Mask detection optical system

Abstract

The utility model discloses a mask detection optical system which comprises an objective lens, a first spectroscope, a second spectroscope, a primary tube lens and a tube lens switching mechanism, wherein the objective lens, the first spectroscope, the primary tube lens, the tube lens switching mechanism and the second spectroscope are sequentially arranged along a detection light path, and at least two secondary tube lenses are connected in the tube lens switching mechanism. The tube lens switching mechanism is used for driving the diode lenses to move so as to switch different diode lenses to move into the detection light path; the light passes through the objective lens and then is transmitted to the first-stage tube lens through the first spectroscope, and then the light passes through the first-stage tube lens and a second-stage tube lens located in the detection light path and then enters the second spectroscope. According to the utility model, the optical magnification factor can be adjusted through the switching tube lens, so that masks with different line widths can be detected, and the detection efficiency is improved.

Description

Technical Field

[0001] The utility model relates to an optical system for mask detection. Background Art

[0002] At present, a mask is a graphic master used in the microelectronic manufacturing process. When detecting the mask, an optical detection system is required to magnify the mask for optical comparison and inspection. A holographic mask inspection system with a spatial filter is disclosed in a Chinese patent with the publication number CN102597890A. In this system, a radiation beam passes through a tube lens and is received by an image sensor. The synthetic field recorded by the image sensor can be used to generate a holographic image of the target part of the mask plate. The holographic image can be compared with a reference image to determine the presence of defects, thereby realizing the detection of the mask.

[0003] Among them, the magnification of the tube lens affects the optical magnification of the mask. When using a tube lens with a small magnification, the optical magnification is small. Therefore, only masks with wide line widths can be detected, but masks with narrow line widths cannot be accurately detected. When using a tube lens with a large magnification, the optical magnification is large. At this time, not only masks with wide line widths can be detected, but also masks with narrow line widths can be detected. However, since the larger the magnification of the tube lens, the larger the optical magnification and the smaller the field of view, when using a tube lens with a large magnification to detect a mask with a wide line width, the detection efficiency is greatly restricted and the detection time is wasted. Therefore, in order to balance the detection efficiency, it is preferred to use a tube lens with a small magnification when detecting a mask with a wide line width. That is to say, when detecting masks with different line widths, a tube lens with a suitable magnification needs to be selected to obtain a suitable optical magnification in order to balance the detection accuracy and efficiency. However, in many existing optical detection systems, only one tube lens is provided. Therefore, during the detection process, the optical magnification is fixed and cannot be changed, and the optical magnification cannot be adjusted by switching the tube lens. Summary of the Utility Model

[0004] The technical problem to be solved by the utility model is to overcome the defects of the prior art and provide an optical system for mask detection, which can adjust the optical magnification by switching the tube lens, and thus can detect masks with different line widths and improve the detection efficiency.

[0005] To solve the above technical problem, the technical solution of the utility model is: an optical system for mask detection, including an objective lens, a first beam splitter, a second beam splitter, a primary tube lens, and a tube lens switching mechanism;

[0006] The objective lens, the first beam splitter, the primary tube lens, the tube lens switching mechanism, and the second beam splitter are arranged in sequence along the detection optical path;

[0007] At least two secondary tube lenses are connected in the tube lens switching mechanism;

[0008] The tube lens switching mechanism is used to drive the secondary tube lens to move so as to switch different secondary tube lenses to move into the detection light path, so that the light passes through the objective lens and then is transmitted to the primary tube lens through the first beam splitter, and then the light passes through the primary tube lens and the secondary tube lens located in the detection light path and then is emitted into the second beam splitter.

[0009] Further, the mask detection optical system also includes a first camera and a second camera;

[0010] The second beam splitter is used to decompose the received light into transmitted light directed to the first camera and reflected light directed to the second camera;

[0011] The first camera is used to capture and collect the transmitted light, and the second camera is used to capture and collect the reflected light.

[0012] Furthermore, the mask detection optical system also includes a lens barrel;

[0013] The second beam splitter is installed in the lens barrel;

[0014] The lens barrel has a first exit portion and a second exit portion, the first camera is connected to the first exit portion, the second camera is connected to the second exit portion, the transmitted light passes through the first exit portion and is emitted to the first camera, and the reflected light passes through the second exit portion and is emitted to the second camera.

[0015] Furthermore, both the first camera and the second camera are TDI cameras.

[0016] A specific structure of the tube lens switching mechanism is further provided, wherein the tube lens switching mechanism comprises a rotating seat and at least two of the secondary tube lenses;

[0017] The rotating seat is rotatably arranged, the diode lenses are connected to the rotating seat and are sequentially spaced along the circumference of the rotating seat, and the rotating seat is used to rotate to switch different diode lenses to move into the detection light path.

[0018] Furthermore, the tube lens switching mechanism also includes a driving motor, which is transmission-connected to the rotating seat and is used to drive the rotating seat to rotate and thus switch different secondary tube lenses to move into the detection light path;

[0019] The rotating seat is provided with mounting through holes corresponding to the diode lenses one by one, and the diode lenses are connected in the corresponding mounting through holes.

[0020] Further, the reticle detection optical system further includes a preview device, and the preview device includes a preview optical path camera, a preview optical path lens, and a preview optical path light source; wherein, the preview optical path lens is connected to the preview optical path camera, the preview optical path light source is located below the preview optical path lens, and the reticle moves to below the objective lens after passing between the preview optical path lens and the preview optical path light source.

[0021] Further, the reticle detection optical system further includes a lens mount, the first beam splitter is installed in the lens mount, and the preview optical path lens is connected to the lens mount through a bracket.

[0022] Further, the reticle detection optical system further includes a focusing device for focusing the objective lens, the objective lens is connected to the focusing device, and the focusing device is used to drive the objective lens to move to adjust the distance between the objective lens and the reticle.

[0023] Further, the first beam splitter is a semi-transmissive and semi-reflective beam splitter, and the second beam splitter is a polarization beam splitter.

[0024] After adopting the above technical solution, the magnifications of the diode lenses connected in the tube lens switching mechanism are different. When it is necessary to detect a reticle with a wide line width, a diode lens with a small magnification is switched through the tube lens switching mechanism and moved into the detection optical path; when it is necessary to detect a reticle with a narrow line width, a diode lens with a large magnification is switched through the tube lens switching mechanism and moved into the detection optical path. It is possible to adjust the optical magnification by switching diode lenses with different magnifications, and thus it is possible to detect reticles with different line widths and at the same time improve the detection efficiency to maximize the detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a perspective view of the reticle detection optical system of the present invention;

[0026] Figure 2 is a front view of the reticle detection optical system of the present invention;

[0027] Figure 3 is a right view of the reticle detection optical system of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] In order to make the content of the present invention easier to be clearly understood, the present invention will be further described in detail below according to specific embodiments and in conjunction with the accompanying drawings.

[0029] Such as Figures 1 to 3As shown in the figure, a mask inspection optical system includes an objective lens 1, a first beam splitter 2, a second beam splitter 3, a diode lens 4, and a lens barrel switching mechanism 100;

[0030] The objective lens 1, the first beam splitter 2, the diode lens 4, the lens barrel switching mechanism 100, and the second beam splitter 3 are arranged in sequence along the detection optical path;

[0031] At least two diode lenses 5 are connected in the lens barrel switching mechanism 100;

[0032] The lens barrel switching mechanism 100 is used to drive the diode lens 5 to move so as to switch different diode lenses 5 to move into the detection optical path. Then, after the light passes through the objective lens 1, it is transmitted through the first beam splitter 2 to the diode lens 4, and then the light passes through the diode lens 4 and the diode lens 5 located in the detection optical path and enters the second beam splitter 3.

[0033] Specifically, the magnifications of the diode lenses 5 connected in the lens barrel switching mechanism 100 are different. When it is necessary to detect a mask 200 with a wide line width, a diode lens 5 with a small magnification is switched by the lens barrel switching mechanism 100 to move into the detection optical path; when it is necessary to detect a mask 200 with a narrow line width, a diode lens 5 with a large magnification is switched by the lens barrel switching mechanism 100 to move into the detection optical path. It is possible to adjust the optical magnification by switching diode lenses 5 with different magnifications, and thus it is possible to detect masks 200 with different line widths and at the same time improve the detection efficiency to maximize the detection efficiency.

[0034] More specifically, if the diode lens 4 is not provided, due to the large entrance pupil of the objective lens 1 and the long distance between the objective lens 1 and the diode lens 5, the aperture of the diode lens 5 needs to be increased and the weight becomes heavier, which will put higher requirements on the load-bearing capacity, stability, and repeatability accuracy of the lens barrel switching mechanism 100, and thus increase the manufacturing cost and manufacturing difficulty. In this embodiment, a hierarchical and parfocal design is adopted, and the diode lens 4 is provided, so as to reduce the aperture and weight of the diode lens 5, and thus reduce the requirements on the load-bearing capacity, stability, and repeatability accuracy of the lens barrel switching mechanism 100, and thus save manufacturing costs and reduce manufacturing difficulty.

[0035] As Figures 1 to 3 shown in the figure, the mask inspection optical system may further include a first camera 6 and a second camera 7;

[0036] The second beam splitter 3 is used to decompose the received light into transmitted light directed to the first camera 6 and reflected light directed to the second camera 7;

[0037] The first camera 6 is used to capture and collect the transmitted light, and the second camera 7 is used to capture and collect the reflected light. Therefore, all information of the chrome layer and the base layer of the mask 200 can be obtained simultaneously through the first camera 6 and the second camera 7, thereby improving the capture rate and detection speed of surface defects of the mask 200.

[0038] like Figures 1 to 3 As shown, the mask detection optical system may further include a lens barrel 8;

[0039] The second beam splitter 3 is installed in the lens barrel 8;

[0040] The lens barrel 8 has a first exit portion 9 and a second exit portion 10, the first camera 6 is connected to the first exit portion 9, the second camera 7 is connected to the second exit portion, the transmitted light passes through the first exit portion 9 to the first camera 6, and the reflected light passes through the second exit portion 10 to the second camera 7.

[0041] Specifically, both the first camera 6 and the second camera 7 can be TDI cameras. In the present embodiment, the pixel size of the TDI camera is 5 μm. The specific structure of the TDI camera is an existing technology well known to those skilled in the art and will not be described in detail in the present embodiment.

[0042] like Figures 1 to 3 As shown, the tube lens switching mechanism 100 includes a rotating seat 11 and at least two of the secondary tube lenses 5;

[0043] The rotating seat 11 is rotatably arranged, the diode lenses 5 are connected to the rotating seat 11 and are sequentially spaced along the circumference of the rotating seat 11 , and the rotating seat 11 is used to rotate to switch different diode lenses 5 to move into the detection light path.

[0044] Specifically, the tube lens switching mechanism 100 may further include a driving motor, which is connected to the rotating seat 11 and is used to drive the rotating seat 11 to rotate and switch different diode lenses 5 to move into the detection light path;

[0045] The rotating seat 11 is provided with mounting through holes corresponding to the diode lenses 5 one by one, and the diode lenses 5 are connected in the corresponding mounting through holes.

[0046] Specifically, the mask detection optical system according to the embodiments of the present application further includes a frame, and the rotating seat 11 is rotatably connected to the frame. In this embodiment, three diode lenses 5 are connected in the tube lens switching mechanism 100, and the magnifications of the three diode lenses 5 are 1.5 times, 2 times, and 2.5 times respectively. By switching different magnification diode lenses 5 into the detection optical path, different magnification optical magnifications can be achieved. Among them, the mask detection optical system according to the embodiments of the present application can achieve a line width detection of 0.72 μm when matching the 1.5 - times diode lens 5, and thus can achieve the technical node of 180 nm in the semiconductor field; it can achieve a line width detection of 0.52 μm when matching the 2 - times diode lens 5, and thus can achieve the technical node of 130 nm in the semiconductor field; it can achieve a line width detection of 0.36 μm when matching the 2.5 - times diode lens 5, and thus can achieve the technical node of 90 nm in the semiconductor field. Therefore, it can efficiently and stably achieve the line width detection of 0.72 μm, 0.52 μm, and 0.36 μm of the mask 200.

[0047] As Figures 1 to 3 shown, the mask detection optical system may further include a preview device, and the preview device may include a preview optical path camera 12, a preview optical path lens 13, and a preview optical path light source 14; wherein, the preview optical path lens 13 is connected to the preview optical path camera 12, the preview optical path light source 14 is located below the preview optical path lens 13, and the mask 200 moves to below the objective lens 1 after passing between the preview optical path lens 13 and the preview optical path light source 14; specifically, when the mask 200 passes between the preview optical path lens 13 and the preview optical path light source 14, the preview optical path camera 12 captures the overall graphic distribution of the mask 200 and the position of the Mark point through the preview optical path lens 13 to generate an overall map, and thus can provide accurate alignment coordinates for subsequent formal detection by the first camera 6 and the second camera 7; in this embodiment, the preview optical path camera 12 may be a line - scan camera, the preview optical path lens 13 may be a low - distortion lens, and the preview optical path light source 14 may be a linear light source.

[0048] As Figures 1 to 3 shown, the mask detection optical system further includes a lens holder 15, the first beam splitter 2 is installed in the lens holder 15, and the preview optical path lens 13 is connected to the lens holder 15 through a bracket 16.

[0049] As Figures 1 to 3As shown, the mask detection optical system may further include a focusing device 17 for focusing the objective lens 1. The objective lens 1 is connected to the focusing device 17, and the focusing device 17 is used to drive the objective lens 1 to move to adjust the distance between the objective lens 1 and the mask 200. Specifically, the specific structure of the focusing device 17 is well-known prior art to those skilled in the art. The focusing device 17 may be connected to the frame, and the focusing device 17 may but is not limited to adopt a WDI autofocus instrument.

[0050] In this embodiment, the first beam splitter 2 may be a semi-transmissive and semi-reflective beam splitter, and the second beam splitter 3 may be a polarization beam splitter. Specifically, the film system of the first beam splitter 2 is used for semi-transmitting and semi-reflecting the detection wavelength, and the film system of the second beam splitter 3 is used for highly transmitting the transmitted light and highly reflecting the reflected light.

[0051] In this embodiment, both the first diode lens 4 and the second diode lens 5 are NUV diode lenses, and the objective lens 1 is a low-magnification and high-numerical-aperture NUV objective lens 1 with a relatively large object field of view. Therefore, it is beneficial to improve the detection efficiency and greatly shorten the detection time. In addition, the numerical aperture of the objective lens 1 can reach 0.8, which can greatly improve the fine measurement accuracy.

[0052] In summary, the magnification ratios of the second diode lenses 5 connected in the tube lens switching mechanism 100 are different. When it is necessary to detect a mask 200 with a wide line width, a second diode lens 5 with a small magnification ratio is switched through the tube lens switching mechanism 100 and moved into the detection optical path. When it is necessary to detect a mask 200 with a narrow line width, a second diode lens 5 with a large magnification ratio is switched through the tube lens switching mechanism 100 and moved into the detection optical path. The optical magnification can be adjusted by switching the second diode lenses 5 with different magnification ratios, so that masks 200 with different line widths can be detected, and the detection efficiency can be improved at the same time, maximizing the detection efficiency.

[0053] In the specific embodiments described above, the technical problems solved, technical solutions and beneficial effects of the present invention are further described in detail. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A mask detection optical system, characterized in that: It comprises an objective lens (1), a first beam splitter (2), a second beam splitter (3), a primary tube lens (4) and a tube lens switching mechanism (100); The objective lens (1), the first beam splitter (2), the primary tube lens (4), the tube lens switching mechanism (100) and the second beam splitter (3) are arranged in sequence along a detection light path; At least two secondary tube lenses (5) are connected to the tube lens switching mechanism (100); The tube lens switching mechanism (100) is used to drive the secondary tube lens (5) to move so as to switch different secondary tube lenses (5) to move into the detection light path, thereby allowing light to pass through the objective lens (1) and then be transmitted to the primary tube lens (4) through the first beam splitter (2). Then, the light passes through the primary tube lens (4) and the secondary tube lens (5) located in the detection light path and then is incident on the second beam splitter (3).

2. The mask detection optical system according to claim 1, characterized in that: Also includes a first camera (6) and a second camera (7); The second beam splitter (3) is used to split the received light into transmitted light directed toward the first camera (6) and reflected light directed toward the second camera (7); The first camera (6) is used to capture and collect the transmitted light, and the second camera (7) is used to capture and collect the reflected light.

3. The mask detection optical system according to claim 2, characterized in that: Also includes a lens barrel (8); The second beam splitter (3) is installed in the lens barrel (8); The lens barrel (8) comprises a first emission portion (9) and a second emission portion (10); the first camera (6) is connected to the first emission portion (9), and the second camera (7) is connected to the second emission portion; the transmitted light passes through the first emission portion (9) and is emitted toward the first camera (6); and the reflected light passes through the second emission portion (10) and is emitted toward the second camera (7).

4. The mask detection optical system according to claim 2, characterized in that: The first camera (6) and the second camera (7) are both TDI cameras.

5. The mask detection optical system according to claim 1, characterized in that: The tube lens switching mechanism (100) comprises a rotating seat (11) and at least two of the secondary tube lenses (5); The rotating seat (11) is rotatably arranged, the diode lenses (5) are connected to the rotating seat (11) and are sequentially spaced along the circumference of the rotating seat (11), and the rotating seat (11) is used to rotate to switch different diode lenses (5) to move into the detection light path.

6. The mask detection optical system according to claim 5, characterized in that: The tube lens switching mechanism (100) also includes a driving motor, which is transmission-connected to the rotating seat (11) and is used to drive the rotating seat (11) to rotate and thereby switch different secondary tube lenses (5) to move into the detection light path; The rotating seat (11) is provided with mounting through holes corresponding one to one with the diode lenses (5), and the diode lenses (5) are connected in the corresponding mounting through holes.

7. The mask detection optical system according to claim 1, characterized in that: The invention also comprises a preview device, the preview device comprising a preview light path camera (12), a preview light path lens (13) and a preview light path light source (14); wherein the preview light path lens (13) is connected to the preview light path camera (12), the preview light path light source (14) is located below the preview light path lens (13), and the mask (200) passes between the preview light path lens (13) and the preview light path light source (14) and then moves to below the objective lens (1).

8. The mask detection optical system according to claim 7, characterized in that: It also comprises a mirror seat (15), wherein the first beam splitter (2) is mounted in the mirror seat (15), and the preview light path lens (13) is connected to the mirror seat (15) via a bracket (16).

9. The mask detection optical system according to claim 1, characterized in that: It also comprises a focusing device (17) for focusing the objective lens (1), the objective lens (1) being connected to the focusing device (17), and the focusing device (17) being used to drive the objective lens (1) to move so as to adjust the distance between the objective lens (1) and the mask plate (200).

10. The mask detection optical system according to claim 1, characterized in that: The first beam splitter (2) is a semi-transmissive, semi-reflective beam splitter, and the second beam splitter (3) is a polarizing beam splitter.

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