Overlay mark structure and photomask

Abstract

The utility model relates to the field of semiconductor device manufacturing, and discloses an overlay mark structure and a photomask, the overlay mark structure comprises a first overlay mark pattern and a second overlay mark pattern, the first overlay mark pattern comprises four groups of sub-overlay marks, the second overlay mark pattern comprises four groups of overlay marks, and the first group of sub-overlay marks and the second group of overlay marks are arranged in parallel. The projection area of the second overlay mark pattern is within the range of the projection area of the first overlay mark pattern; each set of sub-overlay marks is of a square structure, and each set of sub-overlay marks comprises a plurality of sub-overlay aligned marks which are distributed at equal intervals in the width direction. Each group of sub-overlay marks is made into a plurality of sub-overlay aligned marks, so that the sub-overlay marks can be filled more easily while normal overlay measurement can be ensured, the filling difficulty is reduced, the marks cannot be damaged in the subsequent process, the pressure is relatively uniformly distributed when the marks are ground, and meanwhile, the alignment precision of the sub-overlay marks is improved. Polycrystalline silicon residues after mark filling and grinding are reduced or even avoided, and the measurement abnormal rate is reduced.

Description

Technical Field

[0001] The utility model relates to the field of semiconductor device manufacturing, in particular to an overlay marking structure and a photomask. Background Art

[0002] Semiconductor technology continues to develop in line with Moore's Law. The critical dimensions are getting smaller and smaller, and the integration of chips is getting higher and higher. This places increasingly stringent requirements on the semiconductor manufacturing process. Therefore, it is necessary to minimize the error of each step in the process as much as possible to reduce device failures caused by errors.

[0003] In the semiconductor manufacturing process, photolithography has been developed as the core technology of each technology generation. In the yellow light process, it is necessary to monitor the position offset between different photolithography layers. The measuring machine determines the position deviation by measuring the overlay marks designed between the current layer and the aligned layer. In the production process, it is necessary to ensure that the overlay marks are complete, clear and easy to identify. The overlay marks are filled after the outer edge of the growth, but the existing overlay marks always have grooves that are not filled during the filling process. This leads to uneven pressure during grinding due to the depression of the unfilled part during the subsequent chemical mechanical grinding, which makes the contrast on the wafer different, and the signal reflection is inconsistent, resulting in uneven grinding. Utility Model Content

[0004] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is to provide an overlay mark structure and a photomask to solve the problem that the overlay mark is not easy to be fully filled and thus causes uneven grinding.

[0005] In order to solve the above technical problems, a technical solution adopted by the utility model is: to provide an overlay mark structure including a first overlay mark pattern and a second overlay mark pattern, the first overlay mark pattern including multiple groups of sub-overlay marks, the second overlay mark pattern including multiple groups of overlay marks, the projection of the second overlay mark pattern is located within the range of the projection of the first overlay mark pattern; each group of the sub-overlay marks is surrounded to form a geometric structure, and each group of the sub-overlay marks includes multiple sub-overlay alignment marks distributed at equal intervals along the width direction, and by setting each group of sub-overlay marks into multiple small sub-overlay alignment marks, the marks can be easily filled, ensuring that the marks are evenly polished and making the overlay measurement signal more stable.

[0006] Furthermore, the four groups of sub-engraving marks and the four groups of overengraving marks are all arranged on four sides to form a square, each group of overengraving marks is located inside each sub-engraving mark and is centrally aligned, and there is no overlap between each group of sub-engraving marks and the overengraving marks.

[0007] Furthermore, the first overlay mark pattern includes four groups of sub-overlay marks, and the second overlay mark pattern includes four groups of overlay marks, wherein two groups of the sub-overlay marks and two groups of the overlay marks are arranged at intervals along an X-axis, and the other two groups of the sub-overlay marks and the other two groups of the overlay marks are arranged at intervals along a Y-axis perpendicular to the X-axis, so that each group of sub-overlay marks and the overlay marks are arranged neatly.

[0008] Furthermore, the length of each group of sub-engraving marks is 20 μm and the width is ≤ 10 μm, so as to ensure that the marks can be measured and reduce polysilicon residue during chemical mechanical polishing.

[0009] Furthermore, each group of the sub-overlay marks includes 2 to 10 sub-overlay aligned marks, and each sub-overlay aligned mark has a length of 20 μm and a width of 0.2 to 1 μm, so as to reduce the mark width and ensure overlay measurement.

[0010] Furthermore, each group of the sub-overlay marks includes four sub-overlay alignment marks, each of which is 20 μm long and 0.4 μm wide, and the spacing between two adjacent sub-overlay alignment marks is 0.8 μm, thereby effectively reducing the abnormality rate on both sides.

[0011] Furthermore, each of the sub-overlay alignment marks and each group of overlay marks are grooves to facilitate visualization and filling.

[0012] The utility model also provides a mask, including a mask body, a fence pattern formed on the mask body, cutting paths formed at the four corners and the center of the fence pattern of the mask body, and respectively forming cutting paths area A, cutting path area B, cutting path area C, cutting path area D and cutting path area E, each of the cutting paths is formed with an overlay mark pattern area, and the overlay mark pattern area includes a first overlay mark pattern and a second overlay mark pattern, so as to form five overlay mark patterns on a wafer.

[0013] Furthermore, the cutting path is filled with black, and the first set of engraved mark patterns and the second set of engraved mark patterns are respectively in different colors, so as to facilitate display on the mask and facilitate identification.

[0014] Furthermore, the overlay mark graphic area also includes a square auxiliary mark located between the first overlay mark graphic and the second overlay mark graphic. The auxiliary mark is aligned with the centers of the first overlay mark graphic and the second overlay mark graphic. The auxiliary mark is marked on the front layer together with the first overlay mark graphic so as to better display the marking position when the second overlay mark graphic is marked on the current layer.

[0015] The overlay mark structure and mask of the utility model have at least the following beneficial effects: by making each group of sub-overlay marks into multiple sub-overlay alignment marks, it is ensured that the sub-overlay marks can be filled more easily while ensuring that the overlay measurement can be performed normally, thereby reducing the difficulty of filling, preventing the marks from being damaged in subsequent processes, and making the pressure of the marks relatively evenly distributed during grinding. At the same time, it reduces or even avoids the polysilicon residue after the mark filling and grinding, thereby reducing the measurement abnormality rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0017] Figure 1 It is a schematic diagram of the top view of the overlay marking structure of the utility model;

[0018] Figure 2 It is a cross-sectional view of the overlay marking structure of the utility model;

[0019] Figure 3 A top view of the light shield of the utility model;

[0020] Figure 4 A top view of an overlay mark pattern on one of the cutting paths of the utility model;

[0021] Figure 5 It is a schematic diagram comparing the abnormality rate curves of the overlay mark structure of the utility model and the existing overlay mark structure;

[0022] Figure 6 This is a top view of the first groove of the utility model after being filled.

[0023] The meanings of the symbols in the accompanying drawings are:

[0024] Mask-1; front layer-2; current layer-3; first overlay mark pattern-4; sub-overlay mark-41; sub-overlay aligned mark-411; second overlay mark pattern-5; overlay mark-51; auxiliary mark-6; substrate-7. DETAILED DESCRIPTION

[0025] The utility model will be further described below in conjunction with the accompanying drawings.

[0026] like Figure 1 and Figure 2As shown, the overlay mark structure of the present invention includes a first overlay mark pattern 4 and a second overlay mark pattern 5. The first overlay mark pattern 4 is an aligned layer measurement mark formed on the front layer 2, and the second overlay mark pattern 5 is an alignment layer measurement mark formed on the current layer 3. In a top view, the projection of the second overlay mark pattern 5 is located within the projection range of the first overlay mark pattern 4 to form an inner circle, and the first overlay mark pattern 4 is an outer circle.

[0027] In this embodiment, the first overlay mark pattern 4 includes multiple groups of sub-overlay marks 41, and the multiple groups of sub-overlay marks 41 can be set to three groups according to the needs of overlay marks. The three groups of sub-overlay marks 41 are arranged in a triangular structure, or other structures. In this embodiment, the first overlay mark pattern 4 includes four groups of sub-overlay marks 41, and each group of sub-overlay marks 41 is a rectangular strip structure and is arranged to form a square. In this embodiment, two groups of sub-overlay marks 41 are arranged at intervals along the X axis, and the other two groups of sub-overlay marks 41 are arranged at intervals along the Y axis to form a "mouth" shape as a whole. There is no overlap or connection between any two adjacent groups of sub-overlay marks 41, so as to form four independent groups of sub-overlay marks 41 and set on the four sides of the front layer 2.

[0028] In this embodiment, the length of each group of sub-overlay marks 41 is 20 μm, and the width of each group of sub-overlay marks 41 is ≤10 μm, so as to meet the measurement requirements and ensure that the first overlay mark pattern 4 can be measured. If the width exceeds 10 μm, it will lead to failure to measure. In this embodiment, each group of sub-overlay marks 41 includes a plurality of sub-overlay alignment marks 411 distributed at equal intervals along the width direction of the sub-overlay marks 41, and the width direction of the two groups of sub-overlay marks 41 distributed along the X-axis spacing is the X-axis direction, and the width direction of the two groups of sub-overlay marks 41 distributed along the Y-axis spacing is the Y-axis direction, wherein each sub-overlay alignment mark 411 is a first groove. It should be noted that the total width of each sub-engraved alignment mark 411 of each group of sub-engraved marks 41 satisfies ≤10μm, so that the width of each sub-engraved alignment mark 411 can be shortened under the premise of ensuring basic measurement. When filling, the filler is more likely to contact the two side walls of the sub-engraved alignment mark 411 to fill it up, and the problem of not being fully filled due to the excessive groove width of the sub-engraved alignment mark 411 will not occur. During grinding, the growth part protruding outside the first groove will be ground flat. At this time, the sub-engraved alignment mark 411 is flat and has no depression relative to the front layer 2, ensuring the accuracy of the measurement result of the measuring machine so that the first engraved mark pattern 4 can be completely and clearly identified to determine whether there is a deviation between the first engraved mark pattern 4 and the second engraved mark pattern 5.

[0029] In this embodiment, each group of sub-overlay marks 41 includes 2 to 10 sub-overlay alignment marks 411, each sub-overlay alignment mark 411 is 20 μm long and 0.2 to 1 μm wide. Most importantly, the total width of each sub-overlay alignment mark 411 of each group of sub-overlay marks 41 is still within 10 μm. Each group of sub-overlay marks 41 may include 2 sub-overlay alignment marks 411, each of which has a width of 1 μm. The spacing between two adjacent sub-overlay alignment marks 411 may be set to 0.8 μm. The overall width is within 10 μm, which can meet the measurement requirements and can also fill the first groove in width.

[0030] like Figure 5 and Figure 6 As shown, in the content defined in this embodiment, each group of sub-overlay marks 41 includes four sub-overlay alignment marks 411, the length of each sub-overlay alignment mark 411 is 20μm, the width of each sub-overlay alignment mark 411 is 0.4μm, and the spacing between two adjacent sub-overlay alignment marks 411 is 0.8μm. Compared with the prior art, the first groove of this embodiment is completely filled. Figure 5 The circled point F is an abnormal point. After the subsequent process, the abnormality rate of the product is significantly reduced from about 40% to about 10%, and the signal of the overlay measurement is more stable.

[0031] In this embodiment, the second overlay mark pattern 5 includes multiple groups of overlay marks 51, and the multiple groups of overlay marks 51 can be set to three groups according to the needs of overlay marks. The three groups of overlay marks 51 are arranged in a triangular structure, or other structures. In this embodiment, the second overlay mark pattern 5 includes four groups of overlay marks 51, and each group of overlay marks 51 is a rectangular strip structure and is arranged to form a square. In this embodiment, two groups of overlay marks 51 are arranged at intervals along the X axis, and the other two groups of overlay marks 51 are arranged at intervals along the Y axis to form a "mouth" shape as a whole. There is no overlap or connection between any two adjacent groups of overlay marks 51, so as to form four independent groups of overlay marks 51 and set on the four sides of the current layer 3. Each overlay mark 51 includes a set of overlay alignment marks, and each overlay alignment mark is a second groove. In this embodiment, the first groove and the second groove are both defined as grooves, and each group of overlay marks 51 is located inside each sub-overlay mark 41 and is centrally aligned to ensure that there is no deviation in the position of the overlay alignment mark 411 and the overlay alignment mark of the measuring machine.

[0032] The photomask of the utility model includes a photomask body, a fence pattern is formed on the photomask body, and cutting paths are formed at the four corners and the center of the fence pattern of the photomask body, which are respectively cutting path area A, cutting path area B, cutting path area C, cutting path area D and cutting path area E. The photomask body is a rectangular sheet structure, with the width of the photomask body as the X-axis, the length of the photomask body as the Y-axis, and the thickness of the photomask body as the Z-axis. In order to facilitate the description of the position of each cutting path, Figure 3 The cutting path area A is located at the upper left corner, the cutting path area B is located at the upper right corner, the cutting path area C is located at the lower left corner, the cutting path area D is located at the lower right corner, and the cutting path area E is located at the center. Each cutting path is formed with an overlay mark graphic area, and the overlay mark graphic area includes a first overlay mark graphic 4, a second overlay mark graphic 5, and a square auxiliary mark 6 located between the first overlay mark graphic 4 and the second overlay mark graphic 5, so as to form five overlay mark graphics on the wafer. The cutting path is filled with black, and the first overlay mark graphic 4, the second overlay mark graphic 5, and the auxiliary mark 6 are different colors for easy display on the mask and easy to distinguish and identify. The first overlay mark graphic 4 and the second overlay mark graphic 5 are the first overlay mark graphic 4 and the second overlay mark graphic 5 in the overlay mark structure, which will not be repeated here. The auxiliary mark 6 is arranged in alignment with the center of the first overlay mark pattern 4 and the second overlay mark pattern 5 and is formed by the interval of multiple short line segments. The auxiliary mark 6 is marked on the front layer 2 together with the first overlay mark pattern 4, and the auxiliary mark 6 does not penetrate the front layer 2. When marking the second overlay mark pattern 5 on the current layer 3, the position of the second overlay mark pattern 5 can be adjusted by the auxiliary mark 6 to reduce or even avoid the deviation between the first overlay mark pattern 4 and the second overlay mark pattern 5. The width of the auxiliary mark 6 is consistent with the width of the first groove, and can also be smaller than the width of the first groove to facilitate filling.

[0033] like Figures 1 to 6 As shown, the marking method of the overlay marking structure of the utility model comprises the following steps:

[0034] S1, drawing a first set of engraved mark patterns 4, a second set of engraved mark patterns 5 and an auxiliary mark 6 on the mask;

[0035] S2, providing a substrate 7 formed with a front layer 2, and spin coating a first photoresist layer on the front layer 2;

[0036] S3, transferring the first overlay mark pattern 4 and the auxiliary mark 6 on the mask to the front layer 2 and developing to form a first overlay development area;

[0037] S4, etching the portion of the front layer 2 corresponding to the first overlay developing area to form a first overlay mark pattern 4 and an auxiliary mark 6;

[0038] S5, filling each group of sub-engraving marks 41 and auxiliary marks 6 on the surface of the wafer through a furnace tube process;

[0039] S6, polishing each group of sub-engraving marks 41 and auxiliary marks 6 on the surface of the wafer by chemical mechanical grinding;

[0040] S7, forming a current layer 3 on the front layer 2 and spin coating a second photoresist layer;

[0041] S8, transferring the second set mark pattern 5 on the mask to the current layer 3 and developing it to form a second set development area;

[0042] S9, etching the portion of the layer 3 corresponding to the second overlay developing area to form a second overlay mark pattern 5.

[0043] In step S1, the designed first set of engraved mark graphics 4, second set of engraved mark graphics 5 and auxiliary marks 6 are first drawn onto the mask layout through the mask design software, and the areas where the first set of engraved mark graphics 4, second set of engraved mark graphics 5 and auxiliary marks 6 are located are set as light-transmitting areas according to the design requirements on the mask design software, and the remaining parts are set as opaque areas. Then, the first set of engraved mark graphics 4, auxiliary marks 6 and second set of engraved mark graphics 5 are placed at the cutting path positions of the upper left, lower left, upper right, lower right and center of the mask, and finally the drawn layout is copied to the mask to complete the drawing of the mark graphics on the mask. Each group of sub-set engraved marks 41 of the first set of engraved mark graphics 4 are rectangular strip structures and are surrounded in a square, and the auxiliary marks 6 are composed of multiple short line segments.

[0044] In step S2 , a first photoresist layer is spin-coated on the front layer 2 so as to be able to transfer the mark onto the front layer 2 .

[0045] In step S3, through the photolithography process, the structure of the first set of engraved mark graphics 4 and auxiliary marks 6 is engraved on the first photoresist layer by utilizing exposure and development, and the first set of engraved mark graphics 4 and auxiliary marks 6 on the mask are copied to the first photoresist layer on the surface of the front layer 2 wafer so that they can be developed on the wafer.

[0046] In step S4, the first set of engraved mark patterns 4 and auxiliary marks 6 on the first photoresist layer are copied onto the front layer 2 through an etching process, and the front layer 2 without the protection of the first photoresist layer is removed by chemical reaction or physical action by utilizing the covering and protective effect of the photoresist film, so as to open a corresponding first groove on the front layer 2, and the groove formed by the auxiliary mark 6 is defined as a third groove, thereby completing the transfer of the first set of engraved mark patterns 4 and the auxiliary mark 6.

[0047] In step S5, silicon oxide and other materials are uniformly grown on the surface of the wafer, the first trench and the third trench through a low-pressure furnace tube to fill the first trench and the third trench.

[0048] In step S6, the surface of the wafer, i.e., the surface of the front layer 2 and the portion extending outside the first groove and the third groove, is polished by chemical mechanical polishing. The surface of the wafer is flattened by a processing technology that combines chemical corrosion and mechanical removal, thereby obtaining a wafer with higher flatness while ensuring material removal efficiency.

[0049] In step S7 , a current layer 3 is formed on the prepared front layer 2 , and a second photoresist layer is spin-coated on the current layer 3 , so as to transfer the second set mark pattern 5 to the current layer 3 .

[0050] In step S8, the second set of engraved mark patterns 5 are engraved on the second photoresist layer by exposure and development through the photolithography process, and the first set of engraved mark patterns 4 on the mask are copied to the second photoresist layer on the surface of the wafer layer 3 so that they can be developed on the wafer.

[0051] In step S9 , the second set of engraved mark patterns 5 on the second photolithography layer are replicated on the current layer 3 through an etching process to open a corresponding second groove on the current layer 3 , thereby completing the transfer of the second set of engraved mark patterns 5 .

[0052] The overlay offset detection method of the overlay mark structure of the utility model detects the overlay offset according to the overlay mark structure, comprising the following steps:

[0053] Detecting the center of the first set of engraved marking patterns 4;

[0054] Detecting the center of the second set of engraved marking patterns 5;

[0055] The offsets of the centers of the first sub-engraving mark pattern 4 and the second sub-engraving mark pattern 5 in the three directions of X, Y and Z are measured to obtain overlay compensation data, and the exposure machine is compensated according to the compensation data.

Claims

1. An overlay marking structure, characterized in that: It includes a first overlay mark pattern and a second overlay mark pattern, the first overlay mark pattern includes multiple groups of sub-overlay marks, the second overlay mark pattern includes multiple groups of overlay marks, the projection of the second overlay mark pattern is located within the range of the projection of the first overlay mark pattern; each group of sub-overlay marks is surrounded to form a geometric structure, and each group of sub-overlay marks includes multiple sub-overlay aligned marks distributed at equal intervals along the width direction.

2. The overlay mark structure according to claim 1, characterized in that: The first overlay mark pattern includes four groups of sub-overlay marks, and the second overlay mark pattern includes four groups of overlay marks. The four groups of sub-overlay marks and the four groups of overlay marks are evenly arranged on four sides to form a square. Each group of overlay marks is located inside each sub-overlay mark and is centrally aligned, and there is no overlap between each group of sub-overlay marks and overlay marks.

3. The overlay mark structure according to claim 2, characterized in that: Two groups of the sub-overlay marks and two groups of the overlay marks are arranged at intervals along an X-axis, and the other two groups of the sub-overlay marks and the other two groups of the overlay marks are arranged at intervals along a Y-axis perpendicular to the X-axis.

4. The overlay mark structure according to claim 3, characterized in that: The length of each group of sub-engraved marks is 20 μm, and the width is ≤10 μm.

5. The overlay mark structure according to claim 4, characterized in that: Each group of the sub-overlay marks includes 2 to 10 sub-overlay aligned marks, and each of the sub-overlay aligned marks has a length of 20 μm and a width of 0.2 to 1 μm.

6. The overlay mark structure according to claim 5, characterized in that: Each group of the sub-overlay marks includes four sub-overlay aligned marks, each of the sub-overlay aligned marks has a length of 20 μm and a width of 0.4 μm, and a spacing between two adjacent sub-overlay aligned marks is 0.8 μm.

7. The overlay mark structure according to any one of claims 1 to 6, characterized in that: Each of the sub-overlay alignment marks and each group of overlay marks are grooves.

8. A photomask, comprising a photomask body, characterized in that: A fence pattern is formed on the mask body, and cutting lanes are formed at the four corners and the center of the fence pattern of the mask body, namely cutting lane area A, cutting lane area B, cutting lane area C, cutting lane area D and cutting lane area E. Each of the cutting lanes forms an overlay mark pattern area, and the overlay mark pattern area includes the first overlay mark pattern and the second overlay mark pattern as described in any one of claims 1 to 7.

9. The photomask according to claim 8, wherein: The cutting path is filled with black, and the first set of engraved mark patterns and the second set of engraved mark patterns are respectively different colors.

10. The photomask according to claim 8, wherein: The overlay mark pattern area further includes a square auxiliary mark located between the first overlay mark pattern and the second overlay mark pattern, and the auxiliary mark is aligned with the center of the first overlay mark pattern and the second overlay mark pattern.

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