel B

[0076] Fb=Focus Channel B Background Offset

[0077] NA=Normal A

[0078] Na=Normal A Background Offset

[0079] NB=Normal B

[0080] Nb=Normal B Background Offset

[0081]

[0082] Please refer to Figure 1The detection imaging system 200 further includes a second relay lens group 2 and a second semi-transparent mirror 12. The imaging unit 210 includes a detection imaging unit 23 and a camera 24. The illumination beam passes through the hollow position of the reflector 10 to generate an intermediate image. The intermediate image is imaged on the surface of the wafer 14 to be detected through the second relay lens group 2, the second semi-transparent mirror 12 and the objective lens 13, and then is acquired by the camera 24 through the detection imaging unit 23 after passing through the objective lens 13.

[0083] In the optical detection device provided in Example 1 of the present application, a focused light beam enters the reflector 10 through the first mask 7, the surrounding of the reflector 10 reflects the incident focused light beam, and then forms an image on the surface of the wafer 14 to be detected through the objective lens 13, the surface of the wafer 14 to be detected reflects the image and then enters the beam splitter 16 through the objective lens 13 and the reflector 10, the image reflected by the beam splitter 16 is acquired by the first detection unit 120, the image transmitted by the beam splitter enters the second mask 17, and the light beam transmitted by the second mask 17 is acquired by the second detection unit 130; the illumination light beam passes through the hollow position of the reflector 10 to generate an intermediate image, the intermediate image is formed on the surface of the wafer 14 to be detected through the objective lens 13, and then acquired by the imaging unit 210 through the objective lens 13.

[0084] The optical detection device provided in Example 1 of the present application uses a reflector with a special shape or position in the optical path so that the imaging beam and the focusing beam are in the same band. Since both the imaging beam and the focusing beam will pass through the objective lens, that is, the objective lens only uses one band and has no requirements for its working distance, the design and processing difficulty and manufacturing cost of the objective lens are reduced.

[0085] Example 2

[0086] See also Fig.10 , is a schematic diagram of the structure of the optical detection device provided in Example 2 of the present application.

[0087] The difference from Example 1 is that the optical detection device provided in Example 2 of the present application can also adopt another mode for the light source module 110, that is, two light sources are adopted, which are denoted as 1 and 2, and the two light sources can alternately flash into the scatterer 3, and then enter the first mask 7 through the scatterer 3; the light spots of the two light sources at the position of the diffuser 3 are conjugate with the entrance pupil of the objective lens 13, and each light source only occupies half of the entrance pupil of the objective lens 13. The structure is more compact by replacing the single light source and the converging lens group with two light sources.

[0088] The optical detection device provided in Example 2 of the present application, the arrangement of other optical components and the optical path transmission method can be referred to in Example 1 and will not be described in detail here.

[0089] The optical detection device provided in Example 2 of the present application uses a reflector with a special shape or position in the optical path so that the imaging beam and the focusing beam are in the same band. Since both the imaging beam and the focusing beam will pass through the objective lens, that is, the objective lens only uses one band and has no requirements for its working distance, the design and processing difficulty and manufacturing cost of the objective lens are reduced.

[0090] Example 3

[0091] See also Fig.11 , is a schematic diagram of the structure of an optical detection device provided in Example 3 of the present application. Only the differences from Example 1 or Example 2 are described below.

[0092] In this embodiment, the second detection unit 130 may also adopt another method, that is, including a second focusing lens group 18 and a second detector 19 , and there are two second detectors 19 , and the light beam focused by the second focusing lens group 18 is acquired by the two second detectors 19 .

[0093] For further information, see Fig.12 , is a schematic diagram of the structure of the second mask 17 provided in Example 3 of the present application.

[0094] In this embodiment, the second mask 17 is a detection grating module, which includes a polarizer 171, a spectroscopic crystal 172 and a detection grating 173 which are sequentially arranged along the propagation direction of the light beam. The polarizer 171 makes the incident light become linearly polarized light. The spectroscopic crystal 172 divides the projected grating image into o light and e light whose polarization directions are perpendicular to each other, and the two polarized images are offset by half a grating period in the direction perpendicular to the detection grating 173. The angle between the light transmission axis of the polarizer 171 and the optical axis of the spectroscopic crystal 172 is adjusted so that when the wafer to be inspected is at the reference zero height, the light intensities of the o light and the e light are equal.

[0095] In this embodiment, a beam splitter prism 26 is also included. The light beam passing through the detection grating 173 enters the beam splitter prism 26, and two moiré fringes with different polarization states are formed by the beam splitter prism 26 and are completely separated in space. The moiré fringes are imaged on two second detectors 19 respectively through the second converging lens group 18. Please refer to Fig.13 .

[0096] The optical detection device provided in Example 3 of the present application, the arrangement of other optical components and the optical path transmission method can be referred to in Example 1 or Example 2 and will not be described in detail here.

[0097] The optical detection device provided in Example 3 of the present application uses a reflector with a special shape or position in the optical path so that the imaging beam and the focusing beam are in the same band. Since both the imaging beam and the focusing beam will pass through the objective lens, that is, the objective lens only uses one band and has no requirements for its working distance, the design and processing difficulty and manufacturing cost of the objective lens are reduced.

[0098] The above are only preferred embodiments of the present application, and only specifically describe the technical principles of the present application. These descriptions are only for explaining the principles of the present application and cannot be interpreted as limiting the scope of protection of the present application in any way. Based on the explanation here, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application, and other specific implementation methods of the present application that can be associated with the technicians in this field without creative work, should be included in the scope of protection of the present application.

Claims

1. An optical detection device, characterized in that: include: An automatic focusing system (100), the automatic focusing system (100) comprising a light source module (110), a first mask (7), a reflector (10), an objective lens (13), a beam splitter (16), a second mask (17), a first detection unit (120) and a second detection unit (130), the light source module (110) being used to emit a focused light beam, and the reflector (10) being hollow in the middle; A detection imaging system (200), the detection imaging system (200) comprising an illumination light source (22), the objective lens (13) and an imaging unit (210), the illumination light source (22) being used to emit an illumination light beam, the focused light beam having the same wavelength as the illumination light beam; The focused light beam enters the reflective element (10) through the first mask (7), the periphery of the reflective element (10) reflects the incident focused light beam, and then forms an image on the surface (14) of the wafer to be detected through the objective lens (13), the surface of the wafer to be detected (14) reflects the image, and then enters the beam splitter (16) through the objective lens (13) and the reflective element (10), the image reflected by the beam splitter (16) is acquired by the first detection unit (120), the image transmitted by the beam splitter (16) enters the second mask (17), and the light beam transmitted by the second mask (17) is acquired by the second detection unit (130); The illumination light beam passes through the hollowed-out position of the reflector (10) to generate an intermediate image, and the intermediate image is imaged on the surface of the wafer (14) to be inspected through the objective lens (13), illuminating the area to be inspected, and then acquired by the imaging unit (210) through the objective lens (13).

2. The optical detection device according to claim 1, characterized in that: The automatic focusing system (100) further comprises a rotatable scatterer (3), and the focused light beam enters the first mask (7) through the scatterer (3).

3. The optical detection device according to claim 2, characterized in that: The light source module (110) comprises a focusing light source (1) and a converging lens group (2); a focusing light beam emitted by the focusing light source is incident on the scatterer (3) via the converging lens group (2).

4. The optical detection device according to claim 2, characterized in that: The light source module (110) comprises two light sources, which can alternately flash into the scatterer (3), the light spots of the two light sources at the position of the diffuser (3) are conjugate with the entrance pupil of the objective lens (13), and each light source only occupies half of the entrance pupil of the objective lens (13).

5. The optical detection device according to claim 2, characterized in that: The automatic focusing system (100) further comprises a coupling lens group (4) and a light homogenizing device (5), and the focusing light beam passing through the scatterer (3) enters the light homogenizing device (5) through the coupling lens group (4) to generate an illumination light spot.

6. The optical detection device according to claim 5, characterized in that: The light homogenizing device (5) is a light homogenizing rod, and the light homogenizing rod is located at the image plane of the coupling lens group (4); or the light homogenizing device (5) is a microlens array, and the microlens array is located at the aperture stop of the coupling lens group (4).

7. The optical detection device according to claim 5 or 6, characterized in that: The reflector (10) is a single reflector, the middle of the single reflector is hollowed out, and the shape of the hollowed out middle is consistent with the shape of the illumination light spot; or the reflector (10) is two reflectors, and the middles of the two reflectors do not overlap to form a hollow, and the illumination light spot passes through the middle of the two reflectors.

8. The optical detection device according to claim 5, characterized in that: The automatic focusing system (100) further comprises an illumination lens group (6), and the illumination light spot enters the first mask (7) through the illumination lens group (6).

9. The optical detection device according to claim 6, characterized in that: In the optical path from the focused light beam to the first mask (7), an aperture stop (25) is also provided at the position of the aperture stop (25) to block the light beam entering the pupil of the objective lens (13); the aperture stop is a semicircle, a small hole or a rectangle with a fixed shape and is symmetrically distributed at the aperture stop; the symmetry axis of the aperture stop passes through the center of the pupil and is perpendicular to the periodic change direction of the first mask (7).

10. The optical detection device according to claim 9, characterized in that: A light switch is also provided at the position of the aperture diaphragm, and the light switch can periodically block the diaphragm, and only blocks one of the symmetrical structures of the diaphragm at the same time, so that the light beam entering the pupil of the objective lens (13) is only located on one side of the pupil of the objective lens (13), and the light beam entering the objective lens (13) from this side is focused on the surface of the wafer (14) to be inspected, and returns along the original path from the other side of the objective lens (13).

11. The optical detection device according to claim 1, characterized in that: The second mask (17) is a detection grating module, and the detection grating module comprises a polarizing plate (171), a spectroscopic crystal (172) and a detection grating (173) which are sequentially arranged along the propagation direction of the light beam, the polarizing plate (171) makes the incident light become linearly polarized light, the spectroscopic crystal (172) separates the projected grating image into o light and e light whose polarization directions are perpendicular to each other, and the two polarized images are offset by half a grating period in a direction perpendicular to the detection grating (173), and the angle between the light transmission axis of the polarizing plate (171) and the optical axis of the spectroscopic crystal (172) is adjusted so that when the wafer to be detected is at a reference zero height, the light intensities of the o light and the e light are equal.

12. The optical detection device according to claim 11, characterized in that: It also includes a beam splitter prism (26), and the light beam passing through the detection grating (173) is incident on the beam splitter prism (26), and two moiré fringes in different polarization states are formed by the beam splitter prism (26) and are completely separated in space.

13. The optical detection device according to claim 12, characterized in that: The second detection unit (130) comprises a second converging lens group (18) and a second detector (19), wherein there are two second detectors (19), and the moiré fringes of two different polarization states passing through the beam splitting prism (26) are imaged on the two second detectors (19) respectively through the second converging lens group (18).

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