Method, device and storage medium for measuring critical dimensions of wafer

Abstract

The present application discloses a method, device and storage medium for measuring the critical dimensions of a wafer. The method comprises: obtaining a signal waveform diagram of each sub-region of the region to be measured in the wafer; aligning the signal waveform diagram of each sub-region with the signal waveform diagram of the surrounding adjacent sub-regions to obtain the signal waveform diagram of the aligned sub-region; performing correlation calculation based on the signal waveform template and the signal waveform diagram of the aligned sub-region to determine the edge point of the region to be measured in the wafer; and measuring the critical dimensions of the wafer according to the edge point of the region to be measured in the wafer. The scheme of the present application can improve the accuracy of measuring the critical dimensions of the wafer.

Description

Technical Field

[0001] The present application generally relates to the field of wafer measurement technology. More specifically, the present application relates to a method, an apparatus and a computer-readable storage medium for measuring a critical dimension of a wafer. Background Art

[0002] In the step of measuring the key dimensions of the internal circuit of a semiconductor wafer, a scanning electron microscope is usually used to scan the surface structure of the wafer sample to complete the measurement of key dimensions such as line width and aperture. Traditionally, the dimensions to be measured are usually measured using a specific edge point extraction algorithm or through correlation calculation of a signal waveform template to complete the measurement of key dimensions such as line width and aperture, where the position with the highest correlation corresponds to the edge point. Specifically, by using a pair of signal waveforms as templates to measure the area to be measured in the grayscale image collected by a scanning electron microscope, it can be ensured that the measurement repeatability error under the same measurement parameter environment is controlled within a certain range.

[0003] After the internal circuit structure of the wafer is imaged by a scanning electron microscope, there will often be image areas with poor flatness in the area to be measured, which affects the repeatability error of the final measurement. The traditional measurement scheme using signal waveform template matching is to use the average signal waveform of a large area divided into several small sub-areas to establish a signal waveform template. However, when the degree of unevenness of the sub-area is large, the deviation of the signal waveform diagram of each sub-area is large. At this time, the established signal waveform template will have a large fluctuation, resulting in poor accuracy of the final measurement result.

[0004] In view of this, there is an urgent need to provide a solution for measuring the critical dimensions of a wafer, so as to improve the accuracy of measuring the critical dimensions of the wafer. Summary of the invention

[0005] In order to at least solve one or more of the technical problems mentioned above, the present application proposes solutions for measuring critical dimensions of a wafer in multiple aspects.

[0006] In a first aspect, the present application provides a method for measuring critical dimensions of a wafer, comprising: obtaining a signal waveform diagram of each sub-region of the wafer to be measured; aligning the signal waveform diagram of each sub-region with the signal waveform diagram of its surrounding adjacent sub-regions to obtain a signal waveform diagram of the aligned sub-region; performing correlation calculation based on a signal waveform template and the signal waveform diagram of the aligned sub-region to determine the edge point of the wafer to be measured; and measuring the critical dimensions of the wafer according to the edge point of the wafer to be measured.

[0007] In one embodiment, the signal waveform graph of each sub-region is registered and aligned with the signal waveform graph of its surrounding adjacent sub-regions to obtain the signal waveform graph of the sub-region after registration and alignment, which includes: registering and aligning the signal waveform graph of each sub-region with the signal waveform graph of its surrounding adjacent sub-regions to determine the corresponding offset between the signal waveform graph of each sub-region and the signal waveform graph of its surrounding adjacent sub-regions; and offsetting the signal waveform graph of each sub-region based on the corresponding offset to obtain the signal waveform graph of the sub-region after registration and alignment.

[0008] In another embodiment, performing a correlation calculation based on the signal waveform template and the signal waveform graph of the sub-area after the registration and alignment to determine the edge point of the area to be measured in the wafer includes: performing a correlation calculation based on the signal waveform template and the signal waveform graph of the sub-area after the registration and alignment to obtain a final coordinate position corresponding to the maximum correlation between the signal waveform template and the signal waveform graph; and determining the edge point of the area to be measured in the wafer according to the final coordinate position corresponding to the maximum correlation.

[0009] In another embodiment, performing a correlation calculation based on the signal waveform template and the signal waveform graph of the sub-area after registration and alignment to obtain a final coordinate position corresponding to the maximum correlation between the signal waveform template and the signal waveform graph includes: performing a correlation calculation based on the signal waveform template and the signal waveform graph of the sub-area after registration and alignment to obtain an initial coordinate position corresponding to the maximum correlation between the signal waveform template and the signal waveform graph; and offsetting the target coordinate position corresponding to the maximum correlation toward the corresponding offset to determine the final coordinate position corresponding to the maximum correlation.

[0010] In yet another embodiment, the critical dimension comprises a line width or an aperture.

[0011] In another embodiment, in response to the critical dimension including the line width, the signal waveform diagram of each sub-area is obtained by the following operation: dividing the area to be measured in the wafer into multiple sub-areas along the longitudinal or transverse direction to obtain the signal waveform diagram of each sub-area of ​​the area to be measured in the wafer.

[0012] In another embodiment, in response to the key dimension including line width, the signal waveform template is obtained by the following operations: obtaining all coordinate points corresponding to the maximum correlation after aligning the signal waveform graph of each sub-area with the signal waveform graph of its surrounding adjacent sub-areas; combining all the coordinate points corresponding to the maximum correlation to obtain the signal waveform template; or combining the coordinate points corresponding to the maximum correlation that meets a preset threshold to obtain the signal waveform template.

[0013] In another embodiment, in response to the critical dimension including an aperture, the signal waveform diagram of each sub-area is also obtained by the following operation: dividing the area to be measured in the wafer into multiple sub-areas along the arc to obtain the signal waveform diagram of each sub-area of ​​the area to be measured in the wafer.

[0014] In yet another embodiment, in response to the critical dimension including an aperture, the signal waveform template is further obtained by: selecting a signal waveform diagram of a sub-area at a target radian; and using the signal waveform diagram of the sub-area at the target radian as the signal waveform template.

[0015] In yet another embodiment, in response to the critical dimension including an aperture, performing correlation calculation based on the signal waveform template and the signal waveform graph of the sub-area after the registration and alignment, it also includes: mapping the signal waveform graph of the sub-area after the registration and alignment to the signal waveform template; and performing correlation calculation based on the signal waveform template and the mapped signal waveform graph.

[0016] In yet another embodiment, the method further comprises: performing an interpolation operation on the signal waveform diagrams of the sub-regions and / or the signal waveform templates.

[0017] In a second aspect, the present application provides an apparatus for measuring critical dimensions of a wafer, comprising: a processor; and a memory on which computer instructions for measuring critical dimensions of a wafer are stored, and when the computer instructions are executed by the processor, multiple embodiments of the aforementioned first aspect are implemented.

[0018] In a third aspect, the present application provides a computer-readable storage medium having stored thereon computer program instructions for measuring critical dimensions of a wafer, wherein when the computer program instructions are executed by one or more processors, multiple embodiments of the aforementioned first aspect are implemented.

[0019] Through the scheme for measuring the critical dimensions of the wafer provided above, the embodiment of the present application first aligns the signal waveform graphs of each sub-region of the area to be measured with the signal waveform graphs of the surrounding adjacent sub-regions to eliminate the impact of unevenness on subsequent measurements, and then performs correlation calculations based on the signal waveform template and the signal waveform graphs of the aligned sub-regions to determine the edge points, and performs correlation calculations through signal waveform templates of the same scale, which greatly improves the accuracy of measuring the critical dimensions of the wafer. Furthermore, in some embodiments, the embodiment of the present application also performs interpolation operations on the signal waveform graphs and / or signal waveform templates of each sub-region to make the signal details richer and provide accurate results for correlation calculations. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] By reading the detailed description below with reference to the accompanying drawings, the above and other purposes, features and advantages of the exemplary embodiments of the present application will become easy to understand. In the accompanying drawings, several embodiments of the present application are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0021] Figure 1 is an exemplary flow chart showing the existing method of measuring wafers based on a signal waveform template;

[0022] Figure 2 is an exemplary schematic diagram showing an existing signal waveform template and an area to be measured;

[0023] Figure 3 is an exemplary flowchart showing a method for measuring a critical dimension of a wafer according to an embodiment of the present application;

[0024] Figure 4 is a flowchart showing an exemplary process for measuring the line width of a wafer according to an embodiment of the present application;

[0025] Figure 5 is an exemplary schematic diagram showing the measurement of line width according to an embodiment of the present application;

[0026] Figure 6 is a flowchart showing an exemplary process for measuring the aperture of a wafer according to an embodiment of the present application;

[0027] Figure 7 is an exemplary schematic diagram showing a measurement aperture according to an embodiment of the present application;

[0028] Figure 8 It is an exemplary structural block diagram of an apparatus for measuring a critical dimension of a wafer according to an embodiment of the present application. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0030] It should be understood that the terms "include" and "comprising" used in the specification and claims of the present application indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0031] It should also be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in this application specification and claims, unless the context clearly indicates otherwise, the singular forms of "a", "an" and "the" are intended to include plural forms. It should also be further understood that the term "and / or" used in this application specification and claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0032] As used in this specification and claims, the term "if" may be interpreted as "when" or "upon" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrase "if it is determined" or "if [described condition or event] is detected" may be interpreted as meaning "upon determination" or "in response to determining" or "upon detection of [described condition or event]" or "in response to detecting [described condition or event]," depending on the context.

[0033] Figure 1 FIG. 1 is an exemplary flow chart showing the existing method of measuring wafers based on a signal waveform template. Figure 1 As shown in, at step S101, the wafer to be tested is loaded into the sample stage of the scanning electron microscope, and at step S102, the sample stage is moved so that the wafer is placed in the lens of the scanning electron microscope. Then, at step S103, the scanning electron microscope is automatically focused, and the internal circuit structure of the wafer is imaged by the scanning electron microscope to obtain a scanning electron microscope image of the wafer. Further, at step S104, a signal waveform template is obtained under the condition of relatively ideal flatness. It can be understood that the signal waveform template is a signal waveform diagram, which is obtained based on the scanning electron microscope image of the wafer. Specifically, a one-dimensional grayscale curve diagram is formed by calculating the mean of the pixel points on each column in the scanning electron microscope image of the wafer, and the one-dimensional grayscale curve diagram is a signal waveform diagram. The existing method is to use the average signal waveform diagram under multiple sub-areas with relatively ideal flatness as the signal waveform template (for example Figure 2 (as shown in Figure a).

[0034] Based on the signal waveform template obtained above, at step S105, a correlation calculation is performed according to the signal waveform template and the signal waveform diagram of the area to be measured. In the implementation scenario, the correlation between the signal waveform template and the signal waveform diagram of the area to be measured can be calculated by a signal correlation analysis algorithm. For example, by not performing time deconvolution on the signal, a certain signal (such as a reference signal) is directly translated to point x, and then another signal is scanned. When the correlation operation scans the two signals to coincide, it means that the correlation is maximum, thereby generating a peak value to obtain a correlation result. In simple terms, it is to continuously move another signal toward the reference signal, and a peak value is generated when the correlation is maximum. Further, at step S106, the critical dimensions of the wafer (such as line width, aperture, etc.) are measured according to the correlation results. It can be understood that at the position of the maximum correlation, the grayscale values ​​of the two signals are close, and the grayscale value of the edge is higher, so the position corresponding to the maximum correlation is the edge point of the measurement area. The distance between the edge points is the measured line width length or aperture diameter.

[0035] Figure 2 FIG. 1 is an exemplary schematic diagram showing an existing signal waveform template and an area to be measured. Figure 2 As shown in , (a) shows the existing signal waveform template, which is obtained under the condition of relatively ideal flatness, including the left area and the right area. (b) shows the condition of relatively ideal flatness of the area to be measured, and (c) shows the condition of poor flatness of the area to be measured. It can be seen from the figure that for the condition of relatively ideal flatness of the area to be measured, there is no deviation between the signal waveform graphs of its sub-areas, such as the signal waveform graph l1 in each sub-area in (b) (such as the area divided by the dotted line in the figure). For the condition of poor flatness of the area to be measured, there will be deviations between the signal waveform graphs of its sub-areas, such as the signal waveform graph l2 in each sub-area in (c) has the problem of left and right offset.

[0036] As can be seen from the above background technology description, the existing method directly calculates the correlation between the signal waveform diagram of each sub-area and the signal waveform template, and the signal waveform template is established based on the average signal waveform of each sub-area. The signal waveform template in this way cannot adapt to the situation of poor flatness, which affects the control of the repeatability error of the final measurement and makes the final measurement result inaccurate.

[0037] Based on this, the present application provides a solution for measuring the critical dimensions of a wafer, which can effectively solve the deviation effect caused by uneven factors and improve the accuracy of wafer measurement.

[0038] The specific implementation of the present application is described in detail below with reference to the accompanying drawings.

[0039] Figure 3FIG. 3 is an exemplary flow chart showing a method 300 for measuring a critical dimension of a wafer according to an embodiment of the present application. Figure 3 As shown in, at step S301, a signal waveform diagram of each sub-region of the area to be measured in the wafer is obtained. As mentioned above, the signal waveform diagram is a one-dimensional grayscale curve diagram formed by calculating the mean value of the pixel points on each column in the scanning electron microscope image of the wafer. In an implementation scenario, the signal waveform diagram of each sub-region of the area to be measured in the wafer can be obtained by dividing the area to be measured in the wafer from a large area into a plurality of small areas.

[0040] In some implementation scenarios, the critical dimension may be, for example, line width or aperture. When measuring a critical dimension of line width, the region to be measured in the wafer may be divided into multiple sub-regions along the longitudinal or transverse direction to obtain a signal waveform diagram of each sub-region of the region to be measured in the wafer. Figure 2 As shown in (b) and (c) of FIG. 1 , the lateral line width is divided into multiple sub-areas along the lateral direction. For the critical dimension to be measured, multiple sub-areas can be divided along the arc of the area to be measured in the wafer to obtain the signal waveform diagram of each sub-area of ​​the area to be measured in the wafer. As an example, along 0°, 22.5°, 45°, 67.5°, 90°, etc. (for example Figure 7 As shown in FIG. 1A , the area to be measured is divided into a plurality of sub-areas to obtain a signal waveform diagram of each sub-area of ​​the area to be measured in the wafer.

[0041] Next, at step S302, the signal waveform graph of each sub-region is aligned with the signal waveform graph of the adjacent sub-region around it to obtain the signal waveform graph of the sub-region after alignment. That is, the embodiment of the present application first aligns the signal waveform graphs of each sub-region to reduce the deviation between the signals at the place where the unevenness is poor. In one embodiment, the signal waveform graph of each sub-region is aligned with the signal waveform graph of the adjacent sub-region around it to determine the first offset between the signal waveform graph of each sub-region and the signal waveform graph of the adjacent sub-region around it, and then the signal waveform graph of each sub-region is first offset based on the first offset to obtain the signal waveform graph of the sub-region after alignment.

[0042] For example, for measuring the line width whose key dimension is the longitudinal direction, the signal waveform graphs of the upper and lower adjacent sub-regions in the same side area can be selected, and the signal waveform graph of the sub-region with slightly better flatness can be used as a reference waveform to align the signal waveform graphs of the upper and lower adjacent sub-regions to determine the offset between the two signal waveform graphs. The alignment between the two signal waveform graphs is completed by moving the corresponding offset. For measuring the line width whose key dimension is the lateral direction, the signal waveform graphs of the front and rear adjacent sub-regions in the same side area can be selected for registration and alignment. For measuring the key dimension of the aperture, the signal waveform graphs of the sub-regions at adjacent arcs can be selected for registration and alignment. As an example, the signal waveform graph at 45° can be registered and aligned with the signal waveform graph at 22.5° or with the signal waveform graph at 67.5°.

[0043] It can be understood that the above-mentioned registration and alignment corresponds to correlation calculation, so in the implementation scenario, the above-mentioned registration and alignment operation can be implemented by, for example, a signal correlation analysis algorithm. According to the previous text, a signal waveform (such as a reference waveform) is translated to point x, and another signal waveform is scanned. When the correlation operation scans that the two signals coincide, the maximum correlation value (peak value) between the two adjacent signal waveforms is obtained. Then, the coordinate points of the two adjacent signal waveforms at the maximum correlation value are determined respectively, and the first offset is determined according to the difference between the corresponding coordinate points, and then the signal waveform of the sub-area after registration and alignment is obtained.

[0044] Furthermore, at step S303, correlation calculation is performed based on the signal waveform template and the signal waveform diagram of the sub-area after registration and alignment to determine the edge point of the area to be measured in the wafer. In other words, the edge point of the area to be measured in the wafer is determined by performing correlation calculations on the signal waveform diagrams of each sub-area after alignment and the signal waveform template respectively. Since the aligned signal waveform diagram eliminates the deviation existing in the case of unevenness, subsequent correlation calculations using the signal waveform template of the same scale can greatly improve the measurement accuracy.

[0045] In some implementation scenarios, when the key dimension to be measured is line width, the above-mentioned signal waveform template can be obtained by the following operations: obtain the coordinate points corresponding to all the maximum correlations after the signal waveform graph of each sub-area is aligned with the signal waveform graph of the adjacent sub-area around it, and combine all the coordinate points corresponding to the maximum correlations to obtain the signal waveform template. Alternatively, the coordinate points corresponding to the maximum correlations that meet the preset threshold can also be combined to obtain the signal waveform template. For example, the points with correlations less than the preset threshold are filtered, and the points with correlations higher than the preset threshold are retained to form a signal waveform template. That is, when measuring the line width, a signal waveform template can be established in the aforementioned alignment process, and the signal waveform template may include one or more.

[0046] When the critical dimension to be measured is the aperture, the signal waveform diagram of the sub-area at the target curvature can be selected to use the signal waveform diagram of the sub-area at the target curvature as the signal waveform template. Preferably, the aforementioned target curvature can be a horizontal curvature (e.g., 0°) or a longitudinal curvature (e.g., 90°).

[0047] In some embodiments, the signal waveform graph and / or signal waveform template of each sub-region may be interpolated to make the signal details richer and more fine-grained to improve the accuracy of correlation calculation. In some embodiments, the interpolation operation may be, for example, spline interpolation. Based on the signal waveform graph constructed above, correlation calculation may be performed with each registered and aligned signal waveform graph to determine the edge point of the measurement area.

[0048] In one embodiment, a correlation calculation can be performed based on the signal waveform template and the signal waveform diagram of the sub-area after registration and alignment to obtain the final coordinate position corresponding to the maximum correlation between the signal waveform template and the signal waveform diagram, and then the edge point of the area to be measured in the wafer is determined according to the final coordinate position corresponding to the maximum correlation. Specifically, in an implementation scenario, a correlation calculation is performed based on the signal waveform template and the signal waveform diagram of the sub-area after registration and alignment to obtain the initial coordinate position corresponding to the maximum correlation between the signal waveform template and the signal waveform diagram, and the target coordinate position corresponding to the maximum correlation is offset to the corresponding offset to determine the final coordinate position corresponding to the maximum correlation.

[0049] That is to say, firstly, the coordinate position corresponding to the maximum correlation between the signal waveform template and the signal waveform graph of the sub-area after registration and alignment is determined by correlation calculation, and then the final coordinate position corresponding to the maximum correlation is determined in combination with the offset in the registration and alignment operation. Among them, the final coordinate position corresponding to the maximum correlation corresponds to the edge point. As an example, assume that the horizontal coordinate of the coordinate position is 100, and the left offset of the signal waveform graph in the above registration and alignment operation is 5. In this scenario, the horizontal coordinate of the final coordinate position corresponding to the maximum correlation is 95, which corresponds to the edge point in the measurement area.

[0050] In one implementation scenario, in response to the critical dimensions including the aperture, the signal waveform of the sub-area after registration and alignment is mapped to a signal waveform template, so as to perform correlation calculation based on the signal waveform template and the mapped signal waveform. Specifically, after mapping the signal waveform of the sub-area after registration and alignment to the horizontal reverse or vertical direction, a correlation calculation method such as line width is used to obtain the coordinate position with the maximum correlation. Then, the coordinates are reversely mapped to the arc to obtain the edge points of the area to be measured in the wafer. The aforementioned mapping process can be implemented, for example, by trigonometric function transformation. This will be discussed later in conjunction with Figure 6 , Figure 7 DETAILED DESCRIPTION More details about the measurement aperture are described.

[0051] Based on the edge points of the wafer area to be measured obtained above, at step S304, the critical dimensions of the wafer are measured according to the edge points of the wafer area to be measured. After the above operations, the edge points of each sub-region can be obtained, and the edge points of the area to be measured can be obtained by, for example, calculating the mean of the edge points of each sub-region. For example, in the case where the critical dimension is the line width, the edge points on the left and right sides are obtained by the mean of the edge points of each sub-region on the left and right sides of the wafer area to be measured, and the line width can be obtained based on the distance between the edge points on the left and right sides. In the case where the critical dimension is the aperture, the aperture radius or diameter can be obtained by the distance between the mean point of the edge points of each sub-region in the wafer area to be measured and the center of the aperture.

[0052] Combined with the above description, it can be seen that the embodiment of the present application first aligns the signal waveform of each sub-area with the signal waveform of the surrounding adjacent sub-areas to eliminate the deviation caused by unevenness. Then, the signal waveform of the aligned sub-area is correlated with the signal waveform template, which improves the accuracy of measuring line width or aperture and enables better measurement repeatability under the same template.

[0053] Figure 4 FIG. 1 is an exemplary flow chart showing a method for measuring the line width of a wafer according to an embodiment of the present application. It should be understood that Figure 4 is the above Figure 3 A specific embodiment of Figure 3 The description also applies to Figure 4 .

[0054] like Figure 4 As shown in, at step S401, a plurality of sub-areas are divided longitudinally or transversely along the area to be measured in the wafer to obtain a signal waveform diagram of each sub-area of ​​the area to be measured in the wafer. Then, at step S402, the signal waveform diagram of each sub-area is aligned with the signal waveform diagram of the upper, lower or left and right adjacent sub-areas. In an implementation scenario, the signal waveform diagram with slightly better flatness of the two aligned signal waveform diagrams is used as a reference waveform. When performing the alignment, for example, a signal correlation analysis algorithm can be used to implement the aforementioned alignment operation to determine the coordinate points of two adjacent signal waveform diagrams at the maximum correlation value.

[0055] Based on the coordinate points at the maximum correlation values ​​obtained above, at step S403, a signal waveform template can be constructed and the signal waveform graph of the sub-region after registration and alignment in each sub-region can be obtained. As mentioned above, the coordinate points corresponding to all the maximum correlations can be combined to obtain a signal waveform template, or points with correlations less than a preset threshold can be filtered, and points with correlations higher than the preset threshold can be retained to form a signal waveform template in combination. In addition, based on the coordinate points corresponding to the maximum correlation, the offset of the signal waveform graph of the corresponding sub-region compared to the signal waveform graph of its adjacent sub-region can be determined. The signal waveform graph of the sub-region after registration and alignment is obtained by moving the signal waveform graph of the corresponding sub-region for the first time according to the offset.

[0056] In some embodiments, in order to make the signal waveform template and the signal waveform diagram of each sub-area more detailed and more fine-grained, at step S404, the signal waveform template and the signal waveform diagram of each sub-area can also be interpolated. In some embodiments, the aforementioned interpolation operation can be, for example, spline interpolation, etc. It can be understood that spline interpolation generally refers to the process of interpolating between adjacent integer coordinates (for example, x=100, x=101) using a piecewise polynomial to obtain a curve function group by solving the three-moment equations. Among them, each segmented interval is a cubic polynomial, and the equation group is obtained by setting a non-kink boundary condition, and the second-order derivative value obtained by the given interpolation point is used as an unknown variable to solve the corresponding function value to achieve the interpolation operation.

[0057] Further, at step S405, the correlation between the signal waveform template and the signal waveform graph of the sub-area after registration and alignment is calculated, so as to determine the edge point of the area to be measured in the wafer at step S406. Similar to the above-mentioned registration and alignment, the final coordinate position corresponding to the maximum correlation between the signal waveform graph of the corresponding sub-area and the signal waveform template can be calculated by, for example, a signal correlation analysis algorithm. Specifically, the initial coordinate position corresponding to the maximum correlation between the signal waveform template and the signal waveform graph of the sub-area after registration and alignment can be determined first, and then the final coordinate position corresponding to the maximum correlation can be obtained by offsetting to the corresponding offset, which corresponds to the edge point of the area to be measured. Thus, at step S407, the line width of the wafer can be measured. For example, the distance between the edge points on the left and right sides of the area to be measured is the line width.

[0058] Figure 5 FIG. 1 is an exemplary schematic diagram showing the measurement of line width according to an embodiment of the present application. Figure 5 The right figure in Figure (a) shows the signal waveforms of the sub-areas on the left and right sides of the area to be measured in the wafer. When the area to be measured in the wafer is not flat, the signal waveforms of the sub-areas will be deviated, for example Figure 5In the right figure of (a), the signal waveforms of the sub-regions on the left and right sides of the right figure have left and right deviations. In the embodiment of the present application, the signal waveforms of each sub-region are first aligned with the signal waveforms of the adjacent sub-regions above or below. For example Figure 5 The signal waveform S1 of a sub-region shown in FIG. (b) is aligned with the signal waveform S2 of the adjacent sub-region above it. Specifically, one signal waveform (such as a reference waveform) can be translated to point x, and the other signal waveform can be scanned. When the correlation operation scans that the two signals overlap, the maximum correlation value between the two adjacent signal waveforms can be obtained, for example Figure 5 As shown in FIG. (c) of FIG. 1 , it can be understood that the signal waveform diagram S1 and the signal waveform diagram S2 are continuously translated until the two signals overlap to achieve registration and alignment, and the coordinate point of the maximum correlation value is obtained.

[0059] The signal waveform template can be determined based on the coordinate positions corresponding to all the maximum correlations or the coordinate positions corresponding to the maximum correlations that meet the preset threshold. The edge points of each sub-region can be determined by calculating the correlation between the signal waveform template and the signal waveform graph of the sub-region after registration and alignment, for example Figure 5 The circles on the left of Figure (a) indicate the edge points measured in each sub-region. As mentioned above, by calculating the average of the edge points of each sub-region, the edge points of the region to be measured in the wafer can be obtained, and the distance between the edge points on the left and right sides of the region to be measured is the line width.

[0060] Figure 6 FIG. 1 is an exemplary flowchart showing an exemplary process for measuring the aperture of a wafer according to an embodiment of the present application. It should be understood that Figure 6 is the above Figure 3 Another specific embodiment of Figure 3 The description also applies to Figure 6 .

[0061] like Figure 6As shown in, at step S601, a plurality of sub-areas are divided along the arc of the area to be measured in the wafer to obtain the signal waveform of each sub-area of ​​the area to be measured in the wafer. Then, at step S602, the signal waveform of each sub-area is aligned with the signal waveform of its adjacent sub-area. Similarly, the signal waveform with slightly better flatness in the two aligned signal waveforms is used as a reference waveform. For example, the signal waveform at 45° is aligned with the signal waveform at 22.5°. When performing alignment, the signal waveforms at different arcs can also be mapped to the horizontal direction or the vertical direction, converted into a line width measurement method, and the aforementioned alignment operation is implemented by, for example, a signal correlation analysis algorithm to determine the coordinate points of the two adjacent signal waveforms at the maximum correlation value. Based on the coordinate position corresponding to the maximum correlation, the first offset of the signal waveform of the corresponding sub-area compared to the signal waveform of its adjacent sub-area can be determined. By moving the signal waveform of the corresponding sub-area for the first time according to the first offset, the signal waveforms after alignment of each sub-area are obtained.

[0062] Then, at step S603, the signal waveform graph of the sub-area at 0° or 90° is selected as the signal waveform template. In some embodiments, in order to make the signal waveform template and the signal waveform graph of each sub-area more detailed and more fine-grained, at step S604, the signal waveform template and the signal waveform graph of each sub-area after registration and alignment can also be interpolated. In some embodiments, the aforementioned interpolation operation can also be, for example, spline interpolation. Further, at step S605, the signal waveform graph of the sub-area after registration and alignment is mapped to the signal waveform template for correlation calculation. In some implementation scenarios, the signal waveform graph of the sub-area after registration and alignment can be mapped to the horizontal reverse or vertical direction by, for example, trigonometric function transformation.

[0063] As an example, assume that the coordinates of a point on an arc are represented as (x, y), and assume that the arc is mapped to a 90° vertical direction. In this scenario, the 360° arc needs to be divided into 360 parts (i.e., one part for each degree), and the distance from the center of the map to the 90° vertical direction corresponds to the distance from the center of the circle to the point on the arc, which can be expressed as Where x and y represent the offsets of the horizontal and vertical coordinates relative to the center of the circle, respectively. Based on this, all points on the arc can be mapped to a straight line, and then the above-mentioned line width measurement process is used for measurement. At step S606, the edge points of the area to be measured in the wafer are determined. Thus, at step S407, the aperture of the wafer can be measured. For example, by finally using coordinate inverse mapping to restore the edge points on the straight line to the arc, the diameter or radius of the aperture can be determined.

[0064] Figure 7FIG. 1 is an exemplary schematic diagram showing the measurement aperture according to an embodiment of the present application. Figure 7 Figure (a) shows the aperture in the wafer, which can be divided into multiple sub-areas along different arcs during measurement, such as 0°, 22.5°, 45°, 67.5°, 90°, 112.5°, 135°, 157.5°, 180°, etc. to obtain the signal waveform of each sub-area. Figure 7 FIG. (b) shows an exemplary signal waveform diagram of two adjacent sub-areas. Figure 6 It can be seen that the signal waveforms of two adjacent sub-areas are first aligned, and then the aligned signal waveforms are correlated with the signal waveform template to obtain the final edge points to determine the diameter or radius of the aperture.

[0065] Figure 8 FIG. 8 is an exemplary structural block diagram of an apparatus 800 for measuring a critical dimension of a wafer according to an embodiment of the present application. Figure 8 As shown in , the device 800 of the present application may include a processor 801 and a memory 802, wherein the processor 801 and the memory 802 communicate with each other via a bus. The memory 802 stores program instructions for measuring the critical dimensions of a wafer. When the program instructions are executed by the processor 801, the method steps described in the above text in combination with the accompanying drawings are implemented: obtaining the signal waveform diagrams of each sub-region of the region to be measured in the wafer; aligning the signal waveform diagrams of each sub-region with the signal waveform diagrams of the surrounding adjacent sub-regions to obtain the signal waveform diagrams of the aligned sub-regions; performing correlation calculation based on the signal waveform template and the signal waveform diagram of the aligned sub-region to determine the edge points of the region to be measured in the wafer; and measuring the critical dimensions of the wafer according to the edge points of the region to be measured in the wafer.

[0066] According to the above description in combination with the accompanying drawings, those skilled in the art can also understand that the embodiments of the present application can also be implemented by a software program. Therefore, the present application also provides a computer-readable storage medium. The computer-readable storage medium stores computer-readable instructions for measuring the critical dimensions of a wafer. When the computer-readable instructions are executed by one or more processors, the present application in combination with the accompanying drawings can be implemented. Figure 3 A method for measuring critical dimensions of a wafer is described.

[0067] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0068] It should be noted that although the operations of the method of the present application are described in a specific order in the accompanying drawings, this does not require or imply that the operations must be performed in this specific order, or that all the operations shown must be performed to achieve the desired results. On the contrary, the steps depicted in the flow chart can be performed in a different order. Additionally or alternatively, some steps can be omitted, multiple steps can be combined into one step, and / or one step can be decomposed into multiple steps.

[0069] It should be understood that when the terms "first", "second", "third" and "fourth" are used in the claims, the specification and the drawings of the present application, they are only used to distinguish different objects, rather than to describe a specific order. The terms "include" and "comprise" used in the specification and claims of the present application indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or their collections.

[0070] It should also be understood that the terms used in this application specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in this application specification and claims, unless the context clearly indicates otherwise, the singular forms of "a", "an" and "the" are intended to include plural forms. It should also be further understood that the term "and / or" used in this application specification and claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0071] Although the implementation methods of the present application are as above, the contents described are only examples adopted to facilitate the understanding of the present application, and are not intended to limit the scope and application scenarios of the present application. Any technician in the technical field described in the present application can make any modifications and changes in the form and details of the implementation without departing from the spirit and scope disclosed in the present application, but the scope of patent protection of the present application shall still be subject to the scope defined in the attached claims.

Claims

1. A method for measuring a critical dimension of a wafer, comprising: Obtaining signal waveform diagrams of each sub-area of ​​the area to be measured in the wafer; Aligning the signal waveform graph of each sub-region with the signal waveform graphs of its surrounding adjacent sub-regions to obtain the signal waveform graphs of the sub-regions after alignment; Performing correlation calculation based on the signal waveform template and the signal waveform diagram of the sub-area after the registration and alignment to determine the edge point of the area to be measured in the wafer; as well as Measuring the critical dimensions of the wafer according to the edge points of the area to be measured in the wafer, In response to the critical dimension including line width, the signal waveform template is obtained by the following operations: Obtaining coordinate points corresponding to all maximum correlations after registering and aligning the signal waveform graphs of each sub-region with the signal waveform graphs of the surrounding adjacent sub-regions; wherein in the registration and alignment, the maximum correlation is obtained when the two signal waveform graphs overlap; Combining all coordinate points corresponding to the maximum correlation to obtain the signal waveform template; or The coordinate points corresponding to the maximum correlation degree that meets the preset threshold are combined to obtain the signal waveform template.

2. The method according to claim 1, wherein registering and aligning the signal waveform graph of each sub-region with the signal waveform graph of its surrounding adjacent sub-regions to obtain the registered and aligned signal waveform graph of the sub-region comprises: Aligning the signal waveform graphs of each sub-region with the signal waveform graphs of its surrounding adjacent sub-regions to determine the corresponding offsets between the signal waveform graphs of each sub-region and the signal waveform graphs of its surrounding adjacent sub-regions; as well as The signal waveform graphs of the sub-regions are offset based on the corresponding offsets to obtain the signal waveform graphs of the sub-regions after the registration and alignment.

3. The method according to claim 2, wherein performing correlation calculation based on the signal waveform template and the signal waveform diagram of the sub-area after registration and alignment to determine the edge point of the area to be measured in the wafer comprises: Performing correlation calculation based on the signal waveform template and the signal waveform graph of the aligned sub-region to obtain a final coordinate position corresponding to the maximum correlation between the signal waveform template and the signal waveform graph; as well as The edge point of the area to be measured in the wafer is determined according to the final coordinate position corresponding to the maximum correlation.

4. The method according to claim 3, wherein performing correlation calculation based on the signal waveform template and the signal waveform graph of the aligned sub-region to obtain a final coordinate position corresponding to the maximum correlation between the signal waveform template and the signal waveform graph comprises: Performing correlation calculation based on the signal waveform template and the signal waveform graph of the aligned sub-region to obtain an initial coordinate position corresponding to the maximum correlation between the signal waveform template and the signal waveform graph; as well as The target coordinate position corresponding to the maximum correlation is offset toward the corresponding offset to determine the final coordinate position corresponding to the maximum correlation.

5. The method according to claim 1 or 2, wherein in response to the critical dimension including line width, the signal waveform diagram of each sub-region is obtained by the following operation: The region to be measured in the wafer is divided into a plurality of sub-regions along the longitudinal direction or the transverse direction to obtain a signal waveform diagram of each sub-region of the region to be measured in the wafer.

6. The method according to any one of claims 1 to 3, further comprising: An interpolation operation is performed on the signal waveform diagram of each sub-area and / or the signal waveform template.

7. A method for measuring a critical dimension of a wafer, comprising: Obtaining signal waveform diagrams of each sub-area of ​​the area to be measured in the wafer; Aligning the signal waveform graph of each sub-region with the signal waveform graphs of its surrounding adjacent sub-regions to obtain the signal waveform graphs of the sub-regions after alignment; Performing correlation calculation based on the signal waveform template and the signal waveform diagram of the sub-area after the registration and alignment to determine the edge point of the area to be measured in the wafer; as well as The critical dimension of the wafer is measured according to the edge point of the area to be measured in the wafer, wherein in response to the critical dimension including the aperture, the signal waveform template is also obtained by the following operations: Selecting a signal waveform diagram of a sub-area at a target arc; and The signal waveform diagram of the sub-area at the target arc is used as the signal waveform template.

8. The method according to claim 7, wherein registering and aligning the signal waveform graph of each sub-region with the signal waveform graph of its surrounding adjacent sub-regions to obtain the registered and aligned signal waveform graph of the sub-region comprises: Aligning the signal waveform graphs of each sub-region with the signal waveform graphs of its surrounding adjacent sub-regions to determine the corresponding offsets between the signal waveform graphs of each sub-region and the signal waveform graphs of its surrounding adjacent sub-regions; as well as The signal waveform graphs of the sub-regions are offset based on the corresponding offsets to obtain the signal waveform graphs of the sub-regions after the registration and alignment.

9. The method according to claim 7 or 8, wherein in response to the critical dimension including an aperture, the signal waveform diagram of each sub-region is obtained by the following operations: The region to be measured in the wafer is divided into a plurality of sub-regions along the arc of the region to be measured in the wafer, so as to obtain a signal waveform diagram of each sub-region of the region to be measured in the wafer.

10. The method according to claim 7, wherein in response to the critical dimension including an aperture, performing correlation calculation based on the signal waveform template and the signal waveform diagram of the sub-region after the registration alignment, further comprises: Mapping the signal waveform graph of the registered and aligned sub-region to the signal waveform template; as well as A correlation calculation is performed based on the signal waveform template and the mapped signal waveform graph.

11. The method according to claim 7, further comprising: An interpolation operation is performed on the signal waveform diagram of each sub-area and / or the signal waveform template.

12. An apparatus for measuring a critical dimension of a wafer, comprising: processor; as well as A memory having computer instructions for measuring critical dimensions of a wafer stored thereon, wherein when the computer instructions are executed by a processor, the method according to any one of claims 1 to 6 is implemented; or, the method according to any one of claims 7 to 11 is implemented.

13. A computer-readable storage medium having stored thereon computer program instructions for measuring critical dimensions of a wafer, wherein when the computer program instructions are executed by one or more processors, the method according to any one of claims 1 to 6 is implemented; or the method according to any one of claims 7 to 11 is implemented.

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