Overlay mark, photomask assembly, and detection method

Abstract

The application provides an overlay mark, a mask assembly and a detection method, and particularly relates to the field of semiconductors. The overlay mark comprises a first mark pattern and a second mark pattern. The first mark pattern comprises a first splicing pattern and a first in-plane pattern, and the first in-plane pattern is arranged on one side of the first splicing pattern. The second mark pattern comprises a second splicing pattern and a second in-plane pattern, and the second in-plane pattern is arranged on one side of the second splicing pattern. When the first mark pattern and the second mark pattern are spliced, the first splicing pattern and the second splicing pattern form an intersection area, and the first splicing pattern and the second splicing pattern have overlapping areas in a first direction and a second direction. The first in-plane pattern is located in an angle area of the second splicing pattern, and the second in-plane pattern is located in an angle area of the first splicing pattern. The CD size required for calculating OVL can be measured at one time by using a measuring tool, and the detection efficiency of overlay precision is improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically to an overlay marking, a photomask assembly, and a detection method. Background Technology

[0002] In semiconductor manufacturing, photolithography is a crucial step in forming the patterned structure of integrated circuits. As chip integration density increases, the size of individual chips (dies) gradually grows, and some products, due to design requirements, have areas exceeding the coverage of the standard image field of a photolithography machine (e.g., larger than 26mm × 33mm). For such products, stitching exposure technology is required. This involves using multiple photomasks to expose the wafer in stages, stitching them together to form a complete chip pattern; this is called a stitched product. Therefore, the critical dimension (CD) and overlay (OVL) accuracy of the stitched area are particularly critical, directly affecting the electrical connectivity performance of the stitched area structure and product yield.

[0003] In existing processes, splicing products requires measuring not only the overprinting errors between multiple photomasks and the previous layer pattern, but also the relative overprinting errors between multiple photomasks within the same layer. This process necessitates switching measurement stations and repeating positioning operations, significantly increasing measurement time. Furthermore, step-by-step measurement may introduce additional positioning errors, affecting the consistency of measurement results. Summary of the Invention

[0004] In view of the problems existing in the prior art, the present invention provides an overlay mark, a photomask assembly and a detection method, which shortens the measurement time while ensuring the alignment accuracy of the splicing area.

[0005] To achieve the above and other related objectives, a first aspect of the present invention provides an overlay mark, comprising: a first mark pattern and a second mark pattern, wherein the first mark pattern includes a first splicing pattern and a first in-plane pattern, and the second mark pattern includes a second splicing pattern and a second in-plane pattern, wherein when the first mark pattern and the second mark pattern are spliced ​​together, the first splicing pattern and the second splicing pattern form an intersection area, and the first splicing pattern and the second splicing pattern have overlapping areas in both a first direction and a second direction; the first in-plane pattern is located within the included angle area of ​​the second splicing pattern, and the second in-plane pattern is located within the included angle area of ​​the first splicing pattern.

[0006] In one example of the present invention, the first splicing pattern includes a first graphic extending along a first direction and a second graphic extending along a second direction, the first direction being perpendicular to the second direction, and the first in-plane pattern being disposed within the area of ​​the reverse extension angle between the first graphic and the second graphic; the second splicing pattern includes a third graphic extending along the first direction and a fourth graphic extending along the second direction, and the second in-plane pattern being disposed within the area of ​​the reverse extension angle between the third graphic and the fourth graphic; when the first marking pattern and the second marking pattern are spliced, the first graphic and the third graphic partially overlap in the first direction, and the second graphic and the fourth graphic partially overlap in the second direction.

[0007] In one example of the present invention, the first graphic intersects the second graphic perpendicularly, and the third graphic intersects the fourth graphic perpendicularly.

[0008] In one example of the present invention, the extension lines of the first shape and the second shape intersect perpendicularly, and the extension line of the third shape intersects perpendicularly with the fourth shape; or, the extension line of the first shape intersects perpendicularly with the second shape, and the extension line of the third shape intersects perpendicularly with the fourth shape.

[0009] In one example of the present invention, the first in-plane pattern includes a fifth graphic, a sixth graphic, and at least one set of seventh graphics. The fifth graphic is arranged parallel to the first graphic, the sixth graphic and the seventh graphic are arranged parallel to the second graphic, and the size of the sixth graphic in the second direction is larger than the size of the seventh graphic. The seventh graphics are symmetrically distributed on both sides of the sixth graphic.

[0010] The pattern on the second surface includes an eighth graphic, a ninth graphic, and at least one set of tenth graphics. The eighth graphic is arranged parallel to the third graphic, and the ninth and tenth graphics are arranged parallel to the fourth graphic. The size of the ninth graphic in the second direction is larger than the size of the tenth graphic, and the tenth graphics are symmetrically distributed on both sides of the ninth graphic.

[0011] In one example of the present invention, after the first marking pattern and the second marking pattern are spliced ​​together, there is a first gap between the first graphic and the eighth graphic, a second gap between the second graphic and the innermost tenth graphic, a third gap between the third graphic and the fifth graphic, and a fourth gap between the fourth graphic and the innermost seventh graphic.

[0012] In one example of the present invention, the boundary of the first in-plane pattern in the first direction is parallel to the boundary of the first spliced ​​pattern and has a first spacing; the boundary of the first in-plane pattern in the second direction is parallel to the boundary of the first spliced ​​pattern and has a second spacing; the boundary of the second in-plane pattern in the first direction is parallel to the boundary of the second spliced ​​pattern and has a third spacing; and the boundary of the second in-plane pattern in the second direction is parallel to the boundary of the second spliced ​​pattern and has a fourth spacing.

[0013] A second aspect of the present invention provides a photomask assembly, the photomask assembly including a first photomask, a second photomask and an overlay mark, wherein the first photomask and the second photomask have a splicing area, and the overlay mark is disposed in the cutting path of the splicing area.

[0014] A third aspect of the present invention provides a detection method based on the above-described photomask assembly, the detection method comprising the following steps:

[0015] A photoresist layer is coated onto an integrated circuit workpiece;

[0016] The first portion of the photoresist layer is exposed using a first photomask;

[0017] A second photomask is used to expose a second portion of the photoresist layer, and there is a splicing area between the first portion and the second portion;

[0018] The exposed photoresist layer is developed to obtain the desired pattern, and the pattern of overlay marks is displayed on the cutting path of the splicing area;

[0019] The key dimensions within the overlay mark are measured using a measuring tool, and the overlay accuracy in the first and second directions is calculated based on the key dimensions.

[0020] In one example of the present invention, the overlay accuracy calculation process includes:

[0021] The relative rotation angle θ = arcsin[(CD5 - design value) / CD9], where CD5 represents the maximum distance between the boundary of the pattern in the second face in the first direction and the boundary of the first splicing pattern, and CD9 represents the boundary length dimension of the pattern in the second face in the first direction;

[0022] The overlay accuracy in the first direction is OVL1 = [(CD1 + CD2) / 2 - (CD3 + CD4) / 2] / 2, where CD1 represents the minimum spacing between the boundary of the second in-plane pattern in the second direction and the boundary of the first spliced ​​pattern; CD2 represents the maximum spacing between the boundary of the second in-plane pattern in the second direction and the boundary of the first spliced ​​pattern; CD3 represents the minimum spacing between the boundary of the first in-plane pattern in the second direction and the boundary of the second spliced ​​pattern; and CD4 represents the maximum spacing between the boundary of the first in-plane pattern in the second direction and the boundary of the second spliced ​​pattern.

[0023] The overlay accuracy in the second direction is OVL2 = [(CD5+CD6) / 2-(CD7+CD8) / 2] / 2, where CD5 represents the maximum spacing between the boundary of the second in-plane pattern in the first direction and the boundary of the first spliced ​​pattern; CD6 represents the minimum spacing between the boundary of the second in-plane pattern in the first direction and the boundary of the first spliced ​​pattern; CD7 represents the maximum spacing between the boundary of the first in-plane pattern in the first direction and the boundary of the second spliced ​​pattern; and CD8 represents the maximum spacing between the boundary of the first in-plane pattern in the first direction and the boundary of the second spliced ​​pattern.

[0024] In summary, the overlay marking provided by the present invention includes a first marking pattern and a second marking pattern. The first marking pattern includes a first splicing pattern and a first in-plane pattern, and the second marking pattern includes a second splicing pattern and a second in-plane pattern. When the first marking pattern and the second marking pattern are spliced ​​together, the first splicing pattern and the second splicing pattern have overlapping areas in both the first and second directions. This area can be used to monitor the critical dimensions of the splicing area. The first in-plane pattern and the second in-plane pattern are respectively used to monitor the critical dimensions of the corresponding in-plane patterns of the photomask. Furthermore, the overlay accuracy of the splicing area in the first and second directions can be calculated by using the critical dimensions between the first in-plane pattern and the second splicing pattern and the critical dimensions between the second in-plane pattern and the first splicing pattern.

[0025] An unexpected effect is that the measurement tool can measure the overlay accuracy, key dimensions, and key dimensions within the photomask surface of the splicing area in the first and second directions in one stop. There is no need for repeated positioning during the measurement process, which reduces the number of measurement stations and makes the measurement more efficient. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the splicing area of ​​a spliced ​​product in an example. Figure 1 (a) is a partial structural diagram of the splicing area. Figure 1 (b) is Figure 1 Scanning electron microscope image in (a);

[0028] Figure 2 for Figure 1 The three states of the critical (CD) dimensions in region I, among which, Figure 2 In (a), the CD size of the splicing area is too small. Figure 2 In the middle (b), the CD size of the splicing area is normal. Figure 2 In the middle (c), the CD size of the splicing area is too large;

[0029] Figure 3 for Figure 1 There are two states of overlay accuracy in Zone I, among which... Figure 3 In the middle (a), the state where no offset has occurred is shown. Figure 3 (b) represents a state where a large offset has occurred;

[0030] Figure 4 This is a schematic diagram of the structure when the overprinted markings of the present invention are spliced ​​in one embodiment;

[0031] Figure 5 This is a schematic diagram of the structure of the first marking pattern in one embodiment of the present invention;

[0032] Figure 6 This is a schematic diagram of the structure of the second marking pattern in one embodiment of the present invention;

[0033] Figure 7 This is a schematic diagram of the structure of the first marking pattern in another embodiment of the present invention;

[0034] Figure 8 This is a schematic diagram of the structure of the second marking pattern in another embodiment of the present invention;

[0035] Figure 9 This is a schematic diagram of the structure when the overprinted markings of the present invention are spliced ​​in another embodiment;

[0036] Figure 10 This is a schematic diagram of the measurement position of the overlay mark of the present invention in one embodiment;

[0037] Figure 11 This is a schematic diagram of the structure of the photomask assembly of the present invention in one embodiment;

[0038] Figure 12 This is a flowchart of one embodiment of the detection method based on a photomask assembly according to the present invention.

[0039] Component designation explanation:

[0040] 100. Overlay mark; 110. First mark pattern; 111. First splicing pattern; 1111. First graphic; 1112. Second graphic; 112. First inner face pattern; 1121. Fifth graphic; 1122. Sixth graphic; 1123. Seventh graphic; 120. Second mark pattern; 121. Second splicing pattern; 1211. Third graphic; 1212. Fourth graphic; 122. Second inner face pattern; 1221. Eighth graphic; 1222. Ninth graphic; 1223. Tenth graphic; 200. First photomask; 300. Second photomask; 400. Splicing area. Detailed Implementation

[0041] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0043] In this document, the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used only for descriptive and distinguishing purposes and should not be construed as indicating or implying relative importance.

[0044] In integrated circuit manufacturing, pre-defined patterns are typically formed using photolithography, for example, transferring patterns from photomasks to wafers. However, the standard image field size of a photolithography machine is limited. When the wafer size exceeds the machine's standard image field, multiple photomasks need to be stitched together to transfer their patterns onto the wafer to form a complete device. During image transfer, issues such as pattern misalignment, discontinuity, and distortion can occur in the stitched areas between adjacent photomasks, leading to lower product yields. Therefore, the critical dimensions and overlay accuracy of the stitched areas are particularly crucial.

[0045] like Figure 1 This diagram illustrates the structure of the splicing area of ​​a spliced ​​product. Figure 1 (a) is a partial structural diagram of the splicing area. Figure 1 (b) is Figure 1 Scanning electron microscope image in (a); Figure 2 for Figure 1 Three states of the critical dimensions in region I: Figure 2 In (a), the CD size of the splicing area is too small. Figure 2 In the middle (b), the CD size of the splicing area is normal. Figure 2 In the middle (c), the CD size of the splicing area is too large. Both too small and too large CD sizes will affect the connection performance of the final product. Figure 3 for Figure 1 Two states of overlay accuracy (OVL) in region I: Figure 3 In the middle (a), the state where no offset has occurred is shown. Figure 3 (b) shows a state with a large offset. If the lateral or longitudinal offset of the photomask in the splicing area exceeds the tolerance range, even if the CD size is normal, it will lead to the deterioration of electrical performance or even functional failure.

[0046] To improve the measurement accuracy of the splicing area of ​​spliced ​​products and shorten the measurement time, this invention provides an overlay mark, a photomask assembly containing the overlay mark, and a detection method based on the photomask assembly.

[0047] Please see Figure 4 The first aspect of the present invention provides an overlay mark 100, which can be used as an alignment mark to monitor the CD size and overlay accuracy OVL of the splicing area between adjacent photomasks in the same layer.

[0048] The overlay marking 100 includes a first marking pattern 110 and a second marking pattern 120. The first marking pattern 110 includes a first splicing pattern 111 and a first in-plane pattern 112. The first in-plane pattern 112 is disposed on one side of the first splicing pattern 111, and the two extend in opposite directions. The second marking pattern 120 includes a second splicing pattern 121 and a second in-plane pattern 122. The second in-plane pattern 122 is disposed on one side of the second splicing pattern 121, and the two extend in opposite directions. The first splicing pattern 111 and the second splicing pattern 121 are used to monitor the critical dimensions of the splicing area, and the first in-plane pattern 112 and the second in-plane pattern 122 are respectively used to monitor the critical dimensions of the corresponding photomask in-plane patterns. When the first marking pattern 110 and the second marking pattern 120 are spliced ​​together, the first splicing pattern 111 and the second splicing pattern 121 form an intersection area, and the first splicing pattern 111 and the second splicing pattern 121 have overlapping areas in both the first direction and the second direction. The first in-plane pattern 112 is located in the included angle area of ​​the second splicing pattern 121, and the second in-plane pattern 122 is located in the included angle area of ​​the first splicing pattern 111.

[0049] It should be noted that in this application, the first direction and the second direction refer to two mutually perpendicular directions within the splicing area. For example, the first direction represents the X direction, and the second direction represents the Y direction. The first splicing pattern 111 and the second splicing pattern 121 have overlapping areas in both the first and second directions. That is, the first splicing pattern 111 and the second splicing pattern 121 have overlapping portions in both the X and Y directions of the splicing area. By measuring the dimensions of the overlapping portions in the X and Y directions, the CD change of the splicing area can be monitored. By comparing the measured CD dimensions with preset values, it can be determined whether the pattern in the splicing area has been deformed. Furthermore, the first in-plane pattern 112 is located within the included angle region of the second splicing pattern 121, meaning that the first in-plane pattern 112 is adjacent to the second splicing pattern 121 in both the X and Y directions; the second in-plane pattern 122 is located within the included angle region of the first splicing pattern 111, meaning that the second in-plane pattern 122 is adjacent to the first splicing pattern 111 in both the X and Y directions. The overlay accuracy of the splicing area can be calculated by the spacing between the first inner pattern 112 and the second splicing pattern 121 in the X and Y directions, and the spacing between the second inner pattern 122 and the first splicing pattern 111 in the X and Y directions.

[0050] Please see Figures 4 to 6In one embodiment, the first splicing pattern 111 includes a first graphic 1111 and a second graphic 1112. The first graphic 1111 extends along a first direction (X direction), and the second graphic 1112 extends along a second direction (Y direction), and the first graphic 1111 and the second graphic 1112 intersect perpendicularly. The second splicing pattern 121 includes a third graphic 1211 and a fourth graphic 1212. The third graphic 1211 extends along the first direction, and the fourth graphic 1212 extends along the second direction, and the third graphic 1211 and the fourth graphic 1212 intersect perpendicularly. When the first marking pattern 110 and the second marking pattern 120 are spliced ​​together, the first splicing pattern 111 and the second splicing pattern 121 form a cross pattern, and the first graphic 1111 and the third graphic 1211 partially overlap in the first direction, which is denoted as the first overlapping area; the second graphic 1112 and the fourth graphic 1212 partially overlap in the second direction, which is denoted as the second overlapping area. The first overlapping area and the second overlapping area intersect to form a splicing repeated exposure area A. The size of the splicing repeated exposure area A in the first and second directions is set according to the size of the actual layout of the splicing area. In this embodiment, the first graphic 1111, the second graphic 1112, the third graphic 1211 and the fourth graphic 1212 are elongated strips, and the size of each graphic should meet the size requirements of the overlay mark 100. The size of the overlay mark 100 should be less than or equal to the limited size of its setting area. In one example, the overlay mark 100 is set in the cutting channel of the splicing area, then the size of the overlay mark 100 is smaller than the size of the cutting channel. Furthermore, the width of the elongated strips of the first graphic 1111 and the third graphic 1211 is the same, and the length is not limited. Similarly, the width of the elongated strips of the second graphic 1112 and the fourth graphic 1212 is the same, and the length is not limited. Additionally, the intersection positions of the first graphic 1111 and the second graphic 1112 of the first splicing pattern 111, and the intersection positions of the third graphic 1211 and the fourth graphic 1212 of the second splicing pattern 121, can be selected according to actual conditions. In this embodiment, the ends of the first graphic 1111 and the second graphic 1112 intersect, and the ends of the third graphic 1211 and the fourth graphic 1212 intersect.

[0051] The extension direction of the inner pattern 112 on the first surface is opposite to that of the first spliced ​​pattern 111, such as... Figure 5 As shown, the first splicing pattern 111 extends to the upper left, and the first in-plane pattern 112 extends to the lower right, meaning the first in-plane pattern 112 is located within the area of ​​the angle formed by the reverse extensions of the first and second patterns 1111 and 1112. The second in-plane pattern 122 extends in the opposite direction to the second splicing pattern 121, as shown... Figure 6As shown, the second splicing pattern 121 extends to the lower right, and the second inner-face pattern 122 extends to the upper left. The second inner-face pattern 122 is located within the angled area formed by the reverse extensions of the third graphic 1211 and the fourth graphic 1212. With this configuration, when the first marking pattern 110 and the second marking pattern 120 are spliced, the first inner-face pattern 112 falls within the intersection area of ​​the third graphic 1211 and the fourth graphic 1212 of the second splicing pattern 121, and the second inner-face pattern 122 falls within the intersection area of ​​the first graphic 1111 and the second graphic 1112 of the first splicing pattern 111.

[0052] Furthermore, the boundary of the first in-plane pattern 112 in the first direction (X direction) is parallel to the boundary of the first splicing pattern 111 in the first direction (first graphic 1111) and has a spacing d1. The boundary of the first in-plane pattern 112 in the second direction (Y direction) is parallel to the boundary of the first splicing pattern 111 in the second direction (second graphic 1112) and has a spacing d2. Similarly, the boundary of the second in-plane pattern 122 in the first direction (X direction) is parallel to the boundary of the second splicing pattern 121 in the first direction (third graphic 1211) and has a spacing d3. The boundary of the second in-plane pattern 122 in the second direction is parallel to the boundary of the second splicing pattern 121 in the second direction (fourth graphic 1212) and has a spacing d4. When the first splicing pattern 111 and the second splicing pattern 121 are spliced ​​together, if the splicing patterns do not shift, the boundaries of the first in-plane pattern 112 in the first and second directions are parallel to the boundaries of the second splicing pattern 121 in the first and second directions, respectively; the boundaries of the second in-plane pattern 122 in the first and second directions are parallel to the boundaries of the first splicing pattern 111 in the first and second directions, respectively. If the splicing patterns shift, the above boundaries will not remain parallel.

[0053] Please see Figures 4 to 6 In one embodiment, the first in-plane pattern 112 includes a fifth graphic 1121, a sixth graphic 1122, and at least one set of seventh graphics 1123. The fifth graphic 1121 is arranged parallel to the first graphic 1111, and the extending direction of the fifth graphic 1121 is opposite to the extending direction of the first graphic 1111. Figure 5 As shown, if the first graphic 1111 extends to the left, then the fifth graphic 1121 extends to the right. The sixth graphic 1122 and the seventh graphic 1123 are both arranged parallel to the second graphic 1112, and the extending directions of the sixth graphic 1122 and the seventh graphic 1123 are opposite to the extending direction of the second graphic 1112. Figure 5As shown, the second graphic 1112 extends upwards, while the sixth graphic 1122 and the seventh graphic 1123 extend downwards. Neither the sixth graphic 1122 nor the seventh graphic 1123 intersects with the fifth graphic 1121. This arrangement allows the first splicing pattern 111 and the first in-plane pattern 112 to be diagonally positioned. When the first marking pattern 110 and the second marking pattern 120 are spliced, the first in-plane pattern 112 is located within the intersection area of ​​the second splicing pattern 121, and the second in-plane pattern 122 is located within the intersection area of ​​the first splicing pattern 111. By measuring the distance between the first in-plane pattern 112 and the second splicing pattern 121, and the distance between the second in-plane pattern 122 and the first splicing pattern 111, the overlay accuracy of the splicing area can be calculated. The sixth graphic 1122 has a larger dimension in the second direction than the seventh graphic 1123 in the second direction. The area where the sixth graphic 1122 and the seventh graphic 1123 are flush is used to monitor the CD of the high-density pattern in the plane, and the area where the sixth graphic 1122 extends beyond the seventh graphic 1123 is used to monitor the CD of the low-density pattern in the plane. The CD of each area is consistent with the size of the actual pattern in the plane it monitors. Each group of seventh graphics 1123 is symmetrically distributed on both sides of the sixth graphic 1122. The seventh graphics 1123 are arranged in groups, and there can be one group or multiple groups. In this embodiment, a total of three groups of seventh graphics 1123 are arranged symmetrically on the left and right sides of the sixth graphic 1122.

[0054] The pattern 122 on the second surface has the same composition as the pattern 112 on the first surface, but in the opposite direction. Specifically, the pattern 122 on the second surface includes an eighth graphic 1221, a ninth graphic 1222, and at least one set of tenth graphics 1223. The eighth graphic 1221 is arranged parallel to the third graphic 1211, and the extending direction of the eighth graphic 1221 is opposite to the extending direction of the third graphic 1211, such as... Figure 6 As shown, if the third figure 1211 extends to the right, then the eighth figure 1221 extends to the left. The ninth figure 1222 and the tenth figure 1223 are both arranged parallel to the fourth figure 1212, and the extension directions of the ninth figure 1222 and the tenth figure 1223 are opposite to the extension direction of the fourth figure 1212, as shown. Figure 6As shown, the fourth graphic 1212 extends downwards, while the ninth graphic 1222 and the tenth graphic 1223 extend upwards. Furthermore, the extension dimension of the ninth graphic 1222 in the second direction is greater than that of the tenth graphic 1223 in the second direction. The area where the ninth graphic 1222 and the tenth graphic 1223 are flush is used to monitor the CD of the high-density pattern area in the plane, and the area where the ninth graphic 1222 extends beyond the tenth graphic 1223 is used to monitor the CD of the low-density pattern area in the plane. The CD of each area is consistent with the actual in-plane pattern CD it monitors. Each group of tenth graphics 1223 is symmetrically distributed on both sides of the ninth graphic 1222. The tenth graphics 1223 are arranged in groups; there can be one group or multiple groups. In this embodiment, three groups of tenth graphics 1223 are arranged symmetrically on the left and right sides of the ninth graphic 1222. The arrangement density of the graphics in the first in-plane pattern 112 and the second in-plane pattern 122 can be designed according to the actual in-plane pattern. In this embodiment, the first in-plane pattern 112 and the second in-plane pattern 122 are identical in shape. When the first marking pattern 110 and the second marking pattern 120 are joined, the second in-plane pattern 122 is centrally symmetrical to the first in-plane pattern 112. In other embodiments, the first in-plane pattern 112 and the second in-plane pattern 122 may be different.

[0055] The fifth graphic 1121, the sixth graphic 1122, the seventh graphic 1123, the eighth graphic 1221, the ninth graphic 1222, and the tenth graphic 1223 are all elongated shapes, and the dimensions of the elongated shapes must meet the overall dimensions of the overlay mark 100. In this embodiment, the distance d from the intersection of the first graphic 1111 and the second graphic 1112 to the intersection of the extension lines of the fifth graphic 1121 and the sixth graphic 1122 satisfies: 0 < d ≤ 10 μm, specifically it can be 5 μm, 8 μm, etc. The distance d from the intersection of the third graphic 1211 and the fourth graphic 1212 to the intersection of the extension lines of the eighth graphic 1221 and the ninth graphic 1222 satisfies: 0 < d ≤ 10 μm, specifically it can be 5 μm, 8 μm, etc. In other embodiments, the fifth graphic 1121, the sixth graphic 1122, the seventh graphic 1123, the eighth graphic 1221, the ninth graphic 1222, and the tenth graphic 1223 can also be regular shapes such as squares, circles, and polygons, and there are no restrictions here.

[0056] Please see Figures 7 to 9To avoid mutual interference from repeated exposures of the overlay mark 100 at 0° and 90°, in another embodiment, the first graphic 1111 of the first splicing pattern 111 and the second graphic 1112 are perpendicular and do not intersect; for example, the extension lines of the first graphic 1111 and the second graphic 1112 are perpendicular. Similarly, the third graphic 1211 and the fourth graphic 1212 of the second splicing pattern 121 are perpendicular and do not intersect; for example, the extension line of the third graphic 1211 is perpendicular to the fourth graphic 1212. In this embodiment, when the first mark pattern 110 and the second mark pattern 120 are spliced, the first graphic 1111 and the third graphic 1211 have a first overlapping area A1 in the first direction, and the second graphic 1112 and the fourth graphic 1212 have a second overlapping area A2 in the second direction. The first overlapping area A1 and the second overlapping area A2 do not interfere with each other.

[0057] In other embodiments, the extension line of the first graphic 1111 may be perpendicular to the second graphic 1112, and the extension line of the third graphic 1211 may be perpendicular to the extension line of the fourth graphic 1212.

[0058] Please see Figure 10 , Figure 10 The measurement position of the overlay mark in the splicing area of ​​the present invention is shown exemplarily. For ease of explanation and comparison, the first in-plane pattern 112 and the second in-plane pattern 122 are rotated at a certain angle in the figure. In actual application, the first in-plane pattern 112 rotates synchronously with the first splicing pattern 111, and the second in-plane pattern 122 rotates synchronously with the second splicing pattern 121. During measurement, a measuring tool such as a Critical Dimension Scanning Electron Microscope (CDSEM) is used to measure the following parameters:

[0059] Key dimensions of pattern 112 on the first face: the dimensions of two positions of the sixth figure 1122, one of which is located beyond the seventh figure 1123, and the other is located below the top of the seventh figure 1123, denoted as CD11 and CD12 respectively.

[0060] Key dimensions of pattern 122 on the second side: the dimensions of two positions of the ninth figure 1222, one of which is the position where the ninth figure 1222 extends beyond the tenth figure 1223, and the other is the position below the top of the tenth figure 1223, denoted as CD21 and CD22 respectively.

[0061] Key dimensions for stitching the repeated exposure area A: key dimension CD101 of the overlapping area of ​​the first pattern 1111 and the third pattern 1211 in the X direction, and key dimension CD102 of the overlapping area of ​​the second pattern 1112 and the fourth pattern 1212 in the Y direction.

[0062] Calculation formula for the splicing area OVL:

[0063] (1) Relative rotation angle θ: arcsin[(CD5 - design value) / CD9], where CD9 is the length of the boundary of the pattern 122 in the second plane in the X direction (the eighth figure 1221), and CD5 is the maximum distance between the boundary of the pattern 122 in the second plane in the X direction (the eighth figure 1221) and the boundary of the first splicing pattern 111 (the first figure 1111).

[0064] (2) OVLX: [(CD1 + CD2) / 2 - (CD3 + CD4) / 2] / 2, where CD1 is the minimum distance between the boundary of the pattern 122 in the second plane in the Y direction (the tenth figure 1223) and the boundary of the first splicing pattern 111 (the second figure 1112), CD2 is the maximum distance between the boundary of the pattern 122 in the second plane in the Y direction (the tenth figure 1223) and the boundary of the first splicing pattern 111 (the second figure 1112); CD3 is the minimum distance between the boundary of the pattern 112 in the first plane in the Y direction (the seventh figure 1123) and the boundary of the second splicing pattern 121 (the fourth figure 1212), CD4 is the maximum distance between the boundary of the pattern 112 in the first plane in the Y direction (the seventh figure 1123) and the boundary of the second splicing pattern 121 (the fourth figure 1212).

[0065] (3)OVLY:[(CD5 + CD6) / 2 - (CD7 + CD8) / 2] / 2,其中,CD5为第二面内图案122在X向的边界(第八图形1221)与第一拼接图案111边界(第一图形1111)之间的最大距离,CD6为第二面内图案122在X向的边界(第八图形1221)与第一拼接图案1十一边界(第一图形1111)之间的最小距离;CD7为第一面内图案112在X向的边界(第五图形1121)与第二拼接图案121边界(第四图形1212)之间的最大距离,CD8为第一面内图案112在X向的边界(第五图形1121)与第二拼接图案121边界(第四图形1212)之间的最小距离。 (3) OVLY: [(CD5 + CD6) / 2 - (CD7 + CD8) / 2] / 2, where CD5 is the maximum distance between the boundary of the pattern 122 in the second plane in the X direction (the eighth figure 1221) and the boundary of the first splicing pattern 111 (the first figure 1111), CD6 is the minimum distance between the boundary of the pattern 122 in the second plane in the X direction (the eighth figure 1221) and the boundary of the first splicing pattern 111 (the first figure 1111); CD7 is the maximum distance between the boundary of the pattern 112 in the first plane in the X direction (the fifth figure 1121) and the boundary of the second splicing pattern 121 (the fourth figure 1212), CD8 is the minimum distance between the boundary of the pattern 112 in the first plane in the X direction (the fifth figure 1121) and the boundary of the second splicing pattern 121 (the fourth figure 1212).

[0066] Compare the above measured values and calculated values with the design values respectively. If within the tolerance range, it means the spliced product is qualified; if exceeding the tolerance range, the spliced product is unqualified. It should be noted that the above process is only a measurement example given by using the overlay marks of this application, and does not limit its protection scope. Any product spliced by using the overlay marks of this application falls within the protection scope of this application.

[0067] Please refer to Figure 11A second aspect of the present invention provides a photomask assembly including the above-mentioned overprinted markings, the photomask assembly being used in image transfer of spliced ​​products.

[0068] Specifically, the photomask assembly includes a first photomask 200, a second photomask 300, and the arbitrary overlay mark 100 described above. The first photomask 200 and the second photomask 300 correspond to different exposure areas, and are joined together to form a photomask assembly with a complete pattern. The joining method of the first photomask 200 and the second photomask 300 is not limited; for example, they can be arranged with their length sides aligned and along their width. The first photomask 200 and the second photomask 300 are joined at a joint area 400. Both the first photomask 200 and the second photomask 300 have dicing channels (not shown) for chip dicing on their outer peripheries. A first marking pattern 110 of the overlay mark 100 is disposed within the dicing channel of the first photomask 200, and a second marking pattern 120 is disposed within the dicing channel of the second photomask 300. After the first photomask 200 and the second photomask 300 are joined, the first marking pattern 110 and the second marking pattern 120 are joined within the dicing channel of the joint area 400 to form the aforementioned overlay mark 100. In one embodiment, one overlay mark 100 is disposed within each of the upper and lower dicing channels of the joint area 400.

[0069] In other embodiments, the photomask assembly may also include a third photomask, a fourth photomask, and more photomasks, and overlay marks 100 may be set in the cutting channels of the splicing areas between adjacent photomasks.

[0070] The first photomask 200 and the second photomask 300 are also provided with their respective marking patterns that correspond to the previous layer. This application does not describe the markings between layers.

[0071] Please see Figure 12 A third aspect of the present invention provides a detection method using the above-described photomask assembly, comprising the following steps:

[0072] S1. Coating a photoresist layer onto an integrated circuit workpiece;

[0073] S2. Expose the first portion of the photoresist layer using a first photomask;

[0074] S3. Expose the second portion of the photoresist layer using a second photomask, where there is a splicing area between the first portion and the second portion;

[0075] S4. Develop the exposed photoresist layer to obtain the desired pattern;

[0076] S5. Use a measuring tool to measure the key dimensions within the overlay mark and calculate the overlay accuracy in the first and second directions based on the key dimensions.

[0077] Specifically, the integrated circuit workpiece in step S1 can be any chip requiring pattern transfer, such as an image sensor, logic device, transistor, etc. The photoresist layer can be applied to the workpiece surface using a spin coating method to achieve a preset thickness.

[0078] Step S2: Place the first photomask 200 on the first part of the photoresist layer for exposure, and obtain the desired image within the cut path of the splicing area 400. Figure 5 or Figure 7 The diagram shown.

[0079] Step S3: Place the second photomask 300 on the second part of the photoresist layer for exposure, and obtain the desired image within the cut path of the splicing area 400. Figure 4 or Figure 9 The diagram shown.

[0080] Step S4: The exposed photoresist layer is developed onto the desired pattern. The development process is not described in detail here, but can be carried out according to the conventional development process in this field.

[0081] The measurement tool in step S5 can be a conventional tool for accurately measuring critical dimensions. In this embodiment, a Critical Dimension Scanning Electron Microscope (CDSEM) is used. A CDSEM can measure all the CDs required for calculating the OVL in a single image, ensuring both accuracy and efficiency.

[0082] Please see Figure 10 The CD dimensions measured in this step include: the key dimensions CD101 in the X direction and CD102 in the Y direction of the spliced ​​repeated exposure area A; the two key dimensions CD11 and CD12 in the first in-plane pattern 112 corresponding to different pattern densities; and the two key dimensions CD21 and CD22 in the second in-plane pattern 122 corresponding to different pattern densities.

[0083] The minimum distance CD1 between the boundary of the second inner pattern 122 in the Y direction and the boundary of the first splicing pattern 111; the maximum distance CD2 between the boundary of the second inner pattern 122 in the Y direction and the boundary of the first splicing pattern 111; the minimum distance CD3 between the boundary of the first inner pattern 112 in the Y direction and the boundary of the second splicing pattern 121; and the maximum distance CD4 between the boundary of the first inner pattern 112 in the Y direction and the boundary of the second splicing pattern 121.

[0084] The maximum distance CD5 between the boundary of the second inner pattern 122 in the X direction and the boundary of the first splicing pattern 111; the minimum distance CD6 between the boundary of the second inner pattern 122 in the X direction and the boundary of the first splicing pattern 111; the maximum distance CD7 between the boundary of the first inner pattern 112 in the X direction and the boundary of the second splicing pattern 121; the minimum distance CD8 between the boundary of the first inner pattern 112 in the X direction and the boundary of the second splicing pattern 121; and the boundary length CD9 of the second inner pattern 122 or the first inner pattern 112 in the X direction.

[0085] In one specific embodiment, the key dimension CD101 of the stitched repeated exposure area A is the width of the overlapping portion of the first pattern 1111 and the third pattern 1211; CD102 is the width of the overlapping portion of the second pattern 1112 and the fourth pattern 1212. The two key dimensions of the first in-plane pattern 112 are: CD11 is the width of the sixth pattern 1122 above the top position of the seventh pattern 1123, and CD12 is the width of the sixth pattern 1122 below the top position of the seventh pattern 1123. The two key dimensions of the second in-plane pattern 122 are: CD21 is the width of the ninth pattern 1222 above the top position of the tenth pattern 1223; CD22 is the width of the ninth pattern 1222 below the top position of the tenth pattern 1223.

[0086] CD1 is the minimum distance between the innermost tenth figure 1223 and the second figure 1112; CD2 is the maximum distance between the innermost tenth figure 1223 and the second figure 1112; CD3 is the minimum distance between the innermost seventh figure 1123 and the fourth figure 1212; and CD4 is the maximum distance between the innermost seventh figure 1123 and the fourth figure 1212.

[0087] CD5 is the maximum distance between the eighth figure 1221 and the first figure 1111; CD6 is the minimum distance between the eighth figure 1221 and the first figure 1111; CD7 is the maximum distance between the fifth figure 1121 and the fourth figure 1212; CD8 is the minimum distance between the fifth figure 1121 and the fourth figure 1212; and CD9 is the length of the fifth figure 1121 or the eighth figure 1221.

[0088] Based on the key dimensions measured above, the overlay accuracy (OVL) of the splicing area can be calculated using the following formula:

[0089] (1) Relative rotation angle θ: arcsin[(CD5-design value) / CD9];

[0090] (2) Overlay accuracy OVLX in the first direction: [(CD1+CD2) / 2-(CD3+CD4) / 2] / 2;

[0091] (3) Overlay accuracy in the second direction: [(CD5+CD6) / 2-(CD7+CD8) / 2] / 2.

[0092] The calculated relative rotation angle θ reflects the offset angle of the splicing area 400 of the first photomask 200 and the second photomask 300; OVLX reflects the overlay accuracy of the splicing area 400 of the first photomask 200 and the second photomask 300 in the X direction; OVLY reflects the overlay accuracy of the splicing area of ​​the first photomask 200 and the second photomask 300 in the Y direction. If the relative rotation angle θ, OVLX, and OVLY all fall within their respective tolerance ranges, it indicates that no offset occurred during splicing or the degree of offset does not affect the product performance.

[0093] If the critical dimensions CD101 and CD102 of the splicing area 400, the critical dimensions CD11 and CD12 of the first inner pattern 112, and the critical dimensions CD21 and CD22 of the second inner pattern 122 are the same as the set values ​​or the difference falls within the tolerance range, it indicates that the spliced ​​product is qualified.

[0094] The overlay marking provided by this invention includes a first marking pattern and a second marking pattern. The first marking pattern includes a first splicing pattern and a first in-plane pattern, and the second marking pattern includes a second splicing pattern and a second in-plane pattern. When the first and second marking patterns are spliced ​​together, they have overlapping areas in both the first and second directions within the splicing surface. This area can be used to monitor the critical dimensions of the splicing area. The first and second in-plane patterns are used to monitor the critical dimensions of the corresponding in-plane patterns of the photomask. Furthermore, the overlay accuracy of the splicing area in the first and second directions can be calculated using the critical dimensions between the first and second in-plane patterns and between the second and first in-plane patterns. Using measurement tools, the overlay accuracy, critical dimensions, and in-plane critical dimensions of the splicing area in the first and second directions can be measured in a single step. No repeated positioning is required during the measurement process, reducing the number of measurement stations and making the measurement more efficient. Therefore, this invention effectively overcomes some practical problems in the prior art and thus has high utilization value and practical significance.

[0095] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A type of overprinted mark, characterized in that, include: The first marking pattern includes a first splicing pattern and a first in-plane pattern, wherein the first in-plane pattern is disposed on one side of the first splicing pattern; The second marking pattern includes a second splicing pattern and a second in-plane pattern, wherein the second in-plane pattern is disposed on one side of the second splicing pattern; Wherein, when the first marking pattern and the second marking pattern are spliced ​​together, the first spliced ​​pattern and the second spliced ​​pattern form an intersection area, and the first spliced ​​pattern and the second spliced ​​pattern have overlapping areas in both the first direction and the second direction; the first in-plane pattern is located in the included angle area of ​​the second spliced ​​pattern, and the second in-plane pattern is located in the included angle area of ​​the first spliced ​​pattern; The first splicing pattern includes a first graphic extending along a first direction and a second graphic extending along a second direction, the first direction being perpendicular to the second direction, and the first in-plane pattern being disposed within the area of ​​the angle between the reverse extensions of the first graphic and the second graphic; The second splicing pattern includes a third graphic extending along a first direction and a fourth graphic extending along a second direction, and the second in-plane pattern is disposed within the area of ​​the angle between the reverse extensions of the third graphic and the fourth graphic; when the first marking pattern is spliced ​​with the second marking pattern, the first graphic and the third graphic partially overlap in the first direction, and the second graphic and the fourth graphic partially overlap in the second direction; The pattern on the first surface includes a fifth graphic, a sixth graphic, and at least one set of seventh graphics. The fifth graphic is arranged parallel to the first graphic, the sixth graphic and the seventh graphic are arranged parallel to the second graphic, and the size of the sixth graphic in the second direction is larger than the size of the seventh graphic. The seventh graphics are symmetrically distributed on both sides of the sixth graphic. The pattern on the second surface includes an eighth graphic, a ninth graphic, and at least one set of tenth graphics. The eighth graphic is arranged parallel to the third graphic, and the ninth and tenth graphics are arranged parallel to the fourth graphic. The size of the ninth graphic in the second direction is larger than the size of the tenth graphic, and the tenth graphics are symmetrically distributed on both sides of the ninth graphic.

2. The overprinting mark according to claim 1, characterized in that, The first graphic intersects the second graphic perpendicularly, and the third graphic intersects the fourth graphic perpendicularly.

3. The overprinting mark according to claim 1, characterized in that, The first shape intersects the extension line of the second shape perpendicularly, and the extension line of the third shape intersects the fourth shape perpendicularly; or, the extension line of the first shape intersects the second shape perpendicularly, and the extension line of the third shape intersects the fourth shape perpendicularly.

4. The overprinting mark according to claim 1, characterized in that, After the first marking pattern and the second marking pattern are spliced ​​together, there is a first gap between the first graphic and the eighth graphic, a second gap between the second graphic and the innermost tenth graphic, a third gap between the third graphic and the fifth graphic, and a fourth gap between the fourth graphic and the innermost seventh graphic.

5. The overprinting mark according to claim 1, characterized in that, The first in-plane pattern has a first gap between its boundary in the first direction and the boundary of the first spliced ​​pattern; the first in-plane pattern has a second gap between its boundary in the second direction and the boundary of the first spliced ​​pattern; the second in-plane pattern has a third gap between its boundary in the first direction and the boundary of the second spliced ​​pattern; and the second in-plane pattern has a fourth gap between its boundary in the second direction and the boundary of the second spliced ​​pattern.

6. A photomask assembly, characterized in that, include: The first photomask, the second photomask, and the overlay mark as described in any one of claims 1-5, wherein the first photomask and the second photomask have a splicing area, and the overlay mark is disposed within the cutting path of the splicing area.

7. A detection method based on the photomask assembly according to claim 6, characterized in that, Includes the following steps: A photoresist layer is coated onto an integrated circuit workpiece; The first portion of the photoresist layer is exposed using a first photomask; A second photomask is used to expose a second portion of the photoresist layer, and there is a splicing area between the first portion and the second portion; The exposed photoresist layer is developed to obtain the desired pattern, and the pattern of overlay marks is displayed on the cutting path of the splicing area; The key dimensions within the overlay mark are measured using a measuring tool, and the overlay accuracy in the first and second directions is calculated based on the key dimensions.

8. The detection method according to claim 7, characterized in that, The process of calculating the overlay accuracy includes: The relative rotation angle θ = arcsin[(CD5 - design value) / CD9], where CD5 represents the maximum distance between the boundary of the pattern in the second face in the first direction and the boundary of the first splicing pattern, and CD9 represents the boundary length dimension of the pattern in the second face in the first direction; The overlay accuracy in the first direction is OVL1 = [(CD1 + CD2) / 2 - (CD3 + CD4) / 2] / 2, where CD1 represents the minimum spacing between the boundary of the second in-plane pattern in the second direction and the boundary of the first spliced ​​pattern; CD2 represents the maximum spacing between the boundary of the second in-plane pattern in the second direction and the boundary of the first spliced ​​pattern; CD3 represents the minimum spacing between the boundary of the first in-plane pattern in the second direction and the boundary of the second spliced ​​pattern; and CD4 represents the maximum spacing between the boundary of the first in-plane pattern in the second direction and the boundary of the second spliced ​​pattern. The overlay accuracy in the second direction is OVL2 = [(CD5+CD6) / 2-(CD7+CD8) / 2] / 2, where CD5 represents the maximum spacing between the boundary of the second in-plane pattern in the first direction and the boundary of the first spliced ​​pattern; CD6 represents the minimum spacing between the boundary of the second in-plane pattern in the first direction and the boundary of the first spliced ​​pattern; CD7 represents the maximum spacing between the boundary of the first in-plane pattern in the first direction and the boundary of the second spliced ​​pattern; and CD8 represents the maximum spacing between the boundary of the first in-plane pattern in the first direction and the boundary of the second spliced ​​pattern.

Images