CN113725196B - Semiconductor structure and forming method thereof - Google Patents

Abstract

The present disclosure relates to semiconductor manufacturing technology, and more particularly, to a semiconductor structure and a method for forming the same. The semiconductor structure includes: the substrate comprises a semiconductor layer and a top interconnection layer positioned on the top surface of the semiconductor layer; an alignment mark located above the semiconductor layer; the dielectric layer is positioned above the semiconductor layer, and comprises a plurality of first repeated structural units which are distributed around the periphery of the alignment mark and are periodically distributed, wherein the first repeated structural units are used for increasing the contrast ratio between the alignment mark and the dielectric layer. The invention can improve the accuracy and definition of the identification of the alignment mark, is beneficial to improving the yield of the semiconductor product and improving the performance of the semiconductor product.

Description

Semiconductor structure and method of forming the same

Technical Field

The present invention relates to the field of semiconductor manufacturing technology, and in particular to a semiconductor structure and a forming method thereof.

Background Art

With the development of planar flash memory, the production process of semiconductors has made great progress. However, in recent years, the development of planar flash memory has encountered various challenges: physical limits, existing development technology limits, and storage electron density limits. In this context, in order to solve the difficulties encountered by planar flash memory and pursue lower production costs per unit storage unit, various three-dimensional (3D) flash memory structures have emerged, such as 3D NOR (3D non-or) flash memory and 3D NAND (3D non-and) flash memory.

Among them, 3D NAND memory takes its small size and large capacity as its starting point, and uses a highly integrated design concept of stacking storage units in a three-dimensional mode to produce memory with high storage density per unit area and efficient storage unit performance. It has become the mainstream process for the design and production of emerging memories.

Wafer bonding is an important step in the semiconductor manufacturing process. However, in the current wafer bonding process, due to the defects of the bonding alignment marks themselves, the alignment marks cannot be accurately identified during the bonding process, which easily leads to alignment deviation or even misalignment, affecting the wafer bonding quality.

Therefore, how to improve the accuracy of alignment mark recognition, thereby improving the yield of semiconductor products, is a technical problem that needs to be solved urgently.

Summary of the invention

The present invention provides a semiconductor structure and a method for forming the same, which are used to solve the problem of low recognition accuracy of alignment marks in the prior art, so as to improve the yield of semiconductor products.

In order to solve the above problems, the present invention provides a semiconductor structure, comprising:

A substrate, the substrate comprising a semiconductor layer and a top interconnection layer located on a top surface of the semiconductor layer;

an alignment mark located above the semiconductor layer;

The dielectric layer is located above the semiconductor layer, and the dielectric layer includes a plurality of first repeating structural units distributed around the periphery of the alignment mark and arranged periodically, wherein the first repeating structural units are used to increase the contrast between the alignment mark and the dielectric layer.

Optionally, the material of the first repeating structure unit is a first metal material, and the first metal material can produce metal dipole resonance under the irradiation of a first wavelength of light to increase the difference in absorption rate between the alignment mark and the dielectric layer under the first wavelength of light.

Optionally, the first repeating structural unit is in the shape of a circle, an ellipse or any polygon.

Optionally, the dielectric layer is located on the top surface of the semiconductor layer, the top interconnect layer penetrates the dielectric layer, and the alignment mark is located in the dielectric layer.

Optionally, the dielectric layer is located on the top surface of the semiconductor layer, and the top interconnect layer penetrates the dielectric layer; and the semiconductor structure further includes:

An isolation layer covers the dielectric layer and the top interconnection layer, the alignment mark is located in the isolation layer, and in a direction perpendicular to the top surface of the semiconductor layer, projections of a plurality of periodically arranged first repeating structural units are distributed around the periphery of the projection of the alignment mark.

Optionally, the alignment mark includes a plurality of main body parts, and a plurality of the first repeating structure units are periodically arranged and distributed around the periphery of the main body parts.

Optionally, the alignment mark includes a plurality of main body portions separated from each other, and the plurality of main body portions are arranged in a windmill shape or an octagonal shape.

Optionally, each of the main bodies has a plurality of second repeating structural units arranged periodically, and the second repeating structural units and the first repeating structural units have different absorptivity to the second wavelength light.

Optionally, the material of the second repeating structure unit is a second metal material, and the second metal material can produce metal dipole resonance when irradiated with the second wavelength light to increase the absorption rate difference between the alignment mark and the dielectric layer under the second wavelength light.

Optionally, the shape of the second repeating structural unit is the same as that of the first repeating structural unit.

Optionally, the size of the second repeating structural unit is different from the size of the first repeating structural unit.

In order to solve the above problem, the present invention further provides a method for forming a semiconductor structure, comprising the following steps:

Providing a substrate, wherein the substrate comprises a semiconductor layer;

An alignment mark, a top interconnect layer and a dielectric layer are formed above the semiconductor layer, wherein the dielectric layer includes a plurality of first repeating structural units distributed around the periphery of the alignment mark and arranged periodically, and the first repeating structural units are used to increase the contrast between the alignment mark and the dielectric layer.

Optionally, the specific steps of forming an alignment mark, a top interconnect layer and a dielectric layer located above the semiconductor layer include:

forming a dielectric layer covering the top surface of the semiconductor layer;

forming the alignment mark, the top interconnect layer, and a plurality of first openings distributed around the periphery of the alignment mark in the dielectric layer;

The first opening is filled with a first metal material to form a plurality of first repeating structural units arranged periodically, wherein the first metal material can generate metal dipole resonance under the irradiation of a first wavelength of light to increase the difference in absorption rate between the alignment mark and the dielectric layer under the first wavelength of light.

Optionally, the specific steps of forming an alignment mark, a top interconnect layer and a dielectric layer located above the semiconductor layer include:

forming a dielectric layer covering the top surface of the semiconductor layer;

forming the top interconnect layer and a plurality of second openings in the dielectric layer;

Filling the first metal material into the second opening to form a plurality of the first repeating structure units arranged periodically;

forming an isolation layer covering the dielectric layer and the top interconnect layer;

An alignment mark is formed in the isolation layer, so that in a direction perpendicular to the top surface of the semiconductor layer, the projections of the plurality of periodically arranged first repeating structure units are distributed around the periphery of the projection of the alignment mark, and the first metal material can produce metal dipole resonance when irradiated with light of a first wavelength, so as to increase the difference in absorption rate between the alignment mark and the dielectric layer under the light of the first wavelength.

Optionally, the first repeating structural unit is in the shape of a circle, an ellipse or any polygon.

Optionally, the specific steps of forming an alignment mark in the isolation layer include:

defining a plurality of main body regions in the isolation layer;

A plurality of second repeating structure units are formed in each of the main body regions and are arranged periodically. The second repeating structure units and the first repeating structure units have different absorptivity to the second wavelength light.

Optionally, the specific steps of forming a plurality of second repeating structural units arranged periodically in each of the main body regions include:

Etching the isolation layer in the main region to form a plurality of third openings arranged periodically;

A second metal material is filled into the third opening to form a plurality of second repeating structural units arranged periodically in each of the main body regions, wherein the second metal material can produce metal dipole resonance when irradiated with the second wavelength light to increase the difference in absorption rate between the alignment mark and the dielectric layer under the second wavelength light.

Optionally, there are multiple main body areas, and the multiple main body areas are arranged in a windmill shape or an octagonal shape.

Optionally, the shape of the second repeating structural unit is the same as that of the first repeating structural unit.

Optionally, the size of the second repeating structural unit is different from the size of the first repeating structural unit.

The semiconductor structure and the method for forming the same provided by the present invention form a plurality of first repeating structural units distributed around the periphery of an alignment mark and arranged periodically in a dielectric layer, and utilize the plurality of first repeating structural units arranged periodically to enhance the light-dark contrast between the alignment mark and the dielectric layer, thereby enabling the accuracy and clarity of alignment mark recognition to be improved during positioning using the alignment mark, thereby helping to improve the yield of semiconductor products and the performance of semiconductor products.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic cross-sectional view of a semiconductor structure in a first specific embodiment of the present invention;

Figure 2 is a schematic top view within the dotted frame in Figure 1;

Figure 3 is an enlarged schematic diagram of the circular dotted frame in Figure 2;

Figure 4 is an enlarged schematic diagram of the square dotted frame in Figure 2;

5 is a flow chart of a method for forming a semiconductor structure in a first specific embodiment of the present invention;

6 is a schematic cross-sectional view of a semiconductor structure in a second specific embodiment of the present invention;

7 is a schematic top view of an alignment mark and a dielectric layer in a second specific embodiment of the present invention;

Figure 8 is an enlarged schematic diagram of the square dotted frame in Figure 7;

FIG9 is an enlarged schematic diagram of the circular dotted frame in FIG7.

DETAILED DESCRIPTION

The specific implementation manner of the semiconductor structure and the method for forming the same provided by the present invention will be described in detail below with reference to the accompanying drawings.

First specific embodiment

In the wafer bonding process, in order to ensure the alignment between the two wafers, the wafer needs to be positioned by identifying the alignment marks on the wafer. However, when the wafer is irradiated with light of a specific wavelength, the alignment mark pattern is blurred due to the low contrast between the alignment mark and the dielectric layer surrounding the alignment mark, and the alignment mark cannot be accurately identified, thereby reducing the accuracy of wafer positioning, affecting the final wafer bonding effect, and further affecting the yield of the final semiconductor product.

In order to improve the accuracy of alignment mark recognition, this specific embodiment provides a semiconductor structure, FIG1 is a cross-sectional schematic diagram of the semiconductor structure in the first specific embodiment of the present invention, FIG2 is a top view schematic diagram in the dotted frame in FIG1, FIG3 is an enlarged schematic diagram in the circular dotted frame in FIG2, and FIG4 is an enlarged schematic diagram in the square dotted frame in FIG2. As shown in FIG1-FIG4, the semiconductor structure includes:

A substrate 10, wherein the substrate 10 comprises a semiconductor layer 11 and a top interconnection layer 13 located on a top surface of the semiconductor layer 11;

an alignment mark, located above the semiconductor layer 11;

The dielectric layer 12 is located above the semiconductor layer 11 , and includes a plurality of first repeating structural units 30 distributed around the periphery of the alignment mark and arranged periodically. The first repeating structural units 30 are used to increase the contrast between the alignment mark and the dielectric layer 12 .

Specifically, the substrate 10 may be, but is not limited to, a silicon substrate. In this specific embodiment, the substrate 10 is described as a silicon substrate. The semiconductor layer 11 is located on the surface of the substrate 10. The semiconductor layer 11 may be a single-layer structure or a multi-layer structure. The semiconductor layer 11 may be a CMOS circuit structure or a stacked structure including a plurality of memory cells. The dielectric layer 12 covers the top surface of the semiconductor layer 11. The semiconductor layer 11 includes a bottom surface facing the substrate 10 and a top surface opposite to the bottom surface. The top interconnect layer 13 penetrates the dielectric layer 12 in a direction perpendicular to the top surface of the semiconductor layer 11. One end of the top interconnect layer 13 is used to electrically connect to the device structure in the semiconductor layer 11, and the other end is used to electrically connect to an external circuit. The dielectric layer 12 may also have an isolation layer 15 covering the dielectric layer 12, the alignment mark and the top interconnect layer 13. The material of the dielectric layer 12 may be, but is not limited to, insulating materials such as oxide materials (e.g., silicon dioxide), nitride materials (e.g., silicon nitride), or oxynitride materials (e.g., silicon oxynitride). The material of the top interconnect layer 13 may be, but is not limited to, a metal material, such as tungsten. The isolation layer 15 may be a single-layer structure or a multi-layer structure. The material of the alignment mark is different from that of the dielectric layer 12, for example, the material of the alignment mark may be a metal material.

In this specific embodiment, a plurality of first repeating structure units 30 arranged periodically are provided in the dielectric layer 12 at the periphery of the alignment mark to increase the light-dark contrast between the alignment mark and the dielectric layer 12 during the light positioning process. For example, the difference in reflectivity or absorptivity of the alignment mark and the dielectric layer 12 to a specific wavelength is adjusted by the plurality of first repeating structure units 30 arranged periodically, so as to improve the accuracy of the alignment mark recognition and thus improve the positioning accuracy. The specific shape, size and material of the first repeating structure unit 30 can be selected by those skilled in the art according to actual needs, as long as the contrast between the alignment mark and the dielectric layer 12 during the irradiation of a specific wavelength can be increased. The plurality mentioned in this specific embodiment refers to more than two.

Optionally, the dielectric layer 12 is located on the top surface of the semiconductor layer 11 , the top interconnect layer 13 penetrates the dielectric layer 12 , and the alignment mark is located in the dielectric layer 12 .

Specifically, the alignment mark is disposed in the dielectric layer 12, that is, the alignment mark is also located on the top surface of the semiconductor layer 11, and the alignment mark is disposed in the same layer as the top interconnection layer 13. The plurality of first repeating structure units 30 arranged periodically in the dielectric layer 12 are distributed around the periphery of the alignment mark in the dielectric layer 12.

In some examples, the plurality of periodically arranged first repeating structure units 30 may be distributed only in a preset region 14 of the dielectric layer 12, and the preset region 14 has the alignment mark. In other examples, the plurality of periodically arranged first repeating structure units 30 may be distributed in all regions of the dielectric layer 12 except the top interconnect layer 13.

Optionally, the material of the first repeating structure unit 30 is a first metal material, and the first metal material can generate metal dipole resonance under the irradiation of a first wavelength of light to increase the difference in absorption rate between the alignment mark and the dielectric layer under the first wavelength of light.

Optionally, the first repeating structure unit 30 is in the shape of a circle, an ellipse or any polygon.

Specifically, the first repeating structure unit 30 is made of the first metal material. The first metal material can be, but is not limited to, copper, as long as it can emit metal dipole resonance under the first wavelength light. Under the irradiation of the first wavelength light, the first wavelength light passes through the isolation layer 15 and irradiates the dielectric layer 12. The plurality of first repeating structure units 30 arranged periodically utilize the metal dipole resonance of the first metal material, that is, the first wavelength light excites the positive and negative dipoles in the first repeating structure unit 14 and generates dipole resonance. The dipole resonance of the first metal material will continue to absorb the first wavelength light, thereby greatly improving the absorption rate of the first wavelength light, thereby increasing the absorption rate difference between the alignment mark and the dielectric layer 12, that is, increasing the light-dark contrast between the alignment mark and the dielectric layer 12, thereby achieving the effect of improving the recognition accuracy of the alignment mark.

The frequency of dipole resonance is related to the period and size of the first repeating structure unit 30. Therefore, by adjusting the period and size of the first repeating structure unit 30, the absorptivity of the dielectric layer 12 can be adjusted. Take the first repeating structure unit 30 as a square and the material as the first metal material as an example. By adjusting the side length a1 and/or the period p1 of the first repeating structure unit 30, the reflectivity of the dielectric layer 12 to light of a specific wavelength (e.g., the first wavelength) can be adjusted, thereby indirectly adjusting the absorptivity of the dielectric layer 12 to light of a specific wavelength, thereby increasing the contrast between the alignment mark and the dielectric layer 12. For example, when the side length a1 of the first repeating structure unit 30 is 460nm and the period p1 is 620nm, at the wavelength of the first wavelength of light of 629.86nm, the reflectivity difference between the dielectric layer 12 and the alignment mark is 51.8%, thereby significantly improving the light-dark contrast between the alignment mark and the dielectric layer 12.

Optionally, the alignment mark includes a plurality of main bodies 141 , and a plurality of periodically arranged first repeating structure units 30 are distributed around the periphery of the main bodies 141 .

Optionally, the alignment mark includes a plurality of main body portions 141 separated from each other, and the plurality of main body portions 141 are arranged in a windmill shape or an octagonal shape.

For example, as shown in FIG2 , the number of the main body parts 141 is 4, and the 4 main body parts 141 are arranged in a windmill shape. A plurality of the first repeating structural units 30 are arranged periodically around each main body part 141, and the gap between two adjacent main body parts 141 is also filled with the plurality of the first repeating structural units 30 arranged periodically.

Optionally, each of the main bodies 141 has a plurality of second repeating structure units 31 arranged periodically, and the second repeating structure units 31 and the first repeating structure units 30 have different absorptivity to the second wavelength light.

Optionally, the material of the second repeating structure unit 31 is a second metal material, and the second metal material can generate metal dipole resonance under the irradiation of the second wavelength light to increase the absorption rate difference between the alignment mark and the dielectric layer 12 under the second wavelength light.

For example, the first repeating structure unit 30 is made of the first metal material. Under the irradiation of the second wavelength light, the plurality of the first repeating structure units 30 with a periodic structure utilize the metal dipole resonance of the first metal material, that is, the second wavelength light excites the positive and negative dipoles in the first repeating structure unit 30 and generates dipole resonance, and the third wavelength light will be continuously absorbed by the dipole resonance in the first metal material, which can greatly improve the absorption rate of the second wavelength light, that is, greatly reduce the reflectivity of the dielectric layer 12 to the second wavelength light. At the same time, the second repeating structure unit 31 is made of the second metal material. Under the irradiation of the second wavelength light, the plurality of the second repeating structure units 31 with a periodic arrangement utilize the metal dipole resonance of the second metal material, that is, the second wavelength light excites the positive and negative dipoles in the second repeating structure unit 31 and generates dipole resonance. For the second wavelength light, the dipole resonance in the second metal material will continuously radiate electromagnetic waves to the outside, thereby greatly improving the reflectivity of the alignment mark to the second wavelength light. The combined effect of the two aspects increases the reflectivity difference between the alignment mark and the dielectric layer 12, that is, increases the light-dark contrast between the alignment mark and the dielectric layer 12. The type of the first metal material is different from the type of the second metal material. For example, the absorptivity of the first metal material to the second wavelength light may be greater than the absorptivity of the second metal material to the second wavelength light.

Optionally, the shape of the second repeating structure unit 31 is the same as that of the first repeating structure unit 30. In one example, the shapes of the second repeating structure unit 31 and the first repeating structure unit 30 are both rectangular.

In order to further improve the contrast between the alignment mark and the dielectric layer 12 , optionally, the size of the second repeating structure unit 31 is different from the size of the first repeating structure unit 30 .

In other examples, the alignment mark may be a solid structure, for example, each of the main parts in the windmill-shaped alignment mark is in a solid rectangular shape, that is, the alignment mark does not have the second repeating structure unit.

In addition, this specific embodiment also provides a method for forming a semiconductor structure. FIG5 is a flow chart of the method for forming a semiconductor structure in the first specific embodiment of the present invention. The schematic diagrams of the semiconductor structure formed in this specific embodiment can be seen in FIG1-FIG4. As shown in FIG1-FIG5, the method for forming a semiconductor structure includes the following steps:

Step S11, providing a substrate 10, wherein the substrate 10 includes a semiconductor layer 11;

Step S12, forming an alignment mark, a top interconnect layer 13 and a dielectric layer 12 located above the semiconductor layer 11, wherein the dielectric layer 12 includes a plurality of first repeating structure units 30 distributed around the periphery of the alignment mark and arranged periodically, and the first repeating structure units 30 are used to increase the contrast between the alignment mark and the dielectric layer 12.

Optionally, the specific steps of forming the alignment mark, the top interconnection layer 13 and the dielectric layer 12 located above the semiconductor layer 11 include:

forming a dielectric layer 12 covering the top surface of the semiconductor layer 11;

forming the alignment mark, the top interconnect layer 13 and a plurality of first openings distributed around the periphery of the alignment mark in the dielectric layer 12;

The first opening is filled with a first metal material to form a plurality of first repeating structure units 30 arranged periodically. The first metal material can generate metal dipole resonance under the irradiation of a first wavelength of light to increase the difference in absorption rate between the alignment mark and the dielectric layer 12 under the first wavelength of light.

Optionally, the first repeating structure unit 30 is in the shape of a circle, an ellipse or any polygon.

Optionally, the specific step of forming the alignment mark, the top interconnect layer 13 and a plurality of first openings distributed around the periphery of the alignment mark in the dielectric layer 12 further includes:

Defining a plurality of main regions in the dielectric layer 12;

A plurality of second repeating structure units 31 arranged periodically are formed in each of the main body regions. The second repeating structure units 31 and the first repeating structure units 30 have different absorptivity to the second wavelength light.

Optionally, the specific steps of forming a plurality of periodically arranged second repeating structure units 31 in each of the main body regions include:

Etching the dielectric layer 12 in the main region to form a plurality of third openings arranged periodically;

A second metal material is filled into the third opening to form a plurality of second repeating structure units 31 arranged periodically in each of the main regions. The second metal material can produce metal dipole resonance when irradiated with the second wavelength light to increase the difference in absorption rate between the alignment mark and the dielectric layer 12 under the second wavelength light.

Optionally, there are multiple main body areas, and the multiple main body areas are arranged in a windmill shape or an octagonal shape.

Optionally, the shape of the second repeating structure unit 31 is the same as that of the first repeating structure unit 30 .

Optionally, a size of the second repeating structure unit 31 is different from a size of the first repeating structure unit 30 .

The semiconductor structure and the method for forming the same provided in this specific embodiment form a plurality of first repeating structural units distributed around the periphery of the alignment mark and arranged periodically in the dielectric layer, and utilize the plurality of first repeating structural units arranged periodically to enhance the light-dark contrast between the alignment mark and the dielectric layer, thereby enabling the accuracy and clarity of alignment mark recognition to be improved during positioning using the alignment mark, thereby helping to improve the yield of semiconductor products and the performance of semiconductor products.

Second specific embodiment

This specific embodiment provides a semiconductor structure. FIG6 is a cross-sectional schematic diagram of the semiconductor structure in the second specific embodiment of the present invention, FIG7 is a top view schematic diagram of the alignment mark and the dielectric layer in the second specific embodiment of the present invention, FIG8 is an enlarged schematic diagram in the square dashed frame in FIG7, and FIG9 is an enlarged schematic diagram in the circular dashed frame in FIG7. This specific embodiment will not repeat the same points as the first specific embodiment, and the following mainly describes the differences from the first specific embodiment.

As shown in FIGS. 6 to 9 , the semiconductor structure includes:

A substrate 40, wherein the substrate 40 comprises a semiconductor layer 41 and a top interconnection layer 43 located on a top surface of the semiconductor layer 41;

an alignment mark 46, located above the semiconductor layer 41;

The dielectric layer 42 is located above the semiconductor layer 41 . The dielectric layer 42 includes a plurality of first repeating structural units 60 distributed around the periphery of the alignment mark 46 and arranged periodically. The first repeating structural units 30 are used to increase the contrast between the alignment mark and the dielectric layer 12 .

In some examples, the plurality of periodically arranged first repeating structure units 60 may be distributed only in a preset region 44 of the dielectric layer 42, and the projection of the alignment mark 46 in a direction perpendicular to the top surface of the semiconductor layer 41 is located in the preset region 44. In other examples, the plurality of periodically arranged first repeating structure units 60 may be distributed throughout the dielectric layer 42.

Optionally, the dielectric layer 42 is located on the top surface of the semiconductor layer 41, and the top interconnect layer 43 penetrates the dielectric layer 42; the semiconductor structure further includes:

The isolation layer 45 covers the dielectric layer 42 and the top interconnection layer 43. The alignment mark 46 is located in the isolation layer 45. In a direction perpendicular to the top surface of the semiconductor layer 41, the projections of the plurality of periodically arranged first repeating structure units 60 are distributed around the periphery of the projection of the alignment mark 46.

Specifically, the alignment mark 46 is located in the isolation layer 45 above the dielectric layer 42. The isolation layer 45 may be made of, but not limited to, insulating materials such as oxide materials (such as silicon dioxide), nitride materials (such as silicon nitride), or oxynitride materials (such as silicon oxynitride).

Take the case where the material of the first repeating structure unit 60 is the first metal material. Under the irradiation of the first wavelength light, part of the first wavelength light passes through the isolation layer 15 and irradiates the dielectric layer 12, and part of the first wavelength light is directly reflected by the alignment mark 46 in the isolation layer 45. The plurality of first repeating structure units 60 arranged periodically utilize the metal dipole resonance of the first metal material, that is, the first wavelength light excites the positive and negative dipoles in the first repeating structure unit 60 and generates dipole resonance. The dipole resonance of the first metal material will continuously absorb the first wavelength light, thereby greatly improving the absorption rate of the first wavelength light, thereby increasing the absorption rate difference between the alignment mark 46 and the dielectric layer 42, that is, increasing the reflectivity difference between the alignment mark 46 and the dielectric layer 42, and further increasing the light-dark contrast between the alignment mark 46 and the dielectric layer 42, and finally achieving the effect of improving the recognition accuracy of the alignment mark 46.

In this specific embodiment, the alignment mark 46 may be a solid structure, and may include a plurality of second repeating structure units 61 arranged in a periodic manner as described in the first specific embodiment.

Taking the case where the dielectric layer 42 includes a plurality of first repeating structural units 60 arranged periodically as shown in FIG8 , and the alignment mark 46 includes a plurality of second repeating structural units 61 arranged periodically as shown in FIG9 , and both the first repeating structural units 60 and the second repeating structural units 61 are squares as an example, the reflectivity difference between the alignment mark 46 and the dielectric layer 42 can be adjusted by adjusting the period p3 and the side length a3 of the first repeating structural unit 60 and the period p4 and the side length a4 of the second repeating structural unit 61. When the side length a3 of the first repeating structural unit 60 is 962nm, the period p3 is 1242nm, and the side length a4 of the second repeating structural unit 61 is 460nm, and the period p4 is 620nm, at the wavelength of the second wavelength light of 636.451nm, the reflectivity difference between the dielectric layer 42 and the alignment mark 46 is 58.2%, thereby achieving a significant improvement in the light-dark contrast between the alignment mark 46 and the dielectric layer 42.

This embodiment also provides a method for forming a semiconductor structure. The schematic diagrams of the semiconductor structure formed in this embodiment can be seen in Figures 6 to 9. This embodiment will not repeat the same points as the first embodiment, and the following mainly describes the differences from the first embodiment.

As shown in FIG. 6 to FIG. 9 , the method for forming a semiconductor structure provided in this specific embodiment includes the following steps:

Step S21, providing a substrate 40, wherein the substrate 40 includes a semiconductor layer 41;

In step S22, an alignment mark 46, a top interconnect layer 43 and a dielectric layer 42 are formed above the semiconductor layer 41. The dielectric layer 42 includes a plurality of first repeating structural units 60 distributed around the periphery of the alignment mark 46 and arranged periodically. The first repeating structural units 60 are used to increase the contrast between the alignment mark 46 and the dielectric layer 42.

Optionally, the specific steps of forming the alignment mark 46, the top interconnect layer 41 and the dielectric layer 42 located above the semiconductor layer 41 include:

forming a dielectric layer 42 covering the top surface of the semiconductor layer 41;

forming the top interconnect layer 43 and a plurality of second openings in the dielectric layer 42;

Filling the first metal material into the second opening to form a plurality of the first repeating structure units 60 arranged periodically;

forming an isolation layer 45 covering the dielectric layer 42 and the top interconnect layer 43;

An alignment mark 46 is formed in the isolation layer 45, so that in a direction perpendicular to the top surface of the semiconductor layer 41, the projections of the plurality of periodically arranged first repeating structure units 60 are distributed around the periphery of the projection of the alignment mark 46, and the first metal material can produce metal dipole resonance when irradiated with a first wavelength of light to increase the difference in absorption rate between the alignment mark 46 and the dielectric layer 42 under the first wavelength of light.

Optionally, the specific steps of forming the alignment mark 46 in the isolation layer 45 include:

defining a plurality of main body regions in the isolation layer 45;

A plurality of second repeating structure units 61 arranged periodically are formed in each of the main body regions. The second repeating structure units 61 and the first repeating structure units 60 have different absorptivity to the second wavelength light.

Optionally, the specific steps of forming a plurality of periodically arranged second repeating structure units 61 in each of the main body regions include:

Etching the isolation layer 45 in the main region to form a plurality of third openings arranged periodically;

A second metal material is filled into the third opening to form a plurality of second repeating structure units 61 arranged periodically in each of the main regions. The second metal material can produce metal dipole resonance when irradiated with the second wavelength of light to increase the difference in absorption rate between the alignment mark 46 and the dielectric layer 45 under the second wavelength of light.

The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims (13)

1. A semiconductor structure, comprising:

The substrate comprises a semiconductor layer and a top interconnection layer positioned on the top surface of the semiconductor layer;

an alignment mark located above the semiconductor layer;

The dielectric layer is positioned on the top surface of the semiconductor layer, the top interconnection layer penetrates through the dielectric layer, the dielectric layer comprises a plurality of first repeated structural units which are distributed around the periphery of the alignment mark and are periodically distributed, the material of each first repeated structural unit is a first metal material, the first metal material can generate metal dipole resonance under the irradiation of light rays with a first wavelength, and the dipole resonance of the first metal material can improve the absorptivity of the light rays with the first wavelength so as to increase the contrast between the alignment mark and the dielectric layer;

The isolation layer covers the dielectric layer and the top interconnection layer, and the alignment mark is positioned in the isolation layer;

The alignment mark comprises a plurality of main body parts, a plurality of first repeated structural units which are periodically distributed encircle the periphery of the main body parts, a plurality of second repeated structural units which are periodically distributed are arranged in each main body part, the second repeated structural units are made of a second metal material, the second metal material can improve the reflectivity of the alignment mark to second wavelength light rays, the first metal material can improve the absorptivity of the medium layer to the second wavelength light rays, and the projections of the plurality of first repeated structural units which are periodically distributed encircle the periphery of the projections of the alignment mark in the direction vertical to the top surface of the semiconductor layer.

2. The semiconductor structure of claim 1, wherein the first repeating structural unit has a shape of a circle, an ellipse, or an arbitrary polygon.

3. The semiconductor structure of claim 1, wherein the alignment mark comprises a plurality of body portions separated from each other, and wherein the plurality of body portions are arranged in a windmill shape or an octagonal shape.

4. The semiconductor structure of claim 1, wherein the shape of the second repeating structural unit is the same as the shape of the first repeating structural unit.

5. The semiconductor structure of claim 1, wherein the size of the second repeating structural unit is different from the size of the first repeating structural unit.

6. A method of forming a semiconductor structure, comprising the steps of:

providing a substrate, wherein the substrate comprises a semiconductor layer;

Forming an alignment mark, a top interconnection layer, a dielectric layer and an isolation layer which are positioned above the semiconductor layer, wherein the top interconnection layer penetrates through the dielectric layer, the isolation layer covers the dielectric layer and the top interconnection layer, the dielectric layer comprises a plurality of first repeated structural units which are distributed around the periphery of the alignment mark and are periodically distributed, the material of the first repeated structural units is a first metal material, the first metal material can generate metal dipole resonance under the irradiation of light rays of a first wavelength, the dipole resonance of the first metal material can improve the absorptivity of the light rays of the first wavelength so as to increase the contrast between the alignment mark and the dielectric layer, the alignment mark is positioned in the isolation layer, the alignment mark comprises a plurality of main body parts, a plurality of first repeated structural units which are periodically distributed encircle the periphery of the main body parts, a plurality of second repeated structural units which are periodically distributed are arranged in each main body part, the second repeated structural units are made of a second metal material, the second metal material can improve the reflectivity of the alignment mark to second wavelength light rays, the first metal material can improve the absorptivity of the medium layer to the second wavelength light rays, and the projections of the plurality of first repeated structural units which are periodically distributed encircle the periphery of the projections of the alignment mark in the direction vertical to the top surface of the semiconductor layer.

7. The method of forming a semiconductor structure of claim 6, wherein forming an alignment mark, a top interconnect layer and a dielectric layer over the semiconductor layer comprises:

forming a dielectric layer covering the top surface of the semiconductor layer;

Forming the top interconnection layer and a plurality of second openings in the dielectric layer;

filling a first metal material into the second opening to form a plurality of first repeated structural units which are periodically arranged;

Forming an isolation layer covering the dielectric layer and the top interconnection layer;

And forming an alignment mark in the isolation layer, so that projections of the plurality of first repeated structural units which are periodically arranged along the direction perpendicular to the top surface of the semiconductor layer are distributed around the periphery of the projections of the alignment mark, and the first metal material can generate metal dipole resonance under the irradiation of the first wavelength light so as to increase the absorption difference between the alignment mark and the dielectric layer under the first wavelength light.

8. The method of claim 6, wherein the first repeating structural unit has a shape of a circle, an ellipse, or an arbitrary polygon.

9. The method of forming a semiconductor structure of claim 7, wherein the forming an alignment mark in the isolation layer comprises:

defining a plurality of body regions in the isolation layer;

And forming a plurality of second repeated structural units which are arranged periodically in each main body area, wherein the second repeated structural units are different from the first repeated structural units in absorptivity of the second wavelength light rays.

10. The method of forming a semiconductor structure of claim 9, wherein the forming a plurality of second repeating structural units in each of the body regions in a periodic arrangement comprises: etching the isolation layer of the main body area to form a plurality of third openings which are periodically arranged;

And filling a second metal material into the third opening, and forming a plurality of second repeated structural units which are periodically arranged in each main body area, wherein the second metal material can generate metal dipole resonance under the irradiation of the second wavelength light so as to increase the absorption difference of the alignment mark and the dielectric layer under the second wavelength light.

11. The method of claim 9, wherein the number of body regions is a plurality, and the plurality of body regions are arranged in a windmill shape or an octagonal shape.

12. The method of forming a semiconductor structure of claim 9, wherein a shape of the second repeating structural unit is the same as a shape of the first repeating structural unit.

13. The method of claim 9, wherein the second repeating structural unit has a different size than the first repeating structural unit.