阅读说明：本技术 一种套刻精度量测标记及其使用方法 (Overlay precision measurement mark and use method thereof ) 是由 刘必秋 于 2020-06-24 设计创作，主要内容包括：本发明提供一种套刻精度量测标记及其使用方法,本发明针对光刻当层,利用DBO衍射量测的特征,同时IBO量测图形不参与衍射结果,相对于传统的IBO量测具有更高的精准度和准确度；在刻蚀后,利用IBO量测标记可以表征刻蚀后套刻精度的性能,弥补DBO量测标记在刻蚀后无法量测的缺点。本发明的套刻精度量测标记不仅可以满足光刻当层套刻精度的检查要求且可以得到刻蚀后相应的套刻精度的测试结果,节省了器件空间,而提供了不同工艺过程中套刻精度测试需求。(The invention provides an overlay accuracy measurement mark and a using method thereof, aiming at a photoetching layer, the invention utilizes the characteristic of DBO diffraction measurement, and meanwhile, an IBO measurement graph does not participate in a diffraction result, so that the overlay accuracy measurement mark has higher accuracy and precision compared with the traditional IBO measurement; after etching, the performance of alignment precision after etching can be represented by using the IBO measurement mark, and the defect that the DBO measurement mark cannot be measured after etching is overcome. The overlay accuracy measuring mark of the invention can not only meet the inspection requirement of the overlay accuracy of the current layer of photoetching, but also obtain the corresponding test result of the overlay accuracy after etching, thereby saving the space of devices and providing the test requirement of the overlay accuracy in different process flows.)

1. An overlay accuracy measurement mark, comprising:

the front layer graphic mark and the current layer graphic mark;

the front layer graphic mark and the current layer graphic mark both comprise a central graphic and a peripheral graphic surrounding the periphery of the central graphic; the central graph and the peripheral graph are respectively composed of a plurality of grating units; each grating unit comprises a plurality of line structures which are arranged in parallel and have the same number, and the adjacent line structures in each grating unit have the same distance;

the grating units in the central pattern in the front layer and current layer pattern marks are the same in number and have the same arrangement; wherein the central patterns in the front layer pattern mark and the current layer pattern mark are in an overlapping distribution shape and have displacement deviation; the central patterns in the front layer pattern mark and the current layer pattern mark are used for measuring the photoetching current layer overlay accuracy based on the optical diffraction principle;

the grating units in the peripheral graph in the front-layer graph mark and the current-layer graph mark are the same in number and are symmetrically distributed around the central graph; and peripheral patterns in the front layer pattern mark and the current layer pattern mark are used for measuring the alignment precision after etching on the basis of an image principle.

2. The overlay accuracy measurement mark according to claim 1, wherein: the number of the line structures in each grating unit is more than or equal to three.

3. The overlay accuracy measurement mark according to claim 1, wherein: the number of the grating units in the central graph marked by the front-layer graph and the current-layer graph is four.

4. The overlay accuracy measurement mark according to claim 3, wherein: and the four grating units in the central graph are distributed according to the upper left position, the upper right position, the lower left position and the lower right position.

5. The overlay accuracy measurement mark according to claim 4, wherein: in the four grating units in the central graph, the line structures in the grating units positioned at the upper left position and the lower right position are vertically arranged; the line structures in the grating units positioned at the upper right position and the lower left position are horizontally arranged.

6. The overlay accuracy measurement mark according to claim 5, wherein: the number of the grating units in the peripheral graph marked by the front-layer graph and the current-layer graph is four.

7. The overlay accuracy measurement mark according to claim 6, wherein: the four grating units in the peripheral graph in the front-layer graph mark are respectively positioned right above the grating unit at the upper left position, right side of the grating unit at the upper right position, left side of the grating unit at the lower left position and right below the grating unit at the lower right position in the central graph in the front-layer graph mark.

8. The overlay accuracy measurement mark according to claim 7, wherein: the four grating units in the peripheral graph in the current-layer graph mark are respectively positioned on the left side of the grating unit at the upper left position, the right upper side of the grating unit at the upper right position, the right lower side of the grating unit at the lower left position and the right side of the grating unit at the lower right position in the central graph in the current-layer graph mark.

9. The overlay accuracy measurement mark according to claim 1, wherein: the width of a line structure of the grating unit in the central graph in the front-layer graph mark is wa 1; the width of the line structure of the raster unit in the central pattern in the current-layer pattern mark is wa 2; the minimum distance between the central pattern and the peripheral pattern is wab, and wab > 3 max (wa1, wa 2).

10. The overlay accuracy measurement mark according to claim 1, wherein: a peripheral pattern in the front layer pattern mark, wherein the width of the line structure in each grating unit is wb 1; the width of the line structure in each grating unit of the peripheral pattern in the current-layer pattern mark is wb2, wb1 ═ wb 2.

11. The overlay accuracy measurement mark according to claim 10, wherein: the width wb1 or wb2 of the line structure in each grating unit of the peripheral patterns in the front layer, current layer pattern mark is greater than 3 max (wa1, wa 2).

12. The method of using an overlay accuracy measurement mark according to any one of claims 1 to 11, comprising at least the following steps:

placing the overlay precision measuring mark with the required size on a product according to the design requirement of the product;

secondly, after photoetching exposure, confirming the performance of photoetching current-layer overlay accuracy by using the central patterns in the front-layer pattern mark and the current-layer pattern mark on the basis of an optical diffraction principle;

and step three, after etching, measuring the alignment precision by utilizing the peripheral patterns in the front layer pattern mark and the current layer pattern mark based on the image principle.

Technical Field

The invention relates to the technical field of semiconductors, in particular to an alignment precision measurement mark and a using method thereof.

Background

The development of semiconductor technology is often limited to the development of photolithography, and the reduction of feature size places more stringent requirements on the overlay accuracy (OVL) of silicon wafers. If the overlay accuracy between the photo-etching layers does not meet the requirement of the design criteria, the function of the front-stage device and the function of the rear-stage connecting line are failed, and the yield loss of the product is directly caused. The alignment precision requirement of the photoetching process is in direct proportion to the technical node of the semiconductor process, namely, higher technical nodes require more accurate alignment precision. After the 28nm technology node is entered, the photoetching alignment precision requirement of photoetching key layers such as a grid layer (Poly) and a Contact hole layer (Contact) reaches 6 nm, and the higher requirement is provided for measuring the alignment precision while the limit of photoetching machines and process capability is basically challenged.

The traditional overlay accuracy measuring method based on image processing mainly adopts a standard optical microscope system under a bright field, and a white light source is used in the measuring process and automatic focusing is carried out through an interferometer. The IBO consists of an inner layer structure and an outer layer structure which respectively represent a front layer or a current layer. The pattern is characterized by adopting a grating structure of periodic lines (lines) and spaces (spaces). The central positions of the previous layer and the current layer are obtained by acquiring images and calculating, so that corresponding displacement deviation is obtained and decomposed into X and Y directions. Compared with the traditional IBO measuring mark, the DBO utilizes the optical diffraction principle to obtain better measuring precision and accuracy of the graph, and can more accurately represent the performance of the overlay precision of the front layer and the rear layer of the current layer of the product.

Because of the influence of etching and other processes, the alignment precision of the current photoetching layer and the alignment precision after etching have certain difference, and the influence of the difference on the alignment precision of an actual product is higher and larger along with the requirement of the alignment precision, so that the process enters the process of 28nm and below, the alignment precision measured by the current photoetching layer is required to be confirmed, the performance of the alignment precision of the layers before and after etching is required to be known, the measurement of the alignment precision of an etching area is used for feeding back in a current layer exposure program, the actual current layer (after etching) alignment precision performance is better and more aligned, but because a DBO measurement mark is sensitive to a bottom layer structure, the DBO measurement mark is only suitable for the measurement of the current photoetching layer, and an accurate measurement result cannot be obtained after etching. The performance of the alignment precision after etching cannot be obtained by singly utilizing the DBO measurement mark in the traditional technology, which is not beneficial to the characterization and optimization of the alignment precision of more advanced processes.

The conventional design is that the IBO (image Based overlay) overlay accuracy mark design can be used for measuring the overlay accuracy after the photolithography exposure and etching, but the measurement accuracy and accuracy are inferior to those of the DBO and CDSEM marks, or the IBO and CDSEM overlay accuracy marks are used respectively, but the IBO and CDSEM overlay accuracy marks occupy too much layout space, which is not beneficial to saving the device cost.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present invention is to provide an overlay accuracy measurement mark and a measurement method, which are used to solve the problems of poor accuracy of overlay accuracy measurement, large occupied space of the measurement mark, and increased production cost in the prior art.

To achieve the above and other related objects, the present invention provides an overlay accuracy measurement mark, at least comprising:

the front layer graphic mark and the current layer graphic mark;

the front layer graphic mark and the current layer graphic mark both comprise a central graphic and a peripheral graphic surrounding the periphery of the central graphic; the central graph and the peripheral graph are respectively composed of a plurality of grating units; each grating unit comprises a plurality of line structures which are arranged in parallel and have the same number, and the adjacent line structures in each grating unit have the same distance;

the grating units in the central pattern in the front layer and current layer pattern marks are the same in number and have the same arrangement; wherein the central patterns in the front layer pattern mark and the current layer pattern mark are in an overlapping distribution shape and have displacement deviation; the central patterns in the front layer pattern mark and the current layer pattern mark are used for measuring the photoetching current layer overlay accuracy based on the optical diffraction principle;

the grating units in the peripheral graph in the front-layer graph mark and the current-layer graph mark are the same in number and are symmetrically distributed around the central graph; and peripheral patterns in the front layer pattern mark and the current layer pattern mark are used for measuring the alignment precision after etching on the basis of an image principle.

Preferably, the number of line structures in each grating unit is greater than or equal to three.

Preferably, the number of the grating units in the central pattern marked by the front layer and the current layer patterns is four.

Preferably, the four grating units in the central graph are distributed according to upper left, upper right, lower left and lower right positions.

Preferably, among the four grating units in the central graph, the line structures in the grating units located at the upper left position and the lower right position are vertically arranged; the line structures in the grating units positioned at the upper right position and the lower left position are horizontally arranged.

Preferably, the number of the grating units in the peripheral pattern marked by the front layer pattern and the current layer pattern is four.

Preferably, four grating units in the peripheral pattern in the front layer pattern mark are respectively located right above the grating unit at the upper left position, right side of the grating unit at the upper right position, left side of the grating unit at the lower left position, and right below the grating unit at the lower right position in the central pattern in the front layer pattern mark.

Preferably, the four grating units in the peripheral pattern in the current-layer pattern mark are respectively located on the left side of the grating unit at the upper left position, on the right top of the grating unit at the upper right position, on the right bottom of the grating unit at the lower left position, and on the right side of the grating unit at the lower right position in the central pattern in the current-layer pattern mark.

Preferably, the width of the line structure of the grating unit in the central pattern in the front layer pattern mark is wa 1; the width of the line structure of the raster unit in the central pattern in the current-layer pattern mark is wa 2; the minimum distance between the central pattern and the peripheral pattern is wab, and wab > 3 max (wa1, wa 2).

Preferably, the peripheral pattern in the front layer pattern mark has a width wb1 of the line structure in each grating unit; the width of the line structure in each grating unit of the peripheral pattern in the current-layer pattern mark is wb2, wb1 ═ wb 2.

Preferably, the width wb1 or wb2 of the line structure in each grating unit of the peripheral pattern in the front layer, current layer pattern mark is greater than 3 × max (wa1, wa 2).

The invention also provides a using method of the overlay accuracy measuring mark, which at least comprises the following steps:

placing the overlay precision measuring mark with the required size on a product according to the design requirement of the product;

secondly, after photoetching exposure, confirming the performance of photoetching current-layer overlay accuracy by using the central patterns in the front-layer pattern mark and the current-layer pattern mark on the basis of an optical diffraction principle;

and step three, after etching, measuring the alignment precision by utilizing the peripheral patterns in the front layer pattern mark and the current layer pattern mark based on the image principle.

As described above, the overlay accuracy measurement mark and the using method thereof of the present invention have the following beneficial effects: aiming at a photoetching current layer, the characteristic of DBO diffraction measurement is utilized, meanwhile, an IBO measurement graph does not participate in a diffraction result, and the accuracy and the precision are higher compared with those of the traditional IBO measurement; after etching, the performance of alignment precision after etching can be represented by using the IBO measurement mark, and the defect that the DBO measurement mark cannot be measured after etching is overcome. The overlay accuracy measuring mark of the invention can not only meet the inspection requirement of the overlay accuracy of the current layer of photoetching, but also obtain the corresponding test result of the overlay accuracy after etching, thereby saving the space of devices and providing the test requirement of the overlay accuracy in different process flows.

Drawings

FIG. 1 is a schematic diagram of a front layer graphic indicia of the present invention;

FIG. 2 is a schematic diagram of a current layer graphic mark according to the present invention;

fig. 3 is a schematic view showing the overlay of the graphic indicia of the previous and current layers 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.

Please refer to fig. 1 to 3. It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to 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 freely, and the layout of the components may be more complicated.

The invention provides an overlay accuracy measuring mark, at least comprising: the front layer graphic mark and the current layer graphic mark; the front layer graphic mark and the current layer graphic mark both comprise a central graphic and a peripheral graphic surrounding the periphery of the central graphic; the central graph and the peripheral graph are respectively composed of a plurality of grating units; each grating unit comprises a plurality of line structures which are arranged in parallel and have the same number, and the adjacent line structures in each grating unit have the same distance; the grating units in the central pattern in the front layer and current layer pattern marks are the same in number and have the same arrangement; wherein the central patterns in the front layer pattern mark and the current layer pattern mark are in an overlapping distribution shape and have displacement deviation; the central patterns in the front layer pattern mark and the current layer pattern mark are used for measuring the photoetching current layer overlay accuracy based on the optical diffraction principle; the grating units in the peripheral graph in the front-layer graph mark and the current-layer graph mark are the same in number and are symmetrically distributed around the central graph; and peripheral patterns in the front layer pattern mark and the current layer pattern mark are used for measuring the alignment precision after etching on the basis of an image principle.

In this embodiment, the overlay accuracy measurement mark is as shown in fig. 1 to 3, wherein fig. 1 is a schematic diagram of a front layer graphic mark according to the present invention; FIG. 2 is a schematic diagram of a current layer graphic mark according to the present invention; fig. 3 is a schematic view showing the overlay of the graphic indicia of the previous and current layers of the present invention.

The overlay accuracy measurement mark in this embodiment includes a front layer graphic mark as shown in fig. 1, where the front layer graphic mark includes a central graphic a and a peripheral graphic b surrounding the central graphic a; the central graph a and the peripheral graph b are respectively composed of a plurality of grating units, each grating unit in the front-layer graph mark comprises a plurality of line structures which are arranged in parallel and have the same number, and the adjacent line structures in each grating unit have the same distance. Further, in the front layer graphic mark, the number of the line structures in each grating unit is more than or equal to three. In the front layer graphic mark of this embodiment, the number of line structures in each grating unit is equal to three. Still further, as shown in fig. 1, the number of the grating units in the central pattern a of the front layer pattern mark is four (three line structures constitute one grating unit).

As shown in fig. 1, for the front layer graphic mark, four grating units in the central graphic a are distributed according to upper left, upper right, lower left and lower right positions, and further, as shown in fig. 1, of the four grating units in the central graphic a, the line structures in the grating units located at the upper left position and the lower right position are vertically arranged; the line structures in the grating units positioned at the upper right position and the lower left position are horizontally arranged.

For the peripheral pattern in the front layer pattern mark, as shown in fig. 1, the number of raster units in the peripheral pattern b is four. Further, as shown in fig. 1, the four grating units in the peripheral pattern b in the front layer graphic mark are respectively located right above the grating unit at the upper left position, right side of the grating unit at the upper right position, left side of the grating unit at the lower left position, and right below the grating unit at the lower right position in the central pattern a in the front layer graphic mark.

As shown in fig. 1, the width of the line structure of the grating unit in the central pattern a in the front layer graphic mark is wa 1; and the width of the line structure in each grating unit of the peripheral pattern b in the front layer pattern mark is wb 1.

The overlay accuracy measurement mark in this embodiment further includes a current layer pattern mark as shown in fig. 2, where the current layer pattern mark includes a central pattern a and a peripheral pattern b surrounding the central pattern a; the central graph a and the peripheral graph b are respectively composed of a plurality of grating units, each grating unit in the current-layer graph mark comprises a plurality of line structures which are arranged in parallel and have the same number, and the adjacent line structures in each grating unit have the same distance. Further, in the current-layer graphic mark, the number of the line structures in each grating unit is greater than or equal to three. In the current-layer graphic mark of this embodiment, the number of line structures in each grating unit is equal to three. Still further, as shown in fig. 2, the number of the grating units in the central pattern a of the current-layer pattern mark is four (three line structures constitute one grating unit).

As shown in fig. 2, for the current-layer graphic mark, the four grating units in the central graphic a are distributed according to upper left, upper right, lower left and lower right positions, and further, as shown in fig. 2, of the four grating units in the central graphic a, the line structures in the grating units located at the upper left position and the lower right position are vertically arranged; the line structures in the grating units positioned at the upper right position and the lower left position are horizontally arranged.

For the peripheral pattern in the current-layer pattern mark, as shown in fig. 2, the number of raster units in the peripheral pattern b is four. Further, as shown in fig. 2, the four grating units in the peripheral pattern b in the current-layer graphic mark are respectively located on the left side of the grating unit at the upper left position, on the right side of the grating unit at the upper right position, on the right side of the grating unit at the lower left position, and on the right side of the grating unit at the lower right position in the central pattern a in the current-layer graphic mark.

Further, in this embodiment, the width of the line structure of the grating unit in the central pattern in the current-layer pattern mark is wa2, and the width of the line structure of the peripheral pattern in the current-layer pattern mark in each grating unit is wb 2.

In the front layer and the current layer of the embodiment, the number of the grating units in the central pattern a in the pattern mark of the current layer is the same and has the same arrangement (i.e. the four grating units in the central pattern are distributed according to the upper left, upper right, lower left and lower right positions); as shown in fig. 3, in which the front layer is shifted in the horizontal direction when the central pattern a in the layer pattern mark is in an overlapping distribution (i.e., the line structure having a width wa1 is superimposed with the line structure having a width wa2, by the same amount for each raster unit in the central pattern, which is a fixed value d).

The central pattern in the front layer and current layer pattern marks is used for photoetching current layer alignment precision measurement based on the optical diffraction principle (DBO).

It can thus be seen that the front layer in the present invention, when the number of the grating units in the peripheral pattern in the layer pattern mark is the same and the grating units are symmetrically distributed around the central pattern (namely, the four grating units in the peripheral pattern in the front layer pattern mark are respectively positioned right above the grating unit at the upper left position, right side of the grating unit at the upper right position, left side of the grating unit at the lower left position and right below the grating unit at the lower right position in the central pattern in the front layer pattern mark; the peripheral pattern b in the front layer and current layer pattern marks is used for measuring the alignment precision after etching based on an image principle (IBO), and the etched layer in the alignment precision measurement after etching is a layer formed after the current layer is etched.

Further, in this embodiment, the width of the line structure of the raster unit in the central pattern in the front layer pattern mark is wa 1; the width of the line structure of the raster unit in the central pattern in the current-layer pattern mark is wa 2; the minimum distance between the central pattern and the peripheral pattern is wab, and wab > 3 max (wa1, wa2), i.e. both wa1 and wa2 take the maximum, three times smaller than the minimum distance between the central pattern and the peripheral pattern is wab.

Further, in this embodiment, in the peripheral pattern in the front layer pattern mark, the width of the line structure in each raster unit is wb 1; the width of the line structure in each grating unit of the peripheral pattern in the current-layer pattern mark is wb2, wb1 ═ wb 2.

In the peripheral pattern b in the previous layer and current layer pattern marks, the width wb1 or wb2 of the line structure in each grating unit is greater than 3 × max (wa1, wa2), that is, the width wb1 or wb2 of the line structure in each grating unit (since wb1 — wb2 are both equal in this embodiment, one of them) is greater than three times the maximum of wa1 and wa 2.

The invention also provides a using method of the overlay accuracy measuring mark, which comprises the following steps:

placing the overlay accuracy measuring marks with required sizes on a product according to the design requirements of the product, and correspondingly placing a front layer graphic mark and a current layer graphic mark in the overlay accuracy measuring marks on the front layer and the current layer of the product respectively;

secondly, after photoetching exposure, confirming the performance of photoetching current-layer overlay accuracy by using the central patterns in the front-layer pattern mark and the current-layer pattern mark on the basis of an optical diffraction principle; and the diffraction spectrum of the central pattern a and the diffraction spectrum of the peripheral pattern b can be distinguished due to the difference in pattern type and size.

And step three, after etching, measuring the alignment precision by utilizing the peripheral patterns in the front layer pattern mark and the current layer pattern mark based on the image principle.

Therefore, the invention can accurately represent the alignment precision of the current layer device of the image by using a graph and can also obtain the result of the alignment precision of the front layer and the rear layer after etching.

In summary, the invention utilizes the characteristic of DBO diffraction measurement for the lithography layer, and the IBO measurement pattern does not participate in the diffraction result, thereby having higher accuracy and precision compared with the conventional IBO measurement; after etching, the performance of alignment precision after etching can be represented by using the IBO measurement mark, and the defect that the DBO measurement mark cannot be measured after etching is overcome. The overlay accuracy measuring mark of the invention can not only meet the inspection requirement of the overlay accuracy of the current layer of photoetching, but also obtain the corresponding test result of the overlay accuracy after etching, thereby saving the space of devices and providing the test requirement of the overlay accuracy in different process flows. 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.