Overlay mark structure and overlay error measurement method

Abstract

The present invention provides an overlay mark structure and an overlay error measurement method. The overlay mark structure includes a front-layer overlay mark and a current-layer overlay mark. The front-layer overlay mark includes multiple first sub-overlay marks, and the current-layer overlay mark includes multiple second sub-overlay marks. The multiple first sub-overlay marks form a first square with a hollow interior, and the multiple second sub-overlay marks form a second square with a hollow interior. The first square surrounds the second square, and the centers of the first and second squares coincide. Each of the first sub-overlay marks includes multiple grooves filled with a marking material. The present invention reduces the load effect problem during etching by providing multiple grooves, increases the etching depth at the location of the front-layer overlay mark, and thus ensures that the front-layer overlay mark is complete and identifiable.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor integrated circuits, and in particular to an overlay mark structure and an overlay error measurement method. Background Art

[0002] In the yellow light process, it is necessary to monitor the position offset between different photolithography layers. The measurement machine determines the position deviation by measuring the overlay mark of the current layer and the overlay mark of the previous layer. Therefore, in the production process, it is necessary to ensure that the overlay mark is complete, clear and easy to identify.

[0003] In the prior art, both the front layer overlay mark and the current layer overlay mark are set as grooves, the front layer overlay mark surrounds the current layer overlay mark, and the front layer overlay mark is set as a large groove. However, the loading effect of dry etching is that the larger the etching area, the slower the etching rate and the shallower the etching. Figure 1 As shown, during the dry etching process to form large trenches, the etching depth in the middle area of ​​the trench is much smaller than that in the edge area. During the filling process, there will be a problem of insufficient filling in the middle area, resulting in incomplete overlay marks on the previous layer and making them difficult to identify. Summary of the Invention

[0004] The purpose of the present invention is to provide an overlay mark structure and an overlay error measurement method, which reduces the load effect problem during etching by setting multiple grooves, increases the etching depth at the position of the front layer overlay mark, and thus ensures that the front layer overlay mark is complete and identifiable.

[0005] In order to solve the above technical problems, according to the first aspect of the present invention, there is provided an overlay mark structure, including a front layer overlay mark and a current layer overlay mark, the front layer overlay mark includes a plurality of first sub-overlay marks, the current layer overlay mark includes a plurality of second sub-overlay marks, the plurality of first sub-overlay marks constitute a first square with a hollow interior, the plurality of second sub-overlay marks constitute a second square with a hollow interior, the first square surrounds the second square, and the centers of the first square and the second square coincide; each of the first sub-overlay marks includes a plurality of grooves filled with marking material.

[0006] Optionally, the cross-section of the groove is square or strip-shaped.

[0007] Optionally, the plurality of grooves are regularly arranged in a first direction and a second direction, and the first direction is perpendicular to the second direction.

[0008] Optionally, the cross-section of the groove is strip-shaped; a portion of the grooves extend in the first direction and are regularly arranged in the second direction to constitute a first group of grooves, and a portion of the grooves extend in the second direction and are regularly arranged in the first direction to constitute a second group of grooves. The first sub-engraving mark includes two groups of first grooves and two groups of second grooves, the first group of grooves and the second group of grooves constitute a first row, and the second group of grooves and the first group of grooves constitute a second row.

[0009] Optionally, the width of the middle area of ​​the strip is smaller than the width of the edge areas on both sides.

[0010] Optionally, the cross section of the groove is bar-shaped, and the cross section of the first sub-overlay mark is also bar-shaped; a row or a column of the grooves are arranged in the first sub-overlay mark, and the extending direction of the grooves is perpendicular to the extending direction of the first sub-overlay mark.

[0011] Optionally, a cross-sectional dimension of the groove is between 0.2 μm and 1 μm, and a length of the first sub-engraved mark is less than or equal to 20 μm, and a width of the first sub-engraved mark is less than or equal to 10 μm.

[0012] Optionally, the front layer overlay mark includes four first sub-overlay marks, and the current layer overlay mark includes four second sub-overlay marks; the first sub-overlay marks and the second sub-overlay marks are both rectangular; two first sub-overlay marks and two second sub-overlay marks extend in the first direction and are arranged in parallel along the second direction, and two first sub-overlay marks and two second sub-overlay marks extend in the second direction and are arranged in parallel in the first direction, wherein the first direction is perpendicular to the second direction.

[0013] To solve the above technical problem, according to a second aspect of the present invention, a method for measuring overlay error is provided, which uses the above-mentioned overlay mark structure for measurement, and includes the following steps:

[0014] Providing a substrate, forming a front layer on the substrate, forming a first photoresist layer on the front layer and performing a first photolithography process to form a first patterned photoresist layer having a front layer overlay mark;

[0015] Using the first patterned photoresist layer as a mask, etching the front layer to form a plurality of grooves in the front layer, and removing the first patterned photoresist layer;

[0016] filling a marking material in the groove to form a front layer overlay mark in the front layer;

[0017] forming a current layer on the front layer, forming a second photoresist layer on the current layer and performing a second photolithography process to form a second patterned photoresist layer having a current layer overlay mark;

[0018] Using the second patterned photoresist layer as a mask, etching the current layer to form a current layer overlay mark pattern in the current layer, and removing the second patterned photoresist layer;

[0019] Filling the marking material in the current layer overlay mark pattern to form the current layer overlay mark; and

[0020] The offset between the overlay mark of the current layer and the overlay mark of the previous layer is measured to obtain an overlay error.

[0021] Optionally, a cross-sectional dimension of a pattern in the first patterned photoresist layer is smaller than a cross-sectional dimension of the groove, and a thickness of the first patterned photoresist layer in an area close to the pattern is smaller than a thickness in other areas to form a step mask.

[0022] In the overlay mark structure and overlay error measurement method provided by the present invention, the front-layer overlay mark includes multiple first sub-overlay marks, each of which includes multiple grooves filled with a marking material. Specifically, the front-layer overlay mark is configured as multiple grooves, which are then filled with the marking material to form the front-layer overlay mark. The provision of multiple grooves in the present invention reduces the loading effect during etching and increases the etching depth at the location of the front-layer overlay mark, thereby ensuring that the front-layer overlay mark is intact and recognizable.

[0023] Furthermore, the width of the middle region of the groove is smaller than the width of the edge regions on both sides, that is, the groove is configured as a structure that is narrow in the middle and wide on both sides, thereby increasing the uniformity of the etching depth.

[0024] Furthermore, the cross-sectional size of the pattern in the first patterned photoresist layer is smaller than the cross-sectional size of the groove, and the thickness of the first patterned photoresist layer in the area close to the pattern is smaller than the thickness in the remaining areas to form a step mask, thereby further optimizing the uniformity of the etching depth. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the structure after a large trench is etched and filled.

[0026] Figure 2 1 is a schematic structural diagram of an overlay mark structure provided by an embodiment of the present invention.

[0027] Figure 3 2 is a schematic structural diagram of an overlay mark structure provided by another embodiment of the present invention.

[0028] Figure 4 3 is a schematic structural diagram of a first sub-overlay mark provided by an embodiment of the present invention.

[0029] Figure 5This is a flow chart of a method for measuring overlay error provided by one embodiment of the present invention.

[0030] Figure 6 It is a cross-sectional schematic diagram after a first patterned photoresist layer is formed on the current layer in the prior art.

[0031] Figure 7 It is a cross-sectional schematic diagram after the groove is formed in the prior art.

[0032] Figure 8 It is a cross-sectional schematic diagram after a first patterned photoresist layer is formed on the current layer according to one embodiment of the present invention.

[0033] Figure 9 It is a cross-sectional schematic diagram after the groove is formed according to an embodiment of the present invention.

[0034] Description of reference numerals:

[0035] 10 - front layer overlay mark; 11 - first sub-overlay mark; 12 - groove; 12a - first group of grooves; 12b - second group of grooves; 20 - current layer overlay mark; 21 - second sub-overlay mark; 30 - front layer; 31 - first patterned photoresist layer; 32 - pattern. DETAILED DESCRIPTION

[0036] The loading effect refers to the situation where, when the etched material is exposed to a reactive plasma or solution, the etching rate of a larger area is slower than that of a smaller area. This is because the reactants are more severely consumed in the larger area, resulting in a lower concentration of the reactants, while the etching rate is directly proportional to the concentration of the reactants. This phenomenon is common in most isotropic etching processes. When forming an overlay mark, the material layer needs to be etched. Due to the loading effect, the area where the overlay mark is located is not easily etched, resulting in the inability to subsequently fill the mark material or a small amount of marking material being filled, resulting in an incomplete overlay mark that is unrecognizable.

[0037] In response to the above problems, the applicant discovered through research that the front-layer overlay mark is set as multiple small grooves (the area where the original front-layer overlay mark is located is a complete large groove), that is, multiple grooves are formed in the area where the front-layer overlay mark is located, and the grooves are filled with marking materials to form the front-layer overlay mark. In this way, the size of the grooves formed by etching is greatly reduced compared with the original groove size (from a large groove to multiple small grooves), thereby reducing the load effect during etching and increasing the etching depth at the position of the front-layer overlay mark, thereby ensuring that the front-layer overlay mark is complete and identifiable.

[0038] After further research, the present invention provides an overlay mark structure, including a front layer overlay mark and a current layer overlay mark, the front layer overlay mark includes a plurality of first sub-overlay marks, the current layer overlay mark includes a plurality of second sub-overlay marks, the plurality of first sub-overlay marks constitute a first square with a hollow interior, the plurality of second sub-overlay marks constitute a second square with a hollow interior, the first square surrounds the second square, and the centers of the first square and the second square coincide; each of the first sub-overlay marks includes a plurality of grooves filled with marking material.

[0039] Accordingly, the present invention also provides an overlay error measurement method, which uses the overlay mark structure as described above to perform overlay error measurement, comprising the following steps: providing a substrate, forming a front layer on the substrate, forming a first photoresist layer on the front layer and performing a first photolithography process to form a first patterned photoresist layer with a front layer overlay mark; etching the front layer using the first patterned photoresist layer as a mask to form a plurality of grooves in the front layer, and removing the first patterned photoresist layer; filling the grooves with a marking material to form a first patterned photoresist layer on the front layer; A previous layer overlay mark is formed in the layer; a current layer is formed on the front layer, a second photoresist layer is formed on the current layer and a second photolithography process is performed to form a second patterned photoresist layer having the current layer overlay mark; the current layer is etched using the second patterned photoresist layer as a mask to form a current layer overlay mark pattern in the current layer, and the second patterned photoresist layer is removed; a marking material is filled in the current layer overlay mark pattern to form a current layer overlay mark; and an overlay error is obtained by measuring the offset between the current layer overlay mark and the previous layer overlay mark.

[0040] In the overlay mark structure and overlay error measurement method provided by the present invention, the front-layer overlay mark includes multiple first sub-overlay marks, each of which includes multiple grooves filled with a marking material. Specifically, the front-layer overlay mark is configured as multiple grooves, which are then filled with the marking material to form the front-layer overlay mark. The provision of multiple grooves in the present invention reduces the loading effect during etching and increases the etching depth at the location of the front-layer overlay mark, thereby ensuring that the front-layer overlay mark is intact and recognizable.

[0041] To make the objects, advantages, and features of the present invention more clearly apparent, the present invention is further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale. They are only used to conveniently and clearly assist in illustrating the purposes of the embodiments of the present invention. In addition, the structures shown in the drawings are often part of the actual structure. In particular, different drawings may need to illustrate different focuses and sometimes use different scales.

[0042] As used in the present invention, the singular forms "a", "an" and "the" include plural objects, unless the content clearly indicates otherwise. As used in the present invention, the term "or" is generally used in a sense including "and / or", unless the content clearly indicates otherwise. As used in the present invention, the term "several" is generally used in a sense including "at least one", unless the content clearly indicates otherwise. As used in the present invention, the term "at least two" is generally used in a sense including "two or more", unless the content clearly indicates otherwise. In addition, the terms "first", "second" and "third" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second" and "third" may explicitly or implicitly include one or at least two of the features, unless the content clearly indicates otherwise.

[0043] Figure 2 is a structural diagram of an overlay mark structure provided by an embodiment of the present invention, Figure 3 FIG. 1 is a schematic structural diagram of an overlay mark structure provided by another embodiment of the present invention. Figure 2 and Figure 3 As shown, the overlay mark structure provided in this embodiment includes a front layer overlay mark 10 and a current layer overlay mark 20, the front layer overlay mark 10 includes a plurality of first sub-overlay marks 11, the current layer overlay mark 20 includes a plurality of second sub-overlay marks 21, the plurality of first sub-overlay marks 11 constitute a first square with a hollow interior, the plurality of second sub-overlay marks 21 constitute a second square with a hollow interior, the first square surrounds the second square, and the centers of the first square and the second square coincide; each of the first sub-overlay marks 11 includes a plurality of grooves 12 filled with marking material.

[0044] In this embodiment, each of the first sub-engraved marks 11 includes a plurality of grooves 12 filled with marking materials, that is, when forming the first sub-engraved mark 11, it is only necessary to etch to form a plurality of grooves 12, and there is no need to etch the entire area where the first sub-engraved mark 11 is located to form a large groove. The etching area is reduced, thereby reducing the load effect problem during etching and increasing the etching depth at the position of the front-layer overlay mark 10, thereby ensuring that the front-layer overlay mark 10 is complete and identifiable.

[0045] In one embodiment of the present invention, the front layer overlay mark 10 includes four first sub-overlay marks 11, two of which extend in a first direction x and are arranged in parallel along a second direction y, and two of which extend in a second direction y and are arranged in parallel along the first direction x, wherein the first direction x is perpendicular to the second direction y, and the four first sub-overlay marks 11 are not connected end to end to form a first square with a hollow interior. The current layer overlay mark 20 includes four second sub-overlay marks 21, two of which extend in a first direction x and are arranged in parallel along a second direction y, and two of which extend in a second direction y and are arranged in parallel along the first direction x, and the four second sub-overlay marks 21 are not connected end to end to form a second square with a hollow interior. In one embodiment, both the first sub-overlay marks 11 and the second sub-overlay marks 21 are rectangular.

[0046] Please refer to Figure 2 and Figure 3 As shown, the cross section of the groove 12 is square or bar-shaped. The square is, for example, a square, and the bar is, for example, a rectangle. Of course, it is not limited to square and bar, and can also be any suitable shape known to those skilled in the art.

[0047] In one embodiment of the present invention, the plurality of grooves 12 are regularly arranged in a first direction and a second direction, and the first direction is perpendicular to the second direction. Figure 2 As shown, the plurality of grooves 12 are regularly arranged in the first direction x and the second direction y to form an array. The spacing between adjacent grooves 12 in the first direction x and the spacing between adjacent grooves 12 in the second direction y can be equal, or of course can be unequal, which can be determined according to actual size and actual needs.

[0048] In one embodiment of the present invention, the cross section of the groove 12 is strip-shaped, and the cross section of the first sub-overlay mark 11 is also strip-shaped. A row or a column of the grooves 12 are arranged in the first sub-overlay mark 11, and the extending direction of the grooves 12 is perpendicular to the extending direction of the first sub-overlay mark 11. Figure 3 As shown, the cross-section of the groove 12 is rectangular, and the cross-section of the first sub-overlay mark 11 is also rectangular. When the first sub-overlay mark 11 extends along the first direction x, a row of the grooves 12 is provided in the first sub-overlay mark 11, and the grooves 12 extend along the second direction y. When the first sub-overlay mark 11 extends along the second direction y, a column of the grooves 12 is provided in the first sub-overlay mark 11, and the grooves 12 extend along the first direction x.

[0049] Figure 4FIG. 1 is a schematic diagram of the structure of the first sub-engraved mark provided by an embodiment of the present invention. Figure 4 As shown, the cross section of the groove 12 is strip-shaped, a portion of the grooves 12 extends in the first direction x and is regularly arranged in the second direction y to form a first group of grooves 12a, and a portion of the grooves 12 extends in the second direction y and is regularly arranged in the first direction x to form a second group of grooves 12b. The first sub-engraved mark 11 includes two first group grooves 12a and two second group grooves 12b. The first group grooves 12a and the second group grooves 12b form a first row, and the second group grooves 12b and the first group grooves 12a form a second row. In one embodiment, the cross section of the groove 12 can be rectangular. In another embodiment, please refer to Figure 4 As shown, the cross-section of the groove 12 is strip-shaped, and the width of the middle area of ​​the strip is smaller than the width of the edge areas on both sides, that is, the width of the middle area of ​​the groove 12 is smaller than the width of the edge areas on both sides (wherein the middle area and the edge areas on both sides refer to the middle and the edge in the extension direction of the groove 12, i.e., the strip, and the width refers to the width in the direction perpendicular to the extension direction of the strip). The groove 12 is set to a structure that is narrow in the middle and wide on both sides. The load effect is that the larger the area, the slower and shallower the etching, and the higher the density, the slower and shallower the etching. Setting the groove 12 to be narrow in the middle and wide on both sides can reduce the middle area to increase the etching rate and etching depth, increase the density at both ends to reduce the etching rate and etching depth, thereby improving the uniformity of the etching depth of the groove 12.

[0050] In one embodiment of the present invention, the cross-sectional size of the groove 12 is between 0.2 μm and 1 μm, the length of the first sub-overlay mark 11 is less than or equal to 20 μm, and the width is less than or equal to 10 μm, but this is not limited thereto.

[0051] The size and arrangement of the grooves 12 in each of the first sub-overlay marks 11 may be the same or different, and may be determined according to actual process conditions and actual requirements.

[0052] In the overlay mark structure provided by an embodiment of the present invention, the front-layer overlay mark 10 includes a plurality of first sub-overlay marks 11, each of which includes a plurality of grooves 12 filled with a marking material. That is, the front-layer overlay mark 10 is configured as a plurality of grooves 12, and the grooves 12 are filled with a marking material to form the front-layer overlay mark 10. The present invention reduces the load effect during etching by providing a plurality of grooves 12, increases the etching depth at the location of the front-layer overlay mark 10, and thereby ensures that the front-layer overlay mark 10 is completely identifiable.

[0053] Furthermore, the width of the middle region of the groove 12 is smaller than the width of the edge regions on both sides, that is, the groove 12 is configured to have a structure that is narrow in the middle and wide on both sides, thereby increasing the uniformity of the etching depth.

[0054] Correspondingly, the present invention also provides an overlay error measurement method, which uses the overlay mark structure as described above to perform overlay error measurement. Figure 5 FIG. 1 is a flow chart of a method for measuring overlay error provided by an embodiment of the present invention. Figure 5 As shown, the overlay error measurement method provided in this embodiment includes the following steps:

[0055] S1: providing a substrate, forming a front layer on the substrate, forming a first photoresist layer on the front layer and performing a first photolithography process to form a first patterned photoresist layer having a front layer overlay mark;

[0056] S2: using the first patterned photoresist layer as a mask, etching the front layer to form a plurality of grooves in the front layer, and removing the first patterned photoresist layer;

[0057] S3: filling a marking material in the groove to form a front layer overlay mark in the front layer; and

[0058] S4: forming a current layer on the front layer, forming a second photoresist layer on the current layer and performing a second photolithography process to form a second patterned photoresist layer having a current layer overlay mark;

[0059] S5: using the second patterned photoresist layer as a mask, etching the current layer to form a current layer overlay mark pattern in the current layer, and removing the second patterned photoresist layer;

[0060] S6: filling the marking material in the current layer overlay mark pattern to form the current layer overlay mark;

[0061] S7: Measure the offset between the overlay mark of the current layer and the overlay mark of the previous layer to obtain an overlay error.

[0062] In step S1, a substrate is provided, a front layer is formed on the substrate, a first photoresist layer is formed on the front layer and a first photolithography process is performed to form a first patterned photoresist layer having a front layer overlay mark. In this embodiment, it is first necessary to produce a photomask having an overlay mark structure as described above, and the areas where the front layer overlay mark and the current layer overlay mark are located are set to be light-transmissive, and the remaining areas are set to be opaque. After the first photoresist layer is formed, the first photoresist layer is exposed and developed using the photomask as a mask, and the front layer overlay mark is formed on the first photoresist layer to form a first patterned photoresist layer. A pattern exposing the front layer is formed in the first patterned photoresist layer (the pattern is a front layer overlay mark pattern, that is, the area where the front layer overlay mark is located is exposed on the front layer).

[0063] In step S2, the front layer is etched using the first patterned photoresist layer as a mask to form a plurality of grooves in the front layer, and the first patterned photoresist layer is removed, thereby forming a front layer overlay mark pattern in the front layer.

[0064] Figure 6 This is a cross-sectional view of the prior art after forming a first patterned photoresist layer on the front layer. Figure 6 As shown, the cross-sectional dimensions of the pattern 32 of the first patterned photoresist layer 31 are equal to the cross-sectional dimensions of the groove 12, that is, the first patterned photoresist layer 31 just exposes the area of ​​the front layer 30 reserved for forming the groove 12. The front layer 30 is then etched using the first patterned photoresist layer 31 as a mask to form the groove 12 in the front layer 30. Figure 7 This is a cross-sectional diagram after the groove is formed in the prior art. Figure 7 As shown, the etching rate near the edge of the trench 12 is greater than the etching rate in the center of the trench 12, which will cause the bottom of the trench 12 to be uneven and the depth of the center area to be smaller than the depth of the edge area.

[0065] Figure 8 FIG is a cross-sectional view of a first patterned photoresist layer formed on a front layer according to an embodiment of the present invention. Figure 8As shown, the cross-sectional dimensions of the pattern 32 within the first patterned photoresist layer 31 are smaller than the cross-sectional dimensions of the trench 12, and the thickness of the first patterned photoresist layer 31 in the area near the pattern 32 is smaller than the thickness in the remaining areas to form a step mask. That is, the first patterned photoresist layer 31 forms a step in the area near the pattern 32, so that the pattern 32 has two cross-sectional dimensions, wherein the area with the first cross-sectional dimension exposes a portion of the front layer 30, and the cross-sectional dimension of the exposed area is smaller than the cross-sectional dimension of the subsequently formed trench 12, and the second cross-sectional dimension is larger than the first cross-sectional dimension and equal to the cross-sectional dimension of the trench 12, and the thickness of the photoresist layer in the area between the first cross-sectional dimension and the second cross-sectional dimension is smaller than the thickness in the remaining areas. This is equivalent to adding a photoresist layer with a reduced thickness in the edge area of ​​the trench 12 to compensate for the uniformity of the etching depth.

[0066] Figure 9 FIG is a cross-sectional view of a groove formed according to an embodiment of the present invention. Figure 9 As shown, the front layer 30 is etched using the first patterned photoresist layer 31 as a mask. Due to the use of a step mask, the thin mask at the edge compensates for the etching unevenness, thereby forming a trench 12 with a relatively flat bottom.

[0067] In step S3, a marking material is filled into the groove 12 to form a front layer overlay mark 10 in the front layer 30. For example, the marking material is first filled into the groove 12, the marking material completely filling the groove 12 and covering a portion of the front layer 30. The marking material is then planarized until the front layer 30 is exposed, forming the front layer overlay mark 10 in the groove 12. In other words, the front layer overlay mark 10 is composed of a plurality of grooves 12 filled with the marking material. In one embodiment, the marking material may be a metal material, but is not limited thereto.

[0068] In step S4, a current layer is formed on the front layer, a second photoresist layer is formed on the current layer, and a second photolithography process is performed to form a second patterned photoresist layer. After the second photoresist layer is formed, the second photoresist layer is exposed and developed using the photomask as a mask, and a current layer overlay mark is formed on the second photoresist layer to form a second patterned photoresist layer. A pattern is formed in the second patterned photoresist layer that exposes the current layer (the pattern is the current layer overlay mark, i.e., the area where the current layer overlay mark is exposed on the current layer). The center of the current layer overlay mark in the second patterned photoresist layer coincides with the center of the front layer overlay mark in the first patterned photoresist layer.

[0069] In step S5, the second patterned photoresist layer is used as a mask to etch the current layer, form a current layer overlay mark pattern in the current layer, and remove the second patterned photoresist layer. The current layer overlay mark pattern is a groove, such as Figure 2 and Figure 3 As shown, since the area where the current layer overlay mark is located is smaller than the area where the previous layer overlay mark is located, the loading effect is alleviated. Therefore, it is not necessary to form multiple grooves in the area where the current layer overlay mark is located. Instead, it is sufficient to form a large groove in the entire area. Of course, in another embodiment, multiple grooves can also be formed in the area where the current layer overlay mark is located.

[0070] In step S6, a marking material is filled into the current layer overlay mark pattern to form a current layer overlay mark. For example, the marking material is first filled into the current layer overlay mark pattern, the marking material completely filling the current layer overlay mark pattern and covering a portion of the current layer. The marking material is then planarized until the current layer is exposed, forming the current layer overlay mark 20 within the current layer overlay mark pattern. In one embodiment, the marking material may be a metal material, but is not limited thereto.

[0071] In step S7, the offset between the current layer overlay mark 20 and the previous layer overlay mark 10 is measured to obtain an overlay error. For example, the center of the previous layer overlay mark 10 and the center of the current layer overlay mark 20 are measured to obtain the offset between the center of the current layer overlay mark 20 and the center of the previous layer overlay mark 10 in the first direction x and the second direction y to obtain the overlay error. The exposure machine can then be compensated based on the overlay error. Since the previous layer overlay mark 10 is composed of multiple grooves 12, the center of the previous layer overlay mark 10 can be determined by the centers of the multiple grooves 12 and the positions of the grooves 12.

[0072] In the embodiment of the present invention, the overlay error measurement is performed using the overlay mark structure described above. Because the overlay mark structure is complete and identifiable, the overlay error between the current layer and the previous layer can be accurately measured. Furthermore, the cross-sectional dimensions of the pattern 32 within the first patterned photoresist layer 31 are smaller than the cross-sectional dimensions of the trench 12, and the thickness of the first patterned photoresist layer 31 in the area near the pattern 32 is smaller than that in the remaining areas, forming a step mask, thereby optimizing the uniformity of the etching depth.

[0073] In summary, in the overlay mark structure and overlay error measurement method provided by the present invention, the front-layer overlay mark includes multiple first sub-overlay marks, each of which includes multiple grooves filled with a marking material. Specifically, the front-layer overlay mark is configured as multiple grooves, which are filled with the marking material to form the front-layer overlay mark. The provision of multiple grooves in the present invention reduces the loading effect during etching, increases the etching depth at the location of the front-layer overlay mark, and thus ensures that the front-layer overlay mark is complete and identifiable.

[0074] Furthermore, the width of the middle region of the groove is smaller than the width of the edge regions on both sides, that is, the groove is configured as a structure that is narrow in the middle and wide on both sides, thereby increasing the uniformity of the etching depth.

[0075] Furthermore, the cross-sectional size of the pattern in the first patterned photoresist layer is smaller than the cross-sectional size of the groove, and the thickness of the first patterned photoresist layer in the area close to the pattern is smaller than the thickness in the remaining areas to form a step mask, thereby further optimizing the uniformity of the etching depth.

[0076] The above description is only a description of the preferred embodiments of the present invention and does not limit the scope of the present invention. Any changes and modifications made by ordinary technicians in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. An overlay marking structure, characterized in that: The present invention comprises a front layer overlay mark and a current layer overlay mark, wherein the front layer overlay mark comprises a plurality of first sub-overlay marks, and the current layer overlay mark comprises a plurality of second sub-overlay marks, wherein the plurality of first sub-overlay marks form a first square with a hollow interior, and the plurality of second sub-overlay marks form a second square with a hollow interior, wherein the first square surrounds the second square, and the centers of the first square and the second square coincide with each other; and each of the first sub-overlay marks comprises a plurality of grooves filled with a marking material; The cross-section of the groove is strip-shaped; a portion of the grooves extends in the first direction and is regularly arranged in the second direction to form a first group of grooves, and a portion of the grooves extends in the second direction and is regularly arranged in the first direction to form a second group of grooves. The first sub-engraving mark includes two first-group grooves and two second-group grooves, the first first-group groove and the first second-group groove form a first row, and the second second-group groove and the second first-group groove form a second row, and the width of the middle area of ​​the strip is smaller than the width of the edge areas on both sides; the first direction is perpendicular to the second direction.

2. The overlay mark structure according to claim 1, wherein: The cross-sectional size of the groove is between 0.2 μm and 1 μm, and the length of the first sub-engraved mark is less than or equal to 20 μm, and the width is less than or equal to 10 μm.

3. The overlay mark structure according to claim 1, characterized in that: The front layer overlay mark includes four first sub-overlay marks, and the current layer overlay mark includes four second sub-overlay marks; the first sub-overlay marks and the second sub-overlay marks are both rectangular; two first sub-overlay marks and two second sub-overlay marks extend in the first direction and are arranged in parallel along the second direction, and two first sub-overlay marks and two second sub-overlay marks extend in the second direction and are arranged in parallel in the first direction, wherein the first direction is perpendicular to the second direction.

4. A method for measuring overlay error, characterized in that: The measurement is performed using the overlay mark structure according to any one of claims 1 to 3, comprising the following steps: Providing a substrate, forming a front layer on the substrate, forming a first photoresist layer on the front layer and performing a first photolithography process to form a first patterned photoresist layer having a front layer overlay mark; Using the first patterned photoresist layer as a mask, etching the front layer to form a plurality of grooves in the front layer, and removing the first patterned photoresist layer; filling a marking material in the groove to form a front layer overlay mark in the front layer; forming a current layer on the front layer, forming a second photoresist layer on the current layer and performing a second photolithography process to form a second patterned photoresist layer having a current layer overlay mark; Using the second patterned photoresist layer as a mask, etching the current layer to form a current layer overlay mark pattern in the current layer, and removing the second patterned photoresist layer; Filling the marking material in the current layer overlay mark pattern to form the current layer overlay mark; and The offset between the overlay mark of the current layer and the overlay mark of the previous layer is measured to obtain an overlay error.

5. The overlay error measurement method according to claim 4, characterized in that: The cross-sectional size of the pattern in the first patterned photoresist layer is smaller than the cross-sectional size of the trench, and the thickness of the first patterned photoresist layer in the area close to the pattern is smaller than the thickness of the remaining area to form a step mask.

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