CN113643237A - Method for analyzing CD uniformity in wafer surface by using SEM review image - Google Patents
Method for analyzing CD uniformity in wafer surface by using SEM review image Download PDFInfo
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- CN113643237A CN113643237A CN202110788969.XA CN202110788969A CN113643237A CN 113643237 A CN113643237 A CN 113643237A CN 202110788969 A CN202110788969 A CN 202110788969A CN 113643237 A CN113643237 A CN 113643237A
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- 238000012552 review Methods 0.000 title claims abstract description 39
- 238000000034 method Methods 0.000 title claims abstract description 34
- 238000005259 measurement Methods 0.000 claims abstract description 15
- 238000003672 processing method Methods 0.000 claims abstract description 11
- 238000001228 spectrum Methods 0.000 claims abstract description 11
- 241001270131 Agaricus moelleri Species 0.000 claims description 2
- 230000008569 process Effects 0.000 abstract description 5
- 238000012545 processing Methods 0.000 abstract description 5
- 238000012544 monitoring process Methods 0.000 abstract description 4
- 230000006872 improvement Effects 0.000 abstract description 2
- 238000010586 diagram Methods 0.000 description 4
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- H01L22/20—Sequence of activities consisting of a plurality of measurements, corrections, marking or sorting steps
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/30—Subject of image; Context of image processing
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- G06T2207/30148—Semiconductor; IC; Wafer
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Abstract
The invention provides a method for analyzing the uniformity of a CD (compact disc) in a wafer surface by utilizing an SEM review image, which comprises the steps of providing an SEM review machine; shooting a plurality of pictures containing a plurality of graphic structures in a CD area to be measured on a wafer by utilizing the shooting function of an SEM review machine; carrying out CD measurement on a plurality of graphic structures of the CD area to be measured on each photo by using a graphic processing method of spectrum fitting; the graph processing method of spectrum fitting is based on that the gray levels of the widest two sides of the graph structure are different to capture two points of the widest area on the graph structure; and measuring the distance between the two points, wherein the distance is used as the CD value required to be measured by the graph structure. Compared with the traditional CD measuring machine, the SEM review machine can collect a large number of images of graphs more quickly, and then through later-stage graph processing, more graph sizes can be obtained in one graph, more monitoring positions can be obtained, great help is brought to process improvement, and meanwhile, a large number of measuring machines are saved.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to a method for analyzing the uniformity of a CD (compact disc) in a wafer surface by utilizing an SEM (scanning electron microscope) review image.
Background
In integrated circuit manufacturing, CD (critical dimension) is a very important parameter in the process of pattern fabrication, and CD measurement is a very common and important step in FAB monitoring. Currently, in the FAB, the most common CD measurement machine is based on SEM measurement, and this method can accurately select and measure the corresponding pattern, but the measurement speed is slow, about 4sites/min, and this method can generally support the measurement requirement of one shot per point.
However, when we need to collect more CD values, for example, the collection of a lot of data in the repeated structure of SRAM to evaluate CDU (CD uniformity), the conventional method will consume a lot of CD metrology machines. Based on the characteristics, a method for directly taking a large number of photos based on an SEM review machine and processing the photos to obtain CD values at the later stage is developed. This method requires repeated photographing without finding a pattern (pattern) precisely, and thus the image collection speed is 25X faster than that of the conventional method. Meanwhile, for the image of the same view, the number of repeated patterns can be measured to be more than 50 e.a.; therefore, in the same time, the new method has to expand the measurement speed by >100X, and multiple positions in the shot/die can be monitored.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, the present invention provides a method for analyzing CD uniformity within a wafer surface by using SEM review image, which is used to solve the problems of the prior art that the speed of measuring CD by a machine is slow and a large number of CD measuring machines are consumed.
To achieve the above and other related objects, the present invention provides a method for analyzing the CD uniformity within a wafer plane using SEM review image, comprising:
step one, providing an SEM review machine;
secondly, shooting a plurality of pictures containing a plurality of graphic structures in a CD area to be measured on the wafer by utilizing the shooting function of the SEM review machine;
thirdly, performing CD measurement on the plurality of graphic structures of the CD area to be measured on each photo by using a graphic processing method of spectrum fitting; the graph processing method of the spectrum fitting captures two points of the widest area on the graph structure based on different gray levels of the two widest sides of the graph structure; and measuring the distance between the two points, wherein the distance is used as the measured CD value of the graph structure.
Preferably, in the second step, the number of the photos including the plurality of graphic structures is 10000 for different regions of the wafer each time by using the shooting function of the SEM review machine.
Preferably, the number of the graphic structures contained in each of the photos in the second step is more than 50 ea.
Preferably, the time taken to take 10000 photos by using the shooting function of the SEM review machine in the second step is 1.5 hours.
Preferably, the pattern structure in the second step is a contact hole pattern, and the contact hole pattern is not completely circular.
Preferably, the graph processing method of spectrum fitting in step three captures two points of the widest area on the contact hole graph based on the difference of the gray scales of the widest two sides of the contact hole graph; and measuring the distance between the two points, wherein the distance is used as the CD value required to be measured by the contact hole pattern.
Preferably, the dimension of the pattern structure in step three is 100X.
As described above, the method for analyzing the CD uniformity in the wafer surface by using the SEM review image according to the present invention has the following advantages: compared with the traditional CD measuring machine, the SEM review machine can collect a large number of images of graphs more quickly, and then through later-stage graph processing, more graph sizes can be obtained in one graph, more monitoring positions can be obtained, great help is brought to process improvement, and meanwhile, a large number of measuring machines are saved.
Drawings
FIG. 1 shows an actual pattern of contact holes in a photo of a CD area to be measured;
FIG. 2 is a schematic diagram showing two points of the widest region of the graph structure captured by the image processing software;
FIG. 3 is a schematic diagram showing the sizes of contact holes in different regions of an SRAM structure;
FIG. 4 is a graph showing the CD uniformity distribution within the wafer plane in the present invention;
FIG. 5 is a flowchart illustrating a method for analyzing the uniformity of CD within a wafer surface using SEM review images according to 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 5. 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 a method for analyzing the uniformity of a CD in a wafer surface by using an SEM review image, as shown in FIG. 5, FIG. 5 is a flow chart of the method for analyzing the uniformity of the CD in the wafer surface by using the SEM review image, and the method at least comprises the following steps:
step one, providing an SEM review machine; the SEM review machine has the function of taking a large number of photos at one time.
Secondly, shooting a plurality of pictures containing a plurality of graphic structures in a CD area to be measured on the wafer by utilizing the shooting function of the SEM review machine; that is, each CD area to be measured on the wafer may take a photo, and each CD area to be measured includes a plurality of graphic structures (or patterns of structures). Further, the number of the graphic structures contained in each of the photos in the second step of this embodiment is greater than 50 ea.
Further, in the second step of this embodiment, the number of photos including a plurality of graphic structures is 10000 for each different area of the wafer by using the shooting function of the SEM review machine.
Further, in the second step of this embodiment, it takes 1.5 hours to take 10000 photos by using the shooting function of the SEM review machine.
Further, the pattern structure in step two of this embodiment is a contact hole pattern, and the contact hole pattern is not completely circular. As shown in FIG. 1, FIG. 1 shows the actual pattern of contact holes in the CD area to be measured in a photograph. The ideal contact hole pattern is circular, and the shape of the contact hole obtained after the actual process is changed and is not completely circular.
Thirdly, performing CD measurement on the plurality of graphic structures of the CD area to be measured on each photo by using a graphic processing method of spectrum fitting; the graph processing method of the spectrum fitting captures two points of the widest area on the graph structure based on different gray levels of the two widest sides of the graph structure; and measuring the distance between the two points, wherein the distance is used as the measured CD value of the graph structure.
Further, the invention further provides a graph processing method of spectrum fitting in step three of this embodiment, which captures two points in the widest region of the contact hole graph based on the difference of gray levels at the widest two sides of the contact hole graph; and measuring the distance between the two points, wherein the distance is used as the CD value required to be measured by the contact hole pattern.
As shown in fig. 2, fig. 2 is a schematic diagram showing two points of the widest region of the graphic structure captured by the image processing software. The distance CD between the two points (steepest) is the measured Critical Dimension (CD) of the pattern structure. For example, in the SRAM structure, different areas of the contact hole measure different CDs, as shown in fig. 3, and fig. 3 is a schematic diagram showing the sizes of the contact holes in different areas of the SRAM structure.
Further, the dimension of the pattern structure in step three of this embodiment is 100X.
The method is a method for directly shooting a large number of photos based on an SEM review machine and processing the photos to obtain CD values at the later stage. The advantages brought by this method are mainly: since the pattern does not need to be found accurately, and only repeated photographing is needed, the image collection speed is 25X faster than that of the traditional method.
The number of repetitive pattern patterns can be measured to >50e.a within the image (photo) of the same area to be measured. Therefore, in the same time, the measurement speed of the new method is increased by more than 100X, and a plurality of positions in the shot/die can be monitored. As shown in fig. 4, fig. 4 is a graph showing the uniformity of CD measurement within the wafer plane according to the present invention. A measurement map (map) can be set according to die to monitor the in-plane uniformity further and to view the performance far from the edge of the wafer.
In actual use, 10000 review pictures are collected by an SEM review machine, the total time is 1.5 hours, and the time is saved by 96 percent compared with the time consumed by the existing CDSEM for 40 hours; data of >50 points can be extracted from each picture, the total count is 500K, and the total amount of data is increased by more than 1000X compared with the inline measurement.
Other advantages of using the method include: independently analyzing CD values of different contact hole patterns (CT patterns) in the image (view image) of the same region to be measured, and feeding back the CD values to OPC for optimization; effectively monitoring the CD value (normal measurement R <140mm) at the edge of the radius (R >145mm) of the wafer, and feeding back to the production line for CD uniformity adjustment.
In summary, compared with the conventional CD measuring machine, the SEM review machine of the present invention can collect a large number of images of a pattern more quickly, and then, through the later pattern processing, more sizes of the pattern can be obtained in one pattern, and more positions can be monitored, which greatly helps to improve the process and save a large amount of measuring machines. 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.
Claims (7)
1. A method for analyzing the CD uniformity in a wafer surface by using an SEM review image is characterized by at least comprising the following steps:
step one, providing an SEM review machine;
secondly, shooting a plurality of pictures containing a plurality of graphic structures in a CD area to be measured on the wafer by utilizing the shooting function of the SEM review machine;
thirdly, performing CD measurement on the plurality of graphic structures of the CD area to be measured on each photo by using a graphic processing method of spectrum fitting; the graph processing method of the spectrum fitting captures two points of the widest area on the graph structure based on different gray levels of the two widest sides of the graph structure; and measuring the distance between the two points, wherein the distance is used as the measured CD value of the graph structure.
2. The method of analyzing the in-wafer CD uniformity using SEM review image of claim 1, wherein: and in the second step, by utilizing the shooting function of the SEM review machine, 10000 pictures containing a plurality of graphic structures are shot in different areas of the wafer each time.
3. The method of analyzing the in-wafer CD uniformity using SEM review image of claim 1, wherein: and in the second step, the number of the graph structures contained in each photo is more than 50 ea.
4. The method of analyzing the in-wafer CD uniformity using SEM review image of claim 2, wherein: and in the second step, the time spent on taking 10000 photos by utilizing the shooting function of the SEM review machine is 1.5 hours.
5. The method of analyzing the in-wafer CD uniformity using SEM review image of claim 1, wherein: and the pattern structure in the second step is a contact hole pattern, and the contact hole pattern is not completely circular.
6. The method of claim 5, wherein the step of analyzing the CD uniformity in the wafer surface by using the SEM review image comprises: the graph processing method of the spectrum fitting in the third step grabs two points of the widest area on the contact hole graph based on different gray scales on the two widest sides of the contact hole graph; and measuring the distance between the two points, wherein the distance is used as the CD value required to be measured by the contact hole pattern.
7. The method of analyzing the in-wafer CD uniformity using SEM review image of claim 1, wherein: the dimension of the pattern structure in step three is 100X.
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Citations (7)
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| US20100158345A1 (en) * | 2008-12-22 | 2010-06-24 | Tadashi Kitamura | Defect And Critical Dimension Analysis Systems And Methods For A Semiconductor Lithographic Process |
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| KR20160061747A (en) * | 2014-11-24 | 2016-06-01 | 세메스 주식회사 | Method of inspecting a wafer |
| US20160341670A1 (en) * | 2015-05-22 | 2016-11-24 | Nanometrics Incorporated | Optical metrology using differential fitting |
| US20170069080A1 (en) * | 2015-09-04 | 2017-03-09 | Kla-Tencor Corporation | Techniques and systems for model-based critical dimension measurements |
| US20180059019A1 (en) * | 2016-08-31 | 2018-03-01 | Kla-Tencor Corporation | Model based optical measurements of semiconductor structures with anisotropic dielectric permittivity |
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2021
- 2021-07-13 CN CN202110788969.XA patent/CN113643237A/en active Pending
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20100158345A1 (en) * | 2008-12-22 | 2010-06-24 | Tadashi Kitamura | Defect And Critical Dimension Analysis Systems And Methods For A Semiconductor Lithographic Process |
| US20110176718A1 (en) * | 2010-01-21 | 2011-07-21 | Hitachi, Ltd. | Apparatus for evaluating degradation of pattern features |
| CN104897706A (en) * | 2014-03-07 | 2015-09-09 | 旺宏电子股份有限公司 | Measurement method of chip or wafer surface structure |
| KR20160061747A (en) * | 2014-11-24 | 2016-06-01 | 세메스 주식회사 | Method of inspecting a wafer |
| US20160341670A1 (en) * | 2015-05-22 | 2016-11-24 | Nanometrics Incorporated | Optical metrology using differential fitting |
| US20170069080A1 (en) * | 2015-09-04 | 2017-03-09 | Kla-Tencor Corporation | Techniques and systems for model-based critical dimension measurements |
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| US20180059019A1 (en) * | 2016-08-31 | 2018-03-01 | Kla-Tencor Corporation | Model based optical measurements of semiconductor structures with anisotropic dielectric permittivity |
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