Preparation method of metal bonding pad and semiconductor device
By forming a metal barrier layer on the top surface of the metal pad and adopting a step-by-step etching method, the problem of difficult removal of by-products during the etching process is solved, the metal pad surface is protected, and the packaging effect and chip yield are improved.
Patent Information
- Application Number
- CN202510919744.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-03
- Publication Date
- 2025-10-17
AI Technical Summary
The byproducts produced during the etching process of existing technologies are difficult to remove, resulting in fluorine precipitation and crystallization on the surface of the aluminum pad, affecting the conductive performance and causing packaging failure, and existing cleaning methods may damage the aluminum layer.
A metal barrier layer is formed on the top surface of the metal pad. A step-by-step etching method is adopted, using the metal barrier layer as an etching stop layer. The passivation structure is first etched to form a first opening, then cleaned with an inorganic acid solution, and then the metal barrier layer is etched to expose the metal pad surface.
It achieves efficient removal of by-products, protects the surface of metal pads, avoids defects and damage, and improves packaging effects and chip yield.
Smart Images
Figure CN120809591A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of semiconductor manufacturing, in particular to a preparation method of metal pad and semiconductor device. BACKGROUND
[0002] In the semiconductor process, the back-end of line (BEOL) mainly involves the construction of metal interconnection layer, to ensure that each transistor and component can be electrically connected, so as to facilitate subsequent testing and packaging. In the preparation of aluminum pad (AlPad) in the back-end process, etching process is needed to open the passivation layer and other film layers, to expose part of the aluminum layer, so as to realize electrical lead-out.
[0003] Please refer to Figures 1 to 3 , the top of the aluminum layer 100 is covered with an anti-reflection layer 101, and the sidewall of the aluminum layer 100 and the anti-reflection layer 101 are covered with a first passivation layer 102 and a second passivation layer 103 in turn, to play the role of insulation protection. In the existing preparation process, in order to realize electrical lead-out, fluorine-containing gas is generally used to etch the second passivation layer 103, the first passivation layer 102 and the anti-reflection layer 101 in turn, to expose part of the surface of the aluminum layer 100. However, a large amount of by-product P containing fluorine will be produced in the etching process. These by-products P are deposited on the sidewall of the slot and the part of the surface of the aluminum layer 100 exposed, and it is also difficult to remove these by-products P in the subsequent wet cleaning process. In addition, when the by-products P meet water vapor, the problem of aluminum pad fluorine precipitation crystal F will occur, which will affect the electrical conductivity, and even lead to packaging failure and chip yield reduction. For this reason, the existing process will use DSP+ solution for cleaning to remove by-products P. Although DSP+ solution has strong removal ability, it will cause damage to the aluminum layer 100, such as large-size pits and other defects, which will also lead to packaging failure and other problems.
[0004] Therefore, a new preparation method is needed to solve the above technical problems. SUMMARY
[0005] The purpose of the present application is to provide a preparation method of metal pad and semiconductor device, to solve the technical problem of how to balance the removal of by-products and the protection of the surface structure of metal pad.
[0006] To solve the above technical problems, the present application provides a preparation method of metal pad, comprising:
[0007] providing a semiconductor structure, the surface of the semiconductor structure forming a metal pad;
[0008] forming a metal barrier layer covering the top surface of the metal pad;
[0009] forming a passivation structure covering sidewalls of the metal pad and sidewalls and top surface of the metal barrier layer;
[0010] etching the passivation structure to form a first opening; and the first opening exposes part of the top surface of the metal barrier layer;
[0011] cleaning the first opening with an inorganic acid solution;
[0012] etching the exposed metal barrier layer to form a second opening; the second opening is in communication with the first opening and exposes part of the top surface of the metal pad.
[0013] Optionally, in the method for preparing the metal pad, the inorganic acid solution comprises a DSP+ solution, and the solution temperature ranges from 20 to 30°C.
[0014] Optionally, in the method for preparing the metal pad, after forming the second opening, the method for preparing the metal pad further comprises cleaning the second opening with an organic acid solution, and the solution temperature ranges from 20 to 40°C.
[0015] Optionally, in the method for preparing the metal pad, an anti-reflection layer is further formed on the metal pad, and the metal barrier layer covers the top surface of the anti-reflection layer.
[0016] Optionally, in the method for preparing the metal pad, the material of the metal barrier layer comprises titanium nitride, and the material of the anti-reflection layer comprises silicon oxynitride.
[0017] Optionally, in the method for preparing the metal pad, in the process of forming the second opening, the metal barrier layer and the anti-reflection layer are etched in sequence until part of the top surface of the metal pad is exposed.
[0018] Optionally, in the method for preparing the metal pad, in the process of etching to form the second opening, the etching gas comprises chlorine and carbon fluoride.
[0019] Optionally, in the method for preparing the metal pad, the passivation structure comprises a first passivation layer and a second passivation layer arranged in layers; and
[0020] In the process of forming the passivation structure, the first passivation layer and the second passivation layer are formed in sequence on the sidewalls of the metal pad and the sidewalls and top surface of the metal barrier layer.
[0021] Optionally, in the preparation method of the metal pad, in the process of forming the first opening, the second passivation layer and the first passivation layer are etched in sequence until part of the top surface of the metal barrier layer is exposed; wherein the etching gas comprises carbon fluoride and oxygen.
[0022] Based on the same inventive concept, the application further provides a semiconductor device prepared by the preparation method of the metal pad.
[0023] In summary, the application provides a preparation method of a metal pad and a semiconductor device. Compared with the prior art, the preparation method of the metal pad is to form a metal barrier layer on the top surface of the metal pad in advance, and then open the metal pad by using a step-by-step etching method. That is, the passivation structure is etched first to form the first opening. And in this etching step, the metal barrier layer acts as an etching stop layer, so that the by-products generated by etching will adhere to the surface of the metal barrier layer instead of the surface of the metal pad. Based on this, the inorganic acid solution with strong cleaning ability can be used to efficiently remove the by-products, and under the protection of the metal barrier layer, the surface of the metal pad will not be damaged. Subsequently, the exposed metal barrier layer is etched and removed, and the metal pad is opened. Therefore, the preparation method provided by the application not only realizes strong removal of by-products, but also protects the metal pad, avoids defects and damage of the metal pad, effectively guarantees the electrical lead-out of the metal pad, and is beneficial to improve the subsequent packaging effect and chip yield. BRIEF DESCRIPTION OF DRAWINGS
[0024] Those skilled in the art will understand that the provided drawings are for better understanding of the application and do not constitute any limitation on the scope of the application.
[0025] Figure 1 is a structural schematic diagram of an aluminum pad in the prior art.
[0026] Figure 2 is a structural schematic diagram of by-products generated by etching the first passivation layer and the second passivation layer in the prior art.
[0027] Figure 3 is a structural schematic diagram of crystallization on the surface of an aluminum pad in the prior art.
[0028] Figure 4 is a flowchart of the preparation method of the metal pad in the embodiment of the application.
[0029] Figure 5 is a structural schematic diagram of a semiconductor structure and a metal pad in the embodiment of the application.
[0030] Figure 6 is a distribution schematic diagram of the metal barrier layer in the embodiment of the application.
[0031] Figure 7 is a structural schematic diagram of forming a first passivation layer and a second passivation layer in an embodiment of the present application.
[0032] Figure 8 is a schematic diagram of etching to form a first opening in an embodiment of the present application.
[0033] Figure 9 is a structural schematic diagram of cleaning the first opening by using DSP+solution in an embodiment of the present application.
[0034] Figure 10 is a schematic diagram of etching to form a second opening in an embodiment of the present application.
[0035] and in the drawings:
[0036] 100-aluminum layer; 101-anti-reflection layer; 102-second passivation layer; 103-second passivation layer;
[0037] 200-metallic pad; 201-main device layer; 202-copper layer; 203-protection layer; 204-isolation layer; 205-anti-reflection layer; 206-metallic barrier layer; 207-first passivation layer; 208-second passivation layer;
[0038] P-byproduct; F-crystal; K1-first opening; K2-second opening. DETAILED DESCRIPTION
[0039] To make the objectives, advantages and features of the present application clearer, the following further describes the present application in combination with the drawings and specific embodiments. It should be noted that the drawings are very simplified and not drawn in proportion, and are only used to facilitate and clarify the purpose of assisting the description of the embodiments of the present application. In addition, the structures shown in the drawings are often a part of the actual structure. In particular, the emphasis of each drawing needs to be different, and sometimes different proportions are used. It should also be understood that, unless specifically described or indicated, the terms "first", "second", "third" and the like in the description are only used to distinguish the components, elements, steps and the like in the description, and are not used to represent the logical relationship or sequential relationship between the components, elements, steps and the like.
[0040] Please refer to Figure 4 The present embodiment provides a preparation method of a metallic pad, comprising:
[0041] Step one S10: providing a semiconductor structure, a surface of the semiconductor structure forming a metallic pad;
[0042] Step two S20: forming a metallic barrier layer, the metallic barrier layer covering a top surface of the metallic pad;
[0043] Step three S30: forming a passivation structure covering the sidewall of the metal pad and the sidewall and top surface of the metal barrier layer;
[0044] Step four S40: etching the passivation structure to form a first opening; and the first opening exposes part of the top surface of the metal barrier layer;
[0045] Step five S50: cleaning the first opening with an inorganic acid solution;
[0046] Step six S60: etching the exposed metal barrier layer to form a second opening; the second opening communicates with the first opening, and exposes part of the top surface of the metal pad.
[0047] Based on this, the preparation method provided by the embodiment realizes the opening of the metal pad by forming a metal barrier layer on the top surface of the metal pad and then using step-by-step etching. Not only is the by-product removed effectively, but also the metal pad is protected from defects and damage, effectively ensuring the electrical lead-out of the metal pad and improving the subsequent packaging effect and chip yield.
[0048] The following will specifically describe the preparation method of the metal pad provided by the embodiment. Figures 4 to 10
[0049] Specifically, the preparation method of the metal pad comprises:
[0050] Step one S10: referring to Figure 5 provides a semiconductor structure, and the surface of the semiconductor structure is formed with a metal pad 200.
[0051] The semiconductor structure referred to in the embodiment is the main device structure of a chip. In the embodiment, the specific device type to which the semiconductor structure belongs is not limited, and regardless of the type of semiconductor device, a plurality of metal pads 200 are arranged on the top thereof to realize the electrical connection of the internal and external structures. Optionally, the material of the metal pad 200 includes but is not limited to aluminum.
[0052] For example, the semiconductor structure includes a main device layer 201, a copper layer 202, and a protective layer 203 surrounding the copper layer 202. Optionally, the material of the protective layer 203 includes, but is not limited to, silicon nitride. Further, an isolation layer 204 is formed between the protective layer 203 and the metal pad 200. Optionally, the material of the isolation layer 204 includes polyethylene oxide (PEOX), which is used to improve the compatibility of the interface between the copper layer 202 and the metal pad 200, and to inhibit intermetallic reaction and improve connection reliability. In the drawings, the metal pad 200 and the copper layer 202 are not directly connected, but in the actual layout, the metal pad 200 and the copper layer 202 are connected to realize electrical connection with the main device layer 201.
[0053] Further, the metal pad 200 is formed by photolithography of a metal pad material layer covering the isolation layer 204. In order to ensure that the metal pad 200 has a better appearance, an anti-reflective layer 205 is covered on the top of the metal pad material layer when etching the metal pad material layer. The anti-reflective layer 205 can reduce the interference of metal surface reflection on exposure in the photolithography stage; and the anti-reflective layer 205 can also play a role in edge protection, improving the photolithography effect. Optionally, the material of the anti-reflective layer 205 includes, but is not limited to, silicon oxynitride.
[0054] Step two S20: please refer to Figure 5 and Figure 6 to form a metal barrier layer 206 covering the top surface of the metal pad 200.
[0055] Based on the anti-reflective layer 205 formed on the metal pad 200, the metal barrier layer 206 covers the surface of the anti-reflective layer 205. It should be noted that the metal barrier layer 206 is not only used as an etching barrier for subsequent etching of the first opening, but also as a sacrificial protective layer for subsequent cleaning of by-products. In addition, the material of the metal barrier layer 206 includes, but is not limited to, titanium nitride, so that the metal barrier layer 206 can also play a role in anti-reflection, which is beneficial to improve the effect of photolithography technology in subsequent processes.
[0056] Optionally, the metal barrier layer 206 is formed by chemical vapor deposition (CVD) or physical vapor deposition (PVD). The film thickness of the metal barrier layer 206 is greater than the film thickness of the anti-reflective layer 205, so as to fully realize its process effect.
[0057] Step three S30: please refer to Figure 7 to form a passivation structure covering the sidewall of the metal pad 200 and the sidewall and top surface of the metal barrier layer 206.
[0058] Since the metal pad 200 is made of aluminum material, and the chemical properties of aluminum are very active, it can react with oxygen at room temperature. Therefore, in order to avoid the metal pad 200 from being oxidized, and to avoid the conductive performance of the metal pad 200 from affecting other film layer structures, after the metal barrier layer 206 is formed, the first passivation layer 207 covering the sidewall of the metal pad 200, the sidewall of the anti-reflection layer 205 and the sidewall and top surface of the metal barrier layer 206 is formed, and then the second passivation layer 208 is formed on the surface of the first passivation layer 207. The first passivation layer 207 and the second passivation layer 208 constitute the passivation structure of the embodiment.
[0059] Optionally, the first passivation layer 207 is formed by using a high-density plasma (HDP) deposition process, and the material of the first passivation layer 207 includes but is not limited to silicon dioxide. In addition, the material of the second passivation layer 208 includes but is not limited to silicon nitride. It can be understood that the adhesion between silicon dioxide and aluminum is better, and silicon dioxide has better stress buffering effect, so the first passivation layer 207 directly contacts the metal pad 200 to serve as a basic protection layer for the metal pad 200. In addition, silicon nitride has better hardness and corrosion resistance, and can effectively block external interference for a long time, so the second passivation layer 208 is coated on the outer surface of the first passivation layer 207. Based on this, the insulation protection of the metal pad 200 is effectively realized under the joint action of the first passivation layer 207 and the second passivation layer 208.
[0060] Step four S40: please refer to Figure 8 , the passivation structure is etched to form a first opening K1; and the first opening K1 exposes part of the top surface of the metal barrier layer 206.
[0061] Optionally, the second passivation layer 208 and the first passivation layer 207 are etched by using fluorine-containing gas in sequence until part of the top surface of the metal barrier layer 206 is exposed. The fluorine-containing gas includes but is not limited to carbon fluoride, and oxygen can also be used as a protective gas during etching.
[0062] During the etching of the passivation structure, a large amount of by-products P will be formed. These by-products P adhere to the inner wall of the first opening K1. Among them, the metal barrier layer 206 and the passivation structure have obvious etching selectivity difference, so as to play the role of etching stop layer in this etching process, so as to avoid the first opening K1 extending to the surface of the metal pad 200, thereby avoiding the by-products P adhering to the surface of the metal pad 200.
[0063] Step five S50: please refer to Figure 9 , using inorganic acid solution to clean the first opening K1.
[0064] Optionally, the inorganic acid solution includes: DSP+ solution, and the solution temperature range is: 20℃-30℃.
[0065] It should be noted that the main components of the DSP+ solution include hydrofluoric acid. The hydrofluoric acid solution can strongly remove the byproduct P. At the same time, it can erode part of the metal barrier layer 206, but it will not erode the anti-reflection layer 205 and the metal pad 200 exposed below the metal barrier layer 206. Thus, in the process of cleaning the first opening K1, the metal barrier layer 206 plays a role of corrosion sacrifice to avoid direct cleaning of the metal pad 200, which causes the surface of the metal pad 200 to be corroded and appear defects such as pits, and takes into account the efficient removal of the byproduct P and the protection of the metal pad 200.
[0066] Step six S60: please refer to Figure 10 , etching the exposed metal barrier layer 206 to form a second opening K2; the second opening K2 communicates with the first opening K1, and exposes part of the top surface of the metal pad 200.
[0067] In the process of etching to form the second opening K2, the metal barrier layer 206 and the anti-reflection layer 205 are etched in sequence until part of the top surface of the metal pad 200 is exposed. The etching gas used includes but is not limited to chlorine and carbon fluoride.
[0068] In addition, after the second opening K2 is formed, there will also be a certain amount of etching residue. Optionally, an organic acid solution is used to clean the second opening K2, and the solution temperature range is: 20℃-40℃. The organic acid solution includes but is not limited to NE111 finished acid solution.
[0069] It should be noted that compared with the inorganic acid solution, the organic acid solution is relatively weak in acidity and has very little corrosive effect on metal materials. Therefore, an appropriate concentration of the organic acid solution can not only effectively remove the etching residue on the surface of the metal pad 200, but also will not damage the surface of the metal pad 200, avoiding affecting the subsequent electrical connection effect of the metal pad 200, which is conducive to improving the packaging effect and chip yield.
[0070] Based on the same concept, the embodiment also provides a semiconductor device. The semiconductor device is prepared by using the preparation method of the metal pad.
[0071] To sum up, the embodiment provides a preparation method of a metal pad and a semiconductor device. In the preparation method of the metal pad, a relatively thick metal barrier layer 206 is formed on the top surface of the metal pad 200 in advance, and then the metal pad 200 is opened by using a step-by-step etching method. That is, the passivation structure is etched first to form the first opening K1. In this etching step, the metal barrier layer 206 serves as an etching stop layer, and the by-product P generated by etching is attached to the surface of the metal barrier layer 206 instead of the surface of the metal pad 200. Based on this, the inorganic acid solution with strong cleaning ability can be used to efficiently remove the by-product P, and the surface of the metal pad 200 is not damaged under the protection of the metal barrier layer 206. Subsequently, the exposed metal barrier layer 206 is etched and removed, and the metal pad 200 is opened. Therefore, the preparation method provided in the embodiment not only realizes strong removal of the by-product P, but also protects the metal pad 200, avoids defects and damage of the metal pad 200, effectively guarantees the electrical lead-out of the metal pad 200, and is beneficial to improving the subsequent packaging effect and chip yield.
[0072] In addition, it should be appreciated that, although the present application has been disclosed with the preferred embodiments as above, the above embodiments are not intended to limit the present application. Any person skilled in the art can make many possible changes and modifications to the technical solutions disclosed above, or modify equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions 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, without departing from the content of the technical solutions of the present application, still belongs to the protection scope of the technical solutions of the present application.
Claims
1. A method for preparing a metal pad, characterized in that: include: Providing a semiconductor structure, wherein a metal pad is formed on a surface of the semiconductor structure; forming a metal barrier layer, wherein the metal barrier layer covers a top surface of the metal pad; forming a passivation structure, the passivation structure covering the sidewalls of the metal pad and the sidewalls and top surface of the metal barrier layer; etching the passivation structure to form a first opening; The first opening exposes a portion of the top surface of the metal barrier layer; Cleaning the first opening with an inorganic acid solution; etching the exposed metal barrier layer to form a second opening; The second opening is connected to the first opening and exposes a portion of the top surface of the metal pad.
2. The method for preparing a metal pad according to claim 1, wherein: The inorganic acid solution includes: DSP+ solution, and the solution temperature range is: 20°C to 30°C.
3. The method for preparing a metal pad according to claim 1, wherein: After forming the second opening, the method for preparing the metal pad further includes: cleaning the second opening with an organic acid solution, and the solution temperature range is: 20° C. to 40° C.
4. The method for preparing a metal pad according to claim 1, wherein: An anti-reflection layer is also formed on the metal pad, and the metal barrier layer covers the top surface of the anti-reflection layer.
5. The method for preparing a metal pad according to claim 4, wherein: The material of the metal barrier layer includes titanium nitride, and the material of the anti-reflection layer includes silicon oxynitride.
6. The method for preparing a metal pad according to claim 4, wherein: During the process of forming the second opening, the metal barrier layer and the anti-reflection layer are sequentially etched until a portion of the top surface of the metal pad is exposed.
7. The method for preparing a metal pad according to claim 1 or 6, wherein: During the process of etching to form the second opening, etching gases used include chlorine and carbon fluoride.
8. The method for preparing a metal pad according to claim 1, wherein: The passivation structure includes a first passivation layer and a second passivation layer that are stacked; and During the process of forming the passivation structure, the first passivation layer and the second passivation layer are sequentially formed on the sidewalls of the metal pad and the sidewalls and top surface of the metal barrier layer.
9. The method for preparing a metal pad according to claim 8, wherein: During the process of forming the first opening, the second passivation layer and the first passivation layer are sequentially etched until a portion of the top surface of the metal barrier layer is exposed; wherein the etching gas used includes carbon fluoride and oxygen.
10. A semiconductor device, characterized in that: The metal pad is prepared by the method for preparing the metal pad according to any one of claims 1 to 9.