Method for forming metal silicide

Abstract

The application relates to a metal silicide forming method, which comprises the following steps: providing a substrate; forming a device structure on the substrate, and forming a nickel-platinum metal layer on the surface of the device structure for preparing a metal silicide layer; performing a first annealing treatment to form the metal silicide layer on the surface of the device structure; after the first annealing treatment, metal contaminants including unreacted nickel-platinum metal layer are left on the surface of the metal silicide layer; under the condition that the temperature is less than or equal to 100 DEG C, the substrate is cleaned by using a first cleaning solution, the metal contaminants are dissolved and removed, and a passivation layer is formed on the surface of the metal silicide layer; the first cleaning solution comprises sulfuric acid, hydrogen peroxide and a functionalized ionic liquid; an intermediate solvent is used to replace the first cleaning solution in which the metal contaminants are dissolved; and a second cleaning solution is used to remove the remaining metal contaminants. The method can reduce the equipment requirement and maintenance cost for removing unreacted nickel-platinum alloy, and can ensure the film forming quality and electrical performance stability of the metal silicide.

Description

Technical Field

[0001] This application relates to the field of integrated circuit technology, and in particular to a method for forming metal silicides. Background Technology

[0002] Metal silicides, with their advantages of simple processing, excellent high-temperature stability, and low resistivity, are widely used to improve the conductivity of polysilicon gates and source / drain regions in integrated circuit transistors and have been extensively studied. Nickel silicide (NiSi), due to its lower silicon consumption ratio during formation compared to other mainstream metal silicides and the absence of significant narrow-line effects, plays a crucial role in improving device conduction efficiency, reducing power consumption, and minimizing device size.

[0003] However, as device sizes continue to shrink, many problems have gradually emerged in the metal silicide fabrication process. Summary of the Invention

[0004] Therefore, it is necessary to provide a method for forming metal silicides to address the technical problems in the prior art, which can at least reduce the equipment requirements and maintenance costs for removing unreacted nickel-platinum alloys, while ensuring the film quality and electrical performance stability of the metal silicides.

[0005] In a first aspect, this application provides a method for forming a metal silicide, comprising: providing a substrate; forming a device structure on the substrate, wherein a nickel-platinum metal layer for preparing a metal silicide layer is formed on the surface of the device structure; wherein the platinum content in the nickel-platinum metal layer is not less than 10%.

[0006] The substrate is subjected to a first annealing process to form a metal silicide layer on the surface of the device structure. After the first annealing process, metal contaminants remain on the surface of the metal silicide layer, including unreacted nickel-platinum metal layers.

[0007] At a temperature of 100°C or less, the substrate after the first annealing treatment is cleaned with a first cleaning solution to dissolve and remove metal contaminants; while dissolving and removing metal contaminants, a passivation layer is formed on the surface of the metal silicide layer; the first cleaning solution includes sulfuric acid, hydrogen peroxide and functionalized ionic liquid;

[0008] An intermediate solvent was used to replace the first cleaning solution containing dissolved metal contaminants, and the substrate after cleaning with the intermediate solvent was then subjected to a first water wash.

[0009] The substrate after the first water wash was cleaned with a second cleaning solution to remove any remaining metal contaminants on the surface of the metal silicide layer.

[0010] In some embodiments, the passivation layer includes a contact layer and a protective layer arranged sequentially in a direction away from the substrate;

[0011] The contact layer is used to reduce contact resistance;

[0012] The protective layer is used to inhibit the oxidation of metal silicides.

[0013] In some embodiments, the temperature range of the first cleaning fluid is 80°C to 100°C.

[0014] In some embodiments, one or more of the following conditions are met:

[0015] In the first cleaning solution, the volume ratio of sulfuric acid, hydrogen peroxide and functionalized ionic liquid is (50~60):(10~20):(25~35).

[0016] In some embodiments, the functionalized ionic liquid contains a basic functional group; the basic functional group is selected from at least one of amino, thioether, or cyano groups.

[0017] In some embodiments, the functionalized ionic liquid comprises an alkyl chain; the alkyl chain is selected from straight-chain alkyl groups having 4 to 8 carbon atoms.

[0018] In some embodiments, the first cleaning solution containing dissolved metal contaminants is replaced with an intermediate solvent, including:

[0019] The functionalized ionic liquid was diluted with a good solvent for ionic liquids;

[0020] The substrate surface was rinsed with isopropanol solution to replace the ionic liquid solvent.

[0021] In some embodiments, the good solvent for the ionic liquid includes at least one of dimethyl sulfoxide or N-methylpyrrolidone.

[0022] In some embodiments, the second cleaning solution comprises hydrochloric acid, hydrogen peroxide, and water in a volume ratio of 1:(2~8):(50~60).

[0023] In some embodiments, the ionic liquid is selected from at least one of 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, and 1-butyl-3-methylimidazolium iodide.

[0024] The method for forming metal silicides provided in this application has the following unexpected technical effects:

[0025] Compared to the high reaction temperatures (170℃~220℃) required for removing metal contaminants using related technologies, the first cleaning solution, which includes sulfuric acid, hydrogen peroxide, and functionalized ionic liquids, can dissolve and remove metal contaminants at a lower temperature while simultaneously forming a protective passivation layer in situ on the surface of the metal silicide layer. This reduces the equipment requirements and maintenance costs for removing unreacted nickel-platinum alloys, avoids the impact of high-temperature wet processes on the thermal stability of nickel-silicon compounds, and ensures the film quality and electrical performance stability of the metal silicide.

[0026] Furthermore, by using water washing, intermediate solvents, and a second cleaning solution, the functionalized ionic liquids adhering to the surface of the metal silicide can be replaced, removing any remaining metal contaminants that may be present, thus further ensuring the cleaning quality. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a scanning electron microscope (SEM) image of a metal silicide surface with damage and depressions in a comparative embodiment;

[0029] Figure 2 This is a schematic flowchart of a metal silicide formation method provided in one embodiment of this application;

[0030] Figure 3 This is a comparison diagram of the surface morphology of the device structure in one embodiment of this application and a comparative example;

[0031] Figure 4 This is a comparison diagram of the cross-sectional morphology of the device structure in an embodiment of this application and a comparative example;

[0032] Figure 5 A comparison diagram of the contact resistance crystal plane distribution test results in an embodiment of this application and a comparative example. Detailed Implementation

[0033] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate preferred embodiments of the application. However, this application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0035] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, parts, regions, layers, doping types, and / or portions, these elements, parts, regions, layers, doping types, and / or portions should not be limited by these terms. These terms are only used to distinguish one element, part, region, layer, doping type, or portion from another element, part, region, layer, doping type, or portion. Therefore, without departing from the teachings of this application, the first element, component, region, layer, doping type, or portion discussed below may be represented as a second element, component, region, layer, or portion; for example, the first doping type may be referred to as the second doping type, and similarly, the second doping type may be referred to as the first doping type; the first doping type and the second doping type are different doping types, for example, the first doping type may be P-type and the second doping type may be N-type, or the first doping type may be N-type and the second doping type may be P-type.

[0036] Spatial relation terms such as “below,” “under,” “below,” “under,” “above,” “above,” etc., are used herein to describe the relationship between one element or feature shown in the figure and other elements or features. It should be understood that, in addition to the orientation shown in the figure, spatial relation terms also include different orientations of the device in use and operation. For example, if the device in the figure is flipped, the element or feature described as “below,” “under,” or “below” will be oriented “above” the other element or feature. Therefore, the exemplary terms “below” and “under” can include both above and below orientations. Furthermore, the device may also include other orientations (e.g., rotated 90 degrees or other orientations), and the spatial descriptive terms used herein will be interpreted accordingly.

[0037] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that when the terms “comprise” and / or “comprising” are used in this specification, the presence of the stated feature, integer, step, operation, element, and / or part is established, but the presence or addition of one or more other features, integers, steps, operations, elements, parts, and / or groups is not excluded. Meanwhile, when used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0038] Embodiments of the invention are described herein with reference to cross-sectional views illustrating ideal embodiments (and intermediate structures) of this application, thus allowing for variations in the illustrated shapes due to, for example, manufacturing techniques and / or tolerances. Therefore, embodiments of this application should not be limited to the specific shapes of the regions shown herein, but rather include shape deviations due to, for example, manufacturing techniques. For instance, implantation regions shown as rectangular typically have rounded or curved features at their edges and / or implantation concentration gradients, rather than a binary change from implantation regions to non-implantation regions. Similarly, the buried regions formed by implantation can result in some implantation in the region between the buried region and the surface traversed during implantation. Therefore, the regions shown in the figures are substantially schematic, and their shapes do not represent the actual shapes of regions of the device and do not limit the scope of this application.

[0039] Figure 1 The demonstration showcased a high-voltage SiC power device with a termination region in related technologies. In this device, the displacement current generated in the termination region under high dV / dt conditions has a long path, requiring it to traverse the entire transition region before flowing out through the source metal. The active region cannot adequately absorb the heat generated by this displacement current, leading to high electric field spikes in the transition region and heat generation from the displacement current, ultimately causing the chip structure to break down and burn out. This also highlights the poor switching performance (UIS) and dynamic reverse bias (DRB) capabilities under unclamped inductive loads.

[0040] In methods for preparing nickel silicide (NiSi), the common approach is to deposit a thin film of elemental nickel (Ni) on a silicon (Si) substrate and dope it with platinum (Pt) to optimize the material's thermal stability. Then, annealing is used to drive a solid-state chemical reaction between the nickel (Ni) and silicon (Si) to obtain nickel silicide (NiSi). However, platinum (Pt) etching is difficult, and removing unreacted metal layers can easily result in platinum (Pt) residue. For example, when preparing nickel-platinum silicides with a platinum (Pt) atomic fraction of 5 at% to 10 at%, the required reaction temperature is 170℃ to 220℃. Excessively high reaction temperatures not only increase equipment requirements and maintenance costs but also cause the generated metal silicides to oxidize during subsequent processes, leading to increased resistance and structural depressions. Figure 1 A scanning electron microscope (SEM) image of a metal silicide surface with damage and depressions is shown in a comparative embodiment.

[0041] In addition, as a precious metal, platinum (Pt) is not recycled in existing cleaning processes, which leads to resource waste and environmental pollution.

[0042] Based on this, please refer to the following: Figure 2 , Figure 2 A method for forming metal silicides provided in this application is shown, including steps S102-S110.

[0043] Step S102: Provide a substrate; a device structure is formed on the substrate, and a nickel-platinum metal layer for preparing a metal silicide layer is formed on the surface of the device structure; the platinum (Pt) content in the nickel-platinum metal layer is not less than 10%.

[0044] Specifically, taking a transistor as an example, the device structure includes a gate structure located on a substrate and a sidewall structure covering the gate sidewalls. The gate structure includes a gate dielectric layer and a gate conductive layer arranged sequentially. Active and drain regions are formed by self-alignment within the active regions of the substrate on both sides of the sidewall structure.

[0045] Subsequently, a deposition and photolithography process is used to pattern the photoresist and mask layer, defining and opening up the formation region of the self-aligned metal silicide in the device structure. A nickel-platinum metal layer covering this formation region is formed using any deposition process; wherein the nickel-platinum metal layer comprises platinum (Pt) with an atomic fraction of 10 at%.

[0046] Step S104: Perform a first annealing process on the substrate to form a metal silicide layer on the surface of the device structure; after the first annealing process, metal contaminants remain on the surface of the metal silicide layer, including unreacted nickel-platinum metal layers.

[0047] Specifically, the first annealing process is a rapid thermal annealing (RTP) process, which reacts nickel with silicon to form a high-resistivity phase Ni₂Si or NiSi. The temperature range for the first annealing is 200℃ to 300℃, for example, 200℃, 250℃, or 300℃. The time range for the first annealing is 10s to 300s, for example, 10s, 100s, 200s, or 300s.

[0048] Step S106: Under a temperature of less than or equal to 100°C, the substrate after the first annealing treatment is cleaned with a first cleaning solution to dissolve and remove metal contaminants; while dissolving and removing metal contaminants, a passivation layer is formed on the surface of the metal silicide layer; the first cleaning solution includes sulfuric acid (H2SO4), hydrogen peroxide (H2O2) and functionalized ionic liquid.

[0049] Specifically, at a temperature of 100°C or less, the substrate is placed in a first cleaning solution to remove metal contaminants (such as unreacted nickel and platinum) adhering to the surface of the metal silicide, and a protective passivation layer is formed in situ on the surface of the metal silicide. The first cleaning solution is a mixed solution comprising sulfuric acid, hydrogen peroxide, and the functionalized ionic liquid. The passivation layer includes a contact layer covering the top surface of the metal silicide and a protective layer covering the contact layer.

[0050] In some embodiments, the temperature conditions include 80°C to 100°C, such as 80°C, 90°C, or 100°C. The cleaning process lasts for at least approximately 5 to 10 minutes.

[0051] In some embodiments, the volume ratio of sulfuric acid (H2SO4), hydrogen peroxide (H2O2), and the functionalized ionic liquid is (50-60): (10-20): (25-35), for example, any value among 55:15:30, 50:20:30, or 60:15:25. The mass concentration of sulfuric acid (H2SO4) is 98%, and the mass concentration of hydrogen peroxide (H2O2) is 37%. In some embodiments, the ionic liquid is selected from at least one of 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), 1-butyl-3-methylimidazolium bromide ([BMIM]Br), and 1-butyl-3-methylimidazolium iodide ([BMIM]I).

[0052] In some embodiments, functionalized ionic liquids are characterized by the introduction of specific transenergetic groups or long alkyl chains onto asymmetric organic cations and inorganic or organic anions, thereby enhancing their strong coordination with target metal ions and improving dissolution efficiency and selectivity. For example, in cation functionalization, imidazole cations are used where the original alkyl chains, such as methyl or butyl, are replaced or attached with basic functional groups selected from at least one of (-NH2), thioether (-S-), or cyano (-CN).

[0053] In some embodiments, the long alkyl chain is selected from straight-chain alkyl groups having 4 to 8 carbon atoms.

[0054] In the above embodiments, sulfuric acid / hydrogen peroxide (H2SO4 / H2O2) can effectively remove nickel contaminants from the substrate surface and oxidize elemental platinum to Pt. 2+ Ions are present. Functionalized ionic liquids interact with soft acid Pt via soft base functional groups. 2+ The strong coordination between them immediately captures and stabilizes Pt. 2+ It forms a soluble complex, inhibiting platinum ion passivation (i.e., Pt). 2+ It will be quickly reduced back to its metallic state and hydrolyzed to precipitate, achieving "instant dissolution and preparation". At the same time, the large amount of coordination energy released during the coordination process compensates for the energy requirement of the oxidation step, significantly reducing the apparent activation energy, so that the dissolution reaction can still proceed efficiently at low temperatures of 80℃~100℃.

[0055] After cleaning, the ionic liquid forms a dense and non-volatile liquid film on the surface of the metal silicide through physical adsorption, chemical action, and molecular self-assembly. This film effectively isolates water molecules and oxygen, achieving passivation protection. Simultaneously, some of the ionic liquid remains between the metal silicide and the protective film, forming a contact layer only nanometers thick. Under the influence of an electric field, the ions in the ionic liquid rearrange to form an electric double layer structure, lowering the energy barrier for charge injection and filling microscopic gaps, increasing the conductive area and further reducing contact resistance.

[0056] Step S108: Replace the first cleaning solution containing dissolved metal contaminants with an intermediate solvent, and perform a first water rinse on the substrate after cleaning with the intermediate solvent. The intermediate solvent includes a good solvent for ionic liquids and isopropanol (IPA).

[0057] Specifically, the substrate is first cleaned using a good solvent capable of efficiently dissolving ionic liquids, thoroughly dissolving and diluting most of the residual ionic liquids on the substrate surface. Then, isopropanol (IPA) is used for displacement rinsing, utilizing the property that isopropanol is fully miscible with the aforementioned good solvent to completely replace and remove the residual good solvents from the substrate surface. The water miscibility of isopropanol (IPA) is then used to connect to the subsequent first water rinse process to remove the remaining first cleaning solution from the substrate surface.

[0058] In some embodiments, the good solvent for the ionic liquid can be at least one of dimethyl sulfoxide (DMSO) or N-methylpyrrolidone (NMP) to ensure a residue-free transition during the replacement process without corroding or damaging the already formed passivation layer.

[0059] Step S110: Use a second cleaning solution to clean the substrate after the first water wash to remove the metal contaminants still remaining on the surface of the metal silicide layer, thereby further improving the surface cleanliness.

[0060] In some embodiments, the second cleaning solution comprises hydrochloric acid (HCl), hydrogen peroxide (H2O2), and water (H2O) in a volume ratio of 1:(2~8):(50~60). For example, the volume ratio may be any value among 1:2:50, 1:5:55, 1:7:50, or 1:8:60.

[0061] In some embodiments, after step S110, the method further includes: performing a second water wash on the substrate at room temperature using, but not limited to, distilled water, high-purity water, or deionized water, to remove surface particulate impurities. Then, steps such as drying and a second annealing are performed to obtain a low-resistivity self-aligned metal silicide from the high-resistivity Ni2Si or NiSi formed by the first annealing treatment.

[0062] In this application, the terms "room temperature" or "normal temperature" generally refer to 4°C to 35°C, for example, 20°C ± 5°C. In some embodiments of this application, "room temperature" or "normal temperature" refers to 10°C to 30°C. In some embodiments of this application, "room temperature" or "normal temperature" refers to 20°C to 30°C.

[0063] In some embodiments, chemical reduction and thermal decomposition methods can be used to recover metallic platinum (Pt) from ionic liquids loaded with platinum (Pt) to achieve the recycling and reuse of precious metals and avoid waste and environmental pollution.

[0064] To evaluate the formation quality of the metal silicide in the formation method provided in this application, the following examples and comparative examples will provide a more detailed description of the application. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the application. For experimental methods not specified in the following examples, please refer to the instructions given in this application, or follow experimental manuals or conventional conditions in the art, or follow the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0065] Example

[0066] (1) A nickel-platinum metal layer consisting of an alloy of 90 at% nickel (Ni) and 10 at% platinum (Pt) is formed on the substrate, and then a first annealing treatment is performed.

[0067] (2) Place the substrate in the first cleaning solution and keep it at 80°C using a constant temperature bath. The first cleaning solution is 55% sulfuric acid (H2SO4) by volume, 15% hydrogen peroxide (H2O2) by volume, and 30% [Dibmim]Cl (1-butyl-2,3-dimethylimidazolium chloride) by volume, which includes alkyl chains and a weakly basic nitrogen-containing heterocycle (imidazolium ring).

[0068] (3) The substrate was cleaned by replacement with dimethyl sulfoxide (DMSO) and isopropanol (IPA), and a first water wash was performed.

[0069] (4) Clean the substrate after the first water wash using a conventional ratio of hydrochloric acid (HCl), hydrogen peroxide (H2O2) and water (H2O).

[0070] (5) Formation of self-aligned silicides.

[0071] Comparative Example

[0072] The main difference from Example 1 is that, in the first step of removing metal contaminants, the cleaning solution used is only a sulfuric acid (H2SO4) / hydrogen peroxide system (H2O2).

[0073] Performance testing experiment

[0074] Figures 3-5 The test results of the surface morphology and contact resistance of the metal silicides obtained in the examples and comparative examples are shown.

[0075] Figure 3 (a) Figure 3 (b) shows the surface morphology characterization results of the device structures in the examples and comparative examples, respectively. Figure 3 As shown in the example, after cleaning, the substrate surface was uniform and free of metal particles or clusters, indicating that the cleaning solution of this application can efficiently dissolve and remove metal contaminants such as platinum (Pt) without secondary residue. After cleaning in the comparative example, obvious clusters of Pt residue were present on the substrate surface, indicating that conventional cleaning processes cannot effectively remove this type of contaminant, and the residual Pt particles will reduce the reliability of subsequent processes.

[0076] Figure 4 (a) Figure 4 (b) shows the cross-sectional morphology of the device structure in the embodiments and comparative examples, respectively. Figure 4 As shown, after cleaning in the embodiment, the amount of depression in the metal silicide layer is only about 2nm, and the depression depth is uniform and extremely small. This indicates that the corrosion damage to the silicide substrate caused by this cleaning process is controlled at an extremely low level. In the comparative example, the depression depth caused by the conventional cleaning process is about twice that of the embodiment. Excessive depression will lead to a reduction in contact area and an increase in contact resistance, affecting the electrical performance of the device.

[0077] Figure 5 (a) Figure 5 Figure (b) shows the circular distribution of contact resistance in the examples and comparative examples, respectively. In the examples, the average Rs is 109.411 Ω / sq, with only 0.18 Ω / sq (0.161%) at 1sig, indicating low and uniform Rs distribution. In the comparative examples, the average Rs increases to 114.386 Ω / sq, with 1sig reaching 14.52 Ω / sq (12.691%), showing increased and uneven Rs distribution. This demonstrates that the present application can effectively reduce contact resistance and ensure its consistency, while conventional processes degrade electrical performance due to problems such as platinum (Pt) residue and excessive silicide corrosion.

[0078] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features of the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0079] The embodiments described above are merely examples of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application.

Claims

1. A method for forming a metal silicide, characterized in that, The method includes: A substrate is provided; a device structure is formed on the substrate, and a nickel-platinum metal layer for fabricating a metal silicide layer is formed on the surface of the device structure; the platinum content in the nickel-platinum metal layer is not less than 10%. The substrate is subjected to a first annealing process to form a metal silicide layer on the surface of the device structure; after the first annealing process, metal contaminants remain on the surface of the metal silicide layer, including an unreacted nickel-platinum metal layer; Under conditions of temperature less than or equal to 100°C, the substrate after the first annealing treatment is cleaned with a first cleaning solution to dissolve and remove the metal contaminants; while dissolving and removing the metal contaminants, a passivation layer is formed on the surface of the metal silicide layer; the first cleaning solution includes sulfuric acid, hydrogen peroxide and functionalized ionic liquid; An intermediate solvent is used to replace the first cleaning solution containing dissolved metal contaminants, and the substrate cleaned with the intermediate solvent is then subjected to a first water wash. The substrate after the first water wash is cleaned with a second cleaning solution to remove any remaining metal contaminants on the surface of the metal silicide layer.

2. The forming method according to claim 1, characterized in that, The passivation layer includes a contact layer and a protective layer arranged sequentially in a direction away from the substrate; The contact layer is used to reduce contact resistance; The protective layer is used to inhibit the oxidation of the metal silicide.

3. The forming method according to claim 1, characterized in that, The temperature range of the first cleaning solution is 80℃~100℃.

4. The forming method according to claim 1, characterized in that, One or more of the following conditions must be met: In the first cleaning solution, the volume ratio of sulfuric acid, hydrogen peroxide and the functionalized ionic liquid is (50~60):(10~20):(25~35).

5. The forming method according to claim 3, characterized in that, The functionalized ionic liquid contains a basic functional group; the basic functional group is selected from at least one of amino, thioether or cyano groups.

6. The forming method according to claim 3, characterized in that, The functionalized ionic liquid contains an alkyl chain; the alkyl chain is selected from straight-chain alkyl groups having 4 to 8 carbon atoms.

7. The forming method according to claim 4 or 5, characterized in that, The method of using an intermediate solvent to replace the first cleaning solution containing dissolved metal contaminants includes: The functionalized ionic liquid was diluted with a good ionic liquid solvent; The substrate surface was rinsed with isopropanol solution to replace the ionic liquid solvent.

8. The forming method according to claim 7, characterized in that, The good solvent for the ionic liquid includes at least one of dimethyl sulfoxide or N-methylpyrrolidone.

9. The forming method according to claim 7, characterized in that, The second cleaning solution comprises hydrochloric acid, hydrogen peroxide, and water in a volume ratio of 1:(2~8):(50~60).

10. The forming method according to claim 7, characterized in that, The ionic liquid is selected from at least one of 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium bromide, and 1-butyl-3-methylimidazolium iodide.

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