An optical detection device

Abstract

The optical detection device provided in the application is characterized in that: the focusing light beam enters the reflecting element through the first mask, the surrounding of the reflecting element reflects the incident focusing light beam, and then the focusing light beam is imaged on the surface of the wafer to be detected through the objective lens; the wafer to be detected reflects the image, and then the image enters the beam splitter through the objective lens and the reflecting element; the image reflected by the beam splitter is acquired by the first detection unit; the image transmitted by the beam splitter enters the second mask, and the light beam transmitted by the second mask is acquired by the second detection unit; the illumination light beam passes through the hollow position of the reflecting element to generate an intermediate image, the intermediate image is imaged on the surface of the wafer to be detected through the objective lens, and then the image is acquired by the imaging unit through the objective lens; and the application uses a special-shaped or positioned reflecting element in the optical path, so that the illumination light beam and the focusing light beam are in the same wave band, the imaging light beam and the focusing light beam pass through the objective lens, that is, the objective lens only uses one wave band, and there is no requirement for the working distance, thereby reducing the design, processing difficulty and manufacturing cost of the objective lens.

Description

TECHNICAL FIELD

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

[0002] In a semiconductor detection device, the numerical aperture of the objective lens used by the detection imaging system is large, and the depth of focus of the objective lens is often in the sub-micron level. However, the moving platform for detecting the wafer has certain irregular motion, the clamp for fixing the wafer has certain warping, and the silicon wafer itself has a geometric structure in the vertical direction, so that the detection plane is easy to exceed the depth of focus of the objective lens. In order to enable the detection system to perform real-time detection within the depth of focus, a real-time automatic focusing system is essential.

[0003] The prior art mainly has coaxial detection. In the coaxial detection scheme, the detection imaging beam and the automatic focusing beam will pass through the objective lens, and the working wavelength of the detection imaging system and the working wavelength of the automatic focusing system are two wavelengths that are far apart. The imaging beam and the automatic focusing beam are combined and separated by a dichroic mirror. The working wavelength of the detection imaging system is a shorter wavelength, which is beneficial to improve the imaging resolution of the system. The wavelength of the automatic focusing system is usually longer, which is convenient for isolation from the imaging wavelength. This requires the objective lens to be designed and coated for the two wavelengths when designed, which increases the difficulty of design and processing of the objective lens and the manufacturing cost. SUMMARY

[0004] Therefore, the present application provides an optical detection device to reduce the difficulty of design and processing of the objective lens and the manufacturing cost.

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

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

[0007] An automatic focusing system (100) comprising a light source module (110), a first mask (7), a reflecting element (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 focusing beam, and the reflecting element (10) is hollow in the middle.

[0008] A detection imaging system (200) comprising an illumination light source (22), the objective lens (13), and an imaging unit (210). The illumination light source (22) is used to emit an illumination beam, and the focusing beam and the illumination beam have the same wavelength.

[0009] The focused light beam enters the first mask (7) and then the reflecting element (10), the periphery of the reflecting element (10) reflects the focused light beam, and then the image is formed on the wafer surface (14) to be detected by the objective lens (13), the wafer surface (14) to be detected reflects the image, and then the image enters the beam splitter (16) through the objective lens (13) and the reflecting 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), 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 hollow position of the reflecting element (10) to generate an intermediate image, and the intermediate image is imaged on the wafer surface (14) to be detected by the objective lens (13), and then the image is acquired by the imaging unit (210) through the objective lens (13).

[0011] In some embodiments, the automatic focusing system (100) further comprises a rotatable scattering body (3), and the focused light beam enters the first mask (7) through the scattering body (3).

[0012] In some embodiments, the light source module (110) comprises a focused light source (1) and a converging lens group (2), and the focused light beam emitted by the focused light source enters the scattering body (3) through the converging lens group (2).

[0013] In some embodiments, the light source module (110) comprises two light sources, which can alternately flash into the scattering body (3), the light spots of the two light sources at the position of the scattering body (3) are conjugated 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 embodiments, the automatic focusing system (100) further comprises a coupling lens group (4) and a light homogenization device (5), and the focused light beam passing through the scattering body (3) enters the light homogenization device (5) through the coupling lens group (4) to generate an illumination light spot.

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

[0016] In some embodiments, the reflecting member (10) is a single mirror with a hollow in the middle, the shape of the hollow is consistent with the shape of the illumination spot; or the reflecting member (10) is two mirrors, and the middle of the two mirrors does not coincide to form a hollow, and the illumination spot passes through the middle of the two mirrors.

[0017] In some embodiments, the auto-focusing system (100) further comprises an illumination mirror group (6), and the illumination spot passes through the illumination mirror group (6) to the first mask (7).

[0018] In some embodiments, in the light path of the focusing beam to the first mask (7), a diaphragm is arranged at the position of the aperture stop (25) to shield the light beam entering the pupil of the objective lens (13), the diaphragm is a fixed shape semicircle or pinhole or rectangle, and is symmetrically distributed at the aperture stop, and the symmetry axis of the diaphragm passes through the center of the pupil and is perpendicular to the period change direction of the first mask (7).

[0019] In some embodiments, the position of the aperture stop is further provided with a light opening, which can periodically shield the diaphragm, and at the same time, only one of the symmetric structures of the diaphragm is shielded, 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 the other side returns along the original path.

[0020] In some embodiments, the second mask (17) is a detection grating module, which comprises a polarizer (171), a light splitting crystal (172) and a detection grating (173) arranged in sequence along the light beam propagation direction, the polarizer (171) makes the incident light into linearly polarized light, the light splitting crystal (172) divides the projection grating image into o light and e light with perpendicular polarization directions, and the two polarization 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 light splitting crystal (172) is adjusted, so that when the wafer to be detected is at the reference zero height, the light intensities of the o light and the e light are equal.

[0021] In some embodiments, a light splitting prism (26) is further included, and the light beam passing through the detection grating (173) enters the light splitting prism (26), and two different polarization state Moiré fringes formed by the light splitting prism (26) 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 the two second detectors (19) are used to image the two different polarized Moire fringes of the light splitting prism (26) through the second converging lens group (18).

[0023] The technical scheme provided by the present application has the following beneficial effects:

[0024] The optical detection device provided by the present application has the following advantages: the focused light beam enters the reflecting member (10) through the first mask (7), the periphery of the reflecting member (10) reflects the incident focused light beam, and then the reflected light beam is imaged on the surface of the wafer to be detected (14) through the objective lens (13), the surface of the wafer to be detected (14) reflects the image, and then the reflected image enters the beam splitter (16) through the objective lens (13) and the reflecting member (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 reflecting member (10) to generate an intermediate image, and the intermediate image is imaged on the surface of the wafer to be detected (14) through the objective lens (13), and then the intermediate image is acquired by the imaging unit (210) through the objective lens (13). The present application uses a special-shaped or specially-positioned reflecting member in the optical path, so that the imaging light beam and the focused light beam are in the same wave band. Since the imaging light beam and the focused light beam both pass through the objective lens, the objective lens only uses one wave band, and the working distance is not required, thereby reducing the design, processing difficulty and manufacturing cost of the objective lens. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical scheme of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application or the prior art description. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0026] Figure 1 The structure schematic diagram of the optical detection device provided by Embodiment 1 of the present application.

[0027] Figure 2 The structure schematic diagram of the light homogenizing device provided by Embodiment 1 of the present application.

[0028] Figure 3 Another structure schematic diagram of the light homogenizing device provided by Embodiment 1 of the present application.

[0029] Figure 4is a structural schematic diagram of the reflecting member provided in Embodiment 1 of the present application.

[0030] Figure 5 is a structural schematic diagram of the reflecting member provided in Embodiment 1 of the present application.

[0031] Figure 6 is a structural schematic diagram of the light barrier provided in Embodiment 1 of the present application.

[0032] Figure 7 is a structural schematic diagram of the reflecting image offset when the wafer to be detected moves upward or downward provided in Embodiment 1 of the present application.

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

[0034] Figure 9 is a schematic diagram of the principle of collecting the working signal provided in Embodiment 1 of the present application.

[0035] Figure 10 is a structural schematic diagram of the optical detection device provided in Embodiment 2 of the present application.

[0036] Figure 11 is a structural schematic diagram of the optical detection device provided in Embodiment 3 of the present application.

[0037] Figure 12 is a structural schematic diagram of the second mask provided in Embodiment 3 of the present application.

[0038] Figure 13 is a schematic diagram of the form of the Moiré fringes of two different polarization states formed by the light splitting prism provided in Embodiment 3 of the present application. DETAILED DESCRIPTION

[0039] The embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0040] In the description of the present application, it should be understood that the terms "upper", "lower", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0041] In addition, the terms "first", "second", etc. are used only for descriptive purposes and are not to be construed as indicating or implying relative importance or an indicated number of technical features. Therefore, the features defined as "first", "second", etc. can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0042] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is further described in detail below in combination with the drawings and embodiments.

[0043] Embodiment 1

[0044] Please refer to Figure 1 The structure schematic diagram of the optical detection device provided by Embodiment 1 of the present application includes an autofocus system 100 and a detection imaging system 200, and the specific implementation modes of each component and the mutual connection relationship thereof are described in detail below.

[0045] The autofocus system 100 includes a light source module 110, a first mask 7, a reflecting member 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 for emitting a focusing light beam. The reflecting member 10 is hollow in the middle.

[0046] The detection imaging system 200 includes an illumination light source 22, the objective lens 13 and an imaging unit 210. The illumination light source 22 is used for emitting an illumination light beam, and the wavelength of the focusing light beam is the same as that of the illumination light beam.

[0047] The optical detection device provided by the present application works as follows:

[0048] The focusing light beam enters the reflecting member 10 through the first mask 7, the surrounding of the reflecting member 10 reflects the incident focusing light beam, and then the image is formed on the surface of the wafer to be detected 14 through the objective lens 13. The image is reflected by the surface of the wafer to be detected 14, and then enters the beam splitter 16 through the objective lens 13 and the reflecting member 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, 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 transmits through the hollow position of the reflecting member 10 to generate an intermediate image, and the intermediate image is imaged on the surface of the wafer to be detected 14 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 optical detection device uses the intermediate hollowed-out reflecting element 10 in the optical path, the illumination light beam can directly pass through the middle of the reflecting element 10, the focusing light beam of the autofocusing system is reflected from the surrounding of the reflecting element 10, and the transmitted and reflected two light beams re-enter the objective lens 13, so that the imaging light beam and the focusing light beam are in the same waveband, because the imaging light beam and the focusing light beam will pass through the objective lens, that is, the objective lens only uses one waveband, and there is no requirement for the working distance, which reduces the design, processing difficulty and manufacturing cost of the objective lens.

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

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

[0053] Please refer to Figure 2 The structure diagram of the light homogenizing device 5 provided for the embodiment 1 is shown.

[0054] In the embodiment, the light homogenizing device 5 is a microlens array structure. The microlens array is located at the intermediate pupil of the coupling lens group 4, and the microlens array is used when the system has a small divergence angle, so as to better meet the actual application requirements.

[0055] Please refer to Figure 3 The other structure diagram of the light homogenizing device 5 provided for the embodiment 1 is shown.

[0056] In the embodiment, the light homogenizing device 5 is a light homogenizing rod. The light homogenizing rod is located at the image plane of the coupling lens group 4, and the light homogenizing rod is used when the system has a large divergence angle, so as to better meet the actual application requirements.

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

[0058] Please refer to Figure 4 The structure diagram of the reflecting element 10 provided for the embodiment 1 is shown.

[0059] In the embodiment, the reflecting member 10 is a single mirror, and the middle part of the single mirror is hollowed out, and the shape of the hollowed-out part 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 the middle part of the single mirror is also rectangular.

[0060] Please refer to Figure 5 , another structural diagram of the reflecting member 10 provided in the embodiment 1.

[0061] In the embodiment, the reflecting member 10 can also be two mirrors, and the middle parts of the two mirrors do not coincide to form a hollow, and the illumination spot can also pass through the middle parts of the two mirrors.

[0062] Please refer to Figure 1 , the auto-focusing system 100 further comprises 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 auto-focusing system, the light path of the light source module 110 from the light source to the first mask 7, in order to make the incident light beam enter the objective lens 13 from the pupil side of the objective lens, a diaphragm is used to block the pupil at the position of the aperture stop 25 of the illumination light beam, for example, the aperture stop 25 can be arranged in the light path passing through the illumination lens group 6.

[0064] Please refer to Figure 6 , a structural diagram of the aperture stop 25 provided in the embodiment.

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

[0066] Further, a light opening is arranged at the position of the aperture stop, and the function of the light opening is to periodically block the semicircle, small hole, rectangle, etc. distributed on the aperture stop, and only one of the symmetric structures is blocked 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 from one side of the pupil is focused on the surface of the wafer to be detected 14. When the wafer to be detected 14 moves up or down, the reflected image (the image refers to the image of the first mask 7 on the surface of the wafer to be detected) will be offset, and returns 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 detecting unit 120 comprises a first converging lens group 20 and a first detector 21. The second detecting unit 130 comprises a second converging lens group 18 and a second detector 19. The first converging lens group 20 and the second converging lens group 18 are used to converge the corresponding light beams and are detected by the first detector 21 and the second detector 19 respectively.

[0068] It can be understood that, in the optical detection device provided in Embodiment 1, the focused light beams emitted by the light source module 110 pass through the scattering body 3, the coupling lens group 4, the light homogenizing device 5, the illumination lens group 6, the aperture diaphragm 25, and then illuminate the first mask plate 7. Then, the light beams pass through the first relay lens group 8, the first half-mirror 9, the reflecting element 10, the second relay lens group 11, the second half-mirror 12, and then the aperture diaphragm is imaged on one side of the pupil of the objective lens 13. Then, the objective lens 13 images the first mask plate 7 on the surface of the sample 14 to be detected. The image of the first mask plate is reflected by the surface of the sample 14 to be detected, and then passes through the objective lens 13 again and exits from the other side of the objective lens pupil. Then, the light beams pass through the second half-mirror 12, the second relay lens group 11, the reflecting element 10, the first half-mirror 9, the third relay lens group 15, and then enter the third half-mirror 16. Part of the light beams is reflected by the third half-mirror 16, is converged by the first converging lens group 20, and is acquired by the first detector 21. Another part of the light beams passes through the third half-mirror 16, enters the second mask plate 17, and then is imaged on the surface of the second mask plate 17. Part of the light beams is blocked by the second mask plate 17, and another part of the light beams is transmitted by the second mask plate 17, is converged by the second converging lens group 18, and is acquired by the second detector 19.

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

[0070] Please refer to Figure 8 The principle diagram of the embodiment provided in the present application shows that the light beams reflected by the sample 14 to be detected overlap the image of the first mask plate 7 on the surface of the second mask plate 17.

[0071] In the present embodiment, the light beam reflected by the wafer 14 to be detected will overlap the image of the first mask 7 on the surface of the second mask 17, which corresponds to CASE 1 when the wafer 14 to be detected is in focus. At this time, the light beam reflected by the wafer 14 to be detected will pass through the second mask 17 and be collected by the second collection lens group 18 and then be collected by the second detector 19, which is recorded as Light intensity 2. When the wafer 14 to be detected is upward out of focus, the light beam reflected by the wafer 14 to be detected will pass through the second mask 17 and be collected by the second collection lens group 18 and then be collected by the second detector 19, which is recorded as Light intensity 1. When the wafer 14 to be detected is downward out of focus, the light beam reflected by the wafer 14 to be detected will pass through the second mask 17 and be collected by the second collection lens group 18 and then be collected by the second detector 19, which is recorded as Light intensity 3.

[0072] Please refer to Figure 9 The working signal collection schematic diagram provided for the present embodiment 1 is shown in FIG. 2. The first detector 21 receives the Normal signal, i.e. the signal not passing through the second mask plate 17, and the second detector 19 receives the Focus signal, i.e. the signal passing through the second mask plate. Channel A is the signal detected by the detector when one of the two light barriers is blocked, i.e. the light barrier is used to block the light barrier distributed on the aperture diaphragm, and Channel B is the signal detected by the detector when the other light barrier is blocked. The details are 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 also includes a second relay mirror 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 cutout position of the reflector 10 to generate an intermediate image. The intermediate image is imaged onto the surface of the wafer 14 to be inspected by the second relay mirror group 2, the second semi-transparent mirror 12 and the objective lens 13, and then captured by the camera 24 through the detection imaging unit 23 after passing through the objective lens 13.

[0083] The optical inspection device provided in Embodiment 1 of this application has a focused beam entering the reflector 10 through the first mask 7. The reflector 10 reflects the incident focused beam around itself, and then the beam is imaged onto the surface of the wafer 14 to be inspected by the objective lens 13. The surface of the wafer 14 to be inspected reflects the image, which 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 beam transmitted by the second mask 17 is acquired by the second detection unit 130. The illumination beam passes through the cutout position of the reflector 10 to generate an intermediate image. The intermediate image is imaged onto the surface of the wafer 14 to be inspected by the objective lens 13, and then acquired by the imaging unit 210 through the objective lens 13.

[0084] The optical detection device provided in Embodiment 1 of this application uses a reflector of a special shape or position in the optical path to make the imaging beam and the focusing beam the same wavelength. Since both the imaging beam and the focusing beam pass through the objective lens, the objective lens only uses one wavelength and there is no requirement for its working distance, which reduces the design, processing difficulty and manufacturing cost of the objective lens.

[0085] Example 2

[0086] Please see Figure 10 This is a schematic diagram of the optical detection device provided in Embodiment 2 of this application.

[0087] Unlike Embodiment 1, the optical detection device provided in Embodiment 2 of this application can also employ two light sources, denoted as 1 and 2, in its light source module 110. These two light sources can alternately flash into the diffuser 3 and then enter the first mask 7 via the diffuser 3. The light spots of the two light sources at the diffuser 3 are conjugate with the entrance pupil of the objective lens 13, and each light source occupies only half of the entrance pupil of the objective lens 13. By replacing the single light source and converging lens group with two light sources, the structure is more compact.

[0088] The optical detection device provided in Embodiment 2 of this application can be referenced in Embodiment 1 for the arrangement of other optical components and the optical path transmission method, and will not be repeated here.

[0089] The optical detection device provided in the embodiment 2 of the present application uses a special shape or position of the reflecting element in the optical path, so that the imaging light beam and the focusing light beam are in the same waveband. Since the imaging light beam and the focusing light beam both pass through the objective lens, the objective lens only uses one waveband, and has no requirement on the working distance, thereby reducing the design, processing difficulty and manufacturing cost of the objective lens.

[0090] Embodiment 3

[0091] Please refer to Figure 11 The structure schematic diagram of the optical detection device provided in the embodiment 3 of the present application is shown in FIG. 3. The following only describes the differences from the embodiment 1 or the embodiment 2.

[0092] In the embodiment, the second detection unit 130 can also adopt another mode, that is, comprising a second converging mirror group 18 and a second detector 19, and the second detector 19 is 2, and the light beam converged by the second converging mirror group 18 is acquired by the 2 second detectors 19.

[0093] Further, please refer to Figure 12 The structure schematic diagram of the second mask 17 provided in the embodiment 3 of the present application is shown in FIG. 4.

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

[0095] In the embodiment, the light splitting prism 26 is further included. The light beam passing through the detection grating 173 is incident into the light splitting prism 26, and the Moiré fringes with two different polarization states formed by the light splitting prism 26 are completely separated in space, and are respectively imaged on the 2 second detectors 19 through the second converging mirror group 18. Please refer to Figure 13 .

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

[0097] The optical detection device provided in the embodiment 3 of the present application uses a special shape or position of the reflecting element in the optical path, so that the imaging light beam and the focusing light beam are in the same waveband. Since the imaging light beam and the focusing light beam both pass through the objective lens, the objective lens only uses one waveband, and has no requirement on the working distance, thereby reducing the design, processing difficulty and manufacturing cost of the objective lens.

[0098] The above merely preferred embodiments of the present application have been described, and the technical principles of the present application have been specifically described, and these descriptions are only for explaining the principles of the present application, and cannot be explained as the limitation of the protection scope of the present application in any way. Based on the explanations herein, any modification, equivalent replacement and improvement made within the spirit and principle of the present application, and other specific embodiments of the present application which can be thought by those skilled in the art without creative labor, should be included in the protection scope of the present application.

Claims

1. An optical detection device, characterized in that, include: An autofocusing system (100) includes 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 beam, and the reflector (10) has a hollow center. The detection imaging system (200) includes an illumination source (22), the objective lens (13) and an imaging unit (210). The illumination source (22) is used to emit an illumination beam, and the focused beam has the same wavelength as the illumination beam. The focused beam enters the reflector (10) through the first mask (7). The surrounding area of ​​the reflector (10) reflects the incident focused beam, which is then imaged onto the surface of the wafer (14) to be tested by the objective lens (13). The surface of the wafer (14) to be tested reflects the image, which 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 (16) enters the second mask (17), and the beam transmitted by the second mask (17) is acquired by the second detection unit (130). The illumination beam passes through the cutout position of the reflector (10) to generate an intermediate image. The intermediate image is imaged onto the surface of the wafer (14) to be inspected by the objective lens (13), illuminating the area to be inspected, and then acquired by the imaging unit (210) through the objective lens (13). In the optical path from the focused beam to the first mask (7), an aperture stop is also provided to block the 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. The axis of symmetry of the aperture stop passes through the center of the pupil and is perpendicular to the periodic change direction of the first mask (7). The aperture stop is also provided with an optical switch. The optical switch can periodically block the aperture stop, and at the same time only one of the symmetrical structures of the aperture stop is blocked, 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 that side is focused on the surface of the wafer (14) to be inspected, and returns from the other side of the objective lens (13) along the original path; The second detection unit (130) includes a second converging mirror group (18) and a second detector (19). The light beam reflected from the surface of the wafer to be tested (14) superimposes the image of the first mask (7) onto the surface of the second mask (17). At this time, the light beam reflected from the wafer to be tested (14) is acquired by the second detection unit (130) after passing through the second mask (17).

2. The optical detection device as described in claim 1, characterized in that, The autofocusing system (100) also includes a rotatable scatterer (3), through which the focused beam enters the first mask (7).

3. The optical detection device as described in claim 2, characterized in that, The light source module (110) includes a focusing light source (1) and a converging mirror group (2). The focused beam emitted from the focusing light source enters the scatterer (3) through the converging mirror group (2).

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

5. The optical detection device as described in claim 2, characterized in that, The autofocus system (100) also includes a coupling mirror group (4) and a light homogenizer (5). The focused beam that passes through the scatterer (3) enters the light homogenizer (5) through the coupling mirror group (4) to generate an illumination spot.

6. The optical detection device as described in claim 5, characterized in that, The light-diffusing device (5) is a light-diffusing rod located at the image plane of the coupling mirror group (4); or the light-diffusing device (5) is a microlens array located at the aperture stop of the coupling mirror group (4).

7. The optical detection device as described in claim 5 or 6, characterized in that, The reflector (10) is a single reflector with a hollow center, the shape of which is consistent with the shape of the illumination spot; or the reflector (10) is two reflectors with the two reflectors not overlapping to form a hollow center, and the illumination spot passes through the center of the two reflectors.

8. The optical detection device as described in claim 5, characterized in that, The autofocus system (100) also includes an illumination lens group (6), through which the illumination spot enters the first mask (7).

9. The optical detection device as described in claim 1, characterized in that, The second mask (17) is a probe grating module. The probe grating module includes a polarizer (171), a beam splitter (172), and a probe grating (173) arranged sequentially along the beam propagation direction. The polarizer (171) makes the incident light linearly polarized. The beam splitter (172) divides the projected grating image into o-light and e-light with mutually perpendicular polarization directions. The two polarized images are misaligned by half a grating period in the direction perpendicular to the probe grating (173). The angle between the transmission axis of the polarizer (171) and the optical axis of the beam splitter (172) is adjusted so that the light intensities of the o-light and e-light are equal when the wafer to be tested is at the reference zero position height.

10. The optical detection device as described in claim 9, characterized in that, It also includes a beam splitter (26), through which the light beam passing through the detection grating (173) enters the beam splitter (26), and the beam splitter (26) forms two different polarization states of moiré fringes that are completely separated in space.

11. The optical detection device as described in claim 10, characterized in that, The second detection unit (130) includes a second converging mirror group (18) and a second detector (19). There are two second detectors (19). The two different polarization states of moiré fringes obtained by the beam splitter (26) are imaged onto the two second detectors (19) by the second converging mirror group (18).

Images