Wafer wet etching method and wafer produced thereby

Abstract

The present application relates to the technical field of semiconductor integrated circuit manufacturing, and in particular to a wafer wet etching method and a wafer produced thereby. The wafer comprises a substrate and a composite metal layer; the composite metal layer covers a preset surface of the substrate; the composite metal layer comprises a first metal layer and a second metal layer; and the first metal layer covers the surface of the second metal layer. By means of the wet etching process provided by the present invention, different masks are provided for different metal layers and the widths of transparent areas of the masks are controlled, so that the problem of dimensional distortion of a bottom metal layer when a conventional process is used for wet etching of a composite metal film is effectively solved, thereby improving the dimensional precision of the bottom layer during wet etching of the composite metal film, and also improving the yield rate and reliability of wafer production.

Description

Wafer wet etching method and wafer thereof TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor integrated circuit manufacturing, and particularly relates to a wafer wet etching method and wafer thereof. BACKGROUND

[0002] With the design of electronic equipment becoming more and more complex, the requirements of electronic equipment on the integration, miniaturization and performance of semiconductor components are higher and higher, therefore, a large number of semiconductor components are made by using MEMS technology, micro-electro-mechanical system (MEMS) as an advanced manufacturing technology platform, microcircuit and micromechanical are integrated on a chip according to functional requirements, the size is usually controlled in millimeter or micrometer level, and has involved force, electricity, light, magnetism, sound and other branches of physics in microscale in many disciplines such as microelectronics, materials, mechanics, chemistry, machinery and the like, wherein, etching is an indispensable process in the manufacturing process of semiconductor components based on MEMS technology, and is one of core steps for realizing microstructure and circuit patterning of semiconductor devices, after the step of photoetching, the photoresist layer on the wafer surface forms an image of circuit design, the etching process is to preserve the material in the place protected by photoresist through chemical or physical means, and to selectively remove the thin film material such as silicon, metal, dielectric and the like on the substrate in the part not covered by photoresist, so as to accurately transfer the pattern on the mask to the semiconductor substrate, the etching process is used to create various microstructures of microelectronic devices, such as gate, source and drain of transistor, interconnecting wire, contact hole, capacitor and other key components.

[0003] Among them, the etching process is mainly divided into wet etching and dry etching, dry etching is usually carried out in a gas phase environment, using gas to react with the substrate surface or physical collision to remove material, wet etching is to use chemical solution to remove the unwanted part of the material surface, in semiconductor manufacturing, silicon wafer or wafer is immersed in a specific chemical solvent, and the target material layer is selectively dissolved by chemical reaction; Among them, wet etching has many advantages compared with dry etching, 1. The equipment used in wet etching is usually relatively simple and low in cost, the operation and maintenance cost is also easy to control, and because it does not involve complex plasma or high vacuum system, the initial investment and running cost may be lower than that of dry etching; 2. Wet etching relies on the selective dissolution ability of specific chemical solution to different materials to achieve good selection, which can be very accurate to select the target material for selective etching without damaging the adjacent protective layer; 3. Wet etching can provide better uniformity on the whole wafer surface, especially in batch processing, liquid medium helps to ensure that all etched areas are subjected to similar chemical action; 4. The etching rate and depth can be controlled more flexibly by adjusting the solution concentration, temperature, pH value and soaking time; However, it should be noted that although wet etching has the above advantages, in modern semiconductor manufacturing process, especially in the case of requiring very high precision, aspect ratio and complex three-dimensional structure, the limitation of wet etching is also obvious:

[0004] 1. Wet etching is generally isotropic, that is, the etching rate in the vertical and parallel directions is close, which leads to insufficient steepness of the side wall, which is not conducive to the formation of high aspect ratio structure; 2. Because the liquid etchant can diffuse to the substrate material under the mask, it may cause lateral etching, affecting the pattern fidelity and line width control, and even causing the collapse of hierarchical structure, resulting in wafer scrap; 3. Wet etching uses a large amount of corrosive chemicals, and the treatment of waste liquid is an environmental challenge and increases the operating cost.

[0005] In combination with FIG. 4, when wet etching is used to etch the composite metal film on the wafer, the existing technology generally etches the composite metal film continuously by making a photoresist mask 4, so that the etching of the bottom metal 6 film is carried out by using the top metal 5 as a mask for wet etching; Wet etching will cause side etching, so that after the wet etching of the top metal 5 is completed, the size of the etched groove is larger than the designed size (i.e. the size of the photoresist mask 4), and when the bottom metal 6 is etched, the size will be increased on the basis of the side etching of the top metal 5, so that the etching size of the bottom metal 6 is distorted; At the same time, the etching of the bottom metal 6 of the composite metal film cannot be observed, and only the etching of the top metal 5 can observe the appearance of the wet etching of the bottom metal 6.

[0006] Therefore, how to improve the size precision of the bottom layer of the composite metal thin film in wet etching is a technical problem to be solved by technical personnel at present. SUMMARY

[0007] To overcome the problems in the related art, the application provides a wafer wet etching method and wafer to improve the size precision of the bottom layer of the metal in wet etching, and solve the technical problem of distortion of the size of the bottom layer of the metal in wet etching of the composite metal film by using the traditional wet etching process.

[0008] To achieve the above-mentioned purpose, the application provides a wafer wet etching method, the wafer comprising a substrate and a composite metal layer, the composite metal layer covering a preset surface of the substrate, the composite metal layer comprising a first metal layer, a second metal layer, …, an Nth metal layer from top to bottom, wherein N≥2, wherein the first metal layer covers the surface of the second metal layer, the second metal layer covers the surface of the third metal layer, …, the (N-1)th metal layer covers the surface of the Nth metal layer, the wet etching method comprising the following steps:

[0009] S1. Coating photoresist on the surface of the first metal layer to form a first photoresist layer;

[0010] S2. Performing photoetching on the first photoresist layer to form a first mask;

[0011] S3. Etching the first metal layer;

[0012] S4. Removing the first mask;

[0013] S5. Coating photoresist on the surface of the first metal layer and the surface of the second metal layer exposed after etching to form a second photoresist layer, and ensuring that the surface of the second photoresist layer is flat, that is, ensuring that the upper surface of the second photoresist layer covering the surface of the first metal layer and the surface of the second metal layer is at the same height, and the same method is used to coat photoresist to ensure that the surface of the Nth photoresist layer is flat, so that the upper surface of the Nth photoresist layer covering the surface of the first metal layer and the surface of the Nth metal layer is at the same height;

[0014] S6. Performing photoetching on the second photoresist layer to form a second mask, wherein the mask corresponding to the first photoresist layer has a first transparent area, the width of the first transparent area is d1, the mask corresponding to the second photoresist layer has a second transparent area, the width of the second transparent area is d2, d1≥d2; wherein the first transparent area is directly above the second transparent area;

[0015] S7. Etching the second metal layer;

[0016] S8. Removing the second mask;

[0017] …

[0018] sequentially coating photoresist on the surface of the first metal layer and the surface of the second metal layer which is exposed after etching, and / or the surface of the Nth metal layer which is exposed, to form an Nth photoresist layer, and ensuring that the upper surface of the Nth photoresist layer is flat, so that the upper surface of the Nth photoresist layer covering the surface of the first metal layer and the surface of the other metal layers is at the same level; the mask corresponding to the Nth photoresist layer has an Nth transparent area with a width of d n , where d1≥d2…≥d n ;

[0019] performing photoetching on the Nth photoresist layer to form an Nth mask; and etching the Nth metal layer;

[0020] removing the Nth mask. Further, before step S1, the method further comprises:

[0021] cleaning the wafer;

[0022] drying the wafer.

[0023] Further, after coating photoresist on the surface of the Nth metal layer to form an Nth photoresist layer, before performing photoetching on the Nth photoresist layer to form an Nth mask, the method further comprises the following processing steps:

[0024] soft baking the Nth photoresist layer, the temperature of the soft baking being the evaporation temperature of the solvent of the photoresist of the Nth photoresist layer.

[0025] Further, performing photoetching on the Nth photoresist layer to form an Nth mask specifically comprises the following sub-steps:

[0026] exposing the Nth photoresist layer;

[0027] post-baking the wafer;

[0028] immersing the wafer in a developing solution to develop the Nth mask.

[0029] Further, etching the Nth-1 metal layer specifically comprises immersing the wafer in an Nth-1 etching solution to etch the Nth-1 metal layer, ensuring that the Nth-1 etching solution does not react with the Nth-1 mask and the Nth metal layer; or ensuring that the Nth-1 etching solution does not react with the Nth-1 mask and the remaining metal layers which have been etched.

[0030] Further, removing the Nth mask specifically comprises immersing the wafer in a photoresist remover to remove the Nth mask.

[0031] using a cleaning solution to rinse the photoresist remover remaining on the wafer.

[0032] Further, the viscosity of the photoresist of the Nth photoresist layer is lower than that of the photoresist of the (N-1)th photoresist layer.

[0033] Further, the Nth photoresist layer and the (N-1)th photoresist layer are made of the same material, the exposure time of the Nth photoresist layer is longer than that of the (N-1)th photoresist layer, and / or the exposure light intensity of the Nth photoresist layer is greater than that of the (N-1)th photoresist layer.

[0034] Further, the (N-1)th metal layer is etched, specifically including immersing the wafer in the (N-1)th etching solution to etch the (N-1)th metal layer, and the (N-1)th etching solution does not react with the (N-1)th mask, the Nth metal layer and the metal layer that has been etched.

[0035] Further, the composite metal layer includes a first metal layer and a second metal layer, the first metal layer covers the surface of the second metal layer, and the wet etching method specifically includes the following steps:

[0036] S1. Coating photoresist on the surface of the first metal layer to form a first photoresist layer;

[0037] S2. Photoetching the first photoresist layer to form a first mask;

[0038] S3. Etching the first metal layer;

[0039] S4. Removing the first mask;

[0040] S5. Coating photoresist on the first metal layer and the second metal layer exposed after etching to form a second photoresist layer, and ensuring that the surface of the second photoresist layer is flat;

[0041] S6. Photoetching the second photoresist layer to form a second mask, the transparent area width of the mask corresponding to the first photoresist layer and the second photoresist layer is equal or the transparent area width of the mask corresponding to the second photoresist layer is narrower than that of the mask corresponding to the first photoresist layer;

[0042] S7. Etching the second metal layer;

[0043] S8. Removing the second mask.

[0044] Specifically, the composite metal layer includes a first metal layer, a second metal layer and a third metal layer, from top to bottom, the first metal layer covers the surface of the second metal layer, the second metal layer covers the surface of the third metal layer, and the wet etching method includes the following steps:

[0045] S1. Coating photoresist on the first metal layer to form a first photoresist layer;

[0046] S2. Performing photoetching on the first photoresist layer to form a first mask;

[0047] S3. Etching the first metal layer;

[0048] S4. Removing the first mask;

[0049] S5. Coating photoresist on the first metal layer and the second metal layer exposed after etching to form a second photoresist layer, and ensuring that the upper surface of the second photoresist layer is flat;

[0050] S6. Performing photoetching on the second photoresist layer to form a second mask, wherein the transparent area width of the mask corresponding to the first photoresist layer and the transparent area width of the mask corresponding to the second photoresist layer are equal, or the transparent area width of the mask corresponding to the second photoresist layer is narrower than the transparent area width of the mask corresponding to the first photoresist layer;

[0051] S7. Etching the second metal layer;

[0052] S8. Removing the second mask;

[0053] S9. Coating photoresist on the first metal layer and the third metal layer exposed after etching to form a third photoresist layer, and ensuring that the upper surface of the third photoresist layer is flat;

[0054] S10. Performing photoetching on the third photoresist layer to form a third mask, wherein the transparent area width of the mask corresponding to the first photoresist layer, the transparent area width of the mask corresponding to the second photoresist layer, and the transparent area width of the mask corresponding to the third photoresist layer are equal, or the transparent area width of the mask corresponding to the second photoresist layer is narrower than the transparent area width of the mask corresponding to the first photoresist layer, and the transparent area width of the mask corresponding to the third photoresist layer is narrower than the transparent area width of the mask corresponding to the second photoresist layer;

[0055] S11. Etching the third metal layer;

[0056] S12. Removing the third mask.

[0057] Further, before step S1, the following steps are further included:

[0058] Cleaning the wafer;

[0059] Drying the wafer.

[0060] Further, after step S1 and before step S2, the following steps are further included:

[0061] The first photoresist layer is subjected to soft baking, and the temperature of the soft baking is the evaporation temperature of the solvent of the photoresist.

[0062] Further, the step S2 comprises:

[0063] The first photoresist layer is subjected to exposure;

[0064] The wafer is subjected to post-baking;

[0065] The wafer is subjected to development in a developing solution to form the first mask.

[0066] Further, the step S3 comprises:

[0067] The wafer is subjected to etching of the first metal layer in a first etching solution, wherein the first etching solution is not reactive with the second metal layer and the first mask.

[0068] Further, the step S4 comprises:

[0069] The wafer is subjected to removal of the first mask in a stripping agent;

[0070] The wafer is subjected to rinsing of the residual stripping agent on the wafer with a rinsing solution.

[0071] Further, the photoresist of the second photoresist layer has a lower viscosity than the photoresist of the first photoresist layer.

[0072] Further, the first photoresist layer and the second photoresist layer are made of the same material, the second photoresist layer has a longer exposure time than the first photoresist layer, and / or the second photoresist layer has a higher exposure light intensity than the first photoresist layer.

[0073] Further, the step S7 comprises:

[0074] The wafer is subjected to etching of the second metal layer in a second etching solution, wherein the second etching solution is not reactive with the first metal layer and the second mask.

[0075] The application further provides a wafer, comprising:

[0076] The wafer is produced by using the wet etching method described above.

[0077] The technical solution provided by the application has the following beneficial effects:

[0078] 1. In the technical solution, a wafer includes a substrate and a composite metal layer, the composite metal layer covers a preset surface of the substrate, the composite metal layer includes a first metal layer, a second metal layer, …, and an Nth metal layer, for example, when there are two metal layers, the first metal layer covers the upper surface of the second metal layer, when etching the wafer, first, photoresist is coated on the first metal layer to form a first photoresist layer, then the first photoresist layer is subjected to photolithography to shape the first photoresist layer into a first mask, the first mask is etched with a circuit pattern, then the first metal layer is etched, during the etching process, the area covered by the first mask can protect the underlying first metal layer from being etched, while the unprotected area is etched, thereby transferring the circuit pattern on the first mask to the first metal layer, after etching, the first mask is removed, then photoresist is coated on the first metal layer again, and the etched area (groove) on the first metal layer is also filled with photoresist, and the surface of the formed second photoresist layer is ensured to be flat to prevent image transfer distortion due to uneven surface of the second photoresist layer, then the second photoresist layer is subjected to photolithography to shape the second photoresist layer into a second mask, wherein the transparent area width of the mask corresponding to the first photoresist layer and the second photoresist layer is ensured to be equal or the transparent area width of the mask corresponding to the second photoresist layer is narrower than that of the mask corresponding to the first photoresist layer, since the first metal layer will have a side etching problem during etching, resulting in the groove size of the etched first metal layer being larger than that of the first mask, when the second photoresist layer is subjected to photolithography using a mask with a transparent area width equal to or narrower than that of the mask corresponding to the first photoresist layer, the size of the groove etched on the first metal layer can be filled to be equal to or smaller than that of the first mask using the formed second mask, then the second metal layer is etched, so that the size of the groove etched on the second metal layer is equal to or smaller than that of the groove on the first metal layer, finally, the second mask is removed, that is, the etching of the wafer is completed, which solves the problem of size distortion of the second metal layer caused by using the first metal layer as a mask for etching the second metal layer when using the traditional wet etching process to etch the composite metal film on the wafer, improves the size precision of the second metal layer wet etching, and improves the yield and reliability of wafer production.

[0079] 2. The wafer wet etching method provided by the present application can be used for etching more than two layers of metal composite layers, and when the metal composite layers further include a third metal layer and the second metal layer covers the surface of the third metal layer, the wet etching method can also be used for etching the third metal layer, the first metal layer and the second metal layer are combined as a "first metal layer" after wet etching according to S1-S7, and the third metal layer is regarded as a "second metal layer", and then wet etching is performed according to S5-S8, so that the third metal layer can be etched, and the etching size precision is improved when etching multiple layers of metal layers.

[0080] 3. In the wafer wet etching method provided by the present application, when the second photoresist layer is subjected to photolithography by using a mask with a width narrower than the corresponding transparent area of the first photoresist layer, a second mask will be formed at the groove sidewall of the first metal layer, the thickness of the second mask is thicker than the etched part of the first metal layer, and after filling the etched part of the first metal layer, the second mask further reduces the size of the groove to be smaller than the size of the groove of the first mask, and then the second metal layer is etched, and the size of the groove formed in the second metal layer is smaller than the size of the groove in the first metal layer. After the above repeated etching method is used to etch the composite metal layer layer by layer, the operator can observe the corresponding size of the etching area of each layer of the composite metal layer from the first metal layer to the bottom layer of the etching area by using an observation device, and the problem that the metal layers other than the first metal layer cannot be observed is solved.

[0081] It should be understood that the foregoing general description and the following detailed description are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0082] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which like reference characters refer to like parts throughout the several views, and in which:

[0083] Fig. 1 is a flow diagram of a wafer wet etching process according to an embodiment of the present application;

[0084] Fig. 2 is a detailed flow diagram of a wafer wet etching process according to an embodiment of the present application;

[0085] Fig. 3 is a structural diagram of a wafer wet etching process according to an embodiment of the present application;

[0086] Fig. 4 is a structural diagram of a wafer wet etching process according to a prior art;

[0087] Figure 5 is a schematic diagram of the width d1, d2 of the transparent area of the mask of each metal layer in the wafer wet etching process according to the embodiment of the present application. 2、 …, d n Schematic diagram of the size relationship.

[0088] Figure: 1, wafer; 10, composite metal layer; 100, first metal layer; 101, second metal layer; 11, substrate; 2, first photoresist layer; 20, first mask; 3, second photoresist layer; 30, second mask; 4, photoresist mask; 5, top metal layer; 6, bottom metal layer. DETAILED DESCRIPTION

[0089] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application.

[0090] Embodiment one:

[0091] The present application provides a wafer wet etching method, the wafer 1 includes a substrate 11 and a composite metal layer 10, the composite metal layer 10 covers the preset surface of the substrate 11, the composite metal layer 10 includes a first metal layer 100 and a second metal layer 101, the first metal layer 100 covers the surface of the second metal layer 101, and the wet etching method includes:

[0092] S1. Coating photoresist on the first metal layer 100 to form a first photoresist layer 2;

[0093] S2. Performing photoetching on the first photoresist layer 2 to form a first mask 20, the first mask 20 is provided with a first transparent area with a width of d1;

[0094] S3. Etching the first metal layer 100;

[0095] S4. Removing the first mask 20;

[0096] S5. Coating photoresist on the first metal layer 100 and the second metal layer 101 exposed after etching to form a second photoresist layer 3, and ensuring that the surface of the second photoresist layer 3 is flat, the second photoresist layer 3 covers the first metal layer 100 not etched and the recesses of the first metal layer 100 and the second metal layer 101 exposed after etching, and thus the second photoresist layer 3 can coat the sidewall of the first metal layer 100 which has been etched and has side etching;

[0097] S6. Perform photoetching on the second photoresist layer 3 to form a second mask 30, and a second transparent area is formed on the second mask 30, and the second transparent area has a width d2. The transparent area width of the mask corresponding to the first photoresist layer 2 is equal to the transparent area width of the mask corresponding to the second photoresist layer 3, or the transparent area width of the mask corresponding to the second photoresist layer 3 is narrower than the transparent area width of the mask corresponding to the first photoresist layer 2, that is, d1≥d2. In this way, the second transparent area is arranged corresponding to the first transparent area, and the width d2 of the second transparent area is ensured to be less than the width d1 of the first transparent area. Thus, when etching the second metal layer, the width of the groove of the etched second metal layer 101 can be effectively prevented from being greater than the width of the groove of the etched first metal layer 100, and the technical problem of the increase of etching size due to the continued side etching of the first metal layer 100 is effectively overcome, and the technical problem that the appearance of the bottom metal wet etching of the composite metal film cannot be observed is also overcome, and only the top metal etching can observe the appearance of the bottom metal wet etching.

[0098] S7. Etch the second metal layer 101.

[0099] S8. Remove the second mask 30.

[0100] When the prior art uses wet etching to etch the composite metal layer 10 on the wafer 1, a photoresist mask is generally made to continuously etch the composite metal layer 10, so that the etching of the second metal layer 101 is wet etching using the first metal layer 100 as a mask. However, wet etching will cause side etching, so that after the wet etching of the first metal layer 100 is completed, the etched groove size is larger than the designed size (i.e. the photoresist mask size), and when the second metal layer 101 is wet etched, the size will be increased on the basis of the side etching of the first metal layer 100, so that the etching size of the second metal layer 101 is distorted.

[0101] In combination with FIG. 1 and FIG. 3, in the embodiment, the wafer 1 comprises a substrate 11 and a composite metal layer 10, the composite metal layer 10 covers a preset surface of the substrate 11, the composite metal layer 10 comprises a first metal layer 100 and a second metal layer 101, the first metal layer 100 covers a surface of the second metal layer 101, when etching the wafer 1, first, photoresist is coated on the first metal layer 100 to form a first photoresist layer 2, then the first photoresist layer 2 is subjected to photolithography to form a first mask 20, the first mask 20 is etched with a circuit pattern, then the first metal layer 100 is etched, in the etching process, the area covered by the first mask 20 can protect the underlying first metal layer 100 from being etched, while the unprotected area is etched, thereby transferring the circuit pattern on the first mask 20 to the first metal layer 100, after the etching is completed, the first mask 20 is removed, then photoresist is coated on the first metal layer 100 again, and the etched area is filled with photoresist to ensure that the surface of the second photoresist layer 3 formed is flat, because the uneven surface of the photoresist layer will cause the light intensity and penetration depth of each part to be different during exposure, which will cause the circuit pattern formed to be deformed or have size deviation, the flatness of the surface of the second photoresist layer 3 can prevent the problem of image transfer distortion, then the second photoresist layer 3 is subjected to photolithography to form a second mask 30, wherein the transparent area width of the mask corresponding to the first photoresist layer 2 and the second photoresist layer 3 is equal or the transparent area width of the mask corresponding to the second photoresist layer 3 is narrower than the transparent area width of the mask corresponding to the first photoresist layer 2, because the first metal layer 100 will have a side etching problem during etching, which will cause the size of the groove obtained by etching the first metal layer 100 to be larger than the size of the first mask 20, when the second photoresist layer 3 is subjected to photolithography using a mask with a transparent area width equal to that of the first photoresist layer 2, a second mask 30 will be formed at the groove sidewall of the first metal layer 100, the second mask 30 will fill the part of the first metal layer 100 that is side etched, thereby reducing the size of the groove, so that the size of the groove with the sidewall covered by the second mask 30 is equal to the size of the first mask 20, then the second metal layer 101 is etched, the size of the groove formed in the second metal layer 101 is equal to the size of the groove on the first metal layer 100, thereby solving the problem that the second metal layer 101 is severely side etched during wet etching of the composite metal layer 10, which causes etching size distortion, when the second photoresist layer 3 is subjected to photolithography using a mask with a narrower transparent area width than the mask corresponding to the first photoresist layer 2, a second mask 30 will be formed at the groove sidewall of the first metal layer 100, the thickness of the second mask 30 is thicker than the part of the first metal layer 100 that is side etched, after the second mask 30 fills the part of the first metal layer 100 that is etched, the second mask 30 further reduces the size of the groove to be smaller than the size of the first mask 20, then the second metal layer 101 is etched, the size of the groove formed in the second metal layer 101 is smaller than the size of the groove on the first metal layer 100,Thus, the etching condition of the second metal layer 101 can be directly observed, and the problem that the second metal layer 101 of the composite metal film cannot be observed is solved. Finally, the second mask 30 is removed, and the etching of the wafer 1 is completed. The method solves the problem that, when the composite metal film on the wafer 1 is etched by using the wet etching method, the etching size of the second metal layer 101 is distorted due to the etching of the second metal layer 101 by using the first metal layer 100 as a mask, improves the size precision of the wet etching of the second metal layer, and improves the yield and reliability of the wafer 1 production.

[0102] In addition, when the composite metal layer 10 further includes a third metal layer, and the second metal layer 101 covers the surface of the third metal layer, the wet etching method can also be applied to the etching of the third metal layer. The first metal layer 100 and the second metal layer 101 are etched by using the wet etching method according to S1-S7. After the etching is completed, the first metal layer 100 and the second metal layer 101 are combined as the "first metal layer 100", and the third metal layer is regarded as the "second metal layer 101". The wet etching method is performed according to S5-S8, so that the third metal layer can be etched, and the size precision of the etching of the multi-layer metal layer is improved.

[0103] Embodiment two:

[0104] The wafer 1 wet etching method further includes, before S1:

[0105] The wafer 1 is cleaned.

[0106] The wafer 1 is dried.

[0107] After S1 and before S2, the method further includes:

[0108] The first photoresist layer 2 is soft-baked, and the soft-baking temperature is the evaporation temperature of the solvent of the photoresist.

[0109] In combination with FIG. 2, in the present embodiment, in order to avoid the influence of contaminants on the surface of wafer 1 on the photoetching of photoresist, the surface of wafer 1 also needs to be cleaned between the coating of first metal layer 100 with photoresist. In the production process, the surface of wafer 1 can be contaminated with organic contaminants (such as grease, solvent residues, particulate matter, etc.), inorganic contaminants (such as metal ions, oxides), and other impurities. These contaminants can reduce the adhesion of photoresist, and in subsequent development and etching steps, peeling and falling off can easily occur, thereby causing the integrity of the circuit pattern to be damaged, and also causing the photoresist layer formed to be non-uniform or to have defects, changing the thickness distribution and photosensitive reaction of photoresist on the surface of wafer 1, so that light cannot accurately pass through the photoresist and reach the surface of composite metal layer 10 in the exposure process, causing pattern transfer distortion, affecting the accuracy and resolution of circuit lines, and reducing the performance and yield of chips made from wafer 1. When wafer 1 is cleaned, pre-cleaning is performed first, and solvent (such as isopropyl alcohol (IPA), ethanol, or other organic solvents) is used to remove oily stains, particles, and loose impurities on the surface of wafer 1. Then, deionized water (deionized water is a highly pure water that has almost completely removed dissolved mineral ions in water through a special purification process, and deionized water has good compatibility with various semiconductor materials and will not cause adverse chemical reactions or physical damage, and can avoid causing circuit defects) is used to rinse wafer 1, removing residual solvents and other soluble substances. Then, an ultrasonic cleaning machine (which uses the cavitation effect generated by ultrasonic waves in a liquid to clean objects) is used to peel off the fine particles attached to the outer surface of wafer 1. Finally, high-pressure nitrogen gas flow is used to blow off the liquid on the surface, preventing stains from being left on the surface after the liquid dries, reducing the risk of recontamination, thereby achieving the cleaning of wafer 1 and avoiding the adverse effects of contaminants on the surface of wafer 1 on the photoetching of photoresist.

[0110] After the coating of photoresist on first metal layer 100 is completed, and before the photoetching of photoresist is performed, wafer 1 needs to be placed in an oven for soft baking of first photoresist layer 2. The temperature set in the oven is the evaporation temperature of the solvent of photoresist. Soft baking of photoresist can evaporate and remove the solvent in the photoresist layer, improving the adhesion and stability of photoresist to composite metal layer 10, preventing subsequent peeling and falling off, and also preventing the solvent from remaining in first photoresist layer 2, causing the transferred circuit pattern to deform during photoetching, and preventing solvent vapor from interfering with the photochemical reaction of photoresist during the exposure process, thereby causing adverse effects on subsequent development.

[0111] Embodiment Three

[0112] The wafer 1 wet etching method, S2 comprises:

[0113] Exposing the first photoresist layer 2;

[0114] post-baking the wafer 1;

[0115] developing the wafer 1 in a developing solution to form the first mask 20.

[0116] S3 includes:

[0117] etching the first metal layer 100 by immersing the wafer 1 in a first etching solution, which does not react with the second metal layer 101 and the first mask 20.

[0118] S4 includes:

[0119] removing the first mask 20 by immersing the wafer 1 in a stripping agent;

[0120] rinsing the residual stripping agent on the wafer 1 with a cleaning solution.

[0121] In this embodiment, to transfer the circuit pattern on the mask to the first photoresist layer 2, the first photoresist layer 2 is exposed to light, such as ultraviolet light, deep ultraviolet light, or extreme ultraviolet light, which is irradiated on the mask, and then passes through the transparent area of the mask to irradiate the first photoresist layer 2. The area irradiated by the light will undergo a chemical reaction, making the exposed area either soluble or insoluble to the developing solution. Then the wafer 1 is sent to an oven for post-baking to accelerate the chemical reaction inside the photoresist and enhance the contrast between the exposed area and the unexposed area. Then the wafer 1 is immersed in a developing solution. When the exposed area becomes soluble to the developing solution, the developing solution will dissolve the exposed area, leaving the remaining area to form the first mask 20. When the exposed area becomes insoluble to the developing solution, the developing solution will dissolve the unexposed area, leaving the exposed area to form the first mask 20, thereby transferring the circuit pattern on the mask to the first photoresist layer 2.

[0122] To etch the first metal layer 100, the wafer 1 is immersed in a first etching solution, which is selective and only strongly reacts with the first metal layer 100 and dissolves the first metal layer 100, but does not react with the second metal layer 101 and the first mask 20. Therefore, the area covered by the first mask 20 will not be etched by the first etching solution, and the second metal layer 101 will not be etched when the first etching solution etches through the first metal layer 100, thereby completing the etching of the first metal layer 100 and transferring the circuit pattern on the first mask 20 to the first metal layer 100, which also avoids damaging the second metal layer 101.

[0123] In combination with FIG. 2 and FIG. 3, then the first mask 20 needs to be removed, since the material of the first mask 20 is actually photoresist, the wafer 1 can be soaked in an ultrasonic cleaning tank filled with a remover to dissolve and remove the first mask 20, wherein the remover can use solvents such as acetone, isopropyl alcohol (IPA), N-methyl pyrrolidone (NMP), etc., in the ultrasonic cleaning tank, the photoresist will quickly fall off due to the action of the solvent and ultrasonic vibration, then deionized water is used to rinse the remover on the wafer 1, and finally high-pressure nitrogen gas flow is used to blow off the liquid on the surface of the wafer 1, and the wafer 1 is dried to prevent residual solvents from affecting the coating of the next photoresist layer, and the removal of the first mask 20 is completed.

[0124] Embodiment four:

[0125] The wafer 1 wet etching method,

[0126] The viscosity of the photoresist of the second photoresist layer 3 is lower than that of the photoresist of the first photoresist layer 2.

[0127] Wherein, when the materials of the first photoresist layer and the second photoresist layer are the same, the exposure time of the second photoresist layer is longer than that of the first photoresist layer, and / or the exposure light intensity of the second photoresist layer is greater than that of the first photoresist layer.

[0128] In addition, S7 includes:

[0129] The wafer 1 is soaked in a second etching liquid to etch the second metal layer 101, and the second etching liquid does not react with the first metal layer 100 and the second mask 30.

[0130] In combination with FIG. 2 and FIG. 3, in this embodiment, the wafer 1 needs to be coated with photoresist twice, when the first photoresist layer 2 is coated, the surface of the first metal layer 100 is a flat surface, and the surface of the coated photoresist can easily form a flat surface. After etching, the circuit pattern is transferred to the surface of the first metal layer 100, causing the surface of the first metal layer 100 to become uneven. When the photoresist is coated on the first metal layer, it needs to fill the etched grooves on the first metal layer 100. If the surface of the second photoresist layer 3 formed is not flat, it will cause the resolution of the photoetching and the quality of the pattern edge after development to decrease, and the circuit pattern to deform. Therefore, the second photoresist layer 3 needs to use photoresist with lower viscosity than the first photoresist layer 2 to improve the flowability of the photoresist during coating, so that the photoresist has better filling performance to ensure that the photoresist can quickly fill the grooves when the photoresist is coated, and the surface of the second photoresist layer 3 formed is flat.

[0131] In combination with FIG. 2 and FIG. 3, since the second etching is performed on the second metal layer 101 on the basis of the first etching, the exposed area of the second photoresist layer 3 is actually located in the groove etched by the first metal layer 100, resulting in that the thickness of the exposed area of the second photoresist layer 3 is thicker than that of the exposed area of the first photoresist layer 2. The photoresist reacts with light because the photoresist contains specific light-sensitive components, which will chemically react under the irradiation of light of a specific wavelength, thereby achieving the control of the solubility of the photoresist. The increase of the thickness of the photoresist layer reduces the exposure sensitivity of the photoresist (the exposure sensitivity refers to the photochemical reaction of the photoresist per unit time under the irradiation of a specific light source, and the exposure sensitivity reflects the response speed and efficiency of the photoresist to light energy) and increases the exposure dose of the bottom photoresist (when light passes through the photoresist layer, the light intensity decays with the depth of the photoresist layer due to the absorption and scattering of light, and the irradiation intensity needs to be increased to chemically react with the photoresist at the bottom). If the viscosity of the photoresist adopted by the first photoresist layer 2 can meet the filling of the groove of the first metal layer 100 and the surface of the second photoresist layer 3 formed after filling is flat, the photoresist adopted by the second photoresist layer 3 is consistent with that of the first photoresist layer. At this time, more time is needed to expose the exposed area, or the exposure irradiation intensity of the second photoresist layer is adjusted to be greater than that of the first photoresist layer. The exposure time and the exposure irradiation intensity can also be increased at the same time, thereby preventing the photoresist in the area to be etched from being completely removed during development, resulting in the problem that the etching of the second metal layer 101 cannot be completed and the circuit pattern cannot be completely transferred to the second metal layer 101.

[0132] In combination with FIG. 2 and FIG. 3, in addition, to achieve the etching of the second metal layer 101, specifically, the wafer 1 is soaked in a second etching solution. The second etching solution has selectivity, and only the second metal layer 101 and the second etching solution have a strong chemical reaction and dissolve the second metal layer 101, and the first metal layer 100 and the second mask 30 do not react. Therefore, the area covered by the second mask 30 will not be etched by the second etching solution, and the bottom metal layer or the substrate 11 will not be etched after the second etching solution etches through the second metal layer 101, thereby completing the etching of the second metal layer 101 and transferring the circuit pattern on the second mask 30 to the second metal layer 101. Also, the first metal layer 100 can be prevented from being damaged.

[0133] Embodiment five

[0134] The composite metal layer includes a first metal layer, a second metal layer and a third metal layer. From top to bottom, the first metal layer covers the surface of the second metal layer, the second metal layer covers the surface of the third metal layer, and the wet etching method comprises the following steps:

[0135] S1. Coating photoresist on the first metal layer to form a first photoresist layer;

[0136] S2. Performing photoetching on the first photoresist layer to form a first mask;

[0137] S3. Etching the first metal layer;

[0138] S4. Removing the first mask;

[0139] S5. Coating photoresist on the first metal layer and the second metal layer exposed after etching to form a second photoresist layer, and ensuring that the upper surface of the second photoresist layer is flat, the second photoresist layer covering the first metal layer, the recess of the first metal layer exposed after etching, and the second metal layer, and the second photoresist layer also being able to cover the sidewall of the first metal layer that has been side-etched during the etching process;

[0140] S6. Performing photoetching on the second photoresist layer to form a second mask, wherein the transparent area width of the mask corresponding to the first photoresist layer and the transparent area width of the mask corresponding to the second photoresist layer are equal, or the transparent area width of the mask corresponding to the second photoresist layer is narrower than the transparent area width of the mask corresponding to the first photoresist layer;

[0141] S7. Etching the second metal layer;

[0142] S8. Removing the second mask;

[0143] S9. Coating photoresist on the first metal layer, the recess of the first metal layer after etching, the recess of the second metal layer, and the third metal layer to form a third photoresist layer, and ensuring that the upper surface of the third photoresist layer is flat, the third photoresist layer covering the first metal layer, the recess of the first metal layer exposed after etching, the recess of the second metal layer, and the third metal layer, and the third photoresist layer also being able to cover the sidewall corresponding to the recess of the first metal layer and the second metal layer that have been etched;

[0144] S10. Performing photoetching on the third photoresist layer to form a third mask, wherein the transparent area width of the mask corresponding to the first photoresist layer, the transparent area width of the mask corresponding to the second photoresist layer, and the transparent area width of the mask corresponding to the third photoresist layer are equal, or the transparent area width of the mask corresponding to the second photoresist layer is narrower than the transparent area width of the mask corresponding to the first photoresist layer, and the transparent area width of the mask corresponding to the third photoresist layer is narrower than the transparent area width of the mask corresponding to the second photoresist layer;

[0145] S11. Etching the third metal layer;

[0146] S12. Removing the third mask.

[0147] Embodiment six

[0148] A wet etching method for a wafer, the wafer comprising a substrate and a composite metal layer, the composite metal layer covering a preset surface of the substrate, the composite metal layer comprising a first metal layer, a second metal layer, …, an Nth metal layer in sequence from top to bottom, wherein N≥4, wherein the first metal layer covers a surface of the second metal layer, the second metal layer covers a surface of the third metal layer, …, the (N-1)th metal layer covers a surface of the Nth metal layer, the wet etching method comprising the following steps:

[0149] S1. coating photoresist on the surface of the first metal layer to form a first photoresist layer;

[0150] S2. performing photolithography on the first photoresist layer to form a first mask;

[0151] S3. etching the first metal layer;

[0152] S4. removing the first mask;

[0153] S5. coating photoresist on the surface of the first metal layer and the surface of the second metal layer exposed after etching to form a second photoresist layer, and ensuring that the surface of the second photoresist layer is flat, i.e. ensuring that the upper surface of the second photoresist layer covering the surface of the first metal layer and the surface of the second metal layer is at the same level, and the same method is used to coat photoresist to ensure that the surface of the Nth photoresist layer is flat, so that the upper surface of the Nth photoresist layer covering the surface of the first metal layer and the surface of the Nth metal layer is at the same level;

[0154] S6. performing photolithography on the second photoresist layer to form a second mask, wherein the mask corresponding to the first photoresist layer has a first transparent area with a width of d1, the mask corresponding to the second photoresist layer has a second transparent area with a width of d2, d1≥d2; wherein the first transparent area is directly above the second transparent area;

[0155] S7. etching the second metal layer;

[0156] S8. removing the second mask;

[0157] …;

[0158] The process proceeds sequentially, coating the surface of the first metal layer and the surfaces of the second, ..., and / or the exposed Nth metal layer with photoresist to form the Nth photoresist layer. The upper surface of the Nth photoresist layer is ensured to be flat, so that the upper surface of the Nth photoresist layer covering the surface of the first metal layer and the grooves and surfaces of the other etched metal layers are at the same horizontal level. The photomask corresponding to the Nth photoresist layer has an Nth transparent area with a width of d. n Where d1≥d2…≥d n Figure 5 shows the wafer with an N-layer metal composite layer, and the transparent area widths d1 and d2 of each mask in each process step. 2、 …、d n This is an illustration; in this way, it can be ensured that each time the photoresist layer is applied, the photoresist layer can cover the sidewall of the groove with the corresponding metal layer that has been etched, preventing it from being further laterally etched. In addition, by setting the width of the transparent area, it can also effectively prevent the actual width of the groove in the lower metal layer from being greater than the width of the groove in the upper metal layer after lateral etching, or the overall etching size distortion from occurring.

[0159] The Nth photoresist layer is photolithographically etched to form the Nth mask; the Nth metal layer is etched.

[0160] Remove the Nth mask.

[0161] Furthermore, prior to step S1, the following steps are also included:

[0162] The wafer is cleaned;

[0163] The wafer is dried.

[0164] Furthermore, after coating the surface of the Nth metal layer with photoresist to form the Nth photoresist layer, and before photolithography is performed on the Nth photoresist layer to form the Nth mask, the following processing steps are also included:

[0165] The Nth photoresist layer is subjected to soft baking, wherein the soft baking temperature is the evaporation temperature of the solvent of the photoresist in the Nth photoresist layer.

[0166] Furthermore, the process of photolithography to form the Nth mask from the Nth photoresist layer specifically includes the following sub-steps:

[0167] The Nth photoresist layer is exposed;

[0168] The wafer is then post-baked;

[0169] The wafer is immersed in a developing solution to form the Nth mask.

[0170] Further, the N-1 metal layer is etched, specifically including immersing the wafer in N-1 etching liquid to etch the N-1 metal layer, ensuring that the N-1 etching liquid does not react with the N-1 mask and the N metal layer, or ensuring that the N-1 etching liquid does not react with the N-1 mask and the remaining metal layers that have been etched.

[0171] Further, the N mask is removed, specifically including immersing the wafer in a degreasing agent to remove the N mask.

[0172] The remaining degreasing agent on the wafer is rinsed with a cleaning liquid.

[0173] Further, the viscosity of the photoresist of the N photoresist layer is lower than that of the photoresist of the N-1 photoresist layer.

[0174] Further, the N-1 photoresist layer and the N photoresist layer are made of the same material, the exposure time of the N photoresist layer is longer than that of the N-1 photoresist layer, and / or the exposure light intensity of the N photoresist layer is greater than that of the N-1 photoresist layer.

[0175] Further, the N-1 metal layer is etched, specifically including immersing the wafer in N-1 etching liquid to etch the N-1 metal layer, the N-1 etching liquid does not react with the N-1 mask, the N metal layer, and the metal layers that have been etched.

[0176] Embodiment Seven:

[0177] The application also provides a wafer 1 produced by the wet etching method described above.

[0178] In this embodiment, the wafer 1 is produced by the wet etching method described above. The wet etching process is simpler than the dry etching process, and the equipment used in the wet etching process is less expensive, which can reduce the equipment cost investment in the production process of the wafer 1. At the same time, the rate of the wet etching process is faster than that of the dry etching process, which can improve the production rate of the wafer 1. In addition, the wet etching method described above also solves the problem of poor etching size precision of the second metal layer 101 of the composite metal layer 10, so that the performance and reliability of the wafer 1 produced by the wet etching method are improved, and the wafer 1 has higher competitiveness compared with the wafer produced by the existing wet etching method.

[0179] The solutions of the present application have been described in detail above with reference to the accompanying drawings. In the above examples, the description of each example is focused on respectively, and the parts not described in detail in a certain example can be referred to the relevant description of other examples. It should also be known by those skilled in the art that the actions and modules involved in the specification are not necessarily required by the present application. In addition, it can be understood that the steps in the method of the embodiments of the present application can be adjusted, combined and reduced in sequence according to actual needs, and the structure in the device of the embodiments of the present application can be combined, divided and reduced according to actual needs.

[0180] The above has described various embodiments of the present application, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical application or improvement of technology in the market, or to enable other ordinary skilled persons in the art to understand the embodiments disclosed herein.

Claims

1. A wafer wet etching method, the wafer comprising a substrate and a composite metal layer, the composite metal layer covering a preset surface of the substrate, the composite metal layer comprising a first metal layer, a second metal layer, …, an Nth metal layer in sequence from top to bottom, wherein N≥2, wherein the first metal layer covers a surface of the second metal layer, the second metal layer covers a surface of the third metal layer, …, and the (N-1) th metal layer covers a surface of the Nth metal layer, characterized in that, The wet etching method comprises the following steps: S1. Coating photoresist on the surface of the first metal layer to form a first photoresist layer; S2. Performing photoetching on the first photoresist layer to form a first mask; S3. Etching the first metal layer; S4. Removing the first mask; S5. Coating photoresist on the surface of the first metal layer and the surface of the second metal layer exposed after etching to form a second photoresist layer, and ensuring that the surface of the second photoresist layer is flat; S6. Performing photoetching on the second photoresist layer to form a second mask, wherein the mask corresponding to the first photoresist layer has a first transparent area with a width of d1, and the mask corresponding to the second photoresist layer has a second transparent area with a width of d2, wherein d1≥d2; S7. Etching the second metal layer; S8. Removing the second mask; ……； The first metal layer surface and the second metal layer surface, …, and / or the exposed Nth metal layer surface are coated with photoresist to form an Nth photoresist layer, and the surface of the Nth photoresist layer is ensured to be flat, the mask corresponding to the Nth photoresist layer has an Nth transparent area, and the width is d n wherein d1≥d2…≥d n ; Performing photoetching on the Nth photoresist layer to form an Nth mask; etching the Nth metal layer; Removing the Nth mask.

2. The method of claim 1, wherein the etchant is a solution of hydrogen peroxide and ammonium hydroxide. Before step S1, further comprising: Cleaning the wafer; Drying the wafer.

3. The wafer wet etching method according to claim 1, characterized in that: After coating photoresist on the surface of the Nth metal layer to form an Nth photoresist layer, before performing photoetching on the Nth photoresist layer to form an Nth mask, further comprising the following processing steps: Soft baking the Nth photoresist layer, and the soft baking temperature is the evaporation temperature of the solvent of the photoresist of the Nth photoresist layer.

4. The method of claim 3, wherein the etchant is a solution of H2O2 and H2SO4. The photoetching on the Nth photoresist layer to form an Nth mask specifically comprises the following sub-steps: Exposing the Nth photoresist layer; Post-baking the wafer; Developing the wafer in a developing solution to form the Nth mask.

5. The wafer wet etching method according to claim 1 or 2, characterized in that: The etching of the Nth-1 metal layer specifically comprises immersing the wafer in an Nth-1 etching solution to etch the Nth-1 metal layer, and the Nth-1 etching solution does not react with the Nth-1 mask and the Nth metal layer.

6. The wafer wet etching method according to claim 1 or 2, characterized in that: The removing of the Nth mask specifically comprises immersing the wafer in a photoresist remover to remove the Nth mask; Using a cleaning solution to rinse the photoresist remover remaining on the wafer.

7. The wafer wet etching method according to claim 1 or 2, characterized in that: The viscosity of the photoresist of the Nth photoresist layer is lower than that of the photoresist of the Nth-1 photoresist layer.

8. The wafer wet etching method according to claim 1 or 2, characterized in that: The materials of the Nth-1 photoresist layer and the Nth photoresist layer are the same, the exposure time of the Nth photoresist layer is longer than that of the Nth-1 photoresist layer, and / or the exposure light intensity of the Nth photoresist layer is greater than that of the Nth-1 photoresist layer.

9. The wafer wet etching method according to claim 1 or 2, characterized in that: The N-1 metal layer is etched, specifically including immersing the wafer in N-1 etching liquid to etch the N-1 metal layer, and the N-1 etching liquid does not react with the N-1 mask, the N metal layer and the metal layer which has been etched.

10. A wafer, characterized by, The application further provides a wet etching method. The application further provides a wet etching method.

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