Critical dimension measuring method and electron beam equipment

Abstract

The invention provides a critical dimension measuring method and electron beam equipment. According to the measurement method, the corresponding signal peak in the scanning information can be accurately captured according to the boundary information of the to-be-measured film layer, and the critical dimension of the to-be-measured film layer can be accurately measured, so that the real boundary of the to-be-measured film layer can still be accurately captured by the electron beam equipment in an automatic measurement mode; the risk that the real film layer boundary is difficult to distinguish under the automatic film layer measurement of the electron beam equipment is effectively reduced, and the accuracy of the measurement result is improved.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, and in particular to a critical dimension measurement method and electron beam equipment. Background Art

[0002] With the development of semiconductor manufacturing technology, the critical dimension (CD) of semiconductor devices is getting smaller and smaller, and the measurement requirements for critical dimensions (e.g., width dimensions) are getting higher and higher. At present, electron beam equipment (e.g., scanning electron microscope SEM) can generally be used to measure the critical dimensions of patterns on wafers, which can theoretically achieve high measurement accuracy. However, in the actual measurement process, when the device captures the boundary of the film layer in automatic mode for measurement, it is often difficult for the device to correctly capture the boundary of the actual film layer to be measured, resulting in the measurement result being unable to represent the critical dimension of the film layer to be measured. Summary of the invention

[0003] The object of the present invention is to provide a critical dimension measurement method to solve the problem in the prior art that it is difficult to correctly capture the boundary of the actual film layer to be measured, thereby causing inaccurate measurement results.

[0004] In this regard, the present invention provides a method for measuring critical dimensions, comprising: providing a sample, wherein at least two film layers are displayed on the surface of the sample, wherein the at least two film layers include a film layer to be measured; placing the sample in an electron beam device, and making the scanning field of view of the electron beam device cover the film layer to be measured, and the scanning field of view of the electron beam device also covers other film layers; using an electron beam to scan the surface of the sample within the scanning field of view to obtain corresponding scanning information, wherein the scanning information has multiple signal peaks corresponding to boundaries of each film layer within the scanning field of view; and, according to the boundary position of the film layer to be measured relative to the boundaries of other film layers, locating the signal peak in the scanning signal corresponding to the boundary position of the film layer to be measured, so as to measure the critical dimensions of the film layer to be measured.

[0005] Optionally, the method of making the scanning field of view of the electron beam device cover the film layer to be tested includes: identifying an auxiliary pattern on the sample to perform an alignment operation; and finding a target pattern containing the film layer to be tested based on the position of the target pattern relative to the auxiliary pattern.

[0006] Optionally, the method for performing the alignment operation also includes: performing parameter comparison between the identified auxiliary pattern and the theoretical auxiliary pattern, and obtaining the degree of fit of the identified auxiliary pattern relative to the theoretical auxiliary pattern; and, determining whether the degree of fit reaches a set value to confirm whether the current alignment operation meets the requirements.

[0007] Optionally, when comparing parameters of the identified auxiliary pattern with a theoretical auxiliary pattern, the comparison parameters include: at least one of: pixels of the image, size of the auxiliary pattern, and shape of the auxiliary pattern.

[0008] Optionally, after finding the target pattern, the method further includes verifying the position coordinates of the target pattern currently found, and the method for verifying the position coordinates includes: setting a verification standard, and the method for setting the verification standard includes: defining the position of the auxiliary pattern as the origin (0, 0), and obtaining the coordinates (X, Y) of the theoretical position of the target pattern from the origin, and combining the size Dx of the target pattern in the X direction and the size Dy of the target pattern in the Y direction to set the verification standard (X±Dx, Y±Dy); and, comparing the coordinates of the actual position of the target pattern currently found with the verification standard, and determining whether the coordinates of the actual position of the target pattern exceed the verification standard, so as to confirm whether the target pattern currently found is the real target pattern.

[0009] Optionally, a groove is formed inward from the surface of the sample, and the at least two film layers sequentially cover the side walls of the groove to surround at least two annular structures in the groove, and the at least two annular structures are displayed on the surface of the sample; and, multiple signal peaks in the scanning signal in the measurement direction of the key dimension correspond one-to-one to the boundaries of each annular structure.

[0010] Optionally, the at least two film layers are stacked on the surface of the sample, wherein at least one film layer boundary of the lower film layer extends below the upper film layer, so that film layer boundaries of different film layers are displayed in the width direction of the film layer to be measured; and, the multiple signal peaks in the scanning signal in the measurement direction of the key dimension correspond one-to-one to the film layer boundaries of each film layer.

[0011] Another object of the present invention is to provide an electron beam device for critical dimension measurement, comprising: a accommodating cavity for placing a sample, wherein at least two film layers are displayed on the surface of the sample, and the at least two film layers include a film layer to be measured; an electron beam unit for emitting an electron beam onto the surface of the sample within its scanning field of view to perform electron beam scanning; an electron detector for collecting secondary electrons excited from the sample surface to generate corresponding scanning information; and an information processing unit for arranging each signal peak in the scanning information to correspond to the boundary position of each film layer within the scanning field of view, and locating the signal peak in the scanning signal corresponding to the boundary position of the film layer to be measured according to the boundary position of the film layer to be measured relative to the boundary positions of other film layers, so as to measure the critical dimension of the film layer to be measured.

[0012] Optionally, the electron beam device further includes: an imaging unit, used to display an image on the sample surface and to identify auxiliary patterns on the sample to perform alignment operations.

[0013] Optionally, the information processing unit is also used to perform parameter comparison between the identified auxiliary pattern and the theoretical auxiliary pattern to obtain the fit of the identified auxiliary pattern relative to the theoretical auxiliary pattern, and determine whether the fit reaches a set value, thereby confirming whether the current alignment operation meets the requirements.

[0014] Optionally, the electron beam device also includes: a positioning unit, used to find the target pattern containing the film layer to be measured according to the position of the target pattern relative to the auxiliary pattern, and locate the film layer to be measured so that the scanning field of view of the electron beam device covers the film layer to be measured.

[0015] Optionally, the information processing unit is also used to set a verification standard, and compare the coordinates of the actual position of the target pattern currently found with the verification standard to determine whether the coordinates of the actual position of the target pattern exceed the verification standard, so as to confirm whether the target pattern currently found is the real target pattern.

[0016] Optionally, the electron beam device is a scanning electron microscope.

[0017] In the critical dimension measurement method provided by the present invention, the corresponding signal peak in the scanning information can be accurately captured according to the boundary information of the film layer to be measured, and the critical dimension of the film layer to be measured can be correctly measured, thereby realizing that the electron beam equipment can still accurately capture the real boundary of the film layer to be measured in the automatic measurement mode, effectively reducing the risk of the electron beam equipment being difficult to distinguish the real film layer boundary when automatically measuring the film layer, and improving the accuracy of the measurement result.

[0018] Furthermore, the measurement method provided by the present invention can also perform a quality assessment on the alignment operation, effectively improving the alignment deviation problem and facilitating improved alignment accuracy, so that the target pattern containing the film layer to be measured can be found more quickly and accurately in the subsequent step.

[0019] Furthermore, in the measurement method provided by the present invention, after finding the target pattern, the position coordinates of the currently found target pattern can be verified, thereby confirming that the current target pattern is the real target pattern, preventing pattern deviation from mispositioning to other patterns, and ensuring that the scanning field of view of the electron beam equipment can ultimately be aligned with the film layer to be measured that actually needs to be measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 FIG. 4 is a flow chart of a method for measuring a critical dimension in an embodiment of the present invention.

[0021] Figure 2 The schematic diagram is a sample having three layers of films arranged in concentric circles on its surface, and the corresponding scanning signal.

[0022] Figure 3 A schematic diagram of a sample having two stacked film layers formed on its surface and a corresponding scanning signal.

[0023] Figure 4 An image of an auxiliary pattern.

[0024] Figure 5 An image of a target pattern.

[0025] Figure 6 It shows an image of the film layer to be tested.

[0026] Figure 7 The figure is a flow chart of a method for aligning the scanning field of view of an electron beam device with a film layer to be measured in one embodiment of the present invention. DETAILED DESCRIPTION

[0027] As described in the background technology, when the electron beam device is measured in the automatic measurement mode, it is often difficult to distinguish the actual boundary of the film layer to be measured, resulting in inaccurate measurement results. Specifically, in the semiconductor processing process, multiple film layers are usually stacked on the substrate to form the required devices or circuits. At this time, when measuring the critical dimensions of the film layer to be measured, it is often interfered by other film layers, so that the electron beam device may mistakenly capture the boundaries of other film layers when measuring in the automatic measurement mode, resulting in measurement errors. In this regard, an optional solution is to switch the automatic measurement mode to the manual measurement mode (Manual mode) and manually capture the boundary of the film layer to be measured. However, manual measurement wastes time and affects production capacity.

[0028] In view of the above technical problems, the present invention provides a critical dimension measurement method, which allows the electron beam device to accurately identify the boundary of the real film layer to be measured in the automatic measurement mode, thereby ensuring the accuracy of the measurement result. Figure 1 As shown, the measuring method includes the following steps.

[0029] Step S100, providing a sample, wherein at least two film layers are displayed on the surface of the sample, and the at least two film layers include a film layer to be tested.

[0030] Step S200, placing the sample on an electron beam device, and making the scanning field of the electron beam device cover the film layer to be tested, and the scanning field of the electron beam device also covers other film layers.

[0031] Step S300 , scanning the sample surface within the scanning field of view using an electron beam to obtain corresponding scanning information, wherein the scanning information includes a plurality of signal peaks corresponding to boundaries of each film layer within the scanning field of view.

[0032] Step S400 , locating a signal peak in the scanning signal corresponding to the boundary position of the film layer to be measured according to the boundary position of the film layer to be measured relative to the boundaries of other film layers, so as to measure the critical dimension of the film layer to be measured.

[0033] That is, in the critical dimension measurement method provided by the present invention, the boundary position of the film layer to be measured relative to the boundaries of other film layers can be preset in the electron beam device, so that after obtaining the scanning signal, the signal peak corresponding to the boundary of the film layer to be measured can be accurately located from the multiple signal peaks of the scanning signal, so that the real boundary of the film layer to be measured can be accurately captured, thereby realizing accurate measurement of the critical dimension of the film layer to be measured.

[0034] Specifically, when measuring the critical dimensions of the film layer to be measured, it is necessary to capture the two boundaries of the film layer to be measured along the measurement direction of the critical dimensions (for example, the width direction), and the boundaries of other film layers may be exposed on the side of the boundaries of the film layer to be measured. Therefore, the boundaries of multiple film layers within the scanning field of view are arranged in sequence along the measurement direction of the critical dimensions. At this time, the signal peaks arranged at the same position in the scanning signal can be located according to the arrangement position of the boundaries of the film layer to be measured in the measurement direction, so that the boundaries of the film layer to be measured can be accurately captured. For example, if the two boundaries of the film layer to be measured are respectively arranged at the second position and the third position among the multiple boundaries, then the corresponding signal peaks in the scanning signal are arranged at the second position and the third position among the multiple signal peaks.

[0035] Furthermore, the measurement method provided by the present invention can also optimize the alignment process of the sample for the electron beam device, which is conducive to more accurate and rapid positioning of the film layer to be measured. Specifically, the alignment process of the sample may include: obtaining the auxiliary pattern on the sample, and identifying the auxiliary pattern to perform an alignment operation; then, comparing the parameters of the identified auxiliary pattern and the theoretical auxiliary pattern to obtain the fit GOA of the identified auxiliary pattern relative to the theoretical auxiliary pattern; wherein, when the fit GOA is greater than or equal to the set value, it means that the device accurately finds the auxiliary pattern, and the recognition accuracy meets the requirements, and the device can continue the subsequent measurement process; on the contrary, when the fit GOA is lower than the set value, it means that the device fails to accurately identify the auxiliary pattern or the recognition accuracy is low, affecting the alignment effect, and the alignment operation can be continued to be adjusted until the alignment accuracy requirements are met. That is, in one embodiment of the present invention, when identifying the auxiliary pattern for alignment operation, the quality of the identified auxiliary pattern is further evaluated to determine whether its alignment operation meets the higher requirements, to ensure a high-precision alignment process, and to effectively solve the problem of alignment deviation (Alignment shift) that is prone to occur when performing the alignment operation.

[0036] Furthermore, the measurement method provided by the present invention can also locate the target pattern containing the film layer to be measured based on the auxiliary pattern, and after finding the target pattern, the position coordinate verification can be performed on the target pattern to confirm whether the currently found target pattern is the real pattern that needs to be measured. Among them, the method of verifying the position coordinates of the target pattern, for example, includes: setting a verification standard Spec, and comparing the coordinates of the actual position of the target pattern found with the verification standard Spec to determine whether the currently found target pattern is the real target pattern that needs to be measured. Among them, when the coordinates of the actual position of the target pattern do not exceed the verification standard Spec, it means that the current target pattern is the real target pattern; conversely, when the coordinates of the actual position of the target pattern exceed the verification standard Spec, it means that the current target pattern is not the real target pattern, and displacement compensation can be performed at this time to find the real target pattern. Therefore, the measurement method in one embodiment of the present invention can effectively reduce the risk of mispositioning to other patterns due to position deviation.

[0037] The following is a further detailed description of the critical dimension measurement method and electron beam device proposed in the present invention in conjunction with specific embodiments. According to the following description, the advantages and features of the present invention will become clearer. It should be noted that the drawings are all in a very simplified form and use non-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 recognized that relative terms such as "above", "below", "top", "bottom", "above" and "below" shown in the drawings can be used to describe the relationship between various elements. These relative terms are intended to cover different orientations of elements other than the orientations depicted in the drawings. For example, if the device is inverted relative to the view in the drawing, an element described as being "above" another element will now be below the element.

[0038] In step S100, a sample is provided, and at least two film layers are displayed on the surface of the sample, and the at least two film layers include a film layer to be tested. For the convenience of description, the film layers other than the film layer to be tested are defined as interference film layers herein.

[0039] In one example, the film layer to be tested and the interfering film layer can be arranged in the horizontal direction, for example, the film layer to be tested and the interfering film layer are arranged in sequence around the same center, thereby forming multiple ring structures. At this time, when the sample surface within the scanning field of view is scanned by an electron beam, the boundary signals of each film layer in the arrangement direction can be obtained, which include the boundary signals of the film layer to be tested and the boundary signals of other interfering film layers.

[0040] For example, a groove may be formed from the sample surface inward, and the film layer to be tested and the interfering film layer may sequentially cover the sidewalls of the groove, thereby surrounding at least two annular structures in the groove, so that at least two annular structures surrounded by the film layer to be tested and the interfering film layer may be displayed on the surface of the sample. At this time, when the sample surface within the scanning field of view is scanned by an electron beam (specifically, the scanning may be performed along the measurement direction of the critical dimension), the boundary signals of each annular structure in the measurement direction of the critical dimension may be obtained, and the boundary signals of each annular structure correspond to the boundary signals of the film layer to be tested and the boundary signals of other interfering film layers.

[0041] by Figure 2 For example, Figure 2 The example shows three film layers, namely the first film layer 110, the second film layer 120 and the third film layer 130. The first film layer 110, the second film layer 120 and the third film layer 130 are sequentially surrounded with the same center, thereby surrounding three annular structures. When it is necessary to measure the maximum opening size D11 surrounded by the first film layer 110 on the inner side (that is, to measure the diameter of the annular structure formed by the first film layer 110), the first film layer 110 can be defined as the film layer to be measured, and the second film layer 120 and the second film layer 130 can be defined as the interference film layer.

[0042] In another example, the film layer to be tested and the interfering film layer can be stacked in a vertical direction, and at least one film layer boundary of the interfering film layer can be displayed on the sample surface, so the boundary of the film layer to be tested and the boundary of the interfering film layer will be displayed on the surface of the sample at the same time. At this time, when the sample surface within the scanning field of view is scanned by an electron beam, the boundary signal of the film layer to be tested and the boundary signal of other interfering film layers will be obtained.

[0043] For example, the film layer to be tested and the interference film layer are stacked, that is, an interference film layer is formed above and / or below the film layer to be tested. Wherein, in the case where an interference film layer is formed below the film layer to be tested, the boundary of the interference film layer located below extends from below the film layer to be tested, so that the boundary of the interference film layer below is simultaneously displayed on the surface of the sample; and, in the case where an interference film layer is formed above the film layer to be tested, the boundary of the interference film layer located above can be completely located on the top surface of the film layer to be tested, that is, the boundary of the film layer to be tested extends from below the interference film layer, so that the boundary of the interference film layer above is simultaneously displayed on the surface of the sample.

[0044] by Figure 3 For example, Figure 3 An upper film layer 210 and a lower film layer 220 are stacked and formed therein. When the width of the upper film layer 210 needs to be measured, the upper film layer 210 can be defined as the film layer to be measured, and the lower film layer 220 can be defined as the interference film layer. The width of the interference film layer is greater than the width of the film layer to be measured, so that both boundaries of the interference film layer in the width direction extend out. Similarly, when the width of the lower film layer 220 needs to be measured, the lower film layer 220 can be defined as the film layer to be measured, and the upper film layer 210 can be defined as the interference film layer.

[0045] In semiconductor manufacturing, the various film layers formed on the substrate are usually graphed to form specific patterns, such as hole patterns, ring patterns, stripe patterns, etc. When measuring the critical dimensions of the film layer to be measured, the pattern containing the film layer to be measured can be defined as a target pattern, that is, a target pattern is formed on the surface of the sample, and the target pattern is at least defined by the film layer to be measured. Based on this, when searching for the film layer to be measured, the target pattern can be preferentially locked on the sample, so that it can be enlarged on the basis of the target pattern to display the film layer to be measured to a greater extent, which is conducive to finding the film layer to be measured faster and improving measurement efficiency. For example Figure 5 In the example of , the target pattern is specifically a ring pattern at a specific position (eg Figure 5 The target pattern is located in the center of the display), and the annular pattern is at least surrounded by the film layer to be measured; and the reference Figure 6 As shown, by enlarging the annular pattern, the film layer to be measured can be displayed to a greater extent, so as to facilitate the measurement of the film layer to be measured. Figure 6 As shown, the annular pattern specifically includes an annular structure surrounded by the first film layer 110 , an annular structure surrounded by the second film layer 120 , and an annular structure surrounded by the third film layer 130 .

[0046] Furthermore, an auxiliary pattern may be formed on the surface of the sample. The auxiliary pattern is set in a specific pattern so that it is easy to identify. When the electron beam device aligns the sample, the auxiliary pattern is easily identified to achieve a rapid alignment process of the sample position. The auxiliary pattern is different from the target pattern. For example, the auxiliary pattern can be any easily identifiable pattern such as an arrow mark or a cross mark. Figure 4 An auxiliary pattern shown in FIG.

[0047] In step S200 , the sample is placed in an electron beam device (eg, a scanning electron microscope SEM), and the scanning field of the electron beam device covers the film layer to be tested, and the scanning field also covers other film layers (ie, interference film layers).

[0048] That is, the scanning field of the electron beam device not only shows the boundary of the film to be measured, but also inevitably shows at least part of the boundary of the interfering film. Figure 6 For example, when measuring the critical dimensions of a ring structure surrounded by a film to be measured (for example, measuring the diameter of the ring structure), the scanning field of the electron beam device will inevitably cover the film boundary of other interfering films while covering the film boundary of the film to be measured. Figure 6 The boundaries of different membrane layers are shown in the figure.

[0049] Among them, the method of making the scanning field of view of the electron beam device cover the film layer to be measured may include: finding a target pattern containing the film layer to be measured on the sample, and the image of the target pattern can be specifically acquired and displayed by the imaging system in the electron beam device; then, the film layer to be measured can be quickly located according to the target pattern, so that the scanning field of view of the electron beam device can eventually cover the film layer to be measured. In addition, when the size of the target pattern is large, since it is difficult to clearly display the film layer to be measured in the same display area, the target pattern can be magnified by a predetermined multiple in the same display area to further select the film layer to be measured; conversely, when the size of the target pattern is small, the film layer to be measured can be clearly displayed at the same time in the same display area, and the film layer to be measured can be directly measured at this time.

[0050] Furthermore, the method for finding a target pattern containing a film layer to be tested on a sample may include: performing an alignment operation on the position of the sample in an electron beam device, so that the desired target pattern can be found more quickly based on the aligned sample. As described above, an auxiliary pattern is formed on the sample, and an alignment operation can be performed based on the auxiliary pattern. Specifically, when performing the alignment operation, an imaging system in the electron beam device acquires an image of the auxiliary pattern and identifies the auxiliary pattern to perform the alignment operation.

[0051] In this embodiment, when performing the alignment operation, it also includes performing a quality assessment on the identified auxiliary pattern to determine its alignment accuracy. The method for performing a quality assessment on the auxiliary pattern may include: setting image assessment parameters (for example, at least one of the pixels, size, shape, etc. of the image of the auxiliary pattern), comparing the corresponding parameters of the identified auxiliary pattern and the theoretical auxiliary pattern, and obtaining the fit GOA of the identified auxiliary pattern relative to the theoretical auxiliary pattern, wherein when the fit GOA is greater than or equal to the set value, it means that the device accurately finds the auxiliary pattern and the recognition accuracy meets the requirements, and the device can continue the subsequent measurement process; conversely, when the fit GOA is lower than the set value, it means that the device fails to accurately identify the auxiliary pattern.

[0052] It should be noted that the alignment operation of the device before measurement is crucial. If the device fails to accurately identify the auxiliary pattern in the initial stage and an alignment error occurs, it will make it difficult to accurately find the target pattern containing the film layer to be measured later, resulting in the area actually measured not being the measurement area desired to be measured. In this embodiment, when performing the alignment operation, a quality assessment is further performed on the alignment operation to improve the alignment accuracy and ensure that the target pattern containing the film layer to be measured can be found more accurately later.

[0053] It should be recognized that in practical applications, the degree of fit GOA of the auxiliary pattern actually identified relative to the theoretical auxiliary pattern can be calculated by calculation. In addition, the corresponding set values ​​can be set according to different evaluation parameters. For example, when the degree of fit for size and shape is greater than or equal to 90%, but the degree of fit for pixels is less than 80%, then it can be considered that the device accurately finds the auxiliary pattern, but the recognition accuracy is poor. At this time, the focusing operation of the auxiliary pattern can be optimized to improve the recognition accuracy, thereby improving the alignment accuracy of the sample. Alternatively, a final set value can be set based on the respective weights of multiple evaluation parameters, by obtaining the comprehensive degree of fit of the auxiliary pattern actually identified relative to the theoretical auxiliary pattern, and comparing it with the set value.

[0054] After the alignment operation is completed based on the auxiliary pattern, the target pattern can be further found based on the position of the target pattern relative to the auxiliary pattern. In a further solution, after the target pattern is found, the position coordinates of the target pattern are also verified to confirm whether the currently found target pattern is the actual pattern to be measured.

[0055] Among them, the method for verifying the position coordinates of the target pattern includes, for example: setting a verification standard Spec, the setting method of the verification standard Spec is, for example, defining the position of the auxiliary pattern as the origin (0, 0), and obtaining the coordinates (X, Y) of the theoretical position of the target pattern from the origin, and on this basis, combining the size Dx of the target pattern in the X direction and the size Dy of the target pattern in the Y direction, and then setting the verification standard Spec (X±Dx, Y±Dy); then, comparing the coordinates of the actual position of the target pattern found with the verification standard Spec to determine whether the target pattern currently found is the real target pattern to be measured. Among them, when the coordinates of the actual position of the target pattern do not exceed the verification standard Spec, it means that the current target pattern is the real target pattern; on the contrary, when the coordinates of the actual position of the target pattern exceed the verification standard Spec, it means that the current target pattern is not the real target pattern, and displacement compensation can be performed at this time to find the real target pattern.

[0056] That is, in a specific example, the method of covering the film layer to be tested by the scanning field of view of the electron beam device can refer to Figure 7 As shown, it specifically includes the following steps performed after placing the sample in the electron beam device.

[0057] Step S210, identifying the auxiliary pattern on the sample to perform an alignment operation, for example, by identifying Figure 4 The auxiliary pattern shown is used for alignment operation.

[0058] Step S220, calculating the degree of fit GOA of the identified auxiliary pattern relative to the theoretical auxiliary pattern.

[0059] Step S230, determine whether the fit GOA reaches a preset value. If so, it means that the device has accurately found the auxiliary pattern and achieved a high recognition accuracy, meeting the requirements of the alignment operation, and the subsequent step S240 can be executed; if not, return to step S210 to correct the alignment operation until the fit GOA reaches the preset value.

[0060] Step S240, based on the position of the target pattern relative to the auxiliary pattern, a target pattern containing the film layer to be tested is found. The target pattern found is, for example, Figure 5 A circular pattern is shown in the center.

[0061] Step S250, obtaining the coordinates of the actual position of the found target pattern.

[0062] In step S260, the coordinates of the actual position of the target pattern are compared with the verification standard Spec to determine whether the coordinates of the actual position of the target pattern exceed the verification standard Spec. If so, it means that the currently found target pattern is the real target pattern to be measured; if not, it means that the current target pattern is not the real target pattern, and the process can return to step S240 to find the target pattern again, and specifically, displacement compensation can be performed based on the pattern found last time to obtain the real target pattern.

[0063] In this way, the film layer to be tested can be further found from the found target pattern, so that the scanning field of the electron beam device can eventually cover the film layer to be tested. Figure 6 As shown, the film layer to be tested is specifically one of the film layers surrounding the annular pattern. As mentioned above, when the size of the target pattern is large, it is difficult to clearly display the film layer to be tested in the same display area. At this time, the target pattern can be enlarged to ensure that the film layer to be tested can be clearly displayed in the same display area.

[0064] That is to say, in this embodiment, firstly, when performing the alignment operation, the quality of the identified auxiliary pattern is evaluated to ensure high alignment accuracy, effectively improve the problem of alignment deviation, and thus improve the subsequent positioning accuracy of the target pattern containing the film layer to be measured; secondly, the position coordinates of the currently found target pattern are verified to further confirm that the current target pattern is the real target pattern, so as to prevent pattern deviation and mispositioning to other patterns.

[0065] In step S300, the surface of the sample within the scanning field of view is scanned by an electron beam to obtain a corresponding scanning signal, wherein the scanning signal has a plurality of signal peaks corresponding to the boundaries of each film layer within the scanning field of view.

[0066] Specifically, when the electron beam scans the sample surface, it will excite secondary electrons on the sample surface. The detector in the electron beam device collects the secondary electrons and further converts them into electrical signals, thereby displaying a scanned image corresponding to the scanned field of view. In this embodiment, the surface of the sample can be scanned along the measurement direction of the key dimension, and the grayscale value corresponding to the measurement direction of the key dimension can be obtained based on the obtained scanned image to form a scan signal. For example, refer to Figure 2 As shown, when the maximum opening size D11 of the annular structure surrounded by the first film layer 110 is measured, the gray value distribution of the annular structure in the direction of its maximum opening size can be obtained, wherein the gray value corresponding to the boundary position of each film layer reaches a peak value.

[0067] In step S400, a signal peak corresponding to the boundary position of the film layer to be tested in the scanning information is located according to the boundary position of the film layer to be tested relative to the boundary positions of other film layers, so as to measure the critical dimension of the pattern to be tested.

[0068] Specific reference Figure 2 As shown, there are the first film layer 110, the second film layer 120 and the third film layer 130 within the scanning field of view, and accordingly, the film layer boundaries of the first film layer 110, the second film layer 120 and the third film layer 130 at least in the measurement direction of the key dimension will be displayed simultaneously in the same scanning field of view, and the corresponding scanning information includes the boundary information of the first film layer 110, the second film layer 120 and the third film layer 130.

[0069] Taking the first film layer 110 as the film layer to be measured, and the need to measure the maximum opening size D11 surrounded by the first film layer 110 as an example, then the measurement boundary of the film layer to be measured (i.e., the first film layer 110) relative to the boundary position of other interfering film layers is the two boundaries arranged in the middle along the corresponding direction. At this time, the relative position of the measurement boundary of the film layer to be measured can be preset in the electron beam equipment, so that the equipment can capture the two signal peaks corresponding to the middle position in the scanning information according to the preset position information in the automatic measurement mode, and measure the distance between the two signal peaks in the middle position to obtain the maximum opening size D11 surrounded by the first film layer 110.

[0070] Similarly, taking the second film layer 120 as the film layer to be measured, and the need to measure the maximum opening size D12 surrounded by the second film layer 120 as an example, then the measurement boundary of the film layer to be measured (i.e., the second film layer 120) relative to the boundary position of other interfering film layers is the two boundaries arranged at the second position and the fifth position along the corresponding direction. At this time, the relative position of the measurement boundary of the film layer to be measured can be preset in the electron beam equipment, so that the equipment can capture the two signal peaks corresponding to the second position and the fifth position in the scanning information according to the preset position information in the automatic measurement mode, and measure the distance between the two signal peaks at the second position and the fifth position to obtain the maximum opening size D12 surrounded by the second film layer 120.

[0071] In addition, in the Figure 3 When the sample shown is measured for width, the scanning field of view includes an upper film layer 210 and a lower film layer 220, and two boundaries of the upper film layer 210 in the width direction and two boundaries of the lower film layer 220 in the width direction can be displayed simultaneously. The corresponding scanning information includes the boundary information of the upper film layer 210 and the boundary information of the lower film layer 220 in the width direction.

[0072] Taking the upper film layer 210 as the film layer to be measured and the width dimension of the upper film layer 210 to be measured as an example, the two boundaries of the film layer to be measured (i.e., the upper film layer 210) relative to the boundary positions of other interfering film layers (i.e., the lower film layer 220) are the boundaries arranged at the second position and the third position along the width direction. At this time, the relative position of the boundary of the film layer to be measured can be preset in the electron beam equipment, so that the equipment can capture the signal peaks corresponding to the second position and the third position in the scanning information according to the preset position information in the automatic measurement mode, and measure the distance between the signal peaks at the second position and the third position to obtain the width dimension D21 of the upper film layer 210.

[0073] Similarly, taking the lower film layer 220 as the film layer to be measured and the width dimension of the lower film layer 220 to be measured as an example, then the two boundaries of the film layer to be measured (i.e., the lower film layer 220) relative to the boundary positions of other interfering film layers (i.e., the upper film layer 210) are the boundaries arranged at the first position and the fourth position along the width direction. At this time, the relative position of the boundary of the film layer to be measured can be preset in the electron beam equipment, so that the equipment can capture the signal peaks corresponding to the first position and the fourth position in the scanning information according to the preset position information in the automatic measurement mode, and measure the distance between the signal peaks at the first position and the fourth position to obtain the width dimension D22 of the lower film layer 220.

[0074] Therefore, in this embodiment, the electron beam equipment can accurately capture the corresponding signal peak according to the boundary information of the film layer to be measured, thereby correctly measuring the key dimensions of the film layer to be measured, effectively reducing the risk of the electron beam equipment being difficult to distinguish the true film layer boundary when automatically measuring the film layer, and improving the accuracy of the measurement results.

[0075] Based on the measurement method described above, this embodiment also provides an electron beam device for critical dimension measurement, and the electron beam device is, for example, a scanning electron microscope (SEM). Specifically, the electron beam device includes: a receiving chamber for placing a sample, an electron beam unit for emitting an electron beam, an electron detector for collecting secondary electrons from the sample surface, and an information processing unit for obtaining the critical dimension of the film layer to be measured based on the scanning information.

[0076] Specifically, when measuring a sample, the sample is first placed in a receiving cavity, and the scanning field of view of the electron beam device covers the film layer to be measured on the sample; then, the electron beam unit is used to emit the electron beam onto the sample surface within its scanning field of view to perform electron beam scanning; then, the electron detector collects secondary electrons excited from the sample surface to generate corresponding scanning information; thereafter, the scanning information is sent to an information processing unit, which is used to arrange each signal peak in the scanning information to correspond to the boundary position of each film layer in the scanning field of view, and locate the signal peak in the scanning signal corresponding to the boundary position of the film layer to be measured according to the boundary position of the film layer to be measured relative to the boundary positions of other film layers, thereby measuring the critical dimensions of the film layer to be measured.

[0077] Furthermore, the electron beam device also includes an imaging unit, which can generate and display corresponding images based on the secondary electrons collected by the electron detector, for example, it can display auxiliary patterns, target patterns and film layers to be tested on the surface of the sample.

[0078] In an optional solution, the imaging unit can also be used to identify the auxiliary pattern on the sample to perform an alignment operation. In addition, when performing the alignment operation, the information processing unit is also used to compare the parameters of the identified auxiliary pattern with the theoretical auxiliary pattern to obtain the fit of the identified auxiliary pattern relative to the theoretical auxiliary pattern, and determine whether the fit reaches a set value, thereby confirming whether the current alignment operation meets the requirements.

[0079] Furthermore, the electron beam device further includes a positioning unit, which can be specifically used to find the target pattern containing the film layer to be measured according to the position of the target pattern relative to the auxiliary pattern, so that the scanning field of view of the electron beam device covers the film layer to be measured. In this embodiment, after finding the target pattern, the information processing unit can also be used to compare the coordinates of the actual position of the target pattern currently found with the verification standard to determine whether the coordinates of the actual position of the target pattern exceed the verification standard, and then confirm whether the target pattern currently found is a real target pattern.

[0080] That is to say, the electron beam equipment in this embodiment can further perform alignment accuracy verification (i.e., quality assessment of the auxiliary pattern) when identifying the auxiliary pattern for alignment operation, so as to achieve a high-precision alignment effect, which is conducive to the subsequent faster and more accurate search for the target pattern containing the film layer to be measured; and, after finding the target pattern, it also includes position coordinate verification of the current target pattern to ensure that the target pattern found is a real target pattern to avoid mispositioning to other patterns due to position deviation; after acquiring the scanning signal, the multiple signal peaks in the scanning signal can be arranged according to the actual positions of the boundaries of each film layer, so that the signal peak at the corresponding position can be accurately captured according to the boundary position of the film layer to be measured, so that the electron beam equipment can still accurately capture the correct film layer boundary in the automatic measurement mode, so as to achieve the measurement of the critical dimensions of the film layer to be measured.

[0081] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other. For the equipment disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description. Although the present invention has been disclosed as above with preferred embodiments, the above embodiments are not intended to limit the present invention. For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified to equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still belong to the scope of protection of the technical solution of the present invention.

[0082] It should also be recognized that the terms described herein are used only to describe specific embodiments and are not intended to limit the scope of the invention. It should be noted that the singular forms "a" and "an" used herein and in the appended claims include plural references unless the context clearly indicates otherwise. For example, a reference to "a step" or "a device" means a reference to one or more steps or devices, and may include secondary steps as well as secondary devices. All conjunctions used should be understood in the broadest sense. And, the word "or" should be understood to have the definition of a logical "or", not a logical "exclusive or", unless the context clearly indicates otherwise.

Claims

1. A method for measuring a critical dimension, characterized in that: include: Providing a sample, wherein at least two film layers are displayed on the surface of the sample, and the at least two film layers include a film layer to be tested; Placing the sample in an electron beam device, and making the scanning field of the electron beam device cover the film layer to be tested, and the scanning field of the electron beam device also covers other film layers; Scanning the sample surface within the scanning field of view using an electron beam to obtain corresponding scanning information, wherein the scanning information has a plurality of signal peaks corresponding to boundaries of each film layer within the scanning field of view; as well as, According to the position of the boundary of the film layer to be measured relative to the boundaries of other film layers, a signal peak corresponding to the boundary position of the film layer to be measured in the scanning signal is located to measure the critical dimension of the film layer to be measured.

2. The method for measuring critical dimensions according to claim 1, characterized in that: The method for making the scanning field of view of the electron beam device cover the film layer to be measured includes: identifying auxiliary patterns on the sample to perform alignment operations; and, The target pattern containing the film layer to be tested is found according to the position of the target pattern relative to the auxiliary pattern.

3. The method for measuring critical dimensions as claimed in claim 2, characterized in that: The method of performing the alignment operation also includes: Comparing parameters of the identified auxiliary pattern with the theoretical auxiliary pattern, and obtaining the fitting degree of the identified auxiliary pattern relative to the theoretical auxiliary pattern; and, Determine whether the fit reaches the set value to confirm whether the current alignment operation meets the requirements.

4. The method for measuring critical dimensions as claimed in claim 3, characterized in that: When the identified auxiliary pattern is compared with the theoretical auxiliary pattern, the comparison parameters include: at least one of the pixels of the image, the size of the auxiliary pattern and the shape of the auxiliary pattern.

5. The critical dimension measuring method according to claim 2, characterized in that: After the target pattern is found, the method further includes verifying the position coordinates of the currently found target pattern. The method of verifying the position coordinates includes: A verification standard is set, wherein the verification standard setting method includes: defining the position of the auxiliary pattern as the origin (0, 0), obtaining the coordinates (X, Y) of the theoretical position of the target pattern from the origin, and combining the size Dx of the target pattern in the X direction and the size Dy of the target pattern in the Y direction to set the verification standard (X±Dx, Y±Dy); The coordinates of the actual position of the target pattern currently found are compared with the verification standard to determine whether the coordinates of the actual position of the target pattern exceed the verification standard, so as to confirm whether the target pattern currently found is the real target pattern.

6. The critical dimension measuring method according to claim 1, characterized in that: A groove is formed inward from the surface of the sample, and the at least two film layers sequentially cover the side walls of the groove to surround at least two annular structures in the groove, and the at least two annular structures are displayed on the surface of the sample; and a plurality of signal peaks in the scanning signal in the measurement direction of the key dimension correspond one-to-one to the boundaries of each annular structure.

7. The critical dimension measuring method according to claim 1, characterized in that: The at least two film layers are stacked on the surface of the sample, wherein at least one film layer boundary of the lower film layer extends below the upper film layer, so that film layer boundaries of different film layers are displayed in the width direction of the film layer to be measured; and the multiple signal peaks in the scanning signal in the measurement direction of the key dimension correspond one-to-one to the film layer boundaries of each film layer.

8. An electron beam device for critical dimension measurement, characterized in that: include: A containing cavity, used for placing a sample, wherein at least two film layers are displayed on the surface of the sample, and the at least two film layers include a film layer to be tested; An electron beam unit, used for emitting an electron beam onto a sample surface within its scanning field of view to perform electron beam scanning; An electron detector, used to collect secondary electrons excited from the sample surface to generate corresponding scanning information; The information processing unit is used to arrange the signal peaks in the scanning information to correspond to the boundary positions of the film layers in the scanning field of view, and locate the signal peak in the scanning signal corresponding to the boundary position of the film layer to be measured according to the boundary position of the film layer to be measured relative to the boundary positions of other film layers, so as to measure the critical dimensions of the film layer to be measured.

9. The electron beam apparatus according to claim 8, characterized in that Also includes: The imaging unit is used to display the image on the sample surface and to identify the auxiliary pattern on the sample to perform alignment operations.

10. The electron beam apparatus according to claim 9, characterized in that The information processing unit is also used to compare the parameters of the identified auxiliary pattern with the theoretical auxiliary pattern to obtain the fit of the identified auxiliary pattern relative to the theoretical auxiliary pattern, and determine whether the fit reaches a set value, thereby confirming whether the current alignment operation meets the requirements.

11. The electron beam apparatus according to claim 9, wherein Also includes: The positioning unit is used to find the target pattern containing the film layer to be measured according to the position of the target pattern relative to the auxiliary pattern, and locate the film layer to be measured so that the scanning field of view of the electron beam device covers the film layer to be measured.

12. The electron beam apparatus according to claim 11, wherein The information processing unit is also used to set a verification standard and compare the coordinates of the actual position of the target pattern currently found with the verification standard to determine whether the coordinates of the actual position of the target pattern exceed the verification standard to confirm whether the target pattern currently found is the real target pattern.

13. The electron beam device according to any one of claims 8 to 12, characterized in that The electron beam device is a scanning electron microscope.

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