Overlay mark forming moire pattern, overlay measurement method using same, and manufacturing method of semiconductor device

Abstract

a first overlay mark having a first center of symmetry and configured to have 180 degree rotational symmetry with respect to the first center of symmetry, forming a pair of first moiré patterns disposed at a center of the overlay mark; a second overlay mark having a second center of symmetry and configured to have 180 degree rotational symmetry with respect to the second center of symmetry, forming a pair of second moiré patterns disposed opposite each other across the first moiré pattern; a third overlay mark having a third center of symmetry and configured to have 180 degree rotational symmetry with respect to the third center of symmetry, forming a pair of third moiré patterns disposed on a first diagonal line with the first moiré pattern in between; and a fourth overlay mark having 180 degree rotational symmetry with respect to a fourth center of symmetry, forming a pair of fourth moiré patterns disposed on a second diagonal line intersecting the first diagonal line with the first moiré pattern in between.

Description

[Technical field]

[0001] The present invention relates to an overlay mark that forms a moire pattern, an overlay measurement method using the same, and a method for manufacturing a semiconductor device. [Background technology]

[0002] A number of pattern layers are sequentially formed on a semiconductor substrate. In addition, a circuit of one layer may be divided into two patterns through double patterning, etc. In order to manufacture a desired semiconductor device, such pattern layers or multiple patterns of one layer must be accurately formed in the desired positions. Therefore, overlay marks, formed simultaneously with the pattern layers, are used to verify that the pattern layers are correctly aligned. The method of measuring overlay using an overlay mark is as follows: First, a structure that is a part of an overlay mark is formed on a pattern layer formed in a previous process, for example, an etching process, at the same time as the formation of the pattern layer, and then, in a subsequent process, for example, a photolithography process, the remaining structure of the overlay mark is formed on a photoresist. Then, an overlay measurement device is used to obtain an image of the overlay structure of the pattern layer formed in the previous process (an image is obtained by transmitting through the photoresist layer) and the overlay structure of the photoresist layer, and the offset value between the centers of these images is measured to measure the overlay value. More specifically, JP 2020-112807 A discloses a method for determining the relative misalignment between different layers or different patterns by capturing an image of an overlay mark formed on a substrate, selecting a number of working zones from the captured image, forming information-bearing signals for each of the selected working zones, and comparing these. In addition, Korean Patent No. 10-1604789 discloses an overlay measurement method in which an image of an overlay mark is acquired, an image of the overlay mark is rotated 180 degrees based on the center of the acquired image, the two images are compared, and if they match, the center of the current image is set as the center of the overlay mark, and if they do not match, the position is changed until they match, and the above steps are repeated while acquiring an image of the overlay mark. In addition, Korean Patent Publication No. 2000-0006182 discloses a method of measuring overlay by forming a moire pattern using overlapping repeated overlay marks, optically observing the moire pattern, and comparing the moire pattern observed with the moire pattern when aligned. In addition, U.S. Patent Publication No. 2021-0072650 discloses a method for forming four pairs of moiré patterns that are rotationally symmetrical by 180 degrees using overlapping one-dimensional grid patterns in the X-axis direction and one-dimensional grid patterns in the Y-axis direction, and using these to measure overlay in the X-axis and Y-axis directions. The method using the image of the moire pattern has an advantage over the method using the image of the overlay mark itself in that it amplifies and represents the misalignment between layers, but has a problem in that noise is generated in the moire pattern due to the influence of interference of light reflected from the overlay mark formed on the current layer. In addition, each moiré pattern shown in U.S. Patent Publication No. 2021-0072650 is formed over a long region from the center of the overlay mark to the outer periphery of the overlay mark, and therefore can be significantly affected by optical aberrations due to tilted optical elements of the overlay measurement device, such as beam splitters. In particular, a moiré pattern for overlay measurement in a specific direction, in which the change in distance from the optical system is large along the direction in which multiple bars are arranged, is significantly affected by optical aberrations due to the large difference between the optical path to the bar close to the center of the overlay mark and the optical path to the bar arranged on the outer periphery. In addition, when an overlay mark is formed using a scanner-type exposure device, the moire patterns arranged along the scanning direction have little variation, while the moire patterns arranged along a direction perpendicular to the scanning direction have large variation. However, in conventional overlay marks, the moire patterns are arranged regardless of the scanning direction, so there is a problem that the variation in the moire patterns arranged along the direction perpendicular to the scanning direction may also have an effect on the overlay measurement stage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-112807 A [Patent Document 2] Korean Patent No. 10-1604789 [Patent Document 3] Korean Patent Publication No. 2000-0006182 [Patent Document 4] U.S. Patent Publication No. 2021-0072650 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention is intended to improve the above-mentioned problems, and has an object to provide an overlay mark that can minimize the effects of optical aberration, a new overlay measurement method using the same, and a manufacturing method for semiconductor elements. Another object of the present invention is to provide an overlay mark that can minimize the effect of the scanning direction of a scanner, a new overlay measurement method using the same, and a manufacturing method of a semiconductor device. [Means for solving the problem]

[0005] In order to achieve the above object, the present invention provides an overlay mark for image-based overlay measurement for determining a relative shift between two or more pattern layers, comprising first to fourth overlay marks, the first overlay mark having a first center of symmetry (COS1) and being rotationally symmetrical by 180 degrees with respect to the first center of symmetry (COS1), the central axes of which are aligned with each other and configured to form a pair of first moiré patterns disposed at a center of the overlay mark, the first moiré patterns being formed by a first grating pattern formed together with a first pattern layer and having a first pitch along a first direction, and a second grating pattern formed together with a second pattern layer so as to overlap the first grating pattern and having a second pitch along the first direction different from the first pitch, the second overlay mark has a second center of symmetry (COS2), and is configured to form a pair of second moire patterns that are rotationally symmetrical by 180 degrees with respect to the second center of symmetry (COS2), have central axes that coincide with each other, and are arranged to face each other across the first moire pattern, the second moire pattern being formed by a third grating pattern formed together with the first pattern layer and having a third pitch along a first direction, and a fourth grating pattern formed together with the second pattern layer so as to overlap the third grating pattern and having a fourth pitch different from the third pitch along the first direction, the third overlay mark has a third center of symmetry (COS3), is rotationally symmetrical by 180 degrees with respect to the third center of symmetry (COS3), and is configured to form a pair of third moire patterns disposed on a first diagonal line sandwiching the first moire pattern, the third moire pattern being formed by a fifth grating pattern formed together with the first pattern layer and having a fifth pitch along a second direction, and a sixth grating pattern formed together with the second pattern layer so as to overlap the fifth grating pattern and having a sixth pitch different from the fifth pitch along the second direction; the fourth overlay mark has a fourth center of symmetry (COS4) and is rotationally symmetrical by 180 degrees with respect to the fourth center of symmetry (COS4), and is configured to form a pair of fourth moire patterns disposed on a second diagonal line intersecting the first diagonal line with the first moire pattern in between, the fourth moire pattern being formed by a seventh grating pattern formed together with the first pattern layer and having a seventh pitch along a second direction, and an eighth grating pattern formed together with the second pattern layer so as to overlap the seventh grating pattern and having an eighth pitch different from the seventh pitch along the second direction; an error in the first direction between the first center of symmetry (COS1) and the second center of symmetry (COS2) indicates an overlay error in the first direction between the first pattern layer and the second pattern layer; An overlay mark forming a moire pattern is provided, characterized in that an error in the second direction between the third center of symmetry (COS3) and the fourth center of symmetry (COS4) indicates an overlay error in the second direction between the first pattern layer and the second pattern layer. The present invention also provides an overlay mark that forms a moire pattern, characterized in that the overlay mark is formed using a scanner-type exposure device, and the second direction is aligned with a scanning direction of the exposure device. The present invention also provides an overlay mark forming a moire pattern, characterized in that the pitch of the first to fourth moire patterns is greater than the optical resolution of an overlay measurement device, and the pitch of the first to eighth grating patterns is smaller than the optical resolution of the overlay measurement device. The present invention also provides an overlay mark forming a moire pattern, wherein the first pitch is equal to the fourth pitch, and the second pitch is equal to the third pitch. The present invention also provides an overlay mark forming a moire pattern, wherein the fifth pitch is the same as the eighth pitch, and the sixth pitch is the same as the seventh pitch. The present invention also provides a method for measuring overlay between multiple successive pattern layers, the method comprising the steps of forming patterns in the multiple successive pattern layers and acquiring a moire pattern image formed by the formed overlay marks, and analyzing the moire pattern image. The present invention also provides an overlay measurement method, wherein the step of acquiring the moire pattern image is a step of acquiring the moire pattern image using an overlay measurement device having a tilted optical element, and in the step of acquiring the moire pattern image, the overlay measurement device is disposed such that a distance between the tilted optical element and the overlay mark increases or decreases as the device progresses in the first direction and is constant as the device progresses in the second direction. Also provided is a method of overlay measurement, characterized in that the tilted optical element is a beam splitter. The method for measuring overlay is characterized in that the step of analyzing the moire pattern image includes the steps of: one-dimensionally projecting a portion of the moire pattern image to obtain a periodic graph; and expressing the periodic graph as a sine wave. In addition, the step of expressing the periodic graph as a sine wave includes fitting values ​​of A0, A1, A2, θ1, θ2, f1, and f2 of Equation 9 through regression analysis so that a difference between the periodic graph and a sine wave expressed by Equation 9 below becomes small.

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[0006] The overlay mark, the novel overlay measurement method using the same, and the semiconductor device manufacturing method according to the present invention have the advantage that the influence of optical aberration can be minimized.

[0007] In addition, the effect of the scanning direction of the scanner can be minimized. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a plan view of one embodiment of an overlay mark according to the present invention. [Diagram 2] 2 is a cross-sectional view of a portion of the first overlay mark shown in FIG. 1; [Diagram 3] 2 is a cross-sectional view of a portion of the second overlay mark shown in FIG. 1; [Figure 4] 2 is a cross-sectional view of a portion of the third overlay mark shown in FIG. 1; [Diagram 5] FIG. 2 is a cross-sectional view of a portion of the fourth overlay mark shown in FIG. [Figure 6] 2 is a diagram showing a simulation result of a moire pattern formed when the overlay mark shown in FIG. 1 is irradiated with light. [Figure 7]FIG. 13 is a diagram for explaining a moire pattern image acquisition step. [Figure 8] 2 shows a signal obtained from the overlay mark shown in FIG. 1; [Figure 9] FIG. 9 is a diagram for explaining the steps of changing the signal shown in FIG. 8 into a sine wave. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiment of the present invention can be modified into various other forms, and the scope of the present invention should not be interpreted as being limited to the embodiment described below. The embodiment of the present invention is provided to more completely explain the present invention to those skilled in the art. Therefore, the shapes of elements in the drawings are exaggerated to emphasize a clearer description, and elements represented by the same reference numerals in the drawings refer to the same elements. Fig. 1 is a plan view of one embodiment of an overlay mark according to the present invention, Figs. 2 to 5 are cross-sectional views of parts of the first to fourth overlay marks shown in Fig. 1, and Fig. 6 is a diagram showing the results of a simulation of a moire pattern formed when light is irradiated onto the overlay mark shown in Fig. 1. Fig. 1 shows a state in which the first to fourth overlay marks 100, 200, 300, and 400 are aligned. 1 and 2, the first overlay mark 100 includes a pair of first grating patterns 110 and a pair of second grating patterns 120 disposed in the center of the overlay mark 10. The pair of first grating patterns 110 are formed side by side with a fixed interval between them. The pair of second grating patterns 120 are formed so as to overlap the first grating pattern 110. The pair of second grating patterns 120 are formed side by side with a fixed interval between them. The first grid pattern 110 is formed with a first pattern layer (lower layer). The first grid pattern 110 has a first pitch P1 along a first direction (the X-axis direction in FIG. 1). The first grid pattern 110 includes a plurality of thin bars. The second grid pattern 120 is formed with a second pattern layer (upper layer). The second grid pattern 120 has a second pitch P2 along a first direction (the X-axis direction in FIG. 1), where the second pitch P2 is different from the first pitch P1. The second grid pattern 120 includes a plurality of thin bars. The first and second grating patterns 110 and 120 form a pair of first moire patterns M1 in the center of the overlay mark 10. That is, when light is irradiated onto the first and second grating patterns 110 and 120, the first moire pattern M1 is formed as shown in FIG. 6 due to an interference phenomenon that occurs when periodic patterns are overlapped. At this time, the pitch P of the first moire pattern M1 M1 is determined by the pitch P1 of the first grating pattern 110 and the pitch P2 of the second grating pattern 120 as shown in the following Equation 1. As can be seen from Equation 1, the pitch P M1 is a value that is far larger than the pitch P1 of the first grating pattern 110 and the pitch P2 of the second grating pattern 120.

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[0010] Here, the pitch P of the first moire pattern M1 M1 is greater than the optical resolution of the overlay measurement device, and the pitch P1 of the first grating pattern 110 and the pitch P2 of the second grating pattern 120 are preferably smaller than the optical resolution of the overlay measurement device in order to minimize noise in the moiré pattern caused by the effects of interference of light reflected from the grating patterns 110 and 120, especially the second grating pattern 120 which is the upper layer. Furthermore, the relative movement of the second grating pattern 120 with respect to the first grating pattern 110 in the arrangement direction of the grating elements (the X-axis direction in this embodiment) causes the first moiré pattern M1 to move. A first moiré gain G M1is determined by the following Equation 2.

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[0011] As can be seen from Equation 2, even if the second grating pattern 120 moves a small distance, the first moire pattern M1 moves a relatively much longer distance, so that even minute overlay errors can be measured from the images of the moire patterns. The first moire pattern M1 has a first center of symmetry COS1. The first moire pattern M1 is rotationally symmetric by 180 degrees with respect to the first center of symmetry COS1. The central axes C1 of the first moire patterns M1 coincide with each other. 1 and 3, the second overlay mark 200 includes a pair of third grating patterns 210 arranged to face each other across the first grating pattern 110 of the first overlay mark 100, and a pair of fourth grating patterns 220 arranged to face each other across the second grating pattern 120. The pair of fourth grating patterns 220 are formed to overlap the third grating pattern 210. The third grid pattern 210 is formed together with the first pattern layer. The third grid pattern 210 has a third pitch P3 along a first direction (the X-axis direction in FIG. 1). The third grid pattern 210 includes a plurality of thin bars. The fourth lattice pattern 220 is formed together with the second pattern layer. The fourth lattice pattern 220 has a fourth pitch P4 along a first direction (the X-axis direction in FIG. 1). Here, the fourth pitch P4 is different from the third pitch P3. The fourth lattice pattern 220 includes a plurality of thin bars. Here, the fourth pitch P4 may be the same as the first pitch P1, and the third pitch P3 may be the same as the second pitch P2. As shown in FIG. 6, the third grid pattern 210 and the fourth grid pattern 220 form a pair of second moire patterns M2 disposed opposite each other with the first moire pattern M1 interposed therebetween. Pitch P of the second moire pattern M2 M2 teeth 、It is determined by the pitch P3 of the third lattice pattern 210 and the pitch P4 of the fourth lattice pattern 220 as shown in the following Equation 3.

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[0012] The second moire gain G, which is the ratio of the relative movement distance of the fourth grating pattern 220 to the movement distance of the second moire pattern M2, is M2 is determined by the following Equation 4. Here, the pitch P of the second moire pattern M2 M2 is greater than the optical resolution of the overlay measurement device, and the pitch P3 of the third grating pattern 210 and the pitch P4 of the fourth grating pattern 220 are preferably smaller than the optical resolution of the overlay measurement device in order to minimize noise in the moiré pattern caused by effects such as interference from light reflected from the grating patterns.

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[0013] As can be seen from Equation 4, even if the fourth grid pattern 220 moves only a small distance, the second moire pattern M2 moves a relatively much longer distance. The second moiré pattern M2 has a second center of symmetry COS2. The second moiré pattern M2 is rotationally symmetric by 180 degrees with respect to the second center of symmetry COS2. The central axes C2 of the second moiré patterns M2 coincide with each other. When aligned, the central axis C1 of the first moiré pattern M1 and the central axis C2 of the second moiré pattern M2 coincide with each other. In FIG. 6, the overlay marks 10 are aligned so that the center of symmetry COS1 of the first moire pattern M1 and the center of symmetry COS2 of the second moire pattern M2 coincide with each other. When the overlay marks 10 are misaligned, the center of symmetry COS1 of the first moire pattern M1 and the center of symmetry COS2 of the second moire pattern M2 do not coincide with each other. By using the difference in a first direction (X-axis direction) between the center of symmetry COS1 of the first moire pattern M1 and the center of symmetry COS2 of the second moire pattern M2, the overlay error in the first direction can be measured. 1 and 4, the third overlay mark 300 includes a pair of fifth grating patterns 310 arranged on the first diagonal line D1 with the first grating pattern 110 of the first overlay mark 100 in between, and a pair of sixth grating patterns 320 arranged on the first diagonal line D1 with the second grating pattern 120 in between. The pair of sixth grating patterns 320 are formed to overlap the fifth grating pattern 310. The fifth grid pattern 310 is formed together with the first pattern layer. The fifth grid pattern 310 has a fifth pitch P5 along the second direction (the Y-axis direction in FIG. 1). The fifth grid pattern 310 includes a plurality of thin bars. The sixth lattice pattern 320 is formed with the second pattern layer. The sixth lattice pattern 320 has a sixth pitch P6 along the second direction (the Y-axis direction in FIG. 1), where the sixth pitch P6 is different from the fifth pitch P5. The sixth lattice pattern 320 includes a plurality of thin bars. As shown in Fig. 6, the fifth lattice pattern 310 and the sixth lattice pattern 320 form a pair of third moire patterns M3 arranged on the first diagonal line D1 with the first moire pattern M1 in between. That is, when light is irradiated onto the fifth lattice pattern 310 and the sixth lattice pattern 320, the third moire pattern M3 is formed as shown in Fig. 6 due to the interference phenomenon that occurs when periodic patterns are overlapped. At this time, the pitch P of the third moire pattern M3 M3 is determined by the pitch P5 of the fifth grating pattern 310 and the pitch P6 of the sixth grating pattern 320, as shown in the following Equation 5. As can be seen from Equation 5, the pitch P M3 teeth 、 This is a value that is far larger than the pitch P5 of the fifth lattice pattern 310 and the pitch P6 of the sixth lattice pattern 320.

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[0014] Here, the pitch P of the third moire pattern M3 M3 is greater than the optical resolution of the overlay measurement device, and the pitch P5 of the fifth grating pattern 310 and the pitch P6 of the sixth grating pattern 320 are preferably smaller than the optical resolution of the overlay measurement device in order to minimize noise in the moiré pattern caused by effects such as interference from light reflected from the grating patterns. Furthermore, the relative movement of the sixth lattice pattern 320 in the arrangement direction of the lattice elements with respect to the fifth lattice pattern 310 causes the third moiré pattern M3 to move. The third moiré gain G M3 is determined by the following Equation 6.

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[0015] As can be seen from Equation 6, even if the sixth grating pattern 320 moves a small distance, the third moire pattern M3 moves a relatively much longer distance, so that even minute overlay errors can be measured from the images of the moire patterns. The third moire pattern M3 has a third center of symmetry COS3. The third moire pattern M3 is rotationally symmetric by 180 degrees with respect to the third center of symmetry COS3. 1 and 5, the fourth overlay mark 400 includes a pair of seventh grating patterns 410 arranged on a second diagonal D2 intersecting the first diagonal D1 with the first grating pattern 110 of the first overlay mark 100 in between, and a pair of eighth grating patterns 420 arranged on the second diagonal D2 with the second grating pattern 120 in between. The pair of eighth grating patterns 420 are formed to overlap the seventh grating pattern 410. The seventh grating pattern 410 is formed together with the first pattern layer. The seventh grating pattern 410 has a seventh pitch P7 along the second direction (the Y-axis direction in FIG. 1). The seventh grating pattern 410 includes a plurality of thin bars. The eighth grid pattern 420 is formed with the second pattern layer. The eighth grid pattern 420 has an eighth pitch P8 along the second direction (the Y-axis direction in FIG. 1), where the eighth pitch P8 is different from the seventh pitch P7. The eighth grid pattern 420 includes a plurality of thin bars. As shown in Fig. 6, the seventh lattice pattern 410 and the eighth lattice pattern 420 form a pair of fourth moire patterns M4 arranged on the second diagonal line D2 with the first moire pattern M1 in between. That is, when light is irradiated onto the seventh lattice pattern 410 and the eighth lattice pattern 420, the fourth moire pattern M4 is formed as shown in Fig. 6 due to the interference phenomenon that occurs when periodic patterns are overlapped. At this time, the pitch P of the fourth moire pattern M4 M4 is determined by the pitch P7 of the seventh grating pattern 410 and the pitch P8 of the eighth grating pattern 420, as shown in the following Equation 7. As can be seen from Equation 7, the pitch P M4 is a value that is far larger than the pitch P7 of the seventh grid pattern 410 and the pitch P8 of the eighth grid pattern 420.

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[0016] Here, the pitch P of the fourth moire pattern M4 M4 is greater than the optical resolution of the overlay measurement device, and the pitch P7 of the seventh grating pattern 410 and the pitch P8 of the eighth grating pattern 420 are preferably smaller than the optical resolution of the overlay measurement device in order to minimize noise in the moiré pattern caused by effects such as interference from light reflected from the grating patterns. Furthermore, the relative movement of the eighth lattice pattern 420 in the arrangement direction of the lattice elements with respect to the seventh lattice pattern 410 causes the movement of the fourth moiré pattern M4. The fourth moiré gain G M4 is determined by the following Equation 8.

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[0017] As can be seen from Equation 8, even if the eighth grating pattern 420 moves a small distance, the fourth moire pattern M4 moves a relatively much longer distance, so that even minute overlay errors can be measured from the images of the moire patterns. The fourth moire pattern M4 has a fourth center of symmetry COS4. The fourth moire pattern M4 is rotationally symmetric by 180 degrees with respect to the fourth center of symmetry COS4. In FIG. 6, the overlay marks 10 are aligned so that the center of symmetry COS3 of the third moire pattern M3 and the center of symmetry COS4 of the fourth moire pattern M4 coincide with each other. When the overlay marks 10 are misaligned, the center of symmetry COS3 of the third moire pattern M3 and the center of symmetry COS4 of the fourth moire pattern M4 do not coincide with each other. By using the difference in the second direction (Y-axis direction) between the center of symmetry COS3 of the third moiré pattern M3 and the center of symmetry COS4 of the fourth moiré pattern M4, the overlay error in the second direction can be measured. Hereinafter, an overlay measurement method using the above-mentioned overlay mark 10 will be described. The overlay measurement method includes the steps of obtaining a moiré pattern image formed by the overlay mark 10 and analyzing the moiré pattern image. The overlay mark 10 is formed simultaneously with forming two successive pattern layers. The step of acquiring the moire pattern images is a step of acquiring images of the first to fourth moire patterns M1, M2, M3, and M4 at once using an overlay measurement device. 。 For example, this is the step of acquiring an image as shown in FIG. This step may be a step of acquiring an overlay mark image using an overlay measurement device including a tilted optical element, a lens L, and a stage S supporting a device D on which an overlay mark 10 is formed. The tilted optical element may be, for example, a beam splitter BS. Fig. 7 is a diagram showing a part of an example of an overlay measurement device to explain the overlay mark image acquisition step. As shown in Fig. 7, in this step, the overlay measurement device is preferably arranged so that the distance between the beam splitter BS, which is an inclined optical element, and the device D on which the overlay mark 10 is formed increases or decreases as it advances in the X-axis direction, which is the direction in which the first moire pattern M1 and the second moire pattern M2 formed by the first overlay mark 100 and the second overlay mark 200 are arranged, and is constant when it advances in the Y-axis direction. That is, the beam splitter BS is arranged at an angle with respect to the X-axis. Capturing the overlay mark image with the overlay measurement device disposed in this manner has the advantage of reducing the influence of optical aberration, since the first overlay mark 100 and the second overlay mark 200 are formed only in the center of the overlay mark 10 based on the X-axis direction. If the total area of ​​the overlay mark 10 is the same, the width in the X-axis direction of the first overlay mark 100 and the second overlay mark 200 is relatively narrower. Therefore, the difference in the distance in the Z-axis direction between both ends in the X-axis direction and the beam splitter BS, which is an inclined optical element, is smaller than that of a conventional overlay mark, thereby minimizing the effect of optical aberration caused by the difference in distance with the inclined optical element. The third overlay mark 300 and the fourth overlay mark 400 are formed over the entire area of ​​the overlay mark 10 based on the Y-axis direction, but the beam splitter BS, which is an inclined optical element, is not positioned at an angle with respect to the Y-axis, so there is little distortion in the Y-axis direction. As a result, the third moire pattern M3 and the fourth moire pattern M4 formed by the third overlay mark 300 and the fourth overlay mark 400 are hardly affected by optical aberrations caused by the inclined optical elements. In the present invention, the first moiré pattern M1 and the second moiré pattern M2, which are arranged in one direction (the X-axis direction in FIG. 1), are arranged close to the center, and this is taken into consideration when acquiring an image of the moiré patterns, and the overlay measurement device is positioned so that the beam splitter BS, which is an inclined optical element, forms an angle with the axis in that direction (the X-axis in FIG. 7), thereby minimizing the effects of optical aberration. The step of analyzing the moiré pattern image may include a step of measuring an offset between an X-axis center of the first moiré pattern M1 and an X-axis center of the second moiré pattern M2 in the acquired moiré pattern image, and a step of measuring an offset between a Y-axis center of the third moiré pattern M3 and a Y-axis center of the fourth moiré pattern M4. Measuring the offset between the X-axis center of the first moire pattern M1 and the X-axis center of the second moire pattern M2 may include the following steps. First, the difference between the X value of the symmetry center COS1 of the first moiré pattern M1 and the X value of the center COI of the acquired moiré pattern image is calculated (S11). In Fig. 6, COI is the center of the image area itself and is unrelated to the symmetry center of the moiré pattern. For convenience, Fig. 6 shows that COI coincides with the symmetry center COS1 of the first moiré pattern M1. As shown in Fig. 6, a partial region R1 of one upper first moire pattern M1 is selected from the acquired moire pattern image. Then, a region R2 that is 180 degrees symmetrical with respect to the center of the acquired moire pattern image is also selected. This region R2 is located in another lower first moire pattern M1. Then, the two-dimensional images of the two selected regions R1 and R2 are projected to one dimension, i.e., all the gray values ​​of the pixels having the same X value in the two-dimensional images are added, the gray values ​​are averaged, or the gray values ​​are normalized. Then, a periodic graph G showing the change in gray value according to the X value can be drawn, as shown in Fig. 8. Since the gray value of the first moire pattern M1 varies depending on the X value, the graph G shown in Fig. 8 can be obtained. As can be seen from FIG. 8, the obtained periodic graph G contains a lot of noise. Such noise may be caused by reinforcement interference due to the actual lattice pattern. Therefore, the high frequency components of the periodic graph G in FIG. 8 are removed and expressed as a sine wave S as shown in FIG. 9. The step of expressing the sine wave S may be a step of fitting the values ​​of A0, A1, A2, θ1, θ2, f1, and f2 in the following Equation 9 through regression analysis so that the difference between the periodic graph G and the sine wave S expressed by the following Equation 9 is minimized. For example, fitting may be performed using various error functions such as MSE (Mean Squared Error), RMSE (Root Mean Squared Error), MAE (Mean Absolute Error), MAPE (Mean Absolute Percentage Error), and MPE (Mean Percentage Error).

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[0018] Next, using two graphs S represented by sine waves obtained from R1 and R2, respectively, the difference between the X value of the center of the first moire pattern M1 and the X value of the center of the obtained overlay mark image is obtained. If the X value of the center of symmetry COS1 of the first moire pattern M1 and the X value of the center COI of the acquired overlay mark image are the same, the two graphs S should have the same shape. If the X value of the center of symmetry COS1 of the first moire pattern M1 and the X value of the center COI of the acquired overlay mark image are not the same, one graph will be offset in the X-axis direction from the other graph. In this case, the offset value indicates the difference between the X value of the center of the first moire pattern M1 and the X value of the center COI of the acquired overlay mark image. Next, in a similar manner, the difference between the X value of the second center of symmetry COS2 of the second moire pattern M2 and the X value of the center COI of the acquired overlay mark image is found (S12). Next, the overlay value in the X-axis direction is calculated using the difference between the previously calculated X value of the first center of symmetry COS1 of the first moiré pattern M1 and the X value of the center COI of the acquired overlay mark image, and the difference between the X value of the second center of symmetry COS2 of the second moiré pattern M2 and the X value of the center COI of the acquired overlay mark image (S13). This difference value is a value magnified by the moire gain value, so by dividing it by the moire gain value, the actual overlay value in the X-axis direction can be obtained. Next, in a similar manner, the difference between the Y value of the third center of symmetry COS3 of the third moiré pattern M3 and the Y value of the center COI of the acquired overlay mark image is determined (S14), and the difference between the Y value of the fourth center of symmetry COS4 of the fourth moiré pattern M4 and the Y value of the center COI of the acquired overlay mark image is determined (S15). Next, the overlay value in the Y-axis direction is calculated using the difference between the previously calculated Y value of the third center of symmetry COS3 and the Y value of the center COI of the acquired overlay mark image, and the difference between the Y value of the fourth center of symmetry COS4 of the fourth moire pattern M4 and the Y value of the center COI of the acquired overlay mark image (S16). Since this difference value is a value magnified by the moire gain value, the actual overlay value in the Y-axis direction can be calculated by dividing it by the moire gain value. The following describes a method for manufacturing a semiconductor device using the overlay mark 10 shown in Fig. 1. The method for manufacturing a semiconductor device using the overlay mark 10 begins with a step of forming the overlay mark 10. The overlay mark 10 is formed while forming two successive pattern layers. The step of forming the overlay mark 10 may be a step of forming the overlay mark 10 using a scanner-type exposure device. In this case, the scanning direction of the exposure device is preferably aligned with the longitudinal direction (Y-axis direction in FIG. 3) of the thin bars constituting the lattice patterns 110, 120, 210, and 220 of the first overlay mark 100 and the second overlay mark 200 arranged at the center. Since the scanning direction of the exposure device can be controlled at a constant speed, distortion of the thin bars in the Y-axis direction is not large, but distortion may occur in the X-axis direction. Therefore, it is preferable to minimize distortion by arranging the thin bars along the X-axis direction perpendicular to the scanning direction at the center. Next, the overlay value is measured using the overlay mark 10. The steps for measuring the overlay value are similar to the above-mentioned overlay measurement method. Finally, the measured overlay value is used for process control for forming two successive pattern layers or two patterns formed separately in one pattern layer, i.e. the derived overlay is utilized for process control to ensure that the successive pattern layers or the two patterns are formed in the desired location. The embodiments described above are merely preferred embodiments of the present invention, and the scope of the present invention is not limited to the described embodiments. Various modifications, variations, or substitutions may be made by those skilled in the art within the technical spirit and scope of the claims of the present invention, and it should be understood that such embodiments also fall within the scope of the present invention. [Explanation of symbols]

[0019] M1 1st Moire Pattern M2 2nd Moire Pattern M3 3rd Moire Pattern M4 4th Moire Pattern COS1 first center of symmetry COS2 second center of symmetry COS3 third center of symmetry COS4 fourth center of symmetry 10 Overlay Marks 100 1st Overlay Mark 110 First grid pattern 120 Second grid pattern 200 2nd Overlay Mark 210 3rd grid pattern 220 4th grid pattern 300 3rd Overlay Mark 310 5th grid pattern 320 6th grid pattern 400 4th Overlay Mark 410 7th grid pattern 420 8th grid pattern

Claims

1. 1. An overlay mark for image-based overlay metrology to determine a relative shift between two or more pattern layers, comprising: Including first to fourth overlay marks, The first overlay mark is First center of symmetry (COS １ ), and the first center of symmetry (COS １ a pair of first moire patterns are formed that are 180 degrees rotationally symmetrical with respect to the overlay mark, have central axes aligned with each other, and are disposed at the center of the overlay mark; the first moire pattern is formed by a first grating pattern formed together with a first pattern layer and having a first pitch along a first direction, and a second grating pattern formed together with a second pattern layer so as to overlap the first grating pattern and having a second pitch different from the first pitch along the first direction; The second overlay mark is Second center of symmetry (COS ２ ), and the second center of symmetry (COS ２ a pair of second moire patterns are formed which are rotationally symmetrical by 180 degrees with respect to the first moire pattern, have the same central axis, and are arranged to face each other with the first moire pattern interposed therebetween; the second moire pattern is formed by a third grating pattern formed together with the first pattern layer and having a third pitch along a first direction, and a fourth grating pattern formed together with the second pattern layer so as to overlap the third grating pattern and having a fourth pitch different from the third pitch along the first direction; The third overlay mark is The third center of symmetry (COS ３ ), and the third center of symmetry (COS ３ a pair of third moire patterns are formed which are rotationally symmetrical by 180 degrees with respect to the first moire pattern and are arranged on a first diagonal line with the first moire pattern in between, the third moire pattern is formed by a fifth grating pattern formed together with the first pattern layer and having a fifth pitch along the second direction, and a sixth grating pattern formed together with the second pattern layer so as to overlap the fifth grating pattern and having a sixth pitch different from the fifth pitch along the second direction; The fourth overlay mark is The fourth center of symmetry (COS ４ ), and the fourth center of symmetry (COS ４ a pair of fourth moire patterns are formed which are rotationally symmetrical by 180 degrees with respect to the first diagonal line, and are arranged on a second diagonal line intersecting the first diagonal line with the first moire pattern in between, the fourth moire pattern is formed by a seventh grating pattern formed together with the first pattern layer and having a seventh pitch along the second direction, and an eighth grating pattern formed together with the second pattern layer so as to overlap the seventh grating pattern and having an eighth pitch different from the seventh pitch along the second direction; The first center of symmetry (COS １ ) and the second symmetry center (COS ２ ) in the first direction indicates an overlay error in the first direction between the first pattern layer and the second pattern layer; The third center of symmetry (COS ３ ) and the fourth symmetry center (COS ４ ) in the second direction indicates an overlay error in the second direction between the first pattern layer and the second pattern layer.

2. the overlay mark is formed using a scanner type exposure device, The overlay mark forming a moire pattern according to claim 1 , wherein the second direction is aligned with a scanning direction of the exposure device.

3. the pitch of the first to fourth moire patterns is greater than an optical resolution of an overlay measurement device; 2. The overlay mark forming a moire pattern according to claim 1, wherein the pitch of the first to eighth grating patterns is smaller than an optical resolution of the overlay measurement device.

4. the first pitch is the same as the fourth pitch; 2. The overlay mark forming a moire pattern according to claim 1, wherein the second pitch is the same as the third pitch.

5. the fifth pitch is the same as the eighth pitch; 2. The overlay mark forming a moire pattern according to claim 1, wherein the sixth pitch is the same as the seventh pitch.

6. 1. A method for measuring overlay between multiple successive pattern layers, comprising: forming a pattern on a plurality of successive pattern layers and acquiring a moire pattern image formed by the formed overlay marks; and analyzing the moire pattern image.

6. An overlay measuring method, wherein the overlay mark is the overlay mark according to claim 1.

7. The step of acquiring a Moire pattern image includes: acquiring a moiré pattern image using an overlay measurement device with tilted optical elements; 7. The overlay measurement method of claim 6, wherein in the step of acquiring the moire pattern image, the overlay measurement device is disposed such that a distance between the tilted optical element and the overlay mark increases or decreases as the device advances in the first direction and is constant as the device advances in the second direction.

8. The method of claim 7, wherein the tilted optical element is a beam splitter.

9. The step of analyzing the Moire pattern image includes: projecting a portion of the moire pattern image in one dimension to obtain a periodic graph; 7. The method of claim 6, further comprising the step of: representing the periodic graph as a sine wave.

10. The step of expressing the sinusoidal wave includes: In order to reduce the difference between the periodic graph and the sine wave expressed by the following Equation 9, A of Equation 9 is calculated by performing a regression analysis. ０ , A １ , A ２ , θ １ , θ ２ , f １ , f ２ 10. The method of claim 9, further comprising the step of fitting values. [0097]

11. A method for manufacturing a semiconductor device, comprising the steps of: forming a plurality of successive pattern layers and forming overlay marks; measuring an overlay value using the overlay marks; and using the measured overlay values ​​for process control for forming a plurality of successive pattern layers; A method for manufacturing a semiconductor device, wherein the overlay mark is the overlay mark according to any one of claims 1 to 5.

12. The step of forming the overlay mark comprises: forming the overlay mark using a scanner type exposure device; The method of claim 11, wherein the second direction is aligned with a scanning direction of the exposure tool.

Images