An overlay mark, device and measurement method

Abstract

The present invention provides an overlay mark, comprising: a first mark group based on imaging, the first mark group comprising: a plurality of first marks respectively located at different process layers of a sample; a second mark group based on diffraction, the second mark group comprising: a plurality of second marks respectively located at different process layers of the sample. The first mark group based on imaging and the second mark group based on diffraction are integrated into the same overlay mark, so that the same overlay mark can be used to realize overlay measurement based on imaging and overlay measurement based on diffraction, which facilitates the selection of a better overlay error measurement method.

Description

Technical Field

[0001] The invention relates to a mark, a device and a measuring method, in particular to an overlay mark and a measuring method for measuring the alignment of upper and lower layers of a semiconductor device. Background Art

[0002] In the field of semiconductor manufacturing technology, the measurement of overlay error between different process layers in the photolithography process is crucial. Only when the current layer is aligned with the existing layer on the wafer substrate can the connection of various parts of the semiconductor device be correct. Excessive overlay error between two process layers is one of the main causes of short circuit and open circuit in semiconductor devices.

[0003] There are two types of overlay error measurement at present: one is based on image recognition technology, called IBO (image based overlay), and the other is based on the principle of optical diffraction, called DBO (diffraction based overlay). As for how to choose the measurement method, it mainly depends on the correction residue of the measurement result model analysis. Smaller residue is conducive to model correction and can obtain smaller overlay error. However, different processes often cause different damages to the overlay mark. For example, the residue of the substrate with metal film deposition is smaller when IBO is used, while the residue of the substrate after chemical mechanical polishing is smaller when DBO is used.

[0004] In actual process, how to select the overlay error measurement method to obtain smaller correction residue is a difficult problem that needs to be solved urgently. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes an overlay marker which is suitable for image-based overlay error measurement and diffraction-based overlay error measurement and has a small size.

[0006] The technical solution of the present invention provides an overlay mark, including: a first mark group based on imaging, the first mark group includes: a plurality of first marks respectively located at different process layers of the sample; a second mark group based on diffraction, the second mark group includes: a plurality of second marks respectively located at different process layers of the sample.

[0007] Optionally, if there is no overlay error between different first marks, the projections of the symmetry centers of different first marks on the sample surface overlap, and the projections of different first marks on the sample surface are staggered; if there is no overlay error between different second marks, the projections of second marks of different process layers on the sample surface overlap.

[0008] Optionally, the first identifier includes a plurality of first sub-identifiers arranged in a centrally symmetrical manner, and the first sub-identifier is a single identifier; the first sub-identifier is a centrally symmetrical structure or a non-centrally symmetrical structure.

[0009] Optionally, the first sub-identifier is in the shape of a cross, a ring, a polygon or a circle.

[0010] Optionally, the second identifier includes one or more second sub-identifiers, and the second sub-identifiers are grating structures.

[0011] Optionally, the second sub-identifier includes: a first grating, the first grating including a plurality of grating bars arranged along a first direction; the second grating including a plurality of grating bars arranged along a second direction, the second direction being perpendicular to the first direction or having an acute angle therewith; the projections of the first grating and the second grating on the sample surface are staggered with each other.

[0012] Optionally, the grating structure is a periodically symmetrical pattern; the number of the first grating and the number of the second grating are both multiple, and the multiple first gratings and the multiple second gratings are centrally symmetrically arranged.

[0013] Optionally, the second identifier includes multiple second sub-identifiers, and the multiple second sub-identifiers are arranged in a centrally symmetrical manner, and the center of symmetry of the second identifier is the same as the center of symmetry of the first identifier; the number of the second sub-identifiers is the same as the number of the first sub-identifiers.

[0014] Optionally, the symmetry center of the first sub-identifier of any process layer is the same as the symmetry center of a second sub-identifier of the same process layer; the symmetry center of the first sub-identifier of other process layers is staggered with the symmetry center of the second sub-identifier of the same process layer.

[0015] Optionally, if the size of the first sub-identifier along the first direction is the same as the size of the second sub-identifier along the first direction; the size of the first sub-identifier along the second direction is the same as the size of the second sub-identifier along the second direction.

[0016] Optionally, the center of the second sub-identifier is arranged along the arrangement box; the center of the first sub-identifier is located at the edge of the arrangement box or inside the arrangement box; or, the center of the first sub-identifier is arranged along the arrangement box; the center of the second sub-identifier is located at the edge of the arrangement box or inside the arrangement box; wherein the arrangement box is a rectangle or a hexagon.

[0017] The technical solution of the present application also provides a device, which includes multiple process layers, each of which includes one or more exposure areas, each of which includes one or more identification areas; and each of which has the above-mentioned overlay identification.

[0018] Optionally, the exposure area is rectangular; there are multiple identification areas, and the identification areas are located at the top corners of the exposure area and / or on the diagonals of the exposure area.

[0019] The technical solution of the present invention also provides a measurement method based on overlay marks, which is characterized in that it includes: performing imaging measurement on the first mark group to obtain a first overlay error between multiple first marks in the first mark group; performing diffraction measurement on the second mark group to obtain a second overlay error between multiple second marks in the second mark group.

[0020] Optionally, it also includes: correcting the process for forming the process layer according to the first overlay error and obtaining a first corrected residual; correcting the process for forming the process layer according to the second overlay error and obtaining a second corrected residual; and selecting an identification group corresponding to the smaller of the first corrected residual and the second corrected residual as a target identification group.

[0021] Optionally, performing imaging measurement on the first mark group to obtain a first overlay error between a plurality of first marks in the first mark group includes: performing imaging measurement on the first mark group to obtain a sample image; obtaining a first position of the first mark according to the sample image; and obtaining the first overlay error according to a position deviation between the first positions of the plurality of first marks;

[0022] Among them, if the first identifier includes multiple first sub-identifiers arranged in a centrally symmetrical manner; obtaining the first position of the first identifier according to the sample image includes: respectively obtaining the first sub-positions of multiple first sub-identifiers in the first identifier; and obtaining the symmetric center of the multiple first sub-positions to obtain the first position.

[0023] Optionally, if there is no overlay error between different second identifiers, the second sub-identifiers of different process layers overlap correspondingly; the second sub-identifiers of different process layers that overlap correspondingly are a sub-identifier group;

[0024] Performing diffraction measurement on the second mark group to obtain a second overlay error between multiple second marks in the second mark group, including: performing diffraction measurement on the second mark group to obtain a diffraction image; obtaining a position deviation between second sub-markers in the sub-marker group according to the diffraction image to obtain a second sub-deviation; the second overlay error includes second sub-deviations of one or more sub-marker groups.

[0025] Optionally, the second sub-identifier includes: a first grating, the first grating includes a plurality of grating bars arranged along a first direction; a second grating, the second grating includes a plurality of grating bars arranged along a second direction, the second direction being perpendicular to the first direction or having an acute angle;

[0026] The second sub-deviation includes a first deviation component along the first direction and a second deviation component along the second direction;

[0027] The second sub-deviation is obtained by obtaining the position deviation between the second sub-identifiers in the sub-identifier group according to the diffraction image, including: obtaining the first deviation component of the first grating of the different process layers along the first direction according to the diffraction image of the first grating in the sub-identifier group; and obtaining the second deviation component of the second grating of the different process layers along the second direction according to the diffraction image of the second grating in the sub-identifier group.

[0028] The overlay mark provided by the technical solution of the present invention includes a first mark group based on imaging and a second mark group based on diffraction. By integrating the first mark group based on imaging and the second mark group based on diffraction into the same overlay mark, the same overlay mark can be used to realize overlay measurement based on imaging and overlay measurement based on diffraction, which facilitates the selection of a better overlay error measurement method.

[0029] Further, if the center of the first sub-logo is located at the edge of the arrangement frame or inside the arrangement frame, the size of the overlay logo depends on the size of the first logo, and the second logo does not occupy additional space, thereby reducing the size of the overlay logo. If the center of the second sub-logo is located at the edge of the arrangement frame or inside the arrangement frame, the size of the overlay logo depends on the size of the second logo, and the first logo does not occupy additional space, thereby reducing the size of the overlay logo. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments, and the advantages and implementation methods of the present invention will become more obvious. The contents shown in the accompanying drawings are only used to explain the present invention and do not constitute any limitation to the present invention. The accompanying drawings are only schematic and not strictly drawn to scale. In the accompanying drawings:

[0031] Figures 1 to 4 It is a structural schematic diagram of a first embodiment of an overlay mark provided by the present invention;

[0032] Figures 5 to 7 It is a structural schematic diagram of a second embodiment of an overlay mark provided by the present invention;

[0033] Figure 8 is a schematic structural diagram of a first embodiment of a device provided by the present invention;

[0034] Figures 9 to 11 It is a flow chart of the steps of the first embodiment of the measurement method based on overlay marking of the present invention. DETAILED DESCRIPTION

[0035] In the semiconductor manufacturing process, in order to select a suitable overlay error measurement method, the existing technology selects two technologies for measurement and then selects the best one. However, the overlay marks based on different technologies are different. In advanced lithography technology, due to the large number of process layers, the available area of ​​the cutting path is limited. If the overlay marks based on image recognition technology and the optical diffraction principle are placed at the same time, it is obviously unrealistic. Therefore, a small overlay mark suitable for image measurement and diffraction measurement is needed.

[0036] The technical solution of the present invention provides an overlay mark, wherein the overlay mark includes a first mark group based on imaging and a second mark group based on diffraction. By integrating the first mark group based on imaging and the second mark group based on diffraction into the same overlay mark, the same overlay mark can be used to realize overlay measurement based on imaging and overlay error measurement based on diffraction, thereby facilitating the selection of a better overlay error measurement method.

[0037] The detection method of the present invention is described in detail below.

[0038] Figures 1 to 4 It is a structural schematic diagram of the first embodiment of the overlay mark of the present invention.

[0039] The following combination Figures 1 to 4 The structure of the first embodiment of the overlay mark of the present application is described in detail.

[0040] Figure 1 A schematic diagram of the structure of the first mark and the second mark of the first process layer 1; Figure 2 It is a structural schematic diagram of the first sub-identifier and the second sub-identifier of the first process layer. Figure 3 A schematic diagram of the structure of the first mark and the second mark of the second process layer; Figure 4 A top view of the entire overlay logo.

[0041] Please refer to Figures 1 to 4 The overlay mark includes: a first mark group based on imaging, the first mark group includes: a plurality of first marks respectively located at different process layers of the sample; a second mark group based on diffraction, the second mark group includes: a plurality of second marks respectively located at different process layers of the sample.

[0042] In this embodiment, the overlay mark has two process layers, which are respectively a first process layer 1 and a second process layer 2. In other embodiments, the number of process layers of the overlay mark may be greater than or equal to three layers.

[0043] In this embodiment, the first identification group includes two first identifications located at the first process layer 1 and the second process layer 2 respectively. The second identification group includes two second identifications located at the first process layer 1 and the yield layer respectively. In other embodiments, the first identification group may include three or more first identifications; the second identification group may include three or more second identifications.

[0044] In this embodiment, if there is no overlay error between different first marks, the projections of the symmetry centers of the different first marks on the sample surface overlap, and the projections of the different first marks on the sample surface are staggered.

[0045] If there is no overlay error between different first marks, and the projections of the symmetry centers of different first marks on the sample surface overlap, then when an overlay error occurs between different process layers, an overlay error occurs between the first mark and the second mark, and the projections of the symmetry centers of the first mark and the second mark on the sample surface will not overlap. The relative position deviation of the symmetry centers of the first mark and the second mark is the overlay error, which makes it easy to calculate the overlay error. The projections of different first marks on the sample surface are staggered, so when performing imaging measurement, the marks of different layers will not affect each other, thereby ensuring image quality and improving measurement accuracy. In other embodiments, if there is no overlay error between different first marks, the symmetry centers of different first marks can have a preset displacement.

[0046] In this embodiment, the first mark is a centrally symmetrical structure, and there is no overlay error between different first marks, and the symmetry centers of the first marks of different process layers coincide; the second mark is a centrally symmetrical structure. The overlay error based on imaging measurement can be obtained by obtaining the deviation of the center position of the first mark of the first process layer 1 and the second process layer 2. In other embodiments, one or both of the first marks of the first process layer and the second process can be an asymmetric structure, and the feature points of the first marks of the first process layer and the second process layer can be used to obtain the overlay error according to the offset between the feature points. The feature points can be corner points or inflection points.

[0047] In this embodiment, the first identification includes a plurality of first sub-identifications 111 arranged in a center-symmetrical manner, and the first sub-identification 111 is a single identification; the first sub-identification 111 is a center-symmetrical structure or a non-center-symmetrical structure.

[0048] Specifically, refer to Figure 1 , the first identifier includes four first sub-identifiers 111 arranged in a central symmetric manner; the symmetric centers of the four first sub-identifiers 111 are arranged in a square, and the first identifier has a first symmetric center O, which is the center of the square. In other embodiments, the first identifier includes two or more other values.

[0049] In this embodiment, the first sub-identification 111 is in the shape of a cross. In other embodiments, the first sub-identification 111 may be in the shape of a ring, a polygon or a circle.

[0050] In this embodiment, the first sub-identifiers 111 of the first process layer 1 and the second process layer 2 have the same shape. In other implementations, the first sub-identifiers 111 of different process layers may be different.

[0051] refer to Figures 1 to 4 If there is no overlay error between different second marks, the projections of the second marks of different process layers on the sample surface overlap.

[0052] The overlap of the projections of the second marks of different process layers on the sample surface can reduce the area of ​​the overlay mark.

[0053] The second identifier includes one or more second sub-identifiers 121. Specifically, in this embodiment, the second identifier includes four second sub-identifiers 121. In other embodiments, the number of the second sub-identifiers 121 may be different from the number of the first sub-identifiers 111.

[0054] In this embodiment, the second identifier includes a plurality of second sub-identifiers arranged in a central symmetric manner, the symmetry center of the second identifier is the same as the first symmetry center O of the first identifier; and the number of the second sub-identifiers 121 is the same as the number of the first sub-identifiers 111. The second sub-identifiers 121 correspond one-to-one to the first sub-identifiers 111. In other embodiments of the present application, the second identifier may be a non-central symmetric structure.

[0055] refer to Figure 2 , the second sub-identification 121 is a grating structure. The second sub-identification 121 includes: a first grating 121a, the first grating 121a includes a plurality of grating bars arranged along a first direction; the second grating 121b includes a plurality of grating bars arranged along a second direction, the second direction is perpendicular to the first direction or has an acute angle; the projections of the first grating 121a and the second grating 121b on the sample surface are staggered.

[0056] The first grating 121a and the second grating 121b are formed of a plurality of periodically distributed strip grooves.

[0057] In this embodiment, the grating structure is a centrally symmetrical figure, and the grating structure has a second symmetry center; the number of the first grating 121a and the number of the second grating 121b are both multiple, and the multiple first gratings 121a and the multiple second gratings 121b are symmetrically arranged around the second center.

[0058] Specifically, the number of the first gratings 121a is two, and the number of the second gratings 121b is two. The first gratings 121a and the second gratings 121b are alternately arranged around the second symmetry center.

[0059] The first grating 121a is a centrosymmetric structure; the second grating 121b is a centrosymmetric structure.

[0060] In other embodiments, the number of the first grating 121a and the number of the second grating 121b can be one or more than two.

[0061] In this embodiment, the center of symmetry of the first sub-identifier 111 in the first identification in any process layer is the same as the center of symmetry of the second sub-identifier 121 in the second identification in the same process layer; the center of symmetry of the first sub-identifier 111 in the first identification in other process layers and the center of symmetry of the second sub-identifier 121 in the second identification in the same process layer are staggered.

[0062] Specifically, in this embodiment, the first sub-identifier 111 is a cross; the center of the cross is the symmetry center of the first sub-identifier 111, and the center of the cross coincides with the second symmetry center of one of the second sub-identifiers 121. In this embodiment, the second sub-identifier 121 corresponds to the first sub-identifier 111 one by one, and the corresponding second sub-identifier 121 coincides with the symmetry center of the first sub-identifier 111. That is, the center of the cross coincides with the arrangement center of the first grating 121a and the second grating 121b.

[0063] In this embodiment, the center of the second sub-logo 121 is arranged along the arrangement frame; the center of the first sub-logo 111 is located at the edge of the arrangement frame or inside the arrangement frame. If the center of the first sub-logo is located at the edge of the arrangement frame or inside the arrangement frame, the size of the overlay logo depends on the size of the first logo, and the second logo does not occupy additional space, thereby reducing the size of the overlay logo.

[0064] In other embodiments, the center of the first sub-logo is arranged along the arrangement frame; the center of the first sub-logo 111 is located at the edge of the arrangement frame or inside the arrangement frame. If the center of the second sub-logo is located at the edge of the arrangement frame or inside the arrangement frame, the size of the overlay logo depends on the size of the second logo, and the first logo does not occupy additional space, thereby reducing the size of the overlay logo.

[0065] Specifically, refer to Figure 1 , the center of the first sub-identification 111 of the first process layer 1 coincides with the center of the second sub-identification 121 , that is, the first sub-identification 111 is located at the vertex of the edge of the rectangular frame.

[0066] refer to Figure 3, the centers of the four first sub-identifiers 111 of the second process layer 2 are respectively located in the middle of the line connecting the centers of adjacent second sub-identifiers 121. In other embodiments, the centers of the four second sub-identifiers of the second process layer 2 are respectively located in the middle of the line connecting the centers of adjacent first sub-identifiers.

[0067] In other embodiments, in each process layer, the symmetric centers of the first sub-identifier 111 and the second sub-identifier 121 may not overlap. The center of the second sub-identifier 121 of each process layer is located at the edge or inside of the arrangement frame.

[0068] In this embodiment, the arrangement frame is a polygon, specifically a rectangle, and the rectangle is a square. In other embodiments, the arrangement frame is other regular polygons or a circle.

[0069] The size of the first sub-identity 111 along the first direction is the same as the size of the second sub-identity 121 along the first direction; the size of the first sub-identity 111 along the second direction is the same as the size of the second sub-identity 121 along the second direction.

[0070] The size of the first sub-identification 111 along the first direction is the same as the size of the second sub-identification 121 along the first direction; the size of the first sub-identification 111 along the second direction is the same as the size of the second sub-identification 121 along the second direction. The requirements of the imaging detection device for the identification resolution can be met while minimizing the size of the overlay identification.

[0071] In this embodiment, the first sub-identification 111 of each process layer has the same size, and the second sub-identification 121 of each process layer has the same size. In other embodiments, the sizes of the first sub-identification 111 of different process layers may be different; the sizes of the second sub-identification 121 of different process layers may be different.

[0072] The top view of the overlay mark of this application is as follows Figure 4 As shown, if there is no overlay error, the projections of the second marks of the first process layer 1 and the second process layer 2 in the second mark group on the surface of the process layer overlap.

[0073] Figures 5 to 7 It is a schematic structural diagram of the second embodiment of the overlay mark of the present invention.

[0074] This embodiment and Figures 1 to 4 The similarities of the embodiments shown are not described in detail here, and the differences include:

[0075] Figure 5 It is a schematic structural diagram of the first sub-identifier 111 and the second sub-identifier 121 of the first process layer 1. Figure 6 A schematic diagram of the structure of the first mark and the second mark of the first process layer 1; Figure 7It is a structural schematic diagram of the first mark and the second mark of the second process layer 2.

[0076] refer to Figure 5 In this embodiment, the first sub-marker 111 is annular, specifically, a rectangular ring. The first sub-marker 111 is an annular groove etched in the first process layer 1 .

[0077] In this embodiment, the second sub-identification 121 of the first process layer 1 is located inside the first sub-identification 111, and the centers of the first sub-identification 111 and the second sub-identification 121 coincide with each other. The size of the second sub-identification 121 along the first direction is smaller than the size of the first sub-identification 111 along the first direction; the size of the second sub-identification 121 along the second direction is smaller than the size of the first sub-identification 111 along the second direction.

[0078] refer to Figure 6 In the first process layer 1 , the symmetric centers of the first sub-identification 111 and the second sub-identification 121 coincide with each other.

[0079] refer to Figure 7 In the second process layer 2, the centers of the first sub-logos 111 are arranged as an arrangement frame, and the second sub-logos 121 are located inside the arrangement frame. The size of the first sub-logo 111 is larger than the second sub-logo 121, so that the first sub-logo 111 is located inside the arrangement frame to reduce the overall size of the overlay mark.

[0080] Figure 8 It is a schematic structural diagram of the first embodiment of the device of the present invention.

[0081] Please refer to Figure 8 The technical solution of the present application also provides a device, which includes a process layer, and the number of the process layers is multiple, and is characterized in that: the process layer includes one or more exposure areas 10, and the exposure area 10 includes one or more identification areas 11; the identification area 11 has an overlay mark.

[0082] In this embodiment, the overlay mark includes a first mark group based on imaging, the first mark group includes: a plurality of first marks respectively located at different process layers of the sample; a second mark group based on diffraction, the second mark group includes: a plurality of second marks respectively located at different process layers of the sample. Figures 1 to 7 The overlay marks of the embodiments are the same. The contents of the first embodiment and the second embodiment of the overlay mark can be cited here.

[0083] The exposure area 10 is rectangular; there are multiple identification areas 11, and the identification areas 11 are respectively located at the top corners of the exposure area 10 and / or on the diagonal lines of the exposure area 10. In the embodiments of the present application, the exposure area 10 can be other polygonal, circular or irregular shapes.

[0084] Specifically, there are eight marking areas 11 , which are respectively located at the vertex corners of the exposure area 10 and the center of the line connecting the center of the exposure area 10 and each vertex corner.

[0085] Fig. 9 It is a structural schematic diagram of the first embodiment of the measurement method based on overlay marking of the present application.

[0086] refer to Fig. 9 , measurement methods based on overlay markings, including:

[0087] SP1, performing imaging measurement on the first mark group to obtain a first overlay error between a plurality of first marks in the first mark group;

[0088] SP2. Perform diffraction measurement on the second mark group to obtain a second overlay error between multiple second marks in the second mark group.

[0089] The following is combined with reference 1 to Figure 7 , the measurement method provided in this embodiment is described in detail.

[0090] In this embodiment, the measurement method further includes: selecting one of the first identification group and the second identification group as a target identification group according to the first overlay error and the second overlay error; and using the measurement method corresponding to the target identification to detect the same type of process layer. The measurement direction includes the imaging measurement or the diffraction measurement.

[0091] Selecting one of the first identification group and the second identification group as a target identification group includes: correcting the process for forming the process layer according to the first overlay error and obtaining a first correction residual; correcting the process for forming the process layer according to the second overlay error and obtaining a second correction residual; and selecting the identification group corresponding to the smaller of the first correction residual and the second correction residual as the target identification group.

[0092] It should be noted that process layers formed by different processes have different correction residues when using different overlay measurement methods; through the overlay identification and measurement method of the present application, an overlay measurement method with a smaller correction residue for the corresponding process layer can be selected as a target measurement method; subsequent overlay measurement of process layers formed by the same process in the target measurement direction can reduce the correction residue and improve the yield. The overlay measurement method includes imaging measurement and diffraction measurement.

[0093] The process includes: photolithography, wet etching or dry etching.

[0094] refer to Fig.10 , execute step SP1, perform imaging measurement on the first mark group, and obtain a first overlay error between multiple first marks in the first mark group, including: SP11, perform imaging measurement on the first mark group to obtain a sample image; SP12, obtain a first position of the first mark according to the sample image; SP13, obtain a first overlay error according to a position deviation between the first positions of multiple first marks.

[0095] Performing imaging measurement on the first mark group to obtain a sample image includes: photographing the first mark group by an imaging device to obtain the sample image, wherein the sample image includes images of multiple first marks. Specifically, in this embodiment, the sample image includes an image of the first mark of the first process layer 1 and an image of the first mark of the second process layer 2.

[0096] Alternatively, the sample image includes a plurality of sub-sample images. Performing imaging measurement on the first mark group, obtaining the sample image includes: causing the imaging device to focus on the first mark of each process layer respectively, so as to image each first mark respectively to obtain a plurality of sub-sample images. Specifically, in this embodiment, the sample image includes: a first sub-sample image of the first mark of the first process layer 1 and a second sub-sample image of the first mark of the second process layer 2.

[0097] Among them, if the first identifier includes multiple first sub-identifiers 111 arranged in a centrally symmetrical manner; obtaining the first position of the first identifier according to the sample image includes: obtaining the first sub-positions of multiple first sub-identifiers 111 in the first identifier respectively according to the sample image; and obtaining the symmetry center of the multiple first sub-positions to obtain the first position.

[0098] In this embodiment, the first sub-identifier 111 has a symmetry center M; the first sub-position is the position coordinate of the symmetry center M of the first sub-identifier 111. Acquiring the first sub-positions of the plurality of first sub-identifiers 111 in the first identifier according to the sample image respectively includes: acquiring the position coordinates of the symmetry centers M of four first sub-identifiers 111 according to the sample image to obtain the first sub-positions;

[0099] Obtaining the symmetry centers of multiple first sub-positions to obtain the first position, including: fitting a square according to the position coordinates of the symmetry center M of the four first sub-identifiers 111, obtaining the position coordinates of the first symmetry center O, and obtaining the first position; or obtaining the symmetry centers of multiple first sub-positions to obtain the first position, including: obtaining the center coordinates of the position coordinates of the symmetry center M of two diagonal first sub-identifiers 111 to obtain the first position.

[0100] In this embodiment, the first overlay error is obtained by obtaining the first position of the first mark of the first process layer 1 and the first position of the first mark of the second process layer 2 and by taking the difference between the first position of the first process layer 1 and the first position of the second process layer 2.

[0101] If there is no overlay error between different second logos, the symmetry centers of different second logos coincide; the second logo includes a plurality of second sub-logos 121 arranged in a centrally symmetrical manner; the second sub-logo 121 includes: a first grating 121a, the first grating 121a includes a plurality of grating bars arranged along a first direction; a second grating 121b, the second grating 121b includes a plurality of grating bars arranged along a second direction, and the second direction is perpendicular to the first direction or has an acute angle.

[0102] It should be noted that, in this embodiment, when there is no overlay error between process layers, the second identifications of different process layers overlap, and the second sub-identifications 121 of different process layers overlap correspondingly, and the correspondingly overlapping second sub-identifications 121 of different process layers are a sub-identification group.

[0103] refer to Fig.11 In this embodiment, step SP2 is executed to perform diffraction measurement on the second mark group to obtain a second overlay error between multiple second marks in the second mark group, including: SP21, performing diffraction measurement on the second mark group to obtain a diffraction image; SP22, obtaining the position deviation between the second sub-markers in the sub-marker group according to the diffraction image to obtain a second sub-deviation; the second overlay error includes the second sub-deviation of one or more sub-marker groups.

[0104] When the process is corrected by the second overlay error, the correction can be performed by one or more second sub-deviations. Correcting the process by using multiple second sub-deviation values ​​can further reduce the correction residue.

[0105] Specifically, a diffraction measurement device is used to perform diffraction measurement on the second mark group to obtain a diffraction image, where the diffraction image is an image formed after the measurement light is diffracted by the second mark group.

[0106] The second sub-deviation is obtained by obtaining the position deviation between the second sub-identifiers 121 in the sub-identifier group according to the diffraction image, including: obtaining the position deviation between the symmetry centers N of different second sub-identifiers 121 according to the diffraction image of the second sub-identifier 121 of different process layers in the same sub-identifier group, and obtaining the second sub-deviation.

[0107] In other embodiments, performing diffraction measurement on the second mark group to obtain a second overlay error between multiple second marks in the second mark group includes: obtaining a second sub-deviation by obtaining a position deviation between second sub-marks 121 in the sub-mark group; obtaining a second overlay deviation by obtaining a median of multiple second sub-deviations of multiple sub-mark groups. The median includes a median or a weighted value; and the weighted value includes an average value.

[0108] The second sub-deviation includes a first deviation component along the first direction and a second deviation component along the second direction; the second sub-deviation is obtained by obtaining the position deviation between the second sub-identifiers 121 in the sub-identifier group according to the diffraction image, including: obtaining the first deviation component of the first grating 121a of different process layers along the first direction according to the diffraction image of the first grating 121a in the sub-identifier group; obtaining the second deviation component of the second grating 121b of different process layers along the second direction according to the diffraction image of the second grating 121b in the sub-identifier group.

[0109] Specifically, in this embodiment, the first direction is perpendicular to the second direction.

[0110] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. An overlay mark, characterized in that: include: A first identification group based on imaging, the first identification group comprising: a plurality of first identifications respectively located at different process layers of the sample; A second mark group based on diffraction, wherein the second mark group includes: a plurality of second marks respectively located at different process layers of the sample.

2. The overlay mark according to claim 1, characterized in that: If there is no overlay error between different first marks, the projections of the symmetry centers of different first marks on the sample surface overlap, and the projections of different first marks on the sample surface are staggered; if there is no overlay error between different second marks, the projections of second marks of different process layers on the sample surface overlap.

3. The overlay mark according to claim 1, characterized in that: The first identifier includes a plurality of first sub-identifiers arranged in a central symmetrical manner, and the first sub-identifier is a single identifier; the first sub-identifier is a central symmetrical structure or a non-central symmetrical structure.

4. The overlay mark according to claim 3, characterized in that: The first sub-marker is in the shape of a cross, a ring, a polygon or a circle.

5. The overlay mark according to any one of claims 1 to 4, characterized in that: The second identifier includes one or more second sub-identifiers, and the second sub-identifier is a grating structure.

6. The overlay mark according to any one of claim 5, characterized in that: The second sub-identifier includes: a first grating, the first grating includes a plurality of grating bars arranged along a first direction; the second grating includes a plurality of grating bars arranged along a second direction, the second direction is perpendicular to the first direction or has an acute angle; the projections of the first grating and the second grating on the sample surface are staggered.

7. The overlay mark according to claim 6, characterized in that: The grating structure is a periodically symmetrical pattern; the first grating and the second grating are both multiple in number, and the multiple first gratings and the multiple second gratings are centrally symmetrically arranged.

8. The overlay mark according to claim 5, characterized in that: The second identifier includes multiple second sub-identifiers, which are arranged in a centrally symmetrical manner, and the symmetry center of the second identifier is the same as the symmetry center of the first identifier; the number of the second sub-identifiers is the same as the number of the first sub-identifiers.

9. The overlay mark according to claim 8, characterized in that: The symmetry center of the first sub-identifier of any process layer is the same as the symmetry center of a second sub-identifier of the same process layer; the symmetry center of the first sub-identifier of other process layers is staggered with the symmetry center of the second sub-identifier of the same process layer.

10. The overlay mark according to claim 9, characterized in that: If the size of the first sub-identifier along the first direction is the same as the size of the second sub-identifier along the first direction; the size of the first sub-identifier along the second direction is the same as the size of the second sub-identifier along the second direction.

11. The overlay mark according to claim 1, characterized in that: The center of the second sub-identity is arranged along the arrangement frame; the center of the first sub-identity is located at the edge of the arrangement frame or inside the arrangement frame; or, the center of the first sub-identity is arranged along the arrangement frame; the center of the second sub-identity is located at the edge of the arrangement frame or inside the arrangement frame; Wherein, the arrangement frame is a rectangle or a hexagon.

12. A device comprising a plurality of process layers, characterized in that: include: The process layer includes one or more exposure areas, and the exposure area includes one or more marking areas; The marking area has the overlay mark as described in any one of claims 1 to 11.

13. The device according to claim 12, characterized in that The exposure area is rectangular; there are multiple identification areas, and the identification areas are located at the top corners of the exposure area and / or the diagonal lines of the exposure area.

14. A method for measuring an overlay mark according to any one of claims 1 to 11, characterized in that: include: Performing imaging measurement on the first mark group to obtain a first overlay error between a plurality of first marks in the first mark group; Perform diffraction measurement on the second mark group to obtain a second overlay error between multiple second marks in the second mark group.

15. The method for measuring an overlay mark according to claim 14, characterized in that: Also includes: Correcting a process for forming the process layer according to the first overlay error, and obtaining a first correction residue; Correcting the process of forming the process layer according to the second overlay error and obtaining a second correction residue; The identification group corresponding to the smaller one of the first revised residual and the second revised residual is selected as the target identification group.

16. The method for measuring an overlay mark according to claim 14, characterized in that: Performing imaging measurement on the first mark group to obtain a first overlay error between a plurality of first marks in the first mark group includes: performing imaging measurement on the first mark group to obtain a sample image; obtaining a first position of the first mark according to the sample image; and obtaining a first overlay error according to a position deviation between the first positions of the plurality of first marks; Among them, if the first identifier includes multiple first sub-identifiers arranged in a centrally symmetrical manner; obtaining the first position of the first identifier according to the sample image includes: respectively obtaining the first sub-positions of multiple first sub-identifiers in the first identifier; and obtaining the symmetric center of the multiple first sub-positions to obtain the first position.

17. The method for measuring an overlay mark according to claim 14, characterized in that: If there is no overlay error between different second marks, the second sub-markers of different process layers overlap correspondingly; The second sub-identifiers corresponding to the overlapping different process layers are a sub-identifier group; Performing diffraction measurement on the second mark group to obtain a second overlay error between a plurality of second marks in the second mark group includes: performing diffraction measurement on the second mark group to obtain a diffraction image; The second sub-deviation is obtained by acquiring the position deviation between the second sub-marks in the sub-mark group according to the diffraction image; and the second overlay error includes the second sub-deviation of one or more sub-mark groups.

18. The method for measuring an overlay mark according to claim 17, characterized in that: The second sub-identification includes: a first grating, the first grating includes a plurality of grating bars arranged along a first direction; a second grating, the second grating includes a plurality of grating bars arranged along a second direction, the second direction being perpendicular to the first direction or having an acute angle; The second sub-deviation includes a first deviation component along the first direction and a second deviation component along the second direction; The second sub-deviation is obtained by obtaining the position deviation between the second sub-identifiers in the sub-identifier group according to the diffraction image, including: obtaining the first deviation component of the first grating of the different process layers along the first direction according to the diffraction image of the first grating in the sub-identifier group; and obtaining the second deviation component of the second grating of the different process layers along the second direction according to the diffraction image of the second grating in the sub-identifier group.

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