Image-based overlay mark and error calculation method of overlay mark

Abstract

The invention discloses an overlay mark based on an image and an error calculation method of the overlay mark. Comprising at least two first marking lines extending in the first direction, at least two second marking lines extending in the second direction, at least two third marking lines extending in the third direction and at least two fourth marking lines extending in the fourth direction. The first marking line and the second marking line are located at the edge of the overlay mark and surround an outer side frame of the overlay mark; the third marking line and the fourth marking line are located at the corner positions of the outer side frame, and the third marking line and the fourth marking line are located on the two sides of the diagonal line of the outer side frame of the overlay mark; a first preset angle exists between the third direction and the first direction; a second preset angle exists between the fourth direction and the first direction. According to the overlay mark provided by the invention, the mark lines in four different directions are arranged in the design of the photomask, so that the complexity of the pattern is increased on the premise of not changing the size of the original mark, and the accuracy of overlay error measurement is further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of overlay marks, and in particular to an overlay mark based on an image and an overlay mark error calculation method. Background Art

[0002] In the wafer manufacturing process, there will be a multi-layer printed structure, and there is a certain alignment deviation between the layers. This deviation is called overlay error (OVL). In the semiconductor field, the deviation between layers is measured by measuring OVL, so as to improve the photolithography process and perform photolithography correction for the next layer. Image-based OVL measurement equipment (ImageBase Overlay, IBO) is a commonly used technical means. IBO obtains the measurement results by shooting the overlay marks (Mark) of the front and back layers and using image processing and other means.

[0003] In the measurement process, the position of the Mark needs to be obtained before measurement. The position of the Mark based on the design value is usually not very accurate, so a second movement is often required to make the image of the Mark located in the center of the camera's field of view. After the first movement, an image is taken and the relative position of the Mark is obtained through template matching. Due to the existence of process and other issues, the image signal of the Mark is easily unclear, which in turn causes the Mark position matching to fail, causing certain problems in the measurement. Summary of the invention

[0004] The present invention provides an image-based overlay mark and an overlay mark error calculation method. Under the premise of keeping the original pattern size unchanged, oblique lines are introduced into the design of the mask (i.e., the photomask), thereby increasing the complexity of the original overlay mark pattern in the prior art, improving the ability to capture the overlay mark, and improving the accuracy of the overlay error measurement.

[0005] According to a first aspect of the present invention, there is provided an image-based overlay marking, comprising:

[0006] at least two first marking lines extending along a first direction, at least two second marking lines extending along a second direction, at least two third marking lines extending along a third direction, and at least two fourth marking lines extending along a fourth direction;

[0007] The first marking line and the second marking line are located at the edge of the overengraved mark, forming an outer frame of the overengraved mark; the third marking line and the fourth marking line are located at the corners of the outer frame of the overengraved mark, and the third marking line and the fourth marking line are located on both sides of the diagonal line of the outer frame of the overengraved mark;

[0008] The first direction is perpendicular to the second direction; a first preset angle exists between the third direction and the first direction; and a second preset angle exists between the fourth direction and the first direction.

[0009] Optionally, the outer border of the overlay mark is a square.

[0010] Optionally, the first preset angle includes 45°; the second preset angle includes 135°.

[0011] Optionally, the third marking line is located on both sides of the first diagonal line of the outer frame, and the fourth marking line is located on both sides of the second diagonal line of the outer frame; wherein, the first diagonal line is parallel to the third direction, and the third marking line is located at the corner positions where the two ends of the first diagonal line are located; the second diagonal line is parallel to the fourth direction, and the fourth marking line is located at the corner positions where the two ends of the second diagonal line are located.

[0012] Optionally, the third marking line is located on both sides of the first diagonal line of the outer frame, and the fourth marking line is located on both sides of the second diagonal line of the outer frame, wherein the first diagonal line is parallel to the third direction, and the third marking line is located at the corners where the two ends of the second diagonal line are located; the second diagonal line is parallel to the fourth direction, and the fourth marking line is located at the corners where the two ends of the first diagonal line are located.

[0013] Optionally, the overlay mark includes at least a first overlay mark arranged on the first layer and a second overlay mark arranged on the second layer.

[0014] Optionally, the second overlay mark is a proportionally enlarged pattern of the first overlay mark, and the first overlay mark is nested in the second overlay mark.

[0015] According to a second aspect of the present invention, a method for calculating an error of an overlay mark is provided, which is applicable to the image-based overlay mark described in any one of the first aspects of the present invention, and the method for calculating an error of an overlay mark comprises:

[0016] Establish a plane rectangular coordinate system based on the overlay marks;

[0017] Acquire an image of the overlay mark, and determine the coordinates of the first endpoint of the third mark line and the first endpoint of the fourth mark line according to the image; the first endpoint of the third mark line and the first endpoint of the fourth mark line are both located at the corner position of the overlay mark;

[0018] The coordinates of the first endpoint of the third marking line connected with the origin in the plane rectangular coordinate system are recorded as a first connecting line, and the coordinates of the first endpoint of the fourth marking line connected with the origin in the plane rectangular coordinate system are recorded as a second connecting line;

[0019] The first connecting line and the second connecting line are orthogonally decomposed in the plane rectangular coordinate system, and the overlay error is calculated according to the decomposition result.

[0020] Optionally, performing orthogonal decomposition on the first connecting line and the second connecting line in the plane rectangular coordinate system, and calculating the overlay error according to the decomposition result, includes:

[0021] Determine the component of the third marking line on the X axis and the component on the Y axis according to the first connecting line and record them as X1 and Y1 respectively; determine the component of the fourth marking line on the X axis and the component on the Y axis according to the second connecting line and record them as X2 and Y2 respectively;

[0022] Summing X1 and X2 gives X a , sum Y1 and Y2 to get Y a ;

[0023] Determine a definition component X' of the third marking line on the X-axis according to the first connecting line, and determine a definition component Y' of the fourth marking line on the Y-axis according to the second connecting line;

[0024] The error component ΔX of the overlay mark on the X-axis is obtained by subtracting X1 and X'; the error component ΔY of the overlay mark on the Y-axis is obtained by subtracting Y1 and Y'.

[0025] Optionally, determining a definition component X' of the third marking line on the X-axis according to the first connecting line, determining a definition component Y' of the fourth marking line on the Y-axis according to the second connecting line, subtracting X1 and X' to obtain an error component ΔX of the overlay mark on the X-axis; and subtracting Y1 and Y' to obtain an error component ΔY of the overlay mark on the Y-axis, comprises:

[0026] The defined components X' and Y' are calculated by formula (1) and formula (2);

[0027]

[0028] Wherein, X' is the definition component of the third marking line on the X axis, Y' is the definition component of the fourth marking line on the Y axis, and L 45 is the length of the first connecting line, L 135 is the length of the second connecting line;

[0029] Subtracting X1 and X' to obtain the error component ΔX of the overlay mark on the X-axis; subtracting Y1 and Y' to obtain the error component ΔY of the overlay mark on the Y-axis, including:

[0030] ΔX and ΔY are calculated by formula (III) and formula (IV):

[0031] ΔX=X a -X ′ (three)

[0032] ΔY=Y a -Y ′ (Four)

[0033] Wherein, ΔX is the error component of the overlay mark on the X-axis, and ΔY is the error component of the overlay mark on the Y-axis.

[0034] The present invention discloses an overlay mark based on an image and an error calculation method for the overlay mark, comprising: at least two first marking lines along a first direction, at least two second marking lines along a second direction, at least two third marking lines along a third direction and at least two fourth marking lines along a fourth direction; the first marking line and the second marking line are located at the edge of the overlay mark, forming an outer frame of the overlay mark; the third marking line and the fourth marking line are located at the corner positions of the outer frame of the overlay mark, and the third marking line and the fourth marking line are located on both sides of the diagonal of the outer frame of the overlay mark; the first direction is perpendicular to the second direction; the third direction has a first preset angle with the first direction; the fourth direction has a second preset angle with the first direction. The overlay mark based on an image and an error calculation method for the overlay mark provided by the present invention, while keeping the original pattern size unchanged, has marking lines in four different directions at the same time, increases the complexity of the overlay mark pattern, improves the ability to capture the overlay mark, and improves the accuracy of overlay error measurement.

[0035] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0037] Figure 1 is a schematic diagram of an image-based overlay mark provided by an embodiment of the present invention;

[0038] Figure 2 is another schematic diagram of an image-based overlay mark provided by an embodiment of the present invention;

[0039] Figure 3is another schematic diagram of an image-based overlay mark provided by an embodiment of the present invention;

[0040] Figure 4 is another schematic diagram of an image-based overlay mark provided by an embodiment of the present invention;

[0041] Figure 5 is another schematic diagram of an image-based overlay mark provided by an embodiment of the present invention;

[0042] Figure 6 is another schematic diagram of an image-based overlay mark provided by an embodiment of the present invention;

[0043] Figure 7 is a flow chart of an error calculation method for overlay marks provided by an embodiment of the present invention;

[0044] Figure 8 It is a schematic diagram of orthogonal decomposition in an error calculation method of an overlay mark provided by an embodiment of the present invention;

[0045] Fig. 9 It is a flow chart of another method for calculating the error of overlay marks provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0047] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0048] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be executed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0049] Figure 1 is a schematic diagram of an image-based overlay mark provided by an embodiment of the present invention, with reference to Figure 1 The embodiment of the present invention provides an image-based overlay mark 100, comprising: at least two first marking lines 1 extending along a first direction A, at least two second marking lines 2 extending along a second direction B, at least two third marking lines 3 extending along a third direction C, and at least two fourth marking lines 4 extending along a fourth direction D; the first marking lines 1 and the second marking lines 2 are located at the edge of the overlay mark 100, forming an outer frame of the overlay mark 100; the third marking lines 3 and the fourth marking lines 4 are located at the corners of the outer frame of the overlay mark 100, and the third marking lines 3 and the fourth marking lines 4 are located on both sides of the diagonal of the outer frame of the overlay mark 100; the first direction A and the second direction B are perpendicular to each other; the third direction C has a first preset angle α with the first direction A; the fourth direction D has a second preset angle β with the first direction A.

[0050] Among them, overlay marks are special patterns used to measure and correct the alignment accuracy between different layers in the photolithography step during the semiconductor manufacturing process.

[0051] Specifically, Figure 1 As shown, the image-based overlay mark 100 provided in the embodiment of the present invention includes at least two first marking lines 1 extending along the first direction A, at least two second marking lines 2 extending along the second direction B, at least two third marking lines 3 extending along the third direction C and at least two fourth marking lines 4 extending along the fourth direction; wherein, the first marking lines 1 and the second marking lines 2 are located at the edge of the overlay mark 100, and constitute the outer frame of the overlay mark 100, that is, the two first marking lines 1 and the two second marking lines 2 are located on the frame line of the outer frame; the third marking lines 3 and the fourth marking lines 4 are located at the corner positions of the outer frame of the overlay mark 100 and on both sides of the diagonal of the overlay mark 100; wherein, the first direction A and the second direction B are perpendicular to each other, there is a first preset angle α between the third direction C and the first direction A, and there is a second preset angle β between the fourth direction D and the first direction A.

[0052] Optionally, the outer border of the overlay mark 100 is a square.

[0053] Optionally, the first preset angle α includes 45°; and the second preset angle β includes 135°.

[0054] Since the lithography machine hopes to obtain more error information of the front layer overlay mark in order to reduce the exposure error of the rear layer, the measurement result of the overlay error is fed back to the lithography machine through the model. Each additional measurable amount of a mark helps to improve the model, so that the compensation value of the model can better improve the lithography process. Therefore, the overlay mark provided by the embodiment of the present invention, on the basis of the original pattern (that is, only having mark lines in the first direction and the second direction), creatively adds a third mark line in the third direction and a fourth mark line in the fourth direction, which can ensure that the complexity of the overlay mark pattern is increased while the size of the original overlay mark pattern remains unchanged, thereby improving the original overlay mark model, so that more reference quantities are available during measurement, and a more complex overlay mark pattern can enhance the ability to capture the overlay mark and improve the accuracy of overlay error measurement.

[0055] Figure 2 is another schematic diagram of an image-based overlay mark provided by an embodiment of the present invention, with reference to Figure 2 Optionally, the third marking line 3 is located on both sides of the first diagonal line L1 of the outer frame, and the fourth marking line 4 is located on both sides of the second diagonal line L2 of the outer frame; wherein, the first diagonal line L1 is parallel to the third direction C, and the third marking line 3 is located at the corner position where the two ends of the first diagonal line L1 are located; the second diagonal line L2 is parallel to the fourth direction D, and the fourth marking line 4 is located at the corner position where the two ends of the second diagonal line L2 are located.

[0056] Specifically, the third marking line 3 is located on both sides of the first diagonal line L1 of the outer frame, and the third marking line 3 is located at the corners at both ends of the first diagonal line L1; the fourth marking line 4 is located on both sides of the second diagonal line L2 of the outer frame, and the fourth marking line 4 is located at the corners at both ends of the second diagonal line L2; wherein, the first diagonal line L1 is parallel to the third direction C, and the second diagonal line L2 is parallel to the fourth direction D.

[0057] Optionally, based on the embodiment of the present invention, Figure 3 is another schematic diagram of an image-based overlay mark provided by an embodiment of the present invention, with reference to Figure 3 The overlay mark 100 may also include a plurality of third marking lines 3 ( Figure 3 The example of six lines on each side is not a limitation of the embodiments of the present invention), and the third marking lines 3 are all located at the corners at both ends of the first diagonal line L1, and only six third marking lines 3 at both ends of the first diagonal line L1 are shown in the figure; it also includes multiple fourth marking lines 4 located on both sides of the second diagonal line L2, and the fourth marking lines 4 are all located at the corners at both ends of the second diagonal line L2, and only six fourth marking lines 4 at both ends of the second diagonal line L2 are shown in the figure.

[0058] Figure 4is another schematic diagram of an image-based overlay mark provided by an embodiment of the present invention, with reference to Figure 4 Optionally, the third marking line 3 is located on both sides of the first diagonal line L1 of the outer frame, and the fourth marking line 4 is located on both sides of the second diagonal line L2 of the outer frame, wherein the first diagonal line L1 is parallel to the third direction C, and the third marking line 3 is located at the corner position where the two ends of the second diagonal line L2 are located; the second diagonal line L2 is parallel to the fourth direction D, and the fourth marking line 4 is located at the corner position where the two ends of the first diagonal line L1 are located.

[0059] Specifically, refer to Figure 4 In an embodiment of the present invention, the third marking line 3 in the overlay mark is located on both sides of the first diagonal line L1 of the outer frame, and the fourth marking line 4 is located on both sides of the second diagonal line L2, wherein the first diagonal line L1 is parallel to the third direction C, the third marking line 3 is located at the corner position where the two ends of the second diagonal line L2 are located, the second diagonal line L2 is parallel to the fourth direction D, and the fourth marking line 4 is located at the corner position where the two ends of the first diagonal line L1 are located.

[0060] Further, based on the embodiments of the present invention, Figure 5 is another schematic diagram of an image-based overlay mark provided by an embodiment of the present invention, with reference to Figure 5 The overlay mark 100 provided in the embodiment of the present invention includes a plurality of third marking lines 3 additionally arranged on both sides of the first diagonal line L1, and the third marking lines 3 are all located at the corner positions at both ends of the second diagonal line L2, and the figure only shows six third marking lines 3 at each end of the second diagonal line L2; it also includes a plurality of fourth marking lines 4 additionally arranged on both sides of the second diagonal line L2, and the fourth marking lines 4 are all located at the corner positions at both ends of the first diagonal line L1, and the figure only shows six fourth marking lines 4 at each end of the first diagonal line L1.

[0061] Figure 6 is another schematic diagram of an image-based overlay mark provided by an embodiment of the present invention, with reference to Figure 6 Optionally, the overlay mark includes at least a first overlay mark 100a disposed on the first layer and a second overlay mark 100b disposed on the second layer.

[0062] Specifically, the overlay mark at least includes a first overlay mark 100a disposed on the first layer (ie, the front layer) and a second overlay mark 100b disposed on the second layer (ie, the current layer).

[0063] Optionally, the second set of engraved marks 100b is a proportionally enlarged pattern of the first set of engraved marks 100a, and the first set of engraved marks 100a is nested in the second set of engraved marks 100b.

[0064] Specifically, the pattern of the second set of engraved marks 100b is a pattern that is proportionally enlarged of the first set of engraved marks 100a, and the first set of engraved marks 100a is nested in the second set of engraved marks 100b.

[0065] The first set of engraved marks and the second set of engraved marks provided in the embodiment of the present invention are both provided with a plurality of third marking lines and fourth marking lines, which can increase the reference quantity of measurement during the lithography process, thereby helping to improve the model so that the compensation value of the model can better improve the lithography process.

[0066] According to the same inventive concept, Figure 7 is a flow chart of an error calculation method for an overlay mark provided by an embodiment of the present invention, with reference to Figure 7 The embodiment of the present invention provides a method for calculating the error of an overlay mark, which is applicable to the image-based overlay mark in any of the above-mentioned embodiments of the invention. The method for calculating the error of the overlay mark includes:

[0067] S1. Establish a plane rectangular coordinate system based on the overlay marks.

[0068] Specifically, according to the overlay mark pattern provided by the embodiment of the present invention, a plane rectangular coordinate system is established, and the plane rectangular coordinate system includes an origin O, an X-axis, and a Y-axis. The origin O is a point on the plane where the overlay mark is located, and can be selected according to actual conditions. For example, in a certain embodiment, the vertex of the lower left corner of the outer frame can be selected as the origin O, the direction of the first direction A is the X-axis direction, and the direction of the second direction B is the Y-axis direction, or the center point of the overlay mark is selected as the origin O, the direction of the first direction A is the X-axis direction, and the direction of the second direction B is the Y-axis direction.

[0069] S2. Acquire an image of the overlay mark, and determine the first endpoint coordinates of the third mark line and the first endpoint coordinates of the fourth mark line according to the image.

[0070] Specific, combined Figure 1 , obtain an image of the overlay mark through the camera, combine it with the rectangular coordinate system determined in the previous step, and determine the first endpoint coordinates of the third marking line 3 and the first endpoint coordinates of the fourth marking line 4 according to the image, wherein the first endpoint of the third marking line 3 and the first endpoint of the fourth marking line 4 are both located at the corner positions of the overlay mark.

[0071] S3. The coordinates of the first endpoint of the connecting plane rectangular coordinate system and the third marking line are recorded as the first connecting line, and the coordinates of the first endpoint of the connecting plane rectangular coordinate system and the fourth marking line are recorded as the second connecting line.

[0072] Specifically, Figure 8 is a schematic diagram of orthogonal decomposition in an error calculation method for overlay marks provided by an embodiment of the present invention, with reference to Figure 8, connect the origin O in the plane rectangular coordinate system and the first endpoint coordinate of the third marking line 3, and record them as the first connecting line OE; connect the origin O in the plane rectangular coordinate system and the first endpoint coordinate of the fourth marking line 4, and record them as the second connecting line OF.

[0073] S4. Perform orthogonal decomposition on the first connecting line and the second connecting line in a plane rectangular coordinate system, and calculate the overlay error according to the decomposition result.

[0074] Specifically, orthogonal decomposition is performed on the first connecting line OE and the second connecting line OF in a plane rectangular coordinate system, and the overlay error is calculated according to the decomposition result.

[0075] On the basis of the above-mentioned embodiment, this embodiment performs orthogonal decomposition on the first connecting line and the second connecting line in a plane rectangular coordinate system, and further refines the calculation of the overlay error according to the decomposition result. Fig. 9 is a flow chart of another method for calculating the error of an overlay mark provided by an embodiment of the present invention, referring to Figure 8 and Fig. 9 ,include:

[0076] S21. Determine the X-axis component and the Y-axis component of the third marking line 3 according to the first connecting line OE and record them as X1 and Y1 respectively; determine the X-axis component and the Y-axis component of the fourth marking line according to the second connecting line OF and record them as X2 and Y2 respectively.

[0077] Specifically, Figure 8 In the figure, the component of the third marking line 3 on the X-axis is determined to be X1 according to the first connecting line OE, that is, X1 is OH, and the component of the third marking line 3 on the Y-axis is Y1, that is, Y1 is OG; the component of the fourth marking line 4 on the X-axis and the component on the Y-axis are determined according to the second connecting line OF and recorded as X2 and Y2 respectively, that is, X2 is OJ and Y2 is OI.

[0078] S22, sum X1 and X2 to get X a , sum Y1 and Y2 to get Y a .

[0079] Specifically, the component OH of the third marking line 3 on the X-axis and the component OJ of the fourth marking line 4 on the X-axis are summed to obtain X a , sum the component OG of the third marking line 3 on the Y axis and the component OI of the fourth marking line 4 on the Y axis to obtain Y a .

[0080] S23 , determining a definition component X′ of the third marking line 3 on the X axis according to the first connecting line OE, and determining a definition component Y′ of the fourth marking line 4 on the Y axis according to the second connecting line OF.

[0081] Specifically, the definition component X' of the third marking line 3 on the X-axis can be calculated according to the first connecting line OE, and the definition component Y' of the fourth marking line 4 on the Y-axis can be determined according to the second connecting line OF. The specific calculation method will be described in detail below and will not be repeated here.

[0082] S24, subtract X1 and X' to obtain an error component ΔX of the overlay mark on the X-axis; and subtract Y1 and Y' to obtain an error component ΔY of the overlay mark on the Y-axis.

[0083] Specifically, the error component ΔX is obtained by subtracting X1 obtained in the above step S21 and X' obtained in the above step S23, and the error component ΔY is obtained by subtracting Y1 obtained in the above step S21 and Y' obtained in the above step S23.

[0084] Optionally, a definition component X' of the third marking line 3 on the X-axis is determined according to the first connecting line OE, a definition component Y' of the fourth marking line 4 on the Y-axis is determined according to the second connecting line OF, and an error component ΔX of the overlay mark on the X-axis is obtained by subtracting X1 and X'; and an error component ΔY of the overlay mark on the Y-axis is obtained by subtracting Y1 and Y', including:

[0085] The defined components X' and Y' are calculated by formula (1) and formula (2);

[0086]

[0087] Wherein, X' is the definition component of the third marking line 3 on the X axis, Y' is the definition component of the fourth marking line 4 on the Y axis, and L 45 is the length of the first connecting line OE, L 135 is the length of the second connecting line OF; where L 45 The length and L 135 It can be calculated through image signal analysis and will not be elaborated here.

[0088] The error component ΔX of the overlay mark on the X-axis is obtained by subtracting X1 and X'; the error component ΔY of the overlay mark on the Y-axis is obtained by subtracting Y1 and Y', including:

[0089] ΔX and ΔY are calculated by formula (III) and formula (IV):

[0090] ΔX=X a -X ′ (three)

[0091] ΔY=Y a -Y ′ (Four)

[0092] Wherein, ΔX is the error component of the overlay mark on the X-axis, and ΔY is the error component of the overlay mark on the Y-axis.

[0093] The error calculation method of the overlay mark provided in the embodiment of the present invention calculates the components of the third mark line and the fourth mark line in the plane rectangular coordinate system, and the error value of the overlay mark can be calculated by the orthogonal decomposition calculation method. The error value is helpful to analyze the lithography distortion at different positions, and the built model can analyze the lithography distortion on the entire wafer.

[0094] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An image-based overlay marking method, characterized in that: include: at least two first marking lines extending along a first direction, at least two second marking lines extending along a second direction, at least two third marking lines extending along a third direction, and at least two fourth marking lines extending along a fourth direction; The first marking line and the second marking line are located at the edge of the overengraved mark, forming an outer frame of the overengraved mark; the third marking line and the fourth marking line are located at the corners of the outer frame of the overengraved mark, and the third marking line and the fourth marking line are located on both sides of the diagonal line of the outer frame of the overengraved mark; The first direction is perpendicular to the second direction; a first preset angle exists between the third direction and the first direction; and a second preset angle exists between the fourth direction and the first direction.

2. The image-based overlay marking according to claim 1, characterized in that: The outer frame of the overlay mark is a square.

3. The image-based overlay marking according to claim 1 or 2, characterized in that: The first preset angle includes 45°; the second preset angle includes 135°.

4. The image-based overlay marking according to claim 2, characterized in that: The third marking line is located on both sides of the first diagonal line of the outer frame, and the fourth marking line is located on both sides of the second diagonal line of the outer frame; wherein, the first diagonal line is parallel to the third direction, and the third marking line is located at the corner positions where the two ends of the first diagonal line are located; the second diagonal line is parallel to the fourth direction, and the fourth marking line is located at the corner positions where the two ends of the second diagonal line are located.

5. The image-based overlay marking according to claim 2, characterized in that: The third marking line is located on both sides of the first diagonal line of the outer frame, and the fourth marking line is located on both sides of the second diagonal line of the outer frame, wherein the first diagonal line is parallel to the third direction, and the third marking line is located at the corners where the two ends of the second diagonal line are located; the second diagonal line is parallel to the fourth direction, and the fourth marking line is located at the corners where the two ends of the first diagonal line are located.

6. The image-based overlay marking according to claim 1, characterized in that: The overlay mark at least includes a first overlay mark arranged on the first layer and a second overlay mark arranged on the second layer.

7. The image-based overlay marking according to claim 6, characterized in that: The second overlay mark is a proportionally enlarged pattern of the first overlay mark, and the first overlay mark is nested in the second overlay mark.

8. A method for calculating the error of an overlay mark, characterized in that: The image-based overlay mark according to any one of claims 1 to 7, wherein the error calculation method of the overlay mark comprises: Establish a plane rectangular coordinate system based on the overlay marks; Acquire an image of the overlay mark, and determine the coordinates of the first endpoint of the third mark line and the first endpoint of the fourth mark line according to the image; the first endpoint of the third mark line and the first endpoint of the fourth mark line are both located at the corner position of the overlay mark; The coordinates of the first endpoint of the third marking line connected with the origin in the plane rectangular coordinate system are recorded as a first connecting line, and the coordinates of the first endpoint of the fourth marking line connected with the origin in the plane rectangular coordinate system are recorded as a second connecting line; The first connecting line and the second connecting line are orthogonally decomposed in the plane rectangular coordinate system, and the overlay error is calculated according to the decomposition result.

9. The error calculation method of overlay mark according to claim 8, characterized in that: Orthogonal decomposition is performed on the first connecting line and the second connecting line in the plane rectangular coordinate system, and overlay error is calculated according to the decomposition result, including: Determine the component of the third marking line on the X axis and the component on the Y axis according to the first connecting line and record them as X1 and Y1 respectively; determine the component of the fourth marking line on the X axis and the component on the Y axis according to the second connecting line and record them as X2 and Y2 respectively; Summing X1 and X2 gives X a , sum Y1 and Y2 to get Y a ; Determine a definition component X' of the third marking line on the X-axis according to the first connecting line, and determine a definition component Y' of the fourth marking line on the Y-axis according to the second connecting line; The error component ΔX of the overlay mark on the X-axis is obtained by subtracting X1 and X'; the error component ΔY of the overlay mark on the Y-axis is obtained by subtracting Y1 and Y'.

10. The error calculation method of overlay mark according to claim 9, characterized in that: Determine the definition component X' of the third marking line on the X-axis according to the first connecting line, determine the definition component Y' of the fourth marking line on the Y-axis according to the second connecting line, and obtain the error component ΔX of the overlay mark on the X-axis by subtracting X1 and X'; The error component ΔY of the overlay mark on the Y axis is obtained by subtracting Y1 and Y', including: The defined components X' and Y' are calculated by formula (1) and formula (2); Wherein, X' is the definition component of the third marking line on the X axis, Y' is the definition component of the fourth marking line on the Y axis, and L 45 is the length of the first connecting line, L 135 is the length of the second connecting line; Subtracting X1 and X' to obtain the error component ΔX of the overlay mark on the X-axis; subtracting Y1 and Y' to obtain the error component ΔY of the overlay mark on the Y-axis, including: ΔX and ΔY are calculated by formula (III) and formula (IV): ΔX = X a -X ′ (III) ΔY = Y a -Y ′ (IV) Wherein, ΔX is the error component of the overlay mark on the X-axis, and ΔY is the error component of the overlay mark on the Y-axis.

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