Photoetching alignment system and method

Abstract

The invention discloses a photoetching alignment system and method, and belongs to the field of photoetching machine alignment. In order to solve the problem that an existing photoetching machine alignment system cannot give consideration to both efficiency and precision, the invention provides a photoetching alignment system which comprises a light source, a light path assembly and a collection assembly; wherein the light path assembly comprises a first lens group, a second lens group and a beam splitter prism, the first lens group and the second lens group are arranged on the same side of the alignment mark, and the beam splitter prism is arranged between the first lens group and the second lens group; wherein the first lens group is used for receiving light emitted by the second lens group; a third lens group is detachably arranged between the first lens group and the beam splitter prism, and the equivalent focal length formed by the focal length of the third lens group and the focal length of the first lens group is larger than the focal length of the first lens group. According to the invention, switching of the alignment system between a high magnification and a low magnification is realized by adding the third lens group, so that rapid identification of an alignment mark is realized under the low magnification, high-resolution image collection of the alignment mark is realized under the high magnification, and the precision of the alignment system is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of photolithography machines, and more specifically, relates to a photolithography alignment system and method. Background Art

[0002] In a photolithography machine, the alignment system is one of its core systems. The alignment system requires fast and accurate alignment in order to improve productivity and yield. Among them, alignment accuracy is one of the core indicators, which is closely related to the resolution of the photolithography machine. Image alignment is a commonly used alignment method, which requires that the captured image is clear and has a certain resolution. However, higher alignment accuracy requires higher image resolution. High resolution means that the alignment system requires a higher magnification. The larger the magnification, the smaller the field of view, which makes it difficult to find marks during alignment and reduces the success rate of finding marks. If the alignment system uses a lower magnification, although it can reduce the time to find the mark during alignment and increase the success rate, it reduces the alignment accuracy of the system.

[0003] Corresponding improvements have also been made to the above problems, such as Chinese patent application number CN202411056619.4, published on September 6, 2024. The patent discloses a photolithography machine alignment system and method for high-precision measurement using light field display, including a mask frame and a workpiece stage, a projection objective lens is arranged between the workpiece stage and the mask frame, and a coaxial alignment system is also provided, including an upper alignment display and a lower alignment display respectively arranged on the mask frame and the workpiece stage for generating a high-precision alignment pattern, an upper light control component and a lower light control component fixedly arranged on the periphery of the projection objective lens, and a first acquisition device for collecting changes in upper light field information through the upper light control component and a second acquisition device for collecting changes in lower light field information through the lower light control component. The alignment display displays a high-precision alignment pattern, and the light control component and the acquisition device are used in combination to obtain nanometer-level alignment accuracy, and the structural complexity is low, reducing the cost and difficulty of semiconductor manufacturing. The shortcomings of this patent are that although high-precision alignment can be achieved, the efficiency is slow and the operation is complicated.

[0004] Another example is Chinese patent application number CN202410145379.9, published on July 26, 2024. The patent discloses a lithography alignment method, device, electronic device and storage medium, wherein the method includes: providing a wafer to be exposed, with multiple alignment marks arranged on the surface of the wafer to be exposed; obtaining a set of absolute positions corresponding to multiple alignment marks, the absolute position set including the absolute position of each alignment mark in the wafer coordinate system; screening data and absolute position sets according to preset marks, screening multiple target alignment marks from multiple alignment marks; inputting multiple target alignment marks into the alignment system to complete the alignment of the wafer to be exposed. The shortcoming of this patent is that the introduction of absolute position increases the computing power resource consumption of the entire process, increases costs and working time. Summary of the invention

[0005] 1. Problems to be solved In view of the problem that the existing lithography machine alignment system cannot take into account both efficiency and precision, the present invention provides a lithography alignment system and method. The present invention realizes the switching of the alignment system between high magnification and low magnification by adding a third lens group, thereby realizing rapid recognition of alignment marks at low magnification and high-resolution image collection of alignment marks at high magnification, thereby ensuring the precision of the alignment system.

[0006] 2. Technical solution To solve the above problems, the present invention adopts the following technical solutions.

[0007] A photolithography alignment system, comprising: Light source: used to provide lighting; Optical path component: used to adjust the illumination light so that it shines on the alignment mark; A collecting component is used to collect images of the alignment marks and image the alignment marks onto the collecting component; Wherein, the optical path component includes a first lens group, a second lens group and a beam splitter prism, the first lens group and the second lens group are arranged on the same side of the alignment mark, and the beam splitter prism is arranged between the first lens group and the second lens group; wherein the first lens group is used to receive the light emitted by the second lens group; a detachable third lens group is arranged between the first lens group and the beam splitter prism, and the equivalent focal length formed by the focal length of the third lens group and the focal length of the first lens group is greater than the focal length of the first lens group.

[0008] Furthermore, the first lens group and the second lens group are arranged opposite to each other; and when the third lens group is arranged on a side close to the first lens group, the third lens group and the first lens group are arranged parallel to, opposite to, or integrated with each other.

[0009] Furthermore, the first lens group, the second lens group and the third lens group each include one or more lenses.

[0010] Furthermore, a collimator is provided between the light source and the optical path component, and the illumination light provided by the light source is shaped into parallel light by the collimator and enters the optical path component.

[0011] Furthermore, the light source is a coaxial light source, and the coaxial light source adopts an LED light source.

[0012] An alignment method using a lithography alignment system as described in any one of the above, comprising the following steps: S1: Initial alignment stage: The illumination light provided by the light source passes through the first mirror group and the second mirror group to achieve positioning alignment marks; S2: Precision alignment stage: Install a third lens group on the side of the alignment mark close to the first lens group to enable the collection component to collect the image of the alignment mark.

[0013] Furthermore, when the third lens group is installed in step S2, the third lens group is connected to the first lens group through a connecting mechanism, and the third lens group is locked with the first lens group through a locking mechanism to form an integrated arrangement.

[0014] 3. Beneficial effects Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention introduces a detachable third lens group into the optical path component, and changes the system magnification of the entire alignment system by introducing or not introducing the third lens group, so that the alignment system can realize rapid recognition of the alignment mark under low system magnification, greatly improving the recognition efficiency; after recognizing the alignment mark, the alignment mark image with high image resolution is collected under high system magnification, thereby improving the alignment accuracy of the entire system; the entire system can ensure rapid recognition of the alignment mark while not affecting the resolution of the alignment mark image, taking into account both efficiency and accuracy; and the structure is simple, without the need for complex structures and equipment, and only the third lens group needs to be introduced, so the cost is low and the practicability is strong; (2) The present invention arranges the first mirror group and the second mirror group relative to each other, and the relative arrangement can form a symmetrical optical path structure, which helps to reduce aberration and distortion in the optical path, ensures that the light beam maintains high stability and consistency during transmission, makes the imaging of the alignment mark clearer and more accurate, and thus improves the accuracy of the alignment system; the third mirror group and the first mirror group can be arranged in a variety of ways, and can be adaptively selected according to the on-site conditions. The parallel arrangement makes the optical path transmission simple and clear, and the light beam has strong stability; the relative arrangement can achieve high precision of the alignment system, and the integrated arrangement is convenient to operate, easy to install and maintain, and has a high degree of integration; (3) The present invention adopts a coaxial light source for lighting, and replaces the traditional light source halogen lamp with an LED light source, thereby improving the light efficiency, reducing the heat generation, and reducing the system volume; and a collimator is also arranged between the light source and the optical path component. The arrangement of the collimator further adjusts the light into a parallel or nearly parallel beam, reduces the scattering and distortion of the light during the transmission process, and enables the light to reach the alignment mark more accurately and be reflected, while reducing external interference and improving the stability of the light source, thereby achieving alignment more accurately and efficiently and ensuring precision; (4) The alignment method of the present invention is simple to operate. By adding or removing the third lens group, the entire alignment system can obtain two magnifications, namely, a high magnification and a low magnification, and realize switching. In the initial alignment stage, a low magnification is used to find the alignment mark, so as to spend less time and improve the success rate; in the fine alignment stage, a high magnification is used to improve the alignment accuracy of the system. No complicated operation requirements are required, and the staff is easy to use, with high efficiency and low cost. In addition, the third lens group can be adjusted according to different on-site usage requirements to achieve different magnification adjustments of the system, and the method has strong applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the overall structure of the present invention. DETAILED DESCRIPTION

[0016] The present invention is further described below in conjunction with specific embodiments and drawings.

[0017] like Figure 1 As shown, a photolithography alignment system comprises: Light source: used to provide illumination light to ensure that the alignment mark can be clearly illuminated; Optical path component: used to adjust the illumination light so that it can be irradiated onto the alignment mark, and to image the alignment mark so that the alignment mark is imaged onto the collection component; the optical path component guides and adjusts the light beam so that the light beam can be accurately irradiated onto the alignment mark, and also collects reflected or diffracted light signals; the alignment mark is set on the surface of the wafer to be exposed, and there are one or more alignment marks; Collection component: used to collect images of alignment marks; by collecting images of alignment marks, the images are processed and analyzed, and features are extracted to calculate the alignment error. The alignment error is usually expressed as the position deviation between the pattern on the mask and the pattern on the wafer; corresponding adjustments are made according to the alignment error to achieve precise alignment.

[0018] Wherein, the optical path component includes a first lens group, a second lens group and a beam splitter prism, the first lens group and the second lens group are arranged on the same side of the alignment mark, and the beam splitter prism is arranged between the first lens group and the second lens group; wherein the first lens group is used to receive the light emitted by the second lens group; a detachable third lens group is arranged between the first lens group and the beam splitter prism, and the equivalent focal length formed by the focal length of the third lens group and the focal length of the first lens group is greater than the focal length of the first lens group.

[0019] The light path of the optical path component in this embodiment is as follows: the light beam generated by the light source passes through the dichroic prism and reaches the second lens group to illuminate the alignment mark on the surface of the wafer to be exposed, and then the light shining on the alignment mark is emitted to the second lens group, the dichroic prism, the third lens group and the first lens group in sequence, and then transmitted to the collection component to realize the collection of the alignment mark image.

[0020] It is explained here that when the optical path component only includes the first lens group and the second lens group, the focal length of the first lens group is f1, the focal length of the second lens group is f2, then the system magnification of the entire alignment system is M1= f1 / f2; when the optical path component introduces the third lens group, since the third lens group and the first lens group form a whole, the focal length formed by the whole, that is, the equivalent focal length is f3, at this time, the system magnification of the entire alignment system is M2= f3 / f2, since the equivalent focal length f3 formed by the focal length of the third lens group and the focal length of the first lens group is greater than the focal length f1 of the first lens group, therefore when the focal length f2 of the second lens group remains unchanged, M1<M2, that is, M1 is the low magnification of the system, and M2 is the high magnification of the system.

[0021] It is worth noting that in the alignment system of the lithography machine, if a higher alignment accuracy is required, the image of the collected alignment mark needs to have a higher resolution, and the higher the system magnification, the higher the image resolution; however, for the entire alignment system, the higher the system magnification, the smaller the field of view, and the smaller the field of view, the more difficult it is to locate the alignment mark. Therefore, there are also disadvantages in simply improving the alignment accuracy by using a high system magnification. The current mainstream way to improve alignment accuracy is to optimize exposure parameters, such as changing exposure time, light intensity, etc., but this method has a slow adjustment efficiency and the effect is not obvious; the second is to use advanced alignment algorithms and models, but this method consumes a lot of computing power and is costly.

[0022] Therefore, in this embodiment, by introducing a detachable third lens group into the optical path component, the system magnification of the entire alignment system is changed by whether the third lens group is introduced or not, so that the alignment system can realize rapid recognition of the alignment mark under low system magnification, thereby greatly improving the recognition efficiency; after recognizing the alignment mark, the alignment mark image with high image resolution is collected under high system magnification, thereby improving the alignment accuracy of the entire system; the entire system can ensure rapid recognition of the alignment mark while not affecting the resolution of the alignment mark image, taking into account both efficiency and accuracy; and the structural composition is simple, without the need for complex structures and equipment, and only the third lens group needs to be introduced, so the cost is low and the practicability is strong.

[0023] In a specific embodiment, the first lens group and the second lens group are arranged opposite to each other; and when the third lens group is arranged close to the first lens group, the third lens group and the first lens group are arranged parallel to, opposite to, or integrated with each other.

[0024] Specifically, the relative arrangement can form a symmetrical optical path structure, which helps to reduce aberrations and distortions in the optical path, ensure that the light beam maintains high stability and consistency during transmission, and make the imaging of the alignment mark clearer and more accurate, thereby improving the accuracy of the alignment system.

[0025] The present application does not specifically limit the specific setting method of the third lens group. It can be parallel, relative or integrated with the first lens group. It only needs to ensure that when it is integrated with the first lens group, the overall focal length, that is, the equivalent focal length, is greater than the focal length of the first lens group. The parallel setting can make the optical path simpler and clearer, help reduce the complexity and uncertainty in the optical path, and then reduce the interference and fluctuation of the light beam during the transmission process, thereby improving the stability and reliability of the light beam; the relative setting can ensure that the light beam maintains a high stability and consistency during the transmission process, making the imaging of the alignment mark clearer and more accurate, thereby improving the alignment accuracy of the entire system; the integrated setting method can make the alignment system more compact and integrated, reduce the number of connections and interfaces between components, simplify the installation and maintenance process of the alignment system, and reduce the difficulty and cost of operation. The diverse setting methods can be adaptively selected according to the on-site conditions, which improves the overall flexibility and adaptability.

[0026] In a specific embodiment, the first lens group, the second lens group and the third lens group each include one or more lenses. The structure is simple and easy to install and maintain.

[0027] In a specific embodiment, a collimator is provided between the light source and the optical path component, and the illumination light provided by the light source is shaped into a parallel light beam generated by the light source through the collimator and enters the optical path component. Specifically, in this embodiment, the collimator is further provided to adjust the light beam into a parallel or nearly parallel light beam, reduce the scattering and distortion of the light during the transmission process, so that the light can reach the alignment mark more accurately and be reflected, and at the same time reduce external interference, improve the stability of the light source, thereby achieving alignment more accurately and efficiently, and ensuring precision.

[0028] Preferably, the light source is a coaxial light source, which ensures that the light can be irradiated vertically to the surface of the object, reducing the shadow and reflection problems caused by oblique light; and the coaxial light source adopts an LED light source, replacing the traditional halogen lamp, thereby improving the lighting efficiency, reducing heat generation, and reducing the system size.

[0029] An alignment method using a lithography alignment system as described in any one of the above, comprising the following steps: S1: Initial alignment stage: The illumination light provided by the light source passes through the first mirror group and the second mirror group to quickly locate the alignment mark; S2: Precision alignment stage: A third lens group is installed on the side of the alignment mark close to the first lens group, so that the collection component can collect a high-resolution image of the alignment mark.

[0030] The alignment method described in the present application is simple to operate. By adding or removing the third lens group, the entire alignment system can obtain two magnifications, namely, a high system magnification and a low system magnification, and switch between them. In the initial alignment stage, a low magnification is used to find the alignment mark so as to spend less time and improve the success rate; in the fine alignment stage, a high magnification is used to improve the alignment accuracy of the system. No complicated operating requirements are required, and it is easy for staff to get started, with high efficiency and low cost; and the third lens group can be adjusted according to different on-site usage requirements to achieve adjustment of different system magnifications, and the method has strong applicability.

[0031] In a specific embodiment, when the third lens group is installed in step S2, the third lens group is connected to the first lens group through a connecting mechanism, and the third lens group is locked with the first lens group through a locking mechanism to form an integrated arrangement. The integrated arrangement of the third lens group and the first lens group enhances the stability of the entire optical path system, reduces the relative movement or vibration between the first lens group and the third lens group, thereby reducing interference factors in the optical path, improving the anti-interference ability and stability of the system, and thus improving the alignment accuracy. In addition, the arrangement of the locking mechanism further consolidates the tightness of the connection between the first lens group and the third lens group, thereby ensuring the stability of the entire alignment system, so that it can work stably and effectively.

[0032] The examples described in the present invention are merely descriptions of the preferred implementation modes of the present invention, and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by engineers and technicians in this field should all fall within the protection scope of the present invention.

Claims

1. A photolithography alignment system, characterized in that: include: Light source: used to provide lighting; Optical path component: used to adjust the illumination light so that it shines on the alignment mark, and image the alignment mark onto the collection component; Collection component: used for collecting images of alignment marks; Wherein, the optical path component includes a first lens group, a second lens group and a beam splitter prism, the first lens group and the second lens group are arranged on the same side of the alignment mark, and the beam splitter prism is arranged between the first lens group and the second lens group; wherein the first lens group is used to receive the light emitted by the second lens group; a detachable third lens group is arranged between the first lens group and the beam splitter prism, and the equivalent focal length formed by the focal length of the third lens group and the focal length of the first lens group is greater than the focal length of the first lens group.

2. A lithography alignment system according to claim 1, characterized in that: The first lens group and the second lens group are arranged opposite to each other; and when the third lens group is arranged on a side close to the first lens group, the third lens group and the first lens group are arranged parallel, opposite or integrated.

3. A lithography alignment system according to claim 1 or 2, characterized in that: The first lens group, the second lens group and the third lens group each include one or more lenses.

4. A lithography alignment system according to claim 1, characterized in that: A collimator is arranged between the light source and the optical path component. The illumination light provided by the light source is shaped into parallel light by the collimator and enters the optical path component.

5. A lithography alignment system according to claim 1 or 4, characterized in that: The light source is a coaxial light source, and the coaxial light source adopts an LED light source.

6. An alignment method using a lithography alignment system according to any one of claims 1 to 5, characterized in that: The steps include: S1: Initial alignment stage: The illumination light provided by the light source passes through the first mirror group and the second mirror group to achieve positioning alignment marks; S2: Precision alignment stage: Install a third lens group on the side of the alignment mark close to the first lens group to enable the collection component to collect the image of the alignment mark.

7. An alignment method according to claim 6, characterized in that: When the third lens group is installed in step S2, the third lens group is connected to the first lens group through the connecting mechanism, and the third lens group is locked with the first lens group through the locking mechanism to form an integrated arrangement.

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