Metal laminate structure and preparation method thereof

Abstract

The present application discloses a metal laminate structure and a method for preparing the same. The metal laminate structure comprises: at least two metal layers, the bottom surfaces of the two metal layers being located on the same substrate; one metal layer having a groove structure, and the other metal layer having an extension structure, wherein the extension structure is embedded in the groove structure to form a planar metal laminate structure. Through the solution of the embodiments of the present application, it is possible to optimize the metal laminate structure, convert the traditional metal laminate structure into a planar metal laminate structure, eliminate the critical dimensional deviation caused by the step height, and reduce the risk of the second metal layer at the intersection of the metal laminate structure being disconnected due to the step height and cracking from the first metal layer.

Description

Technical Field

[0001] The present application generally relates to the field of semiconductor technology. More specifically, the present application relates to a metal stack structure and a method for preparing the metal stack structure. Background Art

[0002] Some existing semiconductor processes involve a special chip manufacturing technology - a double-layer metal stacking process. This process is a process technology used to achieve interconnection between different metal layers. It aims to form the interconnection structure inside the chip through steps such as metal layer deposition, photolithography, and etching.

[0003] In the existing double-layer metal stacking process, when the first metal layer is completed and the second metal layer is etched, the second metal layer is prone to defocusing in the area where the metal stacking structure is formed due to the step height caused by the thickness of the first metal layer. This will cause the critical dimension at the top of the metal stacking structure to be smaller.

[0004] Currently, this type of deviation cannot be specifically compensated or corrected using Optical Proximity Correction (OPC) technology. Due to variations in metal layer thickness and step height, OPC technology can improve this issue but cannot completely eliminate it. This defect reduces yield. Furthermore, the height difference after the first metal layer is formed in existing technology can also cause the second metal layer to break or crack at the side where it is stacked with the first metal layer to form the metal stack structure, further reducing product yield and preventing mass production.

[0005] In view of this, there is an urgent need to provide a metal stacking process solution to optimize the metal stacking structure and eliminate the uncontrollable problem of the key dimensions of the top surface of the metal stacking structure. At the same time, it can also solve the risk of the second metal layer at the overlapping part of the metal stacking structure being disconnected and cracked from the first metal layer due to the step height. Summary of the Invention

[0006] In order to at least solve one or more of the technical problems mentioned above, the present application proposes a metal stacking process solution in multiple aspects.

[0007] In a first aspect, the present application provides a metal stacked structure comprising: at least two metal layers, the bottom surfaces of the two metal layers being located on the same substrate; one of the metal layers having a groove structure, and the other metal layer having an extension structure, the extension structure being embedded in the groove structure to form a planar metal stacked structure.

[0008] In some embodiments, at least two metal layers include: a first metal layer and a second metal layer; the first metal layer includes: a linear conductive portion and at least two protruding conductive portions, the protruding conductive portions are connected to the linear conductive portion to form a groove structure, the protruding conductive portions are the groove walls of the groove structure, and the linear conductive portion is the groove bottom of the groove structure; the second metal layer includes: a strip-type conductive portion and an embedded conductive portion extending from one side of the strip-type conductive portion, wherein the embedded conductive portion is embedded in the groove structure and connected to the linear conductive portion.

[0009] In some embodiments, at least two metal layers include: a first metal layer and a second metal layer; the second metal layer includes: a linear conductive portion and at least two protruding conductive portions, wherein the protruding conductive portion is connected to the linear conductive portion to form a groove structure, the protruding conductive portion is the groove wall of the groove structure, and the linear conductive portion is the groove bottom of the groove structure; the first metal layer includes: a strip-type conductive portion, and part of the strip-type conductive portion is embedded in the groove structure.

[0010] In some embodiments, in the first metal layer, the protruding conductive portion is a conductive portion extending along the length direction of the linear conductive portion, and the protruding conductive portion is perpendicular to the linear conductive portion to form a caliper-shaped or U-shaped groove structure; in the second metal layer, the embedded conductive portion is perpendicular to the strip-shaped conductive portion.

[0011] In some embodiments, the outwardly protruding conductive portion is a conductive portion extending toward the same side of the linear conductive portion, and the outwardly protruding conductive portion is perpendicular to the linear conductive portion to form an F-shaped groove structure.

[0012] In some embodiments, the top surface of the second metal layer has an epitaxial surface compared to the bottom surface thereof. The epitaxial surface is located at the bottom of the groove structure and covers a portion of the first metal layer.

[0013] In some embodiments, the metal stack structure further includes a barrier layer; the barrier layer covers the surface of the first metal layer and the junction between the first metal layer and the second metal layer to serve as an intermediate dielectric layer of the metal stack structure.

[0014] In a second aspect, the present application provides a method for preparing a metal stacked structure, including: preparing a first metal layer having a first structure; depositing a second metal layer on the first metal layer; coating photoresist on the second metal layer; developing and curing the photoresist in the target area; and etching to form a second metal layer having a second structure using a photolithography process, so that the first metal layer and the second metal layer form a planar metal stacked structure; wherein, when the first structure is a groove structure, the target area includes an area embedded in the groove structure and an area extending along the opening direction of the groove structure, and the second structure includes an extended structure embedded in the groove structure; when the first structure is an extended structure, the target area includes a groove-shaped area semi-surrounding the extended structure, and the second structure includes a groove structure embedded in the extended structure.

[0015] In some embodiments, preparing a first metal layer having a first structure includes: depositing a first metal layer on a substrate; coating a photoresist on the first metal layer; developing and curing the photoresist in a preset area; and etching to form a first metal layer having a first structure using a photolithography process; wherein, when the first structure is a groove structure, the preset area includes a linear area and at least two protruding areas, the linear area and the protruding area are connected to form a groove shape, the linear area is the groove bottom, the protruding area is the groove wall, the first metal layer includes a linear conductive portion located in the linear area and a protruding conductive portion located in the protruding area, and the target area includes a stripe The first metal layer includes a strip-shaped conductive portion located in the strip-shaped area and a mosaic area extending from the strip-shaped area, the mosaic area is mosaicked in the preset area, and the second metal layer includes a strip-shaped conductive portion located in the strip-shaped area and a mosaic conductive portion located in the mosaic area; when the first structure is an extended structure, the preset area includes a strip-shaped area, the first metal layer includes a strip-shaped conductive portion located in the strip-shaped area, the target area includes a linear area and at least two protruding areas, the linear area and the protruding area are connected and are in the shape of a groove that semi-surrounds the preset area, the linear area is the groove bottom, the protruding area is the groove wall, and the second metal layer includes a linear conductive portion located in the linear area and a protruding conductive portion located in the protruding area.

[0016] In some embodiments, the target area further includes: an area located at the bottom of the groove structure and covering a portion of the top surface of the first metal layer.

[0017] Through the metal stacking structure provided above, the embodiment of the present application designs one metal layer in the double metal layer to have a groove structure, and designs the other metal layer to have an extended structure. The extended structure extends into the groove structure and is interconnected with the adjacent metal layer in an interlocking form, thereby converting the three-dimensional metal stacking structure of the traditional stacking method into a planar metal stacking structure, eliminating the final product defects caused by the step height of the first metal layer in the existing double metal stacking process. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other objects, features and advantages of the exemplary embodiments of the present application will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present application are shown in an exemplary and non-limiting manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0019] Figure 1 A schematic cross-sectional view of a metal stack structure prepared by an existing metal stack process is shown;

[0020] Figure 2 An electron microscope image of a metal stack structure prepared by an existing metal stack process is shown;

[0021] Figure 3An exemplary top view of a metal stack structure according to some embodiments of the present application is shown;

[0022] Figure 4 Shown Figure 3 AA of the metal stack structure shown cross-section;

[0023] Figure 5 shows cross-sectional views of metal stacked structures according to other embodiments of the present application;

[0024] Figure 6 illustrative top views of metal stacked structures according to other embodiments of the present application;

[0025] Figure 7 Shown Figure 6 BB of the metal stack structure shown cross-sectional view;

[0026] Figure 8 shows cross-sectional views of metal stacked structures according to other embodiments of the present application;

[0027] Figure 9 An exemplary flow chart showing a method for preparing a metal stacked structure according to some embodiments of the present application;

[0028] Figure 10 An exemplary flow chart showing a method for preparing a first metal layer according to some embodiments of the present application is shown;

[0029] Figure 11 A schematic diagram showing a process for preparing a metal stacked structure according to some embodiments of the present application;

[0030] Figure 12 Schematic diagrams showing the preparation process of metal stacked structures according to other embodiments of the present application;

[0031] Description of reference numerals:

[0032] 11 - first metal layer; 12 - second metal layer; 101 - linear conductive portion; 102 - protruding conductive portion; 103 - strip-shaped conductive portion; 104 - embedded conductive portion; 13 - substrate; 14 - barrier layer. DETAILED DESCRIPTION

[0033] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0034] It should be understood that the terms "include" and "comprising" used in the description and claims of this application indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0035] It should also be understood that the terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit this application. As used in this specification and claims, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise. It should also be further understood that the term "and / or" as used in this specification and claims refers to any and all possible combinations of one or more of the associated listed items, including and including these combinations.

[0036] As used in this specification and claims, the term “if” can be interpreted as “when” or “upon” or “in response to determining” or “in response to detecting,” depending on the context. Similarly, the phrase “if it is determined” or “if [described condition or event] is detected” can be interpreted as meaning “upon determination” or “in response to determining” or “upon detection of [described condition or event]” or “in response to detecting [described condition or event],” depending on the context.

[0037] The specific implementation of the present application will be described in detail below with reference to the accompanying drawings.

[0038] Example application scenarios

[0039] A metal stack structure consists of two superconductors sandwiched between a very thin insulating layer or normal conductor. This thin layer serves as the barrier layer in the semiconductor structure. The metal stacking process plays a key role in the preparation of metal stack structures, involving the precise control and stacking of superconducting materials and barrier layers.

[0040] Some existing semiconductor processes involve a special chip manufacturing technology - a double-layer metal stacking process. This process is a process technology used to achieve interconnection between different metal layers. It aims to form the interconnection structure inside the chip through steps such as metal layer deposition, photolithography, and etching.

[0041] Figure 1 shows a schematic cross-sectional view of a metal stack structure prepared by an existing metal stack process, Figure 2 An electron microscope image of a metal stack structure prepared by an existing metal stack process is shown. Figure 1As shown, in the existing metal stacking process, after completing the first metal layer and etching the second metal layer, a step height difference will be generated at the location where the metal layers overlap. This will cause the focus depth of the light source used in the photolithography process to produce an error at the overlap, resulting in a defocus problem. The defocus phenomenon will further cause the critical dimension (CD) of the top line width of the formed metal stack structure to be too small. Although OPC technology can improve this problem, it cannot completely solve this defect. This defect will reduce the yield. In addition, the height difference after the first metal layer is formed in the existing technology will also introduce the problem of the second metal layer being disconnected or cracked on the side of the stack where it forms the metal stack structure with the first metal layer, which will also reduce the product yield and make the product unable to be mass-produced.

[0042] Exemplary application scenarios

[0043] In view of this, an embodiment of the present application provides a metal stacking process solution, which, through the mutual cooperation of a groove structure and an extended structure, interlocks and interconnects two metal layers on the same plane, thereby converting the traditional metal stacking structure into a planar metal stacking structure and eliminating the CD deviation caused by the step height.

[0044] Figure 3 An exemplary top view of a metal stacked structure according to some embodiments of the present application is shown. Figure 4 Shown Figure 3 AA of the metal stack structure shown Cross-section diagram, Figure 6 shows exemplary top views of metal stacked structures according to other embodiments of the present application, Figure 7 Shown Figure 6 BB of the metal stack structure shown Cross-sectional view.

[0045] See also Figure 3 or Figure 6 The metal stacked structure in the embodiment of the present application includes at least two metal layers, the bottom surfaces of the two metal layers are located on the same substrate, one metal layer has a groove structure, and the other metal layer has an extension structure, and the extension structure is embedded in the groove structure to form a planar metal stacked structure.

[0046] As an example, the material of the metal layer may be aluminum or other metal materials, and the substrate may be a silicon substrate.

[0047] For the convenience of description, we refer to the metal layer prepared first on the substrate 13 as the first metal layer 11 and the metal layer prepared later as the second metal layer 12 according to the preparation order. That is to say, the above-mentioned at least two metal layers include: the first metal layer 11 and the second metal layer 12.

[0048] like Figure 3 and Figure 4 As shown, the first metal layer 11 has a groove structure, and the first metal layer 11 is generally caliper-shaped. A portion of the second metal layer 12 extends from one side of the other portion and fits into the groove structure of the first metal layer 11, so that the first metal layer 11 and the second metal layer 12 are transformed from overlapping in the vertical direction to being connected in the horizontal direction. The resulting metal stack structure is converted from a traditional stacking junction to a planar junction. It should be noted that the vertical direction refers to the direction perpendicular to the substrate, and the horizontal direction refers to the direction parallel to the substrate.

[0049] The following further combines Figure 3 and Figure 4 The structure of the planar metal stacked structure is described. Figure 3 As shown, the first metal layer is a metal layer with a groove structure, and the groove structure can be formed by the linear conductive portion 101 and the protruding conductive portion 102 in the first metal layer 11. In other words, the first metal layer 11 includes: a linear conductive portion 101 and at least two protruding conductive portions 102, the linear conductive portion 101 refers to Figure 3 The conductive areas of the first metal layer 11 located on the leftmost and rightmost sides of the substrate 13, the two protruding conductive portions 102 refer to Figure 3 The conductive areas are respectively connected to the linear conductive part 101 and isolated from each other. In this embodiment, the protruding conductive part 102 is connected to the linear conductive part 101 to form a groove structure, the protruding conductive part 102 is the groove wall of the groove structure, and the linear conductive part 101 is the groove bottom of the groove structure.

[0050] It should be noted that due to Figure 3 and Figure 4 The diagram shows a partial structure of a semiconductor product. Therefore, in an actual product, the linear conductive portion 101 may not be located at the leftmost or rightmost side of the substrate 13. The description of the position and direction of the linear conductive portion 101 is only for the convenience of indication. Figure 3 The linear conductive portion 101 is provided so that those skilled in the art can understand the solution of the embodiment of the present application.

[0051] It needs to be further explained that Figure 3 and Figure 4 What is shown is a schematic diagram of a partial structure of a semiconductor product. In an actual product, the number of the protruding conductive parts 102 may not be limited to two, and the first metal layer 11 may have multiple protruding conductive parts 102 to form multiple groove structures.

[0052] Matching the structure of the first metal layer 11, the second metal layer 12 includes: a strip-shaped conductive portion 103 and an embedded conductive portion 104 extending from one side of the strip-shaped conductive portion 103. The embedded conductive portion 104 is embedded in the groove structure of the first metal layer 11 and connected to the linear conductive portion 101 in the first metal layer 11. Figure 3 As shown, the sidewalls of the embedded conductive portion 104 in the second metal layer 12 are respectively connected to the bottom and the wall of the groove structure.

[0053] In conventional metal stacking processes, the strip-shaped conductive portion 103 of the second metal layer 12 overlaps the linear conductive portion 101 of the first metal layer 11, resulting in a step height at the overlap. This, in turn, reduces the focus depth of the light during etching of the second metal layer 12. In this embodiment, a recessed structure is formed by the protruding conductive portion 102 connected to the linear conductive portion 101, and an extended structure is formed by the interlocking conductive portion 104 extending from one side of the strip-shaped conductive portion 103. This transforms the original stacked metal structure into a planar interlocking metal structure, eliminating the defocusing effect caused by the step height.

[0054] In a metal stack structure, the metal lines in two adjacent metal layers are designed to be perpendicular to each other for reasons such as reducing crosstalk, lowering electromagnetic interference, and reducing signal transmission loss. In order to optimize signal integrity, reduce crosstalk and electromagnetic interference, and control trace impedance, in some embodiments, such as Figure 3 As shown, the protruding conductive portion 102 in the first metal layer 11 extends along the length of the linear conductive portion 101. The protruding conductive portion 102 is perpendicular to the linear conductive portion 101, forming a caliper-shaped or U-shaped groove structure. In other words, in this groove structure, the groove wall is perpendicular to the groove bottom. Correspondingly, in the second metal layer 12, the interlocking conductive portion 104 is perpendicular to the strip-shaped conductive portion 103.

[0055] It should be noted that the above-mentioned vertical design between the conductive parts is intended to optimize the signal transmission quality in the metal stacked structure. In other embodiments, the protruding conductive part 102 may also form a certain angle with the linear conductive part 101. For example, the protruding conductive part 102 may form a Y-shaped or Y-shaped groove structure with the linear conductive part 101. Correspondingly, the end of the embedded conductive part 104 that is not connected to the strip-type conductive part 103 is triangular in shape to be embedded in the fork of the Y.

[0056] exist Figure 3 and Figure 4 In the illustrated embodiment, the first metal layer is a metal layer having a groove structure, and the second metal layer is a metal layer having an extended structure. In other embodiments, the second metal layer may have a groove structure, and the first metal layer may have an extended structure. This case is described below.

[0057] like Figure 6 and Figure 7 As shown, the second metal layer 12 includes a linear conductive portion 101 and at least two protruding conductive portions 102. The protruding conductive portions 102 connect to the linear conductive portion 101 to form a groove structure. The protruding conductive portions 102 serve as the groove walls, while the linear conductive portions 101 serve as the groove bottom. Meanwhile, the first metal layer 11 includes a strip-shaped conductive portion 103, which partially fits within the groove structure, completing the interconnection.

[0058] It should be noted that due to Figure 6 and Figure 7 What is shown is a schematic diagram of the partial structure of a semiconductor product, which only shows two planar metal stacked structures located on the left and right sides of the substrate respectively. In fact, the second metal layer 12 may include multiple protruding conductive parts 102 to form multiple groove structures, and the first metal layer 11 may also include multiple strip-type conductive parts 103 and be respectively embedded in the multiple groove structures.

[0059] In some embodiments, the line width of the portion of the strip-shaped conductive portion 103 embedded in the groove structure is the same as the line width of the other portions. In this case, the two portions can be directly regarded as a whole, both of which are the strip-shaped conductive portion 103. In other embodiments, the line width of the portion of the strip-shaped conductive portion 103 embedded in the groove structure may be different from the line width of the other portions. In this case, reference can also be made to Figure 3 , the interlocking portion is considered to be an interlocking conductive portion extending from the main body portion, and the main body portion is regarded as a strip-type conductive portion.

[0060] Similar to the previous embodiment, in order to improve the signal transmission quality in the metal stack structure, in the second metal layer 12, the protruding conductive portion 102 is a conductive portion extending toward the same side of the linear conductive portion 101, and the protruding conductive portion 102 is perpendicular to the linear conductive portion 101 to form an F-shaped groove structure, and the strip-type conductive portion 103 in the first metal layer 11 is embedded in the opening of the F-shaped groove structure.

[0061] It should be noted that, similar to the embodiment in which the first metal layer has a groove structure, in other embodiments, the protruding conductive portion 102 may also form a certain angle with the linear conductive portion 101 .

[0062] The above embodiments introduce an optimized metal stack structure, which can eliminate the defocusing problem in the development process when etching the second metal layer by converting the stacked metal stack structure into a planar metal stack structure.

[0063] Some embodiments of the present application further design the above-mentioned development process to reserve a buffer space for etching the second metal layer. Specifically, regardless of whether the second metal layer 12 has a groove structure or an extended structure, the top surface of the second metal layer 12 has an epitaxial surface compared to its bottom surface. This epitaxial surface is located at the bottom of the groove structure and covers a portion of the first metal layer.

[0064] like Figure 4 As shown, at the location where the first metal layer 11 and the second metal layer 12 meet, there is an epitaxial surface on the top of the embedded conductive portion 104 in the second metal layer 12, which covers at least part of the top surface of the linear conductive portion 101 of the first metal layer 11, and may also cover part of the top surface of the protruding conductive portion 102 of the first metal layer 11. Figure 7 As shown, at the junction of the first metal layer 11 and the second metal layer 12, an epitaxial surface is present on top of the linear conductive portion 101 and / or the protruding conductive portion 102 in the second metal layer 12, covering a portion of the top surface of the strip-shaped conductive portion 103 in the first metal layer 11. This epitaxial surface design can improve the area and electrical performance of the planar metal stack structure, better meeting application requirements.

[0065] Furthermore, a barrier layer 14 is required between the first metal layer 11 and the second metal layer 12. The barrier layer 14 acts as an intermediate dielectric layer of the metal stack structure to prevent leakage. In order to facilitate those skilled in the art to understand the structure of the barrier layer 14, Figure 5 shows a cross-sectional view of a metal stack structure according to some other embodiments of the present application, Figure 8 The cross-sectional views of the metal stack structures of other embodiments of the present application are shown as follows: Figure 5 and Figure 8 As shown, the metal stack structure further includes a barrier layer 14, which covers the surface of the first metal layer 11 and the junction between the first metal layer 11 and the second metal layer 12. As an example, the material of the barrier layer 14 can be aluminum oxide Al2O3.

[0066] It should be noted that Figure 5 The cutting direction in Figure 4 The cutting direction is consistent with Figure 8 The cutting direction in Figure 7 The cutting direction is the same as in Figure 5 and Figure 8 The metal stack structure shown includes a barrier layer 14, Figure 4 and Figure 7 The metal stack structure shown does not include the barrier layer 14. In other words, Figure 5 The metal stack structure shown in Figure 4 A barrier layer 14 is added to the metal stack structure shown. Figure 8The metal stack structure shown in Figure 7 A barrier layer 14 is added to the metal stack structure shown.

[0067] The above embodiments introduce a planar metal stacked structure. The following describes a method for preparing the planar metal stacked structure.

[0068] Figure 9 An exemplary flow chart of a method 900 for preparing a metal stacked structure according to some embodiments of the present application is shown. Figure 9 As shown, the method includes:

[0069] In step S901, a first metal layer having a first structure is prepared;

[0070] In step S902, a second metal layer is deposited on the first metal layer;

[0071] In step S903, a photoresist is coated on the second metal layer;

[0072] In step S904, the photoresist in the target area is developed and cured;

[0073] In step S905 , a second metal layer having a second structure is formed by etching using a photolithography process, so that the first metal layer and the second metal layer form a planar metal stacked structure.

[0074] According to the above Figure 3-Figure 8 It can be seen from the contents of the described embodiments that the first metal layer can be a metal layer with a groove structure or a metal layer with an extended structure.

[0075] When the first structure is a groove structure, the target area in step S904 includes the area embedded in the groove structure and the area extending along the opening direction of the groove structure, and the second structure in step S905 includes an extended structure embedded in the groove structure. As an example, the structure of the first metal layer having the first structure and the second metal layer having the second structure can be referred to in conjunction with the above. Figure 3 and Figure 4 Described embodiment.

[0076] When the first structure is an extended structure, the target area in step S904 includes a groove-shaped area that semi-encloses the extended structure, and the second structure in step S905 includes a groove structure embedded in the extended structure. As an example, the structure of the first metal layer having the first structure and the second metal layer having the second structure can be referred to in conjunction with the above. Figure 6 and Figure 7 Described embodiment.

[0077] Furthermore, in some embodiments, Figure 5 or Figure 8As shown, a barrier layer needs to be set between the first metal layer and the second metal layer to prevent leakage. Therefore, between step S901 and step S902, a step of depositing a barrier layer on the first metal layer can also be performed to cover the exposed surface of the first metal layer with the barrier layer. At this time, step S902 needs to deposit the second metal layer on the barrier layer and the exposed substrate.

[0078] In the above embodiment, the second metal layer with the second structure is prepared by photolithography, and the metal surface is precisely processed through steps such as illumination, development, and etching. The first metal layer with the first structure can also be prepared by photolithography.

[0079] Figure 10 An exemplary flow chart of a method 1000 for preparing a first metal layer in some embodiments of the present application is shown. It can be understood that the method for preparing the first metal layer is a specific implementation of the aforementioned step S901. Figure 9 The features described can be applied similarly here. Figure 10 As shown, the method includes:

[0080] In step S1001, a first metal layer is deposited on a substrate;

[0081] In step S1002, a photoresist is coated on the first metal layer;

[0082] In step S1003, the photoresist in the predetermined area is developed and cured;

[0083] In step S1004 , a first metal layer having a first structure is formed by etching using a photolithography process.

[0084] According to the above Figure 3-Figure 8 It can be seen from the contents of the described embodiments that the first metal layer can be a metal layer with a groove structure or a metal layer with an extended structure.

[0085] When the first structure is a groove structure, the preset area includes a linear area and at least two protruding areas, the linear area and the protruding area are connected and form a groove shape, the linear area is the groove bottom, the protruding area is the groove wall, and the first metal layer includes a linear conductive portion located in the linear area and a protruding conductive portion located in the protruding area. At this time, when the second metal layer is subjected to a photolithography process, the target area includes a strip area and an interlocking area extending from the strip area, the interlocking area is interlocked in the preset area, and the second metal layer includes a strip conductive portion located in the strip area and an interlocking conductive portion located in the interlocking area. As an example, the structure of the first metal layer having the first structure and the second metal layer having the second structure can be referred to in conjunction with the foregoing. Figure 3 and Figure 4 Described embodiment.

[0086] When the first structure is an extended structure, the preset area includes a strip area, and the first metal layer includes a strip conductive portion located in the strip area. At this time, when the second metal layer is subjected to a photolithography process, the target area includes a linear area and at least two protruding areas, the linear area and the protruding area are connected and are in the shape of a groove that semi-surrounds the preset area, the linear area is the groove bottom, the protruding area is the groove wall, and the second metal layer includes a linear conductive portion located in the linear area and a protruding conductive portion located in the protruding area. As an example, the structure of the first metal layer having the first structure and the second metal layer having the second structure can be referred to in conjunction with the above. Figure 6 and Figure 7 Described embodiment.

[0087] In order to facilitate understanding by those skilled in the art, Figure 11 and Figure 12 The preparation processes of the two metal stacked structures shown in the above embodiments are described in detail. Figure 11 A schematic diagram showing the preparation process of the metal stacked structure of some embodiments of the present application is shown. Figure 12 Schematic diagrams showing the preparation process of metal stacked structures according to other embodiments of the present application.

[0088] See first Figure 11 In step a, an oxide layer is deposited and grown on the silicon substrate to complete the preparation of the zero mark layer. In practical applications, the material of the oxide layer can be SiO2.

[0089] In step b, a first metal layer of a certain thickness, a dielectric anti-reflective coating (DARC), and a photoresist layer are deposited and grown on the oxide layer. The DARC is a material layer used in semiconductor manufacturing to reduce light reflection during the photolithography process. The material can be silicon oxynitride or other nitrogen-containing compounds. Its main function is to reduce light reflection during the photolithography process, thereby reducing a series of process problems caused by light reflection, such as standing wave effect, reduced exposure latitude, impaired critical dimension uniformity, and blurred pattern edges. The DARC can also prevent the acid catalyst in the photoresist from neutralizing with the nitrogen-containing amino groups in the DARC, thereby avoiding photoresist poisoning and reducing deformation of the photoresist pattern or photoresist residue. In step b, the photoresist layer in the preset area needs to be developed and cured, wherein the preset area includes a linear area and at least two protruding areas, the linear area and the protruding areas are connected to form a groove shape, the linear area is the groove bottom, and the protruding area is the groove wall. The developed photoresist layer is caliper-shaped or U-shaped from a top-down perspective.

[0090] In step c, etching of the first metal layer is performed and the etching stops on the oxide layer, the solidified photoresist is cleaned off and wet cleaning is performed, and the obtained first metal layer is caliper-shaped or U-shaped when viewed from above. Specifically, the first metal layer includes: a linear conductive portion and at least two protruding conductive portions, the protruding conductive portions are connected to the linear conductive portion to form a groove structure, the protruding conductive portions are the groove walls of the groove structure, and the linear conductive portion is the groove bottom of the groove structure. Furthermore, the protruding conductive portion is a conductive portion extending along the length direction of the linear conductive portion, and the protruding conductive portion is perpendicular to the linear conductive portion.

[0091] In step d, a barrier layer is formed on the first metal layer having the first structure. The barrier layer may be made of aluminum oxide. From a top view, the barrier layer also has a caliper shape or a U shape.

[0092] In step e, a second metal layer is deposited. In this step, the second metal layer covers the exposed oxide layer and the barrier layer.

[0093] In step f, a photoresist is applied to form a photoresist layer, and the photoresist in the target area is cured by development. Figure 11 As shown in the pink area of ​​step f, from a top view, the target area includes a strip area and a mosaic area extending from the strip area, and the mosaic area is mosaicked in the preset area, that is, the mosaic area is mosaicked in the groove structure of the first metal layer.

[0094] In step g, the second metal layer is etched, stopping at the oxide layer. The solidified photoresist is then removed and wet cleaned, resulting in a planar metal stack structure. In this metal stack structure, the second metal layer has a second structure, which is an extended structure. Specifically, the second metal layer having the second structure includes a strip-shaped conductive portion and an interlocking conductive portion extending from one side of the strip-shaped conductive portion. The interlocking conductive portion is interlocked within the groove structure of the first metal layer and connects to the linear conductive portion in the first metal layer.

[0095] See below Figure 12 ,right Figure 6 and Figure 7 The preparation process of the metal stacked structure is described. Figure 12 As shown, in step a, an oxide layer is deposited and grown on the silicon substrate to complete the preparation of the zero mark layer. In practical applications, the material of the oxide layer can be SiO2.

[0096] In step b, a first metal layer of a predetermined thickness, a dielectric anti-reflective coating (DARC), and a photoresist layer are deposited on the oxide layer. The DARC is a material used in semiconductor manufacturing to reduce light reflection during the photolithography process. It can be made of silicon oxynitride or other nitrogen-containing compounds. Its primary function is to reduce light reflection during the photolithography process, thereby alleviating a series of process issues caused by light reflection, such as standing wave effects, reduced exposure latitude, impaired critical dimension uniformity, and blurred pattern edges. The DARC also prevents the acid catalyst in the photoresist from neutralizing with the nitrogen-containing amino groups in the DARC, thereby avoiding photoresist poisoning and reducing photoresist pattern deformation or residual photoresist. In step b, the photoresist layer is developed and cured in predetermined areas. These predetermined areas include strip-shaped areas. The developed photoresist layer appears straight when viewed from above.

[0097] In step c, the first metal layer is etched and stopped on the oxide layer, the solidified photoresist is removed and wet cleaning is performed, and the resulting first metal layer is in a straight line shape when viewed from above. Specifically, the first metal layer includes a strip-shaped conductive portion.

[0098] In step d, a barrier layer is formed on the first metal layer having the first structure. The barrier layer may be made of aluminum oxide. From a top view, the barrier layer is also in a straight line shape.

[0099] In step f, a photoresist is applied to form a photoresist layer, and the photoresist in the target area is cured by development. Figure 12 As shown in the pink area of ​​step f, from a top-down perspective, the target area consists of a linear region and at least two protruding regions. The linear region and the protruding regions are connected and form a groove that semi-encloses the predetermined area. The linear region is the groove bottom, and the protruding regions are the groove walls. From a top-down perspective, the target area forms an F shape.

[0100] In step g, the second metal layer is etched, stopping at the oxide layer. The solidified photoresist is removed and wet cleaned to obtain a planar metal stack structure. In this metal stack structure, the second metal layer has a second structure, which is a groove structure. Specifically, the second metal layer having the second structure includes: a linear conductive portion and at least two protruding conductive portions, wherein the protruding conductive portions are connected to the linear conductive portion to form a groove structure, the protruding conductive portions serving as groove walls, and the linear conductive portions serving as groove bottoms.

[0101] Furthermore, in combination with the above Figure 11 or Figure 12In the described embodiments, the first and second metal layers can be aligned at their intersection to form a planar metal stack structure with consistent overall height. Alternatively, in step f, the target area of ​​the developed and cured material can be expanded outward to a certain extent so that it covers a portion of the first metal layer, thereby reserving a buffer space for etching the second metal layer. Specifically, in some embodiments, the target area can also include an area located at the bottom of the groove structure and covering a portion of the top surface of the first metal layer.

[0102] By adjusting the target area, the top surface of the second metal layer can have an epitaxial surface compared to its bottom surface, and the epitaxial surface is located at the bottom of the groove structure and covers part of the first metal layer. Figure 11 When preparing a metal stacked structure in the process shown, at the location where the first metal layer and the second metal layer meet, an epitaxial surface will exist on the top of the embedded conductive portion in the second metal layer, which at least covers part of the top surface of the linear conductive portion of the first metal layer, and may also cover part of the top surface of the protruding conductive portion of the first metal layer. Figure 12 When fabricating a metal stack structure using the illustrated process, at the junction of the first and second metal layers, an epitaxial surface forms on top of the linear conductive portions and / or protruding conductive portions of the second metal layer, partially covering the top surface of the strip-shaped conductive portions of the first metal layer. This epitaxial surface design optimizes the area and electrical performance of the planar metal stack structure, making it more suitable for application requirements.

[0103] By combining the previous Figures 9-12 The various methods described can improve the process difficulty of existing metal stack structures, make the process capability more stable, and shorten the time to mass production.

[0104] In addition, the thickness of the second metal layer prepared by the existing process needs to be at least 1.5 times thicker than the thickness of the first metal layer in order to improve the step height effect brought by the first metal layer. By preparing a planar metal stacked structure through the above method, this requirement can be reduced. The second metal layer only needs to be 1.2 times thicker than the first metal layer, thereby further optimizing the metal stacked structure.

[0105] Although multiple embodiments of the present application have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Those skilled in the art can conceive of many changes, modifications, and alternatives without departing from the thought and spirit of the present application. It should be understood that in the process of practicing the present application, various alternatives to the embodiments of the present application described herein can be adopted. The accompanying claims are intended to define the scope of protection of the present application and therefore cover equivalents or alternatives within the scope of these claims.

Claims

1. A metal laminate structure, characterized in that: include: at least two metal layers, wherein bottom surfaces of the two metal layers are located on the same substrate; One of the metal layers has a groove structure, and the other metal layer has an extension structure, wherein the extension structure is embedded in the groove structure to form a planar metal stacked structure; The at least two metal layers include: a first metal layer (11) and a second metal layer (12); the first metal layer (11) includes: a linear conductive portion (101) and at least two protruding conductive portions (102), the protruding conductive portions (102) are connected to the linear conductive portion (101) to form a groove structure, the protruding conductive portions (102) are groove walls of the groove structure, and the linear conductive portion (101) is the groove bottom of the groove structure; the second metal layer (12) includes: a strip-type conductive portion (103) and an embedded conductive portion (104) extending from one side of the strip-type conductive portion (103), wherein the embedded conductive portion (104) is embedded in the groove structure and connected to the linear conductive portion (101).

2. The metal laminate structure according to claim 1, wherein: In the first metal layer (11), the protruding conductive portion (102) is a conductive portion extending along the length direction of the linear conductive portion (101), and the protruding conductive portion (102) is perpendicular to the linear conductive portion (101) to form a caliper-shaped or U-shaped groove structure; In the second metal layer (12), the embedded conductive portion (104) is perpendicular to the strip-shaped conductive portion (103).

3. A metal laminate structure, characterized in that: include: at least two metal layers, wherein bottom surfaces of the two metal layers are located on the same substrate; One of the metal layers has a groove structure, and the other metal layer has an extension structure, wherein the extension structure is embedded in the groove structure to form a planar metal stacked structure; The at least two metal layers include: a first metal layer (11) and a second metal layer (12); the second metal layer (12) includes: a linear conductive portion (101) and at least two protruding conductive portions (102), the protruding conductive portions (102) are connected to the linear conductive portion (101) to form a groove structure, the protruding conductive portions (102) are the groove walls of the groove structure, and the linear conductive portions (101) are the groove bottoms of the groove structure; the first metal layer (11) includes: a strip-type conductive portion (103), and a portion of the strip-type conductive portion (103) is embedded in the groove structure.

4. The metal laminate structure according to claim 3, characterized in that: The outwardly protruding conductive portion (102) is a conductive portion extending toward the same side of the linear conductive portion (101), and the outwardly protruding conductive portion (102) is perpendicular to the linear conductive portion (101) to form an F-shaped groove structure.

5. The metal laminate structure according to any one of claims 1 to 4, characterized in that: The top surface of the second metal layer (12) has an epitaxial surface compared to its bottom surface, and the epitaxial surface is located at the bottom of the groove structure and covers part of the first metal layer (11).

6. The metal laminate structure according to any one of claims 1 to 4, characterized in that: Also includes: a barrier layer (14); The barrier layer (14) covers the surface of the first metal layer (11) and the junction between the first metal layer (11) and the second metal layer (12), so as to function as an intermediate dielectric layer of the metal stack structure.

7. A method for preparing a metal laminate structure, characterized in that: include: preparing a first metal layer having a first structure; depositing a second metal layer on the first metal layer; coating a photoresist on the second metal layer; developing and curing the photoresist in the target area; as well as Etching to form a second metal layer having a second structure using a photolithography process, so that the first metal layer and the second metal layer form a planar metal stacked structure; Wherein, when the first structure is a groove structure, the target area includes an area embedded in the groove structure and an area extending along the opening direction of the groove structure, and the second structure includes an extended structure embedded in the groove structure; When the first structure is an extended structure, the target area includes a groove-shaped area that semi-surrounds the extended structure, and the second structure includes a groove structure embedded in the extended structure, wherein the target area also includes: an area located at the bottom of the groove structure and covering part of the top surface of the first metal layer.

8. The method for preparing a metal laminate structure according to claim 7, wherein: The preparation of the first metal layer having the first structure comprises: depositing a first metal layer on the substrate; coating a photoresist over the first metal layer; Developing and curing the photoresist in a predetermined area; and Etching to form a first metal layer having a first structure using a photolithography process; Wherein, when the first structure is a groove structure, the preset area includes a linear area and at least two protruding areas, the linear area and the protruding areas are connected to form a groove shape, the linear area is the groove bottom, and the protruding areas are the groove walls, the first metal layer includes a linear conductive portion located in the linear area and a protruding conductive portion located in the protruding area, the target area includes a strip area and a mosaic area extending from the strip area, the mosaic area is mosaicked in the preset area, and the second metal layer includes a strip conductive portion located in the strip area and a mosaic conductive portion located in the mosaic area; When the first structure is an extended structure, the preset area includes a strip-shaped area, the first metal layer includes a strip-shaped conductive portion located in the strip-shaped area, the target area includes a linear area and at least two protruding areas, the linear area and the protruding area are connected and are in the shape of a groove that semi-surrounds the preset area, the linear area is the groove bottom, the protruding area is the groove wall, and the second metal layer includes a linear conductive portion located in the linear area and a protruding conductive portion located in the protruding area.

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