Overlay measurement method

Abstract

This disclosure provides a method for measuring overlay accuracy. The method includes: providing a semiconductor substrate, on which a core region, a first pattern to be measured located at the edge of the core region along a first direction, and a second pattern to be measured located at the edge of the core region along a second direction are formed; wherein the first pattern to be measured and the second pattern to be measured have the same height; the first pattern to be measured extends along the first direction and includes at least a first end measurement region; the second pattern to be measured extends along a second direction and includes at least a second intermediate measurement region; a first offset of the first pattern to be measured in the second direction is determined by the first end measurement region; and a second offset of the second pattern to be measured in the first direction is determined by the second intermediate measurement region.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor technology, and to, but is not limited to, a method for measuring overlay accuracy. Background Technology

[0002] Overlay accuracy is a crucial online monitoring parameter in integrated circuit manufacturing processes. It's used to monitor the alignment (or offset) between the current layer pattern and the previous layer pattern. In related technologies, the overlay accuracy of the current and previous layer patterns can be measured using a High Voltage Scanning Electron Microscope (HVSEM). For example, the critical dimension (CD) of the previous layer pattern can be measured using the back-scattered electron (BSE) signal of the HVSEM to obtain one center of gravity, and the critical dimension of the current layer pattern can be measured using the secondary electron (SE) signal of the HVSEM to obtain another center of gravity. The offset between the centers of gravity of the current and previous layer patterns is the overlay accuracy.

[0003] However, the overlay accuracy measurement method in related technologies is applicable when the layer pattern and the previous layer pattern are not in the same layer, that is, when the height of the layer pattern and the previous layer pattern are inconsistent. When the height of the two patterns is the same, the offset of the pattern cannot be measured by the overlay accuracy measurement method in related technologies. Summary of the Invention

[0004] In view of this, the present disclosure provides a method for measuring overlay accuracy.

[0005] This disclosure provides a method for measuring overlay accuracy, the method comprising:

[0006] A semiconductor substrate is provided, on which a core region, a first pattern to be measured located at the edge of the core region along a first direction, and a second pattern to be measured located at the edge of the core region along a second direction are formed; wherein the first pattern to be measured and the second pattern to be measured have the same height; the first pattern to be measured extends along the first direction and includes at least a first end measurement region; the second pattern to be measured extends along the second direction and includes at least a second intermediate measurement region;

[0007] The first offset of the first pattern to be measured in the second direction is determined by the first end measurement area;

[0008] The second offset of the second pattern to be measured in the first direction is determined through the second intermediate measurement area.

[0009] In some embodiments, the first end measurement region includes a plurality of first sub-patterns extending along the first direction and arranged along the second direction; determining the first offset of the first pattern to be measured in the second direction includes:

[0010] Obtain the first difference in the critical dimensions of two adjacent first sub-patterns in the first end measurement area to determine the first offset.

[0011] In some embodiments, the first pattern to be measured further includes a third sub-pattern extending along the first direction, and the third sub-pattern is not located in the first end measurement area; the third sub-pattern is arranged alternately with a plurality of the first sub-patterns;

[0012] The first sub-patterns located adjacent to each other in the first end measurement area are distributed on both sides of the third sub-pattern along the second direction.

[0013] In some embodiments, the first sub-pattern further includes a first intermediate measurement area;

[0014] The first intermediate measurement area is not adjacent to the third sub-pattern, and the critical dimension of the first sub-pattern located in the first end measurement area is greater than the critical dimension of the first sub-pattern located in the first intermediate measurement area.

[0015] In some embodiments, the method further includes:

[0016] The first offset of the first pattern to be measured in the second direction is determined through the first intermediate measurement area.

[0017] In some embodiments, determining the first offset of the first pattern to be measured in the second direction includes:

[0018] Obtain the second difference in the key dimensions of two adjacent first sub-patterns in the first intermediate measurement area to determine the first offset.

[0019] In some embodiments, determining the first offset of the first pattern to be measured in the second direction includes:

[0020] The first difference or the second difference is determined as the first offset; or...

[0021] The first offset is obtained by performing a weighted average on the first difference and the second difference.

[0022] In some embodiments, determining the first offset of the first pattern to be measured in the second direction includes:

[0023] The first difference and the second difference are divided into equal parts to obtain the first equal-part difference and the second equal-part difference.

[0024] The first or second division difference value is determined as the first offset; or...

[0025] The first offset is obtained by performing a weighted average of the first and second equal division differences.

[0026] In some embodiments, the second intermediate measurement area includes a plurality of second sub-patterns extending along the second direction and arranged along the first direction; determining the second offset of the second pattern to be measured in the first direction includes:

[0027] Obtain the third difference between the key dimensions of two adjacent second sub-patterns in the second intermediate measurement area to determine the second offset.

[0028] In some embodiments, the second pattern to be measured further includes a fourth sub-pattern extending along the second direction, and the fourth sub-pattern is not located in the second intermediate measurement area;

[0029] The fourth sub-pattern is arranged alternately with multiple second sub-patterns, and the second intermediate measurement area is not adjacent to the fourth sub-pattern.

[0030] In some embodiments, the second pattern to be measured further includes a second end measurement area;

[0031] The critical dimension of the second sub-pattern located in the second end measurement area is larger than the critical dimension of the second sub-pattern located in the second middle measurement area, and the adjacent second sub-patterns in the second end measurement area are distributed on both sides of the fourth sub-pattern along the first direction.

[0032] In some embodiments, the method further includes:

[0033] The second offset of the second pattern to be measured in the first direction is determined by the second end measurement area.

[0034] In some embodiments, determining the second offset of the second pattern to be measured in the first direction includes:

[0035] Obtain the fourth difference of the key dimensions of two adjacent second sub-patterns in the second end measurement area to determine the second offset.

[0036] In some embodiments, determining the second offset of the second pattern to be measured in the first direction includes:

[0037] The third difference or the fourth difference is determined as the second offset; or...

[0038] The second offset is obtained by performing a weighted average on the third and fourth differences.

[0039] In some embodiments, determining the second offset of the second pattern to be measured in the first direction includes:

[0040] The third difference and the fourth difference are divided into equal parts to obtain the third equal-divided difference and the fourth equal-divided difference.

[0041] The third or fourth division difference value is determined as the second offset; or...

[0042] The second offset is obtained by performing a weighted average of the third and fourth equal division differences.

[0043] The overlay accuracy measurement method provided in this embodiment of the invention, since the first and second patterns to be measured are located at the edges of the core region in the first and second directions respectively, and the first and second patterns to be measured have the same height, can measure the first offset of the first pattern to be measured in the second direction and the second offset of the second pattern to be measured in the first direction through the first end measurement area of ​​the first pattern to be measured and the second middle measurement area of ​​the second pattern to be measured, respectively, thereby obtaining the overlay accuracy of the first and second patterns to be measured. In this way, the obtained overlay accuracy can be used to correct subsequent processes and improve the yield of integrated circuit fabrication. Attached Figure Description

[0044] In the accompanying drawings (which are not necessarily drawn to scale), similar reference numerals may describe similar parts in different views. Similar reference numerals with different letter suffixes may indicate different examples of similar parts. The drawings illustrate, by way of example and not limitation, the various embodiments discussed herein.

[0045] Figure 1 A flowchart illustrating the method for measuring overlay accuracy provided in this embodiment of the disclosure;

[0046] Figure 2 This is a schematic diagram of the structure of the first pattern to be measured provided in an embodiment of this disclosure;

[0047] Figure 3 This is a schematic diagram of the structure of the second pattern to be measured provided in an embodiment of this disclosure;

[0048] Figure 4a A schematic diagram of the planar structure of the core area, the first pattern to be measured, and the second pattern to be measured provided in an embodiment of this disclosure;

[0049] Figure 4b Provided for the embodiments of this disclosure Figure 4a An enlarged view of the first pattern to be measured;

[0050] Figure 4c Provided for the embodiments of this disclosure Figure 4a Scanning electron microscope image of the first pattern to be measured;

[0051] Figure 4d Provided for the embodiments of this disclosure Figure 4a An enlarged view of the second pattern to be measured;

[0052] Figure 4e Provided for the embodiments of this disclosure Figure 4a Scanning electron microscope image of the second pattern to be measured;

[0053] Figure 5a This is a schematic diagram illustrating the measurement of the overlay accuracy of each wafer after development, as provided in an embodiment of this disclosure.

[0054] Figure 5b This is a schematic diagram illustrating the measurement of the overlay accuracy of each wafer after etching, as provided in an embodiment of this disclosure. Detailed Implementation

[0055] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0056] In the following description, numerous details are set forth in order to provide a more thorough understanding of this disclosure. However, it will be apparent to those skilled in the art that this disclosure may be practiced without one or more of these details. In other instances, to avoid confusion with this disclosure, certain technical features well-known in the art have not been described; that is, not all features of actual embodiments are described herein, nor are well-known functions and structures described in detail.

[0057] In the accompanying drawings, for clarity, the dimensions of layers, areas, and elements, as well as their relative dimensions, may be exaggerated. The same reference numerals denote the same elements throughout.

[0058] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, components, areas, layers, and / or portions, these elements, components, areas, layers, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer, or portion from another element, component, area, layer, or portion. Therefore, without departing from the teachings of this disclosure, the first element, component, area, layer, or portion discussed below may be referred to as a second element, component, area, layer, or portion. And the discussion of a second element, component, area, layer, or portion does not imply that the first element, component, area, layer, or portion necessarily exists in this disclosure.

[0059] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprise” and / or “comprising,” when used in this specification, identify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0060] This disclosure provides a method for measuring overlay accuracy. Figure 1 A schematic flowchart of the method for measuring overlay accuracy provided in this embodiment of the present disclosure is shown below. Figure 1 As shown, the method for measuring overlay accuracy includes the following steps:

[0061] Step S101: Provide a semiconductor substrate, on which a core region, a first pattern to be measured located at the edge of the core region along a first direction, and a second pattern to be measured located at the edge of the core region along a second direction are formed; the first pattern to be measured and the second pattern to be measured have the same height; the first pattern to be measured extends along the first direction and includes at least a first end measurement area; the second pattern to be measured extends along the second direction and includes at least a second middle measurement area.

[0062] In this embodiment of the disclosure, the semiconductor substrate may be a silicon substrate, or it may include other semiconductor elements, such as germanium (Ge), or include semiconductor compounds, such as silicon carbide (SiC), gallium arsenide (GaAs), gallium phosphide (GaP), indium phosphide (InP), indium arsenide (InAs), or indium antimonide (InSb), or include other semiconductor alloys, such as silicon germanium (SiGe), gallium arsenide phosphide (GaAsP), aluminum indium arsenide (AlInAs), aluminum gallium arsenide (AlGaAs), gallium indium arsenide (GaInAs), gallium indium phosphide (GaInP), and / or gallium indium arsenide phosphide (GaInAsP) or combinations thereof.

[0063] In this embodiment of the disclosure, the core region is adjacent to the memory array, and functional circuits such as the sense amplifier (SA) and the sub wordline driver (SWD) are formed in the core region.

[0064] In this embodiment, the first pattern to be measured is located at the edge of the core region along a first direction, and the second pattern to be measured is located at the edge of the core region along a second direction. The first and second directions are on the same plane and intersect each other; for example, the first direction may be perpendicular to the second direction. In this embodiment, the first direction may be the X-axis direction, and the second direction may be the Y-axis direction. In other embodiments, the first direction may also be the Y-axis direction, and the second direction may also be the X-axis direction.

[0065] In this embodiment of the disclosure, the first pattern to be measured and the second pattern to be measured have the same height, that is, the first pattern to be measured and the second pattern to be measured are located on the same layer. Therefore, the overlay accuracy of the first pattern to be measured and the second pattern to be measured cannot be calculated by the method of offset between the center of gravity of the current layer pattern and the previous layer pattern in the related technology.

[0066] In some embodiments, the first pattern to be measured extends along a first direction and the second pattern to be measured extends along a second direction. That is, the first pattern to be measured and the second pattern to be measured in this embodiment extend in different directions. Therefore, the overlay accuracy in different directions can be determined by the first pattern to be measured and the second pattern to be measured respectively.

[0067] In this embodiment, the first pattern to be measured includes at least a first end measurement area, which is a region at any end of the first pattern to be measured along a first direction. In other embodiments, the first pattern to be measured also includes a first intermediate measurement area, which is not located at either end of the first pattern to be measured along the first direction. The second pattern to be measured includes at least a second intermediate measurement area, which is not located at either end of the second pattern to be measured along a second direction. In other embodiments, the second pattern to be measured also includes a second end measurement area, which is a region at any end of the second pattern to be measured along the second direction.

[0068] Figure 2 This is a schematic diagram of the structure of the first pattern to be measured provided in an embodiment of this disclosure. Figure 3 This is a schematic diagram of the structure of the second pattern to be measured provided in an embodiment of this disclosure, such as... Figure 2 As shown, the first pattern to be measured 10 includes a plurality of first sub-patterns 101 extending along a first (X-axis) direction and arranged along a second (Y-axis) direction; the first pattern to be measured 10 includes a first end measurement area A1 and a first intermediate measurement area A2, that is, both the first end measurement area A1 and the first intermediate measurement area A2 include a plurality of first sub-patterns 101 extending along the X-axis direction and arranged along the Y-axis direction; wherein, the critical dimension d1 of the first sub-pattern 101 located in the first end measurement area A1 is larger than the critical dimension d2 of the first sub-pattern 101 located in the first intermediate measurement area A1. Figure 3 As shown, the second pattern to be measured 20 includes a plurality of second sub-patterns 201 extending along the Y-axis and arranged along the X-axis, and the second pattern to be measured 20 includes a second end measurement area B1 and a second intermediate measurement area B2, that is, both the second end measurement area B1 and the second intermediate measurement area B2 include a plurality of second sub-patterns 201 extending along the Y-axis and arranged along the X-axis; the critical dimension d3 of the second sub-pattern 201 located in the second end measurement area B1 is greater than the critical dimension d4 of the second sub-pattern 201 located in the second intermediate measurement area B1.

[0069] It should be noted that, since the first pattern to be measured 10 and the second pattern to be measured 20 are located at the edge of the core region and the core region is adjacent to the storage array, the end regions of the first pattern to be measured 10 and the second pattern to be measured 20, namely the first end measurement area A1 and the first end measurement area B1, are usually used to make the contact hole patterns for connecting to the storage array. Therefore, the critical size of the first sub-pattern located in the first end measurement area is usually larger than the critical size of the first sub-pattern in the first intermediate measurement area, and the critical size of the second sub-pattern located in the second end measurement area is usually larger than the critical size of the second sub-pattern in the second intermediate measurement area.

[0070] In some embodiments, please continue to see Figure 2The first pattern to be measured 10 also includes a third sub-pattern 102 extending along the X-axis direction. The third sub-pattern 102 is arranged alternately with a plurality of first sub-patterns 101. The third sub-pattern 102 is not located at the end of the first pattern to be measured 10 along the X-axis direction, that is, the third sub-pattern 102 is not located in the first end measurement area A1.

[0071] In some embodiments, the third sub-pattern 102 is not located in the first intermediate measurement area A2, and the third sub-pattern 102 is not adjacent to the first intermediate measurement area A2.

[0072] In some embodiments, please continue to see Figure 3 The second pattern to be measured 20 also includes a fourth sub-pattern 202 extending along the Y-axis direction. The fourth sub-pattern 202 is arranged alternately with multiple second sub-patterns 201. The fourth sub-pattern 202 is not located at the end of the second pattern to be measured 20 along the Y-axis direction, that is, the fourth sub-pattern 202 is not located in the second end measurement area A2.

[0073] In some embodiments, the fourth sub-pattern 202 is not located in the second intermediate measurement area B2, and the fourth sub-pattern 202 is not adjacent to the second intermediate measurement area B2.

[0074] Step S102: Determine the first offset of the first pattern to be measured in the second direction through the first end measurement area.

[0075] In some embodiments, the first offset of the first pattern to be measured in the second direction can also be determined by the first intermediate measurement area, or by the first end measurement area and the first intermediate measurement area.

[0076] Step S103: Determine the second offset of the second pattern to be measured in the first direction through the second intermediate measurement area.

[0077] In some embodiments, the second offset of the second pattern to be measured in the first direction can also be determined by the second end measurement area, or by the second end measurement area and the second intermediate measurement area.

[0078] It should be noted that steps S102 and S103 are not strictly ordered. In some embodiments, the second offset can be determined first and then the first offset.

[0079] In the embodiments provided in this disclosure, since the first pattern to be measured and the second pattern to be measured are located at the edges of the core region in the first direction and the second direction, respectively, and the first pattern to be measured and the second pattern to be measured have the same height, the first offset of the first pattern to be measured in the second direction and the second offset of the second pattern to be measured in the first direction can be measured through the first end measurement area of ​​the first pattern to be measured and the second middle measurement area of ​​the second pattern to be measured, respectively, thereby obtaining the overlay accuracy of the first pattern to be measured and the second pattern to be measured. In this way, the obtained overlay accuracy can correct subsequent process steps and improve the fabrication yield of integrated circuits.

[0080] The following describes the method for measuring overlay accuracy in this embodiment of the present disclosure using the core region of a Dynamic Random Access Memory (DRAM), a first pattern to be measured located at the edge of the DRAM core region along a first direction, and a second pattern to be measured located at the edge of the DRAM core region along a second direction as examples. The first pattern to be measured can be a pattern of a metal contact structure, and the second pattern to be measured can be a pattern of a second metal layer. Since the first and second patterns to be measured have different heights after development inspection (ADI), the overlay accuracy measurement method in related technologies can be used to measure the alignment of the first and second patterns to be measured. However, after etching inspection (AEI), the first and second patterns to be measured are located on the same layer (i.e., the first and second patterns to be measured have the same height), therefore, the overlay accuracy measurement method in related technologies cannot be used to measure the alignment of the first and second patterns to be measured.

[0081] Figure 4a This is a schematic diagram of the planar structure of the core area, the first pattern to be measured, and the second pattern to be measured, provided in an embodiment of this disclosure. Figure 4b and 4d They are respectively Figure 4a Enlarged views of the first and second patterns to be measured. Figure 4c and 4e They are respectively Figure 4a Scanning electron microscope (SEM) images of the first and second patterns to be measured, shown below in conjunction with... Figures 4a-4e The method for measuring the overlay accuracy in the embodiments of this disclosure is described.

[0082] like Figure 4aAs shown, the core region 301 is adjacent to the storage array 302. The core region 301 may include a first core region 3011 and a second core region 3012. The first pattern to be measured 10 may be located at the edge of the first core region 3011 along the X-axis direction, and the second pattern to be measured 20 may be located at the edge of the second core region 3012 along the Y-axis direction. In this embodiment, the first pattern to be measured 10 and the second pattern to be measured 20 have the same height.

[0083] In this embodiment of the disclosure, the first core region 3011 may be a word line driver region, and the second core region 3012 may be a sense amplifier region. In other embodiments, the first core region 3011 and the second core region 3012 may also be other functional circuit regions.

[0084] like Figure 4b and 4c As shown, the first pattern to be measured 10 includes a first sub-pattern 101 and a third sub-pattern 102 extending along the X-axis direction, and the third sub-pattern 102 and a plurality of first sub-patterns 101 are alternately arranged along the Y-axis direction.

[0085] Please continue reading Figure 4b and 4c The first pattern to be measured 10 includes a first end measurement area A1 located at any end of the first pattern to be measured 10 along the X-axis direction, and a first intermediate measurement area A2 located in the middle of the first pattern to be measured 10. In this embodiment of the present disclosure, the third sub-pattern 102 is not located at the end of the first pattern to be measured 10, and the third sub-pattern 102 is not located in the first end measurement area A1 and the first intermediate measurement area A2.

[0086] In this embodiment of the disclosure, the first intermediate measurement area A2 is located between adjacent third sub-patterns 102, and there is at least one first sub-pattern 101 between the first intermediate measurement area A2 and the third sub-pattern 102, that is, the first intermediate measurement area A2 and the third sub-pattern 102 are not adjacent.

[0087] It should be noted that in this embodiment of the present disclosure, both the first end measurement area A1 and the first intermediate measurement area A2 include two first sub-patterns. In other embodiments, both the first end measurement area A1 and the first intermediate measurement area A2 may also include at least two first sub-patterns.

[0088] In some embodiments, please continue to see Figure 4b and 4c The first sub-patterns 101-1 and 101-2, which are adjacent to each other in the first end measurement area A1, are distributed on both sides of the third sub-pattern 102 along the Y-axis.

[0089] In some embodiments, the critical dimension of the first sub-pattern 101 located in the first end measurement area A1 is greater than the critical dimension of the first sub-pattern 101 located in the first middle measurement area A2.

[0090] In some embodiments, the first pattern to be measured 10 may include a plurality of first end measurement areas A1 and a plurality of first intermediate measurement areas A2, according to embodiments of this disclosure. Figure 4c The diagram shows two first end measurement areas A1 and two first intermediate measurement areas A2.

[0091] In some embodiments, the first offset can be determined by the following steps: obtaining a first difference in the key dimensions of two adjacent first sub-patterns in the first end measurement area to determine the first offset, or obtaining a first difference in the key dimensions of two adjacent first sub-patterns in the first end measurement area and a second difference in the key dimensions of two adjacent first sub-patterns in the first intermediate measurement area to determine the first offset.

[0092] In this embodiment of the present disclosure, the key dimensions of each first sub-pattern in the first end measurement area or the first intermediate measurement area can be measured by a key dimension scanning electron microscope, thereby obtaining a first difference or a second difference in the key dimensions of two adjacent first sub-patterns in the first end measurement area or the first intermediate measurement area.

[0093] In some embodiments, the first offset can be determined by the following steps: determining a first difference or a second difference as the first offset.

[0094] In some embodiments, when the first pattern to be measured includes only a first end measurement area, the first difference in the critical dimension measured through the first end measurement area can be determined as the first offset; or, when the area to be measured in the first pattern to be measured includes only a first intermediate measurement area, the second difference in the critical dimension measured through the first intermediate measurement area can be determined as the first offset.

[0095] Please continue reading Figure 4b In the first end measurement area A1, two adjacent first sub-patterns are first sub-pattern 101-1 and first sub-pattern 101-2, where the key dimension of first sub-pattern 101-1 is d5 and the key dimension of first sub-pattern 101-2 is d6. Therefore, the difference between the key dimensions of first sub-pattern 101-1 and first sub-pattern 101-2 is d5-d6. Thus, the first offset can be d5-d6.

[0096] In other embodiments, when the area to be measured in the first pattern to be measured includes multiple first end measurement areas, the average, mode, or median of multiple first differences determined by two adjacent first sub-patterns in each first end measurement area can be determined as the first offset; or, when the area to be measured in the first pattern to be measured includes multiple first intermediate measurement areas, and each first intermediate measurement area includes multiple pairs of adjacent first sub-patterns, the average, mode, or median of multiple second differences determined by any two adjacent first sub-patterns in each first intermediate measurement area can be determined as the first offset.

[0097] In some embodiments, when the first pattern to be measured includes both a first end measurement area and a first middle measurement area, the first offset can also be determined by the following steps: performing a weighted average of the first difference and the second difference to obtain the first offset.

[0098] In this embodiment of the disclosure, the first offset obtained by measuring the first end measurement area or the first intermediate measurement area in the first pattern to be measured has different weighting coefficients. For example, the first offset obtained by measuring the first end measurement area has a first weighting coefficient, and the first offset obtained by measuring the first intermediate measurement area has a second weighting coefficient. Then, the first offset = (first difference * first weighting coefficient + second difference * second weighting coefficient) / 2.

[0099] In this embodiment of the disclosure, the first weighting coefficient can be 30% or 80%, and correspondingly, the second weighting coefficient can be 70% or 20%. In other embodiments, both the first weighting coefficient and the second weighting coefficient can be 50%.

[0100] In some embodiments, when the area to be measured in the first pattern to be measured includes multiple first end measurement areas and multiple first intermediate measurement areas, it is necessary to assign weights to each first difference and each second difference, and finally calculate the average to obtain the first offset.

[0101] In some embodiments, the first offset can also be determined by the following steps: dividing the first difference and the second difference into equal parts to obtain the first equal-division difference and the second equal-division difference; and determining the first equal-division difference or the second equal-division difference as the first offset.

[0102] Here, equal division refers to dividing the first difference or the second difference into equal parts according to a specific number of equal parts, obtaining equal parts with the same number of equal parts, and extracting a preset number of equal parts as the first or second equal difference. For example, the first difference or the second difference can be divided into two equal parts, and one half of the first difference or one half of the second difference can be extracted as the first equal difference, or one half of the second difference can be extracted as the second equal difference.

[0103] In this embodiment of the present disclosure, when the first pattern to be measured includes only a first end measurement area, the first division difference value of the key dimension measured through the first end measurement area can be determined as the first offset; or, when the first pattern to be measured includes only a first middle measurement area, the second division difference value of the key dimension measured through the first middle measurement area can be determined as the first offset.

[0104] Please continue reading Figure 4b In the first end measurement area A1, two adjacent first sub-patterns are first sub-pattern 101-1 and first sub-pattern 101-2, where the key dimension of first sub-pattern 101-1 is d5 and the key dimension of first sub-pattern 101-2 is d6. Therefore, the difference between the key dimensions of first sub-pattern 101-1 and first sub-pattern 101-2 is d5-d6. Thus, the first offset can be (d5-d6) / 2.

[0105] In other embodiments, when the first pattern to be measured includes multiple first end measurement areas, the average, mode, or median of multiple first division differences determined by two adjacent first sub-patterns in each first end measurement area can be determined as the first offset; or, when the first pattern to be measured includes multiple first intermediate measurement areas, and each first intermediate measurement area includes multiple pairs of adjacent first sub-patterns, the average, mode, or median of multiple second division differences determined by any two adjacent first sub-patterns in each first intermediate measurement area can be determined as the first offset.

[0106] In some embodiments, when the first pattern to be measured includes both a first end measurement area and a first middle measurement area, the first offset can also be determined by the following steps: performing a weighted average of the first equal division difference value and the second equal division difference value to obtain the first offset.

[0107] In this embodiment, the process of weighting the first and second equal division differences is similar to the process of weighting the first and second differences in the above embodiment, and will not be repeated here.

[0108] like Figure 4d and 4e As shown, the second pattern to be measured 20 includes a second sub-pattern 201 and a fourth sub-pattern 202 extending along the Y-axis direction, and the fourth sub-pattern 202 and a plurality of second sub-patterns 201 are arranged alternately along the X-axis direction.

[0109] Please continue reading Figure 4d and 4eThe second pattern to be measured 20 includes a second end measurement area B1 located at any end of the second pattern to be measured along the Y-axis direction, and a second intermediate measurement area B2 located in the middle of the second pattern to be measured 20. In this embodiment of the present disclosure, the fourth sub-pattern 202 is not located at the end of the second pattern to be measured 20, and the fourth sub-pattern 202 is not located in the second end measurement area B1 and the second intermediate measurement area B2.

[0110] In this embodiment of the present disclosure, the second intermediate measurement area B2 is located between adjacent fourth sub-patterns 202, and there is at least one second sub-pattern 201 between the second intermediate measurement area B2 and the fourth sub-pattern 202, that is, the second intermediate measurement area B2 and the fourth sub-pattern 202 are not adjacent.

[0111] It should be noted that in this embodiment of the present disclosure, both the second end measurement area B1 and the second intermediate measurement area B2 include two second sub-patterns. In other embodiments, both the second end measurement area B1 and the second intermediate measurement area B2 may also include at least two second sub-patterns.

[0112] In some embodiments, please continue to see Figure 4d The second sub-patterns 201-3 and 201-4, which are adjacent to each other in the second end measurement area B1, are distributed on both sides of the fourth sub-pattern 202 along the X-axis direction.

[0113] In some embodiments, the critical dimension of the second sub-pattern 201 located in the second end measurement area B1 is greater than the critical dimension of the second sub-pattern 201 located in the second middle measurement area B2.

[0114] In some embodiments, the second pattern to be measured 20 may include a plurality of second end measurement areas B1 and a plurality of second intermediate measurement areas B2, according to embodiments of this disclosure. Figure 4d Only one second end measurement area B1 and one second intermediate measurement area B2 are shown in the figure.

[0115] In some embodiments, the second offset can be determined by the following steps: obtaining a third difference between the key dimensions of two adjacent second sub-patterns in the second intermediate measurement area to determine the second offset; or obtaining a third difference between the key dimensions of two adjacent second sub-patterns in the second intermediate measurement area and a fourth difference between the key dimensions of two adjacent second sub-patterns in the second end measurement area to determine the second offset.

[0116] In this embodiment of the disclosure, the key dimensions of each second sub-pattern in the second intermediate measurement area or the second end measurement area can be measured by a key dimension scanning electron microscope, thereby obtaining the third or fourth difference of the key dimensions of two adjacent second sub-patterns in the second pattern to be measured.

[0117] In some embodiments, the second offset can be determined by the following step: determining a third difference or a fourth difference as the second offset.

[0118] In this embodiment of the disclosure, when the second pattern to be measured includes only one second intermediate measurement area, the third difference of the key dimension measured through the second intermediate measurement area can be determined as the second offset; or, when the second pattern to be measured includes only one second end measurement area, the fourth difference of the key dimension measured through the second end measurement area can be determined as the second offset.

[0119] Please continue reading Figure 4d As shown, the two adjacent second sub-patterns in the second intermediate measurement area B2 are the second sub-pattern 201-1 and the second sub-pattern 201-2, respectively. The key dimension of the second sub-pattern 201-1 is d7, and the key dimension of the second sub-pattern 201-2 is d8. Therefore, the difference between the key dimensions of the second sub-pattern 201-1 and the second sub-pattern 201-2 is d7-d8. Thus, the second offset can be d7-d8.

[0120] In other embodiments, when the second pattern to be measured includes multiple second end measurement areas, the average, mode, or median of multiple fourth differences determined by two adjacent second sub-patterns in each second end measurement area can be determined as the second offset; or, when the second pattern to be measured includes multiple second intermediate measurement areas, and each second intermediate measurement area includes multiple pairs of adjacent second sub-patterns, the average, mode, or median of multiple third differences determined by any two adjacent second sub-patterns in each second intermediate measurement area can be determined as the second offset.

[0121] In some embodiments, when the second pattern to be measured includes both a second end measurement area and a second middle measurement area, the second offset can also be determined by the following steps: performing a weighted average of the fourth difference and the third difference to obtain the second offset.

[0122] In this embodiment of the disclosure, the second offset obtained by measuring the second end measurement area or the second intermediate measurement area in the second pattern to be measured has different weighting coefficients. For example, the second offset obtained by measuring the second intermediate measurement area has a third weighting coefficient, and the second offset obtained by measuring the second end measurement area has a fourth weighting coefficient. Then, the second offset = (third difference * third weighting coefficient + fourth difference * fourth weighting coefficient) / 2.

[0123] In this embodiment of the disclosure, the third weighting coefficient can be 40% or 90%, and correspondingly, the fourth weighting coefficient can be 60% or 10%. In other embodiments, both the third and fourth weighting coefficients can be 50%.

[0124] In some embodiments, when the second pattern to be measured includes multiple second end measurement areas and multiple second intermediate measurement areas, it is necessary to assign weights to each fourth difference and each third difference, and finally calculate the average to obtain the second offset.

[0125] In some embodiments, the second offset can also be determined by the following steps: dividing the third difference and the fourth difference into equal parts to obtain the third equal-division difference and the fourth equal-division difference; and determining the third equal-division difference or the fourth equal-division difference as the second offset.

[0126] Here, equal division refers to dividing the third or fourth difference into a specific number of equal parts, resulting in the same number of equal parts as the number of equal parts. A predetermined number of these equal parts are then extracted as the third or fourth equal difference. For example, the third or fourth difference can be divided into two equal parts (half a third difference or half a fourth difference), and one half of the third difference can be extracted as the third equal difference; or, one half of the fourth difference can be extracted as the fourth equal difference.

[0127] In this embodiment of the present disclosure, when the area to be measured in the second pattern to be measured includes only one second end measurement area, the fourth division difference value of the key dimension obtained by measuring through the second end measurement area can be determined as the second offset; or, when the area to be measured in the second pattern to be measured includes only one second middle measurement area, the third division difference value of the key dimension obtained by measuring through the second middle measurement area can be determined as the second offset.

[0128] Please continue reading Figure 4d As shown, the two adjacent second sub-patterns in the second intermediate measurement area B2 are the second sub-pattern 201-1 and the second sub-pattern 201-2, respectively. The key dimension of the second sub-pattern 201-1 is d7, and the key dimension of the second sub-pattern 201-2 is d8. Therefore, the difference between the key dimensions of the second sub-pattern 201-1 and the second sub-pattern 201-2 is d7-d8. Thus, the second offset can be (d7-d8) / 2.

[0129] In other embodiments, when the area to be measured in the second pattern to be measured includes multiple second end measurement areas, the average, mode, or median of multiple fourth division differences determined by any two adjacent second sub-patterns in each second end measurement area can be determined as the second offset; or, when the area to be measured in the second pattern to be measured includes multiple second intermediate measurement areas, and each second intermediate measurement area includes multiple pairs of adjacent second sub-patterns, the average, mode, or median of multiple third division differences determined by any two adjacent second sub-patterns in each second intermediate measurement area can be determined as the second offset.

[0130] In some embodiments, when the second pattern to be measured includes both the second end measurement area and the second middle measurement area, the second offset can also be determined by the following steps: performing a weighted average of the third and fourth equal division differences to obtain the second offset.

[0131] In this embodiment, the process of weighting the third and fourth equal division differences is similar to the process of weighting the third and fourth differences in the above embodiment, and will not be repeated here.

[0132] In some embodiments, in the integrated circuit manufacturing process, it is generally necessary to measure the overlay accuracy of the pattern after pattern transfer and after etching to obtain the overlay accuracy during the pattern transfer process and the overlay accuracy during the etching process, respectively, so as to compensate for deviations in subsequent processes and make the subsequent processes meet the process requirements.

[0133] In some embodiments, to achieve more accurate measurement results, the same die is typically selected for measurement in both the ADI and AEI processes.

[0134] Figure 5a and 5b These are schematic diagrams showing the measurement of the overlay accuracy of each wafer after development and etching, respectively, according to embodiments of this disclosure. Figure 5a As shown, a specific number of dies were selected for ADI overlay accuracy measurement. In Figure 5a, directional curves represent the offset and direction of each die. After etching, the same dies sampled in the same manner as during the development process (e.g.,...) were selected. Figure 5b (As shown) to measure the accuracy of the engraving.

[0135] The overlay accuracy measurement method provided in this embodiment of the invention, since the first and second patterns to be measured are located at the edges of the core region in the first and second directions respectively, and the first and second patterns to be measured have the same height, can measure the first offset of the first pattern to be measured in the second direction and the second offset of the second pattern to be measured in the first direction through the first end measurement area of ​​the first pattern to be measured and the second middle measurement area of ​​the second pattern to be measured, respectively, thereby obtaining the overlay accuracy of the first and second patterns to be measured. In this way, the obtained overlay accuracy can be used to correct subsequent processes and improve the yield of integrated circuit fabrication.

[0136] In the several embodiments provided in this disclosure, it should be understood that the disclosed devices and methods can be implemented in a non-target manner. The device embodiments described above are merely illustrative; for example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or components may be combined, or integrated into another system, or some features may be ignored or not executed. In addition, the various components shown or discussed are coupled to each other or directly coupled.

[0137] The features disclosed in the several method or device embodiments provided in this disclosure can be arbitrarily combined without conflict to obtain new method or device embodiments.

[0138] The above are merely some embodiments of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A method for measuring overlay accuracy, characterized in that, The method includes: A semiconductor substrate is provided, on which a core region, a first pattern to be measured located at the edge of the core region along a first direction, and a second pattern to be measured located at the edge of the core region along a second direction are formed; wherein the first pattern to be measured and the second pattern to be measured have the same height; the first pattern to be measured extends along the first direction and includes at least a first end measurement region; the second pattern to be measured extends along the second direction and includes at least a second intermediate measurement region; The first offset of the first pattern to be measured in the second direction is determined by the first end measurement area; The second offset of the second pattern to be measured in the first direction is determined by the second intermediate measurement area; The first end measurement area includes a plurality of first sub-patterns extending along the first direction and arranged along the second direction; determining the first offset of the first pattern to be measured in the second direction includes: Obtain the first difference in the key dimensions of two adjacent first sub-patterns in the first end measurement area to determine the first offset; The first pattern to be measured further includes a third sub-pattern extending along the first direction, and the third sub-pattern is not located in the first end measurement area; the third sub-pattern is arranged alternately with a plurality of the first sub-patterns; The first sub-patterns located adjacent to each other in the first end measurement area are distributed on both sides of the third sub-pattern along the second direction; The first sub-pattern also includes a first intermediate measurement area; The first intermediate measurement area is not adjacent to the third sub-pattern, and the critical dimension of the first sub-pattern located in the first end measurement area is larger than the critical dimension of the first sub-pattern located in the first intermediate measurement area; The second intermediate measurement area includes a plurality of second sub-patterns extending along the second direction and arranged along the first direction; Determining the second offset of the second pattern to be measured in the first direction includes: Obtain the third difference of the key dimensions of two adjacent second sub-patterns in the second intermediate measurement area to determine the second offset; The second pattern to be measured also includes a fourth sub-pattern extending along the second direction, and the fourth sub-pattern is not located in the second intermediate measurement area; The fourth sub-pattern is arranged alternately with multiple second sub-patterns, and the second intermediate measurement area is not adjacent to the fourth sub-pattern; The second pattern to be measured also includes a second end measurement area; The critical dimension of the second sub-pattern located in the second end measurement area is larger than the critical dimension of the second sub-pattern located in the second middle measurement area, and the adjacent second sub-patterns in the second end measurement area are distributed on both sides of the fourth sub-pattern along the first direction.

2. The method according to claim 1, characterized in that, The method further includes: The first offset of the first pattern to be measured in the second direction is determined through the first intermediate measurement area.

3. The method according to claim 2, characterized in that, Determining the first offset of the first pattern to be measured in the second direction includes: Obtain the second difference in the key dimensions of two adjacent first sub-patterns in the first intermediate measurement area to determine the first offset.

4. The method according to claim 3, characterized in that, Determining the first offset of the first pattern to be measured in the second direction includes: The first difference or the second difference is determined as the first offset; or... The first offset is obtained by performing a weighted average on the first difference and the second difference.

5. The method according to claim 4, characterized in that, Determining the first offset of the first pattern to be measured in the second direction includes: The first difference and the second difference are divided into equal parts to obtain the first equal-part difference and the second equal-part difference. The first or second division difference value is determined as the first offset; or... The first offset is obtained by performing a weighted average of the first and second equal division differences.

6. The method according to claim 1, characterized in that, The method further includes: The second offset of the second pattern to be measured in the first direction is determined by the second end measurement area.

7. The method according to claim 6, characterized in that, Determining the second offset of the second pattern to be measured in the first direction includes: Obtain the fourth difference of the key dimensions of two adjacent second sub-patterns in the second end measurement area to determine the second offset.

8. The method according to claim 7, characterized in that, Determining the second offset of the second pattern to be measured in the first direction includes: The third difference or the fourth difference is determined as the second offset; or... The second offset is obtained by performing a weighted average on the third and fourth differences.

9. The method according to claim 8, characterized in that, Determining the second offset of the second pattern to be measured in the first direction includes: The third difference and the fourth difference are divided into equal parts to obtain the third equal-divided difference and the fourth equal-divided difference. The third or fourth division difference value is determined as the second offset; or... The second offset is obtained by performing a weighted average of the third and fourth equal division differences.

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