Overlay mark mask pattern and overlay error measuring method

Abstract

According to the overlay mark mask pattern and the overlay error measurement method, the density of the front-layer pattern is increased by introducing the front-layer auxiliary pattern into the front-layer pattern, damage possibly generated in the CMP process is effectively improved, CMP residues caused by damage are reduced or even avoided, and therefore the accuracy and stability of overlay error measurement are improved. Besides, the extension direction of the front-layer auxiliary sprite is perpendicular to the extension direction of the front-layer alignment sprite and the extension direction of the current alignment sprite, so that interference on existing light and dark stripes of the grating can be avoided, and the accuracy of obtaining the pattern position information by scanning the light and dark stripes of the overlay mark pattern grating is ensured. Therefore, the overlay mark mask pattern not only improves the contrast ratio of the overlay mark and the stability of a scanning signal, but also reduces measurement abnormity caused by CMP (Chemical Mechanical Polishing) residues, finally realizes interlayer alignment with higher precision, and has important significance for improving the overall performance and reliability of a semiconductor manufacturing process.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit manufacturing technology, and in particular to a method for measuring overlay marking mask patterns and overlay error. Background Technology

[0002] like Figure 1 and Figure 2 As shown, the overlay error refers to the positional offset between the current layer pattern 12 and the previous layer pattern 11. This parameter is crucial for the accuracy of semiconductor manufacturing processes. Currently, the main method for measuring overlay error is to obtain the positional information of the pattern by scanning the bright and dark stripes of the overlay mark grating under the optical microscope of the overlay measurement machine, and then calculate the center position offset between the current layer pattern 12 and the previous layer pattern 11.

[0003] However, with the continuous advancement of semiconductor process technology, the accuracy requirements for overlay offset are increasing. Existing overlay mark pattern designs are susceptible to process damage, such as chemical mechanical polishing (CMP) residues, which can lead to abnormalities and instability in overlay measurements. Current methods, such as adjusting the pitch of the overlay mark sub-patterns or optimizing the overlay mark segments, are no longer sufficient to meet increasingly stringent process requirements. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for measuring overprinting mark mask patterns and overprinting error, which solves the problem that overprinting mark patterns are easily damaged by the process, leading to measurement abnormalities and instability in the prior art.

[0005] To achieve the above and other related objectives, the present invention provides an overlay marking mask pattern, the overlay marking mask pattern comprising:

[0006] The front-layer graphic includes four front-layer graphic units with fourfold rotational symmetry. Each front-layer graphic unit includes a front-layer alignment graphic unit and a front-layer auxiliary graphic unit. Each front-layer alignment graphic unit includes multiple front-layer alignment sub-graphics distributed at fixed intervals. Each front-layer auxiliary graphic unit includes multiple front-layer auxiliary sub-graphics distributed at fixed intervals. The extension direction of the front-layer alignment sub-graphics is perpendicular to the extension direction of the front-layer auxiliary sub-graphics.

[0007] The current alignment pattern comprises four current alignment pattern units with fourfold rotational symmetry. Each current alignment pattern unit includes multiple current alignment sub-patterns distributed at fixed intervals. The front-layer auxiliary pattern unit extends along its extension direction through the projection of the corresponding current alignment pattern unit onto the front-layer pattern. The extension direction of the front-layer auxiliary sub-pattern in the front-layer auxiliary pattern unit is perpendicular to the extension direction of the current alignment sub-pattern in the corresponding current alignment pattern unit. The centers of the front-layer alignment sub-pattern in the front-layer alignment pattern unit and the current alignment sub-pattern in the corresponding current alignment pattern unit are aligned one-to-one.

[0008] Optionally, the line width of the previous alignment sub-pattern is W1 and the pitch is S1, the line width of the current alignment sub-pattern is W2 and the pitch is S2, (1-5%)W1≤W2≤(1+5%)W1, and S1=S2.

[0009] Optionally, the linewidth of the front layer alignment sub-pattern is W1, the pitch is S1, 500nm≤W1≤1300nm, and 1000nm≤S1≤2600nm.

[0010] Furthermore, the line width of the front auxiliary sub-graphic is W3, the pitch is S3, W3 < W1, and S3 < S1.

[0011] Furthermore, the linewidth of the front auxiliary sub-pattern is W3, the pitch is S3, 90nm≤W3≤110nm, and S3=2W3.

[0012] Optionally, the extension direction of the front-layer auxiliary patterning unit exceeds the size of the projection of the corresponding current alignment patterning unit onto the front-layer pattern by 195nm to 205nm, and the projection of the extension direction of the current alignment sub-pattern onto the front-layer pattern exceeds the size of the front-layer auxiliary patterning unit by more than 50nm.

[0013] Optionally, the number of the previous alignment sub-graphics in the previous alignment graphic unit is equal to the number of the current alignment sub-graphics in the current alignment graphic unit.

[0014] Optionally, the polarity type of the mask for the front layer pattern is a bright field mask.

[0015] Optionally, the four front-layer alignment pattern units are two centrally symmetrical first front-layer pattern units and two centrally symmetrical second front-layer pattern units. The extension direction of the first front-layer sub-pattern in the first front-layer pattern unit is perpendicular to the X direction of the optical signal scanning of the overlay measuring instrument, and the extension direction of the second front-layer sub-pattern in the second front-layer pattern unit is perpendicular to the Y direction of the optical signal scanning of the overlay measuring instrument, wherein the X direction and the Y direction are perpendicular to each other in the same plane.

[0016] The present invention also provides a method for measuring overprinting error, the method comprising:

[0017] The overlay mark pattern is prepared based on the overlay mark mask pattern described in any of the above;

[0018] The front grating light and dark fringes of the previous alignment pattern and the current grating light and dark fringes of the current alignment pattern are obtained by using an overlay measurement machine; wherein, four of the four front alignment pattern units constitute the front alignment pattern, and four current alignment pattern units constitute the current alignment pattern.

[0019] The offset between the center of the bright and dark fringes of the previous grating and the center of the bright and dark fringes of the current grating is measured to obtain the overlay error between the alignment pattern of the previous layer and the alignment pattern of the current layer.

[0020] As described above, the overlay mark mask pattern and overlay error measurement method of the present invention have the following beneficial effects: By introducing a front-layer auxiliary pattern into the front-layer pattern to increase the density of the front-layer pattern, the damage problems that may occur during CMP are effectively improved, reducing or even avoiding CMP residues caused by this, thereby improving the accuracy and stability of overlay error measurement. Furthermore, since the extension direction of the front-layer auxiliary sub-pattern is perpendicular to the extension directions of the front-layer alignment sub-pattern and the current alignment sub-pattern, interference with existing grating bright and dark fringes can be avoided during overlay error measurement, ensuring the accuracy of obtaining pattern position information by scanning the bright and dark fringes of the overlay mark pattern grating. Therefore, this overlay mark mask pattern not only improves the contrast of the overlay marks and the stability of the scanning signal, but also reduces measurement anomalies caused by CMP residues, ultimately achieving higher-precision interlayer alignment, which is of great significance for improving the overall performance and reliability of semiconductor manufacturing processes. Attached Figure Description

[0021] Figure 1 The diagram shown is a top view of the structure of an overlay marking pattern in the prior art.

[0022] Figure 2 This diagram illustrates how CMP residues in the current layer pattern cause abnormal waveform measurements of corresponding overlay errors in existing technologies.

[0023] Figure 3 The diagram shown is a top view of the front layer pattern in the overlay marking mask pattern of the present invention.

[0024] Figure 4 The diagram shown is a top view of the overlay marking mask pattern of the present invention.

[0025] Figure 5The diagram shows a flowchart of the overlay error measurement method of the present invention.

[0026] Figure 6 The diagram shows a waveform for measuring overlay error corresponding to the current alignment pattern according to the present invention.

[0027] Component labeling description: 1. Marking pattern, 11, 21. Previous layer pattern, 12. Current layer pattern, 13. CMP residue, 21. Previous layer pattern unit, 211. Previous layer alignment pattern unit, 212. Previous layer auxiliary pattern unit, 213. Previous layer alignment sub-pattern, 214. Previous layer auxiliary sub-pattern, 215. First previous layer pattern unit, 216. Second previous layer pattern unit, 217. First previous layer sub-pattern, 218. Second previous layer sub-pattern, 22. Current alignment pattern unit, 221. Current alignment sub-pattern, S10~S30 steps. Detailed Implementation

[0028] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0029] Please see Figures 3 to 6 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0030] This embodiment provides a mask pattern for overlay marking, for reference. Figure 3 and Figure 4 The overlay marking mask pattern includes:

[0031] Front-end graphics; such as Figure 3 As shown, it includes four front-layer graphic units 21 with fourfold rotational symmetry. Each front-layer graphic unit 21 includes a front-layer alignment graphic unit 211 and a front-layer auxiliary graphic unit 212. The front-layer alignment graphic unit 211 includes a plurality of front-layer alignment sub-graphics 213 distributed at fixed intervals. The front-layer auxiliary graphic unit 212 includes a plurality of front-layer auxiliary sub-graphics 214 distributed at fixed intervals. The extension direction of the front-layer alignment sub-graphics 213 is perpendicular to the extension direction of the front-layer auxiliary sub-graphics 214.

[0032] Currently aligned graphics; such as Figure 4As shown, it includes four current alignment graphic units 22 with fourfold rotational symmetry. Each current alignment graphic unit 22 includes multiple current alignment sub-graphics 221 distributed at fixed intervals. The front auxiliary graphic unit 212 extends through the projection of the corresponding current alignment graphic unit 22 onto the front graphic. The extension direction of the front auxiliary sub-graphic 214 in the front auxiliary graphic unit 212 is perpendicular to the extension direction of the current alignment sub-graphic 221 in the corresponding current alignment graphic unit 22. The center of the front alignment sub-graphic 213 in the front alignment graphic unit 211 is aligned with the center of the current alignment sub-graphic 221 in the corresponding current alignment unit 22.

[0033] The overlay mark mask pattern in this embodiment increases the density of the previous layer pattern by introducing an auxiliary pattern within it. This effectively mitigates potential damage during CMP (Continuous Metallurgy) and reduces or even eliminates CMP residue, thereby improving the accuracy and stability of overlay error measurement. Furthermore, since the extension direction of the auxiliary sub-pattern is perpendicular to both the previous alignment sub-pattern and the current alignment sub-pattern, interference with existing grating fringes is avoided during overlay error measurement, ensuring the accuracy of obtaining pattern position information by scanning the overlay mark pattern grating's fringes. Therefore, this overlay mark mask pattern not only improves the contrast of the overlay marks and the stability of the scanning signal but also reduces measurement anomalies caused by CMP residue, ultimately achieving higher-precision interlayer alignment. This is of great significance for improving the overall performance and reliability of semiconductor manufacturing processes.

[0034] It should be noted that the four front-layer auxiliary graphics units 212 of the four front-layer graphics units 21 that are fourfold rotationally symmetrical constitute the front-layer auxiliary graphics in this embodiment.

[0035] Specifically, as an example, the linewidth of the previous alignment sub-pattern 213 is defined as W1, and the pitch as S1. The linewidth of the current alignment sub-pattern 221 is defined as W2, and the pitch as S2. Then, (1-5%)W1≤W2≤(1+5%)W1, and S1=S2. Preferably, in this embodiment, W1=W2, that is, the linewidth of the current alignment sub-pattern 221 is designed to be equal to the linewidth and pitch of the previous alignment sub-pattern 213, and their centers are aligned. Furthermore, preferably, the number of previous alignment sub-patterns 213 in the previous alignment pattern unit 211 is equal to the number of current alignment sub-patterns 214 in the current alignment pattern unit 22, in order to avoid wasting layout resources and improve the efficiency of overlay error measurement.

[0036] As an example, the linewidth of the front-layer alignment sub-pattern 213 is W1, the pitch is S1, 500nm≤W1≤1300nm, and 1000nm≤S1≤2600nm. Inventively, W1 can be 500 nm, and W2 can be 510 nm or 520 nm.

[0037] As a preferred example, the linewidth of the front auxiliary sub-pattern 214 is W3, and the pitch is S3, where W3 < W1 and S3 < S1. As a further example, 90nm ≤ W3 ≤ 110nm, and S3 = 2W3. That is, the linewidth of the front auxiliary sub-pattern 214 is smaller than the linewidth of the front alignment sub-pattern 213, and the pitch of the front auxiliary sub-pattern 214 is smaller than the pitch of the front alignment sub-pattern 213. The front auxiliary sub-pattern 214 is more elongated than the front alignment sub-pattern 213. By reducing the linewidth and pitch of the front auxiliary sub-pattern 214, load unevenness during the CMP process can be further reduced, thereby reducing potential damage during polishing and improving the quality and efficiency of CMP.

[0038] As a preferred design example, the edge of the front auxiliary pattern unit 212 is not aligned with the edge of the corresponding current alignment pattern unit 22. For example, the extension direction of the front auxiliary pattern unit 212 exceeds the size of the projection of the corresponding current alignment pattern unit 22 onto the front pattern by 195nm to 205nm, such as 195nm, 200nm, or 205nm. The projection of the extension direction of the current alignment sub-pattern 221 onto the front pattern exceeds the size of the front auxiliary pattern unit 212 by more than 50nm. This improves the resolution of the current alignment pattern unit 22, provides a clearer reference point during optical measurement, and thus improves the accuracy of the measurement.

[0039] As an example, see reference Figure 3 The four front-layer alignment pattern units 211 are two centrally symmetrical first front-layer pattern units 215 and two centrally symmetrical second front-layer pattern units 216. The extension direction of the first front-layer sub-pattern 217 in the first front-layer pattern unit 215 is perpendicular to the X-direction of the optical signal scanning of the overlay measurement instrument (reference). Figure 3 The extension direction of the second front-layer sub-pattern 218 in the second front-layer pattern unit 216 is perpendicular to the Y-direction of the optical signal scan of the overlay measurement instrument (refer to the X scan). Figure 3In the X-scan (Y scan), the X and Y directions are perpendicular to each other in the same plane. Therefore, when the optical signal of the overlay measurement machine scans the X direction, the first front-layer pattern unit 215 and the corresponding current alignment pattern unit 22 can output bright and dark stripes that reflect position information. Since the extension direction of the front-layer auxiliary sub-pattern 214 in the front-layer auxiliary pattern unit 212 corresponding to the first front-layer pattern unit 215 is perpendicular to the extension direction of the first front-layer sub-pattern 217 and the current alignment sub-pattern 221, interference with the existing grating bright and dark stripes can be avoided when measuring overlay error, ensuring the accuracy of obtaining pattern position information by scanning the bright and dark stripes of the overlay mark pattern grating. When the optical signal of the overlay measurement machine scans the Y direction, the second front layer graphic unit 216 and the corresponding current alignment graphic unit 22 can output bright and dark stripes that reflect position information. Since the extension direction of the front auxiliary sub-graphic 214 in the front auxiliary graphic unit 212 corresponding to the second front layer graphic unit 216 is perpendicular to the extension direction of the second front sub-graphic 218 and the current alignment sub-graphic 221, interference with the existing grating bright and dark stripes can be avoided when measuring overlay error, ensuring the accuracy of obtaining graphic position information by scanning the bright and dark stripes of the overlay mark graphic grating.

[0040] As a preferred example, the polarity type of the mask for the front layer pattern is a bright field mask, that is, the front layer pattern is defined by the opaque area of ​​the mask. Combined with the selection of a specific photoresist type, a clearer and more accurate pattern can be formed during the photolithography process, thereby reducing or even avoiding the deformation or peeling of the front layer auxiliary pattern in subsequent processes.

[0041] This embodiment also provides a method for measuring overlay error, such as Figure 5 As shown, the overlay error measurement method includes:

[0042] S10, an overlay mark pattern is prepared based on the overlay mark mask pattern described in any of the above.

[0043] S20, a scaling and measuring machine is used to acquire the front grating bright and dark stripes of the front alignment pattern and the current grating bright and dark stripes of the current alignment pattern; wherein, the four front alignment pattern units 211 of the four front pattern units 21 constitute the front alignment pattern, and the four current alignment pattern units 22 constitute the current alignment pattern.

[0044] S30, measure the offset between the center of the bright and dark fringes of the previous grating and the center of the bright and dark fringes of the current grating, thereby obtaining the overlay error between the alignment pattern of the previous layer and the alignment pattern of the current layer.

[0045] The overlay error measurement method in this embodiment uses an overlay mark pattern prepared with a specific overlay mark mask for measurement. The accuracy and stability of the measurement are improved by designing the front auxiliary pattern.

[0046] refer to Figure 6 The diagram shows the overlay error measurement waveform corresponding to the current alignment pattern in this embodiment. Since there are no chemical mechanical polishing residues, there will be no abnormalities or instability in the overlay measurement caused by them.

[0047] Table 1 below summarizes the comparison of residual mean + 3 Sigma, quality factor, contrast precision, kernel 3 Sigma, and total indicator score mean + 3 Sigma between the overlay mark mask pattern (NEW) prepared in this embodiment and the overlay mark pattern (OLD) of the prior art. It can be seen that the OVL residual is reduced by 20.32%, the Recipe measurement stability is improved by 44.32%, the mark contrast is improved by 54.10%, and the Scan signal stability is improved by 57.94%.

[0048]

[0049] Table 1

[0050] In summary, the overlay mark mask pattern and overlay error measurement method of the present invention, by introducing a front-layer auxiliary pattern into the front-layer pattern to increase the density of the front-layer pattern, effectively improves the damage problems that may occur during CMP, reduces or even avoids CMP residues caused by it, thereby improving the accuracy and stability of overlay error measurement. Furthermore, since the extension direction of the front-layer auxiliary sub-pattern is perpendicular to the extension directions of the front-layer alignment sub-pattern and the current alignment sub-pattern, interference with the existing grating bright and dark fringes can be avoided during overlay error measurement, ensuring the accuracy of obtaining pattern position information by scanning the bright and dark fringes of the overlay mark pattern grating. Therefore, this overlay mark mask pattern not only improves the contrast of the overlay marks and the stability of the scanning signal, but also reduces measurement anomalies caused by CMP residues, ultimately achieving higher-precision interlayer alignment, which is of great significance for improving the overall performance and reliability of semiconductor manufacturing processes. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has high industrial applicability.

[0051] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A mask pattern for overlay marking, characterized in that, The overlay marking mask pattern includes: The front-layer graphic includes four front-layer graphic units with fourfold rotational symmetry. Each front-layer graphic unit includes a front-layer alignment graphic unit and a front-layer auxiliary graphic unit. Each front-layer alignment graphic unit includes multiple front-layer alignment sub-graphics distributed at fixed intervals. Each front-layer auxiliary graphic unit includes multiple front-layer auxiliary sub-graphics distributed at fixed intervals. The extension direction of the front-layer alignment sub-graphics is perpendicular to the extension direction of the front-layer auxiliary sub-graphics. The current alignment pattern comprises four current alignment pattern units with fourfold rotational symmetry. Each current alignment pattern unit includes multiple current alignment sub-patterns distributed at fixed intervals. The front-layer auxiliary pattern unit extends along its extension direction through the projection of the corresponding current alignment pattern unit onto the front-layer pattern. The extension direction of the front-layer auxiliary sub-pattern in the front-layer auxiliary pattern unit is perpendicular to the extension direction of the current alignment sub-pattern in the corresponding current alignment pattern unit. The centers of the front-layer alignment sub-pattern in the front-layer alignment pattern unit and the current alignment sub-pattern in the corresponding current alignment pattern unit are aligned one-to-one.

2. The overlay marking mask pattern according to claim 1, characterized in that: The line width of the previous alignment sub-pattern is W1 and the pitch is S1. The line width of the current alignment sub-pattern is W2 and the pitch is S2. (1-5%)W1≤W2≤(1+5%)W1, S1=S2.

3. The overlay marking mask pattern according to claim 1 or 2, characterized in that: The linewidth of the front-layer alignment sub-pattern is W1, the pitch is S1, 500nm≤W1≤1300nm, and 1000nm≤S1≤2600nm.

4. The overlay marking mask pattern according to claim 2, characterized in that: The line width of the front-layer auxiliary sub-graphic is W3, the pitch is S3, W3 < W1, and S3 < S1.

5. The overlay marking mask pattern according to claim 4, characterized in that: The linewidth of the front auxiliary sub-pattern is W3, the pitch is S3, 90nm≤W3≤110nm, and S3=2W3.

6. The overlay marking mask pattern according to claim 1, characterized in that: The extension direction of the front-layer auxiliary pattern unit exceeds the size of the projection of the corresponding current alignment pattern unit onto the front-layer pattern by 195nm~205nm, and the projection of the extension direction of the current alignment sub-pattern onto the front-layer pattern exceeds the size of the front-layer auxiliary pattern unit by more than 50nm.

7. The overlay marking mask pattern according to claim 1, characterized in that: The number of the previous alignment sub-graphics in the previous alignment graphic unit is equal to the number of the current alignment sub-graphics in the current alignment graphic unit.

8. The overlay marking mask pattern according to claim 1, characterized in that: The polarity type of the mask for the front layer pattern is a bright field mask.

9. The overlay marking mask pattern according to claim 1, characterized in that: The four front-layer alignment pattern units are two centrally symmetrical first front-layer pattern units and two centrally symmetrical second front-layer pattern units. The extension direction of the first front-layer sub-pattern in the first front-layer pattern unit is perpendicular to the X direction of the optical signal scanning of the overlay measuring instrument. The extension direction of the second front-layer sub-pattern in the second front-layer pattern unit is perpendicular to the Y direction of the optical signal scanning of the overlay measuring instrument. The X direction and the Y direction are perpendicular to each other in the same plane.

10. A method for measuring overlay error, characterized in that, The method for measuring overlay error includes: An overlay mark pattern is prepared based on the overlay mark mask pattern according to any one of claims 1 to 9; The front grating light and dark fringes of the previous alignment pattern and the current grating light and dark fringes of the current alignment pattern are obtained by using an overlay measurement machine; wherein, four of the four front alignment pattern units constitute the front alignment pattern, and four current alignment pattern units constitute the current alignment pattern. The offset between the center of the bright and dark fringes of the previous grating and the center of the bright and dark fringes of the current grating is measured to obtain the overlay error between the alignment pattern of the previous layer and the alignment pattern of the current layer.

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