Method and system for obtaining optimal exposure condition

Abstract

The invention provides a method and a system for acquiring an optimal exposure condition, and belongs to the field of semiconductors. The method for acquiring the optimal exposure condition comprises the following steps: acquiring a target pixel and a pixel sum of a photoetching pattern in each SEM image based on the SEM images; and subtracting the target pixel from the pixel sum of the photoetching pattern to obtain the contour deviation of different positions in the SEM image along with the change of the exposure condition. And obtaining the CD value of the photoetching pattern based on the contour deviation. And determining a sub-exposure condition of each SEM image based on the CD value of the photoetching pattern. And carrying out data fitting on the sub-exposure conditions obtained by the SEM images of the wafer under different exposure conditions to obtain the optimal exposure condition of the wafer. According to the method, the SEM images of the wafer under different exposure conditions are acquired, the target pixel and the pixel sum of the photoetching pattern in each SEM image are acquired, and data fitting can be performed on the contour extracted from each pattern in the SEM images, so that the accuracy of acquiring the optimal exposure condition can be improved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method and system for obtaining optimal exposure conditions. Background Art

[0002] In the daily work of photolithography, checking FEM (Focus energy matrix) to determine the best running conditions is a common task. Figure 1 and Figure 2 As shown, there are two main methods for judging FEM at present. The first is to calculate the process window based on the CD value measured by image to obtain the PWA result. This part uses the commercial silitho software to obtain a Figure 1 The curve graph shown in the figure. The coordinates of the center point of the curve graph are the more accurate running conditions of the photolithography wafer. However, apart from the CD part, it is also necessary to check the outline of the graphic. If the outline of the graphic is as follows Figure 2 The pattern profiles at a and b shown in the figure cannot meet the design requirements. Based on experience, they cannot meet the running conditions, which will also affect the formulation of the best running conditions. Apart from the image judgment part, the first is that most of the PWA parts are drawn based on the CD value of a certain point or a certain section of the graphic in the SEM image. In this case, the choice of CD measurement method and the failure mode of the actual graphic will affect the output of the final best running conditions.

[0003] It should be noted that the information disclosed in the background technology section of the invention is only intended to deepen the understanding of the general background technology of the invention, and should not be regarded as an admission or suggestion in any form that the information constitutes prior art already known to those skilled in the art. Summary of the invention

[0004] The object of the present invention is to provide a method and system for obtaining optimal exposure conditions, so as to solve the problem that the optimal exposure conditions for lithography cannot be effectively obtained.

[0005] In order to solve the above technical problems, the present invention provides a method for obtaining optimal exposure conditions, comprising:

[0006] A wafer is provided, and SEM images of the wafer under different exposure conditions are obtained;

[0007] Based on the SEM image, the target pixel and the pixel sum of the photolithography pattern in each SEM image are obtained;

[0008] Subtract the target pixel from the pixel sum of the lithographic pattern to obtain the profile deviation of different positions in the SEM image as the exposure conditions change;

[0009] Based on the profile deviation, obtaining a CD value of the photolithography pattern;

[0010] Determining a sub-exposure condition of each SEM image based on the CD value of the photolithographic pattern;

[0011] The sub-exposure conditions obtained from the SEM images of the wafer under different exposure conditions are data fitted to obtain the optimal exposure conditions for the wafer.

[0012] Preferably, the exposure conditions include exposure energy and exposure focus.

[0013] Preferably, acquiring the target contour of the wafer to acquire the target pixels of the target contour comprises:

[0014] Based on the SEM image, extracting the contour of the photolithography pattern in the SEM image to obtain the pixel sum of the photolithography pattern in the SEM image;

[0015] The average value of the pixels of the photolithographic pattern in the SEM image is calculated, and the average value of the pixels is the target pixel.

[0016] Preferably, acquiring the target contour of the wafer to acquire the target pixels of the target contour comprises:

[0017] A wafer is provided, a target contour of the wafer is extracted from a known database of the wafer, and target pixels of the target contour are obtained.

[0018] Preferably, the step of acquiring the pixel sum of the photolithographic pattern in each SEM image based on the SEM image comprises:

[0019] Based on the SEM image, extracting a contour in the SEM image;

[0020] Based on the extracted contours, the pixel sum of the lithographic pattern in each SEM image is obtained.

[0021] Preferably, acquiring a CD value of a lithography pattern based on the profile deviation comprises:

[0022] Based on the SEM image, the size represented by each pixel is obtained;

[0023] Based on the size and profile deviation represented by each pixel, the CD value of the lithographic pattern is obtained.

[0024] Preferably, the determining of the sub-exposure conditions of each SEM image based on the CD value of the photolithographic pattern comprises:

[0025] The CD value is input into the PWA software to obtain the sub-exposure condition in one SEM image.

[0026] Preferably, performing data fitting on sub-exposure conditions obtained from SEM images of wafers under different exposure conditions to obtain the best exposure conditions for the wafer comprises:

[0027] The sub-exposure conditions under different exposure conditions are fitted into a Poisson curve, and the exposure condition corresponding to the center point of the Poisson curve is the optimal exposure condition for the wafer.

[0028] Based on the same inventive concept, the present invention also provides a system for obtaining optimal exposure conditions, comprising:

[0029] An acquisition module is used to provide a wafer and acquire SEM images of the wafer under different exposure conditions; based on the SEM images, acquire the target pixel and the pixel sum of the photolithography pattern in each SEM image;

[0030] The calculation module subtracts the target pixel from the pixel sum of the photolithography pattern to obtain the profile deviation of different positions in the SEM image that changes with the exposure conditions; based on the profile deviation, the CD value of the photolithography pattern is obtained; based on the CD value of the photolithography pattern, the sub-exposure condition of each SEM image is determined; and the sub-exposure conditions obtained from the SEM images of the wafer under different exposure conditions are data-fitted to obtain the optimal exposure condition of the wafer.

[0031] Preferably, the calculation module is integrated into the PWA software.

[0032] Compared with the prior art, the method for obtaining the optimal exposure condition of the present invention has the following advantages:

[0033] The present invention obtains SEM images of wafers under different exposure conditions, and obtains the target pixel and the pixel sum of the photolithographic pattern in each SEM image. Then, the target pixel is subtracted from the pixel sum of the photolithographic pattern to obtain the profile deviation of different positions in the SEM image that changes with the exposure conditions. Then, based on the profile deviation, the CD value of the photolithographic pattern is obtained. Based on the CD value of the photolithographic pattern, the sub-exposure condition of each SEM image is determined; the sub-exposure conditions obtained from the SEM images of the wafer under different exposure conditions are data fitted to obtain the optimal exposure condition of the wafer. In this method, the profile extracted from each pattern in the SEM image can be data fitted, thereby improving the accuracy of obtaining the optimal exposure condition.

[0034] The system for obtaining optimal exposure conditions provided by the present invention and the method for obtaining optimal exposure conditions provided by the present invention belong to the same inventive concept. Therefore, the system for obtaining optimal exposure conditions provided by the present invention has at least all the advantages of the method for obtaining optimal exposure conditions provided by the present invention, and can improve the accuracy of exposure conditions of the photolithography process. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a fitting curve diagram of exposure energy and exposure focal length in one embodiment;

[0036] Figure 2 is a SEM image of a failed etched pattern in one embodiment;

[0037] Figure 3 is a flow chart of a method for obtaining optimal exposure conditions in one embodiment of the present invention;

[0038] Figure 4 is an optimal exposure focal length diagram of a metal layer in one embodiment of the present invention;

[0039] Figure 5 In one embodiment of the present invention Figure 4 Schematic diagram of the distribution of the major axis in the elliptical curve fitted with the optimal exposure focal length;

[0040] Figure 6 is a schematic diagram of extracting the outline of a photolithography pattern in the SEM image based on the SEM image in one embodiment of the present invention;

[0041] Figure 7 is a schematic diagram of obtaining profile deviations of different positions in a SEM image as exposure conditions change in one embodiment of the present invention;

[0042] Figure 8 is a Poisson curve diagram of a SEM image in one embodiment of the present invention;

[0043] Fig. 9 It is a Poisson curve diagram of the SEM image under different exposure conditions in one embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to make the purpose, advantages and features of the present invention clearer, the method and system for obtaining the optimal exposure conditions proposed by the present invention are further described in detail in combination with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not in precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. It should be understood that the drawings in the specification do not necessarily show the specific structure of the present invention in proportion, and the illustrative features used to illustrate certain principles of the present invention in the drawings in the specification will also be slightly simplified. The specific design features of the present invention disclosed herein include, for example, specific dimensions, directions, positions and shapes, which will be determined in part by the specific application and use environment. In addition, in the embodiments described below, the same figure mark is sometimes used in common between different drawings to represent the same part or a part with the same function, and its repeated description is omitted. In this specification, similar numbers and letters are used to represent similar items, so once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0045] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0046] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0047] The core idea of ​​the present invention is to provide a method for obtaining optimal exposure conditions, which can obtain the optimal exposure conditions.

[0048] In order to realize the above idea, the present invention provides a method for obtaining the optimal exposure condition. Figures 1 to 9 A specific implementation of a method for obtaining optimal exposure conditions disclosed herein includes the following steps S1 to S6.

[0049] Step S1: providing a wafer, and obtaining SEM images of the wafer under different exposure conditions.

[0050] Specifically, refer to Figure 3 As shown, a wafer is provided, and SEM images of the wafer under different exposure conditions are obtained by an electronic scanning mirror. The exposure conditions include exposure energy and focal length. By changing different exposure energies and focal lengths, the wafer is etched, and the SEM image of the wafer after etching is obtained.

[0051] Step S2: Based on the SEM image, the target pixel and the pixel sum of the photolithography pattern in each SEM image are obtained.

[0052] Specifically, refer to Figure 3 and Figure 6As shown, obtaining the target contour of the wafer to obtain the target pixel of the target contour includes: first, based on the SEM image, extracting the contour of the photolithography pattern in the SEM image to obtain the pixel sum of the photolithography pattern in the SEM image. Then, the average value of the pixels of the photolithography pattern in the SEM image is calculated, and the average value of the pixels is the target pixel. In addition, obtaining the target contour of the wafer to obtain the target pixel of the target contour includes: providing a wafer, extracting the target contour of the wafer from a known database of the wafer, and obtaining the target pixel of the target contour. That is, a known database of wafer etching can be provided by other process departments, from which the target contour of the wafer under the optimal etching conditions is selected. Then, the target pixel of the SEM image under the exposure condition can be obtained through the target contour.

[0053] Based on the SEM image, the pixel sum of the photolithographic pattern in each SEM image is obtained, which includes: first, based on the SEM image, the contour in the SEM image is extracted to obtain the following: Figure 6 Then, based on the extracted contours, the pixel sum of the lithographic pattern in each SEM image is obtained.

[0054] Step S3: subtract the target pixel from the pixel sum of the photolithographic pattern to obtain the profile deviation of different positions in the SEM image as the exposure conditions change.

[0055] Step S4: based on the profile deviation, obtaining a CD value of the photolithography pattern.

[0056] Specifically, refer to Figure 3 and Figure 7 As shown, based on the profile deviation, obtaining the CD value of the lithographic pattern includes: first, based on the SEM image, obtaining the size represented by each pixel. Then, based on the size represented by each pixel and the profile deviation, the following is obtained: Figure 7 The data shown at c in the figure is used to obtain the CD value of the photolithography pattern, where the CD value is the line width of each photolithography pattern, i.e., the critical dimension of the photolithography pattern.

[0057] Step S5: determining the sub-exposure condition of each SEM image based on the CD value of the photolithographic pattern.

[0058] Specifically, refer to Figure 3 and Figure 8 As shown, based on the CD value of the photolithographic pattern, determining the sub-exposure condition of each SEM image includes: inputting the CD value into the PWA software to obtain the sub-exposure condition in a SEM image. Inputting the CD value into the PWA software to perform Poisson curve fitting to obtain the defect of focal length with respect to exposure energy, forming a Figure 8 The elliptical structure shown in FIG. Then, the center point of the elliptical structure is the sub-exposure condition.

[0059] Step S6: performing data fitting on the sub-exposure conditions obtained from the SEM images of the wafer under different exposure conditions to obtain the optimal exposure condition for the wafer.

[0060] Specifically, refer to Figure 3 , Figure 8 and Fig. 9 As shown in FIG. 1 , the sub-exposure conditions obtained from the SEM images of the wafer under different exposure conditions are fitted to obtain the focal length of the wafer with respect to the exposure energy as shown in FIG. Fig. 9 The curve diagram shown. Fig. 9 The center point of the elliptical structure is the optimal focal length and exposure condition for the wafer. Fig. 9 and Figure 8 It can be seen from the data that Fig. 9 The major axis of the elliptical structure is smaller than Figure 8 The major axis of the elliptical structure in Fig. 9 The center point of the curve of the elliptical structure in the image gives a more accurate focus and exposure energy.

[0061] Ginseng Figure 4 and Figure 5 As shown, taking the 28HK back-end metal layer as an example, it is found that the optimal energy and optimal focal length of the entire image are different, and the optimal energy and optimal focal length of some areas that are difficult to measure are the images that really limit the process window. Therefore, the method for obtaining the optimal exposure condition provided in this embodiment can measure the patterns in all areas of the entire image, thereby improving the accuracy of obtaining the empirical optimal exposure condition, and also improving the lithography process, thereby improving the reliability of the device performance.

[0062] To realize the above idea, this embodiment also discloses a system for obtaining the best exposure conditions, including: an acquisition module, used to provide a wafer, obtain SEM images of the wafer under different exposure conditions; based on the SEM image, obtain the target pixel and the pixel sum of the photolithography pattern in each SEM image. A calculation module, subtracts the target pixel from the pixel sum of the photolithography pattern to obtain the profile deviation of different positions in the SEM image that changes with the exposure conditions; based on the profile deviation, obtain the CD value of the photolithography pattern; based on the CD value of the photolithography pattern, determine the sub-exposure condition of each SEM image; perform data fitting on the sub-exposure conditions obtained from the SEM images of the wafer under different exposure conditions to obtain the best exposure conditions for the wafer. The calculation module is integrated in the PWA software.

[0063] The system for obtaining optimal exposure conditions provided in this embodiment and the method for obtaining optimal exposure conditions provided in this embodiment belong to the same inventive concept. Therefore, the system for obtaining optimal exposure conditions provided in this embodiment has at least all the advantages of the method for obtaining optimal exposure conditions provided in the present invention, and can improve the accuracy of exposure conditions of the lithography process.

[0064] In summary, the above embodiments provide detailed descriptions of different configurations of the method and system for obtaining optimal exposure conditions. Of course, the above description is only a description of the preferred embodiments of the present invention, and is not any limitation to the scope of the present invention. The present invention includes but is not limited to the configurations listed in the above implementations. Those skilled in the art can draw inferences based on the contents of the above embodiments. Any changes and modifications made by those of ordinary skill in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A method for obtaining optimal exposure conditions, characterized in that: include: A wafer is provided, and SEM images of the wafer under different exposure conditions are obtained; Based on the SEM image, the target pixel and the pixel sum of the photolithography pattern in each SEM image are obtained; Subtract the target pixel from the pixel sum of the lithographic pattern to obtain the profile deviation of different positions in the SEM image as the exposure conditions change; Based on the profile deviation, obtaining a CD value of the photolithography pattern; Determining a sub-exposure condition of each SEM image based on the CD value of the photolithographic pattern; The sub-exposure conditions obtained from the SEM images of the wafer under different exposure conditions are data fitted to obtain the optimal exposure conditions for the wafer.

2. The method for obtaining the optimal exposure condition according to claim 1, characterized in that: The exposure conditions include exposure energy and exposure focus.

3. The method for obtaining optimal exposure conditions according to claim 1, characterized in that: The step of obtaining a target contour of the wafer to obtain target pixels of the target contour includes: Based on the SEM image, extracting the contour of the photolithography pattern in the SEM image to obtain the pixel sum of the photolithography pattern in the SEM image; The average value of the pixels of the photolithographic pattern in the SEM image is calculated, and the average value of the pixels is the target pixel.

4. The method for obtaining optimal exposure conditions according to claim 1, characterized in that: The step of obtaining a target contour of the wafer to obtain target pixels of the target contour includes: A wafer is provided, a target contour of the wafer is extracted from a known database of the wafer, and target pixels of the target contour are obtained.

5. The method for obtaining optimal exposure conditions according to claim 1, characterized in that: Based on the SEM images, the pixels and the sum of the photolithographic patterns in each SEM image are obtained, including: Based on the SEM image, extracting a contour in the SEM image; Based on the extracted contours, the pixel sum of the lithographic pattern in each SEM image is obtained.

6. The method for obtaining optimal exposure conditions according to claim 1, characterized in that: The obtaining of the CD value of the lithography pattern based on the profile deviation comprises: Based on the SEM image, the size represented by each pixel is obtained; Based on the size and profile deviation represented by each pixel, the CD value of the lithographic pattern is obtained.

7. The method for obtaining optimal exposure conditions according to claim 1, characterized in that: The sub-exposure condition of each SEM image is determined based on the CD value of the photolithography pattern, including: The CD value is input into the PWA software to obtain the sub-exposure condition in one SEM image.

8. The method for obtaining optimal exposure conditions according to claim 1, characterized in that: The data fitting of the sub-exposure conditions obtained from the SEM images of the wafer under different exposure conditions to obtain the optimal exposure conditions for the wafer includes: The sub-exposure conditions under different exposure conditions are fitted into a Poisson curve, and the exposure condition corresponding to the center point of the Poisson curve is the optimal exposure condition for the wafer.

9. A system for obtaining optimal exposure conditions, characterized in that: include: An acquisition module is used to provide a wafer and acquire SEM images of the wafer under different exposure conditions; Based on the SEM image, the target pixel and the pixel sum of the photolithography pattern in each SEM image are obtained; The calculation module subtracts the target pixel from the pixel sum of the photolithography pattern to obtain the profile deviation of different positions in the SEM image that changes with the exposure conditions; based on the profile deviation, the CD value of the photolithography pattern is obtained; based on the CD value of the photolithography pattern, the sub-exposure condition of each SEM image is determined; and the sub-exposure conditions obtained from the SEM images of the wafer under different exposure conditions are data-fitted to obtain the optimal exposure condition of the wafer.

10. The system for obtaining optimal exposure conditions according to claim 9, characterized in that: The calculation module is integrated into the PWA software.

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