Weakly acidic tungsten CMP post-cleaning agent with low metal corrosion and preparation method and application thereof

Abstract

The invention relates to a weak acid tungsten CMP post-cleaning agent with low metal corrosion and a preparation method and application thereof. The weak acid tungsten CMP post-cleaning agent with low metal corrosion comprises the following components in parts by weight: 5-30 parts of a functional agent; 5-25 parts of a composite additive; 0.5 to 15 parts of a pH regulator; 70 to 95 parts of ultrapure water; the functional agent is a hydroxyl flavone derivative compound; the composite additive comprises a triazine ring compound and a phosphorus-containing ureido compound. The cleaning agent provided by the invention can effectively remove residual metal pollutants on the surface of the wafer, especially tungsten chips, tungsten oxides on the surface and free tungsten ions, can effectively improve the generation of surface defects of the semiconductor wafer during cleaning after tungsten CMP, and improves the quality of the wafer. And the cleaning agent provided by the invention can still keep extremely excellent cleaning efficiency under the pure soaking process condition of not needing an ultrasonic process to be matched with cleaning.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor manufacturing technology, and in particular relates to a weakly acidic tungsten post-CMP cleaning agent with low metal corrosion, a preparation method and an application thereof. Background Art

[0002] Chemical mechanical polishing (CMP) is a technique used to flatten the wafer surface during the integrated circuit manufacturing process to address photolithography depth of focus issues, thereby improving component integration and performance. As the process evolves, defects introduced by this process become a pressing issue, including residual contaminant particles, polishing fluid residue, and metal contaminants left on the wafer surface after polishing.

[0003] In existing semiconductor manufacturing processes, tungsten is widely used in multi-layer metal interconnect technology to form plugs that connect vertically between metal layers and to create local interconnects to connect different metal layers. Because tungsten thin films have excellent gap-filling capabilities, tungsten metal is filled into contact holes to form tungsten plugs, followed by chemical mechanical planarization (CMP) to remove excess tungsten.

[0004] Traditional tungsten metal often leaves a lot of residual particles after the CMP process, and tungsten easily reacts with residual polishing fluid to form tungsten oxide, causing metal contamination. After the chemical mechanical planarization (CMP) process, wet cleaning is typically used to remove contaminants from the wafer surface. Existing technologies can achieve this by exploiting the solubility of tungsten oxide in strong acid environments. However, corrosion inevitably occurs, leading to excessive tungsten loss and roughening and pitting of the wafer surface. These defects can result in high contact resistance, causing failure of the connection between the device and the metal wire, and seriously affecting product yield.

[0005] Therefore, in the current field of chip cleaning after tungsten CMP process, there is an urgent need to develop new chip cleaning agents and cleaning methods that can effectively remove residual pollutants on the wafer surface. In particular, there is a more urgent industrial application demand for new cleaning agents that are damage-free, highly efficient, and chip-free. They can effectively improve the generation of surface defects on semiconductor wafers during post-tungsten CMP cleaning. Summary of the Invention

[0006] The technical problem solved by the present invention is that the metal contaminants remaining on the surface of the wafer can be effectively removed, and the generation of surface defects of the semiconductor wafer can be effectively improved during the post-Tungsten CMP cleaning.

[0007] In view of the technical problems existing in the prior art, the present invention provides a low metal corrosion weak acid tungsten CMP post-cleaning agent and its preparation method and application, which can maintain extremely excellent cleaning efficiency under pure immersion process conditions without the need for ultrasonic cleaning process.

[0008] It should be noted that, in the present invention, unless otherwise specified, the specific meaning of "including" in relation to composition limitations and descriptions includes both open-ended "including", "comprising", etc. and similar meanings, as well as closed-ended "consisting of..." etc. and similar meanings.

[0009] In order to solve the above-mentioned technical problems, the present invention adopts the following solutions:

[0010] A low metal corrosion weak acid tungsten CMP post-cleaning agent, calculated by weight, comprises the following components:

[0011] 5-30 parts of functional agent;

[0012] 5-25 parts of composite additives;

[0013] 0.5-15 parts of pH regulator;

[0014] 70-95 parts of ultrapure water;

[0015] Wherein, the functional agent is a hydroxyflavone derivative compound;

[0016] The composite additive comprises a triazine ring compound and a phosphorus-containing urea compound.

[0017] Furthermore, the functional agent is one or more of catechin, epigallocatechin gallate, and kaempferol-3-O-rhamnoside.

[0018] Furthermore, the mass ratio of the triazine ring compound to the phosphorus-containing urea compound is 1-4:1.

[0019] Furthermore, the triazine ring compound is one or more of tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, trishydroxyethyl isocyanurate, and tris(4-tert-butyl-3-hydroxy-2,6-xylyl) isocyanurate.

[0020] Furthermore, the phosphorus-containing urea compound is one or more of urea phosphate, imidourea phosphate, and guanyl urea phosphate.

[0021] Furthermore, the pH regulator is one or more of salicylic acid, benzoic acid, DL-mandelic acid, benzenesulfonic acid, and pteroic acid.

[0022] Furthermore, the cleaning agent is weakly acidic, and the pH value of the cleaning agent is 4-7.

[0023] The present invention also discloses a method for preparing the above-mentioned low metal corrosion weakly acidic tungsten post-CMP cleaning agent, comprising the following steps:

[0024] Step 1: Weigh each component in its respective amount;

[0025] Step 2: Stir all components at room temperature until all materials are completely dissolved, thereby obtaining the low metal corrosion weakly acidic tungsten post-CMP cleaning agent.

[0026] The present invention also discloses a method for using the above-mentioned low metal corrosion weak acid tungsten post-CMP cleaning agent, comprising the following steps:

[0027] Step 1: The low metal corrosion weak acid tungsten post-CMP cleaning agent is prepared into an aqueous solution with a mass percentage concentration of 10-100% by ultrapure water, and then the aqueous solution is used to soak a tungsten wafer at room temperature for 5-30 minutes to obtain a soaked tungsten wafer;

[0028] Step 2: Rinse the soaked tungsten wafer in ultrapure water to complete the cleaning process of the tungsten wafer.

[0029] The invention also discloses a use of the above-mentioned weakly acidic tungsten post-CMP cleaning agent with low metal corrosion in cleaning semiconductor chips.

[0030] In the present invention, in order to further improve the performance of the cleaning agent, the raw material components can be optimized, the functional agent is 10-25 parts; the composite additive is 12-20 parts; the pH regulator is 5-10 parts; and ultrapure water is 75-90 parts.

[0031] In the present invention, the functional agent is preferably epigallocatechin gallate.

[0032] In the present invention, the mass ratio of the triazine ring compound to the phosphorus-containing urea compound is preferably 2:1.

[0033] In the present invention, the triazine ring compound is preferably tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate.

[0034] In the present invention, the phosphorus-containing urea-based compound is preferably guanyl phosphate urea.

[0035] In the present invention, the ultrapure water used is deionized water with a resistance of ≥18 MΩ.

[0036] In the present invention, the pH adjuster is preferably pteroic acid.

[0037] In the present invention, the pH value of the cleaning agent is preferably 4.5-6.5.

[0038] In the present invention, in step 2 of the method for using the cleaning agent, the soaked tungsten wafer is rinsed in ultrapure water for two or more rinses.

[0039] In the present invention, the functional agent has a special role:

[0040] First, the flavonoid structure contained in the functional agent of the present invention can interact with the tungsten surface, making it easy for the functional agent to form a passivation film on the chip surface, with good film-forming stability, reducing the contact between the tungsten surface and the corrosive medium, inhibiting the formation of an oxide film, and avoiding excessive loss of tungsten, thereby achieving the effect of inhibiting metal corrosion.

[0041] Secondly, the functional agent of the present invention can capture free metal ions attached to the chip surface and in the solution system, coordinate with the metal ions, exist in the form of a stable soluble complex and be carried away from the chip surface with the flowing cleaning agent, thereby achieving a good cleaning effect.

[0042] Third, the functional agent of the present invention contains multiple hydrophilic hydroxyl polar groups, which improves its own hydrophilicity and water solubility, and at the same time creates strong hydrogen bonding within and between molecules, further improving the solubility of the compound and providing a basis for the stability of subsequent cleaning agents.

[0043] In the present invention, the composite additive has a unique role:

[0044] First, the triazine ring structure unique to triazine ring compounds in the composite additive introduces a stable benzene ring and a hydrophilic group, which increases its own conjugation and can form a rich hydrogen bond network with itself and other components, further improving the thermal stability and solubility of the cleaning agent.

[0045] Secondly, the lone electron pair of the nitrogen atom in the triazine ring gives it a supramolecular metal coordination compound skeleton, which can dissolve the oxide film on the chip surface and then form coordination bonds with tungsten atoms, thereby promoting chemical adsorption of the cleaning agent on the tungsten surface to slow down corrosion. It can also be used in conjunction with functional agents to increase its permeability and adhesion on the surface of tungsten wafers through the adsorption of the flavonoid structure on the benzene ring and the hydrogen bonding effect, thereby isolating the corrosive medium, improving the lubrication effect, and preventing residues from adhering to the chip surface again to cause secondary pollution.

[0046] Third, phosphorus-containing urea compounds can dissolve the oxide film produced on the chip surface and then enter the cleaning agent system. Their unique phosphate groups and urea groups easily form coordination bonds with tungsten atoms, thereby promoting chemical adsorption of the cleaning agent on the tungsten surface to slow down corrosion.

[0047] Fourthly, phosphorus-containing urea compounds contain multiple nitrogen groups, which can adsorb phenolic hydroxyl groups in triazine compounds / flavonoid compounds and form hydrogen bonds with carbonyl oxygen atoms in flavonoid compounds / triazine compounds. In addition, the hydrogen bonds formed between molecules link the molecules together to form a hydrogen bond network, thereby forming an organized structure, which is covered on the metal surface through adsorption to enhance the protection of the metal.

[0048] In the present invention, the pH regulator can adjust the cleaning agent system to a weakly acidic environment, inhibit the formation of metal oxides, and avoid excessive loss of tungsten.

[0049] At the same time, the pH regulator can chelate the metal ions remaining on the surface and detach them from the tungsten surface under the flushing action of ultrapure water, and promote the formation of a passivation film, thereby avoiding direct contact between the corrosive medium and the tungsten surface and accelerating corrosion.

[0050] The low metal corrosion weakly acidic tungsten post-CMP cleaning agent, preparation method and application of the present invention have the following beneficial effects:

[0051] 1. The functional agent used in this invention has a hydroxyl-modified flavonoid structure and excellent solubility, ensuring the stability of the entire system. Its coordination with metal ions accelerates the dissolution of the oxide layer on the tungsten surface and forms a stable, soluble complex with the metal ions in the system, freeing contaminants from the tungsten surface. Furthermore, the functional agent adsorbs on the tungsten surface to form a passivation film, preventing the regeneration of the oxide film. It also inhibits contact between corrosive media and the tungsten surface, preventing excessive consumption of tungsten.

[0052] 2. The combination of the functional agent and the composite additive of the present invention can achieve rapid dissolution of metal oxides while inhibiting uneven corrosion of the substrate by the corrosive medium, ensuring that the surface of the tungsten wafer is smooth and low in corrosion after cleaning.

[0053] 3. After the components of the cleaning agent of the present invention are mixed, intermolecular interaction forces may occur based on their respective structural characteristics, and after mutual dissolution and promotion, the lubricity and solubility of each other may be improved and stimulated. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 : Microscope image of tungsten wafer before cleaning at 100 times magnification;

[0055] Figure 2 : A microscope picture magnified 100 times of a tungsten wafer after cleaning with the cleaning agent of Example 1 of the present invention;

[0056] Figure 3 : A microscope picture magnified 100 times of a tungsten wafer after being cleaned using the cleaning agent of Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0057] The present invention will be further described below with reference to specific embodiments and accompanying drawings:

[0058] Table 1 Components and weight ratios of the cleaning agents of Examples 1-7

[0059]

[0060]

[0061] Table 2 Components and weight ratios of the cleaning agents of Comparative Examples 1-6

[0062]

[0063] Table 3 Test results

[0064]

[0065] The preparation method of the cleaning agent of the present invention comprises the following steps:

[0066] Step 1: Weigh each component in its respective amount;

[0067] Step 2: Stir all components at room temperature until all materials are completely dissolved, thereby obtaining the low metal corrosion weakly acidic tungsten post-CMP cleaning agent.

[0068] The method for using the cleaning agent of the present invention comprises the following steps:

[0069] Step 1: A low metal corrosion weak acid tungsten post-CMP cleaning agent is prepared with ultrapure water to prepare an aqueous solution with a mass percentage concentration of 40%, and then the aqueous solution is used to soak a tungsten wafer at room temperature for 20 minutes to obtain a soaked tungsten wafer;

[0070] Step 2: Rinse the soaked tungsten wafer in ultrapure water to complete the cleaning process of the tungsten wafer.

[0071] About performance testing and description:

[0072] The test method for tungsten metal corrosion is a static corrosion test:

[0073] Step 1: Cut the tungsten wafer into 2cm*2cm square pieces and pre-treat them with 1wt% ammonia solution at room temperature for 5 minutes. Rinse with ultrapure water and blow dry with nitrogen.

[0074] Step 2: Use a microscope to take a picture of the tungsten wafer, see Figure 1 The film thickness and resistivity of tungsten wafers were tested with four probes to determine the functional relationship between tungsten thickness and resistivity, which was used to calculate the tungsten corrosion rate ( Right now );

[0075] Step 3: Take another 10mL of cleaning agent and soak the tungsten wafer at room temperature for 4 hours for static etching. Rinse with ultrapure water and blow dry with nitrogen.

[0076] Step 4: Use a microscope to take pictures of the tungsten wafer after etching for comparison. Figure 2 and Figure 3The film thickness of the tungsten wafer after corrosion was tested with a four-probe method. The corrosion rate was then calculated based on the change in thickness of the tungsten wafer before and after corrosion, thereby investigating the corrosion of the metal by different cleaning agents. The test results are shown in Table 3.

[0077] Analysis of the test results:

[0078] Based on Table 3, it can be seen that the corrosion rate of the cleaning agent provided by the embodiment of the present invention on tungsten metal is lower than And there is no residue after cleaning.

[0079] In Comparative Example 1, the phosphorus-containing urea compound is used alone as an additive. Due to the lack of the addition of the triazine ring compound, the coordination effect and hydrogen bonding effect are weakened, resulting in weakened cleaning ability and severe corrosion.

[0080] Comparative Example 2 uses triazine ring compounds alone as additives. Due to the lack of phosphorus-containing urea compounds, the cleaning ability is weakened and the corrosion is severe.

[0081] It can be seen that the present invention adopts a combination of a phosphorus-containing urea compound and a triazine ring compound as a composite additive, which can significantly improve the protection ability of tungsten metal and reduce tungsten metal corrosion.

[0082] In Comparative Example 3, due to the lack of functional agent, the passivation effect was weakened, resulting in severe corrosion.

[0083] Comparative Example 4 uses 3',5,7-trihydroxy-3,4'-dimethoxyflavone as a functional agent. Although it has a flavonoid structure, its passivation film-forming effect is weakened, resulting in a weakened corrosion resistance.

[0084] Comparative Example 5 uses a non-flavonoid substance as a functional agent, which weakens the passivation effect and causes a weakening of the corrosion resistance. Therefore, it can be seen that the present invention uses a specific functional agent to significantly reduce metal corrosion.

[0085] Comparative Example 6 uses citric acid as the pH regulator, but the passivation film-forming effect is weakened, resulting in a weakened anti-corrosion effect.

[0086] Further comparison is made through the accompanying drawings in the specification:

[0087] Figure 1 This is a microscope picture of a tungsten wafer before cleaning at 100 times magnification; Figure 2 This is a microscope image magnified 100 times after a tungsten wafer was cleaned using the cleaning agent of Example 1 of the present invention; Figure 3 This is a microscope picture magnified 100 times of a tungsten wafer after being cleaned using the cleaning agent of Comparative Example 3 of the present invention.

[0088] pass Figure 1 and Figure 2 The comparison shows that Figure 1 For the state of clean tungsten wafer, Figure 2 The tungsten wafer cleaned with the cleaning agent prepared in Example 1 of the present invention is similar to the tungsten wafer in surface appearance. Figure 1 There is almost no difference. There is almost no corrosion on the tungsten wafer after cleaning, and the cleaning effect is good.

[0089] pass Figure 1 and Figure 3 The comparison shows that Figure 1 For the state of clean tungsten wafer, Figure 3 The large bright spots are caused by corrosion and dirt, which means that the tungsten wafer was severely corroded and had a rough surface after being cleaned with the cleaning agent in Comparative Example 3. In Comparative Example 3, due to the lack of functional agent, the passivation effect was weakened, resulting in severe corrosion.

[0090] The cleaning agent provided by the present invention can effectively remove metal contaminants remaining on the wafer surface, especially tungsten debris, as well as tungsten oxides and free tungsten ions on the surface. It can effectively improve the generation of surface defects on semiconductor wafers during post-tungsten CMP cleaning. Moreover, the cleaning agent provided by the present invention can maintain extremely excellent cleaning efficiency under pure immersion process conditions without the need for ultrasonic cleaning.

[0091] The present invention has been described above by way of example in conjunction with the embodiments and accompanying drawings. It is obvious that the implementation of the present invention is not limited to the above-mentioned methods. As long as various improvements are made using the method concepts and technical solutions of the present invention, or the concepts and technical solutions of the present invention are directly applied to other occasions without improvement, they are all within the scope of protection of the present invention.

Claims

1. A weakly acidic tungsten post-CMP cleaning agent with low metal corrosion, characterized in that: Calculated by weight, it includes the following components: Wherein, the functional agent is a hydroxyflavone derivative compound; The composite additive comprises a triazine ring compound and a phosphorus-containing urea compound.

2. The low metal corrosion weak acid tungsten post-CMP cleaning agent according to claim 1, characterized in that: The functional agent is one or more of catechin, epigallocatechin gallate, and kaempferol-3-O-rhamnoside.

3. The low metal corrosion weak acid tungsten post-CMP cleaning agent according to claim 1, characterized in that: The mass ratio of the triazine ring compound to the phosphorus-containing urea compound is 1-4:

1.

4. The low metal corrosion weakly acidic tungsten post-CMP cleaning agent according to claim 1, characterized in that: The triazine ring compound is one or more of tris(3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, trishydroxyethyl isocyanurate, and tris(4-tert-butyl-3-hydroxy-2,6-xylyl) isocyanurate.

5. The low metal corrosion weak acid tungsten post-CMP cleaning agent according to claim 1, characterized in that: The phosphorus-containing urea compound is one or more of urea phosphate, imidourea phosphate, and guanyl urea phosphate.

6. The low metal corrosion weakly acidic tungsten post-CMP cleaning agent according to claim 1, characterized in that: The pH regulator is one or more of salicylic acid, benzoic acid, DL-mandelic acid, benzenesulfonic acid, and pteroic acid.

7. The low metal corrosion weakly acidic tungsten post-CMP cleaning agent according to claim 1, characterized in that: The cleaning agent is weakly acidic, and the pH value of the cleaning agent is 4-7.

8. A method for preparing the low metal corrosion weakly acidic tungsten post-CMP cleaning agent according to any one of claims 1 to 7, characterized in that: The steps include: Step 1: Weigh each component in its respective amount; Step 2: Stir all components at room temperature until all materials are completely dissolved, thereby obtaining the low metal corrosion weakly acidic tungsten post-CMP cleaning agent.

9. A method for using the low metal corrosion weak acid tungsten post-CMP cleaning agent according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step 1: The low metal corrosion weak acid tungsten post-CMP cleaning agent is prepared into an aqueous solution with a mass percentage concentration of 10-100% by ultrapure water, and then the aqueous solution is used to soak a tungsten wafer at room temperature for 5-30 minutes to obtain a soaked tungsten wafer; Step 2: Rinse the soaked tungsten wafer in ultrapure water to complete the cleaning process of the tungsten wafer.

10. Use of the low metal corrosion weakly acidic tungsten post-CMP cleaning agent according to any one of claims 1 to 7 in cleaning semiconductor chips.

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