A three-dimensional overlay mark and overlay error measurement apparatus calibration method

Abstract

The embodiment of the present application discloses a kind of three-dimensional overlay mark and overlay error measurement equipment calibration method.Three-dimensional overlay mark includes substrate and multiple overlay marks on substrate;In multiple overlay marks, the height of the vertical projection of any two overlay marks on the first plane is different;The first plane is perpendicular to the plane where substrate is located.Due to the height of overlay mark in the first plane extension direction is different, the distance of different height overlay mark and shooting point is different, that is, the different height overlay mark forms the different defocus degree that image can express. Thus, once image shooting can obtain the image of overlay mark under different defocus range, without moving the position of overlay mark repeatedly traversing measurement, greatly improve the calibration efficiency of overlay error measurement equipment, avoid environmental factors to cause interference during long time calibration;It can also avoid that overlay mark is offset in horizontal direction, influence calibration precision.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the technical field of semiconductor manufacturing, and particularly relate to a three-dimensional overlay mark and an overlay error measurement device calibration method. BACKGROUND

[0002] With the size of integrated circuits represented by chips becoming smaller and smaller, the feature line width of the photolithography process in the integrated circuits is also reduced. Currently, there are two solutions for solving overlay error measurement, i.e., a first solution of a diffraction based overlay (DBO) scheme based on diffraction principle and a second solution of an image based overlay (IBO) scheme. Both of the above two solutions need to control the aberration of an optical diffraction / imaging system. Especially for the IBO overlay error measurement scheme, the asymmetric type aberration of the imaging system, such as coma and astigmatism, will directly and indirectly affect the measurement result.

[0003] In order to solve the influence of the aberration in the overlay error measurement device of the IBO scheme, according to the axial and vertical distribution characteristics of the asymmetric aberration which has a greater influence on the measurement result, a commonly used calibration method is as follows: taking images of the mark at different positive and negative defocus positions, analyzing the relative shift of the mark images at different defocus amounts, and thus obtaining the influence of the aberration-defocus two-dimensional cross variable on the calibration index. However, the above calibration method has two problems: (1) since the mark needs to be vertically moved together with the moving table within a certain vertical range before and after the focal plane, the position deviation caused by the vertical movement and the coupled horizontal position deviation are introduced into the calibration index, which leads to a significant reduction in the calibration accuracy. (2) The calibration process needs to repeatedly measure within a certain positive and negative defocus range above and below the focal plane position, which is low in calibration efficiency. At the same time, long-time measurement will couple the influence of environmental factors such as temperature fluctuation and mechanical jitter, and the anti-interference ability of the calibration method is poor. SUMMARY

[0004] Based on the defects of the above existing technology, the present application provides a three-dimensional overlay mark and an overlay error measurement device calibration method to improve the calibration efficiency and accuracy of the overlay error measurement device.

[0005] In a first aspect, an embodiment of the present application provides a three-dimensional overlay mark for calibrating an overlay error measurement device, the three-dimensional overlay mark comprising:

[0006] a substrate;

[0007] A plurality of overlay marks on the substrate, wherein a height of a vertical projection of any two of the overlay marks on a first plane is different; and the first plane is perpendicular to a plane on which the substrate is located.

[0008] In a second aspect, the embodiment of the present application further provides a method for calibrating an overlay error measurement device, which is suitable for the three-dimensional overlay mark of the first aspect of the present application, and comprises:

[0009] acquiring images of a plurality of overlay marks in the three-dimensional overlay mark; wherein a height of a vertical projection of any two of the overlay marks on a first plane is different; and the first plane is perpendicular to a plane on which the substrate is located;

[0010] calibrating the overlay error measurement device according to the offset of the images of the plurality of overlay marks.

[0011] The three-dimensional overlay mark provided by the embodiment of the present application comprises a substrate and a plurality of overlay marks on the substrate; wherein a height of a vertical projection of any two of the overlay marks on a first plane is different; and the first plane is perpendicular to a plane on which the substrate is located. Since the heights of the overlay marks in the first plane are different, the distances between the overlay marks of different heights and a shooting point are different, that is, the images formed by the overlay marks of different heights can represent different degrees of defocus. Thus, the images of the overlay marks in different defocus ranges can be obtained by one image shooting, without moving the positions of the overlay marks for repeated traversal measurement, which greatly improves the calibration efficiency of the overlay error measurement device, avoids the interference of environmental factors on the calibration in a long-time calibration process, and also avoids the position offset of the overlay marks in the horizontal direction, which affects the calibration accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 A top view of the three-dimensional overlay mark provided by the embodiment of the present application;

[0013] Figure 2 A sectional view along the A-A' direction; Figure 1

[0014] Figure 3 A top view of another three-dimensional overlay mark provided by the embodiment of the present application;

[0015] Figure 4 A sectional view of the three-dimensional overlay mark shown in FIG. 8; Figure 3

[0016] Figure 5 Another sectional view of the three-dimensional overlay mark shown in FIG. 8; Figure 3

[0017] Figure 6 ​​​This is a schematic diagram of an imaging simulation of a three-dimensional overlay mark provided in an embodiment of the present invention;

[0018] Figure 7 A cross-sectional view of a three-dimensional overlay mark provided in an embodiment of the present invention;

[0019] Figure 8 This is a schematic diagram of an imaging simulation of another three-dimensional overlay mark provided in an embodiment of the present invention;

[0020] Figure 9 A cross-sectional view of another three-dimensional overlay mark provided in an embodiment of the present invention;

[0021] Figure 10 for Figure 9 The cross-sectional view of the three-dimensional overlay mark along another section direction is shown;

[0022] Figure 11 An imaging simulation diagram of another three-dimensional overlay mark provided in an embodiment of the present invention;

[0023] Figure 12 A cross-sectional view of another three-dimensional overlay mark provided in an embodiment of the present invention;

[0024] Figure 13 for Figure 12 The cross-sectional view of the three-dimensional overlay mark along another section direction is shown;

[0025] Figure 14 This is a flowchart of a calibration method for an overlay error measurement device provided in an embodiment of the present invention. Detailed Implementation

[0026] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0027] This invention provides a three-dimensional overlay mark, which can be used alone to calibrate overlay error measurement equipment, or to adjust the overlay accuracy during semiconductor chip fabrication. Figure 1 This is a top view of a three-dimensional overlay mark provided in an embodiment of the present invention. Figure 2 for Figure 1 A cross-sectional view along the A-A' direction, as shown below. Figure 1 and Figure 2 As shown, the three-dimensional overlay markings provided in this embodiment of the invention include: a substrate 1; a plurality of overlay markings 2 located on the substrate 1, wherein any two overlay markings 2 have different heights in their vertical projections onto a first plane; the first plane is perpendicular to the plane on which the substrate 1 is located.

[0028] Reference Figure 1 and Figure 2 The three-dimensional overlay mark comprises a substrate 1 and a plurality of overlay marks 2 on the substrate 1. Different from the prior art, in the embodiment of the present application, the height of the vertical projection of any two overlay marks 2 in the plurality of overlay marks 2 on the first plane perpendicular to the substrate 1 is different. The substrate 1 can be a substrate used to set the three-dimensional overlay mark in the overlay error measurement device, or can be a wafer to be etched. The overlay mark 2 refers to a plurality of microstructures formed on the substrate 1, and the plurality of microstructure-shaped overlay marks 2 constitute the overall structure of the three-dimensional overlay mark.

[0029] It can be understood that in the application process of the three-dimensional overlay mark, the imaging light source is shot from above the substrate 1 to the overlay mark 2 on the substrate 1, and the image of each overlay mark 2 is formed according to the light reflected back by the overlay mark 2. The direction of light transmission is the extension direction of the first plane, and the extension direction of the first plane is vertical, and the extension direction of the plane where the substrate is located is horizontal.

[0030] The plane perpendicular to the substrate 1 is defined as the first plane, and the height of any two overlay marks 2 in the extension direction of the first plane is different, that is, the height in the vertical direction is different. Hereinafter, the height of the overlay mark 2 in the extension direction of the first plane can also be referred to as the height of the overlay mark 2.

[0031] As can be known from the background art, in the working process of the overlay error measurement device, the aberration generated by the imaging system is the main factor affecting the accuracy of the measurement result. As can be understood by those skilled in the art, different types of aberrations have different sensitivities to vertical distance. Some aberrations are more sensitive at positions close to the focal plane, and the change is obvious. Some aberrations are more sensitive at positions far from the focal plane, and the change is obvious. It should be noted that the distance from the focal plane mentioned in the embodiment is the distance between the vertical focal plane, that is, the defocus amount. When the device is calibrated, a calibration index is established according to the corresponding relationship between the aberration and the defocus amount. The overlay error measurement device can compensate for the aberration existing in the overlay mark image during work according to the calibration index, improve the accuracy of error measurement, and further ensure the overlay precision during lithography.

[0032] In this embodiment of the invention, since the height of the overlay marks varies along the extension direction of the first plane, the distance between the overlay marks at different heights and the shooting point varies, meaning that the images formed by overlay marks at different heights can represent different degrees of defocus. Therefore, defocused images of the overlay marks at different defocus levels can be obtained with a single image capture, eliminating the need for repeated measurements by moving the overlay marks. This greatly improves the calibration efficiency of the overlay error measurement equipment and avoids interference from environmental factors during long-term calibration. It also prevents the horizontal position of the overlay marks from shifting during vertical movement, thus avoiding any impact on calibration accuracy.

[0033] In this embodiment of the invention, the number, specific shape, arrangement and height distribution of the overlay marks on the substrate are not limited. Those skilled in the art can set the overlay marks according to the different aberration types to be calibrated. Figure 1 and Figure 2 The overlay mark 2 shown is a wall-like structure, with multiple overlay marks 2 arranged in the same direction. At the same time, the height of the overlay marks 2 arranged in the same direction gradually increases, but the actual arrangement is not limited to this.

[0034] The three-dimensional overlay marking provided in this invention includes a substrate and multiple overlay markings located on the substrate. Among the multiple overlay markings, any two overlay markings have different heights in their vertical projection onto a first plane. The first plane is perpendicular to the plane containing the substrate. Because the overlay markings have different heights in the direction of extension of the first plane, the distance between the overlay markings at different heights and the shooting point is different, meaning that the images formed by overlay markings at different heights can represent different degrees of defocus. Therefore, images of overlay markings at different defocus ranges can be obtained with a single image capture, eliminating the need to move the overlay markings for repeated measurements. This greatly improves the calibration efficiency of the overlay error measurement equipment and avoids interference from environmental factors during long-term calibration. It also prevents the overlay markings from shifting horizontally, thus affecting calibration accuracy.

[0035] For example, the following describes several specific embodiments of possible overlay marking configurations.

[0036] Figure 3 This is a top view of another three-dimensional overlay mark provided in an embodiment of the present invention. Figure 4 for Figure 3 The cross-sectional view of the three-dimensional overlay mark shown is shown. Figure 5 for Figure 3 Another cross-sectional view of the three-dimensional overlay mark shown. (Reference) Figures 3-5In some possible embodiments, the plurality of overlay marks can include a plurality of first overlay marks 3 arranged along a first axis X and a plurality of second overlay marks 4 arranged along a second axis Y; in the first overlay marks 3 arranged along the first axis X, any two first overlay marks 3 have different vertical projection heights in the first plane, in the second overlay marks 4 arranged along the second axis Y, any two second overlay marks 4 have different vertical projection heights in the first plane, and / or any one first overlay mark 3 and any one second overlay mark 4 have different vertical projection heights in the first plane; wherein the extension direction of the first axis X and the extension direction of the second axis Y intersect.

[0037] wherein, Figure 4 is Figure 3 a vertical sectional view along the extension direction of the first axis X, Figure 5 is Figure 3 a vertical sectional view along the extension direction of the second axis Y, as Figures 3-5 shown, the overlay marks can be arranged to include a plurality of first overlay marks 3 arranged along a first axis X and a plurality of second overlay marks 4 arranged along a second axis Y. Wherein, any two first overlay marks 3 have different heights in the extension direction of the first plane, any two second overlay marks 4 have different vertical projection heights in the first plane, and / or any one first overlay mark 3 and any one second overlay mark 4 have different heights in the extension direction of the first plane. The distribution of different heights of the overlay marks can be achieved by the above two ways or a combination of the two ways. Figure 4 and Figure 5 The height of the first overlay mark 3 and the second overlay mark 4 in the vertical direction in the figure is the vertical projection height in the first plane. The rectangle filled with diagonal lines in the figure represents the first overlay mark 3, and the rectangle filled with grid represents the second overlay mark 4.

[0038] It should be noted that the sectional views shown in the embodiments of the present application are all vertical to the substrate and along the first axis X or the second axis Y direction extension plane as the sectioning surface,

[0039] Wherein, the extension direction of the first axis X and the extension direction of the second axis Y intersect. The advantage of such arrangement is that the overlay marks 2 are arranged in two intersecting directions, the overlay marks 2 can be distributed in a larger area of the field of view, more field of view information is used, and more available overlay mark images are provided for subsequent analysis and processing. And the overlay mark image can also better reflect the change of the aberration in the two directions in the two-dimensional horizontal plane.

[0040] Optionally, the present application does not limit the distance between the adjacent overlay mark edges, and the distance between the adjacent overlay marks can be the same or different, but the imaging of the adjacent two overlay marks should not interfere with each other, and the accurate and complete image of each overlay mark should be obtained.

[0041] For example, the distance between the adjacent overlay marks can be designed according to the wavelength of the illumination spectrum of the overlay error measurement device. In a possible embodiment, the distance d between any two adjacent overlay marks 2 is greater than or equal to 4λ, wherein λ is the center wavelength of the illumination spectrum of the overlay error measurement device.

[0042] Specifically, in order to avoid the imaging interference of the adjacent overlay marks, the distance d between any two adjacent overlay marks 2 is greater than or equal to four times the center wavelength λ of the illumination spectrum of the overlay error measurement device. The distance d between the adjacent two overlay marks 2 refers to the minimum distance between the vertical projections of the adjacent two overlay marks 2 on the substrate. According to the actual test, in the three-dimensional overlay mark image obtained under this setting mode, the images of each overlay mark 2 are independent and clear. It can be understood that the distance d between the adjacent overlay marks 2 includes the distance between the adjacent first overlay marks 3, the distance between the adjacent second overlay marks 4, and the distance between the adjacent first overlay mark 3 and the second overlay mark 4.

[0043] Figures 3-5 In the illustrated embodiment, the distance between each first overlay mark 3 is the same, and the distance between each second overlay mark 4 is also the same, and the actual setting mode is not limited thereto.

[0044] Optionally, the distance between the adjacent overlay marks can still be designed according to the wavelength of the illumination spectrum of the overlay error measurement device. Figures 3-5 In a possible embodiment, the height of the vertical projection of the first overlay mark 3 on the first plane gradually increases in the extension direction of the first axis X, and the height of the vertical projection of the second overlay mark 4 on the first plane gradually increases in the extension direction of the second axis Y.

[0045] Specifically, in the present application, the height of the first overlay mark 3 arranged along the first axis X in the extension direction of the first plane gradually increases, and the height of the second overlay mark 4 arranged along the second axis Y in the extension direction of the first plane gradually increases, that is, the height of the overlay mark near the starting point of the first axis X and the second axis Y is low, and the height of the overlay mark 2 gradually increases in the extension direction of the first axis X and the second axis Y. Under this setting mode, the height of the overlay mark 2 can cover a larger range of defocus amount changes, and the simulated defocus amount of the overlay mark 2 gradually increases or decreases, which is beneficial to the subsequent analysis and processing of the image.

[0046] Of course, in other embodiments not shown, the height of the first set of marks 3 in the first plane can gradually decrease along the extension direction of the first axis X, the height of the second set of marks 4 in the first plane can gradually decrease along the extension direction of the second axis Y, or the height of the first set of marks 3 in the first plane can gradually decrease along the first axis X, the height of the second set of marks 4 in the first plane can gradually increase along the second axis Y, etc.

[0047] Optionally, the specific values of the height difference between adjacent first set of marks 3 and the height difference between adjacent second set of marks 4 are not limited in the embodiments of the present application, and can be set according to actual needs by those skilled in the art.

[0048] For example, still referring to Figures 3-5 In a possible embodiment, the height difference d of the vertical projection of any two adjacent first set of marks 3 on the first plane can be a fixed value; and the height difference d of the vertical projection of any two adjacent second set of marks 4 on the first plane can be a fixed value.

[0049] That is, the increase amplitude of the height of the first set of marks 3 arranged along the first axis X is the same, and the increase amplitude of the height of the second set of marks 4 arranged along the second axis Y is the same. The height of the first set of marks 3 and the height of the second set of marks 4 respectively satisfy linear distribution. In this setting mode, the change amplitude between different defocus amounts simulated by adjacent set of marks 2 is the same, which is suitable for the case of collecting set of mark images with the same defocus interval near the focal plane position, i.e. is more suitable for analyzing the aberration which changes obviously under different defocus amounts near the focal plane.

[0050] In addition, those skilled in the art can understand that different types of aberrations have different symmetries, some aberrations are center-symmetric, such as spherical aberration, and some aberrations are asymmetric, such as coma and astigmatism, etc. Therefore, in the embodiments of the present application, the overall symmetry of the set of mark height can also be adjusted to make the three-dimensional set of mark better match the aberration of different symmetry directions.

[0051] Optionally, the height difference d between adjacent first set of marks 3 and the height difference d between adjacent second set of marks 4 can be equal, at this time, the change amplitude of the height of the first set of marks 3 and the second set of marks 4 along the extension direction of the first axis X and the second axis Y is the same. When the set of mark height is uniform and changes regularly, the subsequent analysis and processing of the set of mark image and the calculation process will be more convenient.

[0052] In addition, optionally, in the embodiments of the present application, the number of first set of marks 3 can be equal to the number of second set of marks 4. For example Figures 3-52n first sets of engraved marks 3 and 2n second sets of engraved marks 4 are respectively arranged therein. Here, n can be an integer greater than or equal to 1.

[0053] When the number of the first set of engraved marks 3 is equal to that of the second set of engraved marks 4, and the height of the 1st first set of engraved marks 3 (the first set of engraved marks 3 labeled 1 in the figure) is the same as that of the 1st second set of engraved marks 4 (the second set of engraved marks 4 labeled 1 in the figure), and the height change trends and amplitudes of the first set of engraved marks 3 and the second set of engraved marks 4 are also the same, the overall engraved marks 2 are symmetric with each other, and the symmetry axis Z coincides with the angular bisector of the first axis X and the second axis Y. For example Figure 3 shows that the first axis X and the second axis Y are perpendicular, and the first set of engraved marks 3 and the second set of engraved marks 4 together form a three-dimensional engraved mark in the shape of a Chinese character 'hui' (a square with a hole in the middle), then the overall engraved marks 2 are symmetric about the diagonal of the 'hui' character. When the height change trend of the first set of engraved marks 3 or the second set of engraved marks 4 changes, the direction of the symmetry axis Z will also change.

[0054] Figures 3-5 In the three-dimensional engraved marks shown in, the overall height of the engraved marks is symmetric about the 45° angular bisector of the first axis X and the second axis Y. Figure 6 is a schematic diagram of imaging simulation of a three-dimensional engraved mark provided by an embodiment of the present invention. Figure 6 The simulation diagram shown in corresponds to the three-dimensional engraved mark in the above Figures 3-5 shown embodiment. Figure 6 Different gray levels shown in represent different imaging intensities, and the darker the gray level, the stronger the imaging intensity. As Figure 6 shown in, the imaging intensities of the engraved marks 2 with different heights are different, and the overall imaging intensity of the three-dimensional engraved marks 2 is symmetric about the 45° angular bisector of the first axis X and the second axis Y, corresponding to the height arrangement of the engraved marks 2. Figure 6 The black solid arrow in represents the 45° angular bisector.

[0055] Figure 7 is a sectional view of a three-dimensional engraved mark provided by an embodiment of the present invention. Figure 7 The top view of the three-dimensional engraved mark shown in can still be referred to as Figure 3 , but the height distribution manner of the engraved marks 2 thereon is different from that in Figure 3 . Figure 7 In, (a) is a vertical sectional view of the three-dimensional engraved mark along the extension direction of the first axis X, and (b) is a vertical sectional view of the three-dimensional engraved mark along the extension direction of the second axis Y. Among them, (a) is the same as the sectional view shown in the above Figure 5 , that is, Figure 5 and Figure 7 shown embodiments, the height arrangement manner of the first set of engraved marks 3 is the same, and the difference lies in the height arrangement manner of the second set of engraved marks 4. Figure 7In the embodiment shown, the height of the second set of markings 4 gradually decreases along the extension direction of the second axis Y. In this configuration, the height of the markings 2 is symmetrical about the 135° angle bisector of the first axis X and the second axis Y. Figure 8 This is a schematic diagram of an imaging simulation of another three-dimensional overlay mark provided in an embodiment of the present invention. Figure 8 The simulation diagram shown corresponds to the above. Figure 7 The three-dimensional overlay marks in the illustrated embodiment. For example... Figure 8 As shown, the imaging intensity of the overall three-dimensional overlay markers is symmetrical along the 135° angle bisector of the first axis X and the second axis Y, corresponding to the height arrangement of the overlay markers. Figure 8 The solid black arrow in the middle represents the bisector of the 135° angle.

[0056] To facilitate the explanation of the specific setting method of the three-dimensional overlay marks, the following embodiments will be described with the number of the first overlay mark 3 and the second overlay mark 4 both being 2n.

[0057] Optional, Figure 9 This is a cross-sectional view of another three-dimensional overlay mark provided in an embodiment of the present invention. Figure 10 for Figure 9 The cross-sectional view of the three-dimensional overlay mark along another section direction is shown. Figure 9 and Figure 10 The top view of the three-dimensional overlay mark shown is... Figure 3 Same as above. (Reference) Figure 3 , Figure 9 and Figure 10 Multiple sets of first-set markings 3 arranged along the first axis X constitute two sets of first-set markings 5, and the two sets of first-set markings 5 ​​are located on both sides of the second axis Y; multiple sets of second-set markings 4 arranged along the second axis Y constitute two sets of second-set markings 6; the two sets of second-set markings 6 are located on both sides of the first axis X;

[0058] In the extension direction of the first axis X, the height of the vertical projection of the first set of markings 3 in the first set of markings group 51 on the first plane gradually increases, and the height of the vertical projection of the first set of markings 3 in the second set of markings group 52 on the first plane gradually decreases; wherein, in the extension direction of the first axis X, the height h1 of the vertical projection of the last first set of markings 3 in the first set of markings group 51 (the first set of markings 3 labeled n in the figure) and the first first set of markings 3 in the second set of markings group 52 (the first set of markings 3 labeled n+1 in the figure) on the first plane is equal;

[0059] In the extending direction of the second axis Y, the height of the vertical projection of the second scribe marks 4 in the first scribe mark group 61 on the first plane gradually decreases, and the height of the vertical projection of the second scribe marks 4 in the second scribe mark group 62 on the first plane gradually increases; wherein in the extending direction of the second axis Y, the height h2 of the vertical projection of the last second scribe mark 4 (the second scribe mark 4 with the number n in the figure) in the first scribe mark group 61 on the first plane is equal to the height h2 of the vertical projection of the first second scribe mark 4 (the second scribe mark 4 with the number n+1 in the figure) in the second scribe mark group 62 on the first plane; wherein the height h1 of the vertical projection of the last first scribe mark 3 (the first scribe mark 3 with the number n in the figure) in the first scribe mark group 61 on the first plane is less than the height h2 of the vertical projection of the last second scribe mark 4 (the second scribe mark 4 with the number n in the figure) in the second scribe mark group 62 on the first plane.

[0060] Specifically, as shown in Figure 3 、 Figure 9 and Figure 10 , the first scribe marks 3 can be divided into two first scribe mark groups 5, and the two first scribe mark groups 5 are respectively located on both sides of the second axis Y, and in the extending direction of the first axis X, the first scribe mark group 51 is close to the starting point of the first axis X, and the second scribe mark group 52 is away from the starting point of the first axis X. Similarly, the second scribe marks 4 can be divided into two second scribe mark groups 6, and the two second scribe mark groups 6 are respectively located on both sides of the first axis X, and in the extending direction of the second axis Y, the first scribe mark group 61 is close to the starting point of the second axis Y, and the second scribe mark group 62 is away from the starting point of the second axis Y. Each first scribe mark group 5 contains n first scribe marks 3; each second scribe mark group 6 contains n second scribe marks 4.

[0061] When the extending direction of the first axis X is perpendicular to the extending direction of the second axis Y, the two first scribe mark groups 51 are symmetrical about the second axis Y, and the two second scribe mark groups 61 are symmetrical about the first axis X.

[0062] Among them, along the extending direction of the first axis X, the heights of the first set of engraved marks 3 in the first first set of engraved mark groups 51 (the first set of engraved marks 3 numbered 1 to n in the figure) gradually increase in the extending direction of the first plane, and the heights of the first set of engraved marks 3 in the second first set of engraved mark groups 52 (the first set of engraved marks 3 numbered n + 1 to 2n in the figure) gradually decrease in the extending direction of the first plane; and the height h1 of the last first set of engraved marks 3 in the first first set of engraved mark groups 51 is the same as the height of the first first set of engraved marks 3 in the second first set of engraved mark groups 52. That is, the heights of two adjacent first set of engraved marks 3 in the first first set of engraved mark groups 51 and the second first set of engraved mark groups 52 are the same. In this setting method, the overall height of the first set of engraved marks 3 first increases and then decreases, and the height of the first set of engraved marks 3 closest to the intersection of the first axis X and the second axis Y is higher than the height of the first set of engraved marks 3 far from the intersection point.

[0063] Correspondingly, along the extending direction of the second axis Y, the heights of the second set of engraved marks 4 in the first second set of engraved mark groups 61 gradually decrease in the extending direction of the first plane, and the heights of the second set of engraved marks 4 in the second second set of engraved mark groups 62 gradually increase in the extending direction of the first plane; and the height h2 of the last second set of engraved marks 4 in the first second set of engraved mark groups 61 is the same as the height of the first second set of engraved marks 4 in the second second set of engraved mark groups 62. That is, the heights of two adjacent second set of engraved marks 4 in the first second set of engraved mark groups 61 and the second second set of engraved mark groups 62 are the same. In this setting method, the overall height of the second set of engraved marks 4 first decreases and then increases, and the height of the second set of engraved marks 4 closest to the intersection of the first axis X and the second axis Y is lower than the height of the second set of engraved marks 4 far from the intersection point.

[0064] The first set of engraved marks 3 numbered 1 to 2n can be respectively called the 1st to 2nth first set of engraved marks 3, and the second set of engraved marks 4 numbered 1 to 2n can be called the 1st to 2nth second set of engraved marks 4. Then the height h1 of the nth first set of engraved marks 3 is the same as the height of the (n + 1)th first set of engraved marks 3; the height h2 of the nth second set of engraved marks 4 is the same as the height of the (n + 1)th second set of engraved marks 4.

[0065] At this time, if the first axis X and the second axis Y are perpendicular (refer to Figure 3 、 Figure 9 and Figure 10 ), the first set of engraved marks 3 and the second set of engraved marks 4 still form a "hui" - shaped three - dimensional engraved mark as a whole. However, in this embodiment, the engraved mark 2 as a whole is symmetric about the first axis X and the second axis Y. Figure 11 This is an imaging simulation diagram of another three - dimensional engraved mark provided by the embodiment of the present invention. Figure 11 The simulation diagram shown corresponds to the above - mentioned Figure 9 andFigure 10 The three-dimensional overlay marks in the embodiments shown. As shown in Figure 11 The imaging intensity of the overall three-dimensional overlay mark is symmetrical along the first axis X and the second axis Y, corresponding to the height arrangement of the overlay mark 2.

[0066] The above embodiments show two different symmetrical ways of the overlay mark in the height dimension, and according to the difference of the symmetry of different types of aberrations, those skilled in the art can also set other possible design schemes of the height of the overlay mark according to the actual situation.

[0067] In addition, still referring to Figure 3 , Figure 9 and Figure 10 In this embodiment, the height h1 of the vertical projection of the last first overlay mark 3 (the nth first overlay mark 3) in the first first overlay mark group 51 on the first plane is less than the height h2 of the vertical projection of the last second overlay mark 4 (the nth second overlay mark 4) in the first second overlay mark group 61 on the first plane. That is, the height h1 of the first overlay mark 3 closest to the intersection of the first axis X and the second axis Y is less than the height h2 of the second overlay mark 4 closest to the intersection of the first axis X and the second axis Y. The height of the first overlay mark 3 is overall less than the height of the second overlay mark 4. Figure 9 and Figure 10 As shown in

[0068] In this way, the height of each first overlay mark 3 gradually increases in the direction of extending from both ends to the center, and the height of each second overlay mark 4 gradually increases on the basis of the height of the first overlay mark 3 (the nth or nth+1 first overlay mark 3) with the highest height in the direction of extending from the center to both ends, that is, the height of the first-nth first overlay mark 3 and the nth+1-2nth second overlay mark 4 gradually increases, and the height of the first-nth second overlay mark 4 and the nth+1-2nth first overlay mark 3 gradually decreases. Therefore, the overlay mark height can cover a larger range of defocus amount changes, and the obtained image information is more comprehensive, and the uniform and regular change of the overlay mark height can simplify the subsequent image analysis and processing and calculation process.

[0069] Among them, for the height difference of adjacent overlay marks in each overlay mark group in the above embodiments, the embodiments of the present application do not make any limitation, and those skilled in the art can design according to the actual calibration needs.

[0070] For example, still referring to Figure 9 and Figure 10In a possible embodiment, in the extension direction of the first axis X, the height difference d of the vertical projection on the first plane of any two adjacent first set of marks 3 in the first first set of marks group 51 is a fixed value, and the height difference d of the vertical projection on the first plane of any two adjacent first set of marks 3 in the second first set of marks group 52 is a fixed value; in the extension direction of the second axis Y, the height difference d of the vertical projection on the first plane of any two adjacent second set of marks 4 in the first second set of marks group 61 is a fixed value, and the height difference d of the vertical projection on the first plane of any two adjacent second set of marks 4 in the second second set of marks group 62 is a fixed value.

[0071] Specifically, Figure 9 and Figure 10 As shown in FIG. 1, the height difference d of the adjacent set of marks in each set of marks group can be set to be equal, and in the extension direction of the first axis X, the heights of the first set of marks 3 in the first first set of marks group 51 have a linear increasing relationship, and the heights of the first set of marks 3 in the second first set of marks group 52 have a linear decreasing relationship. Correspondingly, in the extension direction of the second axis Y, the heights of the second set of marks 4 in the first second set of marks group 61 have a linear decreasing relationship, and the heights of the second set of marks 4 in the second second set of marks group 62 have a linear increasing relationship. Overall, the heights of the first set of marks 3 have a linear increasing relationship with the heights of the second set of marks 4, and the heights of the second set of marks 4 have a linear decreasing relationship with the heights of the first set of marks 3. In this setting mode, the change amplitude between the different defocus amounts simulated by the adjacent set of marks 2 is the same, which is suitable for the case of collecting set of mark images at the same defocus interval near the focal plane position, and is more suitable for analyzing the aberration which changes relatively obviously at different defocus amounts near the focal plane.

[0072] Exemplarily, Figure 12 Another cross-sectional view of a three-dimensional set of mark provided by an embodiment of the present application is shown in FIG. 2, Figure 13 as shown in FIG. 2, Figure 12 a cross-sectional view of the three-dimensional set of mark along another cross-sectional direction is shown in FIG. 3, and Figure 12 and Figure 13 In other possible embodiments, in the extension direction of the first axis X, the height difference of the vertical projection on the first plane of the adjacent two first set of marks 3 in the first first set of marks group 51 gradually decreases, and the height difference of the vertical projection on the first plane of the adjacent two first set of marks 3 in the second first set of marks group 52 gradually increases.

[0073] In the extension direction of the second axis Y, the height difference between the vertical projections of two adjacent second set marks 4 in the first second set mark group 61 on the first plane gradually decreases, while the height difference between the vertical projections of two adjacent second set marks 4 in the second second set mark group 62 on the first plane gradually increases.

[0074] Specifically, such as Figure 12 and Figure 13 As shown in the figure, in this embodiment, the height variation rate of the overlay marks 2 at different positions can be set to be different. For example, along the extension direction of the first axis X, in the first set of first overlay marks 51, the height difference between two adjacent sets of first overlay marks 3 gradually decreases, and in the second set of first overlay marks 52, the height difference between two adjacent sets of first overlay marks 3 gradually increases. That is, the increase in height of the 1st to nth sets of first overlay marks 3 gradually decreases, and the decrease in height of the (n+1)th to 2nth sets of first overlay marks 3 gradually increases, and the heights of the 1st to nth sets of first overlay marks 3 and the (n+1)th to 2nth sets of first overlay marks 3 are completely symmetrical.

[0075] Correspondingly, along the second axis Y-direction, within the first set of second markings 61, the height difference d between two adjacent second markings 4 gradually decreases, while within the second set of second markings 62, the height difference d between two adjacent second markings 4 gradually increases. That is, the decrease in height of the 1st to nth second markings 4 gradually decreases, while the increase in height of the (n+1)th to 2nth second markings 4 gradually increases, and the heights of the 1st to nth second markings 4 and the (n+1)th to 2nth second markings 4 are completely symmetrical.

[0076] Figure 12 and Figure 13 The illustrated embodiment is more suitable for scenarios requiring more sampling points near specific vertical positions. For example, near the focal plane, out-of-focus images need to be acquired with a smaller defocus interval, while in out-of-focus areas outside a certain defocus range, out-of-focus images can be acquired with a larger defocus interval. In the aforementioned calibration scenario, utilizing... Figure 12 and Figure 13 The three-dimensional overlay marks shown can ensure both measurement accuracy and measurement efficiency.

[0077] Of course, in other testing and calibration scenarios, such as in defocused areas outside a certain defocus range, defocused images need to be acquired with a smaller defocus interval, while defocused images can be acquired with a larger defocus interval near the focal plane. The height change rate of the overlay mark can be adaptively adjusted so that the three-dimensional overlay mark can meet the needs of more testing and calibration scenarios.

[0078] Exemplarily, in a possible embodiment, the heights of the vertical projections of the first overlay marks 3 on the first plane as a whole satisfy a normal distribution curve or a reversed normal distribution curve; the second overlay marks 4 each include a first part 41 and a second part 42 connected with each other, the first part 41 is located on the substrate, and the second part 42 is located on a side of the first part 41 away from the substrate 1, the heights of the first parts 41 of the second overlay marks 4 are equal, and the heights of the vertical projections of the second parts 42 on the first plane as a whole satisfy a normal distribution curve or a reversed normal distribution curve.

[0079] Specifically, as shown in FIGS. 1 and 2, the heights of the vertical projections of the first overlay marks 3 on the first plane as a whole satisfy a normal distribution curve or a reversed normal distribution curve, i.e., the height curves of the first to the n th first overlay marks 3 satisfy normal distribution characteristics or reversed normal distribution characteristics. Figure 12 and Figure 13 The normal distribution curve is a symmetrical curve, and the change rate of the curve near the symmetrical axis is small, and the change rate of the curve increases from the symmetrical axis to both ends. The reversed normal distribution curve is a curve formed by turning the normal curve 180 degrees. In this embodiment, the heights of the first overlay marks 3 as a whole satisfy a normal distribution curve or a reversed normal distribution curve, so that near the intersection of the first axis X and the second axis Y, the change rate of the heights of the adjacent first overlay marks 3 is small, and the change rate of the heights of the adjacent first overlay marks 3 gradually increases from the intersection to both ends, i.e., the height difference of the adjacent first overlay marks 3 near the intersection is small.

[0080] Meanwhile, the second overlay marks 4 each include a first part 41 and a second part 42 connected with each other, the first part 41 is connected with the substrate, and the second part 42 is connected with the first part 41. The heights h3 of the first parts 41 of the second overlay marks 4 are all the same, and the height values of the second parts 42 as a whole satisfy a normal distribution curve or a reversed normal distribution curve, i.e., the height values of the second parts 42 after the height values of the first parts 41 are subtracted satisfy a normal distribution curve or a reversed normal distribution curve.

[0081] Among them, the height h3 of the first part 41 can be the same as the height of the highest first overlay mark 3, i.e., the height of the first part 41 and the height of the n th or n+1 th first overlay mark 3 are both h3, so that the overall height of the second overlay mark 4 is above the overall height of the first overlay mark 3, and the overlay mark height can cover a larger range of focus variation.

[0082] It should be noted that in this embodiment, when the overall height of the first set of engraved marks 3 conforms to a normal distribution curve, the overall height of the second part of the second set of engraved marks should conform to an inverse normal distribution curve, so that the height of the last first set of engraved marks 3 in the first first set of engraved mark group 51 is less than the height of the last second set of engraved marks 4 in the first second set of engraved mark group 61. In addition, the height conforming to the normal distribution curve described in this embodiment means that the height values conform to the characteristics of the normal distribution curve, and it does not mean that each height value must be the same as the value in a certain normal distribution curve.

[0083] Optionally, still referring to Figures 3-13 , in the embodiment of the present invention, the first set of engraved marks 3 and the second set of engraved marks 4 may be wall structures. The plane where the first set of engraved marks 3 is located is parallel to the second axis Y, and the plane where the second set of engraved marks 4 is located is parallel to the first axis X.

[0084] Specifically, as Figures 3-13 shown, both the first set of engraved marks 3 and the second set of engraved marks 4 are wall structures. The wall structure means that the perpendicular projection of the nested engraved marks 2 on the substrate extends in a certain direction. Among them, the plane where the first set of engraved marks 3 is located is parallel to the second axis Y, and the plane where the second set of engraved marks 4 is located is parallel to the first axis X, that is, the perpendicular projection of the first set of engraved marks 3 on the substrate extends in the direction parallel to the second axis Y, and the perpendicular projection of the second set of engraved marks 4 on the substrate extends in the direction parallel to the first axis X. When the first axis X and the second axis Y are perpendicular, the first set of engraved marks 3 and the second set of engraved marks 4 form a "hui" - shaped three - dimensional nested engraved mark.

[0085] Optionally, continue to refer to Figure 3 , in some possible embodiments, in the extending direction of the first axis X, the length of the first set of engraved marks 3 in the extending direction of the second axis Y first decreases and then increases; in the extending direction of the second axis Y, the length of the second set of engraved marks 4 in the extending direction of the first axis X first decreases and then increases; the lengths of the first set of engraved marks 3 and the second set of engraved marks 4 near the intersection of the first axis X and the second axis Y are the smallest.

[0086] As Figure 3 shown, along the extending direction of the first axis X, the length of the first set of engraved marks 3 in the extending direction of the second axis Y first decreases and then increases, that is, along the extending direction of the first axis X, the lengths of the perpendicular projections of the 1st - 2n first set of engraved marks 3 on the substrate first decrease and then increase; correspondingly, along the extending direction of the second axis Y, the length of the second set of engraved marks 4 in the extending direction of the first axis X first decreases and then increases, that is, along the extending direction of the second axis Y, the lengths of the perpendicular projections of the 1st - 2n second set of engraved marks 4 on the substrate also first decrease and then increase.

[0087] When the first set of marks 3 can be divided into two first set of mark groups 5, along the extending direction of the first axis X, the length of the first set of marks 3 in the first first set of mark group 51 gradually decreases, the length of the first set of marks 3 in the second first set of mark group 52 gradually increases, and the length of the first set of marks 3 closest to the intersection of the first axis X and the second axis Y is the smallest. When the second set of marks 4 can be divided into two second set of mark groups 6, along the extending direction of the second axis Y, the length of the second set of marks 4 in the first second set of mark group 61 gradually decreases, the length of the second set of marks 4 in the second second set of mark group 62 gradually increases, and the length of the first set of marks 3 and the second set of marks 4 closest to the intersection of the first axis X and the second axis Y is the smallest, in other words, the length of the first set of marks 3 and the second set of marks 4 closest to the center of the three-dimensional set of marks is the smallest.

[0088] Figure 3 The n th first set of marks 3, the n+1 th first set of marks 3, the n th second set of marks 4 and the n+1 th second set of marks 4 are closest to the intersection of the first axis X and the second axis Y, and then the length of the n th first set of marks 3, the n+1 th first set of marks 3, the n th second set of marks 4 and the n+1 th second set of marks 4 is the smallest. When the length difference of each adjacent set of marks 2 is the same, the vertical projection of the first set of marks 3 on the plane where the substrate is located is symmetrical about the second axis Y; and the vertical projection of the second set of marks 4 on the plane where the substrate is located is symmetrical about the first axis X.

[0089] Under this arrangement of the first set of marks 3 and the second set of marks 4, the set of marks 2 can be scattered in a larger area of the field of view, more field of view information can be used, and more available set of mark images can be provided for subsequent analysis and processing.

[0090] Based on the same inventive concept, the embodiment of the present application also provides a set of mark error measurement device calibration method, which is suitable for the three-dimensional set of mark provided by any embodiment of the present application, Figure 14 The flow chart of the set of mark error measurement device calibration method provided by the embodiment of the present application is shown in Figure 14 The calibration method comprises the following steps:

[0091] S110, acquiring images of a plurality of set of marks in the three-dimensional set of marks.

[0092] Among the plurality of set of marks, the vertical projection height of any two set of marks on the first plane is different; and the first plane is perpendicular to the plane where the substrate is located;

[0093] S120, calibrating the set of mark error measurement device according to the offset of the images of the plurality of set of marks.

[0094] The specific implementation manner of calibrating the overlay error measurement device according to the offset of the images of the plurality of overlay marks can be selected by those skilled in the art according to actual needs, and the embodiments of the present application do not repeat or limit this.

[0095] The overlay error measurement device calibration method provided by the embodiments of the present application includes all the technical features and corresponding beneficial effects of the three-dimensional overlay marks provided by any of the embodiments of the present application, which will not be repeated here.

[0096] Note that the above are only the preferred embodiments of the present application and the technical principles applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments herein, and those skilled in the art can make various obvious changes, re-adjustments, mutual combinations and substitutions without departing from the scope of the present application. Therefore, although the present application has been described in more detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the appended claims.

Claims

1. A three-dimensional overlay mark, characterized in that, A three-dimensional overlay mark for calibrating an overlay error measurement apparatus, the three-dimensional overlay mark comprising: a substrate; a plurality of overlay marks on the substrate, wherein any two of the plurality of overlay marks have different heights of vertical projections on a first plane, the first plane being perpendicular to a plane on which the substrate lies, and wherein an image of the plurality of overlay marks is obtained by taking one image of the three-dimensional overlay mark at different defocus ranges; the plurality of overlay marks comprising a plurality of first overlay marks arranged along a first axis and a plurality of second overlay marks arranged along a second axis; any two of the first overlay marks arranged along the first axis have different heights of vertical projections on the first plane, any two of the second overlay marks arranged along the second axis have different heights of vertical projections on the first plane, and / or any one of the first overlay marks has a different height of vertical projection on the first plane than any one of the second overlay marks, wherein the first axis and the second axis are intersected.

2. The three-dimensional overlay mark of claim 1, wherein, the heights of vertical projections on the first plane of the first overlay marks arranged along the first axis gradually increase, and the heights of vertical projections on the first plane of the second overlay marks arranged along the second axis gradually increase.

3. The three-dimensional overlay mark of claim 2, wherein, any two adjacent first overlay marks have a fixed difference in height of vertical projection on the first plane, and any two adjacent second overlay marks have a fixed difference in height of vertical projection on the first plane.

4. The three-dimensional overlay mark of claim 1, wherein, the plurality of first overlay marks arranged along the first axis comprises two groups of first overlay marks, the two groups of first overlay marks being located on two sides of the second axis; the plurality of second overlay marks arranged along the second axis comprises two groups of second overlay marks, the two groups of second overlay marks being located on two sides of the first axis; the heights of vertical projections on the first plane of the first overlay marks in a first group of first overlay marks gradually increase along the first axis, and the heights of vertical projections on the first plane of the first overlay marks in a second group of first overlay marks gradually decrease along the first axis, wherein a last first overlay mark in the first group of first overlay marks has a same height of vertical projection on the first plane as a first first overlay mark in the second group of first overlay marks; the heights of vertical projections on the first plane of the second overlay marks in a first group of second overlay marks gradually decrease along the second axis, and the heights of vertical projections on the first plane of the second overlay marks in a second group of second overlay marks gradually increase along the second axis, wherein a last second overlay mark in the first group of second overlay marks has a same height of vertical projection on the first plane as a first second overlay mark in the second group of second overlay marks. The height of the vertical projection of the last first set of marks in the first set of mark groups on the first plane is less than the height of the vertical projection of the last second set of marks in the first set of mark groups on the first plane.

5. The three-dimensional overlay mark of claim 4, wherein, In the extension direction of the first axis, the height difference of the vertical projection of any two adjacent first set of marks in the first set of mark groups on the first plane is a fixed value, and the height difference of the vertical projection of any two adjacent first set of marks in the second set of mark groups on the first plane is a fixed value. In the extension direction of the second axis, the height difference of the vertical projection of any two adjacent second set of marks in the first set of mark groups on the first plane is a fixed value, and the height difference of the vertical projection of any two adjacent second set of marks in the second set of mark groups on the first plane is a fixed value.

6. The three-dimensional overlay mark of claim 4, wherein, In the extension direction of the first axis, the height difference of the vertical projection of any two adjacent first set of marks in the first set of mark groups on the first plane gradually decreases, and the height difference of the vertical projection of any two adjacent first set of marks in the second set of mark groups on the first plane gradually increases. In the extension direction of the second axis, the height difference of the vertical projection of any two adjacent second set of marks in the first set of mark groups on the first plane gradually decreases, and the height difference of the vertical projection of any two adjacent second set of marks in the second set of mark groups on the first plane gradually increases.

7. The three-dimensional overlay mark of claim 6, wherein, The height of the vertical projection of the first set of marks on the first plane as a whole satisfies a normal distribution curve or a reverse normal distribution curve. The second set of marks comprises a first part and a second part connected to each other, the first part is located on the substrate, and the second part is located on the side of the first part away from the substrate, the height of the vertical projection of the first part of each second set of marks on the first plane is equal, and the height of the vertical projection of the second part on the first plane as a whole satisfies a normal distribution curve or a reverse normal distribution curve.

8. The three-dimensional overlay mark of claim 1, wherein, The first set of marks and the second set of marks are wall structures, the plane where the first set of marks is located is parallel to the second axis, and the plane where the second set of marks is located is parallel to the first axis.

9. The three-dimensional overlay mark of claim 8, wherein, In the extension direction of the first axis, the length of the first set of marks in the extension direction of the second axis first decreases and then increases; in the extension direction of the second axis, the length of the second set of marks in the extension direction of the first axis first decreases and then increases; and the lengths of the first set of marks and the second set of marks near the intersection of the first axis and the second axis are the smallest.

10. The three-dimensional overlay mark of claim 1, wherein, The spacing between any two adjacent sets of marks is greater than or equal to 4λ; wherein λ is the center wavelength of the illumination spectrum of the set of mark error measuring equipment.

11. The three-dimensional overlay mark of claim 1, wherein, The number of the first set of marks is equal to the number of the second set of marks.

12. A calibration method for an overlay error measuring device, characterized in that, The three-dimensional overlay mark according to any one of claims 1-11, comprising: acquiring images of a plurality of overlay marks in the three-dimensional overlay mark; wherein, in the plurality of overlay marks, the height of the vertical projection of any two overlay marks on a first plane is different; the first plane is perpendicular to the plane on which the substrate is located; calibrating the overlay error measurement device according to the offset of the images of the plurality of overlay marks.

Images