Composite metal grid and method of making same

Abstract

The application provides a composite metal grid and a preparation method thereof. The preparation method of the composite metal grid comprises the following steps: forming a core mold layer on a substrate; etching the core mold layer to form a plurality of first grooves; forming a first protective layer, the first protective layer covering the top surface of the core mold layer and the sidewall and bottom surface of the first grooves and defining a second groove in the first grooves; filling a first metal layer at the bottom of the second groove; trimming the sidewall of the second groove above the first metal layer to form a third groove, the width of at least a partial area of the third groove being greater than the width of the first metal layer; filling a second metal layer at the bottom of the third groove; filling a second protective layer in the third groove; and removing the core mold layer and the first protective layer above the core mold layer. Thus, the problem of non-perpendicular profile of the composite metal grid can be solved, and the light transmittance and light blocking rate of the grid and the amount of light received by the pixel unit are improved. The composite metal grid is prepared by using the above preparation method.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of composite metal grid, in particular to a composite metal grid and a preparation method thereof. BACKGROUND

[0002] Figures 1 to 4 A process schematic diagram of a preparation method of an existing composite metal grid. The steps of preparing a composite metal grid of a backside illumination image sensor (BSI) are as follows: as shown in FIG. 1, a first metal layer 11, a second metal layer 12, a silicon oxide layer 13, an amorphous carbon layer 14, a silicon oxynitride layer 15, an anti-reflective coating (BARC) 16 and a patterned photoresist layer 17 are sequentially formed on a substrate 10; as shown in FIG. 2, the anti-reflective coating 16, the silicon oxynitride layer 15, the amorphous carbon layer 14 and the silicon oxide layer 13 are sequentially etched until the second metal layer 12 is exposed, taking the patterned photoresist layer 17 as a mask; as shown in FIG. 3, the second metal layer 12 and the first metal layer 11 are etched through under the protection of the patterned silicon oxide layer 13a; as shown in FIG. 4, a protective oxide layer 18 is formed on the substrate 10, and the protective oxide layer 18 covers the top surface and the sidewall of the patterned silicon oxide layer 13a and covers the sidewall of the remaining second metal layer 12 and the first metal layer 11. Figure 1 Figure 2 Figure 3 Figure 4

[0003] In the step of sequentially etching the anti-reflective coating 16, the silicon oxynitride layer 15, the amorphous carbon layer 14 and the silicon oxide layer 13 until the second metal layer 12 is exposed, the etched amorphous carbon layer 14 is used as a mask for etching the silicon oxide layer 13, and the patterned silicon oxide layer 13a is used as a mask for etching the second metal layer 12 and the first metal layer 11. After the pattern transfer of multiple mask material layers, the sidewalls of the first metal layer 11 and the second metal layer 12 etched are not perpendicular, which causes the profile of the composite metal grid formed after the sidewalls of the first metal layer 11 and the second metal layer 12 are wrapped by the protective oxide layer 18 to be not perpendicular, resulting in poor light transmittance of the composite metal grid, failure of the image sensor in the terminal reliability test of temperature and humidity bias life test (THB), and easy bulging of the protective oxide layer in the terminal reliability test. SUMMARY

[0004] One of the purposes of the present application is to solve the problem of the non-perpendicular profile of the composite metal grid, improve the light transmittance and light blocking rate of the composite metal grid, reduce the crosstalk problem, solve the problem of easy failure of the image sensor in the terminal reliability test, and also improve the amount of light received by the pixel unit corresponding to the composite metal grid, provide light sensitivity, and improve the image quality of the image sensor.

[0005] ​​​​To achieve the above object, the present application provides a method for manufacturing a composite metal grid. The method comprises the following steps: providing a substrate, forming a core mold layer on the substrate, forming a patterned mask layer on the core mold layer, etching the core mold layer to form a plurality of first grooves under the mask of the patterned mask layer, the first grooves penetrating through the core mold layer, forming a first protective layer on the substrate, the first protective layer covering the top surface of the core mold layer and the sidewall and bottom surface of the first grooves, the first protective layer defining a second groove in each of the first grooves, filling a first metal layer in the bottom of the second groove, trimming the sidewall of the second groove above the first metal layer to form a third groove, the width of at least a part of the third groove being greater than the width of the first metal layer and less than the width of the first groove, filling a second metal layer in the bottom of the third groove, the material of the second metal layer being different from that of the first metal layer, filling a second protective layer in the third groove, the second protective layer filling the third groove, and removing the first protective layer above the core mold layer and the core mold layer to form the composite metal grid.

[0006] Optionally, the method for filling the first metal layer in the bottom of the second groove comprises the following steps: forming a first metal material layer on the substrate, the first metal material layer covering the first protective layer and filling the second groove, removing the first metal material layer above the first protective layer, and back-etching the first metal material layer to remove part of the first metal material layer in the second groove and retain the first metal material layer at the bottom of the second groove as the first metal layer.

[0007] Optionally, the method for filling the second metal layer in the bottom of the third groove comprises the following steps: forming a second metal material layer on the substrate, the second metal material layer covering the first protective layer and filling the third groove, removing the second metal material layer above the first protective layer, and back-etching the second metal material layer to remove part of the second metal material layer in the third groove and retain the second metal material layer at the bottom of the third groove as the second metal layer.

[0008] Optionally, in the step of forming the first protective layer on the substrate, the cross section of the second groove is rectangular.

[0009] Optionally, in the step of trimming the sidewall of the second groove above the first metal layer to form the third groove, the cross section of the third groove is inverted trapezoidal, the bottom width of the third groove is greater than or equal to the width of the first metal layer, and the top opening width of the third groove is greater than the bottom width of the third groove.

[0010] Optionally, after filling the second metal layer in the third groove, before filling the second protective layer in the third groove, the sidewall of the third groove above the second metal layer is trimmed to at least make the bottom of the sidewall of the third groove above the second metal layer outwardly expand; and a third metal layer is filled in the third groove, wherein the third metal layer covers the second metal layer.

[0011] Optionally, after the sidewall of the third groove above the second metal layer is trimmed, the cross section of the third groove above the second metal layer is rectangular.

[0012] Optionally, in the step of trimming the sidewall of the second groove above the first metal layer to form the third groove, the cross section of the third groove is rectangular.

[0013] Optionally, the first protective layer and the second protective layer are made of the same material.

[0014] Another aspect of the present application provides a composite metal grid. The composite metal grid comprises a first protective layer, a first metal layer, a second metal layer and a second protective layer on a substrate; the first protective layer defines a stepped groove, and the first metal layer, the second metal layer and the second protective layer are sequentially stacked from the bottom of the stepped groove and fill the stepped groove; in the stepped groove, at least the width of the second metal layer in a partial region is greater than the width of the first metal layer.

[0015] The composite metal grid and the preparation method thereof have the following unexpected technical effects: the verticality of the sidewall of the first recess in the core mold layer is good, so that the verticality of the sidewall of the first protective layer is good, the problem of the non-perpendicular profile of the composite metal grid is solved, the light transmittance of the composite metal grid is improved, the problem that the image sensor is prone to failure in the terminal reliability test is solved, the process steps of stacking multiple mask material layers on the metal layer are reduced, that is, the process is simplified, and the production time and cost are reduced; the composite metal grid comprises the first metal layer and the second metal layer which are stacked in the recess defined by the first protective layer and are different in material, the reflectivity of the metal layers of different materials is different, so that the unexpected technical effects are achieved: the light blocking rate of the composite metal grid can be improved, and the generation of interference effect can be avoided, and the problem of crosstalk is reduced; the first metal layer, the second metal layer and the second protective layer are sequentially filled in the recess of the first protective layer, and the first protective layer can tightly wrap the first metal layer, the second metal layer and the second protective layer inside, so that the unexpected technical effects are achieved: the probability of bulging of the first protective layer in the terminal reliability test is reduced; in addition, after the first metal layer is filled in the bottom of the second recess, the sidewall of the second recess above the first metal layer is trimmed to form a third recess, the width of at least a part of the third recess is greater than the width of the first metal layer and less than the width of the first recess, and then the second metal layer and the second protective layer are sequentially filled in the third recess, so that the width of at least a part of the second metal layer is greater than the width of the first metal layer, so that the unexpected technical effects are achieved: the convergence of incident light can be increased, the light quantity received by the corresponding pixel unit of the composite metal grid is increased, the light sensitivity is provided, the image quality of the image sensor is improved, and the key size of the composite metal grid is adjusted. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A schematic view of a preparation method of an existing composite metal grid in which multiple material layers are deposited on a metal layer.

[0017] Figure 2 A schematic view of a preparation method of an existing composite metal grid in which a silicon oxide layer is patterned.

[0018] Figure 3 A schematic view of a preparation method of an existing composite metal grid in which a metal layer is patterned.

[0019] Figure 4 A schematic view of a preparation method of an existing composite metal grid in which an oxide layer is covered on the sidewall of the metal layer.

[0020] Figure 5A flow chart of a method for manufacturing a composite metal grid according to an embodiment of the present application.

[0021] Figure 6 A schematic view of forming a patterned mask layer on a mandrel layer according to an embodiment of the present application.

[0022] Figure 7 A schematic view of forming a first protective layer on a mandrel layer according to an embodiment of the present application.

[0023] Figure 8 A schematic view of forming a first metal material layer on a first protective layer according to an embodiment of the present application.

[0024] Figure 9 A schematic view of performing a planarization process on a first metal material layer according to an embodiment of the present application.

[0025] Figure 10 A schematic view of performing a back etching process on a first metal layer to form a first metal layer according to an embodiment of the present application.

[0026] Figure 11 A schematic view of performing a trimming process on a second recess to form a third recess according to an embodiment of the present application.

[0027] Figure 12 A schematic view of forming a second metal material layer on a first protective layer according to an embodiment of the present application.

[0028] Figure 13 A schematic view of performing a planarization process on a second metal material layer according to an embodiment of the present application.

[0029] Figure 14 A schematic view of performing a back etching process on a second metal material layer to form a second metal layer according to an embodiment of the present application.

[0030] Figure 15 A schematic view of forming a second protective layer on a first protective layer according to an embodiment of the present application.

[0031] Figure 16 A schematic view of grinding a first protective layer and a second protective layer according to an embodiment of the present application.

[0032] Figure 17 A schematic view of a composite metal grid according to an embodiment of the present application.

[0033] Figure 18 A schematic view of performing a trimming process on a second recess to form a third recess according to another embodiment of the present application.

[0034] Figure 19 A schematic view of forming a second metal material layer on a first protective layer according to another embodiment of the present application.

[0035] Figure 20 This is a schematic diagram of the second metal material layer after planarization treatment in another embodiment of the present invention.

[0036] Figure 21 This is a schematic diagram of forming a second metal layer by etching back the second metal material layer in another embodiment of the present invention.

[0037] Figure 22 This is a schematic diagram of forming a second protective layer on a first protective layer in another embodiment of the present invention.

[0038] Figure 23 This is a schematic diagram of the first and second protective layers after grinding in another embodiment of the present invention.

[0039] Figure 24 This is a schematic diagram after removing the core mold layer in another embodiment of the present invention.

[0040] Figure 25 This is a schematic diagram of filling a third metal layer in a third groove according to an embodiment of the present invention.

[0041] Explanation of reference numerals in the attached figures:

[0042] ( Figures 1 to 4 10-Substrate; 11-First metal layer; 12-Second metal layer; 13-Silicon oxide layer; 14-Amorphous carbon layer; 15-Silicon oxynitride layer; 16-Anti-reflective coating; 17-Patterned photoresist layer; 18-Protective oxide layer;

[0043] ( Figures 6 to 23 100 - Substrate; 101 - Pixel unit; 102 - Deep trench; 103 - First oxide layer; 104 - Barrier layer; 105 - Second oxide layer; 201 - Core mold layer; 201a - First groove; 202 - Patterned mask layer; 203 - First protective layer; 204 - Second groove; 205a - First metal material layer; 205 - First metal layer; 206 - Third groove; 207a - Second metal material layer; 207 - Second metal layer; 208 - Second protective layer; 209 - Third metal layer. Detailed Implementation

[0044] The composite metal grid and its preparation method proposed in this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this invention will become clearer from the following description. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of this invention.

[0045] In the description of the present application, it needs to be understood that the terms "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the elements referred to must have a particular orientation or be constructed in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second", "third" can explicitly or implicitly include one or more features. In the description of the present application, the meaning of "multiple" is two or more, at least one refers to one, two or more, unless otherwise explicitly specified.

[0046] Figure 5 The flow chart of the preparation method of the composite metal grid provided by an embodiment of the present application is shown in FIG. 1. Figure 5 As shown in FIG. 1, the preparation method of the composite metal grid comprises the following steps:

[0047] Step S1, providing a substrate, forming a core mold layer on the substrate;

[0048] Step S2, forming a patterned mask layer on the core mold layer, etching the core mold layer to form a plurality of first grooves under the masking of the patterned mask layer, the first grooves penetrating through the core mold layer;

[0049] Step S3, forming a first protective layer on the substrate, the first protective layer covering the top surface of the core mold layer and the sidewall and bottom surface of the first grooves, the first protective layer defining a second groove in each first groove;

[0050] Step S4, filling the first metal layer at the bottom of the second groove;

[0051] Step S5, trimming the sidewall of the second groove above the first metal layer to form a third groove, at least the width of the third groove in a partial region is greater than the width of the first metal layer and less than the width of the first groove;

[0052] Step S6, filling the second metal layer at the bottom of the third groove, the material of the second metal layer being different from that of the first metal layer;

[0053] Step S7, filling the second protective layer in the third groove, the second protective layer filling the third groove;

[0054] Step S8, removing the first protective layer above the core mold layer and removing the core mold layer, to form the composite metal grid.

[0055] It should be understood that, although Figure 5 The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 5 At least some of the steps in the process may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but may be executed at different times. The execution order of these steps or stages is not necessarily sequential, but may be executed in turn or alternately with other steps or at least some of the steps or stages in other steps.

[0056] Figures 6 to 17 This is a step-by-step schematic diagram of a method for preparing a composite metal grid according to an embodiment of the present invention. The following is in conjunction with... Figure 5 , Figures 6 to 17 The method for preparing the composite metal grid in this embodiment will be described.

[0057] refer to Figure 6 As shown, step S1 is performed, a substrate 100 is provided, and a core mold layer 201 is formed on the substrate 100.

[0058] In this embodiment, the substrate 100 can be a silicon substrate, a germanium substrate, a silicon-germanium substrate, silicon-on-insulator (SOI) or germanium-on-insulator (GOI), etc., and certain doped particles can be injected into the substrate to change the electrical parameters according to design requirements.

[0059] like Figure 6 As shown, a plurality of pixel units 101 have been formed in the substrate 100, and the plurality of pixel units 101 are separated by deep trenches 102. A first oxide layer 103 is formed on the surface of the substrate 100, and the deep trenches 102 penetrate the first oxide layer 103. A barrier layer 104 is formed on the first oxide layer 103, covering the top surface of the first oxide layer 103 and the inner surface of the deep trenches 102. A second oxide layer 105 is formed on the barrier layer 104, covering the barrier layer 104 and filling the deep trenches 102. The barrier layer 104 and the second oxide layer 105 in the deep trenches 102 constitute an isolation structure between the pixel units 101. Since the deep trenches 102 are relatively deep, there may be voids in the second oxide layer 105 filling the deep trenches 102.

[0060] Exemplarily, the material of the first oxide layer 103 and the second oxide layer 105 can be the same, for example, both are silicon oxide layers, and the material of the barrier layer 104 can be different from the second oxide layer 105, for example, the barrier layer 104 is a silicon nitride layer, but is not limited thereto.

[0061] In this embodiment, the core mold layer 201 is actually formed on the second oxide layer 105, but is not limited thereto. The core mold layer 201 can be an amorphous carbon layer, but is not limited thereto.

[0062] Referring to Figure 6 and Figure 7 As shown in FIG. 2, step S2 is performed to form a patterned mask layer 202 on the core mold layer 201, and under the mask of the patterned mask layer 202, the core mold layer 201 is etched to form a plurality of first grooves 201a penetrating through the core mold layer 201. The patterned mask layer 202 defines the formation position of the composite metal grid.

[0063] Exemplarily, the patterned mask layer 202 is a photoresist layer. The method for forming the patterned mask layer 202 on the core mold layer 201 can include: coating photoresist on the core mold layer 201 to form a photoresist layer, and exposing and developing the photoresist layer to form the patterned mask layer 202.

[0064] Exemplarily, a dry etching process is used to etch the core mold layer 201 to form the first grooves 201a, but is not limited thereto.

[0065] Referring to Figure 7 As shown in FIG. 3, the first grooves 201a are formed above the deep trenches 102, and the subsequently formed composite metal grid is located above the deep trenches 102, so that the incident light can pass through the composite metal grid into the pixel unit 101.

[0066] Continuing to refer to Figure 7 As shown in FIG. 4, step S3 is performed to form a first protective layer 203 on the substrate 100, the first protective layer 203 covers the top surface of the core mold layer 201 and covers the sidewall and bottom surface of the first grooves 201a, and the first protective layer 203 defines a second groove 204 in each first groove 201a.

[0067] It should be noted that the thickness of the first protective layer 203 can be determined according to actual conditions, for example, the thickness of the first protective layer 203 can be selected according to the width of the metal layer in the composite metal grid.

[0068] In this embodiment, the first protective layer 203 can be formed by a sub-atmospheric chemical vapor deposition (SACVD) process. The SACVD process can make the deposited film layer have good conformality, so that the shape consistency of the second recess 204 and the first recess 201a can be improved. In other embodiments, the first protective layer 203 can also be formed by a plasma enhanced chemical vapor deposition (PECVD) process or an atmospheric pressure chemical vapor deposition (APCVD) process, etc.

[0069] For example, the material of the first protective layer 203 includes, but is not limited to, silicon oxide.

[0070] Referring to Figure 10 As shown, step S4 is performed to fill the first metal layer 205 at the bottom of the second recess 204.

[0071] For example, the method of filling the first metal layer 205 at the bottom of the second recess 204 can include: as shown in Figure 8 As shown, a first metal material layer 205a is formed on the substrate 100, the first metal material layer 205a covers the first protective layer 203 and fills the second recess 204; as shown in Figure 9 As shown, the first metal material layer 205a is subjected to a planarization treatment, such as a chemical mechanical polishing process, to remove the first metal material layer 205a above the first protective layer 203, wherein the first protective layer 203 can be used as a polishing stop layer of the first metal material layer 205a; as shown in Figure 10 As shown, the first metal material layer 205a is subjected to a back etching to remove part of the first metal material layer 205a in the second recess 204 and retain the first metal material layer 205a at the bottom of the second recess 204 as the first metal layer 205.

[0072] For example, the material of the first metal layer 205 includes, but is not limited to, tungsten. For example, the thickness of the first metal layer 205 can be less than or equal to 1 / 2 of the depth of the second recess 204, but is not limited thereto.

[0073] As shown in Figure 11 As shown, step S5 is performed to trim the sidewall of the second recess above the first metal layer 205 to form a third recess 206, at least part of the width of the third recess 206 is greater than the width of the first metal layer 205 and less than the width of the first recess 201a, wherein the trimming of the sidewall of the second recess above the first metal layer 205 needs to ensure that the first protective layer 203 is not etched through to expose the core mold layer 201, and the width of the first metal layer 205 is equal to the width of the untrimmed part of the second recess 204.

[0074] As shown in Figure 10As shown in the figure, the cross section of the second groove 204 can be rectangular before the side wall of the second groove 204 is trimmed, but is not limited to this; correspondingly, the cross section of the first metal layer 205 filled at the bottom of the second groove 204 is also rectangular. In the embodiment, as shown in the figure, the cross section of the third groove 206 formed by trimming the side wall of the second groove above the first metal layer 205 can be an inverted trapezoid, the bottom width of the third groove 206 is greater than or equal to the width of the first metal layer 205, and the top opening width of the third groove 206 is greater than the bottom width of the third groove 206. Figure 11

[0075] For example, a dry etching process can be used to trim the side wall of the second groove above the first metal layer 205, but is not limited to this.

[0076] As shown in the figure, step S6 is performed, the second metal layer 207 is filled at the bottom of the third groove 206, the material of the second metal layer 207 is different from that of the first metal layer 205, the second metal layer 207 is filled above the first metal layer 205 and covers the first metal layer 205. Figure 14

[0077] For example, the method of filling the second metal layer 207 at the bottom of the third groove 206 can include: as shown in the figure, forming a second metal material layer 207a on the substrate 100, the second metal material layer 207a covers the first protective layer 203 and fills the third groove 206; as shown in the figure, performing a planarization treatment on the second metal material layer 207a, such as using a chemical mechanical polishing process to remove the second metal material layer 207a above the first protective layer 203, the first protective layer 203 acts as a polishing stop layer of the second metal material layer 207a; as shown in the figure, performing a back etching on the second metal material layer 207a, removing part of the second metal material layer 207a in the third groove 206 and retaining the second metal material layer 207a at the bottom of the third groove 206 as the second metal layer 207. Figure 12 Figure 13 Figure 14

[0078] For example, the material of the second metal layer 207 includes but is not limited to aluminum.

[0079] It should be noted that in the embodiment, when the cross section of the third groove 206 is an inverted trapezoid, the cross section of the second metal layer 207 filled at the bottom of the third groove 206 is also an inverted trapezoid, and the bottom width of the second metal layer 207 is greater than or equal to the width of the first metal layer 205, and the top width of the second metal layer 207 is greater than the bottom width of the second metal layer 207. Since the reflectivity of the trapezoidal metal layer is high, when the cross section of the second metal layer 207 is an inverted trapezoid, the amount of light received by the pixel unit below the composite metal grid can be significantly increased, the light sensitivity is improved, and the performance of the back-illuminated pattern sensor is improved.​​​​​

[0080] In order to ensure that the second protective layer formed subsequently can cover and protect the second metal layer 207 after grinding, in this embodiment, the top surface of the second metal layer 207 needs to be lower than the top surface of the core mold layer 201.

[0081] like Figure 15 As shown, in step S7, the second protective layer 208 is filled into the third groove 206, and the second protective layer 208 completely fills the third groove 206. Specifically, as shown... Figure 15 As shown, a second protective layer 208 is formed on the first protective layer 203, and the second protective layer 208 covers the first protective layer 203 and fills the third groove 206;

[0082] For example, the second protective layer 208 is made of the same material as the first protective layer 203, but is not limited thereto. The material of the second protective layer 208 includes, but is not limited to, silicon oxide.

[0083] refer to Figure 17 As shown, step S8 is performed to remove the first protective layer 203 above the core mold layer 201 and remove the core mold layer 201 to form a composite metal grid.

[0084] Specifically, such as Figure 16 As shown, the second protective layer 208 and the first protective layer 203 above the core mold layer 201 are removed using processes such as chemical mechanical polishing, while retaining the second protective layer 208 within the first groove 201a; Figure 17 As shown, core mold layer 201 is removed.

[0085] Figures 18 to 24 This is a step-by-step schematic diagram of a method for preparing a composite metal grid according to another embodiment of the present invention.

[0086] In another embodiment of this application, after the first metal layer 205 is filled into the second trench 204, as... Figure 18 As shown, the sidewall of the second groove above the first metal layer 205 is trimmed to form a third groove 206. The cross-sectional shape of the third groove 206 is rectangular, and the width of the third groove 206 is greater than the width of the first metal layer 205; as shown Figure 19 As shown, a second metallic material layer 207a is formed on the substrate 100, the second metallic material layer 207a covering the first protective layer 203 and filling the third groove 206; as Figure 20 As shown, the second metallic material layer 207a above the first protective layer 203 is removed; as Figure 21As shown, the second metal material layer 207a is etched back to remove a portion of the second metal material layer 207a within the third groove 206, while retaining the second metal material layer at the bottom of the third groove 206 as the second metal layer 207. The cross-sectional shape of the second metal layer 207 is consistent with the cross-sectional shape at the bottom of the third groove 206, i.e., both are rectangular, and the width of the second metal layer 207 is greater than the width of the first metal layer 205. Figure 22 As shown, a second protective layer 208 is formed on the first protective layer 203, the second protective layer 208 covering the first protective layer 203 and filling the third groove 206; as Figure 23 As shown, the second protective layer 208 and the first protective layer 203 above the core mold layer 201 are removed using processes such as chemical mechanical polishing, while the second protective layer 208 within the first groove 201a is retained. The core mold layer 201 serves as a polishing stop layer for the second protective layer 208 and the first protective layer 203. Figure 24 As shown, the core mold layer 201 is removed to form a composite metal grid.

[0087] It should be noted that, in this application, the cross-sectional shape of the third groove 206 includes, but is not limited to, an inverted trapezoid and a rectangle, and can be designed according to actual conditions.

[0088] Figure 25 This is a schematic diagram illustrating the filling of a third metal layer within a third groove according to one embodiment of the present invention. In another embodiment of this application, refer to... Figure 25 As shown, after the second metal layer 207 is filled at the bottom of the third groove 206 and before the second protective layer 208 is filled in the third groove 206, the sidewall of the third groove above the second metal layer 207 can be trimmed, at least so that the bottom of the sidewall of the third groove above the second metal layer 207 expands outward toward the core mold layer 201, and then the third metal layer 209 is filled in the third groove 206, covering the second metal layer 207.

[0089] Among them, reference Figure 25 As shown, after trimming the sidewalls of the third groove 206 above the second metal layer 207, the cross-section of the third groove above the second metal layer 207 can be rectangular; correspondingly, the cross-section of the third metal layer 209 filling the third groove above the second metal layer 207 can also be rectangular. The width of the third metal layer 209 can be greater than the top surface width of the second metal layer 207. The top surface of the third metal layer 209 needs to be lower than the top surface of the core mold layer 201 to reserve space for the subsequent filling of the second protective layer 208. The material of the third metal layer 209 can be different from the material of the second metal layer 207.

[0090] In another embodiment of the present application, after the second metal layer 207 is filled in the third recess 206, before the second protective layer 208 is filled in the third recess 206, the third metal layer 209 can be directly filled in the third recess 206. At this time, since the sidewall of the third recess 206 is not trimmed, the third recess above the second metal layer 207 still retains the original shape, so that the cross-sectional shape of the third metal layer 209 is the same as that of the second metal layer 207, and the width of at least part of the third metal layer 209 is greater than the top width of the second metal layer 207. For example, when the second recess above the first metal layer 205 is trimmed to form a third recess with an inverted trapezoidal cross section, the cross sections of the third metal layer 209 and the second metal layer 207 are both inverted trapezoidal. When the second recess above the first metal layer 205 is trimmed to form a third recess with a rectangular cross section, the cross sections of the third metal layer 209 and the second metal layer 207 are both rectangular.

[0091] It should be noted that the third metal layer 209 with a larger filling width is added on the first metal layer 205 and the second metal layer 207, which helps to improve the light blocking rate of the composite metal grid, and further increases the convergence of incident light, increases the amount of light received by the corresponding pixel unit of the composite metal grid, and provides light sensitivity.

[0092] The present application provides a composite metal grid, which is made by the preparation method of the composite metal grid described above. The composite metal grid can be applied to a back-illuminated image sensor.

[0093] Reference Figure 17 and Figure 24 As shown in FIGS. 1-4, the composite metal grid includes a first protective layer 203, a first metal layer 205, a second metal layer 207, and a second protective layer 208 on a substrate 100; the first protective layer 203 defines a stepped recess, and the first metal layer 205, the second metal layer 207, and the second protective layer 208 are sequentially stacked upward from the bottom of the stepped recess and fill the recess; the materials of the first metal layer 205 and the second metal layer 207 are different, and in the stepped recess, the width of at least part of the second metal layer 207 is greater than that of the first metal layer 205. In the present application, the "width" refers to the horizontal dimension in the drawing.

[0094] The bottom surface and the sidewall of the stepped recess are both defined by the first protective layer 203, the first protective layer 203 wraps the bottom surface and the sidewall of the first metal layer, and also wraps the sidewall of the second metal layer 207 and the second protective layer 208. The stepped recess in the first protective layer 203 includes a third recess 206 and a non-trimmed part of a second recess below the third recess 206.

[0095] The cross section of the first metal layer 205 can be rectangular, and the cross section of the second metal layer 207 can be inverted trapezoidal or rectangular, but is not limited thereto. The bottom surface of the second metal layer 207 is close to the first metal layer 205, and the top surface of the second metal layer 207 is away from the first metal layer 205; for example, when the cross section of the first metal layer 205 is rectangular and the cross section of the second metal layer 207 is inverted trapezoidal, the width of the bottom surface of the second metal layer 207 is greater than or equal to the width of the first metal layer 205, and the width of the top surface of the second metal layer 207 is greater than the width of the bottom surface of the second metal layer 207; when the cross section of the first metal layer 205 is rectangular and the cross section of the second metal layer 207 is rectangular, the width of the second metal layer 207 is greater than the width of the first metal layer 205.

[0096] In the present application, the composite metal grid is in a mesh shape, and the first protective layer 203 is also in a mesh shape on the top surface of the substrate 100. The outer side wall of the first protective layer 203 away from the first metal layer serves as the mesh side wall of the composite metal grid, and the first protective layer 203 and the second protective layer 208 jointly enclose the first metal layer 205 and the second metal layer 207.

[0097] In some embodiments of the present application, as shown in Figure 25 The composite metal grid can further include a third metal layer 209, which is located between the second metal layer 207 and the second isolation layer 208. The width of at least a partial region of the third metal layer 209 is greater than the width of the top surface of the second metal layer 207. For example, the cross section of the third metal layer 209 can be rectangular or inverted trapezoidal.

[0098] In the present embodiment, the thickness (i.e. the size in the vertical direction) of the first metal layer 205, the second metal layer 207, and the third metal layer 209 can be determined according to the performance requirements of the composite metal grid. Figure 17 Figure 24 The material of the third metal layer 209 can be different from the material of the second metal layer 207.

[0099] For example, the material of the first protective layer 203 and the second protective layer 208 can be the same, such as both being a silicon oxide layer, but is not limited thereto.

[0100] ​The composite metal grid and the preparation method thereof have the unexpected technical effects that the side wall perpendicularity of the first recess 201a is good, the side wall perpendicularity of the first protective layer 203 is good, the profile of the composite metal grid is perpendicular, the light transmittance of the composite metal grid is improved, the problem that the image sensor is prone to failure in terminal reliability testing is solved, the process steps of stacking a plurality of mask material layers on the metal layer are reduced, that is, the process is simplified, the production time and the production cost are reduced, the light blocking rate of the composite metal grid is improved, the generation of interference effects is avoided, and the crosstalk problem is reduced, the first metal layer 205, the second metal layer 207 and the second protective layer 208 are sequentially filled in the recess defined by the first protective layer 203, the first protective layer 203 can tightly wrap the first metal layer 205, the second metal layer 207 and the second protective layer 208 inside, the unexpected technical effect is that the probability of the first protective layer bulging in terminal reliability testing is reduced, the width of at least a part of the third recess 206 is greater than the width of the first metal layer 205 and less than the width of the first recess 201a, the second metal layer 207 and the second protective layer 208 are sequentially filled in the third recess 206, the width of at least a part of the second metal layer 207 is greater than the width of the first metal layer 205, the unexpected technical effect is that the convergence of incident light is increased, the light quantity received by the corresponding pixel unit of the composite metal grid is increased, the light sensitivity is provided, the image quality of the image sensor is improved, and the key size of the composite metal grid is adjusted.

[0101] The above description is only a description of the preferred embodiments of the present application, and does not limit the scope of the present application in any way. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present application without departing from the spirit and scope of the present application, therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application, which does not deviate from the technical solutions of the present application, belongs to the protection scope of the present application.

Claims

1. A method for preparing a composite metal grating, characterized in that, include: Provide a substrate, on which a core mold layer is formed; A patterned mask layer is formed on the core mold layer. Under the cover of the patterned mask layer, the core mold layer is etched to form a plurality of first grooves, the first grooves penetrating the core mold layer. A first protective layer is formed on the substrate, the first protective layer covering the top surface of the core mold layer and the sidewalls and bottom surface of the first groove, the first protective layer defining a second groove in each of the first grooves; A first metal layer is filled at the bottom of the second groove; The sidewall of the second groove above the first metal layer is trimmed to form a third groove, and at least a portion of the width of the third groove is greater than the width of the first metal layer and less than the width of the first groove. A second metal layer is filled at the bottom of the third groove, and the second metal layer is made of a different material than the first metal layer; A second protective layer is filled into the third groove, and the second protective layer completely fills the third groove; as well as The first protective layer above the core mold layer is removed, and the core mold layer is also removed to form the composite metal grid.

2. The method for preparing the composite metal grid as described in claim 1, characterized in that, The method of filling the bottom of the second groove with a first metal layer includes: forming a first metal material layer on the substrate, the first metal material layer covering the first protective layer and filling the second groove; removing the first metal material layer above the first protective layer; and etching back the first metal material layer to remove a portion of the first metal material layer in the second groove and retaining the first metal material layer at the bottom of the second groove as the first metal layer.

3. The method for preparing the composite metal grid as described in claim 1, characterized in that, The method of filling the bottom of the third groove with a second metal layer includes: forming a second metal material layer on the substrate, the second metal material layer covering the first protective layer and filling the third groove; removing the second metal material layer above the first protective layer; and etching back the second metal material layer to remove a portion of the second metal material layer in the third groove and retaining the second metal material layer at the bottom of the third groove as the second metal layer.

4. The method for preparing the composite metal grid as described in claim 1, characterized in that, In the step of forming the first protective layer on the substrate, the cross-section of the second groove is rectangular.

5. The method for preparing the composite metal grid as described in claim 4, characterized in that, In the step of trimming the sidewall of the second groove above the first metal layer to form the third groove, the cross-section of the third groove is an inverted trapezoid, the bottom width of the third groove is greater than or equal to the width of the first metal layer, and the top opening width of the third groove is greater than the bottom width of the third groove.

6. The method for preparing the composite metal grid as described in claim 5, characterized in that, After the second metal layer is filled at the bottom of the third groove and before the second protective layer is filled in the third groove, the sidewall of the third groove above the second metal layer is trimmed so that at least the bottom of the sidewall of the third groove above the second metal layer is expanded outward; the third metal layer is filled in the third groove, and the third metal layer covers the second metal layer.

7. The method for preparing the composite metal grid as described in claim 6, characterized in that, After the sidewall of the third groove above the second metal layer is trimmed, the cross-section of the third groove above the second metal layer is rectangular.

8. The method for preparing the composite metal grid as described in claim 4, characterized in that, In the step of trimming the sidewall of the second groove above the first metal layer to form the third groove, the cross-section of the third groove is rectangular.

9. The method for preparing the composite metal grid as described in claim 1, characterized in that, The first protective layer and the second protective layer are made of the same material.

10. A composite metal grid, characterized in that, The composite metal grid is manufactured using the method for preparing a composite metal grid as described in any one of claims 1 to 9. The composite metal grid includes a first protective layer, a first metal layer, a second metal layer, and a second protective layer located on a substrate. The first protective layer defines a stepped groove. The first metal layer, the second metal layer, and the second protective layer are stacked sequentially from the bottom of the stepped groove and fill the stepped groove. In the stepped groove, at least a portion of the width of the second metal layer is greater than the width of the first metal layer.

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