A multi-stage alignment system and method

Abstract

A multi-level alignment system and method are disclosed, belonging to the field of precision alignment technology. The multi-level alignment system includes: a target holding module for holding a target object with a target mark and a first grating; a motion module for holding an alignment object with an alignment mark and a second grating; a first alignment module, which, based on the alignment mark, drives the motion module to move the alignment object directly below the target object; and a second alignment module, including an imaging correction component, a coarse alignment component, and a fine alignment component. The imaging correction component extracts the target mark and focuses the coarse and fine alignment components; the coarse alignment component achieves coarse alignment between the alignment object and the target object; and the fine alignment component achieves fine alignment between the alignment object and the target object. This invention, based on a multi-level alignment and third-order grating structure design, reduces the impact of system errors on alignment accuracy, significantly improving the alignment accuracy of nanoimprinting.

Description

Technical Field

[0001] This invention relates to the field of precision alignment technology, and more particularly to a multi-stage alignment system and alignment method. Background Technology

[0002] Nanoimprint lithography, as an advanced micro-nano manufacturing technology, has been widely used in many fields such as semiconductors, optical components, and biochips in recent years. The core of this technology lies in high-precision alignment. During nanoimprint lithography, precise alignment between the wafer and the template is crucial to ensuring processing quality and the performance of the final product. Poor alignment can easily lead to pattern distortion, poor repeatability, and even production defects.

[0003] To improve alignment accuracy, existing Chinese patent application CN114326340A discloses a high-precision nanoimprint alignment method and system. It obtains the light intensity distribution map of the interference pattern based on the interference pattern, and high-precision alignment can be achieved directly through the light intensity of the corresponding group of interference lights based on the phase difference calculation. However, it is highly dependent on the stability and repeatability of the nanoimprint equipment and alignment system. At the same time, it is affected by the resolution limit of the traditional optical system, which can easily lead to a deviation between the exposed pattern and the actual position, affecting the alignment accuracy.

[0004] Chinese patent application CN118799367A discloses a high-precision alignment method for nanoimprint wafers based on multi-scale image recognition. By extracting the center points of the contours from images at three scales, a refined image at each scale is constructed, making the contour structure clearer and improving the accuracy of determining the marker points. Then, by combining the curvature feature values ​​of the contour lines at the three scales, the coordinates of the marker points are found, further improving the accuracy of determining the marker points. It can be seen that this technology improves accuracy by combining image processing with traditional mechanical or optical positioning. However, in practical applications, its alignment process involves multiple alignment calculations, processing a huge number of patterns, resulting in low efficiency and affecting the overall work efficiency.

[0005] Therefore, it is imperative to develop a new alignment system and method to address the current deficiencies and shortcomings. Summary of the Invention

[0006] In view of this, the main objective of the present invention is to provide a multi-level alignment system and alignment method, which, based on the multi-level alignment and the structural design of a third-order grating, reduces the influence of system errors on alignment accuracy and greatly improves the alignment accuracy of nanoimprinting.

[0007] To achieve the above objectives, as a first aspect of the present invention, a multi-level alignment system is proposed, comprising: a target holding module for carrying a target object having a target mark and a first grating; a motion module for carrying an alignment object having an alignment mark and a second grating, the motion module having multiple degrees of freedom of movement in multiple directions; a first alignment module, which, based on the alignment mark, drives the motion module to move the alignment object directly below the target object; and a second alignment module, comprising an imaging correction component, a coarse alignment component, and a fine alignment component; wherein: the imaging correction component focuses the coarse and fine alignment components based on the target mark; the coarse alignment component, based on the target mark and the alignment mark, drives the motion module to achieve coarse alignment between the alignment object and the target object; and the fine alignment component, based on the first and second gratings, drives the motion module to achieve fine alignment between the alignment object and the target object.

[0008] A second aspect of the present invention provides an alignment method employing the aforementioned multi-stage alignment system. The alignment method includes: a first alignment module obtaining a first relative error between the alignment mark and the target mark based on the alignment mark and the target mark; a motion module moving the alignment object directly below the target object according to the first relative error, and allowing the alignment mark to enter the field of view of the first alignment module; an imaging correction component extracting and moving the target mark to the center position of the field of view of the second alignment module for acquisition and focusing by the second alignment module; a coarse alignment component obtaining a second relative error between the alignment mark and the target mark based on the target mark and the alignment mark; and a motion module performing coarse alignment between the alignment mark and the target mark according to the second relative error; and a fine alignment component obtaining a third relative error between the first grating and the second grating based on the first grating and the second grating; and a motion module performing fine alignment between the alignment mark and the target mark according to the third relative error.

[0009] Based on the above technical solution, it can be seen that the technical solution of the present invention has at least one of the following beneficial effects compared with the prior art:

[0010] 1) By designing a three-stage alignment method of preliminary alignment, coarse alignment, and fine alignment, the alignment accuracy is improved from the submicron level to the nanometer level, reducing the dependence of alignment accuracy on the stability and repeatability of the application equipment and alignment system, and ensuring high-precision alignment between the target object and the alignment object during the alignment process.

[0011] 2) Design a third-order grating structure to reduce the impact of system errors on the precision alignment accuracy.

[0012] It should be understood that the description in the Summary of the Invention is not intended to limit the key or essential features of the embodiments of the present invention, nor is it intended to restrict the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0013] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below.

[0014] Figure 1 This is a schematic diagram of the structure of a multi-level alignment system according to an embodiment of the present invention;

[0015] Figure 2 This is a flowchart of the alignment method according to an embodiment of the present invention;

[0016] Figure 3 This is a wafer marking configuration diagram according to an embodiment of the present invention;

[0017] Figure 4 This is a template markup setting diagram according to an embodiment of the present invention;

[0018] Figure 5 This is a schematic diagram of the imaging field of view of the image acquisition device of the first alignment module in an embodiment of the present invention;

[0019] Figure 6 This is a schematic diagram of the imaging field of view of the image acquisition device of the second alignment module in an embodiment of the present invention;

[0020] Figure 7 This is a diagram of a third-order grating structure according to an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of the invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0023] The first part of this invention proposes a multi-level alignment system, such as Figure 1As shown, the system includes: a target holding module 300 for carrying a target object 700 with a target mark and a first grating; a motion module 500 for carrying an alignment object 600 with an alignment mark and a second grating, the motion module 500 having multiple degrees of freedom of movement; a first alignment module 100, which, based on the alignment mark, drives the motion module 500 to move the alignment object 600 directly below the target object 700; and a second alignment module 200, including an imaging correction component 400, a coarse alignment component, and a fine alignment component; wherein: the imaging correction component 400 focuses the coarse and fine alignment components based on the target mark; the coarse alignment component, based on the target mark and the alignment mark, drives the motion module 500 to achieve coarse alignment between the alignment object 600 and the target object 700; and the fine alignment component, based on the first and second gratings, drives the motion module 500 to achieve fine alignment between the alignment object 600 and the target object 700.

[0024] In a preferred embodiment, the motion module 500 has three degrees of freedom in the x, y, and z directions, ensuring the required accuracy for positional movement.

[0025] In a preferred embodiment, the first alignment module 100 obtains a first relative error based on the alignment mark and the target mark, and sends the first relative error to the motion module 500. The motion module 500 moves the alignment object 600 directly below the target object 700 according to the first relative error. The first alignment module 100 achieves preliminary alignment between the alignment object 600 and the target object 700, thereby improving alignment accuracy.

[0026] In a preferred embodiment, the coarse alignment component obtains a second relative error based on the target mark and the alignment mark, and sends the second relative error to the motion module 500. The motion module 500 performs coarse alignment between the alignment mark and the target mark based on the second relative error.

[0027] In a preferred embodiment, the fine alignment component obtains a third relative error based on the first grating and the second grating, and sends the third relative error to the motion module 500. The motion module 500 performs fine alignment between the alignment mark and the target mark based on the third relative error.

[0028] In a preferred embodiment, the first and second gratings are formed by a periodic structure. To reduce the impact of systematic errors on the alignment accuracy, both the first and second gratings adopt a third-order grating structure, such as... Figure 7As shown, the structural period of the first and third order gratings of the first grating is T1, and the structural period of the second order grating is T1+0.05μm; the structural period of the second order grating of the second grating is T1, and the structural period of the first and third order gratings is T1+0.05μm. By setting a three-order grating structure, the calculation of average values ​​is used to reduce calculation errors or systematic errors, making the alignment results more robust. The first and second gratings can use common moiré patterns.

[0029] In a preferred embodiment, the first alignment module 100 acquires an alignment mark and sends first movement information to the motion module 500, which moves the alignment object 600 directly below the target object 700 to achieve preliminary alignment. The coarse alignment component acquires the target mark and the alignment mark and sends second movement information to the motion module 500, which moves the alignment object 600 to perform coarse alignment with the target object 700. The fine alignment component acquires the first grating and the second grating and sends third movement information to the motion module 500, which moves the alignment object 600 to perform fine alignment with the target object 700.

[0030] The image acquisition devices of both the first alignment module 100 and the second alignment module include a CCD / CMOS camera and an imaging lens.

[0031] The imaging correction module 400 is used to adjust the focal length of the target mark and alignment mark acquired by the CCD / CMOS camera, realize the focusing function, and ensure that the image is within the camera's depth of field and reaches the focusing state when the CCD / CMOS camera acquires the image, so as to ensure clear imaging and increase alignment accuracy.

[0032] In this multi-level alignment system, a first alignment module and a second alignment module are paired to form an alignment unit. Each alignment unit acquires one alignment mark, and the number of alignment units is the same as the number of alignment marks on the object being aligned. The number of alignment marks on the object being aligned is the same as the number of target marks on the target object. To improve the alignment accuracy between the object being aligned and the target object, different numbers of alignment marks and target marks may be used.

[0033] The multi-stage alignment system of this invention reduces the dependence of alignment accuracy on the stability and repeatability of mechanical equipment and alignment system by designing a three-stage alignment method of preliminary alignment, coarse alignment and fine alignment, and ensures high-precision alignment between the target object and the alignment object. This alignment system can be applied to the alignment of wafers and templates in other semiconductor processing equipment such as nanoimprint lithography machines and photolithography machines, or other occasions that require high-speed alignment.

[0034] The second part of this invention proposes an alignment method, such as... Figure 2 As shown, alignment is performed using the aforementioned multi-level alignment system, and the alignment method includes:

[0035] S1: The first alignment module obtains the first relative error between the alignment mark and the target mark based on the alignment mark and the target mark. The motion module moves the alignment object directly below the target object according to the first relative error, and allows the alignment mark to enter the field of view of the corresponding image acquisition device of the first alignment module.

[0036] S2: The imaging correction component extracts and moves the target marker to the center of the field of view of the corresponding image acquisition device of the second alignment module, so as to perform the second alignment module acquisition and focusing;

[0037] S3: The coarse alignment component obtains a second relative error between the alignment mark and the target mark based on the target mark and the alignment mark, and the motion module performs coarse alignment between the alignment mark and the target mark according to the second relative error;

[0038] S4: The fine alignment component obtains a third relative error between the first grating and the second grating based on the first grating and the second grating, and the motion module achieves fine alignment between the alignment mark and the target mark based on the third relative error.

[0039] In a preferred embodiment, the alignment method further includes: coordinate setting, such as... Figure 1 As shown, a first coordinate system xoy is established with the center point of the target object 700 as the origin, a second coordinate system x′oy′ is established on the target surface of the corresponding image acquisition device of the second alignment module, and a third coordinate system x″oy″ is established on the target surface of the corresponding image acquisition device of the first alignment module.

[0040] In a preferred embodiment, the motion module 500 returns to its original position, with its center point coinciding with the center point of the first coordinate system xoy. The long side of the alignment object 600 coincides with the x-axis of the first coordinate system xoy, and the short side of the alignment object 600 coincides with the y-axis of the first coordinate system xoy. After the motion module 500 returns to its original position, the first alignment module 100 scans and acquires the center point coordinates and rotation angle of the alignment mark in the third coordinate system, transforming them to absolute coordinates in the first coordinate system. In the first coordinate system, the first relative error between the alignment mark and the target mark is calculated. Based on the first relative error, the motion module 500 carries the alignment object 600 and moves it directly below the target mark, allowing the alignment mark to enter the field of view of the corresponding image acquisition device of the first alignment module.

[0041] In a preferred embodiment, the imaging correction component 400 extracts the coordinates of the target mark in the second coordinate system, moves the target mark to the center of the field of view of the corresponding image acquisition device of the second alignment module, and performs acquisition and focusing by the second alignment module 200.

[0042] In a preferred embodiment, the coarse alignment component identifies the center point coordinates and rotation angle of the target mark and the alignment mark in the second coordinate system, and converts the alignment mark to the absolute coordinates in the first coordinate system, and calculates the second relative error between the alignment mark and the target mark; the motion module 500 carries the alignment object to perform coarse alignment between the alignment mark and the target mark based on the second relative error.

[0043] In a preferred embodiment, identifying the target mark and the center point coordinates and rotation angle of the alignment mark in a second coordinate system using a coarse alignment component includes the following steps:

[0044] The coarse alignment component acquires the overlapping image of the target marker and the alignment marker, and converts the image into a grayscale image;

[0045] The grayscale image is denoised, and the image contour is extracted.

[0046] Establish the minimum bounding rectangle of the outline, and obtain the center coordinates and rotation angle of the minimum bounding rectangle, that is, the center coordinates and rotation angle of the target mark and alignment mark in the second coordinate system.

[0047] In the above embodiments, the grayscale image conversion and grayscale image denoising can be performed using conventional image processing techniques in the field, as long as a clear image outline can be obtained.

[0048] In a preferred embodiment, the rotation angle of the target mark of the target object or the alignment mark of the alignment object in the second coordinate system is calculated by the angle θ between the target mark of the target object or the alignment mark of the alignment object and the x-axis direction vector of the target surface of the corresponding image acquisition device of the second alignment module.

[0049] In a preferred embodiment, the target mark of the target object and the alignment mark of the alignment object in the multi-level alignment system can be a cross mark, a square mark, an "L" pattern, or a dot mark, etc. These are any marks or features used to perform alignment, but do not mean that they are all present.

[0050] In a preferred embodiment, the light intensity distribution of the first grating and the second grating in the second coordinate system is identified by the fine alignment component and converted into a phase difference. The third relative error ΔS3 of the first grating and the second grating is calculated. The motion module 500 carries the alignment object to perform fine alignment between the alignment mark and the target mark based on the third relative error.

[0051] The third part of this invention proposes an alignment device that uses the above-described alignment method to align a target object and an alignment object. This alignment device is applicable to alignment in nanoimprint lithography, alignment of wafers and templates in other semiconductor processing equipment such as photolithography machines, or other applications requiring high-speed alignment, wherein the wafer is the alignment object and the template is the target object.

[0052] Example

[0053] To achieve precise alignment between the wafer and the template, the following methods are employed: Figure 1 The multi-stage alignment system shown includes: an alignment module 100, a second alignment module 200, a preliminary alignment support module 300, an imaging correction module 400, a wafer motion module 500, an imprint wafer 600, and an imprint template 700.

[0054] Coordinate settings, such as Figure 1 As shown, a first coordinate system xoy is established with the center point of template 700 as the origin, a second coordinate system x′oy′ is established on the camera target surface of the second alignment module 200, and a third coordinate system x″oy″ is established on the camera target surface of the first alignment module 100. The wafer motion module 500 has three degrees of freedom of motion: x, y, and z. When it is in the zero position (initial position), the center point of the wafer motion module 500 coincides with the origin o of the first coordinate system xoy, the x-axis, and the y-axis, that is, the wafer motion module 500 returns to its original position.

[0055] The wafer motion module 500 is mainly used to carry the wafer 500 and move it to the target coordinate point. It has position limits for the wafer 500 installation. During design, the center of the wafer motion module 500 coincides with the center of the wafer position limit. The long side of the large rectangle in the wafer 600 coincides with the x-axis of the first coordinate system xoy, and the short side coincides with the y-axis of the first coordinate system xoy. The wafer 600 is mounted manually or mechanically. Due to mechanical tolerances during installation, the center point of the wafer 600 may deviate from the design point, but the deviation is small, generally within a 1mm diameter range.

[0056] like Figure 3 As shown, wafer 600 has eight alignment marks, specifically marks 601 to 608, and the second grating of wafer 600 has eight moiré marks, specifically marks 609 to 616. The actual position of the center point of alignment mark 601 is determined as follows:

[0057]

[0058] Where 's' represents the actual position, and the other alignment marks 602 to 608 follow the same pattern.

[0059] like Figure 4 As shown, template 700 has eight target marks, specifically marks 701 to 708, and the first grating of template 700 has eight moiré marks, specifically marks 709 to 716. The actual position of the center point of target mark 701 is determined as follows:

[0060]

[0061] Where w represents the target location, and other target markers 702 to 708 follow the same pattern.

[0062] The formal alignment procedure is as follows:

[0063] Step 1: First, move the wafer motion module 500 back to its original position, aligning it with the first coordinate system xoy. The first alignment module 100 then scans and acquires the coordinates P″ of the center point of the wafer alignment mark 601 on the wafer 600 in the third coordinate system x"oy". 601 =(x″ 601 ,x″ 601 and rotation angle like Figure 5 As shown. The upper left corner of the camera of the first alignment module 100 is installed at coordinate point P in the first coordinate system xoy. 预 =(x 预 ,y 预 The imaging field of view of the first alignment module 100 needs to be at least greater than 1.2 mm. 2 The center point of the wafer alignment mark 601 may be misaligned within a diameter of 1 mm due to installation errors. 2 The key is to ensure that the edges of the wafer alignment mark 601 are all within the field of view of the initial alignment camera.

[0064] Transform the coordinates of the center point of wafer alignment mark 601 to absolute coordinates in the first coordinate system xoy. The coordinate transformation formula is:

[0065]

[0066] Three points define a plane; therefore, obtaining the geometric alignment marks 603 and 608 on the other two sides of the wafer alignment mark 601 allows for preliminary alignment. Similarly, the coordinates of the center points of wafer alignment marks 603 and 608 in the first coordinate system xoy are respectively... and After obtaining the center point coordinates in the first coordinate system xoy for each alignment mark, the wafer motion module 500 needs to be returned to its original position.

[0067] Calculate the first relative error between the wafer alignment mark 601 and the template target mark 701 in the first coordinate system xoy. y represents initial alignment, and i represents 1 to 8. The specific calculation method is as follows:

[0068] Motion alignment is performed using the nonlinear least squares method. Under this motion alignment condition, the coordinates (x" of the wafer alignment mark 601 are used. 60i y6 " 0i( ) is the alignment point, and the coordinates of template target mark 701 in the first coordinate system are: For translation and rotation alignment in two-dimensional space, let the rotation matrix be R and the translation vector be t. Then, for each wafer alignment mark or template target mark point, the error vector... Sum of squared errors of n groups of labels The rotation matrix R and translation vector t are solved by minimizing the sum of squared errors S using nonlinear optimization algorithms such as gradient descent or Newton's method. The result is obtained from the rotation matrix. Based on the translation vector t, we obtain Thus, calculate In this calculation process, the first relative error needs to be calculated using three wafer alignment marks.

[0069] The first alignment module 100 transmits the first relative error ΔS1 to the wafer motion module 500. The wafer motion module 500 receives the first relative error ΔS1 input by the first alignment module 100, carries the wafer 600, and moves the wafer alignment mark 601 directly below the template target mark 701, so that the wafer alignment mark 601 enters the camera's field of view and corresponds one-to-one with the template target mark 701, thus completing the preliminary alignment process.

[0070] Step 2: The imaging correction module 400 is mainly used to extract the coordinates of the template target mark 701 in the second coordinate system and move the template target mark 701 to the center of the camera's field of view. At the same time, it realizes the focusing function to ensure that the coarse alignment component and the fine alignment component acquire overlapping images within the camera's depth of field, i.e., in a focused state.

[0071] Step 3: In the first coordinate system xoy, the coordinates of template target marker 701 are... The overlap image of template target mark 701 and wafer alignment mark 601 is obtained through the coarse alignment component, such as... Figure 6 As shown, after image processing, the center point coordinates of the template target mark 701 in the second coordinate system x′oy′ are obtained as (x′ 701 ,y′ 701 and rotation angle The center point coordinates of wafer alignment mark 601 in the second coordinate system x′oy′ are (x′ 601 ,y′ 601 Align the wafer with the coordinates (x′) of mark 601. 601 ,y′ 601 The absolute coordinates after transformation to the first coordinate system xoy are: The conversion formula is as follows:

[0072]

[0073] By analogy, the coordinates of the center points of wafer alignment marks 602 to 608 in the first bounded coordinate system xoy are obtained.

[0074] The second relative error ΔS2 between wafer alignment mark 601 and template target mark 701 is calculated. The calculation steps are the same as the first relative error ΔS1 in the preliminary alignment step (first step). The difference is that when calculating the second relative error, eight wafer alignment marks and template target marks need to be input.

[0075] The error is transmitted to the wafer motion module 500. The wafer motion module 500 receives the second relative error ΔS2 input from the coarse alignment component and carries the wafer 600 to perform coarse alignment between the wafer alignment mark 601 and the template target mark 701, with an alignment accuracy reaching the sub-micron level.

[0076] The image processing steps are as follows: After image processing, the center point coordinates and rotation angles of the template target mark 701 and the wafer alignment mark 601 in the second coordinate system x′oy′ are obtained.

[0077] a: Convert the overlapping image of template target mark 701 and wafer alignment mark 601 obtained by the coarse alignment component into a grayscale image;

[0078] b: The grayscale image is processed using methods such as Gaussian filtering to reduce noise from overlapping images;

[0079] c: Extract the contours of overlapping images using methods such as threshold segmentation;

[0080] d: Construct the minimum bounding rectangle of the outline, and obtain the center coordinates and rotation angle of the minimum bounding rectangle;

[0081] e: Finally, obtain the center point coordinates and rotation angle of the template target mark 701 and the wafer alignment mark 601 in the second coordinate system x′oy′.

[0082] Step 4: Taking the wafer moiré markings 609 and 616 and the template moiré markings 709 and 716 in one corner as examples. The template moiré markings 709 and 716 and the wafer moiré markings 609 and 616 all employ a third-order grating structure, such as... Figure 7 As shown, the first and third order grating structure period of template moiré patterns 709 and 716 is T1, and the second order grating structure period is T1+0.05μm; the second order grating structure period of wafer moiré patterns 609 and 616 is T1, and the first and third order grating structure periods are T1+0.05μm.

[0083] During the fine alignment process, the light intensity distribution of template moiré patterns 709 and 716 and wafer moiré patterns 609 and 616 in the second coordinate system x′oy′ is identified using the fine alignment component, and the phase information of each moiré pattern is obtained. First, the phase information extracted from the first-order moiré pattern signal is compared with the phase information extracted from the second-order moiré pattern signal to obtain the first phase difference. Then, the phase information extracted from the third-order moiré signal is compared with the phase information extracted from the second-order moiré signal to obtain the second phase difference. Take the average of the two. The relative positional offset of the wafer moiré mark 609 and the template moiré mark 709 during alignment is: The relative positional offset of the wafer moiré mark 616 and the template moiré mark 716 during alignment is: The relative positional offsets of wafer moiré marks 610–615 and corresponding template moiré marks 710–715 are obtained in this manner. The sum of the squares of the relative displacement offsets of these eight templates / wafers is then calculated. Where J represents the wafer, M represents the template, and T represents the transpose matrix. The rotation matrix R and translation vector t are solved by minimizing the sum of squared errors S using nonlinear optimization algorithms such as gradient descent or Newton's method. The result is obtained from the rotation matrix. Based on the translation vector t, we obtain Thus, calculate j represents fine alignment, i represents 1 to 8, and is transmitted to the wafer motion module 500; the wafer motion module 500, based on the third relative error ΔS3, carries the wafer 600 to perform fine alignment of the wafer alignment mark 601 with the template target mark 701, with an alignment accuracy of several nanometers.

[0084] In the above process, the first alignment module 100, the coarse alignment component, and the fine alignment component all need to pre-focus before acquiring the image. The focusing process can utilize image gradient information. Gradient operators (such as the Sobel operator, Scharr operator, etc.) are used to process the image acquired by the camera, calculate the gradient value of each pixel, and then analyze the gradient values ​​of the entire image to find the region or pixel with the largest gradient value. Based on this information, the lens position is adjusted to achieve the sharpest image.

[0085] By employing the aforementioned three-stage alignment method—preliminary alignment, coarse alignment, and fine alignment—the dependence of alignment accuracy on the stability and repeatability of the equipment and alignment system is reduced, ensuring high-precision alignment between the template and the wafer during the alignment process. Equipment using this alignment system and the three-stage alignment method can be applied in semiconductor manufacturing, photolithography, nanoimprint lithography, and other fields, playing a crucial role in precise alignment, assisting production, improving product quality, and increasing production efficiency.

[0086] The foregoing has described specific embodiments of the present invention. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims may be performed in a different order than that shown in the embodiments and may still achieve the desired results. Furthermore, the processes depicted in the drawings do not necessarily require the specific or sequential order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0087] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-stage alignment system, characterized in that, include: The target holding module is used to hold a target object equipped with a target mark and a first grating; A motion module is used to carry an alignment object equipped with alignment marks and a second grating, and the motion module has multiple degrees of freedom of movement in multiple directions; The first alignment module, based on the alignment mark, drives the motion module to move the alignment object to directly below the target object; The second alignment module includes an imaging correction component, a coarse alignment component, and a fine alignment component; in: The imaging correction component focuses the coarse alignment component and the fine alignment component based on the target mark; The coarse alignment component drives the motion module to achieve coarse alignment between the alignment object and the target object based on the target mark and the alignment mark; The precision alignment component, based on the first and second gratings, drives the motion module to achieve precise alignment between the alignment object and the target object.

2. The multi-stage alignment system according to claim 1, characterized in that, The motion module has three degrees of freedom in the x, y, and z directions.

3. The multi-stage alignment system according to claim 1, characterized in that, Both the first grating and the second grating adopt a third-order grating structure, wherein, The first-order grating and the third-order grating have the same structural period, while the second-order grating has a different structural period than the first-order grating and the third-order grating.

4. The multi-stage alignment system according to claim 1, characterized in that, The first alignment module obtains a first relative error based on the alignment mark and the target mark, and sends the first relative error to the motion module. The motion module moves the alignment object to directly below the target object according to the first relative error. The coarse alignment component obtains a second relative error based on the target mark and the alignment mark, and sends the second relative error to the motion module. The motion module performs coarse alignment between the alignment mark and the target mark based on the second relative error. The precision alignment component obtains a third relative error based on the first grating and the second grating, and sends the third relative error to the motion module. The motion module performs precision alignment between the alignment mark and the target mark based on the third relative error.

5. An alignment method, characterized in that, Alignment is performed using a multi-stage alignment system as described in any one of claims 1-4, the alignment method comprising: The first alignment module obtains a first relative error between the alignment mark and the target mark. The motion module moves the alignment object directly below the target object according to the first relative error and allows the alignment mark to enter the field of view of the first alignment module. The imaging correction component extracts and moves the target marker to the center of the field of view of the second alignment module in order to enable the second alignment module to acquire and focus. The coarse alignment component obtains a second relative error between the alignment mark and the target mark based on the target mark and the alignment mark, and the motion module performs coarse alignment between the alignment mark and the target mark according to the second relative error; The precision alignment component obtains a third relative error between the first grating and the second grating based on the first grating and the second grating, and the motion module achieves precision alignment between the alignment mark and the target mark based on the third relative error.

6. The alignment method according to claim 5, characterized in that, Also includes: A first coordinate system is established with the center point of the target object as the origin. A second coordinate system is established on the target surface of the corresponding image acquisition device of the second alignment module. A third coordinate system is established on the target surface of the corresponding image acquisition device of the first alignment module.

7. The alignment method according to claim 6, characterized in that, The coarse alignment component identifies the center point coordinates and rotation angle of the target mark and the alignment mark in the second coordinate system, and transforms the alignment mark to the absolute coordinates in the first coordinate system, and calculates the second relative error between the alignment mark and the target mark. The motion module performs coarse alignment of the alignment mark and the target mark based on the second relative error, carrying the alignment object.

8. The alignment method according to claim 7, characterized in that, The process of identifying the target mark and the center point coordinates and rotation angle of the alignment mark in the second coordinate system through the coarse alignment component includes: The coarse alignment component acquires an image of the overlap between the target marker and the alignment marker, and converts the image into a grayscale image; The grayscale image is denoised to extract the image contour. Establish the minimum bounding rectangle of the contour, and obtain the center coordinates and rotation angle of the minimum bounding rectangle, that is, the center coordinates and rotation angle of the target mark and alignment mark in the second coordinate system.

9. The alignment method according to claim 5, characterized in that, The light intensity distribution of the first grating and the second grating in the second coordinate system is identified by the precision alignment component, and converted into phase difference to calculate the third relative error between the first grating and the second grating. The motion module, based on the third relative error, carries the alignment object to perform precise alignment between the alignment mark and the target mark.

10. The alignment method according to claim 6, characterized in that, Also includes: The motion module is repositioned by aligning its center point with the center point of the first coordinate system, aligning the long side of the object with the x-axis of the first coordinate system, and aligning the short side of the object with the y-axis of the first coordinate system. The repositioning step of the motion module includes: The center point coordinates and rotation angle of the alignment mark in the third coordinate system are obtained by scanning through the first alignment module, and then converted to the absolute coordinates in the first coordinate system. In the first coordinate system, the first relative error between the alignment mark and the target mark is calculated. Based on the first relative error, the motion module carries the alignment object and moves it directly below the target mark, allowing the alignment mark to enter the field of view of the corresponding image acquisition device of the first alignment module.

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