阅读说明：本技术 掩膜板和修正套刻精度的方法 (Mask plate and method for correcting alignment precision ) 是由 陶文杰 尹聪 丁凯 游凯 张鹏真 于 2020-12-22 设计创作，主要内容包括：本发明提供了一种掩膜板和修正套刻精度的方法。该掩膜板包括相互分离的第一图形区域和/或第二图形区域,第一图形区域和第二图形区域均包括曝光图形,曝光图形包括：多个曝光单元组,各曝光单元组包括多个曝光单元,各曝光单元组的曝光单元以相同的对称中心呈中心对称设置；平移至相同对称中心的第一图形区域的曝光图形和第二图形区域的曝光图形无重叠。采用上述掩膜板可以在参考层上形成多个第一对准标记图形,并在当前层上形成多个第二对准标记图形,并灵活地获取任意一组或多组未变形的第一对准标记单元和第二对准标记单元的光信号,从而避免了由于掩膜板损伤而导致的对套刻精度测量的影响。(The invention provides a mask plate and a method for correcting alignment precision. The mask plate comprises a first graph area and/or a second graph area which are separated from each other, wherein the first graph area and the second graph area respectively comprise exposure graphs, and the exposure graphs comprise: the exposure unit groups comprise a plurality of exposure units, and the exposure units of the exposure unit groups are arranged in a centrosymmetric manner by the same symmetric center; the exposure pattern of the first pattern region and the exposure pattern of the second pattern region translated to the same center of symmetry do not overlap. By adopting the mask plate, a plurality of first alignment mark patterns can be formed on the reference layer, a plurality of second alignment mark patterns can be formed on the current layer, and optical signals of any one or more groups of undeformed first alignment mark units and second alignment mark units can be flexibly acquired, so that the influence on overlay precision measurement caused by damage of the mask plate is avoided.)

1. A mask plate comprises a first pattern area and/or a second pattern area which are separated from each other, and is characterized in that the first pattern area and the second pattern area both comprise exposure patterns, and the exposure patterns comprise:

the exposure unit groups comprise a plurality of exposure units, and the exposure units of the exposure unit groups are arranged in a central symmetry mode by the same symmetry center;

the exposure pattern of the first pattern region and the exposure pattern of the second pattern region translated to the same center of symmetry do not overlap.

2. A mask according to claim 1, wherein in the exposure pattern of the first pattern region or the exposure pattern of the second pattern region, the exposure units are distributed in a plurality of rows and a plurality of columns in the first direction and the second direction, respectively, and the exposure units located in different exposure unit groups are located in different rows and different columns, respectively.

3. A mask according to claim 2, wherein in the exposure pattern of the first pattern region or the exposure pattern of the second pattern region, the first direction is defined as a Y-axis direction, the second direction is defined as an X-axis, the exposure units are located in four quadrants divided by the X-axis and the Y-axis, each column of the exposure units is distributed along the Y-axis direction, and the number of the exposure units located in each quadrant is the same.

4. A mask according to claim 3, wherein in the first pattern region or the second pattern region, each of the exposure units includes a plurality of exposure regions arranged in an X-axis direction or a plurality of exposure regions arranged in a Y-axis direction.

5. A mask plate according to claim 4, wherein the exposure regions in each of the exposure units in the same quadrant have the same arrangement direction, and the exposure regions in each of the exposure units in different quadrants have different arrangement directions.

6. A mask plate according to claim 4, wherein the adjacent exposure areas in each exposure unit have equal distance.

7. A mask plate according to claim 4, wherein the minimum distance between the exposure areas in adjacent exposure units is H₁Width of the exposure region and the H₁The ratio of (1-4): 1.

8. a method for measuring overlay accuracy is characterized by comprising the following steps:

forming a plurality of first alignment mark patterns on a reference layer of a substrate and a plurality of second alignment mark patterns on a current layer of the substrate using a mask of any one of claims 1 to 7, a first pattern region in the mask for forming the first alignment mark patterns and a second pattern region in the mask for forming the second alignment mark patterns;

dividing the first alignment mark pattern into a plurality of groups of first alignment mark units which are in one-to-one correspondence with the exposure unit groups in the first pattern region, dividing the second alignment mark pattern into a plurality of groups of second alignment mark units which are in one-to-one correspondence with the exposure unit groups in the second pattern region, wherein the number of the first alignment mark units is equal to that of the second alignment mark units, the first alignment mark units in each group are in central symmetry by taking a first central point as a symmetry center, and the second alignment mark units in each group are in central symmetry by taking a second central point as a symmetry center;

and recording the positions of the first central points of any one or more groups of the first alignment mark units on the substrate as first positions, recording the positions of the second central points of any one or more groups of the second alignment mark units on the substrate as second positions, and calculating the overlay error by using the distance between the first positions and the second positions.

9. The method of claim 8, wherein a pitch between adjacent sets of the first alignment mark patterns, a pitch between adjacent sets of the second alignment mark patterns, and a pitch between adjacent first alignment mark patterns and adjacent second alignment mark patterns are equal.

10. The method of claim 8 or 9, wherein the first alignment mark pattern and the second alignment mark pattern are rectangles having the same size.

11. The metrology method of claim 8, wherein the first alignment mark pattern has a first projected pattern on the substrate, the second alignment mark pattern has a second projected pattern on the substrate, the first projected pattern and the second projected pattern are defined in four quadrants separated by an X-axis and a Y-axis, the first projected pattern and the second projected pattern in the same quadrant form a matrix distribution, and the first projected pattern and the second projected pattern in the same quadrant form an axisymmetric arrangement or a centrosymmetric arrangement.

Technical Field

The invention relates to the technical field of photoetching, in particular to a mask plate and a method for correcting alignment precision.

Background

In the manufacturing process of semiconductor devices, a photolithography process is usually required, the photolithography process is a process of transferring a pattern on a mask to the surface of a substrate coated with a photoresist through steps of alignment, exposure, development and the like, and the photolithography process forms a patterned photoresist layer on the surface of the substrate and then performs etching or ion implantation.

The current manufacturing process of semiconductor devices such as NAND memories generally requires tens of photolithography steps, and factors affecting the photolithography process error include the accuracy of alignment in addition to the photolithography machine. Overlay accuracy (OVL) is a measure of the accuracy of the alignment of a lithographic pattern when placed on a substrate with a previously defined pattern. Since a semiconductor device is formed by stacking a plurality of layers of materials, it is necessary to ensure the alignment accuracy of each layer with respect to the preceding layer, which is measured during the manufacturing process of each layer.

Currently, a commonly used overlay accuracy Measurement pattern is an optical ibo (Image Based overlay), and the Measurement pattern is divided into a Box-in-Box (BIB) pattern and a raster pattern (AIM). The AIM pattern generally comprises two periodic structures, wherein one periodic structure is positioned at an anterior layer and is a reference layer pattern, the other periodic structure is positioned at a current layer and is a current layer pattern, and the overlay offset is obtained by calculating the position change of the two periodic structures, so that the overlay accuracy of the current layer relative to the reference layer (the anterior layer) is obtained.

However, for the existing AIM OVL mask, there is a case that the mask may be damaged due to process reasons, for example, damage to the mask caused by a Chemical Mechanical Polishing (CMP) process in a process of manufacturing the mask, and in this case, there is inevitably an error in pattern recognition, thereby affecting measurement of overlay accuracy.

Disclosure of Invention

The invention mainly aims to provide a mask plate and a method for correcting alignment precision, and aims to solve the problem that the measurement of the alignment precision is influenced due to the damage of the mask plate in the prior art.

In order to achieve the above object, according to an aspect of the present invention, there is provided a mask including a first pattern region and/or a second pattern region separated from each other, each of the first pattern region and the second pattern region including an exposure pattern, the exposure pattern including: the exposure unit groups comprise a plurality of exposure units, and the exposure units of the exposure unit groups are arranged in a centrosymmetric manner by the same symmetric center; the exposure pattern of the first pattern region and the exposure pattern of the second pattern region translated to the same center of symmetry do not overlap.

Further, in the exposure pattern of the first pattern region or the exposure pattern of the second pattern region, the exposure units are distributed in a plurality of rows and a plurality of columns along the first direction and the second direction, respectively, and the exposure units located in different exposure unit groups are located in different rows and different columns, respectively.

Furthermore, in the exposure pattern of the first pattern region or the exposure pattern of the second pattern region, the first direction is defined as a Y-axis direction, the second direction is defined as an X-axis, the exposure units are located in four quadrants divided by the X-axis and the Y-axis, each row of the exposure units is distributed along the Y-axis direction, and the number of the exposure units located in each quadrant is the same.

Further, in the first pattern region or the second pattern region, each exposure unit includes a plurality of exposure regions arranged in the X-axis direction or a plurality of exposure regions arranged in the Y-axis direction.

Furthermore, the exposure regions in the exposure units in the same quadrant have the same arrangement direction, and the exposure regions in the exposure units in different quadrants have different arrangement directions.

Further, the adjacent exposure areas in each exposure unit have equal spacing.

Further, the minimum distance between exposure areas in adjacent exposure units is H₁Width of exposure region and H₁The ratio of (1-4): 1.

according to another aspect of the present invention, there is provided a method for measuring overlay accuracy, including: forming a plurality of first alignment mark patterns on a reference layer of a substrate by adopting the mask plate, and forming a plurality of second alignment mark patterns on a current layer of the substrate, wherein the first pattern area in the mask plate is used for forming the first alignment mark patterns, and the second pattern area in the mask plate is used for forming the second alignment mark patterns; dividing the first alignment mark pattern into a plurality of groups of first alignment mark units which are in one-to-one correspondence with the exposure unit groups in the first pattern area, dividing the second alignment mark pattern into a plurality of groups of second alignment mark units which are in one-to-one correspondence with the exposure unit groups in the second pattern area, wherein the number of the first alignment mark units is equal to that of the second alignment mark units, the first alignment mark units of each group are in central symmetry by taking the first central point as a symmetry center, and the second alignment mark units of each group are in central symmetry by taking the second central point as a symmetry center; and recording the position of the first central point of any one or more groups of first alignment mark units on the substrate as a first position, recording the position of the second central point of any one or more groups of second alignment mark units on the substrate as a second position, and calculating the overlay error by using the distance between the first position and the second position.

Further, the pitch between adjacent sets of the first alignment mark patterns, the pitch between adjacent sets of the second alignment mark patterns, and the pitch between adjacent first alignment mark patterns and adjacent second alignment mark patterns are equal.

Further, the first alignment mark pattern and the second alignment mark pattern are rectangles having the same size.

Furthermore, the first alignment mark pattern has a first projection pattern on the substrate, the second alignment mark pattern has a second projection pattern on the substrate, the first projection pattern and the second projection pattern are defined to be located in four quadrants separated by the X axis and the Y axis, the first projection pattern and the second projection pattern located in the same quadrant form a matrix distribution, and the first projection pattern and the second projection pattern located in the same quadrant form an axisymmetric arrangement or a centrosymmetric arrangement.

The technical scheme of the invention is that the mask plate comprises a first graph area and/or a second graph area which are separated from each other, the first graph area and the second graph area respectively comprise exposure graphs which are used for passing through an exposure light source, each exposure graph comprises a plurality of exposure unit groups, each exposure unit group comprises a plurality of exposure units, the exposure units in each exposure unit group are arranged in a central symmetry mode by the same symmetry center, and the exposure graphs of the first graph area and the second graph area which are translated to the same symmetry center are not overlapped. When the mask plate is damaged to cause the projection position of a certain first alignment mark pattern or a second alignment mark pattern to deform, the first alignment mark pattern formed after photoetching is provided with a plurality of groups of first alignment mark units which are in one-to-one correspondence with the exposure unit groups in the first mask plate, the first alignment mark units in different groups are arranged in a staggered manner, the second alignment mark pattern is provided with a plurality of groups of second alignment mark units which are in one-to-one correspondence with the exposure unit groups in the second mask plate, and the second alignment mark units in different groups are arranged in a staggered manner, so that the optical signals of any one group or a plurality of groups of undeformed first alignment mark units and second alignment mark units can be flexibly acquired, therefore, the alignment error is calculated by calculating the positions of the first central point of any group of the first alignment mark units and the second central point of any group of the second alignment mark units on the substrate, and the influence on the alignment precision measurement caused by the damage of the mask plate is avoided.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 is a schematic top view showing an exposure pattern of a first pattern region and an exposure pattern of a second pattern region, which are translated to the same symmetry center, in a mask provided in an embodiment of the present application, wherein the exposure pattern of the first pattern region and the exposure pattern of the second pattern region are located in four quadrants separated by an X axis and a Y axis;

FIG. 2 is a schematic diagram illustrating a top view structure of the first pattern region shown in FIG. 1, wherein the exposure pattern is divided into a plurality of exposure unit groups;

FIG. 3 is a schematic diagram illustrating a top view structure of the second pattern region shown in FIG. 1, wherein the exposure pattern is divided into a plurality of exposure unit groups;

fig. 4 is a schematic top view showing an exposure pattern of a first pattern region and an exposure pattern of a second pattern region, which are translated to the same symmetry center, in another mask provided in the embodiment of the present application, wherein the exposure pattern of the first pattern region and the exposure pattern of the second pattern region are located in four quadrants separated by an X axis and a Y axis;

FIG. 5 is a schematic diagram illustrating a top view structure of the first alignment mark pattern shown in FIG. 4, wherein the exposure pattern is divided into a plurality of exposure unit groups;

FIG. 6 is a schematic diagram illustrating a top view structure of the second alignment mark pattern shown in FIG. 4, wherein the exposure pattern is divided into a plurality of exposure unit groups;

fig. 7 is a schematic top view illustrating a position of a first alignment mark pattern and a second alignment mark pattern on a wafer in a method for correcting overlay accuracy according to an embodiment of the present disclosure, wherein the first alignment mark pattern and the second alignment mark pattern are located in four quadrants separated by an X axis and a Y axis;

FIG. 8 is a schematic diagram illustrating a top view of the first alignment mark pattern shown in FIG. 7, wherein the first alignment mark pattern is divided into a plurality of groups of first alignment mark units;

FIG. 9 is a schematic diagram illustrating a top view of the second alignment mark pattern shown in FIG. 7, wherein the second alignment mark pattern is divided into a plurality of groups of second alignment mark units;

fig. 10 is a schematic top view illustrating a position of a first alignment mark pattern and a second alignment mark pattern on a wafer in another method for correcting overlay accuracy according to an embodiment of the present disclosure, wherein the first alignment mark pattern and the second alignment mark pattern are located in four quadrants separated by an X axis and a Y axis;

FIG. 11 is a schematic diagram illustrating a top view of the first alignment mark pattern shown in FIG. 10, wherein the first alignment mark pattern is divided into a plurality of groups of first alignment mark units;

fig. 12 is a schematic top view illustrating a second alignment mark pattern shown in fig. 10, wherein the second alignment mark pattern is divided into a plurality of groups of second alignment mark units.

Wherein the figures include the following reference numerals:

10. a first graphic region; 101. a first exposure region; 110. a first exposure unit group; 111. a first exposure unit; 20. a second graphic region; 201. a second exposure region; 210. a second exposure unit group; 211. a second exposure unit; 30. a first alignment mark pattern; 310. a first alignment mark unit; 40. a second alignment mark pattern; 410. and a second alignment mark unit.

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged under appropriate circumstances in order to facilitate the description of the embodiments of the invention herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

As described in the background art, there is a situation in the prior art that the mask may be damaged due to a process reason, for example, the damage to the mask caused by a chemical mechanical polishing CMP process in a process of manufacturing the mask, and this situation inevitably causes an error in pattern recognition, thereby affecting measurement of overlay accuracy.

The inventors of the present invention have studied in view of the above problems, and have proposed a mask plate, as shown in fig. 1 to 6, including a first pattern region 10 and/or a second pattern region 20 that are separated from each other, each of the first pattern region 10 and the second pattern region 20 including an exposure pattern, the exposure pattern including: the exposure unit groups comprise a plurality of exposure units, and the exposure units of the exposure unit groups are arranged in a centrosymmetric manner by the same symmetric center; the exposure pattern of the first pattern region 10 and the exposure pattern of the second pattern region 20, which are shifted to the same center of symmetry, do not overlap.

It should be noted that the first pattern region 10 and the second pattern region 20 may be different exposure regions in the same mask, or may be exposure regions in different masks.

The mask plate can be adopted to form a plurality of first alignment mark patterns on the reference layer, and a plurality of second alignment mark patterns are formed on the current layer, the complementary exposure patterns can ensure that the second alignment mark patterns and the projection positions of the first alignment mark patterns on the wafer do not overlap, the first alignment mark patterns formed after photoetching are provided with a plurality of groups of first alignment mark units which are in one-to-one correspondence with the exposure unit groups in the first mask plate, the first alignment mark units positioned in different groups are arranged in a staggered mode, the second alignment mark patterns are provided with a plurality of groups of second alignment mark units which are in one-to-one correspondence with the exposure unit groups in the second mask plate, the second alignment mark units positioned in different groups are arranged in a staggered mode, when one first alignment mark pattern or one second alignment mark pattern is deformed due to damage of the mask plate, the optical signals of any one group or more groups of undeformed first alignment mark units and second alignment mark units can be flexibly obtained, therefore, the alignment error is calculated by calculating the positions of the first central point of any group of the first alignment mark units and the second central point of any group of the second alignment mark units on the substrate, and the influence on the alignment precision measurement caused by the damage of the mask plate is avoided.

Exemplarily, as shown in fig. 2 and 5, in the first pattern region 10, a plurality of exposure unit groups included in the exposure pattern are first exposure unit groups 110, each first exposure unit group 110 includes a plurality of first exposure units 111, and the first exposure units 111 of each first exposure unit group 110 are arranged in central symmetry with the same center of symmetry; as shown in fig. 3 and 6, in the second pattern region 20, the plurality of exposure unit groups included in the exposure pattern are second exposure unit groups 210, each of the second exposure unit groups 210 includes a plurality of second exposure units 211, and the second exposure units 211 of each of the second exposure unit groups 210 are arranged in central symmetry with the same center of symmetry.

In a preferred embodiment, in the exposure pattern of the different pattern regions (the first pattern region 10 or the second pattern region 20), the exposure units are distributed in a plurality of rows and a plurality of columns along the first direction and the second direction, respectively, the exposure units located in different exposure unit groups are located in different rows and different columns, respectively, and the first direction and the second direction have an angle therebetween, as shown in fig. 4 to 6.

In the above preferred embodiment, by respectively locating the exposure units in different exposure unit groups in the mask plate in different columns, it is possible to avoid simultaneously acquiring optical signals of adjacent exposure units in different groups, so that when a certain first alignment mark pattern or second alignment mark pattern is deformed due to damage of the mask plate, the optical signals of any group of undeformed first alignment mark units and second alignment mark units can be more flexibly acquired, and then the overlay error is calculated by calculating the positions of the acquired first center point of any group of first alignment mark units and the acquired second center point of any group of second alignment mark units on the substrate.

In the exposure pattern of the first pattern region 10 or the exposure pattern of the second pattern region 20, which defines the first direction as the Y-axis direction and the second direction as the X-axis, the exposure units may be located in four quadrants divided by the X-axis and the Y-axis, and each column of the exposure units is distributed along the Y-axis direction. Exemplarily, as can be seen in fig. 1 to 4, the first exposure unit 111 and the second exposure unit 211 are each independently located in four quadrants partitioned by the X axis and the Y axis, and each column of the first exposure unit 111 and each column of the second exposure unit 211 are distributed in the Y axis direction. In order to enable acquisition of light signals of uniform intensity by each exposure unit group, it is preferable that the number of exposure units located in each quadrant be the same.

In order to facilitate the fabrication of a mask, it is preferable that each of the exposure units includes a plurality of exposure regions arranged in an X-axis direction or a plurality of exposure regions arranged in a Y-axis direction in the first pattern region 10 or the second pattern region 20. Illustratively, as shown in fig. 2 and 5, in the first pattern region 10, each of the first exposure units 111 includes a plurality of first exposure regions 101 arranged in the X-axis direction or a plurality of first exposure regions 101 arranged in the Y-axis direction; as shown in fig. 3 and 6, in the second pattern region 20, each of the second exposure units 211 includes a plurality of second exposure regions 201 arranged in the X-axis direction or a plurality of second exposure regions 201 arranged in the Y-axis direction.

More preferably, the exposure regions in the exposure units located in the same quadrant have the same arrangement direction, and the exposure regions in the exposure units located in different quadrants have different arrangement directions. For example, as shown in fig. 2 and 5, in the first pattern area 10, the first exposure areas 101 in the respective first exposure units 111 located in different quadrants have different arrangement directions; as shown in fig. 3 and 6, in the second pattern area 20, the second exposure areas 201 in the second exposure units 211 located in different quadrants have different arrangement directions.

More preferably, the adjacent exposure areas in each exposure unit are equally spaced. The exposure regions of the first pattern region 10 and/or the second pattern region 20, which are disposed at an equal interval, enable a mask manufacturing process to be simpler.

The minimum distance between the exposure areas in adjacent exposure units is H₁Width of exposure region and H₁The ratio of (1-4): 1. the overlay accuracy of the measurement can be further improved by increasing the number of exposure regions in the first pattern region 10 and/or the second pattern region 20 and reducing the pitch.

According to another aspect of the present invention, there is also provided a method of correcting overlay accuracy, comprising:

forming a plurality of first alignment mark patterns on a reference layer of a substrate by adopting the mask plate, and forming a plurality of second alignment mark patterns on a current layer of the substrate, wherein a first pattern area 10 in the mask plate is used for forming the first alignment mark patterns, and a second pattern area 20 in the mask plate is used for forming the second alignment mark patterns;

dividing the first alignment mark pattern into a plurality of groups of first alignment mark units which are in one-to-one correspondence with the exposure unit groups in the first pattern area 10, and dividing the second alignment mark pattern into a plurality of groups of second alignment mark units which are in one-to-one correspondence with the exposure unit groups in the second pattern area 20, wherein the number of the first alignment mark units is equal to that of the second alignment mark units, each group of the first alignment mark units is in central symmetry by taking the first central point as a symmetry center, and each group of the second alignment mark units is in central symmetry by taking the second central point as a symmetry center;

and recording the position of the first central point of any one or more groups of first alignment mark units on the substrate as a first position, recording the position of the second central point of any one or more groups of second alignment mark units on the substrate as a second position, and calculating the overlay error by using the distance between the first position and the second position.

By adopting the method for correcting the overlay accuracy, when a certain first alignment mark pattern or second alignment mark pattern is deformed due to damage of the mask plate, the positions of the first central points of any one or more groups of first alignment mark units and the second central points of any one or more groups of second alignment mark units on the wafer can be flexibly selected to calculate the overlay error, so that the influence on the overlay accuracy measurement due to damage of the mask plate is avoided.

An exemplary embodiment of a method of correcting overlay accuracy provided in accordance with the present invention will be described in more detail below with reference to fig. 7-12. These exemplary embodiments may, however, be embodied in many different forms and should not be construed as limited to only the embodiments set forth herein. It should be understood that these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of these exemplary embodiments to those skilled in the art.

Since the exposure pattern of the first pattern region 10 and the exposure pattern of the second pattern region 20 translated to the same center of symmetry do not overlap, the projection positions of the first alignment mark pattern 30 and the second alignment mark pattern 40 on the substrate do not overlap.

To obtain the positions of the first and second alignment mark patterns 30 and 40 on the substrate, i.e., the first and second positions, respectively, in order to calculate the overlay error using the distances between the first and second positions, it may be defined that the first and second alignment mark patterns 30 and 40 are located in four quadrants divided by the X-axis and the Y-axis, as shown in fig. 7 and 10.

In a preferred embodiment, the first pattern region 10 and the second pattern region 20 are independently located in two masks, wherein the exposure pattern in one mask is used to provide a reference alignment pattern, the reference layer of the wafer is subjected to photolithography by using the mask to form a plurality of first alignment mark patterns 30 on the reference layer, the exposure pattern in the other mask is used to provide a current alignment pattern, the current layer of the wafer is subjected to photolithography by using the mask to form a plurality of second alignment mark patterns 40 on the current layer, and the second alignment mark patterns 40 are not overlapped with the projection positions of the first alignment mark patterns 30 on the substrate, as shown in fig. 7 and 10. The two masks may also have a body pattern for forming a channel or a via hole in the semiconductor device.

In another preferred embodiment, the first pattern region 10 and the second pattern region 20 are located in the same mask, the exposure pattern in the first pattern region 10 is used to provide a reference alignment pattern, a reference layer of the wafer is subjected to photolithography using the first pattern region 10 in the mask to form a plurality of first alignment mark patterns 30 on the reference layer, the exposure pattern in the second pattern region 20 is used to provide a current alignment pattern, a current layer of the wafer is subjected to photolithography using the second pattern region 20 in the mask to form a plurality of second alignment mark patterns 40 on the current layer, and the second alignment mark patterns 40 do not overlap with the projection positions of the first alignment mark patterns 30 on the substrate. The mask may further have a body pattern for forming a channel or a via hole in the semiconductor device.

For example, the first alignment mark patterns 30 are divided into a plurality of groups of first alignment mark cells 310 corresponding to the first exposure unit groups 110 one by one, as shown in fig. 8 and 11, and the second alignment mark patterns 40 are divided into a plurality of groups of second alignment mark cells 410 corresponding to the second exposure unit groups 210 one by one, as shown in fig. 9 and 12, the first alignment mark patterns 30 of the respective groups of first alignment mark cells 310 located in the diagonal quadrants are centrally symmetric with respect to the first center point as the symmetry center, and the second alignment mark patterns 40 of the respective groups of second alignment mark cells 410 located in the diagonal quadrants are centrally symmetric with respect to the second center point as the symmetry center, it is understood that the first center point and the second center point do not refer to the symmetry center of a single pattern in the conventional sense.

In a preferred embodiment, the number of the first exposure units 111 in each quadrant is the same, and the number of the second exposure units 211 in each quadrant is the same, so that the number of the first alignment mark patterns 30 in each quadrant is the same, and the number of the second alignment mark patterns 40 in each quadrant is the same. By respectively setting the number of the first alignment mark patterns 30 and the number of the second alignment mark patterns 40 in each quadrant to be the same, it can be ensured that any one group of the first alignment mark units 310 and the second alignment mark units 410 can be selected, and the number of the first alignment mark patterns 30 and the number of the second alignment mark patterns 40 can be set to be the same, so that the calculated overlay error between the first center point of the first alignment mark unit 310 and the second center point of the second alignment mark unit 410 is more accurate.

The first alignment mark pattern 30 and the second alignment mark pattern 40 may be rectangles having the same size, as shown in fig. 7 to 12. Preferably, the aspect ratio of the first alignment mark pattern 30 and the second alignment mark pattern 40 is 3 to 30: 1. the above aspect ratio range enables the same number of first and second alignment mark patterns 30 and 40 to be distributed in a smaller area while ensuring image recognition accuracy.

In a preferred embodiment, the minimum distance between the first exposure regions 101 in adjacent first exposure units 111 in the mask is H₁Width and H of the first exposure region 101₁The ratio of (1-4): 1, the minimum distance between the first alignment mark patterns 30 in each adjacent set of first alignment mark units 310 is H₁The width of the first alignment mark pattern 30 and H₁The ratio of (1-4): 1, the minimum distance between the second exposure areas 201 in the adjacent second exposure units 211 in the mask plate is H₁Width and H of the second exposure region 201₁The ratio of (1-4): 1, the minimum distance between the second alignment mark patterns 40 in each adjacent group of the second alignment mark units 410 is H₂The width and H of the second alignment mark pattern 40₂The ratio of (1-4): 1. the overlay accuracy of the measurement is improved by increasing the number of the first and second alignment mark patterns 30 and 40 and decreasing the pitch.

In a preferred embodiment, the pitch between adjacent sets of first alignment mark patterns 30, the pitch between adjacent sets of second alignment mark patterns 40, and the pitch between adjacent first alignment mark patterns 30 and second alignment mark patterns 40 are equal.

The first alignment mark pattern 30 has a first projected pattern on the substrate, and the second alignment mark pattern 40 has a second projected pattern on the substrate, defining that the first projected pattern and the second projected pattern are located in four quadrants divided by the X-axis and the Y-axis, preferably, the first projected pattern and the second projected pattern located in the same quadrant form a matrix distribution, and the first projected pattern and the second projected pattern located in the same quadrant form an axisymmetric arrangement or a centrosymmetric arrangement.

The method for correcting the overlay accuracy according to the present invention will be further described with reference to the following examples.

Examples

The above embodiment provides a method for correcting overlay accuracy, including the following steps:

providing a first mask plate with a first pattern area 10, wherein the first pattern area 10 is used for forming a reference alignment pattern, photoetching is carried out on a reference layer of a wafer by adopting the first mask plate so as to form a plurality of first alignment mark patterns 30 on the reference layer, a second mask plate with a second pattern area 20 is provided, the second pattern area 20 is used for forming a current alignment pattern, photoetching is carried out on the current layer of the wafer by adopting the second mask plate so as to form a plurality of second alignment mark patterns 40 on the current layer, and the projection positions of the second alignment mark patterns 40 and the first alignment mark patterns 30 on the wafer are not overlapped;

acquiring the positions of the first alignment mark pattern 30 and the second alignment mark pattern 40 on the wafer, respectively, and defining that the first alignment mark pattern 30 and the second alignment mark pattern 40 are located in four quadrants separated by the X axis and the Y axis, as shown in fig. 10;

the first alignment mark patterns 30 are divided into two groups of first alignment mark units 310, and the first alignment mark patterns 30 in the dotted lines are A₁The first alignment mark pattern 30 outside the dotted line is set as B₁Set, example 1 is shown in figure 2 and example 2 is shown in figure 5;

the second alignment mark patterns 40 are divided into two groups of second alignment mark units 410, the second alignment mark pattern 40 in the dotted line is A₂The second alignment mark pattern 40 outside the dotted line is set as B₂Group, example 1 is as shown in FIG. 3Example 2 is shown in fig. 6;

when A is₁When the first alignment mark patterns 30 in the set are defective due to damage of the first mask, B is used₁First center point and a of first alignment mark unit 310 of the group₂Group B or B₂Calculating an overlay error at a position of a second center point of the second alignment mark unit 410 of the group on the wafer;

when B is present₁When the first alignment mark patterns 30 in the set are defective due to damage of the first mask, a is used₁First center point and a of first alignment mark unit 310 of the group₂Group B or B₂Calculating an overlay error at a position of a second center point of the second alignment mark unit 410 of the group on the wafer;

when A is₂When the second alignment mark pattern 40 in the group has a defect due to damage of the second mask, the method A is used₁Group B or B₁First center point and B of first alignment mark unit 310 of the group₂Calculating an overlay error at a position of a second center point of the second alignment mark unit 410 of the group on the wafer;

when B is present₂When the second alignment mark pattern 40 in the group has a defect due to damage of the second mask, the method A is used₁Group B or B₁First center point and a of first alignment mark unit 310 of the group₂The overlay error is calculated from the position of the second center point of the second alignment mark unit 410 of the group on the wafer.

From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:

by adopting the method for correcting the overlay accuracy, when a certain first alignment mark pattern or second alignment mark pattern is deformed due to damage of the mask plate, the positions of the first central points of any one or more groups of first alignment mark units and the second central points of any one or more groups of second alignment mark units on the wafer can be flexibly selected to calculate the overlay error, so that the influence on the overlay accuracy measurement due to damage of the mask plate is avoided.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.