Overlay mark structures and overlay offset detection methods

Abstract

The present application relates to the technical field of integrated circuits, and provides a set of marking structure and set of offset detection method. The first set of marking pattern and the second set of marking pattern are in triangular structure; the first set of marking pattern and the second set of marking pattern are formed in different layers of wafer substrate, and the projection area of the first set of marking pattern is located in the projection area of the second set of marking pattern. The offset amount of the center of the first set of marking and the second set of marking pattern in X, Y and Z directions can be obtained to obtain set of compensation data, and the exposure machine is compensated according to the compensation data. When the image of the set of marking pattern in one direction is damaged, the present application does not affect the judgment of the deviation, thereby improving the reliability of the set of marking pattern.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit technology, and specifically to an overlay marking structure and an overlay offset measurement method. Background Technology

[0002] In current semiconductor manufacturing processes, multiple photolithography masking processes are required. To ensure product performance, the mask patterns of each layer must be precisely aligned, i.e., overlay alignment. To solve this problem, alignment patterns are typically set in the photolithography process, and optical alignment is performed on these alignment patterns to achieve alignment between layers.

[0003] Structural reference for alignment graphics in the prior art Figures 1a to 1d These correspond to several graphic types, including AIM, Box in Box, Bar in Bar, and Bar in Box. The common feature of existing alignment graphics is that they all use a combination of square positioning graphics. Offset is detected by measuring the offset in the X and Y dimensions, and the Overlay error value is calculated to compensate for the alignment of the lithographic image.

[0004] The existing technical solutions have the following shortcomings:

[0005] 1. In photolithography, there is a certain probability that the alignment image will be damaged. If the pattern in one direction is damaged, the positioning effect of the offset will be worse, thus misleading the compensation value.

[0006] 2. The overall size of the graphic is large, taking up a lot of space. Summary of the Invention

[0007] The purpose of this invention is to provide an overlay marking structure and an overlay offset measurement method, improve the pattern of the overlay marking structure, reduce the impact of pattern damage on overlay offset error detection, and achieve a more reliable and accurate overlay offset detection effect.

[0008] To achieve the above objectives, some embodiments of the present invention provide the following technical solutions:

[0009] Overlay marking structure, including:

[0010] The first set of engraving patterns and the second set of engraving patterns are in a triangular structure;

[0011] The first set of marking patterns and the second set of marking patterns are formed on different layers of the wafer substrate, and the projected area of ​​the first set of marking patterns is within the range of the projected area of ​​the second set of marking patterns.

[0012] Overlay compensation data is obtained by measuring the offset of the center of the first set of markings and the second set of markings in the X, Y, and Z directions, and the exposure machine is compensated based on the compensation data.

[0013] In some embodiments of the present invention, both the first set of engraving patterns and the second set of engraving patterns are in the form of an equilateral triangle structure.

[0014] In some embodiments of the present invention, the positions of the first set of engraving marks and the second set of engraving marks are configured such that, when the engravings are aligned, the center of the first set of engraving marks and the center of the second set of engraving marks are aligned, and the two engraving marks are arranged in parallel.

[0015] In some embodiments of the present invention, the first set of engraving patterns is proportionally reduced to the second set of engraving patterns, and the outer edges of the first set of engraving patterns are parallel to the outer edges of the second set of engraving patterns.

[0016] In some embodiments of the present invention, the overlay offset detection structure further includes:

[0017] Image acquisition mechanism: used to acquire images of the first set of marking patterns, and images of the second set of marking patterns;

[0018] Processor: Acquires the image of the first set of marking patterns and locates the center of the first set of marking pattern images; acquires the image of the second set of marking patterns and locates the center of the second set of marking pattern images; analyzes the offset of the center of the first set of marking patterns and the center of the second set of marking patterns in the X, Y, and Z directions to obtain overlay compensation data; and generates compensation data for the exposure machine based on the compensation data.

[0019] In some embodiments of the present invention, the first set of engraving patterns and the second set of engraving patterns are arranged in the form of Box in Box, Bar in Bar, and Bar in Box structures.

[0020] The second embodiment of the present invention further provides a method for detecting overprint offset, which uses the overprint mark structure described above to detect overprint offset, and includes the following steps:

[0021] Detect the center of the first set of engraved patterns;

[0022] Detect the center of the second set of engraved patterns;

[0023] The offset of the center of the first set of markings and the second set of markings in the X, Y and Z directions is measured to obtain the overlay compensation data, and the exposure machine is compensated according to the compensation data.

[0024] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0025] 1. By designing the overlay marking pattern as a triangle, the center of the triangle can be located using its two sides. The overlay deviation can be determined based on the discrepancy between the centers of the two overlay marking patterns, generating compensation data. Even if the image of the overlay marking pattern is damaged in one direction, it will not affect the judgment of the deviation, thereby improving the reliability of the overlay marking pattern.

[0026] 2. Compared to square markings, triangular markings take up less space, which reduces the impact on the photolithography process. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1a This is a schematic diagram of the first embodiment of the overlay pattern in the prior art;

[0029] Figure 1b This is a schematic diagram of the second implementation structure of the overlay pattern in the prior art;

[0030] Figure 1c This is a schematic diagram of the third implementation structure of overlay pattern in the prior art;

[0031] Figure 1d This is a schematic diagram of the fourth implementation structure of overlay pattern in the prior art;

[0032] Figure 2a This is a schematic diagram of the alignment state of the first embodiment of the overlay pattern of the present invention;

[0033] Figure 2b This is a schematic diagram of the alignment state of the second embodiment of the overprinted pattern structure of the present invention;

[0034] Figure 2c This is a schematic diagram of the alignment state of the third embodiment of the overprinted pattern of the present invention;

[0035] Figure 2d This is a schematic diagram of the alignment state of the fourth embodiment of the overlay pattern of the present invention;

[0036] Figure 3a This is a schematic diagram of the offset state of the first embodiment of the overprinted pattern of the present invention;

[0037] Figure 3bThis is a schematic diagram of the offset state of the second embodiment of the overprinted pattern of the present invention;

[0038] Figure 3c This is a schematic diagram of the offset state of the third embodiment of the overprinted pattern of the present invention;

[0039] Figure 3d This is a schematic diagram of the fourth embodiment of the overprinted pattern of the present invention, showing the offset state of the structure.

[0040] Figure 4 This is a comparison diagram of the overlay deviation detection status between existing technologies and the present invention;

[0041] In the above figures:

[0042] 1- The first set of engraved markings;

[0043] 2-Second set of engraved markings. Detailed Implementation

[0044] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0045] The first embodiment of the present invention provides an overlay marking structure to solve the problem of overlay alignment in photolithography.

[0046] The overlay marking structure reference provided by this invention Figures 2a to 2d The specific structure is as follows.

[0047] The overlay marking structure includes a first set of marking patterns 1 and a second set of marking patterns 2 in a triangular structure; the first set of marking patterns 1 and the second set of marking patterns 2 are formed on different layers of the wafer substrate, and are usually processed on two adjacent layers.

[0048] The first set of marking graphics 1 and the second set of marking graphics 2 both form a triangular projection, and the positions of the two marking graphics are configured such that the projected area of ​​the first set of marking graphics 1 is within the range of the projected area of ​​the second set of marking graphics 2.

[0049] Specifically, the area of ​​the first set of engraving patterns 1 can be smaller than the area of ​​the second set of engraving patterns 2, so that the first set of engraving patterns 1 is completely located within the range of the second set of engraving patterns 2; or, the first set of engraving patterns 1 and the second set of engraving patterns 2 can use the same pattern, and the two can be in the same position in different layers, so that the positions of the two patterns coincide after they are formed.

[0050] Alternatively, in some embodiments of the present invention, the area of ​​the first set of marking patterns 1 is proportionally reduced to the area of ​​the second set of marking patterns 2. That is, the shapes of the triangles in the two sets of marking patterns are the same.

[0051] Furthermore, in some embodiments of the present invention, the three sides of the first set of engraving patterns 1 are parallel to the three sides of the second set of engraving patterns 2.

[0052] Because of the use of triangular markers, the position of a triangle can be easily located based on its centroid, circumcenter, incenter, or orthocenter. Furthermore, for ease of measurement, the positions of the two overlay markers can be configured so that the five centers of the two overlay markers align during overlay alignment. Consequently, the overlay deviation can be located based on the positional deviation of the five centers after overlay.

[0053] With the aforementioned structure, the positional deviation of the two overlay marking patterns during photolithography can reflect the positional deviation of the overlay patterns. Specifically, overlay compensation data can be obtained by measuring the offset of the center of the first overlay marking pattern and the center of the second overlay marking pattern in the X, Y, and Z directions, and the exposure machine can be compensated based on this compensation data.

[0054] Furthermore, in some embodiments of the present invention, for easier positioning of deviations, both the first set of engraving marks 1 and the second set of engraving marks 2 are projected as equilateral triangles. The positions of the first set of engraving marks 1 and the second set of engraving marks 2 are configured such that, during engraving alignment, the centers of the first set of engraving marks 1 and the second set of engraving marks 2 are aligned, and the two engraving marks are set in parallel, that is, the three sides of the two engraving mark triangles are parallel.

[0055] To enable automated detection and positioning, in some embodiments of the present invention, the overlay marking structure further includes:

[0056] Image acquisition mechanism: used to acquire images of the first set of marking patterns, and images of the second set of marking patterns;

[0057] Processor: Acquires the image of the first set of marking patterns 1 and locates the center of the first set of marking patterns 1 image; acquires the image of the second set of marking patterns 2 and locates the center of the second set of marking patterns 2 image; obtains marking compensation data by measuring the offset of the center of the first set of marking patterns 1 and the center of the second set of marking patterns 2 in the X, Y, and Z directions; and compensates the exposure machine based on the compensation data.

[0058] It should be noted that, for an equilateral triangle, the center refers to the center of the triangle (where the centroid, circumcenter, incenter, and orthocenter coincide); for a non-equilateral triangle, it refers to the centroid, circumcenter, incenter, or orthocenter.

[0059] During overlay alignment, the first overlay mark pattern 1 and the second overlay mark pattern 2 have a default alignment position, for example, they may be center-aligned. When an overlay position offset occurs, the default overlay alignment position shifts, for example, the center position deviates. This positional offset can be analyzed from the images of the first overlay mark pattern 1 and the second overlay mark pattern 2.

[0060] The following will provide implementation methods for a first set of marking patterns 1 and a second set of marking patterns 2, which are different from each other.

[0061] The first set of engraving marks (Figure 1) and the second set of engraving marks (Figure 2) are arranged in a Box in Box, Bar in Bar, and Bar in Box structure. The details are explained below.

[0062] In some embodiments of the present invention, the first set of engraving patterns 1 is a closed triangular region, or the first set of engraving patterns 1 includes a first side of the first set of engravings, a second side of the first set of engravings, and a third side of the first set of engravings, which together form a non-closed triangular region.

[0063] In some embodiments of the present invention, the second set of engraving patterns 2 is a closed triangular region, or the second set of engraving patterns 2 includes a first side of the second set of engravings, a second side of the second set of engravings, and a third side of the second set of engravings, which together form a non-closed triangular region.

[0064] Based on the aforementioned implementation structure of each overprinted marking pattern, there are implementations with the following combinations of marking patterns.

[0065] refer to Figure 2a The first set of engraved markings, 1, forms a closed triangular area, and the second set of engraved markings, 2, forms a closed triangular area.

[0066] refer to Figure 2b In the form of "Bar in Bar", the first set of markings, graphic 1, represents a non-closed triangular region enclosed by three sides, and the second set of markings, graphic 2, also represents a non-closed triangular region enclosed by three sides.

[0067] refer to Figure 2c The first set of markings, 1, is a non-closed triangular area surrounded by three non-closed sides, while the second set of markings, 2, is a closed triangular area.

[0068] refer to Figure 2dIn the form of a bar in a box, the first set of engraved markings 1 is a closed triangular area, and the second set of engraved markings 2 includes a non-closed triangular area surrounded by three non-closed sides.

[0069] The second embodiment of the present invention further provides a method for detecting overprint offset, which uses the overprint mark structure described in Embodiment 1 to detect overprint offset, and includes the following steps.

[0070] Detect the center of the first set of engraved pattern 1;

[0071] Detect the center of the second set of engraved pattern 2;

[0072] The offset of the center of the first set of marking patterns 1 and the center of the second set of marking patterns 2 in the X, Y, and Z directions is used to obtain the overlay compensation data, and the exposure machine is compensated according to the compensation data.

[0073] Specifically, the area of ​​the first set of engraved marking patterns 1 is smaller than the area of ​​the second set of engraved marking patterns 2, and it lies within the projection range of the second set of engraved marking patterns 2. (See reference...) Figures 2a to 2d This is a diagram showing the alignment state of the engraving. At this point, the centers of the first engraving mark pattern 1 and the second engraving mark pattern 2 coincide. (Reference) Figures 3a to 3d This is a schematic diagram of the overlay deviation state. At this time, there is a deviation between the center positions of the first overlay mark pattern 1 and the second overlay mark pattern 2. Taking the deviation direction shown in the diagram as an example, the deviation direction is along the Z-axis, and this deviation can be obtained through analysis of the overlay mark images.

[0074] by Figure 3b Taking the illustrated implementation structure as an example, the directions of the three sides of the triangle are defined as follows: the side perpendicular to the X direction is the first side, the side perpendicular to the Y direction is the second side, and the side perpendicular to the Z direction is the third side. Assuming that during the photolithography process, the first set of marking patterns 1 is damaged on one side in the third direction, the center position of the first set of marking patterns 1 can be located using the first and second sides. Similarly, if the second set of marking patterns 2 is damaged in the first direction, the center position of the second set of marking patterns 2 can be located using the second and third sides. That is, even when the marking patterns of the triangle are damaged in one direction, the direction and displacement of the overlay deviation can still be located.

[0075] refer to Figure 4 Compared with the existing technology, the present invention modifies the positioning of two dimensions, X and Y, to positioning in three directions, X, Y and Z, which can achieve a more reliable overlay deviation detection effect.

[0076] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. It should be noted that any modifications, equivalent substitutions, and improvements made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of this patent application should be determined by the scope of the appended claims.

Claims

1. An overlay marking structure, characterized in that, include: The first set of engraving patterns and the second set of engraving patterns are in a triangular structure; The first set of marking patterns and the second set of marking patterns are formed on different layers of the wafer substrate, and the projected area of ​​the first set of marking patterns is within the range of the projected area of ​​the second set of marking patterns. The offset of the centers of the first set of marking patterns and the second set of marking patterns in the X, Y, and Z directions is used to obtain overlay compensation data, and the exposure machine is compensated according to the compensation data. Both the first set of engraving patterns and the second set of engraving patterns are in the form of equilateral triangles. The positions of the first set of engraving marks and the second set of engraving marks are configured such that, when the engraving is aligned, the center of the first set of engraving marks and the center of the second set of engraving marks are aligned, and the two engraving marks are set in parallel. In an equilateral triangle, the direction of the three sides is defined as follows: the side perpendicular to the X direction is the first side, the side perpendicular to the Y direction is the second side, and the side perpendicular to the Z direction is the third side. When the marking pattern of a triangle has damage in one direction, the center position of the marking pattern is located by locating the undamaged edge.

2. The overlay marking structure as described in claim 1, characterized in that, The first set of engraved markings is proportionally smaller than the second set of engraved markings, and the outer edges of the first set of engraved markings are parallel to the outer edges of the second set of engraved markings.

3. The overlay marking structure as described in claim 1, characterized in that, Further includes: Image acquisition mechanism: used to acquire images of the first set of marking patterns, and images of the second set of marking patterns; Processor: Acquires the image of the first set of marking patterns and locates the center of the first set of marking pattern images; acquires the image of the second set of marking patterns and locates the center of the second set of marking pattern images; analyzes the offset of the center of the first set of marking patterns and the center of the second set of marking patterns in the X, Y, and Z directions to obtain overlay compensation data; and generates compensation data for the exposure machine based on the compensation data.

4. The overlay marking structure as described in any one of claims 1 to 3, characterized in that, The first set of engraving patterns and the second set of engraving patterns are arranged in the form of Box in Box, Bar in Bar, and Bar in Box.

5. A method for detecting overlay offset, characterized in that, The detection of overlay misalignment using the overlay marking structure described in any one of claims 1 to 4 includes the following steps: Detect the center of the first set of engraved patterns; Detect the center of the second set of engraved patterns; The offset of the center of the first set of marking marks and the second set of marking marks in the X, Y and Z directions is measured to obtain the overlay compensation data, and the exposure machine is compensated according to the compensation data; When the marking pattern of a triangle has damage in one direction, the center position of the marking pattern is located by locating the undamaged edge.

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