A method for manufacturing a semiconductor structure
By depositing a titanium-tungsten alloy layer on the surface of an aluminum pad as a sacrificial protective layer, the problems of aluminum fluoride compounds and fluoride ion residues were solved, thereby improving the stability and yield of the semiconductor structure and avoiding process damage.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- QINGDAO AUCMA YUNLIAN INFORMATION TECHNOLOGY CO LTD
- Filing Date
- 2024-12-17
- Publication Date
- 2026-06-23
AI Technical Summary
In the prior art, the problem of aluminum fluoride compounds and fluoride ion residues affects the bonding and yield test results of semiconductor structures, and existing solutions are difficult to completely remove or may damage the process.
An additional titanium-tungsten alloy layer is deposited on the surface of the aluminum pad as a sacrificial protective layer. The passivation layer opening is formed by dry etching and the sacrificial protective layer is removed by wet cleaning. This reduces the chance of fluoride ions coming into contact with the aluminum pad, avoids the generation of aluminum fluoride compounds, and removes by-product residues simultaneously in the wet cleaning step.
It effectively reduces aluminum fluoride compounds and fluoride ion residues, improves the stability and yield of semiconductor structures, avoids damage to the passivation layer and aluminum pads, and maintains cleaning capabilities.
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Figure CN122270184A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor technology and relates to a method for fabricating a semiconductor structure. Background Technology
[0002] Aluminum (Al) is commonly used as a bonding pad in wafer fabrication due to its low melting point, good electrical conductivity, and excellent air stability. The aluminum pad serves as the interconnect interface between the wafer and the external environment, and is also the final step in the integrated circuit manufacturing process. It is typically formed by physical vapor deposition (PVD) on the top metal surface of the wafer to create a thin aluminum film. Furthermore, to protect the semiconductor surface from environmental contamination such as chemical pollutants, harmful particles, or moisture, a passivation layer, usually silicon nitride or silicon oxide, is deposited on the aluminum pad. Then, photolithography and etching processes are used to selectively expose specific areas of the passivation layer to reveal the aluminum pad, which serves as the lead for testing electrical properties and packaging, preparing for subsequent packaging work. The exposure of the passivation layer requires a dry etching process using fluorine (F) plasma. The use of fluorine plasma presents two problems: firstly, it is difficult to avoid contact between the fluorine plasma and the aluminum pad surface, which generates aluminum fluoride compounds (AlF₂) that are difficult to remove. x This can affect subsequent bonding and yield test results; on the other hand, fluoride ions are difficult to completely remove, and when wafer shipment lots are left for a long time and the storage environment is poor, fluoride precipitation and crystallization can easily occur.
[0003] One method for removing aluminum fluoride compound residues is to use multiple ashing processes combined with wet cleaning. However, when there are a lot of aluminum fluoride compound residues, it is difficult to remove them completely, and multiple cleaning processes will aggravate the damage and electrochemical corrosion of the aluminum pads.
[0004] To avoid AlF x One way to address the residue is to use non-metallic films such as silicon nitride or silicon oxide as sacrificial layers to protect the aluminum pad. However, these non-metallic films are difficult to remove and can easily damage the passivation layer and the surface of the aluminum pad that the process is intended to preserve.
[0005] To reduce fluoride ion residue, one approach is to reduce the proportion of fluoride ions used in dry etching or reduce the introduction of fluoride into wet cleaning solutions, but this will reduce etching and cleaning capabilities to some extent. Another approach is to use a large amount of deionized water (DI) in the wet cleaning process, but this still cannot completely remove fluoride ion residue.
[0006] Therefore, how to provide a method for fabricating semiconductor structures to reduce aluminum fluoride compound residues and fluoride ion residues has become an important technical problem that urgently needs to be solved by those skilled in the art.
[0007] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention
[0008] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for fabricating a semiconductor structure to solve the problems in the prior art where residual aluminum fluoride compounds affect bonding and yield test results, and residual fluoride ions affect wafer quality.
[0009] To achieve the above and other related objectives, the present invention provides a method for fabricating a semiconductor structure, comprising the following steps:
[0010] A substrate is provided, and an aluminum layer is formed on the substrate;
[0011] A sacrificial protective layer is formed on the aluminum layer, the sacrificial protective layer comprising a titanium-tungsten alloy layer;
[0012] The sacrificial protective layer and the aluminum layer are graphically represented to obtain an aluminum pad, the upper surface of which is covered by the sacrificial protective layer;
[0013] A passivation layer is formed, and a stacked structure consisting of the aluminum pad and the sacrificial protective layer on the upper surface of the aluminum pad is encapsulated in the passivation layer;
[0014] A passivation layer opening is formed in the passivation layer using dry etching. The plasma used in the dry etching contains fluorine ions. The passivation layer opening is located above a predetermined region of the stacked structure, and the bottom surface of the passivation layer opening rests on the surface of the sacrificial protective layer.
[0015] The exposed sacrificial protective layer is removed by wet cleaning to expose the aluminum pad in the predetermined area.
[0016] Optionally, forming an opening in the passivation layer using dry etching includes the following steps:
[0017] A photoresist layer is formed on the passivation layer;
[0018] The photoresist layer is patterned to obtain an opening in the photoresist layer;
[0019] Using the patterned photoresist layer as a mask and the sacrificial protective layer as an etch stop layer, the passivation layer is dry-etched to obtain the passivation layer opening.
[0020] Optionally, before using wet cleaning to remove the sacrificial protective layer, a dry cleaning step is included to remove the photoresist layer and dry etching residues.
[0021] Optionally, the cleaning solution used in the wet cleaning process includes hydrogen peroxide.
[0022] Optionally, the temperature of the cleaning solution used in the wet cleaning process is less than 50°C.
[0023] Optionally, the mass percentage of tungsten in the titanium-tungsten alloy layer ranges from 5% to 20%.
[0024] Optionally, the passivation layer includes one or more of a silicon oxide layer and a silicon nitride layer.
[0025] Optionally, the passivation layer may have a single-layer or multi-layer structure.
[0026] Optionally, the upper surface of the substrate is provided with through holes, and the aluminum layer is also filled into the through holes.
[0027] Optionally, before forming the aluminum layer on the substrate, the step of forming a diffusion barrier layer is further included.
[0028] As described above, the method for fabricating the semiconductor structure of the present invention includes the following steps: providing a substrate and forming an aluminum layer on the substrate; forming a sacrificial protective layer on the aluminum layer, the sacrificial protective layer including a titanium-tungsten alloy layer; patterning the sacrificial protective layer and the aluminum layer to obtain an aluminum pad, the upper surface of the aluminum pad being covered by the sacrificial protective layer; forming a passivation layer, the stacked structure consisting of the aluminum pad and the sacrificial protective layer on the upper surface of the aluminum pad being covered in the passivation layer; forming an opening in the passivation layer by dry etching, the passivation layer opening being located above a predetermined area of the stacked structure, the bottom surface of the passivation layer opening remaining on the surface of the sacrificial protective layer; and removing the exposed sacrificial protective layer by wet cleaning to expose the aluminum pad in the predetermined area. This invention addresses the generation of aluminum fluoride compounds and fluoride ions by depositing an additional titanium-tungsten alloy layer as a sacrificial protective layer on the aluminum pad surface. This reduces the chance of fluoride ions directly contacting the aluminum pad during the dry etching process to open the passivation layer, thereby preventing the generation of aluminum fluoride compounds and reducing fluoride ion residue on the aluminum pad surface. In the subsequent wet cleaning step to remove the sacrificial protective layer and expose the aluminum pad, all byproducts generated during the etching stage are removed simultaneously with the sacrificial protective layer. The titanium-tungsten alloy layer used in this invention is easily deposited on the aluminum pad surface without interfering with its properties. Furthermore, the removal conditions for the titanium-tungsten alloy layer are gentler, preventing damage to the passivation layer and the aluminum pad surface that the process aims to preserve. Additionally, for the unopened areas of the aluminum pad, the passivation layer is separated from the upper surface of the aluminum pad by the titanium-tungsten alloy layer. The strong interaction between the titanium-tungsten alloy layer and the aluminum layer helps limit aluminum diffusion, and the stable properties and strong oxidation resistance of the titanium-tungsten alloy layer contribute to a more stable structure at the edge of the aluminum pad. Attached Figure Description
[0029] Figure 1 The diagram shows the structure obtained after the aluminum pad, passivation layer and photoresist layer are formed on the substrate during the formation of an aluminum pad, and after exposure and development to obtain the opening of the photoresist layer.
[0030] Figure 2 The diagram shows the structure obtained after dry etching of the passivation layer based on the opening of the photoresist layer during the formation of an aluminum pad, revealing the aluminum pad.
[0031] Figure 3 This diagram shows the structure obtained after removing the photoresist layer during the formation of an aluminum pad.
[0032] Figure 4 The diagram shows that aluminum fluoride compounds remain on the sidewalls and bottom of the opened area.
[0033] Figure 5 The diagram shows a process flow chart of the method for fabricating the semiconductor structure of the present invention.
[0034] Figure 6The diagram shown is a schematic diagram of the structure obtained after forming an aluminum layer on a substrate according to the semiconductor structure fabrication method of the present invention.
[0035] Figure 7 The diagram shows a schematic of the structure obtained after forming a sacrificial protective layer on an aluminum layer, as described in the method for fabricating the semiconductor structure of the present invention.
[0036] Figure 8 The diagram shown is a schematic diagram of the structure obtained after forming a photoresist layer on a sacrificial protective layer and patterning the photoresist layer, which is a method for fabricating the semiconductor structure of the present invention.
[0037] Figure 9 The diagram shown is a schematic representation of the structure obtained after the formation of a sacrificial protective layer and an aluminum layer, illustrating the semiconductor structure fabrication method of the present invention.
[0038] Figure 10 The diagram shown is a schematic diagram of the structure obtained after forming a passivation layer in the semiconductor structure fabrication method of the present invention.
[0039] Figure 11 The diagram shown is a schematic of the structure obtained after forming a photoresist layer on a passivation layer and patterning the photoresist layer, as described in the method for fabricating the semiconductor structure of the present invention.
[0040] Figure 12 The diagram shown illustrates the structure obtained after dry etching of the passivation layer to obtain an opening in the passivation layer, which is a method for fabricating the semiconductor structure of the present invention.
[0041] Figure 13 The diagram shows a schematic of the structure obtained after removing the exposed sacrificial protective layer to expose the aluminum pad in a predetermined area, as described in the method for fabricating the semiconductor structure of the present invention.
[0042] Explanation of reference numerals in the attached figures
[0043] 101 base
[0044] 102 Aluminum Pad
[0045] 103 Passivation layer
[0046] 104 Photoresist layer
[0047] 105 Openings in the photoresist layer
[0048] 106 Aluminum Fluorine Compounds
[0049] Steps S1 to S6
[0050] 201 base
[0051] 2011 Silicon nitride layer
[0052] 2012 Low-K dielectric layer
[0053] 2013 Through Hole
[0054] 202 aluminum layer
[0055] 202a Aluminum Pad
[0056] 203 Diffusion Barrier Layer
[0057] 204 Sacrificial Protection Layer
[0058] 205 photoresist layer
[0059] 206 passivation layer
[0060] 2061 silicon oxide layer
[0061] 2062 silicon nitride layer
[0062] 207 Passivation layer opening
[0063] 208 photoresist layer Detailed Implementation
[0064] Please see Figures 1 to 3 The diagram shows the structural features of an aluminum pad formed through various steps, where:
[0065] (1) As Figure 1 As shown, an aluminum pad 102, a passivation layer 103 and a photoresist layer 104 are first formed on a substrate 101, and then exposure and development are performed to obtain an opening 105 in the photoresist layer.
[0066] (2) Figure 2 As shown, the passivation layer 103 is dry-etched based on the photoresist layer opening 105 to expose the aluminum pad 102;
[0067] (3) Figure 3 As shown, dry cleaning is performed to remove the photoresist layer 104, followed by wet cleaning.
[0068] In the above steps, during the process of dry etching the passivation layer 103 based on the photoresist layer opening 105 to expose the aluminum pad 102, it is easy to over-etch the aluminum pad 102 to the bottom, causing the dry etching gas to contact the bottom aluminum layer, resulting in the generation of a large amount of aluminum fluoride compound residue. These aluminum fluoride compound residues are difficult to remove, making the open area prone to severe pitting defects and aluminum fluoride compound residue defects.
[0069] For example, please refer to Figure 4 The diagram shows that after the dry cleaning and wet cleaning steps, aluminum fluoride compound 106 remains on the sidewalls and bottom of the opened area.
[0070] Through extensive analysis, research and experimentation, the inventors of this application have improved the manufacturing process of aluminum pads, which can help reduce the residual aluminum fluoride compounds and fluoride ions on the surface of aluminum pads and improve structural stability.
[0071] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.
[0072] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, or components.
[0073] Features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.
[0074] In the detailed description of embodiments of the present invention, for ease of explanation, the schematic diagrams illustrating the device structure may be partially enlarged without adhering to the general scale, and the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. Furthermore, in actual manufacturing, the three-dimensional spatial dimensions of length, width, and depth should be included.
[0075] For ease of description, spatial relation terms such as “below,” “under,” “lower than,” “below,” “above,” and “upper” may be used herein to describe the relationship between one element or feature shown in the accompanying drawings and other elements or features. It will be understood that these spatial relation terms are intended to include directions other than those depicted in the drawings for devices in use or operation. Furthermore, when a layer is referred to as being “between” two layers, it may be the only layer between the two layers, or there may be one or more layers in between.
[0076] In the context of this application, the structure described above the first feature may include embodiments in which the first and second features are in direct contact, or embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.
[0077] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.
[0078] This invention provides a method for fabricating a semiconductor structure; please refer to [link / reference]. Figure 5 The diagram shows the process flow of this method, which includes the following steps:
[0079] S1: Provide a substrate, and form an aluminum layer on the substrate;
[0080] S2: A sacrificial protective layer is formed on the aluminum layer, the sacrificial protective layer comprising a titanium-tungsten alloy layer;
[0081] S3: Graphicalize the sacrificial protective layer and the aluminum layer to obtain an aluminum pad, the upper surface of which is covered by the sacrificial protective layer;
[0082] S4: Form a passivation layer, in which a stacked structure consisting of the aluminum pad and the sacrificial protective layer on the upper surface of the aluminum pad is encapsulated;
[0083] S5: A passivation layer opening is formed in the passivation layer by dry etching. The plasma used in the dry etching contains fluorine ions. The passivation layer opening is located above a preset area of the stacked structure. The bottom surface of the passivation layer opening rests on the surface of the sacrificial protective layer.
[0084] S6: Use wet cleaning to remove the exposed sacrificial protective layer to expose the aluminum pad in the preset area.
[0085] The following section will detail each of the above steps in conjunction with the structural diagram.
[0086] Please refer to the following first. Figure 6 Perform step S1: Provide a substrate 201 and form an aluminum layer 202 on the substrate 201.
[0087] As an example, the substrate 201 can be a silicon substrate, germanium substrate, germanium-silicon substrate, silicon carbide substrate, or a III-V compound substrate (such as gallium nitride, gallium arsenide, etc.), or a composite substrate such as silicon-on-insulator (SOI), germanium-on-insulator (GOI), or germanium-silicon-on-insulator. The substrate 201 can be doped or undoped, and can contain doped regions of various concentrations or electrical types to achieve different functions. A semiconductor device (not shown), such as a MOS transistor, can be formed in the substrate 201, and the substrate 201 can include an interconnect layer electrically connected to the semiconductor device. The interconnect layer includes at least one metal interconnect line, and includes interlayer vias and interlayer dielectric layers.
[0088] In one embodiment, for example Figure 6 As shown, the substrate 201 includes a silicon nitride layer 2011 on an interconnect layer (not shown) and a low-k dielectric layer 2012 on the silicon nitride layer 2011. A via 2013 is provided on the upper surface of the substrate 201, the via 2013 penetrating the low-k dielectric layer 2012 and the silicon nitride layer 2011. The aluminum layer 202 is also filled into the via 2013 to electrically connect with the underlying interconnect layer.
[0089] As an example, the aluminum layer 202 can be formed using physical vapor deposition (PVD), chemical vapor deposition (CVD), or other suitable methods.
[0090] As an example, in order to prevent aluminum from diffusing into the underlying material layer, a step of forming a diffusion barrier layer 203 is included before forming the aluminum layer 202 on the substrate 201. The diffusion barrier layer 203 may be selected from one or more of titanium (Ti) layer, titanium nitride (TiN) layer, tantalum (Ta) layer, and tantalum nitride (TaN) layer, or other suitable material layers.
[0091] As an example, the surface of the aluminum layer 202 can be a flat surface or it can have a certain depression at the through hole.
[0092] Please see again Figure 7 Step S2 is performed: a sacrificial protective layer 204 is formed on the aluminum layer 202, wherein the sacrificial protective layer 204 includes a titanium-tungsten alloy layer.
[0093] Specifically, the material selection for the sacrificial protective layer 204 needs to consider the following factors:
[0094] (1) The sacrificial protective layer 204 needs to be able to be deposited well on the surface of the aluminum layer and not easily peeled off;
[0095] (2) The surface of the sacrificial protective layer 204 can be well deposited with a passivation film;
[0096] (3) The sacrificial protective layer 204 and the passivation layer have a high selectivity in the subsequent dry etching process of opening the passivation layer, ensuring that the sacrificial protective layer 204 cannot be etched through in the dry etching process of opening the passivation layer so that the dry etching plasma can contact the aluminum pad.
[0097] (4) The presence of the sacrificial protective layer 204 cannot affect the film properties of the passivation layer and the aluminum pad;
[0098] (5) The subsequent wet cleaning solution needs to have a certain etching rate on the sacrificial protective layer 204 to ensure that the sacrificial protective layer 204 can be removed without damaging the passivation layer and aluminum pad.
[0099] In this embodiment, titanium-tungsten alloy (TiW) is selected as the sacrificial protective layer 204, which can well meet the above conditions.
[0100] As an example, in the titanium-tungsten alloy layer, the mass percentage of tungsten ranges from 5% to 20%, such as 8%, 10%, 12%, 15%, etc.
[0101] Specifically, the thickness of the titanium-tungsten alloy layer can be adjusted according to the thickness and material of the passivation layer to be opened, and no specific limitation is made here.
[0102] Please see again Figures 8 to 9 Step S3 is performed: the sacrificial protective layer 204 and the aluminum layer 202 are graphically visualized to obtain an aluminum pad 202a, the upper surface of which is covered by the sacrificial protective layer 204.
[0103] As an example, graphically representing the sacrificial protective layer 204 and the aluminum layer 202 includes the following steps:
[0104] (1) As Figure 8 As shown, a photoresist layer 205 is formed on the sacrificial protective layer 204 by spin coating or other suitable methods, and the photoresist layer 205 is patterned by photolithography processes such as exposure and development.
[0105] (2) Figure 9 As shown, the patterned photoresist layer 205 is used as a mask to dry etch the sacrificial protective layer 204 and the aluminum layer 202 to obtain the aluminum pad 202a, the upper surface of which is covered by the sacrificial protective layer 204.
[0106] As an example, the steps for removing the photoresist layer 205, and the methods for removing the photoresist layer 205, include but are not limited to wet stripping.
[0107] Please see again Figure 10 Step S4 is performed: a passivation layer 206 is formed, in which a stacked structure consisting of the aluminum pad 202a and the sacrificial protection layer 204 on the upper surface of the aluminum pad 202a is wrapped in the passivation layer 206.
[0108] As an example, the passivation layer 206 can be a single-layer structure or a multi-layer structure.
[0109] As an example, the passivation layer 206 includes one or more of a silicon oxide layer and a silicon nitride layer. In one embodiment, for example... Figure 10 As shown, the passivation layer 206 includes a silicon oxide layer 2061 and a silicon nitride layer 2062 deposited sequentially.
[0110] Please see again Figures 11 to 12 Step S5 is performed: a passivation layer opening 207 is formed in the passivation layer 206 by dry etching. The plasma used in the dry etching contains fluorine ions. The passivation layer opening 207 is located above the preset area of the stacked structure. The bottom surface of the passivation layer opening 207 rests on the surface of the sacrificial protection layer 204.
[0111] As an example, forming the passivation layer opening 207 in the passivation layer 206 using dry etching includes the following steps:
[0112] (1) As Figure 11 As shown, a photoresist layer 208 is formed on the passivation layer 206 by spin coating or other suitable methods, and the photoresist layer 208 is patterned by photolithography processes such as exposure and development.
[0113] (2) Figure 12 As shown, the patterned photoresist layer 208 is used as a mask, and the sacrificial protection layer 204 is used as an etch stop layer. The passivation layer 206 is dry-etched to obtain the passivation layer opening 207.
[0114] As an example, the etching gas used in the dry etching process includes, but is not limited to, fluorine-containing compounds such as CF4, CHF3, C3F8, and C4F8, which can be ionized to generate fluorine ions that bombard the surface of the passivation layer 206 to achieve etching.
[0115] Specifically, the dry etching stopping on the sacrificial protective layer 204 can reduce the effect of plasma on aluminum, avoid severe pitting defects in the passivation layer open area, and reduce aluminum fluoride (AlF) compounds. xThe formation of residual fluoride ions and voids refers to the formation of tiny holes or pits on the surface of the film, while aluminum fluoride compound residual defects refer to aluminum fluoride compound particles attached to the sidewalls and bottom of the open area. Both void and aluminum fluoride compound residual defects have a serious impact on device performance, such as affecting subsequent bonding and yield test results. Under certain conditions, such as when the shipment lot is left for a long time in a poor environment, fluoride ion residual can easily precipitate and crystallize, affecting product quality.
[0116] As an example, after forming the passivation layer opening 207, a dry stripping step is included to remove the photoresist layer 208 and dry etching residues. The dry stripping uses plasma or chemical gases to remove the photoresist layer 208 and dry etching residues, typically performed in a low-pressure plasma environment. Advantages of dry stripping include better directionality and linewidth control.
[0117] Please see again Figure 13 Perform step S6: use wet stripping to remove the exposed sacrificial protective layer 204 to expose the aluminum pad 202a in the preset area.
[0118] As an example, the cleaning solution used in the wet cleaning includes hydrogen peroxide (H2O2), and the hydrogen peroxide wet cleaning method can effectively remove the sacrificial protective layer 204, photoresist residues, and aluminum fluoride compounds (if any).
[0119] In some embodiments, the cleaning solution used in the wet cleaning is not limited to H2O2, but can also be an EKC580+H2O2 system, etc. EKC580 is a highly concentrated photoresist remover, and mixing it with hydrogen peroxide can also achieve good cleaning results.
[0120] As an example, the temperature of the cleaning solution used in the wet cleaning is less than 50°C, such as cleaning solutions at 40°C, 30°C, or room temperature.
[0121] Thus, a semiconductor structure containing an aluminum pad was fabricated.
[0122] Specifically, this invention uses a titanium-tungsten alloy layer as the sacrificial protective layer 204, and combines it with hydrogen peroxide or a hydrogen peroxide-based wet cleaning solution. This not only gently removes the titanium-tungsten alloy layer without damaging the passivation layer and aluminum pad surface that the process aims to retain, but also avoids introducing additional fluoride ions like other cleaning solutions (such as hydrofluoric acid solutions), thus further reducing fluoride ion residue. In other words, this invention can further reduce fluoride ion residue without compromising cleaning efficiency. If non-metallic films such as silicon nitride or silicon oxide are used as the sacrificial protective layer 204, it will be more difficult to remove than the titanium-tungsten alloy layer. Furthermore, if silicon oxide and silicon nitride layers are used as the sacrificial protective layer 204, hydrofluoric acid solution and high-temperature hot phosphoric acid are required for removal, respectively. The use of these two acid solutions is difficult to avoid causing damage to the passivation layers of silicon oxide and silicon nitride layers that the process itself needs to retain, which is undesirable. For example, the use of hydrofluoric acid solution will etch the surface of the aluminum pad and damage it. The temperature of high-temperature hot phosphoric acid is generally greater than 100°C. In a high-temperature environment, the copper (Cu) enrichment and migration at the grain boundaries of the aluminum pad is easily aggravated, which will lead to an intensified galvanic reaction on the surface of the aluminum pad and cause corrosion of the aluminum pad surface.
[0123] Specifically, for the unopened area of the aluminum pad 202a, the passivation layer 206 and the upper surface of the aluminum pad 202a are separated by the sacrificial protection layer 204, i.e., the titanium-tungsten alloy layer. Due to the strong interaction between the titanium-tungsten alloy layer and the aluminum layer, it helps to limit aluminum diffusion. For example, when a titanium-tungsten alloy layer with a tungsten mass content of 10% acts as a barrier layer, it forms a strong interaction with the aluminum, and Al is formed between the grain boundaries of the two at different time stages. 12 Over a long period of time, a monoclinic phase alloy, Al4W, will also form from the two alloys W and Al5W. These alloy materials are stable and can limit Al diffusion to the greatest extent, thus playing a good blocking role. In addition, due to the excellent thermal stability and strong oxidation resistance of the titanium-tungsten alloy layer, for example, no peeling occurs even at 750°C in an oxygen atmosphere, which makes the structure of the edge region of the aluminum pad 202a more stable.
[0124] In summary, the method for fabricating the semiconductor structure of the present invention includes the following steps: providing a substrate and forming an aluminum layer on the substrate; forming a sacrificial protective layer on the aluminum layer, the sacrificial protective layer including a titanium-tungsten alloy layer; patterning the sacrificial protective layer and the aluminum layer to obtain an aluminum pad, the upper surface of the aluminum pad being covered by the sacrificial protective layer; forming a passivation layer, the stacked structure consisting of the aluminum pad and the sacrificial protective layer on the upper surface of the aluminum pad being covered in the passivation layer; forming an opening in the passivation layer by dry etching, the passivation layer opening being located above a predetermined area of the stacked structure, the bottom surface of the passivation layer opening remaining on the surface of the sacrificial protective layer; and removing the exposed sacrificial protective layer by wet cleaning to expose the aluminum pad in the predetermined area. This invention addresses the generation of aluminum fluoride compounds and fluoride ions by depositing an additional titanium-tungsten alloy layer as a sacrificial protective layer on the aluminum pad surface. This reduces the chance of fluoride ions directly contacting the aluminum pad during the dry etching process to open the passivation layer, thereby avoiding or significantly reducing the generation of aluminum fluoride compounds and minimizing fluoride ion residue on the aluminum pad surface. In the subsequent wet cleaning step to remove the sacrificial protective layer and expose the aluminum pad, all byproducts generated during the etching stage are removed simultaneously with the sacrificial protective layer. The titanium-tungsten alloy layer used in this invention is easily deposited on the aluminum pad surface without interfering with its properties. Furthermore, the removal conditions for the titanium-tungsten alloy layer are gentler, preventing damage to the passivation layer and the aluminum pad surface that the process aims to preserve. Additionally, for the unopened areas of the aluminum pad, the passivation layer is separated from the upper surface of the aluminum pad by the titanium-tungsten alloy layer. The strong interaction between the titanium-tungsten alloy layer and the aluminum layer helps limit aluminum diffusion, and the stable properties and strong oxidation resistance of the titanium-tungsten alloy layer contribute to a more stable structure at the edge of the aluminum pad. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.
[0125] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.
Claims
1. A method of fabricating a semiconductor structure, the method comprising: Includes the following steps: A substrate is provided, and an aluminum layer is formed on the substrate; A sacrificial protective layer is formed on the aluminum layer, the sacrificial protective layer comprising a titanium-tungsten alloy layer; The sacrificial protective layer and the aluminum layer are graphically represented to obtain an aluminum pad, the upper surface of which is covered by the sacrificial protective layer; A passivation layer is formed, and a stacked structure consisting of the aluminum pad and the sacrificial protective layer on the upper surface of the aluminum pad is encapsulated in the passivation layer; A passivation layer opening is formed in the passivation layer using dry etching. The plasma used in the dry etching contains fluorine ions. The passivation layer opening is located above a predetermined region of the stacked structure, and the bottom surface of the passivation layer opening rests on the surface of the sacrificial protective layer. The exposed sacrificial protective layer is removed by wet cleaning to expose the aluminum pad in the predetermined area.
2. The method of fabricating a semiconductor structure of claim 1, wherein, The process of forming an opening in the passivation layer using dry etching includes the following steps: A photoresist layer is formed on the passivation layer; The photoresist layer is patterned to obtain an opening in the photoresist layer; Using the patterned photoresist layer as a mask and the sacrificial protective layer as an etch stop layer, the passivation layer is dry-etched to obtain the passivation layer opening.
3. The method of claim 2, wherein: Before using wet cleaning to remove the sacrificial protective layer, the process also includes a dry cleaning step to remove the photoresist layer and dry etching residues.
4. The method of fabricating a semiconductor structure according to any one of claims 1-3, wherein: The wet cleaning process uses hydrogen peroxide as the cleaning solution.
5. The method of claim 4, wherein: The temperature of the cleaning solution used in the wet cleaning process is less than 50°C.
6. The method of claim 1, wherein: In the titanium-tungsten alloy layer, the mass percentage of tungsten ranges from 5% to 20%.
7. The method of claim 1, wherein: The passivation layer can be a single-layer or multi-layer structure.
8. The method of fabricating a semiconductor structure of claim 1 or 7, wherein: The passivation layer includes one or more of silicon oxide and silicon nitride layers.
9. The method of fabricating a semiconductor structure of claim 1, wherein: The upper surface of the substrate is provided with through holes, and the aluminum layer is also filled into the through holes.
10. The method of claim 1, wherein: Before forming an aluminum layer on the substrate, the step of forming a diffusion barrier layer is also included.