Overlay mark and method for measuring accuracy of overlay precision correction

Abstract

The present application provides a kind of overlay mark and the method for correcting overlay precision measurement accuracy, the overlay mark includes: front layer overlay mark and when layer overlay mark;Front layer overlay mark includes the first pair of front layer marks arranged along the first direction, the second pair of front layer marks arranged along the second direction and the third pair of front layer marks arranged along the third direction;When layer overlay mark includes the first pair of when layer marks, the second pair of when layer marks and the third pair of when layer marks, also includes the fifth pair of when layer marks between the first pair of when layer marks and the center mark in the center region.The present application sets center mark in the center region of when layer overlay mark, obtains the asymmetry of front layer overlay mark by the distance of the first pair of front layer marks in front layer overlay mark to center mark, to finally obtain the overlay precision compensation value containing asymmetry, to obtain accurate overlay precision, reduce wafer scrap due to inaccurate overlay precision measurement.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a kind of overlay marks and the method for correcting overlay precision measurement accuracy. BACKGROUND

[0002] In the manufacture of semiconductor integrated circuits, multiple photolithography is needed, and the alignment accuracy of photolithography machine, i.e., overlay precision (OVL, Overlay), needs to meet certain design requirements. In the prior art, overlay precision is usually obtained by measuring overlay marks using a measurement device, mainly by collecting signal differences between the front layer and the current layer to calculate overlay precision values.

[0003] However, the overlay marks of the current layer are generally regular, but the overlay marks of the front layer may be deformed after etching, medium layer deposition and chemical polishing. The deformed overlay marks are asymmetric, which affects the interpretation of overlay precision signals and ultimately affects the accuracy of overlay precision measurement, resulting in wafer scrap.

[0004] Figure 1 is an ideal cross-sectional view of the front layer overlay mark and the current layer overlay mark, Figure 2 is an actual cross-sectional view of the front layer overlay mark and the current layer overlay mark. Please refer to Figure 1 , the current layer overlay mark 10 and the front layer overlay mark 20 are regular, and the overlay precision can be directly measured to obtain a more accurate result. Please refer to Figure 2 , the current layer overlay mark 10 is regular, but one of the front layer overlay marks 20 is deformed, resulting in asymmetry of the front layer overlay mark 20, which causes the measurement result to be distorted. SUMMARY

[0005] The present application aims to provide an overlay mark and a method for correcting overlay precision measurement accuracy, which corrects the problem of overlay precision measurement distortion caused by the asymmetry of the overlay mark, obtains accurate overlay precision results, and reduces wafer scrap caused by inaccurate overlay precision measurement.

[0006] To solve the above technical problems, the present application provides an overlay mark, comprising a front layer overlay mark and a current layer overlay mark.

[0007] The front layer overlay mark comprises a first pair of front layer marks arranged along a first direction and symmetrically centered with respect to the center of the front layer mark, a second pair of front layer marks arranged along a second direction and symmetrically centered with respect to the center of the front layer mark, and a third pair of front layer marks arranged along a third direction and symmetrically centered with respect to the center of the front layer mark.

[0008] The when-layer overlay marks comprise a first pair of when-layer marks arranged along a first direction and centrosymmetric relative to a when-layer mark center, a second pair of when-layer marks arranged along a second direction and centrosymmetric relative to the when-layer mark center, and a third pair of when-layer marks arranged along a third direction and centrosymmetric relative to the when-layer mark center;

[0009] The when-layer overlay marks are located inside the front-layer overlay marks, and the when-layer mark center coincides with the front-layer mark center in a direction perpendicular to the overlay marks;

[0010] The when-layer overlay marks further comprise a fifth pair of when-layer marks arranged along the first direction and centrosymmetric relative to the when-layer mark center, and a center mark located in a center region of the when-layer overlay mark center, the fifth pair of when-layer marks being located between the first pair of when-layer marks, and the center of the center mark coinciding with the when-layer mark center.

[0011] Optionally, the first direction is perpendicular to the second direction, and the positive direction of the third direction forms an acute angle with the positive direction of the first direction.

[0012] Optionally, the front-layer overlay marks further comprise a fourth pair of front-layer marks arranged along a fourth direction and centrosymmetric relative to a front-layer mark center, and the when-layer overlay marks further comprise a fourth pair of when-layer marks arranged along the fourth direction and centrosymmetric relative to the when-layer mark center; the positive direction of the fourth direction forms an obtuse angle with the positive direction of the first direction.

[0013] Optionally, the positive direction of the third direction forms an angle of 45 degrees with the positive direction of the first direction, and the positive direction of the fourth direction forms an angle of 135 degrees with the positive direction of the first direction.

[0014] Optionally, the marks in the front-layer overlay marks and the marks in the when-layer overlay marks are all in the form of strips, the extension direction of the strip-shaped marks is perpendicular to the arrangement direction, and the extension direction of the center mark is the same as the extension direction of the fifth pair of when-layer marks.

[0015] Optionally, the front-layer overlay marks are in the form of a regular octagon, and the first pair of when-layer marks, the second pair of when-layer marks, the third pair of when-layer marks, and the fourth pair of when-layer marks in the when-layer overlay marks also form a regular octagon.

[0016] Correspondingly, the application further provides a method for correcting the accuracy of overlay precision measurement, comprising the following steps:

[0017] Manufacturing the overlay marks as described above;

[0018] measuring a distance between each pair of the front layer marks in the front layer overlay marks, measuring a distance between each pair of the on layer marks in the on layer overlay marks, measuring a distance from each mark in the fifth pair of the on layer marks to the center mark, and measuring a distance from each mark in the first pair of the front layer marks to the center mark;

[0019] determining whether a difference between the distance from each mark in the fifth pair of the on layer marks to the center mark is greater than a precision of the CDSEM machine; if yes, checking and repairing the CDSEM machine, and then re-measuring the overlay marks;

[0020] if no, obtaining the mark center of the on layer overlay marks according to the distance between each pair of the on layer marks;

[0021] obtaining the mark center of the front layer overlay marks according to the distance between each pair of the front layer marks and the distance from each mark in the first pair of the front layer marks to the center mark;

[0022] obtaining an actual overlay precision OVL1 according to the mark center of the on layer overlay marks and the mark center of the front layer overlay marks, obtaining a measured overlay precision OVL2 by measuring the overlay marks, and obtaining an overlay precision compensation value Offset = OVL1 - OVL2;

[0023] correcting the measured overlay precision according to the overlay precision compensation value Offset.

[0024] Optionally, the mark center of the on layer overlay marks is M = (A3 + A4 + A5 + A6) / 8, where A3 is a distance between the first pair of the on layer marks, A4 is a distance between the second pair of the on layer marks, A5 is a distance between the third pair of the on layer marks, and A6 is a distance between the fourth pair of the on layer marks.

[0025] Optionally, the mark center of the front layer overlay marks is N = N2 - N1, where N1 = (A7 + A8 + A9 + A10) / 8, and N2 = (A11 - A12) / 2, where A7 is a distance between the first pair of the front layer marks, A8 is a distance between the second pair of the front layer marks, A9 is a distance between the third pair of the front layer marks, A10 is a distance between the fourth pair of the front layer marks, A11 is a distance from one of the marks in the first pair of the front layer marks to the center mark, and A12 is a distance from the other of the marks in the first pair of the front layer marks to the center mark.

[0026] Optionally, the checking of the CDSEM machine includes checking whether the CDSEM machine measures incorrectly and checking a process recipe of the CDSEM machine, and the repairing of the CDSEM machine includes modifying the process recipe of the CDSEM machine.

[0027] In summary, the overlay mark and the method for correcting the accuracy of overlay precision measurement provided by the present application, the front layer overlay mark comprises a first pair of front layer marks arranged along a first direction and symmetrically centered relative to a front layer mark center, a second pair of front layer marks arranged along a second direction and symmetrically centered relative to the front layer mark center, and a third pair of front layer marks arranged along a third direction and symmetrically centered relative to the front layer mark center; the current layer overlay mark comprises a first pair of current layer marks arranged along the first direction and symmetrically centered relative to a current layer mark center, a second pair of current layer marks arranged along the second direction and symmetrically centered relative to the current layer mark center, and a third pair of current layer marks arranged along the third direction and symmetrically centered relative to the current layer mark center; the current layer overlay mark is located inside the front layer overlay mark, and the current layer mark center and the front layer mark center coincide in a direction perpendicular to the overlay mark; the current layer overlay mark further comprises a fifth pair of current layer marks arranged along the first direction and symmetrically centered relative to the current layer mark center, and a center mark located in the center region of the current layer overlay mark, the fifth pair of current layer marks is located between the first pair of current layer marks, and the center of the center mark coincides with the current layer mark center. The unexpected effect of the present application is that the center mark is arranged in the center region of the current layer overlay mark, the asymmetric amount of the front layer overlay mark is obtained through the distance from the first pair of front layer marks in the front layer overlay mark to the center mark, and finally the overlay precision compensation value containing the asymmetric amount is obtained, thereby the problem of overlay precision measurement distortion caused by the asymmetry of the overlay mark can be corrected, accurate overlay precision result is obtained, and wafer scrap caused by inaccurate overlay precision measurement is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is an ideal cross-sectional view of the front layer overlay mark and the current layer overlay mark.

[0029] Figure 2 is an actual cross-sectional view of the front layer overlay mark and the current layer overlay mark.

[0030] Figure 3 is a top view of the overlay mark provided by an embodiment of the present application.

[0031] Figure 4 is a flowchart of the method for correcting the accuracy of overlay precision measurement provided by an embodiment of the present application.

[0032] Figure 5 is a size schematic view of the current layer overlay mark in the overlay mark provided by an embodiment of the present application.

[0033] Figure 6 is a size schematic view of the front layer overlay mark in the overlay mark provided by an embodiment of the present application.

[0034] BRIEF DESCRIPTION OF DRAWINGS:

[0035] 10 - when the layer of marking; 11 - the first pair of when the layer of marking; 11a - the first when the layer of marking; 11b - the second when the layer of marking; 12 - the second pair of when the layer of marking; 12a - the third when the layer of marking; 12b - the fourth when the layer of marking; 13 - the third pair of when the layer of marking; 13a - the fifth when the layer of marking; 13b - the sixth when the layer of marking; 14 - the fourth pair of when the layer of marking; 14a - the seventh when the layer of marking; 14b - the eighth when the layer of marking; 15 - the fifth pair of when the layer of marking; 15a - the ninth when the layer of marking; 15b - the tenth when the layer of marking; 16 - the center marking; 20 - the front layer of marking; 21 - the first pair of front layer of marking; 21a - the first front layer of marking; 21b - the second front layer of marking; 22 - the second pair of front layer of marking; 22a - the third front layer of marking; 22b - the fourth front layer of marking; 23 - the third pair of front layer of marking; 23a - the fifth front layer of marking; 23b - the sixth front layer of marking; 24 - the fourth pair of front layer of marking; 24a - the seventh front layer of marking; 24b - the eighth front layer of marking. DETAILED DESCRIPTION

[0036] The core idea of the present application is to design a set of marking capable of detecting the asymmetry of the front layer of marking, after the marking is made, the actual overlay accuracy containing the asymmetry is obtained by measuring the distance of each marking by CDSEM machine, at the same time, the overlay accuracy is obtained by measuring the marking, the overlay accuracy compensation value is obtained according to the actual overlay accuracy and the measured overlay accuracy, so as to correct the measured overlay accuracy according to the overlay accuracy compensation value.

[0037] Specifically, the present application provides a set of marking, comprising a front layer of marking and a when the layer of marking; the front layer of marking comprises a first pair of front layer of marking arranged along a first direction and center-symmetric relative to the center of the front layer of marking, a second pair of front layer of marking arranged along a second direction and center-symmetric relative to the center of the front layer of marking, and a third pair of front layer of marking arranged along a third direction and center-symmetric relative to the center of the front layer of marking; the when the layer of marking comprises a first pair of when the layer of marking arranged along the first direction and center-symmetric relative to the center of the when the layer of marking, a second pair of when the layer of marking arranged along the second direction and center-symmetric relative to the center of the when the layer of marking, and a third pair of when the layer of marking arranged along the third direction and center-symmetric relative to the center of the when the layer of marking; the when the layer of marking is located in the inner side of the front layer of marking, and the center of the when the layer of marking and the center of the front layer of marking coincide in the direction perpendicular to the set of marking; the when the layer of marking further comprises a fifth pair of when the layer of marking arranged along the first direction and center-symmetric relative to the center of the when the layer of marking, and a center marking in the center area of the when the layer of marking, the fifth pair of when the layer of marking is located between the first pair of when the layer of marking, and the center of the center marking coincides with the center of the when the layer of marking.

[0038] Accordingly, the present application also provides a method for correcting the accuracy of overlay measurement, comprising: manufacturing the overlay mark as described above; measuring the distance between each pair of front layer marks in the front layer overlay mark, measuring the distance between each pair of current layer marks in the current layer overlay mark, measuring the distance between each mark in the fifth pair of current layer marks and the sixth mark, and measuring the distance between each mark in the first pair of front layer marks and the sixth mark; determining whether the difference between the distance between each mark in the fifth pair of current layer marks and the center mark is greater than the accuracy of the CDSEM machine; if yes, checking and repairing the CDSEM machine, and then continuing to determine whether the difference between the distance between each mark in the fifth pair of current layer marks and the center mark is greater than the accuracy of the CDSEM machine; if no, obtaining the mark center of the current layer overlay mark according to the distance between each pair of current layer marks; obtaining the mark center of the front layer overlay mark according to the distance between each pair of front layer marks and the distance between each mark in the first pair of front layer marks and the sixth mark; obtaining the actual overlay precision OVL1 according to the mark center of the current layer overlay mark and the mark center of the front layer overlay mark, measuring the overlay mark to obtain the measured overlay precision OVL2, and obtaining the overlay precision compensation value Offset = OVL1- OVL2; and correcting the measured overlay precision according to the overlay precision compensation value Offset.

[0039] The present application has the unexpected effect that: the center mark is arranged in the center region of the current layer overlay mark, the asymmetry of the front layer overlay mark is obtained through the distance between the first pair of front layer marks in the front layer overlay mark and the center mark, and finally the overlay precision compensation value containing the asymmetry is obtained, thereby the problem of overlay precision measurement distortion caused by the asymmetry of the overlay mark can be corrected, accurate overlay precision result is obtained, and wafer scrap caused by inaccurate overlay precision measurement is reduced.

[0040] To make the objectives, advantages and features of the present application more apparent, the following further describes the present application in detail in combination with the drawings and specific embodiments. It should be noted that the drawings are very simplified and not drawn to scale, and are only used to facilitate and clarify the purpose of assisting the description of the embodiments of the present application. In addition, the structures shown in the drawings are often part of the actual structures. In particular, the emphasis shown in each drawing is different, and sometimes different scales are used.

[0041] As used in the present application, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. As used in the present application, the term "or" is generally employed in its sense of "and / or" unless the content clearly dictates otherwise. As used in the present application, the term "plurality" is generally employed in its sense of "at least one" unless the content clearly dictates otherwise. As used in the present application, the term "at least two" is generally employed in its sense of "two or more" unless the content clearly dictates otherwise. In addition, the terms "first," "second," "third," are used merely for descriptive purposes and are not necessarily intended to refer to relative importance or a quantity of the technical features indicated. Thus, features defined with "first," "second," "third" can explicitly or implicitly include one or at least two of the features.

[0042] Figure 3 is a top view of overlay marks provided by an embodiment of the present application. As shown in Figure 3 The overlay marks provided by the embodiment of the present application include a front layer overlay mark 20 and a current layer overlay mark 10. The front layer overlay mark 20 includes a first pair of front layer marks 21 arranged along a first direction x1 and symmetrically centered with respect to a center of the front layer marks, a second pair of front layer marks 22 arranged along a second direction x2 and symmetrically centered with respect to the center of the front layer marks, and a third pair of front layer marks 23 arranged along a third direction x3 and symmetrically centered with respect to the center of the front layer marks. The current layer overlay mark 10 includes a first pair of current layer marks 11 arranged along the first direction x1 and symmetrically centered with respect to a center of the current layer marks, a second pair of current layer marks 12 arranged along the second direction x2 and symmetrically centered with respect to the center of the current layer marks, and a third pair of current layer marks 13 arranged along the third direction x3 and symmetrically centered with respect to the center of the current layer marks.

[0043] The current layer overlay mark 10 is located inside the front layer overlay mark 20, and the center of the current layer marks and the center of the front layer marks coincide in a direction perpendicular to the overlay marks. Specifically, for example, the first pair of front layer marks 21 includes a first front layer mark 21a and a second front layer mark 21b, and the first front layer mark 21a and the second front layer mark 21b are arranged along the first direction x1 and symmetrically centered with respect to the center of the front layer marks. The first pair of current layer marks 11 includes a first current layer mark 11a and a second current layer mark 11b, and the first current layer mark 11a and the second current layer mark 11b are arranged along the first direction x1 and symmetrically centered with respect to the center of the current layer marks. In the first direction x1, for example, from the negative direction to the positive direction, the second front layer mark 21b, the second current layer mark 11b, the first current layer mark 11a, and the first front layer mark 21a are arranged in sequence.

[0044] Similarly, the second pair of front layer marks 22 includes a third front layer mark 22a and a fourth front layer mark 22b, which are arranged along the second direction x2 and are centrally symmetric relative to the front layer mark center; the second pair of through layer marks 12 includes a third through layer mark 12a and a fourth through layer mark 12b, which are arranged along the second direction x2 and are centrally symmetric relative to the through layer mark center. In the second direction x2, for example, from the negative direction to the positive direction, the fourth front layer mark 22b, the fourth through layer mark 12b, the third through layer mark 12a and the third front layer mark 22a are arranged in turn.

[0045] The third pair of front layer marks 23 includes a fifth front layer mark 23a and a sixth front layer mark 23b, which are arranged along the third direction x3 and are centrally symmetric relative to the front layer mark center; the third pair of through layer marks 13 includes a fifth through layer mark 13a and a sixth through layer mark 13b, which are arranged along the third direction x3 and are centrally symmetric relative to the through layer mark center. In the third direction x3, for example, from the negative direction to the positive direction, the sixth front layer mark 23b, the sixth through layer mark 13b, the fifth through layer mark 13a and the fifth front layer mark 23a are arranged in turn.

[0046] The through layer marking mark 10 also includes a fifth pair of through layer marks 15 arranged along the first direction x1 and centrally symmetric relative to the through layer mark center, and a center mark 16 located in the center region of the through layer marking mark, the center of the center mark 16 coincides with the through layer mark center. Please refer to Figure 3 As shown, the through layer marking mark 10 also includes a fifth pair of through layer marks 15 and a center mark 16, the fifth pair of through layer marks 15 includes a ninth through layer mark 15a and a tenth through layer mark 15b, which are arranged along the first direction x1 and are centrally symmetric relative to the through layer mark center, the center mark 16 is located in the center region of the through layer marking mark 10, the center of the center mark 16 coincides with the through layer mark center. In the first direction x1, for example, from the negative direction to the positive direction, the second front layer mark 21b, the second through layer mark 11b, the tenth through layer mark 15b, the center mark 16, the ninth through layer mark 15a, the first through layer mark 11a and the first front layer mark 21a are arranged in turn.

[0047] In the embodiment of the present application, the in-layer overlay mark 10 generally does not deform, and the center of the mark can be measured by the first pair of in-layer marks 11, the second pair of in-layer marks 12 and the third pair of in-layer marks 13. The pre-layer overlay mark 20 can deform, and the center of the mark in the pre-layer can be measured by the first pair of pre-layer marks 21, the second pair of pre-layer marks 22 and the third pair of pre-layer marks 23. According to the distance from each pre-layer mark in the first pair of pre-layer marks 21 to the center mark 16, the amount of asymmetry of the pre-layer overlay mark 20 can be obtained. According to the center of the pre-layer overlay mark 20 in the pre-layer and the amount of asymmetry, the center of the pre-layer overlay mark 20 can be obtained. Finally, the overlay accuracy compensation value containing the amount of asymmetry is obtained, thereby correcting the overlay accuracy measurement distortion caused by the asymmetry of the overlay mark, obtaining accurate overlay accuracy results, and reducing the wafer scrap caused by inaccurate overlay accuracy measurement.

[0048] In an embodiment of the present application, the pre-layer overlay mark 20 is a regular hexagon, and the first pair of in-layer marks 11, the second pair of in-layer marks 12 and the third pair of in-layer marks 13 in the in-layer overlay mark 10 also form a regular hexagon. The included angle between the first direction x1, the second direction x2 and the third direction x3 is 60 degrees.

[0049] In another embodiment of the present application, the first direction x1 is perpendicular to the second direction x2, and the included angle between the positive direction of the third direction x3 and the positive direction of the first direction x1 is an acute angle.

[0050] In the embodiment, the pre-layer overlay mark 20 further includes a fourth pair of pre-layer marks 24 arranged along a fourth direction x4 and center-symmetric with respect to the center of the pre-layer mark, and the in-layer overlay mark 10 further includes a fourth pair of in-layer marks 14 arranged along the fourth direction x4 and center-symmetric with respect to the center of the in-layer mark. The included angle between the positive direction of the fourth direction x4 and the positive direction of the first direction x1 is an obtuse angle. Please refer to Figure 3 As shown in the figure, the fourth pair of pre-layer marks 24 includes a seventh pre-layer mark 24a and an eighth pre-layer mark 24b, and the seventh pre-layer mark 24a and the eighth pre-layer mark 24b are arranged along the fourth direction x4 and center-symmetric with respect to the center of the pre-layer mark. The fourth pair of in-layer marks 14 includes a seventh in-layer mark 14a and an eighth in-layer mark 14b, and the seventh in-layer mark 14a and the eighth in-layer mark 14b are arranged along the fourth direction x4 and center-symmetric with respect to the center of the in-layer mark. In the fourth direction x4, for example, from the negative direction to the positive direction, the eighth pre-layer mark 24b, the eighth in-layer mark 14b, the seventh in-layer mark 14a and the seventh pre-layer mark 24a are arranged in sequence.

[0051] In an embodiment of the present application, the positive direction of the third direction x3 forms an angle of 45 degrees with the positive direction of the first direction x1, and the positive direction of the fourth direction x4 forms an angle of 135 degrees with the positive direction of the first direction x1. As a preferred embodiment, the front layer overlay mark 20 is a regular octagon, and the first pair of layer marks 11, the second pair of layer marks 12, the third pair of layer marks 13 and the fourth pair of layer marks 14 in the current layer overlay mark 10 also form a regular octagon.

[0052] In an embodiment of the present application, the marks in the front layer overlay mark 20 and the marks in the current layer overlay mark 10 are all strip-shaped, the extension direction of the strip-shaped marks is perpendicular to the arrangement direction, and the extension direction of the center mark 16 is the same as the extension direction of the fifth pair of layer marks 15. For example, the first front layer mark 21a and the second front layer mark 21b in the first pair of front layer marks 21 are arranged along the first direction x1, and the extension direction thereof is the second direction x2. The ninth layer mark 15a and the tenth layer mark 15b in the fifth pair of layer marks 15 are arranged along the first direction x1, and the extension direction thereof is the second direction x2. The extension direction of the center mark 16 is also the second direction x2.

[0053] Please continue to refer to Figure 3 In the embodiment shown, the shape and size of each mark are the same. For example, the length L1 of the mark is 10 μm, the width L2 of the mark is 1.08 μm, the distance L3 between adjacent front layer marks and layer marks is 1.08 μm, and the distance L4 between a pair of front layer marks (for example, from the left side of the second front layer mark 21b to the right side of the first front layer mark 21a) is 34 μm, but the present application is not limited thereto.

[0054] The overlay mark provided by the present application comprises a first pair of front layer marks 21 arranged along a first direction x1 and symmetrically centered relative to a center of the front layer marks, a second pair of front layer marks 22 arranged along a second direction x2 and symmetrically centered relative to the center of the front layer marks, and a third pair of front layer marks 23 arranged along a third direction x3 and symmetrically centered relative to the center of the front layer marks; the overlay mark 10 comprises a first pair of when layer marks 11 arranged along the first direction x1 and symmetrically centered relative to a center of the when layer marks, a second pair of when layer marks 12 arranged along the second direction x2 and symmetrically centered relative to the center of the when layer marks, and a third pair of when layer marks 13 arranged along the third direction x3 and symmetrically centered relative to the center of the when layer marks; the overlay mark 10 is located at the inner side of the front layer overlay mark 20, and the center of the when layer marks coincides with the center of the front layer marks in a direction perpendicular to the overlay mark; the overlay mark 10 further comprises a fifth pair of when layer marks 15 arranged along the first direction x1 and symmetrically centered relative to the center of the when layer marks, and a center mark 16 located in the center region of the overlay mark, the fifth pair of when layer marks 15 is located between the first pair of when layer marks 11, and the center of the center mark 16 coincides with the center of the when layer marks. The unexpected effect of the present application is that the center mark 16 is arranged in the center region of the overlay mark 10, the asymmetric amount of the front layer overlay mark 20 is obtained through the distance between the first pair of front layer marks 21 and the center mark 16 in the front layer overlay mark 20, and finally the overlay precision compensation value containing the asymmetric amount is obtained, thereby the problem of overlay precision measurement distortion caused by the asymmetry of the overlay mark can be corrected, accurate overlay precision result can be obtained, and the wafer scrap caused by inaccurate overlay precision measurement can be reduced.

[0055] The present application further provides a method for correcting the accuracy of overlay precision measurement. Figure 4 The flow chart of the method for correcting the accuracy of overlay precision measurement provided by an embodiment of the present application is shown in Figure 4 The method for correcting the accuracy of overlay precision measurement provided by the embodiment of the present application comprises the following steps:

[0056] S1: manufacturing the overlay mark as described above;

[0057] S2: measuring the distance between each pair of front layer marks in the front layer overlay mark, measuring the distance between each pair of when layer marks in the when layer overlay mark, measuring the distance between each mark in the fifth pair of when layer marks and the center mark, and measuring the distance between each mark in the first pair of front layer marks and the center mark by using a CDSEM machine;

[0058] S3: judging whether the difference between the distances from each mark in the fifth pair of when layer marks to the center mark is greater than the accuracy of the CDSEM machine;

[0059] S4: if yes, then check the CDSEM machine, and then repeat the judgment of whether the difference between the distance of each mark in the current layer mark pair to the center mark is greater than the precision of the CDSEM machine;

[0060] S5: if no, then obtain the mark center of the current layer overlay mark according to the distance between each pair of current layer marks;

[0061] S6: obtain the mark center of the previous layer overlay mark according to the distance between each pair of previous layer marks and the distance of each mark in the first pair of previous layer marks to the center mark;

[0062] S7: obtain the actual overlay precision OVL1 according to the mark center of the current layer overlay mark and the mark center of the previous layer overlay mark, obtain the measured overlay precision OVL2 by measuring the overlay mark, and obtain the overlay precision compensation value Offset = OVL1 - OVL2;

[0063] S8: correct the measured overlay precision according to the overlay precision compensation value Offset.

[0064] Figure 5 is a size diagram of a current layer overlay mark in an overlay mark provided by an embodiment of the present application, Figure 6 is a size diagram of a previous layer overlay mark in an overlay mark provided by an embodiment of the present application. The following will be described in detail in combination with Figure 4 and Figure 3 , Figure 5 , Figure 6 The method for correcting the overlay precision measurement accuracy described in the present embodiment will be described in detail.

[0065] In step S1, the overlay mark is made as described above. The overlay mark is made to measure the overlay precision of the current layer and the previous layer, so the previous layer overlay mark 20 is made at the same time when the previous layer is made, and the current layer overlay mark 10 is made at the same time when the current layer is made.

[0066] In step S2, the CDSEM (Critical Dimension Scanning Electron Microscope) machine is used to measure the distance between each pair of previous layer marks in the previous layer overlay mark 20, measure the distance between each pair of current layer marks in the current layer overlay mark 10, measure the distance of each mark in the fifth pair of current layer marks 15 to the center mark 16, and measure the distance of each mark in the first pair of previous layer marks 21 to the center mark 16.

[0067] Please refer to Figure 3 and Figure 5 , the CDSEM machine is used to measure the distance between each pair of current layer marks in the current layer overlay mark 10 and measure the distance of each mark in the fifth pair of current layer marks 15 to the center mark.

[0068] Specifically, the distance A1 from the ninth in-layer mark 15a to the center mark 16 and the distance A2 from the tenth in-layer mark 15b to the center mark 16 are measured. The distance A1 can be the distance between the right side of the ninth in-layer mark 15a and the right side of the center mark 16, and the distance A2 can be the distance between the left side of the tenth in-layer mark 15b and the left side of the center mark 16, i.e. the distance A1 and the distance A2 are both the width of a mark plus the distance between two marks. Of course, the distance A1 and the distance A2 can also be only the distance between two marks, which is not limited in the present application.

[0069] The distance A3 between the first in-layer mark 11a and the second in-layer mark 11b in the first pair of in-layer marks 11 is measured, the distance A4 between the third in-layer mark 12a and the fourth in-layer mark 12b in the second pair of in-layer marks 12 is measured, the distance A5 between the fifth in-layer mark 13a and the sixth in-layer mark 13b in the third pair of in-layer marks 13 is measured, and the distance A6 between the seventh in-layer mark 14a and the eighth in-layer mark 14b in the fourth pair of in-layer marks 14 is measured. In the present embodiment, the distance between a pair of in-layer marks refers to the distance between the outer sides of the two in-layer marks. For example, the distance A1 between the first pair of in-layer marks 11 refers to the distance between the right side of the first in-layer mark 11a and the left side of the second in-layer mark 11b.

[0070] Please refer to Figure 3 and Figure 6 It is shown that the distance between each pair of front layer marks in the front layer overlay mark 20 is measured, and the distance from each mark in the first pair of front layer marks 21 to the center mark 16 is measured.

[0071] Specifically, the distance A11 from the first front layer mark 21a to the center mark 16 and the distance A12 from the second front layer mark 21b to the center mark 16 in the first pair of front layer marks 21 are measured. The distance A11 can be the distance between the left side of the first front layer mark 21a and the right side of the center mark 16, and the distance A12 can be the distance between the right side of the second front layer mark 21b and the left side of the center mark 16, i.e. the distance A11 and the distance A12 are both the distance between two marks. Of course, the distance A11 and the distance A12 can also be the width of a mark plus the distance between two marks, which is not limited in the present application. In addition, the distance A11 from the first front layer mark 21a to the center mark 16 and the distance A12 from the second front layer mark 21b to the center mark 16 in the first pair of front layer marks 21 refer to the distance in the horizontal direction, i.e. the distance from the projection of the center mark 16 in the front layer to the first front layer mark 21a, and the distance from the projection of the center mark 16 in the front layer to the second front layer mark 21b.

[0072] The distance A7 between the first pair of front layer marks 21, the distance A8 between the second pair of front layer marks 22, the distance A9 between the third pair of front layer marks 23, and the distance A10 between the fourth pair of front layer marks 24 are measured. In this embodiment, the distance between a pair of front layer marks refers to the distance between the outer sides of the two front layer marks. For example, the distance A7 between the first pair of front layer marks 21 refers to the distance between the right side of the first front layer mark 21a and the left side of the second front layer mark 21b, but is not limited thereto.

[0073] In step S3 and step S4, it is determined whether the difference between the distance of each mark in the fifth pair of layer marks 15 to the center mark 16 is greater than the precision of the CDSEM machine. If so, the CDSEM machine is checked, and then the determination of whether the difference between the distance of each mark in the fifth pair of layer marks 15 to the center mark 16 is greater than the precision of the CDSEM machine is repeated.

[0074] It is determined whether the difference between the distance of each mark in the fifth pair of layer marks 15 to the center mark 16 is greater than the precision of the CDSEM machine, i.e. whether the difference between the distance A1 of the ninth layer mark 15a to the center mark 16 and the distance A2 of the tenth layer mark 15b to the center mark 16 is greater than the precision of the CDSEM machine. When the precision of the CDSEM machine is 1 nm, it is determined whether A1-A2>1 nm is true.

[0075] If so, i.e. A1-A2>1 nm, step S4 is performed to check and repair the CDSEM machine. In one embodiment, checking the CDSEM machine includes checking whether the CDSEM machine measures incorrectly and checking the recipe of the CDSEM machine, i.e. determining whether the measurement is incorrect or the machine itself is the problem, and if the machine itself is the problem, the recipe of the CDSEM machine needs to be modified, i.e. repairing the CDSEM machine includes modifying the recipe of the CDSEM machine.

[0076] If the measurement is incorrect or after modifying the recipe of the CDSEM machine, step S2 is continued, i.e. the overlay marks are measured again. Specifically, the distance between each pair of front layer marks in the front layer overlay marks 20 is measured by the CDSEM machine, the distance between each pair of layer marks in the layer overlay marks 10 is measured, the distance of each mark in the fifth pair of layer marks 15 to the center mark 16 is measured, and the distance of each mark in the first pair of front layer marks 21 to the center mark 16 is measured.

[0077] If no, i.e. A1-A2≤1nm, then step S5 is performed to obtain the mark center of the in-layer overlay mark 10 according to the distance between each pair of in-layer marks. The mark center of the in-layer overlay mark 10 is M=(A3+A4+A5+A6) / 8, where A3 is the distance between the first pair of in-layer marks 11, A4 is the distance between the second pair of in-layer marks 12, A5 is the distance between the third pair of in-layer marks 13, and A6 is the distance between the fourth pair of in-layer marks 14.

[0078] In step S6, the mark center of the pre-layer overlay mark 20 is obtained according to the distance between each pair of pre-layer marks and the distance from each of the first pair of pre-layer marks 21 to the center mark 16. The mark center of the pre-layer overlay mark 20 is N=N2-N1, where N1=(A7+A8+A9+A10) / 8, N2=(A11-A12) / 2, where A7 is the distance between the first pair of pre-layer marks 21, A8 is the distance between the second pair of pre-layer marks 22, A9 is the distance between the third pair of pre-layer marks 23, A10 is the distance between the fourth pair of pre-layer marks 24, A11 is the distance from one of the first pair of pre-layer marks 21 (specifically the first pre-layer mark 21a) to the center mark 16, and A12 is the distance from the other of the first pair of pre-layer marks 21 (specifically the second pre-layer mark 21b) to the center mark 16. N1 is the center of the pre-layer overlay mark 20 in the pre-layer, and N2 is the offset of the pre-layer overlay mark 20 relative to the center of the in-layer overlay mark 10, i.e. the asymmetry of the pre-layer overlay mark 20. The mark center N=N2-N1 of the pre-layer overlay mark 20 includes the asymmetry of the pre-layer overlay mark 20.

[0079] In step S7, the actual overlay precision OVL1 is obtained according to the mark center of the in-layer overlay mark 10 and the mark center of the pre-layer overlay mark 20, the measured overlay precision OVL2 is obtained by measuring the overlay marks, and the overlay precision compensation value Offset=OVL1-OVL2 is obtained. The actual overlay precision OVL1 is calculated according to the measured distance, and the measured overlay precision OVL2 is obtained directly by the measuring equipment.

[0080] In step S8, the measured overlay precision is corrected according to the overlay precision compensation value Offset.

[0081] Compensating the asymmetry of the pre-layer overlay mark 20 into the measured overlay precision can correct the problem of overlay precision measurement distortion caused by the asymmetry of the overlay mark, and obtain an accurate overlay precision result, thereby reducing the wafer scrap caused by inaccurate overlay precision measurement.

[0082] The method for correcting the measurement accuracy of overlay precision provided by the present application comprises the following steps: firstly, making the overlay mark as described above; then, measuring the distance between each pair of front layer marks in the front layer overlay mark, measuring the distance between each pair of current layer marks in the current layer overlay mark, measuring the distance between each mark in the fifth pair of current layer marks and the center mark, and measuring the distance between each mark in the first pair of front layer marks and the center mark; then, judging whether the difference between the distance between each mark in the fifth pair of current layer marks and the center mark is greater than the precision of the CDSEM machine; if yes, checking and repairing the CDSEM machine, and then re-measuring the overlay mark; if no, obtaining the mark center of the current layer overlay mark according to the distance between each pair of current layer marks, obtaining the mark center of the front layer overlay mark according to the distance between each pair of front layer marks and the distance between each mark in the first pair of front layer marks and the center mark, obtaining the actual overlay precision OVL1 according to the mark center of the current layer overlay mark and the mark center of the front layer overlay mark, measuring the overlay mark to obtain the measured overlay precision OVL2, and obtaining the overlay precision compensation value Offset = OVL1- OVL2; and correcting the measured overlay precision according to the overlay precision compensation value Offset. The unexpected effect of the present application is that the center mark is arranged in the center region of the current layer overlay mark, the asymmetry of the front layer overlay mark is obtained through the distance between the first pair of front layer marks in the front layer overlay mark and the center mark, and finally the overlay precision compensation value containing the asymmetry is obtained, so that the problem of overlay precision measurement distortion caused by the asymmetry of the overlay mark can be corrected, the accurate overlay precision result can be obtained, and the wafer scrap caused by the inaccurate overlay precision measurement can be reduced.

[0083] The above description is only a description of the preferred embodiments of the present application, and does not limit the scope of the present application in any way. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present application without departing from the spirit and scope of the present application by using the disclosed methods and technical contents. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application, without departing from the technical solutions of the present application, all belong to the protection scope of the present application.

Claims

1. A method for calibrating the accuracy of overlay measurement, characterized in that, Includes the following steps: Create overlay marks; the overlay marks include front layer overlay marks and current layer overlay marks; the front layer overlay marks include a first pair of front layer marks arranged along a first direction and centrally symmetrical with respect to the center of the front layer marks, a second pair of front layer marks arranged along a second direction and centrally symmetrical with respect to the center of the front layer marks, and a third pair of front layer marks arranged along a third direction and centrally symmetrical with respect to the center of the front layer marks; the current layer overlay marks include a first pair of current layer marks arranged along a first direction and centrally symmetrical with respect to the center of the current layer marks, a second pair of current layer marks arranged along a second direction and centrally symmetrical with respect to the center of the current layer marks. The system includes a first pair of overprinted marks and a third pair of overprinted marks arranged along a third direction and centrally symmetrical with respect to the center of the first pair of overprinted marks; the overprinted marks are located inside the previous overprinted marks, and the center of the first pair of overprinted marks coincides with the center of the previous overprinted marks in a direction perpendicular to the overprinted marks; the overprinted marks also include a fifth pair of overprinted marks arranged along the first direction and centrally symmetrical with respect to the center of the first pair of overprinted marks, and a center mark located in the central region of the overprinted marks, the fifth pair of overprinted marks being located between the first pair of overprinted marks, and the center of the center mark coinciding with the center of the first pair of overprinted marks; The first direction is perpendicular to the second direction, and the angle between the positive direction of the third direction and the positive direction of the first direction is an acute angle; The preceding layer overprinting marks further include a fourth pair of preceding layer marks arranged along the fourth direction and centrally symmetrical with respect to the center of the preceding layer marks; the current layer overprinting marks further include a fourth pair of current layer marks arranged along the fourth direction and centrally symmetrical with respect to the center of the current layer marks; the angle between the positive direction of the fourth direction and the positive direction of the first direction is an obtuse angle. The CDSEM instrument is used to measure the distance between each pair of previous layer marks in the previous layer overlay marks, the distance between each pair of current layer marks in the current layer overlay marks, the distance from each mark in the fifth pair of current layer marks to the center mark, and the distance from each mark in the first pair of previous layer marks to the center mark; the mark center of the current layer overlay marks is M=(A3+ A4+ A5 + A6) / 8, where A3 is the distance between the first pair of current layer marks, A4 is the distance between the second pair of current layer marks, A5 is the distance between the third pair of current layer marks, and A6 is the distance between the fourth pair of current layer marks; Determine whether the difference in distance from each mark to the center mark in the fifth pair of current layer marks is greater than the accuracy of the CDSEM machine; if so, inspect and repair the CDSEM machine, and then remeasure the overlay marks. If not, the mark center of the overlay mark in the current layer is obtained based on the distance between each pair of current layer marks; The mark center of the front layer overlay mark is obtained based on the distance between each pair of front layer marks and the distance from each mark in the first pair of front layer marks to the center mark; The actual overlay accuracy OVL1 is obtained by comparing the center of the current layer overlay mark with the center of the previous layer overlay mark. The overlay accuracy OVL2 is obtained by measuring the overlay mark. The overlay accuracy compensation value Offset = OVL1 - OVL2 is obtained. The measurement overlay accuracy is corrected based on the overlay accuracy compensation value Offset.

2. The method for calibrating the accuracy of overlay measurement according to claim 1, characterized in that, The center of the front layer overprinted mark is N=N2-N1, where N1=(A7+A8+A9+A10) / 8, N2=(A11-A12) / 2, where A7 is the distance between the first pair of front layer marks, A8 is the distance between the second pair of front layer marks, A9 is the distance between the third pair of front layer marks, A10 is the distance between the fourth pair of front layer marks, A11 is the distance from one of the marks in the first pair of front layer marks to the center mark, and A12 is the distance from the other mark in the first pair of front layer marks to the center mark.

3. The method for calibrating the accuracy of overlay measurement according to claim 1, characterized in that, Inspecting a CDSEM machine includes checking for measurement errors and reviewing the process formulation. Repairing a CDSEM machine involves modifying the process formulation.

4. The method for calibrating the accuracy of overlay measurement according to claim 1, characterized in that, The angle between the positive direction of the third direction and the positive direction of the first direction is 45 degrees, and the angle between the positive direction of the fourth direction and the positive direction of the first direction is 135 degrees.

5. The method for calibrating the accuracy of overlay measurement according to claim 4, characterized in that, The marks in the preceding layer overprinted marks and the marks in the current layer overprinted marks are both strip-shaped, with the extension direction of the strip-shaped marks perpendicular to the arrangement direction, and the extension direction of the center mark is the same as the extension direction of the fifth pair of current layer marks.

6. The method for calibrating the accuracy of overlay measurement according to claim 5, characterized in that, The front layer overlay mark is a regular octagon, and the first pair of overlay marks, the second pair of overlay marks, the third pair of overlay marks and the fourth pair of overlay marks also form a regular octagon.

Images