An optical structure

Abstract

The present invention discloses an optical structure, belonging to the technical field of mask plate detection, comprising a reflector group, the reflector group is connected to two industrial cameras, a PBS prism group is arranged at the bottom of the reflector group, a transmission mirror group is arranged below the PBS prism group, and an objective lens group is arranged below the transmission mirror group. By adopting the PBS prism group, reflected light and transmitted light can be accurately separated from a beam of mixed light and transmitted to two industrial cameras at the same time, respectively, overcoming the shortcomings of the prior art in processing imaging light sources containing both reflected light and transmitted light, so that in application scenarios such as mask plate detection, reflected light imaging and transmitted light imaging information can be obtained simultaneously, providing the possibility for comprehensive evaluation of mask plate characteristics.

Description

Technical Field

[0001] The invention relates to an optical structure and belongs to the technical field of mask plate detection. Background Art

[0002] In the field of mask inspection, reflected light and transmitted light correspond to different inspection conditions and are used to evaluate different characteristics of the mask. Reflected light inspection is mainly used to identify tiny defects on the mask surface, such as scratches, pits, and bumps. These defects may cause errors in pattern transfer during the photolithography process. In addition, the thickness of the film on the mask surface and the flatness of the mask surface can be measured by analyzing the interference fringes of the reflected light. Transmitted light inspection is mainly used to identify pattern defects on the mask, such as broken lines, inconsistent line widths, missing patterns, etc. These defects will directly affect the pattern transfer during the photolithography process.

[0003] In addition, it can also be used for transparency detection to ensure that light will not be significantly attenuated or distorted when passing through these areas; to detect alignment marks on the mask to ensure accurate alignment between the mask and the silicon wafer during the photolithography process; and to evaluate the resolution of the mask to ensure that it can support high-resolution photolithography. In the field of more advanced mask detection, even reflected light and transmitted light are turned on at the same time for actual measurement production to apply to special working conditions.

[0004] In today's mainstream optical imaging systems, they use prisms in the optical structure to transmit only one type of light (containing only reflected light or transmitted light) or a mixed light (containing both reflected light and transmitted light) semi-reflectively and semi-transmittively to two cameras respectively.

[0005] When the imaging light source uses only a single light source (including only reflected light or transmitted light), adding a prism can easily achieve half reflection and half transmission and transmit it to two cameras at the same time. However, when the imaging light source uses two light sources at the same time (including both reflected light and transmitted light), there is no mature technical means on the market to accurately separate the reflected light and the transmitted light and transmit them to two cameras at the same time. Summary of the invention

[0006] The object of the present invention is to provide an optical structure to solve the problems raised in the above background technology.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] Compared with the prior art, the present invention provides an optical structure, including a reflector group, the reflector group is connected to two industrial cameras, a PBS prism group is arranged at the bottom of the reflector group, a transmission lens group is arranged below the PBS prism group, and an objective lens group is arranged below the transmission lens group; the PBS prism group includes a shell, a polarization splitter prism is arranged inside the shell, and a plurality of through holes for light to pass through are opened on the shell.

[0009] Furthermore, the polarization beam splitter prism is formed into a cubic structure by coating a multilayer film structure on the inclined surfaces of two right-angle prisms and then gluing them together.

[0010] Furthermore, the reflector group includes a connector and a fixing seat for connecting to an industrial camera, the cross-section of the fixing seat is a right triangle, a prism is arranged on the inclined side of the fixing seat, a notch corresponding to the prism is opened on the inclined side of the fixing seat, and a fixing plate for fixing the prism is connected to the fixing seat by bolts.

[0011] Furthermore, the transmission mirror group includes a fiber optic light source, and a light source reflector group 1 and a light source reflector group 2 for changing the light transmission angle are arranged on one side of the fiber optic light source, and a lens barrel is arranged at the bottom of the light source reflector group 2.

[0012] Furthermore, the objective lens group includes a plurality of objective lenses and a switch for driving the plurality of objective lenses.

[0013] Furthermore, it also includes a fixed plate, and the reflector group, PBS prism group and transmission mirror group are installed on the fixed plate.

[0014] Furthermore, it also includes a mounting plate, on which a mounting platform is slidably connected via a slide rail, and a motor for driving the mounting platform to move up and down is arranged on the mounting plate, and the mounting platform is connected to the objective lens group.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] By using the PBS prism group, the reflected light and the transmitted light can be accurately separated from a mixed light beam and transmitted to two industrial cameras at the same time. This overcomes the shortcomings of the existing technology in processing imaging light sources containing both reflected light and transmitted light. In application scenarios such as mask plate inspection, the reflected light imaging and transmitted light imaging information can be obtained simultaneously, making it possible to comprehensively evaluate the characteristics of the mask plate.

[0017] The platform only needs to move once to obtain two imaging pictures. Compared with the traditional technology that may need to move twice to obtain reflected light and transmitted light imaging due to various factors of the motion system, the present invention greatly improves the detection efficiency. At the same time, it solves the positioning error problem of inaccurate alignment when the two pictures are overlapped and compared, effectively improves the detection accuracy, and reduces the occurrence of misjudgment of mask quality due to detection errors, which is of great significance for improving the production quality and efficiency of related industries such as lithography processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0019] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0020] Figure 2 It is a rear view of the overall structure of the present invention;

[0021] Figure 3 It is a schematic diagram of the internal structure of the reflector assembly of the present invention;

[0022] Figure 4 It is a structural schematic diagram of the PBS prism group of the present invention;

[0023] Figure 5 It is a schematic structural diagram of the transmission lens assembly of the present invention.

[0024] In the figure: 1, fixing plate; 2, reflecting mirror group; 3, PBS prism group; 4, transmission mirror group; 5, objective lens group; 6, mounting plate; 7, mounting table; 8, motor; 201, fixing seat; 202, prism; 203, fixing plate; 301, shell; 302, through hole; 303, polarization beam splitter prism; 401, fiber optic light source; 402, light source reflecting mirror group 1; 403, light source reflecting mirror group 2; 404, lens barrel. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] See also Figure 1-Figure 5, the present invention provides a technical solution:

[0027] like Figure 1-Figure 2 As shown, an optical structure includes a reflector group 2, which is connected to two industrial cameras, a PBS prism group 3 is arranged at the bottom of the reflector group 2, a transmission lens group 4 is arranged below the PBS prism group 3, and an objective lens group 5 is arranged below the transmission lens group 4; the PBS prism group 3 includes a shell 301, and a polarization beam splitter prism 303 is arranged inside the shell 301. The polarization beam splitter prism 303 is formed into a cubic structure by coating a multilayer film structure on the inclined surfaces of two right-angle prisms and then gluing them together. The shell 301 is provided with a plurality of through holes 3 for light to pass through. 02, so that after the mixed light enters the PBS prism group 3, the reflected light and the transmitted light can be accurately separated according to the polarization characteristics of the light. The reflected light is reflected along a specific optical path to the reflector group 2, and the transmitted light continues to be transmitted downward through the polarization beam splitter prism 303. By adopting the PBS prism group 3, the reflected light and the transmitted light can be accurately separated in a beam of mixed light and transmitted to two industrial cameras respectively at the same time. Only one movement of the platform is required to obtain two imaging pictures, and the positioning error problem of inaccurate alignment when the two pictures are overlapped and compared when the motion system moves twice due to various factors is solved.

[0028] Furthermore, it also includes a fixed plate 1 and a mounting plate 6, and the reflector group 2, the PBS prism group 3 and the transmission lens group 4 are mounted on the fixed plate 1. The fixed plate 1 provides a stable mounting base for these optical components to ensure the relative position stability between the components, thereby ensuring the accuracy and stability of the optical path. The mounting plate 6 is slidably connected with a mounting platform 7 through a slide rail, and the mounting plate 6 is provided with a motor 8 for driving the mounting platform 7 to move up and down. The mounting platform 7 is connected to the objective lens group 5. The mounting platform 7 is driven up and down by the motor 8 to adjust the height position of the objective lens group 5, and then the focal length and other parameters of the entire optical structure are adjusted to adapt to detection objects such as mask plates with different thicknesses or different detection requirements.

[0029] Among them, the objective lens group 5 can switch different objective lenses according to different detection requirements to adjust the imaging magnification, resolution and other parameters of the detection object such as the mask plate, so as to make the detection more accurate and comprehensive.

[0030] like Figure 3 As shown, the reflector group 2 includes a connector and a fixing seat 201 for connecting to an industrial camera. The cross-section of the fixing seat 201 is a right triangle. A prism 202 is arranged on the inclined side of the fixing seat 201. A notch corresponding to the prism 202 is opened on the inclined side of the fixing seat 201. A fixing plate 203 for fixing the prism 202 is connected to the fixing seat 201 by bolts. The above structure can be used to receive the reflected light separated by the PBS prism group 3 and transmit it to the industrial camera connected thereto to obtain the reflected light imaging information.

[0031] like Figure 5 As shown, the transmission mirror group 4 provides the optical path basis of the transmitted light part for the entire optical structure. The transmission mirror group 4 includes an optical fiber light source 401. One side of the optical fiber light source 401 is provided with a light source reflector group 1 402 and a light source reflector group 2 403 for changing the light transmission angle. The bottom of the light source reflector group 2 403 is provided with a lens barrel 404. The light generated by the optical fiber light source 401 is transmitted in the lens barrel 404 after the light source reflector group 1 402 and the light source reflector group 2 403 adjust the angle and act together with the light from the objective lens group 5. Finally, part of the light is separated through the PBS prism group 3 and transmitted to another industrial camera

[0032] Furthermore, the objective lens group 5 includes a plurality of objective lenses and a switch for driving the plurality of objective lenses.

[0033] The working process of this embodiment is as follows: in practical application, firstly, the mask plate to be detected is placed at a suitable position below the objective lens group 5, and the optical fiber light source 401 is started. After the light source reflector group 1 402 and the light source reflector group 2 403 adjust the angle, the light is transmitted in the lens barrel 404 and directed to the mask plate. The mixed light reflected and transmitted from the mask plate enters the objective lens group 5. After the objective lens group 5 processes the light according to the preset parameters, the light enters the PBS prism group 3. In the PBS prism group 3, according to the characteristics of the polarization beam splitter prism 303, the reflected light is separated and reflected to the reflector group 2, and the light is transmitted to the objective lens group 5. The incident light continues to be transmitted through the polarization beam splitter prism 303, and the reflector group 2 transmits the received reflected light to an industrial camera connected to it, while the transmitted light is received by another industrial camera. During the detection process, the height of the objective lens group 5 can be adjusted according to the specific situation of the mask plate by driving the mounting table 7 up and down through the motor 8, thereby adjusting the focal length and other parameters to obtain clearer and more accurate imaging. At the same time, the switch in the objective lens group 5 can switch different objective lenses according to the detection requirements, further optimize the imaging effect, and finally realize the comprehensive and accurate detection and evaluation of the reflected light and transmitted light characteristics of the mask plate.

[0034] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An optical structure, comprising a reflector assembly (2), characterized in that: The reflector group (2) is connected to two industrial cameras, a PBS prism group (3) is arranged at the bottom of the reflector group (2), a transmission mirror group (4) is arranged below the PBS prism group (3), and an objective lens group (5) is arranged below the transmission mirror group (4); The PBS prism group (3) comprises a shell (301), a polarization beam splitting prism (303) is arranged inside the shell (301), and a plurality of through holes (302) for light to pass through are provided on the shell (301).

2. An optical structure according to claim 1, characterized in that: The polarization beam splitting prism (303) is formed into a cubic structure by coating a multilayer film structure on the inclined surfaces of two right-angle prisms and then gluing them together.

3. An optical structure according to claim 1, characterized in that: The reflector assembly (2) comprises a connector for connecting to an industrial camera and a fixing seat (201); the fixing seat (201) has a right triangle cross section; a prism (202) is arranged on the inclined side of the fixing seat (201); a notch corresponding to the prism (202) is provided on the inclined side of the fixing seat (201); and a fixing plate (203) for fixing the prism (202) is connected to the fixing seat (201) by bolts.

4. An optical structure according to claim 1, characterized in that: The transmission mirror group (4) comprises an optical fiber light source (401), one side of the optical fiber light source (401) is provided with a light source reflector group 1 (402) and a light source reflector group 2 (403) for changing the light transmission angle, and a lens barrel (404) is provided at the bottom of the light source reflector group 2 (403).

5. An optical structure according to claim 1, characterized in that: The objective lens group (5) comprises a plurality of objective lenses and a switch for driving the plurality of objective lenses.

6. An optical structure according to claim 1, characterized in that: It also comprises a fixed plate (1), on which the reflector group (2), the PBS prism group (3) and the transmission mirror group (4) are mounted.

7. An optical structure according to claim 1, characterized in that: The invention also comprises a mounting plate (6), wherein a mounting platform (7) is slidably connected to the mounting plate (6) via a slide rail, and a motor (8) is provided on the mounting plate (6) for driving the mounting platform (7) to move up and down, and the mounting platform (7) is connected to the objective lens group (5).

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