Alignment mark structure and wafer bonding alignment method

Abstract

The application provides an alignment mark structure and a wafer bonding alignment method, the alignment mark structure comprises a first metal layer mark and a second metal layer mark, the second metal layer mark is located on the first metal layer mark, and the projection of the first metal layer mark overlaps with the projection of the second metal layer mark; the first metal layer mark comprises a first alignment mark and a first blank area in the first alignment mark, the second metal layer mark comprises a second alignment mark and a second blank area in the second alignment mark, and the projection of the second blank area is located in the projection of the first alignment mark. In this way, the alignment mark structure meets the size requirement and alignment accuracy of the design rule, and since the first alignment mark and the second alignment mark both have blank areas, the process stability of the first metal layer mark and the second metal layer mark is improved, so that the problems of dish-shaped concave and defects on the surface of the alignment mark structure are effectively avoided.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit technology, and in particular to an alignment mark structure and a wafer bonding alignment method. Background Technology

[0002] When bonding wafers, large alignment marks are typically required for inter-wafer alignment to achieve both alignment accuracy and stability. However, when large alignment marks are formed through etching, chemical mechanical polishing (CMP), and electroplating (ECP) processes, these large marks can easily affect process stability, thus making it easier for dishing or defects to form on the alignment mark surface. Summary of the Invention

[0003] The purpose of this invention is to provide an alignment mark structure to solve the problem of disc-shaped depressions and defects caused by the large size of the alignment mark.

[0004] To solve the above-mentioned technical problems, the present invention provides an alignment mark structure, comprising:

[0005] A first metal layer mark and a second metal layer mark, wherein the second metal layer mark is located on the first metal layer mark, and the projection of the first metal layer mark overlaps with the projection of the second metal layer mark;

[0006] The first metal layer mark includes a first alignment mark and a first blank area located in the first alignment mark, and the second metal layer mark includes a second alignment mark and a second blank area located in the second alignment mark, wherein the projection of the second blank area is located within the projection of the first alignment mark.

[0007] Optionally, in the alignment mark structure, the second metal layer mark further includes a third alignment mark, the second alignment mark surrounding the third alignment mark, and the second blank area located between the second alignment mark and the third alignment mark.

[0008] Optionally, in the alignment mark structure, the projection shape of the first blank area and the projection shape of the third alignment mark are both cross-shaped, and the projection of the first blank area is located within the projection of the third alignment mark.

[0009] Optionally, in the alignment mark structure, the first metal layer mark further includes a plurality of staggered first redundant alignment marks, all of which are located in the first blank area.

[0010] Optionally, in the alignment mark structure, the first metal layer mark further includes a plurality of second redundant alignment marks, all of which are arranged around the first alignment mark in a staggered manner, and the projections of all the second redundant alignment marks are located within the projection of the second alignment mark.

[0011] Optionally, in the alignment mark structure, the projection shape of both the first redundant alignment mark and the second redundant alignment mark includes a square shape.

[0012] Optionally, in the alignment mark structure, the projection shape of the first alignment mark, the projection shape of the second alignment mark, and the projection shape of the second blank area are all cross-shaped, wherein the outer contour width of the second alignment mark is greater than the outer contour width of the first alignment mark.

[0013] Optionally, in the alignment mark structure, the first alignment mark includes a plurality of staggered first alignment sub-marks, the first blank area is located between adjacent first alignment marks, wherein the projected shape of each first alignment sub-mark includes a square.

[0014] Optionally, in the alignment mark structure, the first metal layer mark further includes a third alignment mark, which surrounds the first alignment mark and the first blank area.

[0015] Based on the same inventive concept, the present invention also provides a wafer bonding alignment method, comprising:

[0016] Two wafers are provided to be bonded, and dicing channels are formed in both wafers, with alignment mark structures formed in the dicing channels of both wafers;

[0017] Identify alignment mark structures in two wafers and match the alignment mark structures in the two wafers to achieve alignment between the two wafers.

[0018] In the alignment mark structure provided by this invention, the alignment mark structure includes a first metal layer mark and a second metal layer mark. The second metal layer mark is located on the first metal layer mark, and the projection of the first metal layer mark overlaps with the projection of the second metal layer mark. The first metal layer mark includes a first alignment mark and a first blank area located within the first alignment mark. The second metal layer mark includes a second alignment mark and a second blank area located within the second alignment mark. The projection of the second blank area is located within the projection of the first alignment mark. Thus, the alignment mark structure is formed by superimposing the first alignment mark in the first metal layer mark and the second alignment mark in the second metal layer mark, ensuring that the alignment mark structure meets the dimensional requirements and alignment accuracy of the design rules. Furthermore, since both the first and second alignment marks have blank areas, the etching uniformity of the etching process, the uniformity of the chemical mechanical polishing process, and the electric field distribution of the electroplating process can be improved. This avoids the problem of dish-shaped depressions and defects on the surface of the first or second metal layer mark when it is formed by etching, chemical mechanical polishing, and electroplating processes, thereby improving the process stability of the alignment mark structure and effectively avoiding the problem of dish-shaped depressions and defects on the surface of the alignment mark structure. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the alignment mark structure according to Embodiment 1 of the present invention;

[0020] Figure 2 This is a schematic diagram of the structure of the first metal layer mark in the alignment mark structure of Embodiment 1 of the present invention;

[0021] Figure 3 This is a schematic diagram of the second metal layer mark in the alignment mark structure of Embodiment 1 of the present invention;

[0022] Figure 4 This is a schematic diagram of the alignment mark structure according to Embodiment 2 of the present invention;

[0023] Figure 5 This is a schematic diagram of the structure of the first metal layer mark in the alignment mark structure of Embodiment 2 of the present invention;

[0024] Figure 6 This is a schematic diagram of the structure of the first alignment mark in the alignment mark structure of Embodiment 2 of the present invention;

[0025] Figure 7 This is a schematic diagram of the second metal layer mark in the alignment mark structure of Embodiment 2 of the present invention;

[0026] Figure 8 This is a schematic flowchart of the wafer bonding alignment method according to an embodiment of the present invention;

[0027] The reference numerals in the attached figures are explained as follows:

[0028] 100-Alignment mark structure;

[0029] 110 - First metal layer mark; 111 - First alignment mark; 111a - First alignment sub-mark; 112 - First blank area; 113 - First redundant alignment mark; 114 - Second redundant alignment mark; 115 - Third alignment mark;

[0030] 120 - Second metal layer mark; 121 - Second alignment mark; 122 - Second blank area; 123 - Third alignment mark. Detailed Implementation

[0031] The alignment mark structure and wafer bonding alignment method proposed in this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of this invention.

[0032] Example 1

[0033] Figure 1 This is a schematic diagram of the alignment mark structure according to Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the structure of the first metal layer mark in the alignment mark structure of Embodiment 1 of the present invention. Figure 3 This is a schematic diagram of the second metal layer mark in the alignment mark structure of Embodiment 1 of the present invention. (Reference) Figure 1 and combined Figure 2 and Figure 3 As shown, this embodiment provides an alignment mark structure 100, which can be used to achieve wafer bonding alignment. Specifically, the alignment mark structure 100 includes a first metal layer mark 110 and a second metal layer mark 120, the second metal layer mark 120 being located on the first metal layer mark 110, and the projection of the first metal layer mark 110 overlapping the projection of the second metal layer mark 120. The first metal layer mark 110 includes a first alignment mark 111 and a first blank area 112 located in the first alignment mark 111. Figure 1 (The illustration of the first blank area 112 is omitted). The second metal layer mark 120 includes a second alignment mark 121 and a second blank area 122 located in the second alignment mark 121. The projection of the second blank area 122 is located within the projection of the first alignment mark 111.

[0034] Therefore, the alignment mark structure 100 is formed by superimposing the first alignment mark 111 in the first metal layer mark 110 and the second alignment mark 121 in the second metal layer mark 120. This ensures that the alignment mark structure 100 meets the size requirements and alignment accuracy of the design rule. Furthermore, since both the first alignment mark 111 and the second alignment mark 121 have blank areas, the uniformity of the etching process, the uniformity of the chemical mechanical polishing (CMP) process, and the electric field distribution of the electroplating process (ECP) can be improved. This avoids the problem of dish-shaped depressions and defects on the surface of the first metal layer mark 110 or the second metal layer mark 120 when the etching process, chemical mechanical polishing process, and electroplating process are formed. This improves the process stability of the alignment mark structure and effectively avoids the problem of dish-shaped depressions and defects on the surface of the alignment mark structure.

[0035] In this embodiment, the alignment mark structure 100 is disposed in the dicing channel of the wafer and can be used to achieve bonding alignment between two wafers.

[0036] In this embodiment, the first metal layer mark 110 and the second metal layer mark 120 are isolated by a dielectric layer, the material of which may be, for example, silicon oxide. It should be noted that, for the purpose of better illustrating the inventive points of this invention, the description and illustration of the dielectric layer between the first metal layer mark 110 and the second metal layer mark 120 are omitted.

[0037] like Figure 1 As shown, the overall projection (i.e., the projection of the alignment mark structure 100) of the first metal layer mark 110 and the second metal layer mark 120 is cross-shaped, meaning that the alignment mark structure 100 is a solid cross-shaped structure. The overall outer contour width W1 of the first metal layer mark 110 is the same as the overall outer contour width W2 of the second metal layer mark 120 (i.e., the outer contour width of the second alignment mark 121), or the overall outer contour width W1 of the first metal layer mark 110 is greater than the overall outer contour width W2 of the second metal layer mark 120.

[0038] For example, the overall outer contour width W1 of the first metal layer mark 110 and the overall outer contour width W2 of the second metal layer mark 120 can both be greater than or equal to 40μm, for example, 40μm to 50μm, to meet the size requirements of large-size alignment marks, thereby making them easier to identify and position, and thus improving alignment accuracy.

[0039] In some embodiments, such as Figure 2As shown, the projected shape of the first alignment mark 111 is a cross-shaped frame (or a hollow cross-shaped frame). The first alignment mark 111 surrounds the first blank area 112, that is, the first alignment mark 111 has a hollow cross-shaped structure. Because the first alignment mark 111 has a first blank area 112, during the process of forming the first alignment mark 111 using etching, chemical mechanical polishing (CMP), or electroplating (ECP), the surface of the first alignment mark 111 is less prone to dishing and defects, thus improving the process stability of the first alignment mark 111.

[0040] like Figure 2 As shown, the projected shape of the first blank area 112 is cross-shaped. The first metal layer mark 110 also includes a plurality of staggered first redundant (dummy) alignment marks 113, all of which are located in the first blank area 112. By setting the first redundant alignment marks 113, the pattern density of the first metal layer mark 110 can be adjusted, which is beneficial to improving the uniformity of the chemical mechanical polishing and etching processes. In addition, since the multiple first redundant alignment marks 113 are staggered, the pressure of the chemical mechanical polishing process can be avoided from concentrating in a specific area, which is beneficial to avoid the problem of depressions on the surface of the first metal layer mark 110.

[0041] Optional, such as Figure 2 As shown, the first metal layer mark 110 also includes a plurality of second redundant alignment marks 114. All the second redundant alignment marks 114 are arranged in a staggered manner around the first alignment mark 111, that is, all the second redundant alignment marks 114 are distributed around the first alignment mark 111. By setting a plurality of second redundant alignment marks 114, the pattern density of the first metal layer mark 110 can be adjusted, which is beneficial to improving the uniformity of the chemical mechanical polishing process and the etching process.

[0042] In this embodiment, the projection shape of the first redundant alignment mark 113 and the projection shape of the second redundant alignment mark 114 both include a square shape, so that the first redundant alignment mark 113 and the second redundant alignment mark 114 have graphic consistency.

[0043] Preferably, the projections of all the second redundant alignment marks 114 are located within the projection of the second alignment mark 121. That is, the projection of the second alignment mark 121 on the first metal layer mark 110 covers all the second redundant alignment marks 114, so as to facilitate the identification of the alignment mark structure 100.

[0044] In this embodiment, the projection shape of the second alignment mark 121 can be a cross-shaped frame (or a hollow cross-shaped frame).

[0045] refer to Figure 3 As shown, in some embodiments, the outer contour width W2 of the second alignment mark 121 is greater than the overall outer contour width W1 of all the second redundant alignment marks 114 (i.e., the overall outer contour width of the first metal layer mark 110), that is, the projection of the outer contour of all the second redundant alignment marks 114 is located between the projection of the outer contour of the second alignment mark 121 and the projection of the inner contour.

[0046] In some embodiments, the outer contour width W2 of the second alignment mark 121 is equal to the overall outer contour width W1 of all the second redundant alignment marks 114, that is, the projection of the outer contour of a portion of the second redundant alignment marks 114 (the projection shape is square) partially overlaps with the projection of the outer contour of the second alignment mark 121. For example, the projection of one or two sides of the outer contour of a portion of the second redundant alignment marks 114 partially overlaps with the projection of the outer contour of the second alignment mark 121.

[0047] like Figure 3 As shown, the second metal layer mark 120 further includes a third alignment mark 123, which is surrounded by the second alignment mark 121. Preferably, the projected shape of the third alignment mark 123 is cross-shaped, that is, the third alignment mark 123 is a solid cross-shaped structure, so that the shape of the third alignment mark 123 is the same as the shape of the first blank area 112.

[0048] In this embodiment, the width W4 of the third alignment mark 123 is greater than the width W5 of the first blank area 112, so that the projection of the third alignment mark 123 on the surface of the first metal layer mark 110 can cover the first blank area 112, that is, the projection of the first blank area 112 is located within the projection of the third alignment mark 123. This is beneficial to improving the alignment accuracy and alignment stability of the alignment mark structure 100. The width W4 of the third alignment mark 123 can be 10μm to 20μm.

[0049] like Figure 3 As shown, the second blank area 122 is located between the third alignment mark 123 and the second alignment mark 121, that is, the third alignment mark 123 and the second alignment mark 121 are separated by the second blank area 122.

[0050] In this embodiment, the projection shape of the second blank area 122 can be a cross shape, and the width W9 of the outer contour of the second blank area 122 can be less than or equal to the width W3 of the outer contour of the first alignment mark 111.

[0051] In this embodiment, the first alignment mark 111, the second alignment mark 121, and the third alignment mark 123 are all protrusions disposed within the dicing channels of the wafer. The protrusions can be made of metal, such as copper, and can be formed by electroplating or electroplating combined with chemical mechanical polishing. Alternatively, the first alignment mark 111, the second alignment mark 121, and the third alignment mark 123 can all be trenches disposed within the dicing channels of the wafer, which can be formed by etching. The trenches are filled with metal, such as copper, and the metal filling the trenches can be formed by electroplating or electroplating combined with chemical mechanical polishing.

[0052] In addition, both the first blank area 112 and the second blank area 122 can be dielectric layers, and the material of the dielectric layer can be, for example, silicon oxide.

[0053] Example 2

[0054] Figure 4 This is a schematic diagram of the alignment mark structure according to Embodiment 2 of the present invention; Figure 5 This is a schematic diagram of the structure of the first metal layer mark in the alignment mark structure of Embodiment 2 of the present invention; Figure 7 This is a schematic diagram of the second metal layer mark in the alignment mark structure of Embodiment 2 of the present invention. (Reference) Figure 4 and combined Figure 5 and Figure 7 As shown, the alignment mark structure 100 provided in this embodiment includes a first metal layer mark 110 and a second metal layer mark 120. The second metal layer mark 120 is located on the first metal layer mark 110, and the projection of the first metal layer mark 110 overlaps with the projection of the second metal layer mark 120. The first metal layer mark 110 includes a first alignment mark 111 and a first blank area 112 located in the first alignment mark 111. The second metal layer mark 120 includes a second alignment mark 121 and a second blank area 122 located in the second alignment mark 121. The projection of the second blank area 122 is located within the projection of the first alignment mark 111.

[0055] refer to Figure 5 and Figure 6 As shown, the difference between the alignment mark structure 100 in this embodiment and that in Embodiment 1 is that the first alignment mark 111 in this embodiment includes a plurality of staggered first alignment sub-markers 111a. The first blank area 112 is located between adjacent first alignment marks 111. In a further embodiment, the first blank area 112 surrounds each first alignment sub-marker 111a.

[0056] In this embodiment, all first alignment markers 111a are arranged along the horizontal and vertical directions. The spacing between two adjacent first alignment markers 111a can be the same to improve the uniformity of the distribution of the first alignment markers 111a.

[0057] In this embodiment, the overall projection shape of all first alignment marks 111a is cross-shaped, that is, the overall shape of the first alignment marks 111 is cross-shaped, so as to match the shape of the second blank area 122. Among them, the projection shape of each first alignment mark 111a includes a square.

[0058] like Figure 7 As shown, the second blank area 122 is cross-shaped. The width W6 of the second blank area 122 (i.e., the inner contour width of the second alignment mark 121) is smaller than the overall width W7 of the first alignment mark 111, so that the projection of the second blank area 122 is completely within the projection of the first alignment mark 111. This helps to improve the alignment accuracy and alignment stability of the alignment mark structure 100. The width W6 of the second blank area 122 can be 20μm to 30μm.

[0059] like Figure 5 As shown, the first metal layer mark 110 further includes a third alignment mark 115, which surrounds the first alignment mark 111 and the first blank area 112. The projection shape of the third alignment mark 115 is a cross-shaped frame, so that the projection shape of the third alignment mark 115 is the same as the projection shape of the second alignment mark 121.

[0060] In this embodiment, the projection of the outer contour of the third alignment mark 115 completely coincides with the projection of the outer contour of the second alignment mark 121 to improve the recognizability of the alignment mark structure 100. The outer contour width W8 of the third alignment mark 115 can be the same as the outer contour width W2 of the second alignment mark 121.

[0061] For example, the outer contour width W8 of the third alignment mark 115 and the outer contour width W2 of the second alignment mark 121 can be greater than or equal to 40μm, for example, 40μm to 50μm, to meet the size requirements of large-size alignment marks, thereby making them easier to identify and position, and thus improving alignment accuracy.

[0062] Figure 8 This is a schematic flowchart of the wafer bonding alignment method provided in this embodiment. Figure 8 As shown, this embodiment provides a wafer bonding alignment method, including:

[0063] Step S1: Provide two wafers to be bonded, both wafers having dicing channels formed therein, and each dicing channel on both wafers having an alignment mark structure. The two wafers to be bonded are a carrier wafer and a device wafer.

[0064] Step S2: Identify the alignment mark structures in the two wafers and match the alignment mark structures in the two wafers to achieve alignment between the two wafers. Specifically, stack the two wafers, namely the carrier wafer and the device wafer, for example, with the carrier wafer at the bottom and the device wafer at the top. Use a microscope to find the alignment mark structures of the carrier wafer and the device wafer respectively. After finding them, move the positions of the carrier wafer and the device wafer using a machine to align the alignment mark structures in the carrier wafer and the product wafer. After the carrier wafer and the device wafer are aligned, perform bonding.

[0065] In summary, in the alignment mark structure and wafer bonding alignment method provided in the embodiments of the present invention, the alignment mark structure includes a first metal layer mark and a second metal layer mark, the second metal layer mark is located on the first metal layer mark, and the projection of the first metal layer mark overlaps with the projection of the second metal layer mark; the first metal layer mark includes a first alignment mark and a first blank area located in the first alignment mark, and the second metal layer mark includes a second alignment mark and a second blank area located in the second alignment mark, the projection of the second blank area is located within the projection of the first alignment mark. Therefore, the alignment mark structure is formed by superimposing the first alignment mark in the first metal layer mark and the second alignment mark in the second metal layer mark. This ensures that the alignment mark structure meets the size requirements and alignment accuracy of the design rules. Furthermore, since both the first and second alignment marks have blank areas, the etching uniformity of the etching process, the uniformity of chemical mechanical polishing, and the electric field distribution of the electroplating process can be improved. This avoids the problem of dish-shaped depressions and defects on the surface of the first or second metal layer mark when it is formed by etching, chemical mechanical polishing, and electroplating processes. This improves the process stability of the first and second metal layer marks and effectively avoids the problem of dish-shaped depressions and defects on the surface of the alignment mark structure.

[0066] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to mutually. In addition, the different parts between embodiments can also be combined with each other, and this invention does not limit this.

[0067] Furthermore, it should be understood that although the present invention has been disclosed above with reference to preferred embodiments, these embodiments are not intended to limit the present invention. For any person skilled in the art, many possible variations and modifications can be made to the technical solutions of the present invention based on the disclosed technical content, or equivalent embodiments can be modified accordingly, without departing from the 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 present invention, shall still fall within the scope of protection of the present invention.

Claims

1. An alignment mark structure, characterized in that, include: A first metal layer mark and a second metal layer mark, wherein the second metal layer mark is located on the first metal layer mark, and the projection of the first metal layer mark overlaps with the projection of the second metal layer mark; The first metal layer mark includes a first alignment mark and a first blank area located in the first alignment mark, and the second metal layer mark includes a second alignment mark and a second blank area located in the second alignment mark, wherein the projection of the second blank area is located within the projection of the first alignment mark.

2. The alignment mark structure as described in claim 1, characterized in that, The second metal layer mark also includes a third alignment mark, the second alignment mark surrounding the third alignment mark, and the second blank area located between the second alignment mark and the third alignment mark.

3. The alignment mark structure as described in claim 2, characterized in that, The projection shape of the first blank area and the projection shape of the third alignment mark are both cross-shaped, and the projection of the first blank area is located within the projection of the third alignment mark.

4. The alignment mark structure as described in claim 3, characterized in that, The first metal layer mark also includes a plurality of staggered first redundant alignment marks, all of which are located in the first blank area.

5. The alignment mark structure as described in claim 4, characterized in that, The first metal layer mark also includes a plurality of second redundant alignment marks, all of which are arranged around the first alignment mark in a staggered manner, and the projections of all the second redundant alignment marks are located within the projection of the second alignment mark.

6. The alignment mark structure as described in claim 5, characterized in that, The projection shape of both the first redundant alignment mark and the second redundant alignment mark includes a square shape.

7. The alignment mark structure as described in claim 1, characterized in that, The projection shapes of the first alignment mark, the second alignment mark, and the second blank area are all cross-shaped, wherein the outer contour width of the second alignment mark is greater than the outer contour width of the first alignment mark.

8. The alignment mark structure as described in claim 1, characterized in that, The first alignment mark includes a plurality of staggered first alignment sub-marks, the first blank area is located between adjacent first alignment marks, wherein the projected shape of each first alignment sub-mark includes a square.

9. The alignment mark structure as described in claim 8, characterized in that, The first metal layer mark further includes a third alignment mark, which surrounds the first alignment mark and the first blank area.

10. A wafer bonding alignment method, characterized in that, include: Two wafers to be bonded are provided, wherein dicing channels are formed in both wafers, and each dicing channel of the two wafers is formed with an alignment mark structure as described in any one of claims 1 to 9; Identify alignment mark structures in two wafers and match the alignment mark structures in the two wafers to achieve alignment between the two wafers.

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