阅读说明：本技术 光掩膜以及光刻光学式叠对标记测量方法 (Photomask and photoetching optical type overlay mark measuring method ) 是由 不公告发明人 于 2019-01-08 设计创作，主要内容包括：本发明提供一种光掩膜及光刻光学式叠对标记测量方法,用于测量芯片制造过程中不同层之间的叠对偏移量,所述光掩膜包括：斜向单元掩膜图案和斜向叠对掩膜标记,所述斜向单元掩膜图案和所述斜向叠对掩膜标记具有相同的斜向方向。采用所述光掩膜将所述斜向单元掩膜图案和所述斜向叠对掩膜标记刻录到半导体衬底上,在所述半导体衬底上形成斜向单元图案和斜向叠对标记。采用光学方法量测所述半导体衬底上当前层的所述斜向叠对标记相对于先前层的所述斜向叠对标记的叠对偏移量；以及根据所述叠对偏移量将所述当前层与所述先前层对准。根据本发明的光掩膜及光刻光学式叠对标记测量方法,能够对应测量半导体衬底中斜向单元图案的叠对偏移量。(The invention provides a photomask and a photoetching optical type overlay mark measuring method, which are used for measuring overlay offset between different layers in the manufacturing process of a chip, and the photomask comprises: the mask comprises an oblique unit mask pattern and an oblique overlay mask mark, wherein the oblique unit mask pattern and the oblique overlay mask mark have the same oblique direction. And recording the oblique unit mask pattern and the oblique overlay mask mark on a semiconductor substrate by adopting the photomask, and forming the oblique unit pattern and the oblique overlay mark on the semiconductor substrate. Measuring the overlay offset of the oblique overlay mark of the current layer relative to the oblique overlay mark of the previous layer on the semiconductor substrate by adopting an optical method; and aligning the current layer with the previous layer according to the overlay offset. According to the photomask and the photoetching optical type overlay mark measuring method, the overlay offset of the inclined unit pattern in the semiconductor substrate can be correspondingly measured.)

1. A photomask, the photomask is rectangular, comprising:

the oblique unit mask pattern is positioned on the photomask and is not parallel to any side of the photomask;

the oblique overlay mask mark is positioned on the photomask and is not parallel to any side of the photomask.

2. The photomask of claim 1,

the oblique unit mask pattern is parallel to the oblique overlay mask mark.

3. The photomask of claim 1,

the photomask is square.

4. The photomask according to any one of claims 1 to 3,

the photomask comprises a plurality of the oblique unit mask patterns and a plurality of the oblique overlay mask marks.

5. The photomask of claim 4,

the number of the plurality of oblique unit mask patterns is equal to the number of the plurality of oblique overlay mask marks, and the plurality of oblique unit mask patterns and the plurality of oblique overlay mask marks are in a one-to-one parallel relationship.

6. A method for measuring a lithographic optical overlay mark, comprising the steps of:

providing a semiconductor substrate, and forming a previous layer on the semiconductor substrate, wherein the previous layer is provided with oblique overlay marks and unit patterns;

forming a diagonal cell pattern and a diagonal overlay mark on a current layer of the semiconductor substrate using the photomask of any of claims 1 to 5;

measuring an overlay offset of the oblique overlay mark of the current layer relative to the oblique overlay mark of the previous layer by adopting an optical measurement method; and

and performing alignment compensation on the diagonal unit pattern of the current layer relative to the unit pattern of the previous layer according to the overlay offset.

7. The method of claim 6, wherein the previous layer of cell patterns comprises diagonal cell patterns.

8. The lithographic optical overlay mark measurement method of claim 6,

calculating an overlay offset of the diagonal overlay mark of the current layer with respect to a diagonal overlay mark of a previous layer using an optical metrology method comprises:

and establishing a rectangular coordinate system by taking the direction of the oblique overlay mark of the current layer as a reference, and calculating a first overlay offset of the oblique overlay mark of the current layer relative to the oblique overlay mark of the previous layer.

9. The lithographic optical overlay mark measurement method of claim 8, further comprising:

establishing a plurality of rectangular coordinate systems based on the directions of the plurality of oblique overlay marks of the current layer, and calculating a plurality of offsets;

and performing alignment compensation on the diagonal unit pattern of the current layer relative to the unit pattern of the previous layer according to the combination of the plurality of offsets.

10. The lithographic optical overlay mark measurement method of claim 6, further comprising:

forming a subsequent layer on the current layer of the semiconductor substrate, and forming a diagonal overlay mark and a cell pattern in the subsequent layer;

establishing a rectangular coordinate system by taking the direction of the oblique overlay mark of the current layer as a reference, and calculating a second overlay offset of the oblique overlay mark of the subsequent layer relative to the oblique overlay mark of the current layer; and

and performing alignment compensation on the unit pattern of the subsequent layer relative to the oblique unit pattern of the current layer according to the second overlay offset.

11. The lithographic optical overlay mark measurement method of claim 10, further comprising:

establishing a plurality of rectangular coordinate systems based on the directions of the plurality of oblique overlay marks of the current layer, and calculating a plurality of second overlay offsets;

and performing alignment compensation on the unit pattern of the subsequent layer relative to the oblique unit pattern of the current layer according to the combination of the plurality of second overlay offsets.

12. The lithographic optical overlay mark measurement method of claim 10, the cell pattern of the subsequent layer comprising an oblique cell pattern.

Technical Field

The invention relates to the technical field of integrated circuit manufacturing, in particular to a photomask and a photoetching optical type overlay mark measuring method.

Background

In semiconductor manufacturing, a photolithography process is developed as a core technology of each technology generation. The photolithography is a process of transferring a circuit structure in the form of a pattern on a photomask (mask) to the surface of a silicon wafer coated with photoresist through the steps of alignment, exposure, development and the like, the photolithography process can form a layer of photoresist masking pattern on the surface of the silicon wafer, and the subsequent process is etching or ion implantation. In a standard CMOS process, tens of photolithography steps are required, and factors affecting the photolithography process error, in addition to the resolution of the photolithography machine, also have the accuracy of alignment.

Lithography Overlay is used to measure the accuracy of alignment between a lithographic pattern placed on a silicon wafer and a previously defined pattern. Since an integrated circuit is composed of a plurality of layers of circuits overlapped, it is necessary to ensure the alignment accuracy of each layer with the preceding or following layers, and if the alignment accuracy is out of the required range, the whole circuit may not complete the design work. During the manufacturing of each layer, therefore, its alignment accuracy with the previous layer is measured.

One commonly used overlay metrology pattern (Mark) is an optical ibo (Image Based overlay), such as a raster pattern (sometimes referred to as AIM, Advanced Image Measurement). The AIM pattern is shown in fig. 1, the AIM pattern comprises parallel overlay marks (dark color) of a previous layer and parallel overlay marks (light color) of a current layer, a transverse overlay offset amount Δ x and a longitudinal overlay offset amount Δ y are calculated by comparing the positions of the two parallel overlay marks, and when the transverse overlay offset amount Δ x and the longitudinal overlay offset amount Δ y are smaller than a set threshold value, the process is within a safety window.

Disclosure of Invention

Problems to be solved by the invention

Most of the existing photomasks are rectangular, and a plurality of repeated rectangular areas are formed on a semiconductor substrate by projection. It is common practice to determine the alignment of cell patterns between two layers of a semiconductor substrate using parallel overlay marks as shown in fig. 1. Specifically, as shown in fig. 1, a plurality of lateral parallel overlay marks or longitudinal parallel overlay marks are formed at the same position in each layer of the semiconductor substrate in parallel to the sides of the rectangular region, and the parallel overlay marks are identical in shape, size, and interval between them. Obtaining the transverse overlay offset delta x or the longitudinal overlay offset delta y of the two layers by optically measuring the parallel overlay marks of the previous layer and the current layer, and entering the next process when the overlay offset is smaller than a set threshold value and the process is within a safety window; and when the overlay offset is larger than or equal to the set threshold, performing rework. The parallel overlay mark is simple in forming method and convenient to use, and is particularly suitable for the situation that most of unit patterns in a semiconductor substrate are parallel unit patterns.

However, with the development of semiconductor technology, in a rectangular region, it is sometimes necessary to manufacture some cell patterns (hereinafter, referred to as oblique cell patterns) that are oblique to the sides of the rectangular region, for example, cell patterns that are parallel to the diagonal lines of the rectangular region, and in this case, the parallel overlay marks cannot accurately represent the overlay shift amounts of these oblique cell patterns. For example, referring to fig. 2, if the parallel cell pattern (lower dotted rectangle) of the current layer deviates from the parallel cell pattern (lower solid rectangle) of the previous layer to the right, the lateral overlay offset Δ x can be calculated by the parallel overlay mark, and it can be seen that, at this time, only a small portion of the right side of the parallel cell patterns of the two layers is misaligned within the safety process window; on the other hand, if the diagonal cell pattern (middle dotted line rectangle) of the current layer at 45 degrees to the side of the rectangular area is deviated to the right from the diagonal cell pattern (middle solid line rectangle) of the previous layer at 45 degrees to the side of the rectangular area, the lateral overlay deviation amount is also Δ x calculated by the parallel overlay marks, but as can be seen from the figure, the diagonal cell pattern is obviously greatly misaligned between the two layers (three sides of the rectangle are already misaligned), which is already beyond the safety process window, and rework is required. It can be seen that the lateral overlay shift Δ x of the parallel overlay mark in the prior art is not suitable for such diagonal cell patterns, and the longitudinal overlay shift Δ y has the same problem. In particular, as the semiconductor technology is developed, such oblique cell patterns may be more and more numerous and their inclination angles may be different, in which case the determination method of the parallel overlay mark may not be applicable at all to the new semiconductor technology.

Technical scheme for solving problems

The present invention has been made in view of the above problems, and an object of the present invention is to provide a photomask and a method for measuring an overlay mark using a lithography optical system, which can completely cope with an oblique cell pattern in a semiconductor substrate and can select an appropriate oblique overlay mark according to the complexity of the oblique cell pattern in the semiconductor substrate.

In one embodiment of the present invention, there is provided a photomask having a rectangular shape, including: the oblique unit mask pattern is positioned on the photomask and is not parallel to any side of the photomask; the oblique overlay mask mark is positioned on the photomask and is not parallel to any side of the photomask;

as an alternative embodiment of the present invention, the oblique unit mask pattern is parallel to the oblique overlay mask mark.

As an alternative embodiment of the invention, the photomask is square.

As an alternative embodiment of the present invention, the photomask includes a plurality of the oblique unit mask patterns and a plurality of the oblique overlay mask marks.

As an optional embodiment of the present invention, the number of the plurality of oblique unit mask patterns is equal to the number of the plurality of oblique overlay mask marks, and the plurality of oblique unit mask patterns and the plurality of oblique overlay mask marks are in a one-to-one parallel relationship.

As another embodiment of the present invention, there is provided a method for measuring a lithographic optical overlay mark, including the steps of: providing a semiconductor substrate, and forming a previous layer on the semiconductor substrate, wherein the previous layer is provided with oblique overlay marks and unit patterns; forming a diagonal cell pattern and a diagonal overlay mark on a current layer of the semiconductor substrate using the photomask according to any one of the above embodiments; measuring an overlay offset of the oblique overlay mark of the current layer relative to the oblique overlay mark of the previous layer by adopting an optical measurement method; and performing alignment compensation on the diagonal unit pattern of the current layer relative to the unit pattern of the previous layer according to the overlay offset.

As an alternative embodiment of the present invention, the unit pattern of the previous layer includes an oblique unit pattern.

As an optional embodiment of the present invention, calculating an overlay offset of the diagonal overlay mark of the current layer relative to the diagonal overlay mark of the previous layer by using an optical metrology method includes: and establishing a rectangular coordinate system by taking the direction of the oblique overlay mark of the current layer as a reference, and calculating a first overlay offset of the oblique overlay mark of the current layer relative to the oblique overlay mark of the previous layer.

As an optional embodiment of the present invention, the method further comprises: establishing a plurality of rectangular coordinate systems based on the directions of the plurality of oblique overlay marks of the current layer, and calculating a plurality of offsets; and performing alignment compensation on the diagonal unit pattern of the current layer relative to the unit pattern of the previous layer according to the combination of the plurality of offsets.

As an optional embodiment of the present invention, the method further comprises: forming a subsequent layer on the current layer of the semiconductor substrate, and forming a diagonal overlay mark and a cell pattern in the subsequent layer.

As an optional embodiment of the present invention, the method further comprises: establishing a rectangular coordinate system by taking the direction of the oblique overlay mark of the current layer as a reference, and calculating a second overlay offset of the oblique overlay mark of the subsequent layer relative to the oblique overlay mark of the current layer; and performing alignment compensation on the unit pattern of the subsequent layer relative to the oblique unit pattern of the current layer according to the second overlay offset.

As an optional embodiment of the present invention, the method further comprises: establishing a plurality of rectangular coordinate systems based on the directions of the plurality of oblique overlay marks of the current layer, and calculating a plurality of second overlay offsets; and performing alignment compensation on the unit pattern of the subsequent layer relative to the oblique unit pattern of the current layer according to the combination of the plurality of second overlay offsets.

As an alternative embodiment of the present invention, the unit patterns of the subsequent layer include oblique unit patterns.

Effects of the invention

According to the method for measuring the photoetching optical type overlay mark, the corresponding oblique overlay marks can be formed on each layer of the semiconductor substrate aiming at the oblique unit patterns, the oblique overlay marks are not parallel to any side of the rectangular region, and the directions of the oblique overlay marks are the same as or similar to the directions of the oblique unit patterns of the semiconductor substrate, so that the measurement accuracy of the interlayer offset of the semiconductor substrate can be greatly improved, and the layers can be accurately aligned. In addition, the inclination direction and/or the number of the inclined overlay marks can be set by self, and the degree of freedom is greatly increased, so that the semiconductor substrate can be used for the situation that the inclination angles of the inclined unit patterns in the semiconductor substrate are different and the complex situation that the inclined unit patterns in the semiconductor substrate are more.

In addition, a rectangular coordinate system can be established according to the oblique overlay mark, and the overlay offset on the X axis and the Y axis in the coordinate system can be measured by taking the established rectangular coordinate system as a reference, so that the alignment degree can be judged.

In addition, the photomask provided by the invention can form the oblique overlay mark on the semiconductor substrate, and the oblique overlay mark can be used for judging the alignment degree of oblique unit patterns among different layers of the semiconductor substrate and also can be used for judging some non-oblique unit patterns (such as circular unit patterns).

Drawings

Fig. 1 is a schematic view showing interlayer misalignment of a measurement cell pattern using a conventional parallel overlay mark.

Fig. 2 is a comparison diagram showing parallel cell patterns and diagonal cell patterns measured by parallel overlay marks.

FIG. 3 is a schematic view of a photomask according to one embodiment of the present invention.

FIG. 4 is a schematic view of a photomask according to another embodiment of the present invention.

Fig. 5 is a schematic view showing interlayer misalignment of an oblique cell pattern measured by an oblique overlay mark according to an embodiment of the present invention.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention in a schematic manner, and the drawings only show the components related to the present invention rather than the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed arbitrarily, and the layout of the components may be more complicated.

A photomask according to an embodiment of the present invention will be described below with reference to the drawings. The invention provides a photomask, wherein a substrate of the photomask can be a glass plate, the glass plate is provided with a thin film layer, specifically, the thin film layer can be MoSi or a lamination of MoSi and Cr, the thickness is not limited, and an oblique unit mask pattern and an oblique overlapping mask mark can be formed in the thin film layer by utilizing electron beam exposure etching. The photomask is rectangular, and the photomask comprises a dicing street region and a chip region as an example, as shown in fig. 3, the internal rectangular region is the chip region, and the periphery of the internal rectangular region is the dicing street region. The photomask includes: oblique unit mask patterns (e.g., the 4 larger stripe patterns in the internal rectangle in fig. 3) located on the photomask and not parallel to any side of the photomask; obliquely overlapping mask marks (e.g., 4 patterns on the periphery of the inner rectangle in fig. 3) are located on the photomask, and are not parallel to any side of the photomask. The oblique unit mask pattern may be a single stripe pattern, or may be a plurality of parallel stripe patterns (in this embodiment, 4 parallel large stripe patterns), and the position and size of the flat stripe pattern are not limited. The distribution and number of the oblique overlay mask marks are not limited (in this embodiment, there are 4 patterns scattered around the inner rectangle). As an example, as shown in fig. 3, the oblique overlay mask is labeled as an AIM pattern composed of two sets of parallel short lines perpendicular to each other, and any one of the parallel short line sets is composed of several parallel short lines. The parallel short lines are not parallel to any side of the photomask.

Optionally, the oblique unit mask pattern and the oblique overlay mask mark are parallel to each other. The oblique direction of the oblique overlay mask mark is defined by the direction of a rectangular coordinate system established during measurement, in one example, as shown in fig. 3, the oblique overlay mask mark is an AIM pattern, the AIM pattern is composed of two groups of parallel short lines perpendicular to each other, and any one of the parallel short lines is composed of a plurality of parallel short lines. The two mutually perpendicular directions are the X axis and the Y axis of a rectangular coordinate system established in measurement. The oblique unit mask pattern and the oblique overlay mask mark are parallel to each other, and it is understood that any one of an X axis and a Y axis of a rectangular coordinate system established in the measurement is parallel to the direction of the oblique unit mask pattern.

Alternatively, the photomask may be square.

Optionally, the photomask includes a plurality of the oblique unit mask patterns and a plurality of the oblique overlay mask marks. The number and positions of the plurality of oblique unit mask patterns and the plurality of oblique overlay mask marks are not limited. As an example, as shown in fig. 4, the photomask includes two directions of oblique unit mask patterns (e.g., an upper two larger stripe patterns and a lower two larger stripe patterns in an inner rectangular region in the drawing, the stripe patterns having two different directions) and two directions of oblique overlay mask marks (e.g., an upper two patterns and a lower two patterns in a periphery of a central rectangular region in the drawing, the patterns having two different directions), wherein the two directions of oblique unit mask patterns are not parallel to each other, and the two directions of oblique overlay mask marks are not parallel to each other.

Optionally, the number of the plurality of oblique unit mask patterns is equal to the number of the plurality of oblique overlay mask marks, and the plurality of oblique unit mask patterns and the plurality of oblique overlay mask marks are in a one-to-one parallel relationship. As an example, as shown in fig. 4, the photomask includes two directions of oblique unit mask patterns (e.g., an upper two larger stripe patterns and a lower two larger stripe patterns in the inner rectangular region in the drawing, the stripe patterns having two different directions) and two directions of oblique overlay mask marks (e.g., an upper two patterns and a lower two patterns in the periphery of the inner rectangular region in the drawing, the patterns having two different directions), wherein the two directions of oblique unit mask patterns are not parallel to each other, and the two directions of oblique overlay mask marks are not parallel to each other. The two oblique overlay marks and the two oblique unit mask patterns are in one-to-one correspondence parallel relation. Specifically, the two oblique unit mask patterns at the upper part in the internal rectangular region in the drawing are parallel to the two oblique overlapping mask marks at the upper part on the periphery of the internal rectangular region in the drawing, and the two oblique unit mask patterns at the lower part in the internal rectangular region in the drawing are parallel to the two oblique overlapping mask marks at the lower part on the periphery of the internal rectangular region in the drawing.

In this way, when the inclination angles of the oblique unit mask patterns existing in the photomask are substantially the same, as shown in fig. 3, a plurality of oblique overlay mask marks or a single oblique overlay mask mark with a single inclination angle may be set, so that the measurement process may be simplified to some extent; when a plurality of oblique unit mask patterns exist in the photomask and their oblique angles are different, a plurality of oblique overlay mask marks may be disposed such that their oblique angles correspond one-to-one to the plurality of oblique unit mask patterns, as shown in fig. 4, so that the offset of each oblique unit pattern can be accurately measured on the semiconductor substrate even if the plurality of oblique unit mask patterns are not parallel to each other.

In the present invention, the directions and the numbers of the oblique unit mask patterns and the oblique overlay mask marks are not limited to the above-described embodiments, and the directions and the numbers of the oblique unit mask patterns and the oblique overlay mask marks may be freely selected according to actual situations on the basis that the oblique unit mask patterns and the oblique overlay mask marks are not parallel to the sides of the photomask.

The invention also provides a measuring method of the oblique overlay mark. Fig. 5 is a schematic view showing an oblique overlay mark according to an embodiment of the present invention. The method for measuring the photoetching optical overlay mark comprises the following steps.

Providing a semiconductor substrate, and forming a previous layer on the semiconductor substrate, wherein the previous layer is provided with oblique overlay marks and unit patterns. Specifically, the oblique overlay mark and the cell pattern are formed in the semiconductor substrate using a photomask having the oblique overlay mask mark and the cell mask pattern.

Optionally, the unit patterns include oblique unit patterns.

As an example, the oblique cell pattern and the oblique overlay mark are formed on a previous layer of the semiconductor substrate through a photomask of the present invention (e.g., the photomask shown in fig. 3 or fig. 4 described above), where the previous layer may be a first line layer of a double pattern (Doublepattern), and the first line layer includes the oblique cell pattern and the oblique overlay mark.

By adopting the photomask, the inclined unit pattern and the inclined overlay mark are formed on the current layer of the semiconductor substrate. As an example, the current layer may be a second line layer of a double pattern, the second line layer including a diagonal cell pattern and diagonal overlay marks. Specifically, referring to fig. 5, two oblique overlay marks having different colors are oblique overlay marks of a previous layer and a current layer, respectively, and may be designed according to a unit pattern of the layers, for example, if the unit pattern of the layers is a line having an angle of 30 degrees with respect to one side of the semiconductor substrate, an oblique overlay mark having an angle of 30 degrees with respect to the one side of the semiconductor substrate may be formed at an arbitrary position in some layers. These diagonal overlay marks may be exactly the same as or similar to the direction of the diagonal cell patterns of the semiconductor substrate. The oblique overlay mark can sufficiently reflect the offset amount in the oblique direction compared with the existing parallel overlay mark, thereby greatly improving the judgment precision of the dislocation of the oblique unit pattern.

Alternatively, when the inclination angles of the oblique unit patterns existing in the substrate are substantially the same, a plurality of oblique overlay marks or a single oblique overlay mark of a single inclination angle may be provided, so that the measurement process can be simplified to some extent. When the shapes and angles of the plurality of oblique unit patterns are different, a plurality of identical oblique overlay marks may be provided, that is, a plurality of oblique overlay marks and the directions and shapes of the plurality of oblique unit patterns may be provided. Size, etc. in one-to-one correspondence. Thus, all the oblique unit patterns in the layer can be measured, and the measurement accuracy is greatly improved. Specifically, when the inclination angles of the oblique unit patterns existing in the substrate are substantially the same, a photomask of fig. 3 may be used to set a plurality of oblique overlay marks or a single oblique overlay mark of a single inclination angle in the semiconductor substrate layer, so that the measurement process can be simplified to some extent; when a plurality of oblique unit patterns exist in the substrate and the oblique angles of the oblique unit patterns are different, a plurality of oblique overlay marks can be arranged by using the photomask of fig. 4, so that the oblique angles of the oblique unit patterns correspond to the oblique unit patterns one by one, and each oblique unit pattern can be accurately measured even if a plurality of oblique unit patterns with different oblique angles exist in the layer of the substrate.

And measuring the overlay offset of the oblique overlay mark of the current layer relative to the oblique overlay mark of the previous layer by adopting an optical measurement method.

And performing alignment compensation on the diagonal unit pattern of the current layer relative to the unit pattern of the previous layer according to the overlay offset.

Optionally, calculating an overlay offset of the oblique overlay mark of the current layer relative to the oblique overlay mark of the previous layer by using an optical metrology method includes: and establishing a rectangular coordinate system by taking the direction of the oblique overlay mark of the current layer as a reference, and calculating a first overlay offset of the oblique overlay mark of the current layer relative to the oblique overlay mark of the previous layer. As an example, referring to fig. 5, the diagonal overlay marks are AIM patterns composed of two sets of parallel short lines perpendicular to each other, and any one of the parallel short line sets is composed of several parallel short lines. The two mutually perpendicular directions are the directions of the X axis and the Y axis of a rectangular coordinate system established in measurement. And acquiring a first overlay offset of the oblique overlay mark by taking the X axis and the Y axis as references, wherein the overlay offset of the oblique overlay mark can fully and correctly reflect the offset of the oblique unit pattern, so that high-precision alignment can be performed. Specifically, taking the oblique unit pattern in fig. 2 as an example, the oblique unit pattern of the current layer deviates from the oblique unit pattern of the previous layer to the right, and the oblique offset of the oblique unit pattern can be directly and accurately obtained by using the first overlay offset measured by the oblique overlay mark, thereby greatly improving the measurement accuracy of the overlay offset of the oblique unit pattern.

Optionally, a plurality of rectangular coordinate systems may be established based on directions of a plurality of oblique overlay marks of the current layer, a plurality of offsets may be calculated, and the oblique unit pattern of the current layer may be aligned and compensated with respect to the unit pattern of the previous layer according to a combination of the plurality of offsets. The accuracy of the plurality of offsets calculated according to the plurality of rectangular coordinate systems of the plurality of oblique overlay marks is high, so that the previous layer can be aligned with the current layer more accurately according to the combination of the offsets with high accuracy, and the alignment of the oblique unit patterns of all the current layers relative to the unit patterns of the previous layer is ensured.

In addition, a subsequent layer may be formed on the current layer of the semiconductor substrate, a diagonal overlay mark and a unit pattern may be formed in the subsequent layer, a rectangular coordinate system may be established based on a direction of the diagonal overlay mark of the current layer, a second overlay offset amount of the diagonal overlay mark of the subsequent layer with respect to the diagonal overlay mark of the current layer may be calculated, and the unit pattern of the subsequent layer may be aligned and compensated with respect to the diagonal unit pattern of the current layer according to the second overlay offset amount.

As described above, the second overlay offset of the current layer with respect to the subsequent layer can be calculated by using the existing diagonal overlay mark of the current layer and the rectangular coordinate system, so as to perform the alignment compensation between the current layer and the subsequent layer.

In addition, similarly, a plurality of rectangular coordinate systems may be established based on the directions of the plurality of oblique overlay marks of the current layer, a plurality of offsets may be calculated, and the oblique unit pattern of the current layer may be aligned and compensated with respect to the unit patterns of the subsequent layer according to a combination of the plurality of offsets. The accuracy of the plurality of offsets calculated according to the plurality of rectangular coordinate systems of the plurality of oblique overlay marks is high, so that the current layer can be aligned with the subsequent layer more accurately according to the combination of the offsets with high accuracy, and the alignment of the oblique unit patterns of all the current layers relative to the unit patterns of the subsequent layer is ensured.

Optionally, the unit patterns of the subsequent layer include oblique unit patterns.

Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.