Method for obtaining critical dimensions of photolithography patterns

Abstract

The present invention provides a method for obtaining the critical dimensions of a photolithographic pattern. The method comprises: providing a wafer having a patterned photoresist layer formed on its surface, the patterned photoresist layer including complementary photoresist patterns and void patterns, the critical dimensions of the mask patterns corresponding to the photoresist pattern and the void pattern being equal; using an electron beam from a scanning electron microscope to scan both the photoresist pattern and the void pattern multiple times, obtaining multiple image frames of the photoresist pattern and multiple image frames of the void pattern; superimposing the multiple image frames of the photoresist pattern to obtain a first image, and superimposing the multiple image frames of the void pattern to obtain a second image; measuring the critical dimension of the photoresist pattern based on the first image to obtain a first critical dimension, and measuring the critical dimension of the void pattern based on the second image to obtain a second critical dimension; and calculating the average of the first and second critical dimensions as a pattern critical dimension measurement value. The pattern critical dimension measurement value obtained in this manner has high accuracy.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for obtaining a critical dimension of a photolithography pattern. Background Art

[0002] During semiconductor manufacturing, a critical dimension scanning electron microscope (CDSEM) is used to measure parameters such as the critical dimension (CD) of nanoscale patterns within semiconductor structures. Typically, after each lithography and etching step, the wafer enters the CDSEM. The CDSEM scans the pattern on the wafer using an electron beam to measure the critical dimensions (CDs). These measurements are then passed to the process end for observing the process window, checking process stability, and modifying process parameters. Therefore, the measured CDs must be stable and accurately reflect the actual CDs of the pattern.

[0003] Because high-energy electron beam scanning bombardment causes the photoresist in the photolithography pattern to shrink, the CDSEM measurement equipment needs to scan multiple frames in succession and then superimpose the signals to reduce the image signal-to-noise ratio when measuring post-photolithography wafers. This makes it difficult to avoid the photoresist shrinking in the next frame after a single-frame electron beam scan, resulting in low accuracy of the measured key dimensions of the photolithography pattern. In order to improve the accuracy of the obtained key dimensions of the photolithography pattern, post-development inspection often uses a smaller number of overlapping frames and energy (landing energy). This makes after-development inspection (ADI) more difficult than after-etch inspection (AEI). In actual operation, this operation cannot significantly reduce the deviation between the measured value and the actual value of the key dimensions of the photolithography pattern, resulting in low accuracy of the measured key dimensions of the photolithography pattern. Summary of the Invention

[0004] One of the purposes of the present invention is to make the key dimension measurement value of the pattern obtained by using a scanning electron microscope machine close to the actual value before the photoresist shrinks, thereby improving the accuracy of the key dimension measurement value of the obtained photolithography pattern, which is conducive to accurately observing the photolithography process window, checking the stability of the photolithography process, and modifying the photolithography process parameters.

[0005] In order to achieve the above-mentioned object, the present invention provides a method for obtaining the critical dimension of a photolithographic pattern. The method for obtaining the critical dimension of a photolithographic pattern comprises:

[0006] A wafer is provided, wherein a patterned photoresist layer is formed on a surface of the wafer. A mask is used for exposure during the patterning process of the photoresist layer. The patterned photoresist layer includes at least one photoresist pattern and at least one gap pattern. The photoresist pattern is formed by retaining a portion of the photoresist during the patterning process of the photoresist layer. The gap pattern is formed by removing a portion of the photoresist during the patterning process of the photoresist layer. The critical dimensions of the mask patterns corresponding to the photoresist pattern and the gap pattern are equal.

[0007] Scanning the photoresist pattern and the gap pattern multiple times using an electron beam of a scanning electron microscope measuring machine to obtain multiple image frames of the photoresist pattern and multiple image frames of the gap pattern, wherein the scanning conditions for scanning the photoresist pattern and the gap pattern are the same;

[0008] Overlaying a plurality of image frames of the photoresist pattern to obtain a first image including the photoresist pattern image, and overlaying a plurality of image frames of the gap pattern to obtain a second image including the gap pattern image;

[0009] Measuring a critical dimension of the photoresist pattern based on the first image to obtain a first critical dimension, and measuring a critical dimension of the gap pattern based on the second image to obtain a second critical dimension; and

[0010] An average of the first critical dimension and the second critical dimension is calculated as a pattern critical dimension measurement value of the patterned photoresist layer.

[0011] Optionally, the patterned photoresist layer includes a plurality of photoresist patterns and a plurality of gap patterns; the first picture includes images of a plurality of photoresist patterns, and the second picture includes images of a plurality of gap patterns; when measuring the critical dimension of the photoresist pattern based on the first picture to obtain a first critical dimension, the critical dimensions of the plurality of photoresist patterns are measured and obtained, and the average of the critical dimensions of the plurality of photoresist patterns is used as the first critical dimension; when measuring the critical dimension of the gap pattern based on the second picture to obtain a second critical dimension, the critical dimension of the plurality of gap patterns is measured and obtained, and the average of the critical dimensions of the plurality of gap patterns is used as the second critical dimension.

[0012] Optionally, the photoresist pattern and the gap pattern are both strip-shaped; the photoresist pattern and the gap pattern extend in parallel; a plurality of the photoresist patterns are arranged in a row and extend in parallel, and a plurality of the gap patterns are arranged in a row and extend in parallel.

[0013] Optionally, at least two of the photoresist patterns and at least one of the gap patterns are arranged in the same row, and two adjacent photoresist patterns define one gap pattern.

[0014] Optionally, both the photoresist pattern and the gap pattern are circular.

[0015] Optionally, the wafer has a test area, and the photoresist pattern and the gap pattern are formed in the same test area.

[0016] Optionally, the first image and the second image are obtained by superimposing the same number of image frames using the same superposition method; and the same measurement algorithm is used to measure the critical dimension of the photoresist pattern based on the first image and the critical dimension of the gap pattern based on the second image.

[0017] Optionally, after the photoresist pattern and the gap pattern are scanned multiple times using an electron beam of a scanning electron microscope measuring machine, a shrinkage amount of the critical dimension of the photoresist pattern and an expansion amount of the critical dimension of the gap pattern are equal.

[0018] Optionally, the method for obtaining the critical dimension of a photolithography pattern further includes: calculating a difference between the first critical dimension and a measured value of a pattern critical dimension of the patterned photoresist layer, and using the difference as a correction value to correct the measured values ​​of critical dimensions of other photoresist patterns to be measured.

[0019] Optionally, multiple pattern groups are provided, one pattern group includes the photoresist pattern and the gap pattern with equal critical dimensions, and the photoresist patterns in different pattern groups have different critical dimensions; multiple correction values ​​corresponding to the multiple pattern groups are obtained to form a database, and when performing critical dimension detection on other photoresist patterns to be measured, the correction value corresponding to the photoresist pattern to be measured in the database is called to correct the critical dimension measurement value of the photoresist pattern to be measured, wherein the correction value whose first critical dimension corresponding to the correction value in the database is closest to the critical dimension measurement value of the photoresist pattern to be measured is the correction value corresponding to the photoresist pattern to be measured.

[0020] In the method for obtaining the critical dimension of a photolithography pattern provided by the present invention, since the critical dimensions of the mask patterns corresponding to the photoresist pattern and the gap pattern are equal, that is, the design values ​​of the critical dimensions of the photoresist pattern and the gap pattern are the same, after multiple electron beam scans, the contraction amount of the critical dimension of the photoresist pattern and the expansion amount of the critical dimension of the gap pattern are the same, and then multiple image frames of the photoresist pattern and multiple image frames of the gap pattern obtained by multiple scanning with the electron beam of a scanning electron microscope measuring machine are superimposed to obtain a first picture including an image of the photoresist pattern and a second picture including an image of the gap pattern, and the critical dimension of the photoresist pattern is measured based on the first picture to obtain the critical dimension of the photoresist pattern. A first critical dimension is obtained, and a second critical dimension is obtained by measuring the critical dimension of the gap pattern based on the second image. Then, an average of the first critical dimension and the second critical dimension is calculated as the pattern critical dimension measurement value of the patterned photoresist layer. In this way, the shrinkage error of the first critical dimension and the expansion error of the second critical dimension can offset each other, avoiding the problem that the photoresist shrinks due to electron beam bombardment and affects the pattern critical dimension measurement value. The pattern critical dimension measurement value is closer to the actual value before the photoresist shrinks, thereby improving the accuracy of the photolithography pattern critical dimension measurement value, which is conducive to accurately observing the photolithography process window, checking the stability of the photolithography process, and modifying the photolithography process parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention provides a flowchart of a method for obtaining a critical dimension of a photolithography pattern according to an embodiment of the present invention.

[0022] Figure 2 A top view of a photoresist pattern provided according to an embodiment of the present invention.

[0023] Figure 3 A cross-sectional view of a photoresist pattern provided in accordance with an embodiment of the present invention.

[0024] Figure 4 A top view of a gap pattern provided in accordance with an embodiment of the present invention.

[0025] Figure 5 A cross-sectional view of a gap pattern provided in one embodiment of the present invention.

[0026] Figure 6 A schematic diagram of a gap pattern located between photoresist patterns provided by an embodiment of the present invention.

[0027] Figure 7 A schematic diagram of a photoresist pattern and a gap pattern provided according to another embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following is a detailed description of the method for obtaining critical dimensions of a photolithographic pattern proposed by the present invention, with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the accompanying drawings are highly simplified and not to exact scale, and are intended solely to facilitate and clearly illustrate the embodiments of the present invention.

[0029] As used in this application, the term "several" is generally used to include the meaning of "at least one", and the terms "at least two" and "a plurality" are generally used to include the meaning of "two or more". In addition, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features specified as "first", "second", and "third" may explicitly or implicitly include one or at least two of the features, unless the content clearly indicates otherwise.

[0030] Figure 1 Flowchart of a method for obtaining critical dimensions of a photolithographic pattern provided by one embodiment of the present invention. Figure 1 As shown, the method for obtaining the critical dimension of the photolithography pattern includes:

[0031] S1. Providing a wafer having a patterned photoresist layer formed on a surface of the wafer. A mask is used for exposure during the patterning of the photoresist layer. The patterned photoresist layer includes at least one photoresist pattern and at least one gap pattern. The photoresist pattern is formed by retaining a portion of the photoresist during the patterning of the photoresist layer. The gap pattern is formed by removing a portion of the photoresist during the patterning of the photoresist layer. The critical dimensions of the mask patterns corresponding to the photoresist pattern and the gap pattern are equal.

[0032] S2, scanning the photoresist pattern and the gap pattern multiple times using an electron beam of a scanning electron microscope measuring machine to obtain multiple image frames of the photoresist pattern and multiple image frames of the gap pattern, wherein the scanning conditions for scanning the photoresist pattern and the gap pattern are the same;

[0033] S3, superimposing a plurality of image frames of the photoresist pattern to obtain a first image including a photoresist pattern image, and superimposing a plurality of image frames of the gap pattern to obtain a second image including a gap pattern image;

[0034] S4, measuring a critical dimension of the photoresist pattern based on the first image to obtain a first critical dimension, and measuring a critical dimension of the gap pattern based on the second image to obtain a second critical dimension; and

[0035] S5 , calculating an average of the first critical dimension and the second critical dimension as a pattern critical dimension measurement value of the patterned photoresist layer.

[0036] Figure 2A top view of a photoresist pattern provided according to an embodiment of the present invention. Figure 3 A cross-sectional view of a photoresist pattern provided in accordance with an embodiment of the present invention. Figure 4 A top view of a gap pattern provided in accordance with an embodiment of the present invention. Figure 5 A cross-sectional view of a gap pattern provided in one embodiment of the present invention.

[0037] refer to Figures 2 to 5 As shown, the method of providing a wafer with a patterned photoresist layer formed on the surface in step S1 may include: providing a mask, wherein a mask pattern corresponding to a photoresist pattern 11 and a gap pattern 12 is formed in the mask, and the critical dimensions of the mask patterns corresponding to the photoresist pattern 11 and the gap pattern 12 are equal; forming a photoresist layer on a wafer 10; exposing the photoresist layer using the mask; and developing the photoresist layer to obtain a patterned photoresist layer, wherein the patterned photoresist layer includes at least one photoresist pattern 11 and at least one gap pattern 12, wherein the photoresist pattern 11 is formed by retaining a portion of the photoresist during the patterning process of the photoresist layer, and the gap pattern is formed by removing a portion of the photoresist during the patterning process of the photoresist layer.

[0038] In the present application, the critical dimensions of the mask patterns corresponding to the photoresist pattern 11 and the gap pattern 12 are equal, which can also be understood as the design critical dimensions of the photoresist pattern 11 and the gap pattern 12 are equal.

[0039] In the present application, the photoresist pattern 11 and the gap pattern 12 have the same shape, which facilitates the subsequent measurement of the critical dimensions of the photoresist pattern 11 and the gap pattern 12 .

[0040] For example, in some embodiments, Figure 2 and Figure 4 As shown, the photoresist pattern 11 and the gap pattern 12 are both strip-shaped, and the key dimensions of the photoresist pattern 11 and the gap pattern 12 refer to the width, that is, Figure 2 and Figure 4 The horizontal dimension.

[0041] Figure 7 Schematic diagram of a photoresist pattern and a gap pattern provided by another embodiment of the present invention. Figure 7 As shown, in some embodiments, the photoresist pattern 11 and the gap pattern 12 may be circular, but not limited thereto. The critical dimensions of the photoresist pattern 11 and the gap pattern 12 may refer to the diameter of the circle, and the diameters of the photoresist pattern 11 and the gap pattern 12 are the same.

[0042] The following description will be made by taking the case where both the photoresist pattern 11 and the gap pattern 12 are in strip shape as an example.

[0043] refer to Figure 2 and Figure 4As shown, the photoresist pattern 11 and the gap pattern 12 can extend in parallel, but are not limited thereto. The photoresist pattern 11 and the gap pattern 12 can also be arranged vertically.

[0044] refer to Figure 2 and Figure 4 As shown, the patterned photoresist layer may include a plurality of photoresist patterns 11 and a plurality of void patterns 12. The plurality of photoresist patterns 11 may be arranged in a row and extend in parallel, and the plurality of void patterns 12 may be arranged in a row and extend in parallel, which facilitates subsequent measurement of critical dimensions of the plurality of photoresist patterns 11 and the plurality of void patterns 12. The plurality of photoresist patterns 11 and the plurality of void patterns 12 may also be arranged in other suitable arrangements. The spacing between the plurality of photoresist patterns 11 and the spacing between the plurality of void patterns 12 may be designed based on actual conditions.

[0045] Figure 6 A schematic diagram of a gap pattern provided in one embodiment of the present invention is located between photoresist patterns. Figure 6 As shown, at least two of the photoresist patterns 11 and at least one gap pattern 12 are arranged in the same row, for example, multiple photoresist patterns 11 and multiple gap patterns 12 are arranged in a row, and two adjacent photoresist patterns 11 define a gap pattern 12, wherein the design critical dimensions of the photoresist pattern 11 and the gap pattern 12 are equal. When normal exposure deviation is ignored, the width of the photoresist pattern 11 is equal to the spacing between the two adjacent photoresist patterns 11, and the spacing between the two adjacent photoresist patterns 11 is the width of the gap pattern 12. In this case, after the electron beam is scanned, the critical dimension shrinkage of the photoresist pattern 11 will be completely equal to the critical dimension expansion of the gap pattern 12. The critical dimensions of the photoresist pattern 11 and the gap pattern 12 have a good complementary effect, and an image frame including the photoresist pattern 11 and the gap pattern 12 can be obtained subsequently, which simplifies the overlay step.

[0046] After forming the photoresist pattern 11 and the gap pattern 12 on the wafer, step S2 is executed to scan the photoresist pattern 11 and the gap pattern 12 multiple times using the electron beam of the scanning electron microscope measuring machine to obtain multiple image frames of the photoresist pattern 11 and multiple image frames of the gap pattern 12, wherein the scanning conditions for scanning the photoresist pattern 11 and the gap pattern 12 are the same.

[0047] In this embodiment, the scanning electron microscope measurement apparatus may be a CDSEM measurement apparatus, but is not limited thereto. The electron beam used for scanning may be a high-energy electron beam. An image frame including the photoresist pattern 11 and / or the void pattern 12 may be formed by collecting secondary electron signal images generated after the electron beam scans the pattern.

[0048] After the electron beam scans the photoresist pattern 11 and the gap pattern 12, the photoresist will shrink, the photoresist pattern 11 will shrink, and the gap pattern 12 will expand. Figure 3 As shown, before the electron beam scanning, the real critical dimension of the photoresist pattern 11 is Real.CDA; after the electron beam scanning, the critical dimension of the photoresist pattern 11 is CDA, which is smaller than Real.CDA; Figure 5 As shown, before the electron beam scanning, the real critical dimension of the gap pattern 12 is Real.CDB; after the electron beam scanning, the critical dimension of the gap pattern 12 is CDB, and CDB is larger than Real.CDB.

[0049] It should be noted that, when the design critical dimensions of the photoresist pattern 11 and the void pattern 12 are the same and the scanning conditions for scanning the photoresist pattern 11 and the void pattern 12 are the same, after the photoresist pattern and the void pattern are scanned multiple times using the electron beam of a scanning electron microscope measuring machine, the critical dimension shrinkage of the photoresist pattern 11 can be equal to the critical dimension expansion of the void pattern 12, and the photoresist pattern 11 and the void pattern 12 are complementary patterns.

[0050] In this embodiment, wafer 10 has a test area, and photoresist pattern 11 and void pattern 12 can be formed within the test area. This prevents electron beam scanning from affecting the photoresist pattern in the active area of ​​the wafer. Photoresist pattern 11 and void pattern 12 can be formed within the same test area, allowing image frames of both photoresist pattern 11 and void pattern 12 to be acquired simultaneously using a pre-configured scanning program.

[0051] Exemplarily, a single scan may scan the photoresist pattern 11 and the space pattern 12. The process of obtaining multiple image frames of the photoresist pattern 11 and multiple image frames of the space pattern 12 may include: performing a first scan to scan the photoresist pattern 11 and the space pattern 12 to obtain one image frame of the photoresist pattern 11 and one image frame of the space pattern 12; performing a second scan to scan the photoresist pattern 11 and the space pattern 12 to obtain one image frame of the photoresist pattern 11 and one image frame of the space pattern 12; and then performing a third to nth scan to obtain multiple image frames of the photoresist pattern 11 and multiple image frames of the space pattern 12.

[0052] The scanning conditions for scanning the photoresist pattern 11 and the gap pattern 12 are the same. Specifically, the scanning conditions for scanning the photoresist pattern 11 and the gap pattern 12 in the same scan can be the same. In this way, after one scan, the critical dimension shrinkage amount of the photoresist pattern 11 and the critical dimension expansion amount of the gap pattern 12 are equal, and the obtained image frame of the photoresist pattern 11 corresponds to the image frame of the gap pattern 12, which is beneficial to improving the accuracy of the subsequently obtained pattern critical dimension measurement value.

[0053] The same scanning conditions may include, but are not limited to, the same electron beam acceleration voltage, the same electron beam current and / or the same scanning speed.

[0054] In some embodiments, reference Figure 2 and Figure 4 As shown, in the step of using the electron beam of the scanning electron microscope measuring machine to scan the photoresist pattern 11 and the gap pattern 12 multiple times, multiple photoresist patterns 11 and multiple gap patterns 12 can be scanned to obtain image frames including multiple photoresist patterns 11 and image frames including multiple gap patterns 12.

[0055] Step S3 is executed to superimpose multiple image frames of the photoresist pattern 11 to obtain a first image including an image of the photoresist pattern 11 , and to superimpose multiple image frames of the gap pattern 12 to obtain a second image including an image of the gap pattern 12 .

[0056] In this embodiment, the first image and the second image can be obtained by superimposing the same number of image frames using the same superposition method, which can avoid different quantitative deviations in the key dimensions of the photoresist pattern 11 and the gap pattern 12 due to different superposition numbers and superposition methods.

[0057] In some embodiments, when an image frame including multiple photoresist patterns 11 and an image frame including multiple gap patterns 12 are superimposed, the obtained first image includes images of the multiple photoresist patterns 11 , and the second image includes images of the multiple gap patterns 12 .

[0058] Step S4 is executed to measure the critical dimension of the photoresist pattern 11 based on the first image to obtain a first critical dimension, and to measure the critical dimension of the gap pattern 12 based on the second image to obtain a second critical dimension.

[0059] In this embodiment, the same measurement algorithm is used to measure the critical dimension of the photoresist pattern 11 based on the first image and the critical dimension of the void pattern 12 based on the second image. For example, when measuring the critical dimension using images, one edge of the photoresist pattern 11 and the void pattern 12 corresponds to a signal peak. The measurement algorithm includes fixing a position of the signal peak as the measurement position. For example, for a sinusoidal signal, the peak position is determined as the measurement position. The critical dimensions of the photoresist pattern 11 and the void pattern 12 are obtained by measuring the distance between two adjacent peaks.

[0060] In step S4, the critical dimension of a photoresist pattern 11 in the first image can be measured as the first critical dimension, and the critical dimension of a void pattern 12 in the second image can be measured as the second critical dimension. This reduces the amount of measurement and simplifies the measurement. When the first image includes multiple images of the photoresist pattern 11 and the second image includes multiple images of the void pattern 12, the critical dimensions of the multiple photoresist patterns 11 can be measured and obtained, and the average of the critical dimensions of the multiple photoresist patterns 11 can be used as the first critical dimension. The critical dimensions of the multiple void patterns 12 can be measured and obtained, and the average of the critical dimensions of the multiple void patterns 12 can be used as the second critical dimension. This helps improve the accuracy of the subsequently obtained pattern critical dimension measurements.

[0061] Step S5 is executed to calculate an average of the first critical dimension and the second critical dimension as a pattern critical dimension measurement value of the patterned photoresist layer.

[0062] It should be noted that there is a shrinkage error of the photoresist pattern 11 between the first critical dimension and the real critical dimension Real.CDA before the photoresist pattern 11 shrinks, and there is an expansion error of the gap pattern 12 between the second critical dimension and the real critical dimension Real.CDB before the gap pattern 12 expands. Since the design critical dimensions of the photoresist pattern 11 and the gap pattern 12 are equal, the shrinkage of the key dimension of the photoresist pattern 11 can be approximately equal to the expansion of the key dimension of the gap pattern 12. Therefore, the shrinkage error of the first critical dimension and the expansion error of the second critical dimension can offset each other, so that the average of the first critical dimension and the second critical dimension is close to the real critical dimension of the pattern before the photoresist shrinks. Using this average as the pattern critical dimension measurement value of the patterned photoresist layer accurately reflects the real critical dimension. Using this pattern critical dimension measurement value, the photolithography process window can be accurately observed, the stability of the photolithography process can be checked, and the photolithography process parameters can be modified.

[0063] In some embodiments, the photoresist pattern 11 and the gap pattern 12 are arranged as follows: Figure 6 As shown, since the images of the photoresist pattern 11 and the void pattern 12 are located in the same picture, the pitch values ​​of the photoresist pattern 11 and the void pattern 12 can be directly measured, that is, the sum of the widths of the adjacent photoresist patterns 11 and void patterns 12 is measured, and half of the pitch value is used as the pattern critical dimension measurement value of the patterned photoresist layer. Compared with measuring the critical dimensions of the photoresist pattern 11 and the void pattern 12 separately, this can simplify the measurement steps.

[0064] The method for obtaining the critical dimension of a photolithographic pattern of the present application is applicable to post-development inspection and can avoid the problem in post-development inspection that electron beam bombardment causes photoresist shrinkage and affects the measurement value of the critical dimension of the pattern.

[0065] In this embodiment, after step S5 , the difference between the first critical dimension and the measured critical dimension of the patterned photoresist layer may be calculated as a first correction value for correcting the measured critical dimensions of other photoresist patterns to be measured.

[0066] In step S1, multiple pattern groups may be provided. Each pattern group includes at least one photoresist pattern and at least one void pattern having the same critical dimensions. The photoresist patterns in different pattern groups have different critical dimensions, and the void patterns in different pattern groups have different critical dimensions. Multiple pattern groups may be provided by providing multiple patterned photoresist layers, or multiple pattern groups may be provided within a single patterned photoresist layer.

[0067] Illustratively, after step S5, multiple first correction values ​​corresponding to multiple pattern groups are obtained to form a database. When performing critical dimension detection on other photoresist patterns to be measured, the first correction value corresponding to the photoresist pattern to be measured in the database is called to correct the critical dimension measurement value of the photoresist pattern to be measured, wherein the first correction value whose first critical dimension corresponding to the first correction value in the database is closest to the critical dimension measurement value of the photoresist pattern to be measured is the first correction value corresponding to the photoresist pattern to be measured.

[0068] After step S5 , a difference between the second critical dimension and the measured critical dimension of the pattern of the patterned photoresist layer may be calculated as a second correction value for correcting the measured critical dimensions of other gap patterns to be measured.

[0069] Specifically, after step S5, multiple second correction values ​​corresponding to multiple pattern groups are obtained to form a database. When performing critical dimension detection on other gap patterns to be measured, the second correction value corresponding to the gap pattern to be measured in the database is called to correct the critical dimension measurement value of the gap pattern to be measured, wherein the second correction value whose second critical dimension corresponding to the second correction value in the database is closest to the critical dimension measurement value of the gap pattern to be measured is the second correction value corresponding to the gap pattern to be measured.

[0070] In the method for obtaining the critical dimension of a photolithography pattern provided by the present invention, since the critical dimensions of the mask patterns corresponding to the photoresist pattern 11 and the gap pattern 12 are equal, that is, the critical dimension design values ​​of the photoresist pattern 11 and the gap pattern 12 are the same, after the electron beam is scanned multiple times in sequence, the critical dimension contraction amount of the photoresist pattern 11 and the critical dimension expansion amount of the gap pattern 12 are the same, and then the multiple image frames of the photoresist pattern 11 and the multiple image frames of the gap pattern 12 obtained by multiple scanning with the electron beam of the scanning electron microscope measuring machine are superimposed to obtain a first picture including the photoresist pattern image and a second picture including the gap pattern image, and the photoresist pattern 11 is measured based on the first picture. The first key dimension of the pattern is obtained, and the second key dimension is obtained by measuring the key dimension of the gap pattern based on the second image. Then, the average of the first key dimension and the second key dimension is calculated as the pattern key dimension measurement value of the patterned photoresist layer. In this way, the shrinkage error of the first key dimension and the expansion error of the second key dimension can offset each other, and the pattern key dimension measurement value is closer to the true value before the photoresist shrinks, avoiding the problem that the electron beam bombardment causes the photoresist to shrink and affects the pattern key dimension measurement value, improving the accuracy of the photolithography pattern key dimension measurement value, and facilitating the accurate observation of the photolithography process window, checking the stability of the photolithography process, and modifying the photolithography process parameters.

[0071] The above description is only a description of the preferred embodiment of the present invention, and does not limit the scope of the rights of the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for obtaining a critical dimension of a photolithographic pattern, characterized in that: include: A wafer is provided, wherein a patterned photoresist layer is formed on a surface of the wafer. A mask is used for exposure during the patterning process of the photoresist layer. The patterned photoresist layer includes at least one photoresist pattern and at least one gap pattern. The photoresist pattern is formed by retaining a portion of the photoresist during the patterning process of the photoresist layer. The gap pattern is formed by removing a portion of the photoresist during the patterning process of the photoresist layer. The critical dimensions of the mask patterns corresponding to the photoresist pattern and the gap pattern are equal. Scanning the photoresist pattern and the gap pattern multiple times using an electron beam of a scanning electron microscope measuring machine to obtain multiple image frames of the photoresist pattern and multiple image frames of the gap pattern, wherein the scanning conditions for scanning the photoresist pattern and the gap pattern are the same; Overlaying a plurality of image frames of the photoresist pattern to obtain a first image including the photoresist pattern image, and overlaying a plurality of image frames of the gap pattern to obtain a second image including the gap pattern image; Measuring a critical dimension of the photoresist pattern based on the first image to obtain a first critical dimension, and measuring a critical dimension of the gap pattern based on the second image to obtain a second critical dimension; and An average of the first critical dimension and the second critical dimension is calculated as a pattern critical dimension measurement value of the patterned photoresist layer.

2. The method for obtaining a critical dimension of a photolithographic pattern according to claim 1, wherein: The patterned photoresist layer includes a plurality of the photoresist patterns and a plurality of the gap patterns; The first picture includes a plurality of images of the photoresist patterns, and the second picture includes a plurality of images of the gap patterns; When measuring the critical dimension of the photoresist pattern based on the first image to obtain a first critical dimension, measuring and obtaining the critical dimensions of a plurality of the photoresist patterns, and taking an average of the critical dimensions of the plurality of the photoresist patterns as the first critical dimension; When measuring the critical dimension of the gap pattern based on the second image to obtain the second critical dimension, the critical dimensions of multiple gap patterns are measured and obtained, and the average of the critical dimensions of the multiple gap patterns is used as the second critical dimension.

3. The method for obtaining a critical dimension of a photolithographic pattern according to claim 1, wherein: The photoresist pattern and the gap pattern are both strip-shaped, and the photoresist pattern and the gap pattern are extended in parallel; a plurality of the photoresist patterns are arranged in a row and extended in parallel, and a plurality of the gap patterns are arranged in a row and extended in parallel.

4. The method for obtaining a critical dimension of a photolithographic pattern according to claim 3, wherein: At least two of the photoresist patterns and at least one of the gap patterns are arranged in the same row, and two adjacent photoresist patterns define one gap pattern.

5. The method for obtaining a critical dimension of a photolithographic pattern according to claim 1, wherein: The photoresist pattern and the gap pattern are both circular.

6. The method for obtaining a critical dimension of a photolithographic pattern according to claim 1, wherein: The wafer has a test area, and the photoresist pattern and the space pattern are formed in the same test area.

7. The method for obtaining a critical dimension of a photolithographic pattern according to claim 1, wherein: The first image and the second image are obtained by superimposing the same number of image frames using the same superposition method; the critical dimension of the photoresist pattern based on the first image and the critical dimension of the gap pattern based on the second image are measured using the same measurement algorithm.

8. The method for obtaining a critical dimension of a photolithographic pattern according to any one of claims 1 to 7, wherein: After the photoresist pattern and the gap pattern are scanned multiple times by an electron beam of a scanning electron microscope measuring machine, the critical dimension shrinkage amount of the photoresist pattern and the critical dimension expansion amount of the gap pattern are equal.

9. The method for obtaining a critical dimension of a photolithographic pattern according to claim 1, wherein: Also includes: A difference between the first critical dimension and a measured critical dimension of the pattern of the patterned photoresist layer is calculated, and the difference is used as a correction value to correct the measured critical dimensions of other photoresist patterns to be measured.

10. The method for obtaining a critical dimension of a photolithographic pattern according to claim 9, wherein: A plurality of pattern groups are provided, wherein one pattern group includes at least one photoresist pattern and at least one space pattern having the same critical dimension, and the photoresist patterns in different pattern groups have different critical dimensions. A plurality of correction values ​​corresponding to the plurality of pattern groups are obtained to form a database. When performing critical dimension detection on other photoresist patterns to be measured, the correction value corresponding to the photoresist pattern to be measured in the database is called to correct the critical dimension measurement value of the photoresist pattern to be measured, wherein the correction value corresponding to the first critical dimension corresponding to the correction value in the database that is closest to the critical dimension measurement value of the photoresist pattern to be measured is the correction value corresponding to the photoresist pattern to be measured.

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